Investigation of the dynamic load unit to hydraulic workstation
2020
Repsa, E., Latvia Univ. of Life Sciences and Technologies, Jelgava (Latvia) | Kronbergs, E., Latvia Univ. of Life Sciences and Technologies, Jelgava (Latvia)
Hydraulic systems of agricultural, forest and road construction machinery are affected by different negative and positive loads. In order to mediate the dynamic properties of the hydraulic system with positive and negative forces, a dynamic load unit is used as an attachment to the hydraulic workstation. Heavy vertical load unit (80 kg) is suspended by an industrial type hydraulic cylinder CD70H25/16+DBDS6G1X/50. The Festo Didactic hydraulic Training Station lets to create the necessary hydraulic control circuit, which is presented. For negative load forces, when the directional valve shifts to load lowering, overrunning load forces occur. Then the actuator moves faster than the pump flow can fill it. Incorporating a pressure control valve called a counterbalance valve is a better way to control running-away loads. The hydraulic control system was developed for adjustment the dynamic load unit with the hydraulic work station. For the hydraulic cylinder piston diameter 25 mm, rod diameter 16 mm and load unit 80 kg the counterbalance valve calculated necessary pressure setting is 27 bar. Physical simulation with the load unit lifting and lowering was realized experimentally. For pressure measurements in pressure and return lines a pressure sensor SCPT-600 was used. Pressure was registered during the load unit lifting and lowering cycles with a service and diagnostic instrument “Service Master” and a portable computer. The obtained pressure diagrams during simulation show that the counterbalance calculated pressure setting 27 bar lets prevent overrunning load forces, when the actuator moves faster than the flow can fill it. Dynamic load unit is equipped with load springs at the end of load lowering, therefore, the linear characteristic of pressure change is observed. At the hydraulic cylinder, there is a throttle screw, by means of which the top end position cushioning of the piston can be set. Thus, the stroke speed of the hydraulic cylinder in the top end position is decelerated and the cylinder moves into the top end position in a dampened form.
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