US3034007A - Electric incandescent lamp - Google Patents

Description

y 1962 H. CHAITEN 3,034,007

ELECTRIC INCANDESCENT LAMP Filed Jan. 23, 1959 I 1nvntof Herc Lol Chai ten,

b9 was/f His Atto neg.

United States 3,034,007 Patented May 8, 1962 ice My invention relates generally to electric incandescent lamps and more particularly to lamps for use in light projectors.

In certain applications, projection lamps having tubular gas-filled glass envelopes or bulbs are operated in a horizontal position. Projection lamps operate at considerably higher bulb and filament temperatures than ordinary incandescent lamps of comparable bulb size, and the hot convection currents arising from the filament impinge upon the region of the bulb above the filament and sweep down around the sides of the bulb. In spite of the gas filling which, at least during operation of the lamp, is above atmospheric pressure and tends to minimize vaporizationof the filament, there is in fact considerable filament evaporation which condenses to form a black deposit on the bulb. The black deposit causes increased absorption of heat by the bulb so that the bulb becomes plastic and is blistered or bulged outwardly under the pressure of the internal gas filling. This blackening and deformation of the bulb renders the lamp useless well in advance of the end of the useful life of the filament and may seriously injure the projector in which the lamp is used.

It has been proposed heretofore to employ anti-blackening grids or screens arranged to be located above the filament during operation of the lamp whereby to intercept the material vaporized from the filament and to break up the convection currents. In accordance with some of those proposals, the screen was in the form of an inverted V-shaped trough arranged symmetrically above the filament. In at least some instances, it has been found that even with a screen of relatively open structure such an arrangement diverts sufficient of the convection currents to the sides of the bulb to cause a gradual blistering or bulging of the bulb at those sides which spreads out toward the top to ultimately merge and form one large blister or bulge. In certain projection equipment, the lamp is located between a reflector and a condensing lens, and the bulging of that side of the bulb adjacent to the lens (referred to hereinafter as the front of the bulb) is especially critical because of the close spacing therebetween.

In accordance with the present invention, I have found that bulging of the front of the bulb can be substantially prevented by tilting the inverted V-shaped screen so that it is arranged asymmetrically with that side or panel thereof nearer the front of the bulb inclined at an acute angle below the horizontal and the other side or panel extending substantially horizontally toward the rear of the bulb. Experience has shown that not only is the blistering or bulging at the front and at the top thereof substantially eliminated but, surprisingly, there is no tendency to increase blistering at the rear of the bulb over the amount occurring thereat with the screen symmetrically arranged with both sides or panels obliquely oriented with respect to the vertical.

Further features and advantages of my invention will appear from the following detailed description of a species thereof, and from the drawing wherein:

FIG. 1 is a front elevation of a projection lamp embodying the invention;

FIG. 2 is a cross-sectional view of the lamp taken along the line 2-2 of FIG. 1, with a somewhat diagrammatic showing of an associated reflector and condensing lens of a projector; and

FIG. 3 is a plan view of the screen before bending and with the position of the'supporting member and the fila- 5 ment indicated thereon.

Referring to FIG. 1, the lamp comprises a tubular glass bulb 1 containing a tungsten filament 2 herein illustrated as the biplane type comprising a plurality of coiled wire sections arranged in staggered relation in closely parallel planes or, when desired, in a single plane. The filament 2 is arranged between support wires 3 and 4 substantially in a plane including the said wires 3, 4 and the axis of the bulb 1. The filament is electrically connected at its ends to wires 3 and 4 through spuds 5. Wire 3 is supported from, and electrically connected to, a lead-in or contact pin 6 and is also connected to a second pin 7 through wire 8. Wire 4 is supported from and electrically connected to pin 9, and is also connected to a second pin 10 (FIG. 2) through a conductor 11 which bridges pins 9 and'10 and which may be a fuse wire.

The filament 2 is supported at each end by a plurality of support wires 12 whichenage the bight portions connecting successive coil segments of the filament and are supported from glass bridges 13 which are, in turn, supported from the support wires 3 and 4. The bulb 1 contains a filling of inert gas, preferably nitrogen, at a substantial pressure, preferably about600 mm. of mercury, or higher, at room temperature.

In accordance with the invention, the lamp contains a screen 14 mounted along its longitudinal center line on the upper support wire Bto be above the filament .2 in normal use of the lamp. As shown in FIG. 2, the lamp isemployed. in a projector in association with a spherical reflector 15 at the rear of the lamp and a condensing lens 16 at the front of the lamp. The screen 14 is folded along its longitudinal center line to form two sides or panels 117 and 18; the panel 17 extends rearwardly in a plane substantially normal to the vertical plane including the wires 3, 4 and the bulb axis so as to be in a horizontal position in use of the lamp, whereas the panel 18 extends toward the front of the lamp in a plane inclined at an angle of about 45 below the horizontal. Although the form of the screen 14 maybe varied considerably, it is shown herein in connection with a 500 watt lamp having a bulb 1 of soft lime glass having a softening point of about 690 C., a diameter of 1% inches and a length of about 3% inches, and wherein the screen is formed from sheet nickel about .015 inch thick, inch long and inch wide. The screen is formed with a row of four holes 19 along each longitudinal edge, and a central row of holes 20; the holes 19 are about 7 inch by inch, and the central holes 20 are each about inch by inch. In this case, the area of the openings 19 and 20 constitutes about 60% of the total area of the screen 14. I have also found that best results are obtained when the screen 14 is not centered longitudinally over the filament but is displaced toward the base of the lamp with the center line 21 (FIG. 3) of a transverse series of holes 19, 20, -'19 over the center of the filament 2.

With the lamp mounted in a projector as shown in FIG. 2, a portion of the convection currents rising along the right hand side of the filament 2 strikes the tilted side or panel 18 of the screen :14 and are deflected away from the front of the bulb Ladjacent the lens 1 6 with the result that blistering thereof is eliminated; at the same time, perhaps because those currents are somewhat cooled in their travel across panels 18 and 17 toward the back of the bulb, they do not cause any increased tendency to blistering at the back of the bulb. Tests have shown a still lesser tendency to blistering when the screen -1 4 is ofiset longitudinally toward the base of the lamp, as shown in FIG. 1 and as indicated in FIG. 3, so that the transverse centerline 21 of the filament 2 is at the center of a transverse series of holes 19, 29,19;

. In spite of the relatively open structure of the screen 14,

it also intercepts particles of tungsten vaporized from the filament 2, to maintain the bulb walls essentially free.

from blackening. I

What I claimas new and desire to secure by Letters Patent of the United States is:

1. An electric incandescent lamp comprising a tubular gas-filled glass bulb, support members extending longitudinall'y within said bulb, a filament mounted between said members substantially in a plane including said members and the axis of said bulb, and a heat shielding and deflecting screen member having a-plurality of openings and-extending longitudinally in said bulb at the side of the filament to pass through said openings, and presenting adeflecting obstruction to another portion of said curand extending longitudinally in said bulb above said filament and attached along its longitudinal center line to the said upper support member, said screen being bent along its said center line to form two panels, one of said panels being in a substantially horizontal plane and the other panel being in a plane tilted downward at an acute angle to the horizontal, said screen allowing a portion of the convection currents arising from the filament to pass through said openings and presenting a deflecting obstruction to another portion of said currents.

3. An electric incandescent lamp comprising a tubular gas-filled glass bulb, support members extending longitudinally within said bulb, a filament mounted between said members substantially in a plane including said memrents when the lamp is operated horizontally with the first-mentioned plane vertical and the screen above the filament.

2..In a projector", an incandescent lamp having a horizontally disposed tubular gas-filled bulb, an upper and a lower support member extending longitudinally and horizontally within said bulb, a filament mounted substantially in a vertical plane including said support members and the axis of said bulb, and a heat shielding and deflecting screen member having'a plurality of openings bers and the axis of said bulb, and a heat shielding and deflecting screen member having a plurality of longitudinal and transverse rows of openings and extending longitudinally in said bulb at the side of said filament with its longitudinal center line in said plane and with a transverse row of said openings centered over the center of said filament, said screen beingbent along its said longitudinal center line to form two panels, one of said panels being in a second plane substantially normal to the firstmentioned plane including the bulb axis and the other I panel being in a third plane tilted toward the filament at an acute angle to the said first-mentioned plane, said screen allowing a portion of the convection currents arising from the filament to pass through said openings and presentingv a deflecting obstruction to another portion of said currents when the lamp is operated horizontally with the first-mentioned plane vertical and the screen above the filament.

References Cited in the file of this patent UNITED STATES PATENTS 1,967,906 Ruttenauer July 24, 1934 2,326,419 Van Horn Aug. 10, 1943 2,862,125 Biggs- Nov. 25, 195.8

Images