US3363578A

US3363578A - Gear pump and thrust plate therefor

Info

Publication number: US3363578A
Application number: US603468A
Authority: US
Inventors: Ronald L Sisson
Original assignee: Clark Equipment Co
Current assignee: Doosan Bobcat North America Inc
Priority date: 1966-12-21
Filing date: 1966-12-21
Publication date: 1968-01-16
Anticipated expiration: 1985-01-16

Description

Jan. 16, 1968 R. SISSON GEAR PUMP AND THRUST PLATE THEREFOR 3 Sheets-Sheet 1 Filed Dec. 21, 1966 I "IINVENTOR RONALD L. SISSON BY Jan. 16, 1968 R. SISSON 3,363,578

GEAR PUMP AND THRUST PLATE THEREFOR Filed Dec. 21, 1966 s sheets-sheet 2 FIG. 2

INVENTOR RONALD SISSON ATTORNEY Jan. 16, 1968 R. L. S SSQN 3,363,578

GEAR PUMP AND THRUST PLATE THEREFOR Filed Dec. 21, 1966 3 Sheets-Sheet 3 l L f 88 9O 84 58 74 82 INVENTOR RONALD L. SISSON ATTORNEY United States Patent 3,363,578 GEAR PUMP AND THRUST PLATE THEREFOR Ronald L. Sisson, Jackson, Mich, assignor to (Ilark Equipment Company, a corporation of Michigan Filed Dec. 21, 1966, Ser. No. 603,468 16 Claims. (Cl. 103-126) ABSTRACT OF THE DISCLOSURE Thrust plate for a gear pump having an internal pressure cavity receiving pumped liquid, and a movable plate actuated by pressure of the liquid in the pressure cavity for engaging and sealing the gears, and including resilient means for sealing the plate.

Cross references In the copending application of Sisson and Shreve Ser. No. 603,467, filed Dec. 21, 1966, there is disclosed and claimed a thrust plate with a single continuous internal cavity, which is utilized in the present invention, that applieation being assigned to the assignee of the present application; that application makes reference to certain prior US. patents also assigned to the assignee of the present application; attention is also directed to another US. patent, No. 2,809,592, dated Oct. 15, 1957, to Miller et al.

Disclosure The problems involved in sealing the gears in a gear pump have been given a great deal of consideration. Thrust plates have been designed for seal-ing the gears and more specifically for applying pressure thereto in certain predetermined areas according to ditferent pressures of the liquid being pumped whereby to produce effective sealing action at all parts of the gears.

The present invention is directed to that main problem and includes a thrust plate construction having an internal pressure cavity for receiving pumped liquid for producing the desired pressures for impressing on the gears in the manner stated, i.e., impressing those pressures in certain predetermined areas on the gears. The construction includes a wear plate directly engaging the gears and movable in response to variation in pressures of the liquid in the internal pressure cavity. The pressure plate is flexible for producing the desired distribution of pressures upon the gears and it is desired to seal the spaces between the wear plate and the other elements of the thrust plate.

It is therefore a main object of the present invention to provide a thrust plate of the foregoing general character including a novel arrangement for sealing the wear plate relative to the remainder of the construction of the thrust plate.

Another object is to provide a construction of the character just referred to in which the sealing means is resilient and the remainder of the thrust plate is arranged so as to prevent the extrusion of the resilient sealing means into the spaces between other elements of the thrust plate.

A still more specific object is to provide a thrust plate of the foregoing general character in which a novel arrangement is provided for directing the pressure of the liquid in the pressure cavity against the resilient sealing means most effectively for producing the desired sealing effect between the wear plate and other elements of the thrust plate.

A still further object is to provide a completely unitary and self-contained thrust plate of novel construction.

Still another object is to provide novel gear pump construction incorporating a thrust plate of the foregoing general character.

Other objects and advantages of the invention will appear from the following detail description taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a sectional view of a gear pump incorporating the thrust plate of the present invention, the section being taken in the plane containing the axes of the gears of the pump;

FIGURE 2 is an end view taken from the left of FIG- URE 1 with the near housing cover assembly removed and exposing the thrust plate of the invention, the thrust plate being viewed from the plane of the line 22 of FIG- URE 1;

FIGURE 3 is a face view of the thrust plate from the side opposite that shown in FIGURE 2, and on an enlarged scale, being oriented according to the plane of the line 33 of FIGURE 1;

FIGURE 4 is a sectional view taken at line 44 of FIGURE 3; and

FIGURE 5 is a setcional view taken at line 5-5 of FIGURE 3.

Referring in detail to the drawings, the gear pump incorporating the thrust plate of the present invention is shown in FIGURE 1 and indicated in its entirety at 10 and includes a housing 12 made up of a central housing member 14, a front cover assembly 16 and a rear cover assembly 18. The pump includes a driving gear 20 and a driven gear 22 intermeshing therewith, in

chambers

24 and 26. The driving gear 20 has shaft elements, preferably integral therewith, 28 and 3t? journalled in suitable bearings 32. It also includes a shaft extension 34 adapted for connection with a driving means. The driven gear 22 has

shaft elements

36 and 38, also preferably integral, journalled in suitable bearings 40. The housing sections may be sealed by suitable gaskets 42 while the shaft extension 34 may be sealed by conventional sealing means 44. The housing also defines an inlet passage 46 (FIGURE 2) and an outlet passage 48.

A fixed thrust plate 50 of suitable construction is interposed between the gears and the inner face 51 of the rear cover assembly 18 receiving the thrust from the gears provided by a semi-rigid thrust plate, or thrust plate means or construction 52, comprising the principal feature of the invention. The positioning of the thrust plate 52 and its detail construction are described hereinbelow.

The thrust plate 52 is constructed for applying pressures against the gears axially thereof in the areas affected by the positive pressures in the liquid being pumped, these latter pressures being exemplified in the gear teeth pockets in different amounts between the outlet passage and inlet passage, as is known.

The thrust plate is disposed in a recess 53 formed in the front cover assembly 16 provided for the purpose, being confined between the gears and the inner surface 54 of the recess, this surface being the effective opposed surface of the front cover assembly 16. The recess 53 has an outer surrounding Wall surface 55. The thrust plate includes a wear plate controlled by the pressure in the internal cavity of the thrust plate, this internal cavity being generally similar to that disclosed and claimed broadly in the copending application referred to above.

Referring to the specific and detail construction of the thrust plate, it includes a rigid backing plate 56 of die cast aluminum or formed steel, for example, having a main planar or flat plate element 58 and a pair of apertures 69 for receiving the shaft elements of the gears, these apertures being surrounded by cylindrical flanges 62 extending perpendicular to the plate element 58 and extending nearly the full depth dimension of the thrust plate. The backing plate also has an opening 64 surrounded by a flange 66 perpendicular to the plate element 58, this opening communicating with the inlet passage 46 of the pump, in the assembly of the thrust plate in the pump.

Opposed to the backing plate 56 is a flexible wear plate 68 substantially coterminous with the plate element 58 and having apertures receiving the flanges 62 and another aperture 72 receiving the flange 64, all in snug but sliding engagement with the flanges. The wear plate 68 is in planar form and disposed parallel to the plate element 58 of the backing plate, defining a pressure cavity 74 therewith. The pressure plate 68 is provided with an aperture 76 for establishing communication between the outlet passage 48 and the pressure cavity 74. The outer surfaces of the

flanges

62 and 66 are swaged to provide line contact engagement and zero clearance with the marginal edges of the

apertures

70 and 72.

Surrounding the backing plate 56 and wear plate 68, and forming a part of the thrust plate, is a gasket 78, of T- shape cross section having a cross-bar element 86 entirely surrounding the plates and engaging the outer marginal edges thereof, the gasket being dimensioned for self-biasing inwardly in snug engagement therewith. The gasket includes an inwardly extending element 82 positioned between the plates and which can be dimensioned for snug engagement therewith and initial biasing of them apart for producing a pre-loading effect on the wear plate. The gasket 78 of rubber or rubber-like material, may be of one piece, the various elements referred to being all integral and positioned and shaped and dimensioned for cooperating with the elements of the backing plate and Wear plate as mentioned. The gasket 78 includes elements 84 surrounding the flanges 62 of the apertures 60, while a portion 82a of the element 82 extends along the flange 66 of the aperture 64. The gasket elements 84 also can be dimensioned for providing a pre-loading effect on the wear plate. However it is not necessary to provide such pre-loading effect by the

gasket elements

82 and 84.

The

elements

84 and 82a of the gasket are provided with a single groove 88 in their under surface (FIGURES 4 and 5), i.e., the surface facing the element 58 of the backing plate. This groove preferably is continuous around each of the flanges 62 as Well as around the flange 66, receiving liquid from the pressure cavity 74 into which the liquid is transmitted from the outlet passage of the pump. The communication between the pressure cavity 74 and the groove 88 is provided by a notch 90 formed in the rib defining one side of the groove. The groove 88 includes segments 88a surrounding the flanges 62 and another segment 88!; extending along one side and the ends of the flange 66. In this area, the groove segment 88b is formed in a portion 82a of the gasket element 82.

The liquid in the pressure cavity 74 enters into the groove 88 and completely fills it around all of the apertures, and upon increase of the pressure of the liquid in the pressure cavity 74, that pressure is exerted in the groove against the gasket and thereby against the wear plate 68, and perpendicular thereto. The wear plate is devoid of restrictive mechanical connection with the backing plate free floating relative thereto. The elements 84 surrounding the apertures 60 and the element 82a are also provided with another groove 92 preferably of rectangular shape and relatively flat in which is disposed a gasket 94 of relatively non-resilient fiber material directly engaging the inner surface of the wear plate 68.

The thrust plate 52 is positioned in the recess 53 (FIG- URE 1) with the backing plate 56 engaging the surface 54 and the wear plate 68 directly engaging the gears. Preferably the recess is of greater dimensions than the

chambers

24, 26 and the thrust plate similarly dimensioned so that the wear plate 68 engages the surface 96 of the central housing member 14. The apertures 60 are also appropriately dimensioned so that the wear plate, around the gear shaft elements, extends radially inwardly beyond the gear teeth to correspondingly engage the hubs of the gears and thereby seal the gear chambers.

The aperture 64 is in constant communication with the inlet chamber 46 while the small aperture 76 is in constant engagement with the outlet passage, and the pumped liquid therein under positive pressure is forced through the aperture 76 into the pressure cavity 74. This increased pressure in the pressure cavity forces the wear plate 68 outwardly against the gears and the surface 96 of the central housing section and in doing so Works against the various elements of the gasket 78. In the case of the outer peripheral portion of the gasket, the liquid works against the radially inwardly extending element 82 and biases or compresses the gasket outwardly into sealing engagement with the peripheral wall 55 of the recess 53, this compressing action on the gasket also spreading the element 82 in axial direction, maintaining a sealing engagement between the gasket and the Wear plate and backing plate. The liquid under pressure in the pressure cavity 74 also works against the gasket elements 84 and compresses them radially inwardly'against the

flanges

62 and 66 and it also works in the groove 88 and against the gasket, forcing the latter axially against the wear plate. In this action, the more rigid fiber gasket 92 directly engages the wear plate and in addition to its liquid scaling function, it provides a direct Wear-resistant and body-maintaining function in the compression of the gasket against the Wear plate 68 and insulates against heat.

The line-contact engagement and zero clearance between the marginal edges of the

apertures

70 and 72 in the wear plate and

flanges

62 and 66 prevents the extrusion of any of the elements of the gasket therebetween and in fact provides a relatively effective seal in itself so that the fiber gasket 92 is actually not necessary.

An advantage of the invention is that the thrust plate can be used in a cast-iron pump housing where a loading area for receiving the thrust plate otherwise would entail an expensive machining operation. The thrust plate would similarly enable a loading area change without affecting the pump housing, since the wear plate would readily adapt to a flat-fitting position against the gears despite any irregularities in the front cover assembly or in the backing plate.

Additionally the thrust plate may be used in connection with different kinds of bearings, (such as 32, 40 FIGURE 1) regardless of the character of those bearings, e.g., whether sleeve bearing, roller bearing, etc., and regardless of the diameter of those bearings Within wide limits.

The zero clearance produced by the sw-aging operation around the flanges provides a longer life of a resilient gasket, and in fact resilient sealing means is not actually required around the

apertures

60 and 64.

The initial tolerances required in the stamped

apertures

70, 72 in the wear plate are not critical because the swaging operation performed provides the desired zero clearance regardless of inaccuracies in the original formation of those apertures.

The edges defining the

apertures

70, 72 remain in engagement with the surfaces of the

flanges

62, 66 at all times throughout the range of movement of the wear plate away from and toward the backing plate, i.e., the wear plate does not move off of or beyond the flanges since the wear plate is substantially thicker than the great est extent of its movement so that at no time is there a condition in which an opening exists in such direction that the gasket could spread or extrude transversely i.e., in the direction of the plane of the thrust plate.

The thrust plate is completely unitary and self-contained, not requiring cooperation of any element of the pump housing to complete its structure.

While I have herein disclosed a preferred form of the invention, it will be understood that changes may be made therein within the spirit and scope of the appended claims.

I claim:

1. A thrust plate for a gear pump comprising a backing plate having an aperture and a flange surrounding the aperture, a wear plate fitted to the backing plate in spaced relation thereto and forming a pressure cavity therebetween, the wear plate having an aperture receiving said flange, and resilient gasket means between the backing plate and wear plate sealing the pressure cavity, the gasket means including an element surrounding said flange and butting the wear plate and having such conformation that liquid under pressure in the pressure cavity forces the gasket perpendicularly into sealing engagement with the wear plate.

2. The invention set out in claim 1 wherein said gasket element surrounding the flange has a groove on the side thereof facing the backing plate and an opening communicating between the groove and the interior of the pressure cavity, the groove thereby being so located that liquid in the groove operates to force the gasket element in the direction stated.

3. The invention set out in claim 1 wherein said wear plate possesses at least a degree of flexibility.

4. The invention set out in claim 3 wherein the thrust plate is adapted for use in a space in which the movement of the wear plate toward and from the backing plate is extremely small, and the corresponding movement of the gasket element in that direction is complementally small, and the thickness of the wear plate is substantially greater than said small amount of movement, whereby the flange always remains projected into the aperture in the wear plate.

5. The invention set out in claim 1 wherein the aperture in the wear plate and the outer surface of the flange are so relatively shaped and dimensioned that substantially line-contact engagement, and zero clearance, are established therebetween.

6. The invention set out in claim 1 wherein said gasket element is provided with a groove on the side thereof facing the wear plate, and a substantially non-resilient fiber gasket is interposed in said groove, in engagement with both the wear plate and flange overlying the opening therebetween.

7. The invention set out in claim 1 wherein the gasket means includes an outer element extending around the outer peripheral edges of the backing plate and wear plate and surrounding and defining the outer edges of said pressure cavity, and forming a liquid seal between the backing plate and pressure plate.

8. The invention set out in claim 7 wherein said outer gasket element has a laterally outward exposed sealing surface continuously around the thrust plate for sealing engagement with a surrounding wall surface extending generally transverse to the planes of the backing plate and wear plate.

9. The invention set out in claim 8 wherein said outer gasket element is substantially T-shape in cross section having an outer element forming said outwardly exposed sealing surface and another element extending laterally inwardly between the backing plate and wear plate.

10. The invention set out in claim 1 wherein said aperture in the backing plate is one of a pair of apertures for receiving gear elements and the thrust plate includes a third aperture adjacent one edge thereof, and the backing plate includes flanges surrounding all of the apertures, the gasket means is a single integral member having an element surrounding each of the flanges and dimensioned for constantly producing an inwardly biasing effect, in sealing engagement with those flanges, said elements together having a continuous groove in the side thereof facing the backing plate, the gasket means having a notch forming a passage communicating between the pressure cavity and the groove, said gasket elements having such dimensions as to produce a constant biasing effect against the wear plate substantially perpendicular thereto for providing a preloaded condition thereon, and the gasket means including outer surrounding element substantially T-shape in cross section including an outer cross bar element providing a surrounding sealing surface substantially perpendicular to the thrust plate for engagement with a surrounding wall surface, said outer gasket element also including an inwardly directed extension between the backing plate and wear plate dimensioned so as to produce a constant biasing effect on the wear plate and producing a preloaded condition thereon, said wear plate having an aperture therethrough communicating with the pressure cavity.

11. For use in a gear pump having gears and a cover assembly having a recess facing the gears, a thrust plate of unitary and self-contained construction adapted to be placed in the recess, and including a backing plate and a wear plate of similar outline size and shape arranged in opposed relation with a space therebetween, the wear plate being detached from the back plate and freely bodily movable toward and from the backing plate, and sealing means mounted on and carried by the backing plate and wear plate and together therewith forming a single pressure cavity of said space and also completing the thrust plate, the sealing means having an element surrounding the backing plate and wear plate, such unitary thrust plate constituting the sole means, except elements of the gears, in the recess and the sole means reacting between the surfaces of the recess and the gears.

12. The invention set out in claim 11 wherein the wear plate is of rigid construction and of planar shape whereby to be enabled to fit flatly against the gears.

13. The invention set out in claim 12 wherein the backing plate is also rigid, whereby to rigidly support the thrust plate as a whole in response to the reaction of the thrust plate being forced against the gears.

14. The invention set out in claim 11 wherein the sealing means includes an element entirely surrounding the thrust plate with a laterally outwardly exposed sealing surface adapted for sealing engagement with the surrounding wall surface of the recess.

15. The invention set out in claim 11 in conjunction with said gear pump, the thrust plate being removably disposed in the recess and the wear plate engaging the gears, and the surrounding element of the sealing means sealingly engaging the surrounding surface of the recess entirely threrearound.

16. The invention set out in claim 15 wherein the wear plate is of rigid character, devoid of restrictive mechanical connection with the backing plate and free floating relative thereto for full engagement with the gears throughout the end area of the gears.

References Cited UNITED STATES PATENTS 2,809,592 10/1957 Miller et a1 103-126 2,816,512 12/ 1957 Murray 103-126 2,853,952 9/1958 Aspelin 103-126 2,967,487 1/ 1961 Nagely 103-126 3,050,010 8/1962 Thrap et a1. 103-126 3,096,719 7/1963 McAlvay 103-126 3,101,673 8/1963 Clark et al. 103-126 3,131,643 5/1964 Marietta 103-126 3,137,238 6/1964 Gordon 103-126 3,174,435 3/1965 Sisson et al. 103-126 3,213,799 10/1965 Trick 103-126 3,294,029 12/ 1966 Clark et al. 103-126 DONLEY J. STOCKING, Primary Examiner. WILBUR I. GOODLIN, Examiner.