US2399798A - Manufacture of electrical condensers - Google Patents

Description

May 7, 1945 R. A. GRoUsE ET AL 2,399,"798

May 7, 1946- R. A. GRoUsE ET AL. 2,399,798

MANUFACTURE OF ELECTRICAL CONDENSERS Filed July 8, 194:5 2 sheetsfsheete NVINTGRS Rmmzo ALFRED Gnomi l and JAM Romke.v

Patented May 7, 1946 MANUFACTURE OF ELECTRICAL CONDENSERS Richard Alfred Grouse andk James Rogers- Londoni, England, asslgnors to A. H. Hunt Limited, London, England, a British company Application July 8, 1943, Serial No. 493,824 In Great Britain July 13, 1942 This invention relates to the manufacture of electrical condensers. Metallised paper, i. e. paper having the metal in the form of a film or thin layer on one sideonly of the paper, is known for use in the manufacture of condensers, the thinness of the metallised paper enabling condensers y to be made having a high capacity and yet; compact in form and light in weight.

In making such' condensers by a process as described in co-pending United State' patent application Serial No. 493,172 it is necessary to supply to the winding machine, two strips of paper with an unmetallised edge, the two strips being of opposite hand, that is to say, looking at the metallised side of the paper as fed to the winding machine, the unmetallised margin must be on the left of one strip and on the right of the other. It is not economical to manufacture strips of paper with a metallised surface and an unmetallised margin directly in th'e form of such strips; it is preferable that wide rolls of paper, such as are supplied by paper manufacturers, should be treated for metallisation over their area considered as a whole. It is an object of the present invention to facilitate the provision of strips of paper having an unmetallised margin along one edge in such form as can be readily wound into condensers of 'the kind desired.

The present invention comprises in the manufacture of electrical condensers from metallised dielectric strips wound together, each strip having an unmetallised margin, the combination of steps for preparing the strips which consists in rst preparing a wide strip of metallised dielectric in a form in which bands of metallisation alternate with unmetallised bands, the bands extending along the length ofthe strip, and then slitting the wide strip along the centre lines of the unmetallised bands and also along lines within the metallised bands.

This provides a plurality of strips of paper of the desired width' each having an unmetallised margin, and alternate strips, as cut from the pa-A per, are automatically of opposite hand Pairs of such strips are taken and then wound into condensers by any desired method, for example thatl the known process of making Mansbridge foil.

Alternatively the paper may be metallised by any desired process such as that described in the United States Patent No. 2,100,045 and the actual process of metallisation forms no part of the present invention.

The invention includes in the manufacture of electrical condensers from metallised dielectric strips wound together, each strip having an unmetallised margin, the combination of steps for preparing the strips which consists in rst metallising a wide strip of dielectric across its whole width, then removing the metal film in bands along the length of the strip, and then slitting the wide strip along the centre lines of th'e demetallised bands and also along lines within the metallised bands.

For slitting the paper any known form of paper slitting machine may be used, or the band may be slit in its passage from one roll to another roll, or plurality of rolls, by grow of stationary knives held in the path of the band, or it may be slit when on a roll by pressing a row of knives against the rotating roll.

Conveniently, electrical faults in the paper may be burnt out during the slitting operation by passing the paper past electrified rollers on its way to the slitting knives.

The following is a description, by way of example, of one apparatus for carrying the invention into effect and of the process of the invention as carried out therein, reference being made to the accompanying drawings in which:

Figure 1 is a diagram of the process and albparatus showing only the essential working parts;

Figure 2 is aplan of part of the apparatus, Figure 1;

Figure 3 shows a pair of rolls of paper, rightand left-hand, when slit;

Figure 4 is a diagrammatic representation of the winding of a condenser from the rolls of Figure 3;

Figure 5 shows the step of the process of demetallising strips upon the paper prior to the passing of the paper through the apparatus of Figure l.

Referring to the diagram, a roll of paper H is taken which has been metallised on one face, for example by the process described in the aforesaid United States Patent No. 2,100,045. 'I'he metallisation may consist of any desired metal, such as copper or, preferably, aluminium and is exceedingly thin but electrically conductive. The metallisation is effected in bands I2 and between the metallised bands there are unmetallised bands I3 which are indicated by broken lines in the drawings (Figure 2) as they do not correspond with any discontinuity in the paper and in the part of the figure where the paper is flat the metallisation is on the underside of the paper. The unmetallised bands may be produced in the metallising process by screening portions of the paper or they may be produced by removing the metallised surface after it has been applied; for example in the case of the metallised layer being produced by the known process of making Mansbridge" foil the unmetallised bands may be produced by removing the metal as described in copending United States patent application Serial No. 493,173, and as hereinafter described in connection with Figure 5 hereof.

The roll of metallised paper I I may conveniently be supported on a central cardboard tube I4 which is slid on to a supporting spindle I5 and the spindle |5 is provided with an appropriate mounting for rotation, not shown in the drawings.

From the roll the paper passes under an electrified metallic electrode roller 2|, in a nearly horizontal direction, then over and in contact with an earthed metallic electrode roller 22 the two rollers being maintained at a potential-difference relative to one another equal to the test voltage which it is desired to apply to the paper of the dielectric. Thence the paper passes under another electrified roller 23, over a second earthed roller 24 and a third electrified roller 25.

The potential of the electrified rollers 2|, 23, 25 relative to the rollers 22, 24 may be, say 600 volts. This figure suits for use in the case of paper which has an extremely thin metallised aluminium or copper surface, the thinness of the paper being about four ten-thousandths of an inch. The speed of passage of the paper is about two feet per second. Under these conditions the metallised bands are maintained at earth potential while a potential of 600 volts is applied to the opposite face of the paper. Any faults in the paper dielectric cause communication between the metallised surface and the electrified rollers; owing to the extreme thinness of the metallisation the effect is that current passing through the metal to the fault becomes concentrated at the fault and the metallised surface immediately around the fault is vaporised and disappears, thereby eliminating the fault. Even the best hard glazed waxed paper if made of the thinness referred to possesses numerous faults against a test voltage as high as 600 and as the paper cornes in contact with the first electrified roller 22 a line of sparks or scintillations which indicate the burning out of the faults appears at the ongoing line of contact of the paper with the roller. Some faults will still remain in the paper after leaving the roller 22 but such faults will be eliminated as they pass the other rollers.

In some cases, especially where exceptionally thin paper is employed, it may be desirable to employ a larger number of electrified rollers. Alternatively the paper may be run through the electrified rollers more than once and rewound before being finally run through and slitted, and in this case the speed of travel of the paper may be increased, as any faults which are not eliminated on the first passage through the apparatus can be eliminated in a second or third passage.

After the elimination of faults the paper is slit. For this purpose any desired slitting machine may be adopted, usually having a gang of knives to make all the slits simultaneously. The arrangement in the drawings is diagrammatic only and shows the paper being wound on to a spindle 41 parallel to a knife-supporting bar 66. On the bar 66 is a block 61 carrying a knife 68 and handle 69. The knife can be brought to any desired position opposite the roll of paper after it has been wound and, the roll of paper being driven by a belt on a pulley 52. the knife can be applied to the roll and will cut into the paper 5 along a slit-line such as the line 50 of Figure 2. One cut is madeat a time completely through to the shaft by lifting the handle 60 and then the block 61 is slid along the bar 66 into position to take another cut. If the blade 69 is made of thin l sheet steel the roll of paper can be satisfactorily slit in this manner.

'A cut is made down each metallised band I2 and also down the middle of each unmetalllsed band I3. Where bands of equal width are rel quired, the cuts are down the middle of the metallised bands, as shown. This produces a number of rolls 45 which, as viewed from the end of the apparatus towards which the paper is travelling, have an unmetallised margin on the lefthand side and a further series of rolls 46 which have an unmetallised margin on the right-hand side.

One of the left-handed rolls 45 thus produced and one of the right-handed rolls 46 are shown together in Figure 3. Tl'iese rolls are taken and are wound together to produce a condenser in the manner indicated in Figure 4, that is to say with the insulated margins of the rolls of paper serving to ensure separation of the two metallised surfaces which constitute electrodes of opposite polarity. In Figure 4 the dielectric of one strip is indicated by a full line at 45 and the dielectric of the other strip is indicated at 46, the two dielectrics being interleaved. The

metallised surface is diagrammatically indicated by chain lines 6|, 62 respectively and it will be seen that the unmetallised margins serve to insulate the metallised portions from each other. The metallised portions of the strips which project at the ends of the roll are of opposite polarity and provide terminals. Conveniently they may be turned over in winding as indicated in Figure 4 so as to present their metallised surfaces endwise and facilitate making electrical connections ste them. A method of effecting this winding of the condensers automatically is described in copending United States patent application Serial No. 493,172. y

Referring now to Figure 5, this shows a roll of tin-coated paper |20 being fed towards a spindie |2| mounted in bearings |22, |23 and driven by a belt on a pulley |24. The spindle |2| therefore draws the paper towards itself and winds it into a roll |25. In the course of its passage the paper passes beneath a spindle |26 supported in bearings |21, |28. On the spindle |26 there are a. number of copper discs |30 which are supported on heat insulating bosses |3| and have electrical heating elements |32 clamped against 50 their side. The heating elements |32 are supplied with electric current by means of tWo slip rings |33, |34 and brushes |35, |36, The edges |31 of the discs |30 are tinned and are brought to a sufficient heat to melt the tin coating on the 55 paper web when they engage it. For this purpose the tin-coated side of the paper must be passed so as to be uppermost and thus to come in contact with the discs and the speed of the spindle |2| is made controllable so that the speed of passage of the paper may be kept at a suitable rate, so that the paper is not scorched although the tin is effectively removed. The rim portions |31 of the discs |30 are made of such a width that they correspond to the width of the strip which is to be demetallised along the length of accesos the paper web I2! and the spacing of the copper discs is such that they demetallise a number of strips of the desired width as the paper comes in contact with them in the course of its progress; the demetallised strips are indicated in the drawing at ill. Excess of tin can be removed from the discs |30 from time to time by applying a wiper thereto while they are rotating and thus no stoppage of the apparatus for removal of tin is necessary.

In order that lthe heated rotating rollers may effectively demetallise the paper it is desirable that the paper should. before being passed through the apparatus of Figure 5, be impreg nated with ilux. A suitable ilux consists of a mixture ofpetroleum jelly 80% and resin 20%, melted together and applied to the paper before the application of the tin coating thereto. The paper is coated with the tin by any well knownY or desired process such as that in common use for making tin-coated paper for the manufacture of "Mansbridge condensers. The process of demetallisation per se is claimed in co-pending United States patent application Serial No. 493,173.

It is an important advantage of the present invention that as the, metallised bands I2 in the original web of paper are cut through, the metallised portions of the cut strips are fully metallised right up to the edge. If the paper were originally selected with metallised and unmetallised bands' of the same width only as that desired for the rolls which are to be Wound into the condenser, the paper would have to be slit along the line of Junction between an unmetallised band and a metallised band and there would be risk of the edge of the metallised portion of -the paper not being fully metallised up to its edge, and of the unmetallised margin left on the adjacent strip carrying here and there a partially metallised portion which would interfere with the insulation of the condenser. Moreover as this risk is lremoved it is possible to make the strips with narrower insulating margins, the design of the condenser is more emcient, and the capacity larger for a given size.

We claim:

A process for the manufacture of an electrical wound paper condenser comprising in combination the steps of first selecting a wide strip of paper metallized over its whole width, then removing bands of metal therefrom so as to leave metallized bands alternating with unmetallized bands, slitting the wide strip along the center lines of the unmetallized bands and also along lines which divide the metallized bands longitudinally, rolling the resulting strips into alternate "right-handed" and "left-handed rolls, selecting a right-handed and a left-handed roll so produced and winding together strips from each roll whereby thin unmetallized edges lie toward opposite ends of thewound condenser,

the strips being wound without any interleaving strips and so that each unmetallized edge is overlapped by the metallized edge of Vthe adjacent strip.

RICHARD ALFRED GROUSE. JAMES ROGERS.

Images