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The Basics
Factors to Consider
General Engineering Notes
Harmonic Motion Drives
Rotational Speed
Sample Problems
Flow Rate Data
Reference Data:
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The Basics
Rotary actuators convert fluid pressure into rotary power, and develop instant torque in either direction. Basic construction consists of an enclosed cylindrical chamber containing a stationary barrier and a central shaft with vane(s) affixed. Fluid pressure applied to either side of the vane will cause the shaft to rotate.
The output torque developed is determined by the area of the vane, the number of vanes, and the fluid pressure applied. Speed of rotation is dependent on the flow and pressure capacities of the hydraulic system. The majority of actuators are constructed with one or two vanes, but are available with three or more for special applications. The theoretical torque output of a multivane unit is greater by a factor equal to the number of vanes times the torque of a single vane unit at equal pressure. The maximum arc of rotation for any actuator depends on the size and construction of the unit, and will always be less than the number of vanes divided into 360º because of the space occupied by the internal barrier(s). The arc of a single vane is approximately 280º, a double vane 100º and a triple vane 50º.
Versatility
Fluid Media:
Actuators can be operated on either pneumatic or hydraulic pressure. The fluid can be air, oil, high water base fluid (HWBF), or fire resistant fluid. Actuators can be assembled with special seals and/or internally plated for specific fluids.
Mounting:
Actuators can be mounted horizontally, vertically or any angle in between. Models are available with flange, end, base or foot mounting provisions.
Actuators are usually mounted in a stationary position with the shaft rotating, but also can be shaft mounted with the housing portion rotating. Some models require mounting dowels to resist torsional forces. See the specific actuator model for mounting details.
Control:
Stopping, starting, acceleration and deceleration of actuators can be controlled by various types of valves in the fluid circuit.
External stops are recommended for most applications, although the arc of oscillation can be controlled by valves or positive internal stops (for light duty applications only).
In most cases special manifolds can be designed to mount servovalves to the actuators allowing sophisticated control of all functions.
Possible Applications
Rotary actuators are adaptable to a wide variety of uses in many different industries. The sketches shown give only an idea of the various possibilities. Actuators can perform a wide range of operations involving rotary or linear motion.
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