Couplings are common motion system components used primarily to transmit torque and compensate for misalignment between two shafts. Safety couplings, or overload couplings, are specially designed couplings that slip or disengage in the event that a pre-determined torque limit is reached. The most common type of safety coupling is a low or backlash free spring-tensioned ball-detent torque limiter. All safety couplings serve as an absolute emergency stop for safe and reliable disengagement between drive and loads. But ball-detent safety couplings have a torque limiter created by a specific mechanical configuration in its design.
The smallest component in this arrangement is the ball-detent itself. At its most basic level, a ball-detent is a mechanical arrangement consisting of a small spherical component (usually metal), a disk spring and a small hole or depression called a detent.
In a ball-detent safety coupling the balls are kept in place within the detent by spring tension. A torque load exceeding the set values for the coupling will push the balls from their detent, hence disengaging and decoupling the two shafts. The disengagement force of the safety coupling is variable and can be set to suit the specific needs of a given application.
There are also multi-position torque limiter configurations that operate with automatic re-engagement. Safety couplings like these use different detent patterns to allow for the balls to re-engage as soon as loads dip below the selected torque threshold.
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