COAXIAL CABLE AND METHOD OF MAKING SAME

• US 20020053446A1
• Filed: 02/14/2000
• Published: 05/09/2002
• Est. Priority Date: 08/14/1997
• Status: Active Grant

• Current Assignee: CommScope Inc. (CommScope Holding Company, Inc.)
• Original Assignee: Alan N. Moe, Bruce J. Carlson, Ronald Vaccaro, Scott M. Adams
• Inventors: MOE, ALAN N., ADAMS, SCOTT M., CARLSON, BRUCE J., VACCARO, RONALD
• Granted Patent: US 6,800,809 B2
• Time in Patent Office: Days
• US Class Current: 174/21C
• CPC Class Codes: H01B 11/1804 Construction of the space inside the hollow inner conductor
• CPC Class Codes: H01B 11/1826 Co-axial cables with at least one longitudinal lapped tape-conductor
• CPC Class Codes: H01B 11/1839 of cellular structure
• CPC Class Codes: H01B 13/016 for manufacturing co-axial cables applying discontinuous insulation H01B13/20

Abstract

A flexible low loss coaxial cable comprises a cylindrical plastic rod, an inner conductor surrounding the plastic rod, a dielectric layer surrounding the inner conductor, and a tubular metallic sheath closely surrounding the dielectric layer. The coaxial cable can further include a protective polymer jacket surrounding the sheath. The cylindrical plastic rod supports the inner conductor in bending and can be formed around a central structural member. The present invention also includes a method of making flexible coaxial cable.

Claims

1. A coaxial cable comprising a plastic rod, a longitudinally-applied inner conductor surrounding said plastic rod, a foam polymer dielectric layer surrounding the inner conductor, and a tubular metallic outer sheath closely surrounding the foam polymer dielectric layer.

2. The coaxial cable of claim 1 wherein said metallic sheath has a diameter of more than 1.0 inches (2 5 cm).

3. The coaxial cable of claim 1 or 2 wherein the ratio of the thickness of the metallic sheath to the cuter diameter of the metallic sheath is no greater than 1.0 percent.

4. The coaxial cable of any of the preceding claims wherein said inner conductor is adhesively bonded to the plastic rod.

5. The coaxial cable of any of the preceding claims further comprising a central structural member within said cylindrical plastic rod such that said central structural member supports said rod.

6. The coaxial cable of claim 5 wherein said central structural member comprises a reinforced plastic material or a metallic material.

7. The coaxial cable of any of the preceding claims wherein said plastic rod is a closed cell foam plastic rod.

8. The coaxial cable according to any of the preceding claims further comprising a solid dielectric between said foam polymer dielectric layer and said sheath.

9. The coaxial cable according to any of claims 1-7 wherein the density of said foam polymer dielectric layer increases radially from said inner conductor to said sheath.

10. The coaxial cable according to claim 1 wherein said plastic rod is cylindrical, said inner conductor is copper and adhesively bonded to said plastic rod, said foam polymer layer is adhesively bonded to said inner conductor, and said smooth-walled tubular metallic outer sheath is copper, said coaxial cable further comprising a protective polymer jacket surrounding said outer sheath and adhesively bonded thereto.

11. A method of making a coaxial cable comprising the steps of:

advancing a plastic rod along a predetermined path of travel;

longitudinally applying an inner conductor onto the plastic rod encircling the plastic rod;

extruding a foamable polymer composition onto the inner conductor to form a cable core; and

forming a tubular metallic outer sheath onto the cable core and encircling the cable core.

12. The method according to claim 11 wherein said step of extruding a foamable polymer composition onto the inner conductor to form a cable core comprises coextruding a foamable polymer composition in surrounding relation to the inner conductor, a solid polymer composition in surrounding relation to the foamable polymer composition, and an adhesive composition in surrounding relation to the solid polymer composition.

13. The method according to any of claims 11-12 wherein said step of extruding a foamable polymer composition onto the inner conductor to form a cable core comprises:

advancing the plastic rod and the inner conductor surrounding the rod into and through an extruder and extruding onto the inner conductor a foamable polymer composition; and

causing the extruded polymer composition to foam and expand to form a cable core comprised of an expanded foam dielectric layer surrounding the advancing inner conductor.

14. The method according to any of claims 11-13 wherein further comprising the step of adhesively bonding the inner conductor to the plastic rod.

15. The method according to any of claims 11-14 further comprising, prior to said step of advancing a cylindrical plastic rod, the step of extruding a polymer composition onto a central structural member to form a cylindrical plastic rod.

16. The method according to any of claims 11-15 wherein said step of advancing a cylindrical plastic rod comprises advancing a closed cell foam plastic rod.

17. The method according to any of claims 11-16 wherein said step of longitudinally applying an inner conductor onto the plastic rod encircling the plastic rod comprise directing a metal strip around the plastic rod.

18. The method according to claim 11 wherein said advancing step comprises advancing a cylindrical plastic rod along a predetermined path of travel;

said longitudinally applying step comprises advancing and forming an inner conductive tube loosely encircling the plastic rod, sinking the inner conductive tube onto the plastic rod, and adhesively bonding the inner conductive tube to the plastic rod;

said extruding step comprises extruding an adhesive composition around the inner conductive tube and extruding a foamable polymer composition onto the adhesive composition surrounding the inner conductive tube to form a cable core; and

said forming step comprises forming a tubular metallic outer sheath loosely encircling the cable core and sinking the sheath onto the cable core to cause compression of the cable core to form a coaxial cable;

said method further comprising the steps of forming a protective polymer jacket around the sheath and adhesively bonding the jacket to the sheath.