WO2021126828A1

WO2021126828A1 - Rotary axial piston pumps and components with ceramic sliding surface interfaces

Info

Publication number: WO2021126828A1
Application number: PCT/US2020/065081
Authority: WO
Inventors: John P. Macharg
Original assignee: Ocean Pacific Technologies
Priority date: 2019-12-16
Filing date: 2020-12-15
Publication date: 2021-06-24

Abstract

Valve and/or port plates, or slippers, which can be suitable for use in rotary axial piston pumps, can include recesses to receive ceramic veneers. The ceramic veneers can be attached using adhesive. The recesses can include one or more sidewalls with negative draft angles to provide for an expansion zone for the adhesive.

Description

ROTARY AXIAL PISTON PUMPS AND COMPONENTS WITH CERAMIC

SLIDING SURFACE INTERFACES

Field

[001] Components suitable for use with rotary axial piston pumps or pressure exchangers, such as valve plates, port plates and piston slippers, are described herein and, in particular, such components having ceramic interface surfaces.

Background

[002] Rotary axial piston pumps (RAPPs) are known in the art and can be constructed for a number of different end-use applications. One category of RAPPs are configured for use in applications, e.g., oil hydraulic transport, that permit the internal components that are subjected to friction to be oil lubricated, thereby helping to reduce the unwanted effects of friction to provide a desired service life. Another category of RAPPs are configured for use in applications, e.g., water hydraulic transport, that do not permit the internal components subjection to friction to be oil lubricated. In such applications, the RAPPs are configured to use plain water without additives or aides as the only friction lubricating medium.

[003] Conventional RAPPs configured for water hydraulic transport service use internal parts, subjected to friction during use, that are specifically configured to include a polymeric low'-fiiction surface feature. Such a conventional RAPPs comprise metallic valve and port plates that include polymeric interface surfaces.

[004] While such RAPPs are configured to address frictional wear effects between adjacent metallic parts during water hydraulic transport use, the use of such RAPPs configured in the manner described require that the water entering the pump be filtered to very high levels to remove particulate matter. If unfiltered to a sufficient degree, the particulate matter in the water can otherwise wear and/or damage polymeric surface feature resulting in metal-to-metal contact, thereby reducing the effective service life of the RAPP. The need to filter the water transported by the RAPPs to protect against unwanted damage and/or reduced service life involves using filtration equipment that adds labor and material costs to the overall cost of operating such RAPPs. Furthermore, wear can adversely impact the precision clearances relied upon for sealing, and can thereby result in loss in pump efficiency and flow. [005] Thus, while RAPPs configured for water transport service are constructed to provide some degree of low friction operation under certain operating conditions, e.g., ultraclean conditions, it is desired that a RAPP be constructed in a manner that permits a more robust operating parameters in water transport services in terms of both improved service life and in terms of reduced water pretreatment requirements. Specifically, it is desired that a RAPP be constructed in a manner comprising internal parts specially developed and engineered to provide an improved degree of friction reduction performance, thereby extending service life when compared to conventional water transport RAPPs.

[006] It is further desired that such RAPPs comprising such construction provide the improved degree of friction reduction performance in a manner that avoids the need to filter the incoming water to ultra-fine standards, thereby reducing the overall equipment and labor costs associated with RAPP operation. Finally, it is desired that such RAPP be constructed in a manner avoiding the use of exotic materials and/or nonconventional manufacturing techniques, thereby minimizing any such impact on material and manufacturing costs.

[007] One solution to the aforementioned problem is to use valve and port plates made entirely of ceramic. Ceramic valve and port plates can advantageously reduce wear and erosion while being manufactured with the precise tolerances, and can be particularly suitable for use in water-lubricated pumps. The ceramic valve and port plates can be used in RAPPs as well as pressure exchangers, for example. Slippers can also be formed entirely of ceramic. However, ceramic can be expensive as compared to metal components.

Summary

[008] In order to reduce the amount of ceramic needed for valve and port plates, while still maintaining advantages of ceramic interface surfaces of the valve and port plates, ceramic veneers can be attached to non-ceramic valve and port plates. Similarly, ceramic veneers can be attached to non-ceramic slippers. The veneers are attached into recesses using an adhesive. If the adhesive is of non-uniform thickness, then precision alignment of the veneers may not occur. For example, if there is excess adhesive, it may not be evenly distributed once the veneer is inserted into the recess. Advantageously, the recesses can include one or more sidewalls with a negative draft angle. In other words, the bottom of the recess has a greater surface area that the opening of the recess. The use of one or more sidewalls with negative draft angles provides space for excess adhesive to flow. Coiraterintuitively, the use of excess adhesive can be advantageous when used in conjunction with one or more sidewalls with negative draft angles. That is because the excess adhesive can flow into the spaces between the sidewalls of the recess and the veneer and, once hardened, lock the veneers in place against removal from the recess. The width of the adhesive in the spaces between the sidewalls of the recess and the veneer can be wider than the width of the opening of the recess, thereby locking the veneer in place.

[009] The valve and/or port plates, as well as the piston slippers, described herein - which include veneers adhesively secured in recesses with sidewalls having negative draft angles - can be incorporated into RAPPs, pressure exchangers or other suitable devices. An exemplary RAPP, such as that disclosed in U.S. Patent No. 10,309,380, which is hereby incorporated by reference in its entirety, can comprise a housing, a swash plate that includes an inclined surface, and a rotor assembly that is positioned adjacent the swash plate. The rotor assembly comprises a rotor-drum that has at least one cylinder bore disposed therein, and that has piston(s) disposed within the respective cylinder bore(s). The pistons are constructed having a ball-shaped end that extends from the cylinder bore(s). At least one slipper is interposed between the swash plate and the rotor-drum. The slipper(s) comprises socket joints for accommodating the piston ball-shaped end(s) therein. The port plate is positioned adjacent an end block that is disposed in the housing open end, and the valve plate that is interposed between the port plate and the rotor-drum. In an exemplary embodiment, the port plate comprises an interface surface that is in contact with the valve plate, and that is formed from ceramic material. In another exemplary' embodiment, the valve plate comprises an interface surface that is in contact with the port plate, and that is formed from a ceramic material. Ln yet another exemplary embodiment, both the valve and port plates have ceramic interface surfaces.

[0010] Unlike the RAPP in the aforementioned patents, either or both of the plates can have interface surfaces formed from one or more ceramic veneers that are adhesively secured in recesses having one or more negative draft angles. Similarly, the slippers can include incorporate ceramic veneers that are adhesively secured in recesses having one or more negative draft angles.

Brief Description of the Drawings

[0011] FIGURE 1 is a cross-sectional view of a RAPP having one or more ceramic veneers on each of a valve plate, port plate and piston slippers; [0012] FIGURE 2 is a plan view of a valve plate suitable for use in the RAPP of FIGURE 1, the valve plate having a plurality of ceramic veneers disposed in recesses having sidewalls with negative draft angles;

[0013] FIGURE 3 is a cross-sectional view of the valve plate of FIGURE 2 taken from line 3-3 of FIGURE 2;

[0014] FIGURE 4 is a close-up view of area IV of FIGURE 3 showing one of the veneers disposed in one of the recesses;

[0015] FIGURE 5 is a close-up view of area V of FIGURE 4 showing one of the veneers disposed in one of the recesses;

[0016] FIGURE 6 is a perspective view of a piston slipper suitable for use in the RAPP of FIGURE 1, showing an annular recess for a ceramic veneer, the recess having sidewalls with negative draft angles;

[0017] FIGURE 7 is a perspective view of the piston slipper of FIGURE 6 with a ceramic veneer inserted into the recess;

[0018] FIGURE 8 is a bottom plan view of the piston slipper of FIGURE 6;

[0019] FIGURE 9 is a cross-sectional view of the piston slipper of FIGURE 6 taken along line 9-9 of FIGURE 8;

[0020] FIGURE 10 is a close-up view of area X of the piston slipper of FIGURE 9 showing the recess;

[0021] FIGURE 11 is a view of the piston slipper similar to that of FIGURE 10, but showing the veneer in the recess;

[0022] FIGURE 12 is a plan view of a port plate suitable for use in the RAPP of FIGURE 1, the port plate having a plurality ceramic veneer disposed in a recesses having sidewalls with negative draft angles;

[0023] FIGURE 13 is a cross-sectional view of the port plate of FIGURE 12 taken from line 13-13 of FIGURE 12; and

[0024] FIGURE 14 is a close-up view of area XIV of FIGURE 13 showing the veneer disposed in one of the recesses.

Detailed Description

[0025] In order to reduce the costs associated with the use of ceramic materials, valve plates, port plates and/or slippers can each be formed from a non-ceramic material and provided with a ceramic interface surface formed from one or more ceramic veneers. The ceramic veneers are received in recesses that have one or more sidewalls with negative draft angles. Preferably, through not necessarily, opposing sidewalls of the recesses have negative draft angles.

[0026] Turning now to a description of a RAPP 30, and with reference to Figure 1, the RAPP 30 can incorporate a set of port and valve plates 10 and 20. The RAPP 30 comprises a stator assembly including a housing 32 having a generally closed first end 34 at one axial end, and having an end block 36 attached to an otherwise opposed open end 38 of the housing 32. The port plate 10 is disposed within the housing 32 and is positioned adjacent an inside surface of the end block 54. The port plate 10 does not rotate relative to the housing 32. A swash plate 40 is disposed within the housing 32 and positioned adjacent an inside surface of the closed first end 34 of the housing 32. The swash plate 40 is a stationary member that does not rotate relative to the housing 3 and provides a smooth flat inclined surface that extends towards the valve plate 20. A rotor assembly 42 is disposed within the housing and comprises a cylindrical rotor-drum 44 that is interposed between the valve plate 20 and the swash plate 40. The rotor-drum 44 is configured to rotate within the housing 32 and comprises an array of axial cylinder bores 46, each fitted with an axial piston 48. Each axial piston 48 comprises a ball-shaped end 50 in swivel engagement with a slider shoe or slipper 52 held against the inclined surface of swash plate 40. The slipper 52 preferably, though not necessarily, includes a ceramic veneer, as will be described in more detail below.

[0027] The slippers 52 are supported in a uniform array and held against swash plate 40 by a shoe pressure plate 54, which bears against the central region of rotor-drum 44 via a hemispherical swivel member 56. At the other end of rotor-drum, the attached valve plate 20 interfaces with the port plate 10 at a sliding interface to serve as a sliding valve control system. The valve plate 20 rotates with the rotor-drum 44 within the housing 32.

[0028] The valve plate 20 is configured having a number of openings therethrough that align with respective openings in the cylinder bores 46. The port plate 10 also comprises openings that are in alignment with inlet and outlet ports extending through the end block 36. As the rotor-drum 44 rotates within the housing 32, the port plate openings align with the valve openings to facilitate fluid inlet and outlet in a manner corresponding to the piston inlet and outlet strokes to provide the desired fluid transport by the RAPP 30.

[0029] Generally speaking, the internal components or parts of such RAPPs that are subjected to frictional forces during pump operation include the interface surfaces between the valve plate 20 and the port plate 10, the interface surfaces between the swash plate 40 and the piston slippers 52, and the interface between the piston ball-shaped end 50 and the slipper 52. Ceramic veneers can be provided on any of those interface surfaces. When the RAPP is configured for use in oil hydraulic transport service, such interface surfaces are lubricated by the oil being transported, which operates to reduce the frictional forces existing at the metallic interfacing surfaces. However, when used for water transport, the water can provide lubrication.

[0030] To reduce the amount of ceramic used, ceramic veneers can be used instead of having the entire body made of ceramic. For example, the valve and port plates can each include one or more ceramic veneers. The valve plate can have multiple ceramic veneers in placed where there will be sliding contact with the port plate. As shown in Figure 2, for example, the valve plate 20 includes multiple ceramic veneers 14. Similarly, as shown in Figure 12, for example, the port plate 10 includes a ceramic veneer 15 received in recesses each having a pair of sidewalls with negative draft angles. Each of the veneers 14, 15 is received in a recess having a pair of sidewalls with negative draft angles. The veneers 14, 15 are adhesively secured in their respective recesses. Excess adhesive can flow into the gaps between the negative draft sidewalls of the recess and the sidewalls of the veneers. This both provides a place for excess adhesive to flow as well as, once hardened, locking the veneer in the recess.

[0031] As shown in the representative example of Figures 3-5, a veneer 14a is received within a recess 22 of the valve plate 20. The recess 22 has a bottom wall 25 and sidewalls 23 with negative draft angles. The negative draft angles of the sidewalls 23 of the recess 22 results in a gap or space 24 between the adjacent bottom portion of the sidewall of the veneer 14a and the sidewalls 23 of the recess 22. The gap 24 can function as an expansion zone for the adhesive to additionally secure the veneer in the recess, as described herein. Preferably, there is a very close fit of the veneer 14a and the entrance of the recess 22. A layer of adhesive 26 attaches the veneer 14a to the bottom wall 25 of the recess 22, as shown in Figure 5. Excess adhesive can flow into the expansion zone or gap 24 and form a bulge 28 of adhesive. Once hardened, that bulge 28 of adhesive can assist with locking the veneer 14a into the recess 22, as the veneer 14a and attached bulge 28 of adhesive will resist vertical movement out of the recess 22 due to the negative draft angle of the sidewalls 23 of the recess 22. Similar structures of the recess 17 and veneer 15 are shown in the port plate 10 of Figures 13 and 14, where the recess 17 includes sidewalls with negative draft angles, which will resemble those of the valve plate 20. [0032] Slippers 52 can also include ceramic veneers 60, as shown in Figure 7. More specifically, the slipper can include an annular recess 58, as shown in Figures 6, 8 and 9. An annular ceramic veneer 60 is adhesively secured in the recess 58, as shown in Figure 7. The recess 58 includes a pair of opposing sidewalls 64 and 66, as well as a bottom wall 62. The sidewalls 64 and 66 of the recess 68 each have a negative draft angle, as shown in Figure 10. The negative draft angle can be of any suitable angle, e.g., 2 degrees or more, by way of nonlimiting example, about 6 degrees. The depth of the recess 68 is about 0.1 inches, although other suitable dimensions can be used. When the ceramic veneer 60 is received in the recess 68, as shown in Figure 11, a gap 74 is created between each sidewall 64 and 66 and the side of the veneer 60. A layer of adhesive 76 attaches the veneer 60 to the bottom wall 62 of the recess 68. Excess adhesive can flow into the expansion zone or gap 74 and create a bulge 78. Having a place for excess adhesive to flow can advantageously help with keeping the veneer 60 coplanar with the bottom wall 62 of the recess 60. In addition, once hardened, the adhesive bulge 78 can help to lock the veneer 60 in place. More specifically, the attached bulge 78 of adhesive will resist vertical movement out of the recess 60 due to the negative draft angle of the sidewalls 64 and 66 of the recess 60. Examples of suitable adhesives include epoxies, acrylics and urethanes, although other adhesives can also be suitable.

[0033] The annular veneer 60 of the slipper 52 can also be configured to resist rotation in the annular recess 58. This is accomplished using a pin 72, which can be metal, that has one end received in an annular bore 68 in the recess and another end received in an annular bore 70 in the veneer 60, as shown in Figure 11. The pin 72 can be adhesively secured in both bores 68 and 70.

[0034] Examples of suitable ceramic materials include metal oxides and metal carbides. Examples of preferred ceramic materials include but are not limited to aluminum oxide, silicon carbide, tungsten carbide and combinations thereof. In an example embodiment, it is desired that the ceramic veneers have a thickness of at least 0.03 inches, and preferably in the range of from about 0.03 to 0.1 inches.

Claims

Claims:

1. A rotary axial piston pump comprising: a housing; a swash plate, the swash plate having an inclined surface; a rotor assembly positioned adjacent the swash plate, the rotor assembly comprising a rotor-drum having at least one cylinder bore disposed therein, and having piston(s) disposed within the respective cylinder bore(s), the pistons having a ball-shaped end extending from the cylinder bore(s); at least one slipper interposed between the swash plate and the rotor-drum, the slipper(s) comprising socket joints for accommodating the piston ball-shaped end(s) therein, the slipper(s) having a swash plate interface surface in contact with the swash plate inclined surface and optionally formed from a ceramic material; a port plate positioned adjacent an end block disposed in the housing open end; and a valve plate interposed between the port plate and the rotor-drum; wherein the port and valve plates each have a ceramic surface at an interface thereof; and wherein the ceramic surface of the at least one of the port and valve plates is a ceramic veneer held in a recess of the at least one of the port and valve plates by an adhesive, the recess having at least one sidewall with a negative draft angle so as to provide an expansion zone for the adhesive to additionally secure the veneer in the recess.

2. The rotary axial piston pump of claim 1, wherein the recess has a pair of sidewalls each with a negative draft.

3. The rotary axial piston pump of claim 1, wherein the ceramic surface of the port plate is the veneer held in the recess and having the at least one sidewall with a negative draft angle.

4. The rotary axial piston pump of claim 1, wherein the ceramic surface of the port plate is a plurality of veneers each held in a separate one of a plurality of recesses, the recesses each having one or more sidewalls with a negative draft angle.

5. The rotary axial piston pump of claim 1, wherein the ceramic surface of the valve plate is the veneer held in the recess and having the at least one sidewall with a negative draft angle.

6. The rotary axial piston pump of claim 1, wherein the ceramic surface of the valve plate is a plurality of veneers each held in a separate one of a plurality of recesses, the recesses each having one or more sidewalls with a negative draft angle.

7. The rotary axial piston pump of claim 1, wherein the port and valve plates each have a ceramic surface at an interface thereof; and wherein the ceramic surface of the port and valve plates is a ceramic veneer held in a recess of the respective one of the port and valve plates by an adhesive, the recesses each having at least one sidewall with a negative draft angle so as to provide an expansion zone for the adhesive to additionally secure the veneers in the recesses.

8. The rotary axial piston pump of claim 9, wherein each of the recesses has a plurality of sidewalls with a negative draft angle.

9. The rotary axial piston pump of claim 1, wherein the swash plate interface surface of the slipper(s) is formed from a ceramic material.

10. The rotary axial piston pump of claim 11, wherein the ceramic material is a ceramic veneer received in a recess of the slipper(s), the recess having one or more sidewalls with negative draft angles.

11. A set of valve and port plates, wherein each of the plates includes a ceramic interface surface for rotatably sliding engagement with the other plate, wherein the ceramic interface surface is a ceramic veneer held in a recess of a respective one of the port and valve plates by an adhesive, the recess having at least one sidewall with a negative draft angle so as to provide an expansion zone for the adhesive to additionally secure the veneer in the recess.

12. The set of valve and port plates of claim 11, wherein the recesses have a pair of sidewalls with negative draft angles.

13. The set of valve and port plates of claim 11, wherein each plate has a plurality of recesses and a different ceramic veneer is disposed in each of the recesses.

14. The set of valve and port plates of claim 11, wherein the plates are suitable for use in either a rotary axial piston pump or pressure exchanger.

15. A slipper suitable for use in a rotary axial piston pump interposed between a swash plate and a rotor-drum, the slipper comprising a socket joint for accommodating a piston ball-shaped end therein, the slipper having a swash plate interface surface formed from a ceramic veneer, wherein the ceramic veneer is received in a recess having at least one sidewall with a negative draft angle so as to provide an expansion zone for the adhesive to additionally secure the veneer in the recess.

16. The slipper of claim 15, wherein the ceramic veneer is annular and the recess is annular.

17. The slipper of claim 16, wherein the sidewalls of the recess each have the negative draft angle.

18. The slipper of claim 16, wherein a pin is received in an aperture in a bottom of the recess and an aperture in the veneer to restrict rotation of the veneer relative to the slipper.