Photo from Mitsubishi Electric spring operating mechanism with a torsion bar
This mechanism have been used to develop higher interrupting capabilities up to 550/420 kV while also providing benefits of increased mechanical reliability and reduced maintenance requirements. The torsion bar mechanisms shown in Figure from Mitsubishi Electric use for GCB , which employed compact, small mass interrupters with high interrupting performance as well as a unique torsion bar spring operating mechanism.
A spring operating mechanism stores mechanical energy in the solid spring. Since the operating characteristics of spring operating mechanisms are less affected by the
change of ambient temperature and loss of mechanical pressure, they show inherently superior in long-term reliability.
The use of a torsion spring divided into two bars makes it possible to design a compact operating mechanism
with large stored energy .
Due to unique advantages of the torsion bar spring mechanism, the mechanism does not require lubrication during its life. Recommended maintenance is limited to visual inspection and a check of basic parameters after 2000 operations.
This makes the mechanism essentially mechanically maintenance-free.