AU463537B2 - Shadow-mask colour picture cathode ray tube - Google Patents

Description

4 6 016 n2 The invention concerns a shadow-mask colour picture

cathode ray tube with three substantially similar electron

beam generating systems arranged in triangular formation around its longitudinal axis, the electron beam generating

systems being assigned respectively to the blue, red and

green emitting phosphor dots on the screen.

It is already known in shadow-mask colour picture

cathode ray tubes• to arrange the three electron beam generating

systems in a symmetrical triangular formation around the

longitudinal axis of the tube. It is also known to arrange the

electron beam generating system in a plane, side by side, so

that the plane passes through the longitudinal axis of the tube. The usual way of arranging these electron beam the generating systems is the symmetrical arrangement around tube axis. In order to obtain an improvement in the landing

accuracy of deflected electron beams, it is normally known to

provide an additional convergence system by which each individ-

ual beam can be separately deflected to a certain extent, and

as a rule this convergence system is dynamically operated,

that is, the corrective convergence deflection of the individ-

ual beam occurs in dependence on the general deflection of the electron beams.

It has become evident that distortion of the tri-

angular arrangement of the electron beams occurs during

deflection so that especially at the edge of the screen the

landing conditions are bad and lead to colour impurity in the

reproduced television image. The object of this invention is to improve a shadow-

mask colour picture cathode ray tube of the type mentioned

earlier, particularly with respect to the disadvantages 463,537

4 6 0 16 n2 disclosed above. According to this invention it is suggested that at least one of the electron beam generating systems be set a greater distance from the longitudinal axis of the tube than the remaining electron beam generating systems. It has become evident that an improvement of the landing conditions is achieved especially in the edge portions of the screen, by the asymmetrical arrangement of the electron beam generating systems about the longitudinal axis of the tube in accordance with this invention. Figure 1 shows a schematic view of a colour picture cathode ray tube as seen from the neck of the tube, the tube being in the usual horizontal position. The cone of the tube, visible from the rear, is indicated by 1, and the neck of the tube by 2. In the neck of the tube 2 are the three electron beam generating systems B, G and R arranged in the known way in atriangle around the longitudinal axis 3 of the tube. The longitudinal axes of the three electron beam generating systems are not exactly parallel to the longitudinal axis of the tube, but are slightly inclined towards it so that they intersect approximately in the plane of the shadow-mask arranged a small spacing in front of the screen. The letters B, G and R .stand for blue, greeen and red, which normally means that the elect- ron beam generating system B is provided for exciting the blue emitting phosphor dots and the other two systems are provided for exciting the corresponding green and red emitting phosphor dots. To facilitate the production of such colour picture tubes, the three electron beam generating systems are virtually the same. 463.537

46 016 /2 According to the invention it is now suggested that at

least one of the electron beam generating systern,in particu-

lar one of the two which excite the green and red phosphor

dots, be set a-greater distance a or c from the longitudinal

axis 3 of the tube than electron beam generating system B.

The spacing of electron beam generating system B from the

longitudinal axis of the tube is represented by b, and the

spacing of electron beam generating system G by c. In the

preferred practical example shown in figure 2, distances a and

c are greater than distance b. Thus this exemplification of

the invention envisages a situation where at least one of the

electron beam generating systems is further from the longitu-

dinal axis 3 of the tube than the remaining two electron beam

generating systems, or as in. the preferred example, two elec-

tron beam generating systems are further from the longitudinal

axis than the remaining one system. Within this exemplifica-

tion of the invention, all three electron beam generating

systems may be equally spaced one from the other as in known

arrangements, so that in the preferred embodiment just mentio-

ned, the arrangement of the three electron beam generating

systems provides for equal spacing between these systems, but

in an assymetrical arrangement of the three systems with res-

pect to the longitudinal axis.

According to a further development of the invention, it

is not necessary that the three electron beam generating sys-

tems be set at the angles of an equilateral triangle. It is

particularly advantageous to make the distance from the longi-

tudinal axis of the tube to that electron beam generating

system which in the operative position of the tube is the

upper one, that is, particularly the blue electron beam 46 3537

46016n2 generating system, smaller than the spacing of the two elec- tron beam generating systems located in a horizontal plane there below from the longitudinal axis. Thus this further

exemplification of the invention envisages a situation wherein, as opposed to a situation in conformity with the earlier exem- plification the three electron beam generating systems are not equally spaced one from the other. Thus in the aforesaid advantageous arrangement, wherein the blue electron beam gener.:;ting system is closer to the longitudinal axis than the other two systems, the situation may arise wherein spacing b of Fig. 2 is smaller than spacings a and c, as before, but additionally wherein the spacings between G and B and between B and R may be equal but are smaller than the spacing between O and R. It will be noted that in each of the preferred arrange- ments mentioned as respective examples of the two approaches. to the practice of this invention, distance b of Fig. 2 is smaller than distances a and c. However, the means by which this is achieved depends on the approach .selected. Without

inferring limitation of the invention to a specific placement of any one.of the electron beam generating systems, it will be seen that in the first approach the unit of the three systems is displaced relative to the longitudinal axis in comparison with prior art, whereas in the second approach it may merely be sufficient to move the blue electron beam generating sys- tem relative to the prior art arrangements, or alternatively to move the G and R systems relative to the prior art arrangements.

463,537

Claims (3)

1. 46016n2

   THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

   i. A shadow-mask colour pictur cathode ray tube with three substantially similar electron beam generating systems arranged

   in triangular formation around the longitudinal axis of the tube,

   the electron beam geneating system being assigned respectively

   to the blue, red and green emitting phosphor dots on the screen

   characterised by the fact that at least one of the electron beam

   generating systems is set a greater distance from the longitudinal

   axis of the tube than the remaining electron beam generating

   systems.
2. 2. Shadow-mask colour picture cathode ray tube according to

   claim i, characterised by the fact that the spacing of the electron

   beam generating system assigned to the blue emitting phosphor

   dots from the longitudinal axis of the tube is less than the spacing

   of the other two electron beam generating systems from the longit

   udinal axis of the tube.
3. 3. Shadow-mask colour picture cathode ray tube according to claim 1 or 2, characterised by the fact that the three electron beam generating systems are equidistant from one another.

   4. Shadow-mask colour picture cathode ray tube according to

   one of claims 1 and 2, characterised by the fact that the distance between the red and the green electron beam generating

   systems is greater than the distance between the red and green

   systems and the blue electron beam generating system.

   S463,537

   46 01 6n2

   Shadow-mask colour picture cathode ray tube according to one of claims 1 and 4, characterised by the fact a convergence arr-

   angement for individual magnetic deflection is assigned to each of the three electron beams.

   6. Shadow-mask colour picture cathode ray tube

   463.537

   46 01 6n2 substantially as described herein with reference to the

   accompanying drawings.

   Dated this 30th day of June, 1972.

   LICENTIA PATENT-VERWALTUNGS-GmbH.

   463.537