Note: Descriptions are shown in the official language in which they were submitted.
CA 02510881 2005-06-14
ldBTHOD OF SEALING 1~C8INL COL~PONSNTS
FIELD OF THE INVENTION
This invention relates to a method of sealing machine
components using electroactive materials. These materials
are generally polymers and have the property of changing
their geometry and dimensions when subjected to a voltage
or electrical field.
BACKGROUND OF THE INVENTION
Sealing concepts are typically based on compression and
interference of some sealing surfaces or deformation of a
generally elastic material placed between them in order to
perform sealing. Movable machine components sealing
requires additional energy consumption and oversized
actuators in order to overcome the frictions that accompany
sealing processes. For example, in the case of a butterfly
valve, a bubble tight sealing between the disc and valve's
body may consist of interference between the disc's
circumference and a soft material on the valve's body.
Material interference drives supplementary energy
consumption generally provided by oversized actuators that
are capable of providing the extra energy in order to
overcome friction loses.
In the past, several devices using electroactive materials
where invented, but none were developed for the purpose of
sealing machine components. The following U.S. Patents,
6,109,852 6,249,076: 6,405,532: 6,475,639; 6,495,642;
6, 545, 384 6, 569, 654: 6, 583, 533; 6, 586, 859; 6, 626, 417;
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6, 679, 836; 6, 664, 718; 6, 682, 500 relate to a variety of
electroactive polymer devices and their specific fields of
application.
BRIEF SUMMARY OF THE INVENTION
A first objective of this invention is to define a sealing
method that virtually eliminates most friction and
deformation losses during a sealing process. More
particularly, this method consists of using electroactive
polymers capable of ensuring adequate sealing, and of
minimizing the energy consumption.
Another objective of this invention is to optimize
machinery actuators, releasing them from the burden of
supplying extra energy for sealing.
This invention presents a method of sealing machine
components using electroactive materials that can be
energized independently through a driver or a separate
electric circuit.
Typically an electroactive polymer actuator is made from
films of electroactive polymers coated on both sides with a
compliant electrode material. When a voltage is applied,
the polymer film can compress in thickness and expands in
area. Both changes convert electrical energy to mechanical
energy and provide the actuation mechanism. Depending on
the nature of the electro-active polymers, this actuation
mechanism can withstand large strains, produce high
actuation pressures and have fast response times.
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According to this invention, an electroactive polymer is
placed between two or more machine components that need to
be sealed. The cross-section of the electroactive polymer
compresses and expands its surface when a voltage is
applied across it. When the voltage is on, electro-active
polymer can expand filling up the gap between the adjacent
sealing surfaces and therefore providing sealing. When the
voltage is off, the electro-active polymer shrinks back to
its initial shape allowing the two machine parts to be
moved without sealing related friction. A mirror function
of this mechanism would be to have the electroactive
polymer accomplish sealing in its passive state, while
relaxing the component fit in the active state.
More particularly, the object of this invention is to
provide a method of sealing at least two machine components
having associated sealing surfaces and one or more
electroactive polymer actuators that change their geometry
in such a way to seal the machine parts when a voltage or
electric field is applied. Electroactive polymer actuators
can provide a number of advantages:
1. Quality sealing for machine parts without interference
frictions
2. Zonger lifetime
3. Control geometry and shape
4. Cost reduction for actuators
5. Control position of mobile parts.
6. Simplify assembly of machine parts
7. Improve manufacturability of machine parts
8. Decrease overall cost of a sealing
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BRIEF DESCRIPTION OF THE DRAWINGS
Figs. 1 (a, b) show cross-sectional views through three
machine parts 1, 2 and 3 that are sealed with an
electroactive polymer actuator 4 placed between their
sealing surfaces.
Fig. 1 (c) shows a cross-section through a pair of parts 5
and 6 and an electroactive polymer 4 that provides a normal
compression force.
Figs. 2 (a, b, c) show a front and two cross-sectional
views of a butterfly valve that has an electroactive ,
polymer actuator strip 4 mounted into the valve body 7, in
the vicinity of the disc 8 circumference when the disc is
in closed position.
Fig. 3 shows a cross-sectional view through a knife valve
that has a knife plate 12 sealed on both faces by two rings
4 of electroactive polymers.
Figs. 4 (a, b, c) show a pinch valve embodying this
invention that consists of an electroactive polymer 4
attached to a hose 13.
DETAILED DESCRIPTION OF THE PREFERED EMBODIMENT
Figs. 2 (a, b, c) illustrate the basic elements of the
preferred embodiment of this invention. A butterfly valve
has a circumferential groove machined into its body 7
around the disc 8 circumference when closed. On this groove
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there is installed an annular band 4 made out of an
electroactive polymer which may or may not be covered by a
protective elastic membrane 10.
When the valve is closed and a seal is required, the
voltage is removed from the electro-active polymer strip 4.
These electroactive polymers then relax and interfere with
the disc 8 around the disc circumference. When the valve
needs to open, a voltage is applied to the electro-active
polymer actuator 4 that compresses and therefore allows
disc 8 to move freely. The valve actuator then rotates disc
8 via torque transmission through shaft 9. The driver of
the electro-active polymer actuator can turn off the
circuit in order to stop disc 8 in a desired intermediate
open position. A mirror function of this mechanism would be
to have the electroactive polymer ring 4 accomplish sealing
in its active state when energized, while relaxing the
component fit in its passive state.
This invention provides an optimized valve packaging at a
lower cost, since the valve main actuator is no longer
required to deliver the extra torque to overcome friction
and elastic deformation of sealing materials.
As is shown in Fig. 3, a knife 12 can move freely up and
down when the electro-active polymer actuator rings axe
energized (radially expanded). According to this
embodiment, de-energizing rings 4 (axially expanded) they
interfere with knife 12 and can stop it in any desired
intermediate position. In closed position, the pair of
electro-active polymer bands 4 seals the knife 12.
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In the Figs. 4 (a, b, c), the electro-active polymer
actuator 4 is connected to a hose 13. Energizing the
electro-active polymer actuator 4, compresses the material
and seals the circuit as in Fig. 4b. De-energizing the
electro-active polymer allows it to expand to its natural
state, thus increasing the cross-sectional area of the
passage. The electro-active polymer geometry and thus the
cross sectional area can be manipulated as desired by
varying the applied voltage.
According to Fig. lc, an electro-active polymer belt 4 can
provide a compressing force in order to accomplish sealing
between sealing faces of parts 5 and 6.
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