A spring return actuator uses a spring to provide the impetus for its return stroke, simplifying the control system and reducing costs. It offers benefits such as low cost, long life, and reduced maintenance. There are many types available for linear and rotary applications, with adjustable damper valves for precise speed settings.
A spring return actuator is a control device that provides unidirectional powered motion with the impetus for its return stroke provided by a spring. For example, a spring return door actuator will only open the door under its own power with the door being closed again by a spring arrangement. The simple solenoid is a good example of a spring return actuator, with the solenoid plunger returned to its neutral position by spring tension. Having the actuator provide only a single power stroke simplifies the actuator control system with commensurate reductions in unit costs and maintenance requirements. The spring return actuator typically has a longer service life, further enhancing the cost savings on such systems.
Conventional bi-directional actuators provide a motorized actuating force for both the working and return strokes. This is typically accomplished by reversing the direction of an electric motor or, in the case of hydraulic and pneumatic systems, by pumping oil or compressed gas to the opposite side of the actuator cylinder. In contrast, a spring return actuator uses only one motorized stroke over half its duty cycle. The impetus for the return stroke which returns the mechanism to its neutral position is provided by a spring arrangement. One of the best examples of this concept is the linear solenoid which uses a spring to return its plunger once power is cut off to the coil.
There are many types of spring return actuator mechanisms available for both linear and rotary output applications. In some cases, the return spring is an integral part of the actuator mechanism, and in others, a separate unit. The rate at which the return spring moves the secondary mechanism is often adjusted to produce a specific reset rate. In many cases, this control function is achieved through a separate hydraulic damper typically featuring an adjustable damper valve mechanism, allowing for precise speed settings.
The single stroke of a spring return actuator offers many benefits, including low installed cost, long life and reduced maintenance. The advantages can be attributed to the relative simplicity of the systems and the reduced number of control elements and duty cycles required for their operation. This means slightly lower initial costs and reduced running costs. It also ensures superior longevity of the actuator and its power supply as only half of the normal duty cycles performed for each actuation.
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