US2095229A

US2095229A - Tamperproof fuse and method of making same

Info

Publication number: US2095229A
Application number: US64806A
Authority: US
Inventors: Frank H Bussmann
Original assignee: Individual
Current assignee: Individual
Priority date: 1936-02-20
Filing date: 1936-02-20
Publication date: 1937-10-12
Anticipated expiration: 1954-10-12

Description

Oct. 12, 1937. F. H. BussMANN TAMPERYPROOF FUSE AND METHOD OF MAKING SAME Filed Feb. 20, 1936 l 1 f a ATTORNEY.

Patented Oct. l2, 1937 UNITED STATESv PATENT OFFICE TAMPEBPEOOF FUSE AND METHOD F MAKING SAME Frank H. Baumann, Richmond Heights, Mo.

Application February 2 0, 1936, Serial No. 64,806

' 19 claim. (ol. sot-119) Another object of my inventionis to provide a relatively simple fuse structure whose total cost l0 shall not be appreciably larger than most of those now in use and that shall be tamper proof on the inside thereof.

In practicing my invention I provide a hollow body member for a fuse having terminals thereon l and a fuse link therein. I further provide a relatively thin coherent coating of electric insulating material on the external surfaces of all electrically conductive parts inside the hollow body and may also provide a similar coating on the inside surfaces of the hollow body.

In the single sheet of drawings,

Figure 1 is a view in section through a plug fuse of gonve'ntionaldeslgn embodying my invention, an

Fig. 2 is a view in section through La plug fuse of a somewhat different design, also embodying my invention.

Referring first to Fig. 1 of the drawing, I have there illustrated a fuse i I including a hollow body member I3, which is here shown as made of porcelain such as is commonly used in fuses of this general design. although I do not desire to be restricted to this material nor to the exact form of structure shown as the principle embodied in my 'ininvention can be applied equally well to other types of fuses. As is shown in Fig. 1 of the drawing, the body i3 hasa chamber I5 therein in the usual manner.

The body i3 is provided with a centercontact il which may be in the form of a hollow rivet having a recess i9 therein in that end thereof extending in the chamber I5. A screw shell contact 2i is provided around an intermediate portion ofthe body I 3-a11 in a manner well known 1n the art.

A fuse element 23, which may include, in addi- 4 nected with the center contact I1, as by a solder joint I1 in the recess I9.

After the fuse has been assembled thus far, I coat all of the surfaces of the exposed parts of the electric conductive -members inside the body 5 with a relatively thin coating of an electric-in'- su'lating material such as lacquer, varnish, shellac enamel or equivalent substances or materials. I may do this by spraying the electrically insulating material or compound into the interior of the 10' body, taking care that not only substantially all of the surface of the fuse element 23 but also the exposed surfaces of center contact member I 1 and of shell contact member 2i, spring 3i, heat coil 2l and the masses of

solder

29, 36 and 31 are 15 thoroughly -covered by this coating, which coat-A ing is indicated by39. It is obvious that at the same time substantially all of the inner surface of the walls of chamber i5 and of the auxiliary vchamber 33 will also be covered, although this is 20 not essential to my invention if the material of the body I3 is electrically non-conducting. The layer on the inside surface of the body is also indicated by the numeral 39.

The fuse assembly may now be completed by 25 providing a transparent window 4I at the top and a closure cap 43, in a manner now well known in the art. When the enclosure is in place, the electric conductive parts referred to above as exposed are not accessible, but if the closure be 30 removed or destroyed in whole or in part, as might be done for the purpose of tampering with the fuse, these parts become exposed and accessible, and where the expression "exposed" is used in the specification and in the claims, it is to be inter- 35 preted as meaning exposed and accessible when there is an opening into the interior oi' thel fuse body.

While I have specifically mentioned the use of a spraying method to provide the coating as above 40 set forth, I do not desire to be limited thereto, since any other equivalent method effective for the same purpose may beI utilized by me and among which methods may be mentioned dipping and brushing.

Referring now to Fig. 2 of the drawing, I have there illustrated a somewhat similar fuse assembly embodying a hollow body member 45 which as shown consists of electric insulating material, such as porcelain. Here again, however, I do not desire to be limited to the use of this or of any particular material. The body 45 is provided with an internal chamber' 41 and the external Vsurface thereof is adapted to be engaged by and held within a suitable socket member.

supported by the body, a fuse link in the electrically connecting the terminals and a. relatively thin tough coherent electric-insulating coating adhering closely to and covering substantially all the surfaces of all the electricallyconductive parts of the terminals and the link in the body, and to the inner surface of the 'hollow body.

8. A fuse comprising a. hollow body member, terminals supported thereby, a fuse link therein electrically connecting the terminals and' a paintlike covering of an electric-insulating material closely adherent to all electric conducting surfaces exposed in the interior of the body member.

9. The method ofrendering a fuse tamper proof which consists in covering substantially all the exposed surface of the fuse link with a coherent and adherent electric insulating coating. l0. 'Ihe method of rendering tamper proof the inside of an enclosed fuse including electric conductive members in a body member, which consists in applying an electric-insulating material to the exposed surfaces of all electric conductive members within the body to provide substantially allof the area of such exposed surfaces with a relatively thin tough closely adherent protective coating.

11. The method of rendering tamper proof the inside of an enclosed fuse including a hollow body member and electric conductive members therein, which consists in covering the exposed interior surface of the body and the exposed surfaces of the electric conductive members therein with a relatively thin electric-insulating coating closely adherent thereto andv covering substantlally the whole area thereof.

12. 'I'he method of rendering tamper proof the interior of a plug fuse including a hollow body of electric-insulating material, terminals supportedbythebodyandafuseelementlnthe body, which method consists ln applying to the interior surface of the' body and the exposed surfaces of the element and of the terminals on the inside of the body a relatively thin tough electric-insulating` coating closely adherent thereto and covering substantially the entire area 4thereof 13. method rendering tamper proof the interior of a plug fuse which method consists 'inpalntingsubstantiallyallsurfaceareasofall 'intheinsldeofthehueelectrically non-conbody.

ducting by the application thereto of a thin tough closely adherent coating of electric-insulating material.

1,5. The method of rendering a plug fuse tamper prooi on the inside thereof, which method consists in preventing electrical connection between its contact members and electrically conductive material which may be placed inside of the fuse to bridge the contact members thereof by `electrically insulating the surface areasy of substantially all electrically conductive parts in the inside of the fuse.

16. The method of rendering a plug fuse tamper proof on the inside thereof, which method includes insulating by a coating of electric insulating material substantially all electric conducting parts with which electric engagement is necessary to effect bridging the fuse by foreign electric conducting material which may be placed in the inside thereof.

17. The method of rendering a plug fuse tamper proof on the inside thereof, which method includes insulating by a relatively thin tough closely adherent coating of electric insulating materlalthesuriaoeofatleastthoseelectrlccou-l 'the inside of the fuse'.

18. A plug fuse comprising a hollow body member. contact terminals thereon. a fuse link and electrical connections in the body normally maintainlngthemsellnkinseriescircultwlththe contact terminals and an adherent covering of electric insulating material on atleast those portions of the electric conductlngparts which it is necessary to cause to be electrically engaged by foreign electric conducting material to bridge the contact terminals, when such foreign ele'ctric conducting material is placed in the hollow body for the purpose of effecting such bridslns.

19. A plug fuse comprising a hollowbody member, contact terminals thereon, a portion of one ofsaidcontactterminalsboingexposedtothe interior of said bodymember,- a fuse link in the body member, electric connections normally maintaining the fuse link in leri circuit rela tion with the contact terminals and an electric insulating coating on the surface of at least those electric conducting parts ln the body, which, if uninsulated ,and mounted together with the other partsoftheelectricconductingmembersinlike manner in a like hollow body member and engaged by foreign electric conducting material inserted in said like hollow body would cause bridsins of the contact i RANK H. BUBSHANN.