08-16-2017, 10:54 PM
Hydraulic actuators: cylinders
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Properties:
.The cylinders have to be good quality steel with close tolerances.
There have to be good sealing both at the piston rod and at the cylinder.
.With time dirt may come in and damage the surfaces. This has to be possibly reduced.
In this case, the leakage will increase all the time.
Calculation of cylinders
1 Stick-slip
2 Transition
3 Normal behaviour
Hydraulic cylinders should be possibly operated in the 3rd region for smooth operation.
If the cylinder is new, the leakage losses are negligibly small so that:
Cushioning of cylinders:
A hard impact of the piston at the end surfaces has to be inhibited kinetic energy has to be absorbed.
This is done by increasing the hydraulic resistance at the end of the stroke.
Swivel vane rotary actuator:
Limited angle in both directions
Maximum angle always smaller than 360
The same torque in both directions