Abstract:
A processing device for processing at least one stack of bags including a plurality of bags, wherein at least one stacking device is provided on which the stack of bags can be arranged in a base position, wherein the bags in the stack of bags have a bag length and a bag width, including providing at least one centering device having at least two centering units disposed opposite one another and disposed so that a driving device can move them relative to one another, towards one another and away from one another, and that the centering unit provided on a first side is at least temporarily coupled with a return side of at least one continuous belt and wherein the centering unit provided on a second side is at least temporarily coupled with the carrying side of at least one continuous belt.

Description:
BACKGROUND 
     The present invention relates to an apparatus and a method for processing stacks of bags and in particular a packaging machine or an apparatus or a device assigned to a packaging machine. The apparatus may serve to center the bags in a stack of bags. It is further possible for the apparatus to serve to separate the bags from a stack of bags and moreover also to open the separated bags, append them to a filling spout, optionally to fill them e.g. with bulk material, to close them and convey them off. 
     Document DE 10 2011 113 879.3 describes a processing device and a method for processing stacks of bags wherein the processing device separates the bags and subsequently appends them to a filling spout of a packaging machine were they are filled with bulk material. This apparatus and the method described therein basically function reliably. However, it has been found that for example comparatively long bags showing a relatively narrow width tend to slip and slide on the stack of bags. Even if the bag shows just minimal lateral movement the bag may be placed onto the filling spout at an angle or offset so that the processing speed decreases or even intervention in the operation is required. 
     It is therefore the object of the present invention to provide a processing device and a method for processing stacks of bags which allow to increase reliability. 
     SUMMARY 
     A processing device according to the invention serves to process at least one stack of bags comprising a plurality of bags. At least one stacking device is provided on which the stack of bags can be placed in a base position. The bags in the stack of bags show a bag length and a bag width. At least one centering device is provided that includes at least two centering units disposed opposite one another and which are disposed so that a driving device can move them relative to one another, toward one another and away from one another. 
     The processing device according to the invention has many advantages. The processing device according to the invention allows increased reliability when processing stacks of bags. The centering device allows to laterally center the bags in a stack of bags. The fact that the centering units are disposed opposite one another and a driving device allows their relative movement toward one another or away from one another allows to reliably center the bags in a stack of bags. 
     In case that when positioning a stack of bags on the stacking device in the base position some or several bags come to be—even slightly—offset, the centering device then reliably centers these bags together with, and/or within, the stack of bags. Thus, a precisely defined position of the bags is ensured prior to further processing. 
     It is possible and also preferred although not required for the centering units disposed opposite to be directly opposite one another. It is also possible for the centering units disposed on different sides to be staggered in the longitudinal direction. It is possible for the quantity of centering units on one of the sides to differ from the quantity of centering units on the other side. For example 2, 3, 4 or more centering units may be provided in the longitudinal direction while the other side shows e.g. one single centering unit or one less than, or else only half the number of, the other side, or any desired other quantity of centering units, or else one continuous centering strip. What is essential is to enable centering between the opposite centering units. 
     In the simplest of cases one centering unit only is provided on each side. Or else it is possible to provide two centering units on one side and one only on the other side. 
     In a preferred specific embodiment the driving device comprises at least one belt. Preferably at least one centering unit may be coupled to the belt at least temporarily. A driving device provided with at least one belt offers many advantages. Preferably the belt is a continuous belt and it is redirected for example over two or more pulleys. This configuration allows a driving unit or driving device to drive the belt by means of a pulley. Or else it is possible for a linear drive to directly act on the carrying side or return side of the belt, driving the belt by linear movement. 
     In particularly preferred specific embodiments at least part of the two centering units disposed on opposite sides is at least temporarily coupled with at least one belt of the driving device. A driving device having for example two or more belts arranged in particular in parallel allows to couple a centering unit with a first belt at least temporarily and to couple a second centering unit with a second belt at least temporarily. In the case of not overly huge processing devices it is in particular preferred to provide just a small quantity of belts and in particular one single belt to which the centering units on opposite sides can be coupled at least temporarily. 
     Particularly preferably at least one centering unit provided on a first side can be coupled at least temporarily with the return side of at least one continuous belt. It is particularly preferred to have at least one centering unit provided on a second side at least temporarily coupled with the carrying side of at least one continuous belt. 
     These configurations offer considerable advantages. The fact that the carrying side of a continuous belt driven in one direction moves in one of the directions while the return side moves in opposite sense in the other direction, allows in a very simple way to obtain opposite-sense movement of the centering units provided on both sides. When a centering unit is coupled on one side with the return side and another centering unit is coupled on the other side with the carrying side, then movement of the belt in a first direction of rotation decreases the distance between the centering units while rotation in the other direction increases the distance between the two centering units. 
     This principle can be utilized advantageously since an adjustable or controlled displacement of the belt allows to adjust the distance between the centering units. The distance may be adjusted by way of the size of the angle of rotation or the size of the linear movement of the belt. 
     It is particularly preferred for the bottom surface of the stacking device to be larger than the surface of the stack of bags. A width of the stacking device is in particular larger than the width of the bags in the stack of bags and the length of the stacking device is likewise larger than the length of the bags in the stack of bags. This is to ensure that the stack of bags is always completely supported on the stacking device. There is no lateral overhang of the stack of bags. 
     In all the configurations it is particularly preferred for at least one centering unit to be configured as, or comprise, a centering finger. It is also possible and preferred for at least one centering unit to include or comprise at least one tine or centering tine. 
     Particularly preferably at least one centering unit is at least temporarily displaceably disposed in a groove of the stacking device. It is for example possible and preferred for at least one centering unit to protrude upwardly from below through the stacking device. On the stacking device, which may for example show a plate on the surface, the stack of bags is disposed which can be centered or positioned on the stacking device as desired due to the centering units passing through from beneath. 
     It is also possible for at least one centering unit to extend at least temporarily from above into the groove in the stacking device or downwardly from above through the groove in the stacking device. 
     Particularly preferably at least one centering unit is disposed in a first position entirely beneath the stacking device or at least beneath a plate of the stacking device. This configuration allows ease of positioning the stack of bags on the stacking device since in particular the centering units disposed on one side can be placed in the first position when a stack of bags is intended to be positioned on the stacking device. The fact that the centering units are displaced to the first position prior to positioning the stack of bags on the feeding side of the stack of bags to the stacking device, they do not project upwardly while positioning the stack of bags on the stacking device and so do not impede positioning the stack of bags in the base position. This variant provides for the bags to be centered within the stack of bags. Movement of the entire stack of bags during centering is not required. Therefore the term of centering in the sense of this application is also intended to mean precise positioning. 
     Preferably a second position of the centering unit is provided in which the centering unit rises, and in particular pivots, upwardly from beneath through the groove. 
     Particularly preferably at least one third position is provided in which the centering unit extends through the groove beyond the top surface of the plate of the stacking device. In this position the stack of bags can subsequently be positioned. 
     In all the configurations it is preferred to provide at least one adjustable and in particular exactly one adjustable stopper defining a bag width and thus in particular limiting the distance which the centering units travel. 
     The adjustable stopper may in particular be displaceable. A travel capturing device may be assigned to the adjustable stopper to allow an automatically controlled adjustment of the bag width. A drive may be provided for controlled adjustment of the adjustable stopper which is for example a linear drive or which varies the adjustable stopper in some other way. The adjustable stopper may for example be provided on a rotary spindle. The travel capturing device may measure a traveled distance directly or else it may infer a set distance for example by way of an absolute encoder or other sensory functions. 
     It is preferred for at least one centering unit to be coupled with the belt through a coupling mechanism. 
     Such coupling mechanism allows controlled coupling and decoupling of the centering unit with and from the belt. 
     It is possible and preferred for the coupling mechanism to comprise at least one spring device. A spring mechanism or a spring device allows to decouple the centering unit from the belt for example by separately arresting or separately moving the centering unit. After deactivating the acting forces this spring device automatically establishes a base state without requiring any drive. 
     Preferably the coupling mechanism comprises at least one coupling unit and at least one movable stopper. 
     For example if the driving device comprises a cylinder having an extending piston rod it is possible for the piston rod to be fixedly connected with a movable stopper that is displaceably arranged on a sliding guide or the like. Only as the movable stopper with the coupling rod is extended far enough for the coupling unit to engage with the movable stopper will the coupling unit and the movable stopper move further in synchrony. 
     Such a coupling mechanism allows for example to move a centering unit on one of the sides only after the centering unit on the other side has already traveled part or even a considerable part of the distance. This is advantageous in particular if the centering unit is first disposed beneath the stacking device on the other side and it must first pivot upwardly. Then it is useful for the centering units to only start approaching one another after the centering unit that is firstly provided beneath the stacking device has already pivoted upwardly. This allows to provide a processing device that is smaller on the whole and thus requires reduced space in width. 
     Preferably the coupling mechanism is therefore set up and configured to establish a coupling between the centering unit and the belt at least in a second position. The coupling mechanism is in particular configured and set up to establish a coupling starting from a second position so that the centering unit and the belt are also coupled in a third position subsequent to the second position. 
     Preferably the coupling mechanism is configured and set up so that in the first position a coupling between the centering unit and the belt is at least substantially released. 
     In the alternative both the centering units may be pivotal so that both the centering units are forced to always travel the same distance. It is possible to provide a separate driving unit for displacing the at least one centering unit on one side. 
     This configuration allows to already displace the centering units to the stopper position on one side before positioning a bag bundle on the stacking device. This is particularly advantageous for bags in a stack of bags that tend to slip sideways in positioning. Positioning the stack of bags immediately abutting a lateral end stopper during processing allows to considerably better prevent single bags or some of the bags from slipping within a stack of bags. This allows considerably higher speeds in placing stacks of bags. 
     However, when processing e.g. particularly stiff bags or bags allowing easy reorganisation such pre-positioning of the centering units on one side of the stack of bags may be dispensed with. Then both of the centering units may approach the stack of bags from both sides for centering and positioning. 
     In all the configurations the centering device on the whole may in particular also serve to guide the bags during the further processing of the bags in the stack of bags. To this end in particular at least two centering units are provided on each side to enable good guiding properties in the longitudinal direction. 
     The processed bags are preferably open-mouth bags having a bag length and an open filling mouth at one end. Preferably at least one marker device is provided. The bag conveying device is in particular suitable and provided for gripping the topmost open-mouth bag off the stack of bags in its base position and to displace it to a take-up position that lies only partially on the stack of bags and in the take-up position. 
     It is preferred to provide at least one bag conveying device. If a marker device is provided, then at least one mark may be put on the open-mouth bags in the take-up position. 
     Preferably the bag conveying device grips the topmost open-mouth bag by its open filling mouth. The bag conveying device comprises in particular at least one suction device. The suction device may be retractably disposed at the bag conveying device. A distance of the take-up position from the base position is in particular shorter than half the bag length and preferably shorter than one fourth of the bag length. The bag conveying device is in particular pivotally received at least at one pivot axis that is in particular disposed above the stacking device. The bag conveying device preferably acts at the open filling mouth. 
     At least one pivot device is provided that is equipped with at least one gripper device. The gripper device of the pivot device is in particular suitable to grasp in a first pivot position the open end of the open-mouth bag in the take-up position. The gripper device of the pivot device is preferably suitable when in a second pivot position to hand over the open-mouth bag to a bag opener and/or to a bag appending device. 
     Advantageously a pivot axis of the pivot device is suitable for pivoting the open filling mouth of the open-mouth bag to a handover position. 
     A lifting device is in particular provided for lifting the bag bottom of the topmost open-mouth bag of the stack of bags in the base position. A fixing device may be provided which fixes the stack of bags gripping the bag bottom. 
     It is preferred to provide at least one product feeder and at least one filling spout for filling the open-mouth bags. At least one closing device is also preferred for closing the open filling mouth of the open-mouth bags. A discharge device may be provided for discharging. 
     The method according to the invention serves for processing at least one stack of bags comprising a plurality of bags. The stack of bags is disposed in a base position on a stacking device. The bags in the stack of bags show a bag length and a bag width. The stack of bags is centered by way of at least one centering device. The centering device comprises at least two centering units disposed opposite one another. The centering units are disposed so they can move relative to one another, toward one another and away from one another. 
     The method according to the invention also has many advantages. The method according to the invention allows reliable processing of stacks of bags where the bags can be centered within the stack of bags. 
     In all the configurations it is preferred to process bags which are open-mouth bags, whose bottom ends are closed and whose top ends have an opening. Or else it is possible to process different types of bags or lengths of tubular sheets. It is in particular also possible according to the invention to center stacks of valve bags. 
     Further advantages of the present invention can be taken from the exemplary embodiments which will be described below with reference to the enclosed figures. 
     Although the exemplary embodiments will be described with reference to processing open-mouth bags, it is possible to process valve bags or other types of bags or else sheets, lengths of sheets, or lengths of tubes lying flat or the like. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The figures show in: 
         FIG. 1  a schematic perspective of the processing device  1 ; 
         FIG. 2  a simplistic view of the processing device according to  FIG. 1  with some components omitted; 
         FIG. 2 b    a top view of an open-mouth bag after marking; 
         FIG. 3  a side view of parts of the processing device according to  FIG. 2  in a side view; 
         FIG. 4  another view of the processing device according to  FIG. 3 ; 
         FIG. 5  a third view of the processing device according to  FIG. 3 ; 
         FIG. 6  a fourth view of the processing device according to  FIG. 3 ; 
         FIG. 7  a fifth view of the processing device according to  FIG. 3 ; 
         FIG. 8  a sixth view of the processing device according to  FIG. 3 ; 
         FIG. 9  a seventh view of the processing device according to  FIG. 3 ; 
         FIG. 10  an eighth view of the processing device according to  FIG. 3 ; 
         FIG. 11  a ninth view of the processing device according to  FIG. 3 ; 
         FIG. 12  a side view of a simplistic processing device; 
         FIG. 13  the centering device of the processing device according to  FIG. 2  in a first position; 
         FIG. 14  the centering device of the processing device according to  FIG. 2  in a second position; and 
         FIG. 15  the centering device of the processing device according to  FIG. 2  in a third position; 
         FIG. 16  another centering device for a processing device according to  FIG. 2  in a first position; and 
         FIG. 17  the centering device according to  FIG. 16  in a second position. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a perspective total view of a packaging machine  100  comprising a processing device  1 . A silo  35  is provided from which the bulk material  26  for bagging is conveyed to a dosing and weighing device  36 . In the exemplary embodiment a weighing system with net-weighing devices is employed where the product  26  for bagging is first collected in a net-weighing device and thereafter filled into the respective open-mouth bag  3 . Beneath the dosing device  36  the product feeder  29  is provided that ends in the filling spout  30  not visible in  FIG. 1 . 
     A casing  34  encloses the processing device  1 . A bag stacking magazine  33  serves to accommodate a number of stacks of bags  2 . The filled open-mouth bags  3  are conveyed off via a discharge device  32 . 
       FIG. 2  shows a schematic, perspective view of the processing device  1  with the housing and other components omitted. 
     The product feeder  29  can be identified in the upper region and it opens into the filling spout  30 . A stack of bags  2 , not shown, is conveyed from the bag stacking magazine  33  to the stacking table  4 . The dimensions of the stacking table  4  may approximately correspond to the bag length  6  and the bag width  48 . Open-mouth bags  3  variable in bag length  6  can in particular be processed. 
     A stack of bags  2  is centered by means of a centering device  50  not shown in  FIG. 2 . This centering device  50  will be described in detail below with reference to the  FIGS. 12 to 17 . For centering, tines  51  and  52  of the centering device  50  approach the stack of bags from outside through the grooves  45  provided on the two sides  46 ,  47  of the stacking table  4 . The tines  52  are pivoted upwardly from beneath on the side  47  and then moved toward the stack of bags  2 , thus centering the stack of bags  2 . 
     The processing device  1  basically works without such a centering device  50 . It has been found though that in particular in the case of stacks of bags  2  comprising a comparatively large quantity of open-mouth bags  3  and/or given high processing speeds the open-mouth bags  3  in the stack of bags  2  may slip sideways or else may be gripped at a slight angle. This may adversely affect a highly precise and rapid filling of open-mouth bags  3 . 
     This is reliably prevented by means of a centering device  50  disposed substantially beneath the stacking device  4 . Depending on the configuration the tines  51  and  52  of the centering device  50  may be located beneath the stacking device  4  when a new stack of bags  2  is positioned on the stacking device  4  to allow the stack of bags to be pushed onto the stacking device  4 . 
     In particular in the case of long, narrow open-mouth bags  3  the bag bottom may drift sideways while the open-mouth bag  3  is transferred to the take-up position. Guiding by the centering device  50  reliably prevents this. 
     The rear end of the stacking table  4  is provided with the lifting device  27  and the fixing device  28  for lifting the bottom end of an open-mouth bag  3  disposed on the stacking device  4 . Subsequently to lifting the bottom end the remainder of the stack of bags  2  lying beneath is fixed by means of the fixing device  28 . 
     At the front end of the stacking device  4  one can recognize the bag conveying device  12  the lower end of which is provided with a suction device  15  or in other cases, with a friction gear for gripping the open filling mouth  8  of an open-mouth bag  3 . 
     The bag conveying device  12  displaces the open-mouth bag  2  to a front position as it is illustrated in  FIG. 6 . The filling mouth  8  of the topmost open-mouth bag  13  rests on the supporting device  38 . In this position the open filling mouth  8  is accessible from beneath in the marking area  44  visible in  FIG. 2 . Then the marker device  25  that is provided beneath the supporting device  38  and is therefore not shown in  FIG. 2  can put at least one mark  7  on the open-mouth bag  3 . A pivot device  18  is equipped with a gripper device  19 . The pivot device  18  comprises a pair of pivot arms with a gripper disposed at each of their ends. The pivot device serves to take over a separated open-mouth bag  3  and to transfer it and hand it over to a bag opener  22  and a bag appending device  23  which ultimately append the opened open-mouth bag  3  to the filling spout  30 . 
     After the open-mouth bag  3  has been filled through the filling spout  30  the open filling mouth  8  of an open-mouth bag  3  is conveyed further by means of the top conveying device  41 . The top conveying device  41  may comprise a closing device  31  for closing the open-mouth bags  3 , or a separate closing device is disposed downstream. The filled open-mouth bag  3  is finally transferred to the discharging belt  32  and discharged. 
       FIG. 2 b    illustrates exemplarily a simplistic open-mouth bag  3  in a top view or a view from beneath respectively. The open-mouth bag  3  is provided with a mark  7  made by the marker device  25 . The marker device  25  is disposed substantially beneath the stacking device  4  and puts the mark  7  in the marking area  44 . 
     The mark  7  includes a designation  42  (“XXX”) and a date  43  (“31.12.20”). The designation  42  may correspond to the trade name or the trademark or else comprise a unique number or the like that preferably unambiguously classifies the contents. The date  43  may indicate or include the best-before date or else for example the bagging date and/or the manufacturing date. It is possible to put multiple designations  42  and/or multiple dates  43  on the open-mouth bag  3 . The data may be printed, punched, or e.g. applied by laser. Electronic data transmission to a readable memory is likewise possible.  FIG. 3  shows a schematic side view of some of the essential components of the processing device  1 . Some of the components and the housing of the processing device have been omitted to facilitate overview and to explain the function. 
     The processing device  1  comprises a height-adjustable stacking device  4  where a stack of bags  2  has been disposed or is being disposed in the base position  5 . The stack of bags  2  comprises a plurality of open-mouth bags  3 , each having a specified bag length  6  and bag width  48 . The open filling mouths  8  of the open-mouth bags  3  are aligned with the front end of the stacking device  4  while the bag bottom  10  is disposed at the rear end of the stacking device  4 , thus forming a stack. 
     In this exemplary embodiment the open-mouth bags  3  have a bag length  6  corresponding to about the length of the stacking device  4 . Longer and in particular shorter open-mouth bags  3  may be used as well. For setting the position of the lifting device  27  and the fixing device  28 , an adjusting device  40  is provided that can be displaced in the direction of the bag length  6 . 
     In the position shown in  FIG. 3  the lifting device  27  has gripped and lifted the rear end of the open-mouth bag  3  in the vicinity of the bag bottom  10 . Subsequently to lifting, the fixing device  28  moves beneath the topmost bag  13  and fixes the remainder of the stack of bags  2  by the bag bottom  10 . 
     The bag conveying device  12  at the front end  9  has an extendible suction device  15  which in the position illustrated in  FIG. 3  is extended and has lowered to an area at the open filling mouth  8 . In this state the suction device  15  is activated, gripping the front filling mouth  8  of the topmost open-mouth bag  13 . 
     Furthermore a pivot device  18  is provided to take over a separated open-mouth bag  3 . The pivot device  18  has a gripper device  19  and is illustrated in  FIG. 3  in the second pivot position  21 . The pivot device  18  is disposed to pivot about the pivot axis  24 . The pivot device  18  serves to take over the topmost open-mouth bag  13  from the take-up position  14  and after the pivot device  18  pivots to the second pivot position  21  it is transferred to the bag opener  22  and the bag appending device  23  shown above the pivot device  18  where an appended open-mouth bag  3  is illustrated in the  FIG. 3 . 
       FIG. 4  shows the situation after retracting the suction device  15  at the bag conveying device  12  so that the filling mouth  8  of the topmost open-mouth bag  13  is lifted off the stack of bags  2 . At the same time the lifting device  27  at the other end  11  can be deactivated so that the bag bottom  10  falls back down onto the stack of bags  2  that the fixing device  28  retains. 
       FIG. 5  shows the position after the bag conveying device  12  has traveled to a front position where the filling mouth  8  of the topmost open-mouth bag  13  lies above the take-up position  14 . Accordingly both the open filling mouth  8  and the bag bottom  10  have been displaced forwardly by a distance  16  in the direction of the open filling mouth  8 . It is possible to pivot the bag conveying device  12  about one or more pivot axes  17 . A different linear movement or a motion resulting in a linear movement is also possible. During the forwardly movement of the bag conveying device  12  the fixing device  28  fixes the rear end of the stack of bags  2  so as to ensure that only one, specifically the topmost, of the open-mouth bags  13  is pulled forward by way of the movement of the bag conveying device  12 . This is to realize an efficient separation of the open filling mouth  8  of the open-mouth bag  13 . 
     In transfer from the position shown in  FIG. 5  to that shown in  FIG. 6  the suction device  15  is displaced downwardly by means of the cylinder device  37  so that the open filling mouth  8  rests on the supporting device  38 . In this position the open filling mouth  8  is accessible from beneath at least in part so that the marker device  25  provided beneath the supporting device  38  can apply at least one mark on the open-mouth bag. The marker device may for example include a laser that applies one or more letters or characters to the outer surface of the open-mouth bag  13 . It is for example possible to mark or label the open filling mouth of the open-mouth bag  13  indicating the filled product, the batch number, the filling date or the best-before date of foodstuff by embossing or spraying onto the open filling mouth or in some other way. 
     A marker beam of the marker device may be directed at the bag immediately from beneath or else it may be deflected by mirrors so as to protect the optics from dirt. 
     In  FIG. 6  one can see that the distance  16  by which the topmost open-mouth bag  13  is pulled forward toward its open filling mouth  8  represents only a minor portion of the bag length  6 . The distance  16  can be selected to suit the application. 
       FIG. 7  shows a situation where the lifting device  27  has been lowered back down onto the rear end of the stack of bags  2  for gripping and then lifting the bag bottom  10  of the next open-mouth bag  3 . 
     This is the situation illustrated in  FIG. 8 . At the same time the pivot device  18  pivots from the second pivot position  21  shown previously to a first pivot position  20  illustrated in  FIG. 9 . In pivoting from the pivot position  21  to the pivot position  20  the gripper device  19  moves from a position noticeably above the stacking device  4  to a position at the level of the stacking device  4  while the gripper device is moved in the longitudinal direction of the open-mouth bags from a central region of the open-mouth bags  3  to the front end. 
     While the gripper device  19  is pivoting the lifting device  27  with the bag bottom  10  remains lifted and the fixing device  28  lowers down to the bottom area of the remaining stack of bags  2 . At the same time the bag conveying device  12  advances some more so as to avoid collision with the pivot device  18 . Depending on the configuration it is also possible for the bag conveying device to remain between the two pivot arms of the pivot device  18  as the pivot device pivots downwardly. In the subsequent pivoting motion from the pivot position  20  to the pivot position  21  the bag conveying device  12  at any rate moves out of the path of motion. 
       FIG. 10  shows the position in which the pivot device  18  in the upper, second pivot position  21  transfers the open-mouth bag  3  hanging off the gripper device  19  to the bag opener  22  and the bag appending device  23 . During pivoting from the pivot position  20  to the pivot position  21  the gripper device  19  moves upwardly and returns, viewed in the longitudinal direction of the open-mouth bags. Thus, in the pivot position  21  the open-mouth bags are hanging in a center area above the stacks of bags  2 . The pivoting of the gripper device  19  neither requires more mounting space nor a larger footprint. 
     Now another open-mouth bag is the topmost open-mouth bag  13  lying on the stack of bags  2 . The stacking device  4  automatically lifts such that what is now the topmost open-mouth bag  13  is approximately on the same level as is the supporting device  38  so that the topmost open-mouth bag  13  can later be taken over by the bag conveying device  12 . 
     In the position illustrated in  FIG. 10  the bottom end  10  of the open-mouth bag  13  has been lifted and the fixing device  28  has fixed the bottom end of the stack of bags  2 . The bag conveying device  12  is in an advanced position in which the pivot device  18  can pivot to the upper, second pivot position  21 . 
       FIG. 11  shows the position after handover of a bag  3  to be filled, from the pivot device  18  to the bag opener  22  and the bag appending device  23 . What is now the topmost open-mouth bag  13  is still lifted by its bottom end by the lifting device  27 . Thereafter the bag conveying device  12  moves back again such that the suction device  15  grips the open filling mouth  8  of what is now the topmost open-mouth bag  13 , lifts it and transfers it to the take-up position  14 . 
       FIG. 12  illustrates a processing device  1  in a simplistic, sectional side view substantially showing the centering device  50  at the schematically illustrated stacking device  4 . The centering device  50  is substantially located beneath the stacking device  4  or beneath the plate  53  of the stacking device  4 . The plate  53  of the stacking device  4  is illustrated in section. The section is through the region of the grooves  45 . 
       FIG. 12  shows a diagrammatic illustration of a first variant where the centering device  50  of the processing device  1  has a pair of pulleys  59  and  60  around which a continuous belt  54  is provided. The belt  54  which is presently wholly continuous has the centering finger  52  attached to it such that the centering finger  52  protrudes perpendicularly or approximately perpendicularly from the belt  54 . This means that as the pulleys  59  and  60  rotate, the centering finger  52  with the belt  54  is conveyed further although it projects perpendicularly from the belt  54 . 
     It is possible for one of the pulleys  59  and  60  to be driven via a motor, presently shown in dashed lines at the pulley  60 , provided as the driving device  49  for driving the belt  54 . Or else, a cylinder  56  with an extendible piston rod  58  may serve as the driving device  49 . The piston rod is firmly connected with the belt  54  via an engaging dog  55 . Extending the piston rod  58  therefore causes a synchronous, counterclockwise movement of the belt  54  in the orientation of  FIG. 12 . Reversely, the belt  54  moves clockwise as the piston rod  58  is retracted. 
       FIG. 12  shows three different positions  61 ,  62  and  63  of the centering device  50 . The second position  62  is shown in a solid line while the first position  61  and the third position  63  are shown in dotted lines. 
     In the first position  61  the centering unit  51  configured as a centering finger is on the left side  46 , farthest remote from the illustrated stack of bags  2 . The centering unit provided on the other side  47  and likewise configured as a centering finger  52  is disposed in the position  61  beneath the plate  53 . Since in the position  61  the tine or centering finger  52  is located beneath the plate  53 , a new stack of bags  3  can be pushed from the side  47  at least approximately to the base position  5 . 
     As the piston rod  58  extends out of the cylinder  56 , the connection point  55  at the belt  54  travels the distance “a” in synchrony, moving toward the pulley  60 . In this way the centering finger  51  pivots from the first position  61  beneath the plate  53  through the groove  45  to a position  62  that is at least partially above the plate  53 , by the distance “a” and at the same time, during transfer from the first position  61  to the second position  62 , the centering finger  51  coupled with the drive belt  54  is transferred by the same distance “a” to the position  62  which is noticeably closer to the stack of bags  2 . 
     As the piston rod  58  extends further out of the cylinder  56  by the distance “b”, the centering finger  52  that is coupled with the carrying side  73  travels from the right in the diagram of  FIG. 12  toward the stack of bags  2  by the distance “b” while in the illustration according to  FIG. 12  the centering finger  51  travels from the left toward the stack of bags by the same distance “b”. Finally the extended position is reached in which the third position  63  is reached. 
     The centering fingers  51  and  52  bear directly against the stack of bags  2 . By way of transferring the centering fingers  51  and  52  each of the open-mouth bags  3  inthe stack of bags  2  has been positioned in the third position  63  and centered. 
     The distance that the piston rod  58  travels and in particular the distance “b” is adapted to the current bag width  48  of the processed open-mouth bags  3 . 
     The centering device  50  allows ease and reliability in centering stacks of bags  2 . Moreover, multiple centering units  51  and  52  placed in series one after the other provide a guide when pulling off the open-mouth bags  3 . Even if a processed open-mouth bag is briefly entirely released for example in the take-up position  14  before the gripper device  19  grips the top filling mouth  8  of the open-mouth bag  3 , the centering device  50  ensures a defined position of the open-mouth bag  3 . It has been found that, given high processing speeds and specific bag materials, some open-mouth bags may slightly slip sideways on the stack of bags in the absence of a centering device  50 . A centering device  50  equipped with multiple centering units with the centering units positioned in series one after the other will show a reliable and reproducible separation and positioning even of long, narrow open-mouth bags, to then be filled. 
     With reference to the  FIGS. 13 to 15  another exemplary embodiment will be discussed where the centering device  50  is provided with a coupling mechanism  70  to allow temporary decoupling of at least one centering unit  51  from the movement of the continuous belt  54 . 
     The driving device  49  is once again a cylinder  56  with an extendable piston rod  58  or else a driven pulley. An engaging dog  55  is connected with the piston rod  58 . The engaging dog  55  is connected with the continuous belt  54 . 
     The engaging dog  55  is provided with a movable stopper  67  provided to move relative to a gliding rod  64  and a coupling rod  57 . In this way the movable stopper  67  can be displaced on the gliding rod  64 . The relative motion between the gliding rod  64 , the coupling rod  57  and the movable stopper  67  is limited by the coupling unit  66  that is configured as a coupling sheet. 
     Firstly, in the first position illustrated in  FIG. 13  the coupling between the coupling unit  66  and the movable stopper  67  is released so that as the piston rod  58  extends, the movable stopper  67  fixedly disposed on the engaging dog  55  moves along and glides on the gliding rod  64 . Further extending has the movable stopper  67  abut against the coupling unit  66  so that then the coupling rod  57  and the coupling rod  58  will move in synchrony. In this way, as the coupling rod  58  extends further out of the cylinder  56 , not only the belt  54  is conveyed but so is the centering unit  51  connected therewith via the coupling rod  57 . 
     While during transfer of the centering unit  52  from the first position  61  (see  FIG. 13 ) to the second position  62  (see  FIG. 14 ), firstly only the centering unit  52  pivots upwardly from the region beneath the plate  53 , the first centering unit  51  will also be linearly displaced as the second position  62  is reached. In the case that the first centering unit were fixedly coupled to the belt  54 , the first centering unit  51  would already be in the position shown in the hatched area in  FIG. 14  after transfer to the second position  62 . Then, more mounting width would be required. 
     Thereafter the centering units  51  and  52  approach one another. Extending of the piston rod  58  out of the cylinder  56  is limited by an adjustable stopper  65  that can be adjusted laterally. When, as the piston rod  58  extends further, the centering unit  51  abuts against the adjustable stopper  65 , the piston rod  58  is prohibited from extending further. The position of the adjustable stopper  65  is set such that in this position the centering units  51  and  52  adequately center the stack of bags  2  with the open-mouth bags  3 . The position of the adjustable stopper  65  is in particular adapted to the width  48  of the open-mouth bags  3 , specifying an intended end position of the centering units  51 ,  52  offset relative to the center line  69  substantially by half the bag width. 
     This position is illustrated in  FIG. 15 . The coupling device  70  with the presently linked coupling device  66  and the adjustable stopper  65  are coupled to one another. For better understanding  FIG. 15  shows on both sides of the stack of bags  2  small distances from the centering fingers  51  and  52  which may, though do not need to, be present when actually centering a stack of bags  3 . 
     As the piston rod  58  retracts back into the cylinder  56 , the spring force of the spring device  68  acts, causing a transfer to the first position  61  illustrated in  FIG. 13 . 
     With reference to the  FIGS. 16 and 17  another exemplary embodiment will now be discussed.  FIG. 16  is a simplistic view of the processing device  1  with the centering device  50  and the plate  53  of the stacking device. In this configuration the centering device  50  is additionally provided with a driving unit  75  for separately moving the centering unit  51 . 
     An adjustable stopper  65  is again provided that is adjusted to the bag width  48 . The adjustable stopper  65  is provided displaceable by way of a driving unit  76 . A travel measuring device  74  can capture the position of the adjustable stopper  65  and/or the distance which the centering unit  51  traveled or a measure characteristic thereof. Thus the travel capturing device  74  allows for example computer-controlled adjustment of the bag width  48 . In this way the bag width  48  can be set automatically for processing bags of different widths. 
     Although such a travel capturing device is not shown in the preceding exemplary embodiments, it is preferably provided therein. 
     In the embodiment variant illustrated in  FIG. 16  the centering unit  51  is positioned at the stopper  65  immediately above the driving unit  75 . This means that the centering unit  51  is directly transferred to its end position which corresponds to the position  63  in the preceding example according to  FIG. 14 . The centering unit  52 , however, remains in the first position  61  beneath the plate  53 . 
     Now when the stack of bags  2  is intended to be centered, the piston rod  58  of the cylinder  56  is extended. The belt  54  is conveyed immediately further and the centering unit  52  pivots upwardly around the pulley  60  and through the groove  45  in the plate  53 . 
     Thereafter the centering unit  52  travels toward the first centering unit  51  as the cylinder  58  extends further until the third position  63  and thus the end position is reached. 
       FIG. 17  shows the intermediate position of the centering unit  52  in the second position  62 . In the third position  63  a position will result as it has been illustrated in  FIG. 15  and discussed with reference to the preceding exemplary embodiment. 
     On the whole the invention provides an advantageous processing device that allows reliable centering and/or separating of the bags. 
     The centering device according to  FIGS. 13 to 15  allows centering and reliably positioning a stack of bags  2 , with the centering units  51  and  52  approaching the stack of bags  2  from both sides  46  and  47 . In the exemplary embodiment according to  FIGS. 16 and 17  the stack of bags is positioned at an end stopper which is formed by the centering units  51 . For the further centering the centering units  52  approach the stack of bags  2  from the other side  47 . 
     In the further processing and separating the open-mouth bags  3  are guided by the centering units  51  and  52  in an advantageous way so as to reliably prevent the open-mouth bags  3  from slipping sideways during pulling forward and in the further processing. 
     On the whole the invention provides an advantageous processing device and an advantageous method which allow to reliably and efficiently separate open-mouth bags from a stack of bags. The required footprint and also the space requirement are low. The output can be considerably increased over the prior art thus resulting in advantages of both mounting space and capacity. In the take-up position, marks and other applications can be applied on the open-mouth bag. 
     The processing device  1  can be controlled by a control device, not shown, provided with one or more light barrier(s) or other sensors to ensure defined positioning during the entire operation. 
     The compact design allows noticeably reduced space requirements so as to allow considerably increased bagging capacities within the same mounting space. 
     
       
         
               
             
               
               
             
           
               
                   
               
               
                 List of reference numerals: 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 processing device 
               
               
                 2 
                 stack of bags 
               
               
                 3 
                 open-mouth bag 
               
               
                 4 
                 stacking device 
               
               
                 5 
                 base position 
               
               
                 6 
                 bag length 
               
               
                 7 
                 mark 
               
               
                 8 
                 open filling mouth 
               
               
                 9 
                 one end 
               
               
                 10 
                 bottom, bag bottom 
               
               
                 11 
                 other end 
               
               
                 12 
                 bag conveying device 
               
               
                 13 
                 topmost open-mouth bag 
               
               
                 14 
                 take-up position 
               
               
                 15 
                 suction device 
               
               
                 16 
                 distance 
               
               
                 17 
                 pivot axis 
               
               
                 18 
                 pivot device 
               
               
                 19 
                 gripper device 
               
               
                 20 
                 first pivot position 
               
               
                 21 
                 second pivot position 
               
               
                 22 
                 bag opener 
               
               
                 23 
                 bag appending device 
               
               
                 24 
                 pivot axis 
               
               
                 25 
                 marker device 
               
               
                 26 
                 bulk material 
               
               
                 27 
                 lifting device 
               
               
                 28 
                 fixing device 
               
               
                 29 
                 product feeder 
               
               
                 30 
                 filling spout 
               
               
                 31 
                 closing device 
               
               
                 32 
                 discharge device 
               
               
                 33 
                 bag stacking magazine 
               
               
                 34 
                 casing 
               
               
                 35 
                 silo 
               
               
                 36 
                 dosing and weighing device 
               
               
                 37 
                 cylinder device 
               
               
                 38 
                 supporting device 
               
               
                 40 
                 adjustment device 
               
               
                 41 
                 upper conveying device 
               
               
                 42 
                 designation 
               
               
                 43 
                 Date 
               
               
                 44 
                 marking area 
               
               
                 45 
                 groove 
               
               
                 46 
                 side 
               
               
                 47 
                 side 
               
               
                 48 
                 bag width 
               
               
                 49 
                 driving device 
               
               
                 50 
                 centering device 
               
               
                 51 
                 centering unit, centering finger 
               
               
                 52 
                 centering unit, centering finger 
               
               
                 53 
                 plate 
               
               
                 54 
                 belt 
               
               
                 55 
                 engaging dog 
               
               
                 56 
                 cylinder 
               
               
                 57 
                 coupling rod 
               
               
                 58 
                 piston rod 
               
               
                 59 
                 pulley 
               
               
                 60 
                 pulley 
               
               
                 61 
                 first position 
               
               
                 62 
                 second position 
               
               
                 63 
                 third position 
               
               
                 64 
                 gliding rod 
               
               
                 65 
                 adjustable stopper 
               
               
                 66 
                 coupling unit, coupling sheet 
               
               
                 67 
                 movable stopper 
               
               
                 68 
                 spring device 
               
               
                 69 
                 center line 
               
               
                 70 
                 coupling mechanism 
               
               
                 72 
                 return side 
               
               
                 73 
                 carrying side 
               
               
                 74 
                 travel capturing device 
               
               
                 75 
                 driving unit 
               
               
                 76 
                 driving unit 
               
               
                 100 
                 packaging machine