Drum a is rigidly secured to lever 1 which turns about fixed axis A . End C of spring 3, running over the drum, is secured to lever 1, end B is anchored to the frame. When lever 1 is turned counterclockwise, spring 3 returns it to its initial position where it is locked by latch 2 which turns about axis D . When latch 2 is turned clockwise, it is disengaged from lever 1 which is turned by spring 3 about axis A until it runs up against stop b . Flat spring 4 holds latch 2 against lever 1.
$152$SL,L$