US2177755A - Gaseous electric discharge lamp device - Google Patents

Description

Oct 1939 w. UYTERHOEVEN GASEOUS ELECTRIC DISCHARGE LAMP DEVICE Filed May 10, 1958 Fig. 2

INVENTOR n m df 11 W m AT ORNEY Patented Oct. 31, 1939 GASEOUS ELECTRIC DISCHARGE LAMP DEVICE Willem Uyterhoeven, Eindhoven, Netherlands, as-

signor to General Electric Company, a corpo ration of New York Application May 10, 1938, Serial No. 207,081 In Germany May 14, 1937 5' Claims. (01. 176-122) The present invention relates to gaseous electric discharge lamp devices generally and more particularly the invention relates to such devices which operate at elevated container temperatures and which are mounted in a heat conservator, such as a sealed envelope,

The light emitted by lamp devices of this type is deficient in rays of certain wave length and it has been proposed heretofore to provide a luminescent material capable of being excited by radiation from said lamp device to emit visible light which complements and supplements the light emitted by said discharge lamp. Preferably the luminescent material is applied to the inner surface of the envelope and a lamp unit of this type is described in co-pending applicatlon Serial Number 163,850, filed September 14, 1937, assigned to the assignee of the present application. I have observed that in lamp units of this type the light emitted by the luminescent material diminishes rapidly during operation of the discharge lamp device to lower the eiiiciency of the lamp unit. I have discovered that this loss in efficiency is due to the deterioration of the luminescent material under the heat emitted by the discharge lamp device.

The object of the present invention is to provide a lamp unit of the above type in which the luminescent material retains its light emitting capacity for a long useful operating life of the lamp unit. Still further objects and advantages attaching to the device and to its use and operation will be apparent to those skilled in the art from the following particular description.

The invention attains its objects by surrounding the gaseous electric discharge lamp device by a gas having heat absorbing properties, such as carbon dioxide or nitrogen, at such pressure that convection currents can occur in the gas during the operation of the device and by providing the envelope with a heat radiating part at which the heat absorbed by said gas is dissipated. The pressure of the gas should be a substantial one since the cooling effect of the convection currents in the gas varies directly as the square of the gas pressure. The heat dissipating part of the envelope is separated from that part of the envelope on which the luminescent material is applied and through which the light from the lamp device and the luminescent material passes. A lamp unit having this structure retains its initial efficiency for a long useful op- Fig. 2 is a front elevational, partly sectional view of another embodiment of the invention.

Like numbers denote like parts in both the figures.

Referring to Fig. -1 the gaseous electric discharge lamp device comprises a tubular container I, such as a quartz container, having an inner diameter of about 4 mm. and having sealed therein thermionic, activated electrodes 2 and 3 of the type which are heated to an electron emitting, arc discharge supporting temperature by the discharge incident thereat. Said electrodes 2 and 3 are separated a distance of about 18 mm. The container i has therein a starting gas, such as argon, at a pressure of about 10 to 20 mm. and a quantity of mercury. Mercury vapor discharge devices of this type are capable of operation with vapor pressures of 10 atm. and

7 higher and preferably the vapor pressure therein during the operation thereof is about 20 atm. The discharge device is mounted in a. heat conservator having a; tubular part 4. Said tubular member 4 consists of vitreous material capable of transmitting visible and ultra violet light, such as Corex glass, and has a press 6 at one end thereof into which the current leads I and 8 of the discharge device are sealed. The space 5 in the tubular part 4 is filled with nitrogen atv a pressure of about 10 cm. at room temperature.

The bulbous part 9 of the heat conservator is fused to the tubular member 4 between the press 6 and the upper end of the discharge device so that the upper part of the tubular member 4 is not enclosed by said bulb 9. The inner surface of the bulb 9 has a coating l0 thereon of luminescent material, such as zinc sulphide, which is light emitting under. excitation by radiation from the discharge lamp. Preferably the space between the bulb 9 and the tubular member 4 is evacuated.

During the operation of the discharge device strong convection currents are set up in the gas in the tubular member 4. These currents carry heat away from the container i upward to the exposed part of the tubular member 4 where it is dissipated. Thus the amount of heat from the container I which strikes the wall of the envelope 9 is considerably less than would be the case were the gas in the tubular member 4, and the tubular member 4 itself omitted. Consequently the temperature of the luminescent coating I0 is considerably lower in the lamp unit described above than in prior devices and the luminescent material retains its light emitting power undiminished, for a long, useful operating life.

The gaseous electric discharge lamp device 11- lustrated in Fig. 2 of the drawing is similar to that shown in Fig. 1 except that in this embodiment the tubular member 4 is omitted and the bulb 9 is provided with a neck I5 which has cemented thereto, in the usual manner, a bayonet base l2 having the two contacts l3 and N thereof connected to the current leads I and 8 of the discharge lamp device. The bulb 9, I5 is filled with a heat absorbing gas, such as nitrogen, at a pressure of about 50 cm. and the neck [5 of the bulb 9, I5 is an elongated one of relatively large area. During the operation of the device the strong convection currents set up in the gas in the bulb 9 carry heat from the discharge lamp up into the neck I5 where it is dissipated by the gas coming into contact with the inner surface of the neck I5. The cooler gas then flows downward (as shown by the arrows and dotted lines II in the drawing) along the coated inner surface of the bulb 9. It is advantageous, therefore, that the heat dissipating capacity of the neck l5 be as large as is consistent with the maintainance of the operating temperature of the container I so that the luminescent coating Hi can be maintained at a temperature lower than that which would cause deleterious changes in the said luminescent coating ID. The heat dissipating capacity of the neck I5 is increased by omitting the luminescent coating ill from the inner surface of the neck l5. When desired, other means for increasing the heat dissipating capacity of the neck [5 can be used in addition to the omission of the coating ID from the said neck I5; for example, the neck I 5 is made of a glass which has a greater heat radiating capacity than the glass of which the spherical part of the bulb consists, when desired; or the outside surface of the neck I5 is roughened or coated 'with a material, such as carbon, which radiates heat strongly, when desired, or all these expedients are used in combination, when desired.

It will be understood, of course, that we contemplate combining all the structural details of both the devices illustrated in the drawing which may be desirable in extreme cases, for example, when the discharge lamp generates a great quantity of heat and the particular luminescent material used is of a kind strongly affected by heat. Other means for increasing the heat dissipating capacity of the heat dissipating part of the envelope can be used, when desired, for example, metal fins or water cooling mechanisms.

While I have shown and described and have pointed out in the annexed claims certain novel features of the invention, it will be understood that various omissions, substitutions and changes in the forms and details of the device illustrated and in its use and operation may be made by those skilled in the art without departing from the broad spirit and scope of the invention.

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

1. An electric lamp comprising in combination a gaseous electric discharge lamp device of the type operating with an elevated container temperature, aheat conservator in which said lamp device is mounted, said conservator having a heat dissipating part, a coating of heat sensitive, luminescent material in said conservator in light receiving relation to said lamp device and remote from said heat dissipating conservator part and a. gaseous filling in said conservator at a pressure such that the heat emitted by said lamp device during the operation thereof causes convection currents in said gas to transfer the heat from said lamp to the heat dissipating part of said conservator to increase the useful life of said material.

2. An electric lamp comprising in combination a gaseous electric discharge lamp device of the type operating with an elevated container temperature, a heat conservator in which said lamp device is mounted, said conservator having a heat dissipating part, a coating of heat sensitive, luminescent material in said conservator in light receiving relation to said lamp device and remote from said heat dissipating conservator part and an infra-red ray absorbing gas in said conservator at a pressure such that the heat emitted by said lamp device during the operation thereof causes convection currents in said gas to transfer the heat from said lamp to the heat dissipating part of said conservator to increase the useful life of said material.

3. An electric lamp comprising in combination a gaseous electric discharge lamp device of the type operating with an elevated container temperature, a heat conservator in which said lamp device is mounted, a coating of heat sensitive, luminescent material in said conservator in light receiving relation to said lamp device and a gaseous filling in said conservator at a pressure such that the heat emitted by said lamp device during the operation thereof causes convection currents in said gas to transfer the heat from said lamp to a heat dissipating part of said conservator removed from said luminescent material to increase the useful life of said material, the heat dissipating part of said conservator having a greater heat dissipating capacity per unit of area than the other parts of said conservator.

4. An electric lamp comprising in combination a gaseous electric discharge lamp device of the type operating with an elevated container temperature, a heat conservator in which said lamp device is mounted, said heat conservator consisting of a tubular member and a bulbous member, said tubular member being partially surrounded by said bulbous member, said lamp device being mounted in the part of said tubular member surrounded by said bulbous member, a coating of heat sensitive, luminescent material on the inner surface of said bulbous member and a gaseous filling in said tubular member at a pressure such that the heat emitted by said lamp device during the operation thereof causes convection currents in said gas to transfer heat from said lamp device to the exposed part of said tubular member to increase the useful life of said luminescent material.

5. An electric lamp comprising in combination a gaseous electric discharge lamp device of the type operating with an elevated container temperature, a heat conservator in which said lamp device is mounted, said heat conservator consisting of a tubular member and a bulbous member, said tubular member being partially surrounded by said bulbous member, said lamp device being mounted in the part of said tubular member surrounded by said bulbous member, a coating of heat sensitive, luminescent material on the inner surface of said bulbous member and a gaseous filling in said tubular member at a pressure such that the heat emitted by said lamp device during the operation thereof causes convection currents in said gas to transfer heat from said lamp device to the exposed part of said tubular member to increase the useful life of said luminescent material, the exposed part of said tubular member having a greater heat dissipating capacity per unit of area than the bulbous part of said conservator.

wnmm UYTERHOEVEN.

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