Abstract: A centering arrangement for controlling relative movement between a series of mold support plates in a stack mold having three or more levels. The centering arrangement uses a plurality of centering devices which are substantially identical, each spanning two mold levels and being connected to three adjacent mold support plates. Each centering device has a shaft generally parallel to an axis of the mold and having an intermediate portion journalled in an intermediate connector to allow rotational movement about a shaft axis, but to restrain relative axial movement between the shaft and the intermediate connector. Helical splines extend from the intermediate portion toward opposite ends of the shaft in oppositely twisting helices. End connectors having cooperating splines engage the splined portions of the shaft and connect the centering device to the outermost of the mold plates to which it is connected.

Abstract: A method and apparatus for distributing melt through three level stack molds. According to the method a crossover manifold is provided between adjacent mold levels of the stack mold, the crossover manifold having a plenum generally coaxial with a mold axis. Melt is introduced into the plenum through an inlet passage and distributed from the plenum to respective nozzle arrays through a separate outlet conduit associated with each mold level. The apparatus includes a crossover manifold mounted between first and second mold levels and having a plenum generally coaxial with the mold axis. An inlet conduit fluidly communicates with the plenum and an injection head to provide a melt path from the injection head into the plenum. A separate outlet conduit is provided for each mold level.