Replaceable air cylinder unit and valve gate for injection molding machines

A mold assembly for use in an injection molding machine having a pair of relatively movable platens and a means for supplying a moldable material to the mold assembly, the mold assembly comprising:

• a cavity plate defining a cavity adapted to receive the moldable material;
• a manifold interposed between the cavity plate and one of the platens for guiding a flow of the moldable material to the cavity plate;
• a support plate positioned adjacent the manifold and including a rear face into which a cup-shaped recess extends, a front face opposite the rear face, and a bore extending between the from face and the recess;
• a nozzle provided in fluid communication between the manifold and the cavity for directing the flow of material into the cavity;
• a valve gate pin extending into the nozzle and being movable between a forward flow-blocking position and a rearward flow-permitting position;
• an actuating means for moving the valve gate pin between tie flow-blocking and flow-permitting positions, the actuating means including a pneumatic actuator secured within the recess of the support plate, the actuator including a cylinder body presenting a front closed end and a rear open end, a movable piston extending through the closed end of the cylinder body and being connected to the valve gate pin, a cap closing off the open end of the cylinder body, and a fastener for holding the cap and cylinder body together as a unit;
• and
• a removable securing means extending through the actuator for securing the actuator within the recess of the support plate so that the actuator can be inserted into the recess and secured in place or pulled from the recess as an assembled unit.