GB1076222A - Improvements in or relating to a device for the emission of sound waves - Google Patents

Abstract

1,076,222. Geophysical prospecting. INSTITUT FRANCAIS DU PETROLE DES CARBURANTS ET LUBRIFIANTS. July 8, 1964 [July 11, 1963; Jan. 23, 1964], No. 28218/64. Heading H4D. [Also in Division F1] A generator for producing a series of pressurewaves which are detected and recorded in marine or terrestrial seismic exploration comprises a tube in which a combustible mixture is detonated, the lower end of the tube being provided with a valve which is opened by the resulting pressure wave to permit propagation of the wave in a surrounding liquid. In one cycle of operation of the generator, electromagnetic valves 7, 15 and 23 are opened for a time and in a sequence controlled by rotary switching arrangement (42, 43), (Fig. 5), to admit into a combustion tube 1 a charge of a pressurized fuel mixture comprising air from a reservoir 4, oxygen from a reservoir 12, and a hydrocarbon such as petrol from fuel injectors 24 and 25; combustion of an oxygen-rich part of the mixture is then initiated by igniters or detonators 28; propagation of the resulting shock wave down the tube converts the combustion into detonation, and a helical baffle 29 may be used to generate turbulence and thereby promote rapid detonation; a spherical valve member 46, movable in vertical guides 47, is held against a seal 48 on the lower end of tube 1 during the fuelling and combustion stages of the cycle by fluid or spring pressure acting on the lower face 53 of a piston 51, but is displaced downwards by the high-pressure gases in the shock front and thus permits the wave to propagate in the liquid surrounding the lower end of tube 1; combustion products are further exhausted through an electromagnetic valve 41. In various modifications (Figs. 2, 3, 4), a resilient washer (63) may be inserted between the valve member 46 and its supporting piston 51, different methods for applying fluid pressure to the piston 51 may be used, the lower end 52 of a valve housing may be tapered to improved propagation of the pressure wave, and the valve assembly may be surrounded by a perforated metal sphere to reduce spurious propagations due to oscillation of the gasbubble released at each detonation.