Patent ID: 6926507

Claim:
A system for injecting a blowing agent into polymeric material within a barrel of a polymer processing apparatus, wherein the polymer processing apparatus includes a screw mounted in the barrel and designed to reciprocate from an accumulation position, in which the screw plasticates polymeric material that accumulates downstream of the screw, and an injection position, in which the screw does not plasticate polymeric material and the accumulated polymeric material is injected through an outlet of the barrel, the system comprising: a conduit having an inlet connectable to a source of blowing agent and an outlet connectable to a port in the barrel to provide a pathway through which blowing agent flows from the source to the polymeric material within the barrel; and a flow controlling system including a bypassing passageway fluidly connected to the conduit at a position between the inlet and the outlet, the flow controlling system designed to selectively direct blowing agent flowing from the source to the polymeric material within the barrel through the bypassing passageway when the screw is in the injection position.