An actuator particularly for accomplishing the swinging motion of a swinging arm comprises two cylinders using a pressurized medium, the piston rods of the cylinders being connected to a structure rotatable in relation to the swinging arm for the purpose of rotating the swinging arm around a rotation axis by the effect of movements of the pistons of the cylinders. The actuator comprises two control valves, of which one control valve is arranged to guide the pressurized medium either to both cylinders while they are coupled in parallel, or solely to one cylinder where its piston rod chamber and piston chamber are coupled together. This results in a movement of the piston outwards, because the pressure is directed to the whole work area of the piston on the side of the piston chamber and on the side of the piston rod chamber only to the work area which is the difference between the cross-sectional areas of the piston and the piston rod. Further, the pressurized medium needs to be supplied only in an amount proportional to said difference for achieving the same speeds of motion as before.
展开▼
