US1881130A - Electrical condenser - Google Patents

Description

Oct. 4, 1932. J. A. PROCTOR ELECTRICAL CONDENSER Filed Sept. 3, 19 s Sheeis-Sheet 1,

mm I IMCa,

DI EMML INVENTOR Oct. 4, 1932. J. A. PROCTOR ELECTRICAL CONDENSER Filed Sept. 3, 1925 3 Sheets-Sheet 2 INVENTOR \fQ/YA W aofof ATTOR N EY 1932- J. A. PROCTOR ELECTRICAL CONDENSER Filed Sept. 5, 1925 3 Sheets-Sheet 3 INVENTOR \jflA/ 91. BEE? PFocToQ ATTORNEY Patented Oct. 4, 1932 UNITED STATES PATENT OFFICE JOHN ALBERT .PIROCTOR, OF LEXINGTON, MASSACHUSETTS, ASSIGNOR, BY MESNE AS- SIGNMENTS, T GENERAL ELECTRIC COMPANY, A COR-PCB ATION OF NEW YORK ELECTRICAL CONDEI'JSER Application filed September 3, 1925. Serial No. 54,190.

This invention relates to electrical condensers, particularly of the sheet type.

The object of the invention is to produce, and the production of, a condenser which is efiicient, sturdy and attractive, of constant capacity, and capable of being manufactured readily and at low cost, to sell at low price, being suitable for use, for example, in radio receiving sets. The invention consists of the improvements in vstructure and manufacturing disclosed hereinafter in connection with the accompanying drawings, of which:

Fig. 1 is an exploded view illustrating partial assembly of the condenser;

Fig. 2 is a diagrammatic elevation illustrating a further step in the manufacture;

Fig. 3 is a petspective, somewhat exploded, illustrating a further step in the process; Fig. 4 is a section of the condenser shown in Fi 5, taken along the line 4-4, illustrating t e final step in the manufacture, and showing the completed structure, the height of the condenser, however, being greatly exag erated for clearness;

1 of Fig. 4 showing the lateral projection of the terminals of the two connection plates;

Fig. 6 is a perspective of the complete condenser of Figs. 4 and 5; a

Fig. 7 is a central section of a modification resembling the condenser of Figs. 4-6 but lacking foil armatures;

Fig. 8 is a perspective illustrating a condenser having a stack like that of Fig. 6 or that of Fig. 7 but having a modified form of clamping plates;

' Fig. 9 is a pers ective illustrating a condenser like that 0 Fig. 8 but having a further modified form of clamping plates; In addition to the desirable features of at tractiveness and of superficial area sufiicient for desired markings, an important desideratum of condensers of this type is the ability to have the capacity maintained constant and at the same time a low manufacturing cost. To these ends, the invention comprises a clamping construction by which the capacity is maintained constant, and the construction is adapted to continuous building up ig. 5 is a plan of the completed condenser from the bottom upward, so that there is no need of interrupting the process to place an element beneath another element which already has been assembled, the labor cost, by this feature, being kept down to the minimum consistent with the sturdy and attractive properties of the device. at?

As illustrated in Fig. 4, the structure comprises two metal end clamping plates B and which hold the condenser stack between them and themselves are held in clamping position as by a central metal rivet, such as the eyelet A; This figure is about double scale, and in addition it is to be understood that the thickness is greatly exaggerated for clearness, the actual thickness of the condenser being usuall less than one-quarter of an inch, this type 0 condenser being particularly adapted for low capacities.

All the plates of conducting and dielectric .material, including end clamping plates B and U, are perforated, as shown, to allow their being placed around the central stud or rivet A which finally clamps together all the elements of the stack and prevents turnin of theconnection plates Q, S, to be describe Each foil sheet is formed with two perforations thru which stud A passes.

The construction is commenced, as indicated in Fig. 1, by setting rivet A vertically, with its lower end headed and its upper end unheaded. Then lower perforated metal clamping plate B is laid down over and around rivet A. Thena few sheets of mica (or one thick mica) C (perforated centrally) are laid down over and around rivet A to 1n-' sulate the metal clamp plate B from the stack which now is to be built upwardly around rivet A. Insulator C, when used as preferred, preferably spaces the condenser stack from metal clamp so that the latter is isolated from the electrostatic action in the stack. The stack is then built up by laying all the rest of the perforated sheets and plates down over and around rivet A.

The two condenser terminals, which project laterall beyond the stack and are of any desired con guration, are shown at W, X, in Figs. 5 and 6. They lie, preferably, not at opposite ends of the stack, but, as shown in 100 Fig. 4:, both above the top of the stack and adjacent one another save for a sheet of mica R between them. This location of the two condenser terminals-W, X which are integral respectively with the two terminal plates or connection plates Q, S, (Figs. 1, 3 and permits the execution of the method hereinafter described in detail, wherein the assembly is effected continuously from the bottom upward without any interruption, as has been usual, to insert an element below after another element had been assembled on top.

The two terminals W, X, of Figs. 5 and 6 are tabs which project from (and preferably as shown are integral portions of) the two thin but stiff metal connection plates Q, and S lying on top (at one end) of the stack, as

shown in Fig. 4, and between one end of the.

stack and clamp plate B. This construction of stiff projecting tab terminals W, X which are integral with the connection plates Q, S, avoids all fragile foil connections to the terminals, particularly in a form like that of Figs. 4-6, where the condenser armatures consist of lead foil sheets.

As shown in Figsrl and 2, after the assembly of rivet A, bottom clamping plate B and insulating sheet C, the stack is built up of alternating sheets of mica (dielectric) and foil armatures; and as shown at the top of Fig. 1, after the stack of perforated micas and foil armatures has been completed, the lower connection plate Q is placed, via its central perforation Q, down over and around rivet A. As shown in Fig. 1, the alternate foils are arranged to project from opposite sides of the stack, and each foil is provided with two perforations, as shown, and the foils are much longer than the width of the stack, for a purpose nowto be described. At this stage, the stud A extends thru only one of the perforations in each foil-sheet, i. e.,-the right-hand 7 holes in the left-hand foils (Fig. 1), and the left-hand holes in the right-hand foils.

As shown in Fig. 2, after lower connection plate Q is assembled on the top end of the stack, the projecting ends of the long lefthand foils are turned up vertically and then brought down horizontally on connection plate Q around stud A, the left-hand holes D of these left-hand foils being entered by stud V. Thereupon, as shown in Fig. 3, an upper insulating sheet T (like lower insulating sheet C of Fig. 1), centrally perforated, is laid down on said folded down foils around rivet A, permissively on adjacent the folded down foils as shown; and then the upper metal connection plate S is laid down around the rivet, permissively in cont-act with insulating sheet R. At this stage, the ends of the long righthand foils (Fig. 3) yet projgect out beyond the stack. Then, as shown in ig. 4., the righthand projecting ends of the long righthand foils, as previously the long lefthand foils, are brought up to the left top of the foils on vertically, and then to the left and down horizontally, so that they contact Wltll the surface of upper connection plate S, the holes D2 in the foils (Fig. 1) being entered by stud V. Then the uppermost insulating sheet T (like lower sheets C and R) is laid on S. Then upper metal end clamping plate U, centrally perforated, 1S laid down on said sheet T around rivet A; and finally the upper head V of the rivet is upset to clamp the entire st ucture as desired. The holes in the folds -over ends of the foils space and thereby insulate them from metal stud A.

The capacity of such a condenser as that shown in Figs. 1-6 may be about 2 micromicro-farads, this being the form constructed with the foils as above described. For condensers of similar structure but of lower capacity (say 250 micro-micro-farads), the form of Fig. 7 may be used, wherein no foils are employed, but where the armatures of opposite potential are the connection plates Q, S, themselves, separated from one another by their mica dielectric R, and insulated from the end clamping plates B, U by mica insulators C and T, as before.

All the mica sheets may be about inch long. All the mica sheet dielectrics between the foil armatures may be 7 inch wide. The end insulating micas C and T may be inch square. The mica R between the two connection plates Q and S in Figs. 4-6 may 106% inch long and inch wide. The foils are narrow enough to provide the insulating margins of mica shown at M1, Fig. 3. The foils are long enough to permit the folding back between clamps B and U, as shown in Fig. 4. j

The end clamping plates B and U are not connected in the circuit, being electrically connected together by compression stud or rivet I and insulated from the condenser stack itself and connection plates Q and S by means of insulating sheets C and T.

The location of both connection plates Q and S at the top of the stack (Figs. 1-6) in connection with the operations of folding the projecting foils over and upon said connection plates, respectively, permits the continuous building up illustrated, i. e., from bottom to top continuously without interruption as heretofore to insert an element below after another element or elements have been first assembled above.

The clamping by the plates B and U, when rivet A is upset, serves not only to maintain constant the capacity of the condenser, but also to initiate and maintain good contact between the respective two foil bunches and tWO connection plates Q, S. -As illustrated in Figs. 2-4:, all the projecting foils of each polarity are grouped together in a bunch on top of their respective connection plates. Clamps B and U also hold connection plates Q and S and their projecting integral tabs W and X from turning to undesired angular positions in the stack relative to the mica insulator C, R and T and the mica-dielectrics between the armatures. Also clamps B and U hold the foils in the positions in which they are assembled so asto preserve the insulation spacing from stud A which is provided by the foil holes.

In the form shown in Fig. 7, without foils as armatures, for lower capacities, the two connection plates Q, and S are located midway Q,

between the clamping plates B and U, being separated from one another by mica dielectric sheet R; and each connection plate is insulated by mica insulating sheets from the adjacent end faces of the metal clamping plates.

The assembly process of Fig. 7 is the same as in Figs. 1-6, save only for the laying of the foils in the latter and bending them up over and down upon the connection plates around stud A.

If the superficial dimensions of clamping plates Band U are sufficiently small, and they are of steel or thick enough not to bend up at their edges, the central rivet A will hold the structure under constant pressure to maintain constant capacity and the desired other clamping functions. In any event, the operation of upsetting the upper end of rivet A is such as to put the condenser stack under the desired mechanical pressure. Altho plates B and U may be of sheet metal, they should not be of such nature as to permit their periph eries to bend away from the stack upon riveting at the center, to an extent sufficient to permit substantial loosening of the condenser elements. But the invention involved in the stack itself may be employed in connection with any desired means of maintaining stack pressure, with any desired form of plates B and U, separately or ointly, and any desired means for forcing them together.

Heretofore the manufacture of this general class of condensers has included building of the condenser stack by girl operatives and temporary clamping of the same by them to permit transport of the incomplete condensers to a more or less distant power machine which applied permanent clamps or clamping means, or both. This invention, however, is of such a nature that it permits an entirely different system of factory production, i. e., it permits the entire completion of the condenser, including permanent. clamping, by the same girl operatives who build the stack, (or at least permits permanent clamping of the condenser without removing it from its assembly device), this being advantageous in eliminating the step of temporary clamping and transfer to a more or less distant finishing or riveting machine, (or first removing the condenser from its assembly device prior to such transfer), thereby reducing cost and insuring a ainst disassembly of the various elements 0 the condenser.

The stack of Fig. 4 is adapted for capacities up to .005 mfd; but above that capacity 1 the stack will have greater thickness. In order to assemble such a thicker stack in the same condenser, i. e., including use of foils having the same spaced holes, the above operations may be modified as follows. Upon completion of the stack and before the application of the first or lower connection plate on its top end, the first group of project ing foils (at left, Fig. 2) may be folded over directly upon the stack. This permits the holes (Fig. 3, Fig. 1) thru the projecting and folded portions of the foils to be centralized around eyelet A, notwithstanding the slight increase in stack thickness for higher capacity. Then connection plate Q may be laid on top of such folded down foils and upon it insulating sheet B (Fig. 3). Then the other set of foils -.(right) is folded up, over, and down on Q, permitting centralizing of their holes around eyelet A, and on them then is laid insulating separator T.

Figs. 6, 8 and 9 illustrate the large extent of superficial areaon the clamping plates, around central rivet A, which is available for desired name-plate marking.

In Fig. 8, the modification of bottom clampingplate B consists of two integral vertical extensions B1, between which fits upper clamping plate U. These extensions B1 serve torenclose those opposite sides of the stack from which the terminal connections W, X, do not project.

In Fig. 9, both clampin plates B and U are modified as in plate B of Fig. 8, plate U having sides U2, which abut sides B1 of plate B, to constitute an enclosure of the opposite sides of the stack.

As shown in Figs. 6, 8 and 9, the end clamping plates, and articularly that which is close to terminals l v, X (as the upper plate U when W and X are located at the top of the condenser stack) are formed with cutaway portions Y, in order to assist the top insulating pilate T in insulating the circuit terminals W, from the metal end clamping plates.

If desired, the operation of folding down the foils to the horizontal positions shown at the left in Fig. 2 may be aided by any suitable mechanism, just as the operation of picking up, the foils from the horizontal position shown at the right in Fig. 2 is effected by any suitable mechanism. But it is usually sufficient to enlist the aid of mechanism for picking up the foils from the horizontal position at the right of F ig. 2, and to leave the subsequent folding down of the foils to the fingers i not difficult for the two bunches of foils to be engaged by the fingers of the operative to push them down and radially toward the central rivet or compression stud, and centralize them; because, as distinguished from the stacked foil-condition shown in Fig. 2 where the foils lie flat on the assembly block and require to be picked up, on the other hand in the picked-up foil-positions their ends are more or less free in the air in position to be folded down.

The eyelet rivet A, as a compression stud, may be a solid rivet; or a form of my condenser may be completed without the use of any riveting machine, when such compres sion stud consists of a bolt with a nut in place of an upset rivet. ith such threaded form of central compression stud, the capacity of the condenser can be adjusted by screwing up the nut.

Preferably, as shown in Figs. 1 and 3 (but not necessarily), the connection plates Q and S, with their terminal tabs W and X, are located at right angles to the oblong foils, i. e., the tabs W and X project from the sides of the stack from which the foils do not project. An advantage of this is that. (Fig. 3) the foils may be laid down with the aid of fixed guide pins projecting up through their per forations D2 (and D3, Fig. 1) the projecting foils subsequently being lifted from off such guide pins to the more or less vertical positions which will facilitate subsequent manual folding down of the foilson top of the condenser stack. Such guide-pins of course facilitate centralizing the foils and their perforations D1, D2 (Fig. 1) with reference to the stud A. That is, the above-described relation between the tabs W and X and the projecting foils of opposite polarity permits the perforated foils being placed over the fixed guide pins and later lifted therefrom without interference by tabs W, X; and also leaves the rest of the condenser free, including tabs W and X, to be depressed in suitable apparatus if desired, in order to Q and S.

push the foils up from off such guide-pins.

In Figs. 8 and 9, the folds of the foils are covered by bent-over sides of one or both of-the end clamping plates B and U, the other ends of the stack being exposed in order to permit the extension beyond the stack of the tabs W and X of the connection plates An alternative form of covering the folds of the foils is a metal plate just like flat clamping plate B of Fig. 1 but much thinner and shaped with bent-up sides like plate B ofFig. 8, and lying on top of flat plate B of Fig. 1, the two bent-up sides of such thin plate extending, like the sides of B1 of plate B of Fig. 8, to cover the folds of the foils.

The condenser hereof preferably is constructed entirely of metal and mica, it being unnecessary and not desirable to simple any of the various forms of artificially pro ufced insulating material for any of the elements of the condenser; the metal parts are the rivet or compression stud A, the end clamping plates B and U and the two connection plates Q and S, and the foils when used, i. e. in the higher capacity forms; the mica parts are the dielectric sheets of the condenser stack, and the insulating separators C, R and T. The end clamping plates B and U furnish all necessary stiffness, and extend over the entire condenser stack, so that there is no need ,of employing thick insulating sheets to impart stiffness to the stack. Also, by the con struction shown, the end clamp plates B and U and compression stud A all are electrically independent of the stack, although mechanically connected together; the foils (when used) being insulated from the compression stud A by the spacings of their central perforations, and the bottom and topmica separators C and T completely insulating the end clamping plates B and U from the condenser stack and from the connection plates Q and S. On account of the fact that clamp plates B and U are metallically connected together by stud A, they may be formed in one piece, as

a flattened tube, the condenser stack with stud A being placed in the tube before complete flattening thereof, the tube then being flattened and the stack compressed and the rivet head upset; or clamps B and U may constitute the two legs of a u clamp. But I prefer the two-part clamp plates Band U as shown.

Connection plates Q and S are sufiiciently thicker than the foils (depending upon the material'of said plates) to be relatively rigid or stiff, that is sufficiently to be suitable for integral projecting terminals W; and X, which may be pe'rmissively flexible by the fingers without disadvantage. These plates Q and S may be, for example, of brass about 1/64 inch thick, or of other metal of suitable thickness and stiffness to serve satisfactorily as terminals. These plates, being thin, occupy little space in the length of the condenser between the end clamping plates B and U.

The holes Q1 and X1 in tabs W and X may serve for the reception of suitable circuit terminals; and these tabs W and X may be of any desired configuration, extended beyond their free ends shown, and adapted to various kinds of terminals of the apparatus with which the condensers are to be used.

The word .mica as used in the claims is intended to mean preferably mica, but permissible to include substantially equivalent sheet insulating material such as any of the artificially produced insulants.

I particularly point out and distinctly claim the part, improvement or combination which I claim as my invention or discovery, as follows:

1. An electrical condenser of the sheet type, comprising a stack of mica dielectr cs and two sets of foils of opposite polarity extending substantially from opposite sides of the stack; two metal clamping plates over the ends of the stack but insulated therefrom; two substantially stiff metalconnection plates both located at one end of the stack near one clamping plate and insulated from one another and from said clamping plate and having terminal portions of desired shape extending in opposite directions laterally beyond the stack between the two foil-sets; the micas, clamping plates and connection plates being centrally perforated; and a metal compression stud extending through said perforations, spaced from the connection plates at their-perforations, and contacting with the clamping plates, holding them at the desired mechanical compression; the foil portions in the condenser stack and portions projecting therefrom each having perforations substantially larger than the stud; and the two rojecting portions of the foil-sets respective y being folded into contact with the respective connection plates, the edges of all said foil perforations surroundin but spaced from the stud; and the central oles thru the micas being smaller than the foil-holes.

2. An electrical condenser of the sheet type comprising a stack of mica dielectrics and two sets of foils of opposite polarity extending substantially from opposite sides of the stack; two metal end clamping plates; two substantially stiff metal connection plates both located at one end of the stack near one of the clamping plates and insulated, from one another and from said clamping plate, the micas, clamping plates and connection plates beingcentrally perforated; a metal compression stud extending through said perforations and s aced from the connection plates at their per orations; the foil portions in and projecting from the stack being perforated; and the .two projecting portions of the foil sets respectively being folded into contact with the respective connection plates, the edges of their perforations being spaced from the compression stud; the connection plates having portions extending laterally beyond the stack as terminals; and'the stack, folded foils and connection plates being held under compression by the clamping plates and central compression stud.

3. An electrical condenser of the sheet type, comprisinga stack of mica: dielectrics and two sets-of foils of opposite polarity; two metal end clamping plates; two substantially stiff metal connection plates located between and insulated from the clamping plates and electrically connected'respectively to said foil sets, and having portions exspaced at the foil-holes from said compression stud and projecting from the stack and the projecting portions being perforated and folded into contact with the respective connection plates; and the said connection lates and folded foil portions of opposite polarity being held together in good contact, by the clariping plates and central compression stu 4. An electrical condenser of the sheet type, comprising two metal end clamping plates; two substantially stifi metal connection plates located between the clamping plates and having portions extending laterally as terminals beyond the clamping plates, all said parts being centrally perforated; a metal compression stud extending through said perforations; said connection plates being spaced from said central stud at their perforations; said connection lates bein insulated from one another and rom the en clamping plates; and the clamping plates extending over the entire area of theend faces of the condenser.

5. An electrical condenser of the sheet sion stud means extending through said perforations and engaging the clamping plates to hold the stack under mechanical compression.

6. An electrical condenser of the sheet type, comprising a stack'of foils and mica dielectrics all centrally perforated; a central metal compression stud extending throu h said perforations, fitting in the holes in t e micas but of smaller diameter than the holes in the foils; metal end clamping plates extending over the end faces of the stack, centrally perforated and engaged by said stud; mica separators between the clamping plates and the stack; and two substantially stiff metal connection plates between the end of the stack and one clamping plate, a mica separating plate being located between the two connection plates; the foils of opposite polarity projecting from opposite sides of the stack and adapted to be folded back in the space near the end clamping plate where the connection plates are located, the faces of such folded foils being in electrical contact with the respective connection plates.

7. An electrical condenser of the sheet type, comprising a thin stack of armature sheets and dielectric sheets, centrally perforated; metal end clamping plates also centrally perforated; a central metal compression stud extending through the perfora said stack including foils of opposite polarity projecting from opposite sides of the stack and adapted to be folded into the space between the end clamping plates; and connection plates located adjacent but insulated from one another at one end of the stack adjacent one clamping plate, and respectively contacting with the folded-over foils of opposite polarity respectively; said connection plates and foils .being insulated from said metal end clamping plates.

9. An electrical condenser of the. sheet type, comprising a condenser stack, metal end clamping plates extending over the end faces of the stack, insulated therefrom and clamping the same; two substantially 'stifi metal connection plates located adjacent one another between one clamping plate and the adjacent end of the stack; sai'd connection plates being insulated from one another, con

nected respectively to the condenser ar1natures of opposite polarity and having integral portions extending laterally beyond the stack and end clamps, as condenser terr'ninals.

10,.An electrical condenser of the sheet type, comprisinga stack of foils and micas, metal end clamping plates extending over the ends of the stack, insulated therefrom and clamping the same; the stack-foils of opposite polarity projecting laterally in bunches from the stack and adapted to be folded into the space between the end of the stack and oneof the two clamping plates; said folded foil hunches being insulated from one another; and condenser terminals respectively connected-with'said folded foils.

"11. An electrical condenser of the sheet type, comprising a stack of foils and micas, metal end clamping plates'extending over the end faces of the stack, insulated therefrom and clamping the same, the foils of opp'osite polarity projectinfg laterally from the stack and adapted to be olded into the space between the stack-end and one of said two clamping plates; and two substantially stiff" metal connection plates lying also in said space and'respectively contacting with said folded foils, said connection plates having integral projections extending laterally from the stack at portions thereof from which the foils do not project.

i 12. In an electrical condenser of the sheet stack type, the improvement which includes a 'stiif metal connection plate located mechanically parallel with the stack-sheets and extending across the end of the stack stiffening the latter from side to side, and a stack armature sheet projecting laterally from the stack and folded over mechanically parallel with said connection plate and into electrical surstud extending through said stack and clamping plates and contacting with the latter to hold the structure under mechanical compression; the edges of the perforations in said armature sheets being spaced from said metal stud, and insulating plates being interposed between said stack and clamping plates, causing said insulation of the clamping plates from the stack.

14. An electrical condenser of the sheet type, which comprises a centrally perforated condenser stack; metal end clamping plates extending over the end faces of the stack and insulated from the stack; condenser terminals; and a metaleyelet rivet extending thru the stack-perforation and engaging the end clamping plates to compress the stack; the armatures of the stack being insulated from said metal rivet.

15, An electrical condenser of tlie sheet type, which comprises a compression stud having an integral annular retaining flange, a centrally-perforated metal end clamp plate strung thereovcr and held by said flange; a stack of centrally perforated condenser elements also strung on said stud and against said clamp plate; a second centrally-per- 1 forated clamp plate also strung on said stud other in lateral relations wherein the perforations of the sheets are in registry and wherein at least one foil of one polarity projects a substantial distance outside of the stack laterally beyond the adjacent dielectric sheet; and subsequently bending up said projecting portion of said foil and then folding it over the top end of the completed foilstaek in a position for terminal contact, with- .in the superficial area of the stack-end, hetween said relatively fragile folded over foil and a relatively stiff connection plate.

17 In an electrical condenser of the sheetstack type, the improvement which includes two flat metal connection plates arranged face to face but insulated from one another by a fiat insulating plate, said three plates having substantially the same superficial dimensions as the stack-sheets and all lying face to face with one end of the stack and mechanically constituting a portion thereof; an armature sheet of one polarity projecting laterally out from the stack and extending back into the stack into face contact with one of said metal connection plates therein; and an armature of opposite polarity projecting laterally out from the stack and.

extending back into the stack into face con:

tact with the other of said metal connection plates therein whereby the two connection plates are connected, within the mechanical limits of the stack, to the opposite-potential stack-armatures; said connection plates having integral portions projecting laterally from the stack as exterior condenser terminals; all whereby the condenser can be built continuously from end to end and the armatures are relieved from duty as exterior condenser terminals.

18. In an electrical condenser of the sheetstack type, the improvement which includes two flat metal connection plates arranged face to face but insulated from one another by a flat insulating plate, said three plates being centrally perforated and strung on a central compression stud; a condenser stack having its dielectric sheets centrally perforated and strung on said stud face to face wvith one of said connection plates and forming one mechanical stack with said three perforated plates; the individual armature sheets of the stack having perforations thru their respective ends and occupied by said stud but the stud being spaced from said armatures; an armature sheet of one polarity having a perforated endprojecting laterally out from the stack and extending back into the stack into face contact with one of said metal connection plates therein, said stud there passing thru the perforation in said end; and an armature sheet of opposite polarity having a perforated end projecting laterally out from the stack and extending back into the stack into face contact with the other of said metal connection plates therein; said stud there passing thru the perforation in said end; and said connection plates having integral portions projecting laterally from the stack as exterior condenser terminals.

19. In an electrical condenser of the sheetstack type, the improvement which includes a metal connection plate located mechanically parallel with the stack-sheets and extending across an end of the stack; a stack-arma ture sheet projecting laterally out from the stack and extending back into face contact with said connection plate; a metal clamp plate located on the other end of the stack,

all said parts being centrally perforated; a compression stud extending thru the perforations of said parts and holding the stack and compression plates together; and an insulating plate located between said connectionplate and the adjacent end of said stud.

20. In an electrical condenser of the sheetstack type, the improvement which includes two fiat metal plates stifi'er than other conducting elements in said stack spaced apart in the stack by a flat insulating sheet of substantially the same superficial dimensions; said metal plates having integral portions projecting laterally from the stack as external condenser terminals.

21. In an electrical condenser of the sheetstack type, the improvement whichincludes two centrally perforated flat metal plates spaced apart in the stack by a centrally perforated fiat dielectric sheet of substantially the same superficial dimensions; said metal stack, means insulating said clamping means from the stack, metal terminal plates for the stack which are stiffer and heavier than the stack armatures, projecting beyond the edge of Said clamping means and held in position 8 1,es1,1so

thereby, the stack armatures having the projecting end portions bent to contact with the terminal plates.

23. The combination with a capacitor stack 5 comprising sheets of foil and insulating material, of metallic clamping means for the stack comprising metal end plates extending across the stack in both directions, means iI1- sulating said clamping means from the stack, 10 metal terminal plates for the stack which are stifier and heavier than the foil and thinner and less stifi than said end plates, said terminal plates projecting beyond the edge of the clamping means and held in position 15 thereby, and said foils having projecting end portions bent for contact with said terminal plates.

JOHN A: PROCTORB

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