US2241968A - Light source - Google Patents

Description

c.y G. sulTs 2,241,968

LIGHT SOURCE May 13, 1941.

Filed June 2l, 1939 His Attorney.

Patented May 13, 194i LIGHT SOURCE Chauncey G. Suits, Schenectady, N. Y., assigner to General Electric Company, a corporation of New York Application :une 21, 1939, serai No. 2so,3s4

(ci. 17o- 122) comms.

'I'he present invention comprises an improved light source and has for its oblect the provision of a device of the luminous discharge type which is capable of highly efficient operation.

'I'he aspects of the invention which I desire to protect herein are pointed out with particularity in the appended claims. The invention itself, to-

gether with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the drawing in which Figs. 1 and 2 are sectional views respectively representing alternative embodiments of the invention.

An understanding of the invention will be aided by considerationof the following table in which are listed the luminous` emciencies (in lumens per watt) which I have found to be obtainable with an arc discharge through various gaseous substances and over a fairly wide range of pressures.

From this table it will be seen that all of these gases have a luminous eiliciency at atmospheric pressure which is so low as to make their use for light production impractical. I have discovered, however, that as the pressure is increased there is a sharp difference in their behavior. Thus, in the case of helium the efficiency is not markedly improved 'even at 100 atmospheres pressure, the indicated increase being only six fold, and the eiilciency at this pressurestill being so low as to be useless for general illumination purposes.

As contrasted with this, I have found that argon and nitrogen have a marked increase in eiliciency as the pressure thereof is increased. Thus, in the case of argon, the luminous emciency is increased more than forty fold when the pressure is increased'to 10U atmospheres, and

substantially equals the efficiency of the incandescent lamps which are in general use. The eleven fold increase in the luminousoutput obtained with 100 atmospheres of nitrogen results in an efficiency which very substantially exceeds that produced by incandescent sources. This sharp increase in eillciency with increased pressure to values which are practical for general illumination purposes makes these gases, argon and nitrogen, unique among the Bases which have been used to support gaseous discharges and was entirely unexpected in view of their low emciency at the low pressures heretofore employed.

The discovery described in the foregoing may Y be utilized by employing either nitrogen or argon at a pressure of from thirty to several hundred atmospheres as an operating medium for an arctype discharge in a light-transmitting container. A particular structure by which this may be done is illustrated in Fig. 1.

In the gure referred to there is shown an elongated envelope I0 which is preferably constituted of a light-permeable vitreous material such as fused quai-tz. It is provided at its ends with enlarged portions il, I2 which respectively enclose aligned discharge. electrodes Il, Il.

These electrodes may appropriately consist ofl tungsten or an equivalent refractory metal.'

In order that the operating gas may be introduced into the envelope Ill at the desired high pressure, the envelope is provided with a special tubulation I8. This is preferably constituted of a metal such as a nickel, iron, cobalt alloy which can be fused directly to glass. The tubulation is joined to the main body of the envelope by means of a graded glass seal whose presence is indicated by the variable cross-hatching applied at I9. I have found that a` tubulation of the character described may be sealed od by welding even u nder pressures as high as several hundred 'atmospheres.

' In order to facilitate the initiation of a discharge between the electrodes I3 and I4 there is provided a pointed auxiliary electrode 2| having its tip in close proximity to the electrode I4. By applying `a relatively low voltage between the electrode I4 and 2|, one may initiate an arc which readily transfers to the electrode i3.

Where it is desired to use pressures materially above thirty atmospheres, ,it is expedient to employ a construction of greater mechanical strength than that shown in Fig. 1. In this connection there is illustrated in Fig. 2 a discharge device, suitable for projection purposes, which comprises a heavy metallic envelope 30 which serves to confine thedischarge space. This envelope is provided with an opening 3| which is occupied by a transparent window 32. The window may consist of glass or quartz and is hermetically sealed to the envelope wall by means of a flanged collar 33 having one edge thereof fused into the body of the window. The other edge of the collar 33 may be integrally fused to or welding thereto.

, conductors 35, 36 for supplying current to a. pair of spaced electrodes 31, 38. Each of the plugs referred to is constituted of fusible vitreous material (e. g. glass) and is provided with a. shaft portion which extends outwardly through the envelope wall. A gas-tight connection between the plug 39 and the end Wall of the envelope is l provided by means of a anged collar 43 which is sealed at its respective edges to the plug and A to the envelope. A functionally similar collar 45 is provided in connection with the plug I0.

A clamping ring 41, which is secured to the envelope by means of bolts 48, protects the collar 45 from the shearing eiects of the pressure existing within the envelope.

'I'he electrodes 31 and 38 dene a discharge path which is adjacent to the window 32. Consequently a discharge between them may be made to project its radiations on to an external object through the window. In order that the discharge referred to may be of high-luminous efficiency, argon or nitrogen at high pressure (i. e. thirty to several hundred atmospheres) is introduced into the discharge space by means of a tubulation 50 which extends through the Wall of the envelope 30. This tubulation may be peri manently connected with a source of high pressure gas or may be sealed oi after gas has once been introduced into the envelope interior. Where the tubulation is left open, it may in some cases be used advantageously to effect a temporary reduction in the gas pressure in the envelope to increase the ease of starting a discharge. An auxiliary electrode is also provided for employment in this connection.

In order to protect the various parts of the device from the excessive temperatures developed during operation, an external cooling jacket is provided in connection with the outer surface of the envelope 30. 'I'his jacket is formed by means of a shell 52 which is somewhat spaced from the envelope so as to provide a. chamber 53 for the circulation of cooling fluid. Such uid may be passed through the chamber by means of appropriate inlet and outlet connections, indicated rei I Letters Patent of the United states is:

1. A light source comprising a metallic container of relatively small cross-section in relation to its length., metallic end-walls closing the extremities of said container, and having restricted openings therein, relatively massive bodies of vitreous material within the container and abutting against the said end-walls thereof. said bodies extending over substantially the entire cross-section of the container and being hermetically joined to the container, conductors extending through said end-wall openings and sealed through said bodies of vitreous material, spaced electrodes respectively supported by said conductors, an operating atmosphere for the electrod comprising a light-producing gas at a pressure in excess of about thirty atmospheres, and a. light-permeable window provided in the lateral wall of the container in position to permit passage therethrough of light generated by a discharge between said electrodes.

2. A light source comprising a metallic container of relatively small cross-section in relation to its length, electrodes within said container, metallic end-walls closing the extremities of said container, at least one of said end-walls having a restricted opening therein, a relatively massive body of -vitreous material within the container and abutting against the said one of said end-walls, said body extending over a substantial portion of the entire cross-section of the container and having metallic means peripherally sealed thereto for hermetcally joining the body to the Wall of the container, a conductor extending through said end-wall Aopening and sealed through said body of vitreous material, said container being connected to one of said electrodes, an operating atmosphere within the container comprising a light-produing gas at a pressure in excess of abou't thirty atmospheres, and a light-permeable window provided in the lateral wall of the container in position to permit passagev therethrough of light generated by a discharge between said electrodes.

3. A light source comprising a metallic container of relatively small cross-section in relation to its length, electrodes within said container, metallic end-walls closing the extremities of said container, at least one of said endwalls having an opening therein, .a body of vitreous material within 'the container and abutting against the said one of said end-walls, an annular collar having an inner edge thereof ernbedded in said body and hermetically joined at its other edge to the wall of the container, a conductor extending through said end-wall opening and sealed through said body of vitreous material, said conductor being connected with one of said electrodes, an operating atmosphere within the container comprising a light-producing gas at a high pressure, and a light-permeable window provided in the wall of the container in position to permit passage therethrough of light generated by a discharge between said electrodes.

lCHAUNCEY G. SUITS.'

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