Pin-less drool prevention system

Abstract

A multi-level stacked mold having at least two and as many as four levels of cavities has a stock distribution mold block centred axially of the stacked mold blocks, the axially extending stock inlet passage to the distribution block connecting with radially off-set stock transfer passages that cross the axially openable mold block interfaces, into the adjoining mold blocks. These openable stock transfer passages, are each provided at their respective, non-encapsulated, radially off-set, opening interfaces with a valveless anti-drool arrangement. The mold flow passage system is subject to continual, extreme, thermal cycling and cyclical mechanical loading, during the repeated opening-and-closing cycles of the mold. Each separable anti-drool sealing interface has a relatively axially displaceable portion extending to bridge the initial gap opening between adjacent mold blocks and serving as an expansible piston means. This extension of the displaceable 'expansible piston means' portion is pressure responsive and serves to increase the internal volume of the adjacent transfer passage, while permitting equalizing the pressure of stock in the passage to atmospheric pressure, thus reducing the likelihood of the drooling of liquid plastic into the opening interspace, or the induction of atmospheric air into the flow passages.