Патент USA US2134439код для вставки
Oct. 25, 1938. E, G, DQRGELO 2,Í34,439 ENERGIZING SYSTEM FOR DISCHARGE TUBES Filed Dec. 27, 1957 E 6€ ßoil‘yeZ, O 2,134,439 Patented Oct. 25, 1938 _ UNITED PATENT OFFICE STATES 2,134,439 ENERGIZING SYSTEM FOR DISCHARGE TUBES Eduard Gerardus Dorgelo, Eindhoven, Nether lands, assignor to N. V. Philips’ Gloeilampen fabrieken, Eindhoven, Netherlands Application December 27, 1937, Serial No. 181,929 i In Germany December 29, 1936 3 Claims. (Cl. 17E-Mél) _ The present invention, which forms a contin~ - of the ñlm can be effected during this period without being perceptible on the screen, and uation-in-part of my copending U. S. patent ap plication Ser. No. 127,756, now Patent #2,130,077, thereby make the use of shutters unnecessary. It is well known that, in shutterless apparatus, relates to a system for periodically energizing it is unnecessary that the light emission be re high-pressure metal-vapor discharge tubes, par duced to zero during the periods of 'movement ticularly when such tubes are used as light of the nlm. On the contrary, if the luminous sources in motion picture apparatus. My invention is especially useful with discharge intensity on the projection screen during move tubes of the type described in U. S. Patents ment of the nlm falls below a given value which #2,094,694 and #2,094,695 to Cornelis Bol et al. depends on the maximumv value of the luminous Such tubes are particularly suited for projection intensity, a “travel ghost” of the picture is not perceptible for physiological reasons. When the purposes because they develop an intrinsic bril liance up to and above 200,000 Int. candles per projection is carried out with relatively small sq. in., and the spectrum of the emitted light variations in luminous intensity, for example, in meets all the requirements of picture projection. comparatively small systems, a shutter may be 15 Furthermore, such tubes have the advantage provided. In such cases the device according to that when they are properly energized, their the invention not only prolongs the life of the light-emission -curve has dark periods of such discharge tube but also effects a certain saving duration that the nlm can be moved during these in current. _ In order that my invention may be clearly periods without the movement being visible on the screen, which makes a shutter unnecessary. understood and readily carried into effect, I shall describe the same in more detail with reference In my above-mentioned application I have de scribed an energizing system for such tubes which to the accompanying drawing, in Which: comprises a circuit connected across an alter nating~current supply and having twoparallel branches. One of these branches comprises a preferably variable ohmic resistance and a rec tiñer, the other branch comprises an impedance and the discharge tube, and a condenser is con nected in series with both these branches. I have found, however, that the life of such tubes depends upon the manner in which the current passes through them, and if this current is periodically interrupted, the life of the tube is materially reduced. More particularly, due to` the reduction of the ionization in the discharge space of the tube, the starting voltage of the tube is increased, which may result in premature destruction of the tube. Furthermore, to main tain a given mean intensity of illumination, it is necessary that the tube has a higher luminous intensity during the periods of light emission, i. e. a larger current must be passed through the tube. Because of the above the life of the tube was considerably shortened. Y The main object of my invention is to over come the above diiliculties and to increase the life of such tubes. For this purpose and in ac-_ cordance with the invention, I use in circuits of the above type a condenser and an impedance of such values that a current will continuously pass through the tube. I make the minimum value of the tube current such that the emission of light from the tube periodically becomes so 10W that the movement' Figure l is a schematic circuit diagram of an arrangement according to the invention, Fig. 2 is a sectionalized view of the discharge tube of Fig. l, ' Fig. 3 is a schematic circuit diagram of an arrangement according to another embodiment il l) of the invention, and Fig. 4 is a graph showing the current- and voltage-time curves of the arrangement of Fig ure 1 when~ the condenser and the impedance have the values in accordance with the invention. As shown in Figure 1, an alternating-current source e, which may be the ordinary lighting or power supply, or a transformer, has one terminal l connected through a condenser C to a point 1, and has its other terminal 2 connected to a point 8. Connected in parallel across points ‘l and 8 is a. branch circuit comprising a rectifier G and a variable resistance R, and a second branch circuit comprising a choke coil L and a discharge tube E. Resistance R may be con nected between points 3 and 4, or between points 45 5 and 6 as shown in Fig. 3. In addition, the choke coil L may be replaced by a resistance. As the discharge tube E, I prefer to use cooled high~pres`sure metal-vapor discharge tubes such as described in the above-mentioned patents. Preferably the tube should be lliquid-cooled and have a mercury-vapor filling of high-pressure, preferably more than 6 atmospheres, for eX ample 150 atmospheres, and should comprise one or more incandescible electrodes protruding 55 2 2,184,439 only slightly from a vaporizable metallic mass which surrounds said electrodes and which con tains mercury or amalgam. With such discharge tubes an intrinsic brillianceof 20,000 Interna points 1r and 8. Hence the inductance voltage tional candles per sq. cm. and upwards, e. g. of curve I8. from 80,000 to 100,000 and more, can readily be obtained, while the spectral composition of the light fully meets the requirements to be complied with for faultless projection. Such a tube is 10 illustrated in Figure 2 in which the reference numeral 3| indicates a transparent envelope, e. g. of quartz, in which are disposed two mer thus produced at the choke can still maintain through vtube E for a short time, a current of decreasing intensity, indicated by portion I9-20 In the meantime rectifier G again becomes operative at a point 2|. At a point 22 an in creasing voltage commences to be set up between the points 1 and 8, and as a result, the current through tube E vbetween points 20 and 23 de creases more slowly than between points I9 and 20, and even increases at point 23. This above cury electrodes 32. The tube is surrounded by -described process is then repeated periodically a cooling jacket 33 of transparent material with a frequency equal to that of the alternating 15 through which cooling water is circulated as in current supply. dicated by the arrows. If, in accordance with the invention, condenser I The circuit arrangement operates as follows. C is given a sufliciently high capacity, it will When terminal 2 is positive, condenser C be periodically discharge only a comparatively small comes charged Aby a potential which is governed amount which means that the voltage across 20 by resistance R, since rectifier G permits the cur ~the same drops only a small amount (see curve rent to ilow in this direction. When the poten part Il), and when choke L is given the proper tial oi terminals I and 2 are reversed, there is inductance, it is possible to maintain the flow consequently set up across tube E a total voltage of current through tube E until the voltage be which is the sum of the voltage of condenser C 25 and the voltage of supply e. It follows therefore that the circuit arrangement illustrated in Figs. 1 and 3 makes it possible »to start and to main tain in operation discharge tubes which have a starting-voltage higher than the highest voltage 30 of the alternating-current source. ' The operation of the circuit arrangements shown in Figs. 1 and 3 is illustrated by the graph of Fig. 4 in which curve 9 represents the volt age curve of the alternating-current source e. When the supply voltage reaches a value corre sponding to point I0 on curve S-which point corresponds to the breakdown voltage of recti fier G-the latter becomes operative and con denser C cornmences to be charged. Whether 40 or not condenser C will become charged to the highest value that can be reached, i. e. to the maximum A. C. voltage indicated by point I2, depends upon the capacity of condenser C and on the value of resistance R that limits the rate 45 of flow of the charging current. In the circuit arrangement illustrated the value of resistance R is such that the condenser voltage, designated by dotted curve II, approaches very closely to the maximum voltage of the alternating-current 50 source. The condenser retains its charge, because rectifier G does not allow passage of current in the reverse direction. After the voltage of the A. C. -source has reached the maximum value at l2, it decreases so that there is set up between the points 1 and 8 of Figs. 1 and 3, a potential difference which is indicated diagrammatically in Fig. 4 by the cross-hatched part. Connected in series across points l and 8 are the discharge tube E and the choke L. When, 60 after the device has been placed in operation, the voltage across points 'I and 8 reaches for the first time, at point I4, a value equal to the breakdown voltage of the discharge tube, indi cated by line I3 in Fig. 4, the tube 'lights up. The iiow of current through the tube is indi cated diagrammatic’ally by the curve I6 which starts at a point I5. The condenser then dis charges through the tube E as indicated by the portion Il of curve II. 70 At a point I8, the potential difference between the points 'I and 8 becomes equal to zero. How ever, the current passing through the discharge ‘ tube is not equal to zero at this moment, because the current in choke II lags in well-known man 75 ner with respectI to the voltage applied across tween the points ‘I and 8 again increases and a renewed increase in current is set up from the point 23 onwards. Thus tube E will not become extinguished but will be supplied with an unin terrupted and periodically varying current. The higher the values of the inductance of choke L and the capacity of condenser C, the less will be the periodical decrease of the current through the tube. In the above system the condenser C, the rectiiler G and the impedance L act as a recti fying circuit, in which C and L together form the smoothing filter. The greater the value of the condenser C and the impedance L, the smaller will be the alternating current ripple on the direct current. When the maximum value oi’ the A. C. is greater than the D. C. the rectiiied current will beperiodically interrupted; but when it is smaller, the rectified current will be uninterrupted. In accordance with the invention the con denser C and the impedance L are so propor tioned that the maximum value of the alternat ing component (curve I 6) of the rectified cur rent will be smaller than the value of the direct component (curve 24) of said rectified current, i. e., so that the current through the tube E will not be interrupted. As a specific example, I have used the follow ing values: Supply voltage e=500 volts; supply frequency f=50 cycles per sec.; operating volt age of discharge tube e=500 volts; a mean tube current 1 or 2 amps.; capacity of condenser C=30 nf; inductance of choke L=from 2 to 3 henries; a resistance R=about from 10 to 100 ohms. With such values, it was found that the life of the tube was about 10 times greater than when supplied with periodically interrupted cur rent. While I have described my invention in con nection with specific examples-and applications, I do not wish to be limited thereto but desire the appended claims to be construed as broadly as permissible in view of the prior art. ' What I claim is: „ l. An energizing system for a high-pressure metal-vapor discharge tube having a contracted discharge path, comprising a source of alternat ing current, and means between said source and said tube for passing through said tube an un interrupted and periodically varying operating current. said means comprising a circuit con 'l i. 3 nected across said supply and having two parallel branches, a condenser in said circuit and in series with both of said branches, ‘a rectiñer in one of said branches, an impedance in said circuit be tween said rectifier and one end of said'source, and a second impedance, said second impedance and discharge tube being connected in series in said second branch. 2. An energizing system for a high-pressure metal-vapor discharge tube having a contracted discharge path, comprising a source of alternat ing current, and a rectifying circuit connected _ 3. An energizing system for a high-pressure metal-vapor discharge tube having a contracted discharge path, comprising a source of alternat ing current, and means associated with said source to rectify said alternating current and to supply to said tube an uninterrupted and pe riodically varying operating current, said means comprising a vcircuit connected across said sup-ply and having two parallel branches, a condenser in said circuit and in series with both oí said 10 branches, a rectiñer in one of said branches, a variable resistance in said circuit between said rectifier and one end of said source, and an im across said supply and having two> parallel` pedance, said impedance and discharge tube being branches, a condenser in 'said circuit and in connected in series in said second branch, said 15 l series with both of sai.’ branches, a rectiiier in condenser and said impedance being propor one of said branches, an impedance in said cir cuit between said rectiñer and one end of said source, and a second impedance, said second impedance and discharge tube being connected y in series in said second branch, said condenser and second impedance being proportioned to cause an uninterrupted and periodically varying current to pass through said tube. tioned to cause the maximum value of the alter nating component of the reotiñed current to be smaller than the value of direct component of 20 said rectiñed current. EDUARD GERARDUS DORGELO.