Ammunition and explosives – Igniting devices and systems – Fuse cord
Reexamination Certificate
1999-09-28
2004-05-25
Nelson, Peter A. (Department: 3641)
Ammunition and explosives
Igniting devices and systems
Fuse cord
C102S275400, C102S275110, C102S275120, C102S275800, C102S318000, C102S322000
Reexamination Certificate
active
06739265
ABSTRACT:
BACKGROUND
1. The Field of the Invention
This invention relates to explosive devices employed to detonate explosive materials of the types used in mining and construction, and to explosive devices used in seismic survey activity. The present invention has particular applicability to explosive devices made of cast explosive materials.
2. Background Art
A. Types of Explosive Devices
Typically, two components are involved in initiating the detonation of an explosive device.
The first of these components is stimulated directly from a control device in order to initiate the explosion. Such components include detonators and transmission lines, such as detonating cords, shock tubes, and electrically conductive wires. In the former, a highly explosive material is concentrated in the small package at the end of a cable that is capable of communicating an electrical or another type of stimulus to the detonator from the detonation control device. A detonating cord, by contrast, is a continuous thread of highly explosive material. Once a stimulus for detonation is applied at the output end of a detonating cord remote from the detonator, the detonating cord detonates along the length thereof in a progressive manner. Shock tubes function in a similar manner. Conductive wires, by contrast, convey electrical current to the explosive device, thereby initiating the detonations of the explosive material of the explosive device.
The use of detonators and transmission lines permits safe, remote initiation of the explosion of explosive devices, but neither is of itself capable of generating adequate energy to produce a shock front suitable to the needs of mining, construction, or seismic survey activity. Therefore, a transmission line or a detonator is used to explode a larger explosive device that is generally made of a less sensitive explosive material than is the detonator or the detonating cord.
An explosive device thus functions to amplify the energy of a detonator, a shock tube, or a detonating cord into an explosion sizable enough to produce a shock wave front that effects useful work. In mining and construction activity, the work performed by the shock wave front is that of initiating the detonation of a relatively insensitive explosive material of large volume. In seismic survey activity, the work performed by the shock wave front is that of producing vibrations that travel through subsurface geological structures and are reflected from the interfaces between subsurface structures possessed of differing qualities. These reflected seismic shock wave fronts are detected remotely from the source of the seismic shock wave front and used in computer calculations to map the locations and extent of such subsurface interfaces between structures possessed of different qualities.
A typical configuration of the elements of a system that produces an explosive detonation used in mining and construction is shown in FIG.
1
. There, a borehole
10
has been drilled to a predetermined depth into a subsurface geological formation
11
, which is to be shattered by explosives, possibly to prepare it for subsequent mechanical removal. An explosive device, in this case an explosive booster device
12
, has been lowered to the bottom
13
of borehole
10
. By way of illustration, operably engaged within explosive booster device
12
is a detonator
14
at the output end of a transmission line, in this case a detonating tube
15
. Detonating tube
15
leads to a selectively operable control device, in this case a detonating tube trigger box
16
. With explosive booster device
12
and detonator
14
thus disposed at the bottom
13
of borehole
10
, a suitable low energy, high volume explosive material
17
has been poured into borehole
10
contacting explosive booster device
12
.
Trigger box
16
is a pedal operated device that ignites a quantity of gun powder comparable in amount to that in a shotgun shell. The gun powder is disposed at the output end of detonating tube
15
remote from detonator
14
. The firing of the quantity of gunpowder in trigger box
16
commences a slow detonation that travels along detonating tube
15
from trigger box
16
to detonator
14
. The arrival of this traveling detonation along detonating tube
15
at detonator
14
sets off detonator
14
, which in turn leads to the explosion of explosive booster device
12
. This explosion produces a shock wave front that travels radially outwardly from explosive booster device
12
. A portion of that shock wave front, which is referred to as a detonating wave front, passes through high volume explosive material
17
, causing the detonation thereof. The entire process is completed within a few milliseconds. In order to contain and drive laterally into geological formation
11
the explosive force of high volume explosive material
17
, the open end
18
of borehole
10
has been stemmed with backfill
19
.
Geological formation
11
in which borehole
10
was drilled and equipped for explosive detonation as shown in
FIG. 1
could be located at the surface of the ground, at the bottom of a mining pit, or underground at the working face of a mine. Typically, an array of boreholes, such as borehole
10
, is prepared together in a rock formation before any detonation occurs. Then, the columns of blasting agent in the borehole matrix are detonated simultaneously or in a nearly simultaneous pattern progression of detonations according to the specific consequences sought. The depth of borehole
10
and the height of the column of the high volume explosive material
17
placed therein are dictated by the nature of geological formation
11
, as well as by the objective of the blasting exercise.
A typical configuration of the elements of a system that produces an explosive detonation used in seismic survey operations is shown in FIG.
2
. There, a borehole
10
has been drilled a predetermined depth into a subsurface geological formation
11
, through which a shock wave front is to be propagated for seismic survey purposes. The shock wave front is reflected off of the interfaces between subsurface structures of differing quality in geological formation
11
. The reflected shock waves are then measured at an array of seismic detectors. The data from the seismic detectors for a number of shock wave fronts from different explosions is then processed to produce a three-dimensional map of the subsurface structures in geological formation
11
.
An explosive device taking the form of explosive seismic device
20
has been lowered to the bottom
13
of borehole
10
. Operably engaged within explosive seismic device
20
is a detonator
14
that communicates with a detonation control box
22
by way of a transmission line taking the form of an electrically conductive wire
21
.
Detonation control box
22
is a hand-operated plunger device that generates an electrical signal that travels along wire
21
from detonation control box
22
to detonator
14
. The arrival of this electrical signal at detonator
14
sets off the highly energetic explosive material of detonator
14
. The energy from detonator
14
in turn causes the explosion of explosive seismic device
20
.
The explosion of explosive seismic device
20
produces a shock wave front that travels radially outward from explosive seismic device
20
, passing through geological formation
11
and being reflected off of subsurface structures therein possessed of differing qualities. The entire process, from activation of detonation control box
22
to the measurement of reflected shock waves at the seismic detectors, is completed in a few milliseconds. To contain the explosive force of explosive seismic device
20
and to drive the resulting shock wave front laterally into geological formation
11
, borehole
10
has been stemmed with backfill
19
. Although borehole
10
is illustrated in
FIG. 2
as being completely stemmed with backfill
19
, boreholes in seismic operations can also be partially stemmed with backfill.
FIG. 3
illustrates a typical configuration of the elements of a system that prod
Badger Farrell G.
Bahr Lyman G.
Clement Roger B.
Nelson Peter A.
The Ensign-Bickford Company
TraskBritt PC
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