US2762077A - Method and machine for casting film - Google Patents

Description

Sept. 11, 1956 R. MARKOWITZ 2,762,077

METHOD AND MACHINE FOR CASTING FILM Filed Feb. 9, 1955 2 Sheets-Sheet 1 INVENTOR RICHARD MARK 0W! 7' Z BY M M ATTORNEYS p 1956 R. MARKOWITZ 2,762,077

METHOD AND MACHINE FOR CASTING FILM Filed Feb. 9, 1955 2 Sheets-Sheet 2 i q Q, 55 3 1 1 l Has 50 63 mllln,

INVENTOR RICHARD MAR/(OM72 ATTORNEYS United States Patent METHOD AND MACHINE FOR CASTING FILM Richard Markowitz, North Brunswick Township, Middlesex County, N. J., assignor to John Waldron Corporafion, New Brunswick, N. J., a corporation of New Jersey Application February 9, 1955, Serial No. 487,013

13 Claims. (CI. 18-15) This invention relates to methods of and apparatus for film casting, especially adapted to the application of a liquid onto a flexible belt or apron adapted to carry it through processing machinery for converting it to a film capable of being stripped from the apron.

It is a general object of the present invention to provide novel methods and apparatus for film casting.

A specific object of the invention is to provide a method of and apparatus for the application of a coating of uniform thickness to an apron having thickness variations and minor undulations of surface.

Another specific object of the invention is to provide a method of and apparatus for the automatic application of a limited width coating to an endless apron or belt, which coating remains parallel to the apron edges despite substantial deviations in the path of the apron.

An important object of the invention resides in the detection of the position of the apron edge and the use of this information to adjust the lateral positioning of the application of the coating.

Another important object of the invention resides in the application of the coating material through transfer from its spreading and metering apparatus, to the surface of the apron where rigidly supported, by means of a relatively soft offset roll to insure transfer of all of the metered material to the apron surface.

Among the important features of the invention as directed to the apparatus may be enumerated the following:

Use of follow-up mechanism to move the apron edge position detecting means in unison with the coating edge determining means.

Arrangement of the reverse roll coating means to provide a coating material fountain between rolls and end dams and the movement of the end dams to determine the positions of the coating edges longitudinally of the rolls.

Arrangement of a plurality of controlled coating material dams to provide a number of spaced films of predetermined width on the apron all parallel to each other.

Use of a relatively soft transfer or offset roll in combination with a stainless steel or similar apron to provide film of uniform thickness in spite of inequalities in the apron surface.

Use of an apron having an engraved or etched surface to configurate the under side of the film.

Other and further objects and features of the invention will be more apparent to those skilled in the art upon a consideration of the following specification and accomfilm casting machine constructed in accordance with the present invention;

Fig. 2 is a front elevation of the film casting machine 2,762,077 Patented Sept. 11, 1956 omitting the liquid film material transfer, metering and offset rolls better to illustrate the adjusting mechanism for the film edge defining dams;

Fig. 3 is a fragmentary top plan view of the machine showing the arrangement of the dam adjusting mechanism;

Fig. 4 is a fragmentary end elevation of the machine, portions of the adjacent secondary frame being cut away for clarity of illustration; I

Fig. 5 is an enlarged fragmentary view of the valve controlled by apron edge position; and

Fig. 6 is a section on line 66 of Fig. 2 showing the dam control tube.

The operation known as continuous film casting is'distinguishable from coating primarily in the use of a surface from which the coating may be stripped resulting, if it has adequate cohesiveness, in a film whose thickness depends primarily on the thickness of coating applied to the basic supporting surface. Where quick drying materials or those where drying may be accelerated by the application of heat, catalyst or the like, are to be cast, the surface providing the initial support may take various forms as simple as a polished rotating drum or web of paper. In some cases, however, a long, slow, drying operation is required to produce the desired film and in accordance with the present invention the coating is applied to a long, highly polished belt or apron, preferably of stainless steel or similar material, which may be passed through suitable driers, ovens or the like, to finally harden the film to its desired condition whereby it may be stripped from the apron and coiled for shipment or subsequent use.

When using such apron several problems arise. It is impossible to provide an apron which will run absolutely true on its driving and idling drums, and it is, moreover, extremely difiicult andcumbersome to provide corrective measures continuously to maintain the apron edges at a uniform spacing from the drum edges. If, therefore, a coating of a predetermined Width is desired, effected by one of the more common expedients of limiting the coating width by side dams on the coating fountain, the lateral travelling of the apron, even'though controlled, prevents the production of a film whose edges are parallel to the edge of the apron, or one having straight edges itself. This is detrimental since it at least interferes with winding or coiling and may require trimming or other waste in eventual use. The apron cannot be controlled to run absolutely straight and uniformly spaced from the drum edge since correction is dependent on detection of lateral movement, and, moreover, fine correction is difficult and costly.

This invention therefore contemplates a means for maintaining the edge of the film uniformly spaced from the apron edge and therefore straight. This is achieved by detecting the position of the apron edge and moving the coating fountain end-dams longitudinally of their drums coincidentally with the lateral movement of the apron.

A further difiiculty arises in the maintaining of a uniform coating thickness due to variations in apron thickness and to certain inequalities in the apron surface so that the conventional hard surfaced transfer roll for the coating material, rotating oppositely tothe' apron travel, does not contact the apron surface all over for complete transfer of the coating material thereto.

In accordance with the present invention this particular problem is solved by interposing a relatively soft resilient roll, or one having a covering of rubber or the like, be-

tween the hard surfaced coating transfer roll and. the

casting apron, where it is supported on its driving drum. This achieves nearly one hundred percent contact between the apron and offset roll surfaces and consequent complete transfer of the coating material, producing a uniform film thickness on the apron without skips or thin V s ots.

The apparatus for carrying out the operations and method defined. aboveapp ear in theseveral figures of the drawing. Figi'l'is wholly schematic'and makes no attemptto show bearings, supports 'and"the like for the various parts of the mechanism-otherthan to illustrate diagrammatically amain frame memberlt) 'fromtwhich are supported by suitable means and driven at their requisite speeds by a suitable source ofpower a plurality of rolls anda drum. j The 'principal'drum'12 is of. large diameter; accurately ground on the surface for uniformity and minimum run out since. it carries "one end of .and drives the endless,.stainless steel belt or apron .13 of a thicknessrof the order of several hundredths of'an inch, preferably highly polished on its face and supported at a.remote,point by an. idler-drum 14. 'The distances between the drum centers may be as much asthe order ..ofone hundred feet,vand obviously intermediate sup ports .mu'st be provided for the belt to prevent sagging, and toeliminate the need for excess tension in the horizontal reaches. The apron, between drums passes through suitable heating and drying ovens, not shown, as 'dictatedlby the nature ofthe materialsforming the lengths. -The"roll 16 is referred to as a transfer roll,

carrying thezfilm mater al frorrrone or more fountains =20 :iniherspace between the rolls and above-them onto the-surface'of the .apron'as will be later described. This transferrollis mounted in .fixed bearings and may be -=providejd withta; doctor blade 21 on its rear face for removing "any vestiges ;of coating not deposited on the iolfsetroll later to be-described;

.FFhe second roll-of the pair is'the metering roll 18 .mounted in bearings which-are micrometrically adjustable horizontally asin'dicated-soas to permit the formation of ra gauging slot between the two rolls through Ewhich -1t-he-coating material, from the fountains passes :in a filmof the samethicknesswas this slot. Both-rolls are rotatedin a clockwise direction as viewed, roll 16 carrying the .film material downwardly (and V 18 wiping away the eXces'sand-maintaining the coating .on 16 of uniform thickness.

Substantially directly beneath transfer roll-16 is the ofiset:rol li23 wholly formedrof relatively soft rubber iorihaving'a metal core .with'a rubber'cover of substantial :;thickness thereon, as shownsat 24. This rolliis likewise driveniinla clockwise direction, as is the apron drum 12 as schematically shown by the chain 25 connecting a source of power:to the sprockets, on all :rollsand Idrum. "This offset roll has close contact with thegsurfaceofroll 16,:permitting no. gap or slot,.and rotatesspreferably at a'similar peripheral speed as..16.-so .asi.tofremove.1all. of

the coating: therefrom, transferringiit .to' its' own surface ninithe same thickness, although obviously itheithickness here may be changed by varying-the relative speedsof these tworolls, the film beingeither-thickened .or thinned :as' desired.

1latters:1thickness and .smoothness,'--so:that' a film is ';de iiposited'ifrom'z23. onto413: ofiuniformi Fthicknesszthroughout A second doctor 22 cleans -roll 18 and returns the coating material 'to' the fountains.

"like.

dating drive chains. bearings for rolls "16, 18 and 23, and in someof .the

and devoid of perforations, weak or thin spots and the controlling run-out ,of the apron lil, but none is shown since many conventional devices are available forthe purpose. Even though these do not accurately .maintain the position of the apron the film supply thereto is kept'parallel to its edges by.adjusting'the dams 26.1ongitudinally of their rolls, thus determining the positions of the edges of the films in accordance with the positions of one edge of the apron, which is detected by a feeler 76 acting through mechanism 31 toposition the, dams, as will be described .in detail subsequently.

"The arrangement of the dam adjusting mechanism'and further features'of the coating apparatus are illustrated in greater detail in'Figs. 2-to 6, inclusive. These figures show secondary frames 32 supported. from the main frame 10 through the journals 33 for a cross shaft accommo- These secondary frames provide figures fragments of the roll drive chains are shown. Each of the secondaryframes 32 is provided with a bracket 35-provided with an open top rectangular notch in which ,is longitudinally ,slidable and non-rotatively fitted a square tube .36, seen in detail in Fig. v6. This is -.held inposition inits notches by cover plates suclras 37,

As viewed from the providingfor a working sliding .fit. top inFig. 3.a.pair of rigid strap members 37 extend rearwardly from. and have their forward ends securedfirmly to'tube '36. These are spaced-apart so as to separate the 'dams'26, to which each is attachedas-shown, to the properpositions to .define the film edges.

In -manycases it is desired to cast severalnarrow strips of'film and rather thanresortto a narrow apron or slitting of the film,cast on a wide apron, intermediate dams .26" (Fig. '2) are;provided,'-thus dividing the foun- These damsmay be mounted and adjustable on a. rod-40 extendingthrough the end dams 26 and clamped therein as shown. dams, seen only in Fig. 2,; maybe longitudinally adjusted tain into several parts.

to fix :the widths of ;the several independent strips of film cast on the wide apron.

Thedams may-be of any'particular type as found most satisfactory for coating machines of: this general character,

'and noiadditional jdetails need be given Of'thfiil' construc- -tion.

The square tube 36 carrying its dams as just described is adjustableilongitudinallyEby means of a suitable, servomotor, such. as the pneumatic diaphragm -n10tor -50, seen in the :drawing, and mounted .on. a :cross bracket 51 carried bythe tuppersportion .of .the left secondary frame a 32. Thehorizontallyslidable output rod-53. of this servomotor slides through a-bear-ingin bracket 54 remotely secured to part 51 and a helical spring-5'5 compressed between this bracket and washer 56 mounted on rod 53 urges the rod toward the left. The outer endof'the rod is bent downwardly andpivoted ina'boss 58 offset both upwardly and forwardly of tube 36 by means of the L-shaped arm '59. clamped about the tube 36,jas. clearly seenin thejfigures. It may be adjustable thereon in any 'simple' manner; .ltwill be seen that operation of the ,rod 53 .will.adjust;.thelposition of .the dams longitudinally of the transfer-and metering rolls and so change the position of the cast film laterally ofthe apparatus.

' Compressed-air'is supplied to the motor from a-suitable source th1ough;pipe60,; the -interposed pressure regulator 61 and a T 62. The T attaches to; hose-1:63 leading to .control :valve :mechanism for :controlling .:operation of The intermediate 7 motor 50. This valve is mounted on a tube 65 having hose 63 attached to its left end being supported from tube 33 by strap 66 to which it is attached by U-bolts as shown. By this arrangement the valve mechanism moves with the dam adjusting tube and provides the necessary follow-up means to insure adequate operation of the mechanism.

Fig. 5 shows the air valve, comprising a fitting 70 secured on the right end of tube 65 and having a reduced diameter hole 71 therein adapted to be partially or fully closed by means of valve pin 72 having a conical end. This pin is carried on rod 73 extending from the arm 74 of a bell crank lever, the other arm 75 of which depends downwardly and is fitted with pad 76 positioned to engage one edge of the stainless steel apron and indicate its position in respect to that of the dams. The bell crank lever is pivoted at 77 in the valve fitting 70 while the rod 73 is bent over toward the left as seen in Fig. 5 and fitted with an adjustable weight 77 to maintain the pad 76 lightly but firmly and continuously in contact with the edge of the apron.

In operation the apron coating or film casting is carried on as explained above, the liquid being delivered from the fountains through the slot between rolls 16 and 18 and forming the coating 100 (Fig. 4) on transfer of roll 16 maintained of uniform thickness by metering roll 18. The coating is transferred to the resilient surface of the ofiset roll 23 forming the coating 101 on this latter roll which because of its close contact and opposition rotation to the belt or drum 12 deposits or casts the film 182 on the stainless steel belt where it is carried to subsequent treatment, stripping and winding.

As mentioned above, this cast film may be in several spaced widths dependent on the number and position of the intermediate dams used, it being understood, of course, that the material used to provide the coating or film does not spread substantially as it travels the short distance along the peripheries of the rolls which carry it, nor does it sag or spread on the apron. All this may be controlled by appropriate relative and actual velocities of the several rolls and the apron. A certain amount of lateral travel of the stainless steel belt is inevitable from accumulated inaccuracies in drum diameters throughout their length, from slack apron edges due to faults in the rolling of the sheet, or from use, from inequalities in apron thickness throughout its width, and for many other reasons. While this run-out may be corrected, as previously mentioned, such correction is ponderous and of insufiicient accuracy to insure a film whose edge is a continuous straight line.

As the apron 13 moves laterally it is followed by the pad 76 under the action of its weight 77 and dependent on the direction of movement more or less compressed air is permitted to leak out around the conical end of rod 72 through the aperture '71, varying pressure acting on the left face of the diaphragm of motor 50, which responds by moving its operating rod 53 in the proper direction, since this rod is balanced between the pressure on one side of the diaphragm and the spring 55. This adjusts the dams to maintain the film edge uniformly spaced from the control edge of the apron.

As the servomotor operates the tube 36 to carry the dams it also carries the tube 65, the air leakage valve and the apron edge follower pad 76, thus terminating the movement at the proper time in the well known followup manner, whereby the edge of the film is maintained parallel to the edge of the apron with a high degree of accuracy at all times. At the same time the operation of the relatively soft, resilient offset roll insures a uniform thickness of coating and hence of film with no opportunity for thin spots, perforations or the like.

I claim:

1. The method of casting film onto a straight edged apron travelling in a path substantially parallel to its edges but subject to lateral deviations therefrom comprising, applying a coating to the apron to be hardened thereon into a strippable film, controlling the width of the coating applied to the apron by positioning the edges of the coating a predetermined distance apart, measuring the deviation of a straight edge of the apron from a predetermined norm and changing said film edge positioning simultaneously in the same direction and to the same degree to maintain the film edges parallel to the apron edges.

2. The method of forming a straight edge film on a longitudinally travelling apron subject to lateral deviations in its path of travel comprising, confining the edges of a liquid coating on a surface, continuously transferring the coating to the apron for hardening thereon into a film and maintaining the coating edges on the apron parallel to the path of deviation of the apron by moving the coating position on the surface laterally in response to apron deviation.

3. Apparatus for casting film having straight edges onto a travelling apron subject to lateral deviations from a straight line path of travel comprising in combination, an endless apron, means supporting said apron for substantially horizontal travel including a metal drum of large diameter relative to apron thickness, a pair of rotatable metal rolls adjustably mounted side by side to provide a coating liquid fountain and a metering slot therebetween, a resilient surfaced rotatable roll beneath one of said rolls of said pair and closely engaging its surface and that of the apron where the latter is drumsupp'onted to transfer the slot metered coating to the apron, means to drive all said rolls and the apron in the same peripheral direction whereby the cooperating surfaces of all rolls and the apron move in opposite directions for complete coating transfer, end dams between said first mentioned rolls to complete the fountain and define the coating edges on said rolls and apron, and means responsive to apron path deviations to adjust said dams laterally to keep the edges of the coating film straight on the apron.

4. The apparatus of claim 3 in which at least one edge of said apron is straight, a feeler biased against said edge and means responsive to changes-in position of said feeler to effect a corresponding change in the positions of said dams; Y

5. The apparatus of claim 3 in which follow-up mech anism moves the feeler in unison with said dams.

6. Apparatus for casting film having straight edges onto a travelling apron subject to lateral deviations from a straight line path of travel comprising in combination, an apron, means supporting said apron for substantially horizontal travel including a metal drum, a pair of rotatable, hard, smooth surfaced rolls adjustably mounted side by side to provide a coating liquid fountain and a metering slot therebetween, a resilient surfaced roll beneath one of said rolls and closely engaging its surface and that of the apron where the latter is drum-supported to transfer the slot metered coating wholly to the apron, means moving the cooperating surfaces of all rolls and the apron in opposite directions for complete coating transfer from fountain to apron, end dams between said first mentioned rolls to complete the fountain and define the coating edges on said rolls and apron, and means responsive to apron path deviations to correspondingly adjust said dams laterally between said rolls to keep the edges of the coating film straight on the apron.

7. The apparatus of claim 6 in which apron path deviation is detected by an edge feeler, a 'servo-motor, means connecting said servo-motor for control by change in position of the feeler and means connecting the servomotor to move the dams in unison and consonant with apron deviation.

8. The apparatus of claim 6 in which said servomotor also moves the feeler in a follow-up operation.

9. Apparatus for casting film having straight edges onto a travelling apron subject to lateral deviations in :its;;:path of travel comprising vin combination, anendtless polishedmetal. apron, a large diameter-metal for and that of the apron at a position on the drum to transferfthe slot metered coating ,trom tthe .engaged metal lroll to ;the apron-ina :film of'uniform thickness in spite .of surface irregularities ot the apron, means moving -,the,-6o9pe r;ating-surfaces of all rolls and the apron in oppo- .-,siteirlirections for gcomplete coating transfer, end dams between said'first mentioned rolls tocornplete the fountain and relatively adjustable to 1 define (the coating edges on Isaid -rolls and apron, and means responsive to apron path deviations to simultaneously adjust said dams laterallyofsaid rolls to keep the edges of the coatingfilm straight-ton' the apron. v

=10. The apparatus as defineddn claim 9 'inwhichsaid -last mentioned means includesa servo-motor connected to adjust said dams, a feeler mechanism responsive to rand biased against one "edge of said apron, means assolciating :the servo-motor --an d :feeler whereby the latter 7 controls the position of the former'andmeansmounting said feeler -rnechanism for .movement by .said servomotor inthesame direction and distance assaid dams.

ApparatuscEor casting film having lstraight edges onto a travelling apron subject to lateral deviations in its path of travel comprising in combination, an end- .less polished metal apron, alar-ge diameter metal drum for driving said apron substantially horizontally, a ,pair .of

hardsmooth surfaced rolls adjustablymounted side by v side to provide a coating liquid tountainand a variable ;.metering slot therebetween,:airelativelysoft resilient roll closely :engaging -the surface of one of said metal rolls and ,that of {the apron at a -position .Ol'l the drum to transfer the slot meteredficoating from theengaged metal roll {tothe apron in-a film of uniform :thickness in spite -of;surfaceirregularities :of :the :apron, means moving thecooperating surfaces-ofallrolls andthe aprondn opposite-directions for-complete coating transfer, end dams between said first mentioned rolls to, complete the fountain 'and adefinezthe coating edges :on the rolls and apron,

,a bar mounted .for rsliding parallel to the roll surfaces,

ameansuoonnectingsaid damsfor movement by said bar,

.a fluid actuated ,servoanotor, means connecting said ,motor .to raotuatevsaid rod in either direction, a=source of fluidtunder pressureconnected to said servoemotor a leakage valve connected in shunt to said servo=motor and having a leakage regulating needle, a stern hinged to the valveflstructure and carrying saidineedle, ,a feeler. on

10 r. said w stem, :means biasing said-feeler against one edge of said apron, and meanssupporting said valve assembly andvstern from said rods-to .move .them in a'follo w up ioperationsimultaneously with saiddams.

12. Apparatus for casting a film onto a travelling apron subject to ,lateral deviations from ,-a straight line path comprising in combination, an .apron having a straight edge, means supporting and continuously driving said apron, means .for continuously delivering a stripe of coating .liquid'tontosaidrmoving apron to form a fiI-m lthereon within-its margins, and means responsive to a lateral movement of said apron edge to produce a correspondingmovement .of the coating liquid delivery means .to vmaintain the coatingtedges parallel to'said apron edge.

13. Apparatus for casting a film onto. a travelling ,apron subject to lateral vdeviations from a straight line ,pa'th "comprising in combination, ,an apron having a straight edge, means supporting and oontinuouslydrivingsaid apron, .means for continuously delivering a stripe of coating liquidonto said moving apron to fonm afilm thereon Within its .margins, means defining the edges of said stripe .and adjustable laterally, means for detectinglateraLmovement iof'the aprontedge and means responsive 'to said detecting means for moving wofysaid movement.

References .Cited in the file of this patent UNITED STATES PATENTS ,edge defining means commensurate with apron edge

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