Abstract:
There is provided a cathode ray tube-base combination wherein a resilient electrically insulating insert is incorporated to provide arc prevention between adjacent tube pins having a high electrical potential difference therebetween. The resilient insert has discretely contoured surfaces formed to provide arc inhibiting barriers when compressively mated with the respective tube closure and base member.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a cathode ray tube and base therefor and more particularly to improved means for achieving better insulation in tube bases wherein there exists high voltage differentials between related tube pins. 
     Advancement in cathode ray tube technology, in particular the tube types employed in color television applications, has resuited in the development of efficient compacted electron gun structures. In keeping with conventional tube construction, these miniaturized gun assemblies are oriented within tube envelope neck portions of reduced diameters. The necessary operating voltages for the various elements of these guns (heaters, cathodes, accelerating and focusing electrodes, etc.) are supplied via an annular array of connector pins sealed into and projecting from the header or stem closure portion of the tube. As the neck diameters of the tube envelopes become smaller, the circumferential spacings between the connector pins likewise decreases. 
     Prior art tubes have evidenced large voltage differentials between certain of the pins in the connector array. This differential, sometimes in the order of 5 KV to 12 KV, has necessitated the incorporation of some form of arc protection into the tube socket, see, for example, U.S. Pat. Nos. 3,466,491 and 3,446,492. Such protection, however, has proven to be incapable of providing adequate arc protection for the newer tube types. 
     Another procedure previously employed, in conjunction with the base of the tube, involved the manual dispensing of a viscous silicone material about a high voltage pin, e.g., the focusing electrode connection, to efffect better electrical isolation from adjacent pins. This process was troublesome because of the long time required for curing the silicone and the need for additional labor to dispense the material. Furthermore, the manual application of the silicone tended to cause bubbles or air pockets to form therin, thus diminishing the intended arcing protection in the tube-base combination. 
     A more recent technique is that set-forth in U.S. Pat. No. 4,040,404, which is assigned to the assignee of the present invention. This patent discloses a cathode ray tube base wherein at least one tube pin isolating means is formed within the base member to provide arc prevention between adjacent tube pins. The disclosed isolation or arc prevention means comprises a cut-out portion in the base member, wherein a flat electrically insulating plug, having a cylindrical pin-engaging aperture therethrough and adhesive on both sides, is placed within the cut-out recess. While this means reduces the arcing problem to a degree, the presence of adhesive on both flat surfaces of the plug necessitates the use of protective release liners to cover the adhesive-containing surfaces until the plug is inserted in the base cut-out. The removal of these liners and accurate placement of the adhesive-coated plugs are time consuming manufacturing procedures. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the invention to reduce and obviate the aforementioned disadvantages that have been evidenced in the art. 
     It is another object of the invention to improve inter-pin insulation in the tube-base combination. 
     Yet another object of the invention is to provide an improved insulation means that is easily and quickly incorporated into the tube-base combination. 
     These and other objects and advantages are achieved in one aspect of the invention wherein an improved insulation member, having discrete topographic features, is formed for facile incorporation into the tube-base combination to accomplish enhanced electrical insolation for at least one of the tube connective pins. It has been found that this discretely contoured insulating insert of the invention effect markedly improved arc reduction in the tube-base combination. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view illustrating the manner in which the improved insulating insert member is associated with the tube and a base; 
     FIG. 2 is an elevational view of the improved insert member showing the advantageous topographical features thereof; 
     FIG. 3 is a plan view of the improved insert member taken along the line 3--3 of FIG. 2; 
     FIG. 4 is a plan view of the insulating insert member taken along the line 4--4 of FIG. 2; and 
     FIG. 5 is an elevational view, partially in section, illustrating the assembled tube-base combination having the improved insulating insert incorporated therein. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For a better understanding of the present improvement invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following specification and appended claims in connection with the aforedescribed drawings. 
     With reference to the drawings, there is shown in FIG. 1 an exploded presentation including a cathode ray tube base 11 formed to receive an annular array of connector pins 13 protruding from the terminal closure portion 15 of a cathode ray tube neck 17. 
     In greater detail, the drawings delineate the terminal closure portion 15 formed of a hermetically sealed, cylindrical glass header having a plurality of annularly spaced-apart connector pins 13 and 13a projecting therefrom. In this instance, the circle of pins has at least one pin 13a oriented with vacant pin positions 19 and 20 on either side thereof. Each pin and pin position is surrounded by an individually formed nubbin of glass, such as 21a, 21b, and 21c, (FIG. 5) raised from the header surface 15. The sealed exhaust tubulation 23 projects axially from the central area of the header 15. 
     The base 11, which is seated contiguously against the tube closure header 15, is formed of a substantially flat, basic circular member 25 having a diameter in keeping with that of the cylindrical closure portion 15 of the tube. This basic member 25 includes a plurality of spatially-related pin receiving means 27 having tapered receiving openings 29 (see FIG. 5); such being annularly oriented to receive the pins 13, 13a . A hollow substantially centrally located crown 31 is an integral part of the basic member 25 oriented in a manner to accommodate the sealed exhaust tubulation 23 therein. 
     A cut-out 33 of the basic member 25 is indented inwardly from the surface 35 thereof facing the header 15. This cut-out 33 has a depth &#34;d&#34; less than the thickness &#34;t&#34; of base member 25. The length of the cut-out extends through a circumferential arc &#34;AL°&#34; and encompasses a plurality of pin receiving means 27 in the base member 11. In this instance, the cut-out portion 33 includes three pin receiving means 27 which, as illustrated, accommodates a group of three sequential nubbin positions 21a, 21b and 21c of the pin circle of the header 15. As exemplarly shown, the middle nubbin 21a of the group has a connector pin 13a protruding therefrom,which can be a high voltage connector pin, while the side-related nubbins 21b and 21c are vacant positions in the pin circle. 
     The purpose of the invention is to minimize the possibility of arcing between the pin 13a and the adjacent pins 13b and 13c on either side thereof. This result has been expeditiously achieved by the provision of an improved, resilient, insulating insert 37 formed in a substantially arcuate shape to fit into the cut-out portion 33 of the base 11. The insert has a thickness &#34;T&#34; that is slightly greater, as for example 0.50 mm., than the depth &#34;d&#34; of the cut-out 33 in the base; and an arcuate length &#34;al°&#34; slightly less, for instance 0.25°, than the arcuate length &#34;AL°&#34; of the cut-out 33. Such exemplarly dimensionings enable the resilient insert 37 to be advantageously compressed between the closure header 15 and the base 11. To enable such compression, the insert member is formed of a soft resilient material, evidencing, for example, a charateristic durometer hardness (Shore scale) substantially within the range of 20 to 40 points, as measured on a Durometer Hardness Tester (Type A2), manufactured by The Store Instrument and Manufacturing Co., Inc. 90-35 Van Wyck Expressway, Jamaica, N.Y. 11435. An example of a suitable material of this nature is silicone rubber. It has been found that a substance of this hardness can be beneficially compressed to fill-in or contiguously conform to the inherent roughness of the header surface, thereby further inhibiting the possibility of arcing thereacross. 
     The insulating insert has opposed surfaces 39 and 41 of dissimilar topographic formations. For example, surface 39, as delineated in FIG. 2, has a plurality of protrusions outstanding therefrom, such being individually formed to mate with the respective tapered openings 29a, 29b and 29c in the base 11. The surface 41 of the insert, as illustrated in FIGS. 2, 4 and 5 has a plurality of shallow cavities 43a, 43b and 43c individually formed therein to contiguously accommodate the respective raised nubbin formations 21a, 21b and 21c on the header surface 15. The respective protrusions on surface 39 and the cavities associated with surface 41 are of like numbers and are located in opposite orientation as structural components of the insert 37. 
     In greater detail, FIGS. 2 and 3 show three protrusions 45a, 45b and 45c from surface 39 whereof at least one, in this instance the middle one 45a, has an axial pin-encompassing aperture 47 therethrough, which has a diameter &#34;x&#34; that is less than the diameter &#34;y&#34; of the pin 13a positioned therein. This middle apertured protuberance 45a is substantially conical in formation and has a substantially tapered aperture entrance 49 ingressing from a central opening 51 in the bottom of the associated cavity 43a in the insert 37. The side related protuberances 45b and 45c are, for example, shaped as substantially conic frustums formed as solid appendages of the soft resilient material of the insert 37. Such formations are dimensioned to contiguously fit as resilient plugs into the tapered openings 29b and 29c in the cut-out portion 33 of the base. 
     Two other surface configurations integrally related with the insert 37 are of additional importance. Attention is directed to the middle conical protrusion 45a of the insert member, which is surrounded at its base by a raised annular compressible cushion 53 of material integrally associated with surface 39 of the insert. Substantially likewise, on the opposed side of the insert, the middle cavity 43a is peripherally circumscribed by a raised annular compressible cushion 55 of material integrally associated with surface 41. When the tube 17 and base 11 are assembled as shown in FIG. 5, these two annular cushions 53 and 55 are compressed to form two additional arc-inhibiting seals around the tube pin 13a contiguous with both the header 15 and the base 11. 
     In use, the insert 37 is positioned within the base cut-out portion 33 with the protursions of surface 39 being seated in the tapered openings 29a, 29b and 29c in the base member 11. 
     The base is then &#34;capped&#34; or assembled on the tube closure portion 15. The tube and base may be held together by the discrete application of an electrically insulating cement, or by frictional adherence means wherein several of the apertures in the base member are diametrically dimensioned to provide frictional affixation with the pins inserted therethrough. 
     It has been found that the improvement as set forth in this invention has markedly reduced the problem of inter-pin arcing in the tube-base combination of tubes wherein certain of the pins exhibit a high electrical potential difference therebetween. 
     While there has been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.