MXPA01006348A - Multiple groove thrust bearing - Google Patents

Abstract

A thrust bearing having a radial taper in its top (land) surface provides improved load distribution when used in high-pressure positive displacement swashplate piston pumps. The thrust bearing includes a plurality of grooves in its land surface which carry and distribute fluid on the top surface during operation of the pump. The fluid is distributed so as to form a hydrodynamic fluid buffer between the thrust bearing and an adjacent pump cam surface, so that the thickness of the fluid buffer is larger in radial regions corresponding to regions of increased load and stress.

Description

MULTIPLE SLOT DRIVE BEARING FIELD OF THE INVENTION This invention relates to a drive bearing, improved for use in positive displacement, high pressure piston pumps. The invention also includes pumps incorporating the improved drive bearing.

BACKGROUND OF THE INVENTION A grouping of field, tapered, unidirectional drive bearings is disclosed in U.S. Patent No. 5,829,338, issued to Chrestoff et al. Figure 1 is a perspective view of the drive bearing of the prior art. The single piece drive bearing 10 incorporates a plurality of bearing pads 12 evenly spaced around the drive bearing 10, circular. Each of the bearing pads 12 in the drive bearing 10 comprises a tapered, integral, rectangular shaped section 14 and a flat, integral, non-tapered section 16. Adjacent to each bearing pad 12, the surface of the bearing assembly 10 is machined or profiled, otherwise, to provide the bearing pad 12 with a lubricant, convergent, integral path or groove 24. Each tapered section 14 has a tapered lifting portion 18 which is the same in outer diameter 20 as it is in the inner diameter 22 of bearing 10. Each fluid feeding slot 24 will facilitate the development of a hydrodynamic pressure zone as along the length of the lifting portion 18, tapered. As explained by Chrestoff et al., The drive bearing 10 is designed for the positioning for the rear of a pump drive plate in a depression in the rear plate of the pump. Rotation in the counterclockwise direction of the drive plate causes the fluid to move from the feed slots 24 to the lift portions 18, tapering in the drive bearing, thereby forming a hydrodynamic film that transports load, pressurized between the drive bearing and the drive plate, which opposes the pressure exerted on the drive plate by the pump. Some fluid advances from the lifting portions 18, tapered to narrow spaces between the flat sections 16 of the bearing, and the adjacent drive plate. In essence, a substantially continuous fluid damping film is formed between the bearing 10 and the adjacent drive plate, to reduce wear on the bearing caused by the operation of the pump. A disadvantage of the prior art drive bearing is that the bearing fluid (which performs the cooling as well as the lubrication functions) has not been ideally distributed in the axial direction during the operation of the pump. Consequently, the drive bearings have more wear and damage in the surface portions near their outer peripheries, than in the surface portions near their inner peripheries. There is a need or desire for a drive bearing that provides better distribution of fluids during pump operation, resulting in more uniform forces being applied across the bearing.

BRIEF DESCRIPTION OF THE INVENTION The present invention is directed to an improved drive bearing that facilitates a better distribution of the bearing fluid, resulting in a more uniform wear of the bearing. The present invention is also directed to pumps that use the improved drive bearing. The drive bearing of the invention includes a plurality of deflection grooves that convey fluid at an angle relative to the rs of the bearing, a circular groove that crosses the deflection grooves that supply water to the surface of the drive bearing and helps to distribute fluid around the bearing, and a rl taper approaching the outer periphery which facilitates the formation of a relatively large fluid buffer near the outer periphery of the bearing.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of the prior art drive bearing described above. Figure 2 is a plan view of a drive bearing of the invention, showing the deflection slots and the circular intersecting groove. Figure 3 is a sectional view taken along line 3-3 of Figure 2, showing the axial taper. Figure 4 is a sectional view of a high pressure positive displacement plate piston pump incorporating the drive bearing of the invention.

DETAILED DESCRIPTION OF CURRENTLY PREFERRED MODALITIES With reference to FIGS. 2 and 3, a drive bearing 100, preferably having a cylindrical configuration, includes an upper surface 112, a bottom surface 114, an inner edge 116, and an outer edge 118. The upper surface 112 is adapted to be placed below a motor plate (further described later) of a pump which, during operation of the pump, can rotate in a counterclockwise direction as shown by the arrow "A". The bottom surface 114 may be placed in a bearing seat, and may include one or more circular depressions 120 that receive mounting pins to hold the bearing in place. The upper surface 112 includes a plurality of misaligned grooves 122 that can extend from the inner edge 116 to the outer edge 118. The grooves 122 are misaligned at an angle relative to the radius of the drive bearing. The misalignment angle between the grooves and the radius of the bearing may be from about 5 to about 60 degrees, preferably from about 15 to about 50 degrees, more preferably from about 25 to about 40 degrees. The direction of misalignment depends on the direction of rotation of the cam or drive plate relative to the drive bearing 100. If the rotation is counterclockwise, then the misalignment in the grooves (viewed from the inner edge 116 to the outer edge 118 of the bearing 100) must also be in the counterclockwise direction, as shown in FIG. shown in Figure 2. If the rotation is clockwise, then the misalignment must be in the clockwise direction. The number of slots 122 must be sufficient to facilitate an adequate distribution of fluid through the upper surface 112 of the bearing 100. The larger the bearing, the more grooves will be necessary to properly distribute the fluid. Large numbers of grooves' 122 provide better distribution of bearing fluid. In general, the slots 122 are uniformly spaced from each other so that the adjacent slots 122 are not more than about 40 degrees apart, preferably not more than about 30 degrees apart, more preferably no more than about 20 degrees apart, more preferably no more than about 10 separate degrees. An inner groove 126 is placed in the upper surface of the bearing 100, preferably near its center, and crosses the misalignment groove 122. Preferably, the inner groove 126 has a circular length, and extends the circular length of the upper surface 112 which allows the groove 126 to cross all of them. the misalignment grooves 122. The inner groove 126 works in tandem with the misalignment in the groove 122 to properly distribute the bearing fluid through the upper surface 112. Fluid from the cam enters the misalignment grooves 122 at points 124, and also it enters the interior groove 126 that helps to distribute the fluid. As further explained further, the rotation of an adjacent cam or drive plate causes some of the fluid to spill on the surface 112 between the slots., with larger amounts of fluid flowing to the outer regions of the surface 112 having the largest taper. According to the invention the upper surface 112 of the bearing 100 has an inwardly directed radial taper, such that the outer edge 118 is shorter than the inner edge 116. The radial taper may cover all or part of the surface 112. In the shown, the upper bearing surface 112 includes a radially tapered, higher portion 128 and a radially tapered, less elevated, outer portion 130 that gradually recedes to the outer edge 118. The tapered, higher portion 128 terminates, and the portion 130 tapered, less raised begins in the inner groove 126. In another embodiment, the inner portion 128 may be non-tapered and the outer portion 130 may be tapered. As explained more fully below, the taper facilitates the formation of a fluid buffer between the upper surface 112 and a pump cam or plate, which is of progressively greater thickness and effectiveness, reaching the outer edge 118 of the bearing 100. This fluid distribution is more ideal than in the prior art bearing, since the outer regions of the bearing 100 are exposed to a progressively higher pressure and a higher rotational speed of the pump cam or pump plate, which inner regions of the bearing 100. Again, the fluid cushion forms between the surface 112 of the bearing 100 and a generally flat rotating bottom of a cam or drive plate. In this way, the fluid buffer is greater in regions where there is more space between the two surfaces. Providing a progressively greater fluid cushion above the outer regions, wear and gradual damage to the bearing 100 is distributed more evenly, resulting in a longer bearing life.

The taper angle does not need to be very large. For example, the taper angle should be less than 1 degree, and preferably it is from approximately 0.1 to 0.5 degree, more preferably approximately 0.15 to 0.25 degree. In the embodiment shown, the radial length of the surface 112 may be approximately 2.5 inches. The depth of the taper at its lowest portion (above the outer edge 18) is preferably about 0.004 to 0.006 inches. The depths of the misalignment grooves 122 and the inner groove 26 may vary with the size of the bearing, size of the pump, number of grooves, and the amount of pressure applied by the pump. In the embodiment shown, the bearing has an outer diameter of approximately 6.5 inches an inner diameter of approximately 4 inches, and an edge thickness of approximately 0.5 inches. The misalignment grooves 122 (having semicircular cross sections) each have a width of approximately 0.60 inches, and a depth of approximately 0.30 inches and an inner radius of approximately 0.30 inches. There are 40 misalignment slots, separated by 9 degrees from each other. The inner groove 126 (which has a rectangular cross section) has a maximum width of about 0.18 inches and a depth of about 0.16 inches. The invention is not limited to those dimensions; Other shapes and sizes of the slots may be more suitable depending on the application. Figure 4 is a cross-sectional view of a high-pressure positive displacement piston plate pump 80 configured with the drive bearing 100 positioned between the rear surface 49 of the drive plate 25 and the rear plate 21 of the bomb. Preferably, the bearing 100 is placed in an annular groove 50 formed in the back plate 21. In addition, the bearing 100 is preferably held in position in the groove 50 by a pin 52 of stainless steel placed in opposite holes 120 formed in the bearing 100 and the back plate 21. Only one individual piston 11 is illustrated in the pump 80, although the pump 80 generally includes as few as five and as many as eleven pistons. In Figure 4, a pump body 13 is completed with a check valve housing 15. The check valve housing 15 is terminated by a gallery 17. A cam spacer 19 supports the pump body 13 away from the pump rear plate 21 which provides a pressure chamber or cavity 23 for the drive plate 25, which is it is rotationally driven by a drive shaft 27. Hexagonal nuts 43 and bolt 51 securely hold the gallery 17, the check valve housing 15, the pump body 13, the cam spacers 19, and the back plate 21, together. When the pump 80 is not in operation, the drive plate 25 will rest on each of the bearing surfaces 112 (see Figure 2) which are integral to the unidirectional, tapered field drive bearing 100. The operation of pump 80 and bearing 100 is as follows. The fluid to be pumped will enter the pump 80 through the inlet channel 33 and is expelled under pressure out of the pump through the outlet channel 35 under the pressure created by the upward stroke of the pistons 11. Each piston 11 has an inlet channel 33 and an outlet channel 35 associated therewith, and inlet channels 33 are connected to a pump inlet 34 while the outlet channels are connected to a pump outlet 36. The check valves 37, 39 suitably control the flow of the pumped fluid to and out of the pump 80. An individual set of check valves 37, 39 is associated with each piston 11. Each channel 33, 35 communicates with a chamber 41 of pressure. Each piston 11 is carried in a cylinder 29 lined in the pump body 13. Conventionally, the pistons 11 are made to reciprocally travel in the cylinder 29 lined by the design and camming action of the cam surface of the drive plate 25 which is driven rotatably by the drive shaft 27. The drive shaft 27 is adapted to be driven, rotatably by a suitable power source known in the art. The drive plate 25 preferably forms part of, and rotates with, the drive shaft 27. A clutch bearing 45 is operatively positioned between the drive plate 25 in each piston 11. The head end 31 of each piston 11 is adapted to abut a corresponding cavity 47 formed integrally in the material comprising the clutch bearing 45 . As the driver plate 25 rotates under the influence of the drive shaft 27, the inner surface of the cluster bearing 45 mounts on the upper drive bearing surface of the drive plate 25, imparting a vertical acceleration component to each piston 11 through of the corresponding cavity 47. As the driver plate 25 rotates in the chamber 23, each piston 11 is urged upward to expel pressurized fluid through the outlet channel 35. During the operation of the pump, rotation in the counter-clockwise direction on the drive plate 25 above the drive bearing 100 will facilitate the generation of a pressurized, load-bearing hydrodynamic film of sufficient thickness between the rear surface 49 of the drive plate 25 and the upper surface 112 of the bearing 100. In general, this hydrodynamic load-carrying film, pressurized, results from the flow of fluid through the slots 122 and 126 which, to a degree, define water channels. fluid with the upper surface 49 of the drive plate 25. The bearing fluid which may be water or oil, or other suitable lubrication / cooling fluid, enters the inlets 124 of the misalignment grooves 122 during rotation of the drive plate. 25 (which can be in the counterclockwise direction, as shown by arrow A in Figure 2). Because the fluid entering the slots 122 initially has an axial force vector, some of the fluid flows over the slots to form a thin hydrodynamic film between the various portions of the bearing surface 112 and the drive plate 25. The portions 128 of inner surface (having a larger elevation) are joined by the inner bearing edge 116, the adjacent misalignment grooves 122, and the inner groove 126. Preferably, the angle of deviation of the grooves 122 is selected so that a thin hydrodynamic film substantially covers the interior surface portions 128 during the operation of the pump. Some of the bearing fluid of the cam supports the inner circular groove 26, after which the fluid enters the inner groove and becomes distributed substantially uniformly along the entire length of the inner groove. The fluid from the inner groove 126 then flows to the radially tapered, lower, outer, surface portions 130, both a) directly, after which some fluid flows from the inner groove directly onto the tapered portions 130 and b) indirectly , from which some of the fluid flows to the outer portions of the misalignment grooves 122 and enters the outer surface portions 130 of these grooves. Preferably, the fluid flow is substantially sufficient to substantially fill the gap between all portions of the surface 112 of the bearing 100 and the drive plate 25, thereby forming a hydrodynamic fluid buffer that is a) thinner in locations radially inward from the circular groove 126, and b) becomes progressively thicker at radially outward locations of the circular groove 126, due to the radially tapered surface 112. This bearing design 100 creates a fluid film cushion, hydrodynamics which are thinner in the inner bearing regions, which are exposed to the least stress, and become progressively thicker in the outer bearing regions which are exposed to progressively greater stresses. Uniform wear of the bearing 100 is facilitated, and the life of the bearing is extended. While the embodiments of the invention described herein are presently preferred, various modifications and improvements can be made without departing from the spirit and scope of the invention. The scope of the invention is indicated in the appended claims, and all changes that fall within the meaning and range of equivalent are proposed to be embraced herein.

Claims (30)

1. A cylindrical drive bearing, comprising: an upper surface, a bottom surface, an inner edge and an outer edge; a plurality of grooves in the upper surface extending from the inner edge to the outer edge; and a radial taper on the upper surface.

The drive bearing according to claim 1, further comprising an inner groove in the upper surface crossing the plurality of grooves extending from the inner edge to the outer edge.

The drive bearing according to claim 1, wherein the top surface comprises a radially tapered, higher, inner portion and a radially tapered, lower, outer portion.

The drive bearing according to claim 1, wherein the top surface comprises a non-tapered, inner portion and a radially tapered, outer portion.

The drive bearing according to claim 1, wherein the grooves extending from the inner edge to the outer edge comprise misalignment grooves.

The drive bearing according to claim 5, wherein the misalignment grooves are positioned at a misalignment angle of about 5-60 degrees of a bearing radius.

The drive bearing according to claim 6, wherein the misalignment angle is about 15-50 degrees.

The drive bearing according to claim 6, wherein the misalignment angle is about 25-40 degrees.

The drive bearing according to claim 1, wherein the grooves separate substantially uniformly, by no more than about 40 degrees.

The drive bearing according to claim 9, wherein the grooves are not separated by more than about 30 degrees.

The drive bearing according to claim 9, wherein the grooves are not separated by more than about 20 degrees.

The drive bearing according to claim 1, wherein the radial taper has a taper angle of less than about 1 degree relative to a bearing radius.

The drive bearing according to claim 12, wherein the taper angle is approximately 0.1-0.5 degrees.

The drive bearing according to claim 12, wherein the taper angle is approximately 0.15-0.25 degrees.

15. A pump comprising the drive cushion according to claim 1.

16. A drive bearing, comprising: an upper surface, a bottom surface, an inner edge and an outer edge; a plurality of misalignment grooves in the upper surface; and a taper on the upper surface.

The drive bearing according to claim 16, wherein the misalignment grooves are misaligned at an angle of about 5-60 degrees of a bearing radius.

18. The drive bearing according to claim 17, wherein the misalignment angle is about 25-40 degrees.

The drive bearing according to claim 16, wherein the taper has a taper angle of less than about 1 degree relative to a bearing radius.

The drive bearing according to claim 19, wherein the taper angle is about 0.15-0.25 degrees.

The drive bearing according to claim 16, further comprising an internal groove in the upper surface crossing the misalignment grooves.

22. The drive bearing according to claim 21, wherein the taper is located on both sides of the inner groove.

23. The drive bearing according to claim 21, wherein the taper is located on only one side of the inner groove.

24. A pump comprising the drive bearing according to claim 16.

25. A drive bearing, comprising: an upper surface, a bottom surface, an inner edge and an outer edge; a plurality of grooves in the upper surface extending outwardly from the inner edge; an inner groove in the upper surface that crosses the plurality of outwardly extending grooves; and a taper on the upper surface.

26. The drive bearing according to claim 25, wherein the taper is located on both sides of the inner groove.

27. The drive bearing according to claim 25, wherein the taper is located only on one side out of the inner slot.

28. The drive bearing according to claim 25, wherein the outwardly extending grooves comprise misalignment grooves.

29. The drive bearing according to claim 27, further comprising a non-tapered upper surface portion on an inner side of the inner groove.

30. A pump comprising the drive bearing of claim 25.