FIELD OF THE INVENTION

The present invention relates in general to pailetiser stations.

BACKGROUND OF THE INVENTION

in the field of transportation and storage of goods, a pallet is a support platform onto which a load of goods is packed. Pallets have standard sizes, and in an example a pallet may have a size of 80 cm x 120 cm or 100 cm x 120 cm. After stacking, the pallet load may be wrapped in plastic foil to obtain a robust unit. In any case, with or without wrapping, the pallet plus its load is treated as a unit, in transportation (in lorries) and in storage.

Although a pallet may carry any type of product, a very practical example of a product (i.e. load of the pallet) used in practice is a rectangular (cardboard) box. Such boxes come in many standard sizes. As far as the efficient use of volume is concerned, it is preferred that stacking is done such as to obtain a close packing, but this is not essential for the present invention. For instance, 10 boxes of 40x30 fit a pallet of 100x120.

While stacking of boxes on a pallet may obviously be done manually, the present invention relates to a pailetiser station where the stacking is done by a robot, indicated as the pailetiser. Apart from the pailetiser for performing the stacking, the pailetiser station requires a pallet supply conveyor for supplying empty pallets, a pallet removal conveyor for removing (outputting) loaded pallets, and at least one box conveyor for supplying boxes to be stacked. For gripping the boxes from the box conveyors) and placing the boxes on the pallet stack, the pailetiser is equipped with a suitable gripping tool, for instance a clamp or a vacuum suction device.

SUMMARY OF THE INVENTION

In prior art, various possibilities are known, either as a matter of principle or as a matter of practice, for the layout of the pailetiser station, particularly the layout of the various conveyor lines. For instance, the pallet removal conveyor may be in line with the pallet supply conveyor, the box conveyor may be at right angles with the pallet conveyors), and the pailetiser may be located in a comer defined by these conveyors. As a matter of fact, in an example, the pallet removal conveyor and the pallet supply conveyor may be combined into a single pallet conveyor passing the palletiser. The pallet conveyor is moving in one direction for supplying a pallet, stops this movement for allowing the palletiser to do the stacking operation, and then moves on in the same direction to move the stacked pallet away and to

simultaneously supply the next pallet.

A problem is that such layout requires much floor space, which is particularly disadvantageous in a facility with plural pailetisers. It is an objective to use the floor area as efficiently as possible.

With a palletiser arranged by, i.e. next to, the conveyor lines, it is inevitable that the palletiser makes transverse movements when picking a box and placing it on a pallet. Such transverse movements entail an inherent safety risk, because personnel may be hit by the transversely moving parts or, worse, become pinched between such parts and stationary objects. As a consequence, it will be necessary to provide for safety measures, either for keeping persons away or for sensing an obstruction and stopping the movement, or both, it is an objective to provide a palletiser station where such transverse movements are reduced to a minimum or are even eliminated completely.

Palletiser stations are known where the pailetisers are implemented as bridges crossing the pallet and/or box conveyors, having for instance one or more pulleys guided along said bridges. A problem is that such palletiser stations have a high building profile, and assembly and maintenance need to be done at a high level. It is an objective to provide a palletiser that has a low building profile, such that assembly and maintenance can to a large extent be done by personnel standing on the ground, while further the assembled palletiser fits in a standard size transport container to allow assembly in a remote assembly facility, followed by shipping in assembled condition to a location of use.

According to the invention, a palletiser station comprises a rotation table for receiving a pallet to be loaded, and for rotating that pallet during the loading process, such as to always have a target position for a box in between a supply position of the box and the pallet centre. Thus, displacing the box to its target position can always be done in a straight line directed to the pallet centre, and It is never necessary to displace the box in transverse direction, and it is never necessary to displace the box beyond the pallet centre.

It is noted that pailetisers comprising a pallet table capable of rotating the pallet are already known. For instance, the company ARPAC has proposed a robot called "ARBOT", visible at https://www.youtube.corn/Watch7vs1saljYFVy-8.

in this case, however, the rotation facility is only used for applying a wrapping around the loaded pallet. While the pallet Is being loaded, the pallet is always kept stationary with respect to the palletising robot and with respect to the box supply conveyor.

In the RJ-31C Robotic Palletiser, proposed by the company FANUC, visible at https://www.youtube.c»m/watch?v=pnAH7Fkyxxc,

a pallet conveyor takes the shape of a rotating table. The table has a radius much larger than the pallet diagonal length, and comprises four pallet receiving parts, each for receiving one pallet, located at a distance from the table rotation axis, so that this rotation axis is outside the pallet footprint. This rotating table conveyor is positioned at the head end of a plurality of box supply conveyors and adjacent a pallet supply conveyor. At one angular position of the rotating table conveyor, a certain pallet receiving part is positioned adjacent the pallet supply conveyor and receives a pallet. The rotating table conveyor is then rotated over 90°, 180° and 270°, to bring this pallet receiving part with said pallet to three different positions at which the pallet the pallet can be loaded by a palletising robot to receive boxes from one of the box supply conveyors. While being loaded, the pallet is kept stationary with respect to the palletising robot and with respect to the box supply conveyor. This apparatus is not capable of rotating a pallet around a vertical axis intersecting the pallet centre.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, features and advantages of the present invention will be further explained by the following description of one or more preferred embodiments with reference to the drawings, in which same reference numerals indicate same or similar parts, and in which:

Figure 1 is a schematic top view of a palletiser station according to the present invention;

Figure 2 is a top view of a loaded pallet, illustrating a possible pattern of 10 boxes in a stacking layer;

Figures 3A-C illustrate rotation of a pallet and placement of a box;

Figure 4 is a block diagram illustrating the control of the palletiser station.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 is a schematic top view of a palletiser station 1 according to the present invention. The figure shows a pallet P to be loaded. The figure further shows an end section of a box conveyor 10, supplying boxes B to be stacked on the pallet P. The conveying direction is indicated by an arrow. The conveyor 10 may be of any known or new type. The type of conveying mechanism, for instance rollers or belt, is not relevant for the present invention. For sake of simplicity, the figure does not show a pallet removal conveyor or pallet supply conveyor.

The (horizontal) conveying direction of the box conveyor 10 will in the following be taken as X-direction. it is to be noted that the boxes B will have horizontal dimensions smaller that the horizontal dimensions of the pallet P, and that the box conveyor 10 will have a width (measured in a horizontal Y-direction

perpendicular to the X-direction) wide enough to accommodate the largest boxes to be expected but smaller than the Y-dimension of the pallet P.

The pallet P is shown in a loading position, which is aligned with the box conveyor 10. Reference numeral 11 indicates a central line of the box conveyor 10, while C indicates the centre (i.e. intersection of diagonals) of the pallet P, assuming the pallet has the usual rectangular shape. In the ideal loading position, centre C is aligned with central line 11, although some tolerance is allowed.

Reference numeral 110 indicates a gripping head of a palletiser 100. The nature of the gripping mechanism of the gripping head 110 is not essential for understanding and practicing the present invention; as a non-limiting example, the gripping head 110 may for instance be a vacuum suction head, engaging horizontal top surfaces of the boxes B, or a clamp, engaging vertical side surfaces of the boxes B.

The gripping head 110 must be able to manoeuvre a box B in various directions.

A first manoeuvring direction is vertical (the Z-direction perpendicular to X and Y). A box B must be lifted from the box conveyor 10, and must be lifted to the appropriate level with respect to the pallet P. It is to be noted that the top surface of the pallet P is a ground level for stacking: this is where a first layer of boxes B will be placed. Then, an optional separation sheet may be placed, and the next boxes B are placed on top of the first layer to define a second layer. It should be clear that each next stacking layer will require the boxes B to be lifted to a higher level. The palletiser 100 must be capable of lifting the gripping head 110 to, at least, the highest required stacking level.

A second manoeuvring direction is the X-direction. A box B must be displaced from the box conveyor 10 to a suitable position above the surface of the pallet P.

A third manoeuvring direction is an angular direction, i.e. a rotation about the Z-axis. It can not be expected that the boxes B on the box conveyor 10 have the same orientation as required on the pallet P. In the case of rectangular boxes, some may need to be oriented with their longitudinal direction aligned with the X-axis while others may need to be oriented with their longitudinal direction aligned with the Y-axis. With only these three manoeuvring directions, it is in practice not possible to cover the entire surface of the pallet P. Therefore, in prior art, a palietiser 100 is also manoeuvring in the Y-direction.

According to the present invention, the palietiser station 1 comprises a rotation table 200 that carries the pallet P in its loading position, and that is capable of rotating the pallet P about the Z-axis over an angular range of at least 180° and preferably at least 360°, most preferably without limits. With the combined rotation of the rotation table 200 and the three manoeuvring directions of the gripping head 110 as mentioned, it is possible to place any box of any size on any position of the pallet, as will be explained in the following.

For rotating the pallet P, a footprint is required having a circular shape with a diameter equal to the length of the pallet's diagonal. The rotation table 200 may be larger and extend beyond this circular footprint, but it is required to keep the space requirements as small as possible. The exact shape of the rotation table's top surface is not essential; it may for instance be a square, rectangular or circular top surface. It may be somewhat smaller that the pallet to be carried, because it is not problematic if the pallet (especially at the pallet corners) slightly projects beyond the rotation table's top surface. The rotation table has a vertical rotation axis, and receives the pallet P centrally, so that in operation the pallet P will be rotated about a vertical axis substantially aligned with its centre C.

Figure 2 is a top view of a possible stacking pattern of 10 boxes B. Each box B has a vertical box centre line, indicated by a symbol ® in the figure, in the vertical projection of figure 2, each individual box centre line has a fixed and known X,Y coordinate. For each box B, it will be possible to rotate the rotation table 200 over a certain angle φ such that the corresponding box centre line Θ is aligned with the central line 11 of the box conveyor 10. This is illustrated in figures 3A-C.

Figure 3A is a view comparable to figuresl and 2 combined, illustrating a situation where a layer of boxes has not been completed yet. Boxes which are in place are illustratively indicated with grey rectangles, while dotted lines indicate a target location where the next box B is to be placed. A symbol & indicates the position where the box centre line of this next box B will be once this next box B has actually been placed at this target location; this will be indicated as a target position centre line. The gripping head 110 is made to engage the box B at a position aligned with its box centre line 0, and to rotate the box B over an angle β to an orientation equal to the orientation of the target location. This rotational orientation of the box B is indicated as the target orientation. It is noted that the required rotation angle β of the gripping head 110 will be dependent on the actual orientation of the box on the box conveyor 10; this required rotation angle β will be indicated as "correction" angle and will, in the situation of figure 3A, typically be approximately 0° or 90°.

The rotation axis of the pallet is assumed to coincide with its centre C. Line L connects target position centre !lne ® with pallet centre C. This line L makes an angle φ with the central line 11 of the box conveyor 10; this angle will be indicated as target angle.

It should be understood that for each and every target position there is one unique target position centre line ® and hence one unique target angle φ. Figure 3B is a view comparable to figure 3A, but now the pallet P has been rotated over said target angle φ, so that the relevant target position centre line ® of the target position is aligned with the central line 11 of the box conveyor 10, positioned in between the pallet centre C and the box conveyor 10. The gripping head 110 has been made to rotate the box B over an adaptation angle Θ equal to φ, so that with respect to the pallet P the box B still has the correct orientation.

It may be noted that, in view of the symmetry of rectangular boxes, rotation over θ = φ is equivalent to rotation over θ = φ - 180°. In the case of square boxes, rotation over θ = φ is even equivalent to rotation over θ = φ - 90°.

it may further be noted that, in view of the symmetry of rectangular boxes, rotation over θ = φ is equivalent to rotation over Θ = 180° - φ in opposite direction, in the case of square boxes, rotation over 8 = φ is even equivalent to rotation over Θ = 90° - φ in opposite direction.

Figure 3C is a view comparable to figure 3B, in which, with respect to the situation shown in figure 3B, the gripping head 110 has been displaced in the

X-direction over the distance required to bring the box B to its destined stacking position.

Thus, whatever the rotational orientation of a box B on the box conveyor 10, and whatever the desired rotational orientation of that box B on the pallet P, and whatever the desired X,Y position of that box B on the pallet P, it is always possible to place such box at any desired X,Y position and in the desired rotational orientation by a linear displacement of the gripping head 110 in X-direction only, in combination with rotations of the gripping head 110 and the rotation table 200 over suitably selected angles Θ and φ, respectively.

It is noted that, as compared to a palletiser without a rotating support table for the pallet, the displacement range required for the gripping head 110 in the

X-direction is less, since the gripping head 110 does not need to be displaced beyond the pallet centre C. It is further noted that the movements of the box do not need to be performed discrete and successive, as in the above explanation, it is further not necessary that the box B is first rotated over angle β and subsequently rotated over angle Θ. It is possible, and even more efficient, that the box B, after having been picked up from the box conveyor 10, is displaced in X-direction and is simultaneously rotated over an angle β + 8.

Further, rotation of the pallet over angle φ may be performed simultaneously, at least partly, with the rotation of the box. It is preferred that, in any case in a last phase of the placement action when the box is close to landing, the rotation speed of the box equals the rotation speed of the pallet, while at all times in this last phase the box orientation is equal to the pallet orientation.

in the above explanation, it was assumed that the boxes B on the box conveyor 10 are aligned with the conveyor centre line 11 , in any case at the position where the gripping head 110 fetches the boxes. The box conveyor 10 may be equipped with alignment means for ensuring such alignment by displacing the boxes in Y-direction, if needed. Alternatively, the pailetiser 100 may comprise compensation means for slightly displacing the gripping head 110 in Y-direction to compensate for any misalignment, if needed. However, in practice, a misalignment of a few

centimetres will cause no problem because the only consequence will be that the gripping head 110 does not hold the box exactly centered. The corresponding transverse deviation of the box can be largely compensated by a small rotation of the pallet rotation table 200.

After stacking the boxes B on to the pallet P, it is customary that the loaded pallet is conveyed to a wrapping station where a transparent foil is wrapped around the stack of boxes. The wrapping is typically done by placing the pallet onto a rotation table which is positioned adjacent a foil holder/dispenser, and making the pallet with its stack of boxes rotate while foil is taken from the foil holder/dispenser, which is only moving in vertical direction. It is a great advantage of the present invention that such wrapping station can be integrated with the pailetiser, because the pailetiser already comprises a rotation table.

Figure 4 is a block diagram illustrating the control of the pailetiser station. A control device 400 has a first control output 401 coupled to the rotatab!e gripping head 110 for controlling the rotational position of the gripping head 110 with respect to a vertical rotation axis. The control device 400 has a second control output 402 coupled to the rotation table 200 for controlling the rotational position of the rotation table 200, Reference numeral 300 indicates a displacement apparatus for displacing the gripping head 110. The displacement apparatus is capable of lifting and lowering the gripping head 110; this functional facility is schematically indicated at block 310. The displacement apparatus is capable of horizontally displacing the gripping head 110 in the X-direction; this functional facility is schematically indicated at block 320.

Preferably, these two functional facilities are controllable individually.

The control device 400 in the embodiment shown has a third control output 431 coupled to the displacement apparatus 300 for controlling the vertical

displacement of the gripping head 110, and a fourth control output 432 coupled to the displacement apparatus 300 for controlling the horizontal displacement of the gripping head 110.

It is noted that the precise design of the displacement apparatus 300 is not essential for implementing the present invention. Various options are available to the skilled person. It is therefore not necessary to describe such design details here.

It is particular noted in this respect that the said horizontal and vertical displacement facilities do not need to be totally separate. It is possible that displacement is executed along a track that has a vertical component as well as a horizontal component, and that the displacement device performs these

displacement components in combination.

It should be dear to a person skilled in the art that the present invention is not limited to the exemplary embodiments discussed above, but that several variations and modifications are possible within the protective scope of the invention as defined in the appending claims. For instance, two or more functions may be performed by one single entity, unit or processor. Even if certain features are recited in different dependent claims, the present invention also relates to an embodiment comprising these features in common. Even if certain features have been described in combination with each other, the present invention also relates to an embodiment in which one or more of these features are omitted. Features which have not been explicitly described as being essential may also be omitted. Any reference signs in a claim should not be construed as limiting the scope of that claim.

in the above, the invention has been explained for an implementation where boxes are always transferred from the box supply conveyor to the pallet in a linear movement aligned with the box supply conveyor's longitudinal direction and towards the pallet centre C. With such loading process, it is nonetheless possible to cover the entire pallet surface by adapting the pallet's angular position so that the box target position on the pallet is always aligned with the box supply conveyor. Alternatively, it is also possible that the palletiser robot takes boxes from an arbitrary conveyor, brings the boxes to a certain reference position in between the robot and the pallet, and then transfers the boxes from that reference position to the pallet in a linear movement towards the pallet centre C, while the pallet's angular position is adapted so that the box target position on the pallet Is always aligned with the said reference position.

in the above, the present invention has been explained with reference to block diagrams, which illustrate functional blocks of the device according to the present invention, it is to be understood that one or more of these functional blocks may be implemented in hardware, where the function of such functional block is performed by individual hardware components, but it is also possible that one or more of these functional blocks are implemented in software, so that the function of such functional block is performed by one or more program lines of a computer program or a programmable device such as a microprocessor, microcontroller, digital signal processor, etc.