US 2435441 A
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Description (OCR text may contain errors)
Feb. 3, 1948. R. A. GROUSE 2,435,441
PROCESS FOR DEMETALLIZING METALLIZED PAPER Fil ed Oct. 20, 1943 s sheets-sneak 1 Feb. 3, 1948. R. A. GROUSE PROCESS FOR DEMETALLIZING METALLIZED PAPER Filed Oct. 20, 1943 3 Sheets-Sheet 2 27v ve/vToR x N Q Feb; 3 v 'PROCES'S FOR DEMETALLIZING' METALLIZED PAPER R. A. GROUSE 3 Sheets-Sheet 3 IN van/70R Filed Oct. 20, 1943 Patented Feb. 3, 1948 UNITED STATES PATENT DFFICE PROCESS FOR 'DEMETAILLIZING METALLIZED PAPER Richard Alfred Grouse, London, England, assignor to A. H. Hunt Limited, London, England, a company of Great Britain ApplicationOctober 20, 1943, Serial No. 507,042 In 'Great Britain October 23, 1942 to constitute a :condenser'providing at least one margin oneach of thestrips is-free of metal. It is :necessary that the margin should be free of metal in order to ensure that there is no flash over .or short circuit from one electrode to the other and the dhigherthe voltage (at which'the condenser is to beused-the wider mustthe margin be. However, in theinterests of compactness the margin should be kept at a minimum value which issuitable for the working voltage at which the condenser is intended to be employed; this, of course, implies that the flash-over voltage will be substantially .in excess of the working voltage, but not so much as to waste space by requiring an undue margin. For example, in-the case of a condenser to workat '150/V011JS it is sufllcient if the flash-over voltage is 'as much as 300 volts. For this purpose a margin no more than ,64 Of an inch wide wouldbe sufficient, but a margin of this degree of narrowness is difiicult to provide by the ordinarymeans. Normally when the metal is deposited 'on the paper, the paper is masked in such a way :as toleave thedesired edge margin, but the masking cannot produce an extremely narrow edgemargin.
It is an object of the present invention toprovide metallised paper which is suitable 'for use in themanufacture of electric condensers and in which the unmetallised margins .or bands are produced withoutmasking the paper in the original Operational producing themetallised surface.
Although in such condensers the provision of an such-paper.
It is agfurther object of the invention to provide-metallisedpaper electriccondensers in which the-unmetallisedportions of'the paper employed are reduced to'the'narrowest satisfactory-dimensions,
The invention comprises a process for producing metallised paper with an unmetallised strip portion or portions thereon characterisedby first metallising "the paper and thereafter removing the metal from the strip-or strips which'it is desired should be unmetallised bybringingthema- ,terial into contact with, and moving itpast, an electrified conductorwhile maintaining the metallised area of the paper of opposite polarity to the conductor so'that current from the conductor burns off the-metal along the saidstrip.
In one form of the process the conductor is'applied to the-unmetallised side of thepaperalong one or both edges thereof .so that the "strip or strips :fromwhich the metalis removed consist of one or both edge margins ofthe paper close to'the conductor. If both edge margins are thus demetallised and the paper is of the width oftwo of the strips eventually desiredfor the condenser, it can'thereafter be slit so as to produce two strips each having along one edgean unmetallisedmargin and along the other edge having the metallised surface extending up to the edge. Such strips are of particular service in winding electric condensers because the edge which has :not been demetallised is convenient for the making of electrical, connection to a terminal, for example as described in patent application No. 493,173.
In another'form of the process the conductor may consist of anarrow'member of awidth suitable to produce the desired unmetallised strip,
applied to the paper on the metallised surface thereof. The paper in such a case may be a web ofa width great enough to-comprise the width of several unmetallised strips parallel to one another, and several-conductors may be applied to the metallised surface simultaneously so .as to produce such unmetallised strips.
The conductor or conductors may consist of a rotatable roller or rollers around which 'the paper ispassed.
The process works best when the metallised surface'is exceedingly thin and preferably the metallised paper employed is paper on which the metallised surface has been produced by condensation of metallic vapour thereon in vacuo as an extremely thin conducting layer, forexample by the process described in U. S. patent specifications Nos. 2,100,045 and 2,153,786.
The inventionincludesa process of manufacture of electric condensers consisting in'taking metallised paper,,producing a demetallised strip I strips.
or strips thereon by means of steps as above described and thereafter winding two or more strips of such paper together into an electric condenser.
The invention further comprises apparatus for demetallising strips of metallised paper in which there is provided in combination means to support a feed-roll of metallised paper, a set of narrow demetallising rollers supported so that the metallised face of the paper can be fed past and in contact with them from the feed roll, means for connecting the set of demetallising rollers to the electric supply so that their potential is opposite to that of the metallised face of the paper and means to receive paper from the demetallising roller and rewind it.
A gang of slitting knives may be set to cut the paper, before it is re-wound, along the centres of the demetallised strips and also along lines extending along the metallised bands between the In this way strips are obtained which are demetallised along one edge and along the other edge are metallised right up to the edge of the paper.
The following is a description, by way of example, of certain forms of apparatus and of the process as carried out therein.
Referring to the accompanying drawings,
Figure 1 is a diagrammatic perspective view of one form of apparatus;
Figure 2 is a detail illustrating the demetallisation of the edge margins of the paper shown in the diagram Figure 1;
Figure 3 is a plan of an alternative apparatus;
Figure 4 is a side elevation of the same.
Referring to Figure 1, I is a core on which is wound a feed roll I2 of paper which has been metallised on one face with an extremely thin conducting layer of aluminium or copper. The roll I2 on its core i I is mounted on a shaft I3 which is supported in bearings not shown in the drawing. The paper is so wound on the roll I2 that the metallised face is the inner face l4 of the paper as it comes off the roll. From the roll I2 the paper is fed past a metallic roll I5 mounted on a suitably supported shaft I5 so that the roll I5 is in electrical contact with the metallised surface of the paper. The roll I5 is connected to the negative or earth terminal of an electric supply as indicated by the wire I Beyond the roll I5 the paper passes upwardly and over the upper surface of another electrical conducting roller i8 which is supported between insulated point bearings i9, 29. The insulated supports for the point bearings are not shown in the drawings and may be of any construction desired, the object being to enable the roller I8, which forms a conductor in contact with the unmetallised surface 2| of the paper, to be maintained (by a connection 22 to the positive terminal of an electric supply) at a substantial potential difference from that of the metallised surface of the paper which is connected to the roll I5.
The potential difference applied is at least as high as that which the condenser will eventually be called upon to bear under workin conditions and preferably considerably higher so as to provide a margin of safety. For example, if the condenser is intended to work under a potential difference of 200 volts, the potential applied to the roller !8 may be of the order of 500 volts. The paper strip on the roll I2 is metallised right up to its edges, and owing to the thinness of the paper the result is that at the edges, as the strip reaches the conductor I8, there is a flash-over of current from the conductor to the metallised surface of the Paper. This flash-over burns back the metallised surface on the paper along the margin during the passage of the paper around the roll I8, producing two demetallised edge margins 23, 24 as shown in Figure 2. If the metallisation on the paper is sufliciently thin this burning back of the edge margins will take place without appreciably carbonising the paper itself. Thus, a demetallised edge margin of the minimum width which will withstand the potential difference applied, is automatically produced along each edge of the paper.
At the same time, any faults which may exist in the dielectric itself are automatically burned out, that is to say, the metallised surface is burned away around the fault during the passage of the paper over the conductor I8 in the manner described in patent application No. 493,173.
From the conducting roller I8, the paper strip, with its two demetallised edge margins is led past a rotating cutting knife 25 so as to be slit into two strips, each having one demetallised margin and one edge along which the metallised surface extends up to the edge. The strips are wound into a roll 26, on a core 21 mounted on a suitably driven shaft 28.
Thereafter the two rolls so produced can be used for winding into an electrical condenser in the manner described in the aforesaid application No. 493,173.
By the above process an edge margin can be produced which is extremely narrow, and, even for high voltages, as great as the paper is able to stand up to as a dielectric, may be less than 64 of an inch.
Referring now to Figures 3 and 4, the apparatus shown comprises two side plates 3|, 32 which extend parallel to one another and in conjunction with suitable spacing members 33, 34 and nuts 35, 36 constitute the frame of the apparatus. On the side plates 3|, 32 at one end there are secured brackets 31, 38 having slots 39 to receive a spindle 4|! which carries a feed roll 4| of metallised paper. The feed roll 4| is wound on a cardboard tube which is supported from the spindle 40 by means of flanged discs 42, 43. The flanged discs have a cylindrical portion which fits inside the cardboard tube and a flange 44 which abuts upon its ends. The two discs are drawn together by means of three bolts 45 which are equidistantly spaced around the spindle 48 and by knurl-headed nuts 46 upon the bolts. The knurl-headed nuts do not engage the disc 43 directly, but interposed between the nuts and the disc are springs 41. Thus the roll 4| is frictionally held with respect to the spindle 40 and the tension which can be ap plied to the paper web 5| from the roll 4| is limited to the force transmissible through the frictional connection. This tends to avoid tearing the paper web, which is very thin, being of the order of thickness of about one-half a thousandth of an inch. The thickness of the metallised layer upon the paper is considerably less, being less than one-fiftieth of a thousandth of an inch and the metallised layer is wound so as to face inwards on the roll and is, therefore, uppermost on the web 5| as it comes away from the roll.
Between the plates 3|, 32 there is mounted at the end nearest the roll 4|, a spindle 52 carrying a roller 53. This roller is made of conducting material, for example, brass, and is in electrical connection with the frame ofthe machine, which is connected to earth. This ensuresthatthezmetall'is'ed' surface of the paper is at earthipotential.
Somewhatabove and to the rightof the spindle 5Zthere is another spindle: 54 which issupported between point bearings provided by screws 55 mounted inan insulating bushing 56 in removable blocks 51' in the side plates 3t, 32 The screws 55 are electrically connected, for example by means of a Wire 58-; to the positive or unearthed terminal ofan electric supply having a voltage of between 500 and 600' volts, direct current. Beyond the spindle 54 and also supported between the side plates 31 32- thereisanother spindle 60 supported in-bearing bushes 61, eachof which works in a vertical slot 62 in theside plate in which it is mounted. The bearing blocks 61 are supported on springs 63 so that they tend to rise and the amount of the rise is limited by means of an adjusting screw 64 in a cap plate 65. The spindle 60 carries a roller 66- over which the paper web '51 passes. By adjusting the screws 64', the exact path of the paper web may be adjusted within fine limits.
Upon the spindle 54' there aremounted a number of narrow disc-like conductors 61 by means of hubs 6 8 which fit the spindle 54-. The diameter of the conducting discs 61 is such that they just touch the paper passing from theroller 53 to the roller 66 in the course of" its path, and the adjustment provided by the-screws B4 is intended to ensure that the discs 61 can engage the paper properly but without producing undue pressure upon it.
The width of theconductors 6T ismadeto correspond with the width of strips which it is desired should be demetallised upon the paper web 5!, and the spacing of the discs corresponds to the desired spacing between the demetallised strips. It is found that as soon as the metallised surface of the paper touches the conductors 6'! thefiow of current at the point of contact is suihcient to burn off and vol'ati'lise the metallised surface of thepaper, the'width so demetallised being only slightly greater than the width of the operative edges of the discs 61'. Consequently the paper, as it comes away fromthe discs 61, presents a metallised surface which is subdivided'by unmetallised bands, shown in the drawing by chain lines'lfl.
Beyond the spring-supported roller 66 the paper web is caused to move downwardly beneath a large feed roller 1| supported on a spindle 12. The paper web passes beneath the feed roller H into a nip provided by a second feed roller 13 which is carried. on a shaft 1 1 mounted in bearing blocks 15. The bearing blocks 15 work in horizontal slots 16 in the side plates 3|, 32, and they are adjustable along the slots by means of a screw 1-! provided with adjusting nuts 18. Thus the roller 13 can be pressed firmly against the roller H and grip the paper web securely. The shaft 14 is extended so as to provide a mounting for a driving pulley (not shown in the drawing) and by this means'thepaper'is drawn through themachine at a suitable speed.
In the" stretch of the web which extends from the roller 66 to the underside of the roller H, a slitting operation is performed upon the paper. To this end there is" mounted in bearings 80, 8| a driven shaft 82 (carrying a pulley, not shown). Upon the shaft 82 there is a gang of circular slitting knives 83 which are spaced apart by cylindrical spacing members 84. The knives 83 are so spaced as to slit the paper down the centre of each of the: demetallised strips 10 andalso down the centre-of each ofthemetallised areas between the strips. In order to ensure that no lateral movement: of the slitting. knives. takes place the gang of knives isurged by aspring toward the side plate 31. The spring 85 is located between the bearing block 80. in the side plate 32 and the end member of the spacing members 84-. At the other end of the gang of knives a thrust washer 86 is caused, by the. pressure of the spring 85, to bear on the bearing block 8|. It will be appreciated that it is important that no lateral movement of the knives should occur as they rotate, otherwise the paper web maybecome torn. It will also be observed that the screws 55 which support the spindle 542 of. the demetallising conductors 61 provide a means of adjustment so that the conductor 51 may be set exactly in line. with the slitting knives 83. Furthermore, the mounting of the feed roll 4| on the spindle 40 is such that the feed roll isautomatically held always in the same positionrelatively tothe spindle, and, therefore, if the spindle 40' is lifted out and a fresh roll of paper substituted when the roll in use has become exhausted, the new roll will automatically come into the. same position relatively to the demetallising. conductors 61 and the slitting knives 83 as was the case with the previous roll. In this way exact repetition of results is maintained.
It will, therefore, be seen that the paper web 5|, by the time it has'passed the slitting knives 83, consists of a number of separate strips of paper; each of which is metallised up to one edge and demetalli ed along its other edge, the demetallised margin being equal to half the width of the demetallised strips [0. After passing the feed roller 13- the strips are separated from one another. Half of. them have demetallised margins along. their'right-hand. edges and the other half have demetallised margins along their lefthand. edges. The former are led on to an upper series of re-winding rolls 90 and the latter on to a lower series of re-winding rolls 9| The rolls 90 are mounted on a driven spindle 92 and the rolls 91: on a. driven spindle 93'. These spindles project beyond the side plate 32 suffiiciently to carry driving pulleys, and they are driven from a driving pulley (not shown) on the spindle 14, The fragility of the paper strips makes it necessary that the force applied to wind them on to the rolls 90 and 91 should be strictly limited. To this end each of the. rolls 9!] and 9l' is supported between two discs 94, 95. The disc 94. has a hub by which it is mounted on the spindle (92 or 93 as the case may be) and the disc 95 is supported from the disc 96 by means of three equidistantly spaced bolts 91: carrying knurled nuts 98 between which and the disc. 95 there are interposed springs 99'. The cores of the re-winding rolls 98 consist of short cylindrical lengths I01 of cardboard tube or other suitable material which are gripped between thediscs 94, 9-5 and are centred by inwardly projecting flanges I08: on these discs, Therefore, the driving force which can be applied to the cores of the re-winding rolls is limited to the force afforded by" the frictional grip and this can be adjusted so as to be as light as desired by means of the nuts 98*. In order to attach the ends of the paper strips- 11 tothe cores In! it is sufiicient to stick them in place with a dab of petroleum jelly or like material.
Once a web of paper has been passed through the various parts of this apparatus and its ends appropriately attached to the re-winding rolls 90, 9|, the rest of the paper can be quickly and automatically demetallised along the strip 70, cut by the cutting knives 85, and re-wound as a series of alternate right-handed and left-handed strips without necessitating undue attention on the part of the operator. From the rolls 90 and 91 the paper can then subsequently be re-wound into a condenser as described, for example, in patent application No. 493,173.
It will be appreciated that if for any purpose the strips of paper are required to be produced With demetallised bands running down their centre or in other positions removed from the edges, this can be arranged with apparatu of the kind illustrated in Figures 3 and 4 by appropriately spacing the discs 57 and omitting the appropriate knives from the gang on the spindle 82. Of course, the re-winding rolls 90, 9| need to be arranged so as to be of appropriate breadth to receive the strips thus produced.
1. The method of demetallizing a selected area of that surface of a strip of very thin paper upon which there has been previously deposited an extremely thin layer of metal, which comprises continuously maintaining in direct contact with the exposed surface of such metal layer two spaced electrical conductors of opposite polarity one of which makes direct electrical contact with a relatively small area of said surface and the other of which makes direct electrical contact with a larger area of that surface, passing sufiicient current through said conductors and metal layer to cause the density of the current passing directly between the conductor of smaller contacting area and the metal layer to be suflicientl high to cause volatilization of the metal directl contacted by said last mentioned conductor, and, while maintaining the current flow, continuously advancing the strip so as to continuously bring fresh areas thereof into contact with said conductors, the speed of advancement being such that volatilization of the metal at the point of contact between the strip and the conductor of smaller strip conducting area proceeds uninterruptedl and an unbroken elongated demetallized area is created.
2. The method of demetallizing a selected area of that surface of a strip of very thin paper upon which there has been previously deposited an extremely thin layer of metal, such metal layer being approximately 000% inch in thickness but having satisfactory conducting properties, which comprises continuously maintaining in direct contact with the exposed surface of such metal layer two spaced electrical conductors of opposite polarity one of which makes direct electrical contact with a relatively small area of said surface and the other of which makes direct electrical contact with a larger area of that surface, passing suificient current through said conductors and metal layer to cause the density of the current passing directly between the conductor of smaller contacting area and the metal layer to be sufiiciently high to cause volatilization of the metal directly contacted by said last mentioned conductor, and, while maintaining the current flow, continuously advancing the strip so as to continuously bring fresh areas thereof into contact with said conductors, the speed of advancement being such that volatilizaticn of the metal at the point of contact between the strip and the conductor of smaller strip conducting area proceeds uninterruptedly and an unbroken elongated demetallized area is created.
. 3. The method of demetallizing a selected area of that surface of a strip of very thin paper upon which there has been previously deposited an extremely thin layer of aluminum, which comprises continuously maintaining in direct contact with the exposed surface of such aluminum layer two spaced electrical conductors. of opposite polarity one of which makes direct electrical contact with a relatively small area of said surface and the other of which makes direct electrical contact with a larger area of that surface, passing sufiicient current through said conductors and aluminum layer to cause the density of the current passing directly between the conductor of smaller contacting area and the aluminum layer to be sufficiently high to cause volatilization of the alu minum directly contacted by said last mentioned conductor, and, while maintaining the current flow, continuously advancing the strip so as to continuously bring fresh areas thereof into contact with said conductors, the speed of advancement being such that volatilization of the aluminum at the point of contact between the strip and the conductor of smaller strip conducting area proceeds uninterruptedly and an unbroken elongated demetallized area is created.
The method of demetallizing a selected area of that surface of a strip of very thin paper upon which there has been previously deposited an extremely thin layer of aluminum, such aluminum layer being approximately .00004 inch in thickness but having satisfactory conducting properties, which comprises continuously maintaining in direct contact with the exposed surface of such aluminum layer two spaced electrical conductors of opposite polarity one of which makes direct electrical contact with a relatively small area of said surface and the other of which makes direct electrical contact with a larger area of that surface, passing sufficient current through said conductors and aluminum layer to cause the density of the current passing directly between the conductor of smaller contacting area and the aluminum layer to be sufiiciently high to cause volatilization of the aluminum directly contacted by said last mentioned conductor and, while maintaining the current flow, continuously advancing the strip so as to continuously bring fresh areas thereof into contact with said conductors, the speed of advancement being such that volatilization of the aluminum at the point of contact be tween the strip and the conductor of smaller strip conducting area proceeds uninterruptedly and an unbroken elongated demetailized area is created.
RICHARD ALFRED GROUSE.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PAILNTS Number Name Date 758,923 Knowlton May 3, 1904 920,970 Mansbridge May 11, 1909 1,154,301 Fogarty Sept. 21, 1915 1,276,731 Crowell Aug. 27, 1918 1,909,079 Steerup May 16, 1933 2,248,057 Bond July 8, 1941 2,310,071 Frisch Feb. 2, 1943