US2510050A

US2510050A - Compressor unloading apparatus

Info

Publication number: US2510050A
Application number: US672842A
Authority: US
Inventors: Alwin B Newton
Original assignee: Chrysler Corp
Current assignee: Old Carco LLC
Priority date: 1946-05-28
Filing date: 1946-05-28
Publication date: 1950-05-30
Anticipated expiration: 1967-05-30

Description

May 3@ 1950 A. NEWTON COMPRESSOR UNLOADING APPARATUS 5 Sheets-Sheet 1.

Filed May 28, 1946 INVENTOR. A L WIN 5. Na/vm/v y :w 119% A. 33. NEWTON COMPRESSOR UNLOADING APPARATUS Filed May 28, 1946 iNVENTOR. ALW/N B. NEWTON 2% 119% A. NEWTON v fi COMPRESSOR UNLOADING APPARATUS Filed May 28, 1946 s Sheets-Sheet 5 INVENTOR.

ALW/N B NEWTON BY COMPRESSOR UNLOADING APPARATUS May 28, 1946 5 Sheets-Sheet 4 Li], bu} I i E INVENTOR. ALW/N Bv NEWTON Tatentecl May 30,

COMPRESSOR UNLOADING APPARATUS Alwin B. Newton, Oakwood, Ohio, assignor to Highland Park, Mich., a

Chrysler Corporation corporation of Delaware Application May 28, 1946, Serial No. 672,842

21 Claims.

The present invention relates to the arts of refrigeration and air conditioning, the invention being applicable to a refrigerating system of the compressor-condenser-evaporator type whether the system be used to cool and dehumidify air for air conditioning purposes or to chill a medium surrounding the evaporator, such as air, brine, or a chemical such as diethylene glycol which would be used for any of the purposes for which refrigerated mediums are used.

The present invention is of particular application to a. refrigerating system including a compressor provided with unloading mechanism as disclosed and claimed in the patent to Charles R. Neeson, No. 2,185,473, issued January 2, 1940. The present invention comprises an improvement thereof whereby the unloader mechanism may be caused to function in an altered manner. In the patented compressor each of a plurality of cylinders of a multiple cylinder compressor is provided with an unloader mechanism of the type which holds the suction valve from its seat, the actuation of each unloading mechanism being controlled by a master valve reflecting the suction pressure or other condition measuring effect. When suction pressure is used the pressure varies in relation to the temperature and latent heat of the air traversing the cooling coil, or the temperature of the medium surrounding the coil. As disclosed and claimed in the patent to Gonzalez, No. 2,304,999 of December 14, 1942, the master valve may be placed under control of a condition responsive part located in the medium being cooled, which controls the master valve unless there is failure of this mechanism and the suction pressure takes over control of the master valve. As disclosed and claimed in my copending application, Serial No. 625,864, filed October 31, 1945 now abandoned, the master valve may be placed under joint control of a suction pressure responsive means and a condition responsive means. Although the present invention may be of utility in connection with a device of the basic character disclosed in the Neeson patent, or the modification claimed in the Gonzalez patent, I prefer its application to a compressor utilizing the improvement disclosed in my copending application identified above.

The object of the present invention is to provide a compressor having a plurality of cylinders, each of a number of which may be selectively rendered inoperative in order to vary the capacity of the compressor, the selection thereof being accomplished by individual cylinder unloading means operated by the application of fluid pressure thereto under control of a master valve, with means whereby the action of the master valve may be selectively altered. As disclosed in the Neeson patent the fluid pressure creating means preferably comprises a compressor driven pump and the individual cylinder unloading means include springs opposing the fluid pressure and acting to unload the cylinders in the absence of fluid pressure, whereby the compressor starts with all controlled cylinders unloaded and remaining unloaded until the pump builds up sufiicient pressure to overcome the unloader springs, thus avoiding initial start under full load. Since the pressures in a, refrigerating system tend to balance or equalize throughout during shutdown, the suction pressure will be high and, immediately upon creation of sufllcient fluid pressure, all of the controlled pistons will be loaded so as to cause the refrigerating system to cool down the medium being cooled as rapidly as possible. When sufficient cooling has been accomplished to lower the suction pressure of the system to a certain point the master valve will move to a succeeding position, thus cutting off fluid pressure from one of the controlled cylinders and causing it to be unloaded. If the remaining operative cylinders are able to do so the suction pressure will be further reduced and the master valve will cause successive reduction of the number of operative cylinders until, either the working cylinders are insuiflcient and the suction pressure rises thereby causing reoperation of a previously unloaded cylinder, or the usual temperature or suction pressure controls cause cessation of operation of the compressor motor. In the latter case the pressure in the system will tend to balance the master valve will return to its original position awaiting recommencement of action. In the system disclosed in Neeson, with a compressor working with dichlorodifluoromethane, the head pressure may be 120 pounds, the normal suction presssure in the neighborhood of 20 to 40 pounds and the balanced pressure in the neighborhood of 60 to pounds. The master valve is controlled to move step by step at, for example, 36 pounds, 34 pounds, 32 pounds, 30 pounds and the like. At each step one additional cylinder is loaded or unloaded as the case may be.

From study of the above patents and application it will be observed that even though the action of the master valve is placed under control of a condition responsive means instead of the suction pressure responsive means, or under control of the combined effect of both, the master valve moves through a set sequence of positions. In certain installations it may be desirable to alter the sequence of operation of the master valve. For example, in meat packing or cold storage houses, or in food locker plants, it may be found desirable to apply the cooling efiect Of a certain number of cylinders over a longer period of time than would be accomplished by permitting the compressor to operate fully loaded after shutdown. It also might be found desirable for economy of operation to have the compressor start with a minimum number of cylinders in operation and cause the unloa er to increase the number of cylinders in operation as the suction pressure drops or the condition responsive means indicates a drop in temperature or humidity, or the like. One way to effect economy, both in initial installation costs and in op erating costs, is to reduce the size of the cornpressor driving motor to such an extent that it will carry the full load only for short periods of time, or to make the motor only large enough to drive, less than the full number of loaded cylinders over long periods of time. Stated in another Way, economy may be eile cted by a system automatically pulling the temperature down from a maximum over a long period of time, and thereafter automatically varying the horsepower input in accordance with the load on the system. One object of my present invention is to make this possible.

a further object of the present invention is to equalize wear between all of the cylinders of the compressor by varying the cylinders in operation at any given instant even though the same total number of cylinders may be in operation at difiere-nt pressures.

A further object of my present invention is to provide means whereby the cylinder selecting means as disclosed by Neeson may operate in the normal manner or may be caused by manual selection to operate through a different cycle, whereby an installation may be left alone to perate under normal control or be caused to operate through a different cycle when an operator is present to guard against overloading or to observe efiects.

The foregoing and other objects and advan tages of my present invention will be apparent to those skilled in the art from a study of the following specification and the accompanying drawings, wherein like numerals refer to like parts throughout.

In the drawings Fig. 1 discloses an embodiment of my invention, sumcient of the compressor being illustrated to show the relationship thereof to the patent to Neeson. wherein a full disclosure of the type of compressor may be had, and disclosing in schematic fashion a control circuit for selectively causing op ration of my improvement; Fig. 2 is a view similar to Fig. 1 showing the initial position assumed by the master valve when the improvement is selectively rendered operative; Fig. is a partial view simi lar to the others showing the master valve in a different stage of operation; Fig. 4 is a View simi lar to Fig. 3 showing the initial stage of opera-- tion of a modified form of the improvement; Fig. is a similar View showing the initial stage of operation of the master valve when the improvement of Fig. 4 is selectively rendered moperative; Fig. 6 is a similar view showing a third position of the master valve of Fig. 4; Fig. '7 is a schematic representation of the means for setesting or rendering inoperative the improvement 4. of Figs. 4, 5 and 6; and Fig. 8 is an operation chart for the modification of Figs. 4 to 7.

Referring to Figs. 1 to 3 inclusive, there is disclosed a portion of the compressor crankcase 20 and end cover 2i, the interior of which is sub-- jected to the suction pressure of the refrigerating system. The cover 2| is provided with an opening 22 to which is bolted the flange 23 of a master valve housing 24. A master valve 25 is mounted within a sleeve H5 fixed within the housing 24 and slides longitudinally thereof. The master valve 25 is provided with a plurality of grooves 26, a first land 2?, first reduced portion 2.8, a second land 29, a second reduced portion til and a third land 3!. The inner end of the master valve 25 is connected, by a threaded member 35 having a ball head, to a cap member 36 provided with a swivel socket to receive and hold the ball head. The cap member 36 is soldered to the inner end of a collapsible-expanslble bellows 31 having its outs-r end soldered to a flange of the valve housing 24. The interior of the valve housing is subjected to suction pressure through an opening 38 so that the pressure acting upon the cap 36 will vary in accordance with the suction pressure. The cap 65 is attached to a central adjusting rod 4?.) extending to the outside of the compressor and movable with the master valve. A threaded extension dl of the valve housing is longitudinally slotted to receive ears 42 of an annular member 43 slidable within ne extension ill and surrounding a reduced,

threaded portion of the rod 40. An adjustment nut 45 is threaded on the extension All and engages the ears d2 in order to vary the compression of a spring 46 surrounding the rod lid and extending from the member {#2 to the. cap 35, and of a spring 39 extending from the cap 35 to a shoulder oi housing Nut ll threaded upon the reduced end of rod 40 and retained in adjusted position by a locknut 48.

The space surrounding the second reduced portion 36 of the master valve is supplied with. oil under pressure through a tube 59, and the reduced portion 28 is connected thereto by means of a drilled passage 5 I. Oil under pressure is supplied to both spaces at all times, and at all posi tions of the master valve whenever the pump is operating, which in the preferred, form is coextensive with operation of the compressor motor. A plurality of unloader pressure supply tubes 52 are connected to thevalve housing 2d and communicate with the interior of the. sleeve 26 through holes spaced longitudinally by distances equal to the spacing of the grooves 25. Whenever a land ,2? or 29 covers one of the holes leading to a tube 52 the pressure supply will be cut on from the individual cylinder unloadi g means connected thereto and sprn of. will cause the suction valve to be lifted from its seat, thereby unloading the clinder. Whenever one of the reduced portions is adjacent a hole leading to a tube 52, pressure will be supplied to the cylinder unloading means and the suction valve will resume functioning to thereby load cylin Step by step action of the master valve is, preserably assured by means of a springloaded ball device 53 engaging the successive grooves 25. Regulation of the pressure effective to cause the master valve to assume a certain position may be effected by adjusting the compression of springs 39 and 46 through the medium of nut 15. Nut l! may be adjusted to engage the end of extension 4! so as to prevent the loading or unloadingof certain of the cylinders by causing the land 29 or space 28 to remain opposite certain of the openings regardless of suction pressure, but in most uses nut 41 will not engage part 4|. As so far described the mechanism is essentially that of the Neeson patent, except for the second reduced portion of the master valve.

In the patent to Gonzalez the end of the master valve operating rod is disclosed as being enclosed in a casing which may be subjected to the pressure of a condition responsive, fluid containing bulb located in the medium being cooled. Such a device is indicated herein as comprising a bell shaped housin member 60 bolted to the flange 23, a reducing connection 6| threaded thereon, there preferably being a gasket 62 between the two, and a shell dome 63 Welded to the member ii! to form a sealed enclosure for the outer end of the master valve device. A tube Ei i provides means for subjecting the interior of the enclosure to a condition responsive pressure, which according to the Gonzalez patent may take ov r control of the master valve to provide more instantaneous reaction to the cooling effect than would be measured by the suction pressure. In such case movement of the master valve would be eifected through substantially the same positions at substantially the same pressures, the reaction being a little faster than as described in Neeson.

As disclosed in my copending application, Serial No. 625,864, the tube 65 may be connected to a part responsive to a condition of the me dium being cooled and acting to modify the control exerted by the suction pressure responsive means to obtain more desirable effects. In such case the master valve would move through only the same positions as in the Neeson or Gonzalez patents.

With the present invention a compressor operating in accordance with the teachings of Neeson, or Gonzalez, or of my prior application above identified, may be modified as follows:

Within the external housing I provide a bracket id extending horizontally above the extension M to which is pivoted a latch member (I having its free end resting against an abutment bracket '52 extending horizontally beneath the extension ll. The latch member is provided with an adjustable screw 73 adapted to engage the end of rod it] at a certain position of the master valve corresponding to a certain suction pressure. The latch member H is normally held in closed posi tion by a latch ill held in operative position by a leaf spring F5. The latch member TI is urged against the abutment 12 by a spring i6 adjustably compressed by means of a nut 17 on a rod i3 attached to bracket 12 and extending through an opening in the latch member. When the latch M is lowered as disclosed in Fig. 2 the master valve will be urged inward by the combined effect of spring 36 and of spring 76 acting through the moment arm supplied by latch member ii. The outer limit of the master valve is preferably defined by a collar 19 located within the bellows 3? and engaging cap 36 as disclosed in Fig. 2. Opening of the latch to permit the mechanism to assume the position of Fig. 2 may be accomplished through energization of a solenoid 85! in series with a compressor motor starter solenoid 8i and a pushbutton switch 82 leading to one side of the control transformer 83. The opposite side of the transformer leads to the solenoid 80 through the usual control devices such as thermostat 8 l, high pressure cutout 84, and suction pressure cutout 86. Closing of the switch 82 results in starting the compressor and opening the latch. Deenergization of solenoid 80 is simul--' taneous with deenergization of the compressor motor starter, which may occur when the temperature is satisfied, or when any of the other usual controls stop the compressor, or when the manual switch 82 is opened. Deenergization of the solenoid causes the latch 14 to resume normal position as indicated in Fig. 1 where it will either latch over the member ll if the suction pressure has been reduced to such an extent, or will be in position to latch over the member 'i'l when it is returned against the abutment 12, there being a bevel 88 provided to permit such action. Preferably the compressor may be operated without energizing solenoid Sill through the medium of a pushbutton switch 89 causing energization of a duplicate motor starter solenoid 90 in a parallel circuit including the

control devices

84, and 86. Thus the compressor may be operated without releasing the latch 14 or with release of the latch 74 as desired. Releasing of the latch may be accomplished when the compressor is running if switch 89 is closed and thereafter switch 82 is closed, or may be accomplished when starting the compressor by the use of switch 82 alone.

The operation of the device as so far disclosed results in the following sequence of action. Let us assume that solenoid 80 is not energized and the latch H is in the position disclosed in Fig. 1. In such case when the system is at rest the master valve is in the position disclosed in Fig. 3 It will be seen that the land 29 is covering four of the five unloader tube openings. Commencement of compressing action after sumcient oil pressure builds up is achieved through the medium of the first cylinder only, thus the cooling eiTec-t will be gradual and extended. After suflicient cooling has been accomplished, cylinders l and 2 will operate as soon as the ball device 53 stops the valve at the second groove 26. At the next reduction in pressure cylinders l, 2 and 3 will operate, and at the next, cylinders I, 2, 3 and 4 will operate at the position of the valve disclosed in Fig. 1.. When the compressor stops the suction pressure will build up and collapse the bellows 3! until rod 40 contacts screw 13 and the valve is back to the position of Fig. 3.

Now if there is an operator standing by to watch for motor overloading, for example when it might be desired to exhaust the system quickly into a charging cylinder, or it is desired to cool down a large installation more quickly, or in any situation where it is desired to start operation with a greater number of cylinders, the switch 82 will be closed to energize solenoid 80 and open latch 14. The suction pressure acting on bellows 31 causes the spring 16 to be compressed until cap 36 strikes abutment sleeve 19 as seen in Fig. 2. In this figure the land 29 has passed beyond certain of the unloader tube openings so that the second, third and fourth cylinders will commence operating as soon as sufficient oil pressure is supplied through tube 50. The suction pressure is now opposed by the combined actions of

springs

46 and 16 so that reduction of pressure at a much higher value will cause initial movement of the master valve. As illustrated, since a difi'erential in pressure suflicient to cause movement of the valve from one position to the next may be far greater than at the normal operating condition, the grooves 26 have been omitted from the end of the valve 25; but if desired they may be utilized as seen in the other modification (Fig. 4). Reduction in pressure will cause cylinders 3, 4 and 7 Sto operate, then cylinders 4 and 5, then cylinder fi alone. At the next stage land 29 covers the opening to. cylinder 5 and opens the opening to cylinder I through the reduced portion 30. Then the action continues so that l and 2 operate together, then i, 2 and 3 and finally l, 2, 3 and 4, at which position the valve strikes the plug 9| closing the end of the valve housing 2 -1 as seen in Fig. 1. It is to be appreciated that not all of the cylinders can operate at any one time, that the number of cylinders operating at the start varies according to desire, and that even though the same number of cylinders may be operating at different times the eifective cylinders are varied so asto more evenly distribute wear. The switch 82 comprises means for selectively causing the master valve to move through a succession of positions as effected by changes in suction pressure through a predetermined range, and when the solenoid is not energized the master valve will move through a portion of the foregoing range. In some cases the compressor may be started by closing both switches 32 and 89. Initial actionwill thereupon commence with both springs in efieot. Switch .82 may be left closed or may now be opened and the latch 74 will be in readiness to retain the member ll so that no further attention of the operator is necessary to cause the normal action to occur on succeeding reoperations of the compressor under control of the temperature or pressure controls.

In the modification disclosed in Figs. 4, 5, 6 and 7 all parts of the valve and valve operating mechanism are essentially the same. In this modification selection of the range of operation is accomplished through the mediumof a modified form of latching deviceand switch. In this form the spring l5 which raises the latch M is omitted and the solenoid I80 is placed above the latch so as to raise it when energized. Energization or the solenoid is accomplished by closing contacts it! and E82. The solenoid and contacts are in parallel with the motor starter solenoid 99 and in series with the

usual controls

84, 85 and 86. The contact m2 is mounted upon a pushrod li il extending through a packing gland ltd and terminating in a knob M5. The rod is preferably urged outwardly by a spring Hit so as to be normally clear of the mechanism. Since the latch it is normally lowered the latching member M will normally be in its outer position thus causing the spring Hi to be normally effective. The rod its may be pushed in to engage the latching member 52 and move it against the abutment 72, simultaneously causing engagement of contact I92 with contact ml, and the solenoid I80 will be energized to raise the latch M. The pushrod Hi3 may be released to deenergize solenoid liiil, but the latch ill will remain in position due to the suction pressure exerted on the bellows and acting through. rod ii screw it and member ii. As soon as the suction pressure has been reduced to a predetermined extent such that rod so no longer presses against screw 73 the latch will drop so that normal operation will occur upon the next reoperation of the compressor. In this modification, as distinguished from the first modification, normal operation commences with both of the springs l5 and lteffective and the bellows'fully collapsed as seen in Fig. 4. In this modification as seen more clearly in Fig. 5 the reduced portion 528 is preferably of such extent as to be capable of uncovering all of the cylinder unloader tubes, and the land i2! is also of different length.

Let us assume that there is no operator stand- I standing ing by to energize the solenoid I86, hence normal operation commences when the motor starts. Such an installation might be installed in a packing house where cooling of the packing house quickly is not a necessity, thus permitting a smaller motor to be used since only a few cylinders will be in operation when the suction pressure remains high over a long period of time. In this case (Fig. 4) cylinder No. I commences operating alone, then i and 2, then I, 2 and '3, then l, 2,3 and l, then I, 2, 3, 4, and 5 (Fig. 5). Now lever "H is in engagement with abutment M and spring "it is no longer-effective. Since the suction pressure has been greatly reduced all live cylinders may work fora greater time without overheatin the motor. Spring it may be so selected or adjusted that it cannot move the master valve for a substantially long time, so as to cause all live cylinders to work for a substantial period of time. Adjustmentof this period is possible through nut 135. At the next stop cylinder i will be cut'ofi so that 2, 3, 1 and operate, then 3, and 5, then :1 and 5, and finally No. 5 alone as seen in Fig. 5. Cylini der No. 5 is preferably kept in operation by so adjusting the iii that the valve stem can move no further, so as to provide means for holding the temperature or for reducing the temperature so that the thermostatic control operates, or for reducing the suction pressure so that the suction pressure control operates, to shut down the motor when cooling is no longer desired.

Now let us assume that there is an operator 0y to watch for overload in the case where quick cooling is desired, or the system is to be exhausted, or some other condition exists de manding operation initially under full load; In this case the pushrool will be pushed in to cause the master valve to assume the position of Fig. 5 and the latch closed to hold the master valve in this position when the compressor starts; The compressor will start with all five controlled cylinders in operation thus drawing down the temperature very quickly. As soon as a prede termined pressure is reached the master valve bellows wiil release its pressure against the member ll and p rmit the latch l to drop, readying the co ressor for normal operation at the next start. Further cooling will result in further steps of the master valve until the position of Fig. 6 is. reached. At any time the compressor may be stopped by the operator and the latch may be disengaged by pushing in on rod 583 when solenoid its": is not energized.

One of the common uses for this'unloader is in coldstorage or packing plants in which there is a great variation in the refrigeration load. Typical examples are stora ges which are operated intermittently, or those in which large quantities of warm produce are placed at infrequent intervals. compressor motor is sufiicient to drive thecompressor at the lower temperatures encountered during normal operations, but in conventional installations .a larger motor must usually be employed in order to operate the compressor at the higher termperatures encountered during pulldown periods or excessive load periods.

Fig. 8 is achart showing by a plot of the suc tion pressure at the compressor the manner in which my unloader makes this larger motor unnecessary. The chart is an assumed chart based. upon observed suction pressure andhorse power.

readings from installations using a compressor Insuch in stallations a small.

employing the basic Neeson unloader, hence the time values are not necessarily exactly accurate. The chart is made up for a compressor having cylinders, the compressor being supplied with an unloader master valve sequence selector made in accordance with the disclosures of Figs. 4, 5, 6, and '7, installed in a building such as described above having a plurality of compartments each cooled by an evaporator coil in parallel with the other coils commonly served by the compressor. It is assumed that when the storage spaces are at their normally cooled temperatures a H. P. motor is sufiicient to drive the compressor and that my unloader is to be arranged to prevent overloading of this 15 H. P. motor at above normal operating conditions.

Referring to Fig. 8 let us assume that the storage rooms have not been cooled for a prolonged period and that it is necessary to pull down from a high temperature to the normal operating temperature. The suction pressure may there fore be in the order of 60 pounds when the compressor is started, and Fig. 8 shows that the required unloader position must be such as to unload all but 3 cylinders of the compressor to prevent overloading the 15 H. P. motor more than an allowable value of approximately 15%. The unloader, by the action previously described positions valve 25 so that 3 cylinders operate and the suction pressure is gradually reduced along the line AB.

As the cold storage spaces are cooled, lower and lower suction temperatures are produced until at a pressure of approximately 12 pounds it is observed that 4 cylinders may operate without seriously overloading the motor. Therefore, the unloader is designed to position valve 25 to allow a fourth cylinder to operate and the suction pressure is then reduced more rapidly along the line BC.

Further reduction in pressure to a value of 4 pounds at C will permit the operation of all 5 cylinders without overloading the motor, and the unloader is therefore adjusted to bring all 5 cylinders into operation at pressures below 4 pounds suction pressure.

In any refrigeration system a so called balance pressure exists which is the suction pressure which will be encountered when all the evaporators are operating at a normal temperature and all cylinders of the compressor are in operation. In the system illustrated in Fig. 8 this pressure is 2 pounds. Any reduction of pressure below 2 pounds would indicate that some of the individual rooms have moved down to the required temperature, and on longer demand refrigeration. This further reduction in suction pressure will cause spring. 46 to expand and unload the compressor in accordance with this reduced refrigeration demand.

This action is illustrated in Fig, 8 along the line D-E, and is characterized by very small pressure changes between steps of capacity. After some operation under normal conditions it may be that a large quantity of warm produce is placed in one or more of the rooms. If this should cause a sufficient increase in load to raise the suction pressure above 4 /2 pounds, as illustrated at F the unloader will prevent overloading of the motor by going back to 4 cylinder operation until the suction pressure has again been reduced as 11- lustrated at FG.

It should be noted that during the pull down or overload periods both

springs

46 and 16 must be overcome by pressure changes and therefore, their combined spring rates determine the pressure change between the steps of unloading. Spring l6 will normally have a much higher spring rate than spring 46 and may if desired be wound closer in one portion of its length than another so that its spring rate increases as it is compressed. This is the type of spring that would produce a small pressure change for a step of unloading at BC, but a large change at a step of unloading at higher pressure as at A-B. However, a satisfactory commercial embodiment of my unloader can be made with equal steps of pressure change by allowing even more cylinders than required to be unloaded at higher pressures.

An important feature of this unloading method is the allowance of larger changes of pressure when the unloader is operating for preventing motor overload than when the unloader is operating because of low capacity requirements. Another important feature is the allowance of an adjustable range of full compressor capacity as that indicated by the space between lines 0 and D.

It is to be appreciated that reference to suction pressure covers pressures as modified by the disclosures of the Gonzalez patent or my above identified application. It is also to be appreciated that other results may be obtained by changing the length of the lands and reduced portions of the master valve or by changing the position of the limiting abutments. It is also to be appreciated that the number of cylinders controlled by the master valve may be altered; either all of the cylinders of compressors having more or less than five cylinders may be controlled, or any portion of the total number of cylinders of a compressor may be controlled. I prefer providing unloading mechanism for each cylinder since initial starting under no load before buildup of oil pressure is thus assured. The outer end of the valve operator may not be enclosed, in which case the bellows will work against atmospheric pressure as in Neeson. Other modifications in detail and arrangement will be readily apparent to those skilled in the art. All such as come within the terms of the following claims are considered to be a part of my invention.

I claim:

1. Unloading mechanism for a variable capacity compressor adapted to be connected to a cooling system and having a plurality of compressing cylinders, each of a number of which may be selectively rendered inoperative in order to vary the capacity of the compressor, comprising a plurality of individual cylinder unloading means each operatively associated with a single cylinder, fluid pressure creating means for operating said individual cylinder unloading means, means for selectively connecting said fluid pressure creating means to said individual cylinder unloading means comprising a master valve adapted to be selectively positioned at a plurality of positions, means subjected to the suction pressure of said compressor to successively position said master valve in a plurality of positions upon fluctuations of suction pressure whereby to operate said cylinder unloading means in certain sequences of combinations, and means to modify the action of said last means whereby to alter the sequential selection of operative cylinders upon variations of suction pressure.

2. Unloading mechanism for a variable capacity compressor adapted to be connected to a cooling system and having a plurality of compressing cylinders, each of a number of which may be selectively rendered inoperative in order to vary the capacity of the compressor, comprising a plurality of individual cylinder unloadingmeans each operatively associated with a single cylinder, fluid pressure creating means for operating said individual cylinder unloading means, means for selectively connecting said fluid pressure creating means to saidindividual cylinder unloading means comprising a master valve adapted to be selectively'positioned at a plurality of positions, master valve moving means subjected to the suction pressure of said compressor to successively position said master valve in a plurality of positions upon fluctuations of suction pressure whereby to cause selection of operative cylinders in various combinations as the suction pressure progressively'changes, and means to modify the action of said last means whereby to alter the combinations of cylinders successively selected.

3. Unloading mechanism for a variable capacity compressor adapted to be connected to'a cooling system and having a plurality of compressing cylinders, each of a number of which may be=se lectively-rendered inoperative in order to vary the capacity of the compressor, comprising. a plurality of individual cylinder unlo rig means each operatively associated with a single cylinder, fluid pressure creating means for operating said individual cylinder unloading means, means for selectively connecting said fluidpressure creating means to said individual cylinder unloading means comprising a master valve adapted to be selectively positioned at a plurality of positions, master valve movinglmeans subjected to the suction pressure of said compressor to successively position said master; valve in a plurality of positions upon fluctuations of. suction pressure wheree by to cause selection. of operative cylinders in various combinations as the suction pressure progressively changes, and means to modify the action of said last means whereby to alter the combinations of cylinders successively selected, said master valve moving means being operative normally to cause the compressor to start compressing witha certainnumber of cylinders in operation and to have a progressively decreasing number of cylinders in operation as the suction pressure drops, and said modifying means being operative to cause said compressor to start compressing with one or more cylinders in operation and to have a progressively increasing number of cylinders in operation as the suction pressure drops. V

4. Unloading mechanism for a variable capacity compressor adapted to be connected to a cooling system and having a plurality of compressing cylinders, each of a number of, which may be selectively rendered inoperative in order to vary the capacity of the compressor, comprising aplurality of individual cylinder unloading means each operatively associated with a single cylinder, fluid pressure creating means for operating said individual cylinder unloading means, means for selectively connecting said fluid pressure creating means to said individual cylinder unloading means comprising a master valve adapted to be selectively positioned at a plurality of positions, master valve moving means subjected to the suction pressure of said compressor to successively position said master valve in a plurality of positions upon fluctuations of suction pressure whereby to cause selection of operative cylinders in various combinations as the suction pressure progressively changes, and means to modify the action of said last means whereby to alter the combinations of cylinders successively selected, said master'valve moving means being operative normally to cause the compressor to start compressing with one or more'cylinders in operation and to have a progressively increasing number of cylinders in operation aszthesuction pressure drops, and said modifying means being operative to cause said compressor to start compressing with a certain number of cylinders in operationandto have a progressively decreasing number of, cylinders in operation as the suction pressure drops.

5. Unloading mechanism for a variable capacity compressor adapted to be connected to a cooling system and having a plurality of, compressing cylinders, each of a number of whichmay be Se:- lectively rendered inoperative in order, to-vary the capacity of the compressor, comprising aplurality of individual cylinder unloading means each operatively associated Witha single cylinder, fluid pressure creating means for operating. said individual cylinder unloading means, means for selectively connecting said fluid pressure creating means to said individual cylinder unloading means comprising a master.- valve adapted to be selectively positioned at a plurality of positions, master valve moving means subjected to the suction pressure of said compressor to; successively position said master valve in a: plurality of positions upon fluctuations of suction pressure whereby to cause selection of operative cylinders in various combinations as thesuction pressureprogressively changes, and means to modify the action of said last means whereby to alter the combinations of cylinders successively selected, said master valve moving means being operative normally to cause the compressor to start compressing with a certain number of cylinders in. operation, thereafter to have a progressively decreasing number of cylinders in operation as the suction pressure drops to a certainpoint, and thereafter to have a progressively increasing number of cylinders in operation as the suction pressure drops still farther, and said modifying means being operative to cause the compressor to start compressing with a certain number of cylinders in operation and to have a progressively increasing number of cylinders in operation as the suction pressure drops.

6. Unloading mechanism for a variable capacity compressor adapted to be. connected to a cooling system, and having a plurality of compressing cylinders, each of a number of which may be selectively rendered inoperative in order to vary the capacity of the compressor, comprising a plurality of individual cylinder unloading. means each operatively associated with a single cylinder, fluid pressure; creating. means for operating said individual cylinder unloading means,.means' for'selectively connecting'said fluid pressure creating means to said individual cylinder unloading means comprising a master valve adapted to be selectively positioned, at a plurality of positions, master valve moving means subjected to the suction pressure of said compressor to successively position said master valve in a plurality of positions upon fluctuations of suction pressure where by to cause selection of. operative cylinders in various combinations as the suction pressure progressively changes, and means to modify the action of said last means whereby to alter the combinations of cylinders successively selected, said master valve moving means being operative normally to cause the compressor to start compressing with acertain: number of cylinders'inoperation, thereafter to have a progressively increasing number of cylinders in operation as the suction pressure drops to a certain point, and thereafter to have a progressively decreasing number of cylinders in operation as the suction pressure drops still farther, and said modifying means be ing operative to cause the compressor to start compressing with a certain number of cylinders in operation and to have a progressively decreasing number of cylinders in operation as the suction pressure drops.

7. Unloading mechanism for a variable capacity compressor having a plurality of cylinders, said mechanism being operable in response to the application of fluid pressure to portions thereof to vary the number of cylinders compressing refrigerant and including a master valve having an inlet port and a plurality of outlet ports and a valve rod capable of being moved to a number of control positions to vary the number of said outlet ports connected in fluid flow relationship to said inlet port and means for selecting the control position of said valve rod, said means comprising an expansible-collapsible device subjected at one side to the suction pressure of the compressor, first spring means opposing the suction pressure when the suction pressure is within limits such that the force thereof against said expansible-collapsible device may be overcome by said first spring means, and second spring means operable to add its force to said first spring means to oppose the suction pressure when the suction pressure is within limits such that the force thereof against said eXpansible-collapsible device may be overcome by the combined forces of said spring means.

8. Unloading mechanism for a variable capacity compressor having a plurality of cylinders, said mechanism being operable in response to the application of fluid pressure to portions thereof to vary the number of cylinders compressing refrigerant and including a master valve having an inlet port and a plurality of outlet ports, said master valve having a portion capable of being moved to a number of control positions to vary the number of said outlet ports connected in fluid flow relationship to said inlet port, and means for selecting the control position of said master valve, said means comprising an expansible-collapSible device subjected at one side to the suction pressure of the compressor, first spring means opposing the suction pressure when the suction pressure is within limits such that the force thereof against said expansible-collapsible device may be overcome by said first spring means, and second spring means operable to add its force to said first spring means to oppose the suction pressure when the suction pressure is within limits such that the force thereof against said expansible-collapsible device may be overcome by the combined forces of said spring means, said first spring means having such effect as to cause movement of said master valve when the suction pressure is near a minimum and the combined forces of said spring means having such effect as to cause movement of said master valve when the suction pressure is greater than a predetermined pressure.

9. A compressor for a refrigerating system comprising a plurality of cylinders each of a number of which having an unloader mechanism associated therewith, an unloader control device having means including a master valve for selecting one or a variable plurality of cylinders to be rendered operative according to the position of said master valve, means for causing the suction pressure of the compressor to control movement of said master valve through a first series of positions as the suction pressure varies throughout a predetermined range, and manually controlled means for causing the suction pressure of the compressor to control movement of said master valve through a second series of positions including said first series as the suction pressure varies throughout a greater range including said predetermined range.

10. A compressor for a refrigerating system comprising a, plurality of cylinders each of a number of which having an unloader mechanism associated therewith, an unloader control device having means including a master valve for selecting one or a variable plurality of cylinders to be rendered operative according to the position of said master valve, means for causing the suction pressure of the compressor to control movement of said master valve through a first series of positions as the suction pressure varies throughout a predetermined range, and manually controlled means for causing the suction pressure of the compressor to control movement of said master valve through a portion only of said series of positions as the suction pressure varies throughout a portion only of said predetermined range.

11. A compressor for a refrigerating system including a compressor control circuit, said compressor comprising a plurality of cylinders each of a number of which having an unloader mechanism associated therewith, an unloader control device having means including a master valve for selecting one or a variable plurality of cylinders to be rendered operative according to the position of said master valve, and means for causing the suction pressure of the compressor to control movement of said master valve through a first series of positions as the suction pressure varies throughout a predetermined range; in combination with manually controlled means for causing the suction pressure of the compressor to control movement of said master valve through a second series of positions including said first series as the suction pressure varies throughout a greater range including said predetermined range, said manually controlled means comprising a secondary control circuit for said compressor in addition to the usual control circuit whereby said compressor may be controlled to operate with unloader selection throughout the greater or lesser ranges.

12. A compressor for a refrigerating system including a compressor control circuit, said compressor comprising a plurality of cylinders each of a number of which having an unloader mechanism associated therewith, an unloader control device having means including a master valve for selecting one or a variable plurality of cylinders to be rendered operative according to the position of said master valve, and means for causing the suction pressure of the compressor to control movement of said master valve through a first series of positions as the suction pressure varies throughout a predetermined range; in combination with manuall controlled means for causing the suction pressure of the compressor to control movement of said master valve through a second series of positions in.- cluding said first series as the suction pressure varies throughout a greater range including said predetermined range, said manually controlled means comprising a secondary control circuit in addition to the usual control circuit and including a solenoid, and latching means movable by said solenoid and: normally limitingmovement of said'master valve to times when the suction pressure'is within said predetermined range but being'renderecl inoperative when said secondary control circuit is caused to energize solenoid.

13. A compressor for a refrigerating sys, including a compressor controlcircuit, said'con' pressor comprisin a plurality of cylinders each of a number of which having an unloaded mechanism associated therewith, an unloader control device having means including a master valve for selecting one or a variable plurality of cylinders to be rendered operative according to the position of said master valve, and for causing the suction pressure of the col lpressor to control movement of said master valve through a first series of positions as tic suction pressure varies throughout a prede rnrined range in combination with manually controlled means for causing the suction pressure of the compressor to control movement of said. mast valve through a portion only of said series of positions as the suction pressure varies throughout a portion only of said predete mined range, said manually controlled means compris a secondary control circuit in addition to the control circuit and including a solenoid, and latching means movable by said solenoid and capable of limitin movement of said master valve to times when the suction pressure is Within said portion of said predetermined range, said latching means being normally inoperative and being rendered operative only when sa d secondary control circuit is caused to energize said solenoid.

1%. A compressor for a refrigerating system including a compressor control circuit, said compressor comprising a plurality of cylinders each of a number of which having a unloader mechanism associated therewith, an unloader control de-- vice having means including a master valve for selecting one or a, variable plurality of cylinders to be rendered operative according to the position of said master valve, and means for causing the suction pressure of the compressor to control movement 01- said master valve through a first series of positions as the suction pressure varies throughout a predetermined range; in combination with manually controlled means for causing the suction pressure of the compressor to control movement of said master valve through a portion only of said series of positions as the suction pressure varies throughout a portion only of said predetermined range, said manually controlled means comprising a secondary control circuit in addition to the usual control circuit and including a solenoid, latching means movable by said solenoid and capable of limiting movement of said master valve to times when. the suction pressure is within said portion of said predetermined range, said latching means being normally inoperative and being rendered operative only when said secondary control circuit is caused to energize said solenoid and an abutment normally limiting movement of said master valve to an extreme position upon maximum suction pressure and cooperating with said latching means to limit movement of said master valve to an intermediate position upon maximum suction pressure.

15. A compressor for a refrigerating system including a compressor control circuit, said compressor comprising a plurality of cylinders each of a number of which having an unloader mech- 16 anism: associated therewith, an unloader control device: having means including a master valve for selecting one or avariable plurality of cylinders-to be rendered operative according to the position of, said master valve, and, means for cans ingthe suction pressureof-the compressor to controlmovement of said master valve through a first series of positions as the suction pressure varies throughout a predetermined range; in combination with manually controlled means for causing the suction pressure of the compressor to control movement or said master valve through-a. portiononly 01- said series of positions as the suction pressure varies throughout a portion only" of said predetermined range, said manuallyv controlledmeanscomprising a secondcontrol'circuit in addition to the usual control circuit and including solenoid; latching means movable by'said solenoid and capable of limiting movement of said master valve to times when-the suction pressure is within said portion of said predetermined range, said latching means being normally inoperative and being rendered operative only when said secondary control circuit is causedto energize-said solenoid, an abutmentnormally limiting movement of said master valveto an extreme position-upon maximum suction pressure and cooperating with said latching means to limitmovement or" said master valve to an intermediate position upon maximum suction pressure, a, spring opposed plunger to move said abutmentand master valve to said in" tel-"mediateposition, and a switch closed upon movement of said plunger to complete said secondary control circuit.

16. A compressor for a refrigerating system including a compressor control circuit, said compressor comprising a plurality of cylinders each of a number of which having an unloadcr mechanism associated therewith, an unloader control device having means including 'a master valve for selecting one or a variable plurality of cylinders to be rendered operative according to the position of said master valve, and means for causing the suction pressure of the compressor to control movement of said master valve through a first series of positions as the suction pressure varies throughout a predetermined range; in combination with manually controlled means for causing the suction pressure of the compressor to control movement of said master valve through a portion only of said series of positions as the suction pressure varies throughout a portion only of said predetermined range, said manually controlled means comprising a secondary control circuit in addition to the usual control circuit and including a solenoid, latching means movable by said solenoid and capable of limiting movement of said master valve to times when the suction pressure is within said portion of said predetermined range, said latching means being normaliy inoperative'and being rendered operative only when said secondary control circuit is caused to energize said solenoid, an abutment normally limiting movement of said master valve to an extreme position upon maximum suction pressure and cooperating with said latching means to limit movement of said master valve to an intermediate position upon maximum suction pressure, a spring opposed plunger to move said abutment and master valve to said intermer iate position, and a switch closed upon movement of said plunger to complete said secondary control circuit, said latching means being capable of frictionally retaining said abutment when the suction pressure is exerted thereagainst even though said plunger may have been released and said solenoid thus deenergized, but releasing said abutment as soon as pressure is released from said abutment by reduction of the suction pressure through operation of the compressor under control of the normal control circuit.

17. An unloading mechanism for a motor driven variable capacity multi-cylinder compressor adapted to be operatively associated with a refrigerating system, said mechanism having a first means to selectively load and unload individual cylinders of said compressor in response to variations in the suction pressure of said system, said first means being operable to select a predetermined maximum number of said cylinders for loaded operation at a predetermined suction pressure and being operable to selectively decrease the number of cylinders loaded for operation at lesser suction pressures corresponding to reduced load requirements of said system and a supplemental means operable to modify the operation of said first means to load a reduced number of said cylinders when the suction pressure of said system exceeds a second predetermined suction pressure.

18. An unloading mechanism for a motor driven variable capacity multi-cylinder compressor adapted to be operatively associated with a refrigerating system, said mechanism having a first means to selectively load and unload individual cylinders of said compressor in response to variations in the suction pressure of said system, said first means being operable to select a predetermined maximum number of said cylinders for loaded operation at a predetermined suction pressure and being operable to selectively decrease the number of cylinders loaded for operation at lesser suction pressures corresponding to reduced load requirements of said system and a supplemental means operable to modify the operation of said first means to unload an increasing number of said cylinders as the suction pressure oi said system increases above the value of a, second predetermined suction pressure.

19. An unloading mechanism for a motor driven variable capacity multi-cylinder compressor adapted to be operatively associated with a refrigerating system, said mechanism having a first means to selectively load and unload individual cylinders of said compressor in response to variations in the suction pressure of said system, said first means being operable to select a predetermined maximum number of said cylinders for loaded operation at a predetermined suction pressure and being operable to selectively decrease the number of cylinders loaded for operation at lesser suction pressures corresponding to reduced load requirements of said system, a supplemental means operable to modify the operation of said first means to load a reduced number of said cylinders when the suction pressure of said system exceeds a second predetermined suction pressure.

20. An unloading mechanism for a motor driven variable capacity multi-cylinder compressor adapted to be operatively associated with a refrigerating system, said mechanism having a first means to selectively unload individual cylinders of said compressor in a defined sequence in response to reductions in the suction pressure of said system below a predetermined suction pressure and having a second means operable to selectively unload individual cylinders of said compressor in a different sequence in response to increases in said suction pressure above a second predetermined suction pressure.

21. An unloading mechanism for a motor driven variable capacity multi-cylinder compressor adapted to be operatively associated with a refiigerating system, said mechanism having a first r' tion pressures of greater value than a second predetermined suction pressure to selectively unload individual cylinders in response to variations of said suction pressure above said second. predetermined pressure, said last mentioned variations being individually of greater magnitude than corresponding variations in said first set.

ALWIN B. NEWTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,607,531 Haight Nov. 16, 1925 1,612,639 Metzgar Dec. 28, 1926 1,649,297 Nelson Nov. 15, 1927 2,185,473 Neeson Jan. 2, 1940 2,304,999 Gonzalez Dec. 14, 1942 Certificate of Correction Patent No. 2,510,050 May 30, 1950 ALWIN B. NEWTON It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 2, line 37, after balance insert and; column 4, line 61, for clinder read cylinder; column 5, line 73, for cutout 84 read cutout 85; column 9, line 56, for on read no; column 15, line 40, for havinga read having an;

and that the said Letters Patent should be read with these corrections therein. that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 29th day of August, A. D. 1950.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.