Abstract: In a process known of per se for manufacturing plastic pipes, in which a liquid resin, a catalyst and sand and glass fibres are introduced into a centrifugal drum where the pipe is formed as the plastic sets, it was previously customary to start or stimulate the thermosetting process by blowing hot air into the centrifugal drum. The air escaping thereby from the inside of the drum contains solvent vapours which pollute the environment. The improved process consists in that the heat required to start the thermosetting process is no longer supplied from the inside by means of hot air, but by means of hot water which is sprayed onto the outside of the centrifugal drum and is fed through a hot water circuit and, after the exothermic thermosetting begins, heats up again in the latter to at least the original temperature, thereby drawing off heat released by the process. Further cooling is achieved by a cold water circuit, which can be switched on selectively to spray the centrifugal drum.

Abstract: The bearing arrangement is suitable in particular for the mounting of molds for the production of plastic pipes by the centrifugal molding process. It has a ball bearing whose inner bearing ring (5) sits on the pipe (3) which is to be freely rotatably mounted and whose outer bearing ring (7) is held in a support ring (13). Covering rings, one (17, 19) of which on each bearing side is coordinated with the inner (5) bearing ring and one (11, 12) with the outer (7) bearing ring, serve for protection from water and humidity. These covering rings (17, 18, 11, 12) are such that, in pairs, they form a labyrinth seal. The covering rings (11) coordinated with the outer, i.e. the fixed, bearing ring (7) are provided with an injection nozzle (31) for lubricating oil and compressed air and with an outflow orifice (22) for water which has entered and a discharge orifice (36) for the lubricating oil.

Abstract: Glass roving is directed through a soaking tub which is supplied with resin and a setting agent, and trained as a flat-pressed band to a forming unit. The forming unit comprises a two-part mold which is formed by the flange portions of two mold discs and becomes automatically coupled in its closing position. The mold discs are supported on separate coaxial shafts, each of which is associated with a drive for opening and closing the mold. One of the mold parts comprises a cylindrical portion by which, upon opening the mold, the finished sleeve is supported. Pusher pistons provided at this mold part becomes effective automatically as the mold is opened to push off the molded sleeve. All working, drive and conveying means, as well as all switching and control elements are under the control of a common programmable central unit.

Abstract: A tube coupling for coupling together one tube to another tube which have predetermined interior and exterior diameters comprises an outer sleeve which has an interior bore with a sealing element lining the bore of an elastic material. The sealing element has an exterior positively engaged sleeve and for this purpose advantageously includes exterior radially extending ribs which engage into dovetail radially extending grooves of the outer sleeve. The sealing element lining the bore of the tube is of an elastic material and it is formed substantially symmetrically in respect to its radial mid plane and includes at each end a plurality of inwardly directed sets of sealing protuberances following each other with cavities adjacent these protuberances into which the protuberances can be deflected by the engaged tube.