PURPOSE: To promote safety by detecting whether positions of solenoid valves in a traveling hydraulic supply and discharge course are in neutral positions, comparing it with a truth value corresponding to a control mode set in advance, and stopping a power source if they don't match each other.
CONSTITUTION: When a right proportional solenoid valve 64 and a left proportional solenoid valve 67 are positioned in neutral positions K by control of a traveling lever, rollers 71 are interlocked with interlocking grooves of extension sections 51 of spools and are in an unmovable state. After that, a signal from a limit switch 72 is outputted to a traveling controller 13, and it is compared with corresponding value in a list of a truth value through a comparison means 73. Then, in the case comparison result is unmatching with each other, a stop signal X74 is outputted to a power source stop means 74 from the comparison means 73. In addition, the power source stop means 74 is made to open a tank, and the supply of pressure oil to hydraulic motors 62 and 65 from hydraulic pumps 63 and 66 is stopped to stop an engine.
SHIMOURA KENICHI
HASHI TAKAAKI
NABCO LTD
Next Patent: Earth fault circuit breaker with remote test capability