Novel Multi-Stage Inertia-Driven Delay and Switching Mechanisms
Richard T. Murray, Jahangir S. Rastegar · 2009
In many systems, an acceleration event triggers some downstream operation. In such devices the “acceleration event of interest” must be identified from among spurious accelerations, which are often of appreciable magnitude — sometimes greater than the event of interest — but are of short duration, perhaps one tenth that of the event of interest. Such devices, therefore, are essentially inertia-driven timing mechanisms. The principles presented here allow for designing practical triggering devices actuated by arbitrarily long acceleration events where traditional mechanical inertia switches would have to be impractically large due to the non-linearity of component motion. Here, during acceleration of the mechanism, a plurality of spring-mass elements are at first immobilized, but are released in succession. The final stage of the chain is then used to trigger some downstream event. The key is that the time during which individual components are permitted to displace is only a fraction of the total delay time. Therefore, the delay elements are never given the opportunity to achieve high velocities and hence do not travel great distances during the duration of the delay. In addition to illustrating the general approach, design examples showing novel mechanisms for immobilizing and successively releasing the inertial elements are offered.