Abstract: A pair of ceramic disks for mixer faucets includes a fixed disk and a smaller mobile disk adapted to slide on the fixed disk within given limits. The fixed disk has on one side a bearing surface adapted to lie against the mobile disk and has two feed openings and one outlet opening through it. The bearing surface of the fixed disk has a closed main rim around the three openings and at least one depression in the surface through only part of the thickness of the fixed disk. In any position of the mobile disk relative to the fixed disk, the bearing surface of the mobile disk bears on the rim all around the depression. The bearing surface further includes an inner rim which in the closed position of the mobile disk isolates the outlet opening from the feed openings.

Abstract: In a "half-turn" type two-disc tap, the two discs are superposed and in contact to adjust the flow rate of a liquid. Each disc has first and second openings situated on respective sides of a predetermined diameter of the disc. The first opening is situated in the central part of the disc and the second opening is situated at the periphery of the disc so that in the closed position of the tap is openings of each disc are separated from the openings of the other disc and in the maximum open position of the tap the first and second openings are respectively and conjointly superposed over an angle just less than 360.degree..

Abstract: A lapping machine having a lapping bed adapted to rotate about a main axis and having an annular lapping surface delimited by an inner circle and an outer circle and into which is cut a spiral groove. Virtually all of at least one confinement ring faces the annular surface and rotates about a fixed axis parallel to the main axis, contains parts to be lapped, and confines movement thereof against the lapping surface. An application disk coaxial with the ring presses the parts in the axial direction agains the lapping surface. The pitch of the groove is not constant whereby between the inner and outer circles, and excluding the inner and outer circles, there is a constant ratio between the pitch ratio .lambda.

Abstract: A tap for liquids comprises a cylindrical hollow body in which are a liquid inlet and a liquid outlet. A fixed disk comprising a single opening for liquid to pass through is disposed in the tap body between the liquid inlet and outlet. A rotary disk comprising a single opening is disposed in contact with the fixed disk, between the latter and the liquid outlet. The rotary disk is rotated relative to the fixed disk by an operating rod between a closed configuration in which each disk closes off the opening in the other disk and an open configuration in which the openings in the disks are at least partially superposed. The opening in the fixed disk has an elongate shape which widens gradually from a relatively narrow first end to a relatively wide second end which is angularly offset relative to the first end by more than 180.degree.. The second end is delimited externally by a circular arc concentric with the disk.