Mechanism for automatic release at specified travel

[tinkertech]

Does anyone know of a mechanism that can release a one-way clutch automatically at a specified travel distance? My need is for a fixed reciprocating motion for both input and output, but the output needs to retract quickly under spring tension at the end of the stroke, independently of the input return stroke. Then the clutch needs to re-engage again when the input completes its return stroke.

A ratchet and pawl probably won't work for me because it's subject to wear and the force on this will be fairly high during the power stroke. I can't risk the tips of the ratchet teeth or pawl breaking under load.

 

[potteryshard]

How about a simple toggle mechanism with a sliding cross-head constrained in one direction only? As soom as the line between the pivot on the two levers drops below the pivot of the crosshead, the crosshead slider will pop up away from the constraining surface allowing free return of the piston. A small spring could be used to allow return of the crosshead slider if the mechanism was to be used in different orientations.

 

[hydtools]

Sounds like you should study the mechanism of a double action only (DAO) trigger in a gun. Pull the trigger: cocks the hammer, releases the hammer, hammer spring drives the hammer to strike. Release the trigger to reset and engage and pick up the hammer. Repeat.

Ted