US2437791A

US2437791A - Pump with unloading bushing

Info

Publication number: US2437791A
Application number: US492383A
Authority: US
Inventors: Jay M Roth; John A Lauck
Original assignee: Borg Warner Corp
Current assignee: Borg Warner Corp
Priority date: 1943-06-26
Filing date: 1943-06-26
Publication date: 1948-03-16
Anticipated expiration: 1965-03-16

Description

Marci-n16, 194s. 4, QRO H ETAL 7 2,437,791

PUMP WITH UNLOADING BUSHING Filed June 26, 1943 2 Sheets-Sheet 1 FE Z 1 K9 T16 v l I 3&5 ,1 l

H fiwerzz ors 1 3 @MBoZ/i ma 2 in \fin CZwL auC/ J. M. ROTH ETAL 2,437,791

PUMP WITH UNLOADING BUSHING Filed June 26, 1943 2 Sheets-Sheet 2 Patented Mar. 16, 1948 UNITE PUMP wrrn momma BUSHING Jay M. Roth, Euclid, and John A. Lauck, South Euclid, Ohio, assignors. by mesne assignments, to Borg-Warner Corporation, Chicago, 111., a corporation of Illinois Application June 26, 1943, Serial No. 492,383

9 Claims. (01!. 103-126) This invention has to do with liquid displacing devices and the like. More particularly, the invention relates to such liquid displacing devices as gear type pumps, with axially adjustable end plates or bushings therefor which are operable to load and unload the pumps, the present invention being an improvement over and special application of the structure disclosed and claimed in Roth and Lauck Serial No. 439,030, filed April 15, 1942, now Patent No. 2,420,622.

Devicesoi the class described are used in various installations, among the more common uses being the delivery of pressure liquid to an accumulator or storage tank, in which liquid is generally maintained under a predetermined pressure or delivery to any other conventional pressure consumer. There are many uses for such a device. By way of example, one use is for operating retractable landing gears for an airplane. Such operating means for the landing gear of an airplane may incorporate an accumulater in which the. pressure is built up to a substantial predetermined amount, and from which fluid is withdrawn under said pressure to operate the landing gear motor.

In such an arrangement as above described, it

- is desirable to maintain the pressure as near a a device which accomplishes the above purposes,

and which will automatically relieve the operating load on the pump when the accumulator has reached the desired pressure.

In this connection, it is another object of this invention to provide a device in which the pump is automatically unloaded by means within the pump housing. More specifically, it is a feature of this invention to provide a construction in which the pump is automatically unloaded by movement of the end plate or bushing means within the pump when the pressure in the accumulator or the pressure being delivered to some other pressure consuming device reaches the desired value.

It is one of the principal objects of this invention to provide a construction in which use 2 bushing effective to provide a liquid pressure operated pumping seal with the adjacent side faces of the intermeshing gears during the time it is desired to generate liquid pressure and further providing for the movement of the end plate or bushing to break the pumping seal and unload the gears when it is desired to discontinue the delivery of pressure liquid.

Another object is to provide a unitary construction in which it is unnecessary to have a separate unloading valve outside of the pump proper. One of the features of this construction is that it is compact and unitary, and eliminates the necessity for a return line separate and distinct from the pump housing, and therefore reduces the vulnerability of the installation to damage by machine-gun the and the like. In this connection, one of the advantages is due to the fact that the pump unloading means and the return conduits therefor are located within the same housing as the pump means.

, It is an object of this invention to provide a construction wherein the end plate or bushing for the pump is loaded with the necessary increment of pressure to maintain the same in close engagement with the pumping means, and thus to increase the emciency of the pumping means, and wherein the end plate or bushing is likewise provided with means moving it away from the pumping means and allowing the fluid to escape from or recirculate around the pumping means for the purpose of unloading the pump, when the delivery pressure has reached the desired value.

It is a further object of this invention to provide a modified construction incorporating an improved form of end plate or bushing arrangement in which the bushing is loaded as a piston. In this connection one feature, which is optional bushing, is the removal of the undercut or low pressure area formed by grooving the bushing on the gear side. This feature is feasible, eSpe-.

cially by reason of the fact that the area of the bushing loaded by the hydraulic pressure is considerably greater than in the principal embodiment.

the operating conditions under which the pump is used.

is made of an axially adjustable end plate or 66 It is a further object of this invention to proporting means (not shown).

a 1 "vlde aconstructioninwhichaminimum number of parts are used to accomplish the-above purposes: a construction which is simplified in design and construction; a construction-which may be made of relatively light material, and which is automatic, necessitating little or no manual operation or care.

Other objects, advantages and uses of the invention, will become more apparent after reading the following specification and claims, and after consideration of the drawings forming a part of the specification, wherein;

Pig. 1 is a sectionaljslde elevational view taken on the lines l-I of Fig. 2, looking in the direction oithe arrows; a I Fig. 2 is a cross-sectional view' taken on the line 2-2 of'Fig. 1, looking in the directions of the arrows; and Y Fig. 8 is a cross-sectional view illustrating a modifled form of invention having a reducing valve added and likewise having a greater portion of the area of the bushing hydraulically loaded.

Referring more in detail to the construction shown in Figs. 1 and 2 of the drawing, there is.

provided a pump housing I!) having pumping means such as the gears l2 and I4, which mesh and performthe pumping operation in the normal manner of ordinary gear pumps.

The housing III has the inlet conduit l6, which opens into the inlet side of the gears I2 and I 4, whereby liquid to be pumped reaches the gears. The inlet conduit has a threaded terminal ll pumping seal relation is to prevent leakage of fluid there'around.

adapted to communicate with a source of liquid to be pumped (not shown). The housing I0 is likewise provided with the outlet conduit [8, which in turn leads to the valve chamber 20 terminating in a threaded connection 22 adapted to deliver to a device (not shown) to be fllled with liquid under pressure. The valve chamber 20 contains a valve means such as the spring pressed ball valve 2|, which normally closes the communication of outlet conduit ill with said valve chamber 20, except when the ball 2| is displaced by forcing fluid therearound under pressure from the pump. The valve 2| at all times prevents the return of pressure from the accumulator to the outlet side of the pump by closing the terminal of conduit l8.

The gears l2 and I4 are provided with oppositely extending shafts or

journals

24, 28 and both gears are driven through a drive engaging means of coupling element 26. This coupling element 26 is adapted to be engaged by a suitable driving means generally similar to that indicated at IOI in Fig. 3, for rotation of the shaft 24 and gears l2 and I4.

The housing I!) preferably has a hollow base, the hollow portion herein being designated 34, and said housing is also preferably provided with a circular flange portion 30 having the bolt holes 32 for attaching the housing assembly to a sup- In the arrangement shown in Figs. 1 and 2 herein, the drive gear 26 of the shaft 24 driving the gears I2 and I4, is adapted to be connected with a suitable driving means in the space 34. Fixed end plate bearing and pumping seal defining means in the form of flanged bushings 38, preferably composed of bronze or the like, include a journal bearing portion 38a for reception of

journals

24 and 28 extending axially from Preferably the bushing 36 is provided with what may be defined as an annular-relieved recess 42, communicating with a small axial drain channel 44 leading into the space, 34, where said liquid may be drained oil in any desired manner, such as by finding its way through a hollow portion 36 of shaft 26 to the space 98, herein referred to as sump 86, on the other side of the gear and out the drain 60 provided for that purpose.

0n the opposite side of the gears l2 and I4, from the stationary flange bushing 38, there is provided a similar but axially adjustable end plate bearing and pumping seal defining means likewise in the form of a flanged bushing bearing 46. These movable or axially adjustable flanged bushing bearings 46 likewise form the bearing support for the

journals

24 and 28.

When the intermeshing gears are delivering liquid under pressure, the surfaces 46a of flanged bushing bearings 46 bear against the side faces I 2a and Ma of gears l2 and I4 and eifect therewith the necessary pumping seal.

An annular relieved recess 52 corresponding in shape to the annular relieved recess 42 is provided inthe movable flange bearing 46, and a 1 drain channel 50 corresponding to the drain v the bushings 46 into the opposite sides of the gears. The radial flange channel 44 is likewise formed in the flange bearings 46. The annular relieved recess 52 serves the purpose of draining ,ofl seepage from the gears l2 and I 4, and of reducing the flange area on which the pumped fluid exerts outward pressure away from the gear. This latter is important, the reason for which will be apparent in the description of the operation hereinafter.

' The drain channel 50 preferably discharges into the small space between the hollow end of the bushing 46 and the left hand ends of the

journals

24 and 28, from whence the fluid so discharged will usually find its way through the centrally orificed end thrust washer 54 into the sump 98 where it will be drawn oil as previously indicated.

The movable flange bearing 46 is mounted in the housing III, with which it has a substantially close flt, which fit provides for limited axial adjustment. A fluid seal ring 56 is shown in Fig. 1 and has been provided to prevent leakage of fluid between the housing l0 and the bearing 46.

Between the movable flanged bearing 46 and housing Hi, there is normally maintained what may be termed an annular pressure channel or chamber 48, when the bearing 46 is in an engaged position with respect to the gear wheels l2 and I4. The function of this pressure chamber 48 will'be described later, but it may be noted that the bearing 46 is'movable, as above mentioned, longitudinally of the

shafts

24 and 28 and away from or toward the gears l2 and I4. The movement of the bearing or bushing away from the side faces of gears l 2 and I4 under predetermined conditions,relieves the load on the pump and allows the liquid to circulate about the gears without being subjected to pressure. The movement of pumping seal engagement with the side face of the gears l2 and I4 increases the load on the pump resulting in the building upof the output pressure.

the flange bearing 46 as shown in Fig. 1 preferably by a spring 68 which is effective to provide the initial pumping seal.

The pressure channel or chamber 48 is connected to the outlet conduit I8 by the fluid passage 62. The pressure channel 48 likewise is provided with an opening to a release means such as the release conduit 64, which leads into what may be termed the chamber 66.

This release chamber 66 comprises a chamber space receiving the hollow threaded sleeve or like closure member 68 which will be described hereinafter, and which carries means closing one end of said chamber 66, and a piston chamber 86 with an opening or port 94 leading to the valve chamber 26. Within the piston chamber 86 is located a sliding piston 88, having a stem 88a effective under selected conditions of pressure to engage ball check valve 14. Piston 88 normally seats against the port 94 and closes the port. There is no communication between the piston chamber 86 and the port 94 for the reason that the slidable piston 88 is always interposed between the two although the piston 88 moves longitudinally in the piston chamber 86 within limits.

The member 68 is hollow and has formed therein a chamber 69. An opening or throat 84' leads from the chamber 69 to the relief or piston chamber 86. The throat 64 is formed by narrowing the chamber 69 near the end thereof, which results in an annular ledge portion forming a seat for the valve 14. This ledge portion is shown at 16. Means such as the port 18 forms a communication for a fluid opening between the chamber 66 and the-chamber 69. These ports 18 may be provided at a channeled portion of the sleeve 68 so as to provide positive communication between the release conduit 64 and the chamber 66, ports 18, and chamber 69.

The threaded plug 16 closes the opposite end of the sleeve 68 and forms a seat for the spring 12 urging the valve 14 in the direction of valve seat 16. This plug 16 is adjustable longitudinally of the sleeve 68 so as to vary the tension of the spring 12. The sleeve 66 itself threads into the housing I6 and is likewise longitudinally adjustable so as to vary the tension of the spring 96 pressing against the piston 88, and so as to regulate the clearance of the end face of the stem 88a of the piston 88 relative to the ball valve 14. The purpose of this will be apparent from the description of the operation of the device.

The fluid seal rings 86 and 82 are provided to prevent leakage of fluid around the sleeve 68. The fluid bypass 96 is connected to the piston chamber 86 between the position of the piston and the adjacent end of the sleeve 68. This fluid bypass 96 is for the purpose of conducting fluid from the piston chamber 86 back into the inlet side of the pump.

A drain 66 is provided for conducting fluid which may be entrapped within the sump 98 and discharging such fluid into the bypass 96 leading to the inlet or into some other low pressure area.

Referring next to the arrangement shown in Fig. 3, there is provided a modified form of pump in which the annular relief recesses 42 and 52 of Fig. 1 have been eliminated, for the reason that they are unnecessary with the bushing or end plate arrangement shown in said Fig. 3, and in which the bushing is loaded as a piston across substantially its entire area on one side. In this 6 whereby the eflective pressure acting to load the bushing or end plate may be controlled.

This arrangement comprises the pump housing II6 which is modified somewhat as compared to the housing I6 of Figs. 1 and 2. In this arrangement the gear H2 is shown as having a hollow drive shaft I24 provided with a knurled or grooved integral drive coupling element I26. This drive coupling element I26 extends into the hollow space I34'provided therefor in the base or flanged portion I36 in a manner generally similar to that in Fig. 1.

The cooperating flexible coupling member I6I, here shown as integral with the drive shaft I62 extends into the space I34 and drivingly engages the drive coupling element I26 in the well known manner. Fluid sealing means comprising the flexible seal ring I63, the washer I64, and the combined end plate and bearing, I65 serves to seal efiectively the space I34, while allowing loadins of the shaft I62 driving the coupling I26 and gear II2.

This modified construction of Fig. 3 is provided with the fixed flanged bushing bearing I38, the outlet conduit H8, the valve chamber I26, the spring pressed ball valve I2 I, the inlet conduit I I6, the port I94, the port-closing piston I88, the spring I58 and the chamber I66, all of which means are generallysimilar to the arrangement shown in Figs. 1 and 2 for the same elements.

The device incorporates a modified form of closure arrangement shown generally at I68, which differs slightly from that of Figs. 1 and 2. It comprises the threaded sleeve I68a inserted in the chamber I66 in a manner generally similar to that of the arrangement shown in Figs. 1 and 2. This sleeve I68a contains a ball valve I14 seated on a shoulder I16, said ball valve being loaded by the spring I12 under pressure of the closure plug I16. The chamber I69 has the ports I18 placing the interior of chamber I 69 into fluid communication with chamber I66. The ball valve I14 is adapted to be engaged by the stem I88a of the piston I86 in the same manner that the ball valve 14 of Fig. 1 is engaged by the stem 88a of piston 88. The gear II2 (as well as the companion gear which is not shown in the cut-away figure but which corresponds generally to the gear I4 in Fig. 1), is abutted on its side opposite the fixed flanged bushing bearing I38 by the axially adjustable or movable flanged bushing bearing I46. This flanged bushing bearing I46 is carried within the housing H6 in the manner indicated in Fig. 3 and forms a bearing for the shaft I24 on the side of the gear M2 on which said movable bushing bearing is located. The flanged bushing bearing I46 differs from the bushing bearing 46 in Fig. l in that it is closed across the portion thereof adjacent the end of the shaft I24 and the end of the shaft (not shown) for the other gear wheel. For convenience in reference, this portion will be called the end portion of said bushing bearing. This arrangement permits the pressure loading of the bushing bearing as if it were a piston.

Between theflanged portions of the bushing bearing, I46, there is provided what may be termed an annular pressure channel or chamber I brought out hereinafter. The end portion of said movable bushing bearing 146' is provided with a clearance or chamber space I49, allowing movearrangement a reducing valve has been added ment of the piston axially of the shaft I24 and savor The outlet conduit II8, between the gears and the ball valve I2I is provided with a fluid passage I62, which discharges into a metering valve chamber I 63 formed in thehousing. This fluid conduit I62 has a relief port I65 leading to the chamber I 66 in the manner shown. The metering valve chamber I63 is formed in the housing H0, and contains a regulablemetering valve designated in its entirety as I61. The metering valve I61 and chamber I63 include a valve guide "I which is fastened in the housing and through which extends a valve I 13, here shown as a poppet munication with the relief type valve which seats on the shoulder or ledge portion forming a valve seat I15, in the chamber I63, but which valve may be moved away from said shoulder I15. The collar I11 is provided,

which collar has a restricted opening through which the stem of the ,valve I13 extends, there being considerable clearance between said stem and the valve body whereby fluid may flow to both sides of the collar I11.

The stem of the valve I13 terminates in an integral head .having portions thereof spaced from the side wall of the chamber I63, whereby the valve I 13may move axially within the chamber I 63, and also whereby fluid entering the chamber I63 from the fluid passage I62, may be conducted past the head portion of the valve I 13 and through the opening in the collar around the valve stem as above indicated.

Coil spring I18 is seated in a space provided therefor in a threaded closure plug I8I urging valve I13 in the direction of seat I15. The plug I 8I may be rotated into or out of the casing or housing IIO to vary the spring pressure acting on the valve I13, as is clearly apparent from the drawing, whereby the hydraulic pressure exerted on the movable bushing I46 may be regulated as hereinafter more fully described. A bushing loading conduit I83 leads from the portion of the chamber I63 between the metering collar I11 and the valve guide "I, said conduit I83 branching with outlet ports to the annular pressure channel I48 and the pressure chamber I 48. Said conduit I83 also has a relief portion l83a leading to the metering valve chamber I63 at what may be termed the bottom end thereof between the shoulder I15 and the closed end of the chamber I63.

There is provided a discharge conduit- I85 leading from the portion of the chamber I63 located between the shoulder I15 and the valve guide IN; This discharge conduit I85 discharges into a cross conduit I81 leading from the portion of the chamber I66 between the plunger I88 and the end of the chambered bolt I68. This cross conduit I81 discharges into the inlet conduit II6 for the pump; in other words, it discharges into the low pressure area for the pump.

It is understood that the pressure on the ball valve I14 may be regulated by adjusting the tension of the spring I12. Byincreasing the size of the insert I10 or the weight of the spring I12, the seating pressure on the ball valve I14 may, if desired, be changed. The particular pressure on said ball valve, however, is not so important sure in the pressure channel 48 chamber 69 from where it flows into will be. readily apparent from an examination of said flgures. When the pumping operation is being performed, the coupling '26 will normally be turned in an anti-clockwise direction as shown in Fig. 1, turning the gears I2 and I4'so as to carry. fluid or-' liquid from the inlet conduit l8 into-the outlet conduit I8. Until the delivery pressure is built up to'a predetermined amount. the ball valve 14 will remain seated. and comconduit 64 will thus be closed oil. By reason of the pressure of the spring 58, the movable bushing bearing 48 will normally move up against the gears ,I2' and, so that fluid from the outlet I8 is "introduced through the fluid passage 62 to the pressure-chamber 48, pressing the movable bushing bearing 46 against the gear wheels I2 and I 4. The resultant force urging the bushings into pumping seal engagement with the gear side faces willremain greater than the oppositely acting force on the gear side by a small difierential determined by the relative areas of surface 46b of the flange exposed to pressure within the pressure channel 48 and the area of surface 46a on the gear side of the bushing flange. The amount of the flange area exposed to the action of the pressure in the channel 48 will remain substantially greater during the pumping action because of the area blocked of! by the teeth of the gear, because of the low pressure area due to the annular relief recess 52, and because of the surface against the portion of the gears which do not carry liquid in the pumping operation. As long as there is substantial presthe bushing will remain in firm pumping seal engagement with the side faces of gears I2 and I4.

When such is the case, the fluid from inlet I6 will be discharged into the outlet I8 and will force tion from the chamber 69 into the piston chamber 86. The fluid from the pressure channel 48 will thus be relieved through the relief conduit 64 into the chamber 66 and through the port 18 into the the piston 96 into the of pressure chamber 86 and out the fluid bypass inlet side of the pump. This release will cause the bushing 46 to move outward some distance, allowing the gears I2 and I4 to rotate substantially free, or in other words, allowing the liquid to circulate about the gears at no appreciable pressure. -The ball valve 2I will engage its seat, and any fluid in the outlet chamber I8 which may be under pressure will be conducted off through the relief conduit 64 above described. Thus it will be seen that the bushings are not held against the wheels I2 and I4 enough to overcome the outward pressure of the fluid in the gears, and the gears are permitted to run substantially free. This relieves the driving means of a substantial load.

in the manner As soon as the pressure exerted on the piston 88 drops as a result of pressure liquid being consumed, this allows the piston 88 to'move back far enough for the ball valve 14 to engage the shoulders 16, thus the relief conduit 64 will be closed and will have the effect of blocking that conduit substantially as effectively as if it did not exist.

cumulator or other consumer. This continues un-* til the discharge pressure rises to a value to again cause piston 88 and plunger 88a to push the ball valve I4 out of engagement with the shoulder I6 and the cycle of operation is repeated.

It is occasionally true that there will be some leakage around the flange portions between the flange and the gears. This entrapped fluid will normally enter the annular channels 42 and 52 and be drawn off through the drains 44 and 50. That fluid going through the drain 44 is discharged ordinarily into the space 34, from whence it will find its way back through the bore 36 of ammo:

shaft 28 into the sump 98 and is drawn oif 1 through the drain 68. It is possible, however, to draw this fluid off in any other manner desired such as by a drain directly from the base 34 into the inlet I8.

The operation of the construction shown in Fig. 3 is generally similar to that of Figs. 1 and 2 except for the metering valve and for the loadin of the movable flange bearing. When the pressure in the accumulator or other consumer (not shown) connected to the outlet of the valve chamber I28 falls below the desired amount, the piston I88 assumes the position shown in Fig. 3 and the ball valve I14 likewise is closed as shown on its seat. The pressure in chamber II8 builds up into the passage I62, the pressure exerted by the spring I58 on the bushing bearing being suflicient to cause some pumping action under such circumstances. Fluid under pressure will enter the metering valve chamber I83, will be metered past the head of the valve I13 through the collar I I1 and into the pressure loading conduit I83. This metered pressure will be exerted onthe surface of the movable flange bearing in the pressure channel I48 and a pressure chamber I49. The increment of such pressure will depend upon the amount of surface under pressure on the loading side of said flange bearing as compared to the amount of surface on the gear side of said flange bearing subjected to pressure.

When the pressure in outlet conduit Ii8 rises above the value of the pressure beyond valve IZI the valve will be opened and pressure liquid delivered therebeyond. When the desired pressure has been reached, the piston I88 will be displaced and unseat the ball valve I14. This allows the pressure in the fiuid passage I62 to discharge through the port I65 and ports I'I8 past the ball into the low pressure area of the cross conduit I81 from where it is led into the inlet port H6. When this occurs the back pressure in the loading conduit I83, pressure channel I48, and pressure chamber I49, will flow out through the metering valve chamber, port I85, into the cross conduit I81 and the movable flange bearing will be relieved of its fluid load allowing it to move away from the gear wheel sufllciently to substantially unload the pump.

It may be noted that if the axial pressure force in the pump exerted on said flanged bearing I48 becomes greater than the increment desired, it may be reduced by adjusting the poppet valve I18 so that it will be unseated at the predetermined pressure. This will allow'the excess pressure .to escape through the discharge conduit I85 to the low pressure area, while retaining the desired increment of pressure acting on the bushing bearing.

type rotor might be used.

It is understood that the foregoing description is merely illustrative of a preferred embodiment of the invention and that the scope of the invention therefore should not be determined thereby but should be determined instead by the appended claims.

-We claim:

1. A device of the class described, comprising in combination a housing, a pair of intermeshing gears forming a pumping means in said housing, each gear having axially extending journals and at least one of said gears having driving means in connection with one of said journals, fixed flange bushing means forming a bearing means for jour. nals on one side ofsaid gears and likewise forming the closure means for the side face of said gears on said side, a movable unloading flanged bushing bearing on the other side of said gears forming a bearing means for the corresponding Journals, said movable flange bushing bearing forming an adjustable closure for the adjacent face of said gears, inlet and outlet means for fluid pumped by said gears, an annular pressure variable channel formed between said housing and the flange portion of said movable bushing bearing, a pressure variable chamber formed between the housing and the end portion of said bushing bearing, conduit means leading from the outlet .side of said gears whereby fluid under pressure is pumped to the annular pressure channel and pressure chamber above mentioned, the arrangement being such that fluid pumped by said gears exerts pressure on said bushing bearing in said pressure chamber, and in said annular pressure channel urging said movable flange bushing hearing against said gears, and valve means relieving the fluid pressure on saidmovable bushing hearing when it reaches a predetermined amount, a metering valve in the fluid conduit means between the pump. outlet and said annular pressure channel and pressure chamber, effective to regulate the pressure applied to said bushing bearing.

2, A device of the class described, comprising in combination a housing, a pair of intermeshing corresponding journals, said movable flanged There are of course a number of modifications ll bushing bearing means forming an adjustable closure for the adjacent side faces of 'said'gears said bushing bearing means having a closed terminal portion, inlet and outlet means for liquid to be pumped by'said gears, an annular pressure variable channel formed between s'aid'housing and the flange portion of said movable bushing bearing, a pressure variable chamber formed between the housing and the closed terminal portion of said bushing bearing, conduit means leading from the outlet side of said gears whereby fiuid'under pressure is pumped to the annular pressure channel and ressure chamber above mentioned, the arrangement being such that fluid pumped by said gears exerts pressure on said bushing bearing in said pressure chamber, and in said annular pressure channel urging said movable flange bushing bearing against said gears, and valve means relieving the fluid pressure on said movable bushing bearing when it reaches a predetermined amount, a manually adjustable metering valve in the fluid conduit means between the pump outlet and the movable bushing bearing.

3. A liquid pressure pump comprising: a housing containing a pair of adjoining substantially cylindrical chambers having generally radially extending end walls. said housing also having a low pressure liquid inlet leading to and a high pressure liquid outlet leading from said chambers; toothed gear members in said housin chambers respectively, said gear members meshing at the juncture of said cylindrical chambers and functioning to generate liquid pressure: bores in the end walls of said housing chambers forming reduced coaxial extensions of said cylindrical chambers. said gear members having journals extending from the opposite sides thereof into said reduced bores: bearing and pumping seal defining means in said housing on at least one side of said gear members, said bearing and pumping seal defining means including tubular portions surrounding the journals and received in the reduced bores on said one side f said gear members and substantially annular flanged portions at one end of said tubular portions received in said cylindrical chambers, said annular flanged portions each having a front face cooperable with the adjacent side face Of its corresponding 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 being subject to the gear generated pressures in said cylindrical chambers in communication with the gear teeth,

each of said annularportions also having a back face normally spaced from the adjacent radial end wall of its associated housing chamber to provide an annular control pressure space at the back face of each of said pressure responsive means effective during aselected range of pump generated pressures to place annular portions; and

ing containing a pair of adjoining substantially cylindrical chambers having generally radially extending end walls, said housing also having a lowpressure liquid inlet leading to and a high pressure liquid outlet leading from said chambers; a toothed gear member in each of said housing chambers, said gear members meshing at the juncture of said cylindrical chambers; bores in the end walls of said housing chambers forming reduced coaxial extensions of said cylindrical chambers, said gear members having journals extending from the opposite sides thereof into said reduced bores; bearing and pumping seal defining means in said housing on at least one side of said gear members, said bearing and pumping seal defining means including tubular portions surrounding said journals and received in the reduced bores on said one side of said gear members and substantially annular flange portions at the inner ends of said tubular portions received in said cylindrical chambers, said annular flange portions each having a front face cooperable with the adjacent side face of its corresponding 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 flange portions during pumping, said front faces being subject to the pressures in saidcylindrical chambers in communication with the gear teeth, each of said annular portions also having a back face normally spaced from the adjacent radial end wall of its associated housing chamber to define with said housing an annular motive chamber for exerting loading pressure on said annular flange portions, said motive chamber being of suflicient capacity to provide for the axial movement of said annular flange portions away from said gear side faces resulting in relatively low pressure return flow of fluid from the outlet of said pump back to the inlet of said pump when the pressure is relieved from said control pressure chamber; means eifective during a selected range of outlet pressures to maintain said annular pressure spaces in communication with pump generated pressures, said means being responsive to the occurrence of a predetermined maximum value of pressure to place said annular motive chambers in communication with said inlet to thu relieve the pressure in communication with said back faces and cause said bearing and seal defining means to move axially away from said gears to thus unload said pump and circulate fluid from the outlet past said flanged annular member front face to said inlet;

said annular pressure spaces in communication with said generated pressures whereby said pres-- sures act on said back faces to urge said front faces into sealing engagement with said gear side faces, said pressure responsive means being further responsive to the occurrence of a prede termined maximum output pressure to place said annular spaces in communication with said inlet 5; A liquid pressure pump comprising: a housing containing a pair of adjoining substantially cylindrical chambers having radial end walls,

saidhousing 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 cylindrical chambers; bores in the end walls of said housing chambers forming reduced coaxial extensions of said cylindrical chambers,

to thus relieve thepressure from acting on said back faces and cause said bearing and seal defining means to move axially away from said seats to unload said pump. I

said gear members having journals extending on the opposite sides thereof into said reduced bores; bearing and pumping seal defining means in said housing on at least one side of said gear members, said bearing and pumping seal deflning means including tubular portions surrounding said journals and received in the reduced bores on'said one side of said gear members and substantially annular flanged portions at the inner ends of said tubular portions received in said cylindrical chambers, said annular flanged portions each having a front face cooperable with the adjacent side face of its corresponding 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 being subject to the pressures in said pressure space at the back face of each lof said annular portions, means defining relief recesses disposed radially inwardly of the roots of the teeth of said gear members, and communicating with the radial inner portions of the area providing said pumping seal; means establishing communication between said relief recesses and a zone under less pressure than the pressure in said outlet under normal pumping conditions; said annular control pressure space being of sufficient capacity to provide for the axial movement of said annular flanged portions away from said gear side faces to provide for the return flow of fluid from the outlet of said pump to the inlet of said pump when the pressure i relieved from said control pressure chamber; means effective during a selected range of outlet pressures to maintain said annular pressure spaces exclusively in communication with pump generated pressures, said last named means being responsive to the occurrence of a predetermined maximum pressure to place said annular spaces in communication with said inlet to thus relieve the pressure in communication with said back faces and cause said bearing and seal 14 said front faces being subject to the pressures in said cylindrical chambers in communication with the gear teeth, each of said annular portions also having a back face normally spaced from the adjacent radial end wall of its associated housing chamber to provide an annular motive pressure space at the back face of each of said annular portions; means establishing communication between said relief recess and said inlet; and means effective during a selected range of outlet pressures to place said annular motive pressure spaces exclusively in communication with pressures generated by said gear members, said means being further responsive to the occurrence of a predetermined maximum pressure in said outlet to place said annular motive pressure spaces in communication with said inlet to thus relieve the pressure in communication with said back faces and cause said bearing and seal defining means defining means to move axially away from said gears to thus unload said pump and recirculate fluid from the outlet past said flanged annular member front face to said inlet.

6. A liquid pressure pump comprising: a housing containing a pair of adjoining substantially cylindrical chambers having generally radially extending end walls, said housing also having an inlet leading to and an outlet leading from said chambers; intermeshing gears in said housing chambers, said gears meshing at the juncture of said cylindrical chambers; bores in the end walls of said housing chambers forming reduced coaxial extensions of said cylindrical chambers, said gear members having journals extending from the opposite sides thereof into said reduced bores; bearing and pumping seal defining means in said housing on at least one side of said gears, said bearing and pumping seal defining means including tubular portions surrounding the journals and received in the reduced bores on at least said one side of said gear members and substantially annular radially extending portions at the inner end of each of said tubular portions received in said first named cylindrical chambers, said annular portions each having a front face cooperable with the adjacent side face of its corresponding gear, said front face and said side face constituting a pair of adjacent faceswhich provide an area forming a pumping seal between said respective gear members and said annular portions during pumping, one of said two last mentioned faces having a relief recess formed therein inwardly of the roots of the gear teeth,

to move axially awayfrom said gears to unload of fluid from the outlet back between the gear side faces and said front faces of said annular portions to said pump inlet.

7. In a liquid pressure gear pump: means defining a housing having a low pressure liquid inlet, a high pressure liquid outlet and an intervening pumping chamber including spaced end walls; intermeshing liquid displacing gears received in said pumping chamber between said end walls; end plate bearing and pumping seal defining means in said chamber, said end plate bearing and pumping seal defining means having a first generally radially extending surface engageable in bearing and pumping seal relation with the adjacent gear side face and being radially outwardly coextensive with the gear teeth, said end plate bearing and pumping seal defining means having a second oppositely facing surface normally separated from the adjacent end wall of said chamber to provide a, space for liquid under pressure generated by said gears effective upon said second surface for holding said first surface in pumping seal relation with said gear side face; conduit defining means eflective' to place said space and second surface in communication with the pressures generated by said gears during a selected range of said pressures; and means responsive to the generation of a selected maximum value of liquid pressure by said gears effective to place said space in communication with a zone of lower pressure than the pressure being generated by said gears, whereby to cause said first surface of said end plate bearing and pumping seal defining means to be moved out of pumping seal engagement with said gear side face and thus unload said pump.

8. In a liquid pressure pump: means defining ahousing having a low pressure liquid inlet, a high pressure liquid outlet and an intervening pump chamber receiving intermeshing gears between the end walls thereof adapted to be driven by an external source of power for generating liquid pressure; axially adjustable bearing and pumping seal defining means in said chamber adjacent at least one side face of each of said gears, said means including a radial flange portion having a first surface on one side thereof radially outwardly coextensive with the gear teeth. said flange portion having a second surface on the opposite side thereof normally separated from the adjacent housing end wall and providing a space for liquid under pressure generated by said gears for urging said radial flange into pumping seal relation with the associated gear said space and second surface in pressure liquid communication with the pressure generated by said gears; and means responsive to the generation of a pressure by said gears having a selected maximum value effective to place said space in communication with said inlet'whereby to cause said first surface of said bearing and pumping seal defining means to move axially out of pumping seal engagement with said gear side face and the liquid in said pump to be recirculated from the outlet of said gears back to the inlet to said gears between said gear side face and said flange to thus relieve the load on' said pump.

9. In a pressure liquid gear pump: means defining a housing having a low pressure liquid inlet, a high pressure liquid outlet and an intervening Dumping chamber including spaced end walls; rotary intermeshing liquid displacing gears received in said pumping chamber between said end walls; end plate bearing and pumping seal defining means in said chamber, said end plate bearing and pumping seal defining means having a first generally radially extending surface enface; conduit defining means effective to place said gear side face; means effective to place said space and second surface in communication with liquid pressure generated by said gears, said means including passage means for leading liquid gageable in bearing and pumping seal relation with the adjacent gear side face and being radially outwardly coextensive with the gear teeth,

said end plate bearing and pumping seal defining means having a second surface opposed to said first surface normally separated from the adjacent end wall of said chamber to Provide a space for liquid under pressure generated by said gears effective upon said second surface for holding said first surface in pumping seal relation with to said space and a reducing valve for producing a drop in the pressure delivered from the outlet of said gears to said space; and means responsive to the generation of a selected maximum value of liquid pressure by said gears to place said space in communication with a zone of lower pressure thanthevalue of said reducer pressure to thus cause said first surface of said end plate bearing and pumping seal defining means to be moved out of sealing engagement with said gear side face and thus relieve the load on said pump.

JAY M. ROTH. JOHN A. LAUCK.

I .REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS