Method of assembling an antenna and over-molding the same with a thermoplastic material

• US 5,836,072 A
• Filed: 07/27/1995
• Issued: 11/17/1998
• Est. Priority Date: 07/27/1995
• Status: Expired due to Term

• Current Assignee: Centurion Industries Incorporated (Laird Limited)
• Original Assignee: Centurion Industries Incorporated (Laird Limited)
• Inventors: McKeown, Douglas, Sullivan, Jonathan Lee, Wilcox, Glen A., Hayes, William P.
• Primary Examiner(s): Arbes, Carl J.
• Application Number:
  US08/508,176
• Time in Patent Office: 1,209 Days
• Field of Search: 29/600, 29/601, 29/605, 264/272.19, 264/272.15, 343/895
• US Class Current: 29/600
• CPC Class Codes: H01Q 9/30 with feed to end of elongated active element, e.g. unipole H01Q9/44 takes precedence
• CPC Class Codes: Y10T 29/49016 Antenna or wave energy "plumbing" making

Abstract

The method of assembling an antenna and over-molding the same with a thermoplastic material is described which ensures that the elongated rod of the antenna is centrally positioned in its molding material and ensures that the helical spring of the antenna is also centrally positioned in the molding material. A sub-assembly is first created by connecting a helical spring to one end of an elongated metal rod and then inserting a threaded location mandrel in the spring. The assembled sub-assembly is then placed in an injection molding tool and is over-molded with a thermoplastic material. During the initial molding process, the metal rod and helical spring are centered in their respective cavities. The molded sub-assembly is then removed from the injection tool and placed in a second injection tool wherein the interior of the helical spring is filled with a thermoplastic material at the same time as an end cap is created. At the same time, the exposed end of the metal rod is also over-molded.

Claims

1. The method of assembling an antenna and over-molding the same with a thermoplastic material, comprising the steps of:

providing an elongated metal rod, metal fitting and elongated helical metal spring;

said metal rod having first and second ends;

said helical spring having first and second ends;

securing the said metal fitting to said first end of said metal rod;

securing said first end of said spring to said metal fitting to create a first sub-assembly;

placing said first sub-assembly into a first injection molding tool, said first injection molding tool having a first elongated cavity for receiving said metal rod therein and a second cavity for receiving said spring;

introducing a flowable thermoplastic material into said first and second cavities of said first injection molding tool to cover substantially all of said metal rod, to cover said metal fitting, and to cover the exterior of said spring except for said second end thereof;

centering said metal rod in said first elongated cavity during the injection of said thermoplastic material therein;

centering said helical spring in said second cavity during the injection of said thermoplastic material therein;

maintaining the spring pitch distance of said spring during the injection of said thermoplastic material into said second cavity;

allowing the thermoplastic material to cure for a predetermined length of time;

removing the over-molded first sub-assembly from said first injection molding tool;

placing said over-molded first sub-assembly into a second injection molding tool, said second injection molding tool having a first cavity formed therein for receiving the over-molded metal rod, a second cavity formed therein for receiving said over-molded spring, and a third cavity located at said second end of said spring;

and introducing a flowable thermoplastic material into said third cavity to fill the interior of said over-molded spring and to create an end cap for the antenna.

2. The method of claim 1 wherein a location mandrel is inserted into the said second end of said spring to create said first sub-assembly and wherein said location mandrel is removed from said spring during the molding operation in said second injection molding tool.

3. The method of claim 1 wherein a sliding bushing holding device is mounted on said metal rod to centrally position said metal rod in said first cavity as said thermoplastic material is injected into said first cavity.

4. The method of claim 1 wherein said flowable thermoplastic material is inserted into said first cavity to over-mold any exposed portion of said second end of said metal rod.

5. The method of assembling an antenna and over-molding the same with a thermoplastic material, comprising the steps of:

providing an elongated metal rod, metal fitting and elongated helical metal spring;

said metal rod having first and second ends;

said helical spring having first and second ends;

securing the said metal fitting to said first end of said metal rod;

securing said first end of said spring to said metal fitting;

inserting a coil form into the interior of said helical spring to create a first sub-assembly;

placing said first sub-assembly into a first injection molding tool, said first injection molding tool having a first elongated cavity for receiving said metal rod therein and a second cavity for receiving said spring;

introducing a flowable thermoplastic material into said first and second cavities of said first injection molding tool to cover substantially all of said metal rod, to cover said metal fitting, and to cover the exterior of said spring except for said second end thereof;

centering said metal rod in said first elongated cavity during the injection of said thermoplastic material therein;

centering said helical spring in said second cavity during the injection of said thermoplastic material therein;

maintaining the spring pitch distance of said spring during the injection of said thermoplastic material into said second cavity through the use of said coil form;

allowing the thermoplastic material to cure for a predetermined length of time;

removing the over-molded first sub-assembly from said first injection molding tool;

placing said over-molded first sub-assembly into a second injection molding tool, said second injection molding tool having a first cavity formed therein for receiving the over-molded metal rod, a second cavity formed therein for receiving said over-molded spring, and a third cavity located at said second end of said spring;

and introducing a flowable thermoplastic material into said third cavity to create an end cap for the antenna.