Method for lifting a material unit from a material arrangement

Abstract

Method for lifting individual material units (2) from a material arrangement (17), comprising the steps: A) Providing a material arrangement (17) of material units (2), wherein, viewed from above onto the material arrangement (17), the material arrangement (17) has a length (L) along a longitudinal direction, a width (B) along a width direction, and a plurality of corners (18, 19, 20, 21), wherein each of the material units (2) has a length (1) and a width (b), wherein the width (b) is less than or equal to the length (1), B) Providing a lifter (3) and attaching it to an engagement surface (16) at one of the corners (18, 19, 20, 21), wherein the engagement surface (16) extends from the corner (18, 19, 20, 21) along the longitudinal direction and along the width direction over a distance not longer than the width (b) of a material unit (2).

Description

The present invention relates to a method for lifting a material unit from a material arrangement, in particular from a pallet. In particular, the material unit can be present in bale form. The bale can have different dimensions in different directions, in particular a width direction and a length direction, as seen from above on the pallet. The material can be, for example, a raw polymer or a mixed polymer material of a rubber mixture.In the preparation of rubber mixtures, crude polymer bales are provided on pallets. The pallets can have different dimensions and designs. The bales are usually removed from the pallet one after the other by a gripper system. This requires position detection of the individual bales. Position detection is difficult, however, since the bales are often packaged in film that protrudes from the sides. In addition, the environment in material processing is often dirty and dusty.In order to ensure smooth, fully automatic operation, however, reliable position detection of the bales must be ensured. For this reason, optical systems are used in part, which are however expensive and often unreliable. Optical solutions such as 3D cameras or laser measurements meet their limits here.Thus, DE 11 2019 000 177 T5, DE 11 2019 000 217 T5, WO 2017 / 146 895 A1 each describe a robot system in which image data are processed for lifting an object from a pallet. EP 2 554 344 B1 discloses a vacuum gripper for lifting food.Alternatively, the bales are removed manually. This represents a heavy physical work and is also prone to errors.It is an object to specify an improved method for lifting individual material units from a material arrangement.In a method of lifting individual units of material from a material array, a material array of units of material is provided. The material units are, for example, cuboidal. These are, for example, bales of raw polymer or a polymer mixed material of a rubber mixture. The material units can be arranged on a pallet. In particular, the material units can be arranged on top of one another in a plurality of layers. Each layer may have a dense packing pattern of the material array.The material arrangement has a length in a plan view from above along a longitudinal direction, a width along a width direction and a plurality of corners. Each of the material units has a length and a width in a plan view from above, wherein the width is less than or equal to the length. The material units can be packed close to one another in a layer and completely fill a pallet in the longitudinal and width directions. The material units are arranged in their longitudinal direction or width direction in particular in each case parallel or perpendicular to the length of the material arrangement and / or a pallet.In the method, a lifter for lifting one of the material units is provided. The lifter is designed, for example, as a vacuum lifter having a vacuum plate.The vacuum plate has, for example, a hard sealing edge for forming a sealing contact with the material unit. The sealing edge can be formed with sharp knives for cutting into the material unit. It has been found that an improved adhesive force can be achieved by introducing an incision compared to pressing the sealing edge into the material unit. The material units can also each have a packaging. The sealing edge can be designed in such a way that the packaging is completely or partially severed when it engages the material units.The material of the sealing edge has in particular a greater hardness than the material of the material unit to be lifted, so that the material of the sealing edge does not deform or deforms only slightly when it is cut into the material unit. The vacuum plate thus does not have a soft rubber seal for establishing contact with the material unit.The lifter is attached to an engagement surface at one of the corners of the material arrangement such that the engagement surface does not extend from the corner along the longitudinal direction and the width direction over a distance longer than the width of a material unit. This is in particular an outer corner of the material arrangement.In this way, it can be ensured that only a single material unit is gripped for all packing patterns without the need to identify the specific packing pattern. Due to the attachment to the corner, the material units are eccentrically lifted if the length of the material unit is greater than the width. The lifter must therefore apply a sufficiently large lifting force. It is possible to employ a lifter other than the vacuum lifter described above as long as a sufficiently large lifting force can be applied.After a material unit has been lifted out, the lifter can be positioned at a further corner, wherein here too, as in the preceding step, the engagement surface is selected. For example, the material arrangement has four corners and the steps are carried out successively at all four corners. The corners can correspond to the corners of the pallet in a densely packed material arrangement.It is also possible that the material arrangement of the respective layer is not packed tightly originally and thus has fewer or more than four outer corners or the corners do not correspond to the corners of the pallet. In this case, it can be detected, for example, by means of a sensor whether a material unit is present in this position at each corner and then only the material units actually present in this position can be lifted at the corners. Detection of an unfilled corner is also possible by placing a lifter on the corner of the pallet in the plane of the respective position and can be detected by the then missing lifting force or a missing negative pressure in the case of a vacuum lifter.It is also possible, after removing a first material unit at a corner, to approach one of the corners of the incomplete material arrangement which has newly formed as a result of the removal of the material unit. This then does not have to be a corner of the pallet or of the original material arrangement.The position of a corner can be easily detected, for example, by means of a sensor on the basis of the height difference from a lower layer or the ground.The position of a corner can be easily detected, for example, by means of a sensor on the basis of the height difference from a lower layer or the ground. It is also possible that, when lifting a material unit, the orientation of the lifted material unit is detected and the position and / or orientation of further material units is thereby determined. For example, light barriers, lasers, mechanical sensors, weight distribution on the lifter or similar technologies can be used for this purpose.For example, all material units at the corners are first removed as described above and then position detection of the further material units is carried out. This is easily possible after removal of material units at the corners, since a height difference from the underlying layer or from the ground can now be detected. For example, optical sensors, ultrasonic sensors, infrared sensors, capacitive sensors, magnetic sensors or tactile sensors can be used for this purpose.The present invention encompasses several aspects, in particular apparatuses and methods. The features, properties and embodiments described for one of the aspects are also intended to apply accordingly to the other aspect.In addition, the description of the subject matter provided herein is not limited to the specific embodiments. Rather, the features of the individual embodiments can be combined with one another-insofar as technically expedient.The subject matters described here are explained in more detail below with reference to schematic exemplary embodiments.The following are shown: FIG. 1 shows a pallet for providing material units in material processing in a perspective view, FIGS. 2a-2k show possible packing patterns of material units in a material arrangement in a plan view from above, FIG. 3 shows a lifter for lifting a material unit in a schematic sectional view, FIG. 4 shows a lifter during the lifting of a material unit in a schematic sectional view, FIG. 5 shows a material unit with an engagement surface for a lifter in a perspective view, FIG. 6 shows a perspective view of an engaging of a lifter on a material unit, FIGS. 7 ato 7 f show method steps during the lifting of a material unit with a view from above onto a material arrangement, FIG. 8 shows a positioning of the lifter in method steps 7 eand 7 fin a perspective view according to one embodiment, FIGS. 9a-9k show a schematic diagram of a method for lifting a material unit in different packing patterns in a plan view from above.Preferably, like reference numerals refer to functionally or structurally corresponding parts of the various embodiments in the following figures.FIG. 1 shows a pallet 1 for providing material units in material processing. For example, the material units can be present in the form of bales. The bales can be of cuboidal design. These are, for example, rubber bales for rubber processing.The pallet 1 has a height H, a width B and a length L. The width B and length L are the dimensions of the pallet 1 in a plan view of the pallet 1 from above, i.e. viewed in the direction of gravity, in particular to the base of the pallet 1 on which the material units lie. In the present case, a pallet 1 with side walls is shown. It is also possible for a pallet 1 without side walls to be used. It is also possible for the material units to be arranged directly on the floor.The pallet 1 serves to provide a plurality of material units 2 which are stacked in a plurality of layers, for example, and which are in close contact with one another in each layer. The top side of each layer is in particular at a uniform height. Only one layer may also be present. The material units 2 can completely fill the pallet 1 in width B and length L. It is also possible for the material units 2 to incompletely fill the pallet 1.FIGS. 2a to 2k show possible packing patterns of a layer of material units 2 in a plan view from above onto a loaded pallet, such as the pallet 1 from FIG. 1. The material units 2 are stacked on top of one another in the pallet 1 and lie close to one another within one layer of the stack. For example, six layers of six material units 2 are stacked one on top of the other. The material units 2 do not overlap within one layer.The material units 2 each have a length 1 and a width b, as seen from above on the pallet 1, wherein length 1 and width b can be different. In the present case, the length 1 is greater than the width b. In the present case, six material units 2 can be closely stacked in a stacking plane. The material units 2 arranged on one another and on top of one another form a material arrangement 17, the length L and width B of which corresponds to the length L and width B of the pallet 1. The material units 2 thus fill the space within the pallet 1 as well as possible. It is also possible that the material arrangement 17 is not arranged on a pallet, for example directly on the floor.The length 1 of a material unit 2 is in the present case half the length L of the material arrangement 17 or of the pallet 1. the width b of a material unit 2 is in the present case one third of the width B of the material arrangement 17. however, other width and length ratios are also possible.The material units 2 can be arranged in a sealed manner in or on the pallet 1 in the eleven packing patterns shown here.For further processing, the material units 2 are to be lifted individually from or from the pallet 1 in a plant, for example, and transported to a device for processing and deposited there. For example, bales are to be laid from the pallet 1 onto a feed belt for processing, for example in an internal mixer.Such bales have dimensions in the range of 500 mm x 300 mm x 100 mm to 800 mm x 400 mm x 250 mm (LxBxH), for example. The weight of a bale is, for example, in the range of 35 kg. However, when delivering several bales may stick to each other, so that large forces (>400 kg) are required to lift the bales.For lifting out the material units 2, it is usually necessary to know the packing pattern in order to be able to lift out the material units 2 individually. Due to the tight contact of the material units 2 with each other, a relatively complex optical system has been necessary for this.FIG. 3 shows a lifter 3 for removing individual material units 2 from or from the pallet 1, which is a vacuum lifter having a vacuum plate 4 with an outlet 5 for extracting air from a cavity 6. The vacuum plate 4 can be fastened at its upper side to a lifting arm 8.The vacuum plate 4 has a hard sealing edge 9. In particular, the sealing edge 9 can be formed with a sharp blade. The sealing edge 9 can be an integral component of the wall 7, which encloses the cavity 6 and in which the outlet 5 is formed. In order to compensate for unevennesses of the material unit 2, the vacuum plate 4 is pressed so firmly against the material unit 2 that the sealing edge 9 is completely in contact with the surface of the material unit 2 in a circumferential manner. In particular, the sealing edge 9 can cut into the material unit 2 and cut through fibers of the material, for example. A vacuum pump 10 is connected to the outlet 5 of the vacuum plate 4 to generate a vacuum.The vacuum plate 4 can be combined, for example, as the last element of a kinematic chain ("end effector") with a robot or crane.The lifter 3 can have a pressing device 11 for pressing the vacuum plate 4 onto the material unit 2 after being placed on the material unit 2. By applying a force from above to a holder 12, the pressing device 11 applies a force from above to the vacuum plate 4.In addition, the lifter 3 can have a pushing-off device 13 for releasing the material unit 2 after depositing and, for example, removing the vacuum of a vacuum lifter.For example, a pressing-off device 13 can be formed by lateral projections which can be pressed downward relative to the vacuum plate 4. For example, the projections are arranged on the holder 12 such that they can be displaced downward in a downward direction and can be displaced downward in an automated manner in order to exert a force on the material unit.Alternatively, pressing on and / or detachment can also take place purely manually. The lateral projections can also be provided only for the lateral positioning of the vacuum plates 4 and do not provide a pressing-off function.FIG. 4 shows a lifter 3 in the form of a vacuum lifter when lifting a material unit 2, The vacuum plate 4 is pressed against the material unit 2 before generating a vacuum in such a way that the sealing edge 9 intersects the material unit 2 in a circumferentially sectional manner or completely. Thus, for example, fibers of the material unit 2 are severed.Below the material unit 2 is, for example, a lower material unit 15 which adheres to the material unit 2. Thus, a greater force must be provided during the lifting process in order to separate the material units 2, 15 from one another. In this case, the material unit 2 first releases from the underlying material unit 15 in a central region, with the result that a deformation occurs with respect to an outer region. The material thus comes off somewhat on the outer side of the sealing edge 9, which, however, is not disadvantageous for the sealing effect on the inner side of the sealing edge 9 due to the cutting of the sealing edge 9 into the material. The sealing edge 9 has a shape which promotes a tight contact on the inner side.Thus, with the lifter 3 shown, a significantly higher force than the pure weight force of the material units 2 can be applied, so that a plurality of material units 2, 15 adhering to one another can also be released from one another.In addition, FIG. 4 shows an outer packaging 14, for example in the form of a film, which is completely severed by the sealing edge 9. The packaging 14 is shown by way of example only on the upper side of the material unit 2, but it can completely surround the material unit 2. A packaging 14 can also be arranged around the lower material unit 15.For example, before the vacuum is generated, a force is applied from above to the vacuum plate 4 in the direction of the material unit 2. The force is, for example, up to 2000 N. The minimum and maximum force depends in particular on the deformability of the material unit.As soon as the material unit 2 circumferentially abuts the sealing edge 9, a vacuum can be generated by suctioning the air from the cavity 6. The vacuum plate 4 is thereby suctioned fast on the material unit. As soon as a sufficient level of the vacuum and thus of the holding force is reached, the material unit 2 can be raised.To deposit the material unit 2, the vacuum plate 4 is ventilated and the vacuum is dissolved. If the material unit 2 still adheres to the vacuum plate 4, the connection can be released manually or via a mechanical pressing-off device 13.The wall 7 can have the dimensionally stable sealing edge 9 as an integral component. The sealing edge 9 is thus not fastened to a housing part of the vacuum plate 4, but forms the lower edge of the wall 7. The material of the sealing edge 9 should not deform, in particular when pressing against the material unit 2, but rather cause an incision in the material unit 2.Different geometries of the vacuum plate 4 and the sealing edge 9 are possible. For example, the vacuum plate 4 has a circular, rectangular, square, triangular, hexagonal or generally polygonal peripheral line. A vacuum lifter can also have a plurality of vacuum plates 4. The holding force of the vacuum lifter can be adjusted in particular via the base area of the vacuum plate 4 surrounded by the sealing edge 9, via the quality of the vacuum, and via the number of vacuum plates 4.The wall thickness of the sealing edge 9 decreases downwards. "Downwards" means here in the direction of the opening of the vacuum plate 4, i.e. usually in the direction of gravity, "upwards" in the opposite direction. The sealing edge 9 tapers downwards. In this way, the sealing edge 9 can cut particularly well into the material unit 2.The sealing edge 9 is formed with a sharp blade. In this way, the vacuum plate 4 can also cut into a material unit 2 provided with a packaging 14 in such a way that the packaging 14 is completely severed and the sealing edge 9 bears directly against the inner material unit 2.The sealing edge 9 is beveled on one side in FIG. 4, i.e., beveled. The slight inclination of the outer side of the sealing edge 9 together with the knife-sharp sealing edge 9 enables good cutting into the material unit 2. the greater inclination of the inner side ensures that the material unit 2 rests closely against the inner side and is also somewhat compressed by the sealing edge 9, so that the sealing effect is improved. The sealing is thus achieved by the material inside the vacuum plate 4.The cutting of the sealing edge 9 into the material also achieves the effect that the material inside the vacuum plate 4 is partially mechanically decoupled from the material outside the vacuum plate 4, so that a deformation of the material outside the vacuum plate 4 does not lead to a detachment of the inner material from the sealing edge 9. The sealing effect is thus maintained even if the outer material is deformed during lifting by the weight force or due to adhesion to material units 2 lying underneath.The sealing edge 9 can have different cutting geometries, for example a straight or saw-tooth-shaped geometry.Such a lifter 3 can also have a plurality of vacuum plates 4 which are fastened to a common lifting arm 8.Due to the good sealing effect, a holding force of about 500 kg is possible, for example, so that material units 2 adhering to one another, such as bales or heads, can also be lifted.In addition, due to the large holding force, it is also not necessary for the lifter 3 to be placed centrally on a material unit 2. For example, it is sufficient that the lifter 3 engages an engagement surface 16 which, viewed in the longitudinal direction, does not extend beyond half the length 1 of the material unit 2. Thus, the material unit 2 can be raised in particular with less than half the length. The material unit 2 can thus be raised eccentrically. This has the additional advantage that the material unit 2 is detached on one side due to the eccentric gripping and the force for lifting is thus reduced.FIG. 5 shows an engagement surface 16 for a lifter 3, in which a lifting of the material unit 2 is possible. The engagement surface 16, for example corresponding to the base surface of a vacuum plate 4, does not extend beyond half the length 1 of the material unit 2, as seen from a corner 23.FIG. 6 shows, by way of example, an eccentric attachment of a lifter 3 to the material unit 2. the engagement surface 16 lies only in a region which, viewed in the longitudinal direction, does not extend over the center of the material unit 2. Regardless of the length and width ratios of the material unit 2, the engagement surface 16 should not extend from a corner 23 of the material unit 2 along a longitudinal direction and along a width direction over a distance greater than the width b of the material unit 2. In this way, it can be ensured that even with a different position of the material unit 2, only a single material unit 2 can be removed from the material arrangement 17 without knowing the exact packing pattern.FIGS. 7a to 7f show steps of a method for lifting individual material units 2 from a pallet 1 by means of a lifter 3, for example by means of the vacuum lifter described above with a particularly high holding force.According to FIG. 7 a, the lifter 3 is first positioned in the region of one of the corners 18, 19, 20, 21 of the material arrangement 17 and a lifting operation is carried out. These are always outer corners. The positioning at the corner 18 is possible with a simple optical system, since the outer contour of the material arrangement 17 or the pallet 1 can easily be recognized or is defined by fixed walls.The lifter 3 only engages an engagement surface 16 which does not extend over a distance longer than the width b of a material unit 2 in the longitudinal direction and width direction of the material arrangement. Thus, the lifter 3 automatically engages only a single material unit 2 in all packing patterns, so that only one material unit 2 is lifted. This is shown in Figures 9a to 9k for all packing patterns and for all corners 18, 19, 20, 21.In FIG. 7 b, one of the material units 2 is now removed from the material arrangement 17 at a corner 18. Subsequently, the lifter 3 is positioned in such a way that it engages with another corner 19 of the material arrangement 17 and thus lifts a further one of the material arrangement 17 out.This is repeated in steps 7c and 7d for the further corners 20, 21. The corners 18, 19, 20, 21 relate here, for example, to the corners of the original material arrangement 17 with a complete packing pattern. However, it is also possible to remove the material units 2 at any desired corner of an incomplete material arrangement 17. It is also possible to use a holding-down device in order to hold down further material units when the material unit 2 is lifted.Thus, with the method used here, without recognizing the packing pattern, the four material units 2 arranged at the corners 18, 19, 20, 21 can be lifted out individually.In FIG. 7 e, the lifter 3 is positioned on one of the remaining material units 2. The position of the two remaining material units 2 can easily be determined by a simple optical system because of the height differences now existing with respect to the underlying plane or the ground.For example, light barriers, lasers, mechanical sensors, a weight distribution on the lifter 3 or similar technologies can be used for this purpose. For example, as shown in FIG. 8, the position of three adjacent side surfaces is determined by one or more sensors 22. By detecting the weight distribution, the orientation of the material unit 2 and thereby the orientation of the remaining material units can be determined. Thus, the arrangement of the material units 2 does not have to be detected in the full position by expensive camera technology, but can be determined when lifting individual material units 2. The lifter 3 can then be attached eccentrically (FIG. 8 ) or centrally (FIG. 7 e ) to the surface of one of the remaining material units 2.As shown in FIG. 7 f, the last material unit 2 is then lifted out in a manner corresponding to that in FIG. 7 e. If the material arrangement 17 has a plurality of planes stacked one above the other, the procedure can again be as shown in FIGS. 7 ato 7 fwith the plane below.With the method described here, it is possible in a cost-effective manner to remove individual material units from a densely packed pallet. The method is particularly robust and operationally reliable, since the position of the individual material units does not have to be visually recognized in a complicated manner. It can also be a redundant system if a recognition of the pack patterns is carried out by a combination of mechanical and optical recognition.Reference numerals denote reference numerals1 Pallet 2 Material unit 3 Lifter 4 Vacuum plate 5 Outlet 6 Cavity 7 Wall 8 Lifting arm 9 Sealing edge 10 Vacuum pump 11 Pressing device 12 Holder 13 Pressing device 14 Packaging 15 Lower material unit 16 Contact surface 17 Material arrangement 18 Corner Material arrangement / Pallet 19 Corner Material arrangement / Pallet 20 Corner Material arrangement / Pallet 21 Corner Material arrangement / Pallet 22 Sensor 23 Corner Material unit B Width Material arrangement / Pallet L Length Material arrangement / Pallet H Height Material arrangement / Pallet b Width Material unit 1 Length Material unit h Height Material unit

Claims

Method for lifting individual material units (2) from a material arrangement (17), comprising the steps: A) providing a material arrangement (17) of material units (2), wherein, as seen from above on the material arrangement (17), the material arrangement (17) has a length (L) along a longitudinal direction, a width (B) along a width direction and a plurality of corners (18, 19, 20, 21), wherein each of the material units (2) has a length (1) and a width (b), wherein the width (b) is less than or equal to the length (1), B) providing a lifter (3) and placing it on an engagement surface (16) at one of the corners (18, 19, 20, 21), wherein the engagement surface (16) moves from the corner (18, 19, 20, 21), 21) starting along the longitudinal direction and along the width direction, does not extend over a distance longer than the width (b) of a material unit (2).Method according to claim 1, wherein steps A) and B) are repeated for lifting a further one of the material units (2), wherein the lifter (3) engages a further one of the corners (18, 19, 20, 21) of the material arrangement (17).Method according to one of the preceding claims, in which the material arrangement (17) has four corners (18, 19, 20, 21) and steps A) and B) are repeated one after the other at the four corners (18, 19, 20, 21).Method according to one of the preceding claims, in which, after lifting at least one material unit (2), the position of a further one of the material units (2) is detected by means of a sensor (22).Method according to one of the preceding claims, in which, during the lifting of at least one of the material units (2), the orientation of the material unit (2) is detected by means of a sensor (22).Method according to one of the preceding claims, in which the width (b) of the material units (2) is less than the length (1).Method according to one of the preceding claims, in which the engagement surface (16) does not extend over a centre of the material unit (2) in the longitudinal direction.Method according to one of the preceding claims, in which the material units (2) are arranged on a pallet (1) with or without side walls.Method according to one of the preceding claims, in which the material units (2) with their length (1) and width (b) are each arranged parallel or perpendicular to the length (L) of the material arrangement (17).Method according to one of the preceding claims, in which, before a vacuum is generated, the vacuum plate (5) is pressed against the material unit (2), so that the sealing edge (9) cuts at least partially into the material unit and forms a sealing contact with the material unit (2).Method according to claim 10, in which the sealing edge has a straight, saw-tooth-like or wavy-cut-like cutting geometry.Method according to one of claims 10 or 11, in which the material unit (2) has a packaging (14), wherein the sealing edge (9) severs the packaging (14).Method according to one of the preceding claims, in which the material units (2) are designed as bales or sheets of a rubber mixture in the material processing for the rubber industry.

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