Plunger 1, sliding along fixed guides a, has a round hole in which round link 2 can slide axially in a direction square to the axis of guide a. Link 2 is subject to the action of flat spring 3. When engaged, plunger 1 and link (pin) 2 are in the position shown in the drawing. If link 2 is depressed through the hole in the frame, plunger 1 will be returned by spring 4 to its initial position, shown in the drawing by dash lines.
$156$SL,L$