Study on Availability of a Twistable Vacuum Bellows

Abstract

A twistable bellows has been newly developed in order to adjust twisted displacement around its axis. The bellows consists of several convolutions with eccentric inner circle to the outer circle. It is experimentally proved that the bellows can be continuously used without failure for more than 1 million times of repeated twist up to 10 degrees of twist angle. Besides, it is also confirmed that the bellows is sufficiently conformable to repeated continuous expansion and contraction displacement, similarly to a normal bellows. Finally, the most suitable eccentric distance was discussed based on the stress distribution in the bellows under the torsional displacement, analyzed by means of finite element method (FEM). From the analytical result, it was supposed that 2 mm of the eccentric distance is the most appropriate for the proposed size of the bellows with a diameter of 70 mm for the outer circle.