Patent Grant
7169262
This invention relates generally to forming a paper or tissue web, and more particularly to apparatuses and methods for improving the fiber distribution within a paper or tissue web.
Paper and tissue are typically manufactured in a continuous sheet on a papermaking machine. One of the most common papermaking machines is the Fourdrinier machine. Fourdrinier machines generally include at least three sections: a wet-end section, a press section, and a dryer section. The wet-end section, which can be 40 to 100 feet in length, is also referred to as the forming section or the Fourdrinier table. In the wet-end section, stock flow is transferred from a headbox onto a moving, endless belt of wire-mesh screen, referred to as the Fourdrinier wire, or simply as the “wire.” Stock flow is normally a combination of wood fibers, fines and fillers, chemical additives such as bonding agents, and water. Wood fibers typically range in length from 400 to 7,000 microns and in width from 20 to 100 microns, depending on the species of the wood. Stock flow typically has a liquid consistency of 99 percent and a fiber consistency of approximately 0.2 to 1 percent (although other fiber consistencies are possible), depending on the grade and weight of the paper or tissue being manufactured.
The function of the headbox is to distribute stock flow with a uniform fiber distribution to the wire in order to produce a sheet of paper having uniform properties across the width of the wire (cross-machine direction), along the length of the wire (machine direction), and through the cross-section of the sheet of paper (Z direction). The headbox distributes stock flow to the wire at an angle other than absolute tangent, referred to as the angle of impingement. If the angle of impingement is steep, i.e., close to absolute tangent, the arrangement of the headbox is referred to as pressure forming. If the angle of impingement is shallow, i.e., not close to absolute tangent, the arrangement of the headbox is referred to as velocity forming.
The wire runs over a breast roll, which is usually located under the headbox. The wire is typically not a permanent part of the papermaking machine and requires periodic replacement. One condition leading to premature failure of the wire is the plugging of the openings in the porous wire by the fibers, fines, and fillers of the web being transported by the wire. Normally, the wire is a delicate, finely woven metal or synthetic fiber cloth that allows for drainage of the water, but retains most of the fibers. The strands of the wire are commonly made of finely drawn and woven, annealed bronze or brass.
After the stock flow is delivered from the headbox to the wire in the wet-end section of a Fourdrinier machine, the fibers are initially held in free suspension within the water as relatively mobile individual fibers or as part of a network, referred to as a floc. The fibers and flocs in the stock flow begin to form a wet sheet of matted pulp, referred to as an embryonic web. While not subscribing to any particular manner in which the embryonic web is formed, normally either bonding agents in the stock flow cause an electro-chemical bond or the bond is produced through physical entanglement. The embryonic web forms as the fibers and flocs in free suspension begin to settle in layers on the wire. Ideally, the fiber distribution within the web would be consistent in the cross-machine direction, the machine direction, and the Z direction. However, due to gravitational forces, the bottom-most layers of fibers that settle directly on the wire are typically more dense than the upper-most layers of fibers. The web normally has boundary layers (i.e., the two external layers of the web, such as the bottom-most layer of fibers that settles directly on the wire and the upper-most layer of fibers) and internal web fibers (fibers in the layers of the web between the two external layers of fibers). The web may consist of approximately 2 to 100 layers of fibers.
In order to assist in the formation of the embryonic web, as the wire moves away from the headbox, various suction devices can be used to drain water from the stock flow. The suction devices in the Fourdrinier machine typically include a series of stationary blades or foils. The stationary foils remove water from the stock flow by creating a vacuum on the downstream side of the blade where the wire leaves the blade surface. As the wire moves across a series of stationary foils, the downstream side of each stationary foil creates a vacuum that pulls water from the stock flow, while the upstream side of each stationary foil pulls the water off of the wire. Some of the wood fibers, fines, and fillers are pulled off of the wire along with the water being pulled off of the wire. The amount of fibers, fines, and fillers that are retained on the wire while the water is being pulled off of the wire is referred to as retention.
Once the wire passes over the stationary foils, the wire normally passes over a drive roll or couch roll, over a series of return rolls, and back to the breast roll. At the end of the wet-end section of the Fourdrinier machine, the web can have a water consistency of approximately 80 percent and a fiber consistency of approximately 20 percent. At this point, the web can normally support its own weight. Other water and fiber consistencies are also possible at this point for enabling the web to support its own weight.
Next, the web can be transferred from the wet-end section of the Fourdrinier machine to the press section at the couch roll. The wet web of paper is normally transferred from the wire of the wet-end section to a screen. The screen can be a woolen felt screen, referred to as a felt, acting as a conveyor belt to carry the web through the press section. The felt is typically porous media that provides space and channels for water removal. The felt can also act as a textured cushion or shock absorber for pressing the moist web without crushing the web. The texture and character of the felt varies according to the grade of the paper being made. The felt normally carries the web through two or more press rolls, which mechanically squeeze water from the web. A variety of suction devices, one of which is commonly referred to as a uhle box, can also be used to remove water from the felt. The press rolls often consist of a steel or cast iron core covered by a bronze or stainless steel inner shell and an outer rubber shell. At the end of the press section of the Fourdrinier machine, the web typically has a consistency of approximately 40 percent water and 60 percent fiber, although other web consistencies at this stage are possible.
After the press section, the web can be transferred to fabric dryer felts that carry the web through the dryer section. The dryer felts are most commonly constructed of a highly permeable cotton blend or open-mesh fabric. The web is normally held firmly against a number of steam-heated cylinders or drums by the dryer felts in order to evaporate the remaining water. As the web passes from one cylinder to another, first the felt side and then the web side are pressed against the heated surfaces of the cylinders. In addition, hot air may be blown onto the web and between the cylinders to vaporize water from the web. At the end of the dryer section, the completed web typically has a consistency of approximately 1 to 10 percent water and approximately 90 to 99 percent fiber, although other web consistencies are possible at this stage.
The quality of the paper web produced in the papermaking process depends in part on the orientation of the fibers and the consistency of fiber distribution when the embryonic web is formed in the wet-end section of the Fourdrinier machine. The orientation of the fibers within the embryonic web first depends on the distribution of the stock flow to the wire by the headbox. In a pressure forming arrangement of the headbox, the web's boundary layer fibers often become impregnated in the wire. When the web is later transferred from the wire, the boundary layer fibers impregnated in the wire are pulled from the web, leaving small holes in the web. These small holes in the web result in a web that is not as smooth on one side as it is on the other (often called the “phenomena of two-sidedness”). Also, in a pressure forming arrangement, the web's internal layer fibers become forcibly and sporadically misaligned. In a velocity forming arrangement of the headbox, the sheet is formed through a thickening mechanism. This thickening mechanism is due in part to gravitational forces pulling the fibers and the water down through the wire, which causes the bottom-most layers of fibers that settle directly on the wire to be more dense than the upper-most layers of fibers. This high-density layer prevents fibers, fines, and fillers from being pulled through the wire (i.e., higher retention). This high-density layer also prevents water from draining through the wire, resulting in two-sidedness. Both the phenomena of two-sidedness and the disparate orientation of internal layer fibers reduce the quality of the finished paper web.
As water is mechanically squeezed from the paper web in the press section, fines, fillers, and fibers become impregnated in the felt carrying the paper web. The fines, fillers, and fibers plug the felt's water removal channels, resulting in the felt becoming less efficient in removing water from the paper web. As the felt in the press section becomes less efficient in removing water from the web, the dryer section must carry the burden of removing more water from the paper web.
A long-standing problem with papermaking machinery and processes is the large amount of energy required to run the machinery and to produce paper in such processes. A significant portion of this energy is consumed within the dryer section of the papermaking machine. Paper webs having poor fiber formation require significantly more heat to dry than paper webs with good fiber formation and distribution. Therefore, the problems described above regarding fiber misalignment and poor fiber distribution result in paper that requires more energy to dry and that is more costly to produce.
In addition, paper having poor fiber formation is typically lower in machine direction tensile strength when compared with the same grade of paper with a more consistent fiber distribution. This may require expensive chemical additives to increase web strength and can require more sizing, coating, calendaring, and converting operations to produce an acceptable paper product. Improving fiber formation by using more highly refined stock fibers can help to address these issues, but at a significantly increased pulp cost.
In light of the problems and limitations described above, a need exists for a method and apparatus for increasing the quality and manufacturing efficiency of a finished paper web by reducing the phenomena of two-sidedness, improving the distribution of internal layer fibers in the web, lowering the cost of web production through reduced energy requirements, reducing the amount of chemical additives needed for acceptable web strengths, enabling the use of less refined or lower quality stock, improving the retention of fines and fillers within the web, and keeping the forming and press fabrics clean. Each embodiment of the present invention achieves one or more of these results.
Preferred embodiments of the present invention provide a papermaking method and apparatus to improve the quality of a paper web by reducing the phenomena of two-sidedness, by improving the alignment and distribution of the fibers in the web, and by reducing the energy requirements of the papermaking process by increasing water removal from the web in the wet-end and press sections of the paper making machine. As used herein and in the appended claims, reference to a paper web is intended to refer to any type of paper or tissue web produced with a papermaking machine.
In some embodiments of the present invention, stock flow, including fibers and water, is discharged from a headbox onto a wire. A vibrational force is transferred to the wire in order to re-align the fibers. In addition, the water from the stock flow is drained to cause the fibers to form a web. The energy imparted to the wire by the vibrational force preferably causes the boundary layer fibers impregnated in the wire to be released from the wire. The energy imparted to the wire by the vibrational force also preferably causes release of internal layer fibers that have begun to form the embryonic web. The internal layer fibers can then re-align and re-settle on the traveling wire in a more natural and uniform pattern. As the internal layer fibers re-settle, the fibers can penetrate into empty voids within the web. Preferably, the vibrational force is transferred to the wire of the papermaking machine before significant water removal takes place, i.e. during the formation of the embryonic web. In some highly preferred embodiments of the present invention, the vibrational force is transferred to the underside of a substantially horizontal wire, such as the wire of a Fourdrinier papermaking machine. In these and other embodiments, a vibrational force is transferred to the forming or press fabrics of the papermaking machine in order to release the fibers, fines, and fillers that have become impregnated in the forming or press fabrics. In such embodiments, the vibrational force can be used in conjunction with conventional suction devices, if desired, in order to maintain the cleanliness and water removal efficiency of the fabrics.
Some preferred embodiments of the present invention employ a papermaking machine vibrational device having a vibrational device frame, at least one vibration-inducing mechanism coupled to the vibrational device frame, and a vibrational head coupled to the vibration-inducing mechanism. Any number of such vibrational devices can be located adjacent to the web-forming wire, adjacent to the press felt, or adjacent to both the web-forming wire and the press felts for imparting vibration to the wire or press felt as described above. The vibrational head of the vibrational device preferably engages the wire or press felt of the papermaking machine to impart a vibrational force to the wire or press felt. In some embodiments, the vibrational device is positioned under the wire or press felt in an orientation perpendicular to the direction of travel of the wire or press felt. The vibrational device can span the entire width or substantially the entire width of the wire or press felt in order to impart the vibrational force to the entire width of the web.
In some embodiments of the present invention, the vibrational device frame is mounted to the papermaking machine frame. The vibrational device frame can have a truss network mountable to the papermaking machine frame and supporting the vibration-inducing mechanisms and the vibrational head under the wire or press felt. In some preferred embodiments, the vibrational device includes a vertical adjustment mechanism coupled to the truss network to allow for vertical adjustment of the vibrational device with respect to the wire or press felt.
The vibration-inducing mechanisms are preferably pneumatic, hydraulic, or electric mechanisms that transfer a vibrational force to the vibrational head and wire or press felt. Although any type of vibration can be transferred to the head (and wire or press felt) in this manner, the vibration is preferably high frequency and low amplitude. Preferably, the frequency and amplitude of the force transferred by the vibration-inducing mechanisms can be varied through the use of a solenoid valve or an amplifier, if desired. In some embodiments, the frequency and amplitude of the force transferred by each vibration-inducing mechanism can be varied independently, in order to impart different forces to different portions of the web. For example, the frequency and amplitude of the forces transferred by two or more vibrational devices spaced in the cross-machine direction can vary to generate different vibration frequencies and amplitudes across the wire or press felt in the cross-machine direction. Preferably, a sliding mechanism is used to couple the vibration-inducing mechanisms to the vibrational head, thereby enabling quick and easy vibrational head replacement (even during operation of the papermaking machine in some embodiments).
The vibrational head preferably includes a land area through which the vibrational force is transferred from the vibrational head to the wire or press felt. In some embodiments of the present invention, the land area includes an upstream portion which slopes vertically downward from the wire or press felt at a lead angle, so that the lead angle pushes water up into the wire or press felt when the vibrational head engages the underside of the wire or press felt. The land area can also include a downstream portion which slopes vertically downward from the wire or press felt at a relief angle, so that the relief angle induces a vacuum when the vibrational head engages the underside of the wire or press felt. In other embodiments of the present invention, the land area has a concave configuration.
In some highly preferred embodiments of the present invention, a lubrication shower is positioned within the wet-end section or within the press section of the Fourdrinier machine upstream from the vibrational device in order to lubricate the wire or press felt, in order to re-fluidize the fibers within the web before the fibers reach the vibrational device, and in order to minimize air entrapment in the nip (i.e., vacuum) formed between the traveling wire or press felt and the vibrating head.
Some embodiments of the present invention provide a vibrational device for use with a papermaking machine having a machine direction and a cross-machine direction, wherein the papermaking machine includes a wire positioned to receive stock flow and movable in the machine direction, and wherein the vibrational device comprises a vibrational device frame; a first vibration isolator coupled to the vibrational device frame to dampen vibration transmission to the papermaking machine; a vibration-inducing mechanism coupled to the vibrational device frame, operable to generate a vibration having a frequency, and positioned laterally with respect to the first vibration isolator in the cross-machine direction; and a vibrational head coupled to the vibration-inducing mechanism and directly contacting the wire to impart the vibration to the wire.
In some embodiments, a method of forming a web in a papermaking machine having a vibrational device with a vibrational device frame is provided, and comprises discharging stock flow onto a wire travelling in a machine direction, wherein the stock flow includes water and fibers; transferring a vibration to the wire with a first vibration-inducing mechanism, wherein the vibration has a first frequency; dampening at least some of the vibration with a first vibration isolator located laterally with respect to the first vibration-inducing mechanism in a cross-machine direction; and draining at least some of the water from the stock flow to cause the fibers to form a web.
In another aspect of the present invention, a vibrational device for use with a papermaking machine having a machine direction and a cross-machine direction is provided, and comprises a vibrational device frame; a first plurality of vibration isolators coupled to the vibrational device frame to at dampen vibration transmitted from the vibrational device; a plurality of vibration-inducing mechanisms coupled to the vibrational device frame and operable to generate respective vibrations each having a respective frequency, wherein the vibration-inducing mechanism is positioned laterally with respect to the plurality of vibration isolators in the cross-machine direction; and at least one vibrational head coupled to the at least one vibration-inducing mechanism and directly contacting the wire to impart vibration from the plurality of vibration-inducing mechanisms to the wire.
In yet another aspect of the present invention, a method of forming a web in a papermaking machine is provided, and comprises transferring vibrations to the wire of the papermaking machine with a plurality of vibration-inducing mechanisms, the vibrations each having a respective frequency; and at least partially isolating the papermaking machine from the vibrations generated by the plurality of vibration-inducing mechanisms with a first plurality of vibration isolators, wherein each of the first plurality of vibration isolators is positioned laterally with respect to each of the plurality of vibration-inducing mechanisms in a cross-machine direction of the wire.
Further objects and advantages of the present invention, together with the organization and manner of operation thereof, will become apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings, wherein like elements have like numerals throughout the drawings.
The present invention is further described with reference to the accompanying drawings, which show a preferred embodiment of the present invention. However, it should be noted that the invention as disclosed in the accompanying drawings is illustrated by way of example only. The various elements and combinations of elements described below and illustrated in the drawings can be arranged and organized differently to result in embodiments which are still within the spirit and scope of the present invention.
In the drawings, wherein like reference numerals indicate like parts:
a is a front elevational view of a vibrational device used in the papermaking machine shown in
b is a front elevational view of an alternative vibrational device according to the present invention, viewed from line 5—5 of
c is a detail view of the vibrational device shown in
d is a detail side view of an alternative vibrational device according to the present invention;
a is a side elevational view of the vertical adjustment mechanism of the vibrational device illustrated in
b is a side elevational view of the vertical adjustment mechanism of the vibrational device illustrated in
a is a cross-sectional view of the vibrational device shown in
b is a cross-sectional view of the vibrational device shown in
c is a cross-sectional view of the vibrational device shown in
a–8e are cross-sectional views of different embodiments of vibrational heads for a vibrational device according to the present invention;
a is a schematic representation of stock flow settling on a wire without a vibrational force;
b is a schematic representation of stock flow settling on a wire with a vibrational force;
With reference to
The headbox 14 is positioned adjacent to the papermaking machine frame 12 in order to distribute stock flow onto the wire 16. Any conventional headbox in the papermaking art can be employed in order to distribute stock flow onto the wire 16. The headbox 14 preferably distributes stock flow to the wire 16 in order to produce a web having uniform properties across the width of the wire 16, referred to as the cross-machine direction (CD), along the length of the wire 16, referred to as the machine direction (MD), and through the cross-section of the web, referred to as the Z direction (Z), as shown in
The wire 16, which may also be referred to as the Fourdrinier wire, is preferably a moving, endless belt of wire-mesh screen. The wire 16 is movably coupled to the papermaking machine frame 12 via several rolls in a manner that provides an endless conveyor belt for receiving and transporting stock flow distributed by the headbox 14. The wire 16 first wraps around the breast roll 22, (which is preferably positioned adjacent to the headbox 14 and generally directly under the headbox 14), stretches from the breast roll 22 across the length of the wet-end section 10 to the couch roll 24, wraps around the couch roll 24, and stretches around the plurality of return rolls 26 to return to the breast roll 22. One having ordinary skill in the art will appreciate that the wire 16 can be driven about other elements in an endless-conveyor arrangement, such as by being passed around one or more sprockets, pulleys, or other preferably rotatable elements.
As shown in
As shown in
The plurality of foil boxes 32 are preferably positioned under the wire 16, downstream from the initial forming board 30, and run in the cross-machine direction. Preferably, each one of the plurality of foil boxes 32 is coupled to the papermaking machine frame 12 and includes a plurality of T-bars 34 and a plurality of stationary (or adjustable) foils or blades 36 coupled to the plurality of T-bars 34. As is conventional in the papermaking industry, the stationary foils 36 are each preferably 2½ inches wide. However, the stationary foils 36 may be any width. The stationary foils 36 each preferably have a lead angle that strips water off of the wire and a surface downstream from the lead angle that creates a vacuum to pull water down from the wire 16. The surface downstream from the lead angle is preferably flat, but can be shaped in a number of different manners to generate vacuum downstream of the lead angle (including without surfaces that are wave-shaped, stepped, multi-faceted, curved convexly and/or concavely, and the like). The lead angle of each subsequent, downstream stationary foil 36 strips the water off of the wire 16 that was pulled down by the vacuum created by the preferably flat surface of the preceding, upstream stationary foil 36. In this manner, water is drained from the wire 16 in the wet-end section 10 and the web begins to form. The wet-end section 10 can include a large number (e.g., 100) of stationary foils 36 coupled to the plurality of foil boxes 32. It should be noted that stationary foils 36 need not necessarily be connected to or otherwise be used in conjunction with foil boxes 32, although foil boxes 32 are a preferred manner of collecting and transporting water from beneath the wire 16. In addition, although T-shaped bars 34 are a highly preferred manner of connecting the stationary foils 36 to associated framework of the papermaking machine, the stationary foils 36 can be connected in desired locations in any other conventional manner, such as by fastening the stationary foils 34 with one or more bolts, screws, clamps, rivets, pins, or other conventional fasteners, by snap-fitting the foils to connecting points on the papermaking machine, and the like. Stationary foils, their manner of operation and connection, and the various forms of stationary foils are also well-known suction devices in the papermaking art and are not therefore described further herein.
The papermaking machine wet-end section 10 preferably also includes at least one vibrational device 100. As shown in
The diagonal truss 112a is coupled between a first end 116a of the horizontal truss 110 and the bracket 114a. The diagonal truss 112b is coupled between a second end 116b of the horizontal truss 110 and the bracket 114b. Rather than using a single horizontal truss to support the vibrational device 100, the pair of diagonal trusses 112a and 112b are preferably used to position the horizontal truss 110 somewhat below the height of the papermaking machine frame 12. However, a single horizontal truss could be used to support the vibrational device 100.
In other preferred embodiments as shown in
Still other truss network shapes and designs are possible for serving the purpose of supporting the vibrational devices 100, 200 adjacent to the wire 16, each one of which falls within the spirit and scope of the present invention. Specifically, any truss element or structure having any shape and being made from any number of elements (including without limitation plates, beams, rods, bars, and the like) connected together in any conventional manner could be used to support the vibrational device 100, 200 from beneath as shown in the figures or from any other location on the vibrational device 100, 200. The resulting truss element or structure can have any shape desired, and can be connected to the papermaking machine frame in any conventional manner (i.e., with or without brackets). Most preferably however, the truss element or structure provides substantially no vertical deflection in the center of the cross-machine direction of the wire 16. Put differently, the truss network preferably provides a mounting base for the vibrational device 100, 200 that runs in the cross-machine direction and is completely stationary with respect to the vertical orientation of the wire 16.
Although the vibrational device 100, 200 is preferably connected to and supported by the horizontal truss 110, 210 as described above, it should be noted that in some alternative embodiments the vibrational device 100, 200 is connected directly to a member of the papermaking machine frame (e.g., a beam, plate, stretcher, or other element running partially or fully across the papermaking machine in the cross-machine direction). This papermaking machine frame member can be rigidly and permanently attached to the remainder of the papermaking machine or can be adjustable as described in more detail below with regard to the horizontal truss 110, 210 in the illustrated preferred embodiments.
With particular reference to
As shown in
A dovetail connection between a bracket 114a, 114b and the papermaking machine frame (or the floor) is a highly preferred manner in which to connect the horizontal truss 110 to the papermaking machine frame (or the floor). One having ordinary skill in the art will appreciate that a number of other manners exist for establishing this connection, some permitting adjustment of the connection location as mentioned above, and others not permitting such adjustment. By way of example only, each bracket 114a, 114b can be attached to the papermaking machine frame or floor by bolts, rivets, pins, screws, nails, or other conventional fasteners, by welding or brazing, by one or more clips or clamps, and the like. Some of the manners of connection permit adjustment of the position of the brackets 114a, 114b, such as bolts or pins releasably received within different apertures along the papermaking machine frame, clips or clamps holding the brackets 114a, 114b to a rail, lip, bar, flange, or other portion of the papermaking machine frame, and the like. In some embodiments, the brackets 114a, 114b can be retained in different positions along the papermaking machine frame by the weight upon the brackets 114a, 114b. Detents, recesses, notches, or other features of the papermaking machine frame can assist in retaining the brackets 114a, 114b in desired positions in such cases.
b is a side elevational view of the vibrational device 200 illustrated in
It should be noted that the various manners described above for adjustably positioning the horizontal truss 110 (via the brackets 114a, 114b, second horizontal trusses 214a, 214b, and the like) apply equally to alternative embodiments of the present invention (e.g., in which no brackets 114a, 114b are employed or in which the vibrational device has no identifiable second horizontal trusses 214a, 214b). In such cases, the ends of the horizontal truss 110, 210 can be permanently or adjustably connected to different locations on the papermaking machine frame or to the ground.
A number of different elements and structures exist for adjusting the height of the horizontal truss 110, 210 at either or both ends thereof. The jackscrew-type vertical adjustment mechanisms 120, 222 described above and illustrated in the figures are well-suited for brackets 114a, 114b or second horizontal trusses on the ends of the truss 110, 210. In other embodiments (whether employing brackets 114a, 114b, second horizontal trusses 214a, 214b, or other structure), the ends of the horizontal truss 110, 210 can be lifted and lowered by any conventional jack mechanism, including without limitation by ratchet or scissor-type jacks connected between the papermaking machine frame or ground and the truss, by conventional hydraulic, pneumatic, or electrical jacks, by shims, by one or more bladders fillable with air or fluid, and the like. One having ordinary skill in the art will appreciate that still other examples of adjusting the height of the truss 110, 210 are possible, each one of which falls within the spirit and scope of the present invention.
Preferably, the brackets 114a and 114b or second horizontal trusses 214a, 214b also include a vibrational isolator (not shown) to isolate the machine frame 12 from any vibrations of the vibrational device 100, 200, and, likewise, to isolate the vibrational device 100, 200 from any vibrations of the papermaking machine frame 12. In one highly preferred embodiment, the vibrational isolator is a pad, block, or other element made from a compressible and vibration-damping material such as rubber, plastic, urethane, wool, cork, and the like positioned between steel blocks within the brackets 114a and 114b or against the second horizontal trusses 214a, 214b. In other embodiments, the vibrational isolator is an gas or fluid bag positioned within the brackets 114a and 114b or against the second horizontal trusses 214a, 214b. Vibration isolators can also be used in those embodiments of the present invention not having brackets 114a, 114b or second horizontal trusses 214a, 214b as described above. Any other conventional vibration isolator can instead be used as desired.
Preferably, the vibrational device frame 102, 202, including the horizontal truss 110, 210 and the diagonal trusses 112a and 112b and brackets 114a and 114b (if used) or the vertical and secondary horizontal truss structure (if used), is constructed of stainless steel. Most preferably, the vibrational device frame 102, 202 is constructed of 316 stainless steel, because 316 stainless steel is largely inert to the caustic and acidic environment of the papermaking machine.
The following description is with reference to the vibrational device 100 illustrated in
With reference again to the embodiment of the present invention illustrated in
In some preferred embodiments, one vibration-inducing mechanism 104 is positioned every one to four feet across the width of the wire 16. For example, for a typical wire 16 having a width of 30 feet, preferably ten vibration-inducing mechanisms 104 are positioned across the width of the wire 16. The number of vibration-inducing mechanisms 104 positioned across the width of the wire 16 is at least partially a function of the power output of each vibration-inducing mechanism 104 and the physical size of each vibration-inducing mechanism 104. However, any number of vibration-inducing mechanisms 104 could be positioned across the width of the wire 16 in any suitable configuration.
The vibration-inducing mechanisms 104 are preferably any type of pneumatic, hydraulic, electric, mechanical or electromagnetic mechanisms that are able to impart a force having a relatively high frequency and a relatively low amplitude to the wire 16. Vibrators and vibration-inducing mechanisms driven pneumatically, hydraulically, electrically, mechanically, or eletro-mechanically are well-known to those skilled in the art, and are not therefore described further herein. In some preferred embodiments, the vibration-inducing mechanisms 104 each impart a force of approximately 20 to 7000 pounds with a frequency of approximately 20 to 2000 Hertz and an amplitude of up to approximately 0.120 inches. However, superior results are achieved when the vibration-inducing mechanisms vibrate at a frequency of at least 1,000 Hertz. Also, the amplitude of the vibrational force may be adjusted so that the vibrational head 106 has a range of vibrational movement and is in direct contact with the wire 16 in only part of the range of vibrational movement. In general, the heavier the weight of the paper being produced and/or the faster the speed of the papermaking machine, the greater the force necessary to vibrate the wire 16. However, the frequencies and amplitudes of the vibrational forces transferred to the wire 16 are preferably independent of the speed at which the wire 16 is travelling (i.e., the papermaking machine speed).
In some embodiments, each one of the vibration-inducing mechanisms 104 is controlled individually so as to impart different forces having different frequencies and/or different amplitudes to different sections of the wire 16 across the width (i.e., the cross-machine direction) of the wire 16. For example, a first vibration-inducing mechanism 104 generates a first vibrational force having a first frequency, and a second vibration-inducing mechanism 104 generates a second vibrational force having a second frequency different from the first frequency. The first vibrational force is transferred to a first section of the wire 16 in the cross-machine direction, and the second vibrational force is transferred to a second section of the wire 16 in the cross-machine direction. The first and second vibrational forces may also have different amplitudes. The frequency and amplitude of the first vibrational force may be controlled independently of the frequency and amplitude of the second vibrational force, and vice versa, so that the frequencies and amplitudes of the vibrational forces may be changed independently during operation of the vibrational device 100, 200. Moreover, the frequencies and amplitudes of the different vibrational forces transferred to the wire 16 in the cross-machine direction are preferably each independent of the speed at which the wire 16 is traveling (i.e., the papermaking machine speed).
By varying the frequencies and amplitudes of the vibrational forces transferred to different sections of the wire 16, the quality of the paper web can be more precisely controlled in the cross-machine direction. For example, the quality of the center of the paper web may be acceptable, but the quality of the edges of the paper web may not be acceptable. In this case, the vibration-inducing mechanisms 104 corresponding to the edges of the paper web may be adjusted to transfer vibrational forces having higher frequencies and/or amplitudes to the edges of the wire 16. In addition, the vibration-inducing mechanisms 104 corresponding to the center of the paper web may be adjusted to transfer vibrational forces having lower frequencies and/or amplitudes to the center of the wire 16. Moreover, the vibration-inducing mechanisms 104 corresponding to the center of the paper web may be turned off or adjusted to not transfer vibrational forces to the center of the wire 16.
The type of vibration-inducing mechanisms 104 used in each application could vary depending upon the type of power source available near the papermaking machine. Each type of vibration-inducing mechanism 104 can be implemented within the vibrational device 100 in the same manner. Most preferably, the vibration-inducing mechanisms 104 are pneumatic turbine vibrators manufactured by Vibco, Inc. of Wyoming, R.I. The most preferred Vibco pneumatic turbine vibrators for use as the vibration-inducing mechanisms 104 are series CCF-L-, W, V, BV, SVR, and HLF. The Vibco pneumatic turbine vibrators are manufactured under one or more of the following patents, the disclosures of which are incorporated herein by reference: U.S. Pat. Nos. 3,870,282; 3,932,057; 3,938,905; 4,389,120; and 4,424,718 insofar as they relate to vibrator devices, their structure, and operation.
The vibrational device 100 illustrated
d illustrates another vibration-inducing mechanism 604 according to the present invention. The vibration-inducing mechanism 604 of
Referring again to the illustrated preferred embodiment of
With reference to both illustrated preferred embodiments of the present invention illustrated in
The vibration isolators 105, 205 can be connected to the vibrational head 106, 206 and to the horizontal truss 110, 210 in a number of different manners, including those described above with reference to the connection between the vibration-inducing mechanisms 104, 204 and the vibrational head 106, 206.
Although the vibration isolators 105, 205 are preferably air bag vibration isolators, one having ordinary skill in the art will appreciate that other types of vibration isolators can instead be employed. For example, other vibration isolators include without limitation pneumatic springs and shocks, hydraulic springs and shocks, electromagnet sets, solenoids, torsion, extension, compression, leaf, and other springs, and the like connected in a manner similar to the air bag vibration isolators described above. While any of these types of vibration isolators can be used to dampen vibrations as also described above, controllable vibration isolators are most preferred to enable the user to control the amount of vibration damping provided by the vibration isolators. Controllable vibration isolators and their operation are well known to those skilled in the art and are not therefore described further herein.
With particular reference to
As shown in
In other embodiments of the present invention, the vibration-inducing mechanisms 104, 204 can be releasably connected to the vibrational element 150, 250 in other manners. For example, the vibration-inducing mechanisms 104, 204 can be releasably connected to the vibrational element 150, 250 by one or more conventional fasteners including one or more bolts, pins, clips, and the like, by one or more tongue and groove joints, by a flange, boss, bracket, rail, or other element or extension on the vibration-inducing mechanisms 104, 204 received within one or more grooves, slots, or other apertures in the vibrational element 150, 250 (and vice versa), and the like. In embodiments where a removable vibrational element 150, 250 is not needed or desired, the vibrational element 150, 250 can be permanently connected to the vibration-inducing mechanisms 104, 204 in any conventional manner desired.
The vibrational element 150, 250 can have any shape and size. However, in some highly preferred embodiments, the vibrational element 150, 250 has a width of approximately one to ten inches and a length approximately equal to the width of the wire 16 in the cross-machine direction. The vibrational element 150, 250 preferably has a land area 160, 260 at the plane of intersection with the wire 16. The land area 160, 260 is the area through which the vibrational force is transferred from the vibrational element 150, 250, through the bottom of the wire 16, and into the web being transported by the wire 16.
In one highly preferred embodiment of the present invention shown in
The vibrational element 150, 250 can have any configuration suitable for engaging the underside of the wire 16 and imparting a vibrational force to the underside of the wire 16. In particular, as shown in
A vibrational element 150, 250 partially or fully spanning the wire 16 in the machine direction and actuated by one or more vibration-inducing mechanisms 104, 204 is preferred. However, vibration can be transmitted to the wire 16 from the vibration-inducing mechanisms 104, 204 in a variety of different manners. The vibration-inducing mechanisms 104, 204 can press directly against the underside of the wire 16 (e.g., at multiple points across the wire 16), can actuate separate elements in constant or intermittent contact with the underside of the wire 16, and the like. In those embodiments not having a vibrational element to which the vibration-inducing mechanisms 104, 204 can be suspended or otherwise supported, the vibration-inducing mechanisms 104, 204 can be mounted upon a rail, bar, plate, frame, or other structure located beneath the wire 16.
The manner in which the vibration-inducing mechanisms 104, 204 exert vibrational force to the underside of the wire 16 depends at least partially upon the type of vibration-inducing mechanisms being used. For example, many conventional vibration-inducing mechanisms have base plates through which generated vibration is transmitted. These vibration-inducing mechanisms can be employed in the vibrational device 100, 200 of the present invention, and can be mounted on a frame or other structure so that their bases are in direct or indirect vibration-transmitting contact with the underside of the wire 16. As another example, one or more solenoids having extendible armatures can be mounted across the underside of the wire 16 so that the armatures can extend into contact with the underside of the wire 16 when the solenoids are actuated. As yet another example, a shaft having multiple cams thereon can be rotatably mounted across the underside of the wire 16 so that rotation of the shaft causes the cams to come into repeated contact with the wire 16 to vibrate the wire 16.
The vibrational device 100, 200 can include two or more independent vibrational heads 106, 206 mounted to a single vibrational device frame 102, 202 (see
Preferably, the vibrational head 106, 206 is a rigid structure capable of transferring a consistent vibrational force from the vibration-inducing mechanism 104, 204 to the vibrational element 150, 250. The vibrational head 106, 206 can be constructed of any material desired, and is preferably constructed of a relatively rigid material such as steel, fiberglass, composites, or combinations thereof. The vibrational head 106, 206 can include plates, angles, tubes, honeycomb or mini-truss elements, or other structural members fastened to the vibrational isolators 105, 205 or the papermaking machine frame 12 in any conventional manner, such as by welding, brazing, pinning, laminating, or bolting. One having ordinary skill in the art will appreciate that still other examples of materials and designs for the vibrational head 106, 206 are possible.
The vibrational element 150, 250 can be constructed of any material that is preferably less abrasive than the material of the wire 16. Preferably, the vibrational element 150, 250 is constructed of material that wears well, in addition to being less abrasive than the material of the wire 16. Most preferably, the vibrational element 150, 250 is constructed of ultra-high, molecular-weight (UHMW) polyethylene.
As best shown in the illustrated preferred embodiment of
According to the method of the invention, the vibrational device 100, 200 is used to impart a vibrational force to the underside of the wire 16 in order to create turbulence within the stock flow. Preferably, this vibrational force is a high frequency, low amplitude force. Creating turbulence within the stock flow keeps the fibers within the stock flow in free suspension, i.e., prevents the fibers from bonding to one another, for a longer period of time. Preferably, sufficient turbulence is created to cause the free suspension of fibers having a length of from approximately 0.5 mm to approximately 12 mm. In order to excite and re-align the fibers, the fibers preferably must be moved a distance equal to at least their length. Thus, sufficient turbulence is created to move the fibers approximately 0.5 mm to approximately 12 mm. During this added time of free suspension or re-fluidization, the fibers are able to re-align with respect to one another. Once the fibers begin to bond to one another after being re-aligned, the fibers re-settle on the wire 16 in a more uniform pattern and penetrate into empty voids in which fibers had not yet settled. This resettling of the fibers results in more consistent fiber distribution in the cross-machine direction, the machine direction, and the Z direction.
High levels of turbulence, although beneficial for good formation, can result in the low retention of fines and fillers in the web due to the disruption of the matted web. However, inter-slurry fiber collisions and collisions between fibers and the wire 16 which occur in increased states of turbulence can have a beneficial influence on the retention of fines and fillers within the web. In addition to creating turbulence within the stock flow, the vibrational force imparted to the underside of the wire 16 by the vibrational device 100, 200, along with the water delivered by the lubrication shower 121, helps to release boundary layer fibers that may have become impregnated in the wire 16 due to the delivery of the stock flow to the wire 16 at the angle of impingement α, especially in a pressure forming arrangement of the headbox 14.
As shown in
In either a pressure forming or a velocity forming arrangement of the headbox 14, water removal and boundary layer fiber bonding normally commences as soon as the stock flow contacts the wire 16. The vibrational device 100, 200 therefore preferably imparts vibrational force to the underside of the wire 16 before an embryonic web is substantially formed. If the vibrational device 100, 200 imparts the vibrational force to the underside of the wire 16 after the embryonic web has substantially formed, the vibrational force may damage or destroy the web. Accordingly, some embodiments of the present invention employ the vibrational devices 100, 200 are preferably positioned within the papermaking machine wet-end section 10 so that the vibrational forces are imparted to the wire 16 before a significant amount of water is removed from the stock flow as distributed by the headbox 14 and before significant formation of the embryonic web. The stock flow distributed onto the wire 16 by the headbox 14 is preferably 99 percent water and 1 percent fibers, although stock flows having different consistencies can be used. Preferably, the vibrational devices 100, 200 are positioned within the papermaking machine wet-end section 10 so that vibrational forces are imparted to the wire 16 before the web has a fiber consistency of 5 percent and a water consistency of 95 percent, i.e., during the formation of the embryonic web.
Moreover, the lubrication shower 121 (if used) preferably injects a sufficient amount of water into the wire 16 so as to act as a non-compressible media that reduces wear of both the vibrational element 150, 250 and the wire 16. The water injected by the lubrication shower 121 is preferably capable of penetrating through the wire 16 and into the web to help release boundary layer fibers impregnated in the wire 16 and to help maintain the free suspension of the fibers (i.e., aid in re-fluidization) in order to prevent or at least delay the formation of the embryonic web.
In some preferred embodiments of the present invention, at least one vibrational device 100, 200 is installed within the wet-end section 10 of an existing papermaking machine. The vibrational devices 100, 200 in the illustrated preferred embodiments of
If additional dwell time is required for formation of the web after the vibrational device 100, 200, auxiliary forming boards (not shown) can be installed downstream from the vibrational device 100, 200. The auxiliary forming boards can replace some of the plurality of stationary foils 36 or can be added to the papermaking machine wet-end section 10 in addition to the plurality of stationary foils 36. Auxiliary forming boards or the plurality of stationary foils 36 can also be an integral part of the vibrational device 100, 200 itself. In addition, existing forming boards 30 can be modified to incorporate the principles of the vibrational device 100, 200 of the present invention.
In some preferred embodiments, after the vibrational device 100, 200 is installed, the vertical orientation of the vibrational device 100, 200 with respect to the wire 16 can be adjusted. In order to adjust the vertical orientation in the illustrated preferred embodiment, an operator rotates the adjustment nut 130, 230 of the vertical adjustment mechanism 120, 222. The adjustment nut 130, 230 adjusts the threaded rod 128a, 224a in the threaded aperture 128b, 224b of the horizontal truss 110, 210, thereby raising or lowering the horizontal truss 110, 210 with respect to the papermaking machine frame and the wire 16.
Preferably, the vertical orientation of the vibrational device 100, 200 is adjusted until the vibrational element 150, 250 engages the underside of the wire 16. Most preferably, the vertical orientation of the vibrational device 100, 200 is adjusted until the vibrational element 150, 250 raises the wire 16 by approximately 0.001 to 0.002 inches. However, the vibrational device 100, 200 can be adjusted so that the vibrational element 150, 250 does not actually contact and engage the wire 16. Also, the vertical orientation of the vibrational device 100, 200 may be adjusted so that the vibrational head 106, 206 has a range of vibrational movement and is in direct contact with the wire 16 in only part of the range of vibrational movement. One skilled in the art will recognize that the vertical adjustment of the vibrational device 100, 200 can depend on the grade of paper being produced or the papermaking machine speed. Although adjustment of the vertical orientation of the vibrational device 100, 200 as described above and shown in the drawings is through the use of a threaded rod and aperture connection, the vertical orientation of the vibrational device 100, 200 can be adjusted with any type of vertical adjustment mechanism or elevator as described above. Moreover, the vertical orientation of the vibrational device 100, 200 can be adjusted manually, if desired.
Once the vibrational device 100, 200 is installed and the vertical orientation with respect to the wire 16 is adjusted, the vibrational force generated by the plurality of vibration-inducing mechanisms 104, 204 is preferably modified depending on the type of paper being produced and the operating speed of the papermaking machine. The operating speed of the papermaking machine, i.e. the velocity of the web, is often from 100 feet per minute to 5000 feet per minute. The vibrational force is preferably adjusted until sufficient turbulence is created in the stock flow to create free suspension of the fibers and sufficient re-alignment of the fibers as described in greater detail above. The vibrational force is preferably varied by altering the input to the plurality of vibration-inducing mechanisms 104, 204. In some highly preferred embodiments, each one of the plurality of vibration-inducing mechanisms 104, 204 can be controlled independently in order (i.e., controlling vibration frequency and/or amplitude) to impart different forces to different portions of the cross-machine direction width of the wire 16. Imparting different forces to different portions of the wire 16 allows the amount of fiber re-alignment to be varied across the width of the wire 16. The control of the input to the vibration-inducing mechanisms 104, 204 is preferably integrated in a closed loop with a conventional digital control system for the papermaking machine.
Whether the vibrational force imparted to the wire 16 by the vibrational device 100, 200 is sufficient is determined by testing the web solids off of the couch roll 24 and press section and sheet samples from the reel section. Typical testing of the sheets includes visual inspection, internal bond, opacity, tear (tensile strength), and crush (compressive strength), smoothness, and any other standardized testing as stipulated by the Technical Association of the Pulp and Paper Institute (TAPPI). Applying a harmonic vibrational force to the web generally improves embryonic web formation and sheet properties with no deterioration of first pass retention, i.e., the fiber, fine, and filler content in the web is not lost. In addition, the phenomena of two-sidedness in the sheet is reduced, since the fiber distribution within the sheet is improved and boundary layer fibers are released from being impregnated in the wire 16.
Sheet profiles, i.e. the characteristics of the sheet in the machine direction, the cross-machine direction, and the Z direction, are generally improved when a harmonic vibrational force is applied to the web as performed in the present invention. Sheet profile characteristics that are generally improved by applying a harmonic vibrational force to the web are strength, sheet weight, moisture content, and solid content. In particular, tensile strength in the machine direction is improved. Sheet properties are improved due to the more consistent re-aligning and re-settling of the fibers into empty voids. As shown in
The use of the vibrational device 100, 200 in the papermaking machine wet-end section 10 results in more water being drained from the web in a more efficient manner. As a result, some of the plurality of stationary foils 36 can be eliminated from the wet-end section 10. Moreover, since water drains more efficiently from the web, the energy required to dry the web in the dryer section of the papermaking machine is reduced. Since water removal is one of the most energy-intensive operations in the industrial papermaking process, a reduction in the energy necessary to dry the web results in a substantial reduction in operating costs.
It should be noted that a vibrational device 100, 200 can be installed beneath the papermaking machine frame 12 so that the vibrational device 100, 200 engages the wire 16 as the wire 16 returns to the headbox 14. In this configuration, the vibrational device 100, 200 positioned beneath the papermaking machine frame 12 acts as a wire-cleaning mechanism as the wire 16 is returned to the headbox 14.
Once the vibrational device 100, 200 has operated within the papermaking machine wet-end section 10 for an extended period of time, the vibrational element 150, 250 may become worn due to constant abrasion from engaging the wire 16. When the vibrational element 150, 250 becomes worn, the vibrational element 150, 250 can preferably be replaced either while the papermaking machine is operating or when the papermaking machine is not operating. Since the vibrational element 150, 250 is preferably coupled to the vibrational isolators 105, 205 and the vibrational head 106, 206 via a sliding mechanism 148, 248, the vibrational element 150, 250 can preferably be slid off of the sliding mechanism 148, 248 and removed from the vibrational head 106, 206. Similarly, a replacement vibrational element 150, 250 can be slid back onto the sliding mechanism 148, 248, even during operation of the papermaking machine.
Although the vibrational device 100, 200 of the present invention provides significant advantages in the papermaking process when used in the wet-end section 10 of a papermaking machine (as described above), the vibrational device 100, 200 can also be employed in the press section of a papermaking machine for improved operation thereof. It is important to note that above discussion regarding the structure and operation of the vibrational device 100, 200 in the wet-end section 10 of the papermaking machine (as shown and described with respect to FIGS. 1–10) applies equally when the vibrational device 100, 200 is employed in the press section of the papermaking machine.
As shown schematically in
The press felt 506, which may also be referred to simply as the “felt,” is preferably a moving, endless belt of cotton mesh fabric. Preferably, the press felt 506 is movably coupled to the papermaking machine frame 12 via several rolls in a manner that provides an endless conveyor belt for receiving and transporting the paper web delivered from the paper machine wet-end section 10. The press felt 506 first wraps around the pick-up roll 510, (which is preferably positioned adjacent to the couch roll 24), stretches from the pick-up roll 510 through the nip created by press rolls 502, wraps partially around the press rolls 502, and stretches around the return rolls 504 to return to the pick-up roll 510. One having ordinary skill in the art will appreciate that the press felt 506 can be driven about other elements in an endless-conveyor arrangement, such as by being passed around one or more sprockets, pulleys, or other preferably rotatable elements.
As shown in
As shown in
In the press section 500, the vibrational device 100 and the water delivered by the lubrication shower 121 help release boundary layer fibers, fines, and fillers that may have become impregnated in the press felt 506 due to the paper web being mechanically pressed into the press felt 506. Thus, the use of the vibrational device 100 in the press section 500 results in a cleaner press felt 506 and more efficient water removal from the paper web.
The embodiments described above and illustrated in the figures are presented by way of example only and are not intended as a limitation upon the concepts and principles of the present invention. As such, it will be appreciated by one having ordinary skill in the art that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present invention as set forth in the appended claims.
This is a divisional of U.S. patent application Ser. No. 10/027,507, now U.S. Pat. No. 6,702,925, filed Dec. 21, 2001, which claims priority to U.S. Provisional Patent Application Ser. No. 60/258,141, filed Dec. 22, 2000.
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| Number | Date | Country | |
|---|---|---|---|
| 20040149415 A1 | Aug 2004 | US |
| Number | Date | Country | |
|---|---|---|---|
| 60258141 | Dec 2000 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10027507 | Dec 2001 | US |
| Child | 10770142 | US |
