COLOUR DISPLAY TUBE

Abstract: The invention relates to a colour display tube having a colour selection electrode 7 which is suspended from the display window by means of pin-shaped members 15 which are inserted in the upright edge 3 of a display window, resilient suspension elements 21 being secured to the colour selection electrode 7. The pin-shaped members 15 have a spherical free end 16 portion which engages in an aperture of a conical portion 22 of the flat resilient suspension element 21, and which has at least three contact points 30 with the conical portion 22. To avoid the flat resilient suspension element 21 from lying against the pin-shaped member 15, the central axis A of the pin-shaped member 15 forms an angle with the X-Y plane, which plane extends perpendicularly to the axis of the combination of the colour selection electrode 7 and a display screen which is provided on the display window.

Description: The invention relates to a colour display tube comprising an envelope having an electrode system for generating three electron beams, a substantially rectangular display window having an upright edge, which window is provided on the inside with a display screen of phosphor elements luminescing in different colours, a substantially rectangular colour selection electrode which is suspended at a short distance from the display screen and which has a large number of apertures which ensure that each electron beam is directed to phosphor elements of one colour, pin-shaped members having a spherical free end portion are provided in the comers of the upright edge of the display window, resilient suspension elements which are substantially perpendicular to the electron beams to be deflected towards the relevant corner being connected to the colour selection electrode, each resilient suspension element being provided with an at least partly conical portion having an aperture on at least one side of this portion, the spherical free end portion of the relevant pin-shaped member with which the resilient suspension element cooperates engaging in the said aperture, and the spherical free end portion and the conical portion having at least three points of contact. Such a colour display tube is known from EP-A1-0240 077. However, it has been found in practice that in a few cases such a colour display tube does not always exhibit a satisfactory colour purity. It is an object of the invention to provide a colour display tube producing a satisfactory colour purity. To this end, a first embodiment of the invention provides a colour display tube as claimed in claim 1. A second embodiment of the invention provides a colour display tube as claimed in claim 2. A third embodiment of the invention provides a colour display tube as claimed in claim 3. The invention is based on the insight that an unsatisfactory colour purity, as produced sometimes by the known colour tubes, is caused by the fact that a projecting part of a resilient suspension element makes contact with the associated pin-shaped member, which is undesirable. Owing to this, the position of the colour selection electrode relative to the display screen is not properly defined which adversely affects the colour purity of the colour display tube. Due to the fact that in a colour display tube according to the invention there is no such contact the colour display tube has a satisfactory colour purity. To facilitate the fusion of the pin-shaped member, said member is provided with a shoulder with which the pin-shaped member is pressed into the upright edge. From US-A-4 387 321 it is known per se that the central axis of a pin-shaped member having a spherical free end portion extends substantially perpendicularly to the associated flat resilient suspension element. Due to this the central axis of the pin-shaped member forms an angle with the said plane, which, dependent on the type of colour display tube used, for example a 90° or a 110° colour display tube, ranges between approximately 30° and approximately 50°. It is remarked that European Patent Application EP-A1-0 289 079, which is part of the prior art under Art. 54(3) EPC, comprises a description of a colour display tube showing the features of claim 1, except for the combination of features that the central axis of the pin-shaped member makes an angle with a plane extending perpendicular to the axis of the combination of colour selection electrode and display screen and is substantially perpendicular to the inner surface of the upright edge of the display window. European Patent Application EP-A1-0 289 079, also comprises a description of a colour display tube showing the features of claim 2, except for the features that the central axis of the pin-shaped member forms an angle α of at least 5° and less than 20° with a plane extending perpendicular to the axis of the combination of colour selection electrodes and display screen and that the conical portion is permanently secured to the spherical free end portion. European Patent Applciation EP-A1-0 289 079 also comprises a description of a colour display tube showing the features of claim 3, except for the features that the central axis of the pin-shaped member forms and angle α of at least 9° and less than 20° with a plane extending perpendicular to the axis of the combination of colour selection electrode and display screen and that the aperture of the conical portion of the resilient member is surrounded by an upright edge directed towards the shoulder having a smallest diameter which is smaller than the largest outside diameter of the associated spherical free end portion and that the upright edge does not make contact with the associated pin-shaped member. In the embodiment of a colour display tube according to the invention as claimed in claim 1 the central axis of a pin-shaped member forms an angle with the said plane and is at least substantially perpendicular to the upright edge of the display window. In practice, the upright edge of the display window is not at right angles to the said plane, but instead the normal to the upright edge is at an angle to said plane. The pin-shaped members are fused into the upright edge. In practice it has proved to be very advantageous to fuse the pin-shaped members perpendicularly into the upright edge. In this case only a minimum quantity of glass, from which the upright edge is manufacture, has to be melted, which is advantageous from an economical point of view. Moreover, if the pin-shaped members are perpendicularly fused, the force necessary for the fusing operation does not exert a torque on the upright edge. Besides, in the case of a substantially perpendicularly fused pin-shaped member a smaller length of said member than in the case of an obliquely fused pin-shaped member suffices to obtain a proper anchoring in the upright edge. Thus, a saving of material is obtained. In the embodiment of a colour display tube according to the invention as claimed in claim 2 the conical portion is a separate portion which is located in the aperture of the resilient element, and the conical portion is permanently secured to the associated spherical free end portion and the resilient suspension element, and the central axis of the pin-shaped member forms an angle of at least 5° and less than 20° with the plane. This construction does not only provide a colour display tube having a satisfactory colour purity but also a readily conceivable and accurate way of suspending the colour selection electrode in the display window by permanently securing the conical portion to the spherical free end portion. In a colour display tube according to the invention as claimed in claim 3, permanent securing is superfluous. The invention will now be explained in more detail with reference to the drawing, in which Fig. 1 is a sectional schematic view of a colour display tube according to the invention, Fig. 2 is a front view of the display window with the colour selection electrode, Fig. 3 is a sectional view of a part of a colour display tube according to the invention, which part comprises, amongst others, a pin-shaped member, Fig. 4 is a sectional view of a pin-shaped member which is perpendicular fused into the upright edge of a display window, and Fig. 5 is a sectional view of a pin-shaped member which is at least substantially perpendicularly fused into the upright edge of a display window. Fig. 1 is a sectional view of a colour display tube according to the invention. The colour display tube comprises an envelope 1 having a substantially rectangular display window 2 with an upright edge. The colour display tube further comprises a cone 4 and a neck 5. A display screen 6 of phosphor elements luminescing in different colours is provided on the display window 2. A substantially rectangular colour selection electrode 7 having a large number of apertures is suspended at a short distance from the display window 2 by means of suspension means 8 which are located near the comers of the said upright edge 3. An electrode system 9 for generating three electron beams 10, 11 and 12 is mounted in the neck 5 of the colour display tube. These beams are deflected by a coil system 13. The apertures of the colour selection electrode 7 arranged relative to the luminescing phosphor elements, such that they direct each electron beam to phosphor elements of one colour. Consequently, it can be said that the colour selection electrode 7 and the display screen 6 belong together and form a combination. Fig. 2 is a front view of the display window 2 comprising the colour selection electrode 7 which has a large number of apertures 14, viewed from the electrode system. Fig. 2 depicts the x-axis and the y-axis and the diagonals D₁ and D₂ in a way which is known to those skilled in the field of display tubes. The axis of the combination of colour selection electrode 7 and display screen (not shown in Fig. 2) is perpendicular to the plane formed by the x-axis and the y-axis and traverses the point of intersection of the x-axis and the y-axis. The colour selection electrode 7 is suspended in the display window 2 by means of suspension means 8 which are located where the diagonals D₁ and D₂ intersect the upright edge 3 of the display window 2. Each suspension means 8 comprises a resilient suspension element 21 which is secured to the colour selection electrode 7, and a pin-shaped member 15 which is arranged in the corner of the upright edge 3. A pin-shaped member is to be understood to mean herein a supporting member having one end portion which can suitably be used for providing the member in the upright edge, and another end portion which can suitably be used for carrying a resilient suspension element (see Fig. 3). Fig. 3 is a sectional view of a part of a colour display tube according to the invention, viewed from the direction of the arrows shown in Fig. 2. The pin-shaped member 15 has a spherical free end portion 16 and a shoulder 23. Thanks to the shoulder 23 the pin-shaped member 15 can be pressed more readily into the upright edge, which is necessary during the fusion operation. The colour selection electrode 7 consists of a thin mask sheet 17 which has a large number of apertures 14 and which is provided with an upright edge 18. A mask edge 19 is attached to the upright edge 18, which mask edge is provided at its corner with a supporting strip 20. The resilient suspension element, which in the present example is a flat resilient suspension element 21, is secured to this supporting strip 20. The flat resilient suspension element 21 forms an angle with the axis of the combination of colour selection electrode 7 and display screen 6, which axis extends perpendicularly to the X-Y plane (in Fig. 3 shown as X-Y), such that the resilient suspension element is substantially perpendicular to the electron beams which are to be deflected towards the relevant corner of the display window 2. The flat resilient suspension element 21 comprises a partly conical portion 22. The portion 22 of the flat resilient suspension element has an aperture 25 in which the spherical free end portion 16 of the pin-shaped member 15 engages. The conical portion 22 may have, for example, a triangular or, in an alternative embodiment, a circular cross-section. The rigidity of the construction is increased in that, dependent upon the cross-section of the conical portion 22, the spherical free end portion 16 and the conical portion 22 have at least three points of contact. Moreover, due to the points of contact the conical portion 22 is centred relative to the spherical free end portion. A projecting edge 31 is required to form the conical portion 22 in the flat resilient suspension element 21. To prevent the projecting edge from contacting the pin-shaped member 15, the shoulder 23 being a large problem in this respect, the central axis of the pin-shaped member 15 forms a predetermined angle with the X-Y plane. This is explained in more detail in Fig. 4 which shows an embodiment of a colour display tube according to the invention. The central axis A of the pin-shaped member 15 preferably forms an angle a of at least 5° with the X-Y plane to make sure that the projecting edge 31 of the flat resilient suspension element 21 is clear of the pin-shaped member 15. It has been found in practice that due to tolerances caused during, for example, the manufacture of the pin-shaped member and during fusing, the projecting edge 31 may come to lie against, for example, the shoulder 23 of the pin-shaped member 15 if the angle α is smaller than 5°. The central axis A of the pin-shaped member 15 is perpendicular to the upright edge 3 of the display window. Perpendicularly fusing the pin-shaped member 15 into the upright edge 3 has advantages as regards the fusion process. For example, in comparison with oblique fusing only a minimal quantity of glass has to be melted, which leads to a rapid and inexpensive fusion process. If the angle α exceeds 20°, the fusion process becomes less advantageous from an economical point of view. Moreover, in the case of perpendicularly fusing a pin-shaped member a smaller length of the member is required than in the case of an obliquely fused pin-shaped member. In the present embodiment, the conical portion 22 is a separate portion 32 which engages in an aperture 33 of the flat resilient suspension element 21. In the manufacturing process of a colour display tube this separate portion 32 is secured to the flat resilient suspension element, for example, by means of laser spot welding, after the colour selection electrode has been accurately suspended in the display window. In Fig. 4 a few welds are indicated by means of reference numeral 34. The projecting edge 31 is a suitable place for obtaining a proper weld. After the separate portion 32 is secured to the flat resilient suspension element 21, the colour display tube is subjected to further processing, for example, the display window is provided with a display screen. Finally, the conical portion 22 is secured to the spherical free end portion 16 of the pin-shaped member, for example, by means of laser welding. Since the free end portion of the pin-shaped member 15 is spherical, the orientation of the conical portion 22 of the flat resilient suspension element 21 relative to the pin-shaped member has no influence. Consequently, the pin-shaped member 15 can be provided on the upright edge 3 at the most favourable angle. Fig. 5 shows an alternative embodiment of a colour display tube according to the invention, in which the conical portion 22 is not welded to the spherical free end portion 16. To prevent that in the case of a blow or shock the conical portion 22 slips off the spherical free end portion 16, the aperture of the conical portion 22 is surrounded by an upright edge 35 having a smallest inside diameter which is smaller than the largest outside diameter of the associated spherical free end portion 16. To avoid any contact between the flat resilient suspension element 21, for example the upright edge 35, and the pin-shaped member 15 the central axis A preferably forms an angle α of at least 9° with the X-Y plane. Due to the tolerance caused during the manufacture of the upright edge 35, it has been found in practice that an angle α smaller than 9° can lead to contact. An angle α larger than 20° is less economical and less desirable for the fusion process. It will be obvious that within the scope of the claims many variations are possible to those skilled in the art. For example, within the scope of the claims other shapes than those shown herein are possible for the pin-shaped member and for the flat-resilient suspension element, i.e. as long as, in dependence upon the resilient suspension element, the pin-shaped member forms an angle with the X-Y plane such that there is no contact with the resilient suspension element.

Claims: A colour display tube comprising an envelope (1) having an electrode system (9) for generating three electrons beams (10, 11, 12), a substantially rectangular display window (2) having an upright edge (3), which display window (2) is provided on the inside with a display screen (6) of phosphor elements luminescing in different colours, a substantially rectangular colour selection electrode (7) which is suspended at a short distance from the display screen and which has a large number of apertures (14), the apertures (14) of the colour selection electrode (7) directing each electron beam to phosphor elements of one colour, a pin-shaped member (15) being fused into each corner of the upright edge (3) , said pin -shaped member having a spherical free end portion (16) and a shoulder (23), resilient suspension elements (21) being secured to the colour selection electrode (7) which suspension elements are substantially perpendicular to the electron beams to be deflected towards the relevant corner, each resilient suspension element being provided with an at least partly conical portion (22), having an aperture on at least one side of this portion, the spherical free end portion (16) of the relevant pin-shaped member (15) with which the resilient element cooperates engaging in said aperture, and the spherical free end portion (16) and the conical portion (22) having at least three points of contact, the resilient suspension element (21) having a projecting part (31) extending beyond the aperture, wherein the central axis of the pin-shaped member (15) makes an angle with a plane extending perpendicular to the axis of the combination of colour selection electrode and display screen and is substantially perpendicular to the inner surface of the upright edge (3) of the display window (2) in such a way that the projecting part (31) does not make contact with the associated pin-shaped member (15). A colour display tube comprising an envelope (1) having an electrode system (9) for generating three electrons beams (10, 11, 12), a substantially rectangular display window (2) having an upright edge (3), which display window (2) is provided on the inside with a display screen (6) of phosphor elements luminescing in different colours, a substantially rectangular colour selection electrode (7) which is suspended at a short distance from the display screen and which has a large number of apertures (14), the apertures (14) of the colour selection electrode (7) directing each electron beam to phosphor elements of one colour, a pin-shaped member (15) being fused into each corner of the upright edge (3), each pin-shaped member having a spherical free end (16) and a shoulder (23), resilient suspension elements (21) being secured to the colour selection electrode (7) which suspension elements are substantially perpendicular to the electron beams to be deflected towards the relevant corner, each resilient suspension element being provided with an at least partly conical portion (22), having an aperture on at least one side of this portion, the spherical free end portion (16) of the relevant pin-shaped member (15) with which the resilient element cooperates engaging in said aperture, and the spherical free end portion (16) and the conical portion (22) having at least three points of contact, the resilient suspension element (21) having a projecting part (31) extending beyond the aperture, wherein the conical portion (22) is a separate part which is located in an aperture (33) of the resilient suspension element (21), and the conical portion (22) is permanently secured to the associated spherical free end portion (16) and to the resilient suspension element (21), and the central axis of the associated pin-shaped member (15) forms an angle α of at least 5° and less than 20° with a plane extending perpendicular to the axis of the combination of colour selection electrode and display screen in such a way that the projecting part (31) does not make contact with the associated pin-shaped member (15). A colour display tube comprising an envelope (1) having an electode system (9) for generating three electrons beams (10, 11, 12), a substantially rectangular display window (2) having an input upright edge (3), which display window (2) is provided on the inside with a display screen (6) of phosphor elements luminescing in different colours, a substantially rectangular colour selection electrode (7) which is suspended at a short distance from the display screen and which has a large number of apertures (4), the apertures (14) of the colour selection electrode (7) directing each electron beam to phosphor elements of one colour, a pin-shaped member (15) being fused into each corner of the upright edge (3), each pin-shaped member having a spherical free end (16) mounted on a shoulder (23), resilient suspension elements (21) being secured to the colour selection electrode (7) which suspension elements are substantially perpendicular to the electron beams to be deflected towards the relevant corner, each resilient suspension element being provided with an at lest partly conical portion (22), having an aperture on at least one side of this portion, the spherical free end portion (16) of the relevant pin-shaped member (15) with which the resilient element cooperates engaging in said aperture, and the spherical free end portion (16) and the conical portion (22) having at least three points of contact, the resilient suspension element (21) having a projecting part (31) extending beyond the aperture, wherein the conical portion (22) is a separate part which is located in an aperture (33) of the resilient suspension element (21), and the central axis of the associated pin-shaped member (15) forms an angle α of at least 9° and less than 20° with a plane extending perpendicular to the axis of the combination of colour selection electrode and display screen in such a way that the projecting part (31) does not make contact with the associated pin-shaped member (15), the aperture of the conical portion (22) of the resilient element being surrounded by an upright edge (35) directed towards the shoulder (23) having a smallest inside diameter which is smaller than the largest outside diameter of the associated spherical free end portion (16), whereby the upright edge (35) does not make contact with the associated pin-shaped member.

Inventors: BONGENAAR, HENDRIK, VAN DER AVOORT, HENRICUS JOZEF MARIA
Applicants: N.V. PHILIPS' GLOEILAMPENFABRIEKEN
Application year: 1988
Main classification: H01J29
IPC codes: H01J29, H01J31