US2825836A - Method and apparatus for establishing electrical contact to a plurality of wires - Google Patents

Description

March 4, 1958 R. ZAPHIROPOULOS ETAL 2,825,836

METHOD AND APPARATUS FOR ESTABLISHING ELECTRICAL CONTACT TO A PLURALITY OF WIRES Filed July 11,. 1955 IN VEN TOR5 establishing electrical tended to improve upon ways and separable sets 'of conductors on grids nearthe target area of color employed near the target area,

deposited on a target.

when impacted and excited .light.

.trum, within certain fromeach other. arenecessary.

of one-half each such or reference member.

Unite METHOD AND APPARATUS F913. ETAELISHENQ ELECTRICAL CONTACT T9 A PLIJiZALlTY F Application My 11, 1955, Serial No. 521,013 4 Claims. c1. BIB- ie) This invention relates to a method and apparatus for contact to each of one or more sets The invention is inmeans for making or more electrically designed for use television tubes.

in the design and construction of color television tubes wherein one or more color-control wd focusing grids are it is often desired to have two electrically separate sets.

of electrically separable conductors.

electrical connections to each of one grid conductors formed into In the case of a single gun color television tube employing color switching near the target it is customary to employ a grid structure of this general type to provide so-called color switching and to serve as one component of a series of electron lens elements. In certain types of such tubes, a large number of very narrow phosphor strips are Each of these phosphor strips is of a composition which emits a selected color of light by a scanning electron or cathode-ray beam. In the present art, a tricoloradditive color system is usually used, that is, three diflerentkinds of phosphor strips are deposited on the target, each adapted to emit a difierent color of light whenimpacted. The three colors so emitted are chosen so that they may readily becombined and color balanced to produce white The three colors chosen will also produce, by

the other colorsof the color speclimitations not material here. 'In color television tubes employing grids near a target area various combinations for deflecting theelectron beam with respect to target area strips such as those hereinbefore described, separate sets of grid conductors which are electrically distinct Since the phosphor strips intheaforementioned types of tubes are arranged in repeating color cycles of the order of asingle picture (do I .ment in width for each such cycle, and since the grid structure or micro-deflecting means has .a spacing beand deflecting conductors .of the order repeating color cycle, agreat number of extremely .accurately positioned, tautlyheld and vibration free grid conductors are necessary. Furthermore, since the color control switching must be applied during the timethe scanning beam is traversing a lineal distance of the same order of magnitude as the distance the grid'conductors are spaced apart, the color control tween the adjacent .or switching signals are necessarily relatively high in frequency, and in fact he in What is ordinarily termed the radio frequency or RF range.

The invention herein relates to anovel method and fixture for making connection to each of several electrically separable'sets of conductors on agrid designed for use near a target area where the grid conductors have previouslybeen mechanically secured to the grid frame A number making simultaneousconnections to a large number of suchconductors. For'examplaa low resistanceelectrical contact is desired to eachand every conductor .in each of problems arise in conductors, ordinarily 2,825,836 Patented Mar. 4, 1958 struction of grids such as those described herein-is that of shielding the connecting and securing structure. The invention herein results'in a connection to the grid-wires which is movable andsolves various'problems rela'ting to shielding as will appear" hereinafter.

It is accordingly a principal object of'the invention to provide a method and fixture "for establishingelectrical contact to a plurality of wires which will provide relatively low electrical resistance at 'R. -F. frequencies-to each of such wires, which resistance will be uniformfor all the wires-contacted and which will not change or vary with age. Another principal object of the invention is to'provide a method and fixture for establishingelectrical contactto each of saidplurality ofwires which is simple, economical, and elficient. Another object ofthe invention is to provide a method and fixturewhich"results in a contacting strip assembly wherein shorts and opens may be easily located and cleared.

Another object of the invention is to'provide a means for contacting a plurality of wires incach of several sets of conductors which'is'fiexible in relation to the'various design considerations encountered in assembling a grid adjacent to'the target area of color'television tubes. More specifically in this connection, it is amongtheobjects of the invention'to provide a method andfixture structure wherein a'connection may be on either end of the grid and to cheer more variously located points on either or both of'such ends, a structure, furthermore, which is movable, both with respect to the grid andfgrid frame and with respect to the other'contacting structures, and a structure which may be easily electron-beamand radiation-shielded, thus avoiding the pick-up of'stray fields or beams which might interfere with'the operation of the grid or grids to which it is connected. It is also'an object of'the inventionto provide a grid contacting structure of such a form that both the contacting structure and the mechanical securing means may be simultaneously shielded as aforementioned. An object of'the invention is to allow simultaneous electrostatic shielding of the contacting structure and mechanical securing means.

Another principal object of the invention is the provision of a method and fixture which is adaptable to automatic and semi-automatic techniques of production. A further object of the invention is the provision of a method and fixture which allows rapid and eificient as sembly. Also an object of the invention is the provision of a method and fixture having numerous other objects and advantages, which will become apparent to those skilled in the art from the specification herein.

In the invention, electrically separable sets of conductors, which have previously been physically secured-in a desired accurate configuration relative to each other within a grid area proper, as defined by the'grid supports, are separated into the desired-number 'of'sets of two sets. In the 'usual' case,whi ch is that'of grids wherein the 'sets'of grid conductors within the grid area properall lie inoneplane, ornearly within one plane, the sets of'gri'd'conductor-s are'separatedadjacent'to each end of the grid area'into sets of'conductors lying inplanes substantially parallel to and above I welding operationand thereby make a 3 each other. Temporary means may be employed to hold the physically separated sets of electrically separable conductors distinct from each other pending further steps of the method. In a preferred method of the invention, conducting metallic strips of a metal other than that employed for the grid conductors are then afiixed to heat conducting positioning parts of a jig or fixture, that is, to an anvil, to one or more spacers, and to a clamping piece. In the cases where there are only two sets of conductors to be separated only one spacer is necessary. The separated sets of grid conductors are arranged to be included within the conducting strips so mounted on the anvil, spacer and top clamp of the fixture and all the pieces are clamped in position. The anvil, spacer, and top clamp are all composed of a heat conducting material, so as to dissipate the heat generated during the desirable electrical and mechanical connection and also to confine the weld to a small section or head near the edges or' the strips. After the conductors have been clamped between the strips mounted on the heat conducting parts, a welding means, preferably of the inert gas-shielded type, is run along the outermost junction of each of the pairs of strips, thereby joining the strips and the conductors in a welded seam, securing the grid conductors bothmechanically and electrically to the joined strips. Due to the variation in the total thermal conductivity of each the various cross-sections involved, and the effect of the anvil, spacer and top clamp, in combination with the dissimilar metals being joined, an irregular ball-shaped connection is made at the end of each conductor to the strips. This connection is so formed that it insures excellent uniform low resistance R. F. electrical contact to each of the grid conductors, and is also trouble-free for very long periods of time. R. F. losses are also at a minimum in this construction. After the weld has been completed, the anvil, spacer, and top clamp may then be removed, as well as the temporary means, if any, used to'keep the sets of conductors physically separated. In the preferred form of the invention, a volatile glue is used to aflix the metallic conducting strips to the anvil, spacer, and top clamp, and the metallic strips are accordingly automatically released from the fixture by the welding operation. The welding operation also preferably trims the excess of the grid conductors extending beyond the metallic strips automatically.

The invention will be more fully understood, and further objects and advantages will appear in connection therewith, by the reference to the following description read in connection with the accompanying drawings, wherein:

Fig. 1 is a diagrammatic view, illustrating a preferred form of the of the method of the invention, with the end portion of a typical grid frame mounted therein; and

Fig. 2 is a cross-sectional view in elevation of said end portion of the frame, showing the completed grid connection made by the method and in the fixture of the invention.

Turning now to a consideration of the figures of the drawings, the same numbers have been used to designate the same parts throughout. In Fig. l, a grid frame 4-9 having a grid support 51 for the fastening of grid conductors 11 by a mechanical means 31, such as a ceramic cement or silica frit combination, is placed in fixture or jig 10. The form of frame 49 and support 51, as well as the mechanical holding means 31, are of course, only illustrative, and other forms of these components may profitably employ the method and fixture of the invention. The-ceramic cement, silica frit combination or other means 31 used to mechanically secure the conductors 11 must, of course, be such that the various sets of grid conductors 13, 15 may be electrically isolated from each other.

Fixture is comprised of a bridge assembly 45 partly in cross-section, fixture for the practice sets of grid conductors mounted on base 47 by screws 43 or other means and having a top or bridging portion 41 lying in a plane parallel to that of the base 47. Arm 35 is mounted on the bridge 35 by means of pivot 39 and supports top clamp 17. Suitable securing means, illustratively the screw 37, serve to secure top clamp 17 in position when the fixture it) has been assembled prior to the welding operation. Also attached to the bridge 45 is an optional shield 33 designed to prevent damage to the grid conductors 11 during the welding operation. Spacer 19 and anvil 21, together with clamp 17, hold the set of conductors 13 between detachable metallic strips 23 and 25 and the set of conductors 15 between detachable metallic strips 27 and 29, in position to efiect a weld by welding torch 53. Metallic strips 23, 25, 27 and 29 are of a metal other than that employed for the grid conductors 11. Spacer 19 is also preferably of a metal other than strips 25 and 27 to avoid any tendency to become welded thereto.

In the application of the method and fixture of the invention, grid frame 49, having electrically separable conductors 11 as described above, is mounted in place on jig or fixture 10. The conductors 11 are separated into the desired sets of conductors 13 and 15 either prior to or after such mounting. Temporary separating means may be employed to hold the sets of conductors 13 and 15 separated until the anvil 21, spacer 19, and top clamp 17 are applied. For example, a narrow glass tape may be placed between the sets of wires 13 and 15 so that the alternate wires forming the one set 15 are below the tape and the rest of the wires 13 are above it. The ends of the wires in set 13 and in set 15 may then be sandwiched between two sets of masking tape to keep them distinct and easily separable. Alternatively, the wires may be separated and immediately placed between the anvil 21, spacer 19 and top clamp 17. A metallic strip 23 is temporarily afilxed to top clamp 17, metallic strips 25 and 27 are aflixed to spacer19, and metallic strip 29 is afiixed to anvil 21. A glue which is easily volatilized is preferred for this operation, since such 'a glue will be volatilized during the welding operation and the strips mounted on clamp 17, spacer 19 and anvil 21 will be released without further efiort. Other means of securing the strips may, of course, be used. Alternatively, strips 23, 25, 27 and 29 may be directly applied to the 13 and 15 during the initial physical separation, in lieu of, for example, the masking tape mentioned hereinabove.

Top clamp 17, spacer 19, and anvil 21 are all made of metal or other material with a relatively high coeflicient of thermal conductivity so as to readily conduct the heat involved during the welding operation, thereby performing as chill rings and confining the weld to the edges 1 of the metallic strips, and, in addition, helping to create a desirable 11. After the. grid conductors in place with each set of conductors 13, 15 encompassed respectively between a pair of strips 23-25, and 27-29, screw 37 or its equivalent is operated to clamp the assembly in position. After the assembly has been so clamped, welding means 53, preferably of the inert gas-shielded type, such as Heliweld or Heliarc, is caused to operate and during such operation to move along adjacent to or in contact wtih the outermost junction of the pairs of strips 23, 25 and 27, 29 effecting the welds of each pair of said strips and the respective sets of conductors 13, 15 included therebetween.

It will be noted from the above that the method of the invention may be practiced by hand, since the anvil 21, spacer 19, and clamp 17 may be provided with a handle or holding means and the welding torch operated manually. During the welding operation, and grid wires 11 are preferably protected from damage by a shield 33. The welding operation, in addition to permanently joining the strips 23, 25 with the set of conductors 13,

type of electrical connection to conductors 11 have been clamped and strips 27, 29 with theset of conductors 15, trims ofi the excess wires insets 13and 15.

Ordinarily the sets of grid conductors 13 and 15 will be separated by a relatively small distance, and spacer 19.; will accordingly be of limited dimensions. For this reason, spacer 19 is preferably of a metal other than that of strips 25 and 27, and preferably such metal has a relatively high thermal capacity, thereby avoiding any tendency to become welded to strips 25 and 27 during the welding operation and permitting ready removal thereafter. Anvil 21 and top clamp 17 may easily be made of larger dimension and accordingly may be of the same or of a different metal than strips 23 and 29.

Referring now to the cross-sectional view of Fig. 2 wherein the end portion of the frame 49 is shown in elevation it will be seen to illustrate the appearance of frame 49 after the welding operation has been completed, resulting in connection to conductors 13 by strip assembly 57 and conductors 15 by strip assembly 59. In Fig. 2, frame 49 is shown removed from the fixture 10. Support 51 and the mechanical holding means 31 physically securing grid conductors 11 are illustrated as before. In addition, a combination electron beam and radiation shield 55, secured to support 51 by screw 61, is shown. Other forms of shield 55 may be employed, and fastened by other means, but it is a special object and advantage of the invention herein that the assemblies 57 and 59 are movable sufiiciently so that shield 55 may be arranged easily and simply to cover both the assemblies 57 and 59 and the mechanical securing means 31, forming an effective shield for both.

Attention is especially directed, at novel character of the electrical connection obtained by the method and fixture of the invention. A portion of the weld, including the connection, is shown in crosssection at 57 and at 59 in Fig. 2. It will be noted in Fig. 2 from an inspection of the contacting strip assemblies 57 and 59 that the ends of the conductor 11, after the weld has been completed, are irregularly ball-shaped in character.

This electrical and mechanical connection is not aifected by the movement of contacting assemblies 57 and 59 to allow the imposition of shield 55. Shield '55 extends as shown in Fig. 2 to cover both the contacting assemblies 57 and 59 and the securing means 31. Shield 55 thereby functions as a radiation shield and a beam shield, and additionally as an electrostatic shield. One of the elec trostatic shielding eifects of shield 55 is to keep securing this point, to the means 31 from charging and discharging and giving undesirable optical and electrical effects such as electrostatic glows. The shielding as aforementioned of course does not affect the efiiciency of the desirable ball-shaped connections to grid conductors 11 in assemblies 57 and 59.

The reason the desired shape and efiicient electrical connection are obtained may be best understood by a consideration of Fig. l. Dissimilar metals are used for the strips 23, 25, 27 and 29 as compared to the grid conductors 11. As the weld is made, more heat is supplied to the strips forming the contacting strips 57 than to the grid conductors 11 included between said srips 57 because of the relative amounts of area of each exposed to the welding means. This heat, however, is confined mainly to the edges of the strips, due to the cooling or chilling efiect occasioned by the relatively high thermal conductivity of anvil 21, spacer 19 and top clamp 17. The strips 23, 25, 27 and 29 are accordingly, during the first instants of the welding operation, rendered more completely in a fluid condition than the ends of the grid conductors 11, and the result is that the ends of grid conductors 11 tend to become ball-shaped in character.

This shaping efiect is enhanced by employing a metal having a relatively high thermal conductivity for the strips 23, 25, 27 and 29. Aluminum is the metal preferred, both for. this reason andbecause of its other. 'advantages, such as low electrical resistance and light weight. In fact, contacting strip assemblies 57 and 59 comprised of aluminum strips 23, 25 and 27, 29 need no furthersupport than that afforded by the separated sets of grid conductors 13 and 15. Other metals, such as silver, may also be used for the strips 23, 25, 27 and 29. Grid conductors 11 may be of stainless steel, and the method and fixture of the invention has been highly successful with the grid conductors 11 composed of this material. However, insofar as the invention herein is concerned, other materials are also satisfactory for grid conductors 11, and, with most such materials, the additional effects occasioned by the relative thermal conductivities will still obtain if strips 23, 25, 27 and 29 of aluminum are employed since aluminum has relatively high thermal conductivity as compared to most metals. Metals other than aluminum may also be used for the contacting strips 23, 25, 27 and 29, even those of relatively low thermal conductivities, since, as pointed out hereinabove, the desirable electrical connection arises from the effect of the total heat supplied and the chilling or limiting of the fixture 10, as well as from the effect due to the inherent thermal conductivity of the metals of the strips 23, 25, 27 and 29 and the grid conductors 11.

Arc Welding is the preferred form of welding, although other types of welding may be employed, such as resistance welding. Inert gas-shielded welding is the preferred form of arc welding. Aluminum, for example, may be welded without a flux with the inert gas-shielded method. When aluminum is welded by this method, an A. C. voltage which has poor regulation and a high open circuit value, or, alternatively, which has superimposed high frequency, is desirable for are stabilization. The shielding gas employed in such a case may be helium or argon, but is not limited thereto. In a specific application of the method and fixture of the invention, helium gas-shielded or Heliarc welding has been found to be very satisfactory. The particular values employed are 41 volts at 13 amperes, for welding aluminum strips to stainless steel grid wires.

The method and fixture of the invention having been described in terms of specific embodiments hereinabove, the invention is to be limited only by the following claims.

We claim:

1. In a grid especially adapted to be used near the target area of a color television tube, a grid contacting assembly for making electrical connections to at least one electrically separable set of grid conductors which have previously secured in a desired physical configuration by a mechanical supporting means on said grid comprising a plurality of extensions of the grid conductors forming said electrically separable set, said extensions protruding beyond said mechanical supporting means; a pair of strips of a metal other than the metal of the grid conductors arranged oppositely of each other to include said extensions; and a seam weld joining said pair of strips and said grid conductor extensions at the outermost junction thereof to form said contacting assembly.

2. The grid contacting assembly of claim 1 comprising in addition a shielding member arranged to simultaneously cover both said mechanical supporting means and said contacting assemblies to provide a shield from electron beams and radiation for said mechanical securing means and said contacting assemblies.

3. The grid contacting assembly of claim 1 wherein said grid conductors are stainless steel and said strips are aluminum.

4. A grid construction especially adapted to be used near the target area of color television tubes comprising: a frame member including a support member; a plurality of grid wires; means including said support member to mechanically secure said grid wires in a desired configuration relative to said frame member; extensions of said -gri wires 'p'rdtruding: beyond saidsupPOrtniexhbeighmoh- -tacting strip :assembly comprisinga pairof stripsuof a -rne'te1lother than that of said 'gridwires'arranged translyersely of and on either side of said extensions,'said strips -.and;said wiresbeing joinedin a.-unitary welded mass at i'the; outermost edges of said strips; a shielding member :.disposed to shield said contacting strip'assembly, grid wire Eextensionsand mechanical securing :means; and connectingjmeans for establishing electrical contact to said contacting strip assembly.

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