Abstract: A Conversion ring is provided for externally flanged mouths of tanks having two distinct locking means, one serving to prevent any axial displacement of the ring in relation to the filler mouth and the other for preventing any rotation of the ring once the latter is placed on the mouth. Both locking means cooperate with the external flange. The conversion ring provides security both as regards the sealing of the tank and as an anti-theft device.

Abstract: An anti-theft cap for closing a filler pipe of a vehicle fuel tank is provided having a body shaped to locate within the end of the filler pipe and a cover portion having sealing means to engage the end of the filler pipe. A cylinder lock mounted in a bore of said body serves to lock and unlock the cap. A carrier member is connected to said cylinder lock so as to rotate therewith between a locked position and an unlocked position. Two conduits are formed in said body diametrically opposite each other and each have one end at a surface of said body and the other end at another surface which other end communicates with the interior of the filler pipe when the cap is in position thereon.A first valve carried by said carrier member communicates at one end thereof with the atmosphere and at the other end thereof with said one end of its respective conduit when said carrier is in said locked position, whereby vapor from the tank may be vented when the pressure in the tank exceeds a predetermined value.

Abstract: The anti-theft plug or cap for the filler of a gasoline tank comprises a plate with a tapping corresponding to threading on the filler, a body rotatable in respect of the said plate, a securing element serving to render the said body integral with the said plate, and a cylindrical lock mounted in the said body and controlling the said securing element. The securing element rotatable with the rotatable body and serving to render the body fixed in relation to said plate, is provided with an elastically deformable arm resiliently removable from the axis of the plug under the action of the said lock, while its free end, when the arm has undergone no deformation, is disengaged from said teeth, although it engages them when the arm has undergone deformation.

Abstract: An anti-theft cap for a screwthreaded base. Said cap comprises a plate provided with a tapped aperture complementary to the screwthread of the base, a body journalled on said plate and in which body a lock is mounted. Said lock comprises a catch which, for one position of the lock, is at a distance from the axis of the cap equal to that of a stop integral with said plate, and, for at least one other position of the lock, is at a different distance. Said stop is elastically movable and adapted to move under the action of the catch when the screwing torque transmitted by said catch exceeds a given value.

Abstract: A cap for a fuel tank of the type comprising a labyrinth path between the fixed elements and the moving elements of the cap. Said labyrinth path is formed by concentric ribs defining grooves which intercommunicate by way of interruptions forming baffles, and a sealing element disposed on said ribs. Said sealing element has at least one projection which is adapted, in one angular position of the sealing element with respect to the labyrinth path, to close said path and, in another angular position, not to close said path.