Abstract:
A dispensing pump, and more particularly, a valve impact type dispensing pump that may be used in a process of manufacturing an electronic product and may dispense an accurate amount of a liquid, such as a liquid synthetic resin, at high speed. The valve impact type dispensing pump can descend a valve rod at high speed and thus can dispense a liquid with high viscosity at high speed. The valve impact type dispensing pump can dispense an accurate amount of a liquid at high speed. Also, the valve impact type dispensing pump can dispense a liquid having high viscosity at high speed due to a fast descending speed of a valve rod.

Description:
INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS 
       [0001]    Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    The present disclosure relates to a dispensing pump, and more particularly, to a dispensing pump that may be used in a process of manufacturing an electronic product and may dispense an accurate amount of a liquid, such as a liquid synthetic resin, at high speed. 
         [0004]    2. Discussion of Related Technology 
         [0005]    Pumps for dispensing liquid are used in various technical fields, such as processes of manufacturing electronic products by using semiconductor chips, and the like. 
         [0006]    In particular, dispensing pumps are widely used in an underfill process of a semiconductor process. The underfill process is usually used in a surface mounting technique, such as a flip chip in which a plurality of metal balls are formed on a surface facing a substrate and which electrically connects the substrate and a semiconductor chip via the plurality of metal balls. If a liquid synthetic resin is applied onto a circumference of the semiconductor chip, the resin is dispersed into a space between the semiconductor chip and the substrate by a capillary phenomenon and is filled in a space between the metal balls. The resin that fills the space between the semiconductor chip and the substrate is hardened so that adhesive strength between the semiconductor chip and the substrate can be improved. In addition, the hardened resin serves as a shock absorber and dissipates heat generated in the semiconductor chip. 
         [0007]    A function of dispensing a liquid at high speed of such dispensing pumps becomes significant. Korean Patent Laid-open Publication Nos. 10-2005-0093935 and 10-2010-0045678 disclose a structure of a pump for dispensing a resin by ascending/descending a valve due to interaction between a cam and a cam follower. Such dispensing pumps according to the related art have excellent performance but have a limitation in speed at which a valve rod descends due to a structure of cam protrusions of a cam member and a structure of a roller. Thus, there are some difficulties in dispensing the liquid at high speed, and in particular, it is difficult to dispense a liquid with high viscosity at high speed. 
       SUMMARY 
       [0008]    One aspect of the present invention provides a valve impact type dispensing pump that may descend a valve rod at high speed and thus may dispense a liquid with high viscosity at high speed. 
         [0009]    Another aspect of the present invention provides a valve impact type dispensing pump including: a pump body; a valve body including an inlet path on which a liquid from an outside is supplied, a reservoir in which the liquid supplied via the inlet path is stored, and a discharge path on which the liquid stored in the reservoir is discharged, the valve body being installed at the pump body; a valve rod pressurizing the liquid stored in the reservoir of the valve body and inserted in the reservoir of the valve body so that the liquid is discharged via the discharge path; an operating rod connected to the valve rod and allowing the valve rod to move relative to the valve body so that a relative motion of the valve rod is allowed within a predetermined distance (gap distance) in a lengthwise direction of the valve rod; a cam member including through hole through which the operating rod passes and cam protrusions formed along a circumferential direction of the cam member based on the through hole and having inclined surfaces formed so that a height of the cam protrusions increases, the cam member being installed at the pump body so that the cam member rotates around the through hole; a rotating unit rotating the cam member; a cam follower including rollers that roll on the inclined surfaces of the cam protrusions when the cam member rotates, the cam follower coupled to the operating rod and allowing the valve rod to move relative to the valve body; and an elastic member installed between the pump body and the cam follower and providing an elastic force to the cam follower so that the cam follower approaches the cam member. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The above and other features and advantages of the present invention will become more apparent by describing in detail embodiments thereof with reference to the attached drawings in which: 
           [0011]      FIG. 1  is a perspective view of a valve impact type dispensing pump according to an embodiment of the present invention; 
           [0012]      FIG. 2  is an exploded perspective view of main elements of the valve impact type dispensing pump illustrated in  FIG. 1 ; 
           [0013]      FIG. 3  is a cross-sectional view taken along a line III-III of the valve impact type dispensing pump of  FIG. 1 ; 
           [0014]      FIG. 4  is a cross-sectional view taken along a line IV-IV of the valve impact type dispensing pump of  FIG. 1 ; 
           [0015]      FIGS. 5 ,  6 ,  7 A,  7 B,  8 A,  8 B,  9 A,  9 B,  10 A,  10 B,  11 A and  11 B are schematic views for explaining an operation of the valve impact type dispensing pump of  FIG. 1 ; and 
           [0016]      FIG. 12  is a cross-sectional view of elements of a valve impact type dispensing pump according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0017]    Embodiments of the present invention will now be described more fully with reference to the accompanying drawings in which exemplary embodiments of the invention are shown. 
         [0018]      FIG. 1  is a perspective view of a valve impact type dispensing pump according to an embodiment of the present invention,  FIG. 2  is an exploded perspective view of main elements of the valve impact type dispensing pump illustrated in  FIG. 1 , and  FIG. 3  is a cross-sectional view taken along a line III-III of the valve impact type dispensing pump of  FIG. 1 . 
         [0019]    Referring to  FIGS. 1 through 3 , the valve impact type dispensing pump according to the present embodiment includes a pump body  100 , a valve body  110 , a valve rod  210 , an operating rod  220 , a cam member  300 , and a cam follower  400 . 
         [0020]    The pump body  100  serves as a housing that supports the entire structure of the valve impact type dispensing pump. The pump body  100  is installed at a transfer device and is moved by the transfer device to allow a liquid to be dispensed. 
         [0021]    The valve body  110  is installed at the pump body  100 . The valve body  110  includes an inlet path  111 , a reservoir  112 , and a discharge path  113 . The liquid stored in an external syringe (not shown) flows to the reservoir  112  via the inlet path  111 . The liquid stored in the reservoir  112  is discharged via the discharge path  113  due to an operation of the valve rod  210  that ascends/descends with respect to the reservoir  112 . A nozzle  120  is connected to the discharge path  113  so as to adjust dispensing characteristics of the liquid. 
         [0022]    The valve rod  210  is inserted in the reservoir  112  and pressurizes the liquid stored in the reservoir  112  so as to discharge the liquid via the discharge path  113 . 
         [0023]    The cam member  300  is disposed above the valve body  110  and the valve rod  210  and is installed at the pump body  100 . The cam member  300  is installed at the pump body  100  so as to rotate around a virtual central axis that extends in a lengthwise direction of the valve rod  210 . A bearing  130  is installed between the cam member  300  and the pump body  100  so that the cam member  300  may rotate with respect to the pump body  100 . 
         [0024]    The cam member  300  rotates by a rotating unit  900 . The rotating unit  900  includes a motor  910 , a driving pulley  920 , a timing belt  930 , and a driven pulley  940 . The motor  910  is installed at the pump body  100 , and the driven pulley  940  is installed at the cam member  300 . The timing belt  930  connects the driving pulley  920  and the driven pulley  940 . If the motor  910  allows the driving pulley  920  to rotate, the driven pulley  940  rotates due to the timing belt  930 . As a result, the cam member  300  rotates. 
         [0025]    The cam member  300  includes through hole  320  and a plurality of cam protrusions  310 . The through hole  320  is formed to penetrate the center of the disc-shaped cam member  300  in a vertical direction. The plurality of cam protrusions  310  are arranged in a circumferential direction of the cam member  300  so that eight cam protrusions  310  are at the same angle intervals (i.e., at intervals of 45 degrees). The cam protrusions  310  are inclined in the same rotation direction along the circumferential direction of the cam member  300 . That is, the cam protrusions  310  include inclined surfaces  311  that are inclined so that the height (see h of  FIG. 3 ) of the cam protrusions  310  may increase gradually clockwise, as illustrated in  FIG. 2 . Cross-sections of the cam protrusions  310  may be formed so that the inclined surfaces  311  are steeply bent from their tops to lower portions. In the present embodiment, the inclined surfaces  311  of the cam protrusions  310  are inclined from their tops in the vertical direction. 
         [0026]    The operating rod  220  is disposed in the through hole  320  of the cam member  300  and is connected to the valve rod  210 . The operating rod  220  is coupled to the cam follower  400  and ascends or descends so that the valve rod  210  may be moved up and down relative to the valve body  110 . 
         [0027]    The cam follower  400  faces a surface on which the cam protrusions  310  of the cam member  300  are formed and ascends/descends with respect to the cam member  300  due to interaction between the cam protrusions  310  and the cam follower  400 . The cam follower  400  includes two rollers  420  that roll on the inclined surfaces  311  of the cam protrusions  310 . Two rollers  420  of the cam follower  400  are disposed at intervals of 180 degrees. 
         [0028]    The cam follower  400  is spline-coupled to the pump body  100  via a spline shaft  440  so that an ascending/descending motion of the cam follower  400  may be performed and relative rotation may be prevented. The cam follower  400  includes a spline boss  430  and is coupled to the pump body  100  via the spline shaft  440  so as to make a linear motion (ascending/descending motion in the present embodiment) approaching the cam member  300  and not to allow relative rotation of the cam follower  400 . 
         [0029]    An elastic member  600  is disposed between the cam follower  400  and the pump body  100  and provides an elastic force so that the cam follower  400  approaches the cam member  300 . In the present embodiment, the elastic member  600  having a shape of a spring  600  is used. The cam follower  400  receives the elastic force of the elastic member  600  and is maintained to be closely adhered to the cam member  300 . 
         [0030]    The valve rod  210  and the operating rod  220  are connected to each other by a gap member  500 . The operating rod  220  is screw-coupled to the gap member  500  and is fixed, and the valve rod  210  is connected to the gap member  500  so that a relative motion of the valve rod  210  to the gap member  500  may be allowed at a predetermined distance in a lengthwise direction of the valve rod  210 . The relative movable distance between the gap member  500  and the valve rod  210  is referred to as a ‘gap distance’ g. 
         [0031]    In the present embodiment, the gap member  500  has a structure illustrated in  FIGS. 2 through 4 . A nut groove  501  is formed in an upper portion of the gap member  500  and is screw-coupled to the operating rod  220 . A tightening groove  502  is formed in the gap member  500  to pass through the nut groove  501 . A tightening hole  503  is formed in the gap member  500  to perforate the tightening groove  502 , and a tightening bolt  504  is screw-coupled to an opposite portion to the tightening hole  503  so as to pressurize the tightening groove  502  to reduce the size of the tightening groove  502  so that screw-coupling between the operating rod  220  and the gap member  500  is not released. 
         [0032]    A hanging groove  505  is formed in a lower portion of the gap member  500  and has a T-shape so that the hanging groove  505  is open in a lateral direction of the gap member  500 . A hanging protrusion  211  is formed on a top end of the valve rod  210 . The hanging protrusion  211  of the valve rod  210  is slid on the hanging groove  505  of the gap member  500  in the lateral direction of the gap member  500  and is engaged therein so that the gap member  500  and the valve rod  210  may be connected to each other. Through the structure, the gap member  500  and the valve rod  210  may be conveniently coupled to or detached from each other. Also, since the valve rod  210  is moved by the operating rod  220  and the gap member  500  only in the vertical direction, the valve rod  210  is not detached from the gap member  500  while the valve rod  210  operates. Only when the operating rod  220  ascends or the valve body  110  is detached from the pump body  100  in order to replace the valve rod  210 , the valve rod  210  is moved relative to the gap member  500  in a direction parallel to the hanging groove  505  so that the valve rod  210  may be easily detached from the gap member  500 . 
         [0033]    Since there is clearance corresponding to the gap distance g between the hanging grove  505  of the gap member  500  and the hanging protrusion  211  of the valve rod  210 , as described above, a time difference occurs between the motion of the operating rod  220  and the motion of the valve rod  210 . That is, when the operating rod  220  ascends in a state where a bottom surface of the gap member  500  and a top surface of the valve rod  210  contact each other, only the operating rod  220  ascends by the gap distance g in a state where the valve rod  210  stops, and if the hanging groove  505  is caught in the hanging protrusion  211 , the operating rod  220  and the valve rod  210  ascend together. When the operating rod  220  descends reversely in this state, only the operating rod  220  descends by the gap distance g in a state where the valve rod  210  stops, and if the hanging groove  505  is caught in the hanging protrusion  211 , the operating rod  220  and the valve rod  210  descend together. Through the structure of the hanging protrusion  211  and the hanging groove  505 , the gap member  500  is connected to the valve rod  210  to interfere each other with the gap distance g allowed. 
         [0034]    Hereinafter, an operation of the valve impact type dispensing pump having the above structure of  FIGS. 1 through 3  will be described. 
         [0035]      FIG. 4  is a cross-sectional view taken along a line IV-IV of the valve impact type dispensing pump of  FIG. 1 ,  FIGS. 5 through 11A  and  11 B are schematic views for explaining an operation of the valve impact type dispensing pump of  FIG. 1 , and  FIG. 12  is a cross-sectional view of elements of a valve impact type dispensing pump according to another embodiment of the present invention. 
         [0036]    Referring to  FIG. 4 , the liquid stored in the external syringe flows to the reservoir  112  of the valve body  110  via the inlet path  111  under uniform pressure. 
         [0037]    If the motor  910  operates in this state, the motor  910  rotates with the driving pulley  920 , and the driven pulley  940  that is connected to the driving pulley  920  via the timing belt  930 , also rotates. The cam member  300  that is coupled to the driven pulley  940  rotates with the driven pulley  940 . 
         [0038]    If the cam member  300  rotates, the rollers  420  of the cam follower  400  roll along the inclined surfaces  311  of the cam protrusions  310 , and the cam follower  400  ascends. Since the cam follower  400  is spline-coupled to the pump body  100 , the cam follower  400  does not rotate but the rollers  420  roll along the inclined surfaces  311  of the cam protrusions  310  so that the cam follower  400  ascends. When the cam follower  400  ascends, the elastic member  600  is pressurized while applying the elastic force to the cam follower  400  in a downward direction. Due to the elastic force of the elastic member  600 , the rollers  420  of the cam follower  400  are maintained in contact with a top surface of the cam member  300 . The operating rod  220  coupled to the cam follower  400  also ascends with the gap member  500 . After the operating rod  220  and the gap member  500  ascend by the gap distance g in a state where the valve rod  210  stops, the hanging groove  505  is caught in the hanging protrusion  211 , and the valve rod  210  ascends with the operating rod  220  and is in the state illustrated in  FIGS. 3 and 4 . When the valve rod  210  ascends, the liquid flows in a space formed in the reservoir  112 , and the space is filled with the liquid. 
         [0039]    If the rollers  420  roll along the inclined surfaces  311  of the cam protrusions  310  and pass through tops of the inclined surfaces  311  of the cam protrusions  310 , the rollers  420  roll down due to the elastic force of the elastic member  600 . The cam follower  400 , the operating rod  220 , and the valve rod  210  descend with the rollers  420 . From the instant that the operating rod  220  and the gap member  500  descend by the gap distance g in a state where the valve rod  210  stops and the hanging groove  505  is caught in the hanging protrusion  211 , the operating rod  220  and the valve rod  210  descend together. The valve rod  210  descends, pressurizes the liquid filled in the space of the reservoir  112 , and discharges the liquid via the discharge path  113 . 
         [0040]    If the cam member  300  rotates consecutively and the rollers  420  ascend and descend along the cam protrusions  310  repeatedly, the valve rod  210  ascends and descends consecutively while undergoing the above-described procedure so that the liquid may be discharged via the discharge path  113 . 
         [0041]    In the above liquid-pumping mechanism, the descending speed of the valve rod  210  greatly affects the discharge amount and discharge speed of the liquid. In order to adjust an accurate discharge amount, an inner diameter of the discharge path  113  may be relatively small. As the descending speed of the valve rod  210  increases, the liquid having high viscosity may be quickly dispensed via the discharge path  113  having a small inner diameter. In particular, when the viscosity of the liquid is high, if the descending speed of the valve rod  210  is not sufficiently high, due to resistance caused by viscosity and resistance of the discharge path  113 , the liquid may not be discharged. However, like in embodiments of the present invention, the gap member  500  is used so that a liquid having high viscosity may be dispensed. In this way, by using the valve impact type dispensing pump according to embodiments of the present invention, the range of the liquid that may be dispersed, may be greatly increased. 
         [0042]    The descending speed of the valve rod  210  may be rapidly improved by using a structure in which the gap member  500  and the valve rod  210  are moved relative to each other by the gap distance g and are interlocked with each other, as described above. 
         [0043]    First, the relationship between the rotational speed of the cam member  300  and the descending speed of the operating rod  220  will be described with reference to  FIGS. 5 and 6 . 
         [0044]    The operating rod  220  starts to descend in a state where the rollers  420  are disposed on the tops of the cam protrusions  310 , as illustrated in  FIG. 5 . If the cam protrusions  310  are moved to the left by rotation of the cam member  300 , the rollers  420  roll on the tops of the cam protrusions  310 , and the operating rod  220  descends. The operating rod  220  descends until the rollers  420  contact the lowermost portion of the top surface of the cam member  300 , as illustrated in  FIG. 6 . 
         [0045]    When a radius of each roller  420  is r, a rotational angle of the roller  420  is α, a substantial rotational radius of the cam member  300  with respect to the roller  420  is R and a rotational angle of the cam member  300  is θ, a horizontal movement distance xh at which the rollers  420  are moved along a circumference of the cam member  300 , may be expressed using Equation 1: 
         [0000]        x   h   =r  sin α= Rθ   (1).
 
         [0046]    A distance xv at which the rollers  420  descend from the tops of the cam protrusions  310  in the vertical direction may be expressed using Equation 2: 
         [0000]        x   v   =r−r  cos α  (2)
 
         [0047]    The horizontal movement distance xh of the rollers  420  obtained in Equation 1 may be differentiated with respect to time, as shown in Equation 3, in order to calculate a horizontal movement speed of the rollers  420 : 
         [0000]        {dot over (x)}   h   =r  cos α{dot over (α)}= R {dot over (θ)}  (3)
 
         [0048]    Equation 3 will be summarized as Equation 4: 
         [0000]    
       
         
           
             
               
                 
                   
                     α 
                     . 
                   
                   = 
                   
                     
                       R 
                       r 
                     
                     · 
                     
                       
                         
                           θ 
                           . 
                         
                         
                           cos 
                            
                           
                               
                           
                            
                           α 
                         
                       
                       . 
                     
                   
                 
               
               
                 
                   ( 
                   4 
                   ) 
                 
               
             
           
         
       
     
         [0049]    Equation 2 may be differentiated with respect to time and Equation 4 is substituted for Equation 2 in order to calculate a speed at which the rollers  420  descend from the tops of the cam protrusions  310  in the vertical direction, as shown in Equation 5: 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       x 
                       . 
                     
                     v 
                   
                   = 
                   
                     
                       r 
                        
                       
                           
                       
                        
                       sin 
                        
                       
                           
                       
                        
                       
                         α 
                         · 
                         
                           α 
                           . 
                         
                       
                     
                     = 
                     
                       
                         r 
                          
                         
                             
                         
                          
                         sin 
                          
                         
                             
                         
                          
                         
                           α 
                           · 
                           
                             R 
                             r 
                           
                           · 
                           
                             
                               θ 
                               . 
                             
                             
                               cos 
                                
                               
                                   
                               
                                
                               α 
                             
                           
                         
                       
                       = 
                       
                         R 
                          
                         
                             
                         
                          
                         
                           θ 
                           . 
                         
                          
                         tan 
                          
                         
                             
                         
                          
                         
                           α 
                           . 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   5 
                   ) 
                 
               
             
           
         
       
     
         [0050]    According to the above Equation 5, the descending speed of the rollers  420  and the operating rod  220  are proportional to tan α. If the rotational speed of the cam member  300  is maintained constant by a motor, the descending speed of the operating rod  220  is substantially determined by tan α. When α corresponding to the rotational speed of the rollers  420  is 0, tan α starts from 0 and increases rapidly as α increases. As a result, when the rollers  420  approach the lowermost portion of the top surface of the cam member  300  compared to the case that the rollers  420  are moved around the cam protrusions  310 , the operating rod  220  descends at much higher speed. According to embodiments of the present invention, the descending speed of the valve rod  210  is rapidly improved using a change of the descending speed of the operating rod  220 . A detailed operating procedure thereof will be described as below. 
         [0051]    First, as illustrated in  FIGS. 7A and 7B , the case that the operating rod  220  and the valve rod  210  descend altogether and the rollers  420  contact the lowermost portion of the top surface of the cam member  300 , will be described. The top surface of the valve rod  210  and the bottom surface of the gap member  500  contact each other, as illustrated in  FIG. 7B . 
         [0052]    If the cam member  300  rotates in this state, the rollers  420  ascend, as illustrated in  FIG. 8A . The operating rod  220  that is connected to the rollers  420  ascends together. While the operating rod  220  ascends by the gap distance g, the valve rod  210  stops as illustrated in  FIG. 8B . 
         [0053]    If the operating rod  220  ascends by the gap distance g or higher, the hanging groove  505  of the gap member  500  and the hanging protrusion  211  of the valve rod  210  are engaged in each other, and the operating rod  220  and the valve rod  210  ascend together, as illustrated in  FIGS. 9A and 9B . 
         [0054]    If the rollers  420  starts to descend from the tops of the cam protrusions  420 , as illustrated in  FIGS. 10A and 10B , while the operating rod  220  is first moved by the gap distance g, only the operating rod  220  descends in a state where the valve rod  210  stops, as illustrated in  FIG. 10B . In this way, while the operating rod  220  is moved at a relatively low speed within the range of the gap distance g, only the operating rod  220  descends, and the valve rod  210  does not descend. 
         [0055]    If the rollers  420  and the operating rod  220  are moved by the gap distance g and ascend to some degree, the gap member  500  impacts the valve rod  210  downwards and pressurizes the valve rod  210  downwards, as illustrated in  FIGS. 11A and 11B . The rollers  420 , the operating rod  220 , the gap member  500 , and the valve rod  210  descend at higher speed than in an area of the gap distance g. 
         [0056]    As described above with reference to  FIGS. 5 and 6 , the descending speed of the rollers  420  increases in proportion to tan α as the rotational angle α of the rollers  420  with respect to the tops of the cam protrusions  310  increases compared to in an initial stage. That is, as the rollers  420  descend from the tops of the cam protrusions  310 , the descending speed of the rollers  420  increases rapidly. In the valve impact type dispensing pump according to embodiments of the present invention, in a state where only the rollers  420  and the operating rod  220  descend in the area of the gap distance g due to the gap member  500  and the descending speed of the operating rod  220  increases, the gap member  500  impacts the valve rod  210  and allows the valve rod  210  to descend at high speed. 
         [0057]    If there is no gap member  500  and the operating rod  220  and the valve rod  210  are fixed to each other, the valve rod  210  starts from the descending speed of 0 to a final speed together with the operating rod  220 . However, by using the gap member  500  according to embodiments of the present invention, after only the operating rod  220  is moved and its descending speed increases in a state where the vale rod  210  stops, the gap member  500  collides with the valve rod  210  at high speed and allows the valve rod  210  to descend. A liquid having high viscosity may be easily and quickly dispensed according to this principle. 
         [0058]    The following Table 1 shows comparison of descending speeds of the valve rod  210  with respect to several gap distances g that are calculated using the gap member  500 . When the cam member  300  rotates with 1000 rpm (θ), the radius r of the roller  420  is 5 mm, the substantial rotational radius R of the cam member  300  with respect to a center of the roller  420  is 13 mm and the height h of the cam protrusions  310  is 2 mm, the descending speeds of the valve rod  210  with respect to the gap distances g are summarized as the following Table 1. As shown in Table 1, even when a gap distance g of 0.3 mm is set to the height h of 2 mm of the cam protrusions  310 , the average descending speed of the valve rod  210  may be increased by 40% or higher compared to the case that the gap distance g is 0. 
         [0000]    
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                 Circumferential 
                   
                   
               
               
                   
                 Distance at 
                 Horizontal 
                 distance at which 
                   
                 Average 
               
               
                   
                 which valve 
                 circumferential 
                 rollers 420 roll in a 
                   
                 descending 
               
               
                 Gap 
                 rod 210 
                 distance at which 
                 range where valve 
                 Total time while 
                 speed of valve 
               
               
                 distance g 
                 descends 
                 rollers 420 roll within 
                 rod 210 descends 
                 valve rod 210 
                 rod 210 
               
               
                 (mm) 
                 (mm) 
                 gap distance g (mm) 
                 (mm) 
                 descends (usec) 
                 (mm/sec) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 0.0 
                 2.0 
                 0.00 
                 4.00 
                 2938 
                 680.7 
               
               
                 0.3 
                 1.7 
                 1.71 
                 2.29 
                 1685 
                 1008.8 
               
               
                 0.6 
                 1.4 
                 2.37 
                 1.63 
                 1191 
                 1172.8 
               
               
                 0.9 
                 1.1 
                 2.86 
                 1.14 
                 836 
                 1315.7 
               
               
                 1.2 
                 0.8 
                 3.25 
                 0.75 
                 551 
                 1451.4 
               
               
                   
               
             
          
         
       
     
         [0059]    The following Table 2 shows calculation of descending speeds of the valve rod  210  when only the radius of the roller  420  is changed to 8 mm on the above-described same conditions. 
         [0000]    
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                   
                 Circumferential 
                   
                   
               
               
                   
                 Distance at 
                 Horizontal 
                 distance at which 
                   
                 Average 
               
               
                   
                 which valve 
                 circumferential 
                 rollers 420 roll in a 
                   
                 descending 
               
               
                 Gap 
                 rod 210 
                 distance at which 
                 range where valve 
                 Total time while 
                 speed of valve 
               
               
                 distance g 
                 descends 
                 rollers 420 roll within 
                 rod 210 descends 
                 valve rod 210 
                 rod 210 
               
               
                 (mm) 
                 (mm) 
                 gap distance g (mm) 
                 (mm) 
                 descends (usec) 
                 (mm/sec) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 0.0 
                 2.0 
                 0.00 
                 5.29 
                 3887 
                 514.5 
               
               
                 0.3 
                 1.7 
                 2.17 
                 3.12 
                 2293 
                 741.5 
               
               
                 0.6 
                 1.4 
                 3.04 
                 2.25 
                 1654 
                 846.4 
               
               
                 0.9 
                 1.1 
                 3.69 
                 1.61 
                 1179 
                 933.0 
               
               
                 1.2 
                 0.8 
                 4.21 
                 1.08 
                 791 
                 1011.0 
               
               
                   
               
             
          
         
       
     
         [0060]    Even in the above case, the descending speed of the valve rod  210  may be increased by 40% or higher only by setting the gap distance g of 0.3 mm compared to the case that there is no gap distance g. When the gap distance g is set to 1.2 mm, the descending speed of the valve rod  210  may be increased by about 100%. 
         [0061]    Since the momentum and kinetic energy of the valve rod  210  are proportional to a descending speed of the valve rod  210  and a square of the descending speed, the liquid may be dispensed at much higher speed compared to the related art. In particular, a liquid having high viscosity may be dispensed by a sufficient force via the discharge path  113  having a relatively small inner diameter. 
         [0062]    The above-described gap distance g may be greater than 0 and less than the height h of the cam protrusions  310 . If the gap distance g is 0, there is no difference between the present invention and the related art. If the gap distance g is greater than the height h of the cam protrusions  310 , the operating rod  220  cannot pressurize the valve rod  210 . 
         [0063]    The height h of the cam protrusions  310  may be less than a value that is obtained by adding the length of the reservoir  112  to the gap distance g. If not, the valve  210  may be excluded from the reservoir  112  of the valve body  110 . 
         [0064]    Although embodiments of the present invention have been described as above, the scope of the present invention is not limited to the above-described embodiments. 
         [0065]    For example, the gap member  500  is coupled to the operating rod  220 , and the valve rod  210  is moved relative to the gap member  500  by the gap distance g but vice versa. The gap member  500  may be coupled to the valve rod  210 , and the operating rod  220  may be moved relative to the gap member  500  by the gap distance g while interfering with each other. In this case, the hanging protrusion  211  may be formed on the operating rod  220  and is caught in the hanging groove  505  of the gap member  500 . 
         [0066]    Alternatively, the gap member  500  may be modified in various ways in which the valve rod  210  and the operating rod  220  may be moved relative to each other to extend within the range of the gap distance g. For example, the gap member  550  having a shape of  FIG. 12  may be used. The gap member  550  may be configured in such a way that hanging protrusions  251  and  261  are disposed on a valve rod  250  and an operating rod  260 , respectively, and the hanging protrusion  251  of the valve rod  250  and the hanging protrusion  261  of the operating rod  260  may be caught in the gap member  550 . In this case, the gap member  550  is configured in such a way that an upper member  551  and a lower member  552  of the gap member  550  may be screw-coupled to each other, the hanging protrusion  261  of the operating rod  260  may be caught in the upper member  551  and the hanging protrusion  251  of the valve rod  250  may be caught in the lower member  552 . The upper member  551  and the lower member  552  that are screw-coupled to each other, rotate relative to each other so that the gap distance g may be adjusted. When the gap distance g is set, relative rotation of the upper member  551  and the lower member  552  is prevented by a tightening bolt  553  so that the gap distance g may be fixed. Also, the upper member  551  of the gap member  550  may be screw-coupled to the operating rod  260 , or the lower member  552  of the gap member  550  may be screw-coupled to the valve rod  250 . 
         [0067]    In  FIGS. 1 and 2 , eight cam protrusions  310  and two rollers  420  are disposed. However, the number of cam protrusions  310  and the number of rollers  420  may be diverse. The shape of the cam protrusions  310  may vary according to their inclined angles and curvatures of inclined surfaces. 
         [0068]    As described above, in a valve impact type dispensing pump according to embodiments of the present invention, a liquid may be dispensed at high speed. 
         [0069]    Also, the valve impact type dispensing pump according to the present invention may dispense a liquid having high viscosity at high speed due to a fast descending speed of a valve rod. 
         [0070]    While embodiments of the present invention have been particularly shown and described, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.