Patent Publication Number: US-6705227-B2

Title: Recto and verso printing press having upper and lower grippers and gripper pad with common center line

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to a recto and verso printing press. A recto and verso printing press of the general type according to the invention described herein has been disclosed in the published German Patent Document DE 3605523 C2. The printing press possesses a turning device having grippers which are arranged on a gripper shaft in a turning drum and can be changed over from recto or first-form printing to recto and verso or first-form and perfecter printing. In recto printing, the sheet to be printed is clamped between a fixed gripper pad and a main gripper. In verso printing, in order to pick up the trailing edge of the sheet, the main gripper, together with an auxiliary gripper arranged at the side of the main gripper, pivots towards the trailing edge of the sheet and clamps the latter between the auxiliary gripper and the main gripper, which has been widened on one side. After a returning pivoting movement towards the gripper pad, the sheet to be printed is placed on the pad again, clamped by the main gripper, and the auxiliary gripper is lowered into a waiting position. 
     A considerable disadvantage of the heretoforeknown turning device is that, as the auxiliary gripper is closed in relation to the main gripper, there is an introduction of force which is off-center relative to the main gripper support, causing a tilting of the main gripper (due to shaft play). After the return pivoting and the placement of the sheet on the gripper pad, the introduction of force changes from the center of the auxiliary gripper to the center of the pad. 
     A result thereof is a return or backward tilting. The continuous alternating tilting leads firstly to increased wear on the bearing points and secondly to register problems, because the clamped sheets are also tilted and therefore stressed. 
     SUMMARY OF THE INVENTION 
     Starting from the aforementioned prior art, it is an object of the invention to provide a tilt-free gripper arrangement which, both in recto printing and in verso printing, operates with register-maintaining transfer and avoids premature wear, as much as possible. 
     With the foregoing and other objects in view, there is provided, in accordance with the invention, a recto and verso printing press, comprising an upper gripper and a lower gripper, respectively, centrally pivotable with respect to an introduction of force, the upper gripper, in recto printing position thereof, being cooperable with a gripper pad fixed to a cylinder of the printing press, the upper gripper and the lower gripper being arranged centrally in relation to one another and to the gripper pad, and having a common center line. 
     In accordance with another feature of the invention, the upper and the lower gripper are shaft-mounted, and the upper gripper and the lower gripper, respectively, are arranged on separate gripper supports, the gripper supports being positioned coaxially to one another. 
     In accordance with a further feature of the invention, the upper gripper support is of annular construction, and the lower gripper support is constructed as a solid shaft and is mounted concentrically with respect to the upper gripper support. 
     In accordance with an added feature of the invention, the upper gripper is actable upon the upper gripper support, and the lower gripper is actable upon the solid shaft serving as the lower gripper support and being mounted within the upper gripper support. 
     In accordance with an additional feature of the invention, the upper gripper support is mounted on a tube enclosing the solid shaft serving as the lower gripper support concentrically, with an annular gap being defined therebetween. 
     In accordance with yet another feature of the invention, the recto and verso printing press further comprises a plurality of sliding bearings arranged in axial distribution in the annular gap for mounting the lower gripper support formed as the solid shaft. 
     In accordance with yet a further feature of the invention, the lower gripper is threadedly secured to the solid shaft serving as said lower gripper support, via a connection part attached radially to the lower gripper support, and the connection part, with the lower gripper integrally molded on an outer end thereof, being guided outwardly through a radial slot formed in the upper gripper support. 
     In accordance with yet an added feature of the invention, the tube arranged between the upper gripper support and the lower gripper support is also formed with at least one radial slot through which one of the lower gripper and the connection part connected thereto extends. 
     In accordance with yet an additional feature of the invention, the upper gripper support comprises two axially spaced cheeks which are permanently connected to one another. 
     In accordance with still another feature of the invention, the recto and verso printing press further comprises a stop threadedly secured to the tube and being arranged axially between the two cheeks of the upper gripper support for limiting a pivoting movement of the upper gripper. 
     In accordance with still a further feature of the invention, the stop is formed with a flange thereon which serves for cooperating with the connection of the upper gripper support. 
     In accordance with still an added feature of the invention, the recto and verso printing press further comprises a compression spring disposed between the connection of the upper gripper support and the flange of the stop, the compression spring serving for generating a clamping force of the upper gripper. 
     In accordance with still an additional feature of the invention, the stop has a further flange, and an adjusting screw is threadedly secured therein, the adjusting screw serving for cooperating with the connection of the upper gripper support. 
     In accordance with another feature of the invention, the lower gripper is of fork-like construction and, in lowered position, encloses the gripper pad on both sides. 
     In accordance with a further feature of the invention, the gripper pad is of fork-like construction and has two fork prongs. 
     In accordance with an added feature of the invention, the lower gripper is of fork-like construction with three spaced fork prongs, and engages with the central fork prong thereof in a depression formed between the two fork prongs of the gripper pad and, with the two outer fork prongs thereof, encloses the gripper pad laterally. 
     In accordance with a concomitant feature of the invention, the lower gripper has a narrow shape and, overall, the two fork prongs of said gripper pad engage laterally around the lower gripper. 
     As a result of the central, centric association of all the gripper parts in relation to one another and to the gripper pad according to the invention, tilting is prevented, and wear and register faults are avoided. 
     By the novel arrangement of the fork prongs, an advantage is provided that a plurality of format widths of the sheet can be gripped, at least by one fork prong, and, therefore, exposed corners can be held as briefly as possible. The result is fewer turned-over or dog-eared corners, which could be produced by the wind resulting from travel movement during return pivoting. Furthermore, the aforementioned advantage permits a higher rotary speed of the printing press. 
     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 recto and verso printing press, 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 cross-sectional view of an embodiment of a gripper arrangement, in open position, comprising an upper and a lower gripper for a recto and verso printing press; 
     FIG. 2 is a view like that of FIG. 1, showing the upper gripper cooperating with a gripper pad fixed to a cylinder, but the lower gripper still being in the lowered or rest position, in recto printing operation and after return pivoting, respectively; 
     FIG. 3 is a sectional view of FIG. 2, taken along the line III—III in the direction of the arrows; 
     FIG. 4 is another view like those of FIGS. 1 and 2, in the closed position of the upper and lower grippers (during the return pivoting phase of the gripper arrangement); 
     FIG. 5 is a sectional view of FIG. 4, taken along the line V—V in the direction of the arrows; 
     FIG. 6 is a sectional view corresponding to that of FIG. 3 (recto printing operation) of a different embodiment of the gripper arrangement, which has been modified with respect to the embodiment according to FIGS. 3 and 5 in that it has a three-prong/fork-like lower gripper and a two-prong/fork-like gripper pad; 
     FIG. 7 shows the gripper arrangement of FIG. 6 in a sectional view corresponding to that of FIG. 5 (return pivoting phase); 
     FIG. 8 is a sectional view corresponding to those of FIG. 3 or FIG. 6 (recto printing operation) of a further embodiment of the gripper arrangement having a two-prong/fork-like gripper pad and narrow lower gripper; and 
     FIG. 9 is a sectional view of the gripper arrangement of FIG. 8 corresponding to those of FIG.  5  and FIG. 7 (return pivoting phase); and 
     FIG. 10 is a perspective view of the gripper arrangement according to FIGS.  1  and  2 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings and, first, particularly to FIGS. 1 to  5  and  10 , thereof, it is noted that a gripper arrangement overall identified by reference numeral  10  is provided on a turning drum  11  represented only fragmentarily and in phantom. The gripper arrangement  10  has an upper gripper  12  and a lower gripper  13 , which are mounted so that they can be pivoted about a common axis  14  lying parallel to the non-illustrated axis of rotation of the turning drum  11 . A significant special feature here resides in the fact that the upper gripper  12  and the lower gripper  13  act upon two gripper supports  15  and  16  mounted concentrically with respect to one another on the turning drum  11 . The upper gripper support  15 , which bears the upper gripper  12 , is of approximately annular construction, and the lower gripper support  16 , which bears the lower gripper  13 , is constructed as a solid shaft. The upper gripper support  15  bearing the upper gripper  12  is mounted on a tube  21  which has a radial spacing (note the annular gap  22 ) from the lower gripper support  16 , i.e., the solid shaft. In the annular gap  22 , a plurality of axially distributed sliding bearings B are seated for mounting the solid shaft  16  in the tube  21 . 
     The upper gripper  12  and the lower gripper  13  are connected to the respective gripper supports  15  and  16  by cheese-head screws  17  and  18 , respectively. The upper gripper  12  is screwed onto the upper gripper support  15  by a connecting part  19  integrally molded radially/tangentially on the outer circumference of the upper gripper support  15 , while the lower gripper  13  has a connecting part  20  connected thereto integrally, which acts radially on the circumference of the lower gripper support  16  (the solid shaft) via the cheese-head screw  18 . The connecting part  20 , and therefore also the lower gripper  13 , projects outwardly through radial slots  23  and  24  formed in the tube  21  and the upper gripper support  15 , respectively. This permits the two grippers  12  and  13  to pivot relative to one another about the common axis  14 . 
     As is believed to be apparent in particular from FIG. 10, the upper gripper support  15  is made up of two axially spaced annular cheeks  45  and  46 , which are permanently connected to one another at three locations  47 ,  48  and  49 . 
     Situated axially between the two cheeks  45  and  46  of the upper gripper support  15  is a partially annular stop  25 , which is permanently connected to the tube  21  by two screws  26  and  27 . The stop  25  serves for limiting the pivoting movement of the upper gripper  12 . For this purpose, the stop  25  has a flange  28 , which cooperates with the connection location  47 . A compression spring  50  arranged between the connection location  47  and the flange  28  serves for producing the clamping force of the upper gripper  12 . 
     At the other or lower end of the stop  25 , a further flange  29  is formed, into which an adjusting screw  30  is screwed, which cooperates with the connection location  48  on the upper gripper support  15 . The adjusting screw  30  serves for adjusting the opening and closing times, respectively, of the grippers  12  and  13 . 
     The gripper arrangement resulting in particular from FIGS. 1,  2  and  10  is overall rotatably mounted at a plurality of non-illustrated bearing locations arranged axially in relation to one another. 
     The upper gripper  12  is provided for cooperating with the lower gripper  13 , conceived and arranged appropriately (note the gripper position in FIGS.  4  and  5 ). The upper gripper  12 , however, also cooperates with a gripper pad  31  (note the gripper position according to FIGS.  2  and  3 ). The gripper pad  31  is fixed by a screw  32  to a pad holder  33 , which is permanently connected to the turning drum  11 . 
     In the gripper position according to FIGS. 2 and 3, which is assumed in the recto printing operation of the press, the lower gripper  13  which, as FIGS. 3 and 10 show, is of fork-like construction and has two fork prongs  34  and  35 , is located in the lowered position as a result of a corresponding rotation of the second shaft  16  in the direction of the arrow  36  (note FIG.  2 ). In this regard, the fork prongs  34  and  35  of the lower gripper  13  engage laterally around the gripper pad  31  (note FIG.  3 ). A sheet  37  is shown disposed on the turning drum  11  and, in this case, is held thereon by being clamped between the upper gripper  12  and the gripper pad  31 . 
     FIGS. 4 and 5 illustrate the last phase of the return pivoting movement of the gripper arrangement  10  before the turning operation of the sheet  37  has been completed. The gripper arrangement  10  had previously carried out a pivoting movement through about 160° in clockwise direction, as shown by arrow  38  and, in this position between the upper gripper  12  and the lower gripper  13 , had picked up the trailing end of the sheet  37  from a non=illustrated preceding cylinder rotating in counterclockwise direction, in order to transfer the sheet  37  to the turning drum  11  rotating in clockwise direction, i.e., the direction of the arrow  51 , as can be seen from FIG.  2 . The sheet turning operation, as such, is otherwise heretofore known prior art in recto and verso printing presses, so that providing a detailed outline of the turning operation herein is believed to be superfluous. 
     In order to attain the closed position of the gripper arrangement  10  illustrated in FIGS. 4 and 5, wherein, as opposed to the open position of the gripper arrangement  10  according to FIGS. 2 and 3, the lower gripper  13  has been pivoted to such an extent that it cooperates with the upper gripper  12 , the (inner) solid shaft  16 , i.e., the lower gripper support, which bears the lower gripper  13 , must have been pivoted through an appropriate angle, in the direction of arrow  39 , relative to the upper gripper support  15  connected to the upper gripper  12 . 
     In the embodiment according to FIGS. 6 and 7, the special feature is provided by the lower gripper  13   a  having three fork prongs  40 ,  41  and  42 , and also the gripper pad  31   a  being of fork-like construction, but only having two fork prongs  43  and  44 . On the other hand, the upper gripper  12  corresponds to the embodiment according to FIGS. 1 to  5 . 
     The embodiment according to FIGS. 8 and 9 differs from the embodiments described hereinbefore with respect to the special feature thereof in that, although the gripper pad  31   b  is of fork-like/two-pronged construction, similar to that in the embodiment according to FIGS. 6 and 7, the lower gripper  13   b  has a narrow shape, so that in the lowered position thereof shown in FIG. 8, wherein the sheet  37  is clamped between the upper gripper  12  and the gripper pad  31   b,  both of the fork prongs  43   b  and  44   b  engage laterally around the lower gripper  13   b.    
     In particular, FIGS. 3,  5 ,  6 ,  7 ,  8  and  9  show that the gripper elements, such as the upper gripper, the lower gripper and the gripper pad, have a common center line  52 . Due to this feature, tilting, wear and register faults are prevented. 
     In this case, the common center line  52  extends perpendicularly to the axis of the gripper shaft.