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Design and Theory

In the event that an actuator is accidentally overloaded while it is mid stroke the actuator has some mid stroke protection.  There are two main types of mid-stroke protection.
  • Clutch
  • Electronic load monitoring


When utilizing a clutch for protection, a ball detent clutch is usually the choice. In this style of clutch, a spring force presses the balls into their detents. When the torque to rotate the shaft becomes too high, the balls force themselves out of their detents against the spring pressure. This allows the motor to turn without the shaft or screw turning, which keeps the actuator from extending. As the clutch continues to rotate, the balls will fall into the next set of detents. If this continues, a ratcheting or clicking sound is heard. This should not be allowed to continue as the clutch will quickly wear.

ball detent clutch exploded view

Electronic load monitoring

In electronic monitoring, a built-in microprocessor monitors the current draw of the motor. If the current draw exceeds the amount required for the load rating for the actuator, the microprocessor will stop the movement of the actuator by cutting power to the motor.

Electronic load monitoring circuitry

Video discussing ways the actuator is protected from overload throughout its stroke.

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