Patent ID: 8265836

Claim:
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.