Compression molding an annular closure shell

A machine for compression molding plastic annular closure shells, which includes:

• a support for rotation around a horizontal axis,
• a plurality of compression molds on said support at angularly spaced positions around said axis,
• each of said molds including a male mold section and a female mold section aligned along an axis perpendicular to said horizontal axis,
• a cam disposed adjacent to said support to move at least one of said mold sections of each mold with respect to the other mold section between a closed position forming a compression mold cavity and an open position spaced from each other,
• said male and female mold sections having associated male and female mold surfaces that generally oppose each other,
• said female mold section including
• a cavity insert at least partially defining said female mold surfaces and having an opening,
• a mold pin extending through said opening and including an interior and a cooling fluid passage in communication with the interior, and
• a spring at least partially disposed in said interior of said mold pin to bias said mold pin toward said male mold section,
• wherein said male and female mold surfaces cooperate to generally define the base wall of the annular closure shell and wherein said mold pin cooperates with said male mold section to generally define the center opening of the annular closure shell,
• such that closure of said male and female mold sections forms an annular mold cavity for receiving and compression molding a mold charge into the annular closure shell having the base wall with the center opening, which at least partially surrounds said mold pin,
• said male mold section including a mold core and a stripper sleeve surrounding said mold core for movement both rotationally and axially of said mold core, a first screw drive coupling said female mold section to said stripper sleeve for rotating said stripper sleeve around said mold core as said at least one mold section is moved between said open and closed positions, and a second screw drive coupling said stripper sleeve to said support to move said stripper sleeve axially over said mold core as said stripper sleeve is rotated around said core, so that said stripper sleeve rotationally and axially removes the annular closure shell molded around said male mold core as said at least one mold section is moved with respect to the other mold section toward said open position.