NZ227628A - Explosives detonator made from two hollow portions fitting together spigot/socket fashion - Google Patents

Description

Priority Oate(s): .?;* Complete Specification Filed: • i-1 . . • . I Class: rr.A2.SA[ &.<+■■ Publication Date: .. a 5 .<iu.ii. m P.O. [journal. No: i . p \ If ,16 JAN 1989,' \L..

NEW ZEALAND PATENTS ACT, 1953 22 7 6 2 No.: Date: COMPLETE SPECIFICATION EXPt0StY£S DETONATOR FOR EXPLSOSIVCS )I/We, AECI LIMITED of 16th Floor, Office Tower, Carlton Centre, Commissioner Street, Johannesburg, Transvaal, Republic of South Africa, a company registered in the Republic of South Africa hereby declare the invention for which £ / we pray that a patent may be granted to jpfc/us, and the method by which it is to be performed, to be particularly described in and by the following statement:- AECI.638 22 7 6 2 8 THIS INVENTION relates to a detonator for explosives; and to a method of making such detonator.

According to one aspect of the invention there is provided a detonator which comprises a housing made up of at least two hollow portions fitting together spigot/socket fashion, one of the portions containing a base charge and having an opening facing into the adjacent portion, and another of the portions containing initiating means for initiating the detonator.

In an embodiment, which we presently prefer for safety reasons, the portion containing the base charge has its opening facing into and fitting within the portion containing the initiating means. In an alternative embodiment the portion containing the initiating means may fit within the portion containing the base charge. In this embodiment care must be taken, particularly if the portion containing the base charge^ also includes a booster, to avoid an accidental explosion rue to physical contact of the spigot portion with sensitive booster material. In either embodiment, the spigot/socket fitting may be a tight sliding fitting.

The detonator may be an instantaneous detonator, in which case the housing may comprise two portions, namely a cup portion containing the base charge whose open end provides said opening, and an initiating portion which may be tubular., iiaving an open end which fits together spigot/socket fashion with the cup portion and a sealed end into which projects the initiating means such as an electrical fuse head or the end of a length of low energy shock tube such as NONEL tube. Instead, the initiating means may be a safety fuse. The initiating portion may have a diaphragm or partition which closes it off between its ends, so 227628 3 that the cup-shaped portion is isolated by this diaphragm from the initiating means.

Typically, however, the detonator will be a delay detonator, in which case the housing may comprise three portions, namely said initiating portion, said cup portion, and, therebetween, a preferably tubular central portion, the portions fitting together in series spigot/socket fashion. In this case the central portion will contain a delay element and, optionally, a sealer element adjacent the initiating portion.

Whether for an instantaneous or a delay detonator, the housing portions are conveniently mouldings of a suitable plastics material, eg a thermoplastics material which can be sealingly crimped, with the use of heat, around the initiating means, or the thermoplastic material may be heat sealed to the intiating means. In every case, the cup portion, which may optionally contain a primer or booster adjacent its mouth in addition to the base charge, is preferably received as a spigot in a socket formed by the adjacent portion. Similarly, in every case the initiating portion is preferably a socket portion within which the adjacent portion is received as a spigot. Thus, in the case of an instantaneous detonator, the cup portion may be received in the initiating portion, its open end or mouth abutting or closely spaced from the diaphragm or partition; and in the case of a delay detonator, the central portion may be received in the initiating portion, abutting or closely spaced from the diaphragm, the cup portion being received in the opposite end of the central portion, abutting the delay element. In this case the initiating portion may have a circumferentially extending radially inwardly projecting annular shoulder in its interior spaced between its ends, the diaphragm closing off the central opening of the annular shoulder and the shoulder acting as a stop for locating the portion which is received in the initiating portion in the correct position. When the diaphragm is omitted, this shoulder may still be retained to function as a stop in this fashion. • 22 7 4 However, instead of the initiating portion having an open end and a sealed end which nay be crimped around the initiating means, the sealed end may instead merely receive the end of an incendiary fuse, which is frictionally or adhesively held therein.

According to another aspect of the invention, a method of making a detonator comprises loading a base charge into a hollow housing portion having an opening, separately assembling at least one other hollow housing portion of the detonator, which is connectable spigot/socket fashion to the portion containing the base charge, then connecting the portions together spigot/socket fashion, one of which contains an initiating means, so that said opening faces into the portion containing the initiating means.

When there are two portions .the .portion containing..the base., charge is preferably fitted into the portion containing the initiator charge in spigot/socket fashion. When there are three portions the portion containing the base charge is preferably fitted as the spigot into one end of a central portion, the other end of the central portion being fitted as the spigot into one end of the portion containing the initiating portion.

The detonator may thus be of the type described hereinabove, and may comprise, depending on whether it is an instantaneous detonator or whether it is a delay detonator, two or three housing portions, namely an initiating portion, a cup portion and, for a delay detonator, also a central portion. In either case, the last method step will be connecting the cup portion spigot/socket fashion to the initiating portion or to the central portion, as the case may be, by means of a frictional fit or optionally with the use of adhesive to strengthen the spigot/socket connection.

The various portions may typically be moulded from thermoplastics material and the initiating portion may be moulded 22 7 6 2 as a hollow tube with said diaphragm between its ends. A NONEL tube or a fuse head will then be connected to the initiating portion by locating the open end of the NONEL tube or the fuse head in the interior of the initiating portion, and welding, crimping or sealing the sealed end of the initiating portion with heat, around the NOBEL tube or the electrical leads of the fuse head, where they intrude into the initiating portion.

When the initiating means is an incendiary fuse it may, as indicated above, instead be held in the sealed end of the initiating portion by friction or adhesive.

The opposite or open end of the initiating portion may then be slid as a socket over the cup portion or central portion as far as the diaphragm permits, to be held in position by friction and/or adhesive. Naturally, the central portion, when used, will have the delay element and optional sealer element loaded therein beforehand, the delay element being recessed from one end of the central portion to provide a space to receive the cup portion; and the delay element (or the sealer element if used) may extend up to the other end of the central portion so that it is adjacent the diaphragm when the detonator is assembled.

By following the above procedure safety is promoted as the initiating and/or central portions can be manufactured in relatively safe circumstances, remote from the cup portion, and the cup portion with booster charge will be fitted to the remainder of the detonator as a final manufacturing step. Work done in the vicinity of the base charge is thus kept to a minimum and is confined to loading of the base charge, and booster or primer charge if employed, into the cup portion, and to connecting the cup portion to the remainder of the detonator.

The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings., in which: Figure 1 shows a schematic sectional side elevation of a detonator in accordance with the invention; 6 22 7 6 2 8 Figure 2 shows a similar view of another detonator in accordance with the invention; Figure 3 shows a partial sectional side elevation of a further detonator in accordance with the invention; Figure 4 shows a view similar to Figure 3 of a yet further detonator according to the invention; and Figure 5 shows a view similar to Figure 2 of a still further detonator according to the invention.

In Figures 1 and 2 of the drawings, reference numeral 10 generally designates a detonator in accordance with the invention. The detonator comprises a housing 12 of thermoplastic plastics material, made up of three moulded portions, namely an initiating portion 14, a central portion 16, and a cup portion 18. The portions 14, 16 and 18 are cylindrical in shape and circular in cross section, the portion 14 being in the form of a tube whose interior is closed off by a diaphragm or partition 2 0 and whose one end is radially inwardly crimped and heat welded or sealed at 22 as described hereunder. The diaphragm 20 closes off the central opening of an annular shoulder 21 in the portion 14. The central portion 16 is in the form of a more or less right cylindrical tube, and the cup portion 18 is in the form of a cup closed at one end by a base 24 and open at its opposite end.

As shown in Figures 1 and 2, the cup portion 18 is received spigot/socket fashion in one end of the central portion 16, the opposite end of the central portion 16 being received spigot/socket fashion in the end of the initiating portion 14 on the side of the diaphragm 2 0 and shoulder 21 opposite the crimped end 22. The end of the central portion 16 which is received in the initiating portion 14 is shown hard up against the shoulder 21, closely spaced from the diaphragm 20. The spigot/socket connections provide a frictional fit, and are strengthened by the employment of adhesive at 26. 7 22 7628 Referring now specifically to Figure 1, the crimped end 22 of the initiating portion 14 is shown crimped around initiating means in the form of a low intensity NONEL shock tube 28 whose free end 3 0 intrudes into the initiating portion 14 on the side of the diaphragm 20 opposite the central portion 16, and is closely spaced from and directed at the centre of, said diaphragm 20. The crimped portion 22 is sealed around the tube 28.

In Figure 1 the central portion 16 contains a delay element comprising a metal sleeve 32 having an incendiary core 34. This delay element is recessed from the end of the portion 16 which receives the cup portion 18 to provide a space for receiving said cup portion 18. At the opposite end of the central portion 16, adjacent the diaphragm 20, is provided a sealer element which comprises a metal annulus 3 6 having a core 38 of incendiary material which leaves a solid oxide residue when it is burnt. The free end of the shock tube 3 0 is directed concentrically along the detonator, in axial alignment with the incendiary core 38. The sealer element is in abutment with the delay element, and extends to the end of the central portion 16 adjacent the diaphragm 20.

In Figure 1 the cup portion 18 is shown containing a pentaerythritol tetranitrate (PETN) base charge 40, at the blind or closed end 24 of the cup portion 18, and, in abutment therewith, a booster or primer charge 4 2 extending to the opposite or open end of the cup portion 18, which faces into the central portion 16, so that the booster charge 42 is in abutment with, or is closely spaced from, the delay element and its incendiary core 34.

Turning to Figure 2, the construction of the detonator is similar to that of Figure 1, except that the NONEL shock tube 28 is replaced by a fuse head 44, provided with electrical leads 46. The fuse head 46 is in the interior of the-initiating-portion 14, on the side of the diaphragm 20 opposite the central portion 16, and the crimped end 22 of the initiating portion 14 is crimped 22 7 6 2 8 8 around said leads 46. A tubular plug 47 is shown around the leads 46 in the crimped end 22. As far as the cup portion 18 and base charge are concerned, their construction is substantially the same as that shown in Figure 1.

The booster or primer 42 will typically be lead azide, lead styphnate or the like.

Turning to Figure 3, in contrast to the delay detonators shown in Figure 1 and in Figure 2, part of an instantaneous detonator is shown. In this case, the initiating means may be either a NONEL shock tube or a fuse head as shown in Figures 1 or 2, or a tube as shown in Figure 4, the initiating portion 14 being essentially similar to that of Figure 1 or Figure 2 or Figure 3, as the case may be; and the cup portion 18, with its booster charge 42 and base charge 40, is essentially similar to that of Figures 1 and 2. It should be noted in particular, however, that the entire central portion 16 is omitted, so that there is no delay element or sealer element.

Turning to Figure 4, the construction is substantially similar to that of Figure 3, and, once again, the same reference numerals are used to designate the same parts, unless otherwise specified. In Figure 4 the diaphragm is shown to be omitted, the central opening of the shoulder 21 being left open. Furthermore, the detonator of Figure 4 is shown with an incendiary fuse 48, instead of the shock tube 30 of Figure 1 or the fuse head 44 of Figure 2. The end of the fuse 48 is received in the end of the portion 14 on the opposite side of the shoulder 21 from the cup portion IE. The fuse 48 abuts the shoulder 21 and is adhesively held in position in the portion 14 by adhesive at 50, or, if the fuse 48 is coated with thermoplastic plastics material, it can be heat welded to the portion 14 at 50.

Turning to Figure 5, the construction shown is similar to Figures 1 and 2, and, except as specified hereunder, like reference numerals refer to like parts. 9 22 7 6 Unlike Figures 1 and 2 but similar to Figures 3 and 4, the central portion 16 is omitted, the cup portion fitting spigot/socket fashion directly into the initiating portion 14. Unlike Figures 1 to 3 but similar to Figure 4, the diaphragm 2 0 is omitted. Similar to Figure 2 a delay element 32, 34 is shown, and there is no sealer element 26, 38. To accommodate the delay element 32, 34, the socket of the portion 14 which receives the portion 18 is substantially longer than in the constructions of Figures 3 and 4.

With regard to Figures 1 and 2, it should be known that the sealer element is employed in Figure 1 when the initiating means is a shock tube, to guard against loss of pressure via the shock tube when the core 34 of the delay element burns. This loss of pressure is not a problem with the construction of Figure 2 as there is no shock tube via which gases can escape, so that the sealer element is omitted.

With regard to Figures 1 to 5, it will be appreciated that various configurations are shown for purposes of illustration, and various other combinations are possible. Thus the diaphragm 2 0 can be omitted from Figures 1 to 3 so that they only have the shoulder 21 as shown in Figures 4 and 5 and, similarly, diaphragms similar to the diaphragms 2 0 of Figures 1 to 3 can be employed in Figures 4 and 5. If desired the initiating means of Figure 5 can be shock tube as shown in Figure 1 or a fuse head as shown in Figure 2 (in which case a sealer element such as that shown at 36, 38 in Figure 1 will be provided between the delay element 32, 34 and the shoulder 21), or the initiating means may be a fuse as shown in Figure 4, in which case the portion 14 will have no crimping at 22. In other words, in each embodiment the diaphragm 2 0 may be present or omitted, as desired; a delay element may be present or omitted as desired; a shock tube, electrical fuse head or incendiary, tube -feed jr.ay be -used as desired as the initiating means, the sealer element 36, 38 being used whenever a shock tube is present and the crimping 22 being 22 7 6 28 present when a shock tube or electrical fuse head is used and being absent when an incendiary tube is used; and the body 12 may, as desired, be either of two-portion construction as shown in Figures 3 to 5 or of three-portion construction as shown in Figures 1 and 2, with the length of the socket of the portion 14 depending on whether a delay element is present or absent, being longer to accommodate a delay element that when there is no delay element.

In use, with reference to Figure 1, a detonation issuing from the free end 3 0 of the shock tube 28 will penetrate the diaphragm 2 0 and initiate the core 38 of the sealer element. This in turn will initiate the core 34 of the delay element, which will after the usual delay initiate the booster charge 42, this in turn initiating detonation of the base charge 40. In the case of Figure 2, electrical initiation of the fuse head 44 will cause deflagration thereof, which will penetrate the diaphragm 20 and initiate deflagration in the core 34 of the delay element. This in turn will initiate the booster charge 42 which initiates detonation of the base charge 4 0 after the usual delay. In the case of Figure 3 initiating of either the shock tube or fuse head, as the case may be, will penetrate the diaphragm 20 and will cause instantaneous detonation of the booster charge 4 2 and then the base charge 40. In Figure 4 the fuse 48 will burn up to its end adjacent the shoulder 21 and will initiate, without a delay, the booster charge 42 which in turn instantaneously initiates the base charge 4 0. In Figure 5 a fuse head, shock tube or fuse, when used, will in each case initiate the delay element 32, 34 directly, which, will after a delay, initiate the booster charge 42 and base charge 40.

During manufacture of the detonators, in each case the base charge and optionally the booster charge will be loaded into the cup portion 18 at a location remote from where the remainder of the detonator is constructed. The initiating portion 14 in turn will be heat sealed or crimped onto the initiating means (either the shock tube of Figure 1 or the fuse head of Figure 2) or will be adhesively secured to the fuse 48 (Figure 4) at 50; and a delay element and optionally a sealer element will be loaded in the portion 14 or the portion 16 when used, to occupy the positions shown in the drawings. The central portion 16 will when used be fitted spigot/socket fashion into the initiating portion 14 as shown, and adhesively secured thereto at 26.

Finally, the cup portion 40 will be slid into the recess at the end of the central portion 16 remote from the initiating portion 14 (Figures 1 and 2) and adhesively secured thereto at 2 6 or, in the case of Figures 3 to 5, the cup portion will be slid directly spigot/socket fashion into the end of the initiating portion 14 on the side of the shoulder 21 remote from the initiating means, and adhesively secured thereto as at 26, either in abutment with the shoulder 21 (Figures 3 and 4) or in abutment with the delay element when used (Figure 5).

In every case the last step in manufacture will be connecting the cup portion 18 and base charge to the remainder of the detonator. This promotes safety. In this regard it should also be noted that, while in principle the end of the central portion 16 could be slid as a spigot into a socket constituted by the open end of the cup portion 18, with the delay element extending to that end of the central portion 16 and the base charge or primer charge being recessed from the open end of the cup portion 18, and while in principle the portion 14 of Figures 3 and 4 could be slid into the cup portion 18 thereof, this is not preferred, as it permits contact and friction between the end of the portion 14 or 16 and the base charge or booster/primer charge. This contact and friction is avoided by inserting the cup portion 18 as a spigot into the socket constituted by the central portion 16 or the portion 14, as the case may be, as shown in the drawings and as described above.

Claims (23)

1. AECI.638 i2 _ 227628 WHAT^We CLAIM IS: * GhftTMS \;1.
2. A detonator for explosives comprising a housing made up of at least two hollow portions fitting together in a tight sliding fitting, spigot/socket fashion,;one of the portions containing a base charge and having an opening facing into the adjacent portion,;and another of the portions containing initiating means-for initiating the detonator.;2.
3. A detonator according to claim 1, wherein the portion 10 containing the base charge has its opening facing into and fitting within the portion containing the initiating means.;3.
4. A detonator according to claim 1 or claim 2, in which the housing comprises two portions,;namely a cup portion containing the base charge whose open 15 end provides said opening facing into the adjacent portion,;and an initiating portion having an open- end which fits together spigot/socket fashion with the cup portion and a sealed end into which the initiating means projects.;4.
5. A detonator according to claim 3 in which the initiating 2 0 portion is tubular.;ft;25;5.
6. A detonator according to claim 3 or 4, in which the initiating portion has a diaphragm or partition which closes off the initiating portion between its ends so that the cup-shaped portion is isolated by this diaphragm from the initiating means.;227628;13;
7. 7. A detonator according to any of claims 2 to 6, in which the initiating means comprises a low energy shock tube or safety fuse.;
8. 8. A detonator according to claim 1 or claim 2, in which the housing comprises a cup portion containing the base charge and having an opening facing into an adjacent portion,;a central portion having one end fitting spigot/socket fashion into the cup portion, said central portion containing a delay element,;and an initiating portion fitting in spigot/socket fashion with the other end of the central portion.;
9. 9. A detonator according to claim 8, in which the central portion contains a sealer element adjacent the initiating portion.;
10. 10. A detonator according to claim 8 or 9, in which the central portion is received at one end in the initiating portion, and the cup portion is received in the opposite end of the central portion.;
11. 11. A detonator according to any one of the preceding claims, in which the housing portions are mouldings of a plastics material.;
12. 12. A detonator according to claim 11, in which the plastics material is a thermoplastics material.;
13. 13. A detonator according to claim 12 in which the thermoplastics material is sealingly crimped or heat sealed.;
14. 14. A detonator according to any of claims 3 to 13 in which the cup portion contains a primer or boost*er adjacent its mouth, in addition to the base charge. ■' MAY 1991^1 227 (528 - 14
15. 15. A detonator according to any of claims 2 to 14, in which the initiating portion has a circumferentially extending radially inwardly projecting annular shoulder in its interior between the ends, to act as a stop for locating the portion which is received in the initiating portion.
16. 16. A detonator according to claim 15, in which the shoulder has a diaphragm extending across and closing off the central opening.
17. 17. A method of making a detonator comprising, loading a base charge into a hollow housing portion having an opening, separately assembling at least one other hollow housing portion of the detonator connectable spigot/socket fashion to the portion containing the base charge, and then connecting the portions together spigot/socket fashion, one of which contains an initiating means so that said opening faces into the portion containing the initiating means.
18. 18. A method according to claim 17, in which the portion containing the base charge is fitted into the portion containing the initiator charge in spigot/socket fashion.
19. 19. A method according to claim 17, in which the portion containing the base charge is fitted as the spigot into one end of a central portion, and the other end of the central portion is fitted as the spigot into one end of the portion containing the initiating portion.
20. 20. A' method according to claim 18 or 19, in which the spigot/socket connections are strengthened by means of a frictional fit or with the use of adhesives.
21. 21. A method according to any of claims 17 to 20, in which the initiating means is an incendiary fuse which is caused to be held in the sealed end of the initiating portion by friction or adhesive. 15 227(528
22. 22. A new detonator substantially as herein described and illustrated with reference to the accompanying drawings.
23. 23. A new method of making a detonator substantially as herein described and illustrated. dated this 31 DAYOFJuL „9o J. PARK & SON