The present invention relates generally to piston pumps and motors and more particularly to a piston-slipper assembly used in piston pumps and motors, wherein such assembly has a ball and socket combination that avoids the need for crimping, swaging or bending of the socket to retain the ball in the socket.
Axial piston pumps and motors are used to power machines or hydraulic and other fluid systems of machines. Piston-slipper assemblies are a component of axial piston pumps and motors. These assemblies take the form of at least two connected components, a piston and a slipper, one with a ball and one with a socket. Existing axial piston-slipper assemblies are crimped, swaged, or bent in order to retain the ball in the socket. Such crimping, swaging or bending can result in damage to coatings on the operable surfaces of the ball and the socket.
The present invention provides a piston-slipper assembly and method for assembling a piston-slipper assembly for use in a hydraulic apparatus such as a piston motor or piston pump. The assembly contains a piston and a slipper, and at least one of the piston or the slipper includes a ball and the other includes a socket. The ball is retained in the socket without crimping, swaging or bending of the socket.
Additionally, coatings may be applied to the operable surfaces of the ball and the socket. Without crimping, swaging or bending of the socket, these coatings may have a lower risk of being damaged. Particularly, a diamond-like coating is applied to at least one of the operable surfaces of the ball or the socket. Such a coating may lower friction and may increase the overall efficiency, for example by 2% to 4%, of pumps or motors using crimpless piston-slipper assemblies according to the present invention.
According to one aspect of the invention, a piston-slipper assembly, particularly for use in a hydraulic apparatus having a swash plate operably associated with a slipper, comprises a first member, having a ball portion and an axially extending neck portion, and a second member, having a socket having a circumferential extent greater than 180-degrees for receiving and retaining the ball portion in the socket while allowing swiveling movement of the ball portion. The second member has a slot in a sidewall for allowing passage of the ball portion and the axially extending neck portion when in a first orientation and precluding removal of the ball portion when in a second orientation.
More particularly, the piston-slipper assembly comprises a first member including a ball portion having a ball diameter and an axially extending neck portion having a width less than the ball diameter, and a second member having a socket configured to receive and retain the ball portion for relative rotational movement. The socket opens along an axis of the socket to an end face of the second member at an opening having a diameter less than the diameter of the ball portion for retaining the ball portion in the socket while allowing swiveling movement of the ball portion within the socket. The ball portion has reliefs provided at diametrically opposed sides of the ball portion that are aligned along a ball diameter of the ball portion perpendicular to the axis of the axially extending neck portion. The reliefs define a reduced diameter portion of the ball portion having a width through the center of the ball portion less than the ball diameter of the ball portion and less than the diameter of the opening. The second member has extending through a side wall thereof a slot that opens to the end face of the second member and has a width greater than the width of the neck portion of the first member, whereby the neck portion can move into the slot to allow the reduced width portion of the ball portion to move through the opening into the socket when the neck portion and the reduced diameter portion of the ball portion are oriented substantially perpendicular to the axis of the socket, after which the neck portion can be rotated out of the slot so that the ball portion will be retained in the socket.
The reliefs may be formed by a flats, grooves or detents on the sides of the ball portion.
The axially extending neck portion may be cylindrical or of another cross-sectional shape.
The first member or the second member may be a piston of a hydraulic apparatus, and the other may be a slipper of a hydraulic apparatus.
The ball portion and socket have confronting operable surfaces, and at least one of the operable surfaces may be coated, such as with a diamond-like material, or made of a material having high resistance to flaking or chipping for improving wear resistance and/or reducing heat and friction.
According to another aspect of the invention, there is provided a hydraulic apparatus including one or more of the aforesaid piston-slipper assemblies and a swash plate operably associated with the one or more piston-slipper assemblies.
According to a further aspect of the invention, a method for assembling a piston-slipper assembly of a hydraulic apparatus includes the steps of aligning in a first orientation an axially extending neck portion of a first member with a slot in a side wall of a socket of a second member, passing a ball portion of the first member into the socket of the second member, and aligning in a second orientation the axially extending neck portion thereby precluding removal of the ball portion from the socket.
As can now be appreciated, a piston-slipper assembly can be assembled without the need to crimp, swage or bend the socket.
The foregoing and other features of the invention are hereinafter described in greater detail with reference to the accompanying drawings.
Piston-slipper assemblies are utilized in axial piston pumps and motors used to power machines or hydraulic and other fluid systems of machines. Oftentimes, such piston-slipper assemblies take the form of at least two connected components, a piston and a slipper, one having a ball and the other having a socket.
The present invention, for use in a hydraulic apparatus, relates to such piston-slipper assemblies with one of a piston or a slipper having a ball and the other having a socket. More particularly, the ball of a piston-slipper assembly of the present invention is retained in the socket without any crimping, swaging, bending, or other mechanical manipulation of the socket. Damage to operable surfaces of the ball and socket that typically occurs during such mechanical manipulation is avoided and a greater ease of manufacturing, lower manufacturing cost, and improved repairability are achieved. A coating, which would otherwise become damaged during mechanical manipulation of the socket, may be applied to the operable surfaces of the ball and the socket. Such coatings may reduce heat and friction and improve wear resistance of operable surfaces due to a lower risk of breaking and degeneration of such coatings, thus leading to greater overall pump or motor efficiency of a hydraulic apparatus utilizing the aforementioned piston-slipper assemblies. Particularly, such coatings may be made of a diamond-like material or another suitable material having high resistance to flaking or chipping known to one of ordinary skill in the art.
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The piston-slipper assemblies 52 together with a cylinder block 62 may rotate about a shaft 64. Reciprocating motions of the piston-slipper assemblies 52 within the cylinder block 62 may cause fluid to be drawn into each cylinder 66 of the cylinder block 62 and then expelled. This pumping may generate increasing and decreasing volumes of fluid. The reciprocating motion may be controlled by the angling of the control plate 56. It will be understood by one having ordinary skill in the art that angling of the cylinder block 62 relative to the control plate 56 may permit additional control of reciprocating motions. The control plate 56 may be angled via interaction of an operating assembly 68. The operating assembly 68 may contain operating components, such as springs, rods, or linkages, and may be operated by a mechanism (not shown) external to the hydraulic apparatus 50. Fluid may be drawn from an inlet 70 of a secondary housing 72, through a valve plate 74, and subsequently pumped into the cylinders 66. The fluid may then be pumped out of the cylinders 66 by the reciprocating motions of the piston-slipper assemblies 52 operative with the cylinder block 62. Subsequently, fluid may be pumped through the valve plate 74 and out an outlet 76 of the secondary housing 72. In an opposite manner, pressurized fluid can be supplied to the apparatus for operation as a motor.
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The slot 110 may allow for passage of the ball portion 92 and the neck portion 96 when the piston 88 and the slipper 90 are aligned in a first orientation. In the first orientation, an axis 118 of the neck portion 96 may be oriented transversely to an axis 120 of the piston 88 for allowing passage of the neck portion 96 into the slot 110. Thus, the first orientation may be when the reduced diameter portion 104 of the ball portion 92 is aligned with the opening 108 of the socket 94 and the neck portion 96 is aligned with the slot 110, allowing for passage of the ball portion through the opening 108 and into the socket 94, and also allowing for passage of the neck portion 96 into the slot 110.
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The slipper 90 may also include an axially extending first passage 126 for delivering fluid or lubricant to the socket 94 of the piston 88. The first passage 126 may extend from the base surface 100, through the base portion 98 and the neck portion 96, and additionally through the ball portion 92 to the operable surface 122.
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Although the invention has been shown and described with respect to a certain preferred embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the drawings. In particular, in regard to the various functions performed by the above described elements (components, assemblies, devices, compositions, etc.), the terms used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent). In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.
This application claims priority to U.S. Provisional Application No. 61/721,095, filed Nov. 1, 2012, which is hereby incorporated herein by reference.
Filing Document | Filing Date | Country | Kind |
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PCT/US2013/066813 | 10/25/2013 | WO | 00 |
Number | Date | Country | |
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61721095 | Nov 2012 | US |