Printing – Printing members – Plate mountings
Reexamination Certificate
1996-04-15
2001-03-20
Asher, Kimberly (Department: 2854)
Printing
Printing members
Plate mountings
C101S375000, C101S177000, C101S217000, C101S142000
Reexamination Certificate
active
06202558
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to offset printing presses and more particularly to an apparatus for reducing procession of a gapless tubular printing sleeve mounted on a cylinder.
BACKGROUND OF THE INVENTION
In offset printing, printed images are transferred from printing plates mounted on plate cylinders to a moving web of material by transfer cylinders known as blanket cylinders. Typically, printing blankets are mounted on the blanket cylinders which have a rubber surface for transferring the printed images. Conventional printing plates and printing blankets are rectangular in shape and are mounted in axial gaps extending along the circumferential surfaces of the corresponding plate cylinders and blanket cylinders. One problem with this design is that at high operational speeds the gaps in the plate and blanket cylinders cause vibrations in the printing press which have the effect of varying the optical densities of the printed image. There are a number of other problems associated with this design which affects the quality of the final printed product. Many of these problems have been solved by making the printing blanket tubular in shape having a gapless outer circumferential surface. Furthermore, by substituting the conventional flat printing plate with a tubular printing form having a gapless outer circumferential surface endless printing is possible. Arrangements of this nature however have several drawbacks.
To mount a tubular printing sleeve, i.e., a tubular printing form or a tubular printing blanket, an air canal is provided at one end of a corresponding cylinder on which the sleeve is to be mounted. The canal supplies pressurized air radially outward through a plurality of passages. As the printing sleeve is placed over the passages, the pressure from the exiting air radially expands the printing sleeve enabling it to be axially mounted onto the circumferential surface of the corresponding cylinder. Since the inner circumference of the printing sleeve is slightly smaller than the outer circumference of the corresponding cylinder, once the printing sleeve is mounted it is stressed in tension by the corresponding cylinder to provide a tight pressure relationship between the printing sleeve and the corresponding cylinder. This pressure relationship fixes the printing sleeve on the corresponding cylinder so that there is no relative movement therebetween during operation of the press.
A problem with this arrangement is that air gets trapped at the interface of the printing sleeve and the corresponding cylinder. During operation of the press this trapped air creates a continually advancing wave in front of a nip between the corresponding cylinder and an adjacent cylinder against which it is pressed causing the printing sleeve to bulge. This phenomena is known as printing sleeve procession. It creates defects in the printed product by forming latent double images.
Several attempts have been made to reduce or eliminate sleeve procession, but none have been successful. One attempted solution was to increase interference between the printing sleeve and corresponding cylinder. Another was to change the material combination of the printing sleeve and the corresponding cylinder surface to a combination having higher coefficients of friction. Both of these attempted solutions failed, since the primary cause of procession does not involve slippage of the printing sleeve relative to the corresponding cylinder.
Another attempted solution was to decrease the normal forces between the corresponding cylinder and its adjacent cylinders. Although this solution reduces the rate of procession, it also reduces the quality of print to an unacceptable level. Still another solution was attempted which involved mechanically fixing the printing sleeve to the corresponding cylinder. This attempt was also unsuccessful because the printing sleeve was too thin to withstand the forces required to stop the procession, and hence the printing sleeve would tear.
The deficiencies in each of these attempts are fundamental and cannot be eliminated.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the present invention is to provide an apparatus that removes fluid waves that cause printing sleeve procession.
The present invention provides an apparatus for reducing procession of a gapless tubular printing sleeve in an offset printing press caused by at least one advancing fluid wave having a certain pressure, comprising: a cylinder adapted to receive the printing sleeve for mounting on its circumferential surface; and means for connecting an interface of the cylinder and the printing sleeve to a region of pressure lower than the pressure in the fluid wave to allow the fluid wave, which is trapped at the interface and advancing in front of a nip between the cylinder and an adjacent cylinder, to escape to the region of low pressure.
In one embodiment of the present invention, the means for connecting the interface of the cylinder and the printing sleeve to a region of low pressure comprises the cylinder having at least one groove extending along its circumferential surface, the trapped fluid wave escaping via the groove.
In another embodiment of the present invention, the means for connecting the interface of the cylinder and the printing sleeve to a region of low pressure comprises the printing sleeve having at least one groove extending along its inner circumferential surface, the trapped fluid wave escaping via the groove.
In a further embodiment of the present invention, the means for connecting the interface of the cylinder and the printing sleeve to a region of low pressure comprises a plurality of small granular particles having spaces formed therebetween, the trapped fluid wave escaping via the spaces.
An advantage of the present invention is that it removes the trapped fluid wave that causes procession of the printing sleeve without reducing the quality of the final printed product.
Another advantage of the present invention is that it eliminates latent double images and hence improves the overall quality of the final printed product.
A further advantage of the present invention is that it removes the trapped fluid wave within several rotations of the cylinder so that the printing operation may proceed almost immediately after mounting the printing sleeve.
These and other objects, characteristics, and advantages of the present invention will become apparent in view of the description and accompanying drawings that follow.
REFERENCES:
patent: 4030415 (1977-06-01), Fellows
patent: 4056057 (1977-11-01), Smith
patent: 4144813 (1979-03-01), Julian
patent: 4332194 (1982-06-01), Gensheimer
patent: 4589339 (1986-05-01), Fischer
patent: 4913048 (1990-04-01), Tittgemeyer
patent: 5245923 (1993-09-01), Vrotacoe
patent: 8532300 (1986-02-01), None
patent: 1 401 695 (1973-07-01), None
Dawley Douglas Joseph
Vrotacoe James Brian
Asher Kimberly
Heidelberger Druckmaschinen AG
Kenyon & Kenyon
LandOfFree
Apparatus for reducing procession of a tubular printing sleeve does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus for reducing procession of a tubular printing sleeve, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus for reducing procession of a tubular printing sleeve will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2490388