Plastic article or earthenware shaping or treating: apparatus – With mechanical means forming or expanding pores
Patent
1991-02-08
1993-08-10
Woo, Jay H.
Plastic article or earthenware shaping or treating: apparatus
With mechanical means forming or expanding pores
264 50, 264174, 425114, 425200, 425205, 425208, B28B 150
Patent
active
052343243
ABSTRACT:
The present invention provides an extruder for highly foamed plastic material for coating a central conductor of a coaxial insulated cable with an insulator made of a mixture of a plastic material, preferably polyethylene, and an inert gas, such as nitrogen gas, to serve as a foaming agent. An inert gas is introduced approximately halfway down the extruder through a lead-in portion. At the lead-in portion of the extruder is a vent portion wherein the screw is provided with a plurality of stirring blades extending radially from the screw toward the inner surface of the extruder. These stirring blades provide a mechanism by which the inert gas is mixed thoroughly into the plastic material. The above invention provides an apparatus for producing an insulating material in which an inert gas (such as nitrogen), rather than hydrocarbon chloride fluoride, is used as a foaming agent, thus avoiding potential harm to the ozone layer.
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Davis Robert B.
Sumitomo Electric Industries Ltd.
Woo Jay H.
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