US2830755A - Rotary compressor - Google Patents

Description

April 15, 1958 J. H. ANDERSON I 2,830,755

ROTARY COMPRESSOR- Filed May 23. 1955 4 Sheets-Sheet l Fiel 15 INVENT OR J ames HAnderson ATTORNEYS April 15, 1958 Filed May 23. 1955 114 fig 107 4 Sheets-Sheet 2 Fie.2

v INVENTOR James H.And.erson ATTORNEYS United States Patent ROTARY COMPRESSOR James H. Anderson, Spring Garden Township, York County, Pa., assignor, by mesne assignments, to Borg- Warner Corporation, Chicago, Ill., a corporation of Illinois Application May 23, 1955, Serial No. 510,439

13 Claims. (Cl. 230-132) This invention relates to air and gas pumps and affords a single stage centrifugal compressor characterized by improved lubrication and cooling, ease of assembly and maintenance, and excellent efiiciency.

Centrifugal gas compressors operate at high rotative speeds and develop considerable heat from friction and from thermodynamic reactions, so that cooling and lubrication are problems of major importance. According to the invention, a considerable quantity of lubricating oil is circulated through the compressor and its bearings and through an oil cooler, .so that the development of heat is resisted and such as is developed is rejected through the cooler. The prime means of circulating the oil is a centrifugal pump of very simple form, so built into the compressor as to entail no penalty in assembling and servicing operations. Such a pump unlike a positive displacement pump, develops a pressure proportional to its rotary speed, and thus has a desirable self-regulating characteristic.

important novelty resides in the way that the compressor housing is divided transversely of the shaft axis into two major components. The first of these includes the supporting base, the major portion of the volute and the gas inlet and discharge connections and a mounting seat which supports and centers. the second major component. This second major component is a machine assembly comprisingthe remainder of the volute, the shaft and shaft bearings, the impeller, the oil pump, storage spaces for oil and substantially all pressure and flow connections for oil.

As a practical matter, the division is between parts which in the main are fixed, and are suited to be permanently connected in a circuit such as a refrigerative circuit, and parts which make up the moving machinery of the compressor and are supported in proper functional relation by the removable part of the housing.

A useful possibility is that a user of one or more compressors may have, and keep in primerunning order, a spare one of the second major components ready for quick assembly with a first major component, thus reducing down periods for repairs to the practicable minimum.

In any event, the (hive shaft isreadily disconnected and removed, and its removal afiords space for removal of said second major component. Hence the machine does not require an objectionable amount of space.

A feature of the invention resides in arrangements which alford a higher vapor pressure on oil in the collecting sump than on oil in the supply reservoir, so that the oil feeds from the sump to the supply reservoir despite the higher elevation of said reservoir. This eliminates need for a pump customarily used.

While it is not necessary to do so, it is considered desirable to construct the oil filter and the oil cooler as separate units capable of independent selection, servicing and replacement. This entails the use of external tubular connections but the connections are small and simple and their use involves. no adverse factors.

The general nature of the invention having been set forth, a preferred embodiment will now be described with reference to the accompanying drawings, to disclose fully the features already mentioned as well as features of advantage which can be better appreciated after a detailed description.

In the drawings:

Figure l is an end view of the compressor, i. e. a view looking to the right in Figure 2.

Figure 2 is a vertical axial section of the compressor looking to the left in Figure l. The shaft and a few shaft-carried components are shown in elevation. The porting is diagrammatic to the extent that the ports are all drawn as if they lay in the plane of section.

Figure 3 is a fragmentary view similar to a portion of Figure 2, but drawn on a larger scale. Certain shaftcarried elements shown in elevation in Figure 2 are here shown in axial section.

Figure 4 is a fragmentary section on the line 4-4 of Figure 3 and on the same scale.

Figure 5 is a left end view of the impeller journal, oil pump rotor and ratchet ring, looking to the right with respect to Figure 3.

Figure 6 is a fragmentary view of the left hub face of the bearing retaining plate (as shown in Figure 3).

Statements of direction, when made without qualification, refer to Figure 2.

As best shown in Figures 1 and 2, the volute 11 is supported on integral feet 12 which are bolted to the foundation (not shown). A flanged discharge connection is shown at 13. A circular machine housing 14, which is a cored casting hereinafter described in detail, has a flange 15 which seats on and is bolted to the mounting rim 16, so that the volute 11 and housing 14 are sealed together in precise coaxial relation, and together define the volute chamber 17 and difiusing throat 18 Whose general form follows known practice in the art.

On the end remote from rim 16 the volute 11 has an integral hollow conical extension 19 which encloses the inlet passage and terminates in an in-turned flange 21 affording an inlet-connection. Engaging and centered by flange 21 and by an annular seat 22 formed within extension 19 adjacent the inner periphery of throat 18, is a streamlined entrance throat member 23. This has an annular shoulder which engages flange 21, is held against rotation by a pin 24 which engages a slot in flange 21 (see Figure 2.), and is locked in place by a snap ring 25, which engages a slot in seat 22. As clearly shown in Figure 2, the throat member 23 flares towards its opposite ends, and is shouldered at 26 where it encircles the entrance eye. of the impeller and affords smooth flow thereinto. The shouldering at 26 and the seal 27, there located, are so clearly shown in Figure 2 that detailed description is unnecessary.

In the entrance throat 23 are mounted a plurality of simultaneously adjustable guide vanes. These are sector shaped vanes 28, streamlined in cross section and rotatable about axes whichlie in planes radial to the throat member. Each vane is carried by a gudgeon 29 journalled in the throat member 23. Each gudgeon carries a bevel pinion 31 all of which areidenti-cal and mesh with a ring gear 32 which encircles the throat member 23. The pinions are so meshed with the ring gear as to give all the vanes the same helical pitch and this pitch may be adjusted by turning the ring gear 32. Conventional means for setting the ring gear would be used, but as this detail is not claimed, illustration is deemed superfluous.

The parts above described, including the housing 14, are the normally static elements of the machine. The housing 14 and the machine components enclosed or supported by housing 14 will next be described, after which the oil flow porting can be explained.

impeller shaft, and extends across reservoir 37 nearly to the plane of the inner face of the right hand wall 41 as defined at the periphery of a circular seat 42 surrounding .an opening into reservoir 37.

The right hand end of hub 39 has a shallow counterbore 43 which receives and centers the thrust bearing disc J .44. The thrust bearing formed on this disc may take .any preferred form, and resists axial shifting of the impeller shaft to the right. The thrust bearing disc is pressed into the counter-bore 43 by an elastic disc which carries a second radial bearing for the impeller shaft. This elastic disc comprises, in one piece, a bored hub 45 which sustains the plain bearing bushing 46 for the impeller shaft, and seats against the thrust bearing disc 43, a peripheral flange 47 which fits into seat 42, and an elastic web 48 connecting hub 45 and flange 47.

The outer face of the right-hand wall 41 has concentric counter-bores, a shallow one at 50 and a much deeper one at 49. These receive and center a retaining plate 51 having a peripheral rim 52. This plate seats on a gasket 53 and is held by machine screws 54. The flange 47 is so dimensioned that when plate 51 is fixed in place, the web 48 is elastically stressed so that hub 45 urges thrust bear- ;ing disc 44 into counter-bore 43 in the end of hub 39. The parts 44 and 45 are held against rotary motion by a stake 55.

The bearing bushing 46 is flanged and is pressed to place in hub 45. As is best shown in Figure 6 a slot 56 is milled in hub 45 and connects the space at the left end of bushing 46 with an oil port 57 drilled through disc 44. This is part of an oil path to bearing bushing 46.

The left face of retaining plate 51 is recessed, so that it and flange 47 on the elastic disc afford a space 58 which is drained to sump 36 by communicating drilled ports in parts 14 and 51. These are indicated in Figures 2 and 3 by the numeral 59. To divert from the impeller shaft any oil which may drain down the left face of plate 51, this face has saw tooth grooves 61. These are simply circular grooves cut into the plate 51 and concentric with the shaft axis. They act as collecting gutters.

For reasons which will appear in connection with operation, it is desired to maintain above lubricating oil in reservoir 37 a vapor pressure which is intermediate the suction pressure and the discharge pressure of the compressor. Means for accomplishing this are shown schematically in Figure 2. The desired oil level in reservoir 37 is indicated by the broken line LL. A tube 62 leads to the interior of inlet throat 23 from a fitting 63 which is screwed into a port leading tothe gas space above line LL in reservoir 37. The fitting 63 encloses a spring loaded relief valve 64 with a restricted port drilled through it. In a refrigerant compressor some refrigerant is dissolved or occluded in the oil and tends to boil off under operating conditions if temperature is raised, or pressure is reduced (or if both these effects are present). Suction pressure being low, the relief valve controls outflow of vapor to maintain in reservoir 37 a definite vapor pressure higher than the existing suction pressure. When the compressor stops, the restricted port permits pressure equalization to occur.

The shrouded vane impeller generally indicated by the numeral 65 is mounted coaxially on the end of a large rotary shaft member which has a journal 66 turning in bearingbushing 46 and spaced from this a second journal 67 turning in the bearing bushing 68 in hub 39. Between the two journals there is a larger cylindrical portion 69 which is ported to serve as the impeller of a centrifugal oil pump and a somewhat larger portionll atranged" to 4 operate a valve and also as means to inhibit reverse rotation.

The hub of the impeller is clamped against the end of the shaft adjacent journal 66 by a heavy machine screw 72 whose head is confined in a centering bushing 73.

A running seal coacting with hub 45 is afforded by the seal ring 74 which is axially shiftable on journal 66 and is keyed thereto by ball key 75. A reaction ring 76 engages impeller 65 and is sealed to journal 66 by the O-ring 77. A spring 78 urges the parts 74 and 76 apart, and so develops the necessary sealing pressure. A seal assembly generally indicated by the numeral 79 is interposed between the members 76 and 51.

The spring-loaded seal ring 74 has a double function, for it is both a seal-and a check valve.. When the compressor is shut down it is spring closed against flow from reservoir 37 past bearing 46 and thence through space 58 and drain passage 59 to sump 36.

When the compressor runs, compressed vapor, at or somewhat below compressor discharge pressure flows at a limited rate between the left-hand shroud plate of impeller 65 and the plate 51, past seal 79, to space 58 where it meets some draining oil, and passes thence with the oil via passage 59 to sump 36.

The effect is to develop pressure in sump 36 and this elevated pressure with the depression of vapor pressure in reservoir 37 caused by connection 62, 64 affords a pressure differential effective to return oil from the sump 36 to reservoir 37, as will be later described in greater detail.

The housing 14 and its hub 39 have a coaxial bore 82 and counter-bore 81 to receive the flanged bushing 68 which is retained by a snap ring 83. A groove 84 encircling bore 82 is provided to supply oil to journal 67 I through oil passages 85 drilled through the bearing bushing 68.

To the right of bearing bushing 68 the bore 82 serves as an inlet passage for the pump impeller 69. As best shown in Figures 3 and 5 the impeller 69 has an annular entrance groove 86, tangent to which are four discharge orifices 87. These lead to an oiftake groove 88. A running seal 89 encircles the right end portion of pump rotor rotation when the compressor is shut down. Back flow of compressed vapor tends to cause such reverse rotation. The pawl 93 is pivoted at 94 in hub 39 and lightly biased to engage by a leaf spring 95. When the compressor runs, and space 91 is under pressure, the pawl acts as a valve and closes port 96.

The pawl 93 performs a third function. The impeller is driven through a slender drive-shaft 98 which is shouldered at 99 and beyond the shoulder is provided with left-hand double threads 101. One of the first steps in disassembling the compressor is to unscrew shaft 98. The ratchet then serves to prevent rotation of the impeller journal unit.

To prevent leakage from the end of counter-bore 81 there is provided a closure cap 102 with an inward projecting sleeve 103. One component 104 of a running seal encircles and is sealed to shaft 98 by an O-ring. The other component 105 of the same running seal is sealed by an O-ring to sleeve 103 which it encircles. A spring 106 loads component 105 toward component 104 (see Figure 3).

The tube 107 is a protective enclosure for shaft 98.

The oil circulation can now be traced. When the compressor runs, the oil impeller 69 receives oil from bore 82, to the right of bearing 68 and discharges it under considerable pressure into chamber 88. Thence it flows asset-51s v a pass e 68 and p pe 1 o aadthreushthe fil r 1 e Fi e and m he filt r a p p 1 2- a d branching passage 113 to groove 84 and bearing 68 and through port 57 and channel 56 to bearing 46. In the absence of pressure, seal 74 arrests flow, but. when there is a considerable pressure head on the oil atbearing 46, seal 74 moves back so that some oil discharges to space 58 and flows thence by way of port 59 to sump 36. A dip pipe 116 delivers oil from sump 36 to reservoir 37 under the pressure difierential between the elevated pressure in sump 36 and the reduced pressure in reservoir 37.

Some oil escapes to the right from bearing 68 and returns directly to the pump. Some escapes to the left and flows via passage 114 directly to reservoir 37. This last flow is regulable by a manually adjustable back pressure valve 115 to maintain a pressure above atmospheric in the space around seal members 104, 105sothat iii-leakage of air will not occur.

Thus there is active oil circulation, aside from the fact that the bearings 63 and 4,6 are always submerged in oil.

Some oil circulates through a cooler, which may be of any type. This flow is derived fromthe supply through a branch of passage 113, which enters 55 through 57 and enters space 91 past the thrust bearing. Port96 being closed when the compressor runs, there is active fiow through passage 116 and nozzle 117 which produces a sort of ejector effect on oil in; reservoir 37. Thus a considerable volume flows through line 118 to; and through cooler 119 (which may be a liquid cooled heat exchanger) and thence via line 121 and passage 122. to the pump inlet.

Thus the cooler is located nearthe suction intake of the pump. This is contrary to the usual practice of putting the cooler under discharge oil pressure, and has proved to be advantageous.

The unit 123, interposed between pump discharge 88 and oil reservoir 37, comprises a ball valve 124 which may close against a downward presented upper seat 126 and is sustained by a slotted bushing 125 which is not a valve seat. In starting up with new oil, it first passes air bubbles but soon closes so as not to present a free path for oil flow.

The compressor has been built and extensively tested. Cooling and lubrication are adequate. The connection 62 and valve unit 63 control the rate of boil-off of occluded refrigerant from oil in reservoir 37 so that it will neither cause foaming nor defeat the operation of the oil pump, and yet will be sufficient to free the oil of refrigerant, deliver the refrigerant to the compressor intake and usefully cool the oil. The valve 124 is effective to collect and purge small air bubbles. This occurs during starting up.

Disconnection of shaft )8 and tubular connection 62. are the first step in disassembly. Then the housing 14 is removed, with the whole rotary mechanism of the compressor. Removal of impeller 65 and plate 51 permit removal of the elastic plate and the thrust hearing. The impeller shaft can then be drawn out to the right, bringing the oil pump rotor with it. Thus the oil pump offers no obstacle to assembly and disassembly.

Obviously, minor components such as seals must be removed and replaced in definite sequences, as will be readily understood from the drawings, particularly Figure 3.

The overhung mounting of the shrouded impeller is desirable from the compressor standpoint. The mounting of the oil pump rotor between bearings is desirable from the oil distribution standpoint. It is made practicable by careful selection of the diameters of the bores in hub 39 and by the use of the elastic plate which positions one radial bearing and assists in positioning the related thrust bearing. Use of a rotary oil pump is essential. to th arr m n from. the assem y s andpoin and advantageous from the operating standpoint.

The compressor above described is available for gen.- eral use including compression of permanent gases. However, it was designed for use as the compressor component of refrigerative circuits, and some of its more refined thermodynamic characteristics are particularly useful in compressing the vapors evolved by volatile liquids. Limitation to the refrigerative field is not implied.

What is claimed is:

1. A centrifugal compressor comprising a fixed unit including at least the major portion of a housing including an axial intake connection and a discharge connection; a self sustaining machine unit including a chambered housing capable of assembly with the fixed unit to complete the latter, said chamber housing enclosing any oilcharged reservoir and oil directing passages, and a fixed hub with axial bore; a radial shaft-bearing mounted in said bore and removable through one end thereof; a thrust hearing at the other end of said bore; a retaining plate for said thrust bearing removably mounted at said other end of said bore and carrying a second radial shaft-bearing; a shaft rotatable in said bearings and withdrawable axially from said bore upon removal of said retaining plate; a rotary oil impeller carried by said shaft within said bore and between said radial bearings; an overhung impeller mounted on the end of said shaft in position to receive gas from said intake and discharge it through said discharge connection; and flow defining means whereby said rotary oil impeller is caused to circulate oil from said reservoir to and through said bear ings and back to the reservoir.

2. The combination with the structure of claim 1 of an oil cooler and connections whereby a part of said oil circulated by the oil impeller is caused to follow a circulating path through said cooler.

3. The combination with the structure defined in claim 1, and in which there is a vapor space above the oil in the reservoir, of a restricted flow connection between said vapor space and said intake, whereby said space is maintained by operation of the compressor at a pressure intermediate the intake'and discharge pressures of the compressor.

4. The combination defined in claim 1 in which there is a sump at a level lower than said reservoir and a drain path through which some oil drains from bearing to sump; means affording a riser conduit from near the bottom of the sump to the reservoir, said reservoir having a vapor space above the oil therein; and means afiording a vapor connection from said vapor space to the compressor intake.

5. The combination defined in claim 1 in which there is a sump at a level lower than said reservoir and a drain path through which oil drains from bearings to said sump; means afiording a riser conduit from near the bottom of the sump to the reservoir, said reservoir having a vapor space above the oil therein; means alfording a vapor connection from said vapor space to the compressor intake; and means alfording a restricted path between the sump and the discharge connection of the compressor.

6. A centrifugal compressor for incorporation in a refrigerative or similar circuit comprising a fixed unit including means defining an axial intake, a portion of a volute and a portion of a diffuser leading from the intake to the volute; a machine housing capable of assembly with the fixed unit and including means completing said volute and diffuser, an oil-charged reservoir and oil directing passages, and a hub with axial bore; a radial shaft-bearing mounted in said bore and removable through one end thereof; a thrust hearing at the other end of said bore; a retaining plate for said thrust bearing removably mounted at said other end of said bore and including a second radial shaft-bearing; a shaft rotatable in said enemas 7 bearings and withdrawable axially from said bore upon removal of said retaining plate; a rotary oil impeller carried by said shaft within said bore and between said radial bearings; an overhung shrouded impeller mounted on the end ofsaid shaft in position to receive gas from said intake and discharge it into said diffuser; and connections whereby said rotary oil impeller circulates oil from said reservoir to and through said bearings and back to the reservoir.

7. In a centrifugal compressor the combination of a housing having an inlet and an outlet for gaseous medium and enclosing a working space for the impeller of a centrifugal compressor, said space communicating with said inlet and with'said outlet, a working space for the impeller-of a centrifugal" oil pump, and an oil reservoir; shaft bearings sustained within said housing; a shaft sustained by said bearings; a centrifugal oil pump impeller and a compressor impeller located in the corresponding working spaces and driven by said shaft; and means defining oil'fiow passages for directing oil from the reservoir through said centrifugal oil pump to said shaft bearings andfrom the bearings through respective branch passages, part through one branch passage to the reservoir and part through another branch passage past said reservoir to the intake of said pump.

8. The combination of the structure defined in claim 7, with an oil cooler interposed in that branch passage which leads to the intake of the oil pump.

9. The combination of the structure defined in claim 7 with an ejector and an oil cooler, the ejector and cooler being interposed in the order stated in that branch passage which leads to the intake of the oil pump, said ejector being activated by oil flowing through the other of said branch passages, the ejector being connected to draw oil from the reservoir and deliver it through the cooler.

10. The combination of the structure defined in claim 7 with an oil seal for the shaft submerged in oil in a part of that branch passage which leads to said reservoir; and back pressure means located in said branch passage between said shaft seal and said reservoir whereby superatmospheric pressure is maintained on the oil submerging said seal, and entrance of atmospheric air through the seal is resisted.

11'. The combination of the structure defined in claim 7 with an oil sump' enclosed by said housing and at a lower level than said reservoir, and means aifording an oil flow path from the oil space in the sump to the oil reservoir; means afiording a vapor path from the compressor outlet to the sump; and a connection affording a flow path from the vapor filled space in the reservoir to the compressor inlet. 12. The combination of the structure defined in claim 7 with an oil sump enclosed by said housing and at a lower level than said reservoir; means affording a restricted oil path from one of said bearings to the sump; means affording a flow path from the oil space in the sump to the oil reservoir; means affording a vapor path from the compressor outlet to the sump; and means affording a suction connection for leading vapor from said reservoir to the compressor inlet.

13. In a centrifugal compressor the combination of a housing having an inlet and an outlet for gaseous medium and enclosing a working space for the impeller of a centrifugal compressor, said space communicating with said inlet and with said outlet, 2. working space for the impeller of a centrifugal oil pump, and an oil reservoir; shaft bearings sustained within said housing; a shaft sustained by said bearings; a centrifugal oil pump impeller and a compressor impeller located in the corresponding working spaces and driven by said shaft; an ejector connected to withdraw oil from said reservoir, and having a propelling jet nozzle; an oil cooler affording a flow path from the ejector to the centrifugal pump intake; and means affording two flow paths from the centrifugal pump discharge, one thereof leading through one bearing to the reservoir and the other leading through the other bearing to the propelling jet nozzle of the ejector.

References Cited in the file of this patent UNITED STATES PATENTS 2,102,345 Wishart Dec. 14, 1937 2,234,777 Pufier Mar. 11, 1941 2,323,802 Dick et al. July 6, 1943 2,400,711 Ponomareif et al May 21, 1946

Images