JP2000256985A - Dehydrator and dehydration for paper web - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simultaneously and economically dehydrate the wet paper web, the forming screen and the conveying screen by nipping the wet paper web from the head box between the forming screen and the conveying screen and allowing them to pass through the first dehydrating means and the air press. SOLUTION: The wet paper web 14 from the head box 12 is conveyed out as it is allowed to come into contact with the open-loop forming screen 16 at its lower face 20, then the forming screen 16 is brought into contact with the web 14 on its upper face 18, then they are nipped in sandwich with the close-loop conveying screen 28 that works in cooperation with the forming screen 16 and conveyed. Then the wet paper web 14 is dehydrated with the first dehydrating means 34 and the water is removed from the paper web 14, the forming screen 16 and the conveying screen 28, as the air flow is allowed to pass through the paper web 14 at least more than 85% in the air press 44.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an apparatus and a method for dewatering a paper web. More specifically, the present invention provides
The present invention relates to an apparatus and a method for simultaneously dewatering a paper web, a forming cloth and a transport cloth using a combination of a first dewatering mechanism and an air press.

[0002]

BACKGROUND OF THE INVENTION Tissue products, such as bath and facial tissue, have a number of features that must be considered in creating a final product that is suitable for its intended purpose and has the desired and desired characteristics. The improved flexibility of the product has been one of the main goals of distinguishing high-end products from common products. In general, the two main components of flexibility include "bulk", which is consistent with low density, and "lack of rigidity". As bulk and stiffness decrease, consumers will perceive the product as having improved flexibility.

[0003] In conventional papermaking techniques, the paper web exiting the headbox is generally supported and transported by a forming cloth, and then transported to a felt that draws mobile water. As the web and felt rotate through the nip formed by the pressure roll and the Yankee dryer, the felt can receive water from the wet paper web. In this nip, a substantial amount of the water present in the wet paper web is squeezed out and sent to the felt. A disadvantage associated with this process is that the paper web is compressed in the nip and loses some of its bulk.

[0004]

SUMMARY OF THE INVENTION In order to maintain bulk,
The felt can be replaced with a carrier cloth. The paper web is not as compressed as the carrier cloth does not get as much water from the paper web as the felt. However, the transport fabric must be wet and dehydrated at certain points in the process. An apparatus and method has been invented that can simultaneously and economically dewater wet paper webs, forming fabrics and carrier fabrics.

[0005]

SUMMARY OF THE INVENTION Briefly, the present invention relates to an apparatus and method for dewatering a paper web. The apparatus includes a headbox capable of emitting a continuous wet paper web. The wet paper web has an upper side and a lower side. A movable closed loop forming fabric contacts the lower surface of the wet paper web and transports the wet paper web away from the headbox. A movable closed-loop transport fabric contacts the upper surface of the wet paper web and cooperates with the forming fabric to sandwich the wet paper web therebetween. The wet paper web, forming fabric and carrier fabric pass through a first dewatering mechanism to remove water.
The wet paper web, forming cloth and carrier cloth are circulated through the air press to remove additional water.

A method of dewatering a wet paper web involves emitting a continuous wet paper web from a headbox. The paper web has an upper side and a lower side. The lower side of the wet paper web is contacted by a movable closed loop forming cloth, and the wet paper web is transported away from the headbox. The upper side of the wet paper web is brought into contact with a movable closed loop carrier cloth cooperating with the forming cloth, between which the wet paper web is sandwiched. Then, the wet paper web, formed cloth, and carrier cloth are
Pass through the dewatering mechanism of 1 and remove water from them. The wet paper web, forming cloth and transport cloth are passed through an air press to remove additional water. The air press is disposed upstream of a position where the paper web is transported to the transport cloth.

[0007] A method of dewatering a wet paper web includes emanating a continuous wet paper web from a headbox.
The wet paper web has an upper side and a lower side. The lower side of the wet paper web is contacted by a movable closed-loop forming cloth,
The wet paper web is transported away from the headbox. The upper side of the wet paper web is brought into contact with a movable closed-loop transport cloth cooperating with the forming cloth, between which the wet paper web is sandwiched. The wet paper web, forming cloth, and transport cloth then pass through a first dewatering mechanism to remove water therefrom. Wet paper web,
The forming fabric and the carrier fabric are passed through an air press to remove additional water. The air press is disposed upstream of a position where the paper web is transported to the transport cloth.

It is an object of the present invention to provide an apparatus and method for dewatering a paper web. A more detailed object of the present invention is to use a first dewatering mechanism and an air press to sequentially pass a wet paper web, a forming cloth and a transport cloth sequentially through a dewatering mechanism and an air press, and a device for dewatering a paper web. Is to provide a way.

Another object of the present invention relates to an apparatus and a method for dewatering a paper web, wherein the paper web, the forming cloth and the transport cloth are all dewatered simultaneously. It is a further object of the present invention to provide an efficient and economical means for simultaneously dewatering a paper web, a forming fabric and a carrier fabric. It is a further object of the present invention to provide an apparatus and method for replacing a carrier cloth with felt utilizing an air press. A further object of the present invention can be implemented with minimal changes to existing equipment. It is an object of the present invention to provide an apparatus and a method for dewatering a paper web and a carrier cloth together. Other objects and advantages of the present invention will become readily apparent to those skilled in the art from the following description and figures.

[0010]

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1, there is shown a papermaking schematic 10 representing the apparatus and method of the present invention. The apparatus includes a headbox 12 that feeds, or dispense, a diluted slurry of fibers to a forming fabric 16 in the form of a continuous wet paper web 14.
The wet paper web 14 is made from cellulosic fibers and water, and exits the headbox 12 to produce approximately
It has a ratio of 100 pounds of water. The paper web 14 has an upper side 18 and a lower side 20. The molding zone 22 is located immediately downstream of the headbox 12 and includes a wet paper web.
14 functions to reduce water content. The water contained in the paper web 14 is reduced to less than about 15 pounds of water per pound of fiber, and preferably to about 10 pounds of water per pound of fiber. In FIG. 1, the forming zone is illustrated as including a suction breast roll 24.

The forming cloth 16 is movable and has a breast roll.
Like 24, it is configured as a closed loop that moves around a plurality of guide rolls 26, two of which are shown. Those skilled in the papermaking arts will appreciate that a number of guide rolls 26 are typically utilized in the loop of the forming fabric 16. Forming cloth 16 is located near headbox 12 and is designed to contact and support lower surface 20 of wet paper web 14. The forming fabric 16 also functions to transport the wet paper web 14 from the headbox 12. The apparatus further includes a carrier cloth 28, the upper surface of the wet paper web 14.
18 and cooperates with the forming fabric 16 to sandwich the wet paper web 14 therebetween. Transport cloth
28 is movable, the compression roll 30 and 6
It is configured as a closed loop that moves around a plurality of illustrated guide rolls 32. As will be appreciated by those skilled in the art, typically, six or more guide rolls 32 will be utilized in the loop of the transport cloth 28. Transport roll 28
Can be composed of a synthetic material such as a thermoplastic material. The preferred thermoplastic material is a water-resistant polyester. Abrasion resistant materials, such as nylon, have been incorporated into the fabric for improved fabric life. Other materials, such as polyphenylene sulfide and polyether ketone, are also available, especially when facing critical operating conditions (eg, high temperatures).

Various types of transport fabrics, each having different structures, woven and mesh patterns, hole structures, etc., are commonly available today. One company that sells carrier fabrics suitable for practicing the present invention is Albany International Corporation, located at PO Box 1970, Albany, NY. Suitable forming cloth
16 is Albany International 94M. Device 10
Includes a first dehydrating mechanism 34 and a second dehydrating mechanism 36. The first dewatering mechanism 34 is a non-compression dewatering means, and can be constituted by one or more stream boxes, one or more vacuum boxes, and a combination of at least one stream box and a vacuum box. Further, the first dehydrating mechanism 34 can be an air knife or a heating device. Heating devices include conventional dryers, infrared dryers, one or more ventilated dryers, sonic dryers, microwave ovens, superheated stream devices, saturated dehydrators, supercritical fluid dehydrators, displacement dehydrators, and the like. A combination of two or more different types of equipment, for example a combination of a heating device and a mechanical device, can be used according to the invention as well as a combination of two or more heating devices.

It has been found that a stream box 38 aligned with one or more, preferably two, vacuum boxes 40 works well. In FIG. 1, two vacuum boxes 40
A single stream box 38 is shown, configured vertically from and slightly offset laterally.
Passage 4 between stream box 38 and two vacuum boxes 40
2, so that the wet paper web 14, the forming cloth 16 and the conveying cloth 28 pass through the passage 42. First dehydration mechanism 3
4 about 10 to 15 pounds of water per pound of fiber about 2 to about
Designed to reduce to the 5 pound range. This corresponds to reducing about 9 to 6% to a concentration range of about 33 to about 16%. Concentration is defined as 100 × (pound of fiber) / (pound of fiber + pound of water). It should be noted that decreasing the value of the concentration (percentage) increases the ratio of pounds of water per pound of fiber.

A first dewatering mechanism 34 reduces the amount of water in the wet paper web 16 to a range of about 3 to about 4 pounds of water / pound of fiber. This corresponds to a concentration of about 25% to about 20%. More specifically, the first dewatering mechanism 34 reduces the amount of water in the wet paper web 16 to a rate of about 3.5 pounds of water / pound of fiber.
This corresponds to a concentration value of about 22%. First dehydration mechanism 3
In 4, the wet paper web 14, the forming cloth 16 and the conveying cloth 28
Must be noted that they are simultaneously dehydrated. The effect of the steam box 38 is to increase the temperature of the water so that water present in the carrier 28 and water in the wet paper web 16 is more easily removed. Vacuum box 40
The water of the wet paper web 16 is displaced or drawn into and through the forming fabric 16 by the action of the steam box 38 with the suction force of the steam box 38. The forming cloth 16 is a fine cloth as compared with the conveying cloth 28, and is made of a material which is easier to receive water from the wet paper web 14 than the conveying cloth 28.

One unique feature of the present invention is that all three layers of wet paper web 16, forming fabric 16 and carrier fabric 28 are simultaneously dewatered in a very efficient and economical manner. This simultaneous dewatering feature eliminates the need to separately dewater the transport cloth 28 upstream of the first dewatering mechanism 34. But,
If a spare dewatering mechanism is to be used, it can be used, but it is not necessary to practice the invention. Immediately downstream of the first dehydration mechanism 34, a second dehydration mechanism
There are 36. The second dewatering mechanism 36 is a non-compression dewatering means, for example, an air press 44 having a passage 46 formed therethrough. The structure and function of the air press are taught in US patent application Ser. No. 08 / 961,915, filed Oct. 31, 1997. The name of this patent application is "Air Press for Dewatering Wet Webs", which is incorporated by reference as part of this patent specification. No. 08 / 647,508, filed May 14, 1998, is the second U.S. patent application that teaches about air presses. The second patent application is entitled "Method and Apparatus for Manufacturing Soft Tissue"
And is incorporated by reference as a part of this patent specification.

The air press 44 comprises an upper air plenum generally associated with one or more vacuum or lower collection devices in the form of a suction box. The wet paper web 14, forming fabric 16 and transport fabric 28 form a sandwich that passes between the air plenum and the vacuum box. Pressurized air is provided to an air plenum ventilation manifold operatively coupled to a source of pressurized fluid such as a compressor or blower. An air plenum fits the plenum cover, which has a bottom surface that is in use proximate to the vacuum box and in close proximity or in contact with the forming fabric 16. The plenum cover extends over substantially the entire width of the wet paper web 14, but is preferably formed and transported.
Formed with slots extending perpendicularly to the machine direction over a width slightly smaller than the width of 16,28, so that air from the air plenum can pass through the two carrier cloths 16,28 and the wet paper web 14. It has become.

The vacuum box of the air press 44 is operatively coupled to a vacuum source and is fixedly mounted on the support structure. The vacuum box includes a cover having an upper surface on which the forming cloth 16 travels. The vacuum box cover is formed with a pair of slots corresponding to the positions of the slots formed in the plenum cover. Pressurized fluid is drawn from the air plenum into a vacuum box, through which the wet paper web 14 is dewatered.

Preferably, the fluid pressure in the air plenum is maintained at or above about 5 pounds per square inch (psi) (about 0.35 bar), preferably from about 5 psi to about 30 psi.
(About 0.35 bar to about 2.07 bar), more preferably about 15 psi (about 1.03 bar). Preferably, the fluid pressure in the air plenum is monitored and controlled at a predetermined level. Air temperature from about 70 ° F (about
21 degrees Celsius) to about 200 degrees F (about 93 degrees C), preferably from about 100 degrees F (about 38 degrees C) to about 200 degrees F (about 93 degrees C), and most preferably about 140 degrees F ( About 60 ° C) to about 200 ° F
(About 93 ° C). Depending on the equipment used to compress the air, the elevated temperature is generated by the heat of compression,
Heat can be applied if desired. However, the heated air need not be heated to elevated temperatures associated with a heated dryer such as a Yankee dryer, or a through-air dryer, which typically has a temperature above 300 ° F. Instead, air press 44
Can use room temperature air at about 70 ° F. (about 21 ° C.), or use air that was first cooled to about room temperature.

The bottom surface of the plenum cover is gently curved so that the wet paper web 14 is easily controlled. The surface is curved towards the vacuum box and around an axis located on the vacuum box side of the wet paper web 14. The bottom curve allows the angle of the combination of forming cloth 16, wet paper web 14, and transport cloth 28 to be changed, sealing the vacuum box against the ingress of outside air, and supporting the wet paper web 14 during the dewatering process. Help. Depending on the angle of the curve, the sometimes required air compression can be applied or not, depending on the state of the process. The necessity of the angle change depends on the pressure difference between the pressure side and the vacuum side, and is preferably about 5 degrees or more,
Specifically, it is about 5 to about 30 degrees, and generally about 7.5 degrees. The top and bottom surfaces of the air press 44 preferably have different radii of curvature. In particular, the radius of the curve at the bottom surface is preferably greater than the radius of the curve at the top surface, so as to form a contact line between the air plenum and the vacuum box at the tip and end of the air press 44. With proper care of the position of the forming cloth 16 and the conveying cloth 28, the sandwich and loading and unloading mechanisms, the radii of curvature of these surfaces may be reversed.

At the leading and trailing edges of the air press 44, there are provided end seals which are kept in constant contact with or very close to the carrier cloth 28. The end seal minimizes escape of pressurized fluid in the machine direction between the air plenum and the vacuum box. A suitable end seal may be constructed from a low friction material such as a resilient plastic compound. The material forming the end seal preferably wears on the two fabrics 16,28. The end seals preferably have curved edges to prevent the fabric from snagging.

The air press 44 is preferably provided with side seals along the side edges of the air press 44 to prevent loss of pressurized fluid. The side seal includes a semi-rigid material that is adapted to deform or flex slightly when exposed to the pressurized fluid of the air plenum. The side seals can form slots for attachment to the vacuum box cover using clamp bars and fasteners or other suitable means. At the cross section, each side seal is L-shaped with the legs protruding from the vacuum box cover. Pressurized fluid from the air plenum causes the legs to flex outwardly and make sealing contact with the outer surfaces of the side seal slots of the plenum cover. Alternatively, the position of the side seals is reversed so that they are fixedly mounted on the plenum cover and make sealing contact with the contact surface formed by the vacuum box cover. In such alternative designs, it is desired that the side seals engage the seal contact surface by pressurized fluid.

As used herein, a seal refers to the relationship between an air plenum and a wet web. The air plenum is not operatively associated with the web, is indirectly in contact with the web, and at least about about 30 inches of mercury or more is delivered to the air plenum when actuated at a predetermined pressure differential over more. 85% or more air flows through the web. Conventional dewatering devices that simply place steam blow tubes, blow nozzles, etc., placed opposite a vacuum or suction box, are not integrally sealed and are comparable when operated with the same energy input. Either one can obtain a dehydration concentration of, or a considerably higher energy input is required to obtain the same dehydration concentration.

The air press is capable of dewatering the cellulosic web to a significantly higher concentration due to the high pressure differential generated mostly across the web and the resulting air flow through the web. In certain embodiments, for example, an air press
About 3% or more, more specifically about 5% or more, such as about 5 to about 20%,
About 7 percent or more, most particularly about 7 to about 20
Percent. Thus, the moisture web concentration upon exiting the air press is at least 33%, preferably at least about 37%, and most preferably at least about 40%.

The pressure differential across the wet web provided by the air press is about 25 to about 25 to 120 mercury inches.
Inches or more of mercury, and in detail, from about 35 to about
About 35 inches of mercury, such as 60 inches of mercury, or more, more specifically, about 40 inches to about 50 inches of mercury.
This is accomplished, in part, by an air press air plenum, from 0 to about 60 pounds per square inch (psig), specifically, from 0 to about 30 psig, and more specifically, from about 5 to about 30 sig.
About 5 psig or more, more particularly about 5 to about 20 psig. Air press collection devices range from 0 to about 29
Inch mercury vacuum, specifically, from about 0 to about 25 inches of mercury vacuum, specifically, from about 0 to about 25 inches of mercury vacuum, more specifically, from about 10 to about 20 inches of mercury, such as about 15 inches of mercury vacuum It preferably functions as a vacuum box operated by vacuum. The collection device preferably, but not necessarily, forms an integral seal with the air plenum, and a vacuum is drawn to facilitate its function as an air and liquid collection device. Preferably, the pressure levels in the air plenum and the collector are monitored and controlled to a predetermined level.

Importantly, the pressurized fluid used in the air press is sealed from the ambient air to create a substantial air flow through the web, thereby increasing the dewatering capacity of the air press. It is. Suitably, the flow of pressurized fluid through the air press is from about 5 to about 500 standard cubic feet per minute (SCFM) per square inch of open area, and in particular, from about 10 to about 200 SCFM / open area. About 10 SCFM / open area square inch like square inch or more,
More particularly, about 40 SCFM / open area square inch, such as about 40 to about 120 SCFM / open area square inch, or more is suitable. Preferably, about 95 percent or more of the pressurized fluid supplied to the air plenum is drawn through the wet web into a vacuum box. For the purposes of the present invention, standard cubic feet per minute means cubic feet per minute per minute as measured at 14.7 pounds per square inch at 60 ° F (16 ° C).

An important feature of the air press 44 described herein is that substantially all of the air entering the plenum is web 14
It is flowing through. The above seal is air press
At least about 85% of the air flowing to 44
Help prevent leakage, so that it is only flowing through. Preventing this air leak is what distinguishes the air press 44 from conventional equipment and allows the process to operate economically while maintaining proper machine speed.

The position control mechanism maintains the air plenum very close to the vacuum box and in contact with the carrier cloth 28. The position control mechanism may include a pair of levers connected by cross members and fixedly attached to the air plenum by suitable fasteners. The end of the lever facing the air plenum is rotatably mounted on the shaft.
The position control mechanism includes a counterbalance cylinder that operatively connects the fixed structure support and one rung. The counterbalance cylinder is adapted to extend or retract, such that the lever rotates about a shaft and the air plenum moves toward and away from the vacuum box.

In use, the control system causes the counterbalance cylinder to be fully extended so that the end seals contact the carrier fabric 28 and the side seals are located in the side seal slots. The air press 44 is activated such that the pressurized fluid fills the air plenum and the semi-rigid side seal engages in a plenum cover seal. The pressurized fluid also creates an upward force that moves the air plenum away from the carrier fabric 28. The control system operates the operation of the counterbalance cylinder to offset this upward force based on the continuous measurement of fluid pressure in the air plenum by the pressure monitoring system. For this reason, the end seal is always very close to or in contact with the transport cloth 28. The control system proportionally reduces the force exerted by the counterbalance cylinder,
Increasing corresponds to irregular pressure drops or peaks. The flow rate of air in the air press 44 is also monitored. As described above, the end seal is formed by the forming cloth 16 and the conveying cloth 28.
Or it will cause excessive wear to the fabric.

The air plenum and vacuum box described above are mounted on a suitable frame structure. The frame structure includes upper and lower support plates separated by a plurality of vertically oriented support bars. The air plenum is adapted to receive a supply of pressurized fluid via one or more suitable air conduits operatively connected by a source of pressurized fluid.
Correspondingly, the vacuum box forms a plurality of vacuum chambers which are preferably operatively coupled to low and high vacuum sources by a suitable vacuum box. The water removed from the wet paper web 14 is separated and removed from the air steam.

The pressurized air flow in the air press 44 is
It must be noted that the water therein will be directed downwardly into the wet paper web 14. The water is withdrawn from the wet paper web 14 and removed, and enters the forming fabric 16 in a combination of pressurized air and vacuum. The transfer cloth 28, the paper web 15, and the forming cloth 16 are simultaneously dehydrated or dried. As previously described, at a rate of about 2 to about 5 pounds of water / pound of fiber, wet paper web 14 enters second dewatering mechanism 36. This corresponds to a concentration of about 33 to about 16%. Upon exiting the second dewatering mechanism 36, the wet paper web 14 has a ratio of about 1.5 to about 2 pounds water / pound of fiber. This corresponds to a concentration of about 40 to about 33%. Preferably, the wet paper web 14 has a concentration of about 1.8 pounds water / pound of fiber or about 36%. Wet paper web 14 is about 1.7 pounds water / fiber fiber or about 37%
Most preferably, it has a concentration of More preferably, the wet paper web 14 has a concentration of about 1.5 pounds water / pound of fiber or about 40%.

As mentioned above, because of the integral seal of the air press 44, substantially all of the air delivered to the pressure plenum flows through the web 14 and when the equipment operates with acceptable energy consumption, The exiting web 14 can have a concentration of about 33 to about 40%. Corporate speeds typically range from about 2,000 to about 10,000 ft / min (ft / min)
And preferably from about 3,000 to about 7,000 ft / min, most preferably about 35,000 ft / min or more.

It is well known to maintain this density that enables the commercial operation of the papermaking machine, with a strong relationship between the density of the web as it is transferred to the Yankee dryer and the speed of the machine that can be maintained. Have a relationship. Many papermaking machines are "dryer limited" in that the ability to dry the web 14 to the required degree of dryness at the creping blade determines the speed of the machine. With non-heated, non-compressed dewatering techniques, it is difficult to maintain machine speed while controlling energy costs. As used herein, an integrally sealed air press 44 operates at a cost offset by the achievable reduction in basis weight associated with using non-compressive dewatering rather than a regular pressure roll.
Enables approximately the same machine speeds that can be achieved with a standard wet press machine (using a given Yankee dryer system).

The main cause of preventing the concentration from being maximized after the second dehydrating mechanism (ie, the air press 44) is the water supported and returned by the transport cloth 28. The transport cloth 28 supports the web 14 to the Yankee dryer 52,
Through pressure roll nip 50. To this end, the carrier cloth 28 begins to become soiled with fibers and chemicals added to the fibers such as wet or dry strength agents and must be cleaned substantially continuously. To clean the carrier cloth 28, a shower including a flooded nip, a scarf or a high-pressure cleaning shower is used.
Shower techniques known in the art are effective in removing fibers and chemicals from the carrier cloth 28, but will exit the carrier cloth 28 while carrying a substantial amount of water in the gap of the carrier cloth 28.
The amount of water supported by the carrier cloth 28 will vary considerably depending on the type of cloth, but will slightly exceed the cloth area of 100 grams per square meter (gsm). If the water is not removed, when the carrier cloth 28 and the wet web 14 come into contact with or before the pick-up shoe (or roll), the water will
Will be returned by capillary force.

To solve this problem, a transport cloth dewatering system can be installed (see US Pat. No. 5,230,776, “Thread Making Machine for Making Soft Crepe Paper Web” and European Patent Application No. 0,526,592). “A means of blowing air through a cloth such as an air knife”). These means can be used to remove some water from the carrier fabric 28 before contacting the wet web 14. Generally, 10 gsm or more of water remains on the carrier cloth 28, despite the considerable amount of energy consumed to dewater the carrier cloth 28. It is unlikely that any of the two aforementioned patented systems can operate at concentrations above about 3,000 ft / min and above about 30%.

However, by operating the transport cloth 28 through the first dewatering means 34 and the air press 44, the first dewatering means 34 and the air press 44
Can be simultaneously dehydrated. This saves energy,
Or if limited by a dryer, the speed of the machine will increase. In this way, the carrier fabric dewatering system can be minimized or eliminated, and the energy used to dewater carrier fabric 28 is saved.

Referring again to FIG. 1, device 10 includes a second
And a transfer shoe 48 disposed downstream of the dehydrating mechanism 36. The transport shoe 48 functions to separate the paper web 14 from the forming cloth 16. Another means for this is that the transport shoe 48 transports the paper web 14 to the transport cloth 28 and is free from the forming cloth 16. Transport shoes 48 are known to those skilled in the art of papermaking. After exiting the conveying shoe 48, the paper web 14 and the conveying cloth 28 are rotated by a rotatable pressure roll 30.
Around a Yankee dryer 52 through a nip 50 formed by the contact of the pressure roll 30. Paper web 14 contains less than about 2 pounds of water / pound of fiber, and no dewatering is required in nip 50 because paper web 14 is low density and low basis weight. This means that the paper web 14 has sufficient bulk to exhibit excellent flexibility and can be sold as a preferred product such as a toilet tissue, facial tissue, and the like. After exiting the nip 50, the paper web 14 passes around the perimeter of the Yankee dryer 52 and is dried by conventional means using thermal energy. After exiting the nip 50, the paper web 14 passes around the periphery of the Yankee dryer 52 and is dried by conventional means using thermal energy.

Referring again to FIG. 1, it can be seen that the cleaning mechanism 54 is in a closed loop of the carrier cloth 28. A cleaning mechanism 54 is positioned adjacent to the moving cloth 28 and functions to remove dirt therefrom. A high pressure shower of water is directed against the carrier cloth 28, loosened, and removes dirt. Pressurized water is sprayed on the carrier cloth 28,
Preferably, the fiber or cellulose particles that may be present are removed therefrom. It is known in the art of papermaking to use a high pressure needle shower with the spray pattern vibrating, as well as the type of spray nozzle, nozzle tip, pressure level, and the like. After using pressurized water to remove dirt,
An air knife, or some type of equipment, is
Can be partially dehydrated or partially dried. As mentioned earlier, this is not necessary,
It can be used based on the type of cloth used and the efficiency of the first and second dehydrating mechanisms 34 and 36.

It should be noted that the multiple guide rolls 32 present in the closed loop of the carrier 28 provide a routine for the carrier 28 to pass through the cleaning mechanism 54 and through the first and second dewatering mechanisms 34 and 36, respectively. There must be. The arrangement and position of the various guide rolls 32 are known to those skilled in the art of papermaking, as well as the length of the loop of the transport cloth 28, the size of the equipment cooperating with the loop of the transport cloth 28, and the speed of the entire papermaking machine. Is determined by a variety of things.

Method With reference to FIG. 1, a method for dewatering wet paper web 14 comprises:
It can be easily understood as the wet paper web 14 progresses through the papermaking apparatus 10. Starting from the left side of the diagram, a continuous wet paper web 14 exits the headbox 12. The wet paper web 14 has an upper side 18 and a lower side 20. Immediately downstream of the headbox 12 is a suction breast roll 24 used to remove a significant amount of water from the wet paper web 14. This removal of water occurs when the lower surface 20 of the wet paper web 14 contacts the movable closed loop forming fabric 16. The forming fabric 16 also functions to convey the wet paper web away from the headbox 12. During a short distance at the outlet of the headbox 12, the upper side 18 of the wet paper web 14 is contacted by a movable, closed-loop transport cloth 28. The carrier fabric 28 cooperates with the forming fabric 16 to sandwich the wet paper web therebetween.

Carrier cloth 28, wet paper web 14, and forming cloth
A three-layer sandwich composed entirely of 16 goes around the first dewatering mechanism 34. The first dewatering mechanism 34 can be comprised of a steam box 38 arranged perpendicular to one or more vacuum boxes 40. A passage 42 passes between the steam box 38 and the vacuum box 40 to form an opening through which the three-layer sandwich is passed. In a first dewatering mechanism 34, water is simultaneously removed, withdrawn from the carrier cloth 28 and passed through the wet paper web 14. Similarly, water in the wet paper web 14 is removed or drawn into the forming cloth 16 and exits the forming cloth 16. The gravity, along with the pressurized air and suction, causes the water to flow down and out of the three layers. Two cloths
The wet paper web 14 is immediately transferred to the second
Go through 6. The second dewatering mechanism 36 is preferably an air press 44 that functions to remove or draw additional water from the wet paper web 14 and the two fabrics 16,28. In the air press 44, water is again simultaneously removed or withdrawn from the transport fabric 28 and enters the wet paper web 14. Similarly, water in the wet paper web 14 is removed or drawn and enters into the forming cloth 16 and exits the forming cloth 16.

After exiting the air press 44, the paper web 14
Then, the two cloths 16 and 18 are directed over the conveying shoe 48 so that the paper web 14 is separated from the forming cloth 16.
The paper web 14 and the transport cloth 28 are then guided around a rotatable pressure roll 30 arranged downstream of the transport shoe 48. Next, the paper web 14 and the transport cloth 16 pass through the nip 50 formed by the rotatable Yankee dryer 52 and the pressure roll 30. At this point, the paper web 14 is transported onto the Yankee dryer 25, and the transport cloth 28 is thermally dried while being rotated by the clean mechanism 54. The paper web 14 does not reduce bulk because acceptable compression does not occur in the nip between the pressure roll 30 and the Yankee dryer 50. With such a large bulk,
This will give the finished product more flexibility than can be achieved using the conventional process of compressing between the compression roll 30 and the Yankee dryer 50 using felt instead of carrier cloth.

Although the present invention has been described with respect to particular embodiments, many alternatives and modifications will become apparent to those skilled in the art in view of the foregoing description.
Thus, the present invention covers all changes and modifications that come within the spirit and scope of the appended claims.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus of the present invention and a manufacturing process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Head box 14 Wet paper web 16 Molding cloth 18 Upper surface 20 Lower surface 24 Suction breast roll 26 Guide roll 28 Conveying cloth 30 Pressure roll 32 Guide roll 34 First dehydrating mechanism 38 Steam box 40 Vacuum box 42 Passage 44 Air press

Continuing on the front page (72) Inventor Stephen Jack Hickey United Kingdom Kent M.E. 20 6 IE Nu Deton Holton Cedar Closed 5 (72) Inventor Frank Steven Heida United States of America 54915 Appleton South Lees Treat 1407 (72) Inventor Frank Gerald Druek United States 54904 Oshkosh Old Oak Road 4730 (72) Inventor Ian Alfred Parris England Kent D.A. 124 4UP Gravesend Orrick Road 12 (72) Inventor Robert Irving Gusky United States 54915 Appleton River Driving 304 (72) Inventor Paul Miles Baden United Kingdom Cumbria Barlow in Furness Hartin Ton Street 29

Claims (20)

[Claims] 1. An apparatus for dewatering a paper web, comprising: a) a headbox capable of delivering a continuous paper web having an upper side and a lower side; b) the lower side of the paper web; Contacting and transporting the paper web away from the headbox;
A closed closed-loop forming cloth; c) a movable closed-loop conveying cloth in contact with the upper side of the paper web and cooperating with the forming cloth to sandwich the paper web therebetween; d) the paper web; First dewatering means for removing water from the forming cloth and the conveying cloth; e) water can be removed from the paper web, the forming cloth, and the conveying cloth; An air press arranged upstream of a place where the paper is transferred to the transfer cloth. 2. The apparatus of claim 1, wherein the air press is integrally sealed such that at least about 85% of the air flowing to the air press flows through the web. 3. The apparatus of claim 1, wherein said web exiting said air press has a concentration of at least about 33%. 4. The apparatus of claim 3, wherein said web exiting said air press has a consistency of at least about 37%. 5. The apparatus of claim 4, wherein said web exiting said air press has a concentration of at least about 40%. 6. The method according to claim 1, wherein the first dewatering means and the air press transfer water from the transport cloth to the paper web, transfer water from the paper web to the forming cloth, and discharge the water from the forming cloth. Item 1. The apparatus according to Item 1. 7. The ratio of pounds of water to pounds of fiber of the web present in the air press is from about 1.5: 1 to about 2: 1.
2. The apparatus according to claim 1, wherein: 8. The apparatus of claim 7, wherein the ratio of pounds of water to pounds of fiber of the web present in the air press is about 1.7: 1. 9. The apparatus of claim 8, wherein the ratio of pounds of water to pounds of fiber of the web present in the air press is about 1.5: 1. 10. An apparatus for dewatering a paper web, comprising: a) a headbox capable of delivering a continuous paper web having an upper side and a lower side; and b) the lower side of the paper web. A movable closed-loop forming fabric disposed adjacent to the headbox for contacting and supporting the same and transporting the paper web away from the headbox; c) contacting the upper surface of the paper web. A movable closed-loop polyester carrier fabric cooperating with the forming fabric to sandwich the paper web therebetween; d) removing water from the paper web, the forming fabric, and the carrier fabric. 1) dewatering means, e) water can be removed from the paper web, the forming cloth, and the carrier cloth, and the paper web is disposed upstream of a place where the paper web is transferred to the carrier cloth; Less inflowing air And an air press which is integrally sealed so that at least 85% of the paper web flows into the web. 11. The air press is between about 70 ° F. and about 200 ° F.
11. The device according to claim 10, having an airflow flowing at a temperature of F. 12. The method of claim 11, wherein the air press is about 100 ° F. to about 200 ° F.
12. The device according to claim 11, having an airflow flowing at a temperature of ° F. 13. The method of claim 12, wherein the air press is about 140 ° F. to about 200 ° F.
13. The device according to claim 12, having an airflow flowing at a temperature of ° F. 14. The molding fabric, the carrier fabric and the web all pass through the first dewatering means, through the air press, and simultaneously dewater both while using a minimum amount of energy. 11. The device according to claim 10, wherein the device comprises: 15. An apparatus for dewatering a paper web, the apparatus comprising: a) a headbox capable of delivering a continuous paper web having an upper side and a lower side; b) the lower side of the paper web; A movable closed-loop forming fabric that contacts and transports the paper web away from the headbox; c) contacts the upper surface of the paper web and cooperates with the forming fabric to remove the paper web from these. A movable closed-loop transport cloth sandwiched between; d) the paper web, the forming cloth and the transport cloth cooperating to form a path through which the paper web, the forming cloth and the transport cloth pass. E) at least one vacuum box having a passage formed therein through which the paper web, the forming cloth, and the transfer cloth pass; and An air press located downstream of the team box and adapted to draw additional water from the forming web and the transfer fabric; andf) the air transferring the paper web to the transfer fabric. A conveying shoe arranged downstream of the press; g) a rotatable pressure roll arranged downstream of the air press and guided by the conveying cloth and the paper web; h) the conveying cloth and the paper web A rotatable Yankee dryer cooperating with the pressure roll to form a nip through which the paper web passes. 16. A paper web having an upper side and a lower side is ejected from a head box; and b) the lower side of the paper web is brought into contact with a movable closed-loop forming cloth to remove the paper web. Transporting away from the headbox; c) sandwiching the paper web between the movable closed loop transport fabric cooperating with the forming fabric and the upper surface of the paper web between them; d) Passing the paper web, the forming cloth and the conveying cloth through a first dewatering means to remove water, e) passing the paper web to an air press arranged upstream of a place where the paper web is conveyed to the conveying cloth; A method of dewatering a paper web comprising passing additional water through a web, a forming cloth and a carrier cloth. 17. The method according to claim 16, wherein said water is simultaneously removed from said paper web, forming cloth and transport cloth in said first dewatering means. 18. The method according to claim 16, wherein said water is simultaneously removed from said paper web, forming cloth and carrier cloth in said air press. 19. A method comprising the steps of: a) ejecting a continuous paper web having an upper surface and a lower surface from a head box; b) contacting the lower surface of the paper web with a movable closed-loop forming cloth; Transporting away from the headbox; c) sandwiching the paper web between the movable closed loop transport fabric cooperating with the forming fabric and the upper surface of the paper web between them; d) E) passing the paper web, the forming cloth and the conveying cloth through a first dewatering means to remove water, and e) applying the paper web to an air press arranged upstream of a place where the paper web is conveyed to the conveying cloth. Removing additional water through a web, a forming cloth, and a conveying cloth, wherein the air press comprises at least a portion of air flowing through the air press.
A method for dewatering a paper web, wherein 85% is integrally sealed such that it flows through said web. 20) a) exiting a continuous paper web having an upper side and a lower side from a head box; and b) contacting the lower side of the paper web with a movable closed-loop forming cloth to remove the paper web. Transporting away from the headbox; c) sandwiching the paper web between the movable closed loop transport fabric cooperating with the forming fabric and the upper surface of the paper web between them; d) Passing a paper web, a forming cloth and a transfer cloth between a first steam box and at least one vacuum box, e) passing an air press through the paper web, the forming cloth and the transfer cloth, Withdrawing the web and the forming and transporting cloth or additional water; f) transferring the paper web to the transporting cloth using a transfer arranged downstream of the air press; g) the transporting cloth. And paper H) around a rotatable pressure roll disposed downstream of the transport shoe, h) a nip formed by the rotatable Yankee dryer and the pressure roll on the transport cloth and the paper web. A step-by-step method.