Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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INTRINSICALLY-SAFE ROOF HAZARD ALERT MODULE
Field of The Invention
The present invention relates generally to an intrinsically-safe warning
device
for providing warning to personnel of an unsafe condition. More specifically,
the
present invention relates to an intrinsically-safe roof hazard warning device
designed
to be attached to the roof of a mine to indicate unsupported roof conditions
or other
unsafe conditions. The device of this invention is especially useful in
underground
mining operations.
Background of the Invention
Underground mines potentially present many hazards to miners and other
workers. Such hazards include, for example, confined spaces, falling rock or
substrate from side walls and roof structures, potentially explosive
atmospheres
(e.g., methane and/or coal dust), heavy equipment, and the like. For example,
during mining operations, roof bolts are used to support and maintain the
stability of
1 S the roof system. Nonetheless, during expansion of such mining areas and
perhaps at
other times, the area beyond the last installed roof bolts or support systems
remains
unsupported and, thus, potentially unstable and hazardous. Miners or other
personnel venturing (unknowingly or otherwise) into such unsupported areas
(i.e.,
beyond the last row of roof bolts) are exposed to hazardous conditions
associated
with the potentially unstable roof structure. Moreover, during cutting into
mine
areas the risk of potentially explosive or hazardous conditions may be
particularly
high since the newly-opened mine shaft may intersect gas pockets or other
concentrated gaseous areas or create high dust levels or may intersect areas
with
particularly weak overburden.
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It would be desirable, therefor, to provide intrinsically-safe warning devices
that render the attendant hazard associated with unsupported roof conditions
or other
hazards more evident. It would also be desirable to provide intrinsically-safe
warning devices which direct a person's attention to read the appropriate
warning
message on the device and, therefore, make the person more likely to comply
with
the warning and avoid the hazard. It would also be desirable to provide
intrinsically-safe warning devices which are inexpensive, self contained,
reliable,
portable, easily installed, easily relocated, and easily removed. Such devices
would
be ideally suited for warning temporary or short-term hazardous conditions.
The
present invention provide such intrinsically safe warning devices. These
devices
represent an engineering intervention strategy especially adapted toward
improving
miners' ability to recognize and avoid the hazardous zone of unsupported mine
roofs.
Summary of the Invention
The present invention relates generally to an intrinsically-safe warning
device for providing warning to personnel of an unsafe condition. More
specifically, the present invention relates to an intrinsically-safe roof
hazard warning
device designed to be attached to the roof of a mine to indicate unsupported
roof
conditions or other unsafe conditions. The device of this invention is
especially
useful in underground mining operations in order to discourage miners from
going
into unsupported mine roof areas by rendering the attendant hazard more
evident,
directing the miner's attention to an appropriate warning message on the
module,
and thus avoiding the hazard beyond the device.
The warning device of this invention is intrinsically-safe, self contained,
simple to use, inexpensive to build and operate, portable, light weight,
compact, and
low-profile. These features make it especially useful as a warning device in
short-
term or temporary hazardous situations where the installation of complex
and/or
bulky warning systems may not be warranted or justified. Since the present
warning device is intrinsically-safe, it can be used in a variety of mining
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environments (including gassy mining environments). By providing an
inexpensive,
readily portable, and easily installed (as well as easily removed) system,
compliance
will likely be significantly improved.
One object of the present invention is to provide an intrinsically-safe hazard
alert module for warning. personnel of a potential hazard, said module
comprising
(a) a case having side walls, a first end wall, and second end wall wherein
the case
has an internal cavity formed by the side walls and first and second end
walls; (b) a
low-voltage power supply within the case comprising one or more direct current
batteries; (c) a switch in electrical contact with the low-voltage power
supply to
activate the module; (d) a light-emitting diode in electrical contact with the
switch
and the low-voltage power supply; and (e) a means to attach the module in
close
proximity to or in a hazard area having a potential hazard such that the light
is
directed towards the area from which personnel are likely to enter the hazard
area;
wherein the module is lightweight, portable, and intrinsically-safe; whereby,
when
the module is activated, the light-emitting diode emits a light to warn
personnel in
the area of the potential hazard and direct their attention to the potential
hazard.
The intrinsically-safe hazard alert module of this invention is especially
adapted for
use in mining applications such as, for example, warning of unsupported roof
structures past the last installed roof bolts. In such case, the modules can
be
directly attached or hung from one or more of the last installed roof bolts to
warn
against entry into the unsupported areas. Once additional roof bolts have been
installed, the old modules (with new batteries if appropriate) or new fully
charged
modules can be moved to the new last installed roof bolts to provide warning
against entry into the new unsupported areas.
These and other features and advantages of the present invention will
become apparent to those skilled in the art upon a reading of the following
detailed
description when taken in conjunction with the drawings wherein there is shown
and described a preferred embodiment of the invention.
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Brief Description of the Drawings
Figure 1 illustrates one embodiment of the intrinsically-safe hazard alert
module showing possible locations for the switch, light, and batteries within
the
case.
Figure 2 illustrates a preferred embodiment of the intrinsically-safe hazard
alert module showing front and side view of the case and a side view of the
cover
plate. This embodiment is especially adapted for use as a roof hazard alert
module
in underground mining operations.
Figure 3 illustrates the assembled intrinsically-safe hazard alert module of
Figure 2 in front and side views.
Figures 4 and 5 illustrate several circuit diagrams suitable for the
intrinsically-safe hazard alert modules of this invention.
Detailed Description of the Preferred Embodiments
The present invention provides an intrinsically-safe warning device for
providing warning to personnel of an unsafe condition. In an especially
preferred
embodiment, the present invention provides an intrinsically-safe roof hazard
warning
device designed to be attached to the roof of a mine to indicate unsupported
roof
conditions or other unsafe conditions. The device of this invention is
especially
useful in underground mining operations or other environments where
potentially
explosive gases and/or dusts may be present.
For purposes of this invention, the term "intrinsically-safe" as applied to
the
module and its electrical circuit is intended to mean that any electrical
sparking
which may occur during normal working conditions is incapable of igniting a
flammable gas or vapor (e.g., 5 to 15 volume percent methane in air). In other
words, to be "intrinsically-safe" a device or circuit must have both
electrical energy
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(e.g., resistance, capacitance, and inductance) and thermal energy at levels
below
that required to ignite a specific hazardous atmosphere (e.g., S to 1 S volume
percent
methane in air). Although the device (and its electric circuit) may be sealed
against
entry of the potentially explosive atmosphere, entry of that atmosphere
through
S failure of the seals, mechanical damage to the device or seals, or the tike
which
allows the potentially explosive atmosphere to contact the electrical circuit
would
not result in ignition. An intrinsically-safe design is distinguished from an
"explosion-proof' design in that, in an explosion-proof device, the
potentially
explosive atmosphere is prevented from contacting the electrical circuit but,
in the
event of some failure of the containment system whereby the potentially
explosive
atmosphere did contact the electrical system, the possibility of ignition
would exist.
Thus, the present intrinsically-safe hazard alert module employs a light-
emitting
diode rather than, for example, an incandescent bulb (which might be suitable
for an
explosion-proof device) since, should the glass portion of such an
incandescent bulb
1 S break, an ignition source (i.e., thermal energy of the filament) would be
present.
The light-emitting diode of the present intrinsically-safe hazard alert
module, even if
broken during operation, would not present such an explosion hazard.
Figure 1 illustrates an intrinsically-safe hazard alert module 10 of the
present
invention. The module 10 has a case with an interior cavity 11 formed by the
side
walls 12 and the first and second end walls (not specifically shown). Located
within the cavity 11 is the low-voltage power supply consisting three 9 V
direct
current batteries 22 in battery holders 20. The on-off switch 16 is located in
a first
recessed portion 1 S of side wall 12. The light-emitting diode 14 is also
located in a
second recessed portion 13 of side wall 12. Preferably the light-emitting
diode 14
2S is of the flashing type. Use of a flashing-type light-emitting diode
increases both
the visibility of the device as well as the battery life. Preferably the light-
emitting
diode 14 flashes at a rate of about 1 to S flashes or pulses per second.
Preferably
the light-emitting diode 14 has a brightly colored lens (e.g., red or caution
yellow)
in order to increase visibility.
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O-rings 18 can be used to seal openings in side wall 12 for the switch 16
and light emitting diode 14. Locating the switch 16 in such. a recess reduces
the
likelihood of accidentally switching off the device as well as providing
additional
protection for the switch. Locating the sight-emitting diode 14 in such a
recess
provides additional protection for the light source. Of course, as one skilled
in the
art will realize, the surfaces of recess 13 could be coated with a light-
reflecting
material to enhance the effect of the light source during operation. Circuit
board 24
can be used to form the circuit between the tow-voltage power source (i.e.,
batteries
22), the switch 16, and the light-emitting diode 14.
Figures 2 and 3 illustrate an intrinsically-safe hazard alert module 10 which
is specifically designed to warn personnel of unsupported roof structures in
an
underground mine. The internal cavity 1 1 is formed in module 10 by the side
walls
12 (Figure 2A), first end wall 28 (i.e., front end wall; Figures 2C and 3B),
and
second end wall 30 (i.e., back end wall; Figures 2B and 3B). The fast end wall
28
and the side walls can be integral (as shown in' Figure 2C) or separate
components.
The second end wall 30 is preferably removable to allow for easy replacement
of
batteries and/or other repair. The removable second end wall 30 can be
attached to
the module 10 via screws 31 (threaded portion not shown) or equivalent
attachment
devices known to the art. It is generally preferred that all openings
(including those
for the switch 16 and the light-emitting diode 14) and the removable second
end
wall 30 be sealed against moisture and dust. Seating can be accomplished using
conventional techniques (e.g., O-rings, pre-formed or formed-in-place gaskets,
and
the like).
The switch 16 is attached to the module 10 through opening 26 in side wall
12. The switch 16 is located in notch 25 to afford protection against
accidental shut
off and/or accidental damage. The light emitting diode 14 is located on the
first
end wall 28. As noted above, the light-emitting diode 14 is preferably of the
flashing type. Use of a flashing-type diode increases both the visibility of
the
device as well as the battery life. Preferably the light-emitting diode 14
flashes at a
rate of about 1 to 5 flashes or pulses per second. Preferably the light-
emitting diode
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14 has a brightly colored lens (e.g., red or caution yellow) in order to
increase
visibility. Located directly.above the light emitting diode 14 and also on the
first
end wall 28 is warning decal 32. Preferably the warning decal 32 is
constructed of
light reflecting material to enhance its visibility. As one of ordinary skill
in the art
will realize, the actual warning on the decal 32 can be. varied depending on
the
intended use (i.e., the hazard for which the warning is to be issued). The
warning
decal 32 in Figure 3A is, of course, specifically for a roof hazard alert
module to
warn miners and other personnel from entering unsupported roof areas.
In operation, the intrinsically-safe roof hazard alert module 10 of Figure 3
(or modules) can be attached, for example, to the last installed roof bolt or
line of
roof bolts (i.e., just before the beginning of the unsupported roof area) via
hook 36
which is attached to the module 10 through clasp or attachment 34. Preferably,
the
hook 36 and clasp 34 can be rotated such that the light-emitting diode can be
directed towards the direction in which personnel will approach the potential
hazard.
I S Of course, other means of attachment could be used. For example, the
module 10
could be attached to a roof bolt via a magnetic device (not shown).
Moreover, the distance from which the module 10 hangs below the roof bolt
could be varied to account for different ceiling heights. For example, in high
coal
seams, module 10 could be extended several feet (or more) from the roof
surface;
whereas in low coal seams, module 10 could be mounted within a few inches (or
even directly on) the roof surface. Indeed, module 10 in Figure 3A could, if
desired
and/or necessary, be mounted with the end wall 28 parallel to the roof surface
to
achieve maximum clearance; of course, in such a case it would be preferred to
modify the placement of the warning decal 32 to make it more visible. In
general,
it is preferred that the module 10 be suspended from the roof at a height
where it
will be easily visible to personnel in the mine while at the same time
allowing for
personnel and equipment to pass underneath the module. For example, it is
generally preferred that the module (and specifically the light-emitting
diode) be
about at or just above eye level so as to be easily visible but high enough so
as not
to significantly impede, for example, placement of additional roof bolts in
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unsupported areas. Indeed, by placing the warning modules at heights which
allows
easy passage of personnel and equipment underneath will encourage leaving the
warning modules in place until additional roof bolts are in place. Once the
additional roof bolts are in place, the module or modules (with new or
recharged
batteries if appropriate) can be placed on or attached to the newly installed
roof
bolts.
As those skilled in the art will realize, the physical dimensions and
materials
of construction of the intrinsically-safe hazard alert modules of the present
invention
are not critical so long as the device can serve its intended purpose.
Nonetheless, it
i 0 is generally preferred that the modules are both portable and lightweight.
Modules
(as illustrated in Figure 3) generally in the range of about 4 to 7 inches
wide, about
3 to 5 inches high, and about 3/4 to 2 inches deep are generally preferably.
Of
course, dimensions larger or smaller may be suitable and even preferred in
some
specific applications. Generally the case or container (i.e., the side walls
12 and
1 S first and second end walls 28 and 30) is a hard and durable material which
can
withstand the rigors of the mining environment; examples of such materials
include,
but are not limited to, high-impact plastics, aluminum, brass, steel, and the
tike.
Generally non-sparking aluminum alloys and brass are preferred due to their
light
weight, strength, and non-sparking characteristics.
20 Electrical circuits suitable for use in the intrinsically-safe hazard alert
modules of the present invention are shown in Figures 4 and 5. Except for
portions
of the switch 16 and warning light 14, all electrical components are located
within
cavity 11. Figure 4 employs two batteries 38 (E1 and E2) in parallel; Figure 5
employs three batteries 38 (E1, E2, and E3) in parallel. In both cases, the
batteries
25 38 are in electrical contact with switch 16 (SWI) via rectifiers 42 (CR1
through
CR4 in Figure 4 and CR1 through CR6 in Figure 5), resistor 46 {R1), and fuse
40
{FI). Rectifiers 42, resistor 46, and fuse 40 are preferably located on
printed circuit
board (PCB) 44. The flashing light-emitting diode 14 (PL1)1is located between
the
switch 16 and the opposite terminal of the batteries 38. Rectifiers 42 are
used to
30 limit current flow in one direction, thereby preventing blown light-
emitting diodes
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in case the batteries are inserted incorrectly. Generally it is preferred that
two
rectifiers 42 be inserted in line with each battery to provide added
protection.
Again, the specific selection of the electrical components is not critical so
long as
the selected components can perform their intended functions.
The batteries can be either non-rechargeable (i.e., disposable) or
rechargeable. Disposable batteries are generally preferred. Generally the
batteries
are in the range of about 2 to 10 volts dc. Generally 9 volt do alkaline (PP3
can
type) disposable batteries are preferred. Switch 16 is preferably an on-off
toggle
type (e.g., model AlOIMYZQ from Augat/Alcoswitch). Fuse 40 is preferably a
fast
acting, low-amperage, subminiature type normally rated at about 1/10 to about
1/4
amperes (e.g., model 251.125 from Littlefuse rated at 1/8 amperes). Any
suitable
rectifiers 42 can be used {e.g., lA, 400 volt silicon rectifiers model 1N4004
from
Motorola). As noted above, the rectifiers are preferably used in pairs with
each
battery in the low-voltage power supply to provide redundancy. Any suitable
light-
emitting diode can be used for the warning light 14. Preferably the warning
light is
a flasher-type (operating at about 1 to 5 pulses per second) to provide
superior
warning capabilities. Preferably the warning light also has a brightly colored
lens
or covering for increased visibility. One preferred indicator or warning light
is a
red flasher type (about 1.5 to about 2.5 pulses per second) light-emitting
diode,
model 5 I OOH 1 FL from Industrial Devices, Inc. The resistor 46 is used to
limit the
current through the rectifiers 42 to the proper range (generally about 0.75
amperes
or less) in the advent of a simultaneous failure of the light-emitting diode
14 and
the fuse 40..
Although the modules illustrated herein generally contain only one warning
light, one of ordinary skill in the art will realize that more than one such
warning
light could be mounted on the same or a different surface of the module if
desired.
For example, the module illustrate in Figure 3A could, if desired, have more
than
one light-emitting diode on end wall 28. Likewise, additional light-emitting
diodes
could be placed on end wall 20 or on various locations on side wall 12 to
increase
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the visibility of the device. Likewise, warning decals similar to decal 32
could be
placed on other module surfaces if desired.
Although the present intrinsically-safe hazard alert module has been
described largely in terms of its use in underground mining applications,
especially
in unsupported roof applications, those of ordinary skill in the art will
readily
realize that the present invention can be used in many other situations and
environments. The present invention is, of course, especially useful in
potentially
hazardous atmospheres such as mining, chemical processing facilities, nuclear
power
plants, dusty areas (metal grinding areas, grain elevators and silos), and the
like.
The following example is provided to illustrate the invention and not to limit
the invention.
Example. Several intrinsically safe roof hazard alert modules were prepared
in accordance with the present specification. Generally, these modules were
constructed similar to the device illustrated in Figures 2 and 3 using the
circuit
diagrams illustrated in Figures 4 and 5. One module (about 5.25 x 5.25 x 1.25
inches) constructed with a non-sparking aluminum case was fitted with three 9
volt
do disposable alkaline batteries (corresponding to the circuit diagram in
Figure 5).
The non-sparking aluminum was Aluminum Alloy 6061 (low magnesium (about 0.8
to 1.2 weight percent; ASTM B209-86) A flasher-type red light-emitting diode
(model SIOOH1FL from Industrial Devices, Inc.) with a flash rate of about 1.5
to
2.5 flashes per second was used. The module was Ftted with a hook (as shown in
Figure 3 for attachment to a roof bolt. Total weight was about 1.1 pounds. A
second module (about 5.25 x 3.25 x 1.25 inches) was constructed in a similar
manner except it was fitted with only two 9 volt do disposable alkaline
batteries
23 (corresponding to the circuit diagram in Figure 4) and with a magnetic-type
. attachment mechanism. Using the same flasher-type red light-emitting diode,
it
weighed about 1.5 pounds. Both units provided good visibility and warning
characteristics. The three-battery model had an estimated battery life of
about 487
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hours (about 121 shifts at 4 hours per shift); the two-battery model had an
estimated
battery life of about 360 hours (about 90 shifts at 4 hours per shift)
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