Keywords

Compliant Mechanisms, Safety and Arming, Pseudo-rigid-body Model, E-Quintet

Abstract

Ratchet and pawl mechanisms are used in safety applications to provide mechanical isolation between inputs and an output to insure that extreme environmental conditions do not inadvertently allow an unexpected output. These devices have become smaller and are approaching a size regime where traditional precision components, such as precision bearings and springs, are not available. This paper introduces the Compliant High-precision E-Quintet Ratcheting (CHEQR) mechanism as a means of exploiting the advantages of compliant mechanisms to create safety devices that eliminate the need for bearings and springs. The pseudo-rigid-body model was used to design a mechanism with the desired force-deflection characteristics, and the result is a radical departure from traditional ratchet and pawl mechanisms. Large-scale proof-of-concept prototypes were followed by micro wire EDM fabrication of precipitation hardened stainless steel devices with flexible segment widths of 50 um. The device was integrated with a 6 mm ratchet wheel and rotary solenoid actuator.

Original Publication Citation

Kennedy, J.A., Howell, L.L., and Greenwood, W., "Compliant High-precision E-Quintet Ratcheting (CHEQR) Mechanism for Safety and Arming Devices," Precision Engineering, Vol. 31, No. 1, pp. 13-21, 27.