SAFETY DEVICE OF WORKING MACHINE

PURPOSE:To prevent a hydraulic motor from starting erroneously by transmitting the drive force, which is given to a direction changeover valve for controlling the motion of the hydraulic motor by a selector valve and a pilot valve, to a relay for controlling a starter motor, and thereby controlling so that the engine does not start. CONSTITUTION:When a selector valve 15 is put in communication with a hydraulic pump 10, the power supply 4 is connected with a relay 16, and the engine concerned 1 does not start even though this relay 16 is energized and a switch 5 is turned on because a starter motor 2 does not start. If the selector valve 15 is shut, a switch 18 is turned off, and as the relay 16 is not energized, the engine 1 is started by turning on the switch 5. Thus the pressure oils from a main hydraulic pump 6 and the abovementioned pump 10 for pilot are supplied to the selector valve 15 and another 8, respectively, and if the selector valve 15 is put in the communicating state, the pressure oil is supplied to a pilot valve 11 to cause switching of the other selector valve 8 so as to drive a hydraulic motor 7. Therefore, the hydraulic motor is free from risk of starting erroneously even though the operation lever is turned by mistake, which should enhance the safety.