BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to a pump provided with diaphragms, and more particularly to a compact pump which is used for a sphygmomanometer or the like.  
           [0002]    A related-art compact pump of this type (disclosed in Japanese Patent Publication No. 2002-106471A) is now described with reference to FIGS.  3  to  4 B. In FIG. 3, a compact pump  1  is provided with two diaphragms  4  for defining pump chambers  3  in a casing  2  which has a rectangular shape in a plan view. Hollow fitting members  5  are provided at respective center parts on a lower face of the diaphragms  4  so as to project downward from the diaphragms  4 , and there is arranged, below the diaphragms  4 , a pivotable member  6  which is adapted to move the lower faces of the diaphragms  4  up and down. The casing  2  is composed of three steps, namely, an upper case  2   a , an intermediate case  2   b , and a lower case  2   c , and the diaphragms  4  are held in the casing  2  in such a manner that flange portions  4   a  of the diaphragms  4  are clamped between the upper case  2   a  and the intermediate case  2   b.    
           [0003]    Moreover, shaft bodies  7  having intake holes  7   a  are provided on the pivotable member  6  in the vicinity of its outer peripheral ends and positioned below the respective center part of the diaphragms  4  so as to project upwardly. By tightly fitting inner faces of the hollow fitting members  5  provided on the diaphragms  4  to outer faces of these shaft members  7 , the diaphragms  4  can be mounted to the pivotable member  6 .  
           [0004]    The diaphragms  4  are partly cut in the respective center parts of their bottoms in order to form air intake valve bodies  8 , and there are formed through holes  9  by the cut. The through holes  9  can be opened or closed by the air intake valve bodies  8 , thus constituting air intake valve sections V 1 .  
           [0005]    Further, a vent hole  10  is formed in a center part of the upper case  2   a , and two annular concave grooves  11  which open downward and communicate with the vent hole  10  are provided on a lower face of the upper case  2   a  at an outer circumference of the vent hole  10 . Vent valve bodies  12  consisting of upper end portions of the diaphragms  4  are fitted by pressure to inner wall faces  11   a  of the annular concave grooves  11 , thus constituting vent valve sections V 2 .  
           [0006]    An eccentric rotation shaft  13  pierces through a center part of the pivotable member  6 . An extended portion  14  which is extended from the intermediate case  2   b  is provided above the pivotable member  6 , and a V-shaped recess  15  which opens downward is formed in a lower part of the extended portion  14 . An upper end portion of the eccentric rotation shaft  13  is loosely fitted in the recess  15  so as to swing freely therein. On the other hand, a rotary body  17  is fixed to an upper end of a rotary drive shaft  16  which is rotatably supported in an upright manner at a center of a lower part of the lower case  2   c , and there is formed, as shown in FIGS. 4A and 4B, a hole  18  in a columnar shape having a determined diameter and a determined depth on an upper face of the rotary body  17  at a position eccentric from its center position. A lower end portion of the eccentric rotation shaft  13  is loosely fitted into the hole  18  so as to swing freely therein.  
           [0007]    A motor casing  20  which contains a motor  19  connected to the rotary drive shaft  16  is directly connected to the lower case  2   c . The lower case  2   c  is provided with a communicating hole  21  which communicates with the motor casing  20 , and in addition, air intake holes  22  are formed in a lower part of the motor casing  20  for introducing outside air into the motor casing  20 .  
           [0008]    In this state, when the rotary drive shaft  16  is driven by the motor  19  to rotate and the rotary body  17  is rotated, the eccentric rotation shaft  13  is caused to rock inside the hole  18 , resulting in an eccentric rotation. This will cause a pivoting motion of the pivotable member  6  thereby to move the lower end portions of the diaphragms  4  up and down. When the lower end portion of one of the diaphragms  4 , for example, is moved downward, negative pressure is generated inside the diaphragm  4 , and the vent valve body  12  will be tightly fitted to the inner wall face  11  a of the annular concave groove  11 . In other words, the vent valve section V 2  is closed, and the air intake valve body  8  opens the through hole  9 . In this manner, the air intake valve section V 1  is shifted into an open state, and air is introduced from the intake hole  7   a  into the diaphragm  4 , as shown by an arrow C.  
           [0009]    Then, when the lower end portion of the diaphragm  4  is moved upward, high pressure will be generated in the diaphragm  4 , and the air intake valve body  8  closes the through hole  9 , shifting the air intake valve section V 1  into a closed state. At the same time, the vent valve body  12  is enlarged in diameter so as to depart from the inner wall face  11   a , and the air is exhausted through the vent valve section V 2 , as shown by an arrow D. Specifically, the air exhausted from the vent valve body  12  passes the annular concave groove  11  and exhausted from the vent hole  10  to the exterior of the casing  2 .  
           [0010]    Also with the upward movement of the diaphragm  4 , negative pressure will be generated in the lower case  2   c , and the air existing in the motor casing  20  flows into the lower case via the communication hole  21 , as shown by an arrow E. This generates negative pressure inside the motor casing  20 , and the outside air is introduced into the motor casing  20  via the air intake hole  22 , as shown by an arrow F.  
           [0011]    In the compact pump, since the hole  18  is formed in a columnar shape having a relatively small diameter in the rotary body  17  eccentrically, it is difficult to insert the lower end portion of the eccentric rotation shaft  13  when they are assembled.  
           [0012]    Further, in order to facilitate the inserting operation, the lower case  2   c  of the compact pump is formed of transparent material so that a worker can insert the eccentric rotation shaft  13  into the hole  18  while confirming the hole  18  from outside of the lower case  2   c . Hence, not only the working efficiency is poor, but also the cost has become high because different materials are employed for the lower case  2   c  and the other upper and intermediate cases  2   a  and  2   b.    
         SUMMARY OF THE INVENTION  
         [0013]    It is therefore an object of the invention to provide a pump provided with diaphragms, which is able to facilitate the assembling operation of the eccentric rotation shaft to improve the operation efficiency.  
           [0014]    In order to achieve the above object, according to the present invention, there is provided a pump, comprising:  
           [0015]    a plurality of diaphragms, which define a plurality of pump chambers;  
           [0016]    a pivotable member, attached to the diaphragms;  
           [0017]    a rotator, having a fitting hole formed in one face eccentrically from a rotation center of rotator; and  
           [0018]    a shaft member, inserted into the fitting hole to connect the pivotable member and the rotator,  
           [0019]    wherein an entrance edge of the fitting hole is chamfered.  
           [0020]    Preferably, a groove portion having slopes extending from a vicinity of the rotation center toward the fitting hole is formed on the one face of the rotator while being inclined downwardly.  
           [0021]    Here, it is preferable that a width of the groove portion is made narrower as closer to the fitting hole.  
           [0022]    In the above configurations, when the shaft member is assembled, the one end portion of the shaft member will be guided by the chamfered portion and the guide groove to be introduced into the fitting hole.  
           [0023]    Therefore, the worker need not insert the end portion of the eccentric rotation shaft into the fitting hole while confirming the fitting hole as in the related-art pump, and the inserting operation can be automatically completed. In this manner, the shaft member can be easily assembled and the working efficiency can be enhanced. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]    The above objects and advantages of the present invention will become more apparent by describing in detail preferred exemplary embodiments thereof with reference to the accompanying drawings, wherein:  
         [0025]    [0025]FIG. 1 is a vertical sectional view of a compact pump showing one embodiment of the present invention;  
         [0026]    [0026]FIG. 2A is a plan view of a rotary body in FIG. 1;  
         [0027]    [0027]FIG. 2B is a vertical sectional view of the rotary body in FIG. 1;  
         [0028]    [0028]FIG. 3 is a vertical sectional view of a related-art compact pump;  
         [0029]    [0029]FIG. 4A is a plan view of a rotary body in FIG. 3; and  
         [0030]    [0030]FIG. 4B is a vertical sectional view of the rotary body in FIG. 3. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    One embodiment of the present invention will be described in detail referring to FIGS. 1 and 2. It is to be noted that for convenience of explanation, the same components as those of the related-art compact pump will be denoted in the drawings with the same reference numerals, and explanation of the components will be omitted. In FIG. 1, a compact pump  23  is provided with a rotary body  24  in place of a rotary body ( 17  in FIG. 3) provided in the related-art compact pump ( 1  in FIG. 3). The rotary body  24  is eccentrically provided with a hole  25  in place of the hole ( 18  in FIG. 3) in the related-art compact pump.  
         [0032]    The rotary body  24  has a hole  25  in a columnar shape, as shown in FIG. 2, in place of the hole ( 18  in FIG. 3) in the related-art pump, and an entrance edge of the hole  25  is chamfered to form a guide inlet  26 . In addition, there is formed a guide groove  27  which inclines downwardly from the vicinity of the center of the rotary body  24  toward the hole  25  while narrowing the width thereof.  
         [0033]    Accordingly, when the eccentric rotation shaft  13  is assembled to the rotary body  24 , in a state where the eccentric rotation shaft  13  is held by the upper case  2   a  and the intermediate case  2   b  together with the pivotable member  6  and the diaphragms  4 , and the rotary drive shaft  16  is pivotally supported by the lower case  2   c . The upper case  2   a  and the intermediate case  2   b  are moved close to the lower case  2   c  to be engaged with each other. Then, the lower end portion of the eccentric rotation shaft  13  is brought near to the center of the rotary body  24 , and guided by the guide groove  27  and the guide inlet  26  to be introduced and inserted into the hole  25 .  
         [0034]    Therefore, a worker need not insert the lower end portion of the eccentric rotation shaft  13  into the hole  25  while confirming the hole  25  as in the related-art pump, and the eccentric rotation shaft  13  can be automatically inserted. This enables the eccentric rotation shaft to be easily assembled, and the working efficiency can be enhanced.  
         [0035]    In this state, when the rotary body  24  is rotated with the rotation of the motor  19 , the lower end portion of the eccentric rotation shaft  13  will be pivoted inside the hole  25  resulting in an eccentric rotation. This will cause the pivoting motion of the pivotable member  6  thereby to move the lower end portions of the diaphragms  4  up and down. When the lower end portion of one of the diaphragms  4 , for example, is moved downward, negative pressure is generated inside the diaphragm  4 , and the vent valve body  12  is tightly fitted to the inner wall face  11  a of the annular concave groove  11 . In this manner, the vent valve section V 2  is closed, and the air intake valve body  8  opens the through hole  9 . In other words, the air intake valve section V 1  is shifted into an open state, and air is introduced from the intake hole  7   a  into the diaphragm  4 , as shown by the arrow C.  
         [0036]    Then, when the lower end portion of the diaphragm  4  is moved upward, high pressure is generated in the diaphragm  4 , and the air intake valve body  8  closes the through hole  9 , shifting the air intake valve section V 1  into a closed state. At the same time, the vent valve body  12  is enlarged in diameter so as to depart from the inner wall face  11  a, and the air is exhausted through the vent valve section V 2 , as shown by the arrow D. Specifically, the air exhausted from the vent valve body  12  passes the annular concave groove  11  and exhausted from the vent hole  10  to the exterior of the casing  2 .  
         [0037]    Also with the upward movement of the diaphragm  4 , negative pressure is generated in the lower case  2   c , and the air existing in the motor casing  20  flows into the lower case  2   c  via the communication hole  21 , as shown by the arrow E. This generates negative pressure inside the motor casing  20 , and the outside air is introduced into the motor casing  20  via the air intake hole  22 , as shown by the arrow F.  
         [0038]    Although the present invention has been shown and described with reference to specific preferred embodiments, various changes and modifications will be apparent to those skilled in the art from the teachings herein. Such changes and modifications as are obvious are deemed to come within the spirit, scope and contemplation of the invention as defined in the appended claims.
In a pump, a plurality of pump chambers are defined by a plurality of diaphragms. A pivotable member is attached to the diaphragms. A rotator has a fitting hole formed in one face eccentrically from a rotation center of rotator. A shaft member is inserted into the fitting hole to connect the pivotable member and the rotator. An entrance edge of the fitting hole is chamfered.