Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
BLASTING INITIATED CONTROL SYSTEM
This invention relates to a blasting initiated
control system and, more particularly to a blasting
initiated mine ventilation control system.
After blasting, it is customary for the miners to
wait for a few hours before going back to the mining
location in order to allow normal ventilation to remove
dust from the ambient air. There has been a long need for
shortening this waiting period. However, this would
require opening of various mine doors and energization of
special blowers at a distance from the mining location and
thus the running of a special ventilation control cable
throughout the mine.
The installation of such a cable is expensive and
has not been justified up to now. It haæ also been thought
of using the existing blasting cable for initiating
ventilation at a predetermined time interval a~ter
blasting. However, this has never been done because of the
danger of accidentally energizing the blasting cable from
the ventilation system in case of maloperation of the
~entilation system.
It is therefore the object of the present
invention to provide a safe control system for operating
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the ventilation equipment from the blasting cable.
The blasting initiated control system, in
accordance with the invention, comprises an optical
interface transmitter adapted for connection to a blasting
cable, an optical interface receiver, a fiber optic link
interconnecting the transmitter to the receiver for
transmitting a light beam from the transmitter to the
receiver upon energization of the blasting cable, a ~irst
timing circuit responsive to the receiver for initiating a
certain function at a first predetermined time interval
after energization of the blasting cable, and a second
timing circuit responsive to the receiver for restoring
the above mentioned function after a second predetermined
time interval.
The first timing circuit preferably comprises a
first timer set to time out after such first predetermined
time interval, an auxiliary timer responsive to the first
timer to momentarily generate an output pulse upon timing
out o~ the first timer and a first relay responsive to the
auxiliary timer to momentarily initiate the above
mentioned function.
The second timing circuit preferably comprises a
second timer set to time out after such second
predetermined time interval, a second auxiliary timer
responsive to the second timer to momentarily generate an
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output s$gnal upon timing out on the second timer and a
second relay responsive to the second auxi~iary timer to
momentarily restore the abovs mentioned function and also
inhibit operation of the first and second circuits.
The control system further comprises a control
circuit including a third relay responsive to a manual
switch for enabling the first and second timing circuits
and responsive to the second relay for restoring the
control system to a stand-by mode. A manual switch may
also be provided for operating the third relay to restore
the control system to a stand-by mode.
The invention will now be disclosed, by way of
example, with reference to the accompanying drawings in
which:
Figure 1 is a block diagram of the control system
in accordance with the invention;
Figure 2 ls a timing diagram of the control
system,
Figure 3 is an embodiment of a circuit diagram of
the control system in accordance with the present
invention.
Referring to Figure 1, there is shown an optical
interface transmitter 10 adapted for connection to a
blasting cable. Upon application of the blasting signal,
the optical interface transmitter generates a light beam
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which propagates down a fiber optic link 12 to an optical
interface receiver 14. The optical interface receiver 14
provides a triggering signal for the time delay control
section of the system which includes an "Initiate" timer
16 identified as timer No. 1 and a "Re~tore" timer 18
identified as timer No. 2. Timers No. 1 and No. 2 are
triggered simultaneously on the rising edge of the
blasting signal as illustrated in the timing diagram shown
in Figure 2 of the drawings. Timer No. 1 triggers an
auxiliary timer 20 identi~ied as auxiliary timer No. 1
which provides a short pulse which momentarily energizes
an output relay 22 identified as output relay No. 1 in the
timing diagram of Figure 2. Timer No. 2 similarly triggers
an auxiliary timer 24 identified as auxiliary timer No. 2
which provides a short pulse which momentarily energizes
an output relay 26 identified as output relay No. 2 in the
timing diagram of Figure 2.
Timers No. 1 and No. 2 may be any suitable
conventional timers operated in the E mode, such as Models
H3CA sold by OMRON, which are provided with pushbuttons on
their control panels which may be set by selecting up to
three digits and a multiplying factor. A range of 0.1
second to 9990 hours is availablo on such timers. The same
type of timers operated in the H mode may be used as
auxiliary timers No. 1 and No~ 2. The auxiliary timers are
preset to provide a one second pulse which simulates the
momentary action of the existing pullcord operated door
switches. The pulse widths of the auxiliary timers can be
lengthened or shortened, as required, by appropriate
selection of their panel settings.
The contacts of output relays 22 and 24 interface
with external circuitry (not shown) and may be used for
initiating predetermined functions such as operation of
blowers and doors after a first predetermined interval
and restoring such functions after a second predetermined
time interval.
The block diagram of Figure 1 also shows an
enable/disable control device 28. This device provides an
"enable" signal to timers No~ 1 and No.-2 upon operation
o~ an enable pushbutton 30. Such signal is shown in the
timing diagram of Figure 2. The manual "enable" signal
allows the blasting cable signal to trigger the timers.
The enable/disable control device is normally disabled by
the operation of relay No. 2. ~oweYer, the control device
may be manually disabled by operating pushbutton 32.
Figure 3 shows an embodiment of a circuit diagram
of the control system in accordance with the present
invention wherein elements corresponding to those hown in
Figure 1 are identified by the same reference characters.
The optical interface transmitter 10 comprises a power
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supply connected to a conventional fiber optic
transmitker. The power supply comprises a trans~ormer T
for stepping down the 220VAC of the blasting cable to
12VAC. The output of the transformer is rectified by diode
D1 and smoothened by capacitors Cl and C2, resi~tor Rl and
Zener diode Zl. The output of the power supply circuit
is appliad to the input terminals of the fiber optic
transmitter through resistor R2. The fiber optic
transmitter may be any suitable fiber optic transmitter
capable of generating a light beam on a fiber optic link
upon appearance of a signal at the input thereof. An
example of such transmitter is HP1510 made by Hewlett
Packard. The light beam transmitt~d over the fiber optic
link is received by a suitable receiver, such as Model
HP2501 also made by Hewlett Packard. The receiver includes
a transistor Ql which is biased into conduction when
photoconductor R3 connected in the biaising circuit of the
trans~stor is illuminated by the light beam transmitted
over the fiber optic link. The output voltage provided by
trans~stor Q1 is applied to the start terminals of timers
No. 1 and No. 2 o~ the Time Delay Control Section of the
system.
The Time Delay Control Section of the system is
energized from a llOVAc source which iB applied to Timers
No. 1 and No. 2 and to a 12VDC and a 5VDc power supply.
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When the power switrh on the Time Delay Control Section of
the system is switched ON, 110V is supplied through
normally closed contacts RY3 1 of a relay winding RY3 to a
panel light labelled STBY indicating that the system in
the Stanby mode. However, triggering of timer~ No. 1 and
No. 2 is inhibited until relay RY3, which controls the
application of common ground to timers No. 1 and No. 2, is
energized. Relay RY3 is energized by depressing ena~le
pushbutton 30. Energization of relay RY3 closes contacts
RY3-1 to energize a panel light labelled READY indicating
that tha system is in the Ready mode and closes normally
open contacts RY3-2 to trigger timers No. 1 and No. 2.
Relay RY3 locks itself operated through its own normally
open contacts RY3-3. When timer No. 1 has timed out, its
outpu~ contacts 16-1 close to trigger auxiliaxy timer No.
1. Auxiliary timer No. 1 momentarily closes its output
contacts 20-1 for about one second or so depending on its
setting to energize a relay winding KYl, which momentarily
closes its normally open contacts RYl-1 to initiata a
function such as energization of a fan, closing of a door,
etc.
When timer No. 2 ha~ timed out, its output
contacts 18-1 close to trigger auxiliary timer No. 2.
Auxiliary timer No. 2 momentarily closes its output
contacts 24-1 to energize a relay winding RY2 which
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momentarily closes its normally open contacts to restore
the operation previously performed by relay RYl. In
addition, relay RY2 opens normally closed contacts RY2-2
in the energization circuit of relay RY3 to automatically
reset the system to a Stanby mode and also in~ibit the
triggering of timers No. 1 and No. 2 until the Enable
pushbutton is depre~ed again.
Although the invention has been disclo~ed with
reference to a preferred embodimenk, it i5 to be
understood it is not limited to such embodiment and that
other alternatives are also envisaged within the scope of
the following claims.
