BACKGROUND OF THE INVENTION
[0001] This invention is concerned generally with a customized low energy method of breaking
rock in a controlled manner.
[0002] As used herein the word "rock" includes rock, ore, coal, concrete and any similar
hard mass, whether above or underground, which is difficult to break or fracture.
It is to be understood that "rock" is to be interpreted broadly.
[0003] A number of techniques have been developed for the breaking of rock using non-explosive
means. These include a carbon dioxide gas pressurisation method (referred to as the
Cardox method), the use of gas injectors (the Sunburst technique), hydrofracturing
and various methods by which cartridges containing energetic substances pressurise
the walls or base of a sealed drill hole to produce penetrating cone fractures (known
as PCF).
[0004] These techniques may be an order of magnitude more efficient than conventional blasting
in that they require approximately 1/10 of the energy to break a given amount of rock
compared to conventional blasting using explosives. The lower energy reduces the resulting
quantity of fly rock and air blast and to an extent allows the rockbreaking operation
to proceed on a continuous basis as opposed to the batch-type situation, which prevails
with conventional blasting.
[0005] Most non-explosive rockbreaking techniques rely on the generation of high gas pressures
to initiate a tensile fracture at the bottom of a relatively short drill hole.
[0006] As used herein the term "propellant" is to be interpreted broadly to include a blasting
agent, propellant, gas-evolving substance, explosive or similar means which, once
initiated, generates high pressure jet material typically at least partly in gaseous
form. Propellants of this nature are known in the art. "Blasting agent" and "propellant"
are used interchangeably in this specification.
SUMMARY OF INVENTION
[0007] The invention provides apparatus for breaking rock which includes a cartridge which
forms an enclosure, a propellant inside the enclosure, and at least one element which
is electrically energisable, characterized in that it is made from inert material
exposed to the propellant which, when energised, initiates combustion of the propellant
to release high pressure material inside the cartridge.
[0008] As used herein "inert material" means a material which, unless energised, cannot
give rise to a spark or other phenomenon which can initiate the blasting agent.
[0009] The element may be in the nature of a filament or electrical resistor.
[0010] The element may be made from any appropriate material but a preferred material is
carbon, eg. in the form of graphite.
[0011] The element may be treated in any appropriate way to enhance the efficiency with
which the propellant is initiated. For example the element may be dipped in or coated
with aluminium powder or any similar agent which gives rise to a sputtering effect
when the element is energised.
[0012] The element may be in the nature of a fusible link ie. a portion of the element may
be disintegrate when an electric current in excess of a predetermined amount is passed
through the element. Disintegration of the element gives rise to the generation of
high energy and relatively small particles which are propelled into the propellant
thereby to initiate combustion of the blasting agent. This approach should be contrasted
with a technique wherein the element in the form of a filament wire is heated by the
passage of electric current to a higher temperature at which the propellant is initiated
but wherein the filament remains integral and does not disintegrate due to the direct
effect of the electric current passing through the filament (see for instance WO-
01/65199).
[0013] The filament may be coated to prevent the propellant, or moisture in the propellant,
from reacting or fusing with the material contained in the filament.
[0014] The filament may for example be a wire or band made from aluminium, nickel-chrome,
carbon or a similar material, or a resistor such as a ceramic metal device which,
when energized, does not fuse or disintegrate but instead, remains integral despite
dissipating sufficient heat to initiate combustion of the propellant.
[0015] The cartridge may include a base and a side wall which extends from the base. The
side wall may be generally cylindrical.
[0016] The cartridge may be made from a malleable material which, in this sense, indudes
a material which is capable of plastic deformation, without fracture, at least to
a predetermined extent.
[0017] The cartridge is preferably made from a plastics material eg. polypropylene, polyethylene
or the like. The scope of the invention is not limited in this regard.
[0018] An upper end of the cartridge, ie. an end which opposes the base, may be domed and
the filament may be located at the upper end.
[0019] It falls however within the scope of the invention to locate the filament at an intermediate
location ie. between opposing ends of the cartridge.
[0020] The filament may be relatively small and thus, when energized, cause the production
of a localized relatively high energy hot spot. On the other hand the filament may
be elongate so that, when energized, the propellant is initiated over a fairly substantial
length or area or at a plurality of points.
[0021] It falls within the scope of the invention to include more than one element in the
cartridge so that initiation of the propellant takes place at more than one location.
Electrical leads to the element may be positioned inside the cartridge or on an outer
surface of the cartridge but preferably are embedded in the material from which the
cartridge is made.
[0022] The electrical leads may be connected to terminals to facilitate connection of the
leads to a control unit. The terminals are preferably on an outer side of the cartridge.
[0023] The terminals may be covered with a removable closure. Alternatively the terminals
may be covered with a frangible or breakable closure. The closure is designed to protect
the terminals from damage or exposure prior to use of the cartridge.
[0024] The element, or elements, as the case may be, with suitable leads or conductors to
the elements and, where applicable control devices such as timing circuits and capacitors
or other energy sources for operating the timing circuits, may be mounted on a suitable
substrate or motherboard, to facilitate handling of these components and assembly
thereof together with the remainder of the cartridge.
[0025] The invention also extends to an element of the aforementioned kind, and to a substrate
which carries the element and, where required, one or more components for use with,
or required to energize, the element.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The invention is further described by way of examples with reference to the accompanying
drawings in which:
Figure 1 is a view in cross section and from the side.of blasting apparatus according
to one form of the invention,
Figures 2 and 3 are views similar to Figure 1 of blasting apparatus according to second
and third forms of the invention,
Figure 4 is an enlarged cross sectional view of a portion of a cartridge illustrating
connecting terminals on the cartridge, and
Figure 5 shows a substrate which carries a filament, for use in the apparatus of the
invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0027] Figure 1 of the accompanying drawings illustrates a hole 10 which is drilled into
a rock mass 12 from a face 14 using conventional drilling equipment. A cartridge 16
is loaded into the hole. In this example the cartridge has a base 18 and a generally
cylindrical wall 20 which extends from the base and which terminates at an upper end,
remote from the base, in a rounded shape 22.
[0028] The cartridge is made from a plastics material using injection techniques which are
known in the art. The cartridge is for example made from a high density plastics material
such as high density polypropylene.
[0029] It is desirable to form the cartridge from a malleable material which enables the
cartridge to be plastically deformed, without rupture, at least to a predetermined
extent eg. of the order of 10%, or more.
[0030] The cartridge forms an enclosure for a propellant material 24 which is of known composition.
The propellant is loaded into the cartridge under factory conditions using techniques
which are known in the art.
[0031] An initiator 26 is located at an upper end of the cartridge. The initiator has an
element when, in this case, is in the form of a filament made from inert material
such as carbon wire which, preferably, is formed into a coil or with a zig zag configuration.
The filament extends from two leads 30 and 32 which pass through the wall of the cartridge
so that filament is exposed, in the interior of the cartridge, to the propellant 24.
The leads 30 and 32 extend to a blasting control unit, not shown, of a type which
is known in the art.
[0032] Stemming 40 is placed into the hole from the rock face covering the cartridge to
a desired extent and is consolidated by being tamped in position.
[0033] The filament is energized by sending a signal of a determined energy content through
the wires 30 and 32 to the filament. The filament is thereby heated and glows creating,
in effect, a localized hot spot which transfers sufficient energy to the propellant,
in the immediate vicinity of the filament, to cause ignition of the propellant.
[0034] The propellant, when ignited, causes the release of high pressure jet material which
is substantially in gaseous form. This material produces a shock wave which is used
to fracture the rock 12, typically with an initial fracture being established at the
bottom 40 of the hole 10.
[0035] The carbon filament 26 is, as noted, inert and consequently it is possible to provide
the cartridge 16 in a form which is ready for use in the sense that the propellant
24 can be loaded into the cartridge even though the initiator 26 is already fixed
to the cartridge. In many other instances it is not possible to provide the cartridge,
loaded with propellant, if the initiator is already fixed to the cartridge for it
is possible inadvertently to energise the initiator and thus cause unwanted combustion
of the propellant. Due to the fact that the filament is made from an inert material
it is believed that this danger is effectively eliminated.
[0036] The filament may be coated with aluminium paint which, when heated, increases the
quantity of energy which is released and, depending on circumstances, can give rise
to a sputtering effect which enhances the efficiency with which the propellant is
ignited.
[0037] The filament could alternatively be in the form of a wire or band and could be made
from aluminium or nickel-chrome. These materials may be of a kind which, when heated
by electric current, fuse and disintegrate. In a variation use is made of a suitable
resistor, made for example from a ceramic/metal composition which, when heated, glows
but does not spatter or disintegrate, and which provides the necessary "hot spot"
to initiate combustion.
[0038] The arrangement shown in Figure 2 is similar in many respect to what is shown in
Figure 1 and where applicable like reference numerals are used to designate like components.
The filament initiator 26 is, however, in this case located at a position more or
less midway between the base 18 and the rounded upper end of the cartridge. The leads
30 and 32 extend from an upper entry point to the filament and are embedded in the
wall 20 of the cartridge. The filament 26 is fired in the same way as what has been
described in connection with Figure 1.
[0039] In the arrangement shown in Figure 3 the filament is not localized in the way shown
in Figures 1 and 2 but, instead, is elongate. The filament extends from end points
of wires 30 and 32 which, as is the case with the Figure 2 embodiment, are embedded
in the side wall 20. The filament is shaped into the form of a ring which extends
around an internal surface of the wall 20. Consequently, when the filament is initiated,
combustion of the propellant 24 takes place over an extended length or area or, otherwise
put, at a plurality of points.
[0040] The filament 26 may be designed and operated so that when energized it is heated
to glow and cause a localized temperature increase of sufficient magnitude to initiate
the blasting agent. Alternatively the filament may be in the form of a fusable link
such that a region of the filament is heated to disintegration point by the passage
of electrical current. Components of the filament which are released upon disintegration
are extremely hot and a sputtering-type action results as the filament disintegrates.
[0041] It is possible to enhance the combustion effect of the filament by coating the filament
at one or more locations with an agent such as aluminium powder or any other substance
which is explosive or flammable by nature. Again small localized hot spots are generated
when an appropriate electrical current is passed through the filament and combustion
of the propellant is therefore initiated effectively simultaneously at a plurality
of locations.
[0042] Also, to protect the filament against reacting with the propellant, or moisture in
the propellant, the filament may be coated with an inert material such as a suitable
lacquer, eg. of nitrocellulose.
[0043] Figure 4 is an enlarged view in cross section of an upper end 22 of a cartridge which
may be of the type shown in any one of Figures 1 to 3. The leads 30 and 32 are, as
has been described, embedded in the wall 20 of the cartridge and terminate in relatively
rigid terminals 50 and 52 respectively, which project outwardly from the cartridge.
The terminals are covered by means of a cap 54 which protects the terminals during
transport and storage of the cartridge. If the terminals are to be accessed to enable
electrical connections to be made to the terminals then the cap is removed. The cap
may for example be threadedly engaged with the cartridge. Alternatively the cap may
be formed substantially integrally with the cartridge or be secured thereto in a manner
which inhibits removal of the cap. In this case the cap includes a lid 56 which is
breakable, or which can be tom from the remainder along a line of weakness, not shown,
to expose the terminals so that electrical connections can be made thereto.
[0044] Figure 5 illustrates another modification which can be made to the aforementioned
principles. Figure 5 shows a cartridge 10 which is filled with propellant 24. A substrate
60 is located in the cartridge. The substrate is made from an inexpensive non-electrically
conductive material, and may be in the nature of a printed circuit board, be formed
from a suitable plastic material, or the like. The substrate may be rigid or flexible.
[0045] Discrete components may be mounted directly to the substrate using techniques which
are known in the electronics art. Alternatively components may be formed on the substrate
using deposition techniques similar to those employed in the manufacture of printed
circuit boards, integrated circuits and the like.
[0046] Thus, using an appropriate technique, a filament 26 is formed on, or is mounted to,
the substrate and leads 62 are formed connecting the substrate to a timing circuit
64. The circuit is also formed on or bonded to the substrate and includes leads 66
which extend to terminals 68. The conductors 30 and 32, which are inherently more
robust than the leads 62 and 64 on the substrate, are directly connected to the terminals.
[0047] The use of the substrate to carry the filament considerably facilitates the manufacture
of the filament and its use and helps in reducing inadvertent damage to the filament
which could arise during manufacture of the cartridge or when the cartridge is installed
in a hole in a rock face. The substrate may be of any appropriate shape or size so
that when the substrate is positioned inside the cartridge the filament 26 is substantially
automatically positioned at a desired location inside the cartridge. Clearly it is
possible to form a plurality of filaments on the substrate so that the individual
filaments are at precisely determined locations relatively to each other inside the
cartridge.
1. Apparatus for breaking rock which includes a cartridge (16) which forms an enclosure,
a propellant (24) inside the enclosure, and at least one element (26) which is electrically
energisable, characterized in that it is made from inert material exposed to the propellant which, when energised, initiates
combustion of the propellant to release high pressure material inside the cartridge.
2. Apparatus according to claim 1 wherein the element is made from a material selected
from carbon, graphite, aluminum, and nickel-chrome.
3. Apparatus according to claim 1 or 2 wherein the cartridge is made from a malleable
material and includes a cylindrical side wall (20), a base (18) and a domed end (22)
which opposes the base.
4. Apparatus according to any one of claims 1 to 3 which includes electrical leads (30,32)
which extend from terminals on an outer side of the cartridge to the element.
5. Apparatus according to claim 4 which includes a removable closure (54) which covers
the terminals.
6. Apparatus according to any one of claims 1 to 5 which includes a substrate (60) on
which the element is mounted and which is embedded in the propellant.
7. Apparatus according to claim 6 which includes a control device (64), for controlling
operation of the element, on the substrate.
8. Apparatus according to any one of claims 1 to 7 wherein the element (26) is in the
form of an elongate filament (26).
1. Vorrichtung zum Brechen von Fels, aufweisend eine Kartusche (16), welche ein Gehäuse
bildet, ein Treibladungsmittel (24) innerhalb des Gehäuses, und zumindest ein Element
(26), welches elektrisch mit Energie versorgbar ist, dadurch gekennzeichnet, dass das Element aus einem inertem Material hergestellt ist, welches, wenn es mit Energie
versorgt wird, eine Verbrennung des Treibladungsmittels initiiert, um in der Kartusche
Hochdruckmaterial freizusetzen.
2. Vorrichtung nach Anspruch 1, wobei das Element aus einem Material hergestellt ist,
welches aus Kohlenstoff, Graphit, Aluminium und Nickel-Chrom hergestellt ist.
3. Vorrichtung nach Anspruch 1 oder 2, wobei die Kartusche aus einem schmiedbaren Material
hergestellt ist und eine zylindrische Seitenwandung (20), eine Basis (18) und ein
domförmiges Ende (22) aufweist, welches der Basis gegenüber liegt.
4. Vorrichtung nach einem der Ansprüche 1 bis 3, aufweisend elektrische Leitungen (30,
32), die sich ausgehend von Anschlüssen auf einer Außenseite der Kartusche zu dem
Element erstrecken.
5. Vorrichtung nach Anspruch 4, aufweisend einen entfernbaren Verschluss (54), welcher
die Anschlüsse abdeckt.
6. Vorrichtung nach einem der Ansprüche 1 bis 5, aufweisend ein Substrat (60), auf welchem
das Substrat angebracht ist, und welches in dem Treibladungsmittel eingebettet ist.
7. Vorrichtung nach Anspruch 6, aufweisend eine Steuereinrichtung (64) zum Steuern des
Betriebs des Elements auf dem Substrat.
8. Vorrichtung nach einem der Ansprüche 1 bis 7, wobei das Element (26) in Form eines
länglichen Filaments (26) vorliegt.
1. Appareil pour briser des pierres qui comprend une cartouche (16) qui forme une enceinte,
une charge (24) à l'intérieur de l'enceinte, et au moins un élément (26) qui est électriquement
excitable, caractérisé en ce qu'il est fait d'un matériau inerte exposé à la charge qui, lorsqu'il est excité, amorce
la combustion de la charge pour libérer le matériau haute pression à l'intérieur de
la cartouche.
2. Appareil selon la revendication 1, dans lequel l'élément est fait d'un matériau choisi
entre le carbone, le graphite, l'aluminium, et le nickel-chrome.
3. Appareil selon la revendication 1 ou 2, dans lequel la cartouche est faite d'un matériau
malléable et comprend une paroi latérale cylindrique (20), une base (18) et une extrémité
voûtée (22) qui s'oppose à la base.
4. Appareil selon l'une quelconque des revendications 1 à 3, qui comprend des fils électriques
(30, 32) qui s'étendent depuis des bornes sur un côté extérieur de la cartouche jusqu'à
l'élément.
5. Appareil selon la revendication 4, qui comprend une enceinte amovible (54) qui couvre
les bornes.
6. Appareil selon l'une quelconque des revendications 1 à 5, qui comprend un substrat
(60) sur lequel l'élément est monté et qui est intégré dans la charge.
7. Appareil selon la revendication 6, qui comprend un dispositif de commande (64) pour
commander le fonctionnement de l'élément, sur le substrat.
8. Appareil selon l'une quelconque des revendications 1 à 7, dans lequel l'élément (26)
est sous la forme d'un filament allongé (26).