US3431454A - Cathode-ray tube magnetic shield and tube mount - Google Patents

Description

March 4, 1969 M. E. SANDERS 3,431,454

CATHODE-RAY TUBE MAGNETIC SHIELD AND TUBE MOUNT Filed July 51, 1967 F! G. i 2

Sheet of 33 Inventor arshall ESanders March 4, 1969 M. E. SANDERS 3,431,454

CATHODERAY TUBE MAGNETIC SHIELD AND TUBE MOUNT Filed July 51, 1267 Sheet 3 of s T 27 2 4e 32 33- I 28 25 33 L l 0?}? 32 1;. 42 l I, 29 m .415; 11.; I 5 I E I" 39 '37 ll u \l 28 "Inventor Marshall E. Sanders ATrofney March 4, W69 E. SANDERS 3,431,454

CATHODE-RAY TUBE MAGNETIC SHIELD AND TUBE MOUNT Filed July 31, 1967 Sheet 3 of 5 Inventor Marshall E. Sanders I By M Uited States Patent aware Filed July 31, 1967, Ser. No. 657,257 US. on. s1s s Int. Cl. H011 29/06 Claims ABSTRACT OF THE DISCLOSURE A magnetic shield and mounting arrangement for a cathode-ray tube includes a support member having an opening that conforms substantially to the contour of the display screen of the tube. A plurality of flexible pieces, formed of magnetic material and dimensioned and shaped to form a closed magnetic circuit when arranged in overlapping relation, are secured to the support to define therewith a chamber for receiving the tube with its screen exposed through the opening. A lock releasably clamps the magnetic pieces in such overlapping relation to hold the tube fixedly in position within the chamber while at the same time shielding it from interfering external magnetic fields.

This invention relates in general to color television receivers and more particularly to a magnetic shield and mounting arrangement for the color cathode-ray tube thereof.

A cathode-ray tube of the type employed in conventional color receivers comprises an array of electron guns which generate and direct a trio of electron beams towards the screen or image area of the tube. This screen comprises an ordered grouping of red, green and blue phosphor dots arranged in a plurality of color triads, each having a red, a green and a blue phosphor dot. Disposed adjacent the screen is a mask having a like plurality of apertures, one in registration with each color triad.

In the ideal situation the three electron beams converge in the plane of the aperture mask and impinge only upon their assigned phosphor dots. However, due to the influence of the earths magnetic field, as well as extraneous magnetic fields emanating from nearby electrical apparatus, the beams may be displaced from their intended paths. When this is experienced the electron beams become misregistered with respect to the phosphor dots and in severe cases may even have access to color dots other than those assigned to them, respectively, and in this manner color impurity is introduced.

Corrective measures employed to protect the beams from interfering fields basically contemplate surrounding that portion of the tube envelope adjacent the shadow mask with a shield of magnetic material. A shield is constructed of a high permeability material and constitutes a magnetic conductor that presents a path of low reluctance to an interfering magnetic field, thus shunting that field around the beams. As a result, the area encompassed by the shield is effectively protected against interfering fields and misregistration is avoided. For reasons of economy, however, a shield of relatively low permeability material is frequently used and is provided with a degaussing coil. It is the function of this coil to apply an alternating electro-magnetic field to the shield and to the shadow mask encircled by the shield to establish the magnetic domains of the shield and the mask in a random pattern and thereby cancel any remanent magnetization attributable to the past effect of a magnetic field. Thus conditioned, these elements can now serve as improved magnetic shunts for any interfering magnetic field encountered thereafter.

Another important consideration for the shield arrangement of a color tube is the facility with which the shield may be assembled and disassembled, recognizing that the tube may require replacement. Since the color tube is not only heavier than its monochrome counterpart of like dimensions but must also support convergence and purity correction devices, in addition to the yoke, the prior art has invariably resorted to cumbersome and expensive arrangements in an effort to meet all the mechanical and magnetic considerations.

It is therefore an object of the invention to provide an improved magnetic shield and mounting arrangement for a color cathode-ray tube.

It is a specific object of the invention to provide a magnetic shield apparatus which also serves to support the cathode-ray tube within the receiver.

It is another object of the invention to provide a shield and mounting arrangement for a cathode-ray tube which simplifies the task of installing and removing the tube from a color television receiver.

It is a still further object of the invention to provide a shield and mounting arrangement which efiects significant economies over prior arrangements.

In accordance with the invention, a magnetic shield and mounting arrangement for a cathode-ray tube having an envelope comprising a funnel section terminated by a display screen comprises a support member having an opening that conforms substantially to the contour of the screen. The shield is formed of magnetic material and has a base portion and a plurality of flexible extension portions extending from the base portion of dimensions and such configuration as to form, collectively a closed magnetic circuit about the funnel section when arranged in a predetermined pattern. The base portion is secured to the support member to define, in conjunction therewith, a chamber for receiving the tube and for present ing its screen to the opening in the support. Finally, means are provided for releasably interlocking selected ones of the shield extension portions across the funnel section to others of the extension portions to shape the entrance of the chamber so that its principal dimensions are less than those of the screen and also to conform the shield portions to the aforementioned pattern about the funnel section of the tube. Locked in this manner, the shield portions clamp the tube fixedly in position within the chamber while at the same time shielding it from interfering magnetic fields external to the chamber.

The features of this invention which are believed to be novel are set forth with particularity in the appended claims. The organization and manner of operation of 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 the several figures of which like reference numerals identify like elements, and in which:

FIGURE 1 is a side view of a television receiver, partly broken away, illustrating one embodiment of the invention;

FIGURE 2 is a perspective view of the magnetic shield and tube mounting structure of the receiver of FIG- URE 1;

FIGURE 3 is a plan view of a magnetic shield element of the type employed in the apparatus shown in FIG- URES 1 and 2;

FIGURE 4 is a sectional view taken along lines 4-4 of FIGURE 1;

FIGURE 5 is a sectional view taken along lines 55 of FIGURE 4;

FIGURE 6 is a plan view of a unitary version of the shield and tube mount structure;

FIGURE 7 is a perspective view of another embodiment of the invention;

FIGURE 8 is an exploded perspective view of still another embodiment of the invention; and

FIGURE 9 is a sectional view taken along lines 99 in FIGURE 8.

The receiver 19 of FIGURE 1 includes a color cathoderay tube E the envelope of which comprises a neck section 12 and a bell section 13 that terminates in an image area or display screen 14. An apertured shadow mask 15 is mounted within bell section 13 immediately behind the screen while a purity device 16, convergence apparatus 17 and a deflection yoke 18 are mounted upon the neck with the yoke seated against the bell portion of the tube. A trio of electron guns, the structure of which is not detailed, is supported within the neck section. The structures of the tube and its accessories are entirely concentional and need not be described further.

In accordance with the invention a single arrangement serves concurrently as a magnetic shield and mounting arrangement for cathode-ray tube 11. It comprises a support member, which in the embodiment of FIGURES 15, is the customary escutcheon 20 having an opening 21 that conforms substantially to the contour of screen 14 of the tube. As seen in FIGURE 2, this embodiment features a pair of flexible pieces or elements Q, Q comprising a plurality of portions 22a22d and 24a-24d, respectively, and formed of magnetic material. A plan view of shield piece 22, which is identical in all respect to element E, is shown in FIGURE 3. It has a lower panel or skirt 22e from which extend end portions 22a and 22d. Between these end portions are intermediate parts 22b and 22c extending at approximatel 45 angles relative to skirt 22a and providing openings or cut away sections in conjunction with ends 22a and 22d. While shield pieces a, 2% are disclosed as being identical, this is not essential in practicing the invention, although the economies of such a construction are obvious. Moreover, the particular configuration or contour of shield portions 22ad and 24a-a' is not critical so long as they satisfy certain requirements of the installation. For example, the shield elements are scalloped or relieved in some fashion in order to permit them to most readily fold over and snugly enclose the bell section of the tube envelope in the manner shown in FIGURES l and 4. Moreover, if the shield extends along the tube envelope as illustrated it is necessary to provide a recess to accommodate the anode terminal button 26. A collar 27 of insulating material may be secured to the rim of this recess to aiford additional protection against high voltage fiashover. Further the dimensions and configurations of the extension portions of shield pieces 22, E are such as to form a closed magnetic circuit when arranged in the pattern shown in FIGURE 1. That is to say, when the shield pieces are in place about tube 11 the intermediate parts foldover or overlap their end parts while the end parts of both pieces 2 2, g t similarly overlap one another. In order to prevent scratching the glass envelope, those edges of the shield which come in contact with the envelope are fitted with strips 29 of tape or other protective material.

The lower extremities or skirts 22c, 24c of the shield pieces preferably have sufiicient depth to overlap the shadow mask support frame 19, see FIGURE 1, when the shield is installed in order to improve the magnetic coupling between the shield and the mask. Additionally, shield pieces 2 2 E include one or more buttons for spacing the edges of the shield portions from the surface of the tube envelope in order to accommodate a pair of degaussing coils 42, 44.

For the purpose of installing the shield, means are pr vided for securing shield pieces 12, E to escutcheon 20 and when so installed they define, in conjunction with the escutcheon, a chamber for receiving tube 11 and for presenting its screen 14 to opening 21 in the escutcheon. To this end, see FIGURES 2 and 3, shield elements Q, E are fitted with L-shaped brackets 28 while escutcheon 20 is provided with four mounting posts 30 having internally threaded channels to receive conventional screw type fasteners. Posts 30 are positioned around the perimeter of escutcheon opening 21, preferably at the corners thereof. Interposed bet-ween posts 30, and likewise arranged about the perimeter of opening 21, are a plurality of alignment pegs 32 each having a rubber sleeve 0r bumper 33. Pegs 32 serve to shape and position shield pieces Q, g3 in forming the cathode-ray tube receiving chamber. The pegs further contribute a measure of support for the tube by adding mechanical strength or stiffening to shield pieces E, 22 which are preferably formed of flexible material so that they may be easily bent into the required configuration for installation.

As best seen in FIGURE 2 the shield is installed by simply folding or curving shield pieces Q, 2 1 to match the contour of opening 21, positioning the skirt portions 22e, 24e against the bumpers 33 with shield end portions 220:, 22d overlapping end portions 24:1, 24:1, respectively, and then securing brackets 28 to posts 30 by threaded fasteners. Having secured pieces 2, 2;4 in position they define the aforesaid tube receiving chamber as clearly illustrated in this figure.

The tube, once admitted into this chamber, is retained there by means releasa'bly locking the shield pieces or portions about the envelope in order to shape the entrance of the chamber so that its principal dimensions are less than those of the tube screen as well as to conform the shield portions to a closed magnetic circuit. More particularly, shield portions 22b, 2412 have latches 35 riveted thereon while shield potions 22c, 24c carry elongated straps 36. Each of straps 36 terminates in an upturned tab 37 threaded to receive a tie bolt 38 while each of latches 35 includes a slotted shoulder or bifurcation 39 for releasably captivating strap tab 37. Each latch 35 further includes an apertured bight 40 that receives the shank of a tie bolt 38 and serves as an arrest for the head of the bolt.

A pair of degaussing coils are associated with the shield, being mounted upon oppositely disposed portions thereof and, when energized, are electromagnetically coupled to the shield. Specifically, coil 42 encircles end portions 22a, 24d while a second coil 44 encloses end portions 24a, 22d. These coils may be connected to a source of alternating electric potential (not shown) to be temporarily energized when the receiver is turned on. Degaussing circuits are exceedingly well known and, since they constitute no part of the subject invention they have not been shown.

After the shield pieces 2 2, 22 have been secured to escutcheon 20 by fasteners that screw brackets 28 to mounting posts 30, and after coils 42, 44 have been positioned in place as illustrated in FIGURE 2, the chamber defined by the shield and escutcheon is ready to receive tube 11. The principal dimensions of the chamber, e.g., its length and width, exceed those of the tube which is inserted through the open mouth of the chamber and advanced until its image screen is framed by opening 21 of the escutcheon. Shield portions 22a, 24d and 22d, 24a: are now folded against diametrically opposed sections of the bell of the tube and the other shield extensions are likewise folded down toward the bell of the tube sufficiently to permit the tabs 37 of straps 36 to be inserted behind the shoulders 39 of latches 35. Tie bolts 38 are inserted through bights 40 to thread into tabs 37 and are then drawn up to complete folding of the shield parts upon one another as shown in FIGURE 1. This, of course, closes the mouth of the chamber about. the envelope or, shapes the entrance of the chamber so that its principal dimensions, as seen in FIGURE 4, are now less than those of image screen 14. In this manner, the shield rcleasably clamps tube l l against escutcheon 20 with its screen in registration with opening 21. Moreover, when the shield portions are arranged in this pattern, a closed magnetic circuit is completed to protect against the adverse influence of magnetic fields external to the shield.

The shield, as well as the shadow mask, are degaussed by subjecting them to an alternating electromagnetic field generated by coils 42, 44. It is recognized that degaussing can also be satisfactorily achieved by mounting coils 42, 44 upon the top and bottom as distinguished from the side portions of the shield. The degaussing COils are energized in a manner well-known in the art to demagnetize the shield, the shadow mask, the escutcheon and any other metallic elements in the vicinity of the shield.

The described two-piece shield construction has been successfully employed in production models of color television receivers in which shield elements gg, 2 4 were constructed of .018" silicon steel (Electrical Grade) M-36 (#1 Core Plate) and each of degaussing coils 42, 44 eifectively constituted approximately 50 turns of #24 copper wire. In these production receivers shield ele ments 2, 2;4 constituted the sole means for clamping a LP22 cathode-ray tube to the escutcheon. In addition to mechanically supporting the tube, elements 2;, E also served to shield the tube from interfering magnetic fields. The subject arrangement thus produced a color cathoderay tube mount which dispensed with the expensive and cumbersome harnesses, springs and other trappings characteristic of prior art practice while, at the same time, simplified the mounting as well as removal of the tube. However, a shield formed of a single strip of magnetic material may be employed with success, the only limitation being the practical consideration of what length of shield element can efiiciently be handled by an assembler. The unitary shield element of FIGURE 6 constitutes in effect, two shield elements of the type shown in FIGURE 3, formed from a single piece of material. Since the shield portions are identical to those of FIGURE 3 they are identified by the same reference numerals. The straps and latches are likewise identical to those employed in the principal embodiment and thus retain their designations. A unitary shield arrangement of this type finds particular application to the smaller dimensioned color reproducing cathode-ray tube, for example, the 11SP22, an 11" tube, since the overall length of a shield for such a tube would not pose a handling problem for the assembler.

Alternatively, the shield arrangement can be formed of more than two elements. For example, the embodiment shown in FIGURE 7 comprises four separate shield elements 5760 each independently secured to escutcheon 20. For reasons of economy elements 57, 59 are of identical configuration, elements 58, 60 may also be identically formed. Except for the angled corner brackets 61 all other constituents of the FIGURE 7 shield and mount are the same as those employed in the principal embodiment of FIGURES 1-5. This arrangement finds particular application in receivers employing the larger cathode-ray tubes where a unitary or even a two piece shield large enough to encompass the tube envelope would be unwieldy and cumbersome to handle. The GP22, a 23" tube, and the 21GP22 a 21" tube, are examples of such tubes.

There are applications where it may not be feasible to secure the magnetic shield and the tube directly to the escutcheon of the receiver. For example, in the embodiment of FIGURES 8 and 9, the shield is afiixed to a support member 65. More particularly, the shield in this instance comprises two elements 2, gag of the type employed in the FIGURES 1-4 embodiment and the support member 65 comprises a dished pan having an opening conforming substantially to the perimeter of the cathoderay tube screen. The shield elements Q, E are riveted or staked to the side walls of pan 65. A pad 66 is afiixed to the inside of each corner of the pan to cushion the tube envelope, see FIGURE 9. The tube is inserted in pan 65 and the end portions of the shield elements are folded down and side portions folded over them and clamped in the fashion previously discussed in respect to the principal embodiment of FIGURES 1-4. It should be noted that the shield construction for this embodiment is not critical, that is, a four-piece or even a one-piece shield member can be substituted for the two-piece apparatus shown. The pan and tube assembly is then attached to the posts 30 of escutcheon 20 or to some other structure in the television receiver cabinet. Employing pan 65 as a support member has several advantages. It afiordsthe designer the freedom to mount the tube to a portion of the television cabinet other than the escutcheon. Additionally, it may be that the cabinet design does not call for an escutcheon, or, it may call for one that is simply a decorative overlay not having the structural strength to support the tube.

In summary, the subject invention contemplates a magnetic shield and mounting arrangement for a color cathode-ray tube in a construction wherein the elements of the magnetic shield function not only as a shield but also as the sole means for mounting the cathode-ray tube to the escutcheon or other support member. The disclosed arrangement is characterized by a simplicity of construction and an economy of parts. Moreover, this construction not only facilitates assembly of the television receiver but greatly simplifies the task of removing the cathode-ray tube should replacement be required.

While particular embodiments of the present 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 broader aspects. Accordingly, 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.

I claim:

1. A magnetic shield and mounting arrangement for a cathode-ray tube having an envelope comprising a funnel section terminated by a display screen, said arrangement comprising:

a support member having an opening conforming substantially to the contour of said screen;

a shield formed of magnetic material comprising a base portion and a plurality of flexible extension portions extending from said base portion, said shield portions having relative dimensions and configuration to form, collectively, a closed magnetic circuit about said funnel section when arranged in a predetermined pattern;

means for securing said shield base portion to said support member to define, in conjunction therewith, a chamber for receiving said tube and for presenting the screen thereof to said opening;

and means for releasably interlocking selected ones of said shield extension portions across said funnel section to others of said extension portions to shape the entrance of said chamber to have principal dimensions less than those of said screen and also to conform said shield portions to said predetermined pattern about said funnel section of said tube to clamp said cathode-ray tube fixedly in positon within said chamber While shielding said tube from interfering magnetic fields external to said chamber.

2. A magnetic shield and mounting arrangement as set forth in claim 1 in which said flexible shield portions are formed from a single strip of magnetic material.

3. A magnetic shield and mounting arrangement as set forth in claim 1 in which said support member comprises an escutcheon for a television receiver cabinet.

.4. A magnetic shield and mounting arrangement as set forth in claim 1 in which said shield comprises two similarly configurated elements.

5. A magnetic shield and mounting arrangement as set forth in claim 1 which further includes degaussing field generating means disposed in magnetic coupling relation to said shield for demagnetizing metallic portions of said tube and said support member.

6. A magnetic shield and mounting arrangement as set forth in claim 4 in which each said shield element comprises end portions and intermediate portions and said closed magnetic circuit is formed by overlapping the end portions of one said element with the end portions of said other element and by overlapping each said intermediate portion with its own adjacent end portion.

7. A magnetic shield and mounting arrangement as set forth in claim 1 in which said shield constitutes the sole means for securing said tube to said support member.

8. A magnetic shield and mounting arrangement as set forth in claim 1 further including a plurality of shield shaping and stiffening members disposed about said opening in said support member.

9. A magnetic shield and mounting arrangement for a cathode-ray tube having an envelope comprising a funnel section and a contiguous panel section terminated by a display screen, said arrangement comprising:

a support member having an opening conforming substantially to the contour of said screen;

a wrap-around shield of fiat-formed magnetic material comprising a base portion encircling said panel section and a plurality of flexible extension portions extending from said base portion into proximity with said funnel section;

means for securing said shield base portion to said support member to define, in conjunction therewith,

a chamber for receiving said tube and for presenting the screen thereof to said opening;

and means for releasably interlocking selected pairs of said extension portions to each other across said funnel section to clamp said cathode-ray tube fixedly in position within said chamber while shielding said tube from interfering magnetic fields external to said chamber.

10. A magnetic shield and mounting arrangement as set forth in claim 9 in which said interlocking means includes adjustment for conforming said extension portions to the contour of said tube funnel section.

References Cited UNITED STATES PATENTS 2,721,995 10/1955 Friend 315-8 X 2,797,408 6/1957 Greatbatch et al. 178-7.82 3,087,013 4/1963 Stastny et al. 1787.9 3,119,900 1/1964 Gray et al. 1787.9 3,255,311 6/1966 Hofmeister et al. l787.9 3,240,985 3/1966 Ammerman et al 3158 3,322,998 5/1967 Norley 3158 3,324,343 6/1967 Norley 315-8 3,340,417 9/1967 Panis et al. 315-8 ROBERT SEGAL, Primary Examiner.

US. Cl. X.R.

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