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Authors: Jon Mueller and Tyler Pocock
Welcome to part three of our six part discussion on the basics of an electric linear actuator and factors to consider when purchasing an actuator. Today we will cover the safety feature options within an electric actuation system.
Depending on the environment and duress that the actuator will be operating in and undergoing, it is wise to reinforce the stability and strength of the actuator. Since TiMOTION is a vertically integrated manufacturer of electric actuators, we are able to customize these features to a customer’s needs. Some safety feature options to consider are:
A. Overload Clutch - The overload clutch is a built in device that slips when the electric actuator reaches a pre-set load limit. The overload clutch connects and disconnects the motor from the lead screw. This slippage prevents the linear actuator from incurring possible damage. This is a great safety feature option on our TA3 industrial linear actuator.
B. PTC Thermistor - A PTC Thermistor essentially acts as a fuse which cuts the power to the motor, protecting the motor from overheating and burning out. Our electric motors have a UL certification option that includes a PTC Thermistor installed inside.
C. Safety Nut - A safety nut is essentially a metal reinforced acme drive nut used to help the linear actuator support a higher load. A safety nut is recommended for loads of 6,000N or more. TiMOTION's durable electric linear actuators also have the option to add this feature to ensure the strength and integrity of the actuator.
D. Push-Only Nut - A standard drive nut will have threads to screw into the extension tube whereas a “push only” nut won’t have threads. This prevents obstructions (animals, people, other furniture, etc.) from being damaged by a retracting linear actuator system. This can be helpful for example in a recliner, where if the foot of the recliner is going from an extended to retracted position and there is an object below the feet of the chair. The foot of the chair will not continue to push force on the object it comes into contact with. Our TA5, TA5L, TA5P, TA6, and TA14 indoor linear actuators would be used in this sort of application.
E. Quick Release – A handle or cable which allows the actuator to be quickly back driven when it is released. The quick release is designed mainly for medical bed applications for when the back rest of a medical bed needs to be quickly laid flat (in case of emergency CPR). Our medically certified linear actuators can come with this option (subject to application needs) seen in our TA1 and TA15 models.
F. Manual Release - The manual release is designed primarily for a medical patient hoist system. The manual release allows the extension tube (inner tube) to release from the front attachment (clevis) and spin freely. This allows the linear actuator to back-drive freely and for a patient to be manually lowered from the patient hoist system. This feature can be easily customized in our TA1 and TA12 model.
G. Manual Crank - The manual crank is a safety feature designed mainly for the medical industry. It allows a medical practitioner to manually operate the bed position in case of emergency or power outages. TiMOTION's TA10 medical actuator has the manual crank option that we can customize depending on customer's application needs.
H. Spring Coil Brake - A spring coil brake is installed and wrapped around the worm gear. It is a unidirectional no-back type brake that is activated automatically by pinion winding and then released when the motor turns.
I. Motor Brake - The motor brake is installed either on the top or bottom of the motor shaft depending on whether the application will be pushing or pulling the load. The motor brake gives the electric actuator the added durability that ensures longevity of the actuator. Since TiMOTION is in the business of manufacturing durable products, most of our electric actuators come standard with a motor brake.
J. Electromechanical Brake - The electromechanical brake slows or stops the motor using electromagnetic force to apply mechanical resistance to the spindle. The electromechanical brake is also installed on the bottom of the motor shaft. This is another great safety feature option on our TA3 industrial linear actuator.
K. Mechanical Brake- A mechanical brake can be added to reinforce stability of the electric actuator when back drive can possibly be a factor with high weight loads.
We hope that this has helped you develop a better understanding and foundation for electric linear actuators. Next, we will explain the various load and speed characteristics to consider for an actuator that can be adjusted to meet an applications' needs. If you have further questions and/or would like help with your next application, TiMOTION would be glad to assist you. We specialize in partnering with our clients while providing quality solutions for their linear motion system needs.