US 3570402 A
Description (OCR text may contain errors)
United States Patent  DETONATOR CONNECTOR 15 Claims, 5 Drawing Figs.
 U.S. Cl 102/22, 102/27, 102/28  lnt.Cl  Field of Search  References Cited UNITED STATES PATENTS 3,173,992 3/1965 Boop l02/20X Primary Examiner Verlin R. Pendegrass Attorney-Cushman, Darby & Cushman ABSTRACT: Detonator connector for rapid assembly of detonator fuse cord and detonator contains two chambers.
These are connected so that detonation of the detonator in one chamber will effect detonation of the fuse cord in the other chamber.
This connector is for use in marine seismographic prospecting and adds to the speed and safety of the operation.
DETONATOJR CGNNE'CTOR This invention relates to a connector for connecting a detonator to a length of detonating fuse cord in marine seismographic prospecting and to a method of seismographic prospecting using said connector.
it has recently been proposed to use a length of detonating' fuse cord as an explosive charge for marine seismographic prospecting in order to diminish the effect on the seismographic record of the expanding and contracting gas bubble produced by firing an explosive charge underwater. in the operation, the detonating fuse cord is stored on reels on a boat and when required an electric detonator is attached to one end of the fuse cord, the electric leading wires of the detonator are coupled in a firing circuit and the reel is thrown into the sea. The movement of the boat unwinds the fuse cord and when the fuse cord is unwoundthe detonator and consequently the fuse cord is fired. The firing circuit incorporates a firing cable which is trailed behind the boat. Usually the cable has a single conductor only, to which one detonator leading wire is attached, the second leading wire being earthed in the sea water to provide an earth return. In this case the fuse cord and detonator leading wire are usually connected to the firing cable by a slipring which, when the reel is thrown into the water, slides down the cable and is engaged by a stopper such as a metal hook forming an end portion of the firing cable.
It is an object of this invention to provide a connector to permit rapid assembly of detonating fuse cord and detonator in marine seismographic prospecting operations.
In accordance with this invention a connector for connecting a detonator to detonating fuse cord comprises a body member formed with two chambers whereinto the detonator and fuse cord respectively may be slidably inserted, said chambers being connected so that detonation of the detonator in one chamber will effect detonation of the fuse cord in the other chamber, which body member is also adapted to retain the detonator and the fuse cord in said chambers.
in a preferred form the chambers are constituted by two substantially parallel intercommunicating cylindrical bores in the body member, longitudinal communication being advantageously provided by forming the chambers as overlapping ores. The body member may be formed so as to retain a detonator as an interference fit but in a preferred form it is formed with one or more external lugs, each having a groove wherein a leading wire of an electric detonator may be anchored. in order to retain the fuse cord in position in its chamber, said chamber preferably extends continuously throughout the length of the body member and a third chamber is formed in the body member into which third chamber the end of the fuse cord may be inserted after being drawn through the body member and doubled backwards. As a further precaution the double-backed end portion of the fuse cord may advantageously have a metal sleeve crimped over it to prevent bending of that portion of the fuse cord. When the sleeve is formed as an end cap it also prevents water from contacting the explosive charge of the fuse cord ut the fuse cord may also be protected from water by a waterproofing composition disposed in the third chamber or over the end ofthe fuse cord.
A portion of metal foil, to which the earth leading wire of the detonator may be attached, may advantageously be attached to the body member to provide a larger area for the earth return. The foil may, for example, be disposed as a sleeve on a portion ofthe body member.
The body member is preferably formed from a resilient plastics material such as polyethylene.
in order to facilitate connection of the fuse cord and detonator to the firing cable, the connector is advantageously provided with one or more metal tie rods, one end of each being preferably moulded into the body member. The free end of the tie rod may be formed as a slipring, adapted in operation to slide down the cable.
A preferred connector has two tie rods each attached at one end to the body member and having its other end formed as a hook, the hooks being adapted to be hooked together in operation to hold the tie rods around. the firing cable so as to act as a slipring. This slipring slides down the firing cable and engages the stopper on the end of the cable. The fuse cord charge is then detonated by passing an electric current through the detonator. The subsequent explosion ruptures the body member of the connector and breaks the slipring so that the broken slipring falls away from the cable. Thus there is no debris left at the end of the firing cable and there is consequently no necessity for special facilities for the discharge of debris. In an alternative form of connector, the free end of a tie rod may be in the form of a hook which in operation may engage a slipring already on the cable.
The invention also includes a method of seismographic prospecting wherein a length of detonating fuse cord is connected to a detonator by means of a connector of the inventron.
Further features of the invention are included in preferred embodiments which are hereinafter described, by way of example only, with reference to the accompanying drawings wherein FIG. 1 is a sectional elevation of aconnector;
FIG. 2 shows a cross section of the connector of FIG. 1 on the line II-II;
FIG. 3 shows diagrammatically an elevation of the connector of FIG. 1 with a detonator and fuse cord inserted therein and attached to a firing cable for firing;
FIG. 4 shows an elevation of another connector with a detonator and fuse cord inserted therein; and
FIG. 5 shows an elevation of a further connector.
In the description like numbers refer to like parts.
The connector shown in FIGS. 1 and 2 has a body 10 of moulded polyethylene having longitudinal bores or cylindrical chambers 12, 13 and 114 formed therein, and having two external lugs 15, each having a groove 16 for anchoring detonator leading wires. Chamber T2 is adapted to hold a detonator and chamber 13, which is formed so as to overlap chamber l2 and communicate therewith, is adapted to hold detonating fuse cord. Chamber M extends only partly through the body and is adapted to hold detonating fuse cord as an interference fit. A metal tie rod l7 is located at one end in the body 10 by moulding therein, and its other end is curled to form a splitring 18.
In marine seismic prospecting operations the connector is used as shown in FIG. 3 to assembly a length of the detonating fuse cord 19 and a detonator Ztl in detonation transmitting relationship and to attach the assembly to a heavy firing cable 21. An end of the fuse cord 1.59 is pushed through chamber 13, doubled backwards and inserted into chamber 14 where it becomes firmly held. Chamber it may advantageously contain a waterproofing composition to protect the end of the fuse cord l9 from sea water. The detonator 20, which has two leading wires 22, 23 insulated for part. of their length but having bared end portions, is inserted into chamber 12 and the leading wires are forced into the grooves lb. The bared end of wire 22 is wound around the tie rod 1.7 and wire 23 is wound around the body 10 with its bared end free to trail in the sea to provide earth" return. The splitring 18 is attached to a metal slipring 24 on cable 21 which is trailed from a ship and, when the assembled fuse cord l9 and detonator 20 are placed in the water, the slipring 24- travels down the cable 21 and becomes engaged by a hook 25 at the end of cable 21. The assembly is thereby firmly attached to the cable and is towed by the ship, and the detonator 2b is also in electrical contact with the cable 21 and may be fired by the passage of a current through the cable.
The connector may conveniently be supplied to the ship either attached to the length of detonator fuse cord, in which case the detonator is attached to the connector on the ship, or with the detonator already in position, in which case the fuse cord is fitted on the ship. If the latter method is adopted, the
modification of the connector shown in FIG. 4 may be advantageously used. In this connector, a metal band 26 is fitted around the body 10 and the bared end of wire 23 is wound around it and firmly held by soldering, this arrangement providing improved earth" return. The wire 22 is also soldered to a tie rod 17.
The connector shown in FIG. has two metal tie rods 17 moulded in the body and formed with hooks 27 at their free ends. The tie rods are curved to enable them to encircle a firingcable as a sliping when the hooks 27 are interlocked. When the detonator 20 is fired and the fuse cord 19 explodes, the connector body 10 is destroyed and the tie rods 17 are separated and fall away from the hook 25.
1. A connector, for connecting a detonator to a detonating fuse cord in marine seismographic prospecting, comprising a body member formed with two substantially parallel intercommunicating bores which permit an electric detonator and a length of detonating fuse cord respectively to be slidably inserted therein and held in such proximity to each other that detonation of the detonator causes detonation of the fuse cord, and at least one metal tie rod attached by one of its ends to the body member and having a free end adapted to join the connector to an electric firing cable.
2. A connector as claimed in claim 1 wherein the body .member comprises mouldable plastics material and one end of the tie rod is moulded into the body member.
3. A connector as claimed in claim 1 wherein the body member is formed of resilient plastics material.
4. A connector as claimed in claim 1 wherein the body member is formed from polyethylene.
5. A connector as claimed in claim 1 wherein the bores overlap partially in cross section.
6. A connector as claimed in claim 1 wherein the body member is adapted to retain a detonator as an interference fit.
7. A connector as claimed in claim 1 wherein the body member is formed with at least one external rigid lug having a groove wherein a leading wire of an electric detonator may be anchored.
8. A connector as claimed in claim 1 wherein the bore for holding the fuse cord extends continuously throughout the length of the body member and the body member defines a third bore into which the end of the fuse cord may be inserted after being drawn through its respective bore in the body member and doubled backwards.
9. A connector as claimed in claim 1 including a portion of metal foil attached to the body member for providing a larger area for electrical grounding.
10. A connector as claimed in claim 9 wherein the foil is disposed as a sleeve on a portion of the body member.
11. A connector as claimed in claim 1 wherein the free end of the tie rod is formed as a slipring adapted in operation to slide down a firing cable and engage a stopper on'the cable end.
12. A connector as claimed in claim 1 having two tie rods, the free end of each rod being formed as a hook, the hooks being adapted to be hooked together in operation to hold the tie rods round an electric firing cable so as to act as a slipring and the body member being destructible by the explosion of a detonator and the portion of fuse cord which, in use, is retained within the body member so as to release the tie rods when the detonator and fuse cord are exploded.
13. A connector as claimed in claim 1 wherein the free end of the tie rod is formed as a split ring adapted in operation to engage a slipring on an electric firing cable.
14. An assembly for use in marine seismographic prospecting comprising a connector as claimed in claim 1 having inserted therein an electric detonator and a length of detonating fuse cord, an end portion of both electric leading wires of the detonator being bared and one bared end portion of one of the leading wires being in electrical contact with the metal tie rod.
15. An assembly as in claim 14 including an electrical firing cable and further including means mechanically and electrically connecting the free end of the tie rod to the cable for sliding movement therealong.