Note: Descriptions are shown in the official language in which they were submitted.
4`
1 The present invention relates to an electronic
delay detonator for delayed detonation after the lapse of
a predetermined delay time in response to a pulse-like
ignition input voltage.
The conventional electric delay detonator specie
fled in JIG K4807 IRIS is an abbreviation of Japanese
Industrial Standard) is such that delay powder is arranged
between an electric ignition device (platinum wire) and
a charge to delay the detonation time. The control of the
oa~cl~r
mixing of this delay wow and management of the charge
I
amount thereof are very troublesome on the one hand, and
the precision of the delay time is generally low on the
other hand. In recent years, with the improved civil
so s
Jo engineering Tao wow, there has been an increasing
demand for an improved time accuracy of the delay detonator.
So far, the accuracy of the electric delay detonator with
delay powder has been limited to +3 to 4% of a set delay
time.
In view of this, some researchers have suggested
on
20 it electronic delay detonator with an electrical circuit
which is low in production cost and high in time accuracy.
For technologies related to the electronic delay detonator,
reference is made to Japanese Patent Laid-Open No. 43454/79
laid open on April 6, 1979, Japanese Patent Laid-Open No.
142496/82 laid open on September 3, 1982, Japanese Patent
- 1 -
~226~)ÇIL9L
1 Laid-Open No. 1~2~198/82 laid open on September 3, 1982,
and US. Patent No. 4,240,350.
! These electronic delay detonators are roughly
n
classified into two types;Aanalog system comprising a time
delay device including a series connection of a resistor
and a capacitor in which the voltage across the capacitor
is utilized, and a digital system comprising a OR oscilla-
ion circuit or a crystal oscillator circuit and a counter
so that the pulses generated by the oscillator circuit
are counted to attain a predetermined delay time.
The former detonator generally comprises a
capacitor for storing electrical energy, a thruster, an
electrical ignition device (such as platinum wire) con-
netted in series with the storage capacitor through the
thruster, a series connection of a resistor and a keeps-
ion for driving the thruster with a predetermined delay
time after application of the electrical energy to the
storage capacitor, a thruster trigger device inserted
between the gate of the thruster and the time-delaying
. .
capacitor for applying the electrical energy stored in the
time-delaying capacitor to the gate of the thruster when
the voltage across the time-delaying capacitor reaches a
predetermined level, and a constant voltage circuit con-
netted across the storage capacitor for applying a constant
voltage across the time-delaying resistor and the keeps-
ion regardless of the input voltage of the storage
capacitor.
The electronic delay detonator with analog
-- 2
l voltage, however, has different delay times depending on
the voltage applied to the storage capacitor and temper-
azure changes, and has not any conspicuous advantage as
- compared with the detonator with powder. Due to
these facts and variations in electrical characteristics
of parts to be used, it is difficult to produce such
analog type detonators of practical use on a mass production
basis.
Generally, the error of charge-discharge cycle
under transient conditions increases with the capacitor S
capacity. If this error is to be reduced to minimum the
capacitorScapacity should desirably be minimized. In the
electronic delay detonator with analog voltage, however,
the time delaying capacitor is used to determine the delay
time, and also used to fire the thruster with the elect
tribal energy stored therein. It is, therefore impossible
a,
to use ye capacitor of a capacity smaller than a predator-
mined value, resulting in the problem of impossibility of
error reduction and the problem of the unavailability of a
wide setting range of delay time.
In the digital system aimed at high accuracy of
delay time, on the other hand, it is common practice to
use an oscillator circuit including an oscillator such as
a crystal oscillator or a ceramic oscillator or a OR
oscillator circuit whereby the oscillation output is
frequency-divided to effect accurate counting of the time.
The detonator with a OR oscillator has the problem of
insufficient accuracy of the oscillation frequency, while
1 the oscillator circuit including a crystal oscillator or
e
I`' the like involves the following inconveniences in the
delaying operation of the electronic delay detonator and
is not of practical value. Specifically, the oscillation
of a crystal oscillator or the like uses the vibrations by
the mechanical displacement of a solid, and accordingly,
it takes a long time such as several hundred milliseconds
for the low-frequency oscillator or several tens of Millie
seconds for the high-frequency oscillator before a pro-
determined vibration frequency is established.
When one tries to delay the time accurately after the application of electrical ignition energy, therefore,
the delay means using the crystal oscillator develops an
error in delay time due to this initial unstable period of
time, making it impossible to use the detonator reliably
for delay blasting. If this initial unstable period is to
be eliminated, it is necessary to excite the crystal oscil-
later circuit with another power supply in advance. In
delay firing or ignition of detonators where electrical
ignition energy is applied to all the detonators at a time
for sequential detonations, however, it is practically
o
impossible to supply stably necessary power per each
detonator because power lines for the crystal oscillator
circuits will be blasted and lost by explosion of a demo-
NATO to be previously exploded. Further, the ordinary electric detonator utilizes two wires for supplying the
electrical ignition energy to the detonator, and the
detonator utilizing such crystal oscillator circuit which
~2~:61~4~ `
requires an additional wire for supplying power thereto will
increase the wiring work cost and is not economical.
If the oscillation frequency of the crystal
oscillator is increased to a higher level such as over several
tens of MHz, it is true that the initial unstable period is
shortened to several milliseconds. With an increased number
of steps of ~requency-divider circuit for counting the delay
time, however, the integrated circuits making up the
frequency-dividing circuit is increased.
Accordingly, an object of the present invention is
to provide an electronic delay detonator with an accurate
delay time.
Another object of the present invention is to
provide an electronic delay detonator in which the delay time
can be set in a wide range.
Still another object of the present invention is to
provide an electronic delay detonator which satisfies the
requirements of compactness, low cost and high operating
reliability.
According to one aspect of the present invention,
there is provided an electronic delay detonator for driving an
ignition device with a predetermined time delay by being
supplied with electrical energy. The detonator comprises
input terminal means for supplying the electrical energy to
the delay detonator; a first capacitor for storing the
electrical energy; means inserted between the input terminal
means and the first capacitor for preventing the stored
electrical energy from being released through the input
-- 5 --
oh
~26~)~4
terminal means; oscillator means electrically connected to the
first capacitor and including a resistor and a second
capacitor, for producing a plurality of pulse signals of a
period proportional to the product of the resistance value of
the resistor and the capacitance value of the second
capacitor, the oscillator means also including a COOS
integrated circuit; means connected across the first capacitor
for generating a constant voltage, the constant voltage
generating means including a series connection of a
diode-connected junction type field effect transistor and a
zoner diode, the COOS integrated circuit being operated by
the constant voltage generated across the zoner diode; means
for counting the plurality of pulse signals and for producing
a first signal upon counting the pulse signals up to a number
corresponding to the predetermined delay time; and means
responsive to the first signal for supplying the electrical
energy stored in the first capacitor to the ignition device.
The features and advantages of the invention will be
made apparent by the detailed description taken in conjunction
with the accompanying drawings, in which:
Fig. 1 is a schematic diagram showing a circuit
according to an embodiment of the present invention;
Figs. 2, PA and 3B are diagrams useful for
explaining the embodiment of Fig. 1;
Fig. 4 is a schematic circuit diagram showing
another embodiment of the present invention;
Fig. 5 is a diagram useful for explaining the
embodiment of Fig. 4; and
-- 6 --
kh/jc
~LZ2~.4~
Fig. 6 is a diagram showing a schematic construction
of an electronic delay detonator according to the present
invention.
The present invention will now be explained in
detail with reference to the various embodiments.
Embodiment 1:
A first embodiment of the invention is shown in Fig.
1. A diode bridge 11 includes diodes 12, 13 connected in
series in a forward direction, and diodes 14, 15 also
connected in series in a forward direction, the diode pairs
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1, ... .
J, ,.
1 being connected in parallel to each other. The junction
point of the diodes 12 and -I and the junction point of
the diodes I and are connected to input terminals 16
and 17, respectively, while the junction point of diodes
13 and 15 and the junction point of the diodes 12 and 14
are connected to terminals 18 and 19, respectively. As a
result, even if the connection between terminals 16, 17
and the positive and negative sides of a blasting machine,
respectively, are interchanged, a positive voltage is
always produced at the terminal 18. Also, even when the
terminals 16 and 17 are shorted by an explosion, the
charges of a capacitor 21 for storing electrical energy
connected between the terminals 18 and 19 are prevented
from being released to the terminals 16, 17.
The pulse-like power applied between the input
terminals 16 end 17 is smoothed and stored in the capacitor
21. The terminal 18 is connected to a terminal of a
junction-type field-effect transistor 22 for constant cur-
rent source, the other terminal of which is connected,
together with the gate thereof, to the terminal 19 through
a plan~r-type zoner diode 23 for voltage regulation. In
other words, the transistor 22 is diode-connected. The
constant voltage produced from the junction point of the
transistor 22 and the diode 23 is applied to the supply
terminal of an integrated timer circuit I including an
oscillator 100, a counter 101 and a counter reset circuit
102 made of COOS The oscillator 100 of the timer circuit
24 is connected with a resistor 25 for determining the
1 oscillation frequency and a temperature-compensated go-
remake capacitor 26. Further, a reset capacitor 27 for
preventing a counting error is connected to the reset
terminal of the reset circuit 102 of the timer circuit 24.
This reset terminal is connected to the terminal 18 through
a diode 28 for discharging the charges of the capacitor 27,
in order to expedite the repetition test for delay time
adjustment.
The terminal 18 is connected with the anode of
the thruster 29 which serves as a delay pulse output supply
switch. The cathode of the thruster 29 is connected to
the terminal 19 through a load, that is, an ignition no-
sister 31 of the electronic delay detonator. The gate of
the thruster is connected through a buffer resistor 32
to the output terminal of the timer circuit 24 on the one
hand, and to the terminal 19 through a noise-absorbing
ceramic capacitor 33 on the other hand.
In this configuration, upon application of a
pulse signal to be used as a source of an ignition energy
for the electronic detonator between the terminals 16 and
17 from a blasting machine (not shown) as shown in Fig. PA,
the voltage between the terminals 18 and 19 of the keeps-
ion 21 is smoothed as shown in Fig. 2B, which voltage is
applied, as a constant voltage as shown in Fig. 2C, through
the transistor 22 and diode 23, to the supply terminal of
the timer circuit 24. As a result, the timer circuit is
actuated and begins to oscillate at a period determined
by the time constant of the capacitor 26 connected in
1 series with thy resistor 25.
This waveform of oscillation is, for example,
as shown in Figs. PA and 3B, in which wren the capacity of
the capacitor 26 is large, the period To lengthens as
shown in Fig. PA, while if the capacity of the capacitor
26 is small, the period To is shortened as shown in Fig.
3B. This oscillation signal is counted by the counter 101
in the timer circuit 24, and when the count reaches a
predetermined value, that is, when a set-up time is
0 reached, a set-up signal used for driving the thruster
pr(~d~c~d
29 is p~4d~i6ed from the output terminal of the timer air-
cult 24, so that the thruster 29 is turned on, and the
charges of the capacitor 21 are applied through the Theresa-
ion I in pulse form to the ignition resistor 31 as shown
in Fig. ED. The time I from the application of the pulse
signal forming the energy source of ignition of the elect
ironic detonator to the application of the pulse to the
ignition resistor 31 makes up a delay time.
When the potential charged to the capacitor 26
reaches a threshold potential VT or VT" of an active
switching element in the oscillator 100, the oscillation
is turned on by the charge-discharge of the capacitor I
so that the charges are rapidly released from the keeps-
ion 26. As a result, the active switching element is
turned off again, so that the charging is resumed. This
operation causes continued oscillation, thereby producing
an oscillation waveform as shown in Fig. PA ox Fig. 3B.
In Figs. PA and 3B, VT designates a threshold value
_ 9
I isle,; .
1 obtained when a comparatively large-capacity capacitor is
used as the capacitor 26, and VT" that obtained when a
capacitor of a comparatively small capacitance is used as
the capacitor 26. The charges in the capacitor 26 are not
completely released due to the internal resistance of the
capacitor 26 even at the time of shorting, that is, upon
turning on of the active switching element, and is normally
charged again when the off-threshold value of the active
switching element is reached. US and Us'' in Figs. PA and
3B represent the off-threshold values (potential of reside
vat charges) corresponding to the large-capacity capacitor
26 and the small-capacity capacitor 26, and in this case,
Us'' is smaller than Vs. When the capacity of the keeps-
ion 26 is especially large, the discharge current in-
creases to such a degree that variations of ON-resistance
of the active switching element poses a very great cause
of error. Also, the source voltage-caused drift and the
temperature-caused drift of the threshold voltage of the
active switching element are another cause of an error in
variation of oscillation frequency.
The embodiment under consideration is intended
to realize a stable OR oscillator circuit operating on the
basis of repetition of charge-discharge of the capacitor,
which has so far been considered not very practical due
to many factors of instability. It is conventionally
known that such active switching elements as a bipolar
transistor and a thruster undergo a drift of threshold
potential with temperature or voltage. The OR oscillation,
-- 10 --
I
1 which generally lacks the frequency stability, is not used
in important applications. Nevertheless, the stability
of threshold voltage of the COOS circuit element (couple-
Monterey field-effect transistor) has been remarkably imp
proved as compared with the conventional active devices since the COOS circuit element, with its low power con-
gumption, is such that the P-channel and N-channel field-
effect transistors function in complementary manner, and
especially, the threshold voltages ox the P-channel and
N-channel field-effect transistors have opposite tempera-
lure coefficients to each other. And further, in view of
the field-effect transistor being a voltage-controlled
device, the change of the threshold voltage due to the
change of the source voltage is not dependent upon the
change of resistance of the P- and N-channel Eield-effect
transistors and is fixed almost to one half of the source
voltage, unlike the conventional switch circuits with a
bipolar transistor.
In this embodiment, the timer circuit 24 formed
I of COOS circuit elements with an improved stability as
compared with the above-mentioned active elements is use,
with the result that stable operation is attained over
wide ranges of temperature and input pulse voltage with
high delay lime accuracy.
Also, according to this embodiment, the capacitor
26 is used only to determine the oscillation frequency,
and therefore it is possible to use a small-capacity
capacitor so that the range of capacity selection thereof
-- 11 --
:~26~
.
1 is not limited or the circuit function is not affected by
the variations in ON-resistance of the active switching
element in the oscillator 100. As a result, the delay
time ma be determined accurately over a wide range. The
setting of the delay time may be effected by changing the
values of the capacitor and/or the resistor 26.
For the reason mentioned above, the capacity of
the capacitor 26 is desirably small. If the circuit
portion is sealed with epoxy resin or the like, however,
the floating capacity and the capacity between capacitor
terminals would be greatly affected, thus making it dip-
faculty to determine a constant charqe-discharge oscilla-
lion frequency of the capacitor and resistor.
According to the present invention, the capacity
of the capacitor need not be very small but may be
chosen such that the discharge current from the capacitor
lies within the discharge current range of the active
elements combined therewith, thus permitting the setting
of the delay time over a wide range. In this embodiment,
the capacitance of the capacitor 26 may preferably lie in
the range of about 100 to 1000 pi.
In the present embodiment, the junction-type
field-effect transistor 22 and the zoner diode 23 maze up
a voltage-regulation circuit. On the other hand, a
conventional circuit uses a resistor and a zoner diode,
which has the disadvantage of unstable operation due to
the current change depending upon the applied voltage
there across. In an improvement of this circuit a
:~260~4 .
1 field-effect transistor is used as a constant-current
element. In a combination of a MOW field-effect transit-
ion and a zoner diode, however, the disadvantage of
temperature dependency is not eliminated in spite ox the
advantage of some effect of constant current obtained.
According to the present invention, this short-
coming has been obviated by a combination of a ever diode
and a junction-type field-effect transistor as a voltage-
regulation circuit. Specifically, the gate-source voltage
of a junction-type field effect transistor 22 is set in
an region where the drain current is stable against temper-
azure change and, as a minor constant-current source, a
planer-type zoner diode 23 of about TV comparatively stable
with temperature change is combined, so that the operation
of the timer circuit 24 is stabilized with an improved time
accuracy on the one hand, and the capacity of the capacitor
21 is reduced by employing the drain current of lima or less
for an increased pulse energy on the other hand.
Further, since the COO timer circuit 24 with a
small current consumption is used, the blasting machine
(electrical energy source) need not be specially bulky as
compared with TTL and may be powered by a layer-built dry
cell or the like. Also, the pulse signal to be used as
a power source is used for both power source of the timer
circuit 24 and the ignition energy of the ignition no-
sister 31 without increasing the capacity of the keeps-
ion 21.
- 13 -
1 Embodiment 2:
The ignition of the electric detonator is usual-
lye made instantaneously with electrical pulse energy. The
switch elements such as a thruster are susceptible to
noises of small pulse width generated under transient
conditions.
With reference to Figs. PA and 5B, upon applique-
lion to the electric detonator of a pulse signal maying
up an energy source for ignition of the electric detonator,
a noise is superimposed on the pulse signal as shown in
Fig. PA, for instance, which often causes a number of
noises of small pulse width in the voltage across the
capacitor 21 as shown in Fig. 5B. Therefore, if the gate
ox the thruster 29 is loft open, these pulse noises may
erroneously turn it on, thus erroneously supplying output
energy to the ignition resistor 31.
To eliminate this inconvenience, it is desirable
to short the gate terminal of the thruster 29 with a high-
speed switching element at the time of applying the pulse
signal making up an energy source.
The embodiment shown in Fig. 4 takes this idea
into consideration. Those component elements in Fig. 1
which are similar to those in Fig. 1 designated with
similar numerals are not described again. As shown in
Fig. 4, the base of a high-speed switching transistor 34
is connected with the terminal 18 through an impedance
element 35 such as a capacitor, the collector thereof to
the gate to the thruster 29, and the emitter thereof to
- 14 -
I
s eye
1 the terminal 19. Upon application ox power, the stying
transistor 34 is turned on so that the gate of the Theresa-
a
ion 29 is shorted, and after the lapse of unstable period
of time To (Fig. 5), the transistor 34 is turned off to
place the gate of the thruster 29 in a respective mode.
In this way, stable operation is secured even against the
noises generated by the rapid rise or the like of the
pulse signal. In Fig. 4, a diode 36 is inserted between
the terminal 18 and the junction point of the capacitor
21 and the transistor 22.
According to the present invention, it is
possible to provide a compact, low-cost delay detonator
with stable time accuracy, as compared with the convent
tonal delay detonators with delay powder. If the delay
pulse generator circuit 37 is integrated with the Dayton-
ion, an LSI including an integration of a COOS oscillator
circuit and a frequency-divider circuit or a counter air-
cult may be combined with a chip capacitor, a chip no-
sister, a mini mold transistor, a mini mold thruster, a
mini mold zoner diode and a mini mold field effect tray-
sister to obtain a hybrid configuration, thus making it
possible to contain the circuit devices in a compact body
of the electric detonator which is comparable in size with
the conventional delay detonators widely used.
As the timer circuit 24, M58482P or MYOPIA of
Mitsubishi Electric Corporation or TC5043C of Toshiba
Corporation may be used.
An example in which the delay pulse generator
~226~4LÇgL
1 circuit is incorporated in the electric detonator is shown in Fig. 6. Specifically, a base charge 43 is in-
sorted into a shell 39 with a closed end. The primer
charge 42 contained in the inner capsule 41 is inserted
into the shell 39. After some time interval the pulse
generator 37 with a delay pulse generator circuit such
as shown in Figs. 1 or 4 built therein is inserted into
the shell 39. The ignition resistor 31 made of an
resistor wire is arranged on the initiator or primer charge
42 side of the pulse generator 37, and ignition device
made of an ignition powder 40 is attached to the ignition
resistor 31. Leg wires 38 are led out from the outer end
of the pulse generator 37.
- 16 -
