Drive box for reciprocal chain - has pawl spring loaded between links but released to reverse drive upon excess chain tension

摘要

The box has slots at each end near the lower edge which allow the chain links to pass through. A swinging pawl is suspended from a pin near the upper part of the box. The pin is mounted on sliding brackets which are pushed downwards by the compression springs so that the end of the pawl is forced into the gap between a pair of links. If the tension on the chain is excessive the force of the springs is overcome and the pawl swings towards the other end of the box, releasing the chain, but ready to take the drive in the reverse direction if required.