Claims
1. A method for arranging at least one corner protector (1) on at least one article (2) covering at least one corner (3) located on it for protecting the article (2) or articles from mechanical damage, e.g. in the case of stacked flat articles or products packed in a furniture warehouse, on loading pallet or other load carrier (1 1 ), for example, conveyed forward by means of a conveyor belt (16), for example, to an essentially predetermined position (12), characterized in that the articles (2), on either side of the corner (3), have contact surfaces (4) which in this case are glued or wrapped in a first operation in at least one layer of shrink/stretch/plastic film for the purpose of stabilising the packed material and protecting the articles, whereupon an industrial robot comprising a gripping device (9) picks up and displaces an essentially flat sheet (5) of preferably pasteboard, cardboard, plastic, and in a second operation rotates its surface of extension towards a nozzle/unit (15) which provides at least a part of the surface of extension with glue in a third operation, whereupon that part of the flat sheet (5) with a self-adjusting, damping and retarding effect, caused by the fact that the gripping device is resiliently suspended in the front part of the industrial robot, is applied to one of the contact surfaces (4), wherein the rest of the flat sheet (5) points away from the corner (3), where it shaped round/after the corner (3) against the contact surfaces (4) to form the corner protector (1 ) in a fifth operation when the articles and the sheet (4) are wrapped with at least one more layer of shrink/stretch/plastic film.
2. A method according to claim 1 , characterized in that after the application of the part of the flat sheet which points away from the corner, it is shaped around/after the corner when a pneumatically driven movement secured in the gripping device applies a pressure against the projecting part of the flat sheet, which bends and shapes the sheet round the corner, whereupon the articles are wrapped with at least one further layer of shrink/stretch/plastic film.
3. A method according to claim 1 or 2, characterized in that the articles are horizontally stacked, having a number of elongated upwardly directed corners (3), extending from a bottommost article (2) to an uppermost article (2), which flat sheet (5) is then a long and narrow flat sheet (10) having two long sides (13) which are turned by the industrial robot (9) so that the sheet points upwards when the pallet (1 1 ) is located in its largely predetermined position (12) before application to the contact surface (4).
4. A method according to any one of the claims 1 - 3, characterized in a computer/processor/PLC, which commands the movements of the industrial robot (9) to displace the flat sheet (5) spatially towards each corner (3) to perform the operations, when the loading pallet (1 1 ) is largely in the fixed position (12), wherein the industrial robot (9) transmits signals via sensors for measuring and indicating distances, e.g. light beams, laser beams or vision to detect the position of the article (2), and hence orientate the position of each corner (3) spatially, which computer/processor/PLC collects information on the spatial position of the corners and commands the industrial robot (9) to approach and move into a position corresponding to the position of the corner (3).
5. A flat sheet for applying the method according to any one of the preceding claims, characterized in that the flat sheet (5) has a number of folding marks (7), e.g. punching, stampings, in order to facilitate shaping after the corner (3) during the fifth stage. |
A method to apply a corner protection and a sheet used for said method
The present invention relates to a method and a device for applying corner protectors over the corners of a number of articles for the purpose of protecting them against mechanical damage. The articles have contact faces on either side of the corner. The articles are in this case wrapped in a first operation with a shrink/stretch/plastic film, whereupon the gripping device of an industrial robot picks up and displaces a flat sheet and rotates its surface of extension in a second operation towards a nozzle or unit which provides the surface of extension with glue in a third operation, whereupon that article of the flat sheet is applied, with a damping and retarding effect of the gripping device, to one of the surfaces of contact in a fourth operation, the rest of the flat sheet pointing away from the corner, so that it is there formed around or after the corner against the surfaces of contact of the corner protector in a fifth operation when the articles are wrapped up with at least one further layer of shrink, stretch or plastic film.
In structures of the type in question currently on the market, different methods are now used to pack different articles, for example in the furniture industry, the window industry, the kitchen industry, with cabinets and hatches, etc., where a number of corners on the article/articles are then to be protected against mechanical damage. Often the articles are stacked flat and lie on a loading pallet which, whilst being conveyed on a conveyor belt, is fed to a predetermined position in which the corners are to be protected with pre- shaped corner protectors which are in most cases applied manually and fixed by tape then covered with stretch film. Alternatively, in individual cases with a machine, which mechanically keeps normally four pre-shaped corner protectors in position, the material, when stationary, is wrapped with plastic film by means of a circulating stretch film machine for fixing the corner protectors. This presents major problems because the corners of the article or articles and the corners of the corner protectors must converge at a precise point in a plurality of axes and at a plurality of angles during the application, whilst at the same time the size of the material may vary or the material may be displaced. This requires considerable precision to ensure that the corner
protectors do not end up in the wrong position. Often the material is stacked slightly askew or it has been displaced, which makes it very difficult to find the corner by machine with a corner protector that is already pre-shaped. Very high precision is required on the handling equipment for stacking the material and for placing the material in the position in which the corner protectors are to be applied. With structures currently on the market this very often results in frequent machine stops due to incorrect positioning, which gives rise to excessively low machine accessibility and reliability. Furthermore a harder (static) contact with the corners is obtained during application because the corner protector either receives the material directly or stops some distance from the material during the application, which often causes damage to the article when a collision occurs. Despite the fact that this expensive equipment must be used, breakdowns easily occur because the slightest fault on the corner protectors or their positioning will cause breakdowns in the machine handling them or faults due to deviations in the position of the material to which the corner protectors are to be applied. Furthermore, the corners become expensive to buy because they have to be produced with a preselected shape. Moreover, they occupy a great deal of space because they are stored one on top of the other in a magazine with a lot of air between them. According to the document US 2003/0051439 A l a machine is used which pre-shapes (folds) the flat corner protectors by means of a mobility in the gripping device before they are then applied to the corners of the article, which by no means solves the problem described above, the same difficulty remaining since the position of the goods deviates in most cases in a plurality of axes and at a plurality of angles. A corner protector that is already folded is fixed in position and will not allow the above-mentioned positioning error.
An object of the present invention is to eliminate the drawbacks associated with the above-mentioned structures by being able to apply corners to a pack which is not placed precisely on a conveyor belt, for example, by applying in a fist operation article of a flat sheet of pasteboard or cardboard to a contact surface which is wrapped in a plastic film or is pre-stabilised, e.g. with a suitable glue. The flat surface is provided with glue and an industrial robot displaces and rotates the sheet which is resiliently fixed in position on the
contact surface, whereupon a wrapping element, comprising shrink/stretch/ plastic film, for example, is wrapped and tightened around the article and the flat sheet, which is then shaped around the corner and the contact surfaces in a fourth operation and forms the corner protector.
Thanks to the invention a method has now been provided, which renders it possible to apply corner protectors easily, reliably and cheaply and cover corners of articles packed on a loading pallet and are not precisely positioned, but lie mainly in a predetermined position on a pallet, e.g. on a conveyor belt, on flat angular wooden panels stacked horizontally one on top of the other, packed in a furniture magazine, for example, in order to protect the article from mechanical damage during continued handling. There are contact surfaces on either side of a corner of an article. According to the invention the articles packed together have these contact surfaces on either side of the corner. The pack is prestabilised in this case in a first operation, e.g. with a shrink/stretch/plastic film or with a suitable glue, whereupon the gripping device of an industrial robot picks up, displaces an essentially flat sheet and rotates its surface of extension in a second operation towards a nozzle/unit which provides part of the surface of extension with glue in a third operation, whereupon that part of the flat sheet, with a damping and regarding effect of the gripping device, is applied to one of the contact surfaces in a fourth operation. This effect is brought about by the fact that the gripping device is resiliently suspended in the front part of the industrial robot. The rest of the flat sheet then points away from the corner, where it is shaped around/after the corner towards the contact surfaces to form the corner protector in a fifth operation when the articles are wrapped with at least another layer of shrink/stretch/plastic film. The surface of extension of an essentially flat sheet is applied in the first operation. The flat sheet is made of pasteboard, cardboard or any other board material protecting against mechanical damage, a material that is rather stiff but still formable. In the fifth operation the article and the flat sheet are covered and wrapped and tightened with some kind of wrapping element, e.g. shrink/stretch/plastic film, elongated tapes or ropes. This method does not therefore require any major precision in terms of positioning the pack for the flat sheet to be displaced and applied in exactly
the right position on a corner. If the position fixing is somewhat skew or not centred, the corner protector will still be given a perfect shape for fitting over the corner and the contact surfaces.
In an alternative embodiment of the method the part of the flat sheet that points away from the corner can, after application, be shaped around/after the corner when a pneumatically driven movement secured in the gripping device applies a pressure against the projecting part of the flat sheet, which bends and shapes the sheet around the corner, whereupon the articles are wrapped with at least one further layer of shrink/stretch/plastic film.
The flat sheet is picked up one at a time by the industrial robot and is located close to the loading pallet in a bundle of flat sheets stacked in a magazine located close to the pallet, whereupon the surface of extension of the flat sheet is displaced and turned towards an nozzle located close to the industrial robot for application of hot melt adhesive, or alternatively unit for the application of double-sided tape/fixing compound. When the corner protectors are removed and when unpacking the articles when they are delivered, it may be difficult to remove any remaining hot melt adhesive. The articles are therefore first wrapped up in a first layer of shrink/stretch/plastic film in the first operation to ensure that the hot melt adhesive does not come into direct contact with the articles. To provide further protection of the contact surfaces during application of the flat sheet with the industrial robot, the hot melt adhesive has elastic properties. The gripping device of the industrial robot is constructed with built-in resilience so that the pressure against the articles does not risk becoming excessive. This produces a damping and retarding effect for mechanically protecting the articles from being moved or damaged. In a variant of the invention the articles have a number of similar angular flat board elements stacked on top of the other to form a pack on the loading pallet, which has a number of elongated upwardly directed corners extending from the bottommost article to the uppermost article, to be covered by a long, narrow flat sheet which is applied by the industrial robot to the contact surfaces, whereupon the flat long and narrow sheet, with long sides pointing upwards, are intended to be fixed in position on part of the contact surface
between the long sides. When the shrink/stretch/plastic film is to be wrapped around the articles, the pallet is rotated about its own axis. The entire process is controlled by a computer/processor/PLC with the capacity to carry out the operations, when the loading pallet is located in the fixed position, by collecting and processing transmitters and sensors which indicate the position of the article in a computer/the processor/PLC that provides information on the position of the corners in the room. The computer/processor/PLC then commands the industrial robot to approach and move into a position corresponding to the position of the corner, in order to carry out the operations, whereupon the computer/processor/PLC later activates a driving device to rotate the loading pallet for performing the third and fourth operations.
The principal advantages of the invention will therefore be that a very simple, functional and low method has been developed for arranging corner protectors on an article when the pack is imprecisely placed on a conveyor belt, for example. The method of applying the flat sheet does not require high precision, which means lower investment costs, operating costs for the equipment, fewer breakdowns, higher machine accessibility and faster application. The articles are further protected against damage during the performance of the operations because the application of the flat sheet is controlled by transmitters (sensors) so that it occupies more exact positions, and because the gripping device is resiliently suspended.
The invention is described in greater detail by means of preferred exemplary embodiments with reference to the drawings enclosed.
Fig. 1 shows a transparent perspective view of a part of a pack of stacked board-shaped articles during the first and second operations and during the third and fourth operations, denoted by dotted lines,
Fig. 2 shows a plan view viewed perpendicularly from above, where the robot displaces the flat sheets for performance of the first and second operations, and
Fig. 3 shows a cross-section of a flat sheet.
As shown in Figs. 1 and 2, a number of articles 2 are shown here stacked one on top of the other, having a number of corners 3. On either side of corners 3 the article 2 has contact surfaces 4. A part of the surface of extensoin of a flat sheet 5 is fixed in position against one contact surface 4 with a securing device 6 having a clamping device. The flat sheet 5, in the form of a flat, long and narrow sheet 10, has two long sides 13, one of which projects from the corner 3. The article 2 and the flat sheet 5 are to be covered and wrapped and tightened by a wrapping element 8 constituting a shrink/stretch/plastic film to form a corner protector, as denoted by the dotted line.
As shown in Fig. 2, a number of articles 2 are here stacked on a load pallet 1 1 after it has been conveyed forward on a conveyor belt 16 to an essentially imprecise predetermined position 12. The flat sheet 5 is picked up an industrial robot 9 from a magazine 14. The industrial robot 9 is designed to displace and turn the surface of extension of the flat sheet 5 towards a nozzle which applies hot melt adhesive 15 to the surface of extension and in turn applies this surface, with a resilient effect, at the same time as it is glued to the contact surface 4.
Fig. 3 shows a cross-section through a flat sheet 5, which has a number of folding marks 7 for facilitating the shaping of the flat sheet 5 during a third and fourth operation.
In summary the process begins according to the invention when the material or articles 2 are in this case either fixed in position with a suitable glue or are pre-filmed with a layer of stretch film, the stretch filmer stops with the first corner of the material turned towards the robot, the robot assembles some of the corner protectors by means of its self-adjusting and resilient gripping device, the stretch filmer rotates the material and rotates any remaining corners towards the robot, the robot assembles the remaining corner protectors and the stretch filmer starts and films, folds and finally fixes the corner protectors. As mentioned above, the gripping device of the robot can
be fitted with a pneumatic arm whose task is to pre-fold the projecting part of the flat sheet so that this is fixed more easily by the stretch film afterwards. This can be used to deal with stiffer sheets which otherwise may be difficult to fold.
The prestabilisation carried out with glue or plastic coating is in most cases an important part of the process because the glue or plastic coating stabilises the material so that the gripping device in question can be applied without pushing away any of the articles. The prestabilisation also enables hot melt adhesive to be used or other glue to be used for fixing the corner protector without the glue coming into contact with the products, which is not preferable.