Patent Application
20240240624
The present disclosure relates to pumps, in particular, ball ends for pistons in pumps.
Traditional pistons and associated shafts, e.g., for piston pumps, are made of tungsten carbide, which provides excellent wear resistance in a fuel pump application. However, tungsten carbide components can also be very dense and heavy, which can be a draw back in certain applications where the weight of the components must be carefully considered.
There remains a need for a highly wear resistant material which is lighter and/or less dense than traditional materials. This disclosure provides a solution for this need.
In accordance with at least one aspect of this disclosure, a system includes, a cylinder barrel configured to rotate within a pump housing of a pump operatively connected to a driving member of the pump via a first shaft. A piston is seated within a bore defined in the cylinder barrel. The piston is operatively connected to the driving member of the pump via a second shaft. The first shaft and the second shaft each include a ball end configured to seat within the driving member. In embodiments, the ball end of at least the second shaft is of silicon nitride.
In embodiments, the ball end can include a bore therethrough defined along a shaft axis extending from a first end of the ball end to a second end of the ball end. An edge of the bore proximate the first end of the ball end can have a rounded edge, and an edge of the bore proximate the second end of the ball end can have a corner, a rounded edge, or a chamfer. In embodiments, a first portion of an outer surface of the ball end can be rounded, where the first portion extends from the first end of the ball end, radially outward from the bore, to a transition point. A second portion of the outer surface of the ball end can be flat, where the second portion extends from the transition portion, parallel to the bore, to the second end of the ball end.
In embodiments, the system can further include the pump. In certain embodiments, the driving member of the pump can be of tool steel. In certain embodiments, the driving member can be of tungsten carbide. In certain embodiments, e.g., where the driving member is of tool steel, the friction coefficient between the ball end of the second shaft and the driving member of the pump can be about 0.11.
In embodiments, the cylinder barrel can include a main cylindrical body; a center recess defined within the main cylindrical body configured to seat the first shaft therein, and a plurality of bores defined in the main cylindrical body configured to allow fluid flow therethrough, and axial translation of the pistons therein. Each respective bore can extend in an axial direction, and can be spaced apart circumferentially relative to one another about the main cylindrical body radially outward of the center recess. The piston can be a plurality of pistons, each piston seated within a respective a respective bore of the plurality of bores. In certain embodiments, the main cylindrical body can be of tool steel. In certain embodiments, the main cylindrical body can be of tungsten carbide. In certain embodiments, the main cylindrical body can by of silicon nitride.
In certain embodiments, the pump can be or can include a piston pump. In certain embodiments, the piston pump can be or include a bent axis variable displacement piston pump. In certain embodiments, the plurality of bores can include at least 7 bores, and up to 13 bores. In certain embodiments, and the plurality of pistons can include at least 7 pistons and up to 13 pistons.
In accordance with at least one aspect of this disclosure, a method can include forming a cylinder barrel of a piston pump, forming a plurality of pistons configured to be inserted into the cylinder barrel, each piston including a shaft having a ball end at a distal end thereof, the ball end being of silicon nitride, and installing the cylinder barrel and plurality of pistons into the piston pump.
In embodiments, forming the cylinder barrel can include forming a main cylindrical body, forming a center recess configured to seat a drive shaft therein, and forming a plurality of bores each extending in an axial direction through the main cylindrical body, the plurality of bores forming a pattern disposed circumferentially about the main cylindrical body radially outward of the center recess, configured to seat a respective piston therein and allow fluid flow therethrough.
In embodiments, installing the cylinder barrel and plurality of pistons into the piston pump can further include, inserting a proximal end of each piston to a respective bore of the plurality of bores, inserting the ball end of each piston shaft into a driving member of the pump, and inserting a drive shaft of the cylinder barrel into the center recess and inserting a ball end of the drive shaft into the driving member of the pump. In certain embodiments, the ball end of the drive shaft can be of silicon nitride. In embodiments, the method can include operating the pump.
These and other features of the embodiments of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description taken in conjunction with the drawings.
So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, embodiments thereof will be described in detail herein below with reference to certain figures, wherein:
Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, an illustrative view of an embodiment of a system in accordance with the disclosure is shown in
In accordance with at least one aspect of this disclosure, e.g., as shown in
With reference now to
In embodiments, each respective piston 110 further includes a piston ring 118 disposed at an end 120 thereof (or integrally formed thereon at an end 120 thereof) configured to form a hydrodynamic seal with an inner surface 122 of the respective bore 116. In certain embodiments, the piston 110 can be of tool steel and the piston ring 118 can be of tool steel. In certain embodiments, only the piston ring 118 is of tool steel. In embodiments, the main cylindrical body 108 can be any one or more of silicon nitride, tool steel, or tungsten carbide. The selection of materials for the main cylindrical body 108 and the piston rings 118 can be selected for reduction of friction coefficient between the two materials, for example.
In embodiments, the cylinder barrel 108 can be connected to a driving member 124 (e.g., a shoulder shaft) of the pump 100 via a first shaft (e.g., drive shaft 106). Each piston can be operatively connected to the driving member 124 of the pump via a second shaft (e.g., a piston shaft) 126. The drive shaft 106 and the piston shaft 126 each include a ball end 128, 130 configured to seat within the driving member 124. In embodiments, the ball end 128 of at least the piston shaft 126 is of silicon nitride. In embodiments, it is contemplated the ball end 130 of the drive shaft 106 can also be of silicon nitride.
In embodiments, as shown in
In certain embodiments, the driving member 124 of the pump 100 can be of tool steel. In certain embodiments, the driving member 124 can be of tungsten carbide. In certain embodiments, e.g., where the driving member 124 is of tool steel, the friction coefficient between the ball end 128 of the second shaft and the driving member 124 of the pump can be about 0.11. While embodiments are described herein with respect to ball end 128 of the piston shaft 126, it is contemplated that the ball end 130 can be the same or similar to that of ball end 128. An embodiment utilizing a driving member 124 of tungsten carbide mated to a ball end 128 of tool steel would have mating interfaces which wear. As wear occurs, tungsten carbide and tool steel mating interfaces can become poorly lubricated and increase in friction coefficient towards unlubricated values of 0.19. Although the wear life of silicon nitride on tool steel has been shown to be an order of magnitude higher than tungsten carbide-tool steel interfaces, as wear occurs between silicon nitride ball ends 128 and tool steel driving members 124, the friction coefficient will tend towards an unlubricated value of about 0.15 (about a 25% decrease compared to the unlubricated tungsten carbide-tool steel value of about 0.19).
In accordance with at least one aspect of this disclosure, with reference to
In embodiments, the method can further include, forming a plurality of pistons (e.g., pistons 110) configured to be inserted into the cylinder barrel, each piston including a shaft (e.g., piston shaft 126) having a ball end (e.g., ball end 128) at a distal end thereof (e.g., opposite the shaft from the piston and cylinder barrel), the ball end being of silicon nitride, and installing the cylinder barrel and plurality of pistons into the piston pump.
In embodiments, installing the cylinder barrel and plurality of pistons into the piston pump can further include, inserting a proximal end of each piston to the respective bore of the plurality of bores, inserting the ball end of each piston shaft into a driving member (e.g., driving member 124) of the pump, and inserting a drive shaft (e.g., shaft 106) of the cylinder barrel into the center recess and inserting a ball end of the drive shaft into the driving member of the pump. In certain embodiments, the ball end of the drive shaft can be of silicon nitride. In embodiments, the method can include operating the pump.
Embodiments provide for a lower density piston ball end, which can reduce the overall weight of the pump. The silicon nitride piston ball end is configured to withstand the load demands of the pump. Embodiments having a silicon nitride piston ball end are naturally more lubricious based on material and wear properties silicon nitride derives from its crystal structure. In combination with its lubricity, engineered versions of silicon nitride can have high strength and high toughness to survive service conditions and also reduce part degradation which provides slower wearing piston ball ends which are rotated or rubbed against mated surfaces (e.g., in the driving member). This can increase the total number service hours of the pistons and associated shafts and even the pump as a whole.
Those having ordinary skill in the art understand that any numerical values disclosed herein can be exact values or can be values within a range. Further, any terms of approximation (e.g., “about”, “approximately”, “around”) used in this disclosure can mean the stated value within a range. For example, in certain embodiments, the range can be within (plus or minus) 20%, or within 10%, or within 5%, or within 2%, or within any other suitable percentage or number as appreciated by those having ordinary skill in the art (e.g., for known tolerance limits or error ranges).
The articles “a”, “an”, and “the” as used herein and in the appended claims are used herein to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article unless the context clearly indicates otherwise. By way of example, “an element” means one element or more than one element.
The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and/or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to “A and/or B”, when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.
As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and/or” as defined above. For example, when separating items in a list, “or” or “and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of” or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e., “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.”
Any suitable combination(s) of any disclosed embodiments and/or any suitable portion(s) thereof are contemplated herein as appreciated by those having ordinary skill in the art in view of this disclosure.
The embodiments of the present disclosure, as described above and shown in the drawings, provide for improvement in the art to which they pertain. While the apparatus and methods of the subject disclosure have been shown and described, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the scope of the subject disclosure.
