JP2009028579A - Bubble generating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bubble generating apparatus capable of easily generating large and small bubbles including fine bubbles and larger bubbles in liquid discharged from an apparatus with simple structure. <P>SOLUTION: In the bubble generating apparatus, an outer cylinder 3 is provided, formed thereinside with a liquid passage 2 comprising an introducing side passage 21 and a discharge side passage 22, an inner cylinder 4 formed thereinside with a water sending passage 41 increasing flow speed is mounted in the introducing side passage 21 of the outer cylinder 3, an edge part 42 is formed on the downstream end side of the water sending passage 41 inside the inner cylinder 4, a given space 5 is formed in the inner circumferential direction at a boundary portion of the introducing side passage 21 on the nearest downstream side of the edge part 42 and the discharge side passage 22, an annular gas chamber 6 communicated with the space 5 is annularly formed between the outer circumference of the inner cylinder 4 and the inner circumference of the outer cylinder 3, the upstream end of the introducing side passage 21 is communicatedly connected to the liquid supply side via a pump 7, and a downstream end of a gas supply hose 8 with an upstream side communicated with the gas supply side is communicatedly connected to a suction port 61 of the annular gas chamber 6. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique for mixing gas in various liquids used according to, for example, fresh water, sea water, and the like, and in particular, microbubbles and large size in liquid discharged from an apparatus with a simple structure. The present invention relates to a bubble generating device that easily generates large and small bubbles such as bubbles.

  Conventionally, for example, various types of bubble generators that can generate large and small bubbles in a liquid by mixing gas in various liquids used according to, for example, fresh water, seawater, and the like have been put to practical use. It is provided.

  However, the conventional bubble generating device is generally complicated in structure, and as a result, has a large number of parts and is expensive. In addition, the internal bubble cleaning device can be easily disassembled to clean the inside. It was also difficult to carry out.

  The present invention has been devised in view of the problems as described above to solve the problems. The object of the present invention is to form microbubbles or larger bubbles in the liquid discharged from the apparatus with a simple structure. An object of the present invention is to provide a bubble generating device capable of easily generating large and small bubbles such as bubbles.

  In order to achieve the above object, the invention of claim 1 is provided with an outer cylinder in which a liquid passage composed of an introduction side passage and a discharge side passage is formed, and the introduction side passage inside the outer cylinder. An edge part that has an inner cylinder with a water supply passage formed inside to increase the flow velocity and that the inner diameter of the inner peripheral surface of the water supply passage is once reduced in a taper shape toward the discharge side passage, and then promotes flow velocity and water pulse separation Is formed on the downstream end side of the water supply passage inside the inner cylinder, and a predetermined gap is formed in the inner circumferential direction at the boundary portion between the introduction side passage and the discharge side passage immediately downstream of the edge portion, and communicates with the gap. An annular air chamber is formed between the outer periphery of the inner cylinder and the inner periphery of the outer cylinder, the upstream end of the introduction side passage is connected to the liquid supply side via a pump, and the upstream side supplies gas. The downstream end of the gas supply hose communicating with the side is connected to the suction port of the annular air chamber. It is made from stage.

  According to a second aspect of the present invention, an outer cylinder having a liquid passage formed of an introduction side passage and a discharge side passage formed therein is provided, and a water supply passage for increasing the flow velocity is provided in the introduction side passage inside the outer cylinder. An inner cylinder formed inside is mounted, and the inner diameter of the inner peripheral surface of the water supply passage is once reduced to a taper shape toward the discharge side passage, and then an edge portion that promotes flow velocity promotion and water vein separation is provided inside the inner cylinder. Formed on the downstream end side of the water supply passage, a predetermined gap is formed in the inner circumferential direction at the boundary portion between the introduction side passage and the discharge side passage immediately downstream of the edge portion, and the annular air chamber communicating with the gap is A gas supply hose formed annularly between the outer periphery of the cylinder and the inner periphery of the outer cylinder, wherein the upstream end of the introduction side passage is connected to the liquid supply side via a pump, and the upstream side is connected to the gas supply side Is connected to the suction port of the annular air chamber and flows from the gas supply side. A flow control valve for controlling the flow rate of the body is made from means provided on the gas supply hose.

As is clear from the above description, the bubble generating device according to the present invention has the following effects.
(1) A structure in which an inner cylinder having an edge portion formed on the downstream end side of the internal water supply passage is simply inserted into the outer cylinder and coupled, and the structure is simple, so it is inexpensive and easy to disassemble and clean. It can be done. Moreover, since fine processing is not required, the processing cost can be reduced, and the product price can be reduced.
(2) Since the size of the generated bubble is determined by the opening of the air valve or a gap provided in the middle of the liquid passage, there is no need to arrange a device having a function of adjusting the size of the bubble inside the passage, Since there is no obstacle for passage, foreign substances can be easily passed. Moreover, if the foreign substance diameter can be specified, the design according to it can be performed.
(3) Gas suction is self-contained by the negative pressure generated in the gap. Since the edge portion of the inner cylinder inserted into the introduction side passage is rapidly reduced and enlarged toward the discharge side passage, the passing liquid jumps over the edge portion and continuously moves to the discharge side passage, and downstream of the introduction side passage. The gap provided between the surface and the upstream surface of the discharge-side passage is hollowed and becomes a negative pressure state, so that a suction force is generated and gas can be sucked into the liquid.
(4) Since the air bubbles generated in the liquid are self-supplied by the negative pressure generated by the air bubble generating device, an air supply device such as a compressor becomes unnecessary.
(5) If it is attached to the hose end, liquid such as water mixed with bubbles can be jetted onto the object.
(6) By discharging, for example, water of a liquid containing microbubbles into the water, if fine dust in the water is attached to the microbubbles generated in the water and carried to the surface of the water, it can be easily removed and the water can be purified. It becomes possible.
(7) Installation at the end of the pipe is possible in the middle of the pipe.
(8) Normally, air is mixed into the water as micronized bubbles from the suction port. Alternatively, a plurality of types of gas can be bubbled and mixed. Moreover, another liquid, for example, a disinfectant, a liquid fertilizer, a coloring agent, etc. can be mixed with the liquid (usually fresh water, seawater) to circulate.
(9) Since the size of the generated bubbles can be controlled by the flow control valve provided in the gas supply hose, various sizes including microbubbles can be obtained simply by connecting to the bubble generator and a commercially available submersible pump. Bubbles can be mixed in the liquid, and bubbles of various sizes can be generated in the liquid by discharging the bubbles into the liquid.

According to the bubble generating device of the second aspect of the invention, in addition to the above-described effect, since the water guide portion of the inner cylinder is reduced in a taper shape, the liquid can flow more smoothly.

Hereinafter, the present invention will be described more specifically based on the best mode for carrying out the invention described in the drawings.
Here, FIG. 1 is an overall configuration diagram in which the bubble generating device is disposed in the liquid, FIG. 2 (A) is a side sectional view of the bubble generating device, and FIG. 2 (B) is an end front view of the downstream end of the inner cylinder. 3A is another side cross-sectional view of the bubble generating device, FIG. 3B is an end front view of the other downstream end of the inner cylinder, and FIG. 4 is still another side cross-sectional view of the bubble generating device. .

  In the figure, the bubble generating device 1 is a device that easily generates large and small bubbles such as microbubbles and large bubbles in fresh water, seawater, and other various liquids with a simple structure. For example, a liquid passage 2 having a circular cross section is provided inside the outer cylinder 3 constituting the bubble generating device 1. The liquid passage 2 includes an introduction-side passage 21 and, for example, a discharge-side passage 22 having a stepped diameter and a smaller inner diameter. While the liquid introduced from the end of the introduction side passage 21 passes through the liquid passage 2, the gas is sucked into the liquid and mixed, and bubbles are generated from the liquid discharged from the end of the discharge side passage 22. It has a structure.

  The outer cylinder 3 constituting the bubble generating device 1 has an inner cylinder 4 mounted in a front-rear direction in an introduction-side passage 21 constituting a liquid passage 2 therein. The inner cylinder 4 is inserted from the inflow side end of the introduction side passage 21 toward the discharge side passage 22. That is, the liquid passage 2 provided in the outer cylinder 3 constituting the bubble generating device 1 is divided into an introduction side passage 21 into which the inner cylinder 4 is inserted and a discharge side passage 22.

  The circular diameter of the introduction side passage 21 formed inside the outer cylinder 3 is larger than the circular diameter of the discharge side passage 22 as described above, and the boundary portion is stepped at a right angle, for example. That is, the boundary portion of the introduction side passage 21 is circular, and an end portion of the smaller concentric discharge side passage 22 is formed inside the circular shape. The tip of the inner cylinder 4 inserted from the introduction-side passage 21 having a large diameter is stopped with a gap 5 at, for example, a perpendicular step portion of the boundary portion.

  When the inner cylinder 4 is inserted into the introduction side passage 21 and attached, a predetermined gap 5 that functions as a ventilation groove is formed at the boundary portion between the inner cylinder 4 attached to the introduction side passage 21 and the discharge side passage 22. The structure is always formed. That is, the inner cylinder 4 inserted into the introduction side passage 21 and the discharge side passage 22 form a predetermined gap 5 and are connected in communication in the front-rear direction.

  The inner cylinder 4 that is inserted into the introduction-side passage 21 of the outer cylinder 3 and attached thereto has a cylindrical shape, and a water supply passage 41 having a circular cross section is formed therein. The water supply passage 41 constitutes a part of the liquid passage 2 together with the introduction side passage 21 and the discharge side passage 22. The inner diameter of the water supply passage 41 is smaller than the inner diameter of the introduction side passage 21 into which the inner cylinder 4 is inserted.

  When the liquid introduced from the introduction port 21a which is the upstream end of the introduction side passage 21 passes through the introduction side passage 21 and enters the water supply passage 41 of the inner cylinder 4 having a smaller inner diameter than this, the fluid continuity principle Facilitates the flow rate. That is, the water supply passage 41 functions as a flow velocity promoting part.

  In addition, an edge portion 42 is formed on the inner peripheral surface of the water supply passage 41 functioning as a flow velocity promoting portion formed inside the inner cylinder 4 on the downstream end side. The edge portion 42 is formed in a shape in which the inner diameter of the inner peripheral surface of the downstream end of the water supply passage 41 is reduced in a tapered shape toward the discharge side passage 22, and fulfills a function of promoting flow velocity and promoting water pulse separation.

  Since the edge portion 42 is provided on the downstream end side of the water supply passage 41 of the inner cylinder 4, the flow velocity of liquid having a flow velocity is rapidly reduced by the edge portion 42 due to the continuity of the fluid by the taper-shaped reduction of the inner diameter. Will be. Further, when flowing from the introduction side passage 21 into the discharge side passage 22, the cross-sectional area of the liquid passage 2 is rapidly contracted and rapidly expanded by the edge portion 42, so that the pressure decreases immediately after passing through the edge portion 42, Suction occurs naturally in the liquid.

  In addition, since the liquid passage 2 expands in a tapered shape from the immediately downstream end of the edge portion 42 toward the discharge side passage 22, the liquid passing through the edge portion 42 jumps over the discharge side passage 22 with an inclination. The water vein separation is promoted and a cavity is formed in the corner portion immediately downstream of the edge portion 42. This hollow portion communicates with the gap 5.

  Then, the corner immediately downstream of the edge portion 42 is hollow and jumps over and the gas at the corner is entrained and becomes a negative pressure state, so that a suction force is naturally generated. A gap 5 communicates with the corner portion where the negative pressure state is established, and a suction force is generated and a gas such as air is sucked and mixed into the liquid passing through the discharge side passage 22 from the gap 5 located at the boundary portion. Thus, bubbles are generated in the liquid discharged from the discharge port 22a of the discharge side passage 22.

By the way, the water supply passage 41 and this edge part 42 formed in the inside of the inner cylinder 4 have a shape as shown in FIGS.
In the inner cylinder 4 shown in FIG. 2, the inner diameter of the water supply passage 41 is the same, for example, circular except for the edge part 42 and the water supply inlet 41a. The water supply inlet 41a is formed so that the inner peripheral edge thereof is rounded and the resistance to the flowing liquid becomes small.

  When viewed from the side, the edge portion 42 of the inner cylinder 4 shown in FIG. 2 is inclined obliquely downward toward the discharge side passage 22 with the top portion 42a sandwiched between the top portion 42a and the top portion 42a. The lower side of the inner surface on the right side is inclined obliquely upward toward the discharge side passage 22, and the inner diameter is rapidly reduced. Further, the upper side of the inner surface on the left side of the figure is inclined obliquely upward toward the discharge side passage 22 across the top part 42a, and the lower side of the left side of the figure is inclined obliquely downward toward the discharge side path 22 across the top part 42a. And the inner diameter is expanding.

  Further, the end surface convex surface 43 or the end surface concave surface 44 having a slight width is at least in the radial direction so that the gap 5 functioning as a ventilation groove is reliably formed on the end surface of the downstream end of the inner cylinder 4 shown in FIG. One is formed. The end surface convex surface 43 abuts on the step surface at the downstream end of the introduction-side passage 21, or the end surface concave surface 44 forms a gap with the step surface at the downstream end of the introduction-side passage 21, whereby the inner cylinder 4 A gap 5 that functions as a ventilation groove is reliably formed between the end surface of the downstream end of the first passage and the step surface of the downstream end of the introduction-side passage 21.

  On the other hand, in the inner cylinder 4 shown in FIG. 3, the cross section of the water supply passage 41 is reduced in a tapered shape toward the discharge side passage 22. Thereby, the flow velocity is promoted in the water supply passage 41 as the edge portion 42 is approached. Other than this, the shape is the same as that shown in FIG.

  Further, in the inner cylinder 4 illustrated in FIG. 4, the end surface convex surface 43 or the end surface concave surface 44 as illustrated in FIG. 2 is not formed on the end surface of the downstream end of the inner cylinder 4, and the water supply passage of the inner cylinder 4 An annular projecting surface 45 is formed on the outer peripheral side of the water supply inlet 41a. The introduction side passage 21 has an inner diameter in the vicinity of the middle, and the introduction port 21a side is slightly stepped from the back side, and the annular protrusion on the outer peripheral side of the inner cylinder 4 is formed on the step surface near the middle where the inner diameter is increased. The surface 45 abuts, and the stepped surface at the downstream end of the inner cylinder 4 does not abut against the stepped surface at the downstream end of the introduction-side passage 21 so that a constant gap 5 that functions as a ventilation groove is formed. ing. In FIG. 4, the water supply passage 41 has the same cross-sectional shape as in FIG. 2, but may have the same cross-sectional shape as in FIG. 3.

  In the introduction side passage 21 in which the inner cylinder 4 is inserted, a circular hole having an inner diameter larger than the outer diameter of the inner cylinder 4 inserted in the inner circumference on the boundary side with the discharge side passage 22 is formed. . The annular air chamber 6 is formed in an annular cavity portion that becomes a gap portion between the outer diameter of the inner cylinder 4 and a circular hole having an inner diameter larger than this.

  On the inner peripheral surface of the introduction side passage 21, a seal groove 21b is formed in the circumferential direction. The cross section of the seal groove 21b has a rectangular shape. An annular sealing material 21c is attached to the sealing groove 21b. A stirring groove 22b is formed on the inner peripheral surface of the discharge side passage 22 in the circumferential direction as necessary. The cross section of the stirring groove 22b has a rectangular shape. The liquid flowing in the discharge side passage 22 is further stirred by the stirring groove 22b, so that gas is further mixed into the liquid.

  The outer cylinder 3 constituting the bubble generating device 1 is formed in, for example, a cylindrical shape, and is formed of an annular thick plate 31 whose outer diameter at the central portion is slightly larger than the front and rear diameters. The annular thick plate 31 is formed with a suction port 61 communicating with the annular air chamber 6 from the outer periphery toward the inner circular hole. Further, for example, a spiral screw thread is formed on the outer periphery of the upstream inlet 21a on the side where the liquid flows into the inlet passage 21 so as to be easily connected to an end of a submersible pump 7 described later.

  An end portion of the annular air chamber 6 formed on the entire outer periphery of the liquid passage 2 communicates with the gap 5 functioning as a ventilation groove. The gas passes through the suction port 61 and flows into the annular air chamber 6, reaches the entire circumferential direction of the annular air chamber 6, and then discharges from the gap 5 that functions as a ventilation groove formed in the inner circumferential direction of the liquid passage 2. Bubbles are generated in the liquid that is sucked into the liquid having a flow velocity passing through the passage 22 side and discharged from the discharge port 22a of the discharge side passage 22.

  The pump 7 installed in water feeds liquid from the liquid supply side to the introduction side passage 21 of the liquid passage 2, and the introduction port 21 a of the introduction side passage 21 is connected to the pump 7. The pump 7 feeds the liquid at a flow rate that generates a force for sucking and mixing gas into the liquid from the gap 5 in the discharge side passage 22 of the liquid passage 2. The pump 7 is supplied with power through a pump power supply 71. In the figure, the pump 7 is a submersible pump that is installed and used in a liquid, but may be a self-priming pump that is installed and used outside a liquid. In this case, the pump 7 and the introduction port 21a of the introduction side passage 21 are connected to each other by a liquid supply hose (not shown).

  The gas supply hose 8 is a gas passage when supplying various types of gas used for the bubble generating device 1 according to, for example, air, ozone, carbon dioxide, or other applications. The upstream side of the gas supply hose 8 is connected to a gas supply side, for example, opened to the atmosphere, an ozone storage tank, a carbon dioxide storage tank, or another gas storage tank.

  Further, the downstream end of the gas supply hose 8 is connected to the suction port 61 of the annular air chamber 6 constituting a part of the bubble generating device 1. The gas on the gas supply side flows through the gas supply hose 8 and flows into the annular air chamber 6, and is sucked into the liquid in the discharge side passage 22 from the gap 5 to be dissolved and becomes bubbles.

  In the middle of the gas supply hose 8, a flow rate control valve 81 for adjusting the flow rate of the gas sucked from the gas supply side is provided. By adjusting the flow rate control valve 81, for example, when the flow rate is reduced, the diameter of bubbles in the liquid is reduced to facilitate the generation of microbubbles. Conversely, when the flow rate is increased, the diameter of bubbles in the liquid is increased. It can be easily generated.

  Next, the operation of the bubble generating device based on the configuration of the best mode for carrying out the invention will be described below.

  The introduction port 21a of the introduction side passage 21 of the outer cylinder 3 constituting the bubble generating device 1 is connected to, for example, a pump 7 installed in water. The flow control valve 81 and the outer cylinder 3 of the bubble generator 1 are connected by the gas supply hose 8. In this case, the downstream end of the gas supply hose 8 is formed on the annular thick plate 31 of the outer cylinder 3 of the bubble generator 1. Connect to the inlet 61. For example, when the gas is air and the liquid is water, the upstream end of the gas supply hose 8 is placed in the atmosphere, and the bubble generating device 1 is placed in the water.

  If the pump 7 is driven and water is supplied in this state, the water vein passing through the edge portion 42 formed at the boundary portion between the introduction side passage 21 and the discharge side passage 22 of the bubble generating device 1 follows the shape of the edge portion 42 according to the speed. Without being inclined, it jumps over, and passes through the inside of the inner cylinder 4 continuously inserted into the introduction side passage 21 while generating a vortex and a negative pressure generating portion a in the corner immediately downstream of the edge portion 42, and on the discharge side Transition to the passage 22.

  At this time, the vortexed water vein entrains and flows down the air at the circumferential corner of the boundary portion between the introduction side passage 21 and the discharge side passage 22, so this portion becomes the negative pressure generating portion a. The negative pressure generated in the circumferential corner is negatively applied to the annular air chamber 6 through the gap 5 formed in the negative pressure generating portion a and the pipe of the gas supply hose 8 from the annular air chamber 6 to the flow control valve 81. And

  In this case, if the flow control valve 81 is fully closed, the atmosphere is not supplied to the negative pressure area, and is not sucked into the water being fed in the liquid passage 2 of the bubble generating device 1. Normal water supply is performed.

  Further, if the flow control valve 81 is opened, the water filled in the annular air chamber 6 before the operation by the negative pressure generated at the circumferential corner of the boundary portion between the introduction side passage 21 and the discharge side passage 22 is filled. Is taken from the gap 5 into the water vein that is fed through the liquid passage 2.

  When the water in the annular air chamber 6 is exhausted, the air starts to be sucked through the gap 5 communicating with the annular air chamber 6 and is taken into the water vein that is fed through the liquid passage 2 of the bubble generating device 1. The water is sucked into the water and discharged into the water from the discharge port 22a of the discharge side passage 22 as water mixed with bubbles.

  The degree of negative pressure varies depending on the opening degree of the flow control valve 81 that controls the amount of air supplied to the water vein that is fed through the liquid passage 2 through the annular air chamber 6 and the gap 5. When fully open, the pressure in the annular air chamber 6 approaches the atmospheric pressure, a large amount of air is entrained into the water vein being fed through the liquid passage 2, and the bubble diameter discharged from the bubble generator 1 into the water is large. Become.

  Conversely, if the valve of the flow control valve 81 that controls the amount of air is throttled, the pressure in the annular air chamber 6 decreases, and the amount of suction into the water vein that is fed through the liquid passage 2 through the gap 5 decreases. The mixed air is micronized and mixed into the water vein, the bubble diameter discharged into the water from the outer tube 3 of the bubble generating device 1 is reduced, and the microbubbles can be generated in the water.

  Note that the present invention is not limited to the best mode for carrying out the invention, and various modifications can be made without departing from the spirit of the invention.

1 is an overall configuration diagram in which a bubble generating device showing the best mode for carrying out the present invention is disposed in a liquid. (A) is a side sectional view of a bubble generating device showing the best mode for carrying out the present invention. (B) is an end front view of the downstream end of the inner cylinder showing the best mode for carrying out the present invention. (A) is another sectional side view of the bubble generator which shows the best form for implementing this invention. (B) is the edge part front view of the other downstream end of the inner cylinder which shows the best form for implementing this invention. It is further another sectional side view of the bubble generator which shows the best form for implementing this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bubble generator 2 Liquid passage 21 Introduction side passage 21a Introduction port 21b Seal groove 21c Seal material 22 Discharge side passage 22a Discharge port 22b Stirring groove 3 Outer cylinder 31 Annular thick plate 4 Inner cylinder 41 Water supply passage 41a Water supply inlet 42 Edge part 42a Top portion 43 End surface convex surface 44 End surface concave surface 45 Annular projection surface 5 Clearance 6 Annular air chamber 61 Inlet 7 Pump 71 Pump power supply 8 Gas supply hose 81 Flow control valve a Negative pressure generating part

Claims (3)

An outer cylinder having a liquid passage formed of an introduction side passage and a discharge side passage is provided inside, and an inner cylinder having a water supply passage formed therein is mounted in the introduction side passage in the outer cylinder. Then, the inner diameter of the inner peripheral surface of the water supply passage toward the discharge side passage is once reduced in a taper shape, and then an edge portion is formed on the downstream end side of the water supply passage inside the inner cylinder for enlarging the flow velocity and promoting water vein separation. A predetermined gap is formed in the inner circumferential direction at a boundary portion between the introduction side passage and the discharge side passage immediately downstream of the edge portion, and an annular air chamber communicating with the gap is formed between the outer circumference of the inner cylinder and the inner side of the outer cylinder. The upstream end of the introduction side passage is connected to the liquid supply side via a pump, and the downstream end of the gas supply hose whose upstream side is connected to the gas supply side is connected to the circumference of the annular air chamber. A bubble generating device characterized in that it is connected in communication with a suction port. An outer cylinder having a liquid passage formed of an introduction side passage and a discharge side passage is provided inside, and an inner cylinder having a water supply passage formed therein is mounted in the introduction side passage in the outer cylinder. Then, the inner diameter of the inner peripheral surface of the water supply passage toward the discharge side passage is once reduced in a taper shape, and then an edge portion is formed on the downstream end side of the water supply passage inside the inner cylinder for enlarging the flow velocity and promoting water vein separation. A predetermined gap is formed in the inner circumferential direction at a boundary portion between the introduction side passage and the discharge side passage immediately downstream of the edge portion, and an annular air chamber communicating with the gap is formed between the outer circumference of the inner cylinder and the inner side of the outer cylinder. The upstream end of the introduction side passage is connected to the liquid supply side via a pump, and the downstream end of the gas supply hose whose upstream side is connected to the gas supply side is connected to the circumference of the annular air chamber. Flow rate that controls the flow rate of gas flowing in from the gas supply side, connected to the suction port Bubble generating device, characterized in that provided in the gas supply hose valve. The bubble generating device according to claim 1 or 2, wherein the edge portion is formed on the inner peripheral surface of the water supply passage so as to protrude in a triangular cross section having inclined surfaces on both sides of the top portion as a boundary.

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