US2832911A - Thermal compensating grid frame - Google Patents

Description

Apt-i129, 1958 H. VAN VELZER THERMAL COMPENSATING GRID FRAME 2 Sheets-Sheet 1 Filed May 27 1954 FlG.3u.

FIG.5.

INVENTOR I HARRY L. VAN VELZER mm MW HIS A ORNE April 29, 1958 H. VAN VELZER 2,832,911

' THERMAL COMPENSATING GRID FRAME Filed May 27, 1954 2 Sheets- Sheet 2 INVENTOR i HARRY L. VAN VELZER 8D? ms W THERMAL CQMPENSATING GRID FRAME Harry L. Van Velzer, Liverpool, N. Y., assignor to General Electric Company, a corporation of New York Application May 27, 1954, Serial No. 432,750

7 Claims. (Cl. 31378) This invention relates in general to cathode ray tubes for color television, and particularly to color kinescopes of the type having a mask comprising a plurality of grid wires interposed between the electron gun assembly and the phosphor screen in intercepting relation. More specitically, this invention relates to a thermal compensating grid frame for maintaining a predetermined schedule of tensions on the grid wires under a variety of ambient temperature conditions.

In kinescope tubes of the type having a mask comprising a multitude of grid wires, there is the perennial problem of maintaining proper tension on the grid wires regardless of ambient temperatures. In ordinary circumstances kinescopes are subjected to great extremes of temperatures, both in the hot and in cold regions of the temperature spectrum. For example, in the process of manufacture during the vacuum-,bakeout process, the entire tube structure is kept at a temperature of some 380 centigrade, for a time in the order of one hour. During the cool-down phase of the bakeout process, it is found that the grid wires cool more rapidly than the surrounding grid frame, with the result that the wires contract. If this were allowed to progress unchecked, there would be a breaking of the grid wires, or a longitudinal extension of these wires with subsequent sagging at normal operating temperatures. At the other extreme of the temperature spectrum, it is not uncommon for the completed kinescope to be stored in cold regions, so that the wires contract, and thus will sag unless some means is provided to keep them taut under these thermal conditions encountered in practice. In solution to these problems, a schedule of anticipated temperature extremes is prepared, and the thermal compensating grid frame structure of this invention is intended to compensate for these temperature variations at all times.

As is well known, the manufacturing cost of color kinescopes constitutes an appreciable portion of the overall cost of color television receivers. Manyof the solutions which have been offered to solve the myriad technical problems affecting kinescope design while meritorious, have nevertheless suffered from the serious disadvantage of complexity, which complexity has contributed in large measure to the expense involved in color kinescope manufacture.

Accordingly, it is an object of this invention to provide an improved color kinescope.

Another object is to provide a construction which will reduce the cost of color kinescopes.

A further object is to provide a thermal compensating grid structure for use in a color kinescope, which structure permits the grid wires to be held with a predetermined tension under a wide range of ambient temperature changes. In one illustrative embodiment of the invention, there is provided a thermal compensating grid frame structure for use in a color kinescope. A plurality of grid wires "ice are secured between apair of frame supports, the distance between the supports determining the tension on the grid wires. A pair of thermal compensating side members are connected to the supports to complete the frame structure, each of the side members comprising a first element, a second element, and at least one intermediate element having a different coeflicient of expansion from the other elements. The first element of each of the pairs is connected at one end respectively, to one of the supports, and the second element of each of the pairs is connected at one end respectively to the other of the supports. The free ends of the first and second elements are connected to the respective ends of the intermediate element, which arrangement permits longitudinal displacement, while lateral movement is restrained. In this manner, the diiferential expansion of the elements changes the tension on the grid wires.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which:

Fig. 1 is a longitudinal cross sectional view of the relative positions of the various elements within the envelope of a color kinescope;

Fig. 2 is an isometric view, partly in section,, disclosing a thermal compensating grid frame structure in accordance with one illustrative embodiment of the invention;

Figs. 3a and 3b are elevation and plan views, respectively, of another illustrative embodiment of a thermal compensating side member in accordance with the invention;

Figs. 4a and 4b are elevation and plan views, respectively, of still another illustrative embodiment of a thermal compensating side member in accordance with the invention; and r 1 Fig. 5 is a diagrammatic showing for the purpose of explaining the relative displacements of the individual elements of the thermal compensating side members.

Referring now to Fig. 1, there is shown a schematic representation of a cathoderay tube structure or kinescope for reproducing a televised image in natural color or in monochrome in accordance with the intelligence being received. The kinescope indicated generally at 1, includes a panel 2, a funnel 3, and a neck portion 4. An electron gun assembly consisting of red, green and blue guns 5, 6 and 7, respectively, is suitably positioned within the neck 4 of the envelope. An electrostatic deflection system 8 is mounted forward of the electron gun assembly to provide convergence of the electron beams at the plane of mask 14. A yoke or magnetostatic deflection coil 9 is positioned around a portion of the neck 4, and provides a means for sweeping the converged beams across the mask. The funnel 3 and panel 2 are provided with complimentary metallic flanges 10 and 11, which are suitably mounted on their respective peripheries. ture is indicated generally at 12. As will be observed from a study of Fig. l, flange It) extends radially .inwardly to provide a supporting seat for frame 12." In the embodiment here illustrated, frame 12 is mounted on. flange 10 by means of screws 13 which pass through holes in flange 1t) and through mating holes 25 (Fig. 2) in the frame. The grid frame '12 supports grid wires 14 in spaced relation as will be presently explained in the descriptionof Fig. 2. A glass plate 15 is mounted on posts 16 which are positioned conveniently'at the cor- A thermal compensating grid frame strucnets of the frame structure 12. The color phosphors, red, green, and blue 17, 18, and 19 (Fig. 2) are alternately applied in strips to the surface of a glass plate 15, thewhole being secured to posts 16 in any conven ient:manner. In the .completed'kinescope, the panel 2 and funnel 3 are joined along the outwardly extending mating portions of flanges and .11.

As best shown inFig. 2, the thermal compensating grid frame structure 12 comprisesa pair of metallic or other electrically conductive frame supports 20 and 21, and a pair of thermal compensating side members indicated generally at 22. In this embodiment the grid wires 14 are arranged vertically and .at predetermined spaced intervals on the frame supports 20 and 21; however, it

should be made clear at this point, that the inventive 3% ance with a method disclosed and claimed in the copending application of Van Velzer, Serial No. 432,831, filed May 27, 1954 and assigned to the assignee of the instant application. The overhanging portions of wires 14 are bunched together in groups of some 15 or wires and secured for conductive connection to the upper and lower frame supports 20 and .21 as indicated at 24. The purpose of .this arrangement is to provide electrical connection from frame supports 20, 21 to the grid wires 14, since in the kinescope here shown, post acceleration is utilized between the mask 14 and the screen. The- supports 20 and 21 are provided with four holes 25 for receiving the screws 13 which secure frame 12 to the flange 10 as previously described.

The thermal compensating side members 22 comprise a first element 26, at least one" intermediate element 27, and a second element 28. As may be seen from Fig. 2, the ends of the elements 26, 28 are secured respectively to members 20 and 21 in any suitable manner such as by means of screws 29. The opposite ends of intermediate elements 27 are respectively secured to elements 28 and '26 in any suitable manner, such as by welding, as indicated at 30 and 31. A screw 32 is passed through elements 26, 27 and 28, so that substantially no motion is permitted in the transverse direction; however, since the intermediate element is slotted as indicated at 32a,

displacement is nevertheless permitted in the longitudinal direction.

Alternate embodiments for the thermal compensating side members in accordance with the invention, are illustrated in Figs. 3 and 4. In these figures the same numeration has been utilized for those components which have their counterpart in Fig. 2. In Fig. 3, intermediate element 27 is made from rectangular stock, the first and second elements 26, 28 being channel members arranged around the periphery of element 27 as shown in the drawing. The embodiment of Fig. 4 is similar to that shown in Fig. 3, with the exception that intermediate element 27 is round in cross section, and the first and second elements 26, 28 are fashioned as semi-round or arcuate members arranged around the circular periphery of element 27. If desired, any tendency toward lateral displacement may be arrested by means of a band 33 passing around the outer portions of the first and second elements 26 and 28.

In order to make clear the operation of the thermal compensating grid frame structure, reference will now be had to Fig. 5 of the accompanying drawing. For purposes of discussion, let usassume that line AA represents a ground or referenceline drawnon support 21 and through the points joining wires 14 tothe sup port 21. Similarly, line BB is drawn on support 20 through the points joining wires 14 ,to the frame support 20. Thus, in the discussion to'follow, line AA will remain fixed, while everything above this line'will be free to move. 7

V AL=the net change in length of an element L=the original length of the element a =the coefiicient of expansion of the element and AT=the change in temperature it is obvious then, that since element 27 is fastened to the upper end of element 28, that it too will be displaced a like distance in the upward direction. However, since element 27 also experienced an expansion itself, it will be moved some distance due to its own expansion which we shall call AL (AL =L a AT). The lower extremity of element 27 is therefore displaced a distance AL -AL Finally, the element, 26 experiences an expansion, say AL (AL =L a3AT). Summing up these displacements by means of superposition principles, the net displacement of the line BB' (corresponding to frame support 21) will be AL AL +AL or AL +AL -AL By appropriately choosing the respective lengths of the elements 26, 27 and 28, as well as the materials from which they are constructed, the net change in distance between AA and BB can be made positive, negative, or conceivably zero, depending upon the particular result desired. For example, when the summation results in a positive sum, then if the wires 14 did not expand, there would be an increase in the dimension measured from AA to BB, and hence, an increased tension on the grid wires 14. However, in practical cases, when the grid frame structure 'is subjected to an increase in temperature, the wires. will also experience an expansion, with the result that the wires 14, will be subjected to some tension representing the difference between its own expansion and that of the thermal compensating side members. On the other hand if the sum is negative, this would result in a decrease'in the dimension from AA to BB' or stated differently, a decreased tension on wires 14.

' While the intermediate element 27 has been described as a single element, it should be understood that one or more elements of the same or different materials may also be used. In addition, it is not necessary that the first, second, and intermediate elements be fabricated as shown in the illustrative embodiments, but other geometric configurations such as curvilinear strips could also be used with equal facility.

While certain specific embodiments have been shown and described, it will, of course, be understood that various other modifications may yet be devised by those skilled in'the art which will embody the principles of the invention and found in the true spirit and scope thereof.

1. In a color kineseo'pe, a thermal compensating grid frame structure, comprising a pair of frame supports, a plurality of grid wires secured between the supports, the distance between said supports determining the tension on said grid wires, and a pair of thermal compensating side members connected to said supports to complete the frame structure, each of said thermal side members comprising longitudinal generally parallel first, second, and third elements having selected coefficients of thermal expansion, said first element being connected at one end to one of the supports, said second element being connected at one end to;the other of the supports, the other ends of said first and second elements being mutually overlapping and being connected to the respective ends of the third element, whereby the differential longitudinal expansion of 1 wherein said first and second elements are positioned around the periphery of said intermediate element.

3. In a color kinescope, a thermal compensating grid frame structure, comprising a pair of frame supports, a plurality of grid wires supported longitudinally between said frame supports, the distance between said supports determining the tension on said grid wires, a pair of thermal compensating side members secured to said supports to form therewith the periphery of a'quadrilateral frame structure, each of said thermal members comprising a first element, a second element, and at ieast one intermediate element having a coefiicient ofexpansion different from the other elements, said elements being secured together and adapted for longitudinal displacement relative to each other, whereby the differential expansion of said elements determines the tension on the grid Wires.

4. In combination, a pair of spaced parallel support members adapted for being mounted in the envelope of a cathode ray tube, means on said support members for supporting a phosphorescent screen therebetween, an array of grid wires supported between said members, said wires being adapted to direct a beam of cathode particles to predetermined portions of said screen and subject to relatively wide ranges of temperature variations, and relatively displaceable spacer means between said members and responsive to variations in temperature for controlling the spacing of said members thereby to minimize un desired alteration of the tension of said grid wires.

5. In combination, spaced parallel support members adapted for being mounted in the envelope of a cathode ray' tube, grid wires supported between said members, said Wires being subject to relatively Wide ranges of tem perature variations, and spacer means between said members including partly overlapping portions of different expansion coefiicients responsive to variations in temperature for controlling the spacing of said members thereby to minimize undesired alteration of the tension of said grid wires.

6. In combination, spaced parallel support members adapted for being mounted in the envelope of a cathode ray tube, grid wires supported between said members, said Wires being subject to relatively wide ranges of temperature variations, and spacer means between said members and responsive to variations in temperature in a given sense for selectively controlling the spacing of said members throughout a range including positive and negative increments.

7. In a color kinescope, a color selection electrode disposed 'in the electron beam path and including a frame having a top and bottom connected by sides, wires extending between the top and bottom, each of said sides comprising first, second and third longitudinal generally parallel members, said first and second members overlapping at one end and being connected at their other ends to said top and bottom respectively, said third member being connected between the distal ends of the overlapping portions of said first and second members, said first, second and third members having selected coeificients of thermal expansion whereby the difierential longitudinal expansion of said members changes the tension of the wires in predetermined relation in response to thermal changes, and means for restraining relative movement of said first, second and third members in a transverse direction.

References Cited in the file of this patent UNITED STATES PATENTS 1,165,934 Amthor Dec. 28, 1915 1,670,124 Reed May 15, 1928 2,027,521 Drake Jan. 14, 1936 2,152,556 Messinger Mar. 28, 1939 2,611,100 'Faulkner et a1 Sept. 16, 1952 2,653,263 Lawrence Sept. 22, 1953 2,736,832 Zaphiropoulos Feb. 28, 1956

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