| 摘要 |
A pneumatic actuator system includes an actuator unit (A) with at least one piston-cylinder type actuator (14) intended for crust breaking operations at electrolytic alumina reduction baths and comprising a working piston and two 5 end position responsive valves (5, 6), and a control unit (B) with a monostable distribution valve (3) having flow restrictions (3b, 3c) for directing pressure air to either side of the actuator piston, and a bistable monitoring valve (2) for letting through or blocking pressure air supply to the distribution valve (3) depending on the position of the forward end position 10 senring valve (6), and a monostable reset valve (1) shifted by the start signal from a stable open position letting through pressure air to one of the control ports of the monitoring valve (2) and an unstable closed position blocking air supply to that monitoring valve control port. Independently of the duration of the start signal the actuator piston will ålways return automatically to its 15 retracted rear end position as the piston reaches its forward end position at a completed working stroke, i.e. should the start signal be shorter the piston will return before performing a complete working stroke. 20 (Fig. 2) |
