Reverse rotation preventing device

A reverse rotation preventing device, comprising:

• a coil spring having a central axis and formed of a number of windings of spring material so as to have a generally cylindrical outer periphery and a generally cylindrical inner periphery and so as to have a starting end winding defining an input side of said spring providing a first end face and a terminating end winding defining an output side of said spring providing a second end face, said first and second end faces facing in opposite directions axially of said spring, said coil spring having a first engaging pawl at said starting end winding and a second engaging pawl at said terminating end winding;
• a fixed ring arranged coaxially with said coil spring and having an internal periphery disposed in proximity to and surrounding said outer periphery of said coil spring;
• an input coupling arranged coaxially with said coil spring and rotatable in a driving direction by a driving force from a driving source, said input coupling having an engageable portion;
• an output coupling arranged coaxially with said spring, supported rotatably and having an output shaft fixed thereto, said output coupling having an engageable portion;
• an output reinforcing ring on said input side of said spring covering said first end face of said spring in the direction axially thereof and having an internal periphery;
• an input reinforcing ring on said output side of said spring covering said second end face of said spring in the direction axially thereof and having an internal periphery;
• an engageable pawl formed on said internal periphery of said input reinforcing ring so as to extend radially inwardly from said internal periphery of said input reinforcing ring for engagement with said engageable portion of said input coupling;
• an engageable pawl formed on said internal periphery of said output reinforcing ring so as to extend radially inwardly from said internal periphery of said output reinforcing ring for engagement with said engageable portion of said output coupling;
• each of said first and second engaging pawls of said coil spring having been formed by bending a portion of the spring material of the respective one of said starting winding and terminating winding along a bend line extending radially of said spring so that said portion extends in the axial direction of said spring;
• said input reinforcing ring having an engaging recess for engaging the one of said engaging pawls on the starting winding of said coil spring, so as to operate said spring in the direction of decreasing spring diameter;
• and
• said output reinforcing ring having an engaging recess for engaging the one of said engaging pawls on the terminating winding of said coil spring, so as to operate said spring in the direction of increasing spring diameter.