Patent ID: 6220027
Filing Date: 2001-04-24
Classification: B66F,F15B

Abstract:
A stacker control of a shelf stacker comprising a swing-shift fork, in particular a stacker for high storage racks, said fork being turnable about at least one vertical axis by a first hydraulic motor and being horizontally movable by a second hydraulic motor with said motors controlled by magnetically operated directional control valves connected to a common electrically operated hydraulic pump, a three-way pressure balance valve provided between said pump and said directional control valves for preferring said first of said hydraulic motors, said three-way pressure balance valve being controlled by control pressures tapped upstream and downstream of said directional control valve of said preferred first hydraulic motor, at least said directional control valve of said preferred first hydraulic motor being designed with a zero position which is open towards a tank, said three-way pressure balance valve being a part of a neutral circulation circuit extending from said pump via said directional control valve of said second hydraulic motor to said tank, said directional control valve of said preferred first hydraulic motor connecting in its zero position to said tank and blocking a pressure line extending from said three-way pressure balance valve towards said directional control valve, wherein said directional control valve of said second hydraulic motor is a magnetically operated directional control valve and is connected to said three-way pressure balance valve via a pressure line containing a three-way flow regulator connected to said tank, said three-way flow regulator being adjustable by a proportional magnet.