GOODS HANDLING DEVICE

Abstract: The invention relates to a goods handling device, in particular for use in a pallet layer picking device, that includes a lifting head (24) having an array of discrete suction devices (40) mounted on a hollow box (28) for lifting engagement with an article or articles to be lifted.

Description: GOODS HANDLING DEVICE The present invention relates to a goods handling device and in particular, but not exclusively, to a layer picking device for use. for example, in goods distribution warehouses. In distribution warehouses, the goods can be stored stacked on pallets and delivered to users on pallets. Frequently, however, a user will not require a whole pallet load of identical goods. Pallets therefore have to be stacked in the warehouse before delivery with layers of different goods, according to the user ' s requirements. Other types of load carriers are also sometimes used but, for the purposes of the present application, all such carriers will be referred to as "pallets " . Traditionally, pallets have been stacked by hand. This is. however, laborious and slow. To automate the layer picking process, layer picking devices have been designed that are capable of transferring goods layer-by-layer from one pallet to another using a suction head with a large suction hood that engages an entire layer of goods. However, these devices have met with only limited success, since the suction head is capable of lifting only certain types of goods, for example complete layers of closely packed boxes or cartons. They are generally unable to lift oddly shaped goods, since these do not form a good seal with the suction heads, or layers that have voids in them, which are either not lifted or. alternatively, "capture " goods from the layer below that being lifted. Such goods therefore have to be picked and stacked manually. It is an object of the present invention to provide a layer picking device that mitigates at least some of the above-mentioned disadvantages. According to the present invention there is provided a goods handling device including a lifting head having a multiplicity of discrete suction devices for lifting engagement with an article or articles to be lifted. The provision of a multiplicity of discrete suction devices allows the device to lift a complete layer of a wide range of goods, of different sizes and shapes, since each item in that layer will be engaged separately by a plurality of suction devices. Oddly-shaped goods can therefore be lifted as easily as rectangular boxes, allowing automation of the stacking operation. Advantageously, said suction devices are arranged in a substantially flat array, such that the article-engaging surfaces of the suction devices lie substantially in a plane. This allows the suction devices to engage a flat layer of goods simultaneously. Advantageously, the lifting head includes between four hundred and four thousand, and preferably between eight hundred and two thousand, discrete suction devices. Advantageously, each suction device includes a flexible device, for example a flexible bellows device, for engagement with an article to be lifted, thereby allowing small differences in the height of the goods to be accommodated. Advantageously, each suction device includes a check valve to prevent air flowing through any suction device that is not in sealed contact with the goods, so preventing any reduction in the vacuum. Advantageously, said suction devices are connected to a common suction chamber. Advantageously, the lifting head is supported by a suspension assembly that includes a lost motion mechanism. Advantageously, said goods handling device includes a plurality of goods receiving stations, said lifting head being mounted for movement between positions directly above each of said goods receiving stations, this arrangement allowing the lifting head to transfer goods readily from one station to another. Advantageously, each said goods receiving station is mounted on a lifting device for raising the goods receiving station to meet the lifting head. This allows the goods to be pre-positioned at an appropriate height for engagement by the lifting head, so providing for efficient operation. Advantageously, each said goods receiving station includes a conveyor for transferring goods to or from the goods receiving station. Advantageously, said lifting head includes a sensing device for sensing any offset in the position of a load relative to the lifting head, thereby allowing any offset in the stacking of the goods to be corrected. Advantageously, the goods handling device includes a control device for adjusting the position of the lifting head, to compensate for any offset in the position of the lifted load relative to the lifting head as sensed by the sensing device. Advantageously, the goods handling device includes a pallet inserter assembly, which is preferably capable of moving independently of the lifting head. According to the present invention there is provided a pallet layer picking device including a goods handling device according to any one of the preceding claims, for transferring goods layer by layer from one pallet to another. An embodiment of the present invention will now be described, by of way of example, with reference to the accompanying drawings, in which: Figure 1 is side view of a pallet stacked with layers of goods; Figure 2 is a plan view of a goods handling device according to the present invention; Figure 3 is a front view of a lifting gantry forming part of the goods handling device; Figure 4 is an end view of the lifting gantry: Figure 5 is a plan view showing the underneath of a lifting head; Figure 6 is a side section through the lifting head; Figure 7 is a top view of the lifting head, depicting a raise/lower mechanism for a sensing device; Figure 8 is an end view of the mechanism shown in Figure 7: Figure 9 is a side view of the mechanism shown in Figure 7; Figure 10 is a side sectional view of a head suspension assembly: and Figure 1 1 is an end view, at an enlarged scale, of a pallet inserter mechanism. Layer picking devices are used for transferring goods from one pallet to another, for example in a goods distribution warehouse. A typical stacked pallet is shown in Figure 1. The pallet 2 is stacked with six layers 4a-4f of goods, which in this example are in the form of rectangular boxes 6. The boxes 6 are stacked in a bond pattern with the periphery of each layer matched to the size and shape of the pallet 2. Because the width of the pallet 2 is not equal to an exact multiple of the width of the boxes 6, each layer contains one or more voids 8. If an attempt is made to pick up the uppermost layer 4a with a traditional layer picking device having a large suction hood, air will flow through the voids in the layer and will either reduce the vacuum, preventing the layer being lifted, or will cause some goods from the next layer 4b to be captured and lifted with the top layer 4a. An example of a pallet stacking installation 10 that includes a goods handling device according to the present invention is shown in plan view in Figure 2. The installation includes three parallel chain conveyors 12a.12b.12c. The two outer conveyors 12a, 12c are intended to receive pallets from the warehouse, which are stacked with goods of a single type, whereas the central conveyor 12b is intended to receive an empty pallet, onto which goods are transferred from the pallets on the outer conveyors 12a.12c. This arrangement is of course changeable, as also is the number and type of the conveyors. Pallets stacked with goods are transferred to the stacking installation 10 from an adjacent warehouse (not shown) through a doorway 14. A roller conveyor 16 extends across the doorway 14, parallel to the chain conveyors 12a.12b.12c. A pair of pallet transfer trucks 18a, 18b, which are also provided with roller conveyors, are provided, one at each end of the three chain conveyors. The transfer trucks 18a.18b are mounted on rails 19 for movement across the ends of the conveyors. A fourth chain conveyor 20 for delivering empty pallets 21 to the installation extends parallel to the three chain conveyors 12a.12b.12c on one side of the installation 10. A gantry 22 extends over the four chain conveyors 12a, 12b.12c and 20. The gantry 22 supports a goods handling device including a lifting head 24 that is mounted for movement along the gantry, perpendicular to the chain conveyors. The central section 26a.26b.26c.26d of each conveyor 12a.12b.12c.20 is provided with a scissor lift that can lift that section of the conveyor and any pallet on that section upwards to meet the lifting head 24. The installation also includes a computer (not shown) for controlling the entire stacking operation, including retrieving and returning pallets of goods from the warehouse, stacking layers of goods on the empty pallet and delivering the loaded pallets to a loading bay. The installation is therefore capable of fully automatic operation. In use, pallets stacked with goods are transferred through the doorway 14 onto the central section of the roller conveyor 16. Each pallet is then transferred in turn to the left (in the direction of arrows 102,103) onto the first transfer truck 18a which transfers the pallet onto one of the outer chain conveyors 12a.12c. The pallet is then transferred in the direction of the arrows 104,110 onto the central section 26a.26c of the respective conveyor, which lifts the pallet to meet the lifting head 24. The lifting head 24 engages and removes the top layer of goods (as described below) and then moves sideways until it is over the central conveyor 12b. The empty or partially stacked pallet on the central conveyor 12b is lifted to meet the head, which releases the lifted layer to place it on top of the pallet or the goods already stacked on that pallet. This process is repeated as often as necessary, transferring layers of goods from the pallets on the outer conveyors 12a.12c onto the pallet on the central conveyor 12b. until that pallet is fully stacked with the desired selection of goods. It is then transferred to the right (in the direction of arrow 109) onto the second transfer truck 18b, which transfers the stacked pallet onto the roller conveyor 16 from where it is removed through the doorway 14 and conveyed to a loading bay for loading onto a delivery lorry. A new pallet is transferred from the fourth chain conveyor 20 onto the central conveyor 12b, and the whole process is then repeated. The central section 26b of the central conveyor 12b and the position of the lifting head 24 may both be adjusted horizontally as layers of goods are being placed on the pallet, to ensure that the goods placed on the pallet are stacked accurately. The lifting head 24. which is shown in more detail in Figures 5 & 6. includes a square box 28 having a top plate 30. a bottom plate 32. and a square frame 34 that extends between the edges of the plates to separate them from each other, forming a void 36 that may be evacuated in use through vents 38 in the top plate 30. The bottom plate 32 is provided with a plurality of threaded apertures 40. in each of which there is provided a suction device 42 (only one of which is shown in the drawings). The suction device 42 includes a rubber bellows 44 and a body 46 that includes a check valve to close the valve in use if the airflow through the device exceeds a predetermined rate. This is to ensure that the vacuum is not reduced by air leaking into the void 36 through suction devices that are not in contact with the object being lifted. In the embodiment shown in the drawings, the lifting head 24 has 1055 suction devices 42. arranged in thirty-seven rows of alternately twenty-nine and twenty-eight suction devices. The lifting head may of course have more or fewer suction devices than this, but in any event will have between four hundred and four thousand discrete devices, and preferably between eight hundred and two thousand. Attached to the lifting head 24 is a load position sensing device 50. which is shown in more detail in Figures 7 to 9. The device includes eight sensors 52. each of which has a touch sensitive probe 54 mounted on a telescopic boom having a linear encoder to sense the position of the probe. In use. the probes are extended towards the load carried by the lifting head until they touch the load and the position of the load is then determined from the readings of the linear encoders. In this way. any offset of the load can be measured. and the position of the lifting head relative to the central section 26b of the central conveyor 12b can be adjusted to compensate for that offset. The probes 52 are mounted on a frame 56, which may be raised or lowered by means of a lifting mechanism comprising a motor 58 that drives a set of belts 60. The raise/lower mechanism allows the height of the sensing device 50 to be adjusted relative to the load, to accommodate loads of different heights. The lifting head 24 is suspended at each corner by means of a suspension assembly 62. one of which is shown in figure 10. The suspension assembly includes a mounting stool 64 that is supported by the gantry 22, and a pair of parallel shafts 66, 68 that extend through two apertures 70 in the lower side of the stool 64 and are connected at their lower ends to the lifting head 24. The first shaft 66 is provided at its upper end with a male self-centring cone 72 that engages in a female self-centring cone 74 mounted in the stool 64. The second shaft 68 engages at its upper end a compression spring 76 that is located between an upper spring retaining washer 78 fixed to the shaft 68 and a lower spring retaining washer 80 that is seated on a mounting block 82 in the stool 64. A rubber buffer 84 is provided on the upper surface of the lifting head 24 to engage the lower side of the stool 64. When the lifting head is at rest, the suspension assembly 62 is configured as shown in figure 10, with the male self-centring cone 72 fully engaged with the female self-centring cone 74. This locates the lifting head in a precise rest position. The spring 76 is compressed between an upper spring retaining washer 78 and the lower spring retaining washer 80, thereby urging the lifting head upwards. The strength of the springs in the suspension assemblies is chosen so that the total force all of them exert on the lifting head when fully compressed is slightly less than the weight of the head. The springs cannot therefore lift the head without external assistance, although they do support most of the weight of the head. When a pallet of goods is lifted by one of the scissor lifts to meet the head 24. the force of the goods pressed against the head is sufficient to lift it slightly from the rest position. The suspension assembly therefore provides a lost motion mechanism, which allows the scissor lift to overrun the position at which the goods first contact the lifting head, without damaging either the goods or the head itself. Further, by lifting the pallet slightly beyond that position, the goods can be pressed against the lifting head, ensuring a good hermetic seal between the goods and as many of the suction devices 42 as possible. The goods handling device also includes a pallet inserter mechanism 82. which is suspended from the gantry 22 for transverse movement across the four conveyors 12a. 12b. 12c, 20. The pallet inserter mechanism 82 includes four retractable arm devices 84. one of which is shown in detail in figure 1 1. Each arm device 84 includes a cantilever arm 86 mounted for rotation about a vertical pivot axis 88, and a drive mechanism 90 for rotating the arm between a retracted position in which it extends parallel to the gantry, and an extended position as shown in figure 1 1 , in which it is perpendicular to the gantry. During operation, the pallet inserter mechanism 82 can travel along the gantry independently of the lifting head 24. to insert pallets where they are required. Empty pallets are brought in on the fourth conveyor 20 and lifted to meet the inserter 82. The arms 86 are rotated to the extended position, where they engage the pallet. The inserter then moves to the position where the pallet is required and, after placing the pallet in that position, the arms 86 retract to release the pallet. In use, an empty pallet to be loaded with goods is placed on the centre section 26b of the central conveyor 12b by the lifting head 24. Pallets with goods to be transferred onto the empty pallet are delivered automatically under computer control to the outer conveyors 12a.12c. The lifting head 24 transfers goods layer-by-layer, again under computer control, to the empty pallet. The sequence is as follows: 1. The lifting head 24 is located over a pallet of goods on one of the outer conveyors, for example 12a. 2. The central section 26a of the conveyor 12a lifts the pallet so that the top layer of goods meets the lifting head 24. The pallet is lifted slightly above the position where the goods first make contact with the head, so that the weight of the lifting head presses the suction devices against the goods, ensuring a good hermetic seal with as many of those devices as possible. 3. A vacuum is applied to the lifting head to support the top layer of goods. 4. The centre section 26a of the conveyor 12a descends. 5. The lifting head 24 moves over the central conveyor 12b. 6. The centre section 26b of the central conveyor 12b lifts to meet the lifting head 24. 7. The vacuum is released, so that the lifting head places the layer of goods on the pallet. 8. The centre section 26b of the conveyor 12b is then lowered. 9. The process is repeated until the pallet has been fully stacked. 10. Optionally, an empty pallet may be inserted into the stack of goods by the pallet inserter 82, allowing the stack to be divided later, for example during delivery. While the layer of goods is being carried by the lifting head 24, the sensing device 50 measures the position of the lifted layer of goods relative to the head and, if any offset is detected, this is corrected by adjusting the position of the lifting head 24 and/or the pallet on the centre section 26b of the central conveyor 12b. The stacked pallet is transferred through the warehouse doorway 14 to a wrapping station (not shown), and from there it is transferred to a loading bay for delivery to the client. Various modifications of the device are possible. For example, the position sensing device 50 shown in Figures 7 to 9 may be replaced by an optical system, for example using laser photocells. This optical system may either be statically mounted or mounted on the lifting head 24. The lifting mechanism 56, 58, 60 may then be omitted.

Claims: CLAIMS 1. A goods handling device including a lifting head having a multiplicity of discrete suction devices for lifting engagement with an article or articles to be lifted. 2. A goods handling device according to claim 1 , wherein said suction devices are arranged in a substantially flat array, such that the article-engaging surfaces of the suction devices lie substantially in a plane. 3. A goods handling device according to claim 1 or claim 2. wherein the lifting head includes between four hundred and four thousand discrete suction devices. 4. A goods handling device according to claim 3, wherein the lifting head includes between eight hundred and two thousand discrete suction devices. 5. A goods handling device according to any one of the preceding claims, wherein each suction device includes a flexible bellows device for engagement with an article to be lifted. 6. A goods handling device according to any one of the preceding claims, wherein each suction device includes a check valve. 7. A goods handling device according to any one of the preceding claims, wherein said suction devices are connected to a common suction chamber. 8. A goods handling device according to any one of the preceding claims, wherein the lifting head is supported by a suspension assembly that includes a lost motion mechanism. 9. A goods handling device according to any one of the preceding claims, said goods handling device including a plurality of goods receiving stations, said lifting head being mounted for movement between positions directly above each of said goods receiving stations. 10. A goods handling device according to claim 9. wherein each said goods receiving station includes a lifting device for raising the goods to meet the lifting head. 1 1. A goods handling device according to any one of the preceding claims, wherein each said goods receiving station includes a conveyor for transferring goods to or from the goods receiving station. 12. A goods handling device according to any one of the preceding claims, wherein said lifting head includes a sensing device for sensing any offset in the position of a load relative to the lifting head. 13. A goods handling device according to claim 12. including a control device for adjusting the position of the lifting, to compensate for any offset in the position of the lifted load relative to the lifting head as sensed by the sensing device. 14. A goods handling device according to any one of the preceding claims, including a pallet inserter assembly. 15. A pallet layer picking device including a goods handling device according to any one of the preceding claims, for transferring goods layer by layer from one pallet to another. 16. A pallet layer picking device substantially as described herein with reference to and as illustrated by the accompanying drawings.

Inventors: WESTON MATTHEW JAMES, WESTON, MATTHEW, JAMES
Applicants: MANNESMANN DEMATIC LTD, WESTON MATTHEW JAMES, MANNESMANN DEMATIC LIMITED, WESTON, MATTHEW, JAMES
Application year: 2000
Main classification: B65G47
IPC codes: B65G47