U.S. patent application number 11/074578 was filed with the patent office on 2005-09-29 for active seal assisted latching assemblies.
Invention is credited to Browne, Alan L., Henry, Christopher P., Herrera, Guillermo A., Johnson, Nancy L., Keefe, Andrew C., Mc Knight, Geoffrey P..
Application Number | 20050212304 11/074578 |
Document ID | / |
Family ID | 34994186 |
Filed Date | 2005-09-29 |
United States Patent
Application |
20050212304 |
Kind Code |
A1 |
Herrera, Guillermo A. ; et
al. |
September 29, 2005 |
Active seal assisted latching assemblies
Abstract
Active seal assisted latching assemblies employing active
materials that can be controlled and remotely changed to effect the
latching. In this manner, in seal applications such as a vehicle
door application, door opening and closing efforts can be minimized
yet seal effectiveness can be maximized.
Inventors: |
Herrera, Guillermo A.;
(Winnetka, CA) ; Keefe, Andrew C.; (Santa Monica,
CA) ; Henry, Christopher P.; (Newbury Park, CA)
; Mc Knight, Geoffrey P.; (Los Angeles, CA) ;
Browne, Alan L.; (Grosse Pointe, MI) ; Johnson, Nancy
L.; (Northville, MI) |
Correspondence
Address: |
KATHRYN A MARRA
General Motors Corporation
Legal Staff, Mail Code 482-C23-B21
P.O. Box 300
Detroit
MI
48265-3000
US
|
Family ID: |
34994186 |
Appl. No.: |
11/074578 |
Filed: |
March 8, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60552781 |
Mar 12, 2004 |
|
|
|
Current U.S.
Class: |
292/251.5 |
Current CPC
Class: |
E05B 81/00 20130101;
F16J 15/022 20130101; F16J 15/027 20130101; Y10S 277/921 20130101;
E05Y 2900/531 20130101; Y10S 292/65 20130101; E06B 7/2314 20130101;
E05C 19/166 20130101; F16J 15/064 20130101; B60J 10/40 20160201;
F16J 15/025 20130101; E05B 15/1607 20130101; E05B 47/0011 20130101;
B60J 10/16 20160201; E05B 47/0009 20130101; Y10T 16/56 20150115;
E05Y 2400/614 20130101; B60J 10/50 20160201; F16J 15/0806 20130101;
E05B 15/16 20130101; E05F 1/00 20130101; E05C 19/001 20130101; C08L
2201/12 20130101; E05Y 2800/67 20130101; F16J 15/028 20130101; B60J
10/244 20160201; E05Y 2900/55 20130101; F16J 15/061 20130101; Y10T
292/11 20150401; B60J 10/15 20160201; E05Y 2201/43 20130101; E05B
81/20 20130101 |
Class at
Publication: |
292/251.5 |
International
Class: |
E05C 003/06 |
Claims
1. A latch for latching two surfaces, comprising: a latch
comprising an engageable portion; a seal structure comprising an
active material, wherein the active material is effective to
undergo a change in shape in response to an activation signal,
wherein the change in shape causes the seal structure to sealingly
and latchingly engage the engageable portion; an activation device
in operative communication with the active material adapted to
provide the activation signal, and a controller in operative
communication with the activation device.
2. The latch according to claim 1, wherein the change in shape
comprises increasing a diameter of the seal structure, wherein the
increase in diameter engages the engageable portion.
3. The latch according to claim 1, wherein the active material
comprises a shape memory alloy, ferromagnetic shape memory alloy, a
shape memory polymer, a piezoelectric material, an electroactive
polymer, a magnetorheological fluid, a magnetorheological
elastomer, an electrorheological fluid, a composites of one or more
of the foregoing materials with non-active material, or a
combination comprising at least one of the foregoing materials.
4. The latch according to claim 1, further comprising a sensor in
operative communication with the controller.
5. The latch according to claim 1, wherein the activation signal
comprises an electric current, a temperature change, a magnetic
field, a mechanical loading or stressing and combinations
comprising at least one of the foregoing signals.
6. A latch for latching a first surface to a second surface,
comprising: a first surface comprising a first member extending
from the first surface, wherein the first member comprises an
active material, wherein the active material is effective to
undergo a change in shape in response to an activation signal; a
second surface comprising a second member extending from the second
surface, wherein the second member comprises the active material,
and wherein the second surface and the second member are
positionally disposed in an opposing relationship to the first
surface and the first member; an activation device in operative
communication with the active material adapted to selectively
provide an activation signal to the active material, wherein the
activation signal effects a change in a shape of the active
material and engages the first member with the second member; and a
controller in operative communication with the activation
device.
7. The latch according to claim 6, wherein the active material
comprises a shape memory alloy, a ferromagnetic shape memory alloy,
a piezoelectric material, an ionic polymer metal composite, a
magnetorheological elastomer, and combinations comprising at least
one of the foregoing materials.
8. The latch according to claim 6, wherein the change in shape
comprises a change of a curvilinear orientation to a substantially
straight shape.
9. The latch according to claim 6, further comprising a sensor in
operative communication with the controller.
10. The latch according to claim 6, wherein the activation signal
comprises an electric current, a temperature change, a magnetic
field, a mechanical loading or stressing and combinations
comprising at least one of the foregoing signals.
11. The latch according to claim 6, wherein the second member
active material is the same as the first member active
material.
12. The latch according to claim 6, wherein the second member
active material is different from the first member active
material.
13. A latch for latching two surfaces, comprising: a first surface
comprising a first member extending from the first surface, wherein
the first member comprises an active material effective to undergo
a change in shape in response to an activation signal; a seal
structure formed of an elastic material disposed on a second
surface, wherein the seal structure and second surface are aligned
with the first member and first member such that the first member
is in operative communication with the seal structure; an
activation device adapted to selectively provide the activation
signal to the active material, wherein the activation signal
effects a change in a shape of the first member to sealingly latch
the seal structure against the first member; and a controller in
operative communication with the activation device.
14. The latch according to claim 13, wherein the activation signal
comprises an electric current, a temperature change, a magnetic
field, a mechanical loading or stressing and combinations
comprising at least one of the foregoing signals.
15. The latch according to claim 13, wherein the active material
comprises a shape memory alloy, a ferromagnetic shape memory alloy,
a piezoelectric material, an ionic polymer metal composite, a
magnetorheological elastomer, and combinations comprising at least
one of the foregoing materials.
16. The latch according to claim 13, wherein the change in shape
comprises a change of a curvilinear orientation to a substantially
straight shape.
17. The latch according to claim 13, wherein the seal structure
comprises the active material, wherein the change in shape of the
seal structure active material volumetrically expands the seal
structure.
18. A process for selectively latching two surfaces, comprising:
positioning a first member in a latching relationship to a second
member, wherein the first member comprises an active material
adapted to undergo a change in shape in response to an activation
signal, wherein the change in shape of the active material latches
the first member to the second member; and activating the active
material and latching the first member to the second member.
19. The process of claim 18, wherein the active material comprises
a shape memory alloy, a ferromagnetic shape memory alloy, a
magnetorheological fluid or elastomer, an electroactive polymer,
piezoelectric material, an ionic polymer metal composite, a
magnetorheological elastomer, and combinations comprising at least
one of the foregoing materials.
20. The process of claim 18, wherein the activation signal
comprises an electric current, a temperature change, a magnetic
field, a mechanical loading or stressing and combinations
comprising at least one of the foregoing signals.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application relates to and claims priority to
U.S. Provisional Application No. 60/552,781 entitled "Active Seal
Assemblies" and filed on Mar. 12, 2004, the disclosure of which is
incorporated by reference herein in their entirety.
BACKGROUND
[0002] This disclosure relates to seals and more particularly, to
active seal assisted latching assemblies that employ active
materials to effect the latching.
[0003] Current methods and assemblies for latching and sealing
opposing surfaces such as doors and trunk lids, for example,
include the use of flexible elastic membranes and/or foam
structures that conform upon pressing contact of the opposing
surfaces to fill the gap between the surfaces where the seal is
required and a separate latching mechanism. Typical materials for
the seal include various forms of elastomers, e.g., foams and
solids that are formed into structures having solid and/or hollow
cross sectional structures. The geometries of the cross sections
are varied and may range from circular forms to irregular forms
having multiple slots and extending vanes. Current typical latching
methods include mechanical assemblies that engage and disengage the
two parts that need to be latched or unlatched.
[0004] Sealing assemblies are typically utilized for sound and/or
fluid (gasses or liquids) management. These seals generally are
exposed to a variety of conditions. For example, for vehicle
applications, door seals generally are exposed to a wide range of
temperatures as well as environmental conditions such as rain,
snow, sun, humidity, and the like. Current materials utilized for
automotive seals are passive. That is, other than innate changes in
modulus of the seal material due to aging and environmental
stimuli, the stiffness and cross sectional geometries of the seal
assemblies cannot be remotely changed or controlled.
[0005] For example, traditional passive door seal design must
compromise between functional adequacy and user's ease of
operation. Typically, improved sealing results from greater contact
area and adequate pressure over the seal length. This approach
generally increases the force required from the user to close the
door as compared to less seal contact area and pressure.
Additionally, manufacturing tolerances which vary over the
perimeter of the doors may require a greater seal compression over
the length of the seal than is necessary to ensure that the point
of the door located the furthest from the door hinge will have
adequate sealing area and pressure to prevent moisture or noise
from entering the vehicle. This may result in more total
compression and force over the entire door than is necessary, thus
increasing the required door closure force. In addition, general
manufacturing issues including interactions of various components
involved in sealing technologies may result in increased
manufacturing cycle time due to the necessity to redesign the seal
to match vehicle conditions.
[0006] Typical latching methods are mechanical assemblies that
involve linkages, pivots, and other mechanical parts that engage
and disengage to latch or unlatch the two parts, for example a car
door to the car doorframe. The latching mechanism may be a manual,
or an electrically powered mechanism such as used for keyless entry
in most modern automobiles. Both mechanisms involve a large number
of moving mechanical parts, manually or electrically actuated to
latch or unlatch, for example an automobile door. These assemblies,
whether manually or electrically actuated, can occupy significant
space, for example with in the door of an automobile, and
freuquently require periodic maintenance such as lubrication.
[0007] Accordingly, it is desirable to have active seal assemblies
that can be controlled and remotely changed to alter the seal
effectiveness, wherein the active seal assemblies change material
properties on demand, for example stiffness, elastic modulus, or
change in geometry, for example, by actively changing the seal
cross-sectional shape. In this manner, in seal applications such as
the vehicle door application noted above, door opening and closing
efforts can be minimized yet seal effectiveness can be maximized.
Furthermore, it is desirable that the active seal assists in the
latching of the two surfaces that need to be sealed.
BRIEF SUMMARY
[0008] Disclosed herein are active seal assisted latching
assemblies that employ active materials to effect the sealing,
latching and methods of use. In one embodiment, a latch for
latching two surfaces comprises a latch comprising an engageable
portion; a seal structure comprising an active material, wherein
the active material is effective to undergo a change in shape in
response to an activation signal, wherein the change in shape
causes the seal structure to seal and latch with the engageable
portion; an activation device in operative communication with the
active material adapted to provide the activation signal; and a
controller in operative communication with the activation
device.
[0009] In another embodiment, a latch for latching a first surface
to a second surface comprises a first surface comprising a first
member extending from the first surface, wherein the first member
comprises an active material, wherein the active material is
effective to undergo a change in shape in response to an activation
signal; a second surface comprising a second member extending from
the second surface, wherein the second member comprises the active
material, and wherein the second surface and the second member are
positionally disposed in an opposing relationship to the first
surface and the first member; an activation device in operative
communication with the active material adapted to selectively
provide an activation signal to the active material, wherein the
activation signal effects a change in the shape of the active
material and engages the first member with the second member; and a
controller in operative communication with the activation
device.
[0010] In yet another embodiment, a latch for latching two surfaces
comprises a first surface comprising a first member extending from
the first surface, wherein the first member comprises an active
material effective to undergo a change in shape in response to an
activation signal; a seal structure formed of an elastic material
disposed on a second surface, wherein the seal structure and second
surface are aligned with the first member and first surface such
that the first member is in operative communication with the seal
structure; an activation device adapted to selectively provide the
activation signal to the active material, wherein the activation
signal effects a change in a shape of the first member to seal and
latch the second member against the first member; and a controller
in operative communication with the activation device.
[0011] A process for selectively latching two surfaces comprises
positioning a first member in a latching relationship to a second
member, wherein the first member comprises an active material
adapted to undergo a change in shape in response to an activation
signal, wherein the change in shape of the active material latches
the first member to the second member.
[0012] The above described and other features are exemplified by
the following figures and detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Referring now to the figures, which are exemplary
embodiments and wherein like elements are numbered alike:
[0014] FIG. 1 illustrates a partial cross sectional view of an
active seal assisted latching assembly in accordance with one
embodiment;
[0015] FIG. 2 illustrates a cross sectional view of an active seal
structure in accordance with one embodiment;
[0016] FIG. 3 illustrates a cross sectional view of an active seal
structure in accordance with another embodiment;
[0017] FIG. 4 illustrates a cross sectional view of an active seal
assisted latching assembly in accordance with another
embodiment;
[0018] FIG. 5 illustrates a cross sectional view of an active seal
assisted latching assembly in an unlatched and latched
configuration in accordance with another embodiment; and
[0019] FIG. 6 illustrates a cross sectional view of an active seal
assisted latching assembly in an unlatched and latched
configuration in accordance with another embodiment.
DETAILED DESCRIPTION
[0020] Disclosed herein are active sealing assemblies and methods
of use, wherein the shape, stiffness, and/or elastic modulus
properties of the active materials employed in the active seal
assemblies can be remotely activated and/or controlled to
selectively provide latching as well as sealing between two
opposing surfaces. For door applications, the active seal
assemblies can be programmed to provide minimal opening and closing
efforts in addition to the increased seal and/or latching
effectiveness properties. Although reference will be made herein to
automotive applications, it is contemplated that the active seal
assemblies can be employed for sealing and latching of opposing
surfaces for various interfaces between opposing surfaces such as
refrigerator doors, windows, drawers, and the like. For automotive
applications, the active seal assisted latching assemblies are
preferably utilized between an opening in a vehicle and a surface
in sliding or sealing engagement with the opening such as a vehicle
door, a side passenger sliding door, window, sunroof, hatch,
tailgate, and the like.
[0021] The active sealing assemblies generally comprise an active
material that is adapted to provide latching engagement as well as
sealing between two opposing surfaces. The active seal assemblies
further include an activation device and a controller in operative
communication with the activation device for providing a suitable
activation signal to the active material. As will be described in
greater detail below, the term "active material" as used herein
refers to several different classes of materials all of which
exhibit a change in at least one attribute such as shape,
stiffness, and/or elastic modulus when subjected to at least one of
many different types of applied activation signals, examples of
such signals being thermal, electrical, magnetic, mechanical,
pneumatic, and the like. One class of active materials is shape
memory materials. These materials exhibit a shape memory effect.
Specifically, after being deformed from their original "memorized"
shape, they can be restored to their original shape in response to
the activation signal. Suitable shape memory materials include,
without limitation, shape memory alloys (SMA), ferromagnetic SMAs,
and shape memory polymers (SMP). A second class of active materials
can be considered as those that exhibit a change in at least one
attribute when subjected to an applied field but revert back to
their original state upon removal of the applied field. Active
materials in this category include, but are not limited to,
piezoelectric materials, electroactive polymers (EAP),
magnetorheological fluids and elastomers (MR), electrorheological
fluids (ER), composites of one or more of the foregoing materials
with non-active materials, combinations comprising at least one of
the foregoing materials, and the like. Of the above noted
materials, SMAs and SMPs based sealing assemblies may further
include a return mechanism to restore the original geometry of the
sealing assembly. The return mechanism can be mechanical,
pneumatic, hydraulic, pyrotechnic, or an actuator based on one of
the aforementioned smart materials.
[0022] During operation, the active material can be configured to
provide an enhancement to a closure mechanism or be configured to
function as a mechanical closure in addition to providing selective
and controlled sealing engagement. Suitable seal materials for use
with the active materials include, but are not intended to be
limited to, styrene butadiene rubber, polyurethanes, polyisoprene,
neoprene, chlorosulfonated polystyrenes, and the like.
[0023] By utilizing the active material in operative communication
with the seal assembly, the active material can change its
stiffness, elastic modulus, shape, or other properties to provide
the seal with improved sealing engagement between opposing
surfaces, provide minimal effort to door opening and closing, as
well as provide a latching mechanism, where desired and configured.
Applying an activation signal to the active material can effect the
property change to engage or disengage the latching seal. Suitable
activation signals will depend on the type of active material. As
such, the activation signal provided for changing the shape,
stiffness and/or elastic modulus properties of the seal structure
may include a heat signal, an electrical signal, a magnetic signal
and combinations comprising at least one of the foregoing signals,
and the like.
[0024] Optionally, the seal assembly may include one or more
sensors that are used in combination with enhanced control logic
to, for example, to maintain the same level of sealing force
independent of environmental conditions, e.g., humidity,
temperature, pressure differential between interior and
environment, logic for when to unlatch or maintain the door latch,
and the like.
[0025] As will be discussed in greater detail below, the active
materials in various embodiments disclosed herein can be configured
to externally control the seal structure, e.g., provide actuator
means, provide an exoskeleton of the seal structure; and/or can be
configured to internally control the seal structure, e.g., provide
the internal skeletal structure of the seal.
[0026] As previously discussed, the active materials permit the
remote and automatic and/or on-demand control of the sealing and/or
latching function and provides enhancements in sealing and/or
latching functionality through software modifications as opposed to
hardware changes. For example, in the case of vehicle doors,
control logic can be utilized to activate the smart material, i.e.,
seal and/or latch assembly, upon opening or closing of the door.
Switches can be disposed in the door handle or door pillars or
doors in operative communication with sensors that activate the
smart material upon door motion, change in door gap with respect to
the vehicle body, movement of the door handle, powered opening of
lock assemblies, and the like. In this manner, opening and closing
can be programmed with minimal effort or resistance as contributed
by forces associated;with the seal assembly.
[0027] The various applications that can be utilized with the
active seal assembly include, but are not intended to limited to,
seal assisted latching; noise reduction; door opening and closing
force reduction; itch reduction and/or elimination; active actuator
assisted sealing; power off sealing; power on sealing; and the
like.
[0028] Turning now to FIG. 1, there is shown an exemplary active
seal assembly, generally indicated as 10. The active seal assembly
10 comprises a seal structure 12 comprising an active material and
disposed on a door surface (not shown). Upon activation, the seal
structure 12 is adapted to change from a first shape (shown as
solid line) to a second shape (shown as dotted line). The seal
structure 12 is in operative communication with a controller and an
activation device 14 which then actuates the active seal assembly
10 under pre-programmed conditions defined by an algorithm or the
like. The seal assembly 10 may further comprise at least one sensor
16 positioned to operatively communicate with the controller and
activation device 14 so as to selectively detect an event such as a
door closure such that an actuation signal is provided to the
active material. In this manner, the seal structure 12 can be used
to selectively change shape so as to engage a latching surface 18
of a vehicle body 20, for example.
[0029] In one exemplary embodiment as shown in FIG. 2, the seal
structure 12 comprises a tube 22 formed of a resilient elastic
material that is filled with or in operative communication with an
active material 24 to selectively change shape, by expansion,
contraction and/or other dimensional parameter. Suitable active
materials include, but are note intended to be limited to, an
electrorheological fluid, a magnetorheological fluid, an
electroactive polymer gel, a dielectric elastomer, and the like.
For example, if the active seal assembly 10 utilizes an
electroactive gel material that swells in volume due to an applied
voltage, the seal assembly 10 may further include a controllable
valve 26 (see FIG. 1) that may be triggered electronically to
engage the latching surface to assist closing, if desired. In these
embodiments, the valve 26 preferably possesses a zero power latch
position so as to remain engaged even if vehicle power is
terminated.
[0030] Other embodiments include maintaining a power-on latch
functionality, which will require a constant actuation signal. In
these embodiments, it is preferred to use capacitors to minimize
drain on the battery. Using dielectric elastomers as an example for
the expanding seal, a sealed tube of the dielectric elastomer is
fabricated with a defined internal pressure. As voltage is applied,
the tube expands in diameter in an amount effective to engage the
latching surface 18, effectively sealing and latching the vehicle's
door and the doorframe.
[0031] Preferably, a base pressure is maintained to enable either
expansion or contraction by changing the volume of the material
inside the seal structure. In one embodiment, the seal assembly 10
may be used to contract the tube 22 before the door is closed, and
then allowed to return to the un-deformed state after closure to
allow for improved sealing and latching. This allows the door to
maintain an adequate seal with reduced closure force. In another
embodiment, the tube 22 may start in a non-deformed position, and
be expanded once the door is closed to provide better contact
between sealing surfaces and improved seal characteristics for
moisture and noise reduction and at the same time latching the
door.
[0032] Another embodiment of a suitable seal structure 12 is shown
in FIG. 3. Either distortions or changes in the radius of the
passive seal structure 22 may be possible through the use of the
active material 24. One approach is to have the generally circular
seal structure 22 deform such that the sealing surface is
contracted prior to closing the door. When the door is brought to
close proximity to the vehicle body 20, then the active material
may be deactivated, allowing the seal to push back against the
sealing surfaces, thus creating more pressure and greater surface
area on the seal for improved sealing and latching of the door to
the vehicle body. This would form a power off seal and active seal
assisted latching. In this manner, passive seal structure 22 is
flexed, thereby storing energy that can be released once the door
is closed. This energy storage reduces the force necessary to close
the door because the active material has previously performed some
of that work. An alternate approach is to close the door in the
relaxed position, and have the seal be partially compressed.
Activating the seal can then be used to further increase the force
on the sealing surfaces. This would constitute a power-on seal and
seal assisted latching.
[0033] Alternatively, a tubular seal may be constructed of a
dielectric elastomer material, and an internal pressure generated
within the tubular structure. Maxwell-related stresses are
generated in a compliant dielectric material by means of a voltage
difference applied to the outer and inner compliant electrodes.
Generated stress causes an increase in surface area of the
dielectric material. By constraining the length of the tube, the
radius of the tube selectively increases. A bias pressure
determines the equilibrium radius of the tube (seal structure) and
activation position. An internal pressure is preferably maintained
within the tubular dielectric elastomer for certain modes of
operation. An external pressure is preferably maintained outside
the tubular dielectric material for other modes of operation. The
equilibrium position preferably requires no activation whereas time
in the activated position is preferably kept to a minimum.
[0034] In an alternative embodiment as shown in FIG. 4, the seal
structure 12 is interposed between two members 26, 28. The seal
structure 12 may be attached to one of the members 26 or 28, or
alternatively, may be attached to a movable member that moves the
seal structure into position between the two members 26, 28. In the
unexpanded configuration, the seal structure preferably has a
dimension that provides clearance between the two members 26, and
28. Upon expansion via actuation of the active material as
previously described, the seal structure engages and seals the two
members 26, 28 and effectively forms a latch. That is, the gap
between the two members 26 and 28 is filled by the seal structure
12. In operation of a door, for example, the door is closed when
the seal structure is in the unpowered state and subsequently
powered to form the expanded shape configuration. In this manner,
the seal structure 12 provides an effective seal and assists in
latching the door to the vehicle surface. As such, power-off
latching and sealing may occur.
[0035] In yet another embodiment shown in FIG. 5, the active seal
assembly 40 includes a pair of opposing actuators 42, 44 disposed
on members 46, 48, respectively. The actuators are shown here as
opposing strips having a curved shape that extends from the members
46, 48, e.g., door and frame surfaces. Upon door closure, the
active seal assembly 40 is activated and the opposing actuators
change their shape from the curved orientation to a substantially
straight shape, thereby locking the respective surfaces 46, 48 in
place and at the same time sealing the surfaces. Alternatively, the
actuators 42, 44 may have a straight shape in the unpowered state
and upon activation assume the curved shape. The change in
curvature permits door closure and latching. Discontinuing the
power will revert the actuators to its straight shape, thereby
providing a power-off assisted latching mechanism.
[0036] In another embodiment shown in FIG. 6, a latching surface 50
includes an active material member 52 extending from the surface 50
(e.g., a portion of the vehicle body). The other latching surface
54, (e.g., a portion of a door), includes a seal structure 56
disposed thereon, shown having a generally circular cross section.
The seal structure 56 is formed of a passive elastic material. Upon
door closure (i.e., the latching surfaces 50, 54 abut one another),
the active material 52 is activated to effect latching and sealing.
Activating the active material member 52 causes a latching
engagement to occur between the two surfaces 50, 54 since upon
activation of the active material member 52, the shape changes from
a substantially straight shape to a curved shape as shown. The
direction and amount of curvature can be tailored.
[0037] Optionally, the seal structure 56 can be formed of the
active material, independently or in addition to the active
material 52 extending from the surface. As such, the generally
circular cross section as shown can selectively expand upon
activation from the first shape to an expanded shape of to provide
greater seal effectiveness as well as provide latching. Operation
of the active material member 52 may proceed in either the
power-off or power-on configuration, as may be desired for
different applications. For example, if active material member 52
is curved in the power off state, the active material member 52 is
preferably activated for the door to close. Once deactivated, the
active material member 52 will revert back to its curved shape
providing sealing and assisted latching engagement between the two
surfaces 50, 54. Alternatively, if the active material member 52
has a straight shape in the power-off state, the active material
member 52 is activated once the surfaces 50, 54 are brought into
close proximity to one another to seal and latch the door, i.e.,
upon activation the active material member 52 changes its shape to
a substantially straightened shape. In the event the seal structure
56 is formed of the active material, the seal structure would
function in the manner described in relation to seal structure 12
of FIGS. 1 and 4.
[0038] As noted, suitable active materials include those that can
effect a selective change in shape, elastic modulus, and/or
stiffness. The changes in shape can be caused by volumetric
expansion of the active material in fluid or solid form or
alternatively, may include spatial changes caused by translation of
the active material, for example. Suitable active materials include
shape memory alloys, ferromagnetic SMAs, shape memory polymers,
piezoelectric materials, electroactive polymers, magnetorheological
fluids and elastomers, electrorheological fluids, composites of one
or more of the foregoing materials with non-active materials,
combinations comprising at least one of the foregoing materials,
and the like.
[0039] Suitable shape memory alloys generally exist in several
different temperature-dependent phases. The most commonly utilized
of these phases are the so-called martensite and austenite phases.
In the following discussion, the martensite phase generally refers
to the more deformable, lower temperature phase whereas the
austenite phase generally refers to the more rigid, higher
temperature phase. When the shape memory alloy is in the martensite
phase and is heated, it begins to change into the austenite phase.
The temperature at which this phenomenon starts is often referred
to as austenite start temperature (As). The temperature at which
this phenomenon is complete is called the austenite finish
temperature (Af). When the shape memory alloy is in the austenite
phase and is cooled, it begins to change into the martensite phase,
and the temperature at which this phenomenon starts is referred to
as the martensite start temperature (Ms). The temperature at which
austenite finishes transforming to martensite is called the
martensite finish temperature (Mf). Generally, the shape memory
alloys are softer and more easily deformable in their martensitic
phase and are harder, stiffer, and/or more rigid in, the austenitic
phase. In view of the foregoing properties, expansion of the shape
memory alloy foam is preferably at or below the austenite
transition temperature (at or below As). Subsequent heating above
the austenite transition temperature causes the expanded shape
memory foam to revert back to its permanent shape. Thus, a suitable
activation signal for use with shape memory alloys is a thermal
activation signal having a magnitude to cause transformations
between the martensite and austenite phases. For those shape memory
materials that are ferromagnetic, a magnetic and/or a thermal
signal can be applied to effect the desired change in shape.
[0040] The temperature at which the shape memory alloy remembers
its high temperature form when heated can be adjusted by slight
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 degree or two depending on the desired
application and alloy composition. The mechanical properties of the
shape memory alloy vary greatly over the temperature range spanning
their transformation, typically providing shape memory effects,
superelastic effects, and high damping capacity.
[0041] Suitable shape memory alloy materials include, but are not
intended to be limited to, 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, and the
like. 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, changes in yield strength, and/or flexural modulus
properties, damping capacity, superelasticity, and the like. A
preferred shape memory alloy is a nickel-titanium based alloy
commercially available under the trademark FLEXINOL from Dynalloy,
Inc. Selection of a suitable shape memory alloy composition depends
on the temperature range where the component will operate.
[0042] Shape memory polymers (SMPs) generally refer to a group of
polymeric materials that demonstrate the ability to return to some
previously defined shape when subjected to an appropriate thermal
stimulus. The shape memory polymer may be in the form of a solid or
a foam as may be desired for some embodiments. Shape memory
polymers are capable of undergoing phase transitions in which their
shape is altered as a function of temperature. Generally, SMPs are
copolymers comprised of at least two different units which may be
described as defining different segments within the copolymer, each
segment contributing differently to the flexural modulus properties
and thermal transition temperatures of the material. The term
"segment" refers to a block, graft, or sequence of the same or
similar monomer or oligomer units that are copolymerized with a
different segment to form a continuous crosslinked interpenetrating
network of these segments. These segments may be combination of
crystalline or amorphous materials and therefore may be generally
classified as a hard segment(s) or a soft segment(s), wherein the
hard segment generally has a higher glass transition temperature
(Tg) or melting point than the soft segment. Each segment then
contributes to the overall flexural modulus properties of the SMP
and the thermal transitions thereof. When multiple segments are
used, multiple thermal transition temperatures may be observed,
wherein the thermal transition temperatures of the copolymer may be
approximated as weighted averages of the thermal transition
temperatures of its comprising segments. With regard to shape
memory polymer foams, the structure may be open celled or close
celled as desired.
[0043] In practice, the SMPs are alternated between one of at least
two shapes such that at least one orientation will provide a size
reduction relative to the other orientation(s) when an appropriate
thermal signal is provided. To set a permanent shape, the shape
memory polymer must be at about or above its melting point or
highest transition temperature (also termed "last" transition
temperature). SMP foams are shaped at this temperature by blow
molding or shaped with an applied force followed by cooling to set
the permanent shape. The temperature necessary to set the permanent
shape is generally between about 40.degree. C. to about 200.degree.
C. After expansion by fluid, the permanent shape is regained when
the applied force is removed, and the expanded SMP is again brought
to or above the highest or last transition temperature of the SMP.
The Tg of the SMP can be chosen for a particular application by
modifying the structure and composition of the polymer.
[0044] The temperature needed for permanent shape recovery can
generally be set at any temperature between about -63.degree. C.
and about 160.degree. C. or above. Engineering the composition and
structure of the polymer itself can allow for the choice of a
particular temperature for a desired application. A preferred
temperature for shape recovery is greater than or equal to about
-30.degree. C., more preferably greater than or equal to about
20.degree. C., and most preferably a temperature greater than or
equal to about 70.degree. C. Also, a preferred temperature for
shape recovery is less than or equal to about 250.degree. C., more
preferably less than or equal to about 200.degree. C., and most
preferably less than or equal to about 180.degree. C.
[0045] Suitable shape memory polymers can be thermoplastics,
interpenetrating networks, semi-interpenetrating networks, or mixed
networks. The polymers can be a single polymer or a blend of
polymers. The polymers can be linear or branched thermoplastic
elastomers with side chains or dendritic structural elements.
Suitable polymer components to form a shape memory polymer include,
but are not limited to, polyphosphazenes, poly(vinyl alcohols),
polyamides, polyester amides, poly(amino acids), polyanhydrides,
polycarbonates, polyacrylates, polyalkylenes, polyacrylamides,
polyalkylene glycols, polyalkylene oxides, polyalkylene
terephthalates, polyortho esters, polyvinyl ethers, polyvinyl
esters, polyvinyl halides, polyesters, polylactides,
polyglycolides, polysiloxanes, polyurethanes, polyethers, polyether
amides, polyether esters, and copolymers thereof. Examples of
suitable polyacrylates include poly(methyl methaciylate),
poly(ethyl methacrylate), poly(butyl methacrylate), poly(isobutyl
methacrylate), poly(hexyl methacrylate), poly(isodecyl
methacrylate), poly(lauryl mnethacrylate), poly(phenyl
methacrylate), poly(methyl acrylate), poly(isopropyl acrylate),
poly(isobutyl acrylate) and poly(octadecylacrylate). Examples of
other suitable polymers include polystyrene, polypropylene,
polyvinyl phenol, polyvinylpyrrolidone, chlorinated polybutylene,
poly(octadecyl vinyl ether), ethylene vinyl acetate, polyethylene,
poly(ethylene oxide)-poly(ethylene terephthalate),
polyethylene/nylon (graft copolymer), polycaprolactones-polyamide
(block copolymer), poly(caprolactone)diniethacrylate-n-butyl
acrylate, poly(norbornyl-polyhedral oligomeric silsequioxane),
polyvinylchloride, urethane/butadiene copolymers, polyurethane
block copolymers, styrene-butadienestyrene block copolymers, and
the like.
[0046] Conducting polymerization of different monomer segments with
a blowing agent can be used to form the shape memory polymer foam.
The blowing agent can be of the decomposition type (evolves a gas
upon chemical decomposition) or an evaporation type (which
vaporizes without chemical reaction). Exemplary blowing agents of
the decomposition type include, but are not intended to be limited
to, sodium bicarbonate, azide compounds, ammonium carbonate,
ammonium nitrite, light metals which evolve hydrogen upon reaction
with water, azodicarbonamide, N,N'dinitrosopentamethylenetetramine,
and the like. Exemplary blowing agents of the evaporation type
include, but are not intended to be limited to,
trichloromonofluoromethane, trichlorotrifluoroethane, methylene
chloride, compressed nitrogen gas, and the like. The material can
then be reverted to the permanent shape by heating the material
above its Tg but below the highest thermal transition temperature
or melting point. Thus, by combining multiple soft segments it is
possible to demonstrate multiple temporary shapes and with multiple
hard segments it may be possible to demonstrate multiple permanent
shapes.
[0047] Suitable piezoelectric materials include, but are not
intended to be limited to, inorganic compounds, organic compounds,
and metals. With regard to organic materials, all of the polymeric
materials with non-centrosymmetric structure and large dipole
moment group(s) on the main chain or on the side-chain, or on both
chains within the molecules, can be used as suitable candidates for
the piezoelectric film. Exemplary polymers include, for example,
but are not limited to, poly(sodium 4-styrenesulfonate), poly
(poly(vinylamine) backbone azo chromophore), and their derivatives;
polyfluorocarbons, including polyvinylidenefluoride, its co-polymer
vinylidene fluoride ("VDF"), co-trifluoroethylene, and their
derivatives; polychlorocarbons, including poly(vinyl chloride),
polyvinylidene chloride, and their derivatives; polyacrylonitriles,
and their derivatives; polycarboxylic acids, including
poly(methacrylic acid), and their derivatives; polyureas, and their
derivatives; polyurethanes, and their derivatives; bio-molecules
such as poly-L-lactic acids and their derivatives, and cell
membrane proteins, as well as phosphate bio-molecules such as
phosphodilipids; polyanilines and their derivatives, and all of the
derivatives of tetramines; polyamides including aromatic polyamides
and polyimides, including Kapton and polyetherimide, and their
derivatives; all of the membrane polymers; poly(N-vinyl
pyrrolidone) (PVP) homopolymer, and its derivatives, and random
PVP-co-vinyl acetate copolymers; and all of the aromatic polymers
with dipole moment groups in the main-chain or side-chains, or in
both the main-chain and the side-chains, and mixtures thereof.
[0048] Piezoelectric material can also comprise metals selected
from the group consisting of lead, antimony, manganese, tantalum,
zirconium, niobium, lanthanum, platinum, palladium, nickel,
tungsten, aluminum, strontium, titanium, barium, calcium, chromium,
silver, iron, silicon, copper, alloys comprising at least one of
the foregoing metals, and oxides comprising at least one of the
foregoing metals. Suitable metal oxides include SiO.sub.2,
Al.sub.2O.sub.3, ZrO.sub.2, TiO.sub.2, SrTiO.sub.3, PbTiO.sub.3,
BaTiO.sub.3, FeO.sub.3, Fe.sub.3O.sub.4, ZnO, and mixtures thereof
and Group VIA and IIB compounds, such as CdSe, CdS, GaAs,
AgCaSe.sub.2, ZnSe, GaP, InP, ZnS, and mixtures thereof.
Preferably, the piezoelectric material is selected from the group
consisting of polyvinylidene fluoride, lead zirconate titanate, and
barium titanate, and mixtures thereof.
[0049] Suitable magnetic materials include, but are not intended to
be limited to, soft or hard magnets; hematite; magnetite; magnetic
material based on iron, nickel, and cobalt, alloys of the
foregoing, or combinations comprising at least one of the
foregoing, and the like. Alloys of iron, nickel and/or cobalt, can
comprise aluminum, silicon, cobalt, nickel, vanadium, molybdenum,
chromium, tungsten, manganese: and/or copper.
[0050] Suitable MR fluid materials include, but are not intended to
be limited to, ferromagnetic or paramagnetic particles dispersed in
a carrier fluid. Suitable particles include iron; iron alloys, such
as those including aluminum, silicon, cobalt, nickel, vanadium,
molybdenum, chromium, tungsten, manganese and/or copper; iron
oxides, including Fe.sub.2O.sub.3 and Fe.sub.3O.sub.4; iron
nitride; iron carbide; carbonyl iron; nickel and alloys of nickel;
cobalt and alloys of cobalt; chromium dioxide; stainless steel;
silicon steel; and the like. Examples of suitable particles include
straight iron powders, reduced iron powders, iron oxide
powder/straight iron powder mixtures and iron oxide powder/reduced
iron powder mixtures. A preferred magnetic-responsive particulate
is carbonyl iron, preferably, reduced carbonyl iron.
[0051] The particle size should be selected so that the particles
exhibit multi-domain characteristics when subjected to a magnetic
field. Diameter sizes for the particles can be less than or equal
to about 1000 micrometers, with less than or equal to about 500
micrometers preferred, and less than or equal to about 100
micrometers more preferred. Also preferred is a particle diameter
of greater than or equal to about 0.1 micrometer, with greater than
or equal to about 0.5 more preferred, and greater than or equal to
about 10 micrometers especially preferred. The particles are
preferably present in an amount between about 5.0 to about 50
percent by volume of the total MR fluid composition.
[0052] Suitable carrier fluids include organic liquids, especially
non-polar organic liquids. Examples include, but are not limited
to, silicone oils; mineral oils; paraffin oils; silicone
copolymers; white oils; hydraulic oils; transformer oils;
halogenated organic liquids, such as chlorinated hydrocarbons,
halogenated paraffins, perfluorinated polyethers and fluorinated
hydrocarbons; diesters; polyoxyalkylenes; fluorinated silicones;
cyanoalkyl siloxanes; glycols; synthetic hydrocarbon oils,
including both unsaturated and saturated; and combinations
comprising at least one of the foregoing fluids.
[0053] The viscosity of the carrier component can be less than or
equal to about 100,000 centipoise, with less than or equal to about
10,000 centipoise preferred, and less than or equal to about 1,000
centipoise more preferred. Also preferred is a viscosity of greater
than or equal to about 1 centipoise, with greater than or equal to
about 250 centipoise preferred, and greater than or equal to about
500 centipoise especially preferred.
[0054] Aqueous carrier fluids may also be used, especially those
comprising hydrophilic mineral clays such as bentonite or
hectorite. The aqueous carrier fluid may comprise water or water
comprising a small amount of polar, water-miscible organic solvents
such as methanol, ethanol, propanol, dimethyl sulfoxide, dimethyl
formamide, ethylene carbonate, propylene carbonate, acetone,
tetrahydrofuran, diethyl ether, ethylene glycol, propylene glycol,
and the like. The amount of polar organic solvents is less than or
equal to about 5.0% by volume of the total MR fluid, and preferably
less than or equal to about 3.0%. Also, the amount of polar organic
solvents is preferably greater than or equal to about 0.1%, and
more preferably greater than or equal to about 1.0% by volume of
the total MR fluid. The pH of the aqueous carrier fluid is
preferably less than or equal to about 13, and preferably less than
or equal to about 9.0. Also, the pH of the aqueous carrier fluid is
greater than or equal to about 5.0, and preferably greater than or
equal to about 8.0.
[0055] Natural or synthetic bentonite or hectorite may be used. The
amount of bentonite or hectorite in the MR fluid is less than or
equal to about 10 percent by weight of the total MR fluid,
preferably less than or equal to about 8.0 percent by weight, and
more preferably less than or equal to about 6.0 percent by weight.
Preferably, the bentonite or hectorite is present in greater than
or equal to about 0.1 percent by weight, more preferably greater
than or equal to about 1.0 percent by weight, and especially
preferred greater than or equal to about 2.0 percent by weight of
the total MR fluid.
[0056] Optional components in the MR fluid include clays,
organoclays, carboxylate soaps, dispersants, corrosion inhibitors,
lubricants, extreme pressure anti-wear additives, antioxidants,
thixotropic agents and conventional suspension agents. Carboxylate
soaps include ferrous oleate, ferrous naphthenate, ferrous
stearate, aluminum di- and tri-stearate, lithium stearate, calcium
stearate, zinc stearate and sodium stearate, and surfactants such
as sulfonates, phosphate esters, stearic acid, glycerol monooleate,
sorbitan sesquioleate, laurates, fatty acids, fatty alcohols,
fluoroaliphatic polymeric esters, and titanate, aluminate and
zirconate coupling agents and the like. Polyalkylene diols, such as
polyethylene glycol, and partially esterified polyols can also be
included.
[0057] Suitable MR elastomer materials include, but are not
intended to be limited to, an elastic polymer matrix comprising a
suspension of ferromagnetic or paramagnetic particles, wherein the
particles are described above. Suitable polymer matrices include,
but are not limited to, poly-alpha-olefins, natural rubber,
silicone, polybutadiene, polyethylene, polyisoprene, and the
like.
[0058] Electroactive polymers include those polymeric materials
that exhibit piezoelectric, pyroelectric, or electrostrictive
properties in response to electrical or mechanical fields. An
example of an electrostrictive-grafted elastomer with a
piezoelectric poly(vinylidene fluoride-trifluoro-ethylene)
copolymer. This combination has the ability to produce a varied
amount of ferroelectric-electrostrictive molecular composite
systems. These may be operated as a piezoelectric sensor or even an
electrostrictive actuator.
[0059] Materials suitable for use as an electroactive polymer may
include any substantially insulating polymer or rubber (or
combination thereof) that deforms in response to an electrostatic
force or whose deformation results in a change in electric field.
Exemplary materials suitable for use as a pre-strained polymer
include silicone elastomers, acrylic elastomers, polyurethanes,
thermoplastic elastomers, copolymers comprising PVDF,
pressure-sensitive adhesives, fluoroelastomers, polymers comprising
silicone and acrylic moieties, and the like. Polymers comprising
silicone and acrylic moieties may include copolymers comprising
silicone and acrylic moieties, polymer blends comprising a silicone
elastomer and an acrylic elastomer, for example.
[0060] Materials used as an electroactive polymer may be selected
based on one or more material properties such as a high electrical
breakdown strength, a low modulus of elasticity--(for large or
small deformations), a high dielectric constant, and the like. In
one embodiment, the polymer is selected such that is has an elastic
modulus at most about 100 MPa. In another embodiment, the polymer
is selected such that is has a maximum actuation pressure between
about 0.05 MPa and about 10 MPa, and preferably between about 0.3
MPa and about 3 MPa. In another embodiment, the polymer is selected
such that is has a dielectric constant between about 2 and about
20, and preferably between about 2.5 and about 12. The present
disclosure is not intended to be limited to these ranges. Ideally,
materials with a higher dielectric constant than the ranges given
above would be desirable if the materials had both a high
dielectric constant and a high dielectric strength. In many cases,
electroactive polymers may be fabricated and implemented as thin
films. Thicknesses suitable for these thin films may be below 50
micrometers.
[0061] As electroactive polymers may deflect at high strains,
electrodes attached to the polymers should also deflect without
compromising mechanical or electrical performance. Generally,
electrodes suitable for use may be of any shape and material
provided that they are able to supply a suitable voltage to, or
receive a suitable voltage from, an electroactive polymer. The
voltage may be either constant or varying over time. In one
embodiment, the electrodes adhere to a surface of the polymer.
Electrodes adhering to the polymer are preferably compliant and
conform to the changing shape of the polymer. Correspondingly, the
present disclosure may include compliant electrodes that conform to
the shape of an electroactive polymer to which they are attached.
The electrodes may be only applied to a portion of an electroactive
polymer and define an active area according to their geometry.
Various types of electrodes suitable for use with the present
disclosure include structured electrodes comprising metal traces
and charge distribution layers, textured electrodes comprising
varying out of plane dimensions, conductive greases such as carbon
greases or silver greases, colloidal suspensions, high aspect ratio
conductive materials such as carbon fibrils and carbon nanotubes,
and mixtures of ionically conductive materials.
[0062] Materials used for electrodes of the present disclosure may
vary. Suitable materials used in an electrode may include graphite,
carbon black, colloidal suspensions, thin metals including silver
and gold, silver filled and carbon filled gels and polymers, and
ionically or electronically conductive polymers. It is understood
that certain electrode materials may work well with particular
polymers and may not work as well for others. By way of example,
carbon fibrils work well with acrylic elastomer polymers while not
as well with silicone polymers.
[0063] 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.
* * * * *