Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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POWER MANAGEMENT OF BLASTING LEAD-IN SYSTEM
BACKGROUND OF THE INVENTION
[0001] This invention relates generally to a blasting system and more
particularly is
concerned with the safe management of power delivered to detonators or
equipment
in a radio frequency or remote wired blasting lead-in system.
[0002] A remote blasting system, for example a system which uses radio
frequency
to control and initiate a blast, normally employs an electronic or software
system,
with or without encryption techniques, to fire the blast. A blast energy
source, which
can be found in a downstream communication unit, is physically connected to
detonators in the system which therefore relies only on logic and software
security
techniques to ensure that the blast is not initiated prematurely nor without
upstream
control.
[0003] A difficulty with this type of remote blasting system is that if a
problem is
encountered in the blasting area there is often uncertainty as to whether or
not the
blast energy source is connected to the detonators. This uncertainty means
that the
blast system cannot unequivocally be declared to be safe nor can it be said
with
impunity that personnel are free to enter the blast site.
[0004] A further risk which can exist is that, once a downstream control unit
is
connected to the detonators, an immediate or premature initiation of the
system,
during power up or connection of a detonator harness, can only be stopped by
an
electronic command signal. This carries with it the consequence that firmware,
software or specific electronic failures can initiate an unplanned blast.
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SUMMARY OF INVENTION
[0005] The invention is concerned with a blasting system which at least partly
addresses the aforementioned problems and which provides for the safe
management of power to detonators in the blasting system.
[0006] The invention provides a blasting system which includes at least one
detonator, a blast energy source, a connection between the blast energy source
and
the at least one detonator, and control equipment for controlling initiation
of the at
least one detonator by causing energy from the blast energy source to be
supplied to
the at least one detonator, and wherein at least one component of the blasting
system is physically movable from an operative position to a safe position,
which is
visible by an operator, at which blast energy from the energy source cannot be
supplied to the at least one detonator.
[0007] The component may be selected from the blast energy source and a link
in
the connection.
[0008] The component may be moved, or be caused to move, in any appropriate
way. The component may for example be movable by means of a biasing
mechanism which is held in a first state when a first acceptable set of
conditions
pertains in the blasting system and which is released to a second state when
an
unacceptable condition arises in the blasting system. In the second state the
component is in the aforementioned safe position.
[0009] This movement of the component to the safe position may be caused or
initiated by at least one of the following:
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a) after a predetermined period of time has elapsed from a given starting time
-
the starting time may for example be a time at which the component was
moved from the safe position to the operative position;
b) after communication was established on the connection by means of the
control equipment followed by a malfunction; and
c) if a malfunction of part or all of the control equipment occurs.
[0010] The control equipment may include an upstream control unit and a
downstream control unit, the latter unit being closer to the detonators than
the former
unit and wherein the downstream unit is incapable of generating a blast
command
signal but can receive a blast command signal from the upstream control unit
and
transfer the blast command signal to the at least one detonator.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The invention is further described by way of examples with reference to
the
accompanying drawings in which:
Figure 1 is a block diagram representation of a blast system according to the
invention;
Figure 2 is a schematic representation of a downstream blast control unit
included in
the blast system of the invention;
Figure 3 illustrates the construction of a mechanism for moving a link in the
blast
system between an operative position and a safe position; and
Figures 4 and 5 show different mechanisms which can interrupt a blasting
process
for safety reasons.
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DESCRIPTION OF PREFERRED EMBODIMENTS
[0012] Figure 1 of the accompanying drawings illustrates a blast system 10
according to the invention which includes a plurality of detonators 12 which
are
connected to a harness 14, a downstream blast control unit 16, an upstream
blast
control unit 18, a connection 20 between the upstream unit and the downstream
unit,
and additional or optional control equipment 22.
[0013] The detonators are installed in a defined blast pattern, in blast
holes, as
desired.
[0014] The connection 20 may be effected via a wired connection i.e. by means
of a
conductor 24, or wirelessly through the medium of a radio system 26 which
includes
two transmitting/receiving antennas respectively connected to the units 16 and
18.
[0015] Figure 2 illustrates, enclosed in dotted outline, the construction of
the
downstream blast control unit 16 which is connected via the harness 14 to the
detonators 12. On an incoming side the unit 16 is connected to a blast energy
source 30. This can be a power source such as a battery, or a voltage step-up
circuit
with a voltage level which is capable of energising a detonator to set off a
blast. As
is noted hereinafter this source can be ejectable from an operative to a safe
position.
Alternatively a similar effect can be achieved by ejecting a connection, not
shown,
which connects the blast energy source to equipment which controls the
application
of energy from the blast energy source to the detonators, from an operative
position
to a safe position, upon the occurrence of an unsafe or potentially unsafe
situation.
[0016] The unit 16 includes first and second timers 32 and 34 which control
respective switches or links 32A and 34A, a voltage monitor 36 which has an
audio
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output 38 and a visual output 40, a link 42 the physical construction of which
is
shown in further detail in Figure 3, and a control circuit 44 which is
responsive to a
receiver and transmitter 46. The control unit and the receiver/transmitter may
be
duplicated, as is indicated in dotted outline in Figure 2, for redundancy
purposes.
[0017]' The link 32A is independently operated by the timer 32 which is
activated
automatically upon start up of the downstream blast control unit 16. At start
up the
link 32A is dosed and it is opened automatically after a predetermined period
which
is measured by the timer 32. This period is independently fixed and it is not
dependent on any component of the system 10. The function of the timer 32 is
to
ensure that the system returns to a state of safety after the predetermined
time
period. The timer 32 may be electronic or mechanical but, preferably, the
timer is not
microprocessor-based i.e. it is not dependent on software or software
routines.
[0018] The link 34A is also in the blast energy path between the blast energy
source
30 and the detonators and, like the link 32A, it is activated upon start up of
the
downstream blast control unit 16. On start up the link is opened and it is
closed after
the timing period of the timer 34. The function of this link is to provide a
safety or
grace period before the system can be armed, during which personnel who armed
the blast system are able to leave the blast site under safe conditions.
[0019] The monitor 36 monitors the voltage on the line downstream of the link
34A.
Detection of a voltage on the line is indicative that the link 34A is closed
and then, to
ensure safe operation, the link 42 must not be closed. If a voltage is
detected on the
line then the audio and visual alarms 38 and 40 respectively are energised.
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[0020] One embodiment of the link 42 is shown in Figure 3. The link can take
on a
variety of forms (see Figures 4 and 5) but it should provide a visible
indication,
ascertainable from a safe distance, that it is in an open or closed state, as
the case
may be. Thus the link should include at least one component which physically
moves, and the position of which is indicative of the state of the link.
[0021] The normal state of the link 42 is open and an active action is
required to
place the link in a closed state. The link is designed to be responsive to any
undesired condition in the blast system, for example a power failure or
malfunction in
the control unit 44 or the timer 32. These events are given only by way of
example
for the link, as stated, could be responsive to any other condition or
parameter which
can be monitored.
[0022] The Figure 3 embodiment of the link 42 includes a housing 50 with a
close
fitting cup-shaped plunger 52. Lower ends of the plunger include contacts 54
and 56
respectively which, when "the plunger is inserted to a maximum extent into the
housing, are brought into direct electrical contact with corresponding
contacts 58 and
60 respectively fixed to an inner surface of the housing at a lower end
thereof.
Conductors 62 and 64 extend from the contacts 58 and 60 and, as shown in
Figure
2, go to the link 34A and a link 66 which is controlled by the control unit
44.
[0023] A spring or any equivalent biasing mechanism 70 is inside the housing
and
normally urges the plunger 52 away to extend out of the housing. A conductor
72 is
embedded in the plunger and extends between the contacts 54 and 56. Two metal
slugs 74 and 76 are fixed to an inner surface of the plunger and oppose
solenoids 78
and 80 mounted to a base 82 of the plunger. If the solenoids are energised and
the
plunger is pushed inwardly then the solenoids exert sufficient attractive
forces which
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act on the metal slugs 74 and 76, to keep the plunger in a retracted position.
If the
power supply to either solenoid is interrupted then the attractive force is at
least
halved or, if both solenoids are de-energised, the attractive force is reduced
to zero.
In each case the biasing force of the spring 70 is then such that,
automatically, the
plunger is pushed out of the housing 50 to a position which is clearly visible
and
which indicates to an observer that the electric connection between the
conductors
62 and 64 is broken.
[0024] The downstream blast control unit is under the control of the control
unit 44.
The control unit 44 will only close the link 66 if a valid command is received
from the
upstream blast control unit 18 which is under operator control. Alternatively
or
additionally a valid signal can be generated by and transmitted from the
additional
control unit 22.
[0025] As is indicated in Figure 1 communication from the upstream unit to the
downstream unit can be established via a physical hard wire connection 24, or
wirelessly over the antenna system 26. In the latter case the antenna which is
shown in Figure 1 as being connected to the downstream blast control unit 16
is
connected to the receiver/transmitter unit 46 of Figure 2.
[0026] The control unit can be responsive to a command instruction from the
upstream unit 18 to interrupt the power supply to one or both the solenoids 78
and 80
thereby to cause the link 42 to be activated whereupon the plunger 52 is
substantially
ejected from the housing 54. A similar process takes place if the control unit
establishes that the integrity of any component or module in the blast system
has
been compromised.
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[0027] The redundancy circuits, marked 44A and 46A, are essentially duplicates
of
the modules 44 and 46 respectively and function in the same way to ensure that
backup is automatically provided upon failure of either module. One or both of
the
circuits can be coupled to the link 42 and cause activation of the link,
thereby placing
the system in a state of safety, if a circuit malfunction occurs.
[0028] The transceiver 46 does not take part in any interlocking or blasting
decisions. Its function is to channel the data stream between the upstream and
downstream control units.
[0029] When a blast is to be established an operator starts up the blast
control unit
16 whereupon the timer 32 commences its timing cycle and closes the link 32A.
Communication is then established between the upstream and downstream control
units as required. The link 42 is closed by the operator pushing on the
plunger 52 so
that it goes into the housing and bridges the contacts 58 and 60. The monitor
36
constantly monitors the line 62 and if a voltage is detected on the line the
operator is
alerted and can take appropriate action. If any malfunction should occur the
link 42
is automatically opened in the manner described.
[0030] If the timing period of the timer 32 is exceeded, for whatever reason,
without
the blasting system being fully armed, then the link 32A automatically opens.
When
this occurs the link 42 is also opened to provide a visual indication that the
system
has been returned to a safe state.
[0031] Once the blasting system has been established and the blasting system
is to
be armed, the link 34A is opened for a predetermined time period, set by the
timer
34, during which all personnel should leave the blast site. On expiry of the
time
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period the link 34A is closed and the detonators can be armed and thereafter
fired
with a blast command signal generated by the control equipment. Thus the timer
34
provides a grace period during which personnel can leave the blast site with
safety
before the electronic control system takes control of the detonators.
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[0032] If a malfunction occurs during the arm and blasting stages then the
physical
link 42 is automatically opened and is moved to a position, which is visible
from a
distance, at which the conductor 62 is electrically disconnected from the
conductor
64. Thus personnel know that they can re-enter the blast site with safety.
[0033] Figure 4 shows a component 42A which can be used in place of the link
42
shown in Figure 3. The component includes opposed solenoids 84 and 86 each of
which acts on a respective latch 88 and 90, mounted for pivotal movement about
a
respective axis 92 and 94. Structure 96 which, according to requirement,
carries a
visible blast energy source (eg. a battery), blast energy converter or a
connector,
designated 98, is held in an operative position (as shown) by the latches 88
and 90.
However, if a command instruction is received from the upstream unit 18 or if
a
malfunction is detected then the power supply to one or both solenoids is
interrupted.
A spring 100 on a plunger 102 of a de-energised solenoid then rotates the
respective
latch in the direction of an arrow 104 or 106, as the case may be. A spring-
loaded
member 108 then forces the structure 96 upwardly to provide a visible
indication of
the circuit interruption.
[0034] One or more electrical contacts in the member 108 or associated with
the
structure 96 are simultaneously broken so that the system is thereby
automatically
placed in a state of safety.
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[0035] Figure 5 shows another possible form of the link 42. A component 42B
includes structure 96B, which can carry a blast energy source or converter, or
a
connector link, and which is mounted for pivotal movement about an axis 110. A
solenoid 84B acts on a latch 88B which moves about a pivot 92B and which can
retain the structure in an operative position, as shown.
[0036] When the structure is moved to the operative position a coil spring,
not
shown, centred on the axis 110, is biased. If for any reason, e.g. a
malfunction
occurring in the blasting circuit, the solenoid is de-energised, the spring
causes the
structure to pivot upwardly, about the axis 110, in the. direction of an arrow
112. A
cam formation 114 on the structure then acts on a spring-loaded plunger 116
and
breaks an electrical connection or connections in the blasting circuit which
is thereby
rendered safe.
[0037] Again, a visible indication is given to personnel of the change of
state, and
the blast site can be re-entered with safety.
