US2441732A - Cathode heater supply from cathode-ray deflecting circuit - Google Patents

Description

y 1948- c. E. TORSCH 2,441,732

CATHODE HEATER SUPPLY FROM CATHODE RAY DEFLECTING CIRCUIT Filed March 28, 1945 70 came; 77/5: 194% we Figk ITO/Vi 55 11v VEN TOR. 63604 21 6 E. 7RscH A TT'ORNEY Patented May 18, 1948 CATHODE HEATER SUPPLY FROM CATH- ODE-RAY DEFLECTING CIRCUIT Charles E. Torsch, Merchantville, N. J assignor to Radio Corporation of America, a corporation of Delaware Application March 28, 1945, Serial No. 585,281

4 Claims.

The present invention relates to electronic apparatus and more particularly to electronic apparatus employing a cathode ray tube, such, for example, as an electronic television scanner.

Television apparatus and similar apparatus incorporate a scanning or camera tube of which there are many and various types. For the purpose of illustration, this invention will be disclosed by way of example in connection with a scanning or camera tube of the so-called storage type such, for example, as the type which is now commonly known in the art as the Iconoscope.

In many television installations lightness of weight and compactness of equipment are desirable. This is particularly true of equipment which is to be installed in a vehicle or a plane, or which is to be transported; and bulk, as well as weight, is a factor to be considered. Where particular emphasis is given to lightness of weight so that the equipment may be portable, it is frequently desirable to rely upon a common source of energy for developing both the high voltage for operating the system, as well as for developing the heater current for the cathode ray emitters. Usually, the heater current isan altemating current of low frequency serving to heat the electron emitters of the discharge tubes generally to be found in such equipment, This heater current may be derived from a low frequency alternating current source or direct current may be employed. However, in the case of the heater for the cathode of the previously mentioned scanning or camera tube, which is to be activated by its heater so as to produce an electron stream, special problems arise since other electrodes within the tubes are operated at very great voltage differences with respect to each other and also with respect to the cathode. Not only are problems of insulation to be overcome, but it is desirable that there be some established frequency relationship between the sources used to produce the high voltage energy and the sources used to develop the heater current and such relationship is had by this invention. Even where a source of direct current is available for supplying the heaters of the discharge tubes in the system, the Iconoscope heater still presents its own peculiar problems because of the necessity for high voltage insulation and a ripple-free or synchronized ripple heater source.

The relationship between the sources used to produce the high voltage energy and the sources used to develop the heater current resulting from use of the present invention prevents any crosstalk efi'ects from giving rise to noticeable ripple in the image. This invention provides for obtaining heater current for the camera tube heater in a novel manner from the deflection sources which, of themselves, serve in a known manner to control the motion or traverse of the scanning cathode ray beam across a target or mosaic element to produce a signal representative of an optical image which has been cast upon this target or mosaic.

In most embodiments of television systems where unilateral scanning is relied upon, the scanning electron beam developed within the tube is controlled in its deflection under the influence of deflection energy of substantially sawtooth wave formation Accordingly, in the present invention, the control energy from which the operating voltages for producing the relatively high voltage, as well as for producing the heater currents, are developed and controlled in a novel manner under the influence of the produced deflecting wave energy. To this end, a novel and effective means has been provided for amplifying, modifying, and controlling a wave derived from the deflection controlling wave to provide the heater current.

It accordingly becomes one of the objects of the invention to provide a television system having included therein a scanning instrumentality in which a scanning beam is developed to scan an area under the influence of a controlling wave, and also in which the heater current energy source which causes the initial release of the electrons to make up the scanning beam is activated by the controlling wave.

Other objects of the invention are those of providing a power supply system for a television or cathode ray tube device wherein the operating voltages are developed from a self-contained unit, and wherein the necessity for providing separate sources for developing the high voltages and the heater currents is avoided by a novel arrangement.

Another object of the invention is to provide a source of heating current for a cathode ray tube from the circuits controlling deflection of the .beam in the tube without the necessity for using extended leads to rotary power supply apparatus of a highly complicated type.

Still another object of the invention is to provide for furnishing heater current for the heater of a cathode ray tube from the deflection control circuits of the tube with a provision for amplifying the heater current and, Where de- 5 sired, for controlling the amplification in a novel 5 manner.

Other objects and advantages of the present invention will, of course, become apparent and immediately suggest themselves to those skilled in the art to which the invention is directed from a reading of the following specification in connection with the accompanying drawing in which;

Fig. 1 shows diagrammatically one suitable form of television apparatus embodying the invention; and 1 Fig, 2 is a conventional showing of a cathode ray camera tube suitable for use with the am a ratus of Fig. 1.

Referring now to the drawing fora further understanding of the invention, 'it will be assumed .for. the purpose of. these considerations that an electron tube I (Fig. 2) of the cathode ray type is provided with suitable ray deflecting means, such as electrostatic deflection plates or electromagnetic deflection coils 43 and 44 included. in a deflecting yoke 22, for example, to

which voltages or currents of saw tooth wave formationareapplied, and the sawtooth wave formation acting upon the deflecting means causes 1e developed cathode ray or scanning beam 3 to traverse a .target area 4 of the cathode ray tube according to a desired pattern ofscanning.

The cathode ray tube I includes a heater 5,,a

cathode 6, a control grid 7, a first anode 8, a, second anode 9 and amosaic structure to which presents the previously mentioned target surfaced.

Inthe illustrative example shown in the drawing, a sawtooth voltage is developed in known manner by a discharge tube I!) to the control grid l2 of which is applied, by way of a coupling condenser M, deflection controlling impulses derived for example from a blocking oscillator or a sync generator (neither shown). A condenser is is charged through a resistor is and discharged upon occurrence of a pulse applied to the grid 52 by way of the condenser It. A con- .nection 2! is provided to which'suitable means for modulating the output wave 22 of the discharge tube is to overcome" keystone distortion may be connected. Methods .of obtaining keystone correction by modulation of the sawtooth wave form .are disclosed in a U. S. patent to QgloblinskmNo. 2,040,813, granted May 12, 1936, and in a copending .U. S. patent application, Serial No. 480,973, filed March .27, 1943, in the name of O. I-IVSchade, issued February 27, 1945, as Patent 2,370,4 6. 7

The modified sawtooth wave so developed is supplied to the control grid 26 .of a horizontal output tube 21 by way of a coupling condenser 28. Polarizing potentials of relatively largemagnitude for certain ofthe elements of the cathode ray-tube I are'provided from the *high kick-back voltage which is developed by the steep wave front of the sawtooth current reversal during retrace time used for deflection purposes in a manner to be described. A connection 3lfrom the plate 33 of the horizontal output tube 21 is made efiectively to the primary winding 36 of an output transformer 33, the other end of the primary winding being connected to a suitable plate supply source indicated at 39. Connection '40 to damping means such as a damping diode (not shown) is included. Examples of damping tube circuits suitable for use are shown in United States Reissue Patent No. Re. 21,400, granted to A. D. Blumlein on .March 19, 1940, and also in a United States PatentNo. 2,280,990, granted to E. L. C. White on April 28, .1942. A I

condenser and resistor combination 45 and 41 .shunted across them. The entire winding 36 is tapped as indicated at 49 to provide a winding section 52 which serves as an auto-transformer secondary and the high voltage impulses generated in this coil section 52 are applied by Way of a coupling condenser 56 and a load resistor til-across the plate and cathode elements BI and 63 of a high voltage rectifier tube 84. Examples of such an arragement are to be found in the disclosure of U. S. Patent No. 2,074,495, granted to AVW. Vance March 27, 1937, and in the copending application of O. H. Schade, Serial No. 578,678, filed February 19, 1945, issued April 6,

v 1948, as Patent 2,439,223.

A high voltage bleeder comprising series connected resistors as shown and potentiometers 58 and 69, for example, provide for connections to the several elements of the cathode ray type camera tube l. The control grid 7, the cathode 6, and the first anode 8 are connected to the point 22, the potentiometer 68 and the potentiometer 09, respectively in the illustrated example. The point of connection 14 of the bleeder resistor combination to the load resistor .59 is highly negative with respect to ground, and the second anode 9 of the samecathode ray tube I will be assumed, for purposes of these considerations, to operate as the most positive element of the system and consequently, it will be connected in i any suitable manner directly to ground.

I The sawtooth voltage 22 which, as stated above, may be modified to provide keystone correction, is also applied through a suitable conductor and coupling condenser is tothe control grid 79 of a tube 8! which servesas an independent amplifier for amplifying the voltage which is effective, by means to be described, to supply heating current for a heater of the camera tube cathode 6. A grid resistor $39 is provided for the tube 33. The plate circuit of the tube 3| includes the primary 82 of a transformer 83 which is or may be compactly constructed and of relatively light weight. The turns ratio of the transformer 83 is high so as to most efliciently match the low resistance representing the hot resistance of the heater 5 which is connected to the secondary 86 of the transformer. An arched voltage wave is present across the terminals 88 and 89 of the camera tube heater. Steep wave fronts are thus avoided.

The heater load and amplifier tube condition is adjusted by a potentiometer .92 which is in series with a resistor 93 in the cathode leg of the tube 3|. A condenser 94 is shunted around the resistance represented by the elements 92 and 93 to serve as a bypass condenser.

,Solely by way of example, the tube may be of the type known in the art as the 6L6, and the potentiometer 92 may have a value of 1,000 ohms withthe resistors 93 andtil having a value of 390 ohms and 470,000 ohms, respectively. The condenser may have a value of .5 mi. The step down ratio of the transformer for a 40 volt peakt'o-peak value of the keystoned sawtooth voltage 22 may be 25 to 1. These values are given by Way of example as being suitable'when a camera tube isemployed having a heater load of 10 ohms;

By employing the separate tube and transformer as disclosed herein, insulation from primary to secondary and from both of these transformer windings to ground is readily obtained. Long cables back to generator slip rings and direct current complexity is eliminated. The high frequency allows the use of a small weight of core lamination in the transformer 83 and the ripple is synchronous with line frequency so that there is no moving pattern of interference. As a result, scanning and shading are not interfered with.

Having now described the invention, what is claimed and desired to be secured by Letters Patent is the following:

1. In a television apparatus wherein is included a camera tube having a target and means to develop an electron beam in combination with means to cause the developed beam to scan the target, electrical wave generating means for producing electrical waves controlling the deflection of the electron beam relative to the target area, independent means for amplifying the wave generated by said electrical wave generating means, transformer means adapted to be energized by the output of said independent amplifying means, and means for developing alternating current energy from said transformer output to provide heating current for the electron beam developing means.

2. In television apparatus wherein is included a camera tube having a target and means to develop the electron beam in combination with means to cause the developed beam to scan the target, electrical impulse generating means, electrical sawtooth wave generating means operative in response to the generated impulses for controlling the deflection of the electron beam relative to the target area, amplifier means having an input connection to which said electrical sawtooth wave is applied, and transformer means supplied by said amplifying means, the output of said transformer means being connected to provide heating current for the electron beam developing means, the heating current being in the form of alternating current energy of a frequency related to the impulse frequency.

3. In television apparatus wherein is included a camera tube having a target and means to develop an electron beam in combination with means to cause the developed beam to scan the target, electrical wave generating means for producing electrical waves controlling the deflection of the electron beam relative to the target area, an independent amplifier tube having a cathode, anode and a control electrode for amplifying the wave generated by said electrical wave generating means, transformer means adapted to be energized by the output of said independent amplifying means, means for developing alternating current energy from said transformer output to provide heating current for the electron beam developing means, and means in series with the cathode of said tube for controlling the interval plate resistance of said tube and thereby the developed heating current.

4. In television apparatus wherein is included a camera tube having a target and means to develop the electron beam in combination with means to cause the developed beam to scan the target, electrical impulse generating means, electrical sawtooth wave generating means operative in response to the generated impulses for controlling the defiection of the electron beam relative to the target area, amplifier means having an input connection to which said electrical sawtooth wave is applied, transformer means supplied by said amplifying means, the output or said transformer means being connected to provide heating current for the electron beam developing means, the heating current being in the form of alternating current ener y of a frequency related to the impulse frequency, and means associated with said amplifier means for controlling the heating current.

CHARLES E. TORSCH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,218,764 Moller et a1 Oct. 22, 1940 2,261,645 Delvaux Nov. 4, 1941 2,265,620 Bahring Dec. 9, 1941

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