Tubular fuse component with end caps with a hermetically sealing plastic sealing body insert

• US 20050057337A1
• Filed: 08/24/2004
• Published: 03/17/2005
• Est. Priority Date: 08/25/2003
• Status: Active Grant

• Current Assignee: Wickmann-Werke GmbH (Littelfuse Incorporated)
• Original Assignee: Wickmann-Werke GmbH (Littelfuse Incorporated)
• Inventors: Richter, Ludger, Jollenbeck, Andre, Baus, Andreas
• Granted Patent: US 7,250,843 B2
• Time in Patent Office: Days
• US Class Current: 337/187
• CPC Class Codes: H01H 85/003 casings for the fusible element
• CPC Class Codes: H01H 85/0418 with ferrule type end contacts
• CPC Class Codes: H01H 85/157 Ferrule-end contacts

Abstract

A fuse component (1) has a fusible conductor (2) which extends in a gas filled cavity (3) within a cylindrical tube (4) between two end surfaces (8). Two end caps (5) of an electrically conductive material are applied to the ends of the tube (4) so that an electrical contact is produced with the fusible conductor (2). At at least one of the two ends of the tube (4), a sealing body of a plastic material, which is predominantly elastically compressible but at the same time capable of creep, is introduced into a gap between the base of the end cap and the end surface (8) of the tube (4) and into a portion of the cavity adjacent to the cap base. The sealing body has been compressed between the end surface (8) and the cap base during the manufacture of the fuse component (1) when positioning the end cap (5). The compressed sealing body (7) attempts to expand again, whereby it expands principally into the cavity (3). If a sudden pressure rise occurs in the cavity shortly after its introduction during the manufacturing process as a result of a temperature increase, it can occur that this overpressure balances out into the external surroundings via a temporarily formed passage between the tube, the sealing body and the end cap. The passage which is formed is then sealed again as a result of the ability of the plastic material to creep.

Claims

1. A fuse component, comprising:

a cylindrical tube having a gas filled cavity and two opposite ends each having an end surface;

a fusible conductor extending in said cavity between said two ends;

two end caps consisting of an electrically conductive material and each comprising a cap base, said end caps being applied to the ends of the tube such that a respective electrical contact with the fusible conductor is provided,

wherein a sealing body of a plastic material, which is predominantly elastically compressible but is at the same time capable of plastic flow, is inserted in a gap between the cap base of at least one of the two end caps and the corresponding end surface of the tube and in a portion of the cavity in the tube adjacent to the cap base, said sealing body being compressed between the end surface and the cap base.

2. The fuse component of claim 1, wherein said sealing body consists of a silicone.

3. The fuse component of claim 1, wherein said sealing body consists of a slightly foamed, closed cell silicone.

4. The fuse component of claim 1, wherein the sealing body fills the entire cap base and penetrates into the portion of the cavity in the tube in the manner of a plug.

5. The fuse component of claim 1, wherein the fusible conductor extends diagonally through the cavity in the cylindrical tube and wherein the two ends of the fusible conductor are connected to opposite surfaces of an outer wall of the tube.

6. The fuse component of claim 5, wherein the tube has a cross-section with a substantially circular internal contour and a substantially rectangular external contour.

7. The fuse component of claim 1, wherein the ends of the fusible conductor are mechanically connected and electrically connected to the end cap between an outer wall of the tube and an inner wall of the end cap by means of a solder connection.

8. The fuse component of claim 1, wherein the sealing body is introduced at only one end and that the other end of the tube is hermetically sealed with a pourable, cured plastic material.

9. The fuse component of claim 1, wherein the end caps are retained by an adhesive connection, wherein the adhesive distributes itself in the gaps between the end surfaces of the tube, the surfaces of the sealing body directed towards the end surfaces and the inner walls of the end caps.

10. A method of manufacturing a fuse component, comprising:

(a) introducing a fusible conductor into the interior of a cylindrical tube, wherein both ends of the fusible conductor are passed around end surfaces of the tube onto an outer wall of the tube;

(b) positioning end caps on the ends of the tube with the ends of the fusible conductor passed around the end surfaces and thereby providing an electrical contact between the end caps and the ends of the fusible conductor, wherein a sealing body of a plastic material, which is predominantly elastically compressible and at the same time capable of creep, is inserted between an inner base of at least one of the two end caps and the end surface of the tube directed towards the inner base, wherein the sealing body is compressed when positioning the end cap;

(c) subjecting the fuse component to a heat treatment at temperatures above 150°

C. in order to ensure an electrical contact and/or to mechanically secure the end caps to the tube; and

,

(d) forming a hermetic seal of the interior as a result of creep of the material of the sealing body.

11. The method of claim 10, wherein a respective sealing body matched to the shape of the end caps is introduced into the end caps, before they are positioned.

12. The method of claim 11, wherein the sealing body is introduced into the caps such that the plastic material covers the cap base with a layer whose thickness is 0.5 mm to 2.5 mm.

13. The method of claim 10, wherein, before positioning the end caps, a thermally settable adhesive is applied to the end surfaces of the tube, the amount of adhesive and the nature of the application being so selected that only as small an amount as possible of the adhesive reaches the interior of the tube during the application and the further manufacturing process.

14. The method of claim 13, wherein soldering paste is applied to the outer surfaces of the tube at the positions where the ends of the fusible conductor engage it.

15. The method of claim 14, wherein the caps are heated before they are positioned so that solder connections are produced with the aid of the soldering paste between the ends of the fusible conductor and the end caps and the adhesive is simultaneously at least partially cured.

16. The method of claim 15, wherein the end caps are heated successively, wherein the end caps are heated by positioning two adjacent electrodes on the end surface of a cap and applying electric current to them.