Patent Publication Number: US-7913989-B2

Title: Section for transporting printed products of variable cutoffs in a printing press folder

Description:
The present invention relates generally to printing presses, and more particularly to a section for transporting printed products of variable cutoffs in a printing press. 
     BACKGROUND OF THE INVENTION 
     U.S. Pat. No. 5,103,703 discloses a sheet cutting apparatus for severing a rapidly-moving web, such as printed paper, into cut sheets in two stages. In the first stage, spaced cuts are made along a transverse cutting line of the web. The web is trained between belts which support the cut portions of the web, and the uncut portions of the web are severed to separate sheets. The sheets are conveyed out of the cutting station and into further apparatus. Preferably, the belts for supporting the web during the second cutting operation are trained around the knife and anvil rolls which make the cuts. The purpose of the belts is to prevent the leading edge of the web or a cut sheet from being projected forward of its support, thus tending to become dog-eared or misfed. The cuts made at the first and second cutting stations can be arranged in various patterns to remedy mis-timing of the respective cutting stations. 
     U.S. Pat. No. 5,695,105 discloses an apparatus for cutting a web at a predetermined length and supplying the same. A cutting roller is provided on its peripheral surface with projecting cutting blades arranged at predetermined intervals circumferentially and extending axially out of the cutting roller. The cutting blades are pressed against the peripheral surface of the receiving roller so as to cut the portion of the web which has passed between the cutting and receiving rollers at a predetermined length. At the downstream side of the cutting means there is provided accelerating means which has a pair of accelerating rollers sandwiching the web and sending the web in the transporting direction at a speed slightly higher than the speed which the cutting means provides. 
     U.S. Pat. No. 6,761,676 discloses a tape transport system for printed products comprising a first tape, a pulley supporting the tape, and a lever arm supporting the pulley, the lever arm including a first side rail and a second side rail, the pulley supported rotatably between the first and second side rails to form a narrow mechanism. 
     SUMMARY OF THE INVENTION 
     A printing press folder is provided. The folder includes a cutting pair cutting a web at a cutting location to form signatures, a pair of transport cylinders forming a first nip and a pair of acceleration cylinders forming a second nip. The pair of transport cylinders receives the signatures downstream of the cutting pair at the first nip and transports the signatures away from the cutting pair. The first nip is separated from the cutting location by a first distance. The pair of acceleration cylinders receives the signatures from the pair of transport cylinders at the second nip and transports the signatures away from the pair of transport cylinders. The second nip is separated from the first nip by a second distance. The pair of transport cylinders is movable with respect to the pair of acceleration cylinders and the pair of acceleration cylinders is movable with respect to the pair of transport cylinder so the first distance and the second distance are selectively variable. 
     A signature transport section is also provided. The signature transport section includes a first pair of cylinders forming a first nip, the first pair of cylinders receiving signatures at the first nip, and a second pair of cylinders forming a second nip. The second pair of cylinders receives signatures from the first pair of cylinders at the second nip at a first velocity and releases the signatures at a second velocity. The first nip and the second nip are separated by a nip distance that is selectively variable as a function of a length of the signatures. 
     A method of transporting signatures of varying lengths in a printing press is also provided. The method includes the steps of separating a first pair of cylinders forming a first nip and a second pair of cylinders forming a second nip by a first nip distance as a function of a first cutoff length, transporting a first signature of the first cutoff with the first pair of cylinders and the second pair of cylinders, separating the first pair of cylinders and the second pair of cylinders by a second nip distance as a function of a second cutoff length and transporting a second signature of the second cutoff with the first pair of cylinders and the second pair of cylinder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is described below by reference to the following drawings, in which: 
         FIG. 1  shows a schematic side view of a printing press folder according to an embodiment of the present invention including a signature transport section transporting signatures of a first cutoff length; and 
         FIG. 2  shows a schematic side view of the signature transport section shown in  FIG. 2  transporting signatures of a second cutoff length. 
     
    
    
     DETAILED DESCRIPTION 
     In the web offset printing process, a continuous web of paper is transported through a printing press. Near the beginning of the press, one or more printing units apply ink to the web to repeatedly create a pattern, or impression, of text and images. A slitter may slit the web into ribbons, which may be longitudinally folded by a former. For the purposes of the present application, the term web also includes ribbons. A web conversion machine, such as a folder, may be used to cut the web into signatures and fold the signatures. 
     Many folders use driven belts or tapes to transport signatures from a cut cylinder to a next operation, such as signature deceleration or folding. These tapes contact the web before the signature is created and have a surface velocity higher than a velocity of the web. The tapes may mark the web or smear the text and images printed on the web. 
     After a signature is created by the cut cylinder, the signature may be accelerated by the tapes from the velocity of the web to the surface velocity of the tapes. The difference between the velocity of the web to the velocity of the tapes, the velocity gain, may be up to 16%. The velocity gain may cause the signature to slip in relation to the tapes. The amount of slip may be dependent upon a number of variables, including tape contact pressure, thickness of the signature, whether the signature has a glossy or matte finish, the amount of ink and silicone coverage, or the condition of the tapes. 
     The rate of signature acceleration may depend on the mass of the signatures and on the normal force and coefficient of friction between the tapes and signatures. These factors may cause position variations in the signatures when they reach the next device, such as a fan or jaw cylinder. Slipping may cause position variations, which can include: signature-to-signature variation at a given press speed, variations due to press speed changes, and variations due to tape wear over time. Position variations may cause the following problems: reduced maximum allowable press speed, increased need for manual phase adjustments, machine damage, and press downtime due to jammed signatures. Such problems may be worse in variable cutoff applications and may become worse as press speeds increase. 
     Effects of varying friction may be controlled by minimizing a distance between the cut cylinder and the tapes and by adding an adjustable “S” wrap roll configuration. 
       FIG. 1  shows a schematic side view of a portion of a folder  100  of a printing press according to an embodiment of the present invention including a signature transport section  10  transporting signatures  40  of a first cutoff length L 1 . Signature transport section  10  includes transport pair  31  and acceleration pair  41 , which transport signatures  40  created by cutting pairs  11 ,  21 . Cutting pairs  11 ,  21  include respective cutting cylinders  12 ,  22  and respective anvil cylinders  14 ,  24 , that perform a double cut on web  38  to create signatures  40 . 
     Cutting cylinder  12  includes knives  18  that are segmented and partially cut, or perforate, web  40  by contacting anvils  20  on anvil cylinder  14  at a cutting location  16  between cylinders  12 ,  14 . Cutting cylinder  22  includes knives  28  that finish the partial cuts by knives  18 , forming signatures  40 , by contacting anvils  30  on anvil cylinder  24  at a cutting location  26  between cylinders  22 ,  24 . Knives  28  may also be segmented. Cylinders  12 ,  14  are phased with respect to cylinders  22 ,  24  to create signatures  40  of length L 1 . Cylinders  12 ,  14  may be driven by a motor  101  and cylinders  22 ,  24  may be driven by a motor  102 . Motors  101 ,  102  may be servomotors. 
     Transport pair  31  includes transport cylinders  32 ,  34  and acceleration pair  41  includes acceleration cylinders  42 ,  44 . Pairs  31 ,  41  contact signatures  40  at nips  36 ,  46 , respectively, and positively grip signatures  40  as pairs  31 ,  41  transport signatures away from cutting pairs  11 ,  21 . Transport pair  31  may be located in relation to cutting pair  21  such that cutting location  26  and nip  36  are separated by a distance X 1 , which is equal to or slightly less than a length L 1  of each signature  40 . Thus, before cutting cylinder  22  cuts web  38 , forming one signature  40 , transport pair  31  engages web  38  at nip  36  and applies tension to web  38 . 
     Cylinders  32 ,  34  of transport pair  31  are rotated by a motor  103  so that each cylinder  32 ,  34  has a surface velocity V 2 , which is equal to or slightly faster than velocity V 1  of web  38 . Surface velocity V 2  may be adjusted to optimize web tension for cutting. Transport pair  31  engages each signature  40  and passes each signature  40  to transport pair  41  at a velocity equal to surface velocity V 2 . Transport pair  31  may be located in relation to acceleration pair  41  such that nips  36 ,  46  are separated by a distance X 2 , which is substantially equal to length L 1  of each signature  40 . Thus, cylinders  42 ,  44  receive signatures  40  just as signatures  40  are being released by cylinders  32 ,  34 . 
     Cylinders  42 ,  44  of acceleration pair  41  are rotated by a motor  104  so that each cylinder  42 ,  44  has a surface velocity V 3 , which is greater than surface velocity V 2 . Acceleration pair  41  engages each signature  40 , accelerates each signature  40 , and passes each signature  40  away from transport section  10  for further processing, for example folding. Acceleration pair  41  accelerates signatures  40  to provide a head to tail distance X 3  between consecutive signatures  40 . Head to tail distance X 3  may be optimized by adjusting velocity V 3 . Surface velocity V 3  may be equal to a speed at which signatures  40  will be transported during the further processing. In one embodiment, signatures  40  may then be delivered by acceleration pair  41  to transport tapes and carried by transport tapes away from nip  46 . In another embodiment, signatures  40  may be carried away by grippers. 
     Each transport cylinder  32 ,  34 ,  42 ,  44  may be covered with an elastomeric material. 
     Pairs  31 ,  41  and may be mounted on respective frames  60 ,  62 . Motors  103 ,  104  may also be mounted on frames  60 ,  62 , respectively. Actuators  64 ,  66  may be provided to move frames  60 ,  62 , respectively, back and forth in directions parallel to a direction of travel of web  38 . As shown in  FIG. 1 , actuators  64 ,  66  have positioned frames  60 ,  62 , respectively, such that nips  36 ,  46  are separated by distance X 2  and nip  36  and cutting location  26  are separated by distance X 1 . The distance between nips  36 ,  46  and the distance between nip  36  and cutting location  26  may be adjusted so that signature transport section  10  may accommodate signatures of varying cutoff lengths. A controller  200  may be provided to control actuators  64 ,  66  and thus the distance between nips  36 ,  46  and the distance between cutting location  26  and nip  36 . Controller  200  may also control motors  101 ,  102 ,  103 ,  104  to adjust the length of signatures created by cutting pairs  11 ,  21  and the velocities of cylinders  32 ,  34 ,  42 ,  44 . 
     Guide belts may be provided to assist in guiding signatures through signature transport section  10 . The guide belts may be provided in circumferential cutouts spaced axially in cylinders  22 ,  24 ,  32 ,  34 ,  42 ,  44 . 
     In an alternative embodiment, frames  60 ,  62  may be manually actuated. 
       FIG. 2  shows signature transport section  10  transporting signatures  50  of a second cutoff length L 2  that is shorter than cutoff length L 1  of signatures  40  shown in  FIG. 1 . To accommodate signatures  50  of length L 2 , frames  60 ,  62  are actuated so that nips  36 ,  46  are separated by a distance X 5 , which is less than distance X 2  ( FIG. 1 ), and cutting location  26  and nip  36  are separated by a distance X 4 , which is less than distance X 1  ( FIG. 1 ). In a preferred embodiment, operations of the printing press and the folder are stopped to change the distances between nips  36 ,  46  and to adjust cutting pairs  11 ,  21  to create signatures of the desired length. 
     Signatures  50  are created by cylinders  12 ,  14 ,  22 ,  24 . Cylinders  12 ,  14  are phased with respect to cylinders  22 ,  24  such that signatures  50  are of a smaller cutoff length L 2  than signatures  40  ( FIG. 1 ). Cylinders  12 ,  14 ,  22 ,  24  may be rotated at varying velocities during each revolution so that printed signatures  50  may vary in length from signatures  40  ( FIG. 1 ). Other techniques of variable double cut signature formation may also be used. 
     Transport pair  31  is located in relation to cutting pair  21  such that cutting location  26  and nip  36  are separated by a distance X 4 , which may be equal to or slightly less than a cutoff length L 2  of each signature  50 . Thus, before cutting cylinder  22  cuts web  38 , forming signature  50 , transport pair  31  engages web  38  at nip  36  and applies tension to web  38 . 
     Cylinders  32 ,  34  of transport pair  31  are rotated by motor  103  so that each cylinder  32 ,  34  has a surface velocity V 5 , which is equal to or faster than velocity V 4  of web  38 . Transport pair  31  engages each signature  50  and passes each signature  50  to acceleration pair  41  at velocity equal to surface velocity V 5 . Transport pair  31  may be located in relation to acceleration pair  41  such that nips  36 ,  46  are separated by a distance X 5 , which is substantially equal to length L 2  of each signature  50 . Thus, cylinders  42 ,  44  may receive signatures  50  just as signatures  50  are being released by cylinders  32 ,  34 . 
     Cylinders  42 ,  44  of acceleration pair  41  are rotated by motor  104  so that each cylinder  42 ,  44  has a surface velocity V 6 , which is greater than surface velocity V 5 . Acceleration pair  41  engages each signature  50 , accelerates each signature  50 , and passes each signature  50  away from transport section  10  for further processing, for example folding. Transport pair  41  accelerates signatures  50  to provide a head to tail distance X 6  between consecutive signatures  50 . Head to tail distance X 6  may be optimized by adjusting velocity V 6 . 
     Frames  60 ,  62  may also be actuated by actuators  64 ,  66 , respectively, so that signature transport section  10  may be adjusted to set the distance between nips  36 ,  46  and the distance between cutting location  26  and nip  36  to accommodate signatures of cutoff lengths that are greater than cutoff lengths L 1  ( FIG. 1 ), L 2 . 
     In alternative embodiments, pairs  31 ,  41  are not mounted on frames  60 ,  62  and the positioning of pairs  31 ,  41  may be adjusted by other mechanisms. For example, shafts of cylinders  32 ,  34 ,  42 ,  44  may be moved in supporting slots to vary the distance between nips  36 ,  46  and the distance between nip  36  and cutting location  26 . The adjustment of the distances between nips  36 ,  46  and the distance between nip  36  and cutting location  26  during a change in printing format advantageously allows signature transport section  10  to transport signatures of various lengths and allows signature transport section  10  to be used in variable cutoff printing presses. 
     In another alternative embodiment, signatures  40  are delivered by nip  46  into an additional nip formed by an additional cylinder acceleration pair. The additional nip would further accelerate signatures  40  to further increase head to tail distance X 6 . 
     In the preceding specification, the invention has been described with reference to specific exemplary embodiments and examples thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative manner rather than a restrictive sense.