PROBLEM TO BE SOLVED: To effectively use pressure oil and reduce operation shock of a lift cylinder by sending whole quantity of pressure oil at an upstream side of a flow distribution valve to a lift control valve side at a neutral position of a rolling control valve.SOLUTION: This device includes a control means 14A returning the rolling control valve 39 to the neutral position 39c and changing over the flow distribution valve 38 to a distribution supply position 38b when the rolling cylinder 11 reaches an operation limit position and a relief valve 36 discharges pressure oil to an oil tank T side, and setting increase rate of pressure oil supply quantity to the lift cylinder 9 side by the lift control valve 42 slower than increase rate of pressure oil supply quantity in operation at the time excluding discharge operation of the relief valve 36 when the lift control valve 42 is operated during discharge operation of the relief valve 36.COPYRIGHT: (C)2011,JPO&INPIT【課題】ローリング制御弁の中立位置で、流量分配弁よりも上流側の圧油の全量を昇降制御弁側へ送り込み可能にし、圧油の有効利用と、昇降用シリンダの作動ショックを少なくする。【解決手段】ローリング用シリンダ11が操作限界位置に達してリリーフ弁36が圧油を油タンクT側へ排出すると、ローリング制御弁39を中立位置39cに戻し、流量分配弁38を分配供給位置38bに切換え、リリーフ弁36の排出作動中に昇降制御弁42が操作されると、その昇降制御弁42による昇降用シリンダ9側への圧油供給量の増加率を、リリーフ弁36の排出作動中以外の時点で操作されるときの圧油供給量の増加率よりも緩やかにする制御手段14Aを備えた。【選択図】図4
