CROSS-REFERENCE TO RELATED APPLICATIONS
FIELD OF THE INVENTION
[0002] The present invention relates in general to an explosive cutting charge device, and
in particular, to an explosive cutting charge device that is hermetically sealed and
has a varying explosive charge weight disposed throughout the device to adjust the
cut performance around the entire profile of the device.
BACKGROUND OF THE INVENTION
[0003] Explosive cutting charges are typically comprised of two basic constructions. Perhaps
the most common type is to use a metal-clad linear explosive product such as a linear
shaped charge ("LSC"). The LSC is generally a tube-shaped device that is cut to a
predetermined length, formed to conform to the shape of the surface to be cut, and
then secured into a multi-piece housing to keep the LSC in that shape and to provide
a means for mounting it to the surface to be cut.
[0004] Problems with linear shaped charges include the fact that cut performance cannot
be tailored as desired around the entire cutting perimeter by varying the explosive
charge weight. This is because the LSC design process normally produces a consistent
(i.e., a "fixed core load"), and not a varying charge weight along the entire length
of the LSC. Also, the process of forming an LSC to a specific cut profile involves
bending into different shapes, which creates density gradients, even cracks sometimes,
within the explosive core, thus degrading cut performance. One way to avoid this problem
is to limit the radius of curvature of the LSC when making a bend; however, this limits
the shapes that the LSC can be manufactured into. Also, an LSC typically has a "no-cut
zone" and may also need a "piggy back charge" to bridge the gap between the ends of
an LSC to allow for redundant initiation. Further, the material used to manufacture
LSC is limited to those materials with sufficient ductility to allow for LSC manufacture
using swaging and drawing processes.
[0005] Also, with LSC designs, the initiation interface is preferentially parallel to one
of the LSC legs. Other orientations are possible, but design complexity is oftentimes
thereby increased so as to preserve reliability. In addition, initiating explosive
charge requirements change with LSC sheath material and core load. With LSC-based
designs, the cut profile is limited by LSC formability. Factors that affect formability
are LSC core load, the metal material used for the sheath or tube, and the direction
of cut relative to the bend plane. Although an LSC can be used to make 3-D cutters,
known designs comprise multiple LSC segments that are joined together. Still further,
an LSC that is hermetically sealed is difficult to achieve because an LSC typically
uses adhesive to seal the exposed cord ends, and adhesive seals generally only seal
to the environmental level (1 x 10
-5 cc sec of He). Hermetic seals can also be achieved by welding end closures on the
LSC. However, this welding is difficult due to the LSC shape and the safety risks
associated with welding on product that contains explosive material.
[0006] A second type of explosive cutting charge is formed by pressing bulk explosive against
an explosive liner and into a housing. Other pieces may be needed to seal the explosive
charge, provide the necessary attachment features to secure it against the surface
to be severed, and provide the interface for attachment of the initiation explosive
device. Although most commonly applied to conical shaped charges, which punch holes
through target materials, the pressed charge may be used to as a cutting charge.
[0007] Problems with pressed charges include the fact that cut performance also cannot be
tailored around the entire cutting perimeter because changes in geometry necessary
to change the explosive charge weight make the press tooling relatively complicated
and difficult to control. Also, density gradients typically occur within pressed charges
as the geometry changes. Even changes in the effective length to diameter ratio of
the pressed charge result in density gradients. Further, pressed powder designs are
limited in cutting shape, where the limitations are due to the shape of tooling that
can be used to press charges and with the difficulties associated with getting powder
into complex shapes before pressing. A 3-D cutting charge may require multiple pressings
and may likely be costly to make and unreliable in function.
[0008] What is needed is an explosive cutting charge that can be hermetically sealed and
in which cut performance can be tailored around the entire cutting perimeter by varying
the explosive charge weight.
SUMMARY OF THE INVENTION
[0009] According to an embodiment of the invention, an explosive cutting charge is formed
by machining or otherwise forming a cavity of a desired configuration within a circular
ring of metal cutting material such as copper or aluminum. The cavity may then be
filled with an explosive material. The cutting characteristics of the cutting charge
may be controlled by the selected cross-section configuration of the cavity. The ring
may contain a booster explosive charge with connections to the active portion of the
ring having the cutting metal material. The invention is not limited to circular rings
and can be of any closed or open form (for example, a generally rectangular or a straight
length).
[0010] Advantages of the explosive cutting charge of embodiments of the invention include
the fact that the explosive cutting charge can be hermetically sealed. Also, cut performance
can be tailored around the entire cutting perimeter by varying the explosive charge
weight. Also, cut consistency, which is related to explosive density, is relatively
less variable than prior art explosive cutting charges. Further, cut performance is
consistent around the entire cut profile, which is due to the continuous explosive
cutting charge liner and explosive load. A corollary to the use of a continuous explosive
liner is that the explosive can be hermetically sealed (1 x 10
-6 cc sec of He), for example, by welding the liner to a second piece to achieve a hermetic
seal before loading with explosive material. In addition, initiation reliability is
relatively high and is not affected by cutting charge design.
[0011] In embodiments of the invention, the initiation interface can be located in any orientation
relative to the cutting charge and the explosive interface can be identical within
the entire product family. The product family can include charges that cut radially
inward, radially outward or any angle in between. Further, the cut profile of the
explosive cutting charge of embodiments of the invention can be relatively more complex
that with either an LSC charge or a pressed charge and can have a three-dimensional
cut. The cut profile limitation of embodiments of the invention are primarily based
upon what shape can be made and that can later be filled with explosive material.
Thus, the limitations come from what can be machined, formed, molded, extruded, etc.
A limitation from the filling process may exist, but are not quantified at this time.
BRIEF DECRIPTION OF THE DRAWINGS
[0012] The various embodiments of the present invention can be understood with reference
to the following drawings. The components are not necessarily to scale. Also, in the
drawings, like reference numerals designate corresponding parts throughout the several
views.
[0013] Figure 1 is a perspective view of a ring-shaped explosive cutting charge in accordance
with an embodiment of the invention;
[0014] Figure 2 is a cross-sectional view of the explosive cutting charge of the embodiment
of Figure 1;
[0015] Figure 3 is a perspective view of a ring-shaped explosive cutting charge in accordance
with another embodiment of the invention;
[0016] Figure 4 is a cross-sectional view of the explosive cutting charge of the embodiment
of Figure 3;
[0017] Figure 5 is a cross-sectional view of an alternative embodiment of the explosive
cutting charge of the embodiment of Figure 3;
[0018] Figure 6 is a top view of another embodiment of an explosive cutting charge as part
of a breaching system according to the invention; and
[0019] Figure 7 is a cross-sectional view of the embodiment of the explosive cutting charge
within the breaching system of Figure 6.
DETAILED DESCRIPTION OF THE INVENTION
[0020] The present invention is more particularly described in the following description
and examples that are intended to be illustrative only since numerous modifications
and variations therein will be apparent to those skilled in the art. As used in the
specification and in the claims, the singular form "a," "an," and "the" may include
plural referents unless the context clearly dictates otherwise. Also, as used in the
specification and in the claims, the term "comprising" may include the embodiments
"consisting of" and "consisting essentially of." Furthermore, all ranges disclosed
herein are inclusive of the endpoints and are independently combinable.
[0021] As used herein, approximating language may be applied to modify any quantitative
representation that may vary without resulting in a change in the basic function to
which it is related. Accordingly, a value modified by a term or terms, such as "about"
and "substantially," may not to be limited to the precise value specified, in some
cases. In at least some instances, the approximating language may correspond to the
precision of an instrument for measuring the value.
[0022] In an embodiment of the invention, an explosive cutting charge is formed by machining
or otherwise forming a cavity of a desired configuration within a circular ring of
metal cutting material such as copper or aluminum. The cavity may then be filled with
an explosive material. The cutting characteristics of the cutting charge may be controlled
by the selected cross-section configuration of the cavity. The ring may contain a
booster explosive charge with connections to the active portion of the ring having
the cutting metal material.
[0023] The foregoing and other features of various disclosed embodiments of the invention
will be more readily apparent from the following detailed description and drawings
of the illustrative embodiments of the invention wherein like reference numbers refer
to similar elements.
[0024] Referring to Figure 1, there illustrated is a perspective view of a ring-shaped explosive
cutting charge 100 in accordance with an embodiment of the invention. Referring also
to Figure 2, there illustrated is a cross-sectional view of the explosive cutting
charge 100 of the embodiment of Figure 1. The ring-shaped cutting charge 100 may comprise
a first ring or "liner" 102 with a cavity 104 formed therein. The cavity 104 runs
the entire circumference of the ring-shaped charge 100, thereby eliminating any "no-cut"
zones inherent in prior art LSC designs and also eliminating the need for a "piggy
back charge" to bridge the gap between the ends of a prior art LSC to allow for redundant
initiation. The first ring 102 may be made from a relatively ductile material, such
as a metal (e.g., copper or aluminum) and may have a thickness contoured for enhanced
cutting performance.
[0025] The embodiment of the ring-shaped cutting charge 100 of Figures 1 and 2 also includes
a second, manifold ring 106 made from a metal material. The second ring 106 may be
welded to the first ring 102 prior to the insertion or loading of the explosive material
into the cavity 104. The explosive may comprise a cast cured explosive material. An
advantage of embodiments of the explosive cutting charge 100 of the present invention
includes the fact that the weight of the explosive charge loaded into the cavity 104
may be made to vary throughout the cavity, thereby tailoring the amount of explosive
force emitted at locations around the ring 100 (i.e., the "cut performance"). Also,
by welding the continuous liner ring 102 to the continuous manifold ring 106, a hermetic
seal (1 x 10
6 cc sec of He) can be achieved.
[0026] Figure 2 illustrates the cut profile of the embodiment of the ring-shaped cutting
charge 100 of the invention. The cut profile includes a chevron-shaped cutting charge
area 108 above which is a cylindrically-shaped booster charge area 110. In general,
the cut profile of the ring-shaped cutting charge 100 of embodiments of the invention
can be relatively more complex than with either a prior art LSC or pressed charge.
The cut profile may take on a three-dimensional shape. A limitation of the cut profile
for embodiments of the invention is primarily based on the shape that can be made
by, e.g., machining, and that can later be filled with explosive material. Thus, any
limitation on the cut profile comes from what can be machined, formed, molded, extruded,
etc.
[0027] In the explosive cutting charge 100 of various embodiments of the invention, initiation
reliability of the explosive is relatively high and is not affected by the cutting
charge design. The initiation interface (e.g., the booster charge area) can be located
in any orientation relative to the cutting charge and the explosive interface can
be identical throughout the entire product family. The product family can include
charges that cut radially inward, radially outward or any angle in between.
[0028] Referring to Figures 3 and 4, there illustrated is another embodiment of an explosive
cutting charge 300 in accordance with the invention. The charge 300 is again ring-shaped,
similar to the cutting charge 100 in Figures 1 and 2, and thus the explosive charge
loaded therein is continuous throughout the cutting charge 300. The charge includes
a liner ring 302 and a manifold ring 304 welded together. The chevron-shaped cutting
charge area 306 is oriented to point vertically downward. Located above the cutting
charge area 306 is the area 308 that houses the booster explosive charge.
[0029] In the alternative embodiment of Figure 5, the explosive cutting charge 300 has the
chevron-shaped cutting charge area 306 oriented horizontally. Further, more than one
cutting charge area can be included in a single explosive cutting charge device 300.
That is, for example, the horizontally oriented cutting charge area 306 of Figure
5 can be combined with the vertically oriented cutting charge area 306 of Figure 4
in the same explosive cutting charge device 300.
[0030] Referring to Figures 6 and 7, there illustrated is another embodiment of an explosive
cutting charge 600 as part of a breaching system according to the invention. The explosive
cutting charge 600 of this embodiment comprises a generally oval, closed design with
one or more straight sections 602 connected with a corner section 604. The charge
600 may be used to produce a breach point in, e.g., steel-reinforced concrete or block
structures. An amount of charge required for a typical roof breaching application
needs to have penetrations at least as deep as a 5400 gr/ft charge into steel. The
goal of the breaching system 600 of Figures 6 and 7 is to enhance the cutting capability
of prior designs.
[0031] The cutting charge or breaching system 600 in accordance with this embodiment of
the invention may have one foot long straight sections 602 of shaped charge, wherein
these sections 602 being linked together by the corner sections 604 to form the overall
breaching system breach point size of interest. This design allows more options for
shaped charge design that result in lower explosive core loading. The breaching system
600 takes advantage of a solid copper liner 606 that has a higher density than the
prior art copper polymer liners. This change, coupled with an optimized charge configuration
and non-fragmenting tamper, enhances severance capability.
[0032] Optimizing linear shaped charge cutting performance is a function of many design
variables that work together to form the penetrating explosive jet. Some of the primary
design variables include apex angle, apex height, charge width, charge height, liner
material, liner thickness, explosive material, explosive loading, explosive height
above the apex and the charge ends, standoff, as well as the top angle. The design
goal is to provide an elongated explosive jet that penetrates to the depth of interest.
[0033] The breaching system 600 of this embodiment of the invention comprises two charge
configurations. The first configuration is a straight twelve inch section 602 and
the second is a corner configuration 604 that connects together the straight sections
602. Multiple pieces of each configuration can be used together to form the overall
breaching system 600 to cover the breaching area of interest. A breach point size
of one foot by one foot may be expanded using multiple lengths of the twelve inch
straight sections 602 to form a hole three feet by three feet. The sections 602-604
may fit together using linkages molded into a plastic housing 608 that houses the
explosive charge 610 and the copper liner 606. By having separate sections of linear
shaped charge, twelve inches or less, the piece parts can be easily carried by a soldier
in the field.
[0034] Each individual linear charge segment 602 has a cap well to allow end initiation
by a #12 strength detonator or standard military detonator. This design feature allows
for flexibility for initiation of the breaching system 600. The operator can choose
to initiate in locations that are best for the situation at hand. The cap well may
be designed into the plastic housing 608 on one end of the charge above where the
charges meet. The friable plastic housing 608 holds the explosive charge and the copper
liner 606 and provides feet 612 to add stability for optimum standoff to the target
as well as providing access for a #12 strength or military detonator. The explosive
charge 610 may comprise PBXN-112, which is cast cured into the friable plastic housing
608. Using a cast cured explosive makes manufacturing of the breaching elements efficient.
The plastic housing 608 holds the explosive 610 while minimizing the fragments compared
to those products made from a metal tamper. The goal is to utilize a relatively brittle
low-density plastic that shatters upon impact. Soldier safety is a key concern when
designing any new breaching system. With a 3000 gr/ft (i.e., constant or non-varying)
shaped charge design used to breach a 3 ft by 2 ft hole, there exists approximately
10 ft of explosive charge (4.3 1b of explosive). At 30 feet away, the predicted overpressure
from 4.3 lbs of PBXN-112 is under 0.5 psi. This value is within the safe zone for
human exposure.
[0035] This written description uses examples to disclose the invention, including the best
mode, and also to enable any person skilled in the art to make and use the invention.
The patentable scope of the invention is defined by the claims, and may include other
examples that occur to those skilled in the art. Such other examples are intended
to be within the scope of the claims if they have structural elements that do not
differ from the literal language of the claims, or if they include equivalent structural
elements with insubstantial differences from the literal languages of the claims.
All citations referred herein are expressly incorporated herein by reference.
1. An explosive cutting charge device, comprising:
cutting material arranged in a configuration;
a cavity formed in the cutting material configuration; and
cast cured explosive material filling the cavity, wherein a weight of the explosive
material is varying or non-varying along a length of the cavity, thereby forming a
cutting charge with a predetermined cut profile shape in the explosive cutting charge
device.
2. The explosive cutting charge device of claim 1, wherein the cutting material comprises
a metal.
3. The explosive cutting charge device of claim 1, wherein the cutting material comprises
one of aluminum and copper.
4. The explosive cutting charge device of claim 1, wherein the cutting material configuration
comprises an enclosed configuration, wherein the cavity is formed throughout the entire
enclosed cutting material configuration.
5. The explosive cutting charge device of claim 1, wherein the cutting material configuration
comprises a closed ring, wherein the cavity is formed throughout the entire closed
ring.
6. The explosive cutting charge device of claim 1, further comprising a manifold connected
with the cutting material configuration, thereby forming a hermetic seal of the cutting
material configuration.
7. The explosive cutting charge device of claim 1, further comprising a manifold connected
with the cutting material configuration, wherein the manifold includes a cavity formed
therein, wherein a booster charge is located within the manifold cavity, wherein the
booster charge is in communication with the explosive material within the cavity of
the cutting material configuration.
8. The explosive cutting charge device of claim 1, wherein one or more cut profile cutting
charge shapes are formed in the explosive cutting charge device.
9. An explosive cutting charge device, comprising:
cutting material arranged in an enclosed configuration;
a cavity formed throughout the entire cutting material enclosed configuration; and
cast cured explosive material filling the cavity, wherein a weight of the explosive
material is varying or non-varying along a length of the cavity, thereby forming a
cutting charge with a predetermined cut profile shape in the explosive cutting charge
device.
10. The explosive cutting charge device of claim 9, wherein the enclosed configuration
comprises a ring.
11. The explosive cutting charge device of claim 9, wherein the cutting material comprises
a metal.
12. The explosive cutting charge device of claim 9, wherein the cutting material comprises
one of aluminum and copper.
13. The explosive cutting charge device of claim 9, further comprising a manifold connected
with the cutting material configuration, thereby forming a hermetic seal of the cutting
material configuration.
14. The explosive cutting charge device of claim 9, further comprising a manifold connected
with the cutting material configuration, wherein the manifold includes a cavity formed
therein, wherein a booster charge is located within the manifold cavity, wherein the
booster charge is in communication with the explosive material within the cavity of
the cutting material configuration.
15. The explosive cutting charge device of claim 9, wherein one or more cut profile cutting
charge shapes are formed in the explosive cutting charge device.
16. An explosive cutting charge device, comprising:
a plurality of explosive charge cutting segments that comprises a breaching device,
wherein each segment comprises a housing that contains an amount of cast cured explosive
material therein, wherein a weight of the explosive material is varying or non-varying,
thereby forming a cutting charge with a predetermined cut profile shape in the explosive
cutting charge device, and wherein each segment has a cap well.
17. The explosive cutting charge device of claim 16, wherein the housing comprises a friable
plastic, and wherein the housing further comprises a copper liner.
18. The explosive cutting charge device of claim 16, wherein the housing comprises a friable
plastic, and wherein the housing further comprises an unvulcanized copper/polymer
compound liner.
19. The explosive cutting charge of claim 16, wherein the plurality of explosive cutting
charge segments are arranged in an enclosed configuration.
20. The explosive cutting charge device of claim 16, wherein one or a plurality of cap
wells are used to detonate the entire device.