Slipper component with ceramic surface

1 . A rotary axial piston pump comprising:

a housing;

a swash plate, the swash plate having an inclined surface;

a rotor assembly positioned adjacent the swash plate, the rotor assembly comprising a rotor-drum having at least one cylinder bore disposed therein, and having piston(s) disposed within the respective cylinder bore(s), the pistons having a ball-shaped end extending from the cylinder bore(s);

at least one slipper interposed between the swash plate and the rotor-drum, the slipper(s) comprising socket joints for accommodating the piston ball-shaped end(s) therein, the slipper(s) having a swash plate interface surface in contact with the swash plate inclined surface;

a port plate positioned adjacent an end block disposed in the housing open end; and

a valve plate interposed between the port plate and the rotor-drum;

wherein the swash plate interface surface comprises an annular ceramic ring attached to the slipper, the annular ceramic ring having an axially facing upper surface, a radially outward surface and a radially inward surface, the axially facing upper surface of the annular ceramic ring facing a lower surface of the slipper, the radially inward surface of the annular ceramic ring being positioned about an inner annular wall of the slipper, and a seal positioned between the radially inward surface of the annular ceramic ring and the inner annular wall of the slipper to restrict pressurized fluid from flowing between the lower surface of the slipper and the axially facing upper surface of the annular ceramic ring, the lower surface of the slipper having a weep groove or channel.

2 . The rotary axial piston pump of claim 1 , wherein an outer annular wall of the slipper surrounds the radially outward surface of the annular ceramic ring, the outer annular wall having a weep hole in communication with the weep groove or channel.

3 . The rotary axial piston pump of claim 2 , wherein the slipper includes an annular recess for partially receiving the annular ceramic ring, the annular recess having the lower surface of the slipper, the inner annular wall and the outer annular wall.

4 . The rotary axial piston pump of claim 1 , wherein the seal comprises an O-ring.

5 . The rotary axial piston pump of claim 1 , wherein the seal comprises a gasket.

6 . The rotary axial piston pump of claim 1 , wherein the seal is elastomeric.

7 . The rotary axial piston pump of claim 1 , wherein the seal surrounds the radially outward surface of the annular ceramic ring.

8 . The rotary axial piston pump of claim 1 , wherein the annular ceramic ring is attached to the slipper using an adhesive.

9 . The rotary axial piston pump of claim 1 , further comprising means for restricting rotation between the slipper and the annular ceramic ring.

10 . The rotary axial piston pump of claim 1 , wherein the annular ceramic ring is held in compression.

11 . The rotary axial piston pump of claim 1 , wherein the annular ring is held in compression by the outer annular wall of the slipper.

12 . A slipper suitable for use in a rotary axial piston pump interposed between a swash plate and a rotor-drum, the slipper comprising a socket joint for accommodating a piston ball-shaped end therein, the slipper having a swash plate interface surface formed from an annular ceramic ring, the annular ceramic ring having an axially facing upper surface, a radially outward surface and a radially inward surface, the axially facing upper surface of the annular ceramic ring facing a lower surface of the slipper, the radially inward surface of the annular ceramic ring being positioned about an inner annular wall of the slipper, and a seal positioned between the radially inward surface of the annular ceramic ring and the inner annular wall of the slipper to restrict pressurized fluid from flowing between the lower surface of the slipper and the axially facing upper surface of the annular ceramic ring, the slipper having a step provided at an intersection of the lower surface of the slipper and the inner annular wall of the slipper to provide a gap between the radially inward surface of the annular ceramic ring and the inner annular wall of the slipper.

13 . The slipper of claim 12 , wherein an outer annular wall surrounds the radially outward surface of the annular ceramic ring.

14 . The slipper of claim 13 , wherein the slipper includes an annular recess for partially receiving the annular ceramic ring, the annular recess having the lower surface of the slipper, the inner annular wall and the outer annular wall.

15 . The slipper of claim 12 , wherein the seal comprises an O-ring.

16 . The slipper of claim 15 , wherein the O-ring surrounds the radially outward surface of the annular ceramic ring.

17 . The slipper of claim 16 , wherein the annular ceramic ring is attached to the slipper using an adhesive.

18 . The slipper of claim 12 , wherein a pin extends between the slipper and the annular ceramic ring to restrict rotation of the ring relative to the slipper.

19 . The rotary axial piston pump of claim 12 , wherein the annular ceramic ring is held in compression.

20 . A method of using the rotary axial piston pump of claim 1 , wherein the slipper includes a fluid passage, radially inward with respect to the inward inner annular wall of the slipper, the method comprising:

supplying pressurized fluid to the swash plate interface surface and the swash plate inclined surface via the fluid passage of the slipper; and

restricting the pressurized fluid from flowing past the seal and between the lower surface of the slipper and the axially facing upper surface of the annular ceramic ring.