Lever 1 is rotated counterclockwise about fixed axis A. Disk 2, mounted freely on shaft A, remains at rest until lever 1 reaches slot a in disk 2. After this, disk 2 begins to rotate together with lever 1, and slider 3, connected by steel band 4 to disk 2, moves to the left. When lever 1 reaches bevelled stop 5, it is withdrawn from slot a and slider 3 is moved to the right by compressed spring 6. This also reverses disk 2. Lever 1, continuing to rotate in the same direction, reaches slot b in disk 2 and slider 3 again moves to the left. Then bevelled stop 7 again disengages lever 1 from disk 2, and slider 3 is moved again to the right by spring 6. Thus, in each revolution of shaft A, slider 3 has two complete strokes (twice to the left and twice to the right).
$1860$FL,4L$