US3090883A - Electric high pressure discharge lamps - Google Patents

Description

May 21, 1963 A. BAUER ELECTRIC HIGH PRESSURE DISCHARGE LAMPS 5 Sheets-Sheet l Filed Aug. 11, 1960 INVENTOR Arnold Bauer M P ATTCENEY I May 21, 1963 A. BAUER ELECTRIC HIGH PRESSURE DISCHARGE LAMPS 5 Sheets-Sheet 2 Filed Aug. 11, 1960 INVENTOR Arnold Bauer M II? &'

ATTORNEY May 21, 1963 A. BAUER ELECTRIC HIGH PRESSURE DISCHARGE LAMPS 5 Sheets-Sheet 3 Filed Aug. 11, 1960 Fig.5

T N E V N BY Arnold Bauer ATTORNE May 21, 1963 A. BAUER ELECTRIC HIGH PRESSURE DISCHARGE LAMPS 5 Sheets-Sheet 4 Filed Aug. 11, 1960 Fig. 7a

Fig. 8

INVENTOR Y Arnold Bauer M P W ATTORNEY May 21, 1963 A. BAUER ELECTRIC HIGH PRESSURE DISCHARGE LAMPS 5 Sheets-Sheet 5 Filed Aug. 11, 1960 Fig. 9

INVENTOR Arnold Bauer BY P ATTORNEY United States Patent ELECTRIC HIGH PRESSURE DISCHARGE LAMPS Arnold Bauer, Augsburg, Germany, assignor to Patent- Treuhand Gesellschaft fiir Electrische Gluhlampen NEBH, Munich, Germany Filed Aug. 11, 1960, Ser. No. 48,888 Claims priority, application Germany Aug. 14, 1959 25 Claims. (Cl. 313-113) This invention relates to lamps, and more particularly to electrical high pressure discharge lamps for such purposes as moving picture projection.

Capacity concentrations aproaching 10 w./cm. as desirable for projection light sources, have already been achieved in electrode-stabilized high pressure lamps in which the discharge laces itself to a thin are burning between the electrodes and the stability of which depends considerably on the condition of the electrode; but prior to this invention wall-stabilized high pressure lamps have not been achieved.

The advantage of the wall stabilization consists in the are being unlimited in its length, and consequently its potential demand, and therefore the capacity and wattage of the lamp, can be increased simply by extension of the arc.

The object of the invention is the creation of a onesided wall stabilized electric high pressure discharge lamp which, without artificial cooling, allows a wall charge of one thousand to five thousand watts per square centimeter, and therefore a capacity concentration of up to w./cm. and more.

According to the invention, at least two magnet poles of opposite polarity are placed closely to the discharge are in such a way that, along the discharge course or at least that part of the discharge course along side of which the arc is to be concentrated, a non-homogeneous field is created, formed of strongly bent field lines which are primarily situated in areas vertical to the discharge axis. Preferably two magnetic pole shoes are so placed that their axes are in transverse position to the axis of the discharge course and together form an angle of less than 180. According to the present invention, a flat or bent metal wall is built in the discharge-enclosing envelope adjacent and impervious to the are so that the bent magnetic field will limit the are from three directions and the said wall will limit it in the fourth direction.

In comparison to quartz glass, the metal wall provided by this invention has the advantage of a wall charge increased by wall dimensions and consequently allows, without additional cooling, a far higher eiliciency concentration than all devices so far known.

A further advanatge of the metal wall is that it can reach a higher temperature than quartz glass. Consequently the difference in temperature between the hot arc gases and the stabilizing wall is lower, which will diminish chances for loss of heat by thermal conduction. To withstand high temperatures, the metallic wall preferably consists of tungsten or molybdenum, free from impurities, such as thorium, which might decrease exit action.

Considering their good electrical conductivity and absence of light filtration, metal walls have so far not been used for stabilization of high pressure arcs. According to this invention, however, the arc is stabilized on only one side by a metal wall and from all the other three directions is compressed by a magnetic field. Preferably, the metal wall also constitutes a light reflector having a shape comparable to that of a concave or recessed mirror. Increased reflection of the metal surface can be achieved through polishing, or .by coating with, for example, rhodium or platinum. The coating will simultaneously serve to increase exit action.

It would be normal expectation that an arc stabilization by an electrically good-conducting metal wall Would include the danger of the arc being short-circuited by the wall. However, I have discovered that a relatively cold gas layer of high electrical resistance will form between the arc and the metal wall, which, together with the potential increase of the metal surface will avoid short circuit of the arc as long as the voltage drop of the arc alongside the metal wall remains below a certain critical value, namely twenty to thirty volts. The magnetic field energy used in conjunction with the aforesaid selected metal for the wall and temperature of the wall, determines the particular value within the permissible critical range of twenty to thirty volts. In the high pressure lamps of the present invention, the voltage intensity is usually of the higher amount, so that it becomes desirable or necessary to construct the wall of individual electrically isolated parts. The metal wall may reach high temperatures even close to but less than the melting point of tungsten or molybdenum which is over 2000" C., but by virtue of the said cold gas layer, no cooling of any kind becomes necessary. It is within the scope of the invention, however, to coat the wall serving the arc stabilization with a high melting heat insulator, which makes it possible to utilize a one-piece wall instead of requiring it to be sectioned into individually isolated parts. By preference high melting heat insulator components are used which simultaneously have high optic reflective capacity, such as aluminum oxide, beryllium oxide or silicon dioxide, available in layers of a thickness less than one millimeter, preferably one to ten microns. In order to intensify heat radiation, the parts of the metallic wall which do not face the discharge are, may also receive an appropriate coating of, for example, tantalum carbide or carbon.

Especially when the magnet poles are placed inside the discharge tank or envelope, not only a straight axial burning arc may be laced in, but it is also possible to lead the arc, of the order provided by the invention, into a certain course, such as a U-course or a zigzag course. This makes it possible to provide a better adaptation to the screen size of projectors and a more even illumination of the picture than has so far been achieved with usual high pressure lamps, without particular provisions, such as comb condenser.

For magnet poles placed inside the discharge envelope, it is more practical to use components with a higher Curie point, such as cobalt or an alloy of cobalt and iron, which will permit a higher operating temperature. The magnetic flux circulating the pole shoes can be guided through a magnet core placed outside the lamp envelope; also the magnetic circuit may be completed by a core placed inside the envelope; or if desired, two individual magnets may be provided. In discharge lamps run by direct current, permanent magnets may be used supplementary to the electro-magnets. Both with direct current and with alternating current, it is practical to include the electro magnet in the discharge circuit. To achieve special discharge courses, more than two pole shoes may be provided to create the non-homogeneous field, or in addition to two primary magnet poles two secondary poles may be provided and arranged with their field functioning oppositely to the magnetic field of the primary poles, both fields being in the region of the discharge arc and thereby increasing its non-homogeneity.

The invented lamps, presented herein, combine the advantages of the Wall stabilization with those of the electrode stabilization. An evenly concentrated, strongly burning arc is produced by the invention; the length of the arc can be increased and the voltage may be freely chosen within a Wide range. By the invention, increased other glass.

Voltage and decreased lamp currents are achieved as compared to prior art electrode stabilized lamps of equal capacity. Furthermore the electrodes of the lamps may 'be reduced over prior art construction, so that the lamps of the present invention are well adapted to serve the impulse industry which is of growing importance to larger film projectors.

The invention may be well applied to rare-gas high pressure lamps, for instance to lamps filled with xenon. The envelopes may be of desired shape, such as globular or elongated and of desired material such as quartz or It is also within the scope of the invention to utilize it as a metal vapor high pressure lamp filled, t or example, mercury vapor with which may be included in addition to the metal vapor a permanent ignition gas to a considerable degree, such as xenon, crypton, argon or other molecular gas the partial pressure of which may be, during operation, either lower or higher than the metal vapor pressure.

Referring to the accompanying drawings, in which like numerals of reference indicate similar parts throughout the several views;

FIGURE 1 shows an especially simple example of lamp embodying the principle comprising the basis of the invention;

FIGURES 2 and 2a show a construction by which a winding-line arc is obtained;

FIGURE 3 is a cross section of a high pressure lamp according to the invention with a straight axis discharge;

FIGURES 3a and 3b are longitudinal sections taken on lines 3a--3a and lib-3b respectively of FIG. 3;

FIGURE 4 is a partial View of a lamp showing the coupling of a magnet core with pole shoes placed inside the lamp envelope;

FIGURE 5 shows the application of the invention to a high pressure lamp with'a metal envelope;

FIGURE 5a shows the electrodes of the lamp of FIG. 5;

FIGURE 6 is a projection lamp with built-in reflector;

FIGURE 7 is a longitudinal section of a high pressure discharge lamp the metallic wall of which is coated with a high melting heat insulator;

FIGURE 7a is a sectional view on line 7a-7a of FIG. 7;

FIGURE 8 is a longitudinal section of a high pressure discharge lampwith a U-form arc;

FIGURE 8a is a perspective view of the metallic wall and magnet of the lamp of FIG. 8;

FIGURE 9 is an elevation, partly in section, of a high pressure discharge lamp providing a recessed reflective wall laminated in direction of the arc; and

FIGURE 9a is a lamp in section showing primary and secondary magnets associated therewith.

In the specific embodiment of the invention illustrated, and referring initially to FIGURE 1, the reference numeral 1 designates two magnet pole shoes which are so placed inside a discharge tank or envelope that they create a non-homogeneous field which is primarily composed of two strongly bent field lines 2. Those field or fiux lines are mainly located in the area designated by the direction of the two-pole shoes. This non-homogeneous magnetic field develops a Lorentz power afiecting the discharge are 3 from three directions, concentrating and stabilizing it magnetically, and forcing it against the metallic wall 4 which is at the fourth side.

By an arrangement shown in FIGURE 2, it is possible to force a high pressure am into a winding-line or Zigzag wave 5. The length of such an arc exceeds by far the length of straight line arcs normally obtained in the prior art by electrode-stabilized arcs. The magnet poles 6 "shown in FIGURE 2a create the Lorentz field indicated A rare gas high pressure lamp embodying the inven- '29 at a location remote from the arc.

tion may, according to FIGURES 3, 3a and 3b, provide an envelope 9 of quartz glass having therein two primary metal electrodes 10 as well as an ignition secondary electrode 11 which is coupled with one of the primary electrodes. The are ignites at 12 (FIG. 3) where the distance between ignition electrode 11 to the primary electrode is the shortest. Assisted by the non-homogeneous magnetic field, the arc is blown rapidly into the straight axis operating position. Two magnets 13 of cobalt or alloy thereof have poles of opposite polarity located adjacent to a met al wall '14 for establishing a field at three sides of an arc (with the wall at the fourth side) for effecting the stabilizing and lacing of the are passing proximate to said wall, pressing the arc magnetically against said wall. As shown, said wall 14 consists of individual tungsten slats that have been smoothed flat on both sides of their tips, and consequently enables the magnet poles to be located proximate to the flats, and, as explained above, affords protection against hot gases. The individual slats composing said wall 14 are sealed into the stem or base 15 of the discharge lamp, and are isolated thereby both individually as well as from the electrodes 10. The thermal energy created by the discharge and supplied to the wolframite slats of wall 14 and to the operating electrodes 10 can be disposed of without additional cooling devices. The two magnets 13 are fixed to the center one of slats 14 by means of a bracket 16 of non-magnetic material such as non-magnetic steel.

It may be here noted that, as shown in FIGURE 4, instead of having permanent magnets inside the envelope, pole shoes 17a may be located inside the envelope 9 and the magnet core 17 located outside the envelope in inductive relation to said shoes for obtaining magnetic coupling therewith.

FIGURES 5 and 5a show a high pressure lamphaving an envelope the major portion of which is metal and is of a character fit for projection purposes. The lamp produces a straight arc which is pushed against the back wall 19 by means of the non-homogeneous. magnetic field produced by magnetic pole shoes 18. The major portion of the envelope is made of nonmagnetic metal, such as brass, and at one end thereof is provided with a screen 21 made of quartz glass or other suitable glass, sealed to the metal portion by lead rings 22. The filling may consist of xenon which in operationreaches a pressure of about twenty-five atmospheres. The light arc 7 may, as a specific example have a length of ten millimeters and a diameter of two millimeters with an applied current flector 25 at one end of the lamp body 26, and the metal wall 27 by which the arc is stabilized as the discharge is forced thereagainst, is so curved that the light is received by the condensing reflector in its full intensity and reflected on a glass screen 29 at the opposite end of the envelope from said reflector. An advantage of this construction is the adaptability to use of a small lamp screen Remainders of foreign gases, especially oxygen, are not easily removable from metal lamps. Consequently zirconium or titanium are therefore usually employed with the metal lamps disclosed herein.

The lamp according to FIGURE 7 has an envelope 30 of quartz glass into which have been scaled a cathode 31, an anode 3-2, and an ignition electrode 33. v

The lamp as disclosed in FIGURE 7 has a quartz glass envelope 30 into which have been sealed a cathode 31,

an anode 32, and an ignition electrode 33. The metallic stabilizing wall 34 is formed with a frontal surface of a tungsten slat 35 sealed into the envelope. Lateral clearances are provided in the edges of the slat 35 behind said wall 34 for receiving two magnet poles 36 in close proximity to said wall. The frontal surface of said wall 34 is provided with a coating 37 of aluminum oxide which has a thickness of five microns, and developed into a reflector. The three remaining sides of the slat not facing the discharge arc, and possibly also parts of the magnets 36, are provided with a film 3 8 of tantalum carbide.

The lamp shown in FIGURES 8 and 8a is provided with two horn-shaped electrodes 39 and with a stabilizing wall 40 consisting of a tungsten or molybdenum sheet on which is carried a horse-shoe magnet 41 and another magnet 42 of bar shape lying between the legs of the horse-shoe magnet 41. The surface of the wall 40 facing the discharge between the electrodes is coated with a layer 43 of aluminum oxide which has a ten micron thickness. This discharge lamp ignites where the two horn-shaped electrodes 39 have minimum distance between them, and is then, under the pressure of the magnetic field of the current leads and electrodes, driven to the electrode points, and by the field supplied by magnets 41 and 42 forced to deploy into the U-shape are 44 indicated in FIGURE 8.

Considering now the showing in FIGURES 9 and 9a of a rare gas high pressure lamp, it may be said briefly that the same comprises a quartz glass envelope of the same order as in FIGURE 7 and here identified by reference numeral 45. Sealed in said envelope are aligned anode 46 and cathode 47, and directed laterally thereof and at the spacing therebetween are shown five tungsten slats 48 also sealed in the envelope. Said slats are isolated from each other and their forward ends proximate to the path of the are are recessed in V-shape and there constitute stabilizing wall for the arc. The non-homogeneous magnetic field by which the arc is pressed toward said wall as indicated at 49 is created by a primary pair of magnets 50 placed outside the envelope and the nonhomogeneity is increased by addition of a secondary pair of magnets 51 also outside the envelope. The polarity direction of the secondary pair of magnets is in reverse of the polarity direction of the primary pair of magnets. These exterior magnets may be either or both electro magnets or permanent magnets.

I claim:

1. An electric high pressure discharge lamp having electrodes and an envelope therefor filled with gas selected from the group of rare gases, metal vapors and mixtures thereof will magnetic lacing and stabilizing of the discharge arc; the characteristic being that close to the discharge arc at least two magnet poles are so placed that, alongside the discharge course for at least that particullar part of the discharge course along which the are discharge is to be laced and compressed, a non-homogeneous magnetic field is composed of strongly bent field lines essentially situated in areas traversing the discharge, said lamp being further characterized by the fact that Within the envelope is provided a metallic wall isolated electrically from the electrodes and so placed that the arc, laced-in magnetically from three sides, is magnetically pressed toward said wall.

2. An electric high pressure discharge lamp in acordance with claim 1, characterized by the fact that the metallic wall is a material of high melting point selected from the group consisting of tungsten and molybdenum.

3. An electric high pressure discharge lamp in accordance with claim 1, characterized by the fact that the surface of the metallic wall facing away from the discharge are has a coating which increases its radiating power.

4. An electric high pressure discharge lamp in accordance with claim 1, characterized by the fact that the metalance with claim 1, characterized 'by the fact that the metallic wall is composed of frontal elements comprising rectangular tungsten slats.

7. An electric high pressure discharge lamp in accordance with claim 1, characterized by the fact that the metallic wall comprises a one-piece element.

8. An electric high pressure discharge lamp in accordance with claim 1, characterized by the fact that the metallic wall comprises a sheeting selected from the group consisting of tungsten and molybdenum and said sheeting has a thickness of one half to three millimeters.

9. An electric high pressure discharge lamp in accordance with claim 1, characterized by the surface of the metallic wall facing the discharge arc comprising a coating of a high melting electrically isolating material less than one millimeter thick.

10. An electric high pressure discharge lamp in accordance with claim 1, characterized by the metallic wall facing the discharge are comprising a coating of electrically isolating material of a high melting oxide selected from the group of aluminum oxide, berylium oxide and silicon dioxide.

11. An electric high pressure discharge lamp in accordance with claim 1, characterized by said metallic wall facing the discharge are comprising a coating having a thickness between one and ten microns.

12. An electric high pressure discharge lamp in accordance with claim 1, characterized by the fact that the nonhomogeneous field is created by two magnetic poles the axes whereof are transverse to the axis of the course of the discharge are and together form an angle of less than 13. An electric high pressure discharge lamp in accordance with claim 1, characterized by the fact that there are two primary magnet poles and two secondary magnet poles situated to produce a field opposing the magnet field of the primary poles at the location of the discharge are for increasing the non-homogeneity of the eifective magnetic field.

14. An electric high pressure discharge lamp in accordance with claim 1, characterized by the magnets being permanent magnets.

15. An electric high pressure discharge lamp in accordance with claim 1, characterized by the magnets being electro-magnets.

16. An electric high pressure discharge lamp in accordance with claim 1, characterized by the fact that the magnet is an electro-magnet and receives its power from the lamp current.

17. An electric high pressure discharge lamp in accordance with claim 1, characterized by the fact that the nonhomogeneous magnet field is created by at least two magnet poles located internally of the envelope.

18. An electric high pressure discharge lamp in accordance with claim 1, characterized by provision of pole shoes internal to the envelope and external magnets in ductively coupled to said pole shoes.

19. An electric high pressure discharge lamp in accordance with claim 1, characterized by the fact that said field is created by poles located internally of the envelope with said poles composed of magnetic material with a high Curie-point and composed at least in part of cobalt.

20. An electric high pressure discharge lamp in accordance with claim 1, characterized by provision of magnetic poles alternating north and south polarity along the discharge course for forcing the are into a winding-line Wave. at

21. An electric high pressure discharge lamp in accordance with claim 1, characterized by a horseshoe magnet with a bar magnet between the legs thereof located behind the metallic wall at the side thereof facing away from the discharge arc forforcing the are into a U-shaped course.

22. An electric high pressure discharge lamp in accordance with claim 1, characterized by at least two magnet poles located outside the envelope.

23. An electric high pressure discharge lamp in accordance with claim'l wherein the envelope consists of quartz glass and the electrodes comprise an anode, a cathode lope comprises a non-magnetic metal body having a 20 vacuum-tight screen at one part thereof, and wherein the metallic wall within the envelope toward which the arc is forced has the shape of a concave mirror for reflecting the light of the arc onto said screen.

25. An electric high pressure discharge lamp in accordance with claim 1, characterized by the fact that the envelope consists of non-magnetic metal body having a vacuum-tight screen inserted into the metal, said body having a part of its interior providing a condensing reflector, the metallic wall within the envelope toward which the arc is forced also being constituted as a mirror arranged to direct light of the arc to said condensing reflector, and said condensing reflector arranged to reflect the light in full intensity to said screen.

References Cited in the file of this patent UNITED STATES PATENTS 2,009,555 Mathiesen' July 30, 1935 FOREIGN PATENTS 886,708 Germany Aug. 17, 1953

Claims (1)

1. AN ELECTRIC HIGH PRESSURE DISCHARGE LAMP HAVING ELECTRODES AND AN ENVELOPE THEREFOR FILLED WITH GAS SELECTED FROM THE GROUP OF RARE GASES, METAL VAPORS AND MIXTURES THEREOF WILL MAGNETIC LACING AND STABILIZING OF THE DISCHARGE ARC; THE CHARACTERISTIC BEING THAT CLOSE TO THE DISCHARGE ARC AT LEAST TWO MAGNET POLES ARE SO PLACED THAT, ALONGSIDE THE DISCHARGE COURSE FOR AT LEAST THAT PARTICULLAR PART OF THE DISCHARGE COURSE ALONG WHICH THE ARC DISCHARGE IS TO BE LACED AND COMPRESSED, A NON-HOMOGENEOUS MAGNETIC FIELD IS COMPOSED OF STRONGLY BENT FIELD LINES ESSENTIALLY SITUATED IN AREAS TRAVERSING THE DISCHARGE, SAID

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