Unità valvolare per un sistema di frenatura antibloccaggio

A valve unit for an anti-lock braking system of a vehicle which has a valve body, a cutoff piston movable in an inner cavity of the valve body, and sliding contact seals arranged at an interface between the cutoff piston and the inner cavity is provided. The internal cavity is hydraulically connectable with a delivery port to a brake caliper, an inlet conduit, and an expansion chamber. The sliding contact seals define with the cutoff piston and the inner cavity an axially movable hydraulic chamber. The cutoff piston is movable between a first position, in which the hydraulic chamber is in fluid communication with the expansion chamber and the delivery port, and not with the inlet conduit, and a second position, in which the hydraulic chamber is in fluid communication with the delivery port and the inlet conduit, and not with the expansion chamber.