Patent Publication Number: US-2012044511-A1

Title: Transfer apparatus for offset printing

Description:
TECHNICAL FIELD 
     The present invention relates to a transfer apparatus for offset printing provided with a blanket roller that is used, when offset printing is performed, for re-transferring (printing) ink, which has been transferred (received) from a plate, to a print target. 
     Priority is claimed on Japanese Patent Application No. 2009-126035, filed on May 26, 2009, the content of which is incorporated herein by reference. 
     BACKGROUND ART 
     In recent years, as a technique of forming an electrode pattern (conduction pattern) for liquid crystal displays or the like on predetermined substrates, there are proposed printing techniques of using a conductive paste as printing ink, instead of fine machining by etching a metal vapor-deposited film or the like. For example, there is proposed a method of forming an electrode pattern on a substrate by use of the intaglio plate offset printing technique (for example, see Patent Document 1 and Patent Document 2). 
     In the case of offset-printing a fine print pattern such as the aforementioned electrode pattern onto a print target such as the aforementioned substrate, high printing accuracy is required. Therefore, as for an offset printing apparatus for performing offset printing with high accuracy, a surface printing apparatus is assumed to be advantageous in which a flat-table-like plate similar to the print target is used as a plate. 
       FIG. 7  shows a conventionally-proposed offset printing apparatus using a flat-table-like plate. On a base  1 , there are provided linear guide rails  2 . In parallel with the linear guide rails  2 , there is provided a ball screw mechanism  3  that is driven by a servo motor  4 . Thereby, it is possible to attach a moving table  7 , on which a flat-table-like plate (master plate)  5  and a print target (workpiece plate)  6  are allowed to be fixed with a predetermined distance spaced from each other, slidably to the linear guide rails  2 . It is also possible to reciprocate the moving table  7  by the ball screw mechanism  3 . 
     Furthermore, at a predetermined site of the base  1 , there is provided a transfer apparatus  8  with a blanket roller  9 . The transfer apparatus  8  includes: a pair of left and right support posts (columns)  10  with a predetermined height that are attached respectively to the left and right sides of the base  1 ; a blanket roller  9  (not shown in the figure) arranged a predetermined distance above the linear guide rails  2  in a direction orthogonal to the longitudinal direction of the linear guide rails  2 , both ends of the blanket roller  9  being rotatably supported by bearings each contained in each support post  10 ; and a drive motor (servo motor)  11  coupled to one end of the blanket roller  9  in a direction of its center of axle. 
     According to the aforementioned offset printing apparatus, the blanket roller  9  is rotated in the transfer apparatus  8  by the operation of the drive motor  11 . In this condition, while the moving table  7  holding a plate  5  and a print target  6  is moved beneath the blanket roller  9  in rotation at a speed in synchronicity with the peripheral velocity of the blanket roller  9 , the blanket roller  9  is brought into contact sequentially with the plate  5  and the print target  6 . Thus, transfer (reception) from the plate  5  to the blanket roller  9  and then re-transfer (print) from the blanket roller  9  to the print target  6 , namely, offset printing can be performed (for example, see Patent Document 3 and Patent Document 4). 
     PRIOR ART DOCUMENT 
     Patent Document 
     
         
         Patent Document 1: Japanese Patent No. 2797567 
         Patent Document 2: Japanese Patent No. 3904433 
         Patent Document 3: Japanese Unexamined Patent Application, First Publication No. H06-15809 
         Patent Document 4: Japanese Unexamined Patent Application, First Publication No. H09-70948 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Present Invention 
     In the process of performing offset printing by use of an offset printing apparatus as shown in  FIG. 7 , it is required that the blanket roller  9  and the plate  5  be pressed against each other with a predetermined contact pressure when transfer (reception) from the plate  5  to the blanket roller  9  is performed. It is also required that the blanket roller  9  and the print target  6  be pressed against each other with a predetermined contact pressure when re-transfer (print) from the blanket roller  9  to the print target  6  is performed. Accordingly, at the time of roller pressurization by the blanket roller  9 , a reactive force to the predetermined contact pressure when the blanket roller  9  is pressed against the plate  5  or the print target  6  acts on the blanket roller  9 . Therefore, a reactive force to the contact pressure acts on the blanket roller  9 . As a result, in the mechanical structure portion of the transfer apparatus  8 , deformation is produced such as deflection of the support posts  10  that support the blanket roller  9 . Due to the deformation of the mechanical structure portion of the transfer apparatus  8 , there is a decrease in geometrical repeatability of the shape, size, position, and the like of the print pattern to be printed from the plate  5  onto the print target  6  via the blanket roller  9 , leading to a problem of deterioration in printing accuracy. 
     The offset printing apparatuses disclosed in Patent Document 3 and Patent Document 4 do not particularly take into consideration the problem of deterioration in printing accuracy due to the aforementioned deformation of the mechanical structure portion of the transfer apparatus  8  at the time of roller pressurization. Therefore, it is not possible to significantly increase the repeatability of the print pattern, leading to a problem of difficulty in printing with higher accuracy. 
     The present invention provides a transfer apparatus for offset printing capable of suppressing deformation of the mechanical structure portion at the time of roller pressurization by the blanket roller, capable of further increasing the geographical repeatability of the print pattern to be printed from the plate to the print target via the blanket roller, and capable of performing printing with higher accuracy than in the conventional art. 
     Means for Solving the Problems 
     A transfer apparatus for offset printing according to the present invention has a construction in which a gate-shaped frame is provided so as to cross over a common moving table or separate moving tables, for holding a plate and a print target, which travel along guides provided on a mount, the gate-shaped frame being made by integrally coupling top ends of columns vertically extending a predetermined distance. Furthermore, a blanket roller, which is rotationally-drivably supported, is attached raisably/lowerably to the gate-shaped frame, and also a raising-lowering actuator for the blanket roller is provided on the gate-shaped frame. As a result, by the raising-lowering actuator, the blanket roller is made capable of being raised/lowered from a height position at which a lowest end of an outer circumferential surface of the blanket roller is a predetermined distance above a surface level of the plate and the print target held on the common moving table or the separate moving tables to a lowered position at which the lowest end is beneath the surface level of the plate and the print target. Furthermore, the blanket roller is made capable of being pressed from above against surfaces of the plate and the print target held on the common moving table or the separate moving tables. 
     In the above construction, both ends of the blanket roller, which extends in a left-right direction orthogonal to a longitudinal direction of the guides provided on the mount, are rotatably held in left and right bearing housings of a roller support frame. In addition, the left and right bearing housings of the roller support frame are raisably/lowerably attached to the gate-shaped frame via vertical linear movement guides, and the raising-lowering actuator is attached to each of the left and right bearing housings of the roller support frame. Therefore, it is possible to raise/lower the blanket roller together with the roller support frame by use of the raising-lowering actuators. 
     In the above construction, the raising-lowering actuators comprise two ball screw mechanisms each of which comprises: a drive motor exposed to an upper portion of the gate-shaped frame; a vertical thread shaft coupled to the drive motor via a gear box; and a nut member threaded to the thread shaft. Furthermore, the nut members of the ball screw mechanisms are attached individually to the left and right bearing housings of the roller support frame. 
     Effect of the Present Invention 
     With the transfer apparatus for offset printing according to the present invention, excellent advantageous effects as follows are obtained. 
     (1) It is constructed such that a gate-shaped frame is provided so as to cross over a common moving table or separate moving tables, for holding a plate and a print target, which travel along guides provided on a mount, the gate-shaped frame being made by integrally coupling top ends of columns vertically extending a predetermined distance. Furthermore, a blanket roller, which is rotationally-drivably supported, is attached raisably/lowerably to the gate-shaped frame, and also a raising-lowering actuator for the blanket roller is provided on the gate-shaped frame. As a result, by the raising-lowering actuator, the blanket roller is made capable of being raised/lowered from a height position at which a lowest end of an outer circumferential surface of the blanket roller is a predetermined distance above a surface level of the plate and the print target held on the common moving table or the separate moving tables to a lowered position at which the lowest end is beneath the surface level of the plate and the print target. Furthermore, the blanket roller is made capable of being pressed from above against surfaces of the plate and the print target held on the common moving table or the separate moving tables. Therefore, with the blanket roller being pressed from above against the plate or the print target held on the common moving table or the separate moving tables with a predetermined contact pressure to thereby perform transfer (reception) or re-transfer (print), a reactive force to the predetermined contact pressure acts upwardly on the blanket roller. Even if the reactive force to the predetermined contact pressure is input to the gate-shaped frame to which the blanket roller is raisably/lowerably attached, it is possible to prevent the possibility that the columns of the frame are deflected in the inward-outward direction, and also to suppress the amount of deformation of the frame. Namely, it is possible to suppress the amount of deformation of the mechanical structure portion other than the blanket roller at the time of the transfer or the re-transfer. Therefore, it is possible to increase the geometrical repeatability of the shape, size, position, and the like of the print pattern. 
     (2) It is constructed such that both ends of the blanket roller, which extends in a left-right direction orthogonal to a longitudinal direction of the guides provided on the mount, are rotatably held in left and right bearing housings of a roller support frame. In addition, the left and right bearing housings of the roller support frame are raisably/lowerably attached to the gate-shaped frame via vertical linear movement guides, and the raising-lowering actuator is attached to each of the left and right bearing housings of the roller support frame. Thus, it is possible to raise/lower the blanket roller together with the roller support frame by use of the raising-lowering actuators. Therefore, the reactive force, of the predetermined contact pressure against the plate or the print target, acting on the blanket roller can be received from the rotary shafts on both sides of the blanket roller to the corresponding raising-lowering actuators via the corresponding bearing housings. Accordingly, it is possible to suppress the deformation of the roller support frame at the time of transfer (reception) or re-transfer (print). Namely, it is possible to further suppress the amount of deformation of the mechanical structure portion other than the blanket roller, and to further increase the geometrical repeatability of the print pattern. 
     (3) The raising-lowering actuators are made of two ball screw mechanisms each of which includes: a drive motor provided so as to be exposed to an upper portion of the gate-shaped frame; a vertical thread shaft coupled to the drive motor via a gear box; and a nut member threaded to the thread shaft. Furthermore, the nut members of the ball screw mechanisms are attached individually to the left and right bearing housings of the roller support frame. Therefore, the heat generated by the raising-lowering motors of the ball screw mechanisms can be directly released to the atmosphere above, and also the thermal deformation of the frame caused by the influence of the heat generated by the raising-lowering motors can be suppressed. Consequently, it is possible to further suppress the amount of deformation of the mechanical structure portion other than the blanket roller at the time of transfer (reception) or re-transfer (print), and hence, it is possible to further increase the geometrical repeatability of the print pattern. 
     (4) With the suppression of geometrical displacement of the print pattern as described above in (1), (2), and (3), it is possible to perform printing with higher accuracy than in the conventional art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic front view showing an embodiment of a transfer apparatus for offset printing according to the present invention. 
         FIG. 2  is a schematic front cutaway view of the transfer apparatus of  FIG. 1 . 
         FIG. 3  is a cross-sectional view of  FIG. 1  taken along the A-A arrow. 
         FIG. 4  is a cross-sectional view of  FIG. 1  taken along the B-B arrow. 
         FIG. 5  is a schematic side view showing a general construction of a transfer apparatus for offset printing provided with the transfer apparatus of  FIG. 1 . 
         FIG. 6  is an enlarged view of a bottom portion functioning as a bed for the transfer apparatus of  FIG. 1  in a mount of the transfer apparatus for offset printing of  FIG. 5 . 
         FIG. 7  is a schematic diagram showing an example of a conventionally-proposed transfer apparatus for offset printing that uses a flat-shaped plate. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereunder is a description of a mode for carrying out the present invention with reference to the drawings. 
       FIG. 1  to  FIG. 6  show an embodiment of a transfer apparatus for offset printing according to the present invention. 
     In the transfer apparatus for offset printing shown in  FIG. 5 , guide rails  13 , for example a pair of guide rails  13 , which extend in one direction, are provided on an upper side of a horizontal mount  12 . To the guide rails  13 , a plate table  15  and a print target table  17  are attached so as to be independently reciprocated (traveled) by individual drive devices (not shown in the figure). The plate table  15  and the print target table  17  are moving tables for respectively holding, for example, a flat-table-like plate  14  and a flat-table-like print target  16  such as a substrate. 
     Furthermore, at a position somewhere in the longitudinal direction of the guide rails  13  where both of the plate table  15  and the print target table  17  can travel (for example, at a predetermined site on the mount  12  corresponding to an intermediate position in the longitudinal direction of the guide rails  13 ), there is provided a transfer apparatus for offset printing  18  of the present invention, which is provided with a blanket roller  19  (hereinafter, referred to as a transfer apparatus  18  of the present invention). In addition, at another position somewhere in the longitudinal direction of the guide rails  13  where the plate table  15  can travel (for example, at a predetermined site on the mount  12  spaced a predetermined distance from the installation site of the transfer apparatus  18  of the present invention to first ends in the longitudinal direction of the guide rails  13 ), there is provided an inking device  20  for inking the plate  14  held on the plate table  15 . 
     The transfer apparatus  18  of the present invention used as the transfer apparatus for offset printing has a construction as shown in  FIG. 1  to  FIG. 4 . 
     Namely, top ends of a pair of left and right columns  23   a  and  23   b  and top ends of a pair of left and right columns  23   c  and  23   d  which have a predetermined dimension in an up-down direction are integrally connected respectively by a beam member  24  horizontally extending in a predetermined distance, to thereby form two gate-shaped frame members  22   a ,  22   b . Furthermore, the two gate-shaped frame members  22   a ,  22   b  are arranged in parallel in a forward-backward direction with a predetermined distance spaced from each other. In addition, summit portions of the gate-shaped frame members  22   a ,  22   b  are integrally connected by a top board member  25 , which has a rectangular plate shape and has its predetermined sites reinforced by ribs  26 , to thereby form a gate-shaped frame  21 . Furthermore, in the frame  21 , the beam members  24  of the gate-shaped frame members  22   a ,  22   b  are arranged at predetermined sites on the mount  12  so as to cross over (pass over) the guide rails  13  in a direction orthogonal to the longitudinal direction of the guide rails  13 , and lower ends of the columns  21   a ,  21   b ,  21   c , and  21   d  are fixed to the mount  12 . Accordingly, with the transfer apparatus  18  being formed in a gate-shaped structure in which the top ends of the left and right columns  23   a  and  23   b  fixed to the mount  12  and the top ends of the columns  23   c  and  23   d  fixed to the mount  12  are integrally connected by the respective beam members  24 , the columns  23   a ,  23   b  and the columns  23   c ,  23   d  arranged on the left and right sides are made highly rigid, making it possible to prevent the columns  23   a ,  23   b ,  23   c , and  23   d  from being deflected in the inward-outward direction (left-right direction). 
     A pair of left and right bearing housings  28   a ,  28   b  spaced a predetermined distance from each other are integrally connected by a coupling member  29  extending in the left-right direction, to thereby form a roller support frame  27 . Furthermore, rotary shafts  30  each provided on each side of the blanket roller  19  are rotatably held respectively in left and right bearing housings  28   a ,  28   b  of the roller support frame  27  via a bearing  31 . In addition, the left and right bearing housings  28   a  and  28   b  of the roller support frame  27  are attached respectively between the columns  23   a  and  23   c  and between the columns  23   b  and  23   d  so as to be vertically slidable via their corresponding linear movement guides  32  extending vertically. The pairs of columns are arranged respectively on the left and right sides of the frame  21  in the forward-backward direction (in the longitudinal direction of the guide rails  13 ). 
     At each of the left and right sites, in the top board member  25  of the frame  21 , above the bearing housings  28   a ,  28   b  of the roller support frame  27 , there is provided a bearing  34  in a penetrating manner. In each bearing  34 , a thread shaft  35 , which vertically extends in a predetermined length, is rotatably held at a part close to its upper end. At this time, as will be described later, a load acting on each thread shaft  35  can be supported by receiving the load from each bearing  34  to the top board member  25  by means of the roller support frame  27  attached to lower portions of the thread shafts  35  via their corresponding nut members  36 . 
     On an upper side of the top board member  25  in the vicinity of each bearing  34 , there is installed a gear box  38 , which is connected to a raising-lowering motor  37  such as a servo motor, via a predetermined support member  39 . Furthermore, to an output side of the gear box  38 , there is coupled via a coupling  40  an end of a protrusion portion of the thread shaft  35  that protrudes to an upper side of the bearing  34 . 
     Each nut member  36 , which is threaded onto each thread shaft  35 , is attached to an upper portion of each of the bearing housings  28   a ,  28   b  of the roller support frame  27  via a predetermined attachment member  41 . Thus, ball screw mechanisms  33  as raising-lowering actuators are formed, each of which is made of: the raising-lowering motor  37 ; the thread shaft  35  rotationally driven through the operation of the raising-lowering motor  37  via the gear box  38 ; and the nut member  36 . As a result, through the rotational drive of the thread shafts  35  via the gear boxes  38  in accordance with the operations of the raising-lowering motors  37  of the ball screw mechanisms  33 , the roller support frame  27  holding the blanket roller  19  can be raised/lowered integrally with the nut members  36 . With the raising/lowering of the roller support frame  27  by the ball screw mechanisms  33 , the blanket roller  19  can be raised/lowered in the range from a height position at which the lowest end of an outer circumferential surface of the blanket roller  19  is a predetermined distance above the upper surfaces of the plate  14  held on the plate table  15  and the print target  16  held on the print target table  17  to a height position at which the lowest end of the outer circumferential surface of the blanket roller  19  is a slight distance beneath the surfaces of the plate  14  held on the plate table  15  and the print target  16  held on the print target table  17 . 
     To the external side of the bearing housing  28   a  of the roller support frame  27 , there is attached a decelerator  43 , which is connected to a rotational drive motor  42 . In addition, to an output shaft (not shown in the figure) of the decelerator  43 , the rotary shaft  30  of the blanket roller  19  held in the bearing housing  28   a  is coupled. As a result, through the operation of the rotational drive motor  42 , it is possible to rotationally drive the blanket roller  19  at a predetermined rotational velocity via the decelerator  43 . 
     As shown in  FIG. 6 , in the mount  12  of the transfer apparatus for offset printing used in the transfer apparatus  18  of the present invention, a multitude of ribs  44  are internally attached in a grid pattern to the mount  12  in the portion functioning as a bed for the transfer apparatus  18  of the present invention, namely, in the region corresponding to the installation sites of the columns  23   a ,  23   b ,  23   c , and  23   d  of the frame  21  and the inside area surrounded thereby. This is to increase the rigidity of the portion functioning as a bed. Therefore, in the transfer apparatus  18  of the present invention, when the blanket roller  19  is brought into contact from above with the plate  14  or the print target  16  with a predetermined contact pressure at the time of performing transfer from the plate  14  to the blanket roller  19  or re-transfer from the blanket roller  19  to the print target  16 , it is possible prevent a positional displacement between the blanket roller  19  held in the frame  21  and the plate  14  held on the plate table  15  or the print target  16  held on the print target table  17  resulting from the deformation by deflection of the portion functioning as a bed in the mount  12  of the transfer apparatus  18  of the present invention, even if a load from the contact pressure acts downwardly on a portion on which the plate table  15  holding the plate  14  or the print target table  17  holding the print target  16  is arranged in the mount  12  or even if a load from a reactive force of the contact pressure acts upwardly on the installation sites of the columns  23   a ,  23   b ,  23   c , and  23   d  of the frame  21  in the mount  12 . 
     In the case of using the transfer apparatus  18 , the plate table  15  holding the plate  14  is sent to the inking device  20  and subjects the plate  14  to inking in advance. 
     Furthermore, through the operations of the raising-lowering motors  37  of the ball screw mechanisms  33  in the transfer apparatus  18  of the present invention, the blanket roller  19  is raised integrally with the roller support frame  27 , to thereby withdraw the blanket roller  19  to a position at which the lowest end of the outer circumference of the blanket roller  19  is the predetermined distance above the upper surfaces of the plate  14  held on the plate table  15  and the print target  16  held on the print target table  17 . In this condition, the plate table  15  holding the inked plate  14  and the print target table  17  holding the print target  16  are moved to positions that correspond to those on an upstream side in the moving direction of the lowest end of the outer circumference of the blanket roller  19  when the blanket roller  19  is rotated for transfer or re-transfer. 
     In this condition, the blanket roller  19  is rotated through the operation of the rotational drive motor  42 . At the same time, the plate table  15  holding the plate  14  starts to move at the velocity in synchronicity with the peripheral velocity of the blanket roller  19  in rotation. When the plate  14  held on the plate table  15  arrives beneath the blanket roller  19 , the blanket roller  19  is lowered integrally with the roller support frame  27  through the operations of the raising-lowering motors  37  of the ball screw mechanisms  33 , and is then caused to be rotated while being pressed against the plate  14  with a predetermined contact pressure. Thereby, transfer (reception) of ink is performed from the inked plate  14  to the blanket roller  19 . 
     After completion of the transfer, the blanket roller  19  is temporarily withdrawn integrally with the roller support frame  27  through the operation of the raising-lowering motors  37  of the ball screw mechanisms  33  so that the lowest end of the outer circumferential surface of the blanket roller  19  is at a height position which is a predetermined distance above the upper surface of the print target  16  held on the print target table  17 . 
     After that, similarly to the case of the transfer, the print target table  17  holding the print target  16  starts to be moved, from the same direction as that for the plate table  15  at the time of the transfer, at a velocity in synchronicity with the peripheral velocity of the blanket roller  19  that is rotated through the operation of the rotational drive motor  42 . When the print target  16  held on the print target table  17  arrives beneath the blanket roller  19 , the blanket roller  19  is lowered integrally with the roller support frame  27  through the operations of the raising-lowering motors  37  of the ball screw mechanisms  33 . Then, the blanket roller  19  is rotated while being pressed against the print target  16  with the predetermined contact pressure. Thereby, re-transfer from the blanket roller  19  to the print target  16 , that is, offset printing onto the print target  16  is performed. 
     At the time of transfer (reception) or re-transfer (print) that is performed by pressing the blanket roller  19  from above against the plate  14  held on the plate table  15  or the print target  16  held on the print target table  17  with the predetermined contact pressure, a reactive force to the contact pressure acts upwardly on the blanket roller  19 . However, the left and right bearing housings  28   a ,  28   b  of the roller support frame  27 , in which the rotary shafts  30  on both sides of the blanket roller  19  are individually held, are attached respectively to the columns  23   a ,  23   c  and the columns  23   b ,  23   d  of the frame  21  via the linear movement guides  32 . In addition, to each of the bearing housings  28   a ,  28   b , the nut member  36  of the corresponding ball screw mechanism  33  as a raising-lowering actuator is attached via the attachment member  41 . Therefore, the reactive force to the contact pressure acting on the blanket roller  19  is directly transmitted from the rotary shafts  30  on both ends of the blanket roller  19  to the corresponding ball screw mechanisms  33  via the corresponding bearing housings  28   a ,  28   b . Accordingly, it is possible to suppress the amount of deformation of the roller support frame  27  by the reactive force to the contact pressure that acts at the time of transfer (reception) and re-transfer (print). 
     The ball screw mechanisms  33  to which the reactive force to the contact pressure is input from the blanket roller  19  via the rotary shafts  30  and the bearing housings  28   a ,  28   b , are adapted to be supported by the gate-shaped frame  21 . Therefore, when the reactive force to the contact pressure is input from the blanket roller  19  to the ball screw mechanisms  33  via the rotary shafts  30  and the bearing housings  28   a ,  28   b , deformation such as deflection of the columns  23   a ,  23   b ,  23   c , and  23   d  of the frame  21  that support the ball screw mechanisms  33  is prevented. Accordingly, it is possible to suppress the amount of deformation of the frame  21  itself. 
     Furthermore, as shown in  FIG. 6 , in the mount  12  of the offset printing apparatus, the inside region surrounded by the installation sites of the columns  23   a ,  23   b ,  23   c , and  23   d , the multitude of ribs  44  are provided on the internal surface side of the mount  12  to increase its rigidity. Therefore, it is possible to suppress the amount of deformation of the mount  12  at the base portions of the columns  23   a ,  23   b ,  23   c , and  23   d  resulting from the reactive force to the contact pressure, and the amount of deformation of the mount  12  transmitted via the tables  15 ,  17 . 
     The raising-lowering motors  37  of the ball screw mechanisms  33  are provided above the top board member  25  of the frame  21 . This allows the heat from the raising-lowering motors  37  to be directly released to the atmosphere above. Therefore, it is possible to suppress the thermal deformation of the frame  21  due to the influence of the heat generated by the raising-lowering motors  37 . 
     Therefore, according to the transfer apparatus  18  of the offset printing apparatus of the present invention, when the blanket roller  19  is pressed from above against the plate  14  or the print target  16  with the predetermined contact pressure to perform transfer (reception) or re-transfer (print), it is possible to suppress to a minimum the deformation of the mechanical structure portion other than the blanket roller  19  such as the frame  21  and the roller support frame  27 , and the deformation of the mechanical structure portion due to the heat generated by the raising-lowering motors  37  for raising/lowering the blanket roller  19 . 
     Namely, when transfer or re-transfer by the blanket roller  19  is performed, it is possible to suppress a relative, positional displacement between the blanket roller  19  and the plate  14  as well as between the blanket roller  19  and the print target  16  resulting from the deformation of the mechanical structure portion. As a result, it is possible to suppress a geometrical displacement of the print pattern such as its shape, size, and position. This makes it possible to perform printing with higher accuracy than conventionally. 
     The present invention is not limited to the embodiment. From the point of view of suppressing a thermal deformation of the frame  21  due to the heat generated by the raising-lowering motors  37  of the ball screw mechanisms  33  as a drive source for raising/lowering the blanket roller  19 , it is desirable that the raising-lowering motors  37  be provided on the upper surface side of the top board member  25  of the frame  21  to allow the heat generated by the raising-lowering motors  37  to be directly released to the atmosphere above. However, if there is a slight possibility that the heat generated by the raising-lowering motors  37  has an influence on the thermal deformation of the frame  21  such as the case where the amount of heat generated by the raising-lowering motors  37  is small, the raising-lowering motors  37  of the ball screw mechanisms  33  may be arranged at sites other than on the upper surface of the top board member  25  of the frame  21 . 
     As raising-lowering actuators, any type of actuators other than the ball screw mechanisms  33  may be used so long as they can be coupled to the bearing housings  28   a ,  28   b  of the roller support frame  27  and can raise/lower the blanket roller  19  integrally with the roller support frame  27  in a predetermined height range. 
     As for the frame  21 , a gate-shaped frame  21  may be constructed by directly coupling the summit portions of the columns  23   a ,  23   b ,  23   c , and  23   d  with the top board member  25 . 
     So long as the plate  14  and the print target  16  are movable beneath the blanket roller  19 , the present invention may be applied to an offset printing apparatus in which the plate  14  and the print target  16  are held on a common moving table that is movable along the guide rails  13 . 
     In the case of improving the volume efficiency, the following construction may be adopted. A plate  14  and a print target  16  are fixedly lined up on the mount. On both sides of the plate  14  and the print target  16 , guide rails are provided along the direction in which the plate  14  and the print target  16  are lined up on the mount. A carriage is attached travelably to the guide rails. To the carriage, the lower ends of the columns  23   a ,  23   b ,  23   c , and  23   d  in the transfer apparatus  18  of the present invention are attached. Then, the frame  21  raisably/lowerably holding the blanket roller  19  is moved with respect to the plate  14  and print target  16  whose positions are fixed as described above. Furthermore, the offset printing apparatus of the present invention may be applied to performing printing on any print target  16  other than a substrate. 
     INDUSTRIAL APPLICABILITY 
     The present invention provides a transfer apparatus for offset printing capable of suppressing the deformation of the mechanical structure portion at the time of roller pressurization by the blanket roller, capable of increasing the geometrical repeatability of the print pattern to be printed from the plate to the print target via the blanket roller, and capable of performing printing with higher accuracy than conventionally. 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
           12 : mount 
           13 : guide rail (guide) 
           14 : plate 
           15 : plate table (moving table) 
           16 : print target 
           17 : print target table (moving table) 
           19 : blanket roller 
           21 : frame 
           22   a ,  22   b : gate-shaped frame member 
           23   a ,  23   b ,  23   c ,  23   d : column 
           27 : roller support frame 
           28   a ,  28   b : bearing housing 
           30 : rotary shaft 
           31 : bearing 
           32  linear movement guide 
           33 : ball screw mechanism (raising-lowering actuator) 
           35 : thread shaft 
           36 : nut member 
           37 : raising-lowering motor 
           38 : gear box