| 摘要 |
For lifting loads, e.g. by means of fork lift trucks, hydraulic cylinders arranged in series are employed, which are connected together by lines. In order to safeguard the two hydraulic cylinders, a valve is located in the piston rod of the hydraulic cylinder which is pressurised first, by way of which the downstream hydraulic cylinder is pressurised. The valve is also designed so that damping is ensured when the hydraulic cylinder pressurised first retracts. The design of the valve provides pipe-break isolation, as well, in case the connecting line between the hydraulic cylinders is no longer functioning. In the downstream hydraulic cylinder, the stroke motion is reduced just before the limit position is reached. With a largely constant oil feed, the excess amount of oil is supplied to the hydraulic cylinder first pressurised. Since the reduction of the oil quantity is done continuously, a completely jerk-free transition is ensured. The damping of the downstream hydraulic cylinder is achieved by having a damping sleeve integrated into piston rod of this cylinder. The oil stored in the damping sleeve is returned to the hydraulic system via spiral grooves that are superimposed on the pressure-relief grooves. Sufficient independence of viscosity is achieved by the superposition of the spiral grooves and the pressure-relief grooves.
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