The travel end expansion valve (1) for a piston type pressure converter (2) whose master cylinder (3) and slave cylinder (4) define a master chamber (9) and a slave chamber (10), respectively, includes an expansion master cylinder (12) which communicates with the slave chamber (10) and in which there can move an expansion main master piston (14) which is mechanically connected by a lever type transmission (11) with progressive effect to an expansion slave pump piston (15) which can move in an expansion slave cylinder (13), the transmission (11) being provided in such a manner that, when the expansion main master piston (14) is at the top dead center, the expansion slave pump piston (15) is at the bottom dead center, and vice versa, while an expansion release actuator (30) can cause the transmission (11) to move.