Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/11—Flash-spinning

Definitions

• the present invention relates to a combination of apparatus for forming a nonwoven fibrous sheet having greater usable width than disclosed by the prior art.
• the present invention relates to a combination of apparatus for forming the edge of flash spun webs by (1) changing the swath throw and lay down pattern of the outer edge spinning positions so that a higher percentage of the edge swath contributes to usable sheet product and (2) reducing the effective width of the moving collection surface used for collecting the web in a sheet structure.
• Patent 3,081,519 (Blades et al.). An apparatus for making a nonwoven fibrous sheet comprising a spinning assembly, a rotating baffle, electrostatic configurations for proper sheet dispersion, and a collection surface is described in
• Tyvek ® are normally constructed of multiple swaths of trapezoidal basis weight profile shape that overlap across the width of the sheet. These types of sheets are disclosed and preferred by Pollock and Shah. However, along the edge of the sheet where there is less overlap
• the present invention relates to an apparatus or combination of apparatus for forming nonwoven fibrous sheets from overlapping swaths of fibrous material.
• the resulting sheets have greater usable width for a given number of spinning packs.
• the combination comprises a plurality of centrally located spinning packs and a plurality of edge spinning packs that are each fitted with a baffle which lays down fibrous material on a moving collection surface.
• the edge spinning packs are fitted with baffles that lay down a relatively narrow swath of fibrous material having a triangular basis weight profile shape.
• the edge spinning packs lay down fibrous material in cooperation with a product guide.
• the fibrous material in the outermost portion of the swath impinges upon and slides down the product guide and onto a moving collection surface.
• the centrally located spinning packs are fitted with baffles that lay down a relatively wide swath of fibrous material having a trapezoidal basis weight profile shape.
• the combination comprises a plurality of centrally located spinning packs and a plurality of edge spinning packs each of which comprises a spinning assembly for spinning a fibrous strand in a generally horizontal path, a rotatable baffle for receiving the strand and deflecting it into a generally vertical plane downward while simultaneously spreading the strand and causing the spread strand to oscillate in the generally horizontal plane, and means for rotating the baffle.
• the baffles as viewed with their axes of rotation in the horizontal position, comprise integral 5 bodies composed of a circular boss portion on a disc portion with a fillet portion extending around the boss portion.
• the centrally located spinning packs have baffles having fillet portions that intersect with the
• 1 ⁇ disc portion to form a generally concave surface and are adapted to form a swath having a trapezoidal basis weight profile shape when the spread strands are deposited on a moving collection surface located below the centrally located spinning packs.
• 15 packs have baffles having fillet portions that intersect with the disc portion to form a generally convex surface and are adapted to form a swath having a triangular basis weight profile shape when the spread strands are deposited on the moving collection surface located below
• the axis of rotation of the baffles is perpendicular to, and coincident with the centers of the top, circular edges of both the boss portion and the disc portion.
• the combination further comprises
• the product guides are adapted to minimize the width of the spread strand by contacting a portion of the spread strand being deflected by the Q baffles of the edge spinning packs and depositing such spread strand portion on the moving collection surface.
• the edge baffle improves yield by reducing edge losses due to low basis weight.
• the product guides reduce the effective width of the moving collection 5 surface used for collecting the spread strand in a sheet structure, eliminate the feathered edge of formed sheet to prevent wraps, and make taking edge trim easier. It will be understood that the edge baffles can be used alone or in combination with the product guides.
• Fig. 1 is a diagrammatic elevation view of an apparatus for depositing plexifilamentary material to a moving collection belt and forming a nonwoven sheet.
• the apparatus includes a spinning assembly, a rotatable baffle, means for rotating the baffle, and collection means located below the baffle.
• Figs. 2, 3 and 4 respectively are front, vertical section and plan views of the preferred trilobal baffle used in the centrally located spinning packs.
• Figs. 5a-5d illustrate a baffle of the type shown in Figs. 2-4, the baffle being shown in the operating position as viewed from the spinning assembly.
• the four views illustrate the effect of the baffle or direction of spread strand travel as it rotates 90 degrees.
• Fig. 5e shows the trapezoidal basis weight profile shape produced by the baffle shown in Fig. 4.
• Figs. 6, 7 and 8 respectively are front, vertical section and plan views of the modified trilobal baffle used in the edge spinning packs.
• Figs. 9a-9d illustrate a modified baffle of the type shown in Figs. 6-8, the baffle being shown in the operating position as viewed from' the spinning assembly.
• the four views illustrate the effect of the baffle or direction of spread strand travel as it rotates 90 degrees.
• Fig. 9e shows the triangular basis weight profile shape produced by the edge baffle shown in Fig. 8.
• Fig. 10 is a schematic top view of the moving collection means and the edge product guides used in the present invention.
• Fig. 11 is an end view of the moving collection means and the edge product guides used in the present invention.
• Fig. 12 shows how the edges of the sheet are built up using the baffle shown in Fig. 4.
• Figs. 13, 14 and 15 show how the sheet edge waste is minimized and usable sheet width is increased by using the baffle shown in Fig. 8 and/or the product guides shown in Figs. 10 and 11.
• a combination of apparatus is used in the present invention to create a nonwoven sheet with greater usable width than with similar apparatus used in the past.
• a modified baffle is used in the edge spinning packs instead of the previously used standard pack baffle that is contained in the centrally located spinning packs.
• the modified baffle is similar to the standard pack baffle shown in Figs. 2-4 and described in U.S. Patents 3,497,918 (Pollock) and 4,666,395 (Shah), except that the lobes and fillet portion are shaped differently to provide a narrower swath having a triangular basis weight profile shape rather than a trapezoidal basis weight profile shape.
• FIG. 1 an apparatus of the present inventive combination is diagrammatically illustrated including a spinning assembly 11, a rotatable baffle 12, an electric motor 13 for rotating the baffle 12 through shaft 14, and a collection surface 15.
• collection surface 15 is preferably an endless belt set up to run around rolls 16 and 17.
• Strand 18, issuing from spinning assembly 11, is spread by baffle 12 and collected on belt (collection surface) 15 and combined with many other strands to form nonwoven sheet 20.
• An electrostatic charging means 23 is provided to charge the spread web as it leaves baffle 12.
• the standard trilobal rotary baffle used in the centrally located spinning packs is shown in Figs. 2-4.
• the baffle 12 is composed of a boss portion 30, a disc portion 31 and a fillet portion 32.
• the boss portion 30 is a right cylinder standing on a planar disc portion 31.
• the axis is perpendicular to, and coincident with the centers of the top, circular edge 34 of the boss portion 30 and the top circular edge 35 of the disc portion 31.
• Fillet portion 32 extends around boss portion
• Fillet portion 32 includes preferably three radially disposed, equispaced lobes 38 which are the outermost part of the general contours of fillet portion
• the upper surfaces 39 of the lobes 38 are slightly wedge-shaped, i.e., the surfaces are narrower near the boss portion 30 than they are near the disc portion 31. This can best be seen in Fig. 4.
• the edges of the wedges are indicated by lines 40; however, it should be understood that in actual construction all inflections in the surface of the fillet portion 32 are gradual. The reason for this will be apparent from the descrip ion hereinafter of-the manner of using the baffle.
• the intersection of the fillet portion 32 with the side 36 of boss portion 30 forms a series of lines, one for each lobe hereinafter referred to as the boss intersection line (B.I.L.) below the top 34 of boss portion 30.
• the B.I.L. is identified in Fig. 2 by the numeral 41; as shown, the B.I.L. 41 is generally an S-shaped curve for each fillet portion 32.
• the intersection of fillet portions 32 with the top surface 37 of disc portion 31 forms a series of lines, one for each fillet portion 32, hereinafter referred to as the disc intersection line (D.I.L.) , inside the top, circular edge of the disc portion 31.
• the D.I.L. is identified in Fig. 4 by the numeral 42; as shown, the D.I.L. 42 is generally slightly concave between the individual lobes 38.- The D.I.L. 42 can also form an equilateral triangle having rounded corners at the lobes 38.
• the spread strand begins to be deflected to the left.
• the center line of the spread strand as it leaves the disc is approximately perpendicular to the disc intersection line (D.I.L.) 42.
• one degree of rotation as the baffle turns from the position shown in Fig. 5a to that shown in Fig. 5b results in the center line being deflected about 1 degree from vertical.
• the baffles must deflect the strand at a great enough angle such that a given minimum swath width and given basis weight profile shape result to meet the blendability needs of the product.
• strand 18 impinges on the point of maximum slope on the left slope of a lobe 38, as shown in Fig. 5b.
• the center line of the spread strand is deflected approximately 35 degrees from the vertical, and this is the point of maximum deflection to the left for this particular embodiment.
• the strand 18 begins to impinge on the upper surface of a lobe 38 and the center line of the spread strand begins to shift back to vertical.
• the baffle has rotated through about another 20 degrees (60 degrees from Fig. 5a) , the strand 18 impinges upon the center of a lobe 38 and is again deflected vertically downward, as shown in Fig. 5c.
• the spread strand Upon further rotation of the baffle, the spread strand begins to impinge upon the right slope of the lobe 38, and the center line of the spread strand is diverted to the right.
• the baffle has rotated about another 20 degrees (80 degrees from Fig. 5a) the spread strand center line is deflected approximately 35 degrees from the vertical, as shown in Fig. 5d, and this is the point of maximum deflection to the right for this particular embodiment.
• a modified rotary baffle is shown as used in the edge spinning packs.
• the modified or edge baffle is similar in many respects to the centrally located spinning pack baffle except that certain contour changes have been made to produce a triangular basis weight profile shape rather than a trapezoidal basis weight profile shape when operated at the same distance to the collection surface as the centrally located spinning pack baffles.
• the major difference is that the intersection of the fillet portion 32 with the top surface 37 of the disc portion 31 (i.e., the D.I.L. 42') is generally convex between the individual lobes 38. In other words, the D.I.L. 42' bows out between each lobe 38 of the trilobal baffle.
• edge baffle described above is preferably used in conjunction with an edge product guide which is depicted in Figs. 10 and 11. Referring now to Fig. 10,
• the spread strand collection means is shown generally at 70, comprising machine frames 71, 72, product guides 73 and 74 and the face of belt guide 75.
• belt guide 75 supports moving belt 76 upon which the spread strands are deposited.
• the baffle speed and direction of rotation and the amounts by which the spread strands are electrostatically charged can be varied to optimize the production of greater sheet width for different basis weights of nonwoven sheet which the invention is designed to produce.
• the baffles of the centrally located spinning packs all operate at the same speed, and while the baffles of the edge spinning packs can often be operated at the same speed as the baffles of the centrally located spinning packs, it will be understood that they can also be operated at a different speed or rotation direction.
• the electrostatic charge level applied to the strands from the edge spinning packs is generally lower (e.g., 60% to 100%, preferably 70% to 80% lower) than that of the charge level being applied to the strands from the centrally located spinning packs.
• edge spinning packs applying strands along each edge of the sheet.
• the space between the edge spinning packs can be varied to control the size and shape of the final sheet being produced.
• the edge spinning packs can be closely spaced for special effects on the edge of the sheet.
• the edge spinning packs can be spaced from one pack centerline to the next, or from one half the next pack centerline. However, this is largely governed by the number of packs used and the type of sheet desired.
• a product guide is preferably used to direct the outward deflection of the spread strand to the laydown belt along both edges.
• the surfaces of the product guides must have surfaces which have low friction and high dielectric strength so that charged strands will easily slide off.
• Polycarbonate has been found to be a preferred material for forming the product guide using currently available commercial flash-spinning solvents.
• the surface placement of the product guide preferably ranges from vertical to 45 degrees from vertical. However, it should be noted that the product guide can be placed at an angle greater than 45 degrees from vertical, although it would not be as effective as the preferred range.
• the product guides are long enough to allow the strands from one to four edge spinning packs being used to impinge on it and slide off onto the moving belt.
• the product guide is used to form a controlled straight edge of laid down strands thick enough so that fibrous material which ,is trimmed from the edge can be pneumatically conveyed as an unbroken tape. This minimizes the problems associated with handling strands having a feathered edge.
• the product guide's distance from the edge is adjustable in the cross machine direction over a distance of about 30 cm.
• Figs. 12, 13, 14 and 15 show the improvement in usable sheet width and reduction in waste (edge trim) that result from use of the edge baffle and/or product guide. Fig.
• Fig. 12 shows how the individual basis weight profile shapes from the centrally located spinning packs 44 stack up at the sheet edge, creating a given usable width 56 and an edge trim waste 52.
• Fig. 12 shows a composite representation of a five (5) layer sheet edge basis weight profile shape having a "usable width" significantly less than that of the full sheet width.
• Figs. 13 shows how the product guide modifies the full sheet profile, narrowing it by causing material 47 to be moved inward to create profile 48, and reducing edge trim waste 53 to less than 52 of Fig. 12.
• Usable sheet width in Fig. 13, 56 is approximately the same as that of Fig. 12.
• edge baffle but no product guide shows the effect of the edge baffle to increase usable sheet width (57 > 56) and reduce waste trim 54 by greatly modifying and improving the sheet edge profile 49.
• Fig. 15 shows the resultant edge 5 profile improvement 51 when using both the product edge guide and the edge baffle. Note that usable width 57 is approximately the same as in Fig. 14, but edge trim waste 55 has been further reduced versus 54 of Fig. 14 0 and 53 of Fig. 13.
• the inventive combination of edge baffles and product guides reduces edge losses by about 50% and increases usable sheet width by about 20 cm.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Textile Engineering (AREA)
• Nonwoven Fabrics (AREA)
• Extrusion Moulding Of Plastics Or The Like (AREA)
• Spinning Methods And Devices For Manufacturing Artificial Fibers (AREA)
• Closures For Containers (AREA)
• Yarns And Mechanical Finishing Of Yarns Or Ropes (AREA)

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• 1991
  • 1991-05-10 JP JP3509409A patent/JP2901756B2/ja not_active Expired - Lifetime
  • 1991-05-10 WO PCT/US1991/003119 patent/WO1992020511A1/en active IP Right Grant
  • 1991-05-10 EP EP91909529A patent/EP0584060B1/en not_active Expired - Lifetime
  • 1991-05-10 ES ES91909529T patent/ES2090334T3/es not_active Expired - Lifetime
  • 1991-05-10 DE DE69121912T patent/DE69121912T2/de not_active Expired - Fee Related

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