[54] Piston overlap
The switching
characteristics of a valve are governed by, among other things,
its piston overlap. A distinction is made between positive,
negative and zero overlap. In the case of positive overlap, the
port in question is completely covered by the piston, while with
negative overlap it is less than completely covered. In the case
of zero overlap, the distances between the control edges of the
piston and of the port are exactly the same.
The individual control edges of the pilot piston can have different overlaps.