WO2014045187A1

WO2014045187A1 - A pyrotechnic based delay arrangement with warning means

Info

Publication number: WO2014045187A1
Application number: PCT/IB2013/058594
Authority: WO
Inventors: Martin George PLICHTA
Original assignee: Plichta Martin George
Priority date: 2012-09-21
Filing date: 2013-09-17
Publication date: 2014-03-27
Also published as: ZA201306962B

Abstract

The invention discloses a delay arrangement in which there is provided a pyrotechnic path having a start end and a discharge end with activation means for initiating a burn at the start end of the pyrotechnic path. The pyrotechnic path is associated with electronic warning means that emits a warning signal to indicate pending or actual initiation of the burn.

Description

DELAY ARRANGEMENT

FIELD OF INVENTION

The present invention relates to a delay arrangement.

More particularly, the present invention relates to a delay arrangement having a pyrotechnic delay initiator with electronic warning capabilities for use in blasting in a mine.

BACKGROUND TO INVENTION

In the past, mining industry explosives were often ignited using a pyrotechnic delay initiator, which typically provided a delay of 30, 60 or 90 minutes. The pyrotechnic delay initiator was attached to igniter cord and safety fuse, which in turn would initiate an explosive train in various blasting applications. However, in modern times, the igniter cord and safety fuse have been largely replaced by shocktube for safety reasons. Unfortunately, the pyrotechnic delay initiator cannot ignite or initiate shocktube directly. The initiation function used with shocktube is currently performed by an igniter or a detonator. Due to the speed of reaction in shocktube once initiated, the explosive train and thus blast takes place almost instantaneously or, at best, after very short delays (measured in seconds).

Therefore, to ensure the safety of operators in a blasting environment in a mine, electrical wiring is used to spatially separate the operators from a blast location. The wiring can be anything from twenty meters to several hundred meters (and in some cases kilometres) in length. Blasting control thus takes place from a remote position at a point of safety, and is generally initiated by an electronic system.

Examples of initiation systems for detonators or initiators include Shot Exploders, Centralized Blasting and Delay Units. These units are not disposable, are normally relatively expensive and require the interconnecting wires from the control unit to the detonator. It is thus desirable to obviate or minimize the length of the interconnecting electrical wiring and to provide an integrated or closely coupled unit with a delay to the detonator. There are however draw backs should such an integration be simply performed. These include accidental activation by an operator and thus instantaneous initiation of a blast without any warning; an unintended initiation should the circuitry fail; and the inability to control a synchronized multi blast.

It is an object of the invention to suggest a delay arrangement, which will assist in overcoming these problems.

SUMMARY OF INVENTION

According to the invention, a delay arrangement includes a pyrotechnic path having a start end and a discharge end; activation means being adapted to initiate a burn at the start end of the pyrotechnic path; and electronic warning means being associated with the pyrotechnic path and being adapted to emit a warning signal to indicate pending or actual initiation of the burn.

The warning means may be provided at the start end.

The warning means may be provided at a selected position between the start end and the discharge end and being adapted to emit the warning signal when the burn passes the selected position.

The warning means may include an electronic circuit having a physically destructible component being adapted to be destroyed to cause the warning signal to be emitted.

The destructible component may be heat destructible being adapted to be melted.

The destructible component may be mechanically destructible being adapted to be ruptured or damaged.

The destructible component may be a wire filament being adapted to be melted by the burn or ruptured by an igniter or detonator.

The warning signal may be a light or an audible sound.

The warning means may be integral with the activation means. The activation means may include manual initiation means, such as an igniter, detonator, lighter or other incendiary device, being adapted to initiate the burn at the start end of the pyrotechnic path.

The activation means may include an electronic circuit having a time clock operatively joined to a controller; programming means for programming the controller with a preselected blast time, at which blast time a blast is permitted in a mine, and for programming the controller with a preselected delay period, being the delay period required for the pyrotechnic path to burn through to the discharge end; and initiation means being adapted to initiate the burn at the start end of the pyrotechnic path when the time clock indicates a time being the delay period before the blast time.

The activation means may be adapted to allow the initiation of the burn only during a predetermined window period before the blast time.

The activation means may be adapted to prohibit initiation of the burn at any time outside the window period.

The window period may expire at a set time interval before the blast time.

The window period may extend from a time 5 hours before the blast time up to a time 1 hour before the blast time.

The blast time may be pre-programmed into the controller during manufacture.

The activation means may be adapted to be activated by a mechanical key or by any other mechanical input, such as by the insertion of a battery.

The activation means may include signalling means being adapted to emit a signal once the activation means has been activated.

The signalling means may include an indicator light or a buzzer.

The activation means may be adapted to be inoperable if any battery associated therewith is flat or has insufficient power for proper functioning. The pyrotechnic path may be a pyrotechnic coil.

The delay arrangement may include a gas reservoir associated with the pyrotechnic path, the gas reservoir being adapted to release gas due to the burn of the pyrotechnic path.

The gas may be smoke being visible to an operator.

The gas may contain an odour or be noxious for easy detection by an operator.

The discharge end of the pyrotechnic path may be operatively joined to conventional detonation equipment and explosives to cause detonation thereof.

BRIEF DESCRIPTION OF DRAWINGS

The invention will now be described by way of example with reference to the

accompanying schematic drawings.

In the drawings there is shown in:

Figure 1: A delay arrangement according to the invention;

Figure 2: A circuit diagram for an activation unit for use with the delay arrangement of Figure 1;

Figure 3: A circuit diagram for a warning unit for use with the delay arrangement of

Figure 1.

DETAILED DESCRIPTION OF DRAWINGS

Referring to Figure 1, there is shown a delay arrangement in accordance with the invention, generally indicated by reference numeral 100. The delay arrangement 100 is adapted to be further joined to conventional detonators, shocktube and explosives for causing a blast in a mine.

The delay arrangement 100 includes a housing 102 defining a chamber 104, which could have one or more sub-compartments. The housing 102 has an input port 106 and an output port 108, both leading to the chamber 104. A pyrotechnic path is provided in the chamber 104, being in the form of a pyrotechnic coil 110 having a start end 112 and a discharge end 114. The pyrotechnic coil 110 is adapted to be ignited by suitable means so that it can burn from the start end 112 to the discharge end 114 according to its specified burn rate. The start end 112 is ignited through the input port 106, the ignition being done either manually by us if an incendiary device, such as a detonator or an igniter or lighter, or automatically by electronic means.

The discharge end 114 is operatively joined to conventional detonation equipment and explosives through outlet port 108 so that a blast can be initiated. Thus, preferably the discharge end 114 is joined to an igniter 116, which extends into a port jacket 118 for receiving and locating shocktube to enable initiation of the shocktube.

In the illustrated housing 102, the chamber 104 has a main compartment 120 and a sub- compartment 122. A gas reservoir 124, otherwise known as a smoking chemical bag, is located within the main compartment 120 and is adapted to be ruptured during or by the burning of the pyrotechnic coil 110 so as to emit smoke and gases from the housing 102. The smoke should be visible to an operator and can be coloured or noxious for easy detection by the operator.

In addition, it is important to warn other operators or miners in the mine that a blast is imminent once the pyrotechnic coil 110 has been or is about to be ignited. As such miners may not be close enough to detect the smoke, additional warning signals, such as flashing lights and an audible siren are prefereable.

A first embodiment of a programmable warning means is embodied in an activation unit 200 shown in Figure 2, which can be proactive. The activation unit 200 includes electronic circuitry being adapted to electronically initiate the start end 112. As such the activation unit 200 will preferably be located within the chamber 104, e.g. within the sub- compartment 122, at or near to the start end 112.

The activation unit 200 includes a peripheral interface controller (PIC) 202 that is powered by battery 204. The controller 202 has a clock frequency that is set by a crystal 206 and related support circuit trimming capacitors 208 and 210. Clearly, as per conventional electronics, the crystal oscillator could also be an internal part of the controller 202. The controller 202 thus is able to function as a real time clock to perform various timing operations.

A secondary battery 212 is supplied to provide power, via switch 214, to the remainder of the circuit of the activation unit 200 that is not already energised by the battery 204. When switch 214 is closed, the controller 202 can detect power supplied by the secondary battery 212 into the circuit via resistor 216 The switch 214 can be a mechanical key or switch or be represented by the insertion of the battery 212 into the activation unit 200. The controller 202 is pre-programmed with a pre-set blast window time period during which period a blast in a mine is permitted. If the switch 214 is closed at a time falling outside of the window time period, then the controller 202 will remain in a dormant state (sleep mode). However, if the switch 214 is closed at a suitable time falling within the window time period, then the controller 202 starts a clock countdown towards the pre-set blast time.

A warning signal that such a countdown has started is signalled to an operator in any one or more of a myriad of ways, including either a light emitting diode (LED) 218 or Buzzer 220. These signals are controlled by the controller 202 and associated support circuitry including transistor 222 and resistors 224 and 226. At the conclusion of the countdown, the controller 202 switches on a silicon controlled resistor (SCR) or thyristor 228, via the circuit network comprised of resistors 230 and 232, and allowing initiator 234 to initiate the start end 112. Initiator 234 can be attached to the activation unit 200 manually or it may be integrally formed therewith.

The warning signal could be multi-staged, in that a first-type warning signal is emitted when the switch 214 is closed, that a second-type warning signal is emitted when the clock countdown starts, and that a third-type warning signal is emitted at the conclusion of the clock countdown, i.e. when the start-end 112 is initiated. Naturally multiple permutations of this basic configuration of the activation unit 200 are possible provided they all result in the successful initiation of initiator 234 at the conclusion of the countdown.

A second embodiment of a non-programmable warning means is embodied in a warning unit 300 shown in Figure 3, which is reactive only. The warning unit 300 includes electronic circuitry being adapted to electronically emit a warning signal at or after the initiation of the start end 112. As such the warning unit 300 will preferably be located within the chamber 104, e.g. within the main compartment 120, at a suitable position along the length of the pyrotechnic coil 110, i.e. at a position corresponding to a predetermined time before the burning of the pyrotechnic coil 110 reaches the discharge end 114.

The warning unit 300 includes an electronic circuit, having a battery 302 being adapted to supply power to a transistor 304. However, a by-pass circuit consisting of resistor 306 and link 308 keeps transistor 304 switched off and thereby prevents the battery 302 from supplying power to the remainder of the circuit.

The link 308 is destructible and is adapted to be destroyed, either by mechanical means, such as physical rupturing or tearing, or by thermal means so that it melts when sufficient heat is applied thereto. The link 308 is thus preferably located in sufficiently close proximity to the pyrotechnic coil 110 so that when the burning of the pyrotechnic coil 110 passes near to the link 308, the heat is sufficient to melt link 308. However, mechanical rupturing could also occur such as when an igniter ignites the start end 112.

The destruction of link 308 causes transistor 304 to switch on and allows current flow through transistor 304 to any number of signalling means in the remainder of the circuit. These signalling means are adapted to warn an operator that the pyrotechnic coil 110 has been initiated or its burning has progressed to certain extent. These signalling means include light and sound for example a light emitting diode (LED) 310 or Buzzer 312. The output intensity of the LED 310 and Buzzer 312 can be limited by resistors 314 and 316 respectively. The resistor 306 can have a very high resistance value, preferably greater than 1ΜΩ, to prevent significant discharge of the battery 302 during the dormant period before rupturing of the link 308.

Claims

A delay arrangement including a pyrotechnic path having a start end and a discharge end; activation means being adapted to initiate a burn at the start end of the pyrotechnic path; and electronic warning means being associated with the pyrotechnic path and being adapted to emit a warning signal to indicate pending or actual initiation of the burn.

A delay arrangement as claimed in claim 1, in which the warning means is provided at the start end.

A delay arrangement as claimed in claim 1, in which the warning means is provided at a selected position between the start end and the discharge end and being adapted to emit the warning signal when the burn passes the selected position.

A delay arrangement as claimed in any one of the preceding claims, in which the warning means includes an electronic circuit having a physically destructible component being adapted to be destroyed to cause the warning signal to be emitted.

A delay arrangement as claimed in claim 4, in which the destructible component is heat destructible being adapted to be melted.

A delay arrangement as claimed in claim 4, in which the destructible component is mechanically destructible being adapted to be ruptured or damaged.

A delay arrangement as claimed in claim 4, in which the destructible component is a wire filament being adapted to be melted by the burn or ruptured by an igniter or detonator.

A delay arrangement as claimed in any one of the preceding claims, in which the warning signal is a light or an audible sound.

A delay arrangement as claimed in any one of the preceding claims, in which the warning means is integral with the activation means.

10. A delay arrangement as claimed in any one of claims 1 to 9, in which the activation means includes manual initiation means for initiating the burn at the start end of the pyrotechnic path.

11. A delay arrangement as claimed in any one of claims 1 to 9, in which the activation means includes an electronic circuit having a time clock operatively joined to a controller; programming means for programming the controller with a preselected blast time, at which blast time a blast is permitted in a mine, and for programming the controller with a preselected delay period, being the delay period required for the pyrotechnic path to burn through to the discharge end; and initiation means being adapted to initiate the burn at the start end of the pyrotechnic path when the time clock indicates a time being the delay period before the blast time.

12. A delay arrangement as claimed in claim 11, in which the activation means is adapted to allow the initiation of the burn only during a predetermined window period before the blast time.

13. A delay arrangement as claimed in claim 12, in which the activation means is adapted to prohibit initiation of the burn at any time outside the window period.

14. A delay arrangement as claimed in claim 11 or 12, in which the window period expires at a set time interval before the blast time.

15. A delay arrangement as claimed in any one of claims 11 to 14, in which the window period extends from a time 5 hours before the blast time up to a time 1 hour before the blast time.

16. A delay arrangement as claimed in any one of claims 11 to 15, in which the blast time may be pre-programmed into the controller during manufacture.

17. A delay arrangement as claimed in any one of claims 11 to 16, in which the activation means is adapted to be activated by a mechanical key or by any other mechanical input, such as by the insertion of a battery.

18. A delay arrangement as claimed in any one of the preceding claims, in which the activation means includes signalling means being adapted to emit a signal once the activation means has been activated.

19. A delay arrangement as claimed in claim 18, in which the signalling means includes an indicator light or a buzzer.

20. A delay arrangement as claimed in any one of the preceding claims, in which the activation means is adapted to be inoperable if any battery associated therewith is flat or has insufficient power for proper functioning.

21. A delay arrangement as claimed in any one of the preceding claims, in which the pyrotechnic path is a pyrotechnic coil.

22. A delay arrangement as claimed in any one of the preceding claims, which includes a gas reservoir associated with the pyrotechnic path, the gas reservoir being adapted to release gas due to the burn of the pyrotechnic path.

23. A delay arrangement as claimed in claim 22, in which the gas is smoke being visible to an operator.

24. A delay arrangement as claimed in claim 22, in which the gas contains an odour or is noxious.

25. A delay arrangement as claimed in any one of the preceding claims, in which the discharge end of the pyrotechnic path is operatively joined to conventional detonation equipment and explosives to cause detonation thereof.