US3814973A - Electric lamps of the vibrating filament type having a conductive coating - Google Patents

Abstract

An incandescent lamp having a movable filament therein which is caused to oscillate in response to the field from a magnet in which at least a portion of the surface of the lamp envelope is coated with an electrically conductive material.

Description

United States Patent 1191 Thouret et a1,

[ June 4, 1974 1 ELECTRIC LAMPS OF THE VIBRATING FILAMENT TYPE HAVING A CONDUCTIVE COATING [75] Inventors: Wolfgang E. Thouret, Verona, N.J.;

Rudolph Kaufman, Bronxville,

[73] Assignee: Duro-Test Corporation, North Bergen, NJ.

22 Filed: Sept. 5, 1972 121 App]. No.2 286,551

52] us. c1 313/313, 313/160, 313/291,

581 Field of Search 315/267; 313/313, 110,

[56 1 References Cited UNlTED STATES PATENTS 2,079,085 5/1937 Richter et all 313/313 X 2,419,177 4/1947 Steadman 313/110 X 2,456,474 12/1948 Wainwright 313/313 X 2,654,042 9/1953 Clarke et 211. 313/291 X 2,714,683 8/1955 Jenkins 313/291 X 3,200,280 8/1965 Thau et a1 313/110 3,355,617 11/1967 Schwartz et a1. 313/313 X 3,549,946 12/1970 Kyp 315/267 Primary Examiner-Alfred L. Brody Attorney, Agent, or FirmDarby & Darby v 71 ABSTRACT An incandescent lamp having a movable filament therein which is caused'to oscillate in response to the field from a magnet in which at least a portion of the surface of the lamp envelope is coated with an electrically conductive material.

7 Claims, 5 Drawing Figures ELECTRIC LAMPS OF THE VIBRATING v FILAMENT TYPE HAVING A CONDUCTIVE COATING Decorative incandescent lamps with vibrating filaments that simulate the flickering movements of a candle flame are commercially available. Lamps of this type have a filament of a relatively thin and flexible material which is formed in a loop of a desired shape. A permanent magnet is mounted either inside the glass lamp bulb or on the outside of the bulb with its magnetic field oriented to react with alternating current flowing through the filament to cause the lamp filament to vibrate. Thealternating current applied to the filament is also of a magnitude to make the filament incandesce so that the impression of a flickering live flame is created for the purposes of esthetic appeal. A lamp of this. general type is disclosed in US. Pat. No. 3,237,053 and French patent 368,913.

Some lamps of the foregoing type, out of-a batch which are made by the same manufacturing techniques,

An additional object is to provide an electric incandescent lamp with a vibrating filament having a conwhich:

become inoperative, that is, cease vibration, or begin to vibrate only slowly or intermittently after a relatively short period of time of operation. One reason for this, among others, is that the glass bulb accumulates an electric chargeon its surface. This charge in turn creates a relatively strong electric field between the inner wall of the lamp bulb and the filament. The electric field produced by the static'charge electrically attracts the filament, which is relatively thin and flexible. In some cases, the attraction is strong enough so that the filament will be moved completely over to the wall of the bulb where it will be held. This, of course, renders the bulb inoperative for its intended purpose of producing a vibrating filament.

The static charge is held by the bulb for a long period of time, due to the excellent insulating properties of the glass. in some cases, it is possible to discharge the builtup static charge merely bytouching the lamp bulb. However, in other cases, this simple expedient will not work. When the thin filament is attracted against the bulb wall by the electric charge. it is often permanently damaged thcrcbyrenderin g the lamp useless even if the static charge could later be dissipated.

The present invention relates to lamps of the vibrating filament type and more particularly to an arrangement for preventing the buildup of a static electric charge on the glass lamp bulb. In accordance with the invention, a coating of a light-transmitting electrically conductive material is deposited on the inside, the outside, or both walls of the bulb. The conductive coating, which is returned to an electric neutral point, acts to dissipate the electric charge which would be built up on the lamp bulb. The coating may also be of a suitable type, forexample of a desired color, so as to produce a novel decorative effect. Thus, the coating performs the dual function both of reducing the buildup of the static electric charge and also of serving as a decorative coating. The latter is particularly esthetically pleasing when used in combination with thevibrating incandescent lamp filament.

It is therefore an object of the present invention to provide a novel incandescent lamp of the type having a vibrating incandescent filament with a coating of conductive material on one of'the walls of the bulb to reduce the static electric charge buildup.

FIG. 1 is an elevational view, partially broken away, of a lamp made in accordance with the invention;

FIG. 2 is an elevational view similar to FIG. 1 the turn with respect thereto;

FIG.- 3 is a view similar to that of FIG. 2 of another embodiment of the invention;

FIG. 4 is a cross-section of a fragment of the lamp bulb wall of FIG. 3; and

FIG. 5 is an elevational view similar to FIG. 1 showing another embodiment of the lamp.

Referring to FIGS. 1 and 2, the lamp of the subject invention includes theusual glass bulb 12 having a threadedbase 13 which forms oneelectrical contact 14 for connection to an alternating current supply (not shown) and asecond contact 15 at its bottom. This is a conventional lamp construction. lt shall be understood that other conventional base constructions, for example a bayonet base, also can be utilized.

Afilament 18 having the shape of a loop extends upwardly from aglass stem 20 mounted within the lamp bulb. The filamentis mounted at itsends 18a and 18b to a pair of lead wires 21a and 21b which'pass throughstem 20 and are respectively connected to thecontacts 14 and 15 ofbase 13. The connection between the ends of the filament and the lead wires can be made by any suitable arrangement, for example, by the use of a suitable electrically conductive cement. Thefilament 18 is preferably made of carbon and is relatively thin and flexible so that it can vibrate in a desired pattern. The filament itself is shaped as desired.

Apin 22 is mounted in thestem 20. The pin is not electrically connected to any other part of the lamp. It has aloop 23 at its upper end to hold apermanent magnet 25. The permanent magnet, which can be of metal, ceramic, or any other suitable material, is shown illustratively as being of elongated bar shape. It should be understood that any suitable shape can be utilized. Also, it should be understood that the permanent magnet can be located on the outer wall of the bulb.

The permanent magnet is oriented with respect to thefilament 18 so that its magnetic field reacts with the alternating current applied to the filament to cause the filament to vibrate, pivoting about the connecting points to the lead wires, in accordance with the classical physical reaction of electromagnetic theory wherein a magnetic field reacting with electric current will produce motion. Sincealternating current is used, the motion generally will be in opposite directions on each side of the plane of the filament when it is at rest.

It has been found that for some reason the motion of thefilament 18 will eventually cause a static electric charge to build up on the wall ofbulb 12. The theoretical reason for the charge build up is not entirely known erably, or weakens the vibrational amplitude. In some cases the filament is permanently damaged when it engages the bulb wall and will stop vibrating entirely or break and thereby render the lamp totally inoperative.

In accordance with the invention, the foregoing disadvantages are overcome by coating at least one of the wall of the bulb with a thin, light transparent electrically conductive coating. It is preferred that the coating be at least on the inner bulb wall. This is shown in FIG. 2 wherein thecoating 30 fully coats the inner wall of the bulb. It also extends over at least a portion of the stem to make contact with one of the leads 21a or 21!). This connects the coating to the neutral electrical points of the alternating current power supply on alternate half cycles of the applied voltage to discharge any static electric charge which is built up on the bulb wall. lnstead of using the coating material to connect the coating to one of the lead wires, a conductive wire or strip can be utilized.

The conductive coating can be of any suitable material which has the necessary electrically conductive properties. For example, it can comprise a metal such as aluminum, silver, gold, copper, tin, etc. It can also comprise another electrically conductive compound, for example, tin oxide. Some semi-conductive compounds, for example gallium phosphide, gallium arsenide, indium arsenide, mercury selenide, also can be used. This will provide a slower rate of leak-off of the charge. The coating and its thickness are selected so that the bulb will still have substantial lighttransmission quantities for the light given off by the filament. This can be accomplished by depositing on the bulb wall by evaporation or cathode-sputtering under vacuum, or any other suitable method, the desired thickness layer of the coating material being used. Such coatings can be made very thin, as small as about ten angstroms.

While the coating layer will absorb some of the light emitted from theincandescent filament 18, this absorption can be kept relatively low by using a very thin layer of the conductive material. Even when the optical absorption of the coating layer or layers is adjusted to less than 10 percent of the incident visible light, the electrical conductivity can be entirely sufficient for the purpose of this invention to prevent the accumulation of an electrical charge on the glass bulb wall. It should be understood that thecoating material 30 can be selected for a particular esthetic effect, for example, by color or by the pattern of deposition.

H08. 3 and 4 show another embodiment of the invention. Here acoating layer 30 is deposited on the inner bulb wall and alayer 32 on the outer bulb wall. As before, the coatings are of any suitable electrically conductive material. Theinner layer 30 is again electrically connected to one of thelead wires 210 or 21b, whichever is the one electrically connected to the threadedportion 14 ofbase 13. Theouter layer 32 also has alower portion 33 which extends to make electrical contact with the threaded portion of thebase 13. Since both the inner andouter coatings 30 and 32 are connected to the same electrical point there is no potential gradient between the two coatings and a charge cannot be built up. ln some cases it might not be necessary to make the extendingportion 33 since the threaded part of the socket into which the lamp is screwed would normally make contact with the lower end of the bulb.

In some applications, for decorative lamps with vibrating filaments, a certain amount of light adsorption through an electrically conductive layer on the glass bulb is desirable. If the coating is properly selected, the light absorption or partial absorption and partial reflection of the light from the filament on the opposite bulb walls can produce interesting and pleasing decorative optical effects. Further, if the electrically conducting layer is made extremelythin, it can produce multi-color effects through optical interference, thus creating the appearance of an irridescent coating on the lamp bulb. In some cases, the desired decorative effects can be obtained without electrically connecting theouter coating 32 to the source of alternating current voltage. It has been found that the inner coating provides the most significant effect with respect to the prevention of charge accumulation.

The accumulation of electrical charges can in many cases also be effectively prevented by coating the bulb only partially. As shown in FIG. 5, only the lower half of the bulb inner wall surface, from the bulb neck to the semi-spherical bowl of the bulb, has a coating 30a thereon. ln general, the coating does not have to cover the entire bulb surface, either inside or outside.

Other suitable patterns, or configurations, for the coating also can be used. For example, a wire mesh" or other suitable configuration which provides an electrically closed surface can be utilized on all or a portion of the one or both of the bulb walls. This provides an interesting decorative effect as well as seeming to prevent charge accumulation.

What is claimed is:

1. In an incandescent lamp the combination comprising, a bulb of transparent vitreous material, an incandescent filament located within said bulb, means for electrically connecting said filament to a source of alternating current, a permanent magnet located with respect to said'filament to interact with the current flowing therethrough to produce vibration of the filament and to cause it to travel through a substantial portion of the internal area of the bulb and adjacent the inner wall of the bulb, an electrically conductive coating of material which is at least partially light transmissive on at least one of the walls of said bulb, and means for electrically connecting said coating to a point of potential with respect to said current source to leak away a static electric charge from'the bulb.

2. A lamp as in claim 1 wherein said electrically conductive coating is located on the inner wall of the bulb.

3. A lamp as in claim 1 wherein said electrically conductive coating is located on the outer wall of said bulb.

6. A lamp as in claim 1 wherein said electrically conductive coating is arrayed in a predetermined pattern.

7. A lamp as in claim 1 wherein said electrically conductive coating is of metal.

Claims (6)

1. 2. A lamp as in claim 1 wherein said electrically conductive coating is located on the inner wall of the bulb.
2. 3. A lamp as in claim 1 wherein said electrically conductive coating is located on the outer wall of said bulb.
3. 4. A lamp as in claim 1 wherein the electrically conductive coating is located on both the inner and the outer walls of the bulb.
4. 5. A lamp as in claim 1 wherein the electrically conductive coating covers only a portion of the surface of the bulb wall.
5. 6. A lamp as in claim 1 wherein said electrically conductive coating is arrayed in a predetermined pattern.
6. 7. A lamp as in claim 1 wherein said electrically conductive coating is of metal.

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