US3038977A - Fuse holder - Google Patents

Description

June 1962 R. P. ARTHUR ETAL 3,038,977

FUSE HOLDER Filed April 4, 1961 INVENTOR ate r are ea- 3,038,977 FUSE HOLDER Richard P. Arthur, Hinsdale, and Neris J. Simkus, Willow Springs, 111., assignors to international Telephone and Telegraph Corporation, New York, N.Y., a corporation of Maryland Filed Apr. 4, 1961, Ser. No. 169,625 8 Claims. (Cl. 200-433) This invention relates to fuse holders and more particularly to holders for grasshopper fuses.

In the electrical arts, wires or bars of fusing material having a low melting point and suspended between two electrodes through which current flows. If the current exceeds a predetermined amount, this fuse wire or bar melts and opens an electrical circuit, thus terminating the current and removing an applied potential to protect delicate electrical equipment from damage by overload conditions. Usually, a burnedout fuse is immediately apparent because the electrical equipment controlled thereby ceases to function. However, in some equipment it is necessary to provide means for signaling a burned-out fuse alarm because the equipment is not under observation and, therefore, a burned-out fuse is not immediately apparent.

One of the best known devices for signaling a burnedout fuse alarm is the so-called grasshopper fuse wherein the fuse wire or bar holds a leaf spring contact in a retracted position against its spring tension. When the fuse burns out, the wire or bar melts, the spring tension is released, and the leaf spring moves from its retracted to its normal position where an electrical circuit is completed to an alarm device. While the grasshopper fuse and all of its associated circuitry has been used for an extremely long period of time, virtually no improvements have been made in devices for holding them. A result is that the grasshopper fuse holder in current use is, relatively speaking, one of the most expensive components used in telephone switching and other electrical equipment.

Accordingly, an object of this invention is to provide a new and improved fuse holder. More particularly, an object is to provide low cost fuse holders for grasshopper type fuses. Another object of this invention is to provide a low cost fuse holder made by a minimum number of inexpensive, general purpose tools.

In accordance with one aspect of this invention, a fuse holder is fashioned from a unitary bracket of electrical insulating material having a number of cavities formed therein. Each cavity is shaped to receive and support a grasshopper fuse, the orientation of the cavities being such that a number of grasshopper fuses are supported in spaced parallel relation. A pair of electrical contact terminals are positioned in each cavity to provide an electrical circuit through which current flows, and a third electrical contact terminal is positioned in the central part of the cavity to provide a path to an alarm device. In this manner, the electrical current may be directed through the fuse wire which supports the leaf spring and if a fuse burns out the leaf spring makes contact with the third terminal to signal an alarm.

The above mentioned and other features and objects of this invention and the manner of obtaining them will become more apparent and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a perspective View of a grasshopper fuse;

FIG. 2 is a front elevation view showing a fuse holding bracket with one good and one burned-out grasshopper fuse;

FIG. 3 is a side elevation view of the bracket of FIG. 1

with a portion broken away to show the manner of inserting electrical contact terminals;

FIG. 4 is an enlarged view of a single fuse holding cavity showing the details thereof;

PEG. 5 is a sectional view of the cavity taken along line 55 of FIG. 4; and

FIG. 6 is a perspective view of the cavity portion shown in 4.

While the principles of a grasshopper fuse are well known, it may be helpful to review them briefly by referring to FIG. 1 which shows a general configuration of such a fuse. It includes an elongated fiat bar 20 of electrical insulating material which may be stamped out of a sheet of phenolic resin material, for example. As shown in this figure, the right-hand end of the plate 2i) includes a longitudinally extending slot 21 and the lefthand end includes a transversely extending slot 22. Surrounding these slots are terminals 23, 24 of electrically conductive material, which may be sheet metal folded over the end of bar 21') and crimp fastened thereto. A downwardly extending leaf spring member 26 is secured between the bar 20 and the end terminal 24. On the opposite end and side of the bar 20 and somewhat secured between the bar and end terminal 23 is an upwardly extending boom portion 27. The fuse wire 28 is attached in any suitable manner (for example, it may be soldered into position) between the upper boom 27 and the lower leaf spring 26. The length of the fuse wire 28 is such that the leaf spring 26 is raised against its spring tension to a retracted position. When the fuse wire burns out, the lower leaf spring moves under its own spring tension to its normal untensioned position where an alarm condition is indicated.

In accordance with one aspect of this invention, a grasshopper fuse holder includes a unitary bracket 30 made of any good electrical insulating material, such as Bakelite, for example. The bracket is fashioned in any suitable manner (as by molding, for example) into a generally rectangular shape with a series of elongated cavities 31 formed one above the other to provide means for receiving and supporting a number of grasshopper fuses in spaced parallel relation, two of which are shown at 32, 33. As shown in the drawing, there is space in the bracket for receiving and supporting five grasshopper fuses. A dotted line 34 indicates the outer contour of the cavities that would be seen if the bracket 30 were viewed from the back.

Each cavity includes an enlarged central portion a having a pair of communicating, reduced portions 12, b extending therefrom in longitudinally aligned and diametrically opposed relation. The depth 1 of each cavity is approximately the same as the transverse dimension 2 of a grasshopper fuse. Therefore, the overall configuration and dimensions of the cavity including the enlarged central and reduced end portions correspond generally to the overall configuration and dimensions of a grasshopper fuse. Thus, as shown at 32, 33 in FiG. 1, a grasshopper fuse may be inserted sideways into and removed from each of the cavities.

To provide electrical connections between each fuse and associated equipment, a number of electrical contact terminals 35-37 are positioned in each cavity. These contacts may be inserted either into the mold at the time of casting or, at a later time, into openings formed in the bracket. First and second terminals 35, 36 are positioned in each of the reduced portions b, b to make electrical contact between a battery B and a Load via the end terminals 24, 23 of the grasshopper fuse. The third contact terminal 37 is placed in the central portion immediately beneath the leaf spring 26 of a grasshopper fuse when it is inserted into the fuse holder; however, unless the fuse is burned-out, the vertical distance d between the leaf spring and the third electrical contact 37 is such that the spring does not touch the third contact. If the fuse does burn out, the leaf spring 26 moves under its own spring tension and makes contact with the third electrical contact 37. This completes a circuit for signaling an alarm to indicate the burned-out fuse condition. To illustrate this operation a burned-out fuse is shown at 33 where the leaf spring 26 is touching the contact 37'.

To polarize the physical positioning of the grasshopper fuse when it is inserted into the cavity, a boss 40 is formed in one of the recessed openings. As shown in FIG. 1, conventional grasshopper fuses normally have a longitudinally extending slot 21 adjacent one end and a transversely extending slot 22 adjacent the other end. In prior fuse holders the practice has been to provide two bolts or screws, a first of which is loosened to receive the slot 21 which is slipped under the screw head. Then the fuse is rotated in the direction of the arrow (R) so that the transversely extending slot 22 fits beneath the other screw head. Thereafter both screws are tightened. Since the invention contemplates using the same type grasshopper fuse, the boss 40 is advantageously positioned so that only the transversely extending slot 22 may be fitted into reduced portion b of the cavity. In this manner it is impossible to insert the grasshopper fuse in any position except the correct one.

To facilitate gripping the grasshopper fuse while it is being inserted into or removed from the cavity, an edge portion of the cavity is recessed, as shown at 41. Preferably, this recessed portion is positioned near terminal 35 (assuming an electrical connection as shown in FIG. 4) so that any electrically conductive portion of the grasshopper fuse which may be touched while a burned-out fuse is being removed is at ground potential. Therefore, if one uses his fingers to remove a fuse, the danger of shock is substantially reduced. Also, the recessed por tion 41 allows insertion of the jaws of pliers, if they are used to remove the fuse. There is no substantial hazard while the fuse is being inserted because the pushing action eliminates contact with the conductive materials.

An advantage of this invention is that the fuse holder requires only one tool of special design and that is the mold in which the bracket is cast. Once the mold is purchased, the brackets can be mass produced for a few cents. In one specific instance, the International Telephone and Telegraph Corporation found that it had a cost savings of approximately 80% to 85% when it adopted the design shown and described herein. More over, the fuse holder is entirely compatible with existing equipment and does not require scrapping existing parts or replacing non-worn-out parts. Finally, the overall dimensions of the fuse holder are the same as the dimensions of commonly used fuse holders so that they may be replaced quickly and easily. However, when new equipment is designed, the dimensions of fuse holders made according to the teachings of this invention may be reduced to allow some degree of miniaturization.

It is to be understood that the foregoing description of a specific example of the invention is not to be considered as a limitation on its scope.

We claim:

1. A holder for grasshopper fuses comprising a bracket of electrical insulating material having elongated cavities formed therein, a central portion of each cavity being enlarged to receive the central portion of a grasshopper filse and the elongated dimension of each cavity being shaped to receive end terminals of a grasshopper fuse, the depth of each cavity being approximately the same as the transverse dimension of a grasshopper fuse, whereby a fuse is received in and supported by each of the cavities, three electrical contact terminals in each cavity, first and second of said contact terminals being placed in the ends of said cavity to make electrical contact with said fuse when inserted into said cavity, and the third of said contact terminals being placed in said central opening to make contact with said grasshopper fuse when said fuse is burned-out.

2. A holder for grasshopper fuses comprising a unitary bracket of electrical insulating materials having a number of spaced parallel elongated cavities formed therein, each cavity being shaped to receive and support a grasshopper fuse when inserted into said cavity, means including a recessed portion formed on one edge of each of said cavities to facilitate removal of a grasshopper fuse from said cavity, three electrical contact terminals positioned in each of said cavities, first and second of said three contact terminals being placed in the ends of said elongated cavity to make electrical contact with a fuse when said fuse is inserted into said cavity, and the third of said contact terminals being placed in a central portion of said cavity to make contact with a leaf spring on said grasshopper fuse when said fuse is burned-out.

3. The fuse hold-er of claim 2 wherein said recessed portion is positioned near the ground side of said fuse.

4. A holder for grasshopper fuses comprising a unitary molded bracket of electrical insulating material having a number of vertically aligned cavities formed therein, each cavity comprising an enlarged central portion having a pair of communicating reduced portions extending therefrom in longitudinally aligned and diametrically opposed relation, said central portion being shaped to re ceive the central portion of a grasshopper fuse and each of said reduced portions being shaped to receive a corresponding end terminal of said grasshopper fuse when said grasshopper fuse is inserted into said cavity, means including a recessed portion formed on one edge of each of said cavities to facilitate gripping said grasshopper fuse while it is removed from said cavity, three electrical contact terminals positioned in each of said cavities, first and second of said three contact terminals being placed in the ends of said cavity to make electrical contact with terminals on the ends of said fuse when inserted into said cavity, the third of said contact terminals being placed in said central position to make contact with a leaf spring on said grasshopper fuse when said fuse is burned-out, and means for applying ground and battery potentials across said first and second contact terminals, said recessed portion being positioned adjacent to said ground terminal thereby reducing the danger of electrical shock while said fuse is being removed from said opening.

5. A holder for grasshopper fuses comprising a unitary bracket of insulating material having a number of elon gated cavities formed therein, each cavity being shaped to receive and support a grasshopper fuse when inserted sideways into said cavity, means comprising a boss formed in one end of each of said cavities for polarizing the physical position of said grasshopper fuse when it is inserted into said cavity, three electrical contact terminals positioned in each of said cavities, first and second of said three contact terminals being placed in opposite ends of said cavity to make electrical contact with each end of a fuse when said fuse is inserted into said cavity, and the third of said contact terminals being placed in a central portion of said cavity to make contact with leaf spring on said grasshopper fuse when said fuse is burned-out.

6. The fuse holder of claim 5 wherein said boss is positioned to expose the grounded side of the fuse to reduce the hazard of shock.

7. A holder for grasshopper fuses comprising a unitary bracket of insulating material having at least one cavity formed therein, said cavity comprising an enlarged central portion having a pair of communicating reduced portions extending therefrom in longitudinally aligned and diametrically opposed relation, said central portion being shaped to receive the central portion of a grasshopper fuse and each of said reduced portions being shaped to receive a corresponding end terminal of said grasshopper fuse when said fuse is inserted into said cavity, means comprising a boss formed in at least one of said reduced portions for polarizing the physical position of said grasshopper fuse when inserted into said cavity, means including a recessed portion formed on one edge of said cavity to facilitate removal of said grasshopper fuse from said cavity, three electrical contact terminals in said cavity, first and second of said three contact terminals being placed in opposite ends of said cavity to make electrical contact with said end terminals on said fuse When said fuse is inserted into said cavity, and the third of said contact terminals being placed in said central portion to make contact with a leaf spring on said grasshopper fuse when said fuse is burned-out.

8. A grasshopper fuse holder comprising a bracket of insulating material having at least one cavity formed therein, said cavity comprising an enlarged central portion having a pair of communicating reduced portions extending therefrom in longitudinally aligned and diametrically opposed relation, said central portion being shaped to receive the central portion of a grasshopper fuse and each of said reduced portions being shaped to receive a corresponding end terminal of said grasshopper fuse when said grasshopper fuse is inserted into said cavity, means comprising a boss formed in at least one of said reduced portions for polarizing the physical position of said grasshopper fuse when it is inserted into said cavity, means including a recessed portion formed in said cavity to facilitate removal of said grasshopper fuse from said cavity, three electrical contact terminals in said cavity, first and second of said three contact terminals being placed in the ends of said cavity to mate with said fuse terminals when said fuse is inserted into said cavity, means for applying ground and battery potentials across the contact terminals placed in the ends of said cavities, said recessed portion being positioned adjacent to said ground terminal, and the third of said contacts being placed in said central opening to make contact with a leaf spring on said grasshopper fuse when said fuse is burned-out.

References Cited in the file of this patent UNITED STATES PATENTS 761,916 Rorty et al June 7, 1904 819,608 Sherwood May 1, 1906 2,923,796 Davis Feb. 2, 1960

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