EP0158938B1

EP0158938B1 - Apparatus for the manufacture of fibrous webs

Info

Publication number: EP0158938B1
Application number: EP85104134A
Authority: EP
Inventors: James Oscar Cheshire; Robert John Marinack; Johannes Archibald Van Den Akker; Douglas Leroy Lindgren
Original assignee: James River Norwalk Inc
Current assignee: Georgia Pacific Consumer Products LP
Priority date: 1984-04-16
Filing date: 1985-04-04
Publication date: 1989-12-20
Also published as: EP0158938A2; JPH032995B2; EP0158938A3; ATE48861T1; DE3574887D1; JPS60231895A

Abstract

Apparatus and method for laying down a fibrous web from a foam-fiber furnish. A headbox includes walls defining an elongate channel extending transversley of the direction of movement of the forming wire. Foam-forming nozzles are positioned to introduce foam-fiber furnish into the channel for turbulence - inducing impact on an oppositely disposed wall defining the channel. The turbulently flowing foam-fiber furnish is then introduced to the headbox slice for discharge onto the forming wire with minimized MD orientation of the fibers.

Description

This invention relates to an apparatus for forming and directing a foam-fiber furnish onto a forming wire in the manufacture of a fibrous web, with a slice positioned and operative to deposit said foam-fiber furnish onto said forming wire; and a headbox channel in direct fluid flow communication with said slice and including an inner wall portion; a plurality of foam-forming openings in fluid flow connection with said headbox channel and positioned and adapted to receive a foamable liquid-fiber furnish and to form and forcible direct foam-fiber furnish having a relatively low viscosity into said channel to impinge upon said inner wall portion and flow throughout said channel, the recited impingement being effective to create turbulence in the low-viscosity foam-fiber furnish in said channel immediately upon its flow through said slice, whereby random orientation of the fibers in the furnish is insured throughout said channel and as it flows through said slice for deposit on said forming wire.
In the manufacture of fibrous webs, such as paper, from a foam-fiber furnish deposited on a forming wire from the slice of a conventional foam-forming headbox, it has been found difficult to maintain a desired random orientation of fibers ensuring optimum MD/CD tensile strength of the formed sheet at the preferred, relatively high wire speeds associated with papermaking. Efforts at achieving a desired fiber orientation have involved delivering the foam-fiber furnish to the slice, immediately upon creation of the furnish.
DE-A-2 620 033 discloses an apparatus for forming and directing a foam-fibre furnish onto a forming wire in the manufacture of a fibrous web, with a slice positioned and operative to deposit said foam-fibre furnish onto said forming wire. A headbox channel in direct fluid flow communication with the slice includes inner wall portions. A plurality of foam-forming openings is in fluid flow connection with said headbox channel and is positioned and adapted to receive the foamable liquid-fibre furnish and to form and forcibly direct foam-fibre furnish having a relatively low viscosity into said channel, whereby the foam-fibre furnish impinges upon the inner wall portion and flows throughout said channel through the slice. The recited impingement creates turbulence in the low-viscosity foam-fibre furnish whereby random orientation of the fibres in the furnish is insured throughout said channel and as it flows through said slice for deposit on said forming wire.
The invention contemplates an improvement on the foregoing explained apparatus in such a manner that a better turbulent flow of the foam-fiber furnish is created to obtain a better random fiber orientation.
The improvement is characterized in that each of said foam-forming openings are nozzles, which comprises means defining a generally tubular fluid passage having regions of alternate lesser and greater cross sectional areas.
Such nozzles with alternate cross sectional areas create a turbulent flow immediately and especially prior said foam-fiber furnish passes said slice.
It is important, how the inner wall portion of the headbox channel is formed. Preferred embodiments of the invention are therefore characterized in that the inner wall portion is substantially planar, curved or cylindrical.
Furthermore the turbulent flow will advantageously be improved with a feature characterized in that said channel is provided with a second array of foam forming nozzles positioned to direct foam-fiber furnish onto an opposing wall of said channel, or with a feature characterized in that a plurality of rows of foam forming nozzles extend longitudinally of said cylindrical channel and so positioned as to direct foam-fiber furnish into said channel in a radial direction.
Another preferred embodiment of the invention is achieved with the feature, characterized in that said foam forming nozzles are so positioned as to direct a stream of foam-fiber furnish into said channel to impinge upon at least one stream of foam-fiber furnish from another of said foam-forming nozzles.
A further preferred embodiment of the invention is characterized in that said second array of nozzles is arranged to forcibly discharge foam-fiber furnish in a non-intersecting path relative to paths of flow of foam-fiber furnish from said first array of nozzles.
The invention apparatus will furthermore be especially effective by a construction characterized in that each said nozzle is about 7.6 cm (about 3 inches) long, said bore is generally cylindrical, said lesser cross sectional areas are of about 1.3 cm (about 1/2 inch) diameter, said greater cross sectional areas are of about 1.9 cm (about 3/4 inch) diameter, and said regions are spaced axially of the nozzle about 1.3 cm (about 1/ 2 inch), and further wherein the recited connection of said nozzles with said headbox is about 5 cm (about 2 inches) from said inner wall portion.
A further preferred embodiment of the headbox channel is characterized by an apparatus according to Claim 1, including wall portions of the headbox defining the channel in substantially direct fluid flow communication with said slice, at least one pair of said wall portions being in mutually confronting spaced relation; and an array of foam forming nozzles connected through one of the confronting wall portions to said headbox channel and positioned and operative to impinge upon the other of said confronting wall portions.
A further preferred embodiment of the invention is characterized in that said channel further is defined by an additional pair of closely spaced confronting wall portions extending transversely of said first recited pair of wall portions; and at least one wall portion of the second recited pair having connected therethrough to said channel a second array of foam forming nozzles positioned and adapted to direct foam-fiber furnish for impingement on the opposite wall portion of said second pair and flow through said slice.
Further preferred embodiments of the invention are characterized in that said impact surface is substantially perpendicular to the polar axis of a nozzle and that said forming wire is linearly movable at a predetermined speed, and the speed at which said furnish is deposited is in excess of the speed of movement of said forming wire.

Brief description of the drawing

Figure 1 is a diagrammatic showing of a web forming apparatus embodying the invention;
Figure 2 is a detailed showing, on an enlarged scale and partly in section, of a portion of the apparatus seen in Figure 1, and illustrating important structural features of the invention.
Figure 3 is a top plan view of the portion of apparatus seen in Figure 2; and
Figures 4 to 7 are showings similar to Figure 2, and illustrating modified embodiments of the invention.

Detailed description of the several embodiments

With more detailed reference to the drawing, there is seen in Figure 1 a web forming apparatus 10 comprising a headbox 11 provided with a channel 11 a leading to throat 12a of an adjustable slice 12 positioned and operative to discharge a foam-fiber furnish onto a forming wire 13 as it passes over a breast roll 14. Adjustment of the slice is afforded by a roof or upper wall 12b of throat 12a mounted for pivotal movement about hinge P, and positionable by a conventional jack means 12c. Suction boxes 15 and 16 are disposed beneath wire 13, and are connected to a vacuum source 17 for receiving both foam and liquid derived from collapsed foam, and drained through the wire. Drained foam and liquid are returned by a pump 18 through conduit 19 to an in-line mixer 20 for reuse, where additional fiber, either dry or as a dispersion, and air are introduced through pipe 33 to conduit 19, by means of a known metering device such as is seen at 32, to form a dispersion of air and fiber in water containing a surfactant in creation of a foamable furnish. From mixer 20, the foamable furnish is fed under pressure by a pump 21 through an input conduit 22 to a manifold 23. It will be understood that elements of the web forming apparatus thus far described are conventional, as exemplified by the referenced U.S. Patent No. 3,938,782.
In especial accordance with the present invention, and with reference also to Figures 2 and 3, improvement over the art resides in that manifold 23 leads to parallel arrays of foamable liquid-fiber furnish inlet nozzles 24 having tubular passages such as bores 25 of alternately increased and decreased cross sectional areas. By such a bore configuration, the decreased cross sectional areas in combination with the increased cross sectional areas respectively effect alternate increases and decreases in the flow speed of the foamable furnish within the nozzles, thereby creating foam-forming tubulence. This same bore configuration is shear inducing, thereby lowering the apparent viscosity of the foam leaving the nozzles.
Further to the nozzles 24, they function as the sole foam forming devices in the present invention, and are disposed in direct fluid flow communication with the channel 11a of headbox 11 defined by substantially planar, generally parallel, relatively closely spaced upper and lower, horizontally extending wall portions 26 and 27, respectively, side wall portions 28 and 29, and front and rear wall portions 30 and 31, respectively. Construction and arrangement of the wall portions is such that the channel 11 a has its major extent in a direction transverse the direction of forming wire movement.
The inlet connections of the one array of eleven nozzles 24 to the headbox extend through wall 26 in such a manner that foam-fiber furnish is directed from nozzles 24 at relatively low viscosity, transversely of the direction of extent of and onto a confronting, interior surface of wall portion 27 of headbox channel 11a. By such cooperative disposition, wall portion 27 serves as a turbulent flow inducing impact surface for the foam-fiber furnish. While the several walls or wall portions have been described and illustrated as being planar and parallel, it should be understood that they may be positioned out of parallel, or may be curved. For example, headbox channel 11a might be defined by a generally cylindrical wall portion.
The inlet connections of the other array of twelve nozzles 24 to the headbox extend through wall 31 to direct foam-fiber furnish onto confronting wall 30, which also functions as an impact surface extending transversely of the direction of entry of foam-fiber furnish from the one array of eleven nozzles 24. As is best seen in Figure 3, the nozzles 24 further are arranged such that the nozzle axes of the one array are between and generally in a plane perpendicular to the general plane of the nozzle axes of the other array.
In a preferred embodiment, the axes of the eleven nozzles 24 of the one array are spaced along the headbox about 5 cm (two inches) apart, as are similarly spaced the twelve nozzles of the other array; by this spacing, the headbox extends about 61 cm (two feet) in the cross machine direction. Additional arrays or fractions thereof may be provided in accommodation of other machine widths. Each of nozzles 24 is about 7.6 cm (3 inches) in length and has a generally undulatory bore configuration defined by alternate convergent and divergent frustoconical sections. Generally, the narrower sections of lesser cross sectional area are about 1.3 cm (1/2 inch) diameter, and the wider sections of greater cross sectional area are about 1.9 cm (3/4 inch) diameter, with a distance between sections of about 1.3 cm (1/2 inch). The distance between the discharge end of each bore 25 and a confronting baffle or wall of channel 11a is about 5 cm (2 inches). By such disposition of the nozzles the streams of foam-fiber furnish flowing from the nozzles at low viscosity impinge partially on one another and fully on the confronting impact surfaces or walls of the headbox channel at relatively short distances from the slice 12.
Since foam flowing from nozzles 24 is at its lowest apparent viscosity, a condition under which it is most likely to become turbulent, the abrupt changes of direction due to the hereinabove described impingements advantageously create considerable turbulence in channel 11a immediately prior to flow of the foam-fiber furnish through the relatively short throat 12a to slice 12 for uniform distribution onto forming wire 13. Throat 12a of slice 12 is about 41 cm (16 inches) long so that the foam with its dispersion of randomly oriented fibers advantageously travels a relatively short distance from the headbox channel through the slice throat, thereby minimizing unidirectional orientation as the foam tends to revert to laminar flow in the slice throat. Hence, apparatus embodying the invention achieves desirable, relatively low MD/ CD ratios of fibrous webs with minimization of the number of moving parts.
In the additional, modified embodiments of the invention as seen in Figures 4 to 6, the foam forming nozzles are in fluid flow communication with the headbox channel at different locations than those hereinabove described. In the additional, modified embodiment seen in Figure 7, the headbox channel is generally cylindrical, affording curved walls as briefly described hereinabove, and the axes of the nozzles are located along the length of the channel as are the axes of the nozzles in Figures 1 to 3.
In Figure 4, the several walls 126 through 131 of headbox 111, similar to the one described in connection with Figures 1 to 3, define a channel 111 a leading to throat 112a for feeding foam-fiber furnish through adjustable slice 112 onto forming wire 113 moving on breast roll 114. Nozzles 124 are similar to the hereinabove described foam forming nozzles 24, and, while arranged in staggered array, are provided only in top wall 126, whereby foam-fiber furnish introduced into the channel impinges upon lower wall 127 as an impact surface.
In Figure 5, reference numerals refer to like numerals as seen in Figures 1, or 3, but with the prefix 2 applied. It is seen that foam forming nozzles 224 are so positioned that one array is connected to the headbox channel 2121a through top wall 226 and the other array is offset as respects the one array and is connected to the channel through bottom wall 227. In this construction the foam-fiber furnish introduced to the headbox channel through upper nozzles 224 impinges upon lower wall 227 and flows through throat 212a, while furnish introduced through lower nozzles 224 impinges on upper wall 226 and mingles with the furnish introduced through the upper nozzles as it flows through throat 212a.
In Figure 6, elements are designated with numerals used to designate like elements of Figures 1, 2 and 3, but with the prefix 3 applied, and it is seen that all nozzles 324 are connected to the headbox channel 311 a through wall 331 for impingement of the foam fiber furnish onto opposite wall 330.
In Figure 7, elements are designated with numerals used to designate like elements of Figures 1, 2, and 3, but with the prefix 4 applied. In Figure 7, the horizontally extending headbox channel 411 a is defined by curved wall portions of a hollow cylindrical structure about 5.7 cm (2 1/4 inches) in diameter and closed at its ends by walls, one of which is seen at 428. A cylindrical channel advantageously affords a compact arrangement for three arrays of foaming nozzles 424 of the type hereinabove described, and whose centerlines are spaced about 5.7 cm (2 1/4 inches) apart along the length of the channel. The arrays are disposed in fluid flow communication with channel 411 in upper left and right quadrants and in the lower right quadrant of the cylindrical wall portions of the channel so that each nozzle is effective to direct foam-fiber furnish transversely of the polar axis of the cylindrical structure onto an opposed curved, cylindrical wall portion serving as an impact surface. The entrance of the slice throat 412a occupies the lower left quadrant. While the nozzles are shown in the same plane for the sake of convenience, it will be understood that the nozzles of each array are staggered as respects the nozzles of the other arrays, so that the spacing between centerlines of the nozzles as between arrays is about 1.9 cm (3/4 inch).
In any of the embodiments shown in Figures 1 to 6, the impact surface is relatively closely spaced from the region of introduction of the foaming nozzle to the relatively low-volume headbox channel, which impact surface also is substantially perpendicular to the axis of a nozzle. In the embodiment shown in Figure 7, essentially the same spatial relationship exists, with the tangent to the cylindrical surface at the center of the impact being substantially perpendicular to the axis of a nozzle. By such cooperative dispositions of the nozzles and impact surfaces, taken with a headbox channel of relatively small volume, turbulent foam flow is achieved throughout the channel and well into the slice throat. This turbulent flow advantageously maximizes random orientation of fibers well into the slice throat and as they exit the slice for deposition on the forming wire.

Claims

1. Apparatus for forming and directing a foam-fiber furnish onto a forming wire in the manufacture of a fibrous web, with a slice (12) positioned and operative to deposit said foam-fiber furnish onto said forming wire (13, 113, 213, 313, 413); and a headbox channel (11a, 111a, 211a, 311a, 411 a) in direct fluid flow communication with said slice (12) and including an inner wall portion (27, 30, 127, 227, 330); a plurality of foam-forming openings (24, 124, 224, 324, 424) in fluid flow connection with said headbox channel (11a, 111a, 211a, 311a, 411a) and positioned and adapted to receive a foamable liquid-fiber furnish and to form and forcible direct foam-fiber furnish having a relatively low viscosity into said channel to impinge upon said inner wall portion (27,30,127, 227, 330) and flow throughout said channel, the recited impingement being effective to create turbulence in the low-viscosity foam-fiber furnish in said channel immediately upon its flow through said slice (12,112, 212, 312, 412) whereby random orientation of the fibers in the furnish is insured throughout said channel and as it flows through said slice for deposit on said forming wire (13, 113, 213, 313, 413);

characterized in that each of said foam-forming openings (24, 124, 224, 324, 424) are nozzles, which comprises means defining a generally tubular fluid passage having regions of alternate lesser and greater cross sectional areas.

2. Apparatus of Claim 1, characterized in that said inner wall portion (27, 30, 127, 227, 330) is substantially planar.

3. Apparatus of Claim 1, characterized in that said inner wall portion is curved.

4. Apparatus of Claim 3, characterized in that said curved inner wall portion is a cylindrical section.

5. Apparatus according to any of Claims 1 to 4 characterized in that said channel (11a, 211a, 311a, 411a) is provided with a second array of foam forming nozzles (124, 224, 324, 424) positioned to direct foam-fiber furnish onto an opposing wall (127, 227, 330) of said channel (111a, 211a, 311a, 411a).

6. Apparatus according to Claim 4 characterized in that a plurality of rows of foam forming nozzles (424) extend longitudinally of said cylindrical channel (411a) so positioned as to direct foam-fiber furnish into said channel (411a) in a radial direction.

7. Apparatus according to any of Claims 1-5 characterized in that said foam forming nozzles (24, 424) are so positioned as to direct a stream of foam fiber furnish into said channel (11a, 411a) to impinge upon at least one stream of foam-fiber furnish from another of said foam-forming nozzles.

8. Apparatus according to any of Claims 1-5 characterized in that said second array of nozzles (124, 224, 324) is arranged to forcibly discharge foam-fiber furnish in a non-intersecting path relative to paths of flow of foam-fiber furnish from said first array of nozzles.

9. Apparatus according to Claim 1, wherein each said nozzle (24,124,224,324) is about 7.6 cm (about 3 inches) long, said bore (25, 125, 225, 325) is generally cylindrical, said lesser cross sectional areas are of about 1.3 cm (about 1/2 inch) diameter, said greater cross sectional areas are of about 1.9 cm (about 3/4 inch) diameter, and said regions are spaced axially of the nozzle about 1.3 cm (about 1/2 inch), and further wherein the recited connection of said nozzles with said headbox (11, 111, 211, 311) is about 5 cm (about 2 inches) from said inner wall portion.

10. Apparatus according to Claim 1 characterized by including wall portions (26, 27, 30; 126, 127; 227, 330, 331) of the headbox defining the channel (11a, 111a, 211a, 311a) in substantially direct fluid flow communication with said slice, at least one pair of said wall portions being in mutually confronting spaced relation; and an array of foam forming nozzles (24, 124, 224, 324, 424) connected through one of the confronting wall portions (26, 126, 227, 331) to said headbox channel and positioned and operative to impinge upon the other of said confronting wall portions (27, 30, 127, 330).

11. Apparatus according to Claim 10, characterized in that said channel (311a) further is defined by an additional pair of closely spaced confronting wall portions (330, 331) extending transversely of said first recited pair of wall portions (326, 327); and at least one wall portion (331) of the second recited pair having connected therethrough to said channel a second array of foam forming nozzles positioned and adapted to direct foam-fiber furnish for impingement on the opposite wall portion (330) of said second pair and flow through said slice (312).

.12. Apparatus of Claim 10 characterized in that said impact surface is substantially perpendicular to the polar axis of a nozzle.

13. Apparatus of Claim 1 or 10 characterized in that said forming wire (13, 113, 213, 313, 413) is linearly movable at a predetermined speed, and the speed at which said furnish is deposited is in excess of the speed of movement of said forming wire.