US2444165A - Pump with pressure bushing - Google Patents

Description

June 29, LAUCK PUMP WITH PRESSURE BUSHING 4 Sheets-Sheet 1 Filed Aug. 16. 1943 June 29, 1948. J. A. LAUCK ruur WITH rnnssunn ausunm 4 shuns-sheet 2 Filed Aug. 16, 1943 fizveni ar:

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PUMP WITH PRESSURE BUSHING Filed Aug. 16. 1943 4 Sheets-Sheet 4 C; 11' reven e),-

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Patented June 29, 1948 PUMP WITH PRESSURE BUSHING John A. Lauck, South Euclid, Ohio, alaignor, by

mesne assignments, to Borg-Warner Corporation, Chicago, 111., a corporation of Illinois Application August 1c, 194:, ser al No. 49s,?

3 Claims. (01. 103-126) This invention is directed to high pressure gear type liquid displacing devices, and particularly to an improved arrangement for maintaining axial adjustable end of plate or bearing bushings in sealed contact with the side faces of the associated gears.

It is an object of this invention to provide an improved arrangement of pressure operating means efl'ecting and maintaining the requisite sealed engagement between the end bushings and the associated faces of the gears, notwithstanding the fact that high output pressures are reached which result in enormous pressures between the gears and the bushings tending to effect separation thereof with a resulting loss of volumetric emciency. This invention is closely related in object to copending Roth and Lauck Serial No. 439,030, filed April 15, 1942, and issued as Patent 2,420,622 of May 13, 1947, and is considered as presenting still another improved solution to the same general problem.

Since it is desired to cause a sealing action between the gears and the associated face plate or. as herein described, movable bushing bearing, in the direction of the associated gear faces, which has a small differential value or increment greater than the oppositely actin pressure between the gear faces and the bushing, is an object to disclose a construction which will accomplish this desired feature.

It is a further object or feature of this invention to provide a bushing means wherein the bushing is movable to and away from the face of the associated gears, and in which the liquid pressure from the outlet of the gears operates to load the bushing urging it against the gears whereby a sealing action with the face of the gears is accomplished. In this connection, it is an object to provide a construction in which the load urging the bushing against the gears will always predominate for the pumping action by a small amount over the oppositely acting force tending to separate the bushings from the gears.

In this connection, it is a further obiect to present a construction in which the fluid used in loading the gears is manually controlled by a release means which prevents overloading the bushing, and further, it is an object to provide an arrangement incorporating one or more metering valves in the fluid conduit system between the pump outlet and the bushing loading surfaces.

It is a further object of this invention to provide an outlet liquid pressure operated unbalanced bushing and bearing construction of the above type in combination with an arrangement providing for automatic reversal of the direction of operation in response only to the reverse rotation of the gear, without requiring any special adjustment or reversal of other parts.

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

It is a further object of the invention to provide a bona fide form of construction in which the movable end plate or bushing bearing is loaded in whole or in part by separate piston means. In this arrangement, it is a feature to present a construction in which the load may be distributed to the portion of the bearing on which the greatest pressure tending to move the bearing away from the gears is exercised. It is a further feature to present a construction in which the proper portion of the bearing is loaded by piston means or otherwise regardless of the direction the pump rotates, it being understood that a reversal of direction of the pump changes the portion of the bearing which is most heavily loaded.

It is an object to present an improved arrangement which is relatively simple to manufacture, which lends itself to modern manufacturing operation, and which is rugged and durable in operation.

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

Fig. 1 is an axial broken-away sectional view, showing the essential elements of a gear pump incorporating a preferred embodiment of my invention;

Fig. 2 is a cross-sectional view taken substantially on the line 2-2 of Fig. 1;

Fig. 3 is a view corresponding generally to that of Fig. l, but showing a modified form wherein separate piston means are used to load the movable bearing, and wherein a metering and relief means are disclosed for controlling th fluid pressure exerted on the movable flange bearing;

Fig. 4 indicates diagrammatically the distribution of pressure in a pumping operation wherein the gears of a gear pump operate with different pressures at different positions with the consequent result, the view being a fragmentary crosssectional view to the Rear wheel of a pump corresponding to those disclosed herein.

Fig. 5 is an axial sectional view of another modified construction, this view being slightly fragmentary, and serving to show a somewhat different arrangement of sealing valve and piston loading means.

Fig. 6 is a cross-sectional view taken on the line 6-6 of Fig. 5 and 8-6 of Fig. 7 looking in the direction of the arrows;

Fig. 7 is a cross-sectional view taken on the line 1-4 of Fig. 5 looking in the direction of the arrows;

Fig. 8 illustrates still another modification, the view illustrating the piston loading of the movable bearing with the use of a. metering valve;

Fig. 9 is a view taken on the line 5-9 of Fig. 8, looking in the direction of the arrows; and

Fig. 10 is a view taken on the line ill-i of Fig. 8 illustrating particularly the valve arrangement controlling the flow of fluid in the bushing loading piston.

Referring more in detail to the drawings. and referring first to the construction shown in Figs. 1 and 2 in particular, in indicates generally a gear type pump with certain conventional portions thereof broken away for the purpose of clarity, the pump including especially a housing I l formed with a pair of internal overlapping bores l2 and I3, receiving therein a pair of gears M and i5, meshing in the general area of overlap of said bores.

Leading to and from said gears l4 and ii, in the area of meshing therebetween, are a pair of main flow passages l and I1, either of which may become the inlet or the discharge passage depending upon the direction of rotation of the gears l4 and ii. The actual terminal connections forming part of the housing have been shown broken away for the purpose of simplicity. it not being deemed necessar to show this conventional structure.

Gears I4 and i5, as will be apparent from Figs. 1 and 2 each include oppositely extending trunnions, journals, or shafts, seated in bearing members as hereinafter more fully described and, as is apparent from the drawing, the bearing members are received in reduced extensions on both sides of the bores l2 and i3. Only the journals ISA and IE3 0f the gear I5 are shown in detail since the corresponding journals of gear I! are identical therewith except that Journal IE3 is provided with a splined extension |5C cooperating with a flexible coupling I8, including a shaft ID for driving gear i5 and a flexible sealing ring iBA.

For the purpose of properly sealing the gears on the side faces thereof, 1 have provided a special arrangement of coaxially adjustable end plates, bushings, or bearings, sometimes herein referred to as bushing bearings, with fluid pressure actuating means. The bearing is indicated generally at in, and this bearing in the modification shown, together with the means for controlling it, form the subject matter in combination to which the present invention is directed.

The gear journal for each gear has interposed between it and the enclosing housing a specially constructed axially adjustable bearing bushing, nut for journal ISA being indicated at 2i, and including a radially extending flange or piston portion 22, sealably fitting the bore receiving the gear it, but having an axial thickness less than the space receiving the same to thus provide an annular high pressure actuating chamber 23 for the purpose to be described. Thus bearing 20 further includes an axially extending tubular portion 24, received in reduced bore 25 and sealed with reference thereto by a flexible seal ring 26.

In a particular part of my invention. a piston 21 is formed as an extension of tubular portion 24 of bushing assembly 2|. As will be apparent from other figures, the piston member 21 may be equally well formed separately from bushing assembly 2i so long as the same is arranged to apply axial pressure to bushing assembly 21.

Piston member 21 is sealed with reference to the bore 28, in which the same operates, by means of a flexible sealing ring 28. A passage 21A leads from the interior of tubular extension 24 for the purpose of placing the same in communication with the low pressure side of the pump as will appear. I contemplate, in the preferred embodiment 9. separate piston (not shown) identical to the piston 21, for cooperation with the bushing assembly of gear l4. However, it will be apparent that a single piston 21 may be made to apply the necessary axial pressure to both of the bushings on one side of the gears.

Discharge fluid pressure is delivered to chamber 23, there applying a first axial force Pl to bushing assembly 2|, by way of small check valves 3| or 32, depending upon the direction of rotation and hence whether the flow passages i6 or H form the outlet passage, then through passages 33 and 34. Passage 33 also leads to the piston member 21 for operating the same to thus supply an additional axial force P2 for urging bushing 2! into engagement with the side or face of gear l5. It is important to note that the effective pressure area of the back side of bushing flange or piston portion 22, in chamber 23, together with the pressure area of the piston 21, are made such that the total of coaxal forces Pi and P2, acting to press bushing flange 22 into contact with gear i5 is always slightly greater than the opposing coaxial force P3 of the fluid attempting to force the bushing bearing 22 away from the gear, this difl'erental. being only a small fraction of the outlet pressure. This is always true when the pump is operating as a pump, regardless of how h1gh-the output pressure may become. It has been observed that even where the output pressure may be in the neighborhood of several thousand pounds per square inch. the diiference between the sum of PI plus P2 on the one hand and P3 on the other is still only a small amount, a few pounds for example. It will then be seen that so long as there extends a small increment of pressure in the direction of bushing engagement with the gear, the bushing can never be forced away from the gear by fluid pressure exerted between the gear and the bushing.

Referring to gear H, it will be apparent that an identical bushing construction will be provided including a piston member, the same not being shown since it is believed to be apparent from a disclosure and description of the structure associated with gear [5.

It will be important to note that the small differential pressure tending to maintain engagement is always present during the pumping action, irrespective of whether the pump is operating at a relatively low pressure or a very high pressure. In other words, the pressure of the frictional engagement between the bushing and the associated face of the gear does not vary appreciably with a change in output pressure from low pressure to a pressure substantially equal to the maximum of the pump, but this pressure differential urging the bushing into contact with the gear always preferably remains at a very low value, as it is usually only necessary, as above pointed out, that the same be a small diflerential greater than the pressure between the bushing and the gear, tending to separate the same.

For the purpose of releasing excess fluid pressure in the assembly on the low pressure side of the bushing 2i, passage 35 leads alternatively to check valves 36 or 31, depending again upon whether passage lb or II is the high pressure side.

Gears i4 and I! are preferably provided on the opposite side thereof about the associated Journal, with similar bushing bearing assemblies, but not necessarily having axial adjustment. Bushing bearing II for gear I5 is shown in Fig. 1 with a tubular extension 4|, said extension having a flexible seal Ha interposed between its outer periphery and the housing II. The corresponding bushing for gear I is not shown, for the purposes of simplicity. In addition, the well known elements of the present type of pump are contemplated, but a detailed description and showing thereof are unnecessary to an understanding of the present embodiment and have been omitted for the purposes of clarity.

Referring next to the construction shown particularly in Fig. 3, there is provided a modification wherein there is preferably a combined metering and release valve, shown in its entirety at 50, interposed between the pressure loaded bushing and the outlet pressure side of the pump, that is, the high pressure side of the pump. In other words, there is a metering valve and a release valve in the circuit comprising the fluid connection to the main flow passages. In the arrangement shown in Fig. 3, this metering and release valve is manually adjustable whereby the pressure necessary to effect a release upon a maximum desired load may be varied if desired.

As shown in Fig. 3, there is provided a bore in the pump housing, here indicated as the axially extending bore 52. This bore 52 is preferably provided with a reduced portion forming a port 54, leading into the high pressure chamber between the end of the bearing member 20, and the pump housing. This high pressure chamber may be designated as the high pressure chamber 58, for purposes of reference.

Seated on an annular ledge portion 58 formed by the reduced bore for the port 54, is a valve 80, the stem of which is here shown as extending axially of the bore 52, and which stem has a guide portion or spider 82. This guide portion 62 is provided with cutaway portions whereby fluid may flow past it, but the said portion 62 "rides in" the bore 52, to assist in maintaining the valve stem in axial alignment with the bore.

The bore 52 is likewise provided with an insert M, which is spaced from the port 5| to form a low pressure chamber 66, and which insert 64 has a hole or passage through the center thereof in which the valve stem of the valve 60 moves. This valve stem for the valve ill preferably has a close sliding flt in the insert, one which is substantially liquid tight.

Spaced axially from the insert 64, toward the outer end of the bore ii! is a collar 68. The stem of the valve Gil passes through this collar 68, and there is sufllcient clearance between the stem and the collar to efl'ect a metering action of fluid passing therebetween. A space between the collar 68 and the insert 64 comprises a high pressure bore chamber III, which communicates with the outer end chamber 12 of the bore 52 by means of the metering passage around the valve stem ill through the collar 88.

The outer end of the bore 52 is closed by a plug H which is externally threaded to engage internal threads in the bore 52 and which is ad- Justable by threading into and out of bore I2 for the purpose hereinafter set forth.

The plug II engages a spring I8 which seats on the portion 82 of valve 80, the pressure on the spring 18 exerted by the plug I4 determining the pressure in the high pressure chamber 56 necessary to unseat valve 6|) from the shoulder portion 58 and relieve excess pressure in the high pressure chamber 56.

The high pressure bore chamber 10 is placed in communication with the annular high pressure chamber 23 and with the high pressure chamber 56 by means of one or more passages 18 for fluid. This is obvious from an examination of Fig. 3. The low pressure chamber 66 is placed in communication with the low pressure side of the pump by means of one or more passages 8|) discharging into the main flow passages IE or I! as the case may be. Valve means, here shown as the spring pressed ball valve 82, closes the low pressure passage to the inlet of fluid from the high pressure side of the pump but permits fluid under pressure in the low pressure passage 80 to escape into the low pressure side of the pump, that is into the "inlet" conduit formed by the main flow passage IE or II as the case may be, depending upon the direction of rotation of the pump. It is believed this operation is obvious from the figure.

The chamber 12 is placed in fluid communication with the high pressure or outlet side of the pump being the main flow passage IE or i'l, depending upon the direction of rotation of the gears. This is accomplished by means of passages 86. These passages are provided with valves 88 which operate in reverse to the valve means 82. These valves 88 are operable on the high pressure side of the pump, the pressure being taken from the main flow passages Iii or H, depending upon the direction of rotation of the pump. Their operation is believed obvious.

The operation of the pump shown in Fig. 3 is as follows. Assume that the gears are rotating in a direction so that the high pressure side of the pump is the main flow passage l1, and that the low pressure side is the main flow passage iii, the fluid flowing to the pump in the passage l6 will be placed under pressure and will enter passage II from where it will be conducted to the device operated by the fluld pressure. The passage ll however will discharge a small quantity of its fluid into the passage 86 past the valve ill! from where it flows into the chamber 12. Upon entering the chamber 12 it will pass the portion 62 of the valve Gil, and be metered between the stem of the valve so and the collar 68. This metering action will cause the fluid pressure in the high pressure chamber 10 to rise and will conduct such fluid pressure through the passages 18 into the high pressure chamber 55 at the end of the piston and into the annular high pressure chamber 23 about the annular flange portion of the bearing or piston.

Since the bushing area subject to pressure in the chamber 56 and the annular chamber 23 is greater than the loaded area on the gear face side of the bushing, the amount of pressure will be suihcient to maintain the bushing bearing in engagement with side face of gear ii. In this connection, a low pressure area on the portion of the hearing which may be called the underside or gear side, at the end, is created by the port means OI which discharges into the hollow end portion of the shaft forming the trunnion for the gear II, from where it may be carried to the low pressure area or discharged outside the pump as desired. This relieves pressure due to leakage between the pump and the side of the bearing. These port means may terminate in an annular portion as indicated in Fig. 3 whereby all entrapped fluid will be relieved through passage 80, as shown by the dotted lines.

When the pressure in the chamber 56 and in the annular chamber 23 reaches a predetermined regulable amount, it will raise the valve Bil from its seat on the ledge portion I58 and allow any excess pressure to escape into the low pressure chamber 68 from which it is conducted into the low pressure side of the pump through passage Oil. The pressure necessary to relieve this valve may be adjusted by manual manipulations of the plug 14 by threading it in or out. If desired a longer stem than that shown to the valve Bil may be provided, so that it will touch the plug I4 when the plug is threaded into the bore a maximum distance, for the purpose of locking the release valve against operation. With this arrangement, of course, any pressure in the outlet of the pump would be reflected to the movable bushing bearing through the metering means, regardless of the amount of the pressure.

Due to the operation of the valves 88 and 82, as is obvious from the drawing, the pump may be run in either direction and identical loading action will take place.

Referring next to Fig. 4, there is here shown schematically the pressure diagram for the gear pump, by which location of the centers of pressures loading the movable bushings, especially in Figs. 5, 6, '7, 8, 9 and 10, hereinafter referred to, may be determined. This schematic arrangement of Fig. 4 is self-explanatory, but it may be noted that the location of the pistons as indicated in Figs. through 10 should be such that they are approximately centered on the points Pl and P5, for each gear wheel.

For the rotation of the gears in one direction, the point P5 represents zero points per square inch, while the point P4 represents approximately maximum points per square inch. It is understood upon reversal of direction of rotation, the point P5 would be the high pressure point and PI the low pressure point. Each of the gears of the gear pump has a corresponding pressure diagram substantially as that shown in Fig. 4.

As shown in this schematic drawing, the maximum pressure is assumed to be 1,000 pounds per square inch. Referring next to Figs. 5, 6, and 'i, there is shown a modified form of construction in which the bushing bearing is pressure loaded by means of separate pistons, preferably so located that the pressure exerted by the pistons on each portion of the periphery of the bearing is in proportion to the outward pressure exerted on the corresponding bearing space adjacent the pump gear, and in which the separate pistons may be loaded in different amounts depending upon the direction of the rotation of the gear wheels, among other things.

For simplification in manufacture, and to secure a more direct thrust on the bearing for pressure loading of the bearing, the bushing bearing Hill, which is a movable bushing bearing in connection with gear wheel II, and the bushing bearing it! which is the corresponding movable bushing bearing in connection with gear wheel I. have been shown as having the flange portion shown in Figs. 1, 2, and 3 eliminated. Likewise. the bushing bearings IM and "i8, which are the fixed bushing bearings, are devoid of flange portions. Flange portions may be added, if desired. The movable bushing hearings in and in are movable axially on the gear wheel trunnion in the same manner that the bushing bearing Ii was movable in connection with the trunnion Ila. There is preferably a low pressure area at the end of each trunnion for the gear II and I! on the movable bushing side, said low pressure chamber for the movable bushing end being numbered I08 and forming a chamber space into which the movable bushings may be moved. Located in reduced axial extensions H0 0! the bore forming the chamber lliB, are the separate pistons H2 and III which bear against the edges of the bushing bearings I00 and I02, on one side thereof as is clear from the drawings. Preferably these pistons are so located that they are adapted to exert pressure against the edge portion directly in axial line with the edge portion receiving the most outward pressure from the fluid in the gear II. lit is understood, however, that the pistons may be located in any convenient position and that more than two for each "side" of the pump may be provided. Springs III are provided for exerting a relatively light pressure on each of the pistons urging the respective bushing in the direction of the gear wheel by an amount sufficient to overcome inertia and friction.

As is apparent from the drawings, Figs. 5, 8, and 7, the pistons on each side of the pump are loaded separately. Thus the pistons III and Ill are loaded and controlled by means of fluid entering through a metering valve H8, while the pistons H3 and H5 are loaded in control by the adjustable metering valve I20. To economize on space and provide a more compact construction, the bores for metering valves H8 and III! are shown as extending across the pump housing instead of axially as in Fig. 1. Either arrangement is equally operable, however, and the choice is one of manufacturing and design advantage.

It will be apparent from the figures, that metering valve I is receives its pressure, if any (depending upon the direction of rotation of the pump), from the main flow passage l1, while the metering valve I20 receives its fluid from and is controlled by. the fluid in the main flow passage ll. Except in their low pressure chambers, the structures forming the metering valve and housing therefor are not connected. The low pressure chambers preferably are connected by passage 660, since they each will have to have an outlet to the low pressure side.

As is clear from examination of Figs. 5, 6, and 7, the construction of the metering valve and release valve in and I20 may be the same as provided in connection with the assembly III of Fig. 3. However, I have disclosed a slightly modifled construction generally similar to that of Fig. 3, except that instead of the plug 14, I have provided a modified closure and adjustment means. This comprises a member I22 which is internally and externally threaded to be inserted into one of the bores of the housing and which carries a threaded insert IN. The caps I28 may be provided to thread down on the threaded insert and hold the latter in position much in the nature of a lock washer or member, while providing a better seal than would be the case without the cap. The insert I is slotted for adjustment with a screw driver or may be otherwise provided with adiusting means by which it may be moved up or down in the metering valve bore whereby the tension on the spring holding the valve seated may be regulated. Otherwise, the valve arrangement is generally similar in construction to that shown in Fig. 3.

The inlet from the high pressure conduit, which may be the passage I28 or I30 as the case may be, depending upon the direction of rotation of the pump gear, communicates with the chamber I2 of the respective valve bores. In the low pressure chambers 00, the passage 80 leads from both valves and has intercommunication so that the discharge may be to the low pressure side of the pump regardless of whether it is the main flow passage I8 or the main flow passage I'I. Check valves 02 are generally similar to those of Fig. 3, except that the assembly is slightly difierent in an inconsequential manner from a patentable standpoint.

The construction oi both metering valves in Fig. 5, Fig. 6, and Fig. 7 may be identical and only one is described for purposes of clarity.

The operation or the device shown in Figs. 5, 6, and 7 follows and it is assumed, i'or the purpose of describing it, that the fluid'enters the pump through the low pressure main flow passage I and, after the pumping operation, is forced out through the high pressure main flow passage II. In order to load properly the bushing I00, the pistons H2 and H4 will have to be loaded, while it is unnecessary ordinarily when the direction of rotation is as indicated, to load the pistons I II and H0. Fluid from the passages II will enter the passages I28 and flow to the valve H8 in the same manner as it flowed to the valve 50.

There the fluid will be metered and conducted through the passages I32 to load the pistons II2 and H4 which load the bushings. When the pressure reaches a certain predetermined amount, the excess fluid will pass through the discharge port 54 and will raise the valve II8 from its seat, allowing excess pressure to escape through the low pressure passage 00 into the main flow passage II. In such arrangement, there is no need for a valve in the passage I20 similar to the valve 08 since there is no inter-communication between the chambers I2 for the two metering valves.

Upon reversal oi the pump the other metering valve I20 will operate, while the valve IIB will remain unloaded. The pressure, upon reversal pump, in the main flow pipe I! will be low, and will allow the valve I I8 to unseat and the pistons H2 and I I4 to move out oi pressure loaded position. In such latter event, the pistons II: and II! will be separately operated and will have no communication 01' fluid pressure with the pistons II! and H4.

Refer next to the modifications shown in Figs. 8, 9, and 10. There is provided a more simple and compact means of piston loading the bushing bearing I00 and its companion bearing I02, by means of two sets of pistons operated without the metering valve but having a release valve for each pair of pistons.

As shown in the drawings, the pump and bushing arrangement may be the same as that of Figs. 5, 6, and '7, except that the metering valve III! and the metering valve I20 have been removed from the assembly. As shown in these figures. the pistons II2, III, Ill, and II! are arranged in approximately the same way as are the similarly numbered pistons of Figs. 8, 9, and 10. The high pressure main flow passage II, for example,

is connected to the chamber I24 for the pistons on one side of the pump, that is, for pistons I I2 and H4 by means or passages I36 and I38 respectively. With this arrangement, when the main flow passage I0 is the low pressure area and the inlet side of the pump, the pistons H3 and III are entirely unloaded, and the pistons H2 and H4 are fully loaded. Upon reversal of the pump, the pistons H3 and II! will be loaded while the pistons H2 and H4 will be allowed to unload through their passages I20 and I38 into the main flow passage II. In this arrangement there is provided a low pressure area at the end of the bushing I00 and I02. This area, herein referred to as space or chamber I40, in reality could be more properly termed an intermediate pressure area in that the pressures are fluid pressures of relatively low amount, escaping along the shaft of the gear and around the piston by leakage, and which enter the space I40 and are conducted by the passage I42 into the discharge area I44. This pressure displaces the ball valve I40 or I40, depending upon which one is on the low pressure side, and escapes through the piston chamber into the inlet side 01' the pump. The passage I50 for each side or roup of pistons acts as the conduit for the escape oi this relatively minute quantity of fluid. It is noted that the spring loading on one of the balls I46 or I40, must be displaced by this minute quantity of fluid, and the pressure necessary to do this furnishes sufficient fluid around the trunnions and hearings to lubricate them.

The passages I52 and I54 correspond in function to the passages I36 and I38 except that passage IH leads from the piston II3 to the main flow passage l5 and the passage I54 leads from the piston I I5 likewise to the main flow passage I6.

It may be understood that with the arrangement shown in Figs. 8, 9, and 10, the end plate of the housing is materially reduced in size and is more compact and lighter. This is an important feature where such pumps are used in the limited space provided in airplanes, for example, and where it is desired to cut down the weight of the pump.

Numerous details or the various figures are obvious and apparently do not need specific description. For example, in Fig. 8 the shafts or trunnions for the gear wheels are both shown as hollow, so that seepage fluid at the ends of the trunnions may be conducted back therethrough to the space I40 where it escapes in the regular way.

While I have described my invention in connection with one specific embodiment thereof, it is to be understood that this is by way of illustration and not by way of limitation, and the scope of my invention is defined solely by the appended claims which should be construed as broadly as the prior art will permit.

I claim:

1. In a. gear type high pressure liquid displacement dlevice including means defining a housing having a .pair of parallel overlapping cylindrical bores, gears in said bores having teeth meshing in the area of said overlapping, said gears having pairs 01' oppositely extending journals, a plurality oi bearing insert bushings received in said bores about said journals and in engagement with the side faces of said gears, means responsive to the outlet pressure on either side of said gears dependent upon the direction of rotation thereof, eiIective to selectively communicate said outlet pressure to the said bushings on at least one side of said gears urging the bushings into sealed relation therewith, including means comprising separate pistons bearing against the ends of said bushings and communicating through pressure metering means with the outlet pressure from said gear pump. and valve means in connection with said pressure metering means relieving the fluid pressure on said pistons above a desired predetermined amount.

2. In a device of the class described a gear pump, movable bushing means adjacent at least one face of each 01' the gears 01 said gear pump, piston means bearing on said movable bushing means. means loading said piston means from the outlet pressures existing in said gear pump, said last mentioned means including pressure metering means and adjustable valve means actuated by excessive pressure over a predetermined amount on said piston means for relieving the excess pressures on said pistons.

3. In a device of the class described. a Bear pump, including movable bushing means adjacent one face of each of the gears oi said gear pump, piston means bearing on said movable bushing means, means loading said piston means irom the outlet pressures existing in said gear pump, said last mentioned means including pressure metering means and adjustable valve means actuated by pressure exceeding a predetermined amount on said piston means for relieving the excess pressure on said piston means. and said piston means being so positioned that the resultant of the forces impressed thereon opposes the resultant of forces acting in an opposite direction on the bushing means.

JOHN A. LAUCK.

REFERENCES CITED The following references are of record in the Certificate of Correction Patent No. 2,444,165.

June 29, 1948.

JOHN A. LAUCK It is hereby certified that error appears in the printed as follows: Column 11, line 20, claim 2, for the that the said Letters Patent should be read with numbered patent requiring correction word pistons read piston means; and

specification of the above this correction therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 28th day of September, A. D. 1948.

THOMAS F. MURPHY,

Assistant osmium of Patents.

ings on at least one side of said gears urging the bushings into sealed relation therewith, including means comprising separate pistons bearing against the ends of said bushings and communicating through pressure metering means with the outlet pressure from said gear pump. and valve means in connection with said pressure metering means relieving the fluid pressure on said pistons above a desired predetermined amount.

2. In a device of the class described a gear pump, movable bushing means adjacent at least one face of each 01' the gears 01 said gear pump, piston means bearing on said movable bushing means. means loading said piston means from the outlet pressures existing in said gear pump, said last mentioned means including pressure metering means and adjustable valve means actuated by excessive pressure over a predetermined amount on said piston means for relieving the excess pressures on said pistons.

3. In a device of the class described. a Bear pump, including movable bushing means adjacent one face of each of the gears oi said gear pump, piston means bearing on said movable bushing means, means loading said piston means irom the outlet pressures existing in said gear pump, said last mentioned means including pressure metering means and adjustable valve means JOHN A. LAUCK.

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

UNITED STATES PATENTS Number Name Date 944,708 Vollmann Dec. 28, 1909 20 1,475,693 Carrey Nov. 27, 1923 1,673,261 Meston et a1 June 12, 1928 2,044,873 Beust June 23, 1936 2,159,748 Miller et a]. May 23, 1939 2 2,212,994 Vrolix Aug. 2'7, 1940 Certificate of Correction Patent No. 2,444,165.

June 29, 1948.

JOHN A. LAUCK It is hereby certified that error appears in the printed as follows: Column 11, line 20, claim 2, for the that the said Letters Patent should be read with numbered patent requiring correction word pistons read piston means; and

specification of the above this correction therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 28th day of September, A. D. 1948.

THOMAS F. MURPHY,

Assistant osmium of Patents.

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