Wireless detonator assembly, and methods of blasting

• US 20070044673A1
• Filed: 03/17/2006
• Published: 03/01/2007
• Est. Priority Date: 03/18/2005
• Status: Active Grant

• Current Assignee: Orica Explosives Technology Pty Limited (Orica Limited)
• Original Assignee: Orica Explosives Technology Pty Limited (Orica Limited)
• Inventors: Hummel, Dirk, Stewart, Ronald, McCann, Michael
• Granted Patent: US 7,568,429 B2
• Time in Patent Office: Days
• US Class Current: 102/206
• CPC Class Codes: F42B 3/113 activated by optical means, e.g. laser, flashlight
• CPC Class Codes: F42B 3/18 Safety initiators resistant to premature firing by static electricity or stray currents
• CPC Class Codes: F42D 1/055 specially adapted for firing multiple charges with a time delay

Abstract

Wireless detonators, and corresponding wireless detonator systems present opportunities for blasting arrangements that avoid the need for physical wire connections between the blasting components. The present application discloses a wireless detonator assembly, a corresponding blasting apparatus, and a method of use thereof. The wireless detonator assembly comprises a charge storage device that is capable of storing charge for discharge into a firing circuit upon receipt of an appropriate wireless command signal to FIRE, from an associated blasting machine. In preferred embodiments, the charge storage device remains or becomes charged, at least for a specific time period, if the wireless detonator assembly receives a suitable “keep alive” command signal from an associated blasting machine—otherwise the charge storage device discharges with little or no effect upon the firing circuit, such that the wireless detonator assembly retain or adopts a safe mode.

Claims

1. A wireless detonator assembly for use in connection with a blasting machine that transmits at least one wireless command signal to the wireless detonator assembly, the wireless detonator assembly comprising:

a detonator comprising a base charge;

command signal receiving and processing means for receiving and processing said at least one wireless command signal from said blasting machine;

a charge storage device for storing electrical energy;

at least one power source to power said command signal receiving and processing means, and to charge said charge storage device, each of said at least one power source capable of supplying a maximum voltage or current that is less than a threshold voltage or current to actuate said base charge; and

a firing circuit in electrical connection with said charge storage device;

whereupon receipt by said command signal receiving and processing means of a command signal to FIRE causes said electrical energy stored in said charge storage device to discharge into said firing circuit, said base charge actuating if a voltage or current in said firing circuit resulting from discharge of said electrical energy from said charge storage device exceeds said threshold voltage or current.

2. The wireless detonator assembly of claim 1, wherein said base charge actuates in response to a signal to FIRE only if said electrical current in said firing circuit is at least 20% greater than a threshold current for firing.

3. The wireless detonator assembly of claim 1, further comprising a firing switch between the charge storage device and the base charge, as part of or in series with the firing circuit, the firing switch biased to an open position and switching to a closed position upon receipt by said command signal receiving and processing means of a signal to FIRE, thereby to cause said electrical energy to discharge from said charge storage device into said firing circuit, to actuate said base charge.

4. The wireless detonator assembly of any one of claims 1 to 3, further comprising a charging switch between a power source and the charge storage device, said charging switch having an open position and a closed position, electrical contact being established -between said power source and said charge storage device when said charging switch adopts said closed position, thereby to cause charging of said charge storage device.

5. The wireless detonator assembly of any one of claims 1 to 4, further comprising a discharging means to bleed charge from said charge storage device via any path except for said firing circuit.

6. The wireless detonator assembly of claim 5, wherein said discharging means comprises an earth.

7. The wireless detonator assembly of claim 1, said wireless detonator assembly further comprising:

a charging switch between the power source and the charge storage device, said charging switch having an open position and a closed position, electrical contact being established between said power source and said charge storage device when said charging switch adopts said closed position, thereby to cause charging of said charge storage device; and

a discharging means to bleed charge from said charge storage device via any path except for said firing circuit;

wherein said charging switch is biased towards an open position such that said charge storage device discharges via said discharging means, and receipt of at least one “

keep alive”

command signal by said command signal receiving and processing means causes said charging switch to adopt a closed position;

thereby to cause charging of said charge storage device.

8. The wireless detonator assembly of claim 7, wherein said “

keep alive”

command signal comprises a continuous signal transmitted by said blasting machine, said charging switch adopting an open position upon removal of, or in the absence of said continuous signal.

9. The wireless detonator assembly of claim 7, wherein said “

keep alive”

command signal causes said charging switch to maintain a closed position for a time period following receipt of said “

keep alive”

signal by said command signal receiving and processing means, said charging switch adopting an open position at the end of said time period unless said command signal receiving and processing means has received another “

keep alive”

signal from said blasting machine during said time period.

10. The wireless detonator assembly of claim 9, wherein said blasting machine transmits a series of “

keep alive”

signals to maintain said charging switch in said closed position so that the charge storage device remains at least substantially charged, said base charge being actuatable by discharge of said electrical energy into said firing circuit upon receipt of a command signal to FIRE.

11. The wireless detonator assembly of claim 7, wherein the discharging means is in electrical connection with the charging switch, such that when the charging switch is in an open position the charge storage device is connected to the discharging means but is not connected to the power supply thereby to cause bleeding of the charge in the charge storage device, and when the charging switch is in a closed position the charge storage device is connected to the power supply but is not connected to the discharging means thereby to cause charging of the charge storage device.

12. The wireless detonator assembly of claim 1, wherein the charge storage device is selected from the group consisting of:

a capacitor, diode, rechargeable battery or activatable battery.

13. The wireless detonator assembly of claim 1, wherein the command signals are selected from the group consisting of:

ARM signals, DISARM signals, FIRE signals, detonator delay times, and detonator firing codes.

14. The wireless detonator assembly of claim 1, further comprising signal transmission means for generating and transmitting at least one communication signal for receipt by the blasting machine.

15. The wireless detonator assembly of claim 14, wherein each communication signal comprises detonator delay times, detonator firing codes, or detonator status information.

16. The wireless detonator assembly of any one of claims 1 to 15, wherein the wireless command signals comprise radio waves, electromagnetic energy, or acoustic energy.

17. The wireless detonator assembly of claim 16, wherein the wireless command signals comprise ULF radio waves.

18. The wireless detonator assembly of claim 16, wherein the wireless command signals comprise radio waves having a frequency of from 100 to 2000 Hz.

19. The wireless detonator assembly of claim 16, wherein the wireless command signals comprise radio waves having a frequency of from 200 to 1200 Hz.

20. The wireless detonator assembly of any one of claims 1 to 19, wherein in use the base charge is located in a detonator shell down a borehole in association with an explosive charge, and at least said signal receiving and processing means, said charge storage device, and said power supply are located at or near a surface of the ground.

21. The wireless detonator assembly of claim 20, wherein at least said signal receiving and processing means, said charge storage device,.and said power supply are located in a top-box at or near a surface of the ground.

22. The wireless detonator assembly of claim 1, wherein said at least one power source comprises an active power source to provide power at least to said signal receiving and processing means, and an energy receiving means for receiving energy from a remote energy source, said energy receiving means transferring said energy to a converting means for converting said energy to electrical energy, said converting means providing said electrical energy to charge said charge storage device.

23. The wireless detonator assembly of claim 22, wherein said remote energy source is a laser, said energy receiving means is a light capture device, and said converting means is a photodiode.

25. A blasting apparatus comprising:

at least one blasting machine capable of transmitting command signals to associated wireless detonator assemblies via wireless communications;

at least one explosive charge;

at least one wireless detonator assembly of any one of claims 1 to 24 associated with each explosive charge and in wireless signal communication with said at least one blasting machine.

26. The blasting apparatus of claim 25 further comprising a central command station, said central command station transmitting command signals to said at least one blasting machine, said at lease one blasting machine responding to said command signals or relaying said command signals to said at least one wireless detonator assembly.

27. A method of blasting at a blast site, the method comprising the steps of:

providing a blasting system according to claim 25;

placing a plurality of explosive charges at the blast site;

associating a wireless detonator assembly with each explosive charge such that actuation of each base charge will cause actuation of each associated explosive charge;

transmitting at least one “

keep alive”

command signal from said at least one blasting machine to each wireless detonator assembly, to cause each charging switch of each wireless detonator assembly to adopt a closed position, thereby to charge each charge storage device;

transmitting a FIRE signal from said at least one blasting machine to each wireless detonator assembly, to cause discharge of electrical energy from each charge storage device into each firing circuit, thereby causing actuation of each base charge.

28. The method according to claim 27, wherein the command signals further comprise delay times for each detonator, thereby to cause the detonators to fire in a specific timing pattern.

29. The method according to claim 27, wherein each detonator comprises a stored firing code, and the command signals further comprise firing codes, each detonator firing only if a stored firing code and a firing code from a command signal correspond.

30. Use of the wireless detonator assembly of any one of claims 1 to 24, in a mining operation.

31. Use of the blasting system of claim 25, in a mining operation.

32. Use according to claim 30 or 31, wherein the mining operation is an automated mining operation comprising robotic placement of explosive charges and wireless detonator assemblies at the blast site.

24. A wireless detonator assembly for use in connection with a blasting machine that transmits at least one wireless command signal to the wireless detonator assembly, the wireless detonator assembly comprising:

a detonator comprising a base charge;

command signal receiving and processing means for receiving and processing said at least one wireless command signal from said blasting machine;

a charge storage device for storing electrical energy

at least one power source to power said command signal receiving and processing means, and to charge said charge storage device, each of said at least one power source capable of supplying a maximum voltage or current that is less than a threshold voltage or current to actuate said base charge;

a firing circuit in electrical connection with said base charge;

a charging switch between a charging power source and the charge storage device, said charging switch having an open position and a closed position, electrical contact being established between said power source and said charge storage device when said charging switch adopts said closed position, thereby to cause charging of said charge storage device; and

a discharging means to bleed charge from said charge storage device via any path except for said firing circuit, the discharging means being in electrical connection with the charging switch, such that when the charging switch is in an open position the charge storage device is connected to the discharging means but is not connected to the power supply thereby to cause bleeding of the charge in the charge storage device, and upon receipt by said command signal receiving and processing means of at least one “

keep alive”

command signal, said charging switch adopting a closed position such that the charge storage device is connected to the power supply but is not connected to the discharging means thereby to cause charging of the charge storage device;

whereupon receipt by said command signal receiving and processing means of a command signal to FIRE said electrical energy stored in said charge storage device is discharged into said firing circuit, said base charge actuating if a voltage or current in said firing circuit resulting from discharge of said electrical energy from said charge storage device exceeds said threshold voltage or current.

33. Any invention as described herein.