shown by a resilient positioning member 17 such as a pair of springs the axial displacement of the spool 16 against the resilient positioning member 17 on either side of the neutral position serves to put orifices 15 extending on either side of the sealing gaskets 14 selectively into communication with one another the resilient positioning member 17 bears at one end against the end of the jacket 10 and at its other end against a shoulder on the nut 11 installing the hydraulic control valve 5 in the housing 6 of the hydraulic manifold 1 is described below in greater detail with reference to fig3 to 5 the housing 6 defines a certain number of sealing bearing surfaces 31 designed to co operate with the sealing gaskets 14 the bearing surfaces 31 are of diameter that decreases going from the inlet of the housing 6 towards the end wall thereof such that the bearing surfaces 31 are stepped the end wall of the housing 6 presents a centering bearing surface 32 for co operating with the centering bearing surface 13 of the jacket 10 and of diameter that is smaller than the diameter of the sealing bearing surfaces 31 the hydraulic control cartridge valve 5 is engaged in the housing 6 until the centering.