Abstract: The invention relates to core used in a mould for casting metal workpieces or molding by injection plastic workpieces for keeping free hollow spaces arranged in the workpieces when the moulds are filled with material.

Abstract: A brush seal (3) is provided to seal two differently pressurized spaces (R.sub.1, R.sub.2) on opposite sides of a rotor (1) cooperating with a stator (2), for example in a gas turbine engine, around a circumferential gap between the rotor (1) and the stator (2). The brush seal (3) includes seal bristles (5) having free ends extending annularly concentrically and parallel to a rotation axis of the rotor (1) and fixed ends received in a seal housing (6). A perimeter rim of the rotor (1) has an axis-concentric circumferential groove (7) therein, and the free ends of the seal bristles (5) reach into this circumferential groove (7). During operation of the rotor (1), fluid boundary layers are formed respectively between the seal bristles (5) and the side walls (9A, 9B) of the circumferential groove (7). The boundary layers (G.sub.I, G.sub.

Abstract: To prepare a ceramic molded article based on silicate or based on alumina, a ceramic starting material containing clay, kaolin, steatite and/or alumina is mixed with a silicate-containing flux, the mixture is made into a molded article and the molded article is heated and dense-sintered. At least some of the flux used is composed of a preferably alkali metal-free glass frit whose beginning of softening is above 850.degree. C.Advantageously, an alkali metal-free boron silicate glass is used in amounts of 0.1-20% by weight of the starting mixture. This process makes it possible to prepare, inter alia, ceramic molded articles comprising a glass phase and a crystalline portion substantially containing Al.sub.2 O.sub.3, in which the glass phase content is 22-34% by weight and comprises 50-68% by weight of SiO.sub.2, 12-22% of Al.sub.2 O.sub.3, 0.1-4.5% of Fe.sub.2 O.sub.3, 0.1-13% of TiO.sub.2, 0.1-23% of CaO, 0.1-9% of MgO, 0-7% of Na.sub.2 O, 0-11% of K.sub.2 O, 0-9% of BaO and 0-23% of B.sub.2 O.sub.

Abstract: For producing moldings composed of cordierite, a batch, which gives the composition of cordierite and contains clay and/or kaolin as well as soapstone and/or talc and also water and an organic aid, is subjected to shear mixing. For this purpose, the batch is placed between 2 bodies, which are at a small distance and move relative to one another, and at the same time the batch is subjected to a shear stress. Preferably, the batch is filled into the gap formed by 2 almost touching cylindrical shear rollers which rotate at different speeds or run in opposite directions. The batch is then deformed to give a molding, and the molding is fired until the cordierite phase is formed.Cordierite bodies of very low coefficients of thermal expansion (for example at most 1.1.times.10.sup.-6 /.degree.C. in all three spatial directions) can be obtained.