Note: Descriptions are shown in the official language in which they were submitted.
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BLASTING AIR TUBE WITH SLEEVE, AND METHOD
TITLE OF THE INVENTION
[0001] Title: Blasting Air Tube With Sleeve, and Method
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
[0002] An inflatable air tube includes a sleeve member arranged concentrically
about
the upper end portion of the air tube to define a receptacle chamber for
receiving a
quantity of bulk explosive blasting powder, thereby to add weight to the air
tube for
positioning and stabilizing the same in the bulk explosive powder during the
depositing of the powder into a blasting hole drilled into the ground. A
plurality of
accurate blasting patterns may be provided in the blasting powder column by
timing
the manual or mechanical insertion of the air tubes into the bulk blasting
powder
relative to the rate of supply of the powder from a source thereof.
DESCRIPTION OF RELATED ART
[0003] In the prior art air tube construction disclosed in the Robert
Australian patent
No. AU 2004200940 required tedious loading requirements. Briefly, these
requirements include loading layers of explosives, then installing the air
tubes, then
loading explosives around the air tube and then another layer of explosives
and so on.
These steps were necessary due to the light weight and buoyancy of the air
filled tube.
Even when these loading steps were followed, the tube would move from its
installed
position when the explosives layer was loaded on and around it. Random and
imprecise positioning was the result.
[0004] The improved design of the present invention was developed to provide
an air
tube having a sleeved top which facilitates automatic weighting of the air
tube when it
is inserted into the discharge of bulk explosives (by auger or pump) into the
borehole
(drill hole). Because of the added weight, the need for the tedious loading
steps is
eliminated and the loading time of a blast hole is substantially decreased
from the ease
of the resulting process. This new process incorporates the loading of the
explosives
and the air tubes at the same time. As the explosives are being loaded into
the blast
hole the air tube with sleeve is placed in the stream (discharge) of bulk
explosives.
The bulk explosives are caught in the cup cavity or chamber created at the top
of the
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air tube by the sleeve; the now weighted air tube is displaced downwardly in a
stabilized manner into the blast hole and is embedded in the explosive column
at the
precise predetermined location. Multiple air tubes can be installed by
following the
same process in series.
100051 Since the axial air-gaps from the sleeved air tubes are to be consumed
in the
detonation and the reduction of explosives in precise vertical areas are the
focus, the
requirement of special precautions to ensure concentric or horizontal aligned
is not of
specific consequence to the blast result. In fact in certain instances the air
gaps
created from the sleeved air tubes may overlap to maintain the desired
explosive
reduction.
[00061 The previous design resulted in inaccurate positioning of the air tubes
in a
column of explosives. With the improved design, near exact placement of the
air tube
can be achieved. The result of accurate placement has yielded expanded
applications
of the product and the axial air-gapping technique. Previously the predominant
application for axial air-gapping was for overall explosive reduction and
ultimately
cost savings. With the improved accuracy of placement from the sleeved air
tube,
specific tasks can be accomplished, resulting from an exact reduction of
explosives in
certain parts of the explosive charge colurnn. The axial air gapping creates a
core of
air within the column of blasting agent that is consumed in the detonation.
Standard
air-gapping separates the column into multiple charges that are interrupted by
the air-
gapping device.
[0007) The Kang U.S. patents Nos. 6,330,860 and 6,631,684 discloses the use of
a
similar air tube, but for a distinctly different purpose. In the first Kang
patent, air
tubes, having the same diameter or slightly smaller than the blast hole, are
used to
create a gap, separating the blasting agent column. This separation creates a
"medium
for sympathetic detonation" within the blast hole between the separated
charges.
Conversely, the air tubes of the present invention are a part of, and a
consumable in,
the blasting agent column and are consumed in the detonation. As a general
rule, the
diameter of the new air tube is equal to or less than 60% of the diameter of
the blast
hole. For example, an eight (8) inch blast hole would utilize an air tube that
would be
approx. 4.8" in diameter (8.0" x .6). The Kang patent has further constraints
in regard
to the length of an air tube. The air tube of the present invention overcomes
this
limitation.
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100081 Furthermore, the aforementioned Kang patent contains fairly complicated
calculations to determine the length of the air tube. These calculations and
resulting
lengths are used to ensure the occurrence of sympathetic detonation. Depending
upon
the diameter of the blast hole, if the length of the Kang tube is too long the
occurrence
of sympathetic detonation will not propagate from one charge to the next. Our
improvement is not limited by the confines of sympathetic detonation. The air
tube of
the present invention generally promotes a standard four foot length in any
size hole
for user convenience; however, any length that does not exceed the length of
the
blasting agent column will still work and will be consumed with the detonation
of the
blasting agent column.
[0009] For a better understanding of the Kang technique, the definition of
sympathetic detonation / propagation is "The detonation of an explosive
material as
the result of receiving an impulse from another detonation through air, earth
or
water." This definition comes from Explosives and Rock Blasting (copyright
1987)
by the Atlas Powder Company.
100101 In the second Kang patent, the diameter sizes of the air tubes are
reduced for
ease of installation into the blast hole. In this change, the sympathetic
detonation
technique and the relating equations and size limitations still exist.
Applicant's
distinction is maintained in its consumable air tube against the Kang medium
for
sympathetic detonation.
SUMMARY OF THE INVENTION
[0011] According to a primary object of the present invention, an inflatable
air tube is
provided including a sleeve member arranged concentrically about the upper end
portion of the air tube to define a receptacle chamber for receiving a
quantity of bulk
explosive blasting powder, thereby to add weight to the air tube for
positioning and
stabilizing the same in the bulk explosive powder during the depositing of the
powder
into a blasting hole drilled into the ground.
[00121 According to a further object of the invention, a method is provided
for
achieving a plurality of accurate blasting patterns in the blasting powder
column
formed in a blasting hole by timing the manual or mechanical insertion of the
air
tubes into the bulk blasting powder being deposited into the blasting hole
relative to
the rate of supply of the powder from a source thereof.
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100131 The air tube initially has a compressed un-inflated flat condition
defining in
the intermediate portion of the tube between the ends thereof a pair of side
walls. The
sleeve member is also flattened and extends concentrically about the upper end
of the
compressed air tube, with the sleeve secured to at least one of the side
walls, whereby
upon inflation of the air tube, the sleeve cooperates with the dome-shaped end
portion
of the air tube to define a receptacle chamber for receiving the bulk
explosive blasting
powder. Owing to the initial compressed state of the air tube and sleeve
member
assembly, the sleeved air tube may be easily transported and stored with a
minimal
amount of space.
BRIEF DESCRIPTION OF THE DRAWINGS
100141 Other objects and advantages of the invention will become apparent from
a
study of the following specification, when viewed in the light of the
accompanying
drawing, in which:
Fig. I is a partly sectioned view of the improved air tube of the present
invention when in the initial collapsed condition, and Fig. 2 is a sectional
view taken
along line 2 - 2 of Fig. 1;
Fig. 3 is a partly sectioned view of the air tube of Fig. 1 when in the
inflated
condition, and Fig. 4 is a sectional view taken along line 4 - 4 of Fig. 3;
Fig. 5 is a sectional view taken along line 5 - 5 of Fig. 1, and Fig. 6 is a
sectional view taken along line 6 - 6 of Fig. 3;
Fig. 7 is a diagrammatic sectional view illustrating the method for
introducing
the weighted air tubes into the blast hole together with the flow of the
explosive
blasting powder; and
Figs. 8 - 12 illustrate various selective patterns of arrangement of the air
tubes
in the blast hole.
DETAILED DESCRIPTION OF THE INVENTION
100151 Referring first more particularly to Figs. I and 2, the air tube 2 is
illustrated in
the collapsed flat condition and includes an upper end portion 2a, a
vertically arranged
intermediate portion 2b, and a lower end portion 2c. Prior to the introduction
of air
into the chamber 6 defined between the parallel air tube side walls 2d and 2e,
the
upper and lower ends of the air tube have a generally arch-shaped
configuration. As
shown in Fig. 1. In accordance with a characterizing feature of the present
invention,
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a tubular sleeve member 8 is arranged concentrically about the air tube upper
end
portion 2a, which sleeve in the collapsed condition of Figs. I and 2 is flat
and is
secured to the air tube side wall 2e by a fastening strip 10, such a heat seal
seam, an
adhesive strip, an adhesive layer between the sleeve member and the air tube,
or the
like. Preferably the upper edge 8a of the sleeve member is even with the
adjacent
edge of the arch-shaped end portion 2a, as shown in Fig. 1. The air tube and
the
sleeve are each formed from a durable flexible synthetic plastic material.
[0016] When air is introduced into chamber 6 via the air valve stem 12, the
air tube is
expanded to the inflated condition of Figs. 3 and 4, and the air valve stem is
closed to
maintain the air tube in the inflated condition. The upper end portion 2a of
the air
tube now has a generally dome-shaped configuration, and the sleeve 8 is
expanded
toward its tubular configuration and cooperates with the outer surface of the
air tube
end portion 2a to define a receptacle chamber 14. The lower inner periphery of
the
sleeve member is in contiguous tight engagement with the outer surface of the
air
tube, thereby to seal the bottom of the receptacle chamber 14.
[00171 Referring now to Fig. 7, as is conventional in the art, bulk explosive
blasting
powder 20 is supplied from a source 22 by variable-speed auger or pump means
24 or
the like and is deposited by gravity into the blasting or bore hole 26 that
has been
drilled into the ground 28. At a given time during the supply of the blasting
powder,
an inflated air tube is manually or mechanically inserted into the flow of
blasting
powder to cause the receptacle chamber 14 defined by the sleeve 8 to be filled
with
the blasting powder, thereby to add weight to the air tube and to reduce the
floating
thereof within the blasting powder flow. The inflated and weighted air tube is
then
introduced into the blasting hole 26 together with the blasting powder flow.
Additional inflated air tubes may be similarly weighted by insertion within
the
blasting powder flow 20 for introduction in a predetermined timed sequence
into the
blasting hole 26.
100181 In practice, blasting agent is delivered to the drill pattern (blast
holes) by a
"bulk truck". This truck has bins for storage of blasting agent. The blasting
agent is
augered from the bins through a discharge tube or auger arm and into the blast
hole.
Rates of discharge vary greatly from truck to truck. A typical range of 100 to
1000
pounds of blasting agent discharged (loaded) per minute exists.
[0019] According to applicant's invention, precise placement of the air tube
can be
achieved through the weighted sleeve. To accomplish exact placement, discharge
per
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minute, by the bulk truck and blast hole loading rate must be considered. The
loading
rate of a blast hole is determined by the hole diameter and the density of the
blasting
agent. Blasting agents range in density from .82g/cc to 1.32g/cc. The most
widely
used is ANFO at a density of .87g/cc. Using ANFO as an example in an 8" blast
hole
the loading rate would be determined as follows:
Hole diameter x hole diameter x .3402 x product density = loading rate in
pounds/foot
8 x 8 x .3402 x .87 = 18.9 pounds per foot
[00201 Knowing the loading rate of 18.9 pounds per foot and assuming a truck
discharge rate of 200 pounds per minute, it can be determined that 10.6 feet
of
blasting agent column will be loaded into the blast hole in one minute.
Pounds per minute - divided by - Pounds per foot = feet loaded per minute 200
/ 18.9 = 10.6 feet loaded per minute
Using this same example, if an air tube is designed to be at 15 feet intervals
throughout a blast hole then each air tube would be installed at a rate of
every 90
seconds.
[0021] Referring to Fig. 8, it will be seen that three inflated weighted air
tubes 2 have
been introduce in vertically staggered relation within the explosive blasting
powder
20 that is introduced into the blasting hole 26 that extends downwardly toward
the
coal seam 30 contained in the ground 28. Conventional stemming materia132,
such
as a layer of dirt, closes the upper end of the blasting hole. In this
application, a
solution is provided for meeting the concern of many blasting operations that
the
damage to the coal or ore seam that is being mined from the blasting of the
rock or
overburden to be removed above the seams. For this application, with the
precise
placement of the sleeved air tubes, an exact reduction of explosives can be
reduced in
the specific area of the explosive charge. Reducing the explosive charge near
the
seam to be mined and recovered will reduce the damage to this seam.
[0022) Referring to Fig. 9, when material is blasted for excavation, the
perimeter
around the blasted and excavated area remains as a wal136 (commonly referred
to as
a"highwall"). Because other mining functions take place beneath this wall,
reducing
the damage to this undisturbed area is a concern for the safety of those
operations.
Generally a blast is designed with a target powder factor (a relationship of
pounds of
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explosives to yards of material to be blasted) that will achieve a desired
blast result.
In many cases this designed powder factor will over shoot or damage the
resulting
wall.
[0023] A reduction of the explosives in the perimeter (outside) blast holes
will reduce
the damage to this wall. With the accurate placement of the sleeved air tubes
2 in the
blasting powder 20, the exact reduction precisely in the area of the wall that
is subject
to damage can be achieved. Overall reductions between 15% to 25% of the
explosive
charge reduce the damage to perimeter walls.
100241 According to a further advantage of the invention, improved
fragmentation
may be achieved through a raised stem height. Referring to Fig. 10, An
explosive
charge 20 in a blast hole 26 must be confined by filling the top portion of
the blast
hole with an inert materia132 such as gravel or drill cutting produced from
drilling the
blast hole (commonly referred to as "stemming"). This confinement helps direct
the
explosive force to fracture the bank of material to be blasted instead of the
energy
being released out the top of the hole. However, in some cases the amount of
needed
material for adequate confinement also creates a considerable amount of poorly
blasted material throughout the area of inert material. With the use of the
sleeved air
tubes 2, explosives can be reduced in the top of the explosive column reducing
the
amount of needed inert confining material and consequently improving the
result of
blasted material.
[0025] In the blasting procedure shown in Fig. 11, the advantage is obtained
of
correct loading through weak areas 40 of overburden. Banks of material to be
blasted
generally are made up of various type of material. In some case there is a
great
variance in the types of material. In instances where the variances create
weak or soft
areas that require considerably less explosives than the remaining bank,
substantially
reducing the explosives used in this area is desirable. Utilizing the sleeved
air tubes 2
with the ability of precise placement, a pre-determined amount of explosive 20
can be
reduced in the weak areas of the bank being blasted. The remaining areas 42 of
the
bank can receive the full load as designed.
100261 Referring now to Fig. 12, a further advantage of the present invention
is the
ability to achieve greater explosive reduction for control blasting. Control
Blasting
refers to situations were rock must be blasted but movement of the blasted
material
must be limited. In these cases a significantly reduced amount of explosives
must be
distributed throughout the rock to be blasted. The precise placement of the
sleeved air
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tubes 2 can accomplish this task. Because of the large amount of reduction
necessary
to accomplish this, sleeved air tubes may overlap in the blast hole.
[0027] According to a further advantage, the sleeved air tubes may be use in
horizontal blasting; which is generally utilized underground with smaller
diameter
holes. When bulk explosives are used it is necessary to blow or pump the
explosives
into the horizontal blast hole. The sleeved air tube allows for the bulk
explosive to
catch and force the air tube into the horizontal blast hole and embed in
place. The
previous air tube had no means of conveyance in this type of loading.
100281 As distinguished from the prior art devices which required time
consuming
loading functions and, even if the steps were closely followed the vertical
position of
the air tube was not completely assured, the improvement of the sleeved top,
for the
purpose of weighting the air tube, in order to embed the air tube in precise
vertical
location within an explosive loaded blast hole, has resulted in the axial air
gap
technique being applied to numerous situations that the prior devices could
not easily
accommodate.
(0029] While in accordance with the provisions of the Patent Statutes the
preferred
forms and embodiments of the invention have been illustrated and described, it
will be
apparent to those skilled in the art that changes may be made without
deviating from
the invention described above.
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