US1480225A - Electrical cut-out - Google Patents

Description

Jan. 8 1924. 133%0325 H. c. SNOOK ELECTRICAL CUT-OUT Filed Sept. 1921 M AM? Patented Jan- 8, 1924.

v UNITED STATES 1,480,225 PATENT OFFICE.

HOMER CLYDE SNOOK, OF SOUTH ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELEC- TRIO COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OI NEW YORK.

ELECTRICAL cur-our.

Application filed September 8, 1921. Serial No. 499,267.

To all whom it may concern:

Be it known thatI, HOMER CLYDE SNooK, a citizen of the United States, residing at South Orange, in the county of Essex, State of New Jersey, have invented certain new and useful Improvements in Electrical Cut- Outs, of which the following is a full, clear, concise, and exact description.

This invention relates to electrical cutouts, and particularly to-the type of cut-out known as the electrical fuse.

It is customary, in electrical fuses, to surround the fuse conductor with a packing or filling material such as, for example, plaster of paris, sand, asbestos, silicic acid, or other suitable insulating substances which will protect the fuse sheath and nearby sub stances from fire or injury upon the premature or delayed disruption of the fusible conductor. It has been found highly desirable, if not absolutely essential, to pack the filler in a loose and evenly distributed mass about the fuse conductor in order to insure the ready diffusion of the liquid or vaporous metal which is liberated when the fuse blows. The use in electric'fuses of such standard fillers as are mentioned above, no doubt diminishes the probability of fire due to the heating or explosion of the fuse sheath, but because of the-great amount of filler needed to effectively quench the electric are which is formed, it is necessary to resort tothe ineflicient and expensive alternative of employing fuses of large dimensions.

It is an object of this invention to provide an electric fuse which employs a comparatively small amount of insulating filler.

In accordance with its object, the present invention contemplates the use of a filling material adapted to rapidly adsorb the vapors liberated within the fuse casing when the fuse conductor melts or volatilizes. It has been found that silica gel, for example, has the peculiar property of readily adsorbing gases because of the very large surface which it has per unit of volume as compared with other substances, the large surface being in the form of very fine minute ores.

within the volume of the granules o the gel. Silica gel is an inorganic material and adsorbs or gives oflf gases by a reversible process which involves merely the changing of its temperature.

Another object of the invention is to provide a fuse which is extremely sensitive and which will blow quietly and immediately upon exposure for the requisite time to the prescribed overload.

It is a further object of the invention to provide a type of fuse which can be manufactured in commercial quantities with the desired degree of uniformity,

Other objects and features of the invention will appear from a consideration of the following description taken in conjunction with the accompanying drawing and the appended claims.

The drawing shows a longitudinal view, part 1n plan and part in section, of an electrical fuse of the cartridge type embodying the features of the invention. The invention is not limited, however, to this particular type of fuse.

Referring to the drawing, 1 re resents the fuse conductor, of any suitab e material, such as lead, arranged within a cylindrical casing 2, and attached by soldering or other suitable means to the terminal caps 3 at the point i. The threaded extensions 5 of the caps 3 are each provided with a nut 6 as a means for connecting the fuse into an electrical circuit. The fusible wire 1 is surrounded with loose, dry particles of silica gel, shown at 7. The material 7 is a hi hly porous gel of silica which ma be formed b mixing an acid, such as hy rochloric aci with a sodium silicate solution, forming a colloidal solution of silicic acid from which the silicious compound sets to a el. The concentrations of the acid and so ium silicate solution must be carefully determined, and care must be taken in bringin' the two together in order to prevent a rapi coagula tion due to the instability of the mixture.

andwashed free from acid and salt. The

water must be very carefully and slowly removed from the washed gel in order that the finished product'may retain the highly porous structure which is exhibited by the gel while in solution. To accomplish this, the material may be subjected to gradually increasing degrees of heat in order that no sudden change may take place. It is to the arcs forme lid structure that silica gel owes its remarkable propert of adsorption which is not 'dis' played y ordinary silicic acid or other fuse fillers. For the purposes of the present in vention silica gel has been found to be more effective in quenching the electric are formed in the fuse if the granular gel is activated by drying in open air or in a partial vacuum The particles of silica l are full of pores and capable of adsor liing gases rapidly and may serve two general -functions in the sto ping or quenching of electric within the fuse casing. One of these functions is that of the adsorption of the un-ionized or non-conducting metallic vapors surrounding the conducting arc and which have been vaporized from the surface of the fuse conductor by the heat liberated upon the blowing of the fuse. By this adsorption of the un-ionized or non-conduct-- ing metallic vapor there is removed from the area of the conducting stream of the arc metallic vapor which otherwise might furnish material which could be further ionized or rendered conducting and thus assist the conducting are stream to persist. It is possible that the adsorption or absorption of these metallic vapors is materially assisted by the thermal capacity of the gas adsorb-.

ingv material, which in the case of silica gel is extremely high. Another function which this filling material may perform because of its orous nature and the large surfaces which 1t presents to gases or vapors is that of causing charged carriers of opposite signs existing in arc streams to come together and discharge their electric charges, thus rendering the arc stream non-conducting. It is well known that oppositely charged carriers in partially conducting gases combine and are discharged, due to the passage of the gases through porous materials. The use of silica gel as a filling material thus insures prompt blowing at the intended maximum capacity of the fuse, it being impossible for the liberated gases to form with the gel an independent conducting path for the current, as often happens when inefficient or defective fillers are used.

Because of the extremely large-surface in r the form of very finepores in the particles of silica gel as compared to all other fillers heretofore used, it will be evident to those skilled in the art that a much smaller fuse may be used than has heretofore been pos-v and hence eliminating the danger of injury to nearby substances.

It is not intended to limit the invention to the use of a filling material of silica gel, since any other material having highly adsorptive properties may also be used.

, What is claimed is LAn electric fuse having a filling material comprising a gelatinous gas adsorbing material.

2. An electric fuse having a filling materiai consisting of silica gel.

3. An enclosed electric fuse having its fuse conductor surrounded by loose, dry particles of silica gel.

. 4. An enclosed electric fuse of the cartridge type having its fuse conductor surrounded by loose, dry granular silica gel.

5. An electric fuse having its fuse conductor surrounded by loose, dry granular silica gel which has been activated.

In witness whereof, I hereunto,subscribe my name this 6th day ofSept. A. D, 1921.

HOMER CLYDE SNOOK.

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