Note: Descriptions are shown in the official language in which they were submitted.
132~913
BACKGROUND OF T~E INVENTION
Field Qf ~ Inve~ion
This inventi4n relates to boosters employed to detonate
explosive materials, such as are u~ed in mining,
construction, and seismic aativity, and ~ore specifically,
to explosive booster~ that effect optimally efficient
detonation of such explosive materials. The present
i~vention has particular applicability to the cast primer
type of explosive booster.
Brief ~esc~iption of the Drawings
In order that the manner in which the advantages and
objects of the invention described herein are obtained, a
more particular description of the invention will be
rendered by reference to specific e~bodiments thereof which
are illustrated in the appended drawings. Understanding
that these drawings depict only typical e~bodiments of the
invention and are therefore not to be considered limiting of
its scope, the invention will ~
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l be described with additional speciEicity and detail through
2 use of the following drawings in which:
3 Fig. 1 is a cross-sectional diagram of a borehole for
4 explosives illustrating a typical arrangement of the
, components used to detonate an explosion therein;
fi Fig. 2A is a cross-sectional perspective view of one
_ example of a known explosive booster;
8 Fig. 2B is a cross-sectional perspective view of a
9 second embodiment of a known explosive booster;
Fig. 2C is a cross-sectional perspective view of a
ll third embodiment of a known explosive booster;
12 Fig. 3A is a velocity trace produced in an explosion
detonated by an explosive booster such as that shown in
-14 Fig. 2A;
Is Fig. 3B is a second velocity trace produced in an
16 explosion detonated by an explosive booster such as that
I_ shown in Fig. 2A;
18 Fig. 3C is a third velocity trace produced in an
19 explosion detonated by an explosive booster such as that
shown in Fig. 2A;
1 Fig. 4A is a velocity trace produced in an explosion
detonated by an explosive booster such as that shown in
23 Fig. 2B;
'7~ Fig. 4B is a velocity trace produced in an explosion
2.; detonated by an explosive booster such as that shown in
7(, Fig. 2C;
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Fig. 5 is a cross-sectional perspective view of a
, preferred embodiment of an explosive booster shaped
:~ according to the teachings of the present invention for high
4 efficiency detonating and arranged with other elements or
s detonating an explosion;
6 Fig. 6A is a velocity trace produced in an explosion
7 detonated by an explosive booster such as that shown in
8 Fig. 2A;
9 Fig. 6B is a second velocity trace produced in an
lo explosion detonated under the conditions prevailing in
Fig. 6A by the inventive explosive booster of Fig. 5
12 oriented in a less than optimal manner relative a charge of
13 explosives;
14 Yig. 6C is a third velocity trace produced in an
IS explosion detonated under the conditions prevailing in
16 Fig. 6A by the inventive explosive booster of Fig. 5
: 17 oriented in a preferred manner relative a charge of
: explosives;
19 Pig. 7A is a velocity trace produced in an explosion
detonated by an explosive booster such as that shown in
21 Fig. 2A; and
22 Fig. 7B is a second velocity trace produced in an
explosion detonated under the conditions prevailing in
2~ Fig. 7A by the inventive explosive booster of Fig. 5;
2.; ~ig. 8 is a perspective view of a generalized
26 embodiment of an explosive booster according to the present
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l invention shown in relation to a reference solid used to
2 define the geometry of the inventive embodiment;
:~ Fig. 9A is a cross-sectional view of a second
embodiment of an explosive booster according to the present
invention;
fi Fig. 9B is a cross-sectional view of a third embodiment
of an explosive booster according to the present invention;
Figs. lOA-lOH are cross-sectional perspective views of
9 various rotationally symmetric alternative embodiments of
lo explosive boosters incorporating the teachings of the
present invention;
Iz Figs. llA-llF are perspective views of various
l3 rotationally asymmetric alternative embodiments of explosive
l4 boosters incorporating the teachings of the present
invention;
16 Figs. 12A-12D are cross-sectional perspective views of
I, various rotationally symmetric alternate embodiments of an
18 explosive booster having composite body portions and
I~) incorporating the teachings of the present invention; and
2~ Figs. 13A-13C are pexspective views of various
~l rotationally asymmetrical alternative embodiments of an
explosive booster having composite body portions and
3 incorporating teachings o~ the present invention.
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132~913
Background Art
In the use of explosives in mining, construction, and
seismic research, it is presently preferred to employ as an
explosive material a blasting agent which is less sensitive,
and accordingly significantly safer to handle and store,
than propellants or high explosives. Such a blasting agent
suitable for use in the mining industry is ANFO, a mixture
of ammonium nitrate and fuel oil. This material resists
detonation when exposed to shock or heat of a degree common
to the mining environment. It is also relatively
inexpensive.
Nevertheless, due to its insensitive nature, a blasting
agent can only be detonated in conjunction with a smail
quantity of a more sensitive or powerful explosive material
which is used to initiate the process. Typically, two
components are involved in initiating the detonation oE an
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explosive material. The first of these components is
~ directly stimulated from a control device in order to
3 initiate the explosion. Such components include blasting
4 caps and detonating cords. In the former, a highly explo-
s sive material is concentrated in a small package at the end
6 of a cable. The cable is capable of communicating an
7 electrical or other type of stimulus to the blasting cap
8 from the detonation control device. A detonating cord, by
9 contrast, is actually a continuous thread of highly
explosive material. A detonating cord detonates along its
11 length in a progressive manner, once a stimulus for
12 detonation is applied at one end. Both blasting caps and
13 detonating cords permit safe, remote initiation of
14 explosions, but neither is of itself capable of generating
adequate energy to start the detonation of a relatively
16 insensitive blasting agent.
Therefore, a second component in the blast initiating
18 process is interposed between the explosive and the blasting
cap or detonating cord. This interposed element of blast
initiation is the booster or primer. A booster functions to
21 amplify the energy of a blasting cap or detonating cord into
~2 an explosion sizable enough to initiate the detonation of a
relatively insensitive explosive material. Boosters are
24 made of high energy materials adequately sensitive to be
2.s detonated by a blasting cap or a detonating cord. Having a
2~ larger mass and more explosive energy than blasting caps or
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detonating cords, a booster will upon detonation produce
enough energy to initiate explosive reactions in an adjacen~
explosive material. A booster is thus critical in most
successful explosive operations as an intermediary between
~ blasting caps or detonating cords and a relatively
6 insensitive explosive material.
, A typical configuration of the elements of an explosive
8 detonation used in mining, construction, or seismic research
~ is shown in Fig. 1. There a borehole 10 has been drilled to
a preselected depth in a rock formation 12 which is to be
shattered by explosives, possibly to prepare it for
12 subsequent mechanical removal. A primer or booster 14 has
l3 been lowered to the end 16 of borehole 10. By way of
14 illustration, operably engaged with booster 14 is a blasting
cap 18 at the end of an electrical conductor 20 which leads
16 to a detonation box 22 or other appropriate detonation
17 control device. With booster 14 and blasting cap 18 thus
disposed at the bottom 16 of borehole 10, a suitable
19 blasting agent 24 has been poured into borehole 10
contacting booster 14.
~l Operation of detonating box 22 will set off blasting
22 cap 18 which in turn detonates primer 14. This detonation
23 releases energy adequate to initiate detonation of blasting
2~ agent 24. The entire process is completed within a few
~5 milliseconds. In order to contain and drive laterally into
26 rock formation 12 the explosive force of blasting agent 24,
~ 132~13
the open end 26 of borehole 10 has been stemmed with
, backfill 28.
3 Rock formation 12 in which borehole 10 was drilled and
4 equipped for explosive detonation as shown in Fig. 1 could
have been at the surface of the ground, at the bottom of a
6 mining pit, or underground at the working face of a mine.
7 Typically an array of boreholes, such as borehole 10, is
8 prepared together in a rock formation before any detonation
9 occurs. Then the columns of blasting agent in the borehole
matrix are detonated simultaneously or in a nearly
Il simultaneous or patterned progression of detonations
12 according to the specific consequences sought. The depth of
13 borehole 10 and the height of the column of blasting agent
14 24 placed therein are dictated by the nature of rock
formation 12, as well as the objectives of the blasting
16 exercise.
17 Since the late nineteenth century, boosters used for
18 the purposes of the initiating explosions have been
19 nitroglycerine products. By accident of circumstances, the
shape of these highly explosive products mirrored the
21 surrounding boreholes in which they were most commonly
22 used. As a result they were shaped into elongated
23 cylinders, typically two inches in diameter by eight inches
2~ in length or five inches in diameter by twenty-five inches
in length.
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, In the late l950's and early 1960's, new powerful
_ booster materials were developed which could be cast into
3 various shapes. The boosters into which these materials
4 were made were termed cast primers, because of the method of
~ their manufacture. Cast primers continued, however, to be
6 produced in the traditional elongated cylindrical shape into
which boosters had previously been formed. A typical cast
8 primer weighing approximately one pound is two inches in
9 diameter and five inches in length. A common cast primer
composition available under the trade mark SuperPrime* is
currently marketed by the Trojan Corporation. SuperPrime *
l~ is comprised of Pentolite, a mixture of PETN and TNT.
l3 Fig. 2A shows a cross-section of a booster 30 having
l4 such a traditional elong~ted cylindrical shape. Booster 30
has sides 32 of height H which is usually substantially
16 greater than the diameter D of congruent circular top end 34
l7 and bottom end 36. Formed in booster 30 is a longitudinally
l~ disposed passageway 38 traversing the height H of booster 30
19 between top end 34 and bottom end 36 thereof. In addition,
a dead-end passageway 40 is formed in booster 30 parallel to
~l passageway 38 and opening onto bottom end 36 exclusively.
;~ Passageway 38 and dead-end passageway 40 cooperate to
~3 receive a means for detonating booster 30. As shown by way
,~ of example in Fig. 2A, a blasting cap 42 has been installed
~, in dead-in passageway 40 with its associated conductor 44
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* Trade mark
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132491
emerging from booster 30 at top end 34 thereof through
~ passageway 38.
3 Explosive boosters capable of housing a dead-end
4 passageway, such as dead-end passageway 40, are termed high-
profile boosters. The properties of the material of which a
6 booster is fabricated and purpose to which the booster is
7 applied are factors that determine how short a high-profile
8 booster of that material can be. Generally, the height H of
9 high-profile boosters ranges upwardly from a minimum of 4.5
inches.
Boosters, such as booster 30, are normally installed in
12 boreholes with the sides 32 thereof parallel to the sides of
13 the borehole. Top end 34 is directed toward and in contact
14 with the explosive material which the booster is intended to
detonate. Top end 34 of booster 30, in contrast with sides
16 32 thereof, functions as the primary surface of booster 30
17 that interfaces with the explosive material 24. As used
18 herein the term "interface surface" will be employed to
19 refer to the primary surface of a booster that would
~u customarily be installed directed toward and in contact with
21 the explosive material to be detonated.
,~ Fig. 2B depicts a low-profile booster 50 having sides
52 of height H and symmetric circular top end 54 and bottom
end 56 of diameter D. While in Fig. 2B, booster 50 is
~; depicted as having a height H less than diameter D, it is
~ ~1. not necessarily the relative relationship of these two
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dimensions which determines whether or not a booster is
~ considered low-profile. Rather, as discussed above, it is
3 the properties of the material of which the booster is made
4 and the purpose for which the booster is used that
ultimately determine whether a booster of a given height H
6 must be low-profile.
7 Lacking dead-end passageways, such as dead-end
8 passageway 40 in Fig. 2A, low-profile boosters cannot
9 operably engage a blasting cap, but can be used only in
lo conjunction with detonating cords. Booster 50, being a low-
11 profile booster, is shown as including only a single
12 passageway 57 longitudinally disposed therein between top
13 end 54 and bottom end 56. Either top end 54 or bottom end
14 56 of low-profile booster 50 could be used as an interface
surface. The installation of a blasting cord 58 in
16 passageway 57 with a retaining knot 59 at bottom end 56 of
17 booster 50 would commonly result, however, in top end 54
18 being the interface surface for booster 50.
The need to employ detonating cords with low-profile
boosters severely limits the circumstances in which they can
21 be used. Low-profile boosters continue, however, to mirror
~2 the shape of the boreholes in which they are commonly used,
~3 as in the ultimate analysis, even with their truncated
~ heights, low-profile boosters are cylindrical in shape.
:~
.; The cylindrical shape in boosters continues to be in
26 evidence in the hybrid booster 60 shown in Fig. 2C. Booster
1324~13
60 is comprised of a cylindrical portion 62, reminiscent of
~ a low-profile booster, joined to a high-profile cylindrical
:3 portion 64. A longitudinally disposed passageway is formed
4 in booster 60 between circular top end 68 of diameter D and
small bottom end 70. Low-profile portion 62 and high-
6 profile portion 64 together, however, have a combined height
7 H which is large enough to permit the formation in booster
8 60 of a dead-end passageway 72 suitable for receiving a
g blasting cap in operable engagement with booster 6Q. The
lo interface surface for booster 60 would correspond under
11 normal usage to top surface 68.
12 Hybrid boosters, such as booster 60, retain the
13 unlimited utility of high-profile boosters, but they are
14 plagued by difficulties relating to their method of manufac-
ture, which necessitates roughly twice the manufacturing
1~ steps required to make traditional single-diameter
l7 cylindrical booster. Hybrid boosters have accordingly been
18 perceived as overly expensive in relation to any benefits
1~ otherwise derivable therefrom.
The energy generated by the detonation of a booster
travels outwardly therefrom in the form of a shockwave front
which is intended to enter an explosive material and
~;~ propagates therethrough. The shockwave front itself
~ produces a corresponding traveling region of local
>, compression of the explosive material. Compression creates
~6 conditions in which the chemical decomposition of the
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132~13
l explosive material into gases can occur. Therefore, behind
2 any ade~uately intense shockwave front passing through an
3 explosive material is a re~ion of expanding gases in which
4 explosion is taking place. The boundary between the
~ compression re~ion and the explosive region is the
6 detonation wave ~ront of the explosion, which also travels
_ through the explosive material as detonation progresses.
8 The detonation wave front for any given explosion has a
9 velocity which v~ries with time over the nonetheless short
IQ duration of that explosion. As the detonation wave front is
II a moving wave front, this means that temporal variations in
12 detonation wave velocity can simultaneously be described as
I3 variations correlated to the position of the detonation wave
I4 front in the exploding material. A common point of
Ii reference for this spatial aspect of detonation wave front
16 velocity variation is the distance from the interface
7 surface or top of the booster that initiated the
I8 explosion. The detonation wave front velocity in an
explosive material is affected by the nature of that
material, the shape in which the material is confined, and
~I the intensity as well as shape of the shockwave front
22 originally projected thereinto from a booster.
Each type of explosive material has a characteristic
optimum detonating wave front velocity at which that
. explosive material decomposes in an ideal manner. At this
26 detonating wave front velocity the maximum possible energy
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l is released in explosive form from each portion of the
2 explosive material through which the detonatin~ wave front
:~ travels. This optimum velocity is the steady-state velocity
4 for the explosive material involved. In theory, it is the
velocity at which a detonating wave front in a particular
6 explosive material constrained in a particular shape will
. tend to travel in the long run, once detonation has been
8 initiated. Velocities of a detonation wave front that are
9 either greater than or less than the steady-state velocity
indicate that less than the full potential explosive energy
11 in the explosive material is being released by the explosion
12 process. In this light, detonation wave front velocity at
13 each point in a charge of exploding material may be taken as
14 an indicator of the quality of the reaction of the chemicals
of that material at each specific location therein.
16 The actual velocity of the detonating wave front in an
17 explosive material can vary dramatically over the course of
18 an explosion. This is particularly true in the region of
1~ the explosive material close to the booster that has
initiated the explosion. If the velocity of the detonating
21 wave front initiated in the explosive material by the
22 booster is less than the steady-state velocity, the
explosion is termed an under-driven detonation~ Typically,
'4 the velocity of the detonating wave front in an under-driven
~; detonation will gradually rise toward the steady-state
26 velocity as the detonating wave front propagates through the
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1 explosive material and the chemical reactions therein drive
~ the rate of reaction and the velocity of the detonating wave
3 front toward an optimum state of product decomposition at
the steady-state velocity.
Detonations in which the velocity of the detonating
6 wave front in the explosive material close to the booster is
_ greater than the steady-state velocity for that explosive
8 material, are called over-driven detonations. In these, the
g velocity of the detonating wave front will diminish,
approaching the steady-state velocity as the detonating wave
11 front travels through the explosive material away from the
12 booster. Occasionally this drop in velocity is so abrupt
13 that the velocity of the detonation wave front falls below
14 the steady-state velocity. Gradually, the detonation wave
1~ front velocity will thereafter rise until the steady-state
1~ velocity is once again achieved. These detonations will
17 generally be considered to be under-driven explosions.
18 In an under driven detonation, the distance from the
19 interface surface or top of the booster at which the
~o velocity of the detonation wave front reaches the steady-
state velocity is termed the run-up distance for that
2~ detonation. An efficient detonation requires that the
steady-state velocity be achieved as promptly as possible.
In terms of the efficient consumption of explosive material,
~; detonating wave front velocities of the under-driven variety
~6 of detonation represent a loss of potential explosive
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2 power. Accordingly, for the designer of an efficient
detonation, the minimizing of the run-up distance is an
important objective.
In an over-driven detonation, the distance from the
s interface surface or top of the booster at which the
6 velocity of the detonation wave front slows to and assumes
7 the steady-state velocity is termed the transient velocity
8 distance. Minimizing the transient velocity distance is not
9 necessarily an objective of the designer of an efficient
detonation, as enhanced shattering action in the immediate
11 area of the booster is achieved in over-driven
12 detonations. This in turn may render more effective the
13 explosive pressure developed in subsequent stages of the
14 explosion.
Accordingly, the overall efficiency of an explosion can
16 be evaluated in terms of whether the detonation is under-
17 driven or over-driven, the time following booster detonation
18 at which steady-state velocity is achieved, and the degree
19 to which that velocity is maintained throughout the balance
of the explosion thereafter. These parameters of an
`~1 explosive detonation will be illustrated through the use of
22 the graphs of Figs. 3A, 3B, and 3C and 4A and 4B, which
23 contain velocity traces for explosions detonated by the
various cylindrical boosters shown in Figs. 2A, 2B, and 2C
~5 and already discussed.
26
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1324~3
l Figs. 3A, 3s, and 3C are examples of velocity traces
2 resulting from the use of various sizes of nitroglycerine
3 boosters of the traditional elongated cylindrical shape,
4 such as booster 30 of Fig. 2A, in a six-inch diameter
borehole to detonate a charge of ANFO. ANFO has a steady-
6 state velocity under those conditions of approximately7 12,000 feet per second. All of the detonations illustrated
8 in Figs. 3A, 3B, and 3C w~re under-driven.
9 Fig. 3A illustrates the velocity trace of a 1.25 pound
lo booster, such as booster 30 of Fig. 2Af having a height of
1l eight inches and a circular diameter of two inches. The
12 detonation wave front velocity in the vicinity of the
13 interface surface at the top of the booster can be seen to
l4 have been substantially less than the steady-state velocity
l; for the material being detonated. For the portion of the
16 velocity trace shown in Fig. 3A, the detonation wave front
17 velocity never did in fact reach the steady-state velocity
for ANFO under the conditions present. Under most circum-
stancesf this would suggest that a booster had been used
which was not adequately large in relation to the energy
21 level of its constituent material for the size of borehole
and type of explosive material detonated.
-3 Pig. 3B illustrates the velocity trace produced by a
?~ larger 2.75 pound boosterf such as booster 30 of Fig. 2Af
~5 having a height o~ eight inches and a circular diameter o
6 three inches. As in Fig. 3Af the detonation illustrated in
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132~91~
Fig. 3B was under-driven. Nevertheless, the resulting
~ velocity trace reveals that the detonation wave front
3 velocity increased rapidly enough that it eventually reached
4 the steady-state velocity at a run-up distance of
.; approximately 21-23 inches. The rapid rise of the
. detonation wave front velocity illustrated in Fig. 3B would
_ under most circumstances be taken as an indication that the
8 detonation illustrated was more efficient than that of
9 Fig. 3A.
Fig. 3C shows the velocity trace resulting from the use
l of yet a larger six pound booster, such as booster 30 of
12 Fig. 2A, which was six inches in diameter and five inches in
l3 height. The additional energy provided by the larger
14 booster is seen to have resulted in a shortened run-up
1~ distance and in enhanced detonation wave front velocities,
16 even where these were less than the steady-state velocity
1~ for ANFO under the conditions present. In the case
18 illustrated in Fig. 3C, the diameter of the booster employed
1(~ was substantially equal to the diameter of the borehole in
") which it was detonated. Prior to the present invention,
_l conventional wisdom was to the effect that such was the
7~ optimum desirable relationship between booster diameter and
23 borehole diameter, if maximally efficient detonation were an
objective.
~; Figs. 4A and 4B are examples of velocity traces of
~6 various other cylindrically shaped boosters, such as the
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low-profile booster 50 of Fig. 2B and the hybrid booster of
Fig. 2C. In each instance, the booster involved was made of
3 Pentolite and used in a ten-inch diameter borehole to
4 detonate a charge of ANFO. ANFO has a steady-state velocity
under those conditions of approximately 14,000 feet per
6 second.
. Fig. 4A shows the velocity trace for a five-pound low-
8 profile booster, such as booster 50 of Fig. 2A. In the
9 immediate vicinity of the booster, the detonation wave front
lo velocity exceeded the steady-state velocity for the
l explosive material being detonated. The detonation wave
12 front velocity dropped abruptly, however, and for a
13 substantial distance from the top of the booster was less
14 than the steady-state velo~ity before it increased to that
l; optimum level. The detonation is thus considered under-
16 driven, and in the case shown in Fig. 4A the run-up distance
1, for the detonation was approximately 24 inches.
18 A velocity trace for a hybrid booster, such as booster
19 60, weighing three pounds is shown in Fig. 4B. The
detonation that resulted was over-driven, as the detonation
21 wave front velocity did not fall below the steady-state
'72 velocity to any substantial degree or for any appreciable
~:~ period. The transient velocity distance shown of approxi-
`7j~ mately 20 inches would suggest that enhanced shattering
, action occurred in the immediate area of the booster with
~ corresponding favorable efects on detonation efficiency.
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1 As is readily appreciable from the velocity traces
2 discussed above, the character of the booster used to
:3 detonate an explosive material can have a significant impact
4 upon the quality of explosion that results. Enhanced
;; detonation efficiency will predictably result in the need to
6 employ a smaller quantity of explosive material for
~ equivalent results. Thus, while a booster represents but a
8 small percentage of the total cost of preparing for a
explosion, manipulation of the type of booster used offers
the potential for large increases in the overall efficiency
ll of the detonation at a small change in its total cost. With
12 this objective in mind, research was commenced to determine
13 on a scientific basis the best suited booster for each
14 varying borehole condition. It was known that changing the
composition of a booster would affect the nature of the
16 detonation that it produced. Apart then from this variable,
1. the object was to maximize the release of energy in the
18 blasting agent employed by manipulating the size, shape, and
19 orientation of the booster employed to initiate its
detonation.
21 Prior to the present invention no single booster had
22 been devised which resulted in minimal weight, optimal
23 detonation efficiency, unlimited functionality due to the
capacity to employ blasting caps, and reasonably acceptable
manufacturing costs.
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SUMMARY OF THE INVENTION
Overview
The broad learnings acquired in the search for a
maximally efficient booster will be set forth below.
. It was initially concluded that the initiating
6 efficiency of a booster is related in a direct way to its
_ diameter. Increasing diameter did not, however, necessarily
8 require an increase in booster mass, unless one remained a
9 prisoner to the traditional elongated cylindrical booster
shape dictated by borehole geometry. In particular, it was
discovered that, rather than increasing the diameter of a
12 booster along its entire length, enlarging the interface
13 surface of the booster only would result in an increase in
~4 the efficiency of the detonation.
1~ Surprisingly, a reduction in the mass or volume of a
16 booster backing its interface surface did not necessarily
17 decrease blast initiation efficiency in relation to a
18 heavier booster with an identical interface surface. In
19 fact, a reduction of booster mass or volume in this fashion
served in numerous instances to actually enhance the
21 effectiveness of the overall detonation. Finally, optimum
booster performance appeared to result when the interface
2:~ surface thereof was relatively planar and was directed
,
; 2~ toward the explosive to be detonated.
2~7 The insight derived collectively from these
76 observations is supportive of a model of the detonation
~. , ~. .,
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1 process in which efficiency is understood to be at least
2 partially a function of the shape of the detonating wave
:3 front as it passes through an explosive material. In
4 particular, the less curvature exhibited by the detonating
, wave front, the more efficient the detonation. In a
6 columnar charge of explosive material, the planar detonating
7 wave front should be oriented normal the longitudinal axis
of the columnar charge and should travel parallel thereto in
9 order to achieve the maximum efficiency attainable.
Objects of the Invention
12 One object of the present invention is to produce an
13 improved booster and method of using such which results in
14 more efficient detonation of a charge of explosive material,
thereby reducing the cost associated with creating a given
16 explosive effect. The achievement of this object of the
17 present invention contemplates a reduction in the amount of
18 explosive material required or a reduction in the number of
19 the boreholes drilled in a given borehole array.
2() Another object of the invention is to provide such an
improved booster without increasing the amount of the
22 material required for its fabrication.
23 Still another object of the present invention is to
reduce the material required to fabricate explosive
2s boosters, while maintaining or increasing the detonation
26 efficiency provided by such boosters. The achievement of
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this object of the present invention contemplates areduction in the cost and effort associated with booster
3 transport and handling.
4 It is an object of the present invention to provide
s such an improved explosive booster as can be used with a
6 blasting cap and thus possesses unrestricted utility.
7 Yet another object of the present invention is to
8 provide a method and apparatus capable of producing a
9 substantially planar detonating wave front in a charge of
explosive material in order to effect maximally efficiency
detonation thereof.
12 A final object of the present invention is to produce
13 an explosive booster as described above which is easy and
inexpensive to manufacture.
1s Additional objects and advantages of the invention will
16 be set forth in the description which follows, and in part
17 will be obvious from the description, or may be learned by
18 the practice of the invention. The objects and advantages
19 of the invention may be realized and obtained by means of
the instruments and combinations particularly pointed out in
21 the appended claims.
22
23 Summary
24 To achieve the foregoing objects, and in accordance
~s with the invention as embodied and broadly described herein,
2fi a booster is provided in one embodiment of the present
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invention comprising a substantially flat interEace surface,
at one end thereof and a body portion terminating at the
interface surface in a base substantially congruent
thereto. The body portion is configured such that the area
of the cross-section of the body portion in at least one
first plane parallel the plane oE the interface surEace is
less than the area of the interface surface. The area of
the cross-section o~ the body po~tion in any second plane
parallel any such first plane is less than or equal to the
area of the interface surface, if the second plane is
located between the interface surface and the first plane and
; oriented parallel any such first plane is less than or equal
to the area of the interface surface. On the other hand, in
any third plane locate~ on the side of the second plane remote
from the interface surface and oriented parallel to the first
plane the area of tbe body portion in the third plane is less
than or equal to the area of the cross-section of the body
portion in the first plane.
A presently preferred shape for the body portion is
that oE a frustum of a cone with the base of the cone
substantially coinciding with the interEace surface.
In another aspect of the present invention, an
~; explosive booster is provided comprising a body portion
having substantially tapered sides and an interface surface
Z5 at the larger end of the body portion disposed generally
~; laterally thereof for contacting an explosive material.
Optionallyr the body portion may urther comprise a plate-
~, ~
~ shaped interface surface support section and a backing
:
~ -20-
' ~
~ ~"'~' ` ' '
132~13
l section. The interface surface support section terminates
2 at one side thereof in a base surface substantially
3 coincident with the interface surface. The backing section
4 has substantially tapered sides and is joined at the larger
:, end thereof to the interface support section on the side
6 thereof opposite from the base surface. The area of the
7 cross-section of the backing section at the larger end
8 thereof is preferably less than or equal to the area of the
9 ~ross-section of the interface support section at the side
thereof opposite from the base surface.
11 The booster of the present invention further comprises
12 at least one passageway, but preferably a plurality of
13 passageways, formed in the body portion for receiving in
14 operable engagement therewith a means for detonating the
booster. Preferably one passageway is a dead-end receptacle
16 for a blasting cap.
17 In an alternative aspect of the present invention, an
18 explosive booster comprising a quantity of selectively
19 detonatable high energy material is formed into a shape
terminating in a planar surface at one thereof. The shape
is so configured that the area of the cross-section of the
2~ shape taken in a plane parallel the planar surface
23 diminishes with the dis~ance of the plane from the planar
24 surface.
~; According to yet another aspect of the present
26 inventisn, a device is provided for producing a substan-
'~ '
~ 132~913
tially planar detonating wave front in an explosive
material. The device comprises a booster in contact with
;3 the explosive material and means operably engaging the
4 booster for detonating the booster to generate a shockwave
front and propa~ate the shockwave front into the explosive
6 material. The booster of such a device comprises a
l generally tapered body portion and a planar interface
8 surface at the larger end of the body portion extending
9 generally laterally thereof for contacting the explosive
material.
11 In still another aspect of the present invention, a
12 method is provided for increasin~ the detonation efficiency
13 of a given quantity of high energy explosive material in
14 relation to an explosive material. The method comprises the
steps of casting or forming the quantity of high energy
16 explosive material into a booster comprising a planar
17 interface surface at one end thereof for contacting the
18 ~xplosive material, a body portion terminating in a base
19 surface substantially coincident with the interface surface,
and at least one passageway formed in the body portion of
21 the booster for receiving in operative engagement therewith
22 a means for detonating the booster. The body portion of the
23 booster is so configured that the area of the cross-section
2~ of the body portion in any first plane parallel the plane of
the interface surface is less than or equal to the area of
26 the interface surface and less than or equal to the area of
.,,.~,.,..,.........
13~
the cross-section of the body portion in any second plane
~ between the first plane and the interface surface and
:~ parallel thereto. Thereafter, in the method of the present
invention, a means for detonating is installed in one o~ the
passageways in the body portion of the booster in operable
6 engagement therewith. ~he booster and the means for
7 detonating operably engaged therewith are located in contact
8 with the explosive material at one end thereof with the
9 planar interface surface of the booster oriented toward the
body of the explosive material. Finally, in the method of
the present invention, the means for detonating is activated
12 to explode the booster, generating a detonating wave front
13 and propagating the detonating wave front through the
14 explosive material:using a relatively short run-up distance
to the steady-state velocity.
16
17
18
19
o
~ '2
~, ~
~- ;25 /
'6
-23-
.~
A~
1324913
DESCRIPTION OF THE PREFERRED EMBODIMENT
2 Fig. 5 depicts a presently preferred embodiment 130 of
:~ a booster incorporating all the teachings of the present
4 invention installed ready for detonation below an explosive
~; material 132 at the bottom 133 of a borehole 134 in a rock
6 formation 136. Preferred embodiment 130 includes a
l substantially flat interface surface 138 directed toward and
8 in contact with the main body of the charge of explosive
9 material 132. It is inherent and acceptable with a booster,
lo such as preferred embodiment 130 installed in the manner
11 shown in Fig. 5, that a small quantity of the explosive
12 material 132 will sift into the space in borehole 134 below
13 interface surface 138 on either side of the booster.
14 Preferred embodiment 130 includes a body portion 140 in
the shape of a frustum of a cone. The larger end 142 or
16 base of body portion 140 substantially coincides with
l7 interface surface 138. Formed in body portion 140
18 traversing the full height H thereof, are longitudinally
19 disposed passageways 146, 148, that communicate between
interface surface 138 and ~mall end 150 of preferred
embodiment 130 remote therefrom. The height H of preferred
embodiment 130 is such that a dead-end passageway 152 may be
2:3 formed in body portion 140 parallel to passageways 146, 148.
~4 Body portion 140 of preferred embodiment 130 may
advantageously be formed of a cast primer material, such as
Pentolite, Composition B, an octol, H6, or other synthetic
~-
-~ 132~913
l cast materials. Materials other than Pentolite require the
2 addition of an internal sensitizer if used in this role. In
3 addition, boosters according to the present invention can be
4 made from nitroglycerine compositions, torpex, emulsion
S explosives, and slurrified blasting-cap-sensitive high
6 explosives. Other compositions such as nitroparaffin will
~ also perform satisfactorily.
8 For best results, preferred embodiment 130 should be
9 installed with the larger planar surface thereof directed
lo toward and in contact with an explosive material 132 in the
11 manner shown in Fig. 5. A blasting cap 154 is installed in
12 dead-end passageway 152 and connected by a cord 156 through
13 passageway 148 to a remote detonation control device (not
14 shown). When thus installed, preferred embodiment 130 and
blasting cap 154, or other suitable means for detonating a
l6 booster, comprise a device for producing a substantially
l7 planar detonating wave front in the explosive material 132.
18 The effectiveness of a booster, such as preferred
l9 embodiment 130, in increasing the detonation efficiency of
an explosive material can be appreciated first by reference
21 to the velocity traces for detonations shown in Figs. 6A-
22 6C. All of these velocity traces were generated by
: ~ :
detonating a charge of ANFO in a six inch diameter borehole
2~ using one-pound Pentolite explosive boosters. Under such
:~
conditions ANFO has a steady-state velocity of approximately
2~ 12rOOO feet per second. The three distinct velocity traces
' _,~
- 1324~i3
shown were obtained merely by altering the shape or orientation
of the booster with which the detonation was initiated. The
mass of high explosive booster material was a constant.
The volume o~ the inventive boosters disclosed herein as
a percentage of the volume of a traditional cylindrical booster
of identical height and base can be determined using known
mathematical algorithms. The data presented below in Table A
have been derived.
Table_A Volumetria Data Derive~ from ~electo~ of
the Inventive Booster~ Disclosed Herein
VOLUME AS A PERCENTAGE OF
FIGURE APPLICAB~E REFERENCE BOOSTER
57%
6B 38%
7B 53%
lOA 33%
llA 33%
llB 33~
llF 48%
Fig. 6A shows a velocity trace resulting from the
detonation of a traditionally shaped cylindrical booster,
such as booster 30 of Fig. 2A, having a di~meter of 2.25
inches and a height of 4.75 inches. After a short initial
period of high velocity, the detonation wave front velocity
fell below the steady state velocity, only to regain that
velocity at a run-up distance of approximately 28-30
inches. The detonation is thus considered to have been
under-driven.
Using an explosive booster having the same weight as
that used in relation to Fig. 6A, but conEigured in the
shape of a conical frustum, such as is typified by preferred
embodiment 130 in Fig. 5, the results depicted in Figs. 6B
-26-
1324913
and 6C were obtained. The one-pound booster employed in both
of the latter instances had a height of 4.50 inches and a
diameter at the larger circular end surface of 3075 inches and
a volume that is about 38 percent of the volume of a
traditional cylindrical booster having a height of 4.50 inches
and a base with a diameter of 3.75 inches. Thus, by shaping
a booster according to the teachings of the present invention,
it should first be appreciated that a given quantity of
high-explosive booster material can be formed into an explosive
booster of diameter enhanced when compared to traditional
cylindrical shapes.
/
~ -
~--
",
1 3 ~ 4 9 1~3
1 The velocity trace in Fig. 6B was produced when such an
~7 inventive booster was detonated with the larger planar
3 surface thereof oriented downward, rather than towar~ the
4 main charge of explosive. A run-up distance of approxi-
S mately 20-22 inches resulted. ~evertheless, while begun as
6 an over-driven detonation, the detonation wave front
7 velocity of the detonation depicted in Fig. 6B plummeted far
8 below the steady-state velocity before increasing again to
9 that optimum speed. As a result, despite a shorter run-up
distance than resulted in the detonation of Fig. 6A, the
ll detonation of Fig. 6B is considered to have produced a less
12 efficient explosion than that associated with Fig. 6A.
13 The velocity trace shown in Fig. 6C is one that
14 resulted from a booster shaped as a conical frustum, such as
preferred embodiment 130 of Fig. 5, and having the A same
l6 dimensions as that used in Fig. 6B, but oriented so that the
17 large planar surface thereof, the interface surface of the
l8 booster, was directed toward the main charge of explosive
l9 material. A run-up distance of a mere 10-12 inches
resulted~ The velocity trace in Fig. 6C thus compares quite
2l favorably with that resulting using a traditional
22 cylindrically shaped booster as in Fig. 6A, or the inverted
23 inventive booster as in Fig. 6B. The results in Fig. 6C
- .
~ 24 when compared with those in Fig. 6a underscore the
j 25 significa~ce of orienting the large planar surface of an
26 ~ P
,., ~
~:. ` ` -, '
'~
~324913
explosive booster according to the present invention toward
the explosive material being detonated.
3 Figs. 7A and 7B permit a comparison of detonation
4 efficiency in boosters having identical diameters, as
opposed to identical weights. In Figs. 7A and 7B an
6 explosive charge of ANFO in a six-inch diameter borehole was
7 detonated using three-inch diameter boosters made of a
8 nitroglycerine composition. ANFO under such conditions has
9 a steady-state velocity of approximately 12,000 feet per
second. Fig. 7A is a velocity trace produced by a booster
of traditional cylindrical shape, such as booster 30 shown
l2 in Fig. 2A. The booster involved, which had a circular
l3 diameter of three inches and a height of five i~ches,
14 weighed approximately two pounds. As seen in Fig. 7A, the
resulting detonation was under-driven with a run-up distance
16 of approximately 27-30 inches.
1~ On the other hand, however, the velocity trace of
l8 Fig. 7B has an improved run-up distance of approximately 22-
inches. The booster involved in Fig. 7B was one
configured according to the teachings of the present
invention as a conical frustum, such as preferred embodiment
2~ 130 of Fig. 5, having a height of 4.75 inches and a circular
diameter at its larger face of three inches. That larger~
Eace was oriented toward the explosive material, thus
serving as the interface surface of the booster. The
26 frustoconical booster had a volume that was about 53 percent
of the volume of a traditional cylindrical booster having a
height of 4.75 inches and a base with a 3-inch diameter.
-29-
'-:
~ 132~913
1 While the boosters used both in Figs. 7A and 7B had
2 identical circular diameters, that of 7B weighed only one
3 pound, half the weight of the cylindrical booster used in
4 Fig. 7A. Accordingly, the present invention includes a
s method for increasing the detonation efficiency of a given
6 quantity of high-energy explosive booster material in
7 relation to an explosive material, reducing in many
8 instances the amount and cost of the charge of explosives
9 required for any given explosive effect. Given the vast
lo quantities of such explosives used annually in the mining
11 industry alone, substantial savings can be expected as a
12 result.
13 The method comprises the steps of casting or forming
14 the quantity of high-energy explosive material into a
booster configured according to the teachings of the present
16 invention, such as preferred embodiment 130 shown in
l? ~ig. 5. Thereafter a means for detonating the booster, such
18 as blasting cap 154, is installed in operable engagement
19 therewith and both are located in contact with an explosive
material, so that the planar interface surface of the
21 booster is in contact with the explosive material and
22 oriented toward the main body thereof. Finally, activating
23 the detonating means to explode the booster generates a
24 detonating wave front and propagates that detonating wave
front through the explosive material with a relatively short
~ 26 3c~
:'
.
13~ 3
l run-up distance, so as to effect efficient detonation of the
2 explosive material.
3 The booster and method of the present invention result
4 in more efficient detonation of an explosive material,
thereby reducing the cost associated with a given explosive
6 effect. The velocity traces shown in Figs. 6A-6C
7 demonstrate that a booster configured according to the
8 present invention provides increased booster efficiency
9 without increasing the amount of material required for
booster fabrication. The velocity traces of Figs. 7A and 7B
11 demonstrate further that the method and device of the
12 present invention actually permit a reduction in the amount
13 of material used to fabricate explosive boosters without
14 detracting from detonation efficiency. In fact, detonation
efficiency is increased.
16 The preferred embodiment 130 shown in Fig. S and the
17 other embodiments disclosed herein provide a booster having
an enlarged diameter or interface surface in combination
1~ with a reduction in the mass or volume of highly explosive
material backing the interface surface. The combination of
these two features of geometric configuration is thought to
22 produce a flatter detonating wave front in the explosive
23 material with which the booster of the present invention is
~4 usedO
2.~ That such advantageous functioning results, regardless
26 of the material of which the booster is constructed, is
~3~13
l apparent in the improvement in performance observable both
2 in relation to Fig. 6C over Eig. 6A, which involved boosters
:3 made of Pentolite, and in Fig. 7B over Fig. 7A, both using
4 nitroglycerine boosters. Optimum booster performance occurs
; when the interface surface thereof is substantially flat or
6 planar and is oriented toward, rather than away from, the
. charge of explosive to be detonated.
8 More generalized geometric parameters for explosive
9 boosters incorporating the teachings of the present
invention will be described below in relation to Figs. 8,
11 9A, and 9B.
12 In Fig. 8, a reference solid 180 is shown overlying an
13 inventive generalized booster embodiment 182. Generalized
14 booster embodiment 182 has a substantially flat interrace
surface 184 at one end thereof which is intended to contact
16 an explosive material with which generalized booster embodi-
ment 182 is to be used. Generalized booster embodiment 182
18 includes in addition a body portion 18S which terminates at
19 interface surface 184 in a base substantially congruent
thereto. Interface surface 184 defines, and in Fig. 8 is
21 coincident with, the floor 186 of reference solid 180.
2~ Floor 186 is congruent with and parallel to an opposed
2~ end surface 187 of reference solid 180. Opposed end surface
24 187 and floor 186 are located a predetermined distance H
apart, oriented such that the sides 188 of reference solid
~'6 180 between floor 186 and opposed end surface 187, if
~ ,~
-`
132~ 3
l intersected by a plane, such as plane 190, which is normal
2 to floor 186, form straight lines, such as lines 192, 194,
:3 which are also normal to floor 186. In this manner,
4 reference solid 180 can be seen to have a broadly prismatic
geometry with a cross-section in any plane parallel to floor
6 186 that is congruent to interface surface 184 of
7 generalized booster embodiment 182.
8 With reference solid 180 overlying generalized booster
9 embodiment 182, as in Fi~. 8, the point 196 on the surface
lo of generalized embodiment 182 maximally remote from
Il interface surface 184 lies in opposed end surface 187 of
12 reference solid 180. Body portion 185 of generalized
13 booster embodiment 182 thus has a height measured normal to
14 interface surface 184 which is equal to the predetermined
~5 distance H between floor 186 and opposed end surface 187 of
16 reference solid 180.
17 In a generalized embodiment of an explosive booster
18 incorporating the teachings of the present invention, such
l9 as generalized booster embodiment 182, each point P on the
surface of body portion 196 is on or interior to reference
~1 solid 180, and at least one such point P is interior to
22 reference solid 180. In this manner the volume of body
23 portion 196 of ~eneralized embodiment 182 is less than the
24 volume of reference solid 180. An explosive booster
~: ~. configured in the manner of generalized booster embodiment
26 182, can in general be expected to possess a detonating
33
13~13
efficiency greater than that of an explosive booster in the
shape of corresponding reference solid 180.
~ No representation is made that an irregularly shaped
4 explosive booster, such as generalized booster embodiment
s 182, would necessarily be easy or inexpensive to
6 manufacture. Nevertheless, such a booster would require
7 less high ener~y explosive material for its fabrication than
8 would a booster taking the form of reference solid 180. The
9 reduction in the mass backing interface surface 184 as
lo compared with the mass which wouId back floor lB6 in a
Il booster configured as reference solid 180 will increase the
12 performance of the resultant booster. How precisely this
13 result arises in a detonation in a borehole is not entirely
14 clear. It is thought to have some relation to the degree of
flatness of the detonating wave front produced in a
borehole-shaped column of explosive material by a booster
fulfilling the shape parameters described in contrast to
18 that produced by a booster of a prismatic nature having
sides that are parallel to the sides of the borehole in
2n which it is detonated.
21 The explosive booster of the present invention can be
22 embodied and characterized in an alternative manner in
3 relation eO the embodiment of an explosive booster 200 shown
~4 in cross-section in Fig. 9A. Booster 200 has an interface
~5 surface 202 at one end thereof and a body portion 204
26 terminating thereat in a base substantially congruent
132~13
l thereto. Interface surface 202 has a slightly convex
2 curvature, indicating that the interface surface of an
:~ explosive booster according to the present invention need
4 not be absolutely flat or planar in order that the booster
~ which includes it is within the teachings of the present
6 invention. Some aspects of detonation wave front
7 propagation are degraded by a interface surface which is not
8 flat, a booster with a slightly irregular or curved
9 interface surface, such as interface surface 202. Neverthe-
less, a booster, such as booster 200, still provides
11 adequate ad`vantages, such as enhanced detonation efficiency
12 and reduced booster weight, as to be a substantial
13 improvement over known boosters of cylindrical shape and
14 thus within the scope of the present invention.
Accordingly, the term "substantially flat" or "planar"
16 when used herein in relation to the interface surface of an
17 explosive booster should be understood to include not merely
18 an absolutely flat interface surface, such as interface
19 surface 184 shown in Fig. 8, but also slightly curved or
irregularly shaped concaved or convexed surfaces, one of
21 which is illustrated as interface surface 202 in Fig. 9A.
22 Each such planar or substantially flat interface surface
~3 will have associated therewith a plane which will be
2~ referred to herein as the plane of that interface surface.
~; Such a plane, as seen from the edge thereof, is depicted in
26 Fig. 9A ~s plane 206.
~ 3~
1 3 ~ 3
Body portion 204 oE booster 200 is configured such that
the area of a cross-section of body portion 204 taken in at
:~ least one first plane parallel to plane 206 is less than the
:4 area of interface surface 202. The area of the cross-
.s section of body portion 206 in any second plane parallel to
any ~uch first plane is less than or equal to the area of
, interface surface 202, if the second plane is located
8 between the first plane and interface surface 202. IE the
first plane is located between the second plane and
interface surface 202, however, the area of the cross-
section of body portion 204 1n the second plane is less than
12 or equal to the area of the cross-section of body portion
13 206 in the first plane. A booster shape consistent with
14 these limitations need not necessarily be symmetric as in
. ..... -
the case of booster 200.
: 16 In the particular example of an inventure booster shown
17 as booster 200 in Fig. 9A, the cross-section of body portion
18 204 taken in every first plane parallel to plane 206 has an
~: area less than the area of interface surface 202.
Furthe'rmore, the area of the cross-section of body portion
`21 204 in any second plane located on the opposite side of any
22 such first plane from interface surface 202 is less than the
23 area of the cross-section of body portion 204 in each such
2~ first plane. Thus, the cross-sectional area of booster 200
.; taken in any plane parallel to plane 206 of inter~face
26
-36-
-
.,:
132~913
l surface 202 diminishes with the distance of the plane of the
2 cross-section from interface surface 202.
3 Even these broad descriptions of booster 200 do not
4 fully encompass all devices within the scope of the present
; invention. Explosive boosters consistent with the teachings
6 of the present invention are possible which would not
7 strictly comport with these descriptions, but which yet
8 would be within the scope of the generalized booster
9 embodiment 182 shown in Fig. 8. Accordingly, booster 200 in
o ~ig. 9A is but a second, albeit relatively general,
Il alternative embodiment of an explosive booster according to
12 the present invention.
13 As shown in Fig. 9A, booster 200 has a height H
14 substantial enough to permit the formation within body
portion 204 of a dead-end receptacle 208 capable of
16 receiving a blasting cap in operable engagement with booster
17 200. Thus, booster 200 is a high-profile booster. In
18 addition, to facilitate the use of a blasting cap with
I9 booster 200, formed within body portion 204 are two
longitudinally disposed passageways 210, 212 traversing the
21 full height H of booster 200 between interface surface 202
22 and opposite end surface 214. The provision of two passage-
23 ways in addition to dead-end receptacle 20~ is entirely
~4 optional. Two passageways afford for additional flexibility
in the use of boosters, such as booster 200, in that the
26 second passageway through such a booster permits the
~1 ~
~ ~32~13
1 connecting cord for a blasting cap for another booster lower
2 at a lo~ation in the same borehole to be threaded through
~ the higher booster. In this manner several boosters can be
4 located at different levels in a single borehole for
simultaneous or sequenced detonation, as desired by the
6 designer of the explosion.
7 The explosive booster of the present invention can be
8 described and further understood in relation to yet another
9 relatively general embodiment of an explosive booster 220
shown in cross-section in Fig. 9B. Booster 220 comprises a
11 body portion 222 having substantially tapered sides 224 and
12 larger and smaller ends 226 and 228, respectively. As can
13 be seen by the profile of sides 224, they are not in any
14 continuous or linear sense tapering at each and every point
thereof. In fact, at smaller end 228 o booster 220, sides
224 thereof flare radially outward for a short distance.
Nevertheless, the term "substantially tapered" as applied
18 herein to the sides of a booster should be understood to
19 include sides, such as sides 224, that taper in an overall
manner from a larger end, such as larger end 226, to a
21 smaller end, such as smaller end 228. While sides, such as
22 sides 224 of booster 220, would not necessarily come within
the scope of the description of an explosive booster
2~ rendered in relation to booster 200 of Fig. 9A, booster 220
is fully within the teachings of the present invention.
26 ~
132~91:3
Booster 220 is provided at larger end 226 of body
portion 222 with a substantially flat interface surface 230
:~ that is disposed generally laterally of body portion 222.
4 Interface surface 230 may be provided with beveled edges 232
S or a concave portion 234, which is effected in the
6 embodiment shown in Fig. 9B by discrete recessed steps
7 236. Concavity in an interface surface, such as interface
8 surface 230, can be effected over either a portion or the
9 entirety of that interface surface using in the alternative
smooth, continuous surfaces. Nevertheless, despite beveled
11 edges 232 and concave portion 234, interface surface 230
12 remains one that is substantially flat or planar for
13 purposes of complying with the teachings of the present
invention.
Formed in booster 220 is a plurality of passageways
16 238, 240 for receiving a means for detonating explosive
17 booster 220. In the embodiment shown, passageway 240 is a
dead-end receptacle for a blasting cap. Thus, booster 220
is a high-profile booster.
Figs. lOA-lOH depict various specific shapes of
21 embodiments of explosive boosters considered to be typical
22 of boosters within the scope of the teachings of the present
23 invention. ln each of these figures and in the remaining
24 figures throughout this disclosure, the depiction of
passageways, such as passageways 238, 240 of Fig. 9B has
26 been eliminated for the sake of simplicity. Comments
...
.
13~4~13
1 rendered earlier in relation to Figs. 2A and 2B, regarding
~ the minimum height H required in a booster if it is to
;~ contain a dead-end receptacle for a blasting cap, apply with
4 equal validity to the possibility of including such a dead-
end receptacle in a booster embodying the present invention.
6 It must be emphasized, however, that the presence of a dead-
7 end receptacle in an explosive booster is not a requirement
8 of the present invention. It is entirely conceivable that
9 circumstances may be advantageous for the manufacture and-
use of low-profile boosters which nevertheless incorporate
11 the teachings of the present invention. As a group, the
12 boosters depicted in Fig. lOA-lOH, unlike the generalized
13 booster embodiment 182 in Fig. 8, are rotationally
14 symmetric, although such a feature is also not a limitation
of the teachings of the present invention.
16 Fig. lOA depicts a booster 250 incorporating teachings
17 of the present invention having a body portion 252 in the
form of a cone. The base 254 of conical body portion 252
19 substantially coincides with the interface surface of
booster 250. It will be appreciated that the configuration
21 of booster 250 advantageously presents an interface surface
22 of enlarged area, while substantially reducing the amount of
, . ~
23 booster material required for fabrication of booster 250 in
24 comparison with that need for a traditional cylindrical
2s booster having an identical interface surface and height H.
. .
~..................................... ~
-
1324913
Fig. lOB depicts a booster 260 incorporating teachings
of the present invention which could be configured as a low-
3 profile booster for use exclusively with detonating cords.4 sooster 260 has a body portion 262 that is a spherical
s segment smaller than a hemisphere separated from a sphere S
6 having a center C by a single plane. The interface surface
~ 264 of booster 260 substantially coincides with the single
8 planar surface of the spherical segment.
9 Fig. lOC depicts a booster 270 incorporating teachings
of the present invention and having a body portion 272 which
Il is a hemisphere of a sphere S having a center C. Booster
12 270 has a circular interface surface 274 which substantially
13 coincides with the planar surface of the hemisphere. An
14 explosive booster shaped as booster 270 is a particularly
compact form of a booster incorporating the teachings of the
16 present invention.
17 Fig. lOD illustrates a booster 280 incorporating
18 teachings of the present invention and having a body portion
19 282 which is a frustum of a spherical segment of a sphere S
having a center C. The frustum of which body portion 282 is
comprised includes larger and smaller substantially planar
22 faces 284 and 286, respectively. Although faces 284 and 286
23 as shown in Fig. lOD are substantially parallel, this is not
2~ a feature required by the teachings of the present inven-
tion. Larger planar face 284 is on the opposite side of
2~ center C ~rom smaller planar face 286 and serves as the
. .
1324~13
1 interface surface for booster 280. Larger planar face 284
2 is accordingly somewhat smaller in area than the area of a
:3 cross-section of body portion 282 taken in a plane parallel
4 larger planar face 284 and passing through center C.
S Nevertheless, as with the case of beveled edges 232 shown in
6 Fig. 9B, minor radial narrowings of the sides of a booster
7 in the vicinity of the interface surface thereof are not
8 considered to detract from the teachings of the present
9 invention generally, although such structure may result in
lo some degradation of the detonation wave front propagated by
a booster having such features.
12 Fig. lOE is a booster 290 incorporating teachings of
13 the present invention and having a body portion 292 that is
14 a parabolic solid generated in relation to parabolic curve
Q. The base of body portion 292 coincides with interface
16 surface 294 of booster 290.
17 Fig. lOF illustrates yet another booster 300
18 incorporating teachings of the present invention. Booster
19 300 has a body portion 302 which is an elliptical solid
; ~ generated in relation to an elliptical curve R of center C
~1 located midway between the focii (not shown) of elliptical
22 curve R. Body portion 302 is further a frustum of such an
elliptical solid and includes larger and smaller substan-
~4 tially planar faces 304 and 306, respectively. Although
faces 304 and 306 as shown in Fig. lOF are substantially
26 parallel, this is not a feature required by the teachings of
_~
'
~312''~
1 the present invention. Larger planar face 304, which
substantially coincides with the interface surface for
:~ booster 300, is on the opposite side of center C from
4 smaller planar face 306, although such a relative
relationship is also not required by the teachings of the
6 present invention.
7 Larger planar face 304 is somewhat smaller in area than
8 the area of a cross-section of body portion 302 taken in a
g plane parallel larger planar face 304 and passing through
center C. Nevertheless, the radial narrowings of the sides
11 308 of booster 300 in the vicinity of the interface surface
l2 thereof do not detract from the teachings of the present
13 invention generally, although such structure may result in
14 some degradation of the donation wavefront propagated by a
booster having such features.
16 Fig. lOG depicts a booster 310 incorporating teachings
: ~
17 of the present invention and having a body portion 312 which
18 is a hemiellipsoid of an elliptical curve R having a center
19 C located midway between the focii (not shown) of elliptical
curve R. Booster 310 has a circular interface surface 314
21 which substantially coincides with the planar surface of the
22 hemiellipsoid. An explosive booster shaped as booster 310
23 will have a height H greater than the diameter D of inter-
24 face surface 314 and will accordingly be of greater height
~S and mass than, for example, a hemispherically shaped
~6
~1
-. .. ~, ,
i32~9~3
~ booster, such as booster 270 of Fi~. lOC, having a similarly
2 sized interface surface.
3 Fig. lOH is an example of a rotationally symmetric
booster 320 incorporating the teachings of the present
invention and having a body portion 322 with sides 324
6 comprised of a plurality of discrete discontinuous steps
7 326. Steps 326, by way of illustration in Fig. lOH fall
8 within an envelope S resembling a frustum of a cone. The
interface surface 328 of booster 320 is located at the
larger end thereof.
Figs. llA-llF depict various specific shapes of embodi-
ments of explosive boosters that are rotationally
asymmetric, but are yet considered to be typical of
14 rotationally asymmetric boosters within the scope of the
teachings of the present invention.
16Fig. llA depicts one embodiment of a booster 330
according to the present invention having a body portion 332
in the shape of a pyramid having three faces. The interface
19surface 334 of booster 330 substantially coincides with the
triangular base of the pyramid.
21 Similarly, Pig. llB shows a booster 340 according to
22 the present invention having a body portion 342 in the shape
23 of a tetrahedron. The interface surface 344 of booster 340
substantially coincides with the four-sided base of the
~ 5 tetrahedron.
2~
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~ 1324913
Yet another embodiment of a booster 350 according to
~ the present invention is shown in Fig. llC. Booster 350 has
3 a body portion 352 which is a frustum of a pyramid. By way
4 of example and not limitation, the pyramid of which body
~ portion 352 is formed as five sides, although a frustum of a
6 pyramid having additional or fewer numbers of sides is
7 considered to be within the scope of the embodiment
8 disclosed. The interface surface 354 of booster 340
9 substantially coincides with the five-sided base of the
frustum.
Fig. llD illustrates a booster 360 according to the
12 teachings of the present invention having a body portion 362
13 that is a triangular prism. Interface surface 364 of
booster 360 substantially coincides with the base of the
prism. End faces 366, 368 of body portion 362 as shown in
16 Fig. llD are substantially normal to interface surface 364.
17 Nevertheless, the effect of inclined faces 370, 372 of body
18 portion 362 on the volume of booster 360 backing interface
1~ surface 364 nevertheless produces a generally tapered shape
in body portion 362, which is considered to be within the
~ 1 scope of the present invention.
22 Fig. llE illustrates yet another booster 380
23 incorporating teachings of the present invention. Booster
~, :
24 380 has a body portion 382 in the shape of a frustum of a
prism. The interface surface 384 of booster 380 substan-
26 tially coincides with the base of the prism.
f~
~ . .. ....
132~913
Finally, Fig. llF depicts a booster 390 having a body
portion 392 which is a frustum of an asymmetrically
3 generated cone. The larger planar face of the frustum
4 comprising the base thereof substantially coincides with
interface surface 394 of booster 390.
6 In yet another aspect of the present invention, an
, explosive booster, such as booster 400 shown in Fig. 12A
8 having a substantially .flat interface surface 402 for
9 contacting a package of explosives is provided with a
lo composite body portion 404 having substantially tapered
11 sides 406. As shown by way of example and not limitation,
12 the larger end 408 of composite body portion 404 is formed
13 into a plate-shaped interface support section 410
14 terminating at one side thereof in a base surface which is
substantially coincident with interface surface 402. The
16 sides 416 of interface support section 410 may be
17 substantially normal to interface surface 402. Composite
18 body portion 404 further includes a backing section 418
~:
:~ 19 having substantially tapered sides 420 and larger and
smaller ends 422 and 424, respectively. Backing section 418
is joined at larger end 422 thereof to interface support
22 section 410 on the side thereof opposite from interface
2~ surface 402.
Sides 406 of composite body portion 404 thus comprise
2s sides 416 substantially normal to interface surface 402 and
:~ 6 sides 420 of backing section 418. Nevertheless, the term
. -~ ~
132~913
"substantially tapered" as applied herein to the sides of a
booster according to the present invention should be
:3 understood to include sides, such as sides 406, which are a
combination of otherwise substantially tapered sides, such
.; as sides 420,and relatively short, albeit nontapering sides,
6 such as 416 of a plate-like interface support section. It
. is adequate for purposes~of the present invention if the
8 sides of a composite body portion, such as composite body
9 portion 404, taper in an overall manner from the interface
o surface of that booster to the smaller end of the backing
section.
I2 Sides 420 of backing secticn 418 do not taper at each
l3 point thereof, but flare outwardly for a short distance at
14 smaller end 424 of backing section 418. Nevertheless, the
term "substantially tapered" as applied herein to the sides
16 of a backing section, such as backing section 418, should be
17 understood to include sides, such as sides 420 that taper in
18 an overall manner from a larger end, such as larger end 422,
19 to a smaller end, such as smaller end 424.
While it is not a requirement of the teachings of the
21 present invention, the area of the cross-section of larger
22 :~end 422 o~ backing section 418 is equal to the area of the
2:3 cross-section of interface surface support section 410 at
the side thereof opposite from interface surface 402. Other
2s embodiments of inventive boosters having composite body
.
: 26 portions, such as composite body portion 404, have other
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~ 132~913
l relative relationships between the areas of these two cross-
2 sections.
3 For example, Fig. 12B illustrates an explosive booster
4 430 having a composite body portion 432 comprising a plate-
~ shaped interface support section 434 and a backing section
6 436 in the shape of a cone. The base or larger end 440 of
_ conical backing section 436 is joined to interface support
8 section 434 at the side thereof opposite the interface
9 surface 442 of booster 430. In booster 430, the area of the
cross-section of backing section 436 a~ larger end 440
1l thereof is less than the area of the cross-section of
l2 interface support section 434 at the side thereof opposite
13 from interface surface 442.
14 Fig. 12C depicts a related alternative embodiment of a
booster 450 according to the present invention. Booster 450
16 includes an interface surface 452, a plate-shaped interface
17 surface support section 454, and a backing section 456
18 taking the form of a frustum of a cone. The base or larger
l9 end 458 o backing section 456 is joined to interface
support section 454 on the side thereof opposite from
21 interface surface 452. In this instance, the periphery of
22 interface surface 452 is provided with beveled edges 460.
23 Similar beveled edges 462 are provided at the periphery of
interface support section 454 on the side thereof opposîte
~5 from interface support surface 452.
~ ~ . ~
.~ -.5~- .
~32~913
Fig. 12D depicts yet anothe~ booster 470 according to
2 the teachings of the present invention having a composite
;~ body portion 472. Substantially flat interface surface 474
is formed on one side of an interface surface support
section 476. A backing section 478 taking the form of a
frustum of a spherical segment of a sphere S having center C
_ is joined at the base or larger end 480 thereof to the side
8 of interface surface support section 476 opposite from
9 interface sur~ace 474. Booster 470 illustrates the special
lo case in which backing section 47~ is a frustum of a
hemisphere. The cross-section of backing section 478 at
larger end 480 thereof is equal to the cross-section of
13 interface surface support section 476.
14 The explosive boosters depicted in Pigs. 12A-12D and
having composite body portions are all rotationally
l6 symmetric. Nevertheless, explosive boosters are possible
17 within the teachings of the present invention that have
18 composite body portions in which either or both the
I9 interface surface support section and the backing section
:~ ,
are rotationally asymmetric. The boosters shown in Figs.
2l 13A-13C are of this latter type.
22 Booster 490 shown in Fig. 13A comprises a plate-s~aped
2~ interace surface support section 492 and a backing section
2~ 494 taking the form of a six-sided pyramid joined thereto.
In the embodiment shown, while the cross-section o~ inter-
26 Eace surface support section 492 on the side thereof
-49-
.~
~2~13
l opposite from interface surface 496 of booster 490 is
2 similar in shape to the six-sided base or larger end 498 of
3 backing section 494, the area of that cross-section of the
4 interface surface support section is larger than that of the
s cross-section of larger end 496 of backing section 494.
6 In Fig. 13B, booster 500 embodying teachings of the
7 present invention includes an interface surface support
8 section 502 having continuously curved sides 504. On the
9 side of interface surface support section 502 opposite from
the interface surface 506 of booster 500 is a backing
11 section 508 formed as a frustum of a three-sided pyramid,
12 the base of which is joined to interface surface support
13 section 502.
14 In Fig. 13C, booster 510 is shown comprising a
rotationally symmetric, circular plate-like interface
16 surface support section 512 and a backinq section 514.
17 Backing section 514 is in the form of a frustum of a prism
having ends 516, 518 generally normal to interface surface
9 support section 512 and faces 520, 522 inclined relative
thereto.
21 The present invention may be embodied in other specific
22 forms without departing from its spirit or essential charac-
,
; 23 teristics. The described embodiments are to be considered
24 in all respects only as illustrative and not restrictive.
The scope of the invention is, therefore, indicated by the
26 appended claims rather than by the foreqoing description.
~ _~ ~
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1~24~13
11 changes which come within the meaning and range of
. equivalency of the claims are to be embraced within their
J scope.
. .''
ll ~.
12
13
14
16
17
18
9 .
~
21
22
- 23
24
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