| 摘要 |
Valve gated injection molding apparatus for coinjecting and/or sequentially injecting two different fluids through a gate into a cavity. An elongated valve pin member is received in an elongated valve sleeve member in alignment with the gate and both are reciprocated rotatably as well as axially by separate actuating mechanisms to control the flow of the fluids through the gate. Each actuating mechanism has a piston driven rack member to provide rotary motion which is then converted to axial movement of the corresponding valve member between the retracted open and forward closed positions. In one embodiment, helical threads on the valve members engage fixed teeth extending inwardly from the surrounding nozzle to convert the rotary motion of each valve member to corresponding axial movement. Linear position transducers on the rack members provide for accurate control of the valve members. This accurate control and the reduction in force required by these rotary axial actuating mechanisms minimizes wear resulting from repeated seating of the valve members.
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