Printing – Rolling contact machines – Rotary
Reexamination Certificate
1999-03-16
2001-11-13
Yan, Ren (Department: 2854)
Printing
Rolling contact machines
Rotary
C101S247000
Reexamination Certificate
active
06314881
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Priority is claimed with respect to European Application No. 98810217.4-2304, filed in the European Patent Office on Mar. 16, 1998, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
The invention relates to a printing group for a printing press, particularly a rotary offset press, having at least one plate cylinder, one blanket cylinder and one counter pressure cylinder, or a further blanket cylinder and a further plate cylinder.
A printing group of this type is known from European Patent document EP-A-0 531 880. In such printing groups, the elements involved in the printing process, such as gears, bearings and cylinders, must be produced and assembled with very high precision, because otherwise printing defects occur in the form of streaks, blotting or double printing. One such printing defect, known as channel streaking, appears more frequently as the print speed increases.
To avoid these defects, it is further known to mount so-called bearer rings on the two end faces of the plate and blanket cylinders. These rings are hardened, cylindrically ground steel rings that run onto one another under pressure. They reinforce the printing group by extensively eliminating the play and elasticity of the cylinder seatings, because the cylinders roll onto the bearer rings under a pre-stress. The bearer rings prevent the cylinders from decreasing their spacing in the cylinder channels, where the compressive stress temporarily breaks down, and then moving slightly further apart again with the next introduction of pressure.
The use of the aforementioned bearer rings, however, has the disadvantage that the spacing between the cooperating cylinders cannot be adjusted. During printing, the compressive stress, that is, the spacing between the blanket and counter pressure cylinders, should be adjustable to permit an adaptation to different paper thicknesses or paper surfaces. With cylindrical bearer rings, the thickness of the blanket cylinder cover would have to be changed for this type of spacing adaptation, which would in turn change the compressive stress between the blanket and plate cylinders. However, the compressive stress here should be constant. Thus, the cover thickness of the plate would also have to be changed. This in turn changes the printing length, which is not permissible in most cases.
Because of these problems, only bearer rings are used between plate and blanket cylinders in the aforementioned printing groups. The bearer rings extensively eliminate the channel impact between these two cylinders, but not the channel impact between the blanket and counter pressure cylinders or the first and a second blanket cylinders.
In European Patent document EP-A-0 531 880, the channel impact between the blanket and counter pressure cylinders or the first and second blanket cylinders is treated with special stops and cylinder arrangements.
It is also known to use rubber blankets in sleeve form to avoid the channel impact. Changing these blankets is an involved process, however, because, for example, the side wall and/or the respective cylinder seating on one side must be removed for changing the sleeves.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a printing group of the aforementioned type, which permits infinitely adjustable axial spacing (i.e. spacing between the axes) for blanket and counter pressure cylinders, or for blanket-blanket cylinders in blanket-blanket printing groups, without sacrificing the advantages of bearer rings.
The above and other objects are accomplished in the context a printing group for a printing press including a plate cylinder, a blanket cylinder operatively coupled to the plate cylinder, and a further cylinder operatively coupled to the blanket cylinder, wherein according to the invention the blanket cylinder includes two end faces each of which has a conical bearer ring, the further cylinder includes two end faces each of which has a conical bearer ring, and there is additionally provided means for applying pressure to the blanket cylinder so that the conical bearer rings of the blanket cylinder roll onto the conical bearer rings of the further cylinder under pressure. In one embodiment of the invention, the further cylinder comprises a counter pressure cylinder and in another embodiment the further cylinder comprises a further blanket cylinder and in this latter embodiment there is additionally provided another plate cylinder operatively coupled to the further blanket cylinder.
In the printing group of the invention, the axial spacing between the blanket and counter pressure cylinders, or between the two blanket cylinders, can be infinitely adjusted, for example, by displacement of the counter pressure cylinder (or of the further blanket cylinder) in its axial direction by means of a spindle. The axial spacing between the plate and blanket cylinders is not changed by this adjustment.
Play between teeth in drive gears can easily be rendered substantially ineffective according to a further feature of the invention, whereby the rolling contact diameter of the bearer rings on the driving cylinder is made smaller than the rolling-contact diameter of the bearer rings on the driven cylinder, while the gears maintain same number of teeth. This arrangement effects a frictional force between the bearer rings that renders play between teeth ineffective. This type of play occurs when the axial spacing between the two cylinders is increased.
Further, advantageous features ensue from the following description of two embodiments of the invention when considered in conjunction with the accompanying drawings.
REFERENCES:
patent: 2503858 (1950-04-01), Waterworth
patent: 3732813 (1973-05-01), Singh et al.
patent: 4926666 (1990-05-01), Gotting et al.
patent: 5901648 (1999-05-01), Roland et al.
patent: 195 01 243 A1 (1995-01-01), None
patent: 0 771 648 A1 (1996-09-01), None
patent: 0 295 449 A2 (1988-05-01), None
patent: 0 531 880 A1 (1992-09-01), None
Grapha-Holding AG
Kinberg Robert
Venable
Yan Ren
LandOfFree
Printing group for a printing press does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Printing group for a printing press, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Printing group for a printing press will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2617034