Abstract:
A dispensing pump, and more particularly, a valve accelerating 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 accelerating 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 accelerating type dispensing pump can dispense an accurate amount of a liquid at high speed. Also, the valve accelerating 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 
     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 
     Field 
     The present disclose 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. 
     Discussion of Related Technology 
     Pumps for dispensing liquid are used in various technical fields, such as processes of manufacturing electronic products by using semiconductor chips, and the like. 
     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. 
     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 
     One aspect of the present invention provides a valve accelerating type dispensing pump that may descend a valve rod at high speed and thus may dispense a liquid with high viscosity at high speed. 
     Another aspect of the present invention provides a valve accelerating 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; a cam member including a 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; an accelerating member assembled with the cam follower to allow relative rotation of the cam follower within a predetermined angle range and installed at the pump body so as to make a linear motion approaching the cam member; and an elastic member installed between the pump body and the accelerating member and providing an elastic force to the accelerating member so that the accelerating member approaches the cam member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG. 1  is a perspective view of a valve accelerating type dispensing pump according to an embodiment of the present invention; 
         FIG. 2  is an exploded perspective view of main elements of the valve accelerating type dispensing pump illustrated in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view taken along a line III-III of the valve accelerating type dispensing pump of  FIG. 1 ; 
         FIG. 4  is a cross-sectional view taken along a line IV-IV of the valve accelerating type dispensing pump of  FIG. 1 ; 
         FIGS. 5A, 5B, 6A, 6B, 7A, and 7B  are schematic views for explaining an operation of the valve accelerating type dispensing pump of  FIG. 1 ; and 
         FIG. 8  is an exploded perspective view of main elements of a valve accelerating type dispensing pump according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will now be described more fully with reference to the accompanying drawings in which embodiments of the invention are shown. 
       FIG. 1  is a perspective view of a valve accelerating type dispensing pump according to an embodiment of the present invention,  FIG. 2  is an exploded perspective view of main elements of the valve accelerating type dispensing pump illustrated in  FIG. 1 , and  FIG. 3  is a cross-sectional view taken along a line III-III of the valve accelerating type dispensing pump of  FIG. 1 . 
     Referring to  FIGS. 1 through 3 , the valve accelerating 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 . 
     The pump body  100  serves as a housing that supports the entire structure of the valve accelerating 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. 
     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. 
     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 . 
     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 . 
     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. 
     The cam member  300  includes a 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 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 formed to be bent from their tops in the vertical direction, as illustrated in  FIGS. 2, 5A, and 5B . 
     The operating rod  220  is disposed in the through hole  320  of the cam member  300  and is coupled to the valve rod  210 . The operating rod  220  is coupled to the cam follower  400  and ascends or descends and allows the valve rod  210  to be moved up and down relative to the valve body  110 . 
     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. 
     The cam follower  400  is assembled with an accelerating member  500  and is installed at the pump body  100 . The accelerating member  500  includes a spline boss  530  and is coupled to the pump body  100  via a spline shaft  520  so as to make a linear motion (ascending/descending motion in the present embodiment) approaching the cam member  400  and not to allow relative rotation of the cam follower  400 . An elastic member  600  is disposed between the accelerating member  500  and the pump body  100  and provides an elastic force so that the elastic member  600  may be moved relative to the accelerating member  500  to approach 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  that is disposed between the accelerating member  500  and the cam member  300 , receives the elastic force of the elastic member  600  from the accelerating member  500  and is maintained to be closely adhered to the cam member  300 . 
     The accelerating member  500  and the cam follower  400  are assembled with each other so that they may rotate relative to each other within a predetermined angle range. Due to interaction between accelerating protrusions  410  formed on the cam follower  400  and angle limiting portions  510  formed on the accelerating member  500 , the accelerating member  500  and the cam follower  400  may be rotated relative to each other within the predetermined angle range. In the present embodiment, the angle limiting portions  510  are long holes that extend in the circumferential direction of the accelerating member  500 . Two angle limiting portions  510  having a shape of long holes face each other in a state where a central axis (operating rod  220 ) of the cam follower  400  is interposed between two angle limiting portions  510 . The accelerating protrusions  410  of the cam follower  400  are formed in the form of rods that extend in a radial direction of the cam follower  400  and protrude from the cam follower  400 . Like the angle limiting portions  510 , two accelerating protrusions  410  are disposed and face each other in a state where the central axis of the cam follower  400  is interposed between two accelerating protrusions  410 . The accelerating protrusions  410  are respectively inserted in the angle limiting portions  510  of the accelerating member  500 . Since the accelerating protrusions  410  are caught in inner walls of the angle limiting portions  510 , the cam follower  400  rotates with respect to the accelerating member  500  within an angle range that is allowed by the angle limiting portions  510 . That is, a relative rotational angle of the cam follower  400  with respect to the accelerating member  500  is limited by interference between the accelerating protrusions  410  and the angle limiting portions  510 . A range of the relative rotational angle of the cam follower  400  with respect to the accelerating member  500  that is limited by interaction between the accelerating protrusions  410  and the angle limiting portions  510  may be greater than 0 degree and less than angle intervals between the cam protrusions  310 . In the present embodiment, a rotatable angle of the cam follower  400  may be greater than 0 degree and less than 90 degrees. The rollers  420  are installed at ends of the accelerating protrusions  410  according to the present embodiment and roll on the inclined surfaces  311  of the cam protrusions  310  of the cam member  300 . 
     Hereinafter, an operation of the valve accelerating type dispensing pump having the above structure of  FIGS. 1 through 3  will be described. 
       FIG. 4  is a cross-sectional view taken along a line IV-IV of the valve accelerating type dispensing pump of  FIG. 1 , and  FIGS. 5A, 5B, 6A, 6B, 7A, and 7B  are schematic views for explaining an operation of the valve accelerating type dispensing pump of  FIG. 1   
     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. 
     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 . 
     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 accelerating member  500  is spline-coupled to the pump body  100  via the spline shaft  520 , the accelerating member  500  does not rotate but the rollers  420  roll along the inclined surfaces  311  of the cam protrusions  310  so that the accelerating member  500  and the cam follower  400  ascend. When the accelerating member  500  ascends, the elastic member  600  is pressurized while applying the elastic force to the accelerating member  500  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  that is coupled to the cam follower  400 , ascends with the valve rod  210 . 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. 
     Referring to  FIGS. 1, 5A, and 5B , when the cam member  300  rotates, the accelerating protrusions  410  of the cam follower  400  are slid along the angle limiting portions  510  of the accelerating member  500  and are caught in left walls of the angle limiting portions  500  based on  FIGS. 5A and 5B . Thus, rotation of the cam follower  400  does not proceed any more. That is, even when the cam member  300  rotates, the cam follower  400  does not rotate with respect to the accelerating member  500 . A concept of a state of force balance between the cam follower  400  and the cam member  300  is as shown in  FIGS. 5A and 5B . A vertical resistance F R  applied to the rollers  420  on the inclined surfaces  311  of the cam protrusions  310  is balanced with a horizontal component force F H  and a vertical component force F V  that are applied to the rollers  420 . The vertical component force F V  is provided by the elastic member  600  and is transferred to the rollers  420  via the accelerating member  500 . The horizontal component force F H  is transferred to the rollers  420  via the pump body  100 —the accelerating member  500 —the cam follower  400 , because the accelerating protrusions  410  are caught in the angle limiting portions  510 . 
     If the rollers  420  roll up to tops of the inclined surfaces  311  of the cam protrusions  310  and ascend, the horizontal component of the vertical resistance F R  that is balanced with the horizontal component force F H  applied to the rollers  420  becomes extinct, as illustrated in  FIGS. 6A and 6B . That is, on the inclined surfaces  311  of the cam protrusions  310 , a force is applied to the rollers  420  in the horizontal direction, and any force other than a frictional force is not applied to the rollers  420  in the vertical direction. As a result, due to the horizontal component force F H  applied by the angle limiting portions  510  to the accelerating protrusions  410 , the rollers  420  bounce off the cam protrusions  310  in the circumferential direction (right direction in  FIGS. 5A, 5B, 6A, 6B, 7A, and 7B ) of the cam member  300 , as illustrated in  FIGS. 7A and 7B . As described above, since the cam follower  400  may rotate with respect to the accelerating member  500  within the angle range that is allowed by the angle limiting portions  510 , the cam follower  400  rotates with respect to the accelerating member  500  that does not rotate, in an opposite direction to a rotation direction of the cam member  300 , and the rollers  420  escape from the tops of the cam protrusions  310  at high speed. In this case, due to the elastic force of the elastic member  600 , the accelerating member  500 , the cam follower  400 , the operating rod  220 , and the valve rod  210  descend. As a result, the liquid filled in the reservoir  112  is pressurized by the valve rod  210  and is discharged via the discharge path  113 . 
     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 so that the liquid may be discharged via the discharge path  113 . 
     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 accelerating member  500  is used so that a liquid having high viscosity may be dispensed. In this way, by using the valve accelerating type dispensing pump according to embodiments of the present invention, the range of the liquid that may be dispersed, may be greatly increased. 
     When there is no interaction between the accelerating protrusions  410  and the angle limiting portions  510  as described above, the descending speed of the valve rod  210  is determined by a rotational speed of the cam member  300 . As illustrated in  FIGS. 6A and 6B , the rollers  420  should roll toward the cam member  300  by a distance D indicated in  FIG. 7A  so that the rollers  420  may be moved from the tops of the cam protrusions  310  to the lowermost portion of the top surface of the cam member  300 , as illustrated in  FIGS. 7A and 7B . In a valve dispensing pump having no accelerating member including angle limiting portions according to the related art, since a cam member should rotate in a state where a cam follower is fixed and rollers should roll up to a bottom surface of the cam member, the descending speed of the valve rod is determined by the rotational speed of the cam member. Even when an elastic member that provides a strong elastic force is used, the descending speed of the valve rod is substantially determined by the rotational speed of the cam member rather than the elastic force of the elastic member. In particular, when an outer diameter of each roller increases, a distance that is required for the rollers to contact the lowermost portion of the top surface of the cam member, increases so that the descending speed of the valve rod is also decreased by the distance. 
     However, in the valve accelerating type dispensing pump according to the present embodiment, when the rollers  420  roll along the inclined surfaces  311  of the cam protrusions  310 , the angle limiting portions  510  push the accelerating protrusions  410  in an opposite direction to the rotation direction of the cam member  300  by using the horizontal component force F H  applied to the rollers  420 , as illustrated in  FIGS. 6A and 6B . The cam follower  400  rotates with respect to the accelerating member  500  due to a force applied by the angle limiting portions  510  to the accelerating protrusions  410  and rotates instantaneously in an opposite direction to the rotation direction of the cam member  300 , as illustrated in  FIGS. 7A and 7B . As a result, the rollers  420  and the cam member  300  are moved in opposite directions, and the rollers  420  roll at much higher speed compared to the related art by the distance D at which the rollers  420  contact the lowermost portion of the top surface of the cam member  300 . Even when the rollers  420  having a relatively large outer diameter are used, due to interaction between the accelerating protrusions  410  and the angle limiting portions  510 , the rollers  420  may be moved relative to the cam member  300  at high speed, and the valve rods  210  may descend due to the elastic member  600  at very high speed. 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. 
     If the rollers  420  contact next cam protrusion  310 , the cam follower  400  that rotates with respect to the accelerating member  500  in an opposite direction to the cam member  300 , rotates in the same direction as the rotation direction of the cam protrusions  310  due to the vertical resistance F R  of the cam protrusions  310 , and the accelerating protrusions  410  are caught in the angle limiting portions  510  in a progressive direction. When the angle range of the angle limiting portions  510  is less than the angle range between the cam protrusions  310 , the accelerating protrusions  410  are first caught in inner walls of the angle limiting portions  510 , and rotation of the cam follower  400  with respect to the accelerating member  500  stops. If the rollers  420  contact next cam protrusion  310 , the cam follower  400  rotates in the same direction as the cam member  300  so that the accelerating protrusions  410  are caught in opposite inner walls of the angle limiting portions  510  and rotation of the cam follower  400  stops. 
     To sum up, in the related art, even when an elastic force of an elastic member is strong, the descending speed of the valve rod is determined by the size of an outer diameter of a roller and a rotational speed of a cam member. However, in the valve accelerating type dispensing pump according to embodiments of the present invention, due to interaction between the angle limiting portions  510  and the accelerating protrusions  410 , the descending speed of the valve rod  210  may be increased using a sufficient elastic force of the elastic member  600 . 
     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. 
     For example, the accelerating protrusions  410  are formed on the cam follower  400 , and the angle limiting portions  510  are formed on the accelerating member  500 . However, the accelerating protrusions  410  may be formed on the accelerating member  500 , and the angle limiting portions  510  may be formed on the cam follower  400 . 
     Also, a bearing that rolls along the inner walls of the angle limiting portion  510  may be installed at the accelerating protrusions  410  so as to reduce friction between the accelerating protrusion  410  and the angle limiting portion  510 . 
     In addition, the angle limiting portions  510  have the shape of long holes, as described above. However, the angle limiting portions  510  may also be formed in the form of long grooves. The accelerating protrusions  410  and the angle limiting portions  510  may be formed in various shapes in which the accelerating member  500  and the cam follower  400  may rotate relative to each other within a predetermined angle range due to interference between the accelerating protrusions  410  and the angle limiting portions  510 . 
     Furthermore, the rollers  420  are installed at the accelerating protrusions  410 , as described above. However, the rollers  420  may be configured in different ways. The accelerating protrusions  410  interfere with the angle limiting portions  510  independently from the rollers  420  so that the rotational angle of the cam follower  400  may be limited, and the rollers  420  may be configured to be coupled to the cam follower  400  separately from the accelerating protrusions  410 . 
       FIG. 8  illustrates another example of accelerating protrusions  551  and angle limiting portions  452 . 
     The accelerating protrusions  551  are formed on an accelerating member  550 , and the angle limiting portions  452  are formed on a cam follower  450 . The angle limiting portions  452  of the cam follower  450  are formed in the form of long grooves having a circular arc shape on a surface that faces the accelerating member  550  along a circumferential direction of the accelerating member  550 . The accelerating protrusions  551  of the accelerating member  550  are formed in the form of rods that extend in a bottom surface of the accelerating member  550  and are inserted in the angle limiting portions  452  of the cam follower  450 . The cam follower  450  rotates with respect to the accelerating member  550  slightly, and the accelerating protrusions  551  are caught in the inner walls of the angle limiting portions  452  such that the cam follower  450  does not rotate any more. The remaining configuration of the accelerating protrusions  551  and the angle limiting portions  452  excluding the above configuration is the same as  FIGS. 1 through 7A and 7B . If rollers  451  of the cam follower  450  roll along cam protrusions  310  in a state where the angle limiting portions  452  are caught in the accelerating protrusions  551  and the cam follower  450  cannot rotate, the angle limiting portions  452  are pushed by the accelerating protrusions  551  so that the cam follower  450  rotates with respect to the accelerating member  550 . As such, the relative speed between the rollers  451  and the cam member  300  increases, and the valve rod  210  may descend at high speed. 
     In the present embodiment, 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. 
     As described above, in a valve accelerating type dispensing pump according to embodiments of the present invention, an accurate amount of a liquid may be dispensed at high speed. 
     Also, the valve accelerating type dispensing pump according to embodiments of the present invention may dispense a liquid having high viscosity at high speed due to a fast descending speed of a valve rod. 
     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.