Multi=web plate of transparent plastics used in greenhouses etc.

摘要

The plate has elongated parallel hollow chambers (3) of rectangular cross-section separated from each other sideways by webs and defined top and bottom by upper (1) and lower bands (2). The webs (4) are spaced from each other by a distance d and the bands of the hollow chambers form cohesive plastics plates with surface profiling formed on the upper band or on one of the inner bands and designed in the form of a cylindrical Fresnel lens with focal length f. The lens extends along the hollow chambers and collects the light. The focal width f is one to ten times the distance d between the relevant band and lower band. The lower bands are each provided in the area of the webs with parallel infra-red reflecting light strips except for a strip of width b. The width b of the non-reflecting strip is calculated from the following formula: b >= a1-(d/f)