| 摘要 |
<p>PURPOSE:To switch a turning motor at two speeds and make the torque at the time of low speed so as not to go up for the safety by forming a crossover loading relief valve into a two-stage relief valve, having a tilting angle adjusting cylinder and this two-stage relief valve interconnected to a pilot pump, and selecting a selector valve through switching operation. CONSTITUTION:A crossover loading relief valve is formed into a two-stage relief valve capable of setting the extent of lifting pressure, and a tilting angle adjusting cylinder 29 and two relief valves 30L, 30R all are interconnected to a pilot pump 24 via a solenoid selector valve 37. In succession, when they are selected by means of switching operation, pilot pressure acts on the cylinder 29 or the two-stage relief valve. When a tilting angle of a turning motor 28 is set to smallness and relief pressure to the pressure-up side, respectively, its turning speed is selected to a standard high speed, and the tilting angle to largeness and the relief pressure to the pressure-down side it is selected to a low speed, respectively. With this constitution, the turning speed is selected to two speeds, thereby improving the extent of operations and simultaneously the safety at the time of low speed turning is secured in this way.</p> |
