CA1139348A - Shadow mask suspension springs for color cathode ray picture tubes - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE:

A rectangular-type color cathode ray picture tube includes a phosphor-screen-bearing faceplate with a rearwardly extending flange and a substantially rectangular shadow mask assembly. The mask assembly is suspended adjacent to but spaced from the faceplate by a plurality of leaf springs spaced about the periphery of the mask assembly. The plane of each spring is substantially parallel to the center axis of the tube. An end section of each spring is anchored to the mask assembly, and a distal end is detachably engaged to an associated stud protruding inwardly from the faceplate flange. The engagement is by movement of the distal end toward and away from the tube axis. Each spring is characterized by having an intermediate active section which in its unloaded state extends away from the mask assembly in a predetermined precurvature. The spring is deflectable through a first position wherein it is engaged with the stud, to a limit position toward the mask assembly wherein the spring provides maximum clearance for the stud and all portions of the spring for facile mask assembly insertion and removal. The precurvature is such that the spring, upon deflection, self-straightens to a substantially planar configuration either upon engagement with the stud wherein the mask assembly has enhanced immunity to shock-induced dislodgement or mispositioning; or the spring approximately self-straightens at the limit position preventing possible overstressing of the spring or at a compromise position intermediate to the first position and the limit position.

Description

1~3~
This disclosure relates to spring means for sus-pending a shadow mask assembly in a rectangular-type color cathode ray picture tube.
Both the prior art and the preferred emhQdiment of this invention will be described in the accompanying drawings in the several figures of which li~e reference numerals identify like elements and i~n which:
Figure 1 is a plan view of a cathode ray picture tube faceplate-shadow mask assembly with the shadow mask partially cut away, and wi~th certain parts shown in exaggerated dimension for clarity of illustration.
Figu,re 2 is a side elevational yiew partially in section of a prior art shadow mask suspension means showing the action of the spring means during mask insertion and removal.
Figure 3 is a side elevational view partially in section illustrating the action of suspension s~ring means according to an embodiment of the invention.
Figure 4 is an elevational view of a single leaf spring extending from a table top, illustratin~ the principle of the embodiment of the inyention shown by figure 3.
Figure 5 is a view similar to figure 3 illustrating another aspect of the embodiment of the inventi,on shown by figure 3.
Figures 6 and 6A are side elevational ~iews of yet another aspect of the figure 3 embodiment of the invention.
' Figure 7 is a perspective view showinq diagram-matically the action of a leaf spring when shocked in a deflected ~curved) state.
Figure 8 is a siae elevational view partially in section of another embodiment of spring means according to the invention.

Figure 9 is a perspective vie~ showing dia~rammatically ~- ~ - 3 -cg/

1~ .`4~3 the action of the spring means according to the figure 8 embodiment of the inventi~on when shocked in a deflected (straight) state.
Fi~ure 10 is an oblique view in perspective partially cut away and sectioned of a corner mask suspension system showing yet another embodiment of the sprin~ means according to the invention.
Figure 11 is a side elevational view partially in section illustratin~ the action of the spring means shown by the figure 10 embodiment of the invention.
With reference to figure 1, a conjoined faceplate and shadow mask assembly 10 of a prior art color cathode ray tube is shown. A phosphor-screen-bearing faceplate 12 is revealed in a cut-away of shadow mask 14. Faceplate 12 has a rearwardly extending flan~e 16. A substantially Eectangular shadow-mask assembly is shown as comprising a frame 20 and the perforated shadow mask 14.
The shadow mask assembly 18 is suspended adjacent to but spaced apart from faceplate 12 by a plurality of leaf springs 22 spaced about the periphery of mask assembly 18 and disposed within a gap 24 between flange 16 and the mask assembly 18. A distal end of each spring 22 is detachably engaged to an associated stud 3~ protruding inwardly fro~
flange 16, with an end section anchored to the mask asse~bly.
The plane of each spring is substantially parallel to the center axis of the tube. Engagement of the distal end of each spring and associated stud is by movement of the distal end toward and away from the tube axis.
The perforations in shadQw mask 14 may, in one common confi~uration, comprise a Pattern of vertical apertures 30, shown greatly enlar~e~, with a registered pattern of phosphor - 3a -~.~ 3'~ t~, stripes 3~ deposited upon faceplate 12. The phosphors are activated by electron beams proj ected by a plurality of electron g~ms, which may comprise a triad of guns located in the neck region of the cathode ray tube envelope (not shown). The phosphors comprise red-light-emitting, green-light-emitting, and blue-light-emittin~ compositions, each of which is excited by an associated electron beam which falls upon the proper phosphor pattern in passage through the apertures 30 of shadow mask 14.
For proper reprod~lction of the color image, it is necessary that each discrete beam be incident upon its own proper stripe. Therein lies the essential function of the shadow mask which, as its narr.e connotes, "shadows" specific phosphors from the two wrong-color associated ~eams. Any rnispositioning of the shadow mask from its predetermined precise location will result in imprecise landing of the beams so that the beams may be in misregistry with the proper color-emitting phosphor. The result can be color impurities, white non-uniformities and other effec~s that degrade color television picture quality.
The misregistration of the shadow mask assembly is attributable to many factors. For example, a cGmmon cause of misregistration is due ~c, the shock-induced dislodgement or mispositioning of the mas}c assembly which may result ~hen ~5 the tube is droppedS for example, on its face. As a result of such shock, one or more of the plurality of the springs may ~e o~erstressed and take a permanent .~errant set to cause permanent mispositioning of the mask assembly.
AnoLher prohlem resulting in mask-assembly-facepl.?.tc? misregistration, is t'ne over-stressing of the :~3~

spring means that support the shadow mask by the action of automatic mask assembly inserter and removal apparatus used in production. One such apparatus is described and claimed in U.S. Patent No. 3,889,812 to BaraT.ski et al, assigned to S the assignee of this invention. The process of successive application of the color phosphors and other screening fluids to the inner surface of the faceplate requires that the shadow mask assenlbly be removed and inserted in proper registration several times. The mask assembly suspension means is, ideally, designed to ensure that the shadow mask is returned to its precise position in relation to the associated screen upon each replacement. But a problem arises in the process of removing and inserting the mask assembly as will be seen by reference to figure 2. A figurative single-lea~
support spring 22 is shown engaged to provide support and alignment of the shadow mask assembly 1~ with faceplate 12.
In this typical prior art support spring configuration, an end section 34 of spring 22 is shown as being anchored to frame 20. A section of distal end 36 of support spring 22 detachably engages an associated stud 38 protruding inwardly from flange 16 of faceplate 12.
During the production process, when it is necessary to remove the shadow ~ask assembly 18 ~rom its mating ~aceplate 1~, or ~o insert it, the plu ality of support s~rilngs 22 (referring also to figure 1) must be disengaged from the plurality OI associated studs 38. Removal ! for example, is accomplished by the aforen;entioned autcmatic apparatus ~s follows: The assembled combination cf shado~.~
mas~ ~ssembly 18 and faceplate 10 is installed in the a-tor.atic 3V machine~ Upon insertion, spring closing finger 4V, sho~n in cross section, enters the available space 24 between support spring 22 alld flange 1~. The distal end 3~ cf S'.'p l '~`t ~.3~

spring 22 is disengaged from stud 38 by the ~ovement of finger ~0 to~ard mask assembly 18, as shown by arrows 42.
The other springs supporting the mask assembly are similarly disengaged at the same time, after which the mask assembly 18 is parted from faceplate 12.
The use of such automatic apparatus greatly facilitates production. However, permanent spring distortion and consequent mask assembly mispositioning can occur as a result of its use. For example, the limit of excursion of spring closing finger 40 is shown by finger position 40B, resulting in turn in overdeflection of spring 22 as shown by spring curvature 22B. Theoretically, it should be possible to adjust the automatic apparatus so that the excursion of finger 40 is sufficient only to disengage spring 22 from stud 38 without overstressing spring 22. This "safe'~ excursion of finger 40 is shown by finger position 40A, and the resulting spring curvature by 22A. However, the dimensions of the flange 16, spring 22 (and its location) and the mask assembly 18, may each deviate somewhat from the design objectives as a result of normal manufacturing variations. As a result o~
a build-up of such tolerance variations, it is often necessary to increase the exc~rsion of finger 40 toward mask assembly 18 to the maximum position 40B shown by figure 2. Positive disengagement of spring 22 from stud 38 is thus assured as a result of this maximum excursion of finger 40; ]lowever, as a consequence spring 22 may be over-deflected, as shown by spring cur~ature 22B, and, as a result, over-stressed. T)~pically, springs are lesigned to be saely deflected to the tip contact point, point 23. The deformation resulting from deflection as shown b; spring c~rvatu.e 22B imposes ~dditional scvcre dcsi~n constrain;s anil is thlls not tolerable. The over-ctress;n~ can -6- ~

cause spring 22 tc take a permanent set as a result of deflection beyond its elastic limit. Not only is spring 22 less able to maintain shadow mask 14 in proper registration because of its permanent set, but i~ may even be so over-stressed as to be unable to sprin~ back sufficiently to reengage stud 38.
In certain types of mask suspension systems such as, for example, a corner suspension system, clearance 1i between the studs extending from the corners, and the lQ suspension spring means, may be insufficient for facile insertion and removal of the mask.
The prior art and mask-mounting spring d~sign is addressed primarily to objectives such as providing by metallic support members to reduce thermal shift, improving attachment means, reducing support spring excursion upon impact, and reducing stress--relieving of the springs due to heating during processing. To cite examples, Cooper et al in U.S. Patent No. 3,524,972 discloses bimetallic strip means with a motion-limiting bumper to prevent deformation of the support upon shock to limit lateral displacement of the ~ounting springs. Similarly, Kautz et al in U.S. Patent No.
3,743,878 discloses a spring-movement limiter means to absorb jolts which m~y force the spring beyond its elastic limit.
Other prior art is addressed to increasing the effective strength of the leaf spring; an example is Yama7aki in U.S. Patent ~o. 3,~10,990 which shows a leaf-spring cor.figuration in which the effective length of the leaf spring is shortened by that length of spring that "rolls" into contact with the support frame of tihe sh~dow masX as the spring is de~ressed.
The result of this effective spring shortening by rollinO is alleged to be a strengthening of the leaf spring agains~
deflection undcr transverse shocl;. Lindemann, in ~T.S. Patent No. 3,452,234, offers a mounting member configuration which permits removal and installation of the mask in the faceplate panel during the several processing steps. Removal is accomplished by depressing the springs toward the mask frame to release them from the mounting studs, a method which has been described in the foregoing account of the prior art.
Other Prior Art

2,755,405 Wilhelm 3~567,986 Bowes et al

3,296,477 Schrader et al 3,573,527 Hafkenscheid et al 3,417,274 Bennett et al 3,619,689 Martin 3,524,974 Kautz 3,781,583 Ornstein 3,541,373 Barr 3,873,875 Miller 3,553,517 DeBernardis 3,898,508 Pappadis Objects of the Invention It is a general object of this invention to provide improved shadow mask suspension means for cathode ray picture tubes.
It is another general object of this invention to provide mask suspension means that will effectively maintsin the shadow mask assembly and associated faceplate in proper registry.
It is a less general object to provide shadow mask suspension spring means which cannot be over-stressed in the process of shadow mask insertion and removal by automatic apparatus.
It is a more specific object to provide shadow mask assembl~l susp;-nsion spring means that provides maximum clearance for the spring-c'osing fingers of automatic mask assemhly inserter and re;no~al apparatus, and maximum clearance between studs and ~spring means.

1139~4~3 It is a specific object to provide mask assembly suspension spring means which afford enhanced immunity to shock-induced dislodgement or mispositioning of the mask assembly.
The invention is used in a rectangular-type color cathode ray picture tube including a phosphor-screen-bearing faceplate with a rearwardly extending flange and a substantially rectangular shadow mask assembly, the mask assembly being suspended adjacent to but spaced from the faceplate by a plurality of leaf springs spaced about the periphery of the mask assembly, the plane of each of which is substantially parallel to the center axis of the tube, with an end section of each anchored to the mask assembly and with a distal end of the spring detachably engaged to an associated stud protruding inwardly from the faceplate flange, the engagement being by movement of the distal end toward and away from the tube axis. Each of the springs is characterized by having an intermediate active section which in its unloaded state extends in a predetermined precurvature away frcm the mask assembly, the precurvature being such that the spring, upon deflection, self-straightens to a substantially planar configuration upon engagement with the stud wherein the mask assembly has enhanced immunity to shock-induced dislodgement or mispositioning.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with objects and advantages thereof, may best be understood, however, by reference to the following description taken in conjunction with the accompanying drawings.

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1~39~48 Description of the Preferred Embodiment Figure 3 shows an embodi~ent of the invention wherein spring 60 is shown as being disposed within a ~ap 62 between a faceplate f,lange 64 and a sha~ow mask,,frame 66 of a shadow mask assembly 65. ~n end section 68 of spring 60 is anchored to a planar side 70 of frame 66. A section of distal end 72 of s~ring 60 is detachably en~a~ed to an associated stud 74 protruding inwardly from flan~e 64. The engagement of distal end 72 witfi stud 74 is by movement of the distal end 72 toward and away from the tube axis. The detachable enga~ement ;~3~

of distal end 72 and stud 74 is by means of an aperture 82 (not visible) in distal end 72. A spring closing finger 76, consisting of a part of the automatic mask insertion and removal apparatus, is illustrated in cross-section and is S shown as being in position to move in the direction shown by arrow 78 to detach distal end 72 of spring 60 from stud 74.
The effect on spring 60 in response to the movement of spring closing finger 76 in direction 78; that is, toward the tube axis, will now be described. The force exerted by spring closing finger 76 is indicated by force Fl. Three positions of spring 60 are shown: when unloaded, precurvature 80; engaged with associated stud 74, curvature 82; and, fully deflected; that is, deflected to the planar side 70 of lS frame 66, curvature 84. The intermediate active section 86, indicated by the bracket symbol, in its unloaded state extends away from the planar side 70 cf frame 66 in a precurvature 80.
The spring of the figure 4 embodiment is characterized by having said precurvature substantially representing the negative of the equation for deflection of a cantilevered beam. As a result, if $he spring 60 is deflected to a position contiguov.s with the planar side 70 in the process of removing or inserting the mask assembly 65 from faceplate 64, the active length 86 of spring 60 approximately self-straightens without being over-stressed to make full-length substantially coplanar contact with frame 66. As a result, the mask assembly 65 can then be removed and inserted without the overstressing of spring 60 by spring cl.osing finger 76. Also, it is apparent that any further deflection at any point by a force Fl, ~2, etc~ aloilg the active portion 86 of spring 72 is pre~ented by the ~ ~ ~`3~J~

consequent supportive action whlch would. then be offered by the planar surface 70 of frame 66 to effectively prevent further deflection and possible overstressing of the spring 72.
The substantially straight-line shape defined by the active length 86 beyond the point of force Fl exerted by finger, which resuits ~rom the application of the equation, yields a secondary advantage in that the remaining portion of the intermediate active section 86 up to the distal end 72 will lie close to the planar surface 70. Thus, maximum clearance is provided between the stud 74 and the top of spring 60.
The principle of this embodiment of the inYention is illustrated by figure 4, wherein is shown in side view a single leaf spring 73. An end section 77 is shown as being anchored to the plane 79 of a table top 78 by clamp ~1. Spring 73 is characterized by having an intermediate active section 83 which, in its unloaded state, extends from plane 79 of table top 78 in a precurvature. Spring 73 is characterized by having its precurvature so defined that if spring 73 is deflected to plane 79 by a force applied at Fl, for example, the stressed part of its active length approximately self-straightens without being over-stressed. Note that due to the uniq~e initial shape of spring 73 when unloaded, the final loaded straight-line shape 75 is accomplished without exceeding the design stress limit. In the fi.nal deflected shape 75, the straight-line shape is substantially coincident with plane 79.
The aforesaid unloaded precur~at~lre 80 of spring 60 shown by figure 3 substantially represents the negati~e of the equation for the deflection of a ca~+ilevered beam, as describe(l ~ ~3 by the formula:
y=x (3L - x) F.H., where x is any selected distance along said planar side of S said frame measured from anchored section 68 of spring 60;
y is a deflection at any point x; L is the total length of said active portion; and F.~I. is the free height of spring 60, measured at the distal end of the active length.
The force Pl is shown in figure 3 as being exerted by spring closing finger 76. The spring 60 according to this invention can be loaded at any point along its active length, as i~dicated by forces F2 and F3, to deflect the spring to planar side 70. The resulting stress in the spring is not affected by the location of the applying force. In brief, the spring can be pushed down to planar side 70 at any point without overstressing, and the stressed part of the active length 86 of spring 60 would substantially define a straight line even without the presence of frame 66. The presence of frame 66 absolutely prevents further deflection, howcver, protecting the spring from overstressing as previously described.
Note however, that since the entire length of the unstressed spring 60 has a precurvature when undeflected ~precurvature 80) according to the aforesaid formula, the ~mstressed distal end 72 of spring 60 when depressed by finger 76 to curvature 54, remains so curved and produces a small residual gap ~5 between distal end 72 of the spring 60 and the plane 70 of frame 66. Si.nce this gap 85 is usually quite small~
it generall.y does not significantly detract from finger inseltio clearance. In the follo-~ing discussion, another cmboditnent cf 1~3'~

this invention is described, which, in addition to other advantages, provides for the complete elimination of the gap 85.
With reference now to figure 5, there is shown a spring configuration 88 disposed within a gap 62 between flange 64 and frame 66. The distal end 91 is shown as being detachably engaged to an associated stud 74. In this aspect of the embodiment described in the foregoing, distal end 91 of spring 88 definea a dog leg; that is, a bend at the distal end 91 directed substantially parallel to the planar side of frame 66 at an angle sufficient to establish orthogonal engagement with stud 74 without interfering with the action of the spring 88 according to this invention.
Another feature associated with this aspect is shown by figure 5 wherein a recess 67 is formed in frame 66 to receive the dog leg. Recess 67 enables the entire active section 89 of spring 88 to self-straighten to the plane of frame 66 as shown without interference from the dog leg.
(Note position of the spring indicated by the dash lines.) Another aspect of the aforedescribed invention ;s shown by the embodiment of figures 6 and 6A. It is to be noted that the end section 94 of spring 92, indicated by the bracket symbol is anchored to planar side 70 of frame 65 and is substa-ntially flat. The distal end 96 of spring 92 (indicated by the bracket), which is designed to be detachably engaged to an associated stud (not shown), is also flat. Ar. intermediate active section 98, in its unloaded state extends from the planar side 70 of frame 66 in a circular arc. The circular arc portion and flat distal end 96 of spring 9 approximates the negative of the e~uation for deflection of a cant;lcvered beam.

1 ~

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As a result, if spring 92 is deflected to the planar side 70 of frame 66 in the process of removing or inserting the mask assembly, the stressed part of its active length approximately self-straightens contiguous to the frame 66 without being overstressed. If deflected far enough, the spring will make substantially full-length coplanar contact with the frame 66, whereby the consequent supportive action of frame 66 will prevent further deflection and possible over-stressing of the spring.
The radius R of the circular arc of the intermediate acti~e section 98, and the length of the distal end 96, are chosen to closely approximate the shape defined by the afore-mentioned equation. T t has been shown in practice that such an approximation can easily be made without apprecia~ly affecting the self-straightening features and the associated overstressing protection provided according to this embodiment of the inventio~.
With regard to the shape of the spring according to the approximation, the radius R is in the range of ~ 1/2 to 6 1/2 inches, and the distal end 96 comprises approximately 50 percent of the active length for experimental springs in this configuration. This embodiment of spring 92 shown by .
figure 6 is considered to be less expensive to manufacture, while substantially accomplishing the ob~ects of the invention.
An additional advantage of such an approximation, as shown by figure 6A, is that the distal end 96 being defined as a straight line in the unloaded s~ate in this embodiment, remains straight after spring 92 is depressed by a spring-closing finger 100. allowing the distal end 96 of spring 92 to move to the plane ~0 of frame 66. The distal end 96 is able to lie substantiall~ flat because its normal straight line configuration is unstressed during depression an~ therefore remains straight~

Finger lO0 is normally located close enough to the distal end to lie over the flat portion of the spring 92, causing the distal end 96 also to lie substan~ially flat as shown and contiguous to plane 70 of frame 66. As a result, maximum possible clearance is provided when the mask assembly is removed or inserted.
The distal end 96 o spring 92 shown by ~igure 6 may also define a dog leg as defined heretofore in connection with figure 5. Similarly, as described heretofore and as shown by figure 5, a recess may be formed in frame 66 to receive the dog leg.
A major problem is the effect of shock in the direction of tube axis which results when a CRT is dropped on its face, for example. In consequence, one or more of 1~ the support springs may be deflected beyond the yield point of the material of the spring; that is, beyond the elastic limit, and the spring will take a final aberrant set. As a result of this shock-induced dislodgement of the mask, the mask apertures will no longer be in registration with the associated phosphor elementc on the faceplate.
The effect of impact on a normally straight suspension spring when it is deflected into a curved configuration is shown diagrammatically by figure 7. Spring 110 is schematically represented as an initially straight spring 111, indicated by the dash line configuration. Spring 110 is curved as indicated as a result of force Fl and represents a spring means cur~red as a result of engagement with an associated stud. Spring 11~ should be viewed as being anchored at end 112 and engaging a faceplate stud at its opposite, or "distal" end. The plane 113 o spring 110 when in its straight-line configuration 111, is indicated. ~2 represcnts ~ }~3~

an additional impulsive force on spring 110 as a result of impact, and the dash-line spring configuration 114 indicates a deflection in the torsional mode. The twist, indicated by arrows 116, is the product of a force-couple S (moment) which is equal to F2 times x, with x representing the maximum twisting moment arm. The presence of this twisting moment appreciably reduces the resistance of the spring to impulsive force F2 and a twisting ~torsional) failure may occur. The magnitude of the twisting of spring 110, as indicated by configuration 114, can be such that spring 110 can be deflected beyond its elastic limit and take a permanent aberrant set.
Figure 8 shows an embodiment of the in~ention ~herein spring 122 provides a solution to the problem of the effect of the aforedescribed shock. Spring 122 is shown as ~eing disposed between a faceplate flange 124 and a shadow mask frame 126 of shadow mask assembly 128. Distal end 130 of spring 122 is shown as being engaged to a stud 134. Spring 122 is characterized by having in its unloaded state a pr~-determined precurvature 132 as indicated by dash-line configuration, away from mask assembly 128. Precurvature 132 is such that spring 122, upon deflection, self-straiglltens to the substantially planar configuration shown upon engagement Wit}l stud 134. .~s a result of this configuration, mask assembl 128 has enhanced immuni~y to shock-induced dislod~ement or mispositioning.
Figure 9 shows diagrammatical]y the action of spring 122 of ~igure 8 in resisting shock. rhe predetermilled curvature 132 away fr~im the associated s';ladow mask assen~ is in;licated.
Precurvaturc 132 accordin.g to the invention is such that sprin~ ]22, ul~on deflection~ self-straiglltens to t!e subatantiai~;

planar confi~uration indicated upon engagement with an associated stud. F2 represents the aforedescribed impulsive force and x represents the maximum twisting moment arm. It will ~e seen -that spring 122, because of its substantially planar configuration according to the invention, remains in its plane 126 upon application of impulsive force F2. in consequence, x is equal to 0, and no moment capable of twisting spring 122 will be produced. Any deflection y that occurs is solely the result of edge-bending~ and is in consequence so small as to be negligible in its effect.
Thus the mask assembly has enhanced immunity to shock induced dislo~dgement or mispositioning because of the substantially planar configuration of spring 122 when engaged with the associated stud.
It is contemplated that in accordance with the invention, the predetermined precurvature 132 of spring 122 could be such that rather than self-straightening upon engagement (for enhanced shock immunity) or at a limit position adjacent the mask assembly as in the figures 4-6 embodiment, (for maximum mask assembly-f~ceplate clearance), it could self-straighten at some intermediate position representing a compromise between optimum shock immunity and optimum clearance.
Fi~ures lO and 11 depict embodiments of my invention incorporated in ihe mask-suspension system of Palac and Dougherty described and claimed in referent copending applicatjon Serial No. (D3090). The system is improved by the addition of a predetermined precurvature of the mask assembly suspension spl3ngs ~ccording to the presellt invention, as will be described.

-1~-` ~igure 10 shows one of four corner sections of a glass faceplate 136 having a rearwardly extending skirt 138. A corner mask suspension device 140 (one of four comprising a mask suspension system for four-corner diagonal mounting), provides for rigidly and stably suspending a substantially rectangular, frameless shadow mask 142 adjacent to but apart from faceplate 136. Mask 142 has a rearwardly extending skirt 144 and an integral flange 146 which extends radially outward. Each mask suspension device 140 comprises a pin 148 affixed to the faceplate s~irt 138, and a leaf spring 150 for detachably interconnecting the corner of mask 142 shown to pin l48.
Means for mounting spring 150 on masX 142 is shown in this embodiment as comprising a bracket 152 having two arms 152A
and 152B for attachment to mask 142 and spring 150. Spring 150 is mounted on mask diagonal 149 and normal to diagonal 149 such that spring 150 extends rearwardly away from the central section of faceplate 136. Where spring 150 is deflected, the distal end 156 travels in an arc inwardly toward the faceplate center axis, all as disclosed and claimed in referent copending application Serial No. (D3090).
The action of leaf spring 150 according to the present invention is described as follows. ~Please refer to figure 11 whicll comprises a side elevational view of a fragment o the figure 10 faceplate-shadow mask assembly.) Spring 150 is characterized by having an intermediate active section 158, indicated by the bracket symbol, which in the unlo~ded state of spring 150 extends a~ay from mask 142 in a prede~er]nined precurvature, 160 indi;:ated by the dash line configuration. Spring 150 is def'ectable through a ~,9 fir`st position, indicated by the solid line configuration of spring 150, wherein it is engaged with pin 148. Spring lS0 is further deflectable to a limit position 162 toward mask 150 wherein spring lS0 provides maximum clearance between pin 148 and all portions of spring 150. The precurvature of spring 150 is such that, according to the invention, the spring upon deflection self-straightens at some compromise position intermediate to the first position and the limit positiGn, and in the limit position, provides maximum clearance between the pin 148 and all portions of spring 150, as shown.
While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its bro~der aspects, and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.

Claims (16)

I CLAIM:

1. In a rectangular-type color cathode ray picture tube including a phosphor-screen-bearing faceplate with a rearwardly extending flange and a substantially rectangular shadow mask assembly, said mask assembly being suspended adjacent to but spaced from said faceplate by a plurality of leaf springs spaced about the periphery of said mask assembly, the plane of each of which is substantially parallel to the center axis of said tube, with an end section of each spring anchored to said mask assembly and with a distal end of said spring detachably engaged to an associated stud protruding inwardly from said faceplate flange, said engagement being by movement of said distal end toward and away from said tube axis, each of said springs being characterized by having an intermediate active section which in its unloaded state extends away from said mask assembly in a predetermined precurvature, said spring being deflectable through a first position wherein it is engaged with said stud, to a limit position toward said mask assembly wherein said spring provides maximum clearance between said stud and all portions of said spring for facile mask assembly insertion and removal, said precurvature being such that said spring, upon deflection;
self-straightens to a substantially planar configuration either upon engagement with said stud wherein said mask assembly has enhanced immunity to shock-induced dislodgement or mispositioning or the spring approximately self-straightens at said limit position preventing possible overstressing of said spring, or at a compromise position intermediate said first position and said limit position.

2. In a rectangular-type color cathode ray picture tube including a phosphor-screen-bearing faceplate with a rearwardly extending flange and a substantially rectangular shadow mask assembly comprising a frame supporting a perforated shadow mask, said assembly being suspended adjacent to but spaced from said faceplate by a plurality of leaf springs spaced about the periphery of said mask assembly, the plane of each of which is substantially parallel to the center axis of said tube, with an end section of each spring anchored to a planar side of said frame of said mask assembly and with a distal end of said spring detachably engaged to an associated stud protruding inwardly from said faceplate flanges said engagement being by movement of said distal end toward and away from said tube axis, each of said springs being characterized by having an intermediate active section which, in its unloaded state extends in a predetermined precurvature away from said mask assembly, said precurvature substantially representing the negative of the equation for a cantilevered beam, said spring being deflectable through a first position wherein it is engaged with said stud, to a limit position toward said mask assembly wherein said spring provides maximum clearance between said stud and all portions of said spring for mask assembly insertion and removal, said precurvature being such that said spring, upon deflection, self-straightens to a substantially planar configuration either upon engagement with said stud wherein said mask assembly has enhanced immunity to shock-induced dislodgement or mispositioning; or the spring approximately self-straightens at said limit position preventing possible overstressing of said spring, or at a compromise position intermediate said first position and said limit position.

3. The spring defined by claim 2 wherein said precurvature is described by the formula:

where x is any selected distance along said planar side of said frame measured from said anchored section of said spring; y is a deflection at any point x; L is the total length of said active section; and F.H. is the free height of said spring measured at the distal end of the active length.

4. For use in a rectangular-type cathode ray picture tube having an envelope including a phosphor-screen-bearing faceplate with a rearwardly extending flange, and a substantially rectangular shadow mask assembly- comprising a frame supporting a perforated shadow mask, the assembly being suspended adjacent to but spaced from said faceplate by a plurality of leaf springs spaced about the periphery of said frame and disposed within a gap between said flange and said frame, with the plane of each spring substantially parallel to the center axis of said tube, with an end section of each anchored to a planar side of said frame and with a distal end detachably engaged to an associated stud protruding inwardly from said flange, said engagement being by movement of said distal end toward and away from said tube axis, each of said springs being characterized by having an intermediate active section which, in its unloaded state, extends away from said planar side of said frame in a precurvature so defined that if said spring is deflected to a position contiguous to said planar side of said frame in the process of removing or installing said mask assembly the active length of said spring approximately self-straightens contiguous to said planar side of said frame without being overstressed, whereby the consequent supportive action of said frame prevents further deflection and possible overstressing of said spring.

5. The spring according to claim 4 wherein a section of said distal end defines a dog leg; that is, a bend at said distal end directed parallel to said planar side of said frame to establish orthogonal engagement with said stud.

6. The apparatus according to claim 5 wherein a recess is formed in said frame to receive said dog leg to enable said active section of said spring to approximately self-straighten to said planar side without interference from said dog leg.

7. For use in a rectangular-type color cathode ray picture tube having an envelope including a phosphor-screen-bearing faceplate with a rearwardly extending flange, and a substantially rectangular shadow mask assembly comprising a frame supporting a perforated shadow mask, the assembly being suspended adjacent to but spaced from said faceplate by a plurality of leaf springs spaced about the periphery of said frame, with the plane of each spring substantially parallel to the center axis of said tube, with an end section of each spring anchored to a planar side of said frame and with 2 distal end detachably engaged to an associated stud protruding inwardly from said flange, said engagement being by movement of said distal end toward and away from said tube axis, with each of said springs being characterized by having an intermediate active section which, in its unloaded state, extends away from said planar side of said frame in a precurvature substantially representing the negative of the equation for deflection of a cantilevered beam such that if said spring is deflected to a position contiguous to said planar side of said frame in the process of removing or installing said mask assembly, the stressed part of its active length approximately self-straightens contiguous to said frame without being overstressed to make full-length substantially coplanar contact with said frame, whereby the consequent supportive action of said frame prevents further deflection and possible overstressing of said spring.

8. The spring means defined by claim 7 wherein said precurvature is described by the formula:

where x is any selected distance along said planar side of said frame measured from said anchored section of said spring; y is a deflection at any point x; L is the total length of said active section; and F.H. is the free height of said spring measured at the distal end of the active length.

9. The spring according to claim 7 wherein a section of said distal end defines a dog leg; that is, a bend at said distal end directed parallel to said planar side of said frame to establish orthogonal engagement with said stud.

10. The apparatus according to claim 9 wherein a recess is formed in said frame to receive said dog leg to enable said active section of said spring to substantially self-straighten to said planar side without interference from said dog leg.

11. For use in a rectangular-type color cathode ray picture tube having an envelope including a phosphor-screen-bearing faceplate with a rearwardly extending flange, and a substantially rectangular shadow mask assembly comprising a frame supporting a perforated shadow mask, the assembly being suspended adjacent to but spaced from said faceplate by a plurality of leaf springs spaced about the periphery of said frame and disposed within a gap between said flange and said frame, with the plane of each spring substantially parallel to the center axis of said tube, with an end section of each anchored to a planar side of said frame and with a distal end detachably engaged to an associated stud protruding inwardly from said flange, said engagement being by movement of said distal end toward and away from said tube axis, with each of said springs being characterized by having said end section anchored to said frame and said distal end substantially flat, and having an intermediate active section which, in its unloaded state, extends away from said planar side of said frame in a circular arc, said spring being characterized by said circular arc portion and said flat distal end approximating the negative of the equation for deflection of a cantilevered beam such that if said spring is deflected to said planar side of said frame in the process of removing or inserting said mask assembly, the stressed part of its active length approximately self-straightens contiguous to said frame without being over-stressed to make substantially full-length coplanar contact with said frame, whereby the consequent supportive action of said frame prevents further deflection and possible over-stressing of said spring.

12. The spring according to claim 11 wherein the radius of said circular arc portion is a radius in a range of 5 1/2 to 6 1/2 inches.

13. The spring according to claim 11 wherein a section of said flat distal end defines a dog leg; that is, a bend at said distal end directed parallel to said planar side of said frame to establish orthogonal engagement with said stud.

14. The apparatus according to claim 13 wherein a recess is formed in said frame to receive said dog leg to enable said intermediate section of said spring to approximately self-straighten contiguous to said planar side without interference from said dog leg.

15. In a rectangular-type color cathode ray picture tube including a phosphor-screen-bearing faceplate with a rearwardly extending flange and a substantially rectangular shadow mask assembly, said mask assembly being suspended adjacent to but spaced from said faceplate by a plurality of leaf springs spaced about the periphery of said mask assembly, the plane of each of which is substantially parallel to the center axis of said tube, with an end section of each anchored to said mask assembly and with a distal end of said spring detachably engaged to an associated stud protruding inwardly from said faceplate flange, said engagement being by movement of said distal end toward and away from said tube axis, each of said springs being characterized by having an intermediate active section which in its unloaded state extends in a predetermined precurvature away from said mask assembly, said precurvature being such that said spring, upon deflection, self-straightens to a substantially planar configuration upon engagement with said stud wherein said mask assembly has enhanced immunity to shock-induced dislodgement or mispositioning.

16. In a shadow-mask-type color cathode ray tube, a mask-faceplate assembly including:
a glass faceplate having a dished central section and a rearwardly extending skirt;
a substantially rectangular, frameless shadow mask having a dished perforate central section and a rearwardly extending skirt, said mask being relatively stiff about its major and minor axes, but torsionally flexible and unstable with respect to its diagonals, said mask having an integral flange extending radially outwardly from the rear edge of said mask skirt to serve as an electron beam shield and to provide added stiffness for said mask; and a corner mask suspension system for rigidly and stably suspending said mask with said dished central section spaced from said central section of said faceplate, consisting of four suspension devices, one at each corner of the mask, each device comprising:
a pin affixed to said faceplate skirt on the associated faceplate diagonal and arranged to extend radially inwardly along said diagonal;
a leaf spring for detachably interconnecting said mask corner to said pin on said faceplate skirt, means for mounting said spring on said mask diagonal and normal to said diagonal such that said spring extends rearwardly away from said central section of said faceplate, and such that when said spring is deflected, the distal end thereof travels on an arc inwardly toward the faceplate central axis, an improvement wherein each of said leaf springs is characterized by having an intermediate active section which in its unloaded state extends away from said mask in a predetermined precurvature said spring being deflectable through a first position wherein it is engaged with said pin to a limit position toward said mask wherein said spring provides maximum clearance between said pin and all portions of said spring for facile mask insertion and removal, said precurvature being such that said spring, upon deflection, self-straightens to a substantially planar configuration either upon engagement with said pin wherein said mask has enhanced immunity to shock-induced dislodgement or mispositioning; or the spring self-straightens at said limit position or at a compromise position intermediate said first position and said limit position to provide maximum clearance between said pin and all portions of said spring.