Heat treatment of helical springs or similarly shaped articles by electric resistance heating

An apparatus for selectively resistance heat treating a plurality of diverse elongated workpieces, each one of the plurality of diverse elongated workpieces having an opposing ends at an angle to an axial length of the one of the plurality of diverse elongated workpieces, the apparatus comprising:

• a plurality of alternative pairs of end insert contacts, an appropriate one of the plurality of alternative pairs of end insert contacts provided for a diverse one of the plurality of diverse elongated workpieces, each one of the plurality of alternative pairs of end insert contacts formed from a solid electrically conductive material and having a seating notch, each one of the plurality of alternative pairs of end insert contacts spaced apart from each other so that the opposing ends of each one of the plurality of diverse elongated workpieces can be at least partially inserted in the seating notches of an appropriate one of the plurality of alternative pairs of end insert contacts, the seating notches in at least one of the plurality of alternative pairs of end insert contacts having an appropriate cross sectional shape different from a cross sectional shape of the seating notches in at least one other of the plurality of alternative pairs of end insert contacts to accommodate the plurality of diverse elongated workpieces;
• a first and a second spaced apart opposing plates, a first end insert contact of each one of the alternative pairs of end insert contacts mounted on the first spaced apart opposing plate, and a second end insert contact of each one of the plurality of alternative pairs of end insert contacts mounted on the second spaced apart opposing plate;
• a drive for rotating the first and the second spaced apart opposing plates to alternatively position the first and the second end insert contacts of each one of the plurality of alternative pairs of end insert contacts at a diverse elongated workpiece insertion and removal station;
• and
• an electric power source for a supply of a current to the first and the second end insert contacts of the one of the plurality of alternative pairs of end insert contacts alternatively positioned at the diverse elongated workpiece insertion and removal station to heat by Joule heating the first and second end insert contacts of the one of the plurality of alternative pairs of end insert contacts alternatively positioned at the diverse elongated workpiece insertion and removal station when the opposing ends of the diverse one of the plurality of diverse elongated workpieces are at least partially inserted into the seating notches of the one of the plurality of alternative pairs of end insert contacts alternatively positioned at the diverse elongated workpiece insertion and removal station.

An electric resistance heat treatment apparatus for a coil spring having a circular cross sectional opposing ends disposed at an angle to an axial length of the coil spring, the electric resistance heat treatment apparatus comprising:

• a pair of cylindrically shaped end insert contacts, each one of the pair of cylindrically shaped end insert contacts formed from a solid electrically conductive material and having a seating notch at least partially semicircular in cross section, the pair of cylindrically shaped end insert contacts spaced apart from each other so that the circular cross sectional opposing ends of the coil spring can be at least partially inserted in the seating notches of the pair of cylindrically shaped end insert contacts;
• an electric power source for a supply of an electric current to the pair of cylindrically shaped end insert contacts;
• an electrical conductor for connection of each one of the pair of cylindrically shaped end insert contacts to the electric power source to heat by Joule heating each one of the pair of cylindrically shaped end insert contacts to approximately a heat treatment temperature when the circular cross sectional opposing ends of the coil spring are at least partially inserted in the seating notches of the pair of cylindrically shaped end insert contacts;
• and
• an end clamp for at least one of the pair of cylindrically shaped end insert contacts, the end clamp applying a compression force against an exposed surface area of the one of the opposing ends of the coil spring at least partially inserted into the seating notch to force an outer perimeter surface area of the at least partially inserted one of the opposing ends of the coil spring against an interior surface area of the seating notch during the supply of the electric current from the electric power source.