Method of retreading pneumatic tires without a mold

Claim 1

A method of retreading a previously used pneumatic tire comprising: removing worn tread from a previously used pneumatic tire carcass and forming a smooth surface thereon while shaping the smooth surface to have a predetermined contour when the carcass is relaxed and free of any external restraint and pressure, selecting an uncured rubber compound formulated to have a curing temperature substantially the same as that temperature at which shrinkage of the tire carcass occurs and forming the selected rubber compound into a thin strip having a predetermined crosssectional configuration shaped in correlation to the difference between said predetermined contour of said tire carcass smooth surface and a right circular cylindrical surface, severing a length slightly less than the circumference of the tire carcass from a supply of cured rubber tread band having a generally rectangular cross-sectional configuration, a tread design in one face thereof, and a generally planar surface on the face thereof opposing said one face, assembling the severed length of tread band and a length of formed thin strip in encircling relation with the smooth surface of the tire carcass and with the strip interposed between the tire carcass and the planar surface of the tread band so that the uncured rubber of the strip presents large areas for bonding to the previously cured rubber of the carcass and tread band while the tread band and carcass are substantially relaxed transversely and are free of any external restraint and pressure, depositing the assembled tread band, strip and tire carcass in a pressure vessel and subjecting the deposited assembly to elevated temperatures at least about the same as the tire carcass shrinkage temperature while maintaining the tread band and carcass substantially relaxed transversely and free of external restraint and pressure other than the ambient conditions existing within the vessel, and vulcanizing the strip and adhering the tire carcass and tread band together while shrinking the tire carcass to such dimensions that the circumference thereof and the tread band length are substantially the same.

Claim 2

A method of retreading a previously used pneumatic tire comprising: removing worn tread from a previously used pneumatic tire carcass and forming a smooth surface thereon while shaping the smooth surface to have a predetermined contour when the carcass is relaxed and free of any external restraint and pressure, selecting an uncured rubber compound formulated to have a curing temperature substantially the same as that temperature at which shrinkage of the tire carcass occurs and forming the selected rubber compound into a thin strip having a predetermined crosssectional configuration shaped in correlation to the difference between said predetermined contour of said tire carcass smooth surface and a right circular cylindrical surface, severing a length slightly less than the circumference of the tire carcass from a supply of cured rubber tread band having a generally rectangular cross-sectional configuration, a tread design in one face thereof, and a generally planar surface on the face thereof opposing said one face, assembling the severed length of tread band and a length of formed thin strip in encircling relation with the smooth surface of the tire carcass and with the strip interposed between the tire carcass and the planar surface of the tread band so that the uncured rubber of the strip presents large areas for bonding to the previously cured rubber of the carcass and tread band while the tread band and carcass are substantially relaxed transversely and are free of any external restraint and pressure, depositing the assembled tread band, strip and tire carcass in a pressure vessel and subjecting the deposited assembly to elevated temperatures at least about the same as the tire carcass shrinkage temperature while maintaining the tread band and carcass substantially relaxed transversely and free of external restraint and pressure other than the ambient conditions existing within the vessel, and vulcanizing the strip and adhering the tire carcass and tread band together while shrinking the tire carcass to such dimensions that the circumference thereof and the tread band length are substantially the same.