The Friends of Ferguson Heritage Ltd. - Draught Control
This animation attempts to show the following sequence:-
the control lever is pushed down.
the lift arms fall, until-
the drag on the plough creates enough pressure on the top
link to compress the spring, which then pushes the
control fork pivot point forward. The valve is then
closed, and further descent of the lift arms is
prevented. The plough continues at this depth, until-
further resistance is met by the plough
the control fork pivot point is pushed forward
oil is pumped to the ram, lifting the lift arms.
The animation doesn't show the effect of a reduction in drag:
that would let the top link, and the control fork, move back,
allowing oil to be drained from the ram again.