Method and device for removing of a top group of surface- extending products of folder-type from a stack of such groups

The invention relates to a method and a device for removing of a top group of surface-extending products of folder-type from a stack of such groups of the kind that is evident from the preamble of the annexed independent method claim and the independent device claim.

When depalletizing, i.e. when emptying a pallet, with surface- extending products it is known to by the aid of a gripper to grip a group of products in order to thereafter move this group to a station for further processing of the products.

A method of the kind in question is known, where one starts out from groups of elongated rectangular between themselves equal surface-extended products, which groups are displaceably stacked to form a stack on a pallet, so that each short side edge area of the top group protrudes out past the respective long side edge of the second topmost group in the stack. A robot controlled gripper thereby grips the top group at its said protruding short side edge area which flares out over the long side edge of the second topmost group, for transport of the gripped group to a station, for further processing of the products. The gripper thereby has two vertically in relation to each other movable jaws which are set against the top and the bottom product or sheet of the group.

By gripping the group in the freely protruding end area only of the group according to what has been described above, the gripping of the group is indeed facilitated, but this means that the risk that the group will bend and the products of the group are displaced in relation to each other in the horizontal plane is increased, which means difficulties to

control the shape of the group (bending state) when placing down the group in the destination station.

US 5 169 284 shows a method and a device of the kind in question, where elongated rectangular between themselves equal groups are stacked abreast of and above each other in layers on a pallet and where a sheet substantially corresponding to the extension of the pallet separates each layer of groups from each other. The sheet protrudes out past the outmost groups in each layer. By displacing the top layer of groups sideways in relation to the under lying sheet, an arm may press down the sheet whereafter a gripper may grip around the groups in the top layer one at a time for transport of the gripped group to a station. The gripper thereby has two vertically in relation to each other movable jaws that are set against the top and bottom surface of the group.

By, as is shown in US 5 169 284, displacing the top layer of groups before the gripping of the group is carried out, the gripping itself of the group is facilitated. However, if the group consists of a stack of surface-extending products that have between themselves substantially equal format and size and substantially completely overlaps each other and that groups in the same plane are arranged a way from each other, and where further the separate products are not bundled together with a band, there is a risk that the products are displaced between themselves in the horizontal plane before the gripper can grip the group which means difficulties to control the shape of the group when placing down the group in the destination station.

In the following description is by "surface-extending products" meant a thin flat product such as a sheet of paper or a folder.

In the following description is by "folder" meant a thin flat folded product with a back such as e.g. a newspaper or a booklet .

In the following description is by "group of surface-extending products" meant a stack of surface-extending products which products have between themselves substantially equal format and size and substantially completely overlap each other in vertical direction. Such a group is also called a "lay" in that case where all the products in the group are oriented in such a way that all equal side edges are placed on top of each other, which for a group of folders means that all folders shall be oriented with the back in the same direction.

In practical handling situations, it has proved that the group which is to be gripped with a gripper and thereafter to be transported as quickly as possible from the stack to a destination station, e.g. an after-treatment station, using a transportation device which carries the gripper, should have a limited thickness because if the groups have a large mass there is a risk for that the products in the group are displaced between themselves and/or that the products in the group are damaged by the gripper, if this must be set with high force against the group in order to prevent displacement of the products therein. By a relatively low mass for the group, further the required drive effect for the transportation device, which may be a robot, is limited. How large a thickness a group may have depends thus among other things on products surface-extension, thickness, weight and the strength of the material from which the products are made.

One object of the invention is to provide a technique to remove the momentary topmost group from a stack of vertically adjacent groups of surface-extending products of folder type

in such a way that one or more of the above mentioned problems are completely or partly removed.

The object is reached by way of the invention.

The invention is specified in the annexed independent method claim.

The invention is also specified in the annexed independent device claim.

Embodiments of the invention are specified in the annexed dependent claims .

The invention will in the following be described in exemplifying form referring to the annexed drawings.

Figure 1 shows schematically a stack formed by groups of folders with sheets lying between on each other lying groups in the stack, and a gripping device for gripping of the top group of the stack.

Figure 2 shows a schematic view of a gripping device for gripping of the top group of the stack.

Figure 3 shows a schematic view of a second embodiment of gripping device for gripping of the top group of the stack.

Figure 4 shows schematically a system for depalletizing.

Figure 1 shows schematically a pallet 2 on which stacks 4 formed of groups 6, 6' of folders are placed. Sheets 8 are arranged between on each other lying groups 6, 6' in a stack 4. The figure further shows a gripping device 10 for gripping of the top group 6 of the stack 4.

Each group 6, 6' consists of surface-extending products 12 of folder type, e.g. printed products such as e.g. newspapers or

booklets, which between themselves are substantially equally oriented and which are rectangular, elongated and substantially completely overlapping in the respective group 6, 6'. The products 12 of folder type show in practice depending on their folded backs 14 somewhat different thicknesses at the backs 14 and the to the back edge 15 opposite edge 16 of the product 12, which e.g. is the case for newspapers .

Vertically adjacent groups 6, 6' may be rotated between themselves e.g. 90 or 180 or 270 degrees around the vertical axis A of the stack, and horisontally adjacent groups 6 respectively 6 ' that are placed on the one and the same sheet 8 may also be rotated between themselves e.g 90 or 180 or 270 degrees around the vertical axis A of the stack, this in order to be able to make use of the surfaces of the pallet 2 and the sheet 8 in the best way and to fill the pallet 2 as surface- efficiently as possible with the smallest possible surface that is not covered by groups 6, 6' of products.

The gripping device 10 for gripping of the top group 6 of the stack 4 comprises at least an upper jaw 18 and at least an lower jaw 20 that are movable in relation to each other by that the upper jaw 18 is arranged to be able to move upwards and downwards in the vertical direction A of the stack and by that the lower jaw 20 is arranged pivotable in relation to the upper jaw 18 and arranged to be able to be pivoted in under a group 6 of products 12 of folder type from the back edge 15 of the group 6. The groups 6, 6' may be placed on the pallet 2 and the sheet 8, respectively, in orientations rotated between themselves , e.g. 90, 180 or 270 degrees such as has been mentioned above or in other angular positions, everything between 0 to 360 degrees, because of which the gripping device 10 is arranged to be able to rotate 360 degrees around a vertical axis whereby the gripping device 10 may be pivoted in

under a group 6 of products 12 of folder type from the back edge 15 of the group 6 irrespective of in which angular position the group 6 has been oriented on the pallet 12 and the sheet 8, respectively. The gripping device 10 is thus movable in both the horizontal plane and the vertical plane and also able to rotate in both the horizontal plane and in the vertical plane by a transporting device (not shown) which will be described more in detail below.

Figure 2 shows a schematic view over a gripping device 10 for gripping of the top group 6 of the stack 4. As mentioned above, the gripping device 10 comprises at least an upper jaw 18 and at least an lower jaw 20 that are movable in relation to each other by that the upper jaw 18 is arranged to be able to move upwards and downwards in the vertical direction A of the stack and by that the lower jaw 20 is arranged pivotable in relation to the upper jaw 18 and arranged to be able to be pivoted in under a top group 6 of products 12 of folder type from the back edge 15 of the group as will be described in more detail below. In the figure is also shown a sheet 8 and a under the sheet 8 arranged further group 6 ' of products 12. The gripping device also comprises a holder 22 for a transportation device (not shown) .

In order to decrease the risk for that the position between the groups 6, 6' themselves in the stack 4 will be disturbed when the lower jaw 20 of the gripping device 10 is brought to gripping engagement under the top group 6 in the stack 4, the group 6 is pressed together using the upper jaw 18 whereby the lower jaw 20 is prevented from displacing the top group 6 in the insertion direction B of the lower jaw 20 in the stack 4 at the same time as the separate products 12 in the group 6 are prevented from being displaced in relation to each other. In order to further decrease the risk for that the position between the groups 6, 6' themselves in the stack 4 will be

disturbed when the gripping device 10 is brought to gripping engagement with the top group 6 in the stack 4, the gripping device 10 preferably further comprises a stop device 24 which temporarily may be placed in contact with the top product 12 of the top group 6. By pressing the group 6 together using the stop device 24, the gripping device 10 is prevented from displacing the top group 6 in the insertion direction B of the lower jaw 20 in the stack 4 at the same time as the separate products 12 in the group 6 are prevented from being displaced in relation to each other. According to what is shown in the figure, the lower jaw 20 is preferably shaped as a substantially flat plate 28 which is pivotally arranged to the housing 30 of the gripping device 10 using a pivoting arm 32. As the upper jaw 18 presses the group 6 together when the lower jaw 20 is brought to gripping engagement under the top group 6 in the stack 4, the lower jaw 20 has such a length that it does not reach all the way to a position directly below the upper jaw 18 whereby the lower jaw 20 thus may be inserted to a position between the back edge 15 of the group 6 and a position directly below the upper jaw 18. Hereby, the clamping force with which the upper jaw 18 and the lower jaw 20 clamps the group 6 is of moderate size. In order to be able to increase the speed with which the gripping device 10 is moved after the gripping device 10 has gripped the group 6, a further upper jaw 26 placed in a position directly above the lower jaw 20 may, when the lower jaw 20 is completely inserted below the top group 6, be arranged to press the group 6 with products 12 against the lower jaw 20 whereby the clamping force with which the group 6 is clamped together may be substantially increased.

As is evident from the figure, the housing 30 is in two pieces and comprises two to each other pivotally arranged housing parts 29, 31. The pivotable arm 32 preferably comprises two profiled parts 34, 36 for increased stability. The movement of

the pivotable arm 32 is preferably controlled with a control cylinder 38 arranged between the housing 30 of the gripping device 10 and the arm 32.

From the figure is also evident that at least one, but preferably two, distance devices 40, 42 are arranged on the housing 30 of the gripping device 10, where the distance devices protrude downwards from the housing 30. The distance devices 40, 42 are at their lower ends 44, 46 provided with contact sensors 48, 50 which may be of e.g. mechanical, electronic or other kind. Optionally, at least one, but preferably two, laser sensors 41, 43 may be arranged for detection of the vertical distance down to the sheet 8.

When the gripping device 10 is to grip a group 6, the gripping device 10 is firstly moved using the transportation device (not shown) to a starting position above the group 6 which position e.g. may be detected using a vision system (not shown) according to what will be described below in more detail, or as an alternative to be detected using the laser sensors 41, 43. After the gripping device has been moved to the starting position above the group 6 which is to be gripped, the gripping device 10 is moved downwards until the contact sensors 48, 50 at the lower ends 44, 46 of the distance devices 40, 42 detect that the distance devices 40,42 have reached down to the upper surface 52 of the sheet 8 whereby the gripping device 10 is in a vertical position where the lower jaw 20 may be inserted between the group 6 and the sheet 8. As an alternative, the gripping device 10 is moved downwards until the laser sensors 41, 43 detect that the gripping device 10 is at a vertical position where the lower jaw 20 may be inserted between the group 6 and the sheet 8. Thus, both the contact sensors 48, 50 and the laser sensors 41, 43 are vertical distance detection devices for detection of the distance which the gripping device 10 shall keep to the

sheet 8 in order for the lower jaw 20 to be able to be inserted between the group 6 and the sheet 8. When this detection of the correct vertical distance takes place, the gripping device 10 stops whereafter the upper jaw 18, and a possible stop 24, is pressed down against the top product 12 of the group 6 at a distance from the back edge 15 of the group. By that the upper jaw 18 is an elongated body with the longitudinal axis parallel with the backs 14 of the products 12, the group 6 with products 12 is stiffened at the following movement. When the group 6 has been pressed down against the sheet 8, the lower jaw 20 is inserted under the group 6 with a pivotal movement, whereafter a possible further upper jaw 26 is pressed down against the top product 12 of the group 6. After the group 6 of products 12 has been gripped in this way, the group 6 is moved to a destination device (not shown) using the transportation device (not shown) . After the group 6 has been left off at the destination device, the gripping procedure above is repeated with the next group on the sheet until all groups on the sheet have been moved. Thereafter, the sheet is removed, whereafter the same procedure is repeated with the next layer of groups until the pallet has been emptied.

As is evident from the figure, the lower jaw 20 has a width which is less than the distance between the distance devices

40, 42 so that the lower jaw 20 is not prevented from being inserted under the group 6.

As an intermediate sheet 8 is placed between vertically adjacent groups 6, 6 ' of surface-extended products 12 of folder type, where the sheet 8 has a somewhat larger surface than the surface of the pallet 2, and where the groups 6, 6' have been placed on the sheet 8 and the pallet 2 , respectively, in such a way that it always is possible for the gripping device to reach a back edge 15 of at least one group

6 and where the back sections of all groups 6 lie retracted from the side edges of the underlying sheet 8, the pallet may be depalletized in an efficient way by that the lower jaw 20 of the gripping device 10 may be inserted under the group along the upper surface 52 of the sheet 8.

The sheet 8 may be of any material that allows for detection of the sheet 8 using the contact sensors 48, 50 at the lower ends 44, 46 of the distance devices 40, 42 and that allow the lower jaw 20 to be able to be inserted between the sheet 8 and the group 6 of products 12. Suitable sheet materials are e.g. cardboard, kraft paper and stiff plastics.

Figure 3 shows a schematic view over a second embodiment of a gripping device 10 for gripping the top group of the stack, which differs from the one shown in figure 2 by that a detection devive 54 in the form of a vision system 54 for detection of said starting position is shown. As is evident from the figure, only the lower housing part 29 of the two- part housing 30 is shown. The gripping device is carried by a transportation device (not shown) which moves the gripping device 10 to the above described engagement with the top group 6 in question in the stack 4. The vision system 54 comprises suitably a camera 56 which may be carried in the vicinity of the gripping device 10 and which with a suitable processor, software and technics of measurement controls the gripping device 10 at the final phase of its mentioned engagement with the top group 6 of the stack 4, so that the gripping device 10 reaches said starting position above the group 6.

Figure 4 shows schematically a system for depalletizing, where the gripping device 10 is shown during depalletizing of a pallet 2 where several stacks 4 are placed side by side, whereby the camera, processor and software are arranged to identify the respective stack 4 in order to piece by piece

remove the groups 6, 6' from the upper end of the respective stack 4 and move the groups 6, 6' in a preferably in advance defined order to a destination device 58 such as a receiving station or an after-treatment station. Such as is evident from the figure, the above described gripping device 10 may also be used at emptying of pallets 2 which do not have sheets between vertically adjacent groups 6, 6 ' of products, as long as an upper surface of an underlying group 6 ' may be used for identifying the lower edge of the upper group 6 according to what has been described above, i.e. that the contact sensors 48, 50 at the lower ends 44, 46 of the distance devices 40, 42 come into contact with the upper surface 53 of the lower group 6' instead of the upper surface of the sheet.

The groups 6, 6' which normally are printed products have usually been produced in advance, and are temporary stored in stacks 4 e.g. on pallets 2 which facilitate transport of products 12 between e.g. different printing works or different machines in one and the same printing works . The groups 6 , 6 ' are often a supplement to a paper and shall then be moved to a destination device in the form of a feeding pocket in which they are inserted in the same orientation, and where the edges are levelled, jogged up, in order to obtain the same position between themselves. Then the groups 6, 6' are moved one at a atime to an inserter in which such a group is inserted in a passing pocket, possibly in an opened folder which is received in the pocket and kept open. The group 6, 6' itself may of course in itself be one single folder, possibly with therein inserted further supplement.

The groups 6, 6' may as mentioned above be placed on the pallet 2 (respectively the sheet) in orientations rotated in relation to each other at angular positions from 0 to 360 degrees, why the gripping device 10 is arranged pivotable 360 degrees around a vertical axis 60 whereby the gripping device

10 may be pivoted in under a group 6 of products 12 of folder type from the back edge 15 of the group 6 irrespective of in which angular position the group 6 has been oriented on the pallet 2 (respectively the sheet) . The gripping device 10 is thus movable in both the horizontal plane and the vertical plane and also pivotable in both the horizontal plane and the vertical plane using a transportation device 62. The transportation device 62 comprises preferably a guiding beam 64 along which a travelling carriage 66 may be moved back and forth. At the travelling carriage 66 is arranged a vertically movable profiled section 68 at which an horisontally pivotable arm 70 is arranged, at the end of which the gripping device 10 is mounted pivotable at 360 degrees. The transportation device 62 may optionally be a traditional industrial robot on the arm of which the gripping device 10 has been mounted.

The invention thus relates to a method for removing a top group 6 of surface-extended products 12 from a stack 4 of on each other stacked groups 6, 6' of surface-extended products 12 where vertically adjacent groups 6, 6' in the stack 4 are separated by a sheet 8, where a gripping device 10 comprises two in relation to each other movable jaws 18, 20 where the lower jaw 20 is arranged to be inserted under the lower side 7 of the top group 6 and where the upper jaw 18 is arranged to be moved above the upper side 5 of the top group 6 whereby the gripping device 10 is arranged to be able to grip around the top group 6 of the stack 4 and to move this group 6 to a destination device 58, where the surface-extended products 12 are folders with backs 14, and further comprising the steps, to:

- move the gripping device 10 using a transportation device 62 to a starting position above the top group 6 where at least one vertical distance detection device 48, 50, 41, 43 of the gripping device 10 is positioned at the outside of the back edge 15 of the group 6, thereafter

- move the gripping device 10 downwards until the vertical distance detection device 48, 50, 41, 43 detects that the gripping device 10 has reached the vertical position where the lower jaw 20 may be inserted between the top group 6 and the sheetδ,

- press down an upper jaw 18 against the top product 12 of the top group 6 at a distance from the back edge 15 of the group, thereafter

- move in a lower jaw 20 between the group 6 and the sheet 8 at the back edge 15 of the group with a pivotal movement whereby the group 6 is clamped and gripped between the upper jaw 18 and the lower jaw 20, and move the group 6 to the destination device 58 using the transportation device 62.

The invention also relates to a device for removing a group 6 of surface-extended products 12 from a stack 4 of on each other stacked groups 6, 6' of surface-extended products 12, where the on each other stacked groups 6, 6' are stacked in such a way that a limiting surface 52, 53 protrudes outside the lower edge 11 of the top group 6, the device comprising a gripping device 10 and a transportation device 62, where the gripping device 10 comprises two in relation to each other movable jaws 18, 20 where the lower jaw 20 is arranged to be inserted under the lower side 7 of the top group 6 and where the upper jaw 18 is arranged to be moved above the upper side 5 of the top group 6 whereby the gripping device 10 is arranged to be able to grip around the top group 6 of the stack 4 and to move this group 6 to a destination device 58 using the transportation device 62, where the surface-extended products 12 are folders with backs 14, and that the gripping device 10 comprises a detection device 54, 41, 43 arranged to detect a starting position above the top group 6 where at least one vertical distance detection device 48, 50, 41, 43 of the gripping device 10 is positioned at the outside of the

back edge 15 of the group 6, where further at least one vertical distance detection device 48, 50, 41, 43 is arranged by using the outside the lower edge 11 of the top group 6 protruding limiting surface 52, 53 to detect when the gripping device 10 has reached the vertical position where the lower j aw may be moved in under the top group 6 , where further the upper jaw 18 is arranged to be able to move upwards and downwards in the vertical direction A of the stack 4 and the lower jaw 20 is arranged pivotable in relation to the upper jaw 18 and arranged to be able to be pivoted in under the group 6 from the back edge 15 of the group 6, whereby the group 6 is arranged to be clamped and gripped between the upper jaw 18 and the lower jaw 20. Thus, the device is adapted to a method as mentioned above, and also a similar method where a protruding underlying group 6', insted of a sheet 8, provides a outside the lower edge 11 of the top group 6 protruding limiting surface 52, 53.

Vertical distance detection devices are on distance devices 40, 42 arranged contact sensors 48, 50 arranged to detect when the distance devices 40,42 have reached down to the outside the lower edge 11 of the top group 6 protruding limiting surface 52, 53, or as an alternative on the gripping device 10 arranged laser sensors 41, 43 arranged to detect when the gripping device 10 is at a vertical position where the lower jaw 20 may be inserted under the top group 6.