Patent ID: 7341640
Filing Date: 2008-03-11
Classification: B29C,B29D,B29K

Abstract:
1. A method of forming an un-vulcanized rubber strip comprising the steps of: obtaining an extruder, the extruder including a casing, a screw shaft disposed within the casing, a head region connected to a downstream end portion of the casing and a die connected to a downstream end portion of the head region; a temperature of each of the casing, the screw shaft and the head region being independently controllable; the die having a plurality of axially collinear and axially connected cavities extending therethrough, including first, second and third cavities, where the first cavity communicates with the downstream end portion of the head region, the second cavity is downstream of the first cavity and the third cavity is downstream of the second cavity; the third cavity having an opening profile in which thickness of the opening profile is progressively reduced from approximately the centerline of the cavity to opposing edges of the opening profile; continuously extruding the rubber through said extruder to form a rubber strip; the step of continuously extruding the rubber further comprising: controlling the temperature of each of the casing, the screw shaft and the head region so that: the temperature of the casing is higher than that in the screw shaft; and the temperature of the head region is higher than that in the casing; and wherein the rubber strip extruded from the die has a profile shape conforming to the opening profile of the third cavity.