US2748238A

US2748238A - Method of welding wires under tension

Info

Publication number: US2748238A
Application number: US438153A
Authority: US
Inventors: Zaphiropoulos Renn
Original assignee: Chromatic Television Laboratories Inc
Current assignee: Chromatic Television Laboratories Inc
Priority date: 1954-06-21
Filing date: 1954-06-21
Publication date: 1956-05-29
Anticipated expiration: 1973-05-29
Also published as: FR1126313A; BE539143A; NL197931A; ES222528A1

Description

y 9, 1956 R. ZAPHIROPOULOS METHOD OF WELDING WIRES UNDER TENSION 2 Sheets-Sheet 1 Filed June 21, 1954 W E W W M m D W m N m 4 T H W "A P Tw g 7 (/76 MOVEMENT if 5 22 :EII3 E In. T 5 47 IN V EN TOR. Pen/1 Zap/w'ra oou/os f". Po g /o/v POgC/ /ON y 1956 R. ZAPHIROPOULOS 2,748,238

METHOD OF WELDING WIRES UNDER TENSION Filed June 21, 1954 2 Sheets-Sheet 2 /8 ,1 f I 56 /5 3 U 5 U j I Z0 Z0 a: Y

:EIl3 5 :EI[5 E INVENTOR.

Ae/m Zaph/ropau/os Mmi llnited States METHGD OF WELDING WHRES UNDER TENSION Application June 21, 1954, Serial No. 438,153

8 Claims. (Cl. 219-10) The present invention relates to a method of securing a plurality of conducting members to a metallic frame or support. More particularly, the invention relates to cathode-ray tubes having a grid of essentially parallel wires adjacent to a striped phosphor screen, or target electrode, and to a method for so positioning these wires as to permit the establishment of a desired relationship between such wires and the phosphor strips of the screen.

Cathode-ray tubes constructed with a grid of essentially parallel wires located adjacent to a striped phosphor screen are now known in the art. Such a grid may form one component of an electron lens system which serves to focus the beam electrons into a pattern of thin lines registered with the phosphor strips of the screen. This PDF (post-deflection-focusing) type of cathoderay tube operation has been set forth by Ernest 0. Lawrence and is illustrated by his U. S. Patent No. 2,692,532, granted Otocber 26, 1954.

In order to facilitate an understanding of the features of the present invention, a brief description of one such form of single-gun PDF tube will now be given. This description should be construed as exemplary rather than limiting, since it will be seen that the invention is obviously applicable to tubes operating along different principles. In general, however, the tube may incorporate a screen, or target electrode, made up of a relatively large number of very narrow component-color phosphor strips laid down in a predetermined sequence and intended to luminesce, when impacted by the cathoderay beam, in colors such as red, green, blue, green, red, green, etc. Obviously, when reference is hereinafter made to the color of a phosphor, what is meant is the color of the light emitted therefrom which reaches the eye of an observer. The phosphors are then aluminized, or in some other manner provided with an electrically conductive coating.

A grid assembly is located adjacent to such a phosphor screen. The grid may be made up of essentially parallel wires, and so related to the phosphor strips of the screen that, in an electron-optical sense, there is a wire aligned with each blue strip, and similarly a wire aligned with each red strip. The red wires are connected to a common terminal, while the blue wires are similarly joined together electrically.

Between the grid wire assembly and the conductive coating on the phosphor screen there may be established a relative difference of potential of such magnitude and polarity as to create a series of converging cylindrical electron lenses for the electrons in the scanning beam. Such converging electrical fields cause the beam electrons to form a fine line pattern on the phosphor screen, this line structure having no necessary direct geometrical relationship to the path covered by the scanning beam in tracing the lines of the raster area.

It will now be appreciated that as the beam electrons travel from the electron gun, they may be focused by the above-described lens structure into a series of lines associated with the phosphor strips. If there is zero atent O i 2,748,238 Patented May 29, 1956 potential difference betwen the red and blue terminals of the wire grid, then these lines formed by the beam electrons will be caused to lie within the boundaries of the green strips. If the wires associated with the red strips are made positive relative to the wires electron-optically related to the blue strips, the beam electrons will be deflected, and the thin lines will now lie within the boundaries of the red strips. Similarly, electrons will strike the blue strips when the wires associated with such strips are relatively positive with respect to the red wires. Different component colors are thus displayed according to the potential difference (if any) existing between the two sections of the grid wire assembly. Accordingly, color control in a cathode-ray tube having a grid assembly of the above nature (whether used for PDF or not) is brought about by a cyclic change in the potentials applied to selected wires of the grid.

in designing one form of grid assembly in which the above principles are utilized, the wires thereof are maintained in position relative to the phosphor strips of the target by means of spacer elements, since the distance between the grid wires and the phosphor-coated surface of the target is critical in many respects. One preferred construction in which the grid wires and the phosphor screen are formed as a single unit is illustrated and described in a United States patent to Renn Zaphiropoulos, No. 2,683,833, granted July 13, 1954.

In the Zaphiropoulos assembly, a light-transmissive base plate (which may be of glass) is employed as a target backing. This base plate is secured to a grid frame by the strand conductors, or wires, of the grid. A pair of spacer bars is afiixed to one surface of the base plate, and defines a window, or target area, therebetween which may be coated with phosphor strips having the desired color characteristics. Means are provided for securing the electrically-conducting wires to the frame so that these wires extend across the window, or target, area of the base plate and are positioned therefrom by the spacer bars. Inasmuch as the grid structure is designed for color switching, or micro-deflection, of the beam in the vicinity of the target electrode, the wires or linear conductors are divided into two sets of alternate strands, and suitable means are provided for applying potentials to each set of strands. To carry this out, the frame is divided into two sections, with each section serving a separate set of strands and also being electrically insulated from the other. Consequently in this form of construction the glass plate is sandwiched between the wires of the grid, on one hand, and the two frame sections on the other. together by the tension of the wires associated with the. outer frame portion, and this pressure acts to hold the frames, base plate, and wires in a unitary assembly.

The color grid structure set forth by Zaphiropoulos in his above-mentioned patent is completely satisfactory insofar as operation is concerned, and produces an image in which there is no color contamination. Nevertheless, it is somewhat time-consuming to manufacture due to the techniques which must be employed. As preferably constructed, each set of grid wires is attached to its associated frame section by hooking the wire over a projection on the frame, laying down the wire across the raster area of the base plate, hooking it over a projection on the opposite side of the same frame, bringing it back across the raster area of the base plate, and so on. A winding operation is thus carried out which, while producing a grid of satisfactory operating characteristics, nonetheless requires a considerable amount of time to complete and hence materially reduces the number of units which may be manufactured within a given time period.

In an attempt to shorten the time required for fabricat-, ing such color grid structures, an alternative method was These two frame sections are pressed devised. This is set forth both in the above-mentioned patent of Renn Zaphiropoulos, No. 2,683,833, as well as hi further application, Serial No. 307,436, filed Sep tember 2, 1952. This consists of winding the grid continuously around the base plate to eliminate the backand-forth motion previously employed. Inasmuch as this leaves a set of wires on the rear, or viewing, side of the base plate which have to be removed prior to operation of the tube, it is necessary to anchor the wires near the two extremities of the base plate. This is done by cementing them in position so that the portion of each turn of wire which is unnecessary to tube operation may be cut out and discarded. Although eliminating one objectionable feature of previous methods of construction, this lastmentioned technique adds a step of cementing the wires in position, and, furthermore, all of the tension of the wires in such a construction is exerted through these ccmentitous bindings. In addition, winding of the grid by such a method still requires a considerable period of time inas much as each wire strand is wound individuall A further step in the development of grid structures of the type under consideration is to extend the idea set forth immediately above and at the same time eliminate the necessity for retaining the wires in position by a cementitious substance, as well as to reduce by a considerable amount the time necessary for completion of the grid structure. These objectives are carried out by utilizing a wire-positioning apparatus which utilizes spools of wire equal in number to the number of wires desired on the finished grid. The continuous conductors obtained by unwinding all of these spools of wire concurrently are caused to extend in substantially parallel fashion. Furthermore, a tensioning device is provided for this set of continuous conductors, so that the wires, which lie in substantially parallel relationship, are maintained under a degree of tension approximately equal to that whicn is desired for the finished grid wire assembly. A metal frame section is then brought into contact with this set of tensioned wires in such a manner that the two oppositelydisposed sections of the frame contact the set of grid wires at the precise points necessary to assure parallel alignment of the wires following an attachment of the wires to the frame section.

In other words, the frame section is laid against the set of parallel wires so that the wires extend across the window area of the frame. At points where the individual wires cross the two frame sections, the former are welded to the frame, with these welds being made successively so that the frame is first welded to each wire of the set at that point furthest removed from the rolls or spools containing the continuous conductors. A similar welding operation is then carried out on the remaining frame member at two oppositely-disposed points, the wires extending beyond the welds are cut off so as to leave a set of tensioned conductors extending across the open area of the frame and secured to the two oppositely-disposed frame members.

The welding process hitherto performed upon the set of grid wires and the frame section in order to secure these two units together is of the type in which a pair of welding electrodes are placed so that one of the elec trodes underlies the lower surface of the frame section crossed by the Wires, and the remaining electrode is brought into contact with the wire surface at a point opposite to that at which the wire contacts the frame. Qurrent is then passed through the wire and the frame side member so as to effect a fusion of the wire metal to the metal of the frame.

A serious difficulty arose in carrying out the above operation, due to the fact that, when the wire was spotwelded to the frame, the tension under which the wire was held caused the wire to break at the point of the weld. The reason underlying this action is that during the welding operation the welding current melts the wire metal, and consequently the strength of the wire is reduced sub- 4' stantially to Zero during the actual welding time. As a result, the tension of the wire causes the wire to pull away from the welding area. The present invention discloses an extremely simple method of preventing this wire breakage during the welding operation, and one which requires substantially no additional time or effort.

One object of the present invention is to provide an improved process for welding together metallic articles.

An additional object of the present invention is to provide an improved process for Welding a plurality of grid wires to a metallic supporting frame.

An additional object of the present invention is to provide a process of the above nature in which breakage of the grid wires due to the welding process is minimized.

A still further object of the present invention is to provide means for retaining a set of grid wires under tension during a welding operation so that melting of any particular grid wire during the welding process will not result in breakage of that wire.

Other objects and advantages of the present invention will be apparent from the following description of a preferred form thereof and from the drawings, in which:

Figure l is a perspective view of one form of apparatus by means of which the method of the present invention may be carried out;

Figure 2 is a side view of Figure 1 showing an additional apparatus for concurrently performing welding operations on two separate grid frames;

Figure 3 by its parts 3a, 3b, 3c shows the progressive movement of the frames;

Figure 4 is a plan VlW of a grid wire and frame assembly such as it appears after the process of the present invention has been completed;

Figure 5 is a side view of a modification of the apparatus of Figure l; and

Figure 6 is an end view of Figure 5.

Referring now to Figures 1 and 2 of the drawings, there is shown a plurality of spools of wire equal in number to the number of grid wires desired in the finished assembly. Only relatively few of these spools have been illustrated for the sake of clarity. These spools are arranged side-by-side or in a matrix, so that the wires, when drawn from the spools and aligned, lie in substantially parallel fashion as best illustrated in Figure 1. Furthermore, these parallel wires are preferably but not necessarily substantially coplanar as again best illustrated in Figure l. in order to accomplish this positioning and to initiate the welding operation which is described herein, the end of the wire from each of these spools it) is secured by a clamp 12 which is only made use of when the equipment is first set up for operation. it has for its purpose the placing of the wires in the position best shown in Figures 1 and 2, where they are maintained under a desired degree of tension by suitable means such as the spring 14. The wires thus placed under tension are drawn out from their respective spools by the wire clamp 12 until they are of sufiicient length to accommodate the weld ing apparatus which is now to be described.

The principal object of the present invention is to permit the continuous production of grid wire assemblies in a minimum period of time and by a process which will be substantially automatic in operation, thus requiring little or no personal attention. To achieve these objectives the following procedures are used: A grid frame in is supported in a movable jig which travels in a direction substantially parallel to the direction in which the wires it extend from the spools it). This movable jig (which is not illustrated in the drawing as it may be of any suitable design) positions and supports the grid frame 16 so that the wires extend across the upper surface thereof and contact two oppositely-disposed side members 2! of the frame. The parallel wires 18 thus extend across the window area defined by the four side members of which the frame 16 is composed, each of the Wires 18 thus having two points of contact with the frame 16. The jig by which the frame 16 is supported causes the latter to contact the wires 18 but at the same time this contact does not force the wires out of their parallel relationship or otherwise disturb their normal position.

As previously brought out, the frame 16 is designed to be moved by its suporting jig in a direction substantially axially or" the wires 18. In order to set up the equipment and initiate the operation thereof, a first frame is placed in such relationship with the wires 18 as to be in the position A set forth in Figures 2 and 3. In order to properly align the wires 18 with respect to the frame 16, a stationary wire-aligning member 22 is employed between the tensioning apparatus 14 and the first position A of the frame. This insures that the wires 18 are parallel with one another and properly spaced with respect to the side members 20. The wire-aligning member 22 preferably consists of a comb-shaped strip (as best shown in Figure 1) having a plurality of slits equal in number to the number of wires 18. The latter, after being respectively drawn through the slits in the wire-aligning member, then cross the upper surface of the frame 16 lying in the position A (best shown in Figure 2) and then through slits in a second and movable wire-aligning member 24 which is shown in its raised position in Fig ures 1 and 2. This second wire-aligning member 24 has a function somewhat similar to that of the first-mentioned wire-aligning member 22 in that it keeps the wires 18 in their parallel position relative to the frame section 16 and does not readily permit a displacement thereof even when the wires 13 are operated upon during the subsequent welding process. As will later be brought out, this second wire-aligning member 24 is arranged to be raised or lowered (as suggested by the dotted outline in Figure 1) to permit a shift of the grid frame 16 from position A to a new position B shown in Figures 2 and 3.

Summing up, therefore, the plurality of tensioned wires 18 pass through the slits in the first wire-aligning member 22, across the upper surface of the two oppositely disposed frame members 20, through the slits in the second wire-aligning member 24 (which is in raised position) and then to the wire clamp 12 which is utilized to maintain the wire tension at this stage of operation.

A retaining strip 26 is now laid over the wires 18 so as to extend substantially transversely to the direction of the wires and also to extend across the upper surface of one of the frame members 21) (as best shown in Figure 1) thereby sandwiching the wires 18 between this retaining strip 26 and the frame member. A pair of diametrically-opposed welding electrodes 28 are brought into position so that one of the electrodes exerts a downward pressure upon the upper surface of the retaining strip 26, and the other of the welding electrodes 28 exerts an upward pressure on the undersurface of the frame number 20. Thus the welding electrodes 28 in effect act to compress therebetween the retaining strip 26, one of the wires 18, and the frame side member number 20.

, The welding electrodes 2% are shown in Figures 1 and 2 as being of substantially linear configuration at their effective welding point, and extend substantially normal to the plane defined by the frame 16 and the grid wires 18. These welding electrodes 28 are furthermore designed to be movable relative to the assembly consisting of the members 18, 2t) and 26 in a direction substantially transverse to the wires and parallel to the direction of the retaining strip. Expressed still differently, the welding electrodes 28 are designed to travel along the retaining strip so that current may be passed through the electrodes-28 while they are centered above each of the wires 18, thus effectively welding one of the wires 18 to both the retaining strip 26 and the frame side member 20. This relative movement of the electrodes 2-3 is indicated by the arrow in Figure l, and may be carried out by any suitable means. Preferably, the welding electrodes possess a progressive intermittent movement with respect to the frame 16, this progression being such that there is no relative movement of the two elements at the precise instants when the welding electrodes 28 are centered above 'each of the wires 18. Current is at those times passed between the electrodes to efiect the weld, following which the current is interrupted and the relative movement between the electrodes 18 and frame 20 continues until the electrodes are centered above the next adjacent wire to the one last welded. This process continues until all the wires 18 have been welded to the one particular frame side member 2%. (As shown in Figure 2, two sets of welding electrodes are actually used, but the operation of a single set has been described above in order to set forth the theory of operation.)

In practice, the frame 16 will start in the position A shown in Figure 2, so that the first weld will be made on that member 21) which is on the right hand side of the frame. It is necessary, of course, that the wire clamp 12 be effective during this period in order to retain the wire tension until the first welding operation has been completed.

According to a principal feature of the present invention, the action of the retaining strip 26 prevents breakage of the grid wires during the welding operation. This is due to the fact that each retaining strip 25 extends for a sufficient lateral distance to either side of the weld made by the electrodes 28 so that the tension of the wire being welded does not act to pull it away from the clamped assembly. This result follows even though the welding process may possibly cause a melting of the wire material to such an extent that the strength of the wire during the welding operation would normally be reduced substantially to zero at the weld point. To accomplish this clamping effect, the width of each of the retaining strips 26 is so chosen that the welding current flows only through a portion of the strip width, with the remaining portion serving solely as a clamp.

After a welding of one of the side members 20 has been completed in the position A shown in Figure 2, the frame 16 is moved by its jig to position B. In the latter location, the remaining one of the side members 20 is welded by a second pair of welding electrodes 28. Concurrently with this welding of the remaining side member 20 of the initial frame 16, a welding of one member of a second frame is carried out, this second frame being in the position A formerly occupied by the initial frame (see Fig. 3b). Expressed differently, one side member of each of two separate frames is welded in a single welding operation by the use of the two pairs of welding electrodes 28 shown in Figure 2. Since the operation of each of these pairs of electrodes is identical, it is believed that the above description is sufficient to make this phase of applicants process completely clear.

Once a welding operation has been completed so that the set of wires 18 is secured to one side of a frame member 16, the wire clamp 12 is no longer necessary and can be dispensed with.

In order to permit the shift of a frame section 16 from position A to position B, it is necessary that the movable wire-aligning member 24 be lowered as indicated in dotted lines in Figures 1 and 2 so that the jig on which the frame 16 is supported may move this frame 16 without hindrance. Any suitable means of raising and lowering this member 24 may be used, and since the particular details thereof constitute no part of the present invention they have not been illustrated.

Figure 3 shows the successive frame movements from position A to position B to a final position C. As illustrated in Figure 3a, one weld is initially performed in position A as indicated by the small x on the upper surface of one of the frame side members 29. The frame is then shifted to position B, and a new frame is brought into position A as shown in Figure 3b. Two welds are then carried out simultaneously, one of these welds being the final one for the initial frame, and the other weld being the first one for the new frame member. The initial frame (now being welded in its entirety) is moved to a new position C as shown in Figure 3c. The projecting ends of the grid wires 18 are then sheared off at the point indicated so that the completed frame assembly after being removed from the welding jig will have the appearance shown in Figure 4. Both retaining strips 26 will overlie the parallel grid wires 18, and the Welds will securely hold the retaining strips 26, grid wires 18, and

rame 16 in a unitary structure.

if desired, additional welds may be made at or near the extreme ends of each retaining strip 26 so as to prevent any looseness between these members and the frame 16 and to result in a better positioning of the assembly during the welding operation.

It will now be recognized that the welding process herein described is capable of continuous operation so as to mass-produce grid structures of the type set forth with a minimum of manual attention and by the employment of relatively simple and inexpensive apparatus.

Although linear welding electrodes have been illustrated in Figures 1 and 2, it is obvious that the particular shape of these elements forms no part of the present invention. For example, if desired the welding electrodes may have a configuration such as shown in Figures and 6. That is, they may be substantially cylindrical in outline so as to permit a rolling movement of the electrodes over the retaining strips 26 and the frame sections 20. These roller electrodes, identified by the reference numeral 3t), are of a type known in the art, and, as in the case of Figures 1 and 2, serve to compress the retaining strips 26, the grid wires 18, and the frame sections 29 therebetween and thus preclude any lateral displacement of the grid wires 18 relative to the members between which they are compressed. In the case of the modification shown in Figures 5 and 6, it may be desirable to apply a continuous welding current to the electrodes 3t or it may be preferable intermittently to interrupt the current and permit it to flow only at the times when the axis of each of the roller electrodes 30 is substantially in line with one of the grid wires 18 (as best shown in Figure 5). The particular type of operation utilized will depend in part upon the composition of the materials used, upon their thickness, and upon the conditions under which the resulting structure is to be operated. Either mode of operation is clearly within the scope of the present disclosure.

Although the present invention is not limited to use with any particular type of frame section or with any particu lar type and size of Wire, nevertheless one arrangement which has operated successfully in actual practice employs stainless steel wire having a diameter of approximately 6 mils, a. rectangular frame section made out of A thick stainless steel, and retaining strips also made of stainless steel and having a thickness of approximately 6 mils. These dimensions, however, are intended to serve merely as examples, and will be modified as determined by practical considerations.

Having thus described the invention, What is claimed is:

l. In the art of welding a plurality of tensioned wires to a frame made up of two sets of oppositely-disposed sections so that the wires extend in substantially parallel relationship across the window area defined by the two sets of o positely-disposed sections, the steps which include lriC-lllilg said tensioned wires so that they have substantially the relative positions desired after welding, bringing said frame into contact with said Wires so that each particular wire of the latter contacts two oppositelydisposed frame sections, spot-welding each wire to each of the two said oppositely-disposed frame sections, and compressing said wire during the Welding operation against Fur that particular frame section which is being welded for a sufficient distance along said wire in each direction from the welding area so that the tension in said wire across the window area of said frame is retained regardless of the detensioning effect induced by softening of the Wire material as a result of the welding operation.

2. A process according to claim 1, in which all of said plurality of wires are welded to said frame in consecutive fashion, and in which the compressing of said each wire against a particular frame section is performed by a retaining strip of electrically-conductive material extending substantially transversely to and overlying said wires in such a. manner that the latter are sandwiched between said retaining strip and said frame section.

3. A process according to claim 2, in which each wire of said plurality is welded to said frame section through the medium of a pair of oppositely-disposed welding electrodes which have a unitary movement relative to said frame section in the general direction of said retaining strip, the two electrodes of said pair respectively contacting said retaining strip and said frame section.

4. A process according to claim 3, in which the relative movement of said welding electrodes and said frame section is of a continuous nature.

5. A process according to claim 3, in which the relative movement of said welding electrodes and said frame section is of an intermittent nature.

6. A method of welding a filamentary conductor under tension to a metallic supporting member which includes the step of clamping said conductor to said supporting member beyond the welding area so that such clamping action tends to maintain the tensioned condition of said conductor when the substance of which the latter is composed tends to change its nature during the welding operation.

7. The process of welding a plurality of tensioned wires to a supporting frame so that they extend across an opening therein, said process including the steps of positioning said frame so that said wires lie across one surface thereof, placing an elongated retaining member over said wires so that the former extends substantially transversely to the direction of said wires, connecting a welding current source between a pair of linear electrodes, bringing the assembly consisting of said frame, said wires and said retaining member between said electrodes, and creating a relative movement between said pair of electrodes and said retaining member and in the general direction of the latter so that by the current from the source the said wires are successively welded to said frame.

8. The process of welding a plurality of tensioned wires to a supporting frame so that they extend across an openi rig therein, said process including the steps of positioning said frame so that said wires lie across one surface thereof, placing an elongated retaining member over said Wires so that the former extends substantially transversely to the direction of said wires, connecting a current source between a pair of roller electrodes, bringing the assembly consisting of said frame, said Wires and said retaining member between said electrodes, and creating a relative movement between said pair of electrodes and said reraining member and in the general direction of the latter so that current from the source is effective to Weld said wires successively to said frame.

Cited in the file of this patent UNITED STATES PATENTS 1,066,536 Dean Oct. 24, 1911 2,479,556 Chanowitz Aug. 23, 1949 FOREIGN PATENTS 355,662 Germany June 29, 1922 388,076 Germany Jan. 8, 1924