SISTEMA PER IL CONTROLLO DINAMICO DELLO SPINGIBARRA IN UN ALIMENTATORE DI BARRE PER UN TORNIO AUTOMATICO

A system for dynamic control of the bar pusher in a bar feeder for an automatic lathe (1), the feeder comprising a bar pusher (12) that is driven by a hydraulic motor (17) and can slide in a guide that is coaxial to the spindle (5) of the lathe, the spindle (5) being provided with a collet (6) for clamping the bar (2), in front of which collet (6) it is possible to position, at an adjustable distance according to the length of the part to be machined, a stroke limiter (7), the hydraulic motor (17) being controlled by a first valve element (21) for adjusting the pressure of the driving liquid and by a second valve element (20) for adjusting the flow-rate of the driving liquid, the valve elements (20, 21) being controlled by a programmable logic unit (22), which comprises respectively a processing element (24) for driving the first valve element (21) and adjusting the pressure of the driving liquid according to a preset behaviour and a regulator (23) for driving the second valve element (20), there being also a transducer (26) for the pressure of the hydraulic motor (17) which is connected in feedback to the processing element (24), the processing element (24) and the regulator (23) being controlled by means (25) that are adapted to set the flow-rate of the driving liquid as a function of the length of the part to be machined.