Abstract: A hollow cylinder is held in a vertical orientation and sent continuously through a heating zone for sintering. In a first phase of the sintering operation, the hollow cylinder stands on a support while the upper end (12) of the cylinder is being sintered. In a second phase the cylinder hangs from a hanging element while its lower end (10) is sintered. A vertical rod is fixed to the base on which the lower end is supported, and extends through the hollow cylinder. A retaining ring is fixed inside the upper end of the hollow cylinder. During the first phase, the upper end vitrifies and contracts so that the retaining ring engages the vertical rod. Longitudinal contraction causes the lower end to lift off the base so that the cylinder is suspended during the second phase.

Abstract: The mold wall forms the boundary of a cavity provided with a filling opening and is divided vertically into several segments, which are connected to each other in such a way that they can separate under the action of a force acting outward from the cavity. At least one pretensioned elastic element is installed outside the cavity, which is in effective contact with at least one segment, so that, because of the pretension, an elastic force acts on the segment in the direction toward the cavity. A tensioning element is provided to pretension the elastic element, this tensioning element being installed outside the mold wall to serve as an abutment for the elastic element, and that the elastic element be made of a creep-resistant material.

Abstract: A hollow cylinder is held in a vertical orientation and sent continuously through a heating zone for sintering. In a first phase of the sintering operation, the hollow cylinder stands on a support while the upper end (12) of the cylinder is being sintered. In a second phase the cylinder hangs from a hanging element while its lower end (10) is sintered. A vertical rod is fixed to the base on which the lower end is supported, and extends through the hollow cylinder. A retaining ring is fixed inside the upper end of the hollow cylinder. During the first phase, the upper end vitrifies and contracts so that the retaining ring engages the vertical rod. Longitudinal contraction causes the lower end to lift off the base so that the cylinder is suspended during the second phase.