MXPA00000446A

MXPA00000446A - Method of calendering a sheet material web carried by a fabric

Info

Publication number: MXPA00000446A
Application number: MXPA/A/2000/000446A
Authority: MX
Inventors: T Otto Kurt; M Perkins James
Original assignee: Kimberlyclark Worldwide Inc
Priority date: 1998-12-30
Filing date: 2000-01-11
Publication date: 2002-05-09

Abstract

A method for calendering the sheet material web includes carrying the sheet material web on one or more carrier fabrics through the calender nip formed by the first and second calender rolls and applying a load to the carrier fabric, and sheet material carried thereby, so as to reduce the thickness of the sheet material web.

Description

METHOD AND APPARATUS FOR CALENDING A FABRIC OF BLADE MATERIAL CARRIED BY A FABRIC BACKGROUND OF THE INVENTION The present invention relates generally to a method and apparatus for calendering a fabric of sheet material, and in particular, to a method and apparatus for calendering a fabric of sheet material while being carried by one or more carrier fabrics. .

It is well known in the field of papermaking, and particularly in the field of manufacturing tis? Ata? És' Co products or facial facepieces, toilet tissue, paper towels and the like, for providing a fabric of sheet material running continuously to traverse an "open pull" before being rolled into rolls. The open pull area, where the dried sheet fabric is momentarily unsupported before being rolled, can provide a place for calendering the fabric, for example, pressing the fabric to reduce the gauge or thickness thereof.

As described in the patent of the States United States No. 5,591,309 issued on January 7, 1997 to Rugowski and others, and the United States of America patent.

No. 5,593,545 issued on January 14, 1997 to Rugowski et al., - - - -. _ .--- ^ __ 2 both yielded to Kimberly-Clark Corporation, the same assignee of the present application, open drafts are a frequent source of sheet breaks and associated production delays. As a result of this, the tissue sheets are often designed to have high resistance in the machine direction in order to remain intact as they are pulled through the open pull. However, high resistance in the machine direction can adversely affect the quality of the fabric in terms of its desired smoothness. Therefore, as explained in U.S. Patent Nos. 5,591,309 and 5,593,545, the removal of open drafts in the tissue manufacturing process can result in a sheet material being made more efficiently. coast and with more desirable properties .. - • _ • - - -. As a result of eliminating the open pull, the fabric of sheet material is typically wound on a roll and then subjected to a calendering operation in a subsequent conversion or finishing process. Frequently, the fabric of sheet material, such as that made by means of the non-creped air drying process (UCTAD) described in U.S. Patent Nos. 5,591,309 and 5,593,545 will have a relatively high volume, with the inherent benefits of increased absorbency and better fiber utilization. In order to achieve certain operating efficiencies, however, the fabric of high volume sheet material will typically be wound on rolls of relatively large diameter. Without an adequate yardage deposited on each roll, the increment of time between the roll rolls change can sometimes be very short from a resource management and logistics point of view.

However, large diameter rolls, composed of high volume base sheets rolled relatively loose which may be susceptible to changes between the layers, may require special handling on the winding reel, during transportation from the reel to the conversion or finishing stations and / or the duration of the conversion and the finishing processes. For example, large spaces may be required - for a temporary storage, ducts may be required between the lines to be expanded and additional personnel and lifting trucks may be required for transportation. In addition, the line speeds in the conversion and finishing lines may need to be reduced to minimize the risks typically associated with unwinding loosely rolled rolls having low interlayer pressures.

SYNTHESIS OF THE INVENTION Briefly stated, in one aspect, the invention is directed to an apparatus for calendering a fabric of sheet material while being carried on or between one or more carrier fabrics. In a preferred embodiment, the apparatus includes a calendering section having the first and second calendering rollers forming a pressure point therebetween. At least one carrier fabric is placed between the first and second calendering rollers.

In an exemplary embodiment, at least one carrier fabric brings the fabric of sheet material from a drying station to a winding section. The first and second calendering rollers apply a load to the carrier fabric and to the fabric of sheet material as they pass through the point of pressure between the calendering rollers, to reduce the gauge, or the thickness of the material fabric. xie sheet. - - • .. ..._. _ ._-_ - --_. In a preferred embodiment, the calendering section includes the first and second carrier webs that have a sandwich shape or hold the fabric of sheet material therebetween. The first and second calendering rollers apply a load to the first and second carrier fabrics across the width thereof as for calendering, or pressing, the tissue held therebetween, so as to thereby reduce the gauge of the fabric. In a preferred embodiment, the first carrier fabric is essentially air impermeable, while the second carrier fabric is essentially air permeable.

In one embodiment, the first carrier fabric includes a reinforcing structure encapsulated in a polymer matrix. Preferably, the polymer matrix is elastic, so as to provide benefits similar to those achieved through the use of calendering a soft pressure point. In such an embodiment, the first and second calendering rolls are preferably made of steel or a similar material to form a hard pressure point therebetween.

Alternatively, when one or more non-elastic carrier fabrics are used, one or both of the first and second calender rollers may include, or be covered with, an elastic material that contacts one or more of the carrier fabrics, such as to form a soft point-of-pressure between the calendering rollers- first ... and. second.

In another aspect of the invention, there is provided a method for calendering the fabric of sheet material as it is carried by the carrier fabric. The method includes carrying the fabric of sheet material over one or more carrier fabrics through the calendering pressure point formed by the first and second calendering rollers and applying a load to the carrier fabric, and a sheet material carried by the same, as to reduce the thickness of the fabric of sheet material.

In yet another aspect of the invention, the calendering apparatus having the first and second calendering rollers can be provided with at least one carrier fabric placed therebetween on a conversion or finishing line for calendering or pressing a fabric of material of sheet to reduce the thickness of the fabric when the fabric is cut into slits additionally when being curled or otherwise processed on the conversion or finishing line.

The present invention provides significant advantages over other calendering processes and apparatus. For example, the apparatus allows the calendering of the fabric of sheet material while it is being carried by one or more carrier fabrics, and more specifically in one aspect, while it is being carried over one or more carrier fabrics from the section. of drying to the winding section. In this form, the open pulling of the forming process can be eliminated as to reduce costs and waste, but without having to calender the fabric of sheet material in its entirety in a separate conversion or finishing station. The resulting reduction in the thickness of the sheet material fabric allows the manufacturer to make smaller diameter rolls that have a sufficient yardage for manufacturing efficiencies and with more uniform interlayer pressures. In this way, the handling and manufacturing problems that can be encountered in the loose and large coils can be avoided.

The present invention, together with other objects and additional advantages, will be better understood with reference to the following detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Many of the features and dimensions depicted in the drawings, and in particular, the presentation of the thickness of the fabric of sheet material and the like, have been somewhat exaggerated for reasons of illustration and clarity.

Figure 1 is a schematic diagram of a paper making machine with a -de section. calendered. - _ ",. _ - - - - Figure 2 is a schematic diagram of an alternate incorporation of a paper making machine with a calendering section.

Figure 3 is a schematic diagram of an alternate incorporation of a paper making machine with a calendering section.

Figure 4 is a schematic diagram of an alternate embodiment of a calendering section.

Figure 5 is a schematic diagram of a conversion / finishing line with a calendering section.

Figure 6 is a schematic diagram of an alternate incorporation of a conversion / finishing line with a calendering section.

Figure 7 is a cross-sectional and partial view of a calendering section having a single carrier fabric holding a fabric of sheet material in a calender pile of soft pressure point.

Figure 8 is a side and partial cross-sectional view of a calendering section having the first-and second-second carrier fabrics supporting a fabric of sheet material in a calender stack of soft pressure point.

Figure 9 is a side and partial cross-sectional view of a calendering section having the first and second carrier fabrics supporting a fabric of sheet material in a calender stack of hard pressure point.

Figure 10 is a cross-sectional view of an incorporation of a carrier fabric.

Figure 11 is a cross-sectional view of an alternate incorporation of a carrier fabric.

Figure 12 is a cross-sectional view of an alternate incorporation of a carrier fabric.

Figure 13 is a cross-sectional view of an alternate incorporation of a carrier fabric.

DETAILED DESCRIPTION OF CURRENTLY PREFERRED INCORPORATIONS It should be understood that the term "fabric", as used herein, is intended to include a sheet material made of one or more layers of material so that a multi-layer sheet material is considered to be a "fabric" of sheet material, regardless of the number of layers, or the number of layers that make up each layer. In addition, the term "longitudinal" as used herein is intended to indicate the direction in which the tissue passes through the formation process in the machine direction, and no attempt is made to limit it to a particular length of the machine. woven, whether cut or otherwise. Similarly, the terms "down", "up", "forward", "forward", "left" and "right" as used herein are intended to indicate the direction relative to the views presented in the figures, and in particular, from a perspective when the fabric and fabrics are seen as they move from the forming section to the dryer section, and then to the calendering section, and finally to the winding section.

Referring to the drawings, figures 1 to 3 show various schematic diagrams for forming a fabric of sheet material without an open pull. An apparatus and method for making such a fabric are set forth in U.S. Patent No. 5,593,545 issued January 14, 1997 and U.S. Patent No. 5,591,309 issued January 7, 1997, both of which are incorporated herein by reference. However, it should be understood by one skilled in the art that the present invention can be used with other forming processes which use fabrics and / or webs to carry a fabric of sheet material without an open pull, and they can be used to calender a variety of fabrics of sheet material, including non-woven polymeric or tissue products, or products other than paper products, including for example, but not limited to, various plastic sheet materials.

As explained in the patents of the States United States Nos. 5,593,545 and 5,591,309, and as shown in Figures 1-3, several representative continuous drying processes for making non-creped continuous drying tissues are illustrated. For the sake of simplicity and clarity, the characteristics and parts in the various alternate embodiments that are essentially similar to features and parts mentioned in other embodiments are identified by the same reference number.

As best seen in Figures 1-3, the paper making machine includes a forming section 10, which includes a head box 12 and the inner and outer forming fabrics 14 and 16. The head box 12 deposits an aqueous suspension of fibers for making paper on an interior forming fabric 12 as it passes through a forming roller 18. The head box can be configured to deposit one or more layers of an aqueous solution - on - the fabric: - internal former ... For example, a three-layer head box can be used to form a tissue fabric for a single-layer toilet having a core layer composed of kraft fibers of soft northern refined wood NB-05 and outer layers of eucalyptus fibers. of Aracruz disunited in a formula of 30% / 40% / 30%, as explained in U.S. Patent No. 5,591,309. An expert in the art must understand that other formulas composed of other raw materials also work well. The outer forming fabric 16 serves to contain the fabric of sheet material which is wet, while passing over the forming roll and releasing some water. A suitable interior forming fabric is an Asten 856 fabric, while a suitable outer forming fabric is an Asten 866 fabric. One skilled in the art should understand that other fabrics, which are well known in the field of papermaking will also work. all right.

The wet fabric 20 is transferred from the inner forming fabric to a transfer section, which includes a wet end transfer fabric 22, with the aid of a vacuum transfer shoe 24. This transfer is preferably carried out with the transfer fabric moving at a slower speed than that of the forming fabric (rapid transfer) to impart stretch to the fabric of final sheet material. A suitable transfer cloth is an Albany Duotex-R-12 fabric, even though, again, an art expert should understand the other fabrics, which are well known in the field of paper making as well. they work fine.

The wet fabric is then transferred to a dryer section 30 which includes one or more continuous dryers 36 and a continuous drying fabric 32. A suitable continuous drying fabric is the Lindsay Wire T-216-3 fabric. It should be understood that one or more transfer, felt or press sections, or none of these can be provided between the forming section and the dryer section. The fabric of wet sheet material 20 is transferred to the continuous drying fabric with the aid of a vacuum transfer roller 34. The continuous drying fabric carries the fabric of sheet material over the continuous dryer 36, which blows air warm through the tissue to dry it while preserving the volume. An example continuous dryer is a Honeycomb dryer that operates at a temperature of up to 350 ° F. It should be understood that there may be more than one continuous dryer in series, depending on the speed and capacity of the dryer. For example, as shown in Figure 2, a single continuous dryer is provided, while the papermaking machines shown in Figures 1 and 3 include two continuous dryers in series. Preferably, the fabric of sheet material has a moisture content of less than or equal to about 10% by weight then it leaves the section-dryer. A fabric of sheet material having a moisture content less than or equal to 10% is referred to as a fabric of "dry" or "dried" sheet material for the purposes of the present invention.

As shown in the embodiments of Figures 1-3, the fabric of dried sheet material 2 is transferred from the continuous drying fabric from the dryer section to a transfer section 50. In particular, the fabric of sheet material 2 , which is dry, is transferred to a first carrier fabric 40 with the help of a transfer roller with vacuum 42. The fabric of sheet material, shortly after transfer, is placed in sandwich form between the first carrier fabric and the second carrier fabric 60 for positively controlling the sheet path. As shown in the embodiment of Figure 2, the second carrier fabric 60 then brings the fabric of dried sheet material to the winding pressure point formed between the reel drum 80 and the reel 82, where it is wound onto a roll 84 Alternatively, as shown in FIGS. 1 and 3, the second carrier fabric 60 passes over two winding drums 81 and 83 before returning to pick up the fabric of dried sheet material again. The fabric of the sheet material is transferred to a winding reel 82 where it is wound on the parent roller 84 or the construction roller at a point between two reels, winding * _A incorporation of an apparatus and a method for winding a fabric of sheet material on a roll is explained more fully in the United States of America patent application Series No. 08 / 934,346, entitled Method and Apparatus for Cutting Slits in a Sheet Material Fabric, filed on September 19 of 1997, and assigned to Kimberly-Clark Worldwide, Inc., the same assignee of the present application and which is incorporated herein by reference.

Alternatively, the fabric of sheet material can be transferred directly from the continuous drying fabric to the spool drum. This is achieved by using vacuum suction from inside the reel drum and / or pressurized air. The fabric is then rolled into a roll on a reel.

In yet another alternate embodiment (not shown), a vacuum drum is used to transfer the fabric from the continuous drying fabric and then pass the fabric on a reel drum for winding on a roll on the winding reel.

Referring to Figures 1-4, the transfer section 50 further includes a calendering section 70 according to the present invention. The calendering section 70 includes a calendering stack 90 composed of a first and a second calendered roller 2.and 94 :. • Preferably, the calendering rolls have a vertical configuration, with the first calendering roll placed directly on the second calendering roll. The first and second calendering rollers 92 and 94 form a pressure point therebetween.

The position and load between the first and second calendering rollers 92 and 94 can be controlled by any number of well-known and conventional calendering stack configurations, including hydraulic and pneumatic systems, position loading configurations, pressure settings of controlled clamping point and the like. A "pressure point" is generally defined as a pinch force between two surfaces. A "soft pressure point" is formed between two rollers where at least one, and perhaps both rollers include an elastic outer covering or covering. A "hard pressure point" is formed between two rolls having a non-elastic outer surface, for example, a steel roll.

In one embodiment of the calendering section 70, shown in Figures 1-3, the first calendering roll 92 is positioned within the first carrier fabric circuit 40 while the second calendering roll is placed within the second carrier fabric circuit. 60 so that the first and second carrier fabrics are placed between the first and second calendering rollers 92, 94 and pass through the pressure point formed between them.

In a preferred embodiment, the second carrier fabric 60 is essentially air impermeable so that the fabric of sheet material tends to adhere to the second carrier fabric 60 upon formation of an air pocket or vacuum therebetween, which preferably has a Air permeability lower than the first carrier fabric. Air permeability, which is the flow of air through a fabric while maintaining a differential air pressure of 0.5 inches across the fabric, is described in the ASTM D737 test method. An essentially air impermeable fabric has an air permeability of less than 50 cubic feet per minute per square foot, and preferably an air permeability of 0. Fabrics suitable for use as the second carrier fabric, include without limitation, an Asten fabric. Coated 960 (air permeability of 0), coated Asten fabric 866 (air permeability of 0). A fabric that is typically coated has a superior knuckle surface area, or a greater area of contact with the fabric of sheet material being held by it, than a non-coated fabric does.

Another fabric suitable for use as the second carrier fabric 60 includes a reinforcing structure 300 at least partially encapsulated in a polymer matrix 302 which is preferably elastic or compressible. The elastic or compressible material has elastomeric properties that allow the material to return to its original state after being deformed, for example, by loading at a pressure point, while an incompressible material, if compressed, will typically remain deformed as in the state compressed after the load is removed. By providing a fabric having a compressible material, benefits similar to those achieved through the calendering of the soft pressure point can be achieved, for example, an improved smoothness, a low clamping point pressure gauge reduction.

In addition, by providing a compressible surface layer on the side of the carrier fabric that contacts the fabric of sheet material, the surface of the fabric that is in contact with the fabric of sheet material can be made essentially monoplane and continuous as to essentially provide a contact area of 100% with the fabric of sheet material. The carrier fabric preferably has a thickness of from about 3 millimeters to about 7.5 millimeters. An exemplary carrier fabric having a compressible outer surface layer is a Caliber Reduction fabric (CR fabric) which is being jointly owned by Kimberly-Clark Corporation and Scapa Group North America Engineered Fabrics Division, located in Raleigh, North Carolina. __ How. Se: shown in Figures 10-13, the reinforcing structure 300 can be made of a woven or non-woven material, including a spiral link fabric, a composite perforated membrane, a woven textile fabric or a non-woven fibrous textile material. The encapsulating material 302, or polymer, is preferably a polyurethane, but it should be understood that it can also be made of a silicone polymer or other similar suitable materials. Preferably, the polymer has a Shore D hardness of 45-60 (about 92 Shore A) but may vary from 0 to 130 plastomer P & J, and it's antistatic. In an exemplary embodiment, the encapsulating material can be made of polyurethane elastomer produced by reacting a polyester based that can be set with a prepolymer. For example, a suitable polyurethane material can be made by combining in a ratio of 0.57: 1 by weight a polyol component (product reference No. 7850801), available from Hyperlast Limited, located in Stockport, Cheshire, United Kingdom, with an isocyanate component (product reference No. 2875021), also available from Hyperlast, according to the technical data sheet Hyperlast 7850801.

Predictable static charge equalization properties can also be achieved through the use of an antistatic polyurethane, or by incorporating electrically conductive materials, such as metal dust, metal. cut metal fibers or textile structures including metal - and / or carbon fibers or fibers in the polymer. The conductive material is preferably predominantly in the surface regions of the carrier fabric which can be used to dissipate the static charge, or alternatively, to maintain a uniform charge when acting on the other electrostatic control / dissipation devices. Devices of this nature, including, for example, but not limited to static rods, static guns, static tinsel and the like, can be used to induce or dissipate the electrostatic charge on the carrier fabric so as to attract or repel the fabric of sheet material carried by it.

The carrier fabrics shown in Figures 10-13 are also fully described in the Kingdom patent application.

United, entitled Transfer Fabric, and filed on the same date as the present application, and which is incorporated herein by reference.

Referring to Figure 10, an incorporation of the reinforcing structure 300 is formed as a spiral link fabric 304 similar to the fabric described in U.S. Patent No. 4,345,730, which is incorporated herein by reference and the which has interdigitated spiral loops 306 which provide members extending in the machine direction and threads in the transverse direction 308 which function as the TD binding wires - pins that join the spiral loops. The .ri.zoa. in spiral 306 and the uniting threads-308 may comprise threads and are preferably made of a polyester such as PET. The Stuffer yarns may be provided in the spiral link fabric to prevent uncontrollable passage of the liquid polyurethane through the spiral link fabric during a single side coating of the spiral link substrate. Preferably, the carrier fabric is formed as a monocoque structure wherein the reinforcing structure is completely impregnated with the polymer that is thick enough to cover both sides of the reinforcing structure, so as to provide an outer surface layer having a surface that makes contact with the fabric of sheet material, and in such a way that the reinforcing structure does not stop.

In the embodiment of Figure 11, the reinforcing structure 300 includes a base fabric made of polyester or polyamide, for example. The woven fabric substrate 310 is impregnated with and encapsulated by a layer of synthetic plastic material, which can be applied as a monocoque coating, or as separate layers on each side of the fabric substrate.

In yet another embodiment, shown in Figure 12, the carrier fabric includes a reinforcing structure 300 made of a woven fabric substrate 312, which is coated on one side, preferably the fabric support surface or the contact side with the fabric. fabric, with the polymer layer 302, such as a polyurethane layer.

In yet another embodiment, shown in Figure 13, the reinforcing structure 300 includes a composite membrane substrate 314, which may be similar to the membrane described in WO 92/02677 or GB A 2235705, both of which are Incorporate here by reference. The membrane substrate 314 is coated with a polymer 302, such as a polyurethane layer to form the carrier fabric. The membrane substrate 314 includes the upper and lower layers 318, 316, each composed of a multiplicity of openings 320 separated by the plains in the transverse direction and in the machine direction. The planes in the transverse direction in the upper layer 318 are preferably reinforced by the yarns in the transverse direction 322, while the plains in the machine direction in the lower layer 316 are reinforced with yarns in the machine direction (not shown). The membranes are preferably made of polyester, polyamide, polyether or polyurethane thermoplastic materials, while the yarns are preferably made of polyamide, polyester or an aramid material.

Other suitable reinforcing structures include wire tow, nonwoven felts and composites, including two or more of a textile fabric, woven textiles, wire tow, perforated membranes or spiral link fabrics. It should be understood that all of the reinforcement structures mentioned above can be coated on one or both sides with an encapsulating material, or these can be impregnated.

The carrier fabrics 40 and 60 can be sewn or not sewn (auger) depending on the configuration of the transfer or calendering section, and in particular, the configuration of the various reels and drums. If the fabric is sewn, the seam must have the ability to pass through a soft or hard calendering pressure point without marking the fabric of sheet material or without disturbing the dynamics of the pressure point. An exemplary embodiment of a seam is described in United Kingdom patent A 2231838 or European patent A 0,518,494, both of which are incorporated herein by reference.

In another embodiment, the underlying reinforcing structure, or the fabric, can be sewn with a pin, while the polymer matrix layer, which makes contact with the fabric, forms a flap along one end of the fabric, as to cover the seam when the fabric is installed. Any remaining separations along the seam are then filled with polyurethane.

The polymer matrix can protect the reinforcing structure against fibrillation, against compaction and wear, and can also hide the seam, where it is present. In addition, the polymer matrix provides a flat contact surface for the presentation to the fabric of sheet material, while allowing the carrier fabric to be sufficiently flexible to allow high roll wrapping angles and the ability to withstand loads up to 600 pounds per linear inch.

"In a preferred embodiment, the first carrier fabric 40 has a greater air permeability than the second carrier fabric 60 so that the fabric of dried sheet material is adhered to the second carrier fabric upon leaving the sandwich between the two fabrics. The first carrier fabric 40 is preferably and essentially permeable to air, and has an air permeability greater than or equal to 100 cubic feet per minute per square foot, and more preferably has an air permeability greater than or equal to 200 cubic feet per minute. per square foot to allow transfer of the fabric onto the first carrier fabric with the help of the vacuum transfer roller 42. Fabrics suitable for use as the first carrier fabric include, without limitation, a wide variety of fabrics such as Asten 866 , Asten 934, Asten 939, Asten 960, Albany 59M, Albany Doutex DD207, Lindsay 543, Lindsay 3070-A33, Appleton Mills Q53F and the like. ".: '-. _- - '- - _-. Preferably, the first and second carrier fabrics will have a contact area or such a high knuckle surface area (finely woven fabric), as possible, so that the lowest pressure point charges can be employed to achieve the reduction desired in the gauge of the sheet material fabric. In particular, an upper knuckle surface contact area will allow the forces applied along the length of the calendering rollers (measured in pounds per linear inch) or transverse to the longitudinal direction of the carrier fabrics to be more evenly distributed. through the knitting surface of sheet material to achieve higher clamping point pressures with lower loading pressures. In addition, a carrier fabric having a relatively smooth and continuous surface, such as a molded, coated or encapsulated carrier fabric described above, will achieve a better contact surface when placed in the form of a sandwich against an opposite fabric. Indeed, some of these types of carrier fabrics can essentially achieve a contact area of 100%.

It should be understood that while in the preferred embodiment the second carrier fabric is essentially air impermeable and the first carrier fabric is essentially air permeable, other combinations of permeable and impermeable fabrics will also work in any position of the first and second carrier fabrics. For example, when the second carrier fabric has a permeability greater than that of the first carrier fabric, an air sheet may be provided on the underside of the second carrier fabric to generate an air pressure such as to retain the fabric on the second fabric. carrier In addition to the difference in air permeability between the carrier fabrics, a slotted glue roller or an air shower and the use of static reductive material and static conductors in the first carrier fabric circuit can be used to further facilitate the separation of the fabric of sheet material from the first carrier fabric. In either case, it should be understood that one or both of the first and second carrier fabrics can be ~~ "coated or encapsulated with an elastic material to improve surface contact, even when such contact or material typically reduces or eliminates the air permeability of the carrier fabric.

The use of a second air permeable carrier fabric will typically allow the fabric to lie flat on the carrier fabric as it passes through the pressure point because any captured air is allowed to escape through the carrier fabric. However, the permeable carrier fabric can also create disturbances of the fabric as it is carried by the fabric. Conversely, even when using a waterproof carrier fabric. can lead to the formation of a bubble when air is trapped between the fabric and the carrier fabric when entering the pressure point, the waterproof carrier fabric typically provides a more stable fabric across the face of the carrier fabric upon exit tissue of the calendering pressure point.

Furthermore, by sandwiching the fabric between a permeable and a waterproof carrier fabric, the capture of air is essentially eliminated since the first carrier fabric, which is in tension, forces air between the fabric and the carrier fabrics , where excess air can escape through the permeable carrier fabric.

Referring to Figure 4, the calendering feed 90 can also be placed on the second carrier fabric 60 in front of the first carrier circuit so that only a single carrier fabric is placed between the first and second calender rolls. In this embodiment, the carrier fabric 60 is again preferably air impermeable, although the permeable fabrics can also be used. In addition, it should be understood that the carrier fabric can be coated or encapsulated with an elastic or compressible material. Where the second carrier fabric is essentially non-elastic, and does not include an elastic coating, the second carrier roller, which contacts the second carrier fabric, preferably includes an elastic material, while the first calender roller, which is directly in contact with the material fabric, the sheet is preferably made of a non-elastic material such as steel or the like. If the second carrier fabric includes an elastic outer surface that contacts the fabric of sheet material, both calender rolls can be made of steel. One skilled in the art should understand, however, that either or both of the first and second or second rollers can be made of a non-elastic steel material or a similar material, or they can have an elastic cover, regardless of the type of carrier fabric or carrier fabrics being passed between them.

In another aspect of the invention, shown in Figures 5 and 6, the calendering stack can be placed in a conversion or finishing line. Typically, after a fabric of dried sheet material is rolled onto a roll in the winding section of the paper making machine, it is transported to a conversion or finishing line where the fabric of sheet material is further cut. in slits, engraving, calendering, curling or otherwise processed. The conversion or finishing lines shown in Figures 5 and 6 are intended to be illustrative, rather than limiting, and such lines may be configured without open pulls to eliminate certain problems associated with them, as indicated above. As shown in Figures 5 and 6, the conversion / finishing line includes an unwinding section 500, a conversion or finishing section 520 and a winding section 540. In an embodiment of the conversion / finishing section, shown in figure 5, the fabric of sheet material which may already have been calendered on the paper making machine as explained above, is carried by a single carrier fabric 60, whose configuration is discussed above. A calendering stack 90 is positioned to calenuate the fabric of dried sheet material as it is carried by the carrier fabric through the pressure point formed between the first and second calender rolls 92 and 94.

Alternatively, as shown in Figure 6, the fabric of dried sheet material is worn, and put in the form of a sandwich between a first and a second carrier fabric 40 and 60. The first and second carrier fabric, with the fabric of material of sheet carried therebetween are passed through the pressure point formed between the first and second calender rollers to further calender the fabric of sheet material.

When using carrier fabrics which are not elastic, for example, which do not have a covering of elastic material such as polyurethane, it is desirable to use a calender pile of soft pressure point. In this configuration, best shown in Figure 7, at least one of the calendering rolls, and preferably the second calendering roll 94 which contacts the second carrier fabric, is coated or covered with an elastic material 97, such like a rubber or urethane. Rollers suitable for use in a calendering stack having a cover may have, but not be limited to, a hardness of 77 Shore A, 82 Shore A, 92 Shore A and 97 Shore A. For example, a roller covered with Resistex, available of Stowe Woodward, at a thickness of 0.75 to 1.00 inches will be adequate. Another suitable cover is Vacuum Static Cast Poiyurethane (part No. CS2510-85) produced by ABBA Rubber International.

It should be understood, however, that rollers having other values of hardness and thickness of the elastic material may also be suitable. A calendering roll having an elastic or deformable surface can be used for either the first or the second calendering roll, or both. In the preferred embodiment, the opposite calender roll 92, which contacts either the first air permeable carrier fabric or directly contacts the fabric of sheet material in a single fabrication configuration, is preferably a steel roll. , or a rigid cooled iron roller. An expert in the art will understand that other non-elastic and rigid materials also work such as aluminum, various compounds and the like.

- Alternatively, when using a carrier fabric having an elastic coating that contacts the fabric of sheet material, such as the fabric described above, with reference to Figures 10-13, both the first and second calender rolls are preferably made of steel, or of a non-elastic type material. However, it should be understood that steel rollers can be used at both locations of the calendering pile in combination with non-elastic fabrics, even though the life of the fabrics, and the ability to control the pressure point can be adversely affected. For this. ~ ^ ~ ^ - - ^ 31 In operation, a fabric of wet sheet material 20 is formed in the forming section and then transferred to the dryer section, either directly, or through a transfer section, of felt or Press (where the fabric is drained.) After passing around or through one or more dryers 36 in the drying section, the fabric of dried sheet material 2 is transferred to a transfer or calendering section which can To be formed within the transfer section, a fabric of dried sheet material made from tissue paper and formed in a continuous drying process typically has a thickness of from about .015 inches to about .050 inches when leaving the Fabric of sheet material The drying section An expert in the art should understand that other thicknesses of the sheet material can be obtained depending on the type of material and the forming process.

In the embodiment shown in Figures 1-3, the fabric of dried sheet material 2 is transferred from the dryer fabric 32 to the first carrier fabric 40, which then sandwiches the fabric with a second carrier fabric 60. The first and second carrier fabrics 40 and 60, with the fabric of dried sheet material 2 placed in the form of sandwich between them, pass through the pressure point formed between the first and second calendering rollers 92 and 94. Typically, depending on the amount of calendering desired (or caliper reduction) the type of fabrics and the corresponding knuckle surface areas and the type of calendering rollers that are being used (hard or soft), loads in the range of between about 0 and 400 pounds per linear inch are applied, and more preferably loads of between about 50 pounds per linear inch and 400 pounds per linear inch will provide a reduction of desired size in the range of about 20-50%, which has a minimal adverse effect on product attributes and touch properties. One skilled in the art should understand that more or fewer percentage reductions may be obtained depending, for example, on the type of sheet material, the amount of charge, and the line speed. For example, a fabric of sheet material made of tissue and formed in the UCTAD process can be calendered to a thickness of between about .020 inches to about .008 inches, depending on the final application of the fabric of sheet material. For example, in an application, a final thickness of .012 inches is the goal. Obviously, the additional load, and / or the alternate line speeds, can also reduce the size of the fabric, but with increasingly adverse effects on the properties and attributes of the fabric. In an alternate incorporation, the fabric can be calendered as it is supported by a single carrier fabric that carries the fabric through the calendering pressure point.

After the calendering operation, the fabric of dried sheet material 2 is transferred from the carrier fabric 60 onto a roller 84 at a pressure point formed between the spool 82 and the reel drum 80 as shown in Figure 2, or at a pressure point formed between the carrier fabric 60 and the spool 82 as shown in Fig. 1. Preferably, the fabric of sheet material can also be calendered in a conversion process with a soft pressure point calender for achieve the final attributes of the fabric. The fabric of sheet material can be calendered in an open draw in the conversion / finishing line or it can be calendered while being carried by a carrier fabric according to the present invention as described above.

The calendering apparatus and the method for calendering a fabric of sheet material provides significant advantages. First, the invention provides calendering of the fabric while it is held on a cloth, which allows the manufacturer to get rid of the open jails. Therefore, sheet breaks and the like are reduced, while simultaneously allowing the manufacture of a more desirable and softer sheet material product. In addition, the invention provides a gauge reduction which greatly reduces the diameter of the roll for a given length of a fabric of sheet material and provides higher and more uniform interlayer pressures. The firmer and smaller rolls can then be more easily handled and processed in the additional conversion and finishing operations.

Although the present invention has been described with reference to preferred embodiments, those skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the invention. As such, it is intended that the above detailed description be seen as illustrative rather than limiting and that they are the appended claims including all equivalents, which are intended to define the scope of the invention.

Claims

R E I V I N D I C A C I O N S

1. A calendering apparatus for reducing the thickness of a fabric of dried sheet material, said calendering apparatus comprises: a first and a second calender roll forming a pressure point therebetween; at least one carrier fabric placed between said first and second calendering rollers, said at least one carrier fabric being adapted to bring said fabric of dried sheet material through the pressure point, whereby the thickness of the fabric of material The dried sheet is reduced and said fabric gives dried sheet material. carried by said at least one carrier fabric passes through the pressure point.

2. The invention as claimed in clause 1, characterized in that said at least one carrier fabric is essentially impermeable to air.

3. The invention as claimed in clause 1, characterized in that said at least one carrier fabric comprises a first carrier web and a second carrier web, said first and second carrier webs are adapted to carry said web material between the webs. same as the fabric of sheet material passes through the pressure point between said first and second calendering rollers.

4. The invention as claimed in clause 3, characterized in that said first carrier fabric is essentially permeable to air and wherein said second carrier fabric is essentially impermeable to air.

5. The invention as claimed in clause 4, characterized in that said air permeability of said first carrier fabric is about 100 cubic feet per minute per square foot or greater.

6. The invention as claimed in clause 4, characterized in that said permeability to. air of said second carrier fabric is about 20 cubic feet per minute per square foot or less.

7. The invention as claimed in clause 2, characterized in that said at least one carrier fabric comprises a reinforcing structure encapsulated at least partially in a polymer.

8. The invention as claimed in clause 7, characterized in that said polymer is a polyurethane polymer.

9. The invention as claimed in clause 1, characterized in that at least one of said first and second calendering rollers is made of steel.

10. The invention as claimed in clause 1, characterized in that at least one of said first and second calendering rollers comprises an elastic material that makes contact with at least one carrier fabric.

11. The invention as claimed in clause 9, characterized in that said other one of the first and second calendering rollers is made of steel.

12. The invention as claimed in clause "1, characterized in that said at least one carrier fabric has a controllable static conductivity.

13. The invention as claimed in clause 12, characterized in that said at least one carrier fabric comprises an electrically conductive material.

14. An apparatus for making a fabric of sheet material comprising: a forming section comprising at least one forming fabric adapted to hold said fabric of sheet material as said fabric of sheet material is formed thereon; a dryer section adapted to dry said fabric of sheet material as the fabric of sheet material is brought through said dryer section; a winding section; Y a calendering section comprising the first and second calendering rollers forming a pressure point and at least one carrier fabric placed between said first and second calendering rollers, said carrier fabric being adapted for. carrying said sheet material fabric as it is transferred from the sheet material from said dryer section to said winding section and to hold said fabric from sheet material as it passes through the point of pressure between the calendering rolls first. and second.

15. The invention as claimed in clause 14, characterized in that said at least one carrier fabric is essentially air impermeable.

16. The invention as claimed in clause 14, characterized in that said at least one carrier fabric comprises a first carrier web and a second carrier web, said first and second carrier webs are adapted to carry said web material between the webs. same as the fabric of sheet material passes through the pressure point between said first and second calendering rollers.

17. The invention as claimed in clause 16, characterized in that said first carrier fabric is essentially permeable to air and wherein said second carrier fabric is essentially air impermeable.

18. The invention as claimed in clause 17, characterized in that said air permeability of said first carrier fabric is about 100 cubic feet per minute per square foot or greater, and said air permeability of said second carrier fabric is "Less than or equal to around 20 cubic feet per minute.

19. The invention as claimed in clause 15, characterized in that said at least one carrier fabric comprises a reinforcing structure at least partially encapsulated in a polymer.

20. The invention as claimed in clause 19, characterized in that said polymer is a polyurethane polymer.

21. The invention as claimed in clause 14, characterized in that at least one of said first and second calendering rollers is made of steel.

22. The invention as claimed in clause 14, characterized in that at least one of said first and second calendering rollers comprises an elastic material contacting said at least one carrier fabric.

23. The invention as claimed in clause 22, characterized in that said other one of said first and second calendering rollers is steel.

24. The invention as claimed in clause 14, characterized in that said winding section comprises a spool adapted to wind said fabric of sheet material in a roll when the fabric of sheet material is transferred from the calendering section to said spool .

25. The invention as claimed in clause 14, characterized in that said dryer section comprises a dryer fabric adapted to bring said fabric of sheet material through said dryer section when the fabric of sheet material is transferred from said at least a forming fabric.

26. The invention as claimed in clause 25, further characterized in that it comprises at least one transfer fabric adapted to transfer said fabric of sheet material from said at least one forming fabric to said at least one drying fabric.

27. The invention as claimed in clause 14, characterized in that said first and second calendering rollers apply a load therebetween in the range of between about 0 pounds per linear inch and about 400 pounds per linear inch.

28. An apparatus for making a fabric of sheet material comprising:. -. "- - - J -, - - a forming section comprising at least one forming fabric adapted to hold said fabric of sheet material as the fabric of sheet material is formed thereon; a dryer section comprising at least one dryer fabric adapted to bring said fabric of sheet material through the dryer section when the fabric of sheet material is transferred from said at least one forming fabric; and a calendering section comprising said first and second calendering rollers forming a pressure point and the first and second carrier fabrics positioned between said first and second calendering rollers., wherein said first carrier fabric is essentially permeable to air and wherein said second carrier fabric is essentially air impermeable, said first and second carrier fabrics are adapted to carry said fabric of sheet material therebetween upon transfer of the fabric of the carrier. sheet material from the dryer section and to hold said fabric of sheet material as it passes through the point of pressure between the first and second calender rolls.

29. A method for calendering a fabric of sheet material, said method comprises: transferring said fabric of sheet material from a dryer section to at least one carrier fabric, said fabric of sheet material having a first thickness upon leaving said dryer section; bringing said fabric of sheet material over said at least one carrier fabric through a calendering pressure point, said calendering pressure point being formed by a first and a second calender rolls; and reducing the thickness of said fabric of sheet material from said first thickness to a second thickness by applying a load to said carrier fabric and said sheet material carried with said first and second calendering rollers at said pressure point.

30. The invention as claimed in clause 29, characterized in that said at least one carrier fabric is essentially air impermeable.

31. The invention as claimed in clause 29, characterized in that said at least one carrier fabric comprises a first carrier fabric and a second carrier fabric, said first and second carrier fabrics carry said fabric of sheet material therebetween, Such a load is applied to said first and second carrier fabrics by passing the fabric of sheet material through the pressure point between said first and second calender rollers.

32. The invention as claimed in clause 31, characterized in that said first carrier fabric is essentially permeable to air and wherein said second carrier fabric is essentially impermeable to air.

33. The invention as claimed in clause 32, characterized in that said air permeability of the first carrier fabric is about 100 cubic feet per minute per square foot or greater.

34. The invention as claimed in clause 29, characterized in that said at least one carrier fabric comprises a reinforcing structure encapsulated at least partially in a polymer.

35. The invention as claimed in clause 34, characterized in that said polymer is a polyurethane polymer.

36. The invention as claimed in clause 29, characterized in that at least one of the first and second calendered rolls is made of steel.

37. The invention as claimed in clause 29, characterized in that at least one of said first and second calendering rollers comprises an elastic material contacting said at least one carrier fabric.

38. The invention as claimed in clause 37, characterized in that said other one of said first and second calendering rollers is steel.

39. The invention as claimed in clause 29, further characterized in that it comprises depositing an aqueous suspension of fiber on a forming fabric to form a fabric of wet sheet material, transferring said fabric of wet sheet material from said forming fabric to said fabric. said dryer section, and drying said fabric of wet sheet material in the dryer section to form a fabric of dried sheet material.

40. The invention as claimed in clause 29, further characterized in that it comprises winding said fabric of sheet material in a roll as the fabric of sheet material is transferred from said calendering section to a spool.

41. The invention as claimed in clause 39, characterized in that said step of drying said fabric of sheet material comprises holding said fabric of sheet material on a dryer fabric as it is carried through the drying section.

42. The invention as claimed in clause 41, further characterized in that said step of transferring said fabric of sheet material from said forming section to said drying section comprises transferring said fabric of sheet material from said at least one forming fabric. to at least one transfer fabric and then transferring said fabric of sheet material from said at least one transfer fabric to said at least one dryer fabric.

43. The invention as claimed in clause 29, characterized in that said step of reducing the thickness of said fabric of sheet material comprises applying a load of between about 50 pounds per linear inch to about 400 pounds per linear inch to said at least one carrier fabric.

44. The invention as claimed in clause 29, characterized in that said second thickness is from about 20% to about 50% of said first thickness. - - - - - - - - -

45. The invention as claimed in clause 29, characterized in that said first thickness of said fabric of sheet material is between about 0.020 inches and about 0.050 inches, and wherein said second thickness of said fabric of sheet material is between about 0.008 inches and about 0.020 inches.

46. A method for calendering a fabric of dried sheet material, said method comprising: providing a fabric of dried sheet material having a moisture content of less than or equal to about 10%; Y bringing said fabric of dried sheet material onto at least one carrier fabric through a calendering pressure point, said calendering pressure point being formed by the first and second calendering rolls.

47. The invention as claimed in clause 46, characterized in that said at least one carrier fabric is impermeable to air.

48. The invention as claimed in clause 46, characterized in that said at least one carrier fabric comprises a first and second carrier fabric carrying said fabric of dried sheet material therebetween.

49. The invention as claimed in clause 48, characterized in that said first carrier fabric is essentially permeable to air and wherein said second carrier fabric is essentially air impermeable.

50. The invention as claimed in clause 47, characterized in that said at least one carrier fabric comprises a reinforcing structure at least partially encapsulated in a polymer.

51. A fabric of dried sheet material having a reduced gauge made by the method as claimed in clause 46.

52. A method to reduce the size of a fabric of sheet material, said method comprises: providing a carrier fabric comprising a reinforcing structure encapsulated at least partially in a polymer matrix, said polymer matrix defining a continuous and essentially monoplane tissue contact surface; holding a fabric of sheet material on said tissue contacting surface of said carrier fabric, said fabric of sheet material having a first thickness; Y passing said carrier fabric with said fabric of sheet material held thereon through a pressure point, said fabric of sheet material having a second thickness after passing through said pressure point, wherein said second thickness is smaller than said first thickness.

53. The invention as claimed in clause 52, characterized in that said carrier fabric is a first carrier fabric, and further comprises the step of providing a second carrier fabric, wherein said fabric of sheet material is supported between said carrier fabrics sprimera and second, and wherein said step of passing said carrier fabric with said fabric of sheet material held thereon through a pressure point comprises passing said first and second carrier fabric with said fabric of sheet material held between the themselves through said pressure point. SUMMARY An apparatus for calendering a fabric of sheet material being carried on or between one or more carrier fabrics, in a referred embodiment, the apparatus includes a calendering section having the first and second calendering rollers forming a pressure point. between them. At least one carrier fabric is placed between the first and second calendering rollers. The first and second calendering rollers apply a load to the carrier fabric and a fabric of sheet material as they pass through the pressure point between the calendering rollers to reduce the gauge., or the thickness of the fabric of sheet material. A method for calendering the sheet material fabric includes bringing the fabric of sheet material over one or more carrier fabrics through the calendering pressure point formed by the first and second calender rolls and applying a load to the carrier fabric. and the sheet material carried thereon, such as to reduce the thickness of the web material.