Patent Publication Number: US-6901860-B2

Title: Printing machine

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a printing machine for making a printing plate by recording and developing an image on the plate, and thereafter printing the image by feeding ink to the plate. 
     2. Description of the Related Art 
     In an ordinary conventional printing machine, a prepress process is carried out first to make a printing plate by exposing the plate placed in contact with a film having a binary black and white image recorded thereon. Then, the plate is loaded into a printing apparatus to carry out a printing process. 
     Recently, printing machines commonly called digital printers have been proposed, one such printer being capable of performing both the prepress process and printing process. A digital printer, as described in U.S. Pat. No. 6,050,188, for example, employs a “computer-to-plate” system for forming an image on a printing plate by directly scanning and exposing the plate with laser beams or the like modulated with image signals. 
     A printing machine as described in U.S. Pat. No. 6,050,188 has, arranged in the same space, plate cylinders for holding printing plates mounted peripherally thereof, blanket cylinders with blankets mounted peripherally thereof, an impression cylinder, image recorders for recording images on the printing plates mounted peripherally of the plate cylinders, and ink feeders for feeding inks to the printing plates mounted peripherally of the plate cylinders. A recording head is disposed close to each plate cylinder for recording images on the printing plate mounted peripherally of the plate cylinder. 
     In the printing machine capable of performing both the prepress process and printing process described above, the recording head is disposed around each plate cylinder even at a printing time. Mists and particles of the inks, water, paper and so on floating in the printing machine tend to adhere to the recording head, The quantity of light for recording could thereby be reduced to record defective images. This results in the inconvenience of having to clean the recording head periodically. 
     SUMMARY OF THE INVENTION 
     The object of this invention, therefore, is to provide a printing machine that minimizes adhesion to a recording head of inks, water, paper particles and so on, thereby to reduce the frequency of cleaning the recording head. 
     The above object is fulfilled, according to this invention, by a printing machine for recording an image on a printing plate, and printing the image by using the printing plate with the image recorded thereon, comprising a plate cylinder for supporting a printing plate as mounted peripherally thereof, an image recorder having a recording head movable along a surface of the plate cylinder in a direction parallel to an axis of rotation of the plate cylinder for recording an image on the printing plate mounted peripherally of the plate cylinder, an ink feeder for feeding ink to the printing plate mounted peripherally of the plate cylinder and having the image recorded by the image recorder, and a moving device, operable at a printing time, for moving the recording head to a retreat position sideways from a moving region where the recording head is moved at an image-recording time. 
     This printing machine, with the moving device operable at a printing time for moving the recording head to the retreat position sideways from the moving region where the recording head is moved at an image-recording time, can prevent adhesion to the recording head of inks, water, paper particles and so on. Thus, the frequency of cleaning the recording head may be reduced. 
     In one preferred embodiment, the printing machine has a shielding plate disposed between the moving region and the retreat position, and defining an opening for allowing passage of the recording head. 
     Preferably, the shielding plate is a side plate for rotatably supporting the plate cylinder. 
     In one preferred embodiment, the printing machine has a gas flow forming device for forming a gas flow directed from the retreat position toward the moving region. 
     Preferably, the gas flow forming device includes a chamber for enclosing the recording head moved to the retreat position, the chamber defining an opening opposed to the moving region for allowing passage of the recording head, and a fan for drawing a gas from outside the printing machine into the chamber. 
     Other features and advantages of the invention will be apparent from the following detailed description of the embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For the purpose of illustrating the invention, there are shown in the drawings several forms which are presently preferred, it being understood, however, that the invention is not limited to the precise arrangement and instrumentalities shown. 
         FIG. 1  is a schematic view of a printing machine according to this invention; 
         FIG. 2  is a perspective view of a principal portion of an image recorder in a first embodiment of this invention; 
         FIG. 3  is a perspective view of a principal portion of an image recorder in a second embodiment of this invention; 
         FIG. 4  is a perspective view of a principal portion of an image recorder in a third embodiment of this invention; 
         FIG. 5  is a perspective view of a principal portion of an image recorder in a fourth embodiment of this invention; 
         FIG. 6  is a schematic side view showing movement of a recording head of the image recorder in the fourth embodiment; 
         FIG. 7  is a perspective view of a principal portion of an image recorder in a fifth embodiment of this invention; and 
         FIG. 8  is a schematic sectional view showing a chamber interior of the image recorder in the fifth embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of this invention will be described hereinafter with reference to the drawings.  FIG. 1  is a schematic view of a printing machine according to the invention. 
     This printing machine makes printing plates by recording and developing images on blank plates mounted on first and second plate cylinders  11  and  12 , feeds inks to the plates having the images recorded thereon, and transfers the inks from the plates through first and second blanket cylinders  13  and  14  to printing paper mounted on an impression cylinder  15 , thereby printing the images on the printing paper. 
     The first blanket cylinder  13  is contactable with the first plate cylinder  11 , while the second blanket cylinder  14  is contactable with the second plate cylinder  12 . The impression cylinder  15  is contactable with the first and second blanket cylinders  13  and  14  in different positions. The machine further includes a paper feed cylinder  16  for transferring printing paper supplied from a paper magazine  27  to the impression cylinder  15 , a paper discharge cylinder  17  with chains  19  wound thereon and on a sprocket  18  for discharging printed paper from the impression cylinder  15  to a paper discharge station  28 . 
     The impression cylinder  15  contactable by the first and second blanket cylinders  13  and  14  has half the diameter of the first and second plate cylinders  11  and  12  and the first and second blanket cylinders  13  and  14 . Further, the impression cylinder  15  has a gripper, not shown, for holding and transporting the forward end of printing paper. 
     The paper feed cylinder  16  disposed adjacent the impression cylinder  15  has the same diameter as the impression cylinder  15 . The paper feed cylinder  16  has a gripper, not shown, for holding and transporting the forward end of each sheet of printing paper fed from the paper magazine  27 . When the printing paper is transferred from the feed cylinder  16  to the impression cylinder  15 , the gripper of the impression cylinder  15  holds the forward end of the printing paper which has been held by the gripper of the feed cylinder  16 . 
     The paper discharge cylinder  17  disposed adjacent the impression cylinder  15  has the same diameter as the impression cylinder  15 . The discharge cylinder  17  has a pair of chains  19  wound around opposite ends thereof. The chains  19  are interconnected by coupling members, not shown, having grippers arranged thereon. When the impression cylinder  15  transfers the printing paper to the discharge cylinder  17 , one of the grippers of the discharge cylinder  17  holds the forward end of the printing paper having been held by the gripper of the impression cylinder  15 . With movement of the chains  19 , the printing paper is discharged to the paper discharge station  28 . 
     The impression cylinder  15  is connected to a drive motor  10  through a belt  22 . The impression cylinder  15 , feed cylinder  16 , discharge cylinder  17  and first and second blanket cylinders  13  and  14  are connected to one another through gears attached to ends thereof, respectively. Further, the first blanket cylinder  13  is connected to the first plate cylinder  11 , and the second blanket cylinder  14  to the second plate cylinder  12  by gears attached to ends thereof, respectively, when the first and second blanket cylinders  13  and  14  are in printing positions described hereinafter. Thus, the drive motor  10  rotates the feed cylinder  16 , impression cylinder  15 , discharge cylinder  17 , first and second blanket cylinders  13  and  14 , and first and second plate cylinders  11  and  12  synchronously with one another. 
     The first plate cylinder  11  has, arranged therearound, an ink feeder  20   a  for feeding black ink (K), for example, to a plate, an ink feeder  20   b  for feeding magenta ink (M) to a different plate, and dampening water feeders  21   a  and  21   b  for feeding dampening water to the plates. The second plate cylinder  12  has, arranged therearound, an ink feeder  20   c  for feeding cyan ink (C) to a plate, an ink feeder  20   d  for feeding yellow ink (Y) to a different plate, and dampening water feeders  21   c  and  21   d  for feeding dampening water to the plates. 
     Further, the first and second plate cylinders  11  and  12  have, arranged therearound, a plate feeder  23  for feeding plates to the periphery of the first plate cylinder  11 , a plate feeder  24  for feeding plates to the periphery of the second plate cylinder  12 , an image recorder  25  for recording images on the plates mounted peripherally of the first plate cylinder  11 , an image recorder  26  for recording images on the plates mounted peripherally of the second plate cylinder  12 , and a plate discharger  29  common to the first and second plate cylinders  11  and  12 . 
     Each of the image recorders  25  and  26  includes a recording head moving mechanism for moving a recording head to a retreat position. The recording head moving mechanism will be described in detail hereinafter. 
     In the printing machine having the above construction, a printing plate drawn from a supply cassette  31  in the plate feeder  23  is cut to a predetermined size by a cutter  32 . A forward end of the printing plate cut into sheet form is guided by guide rollers and a guide member, and clamped by a clamping jaw on the first plate cylinder  11 . Then, the first plate cylinder  11  is rotated by a motor, whereby the printing plate is wound peripherally of the first plate cylinder  11 . The rear end of the printing plate is clamped by a different clamping jaw. While, in this state, the first plate cylinder  11  is rotated at low speed by the motor, the image recorder  25  irradiates the surface of the plate mounted peripherally of the first plate cylinder  11  with a modulated laser beam for recording an image thereon. 
     Similarly, a printing plate drawn from a supply cassette  33  in the plate feeder  24  is cut to a predetermined size by a cutter  34 . A forward end of the printing plate cut into sheet form is guided by guide rollers and a guide member, and clamped by a clamping jaw on the second plate cylinder  12 . Then, the second plate cylinder  12  is rotated by a motor, whereby the printing plate is wound peripherally of the second plate cylinder  12 . The rear end of the printing plate is clamped by a different clamping jaw. While, in this state, the second plate cylinder  12  is rotated at low speed by the motor, the image recorder  26  irradiates the surface of the plate mounted peripherally of the second plate cylinder  12  with a modulated laser beam for recording an image thereon. 
     The first plate cylinder  11  holds two printing plates mounted peripherally thereof, one for printing in the black ink and the other in the magenta ink. These two printing plates are arranged in evenly separated positions, i.e. in positions separated from each other by 180 degrees. The image recorder  25  records images on these printing plates. Similarly, the second plate cylinder  12  holds two printing plates mounted peripherally thereof, one for printing in the cyan ink and the other in the yellow ink. These two printing plates also are arranged in evenly separated positions. The image recorder  26  records images on these printing plates to complete a platemaking process. 
     The platemaking process is followed by a printing process for printing the printing paper with the plates mounted on the first and second plate cylinders  11  and  12 . The printing process is carried out as follows. 
     First, each dampening water feeder  21   a ,  21   b ,  21   c ,  21   d  and each ink feeder  20   a , 20   b , 20   c ,  20   d  are placed in contact with only a corresponding one of the plates mounted on the first and second plate cylinders  11  and  12 . Consequently, dampening water and inks are fed to the plates from the corresponding water feeders  21   a ,  21   b ,  21   c ,  21   d  and ink feeders  20   a ,  20   b ,  20   c ,  20   d , respectively. The inks fed to the plates are transferred to the first and second blanket cylinders  13  and  14 , respectively. 
     Then, the printing paper is fed to the paper feed cylinder  16 . The printing paper is subsequently passed from the paper feed cylinder  16  to the impression cylinder  15 . The impression cylinder  15  continues to rotate in this state. Since the impression cylinder  15  has half the diameter of the first and second plate cylinders  11  and  12  and the first and second blanket cylinders  13  and  14 , the black and cyan inks are transferred to the printing paper wrapped around the impression cylinder  15  in its first rotation, and the magenta and yellow inks in its second rotation. 
     The forward end of the printing paper printed in the four colors is passed from the impression cylinder  15  to the paper discharge cylinder  17 . This printing paper is transported by the pair of chains  19  to the paper discharge station  28  to be discharged therein. 
     Upon completion of the printing process, the plates used in the printing are discharged to the plate discharger  29 . Then, the first and second blanket cylinders  13  and  14  are cleaned by a blanket cleaning unit, not shown, to complete the printing process. 
     In such a printing machine as described above, where the recording heads of the image recorders  25  and  26  are arranged close to the first and second plate cylinders  11  and  12  at a printing time, mists and particles of the inks, water, paper and so on floating in the printing machine tend to adhere to the recording heads. In this printing machine, therefore, the recording head moving mechanism moves each recording head to a retreat position at a printing time. 
     The construction of the image recorders  25  and  26  will be described hereinafter.  FIG. 2  is a perspective view showing a principal portion of the image recorder  25  in the printing machine according to a first embodiment of this invention. 
     The image recorder  26  has the same construction as the image recorder  25 , and will not particularly be described. 
     The image recorder  25  includes a recording head  201  and a recording head moving mechanism  202 . The recording head moving mechanism  202  has a support member  204  extending between a pair of side plates  209  rotatably supporting the first plate cylinder  11  through bearings  230 , a pair of guide rails  208  fixed to a side surface of the support member  204 , and a ball screw  207  extending parallel to the guide rails  208 . The pair of guide rails  208  and the ball screw  207  are parallel to an axis  231  of the first plate cylinder  11 . The ball screw  207  is connected through a speed reducer  205  to a motor  206  fixed an end of the support member  204 . The ball screw  207  is meshed with a nut  211  attached to a support plate  210  supporting the recording head  201 . Thus, the motor  206  is operable to rotate the ball screw  207 , thereby to move the recording head  201  parallel to the axis  231  of the first plate cylinder  11 . 
     In time of recording an image, this recording head moving mechanism  202  moves the recording head  201  at constant speed through a moving region  220  between a recording start position A shown in solid lines in  FIG. 2 and a  recording finish positions B shown in phantom lines to record the image on the printing plate mounted peripherally of the plate cylinder  11 . After recording the image, the recording head  201  is moved to a retreat position  221  shown in phantom lines C in  FIG. 2 , which is displaced sideways from the moving region  220 . The recording head  201  is kept on standby in the retreat position  221  until a next image recording time. 
     By keeping the recording head  201  on standby in the retreat position  221  at a printing time, the above printing machine minimizes the chance of the recording head  201  being contaminated by the inks, water, paper particles and so on dispersed in the printing machine. 
     Other embodiments of this invention will be described next.  FIG. 3  is a perspective view showing a principal portion of an image recorder  25  in the printing machine according to a second embodiment of this invention. In the following description, like reference numerals are used to identify like parts which are the same as in the first embodiment and will not particularly be described again. 
     The image recorder  25  in the second embodiment, as does the image recorder  25  in the first embodiment, includes a recording head  201  and a recording head moving mechanism  202 . 
     The image recorder  25  in the second embodiment further includes a chamber  203  for enclosing the recording head  201  moved to the same retreat position as in the first embodiment, and defining an opening, not shown, opposed to the moving region  220  for passage of the recording head  201 , a shielding door  212  for opening and closing the opening  212 , and a door moving mechanism  213  for moving the shielding door  212  between opening and closing positions. The chamber  203  is disposed on an extension of the direction of movement of the recording head  201 , and laterally outwardly of one side plate  209 . 
     The door moving mechanism  213  includes a pair of guide rails  217  attached to the side plate  209  adjacent the chamber  203 , a rack  214  fixed to a side surface of the shielding door  212 , and a pinion  216  engaged with the rack  214 . The pair of guide rails  217  extend perpendicular to the direction of movement of the recording head  201  and parallel to the rack  214 . The pinion  216  is attached to a rotary shaft of a motor  215 . With the door moving mechanism  213  having the above construction, the pinion  216  is rotatable by the motor  215  to move the rack  214  engaged with the pinion  216 , thereby to move the shielding door  212  in directions perpendicular to the direction of movement of the recording head  201 . 
     This printing machine can further reduce the chance of the recording head  201  being contaminated by the inks, water, paper particles and so on dispersed in the printing machine, with the shielding door  212  closing the opening formed for passage of the recording head  201  at least when the recording head  201  is in the retreat position  221 . 
       FIG. 4  is a perspective view showing a principal portion of an image recorder  25  in the printing machine according to a third embodiment of this invention. 
     The image recorder  25  in the third embodiment, as does the image recorder  25  in the second embodiment, includes a recording head  201 , a recording head moving mechanism  202  and a chamber  203 . 
     However, the image recorder  25  in the third embodiment does not include the shielding door  212  or door moving mechanism  213 . The chamber  203  of the image recorder  25  has a gas intake fan  218 . The fan  218  draws air as a gas from outside the printing machine into the chamber  203 , and feeds the air from the chamber  203  to the interior of the printing machine through the opening for the opening for passage of the recording head  201 . Thus, air currents are formed to flow from outside to inside of the printing machine. 
     Preferably, the fan  218  draws fresh air from outside the printing machine through an air duct not shown. The fan  218  need not be driven at all times, but will serve the purpose if driven at least during a printing operation. 
     In this printing machine, the air currents from outside to inside of the printing machine prevent the inks, water, paper particles and so on dispersed in the printing machine from entering the retreat position  221 . This feature can further reduce the chance of the printing machine being contaminated by the inks, water, paper particles and so on. 
       FIG. 5  is a perspective view showing a principal portion of an image recorder  25  in the printing machine according to a fourth embodiment of this invention.  FIG. 6  is a schematic side view showing movement of a recording head  201  of the image recorder  25  in the fourth embodiment. 
     The image recorder  25  in the fourth embodiment, as does the image recorder  25  in the second embodiment, includes a recording head  201 , a recording head moving mechanism  202  and a chamber  203 . 
     However, the image recorder  25  in the fourth embodiment does not include the door moving mechanism  213 . The recording head  201  has a shielding door  212  attached to a position thereof opposed to the moving region  220  when the recording head  201  is in the chamber  203 . Thus, the shielding door  212  is movable with the recording head  201  to close the opening for passage of the recording head  201  when the recording head  201  is in the chamber  203 . 
     As shown in  FIG. 6 , the shielding door  212  has shock absorbing elements  240  such as sponges attached to positions thereof opposed to the recording head  201 . Even when the shielding door  212  collides with the side plate  209  or chamber  203  in closing the passage opening, the impact of collision is absorbed to avoid damage to the machine. 
     The above printing machine can close the opening for passage of the recording head  201 , without providing the door moving mechanism  213 , when the recording head  201  in the retreat position  221 . This simple construction effectively reduces the chance of the recording head  201  being contaminated by the inks, water, paper particles and so on dispersed in the printing machine. 
       FIG. 7  is a perspective view of a principal portion of an image recorder  25  in the printing machine according to a fifth embodiment of this invention.  FIG. 8  is a schematic sectional view showing a chamber interior of the image recorder  25  in the fifth embodiment. 
     The image recorder  25  in the fifth embodiment, as does the image recorder  25  in the second embodiment, includes a recording head  201 , a recording head moving mechanism  202  and a chamber  203 . 
     However, the image recorder  25  in the fifth embodiment does not include the door moving mechanism  213 . A gas jet nozzle  250  is connected to an air compressor not shown, to form an air curtain (a flow in the direction of an arrow shown in  FIG. 8 ) along an opening of the chamber  203  as a barrier between the retreat position  221  and moving regions  220 . The gas flow delivered from the gas jet nozzle  250  prevents movement of the inks, water, paper particles and so on between the retreat position  221  and moving regions  220 . 
     The above printing machine can block flow of the inks, water, paper particles and so on between the retreat position  221  and moving regions  220 , without providing the door moving mechanism  213 . This simple construction effectively reduces the chance of the recording head  201  in the retreat position  221  being contaminated by the inks, water, paper particles and so on dispersed in the printing machine. 
     In the foregoing embodiments, one of the side plates  209  rotatably supporting the plate cylinder  11  is used as a shielding plate. Instead, a shielding plate may be provided separately from the side plate. 
     This invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention. 
     This application claims priority benefit under 35 U.S.C. Section 119 of Japanese Patent Application No. 2002-326208 filed in the Japanese Patent Office on Nov. 11, 2002, and Japanese Patent Application No. 2003-198246 filed in the Japanese Patent Office on Jul. 17, 2003, entire disclosure of which is incorporated herein by reference.