US 3064449 A
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Description (OCR text may contain errors)
Nov. 20, 1962 R. N. RIGNEY REFRIGERANT COMPRESSOR 6 Sheets-Sheet l Filed Nov. 28, 1960 INVENTOR. M /G/VE/ L7/CHAP@ Nov. 20, 1962 R. N. RIGNEY REFRIGERANT COMPRESSOR 6 Sheets-Sheet 2 Filed Nov. 28. 1960 INVENTOR. 704,420 M /G/z/Ey www Nov. 20, 1962 R. N. RIGNEY 3,064,449
REFRIGERANT COMPRESSOR Filed Nov. 28. leso e sheets-sheet s 5 76 JNVENTOR. 4Q/acme@ M leben/Ey rrae/l/grs.
Nov. 20, 1962 R. N. RIGNEY REFRIGERANT COMPRESSOR 6 Sheecs-Sheecl 4 Filed Nov. 28, 1960 INVEN TOR.
Afro/@Mfrs Nov. 20, 1962 R. N. RIGNEY REFRIGERANT COMPRESSOR 6 Sheets-Sheet 5 Filed NOV. 28, 1960 lm/ENTOR.
Nov. 20, 1962 R. N. RIGNEY 3,064,449
REFRIGERANT COMPRESSOR Filed Nov. 28, leso 6 Sheets-Sheet 6 INVENTOR.
' ten Patented Nov. 20, 1962 fornia Filed Nov. 28, 19h41, Ser. No. 72,093 21 Caims. CL 62-476) This invention relates generally to refrigeration systems, and more particularly refrigerant compression in such systems, the invention being characterized in the provision of a novel and improved motor-driven comressor unit, as well as in the combination of such a unit in a refrigerant system.
It is a general object of the invention to provide a novel compressor and motor unit in which iluid lubricant is contained and becomes entrained in flowing refrigerant during compressor operation, the motor and compressor unit incorporating separator means operable to separate the lubricant from the compressed refrigerant prior to flow of the latter from the motor-compressor unit to condenser means in the system, thereby preventing excessive accumulation of lubricant in the refrigerant flowing to the condenser. It is also an important object l of the invention to utilize the compressed refrigerant for cooling the electric motor driving the compressor, such cooling being accomplished in a particularly advantageous and novel manner through the incorporation of passages within the motor-rotor structure Within which the compressed refrigerant is flowable in heat transfer relation with the motor-rotor structure, these passages presenting very little obstruction to the flow of compressed refrigerant. At the same time, the rotor structure forming the passages is operable to effect centrifugal separation of the uid lubricant from the compressed refrigerant as the latter tlows through the motor in cooling relation therewith, all as will be described.
The invention is also characterized in the combination of the elements making up the motor-driven compressor assembly, these elements including a manifold, an electric motor and rotary compressor/ means located between the motor and manifold and rotatable by the motor for compressing the refrigerant. This assembly contains passages for flowing circulating refrigerant through the manifold to the compressor means to be compressed thereby, these passages also acting to return the compressed refrigerant to the manifold to be circulated outside the assembly for cooling and to be returned in compressed and cooled state to the manifold. In addition, the assembly contains other passages for receiving the compressed and cooled refrigerant returned to the manifold from outside the assembly for flowing refrigerant through the manifold and compressor means to the motor in cooling relation therewith and for returning the refrigerant from the motor back through the compressor means to the manifold for circulation therefrom into the refrigerating system outside the assembly. As will be seen, maximum utilization of available space to provide for flow of the refrigerant Within the assembly to accomplish these functions is made possible by locating the manifold, compressor means, and motor in relationships described and to be described.
These other features and objects of the invention, as Well as the details of an illustrative embodiment, will be more fully understood from the following detailed description of the drawings in which:
FIG. 1 is a schematic showing of a refrigeration system incorporating the invention;
FIG. 2 is an enlarged elevation taken in section through the motor-driven compressor assembly;
FG. 3 is a section taken on line 3 3 of FIG. 2;
FIG. 4 is a section taken on line 4 4 of FIG. 2;
FIG. 5 is a View like FIG. 4, showing elements of the compressor rotated with respect to the positions of these same elements shown in FIG. 4;
FIG., 6 is a section, partly broken away, taken on line 6 6 of FIG. 2;
FIG. 7 is a section taken on line 7 7 of FIG. 2;
FIG. 8 is a section taken on line 8 8 of FIG. 2;
FIG. 9 is a section taken on line 9 9 of FIG. 3;
FIG. l0 is an exploded perspective showing of the basic elements of the motor-driven compressor assembly shown in det-ail in FIG. 2; and,
FG. 11 is a schematic showing of the circulation of refrigerant through the motor-driven compressor elements illustrated in block form.
Referring first to FIG. 1, a particular refrigeration system incorporating the invention is shown to include a motor-driven compressor assembly generally designated at 10, the latter including a manifold 11 having connected therewith a refrigerant delivery or exhaust duct 12, a refrigerant return or suction duct 13, and other refrigerant outlet and inlet ducts 14 and 15, the functions of which will be later described. The assembly 10 also is shown in FIG. 1 as incorporating a pair of housings 16, which will be understood as joined to opposite faces of the manifold, so that the housings extend endwise oppositely from the manifold.
Tracing through the circulation of refrigerant Within the system, the supply refrigerant, typically but not necessarily comprising Freon 12, passes through duct 12 to and is delivered at 13 to a receiver 19. From the latter the liquiiied refrigerant passes through a heat exchanger 29, an expansion valve 21 and then through an evaporator 22. After passing through the latter, the refrigerant is returned at 23 through the heat exchanger 20 and then returned as suction gas through the duct 13 to the compressor assembly 10. i
It will also be observed in FIG. 1 that super-heated compressed Freon or refrigerant is circulated from the outlet duct 14 through a pre-cooler unit indicated at 24, the purpose of which is to cool the Freon, removing its super-heat so that the cooled, compressed Freon may be circulated back through the inlet duct 15 into the assembly 11) for cooling the motor, as will be further described. Typically, but not necessarily, the superheated and compressed Freon discharged from the unit 10 through the duct 14 has a temperature around 230 F. and the cooled Freon is returned through the duct 15 at a temperature of around F. After passing in cooling relation with the motor in the assembly 1t), the compressed Freon is exhausted to the system through duct 12 at a temperature of around 187 F. These temperatures are merely illustrative of typical operating conditions, and are not to be taken as limiting the operating temperatures of the present or equivalent systems or units.
Referring now to FIGURES l0 and 11 for a broad understanding of the arrangement and operation of the motor, compressor and manifold elements of the compressor assembly, it will be seen from FIG. 1l that a pair of compressor units 25 are located at opposite sides of the central manifold 11 and two electric motors 26 are placed or located endwise outwardly of the compressors 25, the elements 11, 25 and 26 thus being arranged in stacked series relation, the advantages of which will appear from the following description.
As broadly conceived, such advantages include the enablement of adequate cooling of the high output compressor and motor units by the compressed refrigerant, which is distributed or circulated to the compressor and motor units from the central manifold 11. Thus, as schematically shown in FIG. 11, suction gas or refrigerant is supplied to the manifold 11, as indicated at 13, and is then distributed at 27 to the compressors 25. Thereafter, the compressed and superheated refrigerant is returned back to the manifold 11 as indicated by the lines 28 for external circulation at 14 to the pre-cooler which is shown in FIG. 1 at 24. The return ow of cooled compressed refrigerant is supplied at 15 to the manifold and is then led or conducted through the compressors to the motors 26, as indicated by the lines 29. The circulating-compressed refrigerant is then returned at 39 back through the compressors 25, typically through the tubular drive shafts therefor, to the central manifold 11, from which the refrigerant was circulated at 12 to the external refrigeration system as previously described. Since the coolant comprises the refrigerant itself, and since the elements 11, 25 and 26 are arranged as described, a very compact compressor assembly is provided with an extremely high output to weight ratio.
Now referring to FIG. 2, the assembly 16 is shown to include the opposite casings or housings 16 having flanges bolted to the opposite faces 31 of manifold block 11,
Vthe bolts being shown at 32. Extending the description to FIGS. V3, 7, 8 and l0, the manifold chamber is shown to include a ring 33 forming a cavity 34 through which access of lubricant between opposite sides or faces of the manifold chamber may be had, the lubricant normally partly filling the interiors of the casings or housings 1 and the cavity 34 of the manifold chamber. v
Located centrally within the chamber 34 is a block 35 containing a bore 36, which is in communication with an outlet or exhaust refrigerant fitting 37 through a duct or passage 38. The latter is formed by leg structure 39 integral with the body and the manifoldrchamber ring 33, as better shown in FIG. 3 and FIG. 7. The bore 36 also-receives the tubular coaxial extents 40 of end plates 41VV for the compressor bodies 42, these bodies and end plates being part of the compressors 25. The tubular extents 40 in turn receive the end extents of hollow shafts 43, which are coaxially mounted by suitable roller bearings 44?, space 45 remaining between the ends of the shafts 43 and bearing retainers 46 to provide a path 45 for exhaust iiow from within the shafts 43 through space 45 and the passage 38 to the exterior refrigerant system.
Also, integral with the manifold chamber is leg structure 47 forming a passage 48 through which suction refrigerant gas flows after entering the manifold fitting 49. Such flow then passes at 48 to the inlet 50 within the body 35 ofY theV manifold, as seen in FIG. 8. The inlet 5t) communicates between opposite faces 51 of the block 35 and furthermore registers with inlets 52 in the end l plates 41 and with inlets 53 in the compressor body 42, as'seen in FIGS. 4 and 5.
Themanifold also includes leg structure 54 forming a-passage 55 through which compressed and superheated refrigerant flows from the compressor chamber to the exterior fitting 56, the latter communicating with duct 14, asshown in FIG. l. Compressed and superheated refrigerant leaves the discharge passage 5.7 within the compressor block, as seen in FIGS. 4, 5 and 9, and is delivered past a reed valve 58 into a passage 59 within the manifold and communicating with the passage 55.
Finally, the manifold includes integral leg structure 60 formingv a passage 61, which communicates between the exterior fitting. 62 and a passage 63 for receiving cornpressed and precooled refrigerant for delivery to the compressor and motor. Passage 63 is in registration with passages 64 and 65 within the compressor end plate 41 and the compressor body 42.
Referring now to the compressor unit, as illustrated in FIGS..4 and 5, the body 42 thereof forms a cylindrical bore 66 through which the shaft 43 extends axially, with respectto the axis 67. Acylindrical piston 63 of smaller diameter than the bore 66 is arranged to rotate about the boreV 66 and eccentrically with respect to the axis 67 as by mounting thepiston upon an eccentric 69 carried by the shaft 43, there being needle bearings 70 between the cylindrical surface of the eccentric and the bore 71 of the piston 68. Such rolling contact of the piston with the bore 66 of the compressor body, all in response to shaft rotation in the direction of the arrow 72, serves to draw suction refrigerant gas through the entrance port 53 into the clearance space 73 between the piston and the bore, which space is then progressively closed or reduced in volume between the rolling line of contact 74 of the piston 68 with bore 66, and the line of engagement 174 between the piston surface and the lip 75 of a follower 76 spring urged into contact with the piston surface. It is clear from FIGS. 4 and 5 that the entrance ports 53 is at one side of the follower 76 and the discharge port 57 is at the opposite side of the follower. Also, communication between space 73 and inlet port 53 is inter'- iupted once the line of contact 74 has moved past the port 53 in a clockwise sense. Accordingly, the pressure within the clearance space 73 and within the delivery port or passage 57 increases as the piston rolls around the bore 66 until such pressure increase is suicient to open the reed valve 53, as viewed in FIG. 9. At such time the compressed and super-heated refrigerant escapes through the manifold to the external line 14, as viewedV in FIG. l and FIG. 6, intermittent delivery occurring once per revolution of the shaft. Delivery pressure alsoV escapes through a valve 78 at the opposite end of the compressor for return to passage 59, valve 78 typically but not necessarily being mounted on end plate 79 of the compressor structure. Y l
Returning to the description of the follower 76, it is shown in FIGS. 2, 4 and 5 to be urged toward the piston 68 by a series of compression springs Sii the opposite ends of which are received within suitable openings 8-1 and 82 formed within the body 42 and the follower 76.
Turning now to the description of the electric motors for rotating the compressors, reference to FIGS. 2, 6 and l0 will show each -motor 26 to include a housing 84, which is bolt-connected to the manifold block 35 by bolts shown at passing through the compressor blocks from the motor housing flange `86. Carried within each -housing 84 is a stator assembly 87 that includes laminations 38 through which extent suitable windings, the end turns of which appear at 89. Mounted for rotation within the stator annulus is a rotary assembly generally indicated at 90, the rotor including annular laminations 91 and end rings 92 and 93, al1 of which are included within the squirrel cage construction of the rotor, the squirrel cage lbars of which appear externally at 94.
The rotor annulus is made integral with the shaft 43 by means of support vanes 95 arranged in spiral convolutions, each vane convolution comprising a series of radial spokes 96 having polygonal cross-sections in planes normal to the spoke radii.
Accordingly, axially spiraling passages 97 are formed between the successive vane convolutions, and the spokes' form radial protuberances projecting into these passages, as typified by the sides 98 and edges 99 of the vanes, all for the purpose of. creating turbulant flow of pre-cooled compressed refrigerant passing through the passages 97, thereby promoting heat transfer. The latter is necessary to cool the rotor structure, and it is furthermore found that the precooled refrigerant passes through the gap v100 formed betwen the rotor laminations and stator laminations 88 for cooling purposes.
Such pre-cooled refrigerant enters the passages 97 between the spiral convolutions 95 from an entrance chamber 101 which communicates with the passage 65 in the compressor body as shown in FIG. 9, through a corresponding passage 102 in the compressor end plate 79 as viewed in. FIG. 9. The compressed refrigerant after passing through the passages 97 iiows radially inwardly toward ports 103 in the tubular shaft 43 near the extreme end of the shaft and thereafter the refrigerant ows back through the shaft bore 104, and` th-us through the motor and compressor to discharge at 45 and 38, as previously described.
An additional and important function of the spiral vane convolutions 95 is to centrifuge outwardly the uid lubricant which becomes entrained within the refrigerant flowing through the compressor. Such entrainment and distribution of the lubricant as a mist for lubricating the bearings, as for example those shown at 105, 70 and 44,
is of course desirable; however, separation of the lubricant from the compressed refrigerant just prior to delivery thereof to the external system is also desired in order not to affect adversely the operation of the latter system. Accordingly, adjacent spokes of the vanes form radial grooves for collecting and centrifugally impelling the lubricant outwardly against the inner bore 166 of the rotor laminations 91, such throwout being opposite in direction to the inward tlow of the refrigerant toward and into the ports 103, thereby accomplishing separation of the refrigerant just prior to exit delivery thereof. Furthermore, the liquid lubricant so separated flows through holes or ports 167 appearing in FIG. 6 in the rotor end plate 198, and the lubricant is thus returned to the sump 159 for-med between the housing S4 and the casing 16. The lubricant from the sump works its way back into the system of passages within the compressor and motor via the follower, as indicated by the arrows '110, and it will be understood that other slight clearances allow return flow of lubricant into the circulating refrigerant. In this connection, FIG. 2 illustrates an annularly discontinuous O-ring 112 sealing off between a flange 113 on the motor housing 84 and casing 16.
Brieiiy, referring now to the overall operation of the compressor assembly, the suction refrigerant enters the manifold through the fitting 49 and through passage 48 and entrance ports 53, 51 and 52 for delivery to the compressor piston. Rotation of the latter carries the refrigerant around the clearance passage 73 and discharges the refrigerant under pressure at 57 for exit delivery past valve 58 and into passages 59 and 55. Thereafter, refrigerant circulates externally in the system through lines 14 and 15 for pre-cooling.
Upon return to the manifold the refrigerant enters through the inlet tting 62, FlG. 3, and through passage 61, to the passage 63, from whence the refrigerant flows endwise through the compressor passages 64, 65 and 102 for delivery to the passages 101 and 97 within the motor. Therein, the pre-cooled and compressed refrigerant cools the motor structure while lubricant is being separated from the refrigerant, whereupon the cleaned refrigerant exits through the ports 103 into the shaft bore 194 to flow back through the motor and compressor units to the manifold. Finally, the refrigerant is delivered through passages 45 and 33 for external circulation, as described in connection with FIG. 1 lines 12, 13, 18 and 23.
l. For combination in a refrigeration system in which refrigerant is cycled through condenser and evaporator means, an assembly including iluid lubricated motor driven compressor means operable to receive return ow of refrigenant from the evaporator means and to pressurize the refrigerant for supply to the condenser means, said assembly containing passage means in which fluid lubricant becomes entrained in -owing refrigerant during compressor operation, said assembly including separator means supporting motor rotor structure outwardly of the separator and inwardly of `motor stator structure and being operable to clean the compressed refrigerant by centrifugally separating lubricant therefrom prior to compressed refrigerant ilow to the condenser means, thereby to prevent excessive accumulation of lubricant in the refrigerant flowing to the condenser.
2. For combination in a refrigeration system in which refrigerant is cycled through condenser and evaporator means, an assembly including a motor and uid lubricated compressor means operable lby the motor to receive return ow of refrigerant from the evaporator means and to pressurize refrigerant for supply to the condenser means, said assembly containing passage means in which uid lubricant becomes entrained in owing refrigerant during compressor operation, said passage means including motor driven rotary passage extent within which the refrigerant has turbulent ow proximate the motor to absorb heat produced by operation of said motor, and separator means operable to clean the compressed refrigerant by centrifugally separating lubricant therefrom prior to compressed refrigerant ow to the condenser means, thereby to prevent excessive accumulation of lubricant in the refrigerant owing to the condenser.
3. The invention as defined in the claim 2 in which said assembly has first inlet and outlet ports communicating with the compressor for passing said return flow of refrigerant to the compressor and for passing the compressed and superheated refrigerant stream to said condenser means to precool the compressed refrigerant stream, and said assembly has second inlet and outlet ports for passing said precooled refrigerant stream to said passage means and separator means and for passing the cleaned refrigerant to the condenser and evaporator means.
4. For combination in a refrigeration system in which refrigerant is cycled through condenser and evaporator means, an assembly including an electric motor and fluid lubricated rotary piston compressor means operable by the motor to receive return flow of refrigerant from the evaporator means and to pressurize refrigerant for supply to the condenser means, said assembly including a shaft for driving the compressor rotary piston in response to motor operation, said assembly containing passages in which fluid lubricant becomes entrained in flowing refrigerant during compressor operation, said passages including motor driven rotary passage extent within Which the refrigerant in gaseous state has turbulent flow proximate the motor to absorb heat produced by operation of said motor, said assembly including separator means mounted in said shaft and operable in response to shaft rotation to clean the compressed refrigerant by centrifuging entrained lubricant therefrom outwardly away from the shaft prior to compressed refrigerant flow to the condenser means, thereby to prevent excessive accumulation of lubricant in the refrigerant flowing to the condenser, said shaft having an inlet and a hollow interior for receiving clean compressed refrigerant flowing from said separator means to said compressor means.
5. The invention, as dened in claim 4, n which the motor rotor and stator are spaced radially outwardly from said shaft and said separator means extends intermediate the shaft and motor rotor, whereby lubricant is centrifuged outwardly toward the motor rotor.
6. The invention as dened in claim 5, in which said separator means comprises vanes carried by the shaft and circularly spaced thereabout, said vanes being integral with the motor rotor to receive heat by conduction therefrom.
7. The invention as defined in claim 6, in which said vanes have protuberances exposed at the vane sides for creating turbulance in the gaseous refrigerant from which lubricant is centrifuged in response to vane rotation, thereby to promote heat transfer from the vanes to the refrigerant.
8. The invention as defined in claim 5 in which said assembly includes a manifold and said compressor includes a chamber receiving the rotary piston, said mamfold and separator means being at axially opposite ends of said chamber, said manifold and chamber containing refrigerant intake and discharge ports communicating with the compressor piston.
9. The invention as dened in claim 8 in which said intake and discharge ports are adapted respectively to pass the return flow of refrigerant to the compressor and to pass the compressed and superheated refrigerant stream to the condenser means to pre-cool the refrigerant stream,
and in which the manifold and compressor chamber have other intake and discharge ports for passing the precooled refrigerant stream to saidv passages and separator means and for passing the cleaned Vrefrigerant from the interior of said shaft to the condenser andY evaporator means. Y
10. The invention, as defined in claim 8, in which the compressor chamber has a cylindrical bore through which said shaft extends axially, said piston having a cylindrical periphery and being mounted eccentrically on said shaft to rotate eccentrically about the shaft axis in rolling contact with the chamber bore in response to shaft rotation, said intake and discharge ports opening into said bore at circularly spaced locations and in which said compressor includes a spring urged follower projecting through said bore between said locations and engaging the piston' periphery to seal off between the intake and discharge ports.
11. The invention, as defined in claim 10, in which the chamber contains a radial slotV receiving the follower to move radially in response to piston rotation, said follower having a pressure shoulder facing away from the piston and being in communication with said discharge port.
12. The invention as defined in claim 4 in which said assembly includes a housing enclosing said compressor and motor, said housing containing liquid lubricant in a reservoir outside the motor and compressor, and to which lubricant entrainment is returnable after separation thereof from the refrigerant.
13. For combination in a refrigeration system in which refrigerant vis cycled through condenser and evaporator means, an assembly including amanifold, a pair of electric motors and a pair of iiuid lubricated rotary piston compressors, the compressorsbeing at opposite sides of the' manifold and between the manifold and said motors, the compressors being operable by the motors to receive return' tiow of refrigerant from the evaporator means and to pressurize refrigerant for supply to the condenser means, said assembly including shaftmeans for driving the compressor rotary' piston in response to motor Voperation, said assembly containing passages in which iiuid lubricant becomes entrained in flowing refrigerant during compressor operation, and in which the refrigerant in gaseous state absorbsheat produced by operation of said motors, and separator meansmounted on said shaft and operable in response to shaftrotation to clean the compressed refrigerant by vcentrifuging entrained lubricant therefrom outwardly away from the shaft means prior to compressed refrigerant iiow to the compressor means, thereby to prevent excessive accumulationV of lubricant in the refrigerant iiowing to the condenser means, said'shaft means having inlets anda hollow interior for receiving clean compressed lubricant iowing from said separator meansI to the manifold andthenV to the compressor and evaporator means.
14. The invention as dened in claim 13 in which each motor rotor and stator is spaced radially outwardly from a shaft and the separator means includes vanes extending intermediate the shaft and each motor rotor, whereby lubricant is centrifuged outwardly toward the motor rotors.
@15. The invention as defined in claim 14 in which said separator vanes are carried by the shaft and are integral with the motor rotors to'r'eceive heat by conduction therefrom.
16. The invention asdeined in claim 13 in which said V- assembly includes housing means enclosing said com- 8: pressors and motors, said housing means containing liquid lubricant reservoirs outside the motors and compressors, and means forming passages through which lubricant is returnable to said reservoirs after lubricant separation from the refrigerant.
17. For combination in a system for transferring heat by circulation of liuid subject to heating and cooling, an assembly including manifold means, motor means,V and rotary compressor means driven by said motor'means for compressing the transfer liuid, said assembly containing passages for liowing circulating iiuid through the manifold and compressor means to said motor means in cooling relation therewith and for returning the iiuid from said motor means back through said compressor means to the manifold means to be circulated therefrom and in said system, said passages including motor driven rotary passage extent within which the liuid has turbulent iiow proximate the motor to absorb heat produced by operation of the motor.
18. The invention as defined in claim 17, including liuid lubricant contained by said assembly, and in which said assembly includes separator means in the path of transfer fluid circulation for separating lubricant from theV heat transfer fluid.V
19. For combination in a refrigerant circulating system, an assembly including a manifold, an electric motor, and rotary compressor means between the motor and manifold and Irotatable by the motor for compressing the refrigerant, said assembly containing first passages for flowing circulating refrigerant through the manifold to the compressor means to be compressed thereby and for returning the compressed refrigerant to the manifold to be circulated outside said assembly for cooling and to be returned in compressed and cooled state'to the manifold,
` said assembly containing other passages for receiving the refrigerant returned to the manifold from outside said assembly, for 'flowing the refrigerant through the manifold and compressor means and the motor in cooling relation therewith and for returning the refrigerant from said motor back through said compressor means to the manifold to be circulated therefrom into said system outside said assembly, said other passages includingmotor driven rotary passage extent within which the refrigerant has turbulent ow proximate the motor to absorb heat produced by operation ofthe motor.
20. The invention as de-ined in claim 19 including uid lubricantl contained by said assembly; and in which said assembly includes rotary separator means driven by said motor in the path of refrigerant circulation for separating fluid lubricant from the circulatory refrigerant.
21. The invention as defined in claim 20 including means connected in series communication with said first passages for receiving and cooling the compressed refrigerant to aV temperature lower than the motor operating temperature prior to return of the compressed refrigerant to said other passages.
References Cited in the tile of this patent UNITED STATES PATENTS