Patent ID: 6719263
Filing Date: 2004-04-13
Classification: B29C,F15B,F16K

Abstract:
An actuator for operating a valve gate to supply a flow of plastic melt intermittently into a mold cavity of a mold assembly, said actuator comprising:a) a stationary cylinder bounded by an end cap and a bottom wall; b) a movable cylinder received within the stationary cylinder, the movable cylinder having a generally cylindrical outer wall and generally flat upper and lower end walls, wherein the upper end wall is proximate the end cap of the stationary cylinder, such that an upper chamber is defined by the space between the upper end wall of the movable cylinder and the end cap of the stationary cylinder; c) a stationary piston received within the movable cylinder, thereby defining (i) a first inner chamber between the lower end wall and the stationary piston and (ii) a second inner chamber between the upper end wall and the stationary piston; d) a support post connecting the stationary piston to the end cap of the stationary cylinder; e) a rod attached to the lower end wall of the movable cylinder, the rod having an end portion configured to form a valve pin at a point proximate a gate to the mold cavity; f) a first port communicating with the upper chamber and the first inner chamber; and g) a second port communicating with the second inner chamber, such that admission of pressurized fluid through the first port generates forces acting on both end walls of the movable cylinder, thereby moving the valve pin to shut off flow to the gate, and admission of pressurized fluid through the second port generates a force acting on the upper end wall of the movable piston, thereby moving the valve pin to an open position, allowing flow through the gate and into the mold cavity.