Abstract:
An asymmetric micro pump may be adapted to provide a greater fluid compression between input and output ports of the micro pump, as well as increased flow rate due to higher actuation frequency. In some instances, asymmetric dual diaphragm micro pumps may be combined into assemblies to provide increased pressure build, improved pumping volume, or both, as desired.

Description:
TECHNICAL FIELD 
   The present invention relates generally to pumps, and more particularly to dual diaphragm pumps. 
   BACKGROUND 
   Modern consumer, industrial, commercial, aerospace and military systems often depend on reliable pumps for fluid handling. For some applications, such as in some instrumentation, sensing and/or control applications, smaller pump systems are often desirable. Although some important advances have been made in micro pump technology, a need still remains for micro pumps that have improved performance characteristics. 
   SUMMARY 
   The present invention generally relates to pumps, and more particularly to dual diaphragm pumps. In some cases, the present invention may provide greater fluid compression between input and output ports of the pump, as well as increased flow rate due to higher actuation frequency, if desired. 
   In one illustrative embodiment of the present invention, a micro pump is provided that includes a pump chamber having a chamber midline, a first surface and a second surface. The first surface includes a first portion that extends at a first acute angle with respect to the chamber midline. The second surface includes a second portion that extends at a second acute angle with respect to the chamber midline. In some cases, the second angle is less than the first angle, and in some cases may be zero or even negative. The micro pump may include a first diaphragm and a second diaphragm disposed within the chamber. The first diaphragm and the second diaphragm may each have at least one aperture disposed therein. 
   In some instances, the first diaphragm is adapted to be electrostatically actuated toward the first surface and/or the second surface, and the second diaphragm is adapted to be electrostatically actuated toward the second surface and/or the first surface. In some cases, the first diaphragm and the second diaphragm are adapted to return to a position proximate the chamber midline by elastic restoring forces, but this is not required in all embodiments. At least one aperture disposed within the first diaphragm may be misaligned with the at least one aperture disposed within the second diaphragm when the first and second diaphragms are positioned proximate to one another. 
   In some cases, the first surface can include a first port. The first diaphragm may be adapted to be electrostatically actuated to a position adjacent to the first surface to seal or substantially seal the first port. Likewise, the second surface can include a second port, and the second diaphragm may be adapted to be electrostatically actuated to a position adjacent the second surface to seal or substantially seal the second port. 
   In some instances, the first diaphragm and the second diaphragm are adapted so that they may be independently electrostatically actuated. For example, the first diaphragm may be adapted such that it can be independently electrostatically actuated to a position adjacent the first surface, so that the first diaphragm seals or substantially seals the first port, or adjacent the second surface. Likewise, the second diaphragm may be adapted such that it can be independently electrostatically actuated into a position adjacent the second surface so that the second diaphragm seals or substantially seals the second port, or adjacent the first surface. In some cases, vertical and/or horizontal stacks of such micro pumps may be provided to increase pumping compression or capacity, and in some cases, improve reliability, as desired. 
   The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The Figures, Detailed Description and Examples which follow more particularly exemplify these embodiments. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
     The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which: 
       FIG. 1  is an exploded cross-sectional view of a micro pump chamber in accordance with an embodiment of the present invention; 
       FIG. 2  is an exploded cross-sectional view of an asymmetric dual diaphragm micro pump in accordance with an embodiment of the present invention; 
       FIG. 3  is an exploded cross-sectional view of an asymmetric dual diaphragm micro pump in accordance with an embodiment of the present invention; 
       FIGS. 4 through 9  schematically illustrate operation of the micro pump of  FIG. 2 ; 
       FIG. 10  is a cross-sectional view of a vertical stack micro pump array deploying two asymmetric dual diaphragm micro pumps in accordance with an embodiment of the present invention; 
       FIG. 11  is a cross-sectional view of a vertical stack micro pump array deploying three asymmetric dual diaphragm micro pumps in accordance with an embodiment of the present invention; and 
       FIG. 12  is a diagrammatic illustration of a massively parallel micro pump array in accordance with an embodiment of the present invention. 
   

   While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. 
   DETAILED DESCRIPTION 
   The following description should be read with reference to the drawings, in which like elements in different drawings are numbered in like fashion. The drawings, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of the invention. Although examples of construction, dimensions, and materials are illustrated for the various elements, those skilled in the art will recognize that many of the examples provided have suitable alternatives that may be utilized. 
     FIG. 1  is an exploded view of a micro pump chamber  10  that includes an upper section  12  and a lower section  14 . In the description that follows, the designations of upper and lower are arbitrary, and are made merely for ease of discussion. In some instances, micro pump chamber  10  may be circular in shape if viewed from above or below. Other shapes are of course contemplated as well. 
   A chamber midline  16  can be seen as extending between upper section  12  and lower section  14 . The term “chamber midline” is not intended to imply that it extends exactly in the middle of the chambers, but rather that it simply divides the chamber into two parts. It should be noted that the spacing between elements in  FIG. 1  has been greatly exaggerated for clarity. When upper section  12  and lower section  14  are positioned next to each other, and in the illustrative embodiment shown in  FIG. 1 , it can be seen that chamber midline  16  will intersect the junction between upper section  12  and lower section  14 . 
   Upper section  12  has a surface  18  that includes a portion  20  that forms an acute angle α with chamber midline  16 . Similarly, lower section  14  has a surface  22  that includes a portion  24  that forms an angle β with chamber midline  16 . In some instances, angle β may be less than angle α. In some cases, angle β may be at least about 0.25 degrees less than angle α. 
   Angle α may be as large as desired to accomplish desired pumping characteristics and may be as large as about 45 degrees. In some particular instances, angle α may be, for example, in the range of about 0.5 degrees to about 5.0 degrees, while angle β may be in the range of about 0 to about 4.75 degrees. In some instances, angle β may be less than about 2.0 degrees and in some cases, and as illustrated with respect to  FIG. 3 , may be equal to about zero, or even negative if desired. 
   It can be noted that setting angle β to be less than angle α can reduce the working volume of, or the total space within micro pump chamber  10  (i.e. between upper section  12  and lower section  14 ). However, in some instances, reducing angle β with respect to angle α can provide improvements in some performance parameters. For example, by reducing angle β with respect to angle α, pumping frequency may be increased. Alternatively, or in addition, reducing angle β with respect to angle α may help increase the pressure differential that can be achieved across micro pump chamber  10 . 
   In the illustrative embodiment, upper section  12  includes a port  26  while lower section  14  includes a port  28 . It should be noted that while micro pump chamber  10  is not symmetric with respect to opposing sides of chamber midline  16  (i.e. upper section  12  is not symmetric to lower section  14 ), micro pump chamber  10  can in some embodiments be symmetric in the left-right direction. In other words, in the illustrative embodiment of  FIG. 1 , the right hand portion of upper section  12  (without reference numbers) may be a mirror image of the left hand portion of upper section  12  (with reference numbers), but this is not required. Similarly, right hand portion of lower section  14  may be a mirror image of the left hand portion of lower section  14 , but this is also not required. 
   In some instances, micro pump chamber  10  including upper section  12  and lower section  14  may be formed from any suitable semi-rigid or rigid material, such as plastic, ceramic, silicon, etc. For example, and in some embodiments, micro pump chamber  10  may be constructed by molding a high temperature plastic such as ULTEM™ (available from General Electric Company, Pittsfield, Mass.), CELAZOLE™ (available from Hoechst-Celanese Corporation, Summit, N.J.), KETRON™ (available from Polymer Corporation, Reading, Pa.), or some other suitable material. 
     FIG. 2  is an exploded view of a micro pump  30  employing micro pump chamber  10  ( FIG. 1 ). Chamber midline  16  ( FIG. 1 ) has been excised from this Figure to better illustrate an upper diaphragm  32  and a lower diaphragm  34 . In the illustrative embodiment, upper diaphragm  32  includes one or more upper apertures  36  and lower diaphragm  34  includes one or more lower apertures  38 . As can be seen in  FIG. 2 , upper apertures  36  may be laterally offset from lower apertures  38 . 
   In some instances, upper apertures  36  may be aligned within upper diaphragm  32  about a circle of a first radius while lower apertures  38  may be aligned within lower diaphragm  34  about a circle of a second radius that is different from the first radius, with both radii having a common center point. In this configuration, the upper apertures  36  are misaligned with the lower apertures  38 , and when the upper diaphragm  32  and the lower diaphragm  34  are situated directly adjacent to one another (e.g. in contact), the upper diaphragm  32  may seal or substantially seal the lower apertures  38  and the lower diaphragm  34  may seal or substantially seal the upper apertures  36 . 
   In some instances, the material used to make the upper diaphragm  32  and the lower diaphragm  34  may have elastic, resilient, flexible or other elastomeric properties, but this is not required in all embodiments. In some cases, upper diaphragm  32  and lower diaphragm  34  may be made from a generally compliant material. For example, upper diaphragm  32  and lower diaphragm  34  may be made from a polymer such as KAPTON™ (available from E.I. du Pont de Nemours &amp; Co., Wilmington, Del.), KALADEX™ (available from ICI Films, Wilmington, Del.), MYLAR™ (available from E.I. du Pont de Nemours &amp; Co., Wilmington, Del.), ULTEM™ (available from General Electric Company, Pittsfield, Mass.) or any other suitable material as desired. 
   As will be discussed in greater detail with respect to  FIGS. 4 through 9 , upper diaphragm  32  and lower diaphragm  34  may be electrostatically actuated through a variety of positions. Upper diaphragm  32  can be electrostatically actuated to a position in which the upper diaphragm is disposed next to surface  18  such that the upper diaphragm seals or substantially seals port  26 . Likewise, the lower diaphragm  34  can be electrostatically actuated to a position in which lower diaphragm  34  is disposed next to surface  22  such that the lower diaphragm seals or substantially seals port  28 . In some cases, the upper diaphragm  32  and the lower diaphragm  34  may be independently electrostatically actuated. For example, the upper diaphragm  32  and the lower diaphragm  34  may move in opposite directions and/or in unison. In some cases, one of the upper diaphragm  32  or lower diaphragm  34  may be electrostatically moved while the other remains stationary. 
   In order to provide for electrostatic actuation of upper diaphragm  32  and lower diaphragm  34 , it will be recognized that upper diaphragm  32 , lower diaphragm  34 , surface  18  and surface  22  may each include a corresponding electrode. Electrodes may be formed of any suitable material, using any suitable technique. By applying voltages between appropriate electrodes, upper diaphragm  32  and lower diaphragm  34  may be moved as desired via electrostatic forces. In some instances, each of the electrodes (not illustrated) may include one or more dielectric layers, either under or above each electrode, to help prevent electrical shorts between the electrodes, particularly when the corresponding components engage one another. 
     FIG. 3  is an exploded view of a micro pump  40  including upper section  12  as discussed with respect to  FIG. 2  and a lower section  42 . Upper diaphragm  32  and lower diaphragm  34  function and are constructed as discussed previously. In this illustrative embodiment, angle β is shown to be about zero degrees, and thus lower section  42  includes a surface  44  that is disposed at least substantially parallel with chamber midline  16  ( FIG. 1 ). In some cases, the lower diaphragm  34  may not need to be electrostatically pulled down toward surface  44 , as elastic restoring forces may provide this function. However, in some embodiments, the lower diaphragm  34  is electrostatically pulled down toward surface  44 . 
     FIGS. 4 through 9  are diagrammatic cross-sections showing an illustrative pumping cycle employing micro pump  30  ( FIG. 2 ). In particular, these Figures illustrate a pumping sequence where the inlet is on the bottom, and the outlet is on the top. An opposite configuration is equally appropriate since the illustrative micro pump may be completely reversible. As referenced previously, and in some illustrative embodiments, upper diaphragm  32  and lower diaphragm  34  may be electrostatically actuated between various positions. As they move, upper diaphragm  32  and lower diaphragm  34  may be considered as defining an upper volume  48 , a lower volume  50  and a middle volume  52 . 
   It should be noted that the spacing between individual components has been exaggerated for clarity in  FIGS. 4 through 9 . In many cases, upper diaphragm  32  and lower diaphragm  34  would actually be in physical contact when moving in unison, as shown, for example, in  FIGS. 4 ,  5  and  6 . 
   Upper volume  48  is formed between portion  20  of surface  18  and upper diaphragm  32 , lower volume  50  is formed between lower diaphragm  34  and portion  24  of surface  22 , and middle volume  52  is formed between upper diaphragm  32  and lower diaphragm  34 . It will be recognized that at particular pumping cycle stages, one or more of upper volume  48 , lower volume  50  and middle volume  52  may essentially disappear (i.e. become zero or substantially zero), depending on the relative positions of upper diaphragm  32  and lower diaphragm  34 . 
   In  FIG. 4 , upper diaphragm  32  and lower diaphragm  34  have both been electrostatically pulled down, thereby sealing port  28 . At this point, fluid (e.g. gas or liquid) is assumed to be contained within upper volume  48 , while lower volume  50  and middle volume  52  are essentially eliminated by the position of upper diaphragm  32  and lower diaphragm  34 . As can be seen, upper apertures  36  and lower apertures  38  do not align with each other or with either of port  26  or port  28 , in order to affect desired seals during each cycle. 
     FIG. 5  illustrates initiation of the pump stroke by simultaneously electrostatically pulling upper diaphragm  32  and lower diaphragm  34  towards the top, thus pushing the fluid that is contained within upper volume  48  through port  26 . In the illustrative embodiment, this may be accomplished by providing appropriate voltages between the electrodes on portion  20  of surface  18  and the upper diaphragm  32  and/or lower diaphragm  34 . In some cases, elastic restoring forces may supplement the movement of the upper diaphragm  32  and lower diaphragm  34  to the position shown in  FIG. 5 , or may be used exclusively.  FIG. 6  illustrates completion of this pump stroke, with both upper diaphragm  32  and lower diaphragm  34  electrostatically pulled up to seal port  26 . At this point, all of the fluid that was in upper volume  48  has been pushed out and expelled through port  26 . During this same stroke new fluid is drawn in to lower volume  50  via port  28 . 
   In  FIG. 7 , upper diaphragm  32  remains in sealing relationship with port  26  while lower diaphragm  34  is electrostatically and/or elastically pulled down, thereby causing the fluid in lower volume  50  to transfer into middle chamber  52  via lower apertures  38  ( FIG. 2 ) within lower diaphragm  34 .  FIG. 8  illustrates the orientation of lower diaphragm  34  completely pulled down electrostatically to seal port  28  while upper diaphragm  32  remains in position sealing port  26 . Finally,  FIG. 9  illustrates the midpoint of movement of upper diaphragm  32  down toward lower diaphragm  34 , wherein fluid may be pulled from middle volume  52  into upper volume  48 . Eventually, the upper diaphragm  32  is pulled down until it is adjacent to the lower diaphragm  34 , as shown in  FIG. 4 , thus completing the pump cycle. The above-described pumping cycle may be repeated to pump more fluid from port  28  to port  26 . 
   In some illustrative embodiments, micro pumps such as micro pump  30  or micro pump  40  may be assembled into micro pump arrays. By arranging micro pumps  30  or micro pumps  40  in series, i.e. the output of a first micro pump  30  or micro pump  40  may be provided to an input of a second micro pump  30  or micro pump  40 . This may create a greater pressure build-up across the micro pump assembly. By arranging micro pumps  30  or micro pumps  40  in parallel, greater pumping volume may be achieved. In some instances, two or more micro pumps  30  or micro pumps  40  may be arranged in series, and a number of the series of micro pumps  30  or micro pumps  40  may then be arranged in parallel to provide a two dimensional pumping array that provides both an improved pressure differential as well as greater pumping volume.  FIGS. 10 through 14  show particular examples of some illustrative micro pump arrays. 
     FIG. 10  illustrates a micro pump array  54  that includes an upper micro pump  56  and a lower micro pump  58 . It should be noted that designations of upper and lower are arbitrary, as micro pump array  54  can be inverted. In the illustrative embodiment, upper micro pump  56  and lower micro pump  58  may be constructed and function as discussed previously with respect to micro pump  40  ( FIG. 3 ). Upper micro pump  56  includes an inlet  60  and an outlet  62 . Lower micro pump  58  includes an inlet  64  and an outlet  66 , with the inlet in fluid communication with the outlet  62  of upper micro pump  56 . 
   Upper micro pump  56  includes an upper diaphragm  68  and a lower diaphragm  70 , as discussed previously with respect to upper diaphragm  32  and lower diaphragm  34  ( FIGS. 2 and 3 ). Similarly, lower micro pump  58  includes an upper diaphragm  72  and a lower diaphragm  74 . Upper diaphragm  68  includes several apertures  76 , and lower diaphragm includes several other apertures  78  that are misaligned with apertures  76  of the upper diaphragm  68 . Similarly, upper diaphragm  72  includes several apertures  80 , while lower diaphragm  74  includes several misaligned apertures  82 . 
   During use, fluid enters inlet  60  and is pumped through to outlet  62  as discussed previously with respect to  FIG. 3 . The fluid then enters inlet  64  and is pumped through to outlet  66 . The fluid pressure increases between inlet  60  and outlet  62 , and then increases again between inlet  64  and outlet  66 . The total pressure differential across the pump array may be the sum of these fluid pressure increases. 
     FIG. 11  illustrates a micro pump array  84  that includes an upper micro pump  86 , an intermediate micro pump  88  and a lower micro pump  90 . Upper micro pump  86  has an inlet  92  and an outlet  94 . Intermediate micro pump  88  has an inlet  96  and an outlet  98 , where the inlet  96  is in fluid communication with outlet  94  of the upper micro pump  86 . Lower micro pump  90  has an inlet  100  and an outlet  102 , wherein the inlet  100  is in fluid communication with the outlet  98  of the intermediate micro pump  88 . Construction and function of upper micro pump  86 , intermediate micro pump  88  and lower micro pump  90  may be the same as described with respect to  FIG. 10  and thus is not further discussed in detail here. 
   During use, fluid enters inlet  92  and is pumped through to outlet  94  as discussed previously with respect to  FIG. 10 . The fluid then enters inlet  96  and is pumped through to outlet  98 . Fluid then enters inlet  100  and is pumped through to outlet  102 . As discussed, the fluid pressure may increase as the fluid passes through each of upper micro pump  86 , intermediate micro pump  88  and lower micro pump  90 . It is contemplated that any number of micro pumps may be stacked in a similar manner to achieve a desired pressure increase. 
     FIG. 12  illustrates a micro pump array  144  that includes a number of pumps (such as micro pump  40  of  FIG. 3 ) arranged in series, with two or more series of pumps arranged in parallel. In the illustrative embodiment, micro pump array  144  includes a first micro pump series  146 , a second micro pump series  148 , a second-to-last micro pump series  150  and a last micro pump series  152 . Each of first micro pump series  146 , second micro pump series  148 , second-to-last micro pump series  150 , last micro pump series  152 , and each of the intermediate micro pump series (not shown) function as discussed with respect to micro pump array  130  ( FIG. 11 ). By placing a number of micro pump series (or arrays) in parallel, fluid pumping capacity may be increased. Also, by placing a number of micro pumps in parallel, the reliability of the pumping system may be increased because if one or more pump cell fails, others may provide compensation, and/or other unused (redundant) micro-pumps may be activated. 
   The invention should not be considered limited to the particular examples described above, but rather should be understood to cover all aspects of the invention as set out in the attached claims. Various modifications, equivalent processes, as well as numerous structures to which the invention can be applicable will be readily apparent to those of skill in the art upon review of the instant specification.