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WO2014057421A1 - Detonation of explosives - Google Patents

Detonation of explosives Download PDF

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Publication number
WO2014057421A1
WO2014057421A1 PCT/IB2013/059199 IB2013059199W WO2014057421A1 WO 2014057421 A1 WO2014057421 A1 WO 2014057421A1 IB 2013059199 W IB2013059199 W IB 2013059199W WO 2014057421 A1 WO2014057421 A1 WO 2014057421A1
Authority
WO
WIPO (PCT)
Prior art keywords
primary
signal
detonation
signal component
optical fibre
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/IB2013/059199
Other languages
French (fr)
Inventor
Elmar Muller
Pieter Stephanus Jacobus Halliday
Xiaojing Zhou
Warwick Belcher
Paul Dastoor
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AEL Mining Services Ltd
Original Assignee
AEL Mining Services Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by AEL Mining Services Ltd filed Critical AEL Mining Services Ltd
Publication of WO2014057421A1 publication Critical patent/WO2014057421A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F42—AMMUNITION; BLASTING
    • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
    • F42B3/00—Blasting cartridges, i.e. case and explosive
    • F42B3/10—Initiators therefor
    • F42B3/113—Initiators therefor activated by optical means, e.g. laser, flashlight
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F42—AMMUNITION; BLASTING
    • F42C—AMMUNITION FUZES; ARMING OR SAFETY MEANS THEREFOR
    • F42C13/00—Proximity fuzes; Fuzes for remote detonation
    • F42C13/02—Proximity fuzes; Fuzes for remote detonation operated by intensity of light or similar radiation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F42—AMMUNITION; BLASTING
    • F42D—BLASTING
    • F42D1/00—Blasting methods or apparatus, e.g. loading or tamping
    • F42D1/04—Arrangements for ignition
    • F42D1/043—Connectors for detonating cords and ignition tubes, e.g. Nonel tubes
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F42—AMMUNITION; BLASTING
    • F42D—BLASTING
    • F42D1/00—Blasting methods or apparatus, e.g. loading or tamping
    • F42D1/04—Arrangements for ignition
    • F42D1/045—Arrangements for electric ignition
    • F42D1/05—Electric circuits for blasting
    • F42D1/055—Electric circuits for blasting specially adapted for firing multiple charges with a time delay

Definitions

  • THIS INVENTION relates to the detonation of explosives. More particularly, the invention relates to the communication of detonation signals to electronic detonators that are to be initiated by means of such detonation signals to cause detonation of an explosive charge with which they are arranged in a detonating relationship, in use.
  • the invention provides a detonation signal transmission assembly.
  • the invention also provides a method of transmitting a detonation signal to an electronic detonator.
  • the invention further provides a connecting device to which an electronic photosensitive detonation signal reader and a length of optical fibre are connectable, in use, in a detonation signal-reading relationship in which the detonation signal reader can read a detonation signal that is transmitted along the length of optical fibre.
  • the Applicant is aware that the broad idea of fibre optic communication has received attention from inventors in the past in applications related to explosives detonation. Such attention has, in the Applicant's experience, been directed either to the use of laser signals in directly initiating detonation or to transmission of optical charging signals, which charging signals are used to charge optically sensitive voltage sources to render such voltage sources capable of generating plasma discharges which then initiate explosive charges with which they are arranged in a detonating relationship.
  • the Applicant has, however, found that the usefulness of fibre optic communication, particularly as communication medium for such optical charging signals in optical detonation systems, is limited by shortcomings in the manner in which these systems approach both signal transmission and utilisation, particularly in that it is generally only a terminal end of a length of optical fibre that can be usefully exploited in this regard.
  • the present invention seeks to provide an alternative approach to signal transmission and utilisation, thereby to enhance the usefulness of fibre optic communication in the communication of detonation signals to electronic detonators that are to be initiated thereby.
  • a detonation signal transmission assembly to transmit, in use, a detonation signal to a detonator to detonate an explosive charge, the assembly including
  • a length of optical fibre connectable, in use, to a primary optical detonation signal generator configured to generate a primary detonation signal, of an optical nature, and to transmit the primary detonation signal along the optical fibre, with the optical fibre being bent to define, along its length, at least one acutely or obtusely angled portion having a vertex; and
  • an electronic photosensitive primary detonation signal reader arrangeable, in use, adjacent the vertex of the angled potion and on a side thereof that defines an external angle of the vertex, thereby to read the optical detonation signal transmitted along the optical fibre through a continuous wall of the optical fibre at the vertex on the side thereof that defines the external angle.
  • the optical fibre may therefore be continuous and uninterrupted, i.e. free of cuts, severances or any other interruptions, at least along the angled portion and particularly at the vertex thereof.
  • the optical fibre would typically be severed at ends thereof when it is not of an endless nature.
  • the angled portions are, however, provided between the several ends.
  • the optical fibre could be arranged in a looped configuration with the primary detonation signal generator, such that respective ends of the optical fibre are connected to the primary detonation signal generator, i.e. commencing from and terminating at the primary detonation signal generator.
  • the optical fibre may, as is conventionally the case, comprise a core surrounded by a cladding, providing the wall thereof.
  • the cladding would typically have a refractive index differing from that of the core.
  • the wall of the optical fibre may be of a material that is sufficiently transparent to the wavelength of the optical primary detonation signal for the signal to leak through the wall at the vertex. It is important to note in this regard that the applicant has surprisingly found that regardless of the transparency of the wall, functional reading of an optical signal can be effected at the vertex of an angled portion of the optical fibre, as is suggested by the present invention, but not along straight portions of the optical fibre.
  • the wall of the optical fibre at least at the vertex, may therefore be of a material that has a refractive index that allows the primary detonation signal to leak through the wall of the optical fibre at the vertex.
  • the material may, in particular, be of a glass or plastic nature. Portions of the optical fibre meeting at the vertex may extend along rays of the vertex in a single bending plane.
  • An internal angle of the vertex may, in particular, be obtuse and from about 100 ° to about 1 10 ° , both values inclusive.
  • the external angle being complemental to 360° with the internal angle, will therefore be from about 250 ° to about 260 ° , both values inclusive.
  • the length of optical fibre has a plurality of angled portions which are associated, in use, with respective primary detonation signal readers in the manner described above.
  • the particular number of angled portions included in the length of optical fibre would typically be dictated by detonation or blast pattern design requirements at a detonation site in/on which the assembly is to be used in the detonation of one or more explosive charges. Such requirements may typically include the number of explosive charges required to be detonated by means of the assembly, the distances between such explosive charges, etc.
  • the assembly may include the primary detonation signal generator, in use.
  • the assembly may also include the primary detonation signal reader, in use.
  • the primary detonation signal generator may be configured to generate and transmit along the optical fibre, as or as part of the primary detonation signal, one or more of a primary start-up signal component, a primary charging signal component, a primary delay signal component and/or a primary firing signal component, each signal component having a signal property that distinguishes it from the other signal components. More particularly, the primary to detonation signal generator may be configured to impart the signal properties that distinguish the signal components from each other by any one or more of intensity modulation, frequency modulation and/or optical phase modulation of the primary detonation signal.
  • Each of the signal components may be based on and thus generated from detonation information available to the primary signal generator, whether being pre-programmed into the generator or otherwise, with such information being encoded into the optical signal by means of the abovementioned modulations.
  • the primary detonation signal generator may, in particular, be a laser generator, with the primary detonation signal comprising a laser pulse generated by the laser generator.
  • the primary detonation signal may either comprise a single signal that comprises one or more of the abovementioned signal components or, alternatively, may comprise a plurality of signals, each of which comprises one or more of the abovementioned signal components.
  • the primary detonation signal is therefore not limited to a single signal transmitted along the optical fibre.
  • the primary detonation signal reader may be capable of and thus adapted to receive, read and process the primary detonation signal.
  • “receive” is meant that, in use, the reader is in a position in range for it to read the primary detonation signal.
  • read is meant that, in use, on receiving the primary detonation signal, the reader is capable of distinguishing/recognising the primary detonation signal as such.
  • processing is meant that, in use, on reading the primary detonation signal, the reader provides some sort of desired predetermined response when it reads primary detonation signal.
  • the primary detonation signal reader may comprise one or more photosensitive primary detonation signal sensors.
  • the photosensitivities of the respective sensors may be such as to provide an electronic response to the primary detonation signal.
  • the primary detonation signal comprises primary detonation signal components as hereinbefore described
  • the respective photosensitivities of the primary detonation signal sensors may be such as to provide respective electronic responses to the respective components.
  • the primary detonation signal reader may therefore read, in use, the primary detonation signal, or components thereof, by means of the primary detonation signal sensors.
  • a primary detonation signal sensor may be provided for each of the primary detonation signal components.
  • the one or more primary detonation signal sensors comprise one or more phototransistors and/or one or more photovoltaic components.
  • the phototransistors and/or photovoltaic components may, in particular, be printed phototransistors and/or printed photovoltaic components, being printed on a substrate with an organic inc.
  • the primary detonation signal reader may include a primary start-up signal component sensor that is sensitive to the primary start-up signal component.
  • the primary detonation signal may then be configured such that sensing of the primary start-up signal component by the primary start-up signal component sensor is required for the primary detonation signal reader to read the primary charging signal component, the primary delay signal component, and/or the primary firing signal component, whichever one or more of these are comprised by the primary detonation signal.
  • the primary detonation signal reader may be configured to produce a response, in use, in the form of a secondary detonation signal, when it reads the primary detonation signal.
  • the secondary detonation signal may, particularly, be of an electronic and/or optical nature.
  • the secondary detonation signal may comprise any one or more of a secondary charging signal component, a secondary delay signal component, and a secondary firing signal component.
  • the secondary signal components may respectively be based on the primary charging signal component, the primary delay signal component, and the primary firing signal component of the primary detonation signal.
  • the detonation signal transmission assembly may include a detonator that is arrangeable, in use, in a detonating relationship with the explosive charge and in electronic and/or optical communication with the primary detonation signal reader in order to receive from the primary detonation signal reader, in use, the secondary detonation signal.
  • the detonator may, in particular, be an electronic detonator including, at least, a voltage source and a fuse head comprising two spaced electrodes between which a resistive bridge is provided, breakdown of which resistive bridge at a breakdown voltage difference generated across it by the voltage source, in use, generates a plasma discharge which is capable of causing, directly or indirectly, detonation of the explosive charge.
  • the secondary charging signal component may, in particular, be an electronic signal.
  • the detonator voltage source may be a chargeable voltage source that is chargeable by the secondary charging signal component, thereby to be rendered ready generating the breakdown voltage difference over the resistive bridge where it was previously not ready to do so.
  • the detonator may also include a detonation delay device that is configured to delay, for a predetermined delay period, in response to the secondary delay signal component in use, generation of the breakdown voltage difference across the electrodes and thus also generation of the plasma discharge and consequential detonation of the explosive charge, in use.
  • a detonation delay device that is configured to delay, for a predetermined delay period, in response to the secondary delay signal component in use, generation of the breakdown voltage difference across the electrodes and thus also generation of the plasma discharge and consequential detonation of the explosive charge, in use.
  • the detonator may further include a detonation initiating device configured to initiate, in response to the secondary firing signal component, detonation of the explosive charge by the detonator.
  • a detonation initiating device configured to initiate, in response to the secondary firing signal component, detonation of the explosive charge by the detonator.
  • Such initiation may be either by allowing generation of the voltage difference by the voltage source across the resistive bridge, which generation may previously have been prevented/obstructed by the initiating device, pending communication of the secondary firing signal component, or by activation of the delay device for elapse of the delay period to commence.
  • the primary detonation signal will initially encode the start-up signal component and be transmitted, along the optical fibre, to the reader, where it will cause the reader to 'wake-up' and thus become susceptible to reading the charging, delay, and firing signal components. Subsequently, the primary detonation signal will be generated to encode the charging signal component and will be transmitted, typically by means of a series of primary detonation signal pulses, to the reader, thereby to cause generation and transmission of the secondary charging signal component and thus cause the chargeable voltage source of the detonator to become charged.
  • the chargeable voltage source may be a capacitor.
  • the primary detonation signal will be generated to encode the delay signal component, which is then transmitted to the reader where the secondary detonation signal will be generated to encode the secondary delay signal component and be transmitted to the delay device.
  • the primary detonation signal will be generated to encode the firing signal component, which is then transmitted to the reader where the secondary detonation signal will be generated to encode the secondary firing signal component and transmitted to the detonator, causing either the time delay device to commence count-down to capacitor discharge and resulting detonation of the explosive charge, or, where no delay device is provided, merely to cause capacitor discharge.
  • an electronic photosensitive primary detonation signal reader arranged adjacent the vertex of the angled portion on a side of the vertex that defines an external angle of the angled portion, the primary detonation signal from the optical fibre through a continuous wall of the optical fibre at the vertex on the side thereof that defines the external angle.
  • An internal angle of the vertex may be from about 100° to about 1 10°, both values inclusive.
  • the external angle may therefore between about 250° and about 260°, both values inclusive.
  • the primary detonation signal may comprise one or more of a primary start-up signal component, a primary charging signal component, a primary delay signal component and/or a primary firing signal component, each signal component having a signal property that distinguishes it from the other signal components.
  • the signal properties of the signal components that distinguish them from one another may be imparted to the signal components by any one or more of intensity modulation, frequency modulation, and/or optical phase modulation.
  • the primary detonation signal may, in particular, be a laser signal.
  • the method may include generating, in response to the primary detonation signal, a secondary detonation signal of an electronic and/or optical nature.
  • the method may then include communicating the secondary detonation signal to an electronic detonator comprising, at least, a voltage source and a fuse head, comprising two spaced electrodes between which a resistive bridge is provided, breakdown of which resistive bridge at a breakdown voltage difference generated across it by the voltage source generates a plasma discharge which is capable of causing, directly or indirectly, detonation of the explosive charge in use.
  • the secondary detonation signal may, in particular, comprise one or more of a secondary charging signal component, based on the primary charging signal component, a secondary delay signal component, based on the primary delay signal component, and a secondary firing signal component, based on the primary firing signal component.
  • the voltage source of the detonator may be a chargeable voltage source. Communication of the secondary charging signal component to the detonator may then charge the voltage source, rendering it capable of generating the breakdown voltage across the resistive bridge.
  • Communication of the secondary delay signal component to the detonator may delay generation of the breakdown voltage across the resistive bridge for a predetermined time period, once commencement of elapse of the delay period is initiated.
  • Communication of the secondary firing signal component to the detonator may either allow generation of the breakdown voltage difference across the resistive bridge, where it was previously prevented in anticipation of receiving the secondary firing signal component, or may initiate commencement of the elapse of the delay period.
  • a connecting device that to which an electronic photosensitive primary detonation signal reader and a length of optical fibre can be connected, in use, in a primary detonation signal-reading relationship, the connector having a body;
  • an optical fibre holding formation provided by the body and being adapted securely to hold a portion of a length of optical fibre and, in so holding the portion of the length of optical fibre in use, bend the portion of the length of optical fibre into an angled configuration, thereby to provide an angled portion of the length of optical fibre, which angled portion has a vertex;
  • a primary detonation signal reader holding formation adapted to hold a primary detonation signal reader, in use, such that, when the reader is held by the holder, the reader can read a primary detonation signal of an optical nature transmitted along the optical fibre from the optical fibre through a continuous wall of the optical fibre at the vertex on the side thereof that defines the external angle.
  • the optical fibre connecting formation may be configured so as to form the angled portion of the optical fibre such that the vertex has an included angle of between about 100 ° and about 1 10 ° .
  • the connecting formation may further be configured such that it bends the optical fibre, at the angled portion, in a single bending plane
  • the body of the device may have a primary optical detonation signal reader receiving formation to which a primary optical detonation signal reader, configured to read, in use, the primary optical detonation signal through a continuous wall of the optical fibre at the vertex, may, in use, be connectable adjacent the vertex of the bent portion of the optical fibre, on a side of the vertex that defines an external angle of the vertex.
  • reference numeral 10 generally indicates a detonation signal transmission assembly in accordance with the invention.
  • the assembly 10 includes a length of optical fibre 12 that is arranged in a looped configuration with a primary detonation signal generator 14, thus leading from and back into the primary signal generator 14.
  • the optical fibre comprises a core which is surrounded by cladding, providing a wall thereof.
  • the cladding has a refractive index differing from that of the core.
  • the wall of the optical fibre is of a material that is sufficiently transparent to the wavelength of a optical primary detonation signal that is generated and transmitted by the primary detonation signal generator, for the signal to leak through the wall at the vertex.
  • the wall of the optical fibre is therefore of a material that has a refractive index that allows the primary detonation signal to leak through the wall of the optical fibre at the vertex
  • the material may, in particular, be a glass or a plastic material.
  • the signal generator 14 comprises a laser generator and is programmed with various detonation parameters from which it is capable of generating one or more primary detonation signals or primary detonation signal components having properties based on the detonation parameters that distinguish them from one another.
  • the signal generator 14 is capable of encoding the detonation parameters into one or more optical signals as a primary detonation signal or components thereof, for transmission along the optical fibre 12.
  • the detonation parameters with which the signal generator 14 is programmed include, in particular, a start-up code, a charging code, a delay code and a firing code.
  • the signal generator 14 may thus be capable of encoding any one or more of these codes, as the primary detonation signal or as primary detonation signal components of the primary detonation signal. Such encoding may particularly be by any one or more of intensity modulation, frequency modulation and/or phase modulation.
  • the primary detonation signal may therefore comprise, when generated, any one or more of a startup signal component, a charging signal component, a delay signal component and/or a firing signal component, the nature and significance of which is as hereinafter described.
  • the primary detonation signal may either comprise a single signal that comprises one or more of the abovementioned signal components or, alternatively, may comprise a plurality of separate sequentially transmitted signals, each of which comprises one or more of the abovementioned signal components.
  • the primary detonation signal is therefore not limited to a single signal transmitted along the optical fibre.
  • the optical fibre 12 is bent such that it defines a plurality of angled portions 1 6 along its length. At each angled portion 1 6, the optical fibre 12 is bent in a single bending plane such that, in plan view as illustrated, each angled portion has a vertex 1 6.1 defining an internal angle 'A' of between about 100 ° and about 1 10 ° .
  • the connecting device 18 is diagrammatically illustrated and has an optical fibre holding formation comprising two angularly spaced optical fibre connecting members 18.1 , 18.2, to which members 18.1 , 18.2 the optical fibre 12 is connected at the angled portions thereof and which members 18.1 , 18.2 urge or bend the optical fibre 12 into the angled configuration.
  • the angular spacing between the connecting members 18.1 , 18.2 is the angle TV.
  • the connector 18 has mounted therein a photosensitive primary detonation signal reader 20, held by a primary detonation signal reader holding formation.
  • the reader 20 comprises a primary detonation signal processing device 22 that, in turn, comprises a plurality of photosensitive primary detonation signal sensors 24.1 , 24.2, 24.3, 24.4.
  • Each signal component sensor 24.1 , 24.2, 24.3, 24.4 comprises a phototransistor or a photovoltaic device, preferably being of an organic or printed nature.
  • the reader 20 therefore reads the primary detonation signal or components thereof by means of the sensors 24.1 , 24.2, 24.3, 24.4.
  • the reader 20 is arranged in the connecting device 18 such that the sensors 24.1 , 24.2, 24.3, 24.4 are in register with the vertex 16.1 of their associated angled portions 1 6.
  • bending of the optical fibre 12 in the manner described renders any optical signal, having a wavelength in the visible light spectrum, travelling along the fibre 12 readable by the sensors (which is sensitive to such a signal) through a continuous and uninterrupted wall of the fibre 12 that comprises the vertex 16.1 . It is thus not necessary to cut or breach the fibre 12 to achieve readability.
  • the signal component sensors 24.1 , 24.2, 24.3, 24.4 are thus also arranged in a primary detonation signal reading relationship with the optical fibre 12. It is important to note that, regardless of the transparency or refractive index of the wall of the optical fibre, such reading cannot effectively be achieved along straight portions of the optical fibre. It is envisaged that optical signals having wavelengths not in the visible light spectrum would also be readable in this manner, but in such a case a different light sensitive component would have to be employed that is sensitive to such a wavelength.
  • Each sensor 24.1 , 24.2, 24.3, 24.4 is sensitive to an individual signal component of the primary detonation signal. Each sensor is also capable of processing their associated signal component by providing an electrical response when the primary detonation signal comprises the particular signal component to which a particular sensor 24.1 , 24.2, 24.3, 24.4 is sensitive and the sensors 24.1 , 24.2, 24.3, 24.4 are exposed to such components.
  • the signal component sensor 24.1 , 24.2, 24.3, 24.4 will therefore be regarded as comprising a primary start-up signal component sensor 24.1 , a primary charging signal component sensor 24.2, a primary delay signal component sensor 24.3 and a primary firing signal component sensor 24.4.
  • the start-up and firing signal component sensors 24.1 , 24.4 are typically sensitive to their associated primary signal components as a function of their conductance, with the responses provided by these sensors 24.1 , 24.4 on receiving their associated primary detonation signal components thus being a change in their conductance, preferably from a lower conductance to a higher conductance.
  • the charging and delay signal component processors 24.2, 24.3 are typically capable of providing components of a secondary detonation signal in response to their associated primary detonation signal components.
  • the charging signal component source 24.2 is capable of generating electrical current and providing a current discharge, as a secondary charging signal component, in response to the primary charging signal component
  • the delay signal component sensor 24.3 is capable of providing a secondary delay signal discharge, as a secondary delay signal component, in response to the primary delay signal component, which secondary delay signal encodes the delay code that was encoded in the primary delay signal component.
  • the secondary detonation signal may therefore typically comprise a current component and a secondary delay signal component.
  • the sensors 24.1 , 24.2, 24.3, 24.4 are interrelated in such a manner that the start-up signal component sensor 24.1 prevents any response by any of the other processors 24.2, 24.3, 24.4 until the start-up signal component sensor 24.1 has read the primary start-up signal component. It will be appreciated that the processor 22 and reader 20 can therefore be regarded as initially being in a 'dormant' condition, until the start-up signal component is received, upon which it 'wakes up'.
  • the reader 20 is in optical and/or electrical communication, along an optical and/or electrical communication line 25, with an electronic explosives detonator 26 which is arranged in a detonating relationship with an explosive charge (not illustrated).
  • an explosive charge not illustrated
  • the explosive charge and the detonator 26 would typically be located inside a borehole at a blasting site.
  • the detonator 26 has a fuse head comprising two spaced apart electrodes between which a resistive bridge is provided, which resistive bridge has a breakdown voltage that, when applied between the electrodes, causes the resistive bridge to break down and generate a plasma discharge which initiates detonation of the explosive charge.
  • the detonator 26 also includes, as a chargeable voltage source, a capacitor.
  • the capacitor is arranged in a secondary charging signal component receiving relationship with the charging signal component processor 24.2 so as to receive the secondary charging signal component of the secondary detonation signal therefrom, thereby to become charged and thus ready to apply the breakdown voltage across the fuse head.
  • the discharge voltage of the capacitor may be about equal to the breakdown voltage of the resistive bridge of the fuse head.
  • the detonator 26 further includes a time delay device that is arranged to inhibit the capacitor from applying the breakdown voltage across the resistive bridge for a predetermined detonation time delay period, even after the capacitor has been sufficiently charged to apply the breakdown voltage.
  • the time delay device is in communication with the delay signal component sensor 24.3 to receive the secondary timing signal component therefrom, which signal component encodes the detonation time delay period.
  • the capacitor and time delay device may both be operatively related to the firing signal processor 24.4, the response of which may prompt the time delay device to commence count-down of the delay period communicated to it by the response of the delay signal processor 24.3, at the end of which period it then allows the capacitor to discharge the charge that has been applied to it by the response of the charging signal processor 24.2.
  • the primary detonation signal generator 14 is therefore typically programmed with the start-up, charging, delay and firing signal codes, which codes it then encodes in respective or combined optical primary detonation signals which are then transmitted along the optical fibre 12.
  • the primary detonation signal/s travel/s along the optical fibre, it becomes readable by the reader 20 through the wall of the optical fibre that provides the vertex 1 6.1 of each angled portion 1 6.
  • the primary detonation signal is read by the reader 20, and more particularly by the sensors 24.1 , 24.2, 24.3, 24.4, depending on the constitution of the primary detonation signal.
  • a typical signal sequence would comprise generating and transmitting, firstly, a primary detonation signal encoding the start-up signal component, thereby rendering the sensors 24.2, 24.3, 24.4 capable of providing responses when reading or sensing their associated primary detonation signal components. Subsequently, a primary detonation signal encoding either or both of the charging signal component and the delay signal component would be generated and transmitted, which components would then be read and processed by their associated charging signal and delay signal sensors 24.2, 24.3, which sensors 24.2, 24.3 would then provide responses, in the form of secondary charging and delay signals, which are communicated respectively to the capacitor and delay devices of the detonator 26, thereby respectively to charge and program the capacitor and the delay device.
  • the primary detonation signal that encodes the charging signal component would typically be pulsed a number of times in order fully to charge the capacitor. Finally, the primary detonation signal will be generated to encode the firing signal component, thereby causing the firing signal sensor 24.4 to allow the delay device to commence count down and, eventually, the capacitor to discharge its charge and thereby cause detonation of the explosive charge.
  • the Applicant has taken an unconventional approach to optical detonation signal exploitation, particularly by reading such a signal through the wall of the optical fibre, thereby rendering it possible to use a looped optical fibre configuration, as described.
  • This is not envisaged in the prior art of which the Applicant is aware, which, to the Applicant's knowledge, only teaches exploiting an optical signal at a terminal end of a length of a length of optical fibre.
  • the applicant has surprisingly found that whilst functional reading of an optical signal transmitted along the optical fibre cannot be effected along straight portions thereof, it can, unexpectedly, can be effected at the vertex of an angled portion of the optical fibre, as is suggested by the present invention since the optical signal has been found to leak through the wall of the optical fibre at the vertex of the angled portion.
  • the wall of the optical fibre, at least at the vertex is of a material that has a refractive index that allows the optical signal to leak through the wall of the optical fibre at the vertex.
  • a single signal can be used functionally to effect a plurality of identical functions along a single length of optical fibre, as described in relation to the present invention, being functionally read from the optical fibre along a length thereof without it being necessary to terminate the length of optical fibre and effect reading at a terminal end thereof.

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Description

DETONATION OF EXPLOSIVES
FIELD OF THE INVENTION
THIS INVENTION relates to the detonation of explosives. More particularly, the invention relates to the communication of detonation signals to electronic detonators that are to be initiated by means of such detonation signals to cause detonation of an explosive charge with which they are arranged in a detonating relationship, in use. The invention provides a detonation signal transmission assembly. The invention also provides a method of transmitting a detonation signal to an electronic detonator. The invention further provides a connecting device to which an electronic photosensitive detonation signal reader and a length of optical fibre are connectable, in use, in a detonation signal-reading relationship in which the detonation signal reader can read a detonation signal that is transmitted along the length of optical fibre.
BACKGROUND TO THE INVENTION
The Applicant is aware that the broad idea of fibre optic communication has received attention from inventors in the past in applications related to explosives detonation. Such attention has, in the Applicant's experience, been directed either to the use of laser signals in directly initiating detonation or to transmission of optical charging signals, which charging signals are used to charge optically sensitive voltage sources to render such voltage sources capable of generating plasma discharges which then initiate explosive charges with which they are arranged in a detonating relationship. The Applicant has, however, found that the usefulness of fibre optic communication, particularly as communication medium for such optical charging signals in optical detonation systems, is limited by shortcomings in the manner in which these systems approach both signal transmission and utilisation, particularly in that it is generally only a terminal end of a length of optical fibre that can be usefully exploited in this regard. The present invention seeks to provide an alternative approach to signal transmission and utilisation, thereby to enhance the usefulness of fibre optic communication in the communication of detonation signals to electronic detonators that are to be initiated thereby.
SUMMARY OF THE INVENTION
IN ACCORDANCE WITH ONE ASPECT OF THE INVENTION, there is provided a detonation signal transmission assembly to transmit, in use, a detonation signal to a detonator to detonate an explosive charge, the assembly including
a length of optical fibre, connectable, in use, to a primary optical detonation signal generator configured to generate a primary detonation signal, of an optical nature, and to transmit the primary detonation signal along the optical fibre, with the optical fibre being bent to define, along its length, at least one acutely or obtusely angled portion having a vertex; and
an electronic photosensitive primary detonation signal reader arrangeable, in use, adjacent the vertex of the angled potion and on a side thereof that defines an external angle of the vertex, thereby to read the optical detonation signal transmitted along the optical fibre through a continuous wall of the optical fibre at the vertex on the side thereof that defines the external angle. The optical fibre may therefore be continuous and uninterrupted, i.e. free of cuts, severances or any other interruptions, at least along the angled portion and particularly at the vertex thereof. Of course, the optical fibre would typically be severed at ends thereof when it is not of an endless nature. The angled portions are, however, provided between the several ends. Typically in the assembly in use, the optical fibre could be arranged in a looped configuration with the primary detonation signal generator, such that respective ends of the optical fibre are connected to the primary detonation signal generator, i.e. commencing from and terminating at the primary detonation signal generator.
The optical fibre may, as is conventionally the case, comprise a core surrounded by a cladding, providing the wall thereof. The cladding would typically have a refractive index differing from that of the core. In order for the primary detonation signal to be readable through the wall of the optical fibre at the vertex, the wall of the optical fibre may be of a material that is sufficiently transparent to the wavelength of the optical primary detonation signal for the signal to leak through the wall at the vertex. It is important to note in this regard that the applicant has surprisingly found that regardless of the transparency of the wall, functional reading of an optical signal can be effected at the vertex of an angled portion of the optical fibre, as is suggested by the present invention, but not along straight portions of the optical fibre. The wall of the optical fibre, at least at the vertex, may therefore be of a material that has a refractive index that allows the primary detonation signal to leak through the wall of the optical fibre at the vertex. The material may, in particular, be of a glass or plastic nature. Portions of the optical fibre meeting at the vertex may extend along rays of the vertex in a single bending plane.
An internal angle of the vertex may, in particular, be obtuse and from about 100° to about 1 10°, both values inclusive. In such a case, the external angle, being complemental to 360° with the internal angle, will therefore be from about 250° to about 260°, both values inclusive.
In a preferred embodiment of the invention, the length of optical fibre has a plurality of angled portions which are associated, in use, with respective primary detonation signal readers in the manner described above. The particular number of angled portions included in the length of optical fibre would typically be dictated by detonation or blast pattern design requirements at a detonation site in/on which the assembly is to be used in the detonation of one or more explosive charges. Such requirements may typically include the number of explosive charges required to be detonated by means of the assembly, the distances between such explosive charges, etc.
The assembly may include the primary detonation signal generator, in use. The assembly may also include the primary detonation signal reader, in use.
The primary detonation signal generator may be configured to generate and transmit along the optical fibre, as or as part of the primary detonation signal, one or more of a primary start-up signal component, a primary charging signal component, a primary delay signal component and/or a primary firing signal component, each signal component having a signal property that distinguishes it from the other signal components. More particularly, the primary to detonation signal generator may be configured to impart the signal properties that distinguish the signal components from each other by any one or more of intensity modulation, frequency modulation and/or optical phase modulation of the primary detonation signal. Each of the signal components may be based on and thus generated from detonation information available to the primary signal generator, whether being pre-programmed into the generator or otherwise, with such information being encoded into the optical signal by means of the abovementioned modulations. The primary detonation signal generator may, in particular, be a laser generator, with the primary detonation signal comprising a laser pulse generated by the laser generator.
It is to be appreciated that the primary detonation signal may either comprise a single signal that comprises one or more of the abovementioned signal components or, alternatively, may comprise a plurality of signals, each of which comprises one or more of the abovementioned signal components. The primary detonation signal is therefore not limited to a single signal transmitted along the optical fibre. The primary detonation signal reader may be capable of and thus adapted to receive, read and process the primary detonation signal. By "receive" is meant that, in use, the reader is in a position in range for it to read the primary detonation signal. By "read" is meant that, in use, on receiving the primary detonation signal, the reader is capable of distinguishing/recognising the primary detonation signal as such. By "processing" is meant that, in use, on reading the primary detonation signal, the reader provides some sort of desired predetermined response when it reads primary detonation signal.
More particularly, the primary detonation signal reader may comprise one or more photosensitive primary detonation signal sensors. The photosensitivities of the respective sensors may be such as to provide an electronic response to the primary detonation signal. When the primary detonation signal comprises primary detonation signal components as hereinbefore described, the respective photosensitivities of the primary detonation signal sensors may be such as to provide respective electronic responses to the respective components. The primary detonation signal reader may therefore read, in use, the primary detonation signal, or components thereof, by means of the primary detonation signal sensors. In some embodiments of the invention, a primary detonation signal sensor may be provided for each of the primary detonation signal components.
Preferably, the one or more primary detonation signal sensors comprise one or more phototransistors and/or one or more photovoltaic components. The phototransistors and/or photovoltaic components may, in particular, be printed phototransistors and/or printed photovoltaic components, being printed on a substrate with an organic inc.
Where the primary detonation signal comprises the primary start-up signal component, the primary detonation signal reader may include a primary start-up signal component sensor that is sensitive to the primary start-up signal component. The primary detonation signal may then be configured such that sensing of the primary start-up signal component by the primary start-up signal component sensor is required for the primary detonation signal reader to read the primary charging signal component, the primary delay signal component, and/or the primary firing signal component, whichever one or more of these are comprised by the primary detonation signal. The primary detonation signal reader may be configured to produce a response, in use, in the form of a secondary detonation signal, when it reads the primary detonation signal. The secondary detonation signal may, particularly, be of an electronic and/or optical nature. The secondary detonation signal may comprise any one or more of a secondary charging signal component, a secondary delay signal component, and a secondary firing signal component. The secondary signal components may respectively be based on the primary charging signal component, the primary delay signal component, and the primary firing signal component of the primary detonation signal.
In use, the detonation signal transmission assembly may include a detonator that is arrangeable, in use, in a detonating relationship with the explosive charge and in electronic and/or optical communication with the primary detonation signal reader in order to receive from the primary detonation signal reader, in use, the secondary detonation signal. The detonator may, in particular, be an electronic detonator including, at least, a voltage source and a fuse head comprising two spaced electrodes between which a resistive bridge is provided, breakdown of which resistive bridge at a breakdown voltage difference generated across it by the voltage source, in use, generates a plasma discharge which is capable of causing, directly or indirectly, detonation of the explosive charge. The secondary charging signal component may, in particular, be an electronic signal. In such a case, the detonator voltage source may be a chargeable voltage source that is chargeable by the secondary charging signal component, thereby to be rendered ready generating the breakdown voltage difference over the resistive bridge where it was previously not ready to do so.
The detonator may also include a detonation delay device that is configured to delay, for a predetermined delay period, in response to the secondary delay signal component in use, generation of the breakdown voltage difference across the electrodes and thus also generation of the plasma discharge and consequential detonation of the explosive charge, in use.
The detonator may further include a detonation initiating device configured to initiate, in response to the secondary firing signal component, detonation of the explosive charge by the detonator. Such initiation may be either by allowing generation of the voltage difference by the voltage source across the resistive bridge, which generation may previously have been prevented/obstructed by the initiating device, pending communication of the secondary firing signal component, or by activation of the delay device for elapse of the delay period to commence.
In use, the primary detonation signal will initially encode the start-up signal component and be transmitted, along the optical fibre, to the reader, where it will cause the reader to 'wake-up' and thus become susceptible to reading the charging, delay, and firing signal components. Subsequently, the primary detonation signal will be generated to encode the charging signal component and will be transmitted, typically by means of a series of primary detonation signal pulses, to the reader, thereby to cause generation and transmission of the secondary charging signal component and thus cause the chargeable voltage source of the detonator to become charged. In a particular embodiment of the invention, the chargeable voltage source may be a capacitor. Next, the primary detonation signal will be generated to encode the delay signal component, which is then transmitted to the reader where the secondary detonation signal will be generated to encode the secondary delay signal component and be transmitted to the delay device. Finally, the primary detonation signal will be generated to encode the firing signal component, which is then transmitted to the reader where the secondary detonation signal will be generated to encode the secondary firing signal component and transmitted to the detonator, causing either the time delay device to commence count-down to capacitor discharge and resulting detonation of the explosive charge, or, where no delay device is provided, merely to cause capacitor discharge.
IN ACCORDANCE WITH ANOTHER ASPECT OF THE INVENTION, there is provided a method of detonating an explosive charge, the method including
generating, by means of a primary optical detonation signal generator, a primary detonation signal of an optical nature;
transmitting the primary detonation signal along an optical fibre that is bent to define, along its length, at least one angled portion having a vertex; and
reading, by means of an electronic photosensitive primary detonation signal reader arranged adjacent the vertex of the angled portion on a side of the vertex that defines an external angle of the angled portion, the primary detonation signal from the optical fibre through a continuous wall of the optical fibre at the vertex on the side thereof that defines the external angle.
An internal angle of the vertex may be from about 100° to about 1 10°, both values inclusive. The external angle may therefore between about 250° and about 260°, both values inclusive.
The primary detonation signal may comprise one or more of a primary start-up signal component, a primary charging signal component, a primary delay signal component and/or a primary firing signal component, each signal component having a signal property that distinguishes it from the other signal components. The signal properties of the signal components that distinguish them from one another may be imparted to the signal components by any one or more of intensity modulation, frequency modulation, and/or optical phase modulation.
The primary detonation signal may, in particular, be a laser signal.
The method may include generating, in response to the primary detonation signal, a secondary detonation signal of an electronic and/or optical nature. The method may then include communicating the secondary detonation signal to an electronic detonator comprising, at least, a voltage source and a fuse head, comprising two spaced electrodes between which a resistive bridge is provided, breakdown of which resistive bridge at a breakdown voltage difference generated across it by the voltage source generates a plasma discharge which is capable of causing, directly or indirectly, detonation of the explosive charge in use. The secondary detonation signal may, in particular, comprise one or more of a secondary charging signal component, based on the primary charging signal component, a secondary delay signal component, based on the primary delay signal component, and a secondary firing signal component, based on the primary firing signal component.
The voltage source of the detonator may be a chargeable voltage source. Communication of the secondary charging signal component to the detonator may then charge the voltage source, rendering it capable of generating the breakdown voltage across the resistive bridge.
Communication of the secondary delay signal component to the detonator may delay generation of the breakdown voltage across the resistive bridge for a predetermined time period, once commencement of elapse of the delay period is initiated.
Communication of the secondary firing signal component to the detonator may either allow generation of the breakdown voltage difference across the resistive bridge, where it was previously prevented in anticipation of receiving the secondary firing signal component, or may initiate commencement of the elapse of the delay period.
IN ACCORDANCE WITH YET A FURTHER ASPECT OF THE INVENTION, there is provided a connecting device that to which an electronic photosensitive primary detonation signal reader and a length of optical fibre can be connected, in use, in a primary detonation signal-reading relationship, the connector having a body;
an optical fibre holding formation provided by the body and being adapted securely to hold a portion of a length of optical fibre and, in so holding the portion of the length of optical fibre in use, bend the portion of the length of optical fibre into an angled configuration, thereby to provide an angled portion of the length of optical fibre, which angled portion has a vertex; and
a primary detonation signal reader holding formation adapted to hold a primary detonation signal reader, in use, such that, when the reader is held by the holder, the reader can read a primary detonation signal of an optical nature transmitted along the optical fibre from the optical fibre through a continuous wall of the optical fibre at the vertex on the side thereof that defines the external angle.
The optical fibre connecting formation may be configured so as to form the angled portion of the optical fibre such that the vertex has an included angle of between about 100° and about 1 10°.
The connecting formation may further be configured such that it bends the optical fibre, at the angled portion, in a single bending plane The body of the device may have a primary optical detonation signal reader receiving formation to which a primary optical detonation signal reader, configured to read, in use, the primary optical detonation signal through a continuous wall of the optical fibre at the vertex, may, in use, be connectable adjacent the vertex of the bent portion of the optical fibre, on a side of the vertex that defines an external angle of the vertex. BRIEF DESCRIPTION OF THE DRAWING
The invention will now be described in more detail, with reference to the accompanying diagrammatic drawing, which shows a detonation signal transmission assembly in accordance with the invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring to the drawing, reference numeral 10 generally indicates a detonation signal transmission assembly in accordance with the invention. The assembly 10 includes a length of optical fibre 12 that is arranged in a looped configuration with a primary detonation signal generator 14, thus leading from and back into the primary signal generator 14.
The optical fibre comprises a core which is surrounded by cladding, providing a wall thereof. The cladding has a refractive index differing from that of the core. In order for the primary detonation signal to be readable through the wall of the optical fibre at the vertex of an angled portion thereof as hereinafter described, the wall of the optical fibre is of a material that is sufficiently transparent to the wavelength of a optical primary detonation signal that is generated and transmitted by the primary detonation signal generator, for the signal to leak through the wall at the vertex. The wall of the optical fibre, at least at the vertex, is therefore of a material that has a refractive index that allows the primary detonation signal to leak through the wall of the optical fibre at the vertex The material may, in particular, be a glass or a plastic material. The signal generator 14 comprises a laser generator and is programmed with various detonation parameters from which it is capable of generating one or more primary detonation signals or primary detonation signal components having properties based on the detonation parameters that distinguish them from one another. In particular, the signal generator 14 is capable of encoding the detonation parameters into one or more optical signals as a primary detonation signal or components thereof, for transmission along the optical fibre 12.
The detonation parameters with which the signal generator 14 is programmed include, in particular, a start-up code, a charging code, a delay code and a firing code. The signal generator 14 may thus be capable of encoding any one or more of these codes, as the primary detonation signal or as primary detonation signal components of the primary detonation signal. Such encoding may particularly be by any one or more of intensity modulation, frequency modulation and/or phase modulation. The primary detonation signal may therefore comprise, when generated, any one or more of a startup signal component, a charging signal component, a delay signal component and/or a firing signal component, the nature and significance of which is as hereinafter described. It is to be appreciated that the primary detonation signal may either comprise a single signal that comprises one or more of the abovementioned signal components or, alternatively, may comprise a plurality of separate sequentially transmitted signals, each of which comprises one or more of the abovementioned signal components. The primary detonation signal is therefore not limited to a single signal transmitted along the optical fibre. The optical fibre 12 is bent such that it defines a plurality of angled portions 1 6 along its length. At each angled portion 1 6, the optical fibre 12 is bent in a single bending plane such that, in plan view as illustrated, each angled portion has a vertex 1 6.1 defining an internal angle 'A' of between about 100° and about 1 10°.
Bending of the optical fibre 12 at the angled portions 1 6 is effected, in each case, by means of a connecting device 18 in accordance with the invention. The connecting device 18 is diagrammatically illustrated and has an optical fibre holding formation comprising two angularly spaced optical fibre connecting members 18.1 , 18.2, to which members 18.1 , 18.2 the optical fibre 12 is connected at the angled portions thereof and which members 18.1 , 18.2 urge or bend the optical fibre 12 into the angled configuration. Naturally, the angular spacing between the connecting members 18.1 , 18.2 is the angle TV.
The connector 18 has mounted therein a photosensitive primary detonation signal reader 20, held by a primary detonation signal reader holding formation. The reader 20 comprises a primary detonation signal processing device 22 that, in turn, comprises a plurality of photosensitive primary detonation signal sensors 24.1 , 24.2, 24.3, 24.4. Each signal component sensor 24.1 , 24.2, 24.3, 24.4 comprises a phototransistor or a photovoltaic device, preferably being of an organic or printed nature. The reader 20 therefore reads the primary detonation signal or components thereof by means of the sensors 24.1 , 24.2, 24.3, 24.4. The reader 20 is arranged in the connecting device 18 such that the sensors 24.1 , 24.2, 24.3, 24.4 are in register with the vertex 16.1 of their associated angled portions 1 6. In this regard, it is to be noted that it has been found, unexpectedly, that bending of the optical fibre 12 in the manner described renders any optical signal, having a wavelength in the visible light spectrum, travelling along the fibre 12 readable by the sensors (which is sensitive to such a signal) through a continuous and uninterrupted wall of the fibre 12 that comprises the vertex 16.1 . It is thus not necessary to cut or breach the fibre 12 to achieve readability. Being so arranged in register with the vertex 1 6.1 , the signal component sensors 24.1 , 24.2, 24.3, 24.4 are thus also arranged in a primary detonation signal reading relationship with the optical fibre 12. It is important to note that, regardless of the transparency or refractive index of the wall of the optical fibre, such reading cannot effectively be achieved along straight portions of the optical fibre. It is envisaged that optical signals having wavelengths not in the visible light spectrum would also be readable in this manner, but in such a case a different light sensitive component would have to be employed that is sensitive to such a wavelength.
Each sensor 24.1 , 24.2, 24.3, 24.4 is sensitive to an individual signal component of the primary detonation signal. Each sensor is also capable of processing their associated signal component by providing an electrical response when the primary detonation signal comprises the particular signal component to which a particular sensor 24.1 , 24.2, 24.3, 24.4 is sensitive and the sensors 24.1 , 24.2, 24.3, 24.4 are exposed to such components. For present purposes and with reference to the primary detonation signal components, the signal component sensor 24.1 , 24.2, 24.3, 24.4 will therefore be regarded as comprising a primary start-up signal component sensor 24.1 , a primary charging signal component sensor 24.2, a primary delay signal component sensor 24.3 and a primary firing signal component sensor 24.4.
The start-up and firing signal component sensors 24.1 , 24.4 are typically sensitive to their associated primary signal components as a function of their conductance, with the responses provided by these sensors 24.1 , 24.4 on receiving their associated primary detonation signal components thus being a change in their conductance, preferably from a lower conductance to a higher conductance. The charging and delay signal component processors 24.2, 24.3, on the other hand, are typically capable of providing components of a secondary detonation signal in response to their associated primary detonation signal components. In particular, the charging signal component source 24.2 is capable of generating electrical current and providing a current discharge, as a secondary charging signal component, in response to the primary charging signal component, whilst the delay signal component sensor 24.3 is capable of providing a secondary delay signal discharge, as a secondary delay signal component, in response to the primary delay signal component, which secondary delay signal encodes the delay code that was encoded in the primary delay signal component. The secondary detonation signal may therefore typically comprise a current component and a secondary delay signal component.
In the processing device 22, the sensors 24.1 , 24.2, 24.3, 24.4 are interrelated in such a manner that the start-up signal component sensor 24.1 prevents any response by any of the other processors 24.2, 24.3, 24.4 until the start-up signal component sensor 24.1 has read the primary start-up signal component. It will be appreciated that the processor 22 and reader 20 can therefore be regarded as initially being in a 'dormant' condition, until the start-up signal component is received, upon which it 'wakes up'.
The reader 20 is in optical and/or electrical communication, along an optical and/or electrical communication line 25, with an electronic explosives detonator 26 which is arranged in a detonating relationship with an explosive charge (not illustrated). In practice, the explosive charge and the detonator 26 would typically be located inside a borehole at a blasting site.
Although not illustrated in detail, the detonator 26 has a fuse head comprising two spaced apart electrodes between which a resistive bridge is provided, which resistive bridge has a breakdown voltage that, when applied between the electrodes, causes the resistive bridge to break down and generate a plasma discharge which initiates detonation of the explosive charge.
The detonator 26 also includes, as a chargeable voltage source, a capacitor. The capacitor is arranged in a secondary charging signal component receiving relationship with the charging signal component processor 24.2 so as to receive the secondary charging signal component of the secondary detonation signal therefrom, thereby to become charged and thus ready to apply the breakdown voltage across the fuse head. The discharge voltage of the capacitor may be about equal to the breakdown voltage of the resistive bridge of the fuse head.
The detonator 26 further includes a time delay device that is arranged to inhibit the capacitor from applying the breakdown voltage across the resistive bridge for a predetermined detonation time delay period, even after the capacitor has been sufficiently charged to apply the breakdown voltage. The time delay device is in communication with the delay signal component sensor 24.3 to receive the secondary timing signal component therefrom, which signal component encodes the detonation time delay period.
The capacitor and time delay device may both be operatively related to the firing signal processor 24.4, the response of which may prompt the time delay device to commence count-down of the delay period communicated to it by the response of the delay signal processor 24.3, at the end of which period it then allows the capacitor to discharge the charge that has been applied to it by the response of the charging signal processor 24.2.
In use, the primary detonation signal generator 14 is therefore typically programmed with the start-up, charging, delay and firing signal codes, which codes it then encodes in respective or combined optical primary detonation signals which are then transmitted along the optical fibre 12. As the primary detonation signal/s travel/s along the optical fibre, it becomes readable by the reader 20 through the wall of the optical fibre that provides the vertex 1 6.1 of each angled portion 1 6. Once it becomes so readable, the primary detonation signal is read by the reader 20, and more particularly by the sensors 24.1 , 24.2, 24.3, 24.4, depending on the constitution of the primary detonation signal. It is expected that a typical signal sequence would comprise generating and transmitting, firstly, a primary detonation signal encoding the start-up signal component, thereby rendering the sensors 24.2, 24.3, 24.4 capable of providing responses when reading or sensing their associated primary detonation signal components. Subsequently, a primary detonation signal encoding either or both of the charging signal component and the delay signal component would be generated and transmitted, which components would then be read and processed by their associated charging signal and delay signal sensors 24.2, 24.3, which sensors 24.2, 24.3 would then provide responses, in the form of secondary charging and delay signals, which are communicated respectively to the capacitor and delay devices of the detonator 26, thereby respectively to charge and program the capacitor and the delay device. The primary detonation signal that encodes the charging signal component would typically be pulsed a number of times in order fully to charge the capacitor. Finally, the primary detonation signal will be generated to encode the firing signal component, thereby causing the firing signal sensor 24.4 to allow the delay device to commence count down and, eventually, the capacitor to discharge its charge and thereby cause detonation of the explosive charge.
With the present invention, the Applicant has taken an unconventional approach to optical detonation signal exploitation, particularly by reading such a signal through the wall of the optical fibre, thereby rendering it possible to use a looped optical fibre configuration, as described. This is not envisaged in the prior art of which the Applicant is aware, which, to the Applicant's knowledge, only teaches exploiting an optical signal at a terminal end of a length of a length of optical fibre.
In particular, the applicant has surprisingly found that whilst functional reading of an optical signal transmitted along the optical fibre cannot be effected along straight portions thereof, it can, unexpectedly, can be effected at the vertex of an angled portion of the optical fibre, as is suggested by the present invention since the optical signal has been found to leak through the wall of the optical fibre at the vertex of the angled portion. It is preferred that the wall of the optical fibre, at least at the vertex, is of a material that has a refractive index that allows the optical signal to leak through the wall of the optical fibre at the vertex. The applicant has found particularly application for this in the transmission of detonation signals in that a single signal can be used functionally to effect a plurality of identical functions along a single length of optical fibre, as described in relation to the present invention, being functionally read from the optical fibre along a length thereof without it being necessary to terminate the length of optical fibre and effect reading at a terminal end thereof.

Claims

1 . A detonation signal transmission assembly to transmit, in use, a detonation signal to a detonator to detonate an explosive charge, the assembly including
a length of optical fibre, connectable, in use, to a primary optical detonation signal generator configured to generate a primary detonation signal, of an optical nature, and to transmit the primary detonation signal along the optical fibre, with the optical fibre being bent to define, along its length, at least one acutely or obtusely angled portion having a vertex; and
an electronic photosensitive primary detonation signal reader arrangeable, in use, adjacent the vertex of the angled potion and on a side thereof that defines an external angle of the vertex, thereby to read the optical detonation signal transmitted along the optical fibre through a continuous wall of the optical fibre at the vertex on the side thereof that defines the external angle.
2. The assembly according to claim 1 , in which portions of the optical fibre meeting at the vertex extend along rays of the vertex in a single bending plane.
3. The assembly according to claim 1 or claim 2, in which an internal angle of the vertex is obtuse and is from about 100° to about 1 10°, both values inclusive, with the external angle therefore being between about 250° and about 260°, both values inclusive.
4. The assembly according to any of claims 1 to 3 inclusive, in which the length of optical fibre has a plurality of angled portions which are associated, in use, with respective primary detonation signal readers in the manner described in claim 1 .
5. The assembly according to any of claims 1 to 4 inclusive, in which the primary detonation signal generator is configured to generate and transmit along the optical fibre, as or as part of the primary detonation signal, one or more of a primary start-up signal component, a primary charging signal component, a primary delay signal component and/or a primary firing signal component, each signal component having a signal property that distinguishes it from the other signal components.
6. The assembly according to claim 5, in which primary detonation signal generator is configured to impart the signal properties that distinguish the signal components from one another by any one or more of intensity modulation, frequency modulation and/or optical phase modulation of the primary detonation signal.
7. The assembly according to any of claims 1 to 6 inclusive, in which the primary detonation signal generator is a laser generator, with the primary detonation signal comprising a laser pulse generated by the laser generator.
8. The assembly according to any of claims 1 to 7 inclusive, in which the primary detonation signal reader comprises one or more photosensitive primary detonation signal sensors, the respective photosensitivities of which are such as to provide an electronic response to the primary detonation signal, or respective electronic responses to the respective components thereof, with the primary detonation signal reader therefore reading, in use, the primary detonation signal or components thereof by means of the primary detonation signal sensors.
9. The assembly according to claim 8, in which the one or more primary detonation signal sensors comprise one or more phototransistors and/or one or more photovoltaic components.
10. The assembly according to claim 9, in which the phototransistors and/or photovoltaic components are printed phototransistors and/or photovoltaic components, being printed on a substrate with an organic ink.
1 1 . The assembly according to claim 5 and any of claims 8 to 10 inclusive, in which the primary detonation signal reader includes a primary start-up signal component sensor that is sensitive to the primary start-up signal component, and the primary detonation signal reader is configured such that sensing of the primary start-up signal component by the primary start-up signal component sensor is required for the primary detonation signal reader to read the primary charging signal component, the primary delay signal component and the primary firing signal component, whichever one or more of these are comprised by the primary detonation signal.
12. The assembly according to any of claims 1 to 1 1 inclusive, in which primary detonation signal reader is configured to produce a response, in use, in the form of a secondary detonation signal, when it reads the primary detonation signal, with the secondary detonation signal being of an electronic and/or optical nature.
13. The assembly according to claim 5 and claim 12, in which the secondary detonation signal comprises any one or more of a secondary charging signal component, a secondary delay signal component and a secondary firing signal component, respectively based on the primary charging signal component, the primary delay signal component and the primary firing signal component of the primary detonation signal.
14. The assembly according to claim 12 or claim 13, which includes a detonator that is arrangeable, in use, in a detonating relationship with the explosive charge and in electronic and/or optical communication with the primary detonation signal reader in order to receive from the primary detonation signal reader, in use, the secondary detonation signal.
15. The assembly according to claim 14, in which the detonator is an electronic detonator including, at least, a fuse head comprising two spaced electrodes between which a resistive bridge is provided, breakdown of which resistive bridge at a breakdown voltage difference generated across it generates a plasma discharge which is capable of causing, directly or indirectly, detonation of the explosive charge, in use.
1 6. The assembly according to claim 13 and claim 15, in which the secondary charging signal component is electronic and the detonator comprises a chargeable voltage source that is chargeable by the secondary charging signal component, thereby to be rendered capable of generating the breakdown voltage difference over the resistive bridge.
17. The assembly according to claim 13 and 14 and one of claims 15 and 1 6, in which the detonator includes a detonation delay device configured to delay for a predetermined delay period, in response to the secondary delay signal component in use, generation of the breakdown voltage difference across the electrodes, and thus also the generation of the plasma discharge to the primary explosive and consequential detonation of the explosive charge, in use.
18. The assembly according to claim 13 and 14 and any of claims 15 to 17 inclusive, in which the detonator includes a detonation initiating device configured to initiate, in response to the secondary firing signal component, detonation of the explosive charge by the detonator, either by allowing generation of the voltage difference across the resistive bridge, which generation is prevented by the initiating device pending communication of the secondary firing signal component, or by activating the delay device for elapse of the delay period to commence.
19. A method of detonating an explosive charge, the method including
generating, by means of a primary optical detonation signal generator, a primary detonation signal of an optical nature;
transmitting the primary detonation signal along an optical fibre that is bent to define, along its length, at least one angled portion having a vertex; and
reading, by means of an electronic photosensitive primary detonation signal reader arranged adjacent the vertex of the angled portion on a side of the vertex that defines an external angle of the angled portion, the primary detonation signal from the optical fibre through a continuous wall of the optical fibre at the vertex on the side thereof that defines the external angle.
20. The method according to claim 19, in which an internal angle of the vertex is from about 100° to about 1 10°, both values inclusive, with the external angle therefore being between about 250° and about 260°, both values inclusive.
21 . The method according to claim 19 or claim 20, in which the primary detonation signal comprises one or more of a primary start-up signal component, a primary charging signal component, a primary delay signal component and/or a primary firing signal component, each signal component having a signal property that distinguishes it from the other signal components.
22. The method according to claim 21 , in which the signal properties of the signal components that distinguish them from one another are imparted to the signal components by any one or more of intensity modulation, frequency modulation, and/or optical phase modulation.
23. The method according to any of claims 19 to 22 inclusive, in which the primary detonation signal is a laser signal.
24. The method according to any of claims 19 to 23 inclusive, which includes generating, in response to the primary detonation signal, a secondary detonation signal of an electronic and/or optical nature and communicating the secondary detonation signal to an electronic detonator comprising, at least, a fuse head comprising two spaced electrodes between which a resistive bridge is provided, breakdown of which resistive bridge at a breakdown voltage difference generated across it generates a plasma discharge which is capable of causing, directly or indirectly, detonation of the explosive charge, in use.
25. The method according to claim 21 and claim 24, in which the secondary detonation signal comprises one or more of a secondary charging signal component, based on the primary charging signal component, and a secondary delay signal component, based on the primary delay signal component, and a secondary firing signal component, based on the primary firing signal component.
26. The method according to claim 25, in which the voltage source of the detonator is a chargeable voltage source and communication of the secondary charging signal component to the detonator charges the voltage source, rendering it capable of generating the breakdown voltage difference across the resistive bridge.
27. The method according to claim 25 or claim 26, in which communication of the secondary delay signal component to the detonator delays generation of the breakdown voltage across the resistive bridge for a predetermined time period, once commencement of elapse of the delay period is initiated.
28. The method according to any of claims 25 to 27 inclusive, in which communication of the secondary firing signal component to the detonator either allows generation of the breakdown voltage difference across the resistive bridge, where it was previously prevented in anticipation of receiving the secondary firing signal component, or initiates commencement of elapse of the delay period.
29. A connecting device that to which an electronic photosensitive primary detonation signal reader and a length of optical fibre can be connected, in use, in a primary detonation signal-reading relationship, the connector having
a body;
an optical fibre holding formation provided by the body and being adapted securely to hold a portion of a length of optical fibre and, in so holding the portion of the length of optical fibre in use, bend the portion of the length of optical fibre into an angled configuration, thereby to provide an angled portion of the length of optical fibre, which angled portion has a vertex; and
a primary detonation signal reader holding formation adapted to hold a primary detonation signal reader, in use, such that, when the reader is held by the holder, the reader can read a primary detonation signal of an optical nature transmitted along the optical fibre from the optical fibre through a continuous wall of the optical fibre at the vertex on the side thereof that defines the external angle.
30. The connector according to claim 29, in which the optical fibre connecting formation is configured so as to form the angled portion of the optical fibre such that the vertex has an included angle of between about 100° and about 1 10°.
31 . The connector according to claim 29 or claim 30, in which the connecting formation is configured such that it bends the optical fibre, at the angled portion, in a single bending plane.
32. The connector according to any of claims 29 to 31 inclusive, in which the body has a primary optical detonation signal reader receiving formation to which a primary optical detonation signal reader, configured to read, in use, the primary optical detonation signal through a continuous wall of the optical fibre at the vertex, is, in use, connectable adjacent the vertex of the bent portion of the optical fibre, on a side of the vertex that defines a major angle of the vertex.
PCT/IB2013/059199 2012-10-08 2013-10-08 Detonation of explosives Ceased WO2014057421A1 (en)

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