US Patent 7152405 Main cylinder with integrated transportation lock

A master cylinder for a vehicle hydraulic brake system has a housing with a bore formed therein, which is open at one end and in which a first pressure piston and a second pressure piston are guided sealingly and displaceably along an axis. Acting counter to an actuating direction upon the first pressure piston is a restrained first restoring spring and upon the second pressure piston a second restoring spring. In order, in a transportation or disassembly state of the master cylinder, to prevent the first pressure piston from being pressed excessively out of the bore, the second pressure piston is supported by means of a stop component counter to the actuating direction positively in the housing of the master cylinder.