Patent Application
20160281505
Valve and port plates having, such as those suitable for use in rotary axial piston pumps or pressure exchangers, are described herein and, in particular valve and port plates having ceramic interface surfaces.
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.
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-friction surface feature. Such a conventional RAPPs comprise metallic valve and port plates that include a polymeric interface surfaces.
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.
Thus, while RAPPs configured for water transport service are constructed to provide some degree of low friction operation under certain operating conditions, e.g., ultra-clean conditions, it is desired that an 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 an 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.
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.
One solution to the aforementioned problem is to use ceramic valve and port plates. 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. However, ceramic can be expensive as compared to metal components, and can fracture.
In order to improve the resistance to fracturing as well as reduce the costs associated with the use of ceramic materials, valve and/or port plates can each be provided with a reinforcing band. The band, which can optionally be metal, can be placed around the plate. The band serves two purposes. One is provide additional strength to the plate, thereby allowing for a reduction in the overall diameter and/or thickness of the plates. The end result is that less ceramic material can translate into a cost savings. The other is to hold the plate together in case of a failure, such as a crack. This can eliminate or at least reduce the spread of debris throughout the pump. The band can hold the plate in compression. This can be accomplished by applying a heated band around a relatively cool ceramic plate, then allowing the heated band to cool and contract to place the ceramic plate in compression. Alternatively, the band could be glued to the ceramic plate.
The banded ceramic valve and/or port plates described herein can be incorporated into RAPPs, pressure exchangers or other suitable devices. An exemplary RAPP, such as that disclosed in U.S. Publ. Appl. No. 2013/0118346, 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. In yet another exemplary embodiment, both the valve and port plates have ceramic interface surfaces. In another exemplary embodiment, the port plate and/or the valve plate may be formed entirely from a ceramic material. Unlike the RAPP in the aforementioned publication, either or both of the plates can have the aforementioned reinforcing band. The band can either be disposed about the outer circumference of the plate, disposed radially inward relative to the outer circumference of the plate or more than one band can be provided with one band in each position.
In one aspect, a set of valve and port plates configured for use in a rotary axial piston pump or pressure exchanger are provided, wherein each of the plates includes a ceramic interface surface for rotatably sliding engagement with the other plate. A reinforcing band radially surrounds one of the ceramic interface surfaces to hold the surface in compression, which can be either the ceramic interface surface of the valve plate or the port plate. Each plate can have its own reinforcing band to hold its ceramic interface surface in compression. Each of the plates ca be ceramic and the reinforcing bands can surround the outer circumference of the plates or a radially inward portion thereof.
In another aspect, the plate or plates having the reinforcing band or bands can be incorporated into a RAPP, a pressure exchanger, or other device. In an exemplary aspect, the RAPP can include a housing, a swash plate having an inclined surface, and a rotor assembly positioned adjacent the swash plate. The rotor assembly can include a rotor-drum having at least one cylinder bore disposed therein, and having piston(s) disposed within the respective cylinder bore(s), wherein the pistons having a ball-shaped end extending from the cylinder bore(s). At least one slipper can be interposed between the swash plate and the rotor-drum. The slipper can have socket joints for accommodating the piston ball-shaped end(s) therein and a swash plate interface surface in contact with the swash plate inclined surface which swash plate interface can optionally be formed from a ceramic material. A port plate is positioned adjacent an end block disposed in the housing open end, and a valve plate interposed between the port plate and the rotor-drum. The port and valve plates each have a ceramic surface at an interface thereof. A reinforcing band is provided surrounding at least a portion, such as the outer circumference or a radially inward portion, of one of the plates, either the valve or port plate, to hold the plate in compression. A second such reinforcing band can be provided about at least a portion of the other of the plates. The band can optionally be formed of a metal.
In one aspect, the reinforcing band is disposed about the outer circumference of the one of the plates. In another aspect, the reinforcing band is disposed radially inward relative to an outer circumference of the plate. In yet another aspect, the reinforcing band is provided with one or more recessed pockets. Either or both of the plates can be formed of a ceramic material, as opposed to just the interface surfaces. Indeed, both plates can be ceramic and each can have their own reinforcing band.
In order to improve the resistance to fracturing as well as reduce the costs associated with the use of ceramic materials, valve and/or port plates can each be provided with a reinforcing band. The valve and/or port plates can be incorporated into a RAPP, pressure exchanger or other device. Although
The valve plate 10 and port plate 20 can be provided as part of a set, as shown in
Turning now to details regarding the bands 12 and 22, they can be made of a metal, such as aluminum, stainless steel, carbon steel, or the like. The metal can be formed from a strip of material which is shaped into a hoop and then lap welded or, alternatively formed into a hoop by cutting using a lathe from stock metal pipe. The metal bands can have a thickness suitable for the application. In the example of a RAPP, the thickness can be between about 0.12 inches and about 0.50 inches. The metal bands can alternatively have a thickness than varies, such as by having one or more rims or flanges. For example, a first alternative band 110 for use with the valve and port plates is depicted in
The plates 10 and 20 do not have to be specially modified to accommodate the bands 12 and 22, such as if they are made of a ceramic material. In such a case, and as illustrated in
Each of the plates 10 and 20 has an interface surface, shown in
In the case of a composite construction, there may be a metal body having a ceramic layer (e.g., in the form of a veneer or the like) covering all or a portion of the interface surfaces. If desired, the layer can be provided in the form of a continuous surface or can be provided in the form of one or more surface features projecting outwardly a distance from the surface to contact the other plate plate. When the entire plate is not formed from a ceramic material, it is desired that such layer have a thickness that is sufficient to provide a desired degree of low-friction service to provide a desired effective service life without unnecessarily adding to the material costs. In an example embodiment, it is desired that the ceramic layer or ceramic surface feature have a thickness of at least 0.03 inches, and preferably in the range of from about 0.03 to 0.1 inches.
Turning now to a description of a RAPP 30, and with reference to
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 10 interfaces with the port plate 20 at a sliding interface to serve as a sliding valve control system. The port plate 20 rotates with the rotor-drum 44 within the housing 32.
The port plate 20 is configured having a number of openings there through, as shown in
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 port plate 20 and the valve 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. 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.
The use of ceramic materials is not limited to the valve and port plates 10 and 20. Indeed, other parts can be formed of ceramic material for the purpose of reducing and controlling unwanted frictional effects between dynamically engaged surfaces. Depending on the particular internal part, the entire part can be formed from a ceramic material, or only a portion of the part can be formed from a ceramic material. For example, the slippers 52 and/or swash plate 40 can incorporate a ceramic material, as described in U.S. Publ. Appl. No. 2013/0118346.
The banded ceramic valve and port plates, as well as the RAPPs incorporating the same, as disclosed herein may be embodied and practiced in other specific forms without departing from the spirit and essential characteristics thereof. The present embodiments disclosed and illustrated herein are therefore to be considered in all respects as illustrative and not restrictive.
