Web guiding apparatus

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates in general to web handling apparatus, and more specifically to apparatus for guiding, controlling tension, and preventing wrinkles, in a moving web.

2. Description of the Prior Art

The metallic strip or foil, such as copper or aluminum, used to wind electrical coils for electrical apparatus, such as distribution transformers, has a thin coating of electrical insulation applied to at least one, and usually to both of its major sides. The insulation is applied wet and subsequently dried and cured to form a thin uniform coating. In the interest of conserving floor space, the insulating coatings are usually applied in one or more vertical coating towers, with vertically disposed ovens drying and curing the wet coatings. With high speed foil coating lines, such as lines which operate at a rate of 100 feet per minute, or more, the length of the drying and curing ovens required becomes appreciable. The overall height of the tower may be reduced by about one-half by utilizing two vertical ovens placed side-by-side for drying and curing each layer of insulation applied to the web. Thus, the web or foil may be coated with liquid insulating means and then dried in the first oven before contacting an upper supporting roll, and then the foil may be directed downwardly over another supporting roll, into the second oven where die insulting coating is cured.

Metallic foil is not perfectly flat, and may often have an appreciable camber, or other imperfections such as gage bands, or floppy edges. The lack of foil flatness combined with other factors such as the width of the foil, high running speeds, air currents, high oven temperatures, dimensional changes of the coatings while drying and curing, and tension buildup in the foil-due to unavoidable friction in the coating line, produce a tendency in the foil to wander laterally, as well as.to wrinkle or even tear, ft has been found that these undesirable characteristics are particularly troublesome above the vertical double ovens of a coating line, where the foil is directed about two 90° turns by the upper support or head rolls.

Therefore, it would be desirable to be able to direct hot, cambered, coated foil about two 90° turns, while edge guiding the foil, controlling the foil tension, and removing waves and preventing wrinkling of the foil.

SUMMARY OF THE INVENTION

Briefly, the present invention is web guiding apparatus which performs the function of directing a moving web, such as hot coated metallic foil, about two 90° turns, while edge guiding the foil, controlling foil tension, and preventing wrinkles therein. The web guiding apparatus includes first and second horizontally spaced parallel rolls mounted for rotation on a common support. When .mounted above two vertically disposed ovens of a coating line, the foil moves upwardly and performs the first turn about the first roll. The foil then travels horizontally to the second roll and performs the second turn about the second roll, and then directed downwardly into the second oven. An adjustable torque drive for driving at least the second roll is mounted on the support. The first roll may also be driven, if desired. The drive is adjusted to provide a free-running surface speed of the driven roll which, relative to the strip speed, will, provide the desired strip tension on each side of the roll. A bow-shaped roll is mounted for rotation on the common support such that it contacts a major surface of the upwardly moving foil before this major surface contacts the first roll. The bowed or curved roll has an inner stationary bowed axle and an outer flexible sleeve which rotates about the bowed axil on bearings. The foil contacts the bowed roll, with the bowed roll urging the edges of the foil outwardly, which overcomes any tendency of the foil to wrinkle. The whole common support, including the first roll, the second or driven roll, and the bowed roll, is pivoted about a vertical axis at one end of the support, adjacent the bowed roll. The centerline of the pivot point is tangent to the bowed roll and substantially aligned with the vertically approaching foil. Means for pivoting the support about this axis is disposed to be responsive to a signal from an edge sensing head located to sense the edge position of the foil after it leaves the second roll. Mounting the bowed roll and the tension adjusting roll on the movable or pivotable support, which pivots to maintain the proper tacking of the foil, prevents the foil from wrinkling between the bowed roll and the first roll, and between the first and second rolls.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and uses of the invention will become more apparent when considered in view of the following detailed description and drawings, in which:

FIG. 1 diagrammatically illustrates a foil coating line which utilizes web guiding apparatus constructed according to the teachings of the invention, and

FIG. 2 is a perspective view of web guiding apparatus constructed according to the teachings of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to the drawings, FIG. 1 diagrammatically illustrates a foil coating line 10, including web guiding apparatus 12 constructed according to the teachings of the invention. FIG. 2 is a perspective view of web guiding apparatus 12, shown pictorially rather than diagrammatically, in order to more clearly illustrate the components of the apparatus and their cooperation. Like reference numerals in FIGS. 1 and 2 indicate like components.

The web coating line 10 uniformly coats one or both major sides of a web 14 of metallic foil, such as aluminum or copper, with a liquid insulating material or enamel. The metallic foil 14 may be of any suitable thickness and width, with foil used for distribution transformer windings generally having a thickness in the range of 2 to 8 mils.

The foil 14 is then unwound from storage reel 16 and guided into coating means 18 via idler or guide roll 20. Coating means 18 applies a coating of liquid insulating means to one or both of the major surfaces or sides 22 and 24 of the foil 14. Coating means 18 is not shown in detail, as the specific type of coating means used is not important to the invention. In general coating means 18 may apply the liquid coating to the foil 14 by directing the foil 14 through a bath of the insulating means, or, the insulating means may be sprayed on the foil 14; or, the insulating means may be applied with an applicator roll.

After one or both of the major surfaces of the foil 14 is coated with liquid insulating means, the foil 14 is directed into heating means, such as oven 26, where the liquid insulating coating is dried. Oven 26 is a vertical oven with the foil 14 leaving the coating means 18 and being directed substantially vertically through the oven 26 as indicated by arrow 28. Coating means 18 may have driven rolls therein which aid in propelling the foil through the coating line.

After the insulating coating on foil 14 is dried, it is directed via web guiding apparatus 12 through two right angle turns which reverse the direction of the foil 14. Thus, web guiding apparatus 12 directs the upwardly advancing foil through two clockwise bends, as illustrated in FIG. 1, first directing the foil from a vertical position into a horizontal position, and then directing it from the horizontal position back into a vertical position. After being directed into the second vertical position, it is then directed downwardly through heating means 30, which may be a vertical oven similar to oven 26, with oven 30 providing the heat for curing the insulating coating. The drying and curing temperatures to which the foil 14 is heated by ovens 26 and 30, respectively, will depend upon the specific coating material utilized. For example, when using an oil modified polyester enamel, such as disclosed in U.S. Pat. No. 3,389,015, which is assigned to the same assignee as the present application, typical drying and curing temperatures are 350^s C. and 450° C., respectively.

3,602,191

After leaving oven 30, the foil 14 is directed through cooling means 32 via idler roll 34, with cooling means 32, as illustrated, being a plurality of perforated pipes disposed on both sides of the foil 14 which are connected to a supply of air. The plurality of pipes direct air over the foil to remove heat therefrom. The cooled foil may then advance about idler rolls 36 and 38 into an “S” bridle drive arrangement, which includes driven rollers 40 and 42, and then foil 14 in wound into a roll 44 by a controlled tension recoiler.

Vertical ovens are used to perform the function of drying and curing the insulating coatings, in order to conserve floor space, and the functions of drying and curing are performed in two closely spaced vertical ovens, respectively, in order to limit the oven height, and thus the building height, on high speed coating lines, such as those lines capable of operating at a rate of 100 feet per minute or more. The directing of the foil 14 from oven 26 into oven 30, above the ovens, is not as simple as providing two spaced idle head rolls, since commercial foil is not flat. Metallic foil may have a camber therein, or gage bands, or floppy edges, or a combination of these and other imperfections, any of which cause guiding problems which become intolerable as the strip width and operating speeds are increased. Further, the high drying and curing temperatures with the resulting dimensional changes of the insulating coatings, as well as uneven heating across the foil width, give rise to tension patterns which may cause the foil to develop waves, and then wrinkle, as it is passed over a roll. Also, there is a tension buildup in the foil due to unavoidable friction in the system. It would be desirable to be able to isolate the tension in the foil between the two heating zones, i.e., ovens 26 and 30. In some instances, with certain types of coating lines, it may even be desirable to add tension to the strip of foil. All of these factors may be controlled when utilizing the web guiding apparatus 12 shown in FIG. 1 which simultaneously edge guides the foil, prevents the foil from wrinkling, and controls the tension in the foil.

In general, web guiding means 12, as illustrated in FIGS 1 and 2, includes support means or frame 50 which is pivotable about a vertical axis 52, with the means for pivotally holding the support 50 being of any suitable construction, such as the ball joint type assembly 53 shown in FIG. 2. The vertical pivot axis 52 must be tangent to roll 80, at the point where the vertically advancing foil first contacts roll 80. The support means 50 has first and second ends 47 and 49, respectively which may also be termed the entering material and exiting material ends, respectively. The vertical pivot axis 52 is disposed at the first or entering material end of the support means 50. The support means 50 is completed with first and second sides 61 and 63, respectively, which are substantially parallel with one another and which join the ends 47 and 49 of the support means 50. Support means 50 pivots about the vertical axis 52, as illustrated by arrows 55 and 57 in FIG. 2, with the support means 50 being supported by roller means disposed at various points on the support means, which may ride on tracks mounted independently from the support means 50. Thus, as shown in FIGS. 1 and 2 rollers 54 and 56 may ride on tracks 58 and 60 respectively. While only two rollers are shown, the tracks 58 and 60 may extend across the width of the support means 50, enabling rollers to also be disposed at locations on the sides of the support means which are opposite to those occupied by rollers 54 and 56.

First and second rolls 62 and 64, which have a longitudinal dimension sufficient to accommodate the widest metallic foil to be coated, are mounted for rotation on the support means 50 at the first and second ends 47 and 49 thereof, with the axes of the rolls 62 and 64 being parallel with one another and is substantially the same horizontal plane. The first roll 62 may be an idle roll, or it may be driven with a torque drive, as desired. The second roll is mounted near the opposite end 49 of support means 50, and this roll is driven by an adjustable torque drive 66, which is mounted on support means 50. Drive 66 may be adjusted to isolate the tension in the strip or foil in the two heating ovens 26 and 30. In other words, the drive 66 may be adjusted such that the free-running surface speed of rolls 64, i.e. the roll speed without a load, is faster than the strip speed, which thus causes an increase in the tension in the portion of the strip before it reaches roll 64, and reduces the tension in the strip after it leaves roll 64; or drive 66 may be adjusted such that the free-running surface speed of roll 64 is less than the strip or foil speed, which causes the drive to act as a drag, increasing the tension in the foil after it leaves roll 64 and reducing the tension in the foil before it reaches the second roll 64. This is true as the actual surface speed of the roll is always the same as the strip speed. Any slippage occurs within the drive system, not between the roll and the strip. While the strip tension may be continuously sensed and converted to a feedback signal for automatically adjusting the free-running drive speed, and thus automatically adjust the affect of the second roll 64 on the strip tension, it has been found that the free-running drive speed may be adjusted to a predetermined value for each strip speed and then left in this predetermined setting until the line speed is changed. A conventional adjustable torque-type drive, such as a drive of the eddy current type, is suitable for this application. The freerunning surface speed of roll 64 may be set by the drive means 66 relative to strip speed, to correct many wrinkle conditions which may occur in the foil. The roll 64, along with its drive means, is mounted on the pivotable frame or support means 50 in order to prevent wrinkling from being reintroduced into the foil, which would be the case were the driven roll to be mounted independently from the pivotable means 50.

The pivotable support means 50, being pivoted about an axis located at the end of the entering material, is moved or pivoted to steer the end at which the driven roll 64 is mounted, with the angular displacement of the support means 50 being responsive to means for edge guiding the foil 14. In other words, it is important that the edge of the foil 14 be directed accurately into the curing oven 30 without lateral wandering or “swimming” of the foil. Edge sensing means 67, which includes a sensing head 68 and edge control means 70, provides a signal for means 72, such as a hydraulic cylinder, which is disposed to move the support means 50 in the direction of arrow 57, or in the direction of arrow 55, as required to correct any wandering of the foil 14. The sensing head 68 may be pneumatic or photoelectric, as desired, with the sensing head disposed to detect the edge of the material and, when an error occurs, to send a signal to the edge control means 70. Edge control means 70 will in turn send a signal to the hydraulic cylinder 72 to adjust the position of the support means 50 to maintain the desired edge position of the foil 14. Since suitable edge guiding apparatus is commercially available, it is not described in detail herein.

In addition to preventing wrinkling of the foil 14 through tension control, a bowed roll 80 is provided which prevents wrinkling of the foil due to heat and tension, as the foil emerges from the drying oven 26. It is important that the bowed roll 80 be mounted such that it contacts the foil 14 prior to its contacting the first upper support roll 62. It is also important to mount the bowed roll 80 for rotation on the movable support means 50, in order to prevent wrinkles from being reintroduced into the foil.

As illustrated in FIGS. 1 and 2, the bowed roll is bent along its axis, and it contacts the major side 24 of the foil 14 as required to remove waves from, and prevent wrinkles in the foil. Adjustable bowed rolls are commercially available which allow the dihedral angle between the foil and the plane of the bow to be varied, and the bowed roll itself is mounted on arms 87 and 89, with the location of the bowed roll 80 relative to the foil 14 being adjustable. The bowed roll 80 includes an inner stationary axle, which may be adjustable to provide the desired radius of curvature, and an outer resilient sleeve which rotates about the stationary bowed axle on ball bearings. The foil 14 moving over the curved surface of the bowed roll 80 is subjected to a crosswise spreading action which imparts a gentle flattening force to the foil. As a general rule, the radius of curvature of the bowed roll 80 must be greater than the length of the incoming span of the foil, in order to prevent uncon

3,602,191 trolled lateral wandering of the foil. The incoming span of the foil is the distance between the bowed roll and the last point at which the foil is supported prior to its coming into contact with the bowed roll. Since the strip is unsupported after being coated, and is unsupported in the drying oven 26, the incoming span of the foil 14 is necessarily long, which would limit the amount of curvature of the bowed roll and would thus limit its effectiveness in removing and preventing wrinkles in the foil 14. However, by mounting the bowed roll on the pivotable frame or support means SO, and by controlling the position of the edge of the foil 14 as the foil leaves the roll 64 and proceeds to the curing oven 30, the limitation on the radius of curvature of the bowed roll 80 is not as critical. In other words, the radius of curvature may be decreased to the dimension required to prevent wrinkles in the foil, without regard to the length of the incoming span of the foil. It has been found that a bowed roll adjusted to have a high point of 0.25 inches will give satisfactory results, with the bowed roll being located relative to the foil to provide about a 10° to 15° wrap of the foil on the surface of the bowed roll.

When the foil emerges from the drying oven 26 the enamel coating, although apparently dry, still contains some solvent, and the resins are uncured. When foil with hot uncured resin passes over a roll, it may stick to the roll and deform the foil. Thus, cooling means 82 may be disposed between the exit end of oven 26 and the bowed roll 80. Cooling means 82 may be constructed in a manner similar to cooling means 32, wherein a plurality of perforated pipes are disposed on opposite sides of the foil 14 and connected to an air supply, in order to circulate air over the hot foil to remove the heat therefrom.

In the operation of the web handling apparatus 12 the drive means 66 would be adjusted for the particular line speed to be utilized, to provide a free-running surface speed of the roller 64 which is predetermined, relative to the foil speed, to provide the desired tensions in the foil in the two heating zones. The angle of wrap of the foil on the bowed roll 80 is set by adjusting the position of the first roll 62. The dihedral angle of the bowed roll 80 would be set to the desired magnitude, and the sensing head 68 would be adjusted, as required, for the particular width of foil being coated. The foil 14 would then be unrolled from the supply roll 16, and coated with a liquid insulating means in the coating means 18. The foil then has the liquid coating dried in the first oven 26, with the elevated temperature of the heated foil being reduced by cooling means 82 as the foil leaves oven 26, to prevent the hot coated foil from sticking to the rolls disposed above the ovens. The foil is then directed over the bowed roll 80 to impart a flattening action thereto, to prevent the formation of wrinkles therein, following which the foil 14 is directed through the remainder of the first 90° turn over the first head roll 62. The foil then proceeds to the second roll 64, and is directed thereby through the second 90° turn. The second roll 64 either aids the foil by virtue of a higher free-running surface speed than the moving foil, or it acts as a drag on the foil by virtue of being adjusted to have a lower free-running surface speed than the foil speed, which controls the tensions in the foil in the two heating zones. The edge of the foil leaving the driven roll 64 is then sensed by sensing head 68, which provides an error signal when the edge is not in the desired location. The error signal is translated into the proper intelligence by the edge control means 70 for controlling a cylinder 72 connected to move the support means 50 about the vertical pivot axis 52. The amount of the displacement of the support means 50 is automatically adjusted to maintain accurate edge control of the foil 14 as it enters the drying oven 30. When the coatings on the foil 14 have been cured in the oven 30, the foil is cooled in cooling means 32 and then rewound into a roll 44 by an adjustable recoiling means. Thus, the web guiding means 12 makes it possible to coat commercial metallic foil of any desirable width, at line speeds of 100 feet per minute, or more, while controlling the tension in the foil, preventing wrinkles in the foil, and while accurately guiding the foil throughout the coating line, providing especially close control in the critical area above the double vertical ovens of the coating line. The web guiding apparatus 12 eliminates problems encountered when directing hot, coated, imperfect metallic foil about two 90° turns at a high rate of speed. Offset pivot guiding of the foil, which in5 eludes a pivotable frame, with the pivoting of the frame being responsive to the position of an edge of the foil, is uniquely combined with means for controlling tension in the foil which includes a driven roll mounted for rotation on the pivotable support means. A bowed roll for removing waves and prevent¹⁰ ing wrinkles in the foil is also mounted for rotation on the pivotable support means, and is located to contact the foil after it leaves the first oven, and before it reaches the first overhead support roll.

While FIG. 1 illustrates only one layer of insulating material being applied to one or both sides of the metallic foil 14, it will be understood that the foil 14 may be subjected to any desired plurality of coating and heating steps, with web guiding apparatus 12 being disposed above each double vertical oven ar2q rangement. For example, it is common to apply and cure four successive coats of insulation, applied one-eighth mil at a time, to achieve a total build dimension of one-half mil per side.

Since numerous changes may be made in the above25 described apparatus and different embodiments of the invention may be made without departing from the spirit thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.