U.S. patent application number 12/019553 was filed with the patent office on 2010-02-04 for frangible shape memory alloy fire sprinkler valve actuator.
Invention is credited to Roger Gilbertson, Alfred Johnson, Valery Martynov.
Application Number | 20100025050 12/019553 |
Document ID | / |
Family ID | 39401141 |
Filed Date | 2010-02-04 |
United States Patent
Application |
20100025050 |
Kind Code |
A2 |
Johnson; Alfred ; et
al. |
February 4, 2010 |
Frangible Shape Memory Alloy Fire Sprinkler Valve Actuator
Abstract
A temperature-activated valve for a conventional fire sprinkler
utilizing a hyperelastic single-crystal shape memory alloy is
described. The shape-memory element expands as it is heated,
forcing a bolt to break, thereby opening the sprinkler valve. The
devices described are less susceptible to accidental breakage than
conventional actuators, and have fewer moving parts. Transition
temperature of the shape memory alloy can be tuned to a narrow
range.
Inventors: |
Johnson; Alfred; (San
Leandro, CA) ; Gilbertson; Roger; (San Leandro,
CA) ; Martynov; Valery; (San Leandro, CA) |
Correspondence
Address: |
SHAY GLENN LLP
2755 CAMPUS DRIVE
SUITE 210
SAN MATEO
CA
94403
UNITED STATES
650-212-1700
info@shayglenn.com
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20090095493 A1 |
April 16, 2009 |
|
|
Family ID: |
39401141 |
Appl. No.: |
12/019553 |
Filed: |
January 24, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60/897,708 |
Jan 25, 2007 |
|
|
|
Current U.S.
Class: |
169/19 ;
29/890.124 |
Current CPC
Class: |
Y10T 29/49405 20150115;
A62C 37/16 20130101; B23P 15/001 20130101; Y10T 137/1797 20150401;
Y10T 137/1662 20150401; Y10T 29/49412 20150115 |
Class at
Publication: |
169/019 ;
029/890.124 |
International
Class: |
A62C 35/68 20060101
A62C035/68; A62C 37/11 20060101 A62C037/11 |
Claims
1. A thermally-activated sprinkler valve assembly comprising: a
fluid passageway having an outlet and configured to connect to a
source of pressurized fluid; a valve over the outlet, the valve
configured to releasably oppose the force of the pressurized fluid;
and a temperature-sensitive actuator coupled to the valve, the
actuator comprising: a frangible bolt; and a shape-memory element
capable of elongating at a pre-determined stress and temperature,
wherein the frangible bolt applies compressive force to the
shape-memory element; wherein the temperature-sensitive actuator is
configured to actuate the valve by breaking the frangible bolt when
the temperature of the shape-memory element reaches or exceeds the
pre-determined temperature.
2. The valve assembly of claim 1, further wherein the
temperature-sensitive actuator is coupled to the valve through a
linkage that is configured to oppose the force of pressurized fluid
and thereby maintain the valve closed.
3. The valve assembly of claim 2, wherein the temperature-sensitive
actuator is positioned in parallel with the linkage.
4. The valved assembly of claim 1, wherein temperature-sensitive
actuator is configured so that force from the pressurized fluid is
not substantially transmitted to the shape-memory element.
5. The valve assembly of claim 1, wherein the plateau stress of the
shape-memory element is approximately the same as the ultimate
tensile strength of the bolt.
6. The valve assembly of claim 1, further comprising a nut securing
the frangible bolt to the shape-memory element.
7. The valve assembly of claim 1, further comprising a frame
portion extending from the fluid passageway.
8. The valve assembly of claim 1, wherein the frangible bolt is
notched.
9. The valve assembly of claim 1, wherein the frangible bolt is a
titanium bolt.
10. The valve assembly of claim 1, wherein the shape-memory element
is a single-crystal CuAlNi alloy or a single-crystal CuAlMn
alloy.
11. The valve assembly of claim 1, wherein the shape-memory element
is a tempered single-crystal shape memory alloy.
12. The valve assembly of claim 1, wherein the shape-memory element
comprises a cylinder at least partially surrounding the frangible
bolt.
13. A thermally-activated sprinkler valve assembly comprising: a
fluid passageway having a valved outlet and configured to connect
to a source of pressurized fluid; a linkage coupled to the valved
outlet and configured to oppose the force of pressurized fluid and
thereby maintain the valve closed; and a temperature-sensitive
actuator coupled to the linkage, wherein the temperature-sensitive
actuator comprises: a frangible bolt; and a shape-memory element
capable of elongating as much as eight percent at a pre-determined
stress and temperature, wherein a length of the frangible bolt
applies compressive force to the shape-memory element.
14. The valve assembly of claim 13, further comprising a nut
securing the frangible bolt to the shape-memory element.
15. The valve assembly of claim 13, wherein the linkage comprises a
bracket.
16. The valve assembly of claim 13, wherein the linkage comprises
two T-shaped brackets.
17. The valve assembly of claim 13, wherein the frangible bolt is
notched.
18. The valve assembly of claim 13, wherein the frangible bolt is a
titanium bolt.
19. The valve assembly of claim 13, wherein the shape-memory
element is a single-crystal CuAlNi alloy or a single-crystal CuAlMn
alloy.
20. The valve assembly of claim 13, wherein the shape-memory
element is a tempered single-crystal shape memory alloy.
21. The valve assembly of claim 13, wherein the shape-memory
element comprises a cylinder at least partially surrounding the
frangible bolt.
22. The valved assembly of claim 13, wherein temperature-sensitive
actuator is configured so that force from the pressurized fluid is
not substantially transmitted to the shape-memory element.
23. The valve assembly of claim 13, wherein the
temperature-sensitive actuator is positioned in parallel with the
linkage.
24. The valve assembly of claim 13, wherein the plateau stress of
the shape-memory element is approximately the same as the ultimate
tensile strength of the bolt.
25. A thermally-activated sprinkler valve assembly comprising: a
fluid passageway having a valved outlet and configured to connect
to a source of pressurized fluid; a linkage bracket coupled to the
valved outlet and configured to oppose the force of pressurized
fluid and thereby maintain the valve closed; and a
temperature-sensitive actuator coupled to the linkage bracket,
wherein the temperature-sensitive actuator comprises: a frangible
bolt; and a shape-memory element capable of elongating as much as
eight percent at a pre-determined stress and temperature, wherein a
length of the frangible bolt applies compressive force to the
shape-memory element, an further wherein the plateau stress of the
shape-memory element is approximately the same as the ultimate
tensile strength of the bolt.
26. Method of making a thermally-activated sprinkler valve assembly
comprising: tuning a shape-memory element comprising single-crystal
shape memory alloy to exert a pre-determined force at a
pre-determined temperature; forming a temperature-sensitive
actuator by coupling a frangible bolt to the shape-memory element
so that the shape-memory element is compressed; and coupling the
actuator to a linkage, wherein the linkage is configured to couple
with the valve of a fluid passageway having a valved outlet to
oppose fluid pressure and maintain the valve closed.
27. The method of claim 26, further comprising connecting the fluid
passageway to a fluid source.
28. The method of claim 26, wherein the step of tuning comprises
tempering the shape-memory alloy by a heat treatment process that
causes controlled partial precipitation of Al.
29. The method of claim 26, further comprising coupling the linkage
to the valve of the fluid passageway.
30. The method of claim 26, wherein the step of coupling the
actuator to the linkage comprises coupling the actuator between two
brackets forming the linkage.
31. The method of claim 26, further comprising matching the plateau
stress of the shape-memory element to the ultimate tensile strength
of the bolt.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit under 35 U.S.C.
.sctn.119 of U.S. Provisional Patent Application No. 60/897,708
(titled "SHAPE MEMORY ALLOY FIRE SPRINKLER VALVE ACTUATOR"), filed
Jan. 25, 2007, which is incorporated by reference as if fully set
forth herein.
INCORPORATION BY REFERENCE
[0002] All publications, patents, and patent applications mentioned
in this specification are herein incorporated by reference in their
entirety as if each individual publication or patent application
was specifically and individually indicated to be incorporated by
reference in its entirety.
BACKGROUND OF THE INVENTION
[0003] The present invention relates to fire safety devices, and
more particularly to thermally actuated sprinklers commonly used in
commercial and residential buildings.
[0004] Large numbers of thermally-actuated fire sprinklers are
installed in structures every year. These sprinklers, generally
installed in the structure's ceiling, are connected to a
pressurized water supply and are intended to release the water into
the room when the temperature in the room indicates that a fire or
conflagration is taking place.
[0005] Multiple techniques have been used to actuate prior art fire
sprinkler heads. Some prior art sprinkler valves bond two
components together with alloys that melt at low temperatures. When
heated above the melting temperature of the eutectic alloy, the
bond between the two components is released, and a control valve is
permitted to open. This type of actuator is subject to failure as
the solder ages and crystallizes, thereby weakening the bond.
[0006] A second type of prior art sprinkler valve uses a sealed
glass tube nearly filled with a liquid that boils at a low
temperature. As ambient temperature increases, the liquid boils,
thereby raising the pressure inside the tube. At a high enough
temperature the tube ruptures, permitting the sprinkler valve to
open. Premature failure may occur, however, if the sprinkler head
is subjected to mechanical shock and the tube is cracked.
[0007] Yet other prior art sprinkler valves incorporate shape
memory components that change shape when a transition temperature
is reached to actuate the sprinkler valve. Some such thermally
actuated valves are described in U.S. Pat. No. 4,176,719; U.S. Pat.
No. 4,549,717; U.S. Pat. No. 4,596,483; U.S. Pat. No. 4,706,758;
U.S. Pat. No. 4,848,388; U.S. Pat. No. 4,896,728; U.S. Pat. No.
5,117,916; U.S. Pat. No. 5,494,113; U.S. Pat. No. 5,622,225; U.S.
Pat. No. 5,924,492; U.S. Pat. No. 6,073,700; U.S. Pat. No.
6,840,329; and U.S. Pat. No. 6,843,465. However, these devices do
not typically control the transition temperature of the shape
memory alloy, and the valve structures may therefore be less
reliable and overly complex.
[0008] False triggering of sprinkler heads can cause damage that is
expensive to repair and contributes to the cost of fire insurance.
Thermally-actuated fire safety devices must meet strict codes.
Described herein are thermally-activated, frangible sprinkler
valves including a shape-memory element that may meet these codes
and address many of the problems identified above.
SUMMARY OF THE INVENTION
[0009] Described herein are thermally-activated valves and methods
or making and using them. The thermally-activated valves described
herein are particularly useful as part of a sprinkler head, though
they may be used as part of any appropriate thermally-activated
valve.
[0010] In general, these thermally-activated sprinkler valve
assemblies include: a temperature-sensitive actuator having a
frangible bolt coupled to a shape-memory element, and a fluid
passageway with a valved outlet. The temperature-sensitive actuator
activates the sprinkler valve when the temperature of the
shape-memory element reaches or exceeds the pre-determined
temperature.
[0011] For example, described herein are thermally-activated
sprinkler valve assemblies including a fluid passageway having an
outlet (configured to connect to a source of pressurized fluid), a
valve over the outlet, where the valve is configured to releasably
oppose the force of the pressurized fluid, and a
temperature-sensitive actuator coupled to the valve. The
temperature-sensitive actuator includes a frangible bolt and a
shape-memory element capable of elongating at a pre-determined
stress and temperature, wherein the frangible bolt applies
compressive force to the shape-memory element. The
temperature-sensitive actuator is configured to actuate the valve
by breaking the frangible bolt when the temperature of the
shape-memory element reaches or exceeds the pre-determined
temperature.
[0012] Any of the valve assemblies described herein may include a
linkage that connects to the valve. For example, the
temperature-sensitive actuator may be coupled to the valve through
a linkage that is configured to oppose the force of pressurized
fluid and thereby maintain the valve closed. The
temperature-sensitive actuator may be positioned in parallel with
the linkage.
[0013] Any appropriate linkage may be used. In general, a linkage
links the actuator with the valve, and can be removed or displaced
by the activation of the actuator. For example, a linkage may be a
linkage bracket, a strut, or the like. In one variation, the
linkage is a linkage bracket formed from two generally "T-shaped"
brackets. The two linkages may connect to each other and to the
valve along one axis (the top of the "T" shape); the actuator may
be connected off-axis, between the bases of the "T" shape.
[0014] The temperature-sensitive actuator may be configured so that
force from the pressurized fluid is not substantially transmitted
to the shape-memory element. Transferring force from the fluid
pressure to the shape-memory element may affect the strain profile
of the shape-memory element, and alter the actuation
temperature.
[0015] The plateau stress of the shape-memory element may be
matched to the ultimate tensile strength of the frangible bolt. For
example, the ultimate tensile strength of the frangible bolt (at
which the bolt will break) may be approximately equal to the
plateau stress of the shape-memory element. Matching the plateau
stress and the ultimate tensile strength in this way may help
insure that the actuator acts in a predictable fashion at a
predetermined temperature.
[0016] The frangible bolt may be coupled or secured to the shape
memory device by a nut or other securing means. For example, the
bolt may be an elongate bolt that passes through a cylindrical
shape-memory element. The bolt may be secured against either end of
the shape-memory element with a flange and/or nut, placing
compressive stress on the shape-memory element.
[0017] A valve assembly may also include a frame portion extending
from the fluid passageway. For example, a valve assembly may
include one or more arms that extend from the fluid passageway. The
frame portion may provide support for other valve assembly
components, such as the linkage.
[0018] The frangible bolt may be modified by including one or more
notches or the like. The frangible bolt may be notched to set or
determine the ultimate tensile strength of the bolt. A notch may be
an annular notch or a side-notch (e.g., a notch on only one or more
sides of the bolt). The notch is typically a small region (compared
to the overall length of the bolt) that has a narrower diameter. A
frangible bolt is typically an elongate shape, and may be
cylindrical (e.g., columnar). Other elongate shapes may also be
used. Commercially available bolts may also be used. For example, a
titanium bolt (e.g., a Ti6Al4V bolt). Other bolts may also be used,
including steel (stainless steel) or the like. The bolt may be
threaded. For example, the bolt may be threaded at one or both
ends, or along the entire length). The bolt may have a head (e.g.,
a flange) or may be used with washers and one or more nuts.
[0019] The shape-memory element may be made of any appropriate
shape memory alloy. Shape-memory alloys capable of elongating up to
7%, 8% or 9% of their length are particularly useful in these
actuators. In particular, the shape-memory element may be a
single-crystal CuAlNi alloy or a single-crystal CuAlMn alloy.
Shape-memory alloys capable of elongating greater than 7% (such as
single-crystal SMAs) typically have a stress plateau that is longer
than other (non single-crystal SMAs). This elongated stress plateau
means that the actuator has a higher tolerance for breaking the
frangible bolt and thereby actuating. In turn, this higher
tolerance translates into a higher tolerance for the shape, type,
orientation and compressive pressure applied by the frangible bolt
component of the actuator.
[0020] The shape-memory element may be a tempered single-crystal
shape memory alloy. Tempering (e.g., heat treating to precipitate
Al from the single-crystal shape memory alloy) may be used to set
the stress profile, including the temperature at which the actuator
will actuate.
[0021] The shape-memory element may be any appropriate shape for
coupling to the frangible bolt so that it can rupture (break) the
bolt when actuation occurs. For example, the shape-memory element
may be a cylinder at least partially surrounding the frangible
bolt. The cylinder may have any appropriate cross-section (e.g.,
circular, elliptical, square, etc.). The shape-memory element may
be a strut or partial tube (e.g., a half-cylinder, etc.).
[0022] Also described herein are thermally-activated sprinkler
valve assemblies including a fluid passageway having a valved
outlet and configured to connect to a source of pressurized fluid,
a linkage coupled to the valved outlet and configured to oppose the
force of pressurized fluid and thereby maintain the valve closed,
and a temperature-sensitive actuator coupled to the linkage,
wherein the temperature-sensitive actuator includes a frangible
bolt, and a shape-memory element capable of elongating as much as
eight percent at a pre-determined stress and temperature. The
frangible bolt applies compressive force to the shape-memory
element. Any of the features described above may also be included
as part of this sprinkler valve assembly.
[0023] Also described herein are thermally-activated sprinkler
valve assemblies including a fluid passageway having a valved
outlet and configured to connect to a source of pressurized fluid,
a linkage bracket coupled to the valved outlet and configured to
oppose the force of pressurized fluid and thereby maintain the
valve closed, and a temperature-sensitive actuator coupled to the
linkage bracket. The temperature-sensitive actuator includes a
frangible bolt and a shape-memory element capable of elongating as
much as eight percent at a pre-determined stress and temperature,
wherein a length of the frangible bolt applies compressive force to
the shape-memory element, an further wherein the plateau stress of
the shape-memory element is approximately the same as the ultimate
tensile strength of the bolt.
[0024] Also described herein are methods of making a
thermally-activated sprinkler valve assembly including the steps
of: tuning a shape-memory element comprising single-crystal shape
memory alloy to exert a pre-determined force at a pre-determined
temperature; forming a temperature-sensitive actuator by coupling a
frangible bolt to the shape-memory element so that the shape-memory
element is compressed; and coupling the actuator to a linkage,
wherein the linkage is configured to couple with the valve of a
fluid passageway having a valved outlet to oppose fluid pressure
and maintain the valve closed.
[0025] The step of tuning may include tempering the shape-memory
alloy by a heat treatment process that causes controlled partial
precipitation of Al.
[0026] The method may also include the step of coupling the linkage
to the valve of the fluid passageway. For example, the step of
coupling the actuator to the linkage may comprise coupling the
actuator between two brackets forming the linkage.
[0027] The method may also include the step of matching the plateau
stress of the shape-memory element to the ultimate tensile strength
of the bolt.
[0028] The method may also include the step of connecting the fluid
passageway to a fluid source. This step may also be used as part of
a method for installing a frangible, temperature-sensitive shape
memory actuator for a sprinkler valve.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1A is a stress-strain-temperature plot for CuAlNi
single crystal shape memory alloy. The alloy is a
CuAl(14.3%)Ni(4.5%), A.sub.f=-40.degree. C. FIG. 1B is a
stress-strain curve for CuAl(14.0%)Ni(4.5%), A.sub.f=+15.degree. C.
FIG. 1C is a correlation of A.sub.f with composition content of Al.
The stress plateau increases 2.2 megapascals for each .degree. C.
increase in ambient temperature.
[0030] FIG. 2A is a stress-strain plot for a notched steel bolt
showing its elongation to failure at the ultimate tensile stress of
the steel. Tensile force reaches a maximum at the upper limit of
elasticity, and diminishes as elongation continues, terminating in
fracture at a fraction of one percent strain.
[0031] FIG. 2B is a stress-strain plot for a notched titanium bolt,
showing the elongation to failure at the ultimate tensile stress.
The titanium bolt was a Ti-6Al-4V bolt notched to 0.056 inch. The
maximum tensile stress is approximately 1999.4 MPa. A diamond-shape
Carbide insert notching tool having 35.degree. angle and 0.015''
tip radius was used to form the notch.
[0032] FIG. 3A shows a side view of one variation of a sprinkler
including a thermally-activated sprinkler valve assembly. FIG. 3B
is a front view of the same sprinkler shown in FIG. 3A.
[0033] FIG. 4A shows a side perspective view of one variation of a
temperature-sensitive actuator coupled to a linkage formed by two
brackets. FIG. 4B shows the notched bolt of the actuator of FIG.
4A, and FIG. 4C shows the actuator and the linkage without the
notched bolt.
[0034] FIG. 5A is a perspective view of one variation of a notched
frangible bolt. FIG. 5B is a side view of the frangible bolt of
FIG. 5A, showing exemplary dimensions (inches). FIG. 5C is a
detailed view of the notched region A indicated in FIG. 5B.
[0035] FIG. 6A is a perspective view of one variation of a
shape-memory element for an actuator. FIG. 6B is a cross-section
through the shape-memory element of FIG. 6A, showing exemplary
dimensions (inches). FIG. 6C is a top view of the shape-memory
element of FIG. 6A.
[0036] FIG. 7A is a perspective view of a first linkage bracket
that may form a linkage. FIG. 7B is a first side view of the
linkage bracket of FIG. 7A, with exemplary dimensions (inches), and
FIG. 7C is another side view of the linkage bracket. FIG. 7D is a
top view of the linkage bracket of FIG. 7A.
[0037] FIG. 8A is a perspective view of a second linkage bracket
that may form a linkage. FIG. 8B is a first side view of the
linkage bracket of FIG. 8A, with exemplary dimensions (inches), and
FIG. 8C is another side view of the linkage bracket. FIG. 8D is a
top view of the linkage bracket of FIG. 8A.
[0038] FIG. 9 illustrates forces acting on a portion of a linkage,
and illustrates how a linkage may oppose the force of water
pressure and impart direction to the actuator after activation.
[0039] FIG. 10 is a phase diagram for CuAlNi(3%).
DETAILED DESCRIPTION OF THE INVENTION
[0040] Described herein are thermally-activated sprinkler valve
assemblies. These thermally-activated sprinkler valve assemblies
may be configured to meet any appropriate performance
specifications, particularly those agreed upon by standard-setting
bodies such as Underwriter Laboratories (UL). For example, the
thermally-activated sprinkler valve assemblies described herein may
meet the UL Standards for Safety for Automatic Sprinklers for Fire
Protection Service, US 199 (10.sup.th edition, Apr. 8, 1997,
revised Dec. 8, 2003). In particular, the thermally-activated
sprinkler valves described herein may outperform currently
available frangible glass, eutectic, and other shape-memory based
sprinkler valves because they may be made particularly
vibration-insensitive, stable, and predictable.
[0041] In general, the thermally-activated sprinkler valve
assemblies described herein include a fluid passageway having an
outlet that is valved (over the outlet), and a
temperature-sensitive actuator that can be activated to open the
valve and allow fluid to flow from the sprinkler. The
temperature-sensitive actuator typically includes a frangible bolt
and a shape-memory element that is coupled to the bolt. Actuation
occurs when the shape-memory element expands at a predetermined
temperature to break the bolt.
[0042] The fluid passageway of the sprinkler may include a threaded
tubular conduit portion which is adapted to be connected to a
conduit network of a fire protection system. The conduit includes a
fluid passage having an inlet for attachment to a pressurized fluid
source, such as a pressurized water source, and an outlet. The
fluid passageway may also be connected to a frame portion or body
region, preferably made from a metal such as brass, stainless
steel, or other durable, non-corroding conventional sprinkler frame
material. For example, the frame may extend from the fluid
passageway region distally and may have one or more arms. A
deflector plate assembly for dispersing water when the sprinkler is
active may also be attached. The fluid passageway is valved, and
may include a valve plug. The valve communicates with a
temperature-sensitive actuator that can be activated to open the
otherwise closed valve. In some variations the
temperature-sensitive actuator communicates with the valve through
a linkage element, also referred to as a linkage, which is
configured to oppose the force applied by the water pressure until
activation. In these variations, activation of the sprinkler occurs
when the actuator displaces the linkage, releasing the valve to
open. In some variations, the frangible bolt acts as the linkage
element.
[0043] The temperature-sensitive actuator (or just actuator)
includes a frangible bolt and a shape-memory element that are
coupled together so that expansion of the shape-memory element may
result in breaking of the frangible bolt. The frangible bolt may
also apply a compression stress on the shape-memory element.
[0044] A shape-memory element may be made of a single-crystal
shape-memory alloy (SMA) that has a very large recoverable strain.
For example, the recoverable strain may be more than nine percent.
This shape-memory element is compressed and held under load by the
frangible bolt. As described in more detail below, the frangible
bolt may be notched or otherwise prepared to fracture at a preset
stress and strain.
[0045] Single crystal shape memory alloys, in addition to having
uniquely large recoverable strain, have a plateau in their
stress-strain relationship that increases with increasing
temperature in a highly predictable manner, as illustrated in FIGS.
1A and 1B. By adjusting composition, and by tempering to tune the
temperature at which a specified stress (and hence force) is
applied by the SMA element, it is possible to precisely match the
force exerted by a frangible bolt, and to elongate it to failure.
See FIG. 2A, showing the stress/strain relationship for a notched
steel bolt, and FIG. 2B showing the stress/strain relationship for
a notched titanium bolt.
[0046] Thus, a high-tolerance actuator may be made by matching the
point on the stress/strain curve from the frangible bolt (the
ultimate tensile strength) with the plateau stress of the
shape-memory element. Matching these characteristics of the
frangible bolt and the shape memory element allows selection of the
precise temperature of actuation, which may be specified. Such
precise actuators may therefore be manufactured at low cost,
because this `tuning` can be done only once per lot of
material.
[0047] In assembling the valve, the actuator including the
shape-memory element and the frangible bolt may be connected to the
valve opposing the fluid pressure so that the force of the fluid
pressure is not substantially communicated to the shape-memory
element. For example, the SMA element and bolt may be offset from
the force of the fluid pressure so that the fluid pressure force is
not directly applied to either the bolt or the shape-memory
element. This means that the bolt may be pre-loaded to its optimum
tension (for the shape-memory element) independent of the force
applied by the pressurized liquid. Since the force applied to the
shape-memory element is not dependent on the (potentially variable)
fluid pressure, the fluid pressure force will not alter the
activation temperature for the actuator.
[0048] In general, the stress plateau in a CuAlNi (or CuAlMn)
single crystal is related to the austenite finish temperature,
A.sub.f, of the material. The stress plateau is determined by the
difference between A.sub.f and the actuation temperature multiplied
by a constant (approximately 2.2 Mpa per .degree. C.). For example,
see FIG. 1A-1C. A.sub.f is the temperature at which transformation
from martensite (low temperature phase) to austenite is completed
at zero stress. A.sub.f is determined primarily by the composition
of the ingot from which the crystal is grown. A composition of 81.2
weight percent Cu, 14.3 weight percent Al, and 4.5 weight percent
Ni, for example, produces an A.sub.f transition temperature near
-40.degree. C.
[0049] Slight variations in composition, even of the order of 0.1
percent, can result in a significant variation of A.sub.f, as shown
in FIG. 1C. Such variations may result from weight measurement
inaccuracies, or evaporation of metal from the melt before or
during the crystal pulling operation, and so are difficult (if not
impossible) to control with the precision necessary to meet
sprinkler specifications. Actuation temperatures for sprinkler
systems are preferably controlled within plus or minus about
3.degree. C. This limitation may be overcome in the sprinkler
valves described herein by tempering the SMA material used.
[0050] At elevated temperatures, Al gradually precipitates as
nanocrystals. FIG. 10 shows a phase diagram for the CuAlNi alloy
system showing the phases that may exist in molten alloy at various
temperatures. Since nanocrystalline Al does not participate in the
phase transformation, controlled precipitation of Al is a method of
precisely tuning the A.sub.f of the material. Controlled selective
precipitation for the purpose of adjusting the actuation
temperature of the SMA is a unique form of tempering.
[0051] The shape-memory element provides the mechanical energy
necessary to actuate the actuators described herein, and actuation
occurs by breaking the frangible bolt and releasing the valve. For
example, a shape-memory element may be a cylinder of
single-crystal, hyperelastic CuAlNi having a transition temperature
above room temperature with a stress plateau at about 200 Mpa.
Other examples of shape-memory elements that may be used are
provided herein, and generally the properties of the shape-memory
element are matched to the properties of the bolt. In this first
example, the shape-memory element is a cylinder with a
cross-section that applies a force of 40 kg at the stress plateau
to a bolt that fractures at 40 kg elongation force when elongated
more than 3% of its length. The frangible bolt may be secured by a
nut that pre-loads the bolt to a tensile 35 kg force (and thus
applies an opposing compressive force to the shape memory element).
The bolt applies this compressive force to the shape memory
element. For example the shape-memory element may be compressed
approximately 9 percent of its length while the SMA is in its
martensitic state.
[0052] FIGS. 3A and 3B shows one variation of a sprinkler having a
thermally-activated sprinkler valve assembly as described. In this
example, the sprinkler 300 includes a temperature-sensitive
actuator 305, connected to a linkage 315, 315', which is held in
communication with a valve (the outside 301 of which is visible in
FIGS. 3A and 3B) and is supported by a frame 331 or body region. A
deflector plate 333 is attached to (or integral with) the frame
331. The frame 331 in this example includes two arms.
[0053] The temperature-sensitive actuator 305 includes a frangible
bolt 309, the bottom of which is visible in FIGS. 3A and 3B, which
is secured to (and compresses) a shape-memory element 321 formed as
a cylinder. The bolt is secured to linkage 315, 315' and held
within the cylinder by a nut 307 on one end, and is also attached
to a washer 311 on the opposite end. The linkage is formed by an
upper bracket 315 and a lower bracket 315' that are held together
between the valve 301 and the frame 331. When the
temperature-sensitive actuator is activated by reaching or
exceeding the pre-determined activation temperature, the
shape-memory element will expand (e.g., greater than 5%, greater
than 6%, greater than 7%, greater than 8% or greater than 9% of its
compressed length), and break the frangible bolt 309. Breaking the
frangible bolt causes the upper and lower brackets of the linkage
to separate under the force provided by the source of liquid (e.g.,
water) pressure, and thereby release the valve opposing the force
of the liquid pressure, allowing water to flow out of the valve.
The water may strike the deflector plate. After activation, the
temperature-sensitive actuator and the linkage may fall way from
the rest of the sprinkler.
[0054] FIG. 3B shows a partial cut-away view of the sprinkler of
FIG. 3A (in which one of the "arms" of the frame 331 have been
removed). In FIG. 3B it is apparent that the linkage is formed by
an upper 315 and lower 315' bracket that are configured so that the
majority of the force of the liquid pressure is opposed by the
linkage, and the temperature-sensitive actuator 305 is mounted in
parallel to the linkage. Thus, the force exerted by the liquid
pressure is not transferred to the frangible bolt via the linkage.
The frangible bolt holds the two approximately right-angle-shaped
linkage members secure until heat causes the SMA element to expand
and fracture the frangible bolt, causing the linkage to collapse
and release the fluid pressure. The compressive force on the
shape-memory element is predominantly applied by the bolt 309, and
the shape-memory element does not receive a substantial amount of
the force from the fluid pressure.
[0055] In this example, it is significant that the force due to
fluid pressure is transferred to the linkage and not to the
frangible bolt because the actuator, consisting of the shape-memory
element and frangible bolt, can be tuned to actuate at a
predetermined temperature (and force) independent of the force
exerted by the fluid force. If this were not so, the actual force
seen by the frangible bolt may depend on the sum of the (variable)
fluid force and the (constant) pre-load force, and the result would
be undesirable variation of the actuation temperature.
[0056] FIG. 4A shows a perspective view of the
temperature-sensitive actuator and linkage similar to that shown in
FIGS. 3A and 3B. In this example, the shape-memory element 421 is a
cylinder that is compressed by the frangible bolt 409 between two
brackets 415, 415' forming a linkage. The two brackets in this
example are nearly identical right-angle-shaped members 415, 415'
that interconnect. One of the brackets 415 has a pointed (or male)
end 416 that mates with concave (or female) end 417 on the other
bracket 415'. The opposite ends of the brackets forming the linkage
418, 418' are also configured to releasably mate with the valve
and/or the frame 331. In this example, these ends are pointed, but
they may be rounded, blunt, or any other appropriate shape. The two
brackets may be identical, each having one convex end and one
concave end.
[0057] FIG. 4B shows the frangible pin from FIG. 4A removed from
the temperature-sensitive actuator, and FIG. 4C shows the
shape-memory element and linkage with the frangible pin removed.
FIGS. 5A-5C also show greater detail of a frangible bolt.
[0058] Any appropriate frangible bolt may be used. In general, a
frangible bolt is an elongate member. The frangible bolt may be a
cylindrical bolt (as shown in FIGS. 4B-5B) including a threaded
portion 422. The threads may mate with a nut. The entire bolt may
be threaded or just one or more regions may be threaded. In some
variations, the thread mates with the linkage. Other bolt shapes
(including unthreaded bolts) may also be used. The bolt 409 may
include a head region 413 that has a flanged portion extending
outward from the elongate length of the bolt. The head region 413
in this example is slotted, but it may be otherwise configured for
securing or gripping.
[0059] A frangible bolt may also be notched. In FIGS. 4B-5C the
notch 411 is shown as an annular cut-out region. FIG. 5C
illustrates this region in greater detail. The notch may be formed
by any appropriate manner, including removing material from the
bolt after it has been formed, or it may be cast as an initial part
of the bolt. In some variations the notch does not extend
annularly, but may be present on only one side or region of the
bolt. Such asymmetric notching may help direct the fracturing of
the frangible bolt. The depth of the notch may help set the
ultimate tensile strength of the frangible bolt (the stress at
which the bolt will fracture), and may therefore help match the
bolt to the shape-memory element, as described below. The notch may
be located at any position along the length of the bolt, and the
location of the notch along the bolt may also help determine the
ultimate tensile strength. In some variations the bolt may include
only one notch or multiple notches.
[0060] The bolt may be made of any appropriate material,
particularly metals including alloys. For example, the bolt may be
a titanium bolt, such as a Ti6Al4V bolt, a steel (e.g., stainless
steel) bolt, or the like.
[0061] FIGS. 6A-6C show one variation of a shape-memory element
that may be used as part of a temperature-sensitive actuator, which
is configured as a cylinder. FIG. 6A shows a perspective view of
this cylindrical shape-memory element, which has a circular
cross-sectional profile (shown in FIG. 6C). The shape-memory
element has a length that is slightly less than length of the bolt.
The cylindrical shape-memory element in this example is hollow, so
that it can surround the frangible bolt.
[0062] Different configurations of shape-memory elements may be
used. For example, a cylindrical shape-memory element may have a
non-circular cross-section (e.g., an elliptical, cross-section, a
square cross-section, etc.). The shape-memory element may be
configured as a strut that is not hollow and which fastens to the
bolt in two or more places. The shape-memory element may be a
partial tube (e.g. a c-shaped tube).
[0063] The shape-memory element may be made of a single-crystal
shape memory alloy, such as a single-crystal CuAlNi alloy or a
single-crystal CuAlMn alloy. In particular, the shape-memory
element may be made of a shape-memory material capable of
elongating up to 7%, 8% or 9% of their length, referred to as
"hyperelastic" shape memory alloys. The exact composition (percent
composition) of the shape-memory alloy may be modified or
pre-determined to help match the stress plateau characteristics of
the shape-memory element with the stress profile (e.g., ultimate
tensile strength) of the frangible bolt.
[0064] By matching the peak strength of the frangible bolt to the
stress plateau of the shape-memory element, assured separation of
the bolt is achieved in a narrow temperature range as the
shape-memory element elongates much more than necessary to cause
the frangible bolt to fracture.
[0065] Thus, the temperature-sensitive actuator may include a
frangible bolt whose peak strength is matched to the stress plateau
of the shape-memory element. For example, the temperature sensitive
actuator may be made by first selecting a desired actuation
temperature A.sub.t. For example, the actuation temperature,
A.sub.t, may be selected from within the range of about -200 to
+200.degree. C. An optimum stress plateau level (S.sub.p) may then
be chosen. For example, S.sub.p may be between 50 and 600 Mpa. The
relationship between the stress plateau level and the activation
temperature may be described by the formula:
S.sub.p=2.3(A.sub.t-A.sub.f)
[0066] Where A.sub.f is the austenite finish temperature of the
shape-memory element, as described above. By choosing a
cross-sectional area X.sub.c of the shape-memory element that
applies force to the frangible bolt, the force exerted by the
shape-memory element F.sub.a can then be determined from the
relationship: F.sub.a=S.sub.p*X.sub.c
[0067] The ultimate strength of the frangible bolt (e.g., a notched
frangible bolt) may then be matched to equal this force (F.sub.a)
and the elongation to failure=E.sub.f, using a suitable margin of
safety to determine the length of the shape-memory element L.sub.a
such that, at the appropriate percent elongation (e.g., 5%, 6%, 7%,
8%, 9% elongation), the actuator will break the bolt while
maintaining the margin of safety. These calculations should also
take into account the compliance of other elements in the
joint.
[0068] Based on this determination, the ingot composition that will
produce single crystal material with A.sub.f can be chosen in order
to make the shape-memory actuator. For example, if the shape-memory
actuator is a cylinder, then a cylinder with a cross-section
X.sub.c, length L.sub.a, and an opening large enough to accommodate
the bolt may be fabricated.
[0069] The shape-memory element can then be compressed. For
example, a press can be used to compress the actuator to its 9
percent limit, and to maintain this shortened length by keeping the
actuator well below A.sub.f.
[0070] To complete assembly of the temperature-sensitive actuator,
the bolt, shape-memory element, and any other elements in the
joint, such as a nut, can then be assembled. The nut can be
tightened so that there is no slack in the joint. Finally, the
remainder of the sprinkler valve body can be installed, including
the linkage.
[0071] Any appropriate linkage may be used to connect the actuator
to the sprinkler. In particular, it may be preferable to use a
linkage that opposes the force of fluid (e.g., water pressure) when
the device is connected to a source of fluid pressure and the valve
is closed. In particular, it may be preferable to use linkages that
do not transfer a substantial portion (if any) of the fluid
pressure to the shape-memory element when the actuator is installed
with the other components of the sprinkler.
[0072] A linkage may connect or couple with the valve that opposes
the fluid pressure from a source of pressurized fluid that is
connected to the fluid passageway of the device. For example, the
linkage may abut or contact a portion of a valve (e.g., a valve
plug), to prevent the fluid pressure from opening the valve. The
linkage may also be connected or coupled to the body of the fluid
passageway (or another portion of the sprinkler body that is
connected to the body of the fluid passageway). In the example
shown in FIG. 3A, the linkage is coupled to the frame 331. In some
variations, the linkage may be configured to readily un-couple from
the valve (and/or frame or sprinkler body) when the actuator
triggers upon braking of the frangible bolt. In some variations,
the frangible bolt may act as the linkage. For example, one end of
the frangible bolt may be coupled to the valve, and the other end
may be functionally coupled to a frame connected to the sprinkler
body.
[0073] A two-piece linkage, such as that shown in FIGS. 3A-3B, 4A
and 4C may be particularly useful. In this example, the linkage
includes an upper (or first) linkage bracket and a lower (or
second) linkage bracket. FIGS. 7A-7D illustrate one variation of an
upper linkage. FIG. 7A shows a perspective view of an upper linkage
bracket 701 having a generally "T" shape. The bracket may be formed
from a single (flat) piece of metal that is cut and bent to form
the shape illustrated. The region of the bracket configured to hold
the actuator 703 is formed by the base of the "T" shape, and may
include a hole or passage 705 through which the actuator (e.g., the
frangible bolt portion of the actuator) may pass. The top of the
"T` shape in this linkage forms three prongs. One of the prongs 709
is configured to communicate with the valve, and the other two
prongs 711 are configured to communicate with (e.g., mate with)
prongs extending from the lower linkage. Although in this example
three prongs are shown, two prongs may be used. Also, the
orientation of the prongs may be different; for example, the two
prongs 711 may be configured to couple with the valve and the
single prong may be configured to couple with the other linkage.
FIG. 7B shows a top view, and FIGS. 7C and 7D show sides view of
the upper bracket 701.
[0074] FIGS. 8A-8D show an example of a lower bracket linkage that
may be used with the upper bracket linkage of FIGS. 7A-7D to couple
with an actuator and the valve of a fluid passageway. The lower
bracket is very similar to the upper bracket, except that the two
prongs that mate with the upper bracket prongs 811, 811' are shaped
to receive the upper bracket prongs.
[0075] The linkage may be configured so that the activation of the
temperature-sensitive actuator causes a predictable release. For
example, FIG. 9 illustrates the cross-section of another variation
of an upper bracket that is configured so that activation of the
actuator, and breaking of the frangible bolt, causes a predictable
release. Although FIG. 9 shows only an upper bracket, a second,
nearly identical lower bracket may have a similar design.
[0076] The upper bracket linkage shown in FIG. 9 is similar in
orientation to the upper bracket linkage shown in FIG. 7C, only
rotated 90 degrees counterclockwise. In this orientation, the first
prong 909 of the bracket is configured to communication with the
valve and oppose the force of the fluid pressure (indicated by
F.sub.water). The opposite prong 911 or prongs are configured to
mate with a lower bracket linkage which in turn mates with the
frame (also referred to as a "yoke") connected to the body of the
fluid passageway. Thus, these prong(s) 911 receive the counter
force, F.sub.yoke, to help balance the F.sub.water and thereby keep
the valve closed while the linkage is intact. In addition to the
forces balance the fluid pressure, the bolt of the
temperature-sensitive actuator also acts on the brackets by
providing a force F.sub.bolt that is also opposed and balanced by
the counterforce from the frame, F.sub.yolk. At equilibrium, the
force of the fluid pressure F.sub.water times the length of the
lever arm L.sub.water (the length seen by the F.sub.water in
relation to the opposing force F.sub.yolk) is balanced by the force
of the bolt, F.sub.bolt, times the lever arm L.sub.bolt, preventing
the bracket from rotating and coming uncoupled. In the example of
FIG. 9, the ratio between the lengths of the lever arms and the
forces applied by the bolt and the fluid (water) on the bracket are
generally balanced as a 1:8 ratio, but any appropriate ration may
be used. During activation, the force applied to the bracket will
unbalance as the bolt breaks, resulting in the rotation and
uncoupling of the bracket, removing the linkage and releasing the
valve.
[0077] A thermally-activated sprinkler valve assembly as
illustrated may be made by any appropriate method, as mentioned
above. In general, this method of making a thermally-activated
sprinkler valve may include first tuning a shape-memory element to
exert a pre-determined force at a pre-determined temperature. In
some variations, tuning involves selecting the activation
temperature (A.sub.t), and setting the austenite finish temperature
(A.sub.f) based on that temperature. This may be accomplished in
part by tempering. For example, a shape-memory element comprising
single-crystal shape memory alloy can be tempered by heat treating
and controlling the partial precipitation of Al from the
single-crystal material. Tweaking the concentration of Al will
adjust the A.sub.f.
[0078] Tuning may include matching the plateau stress of the
shape-memory element to the ultimate tensile stress (the breaking
point) of the frangible bolt. Stress profile may be examined
periodically to determine the plateau stress (as shown in FIGS. 1A
and 1B), or it may be calculated. The shape-memory material may
also be tuned by otherwise manipulating the composition of the
shape-memory material (e.g., doping, etc.). The ultimate tensile
strength of the bolt may also (or alternatively) be set based on
the shape-memory element (e.g., the plateau stress). For example,
the bolt shape and size may be selected to set the ultimate tensile
strength. Thus, the bolt may be notched or otherwise treated to set
the approximate ultimate tensile strength of the bolt.
[0079] The temperature-sensitive actuator may then be formed by
coupling the frangible bolt to the shape-memory element so that the
shape-memory element is compressed by the frangible bolt. Finally,
the actuator may be attached to the rest of the thermally-activated
sprinkler by coupling the actuator to a linkage, wherein the
linkage is configured to couple with the valve of a fluid
passageway having a valved outlet to oppose fluid pressure and
maintain the valve closed.
[0080] The assembled sprinkler may then be attached to a fluid
source.
Examples
[0081] Temperature-sensitive actuators were made by cutting
shape-memory elements with an abrasive wheel from Cu-14.0Al-4.5Ni
tubing (OD=0.235'', ID=0.115''). No subsequent machining was
performed. The shape-memory elements were approximately 0.451'' to
0.478'' long. The shape-memory elements were compressed and
constrained with the brass 4-40 button headed notched screws and
brass nuts. Notch size was 0.070''+/-0.001''. Assemblies were
individually tested by immersion in hot water, the temperature of
which was monitored with alkaline thermometer. The average
actuation temperature was 49.375.degree. C. (standard deviation of
1.96).
[0082] In another example, cylinders of shape-memory material were
machined from 0.25'' diameter Cu-14.0Al-4.5Ni (OD=0.23'';
ID=0.11''; L=0.483''). Machined cylinders were compressed to
L=0.450'' and constrained with brass 4-40 button headed notched
screws and brass nuts. Notch size is 0.070''+/-0.001''. On average,
the devices actuated between 45-46.degree. C. Afterwards, the
cylinders were quenched from 950 C into salt water, compressed and
constrained again, and actuated at an average temperature of
46.2.degree. C. (standard deviation of 2.20). These shape-memory
cylinders were compressed using frangible bolts made of 4-40 SS,
having a notch of 0.070''. These actuated at approximately
62.degree. C. (screw strength -2550N).
[0083] In yet another example, shape-memory elements were machined
from 0.25'' diameter Cu-13.9Al-4.5Ni rod (OD=0.23''; ID=0.11'';
L=0.49''). These cylinders were quenched from 950.degree. C. into
salt water, compressed and constrained. In this example, lowering
the Al content by 0.1% resulted in increase of actuation
temperature by .about.15 C.
[0084] Although the devices described herein are configured as
sprinkler valves, other configurations may also be used with the
temperature-sensitive actuators described. For example, a
temperature-sensitive actuator may be used as part of a release
valve for pressurized fluids including gasses. While the methods
and devices have been described in some detail here by way of
illustration and example, such illustration and example is for
purposes of clarity of understanding only. It will be readily
apparent to those of ordinary skill in the art in light of the
teachings herein that certain changes and modifications may be made
thereto without departing from the spirit and scope of the
invention.
* * * * *