Metal working – Method of mechanical manufacture – Electrical device making
Patent
1996-12-26
1999-01-26
Echols, P. W.
Metal working
Method of mechanical manufacture
Electrical device making
29611, 29619, 29858, 26427218, 264278, 425125, 219541, 219544, H05B 300, H01C 1704, H01C 1728, H01R 4300
Patent
active
058625852
DESCRIPTION:
BRIEF SUMMARY
THIS INVENTION relates to electrofusion couplers or welding muffs which are used for connecting lengths of plastics pipe end to end in manner known per se. Such an electrofusion coupler is disclosed, for example, in GB2090558.
In manufacture or the electrofusion coupler or GB2090558, a tubular plastics shell or preform is first produced by injection moulding, the preform having upstanding integral studs. An electrical resistance heating wire is then secured to one of these studs on the preform, is wound in a number of turns around the preform from that stud to the other stud and is secured to that stud. The wire is secured to each stud by looping the wire around the stud and over the free end of the stud. A terminal shell or cap is subsequently forced over each stud to make good electrical contact with the wire looped around the stud. The wound preform is then placed in an injection mould, to form the core of the mould, and an outer layer of thermoplastics material is moulded around the wound preform.
The present invention, however, relates to a method of manufacturing an electrofusion coupler which dispenses with the need for making a thermoplastics preform to carry the heating winding and in which the heating wire is wound directly on a mould core or mandrel from which the finished electrofusion coupler is eventually stripped. The invention also relates to apparatus for carrying out the method and to an electrofusion coupler produced by the method of using the apparatus.
According to one aspect or the invention, there is provided a method of forming an electrofusion coupler, comprising providing a mandrel having at spaced apart locations therealong first and second terminal holders which can be retracted into the mandrel inwardly or the peripheral surface thereof, and can be extended outwardly from the peripheral surface thereof, the method including the steps or providing a continuous length of electrical resistance heating wire, mounting a first terminal in the first said terminal holder and securing the first terminal to said wire, winding the wire around the mandrel from said first terminal and said first terminal holder for a plurality of turns, mounting a second terminal in the second terminal holder and securing the second terminal to the wire with the wire being maintained in tension between said first and second terminals, subsequently cutting the wire extending beyond said second terminal, moulding around the wound mandrel and the terminals, supported by said terminal supports, a sleeve or thermoplastics material, leaving portions of the terminal exposed on the exterior of the sleeve, allowing the thermoplastics material to solidify, retracting the terminal supports within the mandrel leaving the terminals supported by the plastics material, and withdrawing the mandrel axially from the sleeve leaving the winding and terminals supported by the plastics sleeve.
According to another aspect of the invention, there is provided apparatus for use in carrying out the above method comprising a mandrel having at spaced-apart locations therealong first and second terminal holders, means for moving said terminal holders between positions in which they are retracted within the mandrel surface and positions in which they project from the mandrel surface, means for winding electrical heating wire around the mandrel from one said terminal support to another, said terminal supports being adapted to hold terminals secured to said heating wire and thereby maintain the wire in tension between the terminal holders, means for cutting the wire at a position adjacent one said terminal holder on the side thereof remote from the other and means for moulding around the mandrel, said terminals and the projecting portions of said terminal supports a sleeve of thermoplastics material.
An embodiment of the invention is described below by way of example with reference to the accompanying drawings, in which:
FIG. 1 is a schematic fragmentary view in section along a mandrel or core of an apparatus embodying the invention,
FIG.
REFERENCES:
patent: 2651768 (1953-09-01), Oortgijsen
patent: 4147926 (1979-04-01), Stahli
patent: 4224505 (1980-09-01), Sturm
patent: 4727242 (1988-02-01), Barfield
patent: 4848718 (1989-07-01), Harrison
patent: 4855574 (1989-08-01), Lodder et al.
Patent Abstract of Japan, Publication No.: JP2030508, Publication Date: 31 Jan. 1990; p. 1 of 1.
Patent Abstract of Japan, Publication No.: JP2022021, Publication Date: 24 Jan. 1990; p. 1 of 1.
Echols P. W.
Glynwed Pipe Systems Limited
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