Method and apparatus for forming a wheel nut with welded cap

Claim 1

The method of forming a wheel nut having polygonal wrench flats, a conical wheel engaging end, and a stainless steel sheath which covers the wrench flats and the end of the nut opposite to the conical end and terminates adjacent the joinder between the wrench flats and the conical end, comprising: bringing a first electrode into pressured contact with the conical nut end; bringing a second electrode into pressured contact with a section of the sheath directly overlying the nut to exert forces between the sheath and the nut in the area adjacent to that contacted by the second electrode; and passing an electric pulse having a duration of less than 30 microseconds and a peak current in excess of 50,000 amperes, between said first and second electrodes, to form a weld between the contacting surfaces of the sheath and the nut at said areas adjacent to the section contacted by the second electrode without deleterious metallurgical changes occurring in the surface of the sheath contacted by said second electrode.

Claim 2

The method of forming a wheel nut having polygonal wrench flats, a conical wheel engaging end, and a stainless steel sheath which covers the wrench flats and the end of the nut opposite to the conical end and terminates adjacent the joinder between the wrench flats and the conical end, comprising: bringing a first electrode into pressured contact with the conical nut end; bringing a second electrode into pressured contact with a section of the sheath directly overlying the nut to exert forces between the sheath and the nut in the area adjacent to that contacted by the second electrode; and passing an electric pulse having a duration of less than 30 microseconds and a peak current in excess of 50,000 amperes, between said first and second electrodes, to form a weld between the contacting surfaces of the sheath and the nut at said areas adjacent to the section contacted by the second electrode without deleterious metallurgical changes occurring in the surface of the sheath contacted by said second electrode.

Claim 9

The method of forming a capped wheel nut having a nut body formed with polygonal wrench flats, a conical wheel engaging end, and a planar end opposite to said conical end, and a sheath formed of 10-25, or a similar composition of stainless steel, the sheath covering the wrench flats and said planar end of the nut body, and terminating adjacent to the joinder between the wrench flats and the conical end, said sheath being provided with shoulder means which contacts a portion of said planar end, said method comprising: bringing a first electrode into pressured contact with the conical end of the nut; bringing a second electrode into pressured contact with the sheath to impose a force between the contacting surfaces of the sheath at said shoulder means only and said planar end portion; charging a capacitance; connecting said capacitance to the first and second electrodes, and discharging said capacitance to pass an electrical current pulse through the sheath and nut body, and welding the sheath to the nut body at said contacting surfaces of said shoulder means and said planar end portion without welding the remaining contacting surfaces of the sheath and nut body and without causing substantial discoloration of the surface of the sheath contacted by the second electrode, or carbon migration in the sheath which may result in later oxidization.

Claim 10

The method of forming a capped wheel nut having a nut body formed with polygonal wrench flats, a conical wheel engaging end, and a planar end opposite to said conical end, and a sheath formed of 10-25, or a similar composition of stainless steel, the sheath covering the wrench flats and said planar end of the nut body, and terminating adjacent to the joinder between the wrench flats and the conical end, said sheath being provided with shoulder means which contacts a portion of said planar end, said method comprising: bringing a first electrode into pressured contact with the conical end of the nut; bringing a second electrode into pressured contact with the sheath to impose a force between the contacting surfaces of the sheath at said shoulder means only and said planar end portion; charging a capacitance; connecting said capacitance to the first and second electrodes, and discharging said capacitance to pass an electrical current pulse through the sheath and nut body, and welding the sheath to the nut body at said contacting surfaces of said shoulder means and said planar end portion without welding the remaining contacting surfaces of the sheath and nut body and without causing substantial discoloration of the surface of the sheath contacted by the second electrode, or carbon migration in the sheath which may result in later oxidization.