US2738567A - Manufacture of capacitors - Google Patents

Description

R. A. GROUSE MANUFACTURE OF CAPACITORS March 20, 195 6 3 Sheets-Sheet 1 Filed Sept. 21, 1951 INve NTg R March 20, 1956 A. GROUSE MANUFACTURE OF CAPACITORS Filed Sept. 21, 1951 3 Sheets-Sheet 2 I III March 20, 1956 R, A. GRO USE 2,738,567

MANUFACTURE OF CAPACITORS Filed Sept. 21, 1951 v 5 Sheets-Sheet 5 a; MU

INV gyr R gmmwrm A, Hg. Hunt CapacitorsDimited;fLondon, England, a Britishcompany Application seqtrfiiiifii 1951, Serial No; 247,624 can. priority; application Greatflfritain July 1s,-.194s 6 Claiins; (CIEAZ9L2ZSE4D This in entigm' relates" to; the manufacture of' roll capacitors' o f the kind-'de's cribddn'the specification of my co pending U. S pat'entgapplication serial No: 70,237, filed January 11;1949} now P'atent No. 2,637,766, granted. May S, 1953'; front which the} present application has been divided. y 1

A'nohject of theinventioiiis to p r'ovidei a process of pigodLicir'ig" strip's of" diel ectriciwhich bear: a series of nie'tall i c filni electrodes is? the purposeof making such capacitors, I p k My co-pending l application aforesaid concerns a capacitor which has foritsessential"operating'portion a strip of Ineta llise d'dielectricwhereof the nietallised surface is subdiyidedhy a continuousnon n' etalli'sed portion extendingin a devious course alon the strip between s parate metallisedjareas" so asjto form a repeatedpattern in which some nietallisediare'as' extend across the strip frorn one edgerand so nei from the other. When the strip is wound into. a r011 diife rlent metallis'e'd areas overlap one another, th'e areas extendingfjrorn one edge being connected'to one pole oi the capacitor and those extending from the other edge being connected. to the otheripple, y A b m a Accordingly; the present invention comprisesa process of producing w eh s o dielectric v v'h h bearl a series iof metallic firm 1etr I eiiteudifr'om'one frprn the .oi' pbsit'e e'dge,,.f sr n capacitors;j cohsistingj in taking Jfitallised on oneifac'e, act: witliQa crenehat'ed i. hileniaiiitainingrthe i1,tfifc ntly difierent from r a. re tfi .n witlfstandinjglthe vari tions o rateofidi'sicha rg j due to the crenellationfof'the rollfe a the pointjofjco'rning' into Contact Between thes irfac n i d dielectric and -of-{the crenel-litte d p'e'rip ery, there i=apassage of electric currentsufli6ie'nt to deme tal-lise {all that part of thesur-faceof' the dielectric comes into; contact with said periphery'and to leave-the said eleetrodes electi ical ly isolated from one 'another betw'e en' the r crenella tions. l, r. V

, Inns-1o. be understood that; the expression iffcrenellated periphery .whichniszremployed in. this, specification and claims is intended. tocdescriheibroadlx met-shape ofrthe per ph ry: wt ex llere i i s1; Q l Pdor, n he or; otherwise holloyyed,ogbqso as tohavwaqidgepf metal a e-t d .hi h s s a sale t wright; i h id naay followa sqgareaor ke atternor a curved or scol i opedrpattern although,for reasons of efiiciency the square pattern ispreferred l kipf fs q m' s. H. a yet; r naterialis passed intorcontact yith a demetallisin'g r i a I i iv -i 1??? wh hvf r a rr ra,.rae 9 e a a fi idielectriq, thespitch ofiwhichipat tfem .incneasesfrom. one

end towards th' otlier' eiid" of the dieleetric'. The repeating pattern may be in the form of anarrow band which deviates alternately towards each edge of the dielectric as itex'ten'ds' alongthellen'gthofthe web. The narrow' band may, for" exarnple, follow a square keyatterifalbhgathe IeiigthpFtheiWeb; The demetallising roller may; however, hayeacrenellated" edgeshaped to come into contact' with" the dielectric alofnga course which forms other rep lea igpattein in order to' pr'ov'ide'particular'arrangeinentsofelectrodes;

According to a feature: of-thejinveht'iori the dielectric web material may be brought "into contact with the dem'etallisingrol lr"byleadifig, the" dielectiic around a substantial plortionofth" p'eripliei'y of the miter,

According to aIfir r featilre of the invention the dielectric web" materialntay be of a' length suflicient for the manufacture of a. number ofcapacitors, the dielectric, affefdenietallisiation', Being wound into a roll whichis later. takenfan'd" lengths of'stripf miwoundfrmp it on toa niaindielt'ojfofin individual capacitor rolls, which mandrel'is suchfth at' after winding acapacitor roll the roIPcan" be slipped oi the m'a'ndrel endw'ise and a" f i'1rther rolil'star'tldthjrori, Preferably the dielectric hasbeen deme tal lised ac'c ding to a' repeating pattern, the'pitch orwhieh"ihcreasesalong the dielectrie,.and the mandrel used is of such diameter that the repeats of the pattern fit'theciidunife'rence of each turn of the roll.

The following" is aidescription by way of" example of one robe- 0 man actH're in accordance with the revamps, reference being made to the accompanying dfawirfgs in which: H

Figure 1 is a representation of one form of rnetal'lised dielectric stripsfor. Winding into a capacitor in accordance Witfimyfco-pendihg U. S." application No. 70,237 noy 'Paten't No. 2, 37,7 6, granted a 5, 1953;

Figures 2, 3 'and-4 arerepresentations of other such strips; 7 a r v V Figure 5 is a'perspectii'ffvieyy of'a demetallising apparatus for 'cairying 'duf'tlie process in'accordance with the .presentinvntion; 4 I I V Figure 6' is'a perspectiye" view of a: demetallising" roller used'in 'the'apparatus of Figure 5 Figure 7 -is the circuit 'diagranr of'the' apparatusshowh F rei nd Figure. i 8- is. adia g rani of a; winding ap'pz'n atils for winding; a strip; of demetallised dielectric-into a capacitor 1-0'11.

Referring to Figllires l to 4, theseshow-portions "of paper dielectric strips' vyhic'h' bea ra series of rnetallised areas"? Siiiih" strips aregshowri in my, ,co-pending..U. S

patent applicati n s e "al 2,637,766, granted May-5,1953; and in aordance with that invention"-v'vhen"a1iy'-oiie str'ipis wound into a roll, acap'acito'risforiii p Thes trip ll' 's'hbwn inFi'g'uie l is coyeredyvith metallised iareas:12-lwhich"efiteild jfroifi one edge 13 off the strip, .and"which" alternate with rnetallis'ed areas'14" er:- tendihgfifrom the otheredge' l s. Thefinetallisedareas 12 .are separated from thewareas 14 by a narrow de metallisedband -16-whi'ch/ follows a key patt'ern; repeating-itself continuously along-the strip? Thepitch 'of the repeats of the. heygpatterngradually increases, being smallest :at the beginningof the -patternat '17 on the band-and longest: at the end ofythe'patterwat '18: The paper is conlpletelyden'ietallised on'the endportions 19 beyond the keyiy patt ern; so as to form plain paper "end strips Which'can be used for the fir st-few turns and=the last few turns when the strip is wound into a capacitor" roll; 7 Tfie increasein pitch-otj-the repeats of the-key pattern dei'netalli'sed band '16 is comelated'to the thicknessofthe paper of which the strip is made, so that if the strip 11, commencing near the end 17 of the pattern, is wound on a mandrel of a particular size, each metallised area plus the width of the demetallised band which cuts it of1 from the next metallised area just occupies the turn of the roll in which it is wound. Therefore, each of the areas 12 will be exactly overlaid in the next turn with an area 14, and if in the completed roll the areas 12 are connected to one pole of the capacitor and the areas 14 to the opposite pole, the result will be a capacitor in which the alternate areas 12 and 14 exactly overlap one another.

The strip shown in Figure 1 comprises comparatively few areas 12 and 14, and in Figure 2 there is shown a strip comprising a much larger number of areas 12 and 14 succeeding one another and separated by a key pattern as in the case of Figure 1. In Figure 2 the strip is too long to be shown in a single piece and has been subdivided into three portions, the chain lines serving to indicate how in actual fact the one portion is joined on to the other.

Where a capacitor is required to work on a higher voltage than the capacitor above referred to, it is possible to use a strip which is demetallised as shown at 70 in Figure 3. Widely spaced metallised areas 71 extend from the edge 72 of the strip and intermediate metallised areas 73 extend from the edge 74. The large demetallised areas between the metallised areas allow for extra turns of nonmetallised dielectric between successive metallised turns of the capacitor.

Another form of strip is shown in Figure 4 and bears metallised areas 81, 82 and 83 which are separated by a demetallised portion 80. As described in my co-pending application aforesaid, when this strip is wound into a roll the result is the equivalent of two capacitors in series with one another.

The strips shown in Figures 1 and 2 can be produced in accordance with the present invention, by the apparatus shown in Figures 5 to 7. Referring to Figure 5, upon a base 21 there is an upstanding support 22 for a number of horizontal spindles which include a spindle 23 on which is mounted for rotation a demetallising roller 24. The roller 24 has a hub 25 made of insulating material in which is a bush 26 to run on the spindle 23. A stem 27 projects from the support 22 and carries an insulating bush 28 on which is mounted a brush holder 29 which supports a brush 30 made of flexible Phosphor bronze strip which bears on the face of the roller 24, and is connected by a wire 31 to a source of electric current.

Also mounted upon the support 22 is a spindle 32 parallel to the spindle 23, and serving to support a roll 33 which consists of a long strip of metallised paper. This is wound on a Bakelite core member 34, and the core member forms a hub which is slipped over a bush 35. The bush 35 runs on the spindle 32, and is pressed against a shoulder on the spindle by means of a spring 36 on the end of the spindle held in place by a nut 37. The bush 35 is screwthreaded on its external surface, and a nut member 38 upon it serves to screw the Bakelite core 34 against a flange formed on the other end of the bush 35 behind the roll 33. Therefore, the roll is held firmly on the bush 35, and is positioned accurately as to its plane by the pressure of the spring 36 against the bush. The strip of metallised paper is led oif the roll 33 as shown at 40 and is led around guide rollers 41, 42, 43 and thence around the demetallising roller 24. From the demetallising roller it passes around a guide roller 44 on to a wind-up roll 45. The guide rollers 41, 42, 43 proyect from a casing 46 which houses ball races to support the rollers so that they turn over easily. The metallrsed face of the paper strip 40 is arranged to come in contact with the demetallising roller 24, and it will be observed that the same metallised face will be in contact with the roller 42. The roller 42 is connected through the metal support 22 to earth, and therefore there will be a potential ditference between this face of the paper and the demetallising roller 24 which, as before described, is connected to an electrical supply. As can be seen from the connection diagram, Figure 7, the electric supply is connected through a resistance 47 to the brush 30 by way of the line 31, and there is a capacitor 48 which connects the brush 30 to a line 49 leading to the roller 42 and earth. These connections are similar to those described in U. S. application No. 679,532, now Patent No. 2,549,966, granted April 24, 1951, for the demetallising process therein described although in this instance the values of the resistance and capacitor have to be such as to meet the requirements of the variations in the rate of electrical discharge due to the shape of the edge of the demetallising roller 24, this roller being described in detail later. As the metallised surface of the paper strip 40 meets the surface of the roller 24, the electrical discharge which takes place between the roller and the metallised surface removes the metallisation from the surface of the paper without, however, burning the paper itself. The metallisation upon the paper is exceedingly thin as referred to in the aforesaid application Ser. No. 679,532, now Patent No. 2,549,966, granted April 24, 1951, namely about 80 millimicrons of aluminium. The paper itself is only about 8 microns thick but is not burnt by the discharge.

The wind-up roll is mounted on a bush 50 on a spindle 51. A nut 52 on the bush 50 serves to tighten the hub 53 of the roll 45 on the bush, and the bush is. held frictionally to the spindle 51 by the pressure of a spring 54, the construction of these parts being similar to the construction of the bush 35 on the spindle 32 already described. There is however a difference in that the spindle 51 instead of being stationary is made rotatable in a boss 55 on the support 22, and is driven at a suitable speed by a pulley mounted on the spindle 51 at the rear side of the support and not appearing in Figure 5 of the drawing. Therefore, the strip 40 will be frictionally driven from the spindle 51 and drawn through the apparatus, but owing to the friction drive afforded by the spring 54 there will be no tendency to snatch or tear the strip 40 when starting the apparatus. It is found desirable to make the earthing roller 42 of a smaller diameter than the other guide rollers, and to determine its exact diameter experimentally to suit the exact running conditions of the machine, so that the metallised paper gets a suitable pressure upon the earthing roller, which is suflicient to ensure that no demetallisation takes place at the surface of the earthing roller itself without being so great as to cause rupture of the paper strip. As will be seen in the drawing, the roller 42 is shown as being of smaller diameter where the strip 40 passes around it, and in practice if any tendency is found to an electric discharge at the contact between the roller 42 and the metallised surface, the diameter of the roller 42 is reduced until it is found that such discharge disappears, because any discharge at this roller would tend to demetallise the paper all over its surface and would, by the partial removal of the metallised surface, reduce the capacity of the capacitors which are the eventual product of the manufacture.

The periphery of the demetallising roller 24 is formed with a pattern which corresponds to the key-pattern shown in Figures 1 and 2. The roller as shown in detail in Figure 6 of the drawing has a key-pattern edge 56 corresponding to the demetallised key-pattern of the line 16 of Figure 1. This extends part of the way round the roller, and the remaining surface of the roller has a plain cylindrical surface shown at 57 and serves to produce the completely demetallised portions 19 of the strip 11 of Figure 1. It will be noted that the key-pattern portion of the edge 56 is made by milling out from the edge a number of notches 5,8 which run out into one face of the roller and by milling out between them other notches 39 which aises to in; "rats the roller. The sot-cites 58 can as rapidly machined by a plain cylindrical milling cutter, but if similar notches were cut'in 'thebpposite face of theroll'er, as they will be of constant width, they would tend at the portion which lies nearest to the axis of the roller gd to run into the metal of the notches oin t he opposite side, or to make the walls between the notches unduly thin. The notches 59 are therefore cut with an endmillirig'cutter, and have a cylindrical bottom. as. can be seenfj'cl'early from'thedrawing. In order to balance the roller and allow for the removal of metal which has taken place in cutting the notches 58, 59, a certain amount of metal is removed by shallow drill holes 60 on the opposite side of the roller near the circumference. The roller is very carefully balanced because it has to be driven by means of the pull exerted by the weak paper strip 40.

For producing a strip such as the strip shown in Figure 2 of the drawing a similar roller to the roller 24 of Figure 6 is used, but the key pattern notches 58, 59 are continued around the greater proportion of its circumference and it is one of the features of the apparatus shown in Figures to 7 inclusive that an appropriate pattern of roller can be provided for all the designs of .capacitor which are to be made within a wide range, and

in order to change from producing paper suitable for one design of capacitor to paper suitable for another design, all that is necessary is to change the demetallising roller, substituting for it another roller of the same diameter but different design and leaving all the adjustments of the apparatus untouched.

After the strip 40 has been wound into the roll 45 until the roll is full, the roll 45 is removed from the apparatus and capacitors are then wound therefrom on any suitable winding apparatus. This may be much simpler than ordinary apparatus for winding paper condensers, and preferably comprises a short stub-mandrel such as 60, Figure 8, which projects from a gear box 61 and is driven by a V-groovedpulley 62 on a driving shaft 63. The strip 40 is wrapped by the operator around the stubmandrel 60 for the first turn by hand, and then the apparatus is started up and a condenser roll 64 is wound up thereon. As will be appreciated there would be a suitable support for the roll 45 from which the strip 40 is unwound, and ordinarily it would be passed around one or more tensioning rollers on its way to the mandrel 60. The mandrel 60 may have a fiat face such as is indicated at 65 to assist in driving the paper strip when the roll 64 is being built up.

As soon as a condenser roll is completely wound on to the mandrel 60, the end turn is stuck temporarily down by a patch of adhesive or by a spot of grease or otherwise, and the condenser roll is slipped endwise off the mandrel, the end of which is left free, as shown in Figure 8 for the purpose and then the winding of a further capacitor upon the mandrel can commence without delay.

The completed rolls are sprayed on the ends in a similar way to that described in U. S. patent application No. 490, now abandoned, to aiford a base of sprayed copper or the line to which terminal wires or terminal caps may be soldered. In practice the diameter of the stub-mandrel 60 may be very small, say or of an inch, from which the small size of the capacitors producible in accordance with the invention may be gauged.

Capacitors A of an inch in diameter and A of an inch long are easily producible according to this invention, and

using the paper 8 microns thick will have a capacity of about 0.01 microfarad. If the thickness of the paper is increased to microns the capacity may be reduced to 0.003 microfarad. In the former case the capacitor will stand a voltage of 150 volts, while with paper 15 microns thick the capacitor may withstand 350 volts, using varnished paper in both cases.

It will be appreciated that although the above descrip titan relatess eeificaiiy to'producinfg the v shown Figuiies' 1: d 2, the trips shown in Figures 3 and 4 may be produced the same process using a suitably shaped demetallisingroller. lnstea'd of thekeypattern edge 56 or the demetallising roller 24; the edge of the demetallising roller for producing the strip shown in either Figure 3 or Figure 4 would be shaped to correspond to the: respective. pattern of demetallisation which is required on the strip.

. It will; be further understood thatthestripszof dielectric described herein as being produced by the process according to the present invention, are by way of example only. Other, and more complex patterns of demetalled dielectrics may be successfully produced in accordance with the invention.

I claim:

1. A demetallising roller having a crenellated periphery for use in a process of producing from dielectric web material metallised on one face, webs of dielectric which bear a series of metallic film electrodes.

2. A process for the production of electrical capacitors, comprising the steps of taking thin flexible dielectric web material that is metallised all over one face, demetallising a band extending continuously along the web which band deviates from side to side of the web thereby subdividing the metallisation into a series of metallic film electrodes forming a repeated pattern in which some of said electrodes extend inwardly from one edge of the web and others extend inwardly from the opposite edge, those electrodes terminating at one edge of the web being electrically insulated by the demetallised band from the electrodes terminating at the opposite edge, spirally winding a single length of said web material so demetallised into a close-wound roll, the electrodes obtained by the demetallisation being so arranged that after winding the electrodes in successive electrode-bearing turns of the roll overlie one another, and electrically connecting a terminal to the electrodes terminating at one edge and another terminal to the electrodes terminating at the opposite edge.

3. A process as claimed in claim 2, wherein the dcmetallised band is such that the pitch of the pattern of electrodes increases from one .end of the length of web material to the other, to take account of the increasing diameter of the roll as it is wound.

4. A process as claimed in claim 2, wherein the demetallised band follows a square key pattern course along the length of the dielectric web.

5. A process as claimed in claim 2, wherein the repeating pattern of electrodes is such as to first provide two isolated electrodes which are opposite one another and extend from opposite edges of the web, and then a single isolated electrode which does not extend from either edge but overlaps in a transverse direction the said first two electrodes, and so on alternately.

6. Apparatus for use in a process for producing from dielectric web material metallised on one face, webs of dielectric bearing a series of metallic film electrodes for winding into a roll capacitor, comprising a frame, a supply spool rotatably mounted thereon to carry a' reel of thin flexible dielectric web material metallised on one face, a winding-up mandrel likewise rotatably mounted on the frame to which the dielectric web is led from the supply spool, a demetallising wheel of electrically conductive material mounted for rotation on the frame in position where the web can be led around a substantial arc of the demetallising wheel periphery with its metallised face in contact therewith on its journey from the supply spool to the winding-up mandrel, an electrode in electrical contact with the demetallising wheel, a further electrode of opposite polarity in contact with the metallised face of the web, and a high tension electrical circuit for supplying current to the electrode which circuit includes acapacitor connected in parallel across the electrodes and a current-limiting resistance connected in 7 8 series in the lead to one of the electrodes, and the deof said electrodes extend inwardly from one edge of the metallising wheel having a crenellated periphery comweb and others extend inwardly from the opposite edge. prising a radially projecting raised rib extending circumferentially around the rim of the wheel which rib deviates References Cited in the file of this Pdtent in substantially regular fashion from side to side of the wheel rim so that the rib which is the only part of the wheel to contact the web demetallises a devious band 6:23:: et a1 g 3 extending continuously along the web thereby subdividing the metallisation thereon into a series of metallic FOREIGN PATENTS film electrodes forming a repeated pattern in which some 10 595,657 Great Britain Dec. 11, 1947 UNITED STATES PATENTS

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