U.S. patent application number 12/301162 was filed with the patent office on 2009-07-16 for detonation interrupter.
This patent application is currently assigned to BLASTECH LTD.. Invention is credited to Andrew Tyas, James Arthur Warren.
Application Number | 20090178548 12/301162 |
Document ID | / |
Family ID | 36660235 |
Filed Date | 2009-07-16 |
United States Patent
Application |
20090178548 |
Kind Code |
A1 |
Tyas; Andrew ; et
al. |
July 16, 2009 |
DETONATION INTERRUPTER
Abstract
A disruptor (10) has a plastics barrel (12) cast from
unreinforced polyurethane so that only plastic deformation of the
barrel occurs during initiation of a cartridge (18) a discharge of
a water charge (24).
Inventors: |
Tyas; Andrew; (Sheffield,
GB) ; Warren; James Arthur; (Sheffield, GB) |
Correspondence
Address: |
Studebaker & Brackett PC
1890 Preston White Drive, Suite 105
Reston
VA
20191
US
|
Assignee: |
BLASTECH LTD.
Sheffield
UK
|
Family ID: |
36660235 |
Appl. No.: |
12/301162 |
Filed: |
May 15, 2007 |
PCT Filed: |
May 15, 2007 |
PCT NO: |
PCT/GB07/01812 |
371 Date: |
February 17, 2009 |
Current U.S.
Class: |
86/50 |
Current CPC
Class: |
F42B 33/062 20130101;
F41B 9/0046 20130101 |
Class at
Publication: |
86/50 |
International
Class: |
F42B 33/06 20060101
F42B033/06 |
Foreign Application Data
Date |
Code |
Application Number |
May 16, 2006 |
GB |
0609670.5 |
Claims
1-17. (canceled)
18. A disruptor comprising a barrel a breech mechanism at a breech
end of the barrel to receive a cartridge of deflagrating
propellant; a charge of liquid, seals in the barrel to prevent the
liquid charge leaking from the muzzle end of the barrel and from
contacting the cartridge; wherein the barrel is cast in a mould
from plastics material whereby, when the cartridge is initiated to
drive the charge from the barrel, the material of the barrel is
distorted plastically but is not fractured.
19. A disruptor as claimed in claim 18, in which the plastics
material is a polyurethane.
20. A disrupter as claimed in claim 18, in which the plastics
material has a static failure strength of between 20 and 60
MPa.
21. A disrupter as claimed in claim 20, in which the plastics
material has a static failure strength of between 30 and 50
MPa.
22. A disrupter as claimed in claim 18, in which the barrel is
between 200 and 600 mm long, has an inner diameter of between 20
and 40 mm and a wall thickness of between 5 and 15 mm.
23. A disrupter as claimed in claim 22, in which the barrel is
between 300 and 500 mm long, has an inner diameter of between 25
and 35 mm and a wall thickness of between 7 and 12 mm.
24. A disriptor as claimed in claim 23, in which the barrel is
between 380 and 420 mm long, has an inner diameter of between 26
and 30 mm and a wall thickness of between 7 and 9 mm.
25. A disrupter as claimed in claim 18, in which the barrel has a
mass of between 200 and 600 g.
26. A disrupter as claimed in claim 25, in which the barrel has a
mass of between 300 and 500 g.
27. A disrupter as claimed in claim 26, in which the barrel has a
mass of between 380 and 420 g.
28. A disrupter as claimed in claim 18, in which the barrel
withstands a propulsive pressure generated at its breech end of
between 500 and 700 bar applied for up to 10 milliseconds.
29. A disrupter as claimed in claim 18, in which the liquid charge
has a mass of between 100 and 150 g.
30. A disruptor as claimed in claim 18, in which the plastics
material is unreinforced by any thing that is not poured with the
plastics material into the mould.
31. A disrupter as claimed in claim 18, in which the barrel has a
cast thread for connection of a breech cap.
32. A method of making a disrupter, comprising the steps of casting
a barrel from thermoplastic polymer in mould; cooling the polymer
so that it solidifies and removing it from the mould; inserting a
deflagrating propellant cartridge at a breech end of the barrel;
connecting on a breech cap; inserting a water projectile, and
providing electrical connections to the cartridge for firing
same.
33. A method as claimed in claim 16, in which the mould is provided
with an internal thread formation at one end of the mould, said
removing step including unscrewing the barrel from the mould; and
said connecting of the breech cap comprises screwing it onto the
thread on the barrel.
Description
[0001] This invention relates to an interrupter, also known as a
disrupter. Interrupters are devices employed to disrupt explosives,
particularly terrorists' explosives.
BACKGROUND
[0002] Interrupters (or disruptors) are distinct from dearmers, at
least in the context of this patent specification. Both dearmers
and interrupters function by driving a projectile into munitions,
disrupting the detonation process so that the explosives in the
munitions are not detonated before the detonation apparatus is
destroyed by the action of the projectile.
[0003] In the case of military munitions, the explosives are almost
invariably encased in metal such as steel so that the dearmer
itself needs to be powered by explosive or propellant means with
sufficient force in order to penetrate the casing. Indeed, with
dearmers in relation to military munitions, the personnel wishing
to disarm the munitions often know its design. This means that
solid projectiles, directed specifically at the detonation
apparatus or fuse of the munitions are often beneficial.
[0004] However, in the case of terrorist bombs (Improvised
Explosive Devices, IEDs), these are invariably an unknown quantity,
but often not usually encased in a steel jacket. Therefore
interrupters do not use a solid projectile and water is most
usually the projectile employed. High velocity solid projectiles
may be detrimental in this case, since the pressure generated by
their impact may inadvertently cause detonation of the (unknown)
explosive material. The propellant is therefore generally a
deflagrating charge that expands rapidly but which produces a less
intense driving impetus than a detonating charge. Water spreads
after it has been fired, and on impact with any target. Therefore
if the exact location of the detonation apparatus is unknown within
the package of munitions, there is a still a high probability of
the projectile being able to disrupt the target.
[0005] Even without an explosive charge, however, the rapid burning
of the propellant in an interrupter accelerates the projectile with
significant force. Consequently, a current design employs a steel
tube, closed at a breech end that houses a propellant cartridge. A
water projectile is disposed in front of the cartridge. The
interrupter is often deployed on a robotic vehicle because, with
terrorist bombs, there is often a danger of remote or timed
detonation that may pose a significant risk to personnel. Robotic
vehicles are often small and nimble, enabling them to be deployed
in many different locations where terrorist bombs may be left.
However, they need to carry other equipment such as cameras so that
they can be remotely steered and aimed. Consequently, disruptors
generally represent a significant load for the robotic vehicle and
reduction of this load is highly desirable.
[0006] GB-A-2083894 discloses a dearmer having a steel barrel, and
metal or water projectile, and the arrangement is typical of that
genre of apparatus, whereas GB-A-2030684 discloses a disrupter
having a similar construction but wherein the projectile, being
either water or a cylindrical body, is driven by expanding gases of
a propellant.
[0007] U.S. Pat. No. 4,779,511 discloses a disposable dearmer which
has a relatively light body, and is only so strong as to "contain
the explosive long enough to expel the slug with the proper
velocity". It is suggested that glass-fibre reinforced plastics may
be suitable, but accepts that the body may be damaged or destroyed
on detonation.
[0008] WO-A-03/058155 discloses an explosive disruptor which is
characterised in being light, indeed, made of plastics material.
The plastics housing contains a precise and predetermined explosive
charge and a projectile. The plastics casing disintegrates on
detonation and the projectile, as well as the explosive charge can
be selected and sized to suit the target. However, although light,
the complete disintegration of the housing and the explosive charge
poses a significant risk of damaging a robotic vehicle, and
surrounding infrastructure.
[0009] It is an object of the present invention to provide a
disruptor that is light but does not pose a significant risk to its
surroundings when fired.
BRIEF SUMMARY OF THE DISCLOSURE
[0010] In accordance with the present invention, there is provided
a disrupter comprising [0011] a barrel [0012] a breech mechanism at
a breech end of the barrel to receive a cartridge of deflagrating
propellant; [0013] a charge of liquid, [0014] seals in the barrel
to prevent the liquid charge leaking from the muzzle end of the
barrel and from contacting the cartridge; wherein [0015] the barrel
is cast in a mould from plastics material whereby, when the
cartridge is initiated to drive the charge from the barrel, the
material of the barrel is distorted plastically but is not
fractured.
[0016] By not being fractured is meant that expanding propellant
gases from the initiated cartridge do not escape through the barrel
wall, but serve only to drive the charge along the barrel, subject
to any loss of energy through such plastic deformation of the
barrel wall.
[0017] The barrel wall, at least in the vicinity of the cartridge,
must be thick enough so that the plastics material can withstand
the strains imposed by initiation and subsequent expansion of the
propellant gasses. The surprising element is how thin the wall can
be and yet be strong enough to withstand such strains, at least on
one occasion, in any event. The absolute thickness depends on the
nature of the plastics material, as well as the strains imposed by
the cartridge.
[0018] Polyurethane is a suitable material. For example, a barrel
approximately 400 mm long, inner diameter 27 mm and wall thickness
8 mm has a mass of around 450 g, and can withstand a propulsive
pressure generated at the breech end of in excess of 500 bar
applied for several milliseconds. This is sufficient to propel a
mass of water of 100-150 g with sufficient velocity to form an
effective disruptor jet. The barrel may undergo significant plastic
deformation but does not fail. It is important that the barrel does
not fail, both to retain the propulsive pressure in order to
produce a jet of sufficient velocity, and to eliminate fragment
hazards which may cause significant collateral damage.
[0019] Polyurethane, with a static failure strength of between
30-50 MPa, has been found to perform well. A barrel of such
dimensions, exposed to a static internal pressure would undoubtedly
fail at a pressure well below 500 bar. Surprisingly, calculations,
based on the static strength of the material, show that the
stresses generated in the barrel by the application of the dynamic
pressure of 500 bar over a few milliseconds, indicate that stresses
well in excess of 50 MPa are experienced by the material. Without
being tied to any particular theory, it appears that some form of,
as yet unquantified, dynamic enhancement of the material strength
occurs when the barrel is loaded at such high rates, and that this
enhancement enables the material to deform plastically without
failing.
[0020] Accordingly, unreinforced plastics material can surprisingly
be employed. At least, the plastics material may be unreinforced by
any thing that is not poured with the plastics material into the
mould.
[0021] The mould may include a thread for connection of a breech
cap.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] An embodiment of the invention is further described
hereinafter, by way of example, with reference to the accompanying
drawing, in which FIG. 1 is a schematic illustration of a disrupter
in accordance with the invention.
DETAILED DESCRIPTION
[0023] In FIG. 1, a disruptor 10 has a tubular barrel 12 of cast
polyurethane. The barrel is approximately 400 mm long, has and
inner diameter of 27 mm and a wall thickness 8 mm. It is screw
threaded at a breech end 14 to receive a breech 16. An electrically
fired deflagration cartridge 18 is disposed inside the breech end
14 of the barrel, within the confines of the breech 16. The
cartridge may be such as employed by a disruptor currently marketed
under the brand Pigstick by A B Precision (Poole) Limited (see
website at http://www.abprecision.co.uk/pdf/pigstick.pdf for
further detail). In any event, the cartridge employs a deflagrating
propellant that does not explosively detonate but which burns
rapidly on initiation producing rapidly expanding gases. An
air-filled space 20 is provided between the cartridge 18 and a
piston 22, which space is pressurised by the expanding gases of the
deflagrating propellant on initiation thereof to a pressure in
excess of 500 bar. Beyond the piston is a charge of water retained
by an end cap 28 which is a sealing, but otherwise loose fit, in
the discharge end 26 of the barrel 12.
[0024] It is a feature of the present invention that the barrel is
not reinforced, since, although this might well strengthen the
barrel, it also reduces its ductility, rendering it brittle. It is
the ductility that on the one hand contains the rapid increase in
pressure, while on the other, the dynamic strength of the material
appears much greater at the strain rates imposed by the cartridge
propellant deflagration than its published static strength
suggests.
[0025] The barrel 12 is cast from molten polyurethane or similar
plastics material in an open mould (not shown). The mould has an
internal thread to form a corresponding thread on the barrel. The
barrel is therefore unscrewed from the mould once the plastics
material has cooled and solidified.
[0026] Consequently, there are low assembly costs so that, despite
being disposed of after each detonation, the cost of a new barrel
is not significant. The breech 16 may also be made from
polyurethane or other suitable plastic. In the current use an
injection moulded polyethylene breech is used such that it does not
require machining of its thread 30 on its internal bore or wire
apertures 32 for the firing wires (not shown). The breech may or
may not be reused a number of times.
[0027] Overall the arrangement is light and can be carried by a
small robotic vehicle. Furthermore, since it does not fragment on
firing, there is no danger of collateral damage to the vehicle. The
current design has a total mass of less than 650 g compared with
re-usable steel barrels and breeches which typically weigh in
excess of 2.5 kg for a similar performance.
[0028] Throughout the description and claims of this specification,
the words "comprise" and "contain" and variations of the words, for
example "comprising" and "comprises", means "including but not
limited to", and is not intended to (and does not) exclude other
moieties, additives, components, integers or steps.
[0029] Throughout the description and claims of this specification,
the singular encompasses the plural unless the context otherwise
requires. In particular, where the indefinite article is used, the
specification is to be understood as contemplating plurality as
well as singularity, unless the context requires otherwise.
[0030] Features, integers, characteristics, compounds, chemical
moieties or groups described in conjunction with a particular
aspect, embodiment or example of the invention are to be understood
to be applicable to any other aspect, embodiment or example
described herein unless incompatible therewith.
[0031] The reader's attention is directed to all papers and
documents which are filed concurrently with or previous to this
specification in connection with this application and which are
open to public inspection with this specification, and the contents
of all such papers and documents are incorporated herein by
reference.
[0032] All of the features disclosed in this specification
(including any accompanying claims, abstract and drawings), and/or
all of the steps of any method or process so disclosed, may be
combined in any combination, except combinations where at least
some of such features and/or steps are mutually exclusive.
[0033] Each feature disclosed in this specification (including any
accompanying claims, abstract and drawings), may be replaced by
alternative features serving the same, equivalent or similar
purpose, unless expressly stated otherwise. Thus, unless expressly
stated otherwise, each feature disclosed is one example only of a
generic series of equivalent or similar features.
[0034] The invention is not restricted to the details of any
foregoing embodiments. The invention extends to any novel one, or
any novel combination, of the features disclosed in this
specification (including any accompanying claims, abstract and
drawings), or to any novel one, or any novel combination, of the
steps of any method or process so disclosed.
* * * * *
References