US794983A - Rheostat. - Google Patents

Description

mmm John W. Howell.

J. W. HOWELL. BHEOSTAT.

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APPLIOATION FILED NOV- 23. 1903.

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UNITED STATES Patented July 18, 1905.

PATENT OFFICE.

JOHN 'VV. HOWELL, NEWARK, NEW JERSEY, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

RH EOSTAT.

h V SPECIFICATION fornring part of Letters Patent No. 794,983, datedJuly 18, 1905,

Application filed November 23, 1908. Serial No. 182.275.

To all whom, it may concern.-

Be it known that I, JOHN W. HOWELL, a citizen of the United States, residing at Newark,

county of Essex, and State of New Jersey, have invented certain new and useful Improvements in Rheostats, of which the following is a specification.

This invention relates to rheostats; and its object is'to provide a device in which both the current-carrying capacity and the resistance can be varied as desired.

I In manyclasses of work it is necessary to varythe resistance of a circuit over a wide range. If the potential of the circuit is constant, the current varies inversely as the re- 'sistance, and if the variation isaccomplished with a rheostat similar to those'now in com- V men use the resistance material of the rheostat I must be such that it will carry without dangerous heating the heavy current flowing in the circuit when the minimum resistance is cut in. 'If the resistance med um 1s a wire, it must .is therefore possible to use a smaller resistance-wire of such capacity that it will carry the current without dangerous heating only when a comparatively heavy .resistance is cut in and to use two or more lengths of the wire in parallel when a greater current is wanted, and as only a small section of the resistancecoil is needed when the larger current is being used the parallel circuits may all be through the resistance material whichwas used in a single circuit to obtain the high resistance. I have therefore provided a rheostat of the slide-wire type having resistancewire wound on a tube and two insulated rods mounted parallel to the tube, on each of which one or any number of contacts bearing on the wire may be adjusted as desired. If one contact is mounted oneach rod at opposite ends of the coil, the maximum resistance is cut in and the fiow'of current in the circuit is small. By bringing the contacts closer together the resistance is reduced and the current increased until the latter approaches the current capacity of the wire. Beyond this point a further reduction of the resistance is made by placing another contact on one of the rods, so as to establish two circuits through the coil, thus effecting the desired reduction and doubling the current-carrying capacity. In this way more contacts may be added to get any desired capacity and the contacts may be adjusted along the rods to get a delicate regulation of the resistance. It will thus be seen that an exceedingly wide range of resistance and capacity relatively to the size of the device is obtained. My invention therefore comprises a rheostat the current-carrying capacity of which is adjustable and in which the resistance in circuit can be regulated as desired for any adjustment of the current-carrying capacity.

It also comprises other novel features which will be definitely indicated in the appended claims.

1n the accompanying drawings, whieh. illustrate one embodiment of my invention, Figure 1 is a top view of my improved rheostat. Fig. 2 is an end view, and Fig. 3 a cross-sec-- tion of the same, and Fig. 4 is a detail view of one of the contacts.

Referring to the drawings, 1 l arestand- .ards by which the rheostat. is mounted on a suitable base and which are arranged to support a metal tube 2, covered with asbestos or other suitable insulating material 3. A resistance-wire 4c is tightly wound on the tube over the asbestos covering 3; Mounted on the standards 1, but insulated therefrom, as

. shown, are rods 5 5, one on either side of the tube and paralleling the tube throughout its length. Contact-carriers 6 6 (shown in detail in Fig. 4:) are adapted to slide on the rods 5 5. The carriers are provided with springmetal sides 7 7 to insure a good contact with the rods and are open at the bottom, so that they can be readily sprung on the rods or withdrawn therefrom. A spring-contact 8 is mounted on the side of each carrier 6 and adapted to bear on the resistance-wire the point of contact with the wire being in line with the end of the carrier. The rods 5 are marked ofi" to a suitable scale to facilitate positioning the contacts on one rod in a definite relation to those on the other. Bindingscrews 9 9 are provided on the rods 5 5 for connecting the device in circuit. I

With the contacts arranged as shown in Fig. 1 there are two circuits of equal resistance through the wire 4, and the current capacity of the rheostat is double that of the wire. The two carriers on one rodcan be adjusted toward or away from the one onthe opposite rod to regulate the resistance in circuit, the marks on the rods enabling the operator to make the two circuits equal in ,resistance. If the two contacts were much closer together, the current flowing through each path would approach the capacity of the wire, and further reductions in the resistance would be made by placing other carriers on therods and moving them into engagement with the wire at another part of the coil, thereby establishing other paths for the current through the coil, decreasing the resistance and increasing the current capacity of the rheostat.

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

1. A rheostat having means for adjusting the current-carrying capacity thereof, and for varying the resistance in circuit for any adjustment of the current-carrying capacity..

2. In a rheostat, a resistance, and means for closing a singlecircuit or a plurality of par allel circuits through the resistance, and for varying the resistance of the single circuit or one of the parallel circuits.

3; In a rheostat, a resistance, and means for closing a single circuit or a plurality of parallel circuits through the resistance, and for varying the resistance of the several circuits. 4. In a rheostat, a resistance, means for connecting a variable portion of said resistance in circuit, and means for establishing parallel. circuitsthrough the resistance, and

varying the resistance of one of the parallel circuits independently of another.

5. In a rheostat, a resistance, and ad ust- 'able contacts for closing a plurality of parallel circuits through the resistance'to obtain a high current-carrying capacity, for varying the resistance oi said circuits, and i OF OPGI'P, ing any circuit to increase the resistance.

6. In a slide-wire rheostat, a resistance, and movablecontacts for closing a circuit through the resistance and varying the amount of resistance in circuit, for establishing parallel circuits through the resistance, and for varying the resistance of the parallel circuits.

'7. In a rheostat, the combination of a single resistance unit, and a plurality of adjustable contacts to establish a number of variable parallel paths for the currentwhereby the capacity or ohmic value of the unit may be va- 1'1G( r 8. A slide-wire rheostat having a tube, resistance thereon, two rods mounted parallel to the tube, and a plurality of contacts adjustably mounted on said rods and adapted to make contact with the wire.

9. In a rheostat, a tube, resistance wound thereon, a plurality of rods parallel to the tube, and a plurality of contacts adapted to be quickly placed on a rod in contact with the resistance-Wire and withdrawn therefrom.

10. In a rheostat, a tube, resistance wound thereon, a plurality of rods marked to a delinite scale mounted parallel to the tube, and a plurality of contacts adapted to be quickly placed on a rod in contact with the resistancewire and withdrawn from the rod. v 11. in a rheostat, standards, a tube mounted thereon, resistance on the tube, two rods mounted on the standards parallel to the tube but insulated from the standards, said rods being marked to a definite scale, and a plurality o1 contacts arranged to be mounted for longitudinal movement on a rod to cross-connect the rod and resistance-coil.

in witness whereof I have hereunto set my hand this-th day of November, 1903.

JOHN VJ. HOWELL. Witnesses:

S. N. Wurrnnnan, JOHN lvirrouruzn, Jr.

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