Patent Publication Number: US-6662721-B2

Title: Rotary press

Description:
The entire disclosure of Japanese Patent Application No. 2000-138334 filed on May 11, 2000 including specification, claims, drawings and summary is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a rotary press for printing a web, and more specifically, to a rotary press adapted to prevent entrainment of a web during plate changing. 
     2. Description of the Related Art 
     Generally, this type of rotary press is composed of a feeder having a roll comprising a web wound in a roll form, a printing unit having printing cylinders, such as blanket cylinders and plate cylinders, for printing the web fed from the feeder, a dryer for drying the web printed by the printing unit, and a folder for folding the web. When changing a plate in a double-sided four-color printing press having four printing units, for example, the printing press is stopped, and the plate cylinder is rotated by about one turn in normal and reverse directions to remove the old plate from the plate cylinder and mount a new plate on the plate cylinder. 
     When rotating the plate cylinder in the normal and reverse by about one turn, if an as-printed state is maintained, namely, if the web is kept taut between the feeder and the dryer, a heavy load may be imposed on the web between the printing units and the dryer to cause tearing of the web. To prevent this problem, a connection between a drive on the folder side and a drive on the printing unit side is cut off by a clutch, and the printing cylinder is rotated by almost two turns in the normal direction. By this measure, the web is slackened beforehand between the printing units and the dryer. 
     Japanese Unexamined Patent Publication No. 165400/1999 discloses a technique which provides a wrap preventing member (press roller, dancer roller) on a web travel route between a printing unit and a folder (and between a feeder and the printing unit), the wrap preventing member being designed to retreat during printing and advance during plate changing to contact the web, so that a slack portion of the web is pressed downward and stretched under a certain tension by the wrap preventing member. According to this technique, the slack portion of the web is prevented from swaying toward the blanket cylinder or the plate cylinder during plate changing and being caught between the plate cylinder and the blanket cylinder positioned below the web. 
     In the rotary press of the above-described publication, the drive clutch is engaged after completion of plate changing, and the web is discharged toward the folder. However, the pressure of the wrap preventing member during plate changing is so high that the web accumulated at the wrap preventing member on the folder side cannot be discharged. Thus, the pressure of the wrap preventing member was weakened after completion of plate changing so that the web accumulated at the wrap preventing member can be discharged. However, the feed amount of the web fed from the feeder (infeed unit), and the feed amount of the web discharged toward the folder are small. Thus, it takes time to discharge the web accumulated at the wrap preventing member. Depending on the paper quality of the web, etc., moreover, the wrap preventing member still fails to ascend. 
     SUMMARY OF THE INVENTION 
     The present invention has been accomplished in consideration of the above problems with the earlier technology. It is the object of the invention to provide a rotary press in which after plate changing is completed, a wrap preventing member can smoothly ascend regardless of its pressure, and can promptly and smoothly return to the state before plate changing. 
     The present invention, which attains the above object, is a rotary press for printing a web fed from a feeder by a printing unit, comprising a wrap preventing member provided on a travel route for the web downstream from the printing unit, the wrap preventing member being adapted to retreat during printing and advance during plate changing to contact the web, and a pinching member provided on the travel route for the web between the feeder and the printing unit, the pinching member being adapted to support the web in a pinching manner, wherein the wrap preventing member is movable in a retreating direction by the web, with the web being supported in the pinching manner by the pinching member. 
     According to this aspect, after plate changing is completed, the wrap preventing member can smoothly ascend regardless of its pressure, and can promptly and smoothly return to the state in which it was in before plate changing. 
     The wrap preventing member may be a press roller, and may be adapted to move upward and downward in accordance with contraction and extension of an air cylinder for the press roller, the air cylinder being mounted so as to face downward. 
     The air cylinder for the press roller may make a contracting motion when the press roller is detected by a sensor provided at a position at which slackness of the web is small. 
     The press roller may be locked by a locking mechanism when the air cylinder for the press roller is maximally contracted. 
     A second wrap preventing member may be provided on the travel route for the web between the feeder and the printing unit and downstream of the pinching member. 
     The second wrap preventing member may be a second press roller, and may be adapted to move upward and downward in accordance with contraction and extension of an air cylinder for the second press roller, the air cylinder for the second press roller being mounted so as to face downward. 
     The air cylinder for the second press roller may make a contracting motion when the second press roller is detected by a sensor provided at a position at which slackness of the web is small. 
     The second press roller may be locked by a second locking mechanism when the air cylinder for the second press roller is maximally contracted. 
     The pinching member may be composed of a pair of plates, and at least one of the plates may be supported so as to be movable toward and away from the other of the plates. 
     After the wrap preventing member is brought into an advancing state, the web may be pinched by the pinching member; with a pinched state of the web being kept, plate changing may be performed by normal and reverse rotations of plate cylinders; after plate changing is completed, the wrap preventing member may be retreated by the web, and then the pinched state of the web by the pinching member may be released. 
     The wrap preventing member may enter into an advancing state after normal rotation of plate cylinders; then, after the plate cylinders are stopped, a second wrap preventing member, provided on the travel route for the web between the feeder and the printing unit and downstream from the pinching member, may be brought into an advancing state; then, with the web being pinched by the pinching member, plate changing may be performed by normal and reverse rotations of the plate cylinders; and after plate changing is completed, the wrap preventing member and the second wrap preventing member may be retreated by the web, and then the pinched state of the web by the pinching member may be released. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
     FIG. 1 is a schematic constitutional drawing of a principal part of a rotary press showing an embodiment of the present invention; 
     FIG. 2 is an explanatory drawing of a web presser of the rotary press; 
     FIG. 3 is an explanatory drawing of a press roller of the rotary press; and 
     FIG. 4 is a process chart showing the order of actions in the rotary press. 
    
    
     DESCRIPTION OF THE INVENTION 
     Preferred embodiments of the rotary press according to the present invention will now be described in detail with reference to the accompanying drawings, which in no way limit the invention. 
     As shown in FIG. 1, the rotary press has, in the order of printing, a feeder  1 , an infeed unit  2 , a printing unit  3  for printing a web W fed from the infeed unit  2 , and a dryer  4  for drying the web W printed by the printing unit  3 , and also has a cooler for cooling the dried web W, a web path portion, and a folder, although none of the cooler, web path portion, and folder are shown. 
     In the feeder  1 , a roll  5  consisting of the web W wound in a roll form is present together with a spare roll (not shown). 
     In the infeed unit  2 , guide rollers  6 ,  7 ,  8 ,  9  for guiding the web W pulled out of the roll  5  to the printing unit  3  are present. Numeral  10  denotes a tension roller, provided between a pair of guide rollers  6  and  7  arranged in an opposed manner. The tension roller  10  is supported by an air cylinder (not shown) such that the roller  10  freely moves in an upward and downward directions, and is always urged in a downward direction at a constant pressure. Thus, the tension roller  10  prevents slackness of the web W fed from the feeder  1 . Numerals  11  and  12  denote a pair of nip rolls. The upper nip roll  11  freely moves in the upward and downward directions by an air cylinder (not shown). During plate changing, the upper nip roll  11  moves downward, and contacts the lower nip roll  12  at a predetermined nip pressure to keep the feed speed of the web W constant. Numeral  13  denotes a constant position control roller, which is provided between a pair of guide rollers  8  and  9  arranged in an opposed manner, and is also located below these rollers  8  and  9  to impart a tension to the web W constantly. 
     The printing unit  3  has four printing units  3   a ,  3   b ,  3   c , and  3   d . Each of these printing units  3   a ,  3   b ,  3   c , and  3   d  is equipped with a pair of blanket cylinders  14   a  and  14   b  sandwiching the traveling web W, a pair of plate cylinders  15   a  and  15   b  in contact with the blanket cylinders  14   a  and  14   b , and inking devices and dampeners (not shown) for supplying water and ink to the plate cylinders  15   a  and  15   b.    
     In the present embodiment, a first press roller (dancer roller)  20  is provided on a travel route of the web W between the printing unit  3  and the dryer  4 , and is located between a pair of guide rollers  21  and  22  arranged in an opposed manner. The first press roller  20  serves as a wrap preventing member adapted to retreat during printing and advance during plate changing to contact the web W. On the travel route of the web W between the infeed unit  2  and the printing unit  3 , a second press roller (dancer roller)  23 , having the same function as that of the first press roller  20 , is provided between a pair of guide rollers  24  and  25  arranged in an opposed manner. On the travel route of the web W between the infeed unit  2  and the second press roller  23 , a web presser  26  is provided as a pinching member for supporting the web W in a pinching manner. The first press roller  20  and the second press roller  23  are movable by the web W in a retreating direction, with the web W being supported in a pinched manner by the web presser  26 . 
     As shown in FIG. 3, the first press roller  20  and the second press roller  23  are each adapted to move upward and downward, while being guided by a guide shaft  28 , between left and right struts  27   a  and  27   b  as a pair erected on a floor. The upward and downward movements of the press roller  20  or  23  take place in accordance with the contraction and extension of a first air cylinder  29  attached downwardly to the strut  27   b . During printing, the first press roller  20  and the second press roller  23  are positioned and fixed (locked), in the most contracted state of the first air cylinder  29 , namely, at the retreat position of the first press roller  20  and the second press roller  23  (see solid lines in FIG.  3 ), by a locking mechanism which is not shown. The locking mechanism is constituted between a connecting member  30  connected to the front end of the piston rod of the first air cylinder  29 , and the second air cylinder  32  attached laterally to the strut  27   b  via a bracket  31 . The second air cylinder  32  functions via a controller, etc. (not shown). That is, the second air cylinder  32  is adapted to act responsive to a detection signal from a proximity sensor (not shown) for detecting the top limit position of the connecting member  30 , and extend in the ON-state of the detection signal, thereby performing the aforementioned locking action. The above devices for pressing the web W are constituted in the same manner as the device disclosed in the aforementioned Japanese Unexamined Patent Publication No. 165400/1999. Thus, reference to the relevant disclosure in this publication is requested, and a detailed description of the pressing devices is omitted herein. 
     The web presser  26 , as shown in FIG. 2, is composed of an upper fixed plate  26   a  constructed, like a bridge, between left and right struts  33   a  and  33   b  as a pair erected on the floor, and a lower movable plate  26   b  movable toward and away from the upper fixed plate  26   a . Front ends of piston rods of third air cylinders  34   a  and  34   b , attached downwardly to the struts  33   a  and  33   b , respectively, are connected to left and right end portions of the lower movable plate  26   b . Upon extension of the third air cylinders  34   a  and  34   b , the lower movable plate  26   b  approaches the upper fixed plate  26   a  to pinch the web W between the lower movable plate  26   b  and the upper fixed plate  26   a . Upon contraction of the third air cylinders  34   a  and  34   b , the lower movable plate  26   b  moves away from the upper fixed plate  26   a  to release the web W. The third air cylinders  34   a  and  34   b  are adapted to act responsive to cylinder phase detection means of the present printing press via a controller, etc. (not shown), and extend at a predetermined time during plate changing (to be described later), thereby performing the above-mentioned pinching action to the web W. 
     The respective rollers and cylinders, which constitute the aforementioned feeder  1 , infeed unit  2 , printing unit  3 , and dryer  4 , are connected by a drive shaft (not shown), and driven by a drive motor of the present printing press provided at a side of the feeder  1 . A clutch (not shown) is provided between the printing unit  3  and the folder, and can be engaged or disengaged so as to or not to transmit rotation from the motor for driving the present printing press. 
     A routine printing operation of the so constituted printing press will be described. First, the nip roll  11  of the infeed unit  2  is in contact with the nip roll  12 , and the blanket cylinders  14   a  and  14   b  of the printing units  3   a  to  3   d  are also in contact with each other. The first air cylinder  29  contracts and the press roller  20  and  23  are positioned and fixed at the retreat position shown by the solid lines in FIG.  3 . At this time, the second air cylinder  32  extends to make a locking motion. Thus, the press rollers  20 ,  23  do not advance to the travel route for the web W. The third air cylinders  34   a ,  34   b  contract, so that the pinching member  26  does not perform a pinching action. When a button for print start is pushed in this state, the respective rollers and cylinders rotate in the normal direction. The web W pulled out of the roll  5  travels in the direction of an arrow A along the guide roller  6 , tension roller  10 , guide roller  7 , nip rolls  11 ,  12 , guide roller  8 , constant position control roller  13 , and guide roller  9 , and is fed to the printing unit  3 . Even if slackness occurs, at this time, in the web W withdrawn from the roll  5 , the slackness is eliminated by the tension roller  10 . The feed speed of the web W is always kept constant by the nip rolls  11 ,  12 . The web W fed to the printing unit  3  is printed, on its face side and back side, in four colors by means of the four printing units  3   a  to  3   d . Then, the web W is introduced into the dryer  4  to have the printed surfaces dried. 
     Next, a plate changing operation will be described based on FIG.  4 . When a start button for plate changing (automatic plate changer) is pushed in S 1 , the nip roll  11  comes into contact with the nip roll  12  in S 2 . In S 3 , after the contacted blanket cylinders  14   a ,  14   b  of the respective printing units  3   a  to  3   d  are brought out of contact, the drive motor for the printing press is driven to rotate the plate cylinders  15   a ,  15   b  of the printing unit  3  by about two turns in the normal direction. At the same time, the clutch for connecting drive for the printing unit  3  to drive on the folder side is disengaged in S 4 . At this time, a slack portion corresponding to nearly the outer periphery of the plate cylinder  15   a  occurs in the web W located between the printing unit  3  and the dryer  4 . In S 5 , the second air cylinder  32  is contracted to release from the locked state, and then the first air cylinder  29  is extended to lower the first press roller  20 , whereby the slackness of the web W is removed. In S 6 , the plate cylinders  15   a ,  15   b  are stopped. Then, the nip rolls  11 ,  12  are brought out of contact in S 7 . If the nip rolls  11 ,  12  are actuated in an attempt to make the tension of the web W constant during plate changing, the web W may be torn. The step S 7  is performed to exclude the possibility of this web tearing. In S 8 , the second air cylinder  32  is contracted to release the locked state, and then the first air cylinder  29  is extended to lower the second press roller  20  slightly. In S 9 , the third air cylinders  34   a ,  34   b  are extended to pinch the web W by the web presser  26 . In S 10 , plate removal starts, the plate cylinders  15   a ,  15   b  of the printing unit  3  rotate by about one turn in the reverse direction, and the old plate from the plate cylinders  15   a ,  15   b  is removed. At this time, the web W travels in the direction opposite to the direction of the arrow A. Thus, in S 11 , the first press roller  20  ascends upon contraction of the first air cylinder  29 , while the second press roller  23  descends upon extension of the first air cylinder  29 . Thus, although the amount of slackness of the web W increases between the infeed unit  2  and the printing unit  3 , this slackness is eliminated, because the web W is pressed downward by the second press roller  23 . In S 12 , plate removal ends, and the rotation of the plate cylinders  15   a ,  15   b  stops. Then, in S 13 , plate supply starts, the plate cylinders  15   a ,  15   b  rotate by about one turn in the normal direction, and anew plate on the plate cylinders  15   a ,  15   b  is mounted. At this time, the web W travels in the direction of the arrow A. Thus, in S 14 , the first press roller  20  descends upon extension of the first air cylinder  29 , while the second press roller  23  ascends upon contraction of the first air cylinder  29 . Thus, although the amount of slackness of the web W increases between the printing unit  3  and the dryer  4 , this slackness is eliminated, because the web W is pressed downward by the first press roller  20 . 
     As described above, the first and second press rollers  20  and  23  move upward and downward in the opposite directions, so that tearing of the web W ahead of or behind the printing unit  3  can be prevented. The occurrence of slackness is also prevented, so that a slack portion of the web W is not caught by the plate cylinder  15   b  or blanket cylinder  14   b  during a plate changing operation. Furthermore, the second press roller  23  is provided between the infeed unit  2  and the printing unit  3 , thus making it possible to deal with voluntary amount of slackness occurring between the infeed unit  2  and the printing unit  3 . 
     In S 15 , plate supply ends, and the rotation of the plate cylinders  15   a ,  15   b  stops. Then, in S 16 , the printing press is rotated at a slower speed, and the clutch connecting drive for the printing unit  3  and drive for the folder is engaged. Upon engagement of the clutch, the web W travels in the direction of the arrow A, and thus the press rollers  20 ,  23  ascend in S 17 . At this time, the web W is pinched by the web presser  26  at an upstream of the second press roller  23 , whereby the feed of the web W from the infeed unit  2  is cut off. Thus, the first press roller  20  on the folder side involving a large amount of slackness, in particular, ascends smoothly regardless of the pressure of the first air cylinder  29 . In S 18 , the ascent position of the press rollers  20 ,  23  is detected by the proximity sensors (not shown). The position of detection by the proximity sensors is a position at which the slackness of the web W is small. Upon this detection, the first air cylinder  29  is contracted maximally in S 19  to return the press rollers  20 ,  23  to the retreat position. At the same time, the second air cylinder  32  extends to lock the press rollers  20 ,  23  at the retreat position. In S 20 , the third air cylinders  34   a ,  34   b  are contracted to release the web W from the pinching member  26 . In S 21 , the plate changing operation is completed. 
     While the present invention has been described in the foregoing fashion, it is to be understood that the invention is not limited thereby, but may be varied in many other ways. For example, the first air cylinder  29  may be placed below the web W so as to face upward, and may be extended to bring the press rollers  20 ,  23  upward. Moreover, the third air cylinders  34   a ,  34   b  may be arranged above the web W so as to face downward, and may be extended to pinch the web W by the pinching member  26 . Furthermore, the press rollers  20 ,  23  and the web presser  26  (upper fixed plate  26   a , lower movable plate  26   b ) need not be elongated continuously in the axial direction, but may be divided into a plurality of parts in the axial direction. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the appended claims.