Patent Publication Number: US-2005118041-A1

Title: Diaphragm pump

Description:
BACKGROUND OF THE INVENTION  
      The present invention relates to a diaphragm pump.  
      Japanese Unexamined Utility Model Publication No. 7-14179 discloses the diaphragm pump. As shown in  FIG. 3 , a diaphragm  92  is supported at an outer peripheral portion  92   a  thereof by a fixing surface (a joint surface)  91   a  of a diaphragm case  91 . The diaphragm case  91  and the diaphragm  92  have defined a pump chamber  93  in the diaphragm case  91 . The diaphragm  92  has fitted at the center thereof a driver (a rod)  94  which is driven so as to reciprocate by a drive source such as an electric motor (not shown). As the reciprocation of the driver  94  causes the deformation (displacement) of the diaphragm  92 , the volume of the pump chamber  93  is increased and decreased, thereby allowing a fluid to flow into and to be discharged out of the pump chamber  93 .  
      In the diaphragm pump, when the pressure in the pump chamber  93  rises in a discharge stroke, while a part of the diaphragm  92  which the driver  94  contacts is supported by the driver  94 , the outside part of the diaphragm  92  which the driver  94  does not contact is not directly supported by the driver  94  and is generally expanded toward the opposite side to the pump chamber  93 . Since even in the last stage of the discharge stroke, the volume of the pump chamber  93  is not sufficiently reduced, the fluid which is not discharged from the pump chamber  93  and remains in the pump chamber  93  is increased, with the result that the pump efficiency of the diaphragm pump deteriorates.  
      In the diaphragm pump, however, the driver  94  includes a fitting member  95  which fits the diaphragm  92  and a flange  96  which is formed on the outside part of the fitting member  95 . The flange  96  is contacted with the diaphragm  92  when the diaphragm  92  is deformed toward the pump chamber  93 , thereby preventing the outside part of the diaphragm  92  from expanding toward the opposite side to the pump chamber  93  in the discharge stroke.  
      In the driver  94  of the diaphragm pump shown in  FIG. 3 , however, since a surface  95   a  of the fitting member  95  which contacts the diaphragm  92  is not formed continuously with a surface  96   a  of the flange  96  which contacts the diaphragm  92 , a boundary between the surface  95   a  and the surface  96   a  is angled. Therefore, the diaphragm  92  deformed in the discharge stroke contacts the angled boundary at an angle of deflection, thereby reducing the durability of the diaphragm  92 .  
     SUMMARY OF THE INVENTION  
      The present invention is directed to a diaphragm pump which improves durability of a diaphragm while maintaining high pump efficiency.  
      The present invention provides the following feature. A diaphragm pump includes a diaphragm, a diaphragm case and a driver. The diaphragm has a center point and an outer peripheral portion. The diaphragm case supports the diaphragm at the outer peripheral portion thereof, thereby defining a pump chamber in the diaphragm case. The driver holds the diaphragm at the center point thereof. The diaphragm is deformed as the driver is reciprocated, thereby accomplishing a fluid to flow into and to be discharged out of the pump chamber. The driver includes a fitting member and a flange. The fitting member fits the diaphragm and has a first surface for contacting the diaphragm. The flange is formed outside the fitting member. The flange has a second surface for contacting the diaphragm when the diaphragm is deformed toward the pump chamber. The second surface of the flange has a first convex surface region which is formed continuously with the first surface of the fitting member.  
      Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments, together with the accompanying drawings, in which:  
       FIG. 1  is a sectional view illustrating a diaphragm pump according to a preferred embodiment of the present invention;  
       FIG. 2  is a sectional view illustrating a diaphragm pump according to another preferred embodiment of the present invention; and  
       FIG. 3  is a sectional view illustrating a prior art diaphragm pump. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      A diaphragm pump according to a preferred embodiment of the present invention will now be described with reference to  FIG. 1 . In the present preferred embodiment, the diaphragm pump is adapted for feeding gas.  
       FIG. 1  shows a sectional view illustrating a diaphragm pump. As shown in  FIG. 1 , the diaphragm pump has a diaphragm case  10  which includes a block  11 , a circular tension plate  12  which is fixedly joined to the block  11 , and a body case  13  in which the block  11  and the tension plate  12  are accommodated. The body case  13  is formed in a cylindrical cover shape with the cover portion thereof located on the upside as seen in  FIG. 1 . The block  11  and the tension plate  12  are received in the body case  13  such that the block  11  is located on the cover side.  
      The block  11  has formed in the end surface thereof facing the tension plate  12  a concave portion  11   a.  The concave portion  11   a  is closed by the diaphragm  14  which is interposed between the block  11  and the tension plate  12 , thereby defining a pump chamber  15 . The diaphragm  14  is made of metallic material and has a circular shape. The block  11  and the tension plate  12  support the diaphragm  14  so as to permit the deformation (displacement) of the diaphragm  14  by holding an annular region of an outer peripheral portion  14   a  of the diaphragm  14  at the joints of the block  11  and the tension plate  12 , or between a fixing surface  31  of the block  11  and a fixing surface  36  of the tension plate  12  which faces the fixing surface  31 .  
      The body case  13  has formed therein a suction passage  17  to which an external low-pressure piping (not shown) is connected, and a discharge passage  18  to which an external high-pressure piping (not shown) is connected. The block  11  has formed in the middle thereof a suction port  25  which connects the pump chamber  15  to the suction passage  17 , and a discharge port  26  which connects the pump chamber  15  to the discharge passage  18 . A suction valve  21  in the form of a reed valve is provided between the suction port  25  in the block  11  and the suction passage  17  in the body case  13 . A discharge valve  22  in the form of a reed valve is provided between the discharge port  26  in the block  11  and the discharge passage  18  in the body case  13 .  
      To the diaphragm  14  is connected a drive unit  24  which drives the diaphragm  14 . The drive unit  24  is formed with a rod  45  functioning as a driver which is driven so as to reciprocate by a drive source such as an electric motor (not shown). The rod  45  holds the diaphragm  14  at the center point thereof between a fitting member  46  which is arranged outside the pump chamber  15  and fits the diaphragm  14  and a fixing member  47  which is arranged inside the pump chamber  15  and fixed to the fitting member  46 . Therefore, the diaphragm  14  is deformed (displaced) as the rod  45  is reciprocated, thereby increasing and decreasing the volume of the pump chamber  15 .  
      Specifically, when the rod  45  is moved in a direction in which the rod  45  leaves the pump chamber  15  (downward in  FIG. 1 ), the diaphragm  14  is deformed toward the opposite side to the pump chamber  15  and the volume of the pump chamber  15  is increased. During a suction process when the diaphragm  14  is deformed toward the opposite side to the pump chamber  15 , gas is introduced from the suction passage  17  to the pump chamber  15  while pushing open the suction valve  21 . In contrast, when the rod  45  is moved toward the pump chamber  15  (upward in  FIG. 1 ), the diaphragm  14  is deformed toward the pump chamber  15  and the volume of the pump chamber  15  is decreased. During a discharge process when the diaphragm  14  is deformed toward the pump chamber  15 , the gas in the pump chamber  15  is discharged to the discharge passage  18  while pushing open the discharge valve  22 .  
      The rod  45  includes the fitting member  46  and a circular flange  49  outside the fitting member  46 . The flange  49  is contacted with the diaphragm  14  when the diaphragm  14  is deformed toward the pump chamber  15 , thereby preventing the outside part of the diaphragm  14  from expanding toward the opposite side to the pump chamber  15  in a discharge stroke. Since even in the last stage of the discharge stroke, the volume of the pump chamber  15  is sufficiently reduced, the fluid which is not discharged from the pump chamber  15  and remains in the pump chamber  15  is decreased, with the result that the pump efficiency of the diaphragm pump is improved.  
      A surface  49   a  of the flange  49  contacting the diaphragm  14  has a convex surface region  51  which is formed continuously with a surface  46   a  (plane) of the fitting member  46  contacting the diaphragm  14  so as to form no angle. Therefore, in a case where the diaphragm  14  is deformed toward the pump chamber  15 , even when the diaphragm  14  contacts the vicinity of a boundary between the contacting surface  46   a  of the fitting member  46  and the contacting surface  49   a  of the flange  49 , the convex surface region  51  will have no angle of deflection, so that the durability of the diaphragm  14  is improved.  
      The contacting surface  49   a  of the flange  49  has a concave surface region  52  in addition to the aforementioned convex surface region  51 . The convex surface region  51  contacts the diaphragm  14  at a portion of the convex surface region  51  adjacent to the fitting member  46  in an annular region. The concave surface region  52  is formed continuously with the convex surface region  51  and contacts the diaphragm  14  at a portion of the concave surface region  52  adjacent to the outer peripheral portion  14   a  in an annular region.  
      As shown in  FIG. 2 , in a case where the contacting surface  49   a  of the flange  49  is formed only by the convex surface region, when the diaphragm  14  is deformed toward the pump chamber  15  with a relatively great curvature radius, a part of the diaphragm  14  adjacent to the outer peripheral portion  14   a  is bent with a relatively great curvature radius at a portion of the diaphragm  14  which is not supported by the contacting surface  49   a  of the flange  49 , such that the part of the diaphragm  14  is interposed between the contacting surface  49   a  and the fixing surface  31 . In the diaphragm  14  shown by chain double-dashed line in  FIG. 2 , the portion of the diaphragm  14  is indicated by an arrow “M”.  
      In the present embodiment, when the diaphragm  14  is deformed toward the pump chamber  15  with a relatively great curvature radius, however, the part of the diaphragm  14  adjacent to the outer peripheral portion  14   a  is bent so as to conform with the contacting surface  49   a  of the flange  49  (or the concave surface region  52 ), that is, the part of the diaphragm  14  is bent in such a state that the part of the diaphragm  14  is supported by the contacting surface  49   a,  such that the part of the diaphragm  14  is interposed between the contacting surface  49   a  and the fixing surface  31 . Such a structure prevents the diaphragm  14  from being bent with a relatively great curvature radius at the portion of the diaphragm  14  which is not supported by the contacting surface  49   a  of the flange  49 , with the result that the durability of the diaphragm  14  is improved.  
      The curvatures of the convex surface region  51  and the concave surface region  52  of the contacting surface  49   a  of the flange  49  are the same. To be more specific, a curvature radius R 1  of a curved line X 1  for the convex surface region  51  and a curvature radius R 2  of a curved line X 2  for the concave surface region  52  as viewed on a plane which extends perpendicularly to the diaphragm  14  in its flat position and passes through a center point P of the diaphragm  14  (i.e. the plane of the drawing of  FIG. 1 ), are the same.  
      Therefore, when the diaphragm  14  is deformed with a relatively great curvature radius toward the pump chamber  15 , a part of the diaphragm  14  contacting either one of the convex surface region  51  and the concave surface region  52  of the flange  49  is prevented from being bent with a greater curvature radius than the other part of the diaphragm  14 , thereby preventing stress caused by bending moment from being applied unevenly to the diaphragm  14  which is in contact with the contacting surface  49   a  of the flange  49 . Consequently, the durability of the diaphragm  14  is further improved.  
      The block  11  has formed a saving recess  48  in the middle of the inner surface of the pump chamber  15 . The saving recess  48  accommodates the fixing member  47  which fixes the rod  45  when the diaphragm  14  deformed toward the pump chamber  15  is located at the top dead center thereof where the volume of the pump chamber  15  is minimized as shown by chain double-dashed line in  FIG. 1 . The inner surface of the pump chamber  15  of the block  11  other than the saving recess  48  forms a regulating surface  32  which provides a limit of deformation of the diaphragm  14  toward the top dead center thereof. That is, when the diaphragm  14  deformed toward the pump chamber  15  is located at the top dead center, the surface of the diaphragm  14  which faces the fluid chamber  15  is brought into contact with the regulating surface  32 , thereby preventing the diaphragm  14  from being further elastically deformed.  
      The regulating surface  32  is shaped so as to conform with the contacting surface  49   a  of the flange  49 . Therefore, in a state where the diaphragm  14  is located at the top dead center thereof, the diaphragm  14  is sandwiched substantially between the entirety of the contacting surface  49   a  of the rod  45  (the flange  49 ) and the entirety of the regulating surface  32  of the block  11 , and the volume of the pump chamber  15  becomes substantially zero, accordingly, thus further improving the pump efficiency of the diaphragm pump.  
      Specifically, the regulating surface  32  includes a convex surface region  33  which is shaped so as to conform with the concave surface region  52  of the contacting surface  49   a  of the flange  49  and a concave surface region  34  which is shaped so as to conform with the convex surface region  51  of the contacting surface  49   a.  The convex surface region  33  is formed smoothly continuously with the fixing surface  31  such that the boundary therebetween forms no angle. The convex surface region  33  supports the diaphragm  14  which is located at the limit of deformation toward the top dead center thereof at a portion of the convex surface region  33  adjacent to the outer peripheral portion  14   a  in an annular region. The concave surface region  34  is formed smoothly continuously with the convex surface region  33  such that the boundary therebetween forms no angle. The concave surface region  34  supports the diaphragm  14  which is located at the limit of deformation toward the top dead center thereof at a portion of the concave surface region  34  adjacent to the center point P of the diaphragm  14  in an annular region.  
      Therefore, even when the diaphragm  14  is located at the limit of its deformation toward the top dead center thereof and shaped to conform with the regulating surface  32 , the vicinities of the boundaries between the fixing surface  31  and the regulating surface  32  and between the convex surface region  33  and the concave surface region  34  will have no angle of deflection, so that plastic deformation of the diaphragm  14  caused by deflection is prevented and reduction of the durability of the diaphragm  14  is prevented, accordingly.  
      The curvatures of the convex surface region  33  and the concave surface region  34  are the same. In addition, the curvatures of the convex surface region  33  and the concave surface region  34  are the same as those of the convex surface region  51  and the concave surface region  52 . To be more specific, the curvature radius R 1 , the curvature radius R 2 , a curvature radius R 3  of a curved line X 3  for the convex surface region  33  and a curvature radius R 4  of a curved line X 4  for the concave surface region  34  as viewed on a plane which extends perpendicularly to the diaphragm  14  in its flat position and passes through the center point P of the diaphragm  14  (i.e. the plane of the drawing of  FIG. 1 ), are the same.  
      Therefore, when the diaphragm  14  is located at the limit of its deformation toward the top dead center thereof, the curvatures of the parts of the diaphragm  14  interposed between the convex surface region  33  of the regulating surface  32  and the concave surface region  52  of the flange  49  and between the concave surface region  34  of the regulating surface  32  and the convex surface region  51  of the flange  49  are prevented from being different, thereby preventing stress caused by bending moment from being applied unevenly to the diaphragm  14  which is located at the limit of its deformation toward the top dead center thereof. Consequently, the durability of the diaphragm  14  is further improved.  
      It is noted that the following embodiments are also practicable without departing from the purpose of the invention.  
      As shown in  FIG. 2 , the contacting surface  49   a  of the flange  49  of the rod  45  is formed only by a convex surface region. In addition, the regulating surface  32  of the diaphragm case  10  (or the block  11 ) is formed only by a concave surface region so as to be shaped to conform with the contacting surface  49   a  of the flange  49 , which is formed only by the convex surface region.  
      In an alternative embodiment to the preferred embodiment, the curvatures of the convex surface region  51  and the concave surface region  52  of the contacting surface  49   a  of the flange  49  are differentiated from each other. In another alternative embodiment to the preferred embodiment, the curvatures of the convex surface region  33  and the concave surface region  34  of the regulating surface  32  are differentiated from each other. In a case where the former and latter alternative embodiments are combined, if the curvature of the concave surface region  34  of the regulating surface  32  is the same as that of the convex surface region  51  of the flange  49 , and if the curvature of the convex surface region  33  of the regulating surface  32  is the same as that of the concave surface region  52  of the flange  49 , the regulating surface  32  is shaped so as to conform with the contacting surface  49   a  of the flange  49 .  
      Although, in the above-mentioned embodiment the diaphragm pump of the present invention is applied to the diaphragm pump for handling the gas, the diaphragm pump of the present invention is not limited to such diaphragm pump, but it is applicable to a diaphragm pump for handling a liquid.  
      Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein but may be modified.