Abstract: The invention relates to a method in connection with a roof drainage apparatus and a roof drainage apparatus. The invention comprises a trough (2) recessed in a roof structure (1), an opening (3) arranged in the bottom of the trough, a water-outlet tube (4) joined to the opening and a means (5) for changing an open water flow into a closed flow when the water flow is increasing. For intensifying the drainage, an element (6) is positioned in the water-outlet tube (4) at a throat after the opening (3), by means of which element the cross-sectional area of the water-outlet tube (4) is regulated in such a manner that the shape of the cross-section of the water-outlet tube (4) remains substantially unchanged at the regulation.

Abstract: A method and an apparatus for measuring the wall thickness of a plastic article, particularly of a hollow rotation-symmetrical plastic article. According to the method, the wall of the plastic article is subjected to infra-red radiation and the intensity of, e.g., the continuously transmitted radiation is measured at preselected points, said intensity being a function of the wall thickness to be measured. At the same time, on one hand, the plastic article and, on the other hand, a radiation source and/or a radiation detector are set in an axial and rotational movement in relation to each other.