Patent ID: 8443597

Claim:
A safety device for hydraulic working machine, comprising: a hydraulic source; a hydraulic actuator that is driven by pressure oil from the hydraulic source; a control valve that controls a flow of pressure oil from the hydraulic source to the hydraulic actuator; an electric lever device that outputs an electrical operation signal, which is a drive instruction for the hydraulic actuator, in correspondence to lever operation; a control unit that controls the control valve in correspondence to the operation signal; and a determination unit that makes a decision as to whether or not the operation signal is within a normal range, wherein: when the determination unit determines that an operation signal is not within the normal range, the control unit allows the hydraulic actuator to be driven with a flow of pressure oil to the hydraulic actuator limited more significantly than in a case where it is decided that an operation signal is within the normal range, upon making a decision that the operation signal is not within the normal range, the determination unit further makes a decision as to whether or not an operation signal is within a limited range which is beyond the normal range by a predetermined extent; and when the determination unit determines that an operation signal is within the limited range, the control unit allows the hydraulic actuator to be driven with a flow of pressure oil to the hydraulic actuator limited more significantly than in a case where it is decided that an operation signal is within the normal range, and when it is decided that an operation signal has exceeded the limited range, the control unit inhibits a flow of pressure oil to the hydraulic actuator.