Shooting pot with combined valve and piston

A metering device for inclusion in a conduit means, said conduit means providing a single path for advancing precise quantities of a thermoplastic material from a source of said material to a mold cavity via a hot runner system including a nozzle means for delivering said material to said mold cavity, said nozzle means having a valve stem communicating with said mold cavity, said metering device comprising:

• a cylinder means for housing a piston means within said hot runner system, spaced from and independent of said valve stem,
• a piston means within said cylinder means for injecting said material,
• a first reservoir in said cylindrical means for receiving said material,
• said first reservoir having inlet means communicating with said source, via said conduit means, providing entry into said cylindrical means and outlet means providing a connection with said conduit means communicating with said nozzle means,
• means for rotating and means for reciprocating said piston means,
• said piston means being movable in a first direction from a first position wherein said inlet means is open to a second position wherein said inlet means is closed by said piston means to block back flow of said material into said conduit means,
• said piston means being movable further in a second direction to a third position to inject said material from said first reservoir through said outlet means toward said nozzle means whereby said piston means is operable dually to function as a valve and to function as a means for advancing said material.