US2181292A

US2181292A - Reflector bulb lamp

Info

Publication number: US2181292A
Application number: US172397A
Authority: US
Inventors: Orrick H Biggs
Original assignee: Hygrade Sylvania Corp
Current assignee: Hygrade Sylvania Corp
Priority date: 1937-11-02
Filing date: 1937-11-02
Publication date: 1939-11-28
Anticipated expiration: 1956-11-28

Description

Nqv. 28, 1939.

. o. H. BIGGS 2.181392 REFLECTOR'BULB LAMP Filed NOV. 2, 1937 lnyemfor':

- Attorney,

Patented Nov. 28,

UNITED STATES PATENT ornea 2,181,292 REFLECTOR BU B LAMP Orrlck n. Biggs, Beverly, Masa, assignor to Hygrade Sylvania Corporation, Salem, Mesa, a, corporation of Massachusetts Application November 2, 1937, Serial No. 112,397

2 Claims. (01. 176-34) The object of this invention is to provide an electric lamp which produces a directed beam of light, and in particular to provide an electric incandescent lamp with a reflecting coating on its bulb and a filament positioned within the reflector to give a directed beam of light.

A further object of the invention is to provide an electric incandescent lamp with a bulb having a bowl portion and a skirt portion, a reflector coating over the interior of the skirt portion, and an incandescent filament set close to the narrow end of the skirt portion to give a directed beam of light through the bowl portion.

Still another object is to provide, for such a lamp, a reflecting layer which is protected by a transparent protective coating which also acts as a getter to increase the useful life of the lamp.

Other objects are to provide a reflecting shield between the filament and the neck of the bulb,- to insure the utilization of light otherwise lost in the neck.

Further objects and advantages of the invention will be evident from the following description, taken in connection with the accompanying drawing, in which:

Figure 1 is a side view, partly in section, of a lamp according to the invention;

Figure 2 is a schematic view of the light from a filament placed in a plane perpendicular to the longitudinal axis of the reflector; and

Figure 3 is a schematic view of the light from a filament placed parallel to, or along the longitudinal axis of the reflector.

While the invention may take various forms a preferred embodiment is shown in Figure 1. With reference to the figure, the lamp bulb contains a bowl portion 2, which may be transparent or translucent, and may be colored, if desired; a skirt portion 3, the interior surface of which carries a layer 4 of reflecting material, such as a metal or an enamel, and which may, if desired, be covered by a thin transparent protective coating 5. The filament 6 is disposed near the narrow portion of the bulb, near the neck I, rather than in its usual position near the center of the bulb, in order to give a narrow light beam. A shield 8 of reflecting material is placed in back of and near the filament, as shown, and may be supported from the leads I, I. The reflecting surface of the shield may be covered with a protective coating if desired. To reduce evaporation of the filament during Operation, an atmosphere of inert gas such as nitrogen, argon or krypton, the latter two being better, and preferably at a pressure above half an atmosphere is used inside the bulb.

Any form of contact base 9 may be attached to the lamp.

If desired, the filament may be arranged in a plane perpendicular to the longitudinal axis of the reflecton; In this case, nearly 50%-of the light emitted by the filament is in the backward direction, denoted roughly by the arrow II, in Figure 2, and would be lost in the neck I of the bulb, if the reflecting shield 8 were not placed behind, and close to the filament. The light in backward directions, such as that schematically shown by arrow I I, is thus reflected by the shield, while the light coming from the front of the fila- -ment will either emerge directly from the lamp or be reflected from the layer 4 as shown by arrow l2, which depicts the path of. a ray of light from filament 6 in Figure 2.

The shield, in such a position, is subjected to the heat absorbed from the filament radiation, and if the lamp is used base up, to the heat carried by convection of the hot gases of the lamp filling. It is thus preferably made of aluminum, which remains bright after subjection to high temperatures, and may be supported from the leads of the filament, but must, of course, ifof metal, be insulated from at least one of the leads to prevent short-circuiting them.

With the filament placed as in the preceding paragraph, nearly 50% of the light has to be reflected from the small shield 8. If, however, the filament is placed parallel to, or along the longitudinal axis of the reflector, as in Figure 3, the small shield 8 is not required to control as large a proportion of the total light or radiation, and may run cooler, thus avoiding damaging its reflecting power. In this case, the light emitted from both sides of the filament is reflected. by the layer 4, as shown by the arrows in Figure 3. The light in the directionpf the arrow I l is nearly zero, since the only part of the filament visible in that direction is about the diameter of the coil. The light in the backward direction is thus nearly zero along arrow H, and small in the general backward direction, so that shield 8 is required to control only a small part of the total emitted light. The shield 8, is preferably curved slightly, or slightly V-shaped as shown in Figure 1, so that light hitting it from the filament will be reflected directly out of the bulb through the clear portion 2.

The reflecting" layer 4 may be of a highly refleeting enamel or the like, either white or colored as desired, or may be of metal, deposited by the well-known chemical processes or by the evaporation process described in copending application Serial No. 691,322, filed September 28, 1933. Silver may be used, if desired, but aluminum will generally be better, because it will retain its brightness better after going through the usual lamp manufacturing processes. The aluminum may be oxidized slightly, either chemically or electrolytically, to form a thin transparent protective coating over its surface. This coating, if formed before the manufacturing processes, will enable the aluminum to withstand the severe heat treatment found beneficial to the lamp during manufacture.

The reflecting layer preferably extends from the neck I of the bulb to the point in of largest diameter of the bulb, but generally not beyond, since any reflector on the bowl surface of the bulb would reflect light in the backward direction, and reduce the emciency of the lamp.

This application is in part a continuation of application Serial Nos. 691,322 and 114,562, filed, respectively, September 28, 1933, and December 7, 1936. Application Serial No. 691,322 was issued July 12, 1938 as United States Patent No. 2,123,706. It will often be desirable, in order to have a mole concentrated and straight filament for refiection purposes, to use a so-called coiled-coil ordoubly-coiled filament, as shown for example in U. S. Patent 2,067,746, issued January 12, 1937, to R. M. Zabel.

The beam from a reflector lamp as shown will generally be narrower when the conical skirt is long and narrow, that is when the angle of the cone is small. It may often be desirable to have a cone angle of say 45 near the filament, as shown in Figure 3, and a cone of much narrower angle at a distance from the filament. The skirt may, of course, be a paraboloid of revolution, if desired, particularly if the filament is so concentrated as to be almost a point source.

What I claim is:

1. In an incandescent lamp, a sealed glass bulb having a bowl portion and a conical skirt portion, a reflecting coating of aluminum on the interior surface of said skirt portion, a thin transparent protective oxide coating over said aluminum coating, a filament of doubly coiled tungsten wire set inside the narrow end of said skirt portion and with its longitudinal axis along the longitudinal axis of the lamp, a V-shaped aluminum shield set behind said filament and supported by the leads to said filament, being insulated from at least one of. said leads, the open end of the V facing toward the bowl portion of the lamp, and a filling of argon at greater than half an atmosphere pressure in the bulb.

2'. In an incandescent lamp, a sealed glass bulb having a bowl portion and a frusto-conical skirt portion, a metallic reflecting coating on the interior surface of said frusto-conical skirt portion, a filament coil of diameter small compared to its length set inside the narrow end of the conical skirt and parallel to the longitudinal axis of said skirt to cooperate with the reflecting coating to direct a beam of reflected light through the bowl portion of the bulb, and a filling of inert gas within said bulb.

ORRICK H. BIGGS.