US2488452A - Circuit arrangement for deflecting the cathode-ray beams in cathoderay tubes - Google Patents

Description

A. J. w. M. VAN OVERBEEK 2,488,452 CIRCUIT ARRANGEMENT FOR DEFLECTING THE CATHODE-RAY BEAMS IN CATHODE-RAY TUBES 2 Sheets-SheeI l Nov. l5, 1949 Filed Nov. 25, 1947 Nov. l5,- 1949 A. J. w. M. VAN ovERBr-:EK 2,488,452

CIRCUIT ARRANGEMENT FOR DEFLECTING THE CATHODE-RAY BEAMS IN CATHODE-RAY TUBES Flled Nov 25, 1947 2 Sheets-Sheet 2 INVENTOR Patented Nov. 15, i949 UNITED CIRCUIT ARRANGEMENT FOR DEFLECTING THE CATHODE-RAY BEAMS IN CATHODE- RAY TUBES Adrianus Johannes Wilhelmus Marie van Overbeek, Eindhoven,

Netherlands, assigner to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application November 25, 1947, Serial No. 787,912 In the Netherlands November 27, 1946 8 Claims, (Cl. 315-21) This invention relates to a circuit-arrangement for deflecting the cathode-ray beam in a cathoderay tube, the end of the beam describing a closed curve.

Circuit-arrangements are known with which the beam performs the aforesaid movement and the end of the beam describes, for instance, a circle, but in this case this is effected by means of suitable deection voltages or currents supplied by separate generators.

With the circuit-arrangement according to the invention the movement of the beam is not effected by means of such separate generators but entirely automatically.

The circuit-arrangement according to the invention exhibits the feature that when the beam hits a collecting electrode within the tube, the beam current inlluences the deflection means in a manner such that the beam moves over this collecting electrode.

In order that the invention may be more clearly understood and readily carried into effect, it will now be described more fully with reference to the accompanying drawing, given by Way of example in which Figure 1 is in part a perspective view of parts of the cathode ray tube and in part a circuit diagram showing an illustrative embodiment of the invention.

Figure 2 is in part a plan view of a collecting electrode and in part a diagrammatic View of the circuit connections to the deflecting means in a modification of the invention.

Figure 3 is a. further modification of Figure 2.

Figures 4 to 7 are partial diagrammatic views ofA the structure of electrodes suitable for use in a cathode ray tube constructed according to the invention.

In Figure l the reference numeral I denotes the cathode of a cathode-ray tube which is not further represented. By means known per se a cathoderay beam 2 is formed which passes through the point 3 if no dellection occurs.

In addition the tube comprises deflection plates 4 and 5 for deflecting the beam in a horizontal direction, and a set of deflection plates (not represented) for deection in a vertical direction. Furthermore it comprises a collecting electrode 5 lwhich is connected to the deflection plate 4 through a lead l. This dellection plate and the collecting electrode are connected, through a common resistance 8, to the positive terminal of a source of potential of which the negative terminal is connected to the cathode I. The plate 5 may be directly connected to the positive terminal of the source of potential so that no potential difference is set up. between plates 4 and 5 if the resistance 8 is not traversed by current.

If the plates for vertical deflection receive a voltage impulse having the correct value the beamV hits the collecting electrode 6 at 9. Due to this the beam-current traverses the resistance 8 and reduces the potential of the deection plate 4 with the result that horizontal deflection in the direction of the arrow I occurs. If the collecting electrode 6 has a sulcient size in e, horizonta1 direction, the end of the beam travels over this electrode until it reaches the point at which the deflection attains the value corresponding with the occurring deflection voltage. This point may, for instance, be located at II. It is pointed out in this respect that the location of point II is variable, for instance by varying either the current strength of the beam or the resistance 8, and furthermore it depends upon the deflecting effect of the deflection system, consequently of the positioning and size thereof, so that the location of this point broadly depends upon the value of the back-.coupling between the collecting electrode and the deflection system.

In the foregoing the fact has not been taken into account that a voltage for directing the beam to the point 9 of the electrode 6 is supplied to the vertical deflection plates, it is true, but that no subsequent vertical deflecting voltage occurs. Owing to this the beam tends to return in a vertical direction to the level of point 3 so that, if the electrode E should have the required size also in a vertical direction, the beam would eventually not be directed to point I I but to point I2 which, consequently, is vertically located at the same level as point 3 and exhibits horizontally the same deviation as point I I. Consequently, the beam will move over the electrode 6, viewed from point 9, in the direction of the arrow I3 to the point I2 which will be called the direction point. Naturally this direction point I2 is only reached if the electrode 6 has a sufcient size.

With each collecting electrode a given arrangement of the deflection means, a constant current strength of the beam and lixed resistance 8 corre sponds to a single direction point. On hitting a collecting electrode the beam will consequently be deflected as long as the point of impact does not coincide with the direction point. In this connection it is pontedout that for deecting the beam use may also be made of collecting electrodes constructed as a resistance electrode, but in this case the current strength in the resistance 8 will be dierent with every new position of the point 3 of impact of the beam on this electrode with the result that in every instance a different direction point corresponds thereto.

Furthermore it is not necessary to use the coupling, shown in Figure 1, between the collecting electrode and the deflection means. For instance, deflection coils may also be used which are inserted in the output circuit of the collecting electrode. Alternatively the deflection coil may be included in the output circuit of a discharge tube, this current being controlled by a voltage which is set up in the input circuit of thetube and depends upon the current strength inV the circuit connected to the collecting electrode.

In the circuit-arrangement shown in Figure 2 a cathode-ray tube (not represented) comprises shape. HIn the present case the expression re--` sistance electrode is to be understood to mean an electrode of which the specific resistance exceeds' that of the metals usually employedV as electrode material. The ring may, for instance, consist of insulating material to which a layer of graphite is applied or which may entirely be made of graphite. This ring is fed from a positive supply through equal resistances l, i5 and i6 located at three equidistant points or, if the cathode of the cathode-ray tube has a negative potential, is earthed through the intermediary of the said resistance. Furthermore three deflection plates Il, I8 and I9 are provided, the positioning of these plates being dis-` placed by 120 with respect to the location where they are connected to the corresponding resistance. When the beam hits the resistance electrode 5I, for instance at 20, which may be ensured by means of a suitable deflection voltage, a voltage variation occurs over each resistance. O'wing to the fact, however, that the electrode has not a negligible but an appreciable resistance, the said Voltage variation depends upon the spacing, measured along the electrode, between point 20 and the junction points of the resistances. Duev to this the voltage drop across the resistance I4 has-the highest value and that across the resistance l5 the lowest value. In this case the potential of the deection plate I1 is lowest and that of plate I8 highest so that the beam experiences a deflection force by which the end of the beam is displaced over the electrode in the direction of the arrow 2|, in other words each point of impact is associated with a direction point which is located before the point of impact and in the direction of the tangent of the circle to be described. If this should not be quite true, for instance at the onset of the movement at 20, so that the direction point associated with the point of impact 2E) is not located on the line tangent to the circle and passing through point 20, the beam itself will choose a path having' a slightly different radius so as to satisfy this requirement, and if the deviation is too large correct adjustment is ensured by varying the phase-shift angle of the positioning of the deection plates with respect to their junction points.

Figure 3 represents another form of construction of the circuit-arrangement according to the invention. 1

4 In this construction the cathode-ray tube comprises a number of collecting electrodes 22 which v,are located in such manner that, Viewed in the direction of the beam, they follow a circle, the spacing between two successive electrodes being smaller than the diameter of the cathode-ray beam. Each electrode is connected to the junction point of two resistances 23 of which the number equals that of the electrodes and which are included in a ring connection which is fed, through resistances 2li at four points. The Voltages for the deflection plates 25 in the tube are taken 01T at four symmetrically located points, the position of each deflection plate being displaced by more than with respect to the point from which the voltage for this plate is taken. If, for instance, the pair of plates 25a is exactly at an angle of 90 with respect to points 2S and 26a, the direction point, on the beam hitting e. g. the electrode 22a, is located on a broken line, extending at right angles to the connecting line 2t, 25a, so that the point of impact tends to shift in the direction of the arrow 27, the direction of which does not correspond with the line tangent to the circular path to be traversed. Fundamentally this can be improved upon by providing that the direction point on the broken line is very distant which consequently means a very high deflection Voltage. On turning, however, the pair of plates 2521 to the represented position, the direction point lies on the broken line '28 and in this case the location of the direction point may be such that it lies exactly in the direction of the line tangent to the circular path.

In this case, however, the difficulty is experienced that the direction point extends in the direction of the tangent, it is true, but this direction may vary under the influence of the factors referred to, for instance the current strength of the beam. Therefore, it is advisable to choose the direction point of each electrode in a manner such that it tends to urge the beam outwards or inwards under normal operating conditions. In the drawing the direction of these direction points is indicated by a broken arrow in several electrodes, which directions are consequently not tangent to the circle formed by the electrodes 22 but point outwardly. These directions result from rotation of the deflection system.

Y' In this case a number of further electrodes 29 should be provided, of which the direction point extends in such manner that the beam, on hitting these electrodes, is urged back to the electrodes 22. This may be effected in a simple manner by connecting such an electrode 29 to an electrode 22 which has the desired direction of thedirection point, for instance the electrode 22h. In this case the beam will pass over the outer edge of the system 22. In the case of possible small variations of the working conditions the movement of the beam will not be affected.

Furthermore it will be appreciated that the direction points of the electrodes 22 may also be such that the beam will describe a smaller circle, in which case other electrodes S0 are provided at the inner side, which cause the beam to pass over the inner wall of the system 22.

The electrodes 29 may, for instance, be partly provided behind the electrodes 22 and at the interstice between two electrodes 22 they may be provided with recesses 29a for purposes which will be explained hereinafter.

It is pointed out that in this kind of circuitarrangements it is not necessary for the end of the beam to describe a circular path, since any other closed curve may be followed, provided that the deflection means are suitably positioned and aiesesg.

thecoupling of the electrodes the deflection means is accommodated to the electrode arrangement in such manner that` the deection means are steadily influenced in the desired manner.

Furthermore the electrodes in a circuit-arrangement as shown in Figure 3 need not be arranged in a manner such that, viewed from the cathode, they are interspaced since they may in part also be positioned one behind the other.

Alternatively the electrode arrangement may be such as to form two curves which are closed in themselves and have a common part. If the beam passes over this common part a choice may be made at the end thereof which of the two curves will be followed. n The principle of such a circuitarrangeme'nt will be explained with reference toVV Figure 4.

The electrodes 32, 33, 34, 35 form part of a system in which the vbeam is adapted to follow a closed curve, the same holding for the electrodes 32, 33, 33, 3l. If the end of the beam rests on the electrode 32 the beam moves to the right, according to the arrow, and hits the electrode 33. The direction point associated with this electrode lies on the line 38, 3'9, 40, the point 40 being the point at which the beam is not deected so that it corresponds to the point 3 shown in Figure l. If in the circuit-arrangement shown in Figure 1 the current-strength of the beam is doubled, as result of which the voltage drop across the resistance 3 is doubled, the `final position of the beam, which corresponds with the said increase in deiiection voltage, may, for instance, be Ila. Thus the direction point l2a ensues. This is utilised in the circuit-arrangement shown in Figure 4.

At a given value of the current-strength of the beam the direction point is located at 38 so that the beam travels from the electrode 33 to the electrode 35, and at a different value of the current strength of the beam the direction point 39 ensues so that the beam travels from the electrode 33 to the electrode 36.

Various arrangements are possible for reversing the direction of travel of the beam on hitting a collecting electrode. By means of such arrangements the beam may at the same time be immobilised.

The latter may, for instance, be effected, in a circuit-arrangement as shown in Figure 3 by interrupting the connection between any of the collecting electrodes and the ring connection of resistances and by connecting this electrode to the diametrically opposite point in the ring connection. On hitting this electrode the direction of travel reverses so that the beam adjusts itself to the edge of this electrode and to the edge of the electrode traversed last.

In this respect it is pointed out, however, that if the direction point e. g. of the electrode 22a is located on the line tangent to the circular path i. e. on the broken line 28, a direction point 3l is produced, likewise on the line 28 but at the other side of the centre point, on detaching this electrode from the ring connection and connecting it to the diametrically oppositepoint of the ring connection. In this case it is possible for this new direction not to intersect the adjacent electrode 22 so that immobilisation'does not occur.

If the direction point 3| is located at a sufficient distance, for instance in the case ofl using the outer direction points, the beam does hit the electrode 22C.

Alternatively a number of electrodes 30 may be provided for this purpose, which tend'to urge the beam outwardly, so that inthis case theV electrode 30 located at the electrodes 22a and 22c may be directly connected to the electrode 29.

It is also possible to reverse the direction of j travel if the collecting electrodes are secondaryemission electrodes and at least at one of the collecting electrodes a further electrode is provided to which a suitable voltage is supplied for suppressing the secondary-emission of the associated collecting electrode. Such a circuit-arrangement will be explained with reference to Figures 3, 5 and 6.

If all the collecting electrodes of the circuitarrangement shown in Figure 3 are secondary-- emission electrodes, the VVvoltage variation, upon the beam hitting an electrode, will be opposite to that in the case of non-secondary-emission electrodes so that the direction of travel is exactly opposite to the direction of the arrow. At one or more of the electrodes 22 shown in Figure 3, for instance at the electrode 4l shown in Figure 5, there is provided Aa grid-shaped electrode 42 and this more particularly between the incident direction of the cathode-ray beam 43 and the electrode 4l.

If the beam hits the electrode 4I while the electrode 42 has a slightly higher potential than 4|, secondary emission occurs and the direction of travel remains unchanged. If, however, the grid receives a potential which is sufficiently negative with respect to the potential of the electrode 4l, the secondary emission is suppressed and the direction of travel is reversed so that the beam is immobilised as depicted in Figure 6, when the beam 43 hits partly the electrode 44 and partly the electrode 45.

If all electrodes are provided with an associated electrode the direction of travel of the beam can be reversed Icompletely.

The circuit-arrangement shown in Figure 5 may, for instance, be used as a call-iinder in automatic telephony systems. The beam steadily rotates over the electrodes until a subscriber takes the receiver from his apparatus and thus causes the voltage of an electrode 42 to drop so that the beam is immobilized in a denite position, That part of the beam passing between the electrodes 44 and 45 in Figure 6, may now be used as a telephony channel if this beam portion falls on a suitably positioned collecting electrode.

If the beam is adjusted to the edge of the electrode system, which is possible e. g. in the circuitarrangement shown in Figure 3, it is advantageous to provide the electrode 29 with recesses 29a so that the passing part of the beam is not or substantially not intercepted.

Finally Figure '7 represents diagrammatically another circuit-arrangement, in which reversal of the direction of travel and consequent immobilisation of the beam is likewise ensured. In this case also a number of electrodes are arranged and connected to the deflection means in such manner that the beam travels from one electrode to the other.

If not deflected the beam may for instance, reach the point lll, the direction point associated with the electrode 46 lying on the line 49, 48, 41.

In accordance with the` current strength of the beam this direction point may now, for instance, occupy the position 48 or 49.

When the beam travels from the electrode 50 to the electrode 4t and the current strength is such that the direction point islocated at 48, the beam passes on to the electrode 5l. If, however,- the direction point is located at 49, the

7 direction of travel is reversed and the beam adjusts itself to the edges of the electrodes 50 and 46.

What I claim is:

1. A cathode-ray deection circuit arrangement comprising a source of cathode-rays having a given free path, a target system displaced from the said free path and charged with respect to the said source of cathode rays, a plurality of deflection elements having given elds about the said cathode-rays, and resistive means to couple the said deflection elements to articulate points on the said target system, said latter resistive means having values at which the said attraction of the target system has an angular coplanar relationship to the said fields of the deflection devices.

2. A cathode-ray deection circuit arrangement comprising a source of cathode-rays having a given free path and diameter, a target system having a plurality of circumferentially arranged collecting electrodes spaced a distance less than the diameter of the said cathode-rays and vectorially displaced from the free path of said cathode-rays, a plurality of resistance elements connected individually between the said successive collecting electrodes to form a resistance mesh, an accelerating voltage supplied to the said target system through the said resistance mesh, a plurality of deflection elements having given fields, and means to join said deection elements severally to an equal number of symmetrically located points on the said resistance mesh, said resistance elements having values at which the vectorial displacement of the free path of the cathode-rays and the target system has an angular, coplanar relationship to the fields of the said deflection elements.

3. A cathode-ray deflection circuit arrangement comprising a source of cathode-rays having a given free path and diameter, a rst target system having a plurality of circumferentially arranged collecting electrodes spaced a distance less than the diameter of the said cathode-rays and vectorially displaced from the free path of said cathode-rays, a plurality of resistance elements connected individually between successive collecting electrodes of the said rst target system to form a resistance mesh, an accelerating voltage supplied to the said rst target system through the said resistance mesh, a plurality of deflection elements having given elds, means to join said deection elements severally to an equal number of symmetrically located points on the said resistance mesh, said resistance elements having values at which the vectorial displacement of the free path of the cathode-rays and the target system has an angular, coplanar relationship to the fields cf the said deflection elements, an auxiliary target system having a plurality of collecting electrodes circumferentially adjacent to the collecting electrodes of the said first target system and means to couple electrically the said collecting electrodes of the said auxiliary target system to given points on the rst target system at which the said cathode-rays will travel along the edge of the collecting electrodes of the said first target system.

4. A cathode-ray deflection circuit arrangement comprising a source of cathode-rays having a given free path and diameter, a target system having a plurality oi collecting electrodes arranged to form a closed curve, said collecting electrodes spaced a distance less than the diameter of the said cathode-rays and vectorially displaced from theree path f said cathode-rays, a plurality of resistance elements connected individually between successive collecting electrodes of the said target system to form a resistance mesh, an accelerating voltage supplied to the said target system through the saidresistance mesh, a plurality of deection elements having given fields, and means to join said deection elements severally to an equal number of symmetrically located points on the said resistance mesh, said resistance elements having values at which the vectorial displacement of the free path of the cathode-rays and the target system has an angular, coplanar relationship to the fields of the said deection elements.

5. A cathode-ray deflection circuit arrangement comprising a. source of cathode-rays having a given free path and diameter, a target system having a plurality of circumferentially arranged collecting electrodes spaced a distance less than the diameter of the said cathode-rays and vectorially displaced from the free path of said cathode-rays, a plurality of resistance elements connected individually between successive collecting electrodes of the said target system to form a resistance mesh, an accelerating voltage supplied to the said target system from the said resistance mesh, a plurality of deilection, elements having given fields, means to join said deflection elements severally to an equal number of symmetrically located points on the said resistance mesh, said resistance elements having values at which the vectorial displacement of the free path of the cathode-rays and the target system has an angular, coplanar relationship to the fields of the said deflection elements, and means to couple one oi the collecting electrodes of the target system to a diametrically opposite point on the said resistance mesh.

6. A cathode-ray deilection circuit arrangement comprising a source of cathode-rays having a given free path and diameter, a target system having a plurality of collecting electrodes arranged to provide at least two closed curves, said collecting electrodes spaced a distance less than the diameter of the said cathode-rays, vectorially displaced from the free path of said cathode-rays and having at least one electrode common to each closed curve, a plurality of resistance elements connected individually between the said successive collecting electrodes, to form a resistance mesh, an accelerating voltage supplied to the said target system from the said resistance mesh, a plurality of deection elements having given fields, means to join said deflection elements severally to an equal number of symmetrically l0- cated points on the said resistance mesh, said resistance elements having values at which the vectorial displacement of the free path of the cathode-rays and the'target system has an angular coplanar relationship to the fields of the said deilection elements, and means to energize at least one of the said deflection elements to divert the said cathode-rays to each of the closed curves of the said target system selectively.

7. A cathode-ray deilection circuit arrangement comprising a source of cathode-rays having a given free path and diameter, a target system having a plurality of circumferentially arranged collecting electrodes spaced a distance less than the diameter of the said cathode-rays and vectorially displaced from the free path of said cathode-rays, at least one of the collecting electrodes of the said target system having an auxiliary electrode. means to provide a voltage to the said auxiliary electrode to control the secondary emissivlty of the said one collecting electrode, a plurality of resistance elements connected individually between successive collecting electrodes of the said target system to forni a resistance mesh, an accelerating voltage supplied to the said target system from the said resistance mesh, a plurality of deflection elements having given ields, and means to join said deflection elements sever-- ally to an equal number of symmetrically located points on the said resistance mesh, said resistance elements having values at which the vectorial displacement ef the free path of the cathode-rays and the target system has an angular, coplanar relationship to the elds of the said deection elements.

8. A cathode-ray tube comprising a source of cathode-rays, a collecting electrode circumferentially arranged and vectorially displaced from the free path of the said cathode-rays, said collecting electrode having a given resistive gradient upon traverse, a plurality of equally spaced taps upon the said collecting electrode, means to supply the said tap points with a source of accelerating potential, a number of defiecting elements equal to the number of said collecting electrode taps having given elds, and means to couple the said collecting electrode taps to the said deecting elements, the said deecting elements having an orientation with respect to the said collecting electrode taps at which the vectorial displacement of the free path of the cathode-rays and the collecting electrode has an angular, coplanar instantaneous relationship to the fields of the deecting elements.

ADRIANUS JOHANNES WILHELMUS MARIE VAN OVERBEEK.

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

UNITED STATES PATENTS Number Name Date 2,185,135 Schlesinger Dec. 26, 1939 2,290,651 Peck July 21, 1942 2,374,666 Cunii May 1, 1945 2,390,256 Hansell Dec. 4, 1945 2,417,450 Sears Mar. 18, 1947

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