Abstract:
A protective device for a printing machine cylinder assures a risk-free flying changeover of printing plates. The protective device includes a rotatable ring that supports a sleeve-shaped cover. The sleeve-shaped cover can be positioned to partially envelop or cover the cylinder at a separation of the cylinder from another cylinder or a roller in the printing machine.

Description:
FIELD OF THE INVENTION 
   The present invention is directed to a protective device for a cylinder of a printing press. The protection device is used for the selective covering of rotating cylinder elements. 
   BACKGROUND OF THE INVENTION 
   A protective device on forme cylinders is known from DE 196 03 666 C2. That protective device is embodied to be pivotable by rotating eccentric bearing bushings. 
   SUMMARY OF THE INVENTION 
   The object of the present invention is directed to providing a protective device for a cylinder of a printing press. 
   In accordance with the present invention, this object is attained by providing a protective device for a cylinder of a printing press that is usable for the selective covering of rotating cylinder elements. The protective device may have a rotatable ring on which a sheath-shaped cover, for the partial covering of a cylinder, is arranged. The cover can be selectively placed into a gap between two cylinders or a gap between a cylinder and a roller. The cover may be provided with its own actuating device. 
   The advantages to be gained by the present invention lie, in particular, in the protection from inadvertent touching of rotating cylinder elements, in the course of printing plate changes, which the protective device provides. The protective device is not connected with eccentric bushings, so that no additional drive mechanism for compensating for different pivot movements is required. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A preferred embodiment of the present invention is represented in the drawings and will be described in greater detail in what follows. 
     Shown are in: 
       FIG. 1 , a schematic end view of a printing group having two plate cylinders which can be brought into and out of contact, wherein the first plate cylinder is in a print-off position, and the associated cover is opened, in 
       FIG. 2 , a schematic end view analogous to  FIG. 1 , with the first plate cylinder in a print-on position and with the cover closed, in 
       FIG. 3 , a schematic end view analogous to  FIG. 1 , with the second plate cylinder in a print-off position, and with the associated cover opened, in 
       FIG. 4 , a cross-section taken along line IV—IV of FIG.  3  through the first plate cylinder, wherein an upper spacing holder  22 , as well as the associated holding roller  17  have been omitted, and in 
       FIG. 5 , a cross section taken along line V—V in accordance with  FIG. 2  in an enlarged partial representation. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring initially to  FIG. 1 , there may be seen a printing group which includes the protective device, generally at  07 , in accordance with the present invention. The printing group, which may be used, for example for flexographic printing, consists of two cylinders  01 ,  02 , each of which can be equipped with printing plates, and which thus are, for example, printing or forme cylinders  01 ,  02 , which can be placed either together or individually against a cylinder  03 , for example a counter-pressure cylinder  03 , as well as a roller  04 , for example a screen roller  04 . The typically individual placement of each of the forme cylinders  01 ,  02  is performed, in each case, by the use of cylinder positioning devices, such as eccentric bearing bushings  06 , as shown in FIG.  4 . In this way, either a print-on position A, or a print-off position B of the forme cylinders  01 ,  02  results. 
   The screen roller  04  is connected with an ink application arrangement, which is not specifically represented. All of the respective cylinders  01 ,  02 ,  03  and the roller  04  can be separately driven, for example by the use of suitable drive motors which are not specifically shown in the several drawings. 
   A protective device  07  for either or both the forme cylinders  01  or  02  consists of a rotatable ring  08 , which is shown most clearly in  FIGS. 4 and 5 , and on which a sheath-shaped or trough-shaped cover  09  is fastened. The cover  09  encloses approximately half of the circumference of the forme cylinder  01  or  02 , as may be seen in  FIGS. 1 ,  2  and  3 . 
   On its interior circumference  11 , the ring  08  has the sheath-shaped cover  09 . On its outer circumference  12 , the ring  08  has two annular tori  13 ,  14 , as seen in  FIG. 5 , which annular tori  13 ,  14  are spaced apart from each other and between which, viewed in the circumferential direction of the ring  08 , a toothed device  16 , or the like, is arranged. 
   The ring  08  is supported by several, for example by four holding rollers  17 , which are arranged evenly distributed over the circumference of the ring  08 . The outer edges of the tori  13 ,  14  act on a roller running surface  18 , which is embodied in the manner of a groove bottom, and which running surface  18  is situated on the circumference of the holding rollers  17 , as seen in FIG.  5 . Lateral walls  19 ,  21  secure the ring  08  supported by the rollers  17  against axial displacement. The holding rollers  17  are supported on the free ends of respective spacing holders  22  in a lateral frame  23 , for example, as is shown most clearly in FIG.  4 . 
   In an out-of-contact position, i.e. in the print-off position B, the periphery of the forme cylinder  01  or  02  is remote from the cover  09  by a minimum distance c, and in a contact position, i.e. in the print-on position A, by a maximum distance d. These two positions and distances are depicted in FIG.  3 . 
   The ring  08  can be rotated manually or by the use of a pinion  24 , which engages the toothed device  16  and which pinion  24  can be driven or rotated, by the use of a drive motor  26  which is fixed in place in the lateral frame. The placement of the drive motor  26  and the pinion  24  is shown most clearly in FIG.  4 . 
   Each cover  09  of the protective device  07  can be rotated between two positions: cover  09  “open” in the position E, or cover  09  “closed” in the position F, each viewed from the operating side of the printing group. A closed position F of an upper cover  09 , and an open position E of a lower cover  09  are shown in FIG.  1 . 
   For exactly fixing the two positions E, F of the cover  09 , limit stop switches, which are not specifically depicted, and which can be fixed in place in the lateral frame, for example, as well as cams which are fixed on the ring, can work together. It is also possible to provide markers fixed on the ring  08  and sensors fixed in place of the lateral frame. 
   The function of the protective device  07  for a printing machine cylinder, in accordance with the present invention, is as follows: 
   Referring initially to the representation in  FIG. 1 , the cylinders  02 ,  03  and the roller  04  rotate in contact with each other, while the first forme cylinder  01  is in the print-off position and the cover  09  associated with the first forme cylinder is in the “open” position E. A plate change can now be performed on cylinder  01  whose cover  09  is in its “open” position. 
   In the representation in  FIG. 2 , all of the cylinders  01 ,  02 ,  03  and the roller  04  rotate in contact with each other. In this case, all of the covers  08  have been rotated into the “closed” position F. 
   In the representation shown in  FIG. 3 , the second forme cylinder  02  is in the print-off position, wherein the cover  09  is in the “open” position E. A plate change can be performed or other work can be done on cylinder  02 . 
   Because of the provision of a suitable locking device, which is not specifically shown, the cover  09  can only be rotated into the position “open” E in the print-off position B of its associated cylinder or roller. 
   It is also possible to use different drive mechanisms for the protective device  07 . For example, toothed belts or the like can be used instead of pinion  24  and motor  26 . 
   It is also conceivable for the cover  09  to have its own actuating drive, which can be operated independently of an actuating drive for bringing a cylinder  01 ,  02  into or out of contact. The cover  09  can be selectively placed into a gap between two cylinders  01 ,  03 ;  02 ,  03 , or into a gap between a cylinder and a roller  01 ,  04 ;  02 ,  04 . 
   In accordance with a second preferred embodiment, which is not specifically represented, in a 10-cylinder satellite printing group two rubber blanket cylinders can each operate against a counter-pressure cylinder in accordance with the imprinter principle. A separate forme cylinder, which can be pivoted in and out, is assigned to each one of the two rubber blanket cylinders. 
   If it is now intended to take one of the two forme cylinders  01 ,  02  out of production, for example for a flying plate change, the respective forme cylinder  01 ,  02  is pivoted away from the associated rubber blanket cylinder and the counter-pressure cylinder, for example by use of eccentric bushings. In this case, each rubber blanket cylinder has its own associated protection device  07 , as described above. The associated protective device  07  can be rotated in such a way that, with the forme cylinder  01 ,  02  stopped and the rubber blanket cylinders rotating, each rubber blanket cylinder is covered in the handling area. 
   Suitably, each cover  09  is supported on both of its ends, typically from the direction of both of the lateral frames. One ring  08 , and the associated holding rollers  17 , are seated fixed in each of the two spaced lateral frames. Only one lateral frame  23  is shown in FIG.  4 . The other of the two lateral frames is essentially the same. 
   While preferred embodiments of a protective device for a printing machine cylinder, in accordance with the present invention, have been set forth fully and completely hereinabove, it will be apparent to one of skill in the art that various changes, in, for example, the overall size of the cylinders, the drives for the cylinders and the like could be made without departing from the true spirit and scope of the present invention which is accordingly to be limited only by the following claims.