US3368047A - Fuse having a sand core - Google Patents

Description

Feb. 6, 1968 c. MOCLURE, JR 3,368,047

FUSE HAVING A SAND coma Filed June 19, 1967 INVENTOR Charles Mc Clure,Jr.

ATTORNEY United States Patent 3,368,047 FUSE HAVING A SAND CORE Charles McClure, Jr., Mercer, Pa., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Continuation-impart of application Ser. No. 435,423,

Feb. 26, 1965. This application June 19, 1967, Ser.

Claims. (Cl. 200120) ABSTRACT OF THE DISCLQSURE This application is a continuation-in-part of copending application Ser. No. 435,423, filed Feb. 26, 1965, now abandoned.

Description of the prior art It is old in the art to make a current limiting fuse by Winding a series of turns of a silver fuse element on a center mandrel or core composed of ceramic or other suitable material, and placing the core and fuse element in a tube which is filled with a special sand. The sand provides an arc quenching action, and also provides some space for temporarily storing the gas produced by the arc.

I have discovered that improved performance can be obtained by also making the center mandrel or core of sand, so that the mandrel or core also contributes to the space available for gas storage.

Summary of the invention According to one embodiment of my invention, I make the mandrel out of sand by pressing it in a mold with a suitable binder and then baking it to eliminate volatile material. The shape of the core or mandrel is cylindrical or ribbed or spiral as desired, according to different embodiments of the invention.

Accordingly, a primary object of my invention is to provide a new and improved fuse offering advantages over any now existing in the art.

Another object is to provide a new and improved fuse having a sand core.

A further object is to provide a new and improved core for a fuse composed of bound sand and rigid enough to wind a fuse element upon, but which will be blown apart, freeing the sand therein, by the energy of the are when the fuse blows.

These and other objects will become more fully apparent after a study of the following specification, when read in connection with the accompanying drawings, in which:

Brief description of the drawings FIGURE 1 is a view partially in cross-section of a fuse constructed according to one embodiment of my invention;

FIG. 2 is a view of the core and fuse element of FIG. 1, showing the core and fuse element in greater detail;

FIG. 3 is a view showing a core and fuse element according to a second embodiment of my invention; and

FIG. 4 is a view showing a core and fuse element according to a third embodiment of my invention.

3,368,47 Patented Feb. 6, 1968 Description of the preferred embodiments Particular reference is made now to FIG. 1, in which the reference numeral 10 generally designates the fuse.

The ferrules 11 and 12 composed of conductive material are mounted on and close the ends of a fuse tube 13 composed of insulating material. Each ferrule has an inwardly extending annular cap for enclosing the end of the mandrel or core 15, the cap of ferrule 11 being shown at 14. The cap 14 may be formed integrally with the remainder of the ferrule 11 and is preferably coaxially disposed therein. The sand core 15 has one end 16 thereof disposed in the cap 14, and has a spiral wound fuse element 17 disposed thereon, with the end of the fuse element 17 being soldered at 18 to the cap 14. The generally cylindrical space 19 between the outer wall of the sand core 15 and the inner Wall of the fuse 13 is filled with sand especially selected for its arc quenching action and for its porosity to provide some space for temporarily storing the gas produced by an arc when the fuse element 17 is melted in response to an overcurrent condition therein and the electrical circuit interrupted.

The manner of attaching the end of the mandrel or core .15 to the ferrule 11 does not constitute part of the instant invention. The core 15 may be attached to the ferrule by utilizing the exterior surface of the core as shown in FIG. 1, which is the preferable method, or the core 15 could, if desired, be attached to the ferrule by drilling into the core or forming the core with a central bore in the end thereof, and utilizing a bolt, pin or stud, mounted in the ferrule and extending into the end of the core or mandrel, somewhat similar to the mounting arrangement shown, for example, in Patent No. 2,523,139, for Fuse issued Sept. 19, 1950 to J. B. Owens, and assigned to the assignee of the instant invention.

Particular reference is made now to FIG. 2, which shows the core 15 and fusible element 17 in somewhat greater detail. The fusible element 17 is seen to be wound on the core with sufficient spacing between turns to provide electrical insulation, and also to provide some mechanical strength if desired and support for the core. The spacing between turns of the embodiment of FIG. 2 may vary according to the method of construction used.

In binding the porous sand of the core or mandrel together, I have found that an epoxy resin makes a suitable binder material. A suitable epoxy resin is one of the Bisphenol-epichlorohydrin type; an example of this is one known in the trade as Shell Epon 828. The epoxy resin is mixed thoroughly with the sand to assure a firm mandrel or core when cured. The amount of epoxy resin is regulated closely to assure that the porosity or density of the mandrel or core is not reduced. A satisfactory proportion between sand and epoxy resin is 200 parts by weight of sand to 1 part by weight of epoxy resin.

After the sand with the added epoxy resin binder which may include an added catalyst is placed in the mandrel or core mold, it is baked to cure the resin binder. The manufacturers recommended time and temperature may be followed. A suitable temperature is C. and a suitable time is 2 hours for the epoxy resin mentioned here inbefore.

If desired, the cure time, as well as the shelf life of the epoxy-sand mixture can be varied by using a selected type of catalyst with the epoxy. Suitable types of catalysts are: diethylene triamine and triethylene tetramine.

A core or mandrel so constructed according to the above teachings is sulficiently rigid so that the fuse element may be tightly wound thereon in a manner which will hold the turns thereof properly spaced; at the same time the sand of the core is so loosely bound by the epoxy resin that energy generated by the are when the fuse blows loosens and frees the sand of the core, so that the space .2 within the sand of the core becomes available for gas storage, and the sand of the core assists the other sand in the fuse tube in extinguishing the arc.

Particular reference is made now to FIG. 3, where a core 25 as seen in cross-section is generally cruciform, and as seen in perspective comprises four generally rectangular support portions disposed at spaced angular intervals of 90 around the longitudinal axis of the core with flat support surfaces extending generally parallel to the longitudinal axis of the core, supporting surfaces 26, 27, 28 and 29 having the turns of a fuse element 30 wound thereon.

Particular reference is made now to FIG. 4. The core or mandrel 45 is seen to be generally spiral in shape, with alternate ridge portions 46 and alternate trough portions 47, and a spiral fuse element 48.

By way of further summary, in constructing my fuse I make the core or mandrel out of sand by placing a mixture of sand and a suitable binder material or bonding agent aforedescribed with or without a catalyst in a mold, and then baking the mixture to eliminate volatile material. This method is suitable for constructing cores according to the embodiments of FIGS. 2, 3 and 4.

The drawings and the aforegoing written description are exemplary and illustrative only and are not to be interpreted in a limiting sense.

I claim as my invention:

1. A fuse comprising, in combination, a normally rigid breakable porous core composed of sand and a binder material, ferrules disposed at the ends of the core respectivcly, a fuse element wound on the sand core and making electrical connection with the ferrules at both ends thereof, a fuse tube composed of nonconductive material enclosing the core and the space thereabout, and additional sand filling the space between the inner Wall of the fuse tube and the core, the sand of the core being freed and loosened by energy generated by the arc when the fuse blows, the sand within the fuse tube and the freed sand of the core assisting in quenching the are created when the fuse element is melted and the electrical circuit therethrough broken, the freed sand of the core and the sand Within the fuse tube both providing space for temporarily storing gases generated by the are when the circuit is interrupted.

2. A fuse according to claim 1 in which the core is additionally characterized as being generally cylindrical in shape.

3. A fuse according to claim 1 in which the core is characterized as being substantially cruciform in cross section.

4. A fuse according to claim 1 in which the core maintains the turns of the fuse element in predetermined spaced relationship with respect to each other until the fuse blows.

5. A fuse according to claim 1 in which the binder material includes an epoxy resin.

6. A fuse according to claim 5 in which the epoxy resin is of the bisphenol-epichlorohydrin type.

7. A fuse according to claim 5 in Which the sand and epoxy resin are proportioned substantially 200 parts by weight of sand to 1 part by weight of epoxy resin.

8. A fuse according to claim 5 including in addition a catalyst added to the epoxy resin to control the cure time.

9. A fuse according to claim 8 in which the catalyst is diethylene triamine.

10. A fuse according to claim 8 in which the catalyst is triethylene tetramine.

References Cited UNITED STATES PATENTS 1,545,550 7/1925 Coates 200- 2,157,907 5/1939 Lohausen 200120 2,315,320 3/1943 Earle 2001 15 2,768,264 10/1956 Jones et al. 200-444 2,917,605 12/1959 Fahnoe 200-114 2,961,514 11/ 1960 Lindell 200-120 3,166,656 1/1965 Hollmann et al 200120 3,196,521 7/1965 Hollmann et a1. 29155.5

FOREIGN PATENTS 20,483 7/1903 Great Britain. 577,805 5/ 1946 Great Britain.

BERNARD A. GILHEANY, Primary Examiner.

H. B. GILSON, Assistant Examiner.

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