Abstract:
Method of influencing ink-trapping behavior of ink-conducting components of a printing unit in a rotary printing press includes disconnecting at a clutch location an inking-unit drive coming from printing-unit cylinders, directly imaging a printing form on a printing-form cylinder within the rotary printing press, and reestablishing the drive connection between the inking unit and the printing-unit cylinders at the clutch location after completing the direct imaging of the printing form; and device for performing the method.

Description:
BACKGROUND OF THE INVENTION 
     FIELD OF THE INVENTION 
     The invention relates to a method of influencing ink-trapping behavior of ink-conducting components of a printing unit in a rotary printing press, and a device for implementing the method. 
     German Patent 23 03 718 which exemplifies the state of the art discloses an ink-supplying arrangement for a printing press, and a method of supplying a rotating printing plate with printing ink. For the purpose of reducing shock in the inking unit and for eliminating slurring in the printed image, a friction drive is provided between rollers of the inking unit, as well as an over-running clutch which engages or becomes active when the speed of the drive is lower than a given working speed. 
     The published German Patent Document DE 28 08 856 C2 discloses an inking-unit drive for a rotary printing press. Provided with this inking-unit drive is a vibrator roller which is disposed between an ink-duct roller and a first ink-transfer roller, and the drive for the entire inking unit results via gearwheels from drive gears of the plate cylinder and/or the blanket cylinder. A drive gear of a lower ink-transfer roller is directly connected to a main drive shaft, whereas all of the remaining driven inking-unit rollers are connected with a drive gear of the plate cylinder. 
     The published German Patent Document DE 18 40 458 A1 discloses a printing press have printing-unit cylinders which are movable forwards in an inching mode for mounting or locking the printing plates. With this construction, it is possible to avoid shocks of a form roller drivable by an adjacent printing-unit cylinder from acting upon the drive elements, by providing a clutch in the vicinity of the gear train connecting the form roller to the adjacent printing-unit cylinder, the clutch being automatically disengageable for operating in the inching mode. 
     Rotary printing presses equipped with units for the direct imaging of the printing forms within the printing units have proven that heating of the printing-form cylinder and the inking unit has extremely undesirable consequences. If the temperature of the printing form or the inking unit is too high as a result of thermal conduction or other forms of heat transfer, the printing form tends to scum, and the ink-trapping behavior thereof deteriorates due to the temperature being too high and due to premature vaporization or evaporation of dampening medium, thus causing a delay in the direct transition into the production printing run. 
     SUMMARY OF THE INVENTION 
     It is accordingly an object of the invention to provide a method and device for influencing ink-trapping behavior which are improved over the prior art particularly in printing presses having units for the direct imaging of printing forms within the respective press during the start-up phase. 
     With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a method of influencing ink-trapping behavior of ink-conducting components of a printing unit in a rotary printing press, which comprises disconnecting at a clutch location an inking-unit drive coming from printing-unit cylinders; directly imaging a printing form on a printing-form cylinder within the rotary printing press; and reestablishing the drive connection between the inking unit and the printing-unit cylinders at the clutch location after completing the direct imaging of the printing form. 
     In accordance with another aspect of the invention, there is provided, in a rotary printing press, a device for performing a method of influencing ink-trapping behavior of ink-conducting components of a printing unit, comprising a clutch system disconnectably connecting at a clutch location an inking-unit drive coming from printing-unit cylinders of the printing unit, the clutch system including an axially acting clutch. 
     In accordance with another feature of the invention, the clutch is of a type actuatable by a pressure medium. 
     In accordance with an alternative feature of the invention, the clutch is an electromagnetically actuatable clutch. 
     In accordance with a further feature of the invention, the clutch is disposed on a shaft of a distributor roller. 
     In accordance with an alternative feature of the invention, the clutch is disposed on a control shaft. 
     In accordance with a concomitant alternative feature of the invention, the clutch is mounted on a journal of a printing-unit cylinder. 
     In the performance of the method steps mentioned hereinbefore, assurance is offered that the temperature of the printing form is kept constant, without any excessive vaporization which would otherwise falsify the set dampening-medium ratio, and with the production of a considerably smaller number of waste copies prior to starting the production run, because the ink-trapping properties of the printing form eliminate scumming. This considerably improves the productivity of a printing press which is equipped accordingly. 
     In a device for performing the method according to the invention, a clutch system at a clutch location includes a clutch operatable in axial direction and subjected to a pressure medium, by means of which the inking unit is disconnectable from the drive. Instead of a clutch to which a pressure medium is applied, it is conceivable to provide an electromagnetically actuated clutch. The respective clutch is disposed on a shaft of a distributor roller or drum. Alternatively, the respective clutch is mounted on a transmission shaft, i.e., a control shaft. 
     Another alternative mounting location for the clutch is the journal of the respective printing-unit cylinder. 
     Other features which are considered as characteristic for the invention are set forth in the appended claims. 
     Although the invention is illustrated and described herein as embodied in a method and device for influencing ink-trapping behavior, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
     The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary sectional view of an inking unit and a printing unit with a clutch system provided, for example, on a distributor roller; 
     FIG. 2 is an enlarged fragmentary view of FIG. 1 showing the clutch thereof actuated by pressure medium; and 
     FIGS. 3 and 4 are fragmentary diagrammatic views of FIG. 1 showing alternative dispositions of the clutch on a control shaft and on a printing-unit cylinder shaft, respectively. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings and, first, particularly to FIG. 1 thereof, there is shown therein an inking unit  1  having inking-unit components, such as, distributor rollers  2  and  3 , for example, which are supported in side walls  4  and  5  of a rotary printing press. Via a distributor-roller drive  6 , motion in an axial direction is imparted to the distributor rollers  2  and  3 . The printing-unit cylinders  8 ,  10  and  12  are illustrated below the inking unit  1 . Of the cylinders, the printing-form cylinder  8  cooperates with a transfer cylinder  10  which, in this case, is a blanket cylinder, the material to be printed is conveyed on the circumference of an impression cylinder  12  shown only diagrammatically. The impression cylinder  12  in the illustrated embodiment has an outer cylindrical surface whereon a plurality of copies may be conveyed, and cooperates at the outer cylindrical surface thereof with a plurality of printing-form cylinders and pairs of blanket cylinders. From the cylinder  12 , the drive of the aforementioned printing-form cylinder  8  and the transfer cylinder  10  takes place via gearwheels  9  and  11  which mesh with one another on the drive side, i.e., the side wall  5 , of the printing press. In order to ensure constant pressing and roll-off conditions between the cylinders  8  and  10 , they are equipped with Schmitz or cylinder bearer rings  13  and  14  rolling off on one another. 
     The imaging units, by means of which a stock of printing-form foils held inside the printing-form cylinder  8  may be conveyed on the circumference of the printing-form cylinder  8  and may be directly imaged in the printing unit, are disposed perpendicularly to the plane of the drawing of FIG.  1  and are therefore not shown. 
     A gearwheel provided on the printing-form cylinder  8  at the operating side of the printing press in the vicinity of the side wall  4  drives the inking unit  1 . That gearwheel meshes with a ratchet wheel  7 . 1  mounted on the control shaft  7 . In the illustrated embodiment, a clutch system  15  is provided on the shaft of the distributor roller  3  and includes a clutch subjected to a pressure medium. During the imaging process of the printing-form cylinder  8 , the inking unit  1  may be disengaged from the drive by means of the clutch and, as a result thereof, does not run dry, thereby eliminating the problem of scumming. The ink balance may be maintained, and the freshly imaged printing form may receive the ink directly from the inking unit without having first to produce a large number of waste copies. 
     Instead of providing the illustrated clutch system  15  on the shaft of the distributor roller  3 , the clutch system  15  may, of course, also be disposed on the control shaft  7 , as shown diagrammatically in FIG. 3, so that the engagement and disengagement, respectively, of the drive of the inking unit  1  may be effected at the ratchet gear  7 . 1 . It is also conceivable to provide the clutch system  15 , instead, on the journal of the printing-form cylinder  8 , as shown in FIG. 4, in order to disconnect the drive of the inking unit  1  and to reestablish it, respectively. 
     FIG. 2 is an enlarged view of the clutch system  15 . 
     Via the ratchet gear  7 . 1 , the drive is transmitted to the distributor roller  3  and therefrom to the inking unit  1 , as mentioned hereinbefore. The clutch system  15  is formed of clutch surfaces  17 . 1  provided on a gearwheel, and clutch surfaces  17 . 2  provided on a clutch bushing  21  which is axially movable on a clutch body  20 . In this regard, the journal of the distributor roller  3  is equipped with an air lead-in  16  for supplying pressure medium to a hollow space formed in the clutch body  20 , thereby bringing the clutch surfaces  17 . 1  and  17 . 2  axially in and out of engagement. With the ratchet gear  7 . 1  of the control shaft  7  in engaged condition, the drive is transmitted from the distributor roller  3  to the gearwheel formed with the clutch surfaces  17 . 1  and which is mounted via bearings  18  and  19  on the journal of the distributor roller  3 . Via the clutch surfaces  17 . 2  provided on the clutch bushing  21 , the drive is transmitted to the clutch body  20  which, via a form-locking or positive connection, is connected to the journal of the distributor roller  3 . In regard to the foregoing, it is noted that a form-locking connection serves to connect two elements together as a result of the shape of the elements themselves, as opposed to a force-locking connection, which locks the elements together due to a force external to the elements. 
     Instead of a pneumatically acting clutch, it is also conceivable to use an hydraulic or an electromagnetic clutch, which would have the same attainable effect.