GB777547A - Improvements in or relating to explosive well-perforating assemblies - Google Patents

Abstract

777,547. Blasting and mining cartridges. WELEX JET SERVICES, Inc. Sept. 26, 1955 [Oct. 8, 1954], No. 27353/55. Class 9 (1). Apparatus for perforating wells comprises a carrier 14 in which shaped charges 18 are pivotally mounted together with arming means 28, firing elements within the apparatus and controlled ' from without being inoperable until the charges have been moved from a position aligned with the longitudinal axis of the carrier through a predetermined angle. Attached to the carrier 14 is a firing head connected to a detonating fuze cord 16 which terminates in a sealed end 104 in the nose 84 of the carrier after passing between flanges 62, Figs. 4, 6, extending from the rear casing 64 of each charge 18. Detents 20 on the flanges interlock as in Fig. 3 to maintain the charges in alignment, the topmost charge engaging the arm 28 and the lowermost charge 18 being held by an explosive squib 22 connected by an electric conductor 24 to a switch 26 in the firing head. Apertures 50 in the carrier allow the charges 18 to be pivoted to the horizontal, Fig. 4, by springs 54 when the squib 22 is fired. The arm 28 is connected through a plunger 30 to the switch 26 and must move through a predetermined angle to close the main firing circuit and so arm the device. Within the casing 64 of each charge is a primary charge 74, Fig. 6, which is initiated by the fuze 16 and a main charge 72 covered by a casing 76 and having a conical cavity fitted with a liner 70. A sealing ring 78 is placed between the casings 64, 76. Within the head, Fig. 3, is a blasting cap 92 and a booster charge 94 connected to the fuze cord 16. The switch 26 comprises a double pole, double throw switch connected to a conductor 12, Fig. 11, passing through the suspension cable for the apparatus and initially in circuit with the squib 22 through the wire 168 and conductor 24. On firing the squib, the lowermost charge 18 is released and moves to the horizontal followed successively by the charges above. The arm 28 then moves out, Fig. 4, and the plunger 30 moves the switch 26 to the up-position, so that the squib circuit is opened and the detonator circuit closed by the members 154, the apparatus is then ready for firing. In operation, the assembly is lowered through tubing 32 to the perforating position and after the squib is fired, the apparatus may still be withdrawn without firing the charges. During withdrawal, the edge of the tube 32 forces the arm 28 and charges 18 into interlocking engagement and an operator grips the lowermost charge as it leaves the tube, to prevent disengagement of the charges. The assembly below the firing head is expendable and may be of brittle aluminium,.the head 10 being of steel. To extend the assembly, an additional carrier 14 may be connected to the end of the first after removal of the nose 84. The apparatus may be adjusted so that the charges move to a pre-arranged position which is not horizontal. A modified carrier comprises side bars on which the charges are pivoted, the charges being separated by discs through which pass the fuze cord 16 and conductor 24. Specification 768,400 is referred to.