US1803486A - Cut-out for incandescent electric lamps - Google Patents

Description

May 5, 1931. H. RAU, JR 1,803,486

CUT-OUT FUR INGANDSSOBIT ELECTRIC LAIPS Filed June 22, 1927 INVENTOR H- R A u J ATTORNEY Patented May 1931 UNITED STATES PATENT OFFICE HENRY MU, .13., 0] NEW YORK, N. Y., ASSIGNOR '10 WESTINGHOUSE LAMP COI- PANY, A CORPOBA'IIQN OF PENNSYLVANIA CUT-OUT'I'OR INGANDESGENT ELECTRIC LAMPS Application filed June 82, 1927. Serial No. 200,560.

This invention relates to incandescent electric lamps which are operated in series and more particularly to a lamp having means incorporated therewith for permittmg the bypass of current upon the failure of the filament of the lamp.

Certain classes of incandescent electric lamps such as those employed for Christmas tree lighting and which may be termed miniature lamps are operated when a given number are connected in series so that the combined voltage of the lamps equals the line voltage supplying the current.

It has heretofore been found that when using a plurality of lamps connected in series, great inconvenience would occur upon a failure of one of the lamps owing to a broken filament or other cause, since such failure breaks the continuity of the circuit and the rest of the lamps are extinguished. Inasmuch as it is difiicult to determine by inspection which lamp is defective, it becomes necessary in order to select which lamp has failed, to test by trial until the defective lamp has been discovered. This procedure involves considerable time and inconvenience and has heretofore caused considerable annoyance in connection with this type of lamp.

The present invention provides a miniature lamp of the Christmas tree type in which supplemental or auxiliary means are provided to permit a flow of current upon failure of the lament or other defect which might prevent a flow of current in the bulb, thereby, preventing the remaining lamps of the series from becoming extinguished and immediately indieating which lamp of the series'is defective.

Various forms of cut-out or resistance elements have been associated with lamps burned in series in order to accomplish the above purpose. Considerable difiiculty has, however, arisen in providing a Christmas tree lamp with a cut-out since the construction of such lamp does not appear to afford any practical way of incorporating a cut-out material. In the large type of lamps, it had been proposed to provide a lamp with a resistance material surrounding the lead-in Wires extending through the tubular portion of the stem. Christmas tree lamps, however, are constructed without a stem, the mount comprising a pair of lead-wires which support a filament, the lead wires being secured between a bulb and the exhaust tube by what is known as a butt sealing operation. Furthermore, a Christmas tree lamp must be made at relatively small cost and any operation which would tend to increasev the same would be objectionable from a manufacturing standpoint.

An object of the present invention is, therefore, to provide an incandescent lamp of the Christmas tree type having incorporated therein a supplemental by-pass or cut-out element of simple construction and at rela tively low cost.

A further object of the invention is to provide an incandescent lamp base with a cut-out element which may be quickly and conveniently installed, producing an article in the form of a lamp base which may be applied to a bulb in the same manner and without changing the factory practice of basing.

In accomplishing the above, the base portion of a miniature or Christmas tree lamp is utilized to carry a substance to provide an electrical connection between the leading-in wires of the lamp but which is normally resistant to prevent a flow of current and which upon a failure of the filament within the lamp will, by reason of the applied excess voltage, be converted into a conductor to permit the passage of current.

In accomplishing the above, it has been found preferable to partially fill the lower portion of the base of a lamp with a layer of powder such as a partially oxidized metallic powder which may be aluminum or iron or the like. This powder is pressed into a compact mass and surrounds a tubular member or eyelet through which one of the leading-in wires extend, or may be disposed in direct contact with a lead wire. The powder is arranged so as to also contact with the metallic shell or base of the lamp to which the opposite leading-in wire is connected. Normally the film of oxide surrounding each particle of the powder constitutes a dielectrlc or resistance which prevents the flow of current between the leads while a flow of current is current from one lead to the other and consequentlya flow of current through the remaining lamps in the series.

When each lamp of a series of lamps is provided with a cut-out of the above character, it will be obvious that a failure of any one of the lamps will not cause a termination of the flow of current, thus, if a lamp becomes extinguished due to a defect, it may readily be detected and removed and a newlamp installed.

Other objects and advantages of the above will be obvious from the following description, reference being had to the accompanying drawing in which Fig. 1 shows an incandescent lamp of the Christmas tree type with the base portion broken away to show the cut-out element and Fig. 2 is a sectional view of a base showing a modified form of the cut-out element.

Fig. 3 is a cross sectional view on an enlarged scale of the base portion of Fig. 1.

Although the invention may be applied to various types of incandescent lamps, the selected embodiment thereof comprisesa bulb 10, having a mount 11, supported therein. This mount usually comprises a filament 12, a pair of lead-in wires 13 and 14 secured to gether by a glass bead 15. In the manufacture of this type of lamp, an exhaust tube 16 is applied to the end of the bulb and sealed by fusion at 17, the leading-in wires passing through thewall of the bulb at the fused portion. The bulb is then exhausted and the exhaust tube is tipped off, thus sealing the bulb from the atmosphere.

A base 18 comprised of a casing or shell is then applied to the bulb and secured thereto by a cement 19, the leading-in wire 14 being soldered to the base at 20. The leading-in wire 14 is usually embedded in the cement, while the leading-in wire 13 extends through the lower end of the base and is soldered to a contact 21. The bases as commonly used, employ a glass insulator ring 22 which surrounds the contact-and thus avoids electrical connection between the same and the metallic shell of the base.

In the present construction, the contact 21 is provided with a tubular member 23 extending into the base. This contact or extending member may as a whole be termed a contactmember or the eyelet. For the purpose of providing for the passage of current between the leading-in wires on a failure of the filament, the lower portion of the base may be filled with a layer of metallic powder 24. This powder surrounds and is in contact with the eyelet and also in contact with the shell of the base. If desirable, however, the eyelet 23 may be dispensed with and the lead wire 13 disposed directly in contact with the metallic powder. The lead wire may be soldered to the contact 21 which is usually in the form of a disc embedded in the insulator ring 22.

Various substances may be employed in the form of powder, for example, particles of conductive materials may be coated with a film of a non-conductive substance which serves as a dielectric, or oxidizable metallic powders may be used such as aluminum or iron. It has been found preferable to employ aluminum powder, since aluminum articles acquire a coating of oxide or film w ich remains substantially uniform, thereby making it possible to introduce a resistance element which will not vary in its resistance properties.

It has been found desirable to apply the aluminum powder in the form of a paste, this being accomplished b mixing the powder with any suitable fluid which will quickly evaporate, such for example as alcohol. The powder may, however, be applied in a dry state in which case it may be tamped or pressed into a comparatively solid body; and as shown in Fig. 2, a disc 25 of any suitable material such as fiber or felt may be disposed Within the base in such position as to prevent the displacement of the powder. The disc may be held from movement by any suitable means, as for example, by riveting over the upper end 26 of the eyelet.

A lamp may be constructed in accordance with the present invention without any appreciable increase in cost, thus providing a lamp which avoids the disadvantages accompanying series lamps as heretofore constructed and possessing the required qualities of operation and efiiciency.

Although a preferred embodiment of the invention is shown and described herein, it is to be understood that modifications may be made therein without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. An incandescent electric lamp comprisng a bulb, a mount having a filament disposed in said bulb and lead wires projecting from said bulb, a base including a metallic shell and a contact member insulated therefrom, and one of the lead wires connected with said contact-member and the other with the shell, a material disposed in contact with said shell and said first named wire, said material being capable of serving as a resistance during the normal operation of the lamp and as a conductor upon the failure of a flow of current through the lamp bulb.

2. An incandescent lamp comprisin a bulb, a filament within said bulb, lead wires extending from said bulb, a base, one of said Ill wires being in contact with said base of powdered material in said base and tact with a portion thereof and with the other leading-in wire, said material serving as an insulator upon a flow of current through said filament and as a, conductor upon the failure of a flow of current through said filament. In testimony whereof, I have hereunto subscribed my name this 21st day of June,

HENRY RAU, JR. 7

a. layer in con-

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