Method for welding thermoplastic materials
First Claim
1. A method of welding adjacent members of a thermoplastic material, comprising the steps of:
- positioning a thermoplastic welding rod between said adjacent members of said thermoplastic material, which welding rod has a solid core of said thermoplastic material and a resistance element embedded below the outer peripheral surface of said welding rod, which resistance element is distributed in surrounding relationship to said solid core along the lengthwise direction of said rod and is embedded a sufficient depth such that burning of said thermoplastic during welding is substantially prevented when a welding current is applied to the resistance element, but not so deep that burning of the thermoplastic material of the core occurs prior to softening of portions of the adjacent members nearest the welding rod;
applying a current to said resistance element;
applying pressure to said members such that the facing surfaces of said members are in contact with said welding rod, said current being applied to said resistance element for a time and intensity sufficient to cause said solid core of said welding rod and portions of said members proximate said welding rod to soften and melt; and
discontinuing said current.
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Accused Products
Abstract
An improved welding rod having a solid homogeneous core of thermoplastic material and a resistance element comprised of a plurality of wires is presented with a method and apparatus for forming the welding rod. The welding rod is positioned between members of the thermoplastic material to be welded and a current and pressure is applied to the resistance element causing the thermoplastic material of the solid core and the adjacent thermoplastic members to fuse and form a unitary weld. Simultaneously the electrical resistance element is embedded in the weld, mechanically reinforcing and strengthening the connection. There is also disclosed a method for electric fusion welding of thermoplastic members wherein the welding rod is pre-attached to one of the thermoplastic members.
64 Citations
32 Claims
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1. A method of welding adjacent members of a thermoplastic material, comprising the steps of:
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positioning a thermoplastic welding rod between said adjacent members of said thermoplastic material, which welding rod has a solid core of said thermoplastic material and a resistance element embedded below the outer peripheral surface of said welding rod, which resistance element is distributed in surrounding relationship to said solid core along the lengthwise direction of said rod and is embedded a sufficient depth such that burning of said thermoplastic during welding is substantially prevented when a welding current is applied to the resistance element, but not so deep that burning of the thermoplastic material of the core occurs prior to softening of portions of the adjacent members nearest the welding rod; applying a current to said resistance element; applying pressure to said members such that the facing surfaces of said members are in contact with said welding rod, said current being applied to said resistance element for a time and intensity sufficient to cause said solid core of said welding rod and portions of said members proximate said welding rod to soften and melt; and discontinuing said current. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of butt welding two coaxial sections of thermoplastic pipe, comprising:
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positioning a thermoplastic welding rod between said sections so that respective adjacent ends of said sections are in contact with opposite sides of said welding rod, said welding rod having a solid core of said thermoplastic material and a resistance element comprising a wire spirally wound about said core and embedded in said rod below the surface of said rod a sufficient depth such that burning of said thermoplastic during welding is substantially prevented when a welding current is applied to the resistance element, but not so deep that burning of the thermoplastic material of the core occurs prior to softening of said adjacent ends, and said core extending in a circumferential direction of said pipe sections; then applying a current to said welding rod for a time and of sufficient intensity to cause said welding rod and said adjacent ends of said pipe sections to melt and fuse; applying pressure axially of said sections to urge said sections together; and maintaining said pressure after said electrical current has been discontinued until said fused ends and welding rod have solidified. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23)
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24. A method of welding two sections of thermoplastic pipe, comprising:
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bending and forming a flexible welding rod into a shape that conforms to the shape of surfaces of the sections to be welded, the welding rod comprising a solid core of thermoplastic material and a resistance element for melting the thermoplastic material, the resistance element comprising a plurality of wires wound about a thermoplastic core in a spiral configuration and embedded in said rod below the surface of said rod a sufficient depth such that burning of said thermoplastic during welding is substantially prevented when a welding current is applied to the resistance element, but not so deep that burning of the thermoplastic material of the core occurs prior to softening of said sections, each wire being spaced from each other wire along the length of said welding rod; positioning the shaped thermoplastic welding rod between the sections so that respective adjacent ends of the sections are in contact with opposite sides of the welding rod; applying a current to the welding rod for a time and of sufficient intensity to cause the welding rod and adjacent portions of the pipe sections to melt and fuse to form a weld; applying pressure to urge the sections together at the weld; and maintaining the pressure until the weld has solidified. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32)
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Specification