US2825749A - Shielding device - Google Patents

Description

March 4, 1958 L. s. GRAY 2,825,749

SHIELDING DEVICE Filed Feb. 10. 1955 United States Patent SHIELDING DEV KZE Linsley S. .Gr y, Blano,1Ill.,..assign01-.to lGrayf Stamping anglManufacturinglCompauYifPlano;11L, a corporation .Of linois ApplicationfFebmaryimy 195.5,:Serial N o.= 4.87 335 '9iClaims. (Cl-174 .35)

This invention relates to shielding devices aandnmore particularly to a shielding device 1 for 'electroni'discharge devices.

It iscommon practice to provide shields forelectron discharge devices-generally referred to as tubes,. in certain applications as when it is desired to shield 'thedischarge device for external radiationpto prevent inductive or capacitive coupling between'theadischarge .devicesand the .apparatus external :to the .discharge :device :being shielded, andaalsowhen it is;desired to limit radiation from the discharge .device. Suchshieldszare formed-inf an electrically :conductive material :and shaped'sto; surround the tube to form :anenclosure therefor. .In .orderz-rto function etiectively, the "shield must be electrically grounded, .usuallyztozthe chassis of the electrical-apparatus.

In addition to the electrical requirements of shielding the tubes, it ,is. also desirableito maintain thetubes firmly in their sockets toprovideproper electrical=contact-between the tube prongs land the socket. .Thisi-is particularly essential when: :the discharge devices :are mounted otherthan in an upright position vonra horizontal chassis, as where the tubes *areqmounted IO'BXiCIldLhOI'lZOIHQllY from a vertically disposed chassis or 'eventto depend. down- :wardly from an inverted :chassis. When theztubesigare mounted ;in this :manner, zany vibration of the chassis will obviously tend to loosen the tube and impair ithe contact between the'tube-prongs :and the-socket. ItziS therefore 7 highly advantageous :to i provide .a tube .--shield which, in addition to :its ashieldingrfunction, will; serve to maintainthe. discharge device firmly on the tubessocket.

The problem of maintaining the tube .in-its socketais aggrevated by therelatively wide variations both in length anddiameter of the tubes in any givenseriesof tubes.

GAshieldingY device which .is to maintain .the tubes firmly in their socket .must be capable of accommodating these wide variations in length and diameter.

A further problem in .the shielding of .the discharge devices arises in the use of the so-called hot chassis type electrical apparatus particularly inmetal-cabinets.

.Since the chassis in ,suchapparatusis not anground potential, it is essential ,that the .chassis be electrically insu- ;lated from the metal, cabinet in order to .prevent the .cabinet vfrom also becoming electrically hot." 7 Since a misplacedtubeshield could provide a conductive path between the chassis and the otherwise insulated metal .cabinet, it is desirable intsuch applications ,to provide a tube shield which cannot become thus misplaced.

An important object of this invention is toprovide a shielding device which will overcome the above-mentioned problems and provide a highly efiectiveshie'ld for the discharge device.

Another object of thisinvention is toprovidesenjimproved shielding device which will maintain the electron 1 tube ffirmly. on :the tube-socket to prevent loosening of ing widely dilferent dimensional tolerances in-both length and-diameter -andato hold --%the :same firmly on --the-,t u,be socket. v

Yet-another object of "this invention is the; provision of agshielding device which obviates :the necessity ofpro vidinga separate base and which maybe directly attachedato-the.chassisqof- -the electrical apparatus to providea direct groundwforthe shielding-device.

-Still another 'object-gof this invention is the 1 provision ofa shielding T-deviceiwhich neednot bedetached from the chassis tozepermitreplacement of the discharge device and which'therefore cannot beqaccidentally misplaced during s er vici n g either-,on the wrong discharge a device ,or tbet-wejen theychassisaand the cabinet. I

-: A furthenobiectof this inventionis to. provide a shielding device 0f, simple andraeconomical construction, which can be easily fabricatedwandmounted on the chassis of t eapp aw A vsstill further objectof .this invention :is -;to provide ashielding device which can .be easilydetached from the tube -,to permitreplacement thereof and thereafter readily reapplied. t otthetube. I ;.These, together with various ancillary objects and'adyantagcswof-this invention will bemore readily appreciated as .thevsarne becomes better understood by reference .tothe following detailed description when y-taken in connection with the. accompanying drawing.

Figure 1 is a rear view ofone-ofthe shield sections;

Fig.2 .;is a side elevational view\of-'the shield section t aken=on,a,planeat right angles to the plane of Fig.4;

Fig. 3 is,a side elevational view of the'shielding device shown mounted on a chassis and clamped in position around aatube, theshield sectionsbeingshownin dotted lines, in their tube .release position;

Fig. 4 is a horizontal sectional view taken on the plane 4--4-of Fig. :3;

Fig. 5 is a-fragmentary sectional view {through the .chassis illustrating the tube shield inthe process of being mounted on the chassis;

:Fig. 6 is a'sectional viewjtaken onthe1planef6-6 of "Fig. 5;

v Fig. 7 is an enlarged fragmentary 'view illustrating 'ihe'shieicl section'm'ounting 'leg in the position thereof when the shield section is clamped around the tube;

Fig. 8 is a fragmentary sectional'view taken on the plane-8+8 of Fig. 7;

Fig. "9 :is a side elevational view of a modified form of shielding device shown mounted on a chassis;

Fig. :10; is a top-planview of the shielding device'illu's- *trated in Fig. '9;

*Fig. I1 is 'a "fragmentary view illustrating the shield section, of -'the"form shown in Fig. 9, in the. process' of being attached to the chassis;

Fig. 12 is an enlarged fragmentary view of one of the shield sections, of the form illustrated in Fig. 9, shown in its released position;

Fig. 13 is a side elevational view of another fo'rm of shielding device shown mounted on a chas'sispand Fig. 14 is a transverse sectional view taken onthe plane 1414 of Fig. 13.

"The shielding deviceof thepresent-invention is' adapted 3' for use with any type electron discharge device, hereinafter referred to as an electron tube or simply a tube, and as shown in the drawings is applied to a tube of the so-called miniature type, it being understood that the size of the shielding device may be varied in accordance with the average dimensions of the tubes in other series so as to be used therewith to effect shielding of the tubes from external radiation and also to shield the tubes against radiation therefrom to other parts of the electrical apparatus. The tubes, indicated generally by the numeral 20, are mounted in a socket 21 which is attached to the chassis 22 of the electrical apparatus. The shielding apparatus is adapted to be mounted on the chassis adjacent the socket 21 to form an enclosure for the tube and thereby efiect shielding of the latter.

' The shielding device of the present invention comprises a plurality of channel-shaped sections formed of an electrically conductive material, which sections are adapted to surround the electron tube and shield the latter. in the embodiments illustrated, a pairof channeled sections,'designated by the numeral 25 in the embodi ment shown in Figs. 1-8, are provided, which shield sections are formed with an arcuate cross section to provide a somewhat cylindrical enclosure for the tube. Provision is made for releasably clamping the shield sections together around the tube and for this purpose the sections are formed so that the side portions 26 thereof overlap, as best shown in Figs. 3 and 4. Advantageously,

the shield sections are identically shaped to-reduce the number of different parts which must be fabricated and accordingly "both of the transversely arcuate shield sections are formed to extend through an arc of more than gens-r49 out of overlapping relation. The mounting means comprises a leg 27 which extends downwardly from the lower end of each of the sections, at a point intermediate the side edges thereof, and preferably, the legs are formed integrally with the respective shield sections. In this embodiment, the leg is formed with a transversely arcuate cross section, as best shown in Fig. 6, and fairs smoothly at the upper end thereof into the downwardly and outwardly flared skirt 28 on the lower end of the shield section. The skirt reinforces the juncture between the shield section and the leg and provides clearance for any obstruction which may be present on the chassis around the tube socket, such as the rivets and the like for attaching the tube socket 21 to the chassis.

A pair of elongated openings 29 (see Fig. 6), here shown as rectangular in shape, are formed in the chassis 22 at opposite sides of the socket 21 and spaced radially therefrom for the reception of the legs 27 on the shield a somewhat greater arc than the intermediate portions of 180 to provide the aforementioned overlap. While it is preferable to have both sections extend through an arc of more than 180 to permit overlap of either seetion on the other section, it is apparent that one of the sections may be formed to extend through an arc of 180 or less in which event the section which extends through the legs to provide a retaining shoulder 32. The length and Width of each of the elongated openings 29 is made such as to snugly receive the enlarged lower end portion 31 of the leg 27 when the latter is inserted therein, as

shown in Figs. 5 and 6, and the lower ends of the legs are rounded as indicated at 33 to facilitate insertion of the legs into the openings. The shield sections and legs are formed of a somewhat resilient material so that the sides of the lower end portion 31 of the legs may deflect inwardly when the legs are inserted therein, the lower end portions thereafter expanding so that the shoulders 32 are effective toretain the shield sections on the chassis.

As previously described, the intermediate portions of the legs are smaller than the lower end portions 31 and are therefore loosely received in the openings 29 and perit limited pivotal movement of the shield sections in these openings. The legs extend downwardly and outwardly from' the shield sections at an angle to the axis thereof such that when the shield sections are disposed :11 around the tube, with the axes of the sections extending ably formed with a small inward taper, from the bottom to thetop thereofand terminate at the upper end above the discharge device in a diameter smaller than the diameter of the tube. Consequently, when the shield sections are clamped together. around the tube, the sections will contact the tube envelope around the periphery thereof .at the uppenend of the tube, as is clearly shown in Fig. 3.

Provision .is. made for mounting the shield sections 23 for movement into and out of shielding position around theelectron tube, to permit removal and replacement of the tube. Preferably, the means, designated generally arranged to support the shield sections directly on the c hassis 22 of the electrical apparatus and insuch a manuser as to provide;properelectrical connection therebetween. This obviates the necessity of providing asepathe shield since it is directly grounded to the chassis instead of being connected thereto through a separate mounting base.

,by the numeral -25, for mounting the shield sections isv 'rate base for mounting the shield sections on the chassis andvalso -provides an improved ground connection .for

In the preferred form of the invention illustrated in Figs. 1-8, the mounting means isarrangedto support the-shield sections 'on the chassis for swinging movement in a plane through the axis of the electron tube, into and 7 normal to the chassis, the legs extend at an angle through the openings 29 as is clearly shown in Figs. 3 and 5. The angle at which the legs extend from the axis of the shield sections is correlated with the. width of the elongated openings .and'the depth of the channel defined by the intermediate portion of the transversely arcuatelegs so that the inner-edges of the intermediate portions of the legs engage the upper radially inward edge of the opening 29 and the back of the channeled legs engages the lower radially outer edge of the opening, when the axis of the shield section is inclined upwardly away from the tube axis. Therefore, as the shield section is moved into position around the tube, the leg 25 will bind between the inner and outer edges of the opening 25 and deform the forward edges and the back of the leg slightly, as shown in Fig. 7 to provide a firm binding contact between the leg and the chassis. This provides a rigid mechanical connection between the shield sections and the chassis, when the shield-sections are clamped together around the tube, and prevents relative movement there'oetween. Consequently, theshield sections will hold the tube firmly in :the. tube socket whereby the tube cannot become loosened and further, a firm electrical contact is established between the shield sections and the chassis to ground the latter. Moreover, the deformation of the legs, produced "when the shield sections are clamped together, tends to flatten the transverselyarcuate lower end portions of the legs and expand the latter in a direction circumferentially .of thetube socket whereby the shoulders 32 underlie the chassis and prevent subsequent accidental removal of the shield sections. 5

A5 isapparent', the angle that the legs must subt'eud with the shield section axis; to provide 1the aforementioned binct1ng"of the' leg-inthe opening will vary with the thickness of the chassis-'22. By-making-this angle --hetween the legand theshieldsection--sueh that the leg will bind in the openin-g' '29' even when very thin chassis material is used, the leg will obviously also bind inathe opening when thicker chassis material is used. In the latter case, theleg-willbegin'to bind in-theopening, as the shield sectionis initially=moved to its shielding position around thetube when theaxis of the shield section is inclined appreciably to the normal to the chassis. Further; movement of the shield section to-shielding-position around the tube will produce bending of the leg relative to the shield section and effect a change of the angle between the ,leg and the -shield section. In this manner, the shielding device will automatically adapt itself to chassis of different thickness.

Onthe other :hand, if the angle between the leg and the-axis of the shield 'section-isinsufiicient to-produce a binding action between the leg and the-edges of the opening '29, when the shield section is disposed around the tube, as'maybe caused by improperly sized openings 29 or repeated use which deforms the shield sections, then'the angle between'the leg andthe shield section can'beincreased bytilting the sections outwardly, as shown in dotted lines in Fig. 3 and pressing the sections downwardly to-bend the legs outwardly. Sincethechanneledlegs are rigid and resist bending, most of-the bendin-gwill occur-at the junction between the leg and the shield section, thereby effectively increasing the angle between the leg and theshield section.

The outwardly flared skirt 28 is preferably formed so as {to extend aroundtheentire lower end of the shield sections. As the shield sections are pivoted upwardly, from the position shown in-dotted lines in'Fig. 3, to the solid line position, the ontwardly fiared skirt engages the electron tube envelope and expands the shield sections.

Further movement of the shield sections toward their position around the tube causes the skirt on one of the shield sections to overlap the other shieldsectionand thereby guide the sections into their overlapping positions shown in solid lines in Figs. 3 and 4. T-hus,- the-skirt serves the multiple function of-reinforcing the juncture between the legs and theshield sectionsand guiding the shield sections into overlapping position. In addition, the skirt provides clearance for any obstruction adjacent'the tube base and permits the shieldto extend into closely spaced adjacency with the chassis-to thereby completely shield the tube.

Conveniently, the upper edge of the shield sections may be inwardly-rolled, as indicated at 35 to provide a smooth upper edge and to reinforce-the shield sections.

A modified form of shielding device-is illustrated in Figs. 9-l2. As in the-preceding embodiment, theshielding device includes a pair of tra'nsversely-arcuate channels 41 dimensioned to snugly grip the-envelope of theelec- :tron tube 42. Preferably, the shield sections taperin- Wardly from the bottom to the top thereof whereby the shield sections grip the tube adjacent the upper end of thelatter to firmly retain the tube in its socket 43 on the chassis 44.

A downwardly and outwardly fiaredskirt 45 is formed on the lower .end of each of the shield'sections, which skirt guides the shield'sections onto the tube and ,into overlapping relation with each other. A leg 46extends downwardly and outwardlyfrorn the lower edge of the skirt, intermediate thfi ide edges of the shield sectionsto provide a mounting leg for the sections. Thelegv is ,adaptcd toextend through an elongatedopening .47 in the chassis ,44ato thj rbY t pp0rt the shield sections directly ;on the. chassis for vyertical swinging movement the lower end of the leg 46 and, as shown in the drawings,

the sections --are positioned :atan :angle to .the chassis such that the apex of the knuckle defined by the leg. 46 and-the locking finger 48is aligned with the pre-punched opening 47 in the chassis 44. The shield section is then pressed in a direction to urge the knuckle through the opening, the locking finger 48 deflecting inwardly towards-the leg 46 as thefinger moves through the opening, zas shown-in'Pig. 11. Afterthe locking finger has passed through the opening, it springs back to its originalposition with respecttothe leg and thereby retains the leg '46 in position in the opening.

The-angle atwhich the leg 46 extends from the axis of 'the shield section is made such that the'under edge of the leg-will engage the upper radially inner edge of the opening-47 andthe rib 49 at the back of the leg and will engage thelower radially outer edge of the opening,

-when theshieldsection 41 is pivoted upwardly to a posi- "tion in which-the-axis thereof is inclined upwardly away 'from'the-axis of the electron tube 42, such as the position to whi ch the-right hand shieldsection is shown in Fig. 9.

Further movement of the shield section into its clamping positionaround the other shieldisection will cause the leg to be 'bentslightly thereby forming a firm binding contact between the leg and the chassis. The extent to which the'leg must be bent, when moving the shield sec tion intoalignment with the'electron tube, will vary with .the size of the opening 47 and the thickness of the .chassis 44 and if this angle through which the leg must be bent is appreciable, some permanent deformation of the leg will occur. However, theleg will still be resiliently urged into firm contact with the chassis to provide a proper ground connection ,thereat.

The under edge of the skirt 45 is undulated as shown inthe drawings, to clear obstructions such as rivets and provided amultiple point contact between the shielding device and the chassis, namely, at each of the four contact points 51 and at the pair of legs 46.

Still another form of the invention is illustrated in Figs. 13 and 14. In this embodiment, the transversley arcuate shield sections 61 are also shaped to extend through an arc of more than so as to overlap along the side portions thereof as indicated at- 62 to thereby resiliently clamp the shield sections together around the electron tube 63, although it is to be understood that the shield sections need not overlap and that other clamping means may be provided. As is conventional, the electron tube is mounted in a socket 64 which is attached .by a flanged locking collar 65 to the chassis 66, as by rivets 67. In this form of the invention, the sections are mounted for swinging movement with the axis thereof at all-times substantially parallel to the axis of the electron tube, into and out of overlapping relation. Conveniently, a pair of laterally extending mounting arms 68vmay be provided on the lower ends of each of the shield sections, adjacent oneof -and the arms are formed of a resilient material to thereby yieldably urge the shield sections in a direction toward thesocket 64. As in'the preceding embodiments,.the shield sections are advantageously formed with a slight inward taper from the bottom to the top thereof to thereby grip the periphery of the tube adjacent the upper end thereof.

As is apparent from Fig. 14, the shield sections are swingable in relatively opposite directions with the: axis thereof parallel to the 'axis of the tube, into and out of overlapping relation around the tube and, conveniently, one. of the side edges of each of the shield sections may be bent outwardly as indicated at 71 to facilitate guiding of the sections into overlapping relation.

From the foregoing it is apparent that the shielding device of the present invention may be mounted directly on the chassis of the. electrical apparatus without the necessity of providing a separate mounting base, and which shielding device is thus arranged to be directly grounded on the chassis. Moreover, the shield sections are formed of a resilient material and shaped to releasably clamp together whereby the shielding device is adapted to snugly grip tubes having different lengths and diameters, within somewhat wide limits. For different tube series, where the tube envelopes differ markedly in size and configuration, different size shielding devices must be fabricated. However, the shielding. device for any series of tubes will adapt itself to the variations in length and diameter of the tubes in that series. The shielding device is therefore arranged to retain the electron tubes in their sockets and, since the shield sections are disposed in closely spaced adjacency to the tubes,

they are effective to radiate the heat from the tubes and maintain cool operation thereof. In the embodiments of the invention shown in Figs. 1-8 and in Figs. 9-12., it is only necessary to provide openings in the chassis adjacent the tube sockets for the reception of the support legs for the tube sections. The tube sections then may be readily mounted on the chassis by inserting the legs through the openings, the legs having provision thereon ther, since the shields are permanently afiixed to the chassis, they cannot become accidentally misplaced between the chassis and the other parts of the electrical apparatus or between the chassis and the cabinet'to provide a conductive path therebetween. This is of particulai' importance in the so-called hot chassis type apparatus since the chassis is not at ground potential and, when such apparatus is used in a metal cabinet, it is necessary to assure that the chassis is not electrically connected to the cabinet.

Since the shielding device is formed in a plurality of sections which extend longitudinallyof the tube, it is apparent that removal of the shielding device can be conveniently and expeditiously effected by separating the sections.

I claim:

1. For use with an electronic apparatus comprising a chassis having a tube socket and an electron discharge device mounted in said socket, a shielding device comprising a pair of cylindrically-shaped shield sections adapted to be arranged in opposedrelation around the discharge device to form an enclosure therefor, a leg formed integrally on the lower end of 'each of said secvtions extending downwardly and outwardly therefrom,

and a pair of openings in said chassis at opposite sides of the tube socket and spaced outwardly therefrom, said legs extending through openings to thereby swing- 8 ably support'said sections and toelectrically connect the shielding device on the chassis, said legs being arranged to bind in saidopenings as said sections are moved into opposed coaxial relation to provide a. firm electrical and mechanical connection between said sections and said chassis.

2. For use with an electronic apparatus comprising a chassis having a tube socket and an electron discharge device mounted in said socket, a shielding device comprising a pair of cylindrically-shaped. shield sections adapted to be arranged in opposed'relation around the discharge device to form a shielding enclosure therefor, a channelshaped leg formed on the lower end of each shield section intermediate the side edges thereof, a pair of openings formed in said chassis on opposite sides of said socket, said legs extending downwardly and outwardly from the lower ends of said sections through said openings to swingably support said sections directly on the chassis, said legs being adapted to bind in said opening .when the shield sections are moved into position around the tube to thereby provide a firm electrical and mechanical connection between the shielding device and the chassis.

3. The combination of claim 2 wherein each of said sections extends through an arc of more than to thereby-releasably clamp said sections together.

4. The combination of claim 3 wherein said sections are shaped to snugly embrace the periphery of said discharge device to thereby retain the discharge device in its socket.

5. For use with an electronic apparatus comprising a chassis having a tube socket and an electron discharge device mounted in said socket, a shielding device comprising a pair of cylindrically-shaped shield sections adapted to be arranged around the discharge device to form a shielding enclosure therefor, a pair of openings in said chassis at opposite sides of said socket, legs formed integrally on said sections extending downwardly through said openings to swingably support the-sections on the chassis, said legs being arranged to bind in said openings as the sections are moved into opposed coaxial relation to provide a firm electrical and mechanical connection between said sections and the chassis, and lateral pro jections formed integrally with the lower ends of said legs adapted to be inserted with the legs through said openings for engaging the underside of said chassis to retain said shield sections thereon.

6. For use with an electronic apparatus comprising a chassis having a tube socket and a tube disposed in said socket, a pair of channel-shaped sections adapted to be arranged around the discharge device to form a shielding enclosure therefor, an integral leg on the lower end of each of said sections extending downwardly and outwardly therefrom, openings in said chassis on opposite sides of said socket adapted to receive said legs and swingably support said sections for movement in a plane through the axis of .the discharge device, said sections having means on the lower ends thereof located between the axis of the shield section and the leg thereof and adapted to engage the chassis to cause the sections to pivot thereon as the sections are moved to a position around the tube whereby to raise said legs into firm contact with the chassis adjacent said openings.

7. A shielding device for use with an electronic apparatus including a chassis having a tube socket and an electron discharge device mounted in said socket, said shielding device' comprising a pair of elongated transversely arcuate shield sections each extending through an arc of more-than 180, said-sections having an outwardly flared skirt formed on the lower ends thereof,a leg formed integrally with said skirts intermediate the side edges of the respective sections and extending downwardly and outwardly from the sections to a point'below the lower end of the'respective section, and a pair of openings bottom of said chassis respectively when said sections are moved into opposed coaxial relation with the side portions of the sections overlapping to firmly clamp the sections together.

8. The combination of claim 7 wherein said legs are transversely arcuate to minimize bending of said legs as 10 2,662,220

the sections are moved into overlapping relation.

9. The combination oi claim 8 including projections on the side of said legs adjacent the lower ends thereof, the length of said openings being sufiicient to permit the passage of said legs and projections therethrough when 5 the sections are initially assembled on the chassis.

References Cited in the file of this patent UNITED STATES PATENTS Saari Dec. 8, 1953 2,701,866 Chapman Feb. 8, 1955

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