Patent Document

BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a rapid exhausting mechanism in a pump unit which is suitable for a small-sized sphygmomanometer for measuring blood pressure at a wrist, for example.  
         [0002]     Conventionally, a small-sized sphygmomanometer is composed so that, for example, a cuff wound around an upper arm is pressurized to a predetermined pressure level by a small-sized air pump, the pressure in the cuff is gradually lowered at a constant-speed by a normal exhausting mechanism after the blood flow is interrupted once by pressing the artery, patterns of the pressure inside the cuff and vibration amplitude incidental to pulsation of the artery are processed by a microcomputer, and the systolic blood pressure and diastolic blood pressure are measured. The rapid exhausting mechanism is to instantaneously exhaust air in the cuff after the measuring process is over, and it is necessary that no air leaks when carrying out pressurization and measurement.  
         [0003]     Generally, it is preferable that characteristics of the normal exhausting mechanism used for a sphygmomanometer reside in a linear decrease in the pressure inside the cuff at a constant speed of 3 mmHg through 4 mmHg per second or so as time elapses and characteristics of the rapid exhausting mechanism reside in a quick descent of the pressure as time elapses.  
         [0004]      FIG. 3  shows such a pump unit equipped with respective exhausting mechanism as described above. In the same drawing, the pump unit  1  is composed of a pump section  2  driven by an electric motor, a normal exhausting mechanism  3  for exhausting air at a constant speed through, for example, a slit, a rapid exhausting mechanism driven by a plunger, and a tubular body  5  having flexibility.  
         [0005]     The normal exhausting mechanism  3  and rapid exhausting mechanism  4  are provided separately from the pump section  2 , and these components are connected by the tubular body  5 . The tubular body  5  connects an exhaust port  6  of the pump section  2 , the normal exhausting mechanism  3  and rapid exhausting mechanism  4  with each other. In addition, the same tubular body  5  is connected to a cuff (not illustrated) wound around, for example, an upper arm. An air path  8  which communicates with a pump chamber  7  of the pump section  2 , normal exhausting mechanism  3 , rapid exhausting mechanism  4  and the cuff is formed inside the tubular body  5 .  
         [0006]     In the pump unit  1  thus constructed, as the pump section  2  is driven, and air is taken from the outside into the pump chamber  7 , the air in the pump chamber  7  is sent into a cuff through the air path  8 . When the pressure in the cuff is pressurized to a predetermined pressure level, air exhaust in the air path  8  is commenced by the normal exhausting mechanism  3 . In synchronization therewith, air of a greater volume than the volume of air exhausted from the normal exhausting mechanism  3  is sent into the cuff from the pump chamber  7 .  
         [0007]     Also, as the cuff is internally pressurized to a predetermined pressure level, the pump section  2  stops its operation, whereby the pressure inside the cuff is gradually lowered by utilizing normal exhaust of the normal exhausting mechanism  3 . At this time, patterns of the pressure inside the cuff and vibration amplitudes incidental to pulsation of the artery are processed by a microcomputer, and the systolic blood pressure and diastolic blood pressure are measured. After the measurement is processed, the air in the cuff is discharged with a breath by the rapid exhausting mechanism  4 .  
         [0008]     However, in the pump unit  1 , the normal exhausting mechanism  3  and rapid exhausting mechanism  4  are provided separately from the pump section  2 . Therefore, the pump unit  1  has a number of components, and its structure is also complicated. In addition, since the rapid exhausting mechanism  4  of the pump unit  1  employs an exclusive plunger as an actuator, the mechanism  4  becomes heavy and large-sized, resulting in an increase in production costs.  
         [0009]     Japanese Patent Publication No. 2000-352379A proposes a relatively small-sized exhausting mechanism. This configuration includes, as an exhausting mechanism in a diaphragm type pump equipped with an actuator for vertically moving a diaphragm, an intake one-way valve having a valve body which is made of a flexible member and is provided so as to correspond to an intake port, and an exhaust one-way valve having a valve body which is made of a flexible member and is provided so as to correspond to an exhaust port. Here, minute concave and convex irregularities are provided on the surface to which the valve bodies comes in contact with, thereby preventing the valve bodies are adhered thereon. The respective one-way valves can be opened in minute differences in pressure between the upstream side and downstream side.  
         [0010]     However, it is ignored air leakage at the position where the minute concave and convex irregularities are provided, which is caused when the upstream side is at a high pressure level.  
       SUMMARY OF THE INVENTION  
       [0011]     It is therefore an object of the invention to provide a small-sized and inexpensive pump unit capable of air leakage even at a high pressure level.  
         [0012]     In order to achieve the above object, according to the invention, there is provided a pump, comprising: 
        a pump case;     a diaphragm, provided in the pump case so as to define a pump chamber communicated with an external member having an air chamber;     a motor, which actuates the diaphragm to introduce air to the air chamber; and     an exhaust valve, which exhausts air in the pump chamber to lower a pressure in the air chamber, the exhaust valve comprising:     an exhaust port, communicated with the pump chamber;     a flexible valve body, having a larger size than the exhaust port and disposed so as to close the exhaust port from a side facing the pump chamber;     an actuator, disposed in an opposite side to the valve body relative to the exhaust port, and driven by the motor so as to be movable between a first position retracted from the exhaust port and a second position passing through the exhaust port so that the valve body is actuated so as to open the exhaust port; and     an urging member, which always urges the actuator to the first position thereof.        
 
         [0021]     With this configuration, when the pressure in the pump chamber is increased, the flexible valve body is pressed against the exhaust port and seals the same. Accordingly, air leaking in such a condition can be reliably avoided while the closing operation of the exhaust port is performed. When the motor drives the actuator so as to move to the second position thereof, the valve body is actuated so that the exhaust port is forcibly opened against the pressure. As a result, the air in the pump chamber is exhausted.  
         [0022]     Further, since the actuator is driven by utilizing the driving force of the motor, it is not necessary to adopt the exclusive plunger having large size and weight. Therefore, a small-sized and inexpensive pump can be obtained.  
         [0023]     Preferably, the pump further comprises: 
        a first gear, coupled with a rotary shaft of the motor;     a second gear, meshing with the first gear to be rotated;     a lever member, pivotably provided about the rotary shaft; and     a clutch mechanism, connecting the second gear and the lever member such that the lever member is pivoted in accordance with the rotation of the rotary shaft.        
 
         [0028]     Here, the lever member is so pivoted as to come into contact with the actuator such that the actuator is moved to the second position thereof against the urging force from the urging member, when the rotary shaft is rotated in the first direction. The lever member is so pivoted as to separate from the actuator in such a direction that the actuator is placed in the second position when the rotary shaft is rotated in the second direction.  
         [0029]     In this case, the actuator is appropriately driven with the small-sized mechanism.  
         [0030]     Preferably, each of the actuator, the first gear, the second gear and the lever member is comprised of a resin material.  
         [0031]     In this case, the parts cost can be further reduced.  
         [0032]     According to the invention, there is also provided a hemodynamometer, comprising: 
        a cuff, adapted to be attached on a patient body and having an air chamber; and     a pump, comprising: 
            a pump case;     a diaphragm, provided in the pump case so as to define a pump chamber communicated with the air chamber;     a motor, which actuates the diaphragm to introduce air to the air chamber; and     an exhaust valve, which exhausts air in the pump chamber to lower a pressure in the air chamber, the exhaust valve comprising: 
                an exhaust port, communicated with the pump chamber;     a flexible valve body, having a larger size than the exhaust port and disposed so as to close the exhaust port from a side facing the pump chamber;     an actuator, disposed in an opposite side to the valve body relative to the exhaust port, and driven by the motor so as to be movable between a first position retracted from the exhaust port and a second position passing through the exhaust port so that the valve body is actuated so as to open the exhaust port; and     an urging member, which always urges the actuator to the first position thereof.   
               
               
 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0043]     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:  
         [0044]      FIG. 1  is a vertical section view of a pump unit according to one embodiment of the invention;  
         [0045]      FIG. 2  is an enlarged plan view of a rapid exhausting mechanism in the pump unit of  FIG. 1 ; and  
         [0046]      FIG. 3  is a vertical section view of a related-art pump unit. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0047]     One embodiment of the invention will be described below in detail with reference to the accompanying drawings. A pump unit according to this embodiment is suitable for a small-sized sphygmomanometer for measuring blood pressure at a wrist.  
         [0048]     As shown in  FIG. 1 , a pump unit  9  is composed so that a pump section  11 , a normal exhausting mechanism  12  and a rapid exhausting mechanism  13 , which are the major parts of the pump unit  9 , are provided internally in a unit case  10 , made of a resin material, which is rectangular in its plan view and is composed of an upper case  10   a , an intermediate plate  10   b  and a lower case  10   c . A motor case  14  is fixed on and attached to the lower face of the unit case  10 , and a motor  15  for driving members in the pump section  11  is accommodated in the motor case  14 . The rotary drive shaft  16  of the motor  15  protrudes into the lower case  10   c  along with its bearing portion  17 . A communication opening  18  is provided between the lower case  10   c  and the motor case  14 . Here, intake ports  19  are provided on the lower part of the motor case  14  in order to take atmospheric air into the motor case  14 .  
         [0049]     A description is given of the principal mechanism of the pump unit  9  on the basis of the structure of the pump section  11 . The pump section  11  is equipped at an intermediate portion between the normal exhausting mechanism  12  and the rapid exhausting mechanism  13 , and is provided with a diaphragm body  21  having two diaphragm portions  21   a  which form pump chambers  20 . The diaphragm body  21  is composed of a member having flexibility such as a rubber material having resiliency or a flexible plastic material, and flange portions  21   b  are placed and fixed between the upper case  10   a  and the intermediate plate  10   b  and are held at the unit case  10 . Hollowed bodies  22  are provided so as to protrude from the lower part center portion of the respective diaphragm portions  21   a  in the diaphragm body  21 , and a rocking body  23  for vertically rocking the lower face of the respective diaphragm portions  21   a  is provided downward of the diaphragm body  21 .  
         [0050]     Axial bodies  24  which are located in the vicinity of both end parts of the rocking body  23  and downward of the center part of the respective diaphragm portions  21   a  and has air intake ports  24   a  protruding upward. And, the inner faces of the respective hollowed bodies  22  are firmly adhered to the outer faces of the respective axial bodies  24 , and the respective diaphragm portions  21   a  are attached to the rocking body  23 . Portions corresponding to the air intake ports  24   a  on the bottom portion of the respective diaphragm portions  21   a  are partially cut off, wherein valve bodies  25  are formed, and the respective air intake ports  24   a  can be closed and opened by the valve bodies  25 , thereby forming valve sections V 1 .  
         [0051]     An eccentric rotary shaft  26  for rocking the rocking body  23  by its eccentric rotation is passed through and fixed at the center part of the rocking body  23 . A protrusion  27  protruded from the intermediate plate  10   b  is provided upward of the rocking body  23 , and a recess  28  is formed at the lower part of the protrusion  27 . On the other hand, a drive gear  29  made of a resin material is fixed at and attached to the upper end of the rotary shaft  16  protruding from downward into the lower case  10   c , and a recess  30  is formed at a position apart from the center position of the upper part of the drive gear  29 . And, the upper end of the eccentric rotary shaft  26  is idly fitted in the recess  28 , and the lower end thereof is idly fitted in the recess  30 .  
         [0052]     In addition, a nozzle  31  is provided so as to protrude from the central part of the upper face of the upper case  10   a  and an exhaust port  31   a  is drilled and provided at the nozzle  31 . A tubular body  32  having flexibility, which communicates to a cuff (not illustrated), is firmly fitted to and connected to the nozzle  31 . On the other hand, two annular grooves  33  are formed so as to face downward, which communicate with the exhaust port  31   a , are formed on the outer circumference of the exhaust port  31   a  on the lower face of the upper case  10   a , and exhaust valve bodies  34  extending from the respective diaphragm portions  21   a  are pressed to the inner wall face forming the annular grooves  33 , wherein exhaust valve portions V 2  are composed.  
         [0053]     Next, a description is given of a structure of the normal exhausting mechanism. The normal exhausting mechanism  12  is provided so as to correspond to the annular grooves  33  communicating with the inside of a cuff through the exhaust port  31   a , and is provided with a valve body  35  formed at a part of the diaphragm body  21  and an adjuster  36  with a screw, which adjusts the exhaust quantity of the valve body  35 . The adjuster  36  is screwed in a screw hole of a hollow cylindrical portion  37  of the intermediate plate  10   b.    
         [0054]     The valve body  35  causes a part of the diaphragm body  21  to protrude upward in the annular groove  33 , and the upper end thereof is formed to be like a closed tube. The valve body  35  is brought into contact with the inside lower face of the annular groove  33 , and a slit  35  communicating with the inside is formed on the circumference of the valve body  35  along the lengthwise direction (the vertical direction in  FIG. 1 ) thereof.  
         [0055]     On the other hand, a press member  36   a  having a greater outer diameter than the inner diameter of the lower end opening of the valve body  35  is formed at the tip end of the adjuster  36  with a screw to become integral therewith, and an engagement groove (not illustrated) into which the tip end of a screwdriver is inserted when adjusting the exhaust quantity is formed at the base end side of the adjuster  36  with a screw. In addition, a through hole  36   b  passed through the both ends of the adjuster  36  is opened and provided at the center part of the adjuster  36  with a screw. The adjuster  36  with a screw is caused to move upward, that is, in the direction along which the adjuster  36  is penetrated into the valve body  35 , by engaging the tip end of a screwdriver with the engagement groove and turning it in the right direction, and move downward, that is, in the direction along which the adjuster  36  comes out of the valve body  35 , by turning the same in the left direction.  
         [0056]     In the normal exhausting mechanism  12 , if the adjuster  36  with a screw is turned in the right direction and is moved to the valve body  35  side, the press member  36   a  is inserted into the valve body  35 . By insertion thereof, the valve body  35  is pressed and widened to be deformed, and in line with the deformation, the slit  35   a  is opened. Air passed through the opening of the slit  35   a  passes through the through hole  36   b  of the adjuster  36  with a screw and is exhausted therefrom. The opening amount of the slit  35   a  can be adjusted by the amount of deformation of the valve body  35  in accordance with the amount of movement of the adjuster  35  with the screw, so that the rate of gradually reducing the pressure inside the cuff can be adjusted. The adjustment is carried out when assembling. Usually, the adjustment is not executed after the assembling, excepting the cases of maintenance and inspection.  
         [0057]     Next, a description is given of a structure of the rapid exhausting mechanism  13 . The rapid exhausting mechanism  13  has an exhaust port  38  drilled at the part of the intermediate plate  10   b , which lets air in the cuff escape. A valve body  39  having a greater area than the area of the opening of the exhaust port  38  is disposed at a high pressure side communicating with the inside of the cuff via the annular groove  33 . The valve body  39  is formed by using a thin rubber sheet  40  having easy deformability such as chloroprene and silicone, etc., and cutting in the same to become almost semi-circular.  
         [0058]     The valve body  39  includes an exhaust lever  42  having an exhaust pin  41  which presses and opens the valve body  39  from the rear side through the exhaust port  38  and a lever driving gear  43 , made of a resin material, for driving the exhaust lever  42 . The lever driving gear  43  is rotatably attached to the other end side of the pivot lever  44 , made of a resin material, one end side of which is pivotably attached to the bearing portion  17 , via a pivot shaft  45  and a coil spring  46  serving as a clutch, and is engaged with the drive gear  29 .  
         [0059]     The Z-shaped exhaust lever  42  is formed by a resin material having an adequate thickness. The exhaust pin  41  is provided so as to protrude from one end portion of the upper face opposed to the exhaust port  38 , and a hinge  47  is provided at the other end portion of the upper face. The exhaust lever  42  is provided at the lower case  10   c  so as to be pivotable about the hinge  47 . The exhaust lever  42  pivots between an opening position where the exhaust pin  41  presses and opens the valve body  39  and a closing position where the exhaust pin  41  is retracted from the exhaust port  38 .  
         [0060]     Further, an engaging section  48  having a plurality of teeth (three teeth in  FIG. 2 ) is formed at the portion corresponding to the lever driving gear  43  at the lower side in the exhaust lever  42 . As shown in  FIG. 2 , the plurality of teeth are formed to be engaged with the gear teeth of the driving gear  43 . A retainer pin  49  is provided so as to protrude from the side of the exhaust lever  42  which is opposite to the side of the engaging section  48 , and a conical coil spring  50  fixed on the retainer pin  49  is disposed between the exhaust lever  42  and the inner wall face of the lower case  10   c  while being compressed. The exhaust lever  42  is always pressed to the closing position by resiliency of the conical coil spring  50 .  
         [0061]     As described above, the lever driving gear  43  is rotatably attached to the other end portion of the pivot lever  44 , one end portion of which is pivotably attached to the bearing portion  17 , via a pivot shaft  45  and a coil spring  46  serving as a clutch. Both sides at the other end portion at the pivot lever  44  are slightly swelled. By both the swelled portions  44   a  and  44   b  being brought into contact with the walls at the lower case  10 , the pivot lever  44  is regulated in terms of its pivot amount in the left and right directions in  FIG. 2 . In addition, an arcuate guide rib  51  for guiding the tip end portion of the pivot lever  44  is provided on the bottom face of the lower case  10   c.    
         [0062]     A flat head portion  45   a  which is flush with the upper face of the lever driving gear  43  is formed on the top portion of the pivot shaft  45  for rotatably supporting the lever driving gear  43 . Further, a recess  43   a  is provided at the middle part of the upper face of the lever driving gear  43 . The coil spring  46  is pressed and provided between the flat head portion  45   a  and the recess  43   a , wherein the lower face of the lever driving gear  43  is brought into press contact with the upper face of the pivot lever  44  by resiliency of the coil spring  46 .  
         [0063]     The lever driving gear  43  rotatably attached to the pivot shaft  45  on the pivot lever  44  is engaged with the drive gear  29  fixed on the rotary drive shaft  16 . When the motor  15  is driven and the drive gear  29  is rotated, the lever driving gear  43  is rotated integral with the drive gear  29 .  
         [0064]     Next, a description is given of operations of the pump unit  9  equipped with a rapid exhausting mechanism as described above. When the motor  15  is driven for rotation in its normal direction and the drive gear  29  is rotated by rotation of the rotary drive shaft  16 , the eccentric rotary shaft  26  eccentrically turns in the pump section  11 , wherein the rocking body  23  is caused to rock, and the lower end portions of the respective diaphragm portions  21   a  of the diaphragm body  21  move vertically. When the lower end portion of one diaphragm portion  21   a  is moved downward, the pressure in the interior of the diaphragm portion  21   a  is made negative, and the exhaust valve body  34  which adheres to the inner wall face of the annular groove  33  closes the exhaust valve portion V 2  and the valve body  25  opens the air intake port  24   a  from its closed state, thereby making the valve portion V 1  open, wherein air intake is carried out from the air intake port  24   a  into the diaphragm portion  21   a  as shown by the arrow E.  
         [0065]     On the other hand, in the rapid exhausting mechanism, if the drive gear  29  normally rotates (in the direction of the arrow A in  FIG. 2 ) by rotation of the motor  15  in its normal direction, the lever driving gear  43  rotates in its normal direction (in the direction of the arrow a in  FIG. 2 ). At this time, since clutch friction is produced due to resiliency of the coil spring  46  between the lever driving gear  43  and the pivot lever  44 , the pivot lever  44  turns in the direction of the arrow C in  FIG. 2  about the bearing portion  17  until the swelled portion  44   a  is brought into contact with the right inner wall of the lower case  10   c  in  FIG. 2 . When, with the contacting, the pivot lever  44  is regulated in terms of its turning, a portion (clutch portion) which is friction-coupled as a clutch between the pivot lever  44  and the swelled portion  44   a  slides, and only the lever driving gear  43  keeps idly rotating along with the drive gear  29 .  
         [0066]     Thus, when the motor  15  normally rotates, the lever driving gear  43  is apart from the engaging section  48  of the exhaust lever  42 . Therefore, the exhaust lever  42  is subjected to a rotating force in the counterclockwise direction in  FIG. 1  due to resiliency of the conical coil spring  50 , wherein the exhaust lever  42  is moved to the closing position, and the rapid exhausting mechanism  13  is brought into an inoperable state. In this situation, the valve body  39  having a greater area than the area of the opening of the exhaust port  38  is pressed to the portion of the intermediate plate  10   b  in the periphery of the exhaust port  38  by the pressure and is deformed so as to follow the profile of the exhaust port  38  and is adhered thereto. Therefore, a closing action of the exhaust port  38  is carried out by the valve body  39 , so that no air leaks even at a high pressure level.  
         [0067]     Next, when the lower end portion of the diaphragm portion  21   a  is vertically moved in the pump  11 , the interior of the diaphragm portion  21   a  is made into high pressure, and the valve body  25  closes the air intake port  24   a  to cause the valve portion V 1  to be closed, and at the same time, the exhaust valve body  34  is made wider than the inner wall face of the annular groove  33 , so that air is exhausted by the exhaust valve portion V 2  as shown by the arrow F. Air exhausted from the exhaust valve body  34  is exhausted through the tubular body  32  from the exhaust port  31   a  communicating with the annular groove  33  and is sent to the cuff side wound around a wrist.  
         [0068]     When the inside of the cuff is pressurized to a determined pressure level, air in the air paths is exhausted by the normal exhausting mechanism  12 , and in line therewith, air of a greater amount than the exhaust amount by the normal exhausting mechanism  12  is further sent into the cuff. Also, when the inside of the cuff is pressurized to a predetermined pressure level, the motor  15  comes to a stop. That is, the pump action stops. Thereby, air in the air path is gradually allowed to escape by using the normal exhausting mechanism  12 . Accordingly, the pressure in the cuff is gradually lowered. At this time, patterns of the inside pressure in the cuff and vibration amplitudes in line with pulsation of the artery are processed by a microcomputer, and the systolic blood pressure and diastolic blood pressure are measured.  
         [0069]     When the motor  15  is rotated inversely after the blood measurement is processed, the drive gear  29  is inverted rotated (in the direction of the arrow B in  FIG. 2 ) in the rapid exhausting mechanism  13 , and the lever driving gear  43  is inverted rotated (in the direction of the arrow b in  FIG. 2 ). At this time, since clutch friction is produced by resiliency of the coil spring  46  between the lever driving gear  43  and the pivot lever  44 , the pivot lever  44  is pivoted in the direction of the arrow D in  FIG. 2  about the bearing portion  17 . If the lever driving gear  43  is rotated by a predetermined amount in line with rotation of the pivot lever  44 , the lever driving gear  43  engages with the engaging section  48  of the exhaust lever  42  during the pivot motion. If the lever driving gear  43  is further rotated, a force of pressing the engaging section  48  from the lever driving gear  43  side to the outside, that is, a rotating force in the clockwise direction in  FIG. 1  is applied to the engaging section  48 , whereby the exhaust lever  42  is pivoted about the hinge  47  from the closing position to the opening position, the valve body  39  is pressed and opened by the exhaust pin  41  and the air in the cuff is forcibly exhausted. Thereafter, the pivot lever  44  is pivoted until the swelled portion  44   b  is brought into contact with the left inner wall of the lower case  10   c  in  FIG. 2 . In this situation, a portion which is friction-coupled as a clutch between the pivot lever  44  and the swelled portion  44   b  slides, and only the lever driving gear  43  idly rotates along with the drive gear  29  until the motor  15  stops driving.  
         [0070]     As described above, in the rapid exhausting mechanism  13  according to the present embodiment, when the inside of the cuff wound around a wrist is pressurized by the pump section  11  and when the blood pressure is measured after the inside of the cuff is pressurized to a predetermined pressure level, the valve body  39 , made of a thin rubber sheet  40 , which has a greater area than the opening area of the exhaust port  38  and has easy deformability is pressed to the intermediate plate  10   b  portion in the periphery of the exhaust port  38 , and at the same time, is deformed and adhered thereto so as to follow the shape of the exhaust port  38 , whereby it is possible to reduce the air leakage even at a high pressure level.  
         [0071]     In addition, component members made of resin materials, which are easy to be manufactured and are relatively inexpensive, such as the intermediate plate  10   b , the exhaust lever  42 , the pivot lever  44 , the drive gear  29  and the lever driving gear  43  are assembled in the unit case  10 , and the drive source does not employ any expensive, heavy, and large-sized plunger, which has been conventionally employed, wherein by utilizing a drive force of a motor  15  for driving the pump section  11 , it is possible to provide a small-sized and inexpensive rapid exhausting mechanism.  
         [0072]     Further, the spring  46  serving as a clutch between the lever driving gear  49  and the pivot lever  44  is accommodated in the lever driving gear  43 , wherein the lever driving gear  43  equipped with a clutch feature can be made compact.  
         [0073]     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.

Technology Category: f