Rotary joints:

A traditional joint might employ some rolling or sliding interaction between the two connected links in the form of a hinge or bearing assembly. The flexonic counterpart moves by deflection, where elastic energy storage provides an increasing resistance to rotation. Other issues when designing flexonic joints include range of motion, axis-drift, off-axis stiffness, and stress concentrations. We have identified several joint designs for possible inclusion within flexonic mechanisms. Below is a simple thin-strip cross-flexure joint. The right graphic depicts a cross-flexure joint in its rotated configuration.



A rotary joint can also be designed by utilizing the twisting degree of freedom of a thin strip. A realization of this joint is proposed and analyzed in detail by Moon, et al [1]. The joint utilizes perpendicular ribs along the flexure region to constrain off-axis motion. The ribs are essentially the intersection of two perpendicular thin strips. The axis of rotation is along the center of the ribbed flexure.



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[1] Moon, Y.-M., Trease, B. P., and Kota, S., "Design of Large Displacement Compliant Joints",DETC2002/MECH-34207, ASME/DETC 27th Biennial Mechanisms and Robotics Conference, Montreal, CANADA, Sep.29~Oct.3, 2002