GB396595A - Improvements in air, gas or smoke extractors - Google Patents

Abstract

396,595. Ventilators ; chimney-tops. MACDONALD, D. F., Inverclyde, Kirn, Argyll. Nov. 24, 1932, Nos. 33220/32 and 5825/33. [Classes 25 and 137.] An air, gas, or smoke extractor comprises a dome or cover 1, Fig. 1, depending into an annular or other channel formed between the extractor shaft 2, a baseplate 5 extending outwardly from the shaft, an upwardly-converging outer band 3 extending all round the extractor and an intermediate wall 4 joined directly to the baseplate and to the band and converging downwardly or lying parallel to the extractor shaft. As shown in Fig. 7, the extractor may be provided with an external shield 17 extending over the gap 19 between the dome 1 and the outer band 3a whereby an extraction effect is produced not only by air currents in the plane of the extractor and flowing across the gap 19 but also by currents normal to the plane of the extractor and flowing across the gap 20 formed between the upper edge of the band 3a and the shield 17. In a modified form the band 3 and the intermediate wall 4 are replaced by a single band in the form of a spherical zone joined near the lower edge to the baseplate. In another modification the dome is adjustably supported by means of a screwed rod operating in a central screwthreaded boss carried by a spider within the upper part of the shaft. In a further modification, Fig. 9, an inlet shaft 36 having an upper cap 38 and lower distributing branches 37, 37a is provided centrally of the extractor shaft and serves to carry the dome 1.