US2691945A

US2691945A - Pressure loaded gear pump

Info

Publication number: US2691945A
Application number: US182254A
Authority: US
Inventors: Edmund F Wichorek
Original assignee: Borg Warner Corp
Current assignee: Borg Warner Corp
Priority date: 1950-08-30
Filing date: 1950-08-30
Publication date: 1954-10-19
Anticipated expiration: 1971-10-19

Description

Oct. 19, 1954 E. F. WICHOREK 2,691,945

PRESSURE LOADED GEAR PUMP Filed Aug. 30, 1950 Eel uRdFZU 'c/aore Patented Oct. 19, 1954 UNITED PRESSURE LOADED GEAR PUMP Edmund F. Wichorek, Euclid, Ohio, assignor to Borg-Warner Corporation, Chicago, 111., a corporation of Illinois Application August 30, 1950, Serial No. 182,254

' 13 Claims. 1

This invention relates to pressure loaded gear pumps and more particularly to an arrangement for insuring proper location of the pressure loadable bushings in a pressure loaded type intermeshing gear pump.

vIn a pressure loaded, intermeshing gear type pump having one or more sets of axially movable, pressure loadable bushings, a part of the output or discharge pressure of the pump is applied to the rear or motive surfaces of the axially adjustable bushings to urge these bushings into sealing engagement with their associated gears. As disclosed in United States Patent No. 2, l20,622 to Roth et al., by carefully selecting the relative areas of the forward surfaces of the bushings and of the motive surfaces of the bushings, it is possible to control within very close limits the actual sealing pressure provided. In practice, this re quires a somewhat higher effective pressure in the direction of seal than in the direction tending to open the seal.

Because the pressure loadable bushings must be axially movable, a certain minimum clearance must be provided between the sides of the bushings and the adjacent sides of the chambers or bores in the pump housing in which the bushings are received. In addition, in order to facilitate production of the pump, the cover section of the housing in which the barrel portions of the bushings are received is provided with holes through which the mounting bolts extend which holes are made somewhat larger in diameter than the diameter of the bolts so that the cover section may be readily aligned with the housing. As a result, if the bushings are located adjacent the discharge side of the pump during assembly then the cover section will be located in accordance with the location of the bushings, will be shifted in the direction of the discharge side. Thus when the pump is finally assembled the bushings may be locked in metal to metal contact with the discharge side of the pump chamber. Accordingly, a pump may be assembled in which the clearance of the bushings adjacent the inlet side of the pump is large enough, because of the corresponding reduction in clearance adjacent the discharge side of the pump, due to lateral or transverse shifting of the bushings and cover section of the housing, to provide a substantial leakage path to inlet pressure. terially the efficiency of the pump.

Also, in the usual form of pressure loaded pump, the pressure loading motive chamber to which output pressure is supplied will be substantially uniformly subjected to the output pres- This, of course, reduces masure; that is to say, at any point on the motive surfaces at the rear of the bushing, the same pressure will exist. This is not true, however, of the forward or gear side face engaging surface of the bushing. This forward surface is normally subjected toa distinct pressure gradient extending from the inlet pressure in the area adjacent the pump inlet, which is the lowest pressure of the gradient, to the outlet pressure in the area adjacent the discharge side of the pump, at which area the pressure gradient is at its highest level. Accordingly, it will be evident that while the total pressure forces acting on the motive surfaces of the bushing may be made to equal the total pressure forces acting on the forward surfaces of the bushing, or to exceed these latter forces, the pressures acting on particular areas of the forward surfaces will not be uniform and the portion of the forward bushing surface nearer the inlet will be subjected to a lesser pressure tending to break the seal than the portion of the forward bushing surface nearer the outlet of the pump. This unbalanced pressure condition tends to twist the bushing in the pump and results in uneven wear, thereby increasing the power required to turn the pump. Wear is, of course, concentrated on the inlet side of the pump.

An object of the present invention is to provide a new and improved pressure loaded type, intermeshing gear pump.

A further object of the present invention is to provide a pressure loaded type intermeshing gear pump wherein the pressure loadable bushings are shifted during assembly of the pump toward the inlet side of the pump to reduce leakage in this area during operation of the pump and also during operation of the pump the bushings are urged toward the adjacent gear side face in the area adjacent the discharge side of the pump so as to compensate to some extent for the pressure gradient over the gear side face engaging surface of the bushings.

In accordance with this invention, a pressure loaded type, intermeshing gear pump having one set of axially movable, pressure loadable bushings may be provided with means for exerting a force so directed that during assembly of the pump the pressure loadable bushings are urged transversely toward the inlet side of the pump and pressed axially toward the gear side face portions adjacent the discharge side of the pump. In accordance with one embodiment of this invention, this means comprises a plunger assooiated with each of the pressure loadable bushings and located so as to engage the rear flanged surface of the pressure loadable bushings at an acute angle with respect to the axis of the pump, the plunger being moved by spring pressure during assembly of the pump and either by spring pressure alone or spring pressure in combination with fluid pressure generated by the pump during the operation of the pump to provide the compensation for the pressure gradient. The plunger has its axis directed so that one component of the plunger force tends to move the associated bushing toward the inlet side of the pump and the other component of the plunger force tends to move the associated bushing toward the associated gear side face portion adjacent the discharge side of the pump.

Other objects and advantages of the present invention will be apparent from the following detailed description thereof taken in conjunction with the drawings wherein:

Fig. 1 is a fragmentary, axial, sectional view of a pressure loaded type, intermeshing gear pump constructed in accordance with one embodiment of this invention;

Fig. 2 is a transverse, sectional view taken substantially along the line 22 of Fig. 1 and showing to advantage the arrangement of the spring-pressed plungers; and

Fig. 3 is a sectional view taken along the line 33 of Fig. 2 showing the location of the springpressed pistons.

Referring now to the drawings and particularly to Fig. 1 thereof, a pump generally similar to that shown in the aforementioned Roth et al. patent is illustrated comprising a sectional housing having a main body portion 5 and a right closure member or cover member 6. These sections are normally bolted together as by the bolts '5 and cooperate to define therewithin a pair of parallel axis, intersecting bores or pumping gear chambers 8 and 9 which are arranged to receive in complementary relationship intermeshing pumping gears I9 and II, respectively. More particularly, bolts I extend through holes la formed in the cover member 6 and are threaded into suitable threaded apertures formed in the housing section. The holes 1a are made somewhat larger in diameter than the shanks of the bolt 3 to permit the cover 6 to be adjusted with respect to the housing during assembly whereby to permit the bushings to be shifted toward the inlet side of the pump. In the embodiment illustrated, the pumping gears have integrally formed therewith hollow journal shafts l2 and I3, respectively, and the left portions of the journal shafts l2 and [3 are received in conventional flanged bushings I4 and I5 mounted in the left portions of the pumping gear chambers 8 and 9. The right portions of the gear journals are received, respectively, in axially adjustable, pressure loadable flanged bushings l6 and I! mounted in the right side of the pumping gear chambers.

In the embodiment illustrated, the upper pumping gear I!) is the driving gear and is rotated in a clockwise direction, as viewed in Fig. 2. In accordance with conventional pump design practice, the journal shaft of the upper gear may be extended to the left, as viewed in Fig. l, and coupled to a suitable power source. Low pressure liquid is introduced into the pump housing at inlet formed in the left side of the pump housing, as viewed in Fig. 2, and high pressure liquid is discharged from the pump housing, through outlet 2| formed in the right side of the housing, the inlet and outlet ports corn-- municating with the inlet and discharge areas of the intermeshing pumping gears. The pressure loadable bushings are normally fitted into the bores with sufficient clearance to permit slight axial movement of the bushings with respect to the bores to establish the desired pressure loaded seal during operation of the pump.

In the operation of a pump of this type, discharge pressure generated by the intermeshing gears may be communicated from the outlet or discharge side thereof to the annular pressure loading areas, designated lea and Ila, in the drawings and located at the back of the bushings, through an axially extending passage 22 formed between the peripheries of the flanged portions of the bushings on the discharge side of the pump at the point of convergence of the flanged portions of the bushings. Areas ltd and Ila cooperate with the adjacent walls of the housing bores 8 and 9 and the peripheries of the barrel portions of the bushings l6 and IT to define annular

pressure loading chambers

23 and 2 5, respectively. The passage 22 extends from the discharge side of the gears to the right,'as viewed in Fig. 1, to the intercommunicating portions of the

pressure loading chambers

23 and 24 at their point of juncture.

Escape of pressure rearwardly from the pressure loading surfaces is substantially prevented by means of an O-ring seal 25 disposed about the periphery of the rear or barrel portions of each bushing in a suitable annular groove formed in the periphery of the bushing or in the adjacent bore wall. Pressure leaking past the O-ring seal may be vented to inlet pressure or to a zone of intermediate pressure in accordance with conventional pressure loaded pump practice as set forth in the above-referenced Roth et al. patent.

Since it is necessary in order to permit the slight axial movement required of the bushings in order to establish a seal, to fit the bushings with some clearance in the bushing receiving chambers the bushings may actually be assembled in such manner that more clearance is provided adjacent the inlet side of the pump than adjacent the discharge side of the pump, that is to say that the axially movable bushings may be slightly off-centered with respect to the axis of the bushing receiving chambers and located nearer the discharge port than the inlet port. This shifted alignment of the bushings is then maintained during operation of the cover section which is then bolted rigidly in position and which follows the location of the bushings or may itself be shifted to'facilitate location of the bushings adjacent the inlet port. Since, in the operation of the pump, the pressure applied to the pressure loading chambers 23 and 2:3 is substantially equivalent to discharge pressure, the leakage path provided by the excessive clearance occurring when the bushings are positioned nearer the discharge port than the inlet port may be sufiicient to materially reduce the efficiency of the pump. For example, tests have indicated that at discharge pressures on the order of 5,000 p. s. i., a leakage passage of .005 diameter will reduce pump output up to fifty per cent.

In accordance with the present invention, there is associated with each of the pressureloadable bushings a spring-pressed plunger or

piston assembly

26 and 21, respectively, which exerts a force tending to move the axially movable pressure-loadable bushings to the left, as viewed in Fig. 2, so that the left sides of their flanged portions en age closely the sides of. the

pump chambers adjacent the inlet. side of. thepump. Since the low-pressure area of. the-pump is, confined. to the area adjacent the; inlet side of the. pump, the fact that. the bushings. areshifted" slightly to the-left causesagap or space on the dischargeside of the pump is not significant. This shifted alignment of; the bushings is then maintained when the assembly of the pump is completed by locking the bolts 1. securely in position, the cover section 6 being then shifted also toward the inlet side ofthe pump.

More particularly, the upper. piston. assembly 2.6 of. this invention comprises, as shown in Fig. 3, a: hollow-bodied pistonZBof generally cylindrical configuration havingits left; or upperendclosed, as viewed in. Fig. 3, and the piston is slidably journaled in a suitably formed, axially extending chamber 29;for'med in the cover member 6 of the pump housing. Associated with the piston. 28 is a helically coiled spring, 30, the left or upper end of. which bears against the inner side-of the cross portion of thepiston, that is the head of the piston, and the right or lower end of which bears against the inner end of a threaded re-- taining member M, which is threaded into the lower right end of chamber, 29; chamber 29 is. in turn suitably threaded toreceive this member 3 l. By selecting the compression of spring 30 and by adjusting the position of member 3!, the force exerted by the spring 3.0 may be closely regulated.

If it, were desirable only to locate the bushings so that their sides adjacent the inlet port were fitted as closely as possible to the adjacent side walls of the housing in this area, then the chamber 36 could be located at right angles to the axis of the pump so that all the forceexerted by the piston would be used in locating the bushings against the. inlet side of the pump housing. However, in the operation of a gear pump of the type herein shown, a pressure gradient exists across the faces of the bushings adjacent to, the gear side faces, the pressure gradient extending from a low pressure value corresponding to the inlet pressure of the pump on the inlet side thereof to a pressure value corresponding to the discharge pressure of the pump at the outlet side thereof. On the other hand, the pressure applied to the motive surfaces 16a and lla is normally substantially uniform over thefull extent thereof. It will be. apparent, therefore, that since the gear side face pressure acting against the loading pressurev in the area. adjacent the discharge side of the pump exceeds the gear side face pressure acting against the loading pres.- sure in, the area adjacent the inlet side of the pump, the axially movable bushings l6. and I1 will tend to engage the gear side faces with, a correspondingly greater force adjacent the inlet side. This unbalanced. arrangement results in.

increased wear and, more particularly, uneven.

wear resulting ultimately in accelerated. deterioration of the pump. In accordance with the present, invention, this factor is taken into ac.- count by locating the piston so that the force exerted by the piston on the bushings is divided into two components, one component urging the bushings toward the inlet. side of the pump andthe other component urging the bushings toward the associated gear side face in the. area thereof adjacent the discharge side of the pump.

More particularly, it will be seen that chamber 29 is located at an acute angle with, respect to the. axis of the pump and the head of the piston.

engages the. rear edgeof the flanged: p rtion. o the: bushing. Iii; acrossthe, corner thereof. This. corner may be beveled as indicated at 3.3; By; selecting the angle. of the axis of. chamber 29 and consequently of, piston. 28, the division of the piston force may be controlled so that either more or less is applied: in the direction tending to move the bushing to, the left, as viewed in. Figs. 2 and 3, or more or less is applied, in the directiontending to. push, the bushing toward the gear side face in the area of the discharge; side of the pump.

llhis force exerted by this spring 3.0. may, in accordancewit-h this invention, be supplemented by supplying discharge pressurefrcm thedischarge sideof the pump to the back of the piston. For this. purpose, a, short angularly extend;- ing passage 32 may be formed in the cover and body section 5, passage 32 communicating at one end with the discharge side of thev pumping gears and at its other end: with the mid-portion of the chamber 29. at, a point located: so that the piston. 28 does not. block the passage, The, hydraulic pressure so sup-plied may, of course,. be regulated by selecting the area of the piston exposed to pressure.

The construction of the piston assembly 2'I- associated with the lower pressure loadable bush-- ing I! isidentical with that of the assembly 26.

From the foregoing, it will be evidentthat the spring pressure,v which is always effective, will during the assembly of: the pump push the bushings to the left and forward, as viewed in; Figs..2 and, 3, and then, after the pump is placed in. operation, as the pump discharge pressure rises; to its operating value and. this pressure is communicated tothe rear of the pistons, the pistons will supplement the force urging the bush.- ings forward and to the left, thus assuring proper location of the bushings in the housing and compensating in. part at least for the pressure gradient across the-gearside face-engaging surfaces of the bushings. In practice, it has been found that the. pump arrangement, disclosed a herein facilitates construction of the pump, para right or left position or an upper or lower position, it will be understood that this is. done solely for the purpose of facilitating description, and that such references relate only to therelative positions of. the parts as shown in the accompanying drawings.

While but: one embodiment of this invention has been shown and described, it will be understood that many changes and modifications may be made therein without. departing from the spirit or scope of the present invention. While it. is desirable in, many applications to employ both spring and hydraulic pressure on the pistons, it will. be apparent that either may be used without the other also.

What is claimed is:

1. A. pressure loaded type,v in-termeshing gearpumpv of the type comprising a housing having a chamber formed therein and aninlet port on the inlet side of, said chamber and a. discharge 7 port on the discharge side of said; chamber, a

pumping gear in said chamber adapted to be engaged on one side face by a bushing, a pressure loadable bushing adapted to engage said gear side face in sealing relation, and springpressed means disposed at an angle with respect to the axis of said gears urging said pressure loadable bushing angularly with respect to said axis and against the inlet side of said pump during assembly of said pump, the spring force being supplemented during the operation of said pump by discharge pressure applied to said means.

2. 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 forcing fluid from said inlet and 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 chamber and having portions cooperable with said housing to provide a pressure chamber, said end plate having an axis of movement parallel to the axis of rotation of said rotatable member, said end plate also having a front face subject to pressures in said pump chamber and cooperable with the adjacent side face of said rotatable member to provide a pumping seal therewith, one of said last two mentioned face-s having a relief recess formed therein to limit the sealing area between said side face and said front face, means establishing communication between said relief recess and said inlet, means establishing communication between said pressure chamber, at the back face of said end plate 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 always exceeds slightly the sealing force acting upon the front face of said end plate whereby it maintains said pumping seal without excessive friction, wear or loss of volumetric er"- ficiency, and means associated with said end plate arranged to provide a first force acting generally at right angles to the direction of the sealing force acting on said back face during the operation of the pump to urge said end plate toward the inlet side of said housing during assembly of the pump thereby to reduce leakage between the periphery of said end plate and the adjacent inner wall of said housing on the inlet side of said pump, said means being arranged to provide a second force acting generally parallel to the direction of said sealing force and in the same direction to urge said end plate toward the adjacent gear side face on the outlet side of said housing.

3. A pump according to claim 2 wherein said force providing means comprises a piston arranged to engage said end plate at an acute angle with respect to the axis of the rotatable member.

4. A pump according to claim 2 wherein said force providing means comprises a springpressed piston adapted to bear against the end plate at an acute angle with respect to the axis of the rotatable member in response to pressure loading.

5. A pump according to claim 2 wherein said force providing means comprises a springpressed piston adapted to bear against the end plate at an acute angle with respect to the axis of the rotatable member in response to pressure loading, and means for supplying discharge pressure from said pump to said piston to supplement the spring force.

6. A pressure loaded type of intermeshing gear pump including a housing having a pair of pumping chambers formed therein and an inlet leading to and an outlet leading fromsaid pumping chambers, intermeshing pumping gears disposed in said chambers and arranged to force liquid from said inlet through said chamber and out of said outlet, bushings associated with each of said pump ing gears, at least one of said bushings being movable along a direction substantially parallel to the axis of rotation of said pumping gears in response to application of discharge pressure to the rear surface thereof to engage the associated gear side face in sealing relation, the forward faces of said bushing being subject to a liquid pressure gradient established during operation of the pump having its minimum pressure level at the inlet and its maximum pressure level at the outlet, and means for exerting a force having its axis at an acute angle with respect to the axis of rotation of said gears whereby one component of said force urges said bushing toward the inlet side of said pump and the other component of said force urges said bushing toward said pumping gear, said means being located so that the component of force exerted to urge said bushing toward said pumping gear is exerted against the portion of said bushing adjacent the discharge side of said pump whereby to compensate for the pressure gradient extending across the gear side face engaging surface of said bushing.

7. A pump according to claim 6 wherein said force providing means comprises a piston adapted to bear against said bushing.

8. A pump according to claim 6 wherein said force providing means comprises a spring-pressed piston adapted to bear against said bushing.

9. A pump according to claim 6 wherein said force providing means comprises a hydraulically actuated piston adapted to bear against said bushing.

10. A pressure loaded type of intermeshing gear pump including a housing having a pair of pumping chambers formed therein and an inlet leading to and an outlet leading from said pumping chambers, intermeshing pumping gears disposed in said chambers and arranged to force liquid from said inlet through said chambers and out said outlet, a bushing associated with each of said pumping gears, at least one of said bushings being movable in a direction substantially parallel to the axis of rotation of said pumping members in response to application of discharge pressure to the rear surface thereof to engage the associated gear side face in sealing relation, the forward surface of said bushing being subject to a pressure gradient'generated by the liquid being pumped from inlet out said outlet, and means for exerting a force on said bushing having its direction at an angle with respect to the axis of said pumping gears whereby one component of said force urges said bushing towards the inlet side of said pump and the other component of said force urges said bushing in a direction parallel to the axis of said pumping gears and towards said pumping gears, said means being located so that the component of force exerted in the direction parallel to the axis of said pumping gears is exerted against the portion of said bushing adjacent the discharge side of the pump and greater than the component of force exerted in the direction toward the inlet side of said pump, whereby to compensate for the pressure gradient extending across the gear side engaging surface of said bushings.

11. A pump according to claim 10 wherein said force providing means comprises a piston adapted to bear against said bushing.

12. A pump according to claim 10 wherein said force providing means comprises a hydraulically actuated piston adapted to bear against said bushing.

13. In a pump, a housing having an inlet and an outlet and providing a pumping cavity, a pumping element, a shiftable end plate closing one end of said cavity in said housing and being subject to pressures in the cavity which increase toward the outlet side of the cavity, said shiftable end plate forming together with means including a portion of said housing a pressure control chamber adjacent said cavity, a back face on said shiftable plate forming a Wall on said pressure control chamber, and means for exerting a force on said end plate having its direction at an angle with respect to the axis of said pumping element whereby one component of said force urges said plate towards the inlet side of said pump and the other component of said force urges said plate towards the pumping cavity, said means being located so that the component of force exerted to urge said plate towards said pumping cavity is exerted against the portion of said plate adjacent the discharge side of said pump to produce balancing forces urging the plate toward the cavity in proportion to the unequal forces urging the plate away from the cavity.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,880,108 Ross Sept. 27, 1932 2,420,622 Roth et a1. May 13, 1947 2,512,025 Lauck June 20, 1950 2,527,941 Lauck et al. Oct. 31, 1950 2,544,988 Gardiner et a1 Mar. 13, 1951