THERMAL MANAGEMENT SYSTEMS FOR SOLID STATE
LIGHTING AND OTHER ELECTRONIC SYSTEMS
CROSS-REFERENCE TO OTHER APPLICATIONS
[0001] This application claims priority of U.S. Provisional Patent Application No.
61/376,866, entitled "Thermal Management Systems for Solid State Lighting and
Other Electronic Systems," filed August 25, 2010, which is herein incorporated in its
entirety by reference.
BACKGROUND OF THE INVENTION
The present invention relates to the illumination arts, lighting arts, solid
state lighting arts, electronics arts, thermal management arts, and related arts.
[0002] Solid state lighting presents substantial thermal management issues due to
the heat sensitivity and low optimal operating temperature of many solid state lighting
devices, combined with low radiative and convective cooling efficiency due to the
low optimal operating temperature. For example, light emitting diode (LED) devices
typically have an optimal operating temperature of about 100 °C or lower, at which
temperatures radiative and convective heat transfer away from the LED devices is
inefficient.
[0003] Passive cooling solutions relying upon a large heat sink in thermal
communication with the solid state lighting devices is of limited effectiveness. Active
cooling can be more effective. For example, synthetic jets have been employed for
cooling in solid state lighting. See, e.g., Arik et al, U.S. Pub. No. 2004/0190305 Al,
which is herein incorporated in its entirety by reference; Bohler et al, Int'l. Appl. No.
WO 2004/100213 A2, which is herein incorporated in its entirety by reference.
Synthetic jets have also been employed in other cooling applications such as cooling
of electronic modules. However, synthetic jets or other active cooling (e.g., fan based
cooling, see e.g. Cao, U.S. Pat. No. 6,465,961) have substantial disadvantages in solid
state lighting applications. The active cooling system occupies valuable space, which
is especially problematic in compact lighting units and/or self contained lighting units
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such as retrofit lamps or light bulbs in which the electronics for driving the solid state
lighting devices off of wall voltage (e.g., 110V a.c. or 220V a.c.) are integrated into
the lighting unit. Positioning of the active cooling sub system in a way that is
sufficiently proximate to the solid state lighting devices in order to provide cooling
while not blocking the optical path is also problematic.
BRIEF DESCRIPTION OF THE INVENTION
[0004] In a first embodiment, an apparatus includes at least one electronic
component. The apparatus also includes an enclosure enclosing the at least one
electronic component. The enclosure includes at least one wall defined by a
membrane. The apparatus further includes an electromechanical transducer
configured to generate a pulsating mechanical deformation of the membrane. The
apparatus also includes one or more openings in the enclosure for facilitating volume
displacement of air from within the enclosure. The volume displacement of air is
provided by the pulsating mechanical deformation of the membrane.
[0005] In a second embodiment, a piezoelectric actuated assembly includes a first
piezoelectric actuator that is fixed at a first end of the first piezoelectric actuator. The
piezoelectric actuated assembly also includes a second piezoelectric actuator that is
fixed at a first end of the second piezoelectric actuator. The piezoelectric actuated
assembly further includes a compliant sheet having a first end that is rigidly attached
to a second end of the first piezoelectric actuator, and a second end that is rigidly
attached to a second end of the second piezoelectric actuator. Application of
alternating current to the first and second piezoelectric actuators generates a pulsating
mechanical deformation of the compliant sheet.
[0006] In a third embodiment, an apparatus includes at least one electronic
component. The apparatus also includes an enclosure enclosing the at least one
electronic component. The enclosure includes at least one wall defined by a
membrane. The apparatus further includes a piezoelectric actuator that is fixed at a
first end and rigidly attached to the membrane at a second end. Application of
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alternating current to the piezoelectric actuator generates a pulsating mechanical
deformation of the membrane.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] These and other features, aspects, and advantages of the present invention
will become better understood when the following detailed description is read with
reference to the accompanying drawings in which like characters represent like parts
throughout the drawings, wherein:
[0008] FIG. 1 is a sectional side view of an embodiment of a directional lamp
having a plurality of light emitting diode (LED) devices on a circuit board, a
collecting reflector, a Fresnel lens, an optical membrane, and one or more transducers
for generating a reciprocating displacement of the optical membrane;
[0009] FIG. 2 is a sectional side view of an embodiment of the directional lamp of
FIG. 1 having openings for enabling synthetic jets from an interior air volume
between the Fresnel lens and the optical membrane;
[0010] FIG. 3 is a sectional side view of an embodiment of the directional lamp of
FIG. 1 wherein the optical membrane comprises the Fresnel lens;
[0011] FIG. 4 is a sectional side view of an embodiment of the directional lamp of
FIG. 1 having one or more transducers for generating a reciprocating displacement of
the collecting reflector;
[0012] FIG. 5 is a perspective view of an embodiment of a panel lamp having
LED devices disposed in a plane in a rectangular housing having a top wall as a
transparent or translucent optical membrane, and one or more transducers for
generating a reciprocating displacement of the optical membrane;
[0013] FIG. 6 is a perspective view of an embodiment of a linear lamp having a
linear array of LED devices disposed in a tubular housing as a transparent or
translucent optical membrane, and one or more transducers spaced along the tubular
housing for generating a reciprocating displacement of the optical membrane;
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[0014] FIG. 7 is a perspective view of an embodiment of an omindirectional lamp
having LED devices on a circuit board, a transparent or translucent optical membrane
horizontally spanning a bulb-shaped envelope of the omindirectional lamp, and one or
more transducers disposed on the bulb-shaped envelope of the omindirectional lamp
for generating a reciprocating displacement of the optical membrane;
[0015] FIG. 8 is a perspective view of an embodiment of an omindirectional lamp
having a bulb-shaped outer transparent or translucent optical element as an optical
membrane, a rigid bulb-shaped inner transparent or translucent optical element, a
plurality of heat sinking fins disposed between the inner and outer optical elements,
and a plurality of transducers for inducing mechanical deformation of the outer optical
element;
[0016] FIG. 9 is a perspective view of an embodiment of an electronic component
cooling application having a plurality of electronic devices disposed on a circuit board
and enclosed in an enclosure having a top wall as a transparent or translucent optical
membrane, and one or more transducers for generating a reciprocating displacement
of the optical membrane;
[0017] FIG. 10 is a perspective view of an embodiment of an LFL replacement
tube having LED devices disposed in two linear arrays on opposite sides of a printed
circuit board that extends through a transparent or translucent housing or enclosure,
which acts as an optical membrane;
[0018] FIG. 11A is a perspective view of an embodiment of a cylindrical tube
made of a flexible material and having a piezoelectric film applied to the flexible
material;
[0019] FIG. 11B is a perspective view of the cylindrical tube when the
piezoelectric film causes the cylindrical tube to shorten;
[0020] FIG. llC is a perspective view of the cylindrical tube of FIG. 11A when
the piezoelectric film causes the cylindrical tube to lengthen;
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[0021] FIG. 12 is a perspective view of an embodiment of an outer transparent or
translucent tube that surrounds the LFL replacement tube of FIG. 10;
[0022] FIG. 13 is a sectional side view of an embodiment of a piezoelectric
optical membrane that may be activated to experience a linear displacement;
[0023] FIG. 14 is a sectional side view of an embodiment of a piezoelectric
actuated assembly in a neutral position including a compliant sheet rigidly attached to
opposing first and second piezoelectric actuators;
[0024] FIG. 15 is a sectional side view of the embodiment of the piezoelectric
actuated assembly of FIG. 14 when the compliant sheet is in a first deformation state;
[0025] FIG. 16 is a sectional side view of the embodiment of the piezoelectric
actuated assembly of FIG. 14 when the compliant sheet is in a second deformation
state;
[0026] FIG. 17 is a sectional side view of an embodiment of a preloaded
piezoelectric actuated assembly during construction of the preloaded piezoelectric
actuated assembly;
[0027] FIG. 18 is a sectional side view of the embodiment of the preloaded
piezoelectric actuated assembly of FIG. 17 wherein the compliant sheet is mounted to
the first and second piezoelectric actuators while a direct current is applied to the first
and second piezoelectric actuators;
[0028] FIG. 19 is a sectional side view of the embodiment of the preloaded
piezoelectric actuated assembly of FIG. 18 in a neutral position once the direct current
has been removed from the first and second piezoelectric actuators;
[0029] FIG. 20 is a sectional side view of the embodiment of the preloaded
piezoelectric actuated assembly of FIG. 19 when the compliant sheet is in a first
deformation state;
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[0030] FIG. 2 1 is a sectional side view of the embodiment of the preloaded
piezoelectric actuated assembly of FIG. 19 when the compliant sheet is in a second
deformation state;
[0031] FIG. 22 is a sectional side view of an embodiment of a weighted
piezoelectric actuated assembly that uses additional weight that has been added to the
compliant sheet and is in a first deformation state;
[0032] FIG. 23 is a sectional side view of the embodiment of the weighted
piezoelectric actuated assembly of FIG. 22 in a second deformation state;
[0033] FIG. 24 is a sectional side view of an embodiment of the preloaded
piezoelectric actuated assembly described above with respect to FIGS. 17-21 that is
disposed within a housing having at least one air inlet opening and at least one air
outlet opening; and
[0034] FIG. 25 is a partial sectional side view of an embodiment of the directional
lamp of FIG. 1 taken within line 25-25, which utilizes a piezoelectric actuated
assembly as described above with respect to FIGS. 14-24.
DETAILED DESCRIPTION OF THE INVENTION
[0035] With reference to FIG. 1, a sectional side view of a directional lamp 10
having rotational symmetry about an optical axis OA is shown, which includes a
plurality of light emitting diode (LED) devices 12 on a circuit board 14, a collecting
reflector 16 which in the illustrative embodiment is conical (although other shapes are
contemplated, such as parabolic or compound parabolic), and a Fresnel lens 18. More
generally, the LED devices 12 can be replaced by one or more other solid state
lighting devices, such as one or more organic LED (OLED) devices, one or more
electroluminescent (EL) devices, or so forth. In a typical configuration, the light
engine 12, 14 is arranged at about the focal length of the Fresnel lens 18 so that the
lens 18 images the light engine at infinity so as to form a directional beam. The
collecting reflector 16 collects large angle light, and may also optionally provide
collimation to assist in forming the beam. In some embodiments, the lens 18 is
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omitted and the reflector 16 alone is relied upon to form the directional light beam. In
another alternative, the lens may be located elsewhere than where shown in FIG. 1,
such as proximate to the LED devices 12. Not shown are additional components such
as electronics, which may be disposed in a module "behind" the light engine 12, 14,
for example in a connector portion 19 (shown in phantom in FIG. 1, and also
including an optional "Edison-type" base for connection of the lamp 10 with a
standard socket).
[0036] An optical membrane 20 is disposed in the beam path. As illustrated, in
certain embodiments, the optical membrane 20 is disposed inside the Fresnel lens 18
(e.g., on the same side of the Fresnel lens 18 as the LED devices 12). However, in
other embodiments, the optical membrane 20 may be disposed outside of the Fresnel
lens 18 (e.g., on an opposite side of the Fresnel lens 18 from the LED devices 12).
The optical membrane 20 is optically transparent or translucent. In some
embodiments, the optical membrane is a transparent or translucent optical window. In
some embodiments, the optical membrane 20 acts optically as a light diffuser by
including diffusing particles or making the membrane 20 of a light scattering material,
or by providing the membrane 20 with a roughened or otherwise light scattering or
light refracting surface, or so forth.
[0037] It is also additionally or alternatively contemplated for the optical
membrane 20 to be a wavelength converting element including, for example, at least
one phosphor compound, or a quantum dot wavelength converter, or so forth. In
some such embodiments, the LED devices 12 may generate white, blue, violet, or
ultraviolet light and the phosphor of the optical membrane 20 is selected such that the
output light (which may be entirely wavelength converted by the phosphor or may be
a mixture of direct and wavelength converted light) is white light. Still further, the
optical membrane 20 may additionally or alternatively provide other optical
functionality, such as providing an anti reflection coating, wavelength selective
filtering to remove ultraviolet light or other light that may be undesirable in the
directional light beam, or so forth.
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[0038] The optical membrane 20 also serves a secondary purpose (besides being
an optical window or other optical element) - the optical membrane 20 serves as an
active cooling element. Toward this end, at least one electromechanical transducer 22
is configured to generate a force or small reciprocating linear displacement dx causing
a pulsating mechanical deformation of the optical membrane 20. The
electromechanical transducer(s) can comprise a plurality of transducers at the
periphery of the optical membrane 20 and spaced at angular intervals around the
optical axis OA, or a single annular transducer may be disposed at the membrane
periphery. In the illustrative embodiment, the transducer 22 generates the
reciprocating linear displacement dx in the plane of the membrane 20 with all
displacements being in phase (e.g., all displacing "inward" at the same instant) so as
to cause the optical membrane 20 to undergo an "up/down" motion indicated by an
up/down arrow 24. In some embodiments, the pulsating mechanical deformation of
the membrane 20 takes the form of excitation of a resonant standing wave drum
membrane mode in the optical membrane 20. Additionally or alternatively, the
pulsating mechanical deformation may include various patterns, and may or may not
be resonant. Still further, it is contemplated for the transducer(s) 22 to generate
displacements in a direction transverse to the membrane, or in a direction intermediate
between in plane and transverse respective to the membrane, or to produce some other
complex motion leading to a pulsating mechanical deformation of the membrane.
The term "pulsating" is intended to broadly encompass periodic motion (for example,
sinusoidal motion, oscillating motion, or a periodic pulse train), quasi periodic motion
(for example, a pulse train in which the pulse frequency varies with time), non
periodic motion such as stochastic motion, or so forth.
[0039] The pulsating mechanical deformation produces a volume displacement of
air with a frequency or other time variation corresponding to the pulsating. This
provides air movement that actively cools the at least one solid state lighting device
(e.g., the illustrative LED devices 12). The active cooling of the solid state lighting
device may operate directly on the solid state lighting device, or indirectly by actively
cooling a heat sink in thermal communication with the solid state lighting device. In
some embodiments, the optical membrane 20 forms at least one wall of an enclosure.
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The term "enclosure" here means a set of walls, surfaces, elements, or so forth which
encloses a volume, or a solid having a cavity enclosing a volume, or so forth, in which
the enclosed volume is substantially airtight except for one or more optional openings
defining synthetic jets or other airflow paths as disclosed herein. The term
"enclosure" as used here is not limited to an external housing or outermost enclosure.
In the illustrative example, the optical membrane 20 and the collecting reflector 16
cooperatively form an enclosure enclosing a volume 26, which is typically filled with
air (although filling with another fluid is also contemplated). The volume
displacement of air provided by the pulsating mechanical deformation of the optical
membrane 20 produces movement of the fluid in the constricted space of the volume
26. In the illustrative example of FIG. 1, it will be noted that a second, smaller air
space 27 is located between the Fresnel lens 18 and the optical membrane 20. This
smaller air space is optionally vented to the exterior, for example via holes in or at the
periphery of the lens 18, so that the air space 27 does not create viscous or flow
resistance to the pulsating mechanical deformation of the membrane 20.
[0040] In some embodiments, the enclosure defined in part by the membrane 20 is
further provided with one or more openings 30 which allow air flow
(diagrammatically indicated for one opening in FIG. 1 by a double arrow F, but
understood to occur at all the openings 30) into or out of the enclosed volume 26. In
some such embodiments, the openings 30 and the membrane 20 cooperate to define
synthetic jets at the openings 30. The volume displacement of air provided by the
pulsating mechanical deformation of the optical membrane 20 and a size of the at
least one opening 30 are selected such that the volume displacement of air provided
by the pulsating mechanical deformation of the optical membrane 20 produces at least
one synthetic jet. To accomplish this, the volume displacement of air should be large
enough, and the opening or openings 30 small enough, so that the volume
displacement of air accelerates air flow into or out of the opening or openings 30, thus
forming one or more synthetic jets. In general, a larger volume displacement of air
increases the air acceleration of the synthetic jet or jets, and similarly a smaller total
area of the opening or openings 30 increases the air acceleration of the synthetic jet or
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jets. The synthetic jet or jets are arranged to enhance air cooling of the at least one
solid state lighting device (e.g., the illustrative LED devices 12).
[0041] In FIG. 1, the synthetic jets enhance air cooling of the LED devices 12
indirectly, by arranging the openings 30 to produce air flow or air turbulence
proximate to heat fins 32 spaced apart around the collecting reflector 16. Without
loss of generality, there are N heat fins spaced apart around the collecting reflector 16
at angular intervals of 360°/N. Note that in this case the rotational symmetry of the
directional lamp 10 is an N fold rotational symmetry. The heat fins 32 are in thermal
communication with the LED devices 12 via the circuit board 14 (which optionally
includes a metal core in thermal communication with the heat sinking fins 32). The
acceleration of air proximate to the heat fins produce air flow and turbulence that
promotes heat transfer from the heat fins to the surrounding ambient by air
convection. The advantage of active cooling is seen in the heat removal equation
Q =hAAT , where A denotes the surface area over which the thermal transfer to
ambient occurs and AT denotes the difference between the temperature of that
surface and the ambient temperature. In general, AT is substantially fixed by the
operating temperature of the solid state lighting device and the ambient temperature.
Thus, AT is usually not available as a design parameter. The surface area A can be
increased to increase the rate of heat removal, as is conventionally done by adding
fins or other surface area enhancing heat dissipating structures to a heat sink. The
parameter h , known as the heat transfer coefficient, is controlled by convective air
flow in passive cooling, and is difficult or impossible to adjust in the passive
configuration. However, by employing active cooling such as a synthetic jet or jets,
the air flow can be substantially increased, sometimes by orders of magnitude, and the
heat transfer coefficient h and consequently the heat transfer rate Q is
correspondingly increased.
[0042] FIG. 2 differs from FIG. 1 in that the openings 30 of FIG. 1 are replaced
by openings 30' placing the smaller air volume 27 enclosed between the lens 18 and
the membrane 20 into fluid communication with the exterior. The openings 30' are
curved so that the synthetic jets are directed downward over the heat sinking fins 32.
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FIG. 3 differs from FIG. 1 in that instead of having the optical membrane 20 and the
separate lens 18, a lens 20' is the optical membrane. A modified electromechanical
transducer 22' operates on the lens/optical membrane 20' to produce the reciprocating
linear displacement dx, this time of the combined lens/optical membrane 20' so as to
drive a pulsating mechanical deformation of the lens/optical membrane 20' as
diagrammatically represented by an up/down arrow 24'. In each of FIGS. 1-3, the
optical membrane 20, 20' is optically transparent or translucent. However, the optical
membrane can have other optical functionality.
[0043] With reference to FIG. 4, a variant embodiment is shown in which an
optical membrane 20" is optically reflective and takes the form of the collecting
reflector. A modified electromechanical transducer 22" operates on the optical
membrane/collecting reflector 20" to generate a generally inward/outward pulsating
mechanical deformation of the optical membrane/collecting reflector 20" as
diagrammatically represented by the double arrows 24". The embodiment of FIG. 4
employs the openings 30 in the optical membrane/collecting reflector 20" to provide
the synthetic jets. In the embodiment of FIG. 4, the conventional Fresnel lens 18
(which does not act as a membrane for cooling) is used. The illustrative transducer(s)
22" produce reciprocating force in the direction normal to the surface of the
membrane/reflector 20". In an alternative configuration, transducers 22"' at opposite
ends of the membrane/reflector 20" produce reciprocating force in the plane of the
reflector surface, so as to produce the pulsating mechanical deformation 24" as a
"buckling" of the membrane/reflector 22".
[0044] Furthermore, in other embodiments, the optical membrane 20" may be
optically transmissive or translucent, and may be spaced apart from (and, in certain
embodiments, generally parallel to) the reflector 16 of FIGS. 1-3, thereby providing a
gap between the optical membrane 20" and the reflector 16. In such an embodiment,
the optical membrane 20" may pulsate in the same manner as the optical membrane
20" illustrated in FIG. 4. However, the air within the gap between the optical
membrane 20" and the reflector 16 will be forced out through openings 30 in the
reflector 16. Furthermore, in certain embodiments, both the optical membrane 20"
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and the reflector 16 may include openings 30, thereby providing two levels of air
volume displacement from within the volume 26.
[0045] The pulsating mechanical deformation 24, 24', 24" of the optical
membrane 20, 20', 20" is intended to provide cooling. It is generally undesirable for
this pulsating to produce audible sound. Accordingly, in some embodiments,
frequency components of the pulsating mechanical deformation at frequencies higher
than 1500 Hz comprise no more than 10% of the total amplitude of the pulsating
mechanical deformation, and in some embodiments no more than 5% of the total
amplitude of the pulsating mechanical deformation, and in some embodiments no
more than 2% of the total amplitude of the pulsating mechanical deformation. More
generally, it is advantageous to have the pulsating mechanical deformation at a
frequency or frequency range that is below the audible range. In some embodiments,
the electromechanical transducer 22, 22', 22" is configured to generate the pulsating
mechanical deformation of the optical membrane at a dominant frequency (i.e., the
frequency component of excitation with the highest amplitude) of less than 100 Hz,
and more preferably at a dominant frequency of 60 Hz or lower. In some
embodiments, the electromechanical transducer 22, 22', 22" is configured to generate
the pulsating mechanical deformation of the optical membrane at a dominant
frequency of 30 Hz or lower. In some embodiments, the electromechanical transducer
22, 22', 22" is configured to generate the pulsating mechanical deformation of the
optical membrane at a dominant frequency of 20 Hz or lower.
[0046] On the other hand, in certain embodiments, if the pulsating mechanical
deformation is too slow, it may produce a visually perceptible light variation. For
example, in the embodiment of FIG. 3, if the pulsating mechanical deformation is too
slow, the movement of the Fresnel lens 20' may produce an optically perceptible
variation. Since the human eye typically cannot perceive motion faster than about 50
Hz, or at most about 100 Hz, in these embodiments motion in a range of 50 Hz or
higher (e.g., 60 Hz or 100 Hz) may be preferable to avoid visually perceptible
illumination variation. More generally, it is advantageous in these embodiments to
have the pulsating mechanical deformation at a frequency or frequency range that is
above the range of visual perception. Ideally, the pulsating mechanical deformation
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should be at a frequency or frequency range that is below the audible range and above
the range of visual perception. However, in practice, there may be no such range
since the lower end of the audible frequency range may overlap the upper end of the
frequency range of visual perception. In such cases, a tradeoff is suitably made,
optionally in combination with sound damping features and/or measures taken to
suppress the noise and/or visual impact of the pulsating mechanical deformation. For
example, visual perception of the pulsating mechanical deformation may be reduced
by judicious selection of the orientation of the motion respective to the optical path.
[0047] Advantageously, the optical membrane 20, 20', 20" can be made large, e.g.
on the order of a few centimeters or larger for a directional lamp sized to comport
with a typical MR or PAR lamp standard. The large size enables effective active
cooling with operation at lower frequency, and the natural resonant frequency of the
larger membrane is typically smaller. Thus, operation of the large optical membrane
20, 20', 20" can be at substantially lower frequency than synthetic jets used for lamp
cooling which are disposed with electronics "behind" the circuit board, because the
size constraints in such cases limit the membrane size in such synthetic jets. In
general, the natural resonance frequency of the membrane is controlled by design
parameters such as membrane area, membrane thickness, and membrane elastic
properties (e.g., elastic modulus).
[0048] The material of the optical membrane 20, 20', 20" should provide sufficient
transparency, translucency, reflectivity, or other requisite optical properties for the
intended optical functionality. Additionally, the material of the optical membrane 20,
20', 20" should provide suitable mechanical properties to accommodate the pulsating
mechanical deformation. These mechanical properties include stiffness, flexibility,
sturdiness, and so forth. Some suitable optical membrane materials include polymers,
aluminum or other metal foils or films, thin glass disks or the like, ceramics, nanofiber
composites, or so forth.
[0049] The electromechanical transducer or transducers 22, 22', 22" can employ
any mechanism suitable for imparting the pulsating mechanical deformation to the
optical membrane 20, 20', 20". For example, in some illustrative embodiments, the
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electromechanical transducer or transducers 22, 22', 22" comprises a piezoelectric
transducer, while in some other illustrative embodiments the electromechanical
transducer or transducers 22, 22', 22" comprises an electromagnet and a suitable
alternating drive current or voltage, while in some other illustrative embodiments the
electromechanical tranducer or transducers 22, 22', 22" employ a
microelectromechanical system (MEMS) technology. In the illustrative embodiments
the optical membrane 20, 20', 20" and the electromechanical transducer 22, 22', 22"
are different elements, which advantageously allows selection of the membrane
material to meet the desired optical and mechanical deformation characteristics
without regard to piezoelectric or other drive-related characteristics. However, it is
contemplated to employ a membrane with integral drive characteristics where a
material has both suitable optical and mechanical deformation characteristics and
suitable drive characteristics. For example, quartz is a transparent material which also
exhibits some piezoelectric behavior, and is contemplated for use as an integral
optical membrane/electromechanical transducer. In the illustrative embodiments, the
electromechanical transducer 22, 22', 22" is proximate to the driven optical membrane
20, 20', 20". Such proximity enables direct, and hence efficient, transfer of the
mechanical force to the membrane. However, it is also contemplated to have the
electromechanical transducer spaced apart from the driven membrane with a suitable
mechanical linkage to transmit the mechanical force from the transducer to the
membrane.
[0050] The directional lamps of FIGS. 1-4 are illustrative examples. The
disclosed active cooling approaches are applicable in directional lamps of other
configurations. As another example (not illustrated), a directional lamp may comprise
a large area circuit board supporting an array of LED devices, optionally disposed in
individual reflector cups, with a Fresnel lens positioned parallel with the circuit board
and closely proximate to and in front of the LED devices, with a large and optionally
finned heat sink disposed behind the circuit board. In such a configuration, the
Fresnel lens is suitably the optical membrane, the enclosure is suitably defined by the
Fresnel lens and the circuit board, and the openings forming the synthetic jets suitably
pass through the circuit board to inject synthetic jets into or across the heat sink
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located behind the circuit board. Moreover, the disclosed active cooling approaches
are applicable to other lamp designs besides directional lamps. With reference to
FIGS. 5-7, some other illustrative types of lamps employing the disclosed active
cooling approaches are described.
[0051] FIG. 5 illustrates a panel lamp, including LED devices 12 (internal
components shown in phantom in FIG. 5) disposed in a plane in a rectangular housing
or enclosure 40 that is mostly opaque, but which has a top wall 42 (e.g., a flat panel)
comprising an optical membrane that is optically transparent or translucent. An
electromechanical transducer 44 running along one side of the wall/optical membrane
42 operates to generate a pulsating mechanical deformation of the optical membrane
42. A bottom wall 45 of the enclosure 40 is thermally conductive, for example
comprising a copper plate, and includes heat sinking fins 46 or other heat radiating
surface extensions. Openings 48 in the bottom wall 45 cooperate with the pulsating
mechanical deformation of the optical membrane 42 to form synthetic jets that
generate air flow across the heat sinking fins 46 to provide active cooling.
[0052] FIG. 6 illustrates a linear (e.g., elongated) lamp, including a linear array of
LED devices 12 (internal component shown in phantom in FIG. 6) disposed in a
tubular housing or enclosure 50 that is transparent or translucent and also serves as the
optical membrane parallel with the elongated light source (i.e., the linear array of
LED devices 12). The tubular enclosure 50 has airtight ends, and includes a
longitudinal bellow 51 that is airtight but allows the diameter of the tubular enclosure
50 to expand or contract. Electromechanical transducers 52 are spaced apart along the
tubular (e.g., elongated) housing or enclosure/membrane 50 and operate to on the
bellow 5 1 to produce a pulsating mechanical deformation of the optical membrane 50
in the form of pulsating expansion/contraction of the tube diameter. Slots 54 provide
openings that cooperate with the pulsating mechanical deformation of the optical
membrane 50 to form synthetic jets that actively cool the LED devices 12. In this
embodiment, the tubular enclosure is in thermal communication with the LED devices
12 (for example, by mounting the LED devices 12 on an inside surface of the tubular
enclosure/optical membrane 50, optionally with sub mount, linear circuit board, LED
socket/connector assembly, or other intermediary components). The LED devices 12
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receive electrical power via an electrical power cable 56 passing through the tubular
enclosure 50. In the illustrative embodiment, there is no separate heat sinking
component, rather, the tubular enclosure/optical membrane 50 is itself thermally
conductive (for example, by including dispersed thermally conductive particles in the
material, or employing a suitably thermally conductive membrane material), and heat
sinking is from the LED devices 12 to the tubular enclosure/optical membrane 50 to
the ambient, aided by the synthetic jets formed at the slots 54 by the
expansion/contraction of the diameter of the enclosing tubular membrane 50. To
achieve the expansion/contraction, the transducers 52 operate synchronously (i.e.
expanding and contracting in phase). In some alternative embodiments, the
transducers 52 operate in a phase pattern that generates the pulsating mechanical
deformation as a traveling wave of tube expansion/contraction that travels along the
length of the housing/membrane 50. This is diagrammatically plotted above the linear
lamp, showing the deformation as a function of linear position for two times t l and t2,
which is greater than tl.
[0053] In a contemplated variation of the embodiment of FIG. 6, the slots 54 may
be omitted and openings provided at both ends of the tube/membrane 50, so that the
traveling waves produce a unidirectional airflow stream through the tube. The tubular
housing or enclosure 50 may have a relatively high degree of rigidity such that the
linear lamp is relatively inflexible. Alternatively, the tubular housing or enclosure 50
may have a relatively high degree of flexibility such that the linear lamp is a flexible
linear lighting strip. In either the panel lamp of FIG. 5 or the linear lamp of FIG. 6,
the optical membrane 42, 50 optionally provides additional optical functionality such
as optical diffusion, wavelength conversion (e.g., using an embedded or dispersed
phosphor), microlensing, or so forth.
[0054] FIGS. 7 and 8 illustrate omnidirectional lamp embodiments based on a
light engine including LED devices 12 on a circuit board 14 (visible in FIG. 7;
internal component diagrammatically indicated in phantom in FIG. 8). In the
embodiment of FIG. 7, the circuit board 14 includes a metal core 14c, and the LED
devices 12 illuminate inside a bulb shaped (e.g., spherical, spheroidal, egg shaped,
and so forth) envelope 60. A transparent or translucent optical membrane 62
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horizontally spans the bulb to divide between an upper volume 63 and a lower volume
64. Electromechanical transducers 66 drive the optical membrane to excite an
"up/down" pulsating mechanical deformation of the optical membrane 62, indicated
by up/down arrow 68. Openings 70 in the circuit board 14 and slots 7 1 in the Edison
connector 19 provide for air flow, with air accelerating through the openings 70
providing the synthetic jets actively cooling the metal core 14c of the circuit board 14.
Although not illustrated, it is contemplated to include grooves, slots, or other airflow
pathways in the metal core 14c to promote air flow across a large surface of the metal
core 14c. Such grooves, slots, or so forth, are preferably designed to balance air flow
proximate to the metal core 14c, which is desired, against increased air flow
resistance that can reduce the effectiveness of the synthetic jets. This balancing
entails, for example, making the grooves, slots, or so forth, of relatively large cross
sectional area so as to reduce their resistance to the air flow. Moreover, optional
openings 72 in the upper portion of the bulb shaped envelope 60 ensure that the upper
volume 63 does not impose resistance on the motion 68 of the optical membrane 62.
As in other embodiments, the optical membrane 62 may optionally be frosted or
otherwise light diffusing, and/or may include a wavelength converting phosphor, or so
forth. In certain embodiments, the membrane 62 may be a transparent optical
window. Furthermore, in certain embodiments, the membrane 62 may be partially
reflective or reflective on portions of the surface of the membrane 62.
[0055] Although illustrated in FIG. 7 as including a single membrane 62, in other
embodiments, a plurality of membranes 62 may instead be used. In certain
embodiments, the multiple membranes 62 may be parallel with each other, similar to
the geometry of the optical membrane 20 and the Fresnel lens 18 illustrated in FIGS.
1 and 2. In certain embodiments, some of the membranes 62 may be relatively rigid
members (e.g., like the Fresnel lens 18 described above with respect to FIGS. 1-4),
whereas some of the other membranes 62 may be more compliant membranes (e.g.,
like the optical membranes 20, 20', 20" described above with respect to FIGS. 1-4),
for example, capable of experiencing deflection caused by the electromechanical
transducers 66. Each of the multiple membranes 62 may be transparent, translucent,
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or reflective. In addition, each of the multiple membranes 62 may be planar, conical,
or of some other shape.
[0056] The embodiment of FIG. 8 employs a bulb-shaped (e.g., spherical,
spheroidal, egg shaped, and so forth) outer transparent or translucent optical element
80 comprising the optical membrane. The bulb-shaped transparent or translucent
optical element 80 is indicated by cross hatching in FIG. 8, and may be configured to
be a diffuser so that the lamp emits omnidirectional illumination over an
omnidirectional illumination latitudinal range spanning at least q=[0°, 120°], or
preferably spanning at least q=[0°, 135°] (where 0° is the "top" of the "light bulb")
responsive to generation of illumination inside the bulb-shaped transparent or
translucent optical element 82 by the light engine 12. Optionally, the outer bulbshaped
transparent or translucent optical element 80 may include a wavelengthconverting
phosphor, so that (by way of illustrative example), the LED devices may
emit ultraviolet, violet, or blue light, and the phosphor of the optical membrane 82 is
selected such that the output light (which may be entirely wavelength converted by
the phosphor or may be a mixture of direct and wavelength converted light) is white
light.
[0057] The lamp of FIG. 8 further includes an inner transparent or translucent
bulb shaped (e.g., spherical, spheroidal, egg shaped, and so forth) optical element 82,
which is rigid and may be configured to be a diffuser so that the lamp emits
omnidirectional illumination over an omnidirectional illumination latitudinal range
spanning at least q=[0°, 120°], or preferably spanning at least q=[0°, 135°] (where 0°
is the "top" of the "light bulb") responsive to generation of illumination inside the
bulb-shaped transparent or translucent optical element 80 by the light engine 12. A
heat sink in thermal communication with the LED devices includes fins 84 that span
between the outer optically transparent or translucent membrane 80 and the rigid inner
transparent or translucent bulb shaped optical element 82. In this embodiment, the
inside of the rigid inner transparent or translucent bulb shaped optical element 82
defines an inner air volume, and an outer air volume is defined between the inner
optical element 82 and the outer membrane 80. Slots 86 proximate to the heat sinking
fins 84 provide limited fluid communication between the inner and outer volumes.
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Electromechanical transducers 88 operate on the outer optically transparent or
translucent membrane 80 to induce a pulsating mechanical deformation of the outer
membrane 80, which cooperates with the slots 86 to form synthetic jets directing air
streams over the proximate fins 84.
[0058] With continuing reference to FIGS. 7 and 8, a base of the omnidirectional
lamp includes a threaded "Edison-type" connector 19 that is adapted to thread into a
conventional Edison-type socket. Accordingly, the omnidirectional lamps of FIGS. 7
and 8 are suitable as a retrofit light bulb. The base optionally contains electronics for
converting the 110V a.c. or other voltage input received at the Edison connector 19
into conditioned electrical power suitable for driving the LED devices 12.
Alternatively, in the embodiment of FIG. 7, wires 19a directly connect the high
voltage a.c. to the circuit board 14, which contains on board circuitry for conditioning
the electrical power to drive the LED devices 12.
[0059] In the illustrative embodiment of FIG. 7, the optical membrane 62 can be
located elsewhere in the bulb 60, and optionally at different orientations (e.g.,
vertically oriented). By placing the membrane 62 in the bulb, it can be made large,
which promotes large air displacement volume at low frequency (so as to be
noiseless). In the embodiment of FIG. 8, the optical membrane is the outer bulb
shaped optical element 80, while the inner bulb shaped element 82 is rigid. However,
this order can be reversed, or both elements can be configured as membranes
contributing to the synthetic jet.
[0060] With reference to FIGS. 1-8, various lamp embodiments have been
described. However, the disclosed active cooling approaches are more generally
suitable for other cooling applications, such as cooling of electronic components, heat
sinks, and so forth. In such cases, the use of a large area membrane (which in these
non-lamp applications may optionally be optically inactive), which may be a part of
the overall enclosure, enables large volume displacement of air and operation at a low
resonant vibrational frequency. In some embodiments for cooling electronic
components including a circuit board, the membrane may be larger than the circuit
board itself.
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[0061] With reference to FIG. 9, an electronic component cooling application is
illustrated. An electronic component 100 (internal component shown in phantom in
FIG. 8) includes a plurality of electronic devices such as integrated circuit (IC)
devices 102 and discrete electronic devices 104 such as resistors or capacitors, all
disposed on a circuit board 106. The electronic component 100 is disposed in an
enclosure 110, which includes a membrane 112 forming a top exterior wall (which, in
certain embodiments, may be transparent or translucent) of the enclosure 110 facing
the electronic devices 102, 104. Two electromechanical transducers 114 generate a
pulsating mechanical deformation of the membrane 112. The membrane 112 is
proximate to the electronic component 100 and includes openings 116, which
cooperate with the pulsating mechanical deformation to provide synthetic jets directed
toward and actively cooling the electronic component 100. In certain embodiments,
the membrane 112 has an area larger than the electronic component 100. Although
illustrated as being planar, in certain embodiments, the membrane 112 may be a nonplanar
membrane. Alternatively or additionally, a heat sink can be employed with the
synthetic jets operating on the heat sink, as shown by way of illustrative example in
FIG. 5. Said another way, in non-lamp embodiments, the configuration of FIG. 5 can
be used, with the membrane 42 being optionally opaque since it does not transmit
light in a non lamp application.
[0062] In certain embodiments, LED fluorescent light (LFL) replacement tubes
may also include electromechanical transducers for generating airflow through the
LFL replacement tubes. FIG. 10 is a perspective view of an embodiment of an LFL
replacement tube 118 having LED devices 12 disposed in two linear arrays on
opposite sides of a printed circuit board 120 that extends through a transparent or
translucent housing or enclosure 122, which acts as an optical membrane. Having the
LED devices 12 on opposite sides of the printed circuit board 120 enables light from
the LED devices 12 to be emitted from the LFL replacement tube 118 for the entire
360 degrees around the LFL replacement tube 118. However, the LFL replacement
tube 118 does not include a linear heat sink through the center of the LFL replacement
tube 118. Rather, the illustrated LFL replacement tube 118 may be used in
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conjunction with other means for inducing cooling air through the LFL replacement
tube 118.
[0063] More specifically, FIG. 11A is a perspective view of an embodiment of a
cylindrical tube 124 made of a flexible material and having a piezoelectric film
applied to the flexible material. As such, when an electrical current is applied to the
piezoelectric film, the flexible material of the cylindrical tube 124 may be caused to
deform. In particular, the electrical current applied to the piezoelectric film may
cause the cylindrical tube 124 to shorten or lengthen. Indeed, in certain embodiments,
an alternating current may cause the cylindrical tube 124 to shorten and lengthen in an
alternating manner. For example, FIG. 1IB is a perspective view of the cylindrical
tube 124 of FIG. 11A when the piezoelectric film causes the cylindrical tube 124 to
shorten. When this happens, air may be forced out of one end of the cylindrical tube
124 due to the shortened length of the cylindrical tube 124, as illustrated by arrow
126. Conversely, FIG. 11C is a perspective view of the cylindrical tube 124 of FIG.
11A when the piezoelectric film causes the cylindrical tube 124 to lengthen. When
this happens, air may be forced out of one end of the cylindrical tube 124 due to the
reduction in the cross-sectional area of the inner volume 128 of the cylindrical tube
124, as illustrated by arrow 130.
[0064] Using the concepts illustrated in FIG. 11, the piezoelectric film applied to
the cylindrical tube 124 may be used to generate an air flow, which may be used to
cool the LFL replacement tube 118 illustrated in FIG. 10. For example, FIG. 12 is a
perspective view of an embodiment of an outer transparent or translucent tube 132
that surrounds the LFL replacement tube 118 of FIG. 10. As illustrated, in certain
embodiments, the cylindrical tube 124 of FIG. 11 may be disposed at one end of the
outer transparent or translucent tube 132. When a current is applied to the
piezoelectric film on the cylindrical tube 124, as described above with respect to FIG.
11, the cylindrical tube 124 may cause cooling air to flow through the LFL
replacement tube 118, as illustrated by arrow 134, thereby providing active cooling of
the LED devices 12 disposed on opposite sides of the printed circuit board 120 within
the LFL replacement tube 118 of FIG. 10. In certain embodiments, more than one
cylindrical tube 124 may be used along the length of the outer transparent or
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translucent tube 132 and the LFL replacement tube 118 to provide cooling air through
the LFL replacement tube 118.
[0065] As described above, piezoelectric transducers are one of the many types of
electromechanical transducers that may be used to create the displacements of the
membranes described herein, which cause volume displacements within enclosures to
facilitate the flow of air across LED devices 12 and/or other electronic devices 104 for
actively cooling of the LED devices 12 and/or other electronic devices 104. Indeed,
in certain embodiments, the membrane that is caused to experience displacements
may itself be part of the piezoelectric transducer. For example, FIG. 13 is a sectional
side view of an embodiment of a piezoelectric optical membrane 136 that may be
activated to experience a linear displacement. As described above, certain materials
(e.g., quartz) are both transparent and exhibit piezoelectric behavior, such that they
may be used as an integral optical membrane/electromechanical transducer as
illustrated in FIG. 13. As such, by passing a current through the piezoelectric optical
membrane 136, the piezoelectric optical membrane 136 may be linearly displaced in a
direction normal to the plane of the relatively flat piezoelectric optical membrane 136,
as illustrated by arrows 138. As described above, by varying the application of
alternating current through the piezoelectric optical membrane 136, the piezoelectric
optical membrane 136 may oscillate between opposite deformed states 140, 142,
thereby causing a change in a volume of an enclosure defined at least partially by the
piezoelectric optical membrane 136. In addition, because the piezoelectric optical
membrane 136 is transparent, it also facilitates the dispersion of light from LED
devices (e.g., the LED devices 12 described above) enclosed within the enclosure that
is defined at least partially by the piezoelectric optical membrane 136. Therefore, the
piezoelectric optical membrane 136 illustrated in FIG. 13 may be used as both an
optical component for the LED devices, as well as enabling active cooling of the LED
devices. As will be appreciated, the piezoelectric optical membrane 136 of FIG. 13
may be applied as the optical membrane 20 in several of the embodiments described
above, such as the directional lamp embodiments illustrated in FIGS. 1-4.
[0066] However, two factors limit the amount of maximum deflection Amax from a
centerline (e.g., in either the "up" or "down" direction) that is possible for the
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piezoelectric optical membrane 136. The first constraint is that the opposite ends 144,
146 of the piezoelectric optical membrane 136 illustrated in FIG. 13 are fixed (e.g.,
cantilevered) and, as such, the entire length of the piezoelectric optical membrane 136
is not allowed to deflect in response to the current flowing through the piezoelectric
optical membrane 136. In many embodiments, opposite ends of the optical
membranes described herein will all be fixed to some point of any given apparatus
(e.g., the lamps and electronic components described herein). The second constraint
is that, even if the piezoelectric optical membrane 136 were not fixed at its opposite
ends 144, 146, the piezoelectric optical membrane 136 is only capable of experiencing
a certain amount of linear deflection normal to the plane of the piezoelectric optical
membrane 136 due to inherent mechanical characteristics of the piezoelectric optical
membrane 136. In other words, there will always be some limitation in the amount of
maximum deflection Amax that is possible in a direction normal to the plane of the
piezoelectric optical membrane 136, as illustrated by arrows 138.
[0067] Therefore, other embodiments may include opposing piezoelectric
actuators having surfaces that, in certain embodiments, may be aligned generally
parallel with each other, and a compliant sheet rigidly attached (e.g., enabling
substantially no movement of the compliant sheet relative to the piezoelectric
actuators) to ends of the opposing piezoelectric actuators. For example, FIG. 14 is a
sectional side view of an embodiment of a piezoelectric actuated assembly 148 in a
neutral position including a compliant sheet 150 rigidly attached to opposing first and
second piezoelectric actuators 152, 154. As illustrated in FIG. 14, respective first
ends 156, 158 of the piezoelectric actuators 152, 154 are fixed (e.g., cantilevered)
such that movement of the respective first ends 156, 158 in a horizontal direction 160
or a vertical direction 162 is minimal. It should be noted that the horizontal and
vertical directions 160, 162 are merely included to aid discussion of the present
embodiments, and is not intended to be limiting. For example, the piezoelectric
actuated assembly 148 may be oriented in any manner with respect to the horizontal
and vertical directions 160, 162.
[0068] As also illustrated in FIG. 14, respective second ends 164, 166 of the
piezoelectric actuators 152, 154 are securely and rigidly attached to opposite first and
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second ends 168, 170 of the compliant sheet 150. More specifically, in certain
embodiments, the second end 164 of the first piezoelectric actuator 152 is attached to
the first end 168 of the compliant sheet 150 such that a generally 90° angle qi is
formed between the first piezoelectric actuator 152 and the compliant sheet 150.
Similarly, in certain embodiments, the second end 166 of the second piezoelectric
actuator 154 is attached to the second end 170 of the compliant sheet 150 such that a
generally 90° angle Q2 is formed between the second piezoelectric actuator 154 and
the compliant sheet 150. However, it should be noted that the angles qi and Q2
illustrated in FIG. 14 merely represent the piezoelectric actuated assembly 148
oriented in a neutral position of one particular embodiment. In other embodiments, as
described in greater detail below (e.g., with respect to FIGS. 17-21), the piezoelectric
actuated assembly 148 the angles qi and Q2 may be different for the piezoelectric
actuated assembly 148 when it is in a neutral position, such that the piezoelectric
actuated assembly 148 is "preloaded" with respect to a particular neutral position.
[0069] The term "compliant" with respect to the compliant sheet 150 is intended
to convey that the compliant sheet 150 is made of a relatively flexible material that is
capable of experiencing deformation in a direction normal to the plane of the
compliant sheet 150 when the rigid connection points formed at the first and second
ends 168, 170 of the compliant sheet 150 move due to bending in the first and second
piezoelectric actuators 152, 154. In addition to being made of a relatively flexible
material, in certain embodiments, the compliant sheet 150 may be used as an optical
membrane as described herein and, as such, the relatively flexible material from
which the compliant sheet 150 is made may also be transparent or translucent,
reflective, and so forth.
[0070] The first and second piezoelectric actuators 152, 154 are configured such
that, when alternating current is applied to the first and second piezoelectric actuators
152, 154, the compliant plate 150 experiences oscillating linear displacement in the
vertical direction 162, as illustrated by arrows 172. For example, FIG. 15 is a
sectional side view of the embodiment of the piezoelectric actuated assembly 148 of
FIG. 14 when the compliant sheet 150 is in a first deformation state, and FIG. 16 is a
sectional side view of the embodiment of the piezoelectric actuated assembly 148 of
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FIG. 14 when the compliant sheet 150 is in a second deformation state. It should be
noted that the maximum deflection Am that is possible for the compliant sheet 150 is
generally greater than the maximum deflection Amax that is possible for the
piezoelectric optical membrane 136 of FIG. 13, assuming that all other characteristics
are equal (e.g., length, thickness, material type, and so forth). More specifically, since
the first and second piezoelectric actuators 152, 154 are made of piezoelectric
materials similar to those of the piezoelectric optical membrane 136 of FIG. 13, the
amount of horizontal deflections Ahor of the first and second piezoelectric actuators
152, 154 are similar to that of the piezoelectric optical membrane 136 of FIG. 13.
However, the maximum deflection Amax of the compliant sheet 150 will be relatively
greater than the horizontal deflections Ahor of the first and second piezoelectric
actuators 152, 154 due to the rigid connections between the first and second
piezoelectric actuators 152, 154 and the compliant sheet 150. As such, using the first
and second piezoelectric actuators 152, 154 to oscillate the compliant sheet 150
between the first and second deformation states illustrated in FIGS. 15 and 16 may
enable a greater amount of volume displacement of air from within an internal volume
174 that is at least partially defined by the first and second piezoelectric actuators 152,
154 and the compliant sheet 150.
[0071] However, as illustrated by FIGS. 15 and 16, the maximum deflection Am
of the compliant sheet 150 occurs both above and below (e.g., in the vertical direction
162) an imaginary line 176 that connects the first and second ends 168, 170 of the
compliant sheet 150 (or the respective second ends 164, 166 of the first and second
piezoelectric actuators 152, 154). In other words, approximately half of the total
deflection of the compliant sheet 150 occurs outside of the internal volume 174 that is
at least partially defined by the first and second piezoelectric actuators 152, 154 and
the compliant sheet 150. In certain embodiments, due to space constraints, it may be
advantageous to design the piezoelectric actuated assembly 148 such that the
compliant sheet 150 is "preloaded" in a neutral position where the compliant sheet
150 is not flat having a plane that is parallel to the imaginary line 176 that connects
the first and second ends 168, 170 of the compliant sheet 150 while in the neutral
position.
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[0072] It should be noted that while FIGS. 14-23 illustrate embodiments of the
piezoelectric actuated assembly 148 having two piezoelectric actuators 152, 154 that
are used to cause the compliant sheet 15 to experience oscillating linear
displacements, in other embodiments, the piezoelectric actuated assembly 148 may
only include one piezoelectric actuator 152, 154, with the other piezoelectric actuator
152, 154 being replaced by a wall or plate that is not actuated and, therefore, remains
relatively fixed in place. In other words, only one of the ends 168, 170 of the
compliant sheet 150 may be attached to a piezoelectric actuator 152, 154, while the
opposite end 168, 170 of the compliant sheet 150 is attached to a wall or plate that is
not actuated. As such, the deflection of the compliant sheet 150 would primarily
occur at the end 168, 170 of the compliant sheet 150 that is attached to the
piezoelectric actuator 152, 154, with the other end 168, 170 of the compliant sheet
150 remaining relatively fixed (e.g., cantilevered) to the opposite fixed wall or plate.
[0073] For example, FIG. 17 is a sectional side view of an embodiment of a
preloaded piezoelectric actuated assembly 148 during construction of the preloaded
piezoelectric actuated assembly 148. As illustrated in FIG. 17, the first and second
piezoelectric actuators 152, 154 may first be mounted such that the respective first
ends 156, 158 of the piezoelectric actuators 152, 154 are fixed (e.g., cantilevered).
Once the respective first ends 156, 158 of the piezoelectric actuators 152, 154 are
fixed, a direct current may be applied to both of the first and second piezoelectric
actuators 152, 154 such that the first and second piezoelectric actuators 152, 154 are
in the first deformation state that is illustrated in FIG. 15.
[0074] While the direct current remains applied, and the first and second
piezoelectric actuators 152, 154 remain in the first deformation state illustrated in
FIG. 17, the compliant sheet 150 may be mounted to the first and second piezoelectric
actuators 152, 154 such that the compliant sheet 150 is laid flat on top of the first and
second piezoelectric actuators 152, 154. In other words, the compliant sheet 150 is
laid flat along the imaginary line 176 that connects the first and second ends 168, 170
of the compliant sheet 150 (or the respective second ends 164, 166 of the first and
second piezoelectric actuators 152, 154) and the first and second ends 168, 170 of the
compliant sheet 150 are rigidly attached to the respective second ends 164, 166 of the
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first and second piezoelectric actuators 152, 154 while the direct current remains
applied to the first and second piezoelectric actuators 152, 154. For example, FIG. 18
is a sectional side view of the embodiment of the preloaded piezoelectric actuated
assembly 148 of FIG. 17 wherein the compliant sheet 150 is mounted to the first and
second piezoelectric actuators 152, 154 while a direct current is applied to the first
and second piezoelectric actuators 152, 154. As such, the compliant sheet 150 is in a
state of minimum stress when the direct current is applied to the first and second
piezoelectric actuators 152, 154 as illustrated in FIGS. 17 and 18. As illustrated, as
opposed to the embodiments illustrated in FIGS. 14-16, the second end 164 of the first
piezoelectric actuator 152 is attached to the first end 168 of the compliant sheet 150
such that the angle qi between the first piezoelectric actuator 152 and the compliant
sheet 150 is substantially less than 90°. Similarly, the second end 166 of the second
piezoelectric actuator 154 is attached to the second end 170 of the compliant sheet
150 such that the angle Q2 between the second piezoelectric actuator 154 and the
compliant sheet 150 is also substantially less than 90°.
[0075] Once the compliant sheet 150 has been rigidly attached to the first and
second piezoelectric actuators 152, 154, the direct current being applied to the first
and second piezoelectric actuators 152, 154 may be removed. Doing so allows the
preloaded piezoelectric actuated assembly 148 to revert to a neutral position. For
example, FIG. 19 is a sectional side view of the embodiment of the preloaded
piezoelectric actuated assembly 148 of FIG. 18 in a neutral position once the direct
current has been removed from the first and second piezoelectric actuators 152, 154.
As illustrated, the neutral position for the preloaded piezoelectric actuated assembly
148 includes the compliant sheet 150 being deformed in such a way that the compliant
sheet 150 is disposed between the first and second piezoelectric actuators 152, 154
within the space that was the interior volume 174 of the embodiment illustrated in
FIGS. 14-16. In other words, the compliant sheet 150 of the preloaded piezoelectric
actuated assembly 148 is predisposed toward the interior volume 174 of the preloaded
piezoelectric actuated assembly 148 away from the state of minimum stress, which is
illustrated in FIGS. 17 and 18.
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[0076] Therefore, when an alternating current is subsequently applied to the first
and second piezoelectric actuators 152, 154, the compliant sheet 150 oscillates
between two deformation states that are closer to the interior volume 174 that is at
least partially defined by the compliant sheet 150 and the first and second
piezoelectric actuators 152, 154. For example, FIG. 20 is a sectional side view of the
embodiment of the preloaded piezoelectric actuated assembly 148 of FIG. 19 when
the compliant sheet 150 is in a first deformation state, and FIG. 2 1 is a sectional side
view of the embodiment of the preloaded piezoelectric actuated assembly 148 of FIG.
19 when the compliant sheet 150 is in a second deformation state. As illustrated in
FIG. 20, in certain embodiments, the first deformation state may include the
compliant sheet 150 being relatively closer (and, in certain embodiments, generally
parallel) to the imaginary line 176 that connects the first and second ends 168, 170 of
the compliant sheet 150 (or the respective second ends 164, 166 of the first and
second piezoelectric actuators 152, 154). As such, in circumstances where space
constraints exist, preloading the compliant sheet 150 toward the interior volume 174
may prove particularly beneficial.
[0077] As described above, actuating the compliant sheet 150 with the first and
second piezoelectric actuators 152, 154 may lead to greater maximum deflections than
would otherwise be possible by simply exciting a piezoelectric membrane. In
addition, in certain embodiments, additional weight may be added to the compliant
sheet 150 to further increase the maximum deflection possible in the compliant sheet
150 due to the additional inertia created by the additional weight. For example, FIG.
22 is a sectional side view of an embodiment of a weighted piezoelectric actuated
assembly 148 that uses additional weight 178 that has been added to the compliant
sheet 150 and is in a first deformation state, and FIG. 23 is a sectional side view of the
embodiment of the weighted piezoelectric actuated assembly 148 of FIG. 22 in a
second deformation state. Although illustrated in FIGS. 22 and 23 as a single weight
178 attached at a midpoint of the compliant sheet 150, in other embodiments, one or
more weights may be added to the compliant sheet 150, and the one or more weights
may be spaced along the compliant sheet 150 in any appropriate manner to create
deflections of the compliant sheet 150 that lead to appropriate volume displacements
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of air from the interior volume 174 through, for example, the synthetic jets described
above.
[0078] The additional weight(s) 178 provide a means for adjusting the natural
frequency of the weighted piezoelectric actuated assembly 148 through the general
equation: w = I m , where w is the natural frequency, k is the spring constant, and
m is the mass. In other embodiments, other means for affecting the amount of
deformation of the compliant sheet 150 may be used (e.g., springs, electric forces,
magnetic forces, pressurized fluid on a back side, and so forth) to adjust the value of
the spring constant k , such that the natural frequency of the weighted piezoelectric
actuated assembly 148 is also adjusted. These other forces may be used as
alternatives to, or as supplemental forces for, the additional weight(s) 178 illustrated
in FIGS. 22 and 23.
[0079] In certain embodiments, the piezoelectric actuated assembly 148 described
above with respect to FIGS. 14-23 may be designed such that the interior volume 174
is at least partially defined by the compliant sheet 150 and the first and second
piezoelectric actuators 152, 154. However, in other embodiments, a separate housing
or enclosure may be used to define the interior volume. For example, FIG. 24 is a
sectional side view of an embodiment of the preloaded piezoelectric actuated
assembly 148 described above with respect to FIGS. 17-21 that is disposed within a
housing or enclosure 180 having at least one air inlet opening 182 and at least one air
outlet opening 184. More specifically, the illustrated embodiment includes two air
inlet openings 182 on opposite first and second lateral sides 186, 188 of the housing
180, wherein the first lateral side 186 is located proximate to the first piezoelectric
actuator 152 and the second lateral side 188 is located proximate to the second
piezoelectric actuator 154. In addition, the illustrated embodiment includes a single
air outlet opening 184 in a top side 190 of the housing 180. As illustrated in FIGS. 20
and 2 1 above, as the alternating current is applied to the first and second piezoelectric
actuators 152, 154, the compliant sheet 150 will oscillate between a first deformation
state (e.g., illustrated in FIG. 20) and a second deformation state (e.g., illustrated in
FIG. 21), thereby causing air to flow through an interior volume 192 defined between
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the enclosure 180 and the compliant sheet 150 and associated first and second
piezoelectric actuators 152, 154, as illustrated by air inlet arrows 194 and air outlet
arrow 196.
[0080] The embodiments of the piezoelectric actuated assemblies 148 illustrated
in FIGS. 14-24 may be applied to any of the embodiments described above with
respect to FIGS. 1-12. For example, all of the embodiments with respect to lamps as
described above with respect to FIGS. 1-8 and 10-12, and the embodiment of the
electronic component assembly of FIG. 9 may all utilize the techniques described
with respect to the piezoelectric actuated assemblies 148 of FIGS. 14-24. As an
example, FIG. 25 is a partial sectional side view of an embodiment of the directional
lamp 10 of FIG. 1 taken within line 25-25, which utilizes a piezoelectric actuated
assembly 148 as described above with respect to FIGS. 14-24. In the illustrated
embodiment, the first piezoelectric actuator 152 is equivalent to the transducer 22
illustrated in FIG. 1 and the compliant sheet 150 is equivalent to the optical
membrane 20 of FIG. 1. As such, as described above, the compliant sheet 150 may be
made of a material that is substantially transparent or translucent. Although
illustrated as being aligned generally orthogonal to the plane of the compliant sheet
150, in other embodiments, the first piezoelectric actuator 152 may be aligned
generally orthogonal to a surface 198 of the collecting reflector 16. Furthermore, as
the directional lamp 10 of FIG. 1 is circular, extending a full 360 degrees around, the
piezoelectric actuated assembly 148 illustrated in FIG. 25 may not actually have first
and second piezoelectric actuators 152, 154 as described herein, but rather may
include either a single piezoelectric actuator that extends 360 degrees around the
directional lamp 10, or a discrete number of piezoelectric actuators generally equally
spaced around the directional lamp 10.
[0081] Furthermore, the piezoelectric actuated assemblies 148 of FIGS. 14-24
may be implemented in other embodiments illustrated in FIGS. 1-12. For example, in
certain embodiments, the compliant sheet 150 may be the integrated lens and optical
membrane 20' illustrated in FIG. 3, or the reflective optical membrane 20" illustrated
in FIG. 4, in each case the transducers 22', 22"' being the piezoelectric actuators of
FIGS. 14-24. In other embodiments, the compliant sheet 150 may be the top wall 42
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of the panel lamp of FIG. 5, with the transducer 44 being a piezoelectric actuator of
FIGS. 14-24. In other embodiments, the compliant sheet 150 may be the membrane
112 of the electrical component assembly of FIG. 9, with the transducers 114 being
the piezoelectric actuators of FIGS. 14-24.
[0082] Indeed, the above detailed descriptions of embodiments of the invention
are not intended to be exhaustive or to limit the invention to the precise form
disclosed above. Although specific embodiments of, and examples for, the invention
are described above for illustrative purposes, various equivalent modifications are
possible within the scope of the invention, as those skilled in the relevant art will
recognize. For example, while steps are presented in a given order, alternative
embodiments may perform steps in a different order. The various embodiments
described herein may also be combined to provide further embodiments.
[0083] From the foregoing, it will be appreciated that specific embodiments of the
invention have been described herein for purposes of illustration, but well-known
structures and functions have not been shown or described in detail to avoid
unnecessarily obscuring the description of the embodiments of the invention. Where
the context permits, singular or plural terms may also include the plural or singular
term, respectively.
[0084] Moreover, unless the word "or" is expressly limited to mean only a single
item exclusive from the other items in reference to a list of two or more items, then
the use of "or" in such a list is to be interpreted as including (a) any single item in the
list, (b) all of the items in the list, or (c) any combination of the items in the list.
Additionally, the term "comprising" is used throughout to mean including at least the
recited feature(s) such that any greater number of the same feature and/or additional
types of other features are not precluded. It will also be appreciated that specific
embodiments have been described herein for purposes of illustration, but that various
modifications may be made without deviating from the invention.
[0085] This written description uses examples to disclose the invention, including
the best mode, and also to enable any person skilled in the art to practice the
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invention, including making and using any devices or systems and performing any
incorporated methods. The patentable scope of the invention is defined by the claims,
and may include other examples that occur to those skilled in the art. Such other
examples are intended to be within the scope of the claims if they have structural
elements that do not differ from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from the literal languages
of the claims.

CLAIMS:
1. An apparatus, comprising:
at least one electronic component;
an enclosure enclosing the at least one electronic component, the enclosure
including at least one wall defined by a membrane;
an electromechanical transducer configured to generate a pulsating mechanical
deformation of the membrane; and
one or more openings in the enclosure for facilitating volume displacement of
air from within the enclosure, wherein the volume displacement of air is provided by
the pulsating mechanical deformation of the membrane.
2. The apparatus of claim 1, wherein the at least one electronic
component comprises at least one light emitting diode (LED) device.
3. The apparatus of claim 2, wherein the membrane is an optical
membrane comprising a transparent or translucent optical diffuser.
4. The apparatus of claim 2, wherein the membrane is an optical
membrane comprising a wavelength converting element including at least one
phosphor compound.
5. The apparatus of claim 2, wherein the membrane is an optical
membrane comprising a refractive lens.
6. The apparatus of claim 2, wherein the membrane is an optical
membrane comprising a reflective surface.
7. The apparatus of claim 1, wherein the at least one electronic
component comprises:
a circuit board; and
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a plurality of electronic devices disposed on the circuit board, the electronic
devices being selected from a group consisting of integrated circuit (IC) devices and
discrete electronic devices.
8. The apparatus of claim , wherein the electromechanical transducer
comprises:
a first piezoelectric actuator that is fixed at a first end of the first piezoelectric
actuator and rigidly attached to a first end of the membrane at a second end of the first
piezoelectric actuator; and
a second piezoelectric actuator that is fixed at a first end of the second
piezoelectric actuator and rigidly attached to a second end of the membrane at a
second end of the second piezoelectric actuator;
wherein application of alternating current to the first and second piezoelectric
actuators generates the pulsating mechanical deformation of the membrane.
9. The apparatus of claim , wherein the volume displacement of air
provided by the pulsating mechanical deformation of the membrane and a size of the
one or more openings are selected such that the volume displacement of air provided
by the pulsating mechanical deformation of the membrane produces at least one
synthetic jet arranged to provide active cooling of the at least one electronic
component.
10. The apparatus of claim 1, wherein the electromechanical transducer is
configured to generate the pulsating mechanical deformation of the membrane in
which frequency components of the pulsating mechanical deformation at frequencies
higher than 1500 Hz comprise no more than 10% of the total amplitude of the
pulsating mechanical deformation.
11. The apparatus of claim 1, wherein the electromechanical transducer is
configured to generate the pulsating mechanical deformation of the membrane at a
dominant frequency of less than 100 Hz.
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12. The apparatus of claim 1, wherein the enclosure comprises the
membrane as a tubular membrane.
13. A piezoelectric actuated assembly, comprising:
a first piezoelectric actuator that is fixed at a first end of the first piezoelectric
actuator;
a second piezoelectric actuator that is fixed at a first end of the second
piezoelectric actuator; and
a compliant sheet having a first end that is rigidly attached to a second end of
the first piezoelectric actuator, and a second end that is rigidly attached to a second
end of the second piezoelectric actuator;
wherein application of alternating current to the first and second piezoelectric
actuators generates a pulsating mechanical deformation of the compliant sheet.
14. The piezoelectric actuated assembly of claim 13, wherein the
compliant sheet is preloaded such that the compliant sheet is deformed away from a
state of minimum stress when the alternating current is not applied to the first and
second piezoelectric actuators.
15. The piezoelectric actuated assembly of claim 13, comprising an
additional weight attached to the compliant sheet.
16. The piezoelectric actuated assembly of claim 13, comprising an
enclosure disposed around the compliant sheet and the first and second piezoelectric
actuators.
17. The piezoelectric actuated assembly of claim 16, wherein the enclosure
comprises at least one opening, wherein a volume displacement of air is provided
through the piezoelectric actuated assembly via the at least one opening by the
pulsating mechanical deformation of the compliant sheet.
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18. The piezoelectric actuated assembly of claim 13, wherein the
compliant sheet comprises an optical membrane of a solid state lighting device.
19. The piezoelectric actuated assembly of claim 13, wherein the
compliant sheet comprises a wall of an enclosure surrounding at least one electronic
component.
20. An apparatus, comprising:
at least one electronic component;
an enclosure enclosing the at least one electronic component, the enclosure
including at least one wall defined by a membrane; and
a piezoelectric actuator that is fixed at a first end and rigidly attached to the
membrane at a second end;
wherein application of alternating current to the piezoelectric actuator
generates a pulsating mechanical deformation of the membrane.