The subject of the present invention is a device for picking up and manipulating sheet-like, flexible objects, particularly expensive fabrics, according to the preamble to Claim 1.
The invention also relates to a method of picking up and manipulating sheet-like flexible objects utilizing the above-mentioned device.
A device including the above-mentioned characteristics is known from published Japanese patent applications Nos. 61101351 and 61101343 in the name of Tokyo luki Ind. Co. Ltd.
These documents describe the use of gripping devices each comprising a first pneumatic suction gripping member which can adhere by contact to a face of an edge portion of fabric to be manipulated and a second gripping member which can press the fabric against the first gripping member and keep it pressed in a firmly gripped condition by acting on the opposite face of the edge portion .
With reference to the gripping devices of these documents, it should be noted that they operate in accordance with a relatively lengthy and labourious picking-up process which requires the fabric to be lifted to a certain height by means of the pneumatic suction device and to be restrained whilst awaiting the completion of three operations (lowering the second gripping member, rotating it in order to bring it beneath the fabric in the region of the suction device, and then raising it against the latter) in order for the fabric to be gripped. Moreover, once the fabric has been lifted, because of its own weight, the fabric in the region of the suction device undergoes a local deformation which tends to favour its detachment. Furthermore, it should be noted that the gripping device requires at least two independent actuators, of which one is subjected to two distinct operations, and the gripping device enables gripping to take place exclusively in peripheral regions of the piece of fabric and is not suitable for gripping in central regions of the piece. For this reason, it also takes up working space which may invade the space outside the piece to be manipulated.
It should also be noted that the solution proposed is designed predominantly for moving whole pieces of fabric and not for picking up individual cut pieces and removing them from the off-cuts.
Finally, the devices do not have any means which render them suitable for handling particularly delicate and expensive materials such as cashmere, silk and any materials which are liable to retain impression marks.
A device for picking up and manipulating plastics sheets is described in published European patent application No. 0111739. Since the manipulation of materials impermeable to air is involved, this device makes use of separate first and second gripping members of which the first gripping member is a pneumatic suction device and the second gripping member is a pincer device. The operation of the separate gripping members described cannot be proposed for the manipulation of fabrics, particularly for picking up and manipulating pieces which are highly permeable to air, especially if they are disposed between off-cuts.
The problem upon which the present invention is based is that of providing a novel picking-up and manipulation device which is also capable of handling, with a firm but light grip, materials which may be quite difficult to pick up and manipulate, particularly expensive fabrics and cut portions thereof, at the same time preventing the problems complained of with reference to the acknowledged prior art.
This problem is solved by the invention by a picking-up and manipulation device formed in accordance with Claim 1.
Further advantages are achieved by the technical solutions of the subordinate claims.
The characteristics and advantages of the invention will become clearer from the following detailed description of a preferred embodiment thereof, described, by way of nonlimiting example, with reference to the appended drawings, in which:
In Figure 1, an apparatus for manipulating flexible objects is generally indicated 1 and utilizes a picking-up device 2 disposed on a vertical slide 3 of a Cartesian robot 4 which, with regard to the aspects not expressly described, is of conventional type.
The picking-up device 2 comprises a cross member 3a (Figure 3) mounted on the slide 3 by means of a mechanical wrist 6 which can bring about angular orientations of the cross member about three (or more) axes X, Y, Z. The mechanical wrist is also of a type known to experts in the art.
A motor 8 controls the movement of two further slides 10a, 10b, by means of a geared transmission 11. The further slides 10a, 10b are driven by means of screws with recirculating balls or other equivalent mechanisms, also of conventional type, and serve to translate two grippers, both indicated 12 and each mounted on a respective slide 10a, 10b, away from and towards a central position beside the geared transmission 11.
Since the grippers are identical, only one of them will be described in detail. Each gripper 12 comprises a first gripping member 13 and a second gripping member 14 combined in the following manner. The second gripping member is formed as a pincer with a first, fixed jaw 15 and a second jaw 16 which is movable in accordance with a law of motion defined by an articulated parallelogram mechanism in which the first jaw is fixed to a fixed bar 18 of the parallelogram whereas the second jaw is fixed to a connecting rod 19 thereof. The fixed bar 18 and the connecting rod 19 are connected to one another by means of first and second rocker arms 20, 21, the rocker arm 20 being pivoted relative to the fixed bar 18 by a pneumatic jack 22.
The second jaw 16 is covered by a resilient pad 25 and, in the embodiment illustrated, has a substantially square shape in plan.
The first jaw 15 comprises a fork-shaped support 27 between prongs 27a, 27b and a base 28 of which an approximately square aperture 29 is formed and houses the first gripping member 13, preferably in a releasable, replaceable manner. In a preferred embodiment of the invention, the first gripping member 13 is, interchangeably, a pneumatic suction device 30 or a mechanical gripping device 33, for example, with needles, with an adhesive surface, or covered with hooks such as those typically present in pull fastenings of the type known by the registered trade mark VELCRO (TM). The pneumatic suction device 30 has appendages 30a, by means of which it is housed and guided between the prongs 27a, 27b, and a perforated suction surface 30b communicating with a manifold 30c connected to an air-suction hose. The mechanical gripping device 33 is preferably movable away from and towards the aperture 29, by means of a jack actuator 32, between an operative position in which the active surface of the device 33 is at the level of the lower surfaces of the prongs 27a, 27b and a detachment position of the device 33 in which it is moved away from the prongs 27a, 27b which act as reaction members to favour the detachment of the fabric gripped from the above-mentioned active surface when the movable jaw 16 is closed onto the fixed jaw 15.
The vertical mobility of the mechanical gripping device, is superfluous, however, in the case of the pneumatic suction device since the fabric can readily be detached by the reversal of the air-flow through the suction device 30.
Finally, a photocell or other similar presence detector, indicated 34, is mounted on the first jaw 15 to detect the gripping between the jaws 15, 16 of the piece to be manipulated.
With reference to Figures 10 to 12, a piece of a garment cut to the desired shape on a cutting table is indicated 50. The piece 50 is to be removed from a fabric off-cut, indicated 51, if possible without moving the off-cut so that other cut pieces lying on the cutting table can be identified and found by the picking-up device of the invention solely with reference to their positions relative to an origin point stored by the cutting apparatus.
In order to grip and subsequently manipulate the piece 50, after the Cartesian robot 4 has been positioned, the picking-up device 2 is driven in a manner such that each gripper 12 is disposed above the piece to be gripped with the perforated surface of the pneumatic suction device 30 substantially parallel to the plane of the cutting table. The cross member 3a is then lowered until the pneumatic suction devices 30 contact the piece to be picked up. Upon activation of the pneumatic suction device, the piece adheres to the perforated active surface of the suction device 30 with the desired lightness of contact and is lifted, together with the cross member 3a. The lifting of the cross member 3a is coordinated with a rotary movement of the mechanical wrist 6 in the direction shown by way of example in Figure 11, that is, about an axis substantially parallel to the plane of closure of the second gripping member (the mutually facing surfaces of the jaws 15, 16) so as to orient the closure plane in a manner consistent with the deformation of the piece gripped due to its own weight and to its mechanical characteristics during its lifting. This minimizes the tendency of the gripped fabric to become detached and improves the firmness of the grip of the pneumatic suction device in comparison with a simple vertical lifting movement of the fabric, ensuring that the fabric is held correctly until the operation of the second gripping members is complete.
These second gripping members are operated at the moment at which the lifting permits the closure movement of the jaws 15, 16. The geometry selected for the articulated parallelogram mechanism permits a notably small travel of the movable jaw 16 in the direction perpendicular to the plane of the first fixed jaw 15, enabling the jaws to be closed after a very limited lifting of the piece. The jack 22 moves the rocker arm 20 so that the second jaw 16 is closed onto the first jaw 15. It should be noted that the second jaw has a relatively extensive active surface so as not to damage the fabric being handled. The surface of the first jaw is also extensive, particularly if it is supplemented by the surface of the first gripper, so that even the most delicate fabrics can be manipulated with complete safety and with relatively low closure pressures between the jaws.
Once the pincer is closed and possibly detached from the piece, the mechanical gripping device 33 continues the desired movement by means of the jack 32, possibly with the subjection of the mechanical wrist 6 to a rotary-translational movement resulting in a rotary-translational movement of the two grippers 12, favouring the spontaneous detachment of the piece 50 from the offcut 51 without causing undesired displacements thereof.
With this technique for collecting the piece from the cutting table, the cut piece is advantageously detached from the production off-cut vertically, cancelling out the effect of entrainment of the piece and of the off-cut, which may assume a certain importance according to the material and the geometry of the cut piece.
Amongst the main advantages of the invention, the following should be noted: