Abstract: A retreading envelope is made by extruding a split tube of rubber which is passed over a rotating stretching wheel to stretch the split tube to a predetermined shape. The stretched split tube is removed from the stretching wheel after moving around a part of the circumference thereof and is turned inside out and placed on a table whereat it is formed and cut into an annular shape preparatory to completion of the retreading envelope.

Abstract: This invention relates to an improvement in the construction of retreading envelopes and to an extrusion apparatus for producing same.The envelopes commonly used in bonding new treads to tire casings are generally uniform in thickness, and, as a result, no provision is made for those areas of the envelope which receive the greatest stress.By utilizing an envelope of U-shaped cross section and one whose thickness is significantly increased in areas of greatest stress, the prior art impediments are effectively overcome.