US2068595A - Gaseous or vapor arc discharge lamp - Google Patents

Description

Jan. 19, 1937. 1.. BURNS GASEOUS OR VAPOR ARC DISCHARGE LAMPS Filed July 31,: 1935 INVENTOR BY 'ATTORNEY Patented Jan. 19, 1937 UNITED STATES GASEOUS OR VAPOR ABC DISCHARGE LAMP Laurence Burns, Revere, Mass., assignor to Bygrade Sylvania Corporation, Salem, Mass., a corporation of Massachusetts Application July 31, 1935, Serial No. 34,006

9 Claims.

This invention relates to electric lamps and more particularly to lamps of the type adapted to produce light by reason of an arc discharge through an ionizable medium such as gas or V p r.

A principal object of the invention is to provide an improved form of arc discharge lamp of the high pressure gas or vapor filled type.

In high pressure are discharge lamps, particu- 10 larly those employing a filling of a condensable ionizable medium such as mercury vapor or the like, there is a tendency under certain conditions of operation, for the arc stream to exhibit pronounced positional instability. This instabill5 ity is revealed in the form of a bowing or wiggling of the main arc column, and occurs in some lamps near the region of power input where the luminous eificiency approaches its maximum. However when the lamp is operated in or near this region the tendency of the arc column to wiggle may be increased to such an extent as to cause a sharp decrease in luminous output. One manner of controlling the positional stability of the arc column is disclosed in application Serial 95 No. 31,754, filed July 17th, 1935 and comprises in general the proportioning of the length of the arc column to the arc current so that the luminous efficiency is maintained in the region of the maximum but with a minimum of positional 3o instability. I have found that the positional stability of the arc column may be enhanced by guiding the vapor flow within the lamp envelope so that the tendency to turbulence of the hot vapors or gases is reduced to a minimum. In

carrying out this phase of the invention there is interposed in the path of the vapor streams guiding members positioned at specially arranged points within the arc column.

Accordingly another object of the invention is to provide an improved method of controlling the flow of the hot gases or vapor within a high pressure vapor or gaseous arc lamp.

A feature of the invention relates to a high pressure vapor or gaseous arc lamp having specially designed baiiies positioned within the lamp to control the convection currents in the hot gases or vapors within the lamp whereby the arc column is maintained in a substantially central position and with a minimum of bowing or wig- Another feature relates to a specially designed baflle for high pressure vapor or gaseous are discharge lamps to maintain the arc column steady andwithout appreciably interfering with the 55 light emission from the lamp.

A further feature relates to the novel organization, arrangement and relative location of parts which go to make up an improved electric lamp of the high pressure vapor or gaseous arc type.

Other features and advantages not specifically enumerated will be apparent after a consideration of the following detailed descriptions and the appended claims.

While the invention will be described in con- 10 nection with one particular type of arc discharge lamp it will be understood that in certain aspects it iscapable of embodiment in other known types without departing from the inventive scope. Furthermore while only those parts of an are 5 discharge lamp are shown to enable the invention to be understood, this is done merely for explanatory purposes and not by way of limitation. Accordingly in the drawing,

Fig. 1 is a longitudinal view of a high pressure 20 arc discharge lamp embodying features of the invention.

Fig. 2 is a transverse sectional view taken along the line 22 of Fig. 1.

Fig. 3 shows a modified form of arc column 25 guiding member or bafile according to the invention.

Fig. 4 is another view of the battle of Fig. 3. Referring more particularly to Figs. 1 and 2 the numeral I indicates any well known form of 30 enclosing envelope such as is ordinarily employed in gas or vapor conduction lamps. Preferably where the lamp is of the high pressure content type and arranged to withstand high temperatures, the envelope I may be of refractory glass 5 such for example as combustion tubing of the required internal diameter and length according to the power input for which the lamp is designed. The tubular portion I may be closed at each end with any well known form of closure 4 and preferably these closure portions 2 are of a softer grade of glass from the portion I, in order that the electrode lead-in wires 3, 4 may be properly sealed in place. Preferably also each leadin wire is provided with a bead 5 of a still softer '45 grade of glass. The lamp envelope after being exhausted in accordance with accepted lamp procedure, is filled with an ionizable medium through which the arc discharge is to be main tained this medium being preferably a conductive vapor such as mercury vapor adapted to be at a relatively high pressure when the lamp is in operation, for example a pressure of the order of from 0.5 to 1.5 atmospheres. In order to facilitate starting, a small quantity of an inert conheat them to an appropriate temperature to drive ductive gas or mixture of gases such as argon or neon may be added to the filling.

Fastened in any suitable manner to each pair of lead-in wires is an electrode 8 preferably of refractory metal such as tungsten, molybdenum or the like carrying a quantity of electron emis'sive material such for example as an oxide or oxides of the alkaline earth metals. Preferably each of the electrodes 6 is in the form of .a wire reversely coiled upon itself to form a double helix whereby the magnetic field of one helix is neutralized by the magnetic field of the other helix when cur rent fiows through the electrode. As will bear:-

parer'it from the drawing each electrode is mounted so that its length is along the longitudinal axis of the envelope I. When the lamp is in operation the lead-in wires for each electrode are connected together as by the straps I so that-a predetermined voltage may be impressed across the electrodes. However, during the manufacture of the lamp the lead-in wires may be separated and current passed through the filament electrodes to out the gases occluded therein and to reduce the electron emissive coating on the filament to the oxide form as is well known in the art.

I have found that when a lamp such as described is connected in a suitable circuit of the required voltage and impedance-characteristics there is a preliminary stage wherein the discharge between the electrodes parts-hes of the nature of a glow discharge, and after a certain interval the heat of the glow discharge raises the electrodes to a sufficiently high temperature that the electrodes become thermionically emissive and thereafter the current between the electrodes produces a discharge having the characteristics of an arc. During this latter stage of the lamp's operation there is a considerable temperature gradient between the central or axial part of the lamp and the lateral or wall part. Furthermore the vapors and gases within the lamp are at arelatively high desirable positional instability. Accordingly as temperature and the hotter gases and vapors tend to rise in the central part of the lamp and flow downwardly along the wall portions. So long as this flow of gases is without appreciable tinbulence the main arc column remains substantially in its central or axial position. however under certain conditions this turbulence may be of such a magnitude as to cause the arc column to bow outwardly toward the envelope wall and 1 this bowing maybe of sufilcient amplitude as to extinguish the arc itself. In some instances the turbulence while not 6! uflieient magnitude to extinguish the arc, may subiect them to considerable positional instability manifested as a wiggling of the arc. I have found that by guiding the hot gases and vapors in their stream ilows from one end of the lamp to the other. that this turbulence can be reduced materially, with the result that the lamp may be operated in the region of its maximum luminous efilciency without danger of the arc column being 'subiected to unshown in the drawing the lamp envelope ha mounted therein at predetermined spaced intervals a series of guiding discs or" baflles L'la'nd.

while thejrawing shows two of these bailieait, will be understood that a greater or less number may beemployed as is found desirable. As will central opening II preferably circular in shape- 1 and larger in diameter than thediameter of the arc column. Preferably h openings it iii-eat 'ing the bames and preventing their displacement.

The bailie rings may be of any suitable material such as metal, glass, quartz or'the like. I have found that the best resultsare obtained by positioning the baiiies in particular places along the length of the envelope. The bailles are preferably positioned so'that their distance from each other and from the arc discharge area of the electrodes bears a predetermined relation to thearc current.

Thus in the case of the two bailies shown in the drawing the distances A, B" and C are preferably equal to or less than twice the arecurrent where the distances A, 3" and "C are in inches and thearc current is in amperes- If desired members I 4 may be positioned in back of each electrode to protect the graded seal from the heat of the electrode and to prevent the pocketing of condensed vapor in back of the electrode as set forth in detail in application Serial No. 23.992, filed May 29, 1935. I have also found that by using reversely coiled filamentary electrodes :the tendency of the arc to positional instability is further reduced probably because the magnetic field at each electrode is substantially negligible. With ordinary inductively'wound filament electrodes the arc column is subjected to the magnetic field of the electrode with consequent liability to deflection should thismagnetic field vary for any reason; particularly when the lamp is being operated on alternating current. Furthermore the manner of forming the filament electrode as 7 shown in the drawing causes the arc current to flow into and out of the lamp equally andsymmetrically through each lead-in wire and there will be no tendency for one lead-in wire to deteriorate more rapidly .than the other.

with the above-described arrangement and location of parts the main arc column, indicated by the dotted lines in Fig. 1 is maintained in its central or axial position and the convection currents in the hot gases and vapors are guided by the members 8, I and I4 so that the very hot gases can rise centrally through the openings i0, whilethe cooler. vapors and gasescan descend without interference in the spaces provided between the-peripheries of the baiiie members and the wall of the envelope thus approximating a lamellar now with a minimum of turbulence, it being understood that preferably the'lamp is operated with its lon-vv rents to-a less turbulent flow. Forthe case where the battle is spaced from. thewall 'velope; Figures 3 and 4- show such,

of Y the .en-

:curved contour. Figure 41s a cross-section on line of-Fig. 3. In. both of these figures the v seen supported from the tube wall I by be seennom 2 each baiile'is provided witha abaiiieof' rods, but may be, of -course, supported in anyv other convenient manner.

'While specific materials and shapes-10f parts are disclosed herein it will be understood'that various modifications and changesmay lie-made therein without departing from the spirit and scope of the invention. Thus while a lamp of the single envelope type is shown, an additional heat conserving outer envelope or jacket may be provided as is well known in the art.

What is claimed is:

1. In an electric lamp of the high pressure arcdischarge type the combination of an enclosing envelope, containing a metallic vapor, a pair of refractory metal electrodes mounted at the ends of said envelope, a plurality of baflle members within the envelope and disposed between the electrodes at least one of said baiile members being of quartz, said bame members having aligned central openings through which the arc column passes the diameter of said openings being at least one and one-half times the diameter of the arc column, said baiiles having portions to guide the cooler portions of the vapor streams for the purpose of maintaining the are stable.

2. In an electric lamp of the high pressure are discharge type the combination of an enclosing envelope containing a filling of mercury vapor, a pair of refractory electrodes within the envelope at opposite ends thereof at least one of said electrodes being provided with material which becomes thermionically emissive when subjected to the heat of the arc current flowing through said electrode, a vapor stream guiding baffie mounted in advance of each electrode at least one of the baflles being of transparent insulating material, each baflle being spaced from the wall of the envelope and having a central opening through which the arc column passes, the spacing of the bailles from the wall being for the purpose of guiding the descending vapor streams with a minimum of turbulence.

3. An electric lamp according to claim 2 in which the baflles are in the form of thin discs supported from the wall of the envelope.

4. An electric lamp according to claim 2 in which the baffles are in the form of rings having their surfaces shaped to guide the stream lines or the vapor filling with a minimum turbulence.

5. In an electric lamp of the high pressure are discharge type the combination of an envelope containing a pair of refractory metal electrodes a filling of metallic vapor within said envelope, and

at least one baille member of quartz within the envelope and disposed between said electrodes each of said members having a central opening to surround the arc column, said members being spaced from the wall of the envelope to provide a guiding path for the relatively cool vapors within the envelope.

6. In an electric lamp of the high pressure are discharge type the combination of an enclosing envelope having a filling of metallic vapor, a. pair of refractory electrodes within the envelope at opposite ends thereof, at least two transparent insulating members within the envelope and positioned between the electrodes for guiding the con vection currents in the vapor filling, each of said members having a central opening through which the arc column passes and being spaced from the electrodes to maintain the arc in a stable position.

'7. In an electric lamp of the arc discharge type the combination 01 a transparent enclosing envelope containing at opposite ends a pair of refractory electrodes, 9. filling oi ionizable medium within said envelope and at least two baflle members of insulating material positioned between the electrodes to stabilize the arc position, each of said bailie members having an arc guiding opening in axial alignment with said electrodes.

8. man electric lamp or the arc discharge type, the combination of a transparent enclosing envelope containing at opposite ends a pair of refractory electrodes, a filling of ionizable medium within said envelope and at least two baflie members of transparent insulating material positioned between the electrodes to stabilize the arc position, each of said baflle members having an arcguiding opening in axial alignment with the electrodes.

9. In an electric lamp or the arc discharge type the combination of a transparent enclosing envelope containing at opposite ends a pair of refractory electrodes, a filling of ionizable medium within said envelope, and at least two baflle members of quartz positioned between the electrodes to stabilize the arc position, each of said baille members having an arc-guiding opening in axial alignment with said electrodes.

LAURENCE BURNS.

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