US3896321A

US3896321A - System for suspending a color selection electrode in a color cathode ray tube

Info

Publication number: US3896321A
Application number: US424017A
Authority: US
Inventors: Stanley J Sedivy
Original assignee: Zenith Radio Corp
Current assignee: Zenith Electronics LLC
Priority date: 1973-12-12
Filing date: 1973-12-12
Publication date: 1975-07-22
Anticipated expiration: 1992-07-22
Also published as: JPS5092678A; CA1022597A; GB1481716A; DE2458857A1; NL7415924A; FR2254874A1; FR2254874B1

Abstract

This disclosure depicts a system for suspending a color selection electrode on the envelope of a color cathode ray tube at a predetermined precise spacing from a faceplate portion of the envelope. The suspension system includes a plurality of highly compact suspension devices spaced around the electrode, each device comprising envelope-mounted means secured in a precise location on the inside of the envelope, and electrodemounted means for retentively engaging the envelope-mounted means. The electrode-mounted means is depicted as comprising rigid bracket means secured to the electrode, the bracket means including or constituting a bimetallic element which, upon heating of the electrode, deflects to cause the electrode to move nearer to the faceplate portion of the envelope. The electrodemounted means also includes a spring supported by the bracket means and means for retentively engaging the envelope-mounted means.

Description

United States Patent [1 1 Sedivy July 22, 1975 [75] Inventor: Stanley J. Sedivy, Chicago Ridge,

[73] Assignee: Zenith Radio Corporation, Chicago,

221 Filed: Dec. 12, 1973 21 Appl. No.: 424,017

FOREIGN PATENTS OR APPLICATIONS 45-32495 1970 Japan 313/85 S Primary Examiner Robert Segal Attorney, Agent, or Firm.lohn H. Coult [57] ABSTRACT This disclosure depicts a system for suspending a color selection electrode on the envelope of a color cathode ray tube at a predetermined precise spacing from a faceplate portion of the envelope. The suspension system includes a plurality of highly compact suspension devices spaced around the electrode, each device comprising envelope-mounted means secured in a precise location on the inside of the envelope, and electrode-mounted means for retentively engaging the envelope-mounted means. The electrode-mounted means is depicted as comprising rigid bracket means secured to the electrode, the bracket means including or constituting a bimetallic element which, upon heating of the electrode, deflects to cause the electrode to move nearer to the faceplate portion of the envelope. The electrode-mounted means also includes a spring supported by the bracket means and means for retentively engaging the envelope-mounted means.

14 Claims, 7 Drawing Figures SHEET PATENTEDJUL 2 2 I975 PATENTEDJUL 2 2 I975 SHEET PO @OQOQQ OOQCQOOO SYSTEM FOR SUSPENDING A COLOR SELECTION ELECTRODE IN A COLOR CATIIODE RAY TUBE CROSS REFERENCE TO RELATED APPLICATIONS This application is related to, but in no way dependent upon, copending applications including Ser. No. 395,334,,filed Sept. 7, 1973, Ser. No. 395,106, filed Sept. 7, 1973 now abandoned, and Ser. No. 285,985, filed Sept. 5, 1972, all assigned to the assignee of the present invention.

BACKGROUND OF THE INVENTION This invention relates to color cathode ray tubes of the type having a color selection electrode, and especially to a system for suspending a color selection electrode in a color tube.

Conventional shadow mask-type color tubes have a shadow mask assembly which comprises a rigid frame upon which is welded a thin, spherically shaped mask having a pattern of electron-transmissive apertures formed therein. The mask assembly is suspended in the tube by a set of leaf springs welded to the sides of the mask frame, usually three in number, which engage studs extending inwardly from a flange on a front panel of the tube.

The present invention has wide-spread applicability, but is particularly useful for suspending a low cost, frameless, flexible color selection electrode of novel construction, described in detail and claimed in the referent copending application Ser. No. 395,334. As described and claimed in another of the referent copending applications, Ser. No. 285,985, it is preferable to mount a mask of the character described at its four corners, rather than at the sides as is conventional. Whereas the teachings of this invention are applicable for mounting color selection electrodes of other types than the shadow mask mentioned, and in arrangements other than four corner suspension configurations, the invention appears to have greatest utility for suspending a frameless mask of the character described.

In the interest of promoting automation of the operation in which a color selection electrode is mounted in a tube, it is desirable that an electrode suspension system be capable of automated or semi-automated mounting. Further, any commercially practicable color selection electrode suspension system must compensate for thermally induced variations in the electrode Q spacing, that is, the critical spacing between the electrode and the phosphor screen. The Q spacing must be accurately maintained in order to preserve registration between the electron beam landing spots and the impinged phosphor elements.

Still further, because of the extreme penalty which must be paid in bulk, weight, and cost for unnecessarily large envelopes, it is highly desirable that an electrode suspension system take up a minimum amount of space in the envelope to permit use of the smallest envelope size possible. Yet another constraint on electrode suspension systems is the requirement that the points of electrode suspension be determinable with extreme precision in order that the electrode, when mounted, will assume a precise spatial relationship to the phosphor pattern on the faceplate of the tube. Still another extremely important consideration is the cost of manufacture of an electrode suspension system.

The described electrode suspension system constraints and requirements converge in a system such as the above-characterized preferred embodiment wherein the suspension devices are located at the four corners of the electrode and wherein cost is a paramount consideration. In a conventional electrode suspension system wherein the electrode suspension devices are located at the sides of the electrode, adequate unused space is available for placement of the suspension devices. The reason for this lies in the fact that in a conventional (rectangular) color cathode ray tube, the sides of the tube bulge outwardly, creating medial spaces along the sides of the electrode in which the suspension devices can be located. In an electrode suspension system of the type with which this invention is concerned, the suspension devices are located in the corners of the tube where available space is very limited.

OTHER PRIOR ART J. H. Duistermaat et al J. H. Duistermaat et al J. Driedijk et al OBJECTS OF THE INVENTION It is a general object of this invention to provide an improved system for suspending a rectangular color selection electrode in a color cathode ray tube.

It is a less general object of this invention to provide an improved suspension system for a color selection electrode which is adaptable for suspending a frameless flexible color selection electrode at the four corners thereof.

It is another object to provide such an electrode suspension system in which the constituent suspension devices are extremely compact and are thus particularly suited for comer mounting a color selection electrode.

It is yet another object to provide such a suspension system which is capable of supporting a color selection electrode directly upon the faceplate of a color cathode ray tube envelope, or alternatively, upon the flange of a flanged-type cathode ray tube front panel.

It is still another object to provide a color selection electrode suspension system having the above-noted properties and features, and yet which is extremely accurate in its location of the electrode and relatively inexpensive to manufacture.

It is still another object to provide a suspension system for a color selection electrode which is capable of thermally compensating the electrode to maintain an appropriate Q spacing, and which does not introduce any thermally induced rotation of the electrode relative to the tube envelope.

BRIEF DESCRIPTION OF THE DRAWINGS The features of the invention which are believed to be novel and unobvious are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of a novel color cathode ray tube as seen from the rear, with a portion of the envelope cut away to reveal a suspension system for a color selection electrode which implements the principles of this invention;

FIG. 2 is an elevational view of the FIG. 1 tube, cut away to show the mask and its suspension system;

FIG. 3 is an enlarged perspective view of a mask suspension device shown in FIGS. l2;

FIG. 4 is an exploded view of the mask suspension device illustrated in FIG. 3;

FIG. 5 is an enlarged sectioned elevational view of the mask suspension device shown in FIGS. 3 and 4;

FIG. 6 is a perspective view, partly broken away, of another embodiment of this invention; and

FIG. 7 is a sectional view taken along lines 77 in FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS This invention is directed to providing an improved system for suspending a generally rectangular color selection electrode on the envelope of a rectangular-type color cathode ray tube. The suspension system of this invention may be used to suspend a color selection electrode in color cathode ray tubes in general which are of the type requiring such an electrode, however it is especially useful for suspending upon the envelope of a color tube a novel, lightweight, flexible shadow mask as described and claimed in the referent copending application Ser. No. 395,334. The system includes a plurality of suspension devices spaced around the electrode; in a preferred embodiment the system includes four suspension devices, one at each corner of the electrode. The lightweight, flexible mask alluded to above is adapted to be supported at its corners so as to permit it to conform to the contour of a cathode ray tube faceplate which it is mounted adjacent. This mask is described and claimed, per se, in the above-noted copending application, Ser. No. 285,985.

FIGS. 1-5 illustrate a color cathode ray tube 10 incorporating a system according to this invention for suspending a color selection electrode, illustrated as taking the form of a shadow mask 11. The tube 10 is depicted as having an envelope with a novel construction comprising a funnel l2 sealed to a generally rectangular, flangeless faceplate 14.

The mask 11 is illustrated as being of a low cost, lightweight, frameless, flexible character, being preferably formed integrally from a single sheet of electrically conductive material such as steel, all as described in detail and claimed in the referent copending application Ser. No. 395,334. The mask 11 is illustrated as having a curved central portion 18 which has formed therein a pattern of electron-transmissive apertures 20. The mask 11 includes a strengthening channel 22 surrounding and joined with the central portion 18.

The mask 11 has a skirt 24 of generally constant depth surrounding and joined with the channel 22. The skirt 24 includes a forwardly directed, outwardly flared body portion terminating in a leading edge portion 28. As described in detail in the referent copending application, the configuration of the strengthening channel 22 and of the skirt 24 is such as to enhance the strength of the mask and to shield, to the maximum degree possible, the phosphor screen 29 on the inner surface of the faceplate 14 from stray or overscanned electrons emanating from electron guns (not shown) in the neck of the tube 10.

The flared body portion of the skirt 24 has formed along each side a plurality of strengthening ribs 30. The ribs on each side of the mask 11 are individually straight, mutually parallel and orthogonal to the tube axis. The ribs 30 are effective to substantially synthesize a load-bearing beam having an effective loadbearing depth which is greater than the depth of any individual rib element 30.

This invention is especially concerned with the provision of a compact, low cost suspension system for corner-suspending a color selection electrode, such as a shadow mask'll, adjacent the faceplate portion of a cathode ray tube. The illustrated preferred system comprises a plurality of mask suspension devices 32, one located at each comer of the mask 11. The mask suspension devices 32 according to this invention each comprise envelope-mounted means, here shown as taking the form of a stud 34, secured in a precise location on the inside of the tube envelope. In the illustrated preferred embodiment, the stud 34 is shown as comprising a body 36 and a foot 38. The foot 38 is cemented, as by means of a frit-type cement, to the inner surface of the faceplate 14. Alternatively, it may be embedded in or otherwise secured to the faceplate 14.

Each suspension device 32 includes electrodemounted means for retentively engaging the envelopemounted means (here shown as the stud 34). In the illustrated preferred embodiment, the electrodemounted means is shown as comprising a rigid bracket 40 having an intermediate portion externally surrounding and embracing a corner of the mask 11. The bracket 40 is secured at opposite ends 42, 44 to adjoining sides of the mask 1 l. The electrode-mounted means further includes coupling means supported by the bracket 40 which comprises a discrete spring 46 and means (to be described) for engaging the stud 34.

In the illustrated preferred embodiment, the bracket 40 comprises two strips of metal which have different coefficients of thermal expansion and which are edgebonded together. The bracket 40 deflects, upon heating of the mask 11, to cause the mask 11 to move nearer to the faceplate 14 so as to provide Q- compensation. By selecting strip materials to have a predetermined difference in thermal coefficient of expansion, and by selecting the length of the

bracket arms

48, 50 appropriately long, a given amount of temperature increase in the electrode will produce an appropriate translation of the mask 11 to effect Q- compensation. That is to say, the mask 11 will be translated nearer to the faceplate 14 a distance effective to maintain registration between the electron beam landings and the phosphor elements constituting the phosphor screen 29.

In accordance with a preferred implementation of the invention, the stud 34 has a lug-receiving opening 52 formed therein which is adapted to receive a lug 54 carried by the spring 46. The body 36 of the stud 34 also includes a guide channel 56 for assisting in mounting the mask 11 in the tube 10. Apparatus which employs a guide channel to provide for automated or semi-automated mask mounting is described and claimed, per se, in my referent copending application Ser. No. 395,106.

In accordance with one aspect of this invention, the spring 46, which may be characterized as a foldedback leaf spring preferably has a reverse bend defining a first leg 58 which is secured to the bracket 40 and an opposed second leg 60 which carries the lug 54. The leg 58 is bifurcated into two

parts

62, 64 which straddle a lug-passing opening 66 in the bracket 40 located on a diagonal of the electrode. As shown with particular clarity in FIGS. 3 and 5, the lug 54 is secured to leg 60 and extends from the out-facing side thereof through the lug-passing opening 66 in the bracket 40 for retentive engagement with the lug-receiving opening 52 in the stud 34 when the mask 11 is operatively mounted in the tube 10.

The suspension device 32, by the novel construction above'described, has the following desirable properties. First, the suspension device is extremely compact, owing in large part to the use of the reverse bent or folded-back spring 46 which arches inwardly from the bracket 40 and which deflects in the unused space above the flared skirt 24 on the mask 11. Second, the spring 46 is protected against possible damage during handling of the mask. Third, by the disclosed arrangement wherein only the spring-biased lug 54 extends beyond the bracket, the suspension device is highly suited to an automated or semi-automated mask mounting operation. Fourth, by the use of a rigid bracket 40 to which is secured spring 46, economies in the fabrication of the. suspension device are achieved, since the bracket 40 can be welded to the mask 1 1 in a loose tolerance attachment operation and the spring 46 subsequently attached precisely to the bracket by a tight tolerance attachment operation. The latter attachment operation (welding, for example) is much easier to hold tolerances on than the operation in which the bracket 40 is secured to the mask 11.

To enhance the engagement/disengagement characteristics of the lug 54 and the stud 34, the lug-receiving opening 52 is preferably generally triangular in shape with rounded comers such that the lug 54 makes a three-point engagement with the opening 52. Further to this end, the lug 54 preferably has at least two sections of increasing taper toward the distal end of the lug 54, or one section of taper and a radius tangent to taper at the small end of the lug. In the illustrated preferred embodiment, two

sections

68, 70 of increasing taper are shown.

As discussed above, due to the need for an extremely compact suspension device when corner mounting is employed, it is desirable that the spring 46, which functions in part to permit disengagement of the lug 54 from the stud 34, require a minimum travel in order to effect the said disengagement. Further, it is necessary in order to preclude excessive vibration of the mask 11 during operation of the tube, and in order to resist excessive mechanical shocks during handling of the tube (which may reach 40 Gs or more), that the suspension devices 32 each exert a predetermined firm loading force on the mask, e.g., in the order of 2.0 pounds. It is desirable, however, that any loading spring employed not be so stiff as to overload the mask when the tube is baked during assembly or when the tube is operating at maximum operating temperatures. It is also desirable that any such loading spring apply a predetermined load to the mask which is relatively constant within a relatively broad tolerance range.

With these objectives and difficulties considered, according to one aspect of this invention, the spring 46 has the afore-described reverse bent, inwardly arched construction and is preferably pre-stressed such that the leg 60 exerts a load on the bracket 40 when the device is not suspending the mask which is substantially equal to the desired loading of the mask by the spring when the mask is mounted in the tube. Second, prestressing of the spring 46 permits the use of a relatively low rate spring. The use of a low rate spring which is pre-stressed has the result that the load which is applied to the mask when mounted in a tube, can be predetermined with lower required tolerances since the associated force-versus-displacement characteristic thereof is relatively shallow. The lower tolerances associated with the relatively low rate spring also imply that the loading of the mask 11 is more constant over a wider range of spring deflections than would be the case if a relatively stiff spring were employed. The lower tolerances permitted by the use of a relatively low rate spring also result in economies in manufacture of the device 32.

To mount the mask 11 in the tube 10, a mounting instrumentality or operator merely aligns the lugs 54 with the guide channels 56 in the studs 34 and translates the mask forwardly until the lugs 54 snap into place in the lug-receiving openings 52 in the studs 34.

To remove the mask from the tube 10, the spring member 46 is expanded to cause the lug 54 to be withdrawn from the lug-receiving opening 52 and thereby permit the mask 11 to be withdrawn.

A mask suspension system comprising four mask suspension devices having the construction shown at 32 was built according to the following specifications and was tested with success in achieving certain major objectives.

In each device 32, the bracket 40 took the form of edge-bonded strips of invar and high expansion alloy 22-3 (carpenter) 3/16 inch (for each material) in thickness and .030 inch in width. The bracket 40 was 2.5 inches long and was welded to the mask skirt 24 at its opposite ends. The spring 46 was composed of stainless steel alloy 17-7, .015 inch in thickness and was welded upon the center section of the bracket 40. The spring was pro-stressed with a load of 1-2 pounds. The lug extended .200 inch from the leg 60, had a diameter of .203 at contact with body 36 and taper angles of 30 (included) and 60 (included). The stud 34 was machined from 430 titanium stainless steel stock and was frit-cemented to the inner surface of the faceplate 14. Satisfactory mask loading characteristics and Q- compensation were achieved.

In accordance with this invention, the electrodemounted means includes a rigid bracket which includes a Q-compensating bimetallic member and which carries a spring and provision for engaging the stud 34. Whereas in the illustrated preferred embodiment the bracket is formed as a single edge-bonded bimetallic strip, it is contemplated that the bimetallic member and the means for securing the member to the color selection electrode may be separate structures. Such a construction is incorporated in the FIGS. 6 and 7 embodiment, described below. Further, whereas the FIGS. 1-5 embodiment has been shown as being adapted for suspending a color selection electrode directly on the faceplate of a color tube which has an envelope consisting of a funnel and a flangeless faceplate, the principles of this invention are equally useful for suspending a color selection electrode on a color tube envelope of the conventional type including a flanged front panel.

FIGS. 6-7 illustrate an embodiment of the invention implementing this modification also.

FIGS. 6 and 7 depict a suspension device 72 for suspending a color selection electrode 74 adjacent the face-plate portion 76 of a front panel 78 having a flange 80. The mask suspension device 72 is generally similar to the device 32 described above, with the below-noted exceptions.

The bracket, rather than comprising a single bimetallic strip, has three parts a bimetallic strip 82 and

bracket members

84, 86 for securing the strip 82 to the flared skirt 88 of the electrode 74. By this arrangement, the bimetallic strip 82 can be mounted without any bends or distortions along its length. The

bracket members

84, 86 may be welded to the electrode 74 and to the bimetallic strip 82 to secure the strip to the electrode 74.

In order to permit mounting of the color selection electrode 74 on the flange 80 of a conventional color cathode ray tube front panel 78, a modified stud 90 may be provided. The stud 90 is illustrated as comprising a body 92, which may be substantially identical to the body 36 of the stud 34, and a foot 92 which is adapted to be embedded in the flange 80 by wellknown stud embedding techniques. The stud embedding operation is performed while the front panel 78, or a localized portion thereof, is warm and soft.

The invention is not limited to the particular details of construction of the embodiments depicted and other modifications and applications are contemplated. Certain changes may be made in the above-described apparatus without departing from the true spirit and scope of the invention herein involved and it is intended that the subject matter in the above depiction shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. For use in a rectangular-type color cathode ray tube, a system for suspending a generally rectangular color selection electrode having a pattern of electrontransmissive apertures on the envelope of the tube at a predetermined'precise spacing from a faceplate portion of the envelope bearing a corresponding pattern of redemissive, blue-emissive and green-emissive phosphor element triads, including four electrode suspension devices spaced around the electrode, one at each corner thereof, each device comprising:

envelope-mounted means secured in a corner location on the inside of the envelope for supporting a corner of a color selection electrode; and

electrode-mounted means for retentively engaging said envelope-mounted means, comprising:

a bracket having an intermediate portion externally surrounding and embracing a corner of the electrode and end portions secured to adjoining sides of the electrode, and

coupling means including a folded-back leaf spring having one leg secured to said intermediate portion of said bracket and arching radially inwardly therefrom, said coupling means including a provision on an opposed leg of said spring for retentively engaging said envelope-mounted means.

2. The apparatus defined by claim 1 wherein said intermediate portion of said bracket includes an edgebonded bimetallic element which, upon heating of the electrode, deflects to cause said electrode to move near to said faceplate portion of said envelope.

3. The apparatus defined by claim 1 wherein said envelope-mounted means includes a metal stud secured to the envelope and having therein a lug-receiving opening, and wherein said provision on said opposed leg of said spring comprises a lug for retentively engaging said lug-receiving opening in said stud when the electrode is operatively mounted in the tube.

4. The apparatus defined by claim 3 wherein said intermediate portion of said bracket includes an edgebonded bimetallic strip and wherein said strip has a lugpassing opening formed therein on a diagonal of the electrode through which said lug passes for operative engagement with said lug-receiving opening in said stud.

5. The apparatus defined by claim 3 wherein said lug has at least two sections of different taper, the taper increasing toward the distal end of the lug.

6. The apparatus defined by claim 4 wherein said spring is pre-stressed such that said opposed leg exerts a load on said strip when said device is not suspending an electrode which is substantially equal to the desired loading of the electrode by said spring when an electrode is mounted in the tube.

7. For use in a rectangular-type color cathode ray tube, a system for suspending a rectangular color selection electrode having a pattern of electron-transmissive apertures on the envelope of the tube at a predetermined precise spacing from a faceplate portion of the envelope bearing a corresponding pattern of redemissive, blue-emissive and green-emissive phosphor element traids, including four electrode suspension devices on the periphery of the electrode, each comprising:

envelope-mounted means secured in a comer location on the inside of the envelope and on a diagonal of the color selection electrode for supporting a comer of a color selection electrode; and

bracket means secured to said electrode, said bracket means including a bimetallic element which, upon heating of the electrode, deflects to cause the electrode to move nearer to said faceplate portion of the envelope, and

coupling means including a discrete, folded-back leaf spring having one leg secured to said bracket means and arching radially inwardly therefrom, said coupling means including a provision on an opposed leg of said spring for retentively engaging said envelope-mounted means, three of said suspension devices fixing in the plane of the mask the spatial position of the mask relative to said faceplate portion, and a redundant fourth suspension device having provision for permitting the fourth corner of the mask to seek an equilibrium position in the plane of the mask.

8. The apparatus defined by claim 7 wherein said envelope-mounted means includes a stud secured to the envelope on a diagonal of said electrode and having said stud is a slot elongated in a direction transverse to said diagonal but parallel to said faceplate portion of the envelope.

10. The apparatus defined by claim 9 wherein said bracket means has a lug-passing opening formed therein through which said lug passes for operative engagement with said lug-receiving opening in said stud.

11. The apparatus defined by claim 10 wherein said spring is pre-stressed such that said opposed leg exerts a load on said bracket means when said device is not suspending an electrode which is substantially equal to the desired loading of the electrode by said spring when an electrode is mounted in the tube.

12. For use in a rectangular color cathode ray tube, a system for suspending on the envelope of the tube at a predetermined precise spacing from a faceplate portion of the envelope which bears a pattern of redemissive, blue-emissive and green-emissive phosphor element triads a generally rectangular, frameless color selection electrode having formed integrally therewith a forwardly directed skirt angled at approximately the angle of maximum beam deflection and having a central region containing a corresponding pattern of electron-transmissive apertures, said system including a plurality of electrode suspension devices spaced around the electrode, one at each corner thereof, each of said devices comprising:

an envelope-mounted stud secured in a precise location in a corner of the faceplate portion of the envelope on a diagonal of the electrode for supporting a corner of a color selection electrode, said stud having a lug-receiving opening on said diagonal;

and electrode-mounted means for retentively engaging said stud, comprising:

bracket means externally surrounding and embracing a corner of the electrode, said bracket having an intermediate portion and end portions secured to the angled skirt on adjoining sides of the electrode, said bracket means including an edgebonded bimetallic strip wrapped around the corner of the electrode on the outside thereof which, upon heating of the electrode, deflects in its own plane to cause said electrode to move nearer to the faceplate, and

a folded-back leaf spring having one leg secured to said bimetallic strip, said spring arching radially inwardly therefrom, the opposed leg of said spring carrying a radially outwardly facing tapered lug for retentively engaging said lugreceiving opening in said stud when the electrode is operatively mounted in the tube.

13. The apparatus defined by claim 12 wherein said bimetallic strip has a lug-passing opening formed thereon on a diagonal of the electrode through which said lug passes for operative engagement with said lugreceiving opening in said stud.

14. The apparatus defined by claim 13 wherein said spring is pre-stressed such that said opposed leg exerts a load on said strip when said device is not suspending an electrode which is substantially equal to the desired loading of the electrode by said spring when an electrode is mounted in the tube.

Claims

1. For use in a rectangular-type color cathode ray tube, a system for suspending a generally rectangular color selection electrode having a pattern of electron-transmissive apertures on the envelope of the tube at a predetermined precise spacing from a faceplate portion of the envelope bearing a corresponding pattern of red-emissive, blue-emissive and green-emissive phosphor element triads, including four electrode suspension devices spaced around the electrode, one at each corner thereof, each device comprising: envelope-mounted means secured in a corner location on the inside of the envelope for sUpporting a corner of a color selection electrode; and electrode-mounted means for retentively engaging said envelopemounted means, comprising: a bracket having an intermediate portion externally surrounding and embracing a corner of the electrode and end portions secured to adjoining sides of the electrode, and coupling means including a folded-back leaf spring having one leg secured to said intermediate portion of said bracket and arching radially inwardly therefrom, said coupling means including a provision on an opposed leg of said spring for retentively engaging said envelope-mounted means.

2. The apparatus defined by claim 1 wherein said intermediate portion of said bracket includes an edge-bonded bimetallic element which, upon heating of the electrode, deflects to cause said electrode to move near to said faceplate portion of said envelope.

4. The apparatus defined by claim 3 wherein said intermediate portion of said bracket includes an edge-bonded bimetallic strip and wherein said strip has a lug-passing opening formed therein on a diagonal of the electrode through which said lug passes for operative engagement with said lug-receiving opening in said stud.

7. For use in a rectangular-type color cathode ray tube, a system for suspending a rectangular color selection electrode having a pattern of electron-transmissive apertures on the envelope of the tube at a predetermined precise spacing from a faceplate portion of the envelope bearing a corresponding pattern of red-emissive, blue-emissive and green-emissive phosphor element traids, including four electrode suspension devices on the periphery of the electrode, each comprising: envelope-mounted means secured in a corner location on the inside of the envelope and on a diagonal of the color selection electrode for supporting a corner of a color selection electrode; and electrode-mounted means for retentively engaging said envelope-mounted means, comprising: bracket means secured to said electrode, said bracket means including a bimetallic element which, upon heating of the electrode, deflects to cause the electrode to move nearer to said faceplate portion of the envelope, and coupling means including a discrete, folded-back leaf spring having one leg secured to said bracket means and arching radially inwardly therefrom, said coupling means including a provision on an opposed leg of said spring for retentively engaging said envelope-mounted means, three of said suspension devices fixing in the plane of the mask the spatial position of the mask relative to said faceplate portion, and a redundant fourth suspension device having provision for permitting the fourth corner of the mask to seek an equilibrium position in the plane of the mask.

8. The apparatus defined by claim 7 wherein said envelope-mounted means includes a stud secured to the envelope on a diagonal of said electrode and having therein a lug-receiving opening on said diagonal, and wherein said provision on said opposed leg of said spring comprises a lug for retentively engaging said lug-receiving opening in said stud when the electrode is operatively mounted in the tube.

9. The apparatus defined by clAim 8 wherein the redundant fourth suspension device is like the other threee devices except that the lug-receiving opening in said stud is a slot elongated in a direction transverse to said diagonal but parallel to said faceplate portion of the envelope.

12. For use in a rectangular color cathode ray tube, a system for suspending on the envelope of the tube at a predetermined precise spacing from a faceplate portion of the envelope which bears a pattern of red-emissive, blue-emissive and green-emissive phosphor element triads a generally rectangular, frameless color selection electrode having formed integrally therewith a forwardly directed skirt angled at approximately the angle of maximum beam deflection and having a central region containing a corresponding pattern of electron-transmissive apertures, said system including a plurality of electrode suspension devices spaced around the electrode, one at each corner thereof, each of said devices comprising: an envelope-mounted stud secured in a precise location in a corner of the faceplate portion of the envelope on a diagonal of the electrode for supporting a corner of a color selection electrode, said stud having a lug-receiving opening on said diagonal; and electrode-mounted means for retentively engaging said stud, comprising: bracket means externally surrounding and embracing a corner of the electrode, said bracket having an intermediate portion and end portions secured to the angled skirt on adjoining sides of the electrode, said bracket means including an edge-bonded bimetallic strip wrapped around the corner of the electrode on the outside thereof which, upon heating of the electrode, deflects in its own plane to cause said electrode to move nearer to the faceplate, and a folded-back leaf spring having one leg secured to said bimetallic strip, said spring arching radially inwardly therefrom, the opposed leg of said spring carrying a radially outwardly facing tapered lug for retentively engaging said lug-receiving opening in said stud when the electrode is operatively mounted in the tube.

13. The apparatus defined by claim 12 wherein said bimetallic strip has a lug-passing opening formed thereon on a diagonal of the electrode through which said lug passes for operative engagement with said lug-receiving opening in said stud.