U.S. patent number 3,774,541 [Application Number 05/139,685] was granted by the patent office on 1973-11-27 for selection control methods for explosive systems.
Invention is credited to Francis H. Bratton.
United States Patent |
3,774,541 |
Bratton |
November 27, 1973 |
SELECTION CONTROL METHODS FOR EXPLOSIVE SYSTEMS
Abstract
Selective control methods are provided for explosive systems
which involve the placement of agents which act by dilution,
physical or chemical means to alter the sensitivity of explosive
(including pyrotechnic) materials or devices wherein: (1) the
release may occur by the melting of the agent, rupture of a
container or by pumping; (2) the agent is confined as a solid, is
within a container capsule, is physically placed or mixed within
the explosive as small or large pieces, is coated or molded on the
walls or other parts of the device, or is held in an inactive
position outside the action zone but is so arranged that it will be
effectively placed on receipt of signal; (3) the signal to
deactivate or activate may be heat supplied by the environment, or
from an activating unit incorporated in the system, or pressure, or
mechanical activation, wherein the signal may be the result of a
command or set, or the output of a transducer control system.
Inventors: |
Bratton; Francis H. (Avon,
CT) |
Family
ID: |
22487836 |
Appl.
No.: |
05/139,685 |
Filed: |
May 3, 1971 |
Current U.S.
Class: |
102/275.1;
102/275.5; 116/67R; 102/221; 116/4 |
Current CPC
Class: |
C06C
5/06 (20130101); F42B 39/14 (20130101); F42D
5/04 (20130101) |
Current International
Class: |
C06C
5/00 (20060101); C06C 5/06 (20060101); F42D
5/04 (20060101); F42B 39/00 (20060101); F42D
5/00 (20060101); F42B 39/14 (20060101); C06c
005/04 () |
Field of
Search: |
;102/27R,28R,29,7R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Pendegrass; Verlin R.
Claims
I claim:
1. A component section for a pyrotechnic and explosive train
designed to be unable to transfer ignition and explosion until
activated comprising: a tubular body serving as a housing means and
having a first end capable of receiving and propagating an ignition
signal and a second end capable of performing a useful explosive
work function, said housing means containing segments of compacted
particulate pyrotechnic and explosive material, at least two
segments of which are separated by a barrier of meltable solid
material and annular sections of absorbent material capable of
absorbing said meltable solid when said meltable solid is heated to
be changed to a flowable liquid phase, said absorbent material
located in proximity to said barrier, wherein said pyrotechnic and
explosive train will be unable to propagate an ignition from said
first end to said second end until an explosure of said component
section to sufficient heat to allow said barrier material to melt
and flow into said absorbent material, said flow will occur and the
component section will transfer an ignition signal from said first
end to said second end and perform a useful explosive work
function.
2. Method of producing pyrotechnic structures in inactive form for
later activation comprising: preparing of a mixture of active
particulate solid pyrotechnic material with a solid deactivating
agent, said deactivating agent being a poor solvent for said
pyrotechnic material, depositing said mixture on a supporting sheet
means in the structure desired for a pyrotechnic function, said
deactivated mixture being solid after deposition has completed, and
wherein said pyrotechnic structure is inactive to initiation
signals due to the presence of said deactivating agent,
transporting said deactivated structure to the point of desired
use, combining said deactivated structure with a layer of material
absorbent to said deactivating agent, causing said pyrotechnic
structure to become active to initiation signals by heating said
structure when in contact with said absorbent material to melt said
deactivating agent and cause said agent to flow into said absorbent
material.
3. The method of producing pyrotechnic structures of claim 2
wherein the mixture of solid pyrotechnic material and solid
deactivating agent is dispersed in and is applied from a liquid
medium.
4. The method of producing pyrotechnic structures of claim 2
wherein the solid deactivating agent is removed by extraction with
a solvent. 5A component section for a pyrotechnic train designed to
carry ignition signals comprising: a tubular body serving as a
housing means and having a first end capable of receiving an
ignition signal and a second end capable of performing a useful
ignition work function, said housing means containing segments of
compacted particulate pyrotechnic compositions; means for
deactivating said pyrotechnic train upon receipt of a predetermined
heat signal, said deactivation means comprising an insert of solid
deactivating agent between said pyrotechnic segments, wherein said
component section will allow propagation of an ignition signal from
said first end to said second end, and wherein upon receipt of said
predetermined heat signal, said deactivating agent will flow into
said pyrotechnic material and render said component section unable
to propagate
said ignition signal from said first end to said second end. 6. The
component section of claim 5 wherein wax is used as the solid
deactivating
agent. 7. The component section of claim 5 wherein the solid
deactivating agent is contained in an annular opening external to
said pyrotechnic
segments. 8. The component section of claim 5 wherein a
longitudinal segment of compacted particulate pyrotechnic material
is replaced with
said solid deactivating agent. 9. The component section of claim 5
wherein one segment contains particulate pyrotechnic composition to
which a solid
deactivating agent has been added in particulate form. 10. A
component section for a pyrotechnic and explosive train designed to
transfer ignition and explosive signals comprising: a tubular body
serving as a housing means and having a first end capable of
receiving and propagating an ignition signal and a second end
capable of performing a useful explosive work function, said
housing means containing a segment of compacted particulate
pyrotechnic composition and a segment of compacted particulate
explosive material capable of detonating from the ignition signal
of said segment of pyrotechnic composition, means for deactivating
said pyrotechnic and explosive train upon receipt of a
predetermined heat signal, said deactivating means comprising an
insert of solid deactivating agent between said pyrotechnic and
explosive segments, wherein said component section will allow
propagation of ignition and explosive signals from said first end
to said second end, and wherein upon receipt of said predetermined
heat signal, said deactivating agent will flow into said explosive
material and render it incapable of detonating from the
ignition
signal of said segment of pyrotechnic composition. 11. A component
section for an explosive train designed to carry explosive signals
comprising: a tubular body serving as a housing means and having a
first end capable of receiving an explosive signal and a second end
capable of performing a useful explosive work function, said
housing means containing a segment of compacted particulate
explosive composition, means for deactivating said explosive train
upon receipt of a predetermined heat signal, said deactivation
means comprising a solid deactivating agent in non-interferring
location in proximity to said explosive segment, wherein said
component section will allow propagation of an explosive signal
from said first end to said second end, and wherein upon receipt of
said predetermined heat signal, said deactiviating agent will flow
into said explosive material and render said component section
unable to propagate
said explosive signal from said first end to said second end. 12. A
component section for an explosive train designed to carry
explosive signals comprising: a tubular body serving as a housing
means and having a first end capable of receiving an explosive
signal and a second end capable of performing a useful explosive
work function, said housing means containing a segment of compacted
particulate explosive composition; means for deactivating said
explosive train upon receipt of a predetermined heat signal, said
deactivating means comprising a liquid deactivating agent contained
in a sealed plastic container in non-interferring location in
proximity to said explosive segment, wherein said component section
will allow propagation of an explosive signal from said first end
to said second end, and wherein upon receipt of said predetermined
heat signal, said deactivating agent will flow into said explosive
material and render said component section unable to propagate said
explosive signal from said first end to said second end.
Description
SUMMARY OF THE DISCLOSURE
The present invention provides methods whereby deactivating
materials may be put into or removed from explosive systems through
techniques which prevent their interference with normal system
operation yet will allow them to alter that operation if a
predetermined event has occurred which makes it desirable or
important to alter the system output. In the simplest type example
an annular wax washer in a pyrotechnic material train allows
ignition to transfer readily through its central hole, but if the
arrangement has been subjected to an elevated temperature the wax
will melt and contaminate the pyrotechnic material and thereby
deactivate the device with respect to its usual initiation signal.
The effects have been shown with pyrotechnic, primary explosive,
and secondary explosive materials in deactivate processes, and with
pyrotechnic materials in activate processes.
In addition some specific agents for preventing detonation of lead
azide on heating are presented.
BACKGROUND OF THE INVENTION
The control of sensitivity of explosives has long been studied and
a brief summary is given here from ENCYCLOPEDIA OF EXPLOSIVES AND
RELATED ITEMS, by Basil T. Federoff, et al., Picatinny Arsenal,
Dover, New Jersey, AD 653,029, Volume 3, 1966, pages D88, 89, 90.
"Desensitization or phlegmatization of an explosive means rendering
it insensitive, or less sensitive to the following actions: heat,
shock, impact, percussion, rifle bullet or friction. Desensitizer
(or phlegmatizer) is a substance which makes insensitive or reduces
the sensitivity of an explosive. -- Desensitized explosives are
those which are made insensitive to the above listed actions. Such
explosives are safe to handle and transport. Typical examples are:
RDX Composition A; PETN/ wax compositions -- "
"Most of the primary explosives (mercury fulminate, lead azide,
Tetracene, etc.) and many high explosives (nitroglycerine, Tetryl,
PETN, RDX, etc.) are too sensitive to be used per se and must be
desensitized. For example lead azide may be desensitized by coating
its crystals either with dextrin or with polyvinyl alcohol. It can
be desensitized by controlling the size and shape of its crystals,
or by precipitating it in colloidal form."
"Liquid high explosives (such as nitroglycerine, nitroglycol or
some other nitric esters) can be desensitized by mixing them with
substances absorbing, or absorbing them. -- The resulting
substances are known as Dynamites. -- As some industries -- require
the use of powerful explosives -- it was necessary to devise safe
methods for their delivery. -- One of the European methods is to
mix nitroglycerine with kieselguhr, ship it, and then leach with
warm water; the nitroglycerine settles to the bottom of the tank
and could easily be removed."
"For desensitization of solid high explosives, the usual procedures
are to coat them with one or more of the following: paraffin,
paraffin oil, waxes, stearic acid, stearates, polyvinyl acetate,
dinitrotoluene, etc. Wohler determined the maximum percentage of
paraffin oil which could be incorporated in a high explosive
without making it detonate incompletely. He name this value
`Phlegmatization Limit` -- "
While the number of means for deactivating explosives is voluminous
and many compositions have been used for both military and
commercial purposes it does not appear that the concept of the
present invention has been applied in the earlier work wherein the
explosive in containment is subjected to an action within the
container to either incorporate or remove a desensitizing agent. It
does not appear in the literature that explosive which has been
prelocated and affixed by either its particulate nature or its
confinement is then subject to controlled or programmed
introduction of a deactivating agent although R. W. Lawrence U.S.
Pat. No. 2,363,254 made use of a wax liner to provide blasting caps
which would not detonate when heated in a fire.
It has also been found that in addition to the mechanical placement
of deactivating agents in devices designed to show a change in
reaction to the usual activation signal on exposure to heat, that
it is possible with certain selected mixtures to rely on simple
mixing. This has been made to perform in a desired fashion such as
burning if the mixture has not been subjected to elevated
temperature. Application of heat, however, will make the material
inactive.
There has been an increasing use of pyrotechnics and explosives in
systems where the ultimate operation of a device or unit would
desirably be related to an experience which that unit has seen
prior to the time for use. For instance, in an arming or firing
system it would be desirable to produce the ignition of the round
if that round had not been exposed to an excessive temperature, as
the excessive temperature might well cause the round to malfunction
in terms of a premature or delayed explosion. In addition, the use
of pyrotechnic and explosive materials to convey information which
is in the nature of logic in isolated systems which contain their
own stored chemical energy for activation is of increasing
interest.
Such links may be provided in an explosive system where the network
may be preset so that if Item A or Event A has occurred a thermal
switch may be thrown to divert the course of a subsequently fired
explosive to Network 1 or Network 2. These may be on either
relatively long time scales or on quite short time.
A conceived utilization of these devices might comprise fuze
systems for stored munitions which in the event of exposure to the
heat of a fire would deactivate or "dud" the usual firing systems.
At the same time or at a slightly higher temperature a destruct or
abort system could be activated by heat to be set off by a
temperature controlled igniter.
The present invention in addition permits the working with
explosive and pyrotechnic assemblies in deactivated form through
such hazardous operations as welding or pressing, bonding, and the
like and would permit the ultimate removal of the deactivating
material from the explosive to activate the device. This would then
consequently provide materials in the nature of explosives which
could be handled as deactivated devices for assembly, storage, and
shipment and which could be subsequently activated at the site of
final use, should this be of importance.
The methods utilized here in addition to being applicable to small
confined units are also suitable to the general procedures involved
in the handling and processing of explosives. Thus the use of a
duddant agent which is subsequently removed in processing would
permit the formation of pyrotechnic and explosive circuits which
would be printed in a dudded form, carried through several
operations and then activated for final use.
OBJECTS OF THE PRESENT INVENTION
It is an object of the present invention to provide systems for
deactivating explosives wherein a solid duddant material is placed
in close proximity, but in an ineffective location, to an explosive
charge and provide that exposure to externally supplied heat or a
selected heat input signal will produce deactivation of the
explosive charge.
It is the object of the present invention to provide dudding
material which may be contained in capsular form or which may be
contained in small plastic or metal containers for release on
command or through the influence of heat or pressure to produce
deactivation of an explosive material.
It is an object of the present invention to provide a system
wherein a dudding agent is physically arranged to be continuous to
the explosive but is in an inactive form.
It is an object of the present invention to provide a system
wherein deactivating material is mixed with a particulate form of
the explosive in such a way that the explosive will propagate
unless the system has been subjected to a certain minimum amount of
heat to allow the dudding agent to deactivate the explosive.
It is an object of the present invention to provide explosive
systems which can be handled while in a deactivated form for
processing and subsequently be activated by simple techniques prior
to use.
It is an object of the present invention to provide a system where
combinations may be used to provide pyrotechnic logic systems by
selective control of different parts of the arrangement with the
introduction or removal of dudding agents on command.
It is a further object of the invention to provide new dimensions
in the concepts of explosive and pyrotechnic logic systems.
BRIEF DESCRIPTION OF THE DRAWING
To illustrate the findings of the present invention a number of
specific examples are described below and several are shown in the
drawing.
FIG. 1 shows a pyrotechnic delay with a wax washer to cause dudding
on heating.
FIG. 2 shows a pyrotechnic delay with a duddant present in its
housing.
FIGS. 3 and 4 show a duddant in a position contiguous to a
pyrotechnic train.
FIG. 5 illustrates a wax washer in position to dud a primary
explosive.
FIG. 6 illustrates a system in which wax may dud a secondary
explosive.
FIGS. 7 and 8 show pyrotechnic material containing wax before and
after heating.
FIG. 9 shows one way heat melting wax activates a system.
The following examples set forth specific embodiments of the
invention and are given in order that the effectiveness of the
invention may be more fully understood. They are included for
illustration only and are not intended in any way to limit the
practice of the invention.
EXAMPLE I
Two assemblies for conducting a burning pyrotechnic signal in a
confined system were constructed as shown in FIG. 1 by placing
three sections of lead 1 jacketed 0.123 inch outside diameter by
0.04 inch inside diameter boron-red lead pyrotechnic material 2
inside a glass tube 3 one-eighth inch in diameter. The two
three-eighths inch long sections of the pyrotechnic material were
separated by a wax washer 4 in which a 0.04 inch hole was present
and which was 0.035 inch thick. This wax washer was made of
pentaerythritol hexastearate which had a melting point of
147.degree. C. It had been melted on an aluminum sheet and allowed
to cool so that the one-eighth inch diameter washer could be cut
from it. The components were held in position by an igniter piece 5
at left and by a smaller piece of glass tubing 3 at right. ght.
One of the assemblies was then ignited and by visual observation it
was determined that the burning signal propagated through the
entire length.
The second assembly was subjected gently to external heat from a
gas burner to allow the wax washer to just melt. Since glass tubing
was being used it was possible to observe that the wax melted
without disturbance of the components in the assembly. The assembly
was fired and burning propagated up to a point where the
pyrotechnic material had been "dudded" by the melted but by then
frozen wax.
EXAMPLE II
A similar experiment was carried out with ceresene wax with a
melting point of 48.degree.-53.degree. C in place of the
hexastearate and gave similar results.
EXAMPLE III
In assemblies similar to those in Example I, washers were prepared
of Halowax 1014 (mp 130.degree.-2.degree. C). Halowax is a trade
name of Koppers, Inc. and is used for chlorinated naphthalenes. One
completed assembly unit was placed in a oven at 80.degree. C for 30
minutes and then removed and fired. This demonstrated that
temperature below the melting point of the wax did not cause
deactivation. A companion test unit was heated by an infrared heat
lamp until visible signs of melting of the wax appeared. This unit
was then tested and failed to propagate. This demonstrated that
"dudding" was effected when the wax was heated to the melting
point. Heating for a modest time below the melting point had been
shown to have no effect on the performance of the unit.
EXAMPLE IV
Glass tubes of the type used for the preparation of the pyrotechnic
assemblies as described in Example I were treated by allowing wax,
in this case Esso Household Wax with a melting point of
50.degree.-3.degree. C and a softening point of 48.degree. C, to
coat the interiors of the tubes with wax films 6, as shown in FIG.
2. Two of the pieces of pyrotechnic material were then inserted as
shown. One test unit was fired at room conditions with a fresh
igniter 5 and propagated in normal fashion. A companion test unit
was then placed in an oven at 80.degree. C for 15 minutes, removed
and a fresh piece of pyrotechnic was attached as an igniter. When
the fresh material was fired it burned normally but the ignition of
the other parts of the assembly did not occur. The wax coating on
the interior surface of the tubing had produced a thermally
controlled dudding effect.
EXAMPLE V
Two assemblies containing three pieces of pyrotechnic material in a
one-eighth inch bore brass tube 7 were made as shown in FIGS. 3 and
4. The center piece on line 4--4 was about one-eighth inch long and
was carefully sliced parallel to and just into the pyrotechnic core
with a razor blade. A formed piece of Esso Household Wax 8 was
inserted above it. The arrangement was made to provide a piece of
wax in contact with the active core of the device. One unit fired
in the usual fashion propagated. A companion unit heated to
180.degree. C in an oven for 10 minutes could not be fired as the
wax in this case had produced a dudding effect in the pyrotechnic
material.
EXAMPLE VI
Two explosive assemblies as shown in FIG. 5 were made to provide
control of initiation of an explosion in a primary explosive from
associated pyrotechnic igniters. Each assembly contained two
one-sixteenth inch thick slices of lead azide 10 in lead separated
by a wax washer 0.07 inch thick 4 and separated in turn from a
three-fourths inch length of boron-red lead pyrotechnic material 5
in lead by a plastic washer 0.04 inch thick 9. The wax used was
Kindt Collins 278B, mp 89.degree.-90.degree. C. One assembly was
placed in an oven at 120.degree. C for 2 hours. When removed and
fired by ignition of pyrotechnic material 5, the pyrotechnic
material burned but did not cause the lead azide 10 to detonate.
The unit was examined and it was established that the pyrotechnic
material had been burned and that the wax had not reached the
pyrotechnic material. In this experiment the primary explosive,
lead azide, was dudded. In the test of the unheated unit the
pyrotechnic material caused the detonation of both pieces of lead
azide.
EXAMPLE VII
Two explosive assemblies were prepared as shown in FIG. 6 to carry
pyrotechnic ignition to detonation of a primary explosive and in
turn to propagate the explosion to a secondary explosive. A very
small core PETN (pentaerythritol tetranitrate) of 2 grains per foot
12 in a lead jacket 0.05 inch in diameter was wrapped with tape 11
to provide a snug fit in a one/eighth inch diameter brass tube.
This was separated by a wax washer 0.04 inch thick having a 0.04
inch hole, and made of Kindt Collins 278V wax, mp 135.degree. C,
from a one-eighth length of lead azide 10 in lead. The lead azide
was separated in turn by a plastic washer 9 from a boron-red lead
igniter. One unit was heated in the oven for 1 hour. When it was
fired the pyrotechnic material burned, the lead azide detonated,
but the PETN did not. The second unit when fired gave detonation of
both the lead azide and the PETN. From examination of the first
unit and other experiments with the PETN in lead and wax it was
determined that the PETN had been dudded by the melted wax.
EXAMPLE VIII
A pyrotechnic mixture was prepared by mixing 15 parts of powdered
boron, 85 parts of red lead (Pb.sub.3 O.sub.4) and 25 parts ground
Fisher No. 700263 HIGH-PYSEAL CEMENT which softens at 130.degree. C
and which resembles sealing wax. The mixture was put into a lead
tube 0.188 inch I. D. .times. 0.290 inch O. D. and reduced in size
by roll drawing in seven stages to an outside diameter of about
0.140 inch. Four 2 inch lengths were cut from the material and
showed the appearance of finely packed powder indicated by 13 in
FIG. 7. Two lengths were ignited with hot wires and burned
completely through. The companion pieces were placed in an oven for
two hours and on examination had the appearance of sintered powder
and some voids as indicated by 14 in FIG. 8. When tested with a
pyrotechnic igniter both of the heated samples failed to ignite and
propagate.
This experiment indicates that pyrotechnic mixtures which will
propagate can have a duddant material incorporated in them which
will cause them to be deactivated by exposure to heat.
EXAMPLE IX
An inactive pyrotechnic material which could be made active later
by removal of a duddant was made in the following experiment.
Twenty parts of boron, 80 parts of barium chromate (BaCrO.sub.4),
both finely divided and 42 parts of paraffin wax (Esso Household
Wax) and about 150 parts of toluene were mixed to form a paste.
Some of the paste was painted on aluminum foil and allowed to dry.
When ignition of the dry mixture with a flame was attempted it did
not ignite. Another portion of the painted foil was activated by
placing a piece of blotting paper over the mixture and pressing
with a hot household iron. This caused the wax to melt and be drawn
into the paper. Following this treatment the residual pyrotechnic
material ignited readily.
EXAMPLE X
In an experiment using similar materials and procedures to those in
Example IX the same dudded pyrotechnic mixture was made. A portion
was placed on aluminum foil in an area about one-eighth inch wide
and 0.015-0.030 thick in a manner to resemble printing. When dry it
was cut into two pieces. One piece was tested with a vigorous flame
and failed to ignite although a small amount of wax vapor did burn
momentarily after the assembly had been heated for several
seconds.
The second piece of foil and dudded pyrotechnic material was firmly
held against a 100 mesh screen with two pieces of blotting paper
along side the mixture. This assembly was then gently washed
several times with carbon tetrachloride (CCl.sub.4) to remove the
wax. After washing the foil with the pyrotechnic was removed and
allowed to dry. When tested with a match it burned vigorously and
intensely.
This experiment demonstrated the removal of a duddant material from
a pyrotechnic mixture by solvent extraction.
EXAMPLE XI
Two units of an ignition transfer system involving a pyrotechnic
delay mixture (boron-red lead) in lead in a brass tube were
assembled as shown in FIG. 9. The pyrotechnic pieces were separated
by solid wax discs 15 located between rolls of filter paper 16
which were about three-eighths inch long and had inside diameters
of about 0.06 inch. One unit was placed in an oven to allow the wax
disc to melt and be absorbed by the paper. This unit when fired
gave ignition transfer and all the pyrotechnic material was
consumed. The other unit was not heated before firing and did not
transfer ignition to the second piece of pyrotechnic material. In
this case the wax prevented transfer until the unit had been
heated. This may be regarded as a "heat to open explosive or
pyrotechnic valve."
EXAMPLE XII
A large number of tests were carried out to show that lead azide
would be deactivated when exposed to heat in the presence of
certain chemical materials. Thus a pellet of lead azide in lead
when heated with tricresyl phosphate, tri p-tolyl phosphate, D.D.T.
(Dichloro diphenyl trichloroethane, mp 107 C), or antimony sulfate
in a small aluminum cap may be carried to 900.degree.-1,100.degree.
F without out explosion. This is far beyond the usual explosion
temperature of about 640.degree. F and was shown with both
dextrinated and polyvinyl alcohol treated lead azide. In addition
as the temperature increased to and passed 640.degree. F fire,
flame or smoke might result but detonation did not occur. In these
experiments the deactivating agents were introduced as solids,
liquids, or as the contents of small plastic pouches. These
released the agents when heat was applied. The amounts of the
materials used were a substantial percentage of the weight of the
explosive. When conventional waxes were used in similar experiments
the lead azide detonated or decomposed sharply at about 640.degree.
F. The rate of heating in these experiments produced 600.degree. F
in about 5 minutes.
* * * * *