MXPA98010072A - Method for improved fast transfer to produce a high volume without macrodoble - Google Patents

Abstract

The present invention relates to a method for improving the rapid transfer of a tissue, such as tissue tissue. The method provides greater angles of convergence (AC) and divergence (AD) of the carrier fabric and of the transfer fabric at the transfer point by deflecting the carrier fabric to the transfer fabric using a deflection element, such as a Roller placed on the vacuum transfer head. The greater angles of convergence and divergence minimize the potential for undesirable macrodoses to be formed in the tissue during the transfer.

Description

METHOD FOR TRANSFER R REQUEST IMPROVED TO PRODUCE A HIGH VOLUME WITHOUT MACRODOBLECES Background In the art of papermaking, many processes are based on wet formation, whereby a dilute aqueous solution of papermaking fibers is deposited on a moving fabric or between two movable porous bands. The solution is drained through the fabric or fabrics to create an embryonic tissue of wet fibers, which are then further processed in a variety of ways, optionally including operations such as pressing, wet molding, rapid transfer, continuous drying, contact drying, creping, micro-creping, coating, calendering, etching, and the like to create a dry woven paper with the desired properties. For many products such as towels, facial and bath paper, absorbent components in absorbent articles, cleansers and the like, the desired attributes may include any of the following: high volume, high absorbency, high wet elasticity, a volume high internal hollow, flexibility, and a high resistance or extensibility under tension. An operation which may be useful to improve some of these properties is the shortening of the tissue. Shortening the weave can achieve a variety of physical properties depending on the mode of execution. One embodiment is the transfer of a fabric from a carrier fabric to a transfer fabric (either a dryer or an intermediate fabric or felt), with the transfer fabric moving at an essentially slower speed than that of the fabric. carrier Such a method involves a differential speed transfer to a slower fabric called fast transfer. The oldest known example of the fast transfer is that of G.W. Dorfel of German Patent No. 2,112,395, entitled "Process and Apparatus for the Treatment of Paper Tissue in a Paper Machine" issued October 7, 1971, which teaches the transfer of a tissue after a pressure point on a felt running at a second pressure point of a press section with the second pressure point running more slowly than the first. This transfer process eliminates blade stretching that occurs frequently during a squeegee and is said to improve the strength properties of the blade. In a similar way, P.J. Valkama in U.S. Patent No. 4,225,384, entitled "Method of Operation of a Machine and Paper, Particularly a Press Section of the same", issued September 30, 1980, teaches a method for making a paper Stretchable or a stretchable card that includes the shortening of the fabric through the Finnish patent 44,334.

An initial example of rapid transfer for tissue is shown by Christian Schiel in U.S. Patent No. 4,072,557, "A Method and Apparatus for Shrinking a Tissue Displacement of Fibrous Material", issued on February 7. from 1978. The Shiel method is presented as an alternative for dry creping for fabrics with insufficient resistance for creping. The process gives a tension in the direction of the upper machine that if the fabric were shortened by the same degree by creping. Rapid transfer to a slower moving fabric occurs through a centrifugal force transfer head, applying differential pneumatic pressure across the wires to move the sheet to the new fabric. The objective is a shrink fabric with a high resistance, not a high volume. Like the present invention, Shiel teaches a rapid transfer configuration in which the carrier fabric deflects upward toward a transfer fabric. Shiel also teaches the use of a small radius of curvature (less than five inches) in the transfer head (here called the carrier fabric deflection element), teaches the use of a suction box above the transfer fabric, and teaches the use of an air pressure delivered through a nozzle in the carrier fabric deflection element to apply a differential pressure through the fabric to effect your transfer. Schiel's drawings show that the transfer fabric moves in a single plane, not deflected by the blow of the carrier fabric deflection element, but any contact force between the two wires will result in the deflection and beating of a wire with the other, reducing the convergence and divergence angles and increasing the size of the contact zone.

Another method more suitable for soft tissue is that of E. ells and T.A. Hensler in U.S. Patent No. 4,440,597 entitled "Concomitant Process and Wet Microcontact Paper" issued April 3, 1984. Wells and Hensler teach the use of a transfer fabric having a hollow volume greater than that of the carrier fabric so that the blade was forced into the hollow volume additional to that of its acceleration. A convex and curved transfer head with a central vacuum slot was used to force the two wires together and to transfer the tissue. Indeed, the invention of Wells and Hensler is much the same as that of Schiel except that the paper weave in Schiel is transferred out of the wire in contact with the transfer head, while in the Wells and Hensler it is transferred on the wire in contact with the transfer head, with positive pressure from the transfer head necessary for transfer in Schiel, while vacuum pressures are required for transfer in Wells and Hensler. The vacuum intake shoe used in Wells and Hensler was related to that taught in commonly assigned US Pat. No. 3,309,263 to R.E. Grobe, "Take and Transfer of Fabric for a Papermaking Machine" granted on March 14, 1967. A related tissue transfer technology is the use of a suction roller for the transfer of a fabric from the forming fabric without the compression at a pressure point as found in Canadian Patent No. 873,651 issued to DC Cronin on June 22, 1971.

The rapid transfer in a non-creped process to make paper towels was shown by R.F. Cook and D.S. Westbrook in a United States of America Patent No. 5,048,589, "Cleaned or Unhandled Towel" issued on September 17, 1991, incorporated herein by reference. The fabric is transferred from the forming fabric to a continuous drying fabric with a differential speed of less than about 10%. A related concept is taught by Bernard Klowak in U.S. Patent No. 4,849,054. "High Volume Recorded Fiber Sheet Material and Apparatus and Method for the Manufacture of the Same", granted on July 18, 1989. In the Klowak method, the fabric is pressed at a solids level of about 30% and transfers to a smooth roller, followed by rapid transfer from the roller onto a highly textured three-dimensional fabric in order to etch the found sheet and the transfer cloth. In that case, there is a relatively small microcompaction of the sheet during rapid transfer (evidenced by very high tissue tensile strength); the increased volume is largely due to the fact that the sheet is macroscopically shaped on the textured fabric (external volume). In contrast, rapid transfer to a relatively flat low volume transfer fabric can result in a significant volume of the sheet at a microscopic level (internal volume) while maintaining a relatively smooth structure macroscopically. Such tissue is taught by T.E. Farrington et al., In the commonly-co-pending application of Great Britain's application 2,279,372 A, "A Soft Tissue Paper", published on January 4, 1995. In the Farrington et al. Method, rapid transfer preferably occurs between the forming fabric and an additional and subsequent relatively soft transfer fabric, from which the sheet will be transferred back onto a continuous dryer fabric (also with an optional quick transfer). This method is related to that taught by Steven A. Engel et al., In the co-pending commonly assigned patent application No. 08 / 036,649 entitled "Method for Making Non-creped and Soft Continuous Drying Sheets" filed on March 24 1993. One or more transfer fabrics are placed between the forming fabric and a subsequent continuous drying fabric. During the transfer of sheet from the forming fabric to the transfer fabric or the transfer from the transfer fabric to the continuous drying fabric, or both, the transfer is from one fabric to another fabric moving at an essentially slower speed. Such a method may result in a stretch in the machine direction (as determined with a standard sheet tension resistance test of a conditioned sheet) of around 5 about 40 percent on an uncreped sheet .

An important aspect of the rapid transfer method shown by Engel et al. Is that the region of contact between the two wires moving at different speeds must be small. In the experimental work, it was learned that the rapid transfer shoe used in the Wells Hensler method significantly limits the success of the rapid transfer process. Under many conditions, the product can be spoiled by the "macrodobleces", which appear as being regions where part of the sheet has been laughed and has doubled back on itself. Macrodobles are believed to be a potential problem in all known forms of rapid transfer, but the severity of the problem or the conditions in which it is feasible will be strongly determined by the nature of the rapid transfer process. Wells and Hensler teach the use of a curved transfer shoe with a constant radius of curvature which is depressed in the extension of the carrier fabric, allowing a significant length of contact between the two fabrics, including contact before and after the groove of emptiness. Under many other desirable operating conditions, the prolonged extension of the area in which the sheet is transferred from one fabric to the other is believed to allow bending of the sheet to occur, resulting in macrodobles. In contrast, Engel et al. Teach the use of a transfer shoe where the carrier fabric and the transfer fabric converge and diverge at the leading edge of the vacuum slot (apparently relying on the presumption that the fabrics are not deformed by the presence of the vacuum and that the fabrics and the fabric do not have thickness, but in fact the contact zone will be finite). By moving toward the "point of contact" between the two tissues, Engel and others provide a rapid transfer system with much more flexibility in terms of successful operating conditions and one which served better to provide internal debranching and bulging. the sheet, rather than merely conforming a sheet to a fabric with a high hollow volume. The use of a relatively smooth transfer fabric is especially useful to achieve the goal of increasing volume and internal smoothness.

Other methods of leaf shortening are known, including dry micro-creping, wet creping and dry creping, and the methods involve transferring between a fabric on a solid roll to a slower moving fabric. Such a method is taught for compacting newspaper to increase thickness in German application DE 1696176, published on September 30, 1976 by H.S. Welsh The invention of Welsh involves a band of movement in contact with the substantial distance with a faster moving roller, said roller entering the area of flB contact with a tissue of paper subject to its surface. The speed difference is said to increase the thickness of the fabric 5 by 2-4%. The fabric is required to be a dryness of 30-50%. A patent granted to S.B. Weldon entitled "Apparatus and process for treating a woven material", United States Patent No. 4,551,199, issued November 5, 1985, describes a similar concept, in which a The textured transfer fabric engages a fabric on a faster moving roller, allowing the fabric to be compressed in the hollow spaces of the fabric and thus closed in place. The process is said to crep, record, add volume and increase the stretch of the blade to be treated. In addition to the vacuum rollers and the vacuum transfer heads, in order to effect the transfer of a sheet from one tissue to another, the jets of. air and air blowers. M.M. Murray and B.H. Andrews in the US Patent No. 3,351,521 entitled "Transfer Mechanism for a Weaving", issued November 7, 1967, teaches the use of an air jet to facilitate the transfer of a wet tissue to a felt . In this system, the air jet serves to release the fabric to be fastened firmly to the forming fabric. The loose paper web is moved through a substantial open loop and is folded around a roller before it is placed in proximity to the felt. The air jet does not place the wet fabric against the felt. The felt seems to be several feet away from the air jet and the vector defined by the flow of the air nozzle does not even interconnect with the felt. There is no mechanism to achieve rapid transfer with this system.

L.B. Osterberg and B.A. Unneberg in Canadian Patent No. 1,029,998"Arrangement for Separating a Wire Paper Fabric in a Papermaking Machine", issued on April 25, 1978, teaches the use of air jets to remove a Fourdrinier tissue when it fails the normal transfer system (for example, after a tissue break or during the ignition). Using air blades or vacuum boxes to help transfer between fabrics (including press felts) is well known, and some small degrees of differential speed are probably common in such processes even when a differential speed is not desired. Positive pulls, in which the leaf is slightly stretched, are very common, but it is conceivable that negative pulls, (resulting in a rapid transfer) have occurred regularly in the commercial operation of conventional leaf transfers. The degree of rapid transfer in such cases is possibly in the order of 5% or less.

Despite the gains made by Engel and others, the rapid transfer in their processes does not yet occur over a finite extension of simultaneous contact between the two wires that move differentially. Therefore, and in the need for a rapid transfer method that provides better control of the geometry of the contact region and allows the control of the contact force between the fabrics, thereby producing an improved internal volume without macrodoblings.

Synthesis of the Invention In general, the invention is a modified fast transfer process for use in wet-laid paper manufacturing processes in which the contact between the carrier fabric and the transfer fabric in the fast transfer zone is defined by a shoe, a roller, or other convex support under the carrier fabric coupled with a transfer shoe with opposite vacuum, which is preferably convex, either curved or angled, in contact with the transfer fabric. This method allows greater angles of convergence and divergence between the two fabrics to be achieved, possibly reducing the length of the contact zone between the two fabrics by a small arbitrary distance or eliminating it altogether, optionally with the aid of a jet or blade. of air in a carrier fabric support shoe. Reducing the contact region between the two fabrics helps reduce the danger of macrodobles and other forms of leaf damage, especially at higher levels of rapid transfer. The reduced contact zone also assists the transfer fabric to obtain an arbitrary texture without the risk of damage to the fabric by excessive friction of the highlighted elements of the transfer fabric.

Therefore, in one aspect, the present invention resides in a method for transferring a fabric held by a carrier fabric to a slower moving transfer fabric wherein the transfer fabric and the carrier fabric converge and diverge as the fabric passes through. transfer onto a vacuum shoe having a vacuum groove and the carrier fabric passes over a deflection element, wherein the vacuum shoe deflects the transfer fabric towards the carrier fabric and the deflection element deflects the carrier fabric towards the shoe of vacuum so that the tissue is transferred to the transfer fabric as the fabric passes over the vacuum slot.

In some embodiments, it is possible for a small but finite gap to be maintained between the fabrics, even when the shear forces at one point of contact may be desirable in many cases for internal debranching of the fabric. Also, the method of this invention can provide additional pressure driving forces for sheet transfer beyond the inherently limited range of pressure with vacuum by providing a lower support shoe under the carrier fabric that not only controls the geometry of the transfer region, but also provide a jet of air or air jets to lift the sheet out of the carrier fabric, decelerating the sheet as desired, and placing it in contact with the transfer fabric. In addition, the method of this invention can provide means for improving control over the geometry and physical operation of the transfer region so that adjustments and modifications can be made easily while the paper machine continues to operate. Such modifications include changing the contact force of the supporting roller or shoe of the carrier fabric, controlling the force profile in the direction of the cross machine, controlling the axial and transverse location of the support shoe as well as the possible inclination of the the shoe; control the air flow rate when the nozzles are used in the carrier cloth support shoe; and controlling the position of the transfer head as well as the level of vacuum in said transfer head.

In the preferred embodiments, the effective angles of convergence and divergence of the two wires may be about 5 degrees or more, preferably about 10 degrees or more, more preferably 20 degrees or more, even more preferably 30 degrees or more. more, and more preferably 45 degrees or more, with another more preferable embodiment comprising the range of 40 to 80 degrees. The divergence angle is believed to be more critical to the success of the invention, so that the angle of convergence can be significantly lower than the divergence angle while still falling within the scope of the present invention. The angles between the fabrics are defined by the angle between the tangents to the wires at a distance of 2 inches up from the leading edge of the slot with vacuum or from the openings with vacuum in the transfer head for the angle of convergence, and at a distance of 2 inches down from the edge of the vacuum slot or from the openings with vacuum in the transfer head for the divergence angle. An alternative definition of the angle, called "convergence angle" alternate "and" alternate divergence angle ", respectively, is identical to the previous definition but at distances of 4 inches rather than two inches from the ends of the empty atk slot or region of openings with vacuum.

Brief Description of the Drawings Figures 1A and IB illustrate the prior art rapid transfer systems.

Figure 2 is a schematic representation of a "macrodoses" in a fabric.

Figure 3 is a schematic representation of a rapid transfer method according to this invention.

Figure 4 is a schematic representation of an alternative method according to this invention.

Figure 5 is a more detailed schematic illustation of the transfer zone in the method of this invention.

Figure 6 is a schematic illustration similar to that of Figure 5, but exhibiting a stationary deflection element with an interior air jet.

Detailed description of the Drawing Referring to Figure 1A, a prior art rapid transfer system is shown schematically as shown by the previously discussed US Pat. No. 4,072,557 to Schiel. Shown is the carrier fabric 1, a pressurized transfer head 2, a transfer fabric 3 and a suction box 4.

Figure IB also schematically illustrates a process of rapid transfer of the prior art as taught by the United States of America Patent Nc. 4,440,597 granted to Wells and others. A vacuum pick-up shoe 5 is shown which deflects the transfer fabric 3 and the carrier cloth 1 in the transfer zone.

Figure 2 is a simple schematic illustration of a "macrodoses", in which certain regions of the tissue are folded over the tissue.

Figure 3 is a schematic illustration of a rapid transfer process according to this invention. The carrier fabric 1 and the transfer fabric 3 are shown converging and diverging in the transfer zone. The carrier fabric is deflected out of its plane towards the transfer fabric by the deflection element 6. The transfer fabric is deflected out of its plane between the surrounding rollers towards the carrier fabric by the vacuum shoe 5. Rather than the contact being achieved by hitting the transfer shoe in the plane of the carrier fabric, the opposite is achieved when the carrier fabric is pushed towards the transfer head.

Figure 4 is a schematic illustration of an alternate embodiment of this invention, wherein the divergence angle between the carrier fabric and the transfer fabric is further increased by the presence of a second deflection element 8 downstream of the transfer point so that the bare carrier fabric (no longer carrying a fabric) deflects away from the transfer fabric. Such a deflection roller can also be placed upstream of the transfer point to increase the angle of convergence, but the roller will have to contact the wet paper tissue and may cause undesired compression of the fabric. For By deflecting the carrier fabric out of the transfer fabric without mechanically compressing the paper tissue, a vacuum box may be desirable to provide a downward force of the carrier fabric and a tissue paper forward of the transfer zone. The vacuum box can be coupled with a steam box on the side of the paper fabric of the carrier fabric to preheat the fabric and improve water removal and possibly improve the properties of the fabric for the rapid transfer phase. The deflection of the carrier fabric upwards from the transfer zone and the additional drain can also be achieved by the use of air jets or an air press, where the air, including the heated air, is struck against the wet tissue, possibly with the vacuum suction down.

The present invention differs over both Schiel and Wells and Henslet in that it provides two deflection elements, one behind each wire approaching the transfer zone, to control the angles of convergence and divergence and to minimize the length of the contact area, in contrast to the methods of the related art in which the wire deflected by the transfer shoe hits the plane of the opposite wire. The present invention is further distinguished from the prior art in that it provides the possibility of a finite separation between the wires through which rapid transfer of tissue takes place without contact between the two wires. Achieving this latest incorporation will require the use of a narrower air knife rather than a mere different pressure over a wide area, with the appropriate directed narrow water jet to lift and decelerate the fabric and press it against the transfer fabric that moves slower The details of the transfer zone in an embodiment of this invention are shown in Figure 5. The vacuum slot 10 is shown inside the vacuum intake shoe 5, the fabric 11 being transferred from the carrier fabric 1 to the fabric transfer 3, the deflection element 6, the angle of divergence "AD" and the angle of convergence "AC". The deflection element of the carrier fabric pushes the fabric and the cloth inside the transfer zone. Figure 5 shows the transfer zone established at the leading edge 12 of the vacuum transfer slot, which is a preferred embodiment, but it is recognized that the relative positions of the deflection element of the carrier fabric and of the transfer shoe can adjust to establish a transfer zone in alternate locations relative to the vacuum transfer shoe, including a tail edge 13 of the transfer slot with vacuum. The transfer is assisted by suction through a vacuum groove or other openings in the transfer shoe or in the suction roller (not shown). Preferably, a transfer shoe was used as taught by Engel and others. Other possible vacuum shoe designs include those of Wells and Hensler as well as those of Grobe and others. The carrier fabric deflection element can be either a stationary shoe or a moving element such as a small radius roller. To help maintain a small point of contact, the effective radius of curvature of the deflection element must be small, and in particular it must be less than about 14 inches, preferably less than about 8 inches, preferably less than about 5 inches, more preferably less than 3 inches, still more preferably less than 2 inches, with the values especially preferred being between 0.2 and 2 inches and particularly within about 0.4 and 1.5 inches. The deformable elements must be included in the used shoes or rollers, or in their respective support means, in order to help maintain a constant separation or a constant compressive load between the two elements. The vacuum slot should be narrow, preferably less than 3 inches, more preferably less than 1.5 inches, more preferably less than 1 inch, and more preferably still less than 0.5 inches.

Since the separation of a carrier fabric from a solid surface can induce vacuum forces at the point of separation, which can be opposed to the transfer of the fabric, it is preferred that the carrier fabric deflection element be equipped with means to break the seal between the carrier fabric and the deflection element. Such means for any stationary rotary deflection element may include grooves, blind holes, channels or grooves on the surface of the element to provide access to the flow of air from the surrounding atmosphere to the point of separation. Other means for breaking the seal between the carrier fabric and the deflection element include the use of a porous surface such as a sintered metal or a porous ceramic. Alternatively, the element may be internally equipped with means for conveying air or steam supplied from within the element itself to the outer surface in order to avoid a vacuum seal. Such means include channels, slots or other openings for conveying the pressurized air to the region of separation on the outer surface on the outer surface, or an integrally porous construction, at least in part, to allow the air to reach a narrow zone or wide on the outside of the deflection element. In an embodiment, a jet of air or steam passes through the deflection element and not only serves to break the vacuum, but it also provides pressure force to move the fabric to the transfer fabric and can, if properly directed with a Finite velocity component or that opposes the direction of the carrier fabric, provide the decelerating force to help cut the tissue as it is transferred. For effective transfer using an air knife or a similar pneumatic system, the air knife preferably should have a narrow opening extending across the width of the fabric, said opening being less than 2 millimeters, preferably less than 1 millimeter. millimeter, and more preferably less than 0.5 millimeters wide, wherein the width is defined as the spacing between the opposing surfaces of the air knife nozzle at the outlet. For effective air velocities, the stagnation pressure inside the air knife (for example, in the plenum of the air knife or in the pneumatic pressure source coupled to the air knife hole) must be greater than 1 pound per square inch above atmospheric pressure, preferably greater than 3 pounds per square inch above atmospheric pressure, more preferably more than 10 pounds per square inch above atmospheric pressure, more preferably even more than 20 pounds per square inch above atmospheric pressure and more preferably more than 50 pounds per square inch over atmospheric pressure, with a range of 5 to 50 pounds per square inch over atmospheric pressure which is believed to be suitable for many conditions.

Figure 6 shows an embodiment wherein the air knife is used to assist in the transfer of the fabric from the carrier fabric to the transfer fabric. A deflection element (in that case a stationary shoe) is shown within which an air nozzle 15 is formed integrally. Alternatively, the air nozzle should be a separate device which is suitably positioned to provide air flow through an opening in the carrier fabric deflection element. It is believed that a narrow air jet, typified by an air knife, may be more a rapid transfer is effective because the air jet can provide a focused force to decelerate the tissue of paper over a narrower area and move it rapidly through flfc through a narrow gap, if desired. An air knife can also be useful to further dewater the wet tissue. If a separation is established, the sheet can be transferred without mechanical compression and friction between the two fabrics.

Several strategies can be perceived to help to maintain a relatively uniform spacing between the vacuum pick-up shoe and the carrier fabric deflection element along the width in the full transverse direction of a paper machine. Any deflection element of the vacuum pick-up shoe can be broken into separately disposable or separately held units through the CD extension, preferably with a pneumatic or hydraulic position or load adjustment being possible. Alternatively, the elements must be spring loaded or pneumatically or hydraulically loaded to maintain a constant support force, allowing the elements to "give" in case the opposite object (the transfer shoe for a unit of the deflection element of carrier fabric or the deflection element for a transfer shoe unit) is very close and exerts excessive force on the paper web. The leading edge of the transfer shoe can desirably have a chamber filled with flexible fluid or polymer that holds the solid low friction outer surface, such that the support camera or base can give in response to the load, help maintain a more uniform load across the element's width.

The rapid transfer operation of the present invention can be used in any process for making paper placed in known number. The formation of the paper sheet can be achieved through a variety of forms, such as twin wire formers, breast roll formers, separator formers, formers of a crescent, and the like. Embryonic tissue can be formed on traditional forming fabrics or on three-dimensional or more textured fabrics. The use of textured forming fabrics is taught by M.K. Ramasubramanian and C.A. Read U.S. Patent No. 5,098,519 entitled "Method for Producing a High-Volume Paper Fabric and Product Obtained With It," issued March 24, 1992 and incorporated herein by reference, and by G.A. Wendt et al. In the Patent of the United States of North America Nc. 4,942,077, entitled "Tissue Fabrics Having a Regular Pattern of Densified Areas", granted on July 17, 1990, also incorporated herein by reference. The removal of a total forming fabric with a formation, directly on a dryer fabric is taught by Wendell J. Morton, in the patent "Process and Apparatus for Forming a Paper Fabric Having Improved Volume and Absorbent Capacity" of the United States of America No. 4,102,737 issued May 16, 1977, incorporated herein by reference.

The fabric can be made with any suitable paper fibers, including fibers derived from wood, cotton, linen, hemp, bagasse, soft rush and other natural materials, as well as mixtures of natural and synthetic fibers in an aqueous solution. Papermaking solutions can include various chemicals and particulates as is known in the art, including temporary and permanent wet strength resins; dry strength additives such as starches and cationic charged polymers; reactive dye components; polymer retention aids; including two-component systems and systems involving silica, clays and the like; mineral and organic fillers; opacifiers, including waxes and microspheres; softeners and debonders; and similar. The fibers may have been subjected to any number of mechanical, chemical and thermal processing steps, including mechanical refinement, chemical cross-linking, steam blasting, mechanical dispersion or kneading; oxidation or sulfonation, exposure to high temperature, etc. After its formation and before rapid transfer, the fabric is preferably from about 19% to about 30% cellulosic fiber by weight, and more preferably from about 19% to about 27% cellulosic fiber by weight. weight.

Suitable carrier fabrics can be typical papermaking fabrics including, for example, Albany 84M and 94M available from Albany International of Albany, New York; Asten 856, 866, 892, 959, 937 and Asten Synweve Design 274, available from Asten Forming Fabrics, Inc. of Appleton, Wisconsin. The carrier fabric can be a woven fabric, a perforated fabric or perforated sheet or a molded band, or a fabric as taught in United States Patent No. 4,529,480 issued to Trokhan. The fabrics or forming felts comprising the non-woven base layers may also be useful, including those from Scapa Corporation made extruded polyurethane foam such as the Spectra series. Relatively smooth forming fabrics can be used, as well as textured fabrics suitable for imparting texture and base weight variations to the fabric.

Suitable transfer fabrics may include fabrics that are also suitable for carriers, such as those mentioned above, and Asten 934 and 939, or Lindsay 952-SC5 and 2164 from Appleton Mills of Appleton, Wisconsin. Additionally, novel three-dimensional fabrics comprising deformable nonwoven top layers, as described in the co-pending co-pending patent application of Lindsay et al., Series No. 08 / 709,427, filed September 6, 1996, entitled " Process to Produce High Volume Tissue Fabrics using Non Woven Substrates ". Rapid transfer can also be done on a continuous drying cloth such as transfer cloth. Suitable continuous drying fabrics include, without limitation, Asten 52B, 803, 920A and 937A, and Velostar P800, 800 and 103A, also made per Asten, as well as Albany 5602 and Lindsay T116 cloth styles and other Lindsay continuous-drying fabrics . The fabrics described in U.S. Patent No. 5,429,686 issued July 4, 1995 to K.F. Chiu and others, may also be appropriate. In general, the transfer fabrics can be relatively smooth, such as the typical forming fabrics, to maximize the shortening and the volume of the sheet, or they can be textured, like the Lindsay continuous drying fabrics mentioned above, to provide texture and three-dimensional structure to the sheet.

The speed difference between the carrier fabric and the transfer fabrics may be greater than 5%, preferably greater than 10%, more preferably greater than 25%, and more preferably greater than 40%, desirably in the range of to 60%.

Following the rapid transfer operation, the fabric is preferably dried with non-compressive drying means. "Non-compressive drying" refers to drying methods such as drying through air; the blow drying of air jet; non-contact drying such as air flotation drying; the blow or superheated steam flow; drying with the microwave and other methods of dielectric drying or radio frequency; the extraction of water by supercritical fluids; the extraction of water by non-aqueous low surface tension fluids; the infrared drying; drying by contact with the melted metal film; and other methods for drying cellulosic tissues that do not involve compressive pressure points or other steps that cause a significant densification or compression of a part of the tissue during the drying process.

The ability to adequately execute rapid transfer to provide the upper internal hollow volume in the sheet toward the present invention especially useful in the production of high volume materials. The high volume is greatly increased by the use of molding in number of one sheet to create a three-dimensional structure after the rapid transfer process. The continuous drying on a highly textured and three-dimensional fabric is an especially preferred method to achieve a high volume. further, special fibers or specially treated fibers can be used to achieve improved absorbance, volume or smoothness. A low density three-dimensional structure can be achieved in part by combining the fast transfer as taught herein with a variety of means including but not limited to the use of specially treated high volume fibers such as laughter or chemically treated fibers as an additive. in the supply, including the fibers taught by CC Van Haaften in the Patent of the United States of North America No.3,339,550 entitled "Sanitary Towel with Interlaced Cellulose Layer" granted on September 5, 1967, which is incorporated herein by reference; mechanical tensioning or "wet tensioning" or wet tissue, including methods taught by M.A. Hermans et al. In U.S. Patent No. 5,492,598 entitled "Method for Increasing the Internal Volume of Dried Tissue Continuously", granted on February 20, 1996, incorporated herein by reference, and M.A. Hermans et al. In U.S. Patent No. 5,411,636, "Method for Increasing the Internal Volume of Pressed Tissue in Numbers," issued May 2, 1995, incorporated herein by reference; molding the fiber on a three dimensional wire or fabric, such as the fabrics described by Chiu et al. in U.S. Patent No. 5,429,686 entitled "Soft Tissue Making Apparatus" issued July 4, 1995 , which was incorporated herein by reference, including differential velocity transfer on or from the three-dimensional wire or fabric; the wet engraving of the leaf; wet creping; and the optional use of chemical binder agents.

The present invention is expected to increase the range of process variables upon which successful rapid transfer can be achieved. In particular, the elimination of the wide contact regions between the two wires is expected to reduce the incidence of macrodobles and allow a more bulky sheet with a stretch in the upper machine direction to be achieved. Improved absorbent properties may be possible with incorporations of low contact or contactless area of the present invention, so that the superior internal volume is possible.

It will be appreciated that the foregoing description, given for purposes of illustration, should not be construed as limiting scope to the invention, which is defined by the claims that follow and all equivalents thereof.

Claims (30)

1. A method for transferring a cellulosic fabric supported by a carrier fabric to a transfer fabric that moves more slowly where the transfer fabric and the carrier fabric converge and diverge as the transfer fabric passes over a vacuum shoe having a groove in it. vacuum and the carrier fabric passes over a deflection element, wherein the vacuum shoe deflects the transfer fabric towards the carrier fabric and the deflection element deflects the carrier fabric towards the vacuum layer so that the fabric is transferred to the transfer fabric when passing the fabric over the vacuum gap.

2. The method as claimed in clause 1 characterized in that the deflection element has a radius of curvature of about 14 inches or less.

3. The method as claimed in clause 1 characterized in that the deflection element has a radius of curvature of about 5 inches or less.

4. The method as claimed in clause 1 characterized in that the deflection element has a radius of curvature of from about 0.2 about 2 inches.

5. The method as claimed in clause 1 characterized in that the angle of divergence between the carrier fabric and the transfer fabric is about 5 degrees or more.

6. The method as claimed in clause 1 characterized in that the angle of divergence between the carrier fabric and the transfer fabric is about 10 degrees or more.

7. The method as claimed in clause 1 characterized in that the angle of divergence between the carrier fabric and the transfer fabric is about 20 degrees or more.

8. The method as claimed in clause 1 characterized in that the divergence angle between the carrier fabric and the transfer fabric is about 30 degrees or more.

9. The method as claimed in clause 1 characterized in that the angle of divergence between the carrier fabric and the transfer fabric is about 45 degrees or more.

10. The method as claimed in clause 1 characterized in that the angle of divergence between the carrier fabric and the transfer fabric is from about 40 about 80 degrees.

11. The method as claimed in clause 1 characterized in that the angle of divergence between the carrier fabric and the transfer fabric is greater than the convergence angle between the carrier fabric and the transfer fabric.

12. The method as claimed in clause 1 characterized in that the deflection element is a roller.

13. The method as claimed in clause 1 characterized in that the deflection element contains a hole through which the pressurized air is directed to the tissue to help transfer the fabric to the transfer fabric.

14. The method as claimed in clause 1 characterized in that the deflection element is provided with the means for breaking or preventing the formation of an empty seal between the carrier fabric and the deflection element.

15. The method as claimed in clause 1 characterized in that the vacuum shoe is convex, having a radius of curvature of about 12 inches or less.

16. The method as claimed in clause 1 characterized in that the vacuum shoe is convex, having a radius of curvature of about 5 inches or less.

17. The method as claimed in clause 1 characterized in that the ratio of the radius of curvature of the vacuum shoe to the radius of curvature of the deflection element is in the range of 0.5 to 2.0.

18. The method as claimed in clause 1 characterized in that the vacuum shoe is concave adjacent to the vacuum slot.

19. The method as claimed in clause 1 characterized in that both the carrier fabric and the transfer fabric are relatively smooth compared to three-dimensional drying fabrics, so that the carrier fabric and the transfer fabric have softness characteristics when forming fabrics .

20. The method as claimed in clause 1 characterized in that the transfer fabric moves at least 10% more slowly than the carrier fabric.

21. The method as claimed in clause 1 characterized in that the transfer fabric moves at least 25% more slowly than the carrier fabric.

22. A method for transferring a cellulosic fabric and sustained by a carrier fabric to a transfer fabric that moves slower where the transfer fabric and the carrier fabric converge and diverge as the transfer fabric passes over a shoe having an opening there and the carrier fabric passes over a deflection element having at least one hole there for discharging pressurized gas, said orifice communicating pneumatically with a source of pressurized gas, wherein the shoe deflects the transfer fabric towards the carrier fabric and the carrier element. Deflection deflects the carrier fabric towards the shoe and the gas discharge from said hole acts to assist in the transfer of the tissue to the transfer fabric.

23. The method as claimed in clause 22 characterized in that said orifice is an air jet nozzle having a nozzle opening of less than about 1 mm coupled directly to a source of pressurized gas having a stagnation pressure greater than 10. pounds per square inch over atmospheric pressure.

24. The method as claimed in clause 22 characterized in that there is a separation between said carrier fabric and said transfer fabric so that both fabrics can not simultaneously engage the fabric.

25. The method as claimed in clause 22, characterized in that the speed difference between the carrier fabric and the transfer fabric is greater than 10%.

26. The method as claimed in clause 1 characterized in that the deflection element is stationary.

27. The method as claimed in clauses 1 or 22, characterized in that said fabric before the transfer fabric has from about 19% to about 30% fibers by weight.

28. The method as claimed in clauses 1 or 22 characterized in that such a fabric before the transfer fabric has from about 19% to about 27% fibers by weight.

29. The method as claimed in clauses 1 or 22 characterized in that such tissue is microcompacted to have volume increase at a microscopic level by the transfer.

30. The method as claimed in clauses 1 or 22 characterized in that the transfer fabric is a continuous textured drying fabric. SUMMARY A method for improving the rapid transfer of a tissue, such as tissue tissue, is described. The method provides greater angles of convergence (AC) and divergence (AD) of the carrier fabric and of the transfer fabric at the transfer point by deflecting the carrier fabric to the transfer fabric using a deflection element, such as a roller placed on the vacuum transfer head. The greater angles of convergence and divergence minimize the potential for undesirable macrodoses to be formed in the weave during the transfer. 1/4 FIG. 2 2 / H • FIG. 3 FIG. 4 3/4 FIG. 5 llk FIG. 6