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[0001] The present invention relates to an electronic detonator system, more specifically to firing of electronic detonators included in such a detonator system.
[0002] Detonators in which delay times, activating signals etc. are controlled electronically, are generally placed in the category electronic detonators. Electronic detonators have several significant advantages over conventional, pyrotechnic detonators. The advantages include, above all, the possibility of changing, or “reprogramming”, the delay times of the detonators and allowing more exact delay times than in conventional, pyrotechnic detonators. Some systems with electric detonators also allow signalling between the detonators and a control unit.
[0003] However, prior-art electronic detonators and electronic detonator systems suffer from certain restrictions and problems.
[0004] In prior-art electronic detonator systems, firing of electronic detonators is initiated by means of a firing command which is sent from a control unit. The receipt of the firing command in a detonator starts a non-interruptible countdown of a delay time stored in the detonator, after which time the detonator detonates. A problem of such a method is that at the same time it is necessary to prevent “duds”, i.e. detonators that do not detonate although a firing command has been given by the control unit, and unintentional detonations, i.e. firing of a detonator although no firing command has been given by the control unit. When a firing command has been given by the control unit, it is to be hoped that all detonators function and that all detonators perceive the firing command.
[0005] In order to prevent duds, the firing command can be implemented in such manner that it will be easily perceived by the detonators, which, however, can result in also other commands being interpreted as a firing command, with the ensuing unintentional firing.
[0006] In an electronic detonator system, where communication between a control unit and a number of electronic detonators occurs electronically, it is also most important that the signalling voltages do not have a level which can result in unintentional firing of the detonators. A low signalling voltage, however, limits the number of detonators which can be connected to one and the same control unit. One reason for the limited number of detonators is that there is always some loss in the signalling, which means that the signalling voltage decreases with the distance from the control unit and thus limits the number of detonators which can be connected to the control unit.
[0007] Nevertheless there is in certain detonation operations a need for using a very large number of detonators in one and the same blast.
[0008] There is thus a need for new methods and systems for firing electronic detonators, which minimise the risk of duds, eliminate the risk of unintentional firing and besides allow a very large number of detonators in one and the same blast.
[0009] An object of the present invention is to provide an electronic detonator system and a method in such a system, allowing reliability and flexibility which essentially obviates the above-mentioned problems of prior-art detonator systems.
[0010] A more concrete object of the present invention is to provide a detonator system, and a method in such a system, which allows functional testing and control of an electronic detonator when this is in a state corresponding to the state immediately prior to detonation. In this description, such a state is referred to as the ready state.
[0011] Another concrete object of the present invention is to provide a detonator system, and a method in such a system, which allows use of a very large number of electronic detonators in one and the same blasting operation.
[0012] The above objects are achieved by the characteristic features that are defined in the appended claims.
[0013] Seen from one aspect, the present invention relates to a method for firing one or more detonators, said method allowing the detonators to be controlled and checked also after they have received the firing command. An advantage of the invention is that the firing command is allowed to have a form which significantly distinguishes from all other commands that are sent to the detonators, whereby the risk of other commands being misinterpreted as being a firing command is practically eliminated. At the same time a check that all detonators have received the firing command is allowed, owing to the possibility of communication with the detonators occurring also after the firing command has been received by the detonators.
[0014] According to an embodiment of the present invention, communication occurs to the electronic detonators by means of digital data packets. Since such digital data packets comprise some overhead, they will always contain at least one binary one and at least one binary zero. By ensuring that the firing command consists of a row of identical data bits, preferably binary zeros, a firing command is provided, which significantly differs from said digital data packets. Besides the digital data packets are advantageously designed in such manner that, if the firing command consists of binary zeros, they comprise as many binary ones as possible, which further emphasises the unique state of the firing command. The number of data bits in the firing command is preferably the same as the number of data bits in the digital data packets.
[0015] According to the invention, controlling and checking of the detonators is thus allowed also after they have received the firing command, and especially checking of the fact that all detonators have received the firing command, by communication with the detonators being possible also after the firing command has been received by the detonators. This is accomplished in an advantageous fashion by the firing command setting the detonators in a ready state, which is the state of the detonators immediately prior to detonation, without a final, non-interruptible countdown of a delay time stored in each detonator being started. A non-interruptible countdown of the delay time is instead started at a later synchronising point which is common to the detonators. Up to the synchronising point, communication between a control unit and the detonators can thus occur, thereby allowing control and checking of these. The synchronising point is indicated by means of a synchronising signal which can easily be perceived by the detonators. Consequently the present invention makes it possible to accomplish firing of electronic detonators, whereby the risk of duds as well as unintentional firing of a detonator is essentially eliminated while at the same time the detonators can be checked when they have received the firing command and are in the ready state, i.e. an armed and fully charged state.
[0016] The signal which is to be interpreted by the detonators as a synchronising signal can be preprogrammed in the system, or alternatively be indicated by the firing command.
[0017] An additional advantage of such a firing method is that the blast can be aborted if it is discovered that the detonator is in an incorrect ready state, or if a detonator has, for instance, not perceived the previously given firing command and thus runs the risk of being a dud.
[0018] In some applications, it may also be advantageous that the time between the sending of the firing command from the control unit and the sending of the synchronising signal is used to send additional firing commands. In this way, the risk of duds is minimised to be practically zero, since the detonators will most probably perceive at least one of the these firing commands. More than one firing command may, however, result in the detonators detonating at an incorrect time, relative to the stored delay times, and therefore a careful consideration should be made before a function of this type is implemented in the system. An electronic detonator system according to the present invention is arranged precisely to prevent duds, and additional firing commands as mentioned above will probably not be necessary. However, rules and regulations in some countries may require precisely such a reiteration of the firing command.
[0019] Seen from another aspect, the present invention allows that the system comprises a plurality of slave control units, with the associated detonators, which are connected to a main control unit, from which main control unit the main control of the system is performed. Each slave control unit ensures that the detonators which are connected thereto function according to the commands given by the main control unit.
[0020] In that case the detonators are controlled by a main control unit, from which commands and enquiries to the detonators are issued. The basic principle of the present invention allows a number of slave control units to be connected to the main control unit. Each of these slave control units controls a set of electronic detonators at the command of the main control unit.
[0021] A delayed firing of the detonators, according to the present invention, thus allows a detonator system with a plurality of blasting machines, i.e. a plurality of coordinated sets of detonators each having a bus to a blasting machine of its own. A firing command can be given to all detonators, after which each blasting machine checks that the detonators associated with this blasting machine are ready to be fired. When all blasting machines indicate that each set of detonators is ready to be fired, an activating command is given to all the blasting machines at the same time. A final, synchronised countdown is then started by all blasting machines sending simultaneously, in response to the activating command, a synchronising signal which results in the non-interruptible countdown of the delay time of the detonators starting at a synchronising point which is common to all detonators. If a blasting machine should indicate that a detonator is in an incorrect ready state, or for some other reason is not ready to be fired, abortion of the firing process is allowed according to the present invention, also after the firing command has been given. Alternatively, the firing process may continue if a fault which is identified in a detonator is considered to be of a non-critical kind. It is then possible to choose to continue the firing process in the same way as if nothing incorrect had been found, or continue the firing process according to an alternative procedure, after modification of suitable steps in the firing process. Also using a plurality of blasting machines makes it possible to provide synchronisation of the detonation of the detonators, with maintained flexibility and reliability.
[0022] It is thus preferred for one of the blasting machines to be given a primary role and thus act as a main blasting machine while the remaining blasting machines are given a secondary role and thus act as slave blasting machines. The entire combined system is then handled from the main blasting machine while each slave blasting machine manages the configuration of detonators associated therewith, based on control commands from the main blasting machine. This arrangement makes it possible to control a very large number of detonators from one and the same blasting machine, i.e. the main blasting machine, without necessitating an increase of the signalling voltage to a level which means that the safety of the system is jeopardised, owing to the possibility of limiting the number of detonators per bus. At the same time, firing according to the present invention allows synchronising of all slave blasting machines in a reliable fashion, so that the detonators detonate according to the previously set plan in spite of the fact that they are connected to different blasting machines.
[0023] The communication between the main blasting machine and the slave blasting machines occurs preferably by means of radio communication or via a bus in the form of a physical cable. It is also possible to use other types of communication between the main blasting machine and the slave blasting machines, such as different forms of microwave communication, acoustic communication or optical communication using e.g. laser. The choice of way of communication between the main blasting machine and the slave blasting machines is usually dependent on the user's requirements for flexibility and reliability, in relation to costs. It is also conceivable that different national or regional regulations require a certain type of communication.
[0024] According to one more aspect of the present invention, test firing of the detonators is allowed, in which these go through all steps leading to detonation, apart from charging of firing power storing means, such as ignition capacitors, and the actual ignition of the explosive charge. The detonators report the result of the test firing to their control unit, whereby a further kind of evaluation of the function of the detonators is allowed. By means of a test firing, it is possible to check that the detonators have perceived correct delay times, that the receipt of said digital data packets functions in a reliable manner, that said synchronising functions in the intended manner, that countdown of delay times occurs at an expected rate, and that the overall function of the detonators is satisfactory.
[0025] The term control unit should, in this description, be considered a generic term for such units as send messages to, and receive responses from, the detonators. Examples of control units is a logging unit, for use when connecting the detonators to the bus and establishing the identity of each detonator, and a blasting machine, for preparing and firing detonators connected to the bus.
[0026] The terms logging unit and blasting machine will be explained in more detail in connection with the following description of a preferred embodiment of the invention.
[0027] For additional description of characteristic features of an example of a system of the general kind that is intended, reference is made to Swedish Patent Application 9904461-2 which is incorporated herewith by reference.
[0028] A preferred embodiment of the invention will be described below with reference to the accompanying drawings, in which
[0029]
[0030]
[0031]
[0032]
[0033]
[0034]
[0035]
[0036] With reference to
[0037] The electronic detonator system
[0038] By way of introduction a preferred embodiment of detonator firing according to the present invention will be described with reference to
[0039] A number of detonators
[0040] As a starting point for the description of a method according to the present invention which is given below, it is assumed that a number of detonators
[0041] A blasting machine is, as mentioned above, the term for the control unit that is used to prepare and fire the detonators
[0042] As illustrated in
[0043] In the preferred embodiment, said response pulses
[0044] With reference to
[0045] A firing command is given (
[0046] First it is preferably checked that all detonators have perceived the firing command (
[0047] When it has been established that all detonators
[0048] In response to the synchronising signal, each detonator starts said countdown of the corresponding delay time (
[0049] With reference to
[0050] Two sets of delay time information are stored in the blasting machine
[0051] As an extra measure of precaution, the delay time is preferably transferred twice to each detonator, an error flag being set in the detonator if this does not perceive the same delay time in both transfers (
[0052] When all delay times have been transferred to the respective detonators, the blasting machine suitably checks that no detonator lacks a delay time (not shown). This occurs, for example, by the blasting machine sending a globally addressed enquiry asking whether a detonator has not set the flag indicating that a delay time is received. At this stage it is also possible to check that no detonator has set the error flag.
[0053] It should emphasised that if a delay time is transferred a third time, the detonators will set the error flag if not the same delay time as before is involved. A change of a previously transferred delay time must therefore comprise two transfers, with an intermediate reset of the error flag. In this way, the delay times can be changed an optional number of times.
[0054] Preferably, it is now checked that ignition capacitor and fuse head are available in each detonator (
[0055] If everything functions so far, it is time to begin charging the ignition capacitor in each detonator. This is performed by an arming command being sent (
[0056] If the detonation process is to be continued, the blasting machine now increases the voltage of the bus
[0057] Preferably said arming, and the associated charging of the ignition capacitors, occurs by an operator physically pressing an arming button on the blasting machine
[0058] When the firing button is pressed (
[0059] According to the invention, the countdown of the delay time stored in each detonator is not started immediately after the firing command has been received in the detonators. In the preferred embodiment, it is instead necessary that additional, for instance fourteen, complete data packets be received in the detonators before the final, non-interruptible, countdown starts. This gives, by communication from the blasting machine
[0060] Should an error be discovered at this stage, there is a possibility of aborting the entire firing process thanks to the fact that said, for instance fourteen, additional data packets must be received before the final countdown is started. This abortion can be provided, for example, by a global resetting command being sent from the control unit or by no further data packets
[0061] The final, non-interruptible, countdown of the delay time thus starts at a synchronising point (
[0062] From the synchronising point onwards, communication with the detonators is no longer possible. After the synchronising signal the detonators do not require any voltage supply from the blasting machine
[0063] Thanks to the fact that the detonators, according to the present invention, can be checked when they are in said ready state, the risk of incorrect function after the synchronising point is, however, reduced to a minimum.
[0064] When the countdown (
[0065] The above-mentioned process is also very well suited to be carried out in a system with a main blasting machine
[0066] A preferred method in a system with main and slave blasting machine as above will now be described.
[0067] The main blasting machine
[0068] When all slave blasting machines
[0069] In an alternative embodiment of the present invention, a test firing is carried out before the detonators are armed and fired, which is schematically illustrated by the flow chart in
[0070] Before the firing process described above is started, it may be desirable to carry out a test firing. The purpose of a test firing can be to check that the detonators
[0071] The test firing is started by the blasting machine
[0072] It should be pointed out that the test firing is not preceded by arming of the detonators. Thus there is no risk of unintentional firing of a detonator in a test firing since voltage is not applied to the ignition capacitors in the detonators.
[0073] If the responses given by the detonators in response to the test firing command should not conform with the expected delay times, first an automatic decision is made whether the entire firing process should be aborted and repeated once more. If the deviation from what is expected is small, an operator may, however, make a decision to let the firing process continue, in which case arming and sharp firing as described above may begin.
[0074] Moreover, the test firing can advantageously have a scaling function, through which the stored delay times are multiplied by a scale factor. In the preferred embodiment, the scale factor is 1, 2, 4, 8 or 16. The higher scale factor is selected to be used, the longer it takes to carry out the test firing. The scaling function is a very useful tool for high resolution checking and test of stored delay times as well as the synchronisation of the detonators, particularly when using a plurality of blasting machines.
[0075] As described above, the test firing results in the detonators giving an analog response pulse on the bus. In this case, such an analog response pulse is about 2 ms, which means that, without using said scaling function, it is not possible to distinguish two response pulses which are less than 2-3 ms from each other. It is desirable for the response pulses not be made shorter than said
[0076] It will be appreciated that a test firing of higher resolution (i.e. a test firing using a higher scale factor) will take longer than a test firing of lower resolution. A test firing with the scale factor
[0077] In conformity with that described above in connection with the firing process, also the test firing can be carried out in a system having a main blasting machine and slave blasting machines. Each slave blasting machine reports the time distribution of the responses from the detonators to the main blasting machine, which in turn evaluates the result of the test firing. In fact, test firing is most desirable, especially when a system with slave blasting machines is used since it is then allowed via the main blasting machine to check that the synchronisation of all slave blasting machines and the detonators connected thereto functions in the intended manner. At the same time the main blasting machine receives information whether correct delay times are stored in the detonators, and whether the countdown rate of these delay times is correct.
[0078] The invention has been described above on the basis of a preferred embodiment. However, this description does not aim at restricting the scope of the invention in any sense. It will be appreciated that modifications can by made within the scope of the invention, as defined in the appended claims.