US2083204A

US2083204A - Braun tube

Info

Publication number: US2083204A
Application number: US694915A
Authority: US
Inventors: Schlesinger Kurt
Original assignee: Individual
Current assignee: Individual
Priority date: 1932-10-25
Filing date: 1933-10-23
Publication date: 1937-06-08
Anticipated expiration: 1954-06-08
Also published as: FR44618E; GB432209A; GB438882A; DE715380C; FR763894A; US2188580A; NL44767C

Description

June 8, 1937- K. SCHLESINGER 2,083,204

BRAUN TUBE Filed Oct. 25, 193:5 4 Sheets-Sheet 1 S27 Egl- L '5 70 9 a z 4 Jm enfor:

June 8, 1937. K, $cHLE5|NGER 2,083,204

BRAUN TUBE Filed 001;. 23, 4933 4 Sheets-Sheet 2 June 8, 1937. K. SCHLESINGER BRAUN TUBE Filed 001;. 23, 1933 4 Sheets-Sheet 3 Jnyenfon- June 8, 1937. K. SCHLESINGER 2,083,204

BRAUN TUBE Filed Oct. 25, 19s; 4 sheets-sheet 4 Unven/or.

M le/W Patented June 8, 1937 UNITED STATES PATENT OFFICE Application October 28, 1933, Serial No. 694,915 In Germany October 25, 1932 10 Claims. (Cl. 250-275) The Braun tube hitherto known reveals the following defects:

(1) The so-called cross-current error, which causes a variation in theimage point position dependent on the intensity of the image point, and is caused by stray electrons flowing to the control plates,

(2) The so-called error in shape, which makes itself noticeable by distortion in the form of the image (for example a trapezoidal form of the image), and is caused by interaction of the marginal fields of the pairs of control plates,

(3) The so-called "ion cross" error, which consists in the fact that the image possesses a light ll cross, and

(4) The lateral attraction error, which is caused by the fact that owing to the complicated structure of the system it is extremely difflcult to centre correctly theemissive surface of the no cathode.

The object of the invention is a Braun tube, which avoids all of the errors referred to, and possesses an extremely simple structure of the system permitting of the proper centering of all 25 parts without the use of special means.

According to the invention, there is employedin place of the two-part deflecting system hitherto known-a three-plate deflecting system, the innermost plate of which is linked up with a 30 positive potential, which is higher than the maximum positive deflection potential occurring, and possesses a slot of suitable size preferably at the center. By means of. this third plate the space between the earthed deflecting plate (earth plate) 35 and the plate connected with the deflecting generator (control plate) is divided into. two parts. In accordance with the invention, the plates are constructed and arranged in such fashion that the electric field of the middle plate 40 is perfectly symmetrical on both sides of the same. The ray proceeding from the anode passes parallel to the earth plate into the space between earth plate and middle plate, is attracted by the high positive bias of the middle 4 plate towards the latter and through the slot and,--owing to the symmetrical nature of the fields-leaves the space between the middle plate and the control plate, in the position of rest, in a direction which is parallel to its direction of 50 entry and is displaced to the extent of a few millimetres in relation thereto.

The second deflecting system, according to the invention, is also constructed as a three-part system, whereby the ray is also bent oil in the space between the earth plate and the middle plate, and deflected, i. e., directed into the space between the middle plate and the control plate. In order to increase the sensitivity of the second system, the plates of this system may possess a trapezoidal basic form, and the edge of the earth plate directed towards the first deflecting system, the edges of the middle and control plates directed away from the first deflecting system and also the slot in the middle plate may conveniently be rounded oil. 1

Since the middle plate, in accordance with the invention, is provided with a positive bias, which is higher than the maximum positive deflecting potential occurring, all stray electrons are attracted towards the middle plate. The control plate accordingly remains perfectly free of crosscurrent, so that the cross-current fault is unable to take place. The "ion cross defect is moved outside of the field of the image by the bending of the ray. Below the plane of entry of the ray the field of the control plate may be screened off without difllculty against the first system by means of a screening plate, which is secured for example to the middle plate. In this manner it is possible to avoid reaction of the marginal fields, and accordingly to obtain images, which are perfectly free of the error in form. Owing to this a disturbing effect on the bent ray by the system alien to the bending direction is entirely avoided. A particular advantage of the arrangement according to the invention is to be seen in the fact that the bending of the ray, necessary for the purpose of avoiding the ion-cross", may be performed separately in the vertical and the horizontal direction.

Since the ray in the arrangement according to the invention possesses merely an extremely small parallax (approximately 4 mm. or less), the system is wholly straight-sighted, so that an extremely simple structure is ensured, which 4 permits of proper centering with the most simple means. Since reaction of the marginal fields is eliminated owing, in accordance with the invention, to the screening oil? of the control plate of the second system, it is possible to dispose the control plate systems extremely close together one behind the other (for example 5 mm. or less). In this manner a very compact system structure is rendered possible.

The sensitivity of the deflecting system according to the invention, which is already very considerable, may be increased toan appreciable extent by disposing the plates, not parallel, but obliquely to each other.

Further, it is possible and forms a further object of this invention to construct the deflecting system itself as light control means. For this purpose it is merely necessary to raise to a slight extent the front edge of the slot in the middle plate of the first system. If the intensity control potential is applied in series with the positive bias to the middle plate-constructed in the manner described-of the first deflecting system, a faultlessly operating shuttering control device is obtained which, dependent on the extent of the light potential, shutters oiI larger or smaller parts of the cathode ray entering the first control plate system. It is naturally also possible to employ a system of this nature as independent light control means.

The high positive bias applied to the middle plate. is conducted in the manner known per se to an auxiliary electrode, which is arranged preferably in front of the deflecting system and then takes up the electronic return current entirely.

Still further objects of the invention will be seen from the following description.

The invention will be more fully understood from the drawings, which show by way of example some forms of embodiment of the tube according to the invention, and also a few circuit diagrams for operating the same.

Fig. 1 shows a Braun tube having two threepart deflecting systems, whilst Figs. 2 and 3 show two particular forms of embodiment of a three-part deflecting system according to the invention, and

Figs. 4 and 5 are two circuit arrangements for operating the tube according to Fig. 1.

Figs. 6 and 7 show diagrammatically two forms of embodiment of the deflecting system according to the invention, constructed simultaneously as light control means. I

Fig. 8 shows a Braun tube furnished with three-part deflecting systems, the middle plate of which is bent to angles.

Fig. 9 shows a Braun tube furnished with threepart deflecting systems, the side parts of which are shortened.

Fig. 10 shows a connection-diagram for the Braun tube shown in Fig. 9.

Fig. 11 shows a view of a Braun tube according to the invention.

Fig. 12 shows a Braun tube with a control element according to the invention in which the systems producing the parallel displacement are constructed as three-plate systems with flatmiddle plate, whilst in Fig. 13 the three-plate system possesses a middie plate which is bent to angles.

In Fig. 1, l is the wall of the Braun tube, 3 the cathode, 2 thmehnelt cylinder, 4 a preliminary anode, 5 an after-concentration cylinder, and 6 the after-acceleration anode. l5 and I 6 are the two three-part deflecting plate systems according to the invention, which consist of the earth plates 8 or I l, the middle plates 9 or ill furnished with the slots l4 or 20, and the control plates ill or 19. The earth plates 8 and I1 are'connected with the preferably earthed anode line I, the middle plates 9 and I8 with the line l2, which is maintained at a suitable positive potential in relation to the anode, whilst to the control plates I 0 or I 9 there are conducted the 7 deflecting potentials indicated in symbolical fashion by the generators l3 and 22. At the same time the preferably annular electrode 23, which intercepts the return current electrons is connected with the line l2. 7 The middle plate It of the second system may be provided with a screening plate 2|, which screens off against the first system. The plate l9 supplied with the deflecting potential of the second system and also the space between the middle plate I8 and the control plate is.

In the case of a tube of 300 mm. in length and mm. diameterof the image screen, operated with an anode potential of approximately 3,000 volts, the deflecting systems may be dimensioned as follows:

1st system: Length of plates 34 mm., width of plates 10 mm., spacing between plates 4 mm., length of slot in the middle plate 4-6 mm., width of the slot greater than 4 mm., preferably approximately 8 mm.

2nd system: Form of plate: rounded trapeze, longest edge of trapeze approximately 25 mm., shortest edge of trapeze approximately 10 mm., height of trapeze approximately 10 mm.

3. System spacing: 2-5 mm. or more.

4. Potential of the middle plate: approximately +200 volts in relation to anode.

The dimensions and potentials may be varied within relatively wide limits.

The ray emerging from the anode 6 passes parallel to the earth plate 8 into the first system l5 between the earth plate and the middle plate, and is drawn by the positive bias of the middle plate towards the same and through the slot M.

Since the plate 9 is constructed and arranged in such fashion that the field is disposed symmetrically on both sides, the ray passing out of the slot l4 into the space between the middle plate and control plate is bent, in the position of rest, to such extent towards the plate 9, that it leaves the space between the plates parallel to its original direction and with a displacement in relation thereto amounting to only a few (approximately 3-4) millimetres. The second deflecting system l6 operates on substantially the same lines. In order to avoid a difference in sensitivity of the plates in different positions of the ray, it is desirable to round off the edges of the plates and also the slot 20 of this second system. The center point of the bounding arc may be situated conveniently approximately at the center of the space between the middle plate and the control plate of the first system.

In Figs. 2 and 3 two additional forms of embodiment of the plate system according to the invention are illustrated, in which the earth plate 8, the middle plate 9 and the control plate l0 are disposed at an angle to each other. With this arrangement the sensitivity of the system may be increased in many cases to a considerable extent.

Fig. 4 shows a circuit for the tube according to the invention, which is particularly adapted for oscillographic purposes. In the same, 24 and 25 are the terminals of a direct current source, say, a rectifier, 26 a condenser, 21 an ohmic high resistance potentiometer 28 an additional condenser. The anode potential is derived from the preferably earthed potentiometer tapping over the line I, and the positive bias from the line l2. The remaining references agree with those in Fig. 1. Naturally it is also possible to employ this circuit for television purposes if the dimensioning is suitably chosen.

An arrangement particularly suitable for television purposes is illustrated by way of example in Fig. 5. In the same 36 is a transformer having the primary winding 39, which may for instance be fed from the mains, and the two

secondary windings

31 and 38, which co-operate with the two rectiflers 34 and 30, the one of which (it) supplies a powerful current at low tension (approximately 100 mllliamperes at 200 volts). and the other of which (85) supplies a high potential with a low current (approximately 3000 volts with .l milliampere). There accordingly results a potential of -3000 volts in 40, zero in" and +200 volts in 40. The anode of the Braun tube is connected with 41, and the positive bias required according to the invention is taken from the potentiometer 3| through the medium of the steadying

members

29 and 30. The condenser 20 may be selected at 1 mf.,

and the total resistance in the line I2 at approximately 100,000 ohms or less.- An essential feature of both circuits is the stiff coupling of the positive bias of the middle plates (ray bending potential) with the anode potential. This coupling ensures reliable operation of the apparatus even upon the occurrence of fluctuations in the anode potential.

In accordance with the invention, the deflecting system at the same time may also be employed as intensity control means. For this purpose the front edge of the slot ll of the middle plate 9 may be bent upward. There is applied to the plate 9 the positive bias in series with the light control potential. The bias may preferably be so selected that with the light control potential being zero the ray just completely passes over the edge of the bent upward portion. Upon the occurrence of the positive light control potential the potential of the middle plate is shifted into positive, the ray drawn closer to the plate, and accordingly a larger or smaller portion oi the ray cut (shuttered) of! at the edge.

Fig. 6 shows a form of embodiment of this kind of an arrangement according to the invention. In the same 8 is the earthed plate, 9 the m ddle plate with the slot i4, and iii the control plate connected with the deflecting potential 63. The plate is furnished with a sharp edge 40, which bounds the part of the slot l4 situated next to the cathode. The positive bias is conducted to i the plate 9 from the battery 43 over the resistance M, whilst the plate receives the light control potential from the generator ii.

In Fig. '7 a particularly sensitive form of emhodiment oi the arrangement is illustrated. In

ithis arrangement, in which the corresponding parts have been given reference characters agreeing with Fig. 6, the system plates have a special dimensioning, the control plate being considerably shorter than the earthed plate. In order to obtain the necessary symmetry of effect it is merely necessary so to select the length and the spacing of the plates that the ratio between the length of the plate (taken from the edge of the plate up to the center of the slot) and the spacing of the plates remains constant. Itmay be desirable to give the rear part of the middle plate-which is hot employed for control purposes-the form illustrated in Fig. 7.

By reducing the size of the control plate and v by accordingly reducing the spacing between the control plate and the middle plate, according to the invention a reduction to a minimum of the parallel displacement of the cathode ray is suc- In the described three-plate arrangement, it has been found that the slot in the middle plate requires to be made relatively wide, in order that the ray does not impinge against any of the plates but is deflected right through the slot.

As shown in Fig. 8, the cathode ray proceeding from the anode 0 is deflected in the space between and 0 only in a direction about the constant angle a, whilst in the space between 2 and 3 the ray has to perform the symmetrical oscillation as shown about the angle In, in order to sweep over the entire image screen.

The applicant has found that it is advisable in all cases in which a deflecting system exerts on the cathode ray a chronologically constant and one-sided deflecting eifect to cause the ray to enter the deflecting system in the closest possible proximity to that particular plate from off which the same is deflected.

Since the sensitiveness of the plates (i. e., the deflection of the ray in millimetres displacement on the screen per volt of deflecting potential) isin inverse proportion to the spacing of the plates, a very considerable increase of the sensitiveness of a particular system, for example to twice the amount, is so obtained. The measure according to the invention is of particular importance in connection with those tubes, in which the bending system (i. e., that system which imparts to the my the necessary constant preliminary deflection for avoiding the ion cross and cross-current errors) is specially separated from the deflecting system proper. In this case the spacial angle of deflection which the bending system is required to impart to the ray is equal to sa ll: when a is the maximum angle to' which each of the deflecting systems is required to deflect the ray each in one plane. If in this case it is desired to perform operations with the same auxiliary potential at the bending system and at the two deflecting systems, and on the other hand not to exceed the deflecting potential given by the equation D Q ir) (e the minimum potential necessary for complete deflection; Ea anode potential; D diameter of the bottomof the bulb; L length of path of ray from the middle of plate system in question to the luminous screen), it is necessary to cause the ray to enter the bending system in the manner according to the invention, 1. e., nearly touching the one plate.

The application of this principle, which forms a further feature of this invention, to the described three-part deflecting system results in the particular form of embodiment shown in Fig. 8, in which the middle plate is bent to angles.

Accordingly the field producers l /6 and/or 2/3, (2 and 6 both representing parts of the bent middle plate) are displaced parallel to themselves in the field directions indicated by the arrows. By a parallel displacement of this nature no variation takes place in the actual path of the ray, if the distances between i and 6, on the one hand, 2 and 3 on the other hand, are not varied and remain the same. In this manner, however, it is ensured that impinging against the deflecting plate 6-2 is not able to occur, even if the slot 8 is small.

In the above considered case of a tube 300 mm. in length and 180 mm. diameter of the image screen, operated with an anode potential of approximately 2000-3000 volts, the systems of the last described type may be dimensioned-as follows:

Length of plates: approximately 34 mm.,

Total width of system: approximately 6 mm.,

Smallest spacing between the plates: approximately 2 mm.,

Effective length of field (length of he parts 2 or 0 each approximately 14-16 mm.

In the former described embodiment having a flat middle plate the system in practice would require to receive a greater total length of approximately 5 mm. as the slot aperture in the middle plate is traversed by the ray at a grazing angle, and therefore requires to be made so large that the same will still allow the passage of a greatly increased section of the ray. In a tube operating with a thickness of ray amounting to 1 mm. the conditions set forth result in a width of slot of approximately 8 mm. In the arrangement according to the invention the width of the slot is reduced to approximately 4 mm., and nevertheless still permits of reliable operation with reduced dimensions throughout.

It has been found that the three-plate systems according to the invention are extremely sensitive even to the smallest magnetic disturbances, and that in consequence it is practically impossible to produce the same from material which is not completely non-magnetic. Thus, for example, nickel, which has been employed without difliculty in the tubes heretofore known, is apt to have such a strong magnetization, particularly at the welding points, that the effect of the arrangement, and more particularly the possibility of large-scale production, is very questionable. According, therefore, to the invention, these parts of the system, i. e., the deflecting systems themselves, and preferably also the holding means pertaining thereto, are produced from completely non-magnetic material.

It has been found to be particularly convenient to employ for this purpose phosphor-bronze preliminarily heated up to red heat and, if this is found desirable, pickled (approximately 80 parts of copper, 20 parts tin and a few thousandths of phosphorus) the supporting members in the tube preferably being made of spring-hard phosphorbronze and the leads of phosphor-bronze wire, whilst the deflecting systems themselves are preferably composed of plates planed by means of stippling dies. The planing by means of stippling dies results in perfectly flat plates, which otherwise would hardly be capable of being produced in practice from phosphor-bronze. Contrary to expectations the necessary dotting has been found to be wholly without objection from an electrical aspect.

In Fig. 8 a form of embodiment of the deflecting system according to the described feature of the invention is illustrated by way of example. In Fig. 8, 5 is the preferably earthed anode, I the earthed plate, I the bent middle plate having the

end portions

6 and 2 of equal length and the slot 8 and provided with a suitable positive bias in relation to the anode, and 3 the control plate connected to the deflecting potential generator 4.

The described arrangements may still show the following faults:

1. A certain diffusion of the ray may occur within the deflecting systems, which diffusion renders the use of large ray currents more dimcult.

2. There may sometimes occur a slight diswall charges.

placement of the image point dependent on its intensity whiclris not caused by the light control.

The applicant has found that the fault referred to under 1 (diffusion effect within the deflecting systems) is caused by a field effect exerted by the outer plates at the level of the transverse slot in the middle plate. According, therefore, to a further feature the invention, the outer plates are constructed in such fashion that the formation of this field of disturbance is avoided. For this purpose it is sufficient to make the outer plates so short that they extend exactly up to the projection of the transverse slot, or do not completely cover the same.

Further it has been found that the fault referred to under 2 (displacement of the image point) is caused by the disturbing influence of According, therefore, to still a further feature of the invention, there is provided preferably on the inner wall of the bulb a metallization, which is raised to a. suitable potential.

According to the invention, this metallization is formed in such fashion that the rear part of the neck of the bulb proceeding approximately from the high potential anode remains free from the metallic coating, and that the coating extends only to such a length into the proper bulb that a considerable distance is maintained between the coating and the ray even in the case of maximum deflection of the ray.

In this manner, it is accomplished that on the one hand insulating difliculties (neck of the bulb) do not result, and that on the other hand the coating is unable to exert any influence on the deflection of the ray. If the coating in the manner known per se were formed in such fashion that the same completely covered the wall of the bulb and extended as far as to the bottom of the bulb, disturbing influences would be exerted on the deflection of the ray, which influences in the case of square pictures would make themselves apparent in a rounding of the corners.

It is known per se to provide metallic wall coatings in Braun tubes, and to raise these to the highest potential occurring in the tube.

The applicant has found that the coating exerts a deconcentrating effect if it is connected in this known manner with the highest potential which occurs in the tube, i. e., the potential of the middle plate of the deflecting system.

This deconcentrating effect may be wholly avoided if the coating is made negative as compared with the ray. An excessive negative potential however causes the intensity of the ray to be considerably diminished.

According, therefore, to the invention, the coating formed as set forth above is connected with a potential, which is weakly negative in relation to the ray, for example with the after-acceleration anode of the system. In this manner a deconcentrating effect and at the same time a diminished intensity are avoided. It is, however, also possible to impart a negative potential to the wall coating, as a slight reduction in the intensity is not critical in itself in the case of strong ray currents.

A form of embodiment of the described arrangement according to the invention is shown by way of example in the Figs. 9-11.

In these figures, I is the bulb of the Braun tube, having the cathode 3 and the space charge control cylinder 2 surrounding the cathode, 4 a first anode, 5 an after-concentration cylinder, which preferably possesses a weakly negative potential as compared with the first anode or the same potential as said anode, and 6 the high-voltage anode (I and 6 form the so-called after-arranged electron-optical system). 9 and i8 are the two three-plate deflecting systems, consisting of the outer plates 8 and H), or I1 and i9, and the bent middle plates 9 and It provided with a transverse .slot and raised to a positive potential as compared with the outer plates. The

plates

8 and 10 I1 being connected to the high-voltage anode, the potential of the bent middle plate is some higher than that of the high-voltage (f. i. 2000 volts) anode.

As illustrated in the drawings, the outer plates 8 and It), or II and I9 may, in accordance with the invention, be made so short that they reach exactly as far as the projection of the transverse slot. For structural reasons, however, it is particularly convenient, in accordance with the invention, to make the outer plates equally as long as the middle plates. In this case, according to the invention, the outer plates are also furnished with transverse slots, the projection of which approximately corresponds with the transverse slot of the middle plate, and if necessary is somewhat larger than this. In this manner it is possible 'to completely avoid the disturbing fields without any structural inconvenience. The

middle plates

9 and 16 are shown in the drawings as flat plates. Preferably, however, the same may be bent to angles. 20 is a screen, which screens of the space between the plates l6 and i9 against the field effect of the system 9. In the same manner, the space between the plates l0 and I5 may be screened ofl against the action of the system i8. 23 is an annular electrode, which is conductively connected with the middle plates and serves the purpose of intercepting the electronic return current. [3 and 22 indicate symbolically the defleeting potential generators.

29 is the metallic coating according to the invention, which is conductively connected with the primary anode, and in consequence possesses a weakly negative potential in relation to the ray 5 emerging from the second deflecting system. Ac-

cording to the invention, the supply of potential to this metallic coating preferably takes place by means of current-feeding brushes, which are secured to the system and rest firmly against the 5 coating. It is convenient, according to the invention," to employ two or more feed brushes.

In Fig. 10 there is shown a connection system, which enables the middle plates of the systems to be imparted a positive potential as compared with 55 the primary anode, without necessity for employing a. special potential source. In the drawings 21 is a potentiometer, 26 and 28 are condensers, and 24 and 25 the terminals of the anode current source.

60 In Fig. 11 there is indicated the preferable position of the metallic coating employed according to the invention.

Particularly important features of this embodiment of the invention are:

65 1. The construction of the outer deflecting plates in such fashion (shortening of the plates or the use of slotted .plates) that disturbing fields, which may increase the diffusion of the ray within the system, are avoided.

70 2. The use of a metallic bulb coating. which eliminates the disturbing effect of wall charges and a. Extends into the bulb only so far that the distance between the coating and the ray is still (5 V sufllciently large even in the caseof maximum the lightdeflection to avoid disturbing influence oi the coating potential on the deflection of the ray, and

b. Is weakly negative as compared with the ray, for example-in the case of three-plate systems, the middle plate of which is linked up with a positive potential as compared with the main anode-is connected with the main anode.

As set forth above, the described three-plate systems may be employed for light-control purposes. Some devices designed for this purpose have been described above in connection with Figures 6 and '7. There will now be described modified forms of light controlling devices making use of three plate systems according to the invention.

The principle of these modified control arrangements according to the invention consists in that a part of the ray disposed between cathode and the scanning plates is displaced parallel to itself by means of a three-plate system and is controlled as regards its intensity, preferably by means of shuttering devices, at a point of the ray which is displaced parallel to the normal path of the ray (herein normal path means that particular path along which the ray would travel if no special means were provided), and is then re-deflected into the normal path by means of a further three-plate system constructed accord ing to the invention.

In accordance with a further feature of the invention, the shuttering device may be disposed within a special concentration field (for example, a cylinder having a negative potential in relation to the ray). When employing suitable cathodes, such as hollow reflector shaped cathodes, in which the emissive substance is provided on the surface of an indirectly heated member, being symmetrical with respect to its axis and having a hollow mirror shape, it has been found that the use of the usual so-called Wehnelt cylinders surrounding the cathode is not absolutely essential. If a cylinder of this kind is nevertheless employed (for example, for precluding the by-light of the cathode), the same may be maintained on cathode potential.

The total control arrangement-preferably consisting of three elements: the system producing the first parallel displacement, the shuttering device preferably located in a concentration field, and the system (re-deflecting system) producing the second parallel displacement may conveniently be arranged in a single, for example tubular container which, in accordance with the invention, possesses both its ends as well as in the interior screening means, which screen or: the individual parts of the system against each other, and are provided with the smallest possible apertures for allowing the passage of the ray. By assembling according to the invention the light control system to form a single structural element the technical construc tion of the tube is greatly simplified. Beyond this the light control arrangement according to the invention acts simultaneously as screening means, which withholds the direct cathode light from the luminous screen.

In the drawings the Figs. 12 and 13 show two forms of embodiment of a tube furnished with intensity control means of the last described type.

In Fig. 12, l is the Braun tube shown broken away (the anode, deflecting plates and image screen have been omitted for simplicitys sake), 2 the hollow reflector cathode, 3 the tube, for example metallic tube, forming the container for control device according to the invention, 4 and [the three-plate systems, l8 the shuttering device, and H the cylinder which produces the concentration field and possesses a suitable negative potential (for example, 200 5 volts) as compared with the ray, and which is insulated against the tube 8, and may be supported, for example, by a support 89. The three-plate systems 4 and B consist of the two plates 8 and I or 0' and 'l' maintained on ray 10 (for example earth) potential and the middle plate 8 or '8'. These middle plates possess a wide outlet'aperture shown in dotted lines, and are supplied with a suitable positive bias (for example, 150-200 volts) as compared with the ray, which bias may be produced for example by means of the battery 22. The light-control potential 23, which is indicated in symbolical fashion as a generator, is connected in series with the battery 22. It has been found that with suitable construction and dimensioning of the shutter device iii, a potential of approximately 10-20 volts is fully suiiicient for obtaining a complete change over from light to dark. The shutter aperture may conveniently be given the form of an equilateral triangle, which is dimensioned and arranged in such fashion that the ray in the case of light control is able to pass through without touching, whilst upon a displacement to "dark a part of the ray is shuttered off by the two equal sides of the triangular aperture, and

upon attaining complete darkness the ray is situated above the apex of the triangle, so that no electrons are able to pass through; The height of the triangle may conveniently be selected at, say, twice the diameter of the ray. By imparting a suitable form to the shutter aperture it is possible without difficulty to obtain any desired graduation curve.

With consideration to the phase conditionwhich otherwise always requires to be maintained it is particularly convenient to make the shutter aperture axially symmetrical, as the use of a phase reversing tube which is otherwise sometimes nec-v essary for obtaining a positive image may then be avoided. It is understood that a knife-edge as fine as possible, which cuts out a larger or smaller portion of the ray in accordance with the position of the same may conveniently be employed in lieu of an apertured shutter. The 50 shuttered (ineffective) portion of the ray may be distributed by cage-like surfaces, which are dispersed above the knife-edge and are maintained on ray (i. e., positive) potential, whereby the said shuttered portions of the ray may be neutralized whilst avoiding excessive heating of these surfaces. The three-plate systems are screened off against each other and against the remaining parts of the system by means of the screening plates 9, l0, l5 and it, which are provided with 60 the ray passage apertures I2, ll, i3 and i4 and are insulated against the middle plates 8 or 8'.

Marginal field effects are thus completely avoided.

At the same time there is obtained by these screening plates a screening of the direct cathode 65 light.

In' the arrangement shown in Fig. 13 (from which the cathode, the anode arranged between the control system and the deflecting plates, the luminous screen and the tube itself have been omitted) the middle plates 8 or 8' are bent to angles. In this manner it is possible to reduce the width of the system to a considerable extent without decreasing the sensitiveness, and to accomplish that the ray is able to pass through the 5 systems 4 and 5 without in the least touching.

24 and 25 are the after-connected deflecting scanning plates, which conveniently may also be constructed as three-plate systems.

The extent of the requisite middle plate bias is dependent on both the sensitiveness of the three-plate system as well as the anode potential. It may be determined readily in each case by experiment. A bias of' 150-200 volts has been found particularly suitable for the systems set forth in their dimensions in the following, with an anode potential of about 2000 volts.

The three-plate systems according to Fig. 1' may conveniently be dimensioned as follows:

Length of plates: 15 mm.

Width of aperture in middle plate 5 mm.

Spacing of plates 2 mm.

Spacing apart of the systems 10 mm.

Total length of the light-control system 40 mm.

Length of the concentration cylinder 6-8 mm.

In the arrangement having bent plates the small spacing between the bent middle plate and the one outer plate may be set at 1 mm, and the spacing between the middle plate and the other outer plate at 2 mm.

As already set forth in detail, the essential feature is that both systems are completely symmetrical, and that the corresponding plates of the two systems are connected to the same potentials. Naturally it is also possible to select other dimensions for the systems, it being however expedient to make the plates as short as possible, as the control sensitiveness, i. e., the extent of displacement of the ray from the adjustment "light to that of dark" decreases when increasing the length of the system.

The operation of the arrangement according to the invention is as follows:

The ray proceeding from the cathode 2 and preferably preliminarily accelerated by a preliminary anode (not shown) which has a relatively low potential, passes along the normal path through the aperture l2 in the screening member 9 into the space between the plates I and 8 of the first displacing system, is bent through the aperture of the middle plate into the space between the

plates

8 and 6 due to the positive bias of the plate 8, and leaves this space parallel to the normal path through the aperture II in the screening member l0, then passing through the concentration cylinder I! and the shuttering device l8 through the aperture 13 into the space between the plates 6 and 8' of the system 5. Due to the positive bias of the plate 8' the ray is here bent through the aperture of the plate into the space between the plates 8 and I, and leaves the space through the aperture M of the screening member l6. Since the systems 4 and 5 are so arranged that their electric field conditions are inversely equal and symmetrical (i. e., the spacing of the plates and the length of the plates is the same if the same potential is supplied to the two middle plates 8 and 8' and if the

outer plates

6 and 1 and 6 and I are also given to the same potential) the ray leaves the system 5 along a path which represents an extension of the path of entry into the system 4. Since, however, it is solely a matter of the plates 8 and 8' (under otherwise equal conditions) having the same potential, and the absolute extent of this potential accordingly in no way influences the direction in which the ray leaves, it will be quite obvious that a displacement of the ray does not take place, no matter whether the auxiliary light-control potential in series with the positive bias of the plates 8 or 8' amounts to 0 or 20 volts. The variations in the potential at the plates 8 and 8' accordingly merely result in that the spacing of the part 25 of the ray, displaced parallel to the normal path, from the middle plate 8, varies dependent on the 5 light control potential. It, therefore. shuttering device is provided in this path 25, the ray is displaced dependent the ray on the variation in the light-control potential along the shuttering device, so that parts thereof ofdifierent size are allowed to pass through the shuttering device. The tube according to the invention may be furnished in the manner known per se with one or more anodes, for example in such fashion that one anode is located between the cathode and the light-control arrangement, and the second anode, preierably raised to a higher potential,

between the light-control device and the deflecting plates. The arrangement according to the invention enables the graduation curve for the change-over from ligh to dark" to be varied as desired by simple variation in the form of the bounding curves of the shuttering device. The arrangement further allows operations to be performed with relatively low anode potentials, and g5 ensures a reliable light control whilst avoiding any variation in the position of the image point.

I claim: p 1. A Braun tube comprising a gas-filled envelope enclosing a cathode and an anode mounted go in operative relationship thereto, a picture receiving screen, two main electrostatical deflecting systems each consisting of a pair of plates for deflecting the cathode ray in two directions perpendicular to each other, said main deflecting 35 systems being mounted between said cathode and said screen, and two auxiliary electrostatical deflecting systems for causing the ray to enter each of said main deflecting systems under a constant angle of inclination with respect to the plates L0 of the respective system, said auxiliary deflecting systems being mounted between said cathode and said main deflecting systems.

2. A Braun tube comprising an evacuated envelope, a gas-filling within said envelope, a cath- 15 ode and an anode mounted in operative relationship thereto for producing a cathode ray, means for concentrating the cathode ray, a picture receiving screen, two deflecting systems mounted between said anode and said screen, 50 each of said systems comprising two outer plates and one middle plate having a transverse slot, said middle plate being mounted in electrical relation symmetrically with respect to said two outer plates and being adapted to be supplied 55 with a constant positive bias with respect to each of the outer plates, one of said outer plates being adapted to be supplied with a constant potential, and the other of said outer plates being adapted to be supplied with a deflecting voltage, and means for connecting all of said electrodes to their respective circuits.

3. A Braun tube comprising an evacuated envelope, a gas-filling within said envelope, a cathode and an anode mounted in operative relationship 65 thereto for producing a cathode ray, means for concentrating the cathode ray, a picture receiving screen, two deflecting systems mounted between said anode and said screen, each of said systems comprising two outer plates and one 70 middle plate having a transverse slot, said middle plate being mounted in electrical relation symmetrically with respect to said two outer plates and being adapted to be supplied with a constant positive bias with respect to each of the outer 75 plates, one of said outer plates being adapted to be supplied with a constant potential, and the other one of said outer plates being adapted to be supplied with a deflecting voltage; an annular electrode mounted between said deflecting systems and said screen, a metallic coating mounted on the wall of said envelope in the vicinity of said annular electrode, means for connecting the middle plates of said deflecting systems with one another and with said'annular electrode, means for connecting those two outer.

plates which are adapted to be connected with a constant potential with one another, with said anode and with said metallic coating, and means for connecting all of said electrodes with their respective circuits.

4. A Braun tube comprising an envelope, a cathode and an anode mounted in operative relationship thereto for producing a cathode ray, means for controlling the intensity of the cathode ray, means for concentrating the ray, a picture receiving screen, two deflecting systems for deflecting the ray in two directions vertical to each other, each of said deflecting systems comprising two outer plates and a middle plate having a transverse slot, said middle plate being bent to angles and being mounted in electrical condition symmetrically with respect to said two outer plates, said middle plate being adapted to be supplied with a constant positive bias with respect to each of said outer plates, one of said outer plates being adapted to be supplied with a constant potential, the other one of said outer plates being adapted to be supplied with a deflecting voltage the maximum amplitude of which is smaller than said positive bias which the middlc plate is adapted to be supplied with.

5. A Braun tube comprising an evacuated envelope, a gas-fllling within said envelope, 2. cathode and an anode mounted in operative relationship thereto for producing a cathode ray, means for concentrating the cathode ray, a picture receiving screen, two deflecting systems mounted between said anode and said screen, each of said systems comprising two outer plates and one middle plate having a transverse slot, said middle plate being mounted in electrical relation symmetrically with respect to said two outer plates and being adapted to be supplied with a constant positive bias with respect to each of the outer plates, one of said outer plates being adapted to be supplied with a constant potential, and the other one of said outer plates being adapted to be supplied with a deflecting voltage, means for screening off the control plates of said deflecting systems against each other, and means for connecting all of said electrodes with their respective circuits.

6. A Braun tube comprising an evacuated envelope, a gas-filling within said envelope, a cathode and an anode mounted in operative relationship thereto for producing a cathode ray, means for concentrating the cathode ray, a picture receiving screen, two deflecting systems mounted between said anode and said screen, each of said systems comprising two outer plates and one middle plate having a transverse slot, said middle plate being arranged in electrical relation symmetrically with respect to said two outer plates and being adapted to be supplied with a constant positive bias with respect to each of the outer plates, one of said outer plates being adapted to be supplied with a constant potential, and the other one of said outer plates being adapted to be supplied with a deflecting voltage, each of said outer plates being shorter than said Iii! middle plate. the ratio between the length of one of said outer plates and its distance from said middle plate being equal to the ratio between the length of the other outer plate and its distance from the middle plate, the length of each plate being equal to the distance its edge from the middle of, the slot of the middle plate.

7. A Braun tube comprising an evacuated envelope, a gas-filling within said envelope, a cathode and an anode mounted in operative relationship thereto for producing a cathode ray, means for concentrating the cathode ray, a picture receiving screen, two deflecting systems mounted between said anode and said scr'een, each of said systems comprising two outer plates and one middle plate having a transverse slot, said middle plate being mounted in electrical relation symmetrically with respect to said two "outer plates and being adapted to be supplied with a constant positive bias with respect to each of the outer plates, one of said outer plates being adapted to be supplied with a constant potential, and the other one of said outer plates being adapted to be supplied with a deflecting voltage, the plates of the deflecting system mounted next to the screen having a trapezoidal basic shape and rounded bounding lines, the slot of the middle plate of said system having an arcuate profile.

8. A Braun tube having a deflecting system comprising two outer plates and a middle plate having a transverse slot, the middle plate being bent to angles and being mounted in electrical relation symmetrically to each of said outer plates, said middle plate being adapted to be supplied with a positive bias with respect to each oi! said outer plates, one oi said outer plates being adapted to be supplied with a constant potential, and the other one of said outer plates being adapted to be supplied with a deflecting voltage.

9. A Braun tube having a deflecting system comprising two outer plates and. one middle plate having a transverse slot, each of said outer plates being mounted in parallel to said middle plate and being considerably shorter than said middle plate, the ratio between the length of one of said outer plates and its distance from said middle plate being equal to the ratio between the length oi the other one of said outer plates and its distance from said middle plate, said middle plate being adapted to be connected with a constant positive bias with respect to each of said outer plates, one of said outer plates being adapted to be connected to a constant potential, the other one of said plates being adapted to be supplied with a deflecting voltage.

10. A Braun tube having a deflecting system comprising two outer plates and one middle plate having a transverse slot, each of said outer plates being about half as long as the middle plate, said middle plate being adapted to be supplied with a constant positive bias with respect to each of said outer plates, one of said outer plates being adapted to be connected to a constant potential, and the other one of said outer plates being adapted to be supplied with a deflecting voltage.

KURT SCI-HESINGER.