The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 10, 1993
Filed:
Feb. 08, 1991
Saburo Kawabata, Kanagawa, JP;
Sumitomo Electric Industries, Ltd., Osaka, JP;
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.