A screw actuator converts rotary motion into linear output motion by transferring the rotation of a motor to a threaded rod with a coarse screw-type thread. Lead screws are commonly used for this purpose and are machined to tighter tolerances for smoother output action. The screw actuator is efficient and cost-effective but has limited torque output compared to hydraulic ram types.
A screw actuator is a mechanical device that converts the rotary motion of an electric, pneumatic or hydraulic motor into linear output motion. This is achieved by transferring the rotation of the motor to a threaded round rod with a coarse screw-type thread. The bar passes through a similarly threaded movable collar that moves up and down the bar as it rotates in either direction. The collar is attached to an actuator arm which transfers the movement of the collar to a secondary mechanism, such as a door or vent. The screw actuator is one of the most efficient, simple and cost effective mechanical actuators, with its only real disadvantage being the limited torque output compared to hydraulic ram types.
Lead screws are a commonly used method of converting an input rotary motion into a linear or rectilinear output motion. A good example of this concept at work is the bench vise found on the workbenches of most DIY enthusiasts. When the vise handle is rotated in either direction, the vise jaws open or close. The basic principle behind this functionality can also be seen when a nut is turned on a bolt. As the nut is turned, it feeds along the bolt shaft threads until it tightens.
The lead screws used in a vise and a screw actuator work exactly the same, but have a different type of thread than what is found on the bolt. These threads generally have a coarser square profile, allowing the nut or driven element to move faster while providing a more powerful driving force. Square wires are also sturdier and less prone to stripping under intense loads. Other than that, the basic principle of motion transfer remains the same.
The lead screws used in a screw actuator are generally machined to tighter tolerances than those used on a vise, which produces a more predictable and smoother output action. The movable collar that travels up and down the screw shaft is attached to an actuator arm, which in turn is attached to the mechanism that the actuator is to operate. The lead screw is rotated by an electric, pneumatic or hydraulic motor, and as it does so, the collar moves the actuator arm and activates the secondary mechanism. To reverse the direction of travel, the motor is simply reversed. The screw drive is extremely efficient, accurate and robust, although generally not as powerful as examples of the hydraulic piston type.
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