Coupling for spiral counterbalance

摘要

A coupling between a twisted rod and a torsion spring of a spiral counterbalance is found to be subject to deformation against the twisted rod from compressive force of the grip of the terminal convolutions of the torsion spring. This problem is solved by using a metal cylinder in the rotation transmission sleeve of the coupling to resist the compressive force and prevent deformation so that the twisted rod can move freely within the coupling. This solution also allows the use of a stronger torsion spring to exert a larger counterbalance force.