Hydrostatic bearing for radial piston pump

Claim 2

For use in a radial piston pump, a piston assembly comprising a piston having a cylindrical body portion with a rearwardly located end face for receiving a fluid medium and applying pumping pressure thereto and a head portion at the forward end of said body portion, said head portion having a cylindrical bore therethrough extending transversely to the longitudinal axis of said body portion, a cylindrical pin received in said bore and extending at each end thereof from the head portion of the piston, and a pair of rollers fixed to said pin at the said ends thereof, said body portion of the piston having a pair of passageways extending from said end face to said bore in the head portion of the piston, and said bore being provided with a recess defining a pressurized area communicating with said passageways with the size of said passageways being such that no significant pressure drop occurs between the fluid being pumped by said end face of the piston and the fluid within said recess, said passageways extending in a direction parallel to the longitudinal axis of the piston and being spaced equal distances from said axis in a common plane which extends through said axis, said common plane extending perpendicularly to the axis of said pin so that the stress concentrations due to changing pumping pressure conditions will be concentrated over a relatively large area due to the curvature of the pin at the outlets of said passageways, the projected area of said pressurized area being generally equal to the area of said end face so that a pressure balance on said pin is maintained when said piston is pumping whereby a hydrostatic bearing is provided for said pin within the head portion of said piston permitting said pin to rotate within said head portion without undue wear.

Claim 3

In a radial piston pump comprised of a cylinder block having at least one radially extending bore, means for rotating said cylinder block about a first rotary axis, a ring positioned about said cylinder block and having a second rotary axis parallel to but spaced from said first rotary axis, and valving means for directing fluid to and removing fluid from said bore in said cylinder block, the improvement comprising a piston assembly arranged for reciprocating movement within said bore in the cylinder block and engagement with said ring at the outer end thereof to pump said fluid through said valving means, said piston assembly including a piston having a body portion slidably received in the bore in the cylinder block, said body portion of the piston having an end face for applying pumping pressure to said fluid, said piston further including a head portion at the outer end thereof which is provided with a bore therethrough extending transversely to the longitudinal axis of said body portion, a cylindrical pin rotatably received in said bore and extending at each end thereof from the head portion of the piston, and a pair of rollers fixed to said pin at the said ends thereof and arranged to contact the inner face of said ring, said body portion of the piston having a passageway therethrough which extends from said end face to said bore in the head portion of the piston, and said bore being provided with a groove defining a pressurized area communicating with said passageway with the size of said passageway being such that no significant pressure drop occurs between the fluid being pumped by said end face of the piston and the fluid within said groove whereby a hydrostatic bearing is provided for said pin within the head portion of said piston permitting said pin to rotate within said head portion as said rollers rotate with respect to said ring face, said groove including a first section extending in a plane which includes said longitudinal axis of the piston and a second section extending in a closed loop path iN said bore in the head portion of the piston and centered upon said axis with the ends of said first section being connected with said second section for fluid communication therebetween, said passageway in the body portion of the piston being in direct fluid communication with said first section of said groove, the projected area of said pressurized area being generally equal to the area of said end face of the piston so that a pressure balance on said pin is maintained when said piston assembly is pumping said fluid from the bore in the cylinder block.

Claim 4

In a radial piston pump comprised of a cylinder block having at least one radially extending bore, means for rotating said cylinder block about a first rotary axis, a ring positioned about said cylinder block and having a second rotary axis parallel to but spaced from said first rotary axis, and valving means for directing fluid to and removing fluid from said bore in said cylinder block, the improvement comprising a piston assembly arranged for reciprocating movement within said bore in the cylinder block and engagement with said ring at the outer end thereof to pump said fluid through said valving means, said piston assembly including a piston having a body portion slidably received in the bore in the cylinder block, said body portion of the piston having an end face for applying pumping pressure to said fluid, said piston further including a head portion at the outer end thereof which is provided with a bore therethrough extending transversely to the longitudinal axis of said body portion, a cylindrical pin rotatably received in said bore and extending at each end thereof from the head portion of the piston, and a pair of rollers fixed to said pin at the said ends thereof and arranged to contact the inner face of said ring, said body portion of the piston having a passageway therethrough which extends from said end face to said bore in the head portion of the piston, and said bore being provided with a groove defining a pressurized area communicating with said passageway with the size of said passageway being such that no significant pressure drop occurs between the fluid being pumped by said end face of the piston and the fluid within said groove whereby a hydrostatic bearing is provided for said pin within the head portion of said piston permitting said pin to rotate within said head portion as said rollers rotate with respect to said ring face, said groove including a first section extending in a plane which includes said longitudinal axis of the piston and a second section extending in a closed loop path iN said bore in the head portion of the piston and centered upon said axis with the ends of said first section being connected with said second section for fluid communication therebetween, said passageway in the body portion of the piston being in direct fluid communication with said first section of said groove, the projected area of said pressurized area being generally equal to the area of said end face of the piston so that a pressure balance on said pin is maintained when said piston assembly is pumping said fluid from the bore in the cylinder block.

Claim 5

In a radial piston pump, a piston assembly according to claim 2 wherein said body portion of the piston is provided with a pair of passageways extending from said end face to said first section of said groove, said passageways extending in a direction parallel to the longitudinal axis of the piston and being spaced equal distances from said axis in said plane of said first section of said groove, said plane extending perpendicularly to the axis of said pin so that stress concentrations due to changing pumping pressure conditions will be concentrated over a relatively large area due to the curvature of the pin at the outlets of said passageways.