US1505600A - Process and apparatus for the manufacture of electrical condensers - Google Patents

Description

PROCESS AND APPARATUS FOR THE MANUFACTURE OF ELECTRIQAL CONDENSERS Filed June 8,. 1920 7 Sheets-Sheetl 513% Mi} Mom Wa dreenleqf Aug. 19 1924. 1,505,600

G. W. PICKARD PROCESS AND APPARATUS FOR THE MANUFACTURE OF ELECTRICAL CONDENSERS Filed June 8, 1920 '7 Sheets-Sheet 2 2 r ammo;

Aug. 19 1924.. 505,600

" s. w. PICKARD PROCESS AND APPARATUS FOR THE MANUFACTURE OF' ELECTR1' CAL" CONDBNSERS Filed June a, pan 7 Sheets- Sheet s ambmfoz 1 Aug. 19, 1924. 1,505,600

G. W. PICKARD PROCESS AND APPARATUS FOR THE MANUFACTURE OF ELECTRICAL CONDENSERS Filed June 8, 1920 '7 Sheets-Sheet 4 Aug. 19 1924. 1,505,600

(5. W. PICKARD PROCESS AND APPARATUS FOR THE MANUFACTURE OF ELECTRICAL CONDENSERS Filed June a, 1920 7 Slieets-Sheet 5 4 ,111 I 95 A1 1 i id" 11 'I I (III a6 Q 1, if

w m" w v mun mun '1 nu I anvmfo c reen Mil'erPd-kaw Aug. 19, 1924. wosmo G. W. PICKARD PROCESS AND APPARATUS FOR THE MANUFACTURE OF EbEGTRICAL CONDENSERS Filed June 8, 1920 7 Sheets-Sheet 6 Aug. 19 1924. I

- G. w. PICKARD raocsss AND APPARATUS FOR THE mmfumcwuaz: OF ELECTRICAL connsnssas Filed June 8, 1920 7 Sheets-Sheet '7 are a-a mt 19,1934.

i i T E 1 PATENT; OFFICE.

ennnunmr wnrr'rriia IPICKARD,

. TO WIRELESS srncmimz Arm uiws. coareaa'rion or new YORK.

CbMPANY,

I form of processesa'nd sheets.

5 me for making mica condensers consisting ofmanent'ly intimate contact with one another,

' 'the interior whatsoever between 7 ing its low ful- Improvements in forth in th knownin hereinafter describ Application filed June a,

To all whom it may mm.- Be it known that l, GREENLEAF WHITTIER Promo, a citizen'of'the United States of America, anda resident of Newton Center, county of Middlesex, and State of Massa'g chusetts, have invented certain new anduse- Processes and Apparatus for the Manufacture of Electrical Condensers, the principles of which are set following specification and ac- V companying drawings, which di'sclosethe the invention hich I nowconsider to bethe-best of; he various forms in which the principles of theiinvention-may be embodied.

This'invention relates to improvements in apparatus for'the manufacture of electrical condensers of the sheet type and more particularly of i the type wherein mica is used for the dielectric The object of'the invention is a simplification of the processes heretofore devise by mica sheets and metal -foil sheets in perof the stack between the sheets being freed as nearly as possible of air, moisture and all material 'other than the d foil sheets themselves, the mica mica an and foil sheets preferably having nothingthem.

Dielectric sheets of material having the i dielectric and mechanical properties of mica required herein may be emplo ed insteadof mica, includdielectric losses, its non-porous characterand its ability to be formed into thin sheets of sufficient, mechanical strength ,for my processes. The foil sheets preferably consist of lead .foil, which is sqmetimes the art as tin-foill, although other metal foils may be employed. The invention consists in the processes ed, and consisting of a small number of steps, wherein the manufacture of the condenser is carried rapidly forward at each 07 severa f the steps; and

the, process is whichcondenser like ofamodification of the process of executed prc ierably in connection with certain apparatus or equivalents as shownin the accompanying drawings, of

- tary condenser as in 1. 1g.

1920. Serial No. 357,500.

apparatus employed in dipping in or coating'ea'ch of the sheets with paraflin and in building the sheets into. a condenser stack as shown in Fig. 2, or into sections which may be used in a sectional condenser shown 'inFig.2

Fig. 2 is an elevation of Fig. 2 is an condenser.

Fig, 3 is an elevation showing that of Fig-'2 may be a-condenser like Fig. 2 showing also a permanent small ,sprin clamp applied to the stack and adapte 'to be per.- manently embedded with. the condenser an inserted with it in the casingof Fig. 4. Fig; 3 is a plan view of thel'rsame which better hows the clampl show ing the. condenser,-with its clamp, m- 'serted into its permanent casing an thus far not provided with a covercasing'" Fig. section,- but with a temporary-,para cured to the top of the casing. 29, the latter being heated. vFigQ 5 being a similar viewa' sectional showing the apparatus of Fig. 6 is an elevation of-Fig. 5, withthe addition of'a-powerful press 27 to initiate the desired cal compression on the condenser, pressure thereafter is to lee-maintained the permanent small -clamp.

- Fig. 7. isa diagr who ing the mass of 'paraflin condenser-in connection with the process of Fig.- 5' Fig.' 5

modification of t is cooling process, I Fi 8 is anelevatioii (partly in' section) showing condenser in its completed form, with cover applied'to the casing; Fig. 8 being a similar view of, a'similar condenser, but modified in conformity with the modified filling and process of F ig. 5

Fig. 9 'of Figs. 5,6, 7 and 55.

Thesimplified process eludes but seven (but which a 5 is an elevation, partly in vertical Fig. 4;,- flin head 30 fseis a modification of the operation or NEWTON 'onii'riia, massaonusm'rs, ASSIGNOR or BOSTON, massncrmsm'rs, A.

permanent condenser for the v I I Fig. 5. 1" of the apparatus high mechamammatic view 'of-ap-.

paratus employed for the purpose of cool- ,surroundinilhe 0 illustrating a i i for asimple iuni- 2- preferably insteps which correspond .g'enf erally with the numbering of the drawings ployed for the urpose of squeezing out this to 7 inclusive. The same steps apply to paraflin from between the s eets to the a sectional condenser as in Fig. 2', but with reatest possible extent with the view of certain treatment interpolated. These steps, caving a condenser'stack consistin onlyv of .5 briefly, are as follows: the sheets of mica. and foil, prefera ly freed First, dipping each mica and 'foil sheet fromall the parafiin which has been temin warm molten paraflin inthe apparatus porarlly employed for the purpose of washof Fig. 1. 1ng out the other undesired foreign mate- Second, building a stack of such dipped rials, i. e., air and moisture. This'coating 1 or coated sheets as shown in Fig. 2 or 2", may be done by treating the loosely-as- 7 this building being done, if desired, in the sembled sheets, in a bath of hot paraflin; apparatus of Fig. 1. (At this stage, if the but the greatlypreferred process is that as condenser is to be sectional, there will be in Fig. 1 of separately coating each sheet interpolated certain treatment to be de- With the paraffin, this being done preferably scribed.) while the process of building up the ma- 85 Third, applying to the built-up condenser terial-stack out of the separate sheets is stack a sma permanent spring clamp as belng eflected, this preference being due to shown in Fi s. 3and 3 the fact that the sheets when wet with Fourth, p acing the condenser with its parafiin or held together by the hardened clamp of Fig. 3 in the permanent condenser parafiin are much more conveniently held casing of Fig. 4. j i together at this stage of the processes than Fifth, filling'around the condenser, with when dry- I clamp in place, and in its casin of Fig. 4, Fig. 1, in elevation, shows the building with hot molten heatin e bedding parafli stand consisting of a horizontal metal plate 25 as hown in Figs. 5 an eith with the 1,two vertical posts 2 at the rear, each of use of a high paraflin-head as in Fig. 5 or these posts being cut away at 3 to aline and by inverting the a paratus of Fig. 4 as guide thesheets of mica during the opera- ,shown in the modi cation of'Fig. 5 nd t1on of building the materlal-stack; and four either with the application of the heatingv g 4 P dBd On the bottom 1. 0 means of Fig; 5 or tw0-0r more fillings of. In-'F1g. 1, the abOVe bu lding stand is hi hl h t d ff or b th, shown as'placed in a waxlng tray 5, the Sixth, supplying permanently-maintain d latter being heated by a very small Bunsen 1 pressure on the condenser while hot, as by burnelfi to p lmply W rm he pa flin the means shown in Fig. 6. shown 1n said tray; In this molten paraflin, 35 S th, li d olidif i th the operator dips each mica and foil sheet, 10 beddin paraflin around the condenser in and the temperature of the 1parafiin in tray its final casing, as shown i Fig. 7; whererm h pp g and ng p r u on are conducted the final t p of n t1on 1s a out 70 cent1grade, i. e., about the p etin th condenser i th f h w temperature which the operators fingers 0 in Fig. 8 or 8'. 1 h I j 'convenlently can endure. Aftereach sheet 10 he condensers made by the processes dipped, i may be allowed to 0001 end hereof are more particularly adapt d f stdred for future use inthe second or builduse under conditlons where it is importantg P P referably, hOWeVeIs the that there shall be minimum electrical losses Sheets r bull n a S k When fr shly 4 in the 'condenser'in service; as in radio teledipped and hot, which is the reason why ll graph transmitters or in power lines, laborth bulld ng nd In F 1g- 1 1 shown S andatorystlendards and the like; The condeng lnslde 0f wexlng y ser stac in any case, ma e emplo ed as y I a unit as in Fig.2 in any desired way or 1t Second buddmg opemhlon' 60 may be constructed in sections as in Fig. The condenser may be built completely 11 2 Which may be grouped inservice in any under a bath of paraflin, but preferably it desired relation of serles, parallel or seriesis built as in Fig. 1 in atmosphere with its parallel, or the con enser may be? con-. lower end in heat-conducting relation structed into sections permanently connected hrough base 1.0f the building stand, with 55 in'series, as in the radio telegraph transmitthe parafiin in tray 5. This building in ting usewhere the condenser is not only conatmosphere permits lessexposureof the opstructed with sections insulated from one erators fingers to th'e i eatectparafiinp The another in the well-known-way, but the seclegs 4 of the building stand hold base 1 tions are permanently connected in series thereof away from the base of tray'5, so that 9' in the we] ow'n'manner, the heated parafi'in can circulate freely As thefirst process,-all the sheets, of both around base 1. The base 1 is heated during mica and foil, are. coated with the parafiin the building operation by the warm wax,

which serves later as a detergent for washand hence during the building operation the ing' out air and moisture-from between the condenser being built is kept warm, i. e., 5 assembled sheets-later steps being em-- both by the,warm coatings on the sheets" 13 paraflin in tray to the metal base 1 and metal posts 2, and by the heat conducted sary thickness of the coating paraflin beupwardlyby the growing stack itself.' This maintenance of heating during the building operation assists in keeping down unnecestween sheets (due to the increasing tendency of the growing stack to squeezeout excess parafiin by gravity) and also assists in tending to avoid the entrapping of air in the stack at this stage (due to the ten dency to greater intimacy of the sheets and the consequent tendency of the liquid paraflin which is being squeezed out to wash out air and moisture from between the sheets rather than to permit entrance or entrapping of air between'thesheets); If the condenser during the building operation becomes insufliciently warm, or if it' appears to the" operator .to havebecome solidified, she may spoon up parafiin out of tray 5 and pour it over the condenser from time to time for. the purpose of keeping warm and soft the paraffin between the sheets.

As the operator puts each foil sheet in place on top of a mica sheet, she can and should observe whether any air bubbles are entrained in the paraflin (as due possibly to incomplete dipping in the paraflin in tray 5), and if there be, and preferably in every case, she smooths down (Squeegees) each foil onthe stack to squeeze out such air;

Likewise, in putting each dipped mica sheet in place on top of a foil sheet, she

presses the mica sheet down on the coated foil sheet beneath it, for the same purpose of squeezing out any air. But in any case the squeegee pressure applied should be slight, to avoid so compressing the stack that when the pressure is released air would enter, due to the springing apart of the resilient .mica sheets after too great compression.

Preferably, the mica sheets have been se= lected to be'of uniform thickness, so that, by the operators counting of such sheets during the building operation, the capacity of thestack may be known at any stage of the building operation, and-so that a.

condenser of a given desired capacity may be. built up outof a definite number ,of sheets. Thus a given condenser stack as 10 of Fig. 2 may be built up in the appa-- ratus of Fig. 1'; or, as shownin Fig. 2,

thecondenser may be built up therein in the form of a sectional condenser, the tem porary markers 11 of Fig. 1 being placed on to of each section as it is built up to the esired capacity. Thus the building operation of Fig. 1 may result in a unitary ."condenser as in Fig. 2, or in a succession a'of sections with intervening markers and adapted to be completed as a sectional-condenser as shown in Fig. 2 wherein the rarily held in .alineme oughly temporary markers 11 of Fig. 1 are replaced by. permanent insulating separators 11 which are placed to project alternately at opposite sides of the stack as shown in parafiin between the sheets in the interior ofthe stack but also the so-called marginal paraffin which isthat between those por" tions of the foils which project out beyond the mica stack. When the stack is thorcooled and the parafiin hardened, the projecting foils 12, at the respective ends of the stack as shown in Fig. 2, are

soldered together so that the foil bunch at each end constitutes a unitary conductor, and to such' respective foil bunches are soldered 'the strip leads '13 and 14: which constitute the terminals of the condenser.

In the sectional condenserof Fig. 2*, at a like stage of operations, the same thingmay be done in respect of each SGOtlOIl, whereupon the foil bunchesof the respective sec-- tions are soldered to the foil bunches of adjacent sections in the usual manner as shown in Fig. 2 the condenser terminals 13 and 14 being thereupon soldered to the'two end sections respectlvely. In the case-of either Fig. 2 or Flg. 2 the upper condenser lead 13 now has soldered to it the upper condenser terminal 15; and the lower condenser terminal 14 hassoldered to it the lowercondenserterminal .16, all in' preparation for the third or clamp-applying operation,

In the caseof a sectional condenser, certain treatment is interpolated (as-referred togenerally above) at the stage before the third or clamp-applying"operation and before the assembly into sections of Fig. 2

and after the completion of the building of a sectional condenser material-stack indicated in Fig. 1 wherein the sections are separated by the temporary separating markers '11. This interpolated treatment is as follows.. The just-built stack of such sections of Fig. 1 is thoroughly and highly heated byimmersion ina bath of hot parafiin (at about 150 C.) so as to permit the application of such pressure as will simulate final compression on the eventual condenser stack in order to permit of measurement ofcapacity. Each section might be heated separately (it is to be tested separately), h

compression is applied; and this may bewhile the stack is in the heatingbath, after being thoroughlyn heated therein, or just after being removed from the bath and while yet thoroughly heated. Thereupon the stack of sections (or the individual sections) are allowed to cool while said mechanical com pression is maintained. Thereupon each sec- .tion is tested for capacity, and, if not correct, the capacity is adjusted. Preferably this is efiected by previously and initially building each section with more sheets of mica and foil than the number calculated for a run of the thickest mica, so that upon this test, the capacity will either be just right or a little .too high, so. that the capacity may be corrected by removing one or more ofthe sheets. Then each section is tested for voltage breakdown, and sections shown by this test to contain bad mica sheets are treated by splitting the sections in half, testing the halves, and putting together good halves of diiferentsections; and in splitting the bad halves, bad quarters, bad eighths and bad sixteenths, and similarly combining the good portions into complete good sections. Thereupon the 00d and correct sections are assembled as in ig. 2 The condenser of Fig. 2 thereupon 1s put 1n a press such as the arbor press 27 of Fig. 6, t e press is operated, and the capacity of the entire condenser measured under compression. Then the compression is relaxed and any necessary adjustment of capacity of the stack is made, this, however, being rarely necessary. If the test shows a broken-down section, such section is replaced with a tested good and accurate section, and

if the test shows faults in soldering together I the foils of adjacent sections, then the soldermg is perfected. Thereupon such sectional condenser is inreadiness for the third or clamp-applymg operation, which at this stage may be employed also on the single is put on the condenser,

unit cendenser of Fig. 2, upon which the above interpolated steps are not necessary.

Third 01' clamp-applying operation.

At this stage, no substantial compression the clamp being simply assembled with the condenser in preparation for further operations.

The clamping means shown in Fig. '3 is sufiiciently massive and strong to maintain permanently the compression later applied to the condenser, but it is small enough to be assembled permanently with the condenser and be received therewith in the permanent v casing for thecondenser. This clamp is preferably a sprin clamp adapted to permanently apply a five pressure to the stack during the later stages of the process and permanently in service, durin which times the temperature of the stac varies and consequently its length also. The spring clamp yields to conform-to such varying length and without injury to or deformation of the condenser it maintains the desired uniform live pressure.

As shown in Fig. 3, the condenser (illustrated, for example, as a sectional condenser as in Fig; 2'. although it may be the simple 7 condenser of Fig. 2) is placed on a base 17 which may be of metal. In fact this base plate 17 may rest on the base 1 of the building stand of Fig. 1 before the building of the steel: (as shown thereing so that the condenser on such plate 17 ma e removed with said plate from the building stand, in such case plate 17 being provided with holes (not shown) corresponding to osts 2 of Fig. 1', so'that it may be slipped own over and up off from said posts. This plate 17 forms the base member of the clamp, and it may be a resilient steel late. On the top of the stack in Fig. 3 is p aced an insulatingsheet 18, which may be of mica or bakelite, and on top of this is placed a steel plate 19, which serves to transmit to the condenser the compression applied from the two clamping members 23 to be described. On top of the steel plate'19 is laced a steel spring late 20 which may e the principal resilient member of the clamping means and which when not compressed assumes a bowed orv convex form (not illustrated). Above this top spring plate 20, the upper or high potential condenser lead 13 is bent down, having soldered to its end the condenser terminal 15.

on top of late 20 are placed two insulators 21, each 0 which may consist of a stack of I mica, sheets, these ser,vin to insulate the metal clamping members rom the upper or high potential end of the condenser. On top of mica stacks 21 respectively are placed two metal clamping members 23 (Fig. 3 Adjusting screws 24 secure clamping members 23 to side bars 22 which at their bottom are secured to base plate 17 by\ screws 25 and 26 respectively. Later on, these screws 25 and 26 hold the resilient plate 20 in flexed condition to apply the pressure resiliently to the condenser, the adjustment being permitted by top bolts 24. In somecases (to be described) screws 25, 26 at the bottom may be the adjustingcscrews, in which case. base plate 17 ma be the resilient member of the dclamp. e insulators 21 should have suflicient thickness to prevent discharge between the top of the condenser and the upper metallic portions of the clamping means. Also said metal parts of the clamp preferably are copper-plated in order to preventlosses injservice by eddy currents in. such parts.

The condenser with the clamping means; I 0 applied but not yet' acting to any sub- 3 I to which the condenser is subjected later in the press of Fig.- 6, yet these screws are not adapted to permit such compression to be initially applied by turning them, and hence the use in a later step, of the press of 6. At this stage, no very great compression is put on the condenser, the clamp being simply more or less loosely applied to the condenser.

Fourth operation, placing in casing.

This operation consists simply in placing the condenser with clamp loosely applied into its permanent casing 29 as shown in Fig. 4. (Here the final cover 38 is shown in a dotted lines indicating that it is not yet applied.) The metal casing 29 is preferably a casting and formed with internal grooves 43 to receive the metal clamping members 23- to center the condenser in the casing,the

bottom plate 17 of the condenser being received and held in a space in the bottom of the casing located between ledges 44, all whereby the condenser is in heat-conducting contact with the metal casing by way of the metal clamping member orplate 17. The permanently-clamped condenser, now perfnanently located in its casing, is now ready or the 3 Fifth or war filling Bythis operation, the. condenser casing and heating operation.

- is filled around the condenser-withits final embedding parafiin 'a'fid thoroughly and highly heatedin preparation forits .sixth or compressing and cleansing operation, whereby the paraflin coatings heretofore existing on the sheets are squeezed out permanently, thereby washing out air and moisture from between the sheets. One manner of executing the filling and heating operation is shown in Fig. 5, where,

. before the filling, the temporary waxing head 30 is applied to permanent casing 29 and the hot paraffin is supplied through the hole 80 to fill the entire casing and head, and wherein the gas burner 81 is used to secure adequate heating. If desired,'however, as an alternative or auxiliary manner of heating, the casing 29 can befilled with a temporary hot parafiinbath, which is then decanted, in order to preliminarily heat the condenser prior to the applicationc of the temporary head 30 and the filling ofi the final embeddingv paraifin. Such possible temporary heating bath mayor may not'i be used in addition to the use of. the burner 81, the principal operation being the same in any case, i. e., to co-operate inadequately heating the condenser in connection with the final parafl'in embedment and the subsequent special compression. Among other permissive variations of the heating operation is that of a continuing flow of hot paraflin through the condenser casing, which may be V efi'ected by providing a small hole in the bot- 7 tom of the casing and a continuous supply of'hot parafiin to the top). y The purpose of the temporary head 30 and its filling at this time is to facilitate the proper conduct of the operation of solidify ing the embedding paraffin after the step of compressing the condenser.

The head 30 is provided with a central tapered internal pin or projection 33 depending from the top and having a hole drilled 85 in its lower end to receive the threaded upper condenser terminal 15 which is soldered to fiexiblelead 13, This construction not only co-operates (in centering the condenser) with the small clamp and the. casing grooves (Fig. 4), but/holds up terminal 15 and lead 13 so that embedding paraifin may fill the space between lead 13 and the top of; the condenser. For the purpose of keeping the paraffin (with which the apparatus is to be filled) away from the upper part of the condenser terminal 15, a nut 34 is threaded on terminal 15, and a. rubber washer 35 is placed between nut 34 and the lower endottapered projection 33. Of course, nut 34 and washer 35 are put ,in place on terminal 15 before temporary head '30 is applied to case ing 29, the nut 34 being first screwed down into or slightly above its proper position and thereafter the head and its tapered internal projection 33areplaced .on top of the casing andon top of the washer 35 respectively. The tapered projection 33, together with the external tapering of the entire head 30, provide an internalspace which is tapered an- I nularly, in order the more readily to permit 1 the removal of the headlater on from the paraffin which by that time has hardened in said annular space in the head. Y

The object of the thorough and high heatingof the condenser at and about the time of the filling operation and the subsequent compressing operation is to cause there moval (especially by way of the compressing operation), of air and moisture vapor from b'etween the sheets of the condenser and from the margins and vicinity of thecondenser.

In Fig. 9 is shown a modification oi the. operation in Fig. f5,'wh'erein the condenser and the apparatus associated with it' is set at an angle so that any air or vapor entrappedbetween the projecting ends of the foil sheets and projecting separators may be ermitted to move upwardly through the bat -0f wax 1 v afiin. This inclined position of Fig. 9 may be maintained not only during the fifth or wax filling and heating operation of Fig. 5, but also during the compressing operation of Fig. 6, and, if desired, during the solidi-' fying operation of Fi 7. Likewise, this inclined position of 1g. 9 may be maintained in connection with the modified op eration of Fig. 5

In pre aration for the compressing operation of ig. 6, the condenser should be so thoroughly heated that all the paraifinon the surfaces of the sheets inside the stack may become liquefied. Depending upon the vari ous permissible ways of applying heat, this heating may require from half an hour to several hours, the temperature of the paraifin bath being maintained'at substantially 135 C., or, in other words, as near as practicable to the melting point of the foil sheets. This fifth operation of waxifilling and heating in final embedding paraflin is preliminary to the sixth or compressing and cleansing operation. p

In this invention, the operation of squeezing the wax coatings from out of the stack and the consequent washing out of air and moisture 'is' conducted after the condenser is inserted in its final casing and after such casing is filled with the final embedding paraflin. Thus at no time subse quent to the sixth or compressing operation is the condenser exposed to the atmosphere,

- and therefore no vacuum treatment is necessaY prior to or during the filling in of the em edding paraflin, provided .thatthe filling and heating and the compressing operat1ons are efiected under the conditions specified herein or by equivalent operations so that not only are the air and moisture re moved from the interior of the condenser, but also from the vicinity of its exterior.- Llkewise, the inventionhereof makes unnecessary the employment of any squeezing out or com ressln o eration prior to the fil 11 ng in o the a embeddmg parafin. lnkewise, f heating means are employed as n Fig. 5, no heating bath prior to the filling in of the embedding parafiin need be emplqyed. I

pon the proper conduct of the above-described filling and heating operation, 'the condenser is ready for the o1- cbmpresging and cleansing operahon.

I The condenser with the apparatus of Fig.

5,-and as et not highly compressed in its resilient cam T is t en placed in a; ress such as thear or. press 27fof Fi 6. f erably, qthe arrangement is suc that-the condenser-may beinjthe inclined position thin tion in'Fig. 6, the condenser yet should be' highly heated and maintained hot, so that the paraflin coatings on the sheets in the con- 1 denser may be liquid. For this purpose, it

maybe desirable to maintain heating by the pl manual application of the flame of a gas burner 82' or in any other suitable manner,

so that the conditions are ready for washing out the interior of the stack by the squeezing of the compression.

As a rule, it is better to resort to the press 27 of Fig. 6, rather than to attempt compression byway of the small permanent clam as by the use of the socket wrench 32 of F 1g. 5, for in the press of Fig. 6 the condenser readil may be subjected to the highest practical mechanical compression, which is desired. The vertical reciprocating standard 350i the press has an opening 36 at its lower'end adapted to permit-the reception of the upper or high potential terminal 15 of the condenser; and the lowerend of standard 35 is applied to the top plate 20 of the condenser at a point between the clamping members of the permanent small. clamp. This press 27 is employed when, as is usually the case, the small permanent spring clamps are designed (as shown-in Fi s. 3. and 4) for the purpose of permitting t e clamps to occupy a small casing with the result that the clamp is not adapted to initiate the highest practicable i In thecompressing operation, the pressureto which the condenser issub ected is approximately one thousand pounds per square inch of the active area of the mlca sheets, i, e., the area of the overlapping portions of the foil sheets in the interior of the condenser. p 7

While the compression is yet by the press 27, the permanent small clamps are screwedup to maintain such compression as by means of a suitable socket wrench 32 (Fig. 6) with handle 33, acting on. the

bolts 24, so that the permanent clampsthereafter hold the condenser under the pressure initiated by the large'press 27.-

maintained By the application of 'thlS pressure, the I liqui condition, are substantially'squeezed out from the interior of the condenser,

carrying with them substantially all of any entrapped air or moisture and thereby imroving the serviceability of the con nser araflin layers between the-sheets, in

v y removing such causes of electrical losses 0rbreakdowns in service.

The application of heat, as by the flame I of'gas burner 81 of'Fi is advantage'ouslycontinued not only efore and during sition shown in Fig. 9. This continuation' the compression, but also after the com- 'pression, and preferably during the maintenance of the condenser in the inclined P0- of heating may beefi'ected while the condenser and its associated apparatus are left in position in the large press 27 of Fig. 6, or the condenser and its associated appara' tus may be restored to the location of Fig.

- mitting the rise up through the hot embedding .paraflin of any air or vapor existingabout the margins of the condenser as the result of the compressing and squeezing out operation; and thetime of this continuation of heating is included in the several hours of heating above specified.

The heating is to be continued, inany case, until the cessation of emergence of all air or vapor bubbles from the surface of the molten parafiin in the top of head 30, including such air or va or as may have been caused toemerge rom between the sheets by. the compression of the hot stack. The time of continuance of the heating after the compressing operation is governed adequately in any case by such observed action oiithe emergence. of bubbles from the top of'the molten paraifin. It is referable that all the necessary heating 0 the condenser be effected in the bath'of em- ;bedding paratfin as bythe continued application of heat thereto, instead vof by the employment of a pre-heating. bath. If desired, however, the continuous flow .of heating paraffin above described in connection with Fig. 5 nia'ly be eflected after the compressing operation and especially in connection with the inclined arrangement of the condenser, as shown in Fig. 9, instead of. the vertical disposition shown-in Fig 5, as an alternative to the'use of burner- 81. In such case, as

above stated in connection with Fig.-5,a

hole 83 '(Fig. 9) may be provided in the bottom of the casing for the exit of the parafiin continuously supplied to the top of head 30. This hole may be closed permanently by a screw plug to stop the circulation. The continuous flow of hot paraffin down between the inclined surfaces of the projecting ends of the foil sheets serves to wash away air or vapor entrapped in the margins of the condenser. Whenthis purpose has been accomplished,.the hole 83 may be closed, the condenser being then ready for the final or solidifying operation of the parafiin remainin 1n" the casing, which is now the final em edding paraflin;

moisture.

' When the heating has been continued to the desired extent of driving the air and vapor out of the parafiin' in casing 29 (it is not important that they be driven out from the parafiin 'in head 30), the condiness for the y Seventh 07" solidifying operation.

This process is that of cooling the paraffin which has been poured into casing 29 around the condenser as in Figs-5, 6 or 9. This operation is illustrated in Fig. 7.

The function of temporary head 30 is to.

assist in causing proper cooling and pre 'vent the formation of voids in the embedding paraflin of the casing around the condenser, thereby producing a' holosteric embedment'. -During the process of cooling, the paraffin in the casing and head decreases largely in volume, andthis contraction, in the absence of the high head 30, would resultin the formation of cracks and voids in the paraflin in the upper part of the casing in the vicinity of the high potential upper end of the condenser. Those voids or cracks are liable to be filled with gases or vapors entrained inthe'paraflin or with atmosphere drawn in from outside the paraflin. Such cracks or voids in the vicinity of the high potential end of the condenser would be liable in service to result'in losses and undue heating. By means of the paraflin in the highhead 30, however, there is maintained a substantial head of paraffin which bears down on-the-surfaces of solidi-.

fication during cooling, thereby closely folatfin keeps liquefied the paraffin in the upper part of the head. Of course, voids or cracks,

in the paraflin in the upper part of the head will be formed finally upon solidificationof' such paraflimbut one object of the-tempo rary head is to provide a sufiicient volume of paraflin above the permanent embedding I tions are such that th apparatus is in readi- 'paraifinin" the casing so that all cracks or -voids which are formed will'be formed inthe paraflin in the head and not in the permanent parafiineembedment in the'casing. As an example of the [general size and proportions of theiemp'orary head 30, it

' may be stated that for a condenser casing 29 about inches high and 4 inches long by. 3 inches wide (internal dimensions), the temporary head -30 may be of the same length and width and of at least so conductedas to cause'the solidification to proceed from the bottom of the casing upwardly to the top of the temporary head,

, i. e., causing the cooling to proceed more slowly at upper partsof the paraffin; incasing and head, for in this way the func-- tions of the temporary high head are best executed. This cooling from the bottom upwardly may be effected either (1) .by ah stracting heat from the bottom'of the emas by room temperature, or

bedding parafiin and without doing any? thing to the top paraflin, or (2) byapplying heat to the top paraflin while permit ting the bottoin to graduall byabst-racting heatfrom the bottom while simultaneously applying heat to the top. Specifically, the latter is preferable for economy of time and in giving better control of the progressive cooling. In practice, the last or preferable manner is effected-(Fig. 7.) by

" cooling the bottom by an air blast from fan 67 while heating the top parafiin by meansof heated copper strips 68 which'extend' down into the top of theparaflin in head. 305 The casing- 29'rests-onsupports '69 which raise it above a table or bench;

andfthe blast from -fan' 67 is directed by a. sheet metal frame toward the lower part of a sideof the casing 29 and the bottom between the supports 69; theiupper part of frame 70 serving as a shield to pre- ..vent theair blast froni contact with the upper part of casing 29 andithehead .30.

The ,copp'er'strips 68 have their outer-ends brought near. together and both are heated in the flame of a Bunsen burner 71 th8 heat being thence conducted'to the other and bent-down ends of the strips which-extend down the paraffin, those ends being separated from the head 30. by heat-insulate .ing' members 72 of felt on thelike.

While a much shorter 'head cool. upwardly ditipnal heat isimparted totheparaifin in head 30' bythehot paraflin which is added I thereto fromtime to time to compensate for the shrinkage of the lower and cooling portions of the paraffin. v

After solidi-fication is completed, by any equivalent process of filling and cooling, head 30 is removed-from casing 29 and from the paraflin body above the casing, this ,removal being readily permitted (on account the ta ered internal annular surfaces of the head upon the application of a Then, by means of a long knife, the parafiin body above the casing is cut and chipped ofl? and'then pared and shaped to a,level with the top of the. casing. The device is now completed save ,for the application of a suitable cover 38 (Fig. 8) of insulating material such as fiber, bakelite or the-like.

' This cover has a central opening for the as 1 flame to the outside of the walls of the he irli threaded condenser terminal 15 and a lower recess for. the nut 34 and rubber washer 35.

When the cover is put in place andsecured to casing39. by screws 53 (Fig. 8) ,:nuts 54; are then threaded on the terminal 15 and screwed on top of them., Terminal 15 is one are pinned together and another nut 55 terminal of the condenser and may be the high potential terminal; and the other or low potential terminal may be the casing 29 when that is of metal, the bottom section of the condenser being'electrically connectedto the casing as shown in. Fig.- 8 at 14 and 16.-

executingthe processes of filling and com: pressing the condenser illustrated in Fig. 5.

,This' gnethod consists in inverting casing 29 during the filling, compressing and cooling operations; and this'involves a modification In Fig. 5 is shown a modifiedmethod of,

consisting in having a cas'ing with its bottom open .as well as itstop, and a separate bot- .tom member finally secured to the bottom.

.of the casing as shown in Fig. 8f as a modification of the assembly shown 1n Fig. 8.

plied to the casing before-"the condenser ll O As shownf'in F ig."5 the cover. 38 is apf (with itspermane'nt small clamp loosely applied) is inserted in the casing 29; and then the casing, with temporarily open bottom the filling of hot molten embedding paraffin.

By this method, the high potential; end of the fcondens er is located at what is temporarily the'bottom ofthe casing (i. e., unti the soas shown in'Fig. 5 is inverted toreceive 'lidification of the embedding paraflin), 'so that the fluid paraflin in the casing consti-- tutes'a fluid'head above the high potential end of the condenser, and so that when the.

,the high potential end of the condenser, and the process :is executed of solidifying" the rem-5 bedding paraflin from the bottom upwardly,

parafl'in will solidify first around the tion, thereby preventing the formation of voids or cracks in the paraflin near the'highpotential end; and any cracks or voids in the parafiin near the low potential end of the condenser (i; e., in what is to be the bottom of the casing) will be relatively innocuous. Also the paraffinby this method. is caused to adhere tothe inside surface of the cover 38- of the casing, as the result of the .parafliu being applied thereto when hot and molten,

thereby filling up with permanent embed ding paraflin any air spaces near the high potential end of the condenser which might permit brush discharging in the service of the condenser..

, By this operation, the use of the temporary waxing head 30- of Fig. 5 may be omitted; althoughin'any case it may be employed wherever it'is desirable to insure against the formation of all cracks or voids anywhere within casing 29, even at what is finally to be the-bottom of the casing the presence of voids, even in the vlcinity of the low, potential end of the condenser, might be deleterious, in that they might rise up toward the high potential end if the condenser were subjected to such service as to.

heat it to such'extent as to liquefy the embedding paraflin.

Imexecuting the above-described method with Fig. 5 the same general processes of adjusting screws at the top order that they may. be accessible for adj ust- -filling, of compressing and solidifying, may

be employed, as above described; and in particular, the heating of the parafiin be followed-out to the proper extent for liquefying the parafiin on the surfaces ofthe sheets in the condenser preliminary to the application .of the squeezing-out .compres-' sion; and in the continuance of the heating to such extent as 'to permit the upward passage of air or gas bubbles from out of the casin 29 to the upper part thereof (or up into t e temporary head, 1n case thatbe employed). I

In Fig. 5%, on account. of the inversion of the condenser, the screws 25 and 26 at'the bottom of the condenser (Fig. 3) will be the ment on the upper end in the inverted position of the condenser, so that the compres- .ing means. better adapted to instances w erein the' sion may be applied throughithe open end of the condenser. In this case, base-plate 17 may be the resilient member of the clamp- This inverted mod'fication is compressionis initiated-by way of the small clamps and without the press. 27 of Fig. 6,] in instances where the cover 38 is of, insulatfor.

in Fig. 5 in on the apparatusof Fig." 5 a permanent base plate 39 (Fig. 8*) is applied to the bottom of the condenser by suitable screws,

to close .up the casing, a gasket 42 placed between the mam casing and base plate 39-.

In any be conducted with the condenser in the in clined position shown-in 9;,but-this is not necessary'or desirable in instanw where air and moisture havebeen eliminated by the compressing and heatingoperations described above.' i

. If desired, one or a number of condensers (each in its permanent casing and finally clamped) as in Fig. 5 but without any head 30, may be placed in the bottom of a very large tank, filled with molten embedding 'paraflin to a considerable height sothat d;

case, the solidfying operation may ferred to herein, such compression is to be.

understood to be preferably the mechanical compression'which is racticable to be applied onthe soft leadfhil sheets,

more per square inch of the active area of and this in practice is aboutLOOO-pounds or each mica sheet, i. e., that partof the mica.

sheet which lies between the overlapping.

whi

foil sheets, this being a pressure amounts to about a ton or more on the enhigh-by. 2" long by 1 wide.

When theword paraflin is used in the claims, it is intended asapplying to any material which is the substantial equivalent 1 of the-embedding material referred here in, which is amixture 0 parafiin and canauba wax.

is to be understood that this does not exclude other materials which might be found As mule limitation to sheets of ma... it

to be equivalent the invention, as to thevaluable properties of for this purpose involvingits low dielectric losses, high dielectric strength and its ability to be formed into thin sheets ofsnflicientmecham ical strength fr my processes.

Iclaimz- 1. The herein-descnbed method of making a condenser which consists in submerging a stack in' a bath of fluid.

. m a casing and then, while in sai bath, ap

lying permanent pressure to the stack to rave out insulating material from a condenser which consists in first subjecting a stack'to a bath of fluid insulating material and to heat inv a casing to drive out moisture and air and then, while in said bath and heated, subjecting the stack to high permanent pressure to bring the sheets of the stack closer together and drive the insulatingmaterial and any contained air or moisture from between the same, forming a permanent filler around the stack of said msulating material in which it is submerged without exposing the stack to atmosphere after its bath therein.

3. The herein-described method of making a condenser which consists in. building a stack of sheets with liquefiable insulating material between the sheets, placing sai stack in a casing in position to be'permanently clamped, subjecting the stack in said casing to a bath of molten insulating ma- ,terial and to heat to liquefy the insulating material between the sheets and drive out air and moisture, applying permanent pressure to the stack while. in the bath and while heated to bring the sheets together and force out the liquefied insulating material from between the sheets together with any contained air or moisture, forming a permanent filler of said insulating material around the stack in said casing without exposin the stack to atmosphere after the I bath ,therein. 1

4. The method of mks an insulationembedded mica; and foil con enser held com pressed permanently by a clamp in a permanent casing enclosing the embedment, which consists in building a stack of sheets of mica and metal foil; assemblin' a permanent clamp with such stack an with a permanent casmg around the stack and clamp; thereafter, before compressing the stack by such clamp, filling the casing aroundthe stack with a permanent'insulation-embedment comprisin hot fluid insulat ing material which is solif at ordinary temperatures; thereafter applying heat until insulating material in fluid condition lies between the surfaces of the sheets of the stack;

thereafter, while the insulating material between the sheets'is fluid, subjecting the stack to high mechanical compression to brin the sheets closer to ther and squeeze out 111 between them e fluid insulating material and'anya1r or moisture between the sheets; mamtaming such close association of the sheets by maintaining such high compression by means of said permanent clamp;

and thereafter solidi ing the insulating -nuaterial'surroundingt e stack as an embedthe casing and extension'with molten mment while the stack islield under said com coated; assembling such stack with a per- ,manent clamp in a permanent casing; then,

before compressing the stack,'filling the casing around the stack with a permanent insulation-embedment comprising hot fluid in-- sulating material of the kind between the sheets of the stack; thereafter, while the insulating material between the sheets is in fluid condition, subjecting the stack to high mechanical compression to bring the sheets. closer together and squeeze out from between them the fluid insulating material and air and moisture between the sheets; maintain ing such close association of the sheets and the exclusion of air or moisture from between them by maintaining such high compression by said permanent clamp; and

thereafter solidifying the insulating embedment while said compression yet is maintained by said clamp.

6. The method of making mica and foil condensers, which consists in building a stack of mica and foil sheets with insulation between them which is liquefiable at tem. peratures not injurious to the foils; thereafter placing such stack in its permanent casing; submerging the stack therein in a permanent embedment of insulating material like that between the sheets and solid at ordinary temperatures but now a hot fluid; applying heat to liquefy the insulating ma terial between the sheets and drive out air from the fluid embedment; and applying and maintaining high pressure to the stack while the insulating material between the sheets is fluid and while the stack is submerged in the fluid insulating material to bring the sheets into closer relation and squeeze out the fluid insulating material from between them; and solidifying the insulating embedment; all wherebythe stack is permanently embedded without ezpiposing subit to the atmosphere after its sai mergence in the fluid embedment, and while maintained under the hi h pressure.

7. The method of ma 'ng mica and foil peratures; thereafter placing the stack in its permanent casingvwhile the same has a temporary extension applied thereto; filling sulating material like that between the sheets, that is, which-is solid at ordinary temperatures; applying heat to liquefy' the insulating material between the sheets and drive out air and moisture. from the influid insulating material from between them; solidifying the insulating material surrounding the stack while maintaining said pressure; and then removing temporary extension from the permanent casing.

8. The method of making mica and foil condensers, which consists in building a stack of sheets with insulating material between them which is liquefiable by a degree of heat which is not injurious to the foils and is solid at ordinary temperatures; thereafter placing such stack in a permanent casing; filling the casing with insulating material like that between the sheets, that is, which is solid at ordinary temperatures and liquefiable by a degree of. heat not injurious to the foils; applying heat to liquefy the insulating material between the sheets while the stack is arranged to allow the escape of air during said heating from the insulating material surrounding the stack; and applying pressure to the stack while submerged in the fluid insulating the material in the permanent casing, to bring the sheets closer together and squeeze out theliquefied insulating material from between them; and solidifying the insulating material surroundin the stack from the bottom upward w 'le maintaining the pressure on the .stack to prevent entrance of air or moisture between the sheets while the insulating material surrounding the stack is in fluid condition.

9; The method of making mica and foil condensers, which consists 1n immersing a stack of foil and mica sheets, while substantially loosely assembled together, in a hot fluid insulating material which is solid at ordinary temperatures; supplying additional heat to the embedding material surrounding the stack to thoroughly heat the latter and establish a fluid condition of insulating material between the sheets which is solid at ordinary temperatures; subjecting the stack while submerged in said fluid insulating embedment and while hot due to such additional heating, to high compression tosqueeze out from between the sheets the "fluid insulating material and any air .or

moisture present between the sheets; and, while maintaining such compression, coolin and solidifying the insulating materia around the compressed stack to constitute a permanent embedment preventing reentrance of air or moisture between the sheets of the'stack. v

GREENLEAF WHl'l'TlI-IR PlCKARD.

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