US3249789A

US3249789A - Electric incandescent projection lamp

Info

Publication number: US3249789A
Application number: US220446A
Authority: US
Inventors: Kenneth S Preschel; Robert W Wright
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1962-08-30
Filing date: 1962-08-30
Publication date: 1966-05-03
Anticipated expiration: 1983-05-03

Description

y 3, 966 K. s. PRESCHEL E AL 3,249,789

ELECTRIC INCANDESCENT PROJECTION LAMP Filed Aug. so, 1962 FQZ.

Inveenflfovs: kenne th S. Pveschel, Robert W. Wr-i h t This invention relates to electric incandescent projec tion lamps, and more particularly to lamps embodying an internal reflector associated with the filament to project a light beam in a desired manner.

In such lamps it is desirable to employ a reflector comprising a glass base member having a reflecting coating on a surface thereof. It is further desirable to arrange that the current-carrying lead-in wires extend through the reflector from the back to the coated front surface thereof. The filament is mounted on said lead-in wires at the front of the reflector in accurate relationship thereto. The lead-in wires thus serve to support the reflector at least in part, and are thereby so located as to provide a minimum of interference with the light reflected from the reflecting surface.

I As disclosed in co-pending application Serial No. 73,064, filed December 1, 1960, Patent No. 3,160,776, for an Electric Incandescent Projection Lamp, and assigned'to the same assignee, it is necessary in lamps of this type to provide insulating means interposed between the lead-in wires and the glass base reflector member, said insulating material having aresistance materially higher than that of said glass base and suflicient to prevent current flow through said glass base between said lead-in wires. The insulating means has a volume resistivity exceeding ohms per centimeter cube at room temperature (25 C.). Steatite, which is chiefly MgO.SiO

3,249,789 Patented May 3, 1966."

the filament. Such dichroic coatings are well known and may consist of an extremely thin coating of suitable metal or a composite coating constructed of a film of a semiconductor such as germanium, silicon, antimony sulfide or selenium, coated with a thin film or films of a dielectric material or materials such as zinc sulfide, magnesium crystals, is preferred although alumina or any other of i I the refractory oxides with good high temperature insulating properties would be satisfactory.

It is a principal object of the present invention to provide an improved insulating support means for the reflector which securely holds the filament in the center of the reflector and is easily assembled.

For a full understanding of the invention attention is directed to the following detailed description and to the drawing wherein:

FIG. 1 is a front elevation of a invention;

FIGS. 2 and 3 are side and rear elevations thereof respectively; and

FIG. 4 is a fragmentary sectional view of the assembly of the glass reflector and one of the lead-in wires.

Referring to the drawing, the lamp illustrated thereby, by way of example, comprises a sealed tubular glass bulb or envelope 10 containing a gaseous filling, for example nitrogen or argon at a pressure of about 1000 mm. at room temperature. The bulb it) contains a filament 11 herein illustrated as a coiled coil of tungsten wire extend ing transversely of the bulb and offset from the longi tudinal axis thereof. The filament 11 is mounted at or near the focus of an internal reflector 12 of any desired shape, for example ellipsoidal, the filament 11 being mounted at or near one of the foci of the ellipsoid. The filament 11 is connected across and between the ends of a pair'of transverse inner lead-in conductor wires 13 which extend through the reflector 12 and also serve as a support therefor.

The reflector 12 is a pressed glass base member 12a (FIG. 4) (of the usual lime or lead glasses used in lamps) having on its front surface a reflecting coating 12!; preferably of vapor-deposited material such as silver or a composite dichroic coating which reflects visible light but transmits the heat or infrared rays incident thereon from lamp comprising the fluoride'or aluminum oxide. For instance, there may be employed a layer of germanium of such a thickness as to transmit about 20% of the visible radiations and coated with a layer of zinc sulfide having an optical thickness of about 250 A. I

The ends of the inner lead-in wires 13 at the back of the reflector 12 are connected to, and supported by, intermediate lead-in support wires 14 which are, in turn, connected toand supported by the ends of a pair of outer lead-in wires 15 sealed in a disk-shaped glass press 16 which closes the end of the bulb (FIG. 2). A seal wire 17 having a composition such as to thermally expand at the same rate as the glass is sealed through the press 16. Exterior of the envelope contact pins 18 are con nected to the seal wires 17 and provide the exterior electrical connection for the lamp. To suitably support the contact pins a plate 19 ofinsulating material is provided which seats closely adjacent to the glass press 16 and secures thecontact pins 18 against movement relative thereto. As is conventional, the lower end of the bulb carries a base 20' and its upper end or dome is masked by an opaque coacting 21 which maybe an internal vapordeposited coating of metal such as an aluminum-copperiron alloy.

The reflector 12 is additionally supported from a pair of dummy lead-in wires 22 by arcuately shaped struts 23 connected as by welding between each of the dummy lead-in wires and the intermediate lead-in wires 14 thus preventing misalignment of the intermediate lead-in wires with respect to the lamp base. The manner of attachment of the reflector 12 to the dummy lead-in wires is illustrated in FIGS. 1 and 3 wherein the reflector is provided with a pair of support pins 24 sealed into bosses 25 provided on the back of the glass reflector and embedded in the glass sufliciently deep to securely hold them therein without coming in contact with the reflective coating 12b. The outer ends of the support pins 24 are ,attached to the arcuate-shaped struts 23 and therefor securely locate the lower part of the reflector with respect to the base. The dummy lead-in wires 22 are sealed in the glass press 16 and connected to dummy contact pins 26 by seal wires 27. p

The inner lead-in wires 13 are provided with an expanded portion 28 (FIG. 4) which, in cooperation with steatite ceramic insulating washers 29 and steatite ceramic insulating bushings 30 provided with flanges 31, securely hold the reflector 12 to the intermediate lead-in support wires 14 when the inner lead-in wires 13 are inserted through openings 32 in the reflector and holes 33 in ceramic disks 29 and are then welded tointermediate lead-in wires 14. The arrangement is such that the body bushing 30 extends into the opening 32 in the reflector. to thereby hold the lead-in support wire out of contact with the reflector and insulate it from the reflecting coating 12b. The intermediate lead-in wires 14 are biased against the ceramic bushings 30 when the weld is made so as to slightly tension the reflector lead-in wires 13 while the weld is made.

Thus, it will be noted that there is provided an improved lamp which eliminates the need for a glass seal or extra clip fastening members for the mirror as were necessary in prior constructions, while still providing the insulation required between the reflector and the lead in wires. The support pins 24 which are not in the direct current path and are spaced relatively far away from each other need not be insulated. While the preferred embodiment of the invention has been given, it will be understood that it is merely exemplary thereof, and the invention may be widely modified within the terms of the appended claims.

What we claim as new and desire to secure by letters Patent of the United States is: I

1. An electric incandescent projection lamp comprising a sealed glass envelope; a glass base reflector member in said envelope having a reflecting coating on a front surface thereof and a pair of support pins embedded in a back surface thereof out of Contact with said reflecting coating; a pair of lead-in conductors extending through said reflector having expanded portions adjacent said front surface; a filament connected across and between said lead-in conductors at the front of said reflector member; first insulating members between said expanded portions and said front surface; separate insulating means surrounding said lead-in conductors adjacent the rear surface of the reflector, and a pair of lead-in support wires secured to said lead-in conductors immediately adjacent said separate insulating means whereby said insulating members, said reflector, and said separate insulating means are securely fastened together and supported by said lead-in support wires, said envelope being provided with a relatively flat press base portion having a pair of electrical contact pins and a pair of dummy contact pins mounted therein; said lead-in support wires being mounted on said contact pins; and struts interconnecting said dummy contact pins and said lead-in support wires and connected to said support pins sealed in the rear of the reflector member.

2. An electric incandescent projection lamp comprising a sealed glass envelope; a glass base reflector member in said envelope having a reflecting coating on a front surface thereof and a pair of support pins embedded in a back surface thereof out of contact with said reflecting coating; a pair of lead-in conductors extending through said reflector having securing portions adjacent said front surface; a filament connected across and between said leaddn conductors at the front of said reflector members; a pair of lead-in support wires secured to said lead-in conductors, insulating means surrounding said lead-in conductors and engaging said front and rear reflector surfaces between said securing portions and said lead-in support wires whereby said reflector and said insulating means are securely fastened together and supported by said lead-in support wires, said envelope being provided with a relatively flat press base portion having a pair of electrical contact pins and a pair of dummy contact pins mounted therein; said leadin support wires being mounted on said contact pins; and a strut interconnecting a respective dummy contact pin 4 and corresponding lead-in support Wire and being connected to a corresponding support pin sealed in the rear of the reflector member.

3. An electric incandescent projection lamp comprising a sealed glass envelope; a glass base reflector member in said envelope having a reflecting coating on a front surface thereof; a pair of lead-in conductors extending through said reflector having expanded portions adjacent said front surface; a filament connected across and between said lead-in conductors at the front of said reflector member; insulating washers between said expanded portions and said front surface; flanged insulating bushings surrounding said lead-in conductors adjacent the rear surface of the reflector, and a pair of lead-in support wires welded transversely across and to said lead-in conductors and biased against said flanged insulating bushings with slight tension in said lead-in conductors whereby said insulating washers, said reflector,

and said flanged insulating bushings-are securely fastened together and supported by said lead-in support wires.

4. An electric incandescent projection lamp comprising a sealed glass envelope; a glass base reflector member in said envelope having spaced openings therethrough and a reflecting coating on a front surface thereof; a pair of leadain conductors extending through the openings in said reflector and having expanded portions adjacent said front surface; a filament connected across and between said lead-in conductors at the front of said reflector mom-ber; first insulating members between said expanded portions and said front surface; separate insulating means surrounding said lead-in conductors adjacent the rear surface of the reflector and extending into said openings to insulate said lead-in conductors from said reflecting coating; and a pair of lead-in support wires welded transversely across and to said lead-in conductors and biased against said separate insulating means with slight tension in said lead-in conductors whereby said insulating members, said reflector, and said separate insulating means are securely fastened together and supported by said lead-in support wires.

References (Iited by the Examiner UNITED STATES PATENTS 1,316,001 9/1919 Teachworth 174 153 X 2,668,946 2/1954 Bennett 174-153 X 2,980,818 4/1961 Harris et al. 313113 3,023,667 3/1962 Lessman 313115 X GEORGE N. WESTBY, Primary Examiner.

C. R. CAMPBELL, Assistant Examiner.