| 摘要 |
A method of positioning sheet elements (5) in the introduction station of a processing machine comprising a transport system consisting of one or more bars (10) of grippers (12) for driving the sheet element (5) to subsequent stations, comprises, starting from a shelf (14) in a rear starting position, engaging means (16, 22) for fixing a sheet element (5) on the shelf (14), then controlling actuators (40, 50, 60) to advance the shelf (14) forward and if necessary sideways and/or askew depending on the readings of the positioning coordinates of the sheet element (5) by opto-electronic means (72, 74, 76), said readings being effected during the advance of the shelf (14) so as to feed and finally stop the leading edge of the sheet element (5) in the grippers (12) of the transport system in a predetermined position, releasing the fixing means (16, 22), and then returning the shelf (14) to the rear starting position. The system for performing the method comprises a shelf (14) provided with means (16, 22) for temporarily fixing the sheet element (5), having a notched leading edge (17) complementary to the grippers (12) of the drive bar (10) driven by actuators (40, 50, 60), opto-electronic means reading the front and/or side edge and/or a distinctive sign of a previous treatment of the sheet element disposed slightly forwardly of the starting position of the shelf, and electronic control means for controlling the actuators of the shelf (14) in dependence on the machine cycle and the results of the readings of the positioning co-ordinates of the sheet element (5) by the opto-electronic means.
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