CONTROL DEVICE FOR HYDRAULICALLY DRIVEN TOOL

摘要

When a start switch (SW3) is depressed, a one-shot multivibrator circuit (15) is actuated to output one pulse. When the pulse enters a self-holding circuit (16), the self-holding circuit (16) is self-held to output an H-level signal until reset. As a result, a transistor (17) is turned on to actuate a relay (R1) for lowering a ram. When the ram reaches the lower limit position, a lower limit switch (LS4) is opened, so that a signal from a one-shot multivibrator circuit (18) causes a self holding circuit (21) to self-hold an H-level signal. The signal is delayed by a delay circuit (22) to turn a transistor (23) on. Therefore, a relay (R2) for raising the ram is actuated. Restarting will not be effected due to the operation of the one-shot multivibrator circuit (15) even when the start switch is kept depressed. Also, the service life of a valve changeover mechanism can be extended owing to the operation of the delay circuit (22). Further, erroneous operations can be prevented by operations of a delay circuit (19) and an AND circuit (24) even when the lower limit switch (LS4) chatters.