Adhesive bonding and miscellaneous chemical manufacture – Surface bonding means and/or assembly means therefor – With separate heating means for work
Patent
1991-11-12
1993-02-23
Wityshyn, Michael G.
Adhesive bonding and miscellaneous chemical manufacture
Surface bonding means and/or assembly means therefor
With separate heating means for work
156158, 1563042, 1563045, 1563046, 156507, B29C 6520, B29C 6530
Patent
active
051886979
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a device for the joining of tubular parts made from plastic, elastically polyvinylidene fluoride, polypropylene and polyethylene (wherein the aligned parts exhibit about the same diameter) by being pushed together and welded on the abutting surfaces of the tubular parts by the effect of heat. More specifically, the invention provides a heating element for softening the area of the beveled abutting surface, of at least one tubular part, and the contact surface of the heating element on the abutting surface of the tubular part is designed corresponding to the abutting surface and is provided on a circular or disk-shaped lug on the heating element and the heating element is provided with a centering and/or calibrating lug for the tubular part.
2. Background Art
The uniting of joining of pipes, fittings or other tubular plastic parts, (e.g., made of PE, PP, PVDF, ECTFE, PPS, PEEK, etc.) heretofore has taken place by butt-welding. In this case the tubular parts are cross-cut evenly and then butt-joined. Then along the butt joint the material of the two parts to be connected is heated to the softening or melting point, whereupon the flowing togethers of the plastic of the two parts leads to a welding. Also in this know butt-welding technique, a welding bead which is at least two to four millimeters thick is formed on the inside surface of the pipe thus produced which, if it is not removed in an expensive way, entails considerable flow losses and/or deposits in the pipe in the area of these welding beads. But often it is technically impossible to machine away such welding seams later on from the pipe inside wall. In this case, an undesirable rise in the flow resistance in the pipe as well as such deposits occurs if liquids with solid particles are transported in the pipe.
Various ways for reduction of these welding beads having already been proposed. Thus DE-A-3 510 552 explains the placing of technically relatively complicated recesses along the abutting surfaces of the two pipe parts to be welded together. These recesses are softened by a tool partially filling them so that after removal of the tool the pipe parts can join one another and be connected to one another. But also in using this known process a significant inside bead appears, which leads to the already mentioned undesirable increase of the flow resistance in the pipe. Also in DD-A-197 216 it is pointed out that, i.e., mold heating elements as well as inside bevels and also reduction of the welding pressure are to lead to a reduction of the inside beads.
BROAD DESCRIPTION OF THE INVENTION
The object of the invention is to provide a device of the initially mentioned type, with which the formation of a welding bead on the inside surface of the tubular parts when they are joined from two plastic tubular parts with essentially the same diameter is practically completely prevented.
This object is achieved in the process according to the invention by the fact that the abutting surfaces of the tubular parts in the direction of the inside pipe space are undercut or recessed so that the edge formed by the inside surface of the tubular part and the abutting surface springs back opposite the edge formed by the outside surface of the tubular part and the abutting surface, and so that the parts in the area of the abutting surfaces in the axial direction essentially are softened equally in depth, then pushed together and, as a result, are welded together.
A device according to the invention is distinguished in that a heating element is provided for applying to and softening the area of the abutting surface at least of a tubular part, and the contact surface of the heating element on the abutting surface of the tubular part is designed to correspond to the undercut or recessed abutting surface.
The device according to the invention is based on the common means of undercutting the abutting surfaces of the two parts--which are to be joined--of the tubular part produced from two parts s
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patent: 3855038 (1974-12-01), Anschutz
patent: 4051218 (1977-09-01), Hotton
patent: 4197149 (1980-04-01), Freitag et al.
patent: 4288266 (1981-09-01), Konrad et al.
patent: 4419067 (1983-12-01), Graafmann
patent: 4801349 (1989-01-01), Dommer et al.
Agru Alois Gruber GmbH
Wityshyn Michael G.
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