Heated cutting blade,cutting head, and blade mounting structure requiring less current and providing improved cutting and method

Abstract

The present invention provides a method and apparatus of reducing current requirements by increasing resistance of the blade structure by reducing the cross sectional area of at least one section of the blade so that the electrical current requirements for heating of the blade to cutting temperature are reduced wherein the power supply and substantially entire unit may be mounted within a hand held unit. Methods of shaping blades to perform various heat distributions for specialty blades for custom cutting are disclosed. Further, an improved blade mounting structure is provided which includes structure for maintaining the legs of the blade parallel to the direction of cut and provides for easy insertion of new blades by maintaining a slotted blade cradle stable and in alignment with the blades and a clamp member away from the blade when the clamp mounting structure is loosened.

I claim: 
     
         1 . A blade for cutting heat sensitive material, comprising:
 a conductive material forming a blade having a first end and a second end;   said blade having between said first end and said second end a section of reduced cross-sectional area producing increased electrical resistance and heating when an electrical current is passed therethrough;
 said blade being provided with a sharpened edge in said section of reduced cross sectional area; 
 said blade being provided with an unsharpened end portion adjacent said first and second ends; 
 said section of reduced cross-sectional area being at one point reduced in cross-sectional area by greater than 50% compared to the cross-sectional area of the ends of the blade. 
   
     
     
         2 . A blade in accordance with  claim 1  wherein said section of reduced cross-sectional area producing increased electrical resistance is provided a resistance point with a resistance lead on each side in the form of a taper of the blade. 
     
     
         3 . A blade in accordance with  claim 1  wherein said taper of the blade in said resistance lead is a linear taper. 
     
     
         4 . A blade in accordance with  claim 1  wherein said taper of the blade in said resistance lead is concave. 
     
     
         5 . A blade in accordance with  claim 1  wherein said taper of the blade in said resistance lead is comprised of a plurality of linear tapers at differing rates of taper. 
     
     
         6 . A blade in accordance with  claim 1  wherein said blade is provided with a plurality of sections of reduced cross-sectional area in series in the blade. 
     
     
         7 . A blade in accordance with  claim 1  wherein said section of reduced cross-sectional area is centrally located between said first end and said second end of said blade. 
     
     
         8 . A blade in accordance with  claim 1  wherein said section of reduced cross-sectional area is located closer to one of said first and second ends of said blade. 
     
     
         9 . A blade in accordance with  claim 1  wherein said blade is substantially U-shaped. 
     
     
         10 . A blade in accordance with  claim 1  wherein said blade is substantially within a single plane. 
     
     
         11 . A blade in accordance with  claim 1  wherein said blade is substantially L-shaped. 
     
     
         12 . A blade in accordance with  claim 1  wherein said blade is comprised of steel. 
     
     
         13 . A blade in accordance with  claim 1  wherein said blade is provided with a sharpened edge between said first end and said second end, wherein said first end is not sharpened and said second end is not sharpened, said unsharpened end portions being of sufficient length for mounting in a blade mounting structure. 
     
     
         14 . A method of cutting a heat sensitive material using an electrically heated cutting blade as set forth in  claim 1 , comprising the step of:
 shaping of the blade to substantially reduce the cross-sectional area of the blade in a section of the blade between a first end portion and a second end portion of the blade to increase electrical resistance and heating of the blade in said section when an electrical current is passed through the blade; and   thereby reducing an amount of current required to heat said section to a predetermined temperature.   
     
     
         15 . A method in accordance with  claim 14  wherein said electrical current is passed between one of said first and second ends of the blade to the other end. 
     
     
         16 . A method in accordance with  claim 14  wherein said blade section of increased resistance is provided with a resistance point and a resistance lead on each side of said resistance point in the form of a taper of the blade. 
     
     
         17 . A method in accordance with  claim 16  wherein said taper of the blade gradually increases resistance and heating of the blade in the taper section. 
     
     
         18 . A method in accordance with  claim 16  wherein said taper of the blade is a linear taper. 
     
     
         19 . A method in accordance with  claim 16  wherein said taper of the blade is non-linear or concave. 
     
     
         20 . A method in accordance with  claim 14  wherein the step of shaping the blade to substantially reduce the cross-sectional area of the blade reduces the cross-sectional area of the blade in said resistance point by more than 50%. 
     
     
         21 . A method in accordance with  claim 14  wherein said first end and said second end of said blade are mounted in a handle unit and including the step of providing said handle unit with a power supply within said handle unit. 
     
     
         22 . A method in accordance with  claim 14  wherein said blade is substantially U-shaped. 
     
     
         23 . A method in accordance with  claim 14  wherein said blade is in a single plane. 
     
     
         24 . A method in accordance with  claim 14  wherein said step of shaping the blade to substantially reduce the cross-sectional area of the blade is repeated to produce a series of sections in the blade of increased electrical resistance and heating of the blade sections when an electrical current is passed through the blade. 
     
     
         25 . A method in accordance with  claim 14  wherein said section of reduced cross-sectional area of the blade is centrally disposed between said first end and said second end of the blade. 
     
     
         26 . A method in accordance with  claim 14  wherein said section of reduced cross-sectional area of the blade is disposed closer to said first end or said second end of said blade. 
     
     
         27 . A method in accordance with  claim 14  wherein said section of reduced cross-sectional area of the blade is sharpened. 
     
     
         28 . An apparatus for making a groove in a heat sensitive material, comprising:
 a blade in accordance with  claim 1 ;   a handheld unit for holding said substantially U-shaped blade;   said blade having at least one section of reduced cross-sectional area to increase its electrical resistance;   a power supply for providing electrical current to said blade; and   said power supply being mounted in said handheld unit.   
     
     
         29 . Apparatus in accordance with  claim 30  having a blade mounting structure, said blade mounting structure including a lower surface below which said blade extends, a stabilizer structure formed at a lower end of said blade mounting structure. 
     
     
         30 . An apparatus in accordance with  claim 29  wherein said stabilizer is comprised of a material having a lower coefficient of friction than the remainder of said blade mounting structure. 
     
     
         31 . An apparatus in accordance with  claim 30  wherein said stabilizer is comprised of polytetrafluoroethylene. 
     
     
         32 . An apparatus for cutting a heat sensitive material using the blade in accordance with  claim 1 , comprising:
 a hand held unit which provides electrical current to a pair of contacts;   a cradle bracket mounted to each of said pair of contacts;   a slotted blade cradle for each of said contacts having a slot for receiving an end portion of said blade;   a clamp for holding said blade in said slot;   a threaded fastener for tightening said clamp against said blade in said slot in said blade cradle; and   a stabilizer mounted laterally of and in front of said slot in said blade cradle.   
     
     
         33 . An apparatus in accordance  claim 32  wherein said stabilizer is comprised of polytetrafluoroethylene.