JPH08208088A - Dual traction roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a roller surface and a roller, capable of maintaining a fixed traction coefficient for a wide range of web tension, a web velocity and a roller diameter. SOLUTION: A roller surface is divided into three portions extended in a peripheral direction, a knurled surface is formed to increase a traction coefficient for one of the center portion and both end portions, and a traction coefficient is reduced for the other portion as a smooth surface. By combing two kinds of traction coefficients, a fixed intermediate traction coefficient between both coefficients is provided. Without increasing the wrinkle sensitivity of a dual traction surface, the slippage and scraches of a web are prevented.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to rollers.
In particular, the present invention relates to rollers that provide constant traction to eliminate web slippage and scratches.

[0002]

In many manufacturing processes, a continuous sheet of paper, film, foil, non-woven or woven material is conveyed in one or more processes that transpose or rewind the material. Adhesive tapes, magnetic tapes, printed products, abrasive products, medical tapes, medical drapes, facial masks, photographic film and photographic paper, reflective sheets, textiles,
Web handling occurs during the manufacture of foils and other products.

During transport of the web during a typical web swap operation, the web passes through a series of rollers that support, guide, drive, and pull the moving web. Each roller generally has three components: a shaft, a shell and a bearing. The surface material and texture of the shell is an important part of its design. The combination of friction and lubrication between the web and rollers, called traction, is determined by operating conditions and the two sides involved. Controlling the web requires traction between the web and the rollers.

Poor traction in the cross-web and machine directions results in slip-related defects. Radial or roller slippage causes scratches on the web. Lateral slippage or shifting of the web causes misalignment and wrinkling of the web. If the traction is very large, wrinkles can be large and creases can occur. Web traction principles are used in manufacturing and device design because in many web processes web scratches and wrinkles and wrinkles are product defects. For webs that are thin and have a large coefficient and are not affected by wrinkles, the rule "large traction is best" can be applied. For products that are not affected by scratches or slippage, the rule "low traction is best" can be applied. However, many modern products require thin, wrinkled webs designed to be as low in material as possible. These products are also scratch-free,
Need a crease-free surface.

The idle roller has a roller surface speed.
When the (peripheral speed) is lower than the web surface speed (peripheral speed), the web may be scratched. This occurs when the force to rotate the roller is greater than the force that can be tolerated from web-to-roller friction. Skid and scratches often occur at high speeds in the web handling process. As the speed increases, the force to rotate or accelerate the roller increases. FIG. 1 shows the relationship between web speed and torque. Required torque (T _R ) to rotate the roller and allowable torque to drive the roller
It is compared (T _A) and. The required torque increases as the speed increases, and the allowable torque decreases as the speed increases. When the permissible torque to drive is less than the torque required to rotate the roller, the roller will slip at speed S, shown as the intersection of the two curves.

Objects moving in a fluid develop a boundary layer. In web handling, an air boundary layer develops near the surface of the web and moves with it. The air layer reduces the friction between the roller and the web. The thickness of the air layer is a function of the roller diameter, the viscosity of the air, the speed and the tension. As the speed increases, the diameter increases and the tension decreases, this thickness and the lubrication effect increase. . As the web speed increases, the air layer grows and lifts the web from the rollers. The web wrapped around the roller and pulled creates a pressure that compresses the air layer between the web and the roller. This pressure decreases as the diameter increases and the tension decreases.

A transition from large traction to small traction occurs when the thickness of the air layer overcomes the combined roughness of the web and roller surfaces. It is possible to increase the roughness of the web or rollers to shift the transition from large traction to small traction. High speed and low tension (154.2m / mi
Large air layers at web handling (greater than n (500 ft / min) and less than 1.75 N / cm (1 lb / in)) require roller design changes to maintain good traction.

The roughened or textured surface is effective in improving traction at high speeds.
The textured surface allows air to escape between the web and the rollers. 1, for example, patterns are added to the roller by a groove or notch (knurling) prevents lubricating the required rotational torque is greater than the allowable torque (T _{A, T)} by keeping the, shown to reduce slippage ing. It is possible to use several different roller roughness patterns. This pattern includes spiral grooves (herringbone pattern), double spiral grooves (diamond pattern), plasma sputter, sandblast,
Includes knurls and various other machined roughness.

Grooves cut into the roller surface may not be sufficient to prevent air lubrication. If the distance between the grooves is larger than 2.5 cm (1 in) and the surface roughness between the grooves is smooth, the lubrication is not sufficiently prevented,
The web will float between the grooves. Roughening, such as scoring, sandblasting, or plasma coating, is the best way to eliminate air lubrication problems.

The general concept of patterning rollers to prevent air lubrication and traction loss is known. However, large traction is not always desirable. Even though large tractions prevent slip and scratch defects, large tractions promote web wrinkling defects.
A wrinkle is a portion of the web that is broken across the web as the web contacts or wraps around the roller surface. Wrinkle-free web handling is desired.

The traction between the web and the roller is
It is an important condition that determines whether the web is wrinkled with rollers. Rollers are essentially wrinkle-free devices. This is because the web does not easily collapse, i.e. bend, in two directions simultaneously. this is,
The concept is to fix the shape. When the web bends to form the cylindrical shape of the roller, it will gain rigidity or resistance to transverse web shear. The web is
It is possible for the entire area of the upstream web to collapse when it is close to the roller and is snug against it without wrinkling. It is the web-to-roller traction that determines whether wrinkles are formed. If the web-to-roller traction is high, the shattered web will not slide laterally into a wrinkle-free shape as it approaches the roller. If the web-to-roller traction is low, the web will slip laterally and not wrinkle.

As described above, even if the roughness of any of several patterns in a roller having a single surface pattern is increased,
It will reduce traction losses from air lubrication. However, these patterns can only maintain the coefficient of friction at the initial value or adjust the lubrication rate. They fail to provide a constant and controllable level of traction and do not address the problem of wrinkling in large tractions. That is, there is an optimum value of traction between the size of the truncation that causes scratches on the web and the size of the traction that causes wrinkles on the web. The desired traction between the web and the roller is greater than the small traction required to prevent slippage and scratches,
Smaller than big traction that can keep wrinkles.

Many types of rollers and bearings attempt to improve web handling. For example, standard oil or grease ball bearings are replaced with air bearings to dramatically reduce the force required to drive the rollers. It addresses the problem of slippage and scratches, but does not address the problem of wrinkling.

The Pegenderm Vacutex roller is a low wrap roller position.
on) reduces slippage and scratches. The Vacutex Roller combines a roller bearing system and an air nozzle system. One live shaft roller uses a shaft and wheel arrangement that creates a mechanical advantage of greater than one-fifth to one,
Mounted on a two wheel cradle. This bearing system reduces the force required to drive the rollers. Nozzle system produces coneda effect suction,
Increase web wrapping and force on rollers. Like the air bearing, this device reduces slip and scratch defects, but will not contribute to wrinkle proneness.

There is a curved roller formed in the shape of a banana and having a constant diameter and a curved shaft or axis of rotation. It is formed as a series of narrow rollers that are stacked next to each other on a curved shaft. A cover of expandable elastomer is pulled over the roller and covered to form a continuous, wide surface. Where each passage of the web tries to enter the downstream roller in the direction perpendicular to the rotation axis,
The curved rollers stretch the web based on the vertical penetration web tracking rule. Due to the rotation of the curved rollers, the center of the web advances straight and both ends move in the lateral direction, resulting in a web that is taut in the lateral direction and free of wrinkles. The web spread rate can be calculated from the span length, wrap angle, web width, and bend depth. If the bending depth is too large, slippage with the roller
Scratches and web breaks occur. Bent rollers typically require large driving forces to drive to line speeds and cannot be applied to low tensions. Another drawback is that the cover has a short life, is complicated, and is speed limited due to strong traction and air lubrication issues.

Both reverse crown and tape bumped rollers are
The roller diameter is characterized by a change in the lateral direction, the diameter of the roller being larger at both ends than in the center. These rollers require good traction between the web and the rollers, non-slip conditions. The larger diameter ends change the web transverse tension conditions of the web entering the roller so that the tension is greater at both ends than in the center. This creates moments on both sides of the web. The opposite moment causes the web to spread as it enters the downstream roller. These rollers have the same drawbacks as curved rollers.

Edge puller nips are widely used in the textile industry for low modulus webs. Two narrow rollers are spring loaded and sandwiched together. The nip grips the web span between the rollers. The web creates traction for these nips and attempts to enter vertically. If the nip is tilted outwards, the web will spread laterally. These nips are difficult to use for high modulus materials, require double-sided contact, and can damage the friable web.

Bingham's flex spreader and American Roller's Alco-Stretcher are two spreaders covered with rubber with diagonal grooves. The surface of these rollers bends as the web tension decreases. The individual spiral fins formed by the grooves bend laterally, pulling the web taut in the width direction. These rollers have a nearly straight cylinder and have a slow spreading action, but they cannot be used in contact with the adhesive side of the web and have limited spread and a thin web falls into the groove. Sometimes.

The "D" bar is a bent bar, or cylinder provided with a convex surface, which draws in the web,
Increase the length and tension of the central path of the moving web. Tightening the center of the web creates a lateral bend from the center to the edges to reduce wrinkles. This device requires the web to slide on the "D" bar and is not used for scratch sensitive products.

Each time the expander roller makes one revolution, it expands and contracts in the lateral direction. The web is wrapped around the expander roller for some or all of the 180 degree lateral expansion range. Wrinkle stop rollers, poly band rollers, and Menzel rollers are expander type rollers.

Wrinkle stop rollers manufactured by Convert Accessories Corporation are similar to curved rollers. A segment that rotates on the shaft supports a flexible sleeve or shroud. But,
The wrinkle stop roller has a cylindrical shape and is not bent. The stretching action occurs by tilting the end plate of the sleeve. The web adheres to the surface of the elastomer and is stretched laterally as the roller rotates. Originally manufactured by Rembo, the Polyband Expander Roller is similar to Wrinkle Stop and other expander rollers. Some polymeric bands, like surgical tubing, are pulled between two tilted end plates. The web wraps around the rollers on the inflating side of the band to smooth out the wrinkles. Polyband rollers are limited to speeds of up to 1000 revolutions per minute due to centrifugal forces. These rollers are usually large indexing torque devices, require large web tension or torque auxiliary motors, and are expensive to maintain due to their complex design.

A wide range of process tensions, velocities and roller diameters are required to provide the desired traction level of the roller surface. There is a need for rollers that are used in products that tend to wrinkle and scratch.

[0023]

SUMMARY OF THE INVENTION The present invention relates to a roller surface for treating a web without causing slippage or scratch defects, and handles the web over a wide range of web tension, web speed and roller diameter. The invention also relates to a roller having such a surface. The roller surface may comprise a plurality of surfaces each having a traction coefficient different from the traction coefficient of the adjacent surface.

The plurality of surfaces can form axial or circumferential stripes. The three circumferentially extending surfaces can be formed such that the surface at the center of the shaft has a large traction coefficient and each surface at both ends of the shaft has a small traction coefficient. Alternatively, it is possible that the surface at the center of the shaft has a low coefficient of friction and each surface at both ends of the shaft has a lower coefficient of friction. Each surface of the shaft end can have an equal traction coefficient.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The dual traction roller of each embodiment of the present invention will be described in detail below with reference to FIGS.

The present invention is a moving web of material in coated or uncoated form, such as paper, films, foils, nonwovens, fabrics, composites and laminates of these materials. Or other rollers and roller surfaces used for transporting flexible continuous sheets. This surface is
It is applicable to idle rollers driven by the web, which may be fixed or part of a moving device, and driven rollers powered by speed or torque control. This roller has a small traction portion (a surface having a small traction coefficient) that prevents the problem of wrinkling, and a large traction portion (a surface having a large traction coefficient) that prevents the problem of slippage. 2-4 show different types of surfaces.

In one embodiment, as shown in FIG. 2 (A), a rough surface with large traction arranged at the center of the roller contact width of 25 to 50% and a smooth surface with small traction arranged at both ends thereof. Combine with a perfect surface.
Further, as shown in FIG. 2 (B), it is possible to arrange a smooth surface having a small traction at the center of the roller and a rough surface having a large traction at both ends thereof.

FIGS. 3 and 4 show another embodiment using both high traction and low traction surfaces. In FIG. 3, a plurality of rough stripes (stripes) and smooth stripes extending in the circumferential direction are used, and in FIG. 4, a plurality of rough stripes and smooth stripes extending in the axial direction are used. It is also possible to use embodiments with different surfaces having different traction coefficients of 3 or more.

The preferred rough surface for application to thin films is a scored pattern as shown in FIG. The distance a between the centers of adjacent notch grooves is 0.25 cm (0.1 in)
Is. The notch height is less than 0.025 cm (0.010 in). This notch pattern is 152.4-609.
Typical fast speeds of 6 m / min (500-2000 ft / min) and 0.44 found in many conversion processes
Low tension of ~ 1.75 N / cm (0.25-1.0 lb / in) prevents air lubrication traction loss. If a rough surface is chosen, a knurled surface is preferred because it facilitates cleaning and reduces traction changes due to attrition.

Various dual traction roller surfaces can be designed with different materials, textures, or geometric patterns. One geometric surface pattern is
It has a simple, laterally varying, high traction center that is easy to machine. Other patterns that divide the high traction surface and the low traction surface in a proportion include radial stripes, lateral stripes, and a low traction central portion.

The traction coefficient (COT) for the web-to-roller case uses the belt equation which describes the relationship of the coefficient of friction to the wound cylindrical surface (roller).
This belt equation is the following equation obtained analytically.

T _high / T _low = e ^mq where T _high is the force on the side the belt slides against, ie the tension on the tension side, and T _low is the force on the side the belt slides from, ie the tension on the slack side. Is. q is the wrap angle in radians and m is the coefficient of friction. Solving this equation for the coefficient of friction, m = [ln (T _high / T _low )] / q A simple test determines T _hight . This test requires a non-rotating roller, web strips, weights, and load measuring spring scales. Attach a weight to one end of the web, wrap the web around the rollers and hang the weight vertically. Attach a scale to the other end of the web. 90 degrees (1.57
The web is pulled in a horizontal plane while maintaining a constant winding angle q of (radian). The weight becomes T _low . The force on the scale required to raise the weight and cause the web to slide against the roller is T _high .

This same test can be run under conditions that represent actual web handling conditions at high web speeds. This test of sliding the web and using a spring gauge is performed at a relatively slow speed and therefore does not represent a manufacturing process. At higher speeds, the ingress of air and the resulting air lubrication change the load ratio relationship required to slide the web on the rollers. Experiments applying the belt equation to a web-to-roller system including air lubrication will measure the traction coefficient.

Direct measurement of the traction coefficient can also be achieved by measuring the force on the web using tension transfer rollers. The web has three roller systems, a first load measuring roller, a second roller having a surface to be tested, and a third separate load measuring roller.
Can be hung. During the passage of the web through these three rollers under the selected conditions, the torque of the brake connected to the second roller is increased until that roller slips. When first slipped, the two load measuring rollers measure T _high and T _low for their selected conditions. At low speeds, this result is similar to the belt equation test. At higher speeds, an air lubrication effect is observed and the calculated m value becomes the traction coefficient.

For the roller surface of FIG. 2, the average traction coefficient can be calculated from the ratio of a smooth surface with a low traction coefficient to a rough surface with a high traction using the following equation:

COT _AVE = (x) COT _low + (1-x) COT _high where x is the area ratio of the surface having a small traction coefficient, and (1-x) is the area ratio of the surface having a large traction. , COT _low is the traction coefficient of the surface with a small traction coefficient, COT _high is the traction coefficient of the surface with a large traction coefficient, COT
_AVE is the weighted average traction coefficient of the two traction surfaces. For the present invention, the average traction coefficient can be any value between the traction coefficient of the low traction coefficient surface and the high traction coefficient surface.

FIG. 6 is a graphical representation of two types of rollers compared to the extreme single surface of a 100% smooth or 100% rough roller surface. A sufficiently smooth roller will immediately become lubricated and will reach 152.4 m / min (500 ft / min).
Cannot overcome a bearing drag smaller than min). 1 notched surface
With a sufficiently rough roller of 00%, 457.2 m / min
Up to (1500 ft / min), it showed no significant air lubrication. The roller surface of the present invention is 152.4-457.2.
It produces a constant traction value over a wide operating range of m / min (500-1500 ft / min). The 50% rough surface version has half the traction coefficient between no lubrication and full lubrication. The 25 percent rough surface version has a quarter traction coefficient between no lubrication and full lubrication.

[Brief description of drawings]

FIG. 1 is a graph showing a web speed, a required torque for rotating a roller, and an allowable torque capable of driving the roller.

FIG. 2 is a plan view of a roller surface of the present invention. Two examples are given.

FIG. 3 is a plan view of a roller surface according to another embodiment of the present invention.

FIG. 4 is a plan view of a roller surface according to another embodiment of the present invention.

FIG. 5 is an enlarged cross-sectional view of a preferred score pattern.

FIG. 6 shows that two types of rollers are 100% smooth or 1
It is a graph figure compared with the roller surface which is rough by 00%.

[Explanation of symbols]

 a Notch spacing b Notch depth A 100% rough B 50% rough C 25% rough D 100% smooth

Claims (8)

[Claims] 1. A roller surface comprising a plurality of portions each having a traction coefficient different from the traction coefficient of adjacent portions. 2. The roller surface of claim 1, wherein the plurality of portions form a stripe extending in the axial direction. 3. The roller surface according to claim 1, wherein the plurality of portions form stripes extending in the circumferential direction. 4. A traction coefficient comprising three portions extending in the circumferential direction, wherein a portion at the center of the shaft has a large traction coefficient, and each portion at both ends of the shaft has a traction coefficient smaller than that of the portion at the center of the shaft. Characterized by having,
The roller surface according to claim 3. 5. The roller surface according to claim 4, wherein each portion at both ends of the shaft has the same traction coefficient. 6. A traction coefficient comprising three portions extending in the circumferential direction, wherein a portion at the center of the shaft has a small traction coefficient, and each portion at both ends of the shaft has a traction coefficient larger than that of the portion at the center of the shaft. Characterized by having,
The roller surface according to claim 3. 7. The roller surface of claim 1, wherein the web is stretched around the surface to remove wrinkles. 8. A roller having the surface according to claim 1 and comprising a plurality of portions each having a traction coefficient different from a traction coefficient of an adjacent portion.