Material or article handling – Load carried along a horizontal linear path – Having gripper means
Patent
1997-07-11
1999-10-12
Valenza, Jospeh E.
Material or article handling
Load carried along a horizontal linear path
Having gripper means
1986891, 198721, 198740, 724051, 271267, 294 65, B65G 3700
Patent
active
059645687
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a device for gripping and handling pieces of sheet material, of the kind comprising a transfer unit that can be moved towards and away from a face of the work piece and can also be moved along a path which the work piece is to follow, and that carries at least one sucker having a flexible peripheral wall with a peripheral lip intended to be placed against a face of the work piece and whose interior is connected to a vacuum source.
A great many such devices are already known and are used in industry for loading and unloading work pieces to and from a work station or for transferring work pieces between successive work stations.
Known devices used for gripping and handling pieces of sheet material include those disclosed and illustrated in documents DE-A-35 00 342 and EP-A-0 585 508.
Gripping and handling devices, especially those designed for use with stock in sheet form, such as sheet metal pieces or panels, are very useful for transferring the work pieces from one point to another provided positioning does not have to be too accurate, for unfortunately the very flexibility of suckers makes them prone to sideways movements, so that it is impossible to position the work pieces with any great accuracy. Situations where this is relevant include, for example, the need for accurate positioning of sheet metal or other kinds of sheet material in relation to a machine tool in order to carry out bending, shearing, punching and other such operations.
It is for this reason that sucker-type gripping and handling devices are not used to manipulate work pieces requiring to be positioned with extreme accuracy.
Another reason why the use of prior art gripping and handling devices is precluded in manipulating operations requiring accuracy of positioning is the fact that the peripheral lips of the suckers, which are made of rubber or similar elastomeric materials for flexibility, are subject sooner or later to wear making the vacuum grip on the work piece unreliable, with the consequence at the very least of the work piece shifting relative to the suckers and, in the worst case, complete failure to grip the work piece.
The invention has been developed in its application to manipulators on numerically controlled sheet metal bending presses, but is not limited to this application.
Presses of this kind are programmed to make a series of accurately positioned bends in a sheet metal panel which can be achieved by numerical control not only of the press but also of the manipulator. The same problem exists for example in shearing and punching presses operating not only on sheet metal but also on cardboard.
Hitherto, in order to guarantee the extreme accuracy of positioning of the work piece relative to the press or other machine tool, use has been made of manipulators having mechanical grippers that grip the sheet metal work piece on both faces, but this leads to problems of size and complexity of construction.
In order to obtain a firm grip on the work piece on only one face, attempts have also been made to use manipulators in which the gripping member consists of a magnetic plate, but with poor results.
The object of the present invention is to provide a device for gripping and handling pieces of sheet material, of the type outlined earlier, which uses suckers and makes it possible to achieve an extremely firm and accurate grip on the work piece and in which the wear to which the sucker lips are subject is of negligible influence and in any case takes a very long time to develop.
According to the present invention, this object is achieved by means of a device characterized in that the transfer unit comprises, for the sucker or for each sucker, a well in which the sucker is located centrally, in that the well or each well comprises a border, made of a sealing and friction material and concentric with the lip of the sucker, in that the peripheral wall of the sucker is flexible enough to permit axial movement of the lip between an expanded position in which the lip projects above the border of the w
REFERENCES:
patent: 3990570 (1976-11-01), Mercier et al.
patent: 4354796 (1982-10-01), Bergman
patent: 4600229 (1986-07-01), Oten
patent: 5207553 (1993-05-01), Konagai
patent: 5879040 (1999-03-01), Nagai et al.
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