Патент USA US2121636код для вставки
June '21, 1938. |__ R, KQLLER 2,121,636 PHOTOELECTRIC DEVICE Filed May 26, 1937 /00 .90 1S7EY6N2/ 1047:‘ 00 70 60 0'0 40 00 20 /0 0 2000 2600 2700 2000 2.900 3000 0/00 .2200 3000 ~ WAVE z?m?/M/W'smwvs) In Ve ht or . Lewis R. Kol Ier, by 70 6000A“ His t’corney. Patented June 21, 1938 _ UNlTE STATES 22121536? PATET-nplm 2,121,636 PHOTOELECTRIC DEVICE Lewis B. Koller, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application May 26, 1937, Serial No. 144,895 2 Claims. The present invention relates to light-sensitive devices and more particularly to photo-electric tubes which respond to ultraviolet light. (Cl. 250—2'7.5) envelope and serves to prevent deposition of ac tive material on the stem. There is an opening ‘Ultraviolet radiation is used for many purposes l2 in the disk sufficiently large so that the rod 5 can pass through without touching the disk. This 5 such as sterilization, health promoting effects, prevents short-circuiting of the electrodes by the etc. In order to obtain the optimum effects from this type of radiation, it is necessary to measure and regulate the intensity of the light. For this purpose, special types of photo-electric tubes 10 have been devised which respond to light of this character. However, since the light is limited to a restricted range in the spectrum, it is di?i cult to design and. manufacture a tube which will have its optimum response in that range. It is 15 even more difficult to duplicate tubes of this char acter. Objects of the present invention are to devise a photo-electric tube which will respond effi ciently to ultraviolet radiation or to radiation in a restricted portion of the ultraviolet region of the spectrum; to improve the manufacturing processes of these tubes to the extent that they can be readily duplicated, even on a quantity pro duction basis, and to provide a tube in which the response curve in the ultraviolet region may be accurately predetermined. In carrying out these objects, a light-sensitive material of known com position is obtained by vaporization from a source of similar composition which can be varied and 30 accurately controlled. The invention will be bet ter understood when reference is made to the following speci?cation and the accompanying drawing in which Fig. 1 is an elevational view of a photo-electric tube improved in accordance 35 with the present invention; Fig. 2 is a view partly in section of the tube shown in Fig. 1; and Fig. 3 is a graph showing the response curves of vari ous types of improved ultraviolet tubes. In Figs. 1 and 2, numeral l designates a glass 40 envelope containing an anode 2 and a light sensitive cathode 3. The anode may take the form of a metal ring supported on the end of a rigid rod 4 which serves as the leading-in con ductor. The cathode consists of a composite ma 45 terial which is sensitive to ultraviolet radiation, and contact is made with the material by means of a rod 5 which terminates in a platinum ribbon secured to the glass. The conductors are con nected to contact pins 6 secured in a base 1. 50 The envelope terminates in a stem 8 in which the conductors are sealed, the stem carrying an exhaust tubulation indicated at 9. A mica disk I0 is secured to the conductor 4 by means of an angle piece II. This disk is of a size snugly to 55 fit the interior of the small neck portion of the material which condenses on the disk. Shield l3 5 prevents active material which passes through the opening from depositing on the stem 8. For introducing the light-sensitive material into the envelope, a capsule I4 is provided. This 10 capsule may be supported from the rod 4. An alloy having predetermined amounts of cadmium and magnesium is made and placed in the cap sule. After the capsule and the anode have been mounted in position, the envelope is evacuated 15 and the bulb is baked out for an hour at 300 deg. C. At temperatures higher than this, there is danger of vaporizing the cadmium out of the alloy in the capsule. After the bake-out, the alloy is vaporized by heating the capsule by high fre 20 quency induced currents until the bulb is covered with an opaque mirror-like deposit. The thick ness of the deposit is determined by the amount of alloy contained in the capsule. A window [5 is then formed by torching with a soft bunsen ?ame after which the tube is again baked for ten minutes at 100 deg. C. to insure uniformity of the deposit. The envelope may be based in the usual manner. The bulbous portion of the envelope except for the window I5 is therefore 30 coated with an alloy of cadmium and magnesium, which I have found profusely emits photo-elec trons when exposed to ultraviolet light. It has also been found that by varying the cadmium and magnesium, the region within which the tube has its optimum response in the ultraviolet region of the spectrum can be varied. This is clearly shown in Fig. 3. As the cadmium is decreased and the magnesium increased, the sensitivity curve moves to the right, indicating 40 an optimum response at a longer wave length. Thus, increasing the concentration of magnesium increases the relative response to long-Wave radi ation, while increasing the concentration of cad mium increases the relative response to short 45 wave radiation. It may be desirable to cut off or materially reduce the sensitivity of the tube at wave lengths less than 2700 Angstroms. In this case, the envelope may be made of a glass 50 such as Corex which absorbs light of the unde sired wave lengths. The curves shown in Fig. 3 were obtained from a tube of this character, and for that reason the maximum values of the curves are not true characteristics of the cathode but 55 2,121,686 are determined by the falling transmission of the basis, because the light-sensitive layer is, of a Hpredetermined character and can be accurately Corex glass toward the shorter wave lengths. The process as described, which involves the use of an alloy or composition within a capsule for obtaining a light-sensitive layer composed’ of all of the elements of the alloy or composition is not limited to cadmium or magnesiumrbut may be employed in connection with'other metals or materials. vIt is of course highly desirable that 10 the vapor pressure of the materials shall be of controlled. 7 What I claim as new, and desire to 'securer'by , Letters Patent of the United States, is: 1. A photo-electric tube comprising an enve lope containing a light-sensitive cathode and an anode, said-cathode including cadmium and magnesium. ' ' V ‘ ' 2. A photo-electric tube comprising an enve lope containlng a light-sensitive cathode’ and» an anode, said cathode consisting of cadmium posite light-sensitive layer will represent in prop-. and-magnesium, the cadmium‘ ranging from 5% the samerorder as the temperatures employed in ?ashing the alloy or composition so that the com‘ er proportion'the elements contained within the . capsule. It is apparent that the improved proc-; 'ess may be employed on ya quantity production to 95%. a, V a . LEWIS R. KOILER. a “in” ,\_._’--———-—-—~~-~ “i'JERTI‘FIUKTE’UFWRBEGTION Patent No; 2,121,656. ’ ' June 21, 1958. LIMIS R, KOLLER. ‘It ishereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, first column, line 11, for the word "as" read at; and that the said Letters Pat ent should be read with this correction therein that‘ the same may conform to the record of the case in the Patent Office, Signed and sealed this 9th day of August, A. D. 1958. (Seal) Leslie Frazer Acting Commissioner of Patents. __. -7 A ' “*lfl?'omm'ir‘l'cpz"TE"'OFUGRRE''G'TI‘O‘N'T" Patent No; 2,121,656. . ' June 21, 1958_ LEWIS R0 KOLLER. ‘It ishereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page > 2, first‘ column, line ll, for the word "as" read at; and that the said Letters Pat eint should be read with this correction therein that‘ the same may conform to the record of the case in the Patent Office‘, ' Signed and sealed this 9th day of August, A. D. 1958. (Seal)- Leslie Frazer Acting Commissioner of‘ Patents.