Piston assembly for rotary hydraulic machines

• US 20050175471A1
• Filed: 02/11/2004
• Published: 08/11/2005
• Est. Priority Date: 02/11/2004
• Status: Active Grant

• Current Assignee: Concentric Rockford Inc. (Concentric AB)
• Original Assignee: VoiceBox Technologies Corporation (Microsoft Corporation)
• Inventors: Kadlicko, George
• Granted Patent: US 7,364,409 B2
• Time in Patent Office: Days
• US Class Current: 417/269
• CPC Class Codes: F04B 1/22 having two or more sets of cylinders or pistons

Abstract

A piston assembly for a hydraulic machine is formed with a part spherical cavity in the piston to receive a spherical bearing of a slipper assembly. The spherical bearing is secured in the cavity by swaging the walls of the piston and subsequently working the wall to provide a clearance to allow relative rotation.

Claims

1. A hydraulic machine comprising a housing, a rotating group rotatably mounted within said housing and including barrel and a plurality of pistons axially slideable in cylinders in said barrel, and a swashplate assembly to engage said pistons and induce reciprocation thereof as said barrel rotates in said housing, a port plate interposed between said barrel and said housing and effective to connect respective ones of said cylinders alternatively with an inlet port and an outlet port, and a slipper assembly acting between said swashplate and said piston to transfer loads therebetween, said slipper assembly including a base having a planar bearing surface engagable with said swashplate and a spherical bearing engagable with a part spherical recess in said piston.

2. A machine according to claim 1 wherein said piston is tubular and said slipper assembly includes a passageway extending through said base from said piston to said planar bearing to supply fluid thereto.

3. A machine according to 2 wherein said base of slipper assembly has a diameter greater than that of said piston and said slippers are retained in engagement with said swashplate by a plate having a plurality of apertures each of which receives a respective one of said pistons and has a marginal portion overlying a respective one of said bases.

4. A machine according to claim 3 wherein said swashplate includes an annular insert providing a planar face over which said slipper assemblies may slide.

5. A slipper assembly for a piston assembly of a rotary hydraulic machine, said slipper assembly comprising a base having a planar bearing surface disposed on one side for engagment with a swashplate and a spherical bearing disposed on an oppositely directed side for engagment with a part spherical recess in said piston.

6. A slipper assembly according to claim 5 wherein a passageway extends through said spherical bearing and said base.

7. A slipper assembly according to claim 6 wherein said base includes a spigot projecting from said oppositely directed side and said spherical bearing is received on said spigot.

8. A slipper assembly according to claim 7 wherein said spherical bearing has a through bore to receive said spigot and and a counterbore to permit enlargement of said spigot to retain said spherical bearing on said spigot.

9. A slipper assembly according to claim 7 wherein said passageway extends through said spigot.

10. A piston assembly for a rotating hydraulic machine comprising a piston having a spherical recess at one end thereof and a slipper assembly including a base having planar bearing surface on one side and a spherical bearing on an oppositely directed side thereof, said spherical bearing being located within said spherical recess to provide limited pivotal movement between said piston and slipper assembly.

11. A piston assembly according to claim 10 wherein said spherical recess has a depth greater than the radius of said spherical bearing and walls of said recess extend beyond an equator of said spherical bearing and conform thereto to secure said spherical bearing in said recess.

12. A piston assembly according to claim 11 wherein a spigot extends from said oppositely directed side of said base and said spherical bearing is secured to said spigot.

13. A piston assembly according to claim 12 wherein said spherical bearing has a through bore to receive said spigot and and a counterbore to permit enlargement of said spigot to retain said spherical bearing on said spigot.

14. A piston assembly according to claim 12 wherein said piston is tubular.

15. A piston assembly according to claim 14 wherein a passageway extends through said base to permit hydraulic fluid to flow from an interior of said piston to said planar bearing surface.

16. A method of forming a piston assembly for a rotary hydraulic machine comprising the steps of forming a part spherical cavity in one end of a piston to an axial depth greater than the diameter of said cavity, inserting therein a complementary spherical bearing of a slipper assembly, and deforining the walls of said cavity to conform to the surface of said spherical bearing.

17. A method according to claim 16 wherein said step of deforming said walls includes the step of applying a radial load about the equator of said spherical bearing after said walls conform to said surface.

18. A method according to claim 17 including the step of inserting a spigot of a base into a bore formed in said spherical bearing and securing said spigot by radially expanding said spigot in said bore.