Torque Limiters

Torque limiters are devices that protect equipment from damage by mechanical overload. These devices help reduce costs by providing efficient operation while reducing production downtime and labor costs. They do this by preventing a larger incident as a result of a jam or overloads caused by worn or broken machine parts, foreign objects lodged in the motor, an operator error or a buildup of production material. Torque limiters are especially useful because they limit any damage from the jam or crash stop by slipping or by causing the motor coupling to disconnect the load entirely.

Torque Limiters are commonly used in vehicles to automatically disengage the clutch at a predetermined torque and provide consistent torque levels. They are cylindrical and appear to have rings which contain the internal assembly of gears and uncoupling device. Torque limiters are usually made from steel and are available in stainless steel for applications in which frequent washdowns are performed to maintain sanitary conditions.

Torque limiters are also known as overload clutches and may be packaged as a shaft coupling and can act as a clamping hub for direct drives. These devices are used with timing belts, driveshafts, sprocket gears in the engines of all kinds of manual automobiles, including cars, trucks and industrial or construction equipment like forklifts.

After a vehicle experiences many overloads at low speeds, internal car systems tend to develop unnecessary torque that can damage many components, such as shafts, gearboxes, chains and couplings if there is a jam. To prevent this, torque limiters set the torque to a specific level, which will extend the life of the car significantly.

Torque Limiter Safety Coupling
Torque Limiters – DieQua Corporation

They do this by uncoupling the drive which is called disconnecting. The torque limiter should be installed as close to a possible source of a jam as possible to allow the system’s inertia to be quickly disconnected from the jammed section, causing it to slowly coast to a stop without any further damage. While some are automatically reset, most require the operator to manually reset the torque limiter. There are four different methods of disconnecting. The first occurs when the shear pin that connects the shafts is destroyed.

Synchronous magnetic torque limiters use permanent magnets that are mounted to the shafts. This is the quickest method, but it creates more backlash than other types. Ball detent limiters transmit force through hard ball-shapes held in place with springs, and pawl and spring methods use springs to hold a drive pawl against a notch in the rotor. Another category of torque limiters slip by letting the drive shaft fun faster than the shaft that is being driven. Overload power is dissipated as heat and this style does not have to be reset. Friction plates and magnetic forces are used to accomplish this.