US2147848A - Arc rupturing device for electric safety fuses - Google Patents

Description

E. LANGE Feb. 5 1, 1939.

ARC RUPTURING DEVICE FRELGTRIC SAFETY FUSES Filed March 23, 193'? Patented Feb. 21, 1939 ARC RUPTURING DEVICE FOR ELECTRIC SAFETY FUSES I Emil Lange, Berlin-Zehlendorf, Germany Application March 23, 1937, Serial No. 132,583 In Germany March 27, 1936 3 Claims.

This invention relates to a safety fuse for high tension electric currents and of the kind wherein fuse wires which connect the terminals of an enclosing casing are adapted, on fusing, to form 5 one arc at a narrow outlet in the casing and another arc in a space the fluid contents*y of which, on being heated by the arc, causes the fluid outside the space to be ejected through the outlet for rupturing the arc.

Fuses of this kind have the property of taking up the full strength of the short-circuit current, and it is therefore necessary to make the structure of dimensions capable of coping with the largest currents that can be expected.

The object of the present invention is to obtain a construction which allows the fuse to be of comparatively small dimensions, and the invention consists essentially in providing the casing with a resistor having one terminal perma- 29 nently connected to the fuse circuit and another terminal arranged so as to attract and make contact with one of the arcs on the fusing of thc wires, thereby reducing the current owing through the arcs.

Fig. l of the accompanying drawing represents a sectional View of ,a fuse constructed according to the invention, and

Fig. 2 is a sectional view a modified form.

Referring first to Fig. 1 it will be seenv that the fuse structure comprises an insulating casing which is closed at one end by a cap |08 forming one terminal of the fuse. The other end of the casing is fitted with an insulating member 2 having a central, narrow opening forming an outlet :i5 for thc uid in the casing. The outlet also forms a seating for a spring pressed valve whereby said outlet is normally closed. An annular metallic member |09 surrounding the outlet forms 'the second terminal of the fuse. Supported centrally within the casing is a tubular insulating member 3 one end of which faces the outlet and is closed by an insulating member |05. A metal conductor |05, fitted in the insulating member |06, forms a contact member between two fuse wires |04 and |03, The wire |04 is attached to the terminal |09, and the Wire |03 is attached to the terminal cap |08.

On the fusing of the wires one arc will be o formed between the connecting member |05 and the terminal |09, and another arc will be formed inside the member 3. The fluid contained in 'the space |02 of the latter will be expanded by the heat and cause the colder fluid in the outside space |0| to be ejected through the narrow outlet, thereby causing an effective rupturing of the arc formed at the outlet.

According to the invention a tubular resistor is arranged within the member 3 with one end in contact with the connecting member |05 5 through the medium of washers` ||3 of copper or other good conducting material. The opposite vend of the resistor is fitted with a similar washer |2, and the central space I4, through which the Wire |03 passesgis fitted with a lining ||5 of 10 asbestos or other insulating material, the resistor being thus enclosed in insulation except for the free end thereof to which the copper washer 2 is connected. Thus, when the wire fuses, the arc will bc attracted by and connect with the resistor through the metal washer ||2, and the current flowing through the arc at the outlet will therefore be reduced in strength. Consequently the pressure curve, which follows the rising strength of the current, will not attain the value of the entire short-circuit current.

Fig. 2 shows a construction in which the resistor |2| is arranged so as to form the outlet of the fuse casing 4. A central tubular member 5, supported as previously described, carries in a closing member 6 of insulating material a conductor ||8 which forms a connecting member between the fuse wires and ||9. The latter passes through a lateral duct in the resistor |2| for connection to an annular terminal |20 mounted so as to be exposed at the side of the casing 4. A cap l, which surmounts the casing 4, is provided with gas outlets |23 and guides a spring controlled valve |22 which normally closes the outlet of the resistor |2|. 35

On the fusing of the wires, the arc formed at the outlet of the casing will be attracted by and connect with the resistor forming said outlet, and the current will be correspondingly reduced.

By a proper dimensioning of the resistor, the 40 current allowed to pass through can be determined, and excessive Values of such current can thus be ebviated. I'his allows a reduction in the size of the fuse structure and also prevents the rupturing of the arc from being retarded by a too strong current.

I claim:

1. An electric safetv fuse of the character described comprising an insulating casing containing a fluid and having at one end thereof a narrow outlet for said fluid, a contact member at each end of the casing, a confined space in said casng communicating with the outlet through a circuitous route, fuse Wires connecting the contacts through the outlet and through said space so that, on a fusing of the Wires, arcs will be formed at the outlet as well as in said space, and so that the heating of the fluid in the latter will cause the fluid outside the space to be ejected through the outlet for rupturing the arc, and a resistor having one terminal permanently connected to the fuse circuit and another terminal arranged in position to attract and connect with one of the arcs for reducing the strength of the current.

2. An electric safety fuse of the character described comprising an insulating casing containing a uid and having at one end thereof a narrow outlet for said fluid, a contact member at each end of the casing, a conned space in said casing communicating with the outlet through a circuitous route, a. pair of fuse wires arranged in series and connecting the contacts through the outlet and through said space so that, on a fusing of the wires, arcs will be formed at the outlet as well as in said space and so that the heating of the uid in the latter will cause the uid outside the space to be ejected through the outlet for ElVIIL LANGE.

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