TRUCK OVERLOAD PROTECTIVE SYSTEM HAVING TRIP SIGNAL SAMPLING MEANS

摘要

An overload protective system continuously monitors the forward overturning moment on a counterbalanced lift truck and prevents further raising of the carriage or further forward tilting of the mast when the tilting moment is excessive. A strain gage sensor connected in an electrical bridge derives a strain signal proportional to the mechanical strain in a load carrying anchor pin for the tilt jack which resists the forward overturning moment acting on the truck; a differential amplifier raises the level of the strain signal; a comparator which receives the output of the differential amplifier derives a trip signal when the strain signal reaches a predetermined magnitude; a shift register receiving clock pulses from an oscillator as a time reference records the history of the comparator output and a decoder analyzes the shift register output and sets a latch when the trip signal comparator output has been present for a predetermined interval of time; and disabling means responsive to setting of the latch de-energize operating coils for blocking valves which inhibit further raising of the carriage or further forward tilting of the mast.