Torque Limiters: Load-separating and holding safety clutches

Torque limiters from the market leader

Torque limiters have proven themselves millions of times over as protection devices in machines and systems. They transmit the torque reliably and with high accuracy during uninterrupted operation. However, no machine is safe from faults and collisions.  Errors in programming or operation or external influences such as foreign objects can lead to overloads. In this case, torque limiters prevent the torque from increasing to an unacceptably high level. They limit the transmitted torque to a set value thus protecting against expensive overload damage.

Torque limiters from the market leader – What are the benefits of using a torque limiter?

In order to provide reliable protection against overload damage, the torque limiter must be optimally suited to the respective application. If the torque transmission is to be completely interrupted in the event of an overload, for example in high-speed drives or where large flywheel masses exist, a load-separating, ball detent type torque limiter is the right choice.

In vertical or inclined axes, the torque must be limited to a defined value but without interrupting the transmission as if it was interrupted, the load would drop or crash in an uncontrolled manner. In this type of application, load-holding friction type torque limiters are more suitable.

Load-separating or load-holding? - Which torque limiter is the right one?

Load-separating torque limiters are safety clutches that completely disconnect the input and output when the preset limit torque for overload is exceeded. Until the limit value is reached, the torque is transmitted by locking elements that are pressed into counterbores (usually balls, ball ended bolts or rollers into pockets or seats) by disc springs. If the limit value is exceeded, these locking elements move out of their counterbores / seats and torque transmission is interrupted.

Depending on their function, load-separating torque limiters are categorised as either ratchetting, synchronous or disengaging / overload devices.

• After the overload has been removed, ratchetting clutches automatically re-engage at any point.
• Synchronous clutches also re-engage automatically, but only after a full rotation - i.e. 360° after disengagement. Other reengagement positions such as every 180° or every 90° can also be achieved in special designs.
• Disengaging / Overload clutches completely disconnect the driven and driving sides of the system and the clutches remain disengaged until they are re-engaged either by hand, by a remotely operated reengagement device or by reversing the drive (dependent on the design).

How load-holding torque limiters work?

Positive-locking or load-holding torque limiters do not interrupt the torque transmission in the event of an overload. They hold the load at the set torque. Positive locking torque limiters use locking elements to only disengage by a limited amount in the event of an overload. The partial disengagement is sensed by a limit switch and the drive is switched off without interrupting the torque transmission.

• Friction torque limiters slip when their preset torque limit is reached. They prevent torque overload but continue to transmit torque at the preset value. 
• Hysteresis clutches transmit the torque without contact via magnetic forces and limit it very precisely to the set value. Compared to permanent magnetic clutches, they deliver a very smooth and shock-free drive torque during the slipping function making them perfect for applications such as bottle capping.

Why torque limiters are so important

Collisions or overloads generate very high torques in the drive train, which can destroy or damage components. Torque limiters reliably protect against this and thus ensure high system availability and productivity. At the same time, they reduce operating costs and minimise repair costs. The cost of damage caused by a single overload can often be more expensive than a torque limiter. By limiting torques to a maximum permissible value, machines with torque limiters can be optimally dimensioned and design safety factors can be reduced.

Why electronic monitoring functions cannot replace mechanical torque limiter

Modern drive systems can be electronically monitored with functions such as motor current measurement. However, the disadvantages are the low measuring accuracy for mechanical variables and the fact that faults are recognised too slowly. Motor current measurement is not quick enough to be able to initiate countermeasures in time to prevent damage in the event of a collision, particularly in the case of hard collisions or high-speed applications.  A mechanical torque limiter is irreplaceable in these situations.

Reliable Torque Limiters from the Market Leader

Benefit from our extensive experience as a leading manufacturer of torque limiters and rely on the quality and reliability of our products. Our high-quality torque limiters ensure maximum safety and efficiency. Contact us today to discuss your specific requirements!