Spherical annular seal member and method of manufacturing the same

A method of manufacturing a spherical annular seal member for use in an exhaust pipe joint and including a spherical annular base member defined by a cylindrical inner surface, a partially convex spherical surface, and large- and small-diameter side annular end faces of said partially convex spherical surface, and an outer layer formed integrally on said partially convex spherical surface of said spherical annular base member, comprising the steps of:

• (a) preparing an expanded graphite sheet serving as a heat-resistant material;
• (b) preparing a metal wire net serving as a reinforcing member and obtained by weaving or knitting a fine metal wire, and, after forming a superposed assembly by superposing said metal wire net on said expanded graphite sheet, convoluting said superposed assembly into a hollow cylindrical shape, to thereby form a tubular base member;
• (c) preparing an aqueous dispersion of a lubricating composition consisting of a polytetrafluoroethylene resin powder, a tetrafluoroethylene-hexafluoropropylene copolymer powder, a hexagonal boron nitride powder, a surfactant, and water;
• (d) preparing another expanded graphite sheet serving as a heat-resistant material, applying said aqueous dispersion onto one surface of said other expanded graphite sheet, and drying the same, to thereby form on a surface of said other expanded graphite sheet a coating layer of a solid lubricant consisting of a polytetrafluoroethylene resin, a tetrafluoroethylene-hexafluoropropylene copolymer, and hexagonal boron nitride;
• (e) superposing said other expanded graphite sheet having said coating layer on another metal wire net serving as a reinforcing member and obtained by weaving or knitting a fine metal wire, and pressurizing a superposed assembly of said other expanded graphite sheet and said other metal wire net by a pair of rollers, to thereby form a flattened outer-layer forming member in which said other expanded graphite sheet and said coating layer are filled in meshes of said other metal wire net;
• (f) convoluting said outer-layer forming member around an outer peripheral surface of said tubular base member with its coating layer facing outside, to thereby form a cylindrical preform;
• and
• (g) fitting said cylindrical preform over an outer peripheral surface of a core of a die, placing the core in the die, and subjecting said cylindrical preform to compression molding in the die in an axial direction of the core,
• wherein said spherical annular base member is formed so as to be provided with structural integrity as said expanded graphite sheet and said metal wire net are compressed and intertwined with each other, and
• wherein, in said outer layer, said other expanded graphite sheet, said coating layer, and said other metal wire net are compressed such that said other expanded graphite sheet and said coating layer are filled in meshes of said other metal wire net, and such that said other metal wire net, said other expanded graphite sheet, and said coating layer are integrated in mixed form.

A spherical annular seal member for use in an exhaust pipe joint, comprising:

• a spherical annular base member defined by a cylindrical inner surface, a partially convex spherical surface, and large- and small-diameter side annular end faces of said partially convex spherical surface;
• and an outer layer formed integrally on said partially convex spherical surface of said spherical annular base member,
• wherein said spherical annular base member includes a reinforcing member made from a metal wire net and a heat-resistant material containing expanded graphite and compressed in such a manner as to fill meshes of the metal wire net of said reinforcing member and to be integrated with said reinforcing member in mixed form, and
• wherein, in said outer layer, a heat-resistant material containing expanded graphite, a solid lubricant consisting of a lubricating composition containing a polytetrafluoroethylene resin, at least one kind of a molten fluorocarbon resin having a melting temperature different from that of the polytetrafluoroethylene resin, and hexagonal boron nitride, and a reinforcing member made from a metal wire net are compressed such that said heat-resistant material and said solid lubricant are filled in meshes of said reinforcing member, and such that said reinforcing member, said heat-resistant material, and said solid lubricant are integrated in mixed form.

A spherical annular seal member for use in an exhaust pipe joint, comprising:

• a spherical annular base member defined by a cylindrical inner surface, a partially convex spherical surface, and large- and small-diameter side annular end faces of said partially convex spherical surface;
• and
• an outer layer formed integrally on said partially convex spherical surface of said spherical annular base member,
• wherein said spherical annular base member includes a reinforcing member made from a metal wire net and a heat-resistant material containing expanded graphite and compressed in such a manner as to fill meshes of the metal wire net of said reinforcing member and to be integrated with said reinforcing member in mixed form, and
• wherein, in said outer layer, a heat-resistant material containing expanded graphite, a solid lubricant consisting of a lubricating composition containing a polytetrafluoroethylene resin, at least one kind of a molten fluorocarbon resin having a melting temperature lower than a melting temperature of the polytetrafluoroethylene resin, and hexagonal boron nitride, and a reinforcing member made from a metal wire net are compressed such that said heat-resistant material and said solid lubricant are filled in meshes of said reinforcing member, and such that said reinforcing member, said heat-resistant material, and said solid lubricant are integrated in mixed form.