US2947590A

US2947590A - Process for converting glow discharge tubes to photoelectric tubes

Info

Publication number: US2947590A
Application number: US718267A
Authority: US
Inventors: James P Hammer
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 1958-02-28
Filing date: 1958-02-28
Publication date: 1960-08-02
Anticipated expiration: 1977-08-02

Description

Aug. 2, 1960 J. P. HAMMER PROCESS FOR CONVERTING GLOW DISCHARGE TUBES TO PHOTOELECTRIC TUBES Filed Feb. 28, 1958 CUTOFF T1 140-150 V. (X

I I!" 9o-1oov V62 INVENTOR JAMES R HAMMER BY WW4??? AGENT United States Patent PROCESS FOR CONVERTING GLOW DISCHARGE TUBES TO PHOTOELECTRIC TUBES James P. Hammer, Endicott, N.Y., assignor to International Business Machines Corporation, New York, N.Y., a corporation of New York Filed Feb. 28, 1958, Ser. No. 718,267

"6 Claims. (Cl. 316-9) The invention relates to a process and apparatus for producing photoelectric devices.

An object of the invention resides in the process whereby a glow discharge device may be converted into a photoelectric device in a most economical manner.

Another object resides in the use of novel, inexpensive apparatus for carrying out the process automatically and in a most economical manner.

Other objects of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of examples, the principle of the invention and the best mode, which has been contemplated, of applying that principle.

In the drawings:

Fig. 1 is an electrical wiring diagram of the apparatus for carrying on the process of the invention.

Fig. 2 is a voltage waveform showing firing and sustaining voltage points of the tubes before and after processing.

The glow discharge tube of which there are a variety in commercial use, such as the type NE2, type 6332 and CClL and others, employ photo-emissive electrode structures comprised mainly of coatings of oxides of such elements as barium and strontium, while others employ electrodes of caesium and other such elements possessing relatively low work functions.

In the main the process comprises impressing upon the electrodes of the glow discharge device an alternating current for a period of time that depends upon the photoelectric characteristics required. In this process, the photo-emissive material is transferred from the electrodes of the tube and deposited, by what is believed to be a sublimation process, upon the inner surface of the envelope surrounding the electrodes. The envelope is generally made of glass or other material through which light energy, or other forms of "energy capable of the photoelectric effect, passes to impinge upon the deposited photo-emissive layer. The period of time mentioned above may be referred to as the aging period.

At this point it might well to consider in the chart below the characteristics of one type of glow discharge tube, for example, the type NEZ. The chart shows the characteristics of ten tube samples before and after processing with respect to firing and sustaining volt-ages obtained under dark and light conditions, the firing and sustaining voltages being identified, respectively, as V and V The processing of these ten samples was achieved by applying .to the electrodes, connected in parallel, a voltagesource of 120 volts rms 60 cycles with a load resistor of 10,000 ohms connected in series with each tube, and for a period of approximately 72 hours. It may be appreciated that characteristics other than those shown in the chart may be realized by varying the aging period either more or less than the 72 hours indicated.

2,947,590 Patented Aug. 2, 1960 Before Processing Alter Processing Tube Sample Number Dark Light Dark Light Vs V, V V.l Vb V, V V.

It may be appreciated from the first column of figures under Dark V that there is a wide tolerance in the dark firing voltages before processing and that the various tubes exhibit very little, if any, photoelectric effects. After processing, however, it may be noted that the tubes have a marked degree of photoelectric properties as is evidenced by the differences in the dark firing volt-ages and the light firing voltages. Moreover, it is to be realized that the aging of these samples for approximately 72 hours under control of the means described does not result in consistent characteristics as is evidenced from the fact that samples 26 and 36 have dark firing potentials, respectively, of 118 volts and 150 volts. It may also be noted that the light firing potentials for the processed samples range from 104 volts to 128 volts.

The apparatus forming part of the present invention is designed to control the aging process so as to produce converted tubes with characteristics that are more nearly consistent. This apparatus is shown in Fig. 2 and comprises three tube stages, respectively, T1, T2 and T3. Stages T1 and T2 are vacuum triodes serving as amplifiers while stage T3 is a thyratron having a relay R1 in the plate circuit thereof. The glow discharge tubes which are to be processed are referenced, respectively, N1, N2, N3 etc. These are shown connected to a circuit path fed by volts AC. 60 cycle source. This circuit path is further conditioned by a potentiometer K and a relay point Rla associated with the relay R1. From a point X in this circuit a line is connected to the control grid Tla of stage T1, a diode D1 at the input thereof serving as a clamp to protect the grid from an excessive negative voltage. The circuit path containing the relay Rla contacts, potentiometer K and the lines L1 and L2, connected to the glow discharge tubes, may be called the aging circuit.

The aging operation is carried out in the absence of light. The apparatus is prepared for operation by first inserting all the tubes to be aged after which the switch S is closed to apply A.-C. current and voltage across all the glow discharge tubes connected to the aging circuit. At the start of the process the potentiometer K will be set so as to provide a relatively high current flow and thereafter, as the tubes age and the current starts to decrease, due to increased voltage drop across the tubes, the potentiometer is readjusted to provide a nearly constant current flow. The current is above the rated current of the glow discharge device but below the arc discharge current.

During the initial phase of the operation at least one tube will start to fire, the firing being done during each positive and negative half cycle. The firing potential will rise with time and as the process continues, a second tube will fire. In view of the voltage regulation characteristics of these tubes when placed in parallel, the tube that initially fired will now fire at random with respect' process is continued in this manner until all tubes have fired; 'The aging process continues until the firing voltage reaches a predetermined value whereupon relay R1 is picked up to open up the Rla relay points in the aging circuit.

By means of this controlled process the converted tubes will have substantially similar characteristics within a half of one volt.

In the circuit diagram the tubes T1 and T2 may be either a type 5965 or a type 6211. The tube T3 may be a 2D 2,l.

The potentiometer K has a range of up to 20,000 ohms.

At the start of the aging process tube '11 is in a nonconducting status; consequently, the grid TZa of tube T2 is positively biased to enable tube T2 to conduct heavily, the effect of which is to make the control grid T311, of thyrat-ron T3, sufiiciently negative to prevent T3 from conducting. When, during the course of the aging process, the voltage at 'point X exceeds the bias potential on the grid Tia of tube T1, conduction through the latter increases. Consequently, conduction through tube T2 drops off and as a result thereof, grid T3a is driven above cutoff thereby enabling T3 to fire to energize the relay R1 to stop the aging process. A reset key RK is provided to restore the circuit to an operating condition for the next process. It may be appreciated that the apparatus may be modified to process tubes of other types with diliering'characteristics. This may be done by using circuit components with values appropriate to the process in question and with the potentiometer K of greater range together with an alternating current and voltage greater than .120 v. R.M.S.

The AC. waveform in Fig. 2 shows the firing and sustaining voltages of the type NEZ tubes. Curve V indicates the dark firing voltage of unprocessed tubes to be between 65 volts to 75 volts and the sustaining voltages to be between 45 volts to 55 volts. Curve V shows the dark firing'voltages of the neon tubes processed according to the invention. These tubes processed according to the invention can be processed within the range 1140 volts to 150 volts and can be held to within a half of one volt tolerance.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art, without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims. 7 What is claimed is:

1. A process for converting a glow discharge device; of the type having photo-emissive material bearing electrodes and having an envelope through which energy, capable of the photoelectric effect, is transmitted; to a photoelectric device comprising impressing upon said electrodes an alternating current and voltage of sufficient power to cause the depositing of said photo-emissive material to the inner surface of said envelope for a'period of time ranging up to approximately 72 hours, depending upon the photoelectric characteristics desired, and conducting the depositing'of said material i-n'the absence of light.

2. A process for converting a glow discharge device;

- t 4 of the type having photo-emissive material bearing electrodes and having an envelope through which energy, capable of the photoelectric effect, is transmitted; to a photoelectric device comprising impressing upon said electrodes an alternating current and voltage of sufficient power above the rated capacity of the glow discharge device to cause the depositing of said photo-emissive material to the inner surface of said envelope for a period of time ranging up to approximately 72 hours, depending upon the photoelectric characteristics desired, and conducting the depositing of said material in the absence of light.

3. A process for convertinga glow discharge device; of the type having photo-emissive material bearing electrodes and having an envelope through which energy, capable of the photoelectric efie'c't, is transmitted; to a photoelectric device comprising impressing upon said electrodes an alternating current and voltage of sufficient power to cause at a controlled rare thedepositing of said photo-emissive material to the inner surface of said envelope for a period of time ranging up to approximately 72. hours, depending upon the photoelectric characteristics desired, and conducting the depositing of said material in the absence or light.

4. A process for converting a glow discharge device; of the type having photo-emissive material bearing clectrodes and having an envelope through which energy, capable of the photoelectric elf'ect, is transmitted; to a photoelectric device comprising impressing "upon said electrodes an alternating current and voltage, the current being above the rated current of said glow discharge device but below the arc discharge current, to cause the depositing of said photo-emissive material to the inner surtac'e of said envelope for a period of time ranging up to approximately 72 hours, depending upon the photoelectric characteristics desired, and conducting the depositing of said material in the absence of light.

5. A process for converting a glow discharge device; of the NEZ type having photo-emissive material bearing electrodes and having an envelope through which light energy, capable of the photoelectric eflfectfis transmitted; to a photoelectric device comprising impressing uponsaid electrodes an alternating current and voltage, 'ofap'proximately v. R.M.S. value, of suflicient power to cause the depositing of said photo-emissive material to the inner surface of said envelope for a period of time ranging'up to approximately 72 hours, depending upon the photoelectric characteristics desired, and conducting the depositing of said material in the absence of light.

6. .A process for converting a glow discharge device; of the NE2 type having photo-emissive material bearing electrodes and having an envelope through which light energy, capable of the photoelectric effect, is transmitted; to a photoelectric device comprising impressing upon said electrodes an alternating current and voltage, of approximately 120 v. R.M.S. value, of sufficient power to cause the depositing of said photo-emissive material to the inner surface of said envelope for a'period of time or approximately 72 hours and conducting the depositing of said material in the absence of light.

References Cited in the file of this patent UNITED STATES PATENTS 1,955,794 Du Mont et al .t Apr. 24, 1934 2,701,849 Penning et a1. Feb. 8, 1955 2,804,365 Flowers Aug. 27, 1957 2,809,087 Veith Oct. 8, 1 57 FOREIGN PATENTS 601,870 Great Britain May 13,1948