Selectively cold worked hydraulic motor/pump shoe

Details Selectively cold worked hydraulic motor/pump shoe Selectively cold worked hydraulic motor/pump shoe

2006-04-11

2006-04-11

Graham, Matthew C. (Department: 3683)

Brakes

Elements

Shoes

C188S25000B, C148S674000, C029S511000, C029S557000

Reexamination Certificate

active

07025182

ABSTRACT:
A method of manufacturing a wear resistant shoe (26) includes upsetting (46) one end portion (38) of cylindrical member to work harden that portion to a substantial depth, machining (48) the cylindrical member portion to finished dimensions and surface hardening (56) a face (28or34) of the machined cylindrical member portion. The cylindrical member may comprise rod stock of a diameter less than the greatest diameter of the finished shoe and be upset or swaged to axially reduce and radially increase the dimensions of the one end portion. A hollow region (30) is formed in an opposite rod stock end portion and the periphery (50) of the hollow region is crimped about a rounded end (18) of the piston (20). The cold work done during the swaging or forming process provides a foundation for hardened faces comprising balance (28) and auxiliary balance (34) lands, forms a crude shape of the shoe, and imparts work hardening and wear property improvements. The harder metal surface provides a foundation for subsequent surface hardening such as coating with TiN. The crimping process used to join the shoe to the piston imparts cold work to the skirt region of the shoe and enhances the wear resistance of the shoe. The cold heading step (46) may be omitted if a hardened rod stock is used, but the skirt should be annealed (66) prior to crimping to the piston.

REFERENCES:
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patent: 5950480 (1999-09-01), Fukushima
patent: 6802916 (2004-10-01), Rateick et al.
patent: 196 52 326 (1997-12-01), None
patent: 56-084468 (1981-07-01), None
“Cold Heading,” from ASM Metals Handbook vol. 14: Forming and Forging, Apr. 1988, pub. by ASM International, 9thedition, pp. 291-298.
“Nickel, Cobalt, and Their Alloys,” ASM Specialty Handbook, Dec. 2000, pub. by ASM International, pp. 376, 377, 384, 385, and 401-406.

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