Patent Publication Number: US-2007096382-A1

Title: Sheet convey apparatus

Description:
BACKGROUND OF THE INVENTION  
      The present invention relates to a sheet convey apparatus which, when conveying sheets obtained by sequentially cutting a web which is fed out, conveys the sheets by lapping the leading edge and trailing edge of two successive sheets.  
      As a conventional sheet convey apparatus which conveys sheets by lapping the leading edge and trailing edge of two successive sheets, one as shown in U.S. Pat. No. 4,302,001 is proposed. This apparatus comprises a cutting device which cuts a paper web, the first feeding device which feeds a cut sheet, the second feeding device which is located downstream of the first feeding device in a sheet convey direction and has a sheet feed speed lower than that of the first feeding device, and a chucking means for chucking the sheets upward between the first and second feeding devices within a range where the edges of the sheet are lapped like fish scales.  
      According to another conventional sheet convey apparatus, one as shown in U.S. Pat. No. 5,275,394 is proposed. This apparatus comprises a belt device which conveys a sheet obtained by cutting a paper web by a cutting device, a lifting means for lifting upward the trailing edge portion of a downstream sheet which is being conveyed by the belt device, and a pickup means for chucking the lifted trailing edge portion. The leading edge portion of an upstream sheet is inserted under the trailing edge portion of the sheet chucked by the pickup means to lap the edges of the two sheets.  
      According to the former sheet convey apparatus described above, the sheets are conveyed with the trailing edge portion of the preceding downstream sheet being chucked by the chucking means. Thus, the sheet is rubbed by the chucking means and accordingly damaged.  
      According to the latter sheet convey apparatus, if the rigidity (hardness) of the sheet to be lifted by the lifting means is relatively low, sometimes the trailing edge portion of the sheet cannot be lifted to a predetermined height. In this case, the trailing edge portion of the sheet cannot be chucked by the pickup means, so the edges of the two sheets cannot be reliably lapped. Also, adjusting operation is required to adjust the lifting amount of the lifting means to match the stiffness (hardness) of the sheet.  
      These problems may be solved by a method of blowing discharge air to the sheet from below so that the trailing edge portion of the downstream sheet is chucked by the chucking means reliably. In this case, to reliably lap the sheets, the operation of adjusting the chucking air discharge timing is necessary so that only the trailing edge of the downstream sheet may be blown up with the discharge air but the leading edge of the upstream sheet may not be blown up. This adjusting operation is cumbersome and time-consuming because the air discharge on/off timing must be adjusted in accordance with the sheet convey speed.  
      The same problem arises when conveying precut sheets in a lapped state.  
     SUMMARY OF THE INVENTION  
      It is an object of the present invention to provide a sheet convey apparatus that can reliably lap the edges of sheets without damaging the sheets.  
      It is another object of the present invention to provide a sheet convey apparatus that does not require adjusting operation.  
      According to the present invention, there is provided a sheet convey apparatus comprising first convey means for conveying a plurality of sheets, second convey means provided downstream of the first convey means in a sheet convey direction and having a convey speed lower than that of the first convey means, air discharge means, provided above the first convey means, for discharging air obliquely downward toward a downstream side of the sheet convey direction to float a trailing edge portion of a sheet, and a rotary body which is rotatably supported above the first convey means and guides the trailing edge portion of the sheet which has floated with the air from the air discharge means. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a side view of a sheet-fed offset rotary printing press to which a sheet convey apparatus according to the first embodiment of the present invention is applied;  
       FIG. 2  is a plan view of the sheet convey apparatus shown in  FIG. 1 ;  
       FIG. 3  is a side view of the sheet convey apparatus shown in  FIG. 1 ;  
       FIG. 4  is a partially cutaway plan view of the air flow rate adjusting device shown in  FIG. 2 ; and  
       FIG. 5  is a plan view of a sheet convey apparatus according to the second embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      A case will be described with reference to FIGS.  1  to  4  wherein a sheet convey apparatus according to the first embodiment of the present invention is applied to a sheet-fed offset rotary printing press.  
      As shown in  FIG. 1 , a sheet convey apparatus  1  according to this embodiment includes a roll  3  around which a web  2  is wound, a cutting device  4  which feeds separately from each other a plurality of sheets obtained by cutting the web  2  fed out from the roll  3  into a predetermined size, and a lapping unit  5  which inserts the leading edge portion of, among two sheets fed from the cutting device  4 , the following sheet under the trailing edge portion of the preceding sheet and conveys the two sheets with their edges being lapped. Note that“the trailing edge portion of the preceding sheet” means“the upstream edge in the sheet convey direction of a sheet located downstream in the sheet convey direction”. Also, “the leading edge portion of the following sheet” means“the downstream edge in the sheet convey direction of a sheet located upstream in the sheet convey direction”.  
      A known sheet-fed offset rotary printing press  6  includes a feeder board  8  which feeds one by one the sheets conveyed from the sheet convey apparatus  1  described above, a printing unit  9  which prints the sheets fed from the feeder board  8 , and a delivery unit  10  which delivers the sheets printed by the printing unit  9 . The printing unit  9  includes two printing units  9 A and  9 B sequentially disposed in the sheet convey direction. Each of the printing units  9 A and  9 B includes a plate cylinder  11  to which ink and water are supplied from an inking device and dampening device (not shown), a blanket cylinder  12  which is in contact with the plate cylinder  11 , and an impression cylinder  13  which opposes the blanket cylinder  12 . A transfer cylinder  14  is arranged between the impression cylinders  13  of the printing units  9 A and  9 B.  
      The delivery unit  10  includes a sprocket  15  coaxial with a delivery cylinder (not shown) which opposes the impression cylinder  13  of the printing unit  9 B, a sprocket  16  rotatably supported at the rear end side of the delivery unit  10 , and a delivery chain  17  applied between the sprockets  15  and  16 . In this arrangement, a sheet fed from the feeder board  8  is printed on its obverse surface with the first color by the printing unit  9 A. The sheet is then conveyed to the printing unit  9 B by the transfer cylinder  14 , and its obverse surface is printed with the second color. The printed sheet is gripping-changed to the delivery pawls (not shown) of the delivery chain  17  and conveyed as the delivery chain  17  runs. When the sheet is conveyed to the rear end side of the delivery unit  10 , the delivery pawls release the sheet, so that the sheet drops onto a pile board (not shown) and is stacked there.  
      The lapping unit  5  of the sheet convey apparatus  1  will be described with reference to  FIGS. 2 and 3 . The lapping unit  5  includes a first conveyor belt  20  (first convey means) which conveys a sheet  19  cut by the cutting device  4 , and a second conveyor belt  21  (second convey means) which is arranged downstream (direction of an arrow A) of the first conveyor belt  20  in the sheet convey direction. The first and second conveyor belts  20  and  21  are arranged on one plane.  
      As shown in  FIG. 2 , the first conveyor belt  20  is formed of one endless belt having a width larger than the width (the length in a direction perpendicular to the sheet convey direction) of the sheet  19 . The endless belt which forms the first conveyor belt  20  is looped between a first driving roller  22  and a driven roller (not shown) arranged in the vicinity of the cutting device  4  to extend in the directions of the arrow A and an arrow B. When the first driving roller  22  is driven to rotate by a first motor  23 , the first conveyor belt  20  travels at a speed V 1  in the direction of the arrow A.  
      As shown in  FIG. 2 , the second conveyor belt  21  is formed of one endless belt having the same width as that of the first conveyor belt  20 . The endless belt which forms the second conveyor belt  21  is looped between a second driving roller  24  and a driven roller (not shown) arranged in the vicinity of the feeder board  8  to extend in the directions of the arrows A and B. When the second driving roller  24  is driven to rotate by a second motor  25 , the second conveyor belt  21  travels at a speed V 2  lower than the traveling speed V 1  of the first conveyor belt  20  in the direction of the arrow A.  
      Above the first conveyor belt  20 , an air pipe  26  is arranged upstream (the direction of the arrow B) of a rotary body  30  (to be described later) in the sheet convey direction. The air pipe  26  extends in the widthwise direction of the sheet  19 , i.e., the first conveyor belt  20 , and is connected to an air supply source (not shown) such as a compressor through a pipe  27 A. The air pipe  26  has air nozzles  28  (air discharge means) that line up equidistantly on one straight line in the axial direction. As shown in  FIG. 3 , the air nozzles  28  are arranged such that their distal ends are directed obliquely downward toward the downstream side of the sheet convey direction (the direction of the arrow A). Air  29  discharged from the air nozzles  28  is blown to a portion between the first driving belt  20  and the rotary body  30 . The air pipe  26  is pivotally supported by a pair of frames  31  ( FIG. 2 ) which oppose each other at a predetermined gap. A blowing angle a of the air  29  discharged from the air nozzles  28  is adjusted by a stepping motor  32  ( FIG. 2 ). The discharge speed of the air  29  is adjusted by an air flow rate adjusting device  34  (to be described later).  
      A gear  32   a  axially mounted on the output shaft of the stepping motor  32  meshes with gears  26   a  and  33   a , as shown in  FIG. 2 . The gear  26 a is axially mounted on an end shaft  26   b  of the air pipe  26 . The gear  33   a  is axially mounted on the rotating shaft of an encoder  33 . In this arrangement, when the stepping motor  32  is driven, the air pipe  26  pivots through the gears  32   a  and  26   a . The pivot amount of the air pipe  26  is detected by the encoder  33  through the gears  32   a  and  33   a . When the blowing angle α of the air  29  reaches a predetermined value, the stepping motor  32  stops driving to fix the blowing angle α of the air  29 .  
      As shown in  FIG. 4 , the air flow rate adjusting device  34  includes an electromagnetic valve  35  having an actuator  35   a  which can advance/retreat, and a valve  36  having one end pivotally mounted on the actuator  35   a  and the other end biased by a coil spring  37  in a direction to separate from the actuator  35   a . When driven by the electromagnetic valve  35 , the valve  36  moves across the boundary portion of the pipe  27 A and a hose  27 B in a direction perpendicular to an air channel to open/close the sectional area of the air channel. The valve  36  has an air passage  36   a  through which the pipe  27 A communicates with the hose  27 B, and an exhaust passage  36   b  through which the pipe  27 A communicates with outer air. In this arrangement, when the electromagnetic valve  35  is driven to change the advancing/retreating amount of the actuator  35   a , the opening amount between the pipe  27 A and hose  27 B is adjusted to adjust the discharge speed of the air  29  to be discharged from the air nozzles  28 .  
      Above the first driving belt  20 , as shown in  FIG. 3 , the rotary body  30  is arranged upstream of the first driving roller  22  in the sheet convey direction to be parallel to the first driving roller  22 . The rotary body  30  is rotatably supported by the pair of frames  31  so as to extend in the widthwise direction of the sheet  19  under conveyance. The rotary body  30  is arranged to correspond to the position of a trailing edge portion  19   a  of a sheet  19 A when a leading edge portion  19   b  of the sheet  19 A conveyed by the first conveyor belt  20  separates from the first conveyor belt  20  and starts to come into contact with the second conveyor belt  21 . In this arrangement, the trailing edge portion  19   a  of the sheet  19 A which floats with the air  29  discharged from the air nozzles  28  comes into contact with the rotary body  30 , so that the floating sheet  19 A is guided.  
      The sheet convey operation of the sheet convey apparatus with the above arrangement will be described. Air has been supplied to the air pipe  26  in advance from an air supply source (not shown) through the pipe  27 A and hose  27 B, and the air nozzles  28  constantly discharge the air  29 . In this state, in  FIG. 1 , the web  2  fed out from the roll  3  is cut by the cutting device  4  into sheets each having a predetermined size. The cut sheets are sequentially fed onto the first conveyor belt  20  of the lapping unit  5 . The fed sheet  19 A is conveyed by the first conveyor belt  20  at the convey speed V 1  in the direction of the arrow A.  
      When the leading edge portion  19   b  of the sheet  19 A separates from the first conveyor belt  20  and comes into contact with the second conveyor belt  21 , as the traveling speed V 2  of the second conveyor belt  21  is lower than the traveling speed V 1  of the first conveyor belt  20 , the convey speed of the sheet  19 A also decreases. At this time, the trailing edge portion  19   a  of the sheet  19 A is located under the rotary body  30 . The air nozzles  28  arranged upstream of the rotary body  30  in the sheet convey direction discharge the air  29  obliquely downward toward the downstream side of the sheet convey direction (direction of the arrow A).  
      Therefore, the air  29  enters under the trailing edge portion  19   a  of the preceding sheet  19 A to float the trailing edge portion  19   a . Thus, a leading edge portion  19   b  of a following sheet  19 B which has been conveyed by the first conveyor belt  20  at the speed V 1  higher than the speed V 2  is inserted under the trailing edge portion  19   a  of the preceding sheet  19 A. The air  29  from the air nozzles  28  urges the leading edge portion  19   b  of the upstream sheet  19 B against the first conveyor belt  20 . Thus, the leading edge portion  19   b  of the sheet  19 B is reliably inserted under the trailing edge portion  19   a  of the preceding sheet  19 A.  
      The air nozzles  28  are arranged, above the first conveyor belt  20 , upstream of the rotary body  30  in the sheet convey direction. Hence, even if the air  29  is constantly discharged, the upper surface of the sheet  19  on the first conveyor belt  20  is blown with air. This urges the sheet  19  against the first conveyor belt  20  so the sheet convey operation is not influenced. After that, when the sheet  19  moves to the second conveyor belt  21  and its trailing edge portion  19   a  is positioned below the rotary body  30 , the air  29  is blown between the lower surface of the trailing edge portion  19   a  and the first conveyor belt  20  to lift up the trailing edge portion  19   a.    
      More specifically, even if the air  29  is discharged constantly, when the trailing edge portion  19   a  of the preceding sheet  19 A is positioned below the rotary body  30 , the trailing edge portion  19   a  floats by the air  29 . The leading edge portion  19   b  of the following sheet  19 B is conveyed as it is pressed (urged) with the air  29  against the first conveyor belt  20 . In this manner, even if the air  29  is discharged constantly, the edges of the sheets that travel continuously can be lapped reliably. Thus, the discharge timing of the air  29  need not be adjusted.  
      The floating trailing edge portion  19   a  of the sheet  19 A comes into contact with the rotary body  30  and is conveyed in the direction of the arrow A as it is guided by the rotary body  30 . In this manner, as the trailing edge portion  19   a  of the preceding sheet  19 A is guided by the rotary body  30 , it will not flutter or waves, so that uncontrolled movement of the sheet is regulated. As the rotary body  30  is rotatably supported, it is rotated in an interlocked manner by the friction generated between the outer surface of the rotary body  30  and the trailing edge portion  19   a  of the sheet  19 A which is in contact with the outer surface of the conveyor belt  20 . Therefore, no rubbing occurs between the sheet  19 A and rotary body  30 , and the trailing edge portion  19   a  will not be damaged. Even when the gap between the cutting device  4  and sheet-fed offset rotary printing press  6  is large, the two, first and second conveyor belts  20  and  21  as the sheet convey means can form the sheet convey path, so that the number of components decreases and the structure is simplified.  
      In the state wherein the trailing edge portion  19   a  of the sheet  19 A is guided by the rotary body  30 , when the sheet  19 A is further conveyed in the direction of the arrow A by the second conveyor belt  21 , the trailing edge portion  19   a  of the sheet  19 A separates from the rotary body  30 . Then, the trailing edge portion  19   a  of the sheet  19 A drops onto the leading edge portion  19   b  of the following sheet  19 B to lap it.  
      In this case, depending on the weight, size, or stiffness (hardness) of the sheet, if the floating amount of the trailing edge portion  19   a  of the sheet  19 A is not sufficient, the discharge speed of the air  29  is adjusted by the blowing angle α of the air  29  discharged from the air nozzles  28  or by the air flow rate adjusting device  34 . As a result, the quantity of air  29  to be supplied under the trailing edge portion  19   a  of the preceding sheet  19 A increases to complement the insufficient floating amount of the trailing edge portion  19   a  . Thus, the edges of the two sheets lap reliably.  
      The second embodiment of the present invention will be described with reference to  FIG. 5 . The second embodiment is different from the first embodiment described above in that the first convey means is formed of a plurality of first conveyor belts  40  and that the second convey means is formed of a plurality of second conveyor belts  41 . The first and second conveyor belts  40  and  41  are formed of narrow endless belts obtained by dividing the conveyor belts  20  and  21  of the first embodiment each into a plurality of portions in the widthwise direction of the sheet to be conveyed. The first conveyor belts  40  line up equidistantly in the widthwise direction of the sheet to be conveyed, and are looped between a first driving roller  22  and a driven roller (not shown) to extend in the directions of arrows A and B.  
      The second conveyor belts  41  having the same total width as that of the first conveyor belts  40  line up equidistantly in the widthwise direction of the sheet to be conveyed to correspond to the first conveyor belts  40 , and are looped between a second driving roller  24  and a driven roller  42  provided in the vicinity of a feeder board  8  to extend in the directions of the arrows A and B.  
      A plurality of air nozzles  43  formed in an air pipe  26  correspond to every other one of the first conveyor belts  40 . Air discharged from the nozzles  43  is blown to diffuse in the widthwise direction of the first conveyor belts  40 .  
      In this arrangement, when the leading edge portion of a sheet which is being conveyed by the first conveyor belts  40  in the direction of the arrow A comes into contact of the second conveyor belts  41 , the convey speed of the sheet decreases. Simultaneously, the air blown from the air nozzles  43  floats the trailing edge portion of the sheet. Thus, the leading edge portion of a following sheet which is being conveyed by the first conveyor belts  40  in the direction of the arrow A is inserted under the trailing edge portion of the preceding sheet which floats. Hence, in the same manner as in the first embodiment, the two successive sheets are conveyed in the direction of the arrow A with the leading edge portion of the upstream sheet underlapping the trailing edge portion of the downstream sheet.  
      While belts are used in this embodiment as a means for conveying the sheet  19 , the sheet may be alternatively conveyed by a rotary roller. While the air  29  is discharged constantly from the air nozzles  28 , it may be alternatively discharged intermittently. While a case has been described wherein the air flow rate adjusting device  34  is used as a means for adjusting the discharge speed of the air to be discharged from the nozzles  28 , the adjusting means is not limited to this. For example, when a DC motor is used as the motor of a blower that constitutes an air supply source which supplies air to the air pipe  26 , the DC power supply voltage to be supplied to the motor may be adjusted. When an AC motor is used as the blower motor, the AC power supply frequency may be adjusted. Alternatively, a regulator or relief valve may be disposed midway along the pipe  27 A.  
      In the above embodiment, the roll-type sheet is cut by the cutting device and pre cut sheets are supplied at a predetermined interval. The present invention can also naturally be applied to a case wherein pre cut sheets are conveyed in a lapping manner. The sheet to be conveyed is not limited to a paper sheet, but can be any sheet-type object, e.g., a plastic sheet or film, which can be printed on its obverse surface.  
      As has been described above, according to the present invention, the leading edge portion of an upstream sheet can be reliably inserted under the trailing edge portion of a downstream sheet. Therefore, the edges of two successive sheets can be lapped reliably. While the air is constantly discharged, the edges of the two sheets can be lapped reliably. Thus, the air discharge timing need not be adjusted. As the trailing edge portion of the floating sheet is guided by the rotary body, the sheet will not be damaged.  
      Even when the sheets are to be conveyed at a relatively long interval, this can be coped with by two sets of belts. Thus, the number of components decreases and the structure is simplified. If the floating amount of the trailing edge portion of the sheet is not sufficient, the air speed or air blowing angle may be adjusted to increase the quantity of air to be supplied under the trailing edge portion of the sheet, so that the edges of the two sheets can be lapped reliably.