Patent ID: 8600628

Claim:
An industrial truck, comprising: a vehicle frame; a first lifting frame that is attached to the vehicle frame; a second lifting frame that is movable in the vertical direction relative to the first lifting frame, the second lifting frame being guided on the first lifting frame; a third lifting frame that is moveable in the vertical direction relative to the first lifting frame, the third lifting frame being guided on the second lifting frame, wherein movement of third lifting frame is coupled to movement of the second lifting frame such that the second lifting frame and the third lifting frame move simultaneously with a transmission ratio; a driver's cab that is moveable in the vertical direction relative to the third lifting frame, the driver's cab being guided on the third lifting frame; and a measuring arrangement comprising: a first optical sensor that is fastened to the first lifting frame, directed toward a surface of the second lifting frame, and configured to contactlessly detect movement of the second lifting frame relative to the first lifting frame by sensing a coincidental surface design of the surface of the second lifting frame; and a second optical sensor that is arranged on the driver's cab, directed toward a surface of the third lifting frame, and configured to contactlessly detect movement of the driver's cab relative to the third lifting frame by sensing a coincidental surface design of the surface of the third lifting frame; wherein the measuring arrangement is configured to determine the lifting height of the driver's cab by adding up the movement of the second lifting frame relative to the first lifting frame detected by the first optical sensor, the movement of the driver's cab relative to the third lifting frame detected by the second optical sensor, and the movement of the third lifting frame relative to the first lifting frame on account of the movement of the third lifting frame being coupled to the movement of the second lifting frame.