System for individual control of multiple valve gates

In an injection molding machine, an apparatus for separately controlling the movement of two or more valve pins wherein each valve pin is driven by a separate fluid driven cylinder, each separate cylinder being mounted on a heated manifold and being interconnected to a separate valve pin for effecting reciprocal movement of the valve pin wherein the reciprocal movement of the valve pin controls the flow of molten plastic being delivered through a nozzle which delivers molten plastic to a gate of a mold, the apparatus comprising:

• a fluid distributor housing having a fluid flow channel which commonly delivers a drive fluid to each of the cylinders, each of the cylinders having a piston slidably mounted within a bore of an enclosed cylinder housing for reciprocal fluid driven movement of the piston within the bore of the cylinder housing;
• each cylinder having a first and a second fluid input port to the bore of each cylinder housing, the first and second fluid input ports being selectively connectable to the fluid flow channel of the fluid distributor housing;
• a drive fluid switch associated with each cylinder, each switch having a drive fluid flow connector and a drive fluid seal, the connector of each switch being connectable to one of the first and second fluid input ports of each cylinder while the seal of each switch is simultaneously operative to act on the other of the first and second fluid input ports of each cylinder.