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Publication numberUS894705 A
Publication typeGrant
Publication dateJul 28, 1908
Filing dateJun 10, 1905
Priority dateJun 10, 1905
Publication numberUS 894705 A, US 894705A, US-A-894705, US894705 A, US894705A
InventorsErnest Schattner
Original AssigneeGen Electric
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Protective device.
US 894705 A
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Description  (OCR text may contain errors)








Specification of Letters Patent.

Patented July 28, mos.

. Application filed June 10, 1905. Serial No. 264,586.

'State of New York, have invented certain newand useful Improvements in Protective Devlces, of which the following is a specifi- The present invention relates to -the distribution .of. electric energy, and more particularly to protectivemeans for preventing a circuit conductor designed for carrying currents of low or safe potential from becoming charged with unsafe potentials.

It is customary to provlde consumption circuits," house circuits, etc., with cut-out devices which are'designed' to operate auto matically to disconnect the circuit upon the passage of abnormal :current, but it sometimes happens that .the consumption or house. circuit has adangerous potential suddenly impressed thereon, asby a power circuit wire coming in contact therewith, so that the translating devices are injured before the cut-out devices operate and where the consumption wires are open-circuited the cut-out devices are whollyino erative to prevent them-from becoming d angerously charged. r

The object of my invention is to. provide means which will insure prompt action of the cut-out devices in a consum tion. or house circuit whenever an abnorma I voltage is imlpressed thereupon.

' In carrying. out my lnventionI connect the opposite clrcult conductors ins deof the cut-outdevlc'es wlth a closed shunt connection of sufiicient resistance to prevent any considerable flow of current therethrough under ordinary conditions but'so constructed that upon an abnormal voltage being impressed upon the" conductors the resistance will be automatically decreased and allow current to pass in sufficient volume to operate the cut-out devices. This shunt may be provided with a ground connection with resistance on each side of the latter-so that when either conductor becomes dangerously charged a sufficient current will be drawn therefrom to ground to actuate its respective cut-out device.

For a more complete understanding of my invention reference may be had to the following detailed description and to the accomg drawing forming a lic-ation in which, I

Figure 1 is a diagrammatic representation of an incandescent house lighting system having fusible cut-outs and provided with panvin part of this-specione form of my protecting device; Fig. 2 is a similar view with the protecting device provided with a ground connection; Fig.3 is a side elevation with part broken away of a protective 3 device provided with a ground.

connection and shown mounted in operative position; Fig.4 is a longitudinal section of the form of protective device'shown in Fig. 1.

' The consumption circuits shown in the drawing have the outer exposed conductor sections 1, 2 connected to the respective inner sections 1, 2 by cut-out fuses 3, 4,, and the inner sections of the conductors areconnected to opposite terminals of incandescent lamps 5 according to the usual practice. Connected tothe inner .conductor sections 1, 2, between the points of attachment of the fuses and the lamps therewith, is a protective shunt'connection fi-with'resistance.

In the constructions shown in Figs. 1 and- 5, resistance units areprovided each consisting of a body 7 of some resistance substance having a negative ter'nperature coefiicient;

that is, the resistance which it offers to the assa e ofan electric current decreases with an increase in temperature. .Among the substances possesslng negative temperature ooefficients magnetite is known to 'have'the self-reducing characteristics to a marked degree, and when itis red hot its resistance is only about one per cent. of what it is at ordinary temperatures. By mixing with magnet-v .ite certain amounts of clay base its critical resistance may be-fixed at any point desired -so that when subjected to ordinary or safe electrical potentials onlya small amount of current will flow therethrough insufficient to perceptibly raise the temperature, but when subjected to an unsafe or abnormal potential sufficient current will .flow to rapidly raise its temperature and permit a rapid increase in the flow of current therethroughl I have employed with good results for certain potentials the following mixture: eighty parts of magnetite and twenty parts of clay base; the latter being composed of clay, flint and spar. This mixture is combined with water and made into desired shapes and baked. A substance such as described may be supported in an insulating tube 8 with a packing 9 of asbestos and metallic end caps 10 screwthreaded to the ends of the tube and bearing at their inner surfaces upon the ends of the body of resistance material.

In the arrangement shown in Fig. 2 the resistance of the shunt connection 6 is divided and a ground lead 11 connected between the sections. As shown in detail in Fig. 4, this lead consists of a metal disk 12 located at the center of the insulating tube 8 and having stud 13 screw-threaded thereto, projecting radially through the side of the tube and adapted to engage a binder contact 14 to which a grounded wire may be attached and carried. by the insulating block 15 upon which are mounted contact clips 16 for reeei\ing' the end caps 10 and provided with binding posts 17. When the caps 10 are screwed up the resistance cylinders 7 are forced into engagement with opposite sides of the disk 12 so that current may pass from one cap 10 through both resistance cylinders 7 and the disk 12 to the opposite cap to, or from either cap through the adjacent resistance cylinder and the grounded connection 11.

When a current of abnormal difl'erence of potential is thrown upon the exposed con ductor sections 1, 2, it operates at once upon the shunt connection 6 whether the circuit be open or closed through the lamps 5, and by means of the increase of voltage across the shunt connection, current in sutlicieiit volume is permitted to pass the cut-out devices 3, 4 to insure their operation.

It is possible for a chargepi: high voltage to be impressed upon one of the conductors 1, 2 without causing a corresponding difference of potential between them, but with the grounded shunt connection shown in Fig. 2 current will be drawn from the conductor of high potential through a part of the resistance device to ground and thereby etlect the operation of the cut-out device in the conductor under high potential charge.

I do not desire to restrict myself to the particular form or arrangement of parts herein shown and described, since it is a pparent that they may be changed and modified without departing from my invention.

What I claim as new, and desire to secure by Letters Patent of the United States, is,-

1. The combination with the conductors of an electric consumption circuit provided with automatic cut-out devices, of a high resistance shunt connection between said conductors having provisions for automatically reducing said resistance.

2. The combination with the conductors of an electric consumption circuit provided with automatic cut-out devices, of a shunt connection between said conductors having a section of resistance material of negative temperature coeflicient.

3. The combination with the conductors of an electric consumption circuit provided with automatic cut-out devices, of a shunt connection between said conductors having a section of resistance material of negative temperature coefficient of such characteristics and proportions that upon the passage of a normal current therethrough the resistance shall not heat up above a certain critical ERNEST SCHAVFNER.



'lELEN ()nroao.

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3368110 *Jul 12, 1965Feb 6, 1968Robert A. TaylorSafety adapter
US3383563 *Dec 6, 1965May 14, 1968Lucas Industries LtdBattery charging systems for road vehicles
US3480835 *Mar 10, 1967Nov 25, 1969Weston Instruments IncThermal rms limiter and semiconductor driving circuit means
US3560797 *Sep 12, 1968Feb 2, 1971RenaultElectric motor protection devices
US4547827 *Jul 5, 1983Oct 15, 1985Shedd Harold EPower surge isolator
Cooperative ClassificationH02H3/023