Apparatus for forming a curing envelope

摘要

An apparatus for forming curing envelopes which apparatus enables the use of a conventional inner tube mold for making a curing envelope preform in the form of an envelope tube which may have a portion thereof easily removed to provide a curing envelope suitable for use in a tire retreading process. A curing envelope is made by placing an annular tube of uncured envelope material in a curing mold having a center core and a mold insert installed therein. The insert includes a pair of coaxial annular rings projecting radially outwardly from the center core and connecting straps for maintaining the axial spacing between the rings. The mold is closed and heat and internal pressure are applied to the envelope tube for curing the envelope tube and urging the tube against the interior cavity surface with the annular rings penetrating into the inner wall of the tube for forming therein corresponding annular grooves. The mold is then opened and the envelope tube is removed from the mold after which the envelope tube is severed along the annular grooves to remove the portion of the inner wall of the envelope tube between the grooves thereby to form a curing envelope of generally U-shape cross-section.