Safety Element Torque Limiters

Torque Limiting Modules
Brunel Torque Limiting Modules have been specifically designed to provide overload protection for applications where very high torques are transmitted and to extend the range covered by Brunel Type JA units. The modular system provides facilities for virtually unlimited torque capacity and lends itself to many transmission applications – chain, belt and gear drives, or shaft-to-shaft gear or flexible coupling drives. The maximum release torque depends on the number and size of Torque Limiting Modules that can be incorporated, and the size of the unit that can be accommodated within the confines of the installation. Internally & externally adjusted modules provide repeatability better than ±5%, however externally adjusted modules are preferred when the application is required to operate within minimal variations between static & dynamic disengagement.

Construction
The Brunel Torque Limiting Module is constructed from the finest quality materials. Many of the vital components are made from high quality tool steels, through hardened to Rockwell C62, and precision ground to close tolerances.

Disengagement
On overload, relative angular movement between flanges X and Y imparts a tangential force (Fu) on the large steel ball, forcing it clear of the detent pocket back against the plunger. This in turn causes the plunger to be forced through the circle of balls overcoming the spring loading on the angle races. In this position, the balls are resting on the large diameter of the plunger, and once this condition is reached the flanges are completely free to rotate independently. A suitable switch can be incorporated in the assembly to switch off the drive motor or operate a warning device when the Torque Limiting assembly disengages. Resetting is a simple matter of first re-aligning the flanges X and Y and then tapping each module plunger back with a soft mallet to allow the circle of balls to return to their original position and the large steel ball to return to its location in the detent pocket.

Normal Operation
The flanges X and Y are driven by a large steel ball 2, located in the detent pocket 1, which is retained by a plunger 3. This in turn is retained axially by means of a system of angled races 6,8 biased by pressure from the Belleville springs 5, acting on a circle of balls 7.

Detent Pockets
Internally & externally adjusted modules can have through hole or blind hole detents . The type of detent is dependent upon the design constraints.
All modules are required to be preloaded. In the case of the through hole module this is done by tightening the set screw at the base of the detent pocket. In the case of the blind hole module this is done by the means of shims under the module.

SELECTION

To apply the modules in the form of a torque limiter, it is necessary to determine the quantity of modules needed for the required torque capacity at a specific radius from the axis of rotation.

No. of Modules

= M

Torque (lb in)

= T

Tangential Force

= Fu

Mounting Radius of Modules

= RAD

M =

T

Fu x RAD

T = M x Fu x RAD