GB1351494A - Automobile vehicles electroacoustical warning devices - Google Patents

Abstract

1351494 Electric horns FABRICA ESPANOLA MAGNETOS SA 22 April 1971 [30 April 1970] 10806/71 Heading G5J An electro-acoustic warning device, Fig. 1, of the type having a vibrating diaphragm (crosssectional area S 1 ) a resonator tube (crosssectional area S 2 ; length l 1 ) and a bell formed of a conical portion (length l 2 ) and an exponentially shaped portion (length l 3 ) the maximum cross-sectional area of said portions being S 3 and S 4 respectively, is made to obey the following relationships, all measurements being in centimeter units (S 3 - S 2 )/l 2 = 0À9 for low pitched sounds 1À1 for high pitched sounds # 0 /l 3 = 17 for low pitched sounds 14 for high pitched sounds and S 4 /S 3 = 11À6 wherein # 0 is the wavelength in cm. of the device's fundamental frequency. For good operation the following should also apply, the coefficient being given within a tolerance of 10% and the parameters being measured in centimeters : where V 2 is the volume (cm.<SP>3</SP>) of the compression chamber. The horn may have a flat plastics piece, e.g. polypropylene, in the trumpet mouth to lie across the mouth to cause the sound output to transmit therethrough to attenuate high frequencies. The thickness of the piece is less than # 0 . To reduce the magnetic reluctance a flanged collar may be inserted between the vibrating diaphragm and the windings so as to increase the "inter gap surface". A special piece made of plastics, e.g. Bakelite (Registered Trade Mark), Fig. 6 (not shown), seats the vibrating diaphragm and is supported on the body.