Displacement Characteristics of One Piece Parallel Spring Movement for Balance (3rd Report)

-Two Circular Springs with Error of Dimension in Thickness-

Abstract

In the parallel spring movement, there is a unique point where regardless of loading position, rectilinear displacement remains unchanged. The point shows no deviation from the origin as long as each of two parallel springs are symmetrical regarding y axis passing through the origin. Error of thickness of the spring, however, causes appreciable error rate of displacement, resulting in the error of a mass to be measured by a balance. As for workableness, the circular spring is better than leaf spring, because high dimensional accuracy can be obtained by such a conventional tool as end milling cutter. Authors aim in the paper to clarify the effect of the error of the minimum thickness of the circular springs on the error rate of displacement by comparison of theoretical analysis with the experiments and Finite Element Method (FEM). The results may be briefed as followings : (1) The error rate of the minimum thickness of the circular spring, Δt_m/t_m0 contributes approximately to the error rate of displacement, independent of the position of loading and sensors. (2) The error rate of displacement is influenced by not only the loading and measuring position but also the ratio of the minimum thickness to the radius, or t_m/R₀.