US2979634A

US2979634A - Projection lamp

Info

Publication number: US2979634A
Application number: US701414A
Authority: US
Inventors: Jr Sandford C Peek; Broek Jan A Van Den
Original assignee: Sylvania Electric Products Inc
Current assignee: GTE Sylvania Inc
Priority date: 1957-12-09
Filing date: 1957-12-09
Publication date: 1961-04-11
Anticipated expiration: 1978-04-11

Description

PROJECTION LAMP Filed Dec. 9, 1957 INVENTORS Ma S .0

N am w. FA M ATTORNEY PROJECTION LAMP Sandford C. Peek, Jr., Hamilton, Mass, and Jan A. Van Den Brock, Ann Arbor, Mich., assignors, by mesne assignments, to Sylvauia Electric Products Inc., Wilmington, Del., a corporation of Delaware Filed Dec. 9, 1957, Ser. No. 701,414 9 Claims. (Cl. 313-113) This invention relates to electric incandescent lamps and especially to lamps designed for use in moving picture projection devices or in other devices requiring a high concentration of light energy on a limited area.

Such lamps have been made heretofore for use with an external reflector, or with a metallic reflector deposited on the inside of the glass bulb of the lamp. When an external reflector was used, it had to be made large compared with the dimensions of the lamp, in order to reflect a suflicient amount of the light in'the desired direction. This necessitated a large enclosure for the project ing system, with consequent cumbersomeness and expense. In addition, there was the difliculty of properly aligning the lamp filament with the reflector, since the lamp has to be made detachable for replacement purposes.

2,979,634 Patented Apr. 11, 19 61 during life much better than do lamps with a reflector coating deposited on the lamp bulb.

When a lamp according to the invention is used in a moving picture projector, the condenser lens or lenses ordinarily used in such apparatus becomes unnecessary, and the film gate can be positioned so that it will be filled with an image of the filament, the image being enough out of focus to be fairly uniform in intensity over the area of the gate. The solid angle of the reflector need only be great enough so that the light rays passing through the film gate will be at the proper angle to fill the objective lens used on the other side of the gate, for focussing the picture on a screen.

The increase in etficiency of useful light output is so great that, in a propector for 8 mm. film, a 50-watt filament in a lamp of our invention can be as effective as a 500-watt filament with an external reflector, thus greatly reducing the amount of heat to be dissipated in the projector or other devices in which the lamp is used. However, because of manufacturing tolerances, voltage requirements and the like, a ISO-watt filament will gen- Eliminating the external reflector and using a reflecting surface deposited on the interior or exterior surface of the lamp bulb provided a more compact unit, but introduced the additional difficulty of forming the glass bulb to a special and very precise shape. The shape could not be controlled precisely enough with the usual methods available for molding glass bulbs. Furthermore, the reflector was on the lamp bulb and the filament was on the lamp mount, so the proper positioning of filament and reflector was diflicult to control accurately when the flare of the mount was sealed to the open end of the bulb. The alignment had to be fixed with precision while the seal was still hot and plastic, and before it solidified. A base then had .to be aflixed to the lamp and aligned.

We have found that the above difliculties can be avoided by making the lamp with an internal reflector, separate from the bulb, and supported solely from the same mount which supports the filament. The reflector and filament can then be aligned directly on the mount before the latter is sealed to the bulb. The filiment can be supported on wires fixed to the reflector support, and the two lined up approximately with each other before they are even attached as a unit to the mount. If the mount is made on a flat glass disc, or header, with rigid lead-in wires extending therefrom to act as contacts for engagement with a suitable socket, the difliculties of aligning the filament and reflector with a subsequentlyattached base, are also eliminated.

Moreover, the filament can be made in a concentrated coil; and the reflector placed very close to the coil, so that a very small reflector will suflice.

With the reflector close to the filament, however, a small change in position of the filament will greatly affect the focusing of the bulb; accordingly, the filament should be one which will not be appreciably deformed on heating to its operating temperature. The filament must remain in a substantially fixed position. Such a filament coil can be made in the manner shown in United States patent application Serial No. 674,364, filed July 26, 1957 by Wilfrid G. Matheson.

"The lamps of our invention maintain their lightoutput e'rally be used.

Other objects, features and advantages of the invention will be apparent from the following specification, taken in conjunction with the attached drawings in which:

Fig. l is a front view of one embodiment of the invention;

Fig. 2 is a side view, partly in section, of the same device; and l Fig. 3 is a back view of the device.

In Fig. 1, a front view of the finished lamp, the tubular glass bulb 1 encloses a reflecting surface 2 and a tungsten filament 3 at or near the focus of the reflecting surface.

The manner in which the reflecting surface 2 and filament 3 are supported, is shown in more detail in Figs. 2 and 3. In Fig.2, the bulb 1 has a disc-like glass header 4 sealed to its neck 5, the latter being of smaller diameter than the main portion 6 of bulb 1. The other end 7 of the bulb is rounded as shown, and preferably covered by the coating 8, which can be of a colored or black enamel glaze suitable for scaling to the glass of the bulb. This coating increases the heat radiation from the top of the bulb so that it operates at a lower temperature. j

In order to provide supports an external contacts, leadin wires 9, 10, 11, 12 are sealed through

nubs

13, 14, 15, 16 in the header 4, a metal capable of scaling to the glass nubs being used. Such metals are well-known in the art. For example, if the bulb 1 is of the soda-lime glass often used in lamps, the lead-in wires 9-12 can be of so-called copper-weld wires, which are of stiff steel with a thin copper sheath.

' fIhe reflecting surface 2 is of metal, for example, silver or aluminum, deposited on the concave surface of the glass piece 17 by methods well-known in the art, forexample, deposition by evaporation and condensation in a vacuum. The glass piece 17 has

nubs

18, 19, 20, 21 on its convex back surface 22. A

short wire

23, 24, 25, 26 extends out of each nub, and is sealed therein, the wires 23-26 extending only part way into the glass in order to be insulated from the metal reflecting surface 2 and to avoid damaging the latter. I

The reflecting surface 2 can, of course, be present on an all-metal piece, if desired, in which case glass beads could be inserted in the lead-in wires to prevent shortcircuit of the filament by the metallic reflecting piece to which the lead-in wires would be mechanically connected; A copper-piece, plated with silver can be used asthe reflector.

Support wires

27, 28, 29, 30 are welded to the

wires

23, 24, 25, 26 one of the latter wires to each support wire. The longer supportwires 29, 30., extend downwardlyand toward each other, being curved slightly to conform to the curvature of glass piece 17, and are welded at their bottom ends to a metal cross-wire 31, which extends between the lead-in wires 11, 12, being welded to each of them. This gives a firm support for the top end of the glass piece 17.

Each of the wires-23, 24, extending from nubs '18, '19, is affixed to one, and one only, of the

supportwires

27, 28, which curve downwardly around the convex back 22 of glass piece 17 to the lead-in wires 9, 10, each being welded to one and one only of said lead-in wires. As a result of this and the additional supporting

wires

27, 28, the glass piece 17 is supported very rigidly from the header 4.

The filament 3 isa coiled-coil of tungsten wire, of a non-sag construction formed as in copending U.S. patent application Serial No. 674,364, filed July 26, 1957, by W. G. Matheson, and assigned to the same assignee as the present application.

In order to support and make electrical connections to the filament 3,

metal support wires

33, 34, are clamped or Welded to the ends thereof, one end to each wire, and the wires are spaced apart by the

transverse spacing wires

36, 37, which are sealed to insulating glass bead 33, their ends being spaced apart in the bead to prevent shortcircuiting of the filament. The

support wires

33, 34 are curved to form bights at their

bottom ends

39, 40 and welded near those ends to, respectively, the

support wires

27, 28, which in turn, are welded to the lead-in wires 10.

In that manner, the filament 3 and the metallic reflecting surface 2 are held in perfect alignment with each other independently of the alignment between header 4 and bulb 1, and, of course, without the need of subsequent alignment with an external reflector. However, due to the closeness of the filament to the reflecting surface, even a small variation in filament position can affect the amount of light reflected to a given spot and so the filament must be formed in a manner which prevents sagging when the filament is heated. A method of so forming a filament is shown in the Matheson application above mentioned.

The filament and reflector can be aligned on the mount by means of jigs, if desired, and the jigs afterward removed.

A metal base shell 43 is attached to the neck 5 of the bulb 1 by the cement 44, and carries the outwardly projecting piece 45, which covers and protects the sealed exhaust tube 46 and, together with the keyway 47, also serves to center the lamp in its socket, the base and socket being shown in copending US. application Serial No. a

553,367, filed December 15, 1955, by William Morgan. The

glass nubs

13, 15, and the like, pass through holes in the bottom of the shell 43, as shown in Fig. 2, so that the lead-in contact wires 9, ll), 11, 12 are insulated from said shell.

: The rounded protuberances 48, which may be three in number, extend radially outward from the base shell 43, to help position the lamp in its socket, as shown in said copending application of William Morgan.

For best results, the reflector should be highlypolished no to give a smooth surface. An elliptical surface can be used, with the filament offset from the focus enough to give fairly uniform illumination at the film gate. A sharp image of the filament would be undesirable.

Very good results have been obtained with a spherical f No condensing lens is necessary with the device of our invention.

In order to give good eificiency and life, the lamp is filled with a gas inert with respect to the filament, preferably at a pressure above atmospheric. A filling of nitrogen at a pressure of about 1000 millimeters of mercury is satisfactory. The exhaust tube 4 can be sealed at a pressure above atmospheric by methods now wellknown in the art, for example as shown in copending U.S. patent application Serial No. 594,305, filed June 27, 1956, now Patent No. 2.837,880, by Alexander Rosenblatt et al., assigned to the some assignee as the present application.

In a lamp having a reflecting surface deposited on the inside of the glass bulb, the metallic vapors from the filament tend to deposit on the reflector, blackening it and reducing its reflective power. When the reflector is spaced from the bulb, however, the convection, currents will carry the vapors upward and away from the reflector, so that they will eventually deposit on the glass bulb. A considerable part of the vapor will deposit on the part of the bulb behind the reflector Where it does not reduce the light output.

Various modifications of the device described can be made by a person skilled in the art without departing from the spirit and scope of the invention.

What we claim is:

1. An electric incandescent lamp comprising a sealed bulb of light-transmitting material, two lead-in wires sealed therethrough, a concentrated coiled filament inside said bulb and connected to said lead-in wires, and a curved metallic reflector inside said bulb and spaced therefrom and having its axis perpendicular to the axis of the bulb, said reflector being in position to reflect light from said filament, said metallic reflector being supported at least partly from said lead-in wires but insulated therefrom.

2. An electric incandescent lamp comprising a sealed bulb of light-transmitting material, said bulb being closed by a substantially flat portion, a reflector inside said bulb and of different curvature than said bulb and having its axis perpendicular to that of said bulb, and'a concentrated coiled filament inside said bulb and in reflecting relationship with said reflector, rigid lead-in wires extending through said substantially flat portion of said bulb to act as'external contact prongs, said reflector being supported from some of said lead-in wires, said filament being supported from some of said lead-in wires on the same substantially flat portion of said bulb as said reflector to maintain the filament and reflector in alignment.

'3. An electric lamp comprising a sealed tubular bulb of light transmitting material, one end of said bulb being closed by a substantially flat header, at least three lead-in wires extending through said header, a curved reflector supported from all of said lead-in wires, and a concen trated coiled filament supported by wires connected to two only of said lead-in wires but insulated from said reflector, said reflector being in position to reflect light from said filament in a direction substantially perpendie ular to the axis of the bulb.

'4. The lamp of claim 2, in which the reflector is a curved rigid glass piece having a reflecting coating on the sidethereof nearest the filament.

5. The lamp of claim 4, in which the reflector is sup ported by wires sealed into the side of the glass piece farthest from the filament, the Wires extending part way only into the glass to be out of contact with the reflecting metal coating. 7

6. An electric lamp comprising a sealed tubular envelope of light-transmitting material, one end of said bulb being closed byaheader, straight, rigid lead-in wiresextending through said header, a curved glass piece in said bulb with its axis perpendicular to the axis of said bulb, said glass piece having aconvex and aconcaye side, with four nubs projecting from its convex side, sup

porting wires sealed into said nubs but extending only partly through the glass piece, a reflecting metal coating on the concave side of said glass piece, a concentrated coiled electrically-conducting filament at the focus of 'said reflecting coating, each end of said filament being connected to an electrically-conducting support wire connected to one of the supporting wires for said glass piece, the supporting wires for said glass piece being connected to the rigid lead-in wires inside said bulb.

7. An electric incandescent lamp comprising a sealed envelope having a light-transmitting portion, a curved reflector in said bulb with its axis perpendicular to that of said bulb, rigid support wires for said reflector, a

concentrated coiled filament, electrically-conducting wires mechanically connected to and extending from said support wires to position said filament in reflecting relationship with said reflector.

8. An electric incandescent lamp comprising a sealed envelope having a light-transmitting portion, a spherical reflecting surface in said bulb, to direct light through said light-transmitting portion, and a concentrated coiled filament in said bulb at a point about halfway between the surface of said reflector and the center of curvature thereof in a direction substantially perpendicular to the axis of the bulb.

9. An electric incandescent lamp comprising a tubular bulb, having a colored end, a header sealed to the opposite end of said bulb and closing the same, lead-in wires sealed through said header, a concentrated coiled filament in said bulb and connected to said lead-in wires, and a concave metallic reflecting surface within said bulb and of different curvature than said bulb and having its axis perpendicular to that of said bulb, said metallic reflecting surface being supported from said lead-in wires but insulated from said filament in position to reflect light out of the clear tubular walls of the bulb and away from the 299,885 Welsh June 3, 1884 654,208 Washbnrn July 24, 1900 1,344,429 Ricker June 22, 1920 1,635,116 Du Breuil July 5, 1927 1,800,926 Baird Apr. 14, 1931 1,835,705 Gilleland et al Dec. 8, 1931 1,863,547 Arbuckle June 14, 1932 1,936,854 Parker Nov. 28, 1933 1,998,967 Reynolds Apr. 23, 1935 2,144,438 Birdseye Jan. 17, 1939 2,795,722 Burgener et a1 June 1'1, 1957