Abstract:
A device and method for transferring flexible flat objects, in particular printed products, between two conveyors. The device includes a first gripper conveyor with first grippers moved along a first gripper conveyor path for hanging transport of the objects in a conveyor direction by gripping a first object edge, a second gripper conveyor with second grippers moved along a second gripper conveyor path, for receiving the objects by gripping a second object edge which lies opposite the first object edge, and at least one actuation device for opening and closing the first and second grippers such that, in a transfer region, the objects may be transferred from the first grippers to the second grippers. The distances of the first and the second grippers are different to one another in front of the transfer region, wherein the distances of the first grippers are smaller than that of the second grippers.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention lies in the field of conveyor technology and relates to a device and to a method for the transfer of flexible, flat objects, in particular printed products, between two conveyors. 
     2. Description of Related Art 
     In conveyor technology and in particular in the field of printing technology, it is often necessary to transfer objects from grippers of a first gripper conveyor into grippers of a second gripper conveyor. Printed products coming from a printing machine are held and conveyed by a gripper. 
     Various ways as to how such a transfer between two gripper conveyors may occur is sketched in EP-B 1321410. EP-A 1834911 describes a further transfer device, with which individual objects are transferred from first grippers to second grippers. The second grippers are arranged in each case below the first grippers. The first grippers are opened in a transfer region, so that the objects, on account of gravity, slide into the co-moved open second grippers, which are thereupon closed. 
     Often, the mutual distance of the grippers between the first and the second gripper conveyor is different, and as a rule the distance of the first grippers is smaller than the distance of the second grippers. In the state of the art, the speeds of the two gripper conveyors are therefore selected adapted to one another such that the first and the second grippers are synchronised in the transfer region and execute no movements relative to one another seen in the conveyor direction, in order not to upset the transfer process by way of displacement in the conveyor direction. 
     On separating out objects transferred in pairs, but also with the transfer of individual objects from a first gripper to a second one, special demands are made to the extent that the object edge which is not gripped is reliably positioned such that it is led as precisely as possible into the open gripper jaw of the second gripper. This, above all, is important with flexible products such as e.g. printed products, since on conveying, they are only held at one product edge and may change their position or deform on account of external influences such as e.g. drafts. 
     With EP-A 1834911, the distance of the first to the second gripper conveyor path is constant in the transfer region. The objects which are released by the first gripper are led into the second gripper supported by gravity by way of a support device in the form of two laterally engaging spirals which define a support surface co-moved with the second gripper taking over. They are temporarily not held during the transfer. Also with EP-B 1321410, the first gripper is opened before the synchronously co-moved second gripper is closed. 
     It is the object of the invention to further improve known devices and methods for the transfer of flexible, flat objects from a first gripper conveyor to a second gripper conveyor, in particular in order to be able to transfer and/or collate the objects in a reliable and easily controllable manner. 
     BRIEF SUMMARY OF THE INVENTION 
     The device according to the invention comprises a first gripper conveyor with first grippers moved along a first gripper conveyor path, for the essentially hanging transport of the objects in a conveyor direction. Hereby, first object edges are gripped by the first grippers. The first grippers are attached on a continuously driven, first drive member and in the case of operation are moved at an essentially constant speed. The objects are conveyed individually or in groups, and with a grouped conveying, the first object edges may lie on one another or be offset from one another within the gripper. Moreover, a second gripper conveyor with second grippers moved along a second gripper conveyor path is present. These grippers receive the objects by way of then gripping a second object edge, which lies opposite the first object edge. They may already contain objects, wherein the objects released by the first grippers may be added to these. The first and the second grippers in each case are attached on a continuously driven first and second drive member respectively, e.g. a chain, wherein the respective conveyor path is fixed by way of suitable guides. Moreover, at least one actuation device is present for opening and closing the grippers, e.g. in the form of control cams or other elements which initiate the opening or closure procedure. Preferably, each conveyor has its own actuation device. The conveyor paths and the actuation device are designed and set up such that a transfer of the objects from the first grippers to the second grippers may take place in a transfer region. The distances of the first grippers amongst one another in front of the transfer region are smaller than the distances of the second grippers there. According to the invention, the distances of the first and/or second grippers are variable along their conveyor path. The distances of the first grippers in the transfer region are reduced compared to their distances in front of the transfer region. Alternatively or additionally, the distances of the second grippers in the transfer region are increased with respect to their distances in front of the transfer region. A difference in the distances of the first and second grippers in front of the transfer region is therefore increased even more. In other words, the path speeds of the first or second grippers, proceeding from the respective constant base drive speeds (e.g. the speed of the drive member) is changed in the transfer region such that the second grippers may catch up with respect to the first grippers. The first grippers are, thus, delayed briefly and/or the second grippers are accelerated. 
     With regard to the method, the following steps are present: conveying the objects with the first gripper conveyor in an essentially hanging manner in the conveyor direction, wherein the first grippers hold the objects on a first object edge; further conveying of the objects by the second gripper conveyor, wherein the second grippers hold a second object edge which lies opposite the first object edge; transfer of the objects from the first grippers to the second grippers in the transfer region by way of opening the first grippers and closing the second grippers; moving the first and the second grippers in a manner such that the distances of consecutive first grippers in front of the transfer region are smaller than the distances of consecutive second grippers in front of the transfer region. According to the invention, the distances along the respective gripper conveyor path of consecutive first and/or second grippers is changed in a manner such that the distances of the first grippers in the transfer region are reduced with respect to their distances in front of the transfer region and/or that the distances of the second grippers in the transfer region are increased with respect to their distances in front of the transfer region. 
     The conveyor speeds of the first and second grippers are selected such that a second gripper is assigned to each first gripper and in the transfer region is moved largely, but not exactly, synchronously with the first gripper. A relative movement of the first and second grippers assigned to one another with a speed component in the conveyor direction is achieved by way of the distance change and the otherwise constant drive speed. The second gripper, thus, catches up with respect to the first gripper, so that the distance of the first and second gripper relative to one another reduces, in particular seen along the main surface of the object. By way of this, the object at both edges is enclosed by grippers and the second object edge is positioned gently in the gripper jaw of the second gripper. Before the second gripper is closed, the object is supported preferably on the trailing gripper limb of a leading second gripper and slides along its outer surface into the open gripper jaw. The trailing gripper jaw for this is elongated in particular with respect to the leading gripper jaw, and forms a surfaced support. One may thus make do without additional support means engaging from the outside. Moreover, one succeeds in realising the transfer region in a space-saving manner, in particular if the objects on transfer are already arranged in an imbricate manner, i.e. with a certain oblique position with respect to the vertical, and the first gripper leads the assigned second gripper in the conveyor direction, with a gripper jaw orientated opposite to the conveyor direction. 
     The distance change is preferably realised by way of the first and/or second gripper being arranged on the first and second drive member respectively, in a projecting manner such that the distance of consecutive grippers may be changed by way of the curvature of the gripper conveyor path. The distances are locally reduced by way of a concave path curvature and are increased by way of the convex path curvature. The grippers may, for example, be connected to the drive member via a lever, wherein the distances of the articulation points of the levers on the drive member are constant. The distance of the grippers is, for example, the distance between a defined location on the gripper and the same location on an adjacent gripper. These reference points may e.g. be the clamping region, the axis of the joint or the base of the gripper. The distance change in another variant may also be achieved by way of pivoting the gripper relative to its drive member. 
     The first and the second drive member is, for example, a chain led in a channel. The articulation points, on which the grippers are fastened on the drive member, preferably have a constant distance to one another. The grippers are e.g. arranged via a lever or other spacer, at a distance to the articulation points, so that the reference points on the gripper itself have a defined distance to the mentioned deflection points. The path of the drive member, which is fixed by the guide elements, is hereinafter called the gripper conveyor path. It may differ from the path of the reference points on the gripper. The latter is determined by the shape of the gripper conveyor path and/or by a pivotability of the levers or spacers relative to drive member, which may likewise be present as the case may be. 
     “Projecting”, for example, means that the reference points, e.g. the joint axis lies at a distance to the articulation point, which is larger than the distance of two adjacent articulation points or which lies within a similar magnitude to this distance. In the latter case, the distance of the joint axis to the articulation point is preferably 0.1 times, particularly preferably at least 0.2 times and further preferably at least 0.5 times the distance of the articulation points of adjacent grippers. 
     Transfer region is to be understood as that region, in which the transfer process of the objects from the first grippers to the second grippers may take place, in particular since the grippers have approached one another to such an extent, that a controlled transfer is possible. The object in the transfer region may be influenced by the first grippers as well as by the second grippers, for example the object already touches a second gripper whilst it is still held by the first gripper. A controlled transfer, with which the objects are gripped at each point in time, takes place, for example, by way of the first grippers only being opened after the second grippers have been closed. 
     The conveyor paths of the first and second grippers are roughly parallel to one another in the transfer region with the exception of the concave/convex dents for the distance change. The distance of the conveyor paths to one another is preferably smaller than a product length, so that the products in a view from above are held overlapping one another, but despite this held individually by grippers, conveyed through the transfer region in a relatively compact and thus space-saving formation. The distance of the conveyor paths is preferably variable for adapting to different formats. 
     In a further operating mode, the second grippers already contain further objects when they enter into the transfer region. Then in the transfer region, they are briefly opened for receiving objects conveyed past by the first grippers. Thereby, the gripper jaws of the second gripper point essentially upwards, so that the objects do not fall out. The transfer device may thus be used for precollection of small groups of objects. 
     Preferably, a stabilisation device is located in front of the transfer region, which stabilises the free edges of the objects held by the first grippers and releases them at a well defined location at the entry of the transfer region. The stabilisation device in the operating mode “precollection” may advantageously also act on the further objects in the second grippers, and position these such that they enter the transfer region in a defined position. The objects held by the first and second grippers, in the operating mode “precollection” are inserted into one another in a comb-like or zip-like manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Examples of the invention are represented in the drawings and described hereinafter. There are shown in a purely schematic manner: 
         FIG. 1  a transfer region with a first gripper conveyor and with a second gripper conveyor, with the transfer of objects from the first grippers into the second grippers; 
         FIGS. 2 and 3  the transfer device of  FIG. 1  in the operational mode “precollection”. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The transfer device  1  comprises a first gripper conveyor  10  with first grippers  12  which are attached on a drive member  16  sketched in  FIG. 3 , here a chain, and are moved in a conveyor direction F. The spatial position of the drive member  16 , and thus the first gripper conveyor path U 1  are defined by a guide member  17  (see  FIG. 3 ), here a guide rail or a canal. The first grippers  12  here are conventional grippers with two, in each case roughly equally long gripper jaws  13 ,  14  which are pivotable about a joint axis  18  and may assume an open position and a clamping position. The first grippers  12  are opened at an opening location S 1  by way of a first actuation device  40  which here is indicated only in a schematic manner and may be designed, for example, as a control cam. For cooperation with the actuation device  40 , the grippers  12  comprise control elements, e.g. cam rollers, in a manner known per se. The first gripper conveyor path U 1  runs obliquely upwards relative to the direction G of gravity. The first grippers  12  convey objects  2  individually or in pairs (not represented) coming from a process situated upstream. Thereby, the objects in each case held at their first edge  3  and the oppositely lying second edges  4 , point downwards corresponding to gravity. 
     The transfer device  1 , moreover, comprises a second gripper conveyor  20  with second grippers  22  which are attached on a drive member  26  which is sketched in  FIG. 3 , here a chain, and are moved in a conveyor direction F. The spatial position of the drive member  26 , and thus the second gripper conveyor path U 2 , is defined by a guide member  27 , here a guide rail or a canal. The second grippers  22  likewise have two gripper jaws  23 ,  24  which are pivotable about a joint axis  28  and whose position relative to one another may be influenced by a second actuation device  50 , e.g. a control cam. The actuation device  50  here opens the second grippers at an opening location S 2  whose position may be variable and closes these at a closure location S 3 . 
     Here, the trailing gripper jaw  23  is extended with respect to the leading gripper jaw  24 . It allows the insertion between two objects  2  which are held by the first grippers  12 , and the deflection of these into different (adjacent) second grippers  22 . Moreover, the extended limb  23  may act as a support surface, along which an object  2  slides into the second gripper  22 . With the release of the objects  2  from the first grippers  12 , the objects  2  are thus also held in a supported manner by way of the extended limbs  23  or a product already bearing thereon. The second gripper conveyor path U 2  here has a deflection of 180° as well as subsequently a section rising upwards with respect to gravity, in which it is located directly below the first gripper conveyor path U 1 . 
     The first and second grippers  12 ,  22  are in each case attached on the drive member  16 ,  26  in a projecting manner via levers  15 ,  25  with a length  11  and  12  respectively. The articulation points  19 ,  29  of the levers  15 ,  25  on the drive member  16 ,  26  are located at a constant first or second distance b 1 , b 2  from one another. With this, depending on the curvature of the path U 1 , U 2 , a variable distance d 1 , d 1 ′ and d 2 , d 2 ′ of the first and second grippers respectively amongst one another results, measured at the reference points, e.g. here between the joint axes  18 ,  28  of adjacent grippers. Here, the first conveyor path U 1  has a section U 1 ′ with a concave curvature. Here therefore, the distances d 1 ′ of the first grippers  12  are reduced with respect to the corresponding distances d 1  in straight path sections with a constant distance b 1 . 
     The length l 1  of the lever  15  is preferably of the same magnitude as the distance b 1  of the articulation points  19  of the grippers  12  on their drive member, so that the change of the distances d 1  of the grippers  12  may be felt. Preferably, |1/b1&gt;0.1, particularly preferably |1/b1&gt;0.2, further preferably |1/b1&gt;0.5. |1 may also be larger than b 1  (|1/b1&gt;1). 
     The levers  15 ,  25  may also be pivotably arranged on the drive member  16 ,  26 , wherein the pivot position may be controllable by way of additional control elements. A distance change of the grippers  12 ,  22  may likewise be achieved by way of this. 
     A stabilisation device  30  is arranged below the first conveyor path U 1 . This here consists of a stationary guide  32 , e.g. of an arched, flat element. It has two surfaces  33 ,  34 , of which one follows the course of the second conveyor path U 2  in the region of its deflection, thus describes a 180° circular arc segment in a plan view of the plane of the drawing. Seen from the second conveyor  20 , the outer surface  33  of the guide  32 , which faces the first gripper conveyor, serves as a support and guide surface for the objects which are held by the first grippers  12 , before the transfer. As  FIGS. 2 and 3  show, the inner surface  34  facing the second gripper conveyor may serve for supporting and positioning any further products  2 ′, which are already held by the second grippers  22 . 
     The conveyor paths U 1 , U 2  of the two gripper conveyors  10 ,  20 , in a region which is hereinafter so called the transfer region T, approach one another to such an extent that an object  2  which is held by one of the grippers  12 ,  22  may be influenced by the other gripper, e.g. lies on this. In this manner, a controlled transfer of the objects  2  may take place. The conveyor paths U 1 , U 2  run towards each other at the entry E of the transfer region T with a reduced distance and then preferably run essentially parallel to one another The transfer region T corresponds roughly to the overlap of the rising sections of the first and second conveyor path U 1 , U 2  respectively, up to the closure location S 3  of the second grippers  22 . The entry E of the transfer region is, for example, that location at which the stabilisation device  30  ends. The gripper conveyors may be part of the superordinate conveyor installation. 
     The conveyor direction F of both gripper conveyors  10 ,  20  is directed obliquely upwards in the transfer region T. 
     The functioning of the transfer device is described hereinafter: 
     In  FIG. 1 , the first grippers  12  convey the objects  2  by way of these being held at the first edge  3 . The second edge  4 , before entry into the transfer region T, is pulled over the outer surface  33  of the guide  32 , so that the objects  2  sag opposite to the conveyor direction F. The second edges  4  are abruptly released again at the entry E of the transfer region. The grippers  12 ,  22  are synchronised such that the second edge  4  on release by the stabilisation device  30 , i.e. at its front end, on account of relaxation, springs into the intermediate space between two trailing grippers jaws of adjacent second grippers  22  or into an open second gripper  22 . The two edges  4  of the objects  2  are positioned on the long gripper jaws  23  by way of this, and specifically at their outer end. The long gripper jaw  23  of a second gripper  22  in the transfer region is flush with the short gripper jaw  24  of the trailing second gripper  22 . It therefore forms a support surface, along which the object may be led into the open gripper jaw of the trailing gripper  22 . 
     This relative movement for introducing the second edges  4  into a respective second gripper  22  is achieved as follows: The first and the second grippers  12 ,  22  are moved essentially synchronously through the transfer region T at speeds which are adapted to one another. Since the distances b 1  of the first grippers (or their articulation points on the drive member) are smaller than the respective distances b 2  of the second grippers  22 , the second gripper conveyor  20  is driven with a correspondingly greater speed. In the concave region U 1 ′ of the first conveyor path U 1 , the path speed of the first grippers  12  is reduced with respect to the base speed of the drive member  16 . The second grippers  22  accordingly catch up with respect to the first grippers  12 . The object is led deeper into the jaw mouth of the second gripper  22  by way of this.  FIG. 1  shows that the second edge  4  in the course of the transfer region T slides more deeply into the gripper jaw of the second gripper  2 , although the distance of the two conveyor paths U 1 , U 2  is even slightly increased in regions on account of the concave curvature. 
     The conveyor paths U 1 , U 2  are shaped, and the grippers  12 ,  22 , for example, controlled also in their pivot position, such that the gripper jaws of two first and second grippers  12 ,  22  assigned to one another, point in essentially the same direction but face one another, at least in the first section of the transfer region (roughly up to the end of the concave section U 1 ′). 
     The second gripper  22  may subsequently be closed at the closure location S 3  by the actuation device  50 . Essentially simultaneously, the first gripper  12  is opened at the opening location S 1  by the actuation device  40 . A particularly controlled transfer is achieved by way of this. The extended trailing gripper jaws  23  of the second grippers  22 , after the transfer, also serve as a support surface for the objects  2 , which then are arranged in a leading manner and in a type of imbricate flow. 
     The operating mode “precollection” is described hereinafter with reference to  FIGS. 2 and 3 . 
     With the precollection, the second grippers  22 , in each case, already hold one or more objects  2 ′. These are firstly conveyed forwards in a hanging manner with the free second edge  4 ′ in front. On entry into the deflection, the second edges  4 ′ slide on the inner surface  34  of the guide  32 . By way of this, it is ensured that the second edges are always located in front of the held first edges  3 ′ of the same product  2 ′ also in the deflection, where they would sag without auxiliary means on account of the gravity. At the end of the deflection, or at the entry of the transfer region T, the second grippers  22  have changed their orientation in space to such an extent, that the second edges  4 ′ from now on lie on the extended gripper jaws  23  of the leading second gripper  22 , by which means the object  2 ′ is supported in a surfaced manner. In the transfer region T, the second grippers may now be opened, and the objects  2  which are held by the first grippers  12 , as described above, are introduced into the second grippers  22 . The guide  32  thereby serves also for keeping the two product flows separate up to the entry of the transfer region T and there to release the second edges  4  of the objects  2  held by the first grippers  12 , in a targeted manner such that they are introduced into the gaps between the further objects  2 ′ in the manner of a zip. 
     Since the opening of the gripper jaw of the second grippers  22  is orientated obliquely upwards in the transfer region, the already detected objects  2 ′ are not displaced, even with a temporary release of the clamping effect. The second grippers  22  here function as collection compartments. The objects to be taken over are aligned with the already held objects  2 ′ at the base of the gripper  22 . After closure of the second grippers  22 , the objects  2 ,  2 ′ are conveyed further in pairs and processed further. 
     In this operating mode, in a simple and advantageous manner, one already achieves a precollection of objects. The second grippers  22  may subsequently run through yet further correspondingly designed transfer regions.