KR20050023340A - Wrinkle reduction assembly - Google Patents

Abstract

The apparatus for reducing wrinkles of the film 102 includes a pair of first cylindrical rollers 100 having a first roller 108a and a second roller 108b, each having a parallel juxtaposition relationship with each other and having a substantially smooth surface, A pair of second cylindrical rollers 110 having a third roller 112a and a fourth roller 112b in parallel juxtaposition relation with each other and having a chevron pattern on at least one surface thereof. The pair is adjacent and spaced apart with respect to the pair of second rollers 110. Also disclosed herein is a method for reducing wrinkles.

Description

Apparatus and method for reducing wrinkles on films {WRINKLE REDUCTION ASSEMBLY}

The present invention relates, in particular, to apparatus and methods for reducing wrinkles in films such as lay flat tubular films.

Vertical form / fill / seal (VFFS) packaging systems are known to be very useful for packaging a variety of pumpable and flowable food and non-food products. An example of such a system is the ONPACK® flowable food packaging system sold by Cryovac / Sealed Air Corporation. VFFS processes are known to those skilled in the art and are described in U.S. Pat. Of which are hereby incorporated by reference in their entirety. In such a process, a lay flat thermoplastic film runs over the forming apparatus to form a tube, a longitudinal (vertical) fin or lap seal is made, and the tube is heated using a heated seal bar. The bottom end seal is made by sealing across. Through the central vertical filling tube, the flowable product is introduced into the formed tubular film. Thereafter, the pouch is completed by sealing the upper end of the tubular segment and cutting it out of the tubular film. This process may be a two step process. In other words, a transverse heating seal is formed in the first step, and in the next step, a pair of separate cooling / clamping means contacts the heating seal just formed to cool and reinforce the seal. In some VFFS processes, the upper transverse seal of the first pouch and the lower transverse seal of the following pouch are made and the pouch cuts, thereby eliminating the need for separate steps to clamp, cool and cut the seal. It is separated into two parts. An example of a commercially available device using such a simpler process is the ONPACK® 2050A VFFS sold by Cryovac / Sealed Air Corporation.

In some cases, spreader fingers are used commercially in VFFS installations such as ONPACK® 2050A. Such an example is disclosed in Research Disclosure 420056, published May 20, 1999. A removable spreader finger set is attached via the support ring to the bottom end of the solid fill tube of the ONPACK® 2050A VFFS device, or directly to the fill tube itself. The upper end of the finger has a shape that can slide through the support ring or filling tube when pivoted down to the position where the edge of the slot is guided. This supports the finger and prevents the spreader finger from inadvertently moving from front to back. The top end of the finger is pressed against the inside of the filling tube, allowing the bottom end of the finger to be pressed towards the inside of the film tube as required during part of the cycle of the apparatus. Spreader fingers may be replaced with fingers of different lengths to fit different pouch lengths. 5 of US Pat. No. 5,038,550, issued to Wirsig et al., Also incorporated herein by reference, also discloses a pair of spreader fingers used to prepare a tubular film to enter a space between a pair of sealing jaws. It is. These fingers are typically located above the transverse sealing assembly but below or below the filling tube region of the device.

In addition, some VFFS installations have a pair of squeezing or voiding rollers, which are described, for example, in FIGS. 1 and 6 of US Pat. No. 6,212,861, issued to Tsuruta, which is incorporated herein by reference. It is indicated by reference numeral "15" in FIG. These rollers, which typically have a smooth hard rubber or synthetic rubber surface, function to remove fluid, oil and other debris from the inner surface of the tubular film from which the transverse seal will be made. This allows transverse seals to be made with less contaminants present in the seal area, resulting in cleaner and stronger seals. These rollers are typically disposed on either side of the vertically sealed tube 48 and match the access and separation cycles of the pair of rollers with the pouch fabrication cycles of the particular apparatus by suitable pneumatic or hydraulic means. The voiding roller is typically located below the bottom of the longitudinal heat sealing device and below the bottom of the filling tube providing food to the formed pouch but above the level of the transverse seal bar. It is advantageous that the rollers help to flatten the pouch and form a bottom “interruption” to allow and support the filling of the next pouch in the filling sequence.

Thus, current conventional VFFS installations are devices that have a set of spring steel spreader fingers and there is a set of smooth squeegee rollers below and downstream thereof.

Unfortunately, the weight of food, such as fluid inside the pouch formed in the VFFS system, tends to corrugate the pouch, thus creating wrinkles immediately after the film runs downward from the spreader finger. Wrinkles may also occur when large chunks, such as a beef cube, are present in close proximity to the longitudinal (vertical) pin or wrap seal. Smooth rollers located downstream of the spreader fingers do not alleviate wrinkle problems.

The presence of such wrinkles results in a defective package or a package that is at least unacceptable to film users or food handlers. In certain applications, such as in sterilization packaging, wrinkles in the packaging material, particularly in the seal area of the package, are considered unacceptable. This is because low acid foods typically packaged in sterile applications require airtight packages to prevent spoilage and ensure safe food.

The inventors have found that using a pair of rollers in a chevron pattern downstream of a pair of smooth rollers can remove most of the wrinkles present in the tubular film. Optionally, the chevron patterned rollers may be disposed upstream of the pair of smooth rollers (and downstream of the spreader fingers, if present), but the effect of reducing wrinkles is reduced.

The present invention reduces the number of rejects in a package manufactured in a VFFS facility by lowering the proportion of packages with corrugated levels that are unacceptable.

Summary of the Invention

In a first aspect, an apparatus for reducing wrinkles in a film includes a first roller and a second roller, wherein the first and second rollers are in parallel juxtaposition relationship with each other, and each roller has a substantially smooth surface. A pair of first cylindrical rollers; A second roller having a third roller and a fourth roller, the third and fourth rollers being in parallel juxtaposition relationship with each other, wherein at least one of the third and fourth rollers has a chevron pattern disposed on its surface A pair of cylindrical rollers; The pair of first cylindrical rollers are adjacent and spaced apart with respect to the pair of second cylindrical rollers.

In a second aspect, a method of reducing wrinkles in a film includes a first roller and a second roller, the first and second rollers having a parallel juxtaposition relationship with each other, and each roller having a substantially smooth surface. A pair of first cylindrical rollers; A third roller and a fourth roller, wherein the third and fourth rollers are in parallel juxtaposition relationship with each other, at least one of the third and fourth rollers has a chevron pattern disposed on the surface thereof; Providing a pair of adjacent and spaced second cylindrical rollers relative to the pair of first cylindrical rollers; Advancing the tubular film such that the film first contacts and passes between the first and second rollers, and then contacts and passes between the third and fourth rollers.

In a third aspect, a method of reducing wrinkles in a film includes a first roller and a second roller, the first and second rollers having a parallel juxtaposition relationship with each other, and each roller having a substantially smooth surface. A pair of first cylindrical rollers; A third roller and a fourth roller, wherein the third and fourth rollers are in parallel juxtaposition relationship with each other, at least one of the third and fourth rollers has a chevron pattern disposed on the surface thereof; Providing a pair of adjacent and spaced second cylindrical rollers relative to the pair of first cylindrical rollers; Advancing the tubular film such that the film first contacts and passes between the third and fourth rollers, and then contacts and passes between the first and second rollers.

1 is a perspective view showing a prior art VFFS apparatus for making a pouch from a lay flat rollstock film;

2 is a schematic perspective view of the apparatus of the present invention,

3 is a plan view showing a pair of chevron pattern rollers of the present invention,

4 is a cross-sectional view of the chevron pattern roller of the present invention,

5 is a side view of the apparatus of the present invention,

6 is a perspective view of a prior art small assembly in which the present invention may be installed;

The invention is described with reference to the above figures, which include various embodiments of different aspects.

1 illustrates a prior art VFFS apparatus that may be used in conjunction with the apparatus and process according to the present invention. VFFS device 40 is schematically shown. This device 40 uses a multilayer ray flat film 41 as rollstock. Products 42, such as bee cubes or other foods or non-foods, in particular pumpable products, are supplied manually or mechanically from a source (not shown), and a predetermined amount of product 42 from the source This funnel 43 or other conventional means reaches the top end of the forming tube 44. The package is formed in the lower portion of the device 40, and the flexible film 41 forming the package is fed from the supply roll 51 onto a specific forming bar (not shown) to form the forming tube 44 (sailer or And a longitudinal seal 47 is provided by the longitudinal heat seal device 46 to form a vertically oriented tube 48. The transverse heating seal bar 45 operates to close and seal across the lower end of the vertically sealed tube 48 to form the pouch 50, immediately after which the product 42 is packaged. The film drive belt 52, powered and directed by the roller, advances the tube 48 and the pouch 50 by a distance as shown, after which the end seal bar 45 is closed, At the same time it seals horizontally across the lower end of the vertically sealed tube 48 and horizontally across the upper end of the sealed pouch 49 to form a product packaged in the sealed pouch 49. Subsequent pouch 50 thereon is filled with the metered product 42, advanced and the packaging cycle is repeated. It is also common to incorporate a cutting knife (not shown) into the end seal bar that operates to cut the lower sealed pouch 49 from the bottom of the upstream pouch 50.

2 is a schematic perspective view of the apparatus 100 of the present invention.

A ray flat tubular film 102 produced by the above-described VFFS process and having a longitudinal seal 104 is disposed between the pair of voiding rollers 106 and then between the pair of chevron pattern rollers 110 in the direction of the arrow. Proceed.

The pair of voiding rollers 106 includes a first roller 108a and a second roller 108b. These rollers function to remove oils, liquids and other materials from the inner surface of the film 102 to prepare for the cross heat sealing step as described. For those skilled in the art, means (not shown), such as voiding roller assemblies, respectively compress the outer surface of the film 102 from the “open” position where the rollers 108a, 108b are separated from each other and from the film. It is known to perform a voiding function by allowing a reciprocation between "closed" positions. Such means include pneumatic or hydraulic means that are tuned to the packaging cycle of the apparatus by suitable timing means to swing or straighten each roller between an open position and a closed position. Also, to move the voiding roller and the chevron patterned rollers, electromechanical means such as linear actuators or servomotors on the mechanical link can be used. In a typical installation, suitable bearing blocks are used, for example, to provide relative movement and support of the voiding rollers. The roller will itself have a journal center, on which the roller is supported by a support means (not shown), which, when in contact with the advancing film 102, will rotate about each axis in the direction of the arrow. will be.

The pair of rollers 110 having a chevron pattern include a first roller 112a and a second roller 112b. These rollers have been found to function to remove wrinkles formed in the lay flat tubular film 102 during the VFFS process. In order to perform the function of straightening the rollers 112a and 112b by reciprocating between each other and from the "open" position separated from the film, between the "closed" positions that respectively squeeze the outer surface of the film 102, Means similar to those used for the voiding roller 106 may be used. Such means include pneumatic or hydraulic means that are tuned to the packaging cycle of the apparatus by suitable timing means to swing or advance each roller between an open position and a closed position. The roller will itself have a journal center, on which the roller is supported by a support means (not shown), which, when in contact with the advancing film 102, will rotate about each axis in the direction of the arrow. will be.

3 is a plan view from above of the pair of rollers 212a and 212b of the chevron pattern of the present invention. The voiding roller is not shown for clarity. The two rollers have a chevron pattern defined by a series of lands 218 and grooves 220 arranged alternately along the length of each roller. These lands and grooves form a helical pattern across the rollers and have the effect of reducing the wrinkles formed on the film as the film passes between these rollers. Looking at the rollers rotating at the time of FIG. 3, a visual effect occurs where the patterns of lands and grooves move towards the outer ends of each roller. Thus, as the film 202 moves as indicated in FIG. 3, the chevron patterned rollers will each rotate in a direction toward the longitudinal centerline of the drawing defined by the film 202.

4 is a partial cross-sectional view of one roller of the chevron pattern of the present invention. The roller 312a has a series of lands 318 and grooves 320 alternate with each other. In a preferred embodiment, the outer surface of the land is relatively flat for smooth and even contact with the lay flat film. The grooves are shown symmetrically to each other. That is, the side of the groove facing the center line 330 of the roller is relatively flat, but the side of the groove facing the side end of the roller is curved. While this is a preferred embodiment, when the film passes between a pair of rollers with a chevron pattern, any suitable geometry of lands and grooves can be considered if there are less wrinkles in the film than without these rollers. The exterior 316 of the cylindrical roller may be constructed of any suitable material. Preferred materials are natural or synthetic rubbers. Hollow cylindrical core 340 may be constructed from any suitable material. Preferred materials are metals, in particular relatively hard and strong materials such as steel or aluminum or hard plastics. The roller 312a will have a hollow core 314 that receives a rod or bearing to facilitate rotation and support of the roller.

5 is a side view of the apparatus of the present invention. The ray flat tubular film 406 passes between the pair of voiding rollers 402a and 402b and between the pair of rollers 404a and 404b having a chevron pattern. Spreader fingers 400 form part of a pair of spreader fingers (for clarity, the other one is not shown), which serves to unfold the tubular film before the tubular film reaches the voiding roller 402. The direction of the film 406 is indicated by the arrow.

6 is a perspective view of a prior art small assembly 510 to which the present invention may be mounted. In the figure, the chain 520 drives the voiding roller assembly 530. A voiding roller 540 of one of a conventional pair of rollers is shown. Arms 550 and 560 may be periodically accessed and spaced apart from one another by any suitable means, such as pneumatic or hydraulic cylinders or servomotors or other mechanical linear actuators (not shown for clarity). For the purposes of the present invention, arms 550 and 560 can extend downward to accommodate a pair of chevron patterned rollers, as better shown in FIG.

Although the present invention has been primarily described as having a pair of chevron pattern rollers downstream of the pair of voiding rollers (usually down), the reverse configuration can also provide several advantages. Thus, the pair of chevron patterned rollers may be disposed upstream (usually upwards) of the pair of voiding rollers in the VFFS system.

Those skilled in the art will appreciate that after reviewing this specification, either one of the voiding roller or the chevron patterned roller can be used in series in multiple pairs. That is, in an alternative embodiment, the film may pass through a pair of chevron pattern rollers, a pair of voiding rollers, and another pair of chevron pattern rollers.

In another embodiment, where the invention is used in a packaging system in which the voiding roller and the chevron pattern roller are not in a flat configuration, ie the advancing film does not move in a straight line in the space between the voiding roller and the chevron roller, An intervening roller, such as a dancer roller, may be disposed between the voiding roller and the chevron roller.

The apparatus and process of the present invention can be performed for any suitable film, with thermoplastic polymer films designed for VFFS. An example is the FS7055® film sold by Cryovac / Sealed Air Corporation. Preferably, the film is sealed at the lowest possible temperature at which a relatively strong seal can be formed. Generally, the film is sealed at a temperature of about 150 ° C to 210 ° C.

The apparatus and process of the present invention can be used to package pumpable products, especially foods.

In use, the pressure applied to the voiding roller and the chevron rubber roller set can be adjusted by appropriate means.

Such a package can be manufactured by a continuous or intermittent VFFS pouch manufacturing process.

EXAMPLE

Example 1

In the test, an ONPACK® 2070B VFFS device was installed to package salted beef cubes using two sterile grade thermoplastic films comprising one transparent film and another opaque white film. . End seal wrinkles generally occur in sterile grade packaging applications, and attempts to remove them have not been successful. To correct the problem of wrinkling, a pair of chevron-patterned rollers (screws engraved on the surface with spiral patterns running from the center of the rollers to both edges) are installed on the 2070B installation with new brackets and drive chains, and the new rollers It was mounted vertically spaced apart from a pair of smooth voiding rollers. The chevron pattern rollers were driven passively. That is, the chevron rollers do not provide the driving force for advancing the film. The smooth voiding roller was driven to provide the driving force for advancing the film. When the rollers approach each other and contact the film passing between them, the degree of pressure exerted by the chevron roller on the film passing between the rollers is important for proper film progression.

When the test film was run, the configuration with the chevron patterned roller vertically above the driven flat squeeze roller contributed somewhat to reducing the occurrence of wrinkles in the film and the final package, but was found not to contribute significantly. There is also a pair of spreader fingers, which were placed above the chevron rollers. It has been found that the distance between the spreader fingers (305 mm to 310 mm) is an important parameter in reducing the frequency and size of wrinkles.

Example 2

The same test as in Example 1 was performed, but here the pair of smooth voiding rollers was modified to be in a position spaced upwardly from the pair of chevron pattern rollers. Also in this test, the voiding rollers did not contact each other in the closed position (with no film between them) because the diameter of the chevron roller was much larger than the diameter of the voiding roller. Seal voiding by the voiding rollers (residual material from the inner surface in the vicinity of which the tubular film is sealed transversely) without the voiding rollers contacting each other and thus not applying a large pressure on the film passing between them Removing) was incomplete.

Nevertheless, when the test film was operated, the incidence of wrinkles was reduced. However, the occurrence of wrinkles was still unacceptably high. It has also been found that the distance between spreader fingers is an important parameter in reducing the frequency and size of wrinkles.

Example 3

Beef chuck roasts were purchased and cut thinly into cube sizes. The cubes were cooked in boiling water for about 30 minutes to have the same level of firmness as in the previous test.

On each transverse half of the roller a pair of chevron patterned rollers with a more dynamic (more steep angle, i.e., the direction of the land and grooves form a smaller angle relative to the direction of the longitudinal axis of the roller) has a In the 2070 apparatus, it was installed in the position spaced vertically upward of a pair of smoothing voiding roller. The chevron pattern rollers were chain driven and the voiding rollers were manually driven.

New brackets were made for the two pairs of rollers, which allowed the voiding rollers to contact each other without the film passing between them, allowing various levels of pressure to be applied to the rollers and the film during the film run. This system greatly reduced the incidence of seal wrinkles compared to the same configuration where the voiding rollers do not contact.

Increasing the pressure on the chevron roller also improved the effect of reducing wrinkles compared to relatively weak pressure. All 69 packages in one row run without end seal creases.

This particular configuration of the spreader finger was bent to a distance of 280 mm (from 305 mm) and the package still did not wrinkle.

It is to be understood that variations and modifications of the invention can be made within the scope of the invention.

For example, in alternative embodiments, chevron pattern rollers can be paired with smooth surfaces, such as, for example, mating rollers 108a and 112b. Such a combination has been found to reduce the wrinkles of a single wound film passing between them, and is expected to provide some effect in reducing the wrinkles of a lay flat tubular film. This alternative configuration will be implemented in combination with a pair of smooth voiding rollers disposed upstream or downstream of the alternative chevron roller / smooth roller configuration.

Although the present invention is primarily described with a pair of chevron patterned rollers or a pair of smooth rollers spaced in a vertical relationship with respect to a pair of chevron rollers and a smooth roller, those skilled in the art will appreciate that each pair of rollers may have any suitable angles and postures relative to one another. It will be appreciated that it may have and be connected and arranged in any plane in the range from vertical to horizontal.

Similarly, as long as there is some effect on reducing wrinkles in the film passing through the pair of rollers, various depths of grooves, various spacings between adjacent lands, various widths of each land and helical on each transverse half of the chevron pattern roller It will be appreciated that any suitable chevron pattern may be used with various angles or pitches of the structure. The horizontal spacing between the lands need not be constant, so the overall pattern on each lateral or transverse half of the roller may not be a strict spiral, from the transverse centerline of the chevron roller of the two lateral edges of the roller. The angle can change. One or more lateral portions of the chevron pattern roller may be a smooth surface if appropriate, such that the chevron pattern appears in one or more bands on the roller.

The present invention provides a wet, flowable and / or low viscosity fluid (e.g. juice and soda), a high viscosity fluid (e.g. seasonings and sauces), a fluid / solid mixture (e.g. soups), gelatin and the like. It can be used to package pumpable products. Non-foods such as fertilizers, automotive oils and engine additives, dry and wet cosmetics, drugs, medical powders such as foot and talcum powder, sand, cement and the like can also be effectively used in the pouches of the present invention. The present invention shows particular utility in packaging dry, flowable and / or pumpable products. Such products include very finely divided or ground products such as flour and cake mixes, rather coarse products such as spices and sugars, and thicker products such as rice and breakfast cereals. Effectively products with larger particles and dry flow and / or pumpable non-food products such as pet food can be packaged.

As used herein, "film" is used to mean a multilayer or single layer film, laminate and web that can be used in conjunction with the present invention. Examples of suitable packaging materials for the VFFS process are FS laminates such as FS 7055 (registered) available from Sealed Air Corporation through the Cryovac Division. These laminates are disclosed in US Pat. No. 4,746,562 to Fant, which is incorporated herein by reference.

Other laminates include SCLAIR® seals, an ethylene / alphaolefin copolymer sold by DuPont Canada and disclosed, for example, in US Pat. No. 4,521,437, issued to Storms, which is incorporated herein by reference. There is a thing based on a film. DuPont Canada's commercial monolayer film is FS-3. Commercial multilayer laminates are CL 303. Many other films and laminates useful for dry or wet fluid packaging are available and can be effectively used in the present invention.

The invention can be used in combination with various plant systems or as a subassembly thereof. Preferred uses are for commercial installations such as VFFS packaging facilities such as ONPACK® 2070, 2002 and 2050 in VFFS applications. However, those skilled in the art will appreciate that the present invention may be used for other plant applications if wrinkle reduction functions are required, whether for packaging or simply for advancing the film, for example as a wind up roll.

Claims (21)

In the apparatus for reducing the wrinkles of the film, (1) a pair of first cylindrical rollers including a first roller and a second roller, wherein the first and second rollers are in parallel juxtaposition relationship with each other, and the rollers have a substantially smooth surface; (Ii) a third roller and a fourth roller, wherein the third and fourth rollers are in parallel juxtaposition relationship with each other, and at least one of the third and fourth rollers has a chevron pattern disposed on its surface; Includes a pair of two cylindrical rollers, The pair of first cylindrical rollers are adjacent and spaced apart with respect to the pair of second cylindrical rollers. Device to reduce the wrinkles of the film. The method of claim 1, The first and second rollers and the third and fourth rollers are freely rotatable about respective axes. Device to reduce the wrinkles of the film. The method of claim 1, The first and second rollers have a smooth outer surface Device to reduce the wrinkles of the film. The method of claim 3, wherein The outer surface of the first and second rollers comprises natural or synthetic rubber Device to reduce the wrinkles of the film. The method of claim 1, The first and second rollers are located above the third and fourth rollers. Device to reduce the wrinkles of the film. The method of claim 1, The third and fourth rollers are located above the first and second rollers. Device to reduce the wrinkles of the film. The method of claim 1, The first and second rollers and the third and fourth rollers are adapted to accommodate the passage of a lay flat film in contact with the rollers. Device to reduce the wrinkles of the film. The method of claim 1, The first and second rollers and the third and fourth rollers are adapted to circulate between an open position and a closed position. Device to reduce the wrinkles of the film. The method of claim 1, At least one of the third and fourth rollers comprises a series of lands and grooves alternating with each other on its surface Device to reduce the wrinkles of the film. The method of claim 1, The third and fourth rollers are adapted to receive the lay flat film in contact with and pass through the rollers, thereby reducing wrinkles present in the film. Device to reduce the wrinkles of the film. The method of claim 1, The third and fourth rollers each have a chevron pattern disposed on its surface. Device to reduce the wrinkles of the film. In the method of reducing the wrinkles of the film, (1) a pair of first cylindrical rollers having a first roller and a second roller, wherein the first and second rollers are in parallel juxtaposition relationship with each other, and wherein each roller has a substantially smooth surface; A third roller and a fourth roller, wherein the third and fourth rollers are in parallel juxtaposition relationship with each other, at least one of the third and fourth rollers has a chevron pattern disposed on the surface thereof; Providing a pair of adjacent and spaced second cylindrical rollers relative to the pair of first cylindrical rollers, (2) advancing the tubular film such that the film first contacts and passes between the first and second rollers, and then contacts and passes between the third and fourth rollers. How to reduce wrinkles on the film. The method of claim 12, The first and second rollers and the third and fourth rollers are freely rotatable about respective axes. How to reduce wrinkles on the film. The method of claim 12, The film first proceeds linearly when contacting and passing between the first and second rollers, and then contacting and passing between the third and fourth rollers. How to reduce wrinkles on the film. The method of claim 12, As the film passes between the third and fourth rollers, wrinkles present in the film are reduced. How to reduce wrinkles on the film. The method of claim 12, The third and fourth rollers have a chevron pattern disposed on the surface thereof. How to reduce wrinkles on the film. In the method of reducing the wrinkles of the film, (1) a pair of first cylindrical rollers having a first roller and a second roller, wherein the first and second rollers are in parallel juxtaposition relationship with each other, and wherein each roller has a substantially smooth surface; A third roller and a fourth roller, wherein the third and fourth rollers are in parallel juxtaposition relationship with each other, at least one of the third and fourth rollers has a chevron pattern disposed on the surface thereof; Providing a pair of adjacent and spaced second cylindrical rollers relative to the pair of first cylindrical rollers, (2) advancing the tubular film such that the film first contacts and passes between the third and fourth rollers, and then contacts and passes between the first and second rollers. How to reduce wrinkles on the film. The method of claim 17, The third and fourth rollers and the first and second rollers are freely rotatable about respective axes. How to reduce wrinkles on the film. The method of claim 17, The film first proceeds linearly when contacting and passing between the third and fourth rollers, and then contacting and passing between the first and second rollers. How to reduce wrinkles on the film. The method of claim 17, As the film passes between the third and fourth rollers, wrinkles present in the film are reduced. How to reduce wrinkles on the film. The method of claim 17, The third and fourth rollers have a chevron pattern disposed on the surface thereof. How to reduce wrinkles on the film.