AU2007203087A1 - Improvements to couplings for modular explosives cartridges - Google Patents

Description

7- P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION PATENT OF ADDITION Invention Title: "IMPROVEMENTS TO COUPLINGS FOR MODULAR EXPLOSIVES CARTRIDGES" The following statement is a full description of this invention, including the best method of performing it known to us:

TITLE

"IMPROVEMENTS TO COUPLINGS FOR MODULAR EXPLOSIVES CARTRIDGES" FIELD OF THE INVENTION 00 THIS INVENTION is concerned with improvements or Smodifications to modular explosives cartridges of the type described in SAustralian Patent Application No 2004200371.

The invention is concerned particularly although not exclusively with improvements or modifications to couplings for modular explosives cartridges.

BACKGROUND OF THE INVENTION It is well known to package explosive compositions in purpose designed packages to assist in transportation and handling of explosives compositions including dry powder or granulated compounds, emulsions, slurries, water gels and the like.

These packages may be adapted to suit charge mass, borehole diameter, borehole length and the like.

Australian Patent Application No AU-A-81802/87 describes the packaging, in non-porous plastic cartridges of from 25mm to 75mm in diameter and 1000mm length, an explosive composition comprising ammonium nitrate, paraffinic oil and foamed or expanded polystyrene beads.

British Patent No 882,665 describes the packaging of ammonium nitrate compositions in paper wrapped cartridges.

British Patent No 2,163,694 describes a modular explosives 2 Scartridge comprising a hermetically sealed explosives filled tube having cexternally threaded formations at opposite ends. These tubular containers may be joined together by a screw-threaded sleeve engaging adjacent ends of tubular containers to form an elongate explosives charge with a detonating 00oO cord extending externally thereof to a distal end formed with a cap well to Sreceive a detonator. A similar device is disclosed in International Publication SNo WO 03/004960.

British Patent No 1,281,421 also describes packaging of an ammonium nitrate explosive in a thin flexible plastic sheath such as polyethylene. This product has detonating cord extending throughout an elongate explosive filled sheath in a unitary charge of up to 20m long. The specification discloses divisible charges in rolls of from 50m to 100m in length whereby charges of selected shorter length can be formed by clamping the sheath at closely spaced intervals and severing the charge therebetween.

The patent specification states that explosive charges according to the invention can be inserted into boreholes at up to 600 from vertical and moreover that with the aid of a bracket shaped slide, these packages can be inserted into horizontal boreholes.

Experience has shown however that thin flexible sheaths of say 0.2mm in wall thickness are prone to perforation by puncture on rough borehole surfaces or by abrasion even on smooth borehole surfaces. If such perforations occur near the lower end of the charge being inserted, there is a risk that a substantial part of the freely flowing particulate explosive zj composition would fall to the bottom of the borehole beyond the end of the c detonating cord without the knowledge of the personnel concerned. Only when the connected charges in adjacent boreholes were detonated would it be discovered that the mechanical and safety aspects of the integrated 00 oO breaking pattern were compromised by the detonation failures in one or more Sboreholes.

SThese soft thin walled explosive packages were found to be difficult and time consuming to insert in to horizontal boreholes and even more prone to puncture and tearing when pushed into the horizontal cavity.

A particular difficulty with such flexible, thin walled elongate explosive charges is that when rolled into conveniently sized coils for packaging, transportation and storage, the tubular sheath is prone to kinking or flattening in parts.

At the position of the kink or flattened region, the cross sectional area of the explosive charge is substantially diminished and with severe kinking, a discontinuity may be formed in the mass of explosive material. This kinking or cross sectional area reduction can also occur when trying to insert elongate thin walled flexible tubular explosive charges into inclined or horizontal boreholes.

It is believed that severe reductions in cross sectional area or discontinuity in the mass of explosive composition may give rise to a condition known as "gapping" where propagation of explosive energy along the charge column is interrupted.

In order to overcome such problems with prior art packaged explosives, particularly for use in perimeter hole blasting for tunnel shaping where the boreholes are horizontally drilled, it has been proposed to use a short, ridged tubular packages adapted for end to end coupling to form a long unitary charge.

00 Originally such explosive packages comprised a stiff paper or cardboard cylinder about 900mm long and about 20mm diameter filled with highly viscous, non flowable cap sensitive emulsion explosive. The paper or cardboard cylinder was open at opposite ends which were shaped to form a socket and spigot engagement between adjacent packages.

Of more recent times these paper or cardboard cylinders have been replaced with a semi rigid plastic tube such as polyethylene with wall thickness of about 1mm.

International Publication No WO 99/46556 describes a modular cartridge explosive wherein male and female couplings having sealing diaphragms are fitted to opposite ends of a tubular cartridge of explosive.

The male coupling engages with an inner wall of one end of the tubular cartridge by an interference fit and the female coupling engages with an outer wall of an opposite end of the tubular cartridge, also by an interference fit. The male coupling includes a pair of diametrically opposed barbs which engage in apertures in the female coupling to resist disconnection between the male and female couplings. While generally effective for its intended purpose, the male/female coupling suffers from the disadvantage that the interference fit between the smooth cylindrical contact surfaces of the tubular cartridge and both the male and female couplings does not provide a positive

O

lock between adjacent cartridges and under tension or torque, full or partial separation can occur between a cartridge tube and a coupling thus creating 0a spatial discontinuity between the adjacent explosives charges. This is a particular risk where tension is applied to a joined string of cartridges to 00 withdraw the string in the event of jamming in the borehole.

A difficulty encountered with these prior art modular explosives tubes is that a close face to face abutment of the explosive composition in adjacent tubes is required to ensure propagation of the explosive force throughout the entire assembly which may for example comprise six tubes frictionally engaged by the socket and spigot fittings.

As typically these tubes are initially filled with a heated mix to reduce viscosity of the normal non-flowable viscous emulsion, the tube contents undergo shrinkage on cooling and can create a gap of 2-3mm between the faces of explosive material when the tubes are joined.

Where "gapping" occurs between adjacent explosive masses, whether due to shrinkage in the tube or human error in assembly, an incomplete explosion can leave one or more portions of the explosive charge in the ground. This is an extremely hazardous situation with cap sensitive explosives in particular, which may be accidentally detonated by impact from an excavator or subsequently in a crushing mill.

Another problem associated with prior art blasting techniques is that where it is required to increase the powder factor or energy factor in the "butt" or base of a borehole, it is common practice to first push a separate primer charge to the butt of the borehole.

SThereafter, a water gel or emulsion explosive is loaded into the borehole typically in a form of a spigot and socket joined tube described above.

Again this procedure is prone to unreliability due gapping 00oO between the primer and the end of the explosive charge and/or between Sadjacent tubes which can lead to ineffectual blasting, rifling of the borehole Sand unexploded explosives left in the borehole.

Yet another disadvantage associated with abovementioned prior art explosive charge is the need to insert a stem plug to close off the borehole after the charge is loaded. This a costly and time consuming process.

Australian Patent 742653 to the same inventor describes an elongate coilable blasting cartridge having a detonating cord extending longitudinally within the tubular casing and terminating in a distal end of enlarged diameter compared with the main part of the tubular casing. This product is available in 4-5 metre lengths and addresses many of the prior art problems referred to above.

Although the coilable elongate blasting cartridge described in Australian Patent No 742653 is not prone to gapping, there exists a need for a modular blasting cartridge construction capable of forming variable cartridge lengths as required but which still has the reliability of the product of Australian Patent No 742653.

The need for a modular blasting cartridge was addressed by the same inventor in Australian Patent Application No 2004200371 which described male and female couplings having barbed barrels forming a secure coupling to a tubular cartridge at opposite ends thereof. The male O and female couplings were connectable to respective female and male couplings of adjacent cartridges by a bayonet-type coupling having piercing 00 members to pierce adjacent membranes during rotation of the bayonet-type N coupling thereby allowing close intermingling of the explosives compositions in adjacent cartridge tubes. While generally satisfactory for their intended purpose, it was noted in practice that when at least one of a pair of cartridges to be coupled contained a densely packed particulate explosives composition, rotation of the male and female couplings to a secure position could be hindered by frictional engagement between the membrane piercing blades and the densely packed explosives composition.. On occasions this could prevent full rotation of the bayonet-type fittings with a risk of disengagement between adjacent cartridges.

SUMMARY OF THE INVENTION It is an aim of the present invention to overcome or ameliorate at least some of the prior art problems associated with modular explosive tubular containers and/or otherwise to provide users with a convenient choice.

According to one aspect of the invention there is provided a coupling system for a modular explosives cartridge, said coupling system comprising:a first coupling member having a tubular shank at one end and a coupling spigot at an opposite end, said coupling spigot comprising one or more radially extending retaining lugs; and, a second coupling member having a tubular shank at one end and a coupling socket at an opposite end, said coupling socket having axially spaced radially inwardly extending walls defining a channel-like recess 00oO therebetween, an outermost one of said walls including one or more locating Sapertures therein to receivably locate respective said one or more lugs, said Sfirst and second coupling members each comprising hollow bodies having openings at opposite ends thereof, and a membrane closure intermediate said opposite ends, said first and second coupling members, in use, being engageable by insertion of said coupling spigot into said coupling socket with said one or more retaining lugs being located in respective one or more locating apertures and rotation of said coupling spigot relative to said coupling socket to engage said one or more retaining lugs between said walls to prevent axial separation of said coupling spigot and said coupling socket, said coupling system including a locking mechanism to prevent disconnection between said coupling spigot and said coupling socket once coupled.

Suitably, said tubular shanks of said first and second coupling members are adapted for coupling to a tubular explosives container.

If required, respective tubular shanks of said coupling spigot and said coupling socket each include at least one circumferential barb formations on an outer wall thereof.

The locking mechanism may comprise one or more resiliently deformable elements which allow relative rotation in one direction between 9 (said coupling spigot and said coupling socket and, when engaged, to prevent relative rotation between said coupling spigot and said coupling socket in an Copposite direction.

Suitably, said one or more resiliently deformable elements 00 engage against a respective said one or more retaining lugs to prevent relative rotation between said coupling spigot and said coupling socket once engaged.

If required, said coupling spigot may include a radially projecting flange member, said flange member, in use, having a face abutting an outer face of said outermost one of said walls of said coupling socket.

Preferably, said coupling spigot and said coupling socket each include alignable indicia, in use, indicative of a locked state between said coupling spigot and said coupling socket.

Suitably, each of said coupling spigot and said coupling socket includes a locating recess, in use, to locate a respective end of a detonating cord located within a tubular explosives container.

Preferably, respective said locating recess of said coupling spigot and said coupling socket are axially aligned in use.

Suitably, respective locating recesses of said coupling spigot and coupling socket terminate adjacent an inner face of respective membrane closures.

Preferably, respective outer faces of respective membrane closures of said coupling spigot and said coupling socket closely abut when said spigot and socket are coupled.

According to another aspect of the invention there is provided a 0 modular explosives cartridge body comprising a coupling spigot and a coupling socket as hereinbefore described, said coupling spigot and coupling 00 socket being coupled to a tubular explosives container at opposite ends thereof.

Throughout this specification and claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers.

BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention may be fully understood and put into practical effect, preferred embodiments of the invention will now be described with reference to the accompanying drawings in which: FIG. 1 illustrates an assembled view of a coupling system for a modular explosives cartridge; FIG. 2 illustrates a side perspective view of a coupling socket; FIG. 3 illustrates a side perspective view of a coupling spigot; FIG. 4 is a perspective view from one end of the coupling spigot of FIG. 3; FIG. 5 is a perspective view from an opposite end of the coupling spigot of FIG. 3; FIG. 6 is a perspective view from one of the coupling socket of 11 SFIG. 2; SFIG. 7 is a side elevational view of the coupling socket of FIG.

2; and FIG. 8 is a perspective view from an opposite end of the 00oO coupling socket of FIG. 2.

SFor the sake of clarity and simplicity, like reference numerals Shave been used for like features in the drawings.

DETAILED DESCRIPTION OF THE DRAWINGS In FIG. 1, the coupling system 1 comprises a coupling spigot 2 and a coupling socket 3 shown in an engaged and locked state.

Coupling socket 3 comprises a hollow tubular shank 4 with spaced circumferential barb formations 5. Between barb formations 5 are spaced rib projections 5a, in use, to prevent relative rotation between coupling members 2 and 5 and a length of plastics tubing (not shown) forming the body of an explosives cartridge. An end flange 6 includes opposed slotted recesses 7 through which an engaging end 8 of coupling spigot 2 can be seen. In the engaged state as illustrated, retaining lugs 9 of coupling spigot 2 are slidably located within and at one end of recesses 7 with a resiliently deformable latch member 10 preventing relative rotation between the spigot and socket members 2,3. This maintains the coupling system in a locked state where disconnection between the coupling spigot 2 and coupling socket 3 is prevented.

Coupling spigot 2 also includes a tubular shank 4 with spaced barb formations 5 and a flange 11 abutting flange 6 of coupling socket 3.

12 SIndicia in the form of arrows 12,13 on respective flanges 6,11 are aligned to cprovide a visual indication that the coupling 1 is in a locked state.

FIG. 2 shows the coupling socket of FIG. 1 in a separated state.

00 More clearly visible in FIG. 2 is an upwardly tapered portion 14 of the lower wall of recess 7 beneath latch member 10. Also visible is a Srecessed land 15 upon which retaining lug 9 is located when in a locked state as shown in FIG. 1. Between tapered portion 14 and land 15 is a step 16 inclined at an acute angle to engage a complementary step 17 in the lower edge of lug 9 as shown in FIG. 1 and FIG. 3.

FIG. 3 illustrates the coupling spigot 2 of FIG. 1 in a separated state.

Coupling spigot 2 includes a tubular spigot 18 projecting in an axial direction away from flange 3. Retaining lugs 9 are diametrically located on the outer surface of spigot 18 as shown more clearly in FIG. 4.

FIG. 4 also shows more clearly a membrane closure 19 adjacent the outer end of spigot 18. Membrane closure 19 may be a plastics or metal foil or a laminate thereof.

FIG. 5 shows an inverted view of the coupling spigot 2 of FIGS.

3 and 4. In this illustration is seen a generally tubular, axially extending recess member 20 to locate an end of a detonating cord such as a NONEL tube. Recess member 20 is supported by radially extending arms 21 extending to an inner side wall surface 22 of the spigot 18. The floor (not shown) of recess member 20 is coincident with the inner surface of 13 membrane closure 19.

FIG. 6 shows an upper perspective view of the coupling socket 3 of FIG. 2.

As shown in FIG. 6, the upper face 23 has diametrically 00oo opposed apertures 24 to receivably locate the retaining lugs 9 of coupling Sspigot 2. Extending away from apertures 24 in a clockwise direction are Schannel-like recesses 25 between axially spaced recess side walls.

Recessed openings 7 in flange 6 communicate with recesses 25. Channellike recesses 25 each terminate in a stop member 26. A membrane closure 27 is visible in FIG. 6.

FIG. 7 shows a side elevational view of the coupling socket of FIGS. 2 and 6. In this view, the diametrically opposed latch members 10,10' and tapered portions 14, 14' are clearly visible.

FIG. 8 shows a perspective view from below of the coupling socket of FIGS. 2, 6 and 7. Like the coupling spigot illustrated in FIG. 5, a generally tubular, axially extending recess member 20 is provided to receivably locate an end of a detonating cord. Similarly, recess member 20 is supported by radially extending arms 21 extending from an inner surface 22 of tubular shank 4. Like the coupling spigot of FIGS. 3 and 5, the floor (not shown) of recess member 20 is coincident with the inner surface of membrane closure 27.

In practice, the coupling socket and spigot fittings are coupled to opposite ends of a fairly stiff or semi-rigid plastics tubing about 1 to metres in length having an outside diameter of 20 25 mm and a wall thickness of about 1 2 mm. A typical plastics composition for such tubing may be a high density polyethylene (HDPE) compound containing an electrically conductive filler such as carbon black to avoid the risk of static electricity discharges during handling. Preferably the barbed ends of the 00 couplings are secured by compressible circular clamps during the assembly of the explosives cartridges which may contain a particulate ANFO emulsion Sexplosive with a NONEL detonating cord extending between respective recess members 20 of opposed coupling sockets and spigots of an explosives cartridge.

In practice, explosives cartridges comprising the coupling system of the present invention are delivered to a mine site in discrete lengths to enable shot firers to assemble a modular explosives charge from a finite number of cartridges coupled end to end via the coupling system according to the invention.

As a coupling spigot of an explosives cartridge is coupled to a coupling socket of another explosives cartridge, the coupling system performs a number of functions. As the engaged socket and spigot couplings are rotated relative to each other, the retaining lugs 9 depress latch members 10 against the tapered recess portions 14 which form tapered ramps to guide the retaining lugs 9 up on to lands 15 where they are frictionally engaged against lands 15 and complementary tapered steps 16,17 of lands 15 and lugs 9 engage. As lugs 9 ride up on to lands latches 10 are released by lugs 9 and resiliently recover to their normal position as shown in FIGS. 1, 2 and 7. In the event that an attempt is made Sto forcibly disconnect the coupling system of the invention, interconnected tapered steps 16,17 disconnect and allow lugs 9 to engage the free ends of latches 10. As the socket and spigot couplings are rotated further, latches deform and wedgingly engage in recesses 7 to prevent further rotation.

00oO The socket and spigot couplings, when engaged in a locked Sposition, have respective membrane closures 27,19 located in close Sproximity such that when the explosives charge is detonated, the detonation shock at the end of the detonation cord of one cartridge is transmitted through the thin frangible membrane closures to the aligned end of a detonating cord in the next successive coupled cartridge.

By providing alignable indicia on the exterior of the coupling members there is a clearly visible indication that the coupled spigot and socket members are in a locked state or otherwise.

If required, the socket and spigot members may be moulded from plastics material of contrasting colours to aid in the assembly of cartridges and modular explosives charges.

Claims (14)

1. A coupling system for a modular explosives cartridge, said Sni Ncoupling system comprising:- a first coupling member having a tubular shank at one end and 00 5 a coupling spigot at an opposite end, said coupling spigot comprising one or more radially extending retaining lugs; and, Sa second coupling member having a tubular shank at one end and a coupling socket at an opposite end, said coupling socket having axially spaced radially inwardly extending walls defining a channel-like recess therebetween, an outermost one of said walls including one or more locating apertures therein to receivably locate respective said one or more lugs, said first and second coupling members each comprising hollow bodies having openings at opposite ends thereof, and a membrane closure intermediate said opposite ends, said first and second coupling members, in use, being engageable by insertion of said coupling spigot into said coupling socket with said one or more retaining lugs being located in respective one or more locating apertures and rotation of said coupling spigot relative to said coupling socket to engage said one or more retaining lugs between said walls to prevent axial separation of said coupling spigot and said coupling socket, said coupling system including a locking mechanism to prevent disconnection between said coupling spigot and said coupling socket once coupled.

2. A coupling system as claimed in claim 1 wherein said tubular shanks of said first and second coupling members are adapted for coupling to a tubular explosives container. O

3. A coupling system as claimed in claim 1 or claim 2 wherein 00 O 0 5 respective tubular shanks of said coupling spigot and said coupling socket each include at least one circumferential barb formations on an outer wall thereof.

4. A coupling system as claimed in any preceding claim wherein the locking mechanism comprises one or more resiliently deformable elements which allow relative rotation in one direction between said coupling spigot and said coupling socket and, when engaged, to prevent relative rotation between said coupling spigot and said coupling socket in an opposite direction.

A coupling system as claimed in claim 4 wherein said one or more resiliently deformable elements engage against a respective said one or more retaining lugs to prevent relative rotation between said coupling spigot and said coupling socket once engaged.

6. A coupling system as claimed in any preceding claim wherein said coupling spigot includes a radially projecting flange member, said flange member, in use, having a face abutting an outer face of said outermost one of said walls of said coupling socket. 18

7. A coupling system as claimed in any preceding claim wherein Ssaid coupling spigot and said coupling socket each include alignable indicia, in use, indicative of a locked state between said coupling spigot and said coupling socket. 00oO

8. A coupling system as claimed in any preceding claim wherein Seach of said coupling spigot and said coupling socket includes a locating recess, in use, to locate a respective end of a detonating cord located within a tubular explosives container.

9. A coupling systema s claimed in claim 8 wherein respective said locating recess of said coupling spigot and said coupling socket are axially aligned in use.

10. A coupling system as claimed in claim 8 or claim 9 wherein respective locating recesses of said coupling spigot and coupling socket terminate adjacent an inner face of respective membrane closures.

11. A coupling system as claimed in any preceding claim wherein respective outer faces of respective membrane closures of said coupling spigot and said coupling socket closely abut when said spigot and socket are coupled.

A modular explosives cartridge body comprising a coupling 19 0 spigot and a coupling socket as claimed in any preceding claim, said coupling spigot and coupling socket being coupled to a tubular explosives container at opposite ends thereof. oo

13. A coupling system substantially as hereinbefore described with C, reference to the accompanying drawings.

14. A modular explosives cartridge body substantially as hereinbefore described with reference to the preferred embodiments described herein. DATED this Second day of July 2007. JOHNSON HI-TECH (AUSTRALIA) PTY LTD By its Patent Attorneys FISHER ADAMS KELLY