US945993A

US945993A - Resistance unit.

Info

Publication number: US945993A
Application number: US23516104A
Authority: US
Inventors: Elihu Thomson
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1904-12-02
Filing date: 1904-12-02
Publication date: 1910-01-11
Anticipated expiration: 1927-01-11

Description

E. THoM'soN.

RESISTANCE UNIT.

APPLICATION FILED DEO.2, 1904.

Patented Jan. 11,1910.

Fig. 5.

Inventor n Elihu Thomson, b5 MMM Dtt'g.

Witnesses:

UNITED STAT-Es PATENT oEEicE.

ELIHU THOMSON, 0F SWAMPSCOTT, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION 0F NEW YORK.

RESISTANCE UNIT.

Specification of Letters Patent.

Patented Jan. 11, 1910.

To all whom 'it may concern:

Be it known that I, ELIHU THOMSON, a citizen of the United States, residin at Swampscott, county of Essex, State of as` saehusetts, have invented certain new and useful Improvements in Resistance Units, of which the following is a specification.

This invention relates to an improved form of resistance unit. While this unit may be used in a great variety of Ways it is believed to be particularly valuable when used for automatic current control or when used in connection with circuits subjected to sudden and heavy rushes of current, as for instance lightning arrester and similar circuits.

In the drawing, Figure 1 is a cross-section of one form of my improved resistance unit showing the granulated resistance material retained in the refractory tube; Fig. 2 is a plan view of the same; Fig. 8 is a resistance unit of cast silicon provided with suitable conducting terminals; Fig. 4 shows a refractory cage for su porting the granulated resistance material) in place; and Fig. 5 is a cross-section on the line 5 5 of Fig. 4.

In Figs. 1 and 2 the non-conducting base 1 of porcelain or other suitable non-conducting material has secured rigidly thereto the

metallic terminal blocks

2 and 3, carrying the binding posts 4 and 5 by which the unit may be connected in circuit. The non-conductin cylinder 6 incloses the resistance material g, and holds it in place. This tube 6 consists preferably of a rough uartz cylinder such as may be made by me ting granulated quartz arounda heated carbon tube or by other Well known processes. A tube of this material has the advantage that it does not become a conductor, except very slightly, even at very high temperatures, and furthermore, does not deteriorate when exposed to the air at these hi h temperatures. The resistance material ma consist of uncombined silicon in granu ar form. This element has a high specific resistance, a high fusing point and a suitable temperature coecient, and furthermore is not readily oxidized at high temperatures; all of which characteristics make it admirably adapted for use as a resistance material for carrying sudden and heavy discharges. The resistance material 7 is preferably packed in a tube 6, and held firmly in place by the two metallic electrodes Sand 9 supported respectively in the terminal blocks 2 and 23 and pressed toward each other by the coil springs 10 and 1l, or other suitable spring mechanism.

At very high temperaturesI the clement silicon may be fused and cast in the form of a prismatic or cylindrical unit as shown in Fig. 3, in which 12 is a silicon cylinder screwthreaded at each end and provided with

metallic caps

13 and 14 of good conducting material to which the circuit may be connected. If desired, the

terminals

12 and 14 may be cast directly to the ends of thev silicon rod instead of being screw-threaded thereto.

In Figs. 4 and 5 is shown a modified form of resistance unit, similar to the form shown in Fig. 1 except that the quartz tube is replaced by a cage of refractory material. This cage consists of longitudinal bars 15 transversely notched to receive the rings 16, thus forming a cylindrical cage within which the resistance material 7is securely held under pressure by the metal electrodes 8 and 9.

The resistance of the units shown in Figs. 1 and 4 may be readily controlled by varying the size of the granulated particles, as well as by increasing the length and crosssection of the unit. As the specific resistance of the element silicon is nearly twice that of ordinary carbon, and furthermore as silicon unlike carbon is able to stand a red heat without oxidation, the units herein described are particularly valuable for use in connection with lightning arresters in place of the ordinary cylindrical resistance units or carbon or graphite.

Aside from the superiority of these resistance units for controlling sudden and heavy rushes of current they possess certain other valuable characteristics because of the peculiar temperature-resistance coeicient of the element silicon. At normal temperatuies cast silicon has a nearly constant resistance so that upon an increase in temperature up to a red heat the electrical resistance increases only slightly. This variation is very much less than is ordinarily found in the metallic elements and above a. red heat the resistance increases somewhat with temperature showing a positive temperature coefficient. This temperature coeiiicient is not, however, a constant for all higher degrees of heat and'at a temperature approximating that of 'melting silver the temperature eoeiicient reverses u sign so that a further heating causes an actual and rather ra id reduction in the resistance of the unit. his negative temperature coefficient makes the resistance units herein described suitable for automatic motor starting rheostats and for other purposes Where it is desirable that the resistance should automatically decrease as the impressed voltage or the current flow increases. The change in temperature coeicient from a slight or positive value to a high negative value thus successively increasing and decreasing the resistance makes the silicon resistance units available for automatic protectors and regulators for a great variety of purposes, such for instance as automatic cut-outs for mercury va or lamps and other translating devices used in series circuits, or as a means for automatically grounding a circuit to static or other abnormal voltage.

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

1. In a resistance unit, a resistance material consisting of granulated silicon, and

means for retaining said material in place under pressure.

2. In a resistance unit, conducting terminals and a resistance material between said terminals, said resistance material consisting of granulated silicon.

3. A resistance unit comprising a quartz tube, a, resistance material consisting of granulated silicon packed Within said tube, conducting terminals in contact with said material, and means'for retaining said resistance material under pressure.

4. A resistance unit comprising a non-conducting tube, a resistance material in granular form packed Within said tube, said resistance material consisting of an incombustible substance having a negative temperature-resistance coefficient at certain temperatures, conducting terminals in contact with said material, and means for retaining said material under yieldin ressure.

In Witness Whereo fhave hereunto set my hand this 14th day of November, 1904.

ELIHU THOMSON. Witnesses:

JOHN A. MCMANUS, Jr., DUGALD MCK. MCKILLOP.