Patent Application
20080141879
The present invention is directed to improvements in printing presses and, more particularly, to a printing press that is capable of providing a variable printed image cutoff.
Typically, a printing press will utilize two printing couples and will have an inking mechanism for each of the two printing couples. The printing couples comprise a pair of plate cylinders that are commonly journaled at their opposite ends in spaced parallel side frames as well as a corresponding pair of blanket cylinders that are similarly journaled in the side frames. Further, the printing press often will include a throw-off mechanism usually based on a system of eccentric sleeves and associated linkages.
For a printing press of this type, the press will commonly be designed to utilize a specific diameter of plate and blanket cylinders. It will be understood that the diameter of the cylinders dictates the printed image cutoff, which is difficult to vary since it involves entirely changing the printing press components by essentially rebuilding the press. Understandably, this is a very costly operation to perform, and it is undesirable from the standpoint of productivity and use of resources.
In other words, there is a great amount of “down time” when it is desired to change the cutoff in a conventional printing press. To achieve this objective, it is also necessary to have multiple different sized components including various diameters of plate and blanket cylinders along with different gears, bearings and the like in order to be able to rebuild the press to achieve a different printed image cutoff. As a result, the cost of changing the cutoff has been a deterrent to achieving the level of flexibility that is desired in a printing press.
A quick changeover variable cutoff printing press typically requires independent motors on every cylinder to facilitate printing without the need for gears. Such motors add cost to the printing press and additional complexity. Some printing presses effect cutoff change by changing printing cylinder sizes while driving each cylinder individually by variable speed devices (mostly electric motors) as well as separately driven inkers and dampeners.
Thus, to facilitate a change in cutoff, conventional variable cutoff printing presses typically require cylinder size change, cylinder gear change, and an inker and dampener drive gear change. The inker and dampener drive gear may remain unchanged if driven by a separate set of variable speed devices, to match the cylinder surface speed of the dampener to the cylinder.
According to one aspect of the invention, a printing press includes gear driven rollers, such as, for example, a plate cylinder and a blanket cylinder, and a pivotable gear train adapted to synchronize rotation of the cylinders, and is able to accommodate a range of cylinder sizes. A blanket cylinder gear may be fixedly mounted to the blanket cylinder. A plate cylinder gear may be fixedly mounted to the plate cylinder and the pivotable gear train may include two or more gears and/or two or more pivotal links. One pivotal link may be disposed between the center of rotation of the plate cylinder and at least one gear of the pivotable gear train. The pivotable gear train may include a first gear meshing with the plate cylinder gear and a second gear meshing with the first gear and the blanket cylinder gear. The variable cutoff printing press may further including a pivotal link between the first gear and the second gear.
According to another aspect of the invention, the gear train may be rotatable between a first position, corresponding to a maximum cylinder diameter, and a second position, corresponding to a minimum cylinder diameter.
According to yet another aspect of the invention, a variable cutoff printing press includes: a drive mechanism; a plate cylinder rotated by the drive mechanism; a plate cylinder gear fixedly mounted to the plate cylinder; a blanket cylinder; a blanket cylinder gear fixedly mounted to the blanket cylinder; and a pivotable gear train adapted to synchronize rotation of the blanket cylinder with rotation of the plate cylinder.
According to still another aspect of the invention, a method of changing cutoff on a variable cutoff printing press is provided. The printing press may initially include at least one initial blanket cylinder and at least one initial plate cylinder each having a first diameter, and the method may include providing a gear train for synchronizing rotation of the at least one initial blanket cylinder with rotation of the at least one initial plate cylinder and replacing the at least one initial plate cylinder and the at least one initial blanket cylinder with a subsequent plate cylinder and a subsequent blanket cylinder, each having a second diameter different than the first diameter, without changing any component in the gear train.
The invention provides infinitely variable cutoff capabilities within a desired range between a minimum and a maximum cutoff as well as quick changeover capabilities.
With reference initially to
As shown in the right-hand portion of
In an essentially identical fashion, as shown in the left-hand portion of
As shown in
If desired, the lower transfer gears 44 and 58 may each be provided in a fixed location in relation to the respective blanket cylinder gear 38 and 52, and may be on the same carriage used for cutoff change when the blanket cylinder is changed. The upper transfer gears 42 and 56 may each be rolled around the respective plate cylinder gear 40 and 54 to accommodate a change in the size of the blanket cylinders 14 and 16 and the plate cylinders 18 and 20.
Within a selected cylinder size range, from a minimum diameter of “a” for the initial plate cylinders 18 and 20, and the initial blanket cylinders 14 and 16, as shown in
As shown in
The printing press 10 has been shown and described with the common cylinder drive 34 linked to each of the plate cylinders 18, 20, 18′, and 20′. However, the printing press 10 may be driven either mechanically or electrically through any one of the gears 38, 42, 44, 52, 54, 56, 58, 76, or 80, that each may be tied in a synchronized fashion for the same pitch velocity.
The inker and dampener drive 32 may be driven by a separate variable speed arrangement adjusted to match the printing cylinder surface velocity. The inker and dampener drive 32 may be an electrical motor, but other types of drives are of course possible.
It should be noted that, although depicted in connection with a printing press that performs offset printing, the invention may be used in other types of variable cutoff printing presses, such as, for example printing presses that use flexography, gravure, etc.
From the foregoing, it will also be appreciated that the actual mounting hardware, as well as the actual drive or drives for the printing press 10 have not been shown. This is because the press drive or drives and other associated components such as mounting hardware, adjustment gears and the like may take any conventional form and are not necessary for understanding the present invention. Thus, the present invention is not dependent on mounting hardware or the drive or drives which can readily be selected and implemented by those of ordinary skill in the art.
While in the foregoing there has been set forth a preferred embodiment of the invention, it will be appreciated that the details herein given may be varied by those skilled in the art without departing from the true spirit and scope of the appended claims.
