Note: Descriptions are shown in the official language in which they were submitted.
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ELECTRONIC DETONATOR SYSTEM
Field of the Invention
The present invention relates to an electronic deto-
nator system, more specifically to firing of electronic
detonators included in such a detonator system.
Background Art
Detonators in which delay times, activating signals
etc. are controlled electronically, are generally placed
in the category electronic detonators. Electronic deto-
nators have several significant advantages over conven-
tional, pyrotechnic detonators. The advantages include,
above all, the possibility of changing, or "reprogram-
ming", 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.
However, prior-art electronic detonators and elec-
tronic detonator systems suffer from certain restrictions
and problems.
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
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detonators function and that all detonators perceive the
firing command.
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.
In an electronic detonator system, where communica-
tion between a control unit and a number of electronic
detonators occurs electronically, it is also most impor-
tant that the signalling voltages do not have a level
which can result in unintentional firing of the detona-
tors. A low signalling voltage, however, limits the num-
ber 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 con-
nected to the control unit.
Nevertheless there is in certain detonation opera-
tions a need for using a very large number of detonators
in one and the same blast.
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.
Summary of the Invention
An object of the present invention is to provide an
electronic detonator system and a method in such a sys-
tem, allowing reliability and flexibility which essen-
tially obviates the above-mentioned problems of prior-art
detonator systems.
A more concrete object of the present invention is
to provide a detonator system, and a method in such a
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system, which allows functional testing and control of
an electronic detonator when this is in a state corre-
sponding to the state immediately prior to detonation.
In this description, such a state is referred to as the
ready state.
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 ope-
ration.
The above objects are achieved by the characteris-
tic features that are defined in the appended claims.
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 com-
mand. 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 occur-
ring also after the firing command has been received by
the detonators.
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
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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.
According to the invention, controlling and check-
ing 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 pos-
sible 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 imme-
diately prior to detonation, without a final, non-inter-
ruptible countdown of a delay time stored in each deto-
nator 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.
The signal which is to be interpreted by the detona-
tors as a synchronising signal can be preprogrammed in
the system, or alternatively be indicated by the firing
command.
An additional advantage of such a firing method is
that the blast can be aborted if it is discovered that
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the detonator is in an incorrect ready state, or if a
detonator has, for instance, not perceived the previous-
ly given firing command and thus runs the risk of being
a dud.
5 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 synchronis-
ing 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 regu-
lations in some countries may require precisely such a
reiteration of the firing command.
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.
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.
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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 coor-
dinated sets of detonators each having a bus to a blast-
s ing 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 indi-
cate 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 syn-
chronising 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 identi-
fied in a detonator is considered to be of a non-critical
kind. It is then possible to choose to continue the fir-
ing 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 synchro-
nisation of the detonation of the detonators, with main-
tained flexibility and reliability.
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
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slave blasting machine manages the configuration of
detonators associated therewith, based on control com-
mands from the main blasting machine. This arrangement
makes it possible to control a very large number of deto-
nators 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 possi-
bility 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 accord-
ing to the previously set plan in spite of the fact that
they are connected to different blasting machines.
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 opti-
cal 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.
According to one more aspect of the present inven-
tion, 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 allow-
ed. By means of a test firing, it is possible to check
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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.
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.
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.
For additional description of characteristic fea-
tures of an example of a system of the general kind that
is intended, reference is made to Swedish Patent Appli-
cation 9904461-2 which is incorporated herewith by refe-
rence.
Brief Description of the Drawings
A preferred embodiment of the invention will be
described below with reference to the accompanying draw-
ings, in which
Fig. 1 is an overall view of a number of units
included in an electronic detonator system,
Fig. 2 is a schematic view of a control unit with
a bus and electronic detonators connected thereto, illu-
strating how communication with said detonators is accom-
plished,
Figs 3a and 3b schematically illustrate how a ques-
tion is asked regarding a predetermined status bit in a
predetermined detonator,
Fig. 4 is a flow chart of a general firing process
according to the invention,
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Figs 5a and 5b are a more detailed flow chart of a
firing method according to the present invention,
Fig. 6 schematically illustrates a detonator sys-
tem with a main blasting machine and a plurality of slave
blasting machines, according to the present invention,
and
Fig. 7 is a flow chart of a general test firing
method according to the present invention.
Description of a Preferred Embodiment
With reference to Fig. 1, a number of units are
shown, which are included in an electronic detonator
system 1 according to an embodiment of the present
invention.
The electronic detonator system 1 comprises a plura-
lity of electronic detonators 10 which are connected to
a control unit 11, 12 via a bus 13. The bus 13 serves to
communicate signals between the control unit 11, 12 and
the detonators 10, i.e. to allow communication there-
between, and to provide power to the detonators 10. The
control unit may consist of a logging unit 11 or a blast-
ing machine 12. The detonator system 1 according to the
invention may also comprise a portable message receiver
14, which is adapted to be carried by the person connect-
ing the detonators 10 to the bus 13. Via the portable
message receiver 14, information is provided regarding,
among other things, when the system 1 is ready for con-
nection of one more detonator. Moreover, a computer 15 is
preferably included in the system 1, said computer being
used to plan the blast. A blasting plan that has been
planned in the computer 15 is transferred to one of said
control units (logging unit 11 and/or blasting machine
12). Alternatively information collected by the logging
unit 11, such as addresses of the electronic detonators
10, can be transferred to the computer 15 for further
processing, after which a blasting plan is transferred to
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the blasting machine 12 for the final preparation of said
detonators 10.
By way of introduction a preferred embodiment of
detonator firing according to the present invention will
5 be described with reference to Fig. 2.
A number of detonators 10 are connected to a control
unit 12 (blasting machine) by means of a bus 13. The con-
trol unit 12 is adapted to send digital data packets 22
to the detonators 10. These data packets 22 communicate
10 instructions and/or questions regarding the state of the
detonators 10. The control unit 12 is besides adapted to
receive responses 24 from the detonators 10. In the pre-
ferred embodiment, the digital data packets 22 consist
of 64 bits. In this preferred embodiment, the responses
are given by the detonators 10 in the form of analog
response pulses 24 on the bus 13. It is preferred for the
detonators 10 to give said response pulses 24 in the form
of short load pulses detectable by the control unit 12.
Such load pulses consist, in a preferred embodiment of
the present invention, of a temporary load modulation for
the detonator, i.e. the power consumption of the detona-
tor is modulated temporarily. However, it will be appre-
ciated that any influence, detectable by the control
unit, on the bus is feasible for this purpose.
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 10 are iden-
tified and connected to the bus 13, and corresponding
addresses are stored in a blasting machine 12.
A blasting machine is, as mentioned above, the term
for the control unit that is used to prepare and fire the
detonators 10. The preceding identification of the deto-
nators 10 could be carried out by means of a logging unit
11, which, when connecting detonators 10 to the bus 13,
logs addresses etc.
As illustrated in Figs 3a and 3b each detonator 10
comprises a status register 31 which contains a number of
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"flags", i.e. information states which can assume either
of two possible values, said flags indicating each infor-
mation state in the detonator 10. Moreover the detonators
advantageously have a unique identity which is used to
5 transfer addressed messages to them. The digital data
packets 22 which the blasting machine 12 sends on the
bus 13 can be globally addressed to all detonators, or
be addressed to one or a few detonators. The digital data
packets 22 can contain a question regarding the state of
10 a certain flag in the detonator 10, in which case a
response is expected from the detonator, or an imperative
command to the detonator 10, in which case no response is
expected. A response is given by the detonators 10 in the
manner indicated above by means of influence, detectable
by the blasting machine 12, on the bus, preferably a
short load pulse 24.
In the preferred embodiment, said response pulses
24 are only given at a positive response (response in
the affirmative) (Fig. 3a) whereas a negative response
(response in the negative) appears as the absence of a
response pulse (Fig. 3b), which is illustrated in the
Figure at 26. Moreover, the appearance of the response 24
from each detonator 10 is identical with the appearance
of the response from any other detonator. In the control
unit 11, 12, the response pulses 24 are interpreted,
which are received from enquiries sent previously (i.e.
digital data packets 22 containing a question regarding
one or more flags, or status bits, in one or more detona-
tors 10). For each status bit, two enquiries are imple-
mented: a first enquiry asking whether the status bit has
the first of two possible values, and a second enquiry
asking whether the same status bit has the second of two
possible values. By selecting a suitable enquiry, the
expected number of response pulses 24 (i.e. the number
of detonators giving a response pulse in response to the
question) can therefore be minimised, thereby facilitat-
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ing the interpretation of the responses in the control
unit 11, 12.
With reference to Fig. 4, the function of the elec-
tronic detonator system 1 according to the invention will
now be described briefly.
A firing command is given (400) by the blasting
machine 12. When the firing command has been received by
the detonators 10, a flag is set in each detonator which
indicates that the firing command is received, and these
detonators will consider the receipt of a predetermined
data bit in a predetermined data packet (for instance,
the first data bit in data packet number 15, counted from
the firing command), which follows the firing command,
as a synchronising signal (410). In response to the syn-
chronising signal (410), a countdown (411) of a delay
time stored in the respective detonators is started. The
data packets following the firing command are used for
checking (402) , (404) , (406) , (408) that the detonators
10 are ready for detonation.
First it is preferably checked that all detonators
have perceived the firing command (401). This is con-
veniently performed by means of an enquiry (in the form
of a digital data packet 22) from the blasting machine
12, said enquiry asking whether there is a detonator
10 which has not perceived the firing command. If no
response is received to this question it is assumed that
all detonators 10 have perceived the firing command. If a
detonator 10 should indicate that it has not received a
firing command, the system is reset (420), or switched
off, and the entire firing process is repeated from a new
start of the system.
When it has been established that all detonators 10
have received and perceived the firing command, a number
of questions (402) , (404) , (406) , (408) preferably follow
regarding the state of certain flags (i.e. status bits in
the status register 31 of the detonators). On the basis
of the responses received, the blasting machine 12 deter-
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mines whether the firing process should continue. If any
fault is found which would seriously jeopardise the
impact and/or safety of the blast, the firing process is
aborted (430). If the detonators 10 are considered to be
in a correct ready state, said synchronising signal is
sent (410) from the blasting machine 12. In the preferred
embodiment, the synchronising signal consists of the
first data bit in data packet number 15, counted from the
firing command.
In response to the synchronising signal, each deto-
nator starts said countdown of the corresponding delay
time (411). When the countdown of the delay time has been
started, it is no longer possible to abort the firing
process. When the countdown in each detonator 10 reaches
"zero", the detonator 10 is caused to detonate (440).
With reference to Figs 5a and 5b, the firing process
will now be described in more detail.
Two sets of delay time information are stored in
the blasting machine 12. This information comprises delay
times for each connected detonator 10. When starting the
system (500), the two sets are checked with regard to
each other (510), with the aim of ensuring (511) that
correct delay times are stored. Should contradictory
information regarding delay times be discovered at this
stage, the operation is aborted and new sets of delay
times are transferred to the blasting machine (515). If
no error is discovered in the delay time information, the
delay times are transferred to the respective detonators
(520) by individually addressed messages in the form of
digital data packets 22.
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 (522).
When the detonators have received the same delay time
twice in a row, a flag is set, indicating that the delay
time is received.
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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.
It should emphasised that if a delay time is trans-
ferred 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.
Preferably, it is now checked that ignition capa-
citor and fuse head are available in each detonator (530)
for the risk of duds to be minimised. This is preferably
performed by checking a number of flags which indicate
when certain voltage levels have been reached in the
ignition capacitors of the detonators 10. If an ignition
capacitor and/or a fuse head is missing in one or some of
the detonators 10, and this is assessed to be a serious
error based on previously set criteria, the firing pro-
cess is aborted (550).
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 (532) by
the blasting machine 12. The arming command is global-
1y addressed, i.e. addressed to all detonators 10, and
results in the ignition capacitors beginning to be charg-
ed by the voltage of the bus 13. The voltage of the bus
13, however, is still so low that the voltage across the
ignition capacitors is kept at a value where there is no
risk of ignition of the detonators 10. Before the voltage
of the bus 13 is increased to a level where the ignition
capacitors begin to be charged to full ignition voltage,
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it is suitably checked that no ignition capacitor already
indicates that the ignition voltage has been reached
(534). Such an indication would indicate an error in the
detonator 10, and an assessment should be made whether
5 the detonation process should be aborted (550).
If the detonation process is to be continued, the
blasting machine now increases the voltage of the bus 13
(536). The ignition capacitors then begin to be charged
to full ignition voltage. A flag in each detonator indi-
10 Gates when full ignition voltage has been reached in the
ignition capacitor. During the charging of the ignition
capacitors, the blasting machine suitably sends global
enquiries, in the form of digital data packets 22, asking
whether a detonator 10 has an ignition capacitor that has
15 reached full ignition voltage. When the first detonator
answers positively (in the affirmative) to this question,
the blasting machine 12 changes to ask the opposite ques-
tion: if a detonator has an ignition capacitor which has
not reached full ignition voltage. When a response (in
the affirmative) to this last question is not received
any longer, it is assumed that the ignition capacitors of
all detonators have reached full ignition voltage (560).
In this manner, the charging of the ignition capacitors
is verified in the shortest possible time.
Preferably said arming, and the associated charging
of the ignition capacitors, occurs by an operator physi-
cally pressing an arming button on the blasting machine
12, which arming button must be pressed all the time for
the charging of the ignition capacitors to be retained.
Firing is suitably initiated by the operator physically
pressing a second button, a firing button, while at the
same time the arming button is kept pressed. On the
blasting machine, a signal (audible or visual) is pre-
ferably given (562), which indicates when all ignition
capacitors are charged to full ignition voltage, i.e.
when the firing button can be pressed.
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When the firing button is pressed (564), a firing
command is sent (566) on the bus 13 by the blasting
machine 12. In the preferred embodiment of the present
invention, the firing command differs from all other
digital data packets 22. that are sent by the blasting
machine 12. The reason for this is that no digital data
packets should, by mistake, run the risk of being mis-
interpreted as a firing command. In fact, the firing
command consists of a digital data packet 22 which only
consists of a sequence of binary zeros. The condition for
a digital data packet 22 to be interpreted as a firing
command is that it should at least contain a certain
number of binary zeros. Preferably, the counting of the
number of zeros is performed in a plurality of indepen-
dent counters in the detonators. l0, a majority decision
deciding whether a firing command has been received. If
a majority of counters indicate the smallest number of
zeros for a firing command, the command is thus inter-
preted as a firing command.
According to the invention, the countdown of the
delay time stored in each detonator is not started imme-
diately after the firing command has been received in the
detonators. In the preferred embodiment, it is instead
necessary that additional, for instance fourteen, com-
plete data packets be received in the detonators before
the final, non-interruptible, countdown starts. This
gives, by communication from the blasting machine 12 by
means of these additional data packets, the possibility
of a last check (570), (572), (574) that each electronic
detonator 10 is in the correct state for the desired
detonation process to be accomplished. It is to be noted
that the contents of these data packets are not
important, but that it is the number of data packets that
is decisive for the countdown to be started. These data
packets could thus have optional contents, contain
enquiries or commands or even consist of repeated firing
commands.
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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 22 being
sent to the detonators 10, which thus do not receive
said, for example fourteen, data packets and thus do not
start the final countdown. It is preferred for a combi-
nation of these abort functions to be used if the firing
is to be aborted, i.e. a resetting command first being
sent, after which no additional data packets are sent,
thereby essentially eliminating the risk of a continued
firing process. In case of an aborted firing, the igni-
tion capacitors will gradually be automatically discharg-
ed by means of discharge resistors arranged in the deto-
nators 10, so-called bleeder resistors. The number of
data packets which must be sent after the firing command
for the countdown of the delay time to be started has
quite optionally been selected to be fourteen in this
example.
The final, non-interruptible, countdown of the delay
time thus starts at a synchronising point (580) which is
delayed in relation to the firing command and common to
all detonators. This synchronising point occurs, in the
preferred embodiment of the present invention, when
receiving in each detonator a predetermined data bit in
a predetermined data packet, which follows the firing
command. In the example described above, the synchroni-
sation point occurs at the receipt of a predetermined
data bit in data packet number 15, counted from the
firing command. However, it is understood that also
other types of delayed synchronisation which allows com-
munication with the detonators 10 also after they have
received a firing command and thus are in a ready state,
are within the scope of the present invention.
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From the synchronising point onwards, communication
with the detonators is no longer possible. After the syn-
chronising signal the detonators do not require any vol-
tage supply from the blasting machine 12 via the bus 13,
but they obtain their necessary voltage supply from a
feeding capacitor in each detonator 10. On second
thoughts, this is a natural consequence of the fact that
the detonation is started since the contact with the
blasting machine 12 may at any time be lost owing to a
detonation in a detonator.
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 mini-
mum.
When the countdown (585) of the delay time in each
detonator reaches "zero", the ignition capacitor is imme-
diately discharged through the fuse head, which results
in essentially instantaneous ignition of the explosive
charge (590) .
The above-mentioned process is also very well suit-
ed to be carried out in a system with a main blasting
machine 62 and a number of slave blasting machines 64,
which is schematically illustrated in Fig. 6. The process
is then analogous with that described above, except that
the main control of the system 1 occurs from the main
blasting machine 62. From the main blasting machine 62,
arming, charging, preparation, checking, firing etc. of
the detonators 10 are ordered by signalling to the slave
blasting machines 64. The slave blasting machines 64 in
turn see to it that the functions ordered are carried out
for the detonators 10 which are connected to the respec-
tive slave blasting machines 64. If applicable, the slave
blasting machines 64 report the results of the functions
to the main blasting machine 62 which is thus allowed to
have the overall control of the entire system 1 without
directly needing to communicate with all detonators 10.
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A preferred method in a system with main and slave
blasting machine as above will now be described.
The main blasting machine 62 is loaded with tables
of delay times for the detonators 10 of the respective
slave blasting machines 64, said delay times being veri-
fied in the same way as described above (510). Each table
is transferred to the corresponding slave blasting
machine 64 which in turn sees to it that the delay times
are transferred (520) to the detonators 10 in the same
way as described above. If an error has been found in
one of the detonators 10, this is reported by the slave
blasting machine 64 of the detonator in question to the
main blasting machine 62. A decision whether the process
is to be aborted will then be made by the main blasting
machine. However, the slave blasting machines 64 can be
arranged to make certain decisions which need not be
forwarded to the main blasting machine 62. For instance,
rules for the conditions under which the entire firing is
to be aborted can be implemented in each slave blasting
machine 64, in which case such a condition, if any, is
communicated back to the main blasting machine, which in
turn sees to it that the firing is aborted.
When all slave blasting machines 64 have reported to
the main blasting machine 62 that delay times are trans-
ferred to the detonators 10, and that everything else
is OK, it is indicated on the main blasting machine 62
that the system 1 is ready for arming. The operator then
presses the arming button (532) and, in case of OK (562),
also the firing button (564), in the same manner as
described above. The main blasting machine 62 orders the
slave blasting machines 64 to carry out arming and fir-
ing, respectively, of detonators associated with the
respective slave blasting machines. When each slave
blasting machine 64 has reported that the corresponding
detonators 10 are ready for detonation (i.e. that the
firing command is received, the ignition capacitor is
charged, a fuse head is available etc), an activating
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command is sent from the main blasting machine 62 to all
slave blasting machines 64 at the same time, which slave
blasting machines, in response to the activating command,
simultaneously give the synchronising signal (508) on the
5 respective buses 13. Thus, synchronisation of all deto-
nators is provided although they are connected to diffe-
rent slave blasting machines 64.
In an alternative embodiment of the present inven-
tion, a test firing is carried out before the detonators
10 are armed and fired, which is schematically illustrated
by the flow chart in Fig. 7. Such test firing will be
described below.
Before the firing process described above is start-
ed, it may be desirable to carry out a test firing. The
15 purpose of a test firing can be_to check that the deto-
nators 10 have perceived correct delay times, that the
receipt of said digital data packets 62 is satisfactory,
that said synchronisation (410), (580) functions in the
intended manner, that the countdown of delay times (411),
20 (585) occurs at an expected rate, and that the overall
function of the detonators is satisfactory.
The test firing is started by the blasting machine
12 sending a test firing command (710) on the bus 13.
After receipt of this test firing command in each deto-
nator there is performed, similarly to the actual fir-
ing command, a synchronisation (720) which is delayed
in relation to the receipt of the test firing command.
Optionally, this is preceded by a check (712), (713) of
certain flags in the detonators 10, like in the case of
the sharp firing. If desired, it is also possible to
check that the test firing command has been perceived
(711) by all detonators 10 and optionally reset (714) the
system 1 and send the test firing command once more. At
the synchronising point the countdown of the delay time
(730) stored in each detonator is started in the same way
as before. When the countdown of the delay time in each
detonator reaches "zero", the detonator gives an analog
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response pulse 26 (740) on the bus 13. This is the same
type of analog response pulse 26 as the one given in the
previously described communication between the blasting
machine 12 and the detonators 10. The blasting machine 12
detects (750) these response pulses 26 and obtains in
this way information about when (i.e. how long after the
synchronising point) each detonator will detonate in a
coming sharp firing, whereby an evaluation of the test
firing is allowed.
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 capa-
citors in the detonators.
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 expect-
ed 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.
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 embo-
diment, the scale factor is l, 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 blast-
ing machines.
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
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are less than 2-3 ms from each other. It is desirable for
the response pulses not be made shorter than said 2 ms
since then there is a risk of the detectability in the
control unit of these response pulses being reduced to
an unacceptably low leve-1. At the same time, however, two
instants of detonation can be significantly closer to
each other than said 2 ms. By using the scaling function,
a high resolution test firing can thus be performed,
which gives a resolution which is considerably higher
than 2 ms.
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 8, for
instance, takes twice as long as a test firing with the
scale factor 4, and therefore it should be taken into
consideration whether a high resolution is really neces-
sary or if preference is given to a quick firing process.
In conformity with that described above in connec-
tion 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 synchro-
nisation of all slave blasting machines and the detona-
tors 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.
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
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sense. It will be appreciated that modifications can by
made within the scope of the invention, as defined in the
appended claims.
