WO1999007032A1

WO1999007032A1 - Process for manufacturing a helix antenna

Info

Publication number: WO1999007032A1
Application number: PCT/DE1998/002188
Authority: WO
Inventors: Reinhold Heiss; Edgar Jochheim; Heiner Thomfohrde; Josef Gleixner
Original assignee: Siemens Aktiengesellschaft
Priority date: 1997-07-31
Filing date: 1998-07-30
Publication date: 1999-02-11

Abstract

A process for manufacturing a helix antenna in a simple manner is characterised by the following steps: 1. an injection-moulded preform (1) made of a metallisable plastic material and consisting essentially of a cylindrical core (4) joined to an antenna foot (5) is injection-moulded with trapezoidal threads (6, 7) protruding around the circumference of the core; 2. a non-metallisable plastic material is injected into the gaps between the threads (6, 7); 3. the metallisable outer surfaces are galvanised; 4. a plastic material that acts as a protective cap (10) is injection-moulded around the region of the threads (6, 7).

Description

Method of making a helix antenna

The present invention relates to a method for producing a helix antenna.

Helix antennas are known and are e.g. applied to wireless communication terminals. Known helix antennas are generally produced by mechanically applying a wire winding to an insulating core and then placing a protective cap over it, with a connection between the wire winding forming the actual antenna and an antenna connection base also having to be established. The production of such a helix antenna is relatively complex and expensive for a mass article.

The object of the present invention is to provide a method of the type mentioned at the outset, which can be carried out easily by machine and causes low costs.

This object is achieved for a method of the above type in that in a first step in an injection molding process, a pre-molded part made of a metallizable plastic is injection molded, which essentially consists of a cylindrical core, at one end of which an antenna base is formed, and above which Extend trapezoidal threads that in a second step, the spaces between the threads are sprayed with a non-metallizable plastic, that in a third step, the metallizable surfaces of the intermediate molding produced in the second step are galvanized, and that in a fourth step, the area with the threads of the intermediate molding are overmolded with a plastic serving as a protective cap. In the method according to the invention, the disadvantages of mechanical wire winding and the associated compromises in terms of producibility are eliminated. Due to the shaping by injection molding, every winding shape, adapted to the ideal theoretical design, can be realized and thereby the antenna performance can be optimized. Since the shaping is done exclusively by injection molding, the manufacturing costs for an antenna can be more than halved compared to the previous manufacturing costs.

An advantageous further development of the method according to the invention is characterized in that the pre-molded part is injection molded with threads which have different pitches. By providing threads with different pitches, i.e. Antenna windings with different increases, the antenna can be further optimized in terms of performance. The mechanical application of a wire winding with different increases has so far not been possible cost-effectively in mass production.

The process according to the invention is described in more detail below with reference to the description of the intermediate products shown in the drawing and the end product.

Show it

FIG. 1 shows the perspective view of a preform,

Figure 2 is a perspective view of an intermediate molding, and

Figure 3 is a perspective and partially sectioned view of the finished product.

First, in a first step, a pre-molded part 1 is produced in an injection molding process. The preform 1 is made essentially of a cylindrical core 4, with an antenna base 5 adjoining one end of the core 4. Trapezoidal threads 6, 7, which are connected to the antenna base 5, rise on the cylindrical core 4. These threads can have different pitches depending on the requirements for the high-frequency properties of the helix antenna to be manufactured. In the example shown here, the threads 6 have a high pitch, while the threads 7 at the free end of the cylindrical core 4 have only a slight pitch. This preform 1 is injection molded from a metallizable plastic, for example a metallizable polyamide.

In a second step of the method according to the invention, the spaces between the individual threads 6 and 7 are covered with a metallizable plastic, e.g. a metallizable polyamide, sprayed out, of course gaps are left in the antenna base 5, i.e. not be sprayed out. That In the intermediate molding 2 thus produced, the surface of the actual antenna part consists of two different materials, namely one made of a non-metallizable plastic and one made of a metallizable plastic. The surface parts made of metallizable plastic correspond to the outer surfaces of the threads 6 and 7. The entire surface of the antenna base 5 of the intermediate molding 2 still consists of a metallizable plastic.

In a third step, the intermediate molding is now galvanized, whereby only the metallizable surface parts of the intermediate molding can be galvanized, i.e. the entire antenna base 5 and the outer surfaces of the threads 6 and 7.

The metal layer applied to the outer surfaces of the threads 6 and 7 is in accordance with the invention Process manufactured helix antenna represents the actual antenna wire.

It can be seen that by changing the injection mold for the preform 1, the threads can be adapted to any requirement.

In a fourth and final step, the antenna area of the intermediate molding 2 is overmolded with a plastic 10.

This plastic 10 also serves as a protective cap for the helix antenna. Depending on the desired mechanical requirements for the helix antenna, the intermediate molding can be molded with a soft or a hard plastic as protection. For example, a thermoplastic elastomer can be used for extrusion coating.

Claims

claims

1. A method for producing a helix antenna, characterized in that in a first step in an injection molding process, a pre-molded part (1) is injected from a metallizable plastic, which consists essentially of a cylindrical core (4), at one end of which Antenna foot (5) is formed, and over the circumference trapezoidal threads (6, 7) rise that in a second step, the spaces between the threads (6, 7) are sprayed with a non-metallizable plastic, that in a third step metallizable surfaces of the intermediate molding (2) produced in the second step are galvanized, and that in a fourth step the area with the threads (6, 7) of the intermediate molding (2) is extrusion-coated with a plastic serving as a protective cap (10).

2. The method according to claim 1, characterized in that the pre-molded part (1) is injected with threads (6, 7) which have different pitches.