Abstract: In forming a mat, a continuous length of wire is fed between a winding plate and a pair of laterally spaced parallel spindles located closely above the plate. The winding plate is adjustable relative to the spindles so that the wire forming the mat can be held gently between the spindles and the plate. A feed member is pivotally mounted for supplying the wire in a continuous alternating manner first to one spindle and then to the other. Each spindle has a helically formed wire guide followed by a screw thread. The wire fed to the spindles is directed into the screw threads by the wire guide. The spindles are rotated in opposite directions to obtain the desired feeding action. The mat is built up from a plurality of juxtaposed wire sections connected at their opposite ends by return bends. Welding members are movably positionable relative to the mat being formed to provide welding of the wire sections together on both sides of the mat.

Abstract: A weldable subassembly for connecting branch pipes to a molded plastic main pipe is formed with a pair of hinged arcuate members adaptable to be placed around the main pipe and welded thereto by electrical current passed through an interposed mat containing electrical heating wires. The arcuate members are pivotally interconnected by a hinge member which extends on one side thereof longitudinally of the main pipe, and which enables separation of the opposite side of the arcuate members so that they may be placed about the pipe. The opposite sides of the arcuate members form a slight gap therebetween which also extends longitudinally of the main pipe and the heating wire mat has a longitudinal edge which is attached, by welding or the like, to the inner surface of one of the arcuate members at a point intermediate the hinge member and the opposite side of the arcuate member.