Patent Application
20100122613
The present invention relates to a folder for a rotary printing press for adjustably tensioning a web and a method of adjusting web tension in a web as a web is cut.
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. Publication No. 2007/0018373 discloses a folder including a cut-off unit capable of varying and cutting a cut-off length of a web fed from a printing machine of the rotary printing machine, and a processor (such as a folder, etc.) for processing a sheet cut off by the cut-off unit. Between the cut-off unit and the processor, the folding machine further includes a first belt conveyor for conveying the sheet at a speed equal to the web, and a second belt conveyor for receiving the sheet from the first belt conveyor at a speed approximately equal to the sheet conveying speed of the first belt conveyor, then varying the conveying speed to a speed approximately equal to the sheet conveying speed of the processor, and delivering the sheet to processor.
A printing press folder is provided. The printing press folder includes a cutting apparatus cutting a moving web to form successive signatures, a first acceleration cylinder and a second acceleration cylinder. The first acceleration cylinder includes a first contacting segment and a first relieved portion circumferentially adjacent to the first contacting segment and the first contacting segment radially protrudes from the first acceleration cylinder with respect to the first relieved portion. The second acceleration cylinder includes a second contacting segment and a second relieved portion circumferentially adjacent to the second contacting segment and the second contacting segment radially protrudes from the second acceleration cylinder with respect to the second relieved portion. The first acceleration cylinder and the second acceleration cylinder grip the web at a gripping location with the first contacting segment and the second contacting segment to create a tension in the web as the web is cut by the cutting apparatus.
A method of varying tension in a web in a printing press folder is also provided. The method includes the steps of providing a first acceleration cylinder including a first contacting segment and a first relieved portion circumferentially adjacent to the first contacting segment, the first contacting segment radially protruding from the first acceleration cylinder with respect to the first relieved portion, and a second acceleration cylinder including a second contacting segment and a second relieved portion circumferentially adjacent to the second contacting segment, the second contacting segment radially protruding from the second acceleration cylinder with respect to the second relieved portion; cutting a moving web to form successive signatures; and gripping the web with the first acceleration cylinder and the second acceleration cylinder at a gripping location with the first contacting segment and the second contacting segment to create a tension in the web as the web is cut by the cutting apparatus.
Further features and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:
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 are in firm contact with the web as the web is cut. A sliding friction between the tapes and the web may create tension in the web as the web is cut. The sliding friction 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.
Cutting pairs 22, 24 each include a respective cutting cylinder 18, 20 and a respective anvil cylinder 19, 21. Cutting cylinder 18 includes one or more segmented knives 57 that partially cut, or perforate, web 40 by contacting anvils 59 on anvil cylinder 19. Cutting cylinder 20 includes one or more knives 58 that finish the partial cuts created by knives 57, forming successive signatures 42 from web 40, by contacting anvils 60 on anvil cylinder 21. Knives 58 may also be segmented. Cylinders 18, 19 are rotated about respective center axes by a motor 130 and cylinders 20, 21 are rotated about respective center axes CA1, CA2 by a motor 120. Motors 120, 130 may be servomotors and may be controlled by a controller 101. Anvil cylinders 19, 21 may each be provided with a respective rubber tape 16, 17 mounted partially around the circumference thereof to control web 40 as web 40 is contacted by respective knives 57, 58. In one embodiment, rubber tapes 16, 17 may each travel along an endless loop that indexes to a new section once the current section of the respective rubber tape 16, 17 becomes worn. In another embodiment, rubber tapes 16, 17 may be integrated onto respective anvil cylinders 19, 21. In other embodiments of the present invention, rubber tapes 16, 17 are not used and knives 57, 58 directly contact anvil cylinders 19, 21.
Acceleration pair 26 includes two acceleration cylinders 30, 31 used to positively grip web 40 as web 40 is cut by cutting cylinder 20. Cylinders 30, 31 are rotated about respective center axes CA3, CA4 by a motor 110, which is controlled by controller 101. Motor 110 may be a servomotor. Outer surfaces of cylinders 30, 31 include respective contacting segments 53, 55 and respective relieved portions 32, 33. Contacting segments 53, 55 are circumferentially separated by relieved portions 32, 33 and contacting segments 53, 55 radially protrude from cylinders 30, 31 with respect to relieved portions 32, 33. Throughout each revolution of cylinders 30, 31 about respective center axes CA3, CA4, contacting segments 53, 55 come into contact with one another, directly or via web 40, to form a nip 35 to engage web 40 at a gripping location 45 between center axes CA3, CA4. Relieved portions 32, 33 allow cylinders 30, 31 to come in and out of contact with web 40 during each revolution about respective center axes CA3, CA4 of cylinders 30, 31. This allows cylinders 30, 31 to be phased by controller 101 so that cylinders 30, 31, via contacting segments 53, 55, contact web 40 a desired amount of time before web 40 is cutting by cutting cylinder 20. The amount of time cylinders 30, 31 grip web 40 before web 40 is cut by cutting cylinder 20 affects the amount of tension in web 40 as web 40 is cut by cutting cylinder 20. In a preferred embodiment, contacting segments 53, 55 may have a circumferential surface length that is approximately equal to length L of signatures 42.
In order for the tension in web 40 to be adjustable via phasing of acceleration cylinders 30, 31, respective axes CA3, CA4 of acceleration cylinders 30, 31 are separated from respective center axes CA1, CA2 of cutting cylinder 20 and anvil cylinder 21 a distance X which is less than length L of signatures 42. A range of adjustment of the tension of web 40 due to phasing of acceleration cylinders 30, 31 may be increased by increasing the difference between length L and distance X and the range of adjustment may be decreased by decreasing the difference between length L and distance X.
Cylinders 30, 31 including contacting segments 53, 55 and relieved portions 32, 33 may be formed by grinding cylindrical rolls or cylindrical sleeves that may be mounted on cylindrical rolls to desired diameters at circumferential locations so that the remaining circumferential portions of the rolls or sleeve that were not ground form contacting segments 53, 55 and circumferential portions the were ground form relieved portions 32, 33. Alternatively, contacting segments 53, 55 may each be one or more strips of material that are joined to surfaces of cylindrical rolls to form cylinders 30, 31 and relieved portions are the circumferential portions of the outer surfaces of cylinders 30, 31 that do not include the strips. Surfaces of contacting segments 53, 55 may be made of elastomeric materials or other materials suitable for the positive control of printed products.
In operation, the phase of the acceleration cylinders 30, 31 can be adjusted to control the tension in web 40. Acceleration cylinders 30, 31 are rotated so that contacting segments 53, 55 have a surface velocity V2 that is greater than the velocity V1 of web 40 as web 40 travels past cutting cylinder 20. When acceleration cylinders 30, 31 form nip 35 and grab web 40 at gripping location 45, web 40 is pulled with an increasing force. This force is proportional to the amount of time acceleration cylinders 30, 31 pull on web 40 before web 40 is cut by cutting cylinder 20 to form each signature 42 and the difference in surface velocity, the velocity gain, between surfaces of contacting segments 53, 55 and web 40. Thus, because cylinders 30, 31 include respective contacting segments 53, 55 and respective relieved portions 32, 33, cylinders 30, 31 may be phased to control the amount of time cylinders 30, 31 pull on web 40 before web 40 is cut by cutting cylinder 20. The amount of time cylinders 30, 31 pull on web 40 before web 40 is cut by cutting cylinder 20 is also dependent upon a distance X between cutting location 35 and gripping location 45.
After web 40 is cut by cutting cylinder 20 to form signature 42, acceleration cylinders 30, 31 may accelerate signature 42 to velocity V2. Signature 42 is then released from cylinders 30, 31 and passed to transport cylinders 40, 41. Transport cylinders 40, 41 may further accelerate signature 42 or may have a surface velocity equal to velocity V2 and simply pass signature 42 downstream for further processing. The acceleration of signatures 42 by acceleration cylinders 30, 31 allows a separation gap to be introduced in between successive signatures 42.
Folder 100 advantageously provides positive control of web 40 and signatures 42 during the signature create process without relying on a controlled slip to set the cut tension. Acceleration cylinders 30, 31 positively hold web 40 and create a tension in web 40 during cutting due to the velocity gain of the surfaces of contacting segments 53, 55 with respect to web 40. This tension is adjustable by adjusting the phasing of acceleration cylinders 30, 31 with respect to one another and web 40 so that web 40 is gripped by acceleration cylinders 30, 31 for a precise, adjustable time before web 40 is cut. The tension in web 40 is also adjustable by adjusting the surface velocity V2 of contacting segments 53, 55 with respect to the surface velocity V1 of web 40.
In one alternative embodiment, each acceleration cylinder 30, 31 may include only a single respective contacting segment 53, 55. In other alternative embodiments, each acceleration cylinder 30, 31 may include more than two respective contacting segments 53, 55.
Folder 100 may also be used in a variable cutoff printing press, with the phasing of acceleration cylinders 30, 31 being adjusted to accommodate changes in signatures length.
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.
