Glow plug

Abstract

A glow-plug .[.ignitor for diesel engines and the like,.]. comprising a tubular body having external screw threads and an adjoining hexagonal formation by which a tool such as a wrench can be applied to the body to screw it into .[.the.]. .Iadd.a .Iaddend.threaded cavity .[.of a cylinder.].. Next to the hexagonal formation is a spade lug connector for bringing current to the plug, the connector being so arranged as to permit the application of either a socket-type wrench or else a box-end wrench. The inner end of the body has an elongate projecting pin on which there is a tightly wound resistance coil that becomes incandescent when excited with the proper electric current. The valleys of the coil show higher temperatures, for a given heating current, due to the radiation and reception of radiated heat involving the opposed surfaces.[.; therefore, starts at lower engine temperatures are improved.]..

We claim: 
     
       1. A diesel glow-plug ignitor comprising, in combination: (a) a tubular metal body having an inner end securely carried in a cylinder opening of an engine,   (b) an electrically conductive core pin insulatedly carried in the bore of the body, physically structurally united therewith, and having a portion projecting from said inner end thereof, said projecting portion of said core pin being coated with insulating material, and   (c) a tight-wound helical igniting coil of resistance wire on said projecting portion of the core pin, having its ends respectively welded to the body and welded substantially to the end of said projecting portion of the pin,   (d) the convolutions of said coil having an insulating oxide coating thereon to prevent them from short-circuiting each other,   (e) said insulating material on the core pin having ceramic-containing insulation and being plasma sprayed thereon to further prevent the convolutions of the coil from electrically contacting the projecting portion of the core pin.   
     
     
       2. The invention as defined in claim 1, wherein: (a) the inner end of the metal body has a plurality of ridges to which the one end of the coil is welded.   
     
     
       3. The invention as defined in claim 1, wherein: (a) an end convolution of the coil is welded at diametrically opposite spots to the core pin.   
     
     
       4. A diesel glow-plug ignitor as defined in claim 1, wherein: (a) said tubular metal body has an hexagonal configuration at one end, to enable it to have a wrench applied to it for installing it in said cylinder,   (b) said core pin having an additional portion projecting from the hexagonal configuration of the body and being externally exposed, and   (c) a spade terminal carried by and welded to the side of the additional portion of the core pin,   (d) said spade terminal being so located and having a small enough dimension so as to facilitate installation of a cup-type socket wrench of similar hexagonal configuration which is intended to be applied to said hexagonal configuration of the body past the spade terminal.   
     
     
       5. A diesel glow-plug ignitor comprising, in combination: (a) a tubular metal body having an inner end securely carried in a cylinder opening of an engine,   (b) an electrically conductive core pin insulatedly carried in the bore of the body and extending through the bore of the body, physically structurally united therewith and having a portion projecting from the inner end thereof,   (c) an insulating sleeve disposed within and in spaced relation to the metal body and surrounding said core pin and spaced therefrom,   (d) a helical igniting coil of resistance wire on the projecting portion of the core pin and being electrically insulated therefrom, said coil having its ends respectively electrically connected to the body and electrically connected substantially to the end of said projecting portion of the pin, and   (e) ceramic cement disposed in the spaces between the body, core pin and sleeve.   
     
     
       6. The invention as defined in claim 5, wherein: (a) the core pin has a shoulder intermediate its ends,   (b) said body having an internal cooperable annular shoulder engaged with the shoulder of the core pin to position the latter.   
     
     
       7. The invention as defined in claim 6, wherein: (a) the shoulder of the core pin has a plasma-sprayed coating of insulation. .Iadd.   
     
     
       8.  A heater plug for use with an internal combustion engine, comprising, in combination: (a) a tubular metal support structure having an outer end and an inner end,   (b) an electrically conductive core pin insulatedly carried in the bore of the support structure, physically structurally united therewith, and having a coil-supporting projecting portion terminating in a free end, said projecting portion being coated with insulating material, and   (c) a helical heater coil of resistance wire on said projecting portion of the core pin, said coil having an outer end welded to the inner end of the support structure and having an inner end welded to the free end of the projecting portion of the core pin,   (d) the convolutions of said heater coil being closely spaced and having an insulating oxide coating thereon to prevent them from short-circuiting each other,   (e) said insulating material on the core pin comprising ceramic-containing insulation which is plasma sprayed thereon to further prevent the convolutions of the coil from electrically contacting the said projecting portion of the core pin..Iaddend. .Iadd.9. The invention as defined in claim 8, wherein:   (a) the inner end of the support structure has a plurality of ridges to which the outer end of the heater coil is welded..Iaddend. .Iadd.10. The invention as defined in claim 8, wherein:   (a) the innermost convolution of the heater coil is welded at diametrically opposite spots to the free end of the core pin..Iaddend. .Iadd.11. A heater plug for use with an internal combustion engine, comprising, in combination:   (a) a tubular metal body having an inner end adapted to be carried in a supporting opening,   (b) an elongate electrically conductive member having a plasma-sprayed insulating coating thereon and insulatedly carried in the bore of the body and extending through said bore, said member being physically structurally united therewith and having a coil-supporting projecting portion terminating in a free end,   (c) an insulating sleeve disposed within and in spaced relation to the metal body and surrounding said elongate conductive member in spaced relation thereto,   (d) a helical coil of resistance wire mounted on said projecting portion of the elongate member and insulated therefrom by said plasma-sprayed coating, said coil having its outer end electrically connected to the inner end of the tubular metal body and having its inner end welded to said free end of the projecting portion, and   (e) ceramic cement disposed in the space between the tubular body and the insulating sleeve and in the space between the insulating sleeve and the elongate conductive member, said cement being forcibly engaged with the inner and outer surfaces of the insulating sleeve under pressure..Iaddend. .Iadd.12. A heater plug for use with an internal combustion engine, comprising, in combination:   (a) a tubular metal body having an inner end adapted to be carried in a supporting opening,   (b) an electrically conductive core pin having a plasma-sprayed insulating coating thereon and insulatedly mounted in the bore of the body and extending therethrough, said core pin being physically structurally united with the tubular metal body and having a coil-supporting projecting portion terminating in a free end,   (c) an insulating ceramic sleeve of generally tubular configuration, disposed within and in spaced relation to the tubular metal body and surrounding said core pin and being spaced therefrom,   (d) a helical coil of resistance wire on the projecting portion of the core pin and having its intermediate convolutions insulated therefrom by said plasma-sprayed insulating coating, said coil having its inner end electrically connected to said free end of the core pin and having its outer end welded to the inner end of the tubular metal body, and   (e) ceramic cement disposed in the space between the tubular metal body and the ceramic sleeve, and in the space between the ceramic sleeve and the core pin, said cement being forcibly engaged with the inner and outer surfaces of the sleeve under pressure..Iaddend.