AU2770602A - Booster - Google Patents

Description

I-

Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

(ORIGINAL)

.0 .0 011. 0 *.00.

0 1 Name of Applicant: Actual Inventor(s): Address for Service: Initiating Explosives Systems Proprietary Limited Bradley Kevin Beikoff DAVIES COLLISON CAVE, Patent Attorneys, 1 Little Collins Street, Melbourne, Victoria 3000.

Invention Title: "Booster" Details of Associated Provisional Application(s): No(s): PR4263/01 The following statement is a full description of this invention, including the best method of performing it known to me/us: P:\OPER\JccSPECIFICATIONSROOSTER lconipIocj dow-261031O2 -1-

BOOSTER

The present invention relates to a booster casing which is adapted to contain a detonator assembly comprising a detonator and signal tube, and to a booster comprising the casing loaded with such an assembly. The invention further relates to a method of loading a blasthole and to a method of blasting using this booster.

In mining operations, blastholes containing packaged or bulk explosive are usually initiated using an initiation system (booster). Typically, this system includes a detonator 10 comprising a high explosive and a booster explosive. When the detonator is fired the booster explosive explodes and, in turn, this causes detonation of the packaged or bulk explosive. Firing of the detonator is usually triggered using a signal tube which runs into the top (neck) of the detonator. The detonator and booster explosive are typically housed in a casing.

During blasthole loading it is important that the signal tube is retained in the detonator and does not become detached from it. For instance, sometimes during loading of a blasthole the booster may snag on discontinuities or obstructions in the blasthole, and when this happens removal of the booster by pulling on the signal tube is sometimes attempted.

20 However, the force needed to pull the signal tube out of the top of the detonator is relatively low, and such attempts to retrieve the booster can lead to detachment of the signal tube. It would therefore be desirable to provide a means for ensuring that the signal tube is retained in the detonator with greater security so that the possibility of detachment of the signal tube is minimised.

Another aspect of blasthole loading concerns the orientation of the detonator in the blasthole. When the blasthole is forward primed, the booster is loaded with the top of the detonator remote from the toe of the blasthole. In this case the signal tube runs out of the detonator and along and out of the blasthole. When the blasthole is reverse primed, the booster is loaded with the top of the detonator closest to the toe of the blasthole. In this arrangement the signal tube must double-back on itself after emerging from the top of the P; OPER~cc\SPECIFICATIONSflOOSTER (coniplaOt)d-c26/03102 -2detonator. It would be desirable to provide a booster casing which permits either forward or reverse priming of a blasthole thereby providing flexibility of loading. Problems can also arise if the signal tube is kinked as it exits the detonator and/or booster casing. It would also be advantageous to provide a booster casing which minimises this.

The present invention seeks to provide a booster casing which meets these various needs without suffering the problems mentioned. Accordingly, the present invention provides a booster casing which is adapted to contain a detonator assembly comprising a detonator and signal tube, the booster casing comprising: oooo 10 an elongate hollow body having an outer periphery; o an opening at one end which is adapted to receive a detonator substantially parallel to the longitudinal axis of the body; S* an open-ended groove extending between the opening and the outer periphery of the body; wherein the groove comprises a signal tube receiving portion and a signal tube retaining 15 portion, the signal tube retaining portion of the groove having upper and lower wall surfaces which curve outwardly to the outer periphery.

In use the function of the signal tube retaining portion is to prevent the signal tube from being pulled out from the detonator by force exerted on the signal tube, irrespective of whether the blasthole being loaded is forward or reverse primed. The signal tube retaining portion will also serve to prevent the detonator being pulled out of its intended position in the casing by force exerted on the signal tube and/or during handling and loading of the booster. Having said this, the design of the casing of the present invention is intended to allow easy removal of the detonator assembly, if necessary. The (outwardly) curved surfaces of the signal tube retaining portion prevent kinking of the signal tube when it exits the groove and is fed in either longitudinal direction along the outer periphery of the casing. The signal tube receiving portion allows the signal tube to be positioned in the signal tube retaining portion of the groove whilst attached to the detonator. The relationship between these portions of the groove may be better understood by reference to P:\OPER\JcSPECIFICATIONS\BOOSTER (Cm~pct,) doc.26/03102 -3how a detonator would be positioned in the casing, and by reference to the design of the detonators typically employed.

The detonator usually takes the form of a cylindrical cartridge. Signal tube runs into the top of the detonator and is attached therein usually by means of a deformable collar into which the signal tube may be inserted. The collar is then deformed (crimped) around the signal tube. The detonator is inserted into the booster casing through the opening with the base of the detonator being fed first into the opening. In position the top of the detonator is preferably completely enclosed by the casing. This protects the detonator from mechanical 10 damage during the blasthole loading process. The signal tube extends from the top of the •detonator and out of the opening in the casing. To restrain the signal tube from unwanted movement it is positioned in the signal tube retaining portion of the open-ended groove via the signal tube receiving portion of the groove. The signal tube retaining portion communicates with the signal tube receiving portion. Usually, the receiving portion is 15 essentially vertical and parallel to the longitudinal axis of the body. The signal tube retaining portion is usually displaced laterally from the blind end of the receiving portion.

Thus, when in use, the signal tube is usually passed vertically down through the receiving portion and then displaced laterally into the retaining portion where it is retained. From the retaining portion the signal tube may run in either longitudinal direction along the outer 20 periphery of the casing (thereby enabling forward or reverse priming). When exiting the retaining portion the signal tube passes over the upper or lower wall surface of this portion.

The shape of the upper and lower wall surfaces of the signal tube retaining portion is an important feature of the present invention. The retaining portion has upper and lower wall surfaces which curve outwardly to the outer periphery, i.e. the exit of this portion (remote from the opening) is flared. This means that when the detonation signal tube exits the retaining portion and is run in either direction along the longitudinal axis of the casing kinking of the signal tube is avoided. In other words, the relevant wall surfaces are smooth, curved surfaces which do not have any sharp edges which would otherwise cause kinking.

P:AOPERyccZSPECIFICATIONS'BOOSTER (conipac) doc-26/3/O2 -4- The signal tube retaining portion of the open-ended groove may be defined by a retaining arm which extends into the groove (thereby dividing the groove into signal tube receiving and retaining portions). Usually the retaining arm is an integral part of the casing. In cross-section the shape of the arm is not critical provided that the portion(s) over which the signal tube will run are smooth and rounded, to avoid kinking of the signal tube. In an embodiment of the invention the end of the retaining arm is provided with a rib which is intended to enhance retention of the signal tube.

The primary function of the retaining arm is to prevent unwanted movement of the signal tube and/or the detonator due to any load which is predominantly along the longitudinal axis of the casing, such as would be exerted in an attempt to withdraw a loaded booster from a blasthole by pulling on the signal tube. The design of the casing of the invention results in this force primarily being exerted on the upper or lower wall surfaces of the 15 signal tube retaining portion where the signal tube contacts these wall portions. When the booster is forward loaded this force would be exerted on the upper wall surface of the retaining portion. When the booster is reverse loaded this force would be exerted on the lower wall portion surface of the retaining portion.

S" 20 The curvature of the wall surfaces of the signal tube retaining portion is also advantageous since this also allows the signal tube to run flush with the body of the booster at least at a portion of the body where the signal tube exits the signal tube retaining portion. This can provide protection to the signal tube and is particularly useful when reverse priming as the body may then protect the signal tube from excessive abrasion against the blasthole walls.

To enable the signal tube to be associated closely with the outer periphery of the casing after exiting the retaining signal tube portion, the outer periphery may include a channel for retaining the signal tube adjacent the outer periphery. The channel may include a pair of tabs through which the signal tube may be pushed and which restricts removal of the signal tube from the channel. The channel will usually be located remote from the intended leading portion of the booster casing.

P:\OPER Jcc\SPECIFICATIONS\BOOSTER oCon)PIOCtIAM-26/031O2 The elongate body of the booster casing is generally cylindrical. In a preferred embodiment the wall thickness of the casing is usually 0.5-2mm, although this can vary over the length of the casing, for example if additional rigidity is required in any particular region. The length of the casing will be determined by the size of the detonator and the volume of booster explosive to be housed. As a general guide the casing is usually 50 to 150mm long. Similar considerations apply to the internal diameter of the casing.

Generally, this is 15 to 10 In a preferred embodiment, the casing is cylindrical with one end of the cylinder comprising a nose cone. Preferably, the nose cone is provided at the end of the casing at which the detonator would be inserted. Thus, the nose cone comprises the detonator opening. This embodiment enables further flexibility when it comes to blasthole loading.

If the nose cone is the leading portion of the booster as it is being inserted into a blasthole, 15 it may guide the booster around obstructions or discontinuities in the blasthole. On the other hand if the leading portion is flat, this portion may be useful in displacing moveable obstructions such as rocks which might otherwise cause lateral deflection of the booster during loading. In this way a single booster may be used to load a vertically oriented blasthole or a horizontally oriented blasthole. The leading portion of the booster may be S" 20 selected accordingly.

The present invention further provides a booster comprising a booster casing as described herein loaded with a detonator assembly and booster explosive. Loading of the booster casing with these components will depend to a large extent on the type of booster explosive being used. Any conventional booster materials may be employed although the form this takes will influence loading of the booster casing.

For example, if the booster explosive is a castable composition, this is poured into the booster casing over a blank which is essentially the same shape as the detonator to be used.

When the composition has set, the blank is removed and the detonator inserted into the cavity formed by the blank in the booster explosive. Alternatively, if the booster explosive ?:\OPERIJkc\SPECIFICATIONS\BOOSTER (munplcC).do.-26/03/02 -6is a soft pliable material it may be inserted into the casing and the detonator then forced into the composition. If a granular booster explosive is used the detonator is usually first positioned (and centred) in the casing and the granular explosive poured into the casing through the open end and around the detonator. In this instance, although equally possible with the other types of explosives mentioned, the open end of the casing remote from the detonator opening would be plugged or capped. After loading of booster explosive and positioning of the detonator (whatever the sequence), the signal tube is then positioned in the signal tube passage as described. Conventional detonators electric, non-electric or electronic) and signal tubes may be used.

The signal tube retaining arm may comprise additional features to prevent unwanted lateral or longitudinal movement of the signal tube. For example, the retaining arm may be provided with one or more tabs extending into the signal tube passage over which the signal tube must be pushed into place. Alternatively, the retaining arm may have an 15 enlarged distal end or flange to prevent unwanted lateral displacement of the signal tube when positioned in the signal tube passage.

a. a.

The booster casing may include additional features to assist with loading and positioning within a blasthole. These features may be integral to the booster casing. Alternatively, the 20 casing may be adapted to connect to one or more separate components which contribute these features. In one embodiment, the casing comprises a loading hose engagement means to engage a loading hose used to position the loaded casing in a blasthole. The loading hose engagement means may take the form of a sleeve for engaging the end of a loading hose, the sleeve having an internal dimension slightly greater than the external dimension of the hose. In this embodiment it is also preferred that the booster casing includes means for preventing contact between the end of the explosive contained and the end of the loading hose. The booster casing may therefore include a tab (or tabs) which projects into the sleeve of the booster casing. The loading hose engagement means is provided at the end of the booster casing remote from the intended leading portion thereof.

Either end of the casing may include such means. In order to protect the explosive from contact with the end of the loading hose the open end of the casing remote from the P:\OPERIJcSPECIFICATIONS\BOSTER (-O~pi-W-C26103102 -7detonator opening may include a plug or cap as described above, irrespective of the type of booster explosive used.

In another embodiment, the casing may comprise means for centring and/or retaining the booster in a blasthole. For instance, the booster may include blasthole engagement means in the form of legs which extend outwardly from the casing and rearwardly from the intended leading portion of the booster casing. The legs are resilient and are deflected inwardly as the booster is pushed into a blasthole. The legs assist in centring the booster in the blasthole and also prevent unwanted movement of the booster, for example due to gravity. The end of each leg may be shaped in such a way that the leg does not snag on the blasthole wall, thereby enabling withdrawal of the booster if necessary. For instance, the ••end of each leg may be provided with a return portion inclined inwardly toward the booster casing such that the blasthole contacts a smooth, curved section at the end of the leg.

15 In a preferred embodiment, the loading hose engagement means and blasthole engagement means are provided as a separate component which is releasably connectable to the booster casing. When the booster casing is cylindrical, this component may take the form of a circular collar which is adapted to be attached to the booster casing. Preferably, the collar provides an interference fit with the booster casing, the internal diameter of it being 20 slightly greater than the external diameter of the casing. The casing and collar may be fitted with retaining means such as tabs and tab-recesses to enable easy attachment of collar to casing.

The booster casing may be made of a variety of materials, including plastics and paper (cardboard). Typically, the casing will be made of an injection mouldable plastic such as polypropylene or polyethylene. The collar, when used, may also be made of the same material.

The present invention also provides a method of loading a blasthole which comprises charging the blasthole with packaged or bulk explosive and priming the blasthole with a booster as described herein. One skilled in the art would be familiar with how the P:\OPER\Jcc\SPECIFICATIONS BOOSTER (conipIney)d-c2613102 -8blasthole may be charged and primed.

The present invention further provides a method of blasting which comprises loading the blasthole as described herein and detonating the booster in order to initiate detonation of the packaged or bulk explosive. The booster may be detonated by conventional techniques.

The present invention will now be illustrated by way of example only by reference to the accompanying figures where: Figure 1 is a perspective view of a booster casing in accordance with the present invention; Figure 2 is a top view of the booster casing of Figure 1; Figure 3 and 4 are perspective views of a loaded booster in accordance with the present invention.

In Figures 1 and 2 the booster casing comprises a hollow elongate body having an outer periphery In the embodiment shown the body is cylindrical. The casing has an opening at one end which id adapted to receive a detonator (not shown) substantially parallel to the longitudinal axis of the body The casing has an open-ended groove extending between the opening and the outer periphery of the body The groove has a signal tube receiving portion and a signal tube retaining portion The signal tube retaining portion of the groove has upper and lower wall surfaces 8) which curve outwardly to the outer periphery of the body In the embodiment depicted the signal tube retaining portion of the groove is defined by a retaining arm (9) which extends into the groove thereby dividing it into signal tub receiving and retaining portions The retaining arm is an integral part of the casing The retaining arm is provided with a rib (10) which is intended to enhance retention of the signal, tube. A further feature of the embodiment shown is that the casing comprises a nose cone (11) which is generally conical in shape.

Figure 3 illustrates a loaded booster in which a signal tube (12) is retained in the signal P:'OPER\Jcc\SPECIFICATIONS\BOOSTER I c-,pklc d-c26103102 -9tube retaining portion defined by the retaining arm The signal tube (12) runs into a detonator (not shown) in the casing from below and this configuration would be suitable for reverse priming of a blasthole. Here the nose cone (11) may help to guide the booster around discontinuities and/or obstructions in a blasthole being loaded. In practice the detonator with signal tube attached is inserted through the opening such that it is completely encased and protected by the casing The signal tube (12) is then moved into position in the signal tube retaining portion of the groove via lateral displacement from the signal tube receiving portion The rib (10) of the retaining arm ensures that the signal tube (12) is held in the desired position. The curvature of the groove to the outer periphery of the body helps to prevent kinking of the signal tube (12) as it exits the casing and runs longitudinally downward along the body In Figure 4 the signal tube (12) runs into the casing from above and this configuration would be suitable for reverse priming of a blasthole. The signal tube (12) is loaded in a similar fashion to that described for Figure 3 but in this case runs upwardly away from the casing around the retaining arm Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Claims (19)

1. A booster casing which is adapted to contain a detonator assembly comprising a detonator and signal tube, the booster casing comprising: an elongate hollow body having an outer periphery; an opening at one end which is adapted to receive a detonator substantially parallel to the longitudinal axis of the body; an open-ended groove extending between the opening and the outer periphery of the body; wherein the groove comprises a signal tube receiving portion and a signal tube retaining portion, the signal tube retaining portion of the groove having upper and lower wall surfaces which curve outwardly to the outer periphery.

2. A casing according to claim 1, wherein the receiving portion is essentially vertical and parallel to the longitudinal axis of the body.

3. A casing according to claim 1 or 2, wherein the wall surfaces are smooth, curved surfaces which do not have any sharp edges. 15

4. A casing according to any one of the preceding claims, wherein the signal tube retaining portion of the open-ended groove is defined by a retaining arm which extends into the groove thereby dividing the groove into signal tube receiving and retaining portions.

A casing according to claim 4, wherein the retaining arm is provided with a rib which is intended to enhance retention of the signal tube.

6. A casing according to any one of the preceding claims, wherein the outer periphery includes a channel for retaining the signal tube adjacent an outer periphery.

7. A casing according to claim 6, wherein the channel includes a pair of tabs through which the signal tube may be pushed and which restricts removal of the signal tube from the channel. P:'OPER~kccSPECIFICATIONSNBOOSTER (Coampid).oC-26/03MO 11

8. A casing according to claim 6 or 7, wherein the channel is located remote from the intended leading portion of the casing.

9. A casing according to any one of the preceding claims, which is cylindrical with one end of the cylinder comprising a nose cone.

10. A casing according to any one of the preceding claims, which comprises loading hose engagement means provided at an end of the casing remote from the intended leading portion thereof.

11. A casing according to any one of the preceding claims, which comprises means for centring and/or retaining the booster in a blasthole.

12. A casing according to claim 11, wherein the casing includes blasthole engagement means in the form of legs which extend outwardly from the casing and rearwardly from the intended leading portion of the casing.

13. A casing according to any one of claims 10 to 12, wherein the casing comprises loading hose engagement means and blasthole engagement means provided as a separate component which is releasably connectable to the casing.

14. A booster casing substantially as hereinbefore described with reference to the accompanying figures.

A booster comprising a booster casing as claimed in any one of claims 1 to 14 loaded with a detonator assembly comprising a detonator and signal tube and with a booster explosive.

16. A booster substantially as hereinbefore described.

17. A method of loading a blasthole which comprises charging the blasthole with packaged or bulk explosive and priming the blasthole with a booster as claimed in claim or 16.

18. A method of loading a blasthole substantially as hereinbefore described. P \OPER\J ,\SPECIFICATIONSBOOSTER (-onP1=).d-26/03/O2 12-

19. A method of blasting which comprises loading a blasthole by the method claimed in claim 17 or 18 and detonating the booster in order to initiate detonation of the packaged or bulk explosive. A method of blasting substantially as hereinbefore described. Dated this 26 th day of March 2002 Initiating Explosives Systems Proprietary Limited by DAVIES COLLISON CAVE 10 Patent Attorneys for the Applicant(s) o• a. a a.