Method and woven mesh heater comprising insulated and noninsulated wire for fusion welding of plastic pieces

Abstract

A woven mesh heater generates a heat emitting surface which provides for uniform spatial distribution of heat and which is self-regulated in the preferred embodiment. The heater is particularly useful in joining together polyethylene pieces. The heater is produced from woven mesh and inserted between polyethylene pieces to be joined. Upon energization with a power source, the heater heats the polyethylene pieces to a temperature so that the pieces melt and fuse together. The heater is formed from a mesh of interleaved conductive wires and resistive wires. Electrical paths are established through the mesh by spot welding at intersection, or crossover, points of the conductive and resistive wires. The spot welding produces an electrical connection between the conductive and resistive wires at the welds. In this way, equal distance and therefore equal resistance paths are obtained. In addition, the resistive wires preferably have a two-layer laminate structure with an inner core of a high conductivity material, such as copper, and an outer surface layer of a ferromagnetic material having a particular Curie temperature. The foregoing two-layer laminate structure causes the temperature of the resistive wires to reach a peak value, provided that energization remains constant. Hence, the woven mesh heater is self-regulating.

Dependencies are inferred from the claim text.