Printing – Printing members – Blanks and processes
Reexamination Certificate
2001-06-27
2004-08-03
Funk, Stephen R. (Department: 2854)
Printing
Printing members
Blanks and processes
C101S375000, C029S895320, C492S049000
Reexamination Certificate
active
06769363
ABSTRACT:
BACKGROUND INFORMATION
The present invention relates to the offset printing blankets, and more particularly, to tubular offset lithographic printing blankets and methods for manufacturing the same.
A web offset printing press typically includes a plate cylinder, a blanket cylinder and an impression cylinder supported for rotation in the press. The plate cylinder carries a printing plate having a rigid surface defining an image to be printed. The blanket cylinder carries a printing blanket having a flexible surface which contacts the printing plate at a nip between the plate cylinder and the blanket cylinder. A web to be printed moves through a nip between the blanket cylinder and the impression cylinder. Ink is applied to the surface of the printing plate on the plate cylinder. An inked image is picked up by the printing blanket at the nip between the blanket cylinder and the plate cylinder, and is transferred from the printing blanket to the web at the nip between the blanket cylinder and the impression cylinder. The impression cylinder can be another blanket cylinder for printing on the opposite side of the web.
A conventional printing blanket is manufactured as a flat sheet. Such a printing blanket is mounted on a blanket cylinder by wrapping the sheet around the blanket cylinder and by attaching the opposite ends of the sheet to the blanket cylinder in an axially extending gap in the blanket cylinder. The adjoining opposite ends of the sheet define a gap extending axially along the length of the printing blanket. The gap moves through the nip between the blanket cylinder and the plate cylinder, and also moves through the nip between the blanket cylinder and the impression cylinder, each time the blanket cylinder rotates.
When the leading and trailing edges of the gap at the printing blanket move through the nip between the blanket cylinder and an adjacent cylinder, pressure between the blanket cylinder and the adjacent cylinder is relieved and established, respectively. The repeated relieving and establishing of pressure at the gap causes vibrations and shock loads in the cylinders and throughout the printing press. Such vibrations and shock loads detrimentally affect print quality. For example, at the time that the gap relieves and establishes pressure at the nip between the blanket cylinder and the plate cylinder, printing may be taking place on the web moving through the nip between the blanket cylinder and the impression cylinder. Any movement of the blanket cylinder or the printing blanket caused by the relieving and establishing of pressure at that time can smear the image which is transferred from the printing blanket to the web. Likewise, when the gap in the printing blanket moves through the nip between the blanket cylinder and the impression cylinder, an image being picked up from the printing plate by the printing blanket at the other nip can be smeared. The result of the vibrations and shock loads caused by the gap in the printing blanket has been an undesirably low limit to the speed at which printing presses can be run with acceptable print quality.
In response to these deficiencies in conventional flat printing blankets, gapless tubular printing blankets were developed by the assignee of the present invention. These gapless tubular printing blankets are described, for example, in U.S. Pat. Nos. 5,768,990, 5,553,541, 5,440,981, 5,429,048, 5,323,702, and 5,304,267.
SUMMARY OF THE INVENTION
The methods for manufacturing gapless tubular printing blankets described above suffer from the deficiency that they produce blankets in batch mode (i.e. one at a time) with a fixed axial length. Batch mode production increases production costs, increases production time, and results in batch to batch variability in the blankets produced.
Commonly-assigned U.S. Pat. No. 6,257,140, which is hereby incorporated by reference herein, describes gapless tubular printing blankets produced continuously and cut to length as desired. The sleeve and print layer are “continuously” formed in that the sleeve forming station continues to form an additional portion of the sleeve while the print layer forming station applies the print layer to the previously formed portion of the sleeve. Wound tapes or cross-head extruders are used to apply various layers.
Commonly-assigned U.S. patent application Ser. No. 09/716,696, which is hereby incorporated by reference herein, provides for ribbon casting of materials to form various layers of a tubular printing blanket. “Ribbon casting” occurs when a liquid material is deposited from a stationary source onto a rotating and translating substrate or that a liquid is deposited from a rotating source onto a translating substrate. A continuous ribbon of liquid material thus can be placed on the substrate. Urethane is used in the ribbon casting process. The urethane sets after a certain time.
Ribbon-casting can be expensive and complicated, and the process slow.
The present invention provides a device for manufacturing a continuous printing blanket comprising:
abase sleeve;
a liquid applicator applying a radiation-curing polymer to the base sleeve; and
a radiation source curing the radiation-curing polymer.
By using radiation, the polymer can be cured almost instantaneously. The present device thus provides for more cost-effective and quicker manufacture of printing blankets. Ribbon casting, while possible with the present device, is not necessary. Standard thin film application devices such as blades, rolls, nozzles, sprayers, anilox roller can be used as the applicator to apply a thin layer of the radiation-curing polymer.
Preferably, a second liquid applicator then applies a second polymer over the cured polymer. The radiation curing polymer thus preferably is a compressible liquid polymer, such as urethane mixed with microspheres, carbon dioxide, a blowing agent or water, for example.
Preferably, the radiation-curing polymer is polyurethane, and the radiation source is ultraviolet light. An electron beam also may be used for curing the polymer.
The present device preferably includes a rotation device for rotating the base sleeve, and the base sleeve and rotation device may be similar to the base device used to form blankets in U.S. patent application Ser. No. 09/716,696.
Optional surface finishers for smoothing the surface may be located along the base sleeve between the applicator and the radiation source and after the radiation source.
The sleeve may be formed continuously, so that a cutting device may be provided to cut the sleeve when a desired sleeve length is reached.
The base sleeve may or may not be part of the finished blanket.
The present invention also provides a method for forming a tubular printing blanket comprising the steps of:
placing a radiation-curable polymer over a base sleeve; and
curing the radiation-curable polymer using a radiation source.
Preferably, the method further includes rotating the base sleeve.
The radiation curable polymer preferably is a compressible material, and the method further includes providing a print layer over the compressible material.
The curing step preferably takes place in a few seconds, although times up to 5 minutes are possible.
A smoothing step may be provided both after and before the curing step.
Preferably, radiation-curing layer and the print layer are made of urethane, and a reinforcing layer is provided between the compressible layer and the print layer. The reinforcing layer is also preferably made of urethane.
Preferably, the radiation-curing layer is made of urethane foam formed by blowing carbon dioxide, air or another blowing agent into the urethane. Compressible microspheres however could also be embedded in the urethane to provide the compressibility.
The reinforcing layer preferably is made of a high durometer urethane of greater than 70 shore A, most preferably about 70 shore D. The reinforcing layer preferably is thinner than the compressible layer.
The print layer preferably is made of a urethane with a durometer of less than 90 shore A and most preferably of about 60 shore A.
The
Palmatier Roland Thomas
Vrotacoe James Brian
Davidson Davidson & Kappel LLC
Funk Stephen R.
Heidelberger Druckmaschinen AG
LandOfFree
Device and method for manufacturing a tubular printing blanket does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device and method for manufacturing a tubular printing blanket, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device and method for manufacturing a tubular printing blanket will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3315453