Multi-section two-way hydraulic cylinder is a special type of hydraulic cylinder. It is mainly used in special situations where the installation space is small but the stroke of the cylinder is relatively large and there is no external force to make it retract. The structure and manufacturing process are relatively complex. By decomposing the multi-stage two-way hydraulic cylinder into multiple single-stage two-way hydraulic cylinders, a multi-stage two-way hydraulic cylinder mechanical-hydraulic coupling dynamics simulation experiment is established. The test results show that when the multi-stage two-way hydraulic cylinder is working, a large hydraulic impact will occur in the rod cavity of the hydraulic cylinder at the moment when the hydraulic cylinder barrel (piston rod) of each stage extends. This impact will affect the service life of the hydraulic cylinder. Therefore, the hydraulic system should be optimized by modifying the multi-stage hydraulic cylinder structure to minimize these hydraulic impacts and improve the reliability of the hydraulic system. The order of the piston extension in the multi-stage cylinder is from large to small, while the order of no-load retraction is generally from small to large. When the input flow rate is the same, the extension speed increases gradually; when the load is constant, the working pressure of the hydraulic cylinder increases gradually.
Multi-stage two-way hydraulic cylinders can usually be designed as 3 to 5-stage double-acting piston cylinders. The cylinder block of the previous stage is also used as the piston rod of the subsequent stage, so the processing technology is quite special. When oil is fed into the rear-end hydraulic port, the pressure oil directly enters the rodless cavity through the outermost cylinder block of the oil cylinder. Under the action of oil pressure, the first-stage cylinder tube with the largest diameter extends first, and then the second-stage and third-stage cylinder tubes extend in sequence (the cylinder tube with the larger cross-sectional area can also be extended first according to the designed pressure-bearing cross-sectional area). extend). When the piston rod begins to extend, the oil in the rod cavity of the lifting cylinder reaches port A through the hole on the piston rod wall and the outside of the central pipe, and then returns to the oil tank through the oil return pipe.