Oiltight hydraulic tappet for controlling an internal combustion engine valve

Claim 1

Hydraulic tappet designed for assembly on a drive for controlling a valve on an internal combustion engine, the said tappet comprising a first cup member having a bottom wall and a cylindrical side wall and sliding axially in relation to the engine frame, and a second member sliding axially inside the said first member; the said first and second members combining to form a first chamber varying in volume and having an inlet duct for activating fluid, the said duct being controlled by an on-off member in such a manner that the said fluid flowing into the said chamber causes one of the said members to slide axially in relation to the other so as to vary the volume of the said chamber; characterized by the fact that it comprises a third annular member having a sleeve, inside the inner bore of which the said second member slides axially, and a ring projecting radially from the said sleeve and connected in fluidtight manner to the said side wall on the said first cup member in such a manner as to form the said first chamber between the said ring and the said bottom and side walls on the said first cup member, and characterised by the fact that it comprises a fourth member made of flexible material and located essentially inside the said first cup member and outside the said sleeve on the said third annular member, the said fourth flexible annular member having a first and second annular edge connected in fluidtight manner respectively to the said ring on the said third member and to the side surface of the said second sliding member in such a manner as to form a second annular chamber for the said activating fluid connected hydraulically, via the said duct, to the said first chamber.