PTC resistance heater

Claim 1

A self-regulating electrical heater device comprising a casing, a resistor element of disc-like configuration disposed within said casing, said resistor element having a layer of a ceramic material of selected thickness and of positive temperature coefficient of resistivity which displays a sharp increase in resistivity when heated to a selected temperature by directing electrical current through said ceramic layer for regulating the heated temperature of said element, said layer of ceramic material having flat surfaces on respective opposite sides thereof which are broad relative to said ceramic layer thickness and having metal layers on said broad flat surfaces providing electrical contact surfaces on said opposite sides of said ceramic layer, pair of electrically-conducting metal terminals disposed within said casing adjacent said respective contact surfaces of said resistance element, a silicone material having a metallic particulate dispersed therein disposed to substantially fill the space between at least one of said terminals and the one contact surface of said element adjacent to said one terminal to provide improved heat-transfer to said one terminal from a selected area of said element contact surface, said one terminal having a plurality of protuberances in a selected pattern thereon extending through said silicone material into electrical engagement with selected spaced areas of said one contact surface, and means cooperating with said casing for resiliently biasing said one terminal to maintain said protuberances extending through said silicone material into said electrical engagement with said one terminal and for disposing the other of said contact surfaces in electrical engagement with the other of said terminals.