GB766872A - Improvements in or relating to cowls for flues and ventilating ducts - Google Patents

Abstract

766,872. Flue and ventilating duct cowls. LACHMANN, G. V. Oct. 28, 1953 [Aug. 6, 1952], No. 19759/52. Class 25 A continuously convexly curved surfaced cowl is apertured in such a manner that for any direction of the outer flow, e.g. wind flow, there will be produced over the major portion of the cowl's surface a static pressure below the free-stream static pressure of the outer flow. The cowl shown in Fig. 1 comprises a hollow cylindrical shaft 1 having a hemispherical dome 2 and longitudinally arranged slits 4 partly edged with protuberances 5. A ridge 3 connects shaft and dome. In the modified cowl of Fig. 2, the ridge 3 is formed by a wire ring 15 and inclined strips 16 are fixed inside the cowl to prevent any rain which may enter slits similar to 4, reaching the flue 12. The cowl shown in Fig. 3 comprises an elliptical cross-sectioned shaft 20 arranged over three square cross-sectioned flues 17, 18, 19, the shaft having slots 22 provided with flanges 20a and a detachable lid 23 in its half-ellipsoidal dome cap 21. Any rain entering the cowl is kept from the flues by a hollow elliptical cross-sectioned screen 24. A screen similar to 24 but of circular cross-section may be provided in a cowl having a cylindrical shaft. Detachable lids such as 23 may be provided in other cowl forms. The shaft of cowl 29, Fig. 4, covering four square cross-sectioned flues, is formed of vertical members 30 of lenticular cross-section topped by a dome 31. The cowl, Fig. 5, has a perforated shaft 33 closed by a dome 34, a wind-directed rotatable shaft 35 mounting a curved shield 38 being fitted such that apertures on the windward side of the shaft are shielded. In a modification of this cowl, the shield 38 comprises two half-portions spring-urged against the inner surface of the shaft 33. The cowl of Fig. 7 comprises a fixed perforate shaft 44 and a rotatable wind-directed partly perforate shaft 43, the wind-vane 46 being so arranged that the imperforate portion 45 of shaft 43 shields the apertures of 44 on the windward side..