Glow-plug

Claim 1

A glow-plug, for air-compression combustion engines, of the type having a housing provided with a tubular element projecting from said housing to define a glow-pin, further having resistance means contained in said glow-pin, and further having electrical feed means electrically insula-tingly mounted in said housing and having an electric current feeding end connected to a rear end of said resistance means, the improvement wherein: - said tubular element is closed at the end thereof away from said housing; - said resistance means is made up of a front coil and of a rear coil, both coils being end-connected and having different coefficients of resistance to temperature, - the free end of said front coil is electrically connected to said closed end of said tubular element, and - said resistance means is entirely contained in said tubular element and packed therein in electrically insulating material to prevent short-circuiting of said resistance means and said glow-pin, - whereby said rear coil is exposed to the glow of said glow-pin when current flows through said resistance means to thereby increase the resistance value of said rear coil as the temperature of said glow-pin rises and thus to reduce the intensity of the heating current to prevent overheating of the glow-plug.