AU616320B2 - Primer - Google Patents

Description

I 3 ,61 32OiAh P/00/011 AUS 1417 Form PATENTS ACT 1952-1973 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE Class: Int. CI: Application Number: Lodged:

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Complete Specification-Lodged: Accepted: Published: o Priority: r r i i Related Art: TO BE COMPLETED BY APPLICANT S Name of Applicant: ICI AUSTRALIA OPERATIONS PROPRIETARY LIMITED S .Address of Applicant: 1 Nicholson Street Melbourne 3001, Victoria Australia Actual Inventor: Address for Service: Russell PETERSON, Tom LOVE Industrial Property Section ICI Australia Operations Proprietary Limited 1 Nicholson Street, P.O. Box 4311 Melbourne 3001, Victoria Australia Complete Specification for the invention entitled: "PRIMER" The following statement is a full description of this invention, including the best method of performing it known to me:-* 'Note: The description is to be typed in double spacing, pica type face, in an area not exceeding 250 mm in depth and 160 mm in width, on tough white paper of good quality and it is to be inserted inside this form.

jr 1 '710/76-L C.J. TII IiiO'. Cornnoiiwcilh Government Irinlcr. Cwnerra

ABSTRACT

0 uo 0~ 0 An explosives primer and process for priming blastholes in which the casing for the explosive and detonator is adapted so as to provide maximum protection for the detonator from physical damage and (ii) to facilitate loading of the detonator into the casing to provide a contact with the explosive. The casing is provided with an aperture through which the detonator may be readily inserted, and once inserted the detonator is substantially completely enclosed by the casing.

0- 3 a 0 'ok1 C o AUS 1417/LRS

PRIMER

01 0 0 00 a 0o ooo0 This invention relates to primers suitable for the detonation of .xplosives.

o 0 o*Oo It is a recommended practice that a delay 0o00 5 detonator be enclosed in a primer when loaded into a blasthole. The primer performs two functions.

Firstly, being reliably initiated by the detonator, it will, in turn, reliably initiate a main charge.

Secondly, the primer protects the detonator from a o 10 mechanical damage during the loading process.

When performing blasting operations, it is desirable that the complete length of the blasthole be exploded. If the whole length is not used then o "butts" may result. A butt is that portion of the o0 o0 15 drillhole remaining in the rock face after firing.

0 o The type of primer used may have an influence on whether or not butts are left in the rock face after firing.

It has been fairly common practice to use a cartridge of emulsion explosive as a primer.

Cartridges have the advantage that the detonator is tai 0 09 0 0 0 0 0 0 0 0 0oo0 S 0OO

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0000 0 0 0 0 4 t a 001 a :as -2completely enclosed, however they do present a number of problems. Carbrldges are large and cumbersome, and can be difficult to handle. They may be unable to fit in a loading hose and can prove to be difficult to load. In addition, the emulsion explosive of the cartridges may be desensitised by shock waves from other explosions propagated in relatively close proximity. It is also believed that the large size and shape of the cartridges may be responsible for the incomplete packing of the explosive used in the blastholes. Consequently, the entire length of the blasthole may not be used in the explosion and is a possible reason why butts are left after the explosion.

15 There have been several attempts to develop a primer which will protect a detonator and which will reliably initiate a main charge, and, at the same time, overcome problems such as those encountered when using cartridges. One example of such a primer comprises a tube of an extruded mixture of PETN and an elastomeric binder into which tube a detonator can be inserted. Another example is where a detonator can be inserted into an RDX/wax mixture in an aluminium shell. In these types of primer, the detonator is in contact with the explosive charge, thus ensuring reliable detonation. Such products have an added attraction of being small (in some cases small enough to be inserted into the end of a loading hose) and are therefore easily handled and relatively easy to transport. In addition, the small diameter of such primers is believed to assist in the explosion of the blasthole to full depth since the explosive used in the blasthole packs completely around the cartridge, allowing complete filling of the blasthole.

.4 -3- Although such prior art devices have enjoyed some commercial success, they have one major disadvantage in that part of the detonator may protrude from the device and thus there is a risk of physical damage to the detonator. The present invention overcomes this disadvantage and provides for a primer wherein the explosive charge can be reliably initiated by the detonator. In addition, the primer of the present invention is small, and can be easily handled and transported, the small size further facilitating passage of the explosion along the complete length of the blasthole.

According to the present invention there is provided a primer comprising a casing, a charge of explosive and a detonator, wherein the casing is adapted so as to receive and locate in contact with o the charge of explosive the detonator, said o detonator residing therein such that it is 4404 o~o substantially completely enclosed by the casing, the 20 casing including an aperture in an exterior surface whose largest dimension exceeds that of the detonator, the aperture being adapted so as to allow 6oo 0insertion of the detonator into the casing.

o coThe primer according to this invention must 00 25 perform at least two functions: 000004 1. it must substantially completely enclose the 6 detonator; and 44 4 4 4 2. it must hold the detonator in contact with a charge of explosives as contained within the casing.

The term "substantially completely enclosed" as used herein means that the casing surrounds the detonator to such an extent that the detonator is protected from any external influences which could !t I 4 -4otherwise prevent the efficient operation of the primer. In the interests of safety it Is also important to avoid damage to the detonator, since a damaged detonator could unexpectedly detonate. Thus, while it is not necessary to enclose the detonator completely, it should be enclosed sufficiently well to ensure an adequate degree of protection. In particular, the casing should be long enough to accomodate the entire length of the detonator without there being any protrusion of the detonator from the casing. This is a significant advantage of the present invention over those of the prior art.

The casing of the primer may be of any 0a C convenient shape, provided that the exterior surface 15 through which the detonator is inserted has a o o °largest dimension exceeding that of the detonator, a a° and provided that the detonator is substantially completely enclosed when contained therein. For ofoo example, the casing may be regular in shape, such as in the case of a cylinder or a prism, or irregular in shape or of any other shape which fulfills the hereinabove-described requirements. Naturally, in 0OOC,' selecting a suitable shape, factors such as ease of handling, method of manufacture, and price would be taken into account. It is common practice in the art to use primers in the form of cylinders, since a a this form can conveniently accomodate/house a wide a mselection of detonators of varying shapes.

Typically, however, many detonators are themselves cylindrical in shape. In the primer of the present invention, a particularly preferred casing is a cylinder open at both ends. In this preferred embodiment, the aperture in the exterior surface of the casing through which the detonator Is loaded is an aperture In the circumferential wall of the cylinder. In this preferred embodiment, the end nearer that end of the detonator to which wiring, 4 59 shock tube or the like Is attached comprises a slot through which pass the detonator wires or initiating signal tube from the detonator to be led down the side of the primer, thus preventing or reducing abrasion of the wires or signal tube on the side of the blasthole.

The casing includes an aperture in an exterior surface, the largest dimension of said exterior surface exceeding that of the detonator, through which aperture the detonator is inserted.

This is quite a different approach from others utilised by the art, and it helps ensure ease of insertion with complete protection. The aperture should naturally be wide enough to facilitate insertion of the detonator, yet not be so wide that protection of the detonator is compromised. There Smay, of course, be a door or plug for the aperture, 4444 but this adds extra and generally unnecessary expense to the manufacture, and it is preferred to have a generally rectangular unclosed aperture.

In an especially preferred embodiment used when the casing is a tube, especially a tube of am circular cross-section, the aperture is of dual owidth, the wider part of the opening being substantially wider than, but not as long as the detonator. The narrower part of the opening, which is narrower than the detonator, extends from one end of the wider part of the opening to the end of the casing. When the tube is made of a suitably resilient material and the end of the tube to which the narrower part extends is open, the detonator can be pressed through the narrower part. The embodiment has the advantage that any wiring or detonation cord is within the casing and is thus protected from physical damage.

Within the casing, the detonator must be held in contact with a charge of explosive contained therein. The holding in place of the detonator may -6be achieved by any convenient holding means, but a typical means Is a spring clip or a series of such clips which grips or grip the circumference of the detonator, holding it In place.

The explosive in the casing which is ignited by the detonator and which in turn sets off the main charge may be selected from any explosive known to be suitable for such a function. It may be, for example, PETN, RDX or a similar high explosive. The explosive may be inserted into the casing and be contained therein in any convenient manner. For example, one side or end of the casing may be sealed and the explosive inserted through the opposite side D ooo 15 the casing. However, in a preferred embodiment the 0 Voo° explosive is located at one end of an elongate 0°°o casing which end is open and through which the explosive is inserted. The explosive is prevented oo. from travelling the entire length of the casing by 20 means of a constriction within the casing, the constriction being placed such that a sufficient quantity of explosive is held by the casing when the oo. space between the end of the tube and the constriction is filled therewith, the constriction 0° 25 comprising an aperture which permits the detonator ooo to contact the explosive.

The material from which the casing is made or*o*a should possess appropriate properties to provide adequate protection of the detonator. For example the material may be a type of rigid plastic such as a polyethylene or polypropylene, or it may be a metal or metal alloy.

SThe primer as hereinabove described is used for priming blastholes in blasting operations. The invention, therefore, further provides a process of priming blastholes using a primer substantially as hereinbefore described. 1 l -7- 0 0 o0 0 0 oo 0I 0 10 0000 In use, the detonator is guided into position in the casing and the primer is inserted, explosive end first, into the loading hose. The loading hose is pushed to the bottom of the blasthole and then withdrawn 300 mm. The compressed air that blows the explosive, for example, "ANFO", into the blasthole is turned on, and the primer is ejected from the loading hose.

The invention is further described with reference to the accompanying drawings which illustrate a preferred embodiment. It is to be understood that the drawings are not intended to limit the scope of the invention in any way.

Figure 1 is a perspective cut-away drawing 15 showing a detonator being inserted into a tube to make a primer according to the invention.

Figure 2 is a perspective cut-away drawing of the embodiment of Figure 1, showing the detonator in place in the tube.

A cylindrical tube 1 which is open at both ends has two contiguous openings in the cylindrical wall, a wide opening 2 and a narrow opening 3. The wide opening is located approximately equidistantly from the ends of the tube and is rectangulbr, being oriented such that the major axis of the rectangle is parallel to the longitudinal axis of the tube.

The wide opening is so dimensioned as to be wider than any detonator which will be inserted into the tube but not as long as the shortest detonator which will be inserted thereinto. Running from this wide opening 2 to one end of the tube is a narrow opening 3 whose major axis is coaxial with the major axis of the wide opening 2. The width of the narrow opening 3 is less than that of any detonator to be inserted into the tube. Within the tube and affixed to the inner wall thereof is a spring clip 4 adapted to hold securely any detonator which is inserted into the tube.

-8- Adjacent to the clip 4 and positioned between that end of the tube 1 to which the narrow opening 3 does not extend and the wide opening 2 is a constriction 5 which corresponds in size and shape to the cross-section of the tube. This constriction has an aperture 6 which is so dimensioned that the end of a detonator 8 can fit through it, the spring clip 4 and aperture 6 being so positioned in relation to each other that a detonator when clipped into place will sit with its free end at or through the aperture 6. Explosive 7 is inserted into the tube through its open end until the space between the open end and the constriction 5 is filled.

A detonator 8 and associated signal tube or 0O Q o 15 wires 9 are inserted into the tube by inserting the a .0 0*o0 free end of the detonator 8 through the wide opening :00 2 and into or into close relationship with the 0O 000 aperture 6 such that the detonator contacts the 0.00 explosive. The end of the detonator on to which the tube or wire Is crimped is then pushed against the narrow opening 3 until it opens, allowing both detonator and signal tube or wires to pass through, ,oo and then it resumes its former shape behind them.

o o 4 O00 The detonator is snapped into the spring clip 4 O 25 which retains it in position. The signal tube or wires are fed through a slot 10 in the tube, at the same end as and located diametrically opposite to the narrow opening, and folded back. The primer r, ,0according to the invention is now ready for loading.

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Claims (10)

1. A primer comprising: a casing; (ii) a charge of explosive; and (iii) a detonator wherein the casing is adapted to receive and locate in contact with the charge of explosive the odetonator, said detonator residing therein such that it is substantially completely enclosed by the casing, the casing including an aperture in an exterior surface whose largest dimension exceeds i that of the detonator, the aperture being adapted so as to allow insertion of the detonator into the Scasing. oo o°2. A primer according to claim 1 wherein the casing is in the shape of a cylinder or tube. 0 3. A primer according to claim 1 or claim 2 wherein the casing is a cylinder or tube open at both ends.

4. A primer according to any one of claims 1 to 3 wherein the aperture in the exterior surface is located in the circumferential wall of a tube. A primer according to any one of claims 2 to 4 wherein the end of the cylinder or tube nearer that end of the detonator to which wiring, shock tube or the like is attached comprises a slot. N. *1 1. 10

6. A primer according to any one of claims 1 to wherein the aperture is of dual width.

7. A primer according to any one of claims 1 to 6 wherein the wider part of the aperture is susbtantially wider than but not as long as the detonator and the narrower part of the opening is narrower than the detonator.

8. A primer according to any one of claims 1 to wherein the aperture is substantially rectangular in shape. 0 0 o o 9. A primer according to any one of claims 2 to 00 8 wherein the detonator is held in contact So with a charge of explosive by a holding a means. 0 00 A primer according to any one of claims 1 to 9 wherein the holding means comprises a spring clip or a series of spring clips. a 11. A primer according to any one of claims 1 to wherein the explosive is inserted into the casing.

12. A primer according to any one of claim 1 to 11 wherein the explosive is located at one end of an elongate casing which end is open and through which the explosive maybe inserted. i I 11-

13. A primer according to any one of claims 1 to 12 wherein the casing further includes a constriction means within the casing wherein the constriction means is located such that a sufficient quantity of explosive is held by the casing within the space between the end of the tube and the constriction.

14. A primer according to any one of claims 1 to 13 wherein the constriction means comprises an aperture which allows the detonator to contact the explosive. A primer according to any one of claims 1 to 4 14 wherein the material from which the casing is o: made is selected from metal, metal alloys or plastics.

16. A process for priming blastholes using a primer as defined in any one of claims 1 to S. comprising the steps of oOoguiding the detonator into position in the casing of the primer. inserting the primer, explosive end first into the locading hose. pushing said loading hose to the bottom of the blasthole. and causing the primer and explosive to be ejected from the loading hose. ~lj~ 12-

17. A primer according to claim 1 substantially an hereinbefore described with reference to accompanying Figures 1 and 2. Dated this day of 1991 00 0 0 o0 0 000 o 0 00 0 B 6Q6Q ICI AUSTRALIA OPERATIONS PROPRIETARY LIMITED By its Duly Authorised Officer 000000 eoe o o o D a ro o m o oo 0 00 0 0l0 0 JOHN R DAV 17, 0 t -T