Background of the Invention Robotic palletizers have been proposed to reduce the manual handling required to stack objects on a pallet or other stack as they are delivered by a conveyor. Most robotic palletizers include a robotic arm which has an object gripping mechanism at one end designed to grip objects from either side. During the palletizing or stacking operation, a gap large enough to accommodate the gripping mechanism at either side of the object must be left in the stack, and this does not allow for the establishment of desired stacking patterns which achieve the most efficient or compact stacking of objects.

Summary of Invention and Object It is the object of the present invention to provide an improved gripping mechanism for holding objects during moving from one position to another by a positioning means such as a robotic palletizer.

The invention provides a gripping mechanism for holding objects for movement from one position to another by means of a positioning means, said gripping mechanism comprising a frame supporting an array of elongate object supporting elements, means for moving each element between an extended position in which the elements are able to be positioned under an object to be lifted, and a retracted position, in which the elements no longer support the object, and clamping means overlying said object supporting elements in the extended position to engage the object when supported by said elements.

It will be appreciated that the above arrangement leaves the sides of the object to be stacked free thereby enabling each object to be closely positioned adjacent another object to maximise the efficiency of the pattern of objects in a stack, or to enable accurate positioning of objects for subsequent packaging.

In a preferred form of the invention, the object supporting elements comprise rod means, with the means for moving said rod means between the extended and retracted positions preferably comprising pneumatic cylinders mounted on said frame.

The rod means may be cylindrical or they may have a flattened configuration to reduce the dropping distance for the gripped objects when the rods are retracted.

The frame may carry an array of suction members which allow the gripping mechanism to lift relatively light objects, such as tier sheets for separating layers of objects in a stack. Alternatively, this function may be performed by a separate mechanism to speed the transfer process. In one form of the invention, the suction members comprise suction cups mounted on the frame between adjacent rod means, the mounting means preferably including means for moving each suction cup from a retracted position within the frame to an extended position below the frame to enable light objects to be picked up by the gripping mechanism.

The invention also provides a system for palletizing or stacking objects, comprising conveyor means for conveying objects to a pick-up zone, means for inhibiting discharge of articles from said conveyor means at said pick-up zone, loading means for transferring objects from said conveyor means to a pallet or stack, said loading means including a gripping mechanism having object support means configured to engage said objects while supported by said conveyor means and to lift said objects through said inhibiting means to the pallet or stack.

In one form of the invention, the object supporting means and the inhibiting means are configured to allow objects to be picked up by said gripping mechanism in one or more of different parts of said pick-up zone.

The gripping mechanism preferably includes a frame supporting an array of elongate object supporting elements and overlying clamping means for holding the objects in engagement with said supporting elements. More specifically, the gripping mechanism is preferably as defined in the above paragraphs.

The inhibiting means preferably comprises an array of spaced upright rods or bars extending along a discharge side of the conveyor means, said array defining gaps through which the object supporting means of said gripping mechanism are able to pass, the number of gaps and the number of object supporting elements being selected to allow the gripping mechanism to operate at at least one pick-up position within said

pick-up zone. In one specific example, the gripping mechanism has six object supporting elements and the inhibiting means has at least thirteen gaps to allow objects to be picked up at seven different pick-up positions. It will be appreciated that by appropriately selecting the number of object supporting elements and gaps, any desired number of pick-up positions within said pick-up zone may be established.

In another embodiment, a single pick up position is provided, and pusher means are provided to locate and square the objects to be picked up at that position.

Preferably pusher means are provided to locate the objects in each direction, including against the inhibiting means, to ensure that the objects are correctly positioned at the pick up position.

The loading means preferably includes a robotic arm on which the gripping mechanism is mounted, said arm being controlled by computer control means and sensor means to automatically pick-up and position objects on a pallet or stack in a desired stacking pattern. A separate robotic arm can be provided for picking up and positioning tier sheets or slip sheets between the layers of a stack of said objects.

Brief Description of the Drawings In order that the invention may be more readily understood, one presently preferred embodiment of the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a schematic plan view of a system for palletizing or stacking objects in accordance with one embodiment of the invention; Figure 2 is a fragmentary plan view of part of the system of Figure 1 illustrating the co-operating between the gripping mechanism and the conveyor; Figure 3 is a fragmentary sectional elevation of the gripper and conveyor taken along the line 3-3 in Figure 2; Figure 4 is a fragmentary sectional plan view taken along the line 4-4 in Figure 3; Figure 5 is a fragmentary sectional side elevation taken along the line 5-5 in Figure 3; Figure 6 is a fragmentary sectional side elevation taken along the line 6-6 in Figure 4; and

Figures 7 and 8 are schematic illustrations of different object stacking patterns and Figures 9 and 10 are a schematic plan and front elevation respectively of a modified pallitizing system embodying the invention.

Description of Preferred Embodiments Referring firstly to Figures 1 and 2 of the drawings, a palletizing system embodying the invention is illustrated in one particular form, suitable for stacking or palletizing tied or untied bundles of corrugated board carton blanks or the like, and includes a conveyor system 1 including a terminating conveyor element 2 having an object pick-up zone 3 defined by a terminal barrier 4 and a side barrier 5 comprising an array of upstanding bars 6 arranged along a discharge side 7 of the pick-up zone 3 of the conveyor element 2. As shown most clearly in Figure 2 of the drawings, the upstanding bars 6 are aligned with conveyor rollers 7 defining the pick-up zone 3 and thereby define gaps 8 which are aligned with the gaps 9 between the adjacent conveyor rollers 7. If desired, an object pushing arm A is positioned adjacent the pick-up zone 3 to enable objects 0 to be pushed from remote positions to the pick-up zone 3 in the manner shown in Figure 1.

The system illustrated in Figure 1 further includes a robotic arm 10 of known construction having a gripping mechanism 11 attached to the free end of the arm 10.

The arm 10 and gripping mechanism 11 operate to pick-up objects 0 from the pick-up zone 3 and transfer those objects O to a pallet P supported on a conveyor C positioned adjacent the arm 10 as illustrated in Figure 1.

The robotic arm 10 is controlled by a computerised controlling mechanism (not shown) which is programmed to control the arm 10 and the gripping mechanism 11 to pick-up objects O from the pick-up zone 3 and deposit them in any desired stacking pattern, such as those illustrated schematically in Figures 1,7 and 8 of the drawings.

Turning now to Figures 2 to 6 of the accompanying drawings, the gripping mechanism embodying the invention includes a frame 13 having a lower generally rectangular frame portion 14 and an upper cantilevered frame portion 15, the frame 13 being secured to the robotic arm 10 in any suitable manner, not illustrated in any detail.

The lower frame portion 14 supports aligned pairs of bearings 14A, each pair of which slideably supports an object supporting element 16 in the form of an elongate

rod. In the present embodiment, an array of six rods 16 are mounted on the frame element 14, with groups of three rods 16 being interconnected by plates 17 to which pneumatic actuating cylinders 18 mounted on the frame element 14 are connecte. As illustrated in Figures 3 and 4, operation of the actuating cylinders 18 causes the rods 16 to be moved from a retracted position illustrated in broken outline in Figures 3 and 4, to an advanced position in which the rods extend from the front of the frame 13, as illustrated in Figures 3 and 4, in which position, the rods 16 are able to be positioned under an object O to be transferred from the pick-up zone 3 to a pallet P. The above operations are performed under the control of the controlling mechanism.

The cantilevered frame elements 15 each support a clamping plate 28 fixed to pneumatic rams 19 operable to move the clamping plate into engagement with the top surface of an object O to hold the object on the supporting rods 16, as illustrated in Figure 3 of the drawings. Once again, the operations of the ram 19 are under the control of the controlling mechanism.

While the rods 16 are illustrated as cylindrical in configuration, they can be made in a flattened configuration, as illustrated by the broken outline in Figure 3, to reduce the distance between the objects to be picked up by the gripping mechanism and a supporting surface, so that withdrawal of the rods 16 causes less disturbance of a stack of objects as they are deposited on a pallet or elsewhere. In such an arrangement, the rods will be supported by linear bearings of known construction.

The lower frame unit 14 also carries an array of four vacuum cup units 20, positioned as shown most clearly in Figure 4 of the drawings between adjacent bearings 14A for rods 16, and including vacuum cups 21. As shown in Figure 6 of the drawings, the vacuum cups 21 are carried by piston rods 22 associated with the vacuum cup units 20 and are able to be positioned in a retracted position as shown in Figure 6 or in a projected position as shown in broken outline in Figure 6 where the cups 21 are adapted to pick-up relatively light objects, such as tier sheets T, which are used to divide layers of a stack, as illustrated in Figure 7 of the drawings.

It will be appreciated from the above description of one preferred embodiment of the invention that the embodiment enables objects O to be lifted from the pick-up zone 3 by the gripping mechanism 11 without obstructing the sides of the object whereby each object is able to be accurately positioned in a stack in a closely adjacent

relationship with other similar objects. Furthermore, by selecting the number of rods 16 and the number of gaps 8 between the upright bars 6, a multiplicity of pick-up positions within the pick-up zone 3 are possible. In the embodiment shown, at least seven pick-up positions may be selected. Furthermore, by mounting suction devices 21 on the frame supporting the rods 16 increases the functionality of the gripping mechanism 11 so that light objects, such as tier sheets T, can be lifted and positioned by the arm 10.

Referring now to Figures 9 and 10 of the drawings, the gripping mechanism 11 (not shown) is adapted to pick-up objects O from the conveyer C at a single pick-up position Pl. In this embodiment, the gripping mechanism has eight rods 16 and the side barrier has nine bars 6. To allow the objects O to be picked up to be positioned at the pick-up position Pi, object pushers 30,31 and 32 are provided to locate the objects in the appropriate position against the side barrier 5 at the pick-up position Pi. In addition, a retractable stack divider plate 33 is provided to ensure stack stability where two adjacent stacks of objectes oui and 02 are formed, as illustrated in Figure 10. For this reason, the pusher 32 has a pair of plates, one on either side of the divider plate 33, as illustrated. Of course, if only one stack of objects is joined, the divider plate 33 will remain retracted.

In use, the pusher 30 is located at the required locating position by the controlling mechanism on the basis of input information relating to the size of the objects O to be picked up. At this time, the pushers 31 and 32 are retracted, the pusher 31 being located clear of the conveyor as illustrated in Figure 9, and the divider plate 33 is down. When the objects comprising stack O1 are delivered against the pusher 30 by the conveyor C, the divider plate 33 is elevated and the stack 02 is delivered by the <BR> <BR> <BR> <BR> conveyor C. The pusher 32 is then activated to square the stacks O1 and 02 against the side barrier 5, and the pusher plate 31 is extended from its home position in direction Y to a position over the conveyor and then extended in direction X towards the stack 02 to square that side of the stack against the reaction force provided by the divider plate 33, as shown in Figure 10. The rods 16 of the gripping mechanism 11 are then <BR> <BR> <BR> extended under the stacks Ol, °2 and the clamps 18 activated to clamp the object stacks against the rods 16, whereupon the pushers 31 and 32 are retracted to their home positions and the stacks O1 and 02 lifted by the gripping mechanism 11 for transfer to the pallet or conveyor, in the manner previously described.

It will be appreciated that a pusher/divider arrangement similar to that described above can be applied to the embodiment of Figures 1 and 2. In such an event, the terminal barrier 4 is replaced by the pusher 30, which is located at the appropriate pick- up position under the control of the control system.

It will also be appreciated that various modifications and alterations may be made to the system described above without departing from the scope and spirit of the invention. For example, while the apparatus described is suitable for picking up bundles of corrugated board blanks, including tied and untied bundles, it can be adapted to pick up any object for subsequent positioning for packaging or other operations.