Printing – Flexible-sheet-securing devices
Reexamination Certificate
2000-04-20
2002-11-05
Evanisko, Leslie J. (Department: 2854)
Printing
Flexible-sheet-securing devices
C101S378000
Reexamination Certificate
active
06474234
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method for locking or clamping a cylinder dressing on a printing machine cylinder, which includes adjusting a first locking or clamping bar for firmly holding the cylinder dressing and a second locking or clamping bar for likewise holding the cylinder dressing, towards one another in a respective tensioning or tautening direction thereof, and to two devices for locking a cylinder dressing on a printing machine cylinder, with a first locking or clamping bar and a second locking or clamping bar.
Such a device is described in the published German Non-prosecuted Patent Application (DE-OS) 21 05 633. In this heretofore known device, a locking or clamping bar for a starting end of a printing plate is displaceable by a screw, and a locking or clamping bar for the ending end of the plate is displaceable by another screw. In practice, however, a single screw for the plate start and a single screw for the plate end are insufficient for uniformly tautening the printing plate over the width or breadth thereof. A respective plurality of screws are arranged next to one another and are tightened in succession by the pressman at the plate start and the plate end, as illustrated in FIG. 3 of the German non-prosecuted application. The multiplicity of operating locations not only make it more difficult to operate the device manually, but also makes it virtually impossible for the device to be automated.
Another such device is described in the published German Prosecuted Application (DE-AS) 22 00 187. In this device, a plurality of adjusting bolts brace a front locking bar against a cylinder gap wall. For locking up a printing plate, the first locking bar is displaced by the adjusting bolts, so that a leading edge of lay marks coincides with a neutral position. The adjustment of the adjusting bolts to be performed in succession by the pressman is similarly as time-consuming as the tightening of the screws of the device described in The published German Non-prosecuted Patent Application (DE-OS) 21 05 633 noted hereinbefore. After the adjusting bolts have been adjusted, the printing-plate leading edge is laid against the leading edge of the lay marks and tightly clamped, and only then is the printing-plate trailing edge introduced into a rear locking bar and tightly clamped. A disadvantage thereof is that no assurance is provided of uniform tautening of the printing plate in the circumferential direction of the plate cylinder, because it is not possible, with this device, to clamp or lock up the printing plate at both ends thereof. So that the neutral position set before tautening is not lost, during the tautening, the printing-plate leading edge is held locally fixed and only the printing-plate trailing edge is pulled. In the case of many printing plates, the somewhat rope-frictionlike effect active between the printing plates and the plate cylinder, cannot be overcome by the clamping at one end, as described, because the tautening or tensioning forces capable of being exerted upon the printing plate are limited by the construction, and because of the risk of tearing or breaking the printing plate.
The published German Patent Document DE 41 34 309 C2 describes a device for positionally accurate quick-action clamping or locking-up a flexible printing plate on a plate cylinder. A front clamping or locking bar of this device is connected laterally to an actuating device formed of a threaded member and a crank fixedly connected thereto. The front clamping or locking bar is displaceable by a thread of the threaded member. The threaded member is not displaceable in a direction axially parallel with the plate cylinder.
The published German Patent Document DE 41 34 365 C2 describes a further device for positionally accurate quick-action clamping or locking-up a flexible printing plate on a plate cylinder. A front clamping bar of the device described in this reference has assigned thereto, in the middle thereof, a center of rotation fixedly disposed in a cylinder gap and, laterally, an actuating device fastened to a machine frame. The actuating device, via an eccentric disposed on a roller lever, engages in an opening formed in a front lower bar, whereon a front clamping bar is fastened. Neither the eccentric nor the roller lever is displaceable in a direction axially parallel to the plate cylinder.
By the devices described in the two last-mentioned German patent documents, namely DE 41 34 309 C2 and DE 41 34 365 C2, therefore, it is not possible to eliminate satisfactorily the disadvantages inherent in the devices described in the two first-mentioned German patent documents, namely the Non-prosecuted Application (DE-OS) 21 05 633 and the Prosecuted Application (DE-AS) 22 00 187.
The German Patent Document DE 42 08 320 A1 describes a method for correcting skewed positions of flexible printing plates on a plate cylinder. According to this method, a rear clamping or locking bar is loosened or unclamped, the position of a front clamping or locking bar is corrected and the rear clamping or locking bar is thereafter reclamped. It is necessary, in this method, to roll a pressure roller or a backup cylinder over the printing plate after the position of the front clamping bar has been corrected. This is time-consuming and presupposes the presence of a pressure roller or a backup cylinder suitable for the purpose.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for locking a cylinder dressing on a printing machine cylinder that is quick-acting and avoids the foregoing disadvantages of heretofore known methods of this general type, and to provide at least one device having few operating locations and by which the method may be performed.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a method for locking a cylinder dressing on a printing machine cylinder, including adjusting a first clamping bar for holding the cylinder dressing, and a second clamping bar for likewise holding the cylinder dressing, towards one another in respective tautening directions thereof, which comprises adjusting the two clamping bars by actuating the same adjusting member, so that, when locking the cylinder dressing, in a first method step, only the first clamping bar is adjusted and, in a second method step, the two clamping bars are adjusted simultaneously.
In accordance with another mode, the method of the invention includes adjusting the two clamping bars towards one another simultaneously, while adjusting the adjusting member in an adjusting direction axially parallel to the printing machine cylinder.
In accordance with a further mode, the method of the invention includes, during tautening, holding the cylinder dressing at the trailing edge thereof by the first clamping bar and at the leading edge thereof by the second clamping bar.
In accordance with a second aspect of the invention, there is provided a device for locking a cylinder dressing on a printing machine cylinder, with a first clamping bar and a second clamping bar, comprising at least one adjusting member adjustable in an adjustment direction axially parallel to the printing machine cylinder for adjusting the two clamping bars in a respective tautening direction thereof, the second clamping bar being supported on the printing machine cylinder via an adjustable stop.
In accordance with another feature of the invention, the adjustable stop is rotatable out of a blocking rotary position wherein the adjustable stop blocks an adjustment of the second clamping bar, into a released rotary position wherein the adjustable stop enables the adjustment of the second clamping bar.
In accordance with a further feature of the invention, the adjustable stop is a two-position eccentric.
In accordance with an added feature of the invention, the first clamping bar is supported on the printing machine cylinder via a spring.
In accordance with a third aspect of the invention, there is provided a device for lockin
Evanisko Leslie J.
Greenberg Laurence A.
Heidelberger Druckmaschinen AG
Locher Ralph E.
Stemer Werner H.
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