Cargo handling control device of forklift truck

1 . A cargo handling control device of a forklift truck, the forklift truck including a lift cylinder configured to raise and lower a fork holding a pallet and a tilt cylinder configured to tilt the fork, the cargo handling control device comprising:

a first detector configured to detect whether a distal portion of the fork inserted into a pallet hole of the pallet is adjacent to an upper wall of the pallet, the first detector being configured to output a detection signal;

a second detector configured to detect whether the distal portion of the fork inserted into the pallet hole of the pallet is adjacent to a lower wall of the pallet, the second detector being configured to output a detection signal;

a third detector configured to detect whether a proximal portion of the fork inserted into the pallet hole of the pallet is in contact with the upper wall of the pallet, the third detector being configured to output a detection signal;

a fork lowering controller configured to control the lift cylinder so that the lift cylinder lowers the fork holding the pallet toward a loading surface;

a pallet posture determination unit configured to determine a posture of the pallet relative to the fork based on the detection signals from the first detector, the second detector, and the third detector, after the fork lowering controller starts controlling the lift cylinder;

a pallet placement controller configured to control the lift cylinder and the tilt cylinder so that the fork is placed on the loading surface depending on the posture of the pallet relative to the fork determined by the pallet posture determination unit; and

a fork withdrawal controller configured to control the forklift truck so that the forklift truck pulls the fork out of the pallet after the pallet placement controller completes controlling the lift cylinder and the tilt cylinder, wherein

the pallet placement controller judges based on the posture of the pallet whether the fork is allowed to be pulled out of the pallet,

when the pallet placement controller judges that the fork is allowed to be pulled out of the pallet, the pallet placement controller controls the lift cylinder so that the lift cylinder stops lowering the fork, and

when the pallet placement controller judges that the fork is not allowed to be pulled out of the pallet, the pallet placement controller controls the tilt cylinder so that tilt cylinder tilts the fork along the loading surface.

2 . The cargo handling control device according to claim 1 , wherein

the pallet posture determination unit determines that the posture of the pallet is a posture that allows the fork to be pulled out of the pallet, when the first detector detects that the distal portion of the fork is not adjacent to the upper wall of the pallet and the third detector detects that the proximal portion of the fork is not in contact with the upper wall of the pallet, and

when the pallet posture determination unit determines that the posture of the pallet is a posture that allows the fork to be pulled out of the pallet, the pallet placement controller controls the lift cylinder so that the lift cylinder stops lowering the fork.

3 . The cargo handling control device according to claim 1 , wherein

the pallet posture determination unit determines that:

the posture of the pallet is a posture that requires the fork to tilt forward, when the first detector detects that the distal portion of the fork is adjacent to the upper wall of the pallet, the second detector detects that the distal portion of the fork is not adjacent to the lower wall of the pallet, and the third detector detects that the proximal portion of the fork is not in contact with the upper wall of the pallet; and,

the posture of the pallet is a posture that requires the fork to tilt backward, when the first detector detects that the distal portion of the fork is not adjacent to the upper wall of the pallet, the second detector detects that the distal portion of the fork is adjacent to the lower wall of the pallet, and the third detector detects that the proximal portion of the fork is in contact with the upper wall of the pallet,

when the pallet posture determination unit determines that the posture of the pallet is a posture that requires the fork to tilt forward, the pallet placement controller controls the tilt cylinder so that the tilt cylinder tilts the fork forward along the loading surface, and

when the pallet posture determination unit determines that the posture of the pallet is a posture that requires the fork to tilt backward, the pallet placement controller controls the tilt cylinder so that the tilt cylinder tilts the fork backward along the loading surface.

4 . The cargo handling control device according to claim 3 , wherein

when the pallet posture determination unit determines that the posture of the pallet is a posture that requires the fork to tilt forward, the pallet placement controller controls the tilt cylinder so that the tilt cylinder tilts the fork forward incrementally by a certain amount until the pallet posture determination unit determines that the posture of the pallet does not require the fork to tilt forward, and

when the pallet posture determination unit determines that the posture of the pallet is a posture that requires the fork to tilt backward, the pallet placement controller controls the tilt cylinder so that the tilt cylinder tilts the fork backward incrementally by a certain amount until the pallet posture determination unit determines that the posture of the pallet does not require the fork to tilt backward.

5 . The cargo handling control device according to claim 1 , wherein

the pallet posture determination unit determines that the posture of the pallet is a posture that requires the fork to immediately stop, when the first detector detects that the distal portion of the fork is adjacent to the upper wall of the pallet and the second detector detects that the distal portion of the fork is adjacent to the lower wall of the pallet, and

when the pallet posture determination unit determines that the posture of the pallet is a posture that requires the fork to immediately stop, the pallet placement controller controls the forklift truck so that an operation of the forklift truck stops.