Abstract:
A printing press folder is provided. The printing press folder includes a pair of cutting cylinders cutting a web at a cutting location to form signatures, a pair of transport cylinders positively gripping and transporting the signatures and a pair of acceleration cylinders positively gripping and transporting the signatures. The transport cylinders define a first nip and the first nip and the cutting location are separated by a first distance that is slightly shorter than a length of each of the signatures. The acceleration cylinders define a second nip. The pair of transport cylinders receives and releases signatures at a first velocity and the pair of acceleration cylinders receives the signatures from the pair of transport cylinders and releases the signatures at a second velocity that is greater than the first velocity. The first nip and the second nip are separated by a distance that is slightly shorter than the length of each of the signatures, such that the transport cylinders release each of the signatures as the acceleration cylinders grip the respective signature and the transport and acceleration cylinders maintain positive control over the signatures during transport. A signature transport apparatus and a method for transporting printed products in a printing press folder are also provided.

Description:
The present invention relates generally to printing presses, and more particularly to an incremental velocity changing apparatus for transporting printed products in a folder of 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 printing press folder includes a pair of cutting cylinders cutting a web at a cutting location to form signatures, a pair of transport cylinders positively gripping and transporting the signatures and a pair of acceleration cylinders positively gripping and transporting the signatures. The transport cylinders define a first nip and the first nip and the cutting location are separated by a first distance that is slightly shorter than a length of each of the signatures. The acceleration cylinders define a second nip. The pair of transport cylinders receives and releases signatures at a first velocity and the pair of acceleration cylinders receives the signatures from the pair of transport cylinders and releases the signatures at a second velocity that is greater than the first velocity. The first nip and the second nip are separated by a distance that is slightly shorter than the length of each of the signatures, such that the transport cylinders release each of the signatures as the acceleration cylinders grip the respective signature and the transport and acceleration cylinders maintain positive control over the signatures during transport. 
     A signature transport apparatus is also provided. The signature transport apparatus includes a pair of first acceleration cylinders positively gripping and transporting the signatures and a pair of second acceleration cylinders positively gripping and transporting the signatures. The first acceleration cylinders define a first nip and the second acceleration cylinders define a second nip. The pair of first acceleration cylinders receive the signatures at a first velocity and a release the signatures at a second velocity and the pair of second acceleration cylinders receive the signatures from the pair of first acceleration cylinders and release the signatures at a third velocity. The first nip and the second nip are separated by a distance that is slightly shorter than the length of each of the signatures, such that the first acceleration cylinders release each of the signatures as the second acceleration cylinders grip the respective signature and the first and second acceleration cylinders maintain positive control over the signatures during acceleration. 
     A method for transporting printed products in a printing press folder is also provided. The method includes the steps of engaging a signature traveling at a first velocity with a pair of first acceleration cylinders, accelerating the signature and releasing the signatures from the pair of first acceleration cylinders at a second velocity, engaging the signature with a pair of second acceleration cylinders just before the signature is released from the pair of first acceleration cylinders so the first and second acceleration cylinders maintain positive control of the signature, and accelerating the signature and releasing the signature from the pair of second acceleration cylinders at a third velocity. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is described below by reference to the following drawings, in which: 
         FIG. 1  schematically shows a portion of a printing press folder including a signature transport apparatus according to one embodiment of the present invention; and 
         FIG. 2  schematically shows a portion of a printing press folder including a signature transport apparatus according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the web offset printing process, a continuous web of paper is transported through a printing 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 that 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 and 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 or deceleration may depend on the mass of the signature and on the normal force and coefficient of friction between the tapes and the signature. These factors may cause position variations in the signature when the signature reaches 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 over time due to, for example, tape wear. 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 printing press folder  100  according to an embodiment of the present invention including a signature transport apparatus  10  and a cutting apparatus  110 . Signature transport apparatus  10  includes transport pair  122  and acceleration pairs  126 ,  130  and cutting apparatus  110  includes cutting pairs  118 ,  119 . Cutting pairs  118 ,  119  include cutting cylinders  11 ,  12  and anvil cylinders  13 ,  14 , respectively. Cylinders  11 ,  13  are rotated about respective center axes CA 1 , CA 2  at an angular velocity W 1 . Cylinders  12 ,  14  may also be rotated about respective center axes CA 3 , CA 4  at angular velocity W 1 . Cutting cylinders  11 ,  12  have respective knives  17 ,  18  which engage anvils  19 ,  20  of anvil cylinders  13 ,  14 , respectively, at cutting locations  15 ,  16 , respectively. Knives  17  are segmented and partially cut, or perforate, web  40  by contacting anvils  19  on anvil cylinder  13 . Web  40  travels at a velocity V 1 . Cutting cylinder  12  includes knives  18  that finish the partial cuts by knives  17 , forming signatures  42 , by contacting anvils  20  on anvil cylinder  14 . Knives  18  may also be segmented. Knives  17  may be phased with respect to knives  18  to create signatures  42  of a length L 1 . 
     Acceleration pairs  126 ,  130  receive signatures  42  from transport pair  122  and incrementally increase the velocity of signatures  42  as signatures  42  travel away from cutting pair  119 . Transport pair  122  includes transport cylinders  22 ,  24 , each having a radius R 1  and rotating about a respective center axis CA 5 , CA 6  at an angular velocity W 2 . Acceleration pair  126  includes acceleration cylinders  26 ,  28 , each having a radius R 2  and rotating about a respective center axis CA 7 , CA 8  at an angular velocity W 3 . Acceleration pair  130  includes acceleration cylinders  30 ,  32 , each having a radius R 3  and rotating about a respective center axis CA 9 , CA 10  at an angular velocity W 4 . Pairs  122 ,  126 ,  130  contact web  40  at nips  34 ,  36 ,  38 , respectively. 
     Just prior to or as web  40  is cut by cutting pair  119 , transport pair  122  engages signatures  42  at nip  34 . Surfaces of cylinders  22 ,  24  of transport pair  122  are traveling at a velocity V 2 , which is equal to velocity V 1 . Transport pair  122  passes signatures  42  to acceleration pair  126  at velocity V 2 . Surfaces of cylinders  26 ,  28  of acceleration pair  126  travel at a velocity V 3 , which is greater than velocity V 2 . Thus, cylinders  26 ,  28  engage signatures  42  at nip  36  and accelerate signatures  42  from velocity V 2  to velocity V 3 . Acceleration pair  126  passes signatures  42  to acceleration pair  130  at velocity V 3 . Surfaces of cylinders  30 ,  32  of acceleration pair  130  travel at a velocity V 4 , which is greater than velocity V 3 . Thus, cylinders  30 ,  32  engage signatures  42  at nip  38  and accelerate signatures  42  from velocity V 3  to velocity V 4 . 
     Signatures  42  may be delivered by acceleration pair  130  to transport tapes  44  and carried by transport tapes  44  away from nip  38  at velocity V 4 . To ensure signatures  42  are always contacting a nip within signature transport apparatus  10 , a signature length L 1  may be slightly longer than a distance X 1  between adjacent nips  16 ,  34 ,  36 ,  38 . 
     Guide belts may be provided to assist in guiding signatures through signature transport apparatus  10 . The guide belts may be provided in circumferential cutouts spaced axially in cylinders  12 ,  14 ,  22 ,  24 ,  26 ,  28 ,  30 ,  32 . 
     Acceleration pairs  126 ,  130  gradually accelerate signatures  42  from velocity V 2  to velocity V 4  in increments, with each acceleration pair  126 ,  130  involved in a discrete step of acceleration. Velocities V 3 , V 4  may be chosen such that the discrete steps of acceleration are each small enough to minimize or eliminate slippage between pairs  122 ,  126 ,  130  and the signature. Thus, signature transport apparatus  10  may maintain positive control over signatures  42  and reduce problems associated with signature position errors while greatly reducing or eliminating reliance on the consistency of a controlled slip. 
     In one embodiment, cylinders  22 ,  24 ,  26 ,  28 ,  30 ,  32  may be geared together and driven by a common drive such that angular velocities W 2 , W 3 , W 4  are equal. The common drive may be velocity matched to a cut cylinder drive driving cylinders  11 ,  12 ,  13 ,  14  so that as cylinders  22 ,  24  grip web  40 , V 2  is equal to a velocity that knives  18  are traveling with respect to the direction of the web. When W 2 , W 3 , W 4  are equal, radiuses R 1 , R 2 , R 3  are gradually increased so that surface velocities V 3 , V 4  gradually increase and signatures  42  are accelerated as signatures  42  travel away from cutting pair  119 . 
     In another embodiment, cylinders  22 ,  24  may be driven by a first motor, cylinders  26 ,  28  may be driven by a second motor and cylinders  30 ,  32  may be driven by a third motor. The desired surface velocities V 2 , V 3 , V 4  may thus be obtained with radii R 1 , R 2 , R 3  being equal and angular velocities W 2 , W 3 , W 4  being unequal. 
     In another embodiment, cylinders  22 ,  24 ,  26 ,  28 ,  30 ,  32  may be driven by the same belt or belts. 
     In further embodiments, acceleration pairs  126 ,  130  may be used in other printed product processing equipment and, may be used to decelerate, rather than accelerate, signatures  42 . Roll radii R 2 , R 3  and angular velocities W 3 , W 4  of cylinders  26 ,  28 ,  30 ,  32  may be chosen to provide a desired deceleration rate. 
       FIG. 2  shows a schematic side view of a portion of a printing press folder  101  according to an embodiment of the present invention including a signature transport apparatus  50  and a cutting apparatus  150 . Signature transport apparatus  50  includes transport pair  162  and acceleration pairs  166 ,  170  and cutting apparatus  110  includes cutting pairs  154 ,  158 . Acceleration pairs  166 ,  170  incrementally accelerate signatures  42  in a manner similar to acceleration pairs  126 ,  130  shown in  FIG. 1 . 
     Pairs  162 ,  166 ,  170  form nips  74 ,  76 ,  78 , respectively, spaced at intervals of a distance X 2 . Cutting pair  158  cuts web  40  at a cutting location  72 , which may be a distance X 2  away from nip  74 . Distance X 2  may be slightly less than length L 1  of signatures  42  ( FIG. 1 ). 
     Cutting pairs  154 ,  158  cut a web  40  traveling in a direction  150  into signatures  42  using respective cutting cylinders  51 ,  52  and respective anvil cylinders  53 ,  54 . Cutting cylinder  51  may include segmented knives  57  that partially cut, or perforate, web  40  by contacting anvils  59  on anvil cylinder  53 . Cutting cylinder  52  includes knives  58  that finish the partial cuts created by knives  57 , forming signatures  42 , by contacting anvils  60  on anvil cylinder  54 . Knives  58  may also be segmented. 
     Cylinders  62 ,  64 , each have a surface velocity V 6  and engage web  40 , traveling at a velocity V 5  that equals velocity V 6 , as cutting pair  158  cuts web  40  to forms signatures  42 . Cylinders  62 ,  64  transport signatures  42 , so that signatures  42  travel at a velocity V 6  as signatures  42  are passed to acceleration pair  166 . Cylinders  62 ,  64  include surface roll segments  63 ,  65 , respectively, that radially protrude from cylinders  62 ,  64  and engage signatures  42  at nip  74 . Surface roll segments  63 ,  65  may be of a length equal to distance X 2  and may be spaced about cylinders  62 ,  64 , respectively, such that gaps between segments  63  and gaps between segments  65  allow tail edges of signatures  42  to smoothly release from cylinders  62 ,  64 . Cylinders  62 ,  64  may be phased so that a tail edge of each signature  42  is released as each signature  42  is grabbed by acceleration pair  166 . 
     Cylinders  66 ,  68 , each have a surface velocity V 7  and engage signatures  42  as signatures  42  are released by transport pair  162 . Cylinders  66 ,  68  transport and accelerate signatures  42 , so that signatures  42  travel at a velocity V 7  as signatures  42  are passed to acceleration pair  170 . Cylinders  66 ,  68  include surface roll segments  67 ,  69 , respectively, that radially protrude from cylinders  66 ,  68  and engage signatures  42  at nip  76 . Surface roll segments  67 ,  69  may be of a length equal to distance X 2  and may be spaced about cylinders  66 ,  68 , respectively, such that gaps between segments  67  and gaps between segments  69  allow tail edges of signatures  42  to smoothly release from cylinders  66 ,  68 . Cylinders  66 ,  68  may be phased so that a tail edge of each signature  42  is released as each signature  42  is grabbed by acceleration pair  170 . 
     Cylinders  70 ,  72 , each have a surface velocity V 8  and engage signatures  42  as signatures  42  are released by acceleration pair  166 . Cylinders  70 ,  72  transport and accelerate signatures  42 , so that signatures  42  travel at a velocity V 8  as signatures  42  are passed away from signature transport apparatus  50 . Cylinders  70 ,  72  may have a constant surface, without surface roll segments, because acceleration pair  170  may release signatures  42  to belts traveling at velocity V 8 . In one embodiment, cylinders  70 ,  72  may include surface roll segments. 
     In a preferred embodiment, cylinders  62 ,  64 ,  66 ,  68 ,  70 ,  72  are driven by a common motor  200  at an angular velocity W. Cylinders  51 ,  52 ,  53 ,  54  may be driven by a motor  201  at angular velocity W, or some other angular velocity. A controller  202  may be provided to control motors  200 ,  201  as desired. In order for acceleration pairs  166 ,  170  to accelerate signatures  42 , cylinders  62 ,  64 ,  66 ,  68 ,  70 ,  72  have increasingly larger pitch radii in each pair  162 ,  166 ,  170 , in relation to direction  150 . Cylinders  66 ,  68  each have a pitch radius R 5  greater than a pitch radius R 4  of each cylinder  62 ,  64  and cylinders  70 ,  72  each have a radius R 6  greater than pitch radius R 5 . In another embodiment, signature acceleration apparatus  50  is used in a different printed product processing machine and radii R 4 , R 5 , R 6  decrease in direction  150  so that signature acceleration apparatus  50  decelerates signatures. 
     With cylinders  62 ,  64 ,  66 ,  68 ,  70 ,  72  being rotated at the same angular velocity W, the velocity gain of each acceleration pair  166 ,  170  is controlled by radii R 4 , R 5 , R 6  of cylinders  62 ,  64 ,  66 ,  68 ,  70 ,  72 . A theoretical limit to a maximum velocity gain may be distance X 2 . An actual limit to a maximum velocity gain may be dependent upon a point at which there is slippage between pairs  162 ,  166 ,  170  and signatures  42 . 
     The number of acceleration cylinders in a signature transport apparatus may be increased or decreased in a signature transport apparatus to achieve a desired rate of acceleration or deceleration, thus a signature transport apparatus may include two acceleration pairs or more than three acceleration pairs. 
     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.