Rotary Actuators Technologies

Rotary actuators convert fluid pressure into rotary motion, and develop instant torque in either direction.

The rotary motion is obtained by applying a fluid under pressure on a piston which pushes a rack. In its turn, the rack actuates a pinion causing the rotation of the shaft. The pinion is mounted between two bearings and can be coupled directly or indirectly with the load. The torque generated by the actuator is measured in N.m (in lbs. or ft lbs.) and is directly proportional to the real pressure (differential pressure = ΔP) applied.
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 dimensions of vane/shaft, the number of vanes, and the fluid pressure applied. Speed of rotation is dependent on the flow capacities of the hydraulic system.
The majority of actuators are constructed with one or two vanes (three or more for special applications). The torque output is proportional to the number of vanes. The maximum arc of rotation for any actuator depends on the size and construction of the unit, and will always be smaller than 360° because of the space occupied by the internal barrier(s): a single vane is approximately 280°, a double vane 100 ° and a triple vane 30 °.
The piston, as in a linear actuator, under hydraulic or pneumatic pressure, moves between two mechanical stops.
This linear displacement is transformed mechanically into a rotary movement of the shaft under the effect of the reversed helical thread of shaft and piston. The opposite direction of the helical thread doubles angular displacement. The combined effects of the helical threads are not neutralized.

The self-lubrication and the hardened surface of helical shaft and piston guarantee the longevity of this type of rotary actuator.


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 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.

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. ln most cases special manifolds can be designed to mount servo valves to the actuators allowing sophisticated control of all functions.

Factors to consider when applying rotary actuators

Light load - Heavy load - consider weight of load and distance from actuator shaft.
Bearing Loads - heavy radial loads without external bearing support.
Shock Loads - consider dropped loads or mechanical failure of associated equipment. Also start - stop - jog and other non mechanical contact, hydraulic shock loads.
Rate of Oscillation - Time to move load thru required angle. Also consider small angle - high rate applications.
Cycle Frequency- how often actuator is cycled. One cycle per minute, one cycle per week etc.
External Stops - external stops should be used to limit angular travel as the actuator abutments (shoes) are not designed as mechanical stops.
Operating Press - should not exceed rated pressure of actuator.

Operating instructions

Installation and initial operation - The drive shaft is to be aligned properly to the counterpart to avoid exceeding the permissible axial and radial forces. Before initial operation the hydraulic system is to be carefully cleaned and bled.

Pressure fluid - Mineral oils, non-flammable fluids, dry or lubricated air.

Filtering - Filtering of the pressure fluid is recommended between pump and part-turn actuator (pressure line). The filter unit should be about 10 microns..

Oil change - Oil changes may be necessary and depend on the size of the system. Oil changes are necessary at shorter intervals with dirty oil. Oil changes inside the actuator should take place when changing the oil in the hydraulic aggregate: there is no oil change during moving cycles. L'actionneur doit être vidangé séparément à l'occasion de la vidange du système: Le volume de fluide contenu dans l'actionneur ne se vidange pas de lui-même en rotation.

Temperature range -10° C bis + 75° C
For higher or lower temperatures please refer to DS dynatec.

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.

  • valve actuating
  • swing of container
  • commande d'une vanne
  • part transfer
  • swivelling of saw
  • drive of blade
  • opening of mould
  • control of door
  • hinged cover
  • fastening of part
  • rotation of camera
  • closing of furnace

Conversion Table

Torque :

IN-LB x 0.1130 = N.m
N.m x 8.851 = IN-LB
N.m X 9.807 = Kgf-m
Kgf-m x 86.799 = IN-LB

Service Pressure :

psi x 0.06895 = BAR
BAR x 14.5 = psi
kPa x 0.1450 = psi
psi x 6.895 = kPa

Volume :

Cubic Inches x 16.39 = CU. CMS
CU. CMS x 0.06102 = Cubic Inches
Gallon x 3.785 = Liter
Liter x 0.264 = Gallon
Gallon x 3785 = CU.CMS
CU. CMS x 0.0002642 = Gallon

Mass :

Kg x 2.2046 = lbs
lbs x 0.4536 = Kg
Hp x 0.7457 = Kw

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