U.S. patent application number 11/078847 was filed with the patent office on 2005-10-20 for devices for holding intermediate positions and articles that contain the same.
Invention is credited to Browne, Alan L., Bucknor, Norman K., Johnson, Nancy L., Jones, Gary L., Mankame, Nilesh D., Meernik, Paul R., O'Kane, James C., Ulicny, John C..
Application Number | 20050230195 11/078847 |
Document ID | / |
Family ID | 34994178 |
Filed Date | 2005-10-20 |
United States Patent
Application |
20050230195 |
Kind Code |
A1 |
Jones, Gary L. ; et
al. |
October 20, 2005 |
Devices for holding intermediate positions and articles that
contain the same
Abstract
Disclosed herein is a strut assembly 10 comprising a locking
device 11 in operative communication with a piston 3, wherein the
locking device 11 comprises an active material operative to resist
motion of the piston 3 in response to an activation signal.
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; activating an active material in
operative communication with the piston 3; and controlling the
motion of the suspended body 60.
Inventors: |
Jones, Gary L.; (Farmington
Hills, MI) ; Mankame, Nilesh D.; (Sterling Heights,
MI) ; Browne, Alan L.; (Grosse Pointe, MI) ;
Johnson, Nancy L.; (Northville, MI) ; Bucknor, Norman
K.; (Troy, MI) ; Meernik, Paul R.; (Redford,
MI) ; Ulicny, John C.; (Oxford, MI) ; O'Kane,
James C.; (Shelby Twp, MI) |
Correspondence
Address: |
General Motors Corporation, Legal Staff
Mail Code 482-C23-B21,
300 Renaissance Center
PO Box 300
Detroit
MI
48265
US
|
Family ID: |
34994178 |
Appl. No.: |
11/078847 |
Filed: |
March 11, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60552791 |
Mar 12, 2004 |
|
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|
Current U.S.
Class: |
188/68 |
Current CPC
Class: |
F16F 2224/0283 20130101;
F15B 21/065 20130101; F16F 9/56 20130101; F15B 15/26 20130101; F16F
9/368 20130101; F16F 2224/045 20130101; F16F 9/466 20130101; F16F
2224/025 20130101; E05B 47/0009 20130101; E05B 81/20 20130101; E05B
51/005 20130101; F16F 9/54 20130101; F15B 15/204 20130101; Y10T
292/17 20150401; Y10T 292/699 20150401; E05B 2015/0493 20130101;
F16F 9/46 20130101; Y10T 292/1082 20150401; E05B 47/0011 20130101;
F16F 15/005 20130101; Y10T 70/5093 20150401; F16F 2224/0258
20130101 |
Class at
Publication: |
188/068 |
International
Class: |
F16D 063/00 |
Claims
What is claimed is:
1. A strut assembly comprising: a locking device in operative
communication with a piston, wherein the locking device comprises
an active material operative to resist motion of the piston in
response to an activation signal.
2. The locking device of claim 1, wherein the active material
comprises a shape memory alloy, a shape memory polymer, a
magnetorheological fluid, an electrorheological fluid,
electroactive polymers, or a combination comprising at least one of
the foregoing shape memory materials.
3. The locking device of claim 1, wherein the locking device is
disposed external to the housing or is disposed inside the
housing.
4. The locking device of claim 1, wherein the active material is
activated by the application of an external stimulus, wherein the
external stimulus is electrical, magnetic, thermal, mechanical,
chemical, or a combination comprising at least one of the foregoing
external stimuli.
5. The locking device of claim 1, wherein the active materials can
change their shape, their stiffness and/or their dimensions in
proportion to an applied external stimulus.
6. The locking device of claim 4, wherein the active material upon
activation increases axial friction on the motion of a piston.
7. A strut assembly comprising: a piston in slideable communication
with a housing; a locking device in operative communication with
the piston, wherein the locking device comprises: a tilt washer in
operative communication with an active material, wherein the tilt
washer is operative to resist the motion of the piston.
8. The strut assembly of claim 7, wherein the active material is a
shape memory alloy.
9. A strut assembly comprising: a piston in slideable communication
with a housing; a locking device in operative communication with
the piston, wherein the locking device comprises: a sleeve; and an
active material in operative communication with the sleeve; wherein
the sleeve is operative to control the motion of the piston and/or
the motion of the housing.
10. The strut assembly of claim 9, wherein the active material is a
shape memory alloy.
11. The strut assembly of claim 9, wherein the sleeve is in
operative communication with a return spring.
12. A strut assembly comprising: a piston comprising a piston head
and a piston rod; wherein the piston is in slideable communication
with a housing; a locking device in operative communication with
the piston, wherein the locking device comprises: a plate in
operative communication with a piston head; wherein the plate is in
slideable communication with the piston rod; a spring stack
disposed between the plate and the piston head; and an active
material in operative communication with the plate; wherein the
active material upon activation is operative to control the motion
of the piston.
13. A strut assembly comprising: a piston comprising a piston head
and a piston rod; wherein the piston rod is in slideable
communication with a housing; a locking device in operative
communication with the piston, wherein the locking device
comprises: a protrusion fixedly attached to a piston head; a
wave-like tubular guide comprising an active material, wherein the
wave-like tubular guide is in slideable communication with the
protrusion; and wherein the wave-like tubular guide is operative to
control the motion of the piston.
14. The strut assembly of claim 13, wherein the active material
comprises a shape memory alloy polymer layer disposed on opposing
surfaces of a shape memory alloy layer.
15. A strut assembly comprising: a piston comprising a piston head
and a piston rod in slideable communication with a housing; wherein
the piston head comprises: a portion having one or more elastic
members; one or more brake shoes, wherein the brake shoes are in
operative communication with the elastic members; and an active
material in operative communication with the brake shoes; wherein
the active material is operative to control the motion of the
piston.
16. A strut assembly comprising: a piston comprising a piston head
and a piston rod, wherein the piston is in slideable communication
with a housing; wherein the housing comprises an electrorheological
fluid or a magnetorheological fluid and wherein the piston head
comprises: an optional permanent magnet, and an electromagnet; and
wherein the optional permanent magnet and the electromagnet are
operative to control the motion of the piston.
17. The strut assembly of claim 16, wherein the optional permanent
magnet and the electromagnet are concentrically arranged.
18. A locking device comprising: a pivot pin having disposed
thereon a ball disk comprising balls; a long arm and a short arm in
rotary communication with a pivot pin; wherein the short arm
comprises detents disposed upon a surface that is opposed to a
surface in contact with a surface of the long arm; and a
cylindrical housing in communication with a surface of the long arm
in opposition to a surface in contact with the short arm, wherein
the housing comprises an actuator, a piston and a spring, and
wherein the actuator comprises a shape memory material operative to
disengage the balls from the detents.
19. A method of operating a strut assembly comprising: displacing a
suspended body in mechanical communication with a piston;
activating an active material in operative communication with the
piston; and controlling the motion of the suspended body.
20. The method of claim 19, wherein the activating of the active
material occurs by the application of an external stimulus to shape
memory material, and wherein the external stimulus is an electrical
stimulus, a magnetic stimulus, a thermal stimulus, a chemical
stimulus, a mechanical stimulus, an ultrasonic stimulus or a
combination comprising at least one of the foregoing external
stimuli.
21. The method of claim 19, wherein the activating of the active
material resists the motion of the piston.
22. The method of claim 19, wherein controlling the motion of the
suspended body comprises locking the suspended body.
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 devices for holding intermediate
positions 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. They are also used in residential homes to
facilitate the locking of doors, storm doors and windows. These
assemblies generally require manual effort to initiate locking when
it is desired to partially or fully open an article (e.g., door,
window, or the like) that is in operative communication with the
strut assembly. For example, a door that is in operative
communication with a strut assembly generally has a small washer
that is manually adjusted to facilitate locking of the strut
assembly in order to prop open the door. This can pose a problem
for users of articles to which the strut assembly is attached, when
for example, the user has both arms engaged in other activity such
as carrying cargo, or the like.
[0004] In addition, strut assemblies that require manual
interaction to facilitate locking are generally not easily
accessible. For example, strut assemblies that are used for
propping open storm doors are generally located at the top of the
storm door and are often not easily accessible to shorter people.
Many practical benefits can accrue from the ability to hold the
swing panel open in any given position until it is moved to a new
position e.g. an opened tailgate will remain comfortably within the
reach of shorter users, the trunk swing panel will not beat against
a piece of luggage that extends outside the trunk, etc.
[0005] It is therefore desirable to use strut assemblies that offer
opportunities for automated locking. It is also desirable to use
strut assemblies that can be used to lock an article that is in
communication with the strut assembly in one position until it is
desired to displace the article to a new position in which it can
be locked once again.
SUMMARY
[0006] Disclosed herein is a strut assembly comprising a locking
device in operative communication with a piston, wherein the
locking device comprises an active material operative to resist
motion of the piston in response to an activation signal.
[0007] Disclosed herein is a strut assembly comprising a piston in
slideable communication with a housing; a locking device in
operative communication with the piston, wherein the locking device
comprises a tilt washer in operative communication with an active
material, wherein the tilt washer is operative to resist the motion
of the piston.
[0008] Disclosed herein is a strut assembly comprising a piston in
slideable communication with a housing; a locking device in
operative communication with the piston, wherein the locking device
comprises a sleeve; and an active material in operative
communication with the sleeve; wherein the sleeve is operative to
control the motion of the piston.
[0009] Disclosed herein is a strut assembly comprising a piston
comprising a piston head and a piston rod; wherein the piston is in
slideable communication with a housing; a locking device in
operative communication with the piston, wherein the locking device
comprises a plate in operative communication with a piston head;
wherein the plate is in slideable communication with the piston
rod; a spring stack disposed between the plate and the piston head;
and an active material in operative communication with the plate;
wherein the active material upon activation is operative to control
the motion of the piston.
[0010] Disclosed herein too is a strut assembly comprising a piston
comprising a piston head and a piston rod; wherein the piston rod
is in slideable communication with a housing; a locking device in
operative communication with the piston, wherein the locking device
comprises one or more protrusions fixedly attached to a piston
head; a wave-like tubular guide comprising an active material,
wherein the wave-like tubular guide is in slideable communication
with the protrusions; and wherein the wave-like tubular guide is
operative to control the motion of the piston.
[0011] Disclosed herein too is a strut assembly comprising a piston
comprising a piston head and a piston rod in slideable
communication with a housing; wherein the piston head comprises a
portion having one or more elastic members; one or more brake
shoes, wherein the brake shoes are in operative communication with
the elastic members; and an active material in operative
communication with the brake shoes; wherein the active material is
operative to control the motion of the piston.
[0012] Disclosed herein too is a strut assembly comprising a piston
that comprises a piston head and a piston rod, wherein the piston
is in slideable communication with a housing; wherein the housing
comprises an electrorheological fluid or a magnetorheological fluid
and wherein the piston head comprises an optional permanent magnet,
and an electromagnet; and wherein the optional permanent magnet and
the electromagnet are operative to control the motion of the
piston.
[0013] Disclosed herein too is a locking device comprising a pivot
pin having disposed thereon a ball disk comprising balls; a long
arm and a short arm in rotary communication with a pivot pin;
wherein the short arm comprises detents disposed upon a surface
that is opposed to a surface in contact with a surface of the long
arm; and a cylindrical housing in communication with a surface of
the long arm in opposition to a surface in contact with the short
arm, wherein the housing comprises an actuator, a piston and a
spring, and wherein the actuator comprises a shape memory material
operative to disengage the balls from the detents.
[0014] Disclosed herein too is a method of operating a strut
assembly comprising displacing a suspended body in mechanical
communication with a piston; activating an active material in
operative communication with the piston; and controlling the motion
of the suspended body.
DETAILED DESCRIPTION OF FIGURES
[0015] FIG. 1 is an exemplary schematic depiction of a strut
assembly 10 that comprises a locking device 11. The locking device
11 comprises a tilt washer 22 in operative communication with an
active element 20 that comprises an active material;
[0016] FIG. 2 is an exemplary schematic representation of a side
view and a front view of a section of the strut assembly 10
depicted in the FIG. 1;
[0017] FIG. 3 is an exemplary schematic representation of the mode
of operation of the locking device 11 of the FIG. 1;
[0018] FIG. 4 is an exemplary schematic representation of one
possible location of the locking device 11 that comprises a sleeve
32 in operative communication with an active element 20. The
locking device can be disposed in the housing if desired;
[0019] FIG. 5 is an exemplary schematic depiction of the strut
assembly 10 wherein the locking device 11 is in operative
communication with a piston rod 12. The active element 20 and the
return spring 30 permit control of the motion of the piston rod
12;
[0020] FIG. 6 is another exemplary schematic depiction of the strut
assembly 10 wherein the locking device 11 is in operative
communication with a piston rod 12. The active element 20 and the
return spring 30 permit control of the motion of the piston rod
12;
[0021] FIG. 7 is an exemplary schematic depiction of the strut
assembly 10 wherein the locking device 11 is in operative
communication with a piston rod 12. The piston rod 12, the active
element 20 and the sleeve 32 are concentrically arranged with the
active element 20 circumferentially disposed upon the sleeve
32;
[0022] FIG. 8 is an exemplary schematic depiction of the strut
assembly 10 wherein the locking device 11 is in operative
communication with a piston rod 12. The locking device comprises a
spring stack 26, which when compressed controls the motion of the
piston rod 12;
[0023] FIG. 9 is an exemplary schematic depiction of the strut
assembly 10 wherein the locking device 11 comprises a wave-like
guide 36 in operative communication with a piston 3. The piston 3
comprises one or more protrusions 48 that are in slideable
communication with the guide 36 that comprises a wave-like inner
surface;
[0024] FIG. 10 is an exemplary depiction of the construction of the
wave-like tubular guide 36;
[0025] FIG. 11 is an exemplary depiction of a strut assembly 10
that comprises a locking device 11 wherein the piston head
comprises brake shoes 54 that are in operative communication with
the piston rod 12 and in slideable communication with the housing
2;
[0026] FIG. 12 is an exemplary depiction of a cross-sectional view
of the central portion 52 of the piston head 12 displayed in the
FIG. 11;
[0027] FIG. 13 is an exemplary depiction of a strut assembly 10
that comprises a locking device 11 wherein the piston head 14
comprises brake shoes 54 that are in operative communication with
the piston rod 12 and in slideable communication with the housing
2. The central portion 52 of the piston head 14 comprises a groove
that engages with the locking rings 62 to lock the strut assembly
10;
[0028] FIG. 14 is an exemplary depiction of a cross-sectional view
of the central portion 52 of the piston head 12 displayed in the
FIG. 11;
[0029] FIG. 15 is an exemplary depiction of a strut assembly 10
wherein the housing 2 comprises a magnetorheological fluid. The
displacement of the strut assembly can be controlled by using a
magnetic field disposed within the housing to change the viscosity
of the magnetorheological fluid;
[0030] FIG. 16 is a depiction of an exemplary embodiment of a front
view of a pivot detent locking device 11;
[0031] FIG. 17 is a depiction of an exemplary embodiment of a rear
view of a pivot detent locking device 11;
[0032] FIG. 18 depicts a sectional view of one embodiment of the
pivot detent locking device 11 when in the locked position; and
[0033] FIG. 19 depicts a sectional view of one embodiment of the
detent-locking device 11 in its unlocked position.
DETAILED DESCRIPTION
[0034] Disclosed herein are locking devices employed in conjunction
with strut assemblies that can advantageously be used to lock an
article (a suspended body) in a desired position. The locking
device advantageously comprises an active element that is in a
frictional relationship with a moveable component of the strut
assembly, such as for example, the piston, thereby facilitating a
locking of the suspended body. A frictional relationship is one
wherein resistance is applied either directly or indirectly to the
motion of a moveable component of the strut assembly due to
friction between the moving components. In one embodiment, the
locking device is in operative communication with a piston, wherein
the locking device comprises an active material operative to resist
motion of the piston in response to an activation signal. In
another embodiment, the locking device is in operative
communication with the housing and is adapted to resist the motion
of the housing. The locking device can be disposed on the cylinder
and can be in operative communication with the piston or can be
disposed on the piston and can be in operative communication with
the cylinder. The locking device can be used to control the motion
of the suspended body and can lock the suspended body when
desired.
[0035] 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 locking devices can be
deployed either inside or outside the strut assemblies. The locking
devices advantageously employ active materials, i.e., materials
that exhibit the ability to respond to an external stimulus by
changing one or more of their properties (e.g. elastic modulus,
crystal structure, or the like).
[0036] 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.
[0037] In one embodiment, the locking device advantageously
increases resistance on the movement of the strut assembly. This
resistance increases the resistance to the motion of a suspended
body that is in operative communication with the strut assembly.
The devices also permit locking of the strut assemblies and hence
of the suspended body without the use of any power or energy i.e.,
they are capable of a power-off locking of the suspended body. The
strut assemblies advantageously permit locking of the article in an
infinite number of positions and can lock the article during any
position along its length of travel. The devices can advantageously
lock the suspended body in any desired position either as the
suspended body is being opened or closed.
[0038] In one embodiment, the positioning or repositioning of the
suspended body that is in operative communication with the strut
assembly is accomplished by the application of a suitable manual
force. In another embodiment, the positioning or repositioning of
an article that is in operative communication with the strut
assembly is accomplished by use of a motive force such as
mechanical energy or electrical energy. Positioning or
repositioning is defined as the motion imparted to the article by
manual force or other motive forces such as mechanical energy,
electrical energy, or the like. The ability to position and lock an
article in a state of equilibrium at one or more desirable points
along the length of its travel is termed detent. The strut
assemblies that employ the locking devices have an infinite detent
capability and permit positioning or repositioning of a suspended
body that is in operative communication with the strut assembly at
any degree of opening with the minimal use of force or
restraint.
[0039] As stated above, the locking devices can comprise components
that are located inside or outside the strut assembly if desired.
In one embodiment, components of the locking device can be in a
supportive relationship with the housing of the strut assembly. A
supportive relationship as defined herein is indicated to mean that
components of the locking device are physically supported by the
housing. In another embodiment, components of the locking device
are in a supportive relationship with a frame that is not in
operative communication with the housing. In yet another
embodiment, the locking device can be in a supportive relationship
with the piston or to a fixture in operative communication with the
piston.
[0040] The locking devices employ active materials (e.g., shape
memory materials) that can be activated by applying an activation
signal to lock the piston of the strut assembly in a desired
position. Shape memory materials generally refer to materials or
compositions that have the ability to remember their original
shape, which can subsequently be recalled by applying an external
stimulus, i.e., an activation signal. Exemplary shape memory
materials suitable for use in the present disclosure include shape
memory alloys, ferromagnetic shape memory alloys, shape memory
polymers 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 active materials used in the strut
assembly 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. Exemplary active
materials in this category are electroactive polymers (dielectric
polymers), piezoelectrics, and piezoceramics. Activation signals
can employ an electrical stimulus, a magnetic stimulus, a chemical
stimulus, a mechanical stimulus, a thermal stimulus, or a
combination comprising at least one of the foregoing stimuli.
[0041] FIG. 1 is an exemplary depiction wherein the locking device
11 is fixedly attached to a strut assembly 10 that comprises a
housing 2 that is in slideable or rotary 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 fluid through the
piston head 14 as it moves forward and backward in the housing 2.
Seals 6 are circumferentially disposed upon the piston head 14 and
seal the space between the piston head 14 and the housing 2. The
seals 6 are concentric with the piston head 14. Additional seals 6
can also be optionally disposed between the piston rod 12 and 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 suspended
member 60 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 FIG. 1 depicts the
suspended body 60 as being contacted by the housing 2 and the
supporting body 50 as being contacted by the piston rod 12, it is
envisioned that the suspended body 60 can be contacted by the
piston rod 12 while the supporting body can be contacted by the
housing 2. Exemplary moveable parts of the strut assembly 10 are
the piston 3, the housing 2, or any other components such as worm
wheels, gears, pinions, or the like, that are in operative
communication with the piston and/or the housing and which
facilitate the displacement of the suspended body 60.
[0042] The locking device comprises a tilt washer 22 that is in
operative communication with an active element 20 that comprises an
active material. The tilt washer 22 is disposed outside the housing
2, but can be disposed internally if desired. In one embodiment,
the tilt washer 22 may be in pivotable communication with the
housing 2 or with another desired frame that may or may not be in
operative communication with the strut assembly 10.
[0043] As can be seen in the FIG. 2, which depicts a side view and
a front view of the locking device 11, the tilt washer 22 comprises
a first end that pivots about a hinge 24 that is affixed to the
outer surface of the housing 2 and a second end that is in
slideable communication with an outer surface of the housing 2. In
one embodiment, the second end of the hinge may be in slideable
communication with the outer surface of the housing 2, via a guide
(not shown). In another embodiment, the hinge 24 comprises an
elastomeric material that flexes to accommodate the change in slope
of the tilt washer that is desirable to lock or unlock the piston
rod 12. The tilt washer 22 also has disposed in it a hole 26
through which passes the piston rod 12. The smallest diameter of
the hole 26 is larger than the diameter of the piston rod 12. When
the suspended body 60 (not shown) is displaced with respect to the
supporting body 50 (not shown), the piston rod 12 travels back and
forth (reciprocates) through the hole 26 in the tilt washer 22
until a surface of the tilt washer 22 contacts the piston rod 12
and exerts axial friction on the piston rod 12 or otherwise
produces mechanical interference that resists the motion of the
piston rod.
[0044] As can be seen in the FIG. 2, the tilt washer has a geometry
effective to contact the piston rod 12 upon activation of the
active element 20. The tilt washer 22 can have any suitable
geometry depending upon the selected application and space
restrictions. A portion of the tilt washer 22 is in operative
communication with the active element 20, which upon activation
promotes displacement of the tilt washer 22. The active element 20
is disposed between the tilt washer 22 and an active element
support panel 28. In its default position, the tilt washer contacts
the piston rod 12 and locks it. Activation of the active element 20
can displace the tilt washer 22 such that the surface of the hole
26 no longer contacts the piston rod 12. This reduces the axial
friction and permits the displacement of the piston rod and hence
of the suspended body 60. In one embodiment, the active element 20
can displace the tilt washer 22 against a restoring force (e.g.,
produced by the elastic deformation of the tilt washer, or produced
by an external biasing spring, or the like) to displace the tilt
washer from its default position.
[0045] FIG. 3 depicts one manner of operating the locking device
11. FIG. 3(a) is an exemplary depiction showing the tilt washer 22
in its default position. In its default position, which will now be
referred to as its first position, the tilt washer 22 acts as a
normally engaged brake and resists the motion of the piston rod 12.
The piston rod 12 can be held in this position even after the
activating signal to the active element is removed or discontinued.
This is referred to as a power-off hold.
[0046] When it is desired to once again displace the suspended body
60, an activating signal is applied to the active element 20,
thereby displacing the tilt washer 22 to a second position. In the
second position, the tilt washer 22 does not contact the piston rod
12 and does not exert any axial frictional on the piston rod 12.
Hence the piston rod 12 can be freely displaced. When it is desired
to lock the suspended body 60 once again, the active element 20 is
once again deactivated. The restoring force of the hinge 24 or that
or a restoring or biasing spring (not shown) can be used to restore
the tilt washer 22 to its original position thereby locking the
piston rod 12.
[0047] As noted above, the active element 20 comprises an active
material (e.g., shape memory material). In one embodiment, the
active element 20 consists essentially of the active material. In
another embodiment, the active element 20 can comprise active
materials and or passive (i.e., non-active) materials. Passive
materials are those that do not recover their original shape after
the application of an external stimulus. The active element 20 can
comprise a single active element or multiple active elements. When
more than one active element is used, they can be arranged in
series or in parallel or combinations thereof.
[0048] In one embodiment, the active element 20 may be part of a
motor that is used to actuate the tilt washer 20. Examples of such
motors are electric stepper motors, inchworms, piezoelectric
inchworms, ultrasonic motors, electrohydrostatic actuators,
nanomotion piezoelectric motors, compact hybrid actuator devices
(CHAD), or the like, or a combination comprising at least one of
the foregoing motors.
[0049] For convenience and by way of example, reference herein will
be made to shape memory alloys. An exemplary active 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, yield
strength, and shape orientation are altered as a finction of
temperature. Generally, in the low temperature, or martensite
phase, shape memory alloys can be plastically deformed and upon
exposure to some higher temperature will transform to an austenite
phase, or parent phase, returning to their shape prior to the
deformation. 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.
[0050] Shape memory alloys can exhibit a one-way shape memory
effect, an intrinsic two-way effect, or an extrinsic two-way shape
memory. Annealed shape memory alloys generally 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.
[0051] Intrinsic 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. 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. Active elements that exhibit an intrinsic
one-way shape memory effect are fabricated from a shape memory
alloy composition that will cause the active elements 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 thermo-mechanical
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.
[0052] 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 alloy
composition.
[0053] Suitable shape memory alloy materials for fabricating the
active elements 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.
[0054] 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.
[0055] The active element 20 may also be an electrically active
polymer. Electrically active polymers are also commonly known as
electroactive polymers (EAP's). The key design feature of devices
based on these materials is the use of compliant electrodes that
enable polymer films to expand or contract in the in-plane
directions in response to applied electric fields or mechanical
stresses. When EAP's are used as the active element 20, strains of
greater than or equal to about 100%, pressures greater than or
equal to about 50 kilograms/square centimeter (kg/cm.sup.2) can be
developed in response to an applied voltage. The good
electromechanical response of these materials, as well as other
characteristics such as good environmental tolerance and long-term
durability, make them suitable for active elements under a variety
of manufacturing conditions. EAP's are suitable for use as an
active element in many strut assembly 10 configurations.
[0056] Electroactive polymer coatings used in strut assembly 10 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, a 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.
[0057] 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.
[0058] Materials used for electrodes 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.
[0059] The electroactive polymers (EAP's) used herein, are
generally conjugated polymers. Suitable examples of EAP's are
poly(aniline), substituted poly(aniline)s, polycarbazoles,
substituted polycarbazoles, polyindoles, poly(pyrrole)s,
substituted poly(pyrrole)s, poly(thiophene)s, substituted
poly(thiophene)s, poly(acetylene)s, poly(ethylene dioxythiophene)s,
poly(ethylenedioxypyrrole)s, poly(p-phenylene vinylene)s, or the
like, or combinations comprising at least one of the foregoing
EAP's. Blends or copolymers or composites of the foregoing EAP's
may also be used. Similarly blends or copolymers or composites of
an EAP with an EAP precursor may also be used.
[0060] The actuator element 20 used in the customizable strut
assembly 10 may also comprise a piezoelectric material. Also, in
certain embodiments, the piezoelectric material may be configured
for providing rapid deployment. As used herein, the term
"piezoelectric" is used to describe a material that mechanically
deforms (changes shape and/or size) when a voltage potential is
applied, or conversely, generates an electrical charge when
mechanically deformed. As piezoelectric actuators have a small
output stroke, they are usually coupled with a transmission (e.g. a
compliant mechanism) that serves to amplify the output stroke at
the expense of a reduction in the output force. As an example, a
piezoelectric material is disposed on strips of a flexible metal
sheet. The piezo actuators are coupled to the sheet in a manner
that causes bending or unbending of the sheet when the actuators
are activated. The ability of the bending mode of deformation in a
flexible shell to amplify small axial strains into larger rotary
displacements is used to advantage. The strips can be unimorph or
bimorph. Preferably, the strips are bimorph, because bimorphs
generally exhibit more displacement than unimorphs.
[0061] In contrast to the unimorph piezoelectric device, a bimorph
device includes an intermediate flexible metal foil sandwiched
between two piezoelectric elements. Bimorphs exhibit more
displacement than unimorphs because under the applied voltage one
ceramic element will contract while the other expands. Bimorphs can
exhibit strains up to about 20%, but similar to unimorphs,
generally cannot sustain high loads relative to the overall
dimensions of the unimorph structure.
[0062] Suitable piezoelectric materials include 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 candidates for the piezoelectric film. Examples of suitable
polymers include, for example, but are not limited to, poly(sodium
4-styrenesulfonate) ("PSS"), poly S-119 (poly(vinylamine)backbone
azo chromophore), and their derivatives; polyfluorocarbons,
including polyvinylidene fluoride ("PVDF"), its co-polymer
vinylidene fluoride ("VDF"), trifluoroethylene (TrFE), and their
derivatives; polychlorocarbons, including poly(vinyl chloride)
("PVC"), polyvinylidene chloride ("PVC2"), and their derivatives;
polyacrylonitriles ("PAN"), and their derivatives; polycarboxylic
acids, including poly(methacrylic acid ("PMA"), and their
derivatives; polyureas, and their derivatives; polyurethanes
("PUE"), and their derivatives; bio-polymer molecules such as
poly-L-lactic acids and their derivatives, and membrane proteins,
as well as phosphate bio-molecules; polyanilines and their
derivatives, and all of the derivatives of tetramines; polyimides,
polyetherimides ("PEI"), and their derivatives; all of the membrane
polymers; poly(N-vinyl pyrrolidone) ("PVP") homopolymer, and its
derivatives, and random PVP-co-vinyl acetate ("PVAc") 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.
[0063] Further, piezoelectric materials can include Pt, Pd, Ni, Ti,
Cr, Fe, Ag, Au, Cu, and metal alloys and mixtures thereof. These
piezoelectric materials can also include, for example, metal oxide
such as 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.
[0064] Shape memory polymers (SMPs) can also be used in the locking
and detent mechanisms. Most commonly, they can be used to provide
means for power-off position holding. Generally, SMP's are
co-polymers comprised of at least two different units which may be
described as defining different segments within the co-polymer,
each segment contributing differently to the elastic 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.
[0065] These segments may be a 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 elastic 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. The previously defined or
permanent shape of the SMP can be set by molding the polymer at a
temperature higher than the highest thermal transition temperature
for the shape memory polymer or its melting point, followed by
cooling below that thermal transition temperature.
[0066] In practice, the SMP's are alternated between one of at
least two shape orientations such that at least one orientation
will provide a size reduction or shape change relative to the other
orientation(s) when an appropriate thermal signal is provided. To
set a permanent shape, the SMP must be at about or above its
melting point or highest transition temperature (also termed "last"
transition temperature). The SMP's are shaped at this temperature
by blow molding, injection molding, vacuum forming, or the like, or
shaped with an applied force followed by cooling to set the
permanent shape. The temperature to set the permanent shape is
about 40.degree. C. to about 300.degree. C. After expansion, the
permanent shape is regained when the applied force is removed, and
the SMP formed device 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. Transition temperatures of suitable
SMPs generally range from about -63.degree. C. to above about
160.degree. C.
[0067] The temperature desired for permanent shape recovery can be
set at any temperature of 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.
[0068] The shape memory polymers used in the active device can be
thermoplastics, interpenetrating networks, semi-interpenetrating
networks, or mixed networks. The polymers can be a single polymer
or a blend of polymers. Polymers can be linear, branched,
thermoplastic elastomers with side chains or any kind of dendritic
structural elements. In one embodiment the shape memory polymer can
be a block copolymer, a graft copolymer, a random copolymer or a
blend of a polymer with a copolymer.
[0069] Stimuli causing shape change can be temperature, ionic
change, pH, light, electric field, magnetic field or ultrasound.
Suitable polymer components to form a shape memory polymer include
polyphosphazenes, polyacrylics, polyalkyds, polystyrenes,
polyesters, polyaramides, polyamideimides, polyarylates,
polyarylsulfones, polyethersulfones, polyphenylene sulfides,
polysulfones, polyimides, polyetherimides,
polytetrafluoroethylenes, polyetherketones, polyether etherketones,
polyether ketone ketones, polybenzoxazoles, polyoxadiazoles,
polybenzothiazinophenothiazines, polybenzothiazoles,
polypyrazinoquinoxalines, polypyromellitimides, polyquinoxalines,
polybenzimidazoles, polyoxindoles, polyoxoisoindolines,
polydioxoisoindolines, polytriazines, polypyridazines,
polypiperazines, polypyridines, polypiperidines, polytriazoles,
polypyrazoles, polycarboranes, polyoxabicyclononanes,
polydibenzofurans, polyphthalides, polyacetals, polyanhydrides,
polyvinyl ethers, polyvinyl thioethers, polyvinyl alcohols,
polyvinyl ketones, polyvinyl halides, polyvinyl nitriles, polyvinyl
esters, polysulfonates, polysulfides, polythioesters, polysulfones,
polysulfonamides, polyureas, polyphosphazenes, polysilazanes,
poly(vinyl alcohols), polyamides, polyester amides, poly(amino
acid)s, 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
methacrylate), poly(ethyl methacrylate), poly(butyl methacrylate),
poly(isobutyl methacrylate), poly(hexyl methacrylate),
poly(isodecyl methacrylate), poly(lauryl methacrylate), poly(phenyl
methacrylate), poly(methyl acrylate), poly(isopropyl acrylate),
poly(isobutyl acrylate) and poly(octadecyl acrylate). 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) dimethacrylate-n-butyl
acrylate, poly(norbomyl-polyhedral oligomeric silsequioxane),
polyvinylchloride, urethane/butadiene copolymers, polyurethane
block copolymers, styrene-butadiene-styrene block copolymers, and
the like. The polymer used to form the various segments in the SMPs
described above are either commercially available or can be
synthesized using routine chemistry.
[0070] The SMP's may be advantageously reinforced with fillers.
Suitable fillers may exist in the form of whiskers, needles, rods,
tubes, strands, elongated platelets, lamellar platelets,
ellipsoids, micro fibers, nanofibers and nanotubes, elongated
fullerenes, and the like.
[0071] FIGS. 4 through 7 depict exemplary embodiments of another
locking device 11 that is disposed outside the housing 2. While the
examples depicted in the FIGS. 4 display the locking mechanism as
being deployed outside the housing 2, it can be located inside the
housing 2 as well. FIG. 4 shows different positions where the
locking device 11 can be deployed.
[0072] With reference now to the FIG. 5, the locking device 11
comprises a sleeve 32 that can be elastically deformed by an active
element 20. In one embodiment, the sleeve 32 contacts the piston
rod 12 in order to prevent the piston rod from being displaced
further along its line of travel. The sleeve 32 can also contact
the housing 2 in order to prevent the housing from being displaced
further along its line of travel. It is generally desirable for the
sleeve 32 to contact that portion of the strut assembly 10 that is
adapted to permit the displacement of the suspended body 60. As
shown in the FIG. 5, the sleeve 32 is in operative communication
with the active element 20, which upon activation can radially
compress the sleeve 32 to contact the outer surface of the housing
2 since in this exemplary embodiment, the housing is fixedly
attached to the suspended body 60. The sleeve 32 is also in
operative communication with optional return springs 30, whose
spring constant can be adjusted to vary the resistance imparted by
the sleeve to the piston rod. The optional return springs are
fixedly attached to supports 29 that are affixed to either the
housing 2 or the suspended body 60.
[0073] In one embodiment, the sleeve 32 can comprise a lining or a
coating (not shown) on the surface that contacts the housing 2. The
lining can be used to modify the frictional properties of the inner
surface of the sleeve or on the corresponding surface of the piston
rod or the housing. An elastic deformation of the sleeve 32 can be
used to vary the frictional force between the sleeve 32 and the
housing 2, by varying the area of contact between the sleeve 32 and
the housing 2, by varying the contact pressure (magnitude and/or
distribution) between the sleeve 32 and the housing 2, or by a
combination thereof. In one embodiment, the default condition of
the sleeve 32 can be selected (e.g., by design, by adjusting the
tension in the return springs 30, or the like) to impart a desired
level of frictional resistance to the motion of the housing 2.
During the operation of the suspended body 60, the elastic
deformation of the sleeve 32 and hence the frictional resistance to
the motion of housing 2, can be adjusted by the active element
20.
[0074] In the default condition of the locking device 11, the
sleeve 32 does not contact the housing 2. In this condition the
active element 20 is considered to be in a strain-free
configuration since it has no residual stress. The active element
20 can be actuated by passing an electric current through it to
induce a martensitic to austenitic phase transition in the shape
memory material material. This transformation is associated with a
large strain recovery, and a correspondingly large recovery force
is exerted if the strain recovery is resisted.
[0075] Upon activation, the active element 20 applies a compressive
radial force to the sleeve 32. The recovery force deforms the
sleeve 32 to increase the contact area and/or the contact pressure,
thereby increasing the frictional resistance to the movement of the
housing 2. The magnitude of the actuation force can be controlled
by either the force applied by the return springs 30 or by the
magnitude of the activation that the active element 20 is subjected
to. The increased frictional resistance imparted by the sleeve 32
to the housing 2 is effective as long as the element active element
20 remains actuated.
[0076] When the current flowing through the active element 20 is
switched off, the shape memory material transforms back to the
martensitic phase, and the sleeve 32 is restored to its default
condition because of the elastic recovery of the sleeve 32 as well
as because of the restoring force applied by the return spring 30.
The recovery process results in pseudo-plastic straining of the
martensitic phase shape memory material element, and hence the
system is restored to its initial configuration.
[0077] FIG. 6 reflects another variation, wherein the positions of
the active element 20 are switched with those of the return spring
30. Here the elastic force of the sleeve counteracts the
compressive force exerted by the return spring 30. The active
element 20 can be configured upon activation to assist and/or
resist the compressive forces of the return spring 30.
[0078] FIG. 7 shows yet another variation of the locking device 11
in which the active element 20 is circumferentially disposed around
the sleeve 32 and in intimate contact with it. The active element
20 can cover the entire sleeve 32 or only a portion of the sleeve
32. In an exemplary embodiment where the active element is made
from a shape memory alloy, the active element 20 is disposed around
the sleeve when the shape memory alloy material is in its
martensitic phase. The sleeve is therefore forced into its most
compact form by extraneous forces acting during the assembly of the
locking device.
[0079] When these forces are removed, the elastic energy stored in
the deformed sleeve 32 will try to recover the original (or
unstressed) configuration of the sleeve 32. In this process the
shape memory alloy material wrapping will get pseudo-plastically
strained. The passage of a current through the element will induce
a martensite to austenite phase transformation in the shape memory
material, which will then exert a substantial recovery force in its
attempt to recover the unstrained configuration of the shape memory
alloy material. The unstrained configuration of the shape memory
alloy material corresponds to the compacted configuration of the
sleeve 32. Therefore, the passage of a current through the active
element will deform the sleeve such as to increase the contact area
and/or pressure between the sleeve 32 and the housing 2. This
enables the assembly comprising the sleeve 32 and shape memory
alloy material to finction as a frictional brake. When the current
is stopped and the shape memory material elements cool down and
convert back to the martensitic phase, the elastic restoring forces
from the sleeve 32 dominate the force in the shape memory material
elements and thereby restore the starting configuration of the
locking device 32.
[0080] Many variations of this concept can be implemented. In one
exemplary variation, the configuration of the active element may be
changed into a stent-like design, in which the shape memory alloy
functions as the sleeve 32 as well as the actuator that controls
the configuration of the sleeve. In another variation, other active
materials such as electro-active polymers, piezoelectrics, or the
like, may be used in place of the shape memory alloy.
[0081] As noted earlier, the locking device can be disposed inside
the housing 2. FIG. 8 is a depiction of one exemplary embodiment of
the strut assembly 10 wherein the locking device 11 comprises a
spring stack 27 that is disposed inside the housing 2 between the
piston head 14 and plate 29 disposed upon the piston rod 12. The
spring stack 27 can be wave springs having washers disposed in
between as shown in the FIG. 8. In another embodiment, the spring
stack 27 can comprise conic springs, known as Belleville washers.
This springs when axially compressed will expand both radially
outward and inward. The spring stack 27 can comprise a single
spring or multiple springs.
[0082] The plate 29 is in operative communication with the piston
head 14 via a number of active elements (e.g., studs 34) that are
axially disposed and are parallel to the direction of travel of the
piston rod 12. The plate 29 is in slideable communication with the
piston rod 12 and is free to move along the piston rod 12 until the
active elements 20 are activated by the application of an external
stimulus. In an exemplary embodiment, each active element 20
comprises a shape memory alloy. The studs 34 are fixedly attached
to the piston head 14. Each stud 34 is in operative communication
with the plate 29. Upon application of the activation signal, the
studs 34 return to their original shape (memorized shape), which
facilitates a displacement of the plate 29 towards the piston head
14, thereby applying a compressive force to the spring stack 27
which compresses the wave springs causing them to expand radially
outwards and contacting the inner surface of the housing 2. The
axial friction between the outer circumference of the wave springs
in the spring stack 27 and the inner surface of the housing 2
promotes the locking of the strut assembly 10. As noted above, when
the studs 34 comprise a shape memory alloy, they can be activated
by the application of heat. An exemplary method of heating is
resistive heating. Other active materials that can be employed in
the active element are electro-active polymers, piezoelectric
materials, or the like.
[0083] In yet another exemplary embodiment depicted in FIG. 9, a
locking device 11 is disposed inside the housing 2. In FIG. 9, the
locking device comprises a guide 36 having at least a corrugated
inner surface. The guide 36 can have an outer corrugated surface if
so desired. In one embodiment, the guide can be tubular. In another
embodiment, the guide can advantageously employ geometries that are
not tubular.
[0084] The corrugated surfaces of the guide 36 are comprised of
alternating convex surfaces 38 and concave surfaces 40 as shown in
the FIG. 9. A convex surface 38 is defined as one in which the
radius of curvature for the surface is located on the housing side
of the guide 36. A concave surface 40 is defined as one in which
the radius of curvature for the surface is located on the piston
rod side of the guide 36. The amplitude of the waves as well as the
wavelength of the waves in the guide 36 can be varied upon the
application. In one embodiment, the guide 36 comprises a shape
memory alloy layer 42 disposed between two shape memory polymer
layers 44, 46 as depicted in the FIG. 9. The shape memory polymer
layers 44, 46 are disposed on opposing surfaces of the shape memory
alloy layer 42 and are in intimate contact with the shape memory
alloy layer 42. The shape memory alloy layer 42 has a wave-like
shape when it is in a stress-free, martensitic condition and this
wave-like shape is imparted to the guide 36. The composition of the
shape memory alloy layer ensures that the guide remains in the
martensitic condition throughout the operating temperature range of
the strut assembly 10. The shape memory polymer is selected such
that its lowest glass transition temperature (Tg) is greater than
the maximum operating temperature that the piston head will
experience during the operation of the strut assembly 10. The guide
36 is designed to ensure that at temperatures below Tg, the
stiffness of the shape memory polymer matrix determines the
stiffness of the guide 36, whereas at temperatures above Tg, the
stiffness of the shape memory alloy layer determines the stiffness
of the guide 36.
[0085] One or more protrusions 48 disposed on the circumferential
surface of the piston head 14 contact the inner surface of the
guide 36. The protrusion 48 is of a size effective to contact the
inner surface of the guide 36 as the piston 3 moves back and forth
in the housing 2. When the guide 36 is contacted by the protrusion
48, it resists relative motion between the piston head 14 and the
housing 2. Only by applying a manual force greater than the
resistance to deformation exerted by the guide 36 can relative
motion between the piston head 14 and the housing 2 occur. When
motion occurs between the piston head 14 and the housing 2, the
protrusion 48 deforms the wave-like surface locally as it contacts
it. The properties of the guide (e.g., its stiffness) and the
geometry of the guide (i.e., the amplitude and wavelength of the
waves, and the like) can be varied by the application of a suitable
external stimulus i.e., an activating signal. Therefore, the
resistance to the motion of the suspended member 60 as well as the
locking of the suspended member 60 can be controlled by varying the
properties and the geometry of the guide 36.
[0086] When the suspended body 60 is in a locked position, the
protrusion 48 is disposed between two concave surfaces 40 of the
tubular guide 36. As described earlier, relative motion between the
piston 3 and the housing 2 requires the local deformation of the
convex surfaces 38 of the tubular guide 36 as the piston 3 travels
back and forth in the housing 2. The force effective to induce this
deformation, and thus to move the suspended member 60, depends on
the stiffness of the tubular guide 36. If the stiffness of the
tubular guide 36 is great enough to resist relative motion under
various applied loads (e.g., weight of the suspended member 60,
wind load, user effort, etc), the tubular guide 36 functions as a
mechanical stop. When the length of the strut assembly 10 has to be
changed, the shape memory polymer is heated to a temperature above
its Tg, whereupon its elastic modulus of the guide 36 decreases.
This reduction in the elastic modulus of the guide 36 reduces the
resistance of the guide 36 to the motion of the suspended body 60.
The suspended body 60 can be moved to a new position while the
shape memory polymer is at a temperature greater than or equal to
about is lower Tg. When the suspended body 60 reaches its desired
position, the heating of the shape memory polymer layer is stopped.
As the shape memory polymer layer cools below the Tg, the stiffness
of the shape memory polymer and hence the guide increases. This
results in locking the suspended body 60 in its new position.
[0087] When the piston 3 is moved relative to the housing 2 during
the period while the shape memory polymer layer is at a temperature
greater than its lowest Tg, the protrusion 48 deforms the guide
locally as it travels past the concave portions of the guide 36.
The stiffness of the shape memory alloy layer, which is not reduced
by the change in temperature of the guide 36, helps restore the
deformed regions to their original shape after the protrusion 48
has passed by. In one embodiment, the guide 36 can retain its
original shape by heating the deformed regions to a temperature
effective to induce a martensitic to austenitic phase
transformation. The martensitic to austenitic phase transformation
facilitates the restoration of the deformed regions to their
original shape.
[0088] The composition of the shape memory alloy layer is chosen
such that it can maintain the integrity of the tubular guide 36
while the shape memory polymer layer undergoes large deformations
and provides significant recovery forces that assist in restoration
of the original configuration of the tubular guide 36. As the shape
memory alloy has high electrical resistivity, the wave-like tubular
guide 36 can be readily heated by passing electric current through
the shape memory alloy elements. Instead of a shape memory alloy,
other electrically conductive materials (e.g. other metals or
alloys) can be used in the composite.
[0089] In yet another exemplary embodiment depicted in the FIGS.
11, 12, 13 and 14, the locking device 11 comprises an internal
expanding brake disposed inside the housing 2. In one embodiment,
depicted in the FIGS. 11 and 12, the internal expanding brake can
be used as a detent with potentially an infinite number of stop
positions. In another embodiment depicted in the FIGS. 13 and 14,
the internal expanding brake can be used as a detent with a small,
finite number of stop positions.
[0090] With reference now to the FIGS. 11 and 12, the piston head
14 can be modified to act as an internal expanding brake that
presses against the inner surface of the housing 2 thereby
permitting the locking of the strut assembly 10 in any desired
position. An exemplary embodiment of this concept is depicted in
the FIG. 11. The piston head 14 comprises two external portions 51
and a central portion 52 that are disposed on the piston rod 12.
The two external portions 51 and the central portion 52 are in
operative communication with the piston rod 12. The central portion
52 of the piston head comprises one or more brake shoes 54 that are
in mechanical communication with the piston rod 12 by elastic
members 56. The elastic members 56 are disposed between the piston
rod 12 and the brake shoes 54 and extend radially outwards from the
piston rod 12 to the brake shoes 54.
[0091] In one embodiment, as depicted in the FIG. 12, the central
portion 52 can have three brake shoes. When the elastic members 56
are unconstrained, the effective outer diameter of the piston head
14 due to the brake shoes 54 is larger than the inner diameter of
the housing 2. In order to be disposed within the housing 2, the
brake shoes 54 are radially compressed and positioned in the
housing. Thus, the elastic restoring force produced by the
compression of the elastic members during assembly gives rise to a
radial force that presses the brake shoes 54 against the inner
surface of the housing 2. This radial force produces an axial
friction between the brake shoes 54 and the inner surface of the
housing 2. As can be seen in the FIGS. 11 and 12, shape memory
alloy wires 58 are wound circumferentially around the brake shoes
54. When activated, the shape memory alloy elements (e.g. wires) 58
facilitate the compression of the elastic members 56, thereby
reducing the axial friction between the brake shoes 54 and the
inner surface of the housing 2. The restoring force of the elastic
members 56 is therefore opposed by the hoop stress induced in the
shape memory alloy element 58.
[0092] In one embodiment, in one manner of operating the strut
assembly 10 depicted in the FIGS. 11 and 12, the brake shoes 54
contact the inner surface of the housing 3 thereby preventing any
displacement of the suspended body 60. The suspended body 60 is
therefore locked. In this default position, the shape memory alloy
element 58 is in its martensitic phase. The elastic force exerted
radially outwards by the brake shoes 54 produces an axial friction
with the inner surface of the housing 3, which facilitates the
locking of the strut assembly 10.
[0093] If it is desired to displace the suspended body 60, an
activating signal is applied to the shape memory element 58. The
activation signal, which is generally in the form of resistive
heating promotes a transformation of the shape memory element 58
from the martensitic state to the austenitic state. This
solid-state transformation produces a large restoring force that
attempts to recover the pseudo-elastic strain induced in the wire
58. This restoring force opposes the elastic force produced by the
elastic members and thus, reduces the radial force, which presses
the brake shoes 54 against the inner surface of the housing 2. Thus
by activating the shape memory element 58, a compressive force is
applied to the brake shoes 54. This compressive force reduces or
eliminates the frictional contact between the brake shoes 54 and
the inner surface of the housing 2, thereby permitting motion of
the piston 3 and hence of the suspended member 60.
[0094] The design of the piston head 14 and the material, geometry,
number and electrical/mechanical connectivity of the shape memory
alloy wires 58 can be selected such that the frictional resistance
can be varied over a wide range e.g., this system can act as an
on--off brake, or it can provide a continuously variable frictional
resistance to the motion of the piston rod 12 and hence to the
suspended member 60. The shape memory alloy wires can be activated
in response to a number of different inputs e.g. the user can
explicitly select the braking force level, or the activation can be
induced by a change in ambient temperature. Other means of
actuation, e.g., electroactive polymers, piezoelectric materials,
or the like may be used instead of the shape memory alloy elements
58.
[0095] In another exemplary embodiment, the strut assemblies
depicted in the FIGS. 11 and 12 can be used to set a finite number
of stops for the piston 3 and the suspended member 60 as displayed
in the FIGS. 13 and 14. As depicted in the FIG. 13, two locking
rings 62 are used to create the desired intermediate locking
positions for the strut assembly 10. While locking rings 62 are
used in the FIG. 13 to function as locking devices 11 for the strut
assembly 10, it is envisioned that alternate devices can be
utilized as well. Further, while the FIG. 13 depicts two locking
rings, additional locking rings can be added to the housing to
create additional positions for locking the strut assembly 10.
[0096] As depicted in the FIG. 13, the piston head 14 comprises a
central portion 52 that comprises one or more brake shoes 54
connected by the elastic members 56 to the piston rod 12. As noted
above, the elastic members are of a size effective to permit the
brake shoes to exert a radial pressure on the inner surface of the
housing 2, when the piston head 14 is assembled inside the housing
2. A shape memory alloy element (e.g. one or more wires) is
disposed between each brake shoe 54 and the piston rod 12 and is in
operative communication with the brake shoe 54 and the piston rod
12. The shape memory elements can be activated to counteract the
elastic force exerted by the elastic members 56 thereby causing a
radial retraction of the brake shoes 54. Each brake shoe 54
comprises a circumferential groove 64 on the surface that contacts
the inner surface of the housing 2. The circumferential groove 64
is of a size effective to that can accommodate the locking ring 62.
When the brake shoes 54 are retracted radially inwards as a result
of the activation of the shape memory alloy elements, the groove in
the brake shoes 54 is disengaged from the locking ring 62. This
disengagement permits motion of the piston 3 and hence of the
suspended member 60.
[0097] In one embodiment, pertaining to the operation of the strut
assembly 10, the suspended member 60 can be displaced towards or
away from the supporting body 50 till the circumferential groove in
the brake shoe 54 encounters a locking ring 62. When the
circumferential groove mechanically engages the locking ring 62,
the strut assembly 10 is locked. Alternatively, the piston head 14
can be permitted to by pass a particular locking ring 62 by
activating the shape memory alloy elements 58. The piston head 14
can then be permitted to engage with another locking ring 62.
[0098] With respect now to the exemplary embodiment depicted in the
FIG. 13, a first locking ring 62 mechanically engages the
circumferential grove on the brake shoe 54 thereby locking the
strut assembly 10. In this locked position, the shape memory alloy
wires 58 are inactive and the brake shoes 54 are pressed against
the locking rings 62 due to the elastic force exerted by the
elastic members 56 which displaces the brake shoes 54 in a radially
outward direction. The suspended member 60 is thus mechanically
locked in position as a result of the mechanical engagement of the
groove with the locking ring 62, which can resist attempts to move
the suspended member 60 in either direction.
[0099] If the suspended member 60 is to be released from this
position, the shape memory alloy elements are activated by heating
(e.g., by passing and electrical current through it). The heating
of the shape memory elements promotes a radial compressive force on
the elastic member 56, thereby disengaging the groove in the brake
shoe 54 from the locking ring 62 and permitting relative motion
between the piston head 14 and the housing 2. The heating of the
shape memory alloy elements 58 is discontinued when the locking
ring 62 no longer engages the circumferential groove in the brake
shoe 54.
[0100] As the shape memory alloy wires cool down, their elastic
modulus decreases. The elastic forces in the elastic members can
now overcome the forces exerted by the shape memory alloy elements
58 and the brake shoes 54 once again move radially outward exerting
a radial pressure against the inner surface of the housing 2. The
piston 3 and hence the suspended member 60 can now be displaced
freely until the piston head 14 encounters a second locking ring.
Thus, if the suspended member 60 is to be locked in another
intermediate position, the suspended member 60 is moved until the
brake shoe 54 engages the next locking ring 62. On the other hand,
if the suspended member 60 is to be moved past the second locking
ring, the shape memory alloy elements are re-activated until the
second locking ring is bypassed. Alternatively, activation of the
shape memory alloy elements can be maintained as long as the
suspended member 60 is to be displaced. The activation can be
switched off when the suspended member 60 is to be locked in
another desired position.
[0101] As noted above, additional locking rings or grooves in brake
shoes can be added to increase the number of intermediate locking
positions available to the suspended member 60. This concept can
also be combined with the embodiments detailed in the FIGS. 9 and
10, where a guide with a corrugated surface is utilized.
[0102] In yet another embodiment depicted in the FIG. 15, the
resistance to fluid flow across the piston head 14 can be used to
provide resistance to the displacement of the suspended member 60.
The displacement of the fluid across the piston head 14 gives rise
to a hydrodynamic resistance that can be used to control the
relative motion of the piston 3 with respect to the housing 2. This
resistance is dependent on the effective viscosity of the fluid
among other things. Therefore, varying the effective viscosity of
the fluid 4 by an external stimulus enables control over the motion
of the suspended body 60. In one embodiment, the fluid 4 can be an
electrorheological fluid or a magnetorheological fluid.
[0103] The term magnetorheological fluid encompasses
magnetorheological fluids, ferrofluids, colloidal magnetic fluids,
and the like. Magnetorheological (MR) fluids and elastomers are
known as "smart" materials whose Theological properties can rapidly
change upon application of a magnetic field. MR fluids are
suspensions of micrometer-sized, magnetically polarizable particles
in oil or other liquids. When a MR fluid is exposed to a magnetic
field, the normally randomly oriented particles form chains of
particles in the direction of the magnetic field lines. The
particle chains increase the apparent viscosity (flow resistance)
of the fluid. The stiffness of the structure is accomplished by
changing the shear and compression/tension modulii of the MR fluid
by varying the strength of the applied magnetic field. The MR
fluids typically develop structure when exposed to a magnetic field
in as little as a few milliseconds. Discontinuing the exposure of
the MR fluid to the magnetic field reverses the process and the
fluid returns to a lower viscosity state.
[0104] Suitable magnetorheological fluids include 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 Fe2O3 and
Fe3O4; iron nitride; iron carbide; carbonyl iron; nickel and alloys
of nickel; cobalt and alloys of cobalt; chromium dioxide; stainless
steel; silicon steel; or the like, or a combination comprising at
least one of the foregoing particles. Examples of suitable iron
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.
[0105] 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 1,000 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 micrometer especially preferred. The particles are
preferably present in an amount between about 5.0 and about 60
percent by volume of the total composition.
[0106] 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.
[0107] 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.
[0108] Aqueous carrier fluids may also be used, especially those
comprising hydrophilic mineral clays such as bentonite and
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.
[0109] 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. 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.
[0110] The activation device can be configured to deliver an
activation signal to the active elements, wherein the activation
signal comprises a magnetic signal. The magnetic signal is a
magnetic field. The magnetic field may be generated by a permanent
magnet, an electromagnet, or combinations comprising at least one
of the foregoing. The strength and direction of the magnetic field
is dependent on the particular material employed for fabricating
the hook element, as well as amounts and location of the material
on the hook. Suitable magnetic flux densities for the active
elements comprised of MR fluids or elastomers range from greater
than about 0 to about 1 Tesla. Suitable magnetic flux densities for
the hook elements comprised of magnetic materials range from
greater than about 0 to about 1 Tesla.
[0111] Electrorheological fluids are most commonly colloidal
suspensions of fine particles in non-conducting fluids. Under an
applied electric field, electrorheological fluids form fibrous
structures that are parallel to the applied field and can increase
in viscosity by a factor of up to 10.sup.5. The change in viscosity
is generally proportional to the applied potential. ER fluids are
made by suspending particles in a liquid whose dielectric constant
or conductivity is mismatched in order to create-dipole particle
interactions in the presence of an alternating current (ac) or
direct current (dc) electric field.
[0112] With reference now to the FIG. 15, optional circular
permanent magnets 66 are disposed around the flow channels 8 in the
piston head 14. The optional circular permanent magnets 66 produce
a magnetic field B2 that influences the viscosity of the fluid 4 in
the channels 8. Circumferentially disposed around the permanent
magnets are electromagnets 68 that are used to apply a second
magnetic field B1 that opposes B2. In one embodiment, the permanent
magnet 66 and the electromagnet 68 are concentric. In another
embodiment, the permanent magnet 66 and the electromagnet 68 are
coaxial but not concentric, i.e., they share the same axis, but are
not concentric. The strength of the magnetic field B2 is fixed,
while that of B1 can be varied by controlling the electric current
flowing through the electromagnets 68. The effective magnetic field
acting on the fluid 4 as it traverses the flow channels 8 is
therefore the difference in strengths between B1 and B2 and this
difference can be controlled by varying the current through the
electromagnet 68. The difference in strength between B1 and B2
determines the viscosity of the fluid in the flow channels. Thus
the hydrodynamic resistance to the strut motion can be adjusted on
demand by varying the current flowing through the
electromagnet.
[0113] In one embodiment, by excluding the permanent magnet and
using only an electromagnet, the hydrodynamic resistance can only
be increased by controlling the electric current through the
electromagnet 68. In another embodiment, the use of two opposing
electromagnets permits a two-way control over the hydrodynamic
resistance, i.e., it can be increase or decreased. In yet another
embodiment, by employing only a permanent magnet adjacent to the
channel, the magnetic circuit that determines the field in the flow
channels can be changed (e.g., by activating an SMA actuator)
thereby controlling the effective field strength in the flow
channel, and consequently the resistance to relative motion between
the cylinder and the piston.
[0114] In yet another exemplary embodiment, a pivot detent locking
device that employs rotary motion to facilitate the locking of a
suspended body 60 is depicted in FIGS. 16 through 19.
[0115] The locking device 11 comprises a multi-bar linkage that
comprises a long arm 72 and a short arm 70 rotatably disposed about
a pivot point, as depicted in FIGS. 16 and 17. FIG. 16 provides a
front view of the locking device 11, while FIG. 17 provides a rear
view of the device 11. The short arm 70 of the locking device 11 is
constrained on the pivot pin 76 between a ball disk 78 and the long
arm 72. Affixed to the opposing surface of the long arm 72 is the
cylindrical cylindrical housing 74, which comprises an actuator 92.
The actuator 92 is in operative communication with a piston 94.
[0116] FIG. 18 is a section view of the pivot detent-locking device
11 in its normally locked position. Locking is accomplished by
using a series balls 82 trapped in the ball disk 78 and engaged in
detents 84 disposed in the short arm 70. The ball disk78 is
attached to the pivot pin 76, which is connected to a piston 94,
having a seal 96 and contained the cylindrical housing 74. The
piston 94 can move axially along the centerline of the cylindrical
housing 74. A spring 88 constrained between the piston 94 and the
long arm provides the reaction/biasing force necessary for the
pivot pin to move the balls 82 trapped in the ball disk 78 to
engage the detents 84 in the short arm 70, thus locking the short
arm 70 relative to the long arm 72 and prohibiting rotation.
[0117] Also contained in the cylindrical housing 74 is an actuator
92, which acts on the opposite side of the piston 94 from the
spring 88. On the opposing side of the actuator 92 is a heater
constrained by a backing plate and located in the end of the
cylindrical housing 74. The heater is also connected to a power
source (not shown).
[0118] Upon receiving a signal from the control circuit (not
shown), the power source 80 provides energy to the actuator 92, in
this case a shape memory polymer or a shape memory alloy, causing
the actuator 92 to expand. FIG. 19 (section view) shows the
detent-locking device 11 in its unlocked position. As the actuator
92 expands, the piston 94 moves the pivot pin 76 axially forcing
the ball disk 78 to move. As the ball disk 78 moves, the balls 82
trapped in the ball disk are free to move axially out of the
detents 84 in the short arm 70. As the clearance between the balls
82 and the detents 84 increases the short arm 70 is free to rotate
about the pivot pin 76, thus allowing the short arms 70 to rotate
freely relative to the long arms 72.
[0119] Upon receiving a signal from the control circuit, the power
source 80 will remove the energy provided to the actuator 92. The
actuator 92 will then start to cool and biased by the spring 88
will contract to its original shape/size. As the spring biasing
force moves the piston 94, the pivot pin 76 will move the balls
disk 78 and the balls 82 contained therein to engage the detents 84
and lock the short arm 70 relative to the long arm 72 thereby
prohibiting rotation.
[0120] An alternate embodiment is the use of opposing serrated
surfaces acting against each other. For example if the detents on
the short arm were replaced by a series of radially spaced
serrations about the pivot axis and the ball disk and balls were
replaced with a disk containing radially spaced serrations, the
serrations on the disk would engage the serration on the short arm,
locking the short arm relative to the long arm and preventing
rotation. The device would operate (lock and unlock) as described
above.
[0121] A benefit of the above device is the ability to hold the
pivot in position without an external energy (power source) being
applied. The device remains fixed until the energy is placed into
the actuator to free the pivot and allow rotation. An additional
benefit is the ability of the device to slip or clutch when the
device is placed under extreme loading, limiting damage to a
closure, hinge or cargo. The locking device 11 depicted in the
FIGS. 16 through 19 can be used in used on simple pivoting hinges
or similar devices.
[0122] The locking devices 11 described above can be advantageously
used for a large number of cycles under varying ambient conditions.
The locking devices employ active materials that permit an owner to
adjust the attributes of the strut to suit the local climatic
conditions and/or his/her anthropometrics. They advantageously
permit a dealer to adjust these attributes at the point of sale to
customize an otherwise mass produced vehicle for a specific buyer
or they permit a service center to adjust the strut attributes to
counteract the effects of wear. They can be manually adjusted and
controlled or computer adjusted and controlled. They can utilize
feed back loops when desired. These adjustments could be made
either via hardware tuning or via software changes.
[0123] 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.
* * * * *