US3575027A

US3575027A - Manufacture of patterned webs

Info

Publication number: US3575027A
Application number: US757353A
Authority: US
Inventors: Paul Eisler
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-09-04
Filing date: 1968-09-04
Publication date: 1971-04-13
Anticipated expiration: 1988-04-13

Abstract

To produce lines of longitudinal slits the length of which can be varied in a regular pattern in a travelling web, suitably of metallic foil for the production of electric resistance heating films, a gapped knife for each limb which may be a rotating knife is given a cycle of movements, the gap remaining clear of the web at intervals to leave bridges between the slits and the longitudinal component of movement of the knife being variable to vary the length of the slits. The foil is supported on a grooved support and the knife may also fold the margins of the slit through 90*, these margins then being folded or crushed right over. The foil may be crimped and be insulated.

Description

United States Patent Inventor Paul Eisler 57 Exeter Road, London, England Appl. No. 757,353

Filed Sept. 4, 1968 Patented Apr. 13, 1971 Priority Jan. 20, 1961, Dec. 1, 1964 Great Britain 2384/61 and 48780/64 Continuation-impart of application Ser. No. 510,278, Nov. 29, 1965, now Patent No. 3,408,735, which is a continuation-in-part of application Ser. No. 165,736, Jan. 12, 1962, now Patent No. 3,283,284.

MANUFACTURE OF PA'I'IERNED WEBS G1 0 Q/ V 341 326 [56] References Cited UNITED STATES PATENTS 845,764 3/1907 Curtis 83/303 2,583,682 1] 1952 Celovsky 72/186 FOREIGN PATENTS 3,521 12/1896 Great Britain 83/332 Primary Examiner-Lowell A. Larson Att0rney-Wats0n, Cole, Grindle & Watson ABSTRACT: To produce lines of longitudinal slits the length of which can be varied in a regular pattern in a travelling web, suitably of metallic foil for the production of electric resistance heating films, a gapped knife for each limb which may be a rotating knife is given a cycle of movements, the gap remaining clear of the web at intervals to leave bridges between the slits and the longitudinal component of movement of the knife being variable to vary the length of the slits. The foil is supported on a grooved support and the knife may also fold the margins of the slit through 90, these margins then being folded or crushed right over. The foil may be crimped and be insulated.

Patented April 13, 1971 6 Sheets-Sheet 1 INYENTOR EL6Z6l- A EEEEEEEEQEQ Pat ehted April 13, 1971 3,575,027

6 Sheets-Sheet 2 INV ENTOR Pag E 08 Zer Patented April 13, 1971 6 Sheets-Sheet 5 cu Y W M T [TR m e 0 V W mmw A E Patented April 13, 1971 3,575,027

6 Sheets-Sheet 4 [NVENTOR 5L6 26/ Patented April 1971- 6 Sheets-Sheet 5 Fig. l3.

|llllllllllw ENTOR P20? EL' E ZeF M ,r 5 3% WEYZSL Patented April 13, 1971 3,575,027

6 Sheets-Sheet 6 20. INVENTOR Zl/Z 5A5 26/- BY 40m MANUFACTURE OF PA'l'lERNED WEBS The present invention is a continuation-impart of my application Ser. No. 510,278, filed Nov. 29, I965 now matured into US. Pat. No. 3,408,735, which was itself a continuation-impart of my application Ser. No. 165,736, filed 12th Jan. l962, now matured into US. Pat. No. 3,283,284,

The invention relates to the production of a material in thin web form having a pattern of at least one series of longitudinal slits with interruption.

One object of the invention is to provide an apparatus for producing such a pattern which lends itself to continuous high speed production in which the length of the slits can be varied without the need to exchange the cutting tool and without the need to have a fixed ratio between the length of the slits and the length of the interruptions.

The apparatus according to the invention by which this object is achieved includes means for drawing the web longitudinally from a supply at a predetermined rate, a support for the web grooved at the location where the slits are to be made, a rotary knife independent of said web drawing means having at least one peripheral gap in its cutting edge, the knife being mounted with its cutting edge projecting into the groove in the support while the gap is deep enough to clear the support, and means for rotating the knife at a predetermined rate whereby to cause it to slit the web bearing an uncut bridge each time the gap passes over the web.

During that phase of the cycle in which the gap is passing over the web, when the incision is terminated and/or commenced, the longitudinal component of the speed of the knife may be substantially equal to the speed of the web and the relative movement between the cutting edge of the knife and the web is substantially perpendicular to the web. Then the length of the interruption will be substantially equal to the length of the gap. During the phase of the cycle in which the knife is making the incision, at least one acceleration and one deceleration may be included in the movement of the knife. The length of the incision can thus be regulated by the choice of the acceleration and deceleration, independently of the length of the interruptions.

The rotary knife will usually always rotate in the same direction. Apart from the gap it may be circular or noncircular.

The length of the slit plus the length of the interruption is determined by the mean speed of rotation of the knife in relation to the rate of movement of the web; by including suitable values of acceleration and deceleration in the incising phase, it is possible (within limits imposed by various practical consideration) to make slits of desired length with interruptions of constant length.

If the web is of very thin material it may be reinforced prior to slitting by lamination to a material such as paper or a filmof synthetic material, or by a coat of lacquer, varnish or the like. The web is desirably held under tension during slitting.

Prior to slitting, the web may be lubricated with a lubricant compatible with any other materials with which the web is coated or laminated, or is to be coated or laminated following slitting.

It is often required to convert the pattern of slits into slots. My US. Pat. No. 3,283,284 aforesaid discloses a product in which this has been accomplished by folding over at least one and preferably both margins of the slit back on to the web.

A development has the margin on at least one and preferably both margins folded through 90 and the margin then folded in a random fashion so that in effect it is crushed to produce a rim along the edge of the slot. The term completion of folding used hereinafter means either a second stage of folding through 90 or such crushing except when the context otherwise requires. Whereas with two folds through 90 so that the margin is doubled back onto the rest of the material, there is a double thickness along the or each edge of the slot, with the aforesaid development a thickening results which is not restricted to double thickness of half or full slot width but forms a rim which may in general be thicker but narrower and may in some cases resemble a flattened zigzag conformation or a conformation of less regular internal structure. With either the original structure or this development, if the pattern of slits is made by a continuous method applied to a moving web drawn from a supply through a cutting station and the conversion into slots is to be made during the same cycle of operations alignment presents difficulties. Methods of overcoming these difficulties are disclosed in my application Ser. No. 5l0,278 filed Nov. 29, 1965 which was itself a continuation-in-part of my application Ser. No. l65,736 aforesaid. The present invention is more particularly concerned with apparatus for putting into practice the method to produce the material with the twice folded over margin or the development of the material having a rim along the edge of the slot.

Apparatus according to the present invention for putting this method of slitting and folding into operation includes means for continuously feeding the web, means for slitting the web longitudinally at intervals of length and partly folding over the margin of the web at least on one side of each slit, and means for completing folding over of the partly folded margin, the means for slitting and partly folding over including at least one common member whereby alignment between the slitting and this part of the folding is directly ensured.

The common member is suitably a grooved support, fixed or a roller over which the web passes, the groove serving to guide in its active position a knife which slits the web and in cooperation with one wall or preferably both walls of the groove effects the first part of the folding over. If one margin only is to be folded over, the cutting edge of the knife is disposed to lie close to one wall of the groove, the folding then being over the other wall, while if both margins are to be folded over the cutting edge is disposed between, preferably midway between the walls of the groove.

The means for completing folding may be mechanical or pneumatic or include both mechanical and pneumatic means. So far as mechanical means for this purpose is included, the grooves also serve to guide such means to ensure alignment thereof. Thus such mechanized means can comprise a plough member which extends along each groove to a position near the knife and serves to hold the partially folded margins in position. Beyond the grooved roller and in the region in which the web leaves it, the plough member incorporates a widened shoe which serves to continue the folding over of the web margins to a position parallel to the unfolded part of the web i.e. in general through so that the folded over margins are folded over onto the web. Between the position where the web leaves the knives and encounters the ploughs, unfolding may be prevented by pneumatic means such as r. et of air and such jets may replace any or all of the length of the plough. Such means can even replace the shoes.

The knives used may be straight or circular knives which are lifted to produce the interruptions between the slits, or they may be rotary knives preferably circular knives with gapped cutting edges to produce the interruptions as above-described. Such knives may be individually easily exchangeable and they may be retained in their correct planes by guides which themselves can be located from the grooved support.

Electric heating films to the production of which the present invention is especially applicable, have a plurality of series of aligned longitudinal slots side by side, alternate series being relatively staggered longitudinally, usually by about half a pitch, where pitch equals slot length plus bridge length, the

web consisting of or incorporating a layer of electrically conductive material so that the slots leave a multiplicity of electrically conductive meander patterns across the web. Such a web can be cut up into individual pieces including one or more repeats of the meander pattern and if a continuous conductive margin of adequate cross section is left on each side to serve as a bus bar or terminal the meander patterns will be electrically in parallel across the margins and if the meander pattern presents a suitable resistance, the individual pieces of web can serve as electrical heating films which if the pattern repeats are identical will have a uniformly distributed constant surface loading when a supply is connected to the margins. For many purposes such a pattern can be designed to operate on a supply voltage (below 50 volts) which is free from danger if human contact should accidentally be made to the conductive material.

Further objects and features of the invention will appear from the following description with reference to the accompanying drawings.

The drawings are highly diagrammatic and the proportions are exaggerated especially as to the thickness of the web and its associated layers, in order to make them clearer. In the drawings:

FIG. 1 is a plan view ofa very short portion of a heating film material as produced in accordance with the invention, made in considerable length, and from which separate heating films containing any desired number of repeats can be cut.

FIG. 2 is another plan view on a smaller scale than FIG. I to illustrate a large number of repeats and to show a pattern of slits without any folding over.

FIG. 3 is a side view ofa machine which may be used for the continuous production of the film according to the invention.

FIGS. 4, 5 and 6 are detail sections on the lines IV-IV, VV and VI-VI respectively of FIG. 3.

FIG. 7 illustrates an alternative form of knife for use in the machine of FIGS. 3 to 6.

FIG. 8 illustrates the use of a circular knife having a single gap in its cutting edge.

FIG. 9 illustrates the use of a circular knife with more than one gap in its cutting edge.

FIGS. [0 and 11 show in side end section on the line XI-XI of FIG. the construction of a composite knife having an adjustable gap in its cutting edge.

FIG. 12 is an end view of a form of apparatus according to the invention using circular knives with gapped cutting edges, which enables the length of the slits to be varied independently of the length of the interruptions.

FIG. 13 is a plan view of FIG. 12.

FIG. 14 is a detail section illustrating the action of the knife.

FIG. 15 is a detail plan illustrating the action of a shoe which completes the folding of the margin of the slits.

FIG. 16 is a similar view to FIG. 14 showing a different profile of knife.

FIGS. 17 and 18 are cross sections of two forms of knife shaft enabling adjacent knives to be relatively adjusted angularly.

FIGS. 19 and 20 are an end view and a perspective detail of another form of apparatus using circular knives with gapped cutting edges.

The example chosen for illustration in FIGS. 1 and 2 is an electric heating film which shows a longitudinal repeating meander pattern so that there are a plurality of series of relatively staggered slots side by side. There are bridges between the slots and the bridges in alternate series are relatively staggered longitudinally by substantially half a pitch and with transverse rows of bridges perpendicular to the length of the film. As will be explained, it is also possible within the scope of the invention to arrange the transverse rows at an inclination or to produce more elaborate dispositions of the bridges and of the meander patterns. Again the invention is also applicable to but a single series of slots or to a plurality of a series of slots all in phase, and to the production of similar patterns to slits without folding over of the margins to convert the slits into slots.

An essential part of a heating film is the conductive foil.

Though in some cases the film may consist of no more than the bare foil pattern suitably held, usually it will be insulated on one or both sides and on the folded margins.

The conductive foil preferred in most applications of the heating film is aluminum foil of about or less than 0.002 inch (0.05 mm.) thickness.

A convenient standard width of arm is then one-eighth inch (3 mm.) but patterns have successfully been made with arms as little as one-sixteenth inch (1.5 mm.) wide. There is no difficulty in making them wider if desired, and a machine can readily be constructed on the lines described later which enables the width to be adjusted in multiples of say one-eighth inch. The aluminum foil may be provided on one side over all or selected parts with a conductive coating, e.g. a readily solderable alloy or a conductive adhesive film which makes connection of selected areas to other conductive surfaces easier, and/or on the other side with an insulating varnish, lacquer, or anodic film, thus constituting a very thin double or triple layer material.

The scope of the invention is, however, not restricted to this foil and covers practically any metallic foil, and can be applied also to electrically conductive film material other than metallic foil and which the term foil" used in this specification is intended to cover for instance carbon or ultrafine metal-powder-coated insulating film the coating of which has a desired resistance value and characteristic. The expression foil is generally used for metal strip up to 0.006 inch (0.l5 mm.) thickness, but for some metals a somewhat thicker strip is still referred to as foil. The present specification uses the term foil in the same sense in relation to metallic foil. Hereinafter only metallic foil will be referred to.

For applications in which the heating film reaches a temperature in excess of that easily tolerated by a convenient insulating covering, or where irrespective of temperature reached by the film the delicate metallic foil pattern is not exposed to damage by outside forces and can be adequately supported, the preferably crimped metallic foil pattern is not sandwiched between insulating layers, but used without such layers. The maintenance of the spacing ofthe arms is however not relied on alone for preventing short cuts, and as mentioned above the metal foil is either lacquered or varnished at least on the surface forming the outside of the folded-over edges, or anodized, if it is of aluminum.

The electrical heating film shown by way of example by FIGS. 1 and 2 which illustrates part of a film made in lengths only limited by the length in which the component materials can be obtained, comprises a conductive foil 11 which is slit longitudinally into parallel narrow arms 12 forming in conjunction with bridges l3 joining the ends of the arms, a succession of meander paths between the first and last arms constituted by the margins I4 which are of greater width than the arms I2, and which can constitute bus bars. The slits 15a between the arms are widened into openings or slots 15 by the margins of the arms being folded over and flattened back on to the arms as at I6. Preferably, the one surface of the foil which is on the outside of the folds at the margins is lacquered, varnished, anodized in the case of aluminum foil, or otherwise covered with an insulating layer so that the neighboring folded margins of adjacent arms are not only spaced from each other by the width of both folded-over edges, but also have two layers of insulation between them which prevents a short out of the electrical path intended to extend through the full length of the meander arms, if neighboring arms should for instance accidentally contact each other at their folded-over margins. A pinhole or other failure of the insulating layer covering any folded-over margin is unlikely to occur just opposite to a corresponding failure in the insulating layer on the opposite folded-over margin of the neighboring arm.

An insulating film 21 of plastic or elastomeric material, of paper or textile, including glass or quartz fiber cloth, may cover one or both sides of the patterned foil, and these insulating coverings may extend into the slots between the meander arms in and beyond the plane of the metallic foil, so that they solidly fill the spaces between adjacent arms. If plastic or elastomeric materials are used as both top and bottom coverings of the foil pattern their junctions through the spaces between the arms of the pattern can be effected by welding while when these films are layers of paper or textile, adhesives or sewing stitches can be used for joining top and bottom insulating films in the spaces between the arms and, where desired, along and beyond the outside edges of the foil pattern.

The present invention provides simple methods for the economic production of the foil pattern by operations on a foil drawn continuously from the roll.

Anodized aluminum foil tapes having their margins folded over have been proposed for magnet windings but the methods used for folding the margins are not applicable to the heating film with its closely spaced lines of interrupted slits. The present invention provides a method in which the foil drawn continuously from the roll is slit and the margins of the foil on at least one side of each slit are by the slitting operation itself folded through about a right angle and folding of the margins through 180 i.e. back onto the arms, is completed immediately thereafter. Preferably the foil is carried in a curved path during slitting when the partial folding is effected towards the concave side of the curved path and it then enters a second path of reverse curvature thereby bringing the folded margins on to the convex side of the reversed path so that the natural tension tends to complete the folding.

The invention further provides apparatus for putting this method into operation which includes means for continuously feeding the foil, means for slitting the foil longitudinally at intervals of length and partly folding over the margins of the foil on at least one side of each slit, and means for completing the folding over of the margins onto the surface of the foil, the slitting means and folding means including at least one common member whereby alignment between the slitting and folding is directly ensured. In this way the problem of alignment which is a serious one with many narrow arms side by side is solved without the necessity for minute adjustments which could go out of order. The common member may be a grooved roller over which the foil passes, the roller having a plurality of grooves at least some of which each guides in its active position one of a plurality of knives which slit the foil and in cooperation with the walls of the groove effect the first part of the folding over of the margin(s) of the foil at the sides of the slit. Each groove which guides a knife also guides one of a plurality of shoe members incorporating each a widened part projecting beyond the roller in the region where the foil leaves it and serving to continue the folding over of the margin(s) of the foil. The interruptions in slitting are obtained by the provision of means to lift each knife into an inactive position at intervals and for guiding it when in this position to remain in line with its groove in the grooved roller. This guiding means can be a stationary comblike guide corresponding with the grooved roller or it may be another grooved roller pressing against the first grooved roller with the foil between at the region where the slitting is effected.

An example of a machine working on the above lines and provided with further devices necessary for producing a heating film such as that shown in FIG. 1 in continuous lengths, that is in lengths only limited by the length in which material can be supplied to it, is shown in FIGS. 3 to 7.

In this machine for example aluminum foil 101 lacquered on one side, coming from a stock roll not shown passes, lacquered side upwards, between two grooved rollers 102,

'103. The grooves in the two rollers are opposite one another.

Their center to center spacing is equal to the minimum width of the arms to be produced and the width of each groove is equal to twice the width of each margin to be folded over at each slit. These rollers can conveniently be built up of discs and spacers.

From the roller 103 the foil passes over a solid roller 104, and between crimping rollers 105, 106. Thereafter in this example it passes over a drum 107 where an insulating covering 108 drawn continuously fromv a stock roll not shown, is laminated to the lacquered side of the foil.

The grooves in the

rollers

102, 103 serve to guide in all positions, knives 109 which are moved between an inactive position shown in solid lines in which the edge of the knife just clears the foil, and an active position shown in chain lines in which the knife slopes downwardly beyond the nip of the

rollers

102, 103 and into the groove in the roller 103. In place of the roller 102, a stationary comblike guide corresponding with the roller 103 could be used to cooperate with roller 103 in guiding the knives as described below with reference to FIGS. 12 to 15. The lower edge of the knife is sharp along the centerline (see FIG. 4) so that it slits the foil. Its section is straight sided and its thickness is less than the width of the groove by twice the thickness of the foil (plus such working clearance as may be necessary), so that the grooves themselves align the knives and the slit is necessarily along the center of the foil overlying the groove and the section of the knife necessarily folds the margins of the slit foil over the sides of the groove i.e. through towards the concave side of the path of the foil over the roller 103. The nip of the

rollers

102, 103 relieves the foil of stresses during slitting.

Stationary blades or ploughs 111 extend into the grooves in the roller 103 and they are shaped while clearing the knives 109 to follow the latter to retain the partly folded foil against the sides of the grooves. Where the foil leaves the roller 103, the shoes project into the space between the

rollers

103, 104 on the left-hand side of the point where the foil passes from the one roller to the other and they are here widened into shoes, see FIG. 6.

In passing from the roller 103 to the roller 104 the 90 folds come on the outside of the roller 104 and the shoe continues the fold beyond the 90. The reversal of curvature of the foil when it runs over the roller 104 puts the folded part into tension and this assists in completing the folding of the margins while the action of the ploughs also ensures that the folding is continued and is not reversed-i.e. the foil is not unfolded back into its original position.

To permit adjustment of the ploughs, they are slotted and held by bolts 112 to their support 113.

The FIG. shows the roller 104 running against the roller 103 but they could be slightly spaced, the shoes being correspondingly shaped.

In the example, endless rubber-covered wires 114 run over loose discs 115 in the grooves in the roller 103 and over a guide roller 116 while a pressure roller 117 squeezes the rubber against the foil passing over the roller 104 after it has left the shoes 111, and thus completes the flattening of the folded margins. Instead a simple pressure roller might be used, but both these devices can be omitted if the shoe is shaped to complete the flattening. Also as explained below with reference to FIGS. 12 and 13 to the ploughs and shoes can be supplemented or replaced by pneumatic means.

If a pattern with the minimum width of arm is to be produced there is a knife and plough in every groove of the roller 103 but for wider arms a corresponding number of grooves is left without knives and ploughs. Thus arms of a width of any multiple of the minimum can be produced on the same machine without changing the groo' ed rollers, merely changing the number of knives and ploughs. Modifications of details of the machine are possible. Thus the knives might be set at the angle indicated for the active position in FIG. 3 and be moved only longitudinally to bring them into the inactive position.

After being crimped between the rollers 105, 106 which may be constructed to leave an uncrimped zone or zones with the crimps l80 out of phase on the opposite sides of such a zone if necessary, the pattern and crimped foil has the insulating covering 108 laminated to it while passing over the drum 107 which may be heated or water cooled according to the requirements of the laminating process. This drum 107 is desirably adjustable a little towards and away from the lower roller 106 in order to prestress the crimped foil if the insulating covering 108 is not elastomeric. On its way to the drum 107 the foil or the covering 108 may be coated and dried if necessary. The covering is led to the drum over a tension controlling roller 118. It will be seen that the foil 101 lies on top of the covering 108 with its lacquered surface towards the latter. The bare foil surface is contacted by the crimping roller 106 and also by two further

metallic rollers

119 and 121. The rollers 106, 121 are earthed while the roller 119 is connected to the live pole of a supply so that current flows longitudinally through the foil from the roller 119 to both the rollers 106 and 121 and thereby heats the foil sufficiently to effect a joint between the foil and the covering 108 which are held pressed together by their path round the drum 107. Some adjustment in the heating effect can be obtained by displacement of the rollers which supply the current, conveniently by mounting the

rollers

119, 121 so that they can be displaced round the axis of the drum 107. On its path from the roller 121 to a further roller 122 the film is cooled and may pass to a rereeling roller or to a coating or covering station at which the bare surface is insulated. It will be clear that instead of using the crimping roller 106 as one of the connecting means in this heating arrangement, a separate roller may be used and that instead of using rollers for making contact rods could be used.

To produce the pattern of arms as in FIG. 1 it is sufficient to divide the knives 109 into two groups of alternate knives and lift each group into its inactive position separately to leave the bridges. Any convenient means may be used for doing this, for example a solenoid or air cylinder for each group controlled through switches themselves operated by a multiple (and preferably adjustable) cam geared to the roller 103. If more elaborate patterns are to be made each knife may be individually lifted into inactive position and lowered into active position by a separate solenoid, air cylinder or other device the pattern being determined by a pattern card or the like, after the fashion of a Jacquard, which may be sensed electrically or photoelectrically, or a moving master pattern geared to the roller and similarly sensed may be used. It is also desirable to impart to the knives a cyclic longitudinal motion, thereby to even out the wear on their cutting edges. The mechanism which lifts and lowers them can incorporate a linkage which does this.

If necessary or desirable the foil may be lubricated before slitting and folding as described later with reference to FIGS. 8 to 18 using a lubricant of the character also described later.

As shown in FIG. 4, the knives are proportioned so that the slit is made midway between the walls of the groove in the roller 103. Thus the margins folded over on opposite sides are of equal width. The edge of the knife might however by asymmetrically disposed giving different widths of margin on opposite sides, or even as indicated in FIG. 7 be at the side of the knife which is here marked 109a. In this case the slit is made by sheering in conjunction with the edge of the righthand wall ofthe groove so that no fold is made here, while the margin on the other side which is folded over has a width equal to the total width of the groove. The parts of the shoes 111 which project into the space between the rollers 103, I04 and which serve to continue the folding beyond 90 need only be shaped for the purpose on the one side.

It will be clear that in the machine above-described with reference to FIGS. 3 to 6 the slit is started by inserting the knife into the groove and the slit is ended by lifting the knife out of the groove. Straight knives are therefore preferably made with a sharp point which can be moved in almost perpendicular direction into and out of the foil.

The knives could be moved in a cycle during which the incision is started by advancing the knife point into the groove and the incision is completed and the interruption produced by withdrawing the knife from the groove. By suitably controlling the cycle of the knife and suitably shaping the knife point, during the withdrawal or entry of the knife point when the incision is terminated or commenced, it can be arranged that the longitudinal component of the speed of the cutting edge of the knife is relatively equal to the speed of the web and the relative movement between the cutting edge of the knife and the web is substantially perpendicular to the web. The cycle of movement can provide for the knife to be moved longitudinally as well as with a radial component relative to the grooved support. In this case the knife can be regarded as a gapped knife, in effect the gap in the cutting edge being simply the space beyond the knife point. The two phases of the cycle of movement of the knife may be controlled so that the phase of the movement when the knife is clear, bears a fixed relationship to the movement of the web to give a fixed length of interruptions and so that during the incision phase the movement of the knife is controllable independently of the movement of the web to give a length of incision which can be varied. Thus the knife may be moved by the aid of relatively adjustable cranks and adjustment of the web food as described below.

Instead of using straight knives rotary circular knives could be used in the above-described machine, the knives being lifted at the requisite intervals to produce the bridges, and the knives also serving to effect the first of folding. Such knives could rotate with a peripheral speed equal to the speed of the web or at a different speed. The same basic method of slitting and folding underlies the apparatus shown in FIGS. 8 to 18 but rotating circular knives with gapped cutting edges are here used which have among other advantages that they do not have to be raised to leave the uncut bridges, these here being produced by the gap in the cutting edges of the knives. As will be explained, not only can this apparatus produce a meander patterned foil (including the folded margins) at high speed with a remarkably small incidence of failure, but in its preferred form enables the repeat length to be varied very easily even during operation.

If as indicated in FIG. 8 a single circular knife 201 having a gap 202 in its cutting edge 203 deep enough to clear the web is used for cutting each series or line of slits in the web 204, the length of the bridges is determined by the ratio ofthe speed at which the web is moving through the cutting station constituted by a roller 205 over which the web passes, with a groove to clear the knife edge, to the peripheral speed of the knife while the gap 202 in the cutting edge of the knife is passing over the web. It is preferred that this ratio should be unity, so that the knife and the web move at the same longitudinal speed, at least while the gap is passing over the web.

For high speed continuous production with the length of the slits constant the peripheral speed of the circular knives and the speed of the web can remain equal throughout the cycle in which case the diameter of the knives at the circle 207 which touches the path of the web will be pitch/x if there is only one gap as in FIG. 8 or an integral multiple of this diameter with a corresponding member of equally spaced gaps. FIG. 9 shows by way of example a knife in which the diameter of the circle 2070 is 3Xpitch/x and the cutting edge 203a has three equally spaced gaps 2020.

Where it is desired to provide for various slit lengths without a separate set of knives for each, means must be provided for variation of the relative speed of the web and the peripheries of the knives. There is thus relative longitudinal movement between the web and the periphery of the knife and this can be positive or negative thus increasing or decreasing the length of the slits. The former requires the knife to be slowed down, the latter it to be speeded up. A mere change of speed ratio which remains constant throughout the cycle would also alter the length of the bridges in the same proportion as the length of the slits, whereas it would usually be required to keep the length of the bridges constant because usually the electrical requirements relate the length of the bridges to the width of the arms of the pattern rather than to the length of the arms of the pattern.

One way of enabling the length of the bridges to be varied in relation to the length of the slits is to make up each knife of two approximately semicircular half knives 201b FIGS. 10 and 11. Thus the length of the gap 202!) can be varied by a relative angular movement of the two half knives, which can be locked together after adjustment by any suitable means such as a bolt engaging through arcuate slots in the half knives or means clamping the knives axially.

To enable the cutting edge to be continuous between the ends of the gap and to provide for folding in the manner to be described, the two half knives are cut away to half thickness over a sector 211 of angle A equal to the maximum overlap to be provided for. With less overlap there will be two corresponding angles B where the cutting edge will only be beveled in one side and the composite knife will have a recess 211 on the other side but this will be quite short and will not prevent folding from being properly effected.

This composite knife arrangement avoids the need for a separate complete set of knives for every different slit length, but if a change is to be made every knife has to be separately adjusted. It is much preferred therefore to use knives with fixed gaps as in FIGS. 8 and 9 and to provide for a variation of i the speed of the knife during the cycle. By making the speed of the knife constant during the interruption phase i.e. when the gap is passing over the web, and confining the variation to the incising phase, the uncut bridges will be constant for all adjustments and the variation will provide for variation in the length of the slit. Preferably the speed of the knife during the interruption phase is such that the length of the uncut bridges is substantially equal to the gap i.e. the ratio of the peripheral speed of the knife to the speed of the web is unity. This permits the gap to be shaped e.g. rounded and/or at such an angle as to give optimum conditions for the start and end of the incision and least danger of tearing the foil.

For one particular length of slit, determined by the diameter of the knife, the knife will rotate at constant speed, but for any other length, the ratio of the mean peripheral speed of the knife to the speed of the web will differ from unity and if the ratio is to be unity during the interruption phase, the rotation of the knife during the incising phase will need to include at least one subphase of acceleration and one subphase of deceleration. Similar considerations will apply if the ratio is fixed, though not unity, during the interruption phase. In the making of a meander pattern such as that of FIGS. 1 and 2 chosen as an example, since the gaps in adjacent knives will be relatively phased I80", in the case of single gapped knives as in FIG. 8 there will need to be two fixed ratio phases per revolution and two variable phases each with at least one subphase of acceleration and deceleration, and a correspondingly greater multiple of the fixed and two variable phases in the case of knives with more than one gap.

One suitable and preferred form of apparatus using circular knives and enabling the length of slit to be varied while maintaining the bridge length constant is shown in FIGS. 12 to 15.

A motor and gearbox unit 301 drives for example through chain gearing 302, 303 respectively, one of a pair of feed and crimping rollers 304, and the input side of a continuously variable speed gear 305. The output side shaft 306 of the gear 305 is journaled in a bearing 307 and on its end carries a grooved crank am 308. The gear 305 and bearing 307 are mounted on a slide 309 movable on a slideway 311 by any convenient means such as a feed screw 312 controlled by a handle 313. For a reason to be explained the control of the gear 305 is also effected from the handle 313, for example through a chain gear 314 and the adjustment of the slide and gear may be indicated on a dial or the like 315. Instead of mounting the gear 305 on the slide 309, the shaft 306 could be provided with universal joints.

Engaging in the groove in the crank arm 308 is a crank pin 316 carried by a second crank arm 317 carried on the end of the input shaft of a change speed gear 318 having a multiplying ratio of Zn when n is the number of gaps in the knives. Manifestly the pin 316 could be carried by the crank arm 308 and arm 317 be grooved or other equivalent eccentric device be used. For the sake of simplicity single gapped knives to be described later are shown and the ratio is then two, but knives with more than one gap (such as the knife shown in FIG. 8) may be needed in some cases. As will be described, the knives are easily exchangeable individually, and the gear 318 may have several selectable ratios to suit knives of different number of gaps.

The output shaft 319 of the gear 318, which carries the knives 321 is noncircular in section to provide a driving engagement, at least over the length carrying the knives, and the knives can be threaded over the shaft laterally by means of a slot 322 formed by inwardly continuing the gap in the cutting edge of the knife to the requisite extent. If the knives have more than one gap, only one gap in each is continued inwardly in this way. By way of example the shaft 319 is shown as of rectangular section as this is simple and gives good support to the knives.

Alternate knives are threaded on from opposite sides so that their gaps are relatively displaced l00 in phase. When in place each knife is retained by a spring clip or the like which retains it firmly but enables it easily to be released for removal.

For example the clip may be a U-shaped spring 323 having both limbs bent over at 324 and engaging each in a recess 325. The walls of the recesses a against which the ends of the spring shut are inclined so that the spring is urged towards the shaft, and the bent over portions 324 bear against the shaft, so avoiding any looseness.

Since with this construction of the shaft 319 alternate knives are threaded from opposite sides, it is essential that the number of gaps in the knife should be odd, otherwise the gaps in one knife would come in line with gaps in the adjacent knives and not midway between, as is required to produce a meander pattern. If some other section of shaft, e.g. triangular, were used, which enabled the alternate knives to be threaded at angles which are an odd submultiple of 350, then an even number of gaps in each knife could be provided, but not a single gap.

The cutting edge and some width of the full thickness of each knife penetrates into a corresponding groove 326 in a grooved support in the form of a roller 327. The spacing center to center of the groove 326 is equal to the minimum spacing center to center of the slots of the pattern and corresponds to the minimum width of the arms of the pattern. During threading on of the knives guiding of them into the slots is facilitated by rods 328 supported on a bar 329 thus forming a comblike guide. There is one rod 328 in line with each part of the roller 327 between the grooves 326, and they assist in guiding the knives and preventing binding of the knives against the sides of the grooves 326, the greater part of which are only of such width as to give small clearance to the knives, see FIG. 14. Additional comb guides can be provided at other positions round the shaft 319 so that the knives are retained accurately on planes perpendicular to the axis of the grooved roller 326. One such further guide comprising rods 331 and a bar 332 is shown in the drawings. The comb guides themselves may be located axially by a part on the guide engaging a groove in the roller 327, thus-ensuring the correct alignment in relation to the grooves. As before a knife can be mounted for every groove, every second groove, every third groove, etc. to enable arm widths of the minimum or multiples thereof to be obtained.

Obviously, since the grooved roller 327 is cylindrical, all the knives must be of the same diameter, but they need not all have the same number of gaps. For example, in a wide machine it may be desired to make several different patterns side by side over different parts of the width of the web. Then there may be a group of knives with say one gap, another group of knives with say three gaps, and another group with say five gaps. Comparatively large spaces may be left between the different groups to provide uncut margins of web between the corresponding patterns of slits. Subsequently, the web may be slit continuously along the centerline or other position within each wide unpatterned zone to separate the several patterns, but in other cases there may be different pattern distributions for different surface loading in different zones of the width.

It will be understood that where several different patterns are produced in this way, the cycle of motion of the knife shaft and ratio of the gear 318 must be suited to the lowest common multiple of the various numbers of gaps, so that the correct speed of the knives is obtained whenever a gap is passing over the web. There will then be an acceleration and deceleration between every gap passage over the web during one revolution of the shaft, but this will not interfere with the adjustment of the desired length of incision which will still depend on the adjustment of the slide 309.

The web 333 passes over the roller 327 and thence over a plain roller 334 having its periphery close to that of the roller 327. From the roller 334 it passes to the feed and crimping rollers 304. During passage over the roller 327 the web is slit and the margins folded over through 90 by the coaction of the knives and roller 326 just as in FIGS. 3 to 6 above-described. Due to the narrow clearance between the knife 321 and the walls of the groove 326, a recess 335 is provided on each side to accommodate the thickness of the web.

To prevent the 90 folds produced by the action of the knives from unfolding when the folds have moved clear of the knives blades or plough members 336 which project into the space between the

rollers

327 and 334, and extend along the grooves to a point near the knives, hold the folds in place. These ploughs widen into shoes 337 in the space between the rollers, and complete the folding over of the margins back on to the web. These shoes are shaped to allow free passage to the uncut bridges in the web. Practical considerations may make it difficult to carry the ploughs 336 close enough to the knives, and a pneumatic means such as a jet of air delivered to this zone by a nozzle 336 may be used to hold the 90 folds in place. it should here be mentioned that if the web is a plain metallic foil, the difficulty of a tendency to unfold may not arise, but if for example a foil has been laminated to a layer of paper, as described below, there is a more serious risk of a tendency to unfold. Air jets may be relied on to hold the 90 folds in place all the way to the point where the web leaves the roller 327, so that the ploughs can be omitted and only shoes be provided. lt would even also be possible to replace the shoes by air jets. Cases may arise in which it is not desired to complete the folding, but to allow the 90 folds to unfold themselves under the elasticity of the material of the web. ln that case the mechanical folding means constituted by the ploughs 334 and shoes 335 are taken out of action suitably by mounting these parts so that they can be swung about the axis of the roller 327, as indicated by the arrow. Taking of these parts out of action may also be necessary if a fault occurs which threatens to lead to tearing of the web or jamming. Pneumatic means can be put out of action simply by cutting off the air supply.

With the shaft 306 aligned with the input shaft to the gear 318, the coupling constituted by the

crank arms

308, 317 and the pin 316 causes these two shafts to rotate in exact synchronism and if this speed is appropriate, the peripheral speed of the knife is equal to the speed of the web; these two speeds are both derived from the same source 301 and the

gearing

302, 303. 305 determines their relationship.

If now the slide 309 is adjusted so that the shaft 306 is no longer aligned with the input shaft to the gear 318, although the two crank

arms

308, 317 are still positively coupled by the pin 316 so that they must revolve at the same mean speed, it will be clear that their relative angular velocity must vary throughout a single revolution. Thus if as will be usual the shaft 306 and arm 308 rotate uniformly the arm 317 and the parts driven thereby will rotate nonuniformly. The variation will be smooth and the cycle will include a phase of acceleration and a phase of deceleration. At the two points in the cycle at which there is a change from acceleration to deceleration and vice versa, the angular velocity of the arm 317 will be practically constant over a short period and the timing in relation to the shaft 319 is arranged so that the gaps in the knives are passing over the web during one of these periods. Further the coupling of the adjustment of the gear 305 with that of the slide 309 can be arranged so that in all positions of adjustment the peripheral speed of the knife during these periods will be the same, so that the knife during these periods will be the same, so that the interruptions will always be of the same length and the adjustment of the slide will only change the length of the slits. The speed of the knife at the passage of the gaps is preferably equal to the speed of the web. (Strictly it can only be equal at one instant or at two instants which can be chosen to synchronize as nearly as possible with the termination and start of the incision.) Depending on which transition occurs at the passage of the gaps the slit will be shortened or lengthened as compared with constant speed and if the adjustment of the slide 309 can carry the one shaft to either side of the other a change from a shorter cut to a longer cut than that given when the shafts are aligned can be obtained.

in the machine as so far described, the feed of the web is imparted solely through the rollers 304. The web comes from a supply in roll form indicated at 339, and the necessary tension is imparted by friction bars 341, before it passes over the

rollers

327 and 334, which are rotated by the web itself, as by this means the forces which the mechanically driven parts exert of the web on the one hand and the strength and dynamic force of the web itself, are balanced.

There is a lower limit to the strength of the web, with which this balancing of forces can be achieved. if the web is thinner than this limit, a complex electronically controlled drive can be used. Preferably, however, ifthe web is too weak, being for instance a very thin metallic foil, it may first be laminated at least on one side to a supporting material such as paper or a film of synthetic material, or be given a coating of varnish or the like. if such a layer is used on one side only, it is preferably arranged so that it is on the outside when the web is passing over roller 326, as in that case when the margins are folded over, this insulating layer will be on the outside and the conductive web in the folds will have the folded-over margins in face to face contact.

As shown in FIG. 7 and as above-described, the knives are of symmetrical section, and the foil is slit midway over the grooves 326, so that equal margins are folded over on the sides of the slits. in particular cases, it may be desired to make the knives of asymmetric section, so that unequal margins are formed, or even as shown in FIG. 9, to make the knives of such section that the cutting edge of the knife 321a is wholly to one side. Then only one margin will be folded over, and there need be only one recess 335a.

As above-described, the interruptions or bridges extend in a line perpendicular to the length and direction of the movement of the web, and each repeat pattern is of generally rectangular outline. it may be desired that the bridges should extend across at a slope or in other words that the general outline of each repeat should be a nonrectangular parallelogram. This can readily be achieved by making the shaft 319 of steep helical form. If it is desired to be able to adjust the helix angle, the shaft may be made flexible in torsion.

One arrangement is shown as FIG. 10. The shaft here comprises an inner member 319a and an outer member 319b, which consists of a spiral spring with square-shaped turns seated on the inner member 319a. The spring is desirably made of rectangular section strip wound with the turns close together. Such a spring can be twisted more or less, and is provided with some means for locking it, for example by compression from the ends between a shoulder and a nut. The member 319a can be solid or hollow.

Another possibility is illustrated in H6. 11. Here, the shaft itself is springy, being made up of a pack of thin leaf springs 319e, these being well lubricated. For the sake of clearness, the springs are shown thicker than would actually be used, and there would therefore be a larger number of them. Again, some means is provided for locking the shaft when the necessary twist has been imparted.

For example, the shaft at points beyond the length which carries the knives may have keyed to it a gear wheel. These gear wheels mesh with two other gear wheels keyed to a shaft journaled to be free to rotate which can be moved to unmesh the wheels. While they are unmeshed the desired twist is imposed on the shaft and the wheels are then remeshed, thus maintaining the desired angular relationship between the ends of the shaft. The gear wheels must be of such size that the second mentioned shaft clears the knives and any other part of the apparatus which might otherwise be in the way. Alternatively, a circular section, solid or hollow shaft could traverse the pack of leaf springs and carry U-clips, which after adjustment of the twist can be locked on the ends of the pack of leaf springs by the action of a shoulder at one end and a nut at the other.

With these adjustable shafts, the slots 322 in the knives are made a loose fit, so that they can accommodate a range of twist of the shaft. With such twisted shafts the exact phase relationship of the gaps to the motion cycle will vary along the shaft, so that there will be a variation in the length of the bridges across the web, but it will be very small in practical cases and is kept to a minimum by arranging that the knife at midlength of the shaft is correctly phased.

More elaborate variations of the pattern of bridges can be achieved by other forms of shaft having the cross section by which the angular disposition of the knives is determined varying or variable along the length of the shaft. Such a shaft may have the angular disposition varying or variable in steps equal to the minimum spacing of the knives. Such a shaft may be made up of rectangular blocks threaded in a central shaft at the desired phase angles and clamped together, as by a shoulder at one end and a nut at the other. In such a case if the total phase variation is substantial, itwill be best to rotate the shaft at constant speed and accept the proportionate change in the length of the bridges or correct these by using knives with variable gap as in FIGS. and 11 where adjustment is made between the relative speed of the shaft and web to change the length of the slits, as described above with reference to FIGS. 5 and 6. In some cases, however, it may be possible to use a repeating cycle of motion per revolution which gives constant bridge length withvariable slit length.

The various parts of the machine are arranged to facilitate examination and exchange. As above-explained, the knives are easily removed and replaced individually, for example, for resharpening. The shaft unit as a whole can be mountedso that it can be moved towards and away from the roller 326. The mounting of the ploughs and shoes enables them to be adjusted and also enables them to be moved into a position in which the operative ends are accessible for examination.

Slitting and folding can be facilitated by lubricating the web. This can conveniently be done by a roller 342 positioned near the tensioning bars 341. After the patterned-web has emerged from the crimping rollers 304 it may pass to equipment such as that described above with reference to FIGS. 33 to 36 for lamination to other materials. In this case, the lubricant should be compatible with the materials with which the webis coated or laminated before or following slitting. It may be a liquid which can be driven off by heat when the web emerges from the crimping rollers 304 or which could serve as a solvent or plasticizer of the solid content of an adhesive by which the subsequent lamination is effected, or be asolvent or plasticizer of or otherwise compatible with a plastic film to which the web is subsequently laminated.

FlG. 19 is a similar view to FIG. 12 of another form of apparatus according to the invention which enables the folding of the margin or margins of the slits tobe completedeither by a further true fold through 90 orby squashing the margin or margins after the first part fold through 90. The FIG. also shows other modifications and developments which can be used independently of one anotherfor example in an apparatus otherwise in accordance with FIGS. 12and 13. So far as the details in FIG. 19 are substantially the same as those of FIGS. 12 and 13 the same references have been used;

In this embodiment a fixed grooved support 401 is used in place of the grooved roller support 327 of FIGS. 12 and 13. This support 401 is conveniently assembled from substantially semicircular discs-402 which have an-axially projecting rim 402 along their periphery and a hole 402!) to be referred to further below, which are clamped together by three bolts 404, with spacers 403 between them to leave grooves round the pan of the surface over which the foil 333 passes.

The foil 333 slides over the peripheral surface of the discs 402 and in order to reduce friction is wetted by a lubricant which is preferably chosen to be one compatible with the adhesive used for laminating the foil to paper, plastic film or textile at a later stage. The lubricant is applied to the underside of the foil by foam roller 405 to which the lubricant is fed through its perforated tubular spindle. Surplus lubricant is caught in a driptray 406. (Feeding and recovery arrangements for the lubricant are not illustrated since arrangements of this kind are well known per se.) If a lubricant has to be used which is not compatible with the laminating adhesive it is cleaned off the foil prior to laminating by foam rollers 415 acting over a driptray 416 against the patterned foil while the foil is supported by roller 334. The foam rollers 415 are fed with cleaning liquid (solvent, water, etc.) or used in conjunction with suction devices 417. For further drying or for evaporation of remnants of lubricant or solvent a heater 418 and shield 419 can be installed to work on the patterned foil after it has left roller 334. The spacers 403 of the stationary foil support 401 have a peculiar shape. It may conveniently be referred to as an irregular polygon but with, in this example, five of its six sides of circular arcuate form. The first side, the top in the FlG., extends to the periphery of the discs 402 and takes part in providing full width support for the incoming foil, the second side clears the knives 321 in their deepest position witha very liberal margin, the third and fifth serve to position precisely air guides or ploughs 407 very close to the periphery of disc 402 and around a part of roller 334 and to act as bearings when these guides or ploughs are swung into and out of position about the axis of discs 402. The fourth side is curved in to uncover the holes 402b in discs 402 and thus to leavea cavity extending axially through the whole foil support 401. This cavity is preferably connected to the suction side of an air exhaust. The sixth side of spacer 403 is straight and lines up with the straight back of disc 402 to form a plane on the foil support 401 to which adjusting plates and support brackets (not shown) can readily be attached.

Blades 407 constituting air guides or ploughs, which are also illustrated in perspective in FIG. 20 each comprise a thin blade which has a thickening strip 408 integral, bonded, soldered, welded or otherwise fixed to it on both sides. These strips 408 render the blade almost as thick as a spacer 403 so that it has a fine sliding fit between two discs 402. The strips have radial grooves, to permit airflow. The rim 402a on the discs 402 prevent the blades 407 from touching the foil while ensuring their close proximity to the foil. The path of the foil traveling to the foil support 401 allows plenty of space for swinging the structure supporting the blades 407 about the axis of the support 401 far enough for the blades to be swung quite clear of the support 401. This is required for feeding the blades in and out, adjusting, inspecting, cleaning or otherwise attending to them.

The configuration of the blade 407 is that of two partcircular arcs end to end one (when the blade is in operative position) havingits center in the axis of the foil support 401 and the other in the axis of roller 334. In this latter portion the blade 407 is split into a fork the gap between the two limbs 407a of the blade starting where the blade changes its direction of curvature. This gap widens gradually towards the outer end. This widening is adjustable by stacking slotted packings or washers 409 on to a rod 410 to come between the limbs 407a of the blades and between adjacent limbs 407a of neighboring blades. The limbs 407a which can be as thick or thicker than the strips 408 have a slot which fits over the rod 410, and reentrants in which an air chamber 411 and hooklike member 412 take a grip. Rubber wedges 411a block the outlet of the air chamber 411 into the gaps between adjacent parts ofneighboring blades so that the air from the air chamber'411 must flow into the gap between the fork limbs 407a towards the fork end where the foil with bent-up edges leaves the foil support 401 and between the limbs 407a and the foil running over the roller 334. Such air flow effects or assists the foldover of the edges.

A handle 413 permits the whole assembly of parts 407 to 412 inclusive to be swung about the axis of the support 402. The air supply to air chamber 411 is through a flexible pipe not shown, the air supply pipe to air chamber 414 underneath the knives if such is provided need not be flexible. Air under pressure supplied to chamber 414 will cooperate with the suction in cavity 402b to keep the foil bent after it has been cut by the knives 321 while the foil still slides over the support 401.

The blades 407 have been referred to as air guides or ploughs. This indicates that the folding of the foil edges need not be done by air as described above but can be done solely by the mechanical action of the blades 407 and particularly by its section 407a if the latter is brought nearer to the foil roller 334. if the foil is soft its edges remain bent-up after it leaves the knives and then assistance of air pressure to keep it so is not needed, although it can be helpful. The limbs 407a can be given a vibratory movement which can also be helpful particularly when the bent-up edge is to be squashed rather than folded down neatly. To use the limbs 4070 as ploughs, when friction between the foil and blade edges occur, has the advantage of simplicity and is quite suitable for relatively low foil speeds. For high foil speeds however it is preferable to use the blades as air guides.

The laminating of the patterned foil to a paper, film, scrim or other textile can be effected directly on the crimp roller when it becomes possible to exert strong pressure on the foil without flattening the crimps in the foil. This has several advantages, a.o. that of being able to use a paper film or textile with a thin coating of adhesive only, of thus effectively using hot melt adhesive coated paper, film or scrim, of permitting a less critical web control subsequent to this laminating, of maintaining the film under control, and of reducing the bulk of the apparatus.

The adhesive coated paper, film or textile 420 is fed in between the robust, larger crimping roller 304 and a laminating roller 421 which can be adjustably and elastically pressed against roller 304. It is preferably hard rubber covered but may be heatable and either bare or covered with silicone rubber, P.T.F.E. or other compounds used for laminating rollers.

lf web 420 is wet coated or for other reasons the adhesive can pass through the slots in the patterned foil on to the crimping roller 304 the latter may become soiled and an axially oscillating cleaning brush and suction foam rubber can be arranged to act on the surface of the crimping roller after the foil and web 420 have been taken off the crimping roller 304 and led round the laminating roller 421.

lnstead of such oscillating brushes working directly on the crimping roller 304, it is possible to prevent this roller becoming soiled with adhesive by interleaving an endless loop of a thin plastic film which is not wetted and/or not attached by the adhesive between the foil and the crimping roller, crimping this film and the foil together, stretching the film after it leaves the crimping roller, cleaning the adhesive off the stretched film and reinterleaving it again. FIG. 19 illustrates this arrangement diagrammatically, the loop of thin plastic being marked 422, rollers for guiding and stretching the film 423 and provision for cleaning and drying the film 424.

These arrangements for combining laminating with crimping can be used in apparatus otherwise as in H6. 12 or even as in FIG. 3, whether with or without a protective loop such as 422. Again a fixed foil support such as 401 could be used in either of these other forms of apparatus. Equally the various forms of rotary gapped knife and its drive as abovedescribed can be used in apparatus with a fixed foil support as in FIGS. 19 and 20.

It is to be understood that in this specification crimping means having undulations disposed perpendicularly to the general surface of the foil and of such character that there is substantially no changes in the thickness of the foil when the crimping is effected. This form of crimping is in itself known and can be eflected by running the foil between two rollers having intermeshing teeth of pitch appropriate to the pitch of the crimps desired. Such crimping confers extensibility to the foil far beyond any such quality possessed by the foil in the flat and it enables the foil to be distorted somewhat in its own place without damage and generally to be handled without damage notwithstanding its thinness.

It will be understood that whether completion of folding is by a further fold through or by crushing the first 90 fold will depend on the shaping of the plough or shoe members such as 111, 335, or 407a where mechanical pressure alone is relied on. Where air pressure alone is relied on or where it contributes the direction in which the air is directed will also be a controlling or assisting factor.

lclaim:

1. Apparatus for cutting at least one longitudinal slit in a web; including means for drawing the web longitudinally from a supply at a predetermined rate; a support for the web grooved longitudinally at each location where a slit is to be made; a rotary knife for each slit to be made, independent of the said web-drawing means and mounted in a longitudinal plane with its cutting edge projecting into a groove in the support to a depth substantially greater than the thickness of the web, the said cutting edge being substantially thicker than the said web but thinner than the width of the groove by more than the thickness ofthe web; means for rotating each knife at a predetermined rate, whereby it is caused to slit the web and simultaneously fold at least one of the slit edges into the groove approximately parallel to the plane of the knife so that immediately after passing each knife the web has a longitudinal slot of which at least one edge is bent out of the plane of the web.

2. Apparatus as set forth in claim 1 for cutting a series of longitudinal slits in a web, wherein each said rotary knife has at least one peripheral gap in its cutting edge deep enough to clear the support; whereby upon rotating each said knife it is caused to slit the web leaving an uncut bridge each time the gap passes over the web.

3. Apparatus as set forth in claim 1 for cutting a pattern of parallel series of slits with the interruptions in adjacent series relatively staggered longitudinally including a gapped rotary knife and groove in the support for each series, and a driving shaft on which the knives are individually exchangeably mounted, the exchange being possible by reason that at least one of the gaps in the rotary knife extends into the center of the knife, being wideenough to permit the knife to be taken off the shaft in the longitudinal plane.

4. Apparatus as set forth in claim 3 in which each knife can be threaded laterally over the driving shaft, such shaft having a noncircular section, the apparatus also including a spring clip or the like, retaining each knife on the shaft, the gaps in the knives and section of the shaft being arranged so that the knives can be mounted with the gaps in adjacent knives substantially in relatively opposite phase.

5. Apparatus as set forth in claim 3 in which the knife driving shaft has a noncircular cross section and the knives have each a corresponding slot enabling it to be threaded over the shaft laterally in a particular angular relationship, at least a group of the knives having the same angular relationship between the slot and the gapped cutting edge, and the cross section of the shaft varying angularly along its length.

6. Apparatus as set forth in claim 5 in which the angular disposition of the cross section of the knife varies in steps equal to the minimum spacing of the knives.

7. Apparatus as set forth in claim 5 in which the shaft is of helical form.

8. Apparatus as set forth in claim 4 also including guide means between the adjacent knife blades to guide the knives in their correct planes in relation to the grooves.

9. Apparatus as set forth in claim 1, including at least one of mechanical and pneumatic further means for completing folding of the margin into contact with the web, said further means being adjustable and also adapted to be taken out of action without preventing the remainder of the apparatus from being operated.

10. Apparatus as set forth in claim 1, also including means for tensioning the web before it is slit and means for drawing the web and tensioning it after it has been slit.

11. Apparatus as set forth in claim 1 in which the kniferotating means is geared to the means for drawing the web by gearing enabling the mean speed of the knife-rotating means in relation to the speed of the web to be varied.

12. Apparatus as set forth in claim 11 in which said gearing includes a coupling by which a cyclic variation including at least one acceleration and one deceleration can be made in every cutting cycle.

13. Apparatus as set forth in claim 12 including an adjustment for the gearing which determined the mean speed of the knife-rotating means and an adjustment for such coupling, said adjustments being so coupled together that the peripheral speed of the knife whenever a gap is passing over the web is substantially in a fixed ratio to the speed of the web.

14. Apparatus for the production of an electrical heating film including means for continuously feeding an electrically conductive foil, means for slitting the foil longitudinally at intervals of length and partly folding over the margins of the foil on at least one side of each slit, means for completion of folding of the partly folded margins of the foil, including at least one member common to the slitting means and folding means whereby alignment between the slitting and folding is directly ensured.

15. Apparatus according to claim 14 in which the common member is a grooved support over which the foil passes, the support having a plurality of grooves, at least some of the grooves each guiding in its active position one of a plurality of knives which slit the foil and in cooperation with the walls of the groove effect the first part of the folding over of the margins of the foil at the sides of the slit, the apparatus also including for each knife guided by a groove, a blade also guided by the groove, each blade incorporating a portion projecting beyond the support in the region where the foil leaves the support and serving to assist in completing the folding of the margins of the foil.

16. Apparatus according to claim 15 in which each blade is in the form of a plough the portion projecting beyond the support serving at least to assist completion of folding of the margins of the foil by engagement therewith.

17. Apparatus according to claim 15 in which each blade is in the form of an air guide, the portion projecting beyond the support being forked to guide air and the apparatus including an air chamber supplying air to the spaces between the limbs of each fork which is thus directed at least to assist completion of folding of the margins of the foil.

18. Apparatus according to claim 15 in which each knife is a gapped rotary knife at all times guided within the groove in the support.

19. Apparatus according to claim 15 in which each knife is of elongated form, the apparatus including means to bring alternately.

21. Apparatus according to claim 19 also including means to bring the knives between inactive position and active position individually according to a predetermined pattern.

22. Apparatus according to claim 15 also including a further roller over which the foil leaving the grooved support is carried, said roller reversing the curvature of the foil.

23. Apparatus according to claim 22 in which the further roller is equipped with means for cleaning the foil passing over it.

24. Apparatus according to claim 22 in which the further roller is succeeded by combined crimping and laminating means including a robust crimping roller and a laminating roller adjustably and clasticall ressed against the crimping roller by which a web to which ghe for] IS to be laminated IS pressed against the foil while it is passing over the crimping roller.

25. Apparatus according to claim 24 further including an endless loop of flexible plastics material which passes between the crimping roller and the foil, and rollers for guiding and stretching the endless loop where it is clear of the crimping roller.

26. Apparatus according to claim 15 in which the grooved support is fixed.

27. Apparatus according to claim 26 in which the support is built up of substantially semicircular discs having thickened rims, the arcuate parts of the peripheries of which guide the foil, and spacers between the discs, shaped to clear the knives and guide the blades.

28. Apparatus according to claim 27 in which an air chamber delivers air under pressure against the foil where it passes over the guide after being slit and part folded the guides being formed to permit the air to continue inwardly past them.

29. Apparatus according to claim 27 in which a cavity in the support communicated with the grooves and enables connection to be made to an air exhausting system.

30. Apparatus according to claim 23, in which the further roller is succeeded by crimping and laminating means including a robust crimping roller and provisions to insure at least a minute distancing of the foil from the teeth of the crimping roller while following their contour.

31. Apparatus according to claim 24,. in which said provision is a flexible plastic film which passes between the crimping roller and the foil, and means for guiding the plastic film at least before and stretching it after it has passed the crimping roller.

Claims

1. Apparatus for cutting at least one longitudinal slit in a web; including means for drawing the web longitudinally from a supply at a predetermined rate; a support for the web grooved longitudinally at each location where a slit is to be made; a rotary knife for each slit to be made, independent of the said web-drawing means and mounted in a longitudinal plane with its cutting edge projecting into a groove in the support to a depth substantially greater than the thickness of the web, the said cutting edge being substantially thicker than the said web but thinner than the width of the groove by more than the thickness of the web; means for rotating each knife at a predetermined rate, whereby it is caused to slit the web and simultaneously fold at least one of the slit edges into the groove approximately parallel to the plane of the knife so that immediately after passing each knife the web has a longitudinal slot of which at least one edge is bent out of the plane of the web.

3. Apparatus as set forth in claim 1 for cutting a pattern of parallel series of slits with the interruptions in adjacent series relatively staggered longitudinally including a gapped rotary knife and groove in the support for each series, and a driving shaft on which the knives are individually exchangeably mounted, the exchange being possible by reason that at least one of the gaps in the rotary knife extends into the center of the knife, being wide enough to permit the knife to be taken off the shaft in the longitudinal plane.

7. Apparatus as set forth in claim 5 in which the shaft is of helical form.

11. Apparatus as set forth in claim 1 in which the knife-rotating means is geared to the means for drawing the web by gearing enabling the mean speed of the knife-rotating means in relation to the speed of the web to be varied.

19. Apparatus according to claim 15 in which each knife is of elongated form, the apparatus including means to bring each knife into an inactive position when an interruption between slits is to be left and to guide the knife when in inactive position to remain in line with its groove in the support.

20. Apparatus according to claim 19 in which the knives are in two groups which are brought into their inactive positions alternately.

24. Apparatus according to claim 22 in which the further roller is succeeded by combined crimping and laminating means including a robust crimping roller and a laminating roller adjustably and elastically pressed against the crimping roller by which a web to which the foil is to be laminated is pressed against the foil while it is passing over the crimping roller.

26. Apparatus according to claim 15 in which the grooved support is fixed.

31. Apparatus according to claim 24, in which said provision is a flexible plastic film which passes between the crimping roller and the foil, and means for guiding the plastic film at least before and stretching it after it has passed the crimping roller.