US794839A - Electric-arc lamp. - Google Patents

Description

Nm794,8391 PATENTED JULY 18, 1905.

M. 11. BAKER & s. P. WILBUR.

ELECTRIC ARC LAMP.

APPLIOAIION FILED JAN. 10. 1903. g

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No. 794,839. PATENTED JULY 18,1905. M. H. BAKER & s. P. WILBUR.

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UNITED STATES Patented July 18, 1905. i

I PATENT OFFICE.

MALCOLM H. BAKER, OF NEW YORK, N. Y., AND SAMUEL P. WILBUR, OF WVILKINSBURG, PENNSYLVANIA, ASSIGNORS TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION PENNSYLVANIA.

ELECTRIC-ARC LAMP.

SPECIFICATION forming part of Letters Patent No. 794,839, dated July 18, 1905.

Application filed January 10, 1903. Serial No. 138,453-

To all whom it may concern:

Be it known that we, MALCOLM H. BAKER, a resident of New York, in the county and State of New York, and SAMUEL P. VVILBUR, a

resident of VVilkinsburg, in the county of Allegheny and State of Pennsylvania, citizens of the United States, have invented certain new and useful Improvements in Electric-A rc Lamps, of which the following is a specification.

The present invention relates to improvements in arc-lamps in which one or both of the electrodes is composed of carbon impregnated or intimately associated with some of the metallic salts which when consumed or highly heated in an electric arc become intensely luminous and constitute a source of light of very high candle-power. Electrodes of this sort are represented by the well-known Bremer type of arc-lamp electrodes. It is understood that when the advantages of electrodes of this class are sought for in a directcurrent arc-lamp it is not necessary that both electrodes should be of the composite character, but the negative electrode may be an ordinary carbon electrode, while the positive should be what we have herein called an impregnated electrode. In using this term we refer to a composite electrode consisting of carbon intimately associated with one or more of the metallic salts, whether such association is obtained by actual impregnation or by intimately mixing, grinding, and baking the elements when held together by a suitable binder.

The form herein proposed as suitable for the arc-lamp electrodes is one which possesses various advantages, among them that of dispensing with all feeding mechanism, the electrodes being stationary and occupying throughout the period of consumption the same relative positions. In other words, the electrodes are stationary with respect to each other and are consumed by an even burning away of the electrode ends when the lamps are actually in operation.

Another advantage of our invention is that of providing a long-trim life without unduly increasing the dimensions of the lamp and without necessarily resorting to the use of a tight inclosing globe, as in the ordinary inclosed arc-lamp. This advantage becomes of special importance when we remember that the composite or impregnated electrodes give off in burning rapid deposits of theimpurities of combustion, thus defeating to some extent the advantages to be derived from using an inclosing bulb or globe.

The increased length of trim-life belonging to our form of lamp is due to the fact that we increase the cubical contents of the electrodes, while the structure of the electrodes is such that their cost is low in comparison with pencil electrodes having approximately the same cubical contents, and their mechanical strength is materially greater.

In our lamp we propose to make one or both of the electrodes of cylindrical shape and in any case to arrange the electrodes concentrically with relation to each other. The inner electrode may be either a cylinder or a solid electrode concentrically arranged with relation to the outer electrode. By constructing the lamp-electrodes in this manner and supporting them in such a way that they point in a downward direction the are formed between their lower ends will be so directed as to be blown downward, whereby the effective radiation of the arc will be disposed in the best possible manner for good and unobstructed illumination. Moreover, the arc will be spread into a fan shape, thus securing a greater separation and more perfect combustion of the incandescent metallic particles. An arclamp having its electrodes thus constituted and arranged will obviously require no feeding mechanism, While the arc will be maintained stable and free from interruption during the operation of the lamp. We find that under the conditions as above outlined the arc is spread and maintained in fan-shaped form without the employment of any magnetic blow-out apparatus, owing to the tendency which exists for causing the arc to assume this shape and maintain it through the action of what we call the local field of the are.

This action is much more pronounced when the impregnated electrodes are employed than when ordinary carbon electrodes are used under similar conditions. It is a function which we have discovered and make use of in our lamp. In other words, when the electrical connections to the two electrodes are properly made-say at the upper ends of two cylindrical electrodes arranged as described abovethe are will naturally assume the fan shape, bowed in a downward direction and will maintain such shape without requiring to be blown downward by a magnetic field. The are may be started by employing a suitable striker or igniter, which through the action of a magnet in series with the electrodes can be drawn out of contact with the electrodes when the lamp begins to operate. As to the action of the lamp during operation we find that the are travels from point to point along'tl1e lower ends of the electrodes, seeking the path of lowest resistance, whereby the electrodes are evenly burned away, thus preventing any obstruction of the luminosity and securing an even burning of the electrodes. In this respect the action of our lamp is similar to that of an inclosed arc-lamp wherein the points of the electrodes burn off evenly. hen em ployed on direct-current circuits, the inner cylinder or rod, as the case may be, will usually be an ordinary carbon electrode. The outer electrode will, however, be impregnated and will constitute the positive electrode of the lamp. Its proportions will be such with relation to those of the inner cylinder or rod that its consumption, measured along its length, will be equal to that of the inner electrode. In general when both electrodes are cylindrical the two cylinders may be made of equal wall thickness when the lamp is to be employed on a direct-current circuit. On the other hand, when the lamp is to be constructed for use with alternating currents the wall of the outer cylinder will be made thinner than that of the inner cylinder, the cubical contents of the two being made equal for obvious reasons. The cylinders or the cylinder and the rod are mounted beneath a suitable bed-plate and screened from air-drafts.

In the accompanyingillustrative drawings, Figure 1 is an end view of two concentric arclamp electrodes, showing the arc bridging two adjacent points on the electrodes. Fig. 2 is a similar view of two electrodes, one of which is a cylinder and the other a rod concentric therewith. Fig. 3 is a vertical section of a cylinder electrode-lamp embodying our invention. Fig. 41 is a diagram of the lampcircuits. Fig. 5 is a vertical section through the lamp-electrodes, illustrating a modified form; and Fig. 6 is a bottom view of the said modified type.

In Fig. l the inner and outer electrodes are shown, respectively, at 1 and 2, the same being arranged concentrically one within the other. For convenience we will assume that the lamp embodying these electrodes is to he used as a direct-current lamp, in which case the electrode 2 will be of composite material carbon and metallic salts-and the electrode 1 may be of similar material, or it may be made of ordinary carbon. The are is illustrated at 3, where it is established across between two adjacent points upon the concentric cylinders, these points being assumed to be so related as to constitute the terminals of a path of comparatively low resistance bet-ween the electrodes. As the electrodes are burned away these points may cease to be in the line of least resistance, whereupon the arc will shift to such points and the electrodes will be uniformly consumed as this process is continued. In practice it is found that the shifting of the arc in this manner is not accompanied by any disagreeable conditions in the light etfccts, being in this respect not materially different from the inclosed arc-lamp, where a similar shifting takes place. By reason of the fact that the cubical contents of the cylinders are considerably greater than those of pencil electrodes, per unit of length, the cylinders may be short and still be of longli't'e, approaching or equaling the life of the carbons in an inclosed arc-lamp. As already stated, thebest arrangement for an alternatingeurrent arclamp would be one in which the outer cylinder was provided with thinner walls than the inner cylinder, the cubical contents, per unit of length, being made the same in both cylinders. The electrodes beingimpregnated or intimately associated with metallic salts, the are itself is filled with incandescent particles while the lamp is burning, and these serve to maintain the are through the zero-point in operating the lamp on alternating current.

In Fig. 3 the electrodes 1 and 2, described above, are shown as incorporated into a lamp structure. The electrodes are rigidly secured to a base 14 by means of suitable holders 15 and 16, set- screws 18 and 19 being employed for making the immediate connection between the holders and the electrodes. The holder 16 is extended downward and spread out at the bottom, so as to form a chamber 17, which acts to confine the heated gases in the neighborhood of the are. In order to avoid interference between the electrode 2 and the holder 15 of the electrode 1, the latter electrode is cut 011' at the top or made shorter than the electrode 2. This construction also serves to prevent interference between the set-screw 19 and the holder 16 of the electrode 2, the said holder being cut away to admit the setscrew 19, as shown at the left of Fig. 3. To establish the are, an ignitera, of some suitable conducting material, is employed, the same being mounted in a holder 5 by means of a setscrew 6, so as to be capable of easy replacement. The holder 5 is rigidly attached to a rod 7, which is fixed to the core 8 of a small series starting-magnet 9.

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When the circuit is inactive, the core 8 is raised to its highest possible position by means of a spring 10, attached to a bracket 11, which is secured by screws 12 12 to the bed-plate 14 and supports the starting-magnet 9. The bed-plate referred to is preferably made of some good heat-resisting insulating material, such as por- WVhen no current is passing through the lamp, the igniter 4is raised by the spring into contact with the electrodes 1 and 2, thus bridging the gap between the electrodes. when current is thrown upon the lamp, the core 8 is drawn down by the action of the magnet 9, thus separating the igniter from the electrodes and establishing the arc. The lamp mechanism will generally be protected by a suitable casing and the arc itself surrounded by a large globe, as in the usual forms of arclamps. Any type of cut-out may be employed.

In lieu of any other cut-out for multiple Work where it is only necessary to interrupt the circuit the stop may strike the bed-plate 14, and thus prevent the igniter 4 from making contact across the electrodes when the latter have burned away beyond the range of the striker. The are may be interrupted by extending the holder 15 down to a suitable point between the electrodes or by introducing any similar foreign substance between the electrodes. In general we prefer to use the form of cut-out described in application Serial No. 129,338, filed by Malcolm H. Baker October In Fig. 5 we show electrodes considerably longer than those illustrated in the other figures of the drawings. When such longer electrodes are used in order to secure greater trim-life, there is the possibility that, owing to the increased amount of chamber-space between the electrodes, the circulation of air might be excessive and tend to allow the are between the electrodes to draw up, and thus be removed from the sphere where its light willbemosteffective. Toprovideagainstthis, we supply horizontal partitions 21 22, of some suitable non-conductingmaterial, such as mica or plaster-of-paris, the same extending across the space between the electrodes and forming subordinate chambers of smaller area. This prevents undue drafts of air and at the same time does not interfere with the proper operation of the lamp, inasmuch as the are on reaching a point immediately below one of the partitions will fuse it and open the chamber above, and so on.

In specifying metallic salts as the ingredicuts to be mixed singly or in combination with carbon for forming one or both of the electrodes we do not wish to confine ourselves to any particular list of salts nor to exclude chemical salts having the characteristic of giving off gases or vapors which become highly luminous under the influence of heat.

The particular form of lamp described in this specification is one in which the electrodes depend from a suitable insulating bed-plate. Naturally the invention would possess advantages whether the electrodes were pointed downward or upward or arranged in a horizontal or angular position. We therefore do not limit ourselves to a construction of lamp in which necessarily the electrodes hang downward from an insulating-support.

7 We claim as our invention 1. In an electric-arc lamp, a pair of concentrically-arranged electrodes, in combination with means for limiting the chamber-space between the two electrodes near the ends thereof and thereby confining the circulation of air in'proximity to the arc.

2. Anelectric-arc lamp, consisting essentially of a pair of concentric electrodes one placed within the other, a bed-plate supporting the said electrodes, starting means for establishing the are between the ends of the electrodes remote from the bed-plate, means for connecting the electrodes with the external circuit, means for limiting the circulation of air at the arcing ends of the electrodes, and a globe surrounding the electrodes.

3. In an electric-arc lamp, a pair of electrodes concentrically arranged, the outer electrode being separated from the inner by an annular chamber, in combination with partitions of insulating material dividing the said chamber into subordinate chambers of smaller area.

Signed at New York, in the county of New York and State of New York, this 3d day of

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