Patent ID: 6338812
Filing Date: 2002-01-15
Classification: B29C,B29L,H01Q

Abstract:
A method for forming a helical antenna having a helical antenna element covered with an insulating layer, the antenna element and the insulating layer being monolithically moulded, and the antenna element having a base which is supported by a metal fitting, the method comprising the steps of:(a) inserting the antenna element into an cylindrical cavity of an first moulding die, an inner diameter of the cylindrical cavity being equal to or slightly greater than an outer diameter of the antenna element; (b) injecting a first insulating resin into the cylindrical cavity to produce a primary moulded product in which the antenna element is monolithically integrated into the first insulating resin, an injection pressure causing the antenna element to expand outward in an radial direction thereof, and further causing a friction force between the antenna element and an inner surface of the first moulding die so that a pitch of the antenna element is maintained during the moulding operation; (c) putting the primary moulded product in a cavity of a second moulding die so that a prescribed gap is formed between a cylindrical surface of the primary moulded product and an inner surface of the second moulding die; and (d) injecting a second insulating resin into the cavity of the second moulding die so that the cylindrical surface of the primary moulded product is monolithically covered with an insulating layer made of the second insulting resin, whereby the antenna element is completely covered with the monolithically formed insulating layer.