U.S. patent application number 15/897334 was filed with the patent office on 2018-11-15 for buckling loop rotary motor.
The applicant listed for this patent is Baoxiang Shan. Invention is credited to Baoxiang Shan.
Application Number | 20180331588 15/897334 |
Document ID | / |
Family ID | 64096233 |
Filed Date | 2018-11-15 |
United States Patent
Application |
20180331588 |
Kind Code |
A1 |
Shan; Baoxiang |
November 15, 2018 |
Buckling Loop Rotary Motor
Abstract
A buckling loop rotary motor is disclosed that has a stator, an
activatable buckling loop and a rotor. The buckling loop is made of
a springy, base band and an activatable active band. An applied
force actuates a portion of loop, causing a localized change of
curvature. When propagated along the buckling loop, the changed
curvature causes rotation of the rotor. In a bi-metallic
embodiment, the thermally actuated active band expands by at least
1% more than the base band, effect a localized change of curvature
that drives the rotor. Thermal activation is by heating or cooling,
or a combination thereof. In an electroactive polymer (EAP), the
active acrylic or silicone EAP is actuated by an electrostatic
charge. The change in thickness, and therefore, length, of the
active EAP relative to the inactive, base material causes a local
change of curvature of the loop that drives rotation of the
rotor.
Inventors: |
Shan; Baoxiang; (Hoboken,
NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Shan; Baoxiang |
Hoboken |
NJ |
US |
|
|
Family ID: |
64096233 |
Appl. No.: |
15/897334 |
Filed: |
February 15, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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62506199 |
May 15, 2017 |
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62506828 |
May 16, 2017 |
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62507300 |
May 17, 2017 |
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62509102 |
May 20, 2017 |
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62597147 |
Dec 11, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02K 9/00 20130101; H02K
1/12 20130101; H01L 41/193 20130101; H02K 11/0094 20130101; H01L
41/12 20130101; H02N 10/00 20130101; H01L 41/047 20130101; H02N
2/10 20130101; H02K 1/22 20130101 |
International
Class: |
H02K 1/22 20060101
H02K001/22; H02K 1/12 20060101 H02K001/12; H02K 9/00 20060101
H02K009/00; H02K 11/00 20060101 H02K011/00; H01L 41/193 20060101
H01L041/193; H01L 41/047 20060101 H01L041/047 |
Claims
1. A buckling loop rotary motor, comprising: a rigid stator,
comprising a cylindrical, inner surface having a circular
cross-section; a buckling loop constrained within said cylindrical,
inner surface to form one or more buckles; wherein, actuation, by a
mechanical stress induced in said buckling loop, causes a change in
curvature of one or more of said buckles that impels said buckling
loop to rotate with respect to said rigid stator about an axis of
rotation located coaxially with a central axis of said cylindrical,
inner surface.
2. The rotary motor of claim 1, wherein, said buckling loop
comprises a ribbon having a width greater than its thickness, said
width being a measurement of said buckling loop in a direction
parallel to said axis of rotation.
3. The rotary motor of claim 2, wherein, said buckling loop
comprises a two-way shape memory active material, and the motor
further comprises one or more heating elements.
4. (canceled)
5. The rotary motor of claim 2 wherein said buckling loop comprises
a base band and an active band, and wherein said active band is
comprised of a first, active material and said base band is
comprised of a second, base material and wherein, in response to an
actuating force, an activated portion of said first, active
material expands in length by at least 0.1% more than said second
material, thereby effecting a change of curvature of said actuated
portion of said buckling loop.
6. The rotary motor of claim of claim 5, wherein, said buckling
loop is a bi-metallic loop and said first, active material has a
coefficient of linear, thermal expansion greater than said second,
base material.
7. The rotary motor of claim of claim 6, wherein, said first,
active material is one of a Titanium alloy, a stainless steel
alloy, a copper alloy or an aluminum alloy, or a combination
thereof.
8. The rotary motor of claim of claim 2, further comprising: a
rotor, sized and shaped to conform, in part, to an inner surface of
said buckling loop; and, one or more heating elements located on
said rotor adjacent to one or more inflection points of one of said
buckles of said buckling loop.
9. The rotary motor of claim 8, wherein, said heating element is a
light emitting diode (LED).
10. The rotary motor of claim 2 further comprising: a rotor, sized
and shaped to conform, in part, to an inner surface of said
buckling loop; and, one or more cooling element located on said
rotor adjacent to one or more inflection points of one of said
buckles of said buckling loop.
11. The rotary motor of claim 10, wherein, said cooling element is
a Pelitier cooling device.
12. The rotary motor of claim 2, further comprising: a rotor, sized
and shaped to conform, in part, to an inner surface of said
buckling loop; and, at least one pair of a heating and a cooling
element disposed on said rotor adjacent to a pair of inflection
points of one of said buckles.
13. The rotary motor of claim of claim 5, wherein said first,
active material is an electroactive polymer (EAP) and said
actuating force is supplied by an electrostatic charge.
14. The rotary motor of claim 13, wherein, said electrostatic
charge is supplied to one or more regions of said buckling loop via
one or more electrical contacts.
15. The rotary motor of claim 13, wherein, said electroactive
polymer has a dielectric constant of at least 2 at room temperature
and 1 KHz.
16. The rotary motor of claim 15, wherein, said electroactive
polymer is one of an acrylic and a silicone, or a combination
thereof.
17. The rotary motor of claim 5, wherein, said first, active
material has an energy density greater than or equal to 0.02
J/cm.sup.3.
18. The rotary motor of claim 17, wherein, said first, active
material is one of an acrylic, a silicone, a piezoelectric, a shape
memory alloy, a metal, and an electrochemo-mechanical conducting
polymer, or some combination thereof.
19. The rotary motor of claim 5, wherein, said second, base
material is a highly elastic material having a yield strain greater
than 0.2%.
20. The rotary motor of claim 19, wherein, said second, base
material is one of a fabric reinforced silicone, a fabric
reinforced polyurethane, a Titanium alloy, a stainless steel alloy,
a copper alloy or an aluminum alloy, or a combination thereof.
21. The rotary motor of claim 5, further comprising: a rotor, sized
and shaped to conform, in part, to an inner surface of said
buckling loop; and, one or more rollers rotatably attached to said
rotor, and situated to contact said buckling loop at an inner
surface of an apex of one or more of said buckles.
22. The rotary motor of claim 21, wherein, said first, active
material comprises an electroactive material, and said rollers
comprise one or more electrical contacts
23. The rotary motor of claim 22, wherein, said buckling loop
further comprises a staggered wiring array formed such that one or
more contact points at an apex of one or more buckles activates
said buckling loop at one or more inflection points of one of said
buckles.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Ser. No. 62/506,199
entitled "Looped Multistable System" filed on May 15, 2017 by
Baoxiang Shan; to U.S. Ser. No. 62/506,828 entitled "Flexible
Actuator and Sensor" filed on May 16, 2017 by Baoxiang Shan; to
U.S. Ser. No. 62/507,300 entitled "Flexible Movement System" filed
on May 17, 2017 by Baoxiang Shan; to U.S. Ser. No. 62/509,102
entitled "Travelling Wave Pumps" filed on Dec. 11, 2017 by Baoxiang
Shan, and to U.S. Ser. No. 62/597,147 entitled "Joined-Band Devices
Configured for Motion" filed on Dec. 11, 2017 by Baoxiang Shan, the
contents of all of which are hereby fully incorporated herein by
reference.
BACKGROUND OF THE INVENTION
(1) Field of the Invention
[0002] The invention relates to a motor for producing rotary motion
using actuation of a flexible band constrained to form a buckled
loop, and more particularly, to a buckling loop rotary motor in
which actuation of the buckled loop may be by a change of curvature
of a portion of the loop through expansion or contraction of a
localized portion of the loop. The loop may have an active and a
base material, and may be bi-metallic, or have active materials
that may be a shape memory alloy (SMA), a bi-morph piezoelectric
polymer (PVDF), an electroactive polymer (EAP), a piezoelectric
material, an electro-restrictive material or a magneto-restrictive
material, or a combination thereof.
(2) Description of the Related Art
[0003] The technical problem of creating rotary motion is inherent
in the technical field of mechanical engineering, as rotary motion
may be used, for instance, to transport objects or to activate
mechanisms, such as, but not limited to, mechanical control
valves.
[0004] Rotary motion that may be driven directly, or indirectly, by
means of an electric current, or voltage, is particularly desirable
for actuating mechanisms, as this facilitates the integration of
the mechanical device with electronic control systems.
[0005] A problem with existing electric motors that often arises
when they are used to actuate mechanisms such as, but not limited
to, control valves, is that existing electronic motors typically
operate at rotational speeds that require reduction gearing to
match their speed of rotation to that required to most effectively
manipulate the valve. Gear mechanisms not only add to the cost and
complexity of such systems, but also tend to be the part of the
device most prone to failure in harsh or adverse environments,
including, but not limited to, extremes of acceleration.
[0006] It is, therefore, highly desirable to have a gearless,
electrically-driven, rotary motor capable of producing the speeds
and torques suitable for actuating mechanical mechanisms such as,
but not limited to, control valves. It is also desirable that such
gearless motors are compact, and simple to construct.
[0007] The relevant existing art includes:
[0008] A paper published in The Proceedings of the Royal Society A:
Mathematical, Physical and Engineering Sciences, on Aug. 16, 2017
by Hamouche et al. entitled "Multi-parameter actuation of a
neutrally stable shell: a flexible gear-less motor" that describes
the design and experimental testing of a morphing structure
consisting of a neutrally stable thin cylindrical shell driven by a
multi-parameter piezoelectric actuation. The shell is obtained by
plastically deforming an initially flat copper disc, so as to
induce large isotropic and almost uniform inelastic curvatures.
Following the plastic deformation, in a perfectly isotropic system,
the shell is theoretically neutrally stable, having a continuous
set of stable cylindrical shapes corresponding to the rotation of
the axis of maximal curvature. Small imperfections render the
actual structure bistable, giving preferred orientations. A
three-parameter piezoelectric actuation, exerted through
micro-fiber-composite actuators, allows the addition of a small
perturbation to the plastic inelastic curvature and to control the
direction of maximal curvature. The authors report on the
fabrication and experimental testing of a prototype and demonstrate
the effectiveness of the piezoelectric actuators in controlling its
shape. The resulting motion is an apparent rotation of the shell,
controlled by the voltages as in a `gear-less motor`, which is, in
reality, a precession of the axis of principal curvature.
[0009] Various implementations are known in the art, but fail to
address all of the problems solved by the invention described
herein. Various embodiments of this invention are illustrated in
the accompanying drawings and will be described in more detail
herein below.
BRIEF SUMMARY OF THE INVENTION
[0010] An inventive buckling loop rotary motor is disclosed.
[0011] In a preferred embodiment, buckling loop rotary motor may
include a rigid stator, an activatable buckling loop and a rotor.
The stator may, for instance, have a cylindrical, inner surface
with a circular cross-section. The buckling loop may, for instance,
be made of a combination of a suitably springy, base band and an
active band. This buckling loop may be constrained within the
cylindrical, inner surface of the rigid stator to form one or more
buckles. The rotor may be sized and shaped to conform, in part, to
an inner surface of the buckling loop.
[0012] The rotary motor may be driven by a stimulus, or force, that
may actuate a portion of the activatable, buckling loop. This
actuation may result in a localized change of curvature of the
buckling loop. This localized change of curvature may propagate
along the buckling loop, causing rotation of the rotor with respect
to the stator. The direction of rotation may be selected by which
portions of the buckling loop are activated, and the axis of
rotation is preferably located coaxially with the central axis of
cylindrical, inner surface of the stator.
[0013] The buckling loop is preferably a continuous ribbon of a
uniform thickness and a uniform width and having no end point, with
the width being greater than the thickness. The material
composition of the buckling loop may, for instance, depend on the
method of actuation.
[0014] In a preferred embodiment, the buckling loop may have a base
band and an active band, with the active band being made of a
first, active material and the base band made of a second, base
material. The materials may be selected such that, in response to
an actuating force, or stimulus, a portion of the first, active
material expands in length more than the second, base band
material, preferably by at least 0.1%, but in more preferred
embodiments by at least 1%. Because the bands are joined together,
the resulting stress may effect a localized change of curvature of
the activated portion of the buckling loop. The energy of this
buckling may then be transformed into rotation of the rotor as the
buckled loop changes shape and attempts to minimize its overall
stress.
[0015] In one preferred embodiment of the present invention, the
buckling loop may be a bi-metallic loop, with the active band
material having a higher coefficient of linear thermal expansion
than the base band material. Such a bi-metallic buckling loop may
be actuated by a localized, electrically-controlled, heating
element such as, but not limited to, an electrical resistor, an
electrical diode, or a light emitting diode (LED), or some
combination thereof.
[0016] Suitable materials for the active band of a bi-metallic
buckling loop include, but are not limited to, Titanium alloys,
stainless steel alloys, copper alloys, aluminum alloy, and
combinations thereof.
[0017] In such a bi-metallic, buckling loop rotary motor, it may be
most energy efficient to activate a buckle at an inflection point
of the buckle. In such a device, the heating elements may,
therefore, be fixed on the rotor adjacent to inflection points of
one or more of the buckles formed in the buckling loop.
[0018] In a further preferred bi-metallic, embodiment of the
invention, the actuation of a portion of the buckling loop may be
provided by a cooling element such as, but not limited to, a
Peltier cooling device.
[0019] As cooling and heating a buckling loop at the same
inflection point may impel the rotor in opposite directions, a
heating and a cooling element may be used in conjunction, with, for
instance, heating being applied to an inflection point on one side
of a buckle while cooling is applied at the corresponding
inflection point on the opposite side of the same buckle. Peltier
devices may be driven to provide either cooling or heating, so
having Peltier devices as the actuating elements may allow for
rotor motor that may be driven in opposite rotational directions by
changing whether they are driven to heat or to cool.
[0020] In a further preferred embodiment of the invention, the
buckling loop may be an electroactive polymer (EAP) activated
buckling loop rotary motor. In such a motor, the active material
may an EAP such as, but not limited to, an acrylic or a silicone
EAP, that act as deformable capacitors, changing their thickness in
response to an applied electric field. Such materials typically
have elastic energy densities well above the 0.02 J/cm.sup.3 to
0.13 J/cm.sup.3 range of more conventional piezoelectric ceramic
materials. An EAP buckling loop, may, for instance, have an EAP
active layer and a suitably springy metal base layer, including
metals typically used to make springs such as, but not limited to,
Titanium alloys, stainless steel alloys, copper alloys, aluminum
alloy, and combinations thereof. A portion of an EAP buckling loop
may, for instance, be actuated by an electrostatic voltage supplied
by suitably located electrical contacts. The activated localized
portion of the EAP buckling loop, in which the activated EAP
material changes shape while the underlying base loop material does
not, may result in localized stresses that may cause a local change
of curvature of the loop that, when propagated along the loop, may
result in rotational motion of the rotor.
[0021] In an alternate embodiment, the rotor may have rollers that
may contact the buckling loop at the apex point of a buckle,
helping maintain the shape of the buckle. Such rollers may also
serve as electrical contacts to activate electroactive materials
such as, but not limited to, electroactive polymers. Activation of
the electroactive material at an inflection point of a buckle by
contact point at the apex of the buckle may, for instance, be
accomplished using staggered wiring array on the buckling loop, as
described in detail below.
[0022] Other materials that may be used as active materials in the
active loop of a buckling loop rotary motor include, but are not
limited to, electorestrictive materials, magnetorestrictive
materials, piezoelectric materials, and shape memory alloys, or
some combination thereof.
[0023] Therefore, the present invention succeeds in conferring the
following, and others not mentioned, desirable and useful benefits
and objectives.
[0024] It is an object of the present invention to provide a
compact, lightweight rotary motor.
[0025] It is a further objective of the present invention to
provide a gearless, electrically controlled rotary motor suitable
for actuating mechanical mechanisms.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0026] FIG. 1A shows a schematic, cross-sectional side view of a
single-buckle, buckling loop constrained within a rigid cylinder,
and a close-up view of an activatable region of the loop prior to
activation.
[0027] FIG. 1B shows a schematic, cross-sectional side view of a
single-buckle, buckling loop constrained within a rigid cylinder,
and a close-up view of an activatable region of the loop after
activation.
[0028] FIG. 2 shows a schematic, cross-sectional side view of a
single-buckle, buckling loop rotary motor of one embodiment of the
present invention.
[0029] FIG. 3 shows a schematic, cross-sectional side view of a
single-buckle, buckling loop rotary motor of a further embodiment
of the present invention.
[0030] FIG. 4 shows an isometric, cut-away view of a single-buckle
buckling loop rotary motor of one embodiment of the present
invention.
[0031] FIG. 5 shows a schematic, cross-sectional, side view of a
multi-buckle, buckling loop rotary motor of one embodiment of the
present invention.
[0032] FIG. 6 shows a schematic, cross-sectional, side view of a
multi-buckle, roller stabilized, buckling loop rotary motor of one
embodiment of the present invention.
[0033] FIG. 7 shows a schematic, cross-sectional, side view of a
multi-buckle, buckling loop rotary motor of another embodiment of
the present invention.
[0034] FIG. 8 shows a schematic, cross-sectional, side view of a
multi-buckle, roller stabilized, buckling loop rotary motor of
further embodiment of the present invention.
[0035] FIG. 9 shows a schematic, top view of a section of a
staggered wiring array of one embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0036] The preferred embodiments of the present invention will now
be described in more detail with reference to the drawings in which
identical elements in the various figures are, as far as possible,
identified with the same reference numerals. These embodiments are
provided by way of explanation of the present invention, which is
not, however, intended to be limited thereto. Those of ordinary
skill in the art may appreciate upon reading the present
specification and viewing the present drawings that various
modifications and variations may be made thereto without departing
from the spirit of the invention.
[0037] FIG. 1A shows a schematic, cross-sectional side view of a
single-buckle, buckling loop 120 constrained within a rigid
cylinder 111, and a close-up view 128 of an activatable region of
the loop prior to activation.
[0038] As shown, the buckling loop 120 may have two regions of
buckle/restraint contact 161 and a buckle apex 162, at each of
which the loop may have a positive or negative curvature greater in
magnitude than the curvature of the loop where it is merely
constrained by the rigid cylinder 111. The single buckle buckling
loop 120 may also have two inflection points 160 at which the
curvature of the loop is zero.
[0039] A portion 127 of the buckling loop 120 may be activated by
an actuating force 126. The nature of the actuating force 126 may
depend on the composition of the buckling loop 120. This situation
may be seen in more detail in a close up of activated portion prior
to activation 128. In this view, the portion to be activated is at
an inflection point of a buckle, and the loop may be made up of an
active band 121 made, at least in part, of a first, active material
122 and a base band 123 made, at least in part, of a second, base
material 124. If, as shown in FIG. 1A, the actuating force 126 is
applied at a point of inflection, the activated portion 127 of the
loop will have zero curvature prior to application of the actuating
force 126.
[0040] FIG. 1B shows a schematic, cross-sectional side view of the
single-buckle, buckling loop 120 constrained within the rigid
cylinder 111 after application of the actuating force, and a
close-up view 129 of the activated region of the loop after
activation.
[0041] As seen in FIG. 1B, the activated portion of the loop now
has a curvature as a result of the active band 121 having expanded
laterally more than the underlying base band 123 to which it may be
attached. The more curved, activated portion of the loop may then
effectively migrate to a region of the loop where the curvature
imparted to the activated portion more closely matches the
curvature of the buckle, such as the buckle loop/restraining rigid
cylinder contact region 161. In doing so, the loop may be moved
rotationally.
[0042] The examples below show how the nature of the actuating
force may depend on the material composition of the active band and
the base band. The direction of rotation of the buckled loop may
also be shown to depend on the material choice and the nature of
the actuating force.
[0043] FIG. 2 shows a schematic, cross-sectional side view of a
single-buckle, buckling loop rotary motor of one embodiment of the
present invention.
[0044] The single-buckle, buckling loop rotary motor 106 shown in
FIG. 1 may include a rigid stator 110, a rotor 135 and a buckling
loop 120.
[0045] In a preferred embodiment, the rigid stator 110 may have a
cylindrical, inner surface 115 having a circular cross-section with
a central axis 146.
[0046] The buckling loop 120 may be constrained within the
cylindrical, inner surface 115 of the rigid stator 110 such that
the buckle 125 may be formed in the loop. The buckling loop 120 is
preferably constructed as continuous ribbon of a uniform thickness,
having a uniform width and having no end point. The width of the
buckling loop 120 may be greater than its thickness, typically by a
factor of at least two, and more preferably by at least a factor of
five. Part of the reason for having a greater width to thickness
ratio may be to minimize the out-of-plane bending, or buckling, of
the loop.
[0047] The rotor 135 may be shaped and sized to conform, in part,
to the inner surface of the buckling loop 120 when constrained, and
buckled, within the cylindrical, inner surface 115 of the rigid
stator 110.
[0048] In a bi-metallic embodiment of the single-buckle, buckling
loop rotary motor 106, the buckling loop 120 may be made of an
active band that may have a first, active material that may have a
higher coefficient of thermal expansion than that of the base
material of which the base band may be made. In such a bi-metallic
embodiment, there may be actuator elements 140 that may be either
heating or cooling elements.
[0049] It is preferable in such a bi-metallic embodiment that, in
response to an actuating force, an activated portion of the first,
active material expands in length by at least 1% more than the
second material, thereby effecting a local change of curvature of
the actuated portion of the buckling loop.
[0050] The active band may, for instance, be make of materials
having a coefficient of linear, thermal expansion greater than
5.times.10.sup.-6 m/m/.degree. C. such as, but not limited to,
fabric reinforced silicone, fabric reinforced polyurethane,
Titanium alloys, stainless steel alloys, copper alloys and aluminum
alloys, or combinations thereof. Particularly suitable materials
may include Titanium alloys such as, but not limited to, so called
Beta titanium alloys, i.e., titanium alloyed in varying amounts
with one or more of molybdenum, vanadium, niobium, tantalum,
zirconium, manganese, iron, chromium, cobalt, nickel, and copper.
This type of alloy may have a strength/modulus of elasticity ratios
almost twice that of 18-8 austenitic stainless steel, allowing for
larger elastic deflections in springs, and a reduced force per unit
displacement. Suitable alloys may include, but are not limited to,
"BETA III" (Ti-11.5 Mo-6.5 Zr-4.6 Sn), Transage 129
(Ti-2Al-11.5V-25n-11.3Zr) or Ti-6Al-4V, or some combination
thereof.
[0051] The base material in such a bi-metallic rotary motor may be
any material with a coefficient of linear, thermal expansion that
is significantly less than that of the active material. Suitable
base materials for a bi-metallic buckling loop include nickel-iron
alloys such as, but are not limited to, Invar, NILO alloy 42,
Kovar, and Dilver P, or some combination thereof.
[0052] When the buckling loop 120 is bi-metallic, with the active
and base materials having a difference in linear thermal
coefficients of expansion, the actuator elements may be heating
elements. An actuator element 140 that is a heating element may,
for instance, be attached to the rotor 135 and located such that
the heat it supplies stresses the buckle 125 of the buckling loop
120, creating a localized region of curvature, that, as it is
propagated, impels the rotor 135 is impelled to rotate in a first
direction of rotation 150 about its axis of rotation 145 located
coaxially with a central axis 146 of said cylindrical, inner
surface 115.
[0053] Suitable electrically controlled heating actuator elements
140 include, but are not limited, to, elements made of materials
having high electrical resistance and a high melting point, such
as, but not limited to, tungsten, nichrome, Kanthal.TM. FeCrAl
alloys, cupronickel, molybdenum disilicide, or devices that emit
heat such as, but not limited to, resistors, diodes and
light-emitting diodes (LEDs), or some combination thereof.
[0054] For optimal use of the heat generated by such heating
actuator elements 140, they are preferably placed at, or near, an
inflection point 160 of a buckle 125, as that is where the change
in curvature they effect may have greatest effect on the rotational
torque of the motor.
[0055] In a further embodiment of the invention, in a
single-buckle, buckling loop rotary motor 106 with a bi-metallic
buckling loop 120 having a difference of coefficient of thermal
expansions of active and base materials, the actuator elements 140
may be cooling elements. Such cooling elements may, for instance,
be a suitable thermoelectric cooling elements such as, but not
limited to, well-known Peltier cooling semiconductor devices.
[0056] As cooling at an inflection point of a buckle 125 may impel
a single-buckle, bi-metallic, buckling loop rotary motor 106 to
rotate in an opposite direction to that it would if that inflection
point had been heated, a heating element and a cooling element may
be used with one placed at each of the corresponding inflection
points of the same buckle. The combination of the heating and the
cooling elements on a single bi-metallic buckle may increase the
torque that may be applied by the motor.
[0057] Furthermore, as a Peltier device may heat or cool, depending
on the direction of the flow, if the actuator elements 140 are
Peltier devices, they may be used to drive a motor in a first
direction of rotation, or in an opposite direction of rotation,
depending on which direction the current through them flows. Having
actuator elements 140 that are Peltier activated devices may,
therefore, allow for gearless, reversible single-buckle,
bi-metallic buckling loop rotary motors.
[0058] FIG. 3 shows a schematic, cross-sectional side view of a
single-buckle, buckling loop rotary motor of a further embodiment
of the present invention.
[0059] The single-buckle, buckling loop rotary motor 106 shown in
FIG. 3 may include a rigid stator 110 with a cylindrical, inner
surface 115 having a circular cross-section in which a buckling
loop 120 may be constrained to form a buckles 125, and a rotor 135,
shaped and sized to fit, in part the inner contour of the
constrained buckling loop. However, in the embodiment depicted in
FIG. 3, the buckling loop 120 may have a first, active material
that is an electroactive polymer (EAP) and in which the actuating
force is supplied by an electrostatic charge. The electrostatic
charge may, for instance, be supplied by one or more electrical
contacts 155.
[0060] The electroactive polymer (EAP) preferably has a dielectric
constant of at least 2, measured at room temperature, i.e., at 293
K (20.degree. C. or 68.degree. F.), and 1 KHz. Note: for scientific
calculations using the absolute temperature scale, room temperature
may sometimes be taken as 300 K to simplify the calculation. The
first, active material may also/or instead, be selected to have an
energy density greater than or equal to 0.02 J/cm.sup.3, and more
preferably to have an energy density greater than or equal to 0.4
J/cm.sup.3.
[0061] Particularly suitable electroactive polymers for use in
rotary motors include, but are not limited to, an acrylic or a
silicone, or a combination thereof. One example of a commercially
available electroactive polymer (EAP) suitable for use in a
buckling loop rotary motor is 3M VHB (Very High Bonding) tape
supplied by the 3M Company, Maplewood, Minn.
[0062] In the EAP buckling loop 120, the base material is
preferably a suitably springy material such as, but not limited to,
a fabric reinforced silicone, a fabric reinforced polyurethane, a
Titanium alloy, a stainless steel alloy, a copper alloy or an
aluminum alloy, or a combination thereof. Further embodiments may
use a base material that may be a highly elastic material. A highly
elastic metal may, for instance, have a yield strain greater than
0.1% and more preferably, a yield strain greater than 1%.
[0063] In a preferred embodiment of such an electroactive,
single-buckle, buckling loop rotary motor 106, there may also be
one or more electrical contacts 155 that may be located on the
rotor 135 such that they may supply the necessary electrical
voltage and current to a region of the buckling loop 120 in a
vicinity of one of the inflection points 160 of the buckles 125.
This voltage may then cause that region of the buckling loop 120 to
develop a stress resulting in imparting a localized curvature to
the loop that may impel the rotor 135 to rotate in a first
direction of rotation 150 about the axis of rotation 145.
[0064] In yet further embodiments of the invention, the active band
of the buckling loop 120 may, for instance, be made wholly, or in
part, of an active material that is an electroactive material such
as, but not limited to, a polyvinylidene fluoride (PVDF) or an
Iodine doped polyacetylene, or a combination thereof.
[0065] In an alternate embodiment of the invention, the active band
of the buckling loop 120 may instead be made wholly, or in part, of
an active material that may be magnetostrictive and may have a
magnetostrictive coefficient greater than 50 microstrains. Regions
of such a buckling loop 120 may be activated by suitable magnetic
sources that may, for instance, be placed on the rotor 135 so as to
activate one of the inflection points 160 of the buckle 125.
[0066] A suitable magnetorestictive material having a
magnetostrictive coefficient greater than 50 microstrains may be a
material such as, but not limited to, Terfenol-D, or Galfenol.
Terfenol-D stands for Ter for terbium, Fe for iron, NOL for Naval
Ordnance Laboratory, and D for dysprosium. It is a material that
may exhibits about 2,000 microstrains in a field of 2 kOe (160
kA/m) at room temperature. A suitable source of magnetic flux may
be a magnet such as, but not limited to, a suitably strong
rare-earth permanent magnet, or an electro-magnet or a combination
thereof.
[0067] The source of magnetic flux may cause a region of the
buckling loop 120 to impart a localized stress to the loop that may
cause localized bending of the loop and so impel the rotor 135 to
rotate in a first direction of rotation 150 about the axis of
rotation 145.
[0068] FIG. 4 shows an isometric, cut-away view of a single-buckle
buckling loop rotary motor of one embodiment of the present
invention.
[0069] The inventive device depicted in FIG. 4 includes a rigid
stator 110 having a cylindrical, inner surface 115 having a
circular cross-section. A buckling loop 120 is shown constrained by
that cylindrical, inner surface 115 to form a buckle 125 that may
be actuated by an actuating force supplied via an actuator element
140 situated on a rotor 135.
[0070] In the embodiment of FIG. 4, the buckling loop 120 may, for
instance, a single layer loop having an active material such as,
but not limited to, a two-way shape memory active material 132.
Such a material effectively remembers two different shapes--one
that it assumes at a higher temperature and one that it assumes at
a lower temperature. Materials that exhibit a two-way shape memory
include, but are not limited to, nickel/titanium alloys, such as
Nitinol.
[0071] The two-way shape memory active material may, for instance,
be actuated by one or more actuator elements 140 that may be
heating or cooling elements, or a combination thereof.
[0072] The two-way shape memory active material may, for instance,
have a greater curvature at a lower temperature and a lesser
curvature at a higher temperature, i.e., it may be bent when cold
and straight when hot. For such a material, a most advantageous
location for an actuator element 140 that is a heating element may
be at, or close to, a region of buckle/restraint contact 161.
[0073] Suitable heating elements include, but are not limited to,
electrically heated elements such as, but not limited to,
resistance wire, resistors, diodes, or light emitting diodes, or
some combination thereof.
[0074] Suitable cooling elements include, but are not limited to,
Peltier devices, which may also, or instead, act as heating
elements.
[0075] FIG. 5 shows a schematic, cross-sectional, side view of a
multi-buckle, buckling loop rotary motor of one embodiment of the
present invention.
[0076] The multi-buckle, buckling loop rotary motor 107 may have a
rigid stator 110 with a cylindrical, inner surface 115 having a
circular cross-section, and a rotor 135. Located between the rotor
135 and the cylindrical, inner surface 115 may be a buckling loop
120 constrained to form a multiplicity of buckles 125. In the
embodiment of FIG. 5, there the buckling loop 120 is shown
constrained to form four buckles 125.
[0077] In a bi-metallic embodiment of the multi-buckle, buckling
loop rotary motor 107, the buckling loop 120 may be made of an
active band that may have an active material that may have a higher
coefficient of thermal expansion than that of the base material of
which the base band may be made. In such a bi-metallic embodiment,
there may be actuator elements 140 that may be either heating or
cooling elements.
[0078] The bi-metallic buckling loop 120 may, for instance, be made
with an active material that may have a coefficient of linear,
thermal expansion greater than 5.times.10.sup.-6 m/m/.degree. C.
Such materials include, but are not limited to, fabric reinforced
silicones, fabric reinforced polyurethanes, Titanium alloys,
stainless steel alloys, copper alloys, aluminum alloy, and
combinations thereof. Particularly suitable active materials may
include Titanium alloys such as, but not limited to, so called Beta
titanium alloys, i.e., titanium alloyed in varying amounts with one
or more of molybdenum, vanadium, niobium, tantalum, zirconium,
manganese, iron, chromium, cobalt, nickel, and copper. This type of
alloy may have a strength/modulus of elasticity ratios almost twice
that of 18-8 austenitic stainless steel, allowing for larger
elastic deflections in springs, and a reduced force per unit
displacement. Suitable alloys may include, but are not limited to,
"BETA III" (Ti-11.5 Mo-6.5 Zr-4.6 Sn), Transage 129
(Ti-2Al-11.5V-2Sn-11.3Zr) or Ti-6Al-4V, or some combination
thereof.
[0079] In such a thermally activated, bi-metallic embodiment of the
buckling loop rotary motor, there may either heating or cooling
elements 140, that may be used to activate localized regions of the
loop. These actuating, heating or cooling, elements are each
preferably located on the rotor 135 opposite one of the two
inflection points 160 of one of the buckles 125.
[0080] A heating element 141 placed on the rotor 135 opposite a
first inflection point of a buckles 125 may, when heated, induce a
stress in the buckling loop 120 that may cause a localized change
of curvature of the loop and so impel the rotor 135 to turn in a
first direction of rotation 150 about an axis of rotation 145 of
the rotor.
[0081] Similarly, cooling element 142 placed on the rotor 135
opposite a second, adjacent inflection point of that same buckles
125, may, when cooled, induce a stress in the buckling loop 120
that may cause a localized change of curvature of the loop and so
impel the rotor 135 to turn in the same, first direction of
rotation 150 about the axis of rotation 145 of the rotor.
[0082] In this way, pairs of heating elements 141 and cooling
elements 142 may be used together to significantly increase the
stresses applied to the buckling loop 120 and therefore increase
the torque of the buckling loop rotary motor.
[0083] If the positions of the heating element 141 and the cooling
elements 142 are switched, the rotor 135 may then be impelled to
turn in an opposite direction to the first direction of rotation
150, thereby facilitating a reversible, but gearless, motor. As
Peltier devices may be either heating or cooling devices, depending
on the direction of the electrical current flowing through them,
switching an actuator element 140 may be accomplished
electronically by switching the direction of current flow through
them.
[0084] FIG. 6 shows a schematic, cross-sectional, side view of a
multi-buckle, roller stabilized, buckling loop rotary motor of one
embodiment of the present invention.
[0085] In the multi-buckle, roller stabilized, buckling loop rotary
motor 108 depicted in FIG. 6, in addition to the rigid stator 110
with a cylindrical, inner surface 115 having a circular
cross-section, the buckling loop 120 constrained within the
cylindrical, inner surface 115, and the rotor 135 contained within
the buckling loop 120, there are one or more rollers 165. The
rollers 165 may be rotatably attached to the rotor 135 and may
serve to assist in constraining the buckling loop 120 to form the
required buckles 125, by, for instance, being situated to contact
the buckling loop at an inner surface of an apex 170 of one or more
of said buckles.
[0086] In a bi-metallic embodiment, the buckling loop 120 may have
an active material having c a material having a coefficient of
linear, thermal expansion greater than the base material, as
described in more detail above regarding other embodiments of
thermally activated, bi-metallic buckling loop rotary motors.
[0087] Similarly, the actuator elements 140 suppling the actuating
force to the thermally activated bi-metallic loop may be either
heating or cooling elements. These are each preferably located on
the rotor 135 opposite one of the two inflection points 160 of one
of the buckles 125, as described in more detail above, regarding
other embodiments of thermally activated buckling loop rotary
motors.
[0088] FIG. 7 shows a schematic, cross-sectional, side view of a
multi-buckle, buckling loop rotary motor of another embodiment of
the present invention, in which a buckling loop 120 is constrained
within the cylindrical, inner surface 115 having a circular
cross-section of a rigid stator 110 and encompasses a rotor
135.
[0089] The multi-buckle, buckling loop rotary motor 107 depicted in
FIG. 7 may have an electroactive buckling loop 120 made of an
active material that is an electroactive polymer (EAP) and in which
the actuating force is supplied by an electrostatic charge. The
electrostatic charge may, for instance, be supplied by one or more
electrical contacts 155 that may be a part of the rotor 135. As
with other electro-active embodiments described above, the actuator
elements 140 are preferable turned on when they are at an
inflection point of a buckle, so that the stress induced in the
buckling loop 120 may be more effective in impelling the rotor 135
to rotate in a first direction of rotation 150 about the axis of
rotation 145 of the rotor.
[0090] The first, active material of such an electroactive buckling
loop may, for instance, be selected to one having an energy density
greater than or equal to 0.02 J/cm.sup.3, and more preferably to
one having an energy density greater than or equal to 0.4
J/cm.sup.3.
[0091] FIG. 8 shows a schematic, cross-sectional, side view of a
multi-buckle, roller stabilized, buckling loop rotary motor of
further embodiment of the present invention.
[0092] In the electro-active embodiment of a multi-buckle, roller
stabilized, buckling loop rotary motor 108 depicted in FIG. 8, the
rollers may now be electrical contact roller 175 and be the means
by which the appropriate electrical current and/or voltages are
supplied to the actuate the appropriate regions of the buckling
loop 120.
[0093] In order for a contact made by the electrical contact roller
175 at an apex 170 of a buckle 125 to actuate an activatable region
143 at an inflection point, a staggered wiring array may need to be
printed, or otherwise associated with the buckling loop 120. One
embodiment of such a staggered wiring array is depicted in FIG.
9.
[0094] FIG. 9 shows a schematic, top view of a section of a
staggered wiring array of one embodiment of the present
invention.
[0095] The staggered wiring array 180 may, for instance, have
actuator elements 140 arranged on one surface of a buckling loop,
and supply electrical contacts 156 arranged on the other surface.
The supply electrical contacts 156 may be joined to actuator
electrical contacts 157 via appropriate electrical contact paths
190, and the actuator electrical contact 157 may extend through the
depth of the buckling loop, so that wiring on one surface of the
loop may then be extended through to contact the actuator elements
140 that may be situated on the other surface of the loop. By
suitable arrangement of the wiring, corresponding 185 supply
contacts and actuator contacts may allow an electrical voltage
applied to the contact at an apex of a buckle to activate an
actuator element 140 located at an inflection point of that
buckle.
[0096] Although this invention has been described with a certain
degree of particularity, it is to be understood that the present
disclosure has been made only by way of illustration and that
numerous changes in the details of construction and arrangement of
parts may be resorted to without departing from the spirit and the
scope of the invention.
* * * * *