Patent ID: 8162647

Claim:
A blowing agent introduction system comprising: an accumulator having an inlet connectable to a source of blowing agent and an outlet connectable to a blowing agent port of an extruder; an inlet shut-off valve associated with the inlet of the accumulator, wherein the inlet shut-off valve has an open configuration that permits blowing agent flow therethrough and a closed configuration that prevents blowing agent flow therethrough; a pressure regulating device designed to control the pressure of blowing agent delivered to the accumulator when the inlet shut-off valve is in the open configuration; a pressure measuring device constructed and arranged to measure pressure of blowing agent in the accumulator; an outlet shut-off valve associated with the outlet of the accumulator, wherein the outlet shut-off valve has an open configuration that permits blowing agent flow therethrough and a closed configuration that prevents blowing agent flow therethrough; and a control system capable of receiving a first input signal from the pressure measuring device representative of the pressure of blowing agent in the accumulator and sending a first output signal to open the outlet shut-off valve to permit the introduction of blowing agent from the accumulator into polymeric material in the extruder.