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Патент USA US3037464

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June 5, 1962
M, A, (300K ETAL
Filed July_l3, 1959
2 Sheets-Sheet 1
wqnue T
40L‘ p.111» KM.» ATTORNEYS
, June 5, 1962
M. A. cooK ETAL
Filed July 15, 1959
2 Sheets-Sheet 2
MEL VIA/A. (‘00K
001/6248 Fl-PACK
I Blyééyz?jk ,fwa
Patented June 5, 19%2
(RDX-TNT-wax) and Ednatol (EDNA-TNT). The
more inexpensive of these explosives are not detonatable
by Primacord, however.
Melvin A. Cook and Douglas H. Pack, Salt Lake City,
Utah, assignors to Intermountain Research and Engi
neering Company, Inc., §alt Lake City, Utah, a corpo
ration of Utah
It has been found that PETN, PETN-TNT mixtures,
RDX and cyclotol are detonated by Pn'macord, but their
high cost and the relatively large quantities required make
it uneconomical to use them as boosters.
Filed July 13, 1959, Ser. No. 826,539
3 Claims. (Cl. 102—24)
The improved booster of the invention gene-rally com
prises a core of Pn'macord-sensitive explosive material
surrounded by a compacted sheath of Primacord-insensi
This invention relates to detonating means for ex
plosives and more particularly to boosters for relatively
tive explosive material of high brisance, said booster
insensitive explosive compositions.
having at least one perforation extending through said
sheath and said core adapted to receive a detonating fuse,
Insensitive explosives, containing a high percentage of
ammonium nitrate and containing non-explosive organic
said core comprising a tube containing Primacord-sen
sitive explosive adjacent to and de?ning at least a portion
sensitizers, have found wide application as blasting ex
plosives. Prilled ammonium nitrate containing 94 per 15 or" the perimeter of said perforation.
One embodiment of the invention is such a booster
cent ammonium nitrate and 6 percent fuel oil and aque
wherein said Primacord-sensitive explosive is pentaeryth
ous slurries of coarse TNT-ammonium nitrate are exam
ritol tetranitrate contained within said tube and wherein
ples of such insensitive explosives. Such compositions
said Primacord-insensitive explosive is cast TNT. A fur
are not detonatable by blasting caps and prior art meth
ods for detonating them include the use of dynamite or
ther embodiment is such a booster wherein said Prima
relatively large quantities of ?ne-grained TNT primers,
cord-sensitive explosive is pentaerythritol tetranitrate con
tained within said tube ‘and said Primacord-insensitive
explosive is a cast mixture of 725 percent by weight of
for example, which are detonated by blasting caps or
Pn'macord. These methods suffer from the disadvantage
of being expensive and further, dynamites, ?ne TNT and
blasting caps are very sensitive to heat and shock.
TNT and 75 percent by weight of composition B.
A preferred form comprises such a booster wherein
In modern large diameter blasting operations using
two perforations are provided and wherein the core com
high ammonium nitrate explosives, Primacord fuse is
prises a tube in a ?gure 8 con?guration containing Prima
the most desirable detonator. The high ammonium ni
trate explosives are not dependably detonatable by Prima
cord, however, and require a booster. Unfortunately,
booster wherein the tube containing Primacordsensitive
explosive is wound in helical fashion adjacent to and de
only a few of the most sensitive explosives are consistent
ly capable ‘of detonation by Primacord containing the
minimum content of PETN, e.g., about 50 grains of
PETN per foot of Primacord.
Of those boosters that
are operable, relatively large quantities of expensive
boostering compositions are required consistently to
booster the ammonium nitrate explosive.
Accordingly, it is an object of the present invention to
provide a booster for insensitive explosives which is con
sistently detonatable by minimum PETN content Prima
It is another object of the invention to provide such a
booster which consistently detonates high ‘ammonium ni
cord-sensitive explosive adjacent the perimeters of said
An alternative embodiment is such a
?ning the perimeter of said perforation.
The method of the invention generally comprises sup
porting a rod, placing a tube containing Primacord-sensi
35 tive explosive contiguous to said rod, compacting a sheath
of Primacord-insensitive explosive about said rod and
tube, and removing said rod from said compacted sheath
to provide a perforation through the sheath adapted to
receive a detonating fuse. A preferred method involves
casting the sheath about the rod and tube.
The tube of
Primacord-sensitive material may be helically wrapped
about the rod, or if two rods are provided, the tube may
be wound in ?gure 8 fashion about said rods.
FIGURE 1 is a view of the tube of Primacord-sensi
trate explosives in either the wet or dry state.
tive explosive positioned on a pair of rods prior to com
A further object of the invention is to provide such a
pacting the sheath of Primacord-insensitive explosive
booster which is inexpensive and utilizes a minimum of
about it.
the expensive Primacord-sensitive materials.
Among the other objects of the invention, one is to
provide a protected core booster in which Primacord is
FIGURE 2 illustrates the casting of Primacord-insen
sitive explosive about the tube according to the invention.
readily and simply threaded for use in blasting opera
Another object of the invention is to provide a booster
FIGURE 3 is a view of a ?nished booster made in ac
making boosters.
FIGURE ‘6 is a cross-sectional view of a booster pre
cordance with the invention.
FIGURE 4 is a cross-sectional view of the booster of
which is much less sensitive to heat, shock, impact, fric
tion and other in?uences causing accidental initiation 55 FIGURE 5 is a view of the tube of Primacord-sensitive
explosive wound helically on a rod prior to compacting
than prior art boosters.
a sheath ‘of Primaoord-insensitive explosive about it.
Another object is to provide improved methods for
pared in accordance with the method illustrated in FIG
Other objects and advantages will be apparent to those
URE 5.
skilled in the art.
The booster as shown in FIGURES 3 and 4 comprises
We have now found that the most important factor
a compact sheath 10 of Primacord-insensitive explosive.
Within the sheath 10 is a tube 11 containing Primacord
sensitive explosives is its detonation pressure or brisance.
sensitive explosive 12 adjacent to the perforations 13.
The term “'brisance” connotes shattering action which is
the embodiment shown, two holes 13 extend through
dependent on the detonation pressure. In the hydrody 65 the booster for receiving Primacord detonating ‘fuse and
namic theory of detonation, the detonation pressure is
the tube 11 is disposed in ?gure 8 con?guration with re
proportional to the density of the explosive and the square
spect ‘to the holes 11.
of the detonation velocity.
While the assembly may assume any desired shape, it
Examples of explosives of high brisance are cast or
is preferred to use the cylindrical form shown for econ
pressed pentolite (PETN-TNT), TNT, tetryl, tetrytol
omy of material and ease of manufacture. It is preferred
(tetryl-TNT), cyclotol (RDX-TNT), composition B
to employ two holes 13 to loop the Primacord fuse
in a booster with respect to its boostering activity on in- '
through, although the boosters of the invention are de
ers were formed in the same manner by casting 25%
pendably detonated by Primacord passing through only
TNT, 75% composition B.
one hole. Accordingly, the booster may have only one
hole with the tube 11 disposed in helical ‘fashion about
the periphery of the hole. In a further modi?cation, two
with 50 grain PETN/foot Primacord threaded through
one only of the holes. All forty of such boosters ?red,
The boosters were then fired
giving a detonation percentage of 100%.
As indicated above, Primacord itself may be used as
holes may be used and the tube helically disposed about
the tube containing the Primacord-sensitive explosive.
each hole.
In a series of tests, we have found that boosters made
As shown in FIGURES 1 and 2, a base 14 is provided
from 6 inch to one foot lengths of 50 grain PETN/foot
with a pair of upstanding pins or rods 15. The tube .11
is wound about the rods 15, the winding being in figure 10 Primacord wound in ?gure 8 fashion contained within a
sheath of 350 grams of cast 75% composition B, 25%
8 form, although helical winding of the tube about the
TNT according to the invention yield 100% detonations
rods may also be used. A form ‘16 of metal or card
with a 50 grain PETN/foot Primacord strand running
board is placed over the wound rods and molten Prima
through one hole only. Such boosters cut a clean hole
cord~insensitive explosive 17 is poured into the form from
through a one inch thick, 6 x 6 inch steel plate.
spout 16. After the assembly has hardened, it is re
moved from the base 14 to yield a booster as shown in
Similarly, we have found that one foot lengths of 200
FIGURE 3 having two perforations extending there
grain PETN/foot and 400‘ grain PETN/foot Primacord
wound in a ?gure 8 core yield 100% detonations when
cast 100% TNT is used as the sheath. As a control, cast
cylinders of 100% composition B without a core failed
FIGURES 5 and 6‘ illustrate a booster contain
ing a single perforation wherein the tube of Primacord
sensitive material is positioned in a helical fashion about
the perforation. Such a booster is suitably prepared by
winding the tube of Primacord-sensitive material helical
ly about a rod 15 and thereafter ?lling the mold 16 with
molten Primacord-insensitive explosive. FIGURE 6 il—
lustrates a cross-section of such a booster, the body 10
being cast Primacord-insensitive explosive, the Prima
cord-sensitive explosive 12 being contained within the
helically wound tube 19 disposed about the perforation 22.
to yield 100% detonation with 50 grain PETN/foot Pri
macord threaded through both holes.
While it is not intended to be bound by any theory of
operation, it is believed that the tube 11 of Primacord
sensitive explosives, adjacent and peripheral ‘to the per
forations, yield detonation waves that interact and rein
force each other to produce a high intensity shock eifect,
thereby detonating the main booster charge 10 which is
otherwise not detonatable by Primacord.
Forms 16 made of cardboard or paper are satisfactory
and it has been found unnecessary to remove the form
from the booster in such cases.
is threaded through one or more of the holes 13 and
An alternative method of compacting the explosive
about the core comprises pressing particulate explosive
knotted to prevent the removal of the booster from the
fuse. The booster may be inserted in a priming cartridge
in the form to yield a compact shaped booster.
The tube 11 may be made of plastic such as polyethyl
of ammonium nitrate explosive or preferably lowered by
itself into the bore hole by suspending it on the Prima
cord line at the appropriate position in the hole. The
ene, vinyl chloride, vinylidene chloride, polyethylene ter
ephthalate or any of the synthetic rubbers or it may be
In use, a Primacord fuse, such as 50 grain PETN/foot,
main charge is then introduced simply by pouring the
loose or slurry explosive into the hole. The Primacord
of cellulosic material such as regenerated cellulose, cel
lulose acetate or cellulose nitrate. Additionally, Prima
cord itself, which contains ?ne grained PETN, may be
used as the tube containing Primacord-sensitive explosive.
The Primacord-sensitive explosive 12 contained within
the tube is preferably ?ne-grained material and may be
accordance with the invention. Cast boosters are pre
ferred because they do not crumble upon wetting or sub
jecting to rough handling. Cast boosters are also less
PETN, RDX, amatol, tetryl and ?ne-grained TNT. The
latter is Primacordsensitive whereas coarse or cast TNT
fuse is initiated electrically as is well known in the art.
Either cast or pressed boosters may be prepared in
We have thus described novel boosters which are con
is Primacordinsensitive. If fine-grained TNT is used in 45 sistently operative for boostering ammonium nitrate ex
plosives which employ a minimum of expensive materials
the tube and the sheath is cast TNT, ‘a sufficiently heavy
and which are consistently detonatable by 50 grain Prima
walled tube must be used to insulate the TNT within the
cord. While the invention has been described in terms of
tube from the heat of the molten TNT which is cast to
certain embodiments, these are to be considered illustra
form the sheath.
The Primacord-insensitive explosive forming the sheath 50 tive rather than limiting and it is intended to cover all
further embodiments that fall within the spirit and scope
10 may be cast or pressed TNT, composition'B (59%
of the appended claims.
RDX—40% TNT—1% wax) or composition B-TNT mix
The above possess high brisance but are not con
sistently detonatable by Primacord containing 50 grains
We claim:
1. A booster for detonating insensitive blasting charges
55 comprising a core of Primacord-sensitive explosive ma
of PETN per foot.
It has been found that cylindrical boosters about three
inches in diameter and two inches long provided with
two holes made in accordance with the invention con
sistently detonate the insensitive ammonium nitrate ex
terial surrounded by a compacted cylindrical sheath of
Primacord-insensitive explosive material of high brisance,
said booster having ‘two perforations extending through
said sheath and said coreadapted to receive a detonating
plosives. Such boosters contain about 300-400 grams 60 fuse, said core comprising a tube in a ?gure 8 con?gura
tion containing Primacord-sensitive explosive adjacent the
of Primacord-insensitive explosive. The tube 11 contain
ing the Primacord-sensitive explosive '12 may contain
about 5 to 10 grams of PETN or its equivalent.
For the
internal surfaces of said perforations.
2. A booster for detonating insensitive blasting charges
comprising a core of Prim-acord-sensitive explosive ma
least sensitive explosives in the sheath 10, more Prima
cord-sensitive explosive should be used to achieve high 65 terial surrounded by a compacted sheath of Primacord
insensitive explosive material of high brisance, said boost
order detonations. For example, forty boosters were
er having at least one perforation extending through
prepared in accordance with the invention, utilizing one
said sheath and said core adapted to receive a detonating
foot lengths of 0.263 inch internal diameter 0.020 inch
fuse, said core comprising a tube containing Primacord
thick (wall thickness plastic tubes containing about 10
grams of PETN each). Twenty of such tubes were 70 sensitive explosive wound in helical fashion adjacent to
and defining the internal surface of said perforation.
wound about the rods 15 in ?gure 8 fashion as shown in
3. A booster for detonating insensitive blasting charges
FIGURE 1 and twenty were wound helically on the rods
Ten of each of the groups were then formed into
comprising a core of pentaerythritol tetranitrate sur
rounded by a compacted cylindrical sheath of trinitro
boosters by casting. a cylinder 3 inches in diameter by 2
inches high from 100% TNT. Ten of each of the boost 75 toluene, said booster having two perforations extending
axially ‘through said sheath and said core adapted to re
ceive a detonating fuse, said core comprising a tube in
a ?gure 8 con?guration containing about 10 grams of
pentaerythritol tetranitrate adjacent the internal surfaces
of said pezforations, said sheath containing about 350 6
2, 617,326
grams of ltrinitrotoluene.
References Cited in the ?le of this patent
Weber ______________ __ Jan. 19, 1923 10
Snelling ______________ __ Dec. 13, 1927
2,9 1 3,982
Moms ______________ __ Nov. 11,
Hagensen ____________ .._ June 29,
Gunther _______________ __ Aug. 3,
Lowe _______________ __ May 31,
Hayes ______________ __ Nov. 24,
Ely et a1. ____________ __ July 12,
Germany ____________ __ Sept. 11, 19013
Germany _____________ __ Feb. 9, 19'37
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