Patent Publication Number: US-2022219925-A1

Title: Sheet processing device

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a National Stage under 35 U.S.C. § 371 of International Application No. PCT/EP2020/061873, filed Apr. 29, 2020, which claims priority to European Patent Application No. 19020332.3, filed May 15, 2019, the contents of all of which are incorporated by reference in their entirety. 
    
    
     The invention relates to a sheet processing device such as a die-cutting machine or a foil stamping machine. 
     It is known practice to move sheets within a sheet processing device from one processing station to another. For this purpose, gripper bars are commonly used which grip a sheet at a first processing station and transport it to another station at which letters and/or patterns are transferred onto the sheet or parts of the sheet are cut out. 
     The quality of the printing and/or cutting process is directly linked to the precision in positioning of the gripper bars at the processing station. 
     Even small offsets of the sheet form the target position can have a huge impact on the production. An offset in the positioning of the gripper bar can lead, for example, to an offset of the printing area on the sheet or to the cutting of processed parts of the sheet. 
     It is therefore essential that the gripper bars are in a precisely defined position when they grip a sheet to be moved through the machine and the processing stations. To this end, the gripper bars are usually locked in a precise position by means of a gripper bar locking device. There are however some constraints regarding the position of and space for such locking device. 
     WO 2018/116157 and WO 2018/006810 disclose gripper bar locking system that use a rotating cam to position a locking lever from a locking position to a rest position and vice-versa. The rotation of the cam is synchronized with the platen press motion. In WO 2018/116157 the locking device is used at the input of the platen, whereas in WO 2018/006810 it is used at the output of the platen. 
     Therefore, it is the objective of the invention to provide a sheet processing device has a gripper bar locking device which can be mounted within a restricted space and allows locking the grippe bar in a precisely defined position. 
     In order to solve this object, the invention provides a sheet processing device comprising a moveable beam being moveable in the vertical direction, a gripper bar for gripping a sheet to be transferred through the sheet processing device, and a gripper bar locking device for locking the gripper bar in a precise position, wherein the gripper bar locking device has a locking lever being pivotable about a pivot axis between a rest position and a locking position. The locking lever may be pivotally mounted to a carriage which is mounted on a linear guide; said carriage is coupled to the moveable beam, in particular in the vertical direction. The linear guide provides for a precise position of the locking lever even if the moveable beam undergoes some unexpected motion, in particular along a non-vertical direction. The carriage allows to add the locking device to existing machines without requiring substantial changes to the moveable beam. 
     The invention provides a gripper bar locking device that translates the vertical movement of the moveable beam into a movement of a locking lever for locking the gripper bar in a precise position. 
     Please note that there is no rotating cam mechanism between the moveable beam and the locking lever. Further, the locking lever does not require much space so that it can be fitted to machines which do not offer much space. 
     Advantageously, the locking lever is connected to the moveable beam such that a vertical movement of the moveable beam is converted into a stroke of a locking end of the locking lever which is larger than the vertical stroke of the moveable beam. This allows the gripper bar locking device to be used even with moveable beams that have only a small vertical stroke. 
     In order to ensure that small horizontal movements of the moveable beam do not affect the position of the locking lever, a sliding guide may be provided for transferring the vertical movement of the moveable beam to the carriage, the sliding guide allowing a movement of the moveable beam with respect to the carriage in a direction which is perpendicular to the vertical direction. 
     In one embodiment of the invention, the carriage has a stop for defining the locking position of the locking lever. Thereby, a very precise position is provided for the gripper bar. 
     Advantageously, the locking lever is a two-armed lever, with the end of the lever which is opposite the locking end being connected to a pull rod. The pull rod serves a (substantially) stationary support for the locking lever so that it is automatically pivoted into the locking position when the carriage is displaced via the moveable beam. 
     In order to ensure that the locking lever reaches the locking position in any case, the arrangement of the pull rod is such that the locking lever is pivoted into the locking position before the carriage reaches to fully displaced position. For allowing the remaining over-stroke of the carriage, a spring is provided within the pull rod. 
     A stop may be provided at the pull rod limiting the movement of the locking lever in one direction. Thereby, the rest position of the locking lever is defined. 
     In one embodiment of the invention, the locking lever is provided with a roller at its locking end. This allows a vertical movement between the gripper bar and the locking lever without significant friction. 
     The gripper bar may comprise an anvil for cooperating with the roller such that the longitudinal position of the gripper bar remains unaffected when there is a vertical movement of the gripper bar with respect to the locking lever. The longitudinal position being the position along the sheet feeding direction. This can be advantageously implemented by having an anvil with a vertical surface portion. Thus, when the roller of the locking lever travels vertically, it rolls over said surface portion and does not affect the position of the gripper bar along the sheet feeding direction. 
     The moveable beam may be a lower part of a platen press. This allows for a simple and direct transfer of the movement of the platen press into a movement of the locking lever. In a platen press, the motion of the movable beam compresses the sheet toward the tools (e.g. knives or stamps) attached to an upper fixed beam. 
     In one embodiment of the invention, the sheet processing device comprises a hot foil stamping press and/or a die-cutting machine. Thus, the sheet can be processed according to requirements. 
    
    
     
       Further features and advantages of the invention will be apparent from the following description of one embodiment of the present invention with the aid of the enclosed drawings, in which: 
         FIG. 1  is a schematic side view of a sheet processing device, 
         FIG. 2  is a detailed perspective view of the sheet processing device of  FIG. 1  showing a gripper bar locking device and a gripper bar, 
         FIG. 3  is a detailed side view with a partial section view of the sheet processing device of  FIG. 2 , 
         FIGS. 4 to 10  are side views of the processing device of  FIG. 3  showing the movement of the gripper bar locking device from the rest position into the locking position, and 
         FIGS. 11 to 13  are side views of the processing device of  FIG. 3  showing the movement of the gripper bar locking device from the locking position into the rest position. 
     
    
    
     In  FIG. 1 , the essential parts of a sheet processing device  10  are shown. Sheet processing device  10  comprises a number of processing stations  12  and a conveyor device  14 . 
     In  FIG. 1 , processing stations  12  are in particular a feeder  16 , a feed board  18 , a stamping station  20 , a foil feed and recovery station  22 , and a receiving station  24 . 
     Feeder  16  provides sheets  26  to subsequent processing stations  12 . For this purpose, sheets  26  are stacked and successively taken off the top of the stack by a transporting member which transports them as far as the directly adjacent feed board  18 . 
     For the sake of clarity, only some sheets  26  are labeled with reference numbers in  FIG. 1  and not all of them. Sheets  26  can be cardboard or paper. 
     At feed board  18 , sheets  26  are laid out by the transporting member, which means that they are laid one after the other with partial overlap. The whole of the layer is then driven along a platform towards stamping station  20 , by means of a belt-type conveyor mechanism. 
     To transport sheets  26  to subsequent processing stations  12 , conveyor device  14  has a conveyor belt  28  and a number of gripper bars  30  attached to conveyor belt  28 . Conveyor belt  28  is arranged in a loop which allows gripper bars  30  to follow a trajectory that passes in succession through stamping station  20 , feed and recovery station  22  and receiving station  24 . 
     Conveyor belt  28  may for example comprise two sets of chains arranged laterally along each side of stamping station  20 . The gripper bars  30  are fixed on the sets of chains with a regular space. 
     Thus gripper bar  30  grips a sheet  26  at the end of feed board  18  and transports it to stamping station  20 . 
     Stamping station  20  comprises a platen press  32  with a top platen  34 , a moveable beam  36 , and a movement mechanism  38 , and a gripper bar locking device  40 . 
     Top platen  34  is fixed in its position and serves as counterpart to moveable beam  36 . Moveable beam  36  is moved by movement mechanism  38  in the vertical direction, i.e. towards top platen  34 . 
     Gripper bar locking device  40  is adapted to lock gripper bar  30  in a precise position such that sheet  26  can be processed precisely by a processing station  12 . Gripper bar locking device  40  will be described with exact details below in the description of  FIGS. 2 and 3 . 
     Foil feed and recovery station  22  comprises a feed reel  42  for providing a foil  44  and a take-up device  46  for removing used foil  44 . 
     Foil  44  is either a metallized plastic foil or a thin metal foil. 
     In the embodiment shown in  FIG. 1 , foil  44  is fed such that it passes through stamping station  20  on its way from feed reel  42  to take up device  46 . 
     At stamping station  20 , sheet  26  is pressed by moveable beam  36  against top platen  34  and foil  44  is arranged between sheet  26  and top platen  34 . Thereby text and/or patterns are transferred from foil  44  onto sheet  26 . Thus stamping station  20  is a hot foil stamping press  48 . 
     After stamping station  20 , sheet  26  is fed to receiving station  24  which collects processed sheet  26 . In particular, receiving station  24  arranges processed sheets  26  back into a stack. To do that, conveyor device  14  is arranged to release each sheet  26  automatically when sheet  26  comes back into line with this new stack. 
     In general, sheet processing device  10  can also comprise a die-cutting machine. 
     Referring to  FIGS. 2 and 3 , the gripper bar locking device  40  is described in detail in the following.  FIG. 2  shows a perspective view of sheet processing device  10  at the outlet of stamping station  20  and  FIG. 3  a side view of sheet processing device  10  at the same outlet. 
     The coordinate system referred to below is shown in  FIGS. 2 and 3  by arrows. The coordinate system is aligned in three dimensions with vertical direction V, sheet feeding direction F, and horizontal direction H. Vertical direction V is aligned with the movement direction of moveable beam  36  and sheet feeding direction F is aligned with the direction in which sheets  26  are moved. Horizontal direction H is aligned perpendicular to vertical direction V and sheet feeding direction F. 
     As can be seen in  FIG. 2 , gripper bar  30  has a body  50 , several gripper arms  52  for gripping sheet  26 , and a fastening system  54  with which gripper bar  30  is attached to conveyor belt  28 . 
     Gripper arms  52  extend away from body  50  in the opposite direction to sheet feeding direction F and are arranged at regular intervals along horizontal direction H. 
     Fastening system  54  has a fastening spring  56  and a fastening anvil  58 , fastening anvil  58  being connected firmly to body  50  of gripper bar  30  and coupled to one end of spring  56 . 
     Hence, gripper bar  30  can be moved in sheet feeding direction F by tensioning spring  56 . 
     As it can be seen in  FIG. 3 , a coupling component  60  is attached to moveable beam  36  by means of bolts, coupling component  60  being essentially L-shaped. A roller  64  is rotatably attached to one end of coupling component  60 . 
     More precisely, roller  64  is attached to an end of coupling component  60  that projects in sheet feeding direction F away from moveable beam  36 . 
     Coupling component  60  is coupled to the movement of moveable beam  36 . 
     Coming back to  FIG. 2 , gripper bar locking device  40  comprises a locking lever  68 , a carriage  70 , a linear guide  72 , a support structure  74 , and a pull rod  76 . 
     Support structure  74  provides the structure for gripper bar locking device  40  through which gripper bar locking device  40  can be positioned within sheet processing device  10 . 
     Linear guide  72  is fixed to support structure  74  and oriented in the vertical direction V. 
     More precisely, linear guide  72  is arranged parallel to the movement direction of moveable beam  36 . 
     Carriage  70  has an U-shaped recess  78 , recess  78  being arranged essentially in sheet feeding direction F which is perpendicular to the movement direction of moveable beam  36 . 
     Carriage  70  is mounted in linear guide  72  via a slide bearing such that carriage  70  can move within linear guide  72  in and opposite to vertical direction V. 
     Carriage  70  is coupled to the vertical movement of moveable beam  36  by a sliding guide  66  formed by recess  78  of carriage  70  and roller  64  of coupling component  60 , roller  64  being adapted to glide inside recess  78  in and opposite to sheet feeding direction F. 
     More precisely, a movement in vertical direction V leads to roller  64  engaging at upper end (in vertical direction V) of recess  78  such that carriage  70  moves as well in vertical direction V. If moveable beam  36  moves downwards in vertical direction V, roller will engage at the lower end of recess  78  pushing carriage  70  downwards as well. 
     Additionally, a small movement of moveable beam  36  in sheet feeding direction F will lead to roller  64  moving further inwards in recess  78  such that moveable beam  36  can move relative to carriage  70  in a direction transverse to vertical direction V. 
     Hence, the movement of moveable beam  36  leads to a vertical movement only of carriage  70  and not to a movement in sheet feeding direction F, which could lead to a displacement of carriage  70  and, hence, of gripper bar locking device  40 . 
     As shown in  FIG. 2 , locking lever  68  is a two-armed lever mounted at carriage  70  with a roller  80  on locking end  82  of lever  68 , and an anvil  84  and a connecting axis  86  on the side of lever  68  opposite to locking end  82 . 
     Locking lever  68  is pivotable about a pivot axis  87  arranged at carriage  70 . More precisely, locking lever  68  is pivotable between a rest position (shown in  FIG. 4 ) and a locking position (shown in  FIGS. 2 and 3 ). 
     Anvil  84  is arranged at a side surface of locking lever  68  facing carriage  70  and defines one stop of the locking lever  68 . 
     In particular, anvil  84  determines the locking position of locking lever  68  by engaging at carriage  70 . This will be explained further with reference to  FIGS. 4 to 10 . 
     Connecting axis  86  forms the connection between locking lever  68  and pull rod  76 . 
     As shown in the partial section view of  FIG. 3 , pull rod  76  has an inner pull rod  88 , an outer pull rod  90 , a spring  92 , and a casing  94 . 
     Outer pull rod  90  is tubular in shape and has a ring-shaped shoulder  96  arranged at the outside of outer pull rod  90 . 
     The inner pull rod  88  has a tapered end which is arranged inside outer pull rod  88 . 
     Outer pull rod  90  and inner pull rod  88  are detachably fixed with each other. A screw connection can be used here. 
     Spring  92  is arranged starting from shoulder  96  in the direction of locking lever  68  and enclosed by casing  94 . Therefore, casing  94  is coupled to the other side of spring  92  and spring  92  is tensioned through a movement of outer pull rod  90  in the direction of locking lever  68 . 
     Casing  94  is tubular in shape and encloses inner pull rod  88 , outer pull rod  90 , and spring  92 . 
     At the end of casing  94  facing locking lever  68  an opening is provided through which inner pull rod  88  can protrude from casing  94 . At the other end of casing  94 , a stop  98  is provided for the outer pull rod  90 . 
     In the following, the movement of the gripper bar locking device  40  from its rest position to the locking position and vice versa is described with reference to  FIGS. 4 to 13 . 
     First, the result of the upward movement of moveable beam  36  on the locking lever is described with reference to  FIGS. 4 to 10 . 
     In  FIG. 4 , gripper bar locking device  40  is in its rest position. More precisely, locking lever  68  is in its rest position and carriage  70  is in terms of its movement in linear guide  72  at the lower stop. 
     Additionally, the side of locking lever  68  opposite to the locking end  82  is at its highest position in vertical direction V and locking end  82  at its lowest. In  FIG. 4 , locking end  82  is covered by sliding guide  66 . 
     From  FIGS. 4 to 5 , moveable beam  36  is starting to move in vertical direction V This is shown by an arrow next to coupling element  60  pointing in vertical direction V. Additionally, gripper bar  30  is advancing in sheet feeding direction F. 
     The movement of moveable beam  36  in vertical direction V leads to a force of roller  64  in recess  78  in vertical direction V. Therefore, carriage  70  is moving as well in vertical direction V. 
     Due to the upward movement of carriage  70 , lever  68  also moves in vertical direction V. Thus inner pull rod  88  and outer pull rod  90  are pulled essentially in vertical direction V by which spring  92  is tensioned. 
     Therefore, spring  92  is inducing a force on locking lever  68  in the counterclockwise direction and locking lever  68  starts to pivot about pivot axis  87  in the counterclockwise direction. 
     Coming now to  FIG. 6 , gripper bar  30  is advancing further in sheet feeding direction F and moveable beam  36  is moving further in vertical direction V. Thus, locking lever  68  is continuing to pivot about pivot axis  87  in the counterclockwise direction. These movements are illustrated in  FIG. 6  by arrows. 
     In  FIG. 7 , gripper bar  30  is not advancing further in sheet feeding direction F due to a stop of conveyor belt  28 . Moveable beam  36  is continuing, however, to move in vertical direction V such that gripper bar locking device  40  is engaging at gripper bar  30 . 
     More precisely, roller  80  of locking lever  68  is engaging at anvil  58 . This is shown in enlarged detail A of  FIG. 7 . 
     Referring now to  FIG. 8 , moveable beam  36  is still moving in vertical direction V and thus carriage  70  as well. Thus, lever  68  pivots further in the counterclockwise direction. 
     Since lever  68  is still pivoting in the counterclockwise direction, roller  80  pushes anvil  58  and, hence, gripper bar  30  is pushed in the sheet feeding direction F resulting in a tensioning of spring  56 . This is illustrated by arrow  100 . 
     The pivoting movement of lever  68  is stopped by anvil  84  engaging at carriage  70  as shown in the enlarged detail B of  FIG. 8 . Hence, locking lever  68  is in its locking position and gripper bar  30  is locked by roller  80  pushing anvil  58  in sheet feeding direction F. 
     Therefore, gripper bar  30  is in a precise position. 
     Comparing  FIG. 8  with  FIG. 4 , it can be seen that the vertical stroke of locking end  82  is larger than the vertical stroke of coupling component  60  and thus larger as the vertical stroke of moveable beam  36 . 
     Hence gripper bar locking device  40  translates the vertical stroke of moveable beam  36  into an even larger vertical stroke of locking end  82  of locking lever  68 . This enables a precise positioning of gripper bar  30  in sheet processing devices  10  and at the same time let the gripper bars  30  travel from one processing station  12  to another. 
     In  FIG. 9 , moveable beam  36  is continuing to move in vertical direction V. As locking lever  68  cannot pivot any further in the counterclockwise direction, spring  92  of pull rod is tensioned leading to an over stroke of pull rod  76 , i.e. outer pull rod  90  is not coupled any more to stop  98  (see  FIG. 3 ). 
     This is illustrated in  FIG. 10  by inner pull rod  88  extending outwards of casing  94 . 
     The over stroke of pull rod  76  leads to a movement of carriage  70  further in vertical direction V such that roller  80  is engaging at a position more upwards at anvil  58 . 
     This means that gripper bar  30  is already fixed in its position before moveable beam  36  reaches its highest point. 
     Referring now to  FIGS. 11 to 13 , the result of the downward movement of moveable beam  36  will be explained. 
     As moveable beam  36  moves downwards, illustrated by an arrow, outer pull rod  90  engages again at stop  98  leading to a movement of locking lever  68  in the clockwise direction. Hence, spring  56  is released again and gripper bar  30  moves slightly in the direction opposite to sheet feeding direction F. 
     In  FIG. 12 , gripper bar  30  continues to advance in sheet feeding direction F and locking lever  68  continues to pivot further in the clockwise direction due to the movement of moveable beam  36  in the direction opposite to vertical direction V. 
       FIG. 13  shows the situation shortly before  FIG. 4 , in which gripper bar  30  has moved a sheet (now shown) away from processing station  12  at which gripper bar locking device  40  is positioned. Locking lever  68  has almost arrived back at its rest position. 
     The embodiment of  FIGS. 1 to 13  show only an example for a usage of gripper bar locking device  40 . 
     In principle, it is conceivable to position gripper bar locking devices  40  at multiple processing stations  12  of sheet processing device  10  and or to position more than one gripper bar locking devices  40  at a processing station  12 .