US1644626A

US1644626A - Electric fuse

Info

Publication number: US1644626A
Application number: US162201A
Authority: US
Inventors: Barklie Robert Henry Douglas
Original assignee: Individual
Current assignee: Individual
Priority date: 1925-10-05
Filing date: 1927-01-19
Publication date: 1927-10-04
Anticipated expiration: 1944-10-04
Also published as: GB265263A

Description

oct. 4,1927. 1,644,626

I R. H. D. BARKLIE ELECTRIC FUSE Filed Jan. 19,4927

' 1mg-f E. j?. arivzw Patented Oct. 4, 1927.

UNITED STATES ROBERT HENRY DOUGLAS BARKLIE, OF PURLEY, ENGLAND.

ELECTRIC FUSE.

Application filed January 19, 1927, Serial No.

This invention consists in improvements in or relating to electric fuses capable of being operated by very small currents such7 for example, as currents of milliamperes and less. i

According to the present invention an electric fuse comprises a film of metal supported on an insulating backing, the thickness of the film being substantially not greater than one ve-,thousandths of an inch.

The invention further comprises an electric fuse comprisinga film of metal which is so thin that it is not self-supporting for the purpose required and which is mounted on an insulating backing such, for instance,

as paper.

The metal film may be prepared in any one of many ways and examples of some o f the methods Aof manufacturing fuses according to the invention will now be described.

In the accompanying drawing the view illustrates one form of holder or mounting for the fuse ofthis invention.v

In its simplest `form arflm .of metal may be `obtained by the known process of beat* y ing as practised in the gold-beaters art. For instance, a gold film may be beaten uni til it is of a thickness that Will obtain when one-thousand square inches of the metal film has a mass of one gramme i. e. thickness is approximately three millionths of an inch. A sheet of paper is coated with gum and the gold film prepared as above is laid on the paper. The composite sheet thus formed is dried and for this. purpose it may be left Qin Vanoven ata temperature of 110 C. for

approximately twelve hours.

The sheet may be then out into strips of required size. It is found that a sheet having a metal film 2 cms. long and 0.11 cms. 1in width will carry a current of 30 milliamperes and `will fuse at approximately milliamperes. Experiments have shown that ,avfuse having the same length but a Awidth cih-0.2 cms-will carry a current `of 60 milliamperes and will fuse at 80 milliamperes. Thus, fuses according tothe inventionwill carryrcurrents the value of which is roughly in proportion tothe Width of the The lengthofthe filmmay be small say, for example, 0.2cms. andfinvorderto make fuses which will vcarry heavier currents,

162,201, and in Great Britain October 5,1925.

several films of metal may be superimposed on the one paper backing so that they are employed m parallel; or several fuse lengths as above described may be y employed in parallel as will be. readily understood. Other metals such as silver and copper can be employed and can be reduced in thickness toV the .required extent by beating; butiof course they will not have identical fusing qualities with those of gold.

It may be therefore said that the inven- `tion comprises an electric fuse which consists of a metal film supported on an insulating backing. the. thickness of the film being less than that which can be obtained lby rolling las films having a thickness of `the order above specified cannot be obtained by known commercial processes for rolling metal foil.

According to another method of preparing the fuse a thin layer of `metal is electrolytically deposited on onesurface of a soluble cathode. For instance, .gold can be deposited on silver. Thereafter the .cathode istreated with a solvent that will dissolve the cathode without attacking the metal film.

In the specific case mentioned the silver. elec trode can be removed by nitricacid of strength. This may be eected by first depositing the gold on a thin strip of silver which is fioated on the solvent. vAfter the silver has been dissolved the gold will be left floating on the surface of the `solvent yand the gold can then be ldrawn out on the surface of a sheet of glass or Celluloid. Alternatively silver can be deposited on an electrode of aluminium and the latter then be dissolved in caustic soda to leave a film of silver floating on the solvent. y

The upper surface of the ,gold or other metal film can be readily Washed while it is von the glass or celluloid surface `from which it has been removed from the solvent. In order to wash the undersurface, the temporarysupport (the glass or celluloid sheet) is dipped into a bath of water atsuchean angle that .although .the Vsupport is im* mersed thegoldpor .metralfilm will float off on vto the surface ofthe water which ,will thereby wash the underside thereof. The metal film can be removed from the Washing Water and be re-Washed in a similar manner as many times as may be foundnecessary and finally itis Washed similarly in alcohol.

The metal film can then be pulled or lifted from the alcohol washing bath on to a film of paper or other insulating material that is prepared in such a manner that when dried the metal film will adhere closely thereto.

LAccording to a further method of preparing fuses in accordance with the present invention, the metal is applied to an insulating backing in a finely divided condition. For instance it may be sprayed under preslsure by well known processes and thereafter consolidated and rendered homogeneous by mechanical treatment such rolling. The metal may be otherwise applied to the in.- sulating backing in a finely divided condition and'subsequently rend-ered homogeneous by rolling. Such methods are particularly suitable in the case of metals such as tin, lead', or tin-lead alloys.

Another method consists in sputtering or flashing metal in a finely divided condition by an ionization process such as a positive ray discharge in vacuo. It is thought unnecessary to describe such processes in detail as they are already-well known and are used, for example, (for other purposes) in flashing a metal such as magnesium in the final treatment'for the evacuation of thermionic tubes. f

A still further ymethod consists in boiling a mass of themetal from which the fuse is to be formed in an electric furnace such as a high frequency induction current furnace. The boiling metal vapour may be conducted on to the surface of an insulating backing and be condensed thereon so as to afford a film of the thickness desired.

As another alternative method a thin lilm of silver may be deposited on to the insulating backing from a silver compound (such as an ammoniacal solution of silver nitrate) by a chemical reducing agent (such as formaldehyde) as in the known art of forming silver mirrors.

When an'electrolytic method of depositing themetal film is resorted tov as described above a. fine deposit can be obtained and the thickness of the film can be reduced consideral processes given above are examples onlyr of the rvarious methods by which the invention can be carried into effect.

A convenient method of mounting fuses made in accordance with this invention comprises a clip-having two jaws or gripping l velements 2.

elements spring pressed towards one another or clamped by means of a screw or other equivalentineans. @ne element is of metal and the other is of rubber or some other compressible material so that the. fuse is gripped by the metal element against the rubberelenient with the former incontact with the metal film constituting the fuse.

.Referring now to the drawing, the above referred to mounting is illustrated in the fig ure and wherein the thin fuse layer of `metal is indicated at l. The fuse strip l at each end is held between metal elements or jaws 2 and 3 between which is interposed a strip of rubber 4, the strip fi having a portion lying between the metal element 3 and the insulating backing of the fuse strip l. The metal layer l of the fuse is thus held at each end in contact with the metal element 2.

Each pair of metal elements 2 and 3, to-.

' or other insulating tube which hold the end caps andthe elements 2 and 3 therein in spaced apart and insulating relation. The parts 2, 3 and t fit tightly within the ends of the insulatingtube 6, so that the fuse strip l will be gripped firmly between the parts at each end and provide a good electrical contact between the strip l and the In assembling the fuse structure, one pair of metal 'elements 2 and 3, and the rubber or like compressible strip 4, 'may be secured within an end cap 5. lOne end of the stripl may then be gripped between Vthe parts 2 and 4; and the assembly inserted within one end of the tube 6. -From the other end of the tube, the metal element A2 and the rubber strip 4; are then inserted so as to retain the end of `the 'fuse strip l between them. Finally, the metal element 3 is forced into the end of the tube and the enel cap 5 fitted over the parts.

F or establishing electrical connection with the fuse, the' tubularfuse assembly may be held betweenthe contact springs 7 which are mountedV in the insulating base 8 provided with binding'posts and nuts y9 for making electrical connection Vbetween the springs 7 and the terminals of an external electric circuit. `V

I claim gl. Armeth'od of manufacturing an electrie fuse "which consists in electrically depositing metal on to a soluble electrode so Vthat the thickness of the metal is substantially not greater'than that of commercially 'beaten gold, dissolving the electrode from the deposited metal and thereafter floating the metal iilm on to an insulating backing and removing the solvent from the composite sheet thus formed.

2. A method of manufacturing an electric fuse which consists in electrically depositing metal on to a soluble electrode so that the thickness of the metal is substantially not greater than that of commercially beaten gold, dissolving the electrode from the deposited metal2 floating the metal-film on a substantially rigid support and removing it thereby from the electrolyte, and thereafter, as often as may be required, immersing the support in a Washing liquid in sucli a manner that the film floats ofi' on to the Washing liquid so that its underside is Washed clear of electrolyte and subsequently floating the film on to al permanent insulating backing.

3. A method of manufacturing an elec-` tric fuse which consists in depositing metal on to a soluble support, thereafter dissolving said support and recovering the metal film on a backing.

4. A method of manufacturing an electric fuse which consists in depositing metal on to a support by a process whereby the thickness of the deposited metal film gradually grows, removing said metal film on to 4the surface of a liquid and subsequently recovering the film from the liquid on to a backm0'.

n testimony whereof I affix my signature.

ROBERT HENRY DOUGLAS BARKLIE.