CA2283468C - A process for the manufacturing of thermoplastic products with high creep strain resistance - Google Patents
A process for the manufacturing of thermoplastic products with high creep strain resistance Download PDFInfo
- Publication number
- CA2283468C CA2283468C CA 2283468 CA2283468A CA2283468C CA 2283468 C CA2283468 C CA 2283468C CA 2283468 CA2283468 CA 2283468 CA 2283468 A CA2283468 A CA 2283468A CA 2283468 C CA2283468 C CA 2283468C
- Authority
- CA
- Canada
- Prior art keywords
- mold
- product part
- pallet
- thermoplastic material
- product
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C66/00—General aspects of processes or apparatus for joining preformed parts
- B29C66/40—General aspects of joining substantially flat articles, e.g. plates, sheets or web-like materials; Making flat seams in tubular or hollow articles; Joining single elements to substantially flat surfaces
- B29C66/47—Joining single elements to sheets, plates or other substantially flat surfaces
- B29C66/472—Joining single elements to sheets, plates or other substantially flat surfaces said single elements being substantially flat
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C51/00—Shaping by thermoforming, i.e. shaping sheets or sheet like preforms after heating, e.g. shaping sheets in matched moulds or by deep-drawing; Apparatus therefor
- B29C51/10—Forming by pressure difference, e.g. vacuum
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C51/00—Shaping by thermoforming, i.e. shaping sheets or sheet like preforms after heating, e.g. shaping sheets in matched moulds or by deep-drawing; Apparatus therefor
- B29C51/26—Component parts, details or accessories; Auxiliary operations
- B29C51/266—Auxiliary operations after the thermoforming operation
- B29C51/267—Two sheets being thermoformed in separate mould parts and joined together while still in the mould
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
- B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
- B29C65/18—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated tools
- B29C65/20—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated tools with direct contact, e.g. using "mirror"
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C66/00—General aspects of processes or apparatus for joining preformed parts
- B29C66/01—General aspects dealing with the joint area or with the area to be joined
- B29C66/05—Particular design of joint configurations
- B29C66/10—Particular design of joint configurations particular design of the joint cross-sections
- B29C66/11—Joint cross-sections comprising a single joint-segment, i.e. one of the parts to be joined comprising a single joint-segment in the joint cross-section
- B29C66/112—Single lapped joints
- B29C66/1122—Single lap to lap joints, i.e. overlap joints
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C66/00—General aspects of processes or apparatus for joining preformed parts
- B29C66/01—General aspects dealing with the joint area or with the area to be joined
- B29C66/05—Particular design of joint configurations
- B29C66/10—Particular design of joint configurations particular design of the joint cross-sections
- B29C66/11—Joint cross-sections comprising a single joint-segment, i.e. one of the parts to be joined comprising a single joint-segment in the joint cross-section
- B29C66/114—Single butt joints
- B29C66/1142—Single butt to butt joints
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C66/00—General aspects of processes or apparatus for joining preformed parts
- B29C66/50—General aspects of joining tubular articles; General aspects of joining long products, i.e. bars or profiled elements; General aspects of joining single elements to tubular articles, hollow articles or bars; General aspects of joining several hollow-preforms to form hollow or tubular articles
- B29C66/51—Joining tubular articles, profiled elements or bars; Joining single elements to tubular articles, hollow articles or bars; Joining several hollow-preforms to form hollow or tubular articles
- B29C66/54—Joining several hollow-preforms, e.g. half-shells, to form hollow articles, e.g. for making balls, containers; Joining several hollow-preforms, e.g. half-cylinders, to form tubular articles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C66/00—General aspects of processes or apparatus for joining preformed parts
- B29C66/50—General aspects of joining tubular articles; General aspects of joining long products, i.e. bars or profiled elements; General aspects of joining single elements to tubular articles, hollow articles or bars; General aspects of joining several hollow-preforms to form hollow or tubular articles
- B29C66/51—Joining tubular articles, profiled elements or bars; Joining single elements to tubular articles, hollow articles or bars; Joining several hollow-preforms to form hollow or tubular articles
- B29C66/54—Joining several hollow-preforms, e.g. half-shells, to form hollow articles, e.g. for making balls, containers; Joining several hollow-preforms, e.g. half-cylinders, to form tubular articles
- B29C66/543—Joining several hollow-preforms, e.g. half-shells, to form hollow articles, e.g. for making balls, containers; Joining several hollow-preforms, e.g. half-cylinders, to form tubular articles joining more than two hollow-preforms to form said hollow articles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C66/00—General aspects of processes or apparatus for joining preformed parts
- B29C66/70—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
- B29C66/71—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the composition of the plastics material of the parts to be joined
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C66/00—General aspects of processes or apparatus for joining preformed parts
- B29C66/70—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
- B29C66/72—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined
- B29C66/723—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the structure of the material of the parts to be joined being multi-layered
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C66/00—General aspects of processes or apparatus for joining preformed parts
- B29C66/70—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
- B29C66/73—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset
- B29C66/739—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the material of the parts to be joined being a thermoplastic or a thermoset
- B29C66/7392—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the material of at least one of the parts being a thermoplastic
- B29C66/73921—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the material of at least one of the parts being a thermoplastic characterised by the materials of both parts being thermoplastics
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D19/00—Pallets or like platforms, with or without side walls, for supporting loads to be lifted or lowered
- B65D19/0004—Rigid pallets without side walls
- B65D19/0006—Rigid pallets without side walls the load supporting surface being made of a single element
- B65D19/0008—Rigid pallets without side walls the load supporting surface being made of a single element forming a continuous plane contact surface
- B65D19/002—Rigid pallets without side walls the load supporting surface being made of a single element forming a continuous plane contact surface the base surface being made of more than one element
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C2791/00—Shaping characteristics in general
- B29C2791/001—Shaping in several steps
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C2791/00—Shaping characteristics in general
- B29C2791/004—Shaping under special conditions
- B29C2791/006—Using vacuum
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C2791/00—Shaping characteristics in general
- B29C2791/004—Shaping under special conditions
- B29C2791/007—Using fluid under pressure
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
- B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
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- B29C66/00—General aspects of processes or apparatus for joining preformed parts
- B29C66/80—General aspects of machine operations or constructions and parts thereof
- B29C66/83—General aspects of machine operations or constructions and parts thereof characterised by the movement of the joining or pressing tools
- B29C66/832—Reciprocating joining or pressing tools
- B29C66/8322—Joining or pressing tools reciprocating along one axis
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- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2023/00—Use of polyalkenes or derivatives thereof as moulding material
- B29K2023/04—Polymers of ethylene
- B29K2023/06—PE, i.e. polyethylene
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
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- B29K2023/00—Use of polyalkenes or derivatives thereof as moulding material
- B29K2023/10—Polymers of propylene
- B29K2023/12—PP, i.e. polypropylene
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
- B29K2105/26—Scrap or recycled material
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
- B29L2031/00—Other particular articles
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- B65D2519/00557—Structures connecting the constitutive elements of the pallet to each other, i.e. load supporting surface, base surface and/or separate spacer without separate auxiliary elements
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- B65D2519/00562—Structures connecting the constitutive elements of the pallet to each other, i.e. load supporting surface, base surface and/or separate spacer without separate auxiliary elements chemical connection, e.g. glued, welded, sealed
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T156/00—Adhesive bonding and miscellaneous chemical manufacture
- Y10T156/10—Methods of surface bonding and/or assembly therefor
- Y10T156/1002—Methods of surface bonding and/or assembly therefor with permanent bending or reshaping or surface deformation of self sustaining lamina
Abstract
A process for the manufacturing of thermoplastic products with a high creep strain resistance. The products are free from reinforcing additives. The process includes at least vacuum forming and/or blow moulding of a thermoplastic material such as a polyolefine. A number of product parts are manufactured from a number of preferably tube- or sheet-shaped work pieces. The work pieces are heated so that the thermoplastic material softens whereby they are given the desired shape by means of a mould and the influence of vacuum and/or pressure. The product parts produced are allowed to cool and post-shrink and are hereafter joined to a unit.
Description
WO 98/40199 PGT/SE981t)0378 A process for the manufacturing of thermoplastic products with high creep strain resistance.
The present invention relates to a process for the manufacturing of products made of thermoplastic material, which products have a high creep strain resistance without the need for reinforcing additives.
Products made of thermoplastic materials can be manufactured by a number of different manufacturing procedures. The most commonly used methods are however, injection moulding, vacuum forming, blow moulding and press moulding.
In some fields of application a high toad carrying capability is required.
Carrying designs made of materials such as steel and concrete will be able to handle a load almost irrespective of factors like time and temperature. This is not the case with thermoplastic materials where relatively small loads can cause a remaining deformation when charged for a long period of time. This phenomenon is called creep strain, creep deformation or creepage. This creep strain is accelerated if the temperature is raised. A design made of thermoplastic material will however be able to withstand loads that are tens of times higher without remaining deformation when charged for shorter periods of time. The relation between the amount of creep strain, time and temperature is depending on type and quality of thermoplastic material.
Carrying thermoplastic designs most often have to be designed to withstand the highest temperature together with the longest period of time and the highest load that it could be exposed to during its useful life. The creep strain can however be decreased by adding filling or reinforcing additives to the thermoplastic material.
Among filling additives that are commonly used can be mentioned minerals such as lime, glass beads and mica while reinforcing additives that are commonly used are fibres such as glass fibres, steel fibres or carbon fibres. It is also known to reinforce a thermoplastic product by integrating a metal design with the product.
This can for example be constituted by a steel rod applied in a profile in the thermoplastic product. These additives and additions will however decrease some of the good qualities naturally occurring in the thermoplastic material. Among those qualities can be mentioned good impact strength, low weight and being a ~ good electric, acoustic and heat insulator. It will also principally be impossible to recycle the material from a product containing additives. The ability to recycle thermoplastic materials is principally compulsory nowadays.
It has, quite surprisingly, according to the present invention, been made possible to manufacture creep stain resistant products of thermoplastic material, without the need of reinforcing additives. Accordingly, the invention relates to a process for the manufacturing of thermoplastic products with a high resistance against creep strain although the products are free from reinforcing additives. The process includes at least vacuum forming and/or blow moulding of a thermoplastic material such as polyethylene, polypropylene or polybutene. The invention is characterised in that a number of product parts are manufactured from a number of preferably tube or sheet shaped work pieces. The work pieces are heated so that the thermoplastic material softens, whereupon they are given the desired shape by means of a mould and the influence of vacuum and/or pressure. The product parts produced are allowed to cool and post-shrink. The product parts are hereafter assembled to a unit.
According to one embodiment of the invention, at least one of the product parts is manufactured through injection moulding by means of a mould comprising one or more mould cavities. A molten thermoplastic material is injected into a mould cavity of the mould. The thermoplastic material is allowed to solidify. The mould can then be opened and product part be removed from the mould. The product part is then allowed to cool completely and post-shrink.
The product parts is alternatively manufactured through injection moulding by means of a mould comprising one or more mould cavities. The mould includes means for injecting a pressurised gas. Molten thermoplastic material is injected into a mould cavity of the mould, whereupon the pressurised gas is injected into the molten thermoplastic material in the mould cavity. The thermoplastic material is allowed to solidify whereupon the gas is evacuated. The mould is then opened and the product part produced is removed from the mould. The product part is allowed to cool completely and post-shrink. It will hereby be possible to manufacture special features such as for example label pockets which are integrated with the article. Such special features are normally not possible to manufacture through vacuum forming or blow moulding.
According to one embodiment of the invention, one or more of the product parts are manufactured in a mould comprising a first and a second mould half. The mould halves include one shape-giving cavity each. The two shape-giving cavities together form a negative depiction of the outer shape of a product part. The mould halves are placed so that a space is formed between the two mould halves and so that the mould cavities are directed towards each other. Two pre-heated sheet shaped work pieces are applied between the two mould halves. The work pieces are individually forced towards the shape-giving surface of the mould cavities by means of vacuum and/or pressure. The mould halves are pressed together while the thermoplastic material is still hot so that the material in the work pieces confounds and a hollow unit is formed. It has shown to be a great advantage to connect the two surfaces on either side of the intermediate hollow space with each other by means of locally placed ridges or tower-like parts on product part containing large straight surfaces. This will increase the mechanical stability of the product as well as the ability to withstand bending when a load is applied.
The product parts preferably form parts such as a deck, a foot or a skid of a pallet, or a deck, a foot, a side wall or a skid of a pallet container or the like.
According to one embodiment of the invention, the injection moulded product parts forms parts such as a foot or a skid to pallet, a foot, a side wall or a skid to a pallet container. These product parts are joined by welding such as butt welding, friction welding or filler welding. The surface of two product parts that are to be joined are heated until they melt when utilising the butt welding procedure.
The heating is preferably achieved by bringing the surfaces to be joined in contact with a heated metal plate. The heated product parts are then pressed towards each other while the melted surfaces are allowed to cool.
When utilising friction welding, the surfaces that are to be joined are rubbed until they melt due to the friction heat. The most commonly used variants of this method is ultra-sonic welding, low frequency welding and rotation welding.
Filler welding used on thermoplastic materials is similar to gas welding with filler bar used on metal. The surface of the joint and a filler bar made of the same thermoplastic material as in the product parts are heated with a hot air blower.
The filler bar is used for filling the joint in a manner similar to that used for metal welding. The tatter method can also be used in combination with the above mentioned methods.
The thermoplastic material used is preferably constituted by a polymer such as polyethylene, polypropylene or polybutene with an average molecular mass in the range 200'000 - 2'000'000 preferably above 300'000. In certain cases, such as for example when manufacturing products with thin walls, polymers with an average molecular mass in the range 1'000'000 - 2'000'000 could show advantageous, while products with heavy walls most often are manufactured of a polymer with an average molecular mass in the range 300'000 - 1'000'000.
According to one embodiment of the invention the tube or sheet shaped work pieces are constituted by a thermoplastic laminate with two or more layers.
The layers are constituted by a combination of two or more of the materials selected from the group, virgin solid thermoplastic material, re-cycled solid thermoplastic material, virgin expanded thermoplastic material and re-cycled expanded thermoplastic material.
. CA 02283468 2006-O1-20 3a According to another aspect of the present invention, there is provided a molding process for the manufacture of a product comprising at least a first product part and a second product part from a thermoplastic material selected from the group consisting of polyethylene, polypropylene and polybutylene which product is free of reinforcing additives, in a mold having a first mold half and a second mold half, which together includes a shape-giving cavity being a negative depiction of the respective product part, the method comprising: forming the first product part, comprising: providing two mold halves, at least one of the mold halves having a projection in the shape-giving cavity thereby forming at least one protrusion in a work piece formed in said mold half; placing the mold halves so that a space is formed between the two mold halves and so that the shape-giving cavity of each mold half is directed toward each other; heating two work pieces which constitute an upper half and a lower half of the product part, thereby softening the thermoplastic material; shaping the work pieces toward the cavity of each mold half with the assistance of vacuum, blowing, and combinations thereof, to form shaped work pieces; moving the mold halves relatively toward one another and pressing the shaped work pieces together while the thermoplastic material is still hot to form a unitary hollow product part with the upper and lower halves of said product part being joined along their edges and by said at least one protrusion to increase mechanical strength and dimension stability; and cooling the first product part produced to the point where it can be removed from the mold though still at an elevated temperature; and further cooling the first product part for 1-2 days until the first product part has reached room temperature and post shrinking has been achieved; forming the second product part, comprising: injecting molten thermoplastic material 3b into one or more mold cavities of the mold; allowing the thermoplastic material to solidify; opening the mold;
cooling the second product part produced to the point where it can be removed from the mold though still at an elevated temperature; and removing the product part from the mold;
further cooling the second product part for 1-2 days until the second product part has reached room temperature and post shrinking has been achieved; and joining the first product part to the second product part and receiving a high creep strain resistant product.
According to still another aspect of the present invention, there is provided a molding process for the manufacture of a product comprising a hollow pallet deck and a at least one hollow pallet skid from a thermoplastic material selected from the group consisting of polyethylene, polypropylene and polybutylene, which product is free of reinforcing additives, in a mold having a first mold half and a second mold half, which together includes a shape-giving cavity being a negative depiction of the respective product part, the method comprising: forming one of either the pallet deck or the at least one skid, comprising:
providing two mold halves, at least one of the mold halves having a projection in the shape-giving cavity thereby forming at least one protrusion in a work piece formed in said mold half; placing the mold halves so that a space is formed between the two mold halves and so that the shape-giving cavity of each mold half is directed toward each other; heating two work pieces which constitute an upper half and a lower half of the product part, thereby softening the thermoplastic material; shaping the work pieces toward the cavity of each mold half with the assistance of vacuum, blowing, and combinations thereof, to form shaped work pieces; moving the mold halves relatively toward one another 3c and pressing the shaped work pieces together while the thermoplastic material is still hot to form a unitary hollow product part with the upper and lower halves of said product part being joined along their edges and by said at least one protrusion to increase mechanical strength and dimension stability; and cooling the first product part produced to the point where it can be removed from the mold though still at an elevated temperature; and further cooling the first product part for 1-2 days until the first product part has reached room temperature and post shrinking has been achieved; forming the other of the pallet deck or at least one skid, from a material having a high creep strain resistance, and free from reinforcing additives in a mold, the mold having a first mold half and a second mold half, which together includes a shape-giving cavity being a negative depiction of the respective product part, the method comprising: providing two mold halves, at least one of the mold halves having a projection in the shape-giving cavity thereby forming at least one protrusion in a work piece formed in said mold half; placing the mold halves so that a space is formed between the two mold halves and so that the shape-giving cavity of each mold half is directed toward each other; heating two work pieces which constitute an upper half and a lower half of the product part, thereby softening the thermoplastic material; shaping the work pieces toward the cavity of each mold half with the assistance of vacuum, blowing, and combinations thereof, to form shaped work pieces; moving the mold halves relatively toward one another and pressing the shaped work pieces together while the thermoplastic material is still hot to form a unitary hollow product part with the upper and lower halves of said product part being joined along their edges and by said at least one protrusion to increase mechanical strength and dimension stability; and cooling the second 3d product part produced to the point where it can be removed from the mold though still at an elevated temperature; and further cooling the second product part for 1-2 days until the second product part has reached room temperature and post shrinking has been achieved; and joining the hollow pallet deck and hollow pallet skids together.
The present invention relates to a process for the manufacturing of products made of thermoplastic material, which products have a high creep strain resistance without the need for reinforcing additives.
Products made of thermoplastic materials can be manufactured by a number of different manufacturing procedures. The most commonly used methods are however, injection moulding, vacuum forming, blow moulding and press moulding.
In some fields of application a high toad carrying capability is required.
Carrying designs made of materials such as steel and concrete will be able to handle a load almost irrespective of factors like time and temperature. This is not the case with thermoplastic materials where relatively small loads can cause a remaining deformation when charged for a long period of time. This phenomenon is called creep strain, creep deformation or creepage. This creep strain is accelerated if the temperature is raised. A design made of thermoplastic material will however be able to withstand loads that are tens of times higher without remaining deformation when charged for shorter periods of time. The relation between the amount of creep strain, time and temperature is depending on type and quality of thermoplastic material.
Carrying thermoplastic designs most often have to be designed to withstand the highest temperature together with the longest period of time and the highest load that it could be exposed to during its useful life. The creep strain can however be decreased by adding filling or reinforcing additives to the thermoplastic material.
Among filling additives that are commonly used can be mentioned minerals such as lime, glass beads and mica while reinforcing additives that are commonly used are fibres such as glass fibres, steel fibres or carbon fibres. It is also known to reinforce a thermoplastic product by integrating a metal design with the product.
This can for example be constituted by a steel rod applied in a profile in the thermoplastic product. These additives and additions will however decrease some of the good qualities naturally occurring in the thermoplastic material. Among those qualities can be mentioned good impact strength, low weight and being a ~ good electric, acoustic and heat insulator. It will also principally be impossible to recycle the material from a product containing additives. The ability to recycle thermoplastic materials is principally compulsory nowadays.
It has, quite surprisingly, according to the present invention, been made possible to manufacture creep stain resistant products of thermoplastic material, without the need of reinforcing additives. Accordingly, the invention relates to a process for the manufacturing of thermoplastic products with a high resistance against creep strain although the products are free from reinforcing additives. The process includes at least vacuum forming and/or blow moulding of a thermoplastic material such as polyethylene, polypropylene or polybutene. The invention is characterised in that a number of product parts are manufactured from a number of preferably tube or sheet shaped work pieces. The work pieces are heated so that the thermoplastic material softens, whereupon they are given the desired shape by means of a mould and the influence of vacuum and/or pressure. The product parts produced are allowed to cool and post-shrink. The product parts are hereafter assembled to a unit.
According to one embodiment of the invention, at least one of the product parts is manufactured through injection moulding by means of a mould comprising one or more mould cavities. A molten thermoplastic material is injected into a mould cavity of the mould. The thermoplastic material is allowed to solidify. The mould can then be opened and product part be removed from the mould. The product part is then allowed to cool completely and post-shrink.
The product parts is alternatively manufactured through injection moulding by means of a mould comprising one or more mould cavities. The mould includes means for injecting a pressurised gas. Molten thermoplastic material is injected into a mould cavity of the mould, whereupon the pressurised gas is injected into the molten thermoplastic material in the mould cavity. The thermoplastic material is allowed to solidify whereupon the gas is evacuated. The mould is then opened and the product part produced is removed from the mould. The product part is allowed to cool completely and post-shrink. It will hereby be possible to manufacture special features such as for example label pockets which are integrated with the article. Such special features are normally not possible to manufacture through vacuum forming or blow moulding.
According to one embodiment of the invention, one or more of the product parts are manufactured in a mould comprising a first and a second mould half. The mould halves include one shape-giving cavity each. The two shape-giving cavities together form a negative depiction of the outer shape of a product part. The mould halves are placed so that a space is formed between the two mould halves and so that the mould cavities are directed towards each other. Two pre-heated sheet shaped work pieces are applied between the two mould halves. The work pieces are individually forced towards the shape-giving surface of the mould cavities by means of vacuum and/or pressure. The mould halves are pressed together while the thermoplastic material is still hot so that the material in the work pieces confounds and a hollow unit is formed. It has shown to be a great advantage to connect the two surfaces on either side of the intermediate hollow space with each other by means of locally placed ridges or tower-like parts on product part containing large straight surfaces. This will increase the mechanical stability of the product as well as the ability to withstand bending when a load is applied.
The product parts preferably form parts such as a deck, a foot or a skid of a pallet, or a deck, a foot, a side wall or a skid of a pallet container or the like.
According to one embodiment of the invention, the injection moulded product parts forms parts such as a foot or a skid to pallet, a foot, a side wall or a skid to a pallet container. These product parts are joined by welding such as butt welding, friction welding or filler welding. The surface of two product parts that are to be joined are heated until they melt when utilising the butt welding procedure.
The heating is preferably achieved by bringing the surfaces to be joined in contact with a heated metal plate. The heated product parts are then pressed towards each other while the melted surfaces are allowed to cool.
When utilising friction welding, the surfaces that are to be joined are rubbed until they melt due to the friction heat. The most commonly used variants of this method is ultra-sonic welding, low frequency welding and rotation welding.
Filler welding used on thermoplastic materials is similar to gas welding with filler bar used on metal. The surface of the joint and a filler bar made of the same thermoplastic material as in the product parts are heated with a hot air blower.
The filler bar is used for filling the joint in a manner similar to that used for metal welding. The tatter method can also be used in combination with the above mentioned methods.
The thermoplastic material used is preferably constituted by a polymer such as polyethylene, polypropylene or polybutene with an average molecular mass in the range 200'000 - 2'000'000 preferably above 300'000. In certain cases, such as for example when manufacturing products with thin walls, polymers with an average molecular mass in the range 1'000'000 - 2'000'000 could show advantageous, while products with heavy walls most often are manufactured of a polymer with an average molecular mass in the range 300'000 - 1'000'000.
According to one embodiment of the invention the tube or sheet shaped work pieces are constituted by a thermoplastic laminate with two or more layers.
The layers are constituted by a combination of two or more of the materials selected from the group, virgin solid thermoplastic material, re-cycled solid thermoplastic material, virgin expanded thermoplastic material and re-cycled expanded thermoplastic material.
. CA 02283468 2006-O1-20 3a According to another aspect of the present invention, there is provided a molding process for the manufacture of a product comprising at least a first product part and a second product part from a thermoplastic material selected from the group consisting of polyethylene, polypropylene and polybutylene which product is free of reinforcing additives, in a mold having a first mold half and a second mold half, which together includes a shape-giving cavity being a negative depiction of the respective product part, the method comprising: forming the first product part, comprising: providing two mold halves, at least one of the mold halves having a projection in the shape-giving cavity thereby forming at least one protrusion in a work piece formed in said mold half; placing the mold halves so that a space is formed between the two mold halves and so that the shape-giving cavity of each mold half is directed toward each other; heating two work pieces which constitute an upper half and a lower half of the product part, thereby softening the thermoplastic material; shaping the work pieces toward the cavity of each mold half with the assistance of vacuum, blowing, and combinations thereof, to form shaped work pieces; moving the mold halves relatively toward one another and pressing the shaped work pieces together while the thermoplastic material is still hot to form a unitary hollow product part with the upper and lower halves of said product part being joined along their edges and by said at least one protrusion to increase mechanical strength and dimension stability; and cooling the first product part produced to the point where it can be removed from the mold though still at an elevated temperature; and further cooling the first product part for 1-2 days until the first product part has reached room temperature and post shrinking has been achieved; forming the second product part, comprising: injecting molten thermoplastic material 3b into one or more mold cavities of the mold; allowing the thermoplastic material to solidify; opening the mold;
cooling the second product part produced to the point where it can be removed from the mold though still at an elevated temperature; and removing the product part from the mold;
further cooling the second product part for 1-2 days until the second product part has reached room temperature and post shrinking has been achieved; and joining the first product part to the second product part and receiving a high creep strain resistant product.
According to still another aspect of the present invention, there is provided a molding process for the manufacture of a product comprising a hollow pallet deck and a at least one hollow pallet skid from a thermoplastic material selected from the group consisting of polyethylene, polypropylene and polybutylene, which product is free of reinforcing additives, in a mold having a first mold half and a second mold half, which together includes a shape-giving cavity being a negative depiction of the respective product part, the method comprising: forming one of either the pallet deck or the at least one skid, comprising:
providing two mold halves, at least one of the mold halves having a projection in the shape-giving cavity thereby forming at least one protrusion in a work piece formed in said mold half; placing the mold halves so that a space is formed between the two mold halves and so that the shape-giving cavity of each mold half is directed toward each other; heating two work pieces which constitute an upper half and a lower half of the product part, thereby softening the thermoplastic material; shaping the work pieces toward the cavity of each mold half with the assistance of vacuum, blowing, and combinations thereof, to form shaped work pieces; moving the mold halves relatively toward one another 3c and pressing the shaped work pieces together while the thermoplastic material is still hot to form a unitary hollow product part with the upper and lower halves of said product part being joined along their edges and by said at least one protrusion to increase mechanical strength and dimension stability; and cooling the first product part produced to the point where it can be removed from the mold though still at an elevated temperature; and further cooling the first product part for 1-2 days until the first product part has reached room temperature and post shrinking has been achieved; forming the other of the pallet deck or at least one skid, from a material having a high creep strain resistance, and free from reinforcing additives in a mold, the mold having a first mold half and a second mold half, which together includes a shape-giving cavity being a negative depiction of the respective product part, the method comprising: providing two mold halves, at least one of the mold halves having a projection in the shape-giving cavity thereby forming at least one protrusion in a work piece formed in said mold half; placing the mold halves so that a space is formed between the two mold halves and so that the shape-giving cavity of each mold half is directed toward each other; heating two work pieces which constitute an upper half and a lower half of the product part, thereby softening the thermoplastic material; shaping the work pieces toward the cavity of each mold half with the assistance of vacuum, blowing, and combinations thereof, to form shaped work pieces; moving the mold halves relatively toward one another and pressing the shaped work pieces together while the thermoplastic material is still hot to form a unitary hollow product part with the upper and lower halves of said product part being joined along their edges and by said at least one protrusion to increase mechanical strength and dimension stability; and cooling the second 3d product part produced to the point where it can be removed from the mold though still at an elevated temperature; and further cooling the second product part for 1-2 days until the second product part has reached room temperature and post shrinking has been achieved; and joining the hollow pallet deck and hollow pallet skids together.
The invention is further illustrated together with enclosed figures showing different embodiments of the invention and a comparative example, whereby, -figure 1 shows, in perspective, product parts of a pallet before the final assembly.
-figure 2 shows, in cross-section, a part of a pallet manufactured through the process according to the invention.
-figure 3 shows, in perspective, product parts of a pallet before the final assembly.
The pallet is manufactured by an alternative process according to the invention.
-figure 4 shows, in perspective, product parts of a pallet before the final assembly.
Figure I shows, in perspective, product parts of a pallet I before the final assembly. The pallet t is manufactured by one embodiment of the process according to the invention. The pallet is made from product parts in the shape of a hollow pallet deck 2 and three similar hollow pallet skids 3. The pallet deck 2 and the pallet skids 3 are individually manufactured in one mould each. The moulds comprise a first and a second mould half which together include a shape-giving cavity which is a negative depiction of the pallet deck 2 and the pallet skids respectively. The mould halves are placed so that an intermediate space is formed between the two halves and so that the cavities are directed towards each other.
Two sheet-shaped, pre-heated work pieces of high-density polyethylene with an average molecular weight greater than 300'000 are then placed between the two mould halves. The two work pieces are then individually shaped towards the cavity of one mould half each by means of vacuum. The two mould halves are then pressed together while the thermoplastic material is still hot so that the material confound and form a hollow unit. The process is repeated for the different moulds so that a required amount of pallet decks 2 and pallet skids 3 are obtained.
The pallet deck 2 and the pallet skids 3 are allowed to cool and post-shrink, which normally takes a day or two, before they are assembled to the final product.
The pallet deck 2 and the pallet skids 3 are provided with a number of joining surfaces 6 intended for the joining of the pallet deck 2 and the pallet skids 3. The joining surfaces 6 are heated by being brought into contact with a hot metal plate.
The parts 2 and 3 are the pressed together while the material in the joining surfaces 6 is still hot, whereby the parts 2 and 3 confounds so that they form a unit in the form of a pallet 1.
Figure 2 shows in cross-section a part of one embodiment of a pallet 1 obtained by the process according to the invention. A pallet skid 3 which is made from two sheet-shaped work pieces which constitute an upper half 3' and a lower half 3"
of a pallet skid 3. The two pallet skid halves 3' and 3" were confounded in connection to the manufacturing as described in connection to figure I.
The upper half and the lower half are, in addition to being joined along the . edges, also joined by a number of local ridge- or tower-like protrusions 7 (see also fig. I ) in larger parallel surfaces to increase the mechanical strength and the dimension stability. A pallet deck 2 is, in a similar way, made of an upper pallet deck half 2" and a lower pallet deck half 2' which halves are confounded in connection to the manufacturing. The two pallet deck halves 2' and 2" are, in addition to being joined along the edges, also joined by a number of local ridge- or tower-like protrusions 7 (see also fig 1 ) in larger parallel surfaces. The pallet skid 3 and the pallet deck 2 are hollow product parts that together form a pallet 1. The pallet skid 3 is joined with the pallet deck 2 by confounding as described in connection to figure 1.
Figure 3 shows, in perspective, parts of a pallet I before the final assembly.
The pallet 1 is manufactured by an alternative embodiment according to the invention.
The pallet 1 is constituted by a number of product parts in the form of a hollow pallet deck 2, three similar pallet skids 3, four corner feet 4 and five centre feet 5.
The pallet deck 2 is given its shape in a mould comprising a first and a second mould half. Each half includes a shape-giving cavity. The two shape-giving cavities together form a negative depiction of the outer shape of the pallet deck 2.
The mould cavities are placed so that an intermediate space is formed between the mould halves and that the two cavities are facing each other. Two pre-heated work pieces of high-density polyethylene with an average molecular weight greater than 300'000 are then placed between the two mould halves. The two work pieces are then individually shaped towards the cavity of one mould half each by means of vacuum. The two mould halves are then pressed together while the thermoplastic material is still hot so that the material confounds and forms a hollow unit.
The parts obtained are allowed to cool so that the thermoplastic material becomes solid whereby the mould is opened and the part is removed. The process is repeated so that a required amount of pallet decks 2 is obtained. The pallet decks 2 are allowed to cool and post-shrink, which normally takes a day or two, before . they are assembled with the other parts to the final product.
The pallet skid 3 is given its shape in a mould comprising a first and a second mould half. Each half includes a shape-giving cavity. The two shape-giving - cavities together form a negative depiction of the outer shape of the pallet skid 3.
The mould cavities are placed so that an intermediate space is formed between the mould halves and that the two cavities are facing each other. A pre-heated tube-shaped work piece of high-density polyethylene with an average molecular weight greater than 300'000 are then placed between the two mould halves, whereby the mould is closed. Air is biown into the tube-shaped work piece and the air in the space between the work piece and the mould is simultaneously ejected, whereby the work piece is forced towards the shape-giving surface of the mould.
A hollow part in the form of a pallet skid is hereby obtained. The part obtained is allowed to cool so that the thermoplastic material becomes solid whereby the mould is opened and the part is removed. The process is repeated so that a required amount of pallet skids 3 is obtained. The pallet skids 3 are allowed to cool and post-shrink, which normally takes a day or two, before they are assembled with the other parts to the final product.
The corner feet 4 and the centre feet S are manufactured by injection moulding in a mould including a number of mould cavities. The mould cavities form negative depictions of the corner feet 4 and the centre feet. An amount of molten thermoplastic material is injected into the mould cavities so that they are substantially filled. The thermoplastic material is then allowed to cool so that the thermoplastic material solidifies whereupon the mould is opened and the corner feet 4 and the centre feet S are removed from the mould. The procedure is repeated so that a desired amount of corner feet 4 and centre feet S are obtained.
The feet parts 4 and S are allowed to cool and post-skrink, which normally takes a day or two, before they are assembled with other parts to the final products.
The pallet deck 2, the pallet skids 3, the corner feet 4 and the centre feet S
are provided with a number of joining surfaces 6 which are heated by being brought into contact with a heated plate. One pallet deck 2, four corner feet 4, five centre feet S and three pallet skids 3 are then pressed together while the thermoplastic material in the joining surfaces is still hot whereby the different parts confounds so that a,unit in the form of a pallet 1 is obtained.
The product parts are, in addition to being joined along the edges, also joined by a number of local ridge- or tower-like protrusions 7 in larger parallel surfaces in order to increase the mechanical and dimensional stability.
Figure 4 shows, in perspective, product parts of a pallet 1 before the final assembly. The pallet 1 is manufactured according to one embodiment of the process mainly corresponding to that described in connection to figure 1. The pallet 1 obtained through the process is intended for use in extreme conditions.
The pallet is made from product parts in the shape of a upper hollow pallet deck 2a, a lower pallet deck 2b and three similar hollow pallet skids 3. The pallet decks 2a and 2b and the pallet skids 3 are individually manufactured in one mould each.
The moulds comprise a first and a second mould half which together include a shape-giving cavity which is a negative depiction of the pallet decks 2a and 2b, and the pallet skids 3 respectively. The mould halves are placed so that an intermediate space is formed between the two halves and so that the cavities are directed towards each other. Two sheet-shaped, pre-heated work pieces of high-density polyethylene with an average molecular weight greater than 300'000 are then placed between the two mould halves. The two work pieces are then individually shaped towards the cavity of one mould half each by means of vacuum. The two mould halves are then pressed together while the thermoplastic material is still hot so that the material confounds and forrrts a hollow unit. The process is repeated for the different moulds so that a required amount of pallet decks 2a and 2 b and pallet skids 3 are obtained. The pallet decks 2a and 2 b, and the pallet skids 3 are allowed to cool and post-shrink, which normally takes a day or two, before they are assembled to the final product. The pallet decks 2a and 2b and the pallet skids 3 are provided with a number of joining surfaces 6 intended for the joining of the pallet decks 2a and 2b and the pallet skids 3. The joining surfaces G are heated by being brought into contact with a hot metal plate.
The parts 2a, 2b and 3 are then pressed together while the material in the joining surfaces 6 is still hot, whereby the parts 2a, 2b and 3 confound so that they form a unit in the form of a pallet 1 .
Exam~l,e A pallet similar to the pallet shown in figure 1 and manufactured according to the process described in connection to figure 1 was placed on two beams so that the pallet was resting on 75 mm wide support surfaces on the two short sides. An ordinary pallet, manufactured through injection moulding was in the same way placed on two beams. The two pallets was manufactured, using the same amount of material, i.e. the two pallets have the same weight. The two pallets also have the same outer dimensions. A point load of 10'000 N was applied for 48 h on each of the two pallets. The temperature was 21°C during the test . The deflection, i.e.
the downwards warping of the pallet was measured at a point half-way between the beams. The test was then repeated with two new pallets as above at a temperature of 40°C. All pallets were manufactured of high-density polyethylene without any additional reinforcing profiles such as beams of metal, neither was any reinforcing fibre or filler material added to the thermoplastic material. The result is shown in the table below.
Table 1.
Test temp. Pallet according to the invention Ordinary pallet Deflection at the centre after 48 h Deflection at the centre after 48 h 21 °C 8 mm 73 mm 40°C 12 mm 130 mm It is evident from the examples that a pallet manufactured according to the present invention will get a deformation considerably lower than the deformation on a pallet manufactured through injection moulding, although the same amount of maferial is used. A similar improvement will be obtained in other types of products, such as pallet containers and containers, made of thermoplastic material.
The invention is not limited by the embodiments shown since these can be varied in different ways within the scope of the invention.
-figure 2 shows, in cross-section, a part of a pallet manufactured through the process according to the invention.
-figure 3 shows, in perspective, product parts of a pallet before the final assembly.
The pallet is manufactured by an alternative process according to the invention.
-figure 4 shows, in perspective, product parts of a pallet before the final assembly.
Figure I shows, in perspective, product parts of a pallet I before the final assembly. The pallet t is manufactured by one embodiment of the process according to the invention. The pallet is made from product parts in the shape of a hollow pallet deck 2 and three similar hollow pallet skids 3. The pallet deck 2 and the pallet skids 3 are individually manufactured in one mould each. The moulds comprise a first and a second mould half which together include a shape-giving cavity which is a negative depiction of the pallet deck 2 and the pallet skids respectively. The mould halves are placed so that an intermediate space is formed between the two halves and so that the cavities are directed towards each other.
Two sheet-shaped, pre-heated work pieces of high-density polyethylene with an average molecular weight greater than 300'000 are then placed between the two mould halves. The two work pieces are then individually shaped towards the cavity of one mould half each by means of vacuum. The two mould halves are then pressed together while the thermoplastic material is still hot so that the material confound and form a hollow unit. The process is repeated for the different moulds so that a required amount of pallet decks 2 and pallet skids 3 are obtained.
The pallet deck 2 and the pallet skids 3 are allowed to cool and post-shrink, which normally takes a day or two, before they are assembled to the final product.
The pallet deck 2 and the pallet skids 3 are provided with a number of joining surfaces 6 intended for the joining of the pallet deck 2 and the pallet skids 3. The joining surfaces 6 are heated by being brought into contact with a hot metal plate.
The parts 2 and 3 are the pressed together while the material in the joining surfaces 6 is still hot, whereby the parts 2 and 3 confounds so that they form a unit in the form of a pallet 1.
Figure 2 shows in cross-section a part of one embodiment of a pallet 1 obtained by the process according to the invention. A pallet skid 3 which is made from two sheet-shaped work pieces which constitute an upper half 3' and a lower half 3"
of a pallet skid 3. The two pallet skid halves 3' and 3" were confounded in connection to the manufacturing as described in connection to figure I.
The upper half and the lower half are, in addition to being joined along the . edges, also joined by a number of local ridge- or tower-like protrusions 7 (see also fig. I ) in larger parallel surfaces to increase the mechanical strength and the dimension stability. A pallet deck 2 is, in a similar way, made of an upper pallet deck half 2" and a lower pallet deck half 2' which halves are confounded in connection to the manufacturing. The two pallet deck halves 2' and 2" are, in addition to being joined along the edges, also joined by a number of local ridge- or tower-like protrusions 7 (see also fig 1 ) in larger parallel surfaces. The pallet skid 3 and the pallet deck 2 are hollow product parts that together form a pallet 1. The pallet skid 3 is joined with the pallet deck 2 by confounding as described in connection to figure 1.
Figure 3 shows, in perspective, parts of a pallet I before the final assembly.
The pallet 1 is manufactured by an alternative embodiment according to the invention.
The pallet 1 is constituted by a number of product parts in the form of a hollow pallet deck 2, three similar pallet skids 3, four corner feet 4 and five centre feet 5.
The pallet deck 2 is given its shape in a mould comprising a first and a second mould half. Each half includes a shape-giving cavity. The two shape-giving cavities together form a negative depiction of the outer shape of the pallet deck 2.
The mould cavities are placed so that an intermediate space is formed between the mould halves and that the two cavities are facing each other. Two pre-heated work pieces of high-density polyethylene with an average molecular weight greater than 300'000 are then placed between the two mould halves. The two work pieces are then individually shaped towards the cavity of one mould half each by means of vacuum. The two mould halves are then pressed together while the thermoplastic material is still hot so that the material confounds and forms a hollow unit.
The parts obtained are allowed to cool so that the thermoplastic material becomes solid whereby the mould is opened and the part is removed. The process is repeated so that a required amount of pallet decks 2 is obtained. The pallet decks 2 are allowed to cool and post-shrink, which normally takes a day or two, before . they are assembled with the other parts to the final product.
The pallet skid 3 is given its shape in a mould comprising a first and a second mould half. Each half includes a shape-giving cavity. The two shape-giving - cavities together form a negative depiction of the outer shape of the pallet skid 3.
The mould cavities are placed so that an intermediate space is formed between the mould halves and that the two cavities are facing each other. A pre-heated tube-shaped work piece of high-density polyethylene with an average molecular weight greater than 300'000 are then placed between the two mould halves, whereby the mould is closed. Air is biown into the tube-shaped work piece and the air in the space between the work piece and the mould is simultaneously ejected, whereby the work piece is forced towards the shape-giving surface of the mould.
A hollow part in the form of a pallet skid is hereby obtained. The part obtained is allowed to cool so that the thermoplastic material becomes solid whereby the mould is opened and the part is removed. The process is repeated so that a required amount of pallet skids 3 is obtained. The pallet skids 3 are allowed to cool and post-shrink, which normally takes a day or two, before they are assembled with the other parts to the final product.
The corner feet 4 and the centre feet S are manufactured by injection moulding in a mould including a number of mould cavities. The mould cavities form negative depictions of the corner feet 4 and the centre feet. An amount of molten thermoplastic material is injected into the mould cavities so that they are substantially filled. The thermoplastic material is then allowed to cool so that the thermoplastic material solidifies whereupon the mould is opened and the corner feet 4 and the centre feet S are removed from the mould. The procedure is repeated so that a desired amount of corner feet 4 and centre feet S are obtained.
The feet parts 4 and S are allowed to cool and post-skrink, which normally takes a day or two, before they are assembled with other parts to the final products.
The pallet deck 2, the pallet skids 3, the corner feet 4 and the centre feet S
are provided with a number of joining surfaces 6 which are heated by being brought into contact with a heated plate. One pallet deck 2, four corner feet 4, five centre feet S and three pallet skids 3 are then pressed together while the thermoplastic material in the joining surfaces is still hot whereby the different parts confounds so that a,unit in the form of a pallet 1 is obtained.
The product parts are, in addition to being joined along the edges, also joined by a number of local ridge- or tower-like protrusions 7 in larger parallel surfaces in order to increase the mechanical and dimensional stability.
Figure 4 shows, in perspective, product parts of a pallet 1 before the final assembly. The pallet 1 is manufactured according to one embodiment of the process mainly corresponding to that described in connection to figure 1. The pallet 1 obtained through the process is intended for use in extreme conditions.
The pallet is made from product parts in the shape of a upper hollow pallet deck 2a, a lower pallet deck 2b and three similar hollow pallet skids 3. The pallet decks 2a and 2b and the pallet skids 3 are individually manufactured in one mould each.
The moulds comprise a first and a second mould half which together include a shape-giving cavity which is a negative depiction of the pallet decks 2a and 2b, and the pallet skids 3 respectively. The mould halves are placed so that an intermediate space is formed between the two halves and so that the cavities are directed towards each other. Two sheet-shaped, pre-heated work pieces of high-density polyethylene with an average molecular weight greater than 300'000 are then placed between the two mould halves. The two work pieces are then individually shaped towards the cavity of one mould half each by means of vacuum. The two mould halves are then pressed together while the thermoplastic material is still hot so that the material confounds and forrrts a hollow unit. The process is repeated for the different moulds so that a required amount of pallet decks 2a and 2 b and pallet skids 3 are obtained. The pallet decks 2a and 2 b, and the pallet skids 3 are allowed to cool and post-shrink, which normally takes a day or two, before they are assembled to the final product. The pallet decks 2a and 2b and the pallet skids 3 are provided with a number of joining surfaces 6 intended for the joining of the pallet decks 2a and 2b and the pallet skids 3. The joining surfaces G are heated by being brought into contact with a hot metal plate.
The parts 2a, 2b and 3 are then pressed together while the material in the joining surfaces 6 is still hot, whereby the parts 2a, 2b and 3 confound so that they form a unit in the form of a pallet 1 .
Exam~l,e A pallet similar to the pallet shown in figure 1 and manufactured according to the process described in connection to figure 1 was placed on two beams so that the pallet was resting on 75 mm wide support surfaces on the two short sides. An ordinary pallet, manufactured through injection moulding was in the same way placed on two beams. The two pallets was manufactured, using the same amount of material, i.e. the two pallets have the same weight. The two pallets also have the same outer dimensions. A point load of 10'000 N was applied for 48 h on each of the two pallets. The temperature was 21°C during the test . The deflection, i.e.
the downwards warping of the pallet was measured at a point half-way between the beams. The test was then repeated with two new pallets as above at a temperature of 40°C. All pallets were manufactured of high-density polyethylene without any additional reinforcing profiles such as beams of metal, neither was any reinforcing fibre or filler material added to the thermoplastic material. The result is shown in the table below.
Table 1.
Test temp. Pallet according to the invention Ordinary pallet Deflection at the centre after 48 h Deflection at the centre after 48 h 21 °C 8 mm 73 mm 40°C 12 mm 130 mm It is evident from the examples that a pallet manufactured according to the present invention will get a deformation considerably lower than the deformation on a pallet manufactured through injection moulding, although the same amount of maferial is used. A similar improvement will be obtained in other types of products, such as pallet containers and containers, made of thermoplastic material.
The invention is not limited by the embodiments shown since these can be varied in different ways within the scope of the invention.
Claims (20)
1.~ A molding process for the manufacture of a product comprising at least a first product part and a second product part from a thermoplastic material selected from the group consisting of polyethylene, polypropylene and polybutylene which product is free of reinforcing additives, in a mold having a first mold half and a second mold half, which together includes a shape-giving cavity being a negative depiction of the respective product part, the method comprising:
forming the first product part, comprising:
providing two mold halves, at least one of the mold halves having a projection in the shape-giving cavity thereby forming at least one protrusion in a work piece formed in said mold half;
placing the mold halves so that a space is formed between the two mold halves and so that the shape-giving cavity of each mold half is directed toward each other;
heating two work pieces which constitute an upper half and a lower half of the product part, thereby softening the thermoplastic material;
shaping the work pieces toward the cavity of each mold half with the assistance of vacuum, blowing, and combinations thereof, to form shaped work pieces;
moving the mold halves relatively toward one another and pressing the shaped work pieces together while the thermoplastic material is still hot to form a unitary hollow product part with the upper and lower halves of said product part being joined along their edges and by said at least one protrusion to increase mechanical strength and dimension stability; and cooling the first product part produced to the point where it can be removed from the mold though still at an elevated temperature; and further cooling the first product part for 1-2 days until the first product part has reached room temperature and post shrinking has been achieved;
forming the second product part, comprising:
injecting molten thermoplastic material into one or more mold cavities of the mold;
allowing the thermoplastic material to solidify;
opening the mold;
cooling the second product part produced to the point where it can be removed from the mold though still at an elevated temperature; and removing the product part from the mold;
further cooling the second product part for 1-2 days until the second product part has reached room temperature and post shrinking has been achieved; and joining the first product part to the second product part and receiving a high creep strain resistant product.
forming the first product part, comprising:
providing two mold halves, at least one of the mold halves having a projection in the shape-giving cavity thereby forming at least one protrusion in a work piece formed in said mold half;
placing the mold halves so that a space is formed between the two mold halves and so that the shape-giving cavity of each mold half is directed toward each other;
heating two work pieces which constitute an upper half and a lower half of the product part, thereby softening the thermoplastic material;
shaping the work pieces toward the cavity of each mold half with the assistance of vacuum, blowing, and combinations thereof, to form shaped work pieces;
moving the mold halves relatively toward one another and pressing the shaped work pieces together while the thermoplastic material is still hot to form a unitary hollow product part with the upper and lower halves of said product part being joined along their edges and by said at least one protrusion to increase mechanical strength and dimension stability; and cooling the first product part produced to the point where it can be removed from the mold though still at an elevated temperature; and further cooling the first product part for 1-2 days until the first product part has reached room temperature and post shrinking has been achieved;
forming the second product part, comprising:
injecting molten thermoplastic material into one or more mold cavities of the mold;
allowing the thermoplastic material to solidify;
opening the mold;
cooling the second product part produced to the point where it can be removed from the mold though still at an elevated temperature; and removing the product part from the mold;
further cooling the second product part for 1-2 days until the second product part has reached room temperature and post shrinking has been achieved; and joining the first product part to the second product part and receiving a high creep strain resistant product.
2. ~The process according to claim 1, further comprising molding at least one additional product part through injection molding by means of a mold comprising one or more mold cavities wherein the mold includes means for injecting a pressurized gas comprising:
injecting molten thermoplastic material into a mold cavity of the mold; and injecting pressurized gas into the molten thermoplastic material in the mold cavity;
allowing the thermoplastic material to solidify;
evacuating the gas;
opening the mold;
removing the product part from the mold;
allowing the product part to cool completely and post-shrink; and joining the post-shrunk at least one additional product part to the product.
injecting molten thermoplastic material into a mold cavity of the mold; and injecting pressurized gas into the molten thermoplastic material in the mold cavity;
allowing the thermoplastic material to solidify;
evacuating the gas;
opening the mold;
removing the product part from the mold;
allowing the product part to cool completely and post-shrink; and joining the post-shrunk at least one additional product part to the product.
3. ~The process according to claim 1, wherein the thermoplastic material is constituted by a polymer with an average molecular mass in the range 200,000-2,000,000.
4. ~The process according to claim 3, wherein the average molecular mass of the thermoplastic material is greater than 300,000.
5. ~The process according to claim 1, wherein the thermoplastic material is constituted by a thermoplastic laminate with at least two layers, wherein the layers are constituted by a combination of at least two of the materials selected from the group consisting of virgin solid thermoplastic material, recycled solid thermoplastic material, virgin expanded thermoplastic material and recycled expanded thermoplastic material.
6. The process according to claim 1, wherein said at least one protrusion joining the upper and lower halves of said first product part has a shape selected from the group consisting of a tower and a ridge.
7. The process according to claim 1, wherein each work piece is in a form consisting of a sheet.
8. The process according to claim 1, wherein the two work pieces are provided in the form of a two separate sheets prior to said heating.
9. The process according to claim 1, further comprising molding work pieces into at least one product part selected from the group consisting of a pallet deck, a foot and a skid of a pallet; and a pallet deck, a foot, a side wall and a skid of a pallet container.
10. The process according to claim 1, further comprising molding one or both work pieces into at least one shape selected from the group consisting of a pallet deck, a foot and a skid of a pallet; and a pallet deck, a foot, a side wall and a skid of a pallet container.
11. The process according to claim 1, wherein the two work pieces are part of a single tube, having a circumferential surface, wherein said circumferential surface serves as both the first and the second work piece.
12. The process of claim 1, wherein the first product part is a first hollow pallet deck and the second product part is at least one hollow pallet skid.
13. The process of claim 12, further comprising molding a second hollow deck member and wherein the product comprises three second product parts, wherein each of the second product parts is a hollow pallet skid.
14. The process according to claim 1, wherein said joining of the first product part to the second product part is by welding.
15. The process according to claim 14, wherein said welding of the hollow pallet deck and the hollow pallet skids includes welding selected from the group consisting of butt welding, friction welding and filler welding.
16. The process according to claim 14, wherein said welding is selected from the group consisting of ultrasonic welding, low frequency welding and rotation welding.
17. A molding process for the manufacture of a product comprising a hollow pallet deck and a at least one hollow pallet skid from a thermoplastic material selected from the group consisting of polyethylene, polypropylene and polybutylene, which product is free of reinforcing additives, in a mold having a first mold half and a second mold half, which together includes a shape-giving cavity being a negative depiction of the respective product part, the method comprising:
forming one of either the pallet deck or the at least one skid, comprising:
providing two mold halves, at least one of the mold halves having a projection in the shape-giving cavity thereby forming at least one protrusion in a work piece formed in said mold half;
placing the mold halves so that a space is formed between the two mold halves and so that the shape-giving cavity of each mold half is directed toward each other;
heating two work pieces which constitute an upper half and a lower half of the product part, thereby softening the thermoplastic material;
shaping the work pieces toward the cavity of each mold half with the assistance of vacuum, blowing, and combinations thereof, to form shaped work pieces;
moving the mold halves relatively toward one another and pressing the shaped work pieces together while the thermoplastic material is still hot to form a unitary hollow product part with the upper and lower halves of said product part being joined along their edges and by said at least one protrusion to increase mechanical strength and dimension stability; and cooling the first product part produced to the point where it can be removed from the mold though still at an elevated temperature; and further cooling the first product part for 1-2 days until the first product part has reached room temperature and post shrinking has been achieved;
forming the other of the pallet deck or at least one skid, from a material having a high creep strain resistance, and free from reinforcing additives, in a mold, the mold having a first mold half and a second mold half, which together includes a shape-giving cavity being a negative depiction of the respective product part, the method comprising:
providing two mold halves, at least one of the mold halves having a projection in the shape-giving cavity thereby forming at least one protrusion in a work piece formed in said mold half;
placing the mold halves so that a space is formed between the two mold halves and so that the shape-giving cavity of each mold half is directed toward each other;
heating two work pieces which constitute an upper half and a lower half of the product part, thereby softening the thermoplastic material;
shaping the work pieces toward the cavity of each mold half with the assistance of vacuum, blowing, and combinations thereof, to form shaped work pieces;
moving the mold halves relatively toward one another and pressing the shaped work pieces together while the thermoplastic material is still hot to form a unitary hollow product part with the upper and lower halves of said product part being joined along their edges and by said at least one protrusion to increase mechanical strength and dimension stability; and cooling the second product part produced to the point where it can be removed from the mold though still at an elevated temperature; and further cooling the second product part for 1-2 days until the second product part has reached room temperature and post shrinking has been achieved; and joining the hollow pallet deck and hollow pallet skids together.
forming one of either the pallet deck or the at least one skid, comprising:
providing two mold halves, at least one of the mold halves having a projection in the shape-giving cavity thereby forming at least one protrusion in a work piece formed in said mold half;
placing the mold halves so that a space is formed between the two mold halves and so that the shape-giving cavity of each mold half is directed toward each other;
heating two work pieces which constitute an upper half and a lower half of the product part, thereby softening the thermoplastic material;
shaping the work pieces toward the cavity of each mold half with the assistance of vacuum, blowing, and combinations thereof, to form shaped work pieces;
moving the mold halves relatively toward one another and pressing the shaped work pieces together while the thermoplastic material is still hot to form a unitary hollow product part with the upper and lower halves of said product part being joined along their edges and by said at least one protrusion to increase mechanical strength and dimension stability; and cooling the first product part produced to the point where it can be removed from the mold though still at an elevated temperature; and further cooling the first product part for 1-2 days until the first product part has reached room temperature and post shrinking has been achieved;
forming the other of the pallet deck or at least one skid, from a material having a high creep strain resistance, and free from reinforcing additives, in a mold, the mold having a first mold half and a second mold half, which together includes a shape-giving cavity being a negative depiction of the respective product part, the method comprising:
providing two mold halves, at least one of the mold halves having a projection in the shape-giving cavity thereby forming at least one protrusion in a work piece formed in said mold half;
placing the mold halves so that a space is formed between the two mold halves and so that the shape-giving cavity of each mold half is directed toward each other;
heating two work pieces which constitute an upper half and a lower half of the product part, thereby softening the thermoplastic material;
shaping the work pieces toward the cavity of each mold half with the assistance of vacuum, blowing, and combinations thereof, to form shaped work pieces;
moving the mold halves relatively toward one another and pressing the shaped work pieces together while the thermoplastic material is still hot to form a unitary hollow product part with the upper and lower halves of said product part being joined along their edges and by said at least one protrusion to increase mechanical strength and dimension stability; and cooling the second product part produced to the point where it can be removed from the mold though still at an elevated temperature; and further cooling the second product part for 1-2 days until the second product part has reached room temperature and post shrinking has been achieved; and joining the hollow pallet deck and hollow pallet skids together.
18. The process of claim 17, comprising forming two hollow pallet decks and three hollow pallet skids.
19.~ The process according to claim 17, wherein said joining of the pallet deck and skid is by welding.
20.~ The process according to claim 19, wherein said welding is selected from the group consisting of ultrasonic welding, low frequency welding and rotation welding.
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE9700859A SE508874C2 (en) | 1997-03-10 | 1997-03-10 | Manufacture of thermoplastic product e.g. pallets, without reinforcing additives |
| SE9700918-7 | 1997-03-14 | ||
| SE9700859-3 | 1997-03-14 | ||
| SE9700918A SE508870C2 (en) | 1997-03-14 | 1997-03-14 | Manufacture of thermoplastic product e.g. pallets, without reinforcing additives |
| PCT/SE1998/000378 WO1998040199A1 (en) | 1997-03-10 | 1998-03-03 | A process for the manufacturing of thermoplastic products with high creep strain resistance |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2283468A1 CA2283468A1 (en) | 1998-09-17 |
| CA2283468C true CA2283468C (en) | 2007-04-10 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2283468 Expired - Fee Related CA2283468C (en) | 1997-03-10 | 1998-03-03 | A process for the manufacturing of thermoplastic products with high creep strain resistance |
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| Country | Link |
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| US (1) | US6458232B1 (en) |
| EP (1) | EP0966346B1 (en) |
| JP (1) | JP4201353B2 (en) |
| AT (1) | ATE242104T1 (en) |
| AU (1) | AU742775B2 (en) |
| BR (1) | BR9809043A (en) |
| CA (1) | CA2283468C (en) |
| DE (1) | DE69815304T2 (en) |
| NO (1) | NO317684B1 (en) |
| NZ (1) | NZ337631A (en) |
| WO (1) | WO1998040199A1 (en) |
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| US9278775B2 (en) | 2006-12-13 | 2016-03-08 | Rehrig Pacific Company | Crate with collapsible wall |
| US20080254170A1 (en) * | 2007-04-12 | 2008-10-16 | Neil Edward Darin | multi-compartment produce container with controlled gas permeation |
| MX2008011075A (en) | 2007-08-28 | 2009-03-03 | Rehrig Pacific Co | Crate with collapsible wall. |
| US8720692B2 (en) | 2007-11-21 | 2014-05-13 | Rehrig Pacific Company | Pallet |
| US7896184B2 (en) | 2007-11-26 | 2011-03-01 | Rehrig Pacific Company | Crate with collapsible wall |
| DK2546160T3 (en) | 2011-07-15 | 2017-07-31 | Chep Technology Pty Ltd | Pallet with support elements formed in one piece and method related thereto |
| US10926916B2 (en) | 2013-03-10 | 2021-02-23 | Rehrig Pacific Company | Crate with retractable wall |
| CN105197344A (en) | 2014-06-25 | 2015-12-30 | 艾尔戴克斯国际公司 | Load bearing structure |
| US10703531B2 (en) | 2016-03-11 | 2020-07-07 | Rehrig Pacific Company | Collapsible crate with wood appearance |
| US10913573B2 (en) | 2016-11-17 | 2021-02-09 | Rehrig Pacific Company | Collapsible container |
| US11597557B2 (en) | 2018-10-04 | 2023-03-07 | Rehrig Pacific Company | Reconfigurable beverage crate |
| US11884483B1 (en) | 2020-08-27 | 2024-01-30 | Rehrig Pacific Company | Collapsible container with slidable retractable wall |
| US11597560B2 (en) | 2020-09-14 | 2023-03-07 | Rehrig Pacific Company | Crate with retractable wall |
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| CN114103035B (en) * | 2021-11-22 | 2024-02-06 | 原秀科技（重庆）有限公司 | Method for producing scissor legs |
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| US3680496A (en) * | 1970-06-08 | 1972-08-01 | Edward B Westlake Jr | Plastic pallet |
| DE2039036A1 (en) * | 1970-08-06 | 1972-02-10 | Ver Deutsche Metallwerke Ag | Tubular support part for plastic pallets made by blow molding |
| US3923948A (en) * | 1971-09-21 | 1975-12-02 | Mobil Oil Corp | Thermoforming plastic articles |
| FR2193689B1 (en) * | 1972-07-26 | 1974-12-27 | Rhone Progil | |
| US4935191A (en) * | 1986-10-16 | 1990-06-19 | Thomas W. Johnson | Process of insection molding with pressurized gas assist |
| EP0284165B1 (en) | 1987-03-27 | 1991-01-02 | Asahi Kasei Kogyo Kabushiki Kaisha | A shaped article of a tetrafluoroethylene polymer |
| US5555820A (en) * | 1988-03-01 | 1996-09-17 | Shuert; Lyle H. | Pallet with plastic legs |
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| US5391251A (en) * | 1990-05-15 | 1995-02-21 | Shuert; Lyle H. | Method of forming a pallet |
| US5197396A (en) * | 1991-08-05 | 1993-03-30 | Penda Corporation | Double deck plastic pallet |
| AU3749693A (en) * | 1992-03-17 | 1993-10-21 | Mauser-Werke Gmbh | Device (blow mould) for producing smooth, closed, double-walled plastic plates and plastic plates produced thereby |
| US5417167A (en) * | 1993-03-03 | 1995-05-23 | Salflex Polymers Ltd. | Plastic pallet |
| US5405567A (en) * | 1993-12-10 | 1995-04-11 | Plastic Pallets, Inc. | Molding of articles from plastics |
| US5795535A (en) * | 1996-03-15 | 1998-08-18 | Sencorp Systems, Inc. | Method of thermoforming plastic articles |
| EP1007585A1 (en) * | 1997-08-27 | 2000-06-14 | The Dow Chemical Company | Rheology modification of interpolymers of alpha-olefins and vinyl aromatic monomers |
-
1998
- 1998-03-03 NZ NZ33763198A patent/NZ337631A/en unknown
- 1998-03-03 AT AT98909902T patent/ATE242104T1/en not_active IP Right Cessation
- 1998-03-03 WO PCT/SE1998/000378 patent/WO1998040199A1/en active IP Right Grant
- 1998-03-03 DE DE1998615304 patent/DE69815304T2/en not_active Expired - Lifetime
- 1998-03-03 EP EP98909902A patent/EP0966346B1/en not_active Expired - Lifetime
- 1998-03-03 AU AU64271/98A patent/AU742775B2/en not_active Ceased
- 1998-03-03 BR BR9809043A patent/BR9809043A/en not_active IP Right Cessation
- 1998-03-03 CA CA 2283468 patent/CA2283468C/en not_active Expired - Fee Related
- 1998-03-03 US US09/380,314 patent/US6458232B1/en not_active Expired - Fee Related
- 1998-03-03 JP JP53950198A patent/JP4201353B2/en not_active Expired - Fee Related
-
1999
- 1999-09-07 NO NO19994342A patent/NO317684B1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| BR9809043A (en) | 2000-08-01 |
| DE69815304D1 (en) | 2003-07-10 |
| NO317684B1 (en) | 2004-12-06 |
| WO1998040199A1 (en) | 1998-09-17 |
| EP0966346A1 (en) | 1999-12-29 |
| NO994342L (en) | 1999-11-04 |
| AU6427198A (en) | 1998-09-29 |
| CA2283468A1 (en) | 1998-09-17 |
| EP0966346B1 (en) | 2003-06-04 |
| NO994342D0 (en) | 1999-09-07 |
| JP2001514589A (en) | 2001-09-11 |
| US6458232B1 (en) | 2002-10-01 |
| NZ337631A (en) | 2001-03-30 |
| DE69815304T2 (en) | 2004-04-29 |
| JP4201353B2 (en) | 2008-12-24 |
| AU742775B2 (en) | 2002-01-10 |
| ATE242104T1 (en) | 2003-06-15 |
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| EEER | Examination request | ||
| MKLA | Lapsed |
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