US2420622A

US2420622A - Pump with pressure loaded bushing

Info

Publication number: US2420622A
Application number: US439030A
Authority: US
Inventors: Jay M Roth; John A Lauck
Original assignee: Borg Warner Corp
Current assignee: Borg Warner Corp
Priority date: 1942-04-15
Filing date: 1942-04-15
Publication date: 1947-05-13
Anticipated expiration: 1964-05-13

Description

May 13, 1947.

J. M. ROTH a-rm. 2, 0, PUMP WITH PRESSURE LOADED BUSHING I Filed April 15, 1942 3 Sheets-Sheet 1 F j friveru arsr c y M3056, dyad y 1947- J. M. ROTH arm.

I PUMP WITH PRESSURE LOADED BUSHING 3 Sheets-sheaf. 2

Filed April 15, 1942 resulted in increased Fatented May i3, wt?

UNITED STATES PATENT steeper FFlCE 2,420,622 7 PUMP WITH PRESSURE LOADED BUSHING Jay M. Roth,

Euclid, Ohio, assignors,

to Borg-Warner Corpo v corporation of Illinois Application April 15, 1942, Serial No. 439,030

- 1 This invention relates to high pressure gear contact with the gears.

It has heretofore been ply the output pressure ample, or 1,000 to 5,000 and higher; the same must be composed principally of lightweight metal since operation is contemplated as a pump ormotor on an aircraft; the same may be required to have a relatively small displacement of from 0.01 cubic inch to 10.0 cubic inches where it must operate either as a pump or motor on an aircraft:

pounds per square inch We have found that all of the above factors 65 several surfaces by pressing the bushings Euclid, and John A. Lauck, South by mesne assignments, ration, Chicago, 111., a g

23 Claims. (Cl. 103126) can be controlled in harmony with one another, and desired results obtained by properly balancing the liquid pressures made to act on the pressure of the pump, irrespective of whether the pump is operating at relatively low pressure or at a very high pressure of the order, for example, of 5,000 pounds per square inch or higher.

7 It is an object of this invention to incorporate an improved unbalanced relationship between the gears and the end bearing bushings or end plates of a high ficiency. improved arrangement of adaptable for lightweight high pressure liquid gear type aircraft pumps.

It is an object to provide an improved construction of an and arrangement in combination with a liquid pressure operated coupling seal.

Another object is the provision of an outlet liquid pressure operated unbalanced bushing and bearing construction of the above type in combination with an arrangement providing for automatic reversal of direction of operation in response only to reverse rotationofthe gears, without requiring any special adjustment or reversal Y of other parts Still another object is the provision of a pumping seal arrangement between the bushing and the enclosing housing which also provides for the against the associated gear face.

It is another object to provide, in a high pressure liquid gear pump, an

such a bushing construction ment of passages erated by the pump, whereby to create a precise small unbalance of axial force acting on said a pumping seal engagement between said bushing and the adjacent radial face of its associated gear.

It is a still further object to provide in a high pressure liquid displacement gear device of the present type an improved arrangement for establishing and maintaining a plurality of liquid pressure zones each having a definite function in connection with the operation of the end plates or bushings and with the coupling seal.

A final object is the provision of an arrangement of the above type which is'equally effective in its operation for supplying pressure as apump or being rotated as a motor by an input pressure liquid stream.

Other and more particular objects, advantages and uses of our invention will become apparent from a reading of the following specification taken in connection with the accompanying drawings forming a part thereof and wherein: 1

Fig. 1 is an axial cross-section view of .a gear pump incorporating the preferred embodiment and is taken substantially on the line i-i of Fig.

Fig. 2 is a cross-section view taken substantially on the line 2-2 of Fig. 1, and showing to advantage the arrangement of the important distribution passages in the end closure plate;

Fig. 3 is a broken-away cross-section view taken substantially on the line 3--3 of Fig. 1 and bringing out to advantage the arrangement for conducting the pressure from the high pressure side of the gear teeth to the back face of the bearing bushings;

Fig. 4 is a cross-section view taken substantially on the line 4-4 of Fig. 1, still further bringing out the arrangement of liquid pressure distribution passages in the end closure plate;

Fig. 5 is a broken-away cross-section view taken substantially on the line 5-5 of Fig. 1, showing the two adjacent complementary end bearing bushings and the closure plugs inserted therebetween for preventing-the leakage of fluid in the area of juncture bushings; Fig. 6 is a broken-away cross-section view taken substantially on the line 6-6 of Fig. 4 and showing the liquid passages communicating with the opposite sides of the gear teeth, which passages may selectively be the inlet or outlet depending upon the direction of rotation of the gears;

Fig. 7 is a broken-away cross-section view taken substantially on the line 1-1 of Fig. 4 and bringing out to still further advantage the arrangein the end closure plate; Fig. 8 is a schematic axial cross-section view bringing out in a simplified form the relationship of the important parts of the preferred embodiment of the present invention;

Fig. 9 is a broken-away schematic cross-section view showing an alternative arrangement to that presented in Fig. 1 for controlling the effective pressure on the end bearing bushings;

Fig. 10 is a another alternative arrangement for controlling the effective pressure acting on the end bearing bushings;

Fig. 11 is a broken-away schematic cross-section view showing still another alternative arrangement for controlling the effective pressure acting onthe end bearing bushings; and

bushing in the direction of the gearto maintain between these bearing broken-away schematic cross-section view showing Fig. 12 is a view similar tom. 9, but showing and the adjacent produce a pumping seal.

an alternative arrangement of the relief recess in the gear and a-passage recess.

Referringin greater detail to the figures of the drawings, 10 indicates generally a liquid gear pump adapted to be driven from an aircraft motor auxiliary power shaft (not shown) and incorporating a preferred embodiment of our invention. Main pump housing ll of lightweight metal, such as aluminum, is formed with parallel overlapping or intersecting cylindrical chambers i2 and i3 receiving gears H and i5 meshing in the overlapping area. Housing end wall closure plate ll of the same lightweight metal is attached to the open end of housing ii as by threaded stud bolts l8. The inner exposed surface of closure member l1 forms end walls i9 and 20 of gear chambers l2 and I3 which end walls extend radially parallel to the opposite end walls 2! and 22, the gears having a coaxial thickness less than the coaxial dimension of chambers l2 and i3 providing annular spaces on both sides of the gears. Gear chamber end walls is, 20, 2i and 22 are formed with reduced

bore extensions

28, 21, 28 and 28 respectively, and the gears l4 and ii are provided with oppositely extending coaxial journals 3i 32, 33 and 34 of smaller cross-section than the extension bores and received coaxially in said bores.

Of particular importance in the present invention is the provision of specially constructed and operated end plates or hearing bushings indicated generally at 33 in Figs. 1 through 8, these bushings being interposed between the housing and the gears and made of a suitable bearing material such as bronze. There are pr ferably four of these bearing bushings 33 each having the same formation and including a tubular portion 31 received in embraced relation about each of the gear journals within an associated bore extension and a radially outwardly extending flange terminal portion 33 received in the adjacent gear chamber in the space between the gear face and the gear chamber end wall. A flexible sealing ring 39 is interposed between the tubular portions 31 of each bushing and the surrounding extension bore for preventing passage of liquid therebetween. The terminal flanges 38 are arranged to have a limited axial piston-like operation or adjustment in chambers i2 and I3 adjacent at least one side of the gears for bringing the gears and flanges into sealed contact, which arrangement provides a pair of annular liquid pressure chambers or spaces 4! and 42 between end walls I9, 20 and the back face or side of the adjacent flanges 38. The tubular portions 31 within

coaxial extensions

26 and 21 likewise have a limited pistonlike adjustment therein. The annular pressure chambers ll and 42 are arranged to be supplied with liquid pressurefrom the high pressure side or the gear teeth by a specially formed .set of conduits and valves later to be described in detail.

The opposite or inner terminal portions of flanges 38 are formed with front or inner radially extending faces 44 parallel to the adjacent side face Ha or face lid of the associated gear It or i5 and arranged to normally engage the same to We have found that where this face has been made coextensive with the gear proper from a point adjacent the journal'radially outwardly to the periphery of the gear teeth. this has resulted in improper operation. when high pressures are approached, then the pressure acting between flange face 44 gear fac becomes sufliciently leading from said relief the right-hand side pressure that may be produced between the bushing front faces 44 and the adjacent gear faces Ma and lie. This must be a relatively small differential pressure of a value that will not produce excessive wear between the bushing surfaces and the gear, surfaces since, if such wear is present, the same would necessarily be accompanied by excess power consumption in turning the pump gears.

We accomplish a solution of the present problem taking the above into consideration by providing a relief recess indicated generally at 46 and located at a position between the gear faces and the adjacent bushing faces 44. This recess 46 is placed in communication with a low pressure zone as will be described in greater detail hereinafter. While we have shown between each bushing front face 44 and the adwould be required in all of the faces important function of the relief recesses 46 is to reduce the efiective pressure area between the flange front faces 44 and the adjacent gear radial faces to a value below the effective pressureor axial force acting in the opposite direction out the back faces 44a of the flanges 38 within annularpressure chambers 4| and 42. -It is important to note that it is only necessaryfor this difierential of pressure or axial force to be a relatively small fraction of the total pressure within annular pressure or axial force acting chambers the extremely high pressure The bushing flanges 38 thus have the pressure on the annular pressure chamber side thereof always slightly predominating to produce an unbalance in the direction of the gear to maintain the required seal with no excess pressure which would produce objectionable wear.

It will be seen that each of the 38 has an arcuate portion in the area of meshing of the gear teeth. It has been found that due to the imperfections of manufacture, the bushing flanges at the terminal portions of surfaces 38:: do not fit accurately, and hence a certain amount of leakage or by-passing of liquid would normall occur between the high pressure side of the gear teeth 6 and the low pressure side, this leakage taking place through these imperfections in the fit. As a solution to this problem, we have provided for the insertion of closure plugs 380.

Main liquid conducti gear teeth and requiring no special adjustment or interchange of parts. applicable whether the gears are being driven by' a motor and thus function as a pump or whether the gears are being rotated as a fluid motor by the introduction to conduit 48 or 49 of high pressure fluid effective to rotate the gears. Forv accomplishing this automatic reversal of operation there is provided a speciaiarramgement of distribution conduits and valves in end closure member l1. Referring first to Figs. 1 through 8 and assuming for purpose of description that gears I4 and I5 are bein driven as a pump in the direction to make conduit 48 the inlet 'low pressure side and conduit 49 the outlet high pressure side,- passage 5| leads from a point in communication with the high pressure side of the gear teeth to a spring pressed ball check valve 52 opening the same and thence through passage 53 to annular pressure chambers 4| and 42. Alternative passage 5 la leads from conduit 48 to spring actuated ball check valve 52a and thence through passage 53a to annular pressure chambers 4| and that may be involved.

I sure which is effective 42. Ball check valves 52 and 52a are oppositely acting, the opening of ball check valve 52 in response to the high pressure in. conduit 49 being effective to admit pressureto ball check valve 52a in the closing direction with the resultthatnne of these valves is always toopen the other. It, therefore, makes no difference which side is the high pressure side of the gear teeth since this relatively high pressure is effective to open the proper one of the valves 52,, 52a and to close the other. The spring actuated check valve 52 or 52a, as the case may be, imposes a slight which the valve is subjected as not to materially enter into the resulting operation of the bushing. For example, the pressure drop imposed by either check valve 52 or 52a will not ordinarily be above the order of 15 to 50 pounds per square inch, while the high pressure at the outlet side of the gear teeth may be of the order of 10,000 to 30,000 pounds per square: inch or higher.

In order for relief recess 46 I provided for producing a pressure drop between relief recess 46 and the low pressure or inlet side of the gear teeth thus to This arrangement is held closed by the pres provide an interme iiate liquid pressure zone having a definite purpose to be pointed out. Passage 56 leads from a point in communication with high pressure conduit 49 on the discharge side of the gear teeth to spring pressed check valve 51 holding the same closed to prevent the passage of liquid through conduit 66 to bore extension 21 while passage 56a. leads from a point in communication with low pressure conduit 48 of the inlet side of the gear teeth to spring pressed ball check valve 51a which will be opened in response to the occurrence of a predetermined intermediate liquid pressure within extension bore 21 acting through passage 58a. It is thus seen that

check valves

51, 51a will alternatively act to shut off the high pressure from. entry into bore extension 21 and prevent the occurrence of a pressure in the extension bore above a predetermined value by relieving ,liquid pressure to either

main passage

48 or 49 depending entirely upon which is the high pressure side of the gear teeth and requiringno special adjustment or interchange of parts.

Bore extensions

26 and 21 are placed in communication with one another through passage 6|. Washer-like elements 62 are positioned in the

bore extensions

26, 21 and are held in engagement with the ends of tubular portions 31 by springs 63 for maintaining an initial engagement between the gear faces and the bushing flanges. A passage 66 formed coaxially through journal 32, gear l and journal 33 places the secondary fluid pressure in communication through a passage 61 with a fluid pressure operated flexible coupling assembly indicated generally at 68. A coaxial passage 1| through journal 3|, gear l4 and journal 34 likewise places the intermediate liquid pressure zone in communication with flexible coupling 68. Gear journal 34 is provided with an extension 12 passing through the wall of housing II and formed on the periphery thereof with coaxially extending splines 13 forming part of flexible coupling assem- .bly 68. A C0llp1iiig member 14 is formed internally with complementary splines cooperating with splines 13 and with a radially extending flange 15 engaging a bearing ring 16, the opposite side of which presses against a flexible ring seal. 11 retained against the housing. Coupling member 14 terminates on the outer end thereof in a spli-ned or gear connector 14a (Fig. 1) adapted to cooperate in driving relation with an auxiliary power shaft of an aircraft engine or other driving means. A compression spring 80 has its inner end engaging a shoulder in the bore or passage 1| of gear I4 and the outer end engaging a member 14 f r eliminating initial end play and effecting initial sealed engagement of flange 15, ring 16 and flexible seal 11. The intermediate liquid pressure communicated through passage 61, as well as that communicated through passage 1| and between splines 13, is effective to cause the operation of the above seal assembly. This intermediate pressure is determined by the drop in pressure across spring pressed

ball check valve

51 or 51a. These check valves are effective tomaintain a small positive pressure on seal assembly 68. This intermediate pressure zone also furnishes a relatively low pressure area for communication with the relieved recess 46 in the bushing which communication is effected through connecting passage 8 In order to re der effective the relief recesses 46 between the gear faces and the flange faces 44, these recesses must be placed in communication with a. pressure considerably lower than that existing in the annular pressure chambers 4|, 42.

In the principal embodiment of the invention this is accomplished by placing the relief recess 46 in communication with the intermediate fluid pressure zone to which the flexible coupling assembly is exposed as this is important to the proper automatic reversibility of the pump. communication is effected by forming each bushing with a. coaxially extending channel or 8|, two such grooves or channels being shown for each bushing as this improves the distribution and makes it possible to employ a smaller crosssection of groove; however it will be apparent that one channel or groove may be employed in each bushing. It will also be apparent that in the case of a very small capacity pump where the relief recess is employed in the bushings on only one side of the gears, then the bushings on the opposite side of the gears will not require any coaxially extending channel or groove.

Fig. 9 shows an alternative construction of gear and bushing for obtaining the required "unbalance" of liquid pressure. Gear 4 has a recessed groove 5 formed therein radially inwardly of the gear teeth adjacent the gear journal, a bushing 6 not requiring any recess in the face thereof. The bushing H6 is provided with a groove 1 similar to the groove 6| in the bushing 36. It will be apparent that the relief groove 5 may be formed on one side only of gear 4 adjacent bushing 6 as shown or the necessary relief may be obtained by having grooves 6 on both sides of the gear. In the former case, of course, the single groove 5 will necessarily have to be larger than where this function is shared by grooves on both sides of the gear.

Fig. 10 shows an alternative bushing construction for obtaining the necessary relief wherein the bushing I26 is formed with a beveled portion |21 to provide the necessary relief and one end of a groove I28 in said bushing communicates with said relief.

Fig. 11 discloses still another alternative arrangement wherein the relief recess 46 of the primary form or its equivalents in the above alternative forms are placed in communication with the low pressure or suction side of the Pump by means of a radial groove or channel |3| in the face of the bushing leading from the relief recess 46 to the inlet or suction side of the pump. This alternative form is, of course, applicable only where it is unnecessary that automatic reversal 'of operation be provided for.

A very satisfactory way of determining the proper size of relief recess to be provided in the bushing or gear, as the case may be, is to successively remove small increments of metal gradually increasing the size of the relief recess, as by turning on a lathe, until it is found on assembly that the bushings are held in close contact with the gear faces at high pressures. Once the exact size has thus been arrived at for the bushing of any particular pump, then it becomes a mere matter of duplication.

Fig. 12 shows an alternative form similar to that of Fig. 9 but differing therefrom in having relief passage recess groove 5 in communication with the low pressure instead of accomplishing this by a coaxial channel in the bushing as in Fig. 9.

While we hav disclosed our invention in connection with certain specific embodiments thereof, it is to be understood that these are by way of example rather than limitation, and it is intended that the invention be defined by the ap- ||5a in'the gear for placing relief 9 pended claims which should be given a scope as broad as consistent with the prior art.

We claim: 1. A liquid pump comprising: a housing having a pump chamber and an inlet leading to and an outlet leading from said pump chamber; means including a rotatable member received in said pump chamber for forcin liquid-from said inlet out Of said housing through said outlet; an end-plate in said pump chamber having a back face normally spaced from the adjacent end wall of said pump chamber and having portions cooperable with said housing to provide a pressure chamber, said end plate also having a front face subject to the pressures in said pump cham-" her and cooperable with the adjacent side face of said rotatable member to provide a pumping seal therewith, one of said two last-mentioned faces having a relief recess formed therein inwardly of its outer periphery to limit the sealing area between said side face and said front face; means establishing communication between said relief recess and said inlet; and means establishing communication between said pressure chamber at the back face of said end plate and saidoutlet, the relation of the area of said back face to said sealing area being such that the force acting upon said back face of said end plate always slightly exceeds the force acting upon said front face of said end plate, whereby to maintain said pumping seal without excessive friction, wear or loss in volumetric efliciency.

2. A pump device comprising: a housing containing a pair of adjoining substantially cylindrical chambers having radial end walls, said housing also having a. high pressure port and a relatively low pressure port communicating with said chambers, a toothed gear member in eachof said housing chambers, said gear members meshing at the juncture of said housing chambers; end plate means in said housing associated with said ear members on at least one side of said gear members, said end plate means including front faces cooperable with the adjacent side faces of the associated gear members, said front faces and said side faces constituting pairs of adjacent faces which provide a pumping seal between said gear members and said endplate means, said front faces being subject to the pressures in said housing chambers, said end plate means also having a backface normally spaced from the adjacent radial end wall of the associated housing chambers and having portions cooperable with said housing to provide pressure space at the back of said end plate means; means establishing communication between said high pressure port and pressure space at the back of said end plate means, whereby to subject the back of said end plate means to the pressure of the fluid in'said high pressure port; a relief recess in one face of each pair of said pairs of adjacent pumping seal providing faces, said relief recesses being disposed inwardly of the root of the teeth of said gear members, respectively, to limit the sealing area between said side faces of said gear members and said front faces of said end plate means; and means establishing communication between said relief recesses and a zone under less pressure than the pressure in said high pressure port.

3. A device comprising: a housing containing a pair of adjoining substantially cylindrical chambers having radial end walls, said housing also having a high pressure port and a relatively low pressure port communicatin with said chambers; a toothed gear member in each of said housback faces of front faces extendin face normally spaced 10 ing chambers, said gear members having radial side faces flush with the side extremities of said teeth, the teeth of said gear members meshing at the juncture of said housing chambers; end

plates in said housing associated with said gear members on at. least one side of said gear members, said end plates each having a front face cooperable with the adjacent side face and teeth of its associated gear member, said front face and said side face constituting a pair of adjacent faces which provide an operating seal between said respective gear members and said bushing members, said front faces being subject to the pressures in said housing chambers, each of said end plates also having a back face normally spaced from the adjacent radial end wall of its associated housing chamber and having portions cooperable with said housing to provide a, pressure space at the back face of each of said end plates; means establishing communication between said high pressure port and the pressure spaces at the said end plates, whereby to subject said back faces to the pressure of the fluid in said high pressure port; a relief recess in one face of each pair of said pairs of adjacent seal providing faces, said relief recesses being disposed inwardly of the'root of the teeth of said gear members, respectively, to limit the sealing area between said side faces of said gear members and said front faces of said bushing members; and means venting said relief recesses to a zone under less pressure than the pressure in said high pressure port, the relation of the areas of said back faces with respect to the sealing areas of said front faces being such that a slight pressure difierential is created which is eflectivc to permit a small amount of fluid to pass between said seal providingfaces from said high pressure port to said relief recesses without excessive loss of volumetric efficiency.

4. A liquid pump comprising: a housing containing a pair of adjoining substantially cylindrical chambers having radial end walls, said housing also having an inlet leading to and an outlet leading from said chambers; a toothed gear member in each of said housing chambers, said gear members meshing at the juncture of said housing chambers; end plates in said housing associated with said gear members on at leastone side of said gear members, said end plates each having afront face cooperable with the adjacent side face of its associated gear member, said front face and said side face constituting a pair of adjacent faces which provide a pumping seal between said respective gear members and said end plates, said radially outwardly to a point at least beyond the root of the teeth of the respective gear members and being subject to the pressures of the liquid in said housing chambers, each of said end plates also having a back from the adjacent radial end wall of its associated housing chamber and having portions cooperable with said housing to provide a pressure space at the back face of each of said end plates and also to provide for limited axial adjustment of said end plates in said housing relative to said gear members; means estab lishing communication between said outlet and the pressure spaces at the back faces of said endspectively, to limit the sealing area between said side faces of said gear members and said front faces of said end plates; and means venting said relief recesses to a zone under less pressure than the pressure in said outlet, the relation of the areas of said back faces with resp ct to said front faces being such that a slight pressure differential i created which is effective to permit a small amount of liquid to pass between said seal providing faces from saidoutlet to said relief recesses to provide a lubricating fllm to eliminate excessive friction and wear, without excessive loss in volumetric efllciency.

5. A pump as defined in claim 4, in which the zone under less pressure than the pressure in the outlet is the inlet, so that a limited return of liquid occurs from said outlet to said inlet.

6. A pump as defined in claim 4, including means acting upon the end'plates effective to maintain a seal between said end plates and gear members during the period of initial operation of the pump.

'7. A. pump comprising: a housing containing a pair of adjoining substantially cylindrical chambers having radial end walls, said housing also having an inlet leading to and an outlet leading from said chambers; a toothed gear member in each of said chambers, said gear members meshing at the juncture of said chambers; bores in the radial end walls of said chambers forming reduced extensions of said chambers, said gear members having journals extending from the opposite sides thereof into said reduced bores; a bushing member in said housing on one side of one of said gear members, said bushing member including a flange disposed in one of said chambers and a tubular neck surrounding one of the journals of said one gear member and received in the reduced bore associated with said journal, said flange having a front face confronting the adjacent side face of said one gear member to form a pumping seal therewith, said front face being subject to the pressures in said one gear chamber, said flange also having a back face normally spaced from the adjacent radial end wall of said one chamber to provide an annular pressure space at the back face of said flange; means establishing communication between said outlet and said annular pressure space to subject said back face to the pressure in said outlet; a relief recess formed in one of the confronting seal forming faces of said gear and bushing members, said relief recess being disposed inwardly of the root of the teeth of said one gear member to limit the sealing area between said side face of said gear-member and said front face of the flange of said bearing member; and means establishing communication between said relief recess and said inlet.

8. A pump comprising: a housing containing a pair of adjoining substantially cylindrical chambers having radial end walls, said housing also having an inlet leading to and an outlet leading from said chambers; a toothed gear member in each of said housing chambers, said gear members meshing at the juncture of said housing chambers; bores in the end walls of said housin chambers forming reduced extensions of said housing chambers, said gear members having journals extending from the opposite side thereof into said reduced bores; bushing members in said housing on at least one side of said gear members, said bushing members including flanges disposed in said housing chambers and tubular necks surrounding the journals and re- 12 ceived in the reduced bores on said one side of said gear members, said flanges each having a front face cooperable with the adjacent side face of its associated gear member, said front face and said side face constituting a pair of adjacent faces which provide a pumping seal. between said respective gear members and said bushing members, said front faces being subject to the pressures in said housing chambers, each of said flanges also having a back face normally spaced from the adjacent radial end wall of its associated housing chamber to provide an annular pressure space at the back face of each of said flanges; means establishing communication between said outlet and the annular pressure spaces at the back faces of said flanges, whereby to subject said back faces to'the pressure developed in said outlet by said gear members; a relief recess in one face of each pair of said pairs of adjacent pumping seal providing faces, said relief-recesses being disposed inwardly of the root of the teeth of-said gear members, respectively, .to limit the sealing area between said side faces of said gear members and said front faces of the flanges of said bushing members; and means establishing communication between said relief recesses and said inlet.

9. A pump comprising: a housing containing a pair of adjoining substantially cylindrical chambers having radial end walls, said housing also having an inlet leading to and an outlet leading from said chambers; a toothed gear member in each of said housing chambers, said gear members meshing at the juncture of said housing chambers; bores in the end walls of said housing chambers forming reduced extensions of said housing chambers, said gear members having journals extending from the opposite sides thereof into said reduced bores; bushing members in said housing on at least one side of said gear-members, said bushing members includin flanges disposed in said housing chambers and tubular necks surrounding the journals and received in the reduced bores on said one side of said gear members, said flanges each having a front face cooperable with the adjacent side face of its associated gear member to provide a pumping seal between said respective gear members and said bushing members, said front faces being subject to the pressures in said housing chambers, each of said flanges also having a back face normally spaced from the adjacent radial end 'wall of its associated housing chamber to provide an annular pressure space at the back face of each of said flanges; means establishing com- -munication between said outlet and the annular pressure spaces at the back faces of said flanges, whereby to subject said back faces to the pressure developed in said outlet by said gear members; a relief recess in said front face of the flange of each of said bushing members; said relief recesses being disposed inwardly of the root of the teeth of said gear members, respectively, to limit the sealing area between said side faces of said gear members and said front faces of the flanges of said bushing members; and means establishing communication between said relief recesses and said inlet.

10. A pump comprising: a housing containing a pair of adjoining ,substantially cylindrical chambers having radial end walls, said housin also having an inlet leading to and an outlet leading from said chambers; a tooth gear member in each of said housing chambers, said gear members meshing at the juncture of said housr 14 lishing communication between said relief recesses and said inlet including passage means ing journals extending from the opposite sides I thereof into said reduced bores; :bushing members in said housing on at least one side of said gear members, said bushing members including flanges disposed in said housing chambers and tubular necks surrounding the journals and received in the reduced bores on said one side of said gear members, said flanges each having a front face cooperable with the adjacent side face of its associated gear member to provide a pumping seal between said respectivegear members and said bushing members, said front faces being subject to the pressures in said housing chame bers, each of said flanges also having a back face normally spaced from the adjacent .radial. end wall of its associated housing chamber to provide an annular pressure space at the back face of each of said flanges; means establishing com munication between said outlet and the annular pressure spaces'at the back faces of said flanges, whereby to subject said back faces'to the pressure developed in said outlet by said gear members; a relief recess in said side face of each of said gear members, said relief recesses being disposed inwardly of the root of the teeth of said gear members, respectively, to limit the sealing area between said side faces of said gear members and said front faces of the flanges iof said bushing members; and means establishing communication between said relief recesses and said inlet.

11. A pump comprising: a housing containing a pair of adjoining substantially cylindrical chambers having radial end walls, said housing also having an inlet leading to and an outlet leading from said chambers; atoothed gear memb'er in each of said housing chambers, said gear members meshing at the juncture of said housing chambers; bores in the end walls of said interconnecting saidreduced boreson said one side ,of sa-idgear members with said inlet; and

flexible seal rings between said journals and said reduced bores on said one sideof said gear members for preventing leakage of pressure fluid from said annular pressure spacesinto said reduced bores.

12. A pump as defined in claim 11, in which the means establishing communication between the relief recessesand the inlet further includes passage means in the bushing members extending along the outer surface of the journals of their associated sear members.

13. A pump as defined in claim 11, in which the means establishing communication between the relief recesses and the inlet further includes a passage in the front face of each of said bushing members. f a

14. A pump as defined in claim l1, in which the journals on said one side of said gear members have a longitudinal passageway communicating at one end with their associated reduced bores, and in which the means establishing communication between the relief recesses and the inlet further includes a passage in each of said gear members interconnecting a relief recess with the longitudinal passageway in the journal thereof.

15. A pump comprising: a housing containing a pair of adjoining substantially cylindrical chambers having radial end walls: a toothed gear member in each of said housing chambers, said gear members meshing at the juncture of said housing chambers, said housing having an inlet communicating with one side of said gears and i an outlet communicating with the opposite side of said gears; bushing members in said housing associated with said gear members on at least 7 one side of said gear members, said bushing housing chambers forming reduced extensions of said housing chambers, said gear members having journals extending from the opposite sides thereof into said reduced bores; bushing members in said housing on at least one side of saidgear members, said bushing members including flanges disposed in said housing chambers and tubular necks surrounding the journals and received in the reduced bores on said one side of said gear members, said flanges each having a members each having'a front face cooperable with the adjacent side fa :e of its associated gear member, said front face and said side face constituting a pair of adjacent faces which provide a pumping seal between said respective gear front face cooperable with the adjacent side face of its associated gear member, said front face and said side face constituting a pair of adjacent faces which provide a pumping seal between said respective gear members and said bushing members, said front faces being subject to the pressures in said housing chambers, each of said flanges also having a back face normally spaced from the adjacent radial end wall of its associated .housing chamber to provide an annular pressure space at the back face of each of said flanges; means establishing communication between said outlet and the annular pressure spaces at the back faces of said flanges, whereby to subject said back faces to the pressure developed in said outlet by said gear members; a relief recess in one face of each pair of said pairs of adjacent pumping seal providing faces, said relief recesses being disposed inwardly of the root of the teeth of said gear members, respectively,to

limit the sealing area between said side faces of members and said bushing members, said front faces beingsubject to the pressures in said housing chambers, each of said bushing members also having a back face normally spaced from the adjacent radial and wall of its associated housing chamber to provide a pressure space at the hack face of each of said bushing members and also to provide for limited axial movement of said bearing membersrelative to said housing; a first conduit means having a one-way check valve therein establishing communication between said outlet and the pressure space at the back face of said bushing members, whereby to subject said back facesto the pressure developed in said outlet by said gear members; a relief recess in one face of each pairof said pairs of adjacent pumping seal providing faces, said relief recesses being disposed inwardly of the root of the teeth of said gear members, respectively, to limit the sealing area between said side faces of said gear members and said front faces of said bushing members; and a second conduit meanshaving a one-way check valve therein establishing communication between said relief recesses and said inlet.

16. A pump as defined in claim 15, including spring means in the housing urging said bushing members toward said gear members to initially maintain a seal at the timesaid pump is started.

17. A pump as defined in claim 15, in which the housing has an opening; a coupling for driving one of said gear members including a connector extending through said opening; fluid pressure responsive means for forming a seal around said opening between said housing and said connector; and passage means communicating with said second conduit means for applying pressure to said fluid pressure responsive seal to prevent leakage from said housing at said coupling.

18. A reversible pump comprising: a housing containing a pair of adjoining substantially cylindrical chambers having radial end walls, a

l toothed gear in each of said housing chambers,

said gear members meshing at the juncture of said housing chambers, said housing having a first port communicating with one side of said gear members and a second port communicating with the opposite side of said gear members; bushing members in said housing associated with said gear members on at least one side of said gear members, said bushing members each having a front face cooperable with the adjacent side face of its associated .gear member, said front face and said side face constituting a pair of adjacent faces which provide a pumping seal between said respective gear members and said bushing members, said front faces being subject to the pressures in said housing chambers, each of said bushing members also having a back face normally spaced from the adjacent radial and .wall of its associated housing chamber to provide a pressure space at the back face of each of said bushing members and also to provide for limited axial adjustment of saidbushing members relative to said gear members; a relief recess in one face of each pair of'said pairs of adjacent pumping seal providing faces, said relief recesses being disposed inwardly of the root of the teeth of said gear members, respectively, to limit the sealing area between said side face of said gear members and said front faces of said bushing members; means providing for automatic reversibility of pumping rotation including a first passage and a second passage in said housing, each of said passages having a one-way check valve therein arranged so that said first and second passages establish communication between said first and second ports, respectively, and the pressure space at the back faces of said bushing members, said check valves being arranged to allow flow only in a direction toward said pressure spaces whereby to subject said back faces to the pressure in said first or second ports depending upon which is under the higher pressure; a third passage and a. fourth passage in said housing each containing a one-way check valve and establishing communication between said relief recesses and said first and second ports, respectively, with the one-way check valves in said third and fourth passages arranged to permit flow only in a direction from said relief recesses toward said first or second ports depending upon which is under lower pressure, the relation of the effective areas of said back faces with respect to said front faces being such that. a slight pressure differential is created which is effective to permit a small quantity of liquid to pass between said seal providing faces from the'high pressure side of the gear members to said relief recesses without excess loss in volumetric efficiency, whereby when said gear membe s are rotating in one direction and said first port is under high pressure and said second port is under a relatively low pressure, fluid under pressure will flow from said first port through said firstpassage to the spaces at the back of said bushing members and saidasmall volume of liquid can pass from said relief recesses through said third passage to said second port, and When said gear members are rotating in the opposite direction and the pressure conditions in said ports are reversed fluid under pressure can flow from said-"'scond port through said second passage to the spaces at the back of said bushing members and said small volume of liquid canlpass from said relief recesses through said fourth passage to said first port; and spring means urging said bushing members toward said gear members to initially maintain a seal at the time said pump is started.

19. A device comprising: a housing containing a pair of adjoining substantially cylindrical chambers having radial end walls; a toothed gear member in each of said housing chambers, said gear members meshing at the juncture of said housing chambers and having oppositely extending supporting journals, said housing having an inlet on the low pressure side of said gear members and an outlet on the high pressure side of said gear members; a bushing member in each of said housing chambers associated with said gear members on at least one side of said gear members, said bushing members each having a front face cooperable with the adjacent side face of its associated gear member to form a seal therewith, said bushing members including generally circular portions complementary to the housing chambers associated therewith and also having complementary meeting surfaces disposed in the zone of juncture of said housing chambers, said bushing members and housing each having a portion thereof removed to conjointly provide a recess at one extremity, at least, of said meeting surfaces; and a closure plug in said recess for preventing leakage of fluid along said meeting faces from the high pressure side of said gears to the low pressure side thereof.

20. A gear type liquid pump, comprising: a housing containing a pair of adjoining substantially cylindrical chambers having radial end walls; a toothed gear member in each of said housing chambers, said gear members meshing at the juncture of said housing chambers and having oppositely extending supporting journals, said housing having an inlet on the low pressure side of said gear members and an outlet on the high pressure side of said gear members; a bushing member in each of said housing chambers associated with said gear members on at least one side of said gear members, said bushing members each having a flange provided with a front face cooperable with the adjacent side face of its associated gear member to form a seal therewith, the flanges of said bushing members including generally circular portions complementary to the housing chambers associated therewith and also having complementary meeting surfaces disposed in the zone of juncture of said housing chambers, said housing and the back faces of said flanges each having a portion there of removed to conjointly provide a recess at one extremity, at least, of said meeting surfaces; and a closure plug in said recess for preventing leakage of liquid along said meeting faces from the high pressure side of said gear members to the low pressure side thereof.

- 21. A liquid pump comprising: a housing having a pump chamber and an inlet leading into and an outlet leading from said pump chamber;

. 17 means including a rotatable member received in said pump chamber for forcing liquid from said inlet out of said housing through said outlet; bearing means, including an end plate portion in said pump chamber having a back face normally spaced from the adjacent end wall ofsaid pump chamber forming a pressure chamber for liquid under pressure for actuating said end plate portion toward said rotatable member, said end plate portion also having a front face subject to the pressures in said pump chamber and cooperable with the adjacent side face of said rotatable member to provide a pumping seal area therewith during pumping; means defining an annular pressure relieving passage in communication with the radial inner portions of said seal area;.means establishing communication between said pressure relieving passage and said inlet; and means establishing communication between said pressure chamber at the back face of said end plate portion and said outlet, the relation of the area of said back face to said sealing area being such that the force acting upon said back face of said end plate portion always slightly exceeds the force acting upon said front face of said end plate portion, whereby to maintain said pumping seal without excessive friction, wear or loss of volumetric efllciency.

22. A pump comprising: a housing containing a pair of adjoining substantially cylindrical chambers having radial end walls, said housing also having an inlet leading to and an outlet leading from said. chambers; a toothed gear member in each of said housing chambers, saidgear members meshing at the juncture of said housing chambers; bores in the end walls of said housing chambers forming reduced extensions of said housing chambers, said gear members having journals extending from the opposite sides th'ereof into said reduced bores; bearing means in said housing on at least one side of said gear members, said bearing means including tubular portions surrounding the journals and received in the reduced bores on said one side of said gear members and substantially annular portions at one end of said tubular portions received in said housing chambers, said annular portions each having a front face cooperable with the adjacent side face of its associated gear member, said front face and said side face constituting a pair of adjacent faces which provide an area forming a pumping seal between said respective gear members and.said

annular portions during pumping, said front faces pressures in said housing annular portions also havfrom the adjacent housing chamber space at the back face of each of said annular portions; means establishing communication between said outlet and the annular pressure spaces at the back faces of saidannular portions, whereby to subject said back faces to the pressure developed in said outlet by said gear members; a relief recess disposed inwardly of the root of the members, respectively,

means establishing communication between said relief recesses and a zone under less pressure outlet.

23. -A pump as defined in claim 22, in which the means for establishing communication between the relief recesses and th'e'zone of less pressure than that in the outlet, includes passage means between the tubular portions of said bearing means and the journals extending from said gear members.

The following references are of record in the JAY M ROTH. JOHN A. LAUCK.

REFERENCES ,CITED Number 1 1,771,863 1,981,619 2,159,748 2,202,912 2,212,994 1,285,819 2,312,891 1,475,683 2,044,873

Number Name Date Schmidt July 29, 1930 Gee Nov. 20, 1934 Miller et al -4- May 23, 1939 Johnson June 4, 1940 Vrolix Aug. 2'7, 1940 Smith Nov. 26, 1918 Ferris Mar. 2, 1943 Carrey Nov. 27, 1923 Beust June 23, 1936 Colbourne Oct. 7, 1902 Smith Dec. 23, 1941 Marco June 15, 1943 FOREIGN PATENTS Country Date Germany Jan. 24, 1928 teeth of said gear and communicating withthe radial inner portions of the area providing said pumping seal; and

than the pressure ins aid