Overload Release Industrial Clutches

Overload release clutches are industrial clutches that have the additional feature of self-disengagement when a preset torque is reached. Upon reaching the preset torque value the clutch is fully disengaged by an internal cam mechanism and no power or torque will be transmitted. The disengagement point typically is adjustable over some range for each size of these industrial clutches.

Once disengaged, these industrial clutches must be re-engaged manually before power can be transmitted. The clutch may also be designed to establish rotational positioning (indexing) between the two rotating bodies. When used in indexing, the re-engagement point of rotation can be defined in degrees, with 1, 2, 4 or more re-engagement points when the clutch is reset. A clutch which can be engaged every 90° will have four re-engagement points for each complete rotation of the driving element. This assures that the driving elements are always synchronized with the driven devices when timing is critical.

Unlike torque limiters, overload release industrial clutches will not tolerate even momentary overload. This is especially useful in applications where safety considerations and protection of sensitive downstream equipment must take precedence over continuous operation.

Selecting Torque Limiters vs. Overload Release Clutches

The nature of the application and the types of driving and driven bodies will determine the proper device selection. Consider, for example, a conveyor being driven by an electric motor. When a jam or backup occurs which prevents the conveyor from moving, use of a torque limiter may present a safety hazard to operating personnel. In this case, if a jam is manually cleared, the torque required to move the conveyor will be immediately reduced, and the motor, which is not disengaged from the conveyor even in a slip condition, will instantly begin moving the conveyor, even while personnel are still clearing the jam, potentially causing injuries.

When a torque limiter is used in a power transmission application, the design engineer must recognize that there will always be 'stored energy' in the system when the driving element is energized, even if the driven device is not moving. Careful consideration to safety factors must be given in this type of environment.

Overload release industrial clutches, in contrast, will positively disengage the conveyor in our example, and will not restart it again until the jam is cleared, and until operating personnel clear the area, positively reset the clutch, and allow the conveyor to resume operation.

Torque limiters are useful in applications where the driven device cannot absorb the full output torque of the driving element. An electric motor driving a bottle capping machine is an example of this kind of application. Sufficient torque must be transmitted to twist the cap into position, but when the cap is tightly fit to the bottle, additional torque would damage the product, the capper, or both. In this case, the torque limiter assures a tight fit of the cap, but not so much torque that any damage occurs, assuring a high level of efficiency with minimum down time in the capping operation.

Read more about torque limiters.