U.S. patent number 3,791,297 [Application Number 05/310,887] was granted by the patent office on 1974-02-12 for explosive package.
This patent grant is currently assigned to Canadian Industries, Limited. Invention is credited to James Glen McKee.
United States Patent |
3,791,297 |
McKee |
February 12, 1974 |
EXPLOSIVE PACKAGE
Abstract
A thermoplastic film package containing a blasting explosive is
provided having particular utility in secondary blasting
operations. The package is especially suitable for aqueous slurry
blasting agents which are filled through a self-closing valved
opening. The package is also provided in the form of a train of
detachably connected side-by-side packages.
Inventors: |
McKee; James Glen (Chateauguay,
Quebec, CA) |
Assignee: |
Canadian Industries, Limited
(Montreal, Quebec, CA)
|
Family
ID: |
4091789 |
Appl.
No.: |
05/310,887 |
Filed: |
November 30, 1972 |
Foreign Application Priority Data
Current U.S.
Class: |
102/317;
102/324 |
Current CPC
Class: |
F42B
3/00 (20130101); F42B 3/087 (20130101) |
Current International
Class: |
F42B
3/087 (20060101); F42B 3/00 (20060101); F42b
003/00 () |
Field of
Search: |
;102/24R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Pendegrass; Verlin R.
Attorney, Agent or Firm: Ballantyne; Donald G.
Claims
What we claim is:
1. A blasting explosive package suitable for use in secondary
blasting comprising a rectangular valve bag made from heat-sealable
thermoplastic film and consisting of a back wall and a front wall,
each made of two-ply panels partially overlapping each other, the
said front and back panels being joined along their entire
periphery, said panels in their common area of overlap being sealed
together in such a manner as to form a tubular dual-valved
self-closing opening extending transversely of the bag, said
self-closing opening being of such a diameter as to allow the
insertion therein of a filling spout, and a blasting explosive
composition contained in said rectangular valve bag.
2. An explosive package as claimed in claim 1 wherein the
thermoplastic film is polyethylene film.
3. An explosive package as claimed in claim 1 wherein the blasting
explosive comprises an ammonium nitrate/fuel oil explosive.
4. An explosive package as claimed in claim 1 wherein the blasting
explosive comprises an aqueous slurry explosive.
5. Explosive packages as claimed in claim 1 detachably connected
together in side-by-side relationship.
Description
This invention relates to a novel explosive package. More
particularly, the invention relates to an improved package for
explosives used in secondary blasting.
In secondary blasting, explosives are employed for the purpose of
breaking up large pieces of rock in open pit operations or for the
dislodgement of rock projections in underground workings and the
like. Generally, in secondary blasting, an explosive charge is
simply placed on the surface of the rock, jammed into a rock
crevice or held against the rock by means of props or poles and
thereafter detonated. In quarry operations, for example, a very
large number of secondary blasts may be required to fragment
boulders for subsequent crushing. Economy and convenience,
therefore, are the principal requisites of any explosive used in
secondary blasting.
In the past, it has been customary to prepare secondary blasting
charges from one or several cartridges of conventional dynamite or
to employ dynamite compositions packaged in small bags. This method
is frequently both costly and inconvenient since charges of this
type do not lend themselves to easy placement on or in the rock. It
has been suggested by J.M.E. Romocki et al. in U.S. Pat. No.
3,534,685, granted on Oct. 20, 1970, to employ for secondary
blasting charges a pulverized ammonium nitrate/fuel oil (AN/FO)
blasting agent contained within a plastic bag, the bag being
especially adapted for simplified priming. While this proposal goes
far towards economizing secondary blasting operations, it has not
solved all of the problems associated therewith. There remains a
need for a yet further improved explosive package for secondary
blasting, which package combines economy of production and use with
safety, convenience and explosive effectiveness.
It is the object of the present invention to provide an improved
explosive package suitable for use in secondary blasting.
It is a further object of the invention to provide a series of
detachably connected explosive packages suitable for use in
secondary explosive blasting.
Other objects of the invention will become apparent
hereinafter.
The improved explosive package of the invention comprises a
bag-like container of thermoplastic film and a blasting explosive
composition contained within said container, said container being
heat-sealed along at least two of its edges and having a valved
filling opening for the introduction of blasting explosive
therein.
The invention may be more fully understood by reference to the
accompanying drawing wherein like numerals indicate like parts and
wherein
FIG. 1 shows a view of a preferred embodiment of a package made in
accordance with the present invention;
FIG. 2 shows a view of the package of FIG. 1 taken along line A--A
thereof;
FIG. 3 shows an alternative form of package; and
FIG. 4 shows a train of the packages of FIG. 1 detachably connected
together.
Referring to FIGS. 1 and 2 of the drawing, there is shown a valve
bag 1 containing an explosive composition. Bag 1 which is of the
general pillowcase type has a back wall 2 and a front wall made of
partially overlapping panels 3 and 4. Panels 3 and 4 are shown as
integral with back wall 2 and thus form with the latter a length of
tube which is closed at both ends by transverse seams 5 and 6.
Except for a limited portion 7 extending transversely of the bag,
panels 3 and 4 are united to each other in their common area of
overlap by seams 8 and 9 extending from transverse seals 5 and 6
respectively to said portion 7. The portion 7 left unsealed in the
common area of overlap between panels 3 and 4 constitutes a tubular
valve opening suitable for insertion into the bag of filling spout
10. When the bag is filled with an explosive mixture, the edge of
panel 3 acts as a valve which closes upon pressure exerted by the
explosive mixture and prevents egress of the latter through the
unsealed portion 7.
The alternative form of the invention illustrated in FIG. 3 shows a
package generally similar to that of FIG. 1 and 2 with the
exception that it comprises a bag having two ply walls. The back
wall 2 is comprised of plies 2A and 2B and the panels 3 and 4 of
the front wall are comprised of plies 3A and 3B and plies 4A and 4B
respectively. Panel 3 which, in the area of overlap with panel 4 is
located inwardly of the bag with respect to said panel 4, is
characterized in that the free edge of its inner ply 3A projects
somewhat beyond the free edge of its outer ply 3B. Except for the
above differences, the bag which the package of FIG. 3 is made of
is similar to that shown in FIGS. 1 and 2. In the package
construction of FIG. 3, the edges of plies 3A and 3B act as dual
valves which close the unsealed portion 7 upon pressure of the
explosive mixture contained in the bag.
FIG. 4 shows a series or train of explosive-filled bags such as
illustrated in FIGS. 1 and 2 or FIG. 3, interconnected by webs 11
of the film material which the bags are made of. Webs 11 have
perforations 12 therein to aid in detaching one package from the
adjacent one when desired.
While AN/FO explosives may be used in the explosive package of the
invention, the preferred explosive for use is an aqueous slurry
mixture comprising a thickened mixture of oxidizer salts and fuels
dispersed in an aqueous solution of the salts. Such a composition
is economic to manufacture and safe to use and is ideally suited to
the aforedescribed container since it results in a package which is
kneadable and which can be wedged into rock fissures or conformed
to rock irregularities. Slurry explosives may also be packaged in
the described container by simple extrusion methods thus to provide
a package of high density. The resultant package resembles somewhat
a small pillow.
The thermoplastic film employed in the container preferably has a
thickness of about 4 mils and double-ply film of 2 mils in each ply
has been used to manufacture superior packages. Double ply
containers exhibit improved tear resistance over single ply
containers. A number of flexible plastic materials combining high
tensile and tear strength are known which may be used in the
construction of the container and which will suggest themselves to
those skilled in the art. A preferred material of construction is
polyethylene having a wall thickness of from about 2 to about 8
mils.
A shown in FIG. 3, the explosive package of the invention may be
provided in a detachable train form. Such a configuration permits
the blaster to choose one, two or more packages as may suit the
needs of the blasting to be undertaken. The connected packages for
multiple use can be simply pleated together in accordion fashion to
provide larger charges. Single containers may be simply detached by
tearing along the perforated or weakened connecting web.
It will be obvious to those skilled in the art that a number of so
called "valved" containers may be suitably employed in the
explosive package of this invention; the principal requirements for
such a container being economy, ease of filling, durability and,
especially, satisfactory retention of the explosive contents. While
the valve container described herein has been shown to be excellent
for the purpose intended, other similar known containers could
doubtlessly be adapted for the purpose. A container of the type
herein described is more fully disclosed by P. T. Jennings et al.
in Canadian Pat. No. 709,244, granted on May 11, 1965.
In use in the field at the blasting site for secondary blasting,
the blaster will prepare an initiation means, for example, a loop
of detonating cord or a detonating cap and fuse or a small primer
charge and place it in contact with the outside wall of the
explosive package. The choice of initiator will depend on the
sensitivity of the secondary blasting explosive used. Such an
initiator may be secured in place by, for example, an adhesive tape
strip. The thus assembled charge is then placed on the rock or
obstruction to be blasted and the charge initiated. Generally,
charges for secondary blasting will range from about 1 to 20 pounds
or more in weight.
The following Example illustrates the improved explosive package of
the invention but it is in no manner to be limited to the
embodiment described.
EXAMPLE
In an underground gold mine at a 3,100 foot level draw point, a
series of 12 secondary blasts were fired using 1 lb. and 21/2 lb.
explosive packages of the invention where a TNT-containing aqueous
ammonium nitrate slurry comprised the explosive composition. Each
explosive package was primed by means of a wrap of a 25 grains/foot
detonating cord and strategically placed against the boulder or the
"hang-up" rock projection to be blasted. The detonating cord
primers were initiated by means of blasting caps and safety fuse.
Excellent fragmentation was obtained on all boulders and hang-ups.
It was noted by mine personnel that the priming and placing of the
packages were simple and speedy and provided excellent contact with
the rock. Because of the nature of the explosive used, the period
required for smoke clearance after blasting was much reduced as
compared to conventional dynamite or AN/FO explosives formerly used
in secondary blasting.
* * * * *