GB460740A - Improvements in sirens - Google Patents

Abstract

460,740. Foghorns. EKMAN, O. I. H. Feb. 12, 1936, No. 4233. [Class 13] [Also in Group XXXIX] In a fluid-operated sound-producing device comprising a diaphragm 1 mounted in a chamber 16 having a constantly open sound emission opening 15 on one side of the diaphragm and a valve-controlled inlet and outlet on the other side of the diaphragm, a chamber 6 for the operating fluid is provided with a series of apertures 13 controlled by a rotary valve 10 which also controls a concentric series of outlet apertures 14 leading from the portion of the chamber 16 behind the diaphragm 1 to the atmosphere or to a pressure below atmospheric. The valve 10 is provided with concentric series of apertures 11, 12 co-operating with the series 13, 14 respectively. The diaphragm is mounted between flanges of the members 2, 3 forming the walls of the chamber 16 and is permitted to have radial expansion by its spacing from a peripheral spacing washer 5 clamped between the flanges. In a modification, Fig. 2, the diaphragm 1 is of square or rectangular shape and is clamped along one edge. Adjacent the opposite edge is provided a series of slots engaged by levers 24 pivoted on knife-edge bearings and adjustably secured to the casing by screws 25. Further modifications are described in which the valve is formed with an apertured flange co-operating with outlet holes in the side wall of the chamber 16 and in which the valve member is mounted in the chamber 6 and is provided with radial grooves associated with apertures in the wall of the chamber 6 and alternating with the apertures 11.