Abstract:
A check valve includes: a base member provided with an inlet channel along which fluid flows in one direction; a valve unit disposed on a valve mounting surface and including a film valve body and a frame body; and a valve seating surface defined on the valve mounting surface at the periphery of the opening of the inlet channel, wherein one or more communicating grooves are formed on the valve mounting surface across the frame body so as to extend from the valve seating surface to the outside of the frame body, wherein the inlet channel is blocked by the film valve body when the film valve body is in contact with the valve seating surface, and wherein the inlet channel and the outside of the frame body are communicated via the communicating grooves when the film valve body is separated from the valve seating surface.

Description:
CROSS-REFERENCE TO THE RELATED APPLICATION(S) 
       [0001]    The present disclosure relates to the subject matters contained in Japanese Patent Application No. 2007-338717 filed on Dec. 28, 2007, which are incorporated herein by reference in its entirety. 
       FIELD 
       [0002]    The present invention relates to a check valve provided in the fluid channel for gas or liquid to allow flow in one direction while preventing reverse flow. The check valve according to the present invention is preferably built into a pump such as a micro-pump for pumping fluid by flexing and vibrating a thin diaphragm. 
       BACKGROUND 
       [0003]    A micro-pump for constantly pumping a relatively small amount of fluid with high accuracy is conventionally provided. Diaphragm pumps are well known as this kind of a pump (for example, see JP-A-2002-106468). In a diaphragm pump, part of a wall of a pump chamber is configured by a flexible thin vibrator called diaphragm. The diaphragm is flexed and vibrated by an actuating device such as a piezoelectric element, thereby ejecting entered fluid outside the pump chamber. 
         [0004]    Such kind of a diaphragm pump is provided with a housing, which forms the pump chamber together with the diaphragm. The housing is provided with a suction channel for introducing fluid into the pump chamber and a discharge channel for ejecting fluid outside the pump chamber. Both of the channels are provided with check valves respectively. In the check valve, a film valve body having elasticity is generally used as shown in JP-A-2002-106468. 
         [0005]    The film valve body is deformed to open the channel by the flow pressure in a desired direction and deformed back to close the channel by the reverse flow pressure in the opposite direction. Various configurations are provided.  FIGS. 7A-7C  respectively show a film valve body adapted to open and close an opening  101  of a channel formed in a housing  100 .  FIG. 7A  shows a cantilever configuration in which a strip film  110  is at one end thereof fixed to the housing  100 . The strip film  110  is swingeable at the other end to open the opening  101  when fluid flows from below as shown in the figure. When fluid flows from above, downward flow pressure forces the strip film  110  in contact with the periphery of the opening  101 , thereby closing the opening  101  to stop the flow. 
         [0006]      FIG. 7B  shows another configuration in which the film  110  covering the opening  101  is at the both ends thereof fixed to the housing  100 . The film  110  is flexed to open the opening  101  by the flow pressure from below.  FIG. 7C  shows another configuration in which the film  110  is at the four corners thereof fixed to the housing  100 . The film  110  is flexed to open the opening  101  by the flow pressure from below. 
         [0007]    A thin and light film valve body is advantageous in that it is surely and immediately opened or closed in response to fluid flow. The film valve body, however, has a limited durability at the edge thereof as it is exposed to fluid flow while the film valve body is repeatedly flexed by flow pressure. As shown in  FIGS. 7B and 7C , the film valve body is fixed at the opposite ends or at the four corners, the remaining free edge is subject to tension stress and easily be torn. Further, the film valve body generally has a difficulty in assembling efficiency since it is delicate and easy to get wrinkled or bent. 
       SUMMARY 
       [0008]    According to an aspect of the invention, there is provided a check valve including: a base member provided with an inlet channel along which fluid flows in one direction; a valve unit disposed on a valve mounting surface defined on one of the faces of the base member and operative to open and close the inlet channel in response to the pressure of fluid; and a valve seating surface defined on the valve mounting surface at the periphery of the opening of the inlet channel, wherein the valve unit includes: a film valve body configured to be in contact with the valve seating surface or to be separated from the valve seating surface; and a frame body on which the film valve body is tightly stretched, wherein one or more communicating grooves are formed on the valve mounting surface across the frame body so as to extend from the valve seating surface to the outside of the frame body, wherein the inlet channel is blocked by the film valve body when the film valve body is in contact with the valve seating surface, and wherein the inlet channel and the outside of the frame body are communicated via the communicating grooves when the film valve body is separated from the valve seating surface. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    A general configuration that implements the various feature of the invention will be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention. 
           [0010]      FIG. 1  is a cross sectional view of a diaphragm pump including a check valve in accordance with an embodiment of the present invention. 
           [0011]      FIGS. 2A and 2B  are cross-sectional views of a check valve in accordance with an embodiment of the present invention, wherein  FIG. 2A  shows the closed state and  FIG. 2B  shows the opened state. 
           [0012]      FIG. 3  is a view seen from a direction shown by an arrow III in  FIG. 2A . 
           [0013]      FIG. 4A  is an exploded perspective view of a valve unit constituting a check valve and  FIG. 4B  is a perspective view thereof after assembly. 
           [0014]      FIGS. 5A and 5B  are perspective views of a valve unit in operation, wherein  FIG. 5A  shows the closed state and  FIG. 5B  is the opened state. 
           [0015]      FIG. 6A  and  FIG. 6B  are plan views of a guide member for positioning the valve unit. 
           [0016]      FIGS. 7A-7C  are perspective views of a conventional check valve. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0017]    A check valve according to an embodiment of the present invention applied in a diaphragm pump will be described with reference to the accompanying drawings. 
         [0018]      FIG. 1  is a cross-sectional view of a diaphragm pump  1  for air pumping according to the embodiment of the present invention. The pump  1  is provided with a disc-shaped diaphragm  10 , a disc-shaped housing  20  and an annular cover  30  flexibly supporting therebetween the diaphragm 10  at the circumference thereof, and a piezoelectric element  40  for activating the diaphragm  10  to be flexed and vibrated. 
         [0019]    The housing  20  has a circular bottom plate  21 . An annular peripheral wall  22  is formed at the upper periphery of the bottom plate  21  in the figure. An inner recess of the peripheral wall  22  is a pump chamber recess  23 . The pump chamber recess  23  is enclosed by the diaphragm  10 , constituting a pump chamber  2 . 
         [0020]    The bottom plate  21  has a pair of connecting pipes  24 A and  24 B projecting downward. The connecting pipe  24 A (the left side in  FIG. 1 ) is on the suction side and the connecting pipe  24 B (the right side in  FIG. 1 ) is on the ejection side. A suction channel  25   a  is formed in the suction side connecting pipe  24 A and an ejection channel  25   b  is formed in the ejection side connecting pipe  24 B. The leading opening end of the suction channel  25   a  constitutes an inlet  26   a  and the leading opening end of the ejection channel  25   b  constitutes an outlet  26   b . A tube (not shown) is connected to the suction side connecting pipe  24 A to introduce air therein. Another tube (not shown) is connected to the ejection side connecting pipe  24 B to introduce air thereout. 
         [0021]    A circular suction side valve housing recess  27   a  is formed on the upper surface of the bottom plate  21  at the position corresponding to the suction side connecting pipe  24 A. The suction channel  25   a  is open to the suction side valve housing recess  27   a . A suction side check valve  50 A in the shape of a disc is fixed to the bottom surface of the suction side valve housing recess  27   a  so as to close the opening of the suction channel  25   a.    
         [0022]    An ejection side valve housing recess  27   b  is formed on the upper surface of the bottom plate  21  at the position corresponding to the ejection side connecting pipe  24 B. The ejection side valve housing recess  27   b  is of the same size and shape as the suction side valve housing recess  27   a , but positioned deeper (lower in the figure). A circular differential recess  28  is formed on the upper surface of the bottom plate  21  at the periphery of the ejection side valve housing recess  27   b . A disc-shaped lid plate  29  is engaged with the differential recess  28  and fixed thereto. An ejection hole  29   a  communicating between the pump chamber recess  23  and the ejecting side valve housing recess  27   b  is formed at the center of the lid plate  29 . The upper surface of the lid plate  29  is coplanar with the upper surface of the bottom plate  21 . An ejection side check valve  50 B in the shape of a disc is housed in the ejection side valve housing recess  27   b  and fixed to the lower surface of the lid plate  29  so as to close the ejection hole  29   a.    
         [0023]    The suction side check valve  50 A allows air to enter into the pump chamber  2  from the suction channel  25   a  and prevents the reverse flow. The ejection side check valve  50 B allows air to enter into the ejection channel  25   b  from the pump chamber  2  and prevents the reverse flow. The suction side check valve  50 A and the ejection side check valve  50 B has the same configuration. The configuration and operation of the check valves  50 A and  50 B of the present invention are described later. 
         [0024]    The cover  30  is equivalent to the housing  20  in external diameter and equivalent to or slightly larger than the pump chamber recess  23  in internal diameter. The lower surface of the cover  30  is joined to the upper surface of the peripheral wall  22 . An annular groove  31  opening inward is formed on the lower surface of the cover  30  at the inner circumferential side. The annular groove  31  has the depth almost equivalent to the thickness of the diaphragm  10 . The diaphragm  10  is, at the edge thereof, fitted in the groove  31 . The cover  30  is placed concentrically on the upper surface of the periphery wall  22  of the housing  20  and joined to the housing  20  with the diaphragm  10  engaged therebetween. The joint between the cover  30  and the housing  20  is available by adhesive bonding or a bolt screwed between the cover  30  and the housing  20 . 
         [0025]    The diaphragm  10  is made of an elastic metal thin plate or other material and shaped like a disc. The piezoelectric element  40  in the shape of a disc of smaller diameter than the internal diameter of the cover  30  is concentrically disposed on one of the sides of the diaphragm  10  (the upper side in  FIG. 1 ) and attached thereto by adhesive or other fastening means. The diaphragm  10  having the piezoelectric element  40  mounted thereon is fitted in the groove  31  of the cover  30  and supported between the cover  30  and the housing  20  as described above. The diaphragm  10  covering the pump chamber recess  23  is airtightly fixed to the housing  20 . The pump chamber recess  23  constitutes the pump chamber  2  enclosed by the housing  20  and the diaphragm  10 . 
         [0026]    Described above is the configuration of the diaphragm pump  1 . The operation thereof is described below. 
         [0027]    A driving signal such as an alternating signal is applied to the piezoelectric element  40 . In response to the applied signal, the piezoelectric element  40  contracts and vibrates in diameter direction, thereby the diaphragm  10  is flexed and vibrated in the upper and lower direction together with the piezoelectric element  40 . 
         [0028]    When the diaphragm  10  is flexed upward (in the direction away from the housing  20 ), the volume of the pump chamber  2  is increased and the pressure therein becomes negative. In response to the negative pressure, the suction side check valve  50 A is opened to force air to enter into the suction channel  25   a  via the inlet  26   a . Air passing through the opened check valve  50 A is forced to enter into the pump chamber  2  via the suction side valve housing recess  27   a . The ejection side check valve  50 B remained closed in response to the negative pressure, therefore air is disallowed to enter from the outlet  26   b.    
         [0029]    When the diaphragm  10  is flexed downward (toward the housing  20 ), the volume of the pump chamber  2  is reduced and the pressure therein becomes positive. In response to the positive pressure, the ejection side check valve  50 B is opened. Air passing through the opened ejection side check valve  50 B is ejected from the outlet  26   b  via the ejection side valve housing recess  27   b  and the ejection channel  25   b . The suction side check valve  50 A remained closed in response to the positive pressure, therefore air in the pump chamber  2  is disallowed to be ejected from the inlet  26   a.    
         [0030]    Repeated suction and ejection operations as above described cause the pumping operations to occur continually. Air drawn into the pump chamber  2  via the inlet  26   b  is pumped out via the outlet  23   b.    
         [0031]    The suction side check valve  50 A and the ejection side check valve  50 B are described below referring to  FIGS. 2  to  5 . They are of the same configuration as described above, therefore they are collectively called a check valve  50  if distinguishing is not necessary.  FIG. 2  is a cross-sectional view of the check valve  50 .  FIG. 3  is a view seen from a direction shown by an arrow III in  FIG. 2A . The check valve  50  is provided with an upstream side valve plate  60  and a downstream side valve plate  70  as shown in  FIG. 2 . The valve plates  60  and  70  are in the same external shape of a disc and concentrically joined to each other. An annular thick portion  61  is formed at the periphery of the lower surface of the upstream side valve plate  60  (the facing surface to the downstream side valve plate  70 ). Thereby, a circular shallow recess  62  is formed inside the annular thick portion  61 . An inlet channel  63  is penetrated at the center of the upstream side valve plate  60 . 
         [0032]    A disc-shaped valve unit  80  is concentrically disposed and fixed at the center of the bottom surface  62   a  of the recess  62 . The valve unit  80  is, as shown in  FIG. 4 , configured by an annular frame body  81  and a film valve body  82  stretched tight on one of the sides of the frame body  81 . The frame body  81  is made of relatively rigid material and preferably a stainless ring about 10 μm in thickness having the cross sectional shape of a rectangle, for example. The valve body  82  is preferably made of a PET film about 2 μm in thickness, which is cut into a circular piece, for example. The valve body  82  is almost equivalent to the frame body  81  in external diameter. The entire edge of the valve body  82  is airtightly joined to one of the sides of the frame body  81  by adhesive or other means. With the valve body  82  side of the valve unit  80  facing the bottom surface  62   a  of the recess  62 , the valve body  82  is attached to the bottom surface  62   a  by adhesive or other means at the edge portion joined to the frame body  81 . The valve unit  80  is thereby fixed to the bottom surface  62   a  of the recess  62  of the upstream side valve plate  60 . 
         [0033]    The thickness of the valve unit  80  (the total thickness of the frame body  81  and the valve body  82 ) is equivalent to the depth of the recess  62 . The valve unit  80  sandwiched between the upper and lower valve plates  60  and  70  is built within the check valve  50 . The downstream side valve plate  60  is joined to the upstream side valve plate  70 , thereby the internal space of the frame body  81  is separated into a compartment constituting an inside space  51  and the external space of the frame body  81  within the recess  62  is separated into another compartment constituting an outside space  52 . The valve unit  80  may not be bonded to the bottom surface  62   a  of the recess  62  and instead it may be only pressed and thereby supported between the upper and lower valve plates  70  and  80 . 
         [0034]    The valve unit  80  is concentrically disposed at the center of the bottom surface  62   a  of the recess  62 . The valve body  82  of the valve unit  80  is normally in contact with the bottom surface  62   a  as shown in  FIG. 2A . The inlet channel  63  of the upstream side valve plate  60  is thereby blocked by the valve body  82 . The area of the bottom surface  62   a  with which the valve body  82  is in contact constitutes a valve seating surface  62   b.    
         [0035]    When air enters through the inlet channel  63 , the flow pressure is applied to the valve body  82  so that it is flexed and swollen toward the downstream side valve plate  70  as shown in  FIG. 2B . On the bottom surface  62   a  of the recess  62 , a plurality of linear communicating grooves  64  extending from the valve seating surface  62   b  to the outside space  52  are formed across the frame body  81 . In the embodiment, four communicating grooves  64  are radially formed with a center on the inlet channel  63 . 
         [0036]    On the downstream side valve plate  70 , formed are a plurality of discharge holes  71  communicating the outside space  52  with the outside and a plurality of back pressure holes  72  communicating the inside space  51  with the outside. As shown in  FIG. 3 , each of the discharge holes  71  and the back pressure holes  72  is a relatively small circular hole. The discharge holes  71  are circumferentially disposed at regular intervals on the downstream side valve plate  70 . The back pressure holes  72  are circumferentially disposed at regular intervals on the downstream side valve plate  70  with one of the holes placed at the center thereof. 
         [0037]    Described above is the configuration of the check valve  50 . The check valve  50  is disposed so as to block the passage of fluid with the upstream side valve plate  60  at the upstream side of fluid and the downstream side valve plate  70  at the downstream side thereof. In the diaphragm pump 1  in  FIG. 1 , the check valve  50  is housed in the suction side valve housing recess  27   a  as the suction side check valve  50 A and in the ejection side valve housing recess  27   b  as the ejection side check valve  50 B. 
         [0038]    For the suction side check valve  50 A, the upstream side valve plate  60  is fixed to the bottom surface of the suction side valve housing recess  27   a  with the inlet channel  63  communicating with the suction channel  25   a . For the ejection side check valve  50 B, the upstream side valve plate  60  is fixed to the lower surface of the lid plate with the inlet channel  63  communicating with the ejection hole  29   a . When the diaphragm  10  is flexed to increase the volume of the pump chamber  2 , the suction side check valve  50 A is opened to force air to enter into the pump chamber  2  while the ejection side check valve  50 B is closed. When the diaphragm  10  is flexed to reduce the volume of the pump chamber  2 , the ejection side check valve  50 B is opened to force air to be ejected from the pump chamber  2  while the suction side check valve  50 A is closed. The opening and closing operations of the check valve  50  is described below. 
         [0039]    The check valve  50  is normally closed with the valve body  82  in contact with the valve seating surface  62   b  as shown in  FIG. 2A  and  FIG. 5A . The check valve  50  is opened when air enters from the inlet channel  63  toward the valve body  82 . For the suction side check valve  50 A, air enters from the inlet channel  63  toward the valve body  82  when air enters from the inlet  26   a  toward the pump chamber  2 . For the ejection side check valve  50 B, air enters from the inlet channel  63  toward the valve body  82  when air in the pump chamber  2  flows out from the ejection hole  29   a  of the lid plate  29  toward the ejection channel  25   b.    
         [0040]    When air enters into the inlet channel  63 , the valve body  82  is flexed and swollen toward the downstream side valve plate  70 . The valve body  82  is thereby separated from the valve seating surface  62   b . The check valve  50  is thereby opened. Air entered into the space between the valve seating surface  62   b  and the valve body  82  flows along the communicating grooves  64  toward outside, passes through the frame body  81  and reaches the outside space  52 .  FIG. 5B  shows air flow by the broken arrow line. Air in the outside space  52  is then discharged from the discharge holes  71  toward the downstream space. The downstream space on the suction side corresponds to the suction side valve housing recess  27   a  communicating with the pump chamber  2 . The downstream space on the ejection side corresponds to the ejection side valve housing recess  27   b  communicating with the ejection channel  25   b.    
         [0041]    When air flow described above is reversed, the check valve  50  is closed to block the reverse flow. For the suction side check valve  50 A, the reverse flow occurs when air flows from the pump chamber  2  toward the suction side check valve  50 A. For the ejection side check valve  50 B, the reverse flow occurs when air enters from the outlet  26   b  toward the pump chamber  2 . 
         [0042]    When the reverse flow occurs, the pressure is applied to the downstream side valve plate  70  to force air to enter into the inside space  51  through the back pressure holes  72 . The valve body  82  is pressed by entered air, thereby brought into contact with the valve seating surface  62   b . The inlet channel  63  is thereby blocked and closed. Air may also enter from the discharge holes  71  and flow into the communicating grooves  64  via the outside space  52 , but air in the communicating grooves  64  is blocked since the valve body  82  is in contact with the valve seating surface  62   b.    
         [0043]    According to the check valve  50  of the present embodiment, the valve body  82  flexing to open and close the inlet channel  63  is stretched tight on the frame body with the edge of the valve body  82  fixed thereto. Therefore, the valve body  82  is reinforced by the frame body  81 . When the valve body  82  is flexed and deformed, the edge thereof is not subject to tension stress due to air flow. The valve body  82  is equally flexed over the entire surface thereof, and therefore damage to the edge such as a tear is prevented. The valve body  82  even using a film maintains high durability. 
         [0044]    Further, since the edge of the valve body  82  is firmly held, the opening and closing operations are smooth and sure. The valve body  82  of the embodiment is preferably used especially when the valve body  82  needs to be thin and light or needs high durability to follow the vibration of the diaphragm  10  at high frequency (for example, when the diaphragm resonates around 20 KHz). Further, since the film valve body  82  is stretched tight on the frame body  81  and configured into the valve unit  80 , the valve body  82  is resistant to bends or wrinkles. This improves work efficiency in assembly. 
         [0045]    In the valve unit  50  of the embodiment, a guide member may be preferably provided to appropriately position the valve unit  80  concentrically on the bottom surface  62   a  of the recess  62  of the upstream side valve plate  60 . FIG.  6 A shows a pair of guide pieces  91  integrally formed with the frame body  81  of the valve unit  80 . The guide piece  91  is a long plate of the same thickness as the frame body  81 , having portions extending outward in diameter direction from the 180 degrees opposite positions on the circumferential surface of the frame body  81 . The leading ends of the guide piece  91  are circular-shaped, having pinholes  92   a  and  92   b  at the center thereof respectively. The pin hole  92   a  is circular while the pin hole  92   b  is long hole extending in diameter direction. In the embodiment, the pin holes  92   a  and  92   b  of the guide piece  91  are engaged with pins  65   a  and  65   b  projected on the bottom surface  62   a  respectively, thereby the valve unit  80  is positioned on the bottom surface  62   a.    
         [0046]      FIG. 6B  shows a guide member  95  made of an annular plate. The guide member  95  has an annular portion  96  having the diameter engageable within the recess  62 . Inside the annular portion  96 , a plurality of guide pieces  97  (four pieces in this example) extending inward in diameter direction are integrally formed. The leading end of each of the guide pieces  97  is bent into the shape of a concave so that it is engaged with the circumferential surface of the frame body  81 . The guide member  95  is engaged within the recess  62  and fixed to the bottom surface  62   a  by adhesive or other means. The valve unit  80  is positioned on the bottom surface  62   a  with the frame body  81  engaged within the guide pieces  97 . 
         [0047]    In the check valve  50  of the embodiment, the frame body  81  of the valve unit  80  is in the shape of a circular ring, but it may be in the shape of a rectangular ring. 
         [0048]    The plurality of communicating grooves  64  are radially arranged, but they may be parallely arranged. 
         [0049]    In the check valve  50  of the embodiment, the downstream side valve plate  70  may be eliminated from the configuration. The upstream side valve plate  60  may be replaced by the housing  20  or the lid plate  29 . In the suction side check valve  50 A, the bottom surface of the suction side valve housing recess  27   a  corresponds to the bottom surface  62   a  of the upstream side valve plate  60 . Then the valve unit  80  may be directly fixed to the bottom surface of the suction side valve housing recess  27   a  to block the opening of the suction channel  25   a.    
         [0050]    In the ejection side check valve  50 B, the lower surface of the lid plate  29  corresponds to the bottom surface  62   a  of the upstream side valve plate  60 . The valve unit  80  may be directly fixed to the lower surface of the lid plate  29  to cover the ejection hole  29   a . The periphery of the opening of the ejection hole  29   a  blocked by the valve body  82  constitutes the valve seating surface  62   b . In any case, on the surface where the valve unit  80  is fixed, communicating grooves corresponding to the communicating grooves  64  are formed extending from the valve seating surface toward the external side of the frame body  81 . 
         [0051]    It is to be understood that the invention is not limited to the specific embodiment described above and that the invention can be embodied with the components modified without departing from the spirit and scope of the invention. The invention can be embodied in various forms according to appropriate combinations of the components disclosed in the embodiment described above. For example, some components may be deleted from the configurations described as the embodiment.