US3846659A

US3846659A - Mounting arrangement for coplanar grids having common flat strip cathode

Info

Publication number: US3846659A
Application number: US00292639A
Authority: US
Inventors: G Casset; J Driffort; P Lebel
Original assignee: FRANCE COULEUR SOC
Current assignee: FRANCE COULEUR SOC; STE FRANCE COULEUR FR
Priority date: 1969-09-10
Filing date: 1972-09-27
Publication date: 1974-11-05
Anticipated expiration: 1991-11-05

Abstract

A color television picture tube, having a plurality of electron guns delivering electron beams and a deflection device for causing the television screen to be swept by said beams, comprises means for supplying parallel and coplanar electron beams at their entrance into the deflection device and means imposing a delay on the video signals controlling two of the guns so that the three elements of a triad of elementary colors of the screen receive quantities of electrons according to the video information corresponding to one and the same televised dot.

Description

United/States "[19 a Casset etal.

1 1 Nov. 5, 1974 [5 MOUNTING ARRANGEMENT FOR COPLANAR cams HAVING COMMON FLAT STRIP CATHODE Inventors: Georges Casset,

Issi-Les-Moulineauxj Jean-Pierre Driffort, Chate-Nay-Malabry; Pierre Lebel, Kremlin-Bicetre, all of France Ste dite France-Couleur, Paris, France Filed: Sept. 27, 1972 Appl. No.: 292,639

Related US. Application Data Division of Ser. No. 857,638, Sept. 10, 1969, Patv No. 3,733,507.

[73] Assignee:

US. Cl. 213/411, 313/417 Int. Cl H0lj 29/02, H01 j 29/46 Field of Search 313/69 C, 170

References Cited UNlTED STATES PATENTS 2,427,888 9/1947 Warren ..3l3/80 Hegbar 313/69 R 2,758,234 8/1956 Hensel 313/69 C 3,215,880 11/1965 Krackhardt 313/82 R 3,448,316 6/1969 Yoshida et a1 313/69 C Primary Examiner-Robert Segal Attorney, Agent, or Firm-Karl F. Ross; Herbert Dubno 1 [57] ABSTRACT A color television picture tube, having a plurality of electron guns delivering electron beams and a deflection device for causing the television screen to be swept by said beams, comprises means for supplying parallel and coplanar electron beams at their entrance into the deflection device and means imposing a delay on the video signals controlling two of the guns so that the three elements of a triad of elementary colors of the screen receive quantities of electrons according to the video information corresponding to one and the same televised dot.

2 Claims, 29 Drawing Figures PATENTEUNUY s 1974 I Bv-5 l l r-a r-s r-4 r-3 M m i Y m z sr E l fig-6 uv 5I974 PATENTEI] ll was 7 3,846,659

SCANNING C URRE N T L INE-SCA NN/NG C URRE N T FRAME-SCANNING 4- CURRENT PATENTEDNUY 5mm x 3,846,659

USN?

MOUNTING ARRANGEMENT FOR COPLANAR GRIDS HAVING COMMON FLAT STRIP CATHODE PRIOR ART Numerous tubes having a plurality of electron beams have been proposed for receiving color television pictures.

The majority of tubes proposed comprise three electron guns, each corresponding to a primary color, normally blue, green and red, the flux of which is controlled respectively by video signals corresponding to these colors, the beams passing through a scanning device or deflector which causes them to sweep the screen of the tube.

The latter comprises triads of elements which light up respectively in blue, green and red under the impact of the beams, with an intensity which depends on the electron flux carried by the latter.

The majority of tubes used at present are of the shadow-mask type, i.e., they contain a mask with hols, each corresponding to a triad of elements of the screen,

through which the beams pass before impinging on the screen; a convergence device trains the three beams through each of the holes in upon the several dots of a respective triad, thus ensuring coincidence between each of the beams and the triad element of the color corresponding to that beam.

Tubes are likewise used for receiving sets wherein the elements of the triads are vertical bands and the electron beams then converge in the gap formed by the vertical wires of a grid brought to a potential different from that of the screen and likewise from that of the electron beams.

One problem which arises for all these receivers is to avoid the deformation of the images at the edges of the screen and to retain the purity of the colors, and this is more difficult to solve the larger the angle of scanning and the more closely the screen surface approaches a plane.

SUMMARY OF THE INVENTION The tube for a color television receiver according to the invention enables a color television image to be obtained without difficulty on a flat screen of large dimensions with a sweep of at least 1 satisfying the condition of purity of color while being of a simpler and more economical construction than conventional tubes of this character.

The color-television receiving tube according to the invention generates a set of electron beams for the illumination of its screen which are parallel to one another and lie in one and the same plane, at least from their entrance into the scanning device, and impinge simultaneously on the elements of different triads, the video information which they carry being staggered in time to restore the coincidence between the dots of the televised object and the image dots on the screen.

The receiving tube according tothe invention may be constructed without a dynamic convergence device, thus permitting a considerably more simple design than that of conventional tubes.

More particularly, our invention aims at providing an improved deflecting device for such a tube to ensure correct scanning of the television screen from parallel and coplanar electron beams supplied thereto.

The tube may be of the shadow-mask type or of the grid type.

BRIEF DESCRIPTION OF THE DRAWING Illustrative embodiments of our invention will now be described with reference to the accompanying drawing in which: 7

FIG. 1 is a diagrammatic view of a portion of a tube of a color television receiver according to the invention;

FIG. 2 is a diagram illustrating an electron-gun as sembly for the tube;

FIG. 3 is a diagrammatic view in perspective of a portion of a mask and of a screen;

FIG. 4 is a diagrammatic view in horizontal section, on a larger scale, of a portion of the mask and the screen of FIG. 3;

FIG. 5 is a diagrammatic view of the tube according to the invention for another form of construction, some members having been omitted for the sake of clarity in the illustration;

FIG. 6 is a front view showing diagrammatically the position of the guns of a tube as shown in FIG. 5;

FIG. 7 is a diagrammatic view, in horizontal section, similar to part of FIG. 5 but with illustration of the beams and drawn to a larger scale;

FIG. 8 is a diagrammatic view in axial section of a deflector according to the invention;

FIGS. 9 to 12 are explanatory diagrams;

FIG. 13 is a top view ofa plate adapted for use in the manufacture of a deflector according to the invention;

FIG. 14 is a view in axial section of a deflector core equipped with plates as shown in FIG. 13;

FIG. 15 is a diagrammatic view in axial section of a deflection device according to the invention;

FIG. 16 is a diagrammatic front view of a portion of a device as shown in FIG. 15;

FIG. 17 shows, diagrammatically, the construction of a line-scanning device;

FIG. 18 shows, diagrammatically, the construction of a frame-scanning device;

FIG. 19 is a diagrammatic view, in cross section through the axis of the tube, of a device for modifying the paths of electron beams;

FIG. 20 is a similar view to FIG. 19 but for another form of construction;

FIG. 21 is a view similar to the two previous Figures but showing yet another embodiment in longitudinal section;

FIG. 22 is a view similar to the three previous Figures but showing a further modification, likewise in longitudinal section;

FIG. 23 is a perspective view of part of an electronbeam generator according to the invention;

FIG. 24 is a front view of a cathode support for such a generator;

FIG. 28 is a perspective view of an electron-lens assembly which can be associated with this generator; and 1 FIG. 29 is a highly diagrammatic view of a receiving tube for color television equipped with such a generator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a color-television-receiving tube according to the invention comprises three guns C C,,, C delivering electron beams F F, F,, respectively.

These electron guns have coplanar axes (FIG. 2) situated in a plane parallel to the major sides of the screen of the tube.

The guns C are so disposed that the beams F which they deliver converge at a single point 13. These beams are subject to the action of means represented diagrammatically by an electron lens 14 bending them in such a manner that, beyond the lens 14, the three beams are propagated along parallel and coplanar paths F F',,, F',, which pass through a scanning device comprising horizontal sweep means 15 and vertical sweep means 16 diagrammatically operated by electromagnetic coils. I

The tube comprises a mask 17 (FIG. 3) and a screen 18. The mask 17 has a multiplicity of holes 19 each associated with a triad of circular areas or

phosphor dots

20,, 20,, and 20, on the screen luminescing respectively in green, in blue and in red under the impact of the elctrons.

7 Instead of lying at the corners of an equilateral triangle, however, as ina conventional mask-type television tube, the areas of a triad-have a horizontal linear distribution. A red area 20 is followed, in horizontal al ign ment, for example by a green-area 20 in turn followed by a blue area 2 0,, wliichjis, again followed by a red area 20, etc. .luxtaposed with this horizontal row of areas or phosphor dots isanother horizontal row comprising adjacent areas offset b'y the width of one I half-area in relation to'the-areas inthe preceding row,

the blue area'being adjacent to redand green areas in the first row, the red area being adjacent to the green and blue areas in the first row etc.A third horizontal row likewise comprises areas disposed side by side, the blue area being adjacent 'to the red and green areas in the second row, the red area being adjacent to green and blue areas in the second row etc. The holes 19 in the mask 17 are aligned horizontally in like manner.

Likewise according to the invention, whereas the video signal corresponding to red, for example, is applied directly to the gun C without any delay, the video signals corresponding to the blue color are applied to the gun C through a line L,, (FIG. 1) having a delay equal to the time which an electron beam takes, in the course of the horizontal sweep, to pass from a position in which it falls on a red area 20, of a triad to a blue area 20,, of another triad in the same horizontal row. not necessarily adjacent. A line L,., applying the green video signals to the gun C introduces a delay double that of the line L,,.

If P,; is the screen spacing, that is to say the distance separating two phosphor dots of the same color in two adjacent triads, and P is the distance separating the axes of two successive perforations 19 in one and the of the guns C and the construction of the electrostatic lens 14 are selected in such a manner that the distance d between the axes of the beams F and F,, and between the axes of the beams F, and F satisfy the formula:

11:0 a/ ad 1.-

in which a is any integer with the exception of 3 and whole multiples of 3. The value a may thus be equal to l, 2, 4 etc FIG. 4 shows, for example, the axis a, of the electron beam corresponding to the red video signal for a dot of the televised picture at a given moment and trained on a red area 20, of the triad T,,, which is the fifth starting from the triad T or central triad in the horizontal row comprising the area 20, At this moment, the beam corresponding to the gun C has an axis a, at a distance d from the axis a, and trained on the blue area 20,, of the central triad T while the beam corresponding to the gun C has an axis a',, at a distance of 2d from the axis a, and falling on the green area 20 of the triad T- symmetrical with the triad T in relation to the central triad T The video signal corresponding to the red component of a dot in the televised object is carried by the beam whose axis is at a',. It causes the quasipoint element 20, of the triad T to be illuminated in red. Because of the intervention of the delay line L,., it is only when the axis a,, of the beam F reaches the blue phosphor dot 20,, of the triad T in the course of the horizontal sweep that the beam F',, will carry the blue video signal for the same televised dot. Similarly, through the intervention of the delay line L... it is only when the axis a, of the beam F, has arrived at'the green phosphor dot 20, of the triad T in the course of the horizontal sweep that it will carry the green video signal throughthe same televised dot.

Consequently, during the horizontal sweep, the three component elements of the triad T, will receive the electron beams corresponding to the video signal of the televised dot not absolutely simultaneously but with the delay introduced by the delay lines L,., L,, yet without these minimum delays being noticed by the viewerbethree beams passing through the scanning device, the

receiving tube may operate without a dynamic convergence device. Not only is the manufacture of the tube simplified but likewise the difficulty in obtaining the purity of colors, originating from the disturbing influ ence of the convergence device on the operation of the scanning device in a conventional'picture tube, is thus eliminated.

The methods of producing phosphors for the tube of a conventional shadow-mask picture tube, using photographic techniques, may be applied with the same facility to the formation of the phosphors on a screen for a picture tube according to the invention.

Reference will now be made to FIGS. 5 to 7, relating to a tube of the grid type according to the invention.

The tube-forming television pictures according to the invention, includes in this form of construction, a screen E (FIG. 5) of the type comprising, side by side, triads T of vertical bands which light up respectively in green, in blue and in red, under the impact of electrons and which have been designated B.,, B, and Br. The triads are adjacent and are distributed regularly with a spacing P E referred to as screen spacing. inside the tube and at a distance from the latter there is a grid G formed by a multiplicity of wires f, parallel to the bands B and equidistant between them, the distance between two successive wires (referred to as grid spacing P being less than the distance between two triads of the screen (P P In many embodiments, the screen spacing P is 0.81 mm and the grid spacing is 0.74 mm, and the distance between the grid and the screen is of the order of 23 mm, these numerical indications having no limiting character. The screen is at a higher electrical potential than the wires of the grid; for example it may be at 25 KV while the grid wires are at 7 KV, these numerical indications having no limiting character.

The tube is equipped with three electron guns C C C,, corresponding respectively to the three primary colors green, blue and red, and their axes av, ab and ar are in one and the same horizontal plane 110 (FIG. 6), which is the median plane of the screen E. The gun C has its axis situated in the vertical median plane 111 of the screen E. In the form of construction described, the axes av, ab and ar converge at a point 112 situated in the plane 111 inside the tube, well upstream of the plane of the grid G.

Divergent electrostatic or electromagnetic lens means, illustrated diagrammatically at 113, are interposed in the paths of the electron beams Fv, Fb and Fr supplied by the several guns and are so designed that, at their exit, the electron beams have parallel axes, as illustrated diagrammatically at ab, a'v, a'r.

The parallel and coplanar electron beams with equidistant axes pass through a deflector 114 illustrated diagrammatically by a horizontal deflection coil 115 and a vertical deflection cell 116.

The arrangement of the election guns and the position of the lens means 113 are such that the distance d between the axis a'v (FIG. 7) of the beam Fv and the axis ab of the beam Fb, equal to the distance between the axis ab and the axis a'r, satisfies the same formula as above, with P the grid spacing and P again the screen spacing.

The distance between two beams need not be an integer of the spacing between two grid wires.

In the absence of a supply current to the

coils

115 and 116, the axis ab encounters the central triad T of the screen E at its central band which may be the blue band BbO, for example, and is equidistant from the wires f-l and f1 of the grid G situated immediately one at each side of the vertical plane 111.

The axis a'v, whose distance from the axis ab has the value d corresponding to the above formula, then en counters the screen at a green band, which is the band Bv-S, in the example illustrated diagrammatically in FIG. 7, passing between the wires f5 and f-6 of the grid, and the axis a'r encounters the screen at a red band, which is the band BrS in the example, the index number given each of the triads and their constituents bands denoting their position relative to the central triad while the positive or negative sign indicates whether they are to the right or to the left of the latter. It will be understood that the illustration in FIG. 7 is very diagrammatic and that in reality the number of triads counted between the intersections of the beam axes in the absence of any deflection may be different from, eg considerably greater than, that which has been illustrated.

The unequivocal correspondence between the three beams and the three types of band of the triads is retained in the course of the sweep.

The speed of the horizontal sweep of the screen by the electron beams is made uniform, in known manner, and the invention provides for applying the information to the central gun and to the left-hand gun in the conventional case of sweeping from left to right, in the present instance to the gun Cb and to the gun Cv, by means of lines Lb and Lv introducing delays in relation to the conductor Lr used to apply the information to the gun Cr.

The time constant of the line Lb is equal to the time necessary for the beam Fb to pass, in the course of the horizontal sweep, from the position in which its axis ab intersects the plane of the grid between the wires f-l and f1 to that in which its axis intersects the plane of the grid between the wires f5 and f6. The time constant of the line Lv is equal to double the time constant of the line Lb. Under these circumstances the signals pertaining to one and the same televised dot are delivered to one and the same triad.

In the example, a picture dot is composed of the triplet BrS, B125, Bv5, the screen being struct by the beams Fb and Fv, carrying the blue and green information corresponding to the same dot as the red information of the beam Fr, after impingement of the beam Fr, in a precise manner with delays which are equal to the time constants but are absolutely negligible in comparison with the duration of retinal persistance. The image of the triplet therefore appears to the viewer under precisely the same conditions as in a conventional tube.

The tube according to the invention uses an improved deflection system, generating uniform fields, which includes a core or sleeve 220 (FIG. 8) of ferrite, in the form of a tulip, whose outer surface comprises a cylindrical portion 221 connected to a substantially frustoconical portion 222 joined in turn to a cylindrical portion 223 of larger diameter. The inner surface of the core 220 comprises a rounded internal portion 224 connected to a substantially frustoconical portion 225 joining to the cylindrical portion 223 along an annular edge 226 having a small radius of curvature in cross section. The axial dimension of the core 220 is relativey short; it may, for example, be of the order of half the diameter of the external edge 226, this indication having no limiting character. The core converges axially from its sharp-edged end 226 to a flat end face 227 of reduced diameter.

The invention provides for the use of such a core, or a similar one, in combination with a vertical deflection coil and a horizontal deflection coil both of which consist, in principle, of a single layer of wire winding 228 shaped by the actual outline of the core in cross section.

In designing the coils, both for the horizontal and for the vertical deflection, we start from a ferrite core or the like as described above on which there is formed a first single-layer winding, with a sinusoidal distribution of its turns, and a second single-layer winding, also with a sinusoidal turn distribution, the regions of greater turn density in the two windings being in mutually orthogonal radial planes. The first winding is energized by the horizontal deflection current and the second winding is fed by the vertical deflection current.

A flat-screen television picture tube is equipped with such a deflector so positioned as to be traversed by the electron beams F F,,, F, or (FIGS. 1 or 5) at a point where their axes are parallel to one another, after passage of the beams throughthe divergent electrostatic or

electromagnetic lens

14 or 113.

FIG. 9 illustrates, in heavy solid lines, the outline of the picture or frame traced as one beam, upon passage through the grid f (in the case of a grid-type) on the screen E comprising triads of parallel bands Bv, Bb, Br, this beam being emitted by a lateral gun, for example the gun Cv of FIG. 5 generating the green image; the picture tube comprises means, known per se, whereby, despite the flat screen, the upper and lower limits of the frame are horizontal lines h h The lateral limits are therefore greatly curved lines, one concave towards the outside and designated 1 the other convex towards the outside and labeled [2;- The frame, that is to say the outline of the image, supplied by the other lateral gun Cr, associated with the red color, is illustrated in thin solid lines; its upper and lower horizontal limits r and r then coincide with lines It and hg but have been illustrated slightly spaced therefrom in order to distinguish them on the Figure; the lateral limits are curved lines 1,, and 1 whose curvatures are opposed to those of the lines I and I with which they have common ends d e, and d e The median sweep lines thus obtained respectively by the green" and the red beam are illustrated at m,- and m,. These scanning lines have reverse curvatures and their maximum distance k, along the horizontal median, is the same as the maximum distances of the lines I and I on the one hand and t and 1 on the other hand on said that median.

The outline of the portion of the television screen swept by the green beam is as shown in heavy dotted lines when, in accordance with the invention, the winding mode for the turns of the vertical-deflection winding is modified so that the corresponding lines of force of the field, instead of being substantially parallel as with a winding having turns distributed in accordance with sinusoidal laws, are in the form of a barrel centered on a horizontal axis, as illustrated diagrammatically in FIG. 10, so that the upper limit of the outline passes from the horizontal line 11 to the oblique line h',,., the lower limit becoming the oblique line h' symmetrical thereto with respect to the horizontal median of the screen, the frame thus assuming the shape of a trapezoid converging to the left, its left-hand limit I being simultaneously straightened to become the vertical straight line I',,., the other lateral limit becoming the vertical straight line 1' at the same time.

The modification to which the area of the screen illuminated by the red beam is subjected for this distribution mode of the turns of the vertical deflection winding is shown in thin dotted lines in FIG, 9: the frame has assumed a trapezoidal shape converging to the right, the passage from the horizontal line 11 to the oblique line 11' taking place through rotation in clockwise direction. The major base t',, of the red trapezoid is here on the left and its minor base t' is on the right. The distance between the adjacent bases of the two areas remains the maximum distance k between the apices of the curved boundaries of the areas whose limits have been drawn in full lines.

A modification of the distribution mode for the turn of the vertical deflection winding which would lead to a field no longer in the form of a barrel' but in the form of a cushion (i.e., with concave rather than convex curvature) would cause opposite distortions to some extent; the green frame would converge to the right and the red frame to the left but their lateral limits would not be straightened.

FIG. 11 illustrates, with similar references and the same training of lines as in FIG. 9 thick or thin, the shape of the green and red frames respectively, for a sinusoidal distribution of the turns of the coils for both horizontal and vertical deflection. The dotted outlines relate to a law of distribution of the turns of the horizontal-deflection winding whereby the lines of force of the corresponding field are not substantially parallel but, on the contrary, assume a barrel shape as illustrated diagrammatically in FIG. 12, in such a manner that the green area bounded by an upper the line 12" and a lower line 11" converges leftward; the red frame has rightwardly converging upper and lower limits 11",, and 11" The lateral limits t,,, and t" of the green area are not straightened and the whole of the green area is displaced toward the left. The left-hand lateral limit of the red area t' is symmetrical with its boundary 1" with reference to the median vertical plane of the screen, and the right-hand limit t" is symmetrical with to boundary t",,. with respect to the same vertical plane. But whereas the lateral limits I and 1 of the original red area were to the left of the lateral limits I and t of the original green area, a relative displacement has taken place in the horizontal direction and in the example illustrated in FIG. 11 it has been sufficient for the lateral limits t",,. and t" of the green area to have come to lie, after modification of the mode of turn distribution, to the left of the corresponding lateral limits t",, and t" of the red area. The distance k between the lateral limits has become very small in the Figure and is now of opposite sign.

We have found that it is possible, by modifying the mode of distribution of the turns of both the vertical deflection and the horizontal-deflection coil, as described above, to obtain green and red areas substantially coinciding with the rectangular blue area provided by the central gun, and therefore to obtain a satisfactory color television picture both with regard to the convergence and with regard to the purity of the colors.

We therefore provide, after determination of these laws of distribution, an annular plate 230 (FIGS. 13 and 14) having a peripheral flange 231 with radial slots 232 representing the distribution mode for the turns of the line-deflection winding as determined above, this plate covering the face 227 of the core 220 as shown in FIG. 14. We further provide of a ring 233, adapted to cover the large-diameter rim 226 of the core 220 and comprising at its edge 234 an array of radiating slots .representing the same law of succession. The construction of a line deflection winding then takes place by stretching the conductor 228 (FIG. 8) around the toroidal body constituted by the assembly of the core 220, the plate 230 and the ring 233, with insertion of that conductor into successive slots in the plate 230 and in the ring 233.

The same procedure is followed for the construction of the frame deflection winding.

Reference will now be made to FIG. 15, relating to a deflector device according to the invention for a form of construction particularly well suited to colortelevision picture tubes wherein the parallel coplanar electron beams entering the deflector are relatively far apart. In this form of construction, a ferrite-core deflector as described above is combined with a single coil 251 energized by fed from the frame-deflection current and influencing the beams before they reach the deflector. The coil 251 may advantageously be produced by placing a toroidal winding of wire in a single layer around a former 252, for example one having a substantially rectangular cross-section, which may be of non-magnetic material. The coil 251 is composed of two groups of turns 253 and 254 (FIG. 16) distributed one at each side of the median horizontal plane and connected in series, the lines of force of the field inside the coil 251 .being strongly cushion-shaped or outwardly concave as represented by the arrows in FIG. 16.

The effect of such a coil is studied by combining it with a main deflector with a toroidal core, as described above, wherein the turns both of the line-deflection coil and of the frame deflection coil are distributed in accordance with a sinusoidal law.

We have found that, simply by selection of the number of turns in the

groups

253 and 254 and by modifying the distribution laws for the turns of each of the deflection coils of the main deflector, we can realize a deflecting device satisfying the strictest conditions for obtaining a suitable color-television picture, even with electron beams spaced 5.6 mm apart at the entrance to the device.

We prefer to use a relatively fine wire, for example one having a diameter of0.5 mm, both for the windings of the deflection coils of the main deflector and for that of the coil 251 serving as a preliminary deflector. The winding of the latter may then be made with contiguous turns.

FIG. 17 illustrates diagrammatically the construction of a line-deflection device formed from a first half-coil 240 and a second half-coil 241 disposed symmetrically one at each side of the diametral vertical plane; each of the halfcoils comprises twenty-two turns per quadrant, for a total of 88 turns, bunched about the horizontal diametral plane P, and the following Table I shows the distribution ofthe turns over 90, the number in the first column showing the order number of the turns (1 indicates the first turn; 2 indicates the second turn etc... the second column showing the angular spacing between the turn and the plane of reference.

The construction of the winding of the frame deflection coil is illustrated in FIG. 18. The turns are counted angularly from a reference position coinciding with the diametral vertical plane. A first half-coil 245 is symmetrical to a second half-coil 246 in relation to the horizontal diametral plane; the distribution of the twentyfive turns per quadrant, corresponding to a total of 100 turns, is given in the accompanying Table II in which the figures in the first column represent the order number of the turns and the figures in the second column indicate the angular spacing of the turns in relation to the vertical plane of reference.

As will be apparent from Table l, the two symmetrical halves of the horizontal-deflection coil 240, 241 (FIG. 17) are separated by a pair of wide gaps, each amounting to 2 X (4835) 8250. The gaps between the

halves

245, 246 of the vertical-deflection coil (FIG. 18) amount each to 2 X (90 7437) 3046, each of these halves being divided into a pair of quadrantal subgroups separated by gaps amounting each to 2 X 609 l2l8.

While the coil 251 of HG. 16 is shown to be generally coextensive with that of

coil

240, 241, it should be noted that the line-scanning current traverses the two halves of the latter coil in parallel whereas the framescanning current, partly passing through coil 251 as de scribed above, enters the two

halves

253, 254 in a series-opposed relationship as far as the vertically oriented magnetic field is concerned. Thus, the lines of force generated thereby are outwardly concave, as shown in FlG. 16, rather than outwardly convex, as illustrated in FlG. 12 for the field generated by the

coil

240, 241. The supplemental magnetic field thus generated is effective in the plane of beam separation, i.e., the horizontal plane 10 (FlG. 2) of (FIG. 6) coinciding with the plane P of FIG. 17.

All the coils and single-layer windings have a sufficiently low impedance to be able to be connected to transistors without the interposition of adaptors. The deflector device according to the invention is therefore suitable for inclusion in a transistorised color-television receiver.

Reference will now be made to FIG. 19, relating to a realization of an

electromagnetic lens

14 or 113. The convergent beams F and F, are subject to the action of magnetic fields illustrated diagrammatically by the lines of

force

30 and 31 developed by

electromagnets

32 and 33 outside the neck 34 of the tube, their

arcuate coils

35 and 36 being surrounded by

windings

37 and 38 through which a direct current flows. The path of the central beam F remains unaffected by the

fields

30 and 31 which are disposed symmetrically, the poles of the same sign of the two electromagnets being substantially diametrically opposite one another.

Reference will now be made to FIG. 20. ln this embodiment, the beam F,\ is influenced by its passage between two

parallel plates

40 and 41, of a magnetic material having a low remanence, which are extended by two

horns

42 and 43, respectively; opposite the two horns are situated the polar ends 45 and 46 of an electromagnet 44 mounted outside the neck 34.

The arrangement for the beam F,- is symmetrical to the previous one in relation to the vertical plane 11.

The beam F, is surrounded by a shield 47 while pass- .ing through the region of the tube bounded by the

plates

40 and 41.

In the embodiment shown in FIG. 21, the guns C C C, emit, through their end grids, into a common grid 50 of cylindrical shape maintained, at the same potential as the end grids. The grid 50 is followed by another grid 51, likewise cylindrical but brought to a potential different from that of the grid 50.

In the form of construction shown in FIG. 22, the beam F, leaving the gun C, is subject to the action of two

parallel plates

52 and 53 respectively carrying positive and negative electrical charges. Similarly, the beam Fr is subject to the action of two

plates

54 and 55 respectively charged negatively and positively.

The action of the plates 52-55 on the beams F, and F renders them parallel to the central beam F,,.

A further feature of our invention resides in an im proved generator of parallel and coplanar electron beams, leading to a considerable additional simplification in the manufacture of a tube, eliminating the necessity for an electron lens, and supplying beams with a precision in positioning greater than that which could be obtained hitherto.

The generator of parallel electron beams according to the invention comprises a cathode 310 (FIG. 23) which may be of the type used in multielectrode electron tubes in the form of a hollow prismatic strip with two large lateral faces 311 and 312 (FIG. 26) and two

small faces

313 and 314. One of the large faces, for example the face 312, is covered with a layer of barium carbonate. Mounted inside the cathode 310, with two parallel strands, is a heating filament 315 covered with an insulator 316.

At each of its ends, the electrode 310 is mounted in an insulating support 317 (FIG. 24), of generally rectangular shape but having, at its longer bottom side 318, a narrower tab 319 defining two

shoulders

320 and 321, the opposite side bearing the reference numeral 322 while the shorter upright sides are designated 323 and 324. The insulating support 317, preferably of mica, has, in its central portion, in the vicinity of its connection to the tab 319, a rectangular

window having sides

326, 327, 328 and 329 through which the cathode 310 passes; a rigid connection therebetween may be obtained by crimping. The mounting of the cathode 310 in the opposite plate (not shown) is similar except that the cathode 310 passes freely through the latter plate.

The support 317 bears against two

uprights

330 and 331 rising from a metal base plate 332 confronting the face 312 of the cathode 310 (FIG. 26) and having a rectangular notch 333 (FIG. 25) for the passage of the tab 319, the

regions

334 and 335 of the plate 332 receiving the

shoulders

320 and 321 of the support 317.

The plate 332, comprises

lateral extensions

336 and 337, whose

edges

338 and 339 have a curved notch 340 and 341, respectively, bounded by

lugs

342 and 343.

Fixing takes place by embedding the extensions or

feet

336 and 337 in sealing webs 345 (only one shown) of glass, the

lugs

342 and 343 and the notch 340 or 341 forming an effective anchorage.

The lateral base plate 332 is adjacent to a central plate 346, in the form of an elongated rectangle, terminating in

lugs

347 and 348 which define a notch 349 and are fixed in the same sealing web 345. A gap 350 is provided between the central plate 346 and the lateral plate 332. Adjacent to the plate 346 but separated from it by a gap 351, is a plate 352 similar to the plate 332, likewise sealed by its ends in the webs 345. The plate 352 comprises

uprights

353 and 354 similar to the

uprights

330 and 331 and serving to carry the aforementioned second cathode-supporting plate similar to the insulating support 317.

In line with the cathode 310, the

plates

332, 346 and 352 have holes, 355, 356 and 357, respectively, whose axes lie in a common plane.

When the assembly is under vacuum, as for example in a tube, and an appropriate heating current flows through the filament 315, the face 312 of the cathode 310 emits electrons and the

plates

332, 346 and 352 with their

respective holes

355, 356 and 357 act as Wehnelt cylinders controlling, for example by means of the potentials applied to these Wehnelt cylinders, the intensity of the electron beams passing respectively through the

holes

355, 356 and 357.

This arrangement affords convenient equalization of the distance between the

Wehnelt cylinders

332, 346, 352 and the confronting'face 312 of the cathode 310, with greater precision than for the distances between three separate cathodes of three electron guns and the corresponding Wehnelt cylinders.

Moreover, only a single cathode has to be heated instead of three cathodes in the case of a three-gun generator with, in consequence, not only a lower current consumption but above all a much smaller quantity of heat to be dissipated, less pollution of the tube and improved stability of the latter.

The self-pollution of the conventional cylindrical cathode, which normally occurs in the course ofthe exhausting step, is considerably reduced because of the apertures provided around the cathode.

In order to prevent the dispersion of the electrons outside the beams, a shielding device 360 is provided at each end of the cathode (FIGS. 26 and 27), comprising a wall 361 parallel to the large faces of the cathode and

perpendicular walls

362 and 363.

Reference will now be made to FIG. 28. A metal block 370, of non-magnetic material, is drilled with three

bores

371, 372 and 373 whose parallel and

coplanar axes

374, 375 and 376 pass through the centers of the

holes

355, 356 and 357 of the Wehnelt cylinders (FIG. 23) and through the centers of

respective holes

377, 378 and 379 formed in a plate 379' and constituting individual grids (collectively designated G for the electron beams.

Such a drilled block 370, brought to a suitable potential, acts as a lens assembly 6, for the electron beams passing through the Wehnelt cylinders and the multiple grid G The precision of the

bores

371, 372 and 373 is greater than that realizable with separate tubes, such as those normally used as electron lenses in electrongun generators.

Such a lens device may be followed by another lens device 380, of similar construction, with three

bores

381, 382 and 383 whose

axes

384, 385 and 386 are aligned with the

axes

374, 375, 376, the block G constituting the device 380 being held at a potential different from that of the block 370.

The assembly of the two drilled blocks advantageously replaces the two groups of tubes normally following the first two grids G, and G, of a multipleelectron-beam generator, for example with an array of separate electron guns. A precise positioning of the confronting faces 387 and 388 of the

blocks

370 and 380 is obtained without difficulty. Equally satisfactory precision is easily obtained with regard to the position of the plate 379' forming the triple grid G A generator of multiple parallel electron beams as described may advantageously be included in the construction of a television picture tube, particularly a color-television tube; the video information corresponding to the three primary colors is then applied, for example, the plates acting as Wehnelt cylinders.

Such a tube is illustrated very diagrammatically in FIG. 29. The generator 390 according to the invention delivers three electron beams 391, 392, 393 which are cylindroconical after passing through electron-lens devices (l -G and whose axes are parallel to one another. The three beams carry the information corresponding respectively to the three primary colors. Their axes are coplanar and they are parallel as they pass through the deflection device, represented diagrammatically by two

coils

395 and 396, which is preferably of the type described above with reference to FIGS. 16 to 18. The coplanar and parallel scanning beams fall on the television screen 398 after passing through a grid 399.

The parallelism of the coplanar beams passing through the

deflection device

395, 396 dispenses with the need for the dynamic convergence means conventional in color-television picture tubes.

The single-cathode generator according to the invention enables beams to be generated with closely juxtaposed axes, thus reducing the aberrations in deflection.

This type of generator may also be included in the construction of a multiple-beam oscillograph tube.

What we claim is:

l. in a color-television picture tube including a screen with luminescent triads of primary colors and a plurality of electron guns with coplanar parallel axes trained upon said screen. the improvement wherein said electron guns comprise a flat strip with an electron-emissive surface forming a common cathode, mounting means for said strip, a plurality of metal plates adjoining each other with boundaries transverse to said strip in a plane parallel to said electron-emissive surface, said plates being provided with respective perforations confronting said electron-emissive surface, and retaining means securing said plates to one another and to said mounting means with said perforations in mutual alignment; said plates including two outer plates and one intermediate plate, said mounting means comprising a pair of end supports for said strips interlockingly engaging said outer plates, said retaining means comprising a fusible body sealingly anchored to extremities of all said plates; said extremities having edges imbedded in said body, said edges forming recesses flanked by converging jaws.

2. The improvement defined in claim I wherein said fusible body consists of glass.

Claims

1. In a color-television picture tube including a screen with luminescent triads of primary colors and a plurality of electron guns with coplanar parallel axes trained upon said screen, the improvement wherein said electron guns comprise a flat strip with an electron-emissive surface forming a common cathode, mounting means for said strip, a plurality of metal plates adjoining each other with boundaries transverse to said strip in a plane parallel to said electron-emissive surface, said plates being provided with respective perforations confronting said electronemissive surface, and retaining means securing said plates to one another and to said mounting means with said perforations in mutual alignment; said plates including two outer plates and one intermediate plate, said mounting means comprising a pair of end supports for said strips interlockingly engaging said outer plates, said retaining means comprising a fusible body sealingly anchored to extremities of all said plates; said extremities having edges imbedded in said body, said edges forming recesses flanked by converging jaws.

2. The improvement defined in claim 1 wherein said fusible body consists of glass.