Note: Descriptions are shown in the official language in which they were submitted.
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FLEXIBLE DUCT SYSTEM
Field of the Invention
This invention relates to flexible ducting. In particular, this invention
relates to flexible ventilation ducting such as that used in the mining
industry, in
which duct sections are joined together to provide fresh air into a mine and
to remove
gases from within the mine.
Background of the Invention
For decades, underground mines around the world have been using
flexible ducting in lay-flat and spiral reinforced configurations (typically
having
diameters from 6 inches to over 120 inches), which are attached to high-
pressure fans
to provide ventilation within the mine. As mine headings advance, sections of
duct,
typically consisting of lengths from 25 feet to over 50 feet, are added to
maintain air
delivery to the working face of the heading. This is necessary to provide
fresh air to
miners working at these locations and to remove noxious gases generated by
blasting
and mining equipment.
Prior art flexible duct systems include ducts in which adjacent sections of
ducting are connected to one another by clips or other similar attachment
devices that
are not permanently attached to the ducting. The clips used on prior art duct
systems
often fall off at fan start up or during blasting, or may be knocked off by
passing
equipment. Often such fallen clips become lost in the muck pile. Accordingly,
the
clips used in prior art duct systems frequently have to be replaced.
The clips used on prior art duct systems can also tear and otherwise
damage the duct material during installation and removal of the duct system.
The
significant manpower costs incurred when installing and removing prior art
ducting is
thus exacerbated by costs associated with repairs and system maintenance.
Further, the joints between adjacent sections of prior art ducting are sealed
by connectors, clamps or other sealing devices in an attempt to minimize joint
leakage. Often vent clips such as "mufti-clips" or connecting couplers are
used. These
are separate clips which must be attached to both adjoining duct sections at
the rime
of installation, which is time consuming. Typical installation errors
associated with
such prior art duct systems include incorrectly installing the clips,
installing clips at
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the wrong location about the end of a duct section, installing too few clips
to
adequately connect adjacent duet sections, or incorrectly putting the ducting
end rings
together. Such errors result in leakage between adjacent duct sections, and
occasionally failure of the duct under the high pressure of the ventilation
fari.
The use of mufti-clips also often results in bunching of the duct tubing at
the joints. Such bunching increases air resistance within the tubing, thus
placing more
energy demands on the ventilation fan.
Also, with conventional duct ventilation systems, the ducting is suspended
by suspending clips colloquially known as "paper clips," which are bent or
coiled
pieces of wire that attach to a messenger cable or screen that runs along the
tunnel and
suspends the assembled ducting. A problem with such clips is that during
installation,
the installer must lift the ducting up to the messenger cable or screen and
then twist
the ducting to clip it on to the messenger cable. This is very time consuming.
Moreover, when removing the ducting, the suspending clips are difficult to
undo and
often the operator may just rip down the ducting and therefore tear the duct
wall,
rendering it in need of repair or useless. Also, such suspending clips are not
as sturdy
as is desirable in a mining environment.
Summary of the Invention
The present invention addresses the above-mentioned problems of the
prior art flexible ducting systems.
The present invention provides a bell-and-spigot arrangement, whereby a
spigot end of one duct section is inserted into a bell end of a next adjacent
duct
section, such that when the duct is inflated the spigot expands against the
bell to form
a substantially air-tight seal.
In the preferred embodiment of the invention, the sections of ducting are
connected together by clips that are permanently attached to one section of
ducting, so
joining together or separating lengths of mine ducting takes significantly
less time
than in prior art flexible duct systems. The invention thus facilitates
quicker duct
installation and removal. The present invention also facilitates correct and
effective
connections, the correct number and position of the clips being pre-determined
since
the clips are pre-attached to the ducting. The operator need only snap
adjoining
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sections of ducting together. Moreover, the present invention eliminates the
need to
purchase separate clips which are hard to install correctly and to remove.
Accordingly, the manpower costs involved in the installation, removal, repair,
and
maintenance of the duct system of the present invention are significantly
reduced.
The duct system of the present invention is easy to assemble in a deflated
condition, and then readily inflate when air is passed through the ducting.
The present invention also reduces energy costs by reducing air pressure
loss arising from joint leakage. When a,ir is pumped into the initially
deflated sections
of ducting, the spigot (outlet) end of the duct section expands fully into the
bell (inlet)
end of the next adjacent duct section, creating a substantially air-tight
seal. The
upstream duct section remains preferably about 4 to 6 inches inside the end
ring of the
next adjacent downstream duct section, effectively providing a substantially
leak
proof joint system. Thus, leakage arising from incomplete duct section seals
and
installation errors associated with prior art duct systems are eliminated.
1 S The present invention also eliminates the bunching of duct tubing at the
joints. Accordingly, joint restriction is eliminated and air resistance is
minimized,
resulting in fan energy savings. Thus, with the duct system of the present
invention,
shorter lengths of ducting (for example, 25 feet) can be used on long
development
runs without the air pressure loss normally associated with the resistance
imparted by
multiple joints and the joint leakage associated with each joint. One
advantage to
using shorter lengths of duct sections is the ability to keep the end of the
duct closer to
the face as the work crew advances.
Another advantage to utilizing shorter lengths of duct sections is that a
shorter duct section damaged by equipment or blasting is cheaper to replace,
so a
large tear from blasting or equipment does not result in the loss occasioned
by a
longer, more expensive length of duct section.
The present invention is interchangeable with other duct systems presently
being used in mines. No transitions or adapters are required. Mines can thus
phase out
the old mufti-clip system gradually, since the present invention can be
connected to
conventional duct sections with standard mufti-clips, while downstream where
duct
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sections of the present invention are utilized the duct sections can be
connected
together according to the invention.
The present invention also provides a rapid attachment system for
suspending the duct from a messenger cable or screen. Each duct section may be
provided with at least one tuck or extension of wall material extending from
an
external surface of the duct wall, by which the duct is suspended by
suspending clips.
The present invention thus provides a flexible ventilation ducting system
comprising at least two flexible duct sections for connection in a bell-and-
spigot
configuration, each having an open spigot end and an open bell end in
communication
therewith, a plurality of first fastening members attached about an exterior
of each
duct section near the spigot end, and a plurality of second fastening members
attached
about an interior of each duct section near the bell end, wherein when the
spigot end
of one duct section is inserted into the bell end of another duct section and
the first
and second fastening means are engaged, air blown through the duct causes the
spigot
end to expand within the bell end to create a substantially air-tight seal
between the
duct sections.
Brief Description of the Drawings
In drawings which illustrate by way of example only preferred
embodiments of the invention,
Figures 1 a, 1 b, and 1 c are schematic drawings views showing the
progressive addition of duct sections to bring fresh air to work crews as the
mine
heading advances.
Figure 2 is an elevational exploded view showing the manner of engaging
the bell end of one flexible duct section to the spigot end of the next
adjacent flexible
duct section.
Figures 3A and 3B are respectively elevational views of standard and
heavy-duty SWS clips for attaching adjacent duct sections.
Figure 4 is an elevational view of the clip of Figure 3A attached to the
outlet end of a duct section.
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Figures SA and SB are respectively elevational views of standard and
heavy-duty "D" Rings fox attaching adjacent duct sections.
Figures 6A to 6D are respectively elevational views of various
embodiments of SWS clips which can be used with the system of the invention.
Figures 7A to 7C are respectively schematic views showing preferred
locations of clips along the circumference of small round, large round and
oval
ducting.
Figure 8 is an elevational view of the extension of duct material extending
from the external surface from a section of flexible duct tubing.
Figure 9 is a perspective view of ducting suspended on a messenger cable.
Figure 10 is a perspective view of round reinforced ducting with a
suspending clip attached to a grommet tuck.
Figure 11 is a perspective view of oval ducting with suspending clips
attached to multiple grommet tucks.
Figure 12 is a perspective view of spiral oval ducting with suspending
clips attached to multiple grommet tucks.
Detailed Description of the Invention
A preferred embodiment of the invention is shown in Figures l and 2. The
ducting system according to the invention comprises flexible duct sections 12,
which
connect in the manner described in detail below. The duct 10, as used in a
mine, is
attached to one or more high-pressure fans to provide ventilation into the
mine. The
duct 10 may vary in diameter and length, and duct sections 12 are added as
needed to
progress deeper into the mine and maintain proximity with the working face of
the
heading 2. For example, Figures 1 a, 1 b, and 1 c illustrate how the addition
of duct
tubing brings fresh air to work crews as the heading 2 advances. Figure 1 c
illustrates
the duct 10 suspended from one or more messenger cables running along the top
of a
mining tunnel, as is conventional.
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The flexible duct sections 12 can be provided in varying configurations,
including round and oval. The duct sections 12 can also be provided in lay-
flat type in
which there is no reinforcement for the duct wall and thus the deflated duct
section 12
can be laid flat when deflated; and a spiral reinforced type in which the duct
section
12 is maintained in a substantially open condition by a reinforcing wire
helically
circumscribing the interior of the duct section 12. The duct section 12 may be
composed of any suitable material, including polyvinyl chloride or woven
polyolefin
fabric flexible sheeting, as is well-known in the art.
As illustrated i.n Figure' l, the present invention comprises a plurality of
duct sections 12, each having a spigot end 14 (which in order to reduce
airflow
resistance is advantageously the outlet end of the duct section 12) and a bell
end 15
(which for the same reason is advantageously the inlet end of the duct section
12).
Thus, in the preferred embodiment air enters the duct section 12 at the bell
end 32 and
exits the duct section at the spigot end 14. For ease of reference for the
operator,
either or both ends of a duct section 12 may be marked, for example by a tag.
The
circumference of the spigot end 14 is slightly smaller than the circumference
of the
bell end 32 so that the spigot end 14 may pass through the bell end 32 and
enter the
lumen of the adjacent duct section 12b.
In the present invention, each duct section 12 is provided with a plurality
of first fasteners 16 that are attached about the exterior surface proximate
to the spigot
end 14 of the duct tubing member 12. In one embodiment the first fastening
member
16 is a clip of the type shown in Figure 6, which illustrates various versions
of clips
16 by way of example only. Within the interior of the same duct section 12,
but
proximate to the bell end 32, are attached a plurality of second fastening
member 34.
In one embodiment the second fastening member 34 is a "D" ring, as shown in
Figure
7, which illustrates different versions of the "D" ring by way of example
only. At both
the bell end 32 and spigot end 14 is an end ring 20 that provides structural
support to
the end of the duct section 12.
Figure 2 illustrates how, according to the present invention, adjacent duct
sections 12a and 12b are secured to one another to create a substantially air-
tight seal
between the spigot end 14 of a first section 12a and the inlet end 32 of a
second
section 12b. The spigot end 14 of the first section 12a is inserted into the
lumen of the
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second section 12b at the bell end 32 of the second section 12b, and each
first
fastening member 16 is attached to the corresponding second fastening member
34 at
the bell end 32. The adjacent duct sections 12a and 12b are thus releasably
attached to
one another. When air is passed through the duct 10 under pressure, for
example, by a
high pressure fan 4, both of the duct sections 12a, 12b expand. As a result,
the exterior
surface of the spigot end 14 of the upstream duct section 12a is forced
against the
interior surface of the downstream duct section 12b, preferably with an
overlap of
about 4 to 6 inches. This method of attachment is repeated by connecting
additional
duct sections 12 as described above, as needed.
The first fastening members 16 are preferably permanently attached to the
spigot end 14 of the duct section 12. One means of attaching the first
fastening
members 16 is illustrated by way of example in Figure 3, wherein a strap 18
such as 1
inch polyvinyl chloride webbing about 5 inches long, or any other suitable
material, is
attached, for example sewn, onto the exterior surface of the duct section 12.
This
secures the fastening member 16 to the duct section 12.
Where the connection between the upstream duct section 12a and the
downstream duct section 12b requires additional strength, the strap 18 may be
reinforced by doubling, as shown for example in Figure 3B, and/or increasing
the
length of strap 18, to thus increase the surface area of the strap 18 which is
available
to be sewn onto the duct section 12. Additional strength may also be obtained
by
utilizing a stronger fastening member 16. In one embodiment, the fastening
member
16 is made of steel, or another suitably strong material. Variations of the
first
fastening member 16, shown by way of example only, are illustrated in Figures
6A to
6D.
The second fastening member 34 is also preferably permanently attached
to the duct section 12. In the oval duct configuration, this helps to align
successive
duct sections 12. One example of means for attaching the second fastening
member
34 is illustrated in Figure SA. A strap 36, similar to the strap 18 for the
first fastening
member 16, or any other suitable material, is attached, for example sewn, onto
the
interior surface of the duct section 12 to secure the attachment means 34.
Again,
where the connection between the first duct section 12a and the second duct
section
12b requires additional strength, the strap member 36 may be reinforced by
adding a
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second strap 34, as shown for example in Figure SB, and/or increasing the
length of
the strap member 36, to thus increase the surface area of the second strap
member 36
which can be sewn on to the duct section 12. Additional strength may also be
obtained by utilizing a stronger fastener 34. In one embodiment, the second
fastener is
a "D" ring made of steel or another suitable material, or the "D" ring may be
larger.
A sufficient number of the first and second fastening members 16, 34 is
required to hold the adjacent duct sections 12a and 12b together. This number
will
vary depending on such factors as the diameter, type and configuration of the
duct
sections 12. For example, for round lay-flat and spiral reinforced ducts, the
following
number of pairs of fastening members 16, 34 is recommended:
12 inch diameter to 29 inch diameter - 4 pairs
30 inch diameter to 41 inch diameter - 5 pairs
42 inch diameter to 53 inch diameter - 6 pairs
54 inch diameter to 60 inch diameter - 8 pairs
61 inch diameter and greater -10 or more pairs
For oval lay-flat and for oval spiral reinforced duct tubing with diameters
of 60 inches or less, it should be sufficient to utilize between 6 and 12
pairs of
fastening members 16, 34. Examples are shown in Figures 7A to 7C. In general,
the
fastening members 16, 34 should be evenly spaced about the duct sections 12.
The present invention also provides a rapid attachment system for
suspending the duct 10 from a messenger cable 58 or screen (not shown). As
illustrated in Figure 8, each duct section 12 may be provided with at least
one tuck 50
of wall material extending from the external surface of the duct section 12,
commonly
known as "grommet tuck." In oval duct tubing 42 inches and more in diameter,
two
grommet tucks 50 are preferably used to support the larger width of the
ducting 10
and to keep it stable when suspended, as shown in Figure 11.
One or more eyelets 52 along the tuck 50 receives attachment clips 54, for
example "S" clips, each of which in turn secures a suspending clip 56; for
example
similar to the first fastening members 16. The suspending clips 56 in turn
clip to the
messenger cable 58 and suspend the duct 10 from the cable 58 as shown in
Figures 3,
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4 and 5. In another embodiment (not shown), the eyelets 52 in the tuck 50 can
receive
the suspending clips 56 directly.
The rapid attachment system described herein may be used to suspend the
various configurations of duct sections 12, including round lay-flat
configurations,
oval lay-flat configurations, round spiral reinforced co~gurations, and oval
spiral
reinforced configurations. Unlike traditional 'paper clips,' the suspending
clips 56
surround and lock to the messenger cable 58. Accordingly, a duct 10 suspended
by
suspending clips 56 is less likely to become detached from the messenger cable
58
due to blasts other dislodging forces that are encountered in a mining
environment.
Preferred embodiments of the invention having been thus described by
way of example, it will be apparent to those skilled in the art that certain
modifications and adaptations may be made without departing from the scope of
the
invention, as set out in the appended claims.
