Printing – Flexible-sheet-securing devices
Reexamination Certificate
1999-11-15
2002-02-12
Hilten, John S. (Department: 2854)
Printing
Flexible-sheet-securing devices
C101S382100
Reexamination Certificate
active
06345575
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a pivotable printing-form changing device for simply and rapidly changing printing forms to be fed to and removed from a cylinder, and to a method for changing printing forms.
The published European Patent Document EP 0 678 382 A1 discloses a device for replacing printing forms for rotary printing machines, especially in web-fed rotary printing machines for printing both sides of a web. Provided on these machines is at least one printing unit that accommodates at least one printing mechanism and a printing-form cylinder taking up the ends of a printing form wound around the surface of the cylinder. This cylinder has clamping devices within a gap and has assigned thereto a discharge device for the printing form that has been released from the plate cylinder and is to be changed, and a feed device for printing forms or plates which are to be newly affixed to the surface of the form cylinder. To the printing-form cylinder of a lower printing mechanism of a printing unit, there is assigned both a pivotable holder and feeder for new printing forms, and a pivotable holder for the printing forms to be removed from the form cylinder, the latter holder serving to pick up and release the printing forms in a downwardly hanging attitude.
The published European Patent Document EP 0 678 383 A1 is concerned with a device for exchanging printing plates in rotary printing machines. A printing unit of a rotary printing machine includes a printing-form or plate cylinder that takes up the two ends of a printing form or plate in a gap, the surface of the printing form or plate being wound around the cylinder, a device accommodating the printing form, that is located at the then time on the printing-form cylinder, after the printing form has been released by the clamping devices of the printing-form cylinder, as well as a device for feeding a new printing form to the printing-form cylinder. The latter device is distinguished by the fact that, at a slight distance from the outer surface of the printing-form cylinder, horizontally movable holding elements fix the leading edge of a printing form to be fed, until a remotely-controlled, engageable pivotable holder throws the leading edge of the printing form to be fed onto the outer surface of the printing-form cylinder.
In the two aforementioned constructions from the respective published German Patent Documents EP 678 383 A1 and EP 678 382 A1, the printing forms slide over suction cups during the clamping movement thereof on the form cylinder. This requires the rear surface of the printing forms which are to be drawn onto the cylinder to have a lubricating film provided thereon. Because this remains an activity that is largely performed manually, however, the lubricating film is not applied uniformly over the rear of the form. Furthermore, after a time, the lubricant is deposited or transferred onto the circumferential surface of the form cylinder and imparts sliding properties thereto which are undesirable and, moreover, necessitate frequent cleaning of the circumferential surface of the form cylinder. Furthermore, the suction cups required here for fixing the rear of the printing forms need an adequate vacuum to ensure the correct functioning of the suction cups. This embodiment calls for a large number of vacuum pumps and, therefore, requires a considerable outlay or expense to provide the vacuum.
The published European Patent Document EP 0 712 725 A2 is concerned with a rolling element for pressing a flexible printing form onto the form cylinder. The rolling element serves to press a flexible printing form onto the form cylinder of a printing unit of a rotary printing machine during a printing-form change. The rolling element includes a number of rollers which are arranged along the circumference of the form cylinder and can be set individually onto the latter. One or more first rollers can be set onto the form cylinder during the mounting of the printing form, and one or more second rollers can be set onto the form cylinder during the removal of the printing form, in the region of the printing form.
The published European Patent Document EP 0 667 237 A1 has disclosed an automated printing-form changing device. In this device for automatically changing printing forms in a printing machine, conceived for a sheet-fed printing machine, a printing form to be fed to the form cylinder is conveyed between driven transport rollers and backpressure rollers. The correspondingly driven transport rollers and the corresponding backpressure rollers are mounted so as to be movable in the axial direction of the form cylinder.
Finally, reference should be made to the published German Patent Document DE 39 40 795 C2 which discloses a method and a device for automatically feeding and removing a printing form, respectively. On a rotary printing machine, the start of the printing form and the end of the printing form are fixed on the form cylinder. The printing form is placed in a storage chamber in a printing form feed and removal device, respectively. The form cylinder is then rotated into a printing form feed position, and the printing form is fed to the clamping device of the form cylinder. In order to remove the printing form, the form cylinder is rotated into a form loosening position, and the clamping element for gripping the printing form end is opened. The form cylinder is then rotated backwards into the printing form feed position, and a clamping flap for gripping a printing form start is opened. The printing form is fed to the storage chamber of the printing form feed and removal device, respectively.
In the heretofore known devices of this general type, not just the leading edge alone, but both the leading edge and the trailing edge of a respectively new printing form are inserted into the cylinder gap. A separate pressure roller is required for this and, during the operation wherein the printing forms are clamped onto the form cylinder, a throw-on or retaining force is necessary, i.e., the delivery rollers, the pressure rollers, and so forth, have to be provided with controllable drives.
SUMMARY OF THE INVENTION
In view of the foregoing prior art, it is an object of the invention to provide a pivotable printing-form changing device configured for respectively feeding printing forms to a form cylinder and removing printing forms from a form cylinder while avoiding any requirement for additional backpressure, pressure or transport rollers.
With the foregoing and other objects in view, there is provided, in accordance with a first aspect of the invention, a device for changing printing forms on form cylinders of rotary printing machines, having a pivotable surface for guiding the printing forms to be changed, which are grippable at an underside thereof, comprising a pivotable printing-form table to which a separately actuatable contact member is assigned, the contact member being throwable onto a surface of a printing form disposed on the printing-form table for positioning the printing form in any selective position.
In accordance with another feature of the invention, the changing device includes a lever extension, the printing-form table and the lever extension being pivotable about a common pivot axis.
In accordance with a further feature of the invention, the changing device includes a separate actuating unit assigned to the printing-form table.
In accordance with an added feature of the invention, the changing device includes an independent actuating unit assigned to the separately actuatable contact member.
In accordance with an additional feature of the invention, the changing device includes separate actuating units, respectively, assigned to the printing-form table and to the contact member, respectively, at least one of the actuating units being constructed as a piston/cylinder unit.
In accordance with an alternative feature of the invention, the changing device includes separate actuating units, respectively, assigned to the printing-form table and to the contact memb
Greenberg Laurence A.
Heidelberger Druckmaschinen AG
Hilten John S.
Lerner Herbert L.
Nguyen Anthony H.
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