AU2020202062B2 - Booster shell - Google Patents

Abstract

A booster shell including a body with a cylindrical wall, having an inner surface surrounding a volume, the inner surface including shock wave focusing formations, the volume configured to receive a booster, to which is connected an elongate flexible conductor, a first end of the body open to the volume and an end piece at a second end of the body preventing access to the volume and a closure comprising a member, engageable with the first end, which defines a passage through which the conductor passes from the volume.

Description

1/3 23 Mar 2020

3 14 2020202062

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14 14 26 26 16 20 90 24 24

12 12 44 44 12 12 22

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FIGURE FIGURE 11 FIGURE FIGURE 22 30 30 28 28 34 34 40

BOOSTER SHELL 21 Jan 2026

BACKGROUND OF THE INVENTION

[0001] This invention relates to a booster shell for use in an explosive application. 2020202062

[0002] In one type of blasting system a borehole is drilled to a depth of, say, 30 meters

and is then charged with an emulsion explosive. A booster is used to initiate the emulsion.

A booster comprises a sensitive explosive charge which is exposed to a detonator and,

normally, the booster is suspended inside the emulsion at a required depth at one end of

a shock tube which is used to ignite the detonator.

[0003] A phenomenon which can be encountered and which is dependent on the

geographic conditions at which the borehole is drilled and on the depth of the borehole is

that the temperature inside the borehole, at the region at which the booster is positioned,

can be high e.g. 80°C or more. It is then necessary to protect the charge in the booster,

for at an elevated temperature, spontaneous combustion and ignition can occur.

[0004] An object of the present invention is to provide a booster shell to address the

aforementioned situation.

SUMMARY OF THE INVENTION

[0005] The invention provides a booster shell for use with a booster to which is connected

an elongate flexible conductor, the booster shell including a body with a cylindrical wall

which has an outer surface, an inner surface which surrounds a volume, a first end which is open to the volume, an opposed second end and an end piece at the second end which 21 Jan 2026 prevents access to the volume, and a closure comprising a member which is removably engageable with the first end and through which is formed a passage, wherein the volume is configured to receive the booster with the elongate flexible conductor passing from the volume through the passage, and wherein the inner surface is formed with shockwave 2020202062 focusing formations characterized in that the shockwave focusing formations comprise a plurality of peaks and troughs which extend in a longitudinal direction on the inner surface and which are configured to ensure that the booster shell is fragmented by the exploding booster and that an emulsion in which the booster shell is located is then reliably initiated.

[0006] The closure member may be engageable with the first end of the body in any

convenient way and preferably use is made of a screw-type formation or a bayonet-type

formation. These structures are nonetheless exemplary and non-limiting.

[0007] The closure member may include an inner surface which is recessed e.g. domed

and which faces onto the volume when the member is engaged with the first end of the

body.

[0008] The passage in the member may comprise a slot which extends from one side of

the member towards a central location.

[0009] The booster body may include a shoulder formation on the inner surface and the

closure member may extend into the volume from the first end to oppose the shoulder

formation. A gap of at least 1mm and preferably of the order of 2mm may be formed between a part of the inner surface of the body and an opposing outer surface of the 21 Jan 2026 closure member when the closure member is engaged with the first end of the body.

[0010] The shockwave focusing formations may be of any appropriate kind and, in a

preferred form of the invention, may comprise a plurality of peaks and troughs which

extend in a longitudinal direction on the inner surface from the first end towards the 2020202062

second end of the body.

[0011] The body of the booster shell may be made from a heat-resistant material e.g. a

suitable refractory material such as a ceramic material. The density of the body may lie

in the region of 0,7 to 0,9. If the density is meaningfully higher then the heat insulating

properties of the booster shell body are reduced. If the density is meaningfully lower then

the physical strength of the body is reduced. An effective compromise density value

which has been established through experimentation, and which is a preferred value, is

of the order of 0,8.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The invention is further described by way of example with reference to the

accompanying drawings in which :

Figure 1 illustrates in perspective a booster shell according to the invention,

Figure 2 illustrates in perspective the booster shell of Figure 1 wherein a body and a

closure of the booster shell are displaced from one another,

Figure 3 is a view of one end of the body in the direction of an arrow 3 in Figure 2,

Figure 4 is a plan view of the closure shown in Figure 2,

Figure 5 is a side view in cross section of the closure taken on a line 5-5 in Figure 4, and 21 Jan 2026

Figure 6 is a side view in cross section showing the body of the booster shell with a

booster located inside the body.

DESCRIPTION OF PREFERRED EMBODIMENT 2020202062

[0013] Figure 1 of the accompanying drawings illustrates in perspective a booster shell

10 according to the invention. The booster shell includes a body 12 and a closure

member 14. These components are shown in Figure 2 displaced from each other.

[0014] The body 12 is made from a refractory material such as a suitable ceramic and

has a density of the order of 0,8. The closure member 14 is made from a similar material.

[0015] The body 12 has a cylindrical wall 16 with an outer surface 18 and an inner surface

20. The inner surface 20 encloses a cylindrical volume 22.

[0016] The body 12 has a first end 24 which is open and which forms a mouth 26 to the

volume 22. An end piece 28 at a second end 30 of the body 12 closes the volume 22 i.e.

it prevents access to the volume 22. An outer surface 34 of the end piece 28 has a frusto

conical shape. An inner surface 36 of the end piece 28 is domed – see Figure 6. A small

shoulder 40 is located at a junction of the end piece 28 and the inner surface 20 (Figure

6).

[0017] The mouth 26 is generally circular in outline and is larger in size than the cross

sectional dimension of the volume 22. A shoulder 44 is formed at a junction of the mouth

26 and the volume 22. The inner surface 20 between the shoulder 44 and the shoulder

40 is formed with a plurality of peaks 46 and troughs 48 which extend in a longitudinal 21 Jan 2026

direction on the inner surface from between the two shoulders (see Figure 3).

[0018] Two opposed shallow channels 50 and 52 respectively extend on the inner

surface 20 from a rim 56 of the mouth 26 to the shoulder 44. Each channel then extends

in a circumferential direction and terminates in a blind upwardly extending channel portion 2020202062

66 (Figure 6).

[0019] The closure member 14 is shown in perspective in Figure 2, in plan in Figure 4

and from one side and in cross section in Figure 5. The closure member 14 has an

upstanding hand grip formation 70 and two small opposed projections 72 and 74 on an

outer surface 76. An inner surface of the closure member 14 has a domed recess 78. A

passage in the form of a slot 80 extends in a radial direction from the outer surface 76 to

a central position on the closure member 14.

[0020] The projections 72 and 74 on the closure member 14 can engage with a sliding

fit with the channels 50 and 52 of the body 12 until a surface of the closure member 14

abuts the shoulder 44. The closure member 14 is then movable with a twisting action

relative to the body 12 so that the projections 72; 74 can enter the respective blind channel

portions 66. This bayonet-type action firmly secures the closure member 14 to the body

12.

[0021] Figure 1 shows the closure member 14 engaged with the body 12. An annular

gap 90 is formed between a surface of the closure member 14 and an opposing surface

of the mouth 26. This gap has a width of the order of 1 to 2mm.

[0022] In use of the booster shell 10 a booster 94, see Figure 6, is placed into the volume 21 Jan 2026

22. The components are configured so that a lower end 96 of the booster 94 rests on the

small shoulder 40. An upper end 98 of the booster 94 is substantially coplanar with the

shoulder 44.

[0023] The booster 94 is of a conventional construction and carries a charge and a 2020202062

detonator (not shown). An elongate flexible shock tube 100 is connected to the detonator

and extends therefrom. The shock tube 100 is passed through the slot 80 before the

closure member 14 is engaged with the body 12. The arrangement is one in which the

booster shell 10 with the booster 94 inside the shell can then be suspended from the

shock tube 100. The upper end 98 of the booster 94 then abuts a lower surface 102

(Figure 5) of the closure member 14. Relative movement of the closure member 14 and

the body 12 is restricted because of the projections 72 and 74 which are located in the

respective blind channel portions 66.

[0024] The assembled booster shell, suspended from the shock tube 100, can then be

lowered into a borehole to the desired depth. Thereafter an emulsion is placed into the

borehole to surround the booster shell. This aspect is conventional and is therefore not

further described.

[0025] The booster shell is made from a refractory material which has significant heat

insulating properties. The density of the material is of the order of 0,8. It has been found

that the refractory material with this density has adequate physical strength and exhibits

an effective heat insulating characteristic which provides thermal protection for the

booster and the detonator in a hot hole.

[0026] When the detonator is initiated the booster charge is fired. The peaks 46 and 21 Jan 2026

troughs 48 are effective shockwave focusing formations and ensure that the booster shell

is fragmented by the exploding booster and that the emulsion is then reliably initiated.

[0027] The domed inner surface 36 at the bottom of the booster body 12, and the domed

recess 78 on the underside of the closure member 14 provide for a limited amount of gas 2020202062

expansion inside the booster shell when the booster is fired. The gap 90 at the interface

of the closure member 14 and the mouth 26 of the body 12 allows some of the gas to

escape from inside the booster shell. These features have been found to be of

importance in ensuring that the booster is effective in initiating the emulsion in which the

booster is suspended.

[0028] It will be understood that the term “comprise” and any of its derivatives (eg

comprises, comprising) as used in this specification is to be taken to be inclusive of

features to which it refers, and is not meant to exclude the presence of any additional

features unless otherwise stated or implied.

[0029] The reference to any prior art in this specification is not, and should not be taken

as, an acknowledgement or any form of suggestion that such prior art forms part of the

common general knowledge.

[0030] In some cases, a single embodiment may, for succinctness and/or to assist in

understanding the scope of the disclosure, combine multiple features. It is to be

understood that in such a case, these multiple features may be provided separately (in

separate embodiments), or in any other suitable combination. Alternatively, where

separate features are described in separate embodiments, these separate features may be combined into a single embodiment unless otherwise stated or implied. This also 21 Jan 2026 applies to the claims which can be recombined in any combination. That is a claim may be amended to include a feature defined in any other claim. Further a phrase referring to

“at least one of” a list of items refers to any combination of those items, including single

members. As an example, “at least one of: a, b, or c” is intended to cover: a, b, c, a-b, a- 2020202062

c, b-c, and a-b-c.

[0031] It will be appreciated by those skilled in the art that the invention is not restricted

in its use to the particular application described. Neither is the present invention restricted

in its preferred embodiment with regard to the particular elements and/or features

described or depicted herein. It will be appreciated that various modifications can be

made without departing from the principles of the invention. Therefore, the invention

should be understood to include all such modifications in its scope.

Claims (10)

CLAIMS 21 Jan 2026

1. A booster shell for use with a booster to which is connected an elongate flexible

conductor, the booster shell including a body with a cylindrical wall which has an

outer surface, an inner surface which surrounds a volume, a first end which is open

to the volume, an opposed second end and an end piece at the second end which 2020202062

prevents access to the volume, and a closure comprising a member which is

removably engageable with the first end and through which is formed a passage,

wherein the volume is configured to receive the booster with the elongate flexible

conductor passing from the volume through the passage, and wherein the inner

surface is formed with shockwave focusing formations characterized in that the

shockwave focusing formations comprise a plurality of peaks and troughs which

extend in a longitudinal direction on the inner surface and which are configured to

ensure that the booster shell is fragmented by the exploding booster and that an

emulsion in which the booster shell is located is then reliably initiated.

2. A booster shell according to claim 1 wherein the closure member is engageable with

the first end of the body by way of a screw-type formation or a bayonet-type

formation.

3. A booster shell according to claim 1 wherein the closure member includes an inner

surface which is recessed.

4. A booster shell according to claim 1 wherein the passage in the closure member 21 Jan 2026

comprises a slot which extends from one side of the member towards a central

location.

5. A booster shell according to claim 1 wherein the body includes a shoulder formation

on the inner surface and the closure member extends into the volume from the first 2020202062

end to oppose the shoulder formation.

6. A booster shell according to claim 1 wherein a gap is formed between a part of the

inner surface of the body and an opposing outer surface of the closure member

when the closure member is engaged with the first end of the body.

7. A booster shell according to claim 6 wherein the gap has a width of from 1mm to

2mm.

8. A booster shell according to claim 1 wherein the body is made from a heat-resistant

material which provides thermal protection for the booster in a hot hole.

9. A booster shell according to claim 8 wherein the heat-resistant material is a ceramic

material.

10. A booster shell according to claim 1 wherein the density of the body is 0,8 g/cm3.