Split piston ring and method of manufacture

Claim 2

Means for sealing the space between a piston and a cylindrical wall comprising: an annular member constructed from a closed ring of plastic material which material coldflows under pressure, said annular member being formed generally circularly about an axis with inner and outer concentric surfaces, first and second side surfaces and first and second mating end portions, said end portions including: radial slits extending through predetermined arcs of said annular member generally perpendicular to the axis thereof; first mating step surfaces on said first and second mating end portions extending between said inner and outer concentric surfaces and from said first side surface to said radial slits; and second mating step surfaces on said first and second mating end portions extending between said inner and outer concentric surfaces and from said second side surface to said radial slits, whereby said coldflow characteristic of said annular member enables said member to permanently deform at said first and second mating step surfaces to prevent gaps from forming between the surfaces thereof as said member or the cylindrical wall wears, said first mating step surfaces being spaced along the circumference of said annular member from said second mating step surfaces, and spaced within the predetermined arcs of said radial slits so that mating gaps cannot attempt to form between respective surfaces of said first and second mating step surfaces and so each first and second step surfaces are relatively free to move with respect to the portion of said annular member across said radial slits therefrom, thereby enabling said annular member to coldflow to seal any gaps which otherwise might form between said end portions.

Claim 3

Means for sealing the space between a piston and a cylindrical wall comprising: an annular member constructed from a closed ring of plastic material which material coldflows under pressure, said annular member being formed generally circularly about an axis with inner and outer concentric surfaces, first and second side surfaces and first and second mating end portions, said end portions including: radial slits extending through predetermined arcs of said annular member generally perpendicular to the axis thereof; first mating step surfaces on said first and second mating end portions extending between said inner and outer concentric surfaces and from said first side surface to said radial slits; and second mating step surfaces on said first and second mating end portions extending between said inner and outer concentric surfaces and from said second side surface to said radial slits, whereby said coldflow characteristic of said annular member enables said member to permanently deform at said first and second mating step surfaces to prevent gaps from forming between the surfaces thereof as said member or the cylindrical wall wears, said first and second step surfaces including inner, outer and center portions, said center portions being generally parallel to said outer concentric surface, and said outer portions extendinG between said outer concentric surface and said center portions and being scarfed with respect to said first and second side surfaces, said outer portions being scarfed to increase the effect of pressure applied thereto when in operation sealing the space between the piston and cylindrical wall so that said scarfed end portions coldflow to prevent gaps from being formed therebetween as said annular member or the cylindrical wall wears.

Claim 4

Means for sealing the space between a piston and a cylindrical wall comprising: an annular member constructed from a closed ring of plastic material which material coldflows under pressure, said annular member being formed generally circularly about an axis with inner and outer concentric surfaces, first and second side surfaces and first and second mating end portions, said end portions including: radial slits extending through predetermined arcs of said annular member generally perpendicular to the axis thereof; first mating step surfaces on said first and second mating end portions extending between said inner and outer concentric surfaces and from said first side surface to said radial slits; and second mating step surfaces on said first and second mating end portions extending between said inner and outer concentric surfaces and from said second side surface to said radial slits, whereby said coldflow characteristic of said annular member enables said member to permanently deform at said first and second mating step surfaces to prevent gaps from forming between the surfaces thereof as said member or the cylindrical wall wears, said first and second step surfaces including inner, outer and center portions, said center portions being generally parallel to said outer concentric surface, and said outer portions extendinG between said outer concentric surface and said center portions and being scarfed with respect to said first and second side surfaces, said outer portions being scarfed to increase the effect of pressure applied thereto when in operation sealing the space between the piston and cylindrical wall so that said scarfed end portions coldflow to prevent gaps from being formed therebetween as said annular member or the cylindrical wall wears.

Claim 5

The means defined in claim 2 wherein said inner portions of said first and second step surfaces extend between said inner concentric surface and said center portions and are orientated on planes which are generally parallel to the axis of said annular member.

Claim 6

The means defined in claim 1 wherein said inner portions of said first and second step surfaces extend between said inner concentric surface and said center portions and are scarfed with respect to said first and second side surfaces.