US3393504A - Packing material - Google Patents

Description

July 23, 1968 c. E. DODGE, JR 3,393,504

PACKING MATERIAL Filed Feb. 8, 1966 INVENTOR. Ct EVE'LAND 5. 00065112 A T TMNEYS.

United States Patent 01 hoe 3,393,504 Patented July 23, 1968 3,393,504 PACKENG MATERIAL Cleveland E. Dodge, J12, Hoosick Falls, N.Y., assignor, by mesne assignments, to Dodge Industries, Hoosick Falls, N.Y., a corporation of Delaware Filed Feb. 8, 1966, Ser. No. 525,951 7 Claims. (Cl. 57144) ABSTRACT OF THE DISCLGSURE A packing material having a core formed of one or more thin polytetrafiuoroethylene tapes, the core being overwrapped with a tensioned tape of the same or similar material. The packing is suited for making gaskets, valve or stem packings and for sealing pipe threads and the like.

A packing material having a core formed of one or more thin polytetrafiuoroethylene tapes, the core being overwrapped with a tensioned tape of the same or similar material. The packing is suited for making gaskets, valve or stem packings and for sealing pipe threads and the like.

This invention is an improved material for making gaskets, packing valves and stems, for sealing pipe threads and for other like uses. It is a continuous, strong and compressible polytetrafiuoroethylene strand composed of a thin outer tape wound about one or more core tapes. It is characterized by chemical inertness and high tensile and compressive strength and is ideally suited for use in packing flanged or threaded connections, valves, stems, stufiing boxes, expansion joints and the like.

The component tapes are composed of polytetrafiuoroethylene or similar materials such as the copolymer of tetrafluoroethylene and hexafiuoropropylene or other copolymers of tetrafiuoroethylene and other unsaturated organic compounds having a terminal ethylenic double bond, for example, ethylene, chlorotrifiuoroethylene or the like. The polymer, polytetrafiuoroethylene, is preferred; however, the term as herein employed includes within its scope the above-mentioned copolymers.

Polytetrafluoroethylene is characterized by chemical inertness to aqueous alkalies, concentrated acids, oxidizing agents and organic solvents. In the form of thin tapes, as employed herein, the material is characterized by a tensile strength of about 9002500 p.s.i. longitudinally and about 50-500 p.s.i. transversely. In forming the material of this invention, unsintered polytetrafiuoroethylene, having a specific gravity of about 1.42.4, may also be used.

The component tape pieces of unsintered or sintered polytetrafiuoroethylene may be between about 1 and 20 mils thick and 0.05 and 0.75 inch wide and may be formed by extrusion. Extrusion of unsintered polytetrafiuoroethylene of the above dimensions is described in U.S. Patent No. 3,002,770 (issued on Oct. 3, 1961 to I. A. Chestnut et al.).

Packing materials have been made by winding a tape about a core and packing materials in other forms have been made from sintered polytetrafiuoroethylene. However, my invention is distinctive and unique, in that both the outside winding and the internal core material are formed from the same or similar thin polymeric tape, and gives unexpected properties. Single, uniform strands of, or other forms of, polytetrafiuoroethylene when used in packing tend to extrude out of the packed joint. My improved packing material is readily formed into useful shapes and does not extrude during service. Due to the strength of the material it remains in place as an efiective and improved packing or seal.

A better understanding of the preparation and use of the present packing material may be had by reference to the accompanying figure which diagrammatically shows the preparation of a packing material of the present invention by winding a tape about three core tapes. Referring to the figure, an outer tape 10 is wound about three core tapes 12, 14 and 16. The core tapes are guided through a conventional wire taping machine not shown which winds the outer tape 10 around the core tapes. Such a machine is manufactured by the Dodge Machine and Tool Company, Hoosick Falls, N.Y., and designated CW 64. The core may contain one or more tapes, preferably between two and thirty. This strand, composed of the outer tape and the core tapes, may be applied to flanged or threaded connections, valves, pump housings or the like. A number of these strands, for example seven, may be used to form the core of a larger strand by winding them in the manner shown in the figure to form a core which is overwound with another similar tape. Such a composite strand has usefulness in applications requiring a greater bulk of packing material.

The packing material of my invention is characterized by high chemical resistance and, .due to the method of winding a polytetrafiuoroethylene tape about a core consisting of one or more similar tapes, by unexpected dimensional stability and strength. The material is serviceable at temperatures between about 400 F. and 600 F., and is characterized additionally by flexibility, high elongation and low friction.

I claim:

1. A packing material comprising at least one outer tape wound about one or more core tapes, the tapes being composed of a material selected from the group consisting of polytetrafiuoroethylene and copolymers of tetrafiuoroethylene and organic compounds having a terminal ethylenic double bond, said tapes being characterized by a longitudinal tensile strength of about 900-2500 p.s.i.

2. The packing material of claim 1, wherein the material is polytetrafiuoroethylene.

3. The packing material of claim .1, wherein the material is extruded unsintered polytetrafiuoroethylene.

4. The packing material of claim 1, wherein the tapes are between about 1 and 20 mils thick and 0.05 and 0.75 inch wide.

5. The packing material of claim 1, containing between 2 and 6 core tapes and l outer tape of unsintered polytetrafluoroethylene.

6. The packing material of claim 1, wherein the extruded material is a copolymer of tetrafluoroethy-lene and hexafiuoropropylene.

7. A packing material comprising at least one outer tape of polytetrafiuoroethylene wound about a plurality of core strands composed of the material of claim 2.

References Cited UNITED STATES PATENTS 1,325,876 12/1919 McClure 161175 2,497,046 2/1950 Kropa et al. 281 2,578,523 12/1951 Llewellyn et al. 28l.4 2,764,506 9/1956 Piccard et al. 28--1 3,306,155 2/1967 Zumeta et al 871 FRANK I. COHEN, Primary Examiner.

W. A. SCHROEDER, Assistant Examiner.

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