AU767744B2 - An explosive device - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicants: r PETER BIGGS THOMAS SKEFFINGTON Invention Title: AN EXPLOSIVE DEVICE The following statement is a full description of this invention, including the best method of performing it known to me/us: 2 AN EXPLOSIVES DEVICE FIELD OF THE INVENTION The present invention relates to an explosives device, for example, to be used in the mining industry as an explosives booster. The invention will be described primarily in relation to this application, but it should be appreciated that the invention is not so limited, and may be applied in other applications requiring explosives devices.

BACKGROUND ART Existing explosives boosters are typically formed from a squat cylindrical container, the explosive material being a solidified liquid that is then wrapped in paper to maintain the explosive integrity. A detonator tube is threaded through the device so as to assume a J-shaped configuration in situ.

Figures 1 to 5 depict schematically an existing explosives booster design which is in current use. The booster A includes an upper opening B to a longitudinal passage C. That passage extends right through the booster, and opens onto a transverse passage D in a bottom of the booster, which extends across the bottom thereof to a short passage E. A hole F opens from passage E into the 25 interior of the booster. A detonator including a short section of metallic material G which is connected to a flexible detonator tube H (typically of plastics) is inserted into the booster. The interior of the booster A is filled with an explosives material I.

S 30 As can be seen in Fig. 4, the detonator has been inserted through hole F to be brought into proximity with •the explosives material. Thus, a charge can be supplied from a remote location via tube H to detonator G, which in turn ignites the explosives material I.

In one preferred application of the prior art booster in a mining application, the booster is lowered into a previously drilled ground bore and, once at a P35648 3 desired location, explosive is introduced (piled or packed) around the outside of the booster. The booster when exploded is destroyed and causes the surrounding explosive to be ignited.

Fig. 5 shows how the booster A hangs from detonator tube H in use (ie during raising, lowering and explosives packing). As can be seen, the side wall of the booster subtends an angle a with respect to horizontal. The offset hanging of the prior art booster leads to collisions and snagging with obstacles in holes and bores into which the booster is inserted. For example, the existing booster can become snagged during lowering into a hole, and may also become snagged if it is desired to remove the booster from a hole prior to detonation.

In addition, should the booster become snagged when lowering into a hole, and it is desired to remove the detonator, then typically the only means available is to break the detonator tube by extreme force, or cutting the tube at surface level), leaving the booster still snagged in the bore. This is dangerous as the detonator is highly explosive.

Prior art boosters also place the detonator inside the booster adjacent to one side thereof. This can increase the tendency of the booster to misfire in use, and to also explode outwards at that adjacent side, without firing the bulk of the booster. This can lead to poor explosion performance and/or entire misfiring.

SUMMARY OF THE INVENTION The present invention in a first aspect provides an explosives device comprising a container for housing explosive therein and being connectable by a release means to an element for raising and lowering the container, wherein the release means is adapted for releasing the element from the container at a predetermined force on the element directed away from the container.

Thus, should the explosives device in accordance with the present invention become ensnared, tangled or P35648 4 otherwise fouled, a user can withdraw the element and, at a predetermined force at a predetermined load), the element can be released from the container. This is especially advantageous when the element is a length of detonator tube and has a detonator attached thereto, as both can be recovered. Recovery is primarily for reasons of safety but optionally the device and detonator can then be further re-used.

Preferably the element is a cord, typically having sufficient length for a bore into which the explosives device is located.

Typically, the container has a protrusion on an in use upper surface thereof to which the release means is fastened and from which it releases in use. Such an arrangement contrasts with prior art devices in which the detonator is typically inserted from the underside of the explosives device, and cannot be released therefrom.

Typically, the protrusion comprises a flange extending therearound and out therefrom, and the release means includes a plurality of hooks which engage the flange, wherein the hooks and/or flange are deformable or '"*frangible to disengage from the flange at the predetermined *9 S° force.

Preferably the release means comprises a pair of lugs opposing the hooks and adapted for fastening engagement with the element.

Typically, the element is a detonation cable although this is not essential. A typical detonation cable provides electrical or chemical connection with explosive in the device to enable its ignition via the detonator. For example the cord can merely be a support element and •detonation can be arranged remotely or via an accompanying .oS.

wire etc. Preferably the container has an opening at the protrusion and through which the detonation cable extends to the interior of the container for detonating the explosive. The release means is preferably adapted for readily interacting with existing (known) detonator and P35648 5 detonator tube arrangements.

In this regard, it is preferred that the detonation cable comprises an enlarged detonator portion at that end which is located in the container, with the detonator portion extending through the opening, and with a narrower detonator tube portion connected to and extending away from the enlarged portion, the connection defining a shoulder in the cable.

Preferably, the opposing lugs of the release means are adapted to fasten against the narrower portion of the detonation cable and such that the lugs prevent the shoulder from being passed therebetween. Thus, the release means releasably fastens the detonator tube and detonator to the container.

Preferably, the container incorporates a hollow recess in an underside thereof such that the protrusion when fitted with the release means can be received in a recess of a like container when in a stacked configuration.

This makes for easy transportation of a number of explosive devices in accordance with the present invention.

Preferably, the container is barrel-shaped. The container and release means are typically formed from a plastics material, optionally by blow and injection moulding respectively.

In a second aspect of the present invention, there is provided an explosives device comprising an elongate barrel-shaped container having a longitudinal axis and adapted for housing explosives therein, the container being *connectable to an element for raising and lowering the container, ~wherein the element is connected to the container •such that, when the cord extends vertically in use, the o container can hang therefrom with its axis generally aligned with or parallel to the element.

The terminology "barrel-shaped" is used herein to refer to a container having outwardly bulging sidewall(s).

Such an arrangement can prevent the vertical offset P35648 6of an explosives booster when hanging from, for example, a detonator tube where the detonator tube constitutes the element).

Typically, in the explosives device of the second aspect the container and element as per the first aspect and the device are adapted for use with a release means as per the first aspect. In a most preferred arrangement, the release means provides for an explosives device that hangs in the desired manner.

The present invention in a third aspect provides a release means for an explosives device of the type including a container for housing explosives therein, the release means being releasably connectable to the container and/or to an element for raising and lowering the container; wherein the release means is adapted for releasing from the container and/or the element at a predetermined force on the element away from the container.

This release can detach the element from the container if required. Preferably the release means is as defined above for the first aspect. Preferably the element is as defined for the first and second aspects.

BRIEF DESCRIPTION OF THE DRAWINGS Notwithstanding any other forms which may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figs 1 to 3 show plan, side and underside plan elevations of a prior art explosives booster; Figs 4 and 5 show schematic in use views of the prior art explosives booster of Figs 1 to 3; Fig. 6 shows a side elevation of a first preferred container forming part of an explosives device in accordance with the present invention; Figs 7, 8 and 9 show, respectively, plan, side and underside plan elevations of a first preferred cap for use with the container of Fig. 6 and in an explosives device in P35648 7 accordance with the present invention; Fig. 10 shows an assembled side elevation of the cap and container of Figs 6 to 9; Fig. 11 shows the device of Fig. 10 when fitted with a detonator; Fig. 12 shows a side elevation of a second preferred container forming part of an explosives device in accordance with the present invention; Figs 13 to 16 show, respectively, plan, side, underside plan and second side elevations of a second preferred cap for use with the container of Fig. 12 and in an explosives device in accordance with the present invention; Figs 17 and 18 show, both in front elevation, opposing engaging fingers, being part of the cap of Figs 13 to 16; Fig. 19 shows a side elevation of the finger of Fig.

18; and Fig. 20 shows an assembled side elevation of the cap and container of Figs 12 to 19.

MODES FOR CARRYING OUT THE INVENTION The prior art device of Figures 1 to 5 has been previously described in the Background Art section of the specification. Preferred forms of the present invention will now be described with reference to Figures 6 to Referring firstly to Figs 6 to 11, an explosives device in the form of explosives booster 10 includes a kegshaped housing 12 and a detonator release cap 14.

The housing 12 has an outwardly curved side wall 16, 30 which reduces the possibility of the housing becoming •coo wedged in a hole the tapering works against the housing becoming wedged in a narrowing of a drilled bore makes for easier release) The housing includes a pair of structural bands 18, 20 provided both for aesthetic purposes and to stabilise the top and base of the housing respectively during transportation and during an explosion. In other words, P35648 7a the booster explodes out from the side wall, thereby maximising its effect with surrounding explosive. The bands can be separate bands that are retro-fitted to the housing after moulding after a blow moulding *ee *oe P35648 formation of the housing), or can be moulded integrally with the housing so that they are contiguous therewith.

A plurality of longitudinal ribs 21 can also be moulded into the side wall again for aesthetic purposes, and to increase the structural stability of the wall. In a preferred embodiment, 8 such ribs are spaced evenly around the housing.

The top of the housing further includes an upwardly projecting hollow boss 22, which opens onto the interior of the housing to communicate therewith. A circumferential flange 24 extends around the boss and can be lockably engaged by cap 14 (described below) In addition, a recess 28 extending inwardly and up from the bottom of the housing is provided. This o 15 enables an assembled like explosives booster the oo€ housing when fitted with a cap) to be stacked on or under oo other like explosives boosters for transportation and :storage.

Referring specifically to Figs 7 to 9, cap 14 for 20 use with the housing 12 is depicted. The cap includes a circular platform 32 with a guide tube 34 extending downwardly therefrom. In addition, a pair of locking lugs 36, 38 extend downwardly from the platform, each provided with a hooked end.

Extending upwardly from the platform 32 are a .".pair of tube engaging fingers 40, 42. The fingers include !respective opposing semi-circular surfaces 44, 46 at inwardly facing ends thereof, and into which a supporting element, usually in the form of a cord or detonator tube, of corresponding size can be captured. The hooked ends of the fingers 40, 42 also define a pair of shoulders 48.

The tube 34 is open at the platform-32, and the opening is covered by a frangible film cover 50, which can be pierced by a detonator (described below) Fig. 10 shows release cap 14 attached to housing 12. As can be seen, guide tube 34 is inserted within boss 22 and locking lugs 36, 38 are snap locked around f- P35648 -9circumferential flange 24. The platform 32 sits on top of boss 22. (Note in Fig. 10, the bands 18, 20 and longitudinal ribs 21. have been removed for clarity) Referring to Fig. 11, a detonator 60 (of known type) is attached crimped) to a cord, most typically a detonator tube 62 (of known type) at end 64. The detonator is shown inserted into the explosives booster in accordance with the present invention. As can be seen, the detonator 60 has been inserted through guide tube 34 to break film cover 50 and extend into the interior of the housing 12. In addition, tube 62 is positioned and clamped between tube engaging fingers 40, 42.

In use, typically the housing 12 (as shown in Fig. 6) is pre-filled with an explosive material at 15 an explosives factory, or on site). The cap 14 is then *attached to the housing in the manner as depicted in Fig.

.e 10, and the cap encloses the explosives material within the

OS..

housing and seals it from the surroundings (the sealing being assisted by film cover 50 and optionally by rubber 20 sealing rings etc.). Thus, the explosives booster as shown in Fig. 10 is ready for transportation, storage and use.

When required for use, the detonator is inserted between fingers 40, 42, with the angled surfaces thereon enabling the detonator to force the fingers apart. The detonator is brought into engagement with film cover 50 and is forced therethrough (typically not requiring too excessive a force) and the detonator is progressively inserted until the detonator attachment end 64 has passed between the fingers. Thus, the detonator reaches the position shown in Fig. 11.

An internal step can be provided within the housing (not shown) and against which the detonator rests once it has reached the position shown in Fig. 11 to prevent it from dropping further within the housing, or should the fingers 40, 42 ever fail to sufficiently clamp the detonator tube). Thus, once the detonator has passed between the fingers, the fingers then snap back and engage P35648 against the detonator tube 62 to clamp the detonator/tube arrangement to the explosives booster.

The explosives booster is now ready for lowering into a drilled bore. The booster is lowered to a desired position, explosive is introduced around the booster, and the booster is then fired. It is typical though not essential to use the detonator tube as the cord for raising and lowering the detonator in use. A separate cord or other element can be fitted to the cap and used as appropriate. In this case, detonation can occur remotely or via a separate detonation wire etc.

Typically, the detonator tube is formed from a plastics material, and has a conductive element extending "therein for supplying a charge to the detonator. The tube 15 typically has sufficient tensile strength for raising, lowering and forceful removal of the detonator from the booster.

The arrangement depicted in Fig. 11 protects the highly explosive detonator and prevents it from inadvertent 20 contact with side walls of the drilled bore etc.

As can also be seen, the axis A of the explosives booster is aligned with the detonator tube, and so the offset that occurs with prior art boosters (with all the attendant disadvantages) is avoided. Thus the booster 25 typically hangs vertically in use, with its axis aligned with the tube.

Furthermore, the detonator 60 is positioned centrally within the explosives booster, thereby minimising potential misfiring (prior art boosters arrange the detonator towards the side wall, increasing the potential of the booster to misfire and explode outwards through the side wall without firing the bulk of the booster).

In addition, the separate mounting of the cap 14 to housing 12 provides a number of advantages.

Specifically, the locking lugs 36, 38 and flange 24 can be designed such that, at a predetermined force (load), the lugs can be released from flange 24. This release can be S P35648 -II effected in, for example, three ways. Firstly, the lugs can deflect outwardly at the predetermined force to thereby release the cap from the housing. Secondly, the lugs can break at a the predetermined force, again to release the cap from the housing. In a third alternative, the flange itself can either deform or break at the predetermined force to allow the cap to be released from housing 12.

As stated above, release of the cap from the housing may be required where, for example, the booster has been lowered into a hole and become snagged, fouled, etc.

Thus, a user pulls upwardly on cord 62, and detonator end 64 is drawn into and against shoulders 48 of the cap. As this force is increased, and at a predetermined level, the **lugs or flange give way to release the cap.

15 Alternatively, for example if the cap is made integral with the housing, then the arrangement can be configured such that the fingers 40, 42 deform or break to release the detonator from the booster.

As a further alternative, both the lugs and the 20 fingers can break or disengage at a predetermined force to release the detonator from the booster.

In any case, the highly explosive detonator and tube can be recovered for safety purposes (eg. to prevent inadvertent detonation). Also, the relatively more 25 expensive detonator and detonator tube can be recovered and can be re-used with a new explosives booster.

Referring now to Figures 12 to 16, where like reference numerals will be used to denote similar or like parts, the explosives booster 10' is in principle the same as that shown in Figures 6 to 11, however the release cap 14' has a more squat and wide configuration than that shown in Figures 6 to 11. In addition the hollow boss 22 is also wider to accommodate this release cap.

Furthermore, the tube engaging fingers 40,42 are supported within an upstanding shroud configuration defined by front shroud quadrants 70 and rear shroud quadrants 72.

The shrouding makes it easier for the release cap 14' to P35648 sit within a recess 28 of a like container, and also protects the fingers 40,42 from becoming ensnared, knocked, and prised apart etc during transportation, storage etc.

The shrouding also improves the aesthetic appearance of the cap 14' As can also be seen, the frangible film 50 is located within a lower platform 74 which closes the upper end of tube 34 and which is spaced below the platform 32 and connected thereto by connectors 75. When the cap 14' is fitted to the housing 12' (Figure 20) the lower platform 74 is recessed within the hollow boss 22, thus further protecting film cover 50 from inadvertent damage, piercing etc.

ooo Referring specifically to Figures 17 to 19, the 15 fingers 40,42 are modified over those shown in Figures 6 to 11. In particular, each finger has a rearwardly projecting lug 76, which in use engages against the platform 32 to delimit the amount of outward pivoting of each finger (eg.

S" when a detonator is inserted between the fingers). In 20 addition, each finger pivots about a downwardly projecting lobe 78, which is attached to the lower platform 74 (eg.

slotted into an appropriate recess, adhered, plastically welded or formed integrally with the platform etc). The narrower lobe makes for easier pivoting.

25 Furthermore, each finger has inwardly scalloped guides 80 which receive and facilitate the sliding insertion of the detonator between the fingers.

Finally, tube 34 is strengthened internally by the formation of three equidistantly spaced webs 82, which facilitate a stable mounting of the tube within the boss 22.

In all other respects, the cap 14' is of similar construction and operation to cap 14 shown in Figures 6 to 11. Furthermore, the operation of the explosive device of Figures 12 to 20 is similar to that of the device of Figures 6 to 11.

Preferred embodiments of the invention have been f- P35648 -13designed so that when a maximum load of 18kg is applied when pulling the detonator upwards, the explosives booster releases the detonator. This readily allows the highly explosive detonator to be removed from the hole, thus lowering the risk of an accident. Prior art designs have no such safety and recovery mechanisms.

Typically, the explosives booster components the housing and cap), are formed from plastic (prior art designs are constructed of less stable and less durable paper). For example, the housing can be formed in a blow moulding process whereas the cap can be formed in an injection moulding process. In a most preferred arrangement, the explosives booster is formed from a red coloured plastics material, as red is known in the mining industry as implying danger, and there are certain aesthetic benefits derived from the colouring and keg-like shape of the preferred explosives booster.

As can be appreciated from the above description and drawings, the preferred explosives booster hangs in a S" 20 true vertical orientation, thereby minimising the potential collision with obstacles when lowering into and removing S* from bores and holes. Prior art designs lean towards one side as a result of their poor geometrical configuration.

As further described above, the detonator is placed into 25 the centre of the booster, whereas prior art designs insert S"the detonator into the bottom of the booster. This central arrangement enhances firing efficiencies.

The preferred explosives booster has also been designed to provide strength in a vertical plane to sustain the weight of bulk explosive material loaded on top of the booster in use. Should too much material be loaded, then the booster is simply released at the predetermined load, and a new booster can be lowered back into the bore.

The preferred booster has curved sides and this reduces the possibility of it becoming wedged in a hole or bore, and also allows for easier entry and exit to and from a hole. Also, it advantageously minimises problems P35648 -14experienced by shot firers (the users of explosive boosters) knocking loose fragments into holes, which can then be caught up around the explosives booster. Again, this increases the safety of the explosives booster.

Because the explosives booster can be manufactured in plastic or similar material, this allows a liquid based explosive material to be used instead of the current solid explosive. The employment of liquid explosives allows the booster to be assembled on site at the mine, under the umbrella of a mine's explosive license.

In the prior art, boosters must be assembled in a factory licensed to manufacture explosives, prior to transportation to the mine, with the attendant risks, damage, expense etc.

As stated above, the base of the explosives 15 booster has been designed with a hollow protrusion to allow economical stacking. In addition, this allows a user to .easily distinguish between the bottom and the top of the booster when loading the detonator therein.

Of course, other shapes of boosters can be 20 employed, and other releasing arrangements between the cap and housing can be employed. For example, the fingers (or a similar arrangement) could include a frangible or perforated section which breaks at a predetermined force.

Alternatively, thinner sections in the lugs that break at 25 predetermined forces (loads) may also be employed to release the cap (and detonator) from the housing.

Whilst the invention has been described with reference to a number of preferred embodiments, it should be appreciated that the invention can be embodied in many other forms.

P35648

Claims (7)

1. 2. A device as claimed in claim 1, wherein the element is a cord having sufficient length for a bore into which the device is located in use.
2. 3. A device as claimed in claim 1 or claim 2, wherein the container has a protrusion on an in use upper surface thereof to which the release means can be fastened and from which it can be released in use.
3. 4. A device as claimed in claim 3, wherein the protrusion comprises a flange extending therearound and out therefrom, and the release means includes a plurality of hooks which engage the flange, wherein the hooks and/or flange are deformable or breakable to disengage from the flange at the predetermined force. A device as claimed in claim 4, wherein the release means comprises a pair of lugs opposing the hooks and :....adapted for fastening engagement with the element.
4. 6. A device as claimed in claim 4 or claim 5, wherein the element is a detonation cable and provides both support and electrical or chemical connection to the explosive device.
5. 7. A device as claimed in claim 6 wherein the P35648
6. 16- container has an opening at the protrusion and through which the detonation cable extends to the interior of the container for detonating the explosive. 8. A device as claimed in claim 7 wherein the detonation cable comprises an enlarged detonator portion at that end which is located in the container, with the detonator portion extending through the opening, and with a narrower detonator tube portion connected to and extending away from the enlarged portion, the connection defining a shoulder in the cable. 9. A device as claimed in claim 8, wherein the opposing lugs of the release means are adapted to fasten against the narrower portion of the detonation cable and such that the lugs prevent the shoulder from being passed therebetween. A device as claimed in any one of claims 7 to 9, wherein the container incorporates a hollow recess in an underside thereof such that the container protrusion when fitted with the release means can be received in a recess of a like container when in a stacked configuration. 11. A device as claimed in any one of the preceding claims, wherein the container is barrel shaped and the container and release means are formed from a plastics material. 12. An explosives device comprising an elongate barrel- 30 shaped container having a longitudinal axis and adapted for housing explosives therein, the container being connectible at one end to an element for raising and lowering the container, wherein the element is connected to the container such that, when the element extends vertically in use, the container can hang therefrom with its longitudinal axis generally aligned with or parallel to the element. P35648
7. 17- 13. A device as claimed in claim 12, wherein the container is as further defined in any one of claims 3,4,7 or 10, and the device is adapted for use with a release means as defined in any one of claims 1, 3 to 5 and 9 to 11 and the element is as further defined in any one of claims 2 or 5 to 9. 14. A release means for an explosives device of the type comprising a container for housing explosives therein, the release means being releasably connectable to the container and/or to an element for raising and lowering the container; wherein the release means is adapted for releasing from the container and/or the element at a predetermined force on the element away form the container. A release means as claimed in claim 14, that is as defined in any one of claims 3 to 5 and 9 to 11. 16. A release means as claimed in claim 14 or claim wherein the element is as defined in any one of claims 2 or 5 to 9. 17. An explosives device substantially as herein described with reference to the accompanying drawings. Dated this 5th day of September 2003 THOMAS CHRISTIAN SKEFFINGTON PETER EDWARD BIGGS 30 By their Patent Attorneys C GRIFFITH HACK "Fellows Institute of Patent Attorneys of Australia Attorneys of Australia P35648