Manual safety control for power press - has two pushbuttons which turn on two transistors simultaneously to supply power to press

摘要

The safety circuit has two self-holding transistors each with a timing circuit that holds the transistor in an actuated state for a given time after the pushbutton of the other transistor has been operated. Each transistor has two parallel relay contacts in series with it and in the power supply for the timing circuit of the other transistor. The transistors operate the relays to which these contacts belong. Only when both transistors are turned on simultaneously is the power press operated. The break contacts of the pushbuttons are connected to the bases of the transistors. The 'make' contacts of the pushbuttons are connected to relays whose changeover contacts are in series with the other relay contacts.