US3203355A

US3203355A - Rotary pump

Info

Publication number: US3203355A
Application number: US299138A
Authority: US
Inventors: Howard M Purcell
Original assignee: Parker Hannifin Corp
Current assignee: Parker Hannifin Corp
Priority date: 1963-07-24
Filing date: 1963-07-24
Publication date: 1965-08-31
Anticipated expiration: 1982-08-31

Description

Aug. 31, 1965 M. PURCELL 3,203,355

ROTARY PUMP Original Filed May 3, 1960 3 Sheets-Sheet 1 LNVENTOR HOWARD M.PURCELL ATTORNEY Aug. 31, 1965 H. M. PURCELL. 3,203,355

ROTARY PUMP Original Filed May 3, 1960 3 Sheets-Sheet .2

INVENTOR.

HOWARD M. PURCELL N s' k WWW ATTORNEY United States Patent 3,203,355 R'OTARY PUMP Howard M. Purcell, Cleveland, Ohio, assignor to Parker- Hannifin Corporation, Cleveland, Ohio, a corporation of Ohio Continuation of application Ser. No. 26,646, May '3, 1960.

This application July 24, 1963, Ser. No. 299,138 18 Claims. (Cl. 103-126) This application is a continuation of my copending application Serial No. 26,646, filed May 3, 1960, and entitled Rotary Pump, this application now being abandoned.

This invention relates to rotary pumps or motors and more particularly to those of the type having a pressure loaded element for sealing the side faces of the rotary member.

In pumps of the type referred to above, as for example, in gear pumps, the rotary members have teeth with spaces or pocket areas therebetween which become filled with liquid under low pressure as the pocket areas pass the pump inlet and which discharge the fluid under high pressure into the pump outlet. The side openings of such pockets are closed by wear plates or bushings. Fluid in pockets which are exposed to the outlet is under pressure and reacts against such wear plates or bushings tending to separate the same from the gear side faces and thus permit leakage of fluid from high pressure areas to areas of low pressure which, if permitted, results in low volumetric efliciency and is thus undesirable. To prevent such separation and leakage, the wear plates or bushings are pressed by means of fluid pressure into sealing engagement with the side faces of the gear teeth, fluid under pressure for this purpose being diverted from the pump outlet and applied against pistons or the like movable by such fluid pressure.

Since the wear plates or bushings are non-rotatable, there is running friction between the same and the gear side faces as the gears rotate, such running friction causing loss of mechanical efliciency and creating undesirable heat. To minimize these adverse characteristics, it is desirable to maintain only the minimum amount of pressure between the wear plates and gear side faces to assure satisfactory sealing.

The construction of the pump parts may be such that during rotation of the gears the total area of any wear plate subject to high pressure tending to move the wear .plate away from the gear may rapidly fluctuate, and hence the total separating force on the wear plate will likewise rapidly fluctuate. It is an object of the present invention to effectively resist such fluctuating forces without applying undue counterforce to the wear plates which would otherwise cause excessive heat and loss of mechanical efliciency.

It is another object to provide a counterforce which increases and decreases as the total separating force increases and decreases so that a substantially uniform differential between the two'forces is maintained, such differential force being suflicient to maintain the wear plate in sealing contact with the rotor without excessive friction.

It is another object to utilize a portion of the fluid from the pump outlet for generating the counterforce described and to trap such fluid portion in a manner so that its pressure will increase and decrease as the fluctuating separating forces on the wear plates increase and decrease but wherein there will be a gradual reduction of the pressure of the trapped fluid whenever its pressure exceeds the pressure of fluid inthe pump outlet for a period of time longer than the cycle time of the fluctuating forces.

Patented Aug. 31, 1965 "ice Other objects will be apparent from the following description and from the drawings in which:

FIGURE 1 is a longitudinal section through the lines 1-1 of FIGURE 3,

FIGURE 2 is a section through lines 2-2 of FIG- URE 3,

FIGURE 3 is a section, partially fragmentary, through the lines 3-3 of FIGURE 1, and

FIGURE 4 is a fragmentary enlarged section view along the lines 4--4 of FIGURE 1.

In the example disclosure of embodiment of the invention the pump structure includes a body 10 and

end closures

11 and 12 secured to the body by screws 13. O-ring seals 14 may be provided between the

end closures

11 and 12 and the body 10. The end closure 11 is formed with a hollow boss 15 containing suitable bearings for the drive shaft 16 and a cap plate 17 is secured to the boss and contains a suitable seal for the outer end of said shaft. The inner end of the shaft 16 has external spline ribs 18 for engagement with one of the meshed pumping gears to be described hereinafter.

The body 10 includes a chamber comprising two longitudinal

cylindrical bores

19 and 19a which intersect at a median plane P (FIGURES 1 and 3). In FIGURE 3 a second plane P has been indicated extending diametrically through the longitudinal centers of the

bores

19 and 19a. At one side of the plane P the body 10 has an internal recess 20 which opens through the walls of the

bores

19 and 19a and provides a receiving zone R for the fluid to be pumped. At the opposite side of the plane P the body 10 has another recess 21 which opens through the walls of the

bores

19 and 19a and Provides a delivery zone D to which the pumping gears deliver the fluid from the receiving zone R. The zone R has an inlet 22 for connection with a fluid inlet conduit and the zone D has an outlet 23 for connection with a fluid delivery conduit.

One set of bearing blocks or bushings (FIGURE 1) 24 and 24a is provided at one end of the body 10 and a second set of bearing blocks or bushings'25 and 25a is provided at the other end of said body. The

blocks

24 and 25 are in the ends of the bore 19 and conform thereto, and the blocks 24a and 25a are in the ends of the bore 19a and conform thereto. The blocks 24 and 24a of the first set solidly abut the end closure 11, and the blocks 25 and 25a are adjacent to but spaced inwardly from the inner side of the end closure 12. The closure 11 is preferably recessed somewhat at 26 (FIGURE 1) to receive the outer ends of the blocks 24 and 24a. These blocks 24 and 24a have flat surfaces 27 which abut at the median plane P, and the blocks 25 and 25a also have flat surfaces 28 which abut at said plane P. All of the blocks or

bushings

24, 24a, 25 and 25a are identical for ease of manufacture and assembly, and suitable sealing means 29 is provided for sealing against fluid egress endwise outwardly about the blocks or between the abutting

flat faces

27 and 28 of the block sets.

A plurality of movable elements or

wear plates

30 and 30a, of a first set, contact with the inner sides of the bearing blocks 24 and 24a, respectively, and have straight edges 31 which abut at the median plane P. Other movable elements or wear

plates

32 and 32a, of a second set, contact with the inner sides of the bearing blocks 25 and 25a respectively,and have straight edges 33 which abut at the median plane P. All of the

wear plates

30, 30a, 32 and 32a peripherally conform to the

bores

19 and 19a except in the region of the fluid receiving zone R. In this region, said wear plates are notched at 34 (FIGURE 3) to allow end filling as well as radial filling of a plurality of tooth pocket areas of the pumping gears with fluid entering at the inlet 22.

As viewed in FIGURES l and 3, each of the

wear plates

30, 30a, 32 and 32a has a central opening 35, and first means comprising an arcuate groove 36 concentric with said opening 35 and including a groove 37 leading from said arcuate groove 36 through the peripheral edge of the plate. Both

grooves

36 and 37 are open to the inner side faces of the respective wear plates. Each groove 36 extends from a point 36a (FIGURE 3) about midway between the receiving zone R and the delivery zone D to a point 36b in the zone in which the rotary pumping gears mesh, and each radial groove 37 is in direct communication with the delivery zone D. The purpose of the

grooves

36, 37 will be described in detail hereinafter.

A rotary member or pumping gear 38 is interposed between the two

movable wear plates

30 and 32 and has its side faces in sealing contact with the inner side faces of said wear plates. Another rotary member or pumping gear 38a is interposed between the two

wear plates

30a and 32a and has its side faces in sealing contact with the inner faces of these wear plates. The two gears mesh across the median plane P as seen in FIGURE 3 and their teeth radially span the wear plate grooves 36.

Each gear 38, 38a has tubular bearing stubs 39 extending through the wear plate openings 35 mounted in roller bearings 40 within the

bearing blocks

24, 24a, 25 and 25a. Each gear has internal spline ribs 41. The spline ribs 41 of the gear 38 engage with the external spline ribs 18 of the drive shaft 16. The gear 38a is driven by the drive shaft 16 through the gear 38, as is best illustrated in FIGURES 1 and 3.

The first means or wear

plate grooves

36 and 37 serve to communicate the pressure existing in outlet recess D to approximately half of the plurality of tooth pocket areas in each gear and also serve to relieve fluid which would otherwise be trapped in the plurality of tooth pocket areas in the gear meshing zone. Such relief is desirable because as the teeth mesh, the pocket area portion occupied by fluid progressively decreases until the pocket area is centered on median plane P, after which it increases. Without the relief, the fluid trapped in such decreasing pocket area portions is forced to compress and develops extremely high pressures which are detrimental to the pump.

The fluid under pressure in the plurality of tooth pocket areas connected by the grooves 36 acts on the adjacent area of the inner faces of the

wear plates

30, 30a, and 32, 32a, tending to separate the wear plates from the gear side faces, which would result in leakage of fluid from the high pressure zone D to the low pressure zone R. Fluid in the tooth pocket areas toward the low pressure cavity R is under low pressure and therefore exerts no appreciable separating force upon the wear plates.

The forces tending to separate

wear plates

30, 30a from the gears are counteracted by the rigid support of bushings =24, 24a by abutment face 26. To counteract the forces tending to separate

wear plates

32, 32a from the gears, two fluid pressure operated

pistons

42, 42a (FIG- URES 1 and 3) are provided. They are respectively mounted in a pair of piston chambers 43 and 43a formed in the end closure 12, and said pistons bear respectively against the bearing blocks and 25a. The

pistons

42 and 42a are spring-loaded at 44 to initially hold the bearing blocks, wear plates and gears in contact. During pump operation, however, the pressure of the delivered fluid in recess D and outlet 23 is applied through second means or

common passages

50, 51, including

branch passages

52, and 54, to the chamber 43 to the motive surface or outer face of piston 42 and through

common passages

50, 51, and

branch passages

53, 55 to chamber 43a and piston 42a to cause the pistons to so press against the bearing blocks 25 and 25a as to counteract the separating force which the delivered fluid exerts on the wear plates. As this separating pressure is concentrated toward the delivery side of the pump, due to the groove 4 36, the counteracting pressure exerted by the

pistons

42 and 42a must be greatest at said delivery side. In order to attain this end, the axes A of the

pistons

42 and 42a and their chambers 43 and 43a are offset toward the delivery side of the pump from the centers C as shown in FIGURE 3.

To prevent any accumulation of pressure which might interfere with seating of the bearing blocks 24 and 24a against the end closure 11, a groove 45 (FIGURES 1 and 2) is formed in the inner side of said end closure 11 and said groove is placed in communication with the fluid receiving zone R by means of registering

passages

46, 47 in said end closure and the body 10 respectively. An O-ring seal 48 is provided around the meeting ends of the pass-

ages

46, 47. The blind passage 46a in FIGURE 2 comes into operation only when the body It) is turned within the closure caps 11 and 12 from the position shown for the purpose of reversing pump rotation. It then registers with the passage 47. An O-ring seal 49 is provided around the outer end of the passage 46a.

The force tending to separate the wear plates from the gear side faces fluctuates as the gears rotate. This is brought about by the fact that the wear plate area exposed to high pressure fluid within tooth pocket areas and in grooves 36 opposite gear tooth side faces fluctuates as the gears rotate. Thus for example, as gear 38 rotates in a counterclockwise direction as viewed in FIG- URE 3, tooth 38b when in the full line position shown covers the end edge 36a of groove 36 and there is high pressure fluid in all the tooth pocket areas to the left of tooth 33b up to and including the tooth pocket area to the left of tooth 380, or six tooth pocket areas in all. Thus, the gear 38 defines with the side face thereof and the wear plate 32 a plurality of tooth pocket areas forming a substantial peripheral area subject to increasing and decreasing fluctuating fluid pressure. At the same instant, seven teeth, from 38b to 38c are opposite groove 36. Thus at this instant wear plate 32 is acted upon by fluid pressurized substantially to the pressure of the fluid in outlet zone D across an area equal to that defined by approximately six tooth pocket areas and seven segments of groove 36 opposite gear teeth. This exerts a definite force on wear plate 32 tending to separate it from the adjacent gear side face.

As gear 38 rotates counterclockwise slightly further so that tooth 38b moves to the position shown in dotted lines in FIGURE 3, the end 3601 of groove 36 opens suddenly into the tooth pocket to the right of tooth 38b and almost instantaneously pressurizes the fluid therein. This suddenly adds the area of another tooth pocket to the area of wear plate 32 subject to high pressure fluid and thus suddenly increases the total force acting on wear plate 32 tending to separate it from the gear side face. It has been found that this sudden increase will actually move the wear plate against the holding force applied by piston 42 so as to cause leakage, unless special provision is made to prevent this eflect. This is particularly true when the area of piston 42 is so selected as to normally apply a relatively small amount of overbalancing force for keeping wear plate 32 in engagement with the gear side face without excessively high contact pressure therebetween. 1

To prevent such sudden increase in the force tending to move wear plate 32 away from the gear, provision is made for trapping the fluid behind

pistons

42 and 42a in the respective chambers 43 and 43a. Since liquid is relatively incompressible, the trapped fluid acts as a solid abutment to prevent such outward movement of the wear plates. Thus check valve 58 prevents any substantial back flow from chamber 43 to outlet recess D and check valve 58a prevents such back flow from chamber 43a. As a sudden increase of force occurs on the inner face of either

wear plate

32, 32a, a very slight outward movement of the wear plate will occur which is transmitted by the respective bushing 25, 25a to the

corresponding piston

42, 42a and cause a rapid rise in pressure of the trapped fluid in the pressure chamber to resist further outward motion of the parts. The outward motion of the wear plates for producing this pressure rise is so slight that it does not affect the seal against the gear side faces. This outward motion is checked and reversed by the sudden build up in pressure within chambers 43, 43a, and also by the gradual decrease of separating forces on

wear plates

32, 32a.

Again considering Wear plate 32 and gear 38, as tooth 38b moves from the dotted position toward the position occupied by gear tooth 38d, there will be no new tooth pocket exposed to pressure in groove 36 until tooth 38e reaches the dotted position shown for tooth 38b. Thus at this region of the gear, with each angular motion of the gear through an arc equal to the angular spacing between gear teeth centers, there will be a sudden increase in area on the wear plate exposed to high pressure equal to the area of one gear tooth pocket area followed by a gradual decrease of such exposed area to the extent of the area of one tooth pocket. From this it is evident that there will be one cycle of sudden increase and gradual decrease in exposed wear plate area for every tooth pocket in the gear during each complete revolution of the gear.

Meanwhile, at the meshing zone of the two gears, the tooth pocket area to the left of tooth 38c has all its area exposed to wear plate 32 except for a very small portion blocked out by the tip of tooth 38f. As gear 38 continues to rotate counterclockwise tooth 38] blocks morean'd more of this tooth pocket area exposed to wear plate 32 until only a very small pocket area 38g, remains exposed to the wear plate and the fluid therein exerts high pressure onto the wear plate until the pocket passes over center of the median plane P. Also, an increasing portion of each tooth pocket of gear 38 moves out of register with wear plate 32 as the pocket passes median plane P. Thus it will be seen that at the meshing zone each tooth pocket gradually is reduced in its area of exposure to the wear plate and there is no substantial sudden increase in area. Force fluctuations on the inner side of the wear plate are thus due primarily to the cyclical increase and decrease in area of high pressure tooth pocket exposure in the vicinity of tooth 38b as already described.

It will be noted that gear 38a is at all times angularly displaced one half the angular distance between tooth centers from the position of gear 38, this being due to the gears being as shown in FIGURE 3 where it is about to suddenly expose the tooth pocket to the right thereof to high pressure in groove 36, tooth 38h is relatively one half a tooth spacing farther onto the corresponding groove 36 and thus gear 38a is at about the midpoint of its cycle for increasing and decreasing the area of exposure to high pressure. As a result, the cycles for this effect for the two gears are out of phase, the high point of one being at about the midpoint of the other. To obtain most eflicient counteraction to the force fluctuations, pressure chambers 43 and 43a are pressurized independently of each other and through

individual check valves

58, 58a. Otherwise, if chambers 43, 43a are interconnected or are connected to the outlet zone D through a common check-valve the volume of trapped fluid for resisting separation movement of the wear plates from the gears is doubled and hence the slight separating movement of each wear plate for compressing the fluid to build up the counteracting pressure will be approximately doubled and thus result in less eflicient sealmg.

Each

check valve

58, 58a is normally seated on a seat 57 by a light spring 60 abutting a closure plug 56 for bores 53. The light springs 60 permit the check valves to unseat readily for filling pressure chambers 43 and 43a with fluid from outlet zone D when the pump is put into operation.

Bleed holes 59 are provided in the check valves to permit delayed balancing of pressures between each pressure chamber 43, 43a and the outlet zone D when the pressure in either pressure chamber tends to rise (as by thermal expansion) or tends to remain (as when pump pressure drops) higher than the pressure in the outlet zone. The bleed ports 59 are of such size that they will not pass an appreciable amount of fluid during the cycles of increasing and decreasing force on the wear plates due to changing areas of tooth pocket exposure and thus do not appreciably effect the counteraction provided by the trapped fluid in the pressure chambers 43, 43a. However, if the pressures in these chambers start to rise above the pressure in outlet zone D due to thermal expansion, a small amount of fluid will bleed through the port 59 from the chamber toward the outlet zone until the pressures are substantially balanced, that is, until the lowest pressure in the chamber during the cycles of fluctuating pressures therein is substantially the same as in the outlet zone D.

Likewise, if the pump has been operating at one high pressure 2500 p.s.i. for example (this being the pressure in outlet zone D), and is cut back to a lower pressure, such as 1000, p.s.i., the bleed ports 59 will permit the pressure in the pressure chambers 43, 43a to correspondingly drop. Without the bleed port the higher pressure would be maintained in the pressure chambers resulting in excessive force on the wear plates for counteracting the pressure exerted on the inner side of the wear plates tending to separate the wear plates from the gears which in turn would lead to excessive friction between the wear plates and gears with consequent excessive heating and loss of mechanical efiiciency.

Packings 64 and

64a seal pistons

42, 42a so as to completely seal pressure chambers 43, 43a whereby all fluid entering or leaving the chambers must pass through check valves 58 and for bleed ports 59. This permits a highly accurate control of pressure and flow conditions for the chambers and their relation to the separating force fluctuations. Thus, it is important to have relatively

large passageways

50, 51, 52, 53, 54 and 55 to permit rapid filling of the pressure chambers 43, 43a when starting the pump. The bleed ports 59 must be small enough to permit no appreciable loss of fluid from the chambers during the separating force fluctuation cycles when the pressure within the chambers rises from substantially pump discharge pressure to a higher pressure and recedes again to discharge pressure. On the other hand, the bleed ports must be large enough to bleed excess pressure from the chambers, due to causes noted above, whenever the pressure in the chambers remains at a value higher than pump discharge pressure for a period of time longer than the cycle time for the fluctuating separating forces. It has been found, for example, that for a gear pump designed to operate at pressures up to 25,000 p.s.i. and speeds up to 2500 rpm, with ten teeth per gear, minimum and maximum areas of 4.38 and 5.13 square inches of wear surface exposed to high pressure, and with a piston area of 5.93 square inches, a .007" diameter for bleed ports 59 provides excellent results. From this it is apparent that it is important that leakproof packings 64, 64a be provided. Otherwise, leakage from the chambers 43, 43a past the

pistons

42, 42a which would be very diflicult to control precisely with normal machining practices and dimensional tolerances, would make it impossible to achieve effective sealing of the wear plates without a substantial overbalance of pressure thereagainst with resulting poor mechanical efiiciency.

I claim:

1. A fluid pressure translating device comprising a housing, a chamber in said housing, an inlet recess leading to and an outlet recess leading from said chamber, a rotary member in said chamber subject to fluid under pressure, said member having a. surface to be sealed, a movable element in engagement with said surface for sealing the same, said movable element defining with said surface a plurality of areas forming a substantially peripheral area extending from said outlet recess to a position in close proximity to said inlet recess with alternating areas thereof subject to fluid under pressure tending to separate the movable element from said surface, first means subjecting said entire substantially peripheral area to increasing and decreasing fluid pressure fluctuating forces as said rotary member rotates, said first means providing pressure communication between said chamber and said outlet recess, at least one of said areas which is otherwise closed to the oulet recess being in communication with said outlet recess through said first means, second means in communication solely with said first means and said outlet recess for applying second forces to said movable element in opposition to said separating'forces whereby said element is maintained in sealing contact with said surface, and third means in communication only with said second means and said movable element for solely causing said second forces to increasingly and decreasingly fluctuate substantially in phase, duration and in like manner with said first forces and maintain a substantially uniform incremental force differential therebetween irrespective .of whether the said first forces are increasing or decreasing.

2. A fluid pressure translating device in accordance with claim 1 wherein said first means includes a groove cooperative with said rotary member to produce said fluid pressure fluctuating forces as said rotary member rotates.

13. A fluid pressure translating device in accordance with claim .1 wherein said third means includes a valve means for causing said second forces to fluctuate. v

4. A fluid pressure translating device in accordance with claim 1 wherein said first means includes a groove cooperative with said rotarymember to produce said fluid pressure fluctuating forces as said rotary member rotates, and said third means includes valve means for causing said second forces to fluctuate.

S. -A fluid pressure translating device in accordance with claim 4 including a piston chamber within said housing, a piston in said piston chamber cooperative with said movable element and said valve means for applying said second forces to said movable element in opposition to said first forces for maintaining said movable element in sealing engagement with said surface.

*6. A fluid pressure translating device in accordance with claim 5 :where said second means is a passage for conducting fluid under pressure from said out-let recess to said piston chamber, said valve means including a bleed port connecting said passage to said recess for permitting a delayed balancing of said fluid fluctuating forces by said second forces.

7. A fluid pressure translating device in accordance with claim 4 including a pair of piston chambers within said housing, a piston in each of said piston chambers cooperative with said movable element and said valve means for applying said second forces to said movable element in opposition to said first forces for maintaining said movable element in sealing engagement with said surface.

8. A fluid pressure translating device comprising a housing, a chamber in said housing, an inlet recess leading to and an outlet recess leading from said chamber, a pair of rotary members in said chamber subject to fluid under pressure, said rotary members each having a surface to be sealed, a movable element in engagement with each of said surfaces for sealing the same, said movable element defining with said surface a plurality of pocket areas forming a pair of substantially peripheral areas extending from said outlet recess to a position in close proximity to said inlet recess with alternating pocket areas thereof subject to fluid under pressure tending to separate the movable element from said surface, a pair of grooves,

each of said grooves subjecting one of said pair of periphtuating forces as said pair of rotary members rotate, said grooves providing pressure communication between said chamber and said outlet recess, at least one of said pocket areas of each of said pair of peripheral areas which is otherwise closed to the outlet recess being in communication with said outlet recess through the groove of each of said pair of grooves, a passage in communication solely with said grooves and said outlet recess for applying second forces to said movable element in opposition to said separating forces whereby said elements are maintained in sealing contact with each of said surfaces, and valve means in communication only with said passage and said movable elements for solely causing said second forces to increasingly and decreasingly fluctuate substantially in phase, duration and in like manner with said first forces and maintain a substantially uniform incremental force differential therebetween irrespective of whether the said first forces are increasing or decreasing. 9. A fluid pressure translating device in accordance with claim 8 wherein said housing includes a pair of piston chambers and said passage includes a pair of branch passages in communication with each of said piston chamers, a piston within each of said piston chambers cooperative with said movable element, and said valve means includes an individual check valve in each of said branch passages for applying said second forces individually to each of said pistons in opposition to said first forces for maintaining said movable elements in sealing engagement with said surfaces.

10. A fluid pressure translating device in accordance with claim 9 wherein said movable elements are wear plates and each of said check valves includes a bleed port for permitting a delayed balancing of said fluid fluctuating forces by said second forces.

11. A fluid pressure translating device comprising a housing, a chamber in said housing, an inlet recess leading to and an outlet recess leading from said chamber, a rotary member in said chamber subject to fluid under pressure, said member having a surface to be sealed, a movable element in engagement with said surface for sealing the same, said movable element defining with said surface a plurality of areas forming a substantially peripheral area extending from said outlet recess to a position in close proximity to said inlet recess with alternating areas thereof subject to fluid under pressure tending to separate the movable element from said surface, first means subjecting said entire substantially peripheral area to increasing and decreasing fluid pressure fluctuating forces as said rotary member rotates, said first means providing pressure communication between said chamber and said outlet recess, at least one of said areas which is otherwise closed to the outlet recess being in communication with said outlet recess through said first means, second means for applying second forces to said movabie element in opposition to said separating forces whereby said element is maintained in sealing contact with said surface, and third means in communication with said second means and said movable element for causing said second forces to increasingly and decreasingly fluctuate in like manner with said first forces and maintain a sub stantially uniform incremental force differential therebetween irrespective of whether the said first forces are increasing or decreasing.

ing to and an outlet recess leading from said chamber,

a rotary member in said chamber subject to fluid under pressure, said member having a surface to be sealed, a

movable element in engagement with said surface for sealing the same, said movable element defining with said surface a plurality of areas forming a substantially peripheral area extending from said outlet recess to a position in close proximity to said inlet recess with alternating areas thereof subject to fluid under pressure tending to separate the movable element from said surface,

first means subjecting said entire substantially peripheral area to increasing and decreasing fluid pressure fluctuating forces as said rotary member rotates, said first means providing pressure communication between said chamber and said outlet recess, at least one of said areas which is otherwise closed to the outlet recess being in communication with said outlet recess through said first means, second means in communication with said first means and said outlet recess for applying second forces to said movable element in opposition to said separating forces whereby said element is maintained in sealing contact with said surface, and third means in communication with said second means and said movable element for causing said second forces to increasingly and decreasingly fluctuate substantially in phase, duration and in like manner with said first forces and maintain a substantially uniform incremental force differential therebetween irrespective of whether the said first forces are increasing or decreasing.

13. A gear pump comprising a housing, a chamber in the housing, an inlet recess leading to and an outlet recess leading from said chamber, a pair of meshed rotary gears in the housing for delivering fluid from said inlet recess to said outlet recess, a bushing for each gear and in contact with the side face thereof for sealing the same, a fluid pressure actuated piston in contact with each bushing for urging the same into sealing contact with the gear side face, passage means leading from the outlet recess to one side of the piston for at all times conducting fluid from said outlet recess against said piston, and a check valve in said passage means for permitting flow of fluid from said outlet recess to said one side of said piston, and a restricted passage of predetermined flow capacity for permitting flow of fluid from said one side of said piston to said outlet recess.

14. The gear pump of claim 13 in which said restricted passage is in said check valve.

15. The gear pump of claim 13 including means in the gear side face cooperating with said gears for communicating increasing and decreasing fluctuating forces to said passage means whereby said pistons move substantially in phase, duration and in like manners with the fluctuating forces.

16. A fluid pressure translating device comprising a housing, a pair of chambers in said housing, an inlet recess leading to and an outlet recess leading from said chambers, a rotary member in each of said chambers subject to fluid under pressure, each of said members having a surface to be sealed, a movable element in engagement with each of said surfaces, means for counteracting the fluid pressure acting to separate the movable elements and the rotary members to maintain the movable elements in engagement with said surfaces, said counteracting means including a pair of fluid pressure operating pistons, each piston being mounted in a piston chamber, spring means for urging each piston toward an associated one of said movable elements, passage means opening into said outlet recess, branch passage means between said passage means and each of said piston chambers for communicating outlet fluid pressure into each piston chamber, individual valve means between said passage means .and said branch passage means for independently pressurizing the piston chambers, each of said valve means being a check valve, said branch passages each including a seat receiving a check valve, a spring urging each check valve upon its associated seat, and a bleed passage in each check valve.

17. The fluid pressure translating device of claim 16 wherein said movable elements each comprise a generally circular plate having a central opening, an arcuate groove in a surface of said plate concentric with said opening, a short groove in said surface between said arcuate groove and opening through a peripheral edge portion of the plate, and said peripheral edge portion including a notch adjacent said short groove.

18. The fluid pressure translating device of claim 17 wherein said arcuate groove has opposite end portions spaced from each other substantially 180 degrees, and said short groove is positioned adjacent one of said end portions.

References Cited by the Examiner UNITED STATES PATENTS 2,420,622 5/47 Roth et al 103126 2,624,287 1/53= llyin 103126 2,772,638 12/56 Nagely 103-216 2,816,512 12/57 Murray 103126 2,865,302 12/58 Murray 103'126 2,870,719 1/59 Murray et a1. l03126 2,924,182 2/ Blasutta et al. 103216 2,974,605 3/61 Murray 103-126 FOREIGN PATENTS 706,979 4/54 Great Britain.

KARL J. ALBRECHT, Primary Examiner.

WIDBUR J. GOODLIN, JOSEPH H. BRANSON, JR., Examiners.

Claims

1. A FLUID PRESSURE TRANSLATING DEIVCE COMPRISING A HOUSING, A CHAMBER IN SAID HOUSING, AN INLET RECCESS LEADING TO AND AN OUTLET RECESS LEADING FROM SAID CHAMBER, A ROTARY MEMBER IN SAID CHAMBER SUBJECT TO FLUID UNDER PRESSURE, SAID MEMBER HAVING SURFACCE TO BE SEALED, A MOVABLE ELEMENT IN ENGAGEMENT WITH SAID SURFACE FOR MOVABLE ELEMENT IN ENGAGEMENT WITH SAID SURFACE FOR SURFACE A PLURALITY OF AREAS FORMING A SUBSTANTIALLY PERIPHERAL AREA EXTENNDING FROM SAID OUTLET RECESS TO A POSITIONN IN CLOSE PROXIMITY TO SAID INLET RECCESS WITH ALTERNATING AREAS THEREOF SUBJECT TO FLUID UNDER PRESSURE TENDING TO SEPARATE THE MOVABLE ELEMENT FROM SAID SURFACE, FIRST MEANS SUBJECTING SAID ENTIRE SUBSTANTIALLY PERIIPHERAL AREA TO INCREASING AND DECREASING FLUID PRESDURE FLUCTUATING FORCES AS SAID ROTARY MEMBER ROTATES, SAID FIRST MEANS PROVIIDING PRKESSURE COMMUNICATION BETWEEN SAID CHAMBER AND SAID OUTLET RECESS, AT LEAST ONE OF SAID AREAS WHICH IS OTHERWISE CLOSED TO THE OUTLET RECESS BEING IN COMMUNICATION WITH SAID OUTTLET RECESS THROUGH SAID FIRST MEANS, SECOND MEANS IN COMMUNICATION SOLELY WITH SAID FIRSTT MEANS AND SAID OUTLET RECESS FOR APPLYING SECOND FORCES TO SAID MOVEABLE ELEMENT IN OPPOSITION TO SAID SEPARRATING FORCES WHEREBY SAID ELEMENT IS MAINTAINED IN SEALING CONTCT WITHH SAID SURFACCE, AND THIRD MEANS IN COMMUNICATION ONLY WITHH SAIDD SECOND MEANS AND SAID MOVABLE ELEMENT FOR SOLELY CAUSING SAID SECOND FORCES TO INCREASINGLY AND DECREASINGLYY FLUCTUATE SUBSTANTIALLY IN PHASE, DURATION AND IN LIKE MANNER WITH SAID FIRST FORCES AND MAINTAIN A SUBSTANTIALLY UNIFORM INCREMENTAL FORCE DIFFERENTIAL THEREBETWEEN IRRESPECTIVE OF WHETHER THE SAID FFIRIST FORCES ARE INCREASING OR DECREASING.