BACKGROUND OF THE INVENTION

[0001] This invention relates generally to the initiation of detonators.

[0002] In a blasting system it is known to make use of an electronic detonator which initiates a group of pyrotechnic delay detonators via a flexible initiating element such as a shock tube or a detonator cord. An electronic detonator used in this way is referred to as a “starter detonator”. A benefit of using a starter detonator is that it allows the remote firing of the pyrotechnic delay detonators from a safe distance using a suitable blast network. An alternative approach would be to replace the pyrotechnic delay detonators with electronic detonators but this is an expensive solution which is often not acceptable.

[0003] A starter detonator application calls for reliable infrastructure including a harness wire and a communication network for allowing connectivity between a blasting machine and the electronic detonator which, in effect, is a remote firing station. The harness wire is however exposed to the potential problems which are associated with wired installations in high risk areas such as wire cut-off and electrical leakage.

[0004] An object of the invention is to address the aforementioned situation.

SUMMARY OF THE INVENTION

[0005] The invention provides a starter detonator assembly which comprises a wireless receiver and an electronic detonator which is configured, in response to receipt by the receiver of a wireless fire signal, to initiate a plurality of pyrotechnic detonators.

[0006] The starter detonator assembly may include a connection arrangement to which the electronic detonator is mounted. A plurality of connection members may form a part of the connection arrangement. The pyrotechnic detonators may respectively be physically connected to the connection members through the use of signal transmission elements such as shock tubes or detonator cords so that, upon initiation of the electronic detonator, the pyrotechnic detonators are initiated.

[0007] The wireless receiver may be responsive to a through-the-earth (TTE) wireless fire command signal transmitted from a blast controller, or control centre. The command signal may be at a frequency which can propagate in a reliable manner for at least a predetermined distance through the earth. For example the frequency may be less than 5kHz and, preferably, is of the order of 3kHz.

[0008] The receiver may be connected to the electronic detonator by means of a suitable conductor (i.e. electrically conductive, light conductive) which transfers the fire command signal from the receiver to the electronic detonator. The use of the conductor allows the electronic detonator to be spaced from the receiver so that when the electronic detonator is initiated damage to the receiver is avoided and the receiver is then available for reuse. [0009] Despite the aforegoing it is possible for the receiver and the electronic detonator to be provided in the form of a single unit i.e. to be of an integral construction.

[0010] The invention further provides a blasting system which includes a starter detonator assembly of the aforementioned kind, a plurality of pyrotechnic detonators, and a blast controller which generates a wireless fire signal, and wherein said electronic detonator, in response to said wireless fire signal, initiates the plurality of pyrotechnic detonators.

[0011] The pyrotechnic detonators may be connected to the connection members of the starter detonator assembly by means of said signal transmission elements.

[0012] The invention also extends to a method of blasting which includes the steps of providing a starter detonator assembly of the aforementioned kind, connecting a plurality of pyrotechnic detonators to said connection arrangement, transmitting a wireless fire command signal from a blast controller, to the wireless receiver of the starter detonator assembly and, in response to receipt of the wireless fire command signal by the wireless receiver, igniting the electronic detonator thereby to cause initiation of the plurality of pyrotechnic detonators.

[0013] The invention further extends to a connection arrangement for use in a blasting system wherein the connection arrangement comprises a wireless receiver, a support, an electronic detonator mounted to the support, a flexible conductor which connects the receiver to the electronic detonator, and a plurality of connection members which are mounted to the support, wherein each connection member is configured to be connected to a respective flexible signal transmission element so that in use when the electronic detonator is fired a resulting explosive front impinges on each flexible signal transmission element which then transmits a signal for initiating a respective pyrotechnic detonator,

BRIEF DESCRIPTION OF THE DRAWING

[0014] The invention is further described by way of example with reference to the accompanying drawing which schematically illustrates the use of a starter detonator assembly according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENT

[0015] The accompanying drawing illustrates a blasting system 10 which includes a starter detonator assembly 12 according to the invention. [0016] The assembly 12 includes a through-the-earth wireless receiver 14 and an electronic detonator 16 which is connected to the receiver 14 by means of a flexible conductor 20.

[0017] The detonator 16 is mounted to a support in the form of a board 22 which carries a number of connection members 24 which are fixed in a reliable manner to a plurality of flexible signal transmission elements 28. Each element comprises a respective length of shock tube or a detonator cord.

[0018] These connection members 24 are positioned relative to the detonator 16 so that when the detonator is fired a resulting explosive front, or shockwave, from the electronic detonator impinges on the signal transmission elements in a manner which causes initiation of the elements. [0019] Each element 28 is connected in a conventional manner to a respective pyrotechnic delay detonator 30, which is deployed in a respective borehole 32 which is charged with explosive material 34.

[0020] The receiver 14 is responsive to signals from a through-the-earth transmitter 40, which is operated by a blast controller 42 at a blast control centre 44. The transmitter 40, which typically works at a frequency of the order of 3kHz, has a transmission envelope 46 of a known size within which through-the-earth wireless signals transmitted by the transmitter can reliably be received.

[0021] Typically the transmitter 40 is deployed in an underground environment on a level which differs from a level of an area at which production is taking place. At the production area blasting is carried out in a conventional manner by means of the pyrotechnic delay detonators 30. The arrangement is one in which the transmitter 40 can be separated from the receiver 14 by a distance of several hundred meters.

[0022] The receiver can be deployed in a tunnel close to the production area, but within the envelope 46 of the signal from the transmitter. When the detonators 30 are to be initiated a fire-command signal is sent through-the-earth from the transmitter 40 to the receiver 14, The receiver 14, upon receipt of the signal, causes the electronic detonator 16 to be fired. In response thereto the signal transmission elements 28 are initiated and transmit firing signals to the detonators 30.

[0023] A benefit of the aforementioned process is that no physical connection is required between the transmitter 40 and the receiver 14. The control centre 44 is meaningfully displaced from the receiver 14 and safety of operation is considerably enhanced. If the receiver is connected to the electronic detonator 16, as indicated, by means of a conductor 20 then the firing of the electronic detonator does not damage the receiver 14 and it is possible to recover the receiver 14 for reuse in a subsequent blasting process. [0024] Despite this it is possible if required to fabricate the receiver 14 and the detonator 16 as an integral assembly.