Axial piston device

Claim 2

An axial piston device comprising a housing having fluid inlet and outlet ports; a drive shaft extending axially within the housing; a cylinder block drivingly affixed to the shaft and having a plurality of concentric axial bores alternately communicating with the inlet and outlet ports upon cylinder block rotation; a piston reciprocably disposed in each bore and having an outer spherical end; a slipper shoe pivotally attached to each piston outer spherical end, the shoes rotary about a common central axis; an inclined or inclinable cam surface mounted in the housing cooperating with the shoes to permit inward and outward piston reciprocation between fully retracted and fully extended positions upon cylinder block rotation; a cage plate aligned parallel to the inclined cam surface and positioned to engage said shoes, said plate having openings through which the shoes extend and drivingly contact the plate; and pilot means engaging said cage plate and radially constraining same to rotate about a rotational axis parallel to and spaced from said shoe central rotational axis whereby each shoe drivingly contacts the cage plate only during inward reciprocation of the attached piston.

Claim 3

The device of claim 1 wherein said cage plate rotational axis is spaced apart from said shoe rotational axis toward said fully extended piston position whereby each shoe drivingly contacts the cage plate upon cylinder block rotation only when angularly positioned within 90* of the fully retracted piston position.

Claim 4

The device of claim 1 wherein said shoe and cage plate each rotate about respective axes perpendicular to the inclined surface which axes intercept the rotational axis of the drive shaft at first and second positions respectively, said first position being located nearer the cylinder block than said second position.

Claim 5

The device of claim 3 wherein said first position is located at a point where a plane containing the centers of the spherical ends of said pistons intercepts the shaft rotational axis.

Claim 6

In an axial piston device having a cylinder block drivingly affixed for rotation with an axially extending shaft, pistons disposed in concentric axial bores of the cylinder block for inward and outward movement therein so that fluid is alternately received and expelled from the bores through valving passages communicating therewith, the pistons having spherically shaped outer ends extending from said bores to cooperate with a cam member inclined or inclinable to the pistons to induce piston reciprocation, an associated slipper shoe universally attached to each piston spherical outer end, said shoes cooperating with said cam member and rotative about a central axis inclined to the shaft axis, and a spider plate oriented parallel to said member and in driven engagement with the shoes, wherein the improvement comprises: pilot means engaging and radially locating said spider plate to rotate about an axis parallel to said shoe central axis, said spider plate axis displaced from said shoe central axis a predetermined distance whereby a slipper shoe central axis a predetermined drivingly engages the spider plate only during inward movement of its associated piston.

Claim 7

In an axial piston device having a cylinder block drivingly affixed for rotation with an axially extending shaft, pistons disposed in concentric axial bores of the cylinder block for inward and outward movement therein so that fluid is alternately received and expelled from the bores through valving passages communicating therewith, the pistons having spherically shaped outer ends extending from said bores to cooperate with a cam member inclined or inclinable to the pistons to induce piston reciprocation, an associated slipper shoe universally attached to each piston spherical outer end, said shoes cooperating with said cam member and rotative about a central axis inclined to the shaft axis, and a spider plate oriented parallel to said member and in driven engagement with the shoes, wherein the improvement comprises: pilot means engaging and radially locating said spider plate to rotate about an axis parallel to said shoe central axis, said spider plate axis displaced from said shoe central axis a predetermined distance whereby a slipper shoe central axis a predetermined drivingly engages the spider plate only during inward movement of its associated piston.

Claim 8

The device of claim 5 wherein said pilot means comprise a centrally located pilot member engaging the spider plate and a pivot constrained to the shaft, the pilot member and pivot having cooperating concentric spherical surfaces where common center lies on said shaft axis at a position displaced from the intersection of said shoe central axis with the shaft axis in a direction away from the cylinder barrel.

Claim 9

The device of claim 5 wherein said pilot means comprise the inclined cam member and a pilot member guided upon the cam member and secured to radially position the spider plate.

Claim 10

The device of claim 7 wherein said pilot member is of a cylindrical shape closely cooperating with a bore in the inclined cam member, the axis of said cam bore being parallel and eccentric to said rotational axis.

Claim 11

The device of claim 5 wherein said pilot means locates the spider plate so that said spider plate axis is displaced from said shoe central axis in a direction toward the outermost position of a piston in its cylinder bore whereby a shoe contacts the spider plate only when angularly positioned with in ninety degrees of the innermost position of a piston in its cylinder bore and only during inward movement of its associated piston.

Claim 12

In an axial piston device having a cylinder block drivingly affixed for rotation with an axially extending shaft, pistons reciprocally disposed in concentric axial bores in the cylinder block and having spherically shaped outer ends adjacent a cam surface inclined or inclinable at an acute angle relative to a plane perpendicular to the axis of said shaft, said shaft axis being intersected at a first point by a plane containing the centers of said spherical surfaces in said piston ends, slipper shoes pivotally attached to said piston spherical ends, a flat connector plate interposed between and sealingly contacting said shoes and the inclined cam surface, conduit means extending through each piston and shoe and the connector plate to said cam surface to alternately connect said axial bores upon cylinder barrel rotation with inlet and outlet passages opening onto said cam surface, a spider plate engaging said shoes to maintain the shoes in close proximity to the connector plate, said spider having enlarged holes through which the shoes extend and drivingly engage the spider plate, and pilot means supported on the shaft universally joined to the spider and connector plates to radially locate same to the shaft, wherein the improvement comprises: said shoes rotative about a central axis extending perpendicularly to the inclined cam surface and intercepting the shaft axis said first point; and the spider and connector plates arranged parallel to the inclined cam surface with a common rotational axis parallel to said shoe rotational axis intercepting the shaft axis at a second point spaced from said first point in a direction away from the cylinder block.

Claim 13

In an axial piston device having a cylinder block drivingly affixed for rotation with an axially extending shaft, pistons reciprocally disposed in concentric axial bores in the cylinder block and having spherically shaped outer ends adjacent a cam surface inclined or inclinable at an acute angle relative to a plane perpendicular to the axis of said shaft, said shaft axis being intersected at a first point by a plane containing the centers of said spherical surfaces in said piston ends, slipper shoes pivotally attached to said piston spherical ends, a flat connector plate interposed between and sealingly contacting said shoes and the inclined cam surface, conduit means extending through each piston and shoe and the connector plate to said cam surface to alternately connect said axial bores upon cylinder barrel rotation with inlet and outlet passages opening onto said cam surface, a spider plate engaging said shoes to maintain the shoes in close proximity to the connector plate, said spider having enlarged holes through which the shoes extend and drivingly engage the spider plate, and pilot means supported on the shaft universally joined to the spider and connector plates to radially locate same to the shaft, wherein the improvement comprises: said shoes rotative about a central axis extending perpendicularly to the inclined cam surface and intercepting the shaft axis said first point; and the spider and connector plates arranged parallel to the inclined cam surface with a common rotational axis parallel to said shoe rotational axis intercepting the shaft axis at a second point spaced from said first point in a direction away from the cylinder block.

Claim 14

The device of claim 10 further comprising an oppositely extending second piston in each axial bore and a second inclined cam surface cooperating with said second pistons to reciprocate same in the axial bores.

Claim 15

The device of claim 10 wherein said pilot means include a pilot member contacting the spider and connector plates and a pivot constrained to the shaft, said pilot member and pivot universally joined upon cooperating concentric spherical surfaces whose common center lies on the shaft axis at said second point.

Claim 16

The device of claim 10 wherein the minimum distance between said first and second points on the shaft axis is determined approximately as where: x minimum distance between said first and second points b maximum allowed variation of the location of one of said axial bore from its nominal location; h maximum allowed variation of the location of one of said spider holes from its nominal location; and theta said acute cam angle.

Claim 17

The device of claim 10 wherein the minimum distance between said first and second points on the shaft axis is determined approximately as where: x minimum distance between said first and second positions; and theta said acute cam angle.