Method for insulating conductors with a crystalline plastic material

Abstract

An extrusion system is provided for covering a conductor (14) with a crystalline thermoplastic elastomer insulating material. The plastic material is tubed onto the conductor by apparatus which includes a core tube (61) that is mounted in an extruder crosshead (41) such that its free end is positioned within the interior of a die (81, 101) and is spaced from an orifice of the die a predetermined percentage of the land length of the die. A flow passage between the core tube (61) and a wall which defines the die cavity is controlled in accordance with the relative value of the thermal energy which is released by the insulating material at the onset of crystallization. In one arrangement, which has been found to be suitable for a crystalline thermoplastic elastomer having a relatively high value of released thermal energy, the die cavity and the core tube are arranged to provide a gradually converging path toward the die opening. For an insulating material having a relatively low value of released thermal energy, the flow passage is modified to provide a diverging portion (105) and then a rapidly converging portion (110) which communicates with the land of the die.

Dependencies are inferred from the claim text.