Patent Publication Number: US-2005126649-A1

Title: Check valve and pump including the same

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to compact and low-profiled check valves having excellent sealing characteristics.  
      2. Description of the Related Art  
      As disclosed in Japanese Unexamined Patent Application Publication No. 2000-274374, an umbrella valve having an umbrella-shaped component and a shaft corresponding to a handle of the umbrella disposed in the center of the umbrella-shaped component is well-known as a small-sized check valve. The umbrella-shaped component is disposed on one of two surfaces, i.e. a sealing surface, of a partition so as to cover a hole bored through the partition. The shaft is supported by the partition such that the umbrella-shaped component is deformably brought into contact with the sealing surface. Thus, the umbrella valve functions as a check valve. More specifically, the umbrella valve allows a stream applying a fluid pressure to the inner side of the umbrella-shaped component to flow through the hole by deforming the umbrella-shaped component, while the umbrella valve blocks a stream applying a fluid pressure to the outer side of the umbrella-shaped component.  
      However, as a result of investigation, the present inventors found that this umbrella valve can have sufficient sealing characteristics only when the sealing surface is sufficiently flat and the sealing surface is in contact with the inner side of the umbrella-shaped component at a uniform pressure. This problem is more remarkable as the umbrella valve is downsized.  
      Moreover, the umbrella valve is used as a check valve for a low-profiled device, for example, a piezoelectric pump. Since the piezoelectric pump is often used for a water-cooled notebook computer, the piezoelectric pump should be ultrathin, and there has been a demand for thinner umbrella valves. Other types of check valves disclosed in Japanese Unexamined Patent Application Publication Nos. 9-250461, 9-329271, and 2003-90447 have the same problem as the above-described check valve.  
     SUMMARY OF THE INVENTION  
      Accordingly, it is an object of the present invention to provide a compact, low-profiled umbrella-type check valve that includes a valve component composed of a single elastic body and that has excellent sealing characteristics.  
      The check valve according to the present invention includes a valve component composed of an elastic material and having a flat circular seal and a shaft extending from the center of the seal; and a partition having a valve-supporting hole sustaining the valve component, a thin circular portion centered at the valve-supporting hole and having a diameter smaller than the seal, and vents through the thin circular portion. The shaft of the valve component is sustained by the valve-supporting hole in the partition, and the seal is deformed toward the partition such that the bottom surface of the seal is in line contact with a circular edge that is defined by the level difference between the partition and the thin circular portion at least in a state where the valve component does not receive fluid pressure.  
      The seal of the valve component may be flat when the valve component is not attached to the partition, and the bottom surface of the seal may be in contact with the thin circular portion at the boundary between the shaft and the seal. Alternatively, the rim of bottom surface of the seal that comes into contact with the circular edge may be annually tapered and the thickness of the seal may be reduced toward the outer rim.  
      The check valve according to the present invention has excellent sealing characteristics regardless of the planarity of the seal since the bottom surface of seal of the valve component is in line contact with the circular edge defined by the level difference between the partition and the thin circular portion. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a longitudinal sectional view illustrating an example of a piezoelectric pump including check valves according to the present invention;  
       FIG. 2  is a longitudinal sectional view illustrating a valve component of the check valve according to the present invention in a free state;  
       FIG. 3  is a longitudinal sectional view of the valve component shown in  FIG. 2  attached to a partition while the check valve is closed;  
       FIG. 4  is a longitudinal sectional view of the above-described valve component while the check valve is open;  
       FIG. 5  is a partly sectioned perspective view of the check valve according to the present invention; and  
       FIG. 6  is a longitudinal sectional view illustrating another embodiment of the check valve according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       FIG. 1  shows an embodiment of a check valve according to the present invention that is used in a piezoelectric pump. A housing  10  includes an upper housing  10   a  and a lower housing  10   b , and a piezoelectric vibrator  11  is hermetically clamped therebetween. The thickness of the piezoelectric vibrator  11  is exaggerated for purposes of illustration, and the actual thickness is less than 1.5 mm. The upper housing  10   a  has a hollow section  13 , and a variable chamber  12  is formed between the hollow section  13  and the piezoelectric vibrator  11 .  
      The upper housing  10   a  has an inlet  14 A and an outlet  14 B for liquid, i.e. cooling water. The inlet  14 A communicates with an inlet reservoir  15 A, whereas the outlet  14 B communicates with an outlet reservoir  15 B. A partition  16 A is disposed between the inlet reservoir  15 A and the variable chamber  12  and a partition  16 B is disposed between the outlet reservoir  15 B and the variable chamber  12 . Check valves  17 A and  17 B are attached to the partitions  16 A and  16 B, respectively. The check valve  17 A allows a stream from the inlet  14 A (the inlet reservoir  15 A), to the variable chamber  12 , and blocks a stream in the opposite direction. On the other hand, the check valve  17 B allows a stream from the variable chamber  12  to the outlet  14 B (the outlet reservoir  15 B), and blocks a stream in the opposite direction.  
      In the above-described piezoelectric pump, when the piezoelectric vibrator  11  deforms to expand the capacity of the variable chamber  12 , the check valve  17 A opens and the check valve  17 B closes, and thus the liquid flows from the inlet  14 A (inlet reservoir  15 A) into the variable chamber  12 . Alternately, when the piezoelectric vibrator  11  deforms to reduce the capacity of the variable chamber  12 , the check valve  17 B opens and the check valve  17 A closes, and thus the liquid flows from the variable chamber  12  into the outlet  14 B (outlet reservoir  15 B). Accordingly, liquid can be pumped by alternately deforming, or vibrating, the piezoelectric vibrator  11 . Such a piezoelectric vibrator is well known.  
      The structures of the check valves  17 A and  17 B are the same, and each include a valve component  17  and a partition  16 . The valve component  17  and the partition  16  will now be described with reference to FIGS.  2  to  5 .  
      The valve component  17  shown in  FIG. 2  is symmetrical with respect to an axis  17 X. The valve component  17  is composed of a single elastic body, and includes a disk seal  171  and a shaft  172  extending orthogonally from the bottom center of the seal  171 . The bottom surface  173  of the seal  171  is preferably flat in a free state, i.e. when the valve component  17  is not attached to the partition  16 . The shaft  172  has a stop shoulder  174  at the tip thereof.  
      The partition  16  is substantially flat, and includes a flat (thick) portion  161  opposing the outer rim of the bottom surface of the seal  171  and a thin circular portion  162  formed in the flat portion  161 . The level difference between the flat portion  161  and the thin circular portion  162  forms a circular edge  163 .  
      A valve-supporting hole  164  that sustains the valve component  17  is formed at the center of the thin circular portion  162 , and a plurality of vents  165  are formed around the valve-supporting hole  164 . These vents  165  communicate with both the variable chamber  12  and the inlet reservoir  15 A or outlet reservoir  15 B shown in  FIG. 1 . The shaft  172  of the valve component  17  is fitted into the valve-supporting hole  164  of the partition  16 , and is fixed thereto by the stop shoulder  174  that protrudes radially from the valve-supporting hole  164 .  
      When the shaft  172  is fixed to the valve-supporting hole  164 , and at least in a state where the seal  171  does not receive fluid pressure, the bottom surface of the seal  171  is in line contact with the circular edge  163  at a position adjacent to the outer rim of the seal  171 . In other words, the bottom surface of the flat seal  171  is deformed to be in contact with the thin circular portion  162  at the boundary between the shaft  172  and the seal  171 , and consequently, the bottom surface of the seal  171  comes into line contact with the circular edge  163  at a position adjacent to the outer rim of the seal  171 , instead of surface contact with the flat portion  161 . The position of the stop shoulder  174  of the shaft  172 , i.e. the length of the valve-supporting hole  164 , is determined such that the seal  171  is deformed as described above. The term “line contact” in this specification does not mean a geometric contact, but a contact of the bottom surface of the seal  171  and the circular edge  163  at the highest contact pressure that can achieve high sealing characteristics.  
      As shown in  FIG. 3 , when the pressure at the top surface of the seal  171  of the valve component  17  is high, the seal  171  is pressed against the circular edge  163  at a high contact pressure to close the fluid channel. As shown in  FIG. 4 , when the pressure at the bottom surface of the seal  171  is high, the seal  171  is separated from the circular edge  163  to open the fluid channel. In this manner, the above-described structure functions as a check valve. When the check valve is closed, the seal  171  of the valve component  17  is in line contact with the circular edge  163  of the partition  16 . As a result, higher sealing characteristics can be achieved compared to a known umbrella valve whose seal is in surface contact with a flat portion. The planarity of the flat portion  161  has little effect on the sealing characteristics. Moreover, when the check valve is open, the fluid channel is smoother and the channel resistance is lower compared to the umbrella valve. In addition, the check valve can be low-profiled compared to the known umbrella valve having an umbrella-shaped valve component.  
       FIG. 6  illustrates another embodiment of the check valve according to the present invention. In this embodiment, an annularly tapered surface  175  is formed along the rim of the bottom surface of flat seal  171  of the valve component  17  by reducing the thickness of the seal  171  toward the outer rim to secure the line contact with the circular edge  163 .