Patent Application
20190169796
The present disclosure relates to methods and apparatuses for dewatering fibrous webs in a papermaking process, and more particularly, to methods and apparatuses for removing water from a capillary cylinder utilized in dewatering fibrous webs in a papermaking process.
In papermaking processes, a papermaking furnish may be formed into a wet fibrous web, and in turn, various devices may be used to remove water from the advancing fibrous web. For example, some manufacturing configurations may include drying devices such as vacuum boxes, hot air dyers, capillary dewatering apparatuses, and Yankee dryers, such as disclosed in U.S. Pat. Nos. 3,301,746; 4,556,450; and 5,598,643.
Utilization of capillary cylinders to dewater a fibrous web can provide various advantages to papermaking processes. For example, a capillary cylinder may be configured to remove water from a fibrous web without heat or other means that may be evaporate water. As such, water removed from a fibrous web with a capillary cylinder may be reclaimed and reused in the papermaking process. In addition, removal of water from a fibrous web with a capillary cylinder may also help improve the effectiveness of downstream drying unit operations, such as a Yankee dryer.
In some configurations, the capillary dewatering apparatus may include a rotating capillary cylinder with a porous shell. During the manufacturing process, the wet fibrous web may be positioned on the capillary cylinder such that water is capillary transferred from the fibrous web into pores in the porous shell. The fibrous web may then advance from the capillary cylinder to additional drying and converting operations. The capillary dewatering apparatus may also include various systems to help increase the amount of water transferred from the fibrous web into the pores. For example, the capillary dewatering apparatus may include a vacuum system connected with the capillary cylinder to create a vacuum pressure within the cylinder. As such, the pneumatic pressure differential between the ambient atmospheric pressure exerted on the fibrous web and the level of vacuum pressure from within the cylinder helps to push water from the fibrous web into the pores. However, as the cylinder rotates, the porous shell may reach a limit of water absorption before the fibrous web advances from the drum. In turn, pressurized air may be used to expel water from the pores that are no longer covered by the fibrous web as the cylinder rotates before such pores are again covered by the advancing fibrous web.
Consequently, it would be beneficial to provide methods and apparatuses for increasing the amount of water that can be removed from a fibrous web with a capillary cylinder by removing water from the pores while the pores are covered with the fibrous web.
In one form, a method for removing water from a wet porous web comprises the steps of: providing a capillary porous media; positioning the web on the capillary porous media, wherein the web is positioned between the capillary porous media and an air-permeable fabric; providing an energy transfer surface in contact with the air-permeable fabric or the capillary porous media; and vibrating the capillary porous media with the energy transfer surface.
In another form, a method for removing water from a wet porous web comprises the steps of: rotating a roll about an axis of rotation, the roll comprising an outer circumferential surface comprising a capillary porous media, wherein the capillary porous media comprises a first surface and a second surface positioned radially inward of the first surface; advancing the web with an air-permeable fabric onto the roll, wherein the web is positioned between the capillary porous media and the air-permeable fabric; providing an ultrasonic horn in contact with the air-permeable fabric or the outer circumferential surface; and vibrating the capillary porous media with the ultrasonic horn to transfer water from the web through the first surface and radially inward toward the second surface.
In yet another form, an apparatus for removing water from a wet porous web comprises: a roll adapted to rotate about an axis of rotation, the roll comprising an outer circumferential surface comprising a capillary porous media, wherein the capillary porous media comprises a first surface and a second surface positioned radially inward of the first surface; an air-permeable fabric adapted to advance the web onto the roll, wherein the web is positioned between the capillary porous media and the air-permeable fabric; and an ultrasonic horn in contact with the air-permeable fabric.
Fibrous structures such as paper towels, bath tissues, and facial tissues may be made in a “wet laying” process in which a slurry of fibers, usually wood pulp fibers, is deposited onto a forming wire and/or one or more papermaking belts such that an embryonic fibrous structure can be formed, after which drying and/or bonding the fibers together results in a fibrous structure. Further processing the fibrous structure can be carried out such that a finished fibrous structure can be formed. For example, in typical papermaking processes, the finished fibrous structure is the fibrous structure that is wound on the reel at the end of papermaking, and can subsequently be converted into a finished product (e.g., a sanitary tissue product) by ply-bonding and embossing, for example. In general, the finished product can be converted “wire side out” or “fabric side out” which refers to the orientation of the sanitary tissue product during manufacture. That is, during manufacture, one side of the fibrous structure faces the forming wire, and the other side faces the papermaking belt, such as the papermaking belt disclosed herein.
The wet-laying process can be configured such that the finished fibrous structure has visually distinct features produced in the wet-laying process. Various forming wires and papermaking belts utilized can be configured to leave a physical, three-dimensional impression in the finished paper. Such three-dimensional impressions are known in the art, particularly in the art of “through air drying” (TAD) processes, with such impressions often being referred to a “knuckles” and “pillows.” Knuckles may be regions formed in the finished fibrous structure corresponding to the “knuckles” of a papermaking belt, i.e., the filaments or resinous structures that are raised at a higher elevation than other portions of the belt. Likewise, “pillows” may be regions formed in the finished fibrous structure at the relatively lower elevation regions between or around knuckles.
Thus, in the description below, the term “knuckles” or “knuckle region,” or the like can be used for either the raised portions of a papermaking belt or the corresponding portions formed in the paper made on the papermaking belt, and the meaning should be clear from the context of the description herein. Likewise “pillow” or “pillow region” or the like can be used for either the portion of the papermaking belt between, within, or around knuckles (also referred to in the art as “deflection conduits” or “pockets”), or the relatively lower elevation regions between, within, or around knuckles in the paper made on the papermaking belt, and the meaning should be clear from the context of the description herein. In general, knuckles or pillows can each be continuous, semi-continuous or discrete, as described herein.
Knuckles and pillows in paper towels and bath tissue can be visible to the retail consumer of such products. The knuckles and pillows can be imparted to a fibrous structure from a papermaking belt in various stages of production, i.e., at various consistencies and at various unit operations during the drying process, and the visual pattern generated by the pattern of knuckles and pillows can be designed for functional performance enhancement as well as to be visually appealing. Such patterns of knuckles and pillows can be made according to the methods and processes described in U.S. Pat. Nos. 4,514,345; 6,398,910; and 6,610,173 as well as U.S. Patent Publication No. 2016/0159007 A1; and U.S. Patent Publication No. 2013/0199741 A1 that describe belts that are representative of papermaking belts made with cured polymer on a woven reinforcing member. Fabric creped belts can also be utilized, such as disclosed in U.S. Pat. Nos. 7,494,563; 8,152,958; and 8,293,072. It is to be appreciated that some papermaking belts may comprise resin molding or resin deflection members, such as disclosed in U.S. Pat. No. 9,322,136, which is incorporated by reference herein. Additional descriptions of resins on papermaking belts are disclosed in U.S. Patent Publication Nos. 2017/0233951 A1; 2016/0090693 A1; 2016/0090692 A1; and 2016/0090698 A1, which are all incorporated by reference herein. The present disclosure relates to methods for making fibrous webs, and in particular, to methods and apparatuses for removing water from a wet fibrous web during the manufacture of a fibrous structure. During the process of making a fibrous structure, various methods and apparatuses may be utilized to remove water from a wet porous web, such as a capillary dewatering apparatus. In some configurations, a capillary dewatering apparatus may include a capillary cylinder having an outer circumferential surface comprising a capillary porous media. A molding member, such as a papermaking belt comprising an air permeable fabric, may advance the wet fibrous web onto the rotating capillary cylinder. As such, the fibrous web is positioned between the capillary porous media and the air-permeable fabric. The capillary porous media comprises a first surface and a second surface positioned radially inward of the first surface, and water flows from the fibrous web through pores in the first surface and radially inward toward the second surface. The capillary dewatering apparatus may also include an energy transfer surface positioned in contact with the air-permeable fabric or the outer circumferential surface, wherein the energy transfer surface operates to vibrate the capillary porous media. In turn, the vibration helps to drive water from the first surface radially inward toward the second surface, allowing additional water to flow from the fibrous web and through pores in the capillary porous media. In some configurations, the energy transfer surface may comprise an ultrasonic apparatus.
It is to be appreciated that various process and equipment configurations may be used to make fibrous structures. For example,
After the aqueous dispersion of fibers is deposited onto the foraminous member 104, the embryonic fibrous web 106 is formed, typically by the removal of a portion of the aqueous dispersing medium by techniques, such as for example, vacuum boxes, forming boards, hydrofoils, and other various equipment known to those of skill in the art. The embryonic fibrous web 106 may travel with the foraminous member 104 about return roll 110 and may be brought into contact with a molding member 114. The molding member 114 may comprise an air permeable fabric 118. The embryonic fibrous web 106 is transferred from the foraminous member 104 onto molding member 114. The transfer may be completed by any means known to those of skill in the art including, but not limited to, vacuum transfer, rush transfer, couch transfer, or combinations thereof. Various approaches to transfer may include those described in U.S. Pat. Nos. 4,440,597; 5,830,321; 6,733,634; 7,399,378; and 8,328,985. During the transfer onto the molding member 114, the embryonic fibrous web 106 may be deflected into deflection conduits or molded into the topology of the molding member 114. In addition, while in contact with the molding member 114, the embryonic fibrous web 106 can be further dewatered to form an intermediate fibrous web 116. The molding member 114 can be in the form of an endless belt 120, also referred to herein as a papermaking belt. In this simplified representation of
It is to be appreciated that the molding member 114 may be configured in various ways, such as an endless belt as just discussed or some other configuration, such as a stationary plate that may be used in making handsheets or a rotating drum that may be used with other types of continuous processes. As previously mentioned, the molding member 114 may comprise an air permeable fabric 118, and as such, the molding member 114 may be foraminous. As such, the forming member 114 may include continuous passages connecting a first surface 128 with a second surface 130. The first surface 128 (or “upper surface” or “working surface”) may be configured as the surface with which the embryonic fibrous web 118 is associated. And the second surface 130 (or “lower surface) may be configured as the surface with which the molding member return rolls 122 are associated. Thus, the molding member 114 may be constructed in such a manner that when water is caused to be removed from the embryonic fibrous web 106 and/or intermediate fibrous web 116 in the direction of the molding member 114, such as by the application of differential fluid pressure such with a vacuum box 132, the water may be discharged from the apparatus 100 without having to again contact the embryonic fibrous web 106 in either a liquid state or vapor state.
As previously mentioned, various methods and apparatuses may be used to dry the intermediate fibrous web 116. Examples of such suitable drying process include subjecting the intermediate fibrous web 116 to conventional and/or flow-through dryers and/or Yankee dryers. In one example of a drying process, the intermediate fibrous web 116 in association with the molding member 114 passes around the molding member return rolls 122 and travels in the direction indicated by directional arrows 126. The intermediate fibrous web 116 may advance to a predryer section or system 134. The predryer system may 134 may include a conventional flow-through dryer (hot air dryer) and/or a capillary dewatering apparatus 136, such as shown in
With continued reference to
As previously mentioned, the predryer system 134 may include a capillary dewatering apparatus 136. As shown in
With continued reference to
It is to be appreciated that the energy transfer surface 164 may be configured in various ways. For example, the energy transfer surface 164 may comprise an energy transfer surface of an ultrasonic apparatus 166. As such, the ultrasonic apparatus 166 may include a horn 168, wherein the ultrasonic apparatus 166 may apply energy to the horn 168 to create resonance of the horn 168 at frequencies and amplitudes so the horn vibrates rapidly in a direction 170. As such, horn 168 may be configured to impart ultrasonic energy to the molding member 114 and/or the capillary cylinder 152 to vibrate the capillary porous media 154. In some ultrasonic device configurations, a generator and stack arrangement may be utilized, wherein the stack may include a transducer module, an amplifier module, and a horn or sonotrode. The generator is adapted to create an electrical signal at a desired frequency and power that may be sent to the stack through a cable. In turn, the transducer module converts the electrical signal to vibration; the amplifier module amplifies the vibration; and the horn or sonotrode comprises the vibrating surface adapted to contact a work piece, such as the molding member 114 and/or the capillary cylinder 152. In some configurations, the generator may include a DYNAMIC digital control XX and the stack may include an Indexed Quick Change Weld Horn Stack 20 kHz, drawing number 180.648.3, available from Herrmann Ultrasonic, Inc. In some configurations, the generator may include a Generator 900DA and the stack may include a 900 Series Stacker, Model 900ae, available from BRANSON Ultrasonics. It is to be appreciated that aspects of the ultrasonic apparatuses 166 may be configured in various ways, such as for example linear or rotary type configurations, and such as disclosed for example in U.S. Pat. Nos. 3,113,225; 3,562,041; 3,733,238; 5,110,403; 6,036,796; 6,508,641; and 6,645,330. In some configurations, the ultrasonic apparatus 166 may be configured as a linear oscillating type sonotrode, such as for example, available from Herrmann Ultrasonic, Inc. In some configurations, the sonotrode may include a plurality of sonotrodes nested together in an axial direction along the axis of rotation 160. In some configurations, horns 168 may be arranged circumferentially about the axis of rotation 160. Various sonotrodes and various cross directional and/or circumferential sonotrode arrangements are available from Herrmann Ultrasonic, Inc. and BRANSON Ultrasonics.
During operation, the molding member 114 advances the wet fibrous web 117 onto the rotating capillary cylinder 152, wherein the wet fibrous web 117 is positioned between the capillary porous media 154 and the air-permeable fabric 118 of the molding member 114. As the capillary cylinder 152 rotates, water or other liquids may be transferred from a wet fibrous web 117, such as the intermediate fibrous web 116 described above, and through pores in the first surface 156 of the capillary cylinder 152. The pneumatic pressure differential between the ambient pressure Pamb exerted on the wet fibrous web 117 and the vacuum pressure P1 from within the capillary cylinder 152 helps to push liquid from the fibrous web 117 into the pores in the first surface 156 of the capillary porous media 154. In addition, the energy transfer surface 164 operates to vibrate the capillary porous media 154, wherein the vibration helps to drive liquids from the first surface 156 radially inward toward the second surface 158. As such, additional liquid can flow from the fibrous web 117 and through the pores in the capillary porous media 154. The molding member 114 then advances the wet fibrous web 117 from the rotating capillary cylinder 152, and the pressurized air P2 may expel liquid from the pores that are no longer covered by the fibrous web 117. As shown in
This application claims the benefit of U.S. Provisional Application No. 62/595,184, filed on Dec. 6, 2017, the entirety of which is incorporated by reference herein.
The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm.”
Every document cited herein, including any cross referenced or related patent or application and any patent application or patent to which this application claims priority or benefit thereof, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
| Number | Date | Country | |
|---|---|---|---|
| 62595184 | Dec 2017 | US |
