U.S. patent application number 14/421452 was filed with the patent office on 2015-08-06 for machine and methods for making rolled dielectric elastomer transducers.
The applicant listed for this patent is Parker-Hannifin Corporation. Invention is credited to Silmon James Biggs, Roger N. Hitchcock, Trao Bach Ly.
Application Number | 20150221861 14/421452 |
Document ID | / |
Family ID | 50101518 |
Filed Date | 2015-08-06 |
United States Patent
Application |
20150221861 |
Kind Code |
A1 |
Biggs; Silmon James ; et
al. |
August 6, 2015 |
MACHINE AND METHODS FOR MAKING ROLLED DIELECTRIC ELASTOMER
TRANSDUCERS
Abstract
A method for making a rolled dielectric elastomer transducer
includes rolling a dielectric film laminate into a solid dielectric
elastomer transducer roll. An apparatus includes a drive mechanism
for receiving a carrier plate with a dielectric film laminate
located on a top surface thereof. The drive mechanism is configured
to drive the carrier plate in a first direction. A scrub roller is
configured to counter-rotate in a second direction relative to the
first direction and frictionally engage the dielectric film to roll
the dielectric film laminate into a solid dielectric elastomer
transducer roll. The apparatus may also include a fixed jaw and a
movable jaw movable relative to the fixed jaw to define a
longitudinal aperture for receiving a solid dielectric elastomer
transducer roll therein. A cutter is configured to segment the
solid dielectric elastomer transducer roll into at least two or
more individual solid dielectric elastomer transducer rolls.
Inventors: |
Biggs; Silmon James; (Los
Gatos, CA) ; Hitchcock; Roger N.; (San Leandro,
CA) ; Ly; Trao Bach; (Mountain View, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Parker-Hannifin Corporation |
Cleveland |
OH |
US |
|
|
Family ID: |
50101518 |
Appl. No.: |
14/421452 |
Filed: |
August 16, 2013 |
PCT Filed: |
August 16, 2013 |
PCT NO: |
PCT/US2013/055299 |
371 Date: |
February 13, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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61734622 |
Dec 7, 2012 |
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61734616 |
Dec 7, 2012 |
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61734609 |
Dec 7, 2012 |
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61719999 |
Oct 30, 2012 |
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61717810 |
Oct 24, 2012 |
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61683860 |
Aug 16, 2012 |
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Current U.S.
Class: |
156/221 ;
156/350; 156/443 |
Current CPC
Class: |
B32B 37/144 20130101;
H01L 41/0836 20130101; Y10T 29/49146 20150115; H01L 41/0475
20130101; Y10T 156/1043 20150115; B32B 2307/202 20130101; B32B
2457/00 20130101; B32B 38/0012 20130101; B32B 2307/204 20130101;
H04R 19/04 20130101; H04R 31/00 20130101; H01L 41/0472 20130101;
H04R 2307/025 20130101; H01L 41/0533 20130101; H01L 41/053
20130101; H01L 41/193 20130101; Y10T 29/4913 20150115; B32B 38/10
20130101; B32B 37/18 20130101; H01L 41/27 20130101 |
International
Class: |
H01L 41/27 20060101
H01L041/27; B32B 38/00 20060101 B32B038/00; B32B 37/18 20060101
B32B037/18 |
Claims
1. A method for making a rolled dielectric elastomer transducer,
comprising: applying an electrode material on a first side and a
second side of a first dielectric film; laminating the first
dielectric film onto a side of a second dielectric film to produce
a dielectric film laminate; and rolling the dielectric film
laminate into a solid dielectric elastomer transducer roll.
2. The method according to claim 1, wherein applying the electrode
material comprises, applying at least a first layer of electrode
material on the first side of the first dielectric film; and
applying at least a second layer of the electrode material on the
second side of the first dielectric film; and wherein the at least
first layer and the at least second layer of the electrode material
are offset relative to each other.
3. The method according to claim 2, further comprising applying at
least one additional first layer of electrode material juxtaposed
and spaced apart from the at least one first layer of the electrode
material on the first side of the first dielectric film, wherein
the at least one additional first layer of electrode material on
the first side of the first dielectric film partially overlaps the
at least one second layer of the electrode material on the second
side of the first dielectric film.
4. The method according to claim 3, further comprising segmenting
the solid dielectric elastomer transducer roll into two or more
individual solid dielectric elastomer transducer rolls at the
region where the at least one additional first layer on the first
side of the first pre-strained dielectric film overlaps with the at
least one second layer of the electrode material on the second side
of the first pre-strained dielectric film.
5. The method according to claim 1, further comprising
pre-straining the first and second dielectric films.
6. The method according to claim 1, further comprising: applying an
electrically conductive adhesive on a first end and a second end of
the solid dielectric elastomer transducer roll; and applying an
electrical terminal on the first and second ends of the solid
dielectric elastomer transducer roll.
7. The method according to claim 6, further comprising applying a
solvent on the first and second ends of the solid dielectric
elastomer transducer roll prior to applying the electrically
conductive adhesive.
8. An apparatus, comprising: a drive mechanism for receiving a
carrier plate having a dielectric film laminate located on a first
surface thereof, the drive mechanism configured to drive the
carrier plate in a first direction; and a scrub roller configured
to counter-rotate in a second direction relative to the first
direction, the scrub roller configured to frictionally engage the
dielectric film to wind the dielectric film laminate into a solid
dielectric elastomer transducer roll.
9. The apparatus according to claim 8, further comprising a motion
control system for controlling the velocity of the drive mechanism
and the scrub roller.
10. The apparatus according to claim 9, wherein the motion control
system is configured to control the velocity of the carrier plate
Vplate in the first direction and the velocity of the scrub roller
Vscrub in the second opposite direction such that
|Vplate|=|Vscrub|.
11. The apparatus according to claim 9, wherein the motion control
system is configured to control the velocity of the carrier plate
Vplate in the first direction and the velocity of the scrub roller
Vscrub in the second opposite direction and to compensate for the
velocity of the solid dielectric elastomer transducer roll such
that |Vplate|-|Vroll, x|=|Vscrub|.
12. The apparatus according to claim 9, wherein the motion control
system is configured to control the velocity of the carrier plate
Vplate in the first direction and the velocity of the scrub roller
Vscrub in the second opposite direction and to compensate for the
velocity of the solid dielectric elastomer transducer roll and to
compensate for dielectric film stretch defined by a stretch
coefficient "k" caused by peel stress such that |Vplate|-|Vroll,
x|=k|Vscrub|.
13. The apparatus according to claim 9, further comprising at least
one sensor to sense force and provide a closed loop feedback
mechanism to the motion control system.
14. The apparatus according to claim 9, further comprising a
covering positioned over an outside surface of the scrub
roller.
15. The apparatus according to claim 14, wherein the covering is
made of a non-stick material.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit, under 35 USC
.sctn.119(e), of U.S. Provisional Application Nos. 61/683,860 filed
Aug. 16, 2012 entitled "ROLL ACTUATORS IN AXIAL TENSION, MODEL AND
DATA"; 61/717,810 filed Oct. 24, 2012 entitled "DIELECTRIC
ELASTOMER TRANSDUCER WITH QUICK-CONNECT TERMINALS"; 61/719,999
filed Oct. 30, 2012 entitled "MACHINE AND METHODS FOR MAKING ROLLED
DIELECTRIC ELASTOMER TRANSDUCERS"; 61/734,609 filed Dec. 7, 2012
entitled "RESONANT FREQUENCIES"; 61/734,616 filed Dec. 7, 2012
entitled "ROLL ACTUATORS"; and 61/734,622 filed Dec. 7, 2012
entitled "SKIN CONTACT WITH DIELECTRIC ELASTOMER ACTUATORS--SYSTEMS
FOR SAFETY"; the entirety of each of which is incorporated herein
by reference.
FIELD OF THE INVENTION
[0002] The present invention is directed in general to
electroactive polymers and more specifically to a rolled dielectric
elastomer transducer and manufacturing processes and apparatus for
making rolled dielectric elastomer transducers.
BACKGROUND OF THE INVENTION
[0003] A tremendous variety of devices used today rely on actuators
of one sort or another to convert electrical energy to mechanical
energy. Conversely, many power generation applications operate by
converting mechanical action into electrical energy. Employed to
harvest mechanical energy in this fashion, the same type of device
may be referred to as a generator. Likewise, when the structure is
employed to convert physical stimulus such as vibration or pressure
into an electrical signal for measurement purposes, it may be
characterized as a sensor. Yet, the term "transducer" may be used
to generically refer to any of the devices.
[0004] A number of design considerations favor the selection and
use of advanced dielectric elastomer materials, also referred to as
"electroactive polymers", for the fabrication of transducers. These
considerations include potential force, power density, power
conversion/consumption, size, weight, cost, response time, duty
cycle, service requirements, environmental impact, etc. As such, in
many applications, electroactive polymer technology offers an ideal
replacement for piezoelectric, shape-memory alloy and
electromagnetic devices such as motors and solenoids.
[0005] An electroactive polymer transducer comprises two electrodes
having deformable characteristics and separated by a thin
elastomeric dielectric material. When a voltage difference is
applied to the electrodes, the oppositely charged electrodes
attract each other thereby compressing the polymer dielectric layer
therebetween. As the electrodes are pulled closer together, the
dielectric polymer film becomes thinner (the Z-axis component
contracts) as it expands in the planar directions (along the X- and
Y-axes), i.e., the displacement of the film is in-plane. The
electroactive polymer film may also be configured to produce
movement in a direction orthogonal to the film structure (along the
Z-axis), i.e., the displacement of the film is out-of-plane. For
example, U.S. Pat. No. 7,567,681 discloses electroactive polymer
film constructs which provide such out-of-plane displacement--also
referred to as surface deformation or as thickness mode
deflection.
[0006] The material and physical properties of the electroactive
polymer film may be varied and controlled to customize the
deformation undergone by the transducer. More specifically, factors
such as the relative elasticity between the polymer film and the
electrode material, the relative thickness between the polymer film
and electrode material and/or the varying thickness of the polymer
film and/or electrode material, the physical pattern of the polymer
film and/or electrode material (to provide localized active and
inactive areas), the tension or pre-strain placed on the
electroactive polymer film as a whole, and the amount of voltage
applied to or capacitance induced upon the film may be controlled
and varied to customize the features of the film when in an active
mode.
[0007] Numerous applications exist that benefit from the advantages
provided by such electroactive polymer films whether using the film
alone or using it in an electroactive polymer actuator. One of the
many applications involves the use of electroactive polymer
transducers as actuators to produce haptic, tactile, vibrational
feedback (the communication of information to a user through forces
applied to the user's body), and the like, in user interface
devices. There are many known user interface devices which employ
such feedback, typically in response to a force initiated by the
user. Examples of user interface devices that may employ such
feedback include keyboards, keypads, game controller, remote
control, touch screens, computer mice, trackballs, stylus sticks,
joysticks, etc. The user interface surface can comprise any surface
that a user manipulates, engages, and/or observes regarding
feedback or information from the device. Examples of such interface
surfaces include, but are not limited to, a key (e.g., keys on a
keyboard), a game pad or buttons, a display screen, etc.
[0008] The feedback provided by these types of interface devices is
in the form of physical sensations, such as vibrations, pulses,
spring forces, etc., which a user senses either directly (e.g., via
touching of the screen), indirectly (e.g., via a vibrational effect
such a when a cell phone vibrates in a purse or bag) or otherwise
sensed (e.g., via an action of a moving body that creates a
pressure disturbance sensed by the user). The proliferation of
consumer electronic media devices such as smart phones, personal
media players, portable computing devices, portable gaming systems,
electronic readers, etc., can create a situation where a
sub-segment of customers would benefit or desire an improved haptic
effect in the electronic media device. However, increasing feedback
capabilities in every model of an electronic media device may not
be justified due to increased cost or increased profile of the
device. Moreover, customers of certain electronic media devices may
desire to temporarily improve the haptic capabilities of the
electronic media device for certain activities.
[0009] Use of electroactive polymer materials in consumer
electronic media devices as well as the numerous other commercial
and consumer applications highlights the need to increase
production volume while maintaining precision and consistency of
the films.
[0010] Conventional rolled dielectric elastomer transducer based
cylindrical actuators are desirable because a cylindrical shape is
functional and familiar. It matches many mechanical components,
such as, for example, solenoids, air cylinders, shock absorbers,
etc. so mounting hardware is readily available, for example, the
clevis, the ball joint, and the threaded rod. Engineers'
familiarity with cylindrical actuators simplifies efforts to
integrate them into new designs. Nevertheless, hollow, rolled
dielectric elastomer tubes and tubes with an internal spring,
called "spring rolls" have some drawbacks. Empty space inside the
tube is wasted, making the transducer larger than strictly
necessary. Also, accumulated tension from winding the outer layers
of the tube tends to buckle and collapse the tube. In a tubular
roll made with a highly prestrained acrylic dielectric, this has
been found to impose a practical limit of only a few turns per
transducer.
[0011] The present disclosure provides various improvements over
conventional hollow rolled dielectric elastomer transducers and
manufacturing processes for making transducers. The present
invention overcomes these drawbacks by winding dielectric elastomer
films into a solid roll. Among the advantages of a solid roll are
that it does not waste space, and it does not collapse as turns are
added. A rolling machine also is disclosed, along with a
manufacturing process, materials, and fixtures for manufacturing
dielectric elastomer actuator rolls with the machine, as described
herein in the detailed description of the invention section of the
present disclosure.
SUMMARY OF THE INVENTION
[0012] In one embodiment, a method comprises providing a dielectric
film laminate and rolling the dielectric film laminate into a solid
dielectric elastomer transducer roll.
[0013] In another embodiment, an apparatus comprises a drive
mechanism for receiving a carrier plate with a dielectric film
laminate located on a top surface thereof. The drive mechanism is
configured to drive the carrier plate in a first direction. A scrub
roller is configured to counter-rotate in a second direction
relative to the first direction and frictionally engage the
dielectric film to roll the dielectric film laminate into a solid
dielectric elastomer transducer roll.
[0014] In yet another embodiment, the apparatus further comprises a
fixed jaw and a movable jaw movable relative to the fixed jaw to
define a longitudinal aperture for receiving a solid dielectric
elastomer transducer roll therein. A cutter is configured to
segment the solid dielectric elastomer transducer roll into at
least two or more individual solid dielectric elastomer transducer
rolls.
[0015] These and other features and advantages of the invention
will become apparent to those persons skilled in the art upon
reading the details of the invention as more fully described below.
In addition, variations of the processes and devices described
herein include combinations of the embodiments or of aspects of the
embodiments where possible are within the scope of this disclosure
even if those combinations are not explicitly shown or
discussed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The invention is best understood from the following detailed
description when read in conjunction with the accompanying
drawings. To facilitate understanding, the same reference numerals
have been used (where practical) to designate similar elements are
common to the drawings. Included in the drawings are the
following:
[0017] FIG. 1 illustrates a solid dielectric elastomer transducer
roll in accordance with one embodiment of the present
invention;
[0018] FIG. 2 illustrates tension .sigma..sub.p that accumulates
when removing film from a liner while winding a hollow rolled
dielectric elastomer transducer;
[0019] FIG. 3 illustrates radial stress .DELTA.P developed in the
hollow dielectric elastomer transducer rolls shown in FIG. 2 caused
by the tension .sigma..sub.p;
[0020] FIG. 4 is a graphical illustration depicting the
accumulation of radial stress .DELTA.P in the hollow dielectric
elastomer transducer rolls shown in FIG. 2 as additional wraps are
added to the hollow rolled dielectric elastomer transducer;
[0021] FIG. 5 illustrates inner windings of a hollow dielectric
elastomer transducer rolls that have collapsed under the
accumulated radial stress P imposed by tension .sigma..sub.p in the
outer windings;
[0022] FIG. 6 illustrates a cylindrical solid dielectric elastomer
transducer roll in accordance with one embodiment of the present
invention;
[0023] FIGS. 7A-7K illustrate a manufacturing process for turning
an electroded dielectric film laminate into a solid dielectric
elastomer transducer roll, as shown in FIGS. 7I and 7K in
accordance with one embodiment of the present invention, where:
[0024] FIG. 7A illustrates lamination of dielectric films in
accordance with one embodiment of the present invention;
[0025] FIG. 7B illustrates cutting a frame away from the dielectric
film laminate in accordance with one embodiment of the present
invention;
[0026] FIG. 7C illustrates removal of the frame from the dielectric
film laminate in accordance with one embodiment of the present
invention;
[0027] FIG. 7D illustrates mounting a carrier plate with the
dielectric film laminate on a rolling machine in accordance with
one embodiment of the present invention;
[0028] FIG. 7E illustrates the process of rolling the dielectric
film laminate by moving the carrier plate under a counter rotating
scrub roller into a solid roll of dielectric elastomer film in
accordance with one embodiment of the present invention;
[0029] FIG. 7F illustrates the process of rolling the dielectric
film laminate shown in FIG. 7E towards the end of the process in
accordance with one embodiment of the present invention;
[0030] FIG. 7G illustrates the carrier plate retracting after the
rolling process is complete in accordance with one embodiment of
the present invention;
[0031] FIG. 7H illustrates transfer of a solid dielectric elastomer
transducer roll to a cutting fixture for segmenting the roll into
individual solid dielectric elastomer transducer rolls shown in
FIG. 7G in accordance with one embodiment of the present
invention;
[0032] FIG. 7I illustrates the solid dielectric elastomer
transducer roll segmented into individual solid dielectric
elastomer transducer rolls in accordance with one embodiment of the
present invention;
[0033] FIG. 7J illustrates application of conductive adhesive into
a terminal cup for electrically attaching to ends of the solid
dielectric elastomer transducer rolls shown in FIGS. 7H and 7I in
accordance with one embodiment of the present invention;
[0034] FIG. 7K illustrates attaching and curing the terminal cups
onto the ends of the solid dielectric elastomer transducer roll
shown in FIG. 1 in accordance with one embodiment of the present
invention;
[0035] FIG. 8 is a detail view of the rolling machine used in steps
illustrated in FIGS. 7D-F in accordance with one embodiment of the
present invention;
[0036] FIG. 9 is a detail view of the cutting fixture for
segmenting the solid dielectric elastomer transducer roll into
individual solid dielectric elastomer transducer rolls shown in
FIGS. 7H and 7J in accordance with one embodiment of the present
invention;
[0037] FIG. 10 is an end view of an individual segmented solid
dielectric elastomer transducer roll in accordance with one
embodiment of the present invention after segmentation and prior to
exposing the end to a solvent;
[0038] FIG. 11 is an end view of an individual segmented solid
dielectric elastomer transducer roll after the application of a
solvent to cause local swelling and separation of the layers in
accordance with one embodiment of the present invention;
[0039] FIG. 12 illustrates a motion control system for controlling
the rolling process of rolling up a solid dielectric elastomer
transducer roll with a carrier plate under a scrub roller as
illustrated in FIGS. 7D-F and FIG. 8 in accordance with one
embodiment of the present invention;
[0040] FIG. 13 illustrates a simplified motion control system for
the rolling process illustrated in FIGS. 7D-F and FIG. 8 where slip
can occur between the scrub roller and a growing solid dielectric
elastomer transducer roll in accordance with one embodiment of the
present invention;
[0041] FIG. 14 illustrates a textile covering positioned over an
outside surface of the scrub roller illustrated in FIG. 13 in
accordance with one embodiment of the present invention;
[0042] FIG. 15 is a detailed view of the textile covering
illustrated in FIG. 14 in accordance with one embodiment of the
present invention;
[0043] FIG. 16 illustrates circumferential lengthening of outer
layers of solid dielectric elastomer transducer roll caused by
rolling a pre-strained dielectric elastomer film with excessive
pre-strain during the rolling process;
[0044] FIG. 17 illustrates a wrinkle mechanism in the loosely
packed space between individual solid dielectric elastomer
transducer rolls in accordance with one embodiment of the present
invention;
[0045] FIG. 18 illustrates an electrode pattern with overlap
regions to provide support in bands between solid dielectric
elastomer transducer rolls to prevent wrinkles that would otherwise
start in the overlapping regions;
[0046] FIG. 19 illustrates a non-limiting example fixture for
positioning electrical terminal caps on ends of a solid dielectric
elastomer transducer roll during curing;
[0047] FIG. 20 illustrates a derivation model of a solid dielectric
elastomer transducer roll in accordance with one embodiment of the
present invention;
[0048] FIG. 21 is a graphical illustration depicting force provided
by each additional ring in a solid dielectric elastomer transducer
roll in accordance with one embodiment of the present
invention;
[0049] FIG. 22 is a graphical illustration depicting capacitance
change versus axial displacement of a solid dielectric elastomer
transducer roll in accordance with one embodiment of the present
invention;
[0050] FIG. 23 is a graphical illustration depicting blocked force
versus applied voltage response of a solid dielectric elastomer
transducer roll in accordance with one embodiment of the present
invention;
[0051] FIG. 24 is a graphical illustration depicting blocked force
versus axial displacement showing the difference between the solid
dielectric elastomer transducer roll in compression versus tension
in accordance with one embodiment of the present invention;
[0052] FIG. 25 is a graphical illustration of blocked force versus
longitudinal displacement showing the difference between the solid
dielectric elastomer transducer roll in compression versus tension
in accordance with one embodiment of the present invention;
[0053] FIG. 26 is a graphical representation of stiffness of solid
dielectric elastomer transducer rolls in accordance with one
embodiment of the present invention;
[0054] FIG. 27 illustrates a solid dielectric elastomer transducer
roll in flat roll mode where the roll is placed under compression
in a radial direction rather than in an axial direction in
accordance with one embodiment of the present invention;
[0055] FIG. 28 illustrates a geometric model of a solid dielectric
elastomer transducer roll in flat roll mode where the roll is
placed under compression in a radial direction in accordance with
one embodiment of the present invention;
[0056] FIG. 29 is a graphical illustration depicting stretch ratio
versus percent compression in a radial direction of a solid
dielectric elastomer transducer roll in accordance with one
embodiment of the present invention;
[0057] FIG. 30 illustrates a static equilibrium diagram of a solid
dielectric elastomer transducer roll in flat roll mode under static
load in accordance with one embodiment of the present
invention;
[0058] FIG. 31 is a graphical illustration depicting capacitance
versus compression in a radial direction of a solid dielectric
elastomer transducer roll in flat roll mode in accordance with one
embodiment of the present invention;
[0059] FIGS. 32A, 32B, 32C and 32D illustrate a solid dielectric
elastomer transducer roll under increasing compression force in a
radial direction in accordance with one embodiment of the present
invention;
[0060] FIG. 33 illustrates a finite element analysis model of a
solid dielectric elastomer transducer roll undergoing radial
compression in accordance with one embodiment of the present
invention; and
[0061] FIG. 34 illustrates the delamination of a solid dielectric
elastomer transducer roll undergoing radial compression in
accordance with one embodiment of the present invention.
[0062] Variation of the invention from that shown in the figures is
contemplated.
DETAILED DESCRIPTION OF THE INVENTION
[0063] Examples of electroactive polymer devices and their
applications are described, for example, in U.S. Pat. Nos.
6,343,129; 6,376,971; 6,543,110; 6,545,384; 6,583,533; 6,586,859;
6,628,040; 6,664,718; 6,707,236; 6,768,246; 6,781,284; 6,806,621;
6,809,462; 6,812,624; 6,876,135; 6,882,086; 6,891,317; 6,911,764;
6,940,221; 7,034,432; 7,049,732; 7,052,594; 7,062,055; 7,064,472;
7,166,953; 7,199,501; 7,199,501; 7,211,937; 7,224,106; 7,233,097;
7,259,503; 7,320,457; 7,362,032; 7,368,862; 7,378,783; 7,394,282;
7,436,099; 7,492,076; 7,521,840; 7,521,847; 7,567,681; 7,595,580;
7,608,989; 7,626,319; 7,750,532; 7,761,981; 7,911,761; 7,915,789;
7,952,261; 8,183,739; 8,222,799; 8,248,750; and in U.S. Patent
Application Publication Nos.; 2007/0200457; 2007/0230222;
2011/0128239; and 2012/0126959, the entireties of which are
incorporated herein by reference.
[0064] In various embodiments, the present invention provides
various improvements over conventional hollow rolled dielectric
elastomer transducers and manufacturing processes for making those
transducers. Embodiments of the present invention overcome these
drawbacks by winding dielectric elastomer films into a solid roll
that does not waste space or collapse as turns are added. A rolling
machine also is disclosed, along with a manufacturing process,
materials, and fixtures for manufacturing dielectric elastomer
actuator rolls with the machine, as described herein in the
detailed description of the invention section of the present
disclosure.
[0065] The various embodiments discussed hereinbelow in connection
with FIGS. 1-19 provide a dielectric elastomer transducer rolls
formed by rolling laminated films into a compact spiral, which will
be referred to herein as "solid." Multiple individual solid
dielectric elastomer transducer rolls may be produced by segmented
cutting of the transducer rolls, where the cutting affords
electrical connections to the ends of the rolls. A conductive
adhesive formulated with solvent may be used to swell the ends of
the roll to improve mechanical and electrical connection of the
rolls to the terminals. Also provided is a rolling machine for
dielectric elastomer actuators comprised of a scrub roller that
counter-rotates with respect to an advancing plate. Another rolling
machine is provided in which motion control is simplified by
spinning the scrub roller faster than the carrier plate advances. A
non-stick textile cover for the scrub roller is provided to
minimize adhesion by minimizing contact area through the use of
knit threads that can locally deflect to minimize contact stress.
An electrode pattern is also provided for transducer rolls in which
electrodes overlap to support areas of the roll that could
otherwise buckle and initiate wrinkles. Also provided are novel
fixtures for cutting the roll and adhering terminals, to be used in
conjunction with the rolling machine.
[0066] The solid transducer rolls overcome buckling problems that
normally would limit the number of turns that can be added to a
hollow type transducer roll. Solid transducer rolls also save space
that is wasted by the hollow type rolls known in the art. A rolling
machine forms solid rolls with geometric tolerances finer than
hand-rolling, at greater speed and lower cost. A compliant,
textile, non-stick cover for the scrub roller in the machine
simplifies motion control and reduces machine cost. An overlapping
electrode pattern prevents wrinkles.
[0067] FIG. 1 illustrates a solid dielectric elastomer transducer
roll 100 in accordance with one embodiment of the present
invention. The solid dielectric elastomer transducer roll 100
comprised of two layers of dielectric film 102, 104, one of which
has been patterned with one or more layers of electrodes 106, 108
on both sides. The layers of dielectric film 102, 104 are wound
together into a tight solid spiral cylinder. The area 110 in which
the electrodes 106, 108 overlap acts as a dielectric elastomer
transducer. Electrical connection to the two plates of the
capacitor can be made where the electrodes 106, 108 meet the ends
of the cylinder. The electrodes 106, 108 are offset relative to
each other to provide electrical connection at the ends 112, 114 of
the solid dielectric elastomer transducer roll 100 such that the
first electrode 106 is accessible at the top 112 and the second
electrode 108 is accessible at the bottom 114 of the transducer
100. Although in the illustrated embodiment, the solid dielectric
elastomer transducer roll 100 has a right circular cylindrical
form, other forms are contemplated such as triangular, square,
rectangular, among other polyhedral forms.
[0068] FIG. 2 illustrates tension .sigma..sub.p that accumulates
when removing film 120 from a liner 122 while winding a hollow 124
rolled dielectric elastomer transducer 126. Some peeling stress o
is unavoidable when removing the film 120 having a thickness "t"
from the liner 122.
[0069] FIG. 3 illustrates radial stress .DELTA.P developed in the
hollow rolled dielectric elastomer transducer 126 shown in FIG. 2
caused by the tension .sigma..sub.p created when the film 120 is
peeled from the liner 122 (not shown). Radial stress .DELTA.P
(pressure) in the compressed layers below must support the tension
of each new wrap.
[0070] FIG. 4 is a graphical illustration depicting the
accumulation of radial stress .DELTA.P in the hollow rolled
dielectric elastomer transducer 126 shown in FIG. 2 as additional
wraps are added to the hollow rolled dielectric elastomer
transducer 126. As more wraps are added the radial stress .DELTA.P
(pressure) in the center increases. If the force becomes large
enough, the inner layers may delaminate and buckle, like an arch
collapsing. As indicated by the radial stress .DELTA.P [Pa] versus
radial distance [m] curve 130 in graph 128, the radial stress
.DELTA.P on the innermost layer 132 is much higher than the radial
stress .DELTA.P on the outermost layer 134.
[0071] In the context of FIGS. 2-4, the peel stress .sigma..sub.p
and strain in a single layer of dielectric film 120 are given below
for values typical of a dielectric elastomer coating:
.sigma. p = .sigma. PEEL t = [ 3.8 N / m ] [ 80 E - 6 m ] = 0.048
MPa Eq . 1 s = .sigma. p Y = [ 0.048 MPa ] [ 0.6 MPa ] = 0.08 = 8 %
strain Eq . 2 ##EQU00001##
[0072] The force balance for a half-wrap of film, as shown in FIG.
3, can be solved for the radial stress .DELTA.P.
F z = - 2 .sigma. p t + 2 r .DELTA. P = 0 Eq . 3 .DELTA. P =
.sigma. p t r = .sigma. PEEL r Eq . 4 ##EQU00002##
[0073] The radial stress .DELTA.P in layer "i" is due to the
accumulated stress of the layers above it as given in the equation
below. For typical values of peel stress .sigma..sub.p on a hollow
rolled dielectric elastomer transducer 126 with 1 mm internal
radius, the calculated pressures have been plotted in FIG. 4.
P i = .DELTA. P i + 0 i .DELTA. P Eq . 5 ##EQU00003##
[0074] FIG. 5 illustrates inner windings 132 of the hollow rolled
dielectric elastomer transducer 126 that have collapsed under the
accumulated radial stress P imposed by tension .sigma..sub.p in the
outer windings 134. This "collapsing of the inner layers" problem
with the conventional hollow rolled dielectric elastomer transducer
126 provides the motivation for the present inventors' development
of the solid dielectric elastomer transducer roll 100 shown in FIG.
6.
[0075] FIG. 6 illustrates a cylindrical solid dielectric elastomer
transducer roll 100 in accordance with one embodiment of the
present invention. The cylindrical solid dielectric elastomer
transducer roll 100 does not exhibit a collapse of the inner layers
136 under the accumulated radial stress P imposed by tension
.sigma..sub.p in the outer windings 138.
[0076] FIGS. 7A-7K illustrate a manufacturing process for turning
an electroded dielectric film laminate 101 into a solid dielectric
elastomer transducer roll 178, as shown in FIGS. 7I and 7K in
accordance with one embodiment of the present invention. The
process rolls the dielectric film laminate 101 into a tight spiral
without an opening extending axially in the center of the solid
dielectric elastomer transducer roll 178.
[0077] FIG. 7A illustrates a step of the process where two
dielectric films 102, 104 are laminated 150 in accordance with one
embodiment of the present invention. The first dielectric film 102
comprises a first electrode layer 106 on a top portion and a second
electrode layer 108 on a bottom portion. The first dielectric film
102 with the electrodes 106, 108 patterned on both sides thereof
are held in tension (pre-stressed) in a rigid frame 152. The first
film 102 with the frame 152 is then laminated to the second
dielectric film 104 while it is still attached to the liner 154
used to coat it. The electroded dielectric film laminate 101 (not
shown in FIG. 7A) comprising the laminated films 102, 104 is
positioned on a carrier plate 156, which will be used to hold the
dielectric film laminate 101 during the rolling process.
[0078] FIG. 7B illustrates another step of the process where the
frame 152 is cut 158 away from the dielectric film laminate 101
(not shown in FIG. 7B) in accordance with one embodiment of the
present invention. The cut path 160 is inside the inner perimeter
of the frame 152.
[0079] FIG. 7C illustrates another step of the process where the
frame 152 is removed 162 from the dielectric film laminate 101 in
accordance with one embodiment of the present invention.
[0080] FIG. 7D illustrates another step of the process where the
carrier plate 156 with the dielectric film laminate 101 is mounted
164 on a rolling machine 166 in accordance with one embodiment of
the present invention. The rolling machine 166 comprises a scrub
roller 168, which rolls up the dielectric film laminate 101.
[0081] FIG. 7E illustrates another step in the process where the
dielectric film laminate 101 on the carrier plate 156 is rolled
into a solid roll of dielectric elastomer film under a counter
rotating 172 scrub roller 168 as the carrier plate 156 is moved 170
in direction 174 by a conveyor or other suitable drive mechanism in
accordance with one embodiment of the present invention. As the
dielectric film laminate 101 is rolled, it is released from the
liner 154. The process continues until the entire dielectric film
laminate 101 is rolled. FIG. 7F illustrates the process of rolling
the dielectric film laminate 101 shown in FIG. 7E towards the end
of the process in accordance with one embodiment of the present
invention.
[0082] FIG. 7G illustrates another step of the process where the
carrier plate 156 is retracted 176 in direction 177 after the
rolling process is complete in accordance with one embodiment of
the present invention. As shown, a solid dielectric elastomer
transducer roll 178 is provided at the end of this step.
[0083] FIG. 7H illustrates another step in the process where the
solid dielectric elastomer transducer roll 178 is transferred 180
to a cutting fixture 182 for segmenting the roll 178 with a cutter
184, such as a blade or slitter, into individual solid dielectric
elastomer transducer rolls shown in FIG. 7G in accordance with one
embodiment of the present invention.
[0084] FIG. 7I illustrates another step in the process where the
solid dielectric elastomer transducer roll 178 is segmented 186
into individual solid dielectric elastomer transducer rolls 178a,
178b, and 178c in accordance with one embodiment of the present
invention.
[0085] FIG. 7J illustrates another step in the process where a
conductive adhesive 192 is applied 190 into an electrical terminal
194 having a cup shape for electrically attaching to ends of the
solid dielectric elastomer transducer rolls 178a, 178b, and 178c
shown in FIGS. 7H and 7I in accordance with one embodiment of the
present invention.
[0086] FIG. 7K illustrates another step in the process where
terminals 194a.sub.1, 194a2 are attached and cured 196 onto the
ends of the solid dielectric elastomer transducer roll 178a,
terminals 194b.sub.1, 194b.sub.2 are attached and cured 196 onto
the ends of the solid dielectric elastomer transducer roll 178b,
and terminals 194c.sub.1, 194c.sub.2 are attached and cured 196
onto the ends of the solid dielectric elastomer transducer roll
178c in accordance with one embodiment of the present
invention.
[0087] FIG. 8 is a detail view of the rolling machine 166 used in
the steps illustrated in FIGS. 7D-G in accordance with one
embodiment of the present invention.
[0088] FIG. 9 is a detail view of the cutting fixture 182 for
segmenting the solid dielectric elastomer transducer roll 178 into
individual solid dielectric elastomer transducers rolls 178a, 178b,
and 178c shown in FIGS. 7I and 7J in accordance with one embodiment
of the present invention. The cutting fixture 182 comprises a
movable jaw 196 and a fixed jaw 198. The movable jaw comprises
alignment slots 202 and the fixed jaw comprises alignment slots
204, which are aligned with the alignment slots 202 of the movable
jaw 202. The cutting fixture comprises an aperture for receiving
the solid dielectric elastomer transducer roll 178 therein. The
movable jaw 196 moves relative to the fixed jaw 198 to define a
longitudinal aperture 200 for receiving and holding the solid
dielectric elastomer transducer roll 178 in place during the
segmenting process. The cutter 184 is advanced through the
alignment slots 202 in the movable jaw 196, through the solid
dielectric elastomer transducer roll 178, and the alignment slots
204 in the fixed jaw 198. The clamping action of the jaws 196, 198
also straightens the solid dielectric elastomer transducer roll 178
within the aperture 200 in preparation for segmentation.
[0089] FIG. 10 is an end view of an individual segmented solid
dielectric elastomer transducer roll 100 in accordance with one
embodiment of the present invention after segmentation and prior to
exposing the end to a solvent.
[0090] FIG. 11 is an end view of an individual segmented solid
dielectric elastomer transducer roll 100' after the application of
a solvent to the end to cause local swelling and separation of the
layers 206, 208, and 210 in accordance with one embodiment of the
present invention. This improves penetration of the conductive
adhesive 192, shown in FIG. 7J. During the curing process 196 shown
in FIG. 7K, the solvent evaporates, leaving inter-digitated glue
that makes a robust electrical and mechanical connection between
the capping end-terminal 194 shown in FIGS. 7J and 7K and the
electrodes 106, 108 of the solid dielectric elastomer transducer
roll 100. In one embodiment, the electrically conductive adhesive
192 may be formulated with a solvent that swells the ends of the
roll 100 to improve mechanical and electrical connection of the
rolls 100 to the terminals 194.
[0091] FIG. 12 illustrates a motion control system 212 for
controlling the process of rolling the dielectric film laminate 101
into a solid dielectric elastomer transducer roll 178 with the
rolling machine 166. The scrub roller 168 portion of the rolling
machine 166 has a radius r.sub.scrub. The motion control system 212
may be any electronic processor or digital logic based programmable
motion controller configured to control the velocity and direction
of rotation of the scrub roller 168 and the velocity and direction
of translation of the carrier plate 156 in accordance with the
present invention. As previously discussed in connection with FIGS.
7D-G, the carrier plate 156 is advanced in direction 174 at
velocity V.sub.plate while the scrub roller 168 is rotated in a
counter direction 172 at velocity V.sub.scrub. As the outer surface
of the scrub roller 168 contacts the dielectric film laminate 101,
the dielectric film laminate 101 begins to roll up to form the
solid dielectric elastomer transducer roll 178. The solid
dielectric elastomer transducer roll 178 grows in diameter until
the carrier plate 156 reaches the end of stroke. As matching the
speeds of the carrier plate 156 and the scrub roller 168 can
improve the rolling process and excess speed on the carrier plate
156 can jam the solid dielectric elastomer transducer roll 178
under the scrub roller 168. On the other hand, if the solid
dielectric elastomer transducer roll 178 is sticky and adheres to
the scrub roller 168, excess velocity on the scrub roller 168 can
lift the solid dielectric elastomer transducer roll 178 off the
liner 154 and wrap it around the scrub roller 168. Each of these
situations can result in damaging the solid dielectric elastomer
transducer roll 178. Accordingly, the motion control system 212 may
be programmed in accordance with the following considerations to
provide various levels of control ranging from the simple to the
complex.
[0092] By way of example, the motion control system 212 may be
configured in various forms from a relatively simple control system
to a more complex control system. In one embodiment, the control
system 212 may be configured to match the velocity of the carrier
plate 156 V.sub.plate in direction 174 and the velocity of the
scrub roller 168 V.sub.scrub in direction 172 such that
|V.sub.plate|=|V.sub.scrub|. In another embodiment, the motion
control system 212 may be configured to account for the velocity of
the transducer roll V.sub.roll in direction 214 as a new variable
to compensate for the movement of the center of the solid
dielectric elastomer transducer roll 178 as the diameter grows such
that |V.sub.plate|-|V.sub.roll, x|=k|V.sub.scrub|. In yet another
embodiment, the motion control system 212 may be configured to
account for a stretch coefficient "k" to compensate for stretching
of the dielectric film laminate 101 as it is peeled from the liner
154 such that |V.sub.plate|-|V.sub.roll, x|=k|V.sub.scrub|.
Finally, in another embodiment, the motion control system 212 may
be configured to employ at least one sensor to sense force and
provide a closed loop feedback mechanism to the motion control
system 212.
[0093] The complexity of the various configurations of the motion
control system 212 outlined above can be avoided if the solid
dielectric elastomer transducer roll 178 does not stick to the
scrub roller 168. In that case, the scrub roller 168 can be rotated
quickly relative to the carrier plate 156 so that it always brushes
the solid dielectric elastomer transducer roll 178 back, as
illustrated below in FIG. 13.
[0094] FIG. 13 illustrates a simplified implementation of the
motion control system 212 that is configured to account for slip
218 that can occur between the scrub roller 168 and the growing
diameter of the solid dielectric elastomer transducer roll 178.
Accordingly, the motion control system 212 may be configured to
control the velocity of the carrier plate 156 V.sub.plate in
direction 174 relative to the velocity of the scrub roller 168
V.sub.scrub in direction 172 such that
|V.sub.plate|<<|V.sub.scrub|.
[0095] FIG. 14 illustrates a textile covering 222 positioned over
an outside surface of the scrub roller 168 illustrated in FIG. 13.
The textile covering 222 is made of a non-stick material to provide
non-stick contact between the scrub roller 168 and the solid
dielectric elastomer transducer roll 178 in accordance with one
embodiment of the present invention. FIG. 15 is a detailed view of
the textile covering 222 provided over the outside surface of the
scrub roller 168 as illustrated in FIG. 14 in accordance with one
embodiment of the present invention. With reference to FIGS. 14 and
15, a suitable non-stick contact between the scrub roller 168 and
the solid dielectric elastomer transducer roll 178 may be achieved
by covering the scrub roller with a knit fabric 222. The knit
fabric 222 minimizes the dielectric-to-roller contact area and thus
minimizes the adhesion force. The knit fabric 222 insures that the
contact area is primarily empty air. Because the knit fibers can
deflect, stress concentrations on the solid dielectric elastomer
transducer roll 178 film are smaller than those provided by, for
example, a roller made of a hard grooved plastic. This protects the
solid dielectric elastomer transducer roll 178 from mechanical
damage during the rolling process.
[0096] FIG. 16 illustrates circumferential lengthening of outer
layers of the dielectric elastomer transducer roll 224 caused by
rolling a pre-strained dielectric elastomer film with excessive
pre-strain during the rolling process. An advantage of the rolling
process according to one embodiment of present invention is the
ability to apply a minimum of pre-strain to the dielectric
elastomer transducer roll during the rolling process. In one
aspect, the minimum pre-strain is only the pre-strain required for
peeling the dielectric film laminate from the liner during the
rolling process. This is useful because excessive pre-strain can
cause relaxation of longitudinal pre-strain that can lead
circumferential lengthening of the outer layers 226 of the
transducer roll 224. As shown in FIG. 16, the outer layers 224 of
the transducer roll 224 have delaminated in some places and not
others, causing buckling. So, even if the inner layers of the
transducer roll 224 do not buckle, the outer layers 224 may slip.
This problem with pre-strain may be minimized by rolling up the
unstrained dielectric film laminate directly from the liner on
which it was coated in accordance with one embodiment of the
present invention.
[0097] FIG. 17 illustrates a wrinkling mechanism in the loosely
packed space between individual electroded solid dielectric
elastomer transducer rolls 178a, 178b in accordance with one
embodiment of the present invention. The bands 226 of un-electroded
film in between electroded solid dielectric elastomer transducer
rolls 178a, 178b can cause rolling problems. The dielectric layers
in these bands 226 are supported only loosely by underlying layers,
and can therefore buckle 228 in response to non-uniform rotation
along the length of the roll 168. This is illustrated in FIG. 17,
where the electroded solid dielectric elastomer transducer rolls
178a, 178b have undergone slightly different rotation relative to
the rotation rates of the band 226 therebetween. The electroded
solid dielectric elastomer transducer rolls 178a, 178b portions of
the transducer roll 178 are supported by the electrodes whereas the
band 226 therebetween is unsupported and can buckle. The force of
peeling the laminate film from the liner can also produce V-shaped
wrinkles in these bands 226. The wrinkles propagate along the
length of the roll as turns are added, which is undesirable. To
minimize this problem, the regions of adjacent electroded solid
dielectric elastomer transducer rolls 178a, 178b can be overlapped
as described hereinbelow in FIG. 18.
[0098] FIG. 18 illustrates an electrode pattern 230 with
overlapping regions 232 to provide support in bands between
adjacent (juxtaposed) layers of electrode materials to be segmented
into individual solid dielectric elastomer transducer rolls 178a,
178b. The electrode pattern 230 prevents wrinkles that would
otherwise start in the overlapping regions 232 and also enables
segmenting the roll into individual solid dielectric elastomer
transducer rolls 178a, 178b. The first dielectric film 102 is shown
delaminated from the second dielectric film 104 for illustration
purposes. As shown, the first and second electrodes 106, 108 are
applied on opposite sides of the dielectric film 102 in a staggered
(offset) manner to create overlapping regions 232. A first side of
the dielectric film 102 includes multiple layers of electrode
106.sub.1, 106.sub.2, and 106.sub.3 material juxtaposed relative to
each other and spaced apart by a gap 235 therebetween. A second
side of the dielectric film 102 includes multiple layers of
electrode 108.sub.1, 108.sub.2, and 108.sub.3 material juxtaposed
relative to each other and spaced apart by a gap 237 therebetween.
The layers of electrodes 106.sub.1, 106.sub.2, and 106.sub.3 on the
first side of the dielectric film 102 are offset or staggered from
the layers of electrodes 108.sub.1, 108.sub.2, 108.sub.3 on the
second side of the dielectric film 102 to create the overlapping
regions 232.sub.1, 232.sub.2 and so on. The second dielectric film
104 is still releasably attached to the liner 154 which is attached
to the carrier plate 156. As previously discussed, the first
dielectric film 102 with the electrodes 106.sub.1, 106.sub.2,
106.sub.3, 108.sub.1, 108.sub.2, and 108.sub.3 formed on each side
thereof is laminated to the second dielectric film 104 on the liner
154.
[0099] FIG. 19 illustrates a non-limiting example of fixture 234
for positioning the electrical terminal caps 194a.sub.1, 194a.sub.2
on ends of a solid dielectric elastomer transducer roll 178a during
curing. The fixture 234 comprises a slot 236 to receive the solid
dielectric elastomer transducer roll 178a and blade terminals 238
for receiving the electrical terminal caps 194a.sub.1, 194a.sub.2.
As previously discussed in FIGS. 7I and 7J, the electrical terminal
caps 194a.sub.1, 194a.sub.2 are filled with an electrically
conductive adhesive 192. The ends of the solid dielectric elastomer
transducer roll 178a are then inserted into each one of the
conductive adhesive 192 filled electrical terminal caps 194a.sub.1,
194a.sub.2 and then a cam 240 is used to apply a clamping force to
the assembled solid dielectric elastomer transducer roll 178a and
conductive adhesive 192 filled electrical terminal caps 194a.sub.1,
194a.sub.2 during the curing process.
[0100] Having described embodiments of solid dielectric elastomer
transducer rolls, methods for manufacturing the solid dielectric
elastomer transducer rolls, and machines for manufacturing the
solid dielectric elastomer transducer rolls, the specification now
turns to a description of capacitance models for a solid dielectric
elastomer transducer roll in axial tension and compression modes as
well as radial (flat mode) compression modes.
[0101] FIG. 20 illustrates a derivation model 300 of a solid
dielectric elastomer transducer roll 302, similar to the solid
dielectric elastomer transducer roll 100, 178 described above, in
accordance with one embodiment of the present invention. The
diagram depicted in FIG. 20 shows the solid dielectric elastomer
transducer roll 302 in a relaxed state and also shows a comparison
of an outer ring 304 of the solid dielectric elastomer transducer
roll 302 in a relaxed state and the outer ring 304' when it is in
tension. The solid dielectric elastomer transducer roll 302 has a
length x.sub.o when the solid dielectric elastomer transducer roll
302 is not in tension and a length (x.sub.o+x) or .lamda.x.sub.o
when tensioned. The model assumes the spiral equivalent of N rings
and the volume inside each ring is conserved due to the
incompressibility of the rings within and the volume of the ring
itself is conserved. Each ring is an annular capacitor and the
total capacitance is the sum of the all N rings.
[0102] The main equations developed in accordance with the model
are:
TABLE-US-00001 Effective Number of Rings in Roll N = ( y 0 t 0 .pi.
) 1 / 2 ##EQU00004## Eq. 6 Blocked Force F total = V 2 .pi. 0 n = 1
N ( ln ( n + 1 ) - ln ( n ) ) - 1 ##EQU00005## Eq. 7 Spring Rate k
= Y(y.sub.0 + y.sub.p)t.sub.0/(x.sub.0 + x.sub.p) Eq. 8 Free Stroke
.DELTA.x .apprxeq. F total k ##EQU00006## Eq. 9 Roll Diameter
D.sub.composite = 2N(t.sub.film + t.sub.elec) Eq. 10
A Spiral is Equivalent to N Rings
[0103] The outer ring 304 of the un-tensioned solid dielectric
elastomer transducer roll 302 has an outer radius b.sub.o that is
equal to the N rings of thickness t.sub.o:
b.sub.0=Nt.sub.0 Eq. 11
[0104] The area of the film is same whether it is laid out flat
(y.sub.ot) or rolled up into a circle (.pi.b.sup.2.sub.o):
A film = y 0 t = .pi. b 0 2 ( Eq . 12 ) y o t 0 = .pi. ( Nt 0 ) 2 (
Eq . 13 ) Nt 0 = ( y 0 t 0 .pi. ) 1 / 2 ( Eq . 14 ) N = ( y 0 t 0
.pi. ) 1 / 2 ( Eq . 15 ) ##EQU00007##
Volume Inside Each Ring is Conserved
[0105] Volume.sub.0=Volume(.lamda.) Eq. 16
Volume.sub.0=.pi.a.sub.0.sup.2x.sub.0 Eq. 17
Volume(.lamda.)=.pi.a.sup.2 Eq. 18
.pi.a.sub.0.sup.2x.sub.0=.pi.a.sup.2.lamda.x.sub.0 Eq. 19
a.sub.0.sup.2=a.sup.2.lamda. Eq. 20
a.sup.2=.lamda..sup.-1a.sub.0.sup.2 Eq. 21
a=.lamda..sup.-1/2a.sub.0 Eq. 22
Volume of Each Ring Itself is Conserved
[0106] Volume.sub.0=Volume(.lamda.) Eq. 23
Volume.sub.0=.pi.(b.sub.0.sup.2-a.sub.0.sup.2)x.sub.0 Eq. 24
Volume(.lamda.)=.pi.(b.sup.2-a.sup.2).lamda.x.sub.0 Eq. 25
.pi.(b.sub.0.sup.2-a.sub.0.sup.2)x.sub.0=.pi.(b.sup.2-a.sup.2).lamda.x
Eq. 26
(b.sub.0.sup.2-a.sub.0.sup.2)=(b.sup.2-a.sup.2).lamda. Eq. 27
b.sup.2=.lamda..sup.-1(b.sub.0.sup.2-a.sub.0.sup.2)+a.sup.2 Eq.
28
b=(.lamda..sup.-1(b.sub.0.sup.2-a.sub.0.sup.2)+a.sup.2).sup.1/2 Eq.
29
Using the results from Eq. 22, this can be simplified further:
b=(.lamda..sup.-1(b.sub.0.sup.2-a.sub.0.sup.2)+a.sup.2).sup.1/2 Eq.
30
b=(.lamda..sup.-1(b.sub.0.sup.2-a.sub.0.sup.2)+(.lamda.-.sup.1/2a.sub.0)-
.sub.2) Eq. 31
b=(.lamda..sup.-1(b.sub.0.sup.2-a.sub.0.sup.2)+.lamda..sup.-1a.sub.0.sup-
.2).sup.1/2 Eq. 32
b=(.lamda..sup.-1(b.sub.0.sup.2-a.sub.0.sup.2+a.sub.0.sup.2)).sup.1/2
Eq. 33
b=(.lamda..sup.-1b.sub.0.sup.2).sup.1/2 Eq. 34
b=.lamda.-.sup.1/2b.sub.0 Eq. 35
Capacitance of the Annular Capacitor
[0107] Initially the capacitance is:
C 0 = 2 .pi. 0 x 0 ln ( b 0 a 0 ) Eq . 36 ##EQU00008##
[0108] After it has been stretched it becomes longer, so that the
length becomes (.lamda.x.sub.0) and the radii (a and b) are no
longer the initial radii (a.sub.0 and b.sub.0):
C ( .lamda. ) = 2 .pi. 0 x 0 .lamda. ln ( b a ) Eq . 37
##EQU00009##
[0109] Substituting results from Equations 22 and 35 allows the
stretched capacitance to be expressed in terms of initial
geometry.
C ( .lamda. ) = 2 .pi. 0 x 0 .lamda. ln ( b a ) Eq . 38 C ( .lamda.
) = 2 .pi. 0 x 0 .lamda. ln ( .lamda. - 1 / 2 b 0 .lamda. - 1 / 2 a
0 ) Eq . 39 C ( .lamda. ) = 2 .pi. 0 x 0 ln ( b 0 a 0 ) .lamda. Eq
. 40 ##EQU00010##
[0110] Capacitance is expected to vary linearly with the stretch
ratio. To get the force each ring provides note that electrostatic
force depends on the change in capacitance with excursion from
rest.
F elec = V 2 .differential. C .differential. x Eq . 41
##EQU00011##
[0111] Note that the stretch ratio can be expressed in terms of
that excursion from rest.
.lamda. = 1 + x x 0 Eq . 42 C ( x ) = 2 .pi. 0 x 0 ln ( b 0 a 0 ) (
1 + x x 0 ) Eq . 43 ##EQU00012##
[0112] The derivative cancels out the initial length of the
actuator (x.sub.0). This means that the electric force will not be
predicted to change as the length of the actuator changes.
.differential. C .differential. x = 2 .pi. 0 x 0 x 0 ln ( b 0 a 0 )
Eq . 44 .differential. C .differential. x = 2 .pi. 0 ln ( b 0 a 0 )
Eq . 45 F elec = ( 1 / 2 ) V 2 .differential. C .differential. x =
V 2 .pi. 0 ln ( b 0 a 0 ) Eq . 46 ##EQU00013##
[0113] Note that the outer radius b.sub.0 is just the inner radius
(a.sub.0) plus the thickness of the film (t.sub.0).
F elec = ( 1 / 2 ) V 2 .differential. C .differential. x = V 2 .pi.
0 ln ( a 0 + t a 0 ) Eq . 47 ##EQU00014##
[0114] To get the total force we must sum up the contributions of
all N of the rings. Note that each ring has an outer radius that is
one thickness greater than the inner radius.
F total = V 2 .pi. 0 n = 1 N ( ln ( ( n + 1 ) t 0 nt 0 ) ) - 1 Eq .
48 ##EQU00015##
[0115] Canceling Like Terms
F total = V 2 .pi. 0 n = 1 N ( ln ( ( n + 1 ) n ) ) - 1 Eq . 49 F
total = V 2 .pi. 0 n = 1 N ( ln ( n + 1 ) - ln ( n ) ) - 1 Eq . 50
##EQU00016##
[0116] The thickness of a layer has not, in fact, disappeared. It
appears in the upper limit of the series (N). The total number of
layers (N) can be expressed simply in terms of the initial
geometry.
F total = V 2 .pi. 0 n = 1 N ( ln ( n + 1 ) - ln ( n ) ) - 1 ,
where N = ( y 0 t 0 .pi. ) 1 / 2 Eq . 51 ##EQU00017##
[0117] The expected capacitance change is the force expression (Eq.
51) without the Voltage term 1/2 V.sup.2:
.differential. C .differential. x = 2 .pi. 0 n = 1 N ( ln ( n + 1 )
- ln ( n ) ) - 1 , where N = ( y 0 t 0 .pi. ) 1 / 2 Eq . 52
##EQU00018##
[0118] Both of the above are measurable. A candidate example
geometry includes 48.8603 rings or approximately 49 rings.
Accordingly, for approximately 49 rings, a predicted force and
capacitance change rate is:
F elec = .pi. 0 V 2 n = 1 N ( ln ( n + 1 ) - ln ( n ) ) - 1 Eq . 53
F elec = .pi. [ 2.85 ] [ 8.854 E - 12 F / m ] [ 1200 V 2 ] n = 1 49
( ln ( n + 1 ) - ln ( n ) ) - 1 Eq . 54 .differential. C
.differential. x = .pi. [ 2.85 ] [ 8.854 E - 12 F / m ] n = 1 49 (
ln ( n + 1 ) - ln ( n ) ) - 1 Eq . 55 ##EQU00019##
[0119] FIG. 21 is a graphical illustration 306 depicting force 308
provided by each additional ring in a solid dielectric elastomer
transducer roll in accordance with one embodiment of the present
invention. Force [N] is shown along the vertical axis and ring
number is shown along the horizontal axis. Accordingly, the
additional force 308 provided by each ring grows linearly with the
ring number. This is in conformity with expectations, as the area
of each ring scales linearly with circumference. The total force of
0.1426 N approximately matches the total force for a model based on
simpler assumptions: i.e., dielectric stacked, not rolled, (Eq.
56).
[0120] The calculation for parallel layers, not rolled up
provides:
F elec = ( 1 / 2 ) V 2 .differential. C .differential. x = ( 1 / 2
) V 2 0 y i z i Eq . 56 ##EQU00020##
Accordingly, the model provides a measurable prediction for
capacitance change:
dC/dx=Ftot/(0.5*(1200 2))=1.9806e-007 [F/m]
[0121] FIG. 22 is a graphical illustration 310 depicting
capacitance change versus axial displacement of a solid dielectric
elastomer transducer roll in accordance with one embodiment of the
present invention. Capacitance C[F] is shown along the vertical
axis and axial displacement x[mm] is shown along the horizontal
axis. The data substantially agrees with the model. In the
graphical illustration 310 capacitance change in two solid
dielectric elastomer transducer rolls with 10 mm active length are
depicted by curves 312 and 14 mm total length are depicted by
curves 314. A peak dC/dx of 8.91E-8 F/m was observed when the
transducer rolls were in tension. Although this is just
(8.9E-8/1.9806E-7)=44% of the expected dC/dx, the active area did
not really experience all of the displacement. Some of the
displacement was taken up by deformation in the passive 4 mm of the
solid dielectric elastomer transducer roll. To estimate the effect
that this compliance will have on measured dC/dx, two cases may be
considered (1) negligible electrode stiffness and (2) a relatively
large electrode stiffness, for example equal to the film
stiffness.
Case 1--Electrode Negligible
[0122] Assuming that the active and passive areas have equal
stiffness (that is, electrode is negligible), then the observed
dC/dx is scaled by (total:active=14 mm:10 mm). The observed dC/dx
is then (14/10)*([8.9E-8 F/m]/[1.9806E-7 F/m])=63% of expected.
Case 2--Electrode Stiff
[0123] If the stiffness of the electrode is not negligible, then it
must be taken into account. In planar devices, it may be observed
that a standard electrode coating on two sides of a film increases
pseudo-DC stiffness of a film by an amount equivalent to
multiplying Young's modulus of the film by two. The roll is
comprised of two compliances in series. The active Area is 10 mm
long and has two layers of electrode, and the passive 4 mm long and
has one layer.
s1=0.010m/(2*Y_film*Area)
s2=0.004m/(1.5*Y_film*Area)
And the proportion of deformation occurring in the active area
is
.DELTA.x.sub.1/.DELTA.x.sub.tot=(5/(5+2.6667)=0.6522.
[0124] Scaling by this factor, dC/dx is found to be
((1/0.6522)*[8.9E-8 F/m])/[1.98E-7 F/m]=69% of expected. In the
absence of control data measuring electrode stiffness directly,
this provides the best estimate of how the observed capacitance
change relates to the nested ring model.
[0125] FIG. 23 is a graphical illustration 316 depicting blocked
force versus applied voltage response 318 of a solid dielectric
elastomer transducer roll in accordance with one embodiment of the
present invention. The response 318 was obtained by measuring a
sample on an INSTRON instrument for measuring tension/compression,
made by INSTRON of Norwood, Mass., at 1200V and a blocked force at
1200V of 0.102N was observed, as shown in FIG. 23. The blocked
force measurement is ([0.102 N]/[0.1363 N])=74% of the model
prediction.
[0126] FIG. 24 is a graphical illustration 320 depicting blocked
force versus axial displacement demonstrating the difference
between the solid dielectric elastomer transducer roll in
compression versus tension in accordance with one embodiment of the
present invention. Measuring blocked force on the INSTRON
instrument, shows a clear difference between using the solid
dielectric elastomer transducer roll in compression 322 versus
tension 324, consistent with the slope differences observed in
dC/dx. In compression, layers of the solid dielectric elastomer
transducer roll undergo localized buckling rather than uniform
compression. This occurs at forces (0.1 N) lower than the Euler
buckling limit for the entire column (1.5N calculated, 1.4 N
observed).
[0127] FIG. 25 is a graphical illustration 326 of blocked force
versus longitudinal displacement showing the difference between the
solid dielectric elastomer transducer roll in compression 328
versus tension 330 in accordance with one embodiment of the present
invention.
[0128] FIG. 26 is a graphical representation 332 of stiffness of
solid dielectric elastomer transducer rolls in accordance with one
embodiment of the present invention. The simplest prediction of
stiffness for the solid rolls is to neglect electrode stiffness and
the rigid boundary conditions:
k.sub.simple=YA/l=[0.6E6 Pa]*([2*160E-3 m]*[40E-6 m])/[14E-3
m]=548.6 N/m.
[0129] This estimate of the stiffness is relatively good. Observed
stiffness is higher than theoretical by only 6-13% in these two
samples.
[582 N/m,621 N/m]/[548.6 N/m]=[1.06 1.13]
[0130] This suggests that the effect of the electrode on the
stiffness of the solid dielectric elastomer transducer rolls is
relatively small and not the 2.times. factor in the active area
that was considered in the dC/dx calculation above. It appears a
better assumption may be to treat the electrode stiffness as
negligible and to estimate that the observed dC/dx is about 63% of
that expected by the model.
[0131] FIG. 27 illustrates a solid dielectric elastomer transducer
roll 400 in flat roll mode where the roll 400 is placed under
compression 402 in a radial direction rather than in an axial
direction in accordance with one embodiment of the present
invention. As shown, a portion of the solid dielectric elastomer
transducer roll 400 is clamped between jaws 404a, 404b such that is
compresses the transducer roll 400 radially rather axially.
Experimental results indicate that the peak capacitance change
dC/dx in radial ("flat roll") mode is approximately 5-times the
capacitance change dC/dx in axial mode.
[0132] FIG. 28 illustrates a geometric model 410 of a solid
dielectric elastomer transducer roll 412 in radial ("flat roll")
mode where the roll 412 is placed under compression in a radial
direction in accordance with one embodiment of the present
invention. The cross-sectional area of the uncompressed roll 412 is
depicted as a circle in phantom, whereas the cross-sectional area
A(x) of the roll 412' under radial compression is depicted in solid
line as a flattened elongated structure with flat regions in the
center over a length l and rounded ends. The model assumes the
following:
[0133] Long out of plane.fwdarw.Plane strain;
[0134] Incompressible.fwdarw.A(x)=A.sub.0; and
[0135] Flat regions slip.fwdarw.Equal strain around perimeter
P.
[0136] The geometric model for the solid dielectric elastomer
transducer roll 412 in radial mode ("flat roll") is described by
the following equations:
P 0 = .pi. x 0 Eq . 57 P ( x ) = 2 + .pi. ( x 0 - x ) Eq . 58 A 0 =
.pi. 4 x 0 2 Eq . 59 A ( x ) = ( x 0 - x ) + .pi. 4 ( x 0 - x ) 2
Eq . 60 A 0 = A ( x ) Eq . 61 .pi. 4 x 0 2 = ( x 0 - x ) + .pi. 4 (
x 0 - x ) 2 Eq . 62 = .pi. ( x 0 2 - ( x 0 - x ) 2 ) 4 ( x 0 - x )
Eq . 63 P ( x ) = 2 + .pi. ( x 0 - x ) Eq . 64 .lamda. P ( x ) = P
( x ) P = P ( x ) .pi. x 0 Eq . 65 C = C 0 .lamda. P 2 Eq . 66
##EQU00021##
[0137] FIG. 29 is a graphical illustration 414 depicting stretch
ratio versus percent compression in a radial direction of a solid
dielectric elastomer transducer roll in accordance with one
embodiment of the present invention. Stretch ration [L/L.sub.0] is
shown along the vertical axis and percent compression [x/x.sub.0]
is shown along the horizontal axis. The curve 416 shows non-linear
behavior of stretch ration versus percent compression.
[0138] FIG. 30 illustrates a static equilibrium diagram 418 of a
solid dielectric elastomer transducer roll 420 in radial
compression ("flat roll") mode under static load in accordance with
one embodiment of the present invention. Static equilibrium is
defined as follows:
F.sub.elec+F.sub.S+F.sub.L=0 Eq. 67
where F.sub.elec is electric force, F.sub.S is spring force and
F.sub.L is an external load. The electric force is proportional to
the capacitance change dC/dx which is in turn proportional to the
stretch ratio of the dielectric layers .lamda.=P/P.sub.0. Because
this stretch is approximately quadratic with respect to compression
of the roll, (FIGS. 29 and 31), the electric force, which is the
slope of the capacitance curve, can be approximated with a single
constant such that dC/dx=k.sub.1x. The spring force is also
approximated well with a single term such that
F.sub.s=k.sub.3x.sup.2
1/2V.sup.2(k.sub.1x)+k.sub.3x.sup.2+F.sub.L=0 Eq. 68
k.sub.1V.sup.2/2 x+k.sub.3x.sup.2+F.sub.L=0 Eq. 69
k.sub.3x.sup.2+(1/2k.sub.1V.sup.2)x+F.sub.L=0 Eq. 70
The equilibrium displacement of the roll subjected to the static
load is found from the roots of the quadratic equation, where
a=k.sub.3, b=1/2 k.sub.1V.sup.2 and c=F.sub.L.
x=[-b.+-. (b.sup.2-4ac)]/2a Eq. 71
The Pseudo-DC Roll Model
[0139] F.sub.elec=1/2V.sup.2dC/dx Eq. 72
F.sub.elec=1/2V.sup.2(k.sub.1x) Eq. 73
F.sub.S=k.sub.3x.sup.2 Eq. 74
F.sub.L=-4,[N],for example.
[0140] FIG. 31 is a graphical illustration 422 depicting
capacitance versus compression in a radial direction of a solid
dielectric elastomer transducer roll in flat roll mode in
accordance with one embodiment of the present invention.
Capacitance C[F] is shown along the vertical axis and compression
x[m] is shown along the horizontal axis. The flat roll model curve
424 provides a reasonable first approximation of the capacitance
change versus compression as compared to the measurements results
426. Potential contributors to the difference between actual
measurements 426 and the model 424 may be that just 7.5 mm of 10 mm
active length was compressed in an INSTRON test instrument and the
rigid boundary may limit extension of the outer layers.
[0141] FIGS. 32A, 32B, 32C and 32D illustrate a solid dielectric
elastomer transducer roll 430 under increasing compression force in
a radial direction in accordance with one embodiment of the present
invention. From left to right, the solid dielectric elastomer
transducer roll 430 undergoes increasing compression force such
that the roll 430 in under no compression force, roll 430' is under
greater compression force than the roll 430, roll 430'' is under
greater compression force than the roll 430', and the roll 430'''
is under greater compression force than the roll 430''. As shown in
FIGS. 32B, 32C and 32D, the roll begins to delaminate as it is
subjected to increasing greater compression forces. This
delamination causes deviation from the model, and presents a
practical limit on compression of the roll.
[0142] FIG. 33 illustrates a finite element analysis model 432 of a
solid dielectric elastomer transducer roll 434 undergoing radial
compression in accordance with one embodiment of the present
invention and indicates where stretch orientation is and is not
well-aligned with the orientation of the layers.
[0143] FIG. 34 illustrates the delamination of inner layers 434 of
a solid dielectric elastomer transducer roll 436 undergoing radial
compression in accordance with one embodiment of the present
invention. As the finite element analysis predicts, delamination
occurs in regions where the principal stretch is oriented through
the thickness of dielectric films.
[0144] As for other details of the present invention, materials and
alternate related configurations may be employed as within the
level of those with skill in the relevant art. The same may hold
true with respect to process-based aspects of the invention in
terms of additional acts as commonly or logically employed. In
addition, though the invention has been described in reference to
several examples, optionally incorporating various features, the
invention is not to be limited to that which is described or
indicated as contemplated with respect to each variation of the
invention. Various changes may be made to the invention described
and equivalents (whether recited herein or not included for the
sake of some brevity) may be substituted without departing from the
true spirit and scope of the invention. Any number of the
individual parts or subassemblies shown may be integrated in their
design. Such changes or others may be undertaken or guided by the
principles of design for assembly.
[0145] Various aspects of the subject matter described herein are
set out in the following numbered clauses in any combination
thereof:
[0146] 1. A method for making a rolled dielectric elastomer
transducer, comprising: applying an electrode material on a first
side and a second side of a first dielectric film; laminating the
first dielectric film onto a side of a second dielectric film to
produce a dielectric film laminate; and rolling the dielectric film
laminate into a solid dielectric elastomer transducer roll.
[0147] 2. The method according to claim 1, wherein applying the
electrode material comprises applying at least a first layer of
electrode material on the first side of the first dielectric film;
and applying at least a second layer of the electrode material on
the second side of the first dielectric film; and wherein the at
least first layer and the at least second layer of the electrode
material are offset relative to each other.
[0148] 3. The method according to claim 2, further comprising
applying at least one additional first layer of electrode material
juxtaposed and spaced apart from the at least one first layer of
the electrode material on the first side of the first dielectric
film, wherein the at least one additional first layer of electrode
material on the first side of the first dielectric film partially
overlaps the at least one second layer of the electrode material on
the second side of the first dielectric film.
[0149] 4. The method according to claim 3, further comprising
segmenting the solid dielectric elastomer transducer roll into two
or more individual solid dielectric elastomer transducer rolls at
the region where the at least one additional first layer on the
first side of the first pre-strained dielectric film overlaps with
the at least one second layer of the electrode material on the
second side of the first pre-strained dielectric film.
[0150] 5. The method according to any one of claims 1 to 4, further
comprising pre-straining the first and second dielectric films.
[0151] 6. The method according to any one of claims 1 to 5, further
comprising applying an electrically conductive adhesive on a first
end and a second end of the solid dielectric elastomer transducer
roll; and applying an electrical terminal on the first and second
ends of the solid dielectric elastomer transducer roll.
[0152] 7. The method according to claim 6, further comprising
applying a solvent on the first and second ends of the solid
dielectric elastomer transducer roll prior to applying the
electrically conductive adhesive.
[0153] 8. An apparatus, comprising a drive mechanism for receiving
a carrier plate having a dielectric film laminate located on a
first surface thereof, the drive mechanism configured to drive the
carrier plate in a first direction; and a scrub roller configured
to counter-rotate in a second direction relative to the first
direction, the scrub roller configured to frictionally engage the
dielectric film to wind the dielectric film laminate into a solid
dielectric elastomer transducer roll.
[0154] 9. The apparatus according to claim 8, further comprising a
motion control system for controlling the velocity of the drive
mechanism and the scrub roller.
[0155] 10. The apparatus according to claim 9, wherein the motion
control system is configured to control the velocity of the carrier
plate V.sub.plate in the first direction and the velocity of the
scrub roller V.sub.scrub in the second opposite direction such that
|V.sub.plate|=|V.sub.scrub|.
[0156] 11. The apparatus according to claim 9, wherein the motion
control system is configured to control the velocity of the carrier
plate V.sub.plate in the first direction and the velocity of the
scrub roller V.sub.scrub in the second opposite direction and to
compensate for the velocity of the solid dielectric elastomer
transducer roll such that |V.sub.plate|-V.sub.roll,
x|=|V.sub.scrub|.
[0157] 12. The apparatus according to claim 9, wherein the motion
control system is configured to control the velocity of the carrier
plate V.sub.plate in the first direction and the velocity of the
scrub roller V.sub.scrub in the second opposite direction and to
compensate for the velocity of the solid dielectric elastomer
transducer roll and to compensate for dielectric film stretch
defined by a stretch coefficient "k" caused by peel stress such
that |V.sub.plate|-V.sub.roll, x|=k|V.sub.scrub|.
[0158] 13. The apparatus according to claim 9, further comprising
at least one sensor to sense force and provide a closed loop
feedback mechanism to the motion control system.
[0159] 14. The apparatus according to any one of claims 9 to 13,
further comprising a covering positioned over an outside surface of
the scrub roller.
[0160] 15. The apparatus according to claim 14, wherein the
covering is made of a non-stick material.
[0161] Also, it is contemplated that any optional feature of the
inventive variations described may be set forth and claimed
independently, or in combination with any one or more of the
features described herein. Reference to a singular item, includes
the possibility that there are plural of the same items present.
More specifically, as used herein and in the appended claims, the
singular forms "a," "an," "said," and "the" include plural
referents unless the specifically stated otherwise. In other words,
use of the articles allow for "at least one" of the subject item in
the description above as well as the claims below. It is further
noted that the claims may be drafted to exclude any optional
element. As such, this statement is intended to serve as antecedent
basis for use of such exclusive terminology as "solely," "only" and
the like in connection with the recitation of claim elements, or
use of a "negative" limitation. Without the use of such exclusive
terminology, the term "comprising" in the claims shall allow for
the inclusion of any additional element--irrespective of whether a
given number of elements are enumerated in the claim, or the
addition of a feature could be regarded as transforming the nature
of an element set forth in the claims. Stated otherwise, unless
specifically defined herein, all technical and scientific terms
used herein are to be given as broad a commonly understood meaning
as possible while maintaining claim validity.
* * * * *