US1788970A - Static device for the automatic and progressive closing of electric circuits - Google Patents

Description

I Jan. 13, 1931. H. ANDRE ET-AL 1,788,970

STATIC DEVICE FOR'THE AUTOMATIC AND PROGRESSIVE CLOSING 013 ELECTRIC CIRCUITS Filed Sept. 30, 1927 llvvmms flE/YQI ANDRE ALFRED nolwwa armed Jan. 13, 1931 UNITED STATES PATENT OFFICE HENRI ANDRE AND ALFRED MONNIER, or rAn-rs, rnANcn STATIC nnvron FOR THE AUTOMATIC AND PROGRESSIVE CLOSING or cmeurrs ELECTRIC Application filed September 30, 1927, Serial No. 223,122, and, in France November 19, 1 926.

The progressive establishment of theicurrent in a circuit has hitherto only been efl'ected automatically by the use of cumbersome mechanism and with a lack of reliability, by reason of the dependency upon movable elements. I

Now the present invention furnishes a static solution ofthe problem by the use of a material of a high negative thermal coefficient of resistance, which is always in the circuit, above or in parallel with a fixed resistance, thereby insuring reliable operation.

In the first place in order that the heating speed of the substance may be sufiiciently reduced, the conductor employed will be given a relatively large surface in relation to the mass. 4

A good example is a flattened bar or a thin band of variable conductive substance.

If the power to be absorbed is great, it is usecliess to expect a prolonged heating per10 According to the invention the special conductor is shunted by a fixed resistance, and the special conductor is so dimensioned that it allows the passage of a very weak current at the start. Under these conditions there are clearly two phases of conductivity. The fixed resistance permits the passage of a limited constant current and thereby heats the special conductor. After a period of heating said special conductor will short circuit the fixed resistance, so that said fixed resist ance will cool ofi.

An improvement in this arrangement consists in advancing the second phase by heating the variable substance with the fixed resistance.

Another improvement consists in arranging several resistance elements in series, and

shunting them by the substance with variable resistive power, care being taken'to so arrange matters as to obtain dliferent heating. durations so as to avoid the simultaneous short circuiting of the elements.

The diagrams of Figure 1 show, by way (if example, three methods ofre'alizin'g circuits in conformity with the invention.

The diagram A functions under the action of the sole substance 3 in the circuit 1, 2, 3.

The diagram B gives an arrangement in which the action of the substance '3 is combined with that of the resistance 4 of fixed type, in parallel.

The diagram C shows an automatic rheostatic system, the whole constituted by three elements of resistance in series 4 4g, 4 each respectivelyshort circuited by the substances having a negative co-efiicient of temperature 31, 32, 33-

As will be understood these diagrams do not determine the action of the heat released by the resistance upon the substance with variable resistance.

This action, if it be desired to have recourse thereto. maybe obtained in a definite. manner by winding the fixed resistance upon thespecial substance with the interposition of an electric insulation between them so as to avoid circulating currents between the elements the potentials of which are not positively equal; this action could also be rendered adjustable by placing at a regulatable distance, a resistant element, heating the special substance in a suitable manner.. If need be a reduction can be made in the speed of action of the fixed resistance by interposing a thermic screen 5 between the heating element and the substance, the screen being of asbestos, mica, or other product capable of resisting heat.

Figure 2 shows an example of realizing a combined arrangement comprising a heating element or fixed resistance 4' wound upon a refractory screen 5 mounted upon the variable element 3.

Figure 3 shows a slightly different realization in which a variation may be made in the relative position of the fixed resistance and of the substance.

In this figure there may be remarked the substance 3" with variable conductivity, the thermic screen '5 and the resistance 3".

By changing the height of the cylindrical stays placed upon the screw-threaded rods 6,v 6 a modification is effected in the action of the fixed resistance upon the element 3" The screen 5, as will be understood, without departing from the spirit of the invention may realize difi'erentvariations utilizing either separately or in combination the arrangements indicated, or any other that may be equivalent.

WVhat We claim and desire to secure by Letters Patent of the United States is 1. In a device for automatically varying the resistance of an electric circuit connected between an utilization apparatus and a terminal of the current source, a high negative temperature-coeflicient variable resistance element, and a second separate resistance ele-' ment connected in parallel to only two points of said variable resistance element and arranged at an adjustable distance therefrom to heat it by convection, the value of resistance of the second element being such that itis much le:-:s than the value of the cold variable element, and much greater than the value of the heated variable element.

2. In a device for automatically varying the resistance of an electric circuit connected between an utilization apparatus and a terminal of the current source, the combination of several resistance elements connected in series, each comprising a high negative temperature-coeflicient variable resistance element and a second separate resistance ele ment connected in parallel to only two points of said variable resistance element and arranged at an adjustable distance therefrom to heat it by convection, the value of resistance of the second element being such that it is much less than the value of the cold variable element, and much greater than the value of the heated variable element.

HENRI ANDRE. ALFRED MONNIER.

Images