When link 1 rotates clockwise, housing 2 is rotated in the same direction by the action of jammed rollers 3 if roll a, sliding along slot b of slider 4, is in a position to the left of line 0-0. In this case slider 4 moves upward. As soon as the slider passes its extreme upward position and the centre of roll a is to the right of line 0-0, housing 2, subject to the weight of slider 4, begins to rotate independently of link 1 because rollers 3 are released.
$2170$WL,3L$