Curing apparatus for retreading system

Claim 1

Apparatus for bonding a pre-cured strip of retread stock to the periphery of a tire casing, said apparatus comprising: at least one annular-shaped member defining a curing chamber for receiving the tire casing to be processed with the strip of retread stock extending around the periphery of the tire casing and in a position spaced radially inwardly from the inner peripheral surface of the chamber with the sides of the casing engaging the walls of the chamber to form a seal for the annular space between the strip and the inner peripheral surface of the annular-shaped member; an inner rim member for engaging the beads of the tire casing positioned within said annular-shaped member to hold the beads with a predetermined axial spacing and to provide an enclosed chamber within the tire casing; a valve including a central elongated cylindrical section and first and second cylindrical end sections, an elongated spool reciprocally slidable in the central elongated cylindrical section and connected to a first piston in said first cylindrical end section and to a second piston in said second cylindrical end section, said central elongated section having a central port therein and second and third ports displaced on either side of the central port, and said spool having a central section shaped to provide a path between the central port and the first port when the spool moves in one direction, and to provide a path between the central port and the second port when the spool moves in the opposite direction; a first pipeline extending from said central port through said inner rim member for introducing a first pressurized fluid into the interior of said tire casing when said spool moves in one direction, and for exhausting the first pressurized fluid from the interior of said tire casing when said spool moves in the opposite direction; a second pipeline extending through said annular-shaped member for introducing a second pressurized fluid at a relatively high temperature into the annular space between the tire and the inner peripheral surface of the annular-shaped member; a source of the first pressurized fluid coupled to the second port; an exhaust line coupled to the third port; a third pipeline extending through the annular-shaped member and coupled to the interior of the first cylindrical end section to introduce the second pressurized fluid from said annular space to one side of the first piston; and a fourth pipeline extending through said inner rim member and coupled to the interior of the second cylindrical end section to introduce the first pressurized fluid from the interior of said tire casing to one side of the second piston, thereby to cause the valve to couple the first pipeline to the source of first pressurized fluid when the pressure of the first pressurized fluid in the tire casing falls below the pressure of the second pressurized fluid in the annular space, and to cause the valve to couple the first pipeline to the exhaust line when the pressure of the first pressurized fluid in the tire casing rises above the pressure of the second pressurized fluid in the annular space, for maintaining a predetermined pressure differential between said first pressurized fluid in the interior of the tire casing and said second pressurized fluid in the annular space.