U.S. patent application number 10/419860 was filed with the patent office on 2004-03-25 for tin alloy sheathed explosive device.
Invention is credited to Hannagan, Harold W., Lee, Dennis R., Posson, Philip L..
Application Number | 20040055495 10/419860 |
Document ID | / |
Family ID | 29273014 |
Filed Date | 2004-03-25 |
United States Patent
Application |
20040055495 |
Kind Code |
A1 |
Hannagan, Harold W. ; et
al. |
March 25, 2004 |
Tin alloy sheathed explosive device
Abstract
A substantially lead-free tin alloy composition that may be used
with sheathed explosive devices in a variety of linear explosive
devices, such as ignition cords, mild detonating cords, and linear
shaped charges. The tin alloy may also be used as a liner for
shaped explosive devices.
Inventors: |
Hannagan, Harold W.; (Napa,
CA) ; Lee, Dennis R.; (Vacaville, CA) ;
Posson, Philip L.; (Cave Creek, AZ) |
Correspondence
Address: |
SWIDLER BERLIN SHEREFF FRIEDMAN, LLP
3000 K STREET, NW
BOX IP
WASHINGTON
DC
20007
US
|
Family ID: |
29273014 |
Appl. No.: |
10/419860 |
Filed: |
April 22, 2003 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60374991 |
Apr 23, 2002 |
|
|
|
Current U.S.
Class: |
102/307 |
Current CPC
Class: |
F42B 1/032 20130101;
F42B 3/28 20130101; C06C 5/04 20130101 |
Class at
Publication: |
102/307 |
International
Class: |
F42B 001/02 |
Claims
We claim:
1. A linear explosive device comprising: a sheath that is
substantially lead-free, wherein said sheath is formed from a tin
alloy comprising: a percentage of zinc of from about 1 percent to
about 6 percent by weight, and a percentage of tin of from about 99
to about 94 percent by weight; wherein said sheath at least
partially encases a reactive material selected from the group
consisting of explosive material, deflagrating material,
pyrotechnic material, and mixtures thereof.
2. The linear explosive device of claim 1, wherein the percentage
of zinc in the tin alloy is about 4 percent by weight.
3. The linear explosive device of claim 1, wherein the percentage
of zinc in the tin alloy is about 6 percent by weight.
4. The linear explosive device of claim 1, wherein said device is
an ignition cord.
5. The linear explosive device of claim 1, wherein said device is a
linear shaped charge.
6. The linear explosive device of claim 1, wherein said device is a
mild detonating cord.
7. An aircraft canopy fracturing system for creating an opening in
the canopy comprising: a transparent material forming at least part
of the aircraft canopy; and a linear explosive device, wherein said
linear explosive device comprises a sheath that is substantially
lead-free, and wherein said sheath is formed from a tin alloy
comprising: a percentage of zinc of from about 1 percent to about
15 percent by weight, and a percentage of tin of from about 80 to
about 99 percent by weight; wherein said sheath at least partially
encases a reactive material selected from the group consisting of
explosive material, deflagrating material, pyrotechnic material,
and mixtures thereof.
8. The aircraft canopy fracturing system of claim 7, wherein the
percentage of zinc in the substantially lead-free sheath is from
about 1 to about 5 percent by weight.
9. The aircraft canopy fracturing system of claim 7, wherein the
percentage of zinc in the substantially lead-free sheath is from
about 7 to about 13 percent by weight.
10. A linear explosive device comprising: a sheath that is
substantially lead-free, wherein said sheath is formed from a tin
alloy comprising: a percentage of zinc of from about 1 percent to
15 percent by weight, and a percentage of tin of from about 80 to
about 99 percent by weight; wherein said sheath at least partially
encases a reactive material selected from the group consisting of
explosive material, deflagrating material, pyrotechnic material,
and mixtures thereof.
11. The linear explosive device of claim 10, wherein said device is
an ignition cord.
12. The linear explosive device of claim 10, wherein said device is
a linear shaped charge.
13. The linear explosive device of claim 10, wherein said device is
a mild detonating cord.
14. A shaped charge explosive device comprising: a concave tamper;
a reactive material disposed within the tamper, wherein the
reactive material is selected from the group consisting of
explosive material, deflagrating material, pyrotechnic material,
and mixtures thereof; and a substantially lead-free liner formed
from a tin alloy comprising: a percentage of zinc of from about 1
percent to about 6 percent by weight, and a percentage of tin of
from about 99 to about 94 percent by weight; wherein said liner at
least partially encases the reactive material within the
tamper.
15. The shaped charge explosive device of claim 14, wherein the
percentage of zinc in the substantially lead-free liner is from
about 1 to about 5 percent by weight.
16. The shaped charge explosive device of claim 14, wherein the
percentage of zinc in the substantially lead-free liner is from
about 7 to about 13 percent by weight.
Description
TECHNICAL FIELD
[0001] This invention relates generally to linear explosive
devices, such as detonating cords and linear shaped charges, having
a lead-free tin alloy sheath or liner and related systems using
such devices. The invention further relates to a lead-free tin
alloy sheathed devices and related systems using them.
BACKGROUND OF THE INVENTION
[0002] Certain types of energetic linear shaped explosive devices,
such as detonating cords and linear shaped charges, can be used for
severing, cutting, fracturing, or impacting a target material or
structure. These devices have a wide range of potential uses, such
as automotive and aircraft safety systems, aircrew escape systems,
military weapon ignition systems, and commercial blasting.
[0003] One example of how such devices may be used is an aircraft
canopy fracturing system. These systems help reduce bodily impact
with and/or injury from the aircraft canopy during seat ejection.
As an ejection seat is jettisoned from an aircraft cockpit, it
passes through the portion of the aircraft where the aircraft
canopy is located during normal flight conditions. Preferably,
during an emergency event that requires evacuation of the aircraft
during flight, the canopy is jettisoned before seat ejection. But
in some instances seat ejection begins before the canopy has been
jettisoned.
[0004] When seat ejection begins prior to jettisoning the aircraft
canopy, the ejection seat must be able to blast entirely through
the canopy in order to escape from the aircraft. A canopy
fracturing system helps reduce the risk to the pilot or occupant of
the aircraft as the ejected seat forces its way through the canopy
by creating an opening in the canopy or by weakening the structure
of the canopy so that the canopy breaks apart under lower impact
forces. In these systems, an explosive or pyrotechnic material
inside the liner or sheath of a of a linear explosive device near
the inside of the canopy propels the liner outward at a high
velocity, thereby penetrating or shattering the canopy before the
ejected seat can collide into the canopy.
[0005] In general, the construction of energetic linear products
historically involves a malleable outer metallic sheath and an
inner core of reactive material. This class of products is normally
produced by filling a length of relatively large diameter metal
tubing with the chosen energetic material, and subsequently
reducing the diametral cross-section by metalworking processes such
as swaging and drawing. The resultant product is greatly reduced in
diameter and substantially elongated. The choice of metal tubing
from which to produce these products is predicated upon the
physical properties of the material, which, among other properties,
must possess exceptional ductility and low work hardening.
[0006] Tubing manufactured from a variety of metallic lead (Pb) or
lead alloys has historically been used to produce these types of
products. One such example can be found in U.S. Pat. No. 3,147,707
to Caldwell. In the past, the use of lead to form the metallic
sheath was desired because of its high density, which in turn
yielded good penetration and shattering forces and also because of
its good metalworking properties. However with the increasing
awareness of environmental contamination and human health concerns
regarding lead poisoning, the use of lead based products has been
prohibited in many applications. Accordingly, it is desirable to
find a sheath or liner material suitable for replacing metallic
lead in order to address human health and welfare concerns that
also possesses acceptable metalworking properties.
[0007] Rodney et al., U.S. Pat. No. 5,333,550, which issued on Aug.
2, 1994 discloses a "lead-free" tin alloy sheath comprised of
mostly tin with the balance antimony. The alloys described in
Rodney '550 include a binary composition (97 percent tin and 3
percent antimony), a ternary composition (96.5 tin, 1.5 percent
copper, and 2 percent antimony), and a quaternary composition (98.5
percent tin, 1 percent bismuth, 0.25 percent copper, and 0.25
percent silver). Rodney '550 also allows lead to be present in the
compositions as an impurity in amounts up to 1.42 percent.
SUMMARY OF THE INVENTION
[0008] The present invention is directed to tin alloys that may be
used to make a sheath or liner for a wide variety of explosive
devices. One embodiment of the present invention involves linear
explosive devices having a sheath that is substantially lead-free.
In this embodiment, the sheath is formed from a tin alloy having
from about 1 to about 6 percent zinc by weight and from about 99 to
about 94 percent tin by weight. The sheath at least partially
encases a reactive material, such as explosive materials,
deflagrating materials, pyrotechnic materials, and mixtures
thereof.
[0009] In one embodiment, the percentage of zinc in the tin alloy
sheath is about 4 percent by weight, while in another embodiment it
is about 6 percent by weight. The linear explosive device may be a
wide variety of devices, such as an ignition cord, a linear shaped
charge, or a mild detonating cord.
[0010] While the present invention may have several uses and work
in a wide array of systems, one embodiment involves an aircraft
canopy fracturing system for creating an opening in the canopy.
This embodiment involves a transparent material that forms at least
part of the aircraft canopy and a linear explosive device. In one
embodiment, the linear explosive device of the canopy fracturing
system has a sheath formed from a tin alloy having from about 1 to
about 15 percent zinc by weight and from about 80 to about 99
percent tin by weight. The reactive material of the linear
explosive device of this embodiment may include explosive material,
deflagrating material, pyrotechnic material, and mixtures
thereof.
[0011] In one embodiment, the sheath of the aircraft canopy
fracturing system has from about 1 to about 5 percent zinc by
weight, while in another the amount of zinc present is from about 7
to about 13 percent of zinc by weight.
[0012] In yet another embodiment of the present invention involves
a linear explosive device having a sheath that is made from a tin
alloy comprising from about 1 to about 15 percent zinc by weight
and from about 80 to about 99 percent by weight of tin. One
embodiment is further directed toward using the tin alloy in a
shaped charge explosive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 shows a cross-sectional view of a linear shaped
charge having a tin alloy sheath contemplated by the present
invention;
[0014] FIG. 2 shows a cross-sectional view of a mild detonating
cord or of an ignition cord having a tin alloy sheath contemplated
by the present invention;
[0015] FIG. 3 shows a cross-sectional side view of a shaped charge
including a tin alloy sheath contemplated by the present
invention;
[0016] FIG. 4 is a graph of penetration vs. standoff for the linear
shaped charge of Example 2;
[0017] FIG. 5 is a graph of penetration vs. standoff for the linear
shaped charge of Example 3; and
[0018] FIG. 6 is a graph of the optimum standoff distance in
relationship to the coreload of the linear shaped charges of
Examples 2 and 3.
DETAILED DESCRIPTION OF THE SUBJECT INVENTION
[0019] The present invention is directed toward a tin alloy
material that can replace traditional lead-based materials in order
to meet environmental health standards while also being compatible
with metalworking requirements. In general, the invention relates
to a wide variety of energetic linear or shaped products using a
tin alloy metallic sheathing or liner. Referring to FIG. 1, the tin
sheath 10 in which an explosive core load 12 is disposed is
comprised of an alloy having 87 to 99 percent by weight tin and the
balance zinc. The amount of tin in the alloy may be less than the
preferred range stated above. For instance, the amount of tin in
the alloy may be at least about 80 percent, or alternatively may
have at least about 83 percent tin. Likewise, the upper range
stated above may also be lower in some alternative embodiments. For
instance, the amount of tin in the alloy may be less than about 97
percent, or even further limited to about 94 percent or less. These
upper and lower ranges can also be combined in any fashion to
create different ranges for the amount of tin in the alloy, such as
ranges from about 80 percent to about 97 percent, from about 83
percent to about 94 percent, and so on.
[0020] A second component of the alloy used in the present
invention is zinc. In general, higher amounts of Zinc in the alloy
increases the rigidity of the material. Thus, by varying the
amounts of Zinc and Tin in the alloy, it is possible to obtain
different physical properties of the alloy. This allows the sheath
material to be tailored to the particular application in which the
device will be used.
[0021] In one embodiment of the present invention, the amount of
zinc added to the alloy causes the rigidity of the sheath to be
increased by about 5 percent or greater than the rigidity of a
similarly constructed sheath made substantially of tin. More
preferably, the rigidity of the sheath is increased by about 10
percent or more from the addition of zinc. Even more preferably,
the addition of zinc to the alloy increases the rigidity of the
sheath by about 15 percent.
[0022] The amount of Zinc added to the alloy also may be described
in terms of its percentage by weight. For instance, the alloy
forming the sheath may comprise from about 1 to about 15 percent
zinc by weight and more preferably comprise from about 1 to about
13 percent zinc by weight. For purposes of this application, a high
zinc alloy may have from about 7 to about 13 percent zinc or more,
while a low zinc alloy may have from about 1 to about 5 percent
zinc alloy. Alternatively, a high zinc alloy may have from greater
than about 8 percent zinc by weight. Likewise, a low zinc alloy may
have less than about 3 percent zinc. As a preferred minimum for any
range of zinc stated herein, the lowest amount of zinc present is
greater than about 0.1 percent zinc by weight.
[0023] The tin/zinc alloy of the present invention has the
advantages of being compatible with metalworking requirements and
also meeting human environmental health standards. In order to meet
human environmental health standards, it is preferred that the
alloy is essentially free of lead. The presence of other impurities
or additives, however, may be possible without departing from the
invention. This invention principally applies to the composition of
linear energetic products, which can take many forms. For example,
this invention can be applied to linear shaped charges, mild
detonating cords, ribbon cords, linear time delays, pyrotechnic
ignition cords, thermal-detonating cords and a variety of other
related products.
[0024] The embodiment of FIG. 1 illustrates an external lead-free
tin alloy sheath 10 having a chevron cross section that surrounds
the explosive core load 12. Preferably, the angle of the chevron
shape is from about 80 to about 100 degrees, and more preferably is
from about 85 degrees to about 95 degrees. In one embodiment, the
angle of the chevron is about 90 degrees with a tolerance of
approximately 3 degrees. The chevron may have other angles and
configurations depending upon the particular application in which
the device will be used.
[0025] In addition to the applicability of the present invention to
a linear shaped charge device as shown in FIG. 1, a skilled artisan
would appreciate that the tin/zinc alloy may be used in different
types of explosive products. For example, FIG. 2 illustrates the
tin/zinc alloy discussed herein used with an ignition cord or with
a mild detonating cord. Other, shaped devices, such as the
generally conical device illustrated in FIG. 3, may also benefit
from use of a tin/zinc alloy. These illustrations, however, do not
limit the applicability of the tin/zinc alloy to other devices,
such as the ones described above.
[0026] Thus, the present invention may be used in the three types
of linear explosive products described by FIGS. 1 and 2, but also
may also be used in applications other than linear devices. A
general description of each of these devices is provided below.
[0027] A linear shaped charge (LSC), such as shown in FIG. 1, may
have a secondary detonating type of explosive, such as PETN, RDX,
HNS, DIPAM, HMX, CH-6, PBXN-5, and HNS II, is loaded into tube made
of a tin/zinc alloy as described herein and then processed by
mechanically swaging and roll forming or stationary die swaging
into a chevron shape that is capable of cutting various target
materials using the Monroe effect of penetration or severence.
[0028] A mild detonating cord (MDC) and an ignition cord,
illustrated in FIG. 2, also may have a secondary detonating type of
explosive as described above that is similarly loaded into a
tin/zinc alloy metallic tube and then processed by swaging and
drawing into a round circular cross-section containing any
specified coreload (grains/ft).
[0029] An ignition cord may have various fuel/oxidizer mixes of
pyrotechnic material loaded into a tin/zinc alloy tube as described
herein and then processed by a mechanical reduction method of
swaging and drawing, so as to produce a linear product that can be
used as a deflagrating ignition source for all types of propellant
gas generators or solid propellant. The coreload can range from a
fraction of a grain per foot to several hundred grains per foot
depending upon the application.
[0030] As shown in FIG. 3, the tin/zinc alloy of the present
invention also may be applied to shaped charges. In general, a
shaped device may have a concave tamper which receives explosive
material and a tin/zinc alloy liner that holds the explosive
material in place and which defines and maintains the explosive
material in a concave configuration to focus the energy of
detonation. Upon detonation, the liner forms a penetrating jet that
propels the tamper at a high velocity toward a target. The tamper
need not be made of the same tin/zinc alloy as the liner, and in
fact, need not be made of a tin/zinc alloy at all.
[0031] A skilled artisan would recognize that the present invention
may be used with other types of applications than described herein,
and that other cross-sectional shapes for linear devices may also
be used, such as rounded, semi-circular, polygonal, or the
like.
[0032] The hollow center of the sheath 10 may be filled with
pyrotechnics either in the form of ignition powder, detonating
powder, or any suitable explosive composition. Several examples of
explosive compositions have been provided above, and additional
compositions may be used in place of the ones described without
departing from the spirit and scope of the present invention. The
selection of a suitable explosive composition ultimately depends
upon the application or intended used of the device.
[0033] The following examples further illustrate that the
advantages and features of the present invention. These features
include a linear shaped explosive device having a lead-free sheath
or liner that is effective for use in an aircraft canopy fracturing
system.
EXAMPLE 1
Metal Sheathed Detonating Cords
[0034] A tube was made from an alloy having a nominal composition
of 92 percent tin and 8 percent zinc, and having an outside
diameter of 0.825 inches and an inside diameter of 0.500 inches.
The tube was filled with HNS II explosive. The ends of the tube
were sealed, and the loaded tube was subsequently reduced in
diameter by a swaging and drawing process. The final diameter of
the linear detonating cord product was 0.074 inches.
[0035] A 12-inch length of the detonating cord was spiral-wrapped
around a 0.250-inch diameter mandrel to examine the flexibility of
the product. The cord was undamaged and demonstrated good strength
and flexibility.
[0036] A second 12-inch length of the detonating cord was tested to
determine the velocity of detonation. A velocity of 6500 meters per
second was recorded, which is regarded as comparable to lead (Pb)
sheathed detonating cords.
[0037] A third 12-inch length was bonded to the surface of a
12-inch by 12-inch square piece of 0.250-inch thick stretched
acrylic, of the type used in construction of aircraft canopy
transparencies. The acrylic fractured properly when the cord was
detonated.
EXAMPLE 2
Linear Shaped Charges
[0038] As in Example 1, a tube was filled with HNS II explosive and
the ends sealed. The loaded tube was progressively swaged until
arriving at a linear shaped charge (LSC) geometry per FIG. 1. This
geometry yielded a coreload of 20 grains per foot of explosive. A
12-inch length of the LSC was attached to a 0.50-inch thick,
2024-T4 aluminum target plate. The LSC was angled in relation to
the target plate surface, so that one end was resting in direct
contact with the plate (i.e., zero standoff distance) and the
opposite end was spaced 0.125-inches off the surface of the plate.
This tapered standoff provides a means of assessing the distance
between the LSC and the target required for optimum performance.
The LSC was detonated and the depth of the resultant groove in the
plate was measured at one-inch intervals. The plotted data appears
in FIG. 4. These data confirm the anticipated performance of a high
efficiency linear cutting charge.
EXAMPLE 3
Linear Shaped Charges
[0039] As in Example 2, a loaded tube was processed by swaging
until arriving at the dimensions shown in FIG. 1. This geometry
yielded an LSC having a coreload of 40-grains per foot of
explosive. The LSC was tested in the manner described in Example 2,
except that the standoff from the target ranged from zero to 0.250
inches. The plot of resultant target penetration vs. standoff
distance is presented in FIG. 5. These data confirm the anticipated
performance of a highly efficient linear cutting charge.
[0040] The data from Examples 2 and 3 were then integrated to
produce the plot presented in FIG. 6, showing the optimum standoff
distance in relationship to the coreload of the LSC.
EXAMPLE 4
Linear Shaped Charges
[0041] A tube made from an alloy having a nominal composition of 96
percent tin and 4 percent zinc was loaded and processed in the
manner described in Examples 2 and 3. From this loaded tube, linear
shaped charges were produced in a variety of coreloads, nominally
between 10 and 60 grains per foot. These various LSC specimens were
then performance tested by conducting penetration tests into
2024-T351 aluminum target plates in the manner described in
previous examples. The resultant data is presented in FIG. 6. It
was determined that the performance of these specimens is
consistent with the known performance of high efficiency lead (Pb)
sheathed LSC.
[0042] Certain of these LSC specimens were performance tested for
penetration into mild steel target plates at zero standoff, a
routine quality control lot acceptance test. It was shown that
these specimens performed comparably with high efficiency lead (Pb)
sheathed LSC.
EXAMPLE 5
Linear Shaped Charges
[0043] As in Examples 1-4, a variety of tubes having a wide range
of tin/zinc composition were loaded and tested for mechanical as
well as detonation properties. These consisted of the following
tin/zinc alloys:
1TABLE 1 Sample No. Tin (% by wt.) Zinc (% by wt.) 1 about 92 about
8 2 about 94 about 6 3 about 96 about 4 4 about 98 about 2
[0044] Each of these compositions was found to process and perform
substantially equally, although it was noted that as the amount of
Zinc in the composition was increased, the alloy exhibited greater
rigidity. As discussed above, this feature allows the sheath of a
device to be customized to the particular application at hand. It
can be seen therefore that the physical requirements of the
specific application can be tailored by the choice of the specific
tin/zinc alloy chosen.
[0045] If there are any additional constituents of the tin/zinc
alloy, it is preferred that they do not adversely affect the
metalworking properties of the alloy. It is further preferred that
any additional constituents do not raise significant human health
and welfare concerns. For instance, it is preferred that the alloy
used remain substantially lead-free, such as by using an alloy
having no more than about 2 percent lead by weight either as an
impurity or as a constituent part of the alloy. More preferably,
however, the substantially free alloy has less than about 1 percent
lead, and even more preferably has no lead. One embodiment of the
present invention addresses these two desired features of health
and workability by forming the sheath or liner from an alloy
consisting essentially of tin and zinc in any of the amounts
described herein. Thus, any other constituents that may be present
in the alloy do not adversely affect human health and welfare
concerns or desired metalworking parameters.
[0046] While the invention has been described in detail with
reference to particular preferred embodiments, persons skilled in
the art will appreciate that various alterations may be made to the
invention as described without departing from the intent, spirit,
and scope of the invention. As such, it is intended that these
variations, adaptations, modifications, and equivalent arrangements
of the present invention fall within the scope of the invention and
the appended claims.
* * * * *