US3638063A

US3638063A - Grid structure for color picture tubes

Info

Publication number: US3638063A
Application number: US790350A
Authority: US
Inventors: Takuji Tachikawa; Akio Ohgoshi; Joshida Susumu; Akira Nakayama; Eiji Ishii
Original assignee: Sony Corp
Current assignee: Sony Corp
Priority date: 1968-01-11
Filing date: 1969-01-10
Publication date: 1972-01-25
Anticipated expiration: 1989-01-25
Also published as: NO124231B; AT292804B; SE348317B; DK140536C; NL6900531A; BE726699A; CS156430B2; GB1240251A; DK140536B; DE1901369B2; FR2000176A1; CH490731A; DE1901369A1; NL149033B

Abstract

A support for the grid structure of a cathode-ray tube in which the support is stressed to compensate for any expansion of the grid wires due to heating, the support having a pair of opposed parallel arms with the grid wires attached to and extending transversely between the arms, and a pair of braces supporting the arms at the Bessel points, the braces being stressed in a direction substantially parallel to the direction of the grid wires so that as the grid wires expand due to heat the braces will expand a corresponding amount to maintain a substantially constant tension of the grid wires.

Description

O United States Patent 1151 3,638,063 Tachikawa et al. 5] Jan. 25, 1972 [54] GRID STRUCTURE FOR COLOR 2,701,847 2/1955 Yanagisawa et al. ..313/269 x I U E UBE I 3,436,585 4/1969 Murakami ..3l3/348 C R T S 3,487,253 12/1969 Scharmann ..313/269 [72] Inventors: Takuji Tachikawa; Akio Ohgoshi; Joshida 2,832,911 4/1958 Van Velzer ..313/78 Susumu; Aklra Nakayama; Eiji lshii, all of Tokyo, Japan 1 Primary ExaminerDavid Schonberg I Assistant ExaminerToby H. Kusmer [73] Asslgnee' Sony Corporation Tokyo Japan Attorney Albert C. Johnston, Robert E. lsner, Lewis H. [22] Filed: Jan. 10, 1969 Eslinger and Alvin Sinderbrand 0 A support forthe grid structure of a cathode-ray tube in which [30] Forelgh pp ation Priority D v the support is stressed to compensate for any expansion of the Jan. 1 1, 1968 Japan ..43/1658 grid Wires due to heating, the pp having a P of pp Jan. 11, 1968 Japan ..43/165 P r arms with the grid Wires attached to and extending transversely between the arms, and a pair of braces supporting 52 0.5.0 ..3l3/348, 313/269 the arms at the Bessel Points, the braces being Stressed in a 5 [nLCL I I Holj 4 direction substantially parallel to the direction of the grid [58] Field of Search ..313/269, 348, 78 Wires so that as the grid wires expand due to heat the braces will expand a corresponding amount to maintain a substan- 5 References Cited tially' constant tension of the grid wires.

UNITED S T PATENTS 9 Claims, 13 Drawing Figures 2,446,271 8/1948 Eitel ..3 13/348 X PATENTEDJAHZSIHTZ 3.638.063

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BY ATTORNEYS PATENTEB M25 i972 SHEET 8 BF 7 TAN/J1 TACHIKAWA AKIO OHGOSHI Sl/Sl/MU YOSHIDA AKIRA NAKAXAMA INVENTOR. EIJI ISHH ATTORNEYS GRID STRUCTURE FOR COLOR PICTURE TUBES This invention relates to a novel grid structure for color picture tubes, and more particularly to a grid structure which is of particular utility when employed in color picture tubes.

As is well known in the prior art, color cathode ray tubes employ, for electron beam postdeflection and focusing, a grid structure such that a plurality of parallel grid wires are stretched across a parallelogramic frame between a pair of opposed sides. Such a grid structure is produced in the following manner. A plurality of parallel grid wires are stretched on a master frame under predetermined'taut conditions and a grid frame is put on the grid wires from inside of the master frame. The grid wires are then fixed to a pair of opposed supports of the grid frame and are thereafter severed along the margins of the grid frame. In this case, the grid frame is prestressed inwardly by a turnbuckle to apply a maximum tension to the grid wires secured to the central portion of the opposed supports of the grid frame and a smaller tension to those fixed to end portions of the supports, ensuring that all the grid wires are subjected to substantially uniform tension by the restoring force of the prestressed grid frame after disassembling it from the master frame.

Such a grid structure may be regarded as one where a plurality of grid wires are stretched at substantially uniform tension on a parallelogramic frame prestressed in a manner to be displaced the most at the center of the frame. When a predetermined positive potential is applied to such a grid structure and electron beams are emitted from the electron gun of a cathode ray tube toward the fluorescent screen thereof, electron beams of several to lO-odd percent strike against the grid wires and are discharged therethrough to thereby heat the grid wires. As a result of this, the temperature of the grid wires is raised several-l degrees and the wires expand. An examination of the expanded grid wires shows that since the displacement of the frame is greatest at the center thereof, elongation of the grid wires of that portion due to thermal expansion is cancelled by the restoring force of the prestressed frame as if the grid wires had not been elongated. Accordingly, the grid wires are still subjected to substantially the same original tension, and hence do not sag. The elongation of the grid wires lying on both sides of the central grid wires cannot be absorbed with the displacement of the frame at those particular portions, since the displacement is basically small. Consequently, when the elongation of the grid wires exceeds the displacement of the frame, the grid wires are likely to sag. Even if the grid wires do not sag, they are not pulled at a predetermined tension and are readily vibrated at great amplitude to lower the picture quality of the reproduced picture when subjected to accidental small shocks.

The above can easily be understood from the fact that when all the grid wires have substantially the same length 1, their elongation resulting from thermal expansion is l and the amount of restoration of the distorted frame is l at the center thereof, the amount of restoration of the frame on both sides of the center thereof is smaller than that at the central portion.

This defect is remarkable especially in the grid structure of a color cathode ray tube of the type where a plurality of ribbonlike grid elements are stretched in parallel with phosphor strips and function as a kind of shadow mask. In this type of structure three electron beams are impinged upon three different color emissive phosphor strips through slits defined between adjacent grid elements.

A grid structure such as described above has been proposed in an attempt to increase the electron beam transmission factor of the so-called shadow mask in which a plate having bored therethrough a plurality of apertures is used as a mask for the electron beam. In such a grid structure, however, the grid elements are secured only at both ends to the frame, so that the grid elements heated by electron beams striking thereon radiate heat mainly through the ends fixed to the frame.

Further, the transmission factor of the electron beam through such a grid is lO-odd to 20-odd percent and the temperature of the grid elements rises up to 100 to 130 C. Consequently remains unchanged. As a result of this, there is the possibility that the electron beam strikes on a phosphor strip other than a predetermined one, especially a phosphor strip adjacent the predetermined one to cause unnecessary color emission. Therefore, the nonuniformity in the tension applied to the grid elements should be avoided.

. Accordingly, one object of this invention is to provide a grid structure which is adapted such that the grid elements are always subjected to a predetermined tension and do not sag dur- .ing operation, though heated by electron beams.

Another object of this invention is to provide a grid structure for shadow-mask type color cathode ray tubes in which the grid elements heated by electron beams do no sag during operation to thereby ensure uniformity in the spacing between adjacent grid elements and hence prevent unnecessary bombardment of the phosphor strips by the electron beam.

Still another object of this invention is to provide a grid structure which is constructed such that the grid elements are protected from shocks applied from the outside and caused by electron beam bombardment.

Other objects, features and advantages of this invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 and 2 are schematic diagrams for explaining the present invention;

FIG. 3 is a plan view showing one example of a grid structure for color cathode ray tubes produced according to this invention;

FIG. 4 is a side view of the grid structure illustrated in FIG.

FIG. 5 is a plan view illustrating another example of the grid structure of this invention;

FIG. 6 is a schematic diagram showing the manner in the grid elements are mounted on a grid frame;

FIG. 7 is a plan view showing another modified form of the present invention;

FIG. 8 is a cross-sectional view taken along the line A-A in FIG. 7;

FIG. 9 illustrates in perspective the plate supports employed in the example of FIG. 7;

FIG. 10 similarly shows in perspective a resilient support;

FIG. 11 is a plan view showing still another modification of the present invention;

FIG. 12 is a side view of the grid structure depicted in FIG. 1 l; and

FIG. 13 is a perspective view of the grid structure shown in FIG. 11. l

FIG. 1 is a schematic diagram showing displacement (indicated by broken lines) of a bar 1 of a length having two fulcra 2A and 28 when subjected to a uniformly distributed load 3 acting substantially perpendicular to the bar. In order to minimize the displacement of the bar 1, the fulcra 2A and 2B are located at such positions that the displacement 6 1 of both end portions of the bar 1 is equal to the displacement 8 of the central portion. Such positions of the fulcra are referred to as the Bessel points, and when the distance from the end of the bar 1 to the fulcrum 2A or 2B is taken as b, b/L=0.223. The length L of the bar does not indicate the actual length but a rang over which the load 3 is applied.

If a pair of such bars are arranged in parallel relation as a pair of opposed frame members of a grid frame, a plurality of grid wires or elements stretched between the frame members which at substantially uniform tension are subjected to the aforementioned uniformly distributed load 3. In other words, where a pair of bars 1 and 1 (not shown) ofa length L constituting two frame members are arranged in parallel relation and a plurality of parallel grid wires or elements are stretched between the bars substantially at right angles thereto under approximately uniformly tensioned conditions and fulcra 2A, 2B and 2A '28 (not shown) respectively supporting the bars are located at positions satisfying the aforementioned requirement b/L=0.223, the bars are deformed to be bent at both ends and between the fulcra by the load caused by the tension of the grid wires or elements in a direction of the tension but the displacement ration, that is, the displacement per unit load is at minimum. Consequently, the displacement ratio of the frame of this invention (indicated by the broken line B in FIG. 2) is far smaller than that of the conventional grid frame (indicated by the full line A in FIG. 2) of the type where the fulcra are located at both ends of two bars constituting the frame members, and accordingly the grid frame of this invention virtually deformed as compared with the deformation of the conventional grid frame. If the rigidity of the bar 1 is increased up to maximum, the deformation ofthe frame can be neglected.

The tension of the rid wires or elements stretched between the two bars I and 1 (not shown) corresponding to the load 3 shown in FIG. 1 is produced by pressing the two bars with a resilient support (not shown) in a direction opposite to the load 3 in a manner to force away the two fulcra 2A and 2A (2A not shown) and 2B and 28' not shown) from each other. Referring now to FIGS. 3 to 10, the construction of the grid structure of this invention will be described in detail by way of example.

As clearly shown in the figures, the grid structure of this invention comprises a frame of a predetermined configuration which consists of bar supports 4 and 4' corresponding to the aforementioned bars I and l and a pair of substantially C- shaped resilient supports 5 and 5 supporting the bar supports 4 and 4 at or in the vicinity of the Bessel points B B and B B thereof, and a plurality of ribbon-shaped grid elements of, for example, stainless steel are stretched between the bar supports 4 and 4' at a predetennined pitch under predetermined distribution of tension. Reference numeral 7 indicates generally the grid structure.

The bar supports 4 and 4' may be formed ofa metal such as iron, stainless steel or the like and in the illustrated example the bar supports 4 and 4' are square in cross section and are bent to conform to the panel to which the grid structure will be attached. The resilient supports 5 and 5' may be formed of a metal such as iron, stainless steel or the like and are substantially C-shaped so as not to disturb the irradiation of the phosphor screen by the electron beam emitted from the electron gun ofa cathode ray tube. It is a matter of course that the supports 5 and 5' may be configured at will so long as they do not disturb the electron beam directed to the fluorescent screen of the cathode ray tube. The grid elements 6 may also be formed ofa metal such as iron, stainless steel or the like.

With such an arrangement, since the pair of bar supports 4 and 4 constituting one portion of the frame are jointed to the resilient supports 5 and 5 as a unitary structure at or in the vicinity of the Bessel joints BA, B and B and B8. The bar supports 4 and 4' may be regarded as a rigid body with respect to the load caused by the tension of the grid elements. Accordingly, when the grid elements 6 that are stretched between the bar supports 4 and 4' uniformly at a predetermined tension expand by heat resulting from the electron beam bombardment thereon, the bar supports 4 and 4 are pulled outwards by the resilient supports 5 and 5' in a parallel relationship by a distance corresponding to the length ofthe grid elements which have been extended by the thermal expansion. Consequently, although the absolute value of the tension is different from the initial one, the initial distribution of the tension over the entire grid elements remains unchanged.

The foregoing description has been made in connection with a grid structure in which the grid elements are of substanlength of the grid elements on the end portions of the bar supparts were. l75 mm and IIEI QfIhF elements of the central portion: 185 mm.) were stretched between the bar supports at a tension of about 350 g. for each grid element, it has been ascertained that although the grid elements were heated by electron beams and extended due to thermal expansion during operation, accidents such as vibration of the grid elements due to nonuniformity of the tension or color contamination due to irregularity of the space between adjacent grid elements were not caused. Further, it has been found that the deviation from the initial distribution of the tension of the grid elements caused by the thermal expansion thereof resulting from the collision of the electron beam therewith were compensated for by the stretch or shrinkage of the grid elements or slight restoring force of the bar supports.

In addition, it has also been found that if the deviation of the length of the grid elements is in a range of :20 percent relative to its mean value, the length of the grid elements extended by the thermal expansion is extremely short and the initial distribution of the tension of the grid elements is maintained during operation by the stretch and shrinkage of the grid elements or by compensation due to the restoring force of the bar supports.

In the prior art a very complicated device is required for stretching grid elements on a grind frame, but this can be readily achieved by the following method. As shown in FIG. 5, for example, a thin stainless steel plate 8 of a predetermined size is first prepared and is subjected to etching to remove selected areas, thus providing metal strips 8a arranged at a predetermined pitch. At the same time, slits 8b are formed for a predetermined number of metal strips 8a (every three metal strips in the figure) in the plate 8 at both marginal portions thereof. In a similar manner, slits 8c are formed in the plate 8 on both sides of the metal strips 8a. Portions 8d separated by the slits 8b are then respectively held by chucks 9A and 9B as shown in FIG. 6. In this case, the number of the chucks 9A and 98 corresponds to that of the portions 8d. The chucks 9B are supplied with a moderate tension in accordance with the thickness and the quality of material of the portions 8d, but such tension may be applied to both of the chucks 9A and 9B Substantially the same tension is applied to the metal strips by means of, for example, a coiled spring 10 as shown in the figure. Under such taut conditions, a pair of bar supports 11 and 11' are disposed under the plate 8 at predetermined positions and the plate 8 is welded to the bar supports. In this case, the bar supports 11 and 11 are supported by a pair of resilient supports at or in the vicinity of their Bessel points, though not shown, and the resilient supports are slightly bent inwardly so as to apply a predetermined tension to the metal strips when the portions 8d are released from the chucks 9A and 9B. It is preferred that the force for bending the two resilient supports be equal to the tension (the total tension of all the metal strips) applied to the metal strips by the spring 10. In such a case when the chucks 9A and 9B are removed, the tension of the metal strips 8a due to the spring 10 is applied to the strips 8a by the resilient supports, so that the tension of the metal strips 8a remains unchanged before and after the removal of the chucks.

Subsequent to the welding of the plate 8, the portions 8d projecting outside of the bar supports 11 and 11' are cut off and both end portions of the slits 8c are also cut off. The slits 8c are provided for facilitating the cutting of the plate 8, and hence they are not always necessary. In the manner described above, the metal strips 8a can readily be stretched between the bar supports 11 and 11 with predetermined distribution of the tension. In this use, the metal strips 8a are coupled together at both ends. It is possible, of course, that the end portions of the metal strips 8b are provided for preventing the plate 8 from becoming creased when applying a tension to the edges of the plate 8 and for ensuring uniformity of the tension applied to each metal strip 80. In the absence of the slits 8b, it is extremely difficult to apply the tension to the metal strips 8a with the predetermined distribution.

While the metal strips 8a are subjected to substantially equal tension by the chucks 9A and 9B in the above example, the distribution of the tension may be changed as desired in accordance with the shapes of the bar supports and the resilient supports and the condition of the resilient supports welded to the bar supports in the vicinity of the Bessel points thereof to ensure uniformity of the tension applied to the metal strips by the resilient supports.

The electron beam transmission factor depends upon the width of the metal strips or the diameter and the pitch of the metal wires, which are usually selected to render the electron beam transmission factor approximately 20 percent in view of the relationship to the width of each phosphor strip of the fluorescent screen of cathode ray tubes.

In FIGS. 7 and 8 there is illustrated another example of this invention, in which reference numeral designates generally a grid structure. A pair of plate supports 12 and 12' are supported by a frame like resilient support 13 at or in the vicinity of their Bessel points to provide a frame of a predetermined configuration, and grid elements 14 in the form of, for example, metal strips are stretched between the pair of platelike supports 12 and 12'.

The plate supports 12 and 12' may be formed of a metal such as iron, stainless steel or the like and, as shown in FIG. 9, one marginal edge of each plate support is curved so as to conform to the surface of the panel of a cathode ray tube with which the finished grid structure will be assembled. The resilient support 13 may also be formed of a metal such as iron, stainless steel or the like and this support 13 has projections 13a at places substantially corresponding to the Bessel points of the plate supports 12 and 12 as illustrated in FIG. 10. Further, the support 13 has L-shaped plate support-retaining members 13b formed integrally at places corresponding to the projections 13a.

The pair of plate supports 12 and 12' are mounted on the retaining members 13b of the resilient support 13 in such a manner that the projections 13a of the support 13 engage the plate supports 12 and 12 at or in the vicinity of their Bessel points, and the plate supports and the resilient supports are held together by predetermined jigs in a manner to produce a predetermined pressure at or in the vicinity of the Bessel points of the plate supports 12 and 12 by the projections 13a of the resilient support 13. Then, the grid elements 14 are stretched between the pair of plate supports 12 and 12 at a predetermined distribution of tension.

With such an arrangement, the pair of plate supports 12 and 7 12' are supported by the projections 13a of the resilient support 13 at or in the vicinity of their Bessel points, so that the equilibrium of the tension is very stable after the grid elements 14 have once been stretched at the predetermined distribution of the tension. Accordingly, the equilibrium of the tension is not lost by a slight variation in the tension after stretching the grid elements 14 and the grid frame is not deformed. Further, the equilibrium of the tension is difficult to loose by thermal expansion of the frame or the grid elements 14 due to a temperature rise during operation, and even if the equilibrium of the tension is lost, the tension promptly balances, so that deformation of the frame is very slight. Consequently, the position of the grid elements 14 is not shifted and the electron beam always impinges upon the fluorescent screen accurately at a predetermined location, so that phenomenon such as color contamination is not caused thereby ensuring reproduction of a clear picture. In addition, since the grid structure described above is simple in construction, its fabrication is easy and the yield is greatly increased. Even if the grid elements 14 are stretched between the plate supports 12 and 12' at substantially uniform tension, the deformation of the frame is very slight as indicated by the dotted line B in FIG. 2. Accordingly, there is no possibility that the position of the grid elements 14 is shifted by a slight deformation of the frame and by thermal expansion of the grid elements or the frame due to a temperature rise. That is, even if the grid elements 14 are stretched at uniform tension, the aforementioned many advantages can still be obtained.

The assembling of the grid structure with the panel of a cathode ray tube can readily be achieved by the same means as mentioned previously or by other known means, and accordingly no description will be given. Further, it is needless to say that the aforementioned method can be used for stretching the grid elements, and the metal wires may be stretched at the grid elements 14 at a predetermined pitch in place of the metal strips.

The foregoing description has been made in connection with only several examples of this invention, and the material, shape and the like of the bar supports, plate supports, grid elements, resilient supports and so on can be suitably selected at will, if necessary. However, the bar supports and the plate supports are desired to be formed of a conductive material so as to establish electric fields between the supports and the grid elements. Further, these supports are not restricted to the bar and plate supports.

When the grid structure is used in color picture tubes the grid elements are caused to vibrate by mechanical vibration due to external shocks or electron beam bombardment. In FIGS. 11 to 13 there is shown still another example of this invention in which the grid structure is designed to prevent such unwanted vibration of the grid elements.

In the figures reference numerals 21A 22B represent substantially C-shaped resilient supports supporting the bar supports 21A and 21B at or in the vicinity of their Bessel points to constitute a grid frame generally designated by 23. Reference numeral 24 identified grid elements such as ribbonlike metal strips which are stretched between the pair of bar supports 21A and 218 at a predetermined tension distribution and pitch. These members are identical with those described in the foregoing examples.

In the present example, a damping rod formed of, for example, a metal wire is provided in contact with the grid elements 24.

For example,

resilient pieces

26A and 26B are planted on the outside of the

resilient supports

22A and 22B substantially at the center thereof, and the damping rod 25 is stretched between the resilient pieces 26A and 268. In this case the damping rod 25 is stretched in a direction of the lines of the raster (in the electron beam-scanning direction) and it is preferred that the damping rod 25 be stretched obliquely in a range of 30 to 45 relative to the electron beam scanning direction.

With such an arrangement, the grid elements 24 are resiliently pressed by the damping rod 25, and hence are not likely to be caused to vibrate by mechanical shocks from the outside and electron beam bombardment. Even if vibration occurs, it is immediately suppressed by the damping rod 25, thus preventing a bad influence by the vibration of the grid elements. The provision of the damping rod 25 avoids not only the vibration of the grid elements but also irregularity in the spacing thereof which results from twisting of the grid elements. Namely, when the grid elements 24 are heated by collision of the electron beam therewith and are to be twisted due to thermal expansion, the damping rod 25 presses the grid elements 24 to prevent twisting of the grid elements to hold the space between adjacent grid elements as predetermined, ensuring that the electron beam impinges only on a predetermined phosphor strip. Further, the provision of the damping rod 25 is only to stretch it in contact with the surfaces of the grid elements and hence can be achieved with great ease. The damping rod 25 may be a mechanically strong metal wire of, for example, tungsten, stainless steel, inconel or the like. The use of such a mechanically strong wire avoids breakage of the damping rod or insufficient pressing of the grid elements as with conventional damping rods of glass fiber in grid structures for the Chromatron (Registered Trademark) type picture tubes.

The damping rod 25 formed of the above-mentioned metals or other ones is preferred in terms of mechanical strength and is free from secondary electron beam emission by the electron beam. It is preferred that the diameter of the damping rod 25 to 30 to 50 microns. With a diameter of, for example, 100 microns, the mechanical strength of the damping rod increased but the reproduced picture is adversely affected by the damping rod. With a diameter of less than 30 microns, the mechanical strength of the rod 25 decreases and its pressing effect of the grid elements becomes weak. With a smaller diameter damping rod, the bad influence on the reproduced picture is decreased correspondingly, but the influence of a damping rod 50 microns in diameter on the reproduced picture is hardly noticeable. According to our experiments, a tungsten wire of a diameter from 30 to 50 microns yields good results. In the foregoing example, the damping rod 25 is stretched between the two resilient pieces 26A and 268 but either or both of them may be dispensed with. The shape and position of the resilient pieces are not limited to those in the above example. For example, it is possible that resilient wires are stretched on the frame on both sides of the grid elements instead of the resilient pieced and the damping rod is stretched between the resilient wires. Further, the damping rod 25 may be attached to the grid elements 25.

It will be apparent that many modifications and variations may be effected without departing from the scope of the novel concepts of this invention.

What is claimed is:

l. A support for the grid elements of a cathode ray tube comprising a pair of opposed parallel arms, a plurality of said grid elements affixed to said arms and extending transversely therebetween, a pair of generally C-shaped braces supporting said arms and attached thereto substantially at the Bessel points and formed to lie in surfaces substantially parallel to the surface defined by said grid elements, said braces being stressed a sufficient amount in a direction substantially parallel to the direction of said grid elements whereby as said grid elements expand said braces expand a corresponding amount to maintain the tension on all of said grid elements substantially uniform.

2. A support for a grid structure of a cathode ray tube comprising a pair of opposed parallel arms, a plurality of flexible grid wires affixed to said arms and extending therebetween, a pair of mechanically resilient braces supporting said arms and attached thereto at locations inwardly spaced from the ends of said arms substantially at the Bessel points, and said braces being stressed in a direction substantially parallel to the direction of said flexible grid wires to apply tension stress to said grid wires whereby as said flexible grid wires expand due to heat generated during the operation of the tube, said braces expand due to their resiliency and their being stressed a corresponding amount to maintain the tension on all of said flexible grid wires substantially uniform.

3. A support in accordance with claim 2 wherein said braces are substantially C-shaped.

4. A support in accordance with claim 2 wherein a damping rod extends over said flexible members to substantially eliminate mechanical vibration of said flexible members.

5. A support in accordance with claim 4 wherein said damping rod is stretched between said braces.

6. A support in accordance with claim 5 wherein said damping rod is flexible and is attached substantially to the center of said braces.

7. A support according to claim 6 wherein the damping rod is inclined relative to flexible grid wires.

8. A support in accordance with claim 6 wherein said damping rod resiliently presses against said flexible members.

9. A support according to claim 8 wherein said damping rod has a diameter of between 30 and 50 microns.

Claims

1. A support for the grid elements of a cathode ray tube comprising a pair of opposed parallel arms, a plurality of said grid elements affixed to said arms and extending transversely therebetween, a pair of generally C-shaped braces supporting said arms and attached thereto substantially at the Bessel points and formed to lie in surfaces substantially parallel to the surface defined by said grid elements, said braces being stressed a sufficient amount in a direction substantially parallel to the direction of said grid elements whereby as said grid elements expand said braces expand a corresponding amount to maintain the tension on all of said grid elements substantially uniform.