System and method for joining plastic materials

A heater comprising a structure having a plurality of physical and electrically interconnected wires,

• said wires comprising in cross section a conductive material surrounded by a ferromagnetic material,
• said wires being spaced from one another to define spaces therebetween such that the area of the spaces between said wires is at least approximately ten times the area of the wires defining the space in the same plane as the wires defining the area,
• said plurality of interconnected wires includes a wire helix and
• a plurality of longitudinally extending circumferentially spaced wires secured to the turns of said helix.

A heater comprising a structure having a plurality of physically and electrically interconnected wires,

• said wires comprising in cross section a conductive material surrounded by a ferromagnetic material,
• said wires being spaced from one another to define spaces therebetween such that the area of the spaces between said wires is at least approximately ten times the area of the wires defining the space in the same plane as the wires defining the area,
• a plurality of generally circular rings formed of round wires and
• a plurality of longitudinally extending circumferentially spaced wires secured to said rings.

A coil structure comprising

• a clamshell device having a pair of members mateable with one another and each having a semi-cylindrical depression having a common axis,
• each said depression having a plurality of parallel conductors perpendicular to the common axis and arranged in first and second groups of a number of conductors,
• interconnection between the conductors in each said group associated with one of said members being such that currents in the two groups flow in opposite directions,
• a first interconnection between one of said conductors of said first member and one of said conductors in the other of said members, and
• a second interconnection between a different one of said conductors of said second of said members and a different one of said conductors in the other of said members.

A saddle fitting for making a side entry into a plastic pipe comprising

• a surface to contact a plastic pipe having a curvature equal to the surface to which the saddle fitting is to be connected,
• said saddle fitting having a further pipe that terminates at one end in said surface of said saddle fitting to define a hole therein,
• a structure of wires surrounding said hole,
• said wires comprising in cross-section a conductive material surrounded by a ferromagnetic material, and
• means adapted to heat said wires to approach their Curie temperature,
• said Curie temperatures lying between the melt temperature and the degradation temperature of the material of the plastic pipe to which the saddle fitting is to be connected.

A coil structure comprising

• a flexible, non-conductive sheet of material,
• a plurality of flexible electrical conductors disposed on said sheet and extending from adjacent one edge to adjacent an opposed edge thereof,
• said conductors having first and second ends,
• said conductors having a configuration in the plane of said sheet such that upon folding said sheet about its centerline between said edges the second end of various of said conductors contacts the first end of an immediately adjacent conductor to provide a continuous electrically conductive path through said conductors.