Quick warm-up lamp

Abstract

A quick warm-up lamp, including a gas filled bulb, and a cathode and an ae mounted in and at opposite ends of the bulb in a spaced apart relationship. A jacket is disposed about the entire bulb so as to provide an insulative space between the bulb and the ambient environment. Each end of the bulb is molded integrally with the jacket into a solid neck which extends from the respective end and is located within the jacket. A lead extends through each neck and is connected to the cathode and the anode, respectively. The above configuration and a particular combination of additives within the bulb ensure that the bulb will warm up quickly to produce light.

Description

STATEMENT OF GOVERNMENT INTEREST

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION

Man is making his move into the ocean more and more with a myriad of types of deep submersibles, some of which are manned and others which are unmanned. The manned submersibles, such as Pisces, are actively involved in laying cable, salvege, and exploration work. The unmanned vehicles, such as the Navy's Cable Underwater Recovery Vehicle (CURV), are mainly involved in salvage work. A recent example of work performed by CURV was its recovery of two aquanauts stranded in a Pisces vehicle at 1,600 feet off the coast of Ireland.

The lighting systems employed by these submersibles, whether they be manned or unmanned, are extremely important to successful completion of a mission. The manned Pisces vehicle requires strong and efficient lighting for enabling the occupants to view underwater objects in a totally dark environment, and the unmanned CURV type of vehicles require the same type of lighting for viewing underwater objects by the use of TV cameras.

In the past the mercury lamp has been used extensively in underwater applications because its spectral output is concentrated in small spectral bandwidths, two of which are transmitted quite well by sea water. However, one of the more undesirable characteristics of the mercury lamp is the start-up time required to produce full output radiation. The mercury arc lamp requires up to 13 minutes to produce full output when the ambient temperature of the water is 32.degree.F., and as little as 6 minutes when the water temperature 90.degree.F. This thermal influence on starting time is explained by the fact that mercury is almost completely condensed when the temperature of the water is 100.degree.F. or less, and the operating conditions are achieved only when the arc volume has been sufficiently heated to vaporize all of the mercury. This start-up time is a hindrance to submersible operations, such as the CURV, because the television cameras with which mercury lamps are being used are relatively insensitive to the low illumination levels offered by the lamp as it is warming up. This situation can lead to operational difficulties unless the lamps are on during the entire mission.

There has been a strong need for an underwater lamp which will have the efficient output of the mercury lamp, but yet have the quick start-up capability and rugged characteristics which are desirable for deep ocean operations. In a mercury lamp which has chemical additives as the plasma medium, adequate vapor pressures for the arc current require an envelope whose cold spot (minimum temperature area) is sufficiently high to maintain desired constituent partial pressures. Because of the non-uniform heating effect obtained by the arc of a mercury short arc discharge, the envelope of the lamp is coated with either a gold or platinum reflective paint. This coating is usually applied to the upper part of the lamp bulb where the top of the bulb meets the arm or seal region of the lamp. When the lamp is tilted from its normal vertical cathode up orientation, a change in the cold spot temperature may occur. If this happens the operating pressure of the discharge can change, and thus the radiating characteristics of the lamp are altered. This condition can be compensated for by either increasing the operating power of the lamp, or by applying additional reflective paint to increase the cold spot temperature of the bulb. Both alternatives are unsatisfactory, the latter being most objectionable from the standpoint of optical collection efficiency. In the instances where short arc lamps are doped with additives whose vapor pressures are less than that of mercury, cold spot considerations are even more important, and higher temperatures have to be maintained.

Higher temperatures are usually obtained by means of placing the short arc lamp in an outer envelope which is evacuated. By means of the vacuum layer about the bulb, heat normally removed from the envelope via convection is now conserved, and thus high bulb wall operating temperatures are obtained. This means of conserving heat has distinct disadvantages when the prior art teachings are followed: (1) breakdown often occurs between the exposed wires leading into the seals of the arc tube when the high voltage starting pulse is applied, thereby causing a sub-torr pressure from out-gassing of the lamp envelope, and (2) the outer envelope is large and greatly increases the overall size of the lens structure.

SUMMARY OF THE INVENTION

The problems of slow warm-up and inefficiency of lamps for underwater applications appeared to reside in the configuration of the lamp as well as the additives within the bulb. Previous attempts to solve the warm-up problem by coating the bulb or placing it in an outer envelope have just brought on other problems. Prior art attempts to provide different additives for the bulb have only reduced the efficiency or locked out the desirable light qualities necessary for underwater work. The present invention has overcome the slow warm-up problem of lamps used in underwater work by providing a unique lamp configuration and high cold fill pressure of the bulb, and has overcome the efficiency problem by providing a unique combination of bulb additives which are under optimum partial pressures.

In the unique lamp configuration a cathode and an anode are mounted within and at opposite ends of a bulb in a spaced apart relationship. A jacket is disposed about the entire bulb so as to provide an insulative space between the bulb and the ambient environment. Each end of the bulb is molded integrally with the jacket into a solid neck which extends from the respective end and is located within the jacket. A lead extends through each neck and is connected to the cathode and the anode, respectively. With this configuration there is no problem of breakdown of the wire lead, and yet the advantages of the vacuum jacketing enables quicker warm-up of the lamp.

Further, the invention provides the bulb with a mixture of chemical additives which enables efficiency. These additives are xenon, mercury, and thallium iodide. It has been found that optimum visible radiant output is enabled by a partial pressure ratio of mercury to mercury, xenon, and thallium iodide of approximately 0.5 for a completely vaporized thallium iodide dose when the lamp is fully warmed. Quick warm-up of the bulb is obtained by providing a high cold pressure of the xenon. This high operating pressure of xenon quickly increases the bulb temperature which subsequently and rapidly increases the partial pressures of the mercury and the thallium iodide.

OBJECTS OF THE INVENTION

An object of the present invention is to overcome the aforementioned problems associated with prior art underwater lamps.

Another object is to provide an efficient and quick warm-up underwater lamp.

Another object is to provide a compact, rugged, quick warm-up and efficient underwater lamp which can be utilized in all attitudes and orientations of service.

These and other objects of the invention will become more readily apparent from the ensuing specification when taken with the drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross-sectional view through the underwater lamp.

FIG. 2 is a graph illustrating efficacy as a function of buffer gas partial pressure ratio.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawing, there is illustrated in FIG. 1 a quick warm-up lamp 10 which includes a bulb 12 and a jacket 14. It is desirable that both the bulb and the jacket be elongated as illustrated in FIG. 1. The jacket 14 is disposed about the entire bulb so as to provide an insulative space 16 between the bulb and the ambient environment. Each end of the bulb is molded integrally with the jacket 14 into solid necks 18 and 20 which are located in the jacket and extend in diametrically opposite directions from the bulb. The bulb 12, jacket 14, and necks 18 and 20 may be constructed of glass or other suitable transparent material which can be molded as described hereinabove.

Mounted within the bulb 12 at opposite ends thereof are a cathode 22 and an anode 24. Both the cathode and the anode may be molded into place within the respective necks 18 and 20 and may be constructed of thorated tungsten and tungsten respectively. Each of the necks 18 and 20 may extend exteriorly beyond the jacket 14 and may be fitted with terminals 26 and 28 at their ends for connection to an outside electrical source (not shown). Electrical leads, such as molybdenum ribbon foil, 30 and 32 may be molded in the necks 18 and 20 along their longitudinal axes and may be connected respectively between the cathode 22 and the terminal 26, and the anode 24 and the terminal 28. This structure eliminates the breakdown of the leads and any outgassing of the lamp bulb.

The invention further provides a unique partial pressure ratio of the additives to the bulb 12. The bulb contains a combination of xenon, mercury, and thallium iodide. The thallium iodide particularly promotes the efficiency of the lamp in an underwater environment by providing a band of light in the 5,300A to 5,400A region. It has been found that optimum visible radiant emission can be obtained by utilizing a partial pressure ratio of mercury to the mercury, xenon, and thallium iodide of approximately 0.5 for a completely vaporized thallium iodide dose when the lamp is warmed up. This relationship is illustrated in FIG. 2 which is a chart illustrating efficacy (lumens per watt) as a function of buffer gas partial pressure ratio. This ratio is a partial pressure of mercury to the partial pressures of mercury, xenon, thallium iodide. It can be seen from this chart that the optimum efficacy is obtained when the partial pressure ratio is approximately 0.5, and this optimum generally runs through a range of 0.50 to 0.65. Further, the quick warm-up characteristic is enhanced by a cold fill pressure of the bulb 12 with the additives at standard temperature and pressure of between 3 to 4 atmospheres. This cold fill pressure enables the xenon quickly to increase the bulb temperature which subsequently and rapidly increases the partial pressures of the mercury and thallium iodide.

With the aforementioned configuration of the lamp and the additives to the bulb an efficient quick warm-up lamp is provided which is especially adapted for underwater use. The lamp can be used for purposes other than underwater lighting, such as outdoor lighting in a large stadium. The lamp is rugged, efficient, and can be oriented in any desired direction.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings, and, it is therefore understood that within the scope of the disclosed invention concept, the invention may be practiced otherwise than specifically described.

Claims

1. A quick warm-up lamp comprising:

a bulb;

a cathode and an anode mounted within and at opposite ends of the bulb in a spaced apart relationship;

a jacket disposed about the entire bulb so as to provide an insulative space between the bulb and the ambient environment;

each end of the bulb being molded integrally with the jacket into a solid neck which extends from the respective end and is located within said jacket; and

a lead extending through each neck and connected to the cathode and the

2. A quick warm-up lamp as claimed in claim 1 including:

3. A quick warm-up lamp as claimed in claim 2 including:

each of said necks extending exteriorly beyond the jacket;

a terminal mounted on each exterior end of the necks; and

each of the leads extending through a respective exterior portion of the

4. A quick warm-up lamp as claimed in claim 3 including:

the bulb and the jacket each being elongated and aligned with one another along their longitudinal axes; and

said ends of the bulb being located along the longitudinal axis of the

5. A quick warm-up lamp as claimed in claim 4 including:

said bulb containing xenon, mercury, and thallium iodide; and

the partial pressure ratio of mercury to mercury, xenon, and thallium iodide being within a range of 0.50 to 0.65 for a completely vaporized

6. A quick warm-up lamp as claimed in claim 5 including:

the cold fill pressure at standard temperature and pressure being between 3 and 4 atmospheres; and

said jacket being evacuated.