GB852428A - Motor-driven drill for placing explosive charges in seismic prospecting - Google Patents

Abstract

852,428. Borehole apparatus. JERSEY PRODUCTION RESEARCH CO. Dec. 13, 1957 [Jan. 14, 1957], No. 38807/57. Classes 9(1) and 85. [Also in Groups XXIV and XXVI] Seismic-prospecting apparatus for placing explosive charges in the seabed comprises a motor housing 13 suspended from a cable (not shown in Figs. 3 and 4) and having an extension 21 of reduced section surrounding a drive shaft 27 detachably coupled to the shaft 61 of a bit 60. Furthermore an annular container 24 filled with dynamite and provided with barbs 25 is supported on the extension 21 by means 59 such as a frangible washer fitted in a groove in a shoulder 53. Resting on the container 24 is a receptacle 19 within which is a reel of wire 45 connected to an igniter 47 embedded in the explosive. A stop 43 prevents upward movement of the receptacle. The bit 60 has spaced mutually perpendicular blades 29, 31, the blade 31 being half the length of blade 29 and each blade is of small pitch relative to a plane perpendicular to the shaft 27. The motor may be electric but a water-driven turbine is preferred. When the drill has entered to the required depth, the motor is withdrawn. Since the barbs 25 prevent upward movement of the container 24, washer 59 breaks and the container 24 slides off the extension 21. The receptacle 19 moves into abutment with the shoulder 53 and the wire 45 pays out as the casing 13 rises so that when the receptacle 19 reaches the surface, the charge can be detonated at any time. The pull on the shaft 27 fractures a shear pin 65 coupling the bit to the shaft 27. In Fig. 4 the shaft 27 is hollow and is screwed into a casing 71 surrounding a deformable sleeve 79 on the bit shaft 61. A sheer pin 82 holds the bit in a plug 81 closing the lower end of casing 71. Water under pressure entering the casing 71 through the shaft 27 forces a piston 75 against the sleeve 79 which may be rubber, so that the sleeve is deformed to give a rigid connection between the shaft 61 and the casing 71.