US3191854A

US3191854A - Compressor units

Info

Publication number: US3191854A
Application number: US245337A
Authority: US
Inventors: Lowler Erik; Akerman Iwan Ernst Roland
Original assignee: Atlas Copco AB
Current assignee: Atlas Copco AB
Priority date: 1960-06-02
Filing date: 1962-10-29
Publication date: 1965-06-29
Anticipated expiration: 1982-06-29

Description

June 29, 1965 LOWLER EIAL COMPRESSOR UNITS Original Filed June 2. 1960 ORNEY United States Patent This application is a division of a plication Serial No. 33,454 filed June 1, 1960, now Patent No. 3,105,630, granted October 1, 1963.

This invention relates to improvements in compressor units in which oil or other suitable liquid is injected in the compression chambers of the compressor for cooling, lubricating and sealing purposes. One object of the invention is to provide an improved control system for such V compressor units. Other and more detailed objects will become apparent as the ensuing tion proceeds.

The invention is illustrated by way of example on the accompanying drawing, in which FIG. 1 illustrates diagrammatically a two stage compressor unit with oil inportion of this specificajection and FIG. 2 illustrates a portion of the valving ar rangements on a somewhat larger scale.

In the drawing 1 indicates the air intake pipe to the com.- pressor which consists of a low pressure portion 2 and a high pressure portion 3. In the illustrated embodiment the compressor portions 2 and 3 are screw type compressors but the invention is also applicable to other types of compressors, such as sliding vane rotary compressors, reciprocating piston compressors, orthe like. The illustrated compressor is provided with an air inlet casing 4 providing an inlet chamber 5 and communicating with the air intake pipe 1 through an air inlet control valve casing e, in which a pneumatically balanced twin valve or

throttle member

7, 8 is movable towards and away from

seats

9, 10 in which the

members

7 and 8, respectively, fit with a suitable clearance, permitting a very reduced flow of air to the inlet chamber 5 in closed position of the member-s 7, 8. The air compressed in the low pressure portion 2 of the compressor is conveyed through a chamber 11 to the high pressure portion 3 and from said high pressure portion a discharge conduit .12 conducts the compressed oil laden air over a spring loaded check valve 13 to a cyclone type oil separator 14 in which a first separation of the main portion of the oil in the compressed air takes place. The separated oil is collected in an oil tank 15 on which the separator 14 is provided. A conduit 16 conveys oil laden air from the separator 14 to a second oil separator 17 which is disposed Within an air receiver 13. The air receiver 18 is provided with an end cover 19 to which the conduit 16 is attached and which together with the oil separator 17 forms an admission chamber 20 in which some separation of oil is also produced. The oil laden air then passes through filter sections or discs 21 of the separator 17 which take care of most of the remaining oil in the compressed air. The oil separator 17 is a cylindrical body in which the filter discs 21 are provided and which is open over the whole cross section towards the admission chamber2il of the separator and provided with an end wall 21 at the outlet end communicating with an air receiver chamber 22 through an opening 23 close to the top of the separator. A further opening 24 is provided in the end wall 21 at the bottom of the separator 17 for draining oil accumulated in the lower portions of the separator to an oil accumulation space 25 at the bottom of the receiver chamber 22. The receiver 18 has a further chamber 26 encircling the separator 17 and they space 25 is partly separated from the receiver chamber 26 by a partition 27 which extends upwards to about half the height of the separator 17. 28 is an air discharge conduit which leads to the conventional air take-out of the compressor unit over. a check valve 75. 29 is an auto-.

matic spring loaded drain valve which opens at a certain low pressure, for instance 2 kilogrammes per square centi meter (kg/cm?) above atmospheric, in order to drain off any condensed water accumulated in the receiver chamber 26.

Two

conduits

30 and 31 convey liquid oil accumulated at 32 in the admission chamber 20 and at 25 in the receiver chamber 22 to separate

suction portions

33 and 34, respectively, of a gear pump 35 which pumps the oil back through a conduit 36 to the oil tank 15. The connections of the

conduits

30, 31 to the pump 35 in the described manner makes it possible to duly consider the difference in pressure between the

spaces

32 and 25. An oil pump 37 draws oil from the oil tank 15 through a conduit 33 and pumps oil through a conduit 39 to an oil cooler 40 provided with a suitable cooling fan 41 mounted on or driven from the main shaft 42 of the compressor. 43 is a spring loaded by-pass valve which is connected in parallel to the oil cooler 41 and 44 is a conduit from the oil cooler to an oil filter 45 from which a conduit 46 leads to injection nozzles 47, 48 in the compression chambers of the compressor. The by-pass valve 43 permits oil to flow directly from the conduit. 39 to the conduit 44 when the resistance in the oil cooler is too great, for instance due to low oil temperature. A check valve 49 with a spring loaded valve member '50 is provided in the conduit 46 which valve is loaded by a very weak spring and by the difference in pressure between the conduit 46 and the oil tank15 which for this purpose is connected to the bottom of the valve casing 49 through a conduit 51. 52 is an adjustablespring loaded by-pass check valve for the pump 37, the setting of which controls the pressure on the oil injected in the compression chambers of the compressor. Said valve also avoids excessive oil pressures when oil temperature is low or compressor speed high.

The present compressor is unloaded through throttling of the air intake passage to the air intake chamber 5 by means of the balanced twin

throttle valve members

7, 8. The unloading device for the compressor is combined with the

twin valve members

7, 8. It consists of a piston valve member 53 provided in a housing 54 and connected to the stem 55 of the

twin valve members

7, 8. A conduit 56 forms a communication between the chamber 26 of the air receiver 18' and the housing 54, said conduit being continued by a conduit 57 leading to the inlet chamber 58 in the air intake pipe 1. The passage in the conduit 57 is controlled by a needle valve member 59 and the communication between the conduit 56 and the conduit 57 is controlled by the Valve member 53 which has a transverse passage formed by a reduced portion or annular groove 60 on the member 53 which in the extreme left hand position on the

valve members

7, 8 provides a communication between the conduit 56 and the conduit 57 and the intake chamber 58. A conduit 61 connects the air receiver 18 to a control valve 62 which is connected to the end of the housing 54 by a conduit 63. The control valve has a vent passage 64 to which the conduit 63 is connected when the control valve is in operative.

When the compressor is at rest, a spring 65 moves the

twin valve members

7, 8 to the left in the figure so that the air intake to the compressor is throttled as far as possible, the only passage to the air intake chamber 5 being the clearance between the

members

7, 8 and the

seats

9, 10. Simultaneously the air receiver 18 is vented to the atmos phere through the conduit 56, the groove 60, the conduit 57 and the air intake chamber 58. The control Valve 62 is then in a position in which the conduit 63 is vented to the atmosphere through the vent passage 64 and the passage in the control valve to the conduit 61 is closed.

The stem 55 of the

twin valve members

7, 8 is also connected to a piston 66 which is movable in a valve casing 67 which also contains a piston valve 68 loaded by a spring 69 and connected by a rod 70 to a button 71. A conduit 72 connects the pressure oil conduit 39 with the casing 67. The opening 73 of said conduit in the casing 67 is controlled by the valve member 68.

When the compressor is at rest no oil pressure exists in the conduit 39 and consequently there is no oil pressure in the conduit 72 and in the space 74 in the housing 67. The spring 69 therefor moves the valve member 68 to close position.

When the compressor is started the

twin valve members

7, 8 throttle the air flow to the inlet chamber so that a certain vacuum is produced in said chamber. The compressor now runs idle and only a small quantity of compressed air is delivered to the receiver 18, which air flows back to the intake chamber 58 through the conduit 56, groove 66, conduit 57, and valve 59 which latter controls the pressure in the receiver 18 when the com pressor runs idle and unloaded. Oil is injected in the compression chambers when the compressor runs idle but the valve member 68 prevents pressure oil from reaching the spacer 74. By running the compressor idle as described it is possible to run the engine and compressor warm.

Now, if it be desired to load the compressor, the button 71 is pulled so that the valve 68 opens the passage from conduit 72 to the space 74 causing oil pressure from the compressor oil pump 37 to act on the piston 66 and to move it to the right in the figure so that the

twin valve members

7, 8 are moved to open position. The air flow through conduit 56 is simultaneously interrupted by the piston valve member 53, and the compressor continues to operate in this condition until a certain pressure, for instance 7 kilogrammes per square centimeter above atmospheric, has been reached. Then the control valve 62 opens a passage from the conduit 61 to the conduit 63 causing the piston valve 53 and the

twin valve members

7, 8 to move to the left in the figure so that the air intake is throttled. The communication between the conduit 56 and the intake chamber 58 is opened and a small quantity of air flows from the receiver 18 to the intake chamber 58. The compressor now runs unloaded with full pressure on the air receiver 13. The air quantity flowing to the receiver when the compressor runs idle or unloaded as above described is suflicient to carry the simultaneously injected cooling oil to the oil separators.

When the pressure in the air receiver has been reduced to a certain extent, for instance to 6 /2 kilogrammes per square centimeter above atmospheric the control valve 62 interrupts the communication between the conduits 61 and 63 and connects the conduit 63 to the vent passage 64 so that the conduit 63 is vented to the atmosphere which permits the oil pressure in the space 74 to move the

twin valve members

7, 8 to the right in the figure thereby reloading the compressor which immediately starts to deliver compressed air to the receiver 18. Simultaneously, the piston valve 53 closes the communication between the conduit 56 and the conduit 57 and the air pressure in the receiver continues to rise until it again reaches the maximum limit, for instance 7 kilogrammes per square centimeter above atmospheric.

It will be appreciated that with the above arrangement failure of the oil pump 37 to deliver pressure oil causes

valve members

7, 8 to move to closed position and the valve member 63 to close the opening 73, so that the compressor cannot produce compressed air for useful work until the defect in the oil injection system has been corrected.

It should also be observed that when the compressor has stopped compressed air in the air receiver 13 cannot flood the compressor with oil since in the absence of oil pressure in the conduit 46 air pressure in the oil tank 15 keeps the valve member 50 closed. The discharge conduit 28 of the compressor contains an automatic spring loaded check valve which when the compressor delivery is interrupted prevents back flow of compressed air from the network connected to the discharge conduit 23.

The invention may be modified in various different ways within the scope of the claims and the above embodiment is only described as an example.

What we claim is:

It. In a compressor unit, a compressor having a compression chamber, means for injecting cooling liquid in said compression chamber, means for conveying compressed fluid from said compressor to a consumer, means in said conveying means for separating cooling liquid from said compressed fluid, means for returning cooling liquid separated by said separating means to the cooling liquid injection means, and means in said return means for blocking cooling liquid fed to said injection means when said compressed fluid conveying means is under pressure and said compressor is at rest.

2. In a compressor unit, a compressor having a compression chamber, means for injecting cooling liquid in said compression chamber, a compressed fluid receiver, means for conveying compressed fluid from said compressor to said receiver, a cooling liquid separator in said receiver, a space in said receiver for collecting cooling liquid before said separator, 21 space in the receiver for collecting cooling liquid after the separator, separate eans for drawing cooling liquid from said first space and said second space, a cooling liquid tank, means for delivering said cooling liquid drawn from the first and second space to said tank, and means for drawing cooling liquid from said tank and for supplying said liquid to said cooling liquid injecting means.

3. In a compressor unit of the character described for supplying and maintaining compressed fluid in a receiver therefor and at a predetermined super-atmospheric pressure and including a compressor and conduit means for conveying said compressed fluid from said compressor to said receiver, the combination which comprises means for injecting a cooling liquid into said compressor, said cooling liquid being admixed in said compressor with compressed fluid delivered thereby into said conduit means, means for separating said cooling liquid from said compressed fluid, a cooling liquid reservoir, means for conducting said cooling liquid from said separating means into said reservoir, means responsive to the operation of said compressor for conducting cooling liquid from said reservoir to said means for injecting cooling liquid into said compressor, and means in said means responsive to said compressor operation and responsive to the pressure in said cooling liquid reservoir and said cooling liquid injection means for interrupting injection of cooling liquid into said compressor when said compressor is at rest and said receiver is under said predetermined super-atmospheric pressure of said compressed fluid therein.

4. In a compressor unit of the character described for supplying and maintaining compressed fluid in a receiver therefor and at a predetermined super-atmospheric pressure and including a compressor and conduit means for conveying said compressed fluid from said compressor to sa d receiver, the combination which comprises means for n ecting a cooling liquid into said compressor, said coolmg liquid being admixed in said compressor with compressed fluid delivered thereby into said conduit means, means in said conduit means for separating said cooling liquid from said compressed fluid, means for returning said cooling liquid separated by said separating means to said means for injecting said cooling liquid into said compressor, an automatic check valve in said compressed fluid conduit means from said compressor for preventing flow in said conduit toward said compressor, and valve ieans in said return means and responsive to the pressure in said separating means and said means for injecting cool- 5 ing liquid for interrupting and preventing cooling liquid injection into said compressor when the pressure in said means for injecting cooling liquid is decreased by a predetermined amount With respect to said predetermined super-atmospheric pressure of said compressed fluid in said separating means.

5. A compressor unit as recited in claim 4 in which said means for injecting cooling liquid includes a pressureresponsive piston valve, and which also includes means in flow communication with compressed fluid in said separating means for applying fluid pressure on said piston valve for urging it in one direction, spring means biasing said piston valve in the same said direction, said valve being in flow communication with said return means, pump means in said return means for applying thereto fluid pressure urging said piston valve in the opposite direction, all said means cooperating for urging said piston valve into a position interrupting said injection of fluid pressure into said compressor when the combined force of said compressed fluid pressure and said spring biasing means exceeds the pressure from said pump means in said return means tending to urge said valve in the opposite direction.

6. In a compressor-unit of the character described for supplying and maintaining a compressed fluid under predetermined super-atmospheric pressure and including a rotary screw compressor having an inlet and an outlet and conduit means for conducting compressed fluid from said outlet of said compressor to an operating discharge connection, the combination which comprises throttling means in said compressor inlet movable from an open position providing substantially unrestricted flow therethrough to a closed position providing substantially throttled and decreased flow through said compressor, pump means responsive to the operation of said compressor for injecting cooling liquid into said compressor for admixture therein with compressed fluid delivered thereby through said outlet thereof into said conduit means, an automatic check valve in said conduit means for preventing back flow therethrough toward said compressor outlet, and means responsive to the operation of said pump means for interrupting said injection of cooling liquid into said compressor upon stopping thereof.

7. In a compressor unit of the character described for supplying and maintaining compressed fluid in a receiver therefor and at a predetermined super-atmospheric pressure and including a compressor and conduit means for conveying said compressed fluid from said compressor to said receiver, the combination which comprises means for injecting a cooling liquid into said compressor, said cooling liquid being admixed in said compressor with compressed fluid delivered thereby into said conduit means, means for separating said cooling liquid from said compressed fluid, a cooling liquid reservoir, first pump means driven by said compressor for pumping and conducting cooling liquid from said separating means to said reservoir, second pump means driven by said compressor for pumping and conducting cooling liquid from said reservoir into said compressor through said means for injectingcooling liquid into said compressor, and means responsive to the operation of said second pump means for interrupting said injection of cooling liquid into said compressor upon stopping of the operation thereof.

8. A compressor unit as recited in claim 7 which also includes flow by-pass means around said second pump means having a relief valve operable at a predetermined maximum pressure for relieving excessive pressure of said cooling liquid fed by said second pump means to said injection means.

9. A compressor unit as recited in claim 7 which also includes cooling means for said cooling liquid in flow communication with said second pump means and through which said cooling liquid is forced by said second pump means, and a flow by-pass around said cooling means having a relief valve responsive to the temperature of said cooling liquid and operable to open said by-pass and to by-pass flow of said cooling liquid around said cooling means depending upon the temperature of said cooling liquid.

References Cited by the Examiner UNITED STATES PATENTS 2,633,804 4/53 Bruce 103228 X 2,983 ,435 5/ 61 Burnell 23 0-207 3,072,320 1/63 Cox 230207 X FOREIGN PATENTS 43 2,252 7/35 Great Britain.

LAURENCE V. EFNER, Primary Examiner.

Claims

1. IN A COMPRESSOR UNIT, A COMPRESSOR HAVING A COMPRESSION CHAMBER, MEANS FOR INJECTING COOLING LIQUID IN SAID COMPRESSION CHAMBER, MEANS FOR CONVEYING COMPRESSED FLUID FROM SAID COMPRESSOR TO A CONSUMER, MEANS IN SAID CONVEYING MEANS FOR SEPARATING COOLING LIQUID FROM SAID COMPRESSED FLUID, MEANS FOR RETURNING COOLING LIQUID SEPARATED BY SAID SEPARATING MEANS TO THE COOLING LIQUID