Air-powered ejection system for preform take out plate assembly

Abstract

The take-out device for use with a machine for injection molding plastic articles such as PET preforms has a plurality of cooling tubes that receive hot preforms from the molding machine, carry them to a position remote from the molds of the machine for cooling, and then eject the cooled preforms onto a conveyor or other handling apparatus. The preforms are retained within the cooling tubes by vacuum pressure, but are then ejected by positive air pressure. A retaining plate spaced slightly outwardly beyond the outer ends of the cooling tubes is shiftable into a closed position in which it momentarily blocks ejection of the preforms during the application positive air pressure, yet allows them to be dislodged slightly axially outwardly from the tubes. Such slight dislodging movement is inadequate to vent the air system to atmosphere such that sufficient dislodging air pressure remains in tubes where the preforms might otherwise tend to stick and resist ejection. After the momentary delay, the plate is shifted to an open position in which all of the dislodged preforms are freed to be pushed out of the tubes by the air pressure. Preferably, the retaining plate is provided with specially shaped holes having pass-through portions that become aligned with the tubes when the plate is in its open position, and smaller diameter blocking portions that become aligned with the tubes when the plate is in its closed position. The smaller diameter blocking portions exceed the diameter of the neck of the preforms but are smaller in diameter than the flanges of the preforms such that surface areas around the blocking portions overlie the flanges to block ejection of the preforms as they undergo their dislodging movement.