Abstract: An engaging structure for a heat sink, an edgefold (2) is provided on each of the two opposite sides of the heat sink unit, respectively, characterized in that at least one engaging cut having a shape is formed in a section connecting the respective edgefolds (2) and a base sheet (5) by punching, respectively, after the edgefolds (2) are formed, the recess in the upper portion of the engaging cut functions as an engaging groove (3), while the projection in the lower portion of the engaging cut functions as an engaging projection (4), the engaging groove (3) is disposed at the top of each of the edgefolds 2, the portion of which corresponding to the engaging grooves (3) partially projects, while the engaging projection (4) is disposed in the base sheet 5 at a conjunction position between the root of edgefold (2) and the base sheet (5), and the engaging projection (4) projects outwards, the engaging grooves (3) of the heat sink unit are engaged with the engaging projections (4) of the previous heat sink unit,

Abstract: Method of making positive-temperature-coefficient thermistor (PTCR) heating element involves steps of depositing an insulation adhesive layer having a predetermined pattern on flat surfaces of two heat-radiating means opposite to each other, placing a metal film having a pattern complementary to that of the insulation adhesive layer on uncoated area of flat surface of each of the two heat-radiating means, arranging in sequence a plurality of PTCR pieces on flat surfaces of heat-radiating means, stacking two processed heat-radiating means, with their flat surfaces facing PTCR pieces, applying compressive pressure to the stacked heat-radiating means with PTCR pieces sandwiched therebetween, and allowing insulation adhesive layer to cure under the compressive pressure so that all components are held together intimately and firmly to form a heating element which is cost effective, relatively safe, highly conductive and capable of generating a high and stable thermal output.

Abstract: A heating set having a plurality of positive temperature coefficient thermistor heating elements (PTCR pieces) sandwiched between two heat radiating devices made of metal with each of the PTCR pieces provided with sprayed-on electrodes having their exposed surfaces making close contact with long metal battens on the outer surfaces of the heat radiating devices through conducting thin metal pieces having predetermined surface areas. The PCTR pieces and the heat radiating devices making electrical contact through the thin metal pieces are bonded together by an electrically nonconductive adhesive spread on the border of the battens around the thin metal plate and on opposite parallel edges on the border of the sprayed-on electrodes of the PTCR pieces.