US2531389A - Method of making capacitors - Google Patents

Description

- 1 Nov. 28, 1950 K H BRANDT 2,531,389

mo!) 01- mane CAPACITORS Filed July 28, 1944 a Sheets-Sheet 1 INVENTOR.

KRISTIAN H. BRANDT M 444';

ATTORNEY Nov. 28, 1950 K. H. BRANDT men or mane CAPACITORS Filed July 28, 1944 8 Sheets-Sheet 2 IN I EN TOR. KRISTIAN H. BRANDT WM ATTORNEY Nov. 28, 1950 K. H. BRANDT 2 2,531,389

min-non OF MAKING CAPACITORS Filed July 28 1944 I 4 8 Shogts-Shet 3 INVENTOR. KRISTIAN H. BRANDT ATTORNEY Nov. 28, 1950 K. H, BRANDT I 2,531,3 9 m'ruon 0F mm; CAPACITORS Filed July 28, 1944 I a sh eet s s h eet 4" INVENTOR. KRISTIAN H. BRANDT Weld ATI'ORNEY' Nov. 28, 1950 K. H. BRANDT 7 2,531,389

METHOD OF MAKING CAPACITORS Filed July 28, 1944 8 Sheets-Sheet 5 INVENTOR. KRISTIAN H. BRANDT ATTORN EY Nov. 28, 1950 K. a. BRAND 2,531,389

METHOD DF'MAKING CAPACITORS Filed July 28, 1944 a Sheds-Sheet 6 FIG. l3.

INVENTOR. KRISTIAN H. BRAN DT ATTORNEY Nov. 28, 1950 K. H. BRANDT 2,531,389

. METHOD OF MAKING CAPACITORS Filed July 28, 1944 8 Sheets-Sheet '7 FIG. l4.

f I a 3 In Q VENTOR. v I KRISTIA BRANDT Wu 44., 541a ATTORNEY Nov. 28, 1950 K. H. BRANDT 2,531,339

' IIETHOD OF MAKING CAPACITORS Filed July 28, 1944 8 Sheets-Sheet 8 FIG. l5.

INVENTOR. KRISTIAN H. BRANDT ATTORNEY Patented Nov. 28, i950 METHOD OF MAKING CAPACITORS Kristian H. Brandt, Red Bank, N. J. Application July 28, 1944, Serial No. 547,094

2 Claims.

(Granted under the act of March 3, 1883, as

amended April30, 1928; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

The present invention relates to capacitors and methods and apparatus for making the same.

Fixed capacitors are ordinarily made up in two forms. One, comprises a stack of plates of metal conducting foil, separated by thin sheets of dielectric material, alternate layers of conducting foil being electrically joined. The other comprises two long strips of metal conducting foil, separated by dielectric material and rolled together so that one edge of one strip of foil is exposed for electrical connection at one end, of the roll, and the opposite edge of the other strip is similarly exposed at the other end of the roll. In the present specification I will describe my invention in connection with the said two forms of fixed capacitors, but it is to be understood that the invention need not be limited thereto.

A good capacitor dielectric should be usable in very thin sheets so that capacitors may be made having relatively high capacity for their size. To be well suited'to high frequency circuits, it should have a high dielectric strength to preclude it against puncture and resultant shorting of the capacitor, 8, low power factor and a relatively fixed dielectric constant over a wide frequency,

istics, to my knowledge they have never been 'suc-- cessfully used as interplate insulation in fixed capacitors prior to my invention. I have worked out a, method 01' using such dielectrics so that the finished capacitors not only are as satisfactory as capacitors in general use, but I find that they are unexpectedly far superior. One possible deterrent to the use of glass or vitreous enamel as a capacitor dielectric has been that processes had not previously been evolved for quantity production so as to allow fabrication of such capacitors of a quality or at a cost to compete with other conventional capacitors.

Recently, largely in view of shortages in certain critical materials, such as mica, it has become increasingly important to find means of using alternate materials in capacitor production.

Extensive use of electrical and electronic equipment in motor vehicles and aircraft has also put additional requirements upon capacitors. such as substantial immunity to temperature changes,

except in a predetermined manner, and insensifly! to vibration.

2 It is, therefore, an object of the present invention to provide capacitors, which will have a high ratio of capacitance to size, which will not be deleteriously affected by extremes of temperature 5 or humidity or sudden fluctuations in tempera.- ture or humidity, and which will not be adversely afiected by vibration incident to vehicular and aircraft installation.

Another-object has been to incorporate into a capacitor a dielectric which has good mechanical and electrical stability, a low power factor, a high dielectric strength and ahigh inherent insulation resistance.

It is a further object of the present invention to provide a, capacitor which is hermetically sealed against moisture, oil, dirt and the like so that it is protected against climatic changes, corrosion, etc.

Another object is to provide a capacitor. which is made of materials which are impervious to deterioration with time and which will form a single unitary structure, the parts of which will not separate even under exacting conditions.

A still further object of this invention is to provide a, capacitor in which the parts are retained in their relative positions mechanically and are not dependent upon fillers, such as wax or other filling compounds frequently used.

Still another object has been to design capacitors which do not include strategic materials and which, in electrical and mechanical characteristics, are superior to, or at least compare favorably with, capacitorsusing strategic materials.

Another object has been to provide apparatus and methods of manufacture for quantity production of such capacitors so as to allow their fabrication upon a practical basis and at a reasonable cost.

I have accomplished the foregoing by designing capacitors utilizing glass or vitreous enamel as their dielectric material which is applied in liquid or paste form and, in some embodiments, metallic conducting plates which are similarly applied in liquid or paste form and by devising methods and means for handling such materials and parts during the various manufacturing steps. The application of "either the dielectric material or the conducting material, as the case may be, in paste or liquid form, may be accomplished by any of several methods. Although I will describe the methods of spraying and dipping, the methods of painting with a brush or applying with a squeegee, preferably through a 56 screen. or pressing, as with a rotary press, may

also be used. However. I do not wish to be limited enamel, which makes it particularly valuable as a dielectric material for capacitors, is the fact that it can be produced in extremely thin films, such as of the order of .0015 to .005 inch in thickness without sufiering the loss of its excellent dielectric characteristics. Likewise, the metallic conducting plates, which are applied in paste or liquid form, can be of the order of .000! to -.00175 inch in thickness. Of course, the materials may be used in my capacitors in thicknesses greater or less than those mentioned, but I believe that they result in eminently satisfactory practical capacitors which have extremely good electrical and mechanical characteristics and are well suited to replace capacitors using mica or paper dielectric, even were there no capacitors.

I shall refer hereinafter to green vitreo enamel or glass to indicate that stage of its manufacture when it has attained sufilcient viscosity and freedom from moisture so that it will not flow, but so that it may nevertheless be bent and handled without cracking and so that it may be readily cut. This green stage may be achieved by a preliminary partial heating or baking, in

-facture of both stacked type and rolled type 4 4 a second die, with extra liquid enamel, for fusing a hermetically sealed envelope about the same Figure 6 is a perspective view of a completed capacitor of the stacked type after the completion of the fusing operation of Figure Figure '1 is a perspective viewgshowing the steps of cutting a ribbon of vitreous enamel into recorder to partially dry the enamal, after it has Figures 1a through 19' show steps in the manu- 5 facture of rolled type capacitors wherein metal foil is used. 7

More specifically, Figure 1 is a perspective view showing the steps of spraying metallic material. in liquid form, through a spraying shield, onto a thin ribbon of vitreous enamel and then cuttin the same, as indicated bythe broken lines, into blanks, each blank comprising a rectangular sheetof vitreous enamel dielectric and a paddleshaped plate of metallic, electrical conductin material.

, Figure 2 is a perspective view showing the step of passing the blanks of Figure 1 through an oven, for firing of the vitreous enamel and the metallic material and the step of stacking a number of said fired blanks, one above the other.

Figure 3 is a perspective view showing the step of placing such a stack of blanks into a die to fuse together the peripheral edges of the enamel sheets to form a monolithic structure;

tangular sheets and of spraying metallic material on toeach one separately, this being a modification of the step shown in Figure 1;

Figure 8 is a perspective view showing the steps of cutting a ribbon of metal foil into paddleshaped plates and of spraying said plates, two at a time, with a thin coating of vitreous enamel;

Figure 9 is a perspective view showing the step of passing the two plate units of Figure 8 through an oven for firing of the enamel and the step of cutting them into individual blanks;

Figure 10 is a perspective view showing the step of stacking the blanks of Figure 9;

Figure 11 is a perspective view showing a modification of thespraying step of Figure 8, wherein a plurality of paddle-shaped metal plates are sprayed with vitreous enamel in one operation, and the step of passing the coated plates through a firing oven;

Figure 12 is a perspective view of another modification of the coating operation, shown in Figure 8 or 11, wherein a plurality of paddle-shaped plates of metal foil are simultaneously dipped into a bath'of liquid vitreous enamel and are then passed through an oven for firing;

Figures 13 and 14 are perspective views showing diagrammatically the machine components and steps of a process for production line" man-v ufacture of roll type capacitors, some of the parts being omitted and others being broken away for clarity, Figure 13 showing the steps of cleaning two ribbons of metal foil,- coating them with enamel, baking them, winding them into rolls and firing them, and Figure 14 showing the steps of attaching terminal wires to the rolls and hermetically sealing them within vitreous enamel envelopes; s

Figure 15 is an elevational view of one of the terminal wire applicators of Figure 14, the retracted positions of the gripper and burner being shown by solid lines and the intermediate position of the gripper by broken lines;

Figure 16' is an elevational view of the tube sealer of Figure 14, the burners being shown in their operating positions and the left burner being cross-sectioned;

Figure 17 is an enlarged cross-sectional view of a rolled type capacitor, manufactured as shown in Figure 13 through 16, the left half showing the capacitor roll after the firing operation and the 5 two spraying plates are substituted for a spraying tube; and

Figure 19 is a perspective view of another modification of said spraying step of Figure 18, wherein a ribbon'of metal foil is dipped into a bath of liquid vitreous enamel.

In my process for the manufacture of stacked type capacitors, shown in Figures 1 through 8. a long ribbon of vitreous enamel i'llm ll (Figure 1), in its green state, is supported upon a fist conveyor 53 which is movable in the direction indicated by the arrow. The said conveyor, and other conveyors which will be referred to herein, may be of stainless steel or any other suitable material. Said enamel film ll may have been a,sai,sse

deposited on said conveyor 88 by spraying, as will hereinafter appear, or in any other suitable manner. A spraying shield 85 is superimposed over said enamel i, said shield being provided with a plurality of paddle-shaped openings 81, equally spaced from each other. The shield 55 may be moved into place for use or it may be permanently supported slightly above the conveyor 58. The spraying shield 55 is so positioned that the extremities of the narrow tab-shaped ends 58 of the paddle-shaped openings 51 project beyond one edge 8I of the ribbon of enamel film II. The

conveyor 88 is made of inert material so that,

during the metal spraying process to be described, the sprayed metal will not become bonded to the conveyor.

A fine spray of metallic, electrical conducting material 88, in liquid form, such as finely powdered silver suspended in a suitable liquid binder vehicle, is then directed at the exposed portions of the vitreous enamel 5| by means of a spray nozzle 81. Said nozzle 81 is preferably oscillating so as to distribute the material 85 evenly. When a desired thickness of metallic conducting material 85 has been deposited and the shield 55 has been removed, the vitreous enamel 5| will have a plurality of thin paddle-shaped plates 88 of metallic conducting material adhering thereto. The ribbon of enamel 5i will.then be severed into a plurality of blanks 13, as indicated by the broken lines (Figure 1), by means of a, cutting die 1| having a plurality of mutually parallel cutting knives 12. Each blank 13 comprises a rectangular sheet 15 of vitreous enamel, one. surface of which is covered by a paddle-shaped plate 88 of metallic material, said plate being of slightly smaller area and having a tab 18 projecting beyond one edge SI of the sheet of enamel.

The Iblanks 13 are then carried by the conveyor 58 through a firing oven 8| (Figure 2). The firing process may be a lengthy one and may require several ranges of heat. Thus, the oven 8| may be a very long one and the conveyor 53 may pass through it at a snail's pace. It may also be desirable to transfer the blanks 13 to another conveyor (not shown) which will carry them through the oven 8|. This conveyor would be much wider so that a plurality of blanks could be plaoed'abreast upon it to be fired simultaneously. After proper firing, the blanks 18 are carried into a chute 83 leading into a rotating stacking machine 85. The chute 83 is provided with an inwardly extending arm 84 which catches one end of each blank 18 so as to cause it to enter the chute endwise. Said stacking machine 85 is provided with a compartment 81 having the configuration of a rectangle with a narrow tab-like extension 88 at each end. The stacking machine 85 is timed to rotate so that one of the fired blanks 13 is dropped into the compartment 81 at each half turn thereof so that the rectangular sheets of enamel 15 are stacked up in register but the metallic tabs 18 of consecutive lblanks 18 extend in opposite directions into the extensions 88. The arm 84 may be omitted if thestacking machine 85 is designed to stop in a position 90 removed from the position shown in Figure 2. Then the blanks 13 could slide in sideways.

After a predetermined number of said blanks 18 have been stacked, they are removed from the stacking machine 85 to a fusing die composed of two parts 8|, 88 (Figure 3). Although, for clarity, only four blanks 18 are shown in Figure 3, it will be understood that any suitable 6 number may be stacked. In the die 8|, 88 the edge portions, of the sheets of vitreous enamel 18, which extend beyond the edges of the metallic plates 88, are fused together so that the several blanks 18 are formed into a monolithic 88 (Figure 4) pierced by horizontal holes, and

a pin or rod I8I passing through the holes of each clip and through the tabs within it and a lead wire I attached to said pin. Although a method using clips 88 is here shown, it will be understood that soldering a lead wire directly to the tabs 18 is a preferred construction where the metallic material has been sprayed on. Then, the tabs 18 need extend only an infinitesimal distance beyond the edge 8I of the vitreous enamel sheets 18; Also, for added strength, the tabs 18 may be as wide as the metallic plates 88 themselves. The construction shown in Figures 4 and 5 is, however, a preferred arrangement where metal foil is used for the plates, as will be referred to hereafter in connection with the processes illustrated in Figures 8 through 12.

If an entire capacitor were made of but one of the monolithic structures 81, described above, there might be a tendency for the large number of blanks 13 to buckle or warp during firing. This tendency is avoided, however, by making the monolithic structures 81 of fewer blanks 13 and then assembling a, number of such structures together (Figures 4 and 5). In this construction, I find it advisable to insert stiffening sheets of vitreous enamel I88 (considerably thicker than the sheets 15 aforementioned, and preferably of the order of .01 to .03 inch), between the several monolithic structures 81 and at the top and bottom of the assembly. If the leads are soldered directly to the tabs 18, they will then be soldered to the tabs of the several structures 81 in the assembly. If the construction shown (Figures 4 and 5) is used, the pins or rods I8I will pass through the clips 88 and tabs 18 of all of the monolithic structures 81 and a lead wire I85 will be attached, by soldering or otherwise, to each of said pins. Although Figure 4 shows an assembly comprising but two of said monolithic structures 81, it will be understood that any number of them may be used. Where but one monolithic structure 81 is to be used for the finished capacitor it is advisable to place a stiffening sheet I88 above and below the stack of blanks 18 or, at least at that end of the stack which has an exposed metallic plate 88 (as the upper end in Figure 3).

The assembly just described (Figures 4 and 5) is then placed into a second fusing die (Figure 5) comprising an upper half I81 and a lower half I88. Slots I I I are provided at both ends of both die components I81, I88 to accommodate the lead wires I 85. The assembly aforesaid of several monolithic structures 81 is placed into said second fusing die I 81, I88 with sufficient liquid vitreous enamel H8 to completely surround it, and firing takes place so that, except for the outwardly extending lead wires I85, the finished capacitor II5 (Figure 6) is a unitary structure completely enclosed and hermetically sealed within a vitreous enamel envelope I I1. Said envelope H1 is fused about the leads I85 which extend through the vitreous enamel as in a radio dispersed about the assembly aforesaid by being sprayed thereon or by dipping the assembly into a tank of enamel or in any other suitable manner.

Although I have described the step of cutting the enamel ribbon I into rectangular sheets I5 (Figure l) as taking place while the enamel is still in its green state, this may be done after firing. In that event, a ribbon of enamel film 5i with a plurality of paddle-shaped metallic plates 59 thereon (as shown in Figure 1) will be fired as a unit and will thereafter be cut so as to iorm blanks I3, which may then be stacked in the manner already described.

In a modified procedure for forming the blanks I3, rectangular sheets of green vitreous enamel I5 are out or punched from ribbons 5i or larger sheets thereof'by any suitable means, such as by a cutting knife IIB (Figure 7). In either case said rectangular sheets I5 may be produced in quantity by moving the vitreous enamel into place, as on a conveyor I2I (Figure 7) and dropping the rectangular sheets onto another conveyor I23. The second conveyor I23 then carries the sheets I5 into position relative to a jig of vertical guide rods I25 (Figure 7), sustained from above, so that a spraying shield I21, vertically slidable on said guide rods I25, may be dropped down over said sheet I5. The shield I2! is provided with a paddle-shaped opening 51 (as previously described above in connection with Figure 1). Metallic conducting material in liquid form 65 may then be sprayed through the shield I21 so as to form a paddle-shaped plate "of metallic conducting material, the extremity of the tab of which projects beyond one edge of the rectangular sheet I5. After the steps illustrated in Figure '7, the blanks I3 resulting therefrom may then be processed as already explained, and illustrated in Figures 2 through 6.

The stacked type capacitors described above incorporate metallic, electrical conducting film, applied in liquid or paste form. A process for fabricating such capacitors, utilizing metal foil for the conducting plates, will now be set forth. In this process a long narrow ribbon of metal foil I28 is fed between guides I3I to a cutting die I33 (Figure 8) which, with cach downward stroke, cuts out two paddle-shaped metal plates I35, the tabs I31 of which are oppositely disposed. Each pair of the plates I35 is then carried by conveyor I39, moving as indicated by the arrow, under a spraying shield I which is provided with a rectangular opening I43. The plates I35, except for the extremities I of the tabs I31, which are covered by the spraying shield Ill, are then sprayed with liquid vitreous enamel I" by means of a spray nozzle I49 (Figure 8). This spraying operation results in a plurality of units I5I, each comprising two metal plates I35 covered, except for the extremities I35 of their tabs I31 by vitreous enamel I41. These units I5I are then passed through a firing oven 8i (Figure 9) (as already described above in connection with Figure 2). The units I5I are then fed by the conveyor r 8 and, therefore, the stacking machine I51 need not be ofvthe rotating type. When a sumcient number of blanks I53 have been fed into the stacking machine I51 they are removed and fused into a monolithic structure and ultimately formed into a finished capacitor (similar to the monolithic structure 31 and the capacitor I I5 described above and illustrated in Figures 3 through 6).

In a modification (Figure 11) of the process Just described, paddle-shaped plates I35 of metal foil are cut out by the use of a suitable cutting die (such as the die I33 of Figure 8 or preferably,

to minimize handling, a die which will cut the metallic ioil so that all of the tabs I31 will extend in the same direction). After cutting, a plurality of these plates I35 are positioned on a fiat surface, spaced from each other and with the tabs I31 all extending in the same direction (Figure 11) A spraying shield I53, provided with a rectangular opening IBI, is positioned over a number of such plates I35 so as to cover up only the extremities I35 of their tabs I31, whereupon vitreous enamel in liquid form I" is sprayed through the shield by means of spray nozzle I". The shield I59 is then removed and the enamel coated plates are moved in the direction of the arrow (Figure 11) into a firing oven 8| by means of a conveyor I53, where they are fired. They may then be cut into individual blanks I53 by means of a cutting die (such as die II shown in Figure 1). The resulting blanks I53 are then subjected to a processing similar to that described above and illustrated in Figures 2 through 6. It is to be noted, that, if desired, the enamel coated plates I35 may first be sent through a baking oven (not shown), to bring the enamel to its green state, may then be cut into blanks I53 and may then be sent through the firing oven II for firing.

In another modification (Figure 12), paddleshaped plates I35 of metallic foil are cut out (for example as shown in Figure 8). A plurality of said plates I35 are then gripped, by the extremities I35 of their tabs I31, and depended from a rack I65 (Figure 12). The rack is lowered to dip the plates I35 into a vat I51 of vitreous enamel I" in liquid form (Figure 12) so that, except for their gripped extremities I45, said plates are completely coated with vitreous enamel. The rack I and enamel coated plates are then carried, as indicated by the arrow (Figure 12), by means of an intermittently moving cable I53, into a firing oven II. The blanks I'II may then be stacked and formed into finished capacitors H5 in any suitable manner, such as is described above and illustrated in Figures 2 through 6.

It is to be noted that, in the last described modification, both surfaces of the metal foil plates I35 are coated with vitreous enamel I". Thus, when the blanks III are stacked, there are two sheets I33 (Figure 9) under a cutt ng knife IIS, which 1 cuts each unit into two blanks I53 which are thereupon carried by anotherconveyor I55 to a stacking machine I51 (Figure 10), provided with a compartment 81 (as already described in connection with the rotating stacking machine 55 oi enamel dielectric I" between consecutive metal conducting plates I35. Although this construction increases the thickness of the finished capacitor II5, it is to be strongly recommended as it precludes the possibility'of electrical shorts or leakage between metal plates I35 through pin holes or air bubbles in the thin sheets of vitreous of vitreous enamel I" are superimposed, pinholes or bubbles in the two sheets will practically never occur in register.

By suitable modifications, coating of both sides of the metallic conducting material or' metal foil may beaccomplished'ineachof theprocesses described above. Thus, in the first process set forth, after a layer of metallic conducting material 85 has been sprayed upon the ribbon of enamel 5| (Figure 1), the spraying shield 55 may be removed and a spraying shield provided with a rectangular opening (such as the shield I59, shown in Figure 11) may be substituted and a coating of liquid enamel I41 may be sprayed over the plate of metallic material 69 except for the extremity of its tab 19, thereby coating both sides of said plate. The procedure may then continue as already described.

Similarly, coating on both sides may be effectuated in the modification illustratedin Figure 7 by spraying liquid enamel I41 through a shield (not shown) with a rectangular openingafter the paddle-shaped plate of metallic material has been sprayed on through the shield I21.

The metal foil plates I35 shown in Figure 8 through II may be coated on both sides in any of several ways. For instance, after spraying enamel on one side of the plates I35 (as illustrated in Figures 8 and 11) they may be turned over and similarly sprayed on the other side.

Enamel coating may also be applied to the untype capacitors. The various steps of the process and suitable machinery to accomplish the same are diagrammatically shown in Figures 13 through 16, two modifications thereof are shown in Figures 18 and 19 and the internal make-up of a capacitor is shown in Figure 17. The capacitors are made up of two long ribbons of metal foil I13, I15. Each such ribbon is separately cleaned, coated with vitreous enamel dielectric I11 and partly baked to allow proper handling. They are then wound together about a core I19 and the resulting roll I8| is thoroughly fired. Electrical terminal wire leads I83 are then attached and the roll I8I is completely encased in a tubular envelope I85 of vitreous enamel. These steps will now be considered in detail.

For eflicient manufacture, the components of the machinery to perform the various steps of the process are preferably positioned substantially linearly. Referring now to Figure 13.- the sequence of the production line is shown from left to right. To the left are two'horizontally disposed, freely rotatable spindles I 81, one above the other, each being receivable to a spool I89, wound with a long ribbon of metal foil I13, I15. To the right of said spindles I81, also one above the other, are two rectangular tanks I9I of acid I93. Two opposite rims I95 of each tank I!" are smoothly rounded (or may b fitted with freely rotatable rollers) and, intermediate said rounded rims, is a partly submerged, smooth surfaced, cylindrical cross piece I91. A second pair of similar tanks (not shown), also one above the other. containing rinsing solution (not shown), are positioned to the right of the acid tanks I9 I. As may be seen in Figure 13, the spool I89 and the acid tank I9I of the lower tier are slightly nearer the observer than the corresponding components of the upper tier. The rinsing solution tanks (not shown) are similarly disposed. To the right of the tanks of rinsing solution (not shown) is a 10 hydrogen furnace I99 provided with two shallow horizontal slots 20I extending completely through it.

Further along to the rightare two spraying tubes 203 (Figure 13), one above the other. Each tube 203 comprises a pair of flat spraying shields 205, one above the other, each such shield bein provided with a rectangular spray opening 201. The shields 205 of each tube 203, are spaced slightly from each other and are joined along their lateral edges, so as to form a shallow passage 209 therebetween. Although the tubes 203 are offset, so that the lower tube and its passage 209 are slightly nearer the observer than the upper tube and its passage, the four openings 201 thereof are in register. Above and below the sprayin tubes 203 are four spray nozzles 2 that direct sprays of vitreous enamel I11, in liquid form, through the openings 201. To the right of the spraying tubes 203 is a baking oven 2I5 pierced by two shallow horizontal slots 2I1. The lower slots 20I, 2I1 of both the hydrogen oven I99 and baking oven 2I5 are slightly nearer the observer than the upper slots thereof.

Still further to the right are four freely rotatable rollers 2I9 (Figure 13) and beyond them a cutter 22I provided with two cutting knives 223, one at a slightly higher level than the other. To the right of the cutter 22I is a winding device (not shown) of any conventional type, which is adapted to grip and rotate a horizontally disposed cylindrical core I19.

The continuation of the production line now to be described is shown at the right in Figure 13 and from left to right in Figure 14, the parts bein shown in their respective positions at an instant when the conveyors 225, 226 have just come to rest. Below the winding device aforesaid (not shown) a conveyor 225 enters the production line from below and it moves to the right through a firing and annealing oven 221 (Figures 13 and 14) pierced by a single passageway 229. Said conveyor 225 moves intermittentl to the right, as indicated by the arrows, and it is provided with a plurality of two piece, substantially Y-shaped clips MI. The said firing and annealing oven 221 is of sufficient length to allow the maintenance of firing temperatures through its left portion and annealing temperatures through its right portion. If desired, two successive ovens (not shown), one for firing and the other for annealing, may be substituted for the single oven 221.

After said conveyor 225 has progressed through the oven 221, it passes between a pair (only the far one is shown) of flux applicators 233 (Figure 14) each of which is a cup 235 having within it a circular pad 231 kept saturated with soldering flux 239. Said conveyor 225 then passes between a pair (only the far one is shown) of solder applicators 2, each of which is an electrically heated cup 243 to which solder 245 is automatically fed. Said flux applicators 233 and solder applicators 24I are movable, horizontally, toward and away from the conveyor 225, as indicated by the arrows. They are normally in their retracted positions but, each time a clip 23I on the conveyor 225 comes to rest between them.v

they move inwardly toward the conveyor to perform their respective operations and they then return to their normal positions.

Further to the right the conveyor 225 passes between a pair of terminal wire applicators 241 (Figures 14 and 15). Each of such applicators a 241 includes a gripper 249 which is normally in a retracted position (shown in solid lines in Figures 14 and 15) and is adapted to grip a horizontally disposed lead-in wire I83, move it toward the conveyor 225, release said wire and then return to its normal position. Positioned directly above each gripper 249, when in its retracted position. is a vertically disposed, stationary. T-shaped chute I (Figures 14 and 15) adapted to hold a column of terminal wires I83. The lower end of each chute 25I is provided with a closure (not shown) which is opened momentarily, each time the gripper moves back to its retracted position, to release one terminal wire I83 and drop it into the gripper 249 below it. Said closure opens when an upwardly extending pin 253 on the gripp r 249 actuates 2. depending finger 255 on the chute 25I. Each terminal wire I83 in the chute 25I comprises a length of wire 251 terminating in a metal disk 259 having a rounded back and a fiat face. which has been previously tinned for soldering.

Encircling the horizontal axis of movement of each gripper 249 is a vertically disposed ringshaped burner 26I which convergingly directs several small flames 263 in the direction of the conveyor 225. Said burner 26I is also normally in its retracted position (as shown in solid lines in Figures 14 and 15), but moves inwardly with the gripper 249, after the gripper has passed beyond its intermediate position (shown in broken lines in Figure 15) and then said burner returns to its retracted position.

Further to the right and positioned at the far side of said conveyor 225 is a tube conveyor 226 (Figure 14), movable intermittently to the right as indicated by the arrow, in synchronism with the movements of said conveyor 225. Extending upward from the said tube conveyor 226 are a plurality of U-shaped tube holders 265, the leading edge of each such holder being provided with an upwardly extending arm 261. Above said conveyor 226 is a stationary, vertically disposed, rectangular tube chute 269 accommodating a plurality of cylindrical vitreous enamel tubes I85. Each tube I85 is of a diameter to allow a capacitor roll I8I to be slid within it and of a length greater than such capacitor roll. The lower end of the tube-chute 269 is provided with a suitable closure (not shown) and latch 21I which allows the discharge of one tube I85 each time a tube holder 265 moves into position below said tube chute. Said closure is opened by coaction between the arm 261 and the latch 21I. The far wall 212 of said chute extends down to about the level of the tube conveyor 226 and is partly cut by a horizontal slot 210.

On the near side of the conveyor 225, opposite the tube chute 269 is a pusher rod 213 (Figure 14) comprising a vertical ring affixed to the end of a horizontal rod, which is normally in a retracted position (as shown in Figure 14) but which is caused to move horizontally, as indicated by the arrow, across the conveyor 225 toward the tube conveyor 226, each time said conveyors 225, 226 come to rest, and then to return to its retracted position.

The tube conveyor 226 extends horizontally for a short distance to the right and then drops downward to a lower level where it again continues on to the right. Just beyond the drop is located a tube sealer 214 (Figures 14 and 16), which includes a pair of mutually parallel rollers 215, 216 and a pair of burners 211. The rollers 215, 216 are disposed transversely above the tube conveyor 226 and are so spaced as to Support 12 one of the vitreous enamel tubes I aforesaid. The left roller 215 is rotated by any conventional means (not shown) so as to cause a tube supported thereon to spin about its axis. The right roller 216 is freely rotatable and it also moves downwardly and to the left a short distance each time the burners 211 return from their operating to their retracted positions, as will now be described. Flanking the tube conveyor 226, abreast of said rollers 215, are two, vertically disposed. horizontally movable, ring-shaped burners 211 (see Figure 14, which shows only the far burner, and Figure 16), each of which convergingly directs needle-pointed flames 219 inwardly. Said burners 211 are normally in retracted positions (as in Figure 14) but move inwardly to their operating positions (Figure 16) each time the tube conveyor 226 comes to rest, to direct their flames 219 at the ends of a spinning tube I85 and then return to their retracted positions. While in their operating positions, said burners 211 oscillate several times a short distance in and out. To the right of the rollers 215, 216 the tube conveyor 226 passes through an annealing oven 28I, which is provided with a horizontal through passageway (not shown).

A process for the manufacture of roll type capacitors, according to my invention and utilizing the machinery components already described and shown in Figures 13 through 16, is as follows:

Referring to Figure 13, the ribbon of metal foil I13 on the upper spool I89 is threaded over the left rim I95, under the rounded cros-piece I91 and over the right rim I95, of the upper tank I9I of acid I93 and is similarly threaded through the second upper tank of rinsing solution (not shown). It is also threaded through the upper slot 20I of the hydrogen furnace I99, through the passage 209 of the upper spraying tube 263 and through the upper slot 2 I 1 of the baking oven 2I5. From the baking oven 2I5 it extends successively over and under the two upper rollers 2I9 and under the upper cutting knife 223 of the cutter 22 I The ribbon of metal foil I15 on the lower spool I89 extends, in a similar manner, through the lower tier of all of the components just described. The ends of the two ribbons of foil I13, I15, after extending through the cutter 22I, are wound about the core I 19, the first couple of turns having been wound on by hand or by a suitable mechanism (not shown).

In operation, the winding device (not shown) will rotate at a steady speed and will pull the two ribbons of metal foil I13, I15, in the directon indicated by the arrow, successively through the various components just mentioned. The metal foil will be suitably cleaned in passing through the baths of acid I93 and rinsing solution and the hydrogen furnace I99. These three steps are intended to free the metal foils I13, I15 of any oxides, chemicals, grease, dirt and impurities which might interfere with the subsequent steps of manufacture or which might detract from the efficiency of the finished capacitor. The order of these cleaning steps may be rearranged or one or more omitted or other cleaning means included, as may be found best for the particular materials being used and the condition thereof.

In passing through the spraying tubes 293 both the upper and lower surfaces of both ribbons of metal foil I13, I15 will be sprayed with a thin coating of vitreous enamel I11. It will be noted, however, that a narrow strip 263 of metal foil along the far edge of the upper ribbon I13 and asaaaee a narrow strip 285 of metal foil along the near edge of the lower ribbon I15 will be left uncoated, in view of the fact that, as already described,

the passages 288 are offset in opposite lateral directions relative to the spray openings 281. The speed of movement of the foils I13, I15, the lengths of the spray openings 281 and the quantity of enamel I11 being sprayed will be so adjusted that the enamel coating will be of a predetermined thickness.

The enamel coated foils I13, I15 are then pulled through the baking oven 2I5, the length of the oven and its temperature being such that the vitreous enamel I11 is given a partial baking until it reaches its green" state. Said coated i'oils I13, I15 are then brought into coser proximity by means of the rollers 2I8 and they then pass through the cutter 22I and around the core I18. They reach the core I18 in superimposed relationship, except that the uncoated strips 283, 285 extend outwardly laterally in opposite directions. When the winding device has wound predetermined lengths of the enamel coated foils I13, I15, about the core I18, to form a capacitor roll I8I, the two cutting knives 223 operate so as to sever said foils.

The capacitor roll I8I is then removed from t e winding device, either manually or by a suitable mechanisrn (not shown), and dropped into one of the Y-shaped clips 23I of the conveyor 225 which carries it through the firin and annealing oven 221. There the vitreous enamel I11 is thoroughly fired so that contiguous layers of enamel fuse together and the capacitor roll I8I becomes a monolithic structure, its internal makeup at that stage being as shown in the left half of Figure 17. The length of the oven 221, the temperatures maintained in the left and right portions thereof and the speed of the conveyor 225 are such as to fire and anneal the vitreous enamel dielectric I11 of the roll I8I according to a predetermined formula. As already mentioned above, in connection with stacked type capacitors, the oven 221 may be provided with a much wider conveyor (not shown) running at a very slow rate upon which a number of capacitor rolls I8I may be placed abreast, After coming out of the oven 221 upon such a conveyor the rolls I 8I would be transferred, manually or by suitable apparatus, to the conveyor 225 for continuation of their processing. The conveyor 225 moves intermittently and carries several capacitor rolls I8I, so that,

after being fired, each roll is moved successively to various positions, at each of which it is brought to rest and is partly processed. Hence, several capacitor rolls I8I which are positioned along the conveyor 225 at any one time are simultaneously subjected to processing operations, succeeding rolls however undergoing succeeding processing steps.

When a capacitor roll I8I is brought to rest between the two flux applicators 233. said applicators, which are normally retracted (as in Figure 14), move inwardly simultaneously against the opposite ends of the capacitor roll, the roll being held above the level of the conveyor 225 by one of the clips 23I. The pads 231 of said flux applicators 233 crumple the uncoated strips 283, 285 of metal foil against the opposite ends of the roll III and also apply soldering flux 238 thereto. Said flux applicators 233 then retract and the conveyor 225 moves the roll I 8I to a position intermediate the two solder applicators I, which move inwardly simultaneously and respectively apply suitable predetermined charges of solder 14 245 to the crumpled strips 283, 285 of foil at both ends of the roll.

Said solder applicators 2 then retract and the roll I8I is moved on to a position between the two terminal wire applicators 241. Each gripper 248 is then in its normal retracted position (shown by solid lines in Figures 14 and 15) and a terminal wire I83 has already been dropped into it (by coaction between pin 253 and finger 255 on the previous outward return stroke of said gripper). The two grippers 248 then move inwardly simultaneously until they reach their intermediate positions (shown by broken lines in Figure 15) at which point the flames 283 will play upon the disks 258 of the terminal wires I83. The grippers 248 and their associated burners 26I then move inwardly together, the flames 263 continuing to heat the disks 258, until the flat faces of the disks abut against the crumpled strips 283, 285. After a short interval, predetermined as being necessary to effect soldered connections between said disks 258 and strips 283, 285, the burners move back to their retracted positions and then the grippers 248 release their respective terminal wires I83 and the burners return to their normal retracted positions, another terminal wire being discharged from each chute 25I and dropped into each gripper at the end of its outward stroke.

The conveyor 225 moves the roll I8I, now fitted with a terminal wire I83 at each end, into position opposite the tube chute 268. As it reaches that position, coaction between one of the arms 281 and the latch 21I causes the lowermost enamel tube I85 in said chute to drop into one of the tube holders 265 on the tube conveyor 228. The pusher rod 213 then moves inwardly from the near side of the conveyor 225 and propels the roll I8I into the said tube I85. The far wall 212 of said tube chute 268 keeps the tube I85 in position during this operation. The pusher rod 213, being ring-shaped, does not interfere with the near terminal wire I83. If the conveyors 225, 228 are too far apart, it may be advisable to position a stationary trough (not shown) between the conveyor 225 and the tube conveyor 228 to help guide each roll I8I into a tube I85.

When a tube I85, with a capacitor roll I8I within it, reaches the point where the conveyor 226 drops downward, said tube falls into position upon the rollers 215, 216 whereupon it is caused to spin about its axis by the rotating roller 215. The two ring-shaped burners 211 move inwardly from their retracted positions (Figure 14) to their operating positions (Figure 16) so that the needlepointed flames 218 play upon the ends of the spinning tube I85. Said burners 211 automaticall v oscillate in and out several times so that the ends of the enamel tube I85, which extend beyond the disks 259, are thoroughly heated throughout and they bend inwardly, curve about the rounded backs of the disks 258 and fuse about the terminal wires I83 so as to take the shape shown in the right half of Figure 17 The flames 218 are purposely needle-pointed so that they concentrate heat on the tube I85 but do not melt the solder 245. By the oscillation of the burners 211 and the spinning of the tube I85, an even temperature is maintained and breakage of the tube is prevented. The burners 211 then retract and the right hand rollers 216 moves to its depressed position, already described, causing the capacitor to roll over said roller into one of the holders 285 which carries it through the annealing oven 28I which anneals the tubular envelope I85. When it leaves said oven 28I it is a finished 4 l5 capacitor 28! (as shown at the right half of Figure 17).

The manufacturing operations up to and including the winding of the capacitor rolls III (as shown in Figure 13) may not be performed with sufficient rapidity to keep the balance of the production line (shown in Figure 14) operating at its maximum capacity. Hence, it is to be understood that two or more complete sets of apparatus (as shown in Figure 13) may be operated simultaneously so as to produce suflicient capacitor rolls Isl to feed one conveyor 12!.

The spraying step described above and illustrated in Figure 13 may be modified as shown in Figure 18, where it is illustrated in use with the upper ribbon of foil I13. In this modification two vertically disposed, coplanar, sprayin plates 2" are substituted for each of the spraying tuba Ill. Said plates 2 are spaced apart just enough to allow the ribbon of metal foil ill to pass therebetween and they are positioned slightly in from one edge of the foil. Spray nozzles 2 above and below the foil I13 will, therefore, coat both surfaces thereof with citreous enamel ill except for a narrow strip 283 along one edge thereof.

Another modification of the spraying step of Figure 13 is illustrated in Figure 19. Here a ribbon of metal foil I13, suspended from an elongated rack "I, is dipped, except for a narrow strip 283 along its upper edge, into a vat 293 of 1 vitreous enamel ill in liquid form.

Still another modification of the spraying operation of Figure 13 consists in substituting for the two spraying tubes two tanks of vitreous enamel (not shown), one above the other, and two wipers (not shown), also one above the other. Each of the metal foils I13, H5 is caused to dip into one of said tanks so as to become completely coated with enamel. After leaving the tanks, each foil I13, I15 passes through a wiper which wipes off the enamel along one edge so as to leave an uncoated strip of foil 28%, 235, similar to such strips as already described.

Although I have described herein a'number of manufacturing processes for the production of several types of capacitors, and have described mechanisms for carrying them out, it is to be understood that the various manufacturing steps and processes described may be grouped into other combinations within the spirit and teaching of the present invention. For instance, a process for manufacturing rolled type capacitors, by spraying or otherwise applying metallic mate rial in liquid or paste form, may be a combination of steps already described and illustrated in Figure 1 and the'process described above and illustrated in Figures 13 and 14. This could be accomplished by laying down a long thin strip of enamel, by spraying or otherwise, then covering it with a long thin strip of metallic conducting and then laying down another layer of enamel in register with the first strip of enamel. Two of these elongated laminated structures would be partially baked and then rolled together. The roll would then be placed on conveyor 225 and further processed as already described and illustrated in Figures 13 and 14.

Another modification might be made in connection with the process already described and illustrated in Figures 1 through 6. This would comprise the steps of dispersing a thin ribbon of vitreous enamel dielectric material Si, in paste or liquid form, as by spraying, and then dispersis ing thereon a plurality of thin paddle-shaped plates ll of metallic coeiiucting material, in paste or liquid form, as by spraying. The ribbon ll and the plates I! would then be partially dried, as in a baking oven, until the enamel reached its green stage. The ribbon of enamel It would then be cut (as in Figure 1) to form blanks II which would then be stacked (as in Figure 2) and the stackof blankswould thenbefired,asinafiring oven ll (Figure 2). This would result in a monolithic structure 81 (Figure 4), which would be assembled into a finished capacitor I it (as shown inFiguresithrough 8). Itistobenotedthat this modified process difiers, from the process of Figuresl through6,inthatthestepsofdrying the enamel II and spraying the metallic material are reversed, the steps of firing and stacking are also reversed and the fusing step (Figure 3) is omitted entirely.

The vitreous enamel to be used in the capacitors described in the present specification should have a melting point lower than the metal foil to be used, so that the enamel may be fired without melting the foil. Also it should be of a type which has good thermal shock resistance in addi tion to the electrical characteristics already set forth. Some of the silicate flint gLasses, such as Schott, heavy silicate flint (International Critical Tables, volume 2, 1927, index number 102), might be used, but with modifications in the formulae, better electrical characteristics may be obtained. Also, the vitreous enamel used should preferably have substantially the same coeflicient of expansion as the metal parts used so as to avoid breakage of the enamel due to temperature changes, both during manufacture and in use.

What is claimed is:

1. A method of producing a rolled type capacitor consisting of dispersing a thin elongated sheet of vitreous enamel dielectric material, in liquid or paste form; dispersing a thin ribbon of metallic conducting material, in liquid or paste form, over said sheet, one edge of said ribbon extending in from one edge of said sheet and the.

other edge of said ribbon extending beyond the other edge of said sheet; dispersing a second sheet of vitreous enamel dielectric material, in liquid or paste form, over said first mentioned sheet and said ribbon, said second sheet being in substantial lateral register with said first mentioned sheet; partially drying said sheets and ribbon so as to form a flexible three-ply structure; forming a second similar three-ply laminated structure by the steps aforesaid; superimposing one of said laminated structures over the other so that the sheets of dielectric material are in substantial lateral register and the ribbons of conducting material are offset laterally in opposite directions; winding said laminated structures together to form a roll; firing said roll into a monolithic structure; and connecting electrical leads to said ribbons.

2. A method of producing a rolled type capacitor consisting of dispersing a thin elongated sheet of vitreous enamel dielectric material, in liquid or paste form; dispersing a thin elongated plate of metallic conducting material, in liquid or paste form, over said sheet, one lateral edge of said plate extending in from one lateral edge of said sheet and the other lateral edge of said plate extending beyond the other lateral edge of said sheet; dispersing a second thin elongated sheet of vitreous enamel dielectric material, in liquid or paste form, over said first mentioned sheet and said plate, in substantial lateral regis- 17 ter with said first mentioned sheet; partially drying said sheets and plate so as to form a flexible three-ply laminated structure; forming a second similar three-ply laminated structure by the steps aforesaid; superimposing one of said laminated structures over the other so that the sheets of dielectric material are in substantial lateral register'and the plates of conducting material are offset laterally in opposite directions; winding said laminated structures together to form a roll; firing said roll into a monolithic structure; connecting electrical leads to' said' plates; dispersing a coating of vitreous enamel dielectric material about said monolithic structure and parts of said leads; and firing said coat-' ing to form a hermetically sealed envelope about the monolithic structure and the coated parts of the leads.

. KRIS'I'IAN H. BRANDT.

18 REFERENCES crran The following references are of record in the tile 0! this patent:

UNITED STATES PATENTS Ballard Apr. 30. 1948

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