GB2113178A

GB2113178A - Process and device for gripping by suction

Info

Publication number: GB2113178A
Application number: GB08300586A
Authority: GB
Inventors: Jean-Pierre Rannou; Jean-Paul Moszkowski; Gerard Assadet
Original assignee: Carnaud Emballage SA
Current assignee: Carnaud Emballage SA
Priority date: 1982-01-11
Filing date: 1983-01-11
Publication date: 1983-08-03
Also published as: IE830053L; IT8319059A0; DK158091B; FR2519619A1; DK158091C; BE895565A; ES518904A0; EP0084479B1; EP0084479A1; GB8300586D0; DK6783A; DK6783D0; DE3362570D1; FR2519619B1; IT1193605B; IE53864B1; ES8308797A1; GR77876B

Abstract

A load which can comprise a plurality of objects (10) arranged in a layer is picked up by suction. A gripping device (15) includes a suction hood (18), with lateral confinement means (22) which extends around the periphery of the perforated bottom (20) of the suction hood (18), and which covers laterally, at least in part, the whole of the load to be picked up. The process and device are especially useful for the removal of a layer of containers 10, such as oil cans, from a pallet, air being sucked through passages through the load to create a pressure reduction between the top and bottom of the load to hold the load. <IMAGE>

Description

SPECIFICATION Process and device for gripping by suction The present invention relates to a process and apparatus for gripping by suction for picking up a load which can comprise a plurality of objects arranged in a layer. The invention relates more particularly, but not exclusively, to the case where several layers of such objects are superimposed with, if appropriate, spacers interposed between successive layers. This is the case, in particular, where objects are stacked in successive layers on a handling pallet. To remove such objects from the pallet layer by layer, it is known to use gripping devices which use a source of suction for picking up objects simultaneously from the same layer. In practice, a gripping device of this type consists of a suction hood which is closed by a perforated bottom at the level of its lower edge and is applied by this bottom against all the objects to be picked up from the same layer. A gripping device of this type is suitable, in particular, if the objects to be picked up are hollow objects, for example bottles, presented mouth up. In fact, provided at least one perforation in the bottom of the hood is located opposite the mouth of one such object, a pressure reduction is created inside the object when the suction hood is applied thereto, and this pressure reduction holds the object against the bottom of the hood, fixes it temporarily thereto and hence enables it to be carried away together with this hood when the hood is raised, the bottom of the hood then simply forming a barrier locally securing this object mechanically in opposition by suction exerted by the source of suction to which the hood is connected. Such a device is also suitable if the objects to be picked up have, at least locally, for the application of the perforated bottom of the suction hood, any surface delimited by a contour located in a plane and thus suitable for leaktight application to the perforated bottom around at least one of the perforations in the latter. However, a gripping device of this type, which, in practice, when picking up a plurality of objects simultaneously, handles each of the objects individually, can prove inadequate if these objects are of arbitrary configuration, and/or, in the case of hollow objects, if the orientation with which these objects present their mouth to the suction hood is arbitrary, it being possible in this case for this mouth to be non-aligned with the perforations in the bottom of this suction hood. Moreover, during the removal of objects stacked on a pallet in successive layers, the device is not capable of removing, with the layer of objects, the spacer which may be interposed between this layer and the next, so that an additional, special and inevitable costly operation must be carried out in order to remove the spacer. It is a main object of the present invention to provide a process and device which overcomes these disadvantages. According to the invention there is provided a process for gripping by suction in which a source of suction is used for picking up a load which can comprise a plurality of objects arranged in a layer, characterised by confining a volume covering the load to be picked up, placing this volume in communication with the source of suction, and sucking air through the load confined in this way, with an air flow rate determined so as to ensure that the load is held by the pressure reduction created between the bottom and the top of the load because of the pressure drop in the flow, which pressure drop is localised and is determined at the level of the load to be picked up. Further according to the invention when the load to be picked up comprises objects arranged in superimposed layers with a spacer interposed between two successive layers, the volume covering the load is adapted to ensure that the objects in the top layer and the spacer underneath that layer are carried away. The invention also comprehends a gripping device layer, which device includes a source of suction, characterised by lateral confinement means suitable for covering laterally, at least in part, the load to be picked up, and connected to a device forming a barrier for mechanically securing the load to be picked up. The load to be picked up is thus covered laterally, at least in part, by a lateral confinement means which determines above the load, a volume which is under reduced pressure, since it is in direct communication with the source of suction, while communication with the atmosphere is substantially obstructed by the load which is covered in this way. Because of the fact that a lateral confinement means, which is arranged around the load to be picked up, confines the volume in which the pressure reduction due to the source of suction exerts its effects, the gripping of the load takes place not individually, object-by-object, by application of the pressure reduction to each of these objects, but generally, for all the objects, because of the drop in pressure of the gas flowing around the objects, in the passage area delimited by the lateral confinement means. Thus, the efficacy of the gripping of the load is independent of the configuration and/or the relative orientation of the objects which make up the load, the only factor which intervenes being the passage area left free between these objects and between the objects and the lateral confinement means which surrounds them. Therefore, objects of arbitrary configuration and/or relative orientation can be handled. Some embodiments of the invention will now be described, by way of example, with reference to the accompanying schematic drawings, in which:- Figure 1 is a view in elevation, partly cut-away, of a gripping device according to the invention, Figure 2 is a view in elevation and partly in section of a layer of objects capable of being picked up by the gripping device of Figure 1, Figure 3 is a view in elevation and partly in section of the gripping device of Figures 1 and 2, illustrating its mode of operation, Figure 4 is a view of the gripping device in cross-section along the line IV-IV of Figure 3, Figure 5 is a similar view to Figure 3, of another embodiment of the invention, and Figure 6 is, on a larger scale, a partial view in sectional-elevation of another gripping device according to the invention.Figures 1 to 4 illustrate, by way of example, the application of the invention to the removal of containers 10, of the form of oil cans, from a pallet. The containers 10 have a substantially square cross-section with widely rounded corners have a spout 11 at the top offset in one of the corners of the square section. These containers 10 are stacked in superimposed layers on any kind of pallet, which is not shown in the figures but which is assumed to be of substantially square contour. Only one such layer of containers 10 is shown in Figure 2, and, by way of example, a boatshaped spacer 12 is associated therewith which spacer separates the layer from the layer underneath. This spacer is sometimes only a simple plane sheet. Within such a layer, the containers 10 are arranged side-by-side with their respective faces juxtaposed. Because of the rounded-off cross-section of the containers passages 14 are created between them, which, for greater clarity, have been shown by shading in Figure 4. Because the spouts 11 are offset they are arranged in a random manner according to the relative angular orientation of the containers 10. For removal from the pallet, all the containers 10 in the same layer must be picked up simultaneously. The gripping device 15 for effecting this, uses a source of suction, in a manner which is in itself known, for example, a fan 16, the aspirating mouth of which is indicated diagrammatically at 17. This fan 16 is arranged in the top part of a suction hood 18, a suitably controlled device 19 for communication with the atmosphere being interposed in known manner between the fan and the suction hood in the embodiment shown. The base of the suction hood 18, in the embodiment shown in Figures 1 to 4, is closed in known manner by a perforated base 20 capable of forming a barrier suitable for mechanically securing the containers to be picked up, in opposition to the source of suction provided by the fan 16. This bottom can be, for example, a suitably perforated metal sheet, a mesh, a system of wires, or any other arrangement forming a suitable barrier. In any case the contour of the base of the suction hood 18, and hence of its perforated base 20, is similar to that of the layer of containers 10 to be picked up. Thus, in the illustrated embodiment, the contour is substantially square. The gripping device 15 comprises lateral confinement means, in the form of a skirt 22, which is capable of laterally covering, at least in part, the whole of the layer of containers 10 to be picked up. As shown in Figures 1 to 4, this skirt can be, a simple vertical downward extension, beyond the perforated base 20, of the side walls of the suction hood 18, which form overall a truncated pyramid. A skirt 22 of this type is rigid. In practice, the lateral confinement means extends around the periphery of the mechanical securing barrier formed by the perforated base 20 of the suction hood 18, and its contour is similar to that of the base. In manner known to those skilled in the art and not described in detail herein, the gripping device 15 is mounted so as to move as a whole between two positions, the one being a removal position and the other an unloading position. In its removal position, the device laterally covers the whole of the layer of containers 10 to be picked up, as mentioned above. That is this removal position, the skirt 22 of the gripping device 15 surrounds the whole of the layer of containers 10 to be picked up, as illustrated in Figures 3 and 4. A skirt 22 of this type, which is integral with the suction hood 18, thus laterally confines the flow path defined for the suction fluid. In Figure 4, for greater clarity the passages 24 thus delimited by the skirt 22 between the skirt and those containers 10 which are at the periphery of the layer of containers is represented by shading. With the gripping device 15 thus in the removal position, the suction fan 16 is switched on and this source of suction ensures a sufficient suction rate to establish the pressure reduction necessary for carrying away the containers 10, across the flow passage 14, 24 whose cross-sectional area is the difference between, the total cross-sectional area of the skirt 22, and the cross-sectional area of the containers. The gripping device 15 is moved, first vertically and then, if appropriate, laterally, until it reaches its unloading position. Because of the pressure reduction generated by the fan 16, the containers 10 are carried as a whole without it being necessary, as in the prior art, for any reduced pressure to be exerted on each individual container. This lifting action is thus independent of the location of the spouts 11 of the containers, relative to the perforations in the base 20 of the suction hood 18. As specified above the only purpose of this base 20 is simply to ensure that the containers 10 are mechanically secured relative to the suction source to which they are subjected. If desired, the suction fan 16 can ensure that the containers 10 are carried away, as described above, with the spacer 12 underneath them. Subsequently, during the movement of the gripping device 15, any suitable means can be used to separate this spacer 12 from the containers 10. For example, as illustrated in Figure 3, mechanical means, such as fingers 25 can be used. These are placed in the path which is followed by the spacer 12, in order to retain the spacer which has sufficient flexibility to be released gradually starting from its periphery. However, it is possible to use blast nozzles which are carried by the suction hood 18 and are capable of projecting gas jets towards the spacer 12 for removing the spacer. Alternatively suction nozzles are applied against the lower face of this spacer 12. When the gripping device 1 5 has arrived at the release position, the pressure reduction is cancelled by means of one of the following operations; stopping of the fan 16, bringing into action of the device 19 for communication with the atmosphere, or closing of the aspirating mouth 17. The containers 10 previously picked up by this gripping device 15 are then released by it. In order to pick up the objects with their support which may be a spacer, or a table, the support must be perforated in any suitable way, either by perforations in the spacer or, when using a table by non-contiguous planks, a perforated metal sheet. The base 20 of the gripping device according to the invention is substantially more perforated than in the prior art, in which any hole which was not located over an object to be picked up led to leaks and proved disadvantageous. Low levels of perforation, always less than 50%, were used. In contrast, according to the present invention, each hole in the base contributes towards the pressure reduction above the objects to be picked up, and also reduces the drop in pressure across the base. High levels of perforation, which can approach 100%, are thus recommended, the base then being a mesh. In the foregoing embodiment the source of suction exerts its effect on the containers 10 through a perforated base. This is not necessarily the case, because of the presence of a skirt 22. As illustrated diagrammatically in Figure 5, it is possible for the connection of the aspirating mouth of the suction fan, indicated by an arrow, at the side of the volume delimited by the skirt 22 and by the member 20 at whose periphery the skirt is formed, which member 20 against which the objects are held can thus be solid without any perforation. The corresponding gripping device is thereby simplified, the suction hood, in particular, being dispensed with. In Figure 5, the containers to be picked up are bottles, which are assumed to be of circular crosssection. In the foregoing, it has been assumed that the skirt 22 is rigid and that it is rigidly fixed to the suction hood. This is not necessarily the case. If desired, at least part of the skirt 22 can move between a removal configuration, in which it is capable of being placed laterally against at least part of the objects to be picked up which are at the periphery of the assembly of objects, and an unloading configuration, in which it is at a distance from the said objects. For example, as illustrated diagrammatically in Figure 6, at least one of the walls 27 of the skirt 22, and in practice each of the said walls, forms a flap articulated by means of a hinge 28 on a support spindle 29 fixed to the suction hood 18. When the associated suction source is in action, the walls 27 of the skirt 22 are automatically drawn against the peripheral objects of the layer. When the action of the suction source is interrupted, the walls are free to move away from the said objects. A spring, not shown, can be associated with each of the walls for this purpose. In a modification, the walls can be released simply under gravity if their support spindles 29 are off-set relative to the periphery of the assembly formed by the objects to be picked up. As described above, the walls 27 of the skirt 22 can also be rigidly fixed to the skirt. In another modification the walls 27 can simply be elastically deformable. It should be emphasised that the base 20 forming a barrier for mechanically securing the load to be picked up has a fundamentally different function from the perforated bottoms of the similar device of the prior art. Although both cases involve mechanical holding of the objects against the suction flow, in the prior art the passage areas for the air flow must be as small as possible in order to prevent stray leaks, whereas according to the invention, it is desired to increase these passage areas, advantageously to reach about 100%, while at the same time ensuring that the objects are held.

Claims

1. A process for gripping by suction in which a source of suction is used for picking up a load which can comprise a plurality of objects arranged in a layer, characterised by confining a volume covering the load to be picked up, placing this volume in communication with the source of suction, and sucking air through the load confined in this way, with an air flow rate determined so as to ensure that the load is held by the pressure reduction created between the bottom and the top of the load because of the pressure drop in the flow, which pressure drop is localised and is determined at the level of the load to be picked up.

2. A process according to Claim 1, characterised in that, when the load to be picked up comprises objects arranged in superimposed layers with a spacer interposed between two successive layers, the volume covering the load is adapted to ensure that the objects in the top layer and the spacer underneath that layer are carried away.

3. A gripping device for picking up a load which can comprise a plurality of objects arranged in a layer, according to the process of Claim 1 or Claim 2, which device includes a source of suction is used, characterised by lateral confinement means suitable for covering laterally, at least in part, the load to be picked up, and connected to a device forming a barrier for mechanically securing the load to be picked up.

4. A device according to Claim 3, characterised in that the said lateral confinement means is rigid.

5. A device according to Claim 3 or Claim 4, characterised in that at least part of the lateral confinement means can move between a removal configuration, in which it is capable of being placed laterally against at least part of those objects to be picked up which are at the periphery of the assembly of those objects, and an unloading configuration in which it is at a distance from those objects.

6. A device according to Claim 5, characterised in that at least part of the lateral confinement means is an articulated flap.

7. A device according to Claim 3, characterised in that at least part of the lateral confinement means is elastically deformable.

8. A device according to any one of Claims 3 to 7, characterised in that the device forming a barrier for mechanically securing the load to be picked up is capable of creating the minimum pressure drop in the air flow towards the source of suction.

9. A process for gripping by suction substantially as herein described with reference to the accompanying drawings.

10. A gripping device for picking up a plurality of objects arranged in a layer, substantially as herein described with reference to the accompanying drawings.