Control mechanism for a mechanical coupling device

A motor-driven control mechanism and a mechanical drive control device controlled thereby, which mechanical drive control device includes a first part and a second part movable relative to said first part in both directions through a stroke defined between two limit positions, and elastic return means acting between said first and second parts;

• said control mechanism comprising linkage means associated with the second part and movable through a stroke simultaneously with the stroke of the second part and acting upon the second part to transfer the second part from a first of said limit positions to a second of said limit positions against the action of said elastic return means, and vice versa, motor-driven positioning means separate from the elastic return means for moving the linkage means under power in both directions throughout the stroke of the linkage means, and elastic force moderating means coupled to said linkage means and opposing the action of the elastic return means throughout the stroke of said second part and thereby reducing the force required to be exerted by said motor-driven positioning means;
• and force moderating means being operable to exert on said linkage means a force which varies through the stroke of the linkage means in both directions as the force exerted by the elastic return means on said second part.