US2644909A - Circuit-arrangement comprising a cathode-ray tube - Google Patents

Description

July 7, 1953 P. H. DE BEURS 2,6

CIRCUIT-ARRANGEMENT COIIPRISING A CATHODE-RAY TUBE Tiled, Feb. 13 ms;

3 INVENTOR PIETER HEN $925 BEURSM AGENT Patented July 7, 1953 CIRCUIT-ARRANGEMENT COMPRISING A ICATHODE-VRAY TUBE "Pieteraflendrik ,De lSeurs, Eindhoven, Netherlands, assignor to Hartford National Bank and a Trust CompanmHartford, Conn., as trustee Application February 13, 1951, Serial No. 210,643

' In the N ether-lands March 6, 1950 This invention relates to a circuit utilizing a cathode-ray tube whose electron beam,may-be deflected through a number. of different stablepositions in accordance, with the demands of an external applied deflection voltage.

A circuit oi-this type is particularly applicable for counting purposes, as the electron-beam may be deflected through successive positions as successive pulses areappliedto the deflection system. Each time the beam has been deflected through all its different positions,,it is necessary to return the beam to its initial; position. The process of returning the beam fromjits final to its initial position is termed fly back, and the time interval in which fly back takes place is termed fly back time. It, is possible to initiate a pulse each time fly back occurs, each pulse representing a number,-which in turn represents the number of'stable beam positions used in the particular application desired. Thus 'a count,- ing process using fly backperiods can be used, the speed of this process beinglimited by the fly back time.

In one known circuitof this kind, the cathoderay tube comprises a plurality'of collecting electrodes, arranged side by side inthe direction:of deflection and connected to taps on a potentiometer, and another tap ofsaid potentiometer is connected to a deflection electrode of this tube.

These taps are so chosen that when a beam strikes one of these electrodes, a deflection voltage is developed as such valueras to direct the beam onto the electrode concerned. The beam is shifted from one position to anotherby supplying a pulse to the deflection system.

In another known circuit of this kind,the beam current of a cathode-ray. tube is divided among a first collecting electrode and oneor more additional collecting electrodes. The first collecting electrode is connected directly to a deflection electrode, and is also connected through a. resistor to a voltage source. In an equilibrium position the beam current is so divided that a deflection voltage is developed correspondingto a fixed beam position. Any small deviation in beam position will change the deflection voltage in such fashion as toreturn the beam to its equilibrium position. The beam is shifted from one position to another by supplying a pulse to the deflection system.

The fly back process is controlled by a gas filled tube whose discharge path is through the deflection electrode of the cathode-ray tube. The voltage of this electrode is proportional to the beam position. When the beam is movedto its final position, this voltage will exceed a predetermined eoiaims. 01. 315-21) is oonnectedto the cathode 2 of thecathode-ray value, discharging the gas-filled tube. Consequently, the voltage of} the deflection electrode is suddenly varied, so that the beam is displaced to its initial position, at which time the gas-filled tube stops discharging. Since the discharging process just outlined takes about 100 microseconds, the fly back time is limited to this value.

This invention reducesthe fly backtime by substituting an electron dischargetube for the gas-filled tube, the potential on the deflection electrode being supplied from the cathode of said electron discharge tube. Means are provided for temporarily increasing the potential at acontrol electrode of the electron discharge tube when 1 this tube conducts. This temporary increase in potential initiates the fly back; process.

In order that the inventionmay be more clearly.

understood and readily carried into efiect,; itwill now be described morefully by reference to the accompanying drawing.

Figs. 1 and 3 show examplesof the. circuit{ v arrangement according to the invention inwhich the beam is stabilized by tributionh Fig. 2 shows adiagram s rving toexplain the operation of the circuit arrangement. I

. The cathode-ray tube I shown in -1 c or nprises a cathode}, means3; 4 for producing a cathode-ray beam which are known. perse and.

which are shown here only diagrammatically, a

set of deflection plates 5, send collecting electrodes I, 8. Means 3, 4 are coupled to. suitably chosen tappings on a supply battery II. The electrode I is arranged in front of the electrode 8 and comprises anumber of apertures such that,

thebeam on being deflected, strikes alternately an element of the electrode I and, through an ape.

erture of this electrode, an elementof theelec trode 8. The current Z a flowing. toijtihe electrode 8 then varies as a function of the deflection volt,-; age V at the deflection electrode 6 in. the manner.

indicated bycurve H in Fig. 2. When the beam passes through an aperture of the electrode 1, the whole of the beam current flowsjto' thelelectrode 8. If, however, the beam is intercepted by the electrode I, the current flowing totheelec trode 8 is zero. :The electrode Bis connected through a conductor 9 to the deflection electrode 6, this electrode furthermore being coupled by way of a resistanceIO to a tapping I I on a bat;

tery II. The negative terminal of the battery tube. The collecting'electrode I is connected to the positive terminal of the battery." Thedeflec tion electrode 5 is connected to a tapping 'on' the battery. I I

The relationship between the current traversing the resistance II] and the voltage of the elec-' trode 6 (point I2) is indicated by a straight re In aposition of equilibrium the current traversingthe conductor 9 is equal'to the current flowing through the resistance III, which implies that the m s f curren -d positions of equilibrium of the beam must correspond to intersections of the curves 2i and 22 in Fig. 2. The intersections 23, 24, 25, 26, 21, 28 correspond to stable positions of the beam, whereas the intersections 29, 30, 3|, 32, 33, 34 provide unstable positions of equilibrium.

More specifically, assume that, at a given moment, the voltage at point 12 is equal to V2. The current flowing through conductor 9 then exceeds the current traversing the resistance It. Due to the difference in current, the existing change on the stray capacitance measured be tween point [2 and ground or the existing change on a capacitor indicated by C in Fig. l coupled to point 12 is decreased. Consequently, the voltage at point IQ will decrease to a value V2 and the beam will move towards the stable position of the beam corresponding to the intersection 25 A similar reasoning applies if the voltage at point I! is somewhat lower than the voltage Vi correspending to the intersection 25. The beam will thus move automatically to the stable position 25-, if the voltage at point l2 lies within the interval between the voltages V3 and V4 correspondin to unstable positions of equilibrium 3| and 32. This interval thus constitutes the attraction sphere of the stable position 25.

Similarly, the voltages exceeding the voltage V5 corresponding to the unstable position 29 belong to the attraction sphere of the natural initial position 35. Consequently, if the voltage at point 12 is higher than V's, the beam moves to the right until position 35 is reached. It should be noted that, if due to battery voltage variation or other cause the resistance line 22 were to be shifted to the left with respect to curve 2|, and if a voltage were applied to point [2 which is higher than the voltage V1, in such manner that the intersection 35 of the straight resistance line 22 and the axis of voltage would lie at V5, a voltage lower than V5, the beam would move to position 23.

The beam may be moved from one stable position to another by supplying a pulse through a conductor L to point 42 in such manner that the voltage at point I2 is suddenly varied into a value which lies within the attraction sphere of the stable position desired.

It is assumed that the beam first occupies the initial position 35. A first negative current pulse supplied to point ['2 then moves the beam to position 23, the second pulse moves the beam from position 23 to position 24, and so forth until after six pulses position 28 is reached. The beam is then adjusted to the left-hand edge of the extreine left-hand aperture '1 of the collecting electrode I.

The seventh pulse moves the beam back to its initial position 35 in a manner which will be described hereinafter. The deflection electrode 6 is connected to the cathode [3 of a vacuum tube ll. The tube It furthermore comprises a'control electrode 15, a secondary-emission collecting electrode l6, and an anode I1. The latter is connected to the positive terminal of the battery I I. The secondary-emission electrode 16 is connected by way of a condenser to the control electrode l3 and by way of a resistance I9 to a tapping on the battery H such that when the tube is nonconducting, the potential of the electrode I6 is materially lower than that of the anode IT. The control electrode 15 is connected by way ofaresistance H to a tapping on the battery, the volt age V: of which is somewhat lower than the volt age Vs, which corresponds to the extreme lefthand stable position (28) of the beam.

As previously mentioned, the sixth counting pulse moves the beam to the extreme left-hand stable position. The potential (V9) of the control electrode I5 is then so much lower than the potential (Vs) of the cathode l3 that the tube l is just non-conductive.

The subsequent seventh pulse at the first instance again reduces the potential at point [2, the beam being driven further to the left. The voltage difference between the electrode [6 and the cathode l3 now drops to a point where tube l4 begins to conduct.

The electrode I6 is struck by an electron current originating from the cathode. Since the electrode I6 is of the s'econdary emission type and the potential of this electrode is lower than that of the anode H, the current of secondary electrons emanating from the electrode is is greater than the incident current of primary electrons, so that a positive current flows by way of resistance I! from the electrode to the battery.

Consequently, the potential of electrode It increases. The variation in voltage of electrode 16 is transferred by way of condenser 20 to the control electrode IS. The tube [4 conducts more current and the potential of electrode I6 undergoes a further increase which, as before, is transferred by way cf condenser 20 to the electrode 15.

Owing to this interaction, the potential of the control electrode l6 increases to a value which is approximately equal to that of the battery voltage, the capacity C being rapidly charged in the positive sense by way of the tube l4.

After a short period of time, the voltage at point l2 has exceeded the voltage V5 and thus has come within the attraction sphere of the initial position 35.

Since the control electrode I5 is not galvanically connected to the electrode 16, the potential ofthis electrode subsequently decreases due to the presence of a resistance Hi. The current of primary electrons flowing to the electrode H; decreases, so that the potential of this electrode undergoes a decrease which is transferred by way of condenser 20 to the electrode 15, tube H being cut-off within a short time.

The beam now moves to the initial position 35.

Fig. 3 shows a variant of the circuit-arrangement in Fig. l, in which identical elements are provided with the same reference numerals.

The deflection electrode 6 of the cathode-ray tube is connected to a cathode H of a discharge tube 40, which in this case may be of the ordinary triode type;

An anode 43 'of this tube is supplied by way of a resistance N and connected by way of a condenser 45 to a control electrode 49 of a second discharge tube 41.

An anode 4B of this tube is connected by way of a resistance 5| to a tapping on the battery II, a. condenser 52 being included between the anode A8 and the control electrode 42 of tube 40. The cathode 50 of tube-t1 is connected to the negative terminal of the battery II. The control electrode d9 of tube 41 is connected by way of a leak resistance 53 to the cathode, so that tube 41 is, normally, conducting.

The control electrode 42 of tube 40 is furthermore connected by way of a leak resistance 46 to a tapping of the battery H such that, if the potential of the deflection electrode 6 has a value which corresponds to that of an arbitrary stable position of the beam in the cathode-ray tube I, the discharge tube 49 is cut-off.

If a shifting pulse supplied through conductor L to point 12 now decreases the potential of point I2 still below the voltage Vs which corresponds to the extreme left-hand stable position (28 in Fig. 2) of the beam, tube 49 becomes conducting and a current flows through the anode supply resistance 44.

The voltage of the anode 43 thus decreases and, due to the capacitive cupling'45, the voltage of the control electrode 49 also decreases. This results in an increase in potential of the anode 48 of tube 41, which increase is transferred by way of a condenser 52 to the control electrode 42 of tube 40.

Tube 40 thus becomes conducting to a greater extent so that, due to the backcoupling by way of tube 41, the potential of the control electrode 42 is increased further, so that tube 40 suddenly: becomes completely conducting and a strong current pulse ensues across the cathode lead of tube 40, which pulse rapidly charges the capacity C in the positive sense, so that the beam is driven to the right and the voltage at point I2 comes within the attraction sphere of the initia1 position 35.

After the current traversing tube40 has attained its maximum value, the condensers 45 and 52 discharge by way of .leak resistances 53 and 46, the potential of electrode 42 decreasing and the potential of electrode 49 increasing. This action is enhanced by the backcoupling so that tube 49 is suddenly cut-off again. i

The circuit-arrangement may be varied within the scope of the invention in various ways. Thus, for example, it is possible for only one of the control electrodes 42 and 49 to be capacitively coupled to the anode of the other tube, while the other coupling is galvanic. As a further alternative, inductive coupling may be substituted for capacitive coupling.

By varying the resistance 51 the maximum variation in potential of the anode 4'8 and hence of the control electrode 42 may be limited, so that it is possible to make the beam fly back from the extreme left-hand position to any one of the intermediate stable positions instead of to the position 35.

What I claim is:

1. In a circuit arrangement including a cathode-ray tube provided with means to generate an electron beam, a deflection electrode to deflect said beam in a given direction and a collecting electrode system disposed in the path of said beam, means coupling said collecting electrode system to said deflection electrode to cause said beam to occupy one of a plurality of inherently stable positions and means to shift the beam from one stable position to a next position; apparatus for controlling the fly back of the beam comprising an electron discharge device having a cathelectrode system disposed in the path of said beam, means coupling said'collecting electrode system to said deflection electrode to cause said beam to occupy one of a plurality of inherently stable positions and means to shift the beam from one stable position to a next position; ap-

paratus for controlling the fly back of the beam comprising an electron discharge device having a cathode, a grid, a secondary emission electrode and an anode, means coupling said device to said deflection electrode to render same conductive,

3. A circuit arrangement, as set forth in claim 1, further including a second electrode discharge device having a cathode, a grid and an anode, the

anode of the first device being coupled to the grid of the second device, the anode of the sec- 0nd device being coupled to the grid of the first device,-at least one of these couplings being capacitive. v 4. In a circuit arrangement including a cathode-raytube provided with a beam source, a dev fiection electrode to deflect said beam in a given direction and a collecting electrode system disposed in the path of said beam and constituted by a first electrode having spaced apertures therein and a rear electrode, means including a connection from said rear electrode to said deflection electrodefor coupling said collecting electrode system to said deflection electrode to cause said beam to occupy one of a plurality of inherently stable positions, a voltage source having a first resistance, means connecting the negative termina1 of said voltage source to saidbeam source and the positive terminal to said front electrode and means connecting a firstpositive tap on said source through said first resistance to said rearelectrode; apparatus for controlling the fly back or said beam comprising an electron discharge device having a cathode, a

grid, a secondary emission electrode and an anode, a capacitor connectingsaid secondary emission electrode to said grid, means connecting said cathode to said deflection electrode and said anode to said front electrode, a second resistance connecting said secondary emission electrode to a second positive tap in said voltage source, and

a third resistance connecting said grid to a third positive tap in said'source, said third tap having ode, a control electrode and an anode, means coupling said device to said deflection electrode to render said device conductive when a potential on the deflection electrode exceeds a predetermined threshold value, the cathode of said device being connected to the deflectionelectrode, and means responsive to conduction in said device to effect a momentary increase in potential on said control electrode.

2. In a circuit arrangement including a cathode-ray tube provided with means to generate an electron beam, a deflection electrode to deflect said beam in a given direction and a collecting a lower value than said second tap, said second tap having a lower value than said first tap.

PIETE-R HENDRIK DE BEURS.

References Cited in the file of this patent v UNITED STATES PATENTS Number

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