Valve gate cylinder and housing with microgap seal

Abstract

An injection molding arrangement including a mold top clamp plate having a means for receiving a plasticizer unit, a manifold retainer plate supporting a melt distribution manifold having a melt distribution channel into which melt from the plasticizer unit is received, a mold cavity plate provided such that the manifold retainer plate is positioned between the mold top clamp plate and the mold cavity plate; the mold cavity plate receiving an injection nozzle in fluid communication with the melt distribution channel for receiving melt to be injected into a mold, a valve gate stem extending into the injection nozzle and axially movable between an open position permitting melt flow and a closed position blocking melt flow, and an actuator for moving the valve gate stem between the open position and the closed position. The actuator includes a cylinder chamber receiving a piston therein, with the valve gate stem coupled to the piston. The piston has an elongate cylindrical sidewall. The cylinder chamber and the piston are sized and otherwise dimensioned to provide a microgap seal along the uninterrupted elongate cylindrical sidewall between an upper chamber of the cylinder chamber and a lower chamber of the cylinder chamber.