US1749772A - Contact-resistance lamp - Google Patents

Description

c F LORENZ CONTACT RESISTANCE LAMP Filed Aug. 1, 1924 March 11, 1930.

Patented Mar. 11, 1930 UNITED STATES PATENT? OFFICE CHARLES FREDERICK LORENZ, 0F EAST ORANGE, NEW JERSEY, ASSIGNOR TO WEST- INGHOUSE LAMP COMPANY, A CORPORATION OF PENNSYLVANIA CON TACT-RESISTAN CE LAMP Application led August 1, 1924. Serial No. 729,463.

This invention relates to an incandescent electric lamp and more particularly to a contact resistance lamp in which the light is produced by two or more electrodes in contact.

Lamps of this nature are operated at relatively low voltage and at high amperage, and the electrodes are locally heated to incandescence at their contacting surfaces due to the imperfect contact between the electrodes or because 0f the limited area of such contact.

This lamp is, in some respects, similar to an arc lamp in that one or more of the electrodes may be slowly consumed and in such case, means must be provided for feeding the electrodes together to maintain a constant and uniform contact therebetween. No appreciable arc, however, is formed.

The electrode material, vaporized from'the electrodes in lamps of this type, as heretofore constructed, rendered the operation of the lamp unsatisfactory because of the deposition of the vaporized material on the wallof the envelope with consequent blackening and discoloration thereof and'loss of eificiency.

One of the objects of this invention is to produce a contact resistance lamp in which discoloration of the bulb is prevented or localized so as not to impair the eiiciency of the lamp.

Another object is t0 produce a contact resistance lamp which will have a high eiliciency and high candle power maintenance.

Another object is to produce an incandescent lamp having a concentrated light source continuous over its entire extent.

Another object is to provide a contact resistance lamp in which the contacting surfaces of the electrode are enclosed.

Another object is to shield that portion of the bulb through which it is desired to transmit the light from the blackening effect of the vaporized electrode material.

Other objects and advantages will hereinafter appear.

In accordance with this invention, a plurality of electrodes are arranged with a portion of their surfaces in contact within an exhausted or s-iilled envelope. The electrodes shoulireferably be composed of material of such nature that they will not stick or become fused together during the operat1on of a lamp. Carbon, in one of its various forms, is particularly suitable for this purpose, particularly the graphitic form of carbon. One or more of the electrodes, however,

may be composed of refractory metal, such as tungsten or molybdenum or alloys thereof.

The area of contact between the electrodes should be relatively small or the contact sufliciently imperfect to produce a high resistance to the flow of the high amperage current at the point of contact, whereby the local heatlng of the electrodes at their points of contact, will be sufficient to render them incandescent and thus produce an illuminating source.

In order to suppress vaporization of the electrodes, the envelope may be filled with an inert gas such as argon or a mixture of inert gases, preferably at a pressure of about one atmosphere. i

In o rder to prevent the vaporized electrode materlal from depositing on the bulb or on that portion thereof through which it is deslred to transmit the light, a shield may be arranged around the electrodes.

-Thls shield may be apertured to permit the light to be transmitted therethrough or it may be formed in part by one of the electrodes, the other electrode contacting with the inner surface thereof whereby the vaporlzatlon of the electrode material occasioned b y local heating, takes place practically entirely on the inside of the shield.

Means may also be provided for feeding one or both of the electrodes as theyI are consumed to` maintain them continuously in contact at a substantially uniform pressure.

In order that this invention may be more fully understood, reference will be had to the accompanying drawings in which' Fig. 1 isa sectional view of/one form of contact resistance lamp embodying this invention; and,

Fig. 2 is a sectional view of a modified form of such a lamp.

The contact resistance lamp shown in Fig. 1 comprises in general, a bulb 1 containing an inert as, as argon, or a mixture of inert gases an a pair of electrodes 2 and 8 electrically connected to and suitably supported from terminals 4 and 5. Y

The electrode 2 is in thel form of a thin l disc or wafer of carbon or other refractory material having a high specific resistance and 1s supported 1n the recessed end ot' a (-yhudrical shield 7 which may be formed of any suitable conducting material such as carbon or metal threaded or otherwise suitably secured to the outer end otl a metal tube 8, the opposite en'd of which is threaded internally of the terminal 4 of the lamp. The terminal 4 is composed of a metal, as copper, and is joined to the neck 9 of the bulb and to au insulating ring 10 or sleeve of glass or other suitable material in a manner well known in the art. The terminal 5 is similarly secured to the opposite end of the insulating sleeve The electrode 3 is in the form of a pencil of carbon, metal or other conducting 1naterial, having an enlarged rear end 11 by which it is secured to a metal tube 12 by threads 13. The tube 12 is arranged concentric with respect to the tube 8 and spaced therefrom by a ring 14 of insulating ma terial, such as mica. The lower end of the tube 12 slidin ly engages a rod 15 of metal or other con uptin material rigidly supported by the terminal 5 of the lamp. A coiled spring 16 may be interposed between the end of the tube 12 and the inner surface of the terminal 5 to exert a constant pressure upon the tube 12 so as to maintain the electrode 3 in constant contact with the electrode 2 and to feed the electrode 3 upwardly as it is consumed. In order to make a good contact between the rod 15 and the tube 12, the lower end ofthe lamp may contain a quantity of mercury 17.

It will thus be noted that the point of contact 18 between the electrodes 2 and 3, is totally enclosed and any vaporization that takes place at the electrode surface will be 'deposited on the inner surface of the cylinder 7 or on the tubes 8 and 12. In order,

however2 to revent an excessive pressure from belng eveloped within the shield or casing which surrounds the electrodes, the tube 8 may have a perforation 19 therein through which the pressure will be equalized on both sides of the shield. y

The high resistance interposed in the circuit by the limited contact area between the electrodes 2 and 3 will produce local heating at the point of contact and since the disc electrode 2 is relatively thin, this heat will be transmitted through the disc and render the outer surface thereof incandescent. Moreover, the current density in the wafer or disc 2 will be high, due to the relatively small sectional area thereof which will also aid in heating this electrode. The cylindrical casing or shield 7, however, because of its relatively large area, will not be highly heated.

The incandescent button or wafer 2 constitutes a concentrated brilliant light sourceot substantially uniform intensity throughout it s entire exposed area. This type of a light source is particularly adapted for the operation of projection apparatus.

In Fig. 2, a modified form of contact resistance lamp is shown in which the light is produced by means of a stack or plurality of wafers or thin discs 20. These discs may be dish-shaped or recessed as at 21 whereby they may be nested one within the other, to assist in maintaining them in proper relation. A pair of metal conductors 22 and 23 are provided for the outer electrodes 24 and 25 of the series of contacting electrodes. The conductor 22 is supported from and is in electrical contact with an external terminal 26. The conductor 23 is threaded or otherwise suitably secured in a carbon or metal block 27 which slidingly engages a metal conductor 28 suitably supported by and in electrical contact with the terminal 29. A helical spring 30 may be'interposed between the low'- er end of the block 27 and the inner surface ofthe terminal 29 to maintain the discs 20 in continuous contact at substantially uniform pressure.

The terminals 28 and 29 are suitably joined to the envelope 31 in a gas tight manner and the envelope is provided with a filling of rare gas to suppress vaporization of the electrodes.

A shield or sleeve 32 of suitable refractory material such as molybdenum is arranged around the discs 20 and is apertured at 33 to permit the light from the disc to be transmitted therethrough. The shield may be supported by a spider 34 from the conductor 22, although, of course, any other suitable supporting means may be provided. The shield or sleeve 32 serves somewhat as a chimney in directing the vaporized material away from the aperture 33 and out of the upper end thereof so that the electrode materlal is deposited on the inner wall of the shield or in the upper end of the lamp where it will not obstruct the light transmitted through the aperture 33.

It will be noted that a lamp has been produced which has a concentrated light source of practically uniform intensity over its entire exposed area and that blackening of the' said means having an aperture for permitting the light emitted from the opposite side of said incandescent body to be transmitted through the Wall of the envelope.

2. A contact resistance lamp comprising an envelope containing electrodes in contact, means for feeding said electrodes together as they are consumed, and means for enclosing the contacting portions of said electrodes to prevent the deposition of electrode material on predetermined portions of the envelope.

3. An incandescent electric lamp comprising an envelope, a comparatively thin electrode therein, asecond electrode contacting with one side of said lrst electrode to heat the same to incandescence, a shield interposed between said contacting surfaces and the Walls of the container said shield having means for exposing a portion of said rst electrode to produce a concentrated continuous light source.

4. A contact resistance lamp comprising an envelope, an electrode in the said envelope, means for preventing the deposition of vaporized electrode material upon the Wall of said envelope, another electrode in said envelope and in contact with said first mentioned electrode and mounted to cooperate With said means for preventing the deposition of vaporized material.

5. A contact resistance -electric incandescent lamp comprising an envelope, a plurality of electrodes therein, a refractory shield surrounding said electrodes to prevent the deposition of electrode material on the wall of said envelope, one of said electrodes cooperating with said shield to prevent said deposition.

6; An incandescent electric lamp comprising a container, a pair of contacting electrodes within said container, an enclosure for partially surrounding said electrodesto prevent the deposition of vaporized material upon the walls of said container, one of said electrodes cooperating with said enclosure to prevent said deposition, and means for equalizing the pressure on opposite sides of said enclosure.

7. A contact resistance lamp comprising a container, a plurality of electrodes therein havinosurfaces in contact, means for partially enclosing the contact portions of said electrodes, one of said electrodes coo rating with said means to completely enc ose the said contacting portions, and means for cqualizing the pressure at opposite sides of said enclosing means.

In testimony whereof, I have hereunto Sllbu scribed my name this 30th day of July, 1924. CHARLES FREDERICK LORENZ.

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