US20050118041A1 - Diaphragm pump - Google Patents

Abstract

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 has a first convex surface region which is formed continuously with the first surface.

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 inFIG. 3, adiaphragm92 is supported at an outerperipheral portion92athereof by a fixing surface (a joint surface)91aof adiaphragm case91. Thediaphragm case91 and thediaphragm92 have defined apump chamber93 in thediaphragm case91. Thediaphragm92 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 thedriver94 causes the deformation (displacement) of thediaphragm92, the volume of thepump chamber93 is increased and decreased, thereby allowing a fluid to flow into and to be discharged out of thepump chamber93.
• In the diaphragm pump, when the pressure in thepump chamber93 rises in a discharge stroke, while a part of thediaphragm92 which thedriver94 contacts is supported by thedriver94, the outside part of thediaphragm92 which thedriver94 does not contact is not directly supported by thedriver94 and is generally expanded toward the opposite side to thepump chamber93. Since even in the last stage of the discharge stroke, the volume of thepump chamber93 is not sufficiently reduced, the fluid which is not discharged from thepump chamber93 and remains in thepump chamber93 is increased, with the result that the pump efficiency of the diaphragm pump deteriorates.
• In the diaphragm pump, however, thedriver94 includes afitting member95 which fits thediaphragm92 and aflange96 which is formed on the outside part of thefitting member95. Theflange96 is contacted with thediaphragm92 when thediaphragm92 is deformed toward thepump chamber93, thereby preventing the outside part of thediaphragm92 from expanding toward the opposite side to thepump chamber93 in the discharge stroke.
• In thedriver94 of the diaphragm pump shown inFIG. 3, however, since asurface95aof thefitting member95 which contacts thediaphragm92 is not formed continuously with asurface96aof theflange96 which contacts thediaphragm92, a boundary between thesurface95aand thesurface96ais angled. Therefore, thediaphragm92 deformed in the discharge stroke contacts the angled boundary at an angle of deflection, thereby reducing the durability of thediaphragm92.
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 toFIG. 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 inFIG. 1, the diaphragm pump has adiaphragm case10 which includes ablock11, acircular tension plate12 which is fixedly joined to theblock11, and abody case13 in which theblock11 and thetension plate12 are accommodated. Thebody case13 is formed in a cylindrical cover shape with the cover portion thereof located on the upside as seen inFIG. 1. Theblock11 and thetension plate12 are received in thebody case13 such that theblock11 is located on the cover side.
• Theblock11 has formed in the end surface thereof facing the tension plate12 aconcave portion11a.Theconcave portion11ais closed by thediaphragm14 which is interposed between theblock11 and thetension plate12, thereby defining apump chamber15. Thediaphragm14 is made of metallic material and has a circular shape. Theblock11 and thetension plate12 support thediaphragm14 so as to permit the deformation (displacement) of thediaphragm14 by holding an annular region of an outerperipheral portion14aof thediaphragm14 at the joints of theblock11 and thetension plate12, or between afixing surface31 of theblock11 and afixing surface36 of thetension plate12 which faces thefixing surface31.
• Thebody case13 has formed therein asuction passage17 to which an external low-pressure piping (not shown) is connected, and adischarge passage18 to which an external high-pressure piping (not shown) is connected. Theblock11 has formed in the middle thereof asuction port25 which connects thepump chamber15 to thesuction passage17, and adischarge port26 which connects thepump chamber15 to thedischarge passage18. Asuction valve21 in the form of a reed valve is provided between thesuction port25 in theblock11 and thesuction passage17 in thebody case13. Adischarge valve22 in the form of a reed valve is provided between thedischarge port26 in theblock11 and thedischarge passage18 in thebody case13.
• To thediaphragm14 is connected adrive unit24 which drives thediaphragm14. Thedrive unit24 is formed with arod45 functioning as a driver which is driven so as to reciprocate by a drive source such as an electric motor (not shown). Therod45 holds thediaphragm14 at the center point thereof between afitting member46 which is arranged outside thepump chamber15 and fits thediaphragm14 and afixing member47 which is arranged inside thepump chamber15 and fixed to thefitting member46. Therefore, thediaphragm14 is deformed (displaced) as therod45 is reciprocated, thereby increasing and decreasing the volume of thepump chamber15.
• Specifically, when therod45 is moved in a direction in which therod45 leaves the pump chamber15 (downward inFIG. 1), thediaphragm14 is deformed toward the opposite side to thepump chamber15 and the volume of thepump chamber15 is increased. During a suction process when thediaphragm14 is deformed toward the opposite side to thepump chamber15, gas is introduced from thesuction passage17 to thepump chamber15 while pushing open thesuction valve21. In contrast, when therod45 is moved toward the pump chamber15 (upward inFIG. 1), thediaphragm14 is deformed toward thepump chamber15 and the volume of thepump chamber15 is decreased. During a discharge process when thediaphragm14 is deformed toward thepump chamber15, the gas in thepump chamber15 is discharged to thedischarge passage18 while pushing open thedischarge valve22.
• Therod45 includes thefitting member46 and acircular flange49 outside thefitting member46. Theflange49 is contacted with thediaphragm14 when thediaphragm14 is deformed toward thepump chamber15, thereby preventing the outside part of thediaphragm14 from expanding toward the opposite side to thepump chamber15 in a discharge stroke. Since even in the last stage of the discharge stroke, the volume of thepump chamber15 is sufficiently reduced, the fluid which is not discharged from thepump chamber15 and remains in thepump chamber15 is decreased, with the result that the pump efficiency of the diaphragm pump is improved.
• Asurface49aof theflange49 contacting thediaphragm14 has aconvex surface region51 which is formed continuously with asurface46a(plane) of thefitting member46 contacting thediaphragm14 so as to form no angle. Therefore, in a case where thediaphragm14 is deformed toward thepump chamber15, even when thediaphragm14 contacts the vicinity of a boundary between thecontacting surface46aof thefitting member46 and the contactingsurface49aof theflange49, theconvex surface region51 will have no angle of deflection, so that the durability of thediaphragm14 is improved.
• The contactingsurface49aof theflange49 has aconcave surface region52 in addition to the aforementionedconvex surface region51. Theconvex surface region51 contacts thediaphragm14 at a portion of theconvex surface region51 adjacent to thefitting member46 in an annular region. Theconcave surface region52 is formed continuously with theconvex surface region51 and contacts thediaphragm14 at a portion of theconcave surface region52 adjacent to the outerperipheral portion14ain an annular region.
• As shown inFIG. 2, in a case where thecontacting surface49aof theflange49 is formed only by the convex surface region, when thediaphragm14 is deformed toward thepump chamber15 with a relatively great curvature radius, a part of thediaphragm14 adjacent to the outerperipheral portion14ais bent with a relatively great curvature radius at a portion of thediaphragm14 which is not supported by the contactingsurface49aof theflange49, such that the part of thediaphragm14 is interposed between the contactingsurface49aand thefixing surface31. In thediaphragm14 shown by chain double-dashed line inFIG. 2, the portion of thediaphragm14 is indicated by an arrow “M”.
• In the present embodiment, when thediaphragm14 is deformed toward thepump chamber15 with a relatively great curvature radius, however, the part of thediaphragm14 adjacent to the outerperipheral portion14ais bent so as to conform with the contactingsurface49aof the flange49 (or the concave surface region52), that is, the part of thediaphragm14 is bent in such a state that the part of thediaphragm14 is supported by the contactingsurface49a,such that the part of thediaphragm14 is interposed between the contactingsurface49aand the fixingsurface31. Such a structure prevents thediaphragm14 from being bent with a relatively great curvature radius at the portion of thediaphragm14 which is not supported by the contactingsurface49aof theflange49, with the result that the durability of thediaphragm14 is improved.
• The curvatures of theconvex surface region51 and theconcave surface region52 of the contactingsurface49aof theflange49 are the same. To be more specific, a curvature radius R1 of a curved line X1 for theconvex surface region51 and a curvature radius R2 of a curved line X2 for theconcave surface region52 as viewed on a plane which extends perpendicularly to thediaphragm14 in its flat position and passes through a center point P of the diaphragm14 (i.e. the plane of the drawing ofFIG. 1), are the same.
• Therefore, when thediaphragm14 is deformed with a relatively great curvature radius toward thepump chamber15, a part of thediaphragm14 contacting either one of theconvex surface region51 and theconcave surface region52 of theflange49 is prevented from being bent with a greater curvature radius than the other part of thediaphragm14, thereby preventing stress caused by bending moment from being applied unevenly to thediaphragm14 which is in contact with the contactingsurface49aof theflange49. Consequently, the durability of thediaphragm14 is further improved.
• Theblock11 has formed a savingrecess48 in the middle of the inner surface of thepump chamber15. The savingrecess48 accommodates the fixingmember47 which fixes therod45 when thediaphragm14 deformed toward thepump chamber15 is located at the top dead center thereof where the volume of thepump chamber15 is minimized as shown by chain double-dashed line inFIG. 1. The inner surface of thepump chamber15 of theblock11 other than the savingrecess48 forms a regulatingsurface32 which provides a limit of deformation of thediaphragm14 toward the top dead center thereof. That is, when thediaphragm14 deformed toward thepump chamber15 is located at the top dead center, the surface of thediaphragm14 which faces thefluid chamber15 is brought into contact with the regulatingsurface32, thereby preventing thediaphragm14 from being further elastically deformed.
• The regulatingsurface32 is shaped so as to conform with the contactingsurface49aof theflange49. Therefore, in a state where thediaphragm14 is located at the top dead center thereof, thediaphragm14 is sandwiched substantially between the entirety of the contactingsurface49aof the rod45 (the flange49) and the entirety of the regulatingsurface32 of theblock11, and the volume of thepump chamber15 becomes substantially zero, accordingly, thus further improving the pump efficiency of the diaphragm pump.
• Specifically, the regulatingsurface32 includes aconvex surface region33 which is shaped so as to conform with theconcave surface region52 of the contactingsurface49aof theflange49 and aconcave surface region34 which is shaped so as to conform with theconvex surface region51 of the contactingsurface49a.Theconvex surface region33 is formed smoothly continuously with the fixingsurface31 such that the boundary therebetween forms no angle. Theconvex surface region33 supports thediaphragm14 which is located at the limit of deformation toward the top dead center thereof at a portion of theconvex surface region33 adjacent to the outerperipheral portion14ain an annular region. Theconcave surface region34 is formed smoothly continuously with theconvex surface region33 such that the boundary therebetween forms no angle. Theconcave surface region34 supports thediaphragm14 which is located at the limit of deformation toward the top dead center thereof at a portion of theconcave surface region34 adjacent to the center point P of thediaphragm14 in an annular region.
• Therefore, even when thediaphragm14 is located at the limit of its deformation toward the top dead center thereof and shaped to conform with the regulatingsurface32, the vicinities of the boundaries between the fixingsurface31 and the regulatingsurface32 and between theconvex surface region33 and theconcave surface region34 will have no angle of deflection, so that plastic deformation of thediaphragm14 caused by deflection is prevented and reduction of the durability of thediaphragm14 is prevented, accordingly.
• The curvatures of theconvex surface region33 and theconcave surface region34 are the same. In addition, the curvatures of theconvex surface region33 and theconcave surface region34 are the same as those of theconvex surface region51 and theconcave surface region52. To be more specific, the curvature radius R1, the curvature radius R2, a curvature radius R3 of a curved line X3 for theconvex surface region33 and a curvature radius R4 of a curved line X4 for theconcave surface region34 as viewed on a plane which extends perpendicularly to thediaphragm14 in its flat position and passes through the center point P of the diaphragm14 (i.e. the plane of the drawing ofFIG. 1), are the same.
• Therefore, when thediaphragm14 is located at the limit of its deformation toward the top dead center thereof, the curvatures of the parts of thediaphragm14 interposed between theconvex surface region33 of the regulatingsurface32 and theconcave surface region52 of theflange49 and between theconcave surface region34 of the regulatingsurface32 and theconvex surface region51 of theflange49 are prevented from being different, thereby preventing stress caused by bending moment from being applied unevenly to thediaphragm14 which is located at the limit of its deformation toward the top dead center thereof. Consequently, the durability of thediaphragm14 is further improved.
• It is noted that the following embodiments are also practicable without departing from the purpose of the invention.
• As shown inFIG. 2, the contactingsurface49aof theflange49 of therod45 is formed only by a convex surface region. In addition, the regulatingsurface32 of the diaphragm case10 (or the block11) is formed only by a concave surface region so as to be shaped to conform with the contactingsurface49aof theflange49, which is formed only by the convex surface region.
• In an alternative embodiment to the preferred embodiment, the curvatures of theconvex surface region51 and theconcave surface region52 of the contactingsurface49aof theflange49 are differentiated from each other. In another alternative embodiment to the preferred embodiment, the curvatures of theconvex surface region33 and theconcave surface region34 of the regulatingsurface32 are differentiated from each other. In a case where the former and latter alternative embodiments are combined, if the curvature of theconcave surface region34 of the regulatingsurface32 is the same as that of theconvex surface region51 of theflange49, and if the curvature of theconvex surface region33 of the regulatingsurface32 is the same as that of theconcave surface region52 of theflange49, the regulatingsurface32 is shaped so as to conform with the contactingsurface49aof theflange49.
• 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.

Claims (7)

1. A diaphragm pump comprising:

a diaphragm having a center point and an outer peripheral portion;

a diaphragm case for supporting the diaphragm at the outer peripheral portion thereof, thereby defining a pump chamber in the diaphragm case;

a driver for holding the diaphragm at the center point thereof, the diaphragm being deformed as the driver is reciprocated, thereby accomplishing a fluid to flow into and to be discharged out of the pump chamber, the driver comprising:

a fitting member for fitting the diaphragm, the fitting member having a first surface for contacting the diaphragm; and

a flange formed outside the fitting member, the flange having a second surface for contacting the diaphragm when the diaphragm is deformed toward the pump chamber, wherein the second surface of the flange has a first convex surface region which is formed continuously with the first surface of the fitting member.

2. The diaphragm pump according toclaim 1, wherein the second surface of the flange has a first concave surface region in addition to the first convex surface region, the first convex surface region contacting the diaphragm at a portion of the first convex surface region adjacent to the fitting member, the first concave surface region being formed continuously with the first convex surface region, the first concave surface region contacting the diaphragm at a portion of the first concave surface region adjacent to the outer peripheral portion of the diaphragm.

3. The diaphragm pump according toclaim 2, wherein curvatures of the first convex surface region and the first concave surface region of the second surface of the flange are the same.

4. The diaphragm pump according toclaim 1, wherein the diaphragm case has a regulating surface which forms an inner surface of the pump chamber and is shaped so as to conform with the second surface of the flange, thereby providing a limit of deformation of the diaphragm toward the pump chamber.

5. The diaphragm pump according toclaim 4, wherein the diaphragm case has a fixing surface for supporting the diaphragm at the outer peripheral portion thereof, the regulating surface being formed continuously with the fixing surface, the regulating surface having a second convex surface region for supporting the diaphragm at a portion of the second convex surface region adjacent to the outer peripheral portion of the diaphragm and a second concave surface region which is formed continuously with the second convex surface region for supporting the diaphragm at a portion of the second concave surface region adjacent to the center point of the diaphragm.

6. The diaphragm pump according toclaim 5, wherein curvatures of the second convex surface region and the second concave surface region of the regulating surface of the diaphragm case are the same.

7. The diaphragm pump according toclaim 6, wherein the second surface of the flange has a first concave surface region in addition to the first convex surface region, the first convex surface region of the second surface contacting the diaphragm at a portion of the first convex surface region adjacent to the fitting member, the first concave surface region of the second surface being formed continuously with the first convex surface region, the first concave surface region contacting the diaphragm at a portion of the first concave surface region adjacent to the outer peripheral portion of the diaphragm, curvatures of the first convex surface region and the first concave surface region of the second surface of the flange and the curvatures of the second convex surface region and the second concave surface region of the regulating surface being the same.

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