Abstract:
An active cooling device in the form of a torsional, oscillating synthetic jet is provided. Fins are oscillated in a manner that creates a flow of air that can be used to cool an electronic device such as a lamp. Embodiments of the active cooling device can be compact and readily incorporated within heat sinks of different sizes and configurations. The flow of air can be provided as jets of air distributed over multiple directions as may be desirable with certain electronics such as an omnidirectional lamp.

Description:
PRIORITY CLAIM 
     This application claims benefit of priority from earlier filed, commonly owned, copending U.S. Provisional Patent Application 61/643,056, filed May 4, 2012, which is hereby incorporated by reference. This application also claims benefit of priority from earlier filed, commonly owned, copending U.S. patent application Ser. No. 13/665,959, filed Nov. 1, 2012, which is also hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The subject matter of the present disclosure relates generally to an active cooling device in the form of a torsional oscillating synthetic jet that can be used e.g., to cool electronic devices including lamps, circuit boards, and others. 
     BACKGROUND OF THE INVENTION 
     Electronic devices can generate significant heat during use. Part of the electrical energy used to operate the device may be converted into heat energy. Depending upon the amount of heat energy created and the construction of the device, it may be necessary to provide for the dissipation of the heat energy to prevent damage to the device and/or provide for proper operation. 
     By way of example, lamps or other electronic devices that include solid state light emitting sources such as e.g., light emitting diodes (LEDs) can provide certain advantages over incandescent type lamps including better energy efficiency and longer life, but these light sources typically require management of certain heat related issues. The junction temperature for a typical LED device, for example, should be below 150° C. and in some LED devices should be below 100° C. or even lower. At these low operating temperatures, radiative heat transfer to the surrounding environment is weak compared with that of conventional light sources. 
     With electronic devices such as LED light sources that need heat management, the convective and radiative heat transfer to the environment can be enhanced by the addition of a heat sink. A heat sink is a component providing a large surface for radiating and convecting heat away from the electronic device. In a typical design, the heat sink is a relatively massive metal element having a large engineered surface area, for example, by having fins or other heat dissipating structures on its outer surface. Where equipped with a large surface area, the heat fins can provide heat egress by radiation and convection. 
     However, even with the use of a heat sink, significant challenges remain for sufficient heat dissipation from an electronic device such as e.g., a lamp. For example, depending upon the amount of light intensity desired, multiple light emitting devices such as LEDs may be desirable. Depending upon e.g., the number of such light emitting devices that are employed, the total thermal power, and other factors, the heat sink alone may not be able to adequately dissipate heat from the lamp through passive means. While increasing the size of the heat sink could improve the dissipation of heat, such may be undesirable because it may also increase the overall size of the electronic device. For example, increasing the size of a heat sink used with a lamp may cause the lamp to exceed specifications for form such as e.g., the ANSI A19 profile. 
     Additionally, some light emitting devices have directional limitations that also present challenges for lamp design. For example, LED devices are usually flat-mounted on a circuit board such that the light output is substantially along a line perpendicular to the plane of the circuit board. Thus, a flat LED array typically does not provide a uniformly distributed, omnidirectional light output that may be desirable for many lamp applications, However, the ability to arrange LEDs so as to provide a more uniformly distributed light output can also be limited by heat management issues that can negatively affect the arrangement that is otherwise optimal for light distribution. 
     Another challenge relates to aesthetics. An electronic device such as a lamp that is designed only with consideration of performance requirements regarding light output, energy usage, thermal management, etc. may not provide an appearance that is pleasing to e.g., certain consumers. Such can affect the marketability of lamp even if it otherwise performs well. 
     Accordingly, an active cooling device that can provide cooling for electronic devices such as e.g., lamps, circuit boards, and others would be useful. Such a device that can also be used compactly and/or discreetly—i.e. without undesirably increasing the size of the electronic device or negatively affecting the aesthetics of the device would also be useful. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The present invention provides an active cooling device in the form of a torsional, oscillating synthetic jet. Fins are oscillated in a manner that creates a flow of air that can be used to cool an electronic device such as a lamp. Embodiments of the active cooling device can be compact and readily incorporated within heat sinks of different sizes and configurations. The flow of air can be provided as jets of air distributed over multiple directions as may be desirable with certain electronics such as an omnidirectional lamp. Additional aspects and advantages of the invention will be set forth in part in the following description, or may be apparent from the description, or may be learned through practice of the invention. 
     In one exemplary embodiment, the present invention provides an active cooling device. The active cooling device defines radial and circumferential directions. The active cooling device includes a plurality of fins spaced apart from each other along a circumferential direction of the cooling device and rotatable about an axis of rotation. A housing defines a plurality of chambers positioned adjacent to each other along the circumferential direction, each chamber defining at least two openings for air flow in and out of the chamber, wherein at least one fin from the plurality of fins is movably positioned within each chamber. An oscillating device is positioned at least partially within the housing and radially inward of the plurality of fins. The plurality of fins are connected with the oscillating device. The oscillating device is structured for causing the plurality of fins to rotate back and forth along the circumferential direction so as to create air flow through the openings in each chamber. 
     In another exemplary embodiment, the present invention includes a lamp that incorporates such exemplary active cooling device. 
     In still another exemplary embodiment, the present invention provides an active cooling device. The device includes a housing defining an internal compartment and a plurality of chambers positioned proximate to each other along a circumferential direction. The plurality of chambers are positioned radially outward of the internal compartment. Each chamber of the plurality of chambers has at least two openings spaced apart from each other along the circumferential direction. A plurality of fins are mechanically connected to each other with each fin positioned in one of the plurality of chambers. The plurality of fins are rotatable within the plurality of chambers and about an axis of rotation so as to create a flow of air through the at least two openings. An oscillating device is positioned at least partially within the internal compartment of the housing and radially inward of the plurality of fins. The plurality of fins are connected with the oscillating device. The oscillating device is structured for causing the plurality of fins to rotate back and forth along the circumferential direction so as to create air flow through the openings in each chamber. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
         FIG. 1  provides an exploded and cross-sectional view of an exemplary embodiment of a lamp incorporating an exemplary active cooling device of the present invention. 
         FIG. 2  is a partial cross-sectional and perspective view of the exemplary lamp with the exemplary active cooling device of  FIG. 1 . 
         FIG. 3  is a perspective view of the exemplary active cooling device of  FIG. 1  shown in a portion of an exemplary heat sink as used in the embodiment of  FIG. 1 . 
         FIG. 4  is a top view of the exemplary assembly shown in  FIG. 3 . 
         FIG. 5  is a perspective view of the exemplary active cooling device of  FIG. 1 . 
         FIG. 6  is a cross-sectional and perspective view of the exemplary active cooling device of  FIGS. 1 and 5 . 
         FIG. 7 . is a top view of the exemplary active cooling device of  FIGS. 1 and 5 . 
         FIG. 8  provides a close-up, cross-sectional and perspective view of the top portion of the exemplary active cooling device from  FIG. 6 . 
         FIG. 9  is a perspective view of an exemplary lamp assembly of the present invention incorporated with an exemplary active cooling device. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
       FIG. 1  illustrates a cross-sectional, exploded view of an exemplary lamp  100  incorporating an exemplary embodiment of an active cooling device  101  of the present invention.  FIG. 2  provides a perspective and cross-sectional view of lamp  100 . Although described in conjunction with lamp  100 , one of skill in the art using the teachings disclosed herein will understand that active cooling device  100  (or other embodiments thereof) could be used to provide cooling for other electronic devices including e.g., printed circuit boards, computers or computer components, and other devices as well. 
     Active cooling device  101  includes a housing  102  ( FIG. 2 ) that operates as a heat sink for lamp  100 . Housing  102  is constructed from an upper portion  104  and a lower portion  106  ( FIG. 1 ) that are joined together. Housing  102  includes a plurality of stationary fins  108  positioned separately from each other along circumferential direction C. Fins  108  can improve the ability of housing  102  to dissipate heat. The shape of housing  102  including fins  108  is provided by way of example only. Other housings of different shapes and configurations may be used with active cooling device  101  as well depending upon the application. For example, where used with a lamp, housing  102  may be provided with aesthetic features that provide a different appearance for lamp  100 . 
     As shown in  FIGS. 1, 3, and 4 , housing  102  defines a plurality of chambers  116  formed by walls  117  that extend along radial direction R from an internal compartment  142 . Chambers  116  are positioned adjacent to each other along circumferential direction C. Each chamber  116  defines at least two openings  118  for a flow of air—into and out of—each chamber  116  as will be further described. With proper positioning to create the air flow desired, more than two openings  118  may be used with each chamber to provide e.g., a larger flow of air in and out of each chamber or to provide further distribution of the direction of air flow. 
     As shown in  FIGS. 3 and 4 , active cooling device  101  also includes a plurality of movable fins  114 . At least one fin  114  is positioned in each chamber  116 . For this exemplary embodiment, fins  114  extend linearly along radial direction R as best seen in  FIG. 4 . However, other shapes such as e.g., arcs may be used for fins  114  as well. The plurality of fins  114  move together as each is connected with, and carried by, a fin support element or ring  140  that extends about circumferential direction C. Ring  140  is connected with a magnet housing  138 . Other mechanisms may be used to connect fins  114  together as well. 
     Referring specifically now to  FIG. 4 , fins  114  are oscillated along circumferential direction C and about axis of rotation A-A by an oscillating device  120 , which is located radially inward of fins  114  and at least partially within an internal compartment  142  ( FIG. 1 ) of housing  102 . For example, in a first phase, oscillating device  120  causes fins  114  to rotate circumferentially in the direction indicated by arrows S (counter-clockwise in  FIG. 4 ) and about axis of rotation A-A. As a result, a jet of air flows out of each chamber  116  though one of the openings  118  as indicated by arrows O and, simultaneously, air flows into each chamber through one of the other openings  118  as indicated by arrow I. Conversely, in a second phase, oscillating device  120  causes fins  114  to rotate circumferentially in a direction opposite to that indicated by arrows S and about axis of rotation A-A. As a result, the flow of air through openings  118  will be reversed so as to provide a jet of air out of each chamber  116  through openings  118  that previously received air into chamber  116  during the first phase. Similarly, in this second phase, air is drawn into each chamber  116  through openings  118  that previously jettisoned air out of chamber  116  during the first phase. 
     By using the oscillating device  120  to provide a cyclic movement of fins  114  between the first and second phases, active cooling device  101  cools housing  102  and, therefore, lamp  100  or another electronic device in which it is configured. The frequency of oscillation between the first and second phases can be controlled to determine the level of cooling desired. 
     Fins  114  can be constructed to have profile that closely matches the cross-sectional shape of chamber  116 . For example, as shown in  FIG. 4 , only a small gap  144  is provided between fin  114  and housing  102  so as to maximize the displacement or air as fins  114  are oscillated between the first and second phases by oscillating device  120 . 
     Referring now to  FIGS. 5, 6, 7, and 8 , for this exemplary embodiment of active cooling device  101 , oscillating device  120  includes a magnetic field generator  122  positioned at least partially within the internal compartment  142  formed by housing  102  and located radially inward of the plurality of fins  114 . At least one magnet  128 , located within magnet housing  138 , is positioned within the magnetic field provided by field generator  122  when activated. Magnetic field generator  122  includes a bobbin  124  about which a plurality of wires or coils  126  are wrapped. By manipulating the current flowing through coils  126 , the magnetic field provided by generator  122  can be controlled and, more importantly, changed in an alternating fashion to create the oscillating movement of fins  114 . For example, an electronic driver or other power device, (not shown) can be positioned in e.g., lower lamp housing  110  (which is different from housing  102  that is used as a heat sink). with base  112  and connected with an external power source so that the driver can provide a controlled current to coils  126 . Manipulation of such current by the driver can be used to change the direction of the magnetic field of field generator  122  in a cyclic manner. In turn, magnet  128  will react in a cyclic manner by oscillating—i.e. rotating back and forth about axis A-A so as to simultaneously oscillate fins  114  within chambers  116 . 
     A pair of torsional elements  130  and  131  are positioned at opposing ends of magnet  128  along the axis of rotation A-A. The torsional elements  130  and  131  are connected between the bobbin  124  and the magnet housing  138  and rotatably support or suspend the magnet  128  within the magnetic field created by magnetic field generator  122 . Referring to  FIG. 8 , for example, torsional element  130  is connected to a key  132  that is slidably received into a channel  134  formed in bobbin  124 —a construction which simplifies the manufacture of torsional element  130 . Key  132  and channel  134  are provided by way of example only. Other constructions for supporting magnet  128  within the magnetic field provided by generator  122  while still allowing magnet  128  to rotate about axis A-A may be used as well. 
     A variety of components may be used for torsional elements  130  and  131 . In one exemplary embodiment, torsional elements  130  and  131  act as bearings that allow the free rotation of magnet  128  about axis A-A. In such an embodiment, torsional elements  130  and  131  do not assist in causing magnet  128  to rotate. Instead, magnet  128  rotates only under the effects of the magnetic field created by generator  122 . 
     In another embodiment, torsional elements  130  and  131  are constructed from a spring or spring-like element such as wound metal coils or a resilient material, e.g., resilient silicone. For this construction, torsional elements  130  and  131  provide for storing and releasing energy during the oscillation of magnet  128  and, therefore, oscillation of fins  114  about axis A-A as generator  122  creates a cyclic, magnetic field. 
     For example, in the position shown in  FIG. 4 , fins  114  are in a neutral position midway between the opposing walls  117  that form chambers  116 . In this neutral position, torsional elements  130  and  131  are configured so as to provide no torque that would urge magnet  128  to rotate. However, as the magnetic field causes the magnet  128  to rotate in the direction of arrow S so that each fin  114  moves towards a wall  117  in chamber  116  in the first phase, torsional elements  130  and  131  are wound or otherwise caused to store potential energy. As the magnetic field is changed by generator  122  so as to cause magnet  128  and fins  114  to rotate in the opposite direction from arrow S in the second phase, this potential energy is released as torsional elements  130  and  131  apply a restorative torque and assist in causing such rotation. After fins  114  pass through the neutral position shown in  FIG. 4  and move towards an opposing wall  117  in chamber  116 , torsional elements  130  and  131  again store potential energy as part of the repeated cycle between the first and second phases. While a variety of configurations may be used, in certain embodiments the current through coils  126  is varied according to the natural frequency of the oscillating device  120  and fins  114 . 
       FIG. 9  provides another exemplary embodiment of lamp  100  of the present invention that may be equipped with an active cooling device such as that described above. Lamp  100  includes a lower lamp housing  110  connected with a lamp base  112 . As shown, base  112  includes threads  103  for connection into a conventional socket to provide electrical power to operate lamp  100 . 
     Lamp  100  includes a heat sink in the form of housing  102 , which is constructed from an upper portion  104  and a lower portion  106  in a manner similar to the embodiments of  FIGS. 1-8 . Housing  102  also includes a plurality of stationary fins  108  for dissipating heat away from the lamp and particularly away from a plurality of light emitting elements  119 . For this exemplary embodiment, stationary fins  108  extend along axial direction A and are spaced apart from each other along circumferential direction C. 
     Heat sink housing  102  includes an active cooling device in a manner previously described so as to create a flow of air through a plurality of openings  118  that are spaced apart along circumferential direction C with some openings  118  at different locations along axial direction defined by axis of rotation A-A. Openings  118  allow for a flow of air between the inside of housing  102  and the environment external to housing  102 . For example, air may flow into, or out of, housing  102  through openings  118 , as previously described. With this exemplary embodiment, openings  118  are spaced apart on both axial sides of light emitting elements  119 —i.e. they may be both above and below light emitting elements  119  when lamp  100  is oriented as shown in  FIG. 9 . Additionally, openings  118  are also positioned so as to cause air—e.g., jets of air—moving therethrough to flow along fins  114  for purposes of improving heat exchange. This air flow may include air that actually passes through opening  118  as well as air that is entrained therein. Other configurations, including different shapes and locations, may be used for openings  118  as well. 
     Heat sink housing  102  may be constructed from a variety of high thermal conductivity materials that will promote the transfer of heat from the thermal load provided by light emitting elements  119  to the ambient environment and thereby reduce the temperature rise that would otherwise result from the thermal load. Exemplary materials can include metallic materials such as alloy steel, cast aluminum, extruded aluminum, and copper, or the like. Other materials can include engineered composite materials such as thermally-conductive polymers as well as plastics, plastic composites, ceramics, ceramic composite materials, nano-materials, such as carbon nanotubes (CNT) or CNT composites. Other configurations may include a plastic heat sink body comprising a thermally conductive (e.g., copper) layer disposed thereupon, such as disclosed in US Patent Publication 2011-0242816, hereby incorporated by reference. Exemplary materials can exhibit thermal conductivities of about 50 W/m-K, from about 80 W/m-K to about 100 W/m-K, 170 W/m-K, 390 W/m-K; or, from about 1 W/m-K to about 50 W/m-K. 
     As stated above, lamp  100  includes a plurality of light emitting elements  119  that are positioned about heat sink  102  and are spaced apart along the circumferential direction C. The embodiment illustrated includes eight LEDs spaced apart circumferentially about the periphery of heat sink  102 . Other numbers of LEDs may be used as well including, for example, six and seven. In addition, other types of light emitting elements  119  other than LED-based elements may be used. 
     A plurality of optical elements  121  are positioned over the LEDs  118 . Optical elements  121  receive light from LEDs  119  and help distribute the same. As used herein, the term “optical elements” may generally refer to one or more of diffusers, reflectors, and/or any associated light management elements such as e.g., lenses; or combinations thereof; or the like. For example, optical elements  121  may be constructed as diffusers that are made from materials (glass, polymers such as polycarbonates, or others) that help scatter light received from LEDs. Again, the lamp of  FIG. 9  is provided by way of example only. The active cooling device of the present invention may be used with lamps of other configurations as well as with other electronic devices. 
     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 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 include 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.