US3073510A - Compressor unloading mechanism - Google Patents

Description

Jan. 15, 1963 R. J. HACKBART ETAL 3,073,510 I COMPRESSOR UNLOADIING MECHANISM Filed Dec. 29, 1960 2 Sheets-Sheet 1 I8 I Q g E Q mm 55335? ROA CH ATTORNEYS Jan. 15, 1963 R. J. HACKBART EI'AL COMPRESSOR UNLOADING MECHANISM 2 Sheets-Sheet 2 Filed Dec. 29, 1960 INVENTOR. REUBEN J. HA CKBART E C. R CA CH Ill! A T T OR N E Y S United States Patent 3,073,510 COMPRESSOR UNLOADING MECHANISM Reuben J. Hackbart and Jerome C. Roach, La Crosse, Wis., assignors to The Trane Company, a corporation of Wisconsin Filed Dec. 29, 1960, Ser. No. 79,318 6 Claims. (Cl. 230--30) This invention relates generally to reciprocating compressors and more specifically to refrigeration reciprocating compressors with unloading means to vary the output capacity of the compressor.

-An object of the invention is to provide a reciprocating compressor with a unique unloading mechanism which allows the output of the compressor to be varied while substantially maintaining constant speed.

A second object of the invention is to provide a reciprocating compressor which incorporates an unloading mechanism that is inexpensive to manufacture and easy to assemble and repair. A further object of the invention is to provide a reciprocating compressor with a two piece unloading mechanism which allows the capacity of the compressor to be varied without excessive .wear on the unloading mechanism.

A fourth object of the invention is to provide a reciprocating compressor which employs a two piece unloading mechanism actuated by oil pressure from the compressor oil pump in response to the suction pressure of the refrigeration system.

A still further object of the invention is to provide a reciprocating compressor which employs an oil pressure actuated two piece unloader mechanism in which the control oil is fed to the unloader mechanism through the wall between the crankcase and the section chamber.

Other objects and advantages of the invention will be clearly apparent as the specification proceeds to describe the invention with reference to the accompanying drawings in which:

, FIGURE 1 is a partial sectional view showing our new and novel unloading mechanism;

FIGURE 2 is a sectional view of a cylinder and unloading mechanism showing a modification of that shown in FIGURE 1;

FIGURE 3 is another sectional View of a cylinder and unloading mechanism showing a still further modification of the unloading mechanism shown in FIGURE 1; and

FIGURE 4 is a partial bottom view of the unloading piston of FIGURE 3.

Referring now to FIGURE 1, numeral 10 designates a multi-cylinder refrigeration compressor in which is shown our new and novel unloading mechanism. For the purpose of description only one cylinder is shown but it is obvious that our novel mechanism can be applied to as many cylinders of the compressor 10 as desired. Our new and novel unloader mechanism is an improvement over that shown in Labus, Patent No. 2,673,025, March 23, 1954 and is controlled in the manner shown in this patent.

In normal operation, suction gas is drawn into the common suction chamber 12 from the evaporator 14 through suction line 15 on the suction or downstroke of'piston 16. Piston i6 is driven through a connecting rod 18 by a crankshaft, not shown. As the piston de scends further the suction gas from the suction chamber 12 is drawn through suction passages 20 and spring biased suction valve 22 into the cylinder defined by cylinder liner 24.

On the compression or upstroke of the piston 16 compressed refrigerant is discharged past spring biased dis- 3,973,510 Patented Jan. 15, 1953 charge valve 26 into the common discharge chamber 28. This compressed refrigerant is then delivered to condenser 30 by conduit 32 wherein it is condensed and delivered to evaporator 14 through receiver 33 and expansion means 34. This cycle is well known in the art and not considered part of the invention.

Looking now specifically at the unloading mechanism, numeral 36 represents the unloading piston which reciprocates in annular wall member 38 which is integral with partition 40 separating the crankcase 42 from the suction chamber 12. 'Abutting shoulder 41 on cylinder liner 24 and engaging piston 36 is an annular ring member 44 which also abuts the head 46 of pins 48 slidably mounted in holes 50. The holes 50 are alternated with the suction passages around the periphery of the upper portion 52 of the cylinder liner 24. Springs 54 act against heads 46 of pins 48 to urge the pins downwardly away from suction valve 22.

An annular ring member 58 abuts shoulder 56 on wall member 38 to retain the annular O- ring seal members 60 and 62 within the seal retainer 64. A snap ring is snapped into recess 66 to retain the annular seal retainer 64, O- rings 60 and 62, and ring member 58 in assembled relationship. It is abvious that O- rings 60 and 62 prevent oil from leaking into the suction chamber and thereby being carried into the refrigeration system.

It should be noted that unloading piston member 36 basically consists of an annular leg portion 67 which has a surface 68 which slidably engages cylinder 24, a seat or base portion 70 perpendicular to annular surface 68 to form a retaining surface for spring '72, and another annular leg portion 73 which has a surface '74 slidably engaging wall 38 and being substantially parallel to annular surface 68 and perpendicular to seat portion 70. It should be noted that a gap could be left between the cylinder liner 24 and the annular piston member 36 to provide a heat barrier, if desired.

Spring member 72 is a single annular spring located between wall 40 and the unloading piston 36 to bias the unloading piston 36 upwardly.

Operation In operation, as described in aforementioned Labus Patent No. 2,673,025, the compressor will start unloaded as shown or will unload during operation of the compressor responsive to suction pressure. If desired, the unloader control mechanism, not shown, may be controlled by other means such as discharge pressure, if desired.

Assuming the cylinder is unloaded as shown, the operation will be herein described. As shown, suction valve 22 is held open by pin members 43 due to the action of spring 72 on the unloading piston 36. Unloading piston 36 in turn acts on pin head 46 through ring mem ber 44 to overcome the bias of springs 54 to force the suction valve 22 to the open position as shown.

Assuming now that the capacity of the cylinder is re quired to handle the load, oil will be fed through oil line 76, oil connection 77, oil passage 78 to cavity St? between the ring member 58 and the piston member 36. This oil 4 leakage of oil from the cavity 30 when oil is being provided to the cavity.

If the controlling means, not shown, senses a change in condition such that the operation of the cylinder is unnecessary the oil pressure will be cut off and oil in cavity 80 will bleed back out of the oil passage 78 and oil line 76. At the same time oil will also leak past unloader piston 36 into spring cavity 82 and bleed through aperture 84 into the crankcase 42. Aperture 84 not only serves to readily bleed the cavity 80 when the oil pressure is cut off but also serves to allow any oil that leaks into spring cavity 82 when oil pressure is being supplied to cavity 80 to be returned to the crankcase 42. When the oil pressure has been relieved from cavity 80 spring 72 will act on piston 36 in the manner previously described.

FIGURES 2-4 are modifications of the unloader mechanism shown in FIGURE 1. In all the figures of this application like parts will be shown and described with the same reference number.

FIGURE 2 is basically the same as FIGURE 1 except the unloading piston has been modified. The unloading piston 92 of FIGURE 2 is L-shaped and has a leg portion 93 slidably engaging the cylinder liner 24 and a base portion 95 which abuts shoulder 86 of annular wall 38 instead of abutting the wall 40 as in FIGURE 1 to provide a limit for downward movement of the piston member and to prevent leakage of oil into the spring pocket 82 and bleed hole 84 when oil is being supplied to cavity 80. The operation of the modification of FIGURE 2 is the same as that of FIGURE 2. The modification of FIG- URE 2 provides an unloading piston which is more readily machined and assembled into position.

The modification of FIGURES 3 and 4 is also basically similar to that shown in FIGURE 1. In FIGURE 3 an annular unloading piston 94 consisting of annular leg portion 97, base portion 99, and leg portions 96 and 98 is employed and individual springs 88 are used in the spring pockets 90 instead of an annular spring member such as that used in the first two designs. The annular leg portion 96 of the unloading piston 94 is longer than the leg portion 98 of the unloading piston 94 in order to seal the spring pockets 90 and the bleed hole 84 from the cavity 80 when oil is being supplied to cavity 80. The operation of this unloading is also the same as the preferred embodiment shown in FIGURE 1.

The herein disclosed new and novel unloader mechanism provides many advantages not present in the prior art. Our two piece unloader obviously is more readily assembled and cheaper in cost since the number of elements present are considerably less than that presently in use. Further, our two-piece unloader provides a construction which greatly lessens the possibility of damage to the O-ring seals since our construction has only one O-ring exposed to a moving surface, which of course is the unloading piston. In contemporary compressors breakage of the seal members causes a great deal of unnecessary expenditure of time and money in order to replace such elements. Our design further incorporates a bleed hole to increase the response of the unloading mechanism to the changes in the controlling condition. Obviously our bleed hole design allows the compressor to unload faster than one which does not provide a secondary means to feed the oil back to the crankcase.

Although we have described in detail the preferred embodiment of our invention, we contemplate that many changes may be made without departing from the scope or spirit of our invention, and we desire to be limited only by the claims.

We claim:

1. In a compressor having a compressing cylinder, said cylinder being defined by a cylinder liner, a suction chamber, a discharge chamber, a crankcase, a crankcase wall member separating said crankcase from said suction chamber, said wall member having an annular upstanding portion defining an annular chamber between said upstanding portion and said cylinder liner, said compressing cylinder having associated therewith a suction valve through which gaseous medium may be admitted from said suction chamber and a discharge valve through which compressed gaseous medium may be discharged into said discharge chamber, and fluid pressure responsive means to control the unloading of said cylinder, said fluid pressure responsive means comprising: an annular piston member slidably mounted in said annular chamber and surrounding said cylinder liner, valve engaging means supported on said annular piston member, spring means acting against said annular piston and tending to move said annular piston member and said valve engaging means toward said suction valve to force said suction valve to open position, sealing means operably associated with said annular piston member and forming a cavity therebetween, means forming a passage in said annular wall member, said passage communicating with a source of fluid to supply fluid to said cavity in response to the load imposed on said compressor in order to force said annular piston member downwardly against the bias of said spring means to allow said suction valve to close, and means forming a bleed hole in said crankcase well member and communicating with said annular chamber to decrease the response time of said fluid pressure responsive means.

2. In a compressor having a compressing cylinder, said cylinder being defined by a cylinder liner, a suction chamber, a discharge chamber, a crankcase, a crankcase wall member separating said crankcase from said suction chamber, said wall member having an annular upstanding portion defining an annular chamber between said upstanding portion and said cylinder liner, said compressing cylinder having associated therewith a suction valve through which gaseous medium may be admitted from said suction chamber and a discharge valve through which compressed gaseous medium may be discharged into said discharge chamber, and fluid pressure responsive means to control the unloading of said cylinder, said fluid pressure responsive means comprising: an annular piston member slidably mounted adjacent said cylinder liner and in said annular chamber, said annular piston member having an L-shaped section composed of a leg portion and a base portion, said leg portion slidably engaging said cylinder liner, said base portion slidably engaging said upstanding annular wall portion and dividing said annular chamber into a first annular chamber and a second annular chamber, valve engaging means separate from and supported on said annular piston, spring means acting against said annular piston and tending to move said annular piston and said valve engaging means toward said suction valve to force said suction valve to open position, sealing means supported in said first annular chamber and forming a cavity between said sealing means and said base portion of said annular piston, means forming a passage in said annular wall member, said passage communicating with a source of fluid to supply fluid to said cavity in response to the load imposed on said compressor in order to force said annular piston member downwardly against the bias of said spring means to allow said suction valve to close and means forming a bleed hole in said crankcase wall member and comma-- nicating with said second annular chamber to readily return fluid from said cavity to said crankcase.

3. The structure of claim 2 wherein an annular shoulder is provided in said annular upstanding portion to limit the downward movement of said annular piston member and to form a fluid seal.

4. In a compressor having a compressing cylinder, said cylinder being defined by a cylinder liner, a suction chamber, a discharge chamber, a crankcase, a crankcase wall member separating said crankcase from said suction chamber, said wall member having an annular upstanding portion defining an annular chamber between said upstanding portion and said cylinder liner, said compressing cylinder having associated therewith a suction valve 3 tion valve to force said suction valve to open position, I 1 50,230 Australia Dec. 13, 1254 7 8,073,510 s I e through which gaseous medium may be admitted from sealing means supported in said first annular chamber said suction chamber and a discharge valve through and forming a cavity between said sealing means and WhlCh compressed gaseous medium may be discharged said base portion of said annular piston, means forming a into said discharge chamber, and fluid pressure responpassage in said annular wall member and communicating sive means to control the unloading of said cylinder, said with a source of fluid to supply fluid to said cavity in refluid pressure responslve means comprising: an annular spouse to the load imposed on said compressor in order piston member slidably mounted adjacent said cylinder to force said annular piston member downwardly against liner and in said annular chamber, said annular piston the bias of said spring means to allow said suction valve member having an L-shaped section composed of a leg to close, and a bleed hole in said crankcase wall member portion and a base portion, said leg portion slidably en- 10 communicating with said second annular chamber to gaging said cylinder liner, said base portion slidably readily return fluid from said cavity.

engaging said upstanding annular wall portion and divid- 6. In a compressor having a compressing cylinder, said ing said annular chamber into a' first annular chamber cylinder being defined by a-cylinder liner, a suction chant:

. and a second annular chamber, said annular piston memher, a discharge chamber, a crankcase, a crankcase wall her having a second leg portion lying substantiallyparallel member separating said crankcase from said suction chame V to the leg portion of said L-shaped section and slidably her, said wall member having an annular upstanding porengaging said annular upstanding wall portion, said section defining an annular chamber'between said upstandond leg portion abutting said crankcase wall member ing portion and said cylinder liner, said compressing cylin-- when said annular piston member is in the down posider having associated therewith a suction valve through tion to provide a downward'limit for said annular piston which gaseous medium may be admitted from said sucmember, valve engaging means supported on said annular tion chamber and a discharge valve through which coma P pr g means g against said annular piston pressed gaseous medium may be discharged into said disand tending to move said annular piston and said valve charge chamber, and fluid pressure responsive means to engaging means toward said suction valve to force said control the unloading of said cylinder, said fluid pressure suction valve to open position, sealing means supported responsive-means comprising: an annular piston member in said first annular c amb r and forming a v y slidably mounted adjacent said cylinder liner and in said between said sealing means and said base portion of said annular chamber, said annular piston member having annular piston, and means forming a passage in aid an L-shaped section composed of a leg portion and a base ann lar wall m m er and comm nica ing wi h a ourc portion, said leg portion slidably engaging said cylinder of fluid t0 PP Y fluid to said cavity in t ponseto the liner, said base portion slidably engaging saidupstanding load imposed 011 said Compressor in Order force Said 7 annular wallportion and dividing said annular chamber annular Piston member nw y against the bias into a first annular chamber and a second annular chamof said spring means to allow said suction valve to close. her, said annular piston member having a second leg por- In a compressor having compressing cylinder, d t-ion lying substantially parallel to the leg portion of said cylinder being defined y a 1 cylinder a suction L-shaped section and slidably engaging said annular up- Qhamber, a discharge fi fl a se, crankcase I standing wall portion, said second leg portion abutting said wall-member separating said crankcase from said succrankcase wall member when said annular'piston member 11011 chambfil, said Wall member having an r P- is in the down position to provide a downward limit for standing Portion defining an annular chamber htZ said annular piston member, valve engaging means sup- Said upstamling Portion said cylinder n r, Said 40 ported on said annular piston, spring means acting against compressing cylinder having associated therewith a 8 said annular piston and tending tomove said annular piston tion valve through hich gaseous medium may be a and said valve engaging means toward said suction valve mitted from said suction chamber and a discharge valve I to force said suction valve to open position, sealing means through-which compressed gaseous medium ay be dis; supported in said first annular chamber and forming a charged IQ said discharge'chambeli n fluid p e '45 cavity between said sealing means and said base portion responsive means'toicontl'ol'rthe, unloading 01 a d cylim ofsaid annular piston, means forming a passage in said ,der, Said fluid P sponsive means compri ing: I V annular wall member and communicating with a source of an annular Piston membef$1id8b1Y mounted adjacent Said fluid to supply fluid to said cavity in response to the load cylinder liner and in Said annular chamber, Said an i imposed on said compressorin order to force said annular 1 I Piston member'haviflg an h p Section composed of a piston member downwardly against the bias of said spring leg portion and a base portion, said leg portion-slidably means to allow said suction valve to close and a bleed f engaging Said cylinder l Said base P 5 i 8 Y hole in said crankcase wallmember communicating s s s said upstanding annular wall p t anddivid-ins with said second annular chamber to readily return fluid 1 said annular chamber into a first annular chamber and from saidicavity. I r a second annular chamber, said annular piston member a havinga second leg portion lying substantially parallel H ReferencesCitedin the file of this patent t th leg pardon (if said tL-slhaped asiecltliglligndszligizlglcy UNITED/STATES PATENTS engaging sai annuar ups an mg w r n, v

v 2,555,005 .Warneke May- 9, 1951 ond leg portion abutting said crankcase wall mem I Labus'et a1; ,uruu Mar. 23, 1954 when saidannular p ston member is m-the down pos1- 9 2,956,729 c s y: l y octl 0 tion to provide a downward limit for said annular piston i .r member, valve engaging means separate from and sup- 2,971,690 Nlcholas F 1961 ported on said annular piston, spring means acting against said annular piston and tending to move said annular. -piston and said valve .engaging means toward said suc-

Claims (1)

1. IN A COMPRESSOR HAVING A COMPRESSING CYLINDER, SAID CYLINDER BEING DEFINED BY A CYLINDER LINER, A SUCTION CHAMBER, A DISCHARGE CHAMBER, A CRANKCASE, A CRANKCASE WALL MEMBER SEPARATING SAID CRANKCASE FROM SAID SUCTION CHAMBER, SAID WALL MEMBER HAVING AN ANNULAR UPSTANDING PORTION DEFINING AN ANNULAR CHAMBER BETWEEN SAID UPSTANDING PORTION AND SAID CYLINDER LINER, SAID COMPRESSING CYLINDER HAVING ASSOCIATED THEREWITH A SUCTION VALVE THROUGH WHICH GASEOUS MEDIUM MAY BE ADMITTED FROM SAID SUCTION CHAMBER AND A DISCHARGE VALVE THROUGH WHICH COMPRESSED GASEOUS MEDIUM MAY BE DISCHARGED INTO SAID DISCHARGE CHAMBER, AND FLUID PRESSURE RESPONSIVE MEANS TO CONTROL THE UNLOADING OF SAID CYLINDER, SAID FLUID PRESSURE RESPONSIVE MEANS COMPRISING: AN ANNULAR PISTON MEMBER SLIDABLY MOUNTED IN SAID ANNULAR CHAMBER AND SURROUNDING SAID CYLINDER LINER, VALVE ENGAGING MEANS SUPPORTED ON SAID ANNULAR PISTON MEMBER, SPRING MEANS ACTING AGAINST SAID ANNULAR PISTON AND TENDING TO MOVE SAID ANNULAR PISTON MEMBER AND SAID VALVE ENGAGING MEANS TOWARD SAID SUCTION VALVE TO FORCE SAID SUCTION VALVE TO OPEN POSITION, SEALING MEANS OPERABLY ASSOCIATED WITH SAID ANNULAR PISTON MEMBER AND FORMING A CAVITY THEREBETWEEN, MEANS FORMING A PASSAGE IN SAID ANNULAR WALL MEMBER, SAID PASSAGE COMMUNICATING WITH A SOURCE OF FLUID TO SUPPLY FLUID TO SAID CAVITY IN RESPONSE TO THE LOAD IMPOSED ON SAID COMPRESSOR IN ORDER TO FORCE SAID ANNULAR PISTON MEMBER DOWNWARDLY AGAINST THE BIAS OF SAID SPRING MEANS TO ALLOW SAID SUCTION VALVE TO CLOSE, AND MEANS FORMING A BLEED HOLE IN SAID CRANKCASE WELL MEMBER AND COMMUNICATING WITH SAID ANNULAR CHAMBER TO DECREASE THE RESPONSE TIME OF SAID FLUID PRESSURE RESPONSIVE MEANS.

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