US2225287A

US2225287A - Electric fuse

Info

Publication number: US2225287A
Application number: US251881A
Authority: US
Inventors: Edward V Sundt
Original assignee: Individual
Current assignee: Individual
Priority date: 1939-01-20
Filing date: 1939-01-20
Publication date: 1940-12-17
Anticipated expiration: 1957-12-17

Description

Dec. 17, 1940. v SUNDT 2,225,287

ELECTRIC FUSE Filed Jan. 20, 1959 "Zn denim":

Zfdzaard 1/. Saudi ax Patented Dec. 17, 1940 I UNITED STATES PATENT OFFICE 4 Claims.

This invention relates to improvements in electric fuses.

One object of the invention is to provide an improved fuse for use in electric circuits such as those designed for carrying high voltage, low amperage current and which may be employed satisfactorily in protecting delicate electric instruments such as galvanometers, thermocouplers, or the like. The improved fuse is adapted also for use in X-ray circuits, television circuits or other circuits employing electronic tubes.

A more specific object of the invention is to provide a fuse of the air-exhausted container type provided with lead wires, the inner ends of which are bridged by a fusible element which is protected against rupture during manufacture and subsequent use by means within the container.

Another object of the invention is to provide a fuse of the type mentioned having lead wires at opposite ends of the container for carrying current through a fusible element and insulating means interconnecting the lead wires for protecting said element against tensile stresses during manufacture.

A further object of the invention is to provide an air-evacuated or vacuum type fuse, the fusible .element and lead wires of which are so related as to minimize the danger of rupturing the element during evacuation of the container and sealing thereof.

Other objects of the invention relate to features of construction and arrangement of parts which will be apparent from a consideration of the following specification and accompanying drawing, wherein:

Fig. 1 is a side elevation of a fuse embodying the present improvements, the fuse being shown in position in a conventional fuse clip or holder;

Fig. 2 is a sectional view taken on line 2-2 of Fig. 1;

Fig. 3 is a detached perspective view of one of the two lead wires of the fuse; and

Fig. 4 is an elevation of the fuse illustrating end caps attached to the lead wires prior to the positioning of the caps on the ends of the fuse capsule or container.

In the drawing, l0 indicates a suitable container or capsule consisting, in the form shown, of a glass tube, the ends of which are open originally but in the completed fuse are sealed in contact with the lead wires which are indicated generally by the numerals ll, Ila. Since the fusible elements employed in low amperage fuses of the character referred to may be extremely delicate (depending on their intended current carrying capacity) and require careful handling to avoid rupture during attachment to the lead wires and installation of the assembly in the container, the lead wires preferably are attached together rigidly by a non-conducting member which is capable of withstanding the stresses imposed during handling.

In the embodiment of the invention illustrated, the intermediate portion of each of the lead wires is shown as bent or folded backwardly upon itself to provide an anchoring tang i2. The tangs of the pair of lead wires to be assembled in a container l0 are embedded in a non-conductor, such as a glass rod [3, the latter being fused to enable such attachment. This member l3 secures the inner portions of the lead wires together rigidly and enables the same to be manipulated as a unit.

The free inner end portions of the lead wires extend laterally of the anchor 13 and terminate preferably in arcuate portions ll, the ends of which portions are flattened as at l5, especially where the selected fusible element is so delicate as to render attachment of the same to the lead wires by soldering or welding either diflicult or impracticable. In such instances, the fusible element I6 preferably is cemented to the inner ends of the wires, at the flattened areas thereof, by a conductive paste of any suitable composition known in the art. Such pastes adhere to the flat areas more firmly than to the cylindrical surface of the wire.

When the wires II, II a have been secured together by the anchoring member i3 and the fusible element It attached to the areas I! as described, the assembly is inserted in the tubular container in and one end of the tube sealed around the wire II by fusion of the end of the tube in a flame in well known manner. The other end of the tube is heated and the wire Ila, instead of extending from the tube along the axis thereof, is off-set from the axial center of the tube as shown, whereby the extreme adjacent end of the tube constitutes the tubulation or passage through which the air in the tube may be exhausted prior to sealing at the tip II. It has been found that by exhausting the air from an end of the container, the rush of air is less likely to fracture the delicate fusible element than where the air is withdrawn through a tubulation or air exhaust in the side of thetube as has been common practice heretofore.

The external portions of the lead wires ll, Ila are of sufficient length to enable the same be secured to the interiors of conducting end caps ll. 'fhuathe ends of the wires preferably are soldered as at II to the interiors of the caps after which suitable cement isinserted in the caps and the latter slipped over the adjacent ends of the container, the lead wires being gathered into the respective caps during the positioning of the latter on the ends of the container. The caps thus inclose not only the entire external portions of the lead wires but the sealing tips of the tube as well. The caps thus shield the tips against breakage, and due to the internal attachment of the lead wires to the caps there is, compared with fuses where the wires are soldered to the exterior of the caps, less likelihood of the wires becoming separated from the caps during insertion of the fuses in conventional fuse clips I! or other forms of fuse holders, such as extractor posts. In addition, the described construction of the fuse avoids the relatively crude or unfinished appearance of air-exhausted fuses where the air is removed laterally through tips intermediate the caps.

The inner end portions of the wires preferably extend into contact with the inner wall of the tube at points opposite the anchoring or connecting member 13 whereby independent vibrations of said ends and relatively movement of the fuse assembly within the tube which would be likely to rupture the delicate fusible element ii, are inhibited. By anchoring the tangs I! to the connecting member IS, the fuse assembly can be inserted or drawn into position in the tube and the completion of manufacture of the fuse can be performed without imposing destructive stresses of the fusible element, as will be apparent. By-

carrying the lead wires out opposite ends of the tube as described, a fuse construction adapted to carry high voltage is provided since there is no danger of arcing between lead wires should the fuse blow as has been the case in high voltage fuses of the type where both lead wires.enter the container at the same end. In such fuses, the voltage capacity thereof is limited by the areover distance between the wires while with the present improvements, the adequate separation of the lead wires of the fuse assures the breaking of the circuit when the fusible element is destroyed by circuit over-load.

While I have shown and described a specific embodiment of the invention for the purpose of illustration, it will be apparent that changes may be made therein without departing from the spirit of the invention. I

What I claim as new and desire to cover by Letters Patent is:

1. A fuse comprising a container, an assembly therein comprising a pair of lead wires sealed 'in the ends of the container, an insulating member contacting the container and uniting said wires within the container at points remote from the inner ends of the wires, and a fusible element bridging the ends of saidwires, said wires having container contacting portions intermediate said ends and said insulating member and cooperating with the latter for anchoring the assembly against transverse movement within the container.

2. A fuse comprising a container, an assembly therein comprising a pair of lead wires. an insulating member connecting said wires at points remote from the inner end portions thereof and arranged in longitudinal contact with the wall of said container, said end portions being shaped for contact with the wall of said container at points opposite said insulating member and cooperating with said insulating member for resisting lateral movement of the assembly within the container, and a fusible element bridging said end portions of said wires.

3. A fuse comprising a tubular container, an assembly sealed therein comprising a pair of lead wires, an insulating member connecting said wires to prevent relative longitudinal movement of said wires within the container and longitudinally contacting the wall of said container, said wires being provided with portions extending into contact with the container wall at points diametrically opposite said insulating member and cooperating therewith for resisting lateral movement of the assembly within said container, and a fusible element connecting said wires within the container.

4. A fuse comprising a container, a pair of lead wires extending into the same and each having an intermediate portion folded back upon itself and terminating in a laterally off-set inner end, a fusible element bridging the inner ends of said wires, and an insulating member within the container connected to said folded intermediate portions of said wires.

EDWARD V. SUNDT.