Load weight measuring device for a multi-stage mast forklift truck

A load weight measuring device for measuring the weight of a load while the load is being lifted by a multi-stage mast forklift truck comprising:

• a mast assembly having:
• a lift bracket for receiving a load weight;
• a multi-stage mast unit having masts;
• and
• a multi-stage lift cylinder unit raising the lift bracket along the masts, the multi-stage lift cylinder unit having lift cylinders each having an oil chamber;
• an oil passage in which hydraulic oil flows;
• a flow regulator valve regulating the maximum flow rate of hydraulic oil, the flow regulator valve connected to one of the oil chambers of the multi-stage lift cylinder unit through the oil passage;
• a pressure sensor detecting a pressure of hydraulic oil and outputting a pressure signal;
• a detecting device detecting which stage of the multi-stage lift cylinder unit is raising the lift bracket and outputting a detection signal;
• a memory storing predetermined parameters corresponding to the stages;
• a selector selecting one or more parameters corresponding to the stages from the predetermined parameters based on the detection signal;
• and
• a calculator calculating the load weight based on the selected parameter and the pressure signal.