U.S. patent application number 12/210674 was filed with the patent office on 2009-01-08 for variable resistance strut assemblies and articles containing the same.
This patent application is currently assigned to GM GLOBAL TECHNOLOGY OPERATIONS, INC.. Invention is credited to Alan L. Browne, Nancy L. Johnson, Gary L. Jones, Nilesh D. Mankame, James C. O'Kane, John C. Ulicny.
Application Number | 20090008844 12/210674 |
Document ID | / |
Family ID | 34994178 |
Filed Date | 2009-01-08 |
United States Patent
Application |
20090008844 |
Kind Code |
A1 |
Browne; Alan L. ; et
al. |
January 8, 2009 |
Variable Resistance Strut Assemblies and Articles Containing the
Same
Abstract
Disclosed herein is a strut assembly 10 comprising of a piston 3
in slideable communication with a housing 2; a seal 6 in operative
communication with the piston 3 and/or the housing 2; wherein the
seal 6 comprises an active material adapted to control the motion
of the piston 3. Disclosed herein too is a method of operating a
strut assembly 10 comprising displacing a suspended body 60 in
mechanical communication with a piston 3; wherein the piston 3
comprises a piston head 14 and a piston rod 12; activating an
active material in operative communication with the piston head 14;
and controlling the motion of the suspended body 60.
Inventors: |
Browne; Alan L.; (Grosse
Pointe, MI) ; Johnson; Nancy L.; (Northville, MI)
; Mankame; Nilesh D.; (Sterling Heights, MI) ;
Ulicny; John C.; (Oxford, MI) ; Jones; Gary L.;
(Farmington Hills, MI) ; O'Kane; James C.; (Shelby
Township, MI) |
Correspondence
Address: |
Quinn Law Group, PLLC
39555 Orchard Hill Place, Suite 520
Novi
MI
48375
US
|
Assignee: |
GM GLOBAL TECHNOLOGY OPERATIONS,
INC.
Detroit
MI
|
Family ID: |
34994178 |
Appl. No.: |
12/210674 |
Filed: |
September 15, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
11077179 |
Mar 10, 2005 |
|
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12210674 |
|
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|
60552791 |
Mar 12, 2004 |
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Current U.S.
Class: |
267/64.13 ;
267/64.23 |
Current CPC
Class: |
F16F 9/46 20130101; F16F
2224/045 20130101; F16F 2224/025 20130101; F16F 9/54 20130101; F16F
9/56 20130101; Y10T 292/699 20150401; E05B 2015/0493 20130101; F15B
15/204 20130101; E05B 47/0011 20130101; Y10T 292/17 20150401; F16F
15/005 20130101; E05B 81/20 20130101; F16F 9/466 20130101; F16F
2224/0283 20130101; Y10T 70/5093 20150401; E05B 51/005 20130101;
Y10T 292/1082 20150401; F16F 9/368 20130101; F16F 2224/0258
20130101; E05B 47/0009 20130101; F15B 15/26 20130101; F15B 21/065
20130101 |
Class at
Publication: |
267/64.13 ;
267/64.23 |
International
Class: |
F16F 5/00 20060101
F16F005/00; F16F 9/04 20060101 F16F009/04 |
Claims
1. (canceled)
2. (canceled)
3. (canceled)
4. (canceled)
5. A strut assembly comprising: a piston in slideable communication
with a housing, wherein the piston comprises a piston head having a
channel in operative communication with a fluid disposed in the
housing; and a flow control element comprising an active material
disposed in the piston head, wherein the flow control element is
operative to control an effective diameter of the channel.
6. The strut assembly of claim 5, wherein the flow control element
comprises one or more layers.
7. The strut assembly of claim 5, wherein the flow control element
comprises a first layer and a second layer, and wherein either the
first layer and/or the second layer comprises the active
material.
8. The strut assembly of claim 7, wherein the second layer
comprises two opposed active elements and that can be used to vary
the effective diameter of a channel by changing the position of the
first layer.
9. The strut assembly of claim 5, wherein the flow control element
is operative to control the resistance to the motion of the
piston.
10. The strut assembly of claim 5, wherein the flow control element
prior to activation can be located so as to effectively maintain
the channel in an open position, a partially open position or a
closed position.
11. The strut assembly of claim 5, wherein an axis of the flow
control element intersects with an axis of the channel.
12. The strut assembly of claim 5, wherein the active material is a
shape memory alloy.
13. A strut assembly comprising: a piston in slideable
communication with a housing, wherein the piston comprises a piston
head having a channel in operative communication with a fluid
disposed in the housing; an elastic member disposed in the channel;
and an active material in operative communication with the elastic
member, wherein the active material is operative to change the
shape of the elastic member.
14. The strut assembly of claim 13, wherein the channel has a
cross-sectional area that is square or rectangular.
15. The strut assembly of claim 13, wherein the elastic member
comprises at least one flat surface that is disposed parallel to at
least one inner surface of the channel prior to activation.
16. The strut assembly of claim 13, wherein each channel comprises
about to about elastic members that are in operative communication
with an active material.
17. The strut assembly of claim 16, wherein the active material is
a shape memory alloy.
18. (canceled)
19. (canceled)
20. (canceled)
21. (canceled)
22. An article employing the strut assembly of claim 5.
23. An article employing the strut assembly of claim 14.
24. (canceled)
25. The strut assembly of claim 5, wherein the flow control element
provides a first level of resistance when the active material is at
a first temperature and wherein the flow control element provides
an increased level of resistance greater than the first level of
resistance when the active material is at an increased temperature
greater than the first temperature.
26. The strut assembly of claim 25, wherein the increased level of
resistance of the flow control element is proportional to the
increased temperature of the active material.
27. The strut assembly of claim 5, wherein the flow control element
has a first cross-sectional shape when the active material is in an
inactivated state, and wherein the flow control element has a
second cross-sectional shape when the active material is in an
activated state.
28. The strut assembly of claim 13, wherein the elastic member
provides a first level of resistance when the active material is at
a first temperature and wherein the elastic provides an increased
level of resistance greater than the first level of resistance when
the active material is at an increased temperature greater than the
first temperature.
29. The strut assembly of claim 13, wherein the elastic material
has a first cross-sectional shape when the active material is in an
inactivated state, and wherein the elastic material has a second
cross-sectional shape when the active material is in an activated
state.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application Ser. No. 60/552,791 filed Mar. 12, 2004, the entire
contents of which are hereby incorporated by reference.
BACKGROUND
[0002] This disclosure relates to variable resistance strut
assemblies and articles that contain the same.
[0003] Strut assemblies are often used in automobiles to facilitate
the opening, locking and positioning of doors, trunks, hoods,
tail-gates, or the like. These assemblies generally do not offer
opportunities for fine control. In addition, these assemblies are
often susceptible to temperature changes and their performance
tends to vary with temperature and other environmental conditions.
The strut assemblies that are commerically available have
functional attributes that are fixed during design and manufacture.
These functional attributes cannot be controlled but can vary with
wear and operating conditions. For example, the fluid used in a
strut assembly may have a viscosity that is chosen to yield optimum
performance in terms of the effort required to extend and retract
the strut over a nominal range of temperatures. If however, the
temperature drops below this nominal range, the viscosity
increases, thereby increasing the effort required to extend and
retract the strut.
[0004] It is therefore desirable to use strut assemblies that offer
opportunities for fine control during opening and closing and which
offer reproducible performance under a variety of different
conditions.
SUMMARY
[0005] Disclosed herein is a strut assembly comprising a piston in
slideable communication with a housing; a seal in operative
communication with the piston and/or the housing; wherein the seal
comprises an active material adapted to control the motion of the
piston.
[0006] Disclosed herein too is a strut assembly comprising a piston
in slideable communication with a housing, wherein the piston
comprises a piston head having a channel in operative communication
with a fluid disposed in the housing; and a flow control element
comprising an active material disposed in the piston head, wherein
the flow control element is operative to control an effective
diameter of the channel.
[0007] Disclosed herein too is a strut assembly comprising a piston
in slideable communication with a housing, wherein the piston
comprises a piston head having a channel in operative communication
with a fluid disposed in the housing; an elastic member disposed in
the channel; and an active material in operative communication with
the elastic member, wherein the active material is operative to
change the shape of the elastic member.
[0008] Disclosed herein too is a method of operating a strut
assembly comprising displacing a suspended body in mechanical
communication with a piston; wherein the piston comprises a piston
head and a piston rod; activating an active material in operative
communication with the piston head; and controlling the motion of
the suspended body.
DETAILED DESCRIPTION OF DRAWINGS
[0009] FIG. 1 is a depiction of an exemplary embodiment of a strut
assembly 10 comprising channels 8 disposed in the piston head 14
and seals 6 disposed between the piston head 14 and the inner
surface of the housing 2;
[0010] FIG. 2 is an exemplary depiction of a seal 6 that comprises
an active material 74 that can be used to vary the friction between
the piston head 14 and the inner surface of the housing 2;
[0011] FIG. 3 is an exemplary depiction of a section of the piston
head 14 and the housing 2, wherein the piston head 14 has a seal 6
that comprises an active material 74. The figure schematically
depicts the seal 6 prior to activation;
[0012] FIG. 4 is an exemplary depiction of the piston head 14 and
the housing 2, wherein the piston head 14 has a seal 6 that
comprises an active material 74. The figure schematically depicts
the seal 6 after activation;
[0013] FIG. 5 is an exemplary depiction of a top view and a side
view of a flow control element 76 that can be used to change the
effective diameter of the channel 8;
[0014] FIG. 6 is an exemplary depiction demonstrating one mode of
using the flow control element 76 to change the effective diameter
of the channel 8; and
[0015] FIG. 7 is an exemplary depiction demonstrating the use of
elastic members 94, 96 in operative communication with active
elements 90, 92 to vary the effective diameter of the channel
8.
DETAILED DESCRIPTION
[0016] Disclosed herein are strut assemblies that can be programmed
or adjusted to display a selected level of resistance to
displacement. The strut assembly comprises an active material (a
shape memory material) that can be activated to vary the amount of
the resistance to any displacement of the moving parts of the strut
assembly. In one embodiment, the active material can change its
shape, size or stiffness in response to the applied activation
signal. Thus by applying an activation signal of a selected
magnitude to the active material, a measured amount of resistance
can be offered by the strut assembly to a displacing force.
[0017] The strut assembly is disposed between the suspended body
and a supporting body and is in operative communication with the
suspended body and the supporting body. The suspended body may be
any device that utilizes spatial positioning such as a door in an
automobile or a residential building; the hood or trunk of a
automobile; the jaws of a vice or a press; the platens on machine
tools such as injection molding machines, compression molding
machines; arbors and chucks on lathes and drilling machines, or the
like. The supporting body can comprise a door frame, an automobile
frame, a aircraft frame, a ship frame, or the like. The suspended
body is generally movable and can be displaced with respect to the
supporting body, which generally occupies a fixed position. The
suspended body can be opened or closed with respect to the
supporting body.
[0018] In one embodiment, the active material that is used to offer
resistance to the displacement of the strut assembly is generally
contained inside of the housing of the strut assembly. In another
embodiment, the active material can be disposed outside the strut
assembly. The active materials are generally employed in a manner
effective to increase the resistance to the motion of the piston
inside the housing.
[0019] With reference to the FIG. 1, which represents the prior
art, a strut assembly 10 comprises a housing 2 that is in slideable
communication with a piston 3. The piston 3 comprises a piston head
14 and a piston rod 12. The piston head 14 is fixedly attached to
the piston rod 12. The housing 2 contains a fluid 4. The piston
head 14 has disposed in it channels 8 that permit the passage of
the fluid 4 across the piston head 14 as it is displaced in the
housing 2. The channels 8 are disposed parallel to the piston rod
12 and have at least one axis of symmetry parallel to the direction
of travel of the piston rod 12. The channel 8 may also have a
convoluted path if desired. The channels 8 can have a cross-section
area that has any desired shape. For example, the cross-sectional
area of the channel can be circular, square, rectangular, or the
like. Seals 6 are circumferentially disposed upon the piston head
14 and seal the space between the piston head 14 and the cylinder
2. Seals 6 can also be optionally disposed between the piston rod
12 and the housing 2. The seals 6 are concentric with the piston
rod 12 and/or the housing 2. The strut assembly 10 is in operative
communication with a supporting body 50 (e.g., the body of the
vehicle) and is also in operative communication with a suspended
body 60 (e.g., a panel that swings back and forth such as a door).
The supporting body 50 and the suspended body 60 are disposed at
opposing ends of the strut assembly 10. While the suspended body 60
is generally displaced with respect to the supporting body 50, it
is possible to have both the supporting body 50 and the suspended
body 60 displaceable with respect to each other.
[0020] As the piston rod 12 slides back and forth in the housing 2
during the expansion or contraction of the strut assembly 10, the
fluid 4 is forced to flow through the channels 8 in the piston head
14. This flow is restricted by the channels 8 and the restricted
flow gives rise to two forces that resist relative motion between
the piston and the cylinder, an elastic force arising out of the
compression of the fluid column that the piston head 14 is pushing
against and a hydrodynamic force arising from the resistance to
fluid flow through the channels 8 in the piston head 14. Friction
brought on by the presence of the seal 6 between the piston head 14
and the inner wall of the housing 2, or between the piston rod 12
and the housing 2, also resists relative motion between the piston
head and the cylinder.
[0021] FIG. 2 represents one exemplary depiction of a seal 6 that
comprises a smart material and which can be used to vary the
friction between an inner surface of the housing 2 and the piston
head 14 to control the motion of the piston 3. The seal 6 comprises
a first layer 72 upon which is disposed a second layer 74. In one
embodiment, the first layer 72 and the second layer 74 are
concentrically disposed, with at least one surface of the first
layer 72 in intimate contact with at least one surface of the
second layer 74. The second layer 74 comprises a soft, easily
deformable elastomer while the first layer 72 comprises an active
material (shape memory material) whose geometry, dimensions and/or
stiffness can be controlled by the application of an external
stimulus.
[0022] Exemplary shape memory materials that can be used in the
first layer 72 are shape memory alloys, electroactive polymers,
hydrogels, or the like. Shape memory materials generally refer to
materials or compositions that have the ability to revert to a
specified original shape (or crystal structure) in response to an
external stimulus, i.e., an activation signal even after they have
been deformed from that original shape (or structure). Exemplary
shape memory materials suitable for use in the present disclosure
include shape memory alloys and ferromagnetic shape memory alloys
and composites of the foregoing shape memory materials with
non-shape memory materials, and combinations comprising at least
one of the foregoing shape memory materials. In another embodiment,
the class of smart materials used in the customizable strut
assembly 10 are those that change their shape in proportion to the
strength of the applied field but then return to their original
shape upon the discontinuation of the field.
[0023] An exemplary smart material is a shape memory alloy. Shape
memory alloys (SMA's) generally refer to a group of metallic
materials that demonstrate the ability to return to some previously
defined shape or size when subjected to an appropriate thermal
stimulus. Shape memory alloys are capable of undergoing phase
transitions in which their elastic modulus (which influences its
stiffness), yield strength, and shape orientation are altered as a
function of temperature. Generally, in the low temperature, or
martensite phase, shape memory alloys can be seemingly plastically
deformed (about 8 to about 10% strain) and upon exposure to some
higher temperature will transform to an austenite phase, or parent
phase, returning to their shape prior to the deformation by
recovering substantially all of the associated strain. Materials
that exhibit this shape memory effect only upon heating are
referred to as having one-way shape memory. Those materials that
also exhibit shape memory upon re-cooling are referred to as having
two-way shape memory behavior.
[0024] Shape memory alloys can exhibit a one-way shape memory
effect, an intrinsic two-way effect, or an extrinsic two-way shape
memory effect depending on the alloy composition and processing
history. Annealed shape memory alloys typically only exhibit the
one-way shape memory effect. Sufficient heating subsequent to
low-temperature deformation of the shape memory material will
induce the martensite to austenite type transition, and the
material will recover the original, annealed shape. Hence, one-way
shape memory effects are only observed upon heating.
[0025] Intrinsic and extrinsic two-way shape memory alloys are
characterized by a shape transition both upon heating from the
martensite phase to the austenite phase, as well as an additional
shape transition upon cooling from the austenite phase back to the
martensite phase. Active materials that exhibit an intrinsic
one-way shape memory effect are fabricated from a suitably
processed shape memory alloy that will cause the active materials
to automatically reform themselves as a result of the above noted
phase transformations. Intrinsic two-way shape memory behavior must
be induced in the shape memory material through processing. Such
procedures include extreme deformation of the material while in the
martensite phase, heating-cooling under constraint or load, or
surface modification such as laser annealing, polishing, or
shot-peening. Once the material has been trained to exhibit the
two-way shape memory effect, the shape change between the low and
high temperature states is generally reversible and persists
through a high number of thermal cycles. In contrast, active
connector elements that exhibit the extrinsic two-way shape memory
effects are composite or multi-component materials that combine a
shape memory alloy composition that exhibits a one-way effect with
another element that provides a restoring force to return the first
plate another position or to its original position.
[0026] The temperature at which the shape memory alloy remembers
its high temperature form when heated can be adjusted by changes in
the composition of the alloy and through heat treatment. In
nickel-titanium shape memory alloys, for instance, it can be
changed from above about 100.degree. C. to below about -100.degree.
C. The shape recovery process occurs over a range of just a few
degrees and the start or finish of the transformation can be
controlled to within a few degrees depending on the alloy
composition.
[0027] Suitable shape memory alloy materials for fabricating the
active materials include nickel-titanium based alloys,
indium-titanium based alloys, nickel-aluminum based alloys,
nickel-gallium based alloys, copper based alloys (e.g., copper-zinc
alloys, copper-aluminum alloys, copper-gold, and copper-tin
alloys), gold-cadmium based alloys, silver-cadmium based alloys,
indium-cadmium based alloys, manganese-copper based alloys,
iron-platinum based alloys, iron-palladium based alloys, or the
like, or a combination comprising at least one of the foregoing
shape memory alloys. The alloys can be binary, ternary, or any
higher order so long as the alloy composition exhibits a shape
memory effect, e.g., change in shape orientation, changes in yield
strength, and/or flexural modulus properties, damping capacity, and
the like.
[0028] The thermal activation signal may be applied to the shape
memory alloy in various ways. It is generally desirable for the
thermal activation signal to promote a change in the temperature of
the shape memory alloy to a temperature greater than or equal to
its austenitic transition temperature. Suitable examples of such
thermal activation signals that can promote a change in temperature
are the use of steam, hot oil, resistive electrical heating, or the
like, or a combination comprising at least one of the foregoing
signals. A preferred thermal activation signal is one derived from
resistive electrical heating.
[0029] Exemplary elastomers that may be used in the first layer 72
are polybutadiene, polyisoprene, polybutadiene-polystyrene diblock
elastomers, polystyrene-polybutadiene-polystyrene triblock
elastomers, polystyrene-polyisoprene-polystyrene triblock
elastomers, acrylonitrile-butadiene-styrene elastomers, or the
like, or a combination comprising at least one of the foregoing
elastomers.
[0030] The seal 6 is placed in the piston head 14 as shown in the
FIG. 3. FIG. 3 is an exemplary schematic depiction reflecting the
default configuration of the seal 6, where the first layer 72 is in
its unactivated state. In this configuration, the resistance to
displacement of the piston 3 in the housing 2 is dictated by the
hydraulic requirements on the seal.
[0031] When the shape memory material in the first layer 72 is
activated, there is a change in the area and/or pressure of contact
between the seal 6 and the inner surface of the housing 2. Upon
activation, the shape memory material expands in size or otherwise
changes its configuration, such that the contact area and/or
pressure between the second layer 74 of the seal and the inner
surface of the housing 2 increases. This change in the contact area
and/or pressure permits an increase in the frictional resistance
between the seal 6 and the housing 2, which permits control over
the user effort required to produce displacement of the suspended
body 60 that is in operational communication with the strut
assembly 10. FIG. 4 is an exemplary depiction of the seal 6 after
activation. In the FIG. 4, it can be seen that the area of contact
between the seal 6 and the inner surface of the housing 2 has
increased significantly when compared with the area of contact
prior to activation as depicted in the FIG. 3.
[0032] In an exemplary embodiment, the shape memory material
utilized in the first layer 72 can be manufactured from a shape
memory alloy and can have a stent-like structure. This will permit
the first layer 72 to exhibit the two-way or `all-around` shape
memory effect. The use of a shape memory alloy in the first layer
72 will permit the seal 6 to remember different shapes
corresponding to different temperatures. Passage of an electric
current through the shape memory alloy material can heat it to
raise its temperature corresponding to the shape of the seal shown
in FIG. 4. Moreover, controlling the current flowing through the
element to achieve an intermediate temperature will result in an
intermediate level of frictional resistance.
[0033] In addition to shape memory alloys, other shape memory
materials that can be used to activate the seals 6 are
electro-active polymers, magneto-rheological elastomers/foams,
smart-material-based reconfigurable oil rings, hydrogels, or the
like. As noted above, the seal, which is generally used to prevent
leakage of fluid across the piston head plays an additional role of
controlling the frictional resistance to the relative motion
between the piston and cylinder. In one embodiment, other active
seals can be used in the strut assembly 10 to facilitate
controlling of the frictional resistance between the piston and the
cylinder. Exemplary locations for such seals are between the piston
rod and the cylinder.
[0034] In yet another embodiment, the channel 8 in the piston head
14 may employ shape memory materials to control resistance to the
displacement of the piston 3. In one exemplary embodiment depicted
in the FIG. 5, the geometry of these channels can be varied by
applying an external stimulus to change the effective diameter of
the channel 8 and therefore the resistance to displacement. As can
be seen in the FIG. 5, the flow control element 76 has an axis AA'
that passes through the center of the hole 82 in the flow control
element 76. In one embodiment, the axis AA' is an axis that passes
through the largest dimension of the flow control element 76. In
another embodiment, the axis AA' divides the flow control element
76 into equal halves.
[0035] The flow control element 76 comprises one or more layers. In
one embodiment, when the flow control element 76 comprises multiple
layers, the layers can be concentric, i.e., they can share the same
axis. The flow control element 76 can have any desired geometry,
i.e., its cross sectional area can be rectangular, circular,
square, or the like. In the exemplary embodiment depicted in the
FIG. 5, the flow control element comprises multiple layers that are
concentrically disposed. The flow control element comprises a first
layer 78 and a second layer 80 that are in operative communication
with each other. In one embodiment, at least one surface of the
first layer 78 is disposed upon and in intimate contact with one
surface of the second layer 80. The first layer 78 and/or the
second layer 80 can comprise an active material. In one embodiment,
the second layer 80 can comprise one or more active elements that
comprise the active material. In another embodiment, the first
layer 78 and/or the second layer 80 comprises two opposed active
elements 84 and 86 that can be used to vary the effective diameter
of the channel 8 by changing the position of the first layer 78.
Opposed active elements as defined herein are those that act in an
opposite fashion from each other. In other words, when element 84
expands as the result of being activated by an external stimulus,
element 86 correspondingly contracts and vice versa.
[0036] Alternatively, the elements 84 and 86 can act in opposition
to each other. In other words, when element 84 expands as the
result of being activated by an external stimulus, element 86
correspondingly expands. Similarly, when element 84 contracts in
size as the result of being activated by an external stimulus,
element 86 correspondingly undergoes a contraction in size.
[0037] The flow control element 76 has disposed in it a hole 82 as
shown in the FIG. 5. In one embodiment, the hole 82 is generally
disposed in the geometric center of the flow control element 76. In
another embodiment, the surface of the hole 82 is perpendicular to
at least one axis of symmetry of the flow control element 76. In
yet another embodiment, the surface of the hole 82 is perpendicular
to the axis AA'. The hole 82 can be of a diameter that is greater
than, equal to or less than the diameter of the flow channel.
[0038] The FIG. 6 depicts a section of the piston head 14 that
comprises one flow channel 8 and the flow control element 76. The
flow control element 76 is inserted adjacent to the flow channel 8
in the piston head 14 such that an axis AA' of the flow control
element 76 intersects an axis BB' of the channel 8. In one
embodiment, the axis AA' of the flow control element 76 is
perpendicular to the longitudinal axis of the channel 8. In another
embodiment, the axis AA' of the flow control element 76 is inclined
at any desirable angle (not shown) to the longitudinal axis BB' of
the channel 8. The longitudinal axis BB' of the channel 8 is an
axis of symmetry that is parallel to the direction of travel of the
piston rod 12.
[0039] With reference now to the FIG. 6, the flow control element
76 has a hole 82 that aligns itself coaxially with the channel 8.
The hole 82 in the flow control element 76 can be moved relative to
the channel 8 in the piston head 12. Thus by varying the magnitude
of the external stimulus supplied to the opposing active elements,
the effective diameter of the channel 8 can be changed. Changing
the effective diameter of the channel 8 promotes variation in
resistance to the displacement of the piston 3 and hence to the
displacement of the suspended body 60 (not shown).
[0040] The default position (i.e. the position when neither of the
active elements is activated) can be chosen on the basis of the
desired functionality. For example, if the default position
corresponds to a partially open channel 8 as shown in the FIG. 6,
the hydrodynamic resistance can be increased or decreased as
appropriate; if the default position corresponds to a fully open
channel, the hydrodynamic resistance can only be increased; and if
the default position corresponds to a fully closed channel, the
hydrodynamic resistance can only be reduced but this arrangement
can be used to hold the suspended body 60 (not shown) open in any
desired position.
[0041] In one embodiment, the flow control element can be disposed
at different locations in the piston head. Instead of disposing the
flow control element at the center of the piston head as depicted
in the FIGS. 5 and 6, it can be disposed proximate to the end of
the piston head. In this embodiment, the geometry of the hole in
the flow control element 76 can be adjusted to afford a further
control over the fluid flow resistance e.g., the channel can have
its shape adjusted to function as a converging or a diverging
nozzle.
[0042] The active elements can be made of pre-strained shape memory
alloy material, which is in its martensitic form in the default
position. As discussed earlier, an electric current can be used to
actuate these elements. Fine control over the channel's effective
diameter can be exercised by controlling the current flowing
through the two opposed active elements. Upon removing the
electrical current, the flow control element 76 returns to its
default position, thereby returning the effective diameter of the
flow control element 76 to its original size.
[0043] In yet another exemplary embodiment, depicted in the FIG. 7,
active elements mounted inside the channel 8 can be used to vary
the geometry and the effective diameter of the channel 9, thereby
varying the hydrodynamic resistance offered to the motion of the
piston 3. FIG. 7 reflects a section of the piston head 14
comprising the channel 8 in which one or more active elements are
disposed. The active elements comprise active materials. The active
elements can be in operational communication with each other if
desired. While the channels 8 can have cross-sectional areas that
are square or rectangular, channels employing other geometrical
cross-sectional areas can be used. The active elements 90, 92 used
in the channel 8 are generally manufactured from a shape memory
alloy, although other smart material based actuators such as
electroactive polymers, or the like, can also be used. The active
elements 90, 92 are each in operational communication with elastic
members 94, 96 respectively. While in the FIG. 7, the active
elements 90, 92 together with the corresponding members 94, 96 are
disposed on opposing surfaces of the rectangular channel 8, they
may be disposed on adjacent surfaces.
[0044] In one embodiment, only a single active element and a
corresponding elastic member may be disposed on a surface of the
channel 8. In another embodiment, two or more active elements along
with their corresponding elastic members can be disposed on the
surfaces of the channel 8. As noted above, the respective active
elements may be in operative communication with each other. In yet
another embodiment, even when one or more active elements are
disposed inside the channel 8, they may be activated individually
independent of each other or cooperatively in combination with one
another.
[0045] The elastic members 94, 96 can be deformed by the active
elements 90, 92 either upon activation or upon deactivation. As
noted above, the active elements 90, 92 are manufactured from a
shape memory material that is in its martensitic form in the
default configuration. Electroactive polymers can also be used as
the active elements. The default configuration is the configuration
of the active elements 90, 92 prior to activation. In one
embodiment, the elastic members are generally flat members having a
length equal to the length of the channel 8 prior to activation. In
another embodiment, the elastic members 94, 96 can extend outside
the channel e.g. are wrapped around the end of the channel such
that the members remain centered with respect to the channel even
after activation. In one embodiment, at least one surface of an
elastic member is disposed parallel to one inner surface of the
channel 8 prior to activation. In another embodiment, the surface
of the elastic member is curved prior to activation. A curved
surface prior to activation is generally used to facilitate
additional deformation of the surface during or after activation.
Varying the curvature of the elastic member prior to activation can
be advantageously used to vary the resistance to piston motion with
minimal activation if desired. Each channel 8 comprises about 1 to
about 4 elastic members that are in operative communication with an
active material.
[0046] The elastic members can be manufactured from spring steel
and are of a thickness effective to allow for deformation by the
active elements while offering sufficient stiffness to resist the
forces exerted by fluid pressure and flow. When the elastic members
94, 96 are deformed, they reduce the effective cross-sectional area
of the channel 8 thereby modifying the resistance to the
displacement of the piston 3 of the strut assembly.
[0047] In one embodiment, in one manner of operating the strut
assembly 10, the active elements 90, 92 in their default
configuration do not deform the elastic members 94, 96. When a
change in resistance to the motion of the suspended body 60 (not
shown) is desired, the active elements 90, 92 are activated.
Activation can be accomplished by resistively heating the active
element. Upon heating the active element, it undergoes a transition
from a martensitic phase to an austenitic phase. This change
permits the active elements 90, 92 to shorten in length, which
increases the curvature of the elastic members 94, 96 as shown in
the FIG. 7. The increase in the curvature of the elastic members
94, 96 constricts the flow across the piston head 14 and
accordingly changes the resistance to the motion of the suspended
body 60.
[0048] When the external stimulus (e.g., the electrical current to
the active element) is terminated, the restoring force exerted by
the elastic members 94, 96 will reestablish the default
configuration of the above arrangement. In one embodiment, the
default configuration of the elastic members 94, 96 can be selected
such that the flow of the fluid across the piston head 14 is
partially blocked (as shown in the FIG. 7), fully blocked or
completely unrestricted, and the geometry of the active element
geometry can be chosen accordingly. In another embodiment, the
compositions of the shape memory alloys can be chosen such that the
transition from martensitic to austenitic can occur because of
operation temperature changes within the fluid and/or changes in
the ambient temperature. In other words, there would not be any
need for an external stimulus to be deliberately applied to
activate the shape memory alloy.
[0049] In yet another embodiment, the elastic members 94, 96 may be
supported by shape memory polymer backing elements (not shown) that
provide a means of holding the changed configuration of the flow
channel even after the activation signal to the active elements 90,
92 is turned off. The pre-compressed backing elements can be
softened when the configuration of the flow channels is to be
changed, the elements then try to regain their original size and in
the process push against the elastic elements 94, 96. When the
elements 94, 96 have been adjusted to the desired position, the
shape memory polymer is allowed to cool and regain its stiff form.
In the stiff form, the shape memory polymer backing elements
support the elastic elements against fluid pressure and flow
forces, thereby providing a means for holding the changed
configuration even after the activation signal to the active
elements 90, 92 is removed or discontinued.
[0050] The variable resistance strut assemblies can be
advantageously used in articles such as automobiles, machine tools,
residential and office buildings where resistance between suspended
bodies (such as doors, windows, or the like) and a supporting body
(such as door frames, or the like) is often desired. The resistance
can be varied at any time during the life cycle of such articles.
Further, the resistance can be varied manually or automatically by
the use of computers. Feed back loops can also be used to vary the
resistance systematically or in order to reproduce certain types of
resistance under certain selected conditions and/or to compensate
for variations in the operating conditions e.g. due to change in
temperature, wear, or the like.
[0051] While the disclosure has been described with reference to an
exemplary embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the disclosure. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
disclosure without departing from the essential scope thereof.
Therefore, it is intended that the disclosure not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this disclosure, but that the disclosure will include
all embodiments falling within the scope of the appended
claims.
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