Method of making polytetrafluoroethylene sealing elements with hydrodynamic action

A method for manufacturing an oil seal having an element made from a disc-like flat washer of polytetrafluoroethylene or the like having an outer circular rim and a generally concentric inner circular rim, comprising the steps of:

• assembling the washer into a metal case between an outer case member having a cylindrical wall and an inner case member,
• then coining one face of each said washer to provide, adjacent said inner rim, hydrodynamic means for returning oil, and
• then piercing said coined washer to provide a desired inner periphery while assuring concentricity of said inner periphery with the cylindrical wall of said outer case,
• said piercing and coining steps cooperating to cause said hydrodynamic means to be properly located relative to said inner periphery.

A method for manufacturing an oil seal having an outer case of metal with a cylindrical radially outer wall for engaging a bore, a resilient washer-like element of polytetrafluoroethylene, and an inner metal case clamping said washer-like element to said outer case, comprising:

• machining a tubular billet of polytetrafluoroethylene to provide a cylindrical outer periphery of desired final dimensions,
• then facing off one end of said billet perpendicular to the cylinder of the outer periphery,
• then slicing said billet at a desired thin distance from said faced end wall to provide a washer and leaving a newly faced end wall,
• then continuing to slice said billet to provide a series of washers, all said washers being the same thickness,
• then assembling each said washer into a case by clamping it between said inner case and said outer case,
• then coining one face of each said washer under severe pressure to form permanent hydrodynamic means for returning leaked fluid, and
• piercing said coined washer to provide a desired inner periphery while assuring concentricity of said inner periphery with cylindrical wall of said outer case.
• said piercing and coining steps cooperating to cause said hydrodynamic means to be properly located relative to said inner periphery.

A method for manufacturing an oil seal having an outer case of metal with a cylindrical radially outer wall for engaging a bore, a resilient washer-like element of polytetrafluoroethylene, and an inner metal case clamping said washer-like element to said outer case, comprising:

• machining a tubular billet of polytetrafluoroethylene to provide a cylindrical tube of desired dimensions,
• then facing off one end wall of said billet perpendicular to the cylinder of the outer periphery,
• then slicing said billet at a desired thin distance from said faced end wall to provide a washer and leaving a newly faced end wall,
• then continuing to slice said billet to provide a series of said washers, all said washers being the same size,
• then assembling each said washer into a case by clamping it between said inner case and said outer case, and
• then coining one face of each said washer under severe pressure to form permanent hydrodynamic means for returning leaked fluid.

A method for manufacturing an hydrodynamic oil seal incorporating a sealing element clamped between an inner case and an outer case having a cylindrical bore-engageable wall, said sealing element being made from a generally flat washer of polytetrafluoroethylene or the like, and having an outer periphery of final desired size and an undersized inner periphery, comprising the steps of:

• clamping said washer between said inner and outer cases,
• then coining one face of each said washer to provide hydrodynamic means for returning leaked fluid, and
• piercing said washer to provide the desired inner periphery concentric with said cylindrical wall,
• said coining and piercing cooperating so that said hydrodynamic means leads from said inner periphery and extends for a desired width.