Oscillating motors are actuators that generate rotation at a certain angle with a hydraulic pressure. They include the vane and piston types. They can be easily mounted because they do not require a link mechanism. Also, these motors are compact and provide a high torque.
(1) Vane type oscillating motor: single vane and double vane types are available. The single vane type operates with a rotation angle of 280 degrees or less, while the double operates with 100 degrees or less, giving the torque twice what the single can produce. Compared to the piston motors, the vane type oscillating motors have simple structures and provide high response. Due caution should be paid to internal leakage inherent in the motor design. Fig. 10.10 shows the vane type oscillating motor.
(2) Piston type oscillating motor: The rack and pinion type and helical spline type are available. Fig. 10.11 shows the rack and pinion type, which uses an opposed single acting cylinder to drive the rack for pinion rotation. Fig. 10.12 shows the helical spline type, which has a piston with a screw mechanism to rotate the shaft. Piston oscillating motors allow the oscillation angle to be adjusted with the cylinder stroke length; therefore, careful consideration of the oscillating angle is not required. They also have very little internal leakage.
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