Abstract:
A bundle gripper for a palletizing machine for picking up respectively at least one bundle and depositing the bundle on a pallet. The bundle gripper including a frame, an adjustable end stop, and at least one gripper finger such that the gripper finger has a front end and is adjustable on the frame. The gripper finger being movable between a first position and a second position. The bundle gripper also including a hold-down clamp coupled to the frame and positioned against the end stop for clamping the bundle against the gripper finger such that a distance between the end stop and the front end of the gripper finger in the second position is changeable to adapt to different lengths of the bundles. The end stop and the gripper finger are each movable to change the distance and the hold-down clamp is correspondingly adjustable to accommodate different lengths of the bundles.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority of the European patent Application 07405365.3, filed on Dec. 20, 2007, the subject matter of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a bundle gripper for a palletizer or palletizing machine. The bundle gripper may pick up respectively at least one bundle of printed or non-printed products from a feeding device and deposit the bundle on a pallet. The bundle gripper includes at least one gripper finger positioned on a frame, which can be moved between a first and a second position. The gripper finger is located at least partially behind an end stop in the first position. In the second position, the gripper finger is located in front of the end stop in a horizontal operating state so that the at least one bundle rests on the gripper finger. The bundle gripper is in a retracted position in the first position, whereas the bundle gripper is in an operating state in the second position. The bundle gripper further includes a hold-down clamp for clamping the bundle positioned on the gripper finger. The hold-down clamp rests against the end stop. The distance between the end stop and a front end of the gripper finger in the second position can be changed for adapting the gripper finger to different bundle lengths. The invention also relates to a method for palletizing bundles of printed or non-printed products with the aid of a palletizing machine. 
     European patent document EP-A-1 801 047 discloses a bundle gripper, which is used to pick up respectively two side-by-side arranged stacks from a feeding device and deposit these stacks on a pallet. Each stack is gripped with two side-by-side arranged gripper fingers or support elements and an above-arranged hold-down clamp. In addition, the gripper fingers can be adjusted by releasing a lever, so that the distance between the end stop and the front end of the gripper fingers in a working position can be changed. For adapting the bundle gripper to different formats, the two gripper fingers upon which the bundles can be placed can be adjusted relative to each other, thereby permitting an adaptation to different stack widths. To deposit the stack on a pallet, the two gripper fingers are pulled back behind an end stop which exposes the stack bottom and causes the stack to drop onto the pallet. Two pairs of gripper fingers are furthermore provided to allow the simultaneous palletizing of two stacks, wherein the spacing between the two stacks can be adjusted. 
     A different stack gripper is known from European patent document EP-A-0 816 272. This document discloses a stack space open toward the bottom and includes a separate guide for each of the four sides of the bundle stack. Two telescopically extendable belts are located in the lower region of the stack space. The product stacks are moved into the stack space while positioned transverse on the extendable belts. Following the insertion of the bundle stack, the guides are adjusted to simultaneously surround and touch the bundle stack. The bundle stack is then deposited on a pallet by shortening the belts with the aid of a lifting movement. 
     SUMMARY 
     It is an object of the present invention to create a bundle gripper of the aforementioned type, which can be adapted without manual intervention to different bundle formats, especially bundle lengths. 
     The above and other objects are accomplished according to one aspect of the invention wherein there is provided a bundle gripper for a palletizing machine for picking up respectively at least one bundle and depositing the bundle on a pallet, the bundle gripper comprising: a frame; an adjustable end stop coupled to the frame; at least one gripper finger coupled to the frame, wherein the gripper finger has a front end and is adjustable on the frame, the gripper finger being movable between a first position and a second position, wherein the gripper finger in the first position is located at least partially behind the end stop away from receipt of the bundle and in the second position is located in front of the end stop in a horizontal operating state to receive the at least one bundle, with the bundle fitting against the end stop; and a hold-down clamp coupled to the frame and positioned against the end stop for clamping the bundle against the gripper finger, and wherein a distance between the end stop and the front end of the gripper finger in the second position is changeable to adapt to different lengths of the bundles, the end stop and the gripper finger are each movable to change the distance, and the hold-down clamp is correspondingly adjustable to accommodate different lengths of the bundles. 
     The bundle gripper according to an embodiment of the invention includes an end stop that may be moved and/or the length of the gripper finger and/or the hold-down clamp can may be adjusted in order to change the spacing. 
     The bundle gripper according to an embodiment of the invention is suitable for picking up printed or non-printed products that may be bound or non-bound. For example, the products may be held together to form a bundle with the aid of a film or with straps. With non-bound stacks, the products may be held together with the aid of an electrostatic charge. For the purpose of this application, a bundle is therefore understood to also include a stack of loose products. The products may be non-printed paper sheets or printed products such as printed signatures, individual sheets, newspapers, magazines, catalogs, books or the like. 
     According to one embodiment of the invention, the end stop may essentially be displaced in a longitudinal direction of the gripper finger in order to adapt to different bundle formats. An end stop of this type may be adjusted relatively quickly and over a comparatively large range size. According to another embodiment of the invention, a stop element includes the end stop and a recess, wherein the gripper finger is arranged within the recess. The recess is open in the front, so that the gripper finger may be moved in and out through the recess. The stop element may form two stop edges, arranged at a distance to each other, between which the gripper finger and the hold-down clamp may be moved. As a result, relatively wide bundles may therefore be gripped with only one gripper finger and a hold-down clamp and the bundles may be stripped off along the end stop for the palletizing. 
     According to one embodiment of the invention, the total length of the gripper fingers and/or the hold-down clamp may be adjusted for adapting to different bundle lengths. The gripper finger and/or the hold-down clamp may advantageously be adjusted in a telescoping manner in a lengthwise direction. 
     According to another embodiment of the invention, a motor may be used to change the distance between the front end of the gripper finger and the end stop or to adjust the length of the hold-down clamp, which permits a particularly fast adjustment to the different bundle formats. An extremely precise adjustment may be achieved, for example, by using a spindle. 
     According to yet another embodiment of the invention, the gripper finger is mounted on an arm at a joint, which allows the gripper finger to be moved between the first position and the second position. By using an arm of this type, the gripper finger may be arranged at an angle in the first position, thus permitting an especially space-saving and/or compact embodiment of the bundle gripper. From the first position, the gripper finger may be pushed in the manner of a shovel underneath a bundle to be palletized. As a result, the gripper finger only assumes a horizontal operating state when fully extended. Therefore, pressure is exerted on the bundle to be gripped only at the instant of contact, which prevents a displacement of the printed products. In order to strip off the bundle, the gripper finger is pulled back from underneath the bundle and is returned to the aforementioned slanted position. The gripper finger in that case may be comparatively long, so that it may be used to palletize bundles of very different lengths. 
     According to yet another embodiment of the invention, the bundle gripper includes two gripper units having respectively one gripper finger, one hold-down clamp, and one end stop. Bundles of different sizes may be palletized simultaneously. One bundle may be palletized with a respective gripper unit and one comparatively wide bundle may be palletized with a plurality of gripper units. 
     According to another embodiment of the invention, the two gripper units are positioned so as to be displaceable along the frame, thus making it possible to change the spacing between the two gripper units. If respectively two bundles are gripped, then the spacing between the two bundles may be changed for the palletizing, for example by placing the two bundles essentially next to each other. The position of the grippers may furthermore be adapted to special requirements for the printed products to be palletized, meaning the grippers do not have to be oriented symmetrical to the stack center. In particular, this may be required for inserting samples into the printed products, which may not be subjected to pressure. 
     The method according to the invention includes adjusting the spacing between the end stop and the front end of the gripper finger in the second position to adapt to a change of the bundle format. Such adjustment may be made by moving the end stop and/or by changing the length of the gripper finger and the hold-down clamp is correspondingly adjustable to accommodate different lengths of the bundles. The format change may also occur immediately after the palletizing of a bundle. Accordingly, during the period when the bundle gripper moves to the position in which at least one other bundle is picked up, the format change may occur so as to make it possible to process all different types of bundles without interrupting the production. Relatively wide bundles may be gripped with the aid of two gripper fingers and two hold-down clamps while comparatively narrow bundles may be gripped between one gripper finger and one hold-down clamp. Therefore, bundles having very different formats and especially having very different lengths may be palletized with this method. For example, bundles may be palletized with lengths (B) ranging approximately from 140-500 mm and bundles with widths (A) ranging approximately from 95-340 mm for the dual bundle productions. In addition, bundles with widths (A) ranging approximately from 340 to 520 mm may be palletized for the single bundle production. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be more readily understood from the following detailed description when read in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a three-dimensional view of a bundle gripper according to the invention; 
         FIG. 2  is a view from the side of the bundle gripper, wherein a comparatively long bundle is gripped; 
         FIG. 3  is a view according to  FIG. 2 , but showing a comparatively short bundle; 
         FIG. 4  is a view of the bundle gripper according to the invention as seen from the front; 
         FIG. 5  is a view from above of the bundle gripper according to the invention; 
         FIG. 6  is a view from the side of a bundle gripper according to one embodiment of the invention, wherein this gripper grips a comparatively long bundle; 
         FIG. 7  is a view as shown in  FIG. 6 , but with a comparatively short bundle; 
         FIG. 8  is a three-dimensional view of a pallet with palletized bundle stack; and 
         FIG. 9  is a view from above of the bundle gripper according to the invention, holding different size bundles. 
     
    
    
     DETAILED DESCRIPTION 
     The bundle gripper  1  includes a frame  6  with a plate  10  for positioning the bundle gripper  1  inside a palletizing machine, not shown herein, such that the bundle gripper  1  may be moved in all spatial directions. The palletizing machine may include a bundle feeding device, for example, a simple belt conveyor. The palletizing machine further may include a loading position on the inside where a bundle layer  4 , consisting of a plurality of bundles  2  and cardboard layers  5  in-between, may be formed on a pallet  3 , as shown in  FIG. 8 . The palletizing machine, the feeding device, and the pallet  3  may be embodied in a manner known per se. The bundles  2  may be made available by the feeding device. The bundles  2  may then be gripped with the bundle gripper  1 , transported to the pallet  3  by the bundle gripper  1 , and deposited in a specific arrangement on the pallet  3 . The bundles  2  may include printed products  9 , for example printed sheets, newspapers, leaflets, catalogs, books and the like. 
     The bundles  2  may be non-bound or bound and respectively have a specific width A, a specific length B, and a specific height C. The bundles  2  may be square in shape. The aforementioned dimensions may vary greatly, wherein the bundle length B may range approximately from 140-500 mm, the bundle width A may range approximately from 95 to 340 mm and the bundle height may approximately reach up to 350 mm. Smaller or larger bundle formats may also be conceivable. The backs of the individual products in two successive bundles do not necessarily have to be aligned parallel. The bundle gripper  1  may be embodied such that the palletizing occurs automatically with the aid of a control unit  7  that is positioned on the frame  6 . Cable conduits  16  are provided for the cables and lines necessary for the control and supply. 
     The bundle gripper  1  may include two units  8  for gripping and depositing the bundles  2 . The units  8  are horizontally displaceable on a carrier  35  shown in  FIG. 1  and on an additional carrier that is not shown herein. The carriers  35  are fixedly connected to the plate  10  with struts  38 . The units  8  are respectively positioned on a positioning rail  13 , extending transverse to the carrier  35 . The positioning rail  13  is connected with guide elements  11  to the carrier  35  as well as to the additional carrier. 
     Referring to  FIG. 4 , a drive belt  36  is provided according to  FIG. 4  for moving the units  8  relative to each other. This drive belt is fitted around rollers  41  and is connected via an attachment  37 , shown in  FIGS. 1 and 4 , to one of the units  8  and via another attachment that is not shown herein to the other unit  8 . If a drive  51  is used to drive the drive belt  36 , the two units  8  are moved either toward each other or away from each other, depending on the direction in which the drive belt  36  is driven. The movements of the units  8  are mirror-inverted as shown in  FIG. 4 . In place of the drive belt  36 , a different suitable drive may also be provided for moving the two units  8 . For example, a spindle drive or a drive with a cylinder could also be provided. If the two units  8  are provided with separate drives, the movements of the gripper units  8  may be independent, wherein the movement direction may be identical. The control unit  7  may also control the movements of the units  8 . 
     The units  8  may include a separate stop element  30 , positioned to be displaceable in horizontal direction along one of the positioning rails  13 . The stop elements  30  are displaced with the aid of two drives  33 , wherein each drive is connected via a spindle  34  to a stop element  30 . These drives  33  are supported on the frame  6 . The stop element  30  in the front is shown in different positions in  FIGS. 2 and 3 , wherein the spacing differs between a stop face  42 , shown in  FIGS. 2 and 3 , and a front side  43  of the positioning rails  13 . This distance is considerably longer in  FIG. 2  than in  FIG. 3 . In these positions, as well as between these positions, the stop elements  30  may be positioned precisely by turning the spindle  34  and may be secured in place. The stop elements  30  for the two gripper units  8  may thus occupy different positions relative to each other. 
     According to  FIG. 1 , each stop element  30  has a lower wall  32  as well as two vertically extending side walls  44 . According to  FIG. 4 , the stop elements  30  are respectively provided between these side walls  44  with a recess  39  that is open in the front and back. The side walls  44  each form a stop edge  31  in the front, which extends substantially vertical. Corresponding to the recess  39 , the edges  31  are arranged at a distance and essentially parallel to each other. The two stop elements  30  are positioned on the rails  13  so that the two stop edges  31  are substantially vertical in all positions. 
     A separate arm  12  may be positioned pivoting on each of the two positioning rails  13 . The arms  12  may be pivoted around a joint  21  at one upper end with the aid of an adjustment cylinder  17  that is positioned on the rail  13 , or with the aid of any other suitable drive. The joints  21  are preferably rotating joints arranged on the positioning rail  13 , in the movement region for the stop elements  30 . The adjustment cylinders  17  respectively comprise a piston rod  18 , which is connected to the arm  12  to rotate at a front end via a joint  19 . At a distance to these rotating joints  19 , a gripper finger  22  is respectively positioned via an articulated connection  40  and a joint  20  on the arm  12 , wherein this gripper finger has an exposed front end  23  at a distance to this connection  40 . The gripper fingers  22  and the front ends  23  together form a support surface  24  on which the bundle  2  and/or  2 ′ is positioned as shown with  FIGS. 2 and 3 . 
     The individual two gripper fingers  22  may be moved between a horizontal orientation and a slanted, shovel-type orientation by activating the adjustment cylinder  17 . With the position shown in front in  FIG. 1 , the gripper finger  22  is raised in the back as may be seen. In this position, the gripper finger  22  is pulled back to a position where the exposed end  23  is located behind the stop face  42 . In the position shown in  FIGS. 2 and 3 , the two gripper fingers  22  respectively project partially and with different lengths over the stop faces  42 . 
     In  FIGS. 2 and 3 , the gripper finger  22  is in the working second position. In  FIGS. 2 and 3 , the length L with which the gripper finger  22  projects over the stop face  42  is indicated with the double arrow L. The length L is determined by the position of the stop elements  30  and/or the stop faces  42 , as well as the front end  23  of the gripper finger  22 , relative to the front sides  43  of the positioning rail  13 . For example, in the position according to  FIG. 2 , the length L is 500 mm, whereas it has a considerably shorter length L′ of 140 mm in  FIG. 3 . Of course it is also possible to adjust any length in-between. 
     A hold-down clamp  25  that is guided vertically along guide rails  29  is furthermore arranged above each gripper finger  22  in the working position. The separate hold-down clamps  25  may be displaced vertically with an adjustment cylinder  26  or a different suitable drive. Each hold-down clamp  25  projects into a recess  39  and the hold-down clamp  25  may be slightly shorter than the gripper fingers  22 . Together with a gripper finger  22 , each hold-down clamp  25  functions to hold in place a bundle  2  and/or  2 ′, so that the bundle  2  and/or  2 ′ may be transported with corresponding movements of the bundle gripper  1  from the feeding device to the pallet  3 . In the process, the bundle  2  and/or  2 ′ rests with its back side  45  and/or  45 ′ against a stop face  42 . The exposed end  23  is preferably located behind a front  47  of the bundle  2  and/or  2 ′, as shown in  FIGS. 2 and 3 , so that the bundles  2  and/or  2 ′ respectively have an overhang  46 , for example with a length of approximately 4-5 cm. However, the overhang  46  may also be less or more and may even be zero. 
     The frame  6  may further include an intermediate cardboard gripper  14  for removing respectively one intermediate cardboard  5  from the intermediate cardboard magazine, not shown herein. The cardboard gripper  14  may deposit the cardboard on the pallet  3 . In order to grip the intermediate cardboard  5  or any other suitable intermediate layers, the gripper  14  includes a plurality of suction device  15 , which are respectively arranged on an arm  48  that may be extended in the manner of a wing. The control unit  7  may also control the intermediate cardboard gripper  14 . However, this intermediate cardboard gripper  14  is not required in principle and could be replaced with a different device arranged on the bundle gripper  1 . 
     An alternative bundle gripper  1 ′ shown in  FIGS. 6 and 7 , which essentially differs from the bundle gripper  1  in that the gripper finger  22 ′ includes a telescopically extendable projection  49  on its front end. The hold-down clamp  25 ′ is also provided with a similar, extendable projection  50 . The two projections  49  and  50  may be moved with the aid of a suitable drive, e.g. with the aid of cylinders that are not shown herein. The projections  49  and  50  may be moved between the fully extended position shown in  FIG. 6  and the retracted position shown in  FIG. 7 . The movement of the projections  49  and  50  may be controlled by the control unit  7 . The gripper fingers  22 ′ and the hold-down clamps  25 ′ may be extended or shortened for adapting them to the length of a bundle  2  and/or  2 ′. The gripper fingers  22 ′ and the hold-down clamps  25 ′ thus project with various lengths over the stop surfaces  42 ′ of the stop elements  30 ′. The stop elements  30 ′ may thus remain in a fixed frontal position, as shown in  FIGS. 6 and 7 . 
     With the bundle gripper  1 ′, the stop elements  30 ′ may be attached fixedly to the frame  6  and/or to the support rails  13 , wherein an embodiment is also conceivable where the stop elements  30 ′ may be moved in the same way as for the bundle gripper  1 . With the latter embodiment, an even larger range of different lengths of the bundles  2  and/or  2 ′ may be covered. A combination embodiment of a bundle gripper  1  with a bundle gripper  1 ′ may be provided for which the gripper finger  22 ′ and the projection  49  and/or the hold-down clamp  25 ′ and the projection  50  are adjusted manually. With the bundle gripper  1  as well as with the bundle gripper  1 ′, a bundle  2  and/or  2 ′ may be gripped and palletized with each unit  8 . The bundles  2  and/or  2 ′ are respectively held between a gripper finger  22  and/or  22 ′ and a hold-down clamp  25  and/or  25 ′. 
     The spacing between these bundles  2  and/or  2 ′ may be adjusted, as explained in the above, by moving the units  8 . However, bundles  2 ″ having a very large bundle width A″ may also be held with the aid of both units  8 , as shown in  FIG. 9 . In that case, the bundle  2 ″ is held by two gripper fingers  22  and/or  22 ′ and two hold-down clamps  25  and/or  25 ′. The bundles  2  and/or  2 ′ or  2 ″, which may be palletized with the bundle gripper  1  and/or  1 ′, may therefore have very different lengths and widths as well as heights. In the process, the position of the gripper units  8  does not necessarily have to be symmetrical to half the width B and/or B′ or B″ of the bundle  2  and/or  2 ′ or  2 ″. 
     The bundle grippers  1  and  1 ′ are each provided with two gripping units  8 . It may be conceivable to have only one or more than two units  8 . 
     In the starting position, the bundle gripper  1  is positioned with the stop surfaces  42  in front of a feeding device that is not shown herein. The two gripper fingers  22  are in the retracted position, on the left according to  FIG. 1 , and the hold-down clamps  25  are in a raised position. The two bundles  2  and/or  2 ′ are supplied to the stop surfaces  42  by the feeding device and are fitted against these surfaces. The two gripper fingers  22  are then moved to the operating position, shown on the right in  FIG. 1 , by correspondingly pivoting the arms  12 . The gripper fingers  22  are moved in the manner of a shovel underneath each bundle  2  and/or  2 ′. The two stop elements  30  are positioned such that they have the desired overhang  46 . By lowering the two hold-down clamps  25  and/or  25 ′, the bundles  2  and/or  2 ′ are clamped. 
     The hold-down clamps  25  and/or  25 ′ may have an upper starting position, which may be adjusted to the bundle height C. The time required for lowering the hold-down clamps  25  and/or  25 ′ onto the bundles  2 ,  2 ′,  2 ″ may be shortened in this way. The control unit  7  may select the upper starting position of the hold-down clamps  25  and/or  25 ′, such that the hold-down clamps  25  and/or  25 ′ are positioned approximately from 50 to 100 mm above the bundle before being lowered. Accordingly, the bundle height C must be transmitted to the control unit  7  by a processing device connected upstream of the palletizing machine and/or must be determined directly by the bundle gripper. 
     The bundle gripper  1  is then moved to the palletizing position, for example with the aid of a known robot arm. In the process, the spacing between the two units  8  may be adjusted during the movement of the gripper unit  1 . For example, the two bundles  2  and/or  2 ′ may be moved close to each other, so that the bundles may finally be deposited on the pallet  3  and/or an intermediate cardboard  5 . The bundles may be deposited by pulling back the two gripper fingers  22  and slightly lifting up the two hold-down clamps  25 . The bundles  2 ,  2 ′,  2 ″ may also be deposited on the pallet  3  so that the bundles  2 ,  2 ′,  2 ″ are pushed from the gripper fingers  22  onto the intermediate cardboard  5  by displacing the stop elements  30 . For this, it may be necessary to compensate the movement of the stop element  30  with the aid of the palletizing machine that holds the bundle gripper  1 . The bundles  2 ,  2 ′,  2 ″ to be deposited thus are immovable relative to the pallet  3 . The bundle gripper  1  may then be moved back to the starting position, wherein the gripper fingers  22  and the hold-down clamps  25  are simultaneously also moved to the starting position. The gripper units  8  as well as the stop elements  30  may also be pre-adjusted to new bundle formats if necessary for the following gripper operation. 
     The stop elements  30  and/or the gripper units  8  may be correspondingly adjusted if the following bundles  2  and/or  2 ′ are to be palletized with a different format. For longer bundle lengths B, the stop elements  30  may be moved toward the back. For shorter bundle lengths B, the stop elements  30  are moved forward, as shown in  FIGS. 2 and 3 . The gripper units  8  may be adjusted analog thereto. Therefore, for larger bundle widths A, the gripper units  8  are moved farther apart and for smaller bundle widths A, the gripper units  8  are moved closer together. An adjustment from two smaller bundles  2 ′ arranged side-by-side to one larger bundle  2 ,  2 ″ may be provided. The adjustments may be made automatically, as explained in the above, or they may be controlled with the aid of a drive. The changeover to a different format may thus be made very quickly during the running production and without manual intervention. 
     If comparatively small bundles  2 ′ with a short bundle length B′ are processed, the stop elements  30  may be moved toward the back. The two separate bundles  2 ′ that are held one behind the other with a gripper unit  8  may be transported and deposited onto a pallet  3 . Therefore, the front  47 ′ of the rear bundle  2 ′ contacts the back  45 ′ of the second bundle  2 ′ in front. The different arrangements of bundles  2 ,  2 ″ deposited on pallets  3  require that at times only one of the gripper units  8  may be utilized. 
     The bundle gripper  1 ′ may be operated in principle as described in the above for the palletizing. However, for a format change the stop elements  30  may not move, but the projections  49  and/or  50  may extend outward for different distances. A combination of the methods used with the bundle grippers  1  and  1 ′ may also be provided, which allows covering an even larger format range. 
     It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.