MXPA00004191A - Azetidinone derivatives for the treatment of hcmv infections - Google Patents

Abstract

A compound of formula (1) wherein Y is S or O;R1 is C1-6 alkyl;(C0-6 alkyl)aryl;(C0-6 alkyl)Het;or R1 is an amino acid analog or dipeptide analog of formula (I) wherein R2 is H, C1-10 alkyl;or an amide or ester group;A is C6-10 aryl, Het or CH-R3 wherein R3 is C1-6 alkyl or (C0-4 alkyl)aryl;and Z is H, C1-6 alkyl, or an acyl;R4 is hydrogen, lower alkyl, methoxy, ethoxy, or benzyloxy;and R5 is alkyl, cycloalkyl, carboxyl group;an aryl;Het or Het(lower alkyl);or R4 and R5 together with the nitrogen atom to which they are attached form a nitrogen containing ring optionally substituted with phenyl or C(O)OCH2-phenyl, said phenyl ring optionally mono- or di-substituted with among others C(O)OR7 wherein R7 is lower alkyl or phenyl (lower alkyl);or a therapeutically acceptable acid addition salt thereof.

Description

AIR PRESS FOR DRAINING A WET TISSUE Background of the Invention There are many characteristics of tissue products such as facial and bath tissue that must be considered when producing a final product that has desirable attributes that make it suitable and preferred for the intended purpose of the product. The improved softness of the product has long been a main objective, and this has been a particularly significant factor in the success of the premium products. In general, the main components of softness include stiffness and volume (density), with lower stiffness and superior volume (lower density), generally improving the perceived softness.

While improved softness is a desire for all types of tissue products, it has been especially challenging to achieve smoothness improvements in non-creped continuous drying sheets. Continuous drying provides a relatively non-compressive method for removing water from a fabric by passing warm air through the fabric until it is dry. More specifically, a wet-laid fabric is transferred from the forming fabric to a highly permeable and rough continuous drying fabric and is retained on the drying fabric continuously until it is dried. The resulting dried fabric is softer and more bulky than a conventionally dried creped sheet because less bonds are formed and because the fabric is less compressed. Therefore, there are benefits to eliminating the Yankee dryer and to make a dried product in continuous non-creped form. The non-creped continuously dried sheets are typically very rough and hard to the touch, however, in comparison to their creped counterparts. This is partly due to the inherently high stiffness and strength of an un-creped sheet, but it is also partly due to the roughness of the continuously dried cloth on which the wet fabric is formed and dried.

Therefore, what is needed and required in the art is a method for manufacturing tissue products having improved softness, and in particular dried tissue products in a continuous form having an improved softness, as well as an apparatus that allows the manufacture of such tissue products.

Synthesis of the Invention It has now been discovered that an improved non-creped continuous dried fabric can be made by dewatering the fabric to more than about a 30 percent consistency prior to the transfer of the wet fabric from a forming fabric to one or more fabrics of slower intermediate transfer before further transfer of the fabric to a continuous drying fabric for final drying of fabric. In particular, by increasing the consistency of a non-creped continuous dried fabric before the point, the differential speed transfer has surprisingly been found to result in: (1) both tension properties in the transverse direction and in the direction of superior machine, contributing to an improved tissue run; and (2) a reduced module, this is an increased smoothing, when the resistance to tension is adjusted to a normal value. This discovery allows the manufacture of tissue products with a lower modulus at given tensile strengths in comparison to even tissue products produced by undergoing differential speed transfer lower consistencies.

One aspect of the present invention relates to an air press for non-compressively dewatering the wet fabric. The air press is a particularly desirable apparatus for draining the continuously dried non-creped fabric around a consistency of 30 percent or greater before the differential velocity transfer. While the jets of pressurized fluid in combination with vacuum devices have been previously discussed in the patent literature such devices have not been widely used in the manufacture of tissue. Mainly, this seems to be due to the fact that it has not been previously recognized that tissue drainage at more than about 30 percent consistency in advance to differential velocity transfer would result in improved product properties identified herein. In addition, the lack of incentive to use such equipment is also believed to be attributable to the difficulties of the actual implementation including tissue tissue disintegration, pressurized fluid leakage, seal and / or fabric wear, and the like. The air press described here overcomes these difficulties provides a practical apparatus for draining a wet fabric levels of consistency not previously thought possible industrially useful speeds without a thermal drain.

Therefore, in an embodiment, an air press for draining a wet weave according to the present invention comprises: support fabrics adapted to have the wet tissue between them transport the wet fabric through the press of air; u first drainage device comprising a pair of sealing members in the transverse direction to the machine including the sealing blades; a second drainage device comprising a sealing member in the transverse direction to the machine formed of a deformable material, the first and second drainage devices can be moved in relation to one another and are adapted to assume a position d operation in which the first second drainage devices are operatively associated with each other and at least one seaming blade sticks on the soporum fabrics and is opposite on the other side of the soporum fabrics by the sealing member formed of a deformable material; and wherein one of the first and second drainage devices comprises an air plenum operatively connects to a source of pressurized fluid and the ot comprises a collection device operably connected to a vacuum source.

In another embodiment, an air press for draining a wet weave according to the present invention comprises: support fabrics adapted to sandwich the wet weave therebetween and convey wet tissue through the air press; A plenum of ai placed on one side of the wet weave and operatively connects to a source of pressurized fluid, the full air comprises a seal assembly which is adapted to move between an operating position and a retracted position. The seal assembly comprises a pair of sealing members in the machine direction and a pair of sealing members in the transverse direction to the machine forming an integral seal with the wet fabric when the sealing assembly is in the operating position; a collection device placed on the opposite side of the wet tissue operatively associated with the air plenum, the collection device defines there a pair of sealing grooves extending across the width of the wet tissue and also defines there a central conduit placed therein. between the sealing grooves and adapted to receive the pressurized fluid from the plenum d and the water from the wet tissue, the collection device comprises the deformable sealing members positioned within the sealing grooves; means for moving the sealing members in the direction of the machine to a contact and out of contact with one of the supporting fabrics, the sealing members in the direction of the machine positioned opposite and forming a seal against the members of the machine. deformable sealing when the sealing assembly is in the operating position; and means for moving the sealing members in the transverse direction of the machine to a contact and out of contact with one of the support fabrics.

The air press is capable of draining the wet fabric at very high consistencies due in large part to the difference in high pressure established through the fabric and to the resultant air flow through the fabric. In particular embodiments, for example, the air press may increase the wet fabric consistency by about 3 percent or more, particularly about 5 percent more, such as from about 5 to about 20 percent, more. particularly about 7 percent or more, and more particularly about 7 percent or more, such as from about 7 to 20 percent. Therefore, the wet fabric consistency upon leaving the air press can be about 25 percent or more, about 2 percent or more, about 27 percent or more, about 28 percent or more, about 29 per cent more, and desirably about 30 percent or more particularly about 31 percent or more, more particularly about 32 percent or more, such as d from about 32 to about 42 percent, more particularly about 33 percent or more, even more particularly about 34 percent or more, such as about 34 to about 42 percent, and even more particularly about 35 percent. percent or more.

The air press is able to achieve these levels of consistency while the machine is operating industrially useful speeds. As used herein, "high speed operation" or "industrially useful speed" for the tissue machine refers to a machine speed of at least as great as any one of the following values or ranges, in feet per second. minute: 1,000; 1,500; 2,000; 2,500; 3,000; 3,500; 4,000; 4,500; 5,000; 5,500; 6,000; 6,500; 7,000; 8,000; 9,000; 10,000, and a range having an upper and lower limit of any of the values listed above. Optional steam showers or the like may be used before the air press to increase the consistency of the rear air press and / or to modify the moisture profile in the direction transverse to the fabric machine. In addition, higher consistencies can be achieved when the machine speeds are relatively low and the residence time in the air press is higher.

The pressure difference across the wet tissue provided by the air press may be about 25 inches of mercury or greater, such as about one to about 120 inches of mercury, particularly about 35 inches of mercury or more, such as from about 35 to about 60 inches of mercury, and m particularly from about 40 to about inches of mercury. This can be achieved partly by full air from the air press while maintaining a fluid pressure on one side of the wet fabric from more than 0 to around 60 pounds per square inch over atmospheric pressure (psig), particularly from more than 0 to about 30 pounds per square inch over atmospheric pressure, m particularly about 5 pounds per square inch over atmospheric pressure or more, such as about 5 about 30 pounds per inch. square inch over the atmospheric pressure, and more particularly still from about 5 about 20 pounds per square inch over the atmospheric pressure. The air press collection device desirably functions as a vacuum box operating at 0 about 29 inches of mercury vacuum, particularly d around 0 to about 25 inches of mercury vacuum particularly from more than 0 to about 25 inches of mercury vacuum, and more particularly from about 10 about 20 inches of mercury vacuum, such as about 15 inches of mercury vacuum. Both pressure levels within both the air plenum and the collection device are desirably monitored and controlled at predetermined levels.

The collection device desirably does not necessarily form an integral seal with the full air pulls a vacuum to facilitate its function as a collecting device for air and liquid. The terms "integral seals" and "integrally seals" are used here to refer to: the relationship between the air plenum and the wet knit where the plenum is operatively associated in indirect contact with the knitted so that around 70 percent or more of the air supplied to the full air flow through the tissue when the full air is operated at a pressure difference through the tissue of about 3 inches of mercury or more, and the ratio between the full air and the collection device where the air plenum is operatively associated and in indirect contact with the tissue the collection device so that about 70 percent or more of the air supplied to the plenum air flows through the tissue to the device of collection when full air and collection device are operated or pressure difference through the tissue of about 3 inches of mercury or more.

Significantly, the pressurized fluid used in the air press is sealed from the ambient air to create substantial air flow through the tissue, which results in a tremendous drainage capacity of the air press. The flow of pressurized fluid through the air press is suitably from about 5 to about 500 standard cubic feet per minute (SCFM) per square inch of open area particularly around about 10 standard cubic feet per minute per square inch of open area or more such as from about 10 to about 200 standard cubic feet per minute per square inch of open area, and more particularly about 40 standard cubic feet per minute per square inch of open area or more, such as d around 40 to about 120 standard cubic feet per minute per square inch of open area. Desirably, 7 percent or more, particularly 80 percent or more, and more particularly 90 percent or more, of the pressurized fluid supplied to the plenum is pulled through the humid tissue into the vacuum box. For the purposes of the present invention, the term "standard cubic foot per minute" means cubic feet per minute measured at 14.7 pounds per square inch absolute and 60 ° F (° F) The terms "air" and "pressurized fluid" are used interchangeably herein to refer to any gaseous substance used in the air press for draining and weaving. The gaseous substance suitably comprises air, vapors or the like. Desirably, the pressurized fluid comprises air at room temperature, or air heated only by the process of pressurization to a temperature of about 300 ° F or less, more particularly about 150 ° F or less.

In an alternative embodiment, a device for draining a wet weave moving in one direction of the machine comprises: a frame structure; support fabrics adapted to have the sandwich in the form of a sandwich; and an air press comprising an air plenum and a collection device placed on the opposite sides of the wet fabric of the support fabrics, the air plenum and the collection device are operatively associated with one another and adapted to establish a Fluj of pressurized fluid through the wet tissue, the plenum of air comprises: stationary components mounted on the frame structure; a sealing assembly that is adapted to move relative to the stationary components between an operating position and a retracted position, the sealing assembly comprises a pair of sealing members in the machine direction and a pair of sealing members in the direction transverse to the machine which together form an integral seal with the wet fabric when the sealing assembly is in the operating position; means for moving the sealing members in the transverse direction of the machine generally perpendicular to a plane containing the wet fabric and to a contact and out of contact with one of the supporting fabrics; means for moving the sealing members in the machine direction generally perpendicular to the plane containing the wet fabric and to contact and out of contact with one of the supporting fabrics; and means for moving the sealing members in the direction of the machine generally parallel to the plane containing the wet fabric and generally perpendicular to the machine direction.

In another alternate embodiment, a device for draining wet tissue moving in a machine direction comprises: a frame structure; support fabrics adapted to have the wet fabric between them in the form of a sandwich; and an air press comprising an air plenum and a collection device positioned on the opposite sides of the wet tissue and the support fabrics, the air plenum and the collection device are operatively associated with one another and adapted to establish a flow of pressurized fluid through the wet tissue, the plenum of air comprises: stationary components mounted on frame structure and defining a car surface generally parallel to the plane containing the wet tissue; sealing assembly that is adapted to move relative to the stationary components between an operating position in which the sealing assembly forms an integral seam with the moist fabric and a retracted position, the sealing assembly defining a surface of generally parallel to the plane that it contains the moist fabric adapted to make contact with the loading surface; means for moving the sealing assembly generally perpendicular to the plane containing the wet fabric, where contact between the control surface and the loading surface interrupts the movement of the sealing assembly to the wet tissue when the sealing assembly reaches the position of operation.

In a further embodiment, a device for draining wet tissue moving in one direction of the machine comprises: a frame structure; d support fabrics adapted to have the wet weave between them in the form of a sandwich; and an air press comprising an air plenum and a collection device positioned on opposite sides of the wet fabric and the supporting fabrics, and full of air and the collection device are operatively associated with one another and adapted to establish a flow of pressurized fluid through the wet tissue, the full air comprises: stationary components mounted on the frame structure; a sealing assembly that is adapted to move relative to the stationary components between an operating position in which the seal assembly forms an integral seal with the wet tissue and a retracted position, inwardly of the sealing faces of the sealing assembly and inward of the front surfaces of the stationary components together defining a chamber for the pressurized fluid, the face surfaces within the sealing assembly that partially define the chamber being generally perpendicular to the plane containing the wet tissue; means for moving the sealing assembly in a generally perpendicular manner to the plane containing moist tissue at a contact and out of contact with one of the support fabrics; and means for applying a loading force to the sealing assembly to hold the seal assembly in an operating position, the loading force being independent of the pressure of the pressurized fluid.

This design of the air press used internal surfaces that are normal to the direction of load to completely isolate the load force from the pressure d full of air. Therefore, the loading force can be maintained at a constant value to provide a suitable seal despite the full air pressure varying from zero to a maximum pressure. Therefore, the loading force does not have to be adjusted in response to pressure changes inside the air press.

With the additions of the air press described herein, the competitive objectives of minimizing leakage and minimizing fabric wear can be achieved both. In particular embodiments, the air press establishes a seal across the width of the wet fabric without having to align the CD sealing members of the air plenum with the hard surfaces on the vacuum box. Rather, the CD sealing member is off-center from the hard surfaces of the vacuum box cover and placed in vacuum conduits. This design rests on an ambient air flow in the vacuum box to create a seal rather than to have to trust or rest on the careful alignment and machining of the arched surfaces that match the full air and the vacuum box.

In another embodiment, an air press for draining a wet fabric includes an air plenum comprising a plenum cover having a bottom surface and a vacuum box comprising a vacuum box cover having a top surface placed on the top. a close proximity to the lower surface of the plenum cover. The air press also includes means for supplying pressurized fluid to the air plenum and means for applying vacuum to the vacuum box. The side seal members of the air press are adapted to reside in contact with the air plenum and the air box. vacuum to minimize the escape of pressurized fluid. The side seal members are attached to one of the air plenum of the vacuum box, and the lateral seal contact surfaces defined by the other of the air plenum and the vacuum box are placed in close proximity. The side sealing members are adapted to flex to a sealing contact with the lateral sealing contact surface with exposure to pressurized fluid to improve the effectiveness of the seal.

Optionally, the air press may include a position control mechanism that functions to maintain full air in close proximity to the vacuum box. In particular, the position of the control mechanism desirably includes a lever mounted rotatably attached to the full d air and a counter balance cylinder attached to the lever. The position control mechanism is adapted to rotate the lever to counter pressure changes inside the plenum. In this way, the air plenum resides in a close proximity or in contact with the fabrics that pass between the air plenum and the vacuum box, without folding the fabrics between them.

In another embodiment, the air press includes an air plenum comprising a plenum cover having a bottom surface, and means for supplying pressurized fluid to the plenum. The air press also includes a vacuum box comprising a vacuum box cover having a top surface positioned in a vicinity close to the bottom surface of the plenum cover, and means for applying vacuum to the vacuum box. An arm that is pivotally mounted on the air plenum comprises the first and second parts, with the first part of the arm being at least partially located within the air plenum. A sealing rod is formed of or mounted on the first part of the arm. The air press also includes means for pivoting the arm in response to fluid pressure within full air.

In this incorporation, the rod-sealing part of the pivotable arm acts as an end seal to prevent the escape of pressurized fluid from between the plenum d and the vacuum box. The sealing bar can conform to irregularities or misalignments of the fabric of the support structure. The end seals, which are also mentioned as CD seals or in the transverse direction, improve the containment of the pressurized fluid and thus result in a more efficient operation of the air press. The loading of the end seals is controlled to keep the sealing bar in contact with the underlying fabric, without causing undue wear of the fabric.

The air press is useful in a variety of machine configurations for draining wet fabrics including paper, tissue, corrugated, linerboard, newspaper, or the like. In particular, the air press can be used on a tissue machine for molding and wet tissue on a three-dimensional fabric and therefore increases the volume of the fabric. The air press can be used in a variety of positions on the machine, particularly where the fabric is placed in the form of a sandwich between two fabrics and where the fabric is transferred to a three-dimensional fabric. Because the pressure difference generated by the air press, significantly larger than what has been possible using conventional vacuum boxes, suction boxes, blow boxes and the like, tissue tissues with relatively high volumes can be created in a mold phase operation using the press of air. Various wet press machine configurations that lend themselves to draining using the air press are described in the patent application of the United States of America, with serial number is unknown filed on the same day as the present application by M. Hermans et al. entitled "Methods for Making Tissue Sheets on a Modified Conventional Wet Press Machine"; US patent application with unknown serial number filed the same day as the present application by M. Hermans et al entitled "Method of Making a Low Density Tissue with a Reduced Energy Input"; the patent application of the United States of America, with an unknown serial number filed on the same day as the present application by F. Drueck et al. entitled "Method for Producing Elastic Fabrics of Low Density", and the patent application of the United States of North America, with unknown serial number, filed on the same day as the present application by S. Chen et al entitled "Low Density Elastic Fabrics and Methods for Making Such Fabrics"; which are incorporated herein by reference.

One aspect of the invention relates to a method for dewatering a cellulosic fabric using a pressurized fluid comprising the steps of: depositing an aqueous suspension of fibers to make paper on an endless forming fabric to form a wet fabric; placing in the form of sandwich and wet tissue between a pair of fluid-permeable fabrics, the wet-weave structure passes in the form of a sandwich through an air press comprising an air plenum and its collection device, the air plenum and the collecting device being operatively associated and integrally sealed so that about 70 percent or more of pressurized fluid delivered to the plenum passes through the wet tissue; supply the pressurized fluid to the full d air to create a pressure difference through the wet fabric of about 25 inches of mercury or higher to transport the wetted fabric through the air press industrially useful speeds to provide a residence time of around 10 milliseconds or less; and dry and weave to a final dryness.

Several embodiments of the air press are described herein in relation to a process for making a continuous drying tissue. Therefore, in one embodiment, a method for making a soft tissue includes the steps of: depositing an aqueous suspension of fibers to make paper on an endless forming machine to form a wet tissue; dewatering and wet tissue to a consistency of about 20 about 30 percent; dewatering in addition to wet fabric using non-compressive drainage media at a consistency of more than about 30 percent; transferring the dewatered fabric in addition to a transfer fabric traveling at a speed of from about 10 about 80 percent slower than the forming fabric; transfer the fabric to a continuous drying fabric; and drying the fabric continuously to a final dryness.

The intermediate transfer fabric or fabrics is traveling at a slower speed than the forming fabric during transfer in order to impart stretch to the sheet. As the speed difference between the forming fabric and the slower transfer fabric increases (sometimes called the "negative pull" or the "rapid transfer") the stretch imparted to the tissue during the transfer is also increased. The transfer fabric can be relatively smooth and taut compared to the rough fabric of a typical continuous drying fabric. Preferably the transfer cloth is as fine as it can be to run from a practical point of view. The grip of the fabric is achieved through the presence of knuckles on the surface of the transfer fabric. In addition, it may be advantageous without one or more of the wet fabric transfer fabrics, with or without the presence of a transfer fabric, to be achieved by using a "fixed separation" or "kiss" transfer in which the fabrics s converge and diverge simultaneously, which will be described hereinafter in detail. Such transfers not only prevent any significant compaction of the fabric while it is in a state of wet bonding formation, but when used in combination with a smooth transfer fabric and / or differential velocity transfer, they observe that they soften the surface of the fabric. and of the final dry leaf.

The speed difference between the forming fabric and the transfer fabric can be from about 10 about 80 percent or more, preferably from about 10 to about 35 percent, and more preferably from about 15 to about about 25 percent, with the transfer fabric being the slowest fabric. The optimal speed difference will depend on a variety of factors, including the particular type of product being made. As mentioned previously, the increase in stretch imparted to the tissue is proportional to the speed difference. For a three layer cleaner dried in continuous or creped form having a basis weight of around 2 grams per square meter per layer, for example, a speed difference in the production of each layer from about d 20 to about 25 per A cent between the forming fabric and the single transfer tel produces a stretch in the final product from about 15 to about 20 percent.

Stretching can be imparted to the fabric using a single differential velocity transfer or two more differential velocity transfers of the humid tissue before drying. Therefore, there may be one or more transfer fabrics. The amount of stretch imparted to the fabric can therefore be divided by 1, 2, 3 or more differential velocity transfers.

The transfer is desirably carried out d so that the resulting "sandwich" (consisting of the transfer d fabric / fabric / forming fabric) comes out for as short a duration as possible. In particular, it emerges only at the leading edge of the vacuum shoe or the transfer shoe slot that is being used to effect the transfer. In fact, the forming fabric and the transfer cloth converge and diverge at the leading edge of the vacuum slot. The intent is to minimize the distance over which the tissue is in simultaneous contact with both fabrics. It has been found that simultaneous convergence / divergence is the key to eliminating macro-doubles and thus improving the softness of the resulting tissue or other product.

In practice, simultaneous convergence and divergence of the two fabrics will occur at the leading edge of the slot with vacuum if a sufficient convergence angle is maintained between the two fabrics as they approach the front edge of the slot with vacuum and if it maintains a sufficient angle of divergence between the two fabrics on the side down to the vacuum slot. The minimum angles of convergence and divergence are around 0.5 degrees or greater, more specifically about 1 degree or greater, more specifically about 2 degree or greater, and even more specifically about 5 degree or more. The angles of convergence and divergence can be the same or different. The larger angles provide a greater margin of error during the operation. A suitable range is from around 1 degree to around 10 degrees. Simultaneous divergence and convergence are achieved when the vacuum shoe is designed with the tail edge of the vacuum slot being sufficiently lowered relative to the leading edge to allow the fabric to diverge immediately upon passing over the leading edge of the slot with emptiness This will be described more clearly in relation to the Figures.

In the placement of the machine with the cloths initially having a fixed spacing to further minimize the compression of the fabric during transfer, the distance between the fabrics must be equal to or greater than the thickness or thickness of the woven fabric so that the woven fabric does not It compresses significantly when transferred to the leading edge of the vacuum slot.

The increased softness is achieved by the use of the air press up the differential speed transfer. This is most preferably used in combination with a section of fixed separation carrier fabric after drying. The calendering of the fabric is not necessary to have desirable levels of softness, but an additional processing of the sheet, such as by calendering, engraving or creping, can be beneficial to further improve the properties of the sheet.

As used herein, the "transfer fabric" is a fabric which is placed between the forming section and the drying section of the fabric manufacturing process. Suitable transfer fabrics are those papermaking fabrics which provide a higher fibr support index and provide a good vacuum seal to maximize web / sheet contact during transfer from the forming machine. The fabric may have a relatively smooth surface contour to impart softness to the fabric, but still have a sufficient texture to grip the fabric and maintain contact during a rapid transfer. Thinner fabrics can produce a higher degree of stretch in the fabric, which is desirable for some product applications.

Transfer fabrics include single layer, multilayer or composite permeable structures. Preferred fabrics have at least some of the following characteristics: (1) on the side of the transfer fabric that is in contact with the wet fabric (the upper lad), the number of yarns in the machine direction (MD) ) per inch (mesh) is from 10 to 200 and the number of threads in the cross machine direction (CD) per inch (count) is also from 10 to 200. Thread diameter is typically smaller than 0.050 inches; (2) On the upper side, the distance between the highest point of the MD knuckle and the highest point of the CD knuckle is from about 0.001 to about 0. 02 or 0.03 inches. Between these two levels, there may be knuckles formed either by MD or CD threads that give the topography of a three-dimensional characteristic; (3) on the upper side, the length of the knuckles MD is equal to or greater than the length of the knuckles CD; (4) If the fabric is made in a multi-layered construction, it is preferred that the bottom cap be of a finer mesh than the top layer to control the depth of penetration of the fabric and maximize fiber retention; and (5) the fabric can be made to show certain geometrical patterns that are pleasing to the eye, which are typically repeated between every 2 to 5 warp threads.

Specific suitable transfer fabrics include, by way of example, those made by Asten Formin Fabrics, Inc., of Appleton Wisconsin and designated 934, 937, 939, and 959. Particular transfer fabrics that can be used also include fabrics described in United States Patent No. 5,429,686 issued July 4, 1995 to Chiu et al., which is incorporated herein by reference. Suitable fabrics may comprise woven fabric, non-woven fabrics, or woven-nonwoven composites. The hollow volume of the transfer fabric may be equal to less than the fabric from which the fabric is transferred.

The forming process and the grip can be conventional as is well known in the papermaking industry. Such forming processes include the Fourdrinier roof formers, (such as the suction chest roll), the separator formers (such as twin wire formers, crescent formers), or the like. Wires or forming fabrics can also be conventional with the finest fabrics with the greatest support of preferred fibers to produce a smoother sheet or fabric. The head boxes used to deposit the fibers on the forming fabric can be layered or uncoated.

The method described herein can be applied to any tissue of tissue, which includes tissues for facial tissue, bath tissue, paper towels, napkin cleaners or the like. Such tissue tissues may be single layer products or multiple layer products, such as two layers, three layers, four layers or more. Single-layer products are advantageous because of their lower cost of manufacture, whereas multi-layer products are preferred by many consumers. For multiple layer products it is not necessary that all the layers of the product are equal, provided that at least one layer is in accordance with the invention. The fabrics can be layered or uncoated (mixed) and the fibers that make up the fabric can be any suitable fibers for making paper.

Suitable base weights for these tissue fabrics can be from about 5 to about 70 gram per square meter (gsm), preferably from about 10 to about 40 grams per square meter, and preferably from about 20 grams per square meter, and preferably from about 20 grams per square meter, and preferably from about 20 grams per square meter. at around 30 grams per square meter. For a single layer bath tissue, it prefers a basis weight of about 25 grams per square meter. For a two-layer tissue, a basis weight of about 20 grams per square meter per layer is preferred. For a three layer tis, a basis weight of about 15 grams per square meter per layer is preferred. In general, higher weight fabrics will require a lower air flow to maintain the same operating pressure in the full air. The width of the air press slots is desirably adjusted to equalize the system to the available air capacity, with wider slots used for heavier weight basis fabrics.

The drying process can be any non-comprehensive drying method which tends to preserve the volume of the wet tissue thickness including, without limitation, continuous drying, infrared irradiation, microwave drying or the like. Due to its commercial availability and practicality, continuous drying is a well-known preferred means for non-compressively drying the fabric. Suitable dried fabrics include, without limitation Asten 920A and 937A, and Velostar P800 and 103A. Dried fabrics in a continuous form may also include those described in United States Patent No. 5,429.68 issued July 4, 1995 to Chiu et al. The fabric is preferably dried to a final dryness without creping, and creping tends to lower the strength of the fabric and volume.

Even though the mechanics are not completely understood, it is clear that the transfer fabric and the continuous drying fabric can make separate independent contributions to the final sheet properties. For example, the smoothness of the sheet surface as determined by a sensory panel can be manipulated over a wide range by changing the transfer fabrics with the same continuous dry cloth. The fabrics produced by the present apparatus method tend to be very two-sided unless they are calendered. The uncalendered fabrics can, however, be folded together with smooth / rough sides outside as required by the specific product forms.

Numerous features and advantages of the present invention will appear from the following description. In the description, reference is made to the accompanying drawings, which illustrate the preferred embodiments of the invention. Tale additions do not represent the full scope of the invention. Reference should now be made to the claims herein to interpret the full scope of the invention.

Brief Description of the Drawings Figure 1 representatively shows a schematic process flow diagram illustrating a method an apparatus according to the present invention for making non-creped continuous dried sheets.

Figure 2 representatively shows an enlarged top floor view of an air press of the process flow diagram of Figure 1.

Figure 3 representatively shows a side view of an air press shown in Figure 2, with part cut out and shown in section for illustration purposes.

Figure 4 representatively shows a vist in amplified section taken generally from the plane of line 4-4 of Figure 3.

Figure 5 representatively shows an enlarged sectional view similar to that of Figure 4, but taken generally from the plane of line 5-5 of Figure 3.

Figure 6 representatively shows a side view of an alternating sealing system for the air press shown in Figures 2 and 3, with cut parts shown in section for purposes of illustration.

Figure 7 representatively shows an amplified side view of a vacuum transfer shoe shown in Figure 2.

Figure 8 representatively shows an amplified side vist similar to that of Figure 7, but illustrating the simultaneous convergence and divergence of the fabrics at the leading edge of a vacuum groove.

Figure 9 is a generalized scheme of the load / elongation curve for the tissue, illustrating the determination of the MD inclination.

Figure 10 representatively shows an enlarged end view of an alternating air press according to the present invention, with an air plenum sealing assembly of the air press in an elevated position relative to the wet fabric and a box of air. empty.

Figure 11 representatively shows a side view of the air press of Figure 10.

Figure 12 representatively shows an enlarged sectional view taken generally from the plane of line 12-12 of Figure 10, but with the seal assembly loaded against the fabrics.

Figure 13 representatively shows an enlarged section vist similar to that of Figure 12 but generally taken from the plane of line 13-13 of Figure 10.

Figure 14 representatively shows a perspective view of several components of the full air seal assembly positioned against the fabrics, with portions cut and shown in section for purposes of illustration.

Figure 15 representatively shows an enlarged sectional view of an alternate seal configuration for the air press of Figure 10.

Figure 16 representatively shows an enlarged schematic diagram of a sealing section of the air press of Figure 10.

Detailed description of the invention The invention will now be described in greater detail with reference to the Figures. Similar elements in the different figures have been given the same reference numbers for purposes of consistency and simplicity. E all the incorporations, illustrated, conventional papermaking operations and apparatus can be used with respect to the head box, the forming fabrics, the tissue transfers, the drying and the creping, all of which will be easily understood by those skilled in the art. in the art of paper making. However, several conventional components are illustrated for purposes of providing the context in which the various embodiments of the invention can be used.

An embodiment of a method and apparatus for manufacturing a tissue is shown representatively in FIG. 1. For simplicity, the various tensioning rollers schematically used to define the various phone runs are shown but not numbered. A paper-making head box 20 injects or deposits an aqueous suspension of paper-making fibers 21 onto an endless forming fabric 22 that is moved around a forming roll 23. The forming fabric 22 allows partially draining of the freshly formed moist fabric. 24 to a consistency of about 10 percent.

After forming, the forming fabric 22 brings the wet fabric 24 into one or more vacuum or suction boxes., which can be employed to provide an additional drainage of the wet fabric 24 while it is held on the forming fabric 22. In particular, a plurality of the vacuum boxes 28 can be used to dewater the fabric 24 to a consistency of from about from 20 to around 30 percent. The illustrated Fourdrinier former is particularly useful for making the heavier weight basis sheets useful as wipers and towels, even when other forming devices such as twin wire formers, u-shaped formers or the like can be employed instead. Hydroperforation, for example, as described in United States Patent No. 5,137,600 issued August 1, 1992 to Barnes et al., May optionally be used to increase the volume of the weave.

The improved drainage of the wet fabric 24 s thus provides by suitable complementary non-compressive drainage means, for example, selected from the group consisting of an air press described here, infrared drying, microwave drying, sonic drying, dry continuously, from a drain with superheated saturated steam, from supercritical fluid drainage, and from displacement drainage. In the illustrated embodiment, the complementary non-compressive draining means comprise an air press 30, described in greater detail hereinafter. The air preps 30 desirably elevates the consistency of the humid fabric 24 to more than about 30 percent, so that in the particular embodiments, the wet fabric has a consistency upon exiting the air press and before the subsequent transfer of the fabric. from around 31 to around 36 percent. In particular embodiments, the air press 30 increases the consistency of the wet fabric by about 5 percent or more, such as about 10 percent.

Desirably, a support fabric 32 is brought into contact with the wet fabric 24 in advance of the air press 30. The wet fabric 24 is placed in a sandwich between the support fabric 32 and the forming fabric 22, and held thus during the pressure drop created by the air press 30. Fabrics suitable for use as a support fabric 3 include almost any fabric, including forming fabrics such as Albany International 94M.

The wet fabric 24 is then transferred from the forming fabric 22 to a transfer fabric 36 moving at a slower speed than that of the forming fabric in order to impart an increased stretch to the fabric. The transfer s is preferably carried out with the aid of a vacuum transfer shoe 37 as described hereinafter with reference to FIGS. 7 and 8. The surface of the transfer cloth 36 is desirably smoother relative to the end of the transfer. providing more softness to the wet fabric 24. The openness of the transfer fabric 36, as measured by its hollow volume, and desirably relatively low and may be about d as well as the forming fabric 22 or even lower. The rapid transfer step can be carried out with many of the methods known in the art, particularly for example, as described in the patent application of the United States of America series No. 08 / 790,980 filed on January 29, 1997 by Lindsay et al. entitled "Improved Rapid Transfer Method for Producing Macrodobles Without High Volume"; U.S. Patent Application Serial No. 08 / 709,427 filed September 6, 1996 by Lindsay et al entitled "Process for Producing High Volume Tissue Fabrics Using Nonwoven Substrates"; U.S. Patent No. 5,667,636 issued September 16, 1997 to S. A. Engel et al .; and U.S. Patent No. 5,607,551 issued March 4, 1997 to T. E. Farrington, Jr., et al .; all of which are incorporated here by reference.

The transfer fabric 36 passes over the rollers 38 and 39 before the wet fabric 24 is transferred to a continuous dryer fabric by traveling at about the same speed, or at a different speed, if desired. The transfer is effected by the vacuum transfer shoe 42, which may be of the same design as that used for the previous transfer. The fabric 24 is dried to a final dryness when the fabric is carried on a continuous dryer 44.

Before a subsequent conversion in the final product form is wound onto a spool 48, the dried fabric 50 can be carried through one or more optional fixed separation fabric pressure point formed between the forming fabrics 52 and 53. The volume or gauge of the fabric 5 can be controlled by the cloth engraving pressure points formed between the rolls 54 and 55., 56 and 57 and 58 and 59. The carrier fabrics suitable for this purpose are Alban International 84M or 94M and Asten 959 or 937, all of which are relatively smooth fabrics, having a fine pattern. The pressure point separations between the various roller pairs can be from about 0.001 inches around 0.02 inches (0.025-0.51 mm). As shown, the fabric carrier section of the machine is designed and operated with a series of fixed separation pressure points that serves to control the gauge of the fabric and can replace the calendering complementing the line. Alternatively, a reel calender can be used to achieve the final gauge or to complement calendering off-line.

The air press 30 is shown in detail in detail by the top view of Figure 2 and the side view of Figure 3, the latter having parts cut away for purposes of illustration. The air press 30 generally comprises an upper air plenum 60 in combination with a lower collection device in the form of a vacuum or suction box 62. The terms "upper" and "lower" are used herein for ease of reference and understanding the drawings and do not want them to restrict the way in which the components are oriented. The sandwich of the wet tis fabric 24 between the forming fabric 22 and the supporting fabric 32 passes between the air plenum 60 and the vacuum box 62.

The illustrated air plenum 60 is adapted to receive a supply of pressurized fluid through the air manifolds 64 operatively connected to a pressurized fluid source d such as a compressor or blower (n shown). The air plenum 60 is provided with a full cover 66 which has a bottom surface 67 that resides during use in close proximity to the vacuum box 62 and in close proximity to or in contact with the support fabric 3.

(Figure 3). The cover of full 66 is formed with the grooves 68 (FIG. 5) extending perpendicular to the machine direction through essentially the full width of the wet fabric 24 but desirably slightly less than the width of the fabrics to allow the passage of the pressurized fluid from the full air through the fabric. the fabrics and the wet fabric.

The vacuum box 62 is operatively connected to a vacuum source and fixedly mounted to a support structure (not shown). The vacuum box 62 comprises a cover 70 having an upper surface 72 on which s moves the forming fabric 22. The vacuum box cover 7 is formed with a pair of slots 74 (Figures 3 and 5) which correspond to the location of the slot 68 in the full cover 66. The pressurized fluid drains the wet tissue 24 from the pressurized fluid being pulled from the plenum 60 into and through the vacuum box 62.

The fluid pressure within the air plenum 6 is desirably maintained at about 5 pounds per square inch (psi) (0.35 bar) or more, and particularly within the range of about 5 to about 30 pounds per square inch (0.35). -2.07 bar), such as around 15 pounds per square inch (1.03 bar). The fluid pressure within the air plenum 60 is desirably monitored and controlled at a predetermined level.

The bottom surface 67 of the plen cover 66 is desirably arched in a gentle manner to facilitate tissue control. The surface 67 is arched towards the vacuum box 62, which is arched about an axis placed on the side of the vacuum box of the fabric 24. The curvature of the lower surface 67 allows an angle change of the fabric combination. of support 32, wet fabric 24, and d forming fabric 22 resulting in a downward force net sealing the vacuum box 62 against the entrance of the outer air and holding the wet fabric 24 during the draining process. The angle of curvature allows the loading and unloading of the air press 30 as required from time to time based upon the process conditions. The change in angle necessarily depends on the pressure difference between the pressure and vacuum sides and is desirably above degrees, and particularly within the range of 5 to 30 degrees typically around 7.5 degrees.

The upper and lower surfaces 72 and 6 desirably have different radii of curvature. In particular, the radius of curvature of the lower surface 67 is desirably larger than the radius of curvature of the upper surface 72 so as to form the contact lines between the air plenum 60 and the vacuum box 62 at the leading and trailing edges. of tail 76 of the air press 30. With proper attention to the position of the support fabric 32 and of the forming machine 22, the sandwich and loading and unloading mechanisms, the radii of curvature of these surfaces can be inverted.

The leading and tail edges 76 of the air press 30 can also be provided with end seals 78 (Figure 3) that are kept in a proximity very close to or in contact with the support fabric 32 at all times. The end seals 78 minimize the escape of the pressurized fluid between the air plenum 60 and the vacuum box 62 in the machine direction. Suitable end seals 78 may be formed of low friction materials such as elastic plastic composites, materials that wear out preferably in relation to fabrics, or the like. The extrem seals desirably have curved edges to avoid the draping of the fabrics.

With further reference to Figures 4 and 5, the air press 30 is desirably provided with the side seal members 80 to prevent loss of the pressurized fluid along the side edges 82 of the air press. The side seal members 80 comprise a semi-rigid material that is adapted to deform or flex slightly when exposed to the pressurized fluid of the plenum 60. The illustrated side seal members 8 define a slot 84 for attachment to the housing cover. vacuum 70 using a gripper bar 85 and a fastener 86 or other suitable means. In the cross-section, each lateral seal member 80 is L-shaped with a leg 88 projecting upwards from the vacuum case cover 70 into a lateral seal groove 89 formed in the plenum cover 66. The fluid Pressurized from the air plenum 60 causes the legs 88 to bend outwardly into a seal contact with the outer surface of the side seal groove 89 of the full 66 cover; as shown in Figures 4 and 5. Alternatively, the position of the side seal members 80 can be reversed, such that they are fixedly fastened to the full cover 66 and make a sealing contact with the contact surfaces defined by l vacuum box cover 70 (not shown). In such alternate design, it is desirable that the side seal member be pushed to contact the sealing contact surface by the pressurized fluid.

A position control mechanism 90 maintains full air 60 in close proximity to the vacuum box 62 in contact with the support fabric 32. The position control mechanism 90 comprises a pair of levers 92 connected by the cross pieces. and fixedly fixed to the full air d by means of the appropriate fasteners 94 (Figure 3) The ends of the levers 92 opposite the air plenum 6 are rotatably mounted on the shaft 96. The position control mechanism 90 also comprises a cylinder of control balance 98 operably connected to a fi xed structural support 99 and one of the crosspieces 93. The balance control cylinder 98 is adapted to extend or retract and thereby cause the levers 92 to rotate about the axis 96, which makes the air plenum 60 moves to approach or move away from the vacuum box 62.

In use, a control system causes the counter balance cylinder 98 to extend sufficiently even that the end seals 78 make contact with the support fabric 32 and the side seal members 80 are placed within the side seal grooves. 89. The air press 30 is activated so that the pressurized fluid fills the full air d 60 and the semi-rigid side seal members 80 or are forced into a sealing contact with the plen cover 66. The pressurized fluid also creates a force upwards which tends to move the air plenum 60 outwardly from the supporting fabric 32. The control system directs counter balance cylinder operation 98 to decentralize this force to above based on the continuous measurements of the fluid pressure d of the air plenum 60 by the pressure monitoring system. The end seals 78 are thus maintained in a proximity very close to or in contact with the support fabric 32 at all times. The control system combats random pressure peaks or drops within the full air 60 by proportionally decreasing or increasing the force applied by the counter balance cylinder 98. The air flow within the air press can also be monitored accordingly., the end seals 78 do not grip the fabric 32 and 22, which could otherwise lead to excessive wear of the fabrics.

An alternating sealing system for the air pre-press 30 is shown representatively in Figure 6. E full of air 100 is provided with a pivotable arm 102 which defines or carries a sealing rod 104 which is adapted to move on the supporting fabric 32 through the anchor of the wet fabric 24 to minimize the escape of the pressurized flui in the machine direction. While only arm 102 is illustrated in Figure 6, it should be understood that second arm at the opposite end of air plenum 100 can be employed and constructed in a similar manner. The air-filled sides 100 can incorporate the side sealing members 80 as described in relation to Figures 2-5 can be fixedly mounted on the vacuum box 62 to minimize or eliminate side runoff of the pressurized fluid.

The pivotable arm 102 desirably comprises rigid material such as structural steel, graphite compounds, or the like. The arm 102 has a first part 10 placed at least partially inside the air plenum 10 and a second part 108 preferably positioned outside the air plenum. The arm 102 is pivotally mounted on the full air 100 by a hinge 110. A bisag seal 112 impervious to pressurized fluid is attached to both the inner surface of a wall 114 of the air plenum 100 and the first part 106 to prevent leakage of pressurized fluid Sealing bar 104 is desirably a spaced element mounted on first portion 106 and urged toward supporting fabric 32 (not shown in Figure 6) by contacting pressurized fluid on the first part. Suitable sealing bars 104 can be formed of a durable material of low coefficient of friction and low strength such as ceramics, heat resistant polymers or the like.

A counter balance bladder 120 having an inflatable chamber 122 is mounted on the second arm portion 108 with the brackets 124 or other suitable means. L chamber 122 is operably connected to a source of fluid under pressure such as air to inflate the chamber. The arm 102 and the bladder 120 are positioned so that the vejig when inflated (not shown) presses against the outer surface of the wall 114 of the air plenum 100 causing the arm to pivot around the hinge 110. Alternatively, A mechanism using pressurized cylinders (not shown) can be used in place of the counter balance bladder as a means for pivoting the arm 102.

A control system is operable to inflate deflate the bladder 120 proportionally in response to fluid pressure within the air plenum 100. For example, to increase the pressure within the air plenum 100, the control system is adapted to increase the pressure within the inflated bladder of the counter balance bladder 120 so that the sealing bar 104 does not grip excessively down against the support fabric 32.

The design of the vacuum transfer shoe 37 used in the transfer cloth section of the process (Figure 1) is more clearly illustrated in Figures 7 and The vacuum transfer shoe 37 defines an empty slot 130 (Figure 7) connected to a vacuum source and having a length of "L" which is suitably from about 0.5 to about 1 inch (12.7-25.4 mm) ). To produce a non-creped continuous dried bath tissue, the proper vacuum slot length is about 1 inch (25.4 millimeters). The vacuum slot 130 has a leading edge 132 and a tail edge 133, forming the corresponding inward and outwardly sloping areas 134 and 135 of vacuum transfer shoe 37. The tail edge 133 of the vacuum slot 130 is recessed in relation to the leading edge 132, which is caused by the different orientation of the outgoing plain area 135 relative to that of the incoming plan area 134. The angle "A" between the planes of the inbound plain area 134 and the outgoing plain area 135 be about 0.5 degrees or greater, more specifically about 1 degree or greater, and even more specifically about 5 degrees or greater in order to provide sufficient separation of the forming fabric 22 and the transfer fabric 36 as it converges and diverge these.

Figure 8 further illustrates the wet tis fabric 24 moving in the direction shown by the arrows to the vacuum transfer shoe 37. Also approaching the vacuum transfer shoe 37 is the transfer fabric 36 moving at a slower speed The angle of convergence between the two incoming fabrics is designated "C". The angle of divergence between the two webs is designated "D". As shown, the two fabrics converge simultaneously and diverge at the point "P", which corresponds to the leading edge 132 of the vacuum slot 130. It is not necessary or desirable for the fabric to be in contact with both fabrics over the length of the vacuum slot 130 to effect the transfer from the forming fabric 22 to the transfer fabric 36. As is evident from Figure 8, neither the forming fabric 22 nor the transfer fabric 36 require deflection more than a small amount. to carry out the transfer, which reduces fabric wear. Numerically, the change in direction of any fabric can be less than 5 degrees.

As mentioned previously, the transfer fabric 36 is traveling at a slower speed than that of the forming fabric 22. If more than one transfer fabric is used, the differential speed between the fabrics may be the same or different. Multiple transfer fabrics can provide operational flexibility as well as a wide variety of fabric / speed combinations to influence the properties of the final product.

The level of vacuum used for differential speed transfers can be from about 3 to about 15 inches of mercury, preferably about 5 inches of mercury. The vacuum shoe (negative pressure) can be supplemented or replaced by the use of positive pressure from the opposite side of the fabric 24 to blow the fabric onto the next fabric in addition to or as a replacement to suck it onto the next fabric with vacuum. Also, a vacuum roller or rollers can be used to replace the vacuum shoes.

. An alternative embodiment of the vacuum press 200 for draining a wet fabric 24 is shown in Figures 10-13. The air press 200 generally comprises an upper air plenum 202 in combination with a lower collection device in the form of a vacuum box 204. The wet tissue 24 travels in a machine direction 205 between the air plenum and the vacuum box while in the form of a sandwich between a top support fabric 206 and a bottom support fabric 208. The air plenum and the vacuum box are operatively associated with each other so that the pressurized fluid supplied to the plenum The air is displaced through the wet fabric and removed or evacuated through the vacuum box.

Each continuous web 206 and 208 is moved over a series of rollers (not shown) to guide, propel and tension the web in a manner known in the art. The fabric tension is set to a predetermined amount, suitably from about 10 to about 60 pounds per inch line (pli), particularly from about 30 to about 5 pounds per linear inch, and more particularly from around. from 35 to about 45 pounds per linear inch. The fabrics that can be useful for transporting the wet fabric 2 through the air press 200 include almost any fluid-permeable tel, for example, Albany International 94M, Appleton Mills 2164B, or the like.

An end view of the air press 20 extending to the width of the wet fabric 24 is shown in Figure 10, and the side view of the air press in the machine direction 205 is shown in Figure 11. E both Figures , several components of the plenum 202 are illustrated in a raised or retracted position relative to the wet tissue 24 and to the vacuum box 204. In the retracted position, effective sealing of the pressurized fluid is not possible. For the purposes of the present invention, a "retracted position" of the air press means that the components of the air plenum 202 do not stick on the wet fabric and the support fabrics.

The illustrated air plenum 202 and the vacuum box 204 are mounted within a suitable frame structure 210. The frame structure illustrated comprises the upper and lower support plates 211 separated by a plurality of vertically oriented support bars 212. The air plenum 202 defines a chamber 214 (Figure 13) which is adapted to receive a supply of pressurized fluid through 1 or more air ducts 215 operatively connected to a pressurized fluid source d (not shown). Correspondingly, the vacuum box 204 defines a plurality of vacuum chambers (described hereinafter in relation to FIG. 13) which are operatively connected in desirable manner to the upper and lower vacuum sources (not shown) by means of suitable fluid conduits 217 and 218, respectively (Figure 11, 12 and 13). The water removed from the moist tissue 24 is then separated from the air streams. Several fasteners for mounting the components of the air press are shown in the Figures but are not marked.

The amplified section views of the air press 200 are shown in Figures 12 and 13. In these Figures the air press is shown in a position d operation wherein the components of the air plenum 202 are lowered to a shock ratio. with the wet fabric 24 and the support fabrics 206 and 208. The degree of shock that has been found to result in an adequate sealing of the pressurized fluid with a minimum contact force and therefore or reduced fabric wear is described in greater detail from here onwards.

The air plenum 202 comprises both stationary components 220 that are fixedly mounted to frame structure 210 and a seal assembly 260 that is movably mounted in relation to the frame structure and the wet fabric. Alternatively, the full air plenum can be mounted movably in relation to a frame structure.

With a particular reference to Figure 13, the stationary components 220 of the air plenum include a pa of upper support assemblies 222 that are spaced apart from one another and placed below the upper support plate 211. The upper support assemblies define the front surfaces 224 which are directed towards each other which partially define between them the plenum chamber 214. The upper support assemblies also define the bottom surfaces 226 which are directed towards the vacuum box 204. In the embodiment illustrated, each bottom surface 226 defines an elongated recess 228 in which an upper pneumatic load tube 230 is fixedly mounted. The upper pneumatic load tubes 230 are suitably centered in the direction transverse to the machine and desirably extend over the full width of the wet tissue.

The stationary components 220 of the air plenum 202 also include a pair of lower support assemblies 240 that are spaced apart from each other vertically spaced from the upper support assemblies 222. The lower support assemblies define the upper surface 242 and the surfaces 244. The upper surfaces 242 are directed toward the lower surfaces 226 of the upper support assemblies 222 and, as illustrated, define the elongated recesses 246 in which the lower pneumatic load tubes 248 are fixedly mounted. The lower pneumatic load tubes 248 are suitably centered in the transverse direction to the machine and suitably extend about 50 to 100 percent of the width of the wet fabric. In the illustrated embodiment, the side support plates 250 are fixedly fastened to the front surfaces 244 of the lower support assemblies and function to stabilize the vertical movement of the seal assembly 260.

With further reference to Figure 14, the sealing assembly 260 comprises a pair of cross-machine direction sealing members mentioned as sealing members CD 262 (Figures 12-14) that are spaced apart from one another, a plurality of clamps 263 (Figure 14) connecting the CD sealing members, and a pair of sealing members in the machine direction mentioned as sealing members MD 264 (Figures 12-14) The sealing members CD 262 they move vertically relative to the stationary components 220. The optional but desirable clamps 263 are fixedly fastened to the CD sealing members to provide a structural support, and thus move vertically together with the CD sealing members. In the machine direction 205 the sealing members MD 264 are placed between the upper support assemblies 222 and between the sealing members CD 262. As described in greater detail hereinafter, parts of the sealing members MD moves vertically relative to the stationary components 220 In the transverse direction to the machine, the MD sealing members are positioned near the edges of the wet weave 24. In a particular embodiment, the MD sealing members move in the direction transverse to the machine in order to accommodate a range of possible wet tissue widths The illustrated CD sealing members 26 include a main vertical wall section 266, a transverse flange 268 projecting outwardly from an upper part 270 of the wall section, and a sealing blade 272 mounted on an opposing bottom portion 274 d the wall section (Figure 13). The flange projecting outwardly 268 thus forms the opposed lower upper control surfaces 276 and 278 which are essentially perpendicular to the direction of movement of the sealing assembly. The wall section 266 and the flange 268 may comprise the separate components or a single component as illustrated.

As noted above, the components of the sealing assembly 260 move vertically between the retracted position shown in Figures 10 and 11 and the operating position shown in Figures 12 and 13. In particular, the wall sections 266 of the members of sealing CD 26 are placed in the control plates d position 250 and slide some in relation to these. The amount of vertical movement was determined by the ability of the transverse flanges 268 to move between the base surfaces 226 of the support assemblies 222 and the upper surfaces 242 of the lower support assemblies 240.

The vertical position of the transverse flanges 268 and therefore of the sealing members CD 262 is controlled by the activation of the pneumatic load tubes 230 248. The load tubes are operatively connected to a pneumatic source and to a control system (not shown) for the air press. The activation of the upper charging tubes 230 creates a downward force on the upper control surfaces 276 of the sealing members CD 262 resulting in a downward movement of the flanges 268 until they are in contact with the upper surfaces 242 of the lower support assemblies 240 or stopped by a superior force caused by the lower load tubes 248 or fabric tension. Retraction of the CD 262 s sealing members achieved by activating the lower charge tubes 24 and deactivating the upper charge tubes. In this case, the lower loading tubes press up on the lower control surfaces 278 and cause the flanges 268 to move towards the bottom surfaces of the upper support assemblies 222. Of course, the upper and lower charge tubes can be operated to press differential to establish the movement of the members d sealing CD. Alternate means for controlling the vertical movement of the CD sealing members may comprise other shapes and connections of pneumatic cylinders, hydraulic cylinders, screws, jacks, mechanical joints, or other suitable means. Proper charging tubes are available from Seal Master Corporatio of Kent, Ohio.

As shown in Figure 13, a pair of bridge plate 279 extend to the spacing between the upper support assemblies 222 and the sealing members CD 262 to prevent the escape of the pressurized fluid. The bumper plates therefore define part of the plenum chamber 214. The bridge plates can be fixedly fixed to the front surfaces 224 of the upper support assemblies to slide relative to the interior surfaces of the CD sealing members, or vice versa. The bent plates can be formed of a low friction, semi-rigid material impermeable to the fluid such as a LEXAN, a sheet metal like.

The sealing blades 272 operate in conjunction with other characteristics of the air press to minimize the escape of the pressurized fluid between the air plenum 202 and the wet tissue 24 in the machine direction. Additionally, the sealing blades are desirably shaped formed in a manner that reduces the amount of fabric wear. In particular embodiments, the sealing blades are formed of elastic plastic compounds, coated metal substrates, ceramics or the like.

With particular reference to Figures 12 and 14, the sealing members MD 264 are spaced apart from one another and adapted to prevent the loss of pressurized fluid along the side edges of the air press. Figures 12 and 14 each show the sealing members MD 264, which are positioned in the transverse direction to the machine near the edge of the wet fabric 24. As illustrated, each sealing member MD comprises a transverse support member 280 , and an end cap strip 282 operatively connected to the transverse support member, and actuators 284 for moving the end cap strip in relation to the transverse support member. The transverse support members 280 are normally positioned near the side edges of the wet fabric 24 and are generally located between the CD sealing members 262. As illustrated, each transverse support member defines the downward channel 281 (Figure 14) in which an end cover strip is mounted. Additionally, each transverse support member defines the circular openings 283 in which the actuators 284 are mounted.

The end cover strips 282 can move vertically in relation to the transverse support members 280 due to the cylindrical actuators 284. The coupling members 285 (FIG. 12) link the end cover strips d to the output shaft of the actuators. cylindrical The coupling members may comprise an inverted T-shaped bar or bars so that the end cover strips can slide within the channel 281, as a replacement.

As shown in Figure 14, both the transverse support members 280 and the end cover strips 282 define grooves for housing a fluid impervious sealing strip 286, such as a similar 0-ring material. The sealing strip helps seal the air chamber 214 of the exhaust air press. The slots in which the sealing strip resides desirably widen in the interface between the transverse support members 280 and the end cover strips 282 to accommodate the relative movement between those components.

A bridge plate 287 (Figure 12) is positioned between the sealing members MD 264 and the upper support plate 211 and is fixedly mounted to the upper support plate. The side parts of the air chamber 214 (Figur 13) are defined by the bridge plate. Sealing means such as a fluid impervious packing material are desirably positioned between the bridge plate and the sealing members MD to allow relative movement therebetween and prevent the loss of the pressurized fluid.

The actuators 284 suitably produce the controlled loading and unloading of the end cover strips 282 against the upper support fabric 206, regardless of the vertical position of the CD 262 sealing members. The load can be accurately controlled to equalize the force of necessary sealing. End cap strips can be retracted when they are not required to eliminate all fabric and end cap wear. Suitable actuators are available from Bimb Corporation. Alternatively, the springs (not shown) can be used to hold the end cover strips against the fabric even though the ability to control the position of the end cover strips can be sacrificed.

With reference to Figure 12, each end cap strip 282 has an upper edge or surface 29 positioned on one side of the coupling members 285, an opposing bottom or edge surface 292 that resides during contact in contact with the fabric. 206, and side edges or surfaces 294 that are in close proximity to the CD sealing members 262. The shape of the bottom surface 292 is suitably adapted to equalize the curvature of the vacuum case 204. Where the sealing members CD 262 hits the fabrics, the bottom surface 292 is desirably shaped to follow the curvature of the fabric stroke. Thus, the bottom surface has a central part 296 which is laterally surrounded in the machine direction by the spaced-apart end portions 298. The shape of the central part 296 generally follows the shape of the vacuum box while the shape of the end portions 298 generally follows the deflection of the fabrics caused by the sealing members CD 262. To prevent wear of the projection end portions 298, the end cover strips s desirably retract before they C 262 sealing members retract. The end cover strips 282 are desirably formed of a material impervious to gas which minimizes fabric wear. Particular materials that may be suitable for end covers include polyethylene, nylon, or the like.

The sealing members MD 264 are desirably movable in the transverse direction to the machine and are therefore slidably disposed against the sealing members CD 262. In the illustrated embodiment, the movement of the sealing members MD 264 in FIG. The cross machine direction is controlled by a bolt or threaded shaft 305 which is held in place by the clamps 306 (Figure 14). The threaded sleeve 305 passes through a threaded opening in the transverse support member 280 and rotation of the shaft causes the sealing member in the machine direction to move along the axis. Alternate means for moving the sealing members MD 264 in the transverse direction to the machine such as pneumatic devices or the like can also be used. In an alternate embodiment, the MD sealing members are fixedly fastened to the CD sealing members so that the complete sealing assembly is raised and lowered together (not shown). In another alternate embodiment, the transverse support members 280 are fixedly fastened to the CD sealing members and the end cover strips are adapted to movers independently of the CD sealing members (n shown).

The vacuum case 204 comprises a cover 30 having an upper surface 302 on which the lower support fabric 208 is displaced. The vacuum case cover 30 and the seal assembly 260 are desirably gently arched to facilitate tissue control. , as described previously in relation to other incorporations. The illustrated vacuum case cover is formed, from the leading edge to the trailing edge in the direction of the machine 205, with a first outer sealing shoe 311, a first sealing vacuum zone 312, a first inner sealing shoe d 313, a series of four upper vacuum zones 314, 316, 318 and 320 surrounding three inner shoes 315, 317 and 319, a second inner sealing shoe 321, a second sealing gap 322, and a second sealing shoe exterior 323 (Figure 13). Each of these shoes and zones desirably extends in the transverse direction to the machine through the full width of the fabric. The shoes include each top surface desirably formed of a ceramic material to move against the lower support fabric 208 without causing significant wear of the fabric. The vacuum box covers and the shoes may be formed of plastics, nylon, coated steel, and the like, and are available from JWI Corporation or IB Corporation.

The four high vacuum zones 314, 316, 318 and 32 are conduits in the cover 300 that are operatively connected to one or more vacuum sources (not shown) that pull a relatively high vacuum level. For example, the vacuum zones can be operated at a vacuum of 0 to 25 inches d of mercury vacuum, and more particularly to about 10 about 25 inches of mercury vacuum. As an alternative to the illustrated conduits, the cover 300 can define a plurality of holes or other shaped openings (not shown) that are connected to a vacuum source to establish a flow of pressurized fluid through the tissue. High vacuum comprise each slot measuring 0.375 inches in the machine direction extending through the full width of the wet fabric. The residence time that any given point of the fabric is exposed to the flow of the pressurized fluid, which in the illustrated embodiment is the time over the slots 314, 316 318 and 320, is suitably about 10 milliseconds less, particularly about about 10 milliseconds. 7.5 milliseconds or less "particularly of 5 milliseconds or less, such as d about 3 milliseconds or less or even about milliseconds or less.The number and width of vacuum slots of high pressure and machine speed The dwell time selected will depend on the type of fibers contained in the wet fabric the desired amount of drainage.

The second first seal sealing zones 312 and 322 can be employed to minimize the loss of pressurized fluid from the air press. Vacuum sealing zones are conduits in the cover 300 that can be operatively connected to one or more vacuum sources (n shown) that desirably pull a relatively lower vacuum level compared to the four vacuum zones. Specifically, the amount of vacuum that is desirable for the sealing vacuum zones is from 0 to about 10 inches of water column, of vacuum.

The air press 200 is desirably constructed so that the sealing members CD 262 are positioned within the sealing vacuum zones 312 and 322. More specifically, the sealing blade 272 of the sealing member CD 262 which is on the side The front of the air press is positioned between, and more particularly centered between, the first outer sealing shoe 311 the first inner shoe 313, in the machine direction. The glue sealing blade 272 of the sealing member CD is similarly positioned between, and more particularly centered between, the inner sealing member shoe 32 and the second outer sealing shoe 323, in the machine direction. As a result of this, the sealing assembly 260 can be lowered so that the CD sealing members deflect the normal course of wet tissue movement 24 and the fabrics 206 and 208 toward the vacuum box, which is shown on a scale slightly exaggerated in Figure 13 for purposes of illustration.

The sealing vacuum zones 312 and 32 function to minimize the loss of pressurized fluid from the air press 200 through the width of the wet tissue 24. E vacuum in the sealing vacuum zones 312 and 322 pull the pressurized fluid from the air plenum 202 and pulls the air environment from the outside of the air press Consequently, an air flow is established from the outside of the air press to the sealing vacuum zones rather than a leak of pressurized fluid in the air. opposite direction Due to the relative difference in vacuum between the upper vacuum zones and the vacuum zones with sealing, however, the vast majority of the pressurized fluid from the plenum air pulls into the high vacuum zones rather than in d areas with vacuum sealing.

In an alternate embodiment which is partially illustrated in Figure 15, no vacuum is removed from either or both of the sealed vacuum zones 312 322. Rather, the deformable seal covers 33 are placed in the sealing areas 312. and 322 (only s shows 322) to prevent leakage of pressurized fluid in the machine direction. In this case, the air press is sealed in the machine direction with the sealing blades 272 that stick on the fabrics 206 and 208 and the wet fabric 24 and by the fabrics and the wet fabric being placed in close proximity to or in contact with the deformable sealing covers 330. This configuration, wherein the CD 262 sealing members stick on the fabrics and the wet fabric and the CD sealing members are opposite on the other side of the fabrics and the wet fabric by the Deformable sealing cover 330 has been found to produce a particularly effective air plenum seal.

The deformable sealing covers 33 desirably extend across the full width of the wet fabric to seal the leading end, the tail end, both the leading end and the tail end of the air press 200. The vacuum zone of Sealing can be disconnected from the vacuum source when the deformable seal cover extends through the full fabric width. E where the tail end of the air press employs a full width deformable seal cover, either a vacuum device or a blow box downstream of the air press can be used to cause the fabric 24 to remain with one of the fabrics. when said fabrics are separated.

The deformable seal covers 33 desirably comprise either a material that is preferably worn in relation to the fabric 208, meaning that when the fabric and the material are in use the material will wear out if it causes significant wear of the fabric, or will comprise material which is elastic and which deflects with the shock of the fabric. In either case, the deformable seal covers are desirably gas impervious, desirably comprising a material with a high hollow volume such as a closed cell foam or the like. In particular incorporation, the deformable seal covers comprise a closed cell foam measuring 0.2 inches in thickness. More desirably, the same deformable seal covers wear to equalize the trajectory of the fabrics. The deformable seals are desirably accompanied by a backing plate 332 for structural support, for example an aluminum casing.

In embodiments where full width sealing covers are not used, sealing means of some kind are laterally required of tissue. Deformable sealing covers, described above, or other means known in the art, can be used to block the flow of pressurized fluid through the fabrics laterally outward of the wet fabric.

The degree of shock of the sealing members CD in the upper support fabric 206 uniformly across the width of the wet fabric has been found to be a significant factor in creating an effective seal through the fabric. The required degree of shock has been found to be a function of the maximum tension of the fabric. the lower upper support fabrics 206 and 208, the pressure difference through the fabric and in this case between the plenum chamber 214 and the sealing vacuum zones 312 and 322, and the spacing between the sealing members CD 262 and the empty box cover 300.

With additional reference to the schematic diagram of the tail sealing section of the air press shown in Figure 16, the minimum desirable amount of shock of the sealing member CD 262 inside the upper supporting fabric 206, h (min), it has been found that the following equation is represented by: A (min) «^ (8sh-J-lj; where : T is the fabric tension measured in pounds per inch; W is the pressure difference across the fabric mediated in pounds per square inch; Y d is the separation in the direction of the machine mediated in inches.

Figure 16 shows the glue sealing member C 262 deflecting the upper support fabric 206 by an amount represented by the arrow "h". The maximum tension of the upper and lower support fabrics 206 and 208 is represented by the arrow "T". The fabric tension can be measured by a model tension meter available from Huyck Corporatio or other suitable methods. The separation between the sealing blade 272 of the sealing member CD and the second inner sealing shoe 321 measured in the machine direction and represented by the arrow "d". The separation "d" of u meaning to determine the stroke is the separation on the side of the pressure difference upper of the sealing blade 272, that is, towards the plenum chamber 214, due to the pressure difference on that side which is more effective on the position of the fabrics and the fabric. Desirably, the separation between the sealing blade and the second outer shoe 323 is approximately equal to or less than the separation "d".

The adjustment of the vertical placement of the CD 262 sealing members to the minimum degree of shock as defined above is a determining factor in the effectiveness of the CD seal. The load force applied to the seal assembly 2 plays a minor role in determining the effectiveness of the seal, it requires putting only the amount necessary to maintain the required degree of shock. Of course, the amount of fabric wear will impact the commercial utility of the air press 200. To achieve an effective seal without essential wear, the degree of impact is desirably equal to or only slightly greater than the minimum degree of shock as defined above. . To minimize the variability of fabric wear across the width of the fabrics, the force applied to the fabric s desirably remains constant over the direction transverse to the machine. This can be achieved with any controlled and uniform loading of the CD sealing members or the controlled position of the CD sealing members and the uniform shock geometry of the CD sealing members.

In use, a control system causes the sealing assembly 260 of the air plenum 202 to be lowered to an operating position. First, the sealing members C 262 are lowered so that the sealing blades 27 stick on the upper support fabric 206 to the degree described above. More particularly, the pressures in the upper and lower load tubes 230 and 248 are adjusted to cause downward movement of the sealing members CD 26 until the movement is stopped by the transverse flanges 268 which contact the support assemblies. lower 24 or until they are balanced by fabric tension. Secondly, the end cover strips 282 of the MD sealing members 264 are lowered into contact with or in close proximity to the upper support fabric. Consequently, the air plenum 202 and the vacuum box 204 s seal both. against the wet tissue to prevent the escape of pressurized fluid.

The air press is then activated so that the pressurized fluid fills the air plenum 202 and an air flow is established through the tissue. In the embodiment illustrated in Figure 13, the upper and lower voids are applied to the upper vacuum zones 314, 316, 318 and 320 and the sealing vacuum zones 312 and 322 to facilitate airflow, sealing and sealing. water removal In the embodiment of Figure 15, the pressurized fluid flows from the plenum to the high vacuum areas 314, 316, 318 and 320, the deformable seal covers 330 seal the air press in the cross machine direction. The resulting pressure difference through the wet fabric and the resultant air flow through the fabric provide efficient tissue drainage.

A number of structural features and operation of the air press contribute to the fact that very little pressurized fluid escapes in combination with a relatively low amount of fabric wear. Initially, the air pre-press 200 uses the sealing members CD 262 which sticks on the fabrics and the wet fabric. The degree of shock was determined to maximize the effectiveness of the CD seal. In one embodiment, the air press utilizes the vacuum sealing zones 312 and 322 to create an ambient air flow into the air press through the width of the wet weave. In another embodiment, the deformable seals members 330 are placed in the sealing vacuum regions 312 and 322 opposite the sealing members CD. In either case, the sealing members CD 262 are desirably positioned at least partially in the conduits of the seals. the vacuum case cover 300 so as to minimize the need for accurate alignment of the matching surfaces between the air plenum 202 and the vacuum case 204. In addition, the seal assembly 260 can be charged against the stationary component such as the lower bearing assemblies 240 which are connected to the frame structure 210. As a result of this, the loading force for the air press is independent of the pressurized fluid pressure inside the air plenum. Te wear is also minimized due to the use of low fabric wear materials and lubrication systems. Suitable lubrication systems may include chemical lubricants such as emulsified oils, binder or other similar chemical or water. Typical lubricant application methods include spraying a diluted lubricant applied in a uniform cross machine direction, a hydraulically or air-atomized solution, a felt cleaner from a more concentrated solution, or other highly effective methods. known in spray system applications Observations have shown that the ability to run at full pressures of higher pressure depends on the ability to prevent leaks. The presence of a leak can be detected from excessive air flows in relation to previous or expected operation, from additional operating noise, d moisture sprays, and in extreme cases, from regular or random flaws in wet tissue including hole and lines. Leaks can be repaired by aligning or adjusting the air press sealing components In the air press, uniform air flows in the direction transverse to the machine are desirable to provide uniform drainage of a fabric. The uniformity of flow in the direction transverse to the machine can be improved with mechanisms such as tapered ducts on the pressure and vacuum sides, shaped using dynamic modeling of computational fluid. Because the basis weight and moisture content may not be uniform in the transverse direction of the machine, it may be desirable to employ additional means to obtain uniform air flow in the transverse direction of the machine, such as independently controlled zones with shock absorbers. on the pressure or vacuum sides for varying the air flow based on the sheet properties, a separator plate d for taking a significant pressure drop in the flow before wet tissue, or other direct means. Alternative methods for controlling drainage uniformity C may also include external devices, such as zoned controlled steam showers, for example, a steam duch Devronizer available from Honeywe11-Measurex Systems Inc., of Dublin, Ohio or the like.

E J E M P L O S The following examples are provided to give a more detailed understanding of the invention. The amounts of particulars, proportions, compositions and parameters are intended to be exemplary, and are not intended to specifically limit the scope of the invention.

As referred to in the examples, the tensile strength MD, the MD stretch, the tensile strength CD are obtained according to the test method TAPPI 494 OM-88"Paper and Cardboard Tensi Breaking Properties" using the following parameters: crosshead speed is 10.0 inches / minute (254 millimeters / minute); The full-scale load is 4.540 grams; the jaw extension (the distance between the jaws, sometimes referred to as the calibration length) is 2.08 inches (50.8 millimeters); and the specimen width is 3 inches (76. millimeters). The stress test machine is a Sintech model CITS-2000 machine, from Systems Integration Technology Inc., of Stoughton, Massachusetts, a division of MTS System Corporation, of Research Triangle Park, North Carolina.

The stiffness of the example sheets can be represented objectively by any the maximum inclination of the elongation / load curve in the machine direction (MD) for the fabric (hereinafter referred to as the "MD tilt") or the stiffness in the fabric. the address of the machine (here defined) which also takes into account the size of the tis and the number of layers of the product. The determination of the inclination MD will be described hereinafter in relation to Figure 9. The inclination MD is the maximum inclination of the curve of elongation / load in the direction of the machine for tissue. The units for MD tilt are kilograms per inch (7.62 centimeters). The MD stiffness was calculated by multiplying the MD inclination by the square root of the caliper quotient divided by the number of layers. The MD rigidity units are (kilograms per 3 inches) -mieras0-5 Figure 9 is a generalized elongation curve for a tissue sheet, illustrating the determination of MD inclination. As shown, two points Pl and P2, the distance between which is exaggerated for purposes of illustration, are selected so that they lie along the elongation / loading curve. The voltage tester is programmed (GAP [General Application Program], version 2.5, System Integration Technology, Inc., of Stoughton, Massachusetts, a subsidiary of MTS Systems Corporation, of Research Triangl Park, North Carolina) so that this calculates a liner regression for the points that are subject to sample d Pl to P2. This was calculated repeatedly on the curv by adjusting the points Pl and P2 in a regular manner along the curve (hereinafter described). The highest value of these calculations is the tilt Max and, when carried out on the direction of the specimen machine, s will be mentioned here as the tilt MD.

The voltage tester program should be set so that five hundred points such as Pl and P2 are taken over an elongation extension of (63.5 millimeters). Est provides a sufficient number of points to essentially exceed any practical lengthening of the specimen With at a crosshead speed of 254 millimeters per minute, it is translated into a point every 0.030 seconds. The program calculates the inclinations between these points by putting the decimal point as the starting point (for example Pl), counting 30 points at point 40 (for example P2) and carrying out a linear regression on those 30 points. This stores the slope of this regression in an array. The program then counts 10 points up to the twentieth point (which becomes Pl) repeats the procedure again (counting thirty points to what would be the fiftieth point (which becomes P2) by calculating the tilt and also storing this in arrangement). This process continues for the complete lengthening of the blade. The Max tilt is then chosen as the highest val for this arrangement. The units of inclination Max s kilograms by 3 inches of specimen width (the tension e of course not dimensional since the length of the extension s divided by the length of the jaw extension.) This calculation is taken into account by the program of the test machine).

E i e m p l o s 1-4 To illustrate the invention, various non-creped continuous dried tissues were produced using the method essentially as illustrated in Figure 1. More specifically, Examples 1-4 were all single-layer, three-layer tissue in which the outer layers comprised deagglutinated and dispersed eucalyptus fibers and the core layer comprised refined northern soft maple kraft fibers. The Cenebr eucalyptus fibers were pulped for 15 minutes at a consistency of 1 percent and drained to a consistency of 30 percent. The pulp was then fed to a Maule shaft disperser. The disperser was operated at 70 degrees Celsius with a force input of 2.2 HPD / T (1.8 kilowatts-days per metric ton) After dispersion, a softening agent (Witc C6027) was added to the pulp in the amount of 7.5 kilograms per metric ton of dry fiber (0.75 percent by weight).

Before forming, the softwood fibers were pulped for 30 minutes at a consistency of 3. percent, while the deagglutinated and dispersed eucalyptus fibers were diluted to a consistency of 2.5 percent. The weight of the overall layer sheet was divided into 35 percent / 30 percent / 35 percent for Examples 1, 2 and 4 at 33 percent / 34 percent / 33 percent for the Example among eucalyptus layers scattered / softened refined wood / eucalyptus scattered. The core layer was refined required levels to achieve the target d resistance values, while the other layers provided volume softness. For a resistance to temporary humidity and in added sec, a reinforcing agent defined co Parez 631 NC was added to the central layer.

These Examples used a 4-layer Beloit Concept Box III. The soft-made kraft supply from the refined north was used in the two central headbox layers to produce a single central layer for the three-layer product described. Reduced turbulence generation inserts were used for about 75 millimeters from the slice and the layer dividers extend p about 150 millimeters beyond the slice. The net slice aperture was about 0.9 inches (23 millimeters), the water flows in all four layers of box fit were comparable. The consistency of the supply fed the head box was around 0.09 percent per pes The resulting three-ply sheet was formed on a roll of suction form of twin forming wire with forming fabrics being Appleton Mills 2164-B fabrics. The speed of the forming fabric varied between 11.8 and 12.3 metr per second. The newly formed fabric was then dewatered to a 25-26 percent consistency using vacuum suction from below the forming fabric without an airlock, and 32-33 percent with an air press before s transferred to the transfer cloth which moved to 9. meters per second (29-35 percent fast transfer) The transfer fabric was an Appleton Mills 2164 -B. A vacuum shoe gauge of about 150-380 millimeters of mercury vacuum was used to transfer the fabric to the transfer fabric.

The fabric was then transferred to a continuous dried fabric that moved at a speed of about 9.1 meters per second. Applet Mills T-124-4 and T-124-7 continuous drying fabrics were used. The fabric was carried over a continuous Honeycomb drier operating at a temperature around 350 degrees F (175 degrees Celsius) and a final dryness of about 94-98 percent consistency was dried.

The production sequence of the example sheets was as follows: four rolls of the leaves of Example 1 s were produced. The consistency data reported in the Table is based on two measurements, one at the beginning and one at the end of the four rolls. The other data shown in the Table represents an average based on four measurements, one po roll. The air press was then turned on. The data just before and just after the activation of the air press are shown in Table 3 (individual data points). This data shows that the air press caused significant increase in voltage values. The process was then modified to decrease the values of tension to level comparable to those of the sheets of Example 1. After the process adjustment period, four rolls of sheets of Example 2 (this invention) were produced. Then, four rolls of the sheets of Example 3 (this invention) are produced using a different continuous drying fabric and with the activated ai press. The air press was turned off and the process was adjusted to regain the tensile strength values comparable to those of the sheets of Example 3. Four rolls of sheets of Example 4 were then produced. The consistency data for each Example in Table 2 is a promed based on two measurements, one at the beginning and one at the end of each set of four rolls. The other data in Table 2 are based on an average of four measurements for each sheet Example, one per roll. In Table 2, the data in the Example were presented in the left column and the data in Example 3 were presented in the column on the right side to remain consistent with Tables 1 and 3, which most data without the air press in the column on the left data with the air press in the column on the right.

Tables 1-3 gave more detailed descriptions of the process conditions as well as the resultant tissue properties for Examples 1-4. As used in Tables 1-3 below, the column headers have the following meanings: "consistency @ rapid transfer is the consistency of the fabric at the point of transfer from the forming fabric to the transfer fabric, expressed as a percent solid, the "MD stress" is the tensile strength in the machine direction, expressed in grams per inch - (7.62 centimeters) in sample width, the "C stress is the tensile strength in the machine direction , expressed as grams per 3 inches (7.62 cm of sample width), "MD stretch" is the stretch of the machine direction, expressed as percent elongation to sample failure, "MD tilt" as defined above , expressed as kilograms per 3 inch (7.62 centimeters) of the sample width; The "caliber" is a 1-leaf gauge measured with a volume micrometer (model TMI 49-72-00, Amityville, New York) having an anvil diameter of 103.2 millimeters and an anvil pressure of 22 grams / square inch (3.39 kilopascals), expressed in microns "MD stiffness" is the stiffness factor in the machine direction as defined above, expressed as (kilograms per inches) - mieras05, "basis weight" is the finished basis weight expressed as grams per square meter; "TAD fabric" means dried cloth continuously; "refiner" is the input d force to refine the core layer, expressed as kilowatts "fast" is the difference in speed between the forming fabric and the slower transfer fabric, divided by the velocity of the transfer fabric and expressed as a percentage "HW / SW" is the breaking of the weight of the fibers of wood dur (HW) and soft wood (SW) in the tissues of single layer d three layers, expressed as a weight percent of total fiber and "Parez" "is the aggregate rate of Parez 631 NC expressed as kilograms per metric ton of the core layer fiber.

A B L A T A B A As shown by the previous Examples, the air press produces significantly higher consistencies upstream of the differential velocity transfer which results in softer sheets as evidenced by the lower module values. Desirably, the modulus (MD stiffness) of the tissue products is at least 2 percent or less than that of the comparable tissue product made without a complementary drain at a consistency of more than about 30 percent. In addition, the tension in the direction of the machine of the tissue products is at least 2 percent or greater, and the tension in the transverse direction of the tissue products is at least 20 percent greater, than that of a comparable tissue product made if draining in addition to a consistency of more than about 30 percent. Additionally, the stretch and direction of the machine of the tissue products is at least 17 percent or greater than that of a comparable tis product made without a complementary drain at a consistency of more than about 30 percent .

The above detailed description has been carried out for the purpose of illustration. Therefore, a number of modifications and changes can be made without departing from the spirit and scope of the present invention. For example, alternate or optional features described as part of one modality may be used to give yet another modality. Additionally, two named components can represent parts of the same structure. In addition, various processes and arrangements of equipment may be employed as described in U.S. Patent No. 5,667,636 issued on September 16, 1997 to S. A. Engel et al. Therefore, the invention should not be limited by the specific embodiments described but only by the claims.

Claims (22)

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

1. An air press for draining a moist fabric comprising: an air plenum comprising a full cover having a bottom surface; means for supplying pressurized fluid to full air; a vacuum box comprising a vacuum box cover having a top surface positioned in close proximity to the lower surface of the full cover d; means for applying vacuum to the vacuum box; the side seal members adapted to contact the air plenum and the vacuum box to minimize the escape of the pressurized fluid, the side seal members attached to one of the air plenum and the vacuum box positioned in close proximity to the surfaces of lateral seal contact defined by the other of the air plenum and the vacuum box, the side seal members adapted to flex to a sealing contact with the lateral seal contact surface with the exposure to the pressurized flui.

2. The air press as claimed in clause 1 characterized in that the side seal members are attached to the vacuum case cover, and the full cover defines the side seal grooves and the side seal contact surfaces.

3. The air press as claimed in clause 1 characterized in that it comprises the end seals attached to the plenum cover.

4. The air press as claimed in clauses 1 or 3, characterized in that it comprises a position control mechanism adapted to keep the air plenum close to the vacuum box.

5. The air press as claimed in clause 4 characterized in that the position control mechanism comprises a lever mounted rotatably attached to full air and a counter balance cylinder adapted to rotate the lever.

6. The air press as claimed in clause 4, characterized in that it comprises a control system adapted to direct the operation of the balance control cylinder in response to measurements of the fluid pressure within the air plenum.

7. The air press as claimed in clauses 1, 2 or 3, characterized in that the upper and bottom surface are arched towards the vacuum box.

8. The air press as claimed in clause 7 characterized in that the top and bottom surfaces have different radii of curvature.

9. An air press for draining a wet weave, which comprises: an air plenum comprising a full roof d having a lower surface; means for supplying pressurized fluid to full air; a vacuum box comprising a vacuum box cover having a top surface positioned in close proximity to the bottom surface of the full cover d; means for applying vacuum to the vacuum box; an arm mounted in a pivot on the air ple and comprising the first and second parts, the first part is located at least partially within the full air and comprises a sealing rod; Y means for pivoting the arm in response to the fluid pressure within the plenum.

10. The air press as claimed in clause 9 characterized in that it comprises a hinge seal d impervious to pressurized fluid and attached to both e full of air and the first part.

11. A device for draining a wet fabric that moves in a direction of the machine, which comprises: a frame structure; support fabrics adapted to sandwich the fabric therebetween; an air press comprising an air plenum and a collection device placed on the opposite sides of the wet tissue and the support fabrics, the air plenum and the collection device are operatively associated with one another and adapted to establish a flow of air. Pressurized fluid through the wet tissue, the air plenum comprises: stationary components mounted on the frame structure and defining a load surface generally parallel to a plane containing the wet tissue; a seal assembly that is adapted to move relative to the stationary components between an operating position in which the seal assembly forms an integral seal for the wet tissue and a retracted position, the seal assembly defining a control surface generally parallel to the plane containing the wet tissue and adapted to make contact with the loading surface; Y means for moving the sealing assembly generally perpendicular to the plane containing the wet fabric, wherein the contact between the control surface and the loading surface interrupts the movement of the sealing assembly towards the wet tissue when the sealing assembly reaches the position of operation.

12. The device as claimed in clause 11 characterized in that the air press is adapted to provide a pressure difference through tissue of from about 25 to about 120 inches of mercury.

13. The device as claimed in clause 12 characterized in that the pick-up device is adapted to operate at more than 0 to about 25 inch of mercury vacuum.

14. The device as claimed in clause 12 characterized in that the plenum is adapted to operate at a pressurized fluid pressure of about 5 pounds per square inch over atmospheric pressure or greater.

15. The device as claimed in clause 12 characterized in that the air press is adapted to provide a pressurized fluid flow of about 10 standard cubic feet per minute per square inch of open area or greater.

16. A method for dewatering a cellulosic fabric using pressurized fluid, comprising: depositing an aqueous suspension of fibers to make paper on an endless forming fabric to form a wet fabric; to place in the shape of a sandwich the moist woven between a pair of fabrics permeable to the fluid; to pass the structure of wet weave in the sandwich form through an air press comprising a full air and collection device, the air plenum and the collecting device being operatively associated and integrally sealed so that around of 70 per cent more of the pressurized fluid supplied to the plenum air through the wet tissue; supply the pressurized fluid to the air plenum to create a pressure difference through the humid tissue of about 25 inches of mercury or greater; transporting the wet weave through the air press at industrially useful speeds to provide a dwell time of about 10 milliseconds or less; Y Dry the fabric to a final dryness

17. The method as claimed in clause 16 characterized in that about 80 percent or more of the pressurized fluid supplied to the plenum passes through the wet tissue.

18. The method as claimed in clause 17 characterized in that about 90 percent or more of the pressurized fluid supplied to the plenum passes through the wet tissue.

19. The method as claimed in clause 16 characterized in that the wet fabric is transported through the air press at industrially useful speeds to provide a dwell time of about d 5 milliseconds or less.

20. The method as claimed in clause 16 characterized in that the pickup device operated at more than 0 to about 25 inches of mercury vacuum.

21. The method as claimed in clause 16, characterized in that the plenum is operated at a pressurized fluid pressure of about 5 pounds per square inch above atmospheric pressure or more.

22. The method as claimed in clause 16 characterized in that the air press provides a pressurized fluid flow of about 10 standard cubic feet per minute per square inch of open area or more R E S U E N An air press for non-compressively dewatering a wet fabric at consistency levels not previously thought possible at industrially useful speeds without thermal drainage.