Fuse assembly having a non-sagging suspended fuse link

• US 4,635,023 A
• Filed: 05/22/1985
• Issued: 01/06/1987
• Est. Priority Date: 05/22/1985
• Status: Expired due to Fees

• Current Assignee: Littelfuse Incorporated
• Original Assignee: Littelfuse Incorporated
• Inventors: Oh, Seibang
• Primary Examiner(s): Broome, Harold
• Application Number:
  US06/736,181
• Time in Patent Office: 594 Days
• Field of Search: 337/163, 337/164, 337/165, 337/166, 337/160, 337/264, 337/255, 337/198, 337/295, 337/296, 337/297
• US Class Current: 337/163
• CPC Class Codes: H01H 85/0417 with parallel side contacts
• CPC Class Codes: H01H 85/055 Fusible members

Abstract

A fuse assembly has a fuse link extending suspended in a housing between a pair of terminal extensions, which the fuse link interconnects electrically. A fuse blowing current-reducing material like tin is carried on the fuse link and spaced from and on opposite sides of the hot spot of the fuse link where the fuse is expected to blow.

Claims

1. In a fuse assembly for interrupting a current flowing therethrough upon certain high current conditions, said assembly including:

a housing made of electrically insulating material and having a space therein;

a conductive fuse-forming element secured in said housing including a pair of terminals that are adapted to be connected into a circuit; and

a fuse link connected between said terminals and suspended in said space without support between end portions thereof so that it can sag against the housing walls when softened below the blowing temperature, and said link having a hot spot portion along its length at which said link is expected to blow under said high current conditions as a result of high temperature effected melting caused by said high current condition in said link, the improvement wherein said link includes fuse blowing current-reducing material spaced from and on opposite sides of said hot spot portion of the fuse link in the region of the fuse where sagging is expected, the spacing of said material being such as to inhibit the softening and sagging tendency of the unsupported portions of the fuse link prior to the desired blowing thereof

4. The fuse assembly or fuse link of claim 1, 2 or 3 in which said fuse blowing current-reducing material is equally spaced on opposite sides of said hot-spot portion.

5. The fuse assembly or fuse link of claim 1, 2 or 3 in which said link has a pair of openings therein on opposite sides of said hot spot portion and said fuse blowing current-reducing material is in the form of a pair of plugs installed in said openings.

8. The fuse assembly or fuse link of claim 4 in which said link is relatively wide and has an aperture formed therein at said hot spot portion suddenly to reduce the cross section of the link thereat.

10. The fuse assembly or fuse link of claim 1, 2, or 3 in which said fuse blowing current-reducing material is tin and the fuse link material is a zinc alloy.

12. The fuse assembly or fuse link of claim 1, 2 or 3 wherein at least said fuse link is planar and has a width in its plane that is many times its thickness.

13. The fuse assembly of claim 1, 2 or 3 wherein said link has a non-circular cross section wherein the longest dimension thereof is many times the thickness thereof, and further wherein the fuse is to be ultimately mounted with an orientation where gravity acts in the direction of the thin dimension thereof.

15. The fuse assembly or fuse link of claim 1, 2 or 3 wherein said fuse blowing current-reducing material is substantially within the central one third of the fuse link.

2. In a plug-in fuse assembly for interrupting a current flowing therethrough upon certain high current conditions, said assembly including:

a housing made of electrically insulating material and having an inner space open to one side thereof and having relatively closely spaced side walls defining cavities forming a fuse link-receiving chamber and relatively narrow passages on opposite sides of said chamber; and

a conductive plug-in fuse-forming element having a pair of confronting, spaced terminal blade portions respectively projecting from said housing through said open side, a pair of extensions of said terminal blade portions in said passages and a fuse link in said chamber suspended in said chamber between said extensions and spaced from said side walls to electrically interconnect the pair of extensions and their related projecting terminal blade portions, said link being adapted to carry said current flow from one terminal blade portion and its related extension to the other terminal blade portion and its related extension, and said link having a hot spot portion along its length at which said fuse link is expected to blow under certain high current conditions as a result of high temperature effected melting of the fuse link material caused by said certain high current conditions in said fuse link, wherein the improvement comprises said fuse link including fuse blowing current-reducing material spaced from and on opposite sides of said hot spot portion of the fuse link in the region of the fuse where sagging is expected, the spacing of said material being such as to inhibit the softening and sagging tendency of the unsupported portions of the fuse link prior to the desired blowing thereof.

14. The fuse assembly of claim 2 wherein said plug-in fuse element is a thin planar plate-like body, and said fuse link has a non-circular cross section where the width thereof is many times the shortest dimension or thickness thereof and said longest dimension thereof is in a plane parallel of said element.

3. A fuse link to be suspended between a spaced apart pair of extensions of terminals that are to be connected in a current carrying circuit to electrically interconnect said terminals and extensions and said fuse link further being adapted to be suspended in a chamber of a housing that is made of electrically insulating material with the fuse link spaced from walls of said housing, said fuse link comprising:

a link of fuse metal having a hot spot portion along its length at which said link is expected to blow under certain high temperature conditions as a result of high current conditions flowing through said link, and

fuse blowing current-reducing material on said link and spaced from and on opposite sides of the hot spot portion of said link, the spacing of said material being such as to inhibit the softening and sagging tendency of the unsupported portions of the fuse link prior to the desired blowing thereof.

7. The fuse link of claim 3 in which said link has a length greater than the distance between the ends thereof.

9. The fuse link of claim 3 in which said link is "S" shaped and in a plane parallel to said housing side walls.

11. The fuse link of claim 3 wherein said hot spot portion is in the center of said fuse link and said fuse blowing current-reducing material is located only in the central portions of said fuse link.

6. The fuse assembly or fuse link of claim in which said plugs have heads overlapping said link to fasten the plugs in the openings.