Importance

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Abstract

Apparatus for forming a tread pattern on a retread tire casing includes a plurality of rigid matrix segments each having a contoured tread pattern thereon. Each matrix segment is removably secured to a respective matrix segment holder. Each matrix segment holder includes guide blocks at the ends thereof, and the matrix segments are arranged in circumferential side-by-side relation. Guide shafts extend through aligned guide bores in adjacent guide blocks of adjacent matrix segment holders for guiding movement of matrix segment between a closed position wherein the matrix segments are in side-by-side abutting relation, and an open position wherein adjacent matrix segments are separated. A spring is received over each end of each guide shaft and captured between a recessed shoulder in the guide block and a threaded nut received over the end of the guide shaft. The springs normally bias the matrix segment into the closed position. In a first embodiment, diverging legs of inverted V-shaped cams extend into diverging bores in adjacent guide blocks for separating the adjacent matrix segments. Outward radial movement of the cams forces the matrix segments apart from the closed position to the open position for receiving a built-up tire casing therein. The compression springs thereafter forcibly return the matrix segments to the closed position wherein the contoured surfaces of the matrix segments are urged against the built up layer of uncured rubber. In a second embodiment, slotted plates extend across adjacent guide blocks for separating the matrix segments.

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First Claim