Patent Publication Number: US-10315173-B2

Title: Mixing device, discharge device provided therewith, and discharge method

Description:
TECHNICAL FIELD 
     The present invention relates to a mixing device for stirring a liquid mixed with solid particles and holding a uniformly mixed state, a discharge device provided with the mixing device, and a discharge method. 
     BACKGROUND ART 
     In a liquid mixed with solid particles having larger specific gravity than the liquid, it is difficult to hold a uniformly mixed state because the solid particles precipitate with the lapse of time. Holding the uniformly mixed state requires the provision of a mixing device and continuous stirring in a vessel in which the liquid mixed with the solid particles is stored. 
     As commonly used mixing devices, there are the motor type in which a propeller-like member is disposed at a tip of a rod connected to a motor power shaft and is rotated for mixing in the liquid mixed with the solid particles, and the magnetic force type in which a stirrer incorporating a magnet or a magnetic body is put in the liquid mixed with the solid particles and is rotated for mixing by the action of a magnetic force exerted from the outside of the vessel. 
     When the liquid mixed with the solid particles is quantitatively discharged and dispensed from the vessel, a discharge device is used which is generally employed to discharge and dispense a liquid material. In the discharge device handling the liquid mixed with the solid particles, however, it is required to one of the various types of mixing devices mentioned above in order to hold the uniformly mixed state. If the liquid mixed with the solid particles is not stirred, a trouble may occur in that the liquid mixed with the solid particles is discharged in a non-uniform state, or that it cannot be discharged because of clogging of a discharge port. 
     A discharge device provided with a mixing device is disclosed in Patent Document 1, for example. Patent Document 1 discloses a discharge device including a vessel, a stirrer for stirring a liquid, and stirrer rotating means for rotating the stirrer by a magnetic force, wherein the stirrer is arranged at a bottom in the vessel of the discharge device that discharges the liquid, and the stirrer has a through-hole penetrating from an upper surface to a lower surface thereof, a projection is formed in the upper surface, and a groove is formed in the lower surface to communicate an outer peripheral surface of the stirrer with the through-hole. 
     Another example of the mixing device is disclosed in Patent Document 2. Patent Document 2 discloses a magnetic driving device comprising a drive rotating member, a driven rotating member disposed in opposing relation to the drive rotating member, drive magnets disposed on an opposing surface of the drive rotating member, and driven magnets disposed on an opposing surface of the driven rotating member in the same number as the drive magnets, wherein the drive magnets and the driven magnets have substantially the same shape and are each constituted as a both-surface 2-pole magnet having one magnetic pole formed over one entire lateral peripheral surface and the other magnetic pole formed over the other entire lateral peripheral surface, the drive magnets and the driven magnets are each attached to the corresponding rotating members such that a central extension line passing the opposing surface of the drive magnet and the opposing surface of the driven magnet are parallel to each other, and when the drive rotating member is rotated, the driven rotating member is rotated by a magnetic force. Patent Document 2 further discloses a mixing device in which the above-mentioned magnetic driving device is used as a means for stirring a liquid in the mixing tank. 
     LIST OF PRIOR-ART DOCUMENTS 
     Patent Documents 
     Patent Document 1: Japanese Patent Laid-Open Publication No. 2005-120956 
     Patent Document 2: Japanese Patent Laid-Open Publication No. 2003-144891 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     Because the solid particles precipitate, it is generally preferable to dispose the stirrer at the bottom of the vessel, like the device disclosed in Patent Document 1, from the viewpoint of generating convection and promoting the stirring in the vessel. In the device disclosed in Patent Document 1, however, because the stirrer arranged at the bottom of the vessel is rotated by the magnetic force from below externally of the vessel, the stirrer comes into a state pressed against the bottom surface of the vessel by the action of its own dead weight and an attraction force exerted from a magnet. When the stirrer comes into such a state, friction is increased, thus causing various problems, e.g., (1) loss of energy for the rotation, (2) wear of the bottom surface and the shaft bearing portion of the stirrer, (3) mixing of dust and debris, which are caused by the friction, into the liquid, and (4) generation of noise attributable to the friction. 
     Furthermore, when the magnetic force is exerted on the stirrer through a bottom portion of the vessel, it is difficult to obtain a satisfactory action at the lower side of the stirrer. In Patent Document 1, the groove is formed in the lower surface of the stirrer to generate a flow streaming toward a bottom center of the vessel. This, however, brings about the problem that when the liquid mixed with the solid particles is stirred and flows through the groove having a bent portion, the particles tend to aggregate into masses, thus adversely affecting the discharge. 
     On the other hand, in the device disclosed in Patent Document 2, which includes a stirring mechanism at the bottom of the vessel, arrangement of the magnets, etc. are designed to reduce a thrust, i.e., a downward force in the direction of a rotation axis, even when a driving force is increased. To support the stirrer (driven rotating member) by a minus thrust (floating force), however, a support shaft has to be disposed at the bottom of the vessel (see FIGS. 4 and 5 in Patent Document 2), or superconducting magnets have to be employed (see FIGS. 6 to 8 in Patent Document 2). Therefore, the bottom shape of the vessel is complicated, or a large-scaled auxiliary device (such as a device for holding a low temperature) is needed. Thus, Patent Document 2 is not suitable for application to the discharge device. 
     Furthermore, when the magnetic force is exerted on the stirrer from the bottom, a difficulty arises in disposing the desired number of stirrers at the desired positions. In a vessel having a relatively large vertical length, therefore, it is hard to perform stirring over the entire inside of the vessel. 
     In view of the above-described situation, an object of the present invention is to provide a mixing device, which can solve the problems resulting from friction between a vessel and a stirrer, which can generate a circulatory flow even below the stirrer, and which allows a desired number of stirrers to be arranged at desired positions. Another object is to further provide a discharge device provided with the mixing device, and a discharge method. 
     Means for Solving the Problems 
     In the known device constituted to exert the magnetic force on the stirrer from the bottom side of the vessel, it is conceivable, for example, to float the stirrer from the bottom surface of the syringe (vessel) by arranging magnets such that poles having the same polarity are positioned to face each other. However, such a solution has a difficulty in forming a discharge flow passage at a center of the bottom surface of the vessel. The inventor has accomplished the present invention based on the conception of exerting the magnetic force on the stirrer from the lateral side. 
     According to a first invention, there is provided a mixing device comprising a stirrer incorporating a magnet, a stirrer holding mechanism that specifies a position of the stirrer by exerting a magnetic force on the stirrer from lateral side, and a rotation mechanism that rotates the stirrer holding mechanism, wherein the rotation mechanism rotates the stirrer holding mechanism, thereby rotating the stirrer. 
     According to a second invention, in the first invention, the stirrer includes a blade having a first acting surface that is widest and that generates flows in a liquid during rotation, and the first acting surface defines a tapered shape gradually narrowing toward an upper end of the blade. 
     According to a third invention, in the second invention, the blade of the stirrer has a second acting surface that is positioned adjacent to the first acting surface and that generates flows in the liquid during the rotation, and the second acting surface defines a tapered shape gradually narrowing toward a lower end of the blade. 
     According to a fourth invention, in the second or third invention, the stirrer has a cutout gradually spreading in an upper half thereof. 
     According to a fifth invention, in any one of the first to fourth inventions, the stirrer has a cutout formed in a lower half thereof. 
     According to a sixth invention, in the fifth invention, the stirrer has a penetration hole that is communicated with the cutout and that is formed coaxially with the rotary shaft. 
     According to a seventh invention, in any one of the first to fifth inventions, the stirrer is of two-blade type. 
     According to an eighth invention, in any one of the first to fifth inventions, the stirrer is of four-blade type. 
     According to a ninth invention, there is provided a discharge device comprising the mixing device according to any one of the first to eighth inventions, a liquid reservoir to which the stirrer holding mechanism is mounted, a nozzle communicating with the liquid reservoir, a compressed gas source, and a discharge controller that adjusts pressure of compressed gas supplied from the compressed gas source to a desired level and supplies the compressed gas. 
     According to a tenth invention, there is provided a discharge device comprising the mixing device according to the sixth invention, a liquid reservoir to which the stirrer holding mechanism is mounted, a nozzle communicating with the liquid reservoir, a plunger arranged in the liquid reservoir, and a plunger driving mechanism that reciprocally moves the plunger. 
     According to an eleventh invention, in the ninth or tenth invention, an inner space of the liquid reservoir has a shape gradually narrowing toward a lower end thereof, and an outer lateral surface of the stirrer defines a gradually narrowing shape while a certain gap is kept between the outer lateral surface and an inner wall of a bottom portion of the liquid reservoir. 
     According to a twelfth invention, in any one of the ninth to eleventh inventions, the stirrer is constituted by a plurality of stirrers, and the stirrer holding mechanism specifies respective positions of the plural stirrers. 
     According to a thirteenth invention, there is provided a discharge method using the discharge device according to any one of the ninth to twelfth inventions, wherein the liquid is discharged from the nozzle while the stirrer is rotated at a constant speed. 
     Advantageous Effects of the Invention 
     With the present invention, since the stirrer can be arranged at the desired position within the vessel, the problems resulting from friction between the vessel and the stirrer can be solved. 
     A circulatory flow can be generated even below the stirrer. 
     In addition, the desired number of stirrers can be arranged at the desired positions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates, in a way partially sectioned in principal parts, a discharge device provided with a mixing device according to a first embodiment. 
         FIG. 2  is an enlarged sectional view of a portion including the mixing device illustrated in  FIG. 1 . 
         FIG. 3  is a sectional view taken along A-A in  FIG. 2 . 
         FIG. 4  is an explanatory view to explain a stirrer used in the mixing device according to the first embodiment. Specifically,  FIG. 4( a )  is a perspective view, and  FIG. 4( b )  is a side view looking at the stirrer from a direction denoted by an arrow B in  FIG. 4( a ) . 
         FIG. 5  is a diagrammatic view to explain flows within a vessel when the mixing device according to the first embodiment is used. Specifically,  FIG. 5( a )  illustrates the flows when looking at the vessel from the front side, and  FIG. 5( b )  illustrates the flows when looking at the vessel from the lateral side. 
         FIG. 6  illustrates, in a way partially sectioned in principal parts, a discharge device provided with a mixing device according to a second embodiment. 
         FIG. 7  illustrates, in a way partially sectioned in principal parts, a discharge device provided with a mixing device according to a third embodiment. 
         FIG. 8  is a perspective view to explain a stirrer used in a mixing device according to a fourth embodiment. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Embodiments for carrying out the present invention will be described below. 
     First Embodiment 
     (1) Mixing Device 
       FIG. 1  illustrates, in a way partially sectioned in principal parts, a discharge device provided with a mixing device according to a first embodiment,  FIG. 2  is an enlarged sectional view of a portion including the mixing device illustrated in  FIG. 1 , and  FIG. 3  is a sectional view taken along A-A in  FIG. 2 .  FIG. 4  illustrates a stirrer used in the mixing device according to the first embodiment. Specifically,  FIG. 4( a )  is a perspective view, and  FIG. 4( b )  is a side view looking at the stirrer from a direction denoted by an arrow B in  FIG. 4( a ) . In the following, the side including a stroke adjustment mechanism  54  in  FIG. 1  is called the upper side, and the side including a nozzle  50  is called the lower side in some cases for convenience in explanation. 
     A mixing device  1  according to this embodiment includes, as main components, a stirrer holding mechanism  2 , a rotation mechanism  11 , and a stirrer  22 . 
     (Stirrer Holding Mechanism) 
     The stirrer holding mechanism  2  in this embodiment includes, as main components, a vessel cover  4 , an outer tube  5 , and a pair of magnets  7 . 
     As illustrated in  FIGS. 1 and 2 , a vessel  3  in which a liquid  32  mixed with solid particles is to be filled is covered at its outer side with the vessel cover  4  having a cylindrical shape. The vessel  3  and the vessel cover  4  are inserted in the outer tube  5  that is disposed coaxially with the vessel cover  4 . A certain gap is kept between the outer tube  5  and the vessel cover  4  such that there occurs no friction between them while the outer tube  5  is rotated. The outer tube  5  is supported by a bearing  6  disposed on a rotation-mechanism supporting member  16 , and is rotated by torque transmitted from a torque generator  12  through a belt  19  that is engaged in a groove formed in an upper outer circumference of the outer tube  5 . The pair of magnets  7  are fitted in openings that are formed in a lower portion of the outer tube  5  in opposing relation. 
     As illustrated in  FIG. 3 , the magnets  7  are fitted in the openings of the outer tube  5  such that one end surface of each magnet is positioned in flush with an inner surface of the outer tube  5 . A substantially half of the magnet  7  is fitted in a circumference wall of the outer tube  5 , and the remaining half of the magnet  7  is fitted in a magnet supporting member  8  that is fixed to the outer side of the outer tube  5  by fastening members  10 . A magnet fixing plate  9  is disposed at an outer end surface of the magnet  7 . Because the magnet fixing plate  9  is detachably fixed by the fastening members  10 , the relevant component, such as the magnet  7 , can be readily attached and detached. Furthermore, the magnet supporting member  8  and the magnet fixing plate  9  are each made of a magnetic material such that they act to attract the magnet and to keep the magnet from moving inwards. 
     An inner space of the vessel  3  has a gradually narrowing shape. In more detail, a most part of the inner space has a cylindrical shape, but a portion of the inner space, which is connected to a discharge flow passage  71  in communication with a nozzle  50 , has a conical shape. A stirrer  22  incorporating a pair of magnets  23  is disposed in the conical portion of the inner space. The above-mentioned magnets  7  are arranged at positions corresponding respectively to the magnets  23  of the stirrer  22  disposed in the vessel  3 . In other words, the magnets  7  and the magnets  23  of the stirrer  22  are arranged to lie on one linear line passing a central axis of the vessel  3 . Furthermore, respective polarities of the magnets  7  and  23  are arranged in such relation that the magnet  7  and the magnet  23  are attracted to each other (i.e., an attraction force acts between them), as denoted by “S” and “N” in  FIG. 3 . With such an arrangement, the stirrer  22  can be held at a desired position by a magnetic force in a state suspended in the vessel  3 . Therefore, the stirrer  22  can be rotated in a state where a gap is kept between the stirrer  22  and a sloped bottom surface of the vessel  3  without causing contact between them. It is hence possible to prevent the troubles attributable to friction, which have been discussed above. 
     The gap between the stirrer  22  and the sloped bottom surface of the vessel  3  is preferably set to, for example, about 1/10 to ⅕ of the inner diameter of the vessel  3 . With that setting, downward flows caused by the stirrer  22  can be utilized for mixing. In the mixing device  1  of this embodiment, since the magnetic force exerts on the stirrer  22  from the lateral side, the gap between the stirrer  22  and the sloped bottom surface of the vessel  3  can be set freely. In the case of mixing a liquid having high viscosity, magnets generating stronger magnetic forces are disposed in both the stirrer  22  and the outer tube  5 . 
     (Rotation Mechanism) 
     The rotation mechanism  11  will be described below with reference to  FIGS. 1 and 2 . 
     The rotation mechanism  11  in this embodiment includes, as main components, a torque generator  12 , a power shaft  13 , a coupling  14 , a rotary shaft  15 , a pulley  18 , and a belt  19 . 
     The torque generator  12  is fixed to the rotation-mechanism supporting member  16  with the aid of posts  21 . The torque generator  12  may be, for example, an electromotor (motor) such as a servo motor or a stepping motor, an air motor rotated by the action of compressed air, or an ultrasonic motor rotated by the action of an ultrasonic wave, but it is not limited to those examples. The operation of the torque generator  12  is controlled by a mixing controller  20  that is separate from a discharge controller  58  described later. 
     The torque generated by the torque generator  12  is transmitted, through the power shaft  13 , to the rotary shaft  15  that is coupled to the power shaft  13  by the coupling  14 . The rotary shaft  15  is rotatably supported by a bearing  17  that is disposed on the rotation-mechanism supporting member  16 . The transmitted torque rotates a pulley  18  fixed to the rotary shaft  15 . With the rotation of the pulley  18 , the torque is transmitted to the outer tube  5  by the belt  19  that is disposed to run around the pulley  18  and the upper part of the outer tube  5 . Furthermore, with the rotation of the outer tube  5 , the magnets  7  are rotated and the stirrer  22  inside the vessel  3  is then rotated by the magnetic force, thus stirring the liquid  32  mixed with the solid particles in the vessel  3 . 
     While, in the above description, the belt  19  and the pulley  18  are used as a mechanism for transmitting motive power, another mechanism using a combination of a chain and a sprocket, or gears can also be used instead. 
     (Stirrer) 
     The stirrer  22  has such a shape as generating circulatory flows on both sides above and under the stirrer  22 . To generate the circulatory flow on the upper side, for example, the stirrer  22  includes, in its upper half part, a cutout spreading upwards and giving, to the stirrer  22 , a shape gradually narrowing toward its upper end such that a surface acting to generate a flow in the liquid during the rotation (i.e., a widest surface extending vertically and being parallel to a line connecting a rotation axis and an inner circumference wall of the vessel) is tapered upwards. To generate the circulatory flow on the lower side, for example, a lateral surface of the stirrer  22  opposing to a sloped surface of a bottom portion of the vessel  3  is formed as a sloped surface similar to the sloped surface of the bottom portion of the vessel  3 , thus giving, to the stirrer  22 , a shape gradually narrowing toward its lower end such that a surface acting to generate a flow in the liquid during the rotation (i.e., a surface being parallel to the line connecting the rotation axis and the inner circumference wall of the vessel and being adjacent to the above-mentioned widest surface) is tapered downwards. The stirrer  22  in this embodiment described below has a shape generating the circulatory flows on both the upper and lower sides. For convenience in explanation, a surface of the stirrer opposing to the inner circumferential wall of the vessel and the opposing surface thereof are called outer lateral surfaces, and a surface of the stirrer, which intersect the outer lateral surfaces substantially at a right angle (i.e., a surface being parallel to the line connecting the rotation axis and the inner circumferential wall of the vessel and extending vertically) is called a front surface below. 
     As illustrated in  FIG. 4( a ) , the stirrer  22  in this embodiment is of the two-blade type including two blades disposed on both sides of the rotation axis. The stirrer  22  is obtained by forming tapered surfaces  24  and  25 , upper cutout surfaces  27 , outer lateral surfaces  26 , a lower cutout  28 , a penetration hole  30 , and holes  31  in a plate-like member having a relatively large thickness. The stirrer  22  has a shape like the feather of an arrow, as illustrated in  FIG. 1 , when looking at the stirrer from the front. A widest flat surface generating flows in the liquid during the rotation is provided by the upper tapered surface  24  (of which right half or left half with the rotation axis interposed between them serves as an acting surface). A flat surface disposed adjacent to the upper tapered surface  24  on the lower side thereof provides the lower tapered surface  25  (of which right half or left half with the rotation axis interposed between them serves as an acting surface). When looking at the stirrer  22  from a direction facing the outer lateral surface thereof, the stirrer  22  has a shape obtained by joining respective long sides of a trapezoid having a steep taper and a trapezoid having a moderate taper to each other through an outer lateral surface  26   b  interposed between the two trapezoids. The reason why the tapered surfaces  24  and  25  are formed as mentioned above is that greater flows can be generated in comparison with the case of not forming those tapered surfaces. Because a steeper tapered surface generates a greater flow, the upper tapered surface  24  serving to mix a larger amount of liquid is formed as a steeper sloped surface. To be adapted for forward and backward rotations, the tapered surfaces  24  and  25  are preferably formed at the rear side as well such that the stirrer has a left-right symmetric shape when viewed from the direction facing the outer lateral surface. 
     A lower portion of the stirrer  22  (i.e., a portion of the stirrer  22  below the outer lateral surface  26   b ) is formed to have outer lateral surfaces  26   c  such that a width between the outer lateral surfaces  26   c  is gradually narrowed downwards in conformity with the shape of the bottom portion of the vessel  3 . Moreover, at a center of the lower portion of the stirrer  22  in the widthwise direction thereof, the lower cutout  28  having a rectangular shape is form to extend from a lower end of the stirrer up to a position corresponding to about a half height of the stirrer (i.e., up to an upper end of the outer lateral surface  26   b ). A width of the lower cutout  28  is set equal to or slightly larger than the diameter of the penetration hole  30 . With that setting, a flow can be generated in a gap between a plunger  52  and the lower cutout  28  as well. A stopper  66  described in a later-described second embodiment may be disposed. 
     On the other hand, in an upper portion of the stirrer  22  (i.e., a portion above the outer lateral surface  26   b ), a flat portion  29  defining a surface parallel to a horizontal plane is formed at a position corresponding to about ¼ of the height descending from an upper end of the stirrer. The penetration hole  30  is formed at a center of the flat portion  29 . Furthermore, the upper cutout surfaces  27  are formed to obliquely extend from opposite ends of the flat portion  29  up to the upper end of the stirrer while approaching the outer lateral surfaces. The stirrer  22  having the upper portion formed as described above can generate a stronger rising flow within the vessel  3 . 
     The penetration hole  30  has a diameter allowing the plunger  52  of a later-described discharge device  46  to operate through the penetration hole  30 , i.e., preferably about 1.5 to 2 times the diameter of the plunger. Moreover, at a position slightly above the outer lateral surface  26   b , a pair of holes  31  are formed to extend perpendicularly to the penetration hole  30  toward the center from the outer lateral surfaces, and the magnets  23  are fitted in the holes  31 , respectively. The hole  31  in which the magnet  23  is fitted has a depth not reaching the penetration hole  30 . A length of the magnet  23  is set shorter than the depth of the hole  31 , and a vacant portion of the hole  31  after fitting the magnet  23  is sealed off to fix the magnet. At that time, preferably, the holes  31  are closed such that an outer lateral surface  26   a  including each hole  31  becomes a flat surface, in order to prevent the solid particles from adhering to and being solidified in a recess, etc. Thus, it is possible to avoid the liquid  32  mixed with the solid particles from entering the inside of the stirrer  22 , and to facilitate maintenance work such as cleaning. 
     (2) Flows within Vessel 
       FIG. 5  diagrammatically illustrates flows within the vessel when the stirrer in this embodiment is actually rotated. Specifically,  FIG. 5( a )  illustrates the flows within the vessel when looking at the stirrer from the front side, and  FIG. 5( b )  illustrates the flows within the vessel when looking at the stirrer from the lateral side. 
     First, the flows on the upper side of the stirrer  22  are described. As illustrated in  FIG. 5( a ) , when looking at the stirrer from the front side, a rising flow  35  generated near the upper end of the upper cutout surface  27  of the stirrer  22  rises along the inner circumferential wall of the vessel  3  and straightly reaches the vicinity of a liquid surface (denoted by symbol  36 ). Thereafter, the flow  36  turns to a falling flow  37  near the plunger  52  at the center of the vessel  3 , and flows downwards to the stirrer  22  along the central side of the vessel  3  (denoted by symbol  38 ). 
     As illustrated in  FIG. 5( b ) , when looking at the stirrer from the lateral side, a rising flow generated near the outer lateral surface  26   b  of the stirrer  22  (denoted by symbol  39 ) rises along the inner circumferential wall of the vessel  3  and straightly reaches a height slightly under the liquid surface (denoted by symbol  40 ). Such a height is substantially the same level at the height at which the flow toward the center appears (denoted by symbol  37 ) when looking at the stirrer from the front side. Thereafter, the flow  40  turns to a falling flow (denoted by symbol  41 ) while involving the liquid near the liquid surface, and flows downwards to the vicinity of a boundary defined by the outer lateral surface  26   b  of the stirrer  22  (denoted by symbol  39 ). 
     Thus, it is understood that circulatory flows are generated above the stirrer  22  by the stirrer  22  having the upper cutout surfaces  27  and the upper tapered surfaces  24 . With those circulatory flows, the liquid  32  mixed with the solid particles, which is present above the stirrer  22 , can be uniformly mixed. 
     Next, the flows on the lower side of the stirrer  22  are described. As illustrated in  FIG. 5( a ) , when looking at the stirrer from the front side, a rising flow  42  is generated in the lower cutout  28 , and it rises while withdrawing a part of the liquid in the discharge flow passage  71  together (denoted by symbol  43 ). To compensate for such a rising flow, a falling flow  44  is generated in the gap between the stirrer  22  and the sloped bottom surface of the vessel  3 . As illustrated in  FIG. 5( b ) , when looking at the stirrer from the lateral side, a falling flow  45  is generated near the outer lateral surface  26   b  of the stirrer  22 . A rising flow  42  denoted by dotted lines in  FIG. 5( b )  are the above-mentioned flows in the lower cutout  28 . 
     Thus, it is understood that circulatory flows are generated under the stirrer  22  by the stirrer  22  having the lower cutout  28  and the lower tapered surfaces  25 . It is further understood that the gap between the stirrer  22  and the sloped bottom surface of the vessel  3  also contributes to generating those circulatory flows. With those circulatory flows, the liquid  32  mixed with the solid particles, which is present under the stirrer  22 , can be uniformly mixed. 
     According to the above-described stirrer  22  in this embodiment, the circulatory flows can be generated in both the upper and lower sides of the stirrer, and the solid particles dispersed in the liquid within the vessel can be stirred into a uniformly mixed state. 
     (3) Discharge Device 
     The mixing device  1  of this embodiment is suitably applied to a discharge device  46  that quantitatively discharges and dispenses the liquid  32  mixed with the solid particles from the vessel  3 . The mixing device  1  is particularly suitable for application to a plunger type discharge device in which a liquid is discharged by opening and closing the discharge port with operation of the plunger  52 . The structure and the operation of the discharge device  46  provided with the mixing device  1  of this embodiment will be described below with reference to  FIGS. 1 and 2 . 
     (Structure) 
     The discharge device  46  includes the vessel (syringe)  3  that stores the liquid  32  mixed with the solid particles. A tip of the syringe  3  is fitted to a connecting member  47  that includes a flow passage constituting a part of the discharge flow passage  71 . A valve seat  48  and a tubular nozzle  50  are disposed in a portion of the connecting member  47 , the portion defining a distal end of the discharge flow passage  71 . The valve seat  48  and the nozzle  50  are supported by a nozzle fixing member  51 . The nozzle fixing member  51  is fixed by screwing to the vessel cover  4  that covers the syringe  3 . The valve seat  48  has a communication hole  49  formed at a center thereof, and the syringe  3  and the nozzle  50  are communicated with each other through the communication hole  49 . The plunger  52  extending through the penetration hole  30  of the stirrer  22  is disposed within the vessel  3 . The plunger  52  is operated to advance and retreat by a plunger driving mechanism  53  in such a manner that the plunger  52  closes and opens the communication hole  49  of the valve seat  48 . 
     A mechanism for specifying a most advanced position of the plunger  52  may be disposed to abruptly stop the plunger immediately before the plunger abuts against the valve seat, thus discharging droplets in a flying fashion. 
     The plunger driving mechanism  53  includes a stroke adjusting mechanism  54  that adjusts a stroke of the plunger  52 , i.e., a distance through which the plunger is moved, and a fixing screw  55  that fixedly maintains the adjusted stroke. The plunger driving mechanism  53  is connected to an adapter  56  and is mounted by inserting an inserted portion  57  of the adapter into an upper opening end of the syringe  3  and by fixing the adapter  56  and the vessel cover  4  together. The operation of the plunger driving mechanism  53  is controlled by a discharge controller  58  connected thereto via a control wiring line  59 . The discharge controller  58  adjusts pressure of compressed gas supplied from a compressed gas source  60  to a desired level, and then supplies the compressed gas to the syringe  3  through a compressed gas pipe  61 . 
     The discharge device  46  is supported by an upper vessel supporting member  63  and a lower vessel supporting member  64 , which are fixed to a base  62 . On that occasion, the discharge device  46  is supported in a state where a certain gap is kept relative to the outer tube  5  of the mixing device  1  that is also fixed to the base  62 . Fixing holes  65  used to fix the base  62  to, e.g., an XYZ driving mechanism or a stationary stand (not illustrated) by fastening members are formed in the base  62  at plural positions. 
     (Operation) 
     The discharge device  46  constituted as described above operates as follows. 
     A state where the tip of the plunger  52  is abutted against the valve seat  48  and the communication hole  49  is closed is assumed to be an initial state. In the initial state, the stirrer  22  is rotated to start stirring. When a discharge start signal is transmitted from the discharge controller  58 , the plunger driving mechanism  53  is operated to ascend the plunger  52 . A distance through which the plunger  52  is ascended at that time is determined by the stroke adjusting mechanism  54 . When the plunger  52  is ascended and the communication hole  49  of the valve seat  48  is opened, the liquid  32  mixed with the solid particles in the syringe  3  is caused to flow into the nozzle  50  by the action of the compressed gas. The liquid  32  mixed with the solid particles, having flowed into the nozzle  50 , passes through a flow passage in the nozzle and is then ejected to the outside from the discharge port. At that time, the liquid  32  mixed with the solid particles is in a state still connecting to a tip of the nozzle  50  (i.e., a state where the connection to the nozzle tip needs to be cut). When a discharge end signal is transmitted from the discharge controller  58  after the lapse of a predetermined time, the plunger driving mechanism  53  is operated to descend the plunger  52 . When the plunger  52  is descended to abut against the valve seat  48  and the communication hole  49  of the valve seat  48  is closed, the liquid  32  mixed with the solid particles in the syringe  3  is caused to depart from the tip of the nozzle  50  and to fly in the form of a droplet. During the above-mentioned process, the stirrer  22  is rotated at a constant speed. 
     The foregoing is the basic operation to perform one cycle of discharge. The above-described basic operation is repeated when performing plural cycles of discharge. 
     Second Embodiment 
     A second embodiment relates to a discharge device including a plurality of stirrers. Such a discharge device is suitable for the case where the vessel (syringe) communicating with the nozzle has a large capacity, or the case using a liquid mixed with particles that tend to precipitate. 
     In a mixing device  1  according to this embodiment, a plurality of stirrers can be disposed in the lengthwise direction of the syringe  3  and can be rotated because magnetic forces are exerted on the syringe  3  from the lateral side instead of being exerted on the syringe  3  from below.  FIG. 6  illustrates, in a way partially sectioned in principal parts, the discharge device provided with the mixing device according to the second embodiment. In the following, only different features from those in the first embodiment are described, and duplicate description of the same features is omitted. 
     The mixing device  1  according to this embodiment includes three stirrers  22  disposed within the vessel  3  at certain intervals. When the stirrer  22  is disposed plural, the corresponding magnet  7  and magnet fixing member have to be also disposed plural. Therefore, this embodiment uses the outer tube  5 , which has a length sufficient to cover a region corresponding to the three stirrers  22 , and which is equipped with three sets of magnets  7 , magnet supporting members  8 , and magnet fixing members  9 . Correspondingly, the rotation mechanism  11  is disposed at an upper position than in the first embodiment. 
     While the bearing  6  supporting the outer tube  5  may be disposed at one position on the side near the stirrer holding mechanism  2 , it is preferably disposed at two positions, as illustrated in  FIG. 6 , so that more stable rotation can be obtained. Stoppers  66  may be disposed on the plunger  52  at certain intervals to avoid the stirrers  22  from being contacted with each other within the vessel  3 . The stoppers  66  are fixed to the plunger  52  to be not rotatable. Between an upper end of each stopper  66  and the stirrer  22 , a gap is kept to such an extent as providing a distance longer than the intended stroke from the viewpoint of not impeding the discharge operation. The interval between the stirrers  22  is preferably about 0.5 to 1.5 times the inner diameter of the vessel  3 . With such an arrangement, flows can be generated above and under each of the stirrers  22 , and uniform mixing can be ensured. While the stirrers  22  are arranged in a coaxially aligned state (i.e., a state where the stirrers are completely overlapped with each other when viewed from above) in this embodiment, the stirrers  22  may be arranged in a state shifted from one another at a certain angle (e.g., 60 degrees). 
     With the above-described discharge device  46  according to this embodiment, discharge work can be performed while solid particles are uniformly mixed in a liquid, even in the case where the vessel (syringe) communicating with the nozzle has a large capacity, or the case using a liquid mixed with particles that tend to precipitate. 
     Third Embodiment 
     A third embodiment relates to an air type discharge device that discharges a liquid in the vessel (syringe)  3  by the action of compressed gas.  FIG. 7  illustrates, in a way partially sectioned in principal parts, the discharge device provided with a mixing device according to the third embodiment. In the following, only different features from those in the first embodiment are described, and duplicate description of the same features is omitted. 
     A discharge device  67  according to this embodiment does not include the plunger  52  and the components associated with the plunger, and it includes, as main components, the vessel  3 , the nozzle  50 , the discharge controller  58  that adjusts pressure of the compressed gas supplied from the compressed gas source  60  to a desired level and then supplies the compressed gas, and the adapter  69  that supplies the compressed gas under the adjusted pressure to the vessel  3  through a tube  68 . The discharge device  67  discharges the liquid by applying the compressed gas under the adjusted pressure to the liquid in the vessel for a predetermined time. 
     The discharge device  67  is supported by a nozzle guide  70  that is disposed on the lower vessel supporting member  64 . Because there is no plunger  52 , the penetration hole  30  is not required to be formed in the stirrer  22 . However, the penetration hole  30  may be formed to generate the flow passing through the penetration hole  30 . 
     With the above-described discharge device  67  according to this embodiment, discharge work can be performed for a liquid material that is not suitable for discharge using the plunger, while solid particles are uniformly mixed in the liquid material. 
     Fourth Embodiment 
     A fourth embodiment relates to a discharge device including a four-blade type stirrer.  FIG. 8  is a perspective view to explain the stirrer used in a mixing device according to the fourth embodiment. In the following, only different features from those in the first embodiment are described, and duplicate description of the same features is omitted. 
     As illustrated in  FIG. 8 , a stirrer  72  includes four blades that are positioned in opposing relation in two pairs about the penetration hole  30  at the center. Thus, the stirrer  72  has a crossed form when viewed from above. As in the two-blade type stirrer  22  in the first embodiment, the each blade has the tapered surfaces  24  and  25 , the upper cutout surfaces  27 , the outer lateral surfaces  26 , the lower cutout  28 , the penetration hole  30 , the flat portion  29 , and the holes  31 . 
     Flows generated by the stirrer  72  are basically similar to the flows ( FIG. 5 ) generated by the stirrer  22 . However, since the number of locations where the flows are generated are increased from two to four, finer flows can be generated in a state divided in a larger number, and the solid particles dispersed in the liquid within the vessel can be stirred into a more uniformly mixed state. 
     While the hole  31  and magnet  23  are each disposed in one pair in this embodiment, two pairs of holes  31  and magnets  23  may be disposed when a greater magnetic force is required depending on the weight of the stirrer itself or the viscosity of the liquid, etc. 
     While the four-blade type stirrer is disclosed in this embodiment, a three-blade type stirrer may also be used depending on the use. 
     INDUSTRIAL APPLICABILITY 
     The present invention is practiced in the following uses, for example:
         application to form a film of a dry lubricant (solid lubricant)   application to form a phosphor layer in an LED module       

     LIST OF REFERENCE SYMBOLS 
       1 : mixing device  2 : stirrer holding mechanism  3 : vessel (syringe)  4 : vessel cover  5 : outer tube  6 : bearing (for outer tube)  7 : magnet (for outer tube)  8 : magnet supporting member  9 : magnet fixing plate  10 : fastening member (for outer tube)  11 : rotation mechanism  12 : torque generator  13 : power shaft  14 : coupling  15 : rotary shaft  16 : rotation-mechanism supporting member  17 : bearing (for rotary shaft)  18 : pulley  19 : belt  20 : mixing controller  21 : post  22 : stirrer  23 : magnet (for stirrer)  24 : upper tapered surface  25 : lower tapered surface  26 : outer lateral surface  27 : upper cutout surface  28 : lower cutout  29 : flat portion  30 : penetration hole  31 : hole  32 : liquid mixed with solid particles  33  to  45 : flows  46 : discharge device  47 : connecting member  48 : valve seat  49 : communication hole  50 : nozzle  51 : nozzle fixing member  52 : plunger  53 : plunger driving mechanism  54 : stroke adjusting mechanism  55 : fixing screw  56 : adapter  57 : inserted portion of adapter  58 : discharge controller  59 : control wiring line  60 : compressed gas source  61 : compressed gas pipe  62 : base  63 : upper vessel supporting member  64 : lower vessel supporting member  65 : hole for fixing  66 : stopper  67 : air type discharge device  68 : tube  69 : adapter (air type)  70 : nozzle guide  71 : discharge flow passage  72 : stirrer S: S pole of magnet N: N pole of magnet