Abstract: A cartridge heater for insertion within a heater bore-hole or cavity having a peripheral cavity wall surface. The cartridge heater includes an elongated generally cylindrical sheath having a heating element disposed therein and having an internal spring chamber intersected by a pair of elongated slots formed in the sheath. A generally V-shaped spring member is disposed within the spring chamber and has a pair of arcuately shaped arm portions projecting outwardly through the elongated slots for frictional engagement against the wall surface of the cavity to retain the cartridge heater within oversize cavities. The spring chamber may be formed as an extension of the forward or rearward ends of the cartridge sheath.

Abstract: A cartridge heater, wherein the terminal lead pins which project from the terminal end of the heater at the outer surface of the electrical insulating end plug, are substantially reduced in length and provided with at least one flat planar surface on what was originally the cylindrical surface of each lead pin. The terminal ends of the external flexible lead wires are then fused to the flat surfaces on each of the lead pins by means of brazing, soldering or welding. An end adapter unit having two longitudinal bores is then threaded up over the two flexible lead wires until the outer casing, which encloses an electrical insulating core having the two circular bores for the flexible wires, is telescoped over the terminal end of the cannister which encloses the cartridge heater.