US2638265A - Compressor unloading apparatus - Google Patents

Description

May l2, 1953 A. B. NEWTON 2,638,265

COMPRESSOR UNLOADING APPARATUS Filed Jan. 3, 1948 3 Sheets-Sheet l IN VEN TOR. HZu/Qz ,3. New far?- owl ira/r/VEYS.

A. B. NEWTON COMPRESSOR UNLOADING APPARATUS May 12, 1953 Filed Jan s, 1948 May 12, 1953 A. B. NEWTON 2,638,265

COMPRESSOR UNLOADING APPARATUS Filed Jan. 3, 1948 3 Sheets-Sheet 3 iffaF/vI/S Patented May 12, 1953 COMPRESSOR LOADING APPARATUS Alwin `B. Newton,'-r.Dayton;:-ho, `to lChrysler Corporation; Highland Park, Mich., a

corporation vof Delaware Vapplicmionuanrifary s, 194s,-ser1aiNu;-444

This invention Vrelates toirefrigerant-compressors and more particularly-to improved-f apparatus for selectively loading1 and-unloading-cylinders thereof 'in response to-predeterminedopern. aan;

ating conditions.V y *Compressor unloading mechanisms and more particularly the unloading mechanism described in Patent No; *2,-185A7-3g1 which Yissuedata CNB/ Neesonv on January 2,--1f947, -are-dependent-upon mechanical Alinkages to operate a masterffcontrol cylinder.u VIt is`-anobject oft-this''inventicneto substitute a hydraulic means-tocontrolf'amaster cylinder. 'A more 4sensitive controle-lisg possible with the hydraulic unloadingl mechanism-Lthan Vwith the mechanism" described inlPaten-t y*No2- 2,185 ,47f3; Ithas Lbeen--observed thateaschange of--approximately 2- pounds of -suction pressure is required'tob cause the apparatus of the patent to move sufficiently to-1oadneof thefcompressor cylinders. YIt is` desirablel to-have a'l-change of approximately 3 pounds in suctionpressure-produce a lchange iromna'complete loading fitoa minimum loading'of the compresscilrsoriviceversa. Therefore,V V*ai mechanism --required whichiis sensitive venough 'to respond toa change-in- -suc- I tion pressure equal to a small increment `of-'th'e desired `three poundwspread; The Size ofUthe increment is determined -byUt-he'number4 ofec'yl'- inders' to be controlledrby-rtheeunloadinglmechaf Anism;Mk It is an 'object-ofthisiinvention-to provide acontrol With-the required-`sensitivity.f --Itis-afurther object' ofthe inventionut 'vide a compressorbunloading mechanism in which small'forces-and-reducedLmovments-of the 'coin-' ponentLpartsvare sufficientetoleload'A orl'unl'oad i position assumed by the mastcrya-lveof f the unloader is the resultant. of a pluralityofrcontrolling operating.iconditionsersting inthemot'or' compressor set. ,The composite controlapparatus is thus 'capablfrslving' 'a plurality-of conditions to dtermine :the-:optimum annt nof compressor...f1oading.: The' hydraulicdmeansor 'controllingthe p osition'iofithe mas'trl'valve:.:the

unloading apparatus-is particularly-adapted -to be influenced byl a multiplicityiof control factors. 1A mechanical control of `the master valve as delscribed in Patent-No. 2,185,473 does not lend itself readily to control in response to moretha'n one operating condition. L-

1t is an` additional object of the invention to provide va means :for interrupting the-supply 4of oil .tounloader pistons associated with the compressor cylinders Vwhere that means so operates that thcol supply'linetolan individual cylinder is eitherropenorclosed-.and is .never partially closed-.With a throttled oil-supply passing therethrough. .l ,1 i i2 rf. ,j .Y .15

It? is a efurthervobject' ofthe linventionfto asso# ciate :with a hydraulically operated master control valve a means to dump the controlling-.oil :from the valvevvhen predetermined suction pressures-are exceededby. the compressor. This provides asafety device which prevents overloadingof the compressorfN/f i .L It 'isi an additional'object of the invention to provide means .tovary theipressure of .oilldelivered to 'Ta hydraulically'op'eratedmaster 'control valve inwrespo'nse 'Ltol overheatingk of -the motor vdriving thecompressor and'in. response to Athe presence .of yanexce'ssive amount'of electric .current in the iield coil ofthe motor.H .y 1 f It is a furtherfobject' of the invention to pro- -vid'evmeansktoautomatically load onecompressor cylinder at thesearliestpossible. moment after .starting the compressor. This is vaccomplished lby concentrating theA entire output of the com-'- presser oil pumpen oneunloader piston yuntil-the voil pressure'is vvsufficiently high'v to "indicate that enough oil is being supplied to operate: through the'rnormal unloader system involving all of the compressor unloadercylinders. The presence of refrigerant in the oiljvvvhich occurs'after approlonged shutdown makes thisfyeature of theunloader'` mechanism particularly desirablebecau's'e a 4mixture of refrigerant''suchv as Freon and'oil cannot be pumped to as high a pressure as could oil'itself.` Thus, if evenlfone` cylinder canfbe loaded immediately after starting, the refrigerant `can-be -pumped out-ofthe oil-and normal operation of 'fthe compressor can rhe obtained-more quickly: y@

Other objects and advantages vvill become more apparent from the following description takenin connection, with theaccompanying drawings-in Fig. 1a. side..e1evaton of.- a.refr igera.nt;,QQ.In pressorcoupled-...tma motor;. f

Fig. 2 is a vertical section taken through the compressor of Fig. l;

Fig. 3 is a View partly in section and partly diagrammatic showing a portion of the compressor and the unloader controls associated therewith;

Fig. 4 is a View partly 'in section and partly diagrammatic "showing a modified fform 'of `control responsive to thear'nount ofcurrent owing in the motor of the motor compressor set;

Fig. 5 is a view taken on the line 5-5 of Fig. 3;

and

Fig. 6 is an enlarged View of la portion 'f FigQB.

In Fig. l a motor compressorset'incorporating my invention is illustrated. Acmpresscr lil is supported by a base l2 and adapted to be driven by an electric motor i4. The armature it of motor I4 is coupled to the main shaft i3 ofthe compressor. The compressor is illustrated in more detail in Fig. 2. 'Ilie compressor illustrated in Fig.2'comprisesfahousing V2l) provided with a bearing 22 in Whichthe-shat lil-'is journaled. A conventional seal -24 may be employed between theshaft I8 and housing 2i) in order to prevent theescape of refrigerant from the compressor housing.

t The shaftA |18 includes'a pair of counterbalances 26 and 28 whichare located thereon .and which tend to smooth vibration by acting'as'lywheels. The front end of the shaft beyond the bearing 22 is provided witha crank pin 30 which is lsurrounded by a bearing ring 32 forming the bearing surface for a plurality of piston rods 34. The number of piston rods corresponds to the num? er of cylinders-in thecompres'sor. The Weight of the'crank pin is counterbalanced by a balance weight 36.

-Each piston rod-34 extends radially towards its associated cylinder 38. The cylinders are-radially, equallyV spaced about the center lines of the compressor. Each cylinder is ofiset-longitudinally of the compressor by anlamount equal tothe distance between centers ofthe piston rods Sli. Eachcylinder'comprises a linerdil which is inserted throughv the outer end ofthe cylinder when aA cylinder head 42 isV removed. A suction manifold 44 surrounds the liners vand communicates With a refrigerating system (notshown) through a suction port provided inthe housing" and` not illustrated herein. rThe suction manifold 44 com- L municates with thev interiord `of the compressor housing through a'plurality of openings t8. The suction manifold is also in communication with the linterior of the vrear or right `hand portion of the compressor of Figt 2 through oneV or more A openingsn50. The entire interior oi the cornpressor is therefore subjected to pressure equal to the suction pressure of the refrigerating system 'with Vwhich it' is associated.

The 'refrigerant "entering the compressor through the 'suction/manifold' 44` is' admitted to each cylinder space through suction valves "v 52. 'The' gas'is="admitted' upon raising 0f' the"4 suction valve 52 and discharged v'from 'the cylinder' upon the-'raising of a discharge valve-54. Piston 5t is adaptedtoreciprocate in-li-ner'-'li0. The details ad operation of t-he piston," seal, liner andvalve assemblyaremorefully set-iorth in Neeson Patent No. 2,137,965, dated November 22,4938. '-Eachof the discharge'ports 58 extends through 'thei'iain housingv 20:*si-iid-`pa'ssesi from the com- Jp'ressorthrough ai' frhainl discharge portl As described in Neeson Patent No. 2,185,473 a 'meansvi'or producing dill-pressure is-provided' at Oil pressure produced iss-used to'iubricate 4 moving `parts of the compressor and to operate an unloader mechanism to be described. A master valve (it is associated with the unloader mechanism and is adapted to control the delivery of oil pressure to unloader mechanisms associated with each compressor cylinder. Oil is delivered under pressure from means E32 to master valve 313. A plurality of tubes (i5 connect the master lvalve iii `to individual unloader 'mechanisms associated with each compressor cylinder. One such unloader mechanism is illustrated in Figs. 2, 3 and 5 and comprises a passage 68, a bore 'it and a member ll which has a portion sealed in bore it .rand-nasa ring portion 'i2 which surrounds liner 40. vRingportion `12 is provided with a channel 573 and-ring piston i4 is adapted to reciprocate in channel i3. A port l5 connects channel with bore "l0 so that'iluid admitted to bore l@ may enter channel i3 and raise piston ld. A plurality of circumferentially spaced unloader pins 32 longitudinally-einher it .and are adapted to liit suction valve 52 so that the suction valve is held in its open position when piston llt is not raised by `iluid pressure. In such case gas entering the cylinder space through the suction valve forced back into suction manifold M. Since the discharge valve remains seated the net effect is an accomplishment of no usual Work. A ever 'it associated with each unloaderpin t2. Each 'it is `pivotally mounted at l'! and has one end thereof secured to a pin v82. The other oi' leach lever l@ is provided with a depending pcrtion lwhich is adaptedto engage the piston M A spring 'i9 is providedrto retain portion lil in contact with piston 'Ht and 'to raise pin 225i when fluid pressure is not `present below piston lll. Pins 82 are adapted to open suction valve and "unload the cylinder when iluid pressure is not present below the piston lli.

When the system is at rest, the suction valves are held in `open position due to the lack of oil pressure beneath the piston lll. When the motor is starting the reciprccation of the compressor pistons 56 will result in no `compression being p formed. However, as the motor reaches a higher speed and oil pressure is built up sufficient pressure will be available-to load the compressor cyl-- inders by movement of pistons lll.

Control mechanisms are adapted to control the delivery of oil to the pistons lli in response to predetermined motor and compressor operatingconditions. The master valve @d comprises a housing 84 having an axial bore t therein. A liner lB8 Whichalso contains an axial bore (it is secured withinrbore te and adapted to receive a piston 92 therein. A spring 94 is contained withinthe boreil and acts upon one end of piston 92to urge it to the left in Fig. 3. The other end ofthe spring t4 reacts upon a cap 96 secured to liner 88. A line @8 is adapted to deliveriiuid to or receive iiuid from a port itil in that-end of liner 8S which is opposite to the 4endcarrying -the spring Siri. The relationship between ythe strength of spring Elli and the pressure of fluid delivered by line 98 will determine thevpositionof piston 92 in bore td. The central yportion of piston 92 is provided with a restricted vdiameter so that a space lcd is provided between the portion 95 and the wall of bore 9U. Housing 184 and liner 88 are lprovided with cooperating aligned openings "which form a port 106. A line |08 connects porty IBSA-with a source of yfluid under pressure. The housing 8a and liner-88l are provided with al plurality of aligned openings which cooperate to. provide aA number .Qfl, axially` .spaceddscharse ports H01.-` Each dis- ;.charge port has aline r66 connected there- "to so that fluid discharged from a port ||0 will .betransported to a passage and a bore 'l0 :associated with the unloader mechanism of one .of the compressor cylinders. Fluid flow commu- ,nication Vis provided in master cylinder64 from linelthrough inlet portl0li, space |04 to 1,discharge ports H0 when piston 92 is positioned .to accomplish this. Axial movement of piston 92 in bore 99 can effectively block, oneor-more of Athe discharge ports ||0 fromthe fluid delivered by line- |08. When any` discharge portl |0. is vso blocked oil is not delivered.. to :the related bore ..10 and the compressor cylinder associated vwith lthat particular port ||0lbecomes unloadeddue to the action of the spring 79 in. its unloader lmechanism, The lines 98 and |08 .are preferably joined to a common line ||2 Whichis connected Yto afsource of iluid under pressure.

i: Piston y92 `is preferably so. constructed thatno partial throttling of the oil supply to anyone -Of'theilines AEivcan occur. The piston 92y preferablycomprises an assembly of a first piston-ele- `ment 93 having an axial rod-95 secured thereto :and a second piston element 91 slidably mounted on the rod 95. The piston elements l93- and 91 -areurged apart `by asmall 'spring 99 which is -weaker than spring v94.. Thepiston--element 9'! :is provided with a plurality of circumferential grooves -|0|1- adapted L-tocoope'rate with a spring .loaded ball detent- |03 mounted in liner 88 to `rpositively positionpistonelement 91 at a plurality'of stations whichwill fully load or unload individual compressorcylinders. AAzstopl |05 may .be provided to assure' lthe loading-of at least a 4minimum number of cylinders. f

To control the position of piston 92 in master valve 64 I have provided a control means I I4 which is associated with line 98. The control means-H4 is-ad'apted to bleed fluid'from line -98hunder predetermined conditions.r f Control means ||4 comprises a normally closed bleed Ailo valve- ||6 and cooperating valve Vseat |20 which 98. bellows ||8 contained within Ycontrol means H4 is adaptedV to position valve H6, Valve modulates or entirely restricts-the owfof yfluid from control means ||4 to line 98.v A spring v|22furgesbellows H8v against a stop member |24 'whichcorresponds to a position wherein valve T|16 s--positioned on seat '|20 and the flow 'of filuidinto control means H4 is completely inter- 'rupted'hese components ofA the control means H4 are'mounted'upona plate "|26 whichis at- -ta'chedto the compressor housing 'I0 vby bolts 'i1-|28'. f A port |30 connects the interiorof bel- `lows ||8jwith the atmosphere. If'desired a f1tting |29 "may be provided'to connect the interior of--bellows H8 to anl external control means 'simnario that shownin my Patent-No. 2,581,329. 'A'cover |32 for the control means I4 is provided -With'openings |34. As the suction pressure withlinthefinterior'fl of the A'compressor housing falls the bellows A| 8 exten/ds" to open valve H6.4 'A lfiuidiiow communication isV provided from valve "|`|6"t`o the compressor housingby tlfieopening Iin valveseat|20 and openin'gs'lS and |34. Oil thus'bled from line 9 8 mayl fall by gravityto theisfumpn' the bottom 'o i the compressor housg and the Dressure.o`f ,`thelluid in lineiliim will beiseiermiilfdby I the' @eignet v0i reliefrrqvided bVv valviefflt.v Thefpositionof piston92 isdeter- 891,93' 55.-. 9 ,-.-.lliis `position. wil1, ,1 eterm ir.1ewhch.0f the compressor cylinders are kia-dectA Continued operation. .of the compressor with certain cylinders loaded will .reflectthis change in;suction pressure in the position of.piston 92. The new position of piston 92 will load additional compressor cylinders thereby repeating the cycle of increasing the suction pressure and repositioning the piston 92.

vControl means |41oads cylinders as the suction pressure increases and unloads cylinders with y decrease in suction pressure.

.-A pairo orifices, and ||9 :are provided in vuidflow communication with line 98. An adjustable needle valve ||5 controls the discharge of oilfrom line ||2 through orifice ||9 and therebyprovides means for varying the sensitivity of the system. Orifice H'I'controls the rate of change of position of piston 92 for anyv given changein the opening of valve H6.

A manual controlma'y be associated with the controlmeans ||4 if rdesired to provide a means for wedging the system toa loaded position. lIfhis manual control `includes anl adjusting screw |40 which is slidably locked in a nut |42 carried by plate |26. A lock nut v`|44 is threaded .on screw |40. A spring |46 is `provided to extend, adjusting screw |40. A threaded cap |48maybe provided to cover this apparatus. Theoperatonby removing cap |40 and turning lock nut |44 `may retract screw |40 and permityspring |23`tovseat valve l lli on seat |20 thereby renderingcontrol H4 inoperative-and preventing its-interference ,withthe loading of `compressor cylinders. During periods of normal-.automatic operation the lock nut |44 is removed so thatscrew |40 is not restricted in its axial movement in response yto movement of bellowsy HB.

Supplemental controls may also ,be provided to unload compressor cylinders by bleedingoil from line 98 and bore 90 in .response to other operating-conditions of the compressor ormotor. The copending application ofV C. R. Neeson, .Seri-al No. 786,273, led November 15, 1947, which has matured into Patent No. 2,522,762, describes an improved -mechanism for bleeding. oil-froman .unloader apparatus in response to increased suction pressure in a compressor thereby-permitting springsllS to unload compressor cylinders.y The hydraulic control meansV described herein for master cylinder 64v is particularly adapted to operate in conjunction with they high suction pressure bleeding device described in the Neeson application. This device is generally designated vby the numeral |50 and is adapted to bleed iluid from bore in master valve 94. A port |49 is provided `in liner 88 and operatively connected `by a line |5I to control means |50. Port l|49 is preferably located axially in liner 88m such a position that piston element 93 will block this port until a predetermined minimum number of compressor cylindersV are loaded.r The control 1means |50 comprises a; housing |52ahaving a cylinder |54. therein and abore |59 extending axially of the housing |52 through one end thereof. A valve element |58 is adaptedto reciprocate in bore |56. Valve element |58 has an axial opening |60 extending therethrough andexposed -to the suction pressure existing in the interior 54 :inthecompressorvhousing.. Legs |62, secure the valve element |53, to the end portionpf` a collapsible. bellows, |64.,y The other end ,othe belseaiedhy: mercenaire., casingl s2.

A spring |66 is provided within the bellows 1N and adapted to react against an a-dusting screw |53 threaded through the top of the casing |52. Adjustment oi the screw |63 presele'cts the compression of Spring 265. Spring'w'b resists collapsing of the bellows H54. Suction `pressure transmitted from the interior '4B of the compressor through axial opening iiil to the cylinder |51l tends to compress bellows |84 thereby producing linear movement of valve element 158 in accordance with variations in suction pressure within the compressor. When the `suction pressure is greatest the valve element |58 is moved inwardly in housing |52 and when the suction pressure is low spring |56 moves valve element l outwardly. Valve element |58 is provided with a pair of adjacent recessed portions v|`||l and Il@ in its surface. A spring pressed ball detent idt is adapted to enter recessed portion I'iil or recessed portion H2 depending on the position ci the valve element |58. A pin |16 in housing |52 limits outward movement of valve element |58. 'Valve element |56 is therefore provided with a first extended position as shown in 3 when the suction pressure is low and a second retracted position when the suction pressure is high. i port its provided in housing |52 adjacent the outer end of valve element |58 communicates With a chamber |80 and a passage Iii. The passage 82 is in fluid ilow communication with line |5| and port |519 which, as eX- piained above is in i'iuid iow communication With bore 9d and line @t unless port H59 is blocked by piston element 953. When valve element '|538 is in the position shown in Fig. 3 the port |73 is blocked thereby and the fluid pressure in line e8 is unaffected by control 15|?. However, when the suction pressure existing in the interior 't6 of the compressor becomes excessive the bellows |54 is collapsed and the valve element |58 retracted until ball Il'li drops into recessed portion VS2 therein. This provides a fluid 'flow communication from line di* through passage |82, chamber li, port 1?'8 and bore it to the interior t6 of the compressor. This provides :a relief for oil pressure in line tu so that the number of discharge ports l lis blocked by piston 92 is increased and more cylinders are unloaded. It is to be understood, however, that if desired control I5!) could be made responsible to discharge pressure or to both discharge pressure and suction pressure.

An additional control adapted to bleed uid from line @o and which is responsive to operating conditions of motor ll may be provided. This control has been designated by the numeral |90. The control tijd consists of a temperature responsive valve |92 which is secured to the housing of the motor The usual iield coil |94 of motor id is diagrazninatcally illustrated and it is the temperature 'thereof which Will determine the operation or' the valve H32. Valve |92 is connected by a line it to line gli which is the source of fluid under pressure to master valve Bd. Line |95 Ableeds oilfrom line @t to valve ISE. A line ist returns oil from valve |92 to the interior it of the compressor housing 2E). The valve |92 is provided with a hollow interior portion and a slidable element 2639. The slidaible element 29|) is adapted for lineaimovement within a guide 202. A port itil operatively connects the interior of the valve |32 to the line m3. Slidable element 2G53 is adapted to selectively open and close port Zeil. The position of slidable element 2|i0 is determined by the deformation or a bimetallic dis-k '296 located Within valve member |32 in close proximityto field coil |94 of motor |13. A rod 129B opeiativelyconnects bimetallic element 2136 and slidableeflement 290. When the temperature voi coil |84 'becomes'excessive 'bimetallic element 20B denects 'to the right in Fig. 3 thereby openjir'i'g port i204 `and permitting oil to be bled from line $8 tothe interior y#i6 of the compressor housing.

A 'resistance wire 20| may be placed in close proximity to the bi-metallic element 206, if desired. The resistance Wire 2M is connected in series with the field coil |Sl of motor I4 and adapted'to Aheat the b'ivmetallic element 2% when :an excessive amount .of electric current is present in the field coil |94. lThe resistance wire 20| possesses'an advantage over the use of direct motor Aheat to actuate birnetallic element 2&6 in that the response .is fquicher. 'In .the event of motor overload an interval 'of .time is required for the entire motor'to heat up. Resistance 23| heats up much faster.

vA' modiied former control responsive to motor `overload'is illustrated in Fig. 4. A valve |92 which is simi-lar to the valve .illustrated in Fig. 3 'is jprovidedwith arod 28 which comprises the move-ble portion 4of a solenoid 2135 and operates Wit-hina sealed tube in solenoid 2t?) as is common solenoid valve construction. The solenoid` 285 vis connected series with the eld coil '|94 of mot-or I4 and is adapted to be actuated to move element 260 to a lposition providing a iiuicl flow communication .between lines |96 and |98 when va predetermined excessive amount of curn rent passes through 'field coil left of motor |55.

One or all 1 of these means for bleeding oil through line |96 in .response to motor overload may be used in an installation.

Operation In the operation `of-lt-he control device hei-ein described it will be seen that fluid under pressure such as 4oil kis deliver-ed to line ||2 by lubricating pump Y62 and that ,line |12 ydivides, to form lines 98 and .|08 with the .line Hi8 serving as the source of iiu'id tobe selectively delivered to a plurality oi"` lines Blunder thecontrol of a master valve lill. Each of the'.l'inesv-it` is connected to a port |10 and the .ports 'HU are spaced axially along master valve 6l so that the position of piston 92 determines which ports IIU are in communication with fluid supplied by line Hi8. Each of the lines' ABtlis adapted to deliver iiuid to the unloading "mechanism described herein and associated with individual cylinders to vload these cylinders when oil is delivered thereto. The position of the piston 92 in the master valve is determined by the fluid 'pressure supplied to the master valve through branch line 9.8 and the modulating valve 1M is adaptedto bleed oil from line 9i! thereby reducing the pressure on piston 92 as the suction `pressure decreases. In other words, as the suction pressure increases the modulating valve lil 'bleeds less fluid from line 98 thereby increasing 'the oil'pressure on 'piston 92 and forcing piston 92 to the right in Figs. 3 and 6 to expose additional ports II to oil delivered by line |68 to load more of the cylinders.

The' lcontrol device iii) is provided 'to bleed iiuid from 'master valve'd and permit spring 9i to move p`iston'92 to theleft to unload additional ycylinders when thevsuction pressure exceeds a predetermined value and piston 92 vis located in a position corresponding to the loading of a predetermined number `of Acompressor cylinders so that'port |49 is uncovered; 'It will be noted that modulating valve I I4 bleeds the greatest amount vice |50 operates to bleed' oil through orice |49l when the suction pressure is great enough to collapse bellows |64.

An additional control |90 is provided to bleed fluid from line 93 and .cause cylinders `to be unloaded When the operating conditions of /thei motor I4 indicate that this Would be desirable by opening the ytemperature responsive valve |92.

The temperature responsive valvey |92 is opened when the motor temperature becomes excessive or when the amount of electric current present in the eld coil |94 becomes excessive.

initial'loadingof onenor more compressor cylin-Y ders is hereinafter described.

An additional supplementary control may be provided to assure the initial loading oi one or more compressor cylinders and after a minimum predetermined oil 'pressure is established to operate the unloader mechanism master valve 64. This concentrates the entire output'` of Vthe oil pump on the one or more unloader pistons until the oil pressure is suiiciently high to indicate that enough oil is beingv supplied to operate through the normal unloader system involving all of the cylinders. This device is generally desig-V nated by the numeral 2I0 and is interposed in the uid supply line ||2 between the fuel pump 62 and themaster valve 64. A line 2|2 connects the fuel pump 62 with the device 24| 0. The device 2 I0 is provided with a housing 2 I4 having an inlet 2 I 6 to which the line 2 I 2 is connected and having a first discharge port 2|8 to which the line ||2 is connected and a second discharge port 220 to which a line 222 is connected. The line 222 is connected vto one of the lines 66 extending between the master valve 64 and the unloader mechanism of an individual cylinder. More than one line 222 could be provided if desired and in that event each line 222 would be connected to a different line 66. The line 66 is provided with a one-,Way valve 224 which prevents oil delivered by line 222 from traveling to the master valve 64 although it permits oil to travel from the master valve through line 66. The housing 2|4 of device 2|0 is provided With a port 2|5 which connectsinlet port 2|6 and discharge port 220. A valve clement 223 is adapted to selectively seal discharge port 2|8 and port 2|5 and carries a valve'stem 230 Which is secured to a piston 232. The piston 232r is adapted to reciprocate in a cylinder 234 provided in housing 2| 4. A spring 236 urges piston` 232 to seat the valve 228 across discharge opening 2|8. A port 238 provides a fluid flow communication between inlet port 2 I 6 and cylinder 234 above piston 232 so that the oil pressure existing in passage 226 exerts a force upon piston 232` tending to unseat valve element 223 from opening 2| 8 and to seat it across port 2|5.

limited time interval the oil pressure Will increase and the 'piston 23,2 will be forced downwardly against l.springz23 thereby unseating valve elel An addieV tional supplementary control which assures theV Ity will thus be seen that when the compressor is initially started the pump 262 Will deliver oilv through line 2I2, passage 226, line 222 lineY 66,

ment 228. This opens discharge port 2|8 and closes port 2|5 so that subsequently the oil delivered by pump 62 Will be transported by lines H2, |08 and 98 to the master valve 64 thereby permitting the operation of the compressor cylinders to be controlled by the mechanism previously described herein.

Althoug'hbut one specic embodiment of the invention is herein shown 'and described it will be understood that various changes maybe made Without departing from the spirit of the invention.v` 1

1'. In ai motor 'driven multi-cylinder compressor-set having a first-'means for unloading indivdual cylinders thereof, a fluid pressure responsivev means adapted to selectively overrule the xedfmember and' a relatively Imovable member,

one of saidmembers being provided Witha plu` rality of"dischar'geports and a first inlet port, said. movable meinberbeing adapted to control the communication of iluid from said inlet port to said individual discharge ports in relation to its position relative'to said xed member,'said`one member having a second inlet port for the admission of fluid to position said movable member relative to said fixed inemben. means operatively; connecting said discharge ports with their respece' the ld'eliv'eryfof'fluid to said second inlet port inV response to suctionfpressure in said compressor.

2. In "a motordriven` multi-cylinder compressorset', unloading meansfin conjunction With individual cylinders operable to unload these cylindersvvhenthe,compressor is at rest, uid pressure creating means operating in unison with said compressor Aand creating suii'icientv pressure vat a minimum speedfto` overcome said unloading means Wherebykto load all of the cylinders, and unloadingy control means responsive to the pressure in: said compressor to connect or disconnect said fluid pressure creating means successively toorfrom nindividual cylinder unloading means, said control v'means rcomprising a master valve havingl a fluid owmconnection vvithfsaid fluid 'pressure' creating 'means and adapted toY be positioned by iiuid pressure at'diierent positions to connect or disconnect different cylinders with saidluid' pressure creating means and a suction pressure responsivejvalve ofthe modulating typeinterpose'd in said'fluid' flovv connection lto" control the ,posi` tion of' saidmaster valve by metering fluid to said mastervralvrejin response to predetermined suction pressure` operatingvconditions o f said set.

In` a motor drivenrmulti-cylinder con'ipres` sor set having a rst meansfor unloading individual cylinders thereofpa uid pressure responsive meanswadapted to selectively overrule' the action of said rst means with respect to individual cylinders to load said individual cylin ders under predetermined operating conditions, j means to deliver uid under pressure to saidiiuid/ aeaaees pressure responsive means including a source of fluid under pressure and a master valve adapted to be positioned by said fluid, said valve comprising a fixed member and a relatively movable member, one of said members being provided with a plurality of discharge ports and a first inlet port, said movable member being adapted to control the communication of fluid from said inlet port to said individual discharge ports in relation to its position relative to said fixed member, said one member having a second inlet port for the admission of fluid to position said movable member relative to said fixed member, means operatively connecting said discharge ports with their respective iluid pressure responsive means, means to deliver iiud from said source to said iirst inlet port and means to deliver iluid from said source to said second inlet port, said last mentioned means including a suction pressure responsive valve of the modulating type adapted to bleed fluid from said master `valve and means forming a fluid flow connection between said master valve and said suction pressure responsive valve including a port in said xed member positioned to be obstructed Vby said movable member until said movable member assumes a position corresponding to the loading of a predetermined number of compressor cylinders.

4. In a motor driven multi-cylinder compressor set having a lirst means for unloading individual cylinders thereof, a fluid pressure responsive means adapted` to selectively overrule the action of said first means with respect to individual cylinders to load said individual cylinders under predetermined operating conditions, means to deliver fluid under pressure to said fluid pressure responsive means including a source of fluid under pressure and a master valve adapted to be positioned by said iiuid, said valve comprising a iixed member and a relatively movable member, one of said members being provided with a plurality of discharge ports and a first inlet port, said movable member being adapted to control the communication of fluid from said inlet port to said individual discharge ports in relation to its position relative to said fixed member, said one member having a second inlet port for the admission of fluid to position said movable member relative to said fixed membe i, means operatively connecting said discharge ports with their respective uid pressure responsive means, means to deliver iluid from said source to said first inlet port, means to deliver .fluid from said source to said second inlet port, apparatus adapted to bleed fluid from said last mentioned means in response to predetermined operating conditions of said set to thereby regulate vthe pressure of fluid delivered to said second inlet port, and means to deliver all of the fluid from said source to the fluid pressure responsive means associated with at least one of the compressor cylinders and to by-pass said master valve until a predetermined fluid pressure is exceeded.

5. In a motor driven multi-cylinder compressor set having a iirst means for unloading individual cylinders thereof, a` fluid pressure responsive means adapted to selectively overrule the action of said rst means with respect to individual cylinders to load said individual cylinders under predetermined operatingl conditions, means to deliver fluid under pressure to said fluid pressure responsive means including a source of fluid under pressure and a master valve adapted to be positioned by said iiuid, said valve comprising a fixed member and a relatively movable member, one of said members being provided With a plurality of discharge ports and a rst inlet port, said 'movable member being adapted to control the communication of fluid from said inlet port to said individual discharge ports in relation to its position relative to said lixed member, said one member having a second inlet port for the admission of fluid to position said movable member relative to said fixed meinber, means operatively connecting said discharge ports with their respective fluid pressure responsive neans, means to deliver fluid from said source to said first inlet port, means to deliver fluid from said source to said second inlet port, apparatus adapted to bleed fluid from said last mentioned means in response to predetermined operating conditions of said set to thereby regulate the pressure of fluid delivered to said second inlet port, a fluid pressure responsive valve interposed in the'path of fluid from said source to said master valve and adapted to prevent the delivery of fluid to said master valve until a predetermined iluid pressure is obtained and means forming a direct iluid .flow communication between said source and the fluid pressure responsive means associated with one of said cylinders and adapted to concentrate all available fluid pressure thereon until a predetermined fluid pressure is exceeded and said fluid pressure responsive valve is opened.

6. In a motor driven multi-cylinder compressor set having a first means for unloading individual cylinders thereof, a fluid pressure responsive means adapted to selectively overrule the action of said first means with respect to individual cylinders to load said individual cylinders under predetermined operating conditions, means to deliver fluid under pressure to said fluid pressure responsive: means including a source of fluid under pressure and a master valve adapted tobe positioned by said fluid, said valve comprising a fixed member and a relatively movable member, one of said members being provided With' a plurality of discharge ports and a first inlet port, said movable inem-ber being adapted toy control the communication of iluid from said inlet port to said individual discharge ports in relation to its position relative to said fixed member, said one member having a second inlet port for the admission of fluid to position said movable member relative to said iixed member, means operatively connecting said discharge ports with their respective iiuid pressure responsive means, means to deliver fluid from said source to said first inlet port, means to deliver fluid from saidv source to said second inlet port, a first apparatus adapted to reduce the pressure of fluid delivered to said second inlet port when the suction pressure in said compressor is less than a predetermined minimum, a second apparatus adapted to reduce the pressure of fluid delivered to said second inlet Iport when the suction pressure in said compressor exceeds a predetermined maxlmum, and means to deliver all of the fluid from said source to the uid pressure responsive means associated with at least one of the compressor cylinders and to by-pass said master valve until a predetermined fluid pressure is exceeded.

7. In a motor driven multi-cylinder compressor set having a rst means for unloading individual cylinders thereof, a uid pressure responsive means adapted to selectively overrule the action of said first means With respect to individual cylinders to load said individual cylinders under predetermined operating conditions, means to deliver fluid under pressure to said iiuid pressure responsive means including a source vof iiuid under pressure and a master valve adapted to be positioned by said fluid, Isaid valve comprising a fixed member and la relatively movable member, one of Isaid members being yprovided with va plurality of discharge ports and a first inlet port, said movable member being adapted to control the communication of fluid from said inlet port to said individual discharge ports in relation to its position relative to said fixed member, said one member having a second inlet port for the admission of fluid to position said movable member relative to said fixed member, means operatively connecting said discharge ports with their respective fluid pressure responsive means, mean-s to -deliver fluid from said source to said first inlet port, means to deliver fiuid from Isaid source to said second inlet port, said xed member being provided with a port so located that under certain conditions it is covered by said movable member and under other conditions it is exposed to fluid delivered by said last mentioned means and apparatus adapted to control the disposition of fluid entering said klast mentioned port by bleeding increasing amounts of fluid from said fixed member through said last mentioned port when the suction pressure in said compressor increases above a predetermined maximum, the covering ofy said last mentioned port by said movable member assuring that a predetermined minimum number of compressor cylinders will be loaded.

8. In a motor driven multi-cylinder compressor set having a first means -for unloading cylinders thereof, a fluid pressure responsive means adapted to selectively overrule the action of said first means with respect to individual cylinders under predetermined operating conditions, means dening a first circuit to deliver fluid under pressure to said fluid pressure responsive means including a source of fluid under pressure and a master valve adapted to be positioned by said fluid and to `selectively connect said source with the uid pressure responsive means of individual cylinders, means defining a second circuit to deliver fluid directly from said source to the fluid pressure responsive means of one cylinder and to by-pass said master valve as an incident to starting of the compressor to thereby concentrate the full pressure of said source on the fluid pressure responsive means of said one cylinder and means to render said second circuit inoperative land said first circuit operative after initial starting of the compressor.

ALW'IN B. NEWTON.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,786,791 Terry Dec. 30, 1930 2,137,219 Aikman Nov. 22, 1938 2,169,554 Buchanan Aug. 15, 1939 2,185,473 Nees'on Jan. 2, 1940 2,304,999 Gonzales Dec. 15, 1942 2,387,117 Buehler Oct. 16, 1945

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