US2446739A - Repeating electric fuse - Google Patents

Description

A 10,1948. J, BRYAN 2,446,739

REPEATING ELECTRIC FUSE Filed Oct. 24, 1947 INVENTOR. John 14 dr'yan A for/rays I Patented Aug, 10, 1948 UNITED sTATEs PATENT OFFICE REPEATING ELECTRIC FUSE John W. Bryan, Traphill, N. C.

Application October 24, 1947, Serial No. 781,862

1 Claim. (01. 200-426) This invention relates generally to improvements in thermal circuit breaking devices in which any desired number of fuse elements may be connected in successive order into a protected circuit without the attention of an attendant.

One of the objects of the invention is to provide an arrangement in which an electrical circuit is broken wherever a pulse of current therein exceeds a predetermined value.

Another object is to provide means for successivelyand automatically connecting into the circuit a new fuse element whenever the preceding element has been burned out.

A further object is the provision of a repeating fuse structure which is inexpensive, easy to manufacture and which is adapted to convenient replacement of inexpensive fuse elements already expended.

Further objects and advantages will be apparent from the description and accompanying drawings, in which:

Figure 1 is a plan view of the repeating electrical fuse.

Figure 2 is a side elevation of the fuse of Figure 1.

Figure 3 is a cross-section of the central portion of the fuse taken along line 3-4 of Figure l.

Figure 4 is anenlarged view of a fuse element suitable for use with the structure of Figure 1.

The repeating fuse is conveniently constructed on a base I I of insulating material but from sheet stock or molded to the desired form. A pair of metallic discs 12 are fastened to the sides, respectively, of the base H by means of a bolt I4 passing through the center of the base, and secured by the nut i5. Electrically and mechanically connected to the discs 12 are a suitable number of studs l6 which project slightly, from the discs and are preferably provided with notches or heads to receive and hold in place a wire loop [9 of a fuse element IS. The loops I! are of sufiicient size to slip over the heads of the studs thus facilitating installation or removal of the fuse elements. The fuse element is constructed of material having electrical and mechanical characteristics selected to burn out at a predetermined current load. The loops is are formed from the fusible material of the fuse element itself thus reducing cost of manufacture and assuring uniformity.

Terminal studs I! are preferably secured to the base by a punching or pressing operation, which also secures one end, respectively, of the contact springs 20 to the base in fixed orientation thereto. The studs Il may be provided with square shanks or keys for the purpose of maintaining the orientation of the spring such that when the free end thereof is released by the breaking or burning of the fuse element the spring unfiexes and moves 7 studs H. The ends of the springs and the studs 7 may be silvered or otherwise plated if desired to improve contact for low voltage applications.

As shown in Figure 1, the fuse element has one.

loop slipped over a stud l6 and the other loop in electrical contact with the flexed spring 20 by way of the hook 26. The tension of the flexed spring maintains good electrical contact from stud ll via spring 20, book 26, fuse element 18 to stud I6.

Any circuit to be protected by the fuse may be connected thereto by way of a lead 2|, lug 23, a first stud II, a first spring 20 and hook 26, a first fuse element iii, a first stud l6, plate l2, center bolt 14, 9. lug 22 secured to the central bolt, and thence to the return lead of the protected circuit.

The springs 20 are of a length suitable to span the space between successive studs ll and contact is maintained between the center bolt and the lug 2| wherein one fuse element connects a spring with a corresponding stud I6. Contact between the first stud l1 and successive studs ll by way of corresponding springs 20 is maintained except where a fuse element holds the corresponding spring away from contact with the next succeeding stud ll.

The last spring in the series, taken clockwise in Figure 1, is provided with a pin 24 and a bridging bar 25 pivoted on the pin 24. This bar is of suitable length to bridge the first stud ll With an auxiliary stud 21 which is mounted-in the base II. A second repeating fuse assembly may be electrically connected to the first by interconnecting the center bolts thereof and the stud 21 of the first assembly to the first stud ll of the second assembly. Two assemblies may be placed on the same base, as shown in Figures 1 and 2. Also a number of units may be assembled on a single interconnecting center bolt and the first studs ll of the various units electrically connected to studs 21 of preceding units. In this manner any desired number of fuse elements may be assembled in an interconnected group of assemblies, and each element is thus connected into the protected circuit in succession as the preceding element breaks the circuit.

When the desired number of protecting fuse elements are assembled, as described, the operation of the repeating fuse is as follows:

The current in the protected circuit enter and .aves the fuse assembly by leads 2! and 22, the current passing through the first spring and fuse element. When a surge of current of sum- 7 cient strength occurs the first fuse element is heated to the fusing temperature, thereby breaking the element and the conducting spring is released. The first spring thereupon snaps over to the second stud I1 and connects the second spring and fuse element into the protected circuit by way ofthe second stud I1, second fuse l8 and the center bolt I4. Any further surge of current of greater than predetermined value causes the second fuse element to burn out and the second spring to make contact with the third spring by way of the third stud II. This action repeats as often as dangerous current surges occur and as long as a fuse element remains on one of the interconnected assemblies. No attendant is required over long periods of time, and the protected circuit is restored quickly after each such current surge without appreciable loss of service. The attendant for equipment employing this improved fuse system may, therefore, by periodic inspection of the fuse assemblies, maintain continuous service. Any burned out elements are readily replaced without disturbing the assembly or the assembly may be quickly removed and replaced if desired.

If it is desired to delay the resumption of service by holding the circuit open for a time after each short circuit or current surge for any desired period in each instance this may be done by employing a mechanical delay element of conventional design to prevent immediate movement of spring 20 from its fiexed position into contact position against the next stud H. For this purpose a dash pot may be employed to slow the motion of the spring or an escapement mechanism may be connected to accomplish a longer delay in the motion of the spring.

Various changes may be made in thedesign and manufacture of the repeating fuse without 4 departing from the spirit of the present invention.

What is claimed is: An automatic multiple fuse comprising an insulated base plate, a centralized terminal plate fixed on said base plate, a series of circumferentially spaced studs projecting therefrom, a se-- ries of circumferentially spaced contacts projecting from said base'plate surrounding said terminal plate in concentrically spaced relation-to said terminal plate, a scrim of conductive leaf springs secured at one end to said contacts and free at their opposite ends, said leaf springs being outwardly tensioned to electrically engage their free ends with circumferentially adjacent ones of said contacts when released so as to bridge adjacent contacts, and fusible elements stretched between said studs and the free ends I of related leaf springs whereby said leaf springs are deflected inwardly and tensioned out of engagement with the contacts related thereto, whereby fusing of one of said fusible elements permits the leaf spring related thereto to spring outwardly and engage the circumferentially adjacent contact and thereby restore a circuit in which said terminal plate and said studs are connected, 9. second series of similar studs, contacts, fusible elements, and leaf springs on the opposite side of said base plate, an intermediate contact between two of adjacent contacts ofthe first series and electrically connected to a contact of the second series, and a bridging element carried by one of the leaf springs of the first series in position to bridge said intermediate contact and an adjacent contact of the first series whenever the last of the first series fusible elements is fused and the related leaf spring is released to engage such adjacent first series contact, whereby the circuit is restored by the first fusible element of the second series thereof.

J OHN W. BRYAN.

REEERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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