US2816512A

US2816512A - Pressure loaded gear pump

Info

Publication number: US2816512A
Application number: US358490A
Authority: US
Inventors: John F Murray
Original assignee: Thompson Products Inc
Current assignee: Northrop Grumman Space and Mission Systems Corp
Priority date: 1953-05-29
Filing date: 1953-05-29
Publication date: 1957-12-17
Anticipated expiration: 1974-12-17

Description

Dec. 17, 1957 J. F. MURRAY 2,816,512

PRESSURE LOADED GEAR PUMP Filed May 1953 Z 15 if M Joy/v FMz/mmy ie 59 nited States Fig 2,816,512

Patented Dec. 17, 1957 PRESSURE LQADED GEAR P John F. Murray, Macedonia, Ohio,

Products,

assignor to Thompson inc, Cleveiand, Ohio, a corporation of Ohio This invention relates particularly to a pressure loaded gear pump wherein an axially movable pressure loadable end plate adapted to sealingly engage an adjacent side face of a rotary fluid displacement member has a motive surface providing a plane area subject to liquid pressure generated by the pump which is offset relative to the motive surface to locate the center of pressure of the plane area in coaxial alignment with the centroid of the separating forces acting on the end plate in an opposite direction thereby to balance the unequal pressure forces normally acting on the end plate.

In gear pump constructions, a pair of rotary intermeshing gears are enclosed by a closely fitting housing which locates an inlet and an outlet at oppositely disposed points of the meshed portions of the gears. Fluid pressures are developed around the periphery of the gears and vary from a minimum at points adjacent the pump inlet to a maximum at points adjacent the pump outlet or pump discharge. There is, therefore, a non-uniform distribution of pressure forces acting on any axially movable pressure loadable end plate provided to sealingly engage the adjacent side faces of the rotary meshing gears tending to separate the end plates from the gears.

In order to counteract such separating forces, pumps have been provided wherein a motive surface is provided on the end plate which is subject to fluid pressure generated by the pump. It will be evident, however, that in accordance with the principles of physics, liquid pressure is exerted with equal intensity in all directions and, accordingly, any motive surface subjected to a fluid pressure will be subjected to a pressure force which is uniformly distributed over the entire motive surface. By virtue of such uniform distribution, the counterbalancing forces will tend to be greater on the inlet side of the pump and the separating forces will tend to be more effective towards the outlet side of the pump thereby producing a twisting tendency on the end plate seriously interfering with the proper operation of the pump.

In accordance with the principles of the present invention, improved means are provided to neutralize and balance the separating force and also to prevent any twisting tendency on the end plates due to the nonuniform separating force. In its broadest aspect, the present invention contemplates the provision of a motive surface on the end plate having a plane area subject to liquid pressure generated by the pump, which plane area is set relative to the motive surface to locate the center of pressure of the plane area in coaxial alignment with the centroid of the separating forces acting on the end plate in an opposite direction, thereby to balance the unequal pressures acting on the end plate.

It is an object of the present invention, therefore, to provide a pressure loaded gear pump wherein an axially movable pressure loadable end plate is utilized and wherein means are provided to neutralize and balance the separating forces acting thereon.

It is a further object of the present invention to minimize twisting tendencies on pressure loadable axially movable end plate means provided in a pressure loaded gear pump.

Another object of the present invention is to provide a motive surface on a pressure loadable axially movable gear pump end plate having a plane area subject to liquid pressure generated by the pump and offset relative to the motive surface to locate the center of pressure of the plane area in coaxial alignment with the centroid of the separating forces acting on the end plate in an opposite direction.

A further object of the present invention is to provide improved sealing means for a pressure loaded gear pump, thereby to increase the volumetric efiiciency.

Yet another object of the present invention is to provide a pressure loaded gear pump of increased pressure capacity.

Many other features, advantages and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description which follows and the accompanying sheet of drawings in which a preferred structural embodiment incorporating the principles of the present invention is shown by way of illustrative example.

On the drawings:

Figure 1 is a cross-sectional view with parts shown in elevation of a pressure loaded gear pump incorporating the principles of the present invention;

Figure 2 is a reduced cross-sectional view taken substantially on line II-II of Figure 1;

Figure 3 is a reduced cross-sectional view taken substantially on line IIIIII of Figure 1; and

Figure 4 is a fragmentary cross-sectional View showing an alternative structural embodiment of the pump structure provided in Figure 1.

As shown on the drawings:

The pump of the present invention is shown generally at 11? and comprises a casing 11 including a housing member 12 and a cover 13 retained in firm assembly with one another by means of a plurality of fasteners indicated generally at 14.

The housing member 12 and the cover member 13 are provided with registering intersecting bores, the housing member 12 including intersecting bores 16 and 17, respectively, and the cover member including intersecting bores 18 and 19, respectively, all of which cooperating to form a pumping cavity in which the other components of the pump 10 are received.

Toward one end of the housing member 12, the bore 16 opens into a reduced bore 20. A somewhat larger bore 21 counterbored as at 22 opens out of the end of the housing member 12 and receives a bearing assembly indicated generally at 23 and a shaft sealing unit indicated generally at 24. A stub shaft 26 is splined as at r 27 to effect a driving connection with a power source and is journalled for rotation in the bearing assembly 23, an additional spline connection being indicated at 28 to effect driving engagement with a shaft extension 29 provided on one side of a driver gear 30 rotatable in the bore 16.

A driven gear 31 meshes with the driver gear 30 and is rotatable in the bore 17.

As is clearly shown in Figure 3, the housing member 12 of the casing 11 is suitably recessed to provide an inlet 32 and an outlet 53 at oppositely disposed points of the meshed portions of the

gears

30 and 31.

In addition to the shaft extension 29 extending from one side of the driver gear 30, a shaft extension 34 is provided on the opposite side of the driver gear 30 and the driven gear 31 is also provided with oppositely extending shaft extensions identified bythe reference chartacters 36 and 37, respectively.

A reduced bore 38 similar to the bore 20 is provided at the end of the bore 17 and a fixed bushing member 39 is located in each respective bore 20 and 38 to provide a journal bearing surface for the

shaft extensions

29 and 36 on the driver gear 30 and the driven gear 31, respectively.

Each of the fixed bushings 39 is provided with a radially extending flange portion indicated at 40 and providing a radially extending sealing face 41 for engaging an adjacent side face of a

corresponding gear

30 or 31.

An axially movable pressure loadable bushing 42 is provided on the other side of each

respective gear member

30 and 31. Each bushing 42 is received for sliding movement in a corresponding pair of adjacent bores 16 and 18 or 17 and 19. Because the casing bores intersect, each bushing is provilded with a fiat chordal section on the outside diameter thereof, thereby to provide a mating joint indicated by the common reference numeral 43 in Figure 2 and in Figure 1.

Each bushing has a radially extending front face which is particularly characterized by a bearing bore or recess 44 receiving and providing a journal bearing surface for a corresponding shaft extension 34 or 37.

The recess 44 terminates at a bottom plane area indicated at 46 which is spaced from the end of each respective shaft extension 34 or 37 in order to afford limited axial movement of each respective bushing 42.

Radially outwardly of the recess 44 is provided a generally annular plane area forming a front sealing face 47 which engages an adjacent side face of the

respective gear members

30 and 31.

It may be noted that each of the

gear members

30 and 31 is provided with conventional annular machining reliefs identified by the reference character 48 which are provided to minimize galling, seizure and binding between the relatively rotatable components of the pump 10.

An annular peripheral groove 49 formed in a peripheral surface of the bushings 42 and extending through the mating joint 43 receives a seal member 50 adapted to engage the walls of the bores 16 and 17 in the housing member 12, thereby effecting a sealing joint between the bushings 42 and the housing member 12 while permitting relative axial movement.

The housing member 12 is also recessed as at 51 to receive a seal member 52 for effecting a sealing joint between the cover member 13, the housing member 12 and the bushings 42.

A passage 53 extends through the driven gear 31 and a passage 54 extends through the driver gear 30, thereby intercommunicating the recesses 44 in the respective bushings 42 and other portions of the pump structure. The recesses 44 communicate with a zone of low pressure, for example, a passageway 56 is provided to communicate the recess 44 with the inlet side of the pump, thereby minimizing dashpot action which would interfere with the axial adjustment movement of the bushing 42 and eliminating high pressure pockets in the pump casing 11.

In order to load the bushings 42 axially to move the bushings 42 into sealing relation with the

gears

30 and 31, a radially extending back face 57 is provided which forms a motive surface for the bushing 42. Continuous biasing means are provided between the cover member 13 and the motive surface provided by the back face 57 in order to exert a continuous biasing force on the bushing 42 tending to maintain the bushing 42 in sealing relation.

In the embodiment of the invention shown in Figures 1 and 2, a bore 58 receives one end of the coil spring 59. Each bushing is additionally provided with a counterbore 60 which provides a radially extending plane area 61 which is adapted to be subjected to fluid pressure generated in the pump 10.

It will be appreciated that since the inlet 32 and the outlet 33 are located at oppositely disposed points of the meshed portions of the

gears

30 and 31, liquid pressures 4 will be developed around the periphery of the

gears

30 and 31 which vary from a minimum at the inlet 32 to a maximum at the outlet 33. There is, therefore, a nonuniform distribution of pressure tending to act on the sealing face 47 to separate the bushing 42 from the

corresponding gear

30 or 31.

In order to neutralize and balance this separating force and also in order to prevent any twisting tendency on the end plate or bushing 42 due to the non-uniform separating force, an equal and opposite force should be applied to the bushing 42 at the centroid of the separating force.

In accordance with the principles of the present invention, the counterbore 60 is formed in the back face 57 so as to be laterally offset with respect to the motive surface provided by the back face 57. As shown in Figure 2, the counterbore 60 is offset towards the outlet side of the pump.

The recess or counterbore 60 in each bushing 42 is referenced to fluid pressure generated by the pump by means of a passageway 62 which extends through each bushing 42 and communicates fluid moved by the

gears

39 and 31 adjacent the discharge or outlet 33.

In order to confine the fluid pressure in the recess or counterbore 60 to act on the plane area 61, the form of the invention shown in Figures 1-3 utilizes a piston member 64 having one end received in the recess or counterbore 60 and having its other end bottomed against an adjoining radially extending wall 66 provided by the cover member 13. A bore 67 is provided in each piston member 64 to bottom the other end of each respective coil spring 59 so that a continuous biasing force will be exerted between the piston 64 and the corresponding bushing 42 to axially load the bushing 42 into sealing relation with the

corresponding gear

30 or 31.

When fluid pressure generated by the pump is communicated to the recess or counterbore 60, it will be appreciated that the piston members 64 will be forced by high pressure against the fixed end of the pump casing 11 provided by the cover member 13 and an equal and opposite pressure will be evenly distributed over the plane area 61 at the bottom of the recess or counterbore 60.

Each piston member 64 is provided with an annular groove 67 which seats a sealing member 68 engaging the side walls of the recess or counterbore 60. A seal ng member 69 is is also provided between the back face 57 of each bushing 42 and the radial wall 66 of the cover member 13 to engage the peripheral surface of each respective piston member 64.

Because of the offset relation of the recess or counterbore 60 with respect to the motive surface afforded by the back face 57, the plane area 61 subject to the liquid pressure generated by the pump will have a center of pressure which is displaced so as to be coaxial with the resultant center of pressure acting on the face 47 of the bushing. In other words, the center of pressure of the plane area 61 on each respective bushing 42 will be offset towards the outlet side of the pump. By locating the center of pressure of the plane area 61 m coaxial alignment with the centroid of the separating forces acting on the bushing 42, the unequal pressure forces acting on the bushing 42 will be balanced. Moreover, any tendency of the bushing 42 to twist in the housing member 12 and in the cover member 13 will be minimized and, accordingly, localized loading will also be minimized.

The embodiment of Figure 4 is identical in all respects with the embodiment of Figure 1, however, the function of the separate piston member 64 is developed by an integral boss 70 extending from the radial wall 66 of the cover member 13, which boss 70 is shaped complementary to each respective recess or counterbore 60 in an adjoining back face .57 of a corresponding bushing 42. The boss 70 is provided with a bore 71 seating the opposite end of the coil spring .59.

In order to provide adequate lubrication for the journal surface between each bushing 42 and a shaft extension 34 or 37, an axial groove indicated at 72 is machined the full length of the bearing bore and extends between the bottom plane area 46 of the recess 44 and a corresponding side face of each

respective gear member

30 and 31.

Although various minor modifications might be suggested by those versed in the art, it should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art.

I claim as my invention:

1. In a fluid pump, a housing having an inlet and an outlet and having a pumping cavity formed therein, pumping means in said cavity to move fluid from said inlet to said outlet, whereby unequal pressure forces in the cavity vary from the inlet side to the outlet side and a backing plate forming a sealing face on the front surface thereof for said cavity in said housing, said backing plate having a back surface recessed to provide a plane area at the bottom of the recess adapted to be subject to fluid pressure and having a center of pressure displaced toward the pump outlet, and means confining fluid pressure generated by said pump in said recess to act on said plane area, thereby to balance unequal pressure forces in the cavity, while sealing against an adjoining side face of said pumping means in said cavity.

2. In a fluid pump, a housing having an inlet and an outlet and having a pumping cavity formed therein, pumping means in said cavity to move fluid from said inlet to said outlet, whereby unequal pressure forces in the cavity vary from the inlet side to the outlet side and a backing plate forming a sealing face on the front surface thereof for said cavity in said housing, said backing plate having a back surface recessed to provide a plane area at the bottom of the recess adapted to be subject to fluid pressure and having a center of pressure displaced toward the pump outlet, a piston having one end received in said recess and the other end bottomed against said housing, and means communicating fluid pressure generated by said pump to said recess to act on said plane area, thereby to balance unequal pressure forces in the cavity, while sealing against an adjoining side face of said pumping means in said cavity.

3. In a fluid pump, a housing having an inlet and an outlet and having a pumping cavity formed therein, pumping means in said cavity to move fluid from said inlet to said outlet, whereby unequal pressure forces in the cavity vary from the inlet side to the outlet side and a backing plate forming a sealing face on the front surface thereof for said cavity in said housing, said backing plate having a back surface recessed to provide a plane area at the bottom of the recess adapted to be subject to fluid pressure and having a center of pressure displaced toward the pump outlet, said housing having a boss portion extending into said recess to confine fluid pressure therein, and means communicating fluid pressure generated by said pump to said recess to act on said plane area, thereby to balance unequal pressure forces in the cavity, while sealing against an adjoining side face of said pumping means in said cavity.

4. In a fluid pump, a housing having an inlet and an outlet and having a pumping cavity formed therein, pumping means in said cavity to move fluid from said inlet to said outlet, whereby unequal pressure forces in the cavity vary from the inlet side to the outlet side and a backing plate forming a sealing face on the front surface thereof for said cavity in said housing, said backing plate having a back surface recessed to provide a plane area at the bottom of the recess adapted to be subject to fluid pressure and having a center of pressure displaced toward the pump outlet, a piston having one end received in said recess and the otherend bottomed against said housing, and means communicating fluid pressure generated by 6 said pump to said recess to act on said plane area, thereby to balance unequal pressure forces in the cavity, and a spring between said piston and said backing plate to continuously bias said backing plate towards the cavity, whereby said backing plate seals against an adjoining side face of said pumping means.

5. In a fluid pump, a housing having an inlet and an outlet and having a pumping cavity formed therein, pumping means in said cavity to move fluid from said inlet to said outlet, whereby unequal pressure forces in the cavity vary from the inlet side to the outlet side and a backing plate forming a sealing face on the front surface thereof for said cavity in said housing, said backing plate having a back surface recessed to provide a plane area at the bottom of the recess adapted to be subject to fluid pressure and having a center of pressure displaced toward the pump outlet, said housing having a boss portion extending into said recess to confine fluid pressure therein, and means communicating fluid pressure generated by said pump to said recess to act on said plane area, thereby to balance unequal pressure forces in the cavity, and a spring between said housing and said backing plate to continuously bias the backing plate towards the cavity, whereby said backing plate seals against an adjoining side face of said pumping means.

6. A fluid pump, comprising a housing having a pair of intersecting bores providing a pumping cavity, a pair of rotary intermeshing gears in said cavity, each gear having shaft portions extending axially of each respective bore, a movable pressure loadable bushing member in each bore having a recess providing a journal bearing surface for a corresponding shaft portion, a front face on each bushing for sealing an adjacent side face of a corresponding gear, a back face on each bushing spaced from an adjacent wall provided by said housing, and a recess in said back face and forming a plane area at the bottom of the recess subject to fluid pressure generated by the pump and having a center of pressure displaced laterally with respect to the center of said back face to balance unequal pressure forces on the front face and means confining said fluid pressure generated by the pump in said recess.

7. A fluid pump, comprising a housing having a pair of intersecting bores providing a pumping cavity, a pair of rotary intermeshing gears in said cavity each having shaft portions extending axially of each respective bore, a movable pressure loadable bushing member in each bore having a recess providing a journal bearing surface for a corresponding shaft portion, a front face on each bushing for sealing an adjacent side face of a corresponding gear, and a back face on each bushing spaced from an adjacent wall provided by said housing, and a cylinder recess in said back face providing a plane area at the bottom thereof, a piston having one end closing said recess and the other end engaging said adjacent Wall of said housing, a spring in said recess bottomed against said bushing and against said piston to continuously bias the piston and the bushing apart, and means communicating fluid pressure generated by the pump to said cylinder recess to act on said plane area for pressure loading said bushing into sealing relation.

8. A fluid pump, comprising a housing having a pair of intersecting bores providing a pumping cavity, a pair of rotary intermeshing gears in said cavity, each gear having shaft portions extending axially of each respective bore, a movable pressure loadable bushing member in each bore having a recess providing a journal bearing surface for a corresponding shaft portion, a front face on each bushing for sealing an adjacent side face of a corresponding gear, and a back face on each bushing spaced from an adjacent wall provided by said housing, a recess in said back face providing a plane area at the bottom thereof, means communicating fluid pressure generated by the pump into the recess, and means extending from said adjacent housing wall into said recess to confine the 7 fluid pressure in said recess for acting over said plane area, thereby to pressure load said bushing into sealing relation.

9. A fluid pump comprising a rotary pumping member having a shaft and a radially extending fluid displacement means, a bushing having a radially extending front face characterized by a recess receiving and providing a journal bearing surface for said shaft, and a generally annular plane area engaging an adjacent side face of the fluid displacement means, said bushing having a plane area at the bottom of said recess spaced from the end of said shaft to permit axial movement of said bushing on said shaft into a sealing relation at said annular plane area with said side face of the fluid displacement means, said bushing having a back face oppositely disposed from said front face, casing means providinga pumping cavity for the pumping member with an inlet at one side thereof and an outlet at the opposite side thereof, said annular plane area being subject to fluid pressures increasing from the inlet side of the pump to the outlet side .of the pump thereby shifting the centroid of separating force laterally of the geometric center of said annular plane area, and means confining fluid pressure generated by the rotary fluid displacement means to a plane area on said back face offset towards the outlet of the pump to provide a center of pressure opposite the centroid of separating force operating on said annular plane area.

10. A fluid pump comprising a rotary pumping member having a shaft and a radially extending fluid displacement means, a bushing having a radially extending front face characterized by a recess receiving and providing a journal bearing surface for said shaft, and a generally annular plane area engaging an adjacent side face of the fluid dis- '8 placement means, said bushing having a plane area at the bottom of said recess spaced from the end of said shaft to permit axial movementof said bushing on said shaft into a sealing relation at said annular plane area with said adjacent side face of said fluid displacement means, said bushing having aback face oppositely disposed from said front face, casing means providing a pumping cavity for the pumping member with an inlet at one side thereof and an outlet at the opposite side thereof, said annular plane area being subject to fluid pressures increasing from the inlet side of the pump to the outlet side of the pump thereby shifting the centroid of separating force laterally of the geometric center of said annular plane area, a recess in said back face providing a plane area at the bottom Ofthe recess offset towards the outlet side of the pump, means communicating fluid pressure generated by I the pump to said recess, and plug means in said recess between said bushing and said casing means confining said fluid pressure in said recess to act on said offset plane areaat the centroid of the fluid pressure forces acting on said bushing in an opposite direction.

References Cited in the file of this patent UNITED STATES PATENTS 2,044,873 Beust June 23, 1936 2,444,165 Lauck June 29, 1948 2,639,672 Johnson May 26, 1953 2,641,192 Lindberg June 9, 1953 2,649,740 Murray et al. Aug. 25, 1953 2,682,836 Orr July 6, 1954 2,695,566 Compton Nov. 30, 1954 2,714,856 Kane Aug. 9, 1955