US3069173A - Sealing means for compressor drive shaft - Google Patents

Description

Dec. 18,` 1962 s. G. BEST SEALING MEANS FOR COMPRESSOR DRIVE SHAFT Filed Dec. 16, 1959 3,569,173 SEALllNG MEANS FR CMPRESSGR DRVE SHAFT t Stanley G. Best, Manchester, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Filed Dec. 16, 1959, Ser. No. 859,973 9 Claims. (Cl. 277-3) This invention relates to sealing means for preventing fluid leakage along a rotatable shaft and, more speelfically, to sealing means particularly adapted for preventing gas flow or leakage along the drive shaft of a compressor adapted to handle fluid in a gaseous state.

It is the general object of the invention to provide sealing means of the type mentioned which is capable of a more positive sealing action than has been obtainable heretofore with sealing means used for a similar purpose and which is yet free of excessive friction and other undesirable characteristics in its operation.

The drawing shows two embodiments of the invention and such embodiments will be described, but it will be understood that various changes may be made from the construction disclosed, and that the drawing and description are not to be construed as defining or limiting the scope of the invention, the claims forming a part of this specification being relied upon for that purpose.

Of the drawing:

FIG. l is a schematic illustration of a compressor driven by an air turbine and equipped with a preferred form of the sealing means of the present invention;

FIG. 2 .is a schematic illustration of an evacuating means and a pressure regulating valve means utilized in an alternative form of the sealing means of the invention; and

FIG. 3 is a schematic illustration of a portion of another alternative form of the invention.

A compressor indicated generally at in FIG. 1 of the drawing is employed in an aircraft air conditioning system and, more particularly, in a refrigeration system forming a part of the aircraft air conditioning system. The said compressor handles a refrigerant, such as one of the freons, in a gaseous state, the refrigerant being introduced to the compressor through an inlet conduit 12 and discharged therefrom at increased pressure and temperature through a discharge conduit 14. The compressor 10 is driven by an air turbine indicated generally at 16 and connected with the compressor by a drive shaft 13. The turbine 16 is supplied with propellant air through an inlet conduit 2t) and is provided with an exhaust or discharge conduit 22 which carries off the spent propellent air.

While the sealing means of the present invention is not limited in its application to refrigerant compressors, its advantages are particularly well illustrated in a consideration of its use with such a compressor. The freon gas or other refrigerant passing through the refrigerant compressor in a refrigeration system must not be permitted to escape outwardly from the compressor along the compressor drive shaft in significant quantity. Such refrigeration systems are usually of the closed cycle type and contain a given quantity of freon gas or other refrigerant. Any loss of the refrigerant, as by escape along the drive shaft of the refrigerant compressor, results in a reduction in the efficiency of operation of the refrigeration system. Further, .air or other gas must not be permitted to flow inwardly along the compressor drive shaft so as to become intermixed with the freon or other refrigerant handled by the compressor. Pollution of the freon or other refrigerant in the refrigeration system by the introduction and intermixing of air or other gas therewlth can be expected to result in a reduction in i United States Patent O 3,569,173 Patented Bec. 18, 1962 refrigeration system eiiciency and in other undesirable effects.

From the foregoing, it will be apparent that a refrigerant compressor, such as the compressor 10, must be equipped with sealing means capable of positive sealing action in preventing gas ow or leakage both outwardly and inwardly along the compressor drive shaft. The sealing means of the present invention provides the required positive sealing action without introducing excessive friction. Generally speaking, the sealing means of the invention comprises a sealing device adapted to restrict the ow of gas along the compressor drive shaft and means defining iirst and second annular chambers disposed respectively on opposite or inboard and outboard sides or" said sealing device. The inboard chamber receives the fluid to be sealed (Le. compressor discharge gas) and the outboard chamber is connected by a suitable fluid passageway with a source of fluid and preferably a gas under pressure. A pressure regulating valve means included in the sealing means is operable to maintain substantially a zero pressure difference between the first and second or inboard and outboard chambers and across the sealing device therebetween. With substantially a zero pressure difference thereacross, the sealing device is able to provide positive sealing action with substantially no gas flow or leakage either inwardly or outwardly along the drive shaft. Moreover, the sealing device does not have to be of an extremely tight fitting type with high friction characteristics in order to provide the necessary positive sealing action.

ln FiG. 1 of the drawing it will 'oe observed that the compressor l@ is provided with a housing or casing 24 which is connected with the inlet and discharge conduits i2 and 14 and which has a fluid tight connection with an inner end portion 26 of a drive shaft housing or sleeve 28. The outer end portion 3i) of the shaft housing or sleeve 28 has fluid tight connection with a turbine housing or casing 32. As shown, the housing or sleeve 28 is generally cylindrical and its inner end portion 26 is of substantially larger diameter than the remaining portion thereof. An annular chamber 34 defined within the inner end portion 26 of the sleeve constitutes the aforementioned first or inboard annular chamber and said chamber is adapted to receive compressor discharge gas as will be explained hereinbelow.

The rst or inboard chamber 34 may receive a flow of compressor discharge gas in a comparatively unrestricted manner or, the flow of compressor discharge to the said chamber may be restricted. In accordance with the presently preferred practice, the flow of compressor discharge gas or refrigerant to the chamber 34 is restricted by a first continuously operable sealing device indicated generally at 36 and comprising an annular sealing element 38. The annular sealing element 33 may take various forms within the scope of the invention, but is preferably of the labyrinth type and is shown supported by a radially inwardly extending annular flange 40 formed integrally at the inner end of the end portion 26 of the sleeve 28. The element 38 continuously engages the outer periphery of an axially extending annular flange 42 formed integrally on the rear face of a rotor 4.4 of the compressor 10.

It will be apparent that gaseous refrigerant discharged from the compressor 1t) will flow radially inwardly along the rear face of the rotor 44 to the area adjacent the inner side of the labyrinth seal 38. The flow of gaseous refrigerant into the chamber 34 or outwardly along the shaft 18 is restricted bythe seal 38, but there is a signicant flow or leakage past the said seal and into said chamber. Obviously, refrigerant pressure in the chamber 34 will increase substantially to the compressor discharge level with the passage of time if there is no avenue of escape in the chamber for the gaseous refrigerant. While the invention is not so limited, such pressure build up of gaseous refrigerant in the chamber 34 is not permitted in the preferred form of sealing means shown in FIG. 1. Means defining a fiuid passageway connecting the chamber 34 with the inlet side of the compressor Si@ is provided and, as shown, said means comprises a conduit 46 which extends between said chamber and the compressor inlet conduit 12. The capacity of the conduit 46 is sufiicient to provide for a refrigerant pressure in the chamber 34 substantially equal to compressor inlet pressure. That is, the said conduit can accommodate sufficient flow of gaseous refrigerant from the chamber 34 to the inlet side of the compressor to prevent pressure build up in said chamber as a result of the continuing introduction of compressor discharge refrigerant to the chamber past the labyrinth seal 38.

Preferably but not necessarily, a static sealing device is provided to prevent the flow of gas along the drive shaft 18 when the said shaft is at rest. is indicated generally at 48 and is shown located within the inboard chamber 34. The construction and operation of said device will be explained fully hereinafter and for the present, it is only necessary to observe that the said device is inoperative during rotation of the drive shaft 18 and that gaseous refrigerant in the chamber 34 is permitted to flow outwardly along the drive shaft 18 past the device during such periods of shaft rotation.

Disposed outwardly of the static sealing device 48 along the shaft 18 is a second continuously operable sealing device indicated generally at 50. The said continuously operable sealing device constitutes the aforementioned sealing device across which a substantially zero pressure difference is maintained. Preferably and as shown, the sealing device f! comprises an annular sealing element 52 which may be a carbon or graphite ring seal of the well known type. The sealing device also comprises a seal support ring 54 which is secured to the sleeve 28 and which supports the sealing element 52 in engagement with the outer radial face of an annular flange 56 formed on the compressor drive shaft 18. Spring means (not shown) may be incorporated to bias the element 52 into engagement with the face of the flange 56 in accordance with conventional practice. With substantially a zero pressure difference provided across the sealing element 52 in a manner to be described, it will ybe seen that a positive sealing action with substantially no gas fiow along the shaft in either direction past said element can be effected without an excessively tight and high friction fit between the element and the iiange 56.

An annular chamber 58 is defined within the sleeve 28 outwardly of the continuously operable sealing device 5f) and constitutes the aforementioned outboard chamber in which a gas pressure is regulated in order to maintain substantially a zero pressure difference across said sealing device. The chamber 58 extends outwardly from the sealing device 50 about the shaft 18 and within the sleeve 28 and is further defined by a central portion of a rotor 60 of the turbine 16. Disposed within the chamber 58 and supported by the sleeve 28 are axially spaced inner and outer bearing units 62, 62 which rotatably support the compressor drive shaft 18. Outwardly of the outer bearing unit 62, the shaft 18 is provided with an integrally formed annular flange 64 and associated with said fiange is a third continuously operable sealing device 66. The sealing device 66 is shown as comprising a support ring 68 which is secured to the sleeve 18 and which carries an annular sealing element 7 t) which may be a spring loaded carbon or graphite ring seal. The sealing element 70 engages the outer radial face of the annular flange 64 and restricts gas flow along the shaft 18 for a purpose to be set forth more fully hereinbelow. Outwardly of the sealing device 68, the sleeve 18 supports an annular sealing element 72 which may be of the labyrinth type as shown and which engages the outer periphery of an axially extending annular ange Y74 formed on the turbine rotor 60.

Such a sealing device It will be apparent that a gas under pressure may be introduced to the outboard chamber 58 and it will be further apparent that the pressure of the gas may be regulated to substantially equal the pressure of the gaseous refrigerant in the inboard chamber 34 whereby to provide substantially a zero pressure difference across the continuously operable sealing device Sti. As mentioned, a regulating valve means for controlling pressure in the outboard chamber 58 is provided and said chamber is connected with a source of gas under pressure by suitable fluid passageway means. In the preferred form of sealing means shown in FIG. l, a conduit 76 communicates with the outboard chamber 58 and extends therefrom to a pressure regulating valve indicated generally at 78. The pressure regulating valve 78 is connected with a supply conduit 8f) which communicates with a source of air or other gas under pressure (not shown). Also connected with the pressure regulating valve 7 S is a conduit 82 which extends therefrom to the aforementioned conduit 46 and which is thus indirectly connected with the inboard chamber 34?.

As shown, the pressure regulating valve 78 comprises a valve member 84 of the poppet type which is movable in one and an opposite direction (rightwardly and leftwardly as shown) to vary the effective area or opening of an orifice 86. The orice 86 is defined at the free end of the supply conduit and within a valve chamber 88 which communicates with the conduit 76. Thus, movement of the poppet valve 84 in said one and opposite directions is effective to vary the fiow of air from the conduit 88 to the valve chamber 88, the conduit 76, and the outboard chamber 58. A valve stem 90 connected at one end to the poppet valve 8d has its opposite end connected to a valve control means comprising a bellows 92 disposed within the valve chamber S8. The bellows 92 receives gaseous refrigerant from the inboard chamber 34 through the conduits 46 and 82 for action on its inner surfaces, the outer surfaces of said bellows being acted on by air in the valve chamber 88 at a pressure substantially equal to the pressure of the air in the outboard chamber 58.

From the foregoing, it will be apparent that the poppet valve 84 will be moved relative to the orifice 86 as ren quired to provide for substantially zero pressure difference between the outboard chamber 58 and the inboard chamber 34 and across the continuously operable sealing device 5t). If the pressure of the gaseous refrigerant in the inboard chamber 34 exceeds the air pressure in the outboard chamber 58, the resultant pressure forces on the regulating valve bellows 92 will cause the said bellows to expand. Expansion of the bellows 92 will result in rightward movement of the poppet valve 84 and an increased effective opening of the orifice 86. An increase in the flow of pressurized air through the valve chamber 88 and the conduit 76 to the outboard chamber 58 will result and the air pressure in said chamber will be increased to equal the pressure of the gaseous refrigerant in the chamber 34. Conversely, if the air pressure in the outboard chamber 58 exceeds the pressure of the gaseous refrigerant in the inboard chamber 34, the valve bellows 92 will collapse moving the poppet valve 84 leftwardly and reducing the effective opening of the orifice 86. This will result in a decreased ow of pressurized air to the outboard chamber 58 and the pressure in said chamber will be reduced to equal the pressure of the gaseous refrigerant in the inboard chamber 34.

It will be observed that the pressurized air within the outboard chamber 58 can only escape from the said chamber past the labyrinth seal 72 4at the outer end of the sleeve 28. It can be expected that only a relatively small flow of air past the seal 72 will occur. Thus, the flow of pressurized air through the regulator valve 78 to the outboard chamber 58 will be slight and the said poppet valve, for yall practical purposes, will completely close the orifice 86 and terminate air ow therethrough when the regulator valve is operating Ito reduce air pressure within the outboard chamber 58. With the poppet valve 84 closing the orifice 86, the leakage flow outwardly past the labyrinth seal 72 results in the necessary reduction in the air pressure in the outboard chamber 58 and it is to be noted that air can be expected to flow from the inner to the outer end portion of the said chamber toward said labyrinth seal. That is, pressurized air in the inner end portion of the chamber S8 can be expected to flow past the outer bearing unit 62 and the sealing device 66 toward the labyrinth seal 72. Such air flow past the outer bearing unit 62 may have detrimental effects on said bearing unit particularly with respect to its lubrication and it is therefore the presently preferred practice to prevent the flow of air over the outer bearing unit in the manner described hereinbelow.

A bypass conduit 94 is provided `and extends between the conduit 76 and the outer end portion of the chamber 58. Said bypass conduit communicates with the chamber 58 outwardly `of the aforementioned sealing device 66 and the outer bearing unit 62 and provides an alternative path for pressurized air flowing from the inner to the outer end portion of the chamber 58 whereby the air is not required to flo-w past the said outer bearing unit and sealing device. The resistance to air flow provided by the sealing device 66 is substantially greater than the resistance encountered by the pressurized air in the alternative path through the conduit 76 and the bypass conduit 94. Thus, it can be expected that there will be substantially no air flow past the outer bearing unit 62 and the sealing device 66 and the detrimental effects of air flow past the said bearing unit will be avoided.

The provision of the previously mentioned static sealing device is optional as indicated and, when provided, the said device may take a variety of forms. Obviously, the continuously operable sealing device 50 is relieved of the task o-f static sealing when the sealing device 48 is provided. As a result, said continuously operable sealing device may be specifically designed to provide positive sealing action only during periods of shaft rotation and with substantially a zero pressure difference thereacross. This permits a sealing device design wherein minimum friction is encountered with the desired positive sealing action during drive shaft rotation.

As shown, the static sealing device 48 comprises an annular sealing element 96 which may be a carbon or graphite ring seal. The said sealing element engages the inner radial face of the annular flange 56 on the drive shaft 18 and is carried by a support ring 98 which has one end portion of a bellows 100 secured to its peripheral portion. The other end portion of the bellows 100 is secured to a radial wall 102 of the sleeve 28 yand said bellows cooperates with the support ring 98, said radial wall of the sleeve 28, the support ring 54 of the sealing device 50, and the annular flange 56 on the shaft 18 to define a gas tight passageway 104 which extends between the sealing element 96 and the sealing element 52 of the sealing device 50. It will be observed that gas flow or leakage either inwardly or outwardly along the shaft 18 past its flange S6 can only occur through the passageway 104. The said passageway is closed to gas flow or leakage at its outer end by the annular sealing element 52 during rotation of the shaft 18 in the manner described above. The annular sealing element 96 is adapted to close said passageway to gas flow or leakage at its inner end when the shaft 18 and the compressor 10 are at rest but when said shaft and compressor are rotating, the element 96 is moved out of engagement with the flange 56 and opens the inner end of the passageway 104 to the flow of gas.

A first or outer sleeve 106 of the sealing device 48 is secured to the shaft 1S by means of a key 108 and is adapted to be rotated with said shaft but is movable axially along the shaft, a keyway 110 which receives the keg/,108 being of sufficient length to permit such axial movement. Provided in the sleeve 106 is an annular recess 112 which receives the inner portion of the aforesaid support ring 98. The radial walls of the recess 112 engage the adjacent radial faces of the support ring 98 on axial movement of the sleeve 106 so as to move the said support ring axially with said sleeve. The sleeve 106 is freely rotatable relative to the said support ring, the bellows 100 or preferably other means not shown serving to secure the said ring against rotation.

Spaced axially inwardly along the shaft 18 from the first or outer sleeve 106 is a second or inner sleeve 114 which is connected to the said shaft by a key 116. The inner sleeve 114 is rotatable with the shaft 18 and is fixedly secured against axial movement relative to said shaft by the key 116 and a cooperating keyway 117. A spring 118 disposed about the shaft 18 between the inner and outer sleeves 114 and 106 biases the sleeve 106 outwardly along said shaft whereby to bias the support ring 98 outwardly and urge the annular sea'ing element 96 into engagement with the inner face of the annular flange 56 to close the inner end of the passageway 104.

A centrifugally operable means comprising a flyweight 120 and connected links 122 and 124- urges the sleeve 106 inwardly along the drive shaft 18 whereby to cause the annular sealing element 96 to open the inner end of the passageway 184. The link 122 is pivotally connected to the inner sleeve 114;- at one end and pivotally connected at its opposite end to one end of the l'nk 124, the opposite end of the link 124 being pivotally connected to the outer and axially movable sleeve 106. The flyweight 120 is connected Vto the links 122 and 124 at their pivotal connection with each other and serves to urge their interconnected ends radially outwardly as the shaft 18 is rotated. Thus, the inner end of the link 124 is drawn axially inwardly along the shaft 18 during rotation of said shaft to move the sleeve 106 and Vthe elements supported thereby axially inwardly as described and open the inner end of the passageway 104. Axial flow of gas past the sleeve 106 to said passage- Way inner end may obviously take place either between said sleeve and the shaft 18 or between the sleeve and the aforementioned support ring 98.

From the foregoing, it will be apparent that the annular sealing element 96 is biased into sealing engagement with the annular flange S6 when the shaft 18 is at rest and closes the inner end of the passageway 104. When the shaft 18 is rotated, the sealing element 96 is moved axially inwardly out of engagement with the inner face of the flange 56 to open the passageway 104 by action of the centrifugally operable means comprising the flyweight 120 and the links 122 and 124. Thus, the static sealing device 48 is operable to prevent gas flow or leakage inwardly and outwardly along the shaft 18 when the shaft is at rest, but the said device is inorerative for such purpose when the shaft is rotated. Since the sealing element 96 of said device is disengaged from the flange 56 during rotation of the shaft, frictional Wear of said sealing element is insignificant. Positive sealing action of the element 96 with the flange 56 with substantially no gas leakage or flow along the shaft past said element and flange can be readily provided for by utilizing a biasing spring 118 of substantial strength.

The preferred form of seaing means described above provides positive sealing action with substantially no gas flow or leakage either inwardly or outwardly along a compressor drive shaft during operation of the compressor and also during periods when the compressor is at rest. Moreover, the positive sealing action is obtained without an excessively tight and high friction fit between the sealing element 52 and the drive shaft flange 56 which is continuously engaged by said element. As a result, friction induced wear of the element is reduced and its effective life is substantially increased. The sealing element 96 in the static sealing device 48 can be expected to exhibit excellent wear characteristics in view of the absence of any signiticant rubbing engagement of said element with the shaft ange 56. The remaining sealing elements included in the sealing means are not required to provide positive sealing action and may there fore be designed for low friction characteristics and long life.

The above-mentioned features and advantages of the preferred form of sealing means are particularly desirable in a refrigerant compressor of the type shown. However, the said sealing means has one limitation which may be unacceptable in certain refrigerant compressor installations and in some other installations of the sealing means as well. The regulating valve 78 is incapable of providing air pressure in the outboard chamber 58 which is lower than atmospheric pressure. In certain refrigeration systems, compressor inlet pressure may be reduced to a subatmospherie level and it will be obvious that the pressure in the inboard chamber 34 will be correspondingly reduced. In such event, the air in the outboard chamber 58, at atmospheric pressure or above, might conceivably leak inwardly along the shaft 18 past the sealing device t) due to the pressure difference occurring across said device. As mentioned above, the introduction of air to the freon gas or other refrigerant results in pollution of such gas or refrigerant which may cause an unacceptable reduction in the efiiciency of operation of the refrigeration system.

In FIG. 2 there is shown a pressure regulating valve indicated generally at 126 and an evacuating means indicated generally at 12S. The said pressure regulating valve and evacuating means are adapted for use in an alternative form of the sealing means of the present invention, the said alternative form of the sealing means being particularly adapted to avoid the above-mentioned' limitation of the preferred form of the sealing means. All elements of the alternative form of the sealing means may be identical with those described above in the preferred form of sealing means with the exception of the regulating valve 78. The said regulating valve is replaced in the alternative form of the sealing means by the regulating valve 126 and the evacuating means 128 is added thereto. Accordingly, only the regulating valve 126 and the evacuating means 128 are shown in FIG. 2, a repetitive illustration of the remaining elements of the sealing means being deemed unnecessary.

The regulating valve 126 has an air chamber 13G defined therewithin and a bellows 132 is disposed within said chamber. A conduit 76a communicating with the air chamber 130 of the regulating valve 126 correspo-nds to the conduit 76 of FIG. l and may be similarly connected with the outboard chamber 53 in FIG. l. A conduit 82a communicating with the interior of the bellows 132 corresponds to the conduit 82 in FIG. l and may be similarly connected to the inboard chamber 34. The bellows 132 is operatively connected with a pivotally supported elongated valve member or lever 134 by means of a link 136. Expansion of the bellows 132 pivots the valve member or lever 134 about a pivot or fulcrum 138 in a clockwise direction as shown and results in a decreased effective opening of an associated orifice 149 and an increased effective opening of an associated orifice 142. The orifice 146 is defined at the free end of a conduit 144 which is connected with the evacuating means 128 and the orifice 142 is defined at the free end of a branch conduit 146. The branch conduit 146 extends from a supply conduit 80a which corresponds to the supply conduit 80 in FIG. l and which is similarly connected with a source of air or other gas under pressure.

It will be apparent that the regulating Valve 126 will operate to balance refrigerant gas pressure in the inboard chamber 34 over a range of pressures including subatmospheric pressures. That is, the regulating valve 126 will provide subatmospheric air pressures in the outboard chamber 58 as required to balance and equal subatmospheric refrigerant pressures in the inboard chamber 34 and provide substantially a zero pressure difference across the continuously operable sealing device Sil between said chambers. When the refrigerant pressure in the inboard chamber 34 is above atmospheric pressure, the bellows 132 will expand as shown in FIG. 2 to adjust the position of the valve member or level 134 to reduce the effective opening of the orifice 141i and increase the effective opening of the orifice 142. Pressurized air will be supplied from the conduit a and the branch conduit 146 through the orifice 142 to the conduit 76a and to the outboard chamber 58 as required to provide for substantially a zero pressure difference between the inboard and outboard chambers and across the sealing device 5t). When the refrigerant pressure in the inboard chamber is subatmospheric, the bellows 132 will be collapsed from the position shown and the orice 142 will be closed by the valve lever 134 while the orifice 140 is opened thereby. Pressurized air will fiow from the outboard chamber S8 through the conduit 76, the valve chamber 13), the orifice 143 and to the evacuating means 128 and the pressure in said outboard chamber will be reduced to provide substantially a zero pressure difference between the inboard and outboard chambers and across the sealing device SQ.

The evacuating means 128 included in the alternative sealing means of the invention may take various forms. Preferably the said means comprises a jet pump device as shown, the conduit 30a being formed with a suitable orifice 148 which is disposed within the conduit 144 and adapted to induce air flow in said conduit away from the orifice 146. The conduit 144 may be provided with a venturi section 150 as shown to enhance the efiiciency of the orifice or nozzle 148.

In FIG. 3 a portion of a second alternative form of the sealing means of the present invention is illustrated. In this form of the sealing means the conduit 46 extending between the inboard chamber 34 and the inlet side of the compressor 10 is provided with a branch conduit 152 which communicates with the discharge side of the compressor. A restriction 154 is provided in the conduit 46 between the inlet side of the compressor and the branch conduit 152 and a restriction 156 is provided in said branch conduit. The relative sizes of the restrictions 154 and 156 or the relative areas of associated orifices 158 and 166 are such that the gaseous pressure therebetween and in the inboard chamber 34 is maintained between the compressor inlet and discharge pressure and above a predetermined level. Obviously, said predetermined pressure level may be selected at a value above atmospheric and so that the inboard chamber pressure will not drop below the lowest pressure obtainable in the outboard chamber 53 with the use of the regulating valve 78 of FIG. l. The aforementioned harmful inward leakage of air along the shaft 18 will thus be positively prevented and contamination of refrigerant will be avoided.

From the foregoing, it will be apparent that each of the alternative forms of sealing means of the present invention provides all of the features and advantages of the aforedescribed preferred form of sealing means of FIG. l. In addition, the said alternative forms of sealing means include provisions whereby substantially a zero pressure difference can be maintained across a continuously operable sealing device over a wide range of pressures extending to subatmospheric levels. In consequence, positive sealing action with desirably low frictional characteristics can be obtained for all conditions of operation ordinarily encountered in the sealing of a refrigerant compressor drive shaft or the like.

The invention claimed is:

1. In a gaseous fiuid compressor which may receive gaseous fluid at subatmospheric pressures and which includes a rotatable drive shaft, the combination of a first sealing device adapted to restrict the flow of gas along the shaft, a second sealing device spaced outwardly along the shaft from said first sealing device and also adapted Chi to restrict the fiow `of' gas therealong, means defining first and second annular chambers disposed about the drive shaft respectively on inboard and outboard sides of said second sealing device, said inboard chamber being adapted to receive compressor discharge gas fiowing outwardly past said first sealing device, means defining a first fluid passageway connecting said inboard chamber with the inlet side of the compressor whereby to provide for gas pressure in said chamber substantially equal to compressor inlet pressure, means defining a second fluid passageway connected with said outboard chamber, a source of air under pressure, evacuating means, and pressure regulating valve means connected with said first and second fluid passageways, and connectible with said source of air under pressure and said evacuating means, said valve means being operable responsive to pressure difference between said first and second passageways and said inboard and outboard chambers to selectively connect said second passageway with said source of air under pressure and said evacuating means whereby to regulate pressure in said outboard chamber so as to maintain substantially zero pressure difference between said chambers and across said second sealing device.

2. In a gaseous iiuid compressor which may receive gaseous iiuid at subatmospheric pressures and which includes a rotatable drive shaft, the combination of a first sealing device adapted to restrict the flow of gas along the shaft, a second sealing device spaced outwardly along the shaft from said first sealing device and also adapted to restrict the fiow of gas therealong, means defining first and second annular chambers disposed about the drive shaft respectively on inboard and outboard sides of said second sealing device, said inboard chamber being adapted to receive compressor discharge gas flowing outwardly past said first sealing device, means defining a first iiuid passageway connecting said inboard chamber with the inlet side of the compressor whereby to provide for gas pressure in said chamber substantially equal to compressor inlet pressure, means defining a second iiuid passageway connected with said outboard chamber, pressure regulating valve means connected with said first and second iiuid passageways, means defining a third fluid passageway connected with a source of air under pressure and with said valve means, means defining a fourth fluid passageway connected with said valve means, and a jet pump in said fourth fluid passageway connectible with a source of air under pressure and adapted to provide a subatmospheric pressure in said fourth fluid passageway, said pressure regulating valve means being operable responsive to pressure difference between said first and second passageways and inboard and outboard chambers to selectively connect said second fluid passageway with said third and fourth fluid passageways whereby to regulate pressure in said outboard chamber so as to maintain substantially Zero pressure difference between said chambers and across said second sealing device.

3. In a gaseous iiuid compressor which includes a rotatable drive shaft, the combination of a first sealing device adapted to restrict the flow of gas along the shaft, a second sealing device spaced outwardly along the shaft from said first sealing device and also adapted to restrict the flow of gas therealong, means for defining first and second annular chambers disposed about the drive shaft respectively on inboard and outboard sides of said second sealing device, said inboard chamber being adapted to receive compressor gas fiowing outwardly past said first sealing device, means defining a fluid passageway connected with said outboard chamber and connectible with a source of gas under pressure, a valve in said passageway adjustable between open and closed positions for controlling the fiow of gas to said outboard chamber, valve control means connected by iiuid passageway means with said inboard and outboard chambers and operable responsive to pressure difference between said chambers to adjust the position of said valve whereby to control fiow 10 to the outboard chamber and to maintain substantially a zero pressure difference between said chambers for inboard chamber pressures above atmospheric pressure, and means for maintaining the pressure of gas in said inboard chamber above atmospheric pressure.

4. In a gaseous fluid compressor which includes a rotatable drive shaft, the combination of a first sealing device adapted to restrict the fiow of gas along the shaft, a seco-nd sealing device spaced outwardly along the shaft from said first sealing device and also adapted to restrict the fiow of gas therealong, means for defining first and second annular chambers disposed about the drive shaft respectively on inboard and outboard sides of said second sealing device, said inboard chamber being adapted to receive compressor gas flowing outwardly past said fisrt sealing device, means defining a rst fluid passageway connesting said inboard chamber with the inlet side of the compressor, means defining a branch passageway connecting said first fluid passageway with the discharge side of said compressor, passageway restricting means disposed in said first and branch passageways so as to provide for 1an inbo-ard chamber pressure which ranges between compresser inlet and discharge pressure but which always excee-ds atmospheric pressure, means, defining a second fluid passageway connected with said outboard chamber and connectible with a source of gas under pressure, a valve in said second passageway adjustable between open and closed positions for controlling the flow of gas to said outboard chamber, and valve control means connected with said first and second passageways and operable responsive to pressure difference between said inboard and outboard chambers to adjust the position of said valve whereby to control fiow to the outboard chamber as required to maintain substantially a zero pressure difference between said chambers and across said second sealing device.

5. In a gaseous iiuid compressor which includes a rotatable drive shaft, the combination of a continuously operable sealing device which restricts the flow of gas along the drive shaft, means defining first and second annular chambers disposed about the drive shaft respectively on inboard and outboard sides of said sealing device, said inboard chamber receiving gas from the discharge side of the compressor, means defining a iiuid passageway for connection of said outboard chamber with a source of gas under pressure, pressure regulating valve means connected by fluid passageway means with said inboard and outboard chambers and operable responsive to pressure difference therebetween to regulate pressure in said outboard chamber whereby to maintain substantially a zero pressure difference between said chambers and across said sealing device, and a static sealing device operatively associated with said drive shaft and adapted to restrict the fiow of gas thereaiong when the shaft is at rest, said sealing device being inoperative when said shaft is rotating.

6. In a gaseous iiuid compressor which includes a rotatable drive shaft, the combination of a continuously oper- -able sealing device which restricts the fiow or gas along the drive shaft, means defining first and second annular chambers disposed about the drive shaft respectively on inboard and outboard sides of said sealing device, said inboard chamber receiving gas from the discharge side of the compressor, means defining a iiuid passageway for connection of said outb-oard chamber with a source of gas under pressure, pressure regulating valve means connected by iiuid passageway means with said inboard and outboard chambers and operable responsive to pressure difference therebetween to regulate pressure in said outboard chamber whereby to maintain substantially a zero pressure difference between said chambers and across said sealing device, and a centrifugally operable sealing device associated with said drive shaft on the inboard side of said continuously operable sealing device and adapted to restrict the tiow of gas therealong when the shaft is at rest and to permit the free flow of gas along said shaft during rotation thereof.

7. in a gaseous fluid compressor which includes a rotatable drive shaft, the combination of a continuously operable sealing device which restricts the flow of gas along the drive shaft, means defining first and second annular chambers disposed about the drive shaft respectively on inboard and outboard sides of said sealing device, said inboard chamber receiving gas from the discharge side of the compressor, means defining a iuid passageway for connection of said outboard chamber with a source of gas under pressure, pressure regulating valve means connected by iiuid passageway means with said inboard and outboard chambers and operable responsive to pressure difference therebetween toregulate pressure in said outboard chamber whereby to maintain substantially a zero pressure difference between said chambers and across said sealing device, and a static sealing device in said inboard chamber comprising a sealing element spring biased in sealing engagement with said drive shaft but movable out of sealing engagement by action of a connected centrifugally operable means and a iiexible closure means defining a gas tight fluid passageway about said shaft between said sealing element and said continuously operable sealing device.

8. In a gaseous iiuid compressor which includes a rotatable drive shaft, the combination of a first continuously operable sealing device adapted to restrict the flow of gas along the drive shaft, a second continuously operable sealing device spaced outwardly along said shaft from said first sealing device and also adapted to restrict the flow of gas therealong, means defining first and second annular chambers disposed about the drive shaft respectively on inboard and outboard sides of said second sealing device, said inboard chamber being adapted to receive compressor discharge gas flowing outwardly past said first sealing device, means defining a first iiuid passageway connecting said inboard chamber with the inlet side of the compressor whereby to provide for gas pressure in said chamber substantially equal to compressor inlet pressure, means defining a second fluid passageway connected with said outboard chamber, a source of air under pressure, evacuating means, pressure regulating valve means connected with said first and second fiuid passageways and connectible with said source of air under pressure and said evacuating means and operable responsive to pressure difference between said inboard and outboard chambers to selectively connect said second passageway with said source of air under pressure and said evacuating means whereby to regulate pressure in said outboard chamber so as to maintain substantially zero pressure difference between said chambers and across said second sealing device, and a static sealing device opera- 12 tively associated with said drive shaft `and adapted to restrict the iiow of gas therealong when the shaft is at rest, said sealing device being inoperative when said shaft is rotating.

9. In a gaseous iiuid compressor which includes a rotatable drive shaft, the combination of a first continuously operable sealing device adapted to restrict the fiow of gas along the drive shaft, a second continuously operable sealing device spaced outwardly along the shaft from said first sealing device and also adapted to restrict the of tiierealong, means defining first and second annular chambers disposed about the drive shaft respectively on inboard and outboard sides of said second sealing device, said inboard chamber being adapted to receive compressor discharge gas flowing outwardly past said first scaling device, means defining a first fiuid passageway connecting said inboard chamber with the inlet side of the compressor whereby to provide for gas pressure in said chamber substantially equal to compressor inlet pressure, means defining a second fluid passageway connected with said outboard chamber, pressure regulating valve means in said second fluid passageway and connected with said first passageway, means defining a third fiuid passageway connectible with a source of air under pressure and with said valve means, means defining a fourth liuid passageway connected with said valve means, a jet pump in said fourth iuid passageway connected with a source of air under pressure and adapted to provide a subatrnospheric pressure in said passageway, said pressure regulating valve means being operable responsive to pressure difference between said inboard and outboard chambers toselectively connect said second iiuid passageway with said third and fourth uid passageways whereby to regulate pressure in said outboard chamber so as to maintain substantially zero pressure difference between said chambers and across said second sealing device, and a static sealing device in said inboard chamber comprising a sealing element spring biased in sealing engagement with said drive shaft but movable out of sealing engagement by action of a connected centrifugally operable means and a flexible closure means defining a gas tight fluid passageway about said shaft between said sealing element and said second continuously operable sealing device.

References Cited in'the file of this patent UNITED STATES PATENTS 1,353,095 Uttech et al. Sept. 14, 1920 2,895,750 Gardner et al. July 2l, 1959 2,911,919 Tucker Nov. 10, 1959 2,913,989 Boardman et al Nov. 24, 1959

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