US3922114A

US3922114A - Hermetic rotary helical screw compressor with improved oil management

Info

Publication number: US3922114A
Application number: US490169A
Authority: US
Inventors: Clark B Hamilton; Jr Harold W Moody; Donald D Schaefer
Original assignee: Dunham Bush Inc
Current assignee: MARSHALL INDUSTRIES Inc
Priority date: 1974-07-19
Filing date: 1974-07-19
Publication date: 1975-11-25
Anticipated expiration: 1992-11-25
Also published as: IT1036316B; DE2529317C2; GB1467573A; SE399304B; ZA753525B; JPS5749757B2; DE2529317A1; SE7507553L; JPS5120109A; BR7504147A; AU8259775A; CA1002017A; FR2278955B1; FR2278955A1

Abstract

A two part, inner, cylindrical housing concentrically carried within a sealed outer enclosure forms with the outer enclosure, a first sealed chamber and within itself, an upper chamber carrying the electric motor and a lower compressor inlet chamber in a vertical array. The compressor discharge gas, including entrained oil, passes through ducts within the motor to cool the motor with the swirling gas and entrained oil discharged against the upper end of the inner cylindrical housing to separate some of the oil from the discharge gas by centrifugal force. Axial ducts carried by the stator move the discharge gas downwardly to further cool the motor. Discharge gas nozzles fluid connected to the stator ducts discharge the gas and entrained oil against the inner wall of the outer enclosure and the oil drains to the bottom of the enclosure which forms an oil sump.

Description

United States Patent Hamilton et al.

1 1 HERMETIC ROTARY HELICAL SCREW COMPRESSOR WITH IMPROVED OIL MANAGEMENT 1751 Inventors: Clark B. Hamilton, Wetherslield;

Harold W. Moody. .1r.; Donald D. Schaefer, both 01 Farmington, all of Conn.

[731 Assignee: Dunham-Bush. lnc., West Hartford.

Conn

[221 Filed: July 19, 1974 [21] Appl No.: 49(L169 1521 U.S. Cl. 1. 417/366; 62/469; 184/616;

[51} Int. Ll. 1. F04B 39/02 [581 Field of Search 417/362, 366, 369, 372,

[561 References Cited UNlTED STATES PATENTS 1809,87 2 10/1957 Warner 417/372 3,334,808 8/1967 Parker et a1. 4. 417/372 3,584,980 6/1971 Cawley 417/372 3618.337 11/1971 Mount 417/366 3.661127 2/1972 Cheers i l i l i i l 417/902 3,790,309 2/1974 Volz a i i i i i a i 412/368 3,796,526 3/1974 Cawley a. .418/97 3.804202 4/1974 Funke 417/372 3,811.805 5/1974 Moody ct a1 a i 4 417/410 Primary Examiner-C. J1 Husar Assistant Examiner-O. T. Sessions Attorney, Agent, or F1'rmSughrue. Rothu ell. Mion, Zinn & Macpeak 1 1 ABSTRACT A two part, inner. cylindrical housing concentrically carried within a sealed outer enclosure forms with the outer enclosure, :1 first sealed chamber and within itself, an upper chamber carrying the electric motor and a lower compressor inlet chamber in a vertical array The Compressor discharge gas, including entrained oil, passes through ducts within the motor to cool the motor with the swirling gas and entrained oil discharged against the upper end of the inner cylindrical housing to separate some of the oil from the discharge gas by centrifugal force. Axial ducts carried hy the stator move the discharge gas downwardly to further cool the motor. Discharge gas nozzles fluid connected to the stator ducts discharge the gas and entrained oil against the inner wall of the outer enclosure and the oil drains to the bottom of the enclosure which forms an oil sump,

11 Claims. 4 Drawing Figures 58 i i i U.S. Patent Nov. 25, 1975 SheetlofZ 3,922,114

FIG]

US. Patent Nov. 25, 1975 Sheet 2 of2 3,922,114

HERMETIC ROTARY HELICAL SCREW COMPRESSOR WITH IMPROVED OIL MANAGEMENT BACKGROUND OF THE INVENTION l. Field of the Invention This invention relates to hermetic, rotary helical screw compressors, and more particularly, to such hermetic compressors in which the hermetic enclosure functions to muffle the sound generated by operation of the compressor and its drive motor, separate oil from the working fluid, act as a heat exchanger between the ambient and the compressed working fluid and act as an oil sump reservoir for the compressor.

2. Description of the Prior Art Rotary helical screw compressors, particularly compressors of large size, are generally driven by electric motors which are separate from the compressor itself and in which the motors are mechanically linked to the compressor by coupling the rotor shaft of the motor to the shaft supporting one of the screw rotors of the compressor. In such systems, it is common to employ as auxiliary equipment, a separate oil pump which delivers to the screw compressor relatively cool oil under pressure for lubricating the moving parts of the compressor and increasing their useful life. The need for oil cooling limits the discharge temperature that the systems can tolerate. In the larger rotary helical screw compressors, the oil, which mixes with the compressor working fluid is separated downstream of the compressor, is filtered, and normally cooled by an external heat exchanger which may be either water cooled or air cooled. In most cases, the oil cooler is necessarily water cooled, and the range of operation is usually established by available water temperatures. Where water is not available or in the case of minimizing the use of water, limitations on the system arise due to the ambient temperature of the air, and there is the problem in maintaining tolerable discharge temperatures of the compressed working fluid.

The auxiliary equipment is expensive and increases the maintenance requirements for systems using such compressors.

Where the compressor is employed within a refrigeration or air conditioning system and the working fluid comprises a refrigerant such as freon, additional problems arise due to the absorption of the refrigerant by the oil and the necessity to separate the oil from the compressed refrigerant gas at the discharge side of the compressor and prior to feeding of the compressed refrigerant gas to the condenser.

Attempts have been made to provide hermetic units wherein the drive motor and compressor are closely coupled mechanically and are positioned with a hermetically sealed enclosure, with the enclosure acting as a sump for the oil, the compressor acting to drive directly the oil pump, and wherein the discharge of the compressor is passed over the motor itself to cool the motor prior to leaving the enclosure.

Since the temperature limitation in the use of such compressors resides in the maintenance of the oil within tolerable temperature limits, and since the temperature of the oil corresponds to that of the discharge gas, the compressor discharge temperature has been maintained at an acceptable value through the use of liquid injection along with some oil injection. The injection of liquid, which in a refrigeration or air condi- 2 tioning system comprises the liquid refrigerant, has been achieved by providing an injection port to a closed thread of the helical screw compressor at a point which lies intermediate of the inlet or suction side of the machine and the discharge side of the machine. Cooling is achieved on the basis that the liquid will expand, flash off as it hits the relatively low pressure environment of the closed thread and cool the contents of that closed thread. Since the expanded liquid is in creased in pressure a relatively small amount, it has minimal effect on the horsepower requirements of the machine. An example of the use of liquid injection for that purpose is U.S. Pat. No. 3,795,117 entitled Injection Cooling of Screw Compressors issuing Mar. 5,

I974, and assigned to the common assignee.

It is an object of the present invention to provide an improved, rotary helical screw compressor of the hermetic type which improves oil management, which constitutes a compact, vertical design and in which a sealed outer enclosure and a two part sealed, inner housing forms an upper, high pressure outlet housing chamber carrying the electric drive motor and a low pressure screw compressor inlet housing chamber supporting the intermeshed rotary helical screws.

4 It is a further object of the invention to provide an improved hermetic rotary helical screw compressor in which the outer enclosure, being at compressor discharge pressure and temperature, enables that enclosure to function as a heat exchanger with respect to am' bient.

It is a further object of the invention to provide an improved rotary helical screw compressor in which the hermetic outer enclosure eliminates the need for a sep arate oil sump, external oil separator, external oil cooler, and acts as a muffler, an oil separator. a heat exchanger and an oil sump reservoir for the hermetic compressor.

SUMMARY OF THE INVENTION The hermetic, rotary helical screw compressor of the present invention includes a closed, vertically oriented generally cylindrical outer enclosure, a two part inner cylindrical housing concentrically positioned within and fixed to the outer enclosure and forming with the outer enclosure a first sealed chamber therebetween. The inner housing includes an upper compressor discharge housing fluid sealed and overlying a lower compressor inlet housing with the upper housing forming a high pressure second chamber and the lower housing forming a third low pressure chamber sealed from the first and second chambers. A compressor inlet tube extends through the outer enclosure wall and through the lower compressor housing and opens up into the third chamber. The third chamber carries intermeshed helical screw rotors rotatably supported within a lower compressor housing and in fluid communication with the inlet tube for compressing a gaseous working fluid supplied to that inlet tube. A compressor discharge pas sage fluid connects the upper end of the first chamber to the lower end of the second chamber. An electric drive motor is coaxially supported within the upper compressor discharge housing above the compressor discharge passage and includes a fixed stator and a concentric rotor rotatably positioned within the same. A quantity of oil is provided within the outer enclosure whose bottom acts as an oil sump. Preferably, an oil pump which is driven by an extension of a rotor shaft underlies one of the screw rotors which is driven by that same shaft and is in fluid communication with the sump. The oil pump delivers oil under pressure to the bearing surfaces. rotor thrust faces and injection parts for lubrication which mixes with the compressor work-- ing fluid passing therethrough and is discharged into the upper. high pressure chamber along with the compressor discharge. First axial fluid passage means are carried by the motor for passing compressed working fluid and entrained oil axially upward to cool the motor and for impingement against the upper end of the corn prcssor discharge housing. Second axial fluid passage means return the compressor discharge, the separated oil and entrained oil axially downward to further cool the motor. and radial passage means fluid connect the lower ends ofthc second axial passage means to permit the compressed working fluid and the entrained and separated oil to move radially outwards of the compressor discharge housing and into the first chamber for gravity separation of the oil and return to the sump Preferably. the first axial passage means comprises ducts formed within the rotor and extending upwardly from one end face ofthe rotor to the other such that ro tation of the rotor provides a swirling action to the compressed gas and entrained oii such that some separation of oil from the gas occurs centrifugally by contact of the swirling gas with the upper end of the compressor discharge housing The first axial passage means may further comprise the air gap between the motor rotor and stator while the second axial passage means preferably comprises ducts formed within the upper compressor discharge housing adjacent the stator outer periphery which extend downwardly from the upper end face of the stator but terminate short of the lower end face thereof. The radial passage means may comprise a plurality of circumferentially spaced radial openings within the upper compressor discharge housing intersecting the axial ducts within the stator, the radial openings may be canted to permit tangential discharge of the working fluid and the entrained oil such that the working fluid sweeps the inner sidewall of the enclosure circumferentially to deposit the entrained oil thereon. Alternatively, the radial passage means may comprise discharge gas nozzles in the form of short elbow tubes having right angle portions including a first radial portion coaxial with the radial openings of the upper compressor discharge housing and secured to the outside of the housing in axial alignment with said opening and a second circumferential portion which extends generally tangentially to the inner periphery of the upper compressor discharge housing and spaced therefrom. The outer enclosure may consist of upper and lower. partially nested enclosure sections which are welded circumfercntially at their exterior juncture line to permit ready separation of the enclosure sections and access to the interior of the hermetic screw compressor BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional, elevation-a1 view of one embodiment ofa vertical. hermetic rotary screw compressor of the present invention with improved oil management.

FIG. 2 is a horizontal sectional view of the hermetic screw compressor of FIG. I taken about line 2-2.

FIG. 3 is a horizontal sectional view ofa modification of the screw compressor embodiment illustrated in FIG. 2. having tangential discharge gas openings.

FIG, 4 is a vertical, sectional. partially schematic view. illustrating the flow of oil and compressor work- 4 ing fluid within the hermetic rotary helical screw com pressor of FIG, 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, this figure illustrates in a vertical sectional view, one embodiment of the hermetic rotary helical screw compressor of the present invention which provides improved oil management. The vertically oriented hermetic screw compressor comprises a two part generally cylindrical outer enclosure 10 con sisting of an upper cup-shaped enclosure section l2 and a lower cupshaped enclosure section 14. The enclosure section 12 is closed off at its upper end by a domed end wall portion [6. while the lower enclosure section 14 is open at its upper end and closed off by a concave bottom wall portion 18. The helical screw compressor is supported such that its axis is generally vertical by means of a plurality of circumferentially spaced enclosure feet 20.

One aspect of the present invention resides in the manner in which the upper enclosure section 12 is joined to the lower enclosure section 14. In this re spect, the upper end of the cylindrical lower enclosure section [4 is provided with a slightly enlarged diameter portion 22, that is, its upper end flares outward such that the internal diameter of that portion is essentially equal to the external diameter ofthe cylindrical portion of the upper enclosure section 12. Thus, the lower end 24 of section [2 nestles telescopingly within the flared portion 22 of the lower enclosure section 14. Appropriately, the two enclosure sections may be sealably welded together at this point as indicated generally at 26 by an external weld line which completely encircles the joined enclosure sections. The cover portion 16 of the upper enclosure section I2 is provided with a discharge boss 28 in the form of a short length of vertical pipe which opens up centrally into the interior of the outer enclosure 10. This discharge boss 28 supports a discharge check valve. indicated generally at 30, which includes interiorly a spring biased movable valve element 32, which normally closes off the passage formed by the discharge boss 28 to the discharge passage 34 of the check valve. The discharge check valve is conventional and forms no part of the present inventionv Supported within the outer enclosure 10 (by means not shown) and coupled thereto is a two part inner housing or casing indicated generally at 36 which consists of an upper outlet housing 38 and a lower inlet housing 40 which are sealably separated from each other by the outlet housing lower end wall 42 and O- ring seal 43.

Housings

38 and 40, are coupled together by means (not shown). They may be formed of cast metal while preferably the upper and lower enclosure sections [2 and 14 of the outer enclosure 10 are formed of sheet metal which is drawn into the desired configuration. The inner housing or casing 36 is concentrically positioned within the outer enclosure 10 and is spaced therefrom such that it is centered generally with respect to the discharge boss 28. The lower end of the inlet housing 40 is closed off by a pump housing assembly 44 which includes an end plate 46 sealably fixed to the bottom end of the inlet housing 40 by way of O-ring 47 and screws (not shown). The outlet housing 38 is closed off at its upper end by means of a motor end cover 48 which may be welded thereto. Essentially. the outlet housing 38 houses the compressor drive motor 50 which consists of a fixed stator 52 ineluding motor windings 54 which concentrically sur round the motor rotor 56. The compressor drive motor 50 may comprise a squirrel cage alternating current motor, and in which case, the windings 54 are powered by connecting the terminals 58 within terminal box 60 to an external source of alternating current (not shown), the terminals 58 protruding through the wall of the lower enclosure section 14 and through insulative bushings 62 and being connected on their opposite sides by way of leads 64 to the motor windings S4. The outlet housing 38 is provided with an opening 66 which supports an annular seal 68 through which the leads 64 protrude, the leads at this point being covered by an outer cover 71 which is sealingly received within the annular seal 68. It should be noted that the inlet hous ing 40 forms with end wall 42 of the outlet housing 38 and the pump housing assembly 44 a low pressure chamber

housing screw rotors

76 and 126 for the compressor, while the compressed working fluid is discharged by way of discharge port 68 into the high pressure chamber 70 which is defined by end plate 42, motor end cover 48, and the outlet housing 38. Further, the chamber 72 which is formed between the outer enclosure and the inner enclosure 36 is at essentially the discharge pressure of the compressor and is thus considered a high pressure chamber with respect to that formed by the inlet housing 40.

The inlet housing 40 acting in conjunction with the outlet housing 36 supports a hollow drive shaft 74 by way of sleeve bearings 80 and 82 within the inlet housing and outlet housing, respectively, for rotation about a vertical axis which coincides with the axis of the inner housing and the outer enclosure and which is aligned with the discharge boss 28. The motor rotor 56 is cantilever mounted to the upper end of shaft 74, the same shaft supporting the female screw rotor 76 intermediate of bearings 80 and 82 while the lower end of that shaft 74 is provided with a pump drive adapter 81 which extends across a counterbored portion 83 of the shaft which counterbore opens up to axial bore 84 extending the complete length of the shaft. The upper end of bore 84 is closed by means of screw 85. The adaptor 81 by way of internal recess 86 and the projection 88 of rotor 90 of a conventional gear type oil pump 92 effects pressurization to oil 94 within the oil sump. The pump housing assembly pump 46 supports the pump 92 which is driven by shaft 74. The pump is not a part of the present invention. The oil 94 which essentially fills the lower cupshaped enclosure section 14 which acts as the sump, and passes through oil strainer 96 and enters through the pump inlet 98 where, by rotation of rotor 90, is forced under pressure to pass through pump discharge outlet 99 to chamber 100. This chamber 100 is defined by a sleeve 102 which slidably supports the female thrust balancing piston 104. A similar sleeve 106 adjacent thereto slidably supports the male thrust balance piston 108 with the oil under pressure filling the

chambers

100 and 110 behind the pistons and defined by the sleeves 102 and 106 and the pump housing assembly plate 46. The oil passes from the chamber 100 to chamber 110 by way of transverse passage 112. Further, oil under pressure is directed upwardly through the hollow shaft 74 via bore 84 for distribution to the various bearings and to thrust surfaces through the many lateral passages illustrated. To the side of the shaft 74, there is supported for rotation, a driven, male rotor support shaft 114 which is supported at respective ends by

sleeve bearings

116 and 118 within the inlet housing 40 and the discharge housing 38, respec tively. Shaft 114 is provided with a bore 120 which extends the length of the same, is open at the bottom to receive oil from chamber 110 but is closed off at the top by an end plug 120. Suitable transverse radial passages within shaft 114 permit oil under pressure to be distributed to the various elements of the screw compressor for lubrication. Shaft 114 supports within a suiable bore 124 the male screw rotor 126 which is intermeshed with and driven by the female screw rotor 76 carried by bore 128 of the inlet housing.

The make-up and relationship of the male and female screw rotors and their manner of operation is well known in the rotary helical screw compressor industry. The hermetic screw compressor of the present invention is provided with a suction or inlet tube 130 which projects through opening 132 within the lower enclosure section 14 and has its inner end force fitted within opening 134 of the inlet housing 40. Bore 124 of the inlet housing is provided with an annular cavity 136 which extends to bore 128 housing the female screw rotor 76, which annular cavity 136 acts as the suction port for the helical screw compressorv Since chamber 72 is at a higher pressure than that within the suction or inlet tube 130, some leakage of oil between the compressor inlet tube 132 and opening 134 can be tolerated since some oil should be present between the intermeshed screws and between those screws and the housing bore to reduce friction, and to improve the seal between the intermeshed screws defining the working chambers or closed threads as the rotors rotate in unison. The lower face 138 ofthe housing end wall 42 acts as the thrust surface for the intermeshed screws.

in this regard, and while not constituting any part of the present invention, the high pressure oil acts on the lower end face of the male and female thrust balance pistons, under a preferred arrangement to provide counterthrust forces which act in opposition to the developed thrust by the screws compressing the working fluid entering the suction or inlet tube 130 and this overthrust is taken up by the thrust surface 147. In opposition thereto, additional oil acts through radial passages 140 of shaft 114 and inclined passages 142 of the male rotor to form a hydrodynamic fluid bearing be tween the upper end face of the male rotor 126 and the thrust surface 138. In similar fashion, radial passages 144 of shaft 74 and inclined passages 146 of the female rotor 76 perform that function with respect to the female rotor. U.S. Pat. No. 3,811,805 illustrates this arrangement.

The relatively low pressure gas or working fluid entering inlet tube 130 is compressed significantly by means of the intermeshed

helical screw rotors

126 and 76 and gas at a much higher pressure is discharged axially by way of discharge port 68 into chamber 70 of the outlet housing 38. Further, the high pressure oil which has been delivered to the intermeshed screws, the end surfaces of those screws and the bearings for the shaft supporting the same, enters chamber 70 partially by way of compressor discharge port 68 and by further means such as the passages at the ends of the sleeve bearings for instance, including inclined passages 148 within housing end wall 42, where this lubricating oil mixes with the high pressure discharge gas.

The present invention is directed primarily to oil management in hermetic helical screw compressors, and particularly with respect to relatively small size belical screw compressors of the vertical type, wherein the hermetic drive motor is mounted coaxially above the helical screw compressor and in direct mechanical drive therewith. In this respect, the electric motor rotor 56 which is fixed to shaft 74 is provided with a series of circumferentially spaced axial slots, ducts or passages I50, FIG. 2. which extend from lower end face 152 to upper end face 154, that is, the complete axial length of the same, and act as vertical passageways for permitting the compressed gas and entrained oil to pass up wardly therethrough. the compressed gas and entrained oil acting to cool the rotor laminations and windings during such passage. Further, the annular air gap 156 existing between rotor 56 and stator 52 creates a second vertical passage for the compressor discharge gas and the entrained oil as the high pressure gas seeks to escape the upper outlet housing 38. Further, three circumferentially spaced, axial passages 158 or ducts are formed within the outlet housing, these passages or ducts forming third upward flow paths for the discharge gas and the entrained oil. Advantageously. since the rotor 56 rotates in the direction of arrow I60, FIG. 2, there is a helical or spiral flow 162, FIG. I, of the discharge gas and entrained oil as it discharges at the upper end face 154 of rotor 56, at least in terms of the gas flow through axial ports 150. The metal end cap 48 which overlies the upper end turn of windings S4 acts as a barrier to continued upward flow ofthe gas and entrained oil, the gas an oil impact being against the inside of the end cover where it is diverted to flow over the windings S4 to cool the same.

Another aspect of the present invention resides in providing a second series of circumferentially spaced ducts or passages 164 within the inner wall of the upper outlet housing 36, these openings being three in numher. and circumferentially spaced with respect to ducts 150. The ducts I64 provide the sole downflow or reverse flow passage for the gas and entrained or separated oil. It is to be further noted that as result of the spiral movement and impingement of the gas and entrained oil against the inside wall of the end cover 48, oil accumulates on that cover and travels down the sides where it collects adjacent the upper end 166 of the outlet casing. It drains vertically down the walls of ducts I64 along with the gas flow to the bottom thereof. The ducts or passages I64 terminate short of the lower end of the outlet housing 38, and radial openings I70 fluid couple the bottom ends of ducts I64 to chamber 72 intermediate of the inner housing or casing 36 and an outer enclosure 10.

In one form of the invention, the radial openings 170 open up into gas discharge nozzles 172. The gas discharge nozzles I72 consists of short pieces of tubing which are in the form of elbows, which have portions at right angles to each other. The discharge nozzles are mounted such that their discharge ends 174 open into chamber 72, in the direction of rotation of the rotor and provide a tangential discharge path. which dis charges the compressor discharge gas and the entrained and separated oil radially outward and somewhat tangentially onto the inner surface l76 of the outer enclosure 10. At this point, most of the remaining oil separates from the compressor discharge gas and contacts the inner wall I76 as the discharge circumferentially sweeps the wall and the oil flows downward towards the bottom of the outer enclosure 10 where it is collected. The oil is maintained at a level which is preferably higher than that of the top of the inlet tube I30 leading to the compressor for the purposes previously described.

While the number of axial ducts 150 within the rotor 56 and the axial flow ducts I58 and 164 within the outlet housing 38 are three in number and equally spaced circumferentially. variations may be made without departing from the scope of the invention.

Further, the ducts are shown as being adjacent the inner and outer periphery of the rotor and stator re spectively, but may be internal thereof depending upon the configuration and structure of the motor components.

In this respect, reference to FIG. 3 illustrates a modified embodiment of the present invention wherein, instead of employing gas discharge nozzles as at 172, the openings 170 within outlet housing 38 at the bottom of ducts I64 are inclined or canted from the radial so as to extend generally nearly tangentially to stator 52, thus directly discharging gas in essentially a tangential flow path into chamber 72 as evidenced by arrows I78. In all other respects, the embodiment of FIG. 3 is similar to that of FIGS. 1 and 2 and like elements of the same have been given like numerical designations. In both the case ofthe FIG. 2 and FIG. 3 embodiments, the gas and entrained oil or separated oil which accumulates on the motor end cover 48 and flows by gravity and moved by gas flow downwardly along the inner surface of that member, to accumulate along the edge I66 of the outlet housing 38, moves downwardly through the ducts 164 and passes into a chamber 72 through the openings I or 170.

Reference to FIG. 4 illustrates schematically the oil and gas flow paths which are sometimes separate and sometimes in unison. In fact, it is the discharge gas which carries a large percentage of the oil flow through the various passages within the outlet housing for discharge into chamber 72. The gas or working fluid enters the compressor by way of inlet tube 130 as indicated by the dotted line arrow, fills the working spaces defined by the intermeshed screws and by way of the closed thread or chamber is discharged at compressor discharge passage 68 from the intermeshed male and

female screws

76 and 126. The passage 68 extends through end wall 42 and the high pressure discharge gas carrying some entrained oil enters chamber 70 of the outlet housing 36. Meanwhile, oil 94 within the bottom of the lower enclosure section I4 which acts as an oil sump, enters the pump inlet 98, is discharged from the pump through outlet 99 and enters chambers 100 and I10 where the oil is distributed through the hollow shafts 76 and 114 to the rotary

helical screws

76 and 126 and to the various bearings of the motor and the screw compressor. The oil flow as indicated by full line arrows, ultimately enters the high pressure outlet housing chamber 70, where it is mixed with the compressor discharge identified by the dotted line arrows. For simplicity, only a single vertical upflow duct is shown. In this case, it constitutes the gap 156 between the motor rotor 56 and the stator 52. The discharge gas with the entrained oil impinges upon the cover 48, and by way of centrifugal force moves radially towards the outside of chamber 70 as defined by casing 36. Impacting cover 48, it reverses its flow and moves downwardly by the way of the ducts 164 where by means of the nozzles 172 in this case, the gas with entrained and separated oil enters chamber 72, oil either falls by way of gravity from the discharge end 174 of the nozzle or impinges against the inner wall I76. The gas moves upwardly as identified by the dotted line arrows for ultimate discharge at the top of the helical screw hermetic rotary screw compressor while the separated oil drains down along the side of the outer enclosure wall 176 to the bottom of the enclosure and accumulates at 94.

From the above, it is seen that oil separation, which is one function of the oil management arrangement of the present invention, is accomplished subsequent to the oil and gas mixture being discharged from the compressor discharge passage 68 and any other oil which it may pick up as it flows vertically upwards within chamber 70, by way of the rotor ducts 150, the rotor/stator air gap 156, and the ducts 158 which lie at the outside of the motor stator. The illustrated ducts are formed within the casing. However, the ducts may in fact be formed within the stator itself. The gas in contact with the motor rotor enters the motor end cap with a swirl ing effect due to the rotation of the motor, and this centrifugal force acts as the second stage of separation by way of impingement the entrained oil onto the surfaces of the end cover, the first stage having occurred at the moment that the high pressure gas and entrained oil discharges from discharge duct 68 into the chamber 70, against the static and rotary motor structure. Circulation of the gas and oil mixture in the motor end cover not only functions to separate oil from the mixture but also cools the motor winding in the process, the gas and oil flowing vertically downward through the alternate passages or ducts 164 between the motor stator and the outlet housing 38. The downward flow of the compressor discharge gas in the three ducts 164 exits either through the nozzles 172 or through the canted or inclined openings 170' and upon entering the chamber 72 between enclosure and the inner housing or casing 36, the velocity of the gas is greatly reduced. This facilitates oil removal therefrom. With openings arranged such that the discharge gas is directed tangentially outwardly against the enclosure inner surface, this wipes the enclosure or shell wall circumferentially with the oil laden gas. Free oil in liquid form and the heavy particles agglomerate on the shell surface and being heavier migrate downwardly into the sump. The oil free gas flows circularly upward continuing to deposit oil particles on the interior wall of the upper enclosure section 12 prior to discharge centrally through the opening defined by discharge boss 28.

In addition to separating the oil from the gas, the hermetic screw compressor of the present invention is designed to effectively reduce noise by means of the heavy, high pressure outer enclosure 10. Sound deadening may be improved by lining soft sheet metal randomly attached by spot welding or the like to the inside of the shell enclosure 10. The gas flow path also functions to provide a muffler effect as it passes through the compressor and motor sections and since the volume of the chamber 72 formed between the inner housing and the outer enclosure is quite large with respect to the chamber volume of chamber 70. There is little discharge line pulsation and its attendant noise.

Forming the shell enclosure with offset welded portions permits the shell or outer enclosure to be readily cut open and re-assembled and repairs to be made. Since the compressor suction tube 130 lies beneath the level of the accumulated oil 94, it may be lightly press fitted into the hole within the compressor inlet housing 40 since a leak at this joint permits, due to the high pressure within the chamber 72, oil to leak into the suc 10 tion gas which is not detrimental and in fact may be beneficial to the system.

Since the chamber 72 defined by the outer enclosure 10 is at discharge pressure and temperature, this enclo sure loses heat to ambient instead of picking it up as occurs in conventional air conditioning compressor enclosures and which would result in some improvement in system performance. Further, since the Compressor comprises a helical screw compressor, it is not necessary to have the enclosure 10 at suction pressure acting as a suction accumulator and housing other devices to protect the compressor from damage due to liquid slugging as is the case with reciprocating compressors.

The employment of the outer enclosure [0 eliminates the need for individual or separate oil sump separator, eliminates the need for a sound muffler or a separate heat exchanger, and lessens the size, weight and cost of the hermetic unit.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

l. A-hermetic rotary helical screw compressor comprising:

a closed, vertically oriented generally cylindrical outer enclosure,

an inner cylindrical housing concentrically fixed within said outer enclosure and forming with said outer enclosure a first sealed chamber therebetween,

said inner housing including an upper compressor discharge housing fluid sealed from and overlying a lower compressor inlet housing, said upper compressor discharge housing forming a second chamber, and

said lower compressor inlet housing forming a third chamber sealed from said first and second chambers,

a compressor inlet tube extending inwardly through said outer enclosure wall and through said lower compressor inlet housing and opening up into said third chamber,

intermeshed helical screw rotors rotatably supported within said lower compressor housing and in fluid communication with said inlet tube for compressing a working fluid supplied to said inlet tube,

a compressor discharge passage fluid connecting the upper end of said first chamber to the lower end of said second chamber,

an electric drive motor coaxially supported within said upper compressor discharge housing above said compressor discharge passage, and including a fixed stator and a concentric rotor rotatably positioned within the same,

a quantity of oil provided within said outer enclosure with the bottom of said outer enclosure forming an oil sump,

an oil pump within said outer enclosure in fluid communication with said sump,

means for delivering oil under pressure from said pump to said screw compressor screw rotors for lubrication and mixing with said compressor working fluid passing therethrough,

a first axial fluid passage means within said motor for passing compressed working fluid and entrained oil ll axially upward to cool the motor and for impingement against the upper end of compressor discharge housing,

second axial fluid passage means within said motor for passing said compressor discharge and entrained oil axially downward to further cool said motor,

and radial passage means fluid connected to the sec ond axial passage means for directing the compressed working fluid and the entrained oil radially outwards of said upper compressor discharge housing and into said first chamber for gravity separation of said oil from said compressed working fluid and return to said sump.

2. The hermetic rotary helical screw compressor as claimed in claim 1, wherein: said first axial passage means comprises ducts formed within said rotor extending upwardly from one end face to the other such that rotation of said rotor provides a swirling action to the compressed gas and the entrained oil such that some separation of oil from the gas occurs centrifugally by contact of the gas with the upper end of the compressor discharge housing.

3. The hermetic rotary helical screw compressor as claimed in claim 2. wherein: said second axial passage means comprises ducts at least partially defined by said stator and extending downwardly from the upper end face of the stator but terminating short of the lower end face thereof.

4. The hermetic rotary helical screw compressor as claimed in claim 2, wherein: said first fluid passage means further comprises the annular air gap between the concentrically positioned rotor and stator.

5. The hermetic rotaty helical screw compressor as claimed in claim 3, wherein: said first fluid passage means further comprises the annular air gap between the concentrically positioned rotor and stator.

6. The hermetic rotary helical screw compressor as claimed in claim 3, wherein: said radial passage means comprise a plurality of circumferentially spaced radial openings within said upper compressor discharge hous- 12 ing. intersecting said circumferentially spaced axial ducts within said stator.

7. The hermetic rotary helical screw compressor as claimed in claim 5. wherein: said radial passage means comprise a plurality of circumferentially spaced radial openings within said upper compressor discharge hous ing. intersecting said circumferentially spaced axial duets within said stator.

8. The hermetic rotary helical screw compressor as claimed in claim 6. wherein: said radial opening means are canted to permit the gaseous compressor discharge working fluid and the entrained oil to be discharged generally tangential to the inner wall of the outer enclosure so as to sweep the inner sidewall of the enclosure circumferentially and to deposit the entrained oil thereon.

9. The hermetic rotary helical screw compressor as claimed in claim 6, wherein: said radial passage means comprise a plurality of nozzles fluid coupled to the discharge sides of said radial opening within said compressor outlet housing with the discharge end of said nozzle opening into said first chamber so as to discharge compressed working fluid and entrained oil in a direction corresponding to the direction of rotation of said motor rotor.

10. The hermetic rotary helical screw compressor as claimed in claim 9, wherein said discharge gas nozzles comprise short elbow tubes having right angle portions including a first radial portion coaxial with the radial openings within the upper compressor discharge housing and secured to the outside of said housing in axial alignment with said openings. and a second circumferential portion which extends generally tangential to the inner periphery of said upper compressor discharge housing and spaced therefrom.

11. The hermetic rotary helical screw compressor as claimed in claim 1, wherein: said outer enclosure consists'of upper and lower partially nested enclosure sections which are welded circumferentially at their exterior juncture line to permit ready separation of the enclosure sections and access to the interior of the hermetic screw compressor.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT N0. 1 3,922,114

DATED 1 November 25, 1975 INV ENTOR( Clark B. Hamilton et al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Colunm 10, in claim 1, line 19 of claim 1 (line 44 of column 10) after "opening" delete [up] Column 10, in claim 1, line 26 of claim 1 (line 51 of column 10) after "said" delete [first] and insert third Signed and Scaled this Amu:

RUTH C. MASON C. MARSHALL Arresting Officer ANN (ommiuiuner ofParerm and Trademark:

Claims

1. A hermetic rotary helical screw compressor comprising: a closed, vertically oriented generally cylindrical outer enclosure, an inner cylindrical housing concentrically fixed within said outer enclosure and forming with said outer enclosure a first sealed chamber therebetween, said inner housing including an upper compressor discharge housing fluid sealed from and overlying a lower compressor inlet housing, said upper compressor discharge housing forming a second chamber, and said lower compressor inlet housing forming a third chamber sealed from said first and second chambers, a compressor inlet tube extending inwardly through said outer enclosure wall and through said lower compressor inlet housing and opening up into said third chamber, intermeshed helical screw rotors rotatably supported within said lower compressor housing and in fluid communication with said inlet tube for compressing a working fluid supplied to said inlet tube, a compressor discharge passage fluid connecting the upper end of said first chamber to the lower end of said second chamber, an electric drive motor coaxially supported within said upper compressor discharge housing above said compressor discharge passage, and including a fixed stator and a concentric rotor rotatably positioned within the same, a qUantity of oil provided within said outer enclosure with the bottom of said outer enclosure forming an oil sump, an oil pump within said outer enclosure in fluid communication with said sump, means for delivering oil under pressure from said pump to said screw compressor screw rotors for lubrication and mixing with said compressor working fluid passing therethrough, a first axial fluid passage means within said motor for passing compressed working fluid and entrained oil axially upward to cool the motor and for impingement against the upper end of compressor discharge housing, second axial fluid passage means within said motor for passing said compressor discharge and entrained oil axially downward to further cool said motor, and radial passage means fluid connected to the second axial passage means for directing the compressed working fluid and the entrained oil radially outwards of said upper compressor discharge housing and into said first chamber for gravity separation of said oil from said compressed working fluid and return to said sump.

3. The hermetic rotary helical screw compressor as claimed in claim 2, wherein: said second axial passage means comprises ducts at least partially defined by said stator and extending downwardly from the upper end face of the stator but terminating short of the lower end face thereof.

6. The hermetic rotary helical screw compressor as claimed in claim 3, wherein: said radial passage means comprise a plurality of circumferentially spaced radial openings within said upper compressor discharge housing, intersecting said circumferentially spaced axial ducts within said stator.

7. The hermetic rotary helical screw compressor as claimed in claim 5, wherein: said radial passage means comprise a plurality of circumferentially spaced radial openings within said upper compressor discharge housing, intersecting said circumferentially spaced axial ducts within said stator.

8. The hermetic rotary helical screw compressor as claimed in claim 6, wherein: said radial opening means are canted to permit the gaseous compressor discharge working fluid and the entrained oil to be discharged generally tangential to the inner wall of the outer enclosure so as to sweep the inner sidewall of the enclosure circumferentially and to deposit the entrained oil thereon.

10. The hermetic rotary helical screw compressor as claimed in claim 9, wherein said discharge gas nozzles comprise short elbow tubes having right angle portions including a first radial portion coaxial with the radial openings within the upper compressor discharge housing and secured to the outside of said housing in axial alignment with said openings, and a second Circumferential portion which extends generally tangential to the inner periphery of said upper compressor discharge housing and spaced therefrom.

11. The hermetic rotary helical screw compressor as claimed in claim 1, wherein: said outer enclosure consists of upper and lower partially nested, enclosure sections which are welded circumferentially at their exterior juncture line to permit ready separation of the enclosure sections and access to the interior of the hermetic screw compressor.