Patent Application
20100089265
The present invention relates generally to printing presses and more particularly to variable cutoff printing presses.
U.S. Pat. No. 5,950,536 discloses a variable cutoff offset press unit wherein a fixed cutoff press is adapted to a variable cutoff press while maintaining the size of the blanket cylinders. A plate cylinder sleeve has a variable outer diameter, whereby a length of an image to be printed is varied proportionally to a variable outer diameter while maintaining an outer diameter of the gapless blanket cylinder sleeve constant. The size of a plate cylinder is changed by using a sleeve mounted over the plate cylinder or adding packing under a plate to increase the diameter of the plate cylinder.
U.S. Pat. No. 6,327,975 discloses a method and apparatus for printing elongate images on a web. A first printing unit prints a first image portion on the web at prescribed spacings, by moving the impression cylinder away from the blanket cylinder each time one first image portion is printed. A second printing unit prints a second image portion on the spacings left on the web by the first printing unit, also by moving the impression cylinder away from the blanket cylinder each time one second image portion is printed. A variable velocity motor rotates each blanket cylinder, while each time the associated impression cylinder is held away to create a space on the web for causing printing of the first or the second printing portion at required spacings.
U.S. Pat. No. 7,066,088 discloses a variable cut-off offset press system and method of operation which utilizes a continuous image transfer belt. The offset printing system comprises at least two plate cylinders adapted to have thereon respective printing sleeves. Each of the printing sleeves is adapted to receive colored ink from a respective ink source. The system further comprises at least a impression cylinder, wherein the image transfer belt is positioned to contact each of the printing sleeves at respective nips formed between respective ones of the plate cylinders and the at least one impression cylinder.
A variable cutoff printing press is provided. The printing press includes a first plate cylinder rotating at a constant angular velocity during each revolution about a first plate cylinder axis and a first blanket cylinder rotating at varying angular velocities and printing on a web during each revolution about a first blanket cylinder axis. The first blanket cylinder comes in and out of contact with the first plate cylinder during operation.
A method of variable cutoff printing is also provided. The method includes, during a single rotation of a first blanket cylinder about a first blanket cylinder axis, rotating the first blanket cylinder and bringing the first blanket cylinder into contact with a first plate cylinder carrying a first image and rotating at a first constant velocity, the blanket cylinder contacting the first plate cylinder and receiving the first image from the first plate cylinder; rotating the first blanket cylinder and bringing the first blanket cylinder out of contact with the first plate cylinder; varying a rotational velocity of the first blanket cylinder after the first blanket cylinder is brought out of contact with the first plate cylinder; rotating the first blanket cylinder and bringing the first blanket cylinder into contact with a web traveling at a second constant velocity, the first blanket cylinder contacting the web and printing the first image on the web; rotating the first blanket cylinder and bringing the first blanket cylinder out of contact with the web; and varying the rotational velocity of the first blanket cylinder again after the first blanket cylinder is brought out of contact with the web.
The present invention is described below by reference to the following drawings, in which:
a shows a table including predicted results for a printing section of the embodiment shown in
b shows a graph illustrating a surface velocity of a contacting portion of a blanket cylinder, for each revolution of the blanket cylinder, according to the predicted results shown in the table of
Inkers 22 disperse ink to plate cylinder 24, which rotates about an axis of plate cylinder 24 and transfers a first inked image to blanket cylinder 26. Blanket cylinder 26 rotates about an axis of blanket cylinder 26 and prints the first inked image on web 14. Axes of blanket cylinder 26 and plate cylinder 24 remain stationary during printing. Inkers 22 and plate cylinder 24 are being rotated so that inkers 22 each have a constant surface velocity that is equal to the surface velocity of plate cylinder 24. Impression cylinder 16 and web 14 also travel at constant velocities so that a surface velocity of impression cylinder 16 equals a velocity of web 14.
The surface velocity of plate cylinder 24 may vary from the surface velocity of impression cylinder 16 and the velocity of web 14. However, while blanket cylinder 26 is receiving a first image from plate cylinder 24 the surface velocity of blanket cylinder 26 is equal to the surface velocity of plate cylinder 24 and while blanket cylinder 26 is printing the first images on web 14 the surface velocity of blanket cylinder 26 is equal to the surface velocity of impression cylinder 16 and the velocity of web 14. Thus, during each 360 degree revolution, if the surface velocity of plate cylinder 24 varies from the surface velocity of blanket cylinder 26, then blanket cylinder 26 accelerates and decelerates during each revolution.
Printing section 30 operates in a manner similar to printing section 20 to print second images on web 14, with inkers 32 and plate cylinder 34 having constant equal surface velocities that may vary from the velocity of web 14 and the surface velocity of impression cylinder 16. As with blanket cylinder 26, blanket cylinder 36 may accelerate and decelerate during each 360 degree revolution when the surface velocity of plate cylinder 34 varies from the surface velocity of impression cylinder 16 and the velocity of web 14.
In this embodiment, a position where blanket cylinder 26 contacts web 14 and a position where blanket cylinder 26 contacts plate cylinder 24 are separated by 180 degrees with respect to the axis of blanket cylinder 26. Also, a position where blanket cylinder 36 contacts plate cylinder 34 and a position where blanket cylinder 36 contacts web 14 are separated by 180 degrees with respect to an axis of blanket cylinder 36. In other embodiments, different angles of separation may be used.
As shown in
In this embodiment, which is a preferred embodiment, printing sections 20, 30 are configured in the same manner, with plate cylinder 24 being the same size as plate cylinder 34, blanket cylinder 26 being the same size as blanket cylinder 36, and contacting portions 27, 37 being the same size. In an alternative embodiment, printing sections 20, 30 may be configured differently from each other.
In operation, blanket cylinder 26 contacts plate cylinder 24 with contacting portion 27 and receives a first image from plate cylinder 24. After contacting portion 27 receives the first image from plate cylinder 24 and contacting portion 27 is no longer in contact with plate cylinder 24, blanket cylinder 26 may be accelerated or decelerated so that contacting portion 27 has a surface velocity that is equal to the velocity of web 14 when contacting portion 27 contacts web 14. When contacting portion 27 prints the first image on web 14 and is no longer in contact with web 14, blanket cylinder 26 may be accelerated or decelerated so that the surface velocity of contacting portion 27 is equal to the surface velocity of plate cylinder 24 when contacting portion 27 comes into contact with plate cylinder 24 again to receive a next first image. As blanket cylinder 26 contacts plate cylinder 24, blanket cylinder 26 is aligned with respect to plate cylinder 24 so that a first inked image carried by plate cylinder 24 is properly transferred to contacting portion 27. After blanket cylinder 26 receives the next first image and comes out of contact with plate cylinder 24, blanket cylinder 26 may be accelerated or decelerated so that contacting portion 27 has a surface velocity that is equal to the velocity of web 14 as contacting portion 27 contacts web 14 and so that contacting portion 27 is properly aligned to print the next first image on web 14.
After blanket cylinder 26 prints a first image on web 14 and the first image passes by area 44, blanket cylinder 36 prints a second image on web 14 directly behind the first image. As blanket cylinder 36 prints the image, blanket cylinder 36 is being rotated so that the surface velocity of blanket cylinder 36 equals the velocity of web 14 and the surface velocity of impression cylinder 16. After blanket cylinder 36 finishes printing the second image on web 14, blanket cylinder 36 may be accelerated or decelerated so that contacting portion 37 has a surface velocity that equals the surface velocity of plate cylinder 34, and is in proper image receiving position when contacting portion 37 contacts plate cylinder 34 to receive a next second image. After blanket cylinder 36 contacts plate cylinder 34 and receives the next second image and contacting portion 37 is out of contact with plate cylinder 34, blanket cylinder 36 may need to be accelerated or decelerated so that the surface velocity of contacting portion 37 equals the velocity of web 14 and so that contacting portion 37 is in a proper position as blanket cylinder 36 prints the next second image on web 14.
Blanket cylinder 26 prints first images on web 14 that are separated from one another by a distance that is equal to the length of each second image printed by blanket cylinder 36. Blanket cylinder 36 prints second images on web 14 that are separated from each other by a distance that is equal to the length of each first image printed by blanket cylinder 26. Thus, blanket cylinders 26, 36 are phased so that each blanket cylinder 26, 36 prints every other image on web 14 and no unprinted space is left between adjacent first and second images printed by blanket cylinders 26, 36, respectively, on web 14.
In one embodiment, each first image printed on web 14 by blanket cylinder 26 may be a first image portion and each second image printed on web 14 by blanket cylinder 36 may be a second image portion, so that the each first image portion and each second image portion form a single continuous image. Thus, together blanket cylinders 26, 36 may act together to print a single image on web 14.
Each cylinder 16, 24, 26, 34, 36 may be driven by a motor 101, 102, 103, 104, 105, respectively. Motors 101, 102, 103, 104, 105 may be controlled by a controller 110, which acts to ensure that blanket cylinders 26, 36 are traveling at appropriate surface velocities when blanket cylinders 26, 36 contact plate cylinders 24, 34, respectively, and web 14 and that blanket cylinders 26, 36 print images on web 14 at appropriate locations. Motors 102, 104 may also drive inkers 22, 32, respectively. In an alternative embodiment, plate cylinders 24, 34 may be driven by a single motor.
In order to vary a cutoff of images printed by printing unit 10, plate cylinders 24, 34 may be altered so that plate cylinders 24, 34 transfer respective first and second replacement images to blanket cylinders 34, 36. This may be accomplished by removing plates, which may be disposed about plate cylinders 24, 34 and carry the respective first and second images, from plate cylinders 24, 34 and replacing the plates with replacement plates that carry the respective first and second replacement images. When the first and second replacement images are of a length that varies from the length of contacting portions 27, 37, respectively, the velocity that blanket cylinders 26, 36 are rotated and the phasing of blanket cylinders 26, 36 may be adjusted so that blanket cylinders 26, 36 properly receive the first and second replacement images from plate cylinders 24, 34, respectively, and print the first and second replacement images in proper alignment on web 14.
a shows a table including predicted results for printing section 20 of the embodiment shown in
For scenario 201, blanket cylinder 26 prints first images on web 14 during 180 degrees of each revolution. The surface velocity of plate cylinder 24 is equal to the velocity of web 14 and blanket cylinder 26 travels at a constant speed during each revolution, with a surface velocity of contacting portion 27 equal to the velocity of web 14. Blanket cylinder 26 does not accelerate or decelerate throughout each revolution.
For scenario 202, blanket cylinder 26 prints first images on web 14 during 120 degrees of each revolution and contacting portion 27 makes up one third of the circumference of blanket cylinder 26. The surface velocity of plate cylinder 24 is more than twice the velocity of web 14. Blanket cylinder 26 accelerates for 60 degrees after printing a first image on web 14 and decelerates for 60 degrees after receiving a first image from plate cylinder 24. After printing a first image on web 14, blanket cylinder 26 rotates 240 degrees in the time it takes web 14 to travel a distance that equals a length of a second image printed by contacting portion 37, in order to be back in proper printing position. While not printing on web 14, contacting portion 27 has an average surface velocity that equals twice the velocity of web 14.
For scenario 203, blanket cylinder 26 prints first images on web 14 during 90 degrees of each revolution. The surface velocity of plate cylinder 24 is more than three times the velocity of web 14. Blanket cylinder 26 accelerates for 90 degrees after printing a first image on web 14 and decelerates for 90 degrees after receiving a first image from plate cylinder 24. After printing a first image on web 14, blanket cylinder 26 rotates 270 degrees in the time it takes web 14 to travel a distance that equals a length of a second image printed by contacting portion 37, in order to be back in proper printing position. While not printing on web 14, contacting portion 27 has an average surface velocity that equals three times the velocity of web 14.
For scenario 204, blanket cylinder 26 prints first images on web 14 during 72 degrees of each revolution. The surface velocity of plate cylinder 24 is more than four times the velocity of web 14. Blanket cylinder 26 accelerates for 108 degrees after printing a first image on web 14 and decelerates for 108 degrees after receiving a first image from plate cylinder 24. After printing a first image on web 14, blanket cylinder 26 rotates 288 degrees in the time it takes web 14 to travel a distance that equals a length of a second image printed by contacting portion 37, in order to be back in proper printing position. While not printing on web 14, contacting portion 27 has an average surface velocity that equals four times the velocity of web 14.
For scenario 205, blanket cylinder 26 prints first images on web 14 during 60 degrees of each revolution. The surface velocity of plate cylinder 24 is more than five times the velocity of web 14. Blanket cylinder 26 accelerates for 120 degrees after printing a first image on web 14 and decelerates for 120 degrees after receiving a first image from plate cylinder 24. After printing a first image on web 14, blanket cylinder 26 rotates 300 degrees in the time it takes web 14 to travel a distance that equals a length of a second image printed by contacting portion 37, in order to be back in proper printing position. While not printing on web 14, contacting portion 27 has an average surface velocity that equals five times the velocity of web 14.
b shows a graph illustrating the surface velocity of contacting portion 27 for each 360 degree revolution of blanket cylinder 26 for scenarios 202, 203, 205 shown in the table of
Blanket cylinder 326 is translated between two positions 326a, 326b by an actuator 130 during each revolution. In position 326a, blanket cylinder 326 receives first images from plate cylinder 24 and a surface velocity of blanket cylinder 326 equals the surface velocity of plate cylinder 24. In position 326b, blanket cylinder 326 prints first images on web 14 and the surface velocity of blanket cylinder 326 equals the velocity of web 14. As blanket cylinder 326 is translated between positions 326a, 326b blanket cylinder 26 may be accelerated or decelerated to ensure that blanket cylinder 326 is traveling at an appropriate velocity when blanket cylinder 326 comes into contact with plate cylinder 24 or web 14.
Blanket cylinder 336 is translated between two positions 336a, 336b by an actuator 132 during each revolution. In position 336a, blanket cylinder 336 receives second images from plate cylinder 34 and a surface velocity of blanket cylinder 336 equals the surface velocity of plate cylinder 34. In position 336b, blanket cylinder 336 prints second images on web 14 and the surface velocity of blanket cylinder 336 equals the velocity of web 14. As blanket cylinder 336 is translated between positions 336a, 336b blanket cylinder 336 may be accelerated or decelerated to ensure that blanket cylinder 336 is traveling at an appropriate velocity when blanket cylinder 336 comes into contact with plate cylinder 34 or web 14.
In order to vary a cutoff of images printed by printing unit 310, plate cylinders 24, 34 may be altered so that plate cylinders transfer first and second replacement images to blanket cylinders 34, 36. This may be accomplished by removing plates, which may be disposed about plate cylinders 24, 34 and carry the respective first and second images, from plate cylinders 24, 34 and replacing the plates with replacement plates that carry the respective first and second replacement images. The velocity that blanket cylinders 326, 336 are rotated and the phasing of blanket cylinders 326, 336 may be adjusted so that blanket cylinders 326, 336 properly receive the first and second replacement images from plate cylinders 24, 34, respectively, and print the first and second replacement images on web 14 so the first and second replacement images are properly aligned and there are no unprinted spaces between the first and second replacement images. The translation of blanket cylinders 326, 336 between respective positions 326a, 336a and respective positions 326b, 336b may also be adjusted so that blanket cylinders 326, 336 contact plate cylinders 24, 36 and web 14 for the proper amount of time to receive and print the replacement images on web 14.
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.
