Patent Publication Number: US-8991404-B2

Title: Process for shredding a tobacco sheet and apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 U.S.C. §119(e) to U.S. provisional Application No. 60/852,407, filed on Oct. 18, 2006, the entire content of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     The shredding of tobacco sheet, especially reconstituted tobacco sheet into uniform pieces or shreds of a predetermined size and shape, facilitates manufacturing operations and is otherwise desirable. If the tobacco sheets include volatile flavorants, such as menthol and/or other ingredients which cause tackiness, there is a need to provide a shredding process which can operate continuously without heat build-up and/or is resistant to clogging from particle build-up. 
     SUMMARY 
     A shredding process according to an embodiment for shredding a tobacco sheet, comprises the steps of: 
     rotating opposing sets of cutter discs in a partially overlapping relation so as to establish a nip, said cutter discs having notches at spaced locations along a peripheral portion of said cutter discs; 
     spacing adjacent pairs of cutter discs of the same set of cutter discs according to a first thickness of a spacer disc; 
     removing extraneous tobacco from amongst said cutter discs by interposing a stripper plate between adjacent pairs of spaced apart cutter discs of the same set of cutter discs while rotating said adjacent pairs of cutter discs relative to said stripper plate, said stripper plate being maintained at a second thickness less than said first thickness; and, 
     feeding a tobacco sheet along a path leading into said nip. 
     In an embodiment of the process, the spacer discs and the cutter discs rotate together. 
     In another embodiment of the process, the spacer discs serve as bushings for the stripper plates. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a graphical representation of an exemplary process of manufacturing a shredded tobacco sheet. 
         FIG. 2  is a top view of an apparatus for shredding a tobacco sheet. 
         FIG. 3  is an end view of an apparatus for shredding a tobacco sheet. 
         FIG. 4  is a top view of a portion of the apparatus of  FIG. 3 . 
         FIG. 5  is a top view of a cutter wheel. 
         FIG. 6  is a top view of a spacer. 
         FIG. 7  is a top view of a stripper plate. 
         FIG. 8  is a top view of an internal stripper plate. 
         FIG. 9  is a top view of an external stripper plate. 
         FIG. 10  is an end view of an apparatus for shredding a tobacco sheet including an internal stripper plate and an external stripper plate. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 1 , a tobacco sheet is formed by mixing together tobacco particles such as tobacco dust with a binder such as guar and water in a process designated generally as  100 . If desired, the tobacco dust and guar is also mixed with a liquid volatile flavorant such as menthol or additional ingredients such as sugar. These processes produce a slurry which is then dried in a drying device  110  to provide a tobacco sheet  112 . The tobacco sheet is about 15 inches to about 72 inches wide and about 0.001 inches to about 0.010 inches thick. For example, the tobacco sheet can be about 0.006 inches thick and about 66 inches wide or the tobacco sheet can be about 0.006 inches thick and about 18 inches wide. The tobacco sheet is carried on an endless conveyor to a guiding device  114  provided above a shredding device  120  (i.e. sheet is substantially vertical when shredded). 
     The tobacco sheet formed by the process  100  and the drying device  110  is cut into generally uniform pieces  116  of a predetermined size and configuration in the shredding device  120 . The uniform pieces  116  can be a various shapes and sizes depending on the configuration of the tobacco shredder. The pieces  116  of the tobacco sheet are then collected in a bin or container  118  for further processing or for use in a product such as a cigarette (not shown). If desired, the pieces  116  of the tobacco sheet may be passed through a filter (not shown) of an appropriate mesh size in order to prevent pieces which are larger than a predetermined size to be rejected. 
     With reference now to  FIG. 2 , a shredder  120  includes a first set of cutter discs  122  provided on a first shaft  142  alongside a second set of cutter discs  124  provided on a second shaft  144 . The shredder  120  can include 500 to 3000 cutter discs  124 , and more preferably about 1,500 to about 2,600 cutter discs. For example, the shredder  120  can include about 2,400 cutter discs  124 . The first shaft  142  has a gear  126  keyed to the first shaft  142  and the second shaft  144  has a gear  128  keyed to the second shaft  144  with the gears engaged with one another so that rotation of the second shaft causes the first shaft to rotate in the opposite direction. 
     The second shaft  144  is provided with a pulley or gear  132 , which is connected to another pulley or gear  134  by a belt or chain  136 . The first and second shafts  142 ,  144  are mounted in a frame  130  by bearings or other suitable, conventional mounting arrangements in order to maintain the first and second shafts in a desired spacing with respect to one another. The pulley or gear  134  is keyed to another shaft which is connected to a motor  138  through a gearbox  140 . In this way, the motor drives the first and second shafts  142 ,  144  at a preferred, predetermined speed to shred the tobacco sheet  112  (see,  FIG. 1 ). 
     Preferably, the cutter discs rotate at a speed of about 35 rotations per minute (rpm) to about 55 rpm, and more preferably about 40 rpm to about 50 rpm. The motor can drive first shaft and the second shaft at different speeds. Preferably, the motor drives the first and second shafts  142 ,  144  at the same speed. 
     With reference to  FIG. 3 , the shafts  142 ,  144  are round in cross section with a flat surface provided at one portion of each shaft. The first shaft  142  carries a plurality of cutter discs  146  and the second shaft  144  carries a plurality of cutter discs  148 . Adjacent cutter discs on the first shaft are spaced apart by a spacer  143  provided between each pair of adjacent cutter discs. In the same way, adjacent cutter discs on the second shaft  144  are spaced apart by a spacer  145  provided between each pair of adjacent cutter discs. In a preferred embodiment, the cutter discs are spaced about 0.01 inches to about 0.05 inches apart. The spacers have a D-shaped opening  184  (shown in  FIG. 6 ), which corresponds to the outer surface of the respective shaft on which the spacers are carried so that the flat surface of the shafts engages the D-shaped opening of the spacers to rotate the spacers with the shafts. Similarly, the cutter discs have a D-shaped opening  170  (Shown in  FIG. 5 ), which corresponds to the outer surface of the respective shaft on which the cutter discs are carried so that the cutter discs rotate with the shafts. 
     Alternatively, as shown in  FIG. 10 , in a preferred embodiment, the shafts  142 ,  144  are keyed shafts and the cutter discs  146 ,  148  have keyed shaft openings. The keyed shaft openings provide easy assembly because the cutter discs slide into position when placed on the shaft. The keyed shaft also provides stability to the cutter discs in that the cutter discs do not wobble. 
     As shown in  FIG. 3 , a stripper plate  172  is likewise provided between each pair of adjacent cutter discs on the first and second shafts  142 ,  144 . Each stripper plate  172  (see also  FIG. 7 ) has an arm  181 ,  182 , which is carried on a respective shaft  150 ,  152  in order to prevent the stripper plates from rotating with the shafts  142 ,  144 . In addition, each stripper plate  172  has a plurality of radially outwardly directed protrusions or bumps  174 ,  176 ,  178  (see  FIG. 7 ), which extend beyond the outer surface of the adjacent cutter discs. The bumps  174 ,  176 ,  178  prevent the shredded tobacco pieces from sticking to the cutter discs and facilitate dropping of the shredded tobacco pieces  116  into the bin or container  118 . Because the stripper plates are carried by the spacers  143 ,  145  and do not rotate with the spacers, the stripper plates each have a circular opening corresponding generally to the outer surface of the spacers  143 ,  145 . 
     As seen in  FIG. 3 , in order to facilitate the dropping of the tobacco sheet pieces  116  (shown in  FIG. 1 ), and to assist in cleaning of the cutter discs, first and second conduits  158 ,  160  are provided for directing compressed air generally toward the associated set of cutter discs. In addition first and second shafts  154 ,  156  are positioned so as to touch one of the bumps of the stripper plates  172  to prevent tobacco sheet pieces from sticking to either the spacers or to the cutter discs. The stripper plates have a thickness which is less than the width of the spacer on which the stripper plate is carried so that the stripper plates do not have excessive friction with the adjacent cutter discs. 
     In an embodiment, as shown in  FIGS. 8 ,  9  and  10 , an internal stripper plate  200  and an external stripper plate  210  can be used in lieu of the stripper plate  172  (shown in  FIG. 7 ). The internal and external stripper plates are not mounted on the spacers. Instead, each internal stripper plate  200 ,  201  is mounted on shaft  300 ,  301  and fits between the cutter discs  146 ,  148 . The internal stripper plate  200 ,  201  also strips out the shreds and tobacco pieces as they are formed and prevents the shreds and tobacco pieces from sticking to the cutter discs. The internal stripper plates  200 ,  201  also facilitate dropping of the shredded tobacco pieces into the bin or container. The internal stripper plates  200 ,  201  include a tobacco shred removal surface  250 , which lies between the peripheral edges of each cutter disc so as to remove tobacco shreds from between the cutter discs. 
     Likewise, each external stripper plate  210 ,  211  is mounted on shaft  300 ,  301  and rides on the outside of the cutter discs  146 ,  148  of each shaft. Preferably, an external stripper plate  210 ,  211  is mounted on each side of the internal stripper plate  200 ,  201 . The external stripper plates  210  clean shreds off of the peripheral edges of the cutter discs  146 ,  148 . 
     In an embodiment, the internal and external stripper plates  200 ,  201 ,  210 ,  211  are supported by a keyed shaft  300 ,  301 , which is fixed at both ends at the frame end plates, thereby preventing the stripper plates  200 ,  210  from rotating with the spacers. 
     Preferably, the internal and external stripper plates  200 ,  201 ,  210 ,  211  have a width of about 0.025 inches to about 0.028 inches. In an embodiment, for example, the center of the first keyed shaft  300  is spaced about 23.750 inches from the center of the second keyed shaft  301 , and the center of the shaft  144  is spaced about 12.000 inches from the center of the shaft  142 . 
     Especially when the tobacco sheet being shredded has menthol and sugar components, it is preferable that the shredder  120  not have significant friction between the oppositely rotating cutter discs of the two shafts  142 ,  144  or between the cutter discs and the stripper plates. Accordingly, the spacers  143 ,  145  maintain the cutter discs of the first shaft out of contact with the cutter discs of the second shaft even though the cutter discs are positioned in a partially overlapping relation so as to establish a nip  500  (Shown in  FIGS. 3 and 10 ). 
     As shown in  FIG. 5 , each of the cutter discs  148  has notches  168  at spaced locations along a peripheral portion of the cutter disc  148 . The curved outer surface of the cutter disc  148  between adjacent notches  168  form segments  166  which correspond generally to the length of the tobacco sheet particles formed by the shredder. In an embodiment, the notches are about 2 mm to about 5 mm wide and about 1 mm to about 5 mm deep. Preferably, the notches are spaced about 5 mm to about 15 mm apart along the cutter wheel. The notch dimensions can be changed to accommodate different shred geometries. Each cutter disc  148  has an inner flat surface  170 , which corresponds to the flat surface of the respective shaft on which the cutter disc is carried so that the cutter disc rotates with the shaft. 
     It is believed that the cutter discs  146 ,  148  cut the tobacco sheet into strips corresponding generally to the distance between adjacent cutter discs  146 ,  148  and that the notches  168  cause the strips of the tobacco sheet to be severed or pulled apart as the notches  168  of adjacent cutter discs  146 ,  148  on the first  142  and second  144  shafts are positioned adjacent one another at the nip  500  between the two shafts  142 ,  144 . In general, the surface speed of the cutter discs  146 ,  148  is slightly greater than the linear speed of the tobacco sheet so that the nip  500  of the cutter discs  146 ,  148  can pull the severed strips of the tobacco sheet apart into uniform segments or shreds. 
     In this way, the shredder  120  is configured for continuous operation to shred a tobacco sheet, especially a tobacco sheet which might include a volatile component such as menthol or another component that may cause tackiness. The shredder can operate continuously without generating excessive heat from friction. In an embodiment, air knives can be provided, as appropriate in order to aid removal of tobacco sheet pieces from the shredder as well as to cool the shredder. If the shredder heats excessively, the high temperature may degrade the tobacco sheet, especially a tobacco sheet which contains menthol and sugar components. 
     In the operation of the shredder for shredding a tobacco sheet, opposing sets of cutter discs are rotated in a partially overlapping relation so as to establish a nip. The cutter discs have notches at spaced locations along a peripheral portion of the cutter discs. The notches of the opposing sets are repetitively brought into superposed relation at the nip, more preferably the notches pass alternately through the nip as shown in  FIG. 10 . Adjacent pairs of cutter discs of the same set of cutter discs are spaced apart according to a first thickness of a spacer disc. Extraneous tobacco is removed from amongst the cutter discs by interposing a stripper plate between adjacent pairs of spaced apart cutter discs of the same set of cutter discs while rotating the adjacent pairs of cutter discs relative to the stripper plate. The stripper plate has a second thickness less than the first thickness. The tobacco sheet is fed along a path leading into the nip. 
     In an embodiment, the opposed cutter discs rotate in contact with each other at the nip as they shred the tobacco sheet. In a preferred embodiment, the opposed cutting edges of the opposed cutter discs are spaced apart and do not contact one another at the nip as the cutter discs rotate. Thus, the tobacco sheet is sheared by close non-contact of the cutter discs, which reduces friction and heat build-up. 
     In this specification, the word “about” is often used in connection with numerical values to indicate that mathematical precision of such values is not intended. Accordingly, it is intended that where “about” is used with a numerical value, a tolerance of 5% is contemplated for that numerical value. 
     Variations and modifications of the foregoing will be apparent to those skilled in the art. Such variations and modifications are to be considered within the purview and scope of the claims appended hereto.