Traditional mechanical torque limiters are not adjustable once the
machine is running, and they can only to be set to handle the peak torque
levels, such as that produced at start-up, making them insensitive to
overloads during normal running. Now available from Lenze, a new range of
torque limiters from the Italian company, OMC, features pneumatic
actuation, which enables the torque to be adjusted remotely while the
machine is running, providing full protection across the operating range.
The type DSR pneumatic torque limiter operation relies on transmitting
torque from one plate to another via rollers that sit in recesses in the
plates. Axial force to hold the plates together is generated by a
pneumatic piston. There is a linear relationship between air pressure and
the torque transmitted; when an overload occurs, the rollers move out of
their recesses causing the plate to open, the movement being detected by
a microswitch. When an overload condition occurs, the torque limiter
gives free release of the drive with no residual torque.
The DSR range is supplied with a 360°, once-per-revolution
synchronisation as standard, but models can also be ordered with
synchronisation to fractions of a revolution, down to 36°. A number of
functions are possible, including being able to make different settings
for forward and reverse rotation, or varying the torque according to
machine speed. The DSR limiter can also act as a disconnect clutch.