Actuators Flashcards
What do actuators do?
Convert hydraulic energy into mechanical energy
Linear actuators convert hydraulic energy into….
Linear energy (force)
Rotary actuators (motors) convert hydraulic energy into….
Rotary energy (torque)
Hydraulic cylinder converts hydraulic energy into…
Linear energy
What types of actuators are there?
Single acting
Double acting
Differential cylinder
Cylinder with end stroke cushioning
How does a single acting cylinder work?
Carry out work in one direction
The fluid flows into the blind area and pushes the piston out
It retracts under spring pressure by the weight of the load
How does a double acting Cylinder work?
Both piston surfaces can be pressurised via a DCV, allowing it to work in both directions
Why is the return stroke twice as fast as the advance stroke on a differential cylinder?
Difference in area between the piston surface and annular surface
Air can enter a hydraulic system by 3 ways…
Low oil levels
Leak on suction side of the pump
Return line above the fluid level
What is fitted to remove air from the system?
Vent screw or automatic vent valve
What is the purpose of a cylinder with end stroke cushioning?
Slows the piston down toward the end of the stroke, preventing excessive impact
Describe the operation of cylinder cushioning?
Exhaust flows out of cylinder freely until…
Plunger enters end cap and flow must now pass through restricted path
Rate of deceleration is controlled by the needle valve
NRV allows free flow of fluid to piston for extension
What controls the rate of deceleration on a cylinder cushion?
Needle valve - adjustable
Vane motor is typically used at what speeds?
Low speeds , suffering from less leakage
What type of speed and torque does the gear motor provide?
Medium speed , low torque applications
