Patent Publication Number: US-4319870-A

Title: Apparatus for the manufacture of fibrous webs

Description:
BACKROUND OF THE INVENTION 
     This invention relates to the manufacture of fibrous webs, and especially to apparatus useful in the manufacture of paper from dry laid fibers. 
     In the manufacture of fibrous webs such as paper, using dry laying techniques, it has been found advantageous to spray particles of binder material onto a dry web to enhance its strength for subsequent operations. A disadvantage of such spraying is the tendency of binder particles to escape the edges of the web, resulting in both waste of binder and contamination of adjacent portions of the apparatus. A solution to this problem has been the provision of means for applying electrostatic charges in such a manner as to ensure impingement of particles on a web. Provision of such means and its operation are, however, costly. 
     The following U.S. patents are representative of prior art believed material to the examination of this application: 
     U.S. Pat. No. 3,536,580 dicloses apparatus for spraying electrostatically charged particles of sizing material onto an oppositely charged fibrous web in a paper making machine. 
     U.S. Pat. No. 3,765,971 discloses apparatus for producing a fibrous web in combination with means for distributing bonding material over the web. 
     U.S. Pat. No. 3, 930,614 discloses apparatus for spraying a traveling web of paper with electrostatically charged liquid. 
     U.S. Pat. No. 3,825,381 discloses (FIG. 10) oppositely disposed baffles 182  that intercept spray droplets of water sprayed onto a web and direct such water into troughs 184 for disposal. 
     It is a general objective of the present invention to provide improved apparatus for manufacturing air laid fibrous webs. 
     It is a further and more specific objective of the invention to provide improved means for directing particulate components onto fibrous webs in the course of its manufacture. 
     SUMMARY OF THE INVENTION 
     In achievement of the foregoing as well as other objectives and advantages, the invention contemplates, in apparatus for forming a fibrous web on a forming wire, the combination of suction box means including an opening disposed to one side of said forming wire to draw air therethrough, means for spraying particulate matter on the side of the web on said forming wire opposite the opening of said suction box means, and baffle means disposed in closely spaced relation to opposite edge portions of said forming wire and said suction box means and cooperative therewith to effect flow of ambient air upwardly over the edges portions of said forming wire and web and through the latter into the opening of said suction box, whereby to ensure full impingement of said particulate matter on said fibrous web. 
     The manner in which the foregoing at well as other objectives and advantages may best be achieved will be more fully understood from a consideration of the following description, taken in light of the accompanying drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a side elevational showing of apparatus embodying the invention, with parts broken away for convenience of illustration; and 
     FIG. 2 is a sectional view taken generally in the plane of line 2--2 in FIG. 1, and looking in the direction of arrows applied thereto. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With more detailed reference to the drawing, there is seen in FIG. 1 a fibrous web forming apparatus 10 comprising a set of dry fiber distributors designated generally by the numeral 11 disposed above a forming wire 12 supported for linear movement above suction boxes designated generally by the numeral 13. Construction and arrangement is such that fibers are laid on forming wire 12, with the aid of suction boxes 13, to form a fibrous web 16. Disposed downstream of the distributors 11 is a spray apparatus 14 including spraying means comprising an array of downwardly directed spray heads 21 operative to direct particles of binder material 15 onto the upper surface of web 16 on forming wire 12, aided by a suction box 17 having its opening disposed beneath wire 12 and opposite spray apparatus 14. Spray apparatus 14 further includes a booth 20 substantially enclosing the array of spray heads 21, and the portion of forming wire 12 and web 16 thereon extending over the suction box opening. Movement of wire 12 and web 16 through booth 20 is accommodated by slots 25 and 26. 
     In especial accordance with the invention, and with reference also to FIG. 2, a pair of elongate baffles means or 18 and 19 are disposed to extend along opposite edge portions or of forming wire 12, in closely spaced relationship thereto and to adjacent sides of the suction box, and in the region of spray apparatus 14. As is seen to advantage in FIG. 2, each of baffles 18 and 19 includes a vertical section 18a  and 19a, respectively, major portions of which confront the sides of the suction box, and an angular section 18b and 19b, respectively, each inclined toward the other in regions between spray heads 21 and the surfaces of forming wire 12 and web 16. The baffles 18 and 19 conveniently are mounted on brackets 22 and 23, respectively, that are so constructed and arranged as to provide for selective adjustments of the baffles (see broken line showings 18, and 19) toward and away from forming wire 12 to allow for variations in the widths of forming wires and fibrous webs being formed thereon. 
     As is seen also in FIG. 2, and in further accordance with the invention, lower walls 27 and 28 of booth 20 are spaced from sides of suction box 17 at 27a and 28a to form elongate openings corresponding substantially to the spacing of baffles 18, 19 from the same sides of the suction box and the edges of forming wire 12. Also, the lower ends of baffle sections 18a, 19a conveniently slidingly engage the lower walls 27, 28, respectively, in accomodation of adjustment of the baffles while effectively forming an air seal ensuring air flow upwardly between the baffles and confronting portions of the suction box and edges of the forming wire, as is shown by air-flow arrows A in FIG. 2. Advantageously, particles of binder material that normally would overshoot edges of the forming wire are entrained in this suction-box-induced, upwardly directed flow of ambient air A between the baffles and the forming wire, whereupon the same particles advantageously are subjected to subsequent inwardly directed flow effected by the angular baffle sections 18b, 19b, followed by downwardly directed, suction-box-induced flow of the same air onto the web. 
     While the invention has been described with reference to a preferred embodiment, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the scope of the appended claims.