U.S. patent application number 16/585931 was filed with the patent office on 2021-04-01 for heat-activated triggering device with bi-metal triggering element.
The applicant listed for this patent is Raytheon Company. Invention is credited to Frederick B. Koehler, Anthony O. Lee, Ward D. Lyman.
Application Number | 20210095944 16/585931 |
Document ID | / |
Family ID | 1000005459746 |
Filed Date | 2021-04-01 |
United States Patent
Application |
20210095944 |
Kind Code |
A1 |
Koehler; Frederick B. ; et
al. |
April 1, 2021 |
HEAT-ACTIVATED TRIGGERING DEVICE WITH BI-METAL TRIGGERING
ELEMENT
Abstract
A heat-activated triggering device, such as for a missile or
munition, includes a bi-metal trigger element, with a breakable pin
of a first metal surrounded by a sleeve made of a second metal that
is different than the first metal. The sleeve may be made of a
shape memory alloy, such as a single-crystal shape memory alloy,
that is pre-compresses around part of the pin. The sleeve may be
configured to put a tension force on the pin as the sleeve passes a
predetermined temperature, for instance a temperature at which the
shape memory feature of the sleeve is activated. The pin may have a
weakened portion, such as a notched portion, at which the pin
breaks. The breaking of the pin may be used to drive a firing pin
into a primer, to initiate a detonation and/or combustion
reaction.
Inventors: |
Koehler; Frederick B.;
(Tucson, AZ) ; Lyman; Ward D.; (Tucson, AZ)
; Lee; Anthony O.; (Tucson, AZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Raytheon Company |
Waltham |
MA |
US |
|
|
Family ID: |
1000005459746 |
Appl. No.: |
16/585931 |
Filed: |
September 27, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F42B 3/11 20130101; F42C
19/0838 20130101; F42C 15/16 20130101 |
International
Class: |
F42C 15/16 20060101
F42C015/16; F42C 19/08 20060101 F42C019/08 |
Claims
1. A heat-activated triggering device comprising: a housing: a
bi-metal triggering element including: a metal pin made of a first
metal; and a sleeve surrounding part of the pin, the sleeve being
made of a second metal different from the first metal, the sleeve
having a first end abutting against the housing and a second end
opposite the first end; a firing pin operatively coupled to the
triggering element, wherein the second end of the sleeve abuts
against the firing pin, such that at a predetermined temperature
the sleeve pushes against the firing pin, causing the metal pin to
break; and a lockout configured to selectively prevent movement of
the firing pin.
2. A heat-activated triggering device comprising: a bi-metal
triggering element including: a metal pin made of a first metal;
and a sleeve surrounding part of the pin, the sleeve being made of
a second metal different from the first metal: a firing pin
operatively coupled to the triggering element; and a lockout
configured to selectively prevent movement of the firing pin
wherein the second metal is a shape memory alloy.
3. The triggering device of claim 2, wherein the shape memory alloy
is pre-compressed, expanding when a predetermined temperature
threshold is exceeded.
4. The triggering device of claim 2, wherein the shape memory alloy
is a single-crystal shape memory alloy.
5. (canceled)
6. The triggering device of claim 1, wherein one end of the metal
pin is attached to the firing pin.
7. The triggering device of claim 6, wherein upon breakage of the
metal pin the one end is driven away from another end of the metal
pin that is opposite the one end of the metal pin, by a force
primary applied by the sleeve.
8. The triggering device of claim 7, wherein the another end of the
metal pin is mechanically coupled to a resilient device.
9. The triggering device of claim 8, wherein the resilient device
includes a Belleville washer stack.
10. The triggering device of claim 1, wherein the metal pin has a
weakened portion.
11. The triggering device of claim 10, wherein the weakened portion
is a notched portion.
12. The triggering device of claim 1, wherein the firing pin and
the sleeve are within a first cavity of a housing of the triggering
device; wherein the lockout is in a second cavity of the housing;
and wherein the triggering element further includes a stay spring
in the first cavity, to prevent movement of loose parts within the
first cavity.
13. The triggering device of claim 12, wherein the lockout includes
an inertial mass that moves against a spring during a predetermined
movement of the triggering device, with movement of the inertial
mass by the predetermined movement of the trigger device engaging a
mechanism of the lockout that prevents movement of the firing
pin.
14. The triggering device of claim 1, further comprising a valve
that selectively passes through products from the firing of a
primer that is initiated by impact from the firing pin.
15. The triggering device of claim 14, further comprising a
mechanical linkage mechanically coupling the firing pin to the
valve.
16. The triggering device of claim 15, wherein the linkage includes
a linking member that translates along with the firing pin, and a
cam mechanism that converts translation of the linking member to
rotation of the valve.
17. A munition including the triggering device of claim 1, a primer
operatively coupled to the firing pin, and a shaped charge, wherein
the triggering device is operatively coupled to the shaped charge
of the munition such that detonation products from the primer
detonate the shaped charge.
18. A method of firing a triggering device, the method comprising:
breaking a metal pin by heating of a sleeve surrounding the metal
pin, wherein the heating of the sleeve puts a force on the metal
pin that breaks the metal pin at a weakened part of the metal pin;
and after the breaking of the metal pin, driving a firing pin into
a primer.
19. The method of claim 18, wherein the sleeve is made of a shape
memory alloy, and expands with heating to put the force on the
metal pin.
20. The method of claim 18, wherein the driving the firing pin
includes primary energy for driving the firing pin being applied by
the sleeve.
Description
FIELD OF THE INVENTION
[0001] The invention is in the field of triggering devices, such as
for triggering explosive charges.
DESCRIPTION OF THE RELATED ART
[0002] One concern with munitions is behavior of stored munitions
in the case of fire or environmental thermal runaway. It is
desirable to have a safety mechanism to prevent problems in slow
cook-off, where the temperature rises in the munition, for example
to prevent a rocket motor from being activated to propel a missile
in such a circumstance.
SUMMARY OF THE INVENTION
[0003] A heat-activated triggering device includes a bimetal
element that uses a shape memory element in contact with a pin
broken by heating of the shape memory element.
[0004] A heat-activated triggering device has a metal element
configured to be broken at a weakened portion, and resilient
devices that provide force to move a firing pin toward a primer
when the metal element is broken.
[0005] According to an aspect of the invention, a heat-activated
triggering device includes: a bi-metal triggering element
including: a metal pin made of a first metal; and a sleeve
surrounding part of the pin, the sleeve being made of a second
metal different from the first metal; a firing pin operatively
coupled to the triggering element; and a lockout configured to
selectively prevent movement of the firing pin.
[0006] According to an embodiment of any paragraph(s) of this
summary, the second metal is a shape memory alloy.
[0007] According to an embodiment of any paragraph(s) of this
summary, the shape memory alloy is pre-compressed, expanding when a
predetermined temperature threshold is exceeded.
[0008] According to an embodiment of any paragraph(s) of this
summary, the shape memory alloy is a single-crystal shape memory
alloy.
[0009] According to an embodiment of any paragraph(s) of this
summary, the metal pin is configured to break at a predetermined
temperature, under force from the sleeve.
[0010] According to an embodiment of any paragraph(s) of this
summary, one end of the metal pin is attached to the firing
pin.
[0011] According to an embodiment of any paragraph(s) of this
summary, upon breakage of the metal pin the one end is driven away
from another end of the metal pin that is opposite the one end of
the metal pin, by a force primary applied by the sleeve.
[0012] According to an embodiment of any paragraph(s) of this
summary, the another end of the metal pin is mechanically coupled
to a resilient device.
[0013] According to an embodiment of any paragraph(s) of this
summary, the resilient device includes a Belleville washer
stack.
[0014] According to an embodiment of any paragraph(s) of this
summary, the metal pin has a weakened portion.
[0015] According to an embodiment of any paragraph(s) of this
summary, the weakened portion is a notched portion.
[0016] According to an embodiment of any paragraph(s) of this
summary, the firing pin and the sleeve are within a first cavity of
a housing of the triggering device.
[0017] According to an embodiment of any paragraph(s) of this
summary, the lockout is in a second cavity of the housing.
[0018] According to an embodiment of any paragraph(s) of this
summary, the triggering element further includes a stay spring in
the first cavity, to prevent movement of loose parts within the
first cavity.
[0019] According to an embodiment of any paragraph(s) of this
summary, the lockout includes an inertial mass that moves against a
spring during a predetermined movement of the triggering device,
with movement of the inertial mass by the predetermined movement of
the trigger device engaging a mechanism of the lockout that
prevents movement of the firing pin.
[0020] According to an embodiment of any paragraph(s) of this
summary, the triggering device further includes a valve that
selectively passes through products from the firing of a primer
that is initiated by impact from the firing pin.
[0021] According to an embodiment of any paragraph(s) of this
summary, the triggering device further including a mechanical
linkage mechanically coupling the firing pin to the valve.
[0022] According to an embodiment of any paragraph(s) of this
summary, the linkage includes a linking member that translates
along with the firing pin, and a cam mechanism that converts
translation of the linking member to rotation of the valve.
[0023] According to an embodiment of any paragraph(s) of this
summary, the triggering device is part of a munition, with the
triggering device operatively coupled to a shaped charge of the
munition such that detonation products from a primer of the
triggering device that is operatively coupled to the firing pin,
detonate the shaped charge.
[0024] According to another aspect of the invention, a method of
firing a triggering device, the method including the steps of:
breaking a metal pin by heating of a sleeve surrounding the metal
pin, wherein the heating of the sleeve puts a force on the metal
pin that breaks the metal pin at a weakened part of the metal pin;
and after the breaking of the metal pin, driving a firing pin into
a primer.
[0025] According to an embodiment of any paragraph(s) of this
summary, the sleeve is made of a shape memory alloy, and expands
with heating to put the force on the metal pin.
[0026] According to an embodiment of any paragraph(s) of this
summary, the driving the firing pin includes primary energy for
driving the firing pin being applied by the sleeve.
[0027] To the accomplishment of the foregoing and related ends, the
invention comprises the features hereinafter fully described and
particularly pointed out in the claims. The following description
and the annexed drawings set forth in detail certain illustrative
embodiments of the invention. These embodiments are indicative,
however, of but a few of the various ways in which the principles
of the invention may be employed. Other objects, advantages and
novel features of the invention will become apparent from the
following detailed description of the invention when considered in
conjunction with the drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0028] The annexed drawings, which are not necessarily to scale,
show various aspects of the invention.
[0029] FIG. 1 is an oblique view of a munition that includes a
triggering device in accordance with an embodiment of the
invention.
[0030] FIG. 2 is another oblique view of a munition that includes a
triggering device in accordance with an embodiment of the
invention.
[0031] FIG. 3 is an oblique view of the triggering device of the
munition of FIG. 1.
[0032] FIG. 4 is a sectional view of the triggering device of FIG.
3.
[0033] FIG. 5 is an oblique view showing some of the working parts
of the triggering device of FIG. 3.
[0034] FIG. 6 is an end view of the triggering device of FIG. 3 in
a first step in the triggering process.
[0035] FIG. 7 is a side view of the triggering device of FIG. 3 in
the first step in the triggering process.
[0036] FIG. 8 is an end view of the triggering device of FIG. 3 in
a second step in the triggering process.
[0037] FIG. 9 is a side view of the triggering device of FIG. 3 in
the second step in the triggering process.
[0038] FIG. 10 is an end view of the triggering device of FIG. 3 in
a third step in the triggering process.
[0039] FIG. 11 is a side view of the triggering device of FIG. 3 in
the third step in the triggering process.
[0040] FIG. 12 is a high-level flow chart of steps in the operation
of the triggering device of FIG. 3.
DETAILED DESCRIPTION
[0041] A heat-activated triggering device, such as for a missile or
munition, includes a bi-metal trigger element, with a breakable pin
of a first metal surrounded by a sleeve made of a second metal that
is different than the first metal. The sleeve may be made of a
shape memory alloy, such as a single-crystal shape memory alloy,
that is pre-compresses around part of the pin. The sleeve may be
configured to put a tension force on the pin as the sleeve passes a
predetermined temperature, for instance a temperature at which the
shape memory feature of the sleeve is activated. The pin may have a
weakened portion, such as a notched portion, at which the pin
breaks. The breaking of the pin may be used to drive a firing pin
into a primer, to initiate a detonation and/or combustion
reaction.
[0042] The firing pin may be mechanically coupled to a linkage that
prevents egress of output from the primer if the firing pin has not
been moved. The linkage may include a cylindrical valve element
with a through hole, the through hole being alignable with an
output channel from the primer when the firing pin has been moved
sufficiently. The movement of the firing pin slides a dowel pin
that is attached to the firing pin. This in turn translates a cam
element that turns the cylindrical element. Partial movement of the
firing pin still may leave the valve closed. Preventing the primer
from prematurely operating to trigger explosion, for example
preventing full operation due to a primer being heated.
[0043] FIGS. 1 and 2 show a missile or munition 10 that includes a
triggering device 12, for triggering a shaped charge 14 for scoring
a motor casing 16 of the missile 10. This is done to prevent firing
of a rocket motor, or explosion of propellant, when the missile or
munition is subjected to a slow cook-off event, for example a fire.
Upon occurrence of a triggering event, such as reaching a
predetermined elevated temperature, the triggering device 12
triggers detonation of the shaped charge 14, scoring and splitting
the motor casing 16, as shown in FIG. 2. This prevents explosion or
a propulsive event, which would be a safety hazard.
[0044] The triggering device 12 also needs to avoid detonation of
the shaped charge 14 from other types of heating, for example
avoiding triggering from aero-thermal heating during flight of the
missile or munition 10. Accordingly the triggering device 12 may
have one or more safety features to prevent undesired triggering of
the shaped charge 14.
[0045] FIGS. 3 and 4 show some details of the triggering device 12.
The device 12 has three general parts: a triggering element 22
which is used to move a firing pin 24 toward a primer 26; an
inertial lock-out 28 used to prevent movement of the firing pin 24
once the missile 10 (FIG. 1) has been launched; and a linkage 32
that is used to selectively open or close a passageway (output
port) 34 through which products from the primer 26 pass. The
operative general parts are located within a casing 38.
[0046] The triggering element 22 includes a metal pin 42 made of a
first metal, surrounded by a sleeve 44 made of a second metal that
is different from the first metal. The term "metal," as used
herein, should be interpreted broadly to include elemental metal,
as well as metal alloys. The sleeve 44 is configured to put a force
on the metal pin 42 when sufficient heat is applied. This force may
be used break the pin 42 at a weakened portion 46 of the pin 42. In
the illustrated embodiment the weakened portion 46 is a notched
portion of the pin 42, but may be a portion otherwise having been
thinned. For example a notch may be uniformly cut or otherwise
formed around the pin 42 to create the weakened portion 46. The
depth of the notch may be selected in order to cause the pin 42 to
break at a predetermined temperature.
[0047] The sleeve 44 may be made of a shape memory alloy, such as a
single-crystal shape memory alloy, such as a copper-aluminum alloy.
The sleeve 44 may be pre-compressed against the pin 42, with a
memory shape puts stresses against the pin 42. As the temperature
rises, the sleeve 44 eventually passes its transition temperature,
undergoing a phase transformation between different structures.
This may occur, for example at around 160.degree. C. The causes the
sleeve 44 to produce a force tending to change its shape. This
force is transmitted to the pin 42, for example placing a force on
the pin 42 that causes a tension within the pin 42. This force may
be used to sever the pin 42 at the weakened section or portion 46
of the pin 42, where the pin 42 preferentially breaks.
[0048] One end 52 of the pin 42 is secured to the firing pin 24,
with the firing pin 24 being hollow and receiving the pin end 52.
An opposite end 54 of the pin 42 extends out of a cavity 58 in
which the firing pin 24 and the sleeve 44 are located. The pin end
54 compresses a stack of springs 62, such as a stack of Belleville
washers, that is in a recess 64 in the casing 38. When the pin 42
breaks at the weakened portion 48, a force separates the portions
of the metal pin on opposite sides of the weakened portion 46. This
force comes mainly from the energy stored in the sleeve 44 that
becomes kinetic energy pushing the pin end 52 and the firing pin 24
to slide within the cavity 58 toward the primer 26. In addition
some of the force moving the pin end 52 and the firing pin 24 may
come as a result of recoil from the breakage of the pin 42. The
compressed springs 62 provide an even loading on the pin 42. This
provides more consistency in the fracture temperature and the force
of the firing pin 24.
[0049] A stay spring 66 is also located within the cavity 58, with
the stay spring 66 being a coil spring that is between a ledge of
the casing 38 bordering the cavity 58. One function of the stay
spring 66 is to keep loose parts, such as the firing pin 24, from
moving around within the cavity 58 after the breakage of the pin
42. The spring 66 may also function to provide an additional and/or
back-up force to move the firing pin 24 toward the primer 26, after
breakage of the pin 42.
[0050] The primer 26 is activated when impacted by the firing pin
24. This in turn may fire a booster 68 that produces
detonation/combustion products, such as flames, hot gasses, and/or
molten material. These products are described herein as being
products of the detonation of the primer 26, even though the
booster 68 is also involved in creating the products that exit the
triggering element 22 to detonate the shaped charge 14 (FIG.
1).
[0051] A dowel pin 82 is located in and moves with the firing pin
24, providing a mechanical connection between the triggering
element 22 and the linkage 32. The dowel pin 82 links the firing
pin 24 to a linking member 84 that in turn converts translational
motion to rotational motion. The linking member 84 slides within a
cavity 88 in the casing 38, and relative to a fixed sleeve 90 that
is also within the cavity 88. With reference in addition to FIG. 5,
the linking member 84 includes a cam slot 92 that receives a cam
follower protrusion 94 on an end of a barrel valve 96. The barrel
valve 96 has a through hole 98 that needs to be aligned with the
outlet port 34 for output (hot gasses and other detonation
products) to exit the device 12 through the outlet port 34. These
products are used to detonate the shaped charge 14 (FIG. 1). The
barrel valve 96 is used as a safety device to prevent exit of the
detonation products unless the firing pin 24 has indeed been
activated to move. The movement of the firing pin 24 moves in
translation the dowel pin 82 and the linking member 84 as well. The
movement of the linking member 84 causes rotation of the barrel
valve 84 about the axis of the barrel valve 84. This occurs through
the interaction of the cam slot 92 and the follower protrusion
94.
[0052] FIGS. 6-11 show the process of triggering the device 12.
FIGS. 6 and 7 show the device 12 in its initial safe state, before
breakage at the weakened portion 46 of the pin 42. In this
condition the barrel valve through hole 98 is not aligned at all
with the outlet port 34, and the solid parts of the barrel valve 96
fully blocks the outlet port 34.
[0053] FIGS. 8 and 9 shows an intermediate step, where the pin 42
has broken and the firing pin 24 has started to move. The barrel
valve 96 has rotated to the point where the through hole 98 has
begun to align with the outlet port 34. However the barrel valve 96
still mostly blocks the outlet port 34. The device 12 is thus still
in a safe condition, with the primer 26 unable to detonate the
shaped charge 14 (FIG. 1).
[0054] FIGS. 10 and 11 show the situation just before the firing
pin 24 impacts the primer 26. The linkage 32 has now turned the
barrel valve 96 so that the through hole 98 is aligned with the
outlet port 34. In this condition the products from the detonation
of the primer 26 by the firing pin 24 can leave the casing 38
through the outlet port 34 to detonate the shaped charge 14 (FIG.
1).
[0055] Returning now to FIG. 4, the triggering device 12 also
includes the inertial lock-out 28, which is used to prevent
movement of the firing pin 24 once the missile 10 (FIG. 1) has been
launched. The components of the lock-out 28 are in a cavity 110 of
the device 12. The cavity 110 may be aligned with the cavity 88,
although other orientations are possible.
[0056] The lock-out 28 includes an inertial mass 114 that is
configured to shift its position in reaction to acceleration from
the launch of the missile 10 (FIG. 1). The mass 114 moves against a
spring force from a spring 116, which biases the position of the
inertial mass 114 to one side of the cavity 110, in the illustrated
embodiment against the fixed sleeve 90. The mass 114 is hollow, and
has a damping orifice 118 inserted in one of its ends, between the
mass 114 and the spring 116. The damping orifice 118 has air
passages therethrough configured to control the movement of the
inertial mass 114 through air resistance.
[0057] Other components are also within the hollow inside the
inertial mass 114: a lockout plunger 122, a plunger spring 124, and
a ball 126. A second ball 128 also initially partially rests in a
groove 134 in the inertial mass 114. The second ball 128 also is
initially in a hole 136 that is between the cavities 58 and 110,
aligned with a groove 138 in the firing pin 24.
[0058] Inertia from the launch of the missile 10 (FIG. 1) causes
the inertial mass 114 to move rightward in the diagram. The
movement of the inertial mass 114 pushes the ball 128 out of the
inertial mass groove 134 and into the firing pin groove 138. The
rightward movement of the inertial mass 114 also allows the ball
126 to emerge from the central hollow of the inertial mass 114,
being pushed by a tip of the lockout plunger 122, under the force
of the plunger spring 124. The ball 126 drops down in the space
left by movement of the inertial mass 114, blocking the inertial
mass 114 from returning to its original position. This blockage of
return movement of the inertial mass 114 keeps the ball 128 engaged
in and indeed locked in the firing pin groove 138. This prevents
movement of the firing pin 24, thereby also preventing the firing
pin 24 from engaging the primer 26.
[0059] Many variations are possible, in that some of the features
described above may be modified or in some instance omitted
altogether. For instance the inertial lock-out 28 (FIG. 4) may have
a different configuration than what is shown. Alternatively or in
addition the linkage 32 (FIG. 4) may have a different
configuration, or may be omitted altogether. In the latter case the
outlet port 34 (FIG. 4) may allow passage of detonation/combustion
products without any blockage. Alternatively a
differently-configured safety device may be employed in the outlet
port 34.
[0060] In operation, with reference now in addition to FIG. 12, a
method 200 of firing the triggering device 12 (FIG. 1) begins in
step 202 with the device 12 being heated until the forces from the
sleeve 44 (FIG. 4) cause the metal pin 42 (FIG. 4) to break, such
as at the notched or weakened portion 46 (FIG. 4).
[0061] In step 204 the breakage of the pin 42 (FIG. 4) causes the
firing pin 24 (FIG. 4) to move toward the primer 26 (FIG. 4). At
the same time, in step 206, the movement of the firing pin 24 acts
through the linkage 32 (FIG. 4) to rotate the barrel valve 96 (FIG.
4), eventually opening the valve 96. Finally in step 208 the firing
pin 24 strikes the primer 26 (FIG. 4), resulting in detonation
products from the primer 26 and the booster 68 (FIG. 4) exiting the
triggering device 12 (FIG. 1) through the outlet port 34 (FIG.
4).
[0062] The triggering device 12 provides many advantages over prior
devices. The use of the shape memory alloy sleeve provides a simple
and easy-to-tune mechanism for triggering based on heating.
[0063] Although the invention has been shown and described with
respect to a certain preferred embodiment or embodiments, it is
obvious that equivalent alterations and modifications will occur to
others skilled in the art upon the reading and understanding of
this specification and the annexed drawings. In particular regard
to the various functions performed by the above described elements
(components, assemblies, devices, compositions, etc.), the terms
(including a reference to a "means") used to describe such elements
are intended to correspond, unless otherwise indicated, to any
element which performs the specified function of the described
element (i.e., that is functionally equivalent), even though not
structurally equivalent to the disclosed structure which performs
the function in the herein illustrated exemplary embodiment or
embodiments of the invention. In addition, while a particular
feature of the invention may have been described above with respect
to only one or more of several illustrated embodiments, such
feature may be combined with one or more other features of the
other embodiments, as may be desired and advantageous for any given
or particular application.
* * * * *