Telescopic rod antenna and method for manufacturing the same

A telescopic rod antenna comprising:

• an antenna element including a plurality of rods slidably coupled to each other, the plurality of rods having different diameters and each being formed of a conductive tube member;
• a holding spring which is fixed to a distal end portion of a smaller-diameter rod of the antenna element and part of which is pressed on an inner surface of a larger-diameter rod, the holding spring serving as a rod coupling element;
• a top portion provided at a tip portion of a smallest-diameter rod of the antenna element, and including both a short cylinder member, which is fitted to the outer periphery of a small-diameter portion formed in advance at the tip portion of the smallest-diameter rod and a stopper member inserted and fixed into an open end of a hollow of the short cylinder member such that the open end is sealed at the tip portion of the smallest-portion rod;
• and
• a ring-shaped seal member provided in a ring-shaped gap in a joint between the smaller-diameter rod having the holding spring at the distal end portion thereof and the larger-diameter rod, for preventing water from soaking into the rods from the outside,
• wherein the ring-shaped seal member is obtained by shaping a thermoplastic resin film strip like a ring, the film strip having at least one projecting portion along a longitudinal direction thereof, and compressing and inserting the ring-shaped film into the ring-shaped gap, adhering a plurality of ring-shaped contact portions, formed along a longitudinal direction on both sides of the ring-shaped film, to an inner surface of the larger-diameter rod and an outer surface of the smaller-diameter rod at a predetermined pressure while the projecting portion of the film strip serves as a basic contact portion, and fluid-tightly sealing a gap between the outer surface of the smaller-diameter rod and the inner surface of the larger-diameter rod.

A method for manufacturing a telescopic rod antenna, comprising:

• a step of obtaining a thermoplastic resin film strip having a preset measurement, on which at least one projecting portion is formed along a longitudinal direction of the film strip;
• a step of shaping the film strip like a ring and inserting the ring-shaped film into a larger-diameter rod from an opening at a distal end portion thereof;
• a step of inserting a smaller-diameter rod, to which a holding spring serving as a rod coupling element is fixed at a distal end portion thereof, into the larger-diameter rod from the opening of the distal end portion of the larger-diameter rod;
• and
• a step of pulling the smaller-diameter rod out of an opening at a tip portion of the larger-diameter rod and compressing the film strip in a ring-shaped gap in a joint between the smaller-diameter rod and the larger-diameter rod in an axial direction of the rods;
• wherein the film strip is curved in a width direction thereof in a plurality of regions into which the film strip is divided by the projecting portion, both end portions of the film strip are brought into contact with each other, and a plurality of ring-shaped contact portions, which are formed among a longitudinal direction on both sides of the film strip, are adhered to an inner surface of the larger-diameter rod and an outer surface of the smaller-diameter rod at a predetermined pressure while the projecting portion serves as a basic contact portion.