US2150007A - Liquid-cooled electric lamp - Google Patents

Description

Patented Mar. 7, .1939

PATENT OFFICE 2 150,007 uoom ooonnn ELE-(HBIO mm 7 John W. Byde, Middlesex, England, nul -nor to I General Electric Company, a corporation of New York Application September 14, 1937, Serial No. 163,835 In Great Britain September 21, 1936 30laims.

My invention relates to electric lamps and similar devices and more particularly to high-intensity electric lamps. Still'more particularly my invention relates to means for cooling such lamps g by a liquid.

My invention is particularly adapted to, and will be described in connection with, high pressure metallic vapor lamps of the type disclosed and claimed in United States application Serial to No.- 46,952, Cornelis Bol at al., filed October 26, 1935. Lamps of this type, having an envelope a few millimeters in diameter, have been cooled heretofore by placing them in a larger tube or jacket through which water is circulated. The

35 distance between the lamp envelope and the jacket was usually not less than flve millimeters and the surface of the lamp was not cooled adequately even though the rate of flow of the water was so great that there was no considerable rise 52% in its average temperature. Bubbles were often formed at the heated surface which interfered greatly with the primary use of the devices, namely as sources in optical projection apparatus, and, also indicated that the surface of the enas velope was not cooled as well as it might be.

One of the objects of the present invention is to provide means for improving the cooling without increasing the rate at which cooling fluid has to be supplied or decreasing materially, by to absorption, the light output of the lamp.

According to my invention, the cooling means comprises a jacket surrounding. the discharge lamp so that fluid can be caused to flow over the envelope of the lampgin a direction generally 35 parallel to the discharge. One'or more partitions are so arranged in the jacket that substantially all the fluid passes by a partition through a channel formed by the space between the partition and the lamp envelope, the cross section of said 40 channel being much less than the mean cross section of the channel through which the fluid passes over the part of the envelope occupied by the discharge. It is to be observed that the latter condition insures that the total length along the 45 discharge occupied by the partitions is small compared with the total length of the discharge. The effect of the partitions on the light emitted by the lamp is therefore small and they do not raise very greatly the pressure required to force a so given flow of water through the jacket. Their eflect in promoting cooling is doubtless due largely to the increase they produce in the velocity of the stream along the surface of the lamp envelope, but it is probably also due to the pro- 55 motion of turbulence. If light is to emerge, at

least part of the vessel must, of course, be of glass or like material, but if light is required in only one direction, a glass window may be suflicient. If the object were, as it might be, to expose the cooling liquid to radiation, the vessel. might be wholly opaque and, for example, of metal. The use of the partitions, rather than of a tube as narrow as the channel, enables a much smaller head of liquid to be used and it makes occasional bubbles less harmful. Further fea- 1o tures and advantages of my invention will appear from the following detailed description of species thereof and from the drawing.

In the drawing, Fig. l is a longitudinal sectional view of a water-cooled high pressure vapor. lamp comprising my invention, and Figs. 2 and 3 are side elevations of modifications with the cooling jacket in section.

Referring to Fig. l, the discharge lamp shown therein is of the extremely high pressure mercury type disclosed in the above-mentioned application of B01 et a1. and comprises a tubular quartz envelope l which may have, for example, an overall length of 80 mm, an external diameter of 6 mm. and an internal diameter of 2 mm. The are gap between the electrodes 5, 8 may be 15 mm. and in operation the discharge may carry one ampere at 800 volts. A tube or jacket 2, which may be of glass and have an internal diameter of 14 mm., is concentrically disposed 3 around the envelope I, and water may be driven through the annular cooling chamber formed thereby from an inlet to an outlet not shown) at the rate of about 2.5 litres per minute. Two

transverse partitions 3, l, each of which may 3 be one millimeter thick and leaves central aperture 8 mm. in diameter, obstruct the flow of water near each electrode and force it to flow through the channel one millimeter wide between the partition and the envelope. The said partitions 3, l are shown as washeror ring-like discs which may be sealed at their peripheries to the surface of the jacket 2. The said partitions may also be formed from the wall of the jacket 2 by pressing the glass inward. It is important that there should be no considerable gap between .the partitions and the jacket through which the water may flow; thus, metal discs fitting the jacket imperfectly were deflnitely less satisfactory.

The upstream partition 3 should be (as shown in Fig.8) somewhat upstream of the face of the upstream electrode 5. The downstream partition 4 is not absolutely n and may be omitted, for it was found that even ii. only parevident on the surface of the envelope I when imperceptible. Howeve the partition 4 provides a factor of safety. If the distance between the electrodes is more than 15 mm., more than two partitions may be required. As a general rule it was found that the effect of each partition', such as is shown, persists for about 15 mm. on the downstream side of it if the rate of now is that stated above.

The partitions need not be P pendicular to the surface of the envelope but may be inclined, for example, as shown in Figs. 2 and 3.

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

1. The combination of an electric discharge lamp comprising a tubular envelope having an electrode sealed in each end thereof, a tubular jacket surrounding said envelope and spaced therefrom to form an annular cooling chamber through which liquid can be caused to flow over said envelope, and a transversely extending partition in said cooling chamber located adjacent to the upstream electrodeand spaced from said envelope to 'form a channel of much smaller cross section than the mean cross section of the channel through which the liquid passes over the part of the envelope occupied by the discharge.

2,150,007 gtition 3 were present, the bubbles which were 2. The combination of an electric discharge lamp comprising a tubular envelope having an electrodesealed in each end thereof, a tubular jacket surrounding said envelope and spaced therefrom to form an annular cooling chamber through which liquid can be caused to flow over said envelope, and a transversely extending par- 'tition in said cooling chamber located adjacent to each of said electrodes and spaced from said envelope to form a channel of much smaller cross section than the mean cross section of the channel through which the liquid passes over the part of the envelope occupied by the discharge. I

3. The combination of an electric discharge lamp comprising a tubular envelope having an electrode sealed in each end thereof, a tubular jacket surrounding said envelope and spaced therefrom to form an annular cooling chamber through which liquid can be caused to flow over said envelope, and a transversely extending partition in said cooling chamber located adjacent to and upstream of the face of the upstream electrode and spaced from said envelope to form a channel of much smaller cross section than the mean cross section of the channel through which the liquid passes over the part of the envelope occupied by the discharge.

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