embodiment of the schematic device shown in fig1 it shows various other features of the device of the invention first the master cylinder comprising a regulator can be produced either in a single operation or produced using two components a doubly cylindrical first component 43 that forms the actual regulator proper as shown in fig2 and a conventional component 44 that forms the master cylinder the component 43 comprises a block pierced with the interposed cylinder 15 and with the contiguous cylinder 22 hydraulic fluid is distributed both to the master cylinder 44 and to the regulator 43 by a bore 45 aligned with each of these two components and leading to the reservoir 32 where they are joined together the two components 43 and 44 are fitted with seals such as 46 to prevent leaks the bore 45 in its portion that enters the component 43 terminates at one end in a communication 48 via which the hydraulic fluid can enter the intermediate cylinder 15 the intermediate cylinder 15 has between the location of the ring 17 and the inlet via which the control rod 6 enters a bore with a cross section 49 which is somewhere between the cross section 20 and the cross section 21 for example in this bore 49 near the point of introduction of the rod 6 a set of o ring seals such as 50 and 51 allow the upstream chamber 18 to be filled with hydraulic fluid without external leakage when the rod 6 is in the retreated position furthermore these seals allow the pressure in the upstream chamber 18 to rise when this rod 6 is depressed.