US3397645A - Fluid pump or motor - Google Patents

Description

Aug. 0, 1968 'B. H. MOSBACHER ETAL 3,397,645

FLUID PUMP OR MOTOR 4 Sheets-Sheet. 1

Filed May 31, 1966 8- 0, 1968 a. H. MOSBACHER ETAL FLUID PUMP 0R MOTOR 4 Sheets-Sheet 2 plz i Filed May 31, 1966 Aug. 20, 1968 a. H. MOSBACHER ETAL FLUID PUMP 0R MOTOR Filed May 31, 1966 4 Sheets-Sheet 5 0, 1968 a. H. MOSBACHER ETAL 3,397,645

Filed May 31, 1966 United States Patent 3,397,645 FLUID PUMP 0R MOTOR Bruce H. Mosbacher and George W. Nelson, Rockford, Ill., assignors to Roper Industries, Inc., Rockford, 11]., a corporation of Illinois Filed May 31, 1966, Ser. No. 553,878 17 Claims. (Cl. 103-126) ABSTRACT OF THE DISCLOSURE A gear pump or motor in which the gears are enclosed in a pump cartridge movable in the pump housing and including a pressure loading end plate at one end of the gears and a gear case rigid with the end plate and extending in close running fit with the gear peripheries. A pressure motive surface is formed on the gear case at a location forwardly of the end plate so that the pressure applied to the motive surface pulls the end plate into close running fit with the end faces of the gears. The gears are preferably arranged in a cluster of four with alternate inlet and discharge zones around the gear cluster, and the discharge passage is formed to extend completely around the gear case to communicate the several discharge passages with the pump outlet and to also provide a radially balanced pressure around the gear case.

This invention relates to fluid pumps or motors and particularly to pumps or motors of the rotary gear type.

Gear pumps or motors have heretofore been made with axially slidable end plates or bushings which are pressed against the end faces of the gears to minimize leakage of fluid across the end faces. The pressure at the gear face side of the end plates, however, is not uniform and varies from a maximum adjacent the discharge zone of the gears to a minimum adjacent the inlet zone. This non-uniform pressure at the gear face side of the end plates tends to cause distortion and tilting of the end plates away from the gear end faces adjacent the discharge zone. It is an object of the present invention to provide a gear pump having an improved arrangement for axially rigidifying and guiding the movable end plate to inhibit distortion and tilting of the end plate relative to the gear end faces due to the non-uniform pressure zones at the gear face side of the end plate.

An important feature of the present invention resides in the provision of a gear pump in which the movable end plate for sealing the end face of the gears has a gear case rigid therewith and extending along the peripheries of the gears to rigidify the end plate and improve the guiding of the end plate for movement in a direction axially of the gears.

Another object of this invention is to provide a gear pump of the type described in which the fluid pressure acting on the outer periphery of the case is balanced in a radial direction so that the case and the end plate rigid therewith are free to float axially in a pump housing to form a proper running seal with the gear end faces.

In the so-called pressure loaded gear type pumps, it is customary to push the end plate or bushing against the end face of the gear by the application of fluid pressure either directly or through a pressure applying member to the rear or outer side of the end plate. However, the gear shafts project from the gear end faces into the end plate or bushing, and this imposes some limitation on the configuration and size of the motive surface which can be provided at the outer face of the end plate and, moreover, requires a relatively complex arrangement for sealing the motive surface from the remaining areas, including the openings in the gear shafts. Another object of this invention is to provide a pressure loaded gear 3,397,645 Patented Aug. 20, 1968 ice pump, which avoids the problems normally encountered when the pressure motive surface is located at the rear side of the end plate or bushing.

Another object of this invention is to provide a pressure loaded gear pump having an improved pressure loading arrangement which enables the use of a motive surface having a simple configuration, which motive surface can be easily sealed from the remaining areas of the pump.

A more particular object of this invention is to provide a pressure loaded gear pump in which the motive surface for the movable end plate or bushing is located in front of the inner gear engaging face of the movable end plate so that pressure applied to the motive surface pulls the movable end plate into close running fit with the end face of the gear.

Another object of this invention is to provide, in a gear pump of the type having multiple inlets and discharges, an improved pump construction which simplifies the passage arrangement for passing fluid to and from the several inlets and discharge units in the pump assembly.

Yet another object of this invention is to provide a pressure loaded multiple gear pump construction which can be more economically manufactured and in which the pump parts subject to wear can be easily replaced.

These, together with other objects and advantages of this invention, will be more readily understood from the following detailed description taken in connection with the accompanying drawings wherein:

FIGURE 1 is a longitudinal sectional view through a gear pump or motor embodying the present invention;

FIG. 2 is a transverse sectional view taken on the plane 2-2 of FIG. 1;

FIG. 3 is a transverse sectional view taken on the plane 33 of FIG. 1;

FIG. 4 is a transverse sectional view taken on the plane 44 of FIG. 1;

FIG. 5 is a longitudinal sectional view through a modified form of pump or motor embodying the present invention;

FIG. 6 is a transverse sectional view taken on the plane 66 of FIG. 5;

FIG. 7 is a transverse sectional view taken on the plane 77 of FIG. 5.

The present invention is particularly adapted for use with a multiple geared pump of the type disclosed in the patent to Mosbacher No. 2,765,749 wherein an even numbered plurality of gears are arranged in the form of a regular polygon to provide inlet and discharge zones in alternate sequence around the gear assembly, and the invention is herein illustrated and described in connection with such a gear pump. It is to be understood, however, that features of the present invention can advantageously be employed in other types of gear pumps, if desired.

The pumping apparatus in general includes a plurality of gears, herein shown four in number and designated 10-13. The gears have shafts 15-18 respectively conveniently formed integrally therewith. The gears are arranged in a regular polygon, herein shown in a square pattern, with each gear meshing with two adjacent gears. While the apparatus can be operated as either a pump or motor element, it is herein generally described in connection with operation as a pump, it being understood that for operation as a motor fluid under pressure is supplied to the apparatus to drive the same. One of these shafts, such as 15, is connected as through a spline connection 21 to a power transmission means or shaft 22 adapted to be driven from any suitable source of power. This multiple gear arrangement provides alternate inlet and discharge zones around the outer periphery of the gear assembly, and, when the gears are rotated in the direction indicated by the arrows in FIGS. 2 and 3, the gear assembly produces inlet zones I externally of the gear assembly adjacent the mesh point of the gears and 13 and adjacent the mesh point of the gears 11 and 12. Discharge zones designated D are formed externally of the gear assembly adjacent the mesh points of the gears 10 and 11 and also adjacent the mesh points of the gears 12 and 13. As shown in FIG. 3, the inlet and discharge zones are arranged in alternate sequence around the gear assembly.

The gears are enclosed in a housing and, in the embodiment shown in FIGS. 1-3, the housing is advantageously formed in two sections. One section includes an end wall 25 and a peripheral wall 26 and the other section includes a second end wall 27 and a peripheral wall 28. In order to facilitate alignment of the sections, a centering flange or rim 29 is provided on one of the sections and extends into a corresponding recess in the peripheral wall of the other section to radially locate the sections when they are joined together as by fasteners 31. A seal ring 32 may be provided between the sections to seal the same. One of these sections has an opening for receiving the drive shaft 22 and, as shown, an opening 35 is formed in the end wall 25 and a rotary shaft seal 36, of conventional construction, is provided for sealing the interface between the drive shaft and the housing. The housing defines a chamber 37 for enclosing the pump components and has fluid inlet and outlet openings therein. For reasons pointed out hereinafter, the inlet opening designated 41 is conveniently located in one of the end walls such as 27 and the outlet opening 42 is located in the peripheral wall portion of the housing.

In the multiple gear pump disclosed in the aforementioned Patent No. 2,765,749, the housing was formed with intersecting pump bores which received the gears, and end or wear plates were located at opposite ends of the gears and mounted for sliding movement in the intersecting pump bores. In accordance with the present invention, the gears are enclosed in a cartridge 43 which is slidably mounted in the pump housing. More particularly, a first or stationary end plate 45 is provided at one end of the gears and has openings 46 for receiving the projecting gear shafts. The stationary end plate is formed with an outer periphery 45a which conforms to the contour of the gear assembly and, as shown in phantom in FIG. 4, has a generally cloverleaf configuration. The stationary end plate is supported against axial movement in a direction away from the gear end faces by a stop plate 47, which stop plate conveniently has a circular periphery 47a, the outer diameter of which is greater than the major dimension of the stationary end plate. The stop plate projects outwardly to engage a shoulder 25a in the housing. As best shown in FIG. 1, the stop plate has openings 48 which receive bosses 45b which surround the shaft openings on the end plate, so as to be radially centered and located thereby. The cartridge 43 includes a second or movable end plate 51 disposed at the other end of the gears, and which movable end plate has openings 52 for receiving the gear shafts. The cartridge also includes a gear case 53 which extends along the peripheries of the gears 10-13 and around the periphery of the stationary plate 45, as is clearly shown in FIG. 1. As best shown in FIG. 3, the gear case has inner peripheral portions 53a which extend into close running fit with the gear peripheries in areas intermediate the mesh points of the gears. In the four-gear pump illustrated, the inner wall 53a of the case has a generally cloverleaf configuration and this same configuration is continued on to the end portion of the case which surrounds the stationary wear plate. The cartridge is axially slidable relative to the pump gears and relative to the stationary end plate 45 and is sealed to the end plate by a seal ring 55. The cartridge and end plates can be made from the same or of a different material than that used in the housing and, for example, the housing may be formed of aluminum or the like for light weight while the case and end plate can be formed of a different material such as bronze alloy for strength and wear characteristics. The shaft bores and the walls of the pump chambers on the case and end plates are preferably lined with a suitable wear resistant material, for example, a lead-tin alloy. Rollers 65 having an outer diameter equal to the pitch diameter of the gears are advantageously provided at each end of the gear shaft with the rollers on adjacent gears disposed in rolling engagement as best shown in FIG. 2 to take up the radial loads on the gears. A pin 66 is conveniently centered through openings 6'7 and 68 in the end plates and the pin arranged to extend through the center of the gear assembly in relatively close adjacency to the path of travel of the gear teeth to produce a pumping action inside the gear assembly. As disclosed in the aforementioned patent to Mosbacher, pressure distribution grooves (not shown) can be formed in the end plates to distribute the fluid pressure around the gear peripheries in such a manner as to direct a radial hydraulic thrust on the gears toward the center of the gear assembly so that the rollers take up the radial hydraulic thrust, and grooves and passages (not shown) can be formed in the end plates to circulate fluid from the inside of the gear assembly through the shaft bores for lubrication of the same. A means such as a light spring 69 is preferably provided for yieldably maintaining the movable end plate against the gear end faces when the pump is idle.

As can be seen, the case 53 is integral or rigid with the end plate 51 and rigidifies the same to minimize distortion or deflection of the end plate away from the gear end faces in the regions adjacent the high pressure zones. In addition, the cartridge 43 provides improved guidance for the movable end plate for movement in a direction axially of the gears and also facilitates machining of the chamber in the housing. Since the cartridge surrounds the gear peripheries, it is not necessary to machine the intersecting pump bores in the housing. Instead, the cartridge is advantageously formed with a circular outer periphery and the pump housing similarly formed with a circular inner wall for receiving the cartridge. The cartridge is also shaped to provide an improved pressure loading arrangement for urging the movable end plate against the gear end faces with a force that is correlative with the pressure at the gear face side of the end plate. As shown, the cartridge has a first peripheral wall portion 43a at the end adjacent the end plate 51 which slidably engages a wall surface 37a on the housing. The cartridge is also formed with a second peripheral wall portion designated 43/1 adjacent the end of the cartridge remote from the movable end wall 51, and which peripheral wall portion slidably engages a second wall surface 371) on the housing. The area bounded by the peripheral surface 4312 on the cartridge is made larger than the area bounded by the peripheral surface 43:: so as to provide a shoulder on the cartridge, which shoulder forms a pressure motive surface designated 43c facing in a direction opposite the gear face side of the end plate 51 and to which fluid pressure may be applied to urge the cartridge and hence the end plate 51 against the gear end face. As best shown in FIGS. 2 and 4, the surfaces 43a and 4312 are circular as viewed crosswise of the pump, and the mating surfaces 37a and 37b on the pump housing are similarly of circular configuration so as to facilitate machining of the same. The effective area of the motive surface 430 corresponds to the difference in the crosssectional areas of the circles 43a and 43b, and this effective area of the motive surface is selected in accordance with the pressure to be applied to the motive surface to pressure load the end plate 51 against the gear end face with a force substantially equal to, but preferably slightly greater than the axial hydraulic thrust on the end plate due to the pressure gradient acting on the gear face side of the end plate. While the surfaces 43a and 4312 are preferably of circular configuration to facilitate machining, it is to be understood that one or both surfaces could be of a different configuration or that one could be eccentric relative to the other, if desired in a particular pump application to thereby provide a non-uniform motive surface extending around the cartridge. As will be seen, the motive surface 43c is spaced a substantial distance from the end plate 51, in the direction which the end plate moves to engage the gear end face, so that pressure applied to the motive surface elfectively pulls the end plate into engagement with the gear end faces.

The hydraulic pressures acting on the outer periphery of the cartridge 43 are advantageously radially balanced so that the fluid pressure does not force the cartridge radially against one side or the other of the housing. As best shown in FIG. 1, seals 71 and 72 are provided for sealing the peripheral surfaces 43a and 43b on the cartridge to the walls 37a and 37b on the housing. The seals are axially spaced apart a substantial distance and discharge openings 74a and 74b are formed in the case and located intermediate the seals 71 and 72. As shown in FIG. 3, the discharge openings 74a and 74b communicate with the discharge zones D and open at the outer periphery of the cartridge intermediate the seals 71 and 72. An annular passageway is formed around the cartridge intermediate the seals and for this purpose either one or both the housing and cartridge are formed with annular recesses designated 76 and 77. As will be seen, the recesses 76 and 77 cooperate to form an annular channel therebetween which collects the fluid from both outlet openings 74a and 74b and which delivers the same to the housing outlet 42. Moreover, since the channels extend completely around the cartridge, they distribute discharge pressure uniformly around the cartridge to radially balance the same. Further, the pressure motive surface 430 communicates with the channels so that discharge pressure is applied directly to the motive surface to urge the cartridge into pressure loading engagement with the gears.

In low Volume pumps, that is, gear pumps having relatively narrow gears as shown in the form of FIG. 1, it is preferable to use substantially the entire width of the gears for the discharge openings. In this embodiment, the inlet openings are formed in one of the end plates and preferably in the movable end plate 51. As also shown in FIGS. 2 and 3, inlet openings or passages 78a and 78b are formed in the end wall 51 and communicate with the inlet zones I. The inlet openings extend laterally through the end plates and open at the outer side of the end plate, as shown in FIG. 2. The housing inlet 41 communicates with the chamber 37 to supply fluid to the pump inlets and the gear shafts are preferably made hollow so as to maintain the pump housing chamber 37 at opposite ends of the gears at substantially inlet pressure. Thus, the only area at above inlet pressure is the annular passageway between the seals 71 and 72, and which passageway is maintained at discharge pressure.

The embodiment illustrated in FIGS. 5-7 is generally similar to that of FIGS. 1-4, and like numerals followed by the postscript are used to designate corresponding parts. In this embodiment, however, the gears have a relatively longer axial length than shown in FIGS. 1-4, and both the inlet and discharge openings are advantageously formed in the case portion of the cartridge. As in the preceding embodiment, the pump is of the fourgear type including gears '13 arranged in a square pattern with each gear meshing with two adjacent gears. The gears are disposed in a housing conveniently formed in two sections including a section 26' and a section 27, and a shaft 22' is connected to one of the gears to drive the same. In the form shown, the housing section 27 has the peripheral wall 28', and the other section 26' is secured to the peripheral wall as by fasteners 31' and sealed thereto as by an O-ring 32.

The gears, when rotated in the direction indicated by the arrows in FIGS. 6 and 7, produce inlet zones I and discharge zones D in alternate sequence around the external periphery of the gear assembly. A first or stationary end plate 45' is disposed at one end of the gear assembly and has openings 46 for receiving the gear shaft 15. The stationary end plate is supported against movement away from the gear end faces and, as shown, engages a boss 47 formed on one of the housing sections 26'. The end plate 45 has an outer periphery which is contoured to conform to the outline of the gear assembly and the rim 47' is preferably similarly formed.

A gear cartridge 43' is slidably disposed in the housing for movement in a direction paralleling the axis of the gears. The cartridge includes a movable end plate 51' disposed at the other end of the gear and a gear case 53' rigid with the movable end plate, which gear case extends axially along the gear assembly and surrounds the periphery of the stationary end plate 45. As shown in FIGS. 6 and 7, the inner wall portions 534: of the case extend into close running fit with the peripheries of the gears in areas intermediate the inlet and discharge zones. As previously described, the stationary wear plate 51 has its outer periphery contoured to be slidably received in the gear case 53 and is sealed thereto as by a seal ring 55.

As in the preceding embodiment, rollers 65 are advantageously provided at opposite ends of each of the shafts with the rollers having an outer diameter corresponding to the pitch diameter of the respective gears so that the rollers are disposed in rolling engagement. Moreover, pressure balancing grooves and lubrication passages (not shown) can be provided in the end plates for adjusting the radial hydraulic thrust on the gears to urge the same toward the center of the gear assembly and for circulating fluid through the shaft openings in the end plate, as described in the aforementioned Mosbacher patent.

The cartridge 43 has a pressure motive surface extending therearound at the end remote from the movable end plate 51. As shown in FIG. 5, the case has a first peripheral wall surface 43a and a second relatively larger peripheral wall surface 43b which define a shoulder or pressure motive surface 430'. The peripheral wall surfaces 43a' and 43b are preferably of circular configuration, to facilitate machining, although it is to be understood that one or both could be of non-circular configuration, if desired to provide a non-uniform pressure motive surface extending around the periphery of the case. In this embodiment, inlet and discharge passages are formed in the case portion of the movable cartridge with the inlet passages spaced axially along the cartridge from the discharge passages. For this purpose, at least three peripheral seals are provide-d between the case and housing, a first seal 71 being located adjacent the end plate 51'; a second seal 72' being located intermediate the ends of the peripheral wall 43a; and a third seal 73' being located at the peripheral wall portion 43b. The seals engage complementary wall portions 37a, 37b and 370' on the housing. As shown in FIG. 6, the case portion 53' of the cartridge has inlet openings 78' which communicate with the inlet zones of the pump gears and open at the outer periphery of the case in an area intermediate the seals 71 and 72. The case also has discharge openings 74 best shown in FIG. 7 which communicate with the discharge zones of the pump gears and open at the outer periphery of the case in an area intermediate the seals 72 and 73. Annular passages are formed in the housing to interconnect the inlets and outlets and to distribute the fluid pressure uniformly around the periphery of the cartridge. As best shown in FIGS. 5 and 6, an annular inlet passage 79' is for-med in the housing intermediate the wall portions 37a and 3711, which annular passage extends completely around the cartridge and communicates the inlets 78' with the housing inlets 41'. The housing also has a discharge passage 76 formed therein intermediate the wall portions 37b and 370 to extend completely around the cartridge and communicate the cartridge outlets 74' with the housing outlet 42'. The remaining portions of the chamber within the pump housing designated 37' may be vented either to inlet or to a means for maintaining an intermediate pressure between pump inlet and pump discharge pressure. As described in connection with the preceding embodiment, a spring means 69' may be provided for yieldably maintaining the movable end plate against the gear end faces, when the pump is stopped.

From the foregoing it will be seen that the case portion of the cartridge rigidifies the movable end plate and inhibits distortion or deflection of the end plate away from the gear end faces due to the high pressure existing in the discharge zones D. Moreover, the cartridge enables location of the pressure motive surface around the external periphery of the gear assembly and at a point spaced axially from the movable end plate so that the end plate is effectively pulled into engagement with the gear end face. The cartridge also simplifies the passage arrangement for interconnecting the plural inlets and outlets of the multiple gear pump and, since the discharge passage extends completely around the cartridge, it will be seen that the radial hydraulic pressures on the outer periphery of the cartridge are balanced so that the cartridge is not pressed against one side of the housing. The cartridge is accordingly free to float axially within the housing so that the movable end plate can maintain a close running fit with the end faces of the gears. The gears, of course, are free to move axially into engagement with their stationary end plate so as to thereby maintain a close running fit at the other end of the gear assembly. Moreover, since the outer periphery of the cartridge does not have to conform to the shape of the gear assembly, it can have a cylindrical periphery to facilitate machining of the pump housing. In the event of wear or damage to the pump mechanism, the cartridge can be removed and repaired or replaced with a different cartridge to thereby recondition the pump.

While in the foregoing description there have been disclosed specific preferred forms of the present invention, it is to be understood that various changes, modifications, omissions and refinements may be adopted which depart from the described forms of the invention without departing from the spirit and scope of the invention. For example, while the invention is herein illustrated and described in conjunction with a four-gear pump or motor, features of the invention are applicable to other types of pumps or motors having a greater or lesser number of gears.

We claim:

1. A rotary gear pump or fluid motor including a housing defining a chamber having a fluid inlet and an outlet, at least two intermeshing gears in said chamber, a pump cartridge mounted in said chamber for sliding movement in a direction paralleling the gear axes, said cartridge including an end plate having an inner face facing in one direction at one end of said gears and a gear case rigid with said end plate and extending from said inner face in said one direction along the peripheries of the gears in close running fit therewith at areas intermediate the points where the gears are in meshing engagement, end wall means engaging the other ends of said gears, said gear case having means defining a motive surface to which loading pressure may be applied to urge said inner face of the end plate against the ends of the gears, said motive surface facing in a direction opposite said one direction and being spaced in said one direction from said inner face of said end plate, seal means extending between said gear case and said housing defining a pressure compartment communicating with said motive surface, means for applying fluid pressure to said pressure compartment to urge said case and end plate in said one direction, and inlet and outlet passage means communicating said housing inlet and outlet with said gears.

2. A gear pump or motor according to claim 1 wherein said pressure compartment communicates with said outlet in said housing.

3. A gear pump or motor according to claim 1 wherein said seal means includes first and second seals between said pump cartridge and said housing, at points spaced apart in a direction paralleling the axis of said gears, said motive surface being located between said first and second seals, said outlet passage means including an outlet opening in said gear case located between said first and second seals and communicating with said outlet in said housing.

4. A gear pump or motor according to claim 3 wherein one of the items comprising said end wall means and said end plate has an inlet passage therein communicating with said inlet in said housing.

5. A gear pump or motor according to claim 1 wherein said seal means includes first, second and third seals between said pump cartridge and said housing at points spaced apart in a direction paralleling the axis of said gears, said motive surface being located between said first and second seals, said gear case having said outlet pass age means formed therein and located between said first and second seals and communicating with said outlet in said housing, said gear case having said inlet passage means formed therein and located between said second and third seals and communicating with said inlet in said housing.

6. An apparatus according to claim 1 wherein said motive surface is spaced from said inner surface of said end plate a distance greater than the length of said gears.

7. An apparatus according to claim 1 wherein said chamber in said housing has a circular configuration and said pump cartridge has annular peripheral faces slidably engaging the walls of the chamber.

8. A rotary gear pump or fluid motor including a housing defining a chamber having a fluid inlet and an outlet, at least two intermeshing gears in said chamber, a first end plate having an inner face engaging a first end of said gears, a pump cartridge mounted in said chamber for sliding movement in a direction paralleling the gear axes, said pump cartridge including a second end plate having an inner face engaging a second end of said gears, said pump cartridge also including a gear case rigid with said second end plate and extending from said second end plate externally of the gears and slidably surrounding the periphery of said first end plate, said gear case having inner wall portions extending into close running fit with the gear peripheries in areas intermediate the mesh point of the gears, said gear case having first and second peripheral portions slidably engaging said housing, said first peripheral portion being located adjacent said first end of said gears and having an outer dimension larger than said second peripheral portion to define a motive surface on the outside of the case facing in a direction opposite the inner face on said second end plate, means for applying fluid pressure to said motive surface to urge said second end plate against said second gear end face, and inlet and outlet passage means communicating said inlet and outlet with said gears.

9. A fluid pump or motor according to claim 8 wherein said outlet passage means extends through said case adjacent said motive surface to apply discharge pressure thereto, said inlet passage means extending through one of said end plates.

10. A fluid pump or motor according to claim 8 wherein said outlet passage means extends through said case adjacent said motive surface to apply discharge pressure thereto, said inlet passage means extending through said case at a point spaced from said outlet passage means in a direction paralleling the gear axes, and means sealing the case to the housing at points intermediate the inlet and outlet passage means.

11. In a rotary gear pump or fluid motor including a housing defining a chamber having an inlet and an outlet, a gear assembly including four gears having separate shafts and arranged in a regular polygon with each gear meshing with two adjacent gear-s to provide inlet and discharge zones in alternate sequence around the gear assembly adjacent the mesh points of adjacent gears, a first end plate having an inner face engaging one end of said gears and openings for receiving the gear shafts, the improvement comprising a pump cartridge mounted in said chamber for sliding movement in a direction paralleling the gear axes, said pump cartridge including a movable end plate having an inner face engaging a second end of said gears, said pump cartridge also including a gear case rigid with said movable end plate and extending therefrom externally of the gear assembly and slidably surrounding the periphery of said first end plate, said gear case having inner wall portions extending into close running fit with the gear peripheries in areas intermediate the mesh points of the gears, and inlet and discharge passage means communicating said inlet and outlet with said inlet and discharge zones.

12. A pump or motor according to claim 11 wherein said discharge passage means includes outlet openings extending through said case and communicating with said discharge zones, and means defining an outlet passageway between the housing and case and extending around the latter to communicate the several outlet openings with the outlet in the housing.

13. A pump or motor according to claim 12 wherein said inlet passage means includes passages in one of said end plates communicating with said inlet zones.

14. A pump or motor according to claim 12 wherein said inlet passage means includes inlet openings extending through said case and communicating with said inlet zones, said inlet and outlet openings opening at the outer side of the case at points spaced apart along the case in a direction paralleling the gear axes, and means defining an inlet passageway between the housing and case and extending around the latter to communicate the several inlet openings with the inlet in the housing.

15. A pump or motor according to claim 12 wherein said case has means defining a motive surface extending around the case adjacent the end thereof remote from said movable end wall and facing in a direction opposite the inner face of the movable end wall to urge the movable end Wall against the gear end faces when pressure is applied to the motive surface, and means for applying fluid at above inlet pressure to said motive surface.

16. A pump or motor according to claim 15 wherein said outlet passageway communicates with said motive surface to apply discharge pressure thereto.

17. In a rotary gear pump or fluid motor including a housing defining a chamber having an inlet and an outlet, :at least two intermeshing gears having separate shafts, a first end plate having an inner face engaging one end of said gears and openings for receiving said gear shafts, the improvement comprising a pump cartridge mounted in said chamber for sliding movement in a direction paralleling the gear axes, said pump cartridge including a movable end plate having an inner face engaging a second end of said gears, said pump cartridge also including a gear case rigid with said movable end plate and extending therefrom externally of the gear peripheries and slidably surrounding the first end plate, said gear case having inner wall portions extending into close running fit with the gear peripheries in areas intermediate the mesh points of the gears, inlet and discharge passage means communicating said inlet and outlet with said intermeshing gears, said discharge passage means including an outlet opening in said case communicating with said gears, and means defining an outlet passageway between the housing and case and extending completely around the latter, said outlet passageway communicating with said housing outlet and said outlet opening in said case.

References Cited UNITED STATES PATENTS 2,470,355 5/1949 Lauck 103-126 2,649,740 8/ 1953 Murray et a1. 103-126 2,765,749 10/1956 Mosbacher 103-126 2,837,031 6/1958 Ilune 103-126 2,993,450 7/1961 Weigert 103-126 3,292,550 12/1966 Gordon 103-126 FRED C. MA'ITERN, JR., Primary Examiner.

WILBUR J. GOODLIN, Assistant Examiner.

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