Abstract: In an apparatus for producing perlite granules, having an expansion tube and one or more burners arranged at one end of the expansion tube, the combustion air is blown into the flame through one or more combustion air nozzles. An additional subsonic nozzle is arranged in at least one combustion air nozzle. In a process for expanding raw perlite in the updraft from a flame, with the introduction of oxygen or oxygen-enriched air into this flame, the oxygen or oxygen-enriched air is introduced axially into the flame through subsonic nozzles.

Abstract: A sliding caliper disc brake comprises a torque member, a caliper member slidably mounted on the torque member for straddling a minor portion of the periphery of a rotatable disc, and an actuator for directly urging a friction pad against one side of the disc to cause the caliper member to slide relative to the torque member to apply by reaction an opposite friction pad onto the other side of the disc. The caliper member is slidably mounted on the torque member by a sliding connection which includes a pin element having a portion slidably received in one of the members. The latter pin element is connected to the other of the members by an arrangement which permits lateral displacement of the pin element with respect to the other of the members. Laterally extending friction surfaces are provided on the pin element and on the other of the members. The latter friction surfaces are axially biassed towards each other so as to provide frictional resistance to the aforegoing lateral displacement.