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Piston bearing structure for fluid pressure cylinder

  • US 9,388,902 B2
  • Filed: 02/24/2012
  • Issued: 07/12/2016
  • Est. Priority Date: 03/23/2011
  • Status: Active Grant
First Claim
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1. A piston bearing structure for a fluid pressure cylinder in which a piston is supported in a cylinder tube, the piston bearing structure comprising:

  • one seal ring housed in a housing groove of the piston and held in sliding contact with the cylinder tube; and

    two backup wear rings housed in the housing groove, held in sliding contact with the cylinder tube and sandwiching the seal ring,whereinthe housing groove includesa first groove which houses the seal ring, andtwo second grooves which are shallower than the first groove and connected to opposite sides of the first groove, andeach of the backup wear rings has an L-shaped cross-sectional shape includinga wear ring portion which is housed in a corresponding one of the second-grooves and is adapted to receive a load of the piston, anda backup ring portion which is housed in the first groove, faces the seal ring and is integrally formed with the wear ring portion,whereinthe wear ring portion includes a pair of opening end portions to form a gap opening,the backup ring portion includes a pair of bias cut opening end portions which are held in contact with each other in a state where the gap opening is maintained,the backup wear ring includes a pressure relief groove which faces the housing groove and extends over the backup ring portion and the wear ring portion, andthe pressure relief groove allows opposite sides of the backup wear ring to communicate between the piston and the cylinder tube, and faces the housing groove over an entire extent of the pressure relief groove in the backup ring portion and the wear ring portion.

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