Patent Publication Number: US-7585146-B2

Title: Stacking device having a system of circulating supports

Description:
BACKGROUND 
     The invention relates to a device for forming stacks of sheet-like products, in particular of paper products, and to a method for stacking products. 
     A device of this type is disclosed, for example, in WO-A-02/22482. In the case of the device described therein, paper products coming from a high-speed printer are supplied in a continuous stream along a conveying direction to a transfer section and are set down on a horizontally oriented, rigid set-down table. The set-down table is lowered vertically during the stacking operation and is filled with the paper products until a stack has a required number of the paper products. The set-down table is then vertically lowered to a delivery section. 
     In the delivery section, a band conveyor reaches through a grid-like set-down table and transports the stack of paper products away. The set-down table, which is now empty, is moved back horizontally by a further band conveyor, counter to the conveying direction, and by more than a length of the set-down table. Then, the set-down table is transported horizontally upward by a further band conveyor into a holding-ready position. 
     As soon as the set-down table is required for receiving a new stack, a further band conveyor conveys the set-down table horizontally, parallel to the conveying direction, and into the delivery section. For an interruption-free formation of stacks, at least one further set-down table is guided in each case horizontally and vertically in the circuit-like table-circulating path. 
     EP-B-0737640 discloses a method and a device for inserting an auxiliary stack picking-up means in a sheet delivery unit of printing machines. In this case, with an uninterrupted supply of further sheets (paper products), an auxiliary stack frame is inserted over a main stack in a running direction of the sheets and synchronously with the movement of a paper product to be set down. The main stack can subsequently be removed, and then the auxiliary stack picking-up means withdrawn, so that the paper products can again be set down on a pallet (set-down table) of the main stack. As an alternative, the auxiliary stack picking-up means receives the new main stack. When the main stack, which has now come to rest on the auxiliary stack picking-up means, is transported away again, a further auxiliary stack picking-up means has to be brought up. 
     SUMMARY 
     In all of the known stacking devices, the extent of the table-circulating path in a feeding direction of a stream of paper products is at least double the length of a set-down table. The large constructional form of the device that is required in these cases results from the shape of the table-circulating path, the shape being composed of rectilinear vertical and horizontal sections. In addition, the associated transportation of the set-down tables perpendicularly with respect to a set-down surface for the paper products restricts the guiding speed of the set-down tables in the table-circulating path. 
     An object of exemplary embodiments of the present invention is to provide a method and a device which make it possible to stack products, in particular paper products, in a variable number, and horizontally one above another, and with little outlay and space being required to hold the stacks ready in a rapid temporal sequence for devices arranged downstream. 
     Exemplary embodiments of a device for forming stacks of sheet-like products, in particular of paper products, may include the paper products supplied in an input stream by a feed conveyor to a transfer section. The device may include at least two set-down tables with at least one set-down surface in each case for stacks of supplied products. The set-down tables may be moved along a circuit-like table-circulating path, an imaginary connecting section running in a circulating direction between positions of a surface central point of the set-down surface during a circulating cycle, and may be flexible at least in some segments of the set-down tables. As a result, the set-down tables may be capable of conforming to shape of curvatures of the table-circulating path, the curvatures being located at least in some parts and subregions of the table-circulating path. An output stream of paper products stacked into stacks may then be removed from a delivery section by a removal conveyor. 
     Owing to the flexible set-down tables adapted to the curvatures of the table-circulating path, it is possible to construct the table-circulating path to be very confined and space-saving, and to give the overall device a very compact constructional form. At the same time, air resistance may be substantially reduced with a more stable transporting position when the set-down tables are moved with a leading front side edge leading in a circulating direction of the table circulating path. As a result, the set-down tables may now be guided in the table-circulating path at a higher speeds and in shorter circulating times. 
     These and other features are described in or are apparent from the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various exemplary details are described herein, with reference to the following figures, wherein: 
         FIG. 1  is a perspective schematic view of an exemplary device for stacking paper products that are arranged downstream of a rotational cutting device; 
         FIG. 2  is a side schematic view of the exemplary device shown in  FIG. 1  for stacking paper products; 
         FIG. 2   a  is an abstracted, schematic view of a table-circulating path of the set-down tables; 
         FIG. 3  is a front schematic view of the exemplary device shown in  FIG. 1  for stacking paper products; 
         FIG. 4  is a side schematic view of an enlarged detail IV taken from the exemplary device shown in  FIG. 3 ; and 
         FIGS. 5   a - 5   d  are side schematic views of locations of the set-down table of the exemplary device shown in  FIG. 1  for stacking paper products, at four different times. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG. 1  is a perspective schematic view of an exemplary device for forming stacks of sheet-like products, in particular of paper products  12 , in one exemplary embodiment of a paper stacker  14 . 
     The paper stacker  14  is arranged downstream of a rotational cutting device  16  of a known type. The rotational cutting device  16  cuts a continuous paper web  18  into individual sheets, which form an input stream of paper products  12  and are guided to the paper stacker  14  by an intermediate conveyor  22  including sheet feed rollers  24 ,  26 . The intermediate conveyor  22 , shown in  FIG. 1 , transports the paper products  12  in a feeding direction Z to a feed conveyor  28 . The feed conveyor  28  takes over the paper products  12  and conveys them on to a transfer section  32 . 
     After reaching a predetermined set-down position  38 , the paper products  12 , which have been newly conveyed, drop downward due to gravitational force causing the paper products  12  to rest on a still empty set-down surface  40  of a set-down table  42  or on a stack  10  of paper products  12  that is already present on the set-down table  42 . The stack  10 , which is increased by each further conveyed paper product  12 , is in each case lowered successively together with the set-down table  42  located in a stacking section  44 . The stack  10  is lowered such that an upper surface of the uppermost paper product  12 , which is located on the stack  10  to be loaded, substantially coincides with an original height of the empty set-down surface  40  of the set-down table  42 . This lowering takes place until the stack  10  has a desired number of the paper products  12  lying one above another. 
     The set-down table  42  carrying the stack  10  is then lowered as far as a lower level of a delivery section  46 . The stack  10 , without the set-down table  42 , is then removed into an output stream by being pushed onto a removal conveyor  48 , which is in the form of a band conveyor. The removal conveyor  48 , which is mounted on a delivery table  50 , transports the stack  10  on to a subsequent destination. 
     The circuit-like guidance of the set-down tables  42  until subsequent loading with paper products  12  will now be described in detail in conjunction with  FIG. 2 . 
       FIG. 2  is a side schematic view of the paper stacker  14  according to the exemplary embodiment. For clarity reasons, an illustration of support and housing elements of the paper stacker  14  has been omitted. As already mentioned in conjunction with the overview illustration in  FIG. 1 , the paper products  12  are brought by the feed conveyor  28  to the transfer section  32  at a conveying speed of approximately 50 m/min to approximately 150 m/min. In the conveying process, the sheet-like paper products  12  take up a substantially horizontal position and are guided with a leading front side edge  52  of each of the paper products  12  leading in the feeding direction Z and in a circulating direction of the table-circulating path  68 . As a result, a stable transporting position with little air resistance and a high conveying speed may be provided for the paper products  12 . The feed conveyor  28  may alternatively be replaced by different embodiments of conveyors, for example, a band conveyor. The conveying speed may also be adapted to individual requirements for specified devices, in particular, transporting, cutting or printing devices that may be used in conjunction with the paper products. 
     Pairs of rollers  30  of the feed conveyor  28  are driven by an associated electric motor  56  via a toothed-belt drive  54 . The electric motor  56  may be driven electrically in such a manner that the paper products  12  are accelerated or braked in the feeding direction Z, and the conveying speed of the paper products  12  is therefore influenced, for example, as a function of a lowering speed of the set-down tables  42  or of a drawing-in speed of the set-down tables  42  into the transfer section  32 . 
     In order to draw the paper products  12  into the transfer section  32 , the paper products  12  are taken from the feed conveyor  28  by a belt conveyor  58  and transported to the set-down position  38 . In this drawing process, the paper products  12  may be actively braked by the belt conveyor  58  and/or may be passively stopped in the set-down position  38  by means of an end stop  60 . In the exemplary embodiment shown in  FIG. 2 , both measures are used in order to obtain a precise set-down position  38  with gentle treatment of the leading front side edge  52  of each of the paper products  12 . The belt conveyor  58  has four mutually parallel axles  62 . 1 ,  62 . 2 ,  62 . 3 ,  62 . 4  fitted with pulleys. The end sides of the axles  62 . 1 ,  62 . 2 ,  62 . 3 ,  62 . 4  form a substantially rectangular arrangement. The belt conveyor  58  is driven by an associated electric motor  64  via the axle  62 . 1 . 
     As an alternative, the paper products  12  may also be transported further by the belt conveyor  58  to an additional unit  66 , shown in  FIG. 2 , for example a continuing conveyor. 
     The set-down tables  42  are moved in a table-circulating path  68 , which is an imaginary connecting section running in a circulating direction U between positions of the surface central point of a set-down surface  40  during a circulating cycle. The table-circulating path  68  is illustrated in  FIG. 2  and  FIG. 2   a  by means of a dashed line and runs parallel to the plane of the illustration. 
     The set-down tables  42  are flexible at some rod-shaped or rib-shaped segments. As a result, a shape of each of the set-down tables  42  may conform to curvatures of the table-circulating path  68 , the curvatures being located at least in some parts and subregions of the table-circulating path. The flexibility of the set-down tables  42  is sign-dependent and direction-dependent, so that only positive curvatures of the set-down tables  42  around the table-circulating path  68  are possible for the set-down surfaces  40  that are convexly curved with regard to the table-circulating path  68 . On the other hand, curvatures of the circulating set-down tables  42  also occur only in planes that lie parallel to the plane in which the table-circulating path  68  runs. 
     Perpendicularly, with respect to the plane of the table-circulating path  68 , the set-down tables  42  are rigid in their circulation. In this manner, the set-down tables  42  act as lateral supports having sufficient stability to support a stack  10  of the paper products  12 . The feature of the direction-dependent flexibility of the set-down tables  42  is achieved by joining together flats that are rigid along longitudinal axes. When the flats are joined together in relation to one another, the flats are pivotable with regard to the longitudinal axes. As an alternative, any set-down tables  42  having the capability of adapting to positive and negative curvatures about the table-circulating path  68  are also conceivable. 
     In addition to the table-circulating path  68  shown in  FIG. 2  and  FIG. 2   a , an alternative arrangement is possible. For example, the table-circulating path  68  may be rotated by, for example, 90° in relation to the feeding direction Z in order to run perpendicularly with respect to the plane of the illustration in  FIG. 2 . 
     As shown in the abstracted, side schematic view in  FIG. 2   a , the table-circulating path  68  may include portions of the transfer section  32 , the stacking section  44  and the delivery section  46 , a return section  72 , a table store  74  and a holding-ready section  76 . The functions of the sections  32 ,  44 ,  46 ,  72 ,  74 ,  76  of the table-circulating path  68  are later described in detail in conjunction with  FIGS. 5   a - 5   d.    
     As shown in  FIG. 2 , the lowering of the horizontally oriented set-down table  42  in the stacking section  44 , which extends from the transfer section  32  to the delivery section  46 , is brought about via side mounts  80 , which engage laterally on both sides of the set-down table  42 , on circulating table-carrying bands  82 . A detailed description of the interacting elements is later described in conjunction with  FIG. 4 . 
     As shown in  FIG. 2 , in the delivery section  46 , the movement of the set-down tables  42  takes place in a removing direction A running substantially parallel to the feeding direction Z. The set-down table  42  is pushed forward by a cam strip  84  which is mounted on a pair of roller chains  86 , is clamped between a driving chain wheel  88 . 1  and four driven chain wheels  88 . 2 ,  88 . 3 ,  88 . 4 ,  88 . 5 , and protrudes outward radially from the pair of roller chains  86 . In the delivery process, the circulating cam strip  84  presses against a trailing end side  89 , e.g., at the rear as seen in the circulating direction U, of the set-down table  42 . As a result, the cam strip  84  moves the set-down table  42  forward in the circulating direction U. The axles of the chain wheels  88 . 1 ,  88 . 2 ,  88 . 3 ,  88 . 4 ,  88 . 5  lie parallel to one another, and with respect to their end surfaces, are arranged in a manner substantially defining a rectangle. For every set-down table  42  transported away by the pair of roller chains  86 , the cam strip  84  performs a complete circulation, which is monitored by a sensor  90 . 
     The driving chain wheel  88 . 1 , which is fed by a further electric motor  92 , accelerates the pair of roller chains  86  gently at an acceleration of less than 2 m/s 2  with the effect of treating the stack as gently as possible. This may be achieved by means of a ramp-like electric activation of the electric motor  92 . The final speed of the pair of roller chains  86  assumed after the acceleration phase can be set in a variable manner. In order to permit a greater acceleration of the set-down table  42 , it is conceivable to bring the stack  10  and the set-down table  42  simultaneously into contact with the cam strip  84  and to accelerate them. 
     With a front side  94  of the set-down table leading ahead in the circulating U, the set-down table  42  encounters a comb-like guide grid  96 . The guide grid  96  has T-shaped grid elements  98 , which are oriented parallel to one another in the removing direction A, in order to deflect the horizontally arriving set-down tables  42  vertically downward into the return section  72 , and therefore, to effect a curvature  99  in the table-circulating path  68 . Only an outer grid element  98  can be seen in  FIG. 2 . 
     After the set-down tables  42  experience a substantially right-angled deflection due to their flexibility, the set-down tables  42  initially come to rest against a vertically oriented guide rail  100 . After a further curvature  102  in a direction counter to the removing direction A, the guide rail  100  includes a slightly horizontally downward inclination. As a result, the guide rail  100  guides the set-down tables  42  with the front side  94  leading from the return section  72  into a table store  74 . 
     While the set-down tables  42  are deflected downward by the guide grid  96 , the stack  10 , which is guided on horizontally oriented upper edges  104  of the grid elements  98 , continues to move in the removing direction A. The guide grid  96  therefore separates a stream of the paper products  12  and a stream of the set-down tables  42 , which have temporarily been guided together in the paper stacker  14 . 
     As soon as the stack  10  protrudes over the guide grid  96  in the removing direction A, the stack  10  is supported by the removal conveyor  48  and is transferred by the latter to a desired destination. The transporting away of the stacks  10  is monitored by means of a further sensor  106  mounted on the guide grid  96 . The speed of the removal conveyor  48  is variable and is preferably between 2 m/min and 20 m/min. 
     The table store  74  can receive a variable number of set-down tables  42 , for example, five set-down tables  42 , can temporarily store the set-down tables  42 , and can sequentially release the set-down tables  42  for further circulation. The set-down tables  42  come to rest horizontally, one above another, in the table store  74 . A further pair of roller chains  108  circulating below the table store  74  is equipped with a further cam strip  110  protruding away from the pair of roller chains  108 . The pair of roller chains  108  runs parallel to the set-down tables  42  between a further driving chain wheel  112 . 1  and two further driven chain wheels  112 . 2 ,  112 . 3 , axles of which are oriented parallel to one another. The driving chain wheel  112 . 1  is driven by a further electric motor  114 . In order to transport away a set-down table  42  from the table store  74 , the cam strip  110  presses against the trailing end side  89  of the set-down table  42 . As a result, the cam strip  110  moves the set-down table  42  forward in the circulating direction U. The set-down table  42  that is inserted into the table store  74 , in each case, is also released again for further circulation. 
     In the circulating direction U, the table store  74  is followed by the holding-ready section  76  that includes a further curvature  116 , which guides the set-down table upward in the vertical direction. For this purpose, the cam strip  110  pushes the set-down table  42 , with the front side  94  leading, to a height of a further sensor  118  until the set-down table  42  is taken over by a table-holding-ready drive  120 . In the holding-ready section  76 , the set-down surfaces  40  are guided substantially at right angles to the position of the set-down surfaces  40  in the stacking section  44 . This structure makes it possible to reduce a dimension of the table-circulating path  68  in the feeding direction Z. Therefore, this structure provides a very compact construction of the paper stacker  14 . 
     The table-holding-ready drive  120  has a toothed belt  124  that circulates between a driving wheel  122 . 1  and a driven wheel  122 . 2  and is fitted on both sides with teeth. The toothed belt  124  interacts with engagement structures  128 , which are formed on an upper side of the set-down tables  42  on both sides in lateral edge regions  126 . 1 ,  126 . 2  of the set-down tables  42  as shown in  FIG. 4 , in such a manner that the teeth of the toothed belt  124  engage in elevations and depressions of the edge regions  126 . 1 ,  126 . 2 . 
     As shown in  FIG. 4 , the structures  128 , with which corresponding toothed-belt drives can interact, may be provided on the upper side and/or a lower side of the set-down tables  42 . If appropriate, a movement of the set-down tables  42  on a driving belt or a driving wheel by means of friction is also possible. 
     The toothed belt  124 , including possible driving belts, are pressed against the set-down tables  42  to be moved in lateral positive-guiding means in the form of further U-shaped guide rails  100 . The entire holding-ready section  76  is equipped with the guide rails  100 , which may be manufactured from plastic. 
     For transferring the set-down tables  42  to the transfer section  32 , the set-down tables  42  are initially moved forward via a further curvature  130  of the guide rails  100  in the circulating direction U by the table-holding-ready drive  120 . Subsequently, the set-down tables  42  are conveyed by a lower strand  132  of a further toothed belt  134  of a horizontally oriented table drawing-in means  136  in a substantially jerk-free and jolt-free manner until the set-down tables  42  reach the set-down position  38 . In the drawing-in process, the circulating toothed belt  134  again interacts with the engagement structure  128 , which is formed on the upper side of the set-down table  42  on both sides in the edge regions  126 . 1 ,  126 . 2 , to move the set-down table  42  forward. The typical duration for the drawing-in operation of a set-down table  42  by the table drawing-in means  136  is 0.4 s to 0.8 s. 
     In the transfer section  32 , as shown in  FIG. 4 , guide rail sections  138  are located on both sides of the set-down table  42  and are designed in a manner such that the guide rail sections  138  can be switched freely. For this purpose, a linkage  140  includes two switching arms  142 . 1 ,  142 . 2  located above the transfer section  32 , and a centrally arranged suspension means  144  vertically displaceable by means of a lifting magnet (not shown). In an upper position of the suspension means  144 , as shown in  FIG. 4  for the end region of the left switching arm  142 . 1 , guide claws  146  engage in rectangular cross-sectional retaining grooves  148  formed laterally on the set-down tables  42 . The retaining grooves  148  form the guide rail sections  138  for the set-down tables  42 . In the case of a vertical displacement of the suspension means  144  downward, the guide claws  146  are folded away outward out of the retaining grooves  148 . As a result, the set-down tables  42  rest freely on the side mounts  80  of the table-carrying bands  82  arranged on both sides of the set-down tables  42 , lowered via a stepping motor  150  shown in  FIG. 3 , and connected via right-handed and left-handed worm drives to guide wheels  152 . 1 ,  152 . 2  of the table-carrying bands  82 . 
     As shown in  FIGS. 3 and 4 , the table-carrying bands  82 , which are arranged on both sides of the set-down tables  42  and circulate in opposite directions, are each equipped with chains  154 . 1 ,  154 . 2  to which the side mounts  80  are resiliently fastened. The side mounts  80 , which extend over an entire side length of a set-down table  42  resting on a side mount  80 , have a cross section that forms a substantially right-angled triangle. A side  156  of the side mounts  80  is located at the top during the lowering process to support the set-down table  42  on the side  156 , and edges  158  are formed to protrude vertically upward to horizontally and laterally bound the positioning region of the set-down tables  42 . The edges  158  may be used instead of the guide rails  100 . 
       FIGS. 5   a - 5   d  are side schematic views of locations of the set-down tables of the paper stacker  14 , which is shown in  FIG. 1  to  FIG. 4 , at four different times. In this case, in contrast to the previous illustrations, only four set-down tables  42 . 1 ,  42 . 2 ,  42 . 3 ,  42 . 4  are located simultaneously in the table-circulating path  68 . In each case six paper products  12 , lying one above another, form a complete stack  10 . 
       FIG. 5   a  shows the paper stacker  14  when setting down a further paper product  12  on an existing, but not yet complete stack  10  in the transfer section  32 . A set-down table  42 . 1  carrying the stack  10  is already located in the lowered state in the stacking section  44 . Located under the set-down table  42 . 1 , likewise in the stacking section  44 , is a set-down table  42 . 2  loaded with a complete stack  10 . Below the set-down table  42 . 2 , a set-down table  42 . 3  is already located in the delivery section  46 . A complete stack  10  that has previously been transported by a set-down table  42 . 4  to the delivery section  46 , is shown on the removal conveyor  48 . The set-down table  42 . 4  has already passed through the return section  72  and is located in the table store  74 . 
     In a next phase shown in  FIG. 5   b , the set-down table  42 . 4  has left the table store  74  again and is already in the holding-ready section  76 . The set-down table  42 . 1  located in the stacking section  44  has been lowered again, and the supported stack  10  already has a further paper product  12  set down on the stack  10 . The set-down table  42 . 2  has also been lowered to the same extent as the set-down table  42 . 1 . The set-down table  42 . 3  is deflected at the guide grid  96  into the return section  72  while the stack  10  supported by the set-down table  42 . 3  is pushed further horizontally in the removing direction A onto the removal conveyor  48 . 
     At the time illustrated in  FIG. 5   c , the set-down table  42 . 3  has already left the return section  72  and is located in the table store  74 . The set-down table  42 . 4  is still located in the holding-ready section  76 , as in the preceding phase, but has now already been grasped by the table-holding-ready drive  120 . The set-down table  42 . 1  has already received the six paper products  12  and has already been lowered further in the stacking section  44  than is envisaged for receiving a further paper product  12 . The removal conveyor  48  has completely taken over the stack  10 , which is still shown on the set-down table  42 . 3  in  FIG. 5   b , and transports the stack  10  away. 
       FIG. 5   d  illustrates a time shortly after the time illustrated in  FIG. 5   c . In this case, the set-down table  42 . 4  has already been partially displaced by the table-holding-ready drive  120  into the transfer section  32  and has been grasped by the table drawing-in means  136 . Within a short time, the set-down table  42 . 4  may be released again by the guide claws  146  ( FIG. 4 ) being folded away, for mounting at the side mounts  80  ( FIG. 4 ) of the table-carrying bands  82 . Therefore, the set-down table  42 . 4  may again be available for receiving a further stack  10 . The set-down tables  44 . 1 ,  44 . 2  located in the stacking section  44  have only been lowered slightly further downward and the set-down table  44 . 3  is still located in the table store  74  as in the preceding phase. 
     The positions of the set-down tables  42  in the table-circulating path  68  are determined at all times by an electronic control device (not shown). Input signals are generated, in particular, by the sensors  90 ,  96 ,  118  in the paper stacker  14 , by devices connected upstream or downstream, for example the rotational cutting device  16 , by the optional additional unit  66 , for example a continuing conveyor, and/or by an operator. The control device produces control and output signals for the electric motors  56 ,  64 ,  92 ,  114 ,  150  of the paper stacker  14 , for devices connected upstream or downstream, for optional additional units  66 , and/or for the operator, as a function of the input signals. 
     While various details have been described in conjunction with the exemplary embodiments outlined above, various alternatives, modifications, variations, improvements, and/or substantial equivalents, whether known or that are or may be presently unforeseen, may become apparent upon reviewing the foregoing disclosure. Accordingly, the exemplary embodiments set forth above are intended to be illustrative, not limiting.