US 5,458,843 A · 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.

Claims23

Dependent claims

The method of feeding a pressurized flow of plastic within a mold located in the mold space of a molding machine, said mold comprising a multi-level stacked mold having at least two levels of mold cavities in mutually stacked relation within axially separable mold blocks, comprising the steps of:

providing an internal flow passage within the mold located in radially off-set relation from the main axis of the mold, and extending through at least a portion of each of two separable adjoining mold blocks, including providing a sealing interface to said passage at the juncture of said mold blocks the flow passage having a first mold block portion and relatively axially movable second mold block portion;
a first displaceable portion of said passage extending from one said mold block portion into abutting, sealing interface relation with a second portion of said passage located in the other said mold block portion to form said passage sealing interface at said juncture;
applying to said displaceable passage portion, with said mold in a closed condition, a limited resilient compressive force sufficient to seal said passage interface in a leak-free condition;
said limited compressive force applying a correspondingly limited force to said mold, to leave said mold in a substantially undeformed condition;
passing molten plastic under pressure through said flow passage and past said passage interface to said mold cavities when in the closed condition;
terminating the flow of said plastic through said passage;
relieving the pressure of said plastic;
and
axially opening said passage interface upon the equalization of said plastic pressure to that of atmosphere.

6 more elements

A method of operating a mold having a separable feed connector radially spaced from the mold main axis and opening to the air substantially simultaneously therewith, said feed connector feeding fluent thermoplastic feed stock to the mold when in a closed condition, including the steps of:

providing a separable connection to the feed connector having a first connector portion, a second connector portion located in aligned relation adjacent said first portion, an axially movable third connector portion secured in sealed feed stock flow conducting relation with one of said connector portions, and resilient loading means to apply a limited load against said portion in use to connect said third portion in compressed relation with the other one of said connector portions in sealed, feed stock conducting relation therewith;
limiting said loading means to limit the loading moment applied by said third portion in deforming relation across the face of said mold;
opening the mold;
simultaneously displacing said first connector portion in gap increasing relation from said second portion;
and
displacing said third portion in gap bridging relation, to maintain said feed connector in instantaneous stock containing relation with said other connector portion while increasing the available internal flow volume of a portion of said stock feed flow path, whereby the feed stock therein is effectively depressurized while said gap is bridged, prior to the opening of said gap to the air.

3 more elements

Dependencies are inferred from the claim text.

Pin-less drool prevention system

Life of this patent

Pin-less drool prevention system

Life of this patent

Abstract

Claims23