Abstract:
Disclosed is a personal watercraft having a water cooling system of an engine, which allows inside of a cooling water passage of an engine or a water passage connected to the cooling water passage to be sufficiently cleaned and a clogged water-supply hole in an expansion chamber to be easily inspected or cleaned. The personal watercraft  1  comprises a first water passage  50  from a water jet pump  7  to a cooling water passage of an engine  4.  Water is forcibly sent by the water jet pump  7  and led to the cooling water passage through the first water passage  50.  The water flows through the cooling water passage while exchanging heat, and the resulting water is discharged outside the watercraft. The personal watercraft  1  further comprises a second water passage  53  opened in a surface of a body of the watercraft and communicating with the first water passage  50,  and an opening/closing means  54  for opening/closing the second water passage  53.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a personal watercraft (PWC) which ejects water rearward and planes on a water surface as the resulting reaction, and more particularly to a personal watercraft having a water cooling system of an engine.  
           [0003]    2. Description of the Related Art  
           [0004]    In recent years, personal watercraft have been widely used in leisure, sport, rescue activities, and the like. The personal watercraft has a straddle-type body structure, and is configured to have a water jet pump that pressurizes and accelerates water sucked from a water intake generally provided on a hull bottom surface and ejects it rearward from an outlet port. Thereby, the personal watercraft is propelled.  
           [0005]    In general, the personal watercraft employs an engine cooling system in which its engine is cooled by the water from the water jet pump and thereafter, the water is discharged outside the watercraft, rather than a closed circulation type engine cooling system of automobile.  
           [0006]    [0006]FIG. 6 is a schematic structure of the engine cooling system of the personal watercraft. In the engine cooling system, a water jet pump  107  is connected to an engine  104  through a pipe  150 . A cooling water passage (water jacket) is formed in the engine  104 . A filter  151  is provided in the pipe  150 . The filter  151  serves to eliminate substances such as small stones and waterborne plants.  
           [0007]    In the personal watercraft using this cooling system, a riding seat is openable/closable or otherwise removable. By opening or removing the riding seat, an opening formed in a deck is exposed. In maintenance and replacement of the filter  151 , the filter  151  is accessible through the opening.  
           [0008]    The cooling water passage formed in the engine  104  will now be described. The engine  104  is comprised of an engine body portion  120 , an exhaust system  130 . The engine body portion  120  is constituted by a cylinder block, a cylinder head, a crankcase, a crankshaft, pistons, and the like. The exhaust system  130  is constituted by an exhaust manifold, an exhaust pipe, an expansion chamber, a water muffler, an exhaust duct, and the like.  
           [0009]    A water passage is formed in the cylinder block and the cylinder head. A water passage is also formed in the exhaust manifold, the exhaust pipe, and the expansion chamber. The cooling water passage of the engine  104  is comprised of these water passages.  
           [0010]    The water is pumped into the pipe  150  by the water jet pump  107 . The water flows through the filter  151  provided in the pipe  150  and then into the water passage of the exhaust system  130 . Part of the water flowing into the water passage of the exhaust system  130  is diverged to flow and circulate through the water passage of the engine body portion  120  and is returned again to the water passage of the exhaust system  130 .  
           [0011]    An outlet of the cooling water passage of the engine  104  is connected to a pipe  156 . A tip end of the pipe  156  extends to a pump room in the water jet pump  107 . In brief, the water is sent into the cooling water passage of the engine by the water jet pump  107  and flows through the cooling water passage while exchanging heat, and the resulting water is sent into the pump room in the water jet pump  107  and discharged outside the watercraft.  
           [0012]    A water-supply hole is provided in the expansion chamber. The cooling water is supplied to the inside of the expansion chamber through the water-supply hole and then sent into the water muffler, together with an exhaust gas.  
           [0013]    In maintenance of the engine or the like of the personal watercraft, the personal watercraft is landed and the water in the cooling water passage of the engine is discharged.  
           [0014]    However, in the personal watercraft having the water cooling system shown in FIG. 6, all the water in the cooling water passage of the engine  104  or the pipes  150 ,  156  is not discharged and is sometimes partially left. Even when all the water is discharged, the substances such as small stones or waterborne plants sometimes still remain in the cooling water passage or the pipes  150 ,  156 . Further, especially after cruising on sea, salt remains adhered to the inner peripheral walls of the cooling water passage of the engine  104  or the pipes  150 ,  156 .  
           [0015]    As described above, the filter  151  is provided on the pipe  150  for eliminating the substances. For ease of maintenance of the filter  151 , it is preferable that a portion of the pipe  150  where the filter  151  is provided is lifted relatively higher so that the filter  151  is readily accessible through the opening exposed by opening or removing the riding seat. Nonetheless, when the pipe  150  is partially higher than an inlet of the cooling water passage of the engine  104 , the water between the higher portion and the inlet of the cooling water passage is difficult to discharge. The ease of discharge of the water is incompatible with the ease of maintenance of the filter  151 . This limits layout of the pipe  150 .  
           [0016]    When the water-supply hole of the expansion chamber is clogged, the exhaust system  130  needs to be disassembled for cleaning the water-supply hole.  
         SUMMARY OF THE INVENTION  
         [0017]    The present invention addresses the above-described condition, and an object of the present invention is to provide a personal watercraft having a water cooling system of an engine, which allows inside of a cooling water passage of an engine or a water passage connected to the cooling water passage of the engine to be sufficiently cleaned.  
           [0018]    Another object of the present invention is to provide a personal watercraft that allows a water-supply hole of an expansion chamber to be easily inspected and cleaned.  
           [0019]    According to the present invention, there is provided a personal watercraft comprising: a water jet pump; a cooling water passage of an engine; a first water passage from the water jet pump to the cooling water passage; a second water passage opened in a surface of a body of the watercraft and communicating with the first water passage; and an opening/closing means for opening/closing the second water passage, wherein a cooling water is forcibly sent to the first water passage by the water jet pump and led to the cooling water passage through the first water passage, the water flows through the cooling water passage while exchanging heat, and the resulting water is discharged outside the body of the watercraft.  
           [0020]    In the personal watercraft so constituted, after the personal watercraft is landed, water in the cooling water passage is discharged from the second water passage by opening the second water passage. Further, a cleaning water can be forcibly supplied from the outside into the cooling water passage and the first water passage through the second water passage. Thus, the inside of the cooling water passage of the engine and the first water passage can be positively cleaned even in the case of using the water passage of ups and downs. Consequently, degree of freedom of layout of the first water passage is improved.  
           [0021]    A first portion of the first water passage may be located higher than an inlet of the cooling water passage, and the second water passage may branch from a position of the first water passage between the first portion and the inlet of the cooling water passage.  
           [0022]    When the first portion of the first passage is located higher than the inlet of the cooling water passage, the water in the first water passage between the first portion and the inlet of the cooling water passage is hardly discharged merely by landing the personal watercraft. However, in the above-mentioned structure, such water can be easily discharged from the second water passage. Further, by forcibly flowing the cleaning water into the first water passage through the second water passage, the cooling water between the first portion and inlet of the cooling water passage can be expelled.  
           [0023]    In the personal watercraft, a filter may be provided in the first water passage, and the second water passage may branch from a position of the first water passage between the filter and an inlet of the cooling water passage.  
           [0024]    When the filter is provided on the first water passage, the water in the first water passage between the filter and the inlet of the cooling water passage is hardly discharged merely by landing the personal watercraft. This is because the water between the filter and the inlet is less likely to flow back through the filter, and therefore is difficult to discharge. However, in the above-mentioned structure, such water is easily discharged through the second water passage. Besides, by forcibly flowing the cleaning water into the first water passage through the second water passage, the water between the filter and the inlet of the cooling water passage can be expelled.  
           [0025]    A tip end of the second water passage may be opened in a rear end face of the body.  
           [0026]    According to the present invention, there is further provided a personal watercraft comprising: an expansion chamber in an exhaust system of an engine; and a water muffler provided at a position downstream of the expansion chamber in the exhaust system of the engine, wherein the expansion chamber has a double-walled structure comprised of inner and outer walls between which water flows and is provided with a water-supply hole in the inner wall to allow water to be supplied into inside of the expansion chamber through the water-supply hole, an inspection hole is formed in the outer wall at a position corresponding to a position of the water-supply hole, and a cap member is removably attached to the inspection hole.  
           [0027]    Since the inspection hole is formed in the outer wall of the double-walled structure of the expansion chamber at the position corresponding to the water-supply hole, the water-supply hole is readily accessible through the inspection hole by removing the cap member. Therefore, the inspection of the water-supply hole can be easily carried out and the water-supply hole can be easily cleaned.  
           [0028]    The exhaust system may be provided with a temperature sensor located downstream of the water-supply hole in an exhaust gas flow path, for detecting temperature of an exhaust gas.  
           [0029]    In the above-mentioned structure, the clogging in the watersupply hole can be quickly found by detecting that the temperature of the exhaust gas is higher than a proper temperature.  
           [0030]    The above and further objects and features of the invention will be more fully be apparent from the following detailed description with accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0031]    [0031]FIG. 1 is a side view of a personal watercraft according to an embodiment of the present invention.  
         [0032]    [0032]FIG. 2 is a perspective view showing a cooling system of an engine of the personal watercraft in FIG. 1.  
         [0033]    [0033]FIG. 3 is a schematic view showing a structure of cooling water passages in an engine body portion and an exhaust system and water passages connected to the cooling water passages.  
         [0034]    [0034]FIG. 4 is a longitudinal sectional view showing a portion where an expansion chamber is connected to a water muffler.  
         [0035]    [0035]FIG. 5 is a rear view showing the personal watercraft in FIG. 1.  
         [0036]    [0036]FIG. 6 is a schematic view showing a cooling system of an engine of the conventional personal watercraft. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0037]    Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.  
         [0038]    [0038]FIG. 1 is a side view of a personal watercraft  1  according to an embodiment of the present invention.  
         [0039]    The personal watercraft  1  has a FRP body. The body is mainly comprised of a hull  2  and a deck  3  covering the hull  2  from above. An engine (internal combustion engine)  4  as a power source is equipped inside of the body comprised of the hull  2  and the deck  3 . The rotation of the engine  4  is transmitted to an impeller  5  through a drive shaft. The impeller  5  and a casing  6  enclosing the outer periphery of the impeller  5  constitute a water jet pump  7 .  
         [0040]    An opening is provided as a water intake  8  in a bottom surface of the hull  2 . The water is sucked from the water intake  8  and fed to the water jet pump  7 . The water jet pump  7  pressurizes and accelerates the water. The pressurized and accelerated water is discharged through a pump nozzle behind the water jet pump  7 , thereby propelling the personal watercraft  1 . The pump nozzle is covered with a steering nozzle  9  provided behind the pump nozzle. In FIG. 1, reference numeral  10  denotes a reverse deflector. The deflector  10  is swung downward to a lower position around a horizontally mounted swinging shaft to deflect the ejected water from the steering nozzle  9  forward, and as the resulting reaction, the personal watercraft  1  moves rearward.  
         [0041]    A straddle-type riding seat  11  is mounted at the center portion of the deck  3 . A steering handle  12  is provided in front of the seat  11 . When the rider steers the steering handle  12  clockwise or counterclockwise, the steering nozzle  9  is swung toward the opposite direction so that the watercraft  1  can be correspondingly turned to a desired direction. A hatch cover  13  is mounted in front of the handle  12  so as to partially cover the deck  3 .  
         [0042]    The seat  11  is openable/closable or removable from the deck  3 . When the rider is driving the watercraft  1 , the seat  11  is mounted on the deck  3 . During maintenance of the engine  4  or the like inside of the body, the seat  11  is opened/removed from the deck  3 . By opening/removing the seat  11 , an opening  14  formed in the deck  3  is exposed, and maintenance operations or the like of equipment such as an engine inside of the deck  3  and the hull  2  can be carried out through the opening  14 .  
         [0043]    [0043]FIG. 2 is a view showing a cooling system of the engine  4  of the personal watercraft  1 . FIG. 3 is a schematic view showing a structure of cooling water passages in an engine body portion  20  and an exhaust system  30  and water passages connected to the cooling water passages. In FIG. 2, portions other than connected portions of the pipes  50 ,  53 ,  56  are not illustrated. In FIG. 3, arrows show a direction of flow of cooling water.  
         [0044]    In the personal watercraft  1 , the water pumped by the water jet pump  7  is used for cooling the engine  4 .  
         [0045]    The engine  4  is comprised of the engine body portion  20 , the exhaust system  30 , and the like. The exhaust gas generated in the engine body portion  20  is discharged from an exhaust outlet  39  formed in a rear end face of the body of the watercraft through the exhaust system  30 .  
         [0046]    The engine body portion  20  is constituted by a cylinder block  21 , a cylinder head  22 , a crankcase (not shown), a crankshaft (not shown), pistons (not shown), and the like. In FIG. 2, only the cylinder block  21  and the cylinder head  22  are illustrated. The exhaust system  30  is constituted by an exhaust manifold  31 , an exhaust pipe  32 , an expansion chamber  33 , a water muffler  34 , an exhaust duct  35 , and the like.  
         [0047]    A water passage is formed in the cylinder block  21  and the cylinder head  22 . A water passage is also formed in the exhaust manifold  31 , the exhaust pipe  32 , and the expansion chamber  33 . The cooling water passage of the engine  4  is comprised of the water passage of the engine body portion  20  and the water passage of the exhaust system  30  and constituted as a water jacket.  
         [0048]    The water passage of the exhaust system  30  is formed by a double-walled structure of the exhaust manifold  31 , the exhaust pipe  32 , and the expansion chamber  33 . To be specific, the exhaust manifold  31 , the exhaust pipe  32 , and the expansion chamber  33  in the exhaust system  30  have at least partially double-walled structure comprised of inner and outer walls between which the cooling water flows.  
         [0049]    The water passage of the cylinder block  21  communicates with the water passage of the cylinder head  22 . The water passage  31   a  of the exhaust manifold  31  communicates with the water passage  32   a  of the exhaust pipe  32 , which communicates with a water passage  33   a  of the expansion chamber  33 . Further, the water passage  31   a  of the exhaust manifold  31  communicates with the water passage of the cylinder block  21 , and the water passage of the cylinder head  22  communicates with the water passage  32   a  of the exhaust pipe  32 .  
         [0050]    A water-supply hole  33   g  for discharging the cooling water in the exhaust gas flowing in the expansion chamber is formed in an inner wall  33   d  of the expansion chamber  33 . A water muffler  34  is mounted downstream of the expansion chamber  33  in an exhaust gas flow path.  
         [0051]    The water jet pump  7  is connected to the exhaust manifold  31  through the pipe  50 . To be specific, a base end of the pipe  50  is connected to the water jet pump  7  and a tip end of the pipe  50  is connected to a cooling water passage inlet  41  formed in the exhaust manifold  31 . The pipe  50  functions as the water passage connecting the water-jet pump  7  to the cooling water passage inlet  41 .  
         [0052]    A filter  51  is provided at an intermediate position of the pipe  50 , for eliminating substances such as small stones and waterborne plants. The filter  51  is located beneath the riding seat  11 . The pipe  50  is curved, for example, substantially inverted-U shaped at a mid portion of the pipe  50  so as to be highest at the position where the filter  51  is provided. The filter  51  is located in the vicinity of the opening  14  so that the filter  51  is readily accessible through the opening  14  exposed when the riding seat  11  is opened or removed from the deck  3 . Consequently, maintenance and replacement of the filter  51  are easily carried out.  
         [0053]    Since the pipe  50  is protruded upward so as to be highest at the filter  51 , the filter  51  is located higher than the cooling water passage inlet  41  formed in the exhaust manifold  31  (see FIG. 2).  
         [0054]    The expansion chamber  33  is connected to the water jet pump  7  through a pipe  56  in such a manner that a base end of the pipe  56  is connected to a cooling water passage outlet  42  formed in the expansion chamber  33  and a tip end of the pipe  56  extends to a pump room in the water jet pump  7 . As defined herein, the pump room refers to an inner space of the casing  6  constituting the water jet pump  7 . The tip end of the pipe  56  is attached to the water jet pump  7  at a position downstream of the base end of the pipe  50  in the water jet pump  7 . The tip end of the pipe  56  is located so that the water in the pipe  56  is suctioned into the pump room by a negative pressure of the water accelerated by the water jet pump  7 .  
         [0055]    [0055]FIG. 4 is a longitudinal sectional view of the portion where the expansion chamber  33  is connected to the water muffler  34 . The expansion chamber  33  is connected to the water muffler  34  through a flexible connecting pipe  37  such as a rubber pipe. The water-supply hole  33   g  is formed in the inner wall  33   d  of the expansion chamber  33  in the vicinity of the connecting pipe  37 . An inspection hole  33   h  is formed in an outer wall  33   e  of the expansion chamber  33  at a position above the water-supply hole  33   g . Preferably, the inspection hole  33   h  is designed to be concentric with the water-supply hole  33   g . This facilitates drilling work. To be specific, a pilot hole for the inspection hole  33   h  and the water-supply hole  33   g  can be formed simultaneously or in a series of work.  
         [0056]    The inspection hole  33   h  is closed by a plug  33   k  as a cap member. A female screw is provided on the inspection hole  33   h  and a male screw is provided on the plug  33   k . These screws are threadedly engaged. That is, the plug  33   k  is removably attached to the inspection hole  33   h.    
         [0057]    A temperature sensor  36  is attached on the water muffler  34  located downstream of the water-supply hole  33   g  in the exhaust gas flow path in the exhaust system  30 . The temperature sensor  36  is adapted to detect the temperature of the exhaust gas flowing through the inside of the water muffler  34 .  
         [0058]    Referring to FIGS. 2, 3 again, the pipe  53  branches from the pipe  50 . That is, the base end of the pipe  53  is connected at an intermediate position of the pipe  50 , i.e., a branch point  59 . The branch point  59  is located between the filter  51  and the cooling water passage inlet  41 . The pipe  53  extends substantially horizontally toward the rear of the personal watercraft  1  without ups and downs such that its tip end extends to a rear end face  15  (see FIG. 5) of the personal watercraft  1  so as to open in a surface of the body of the watercraft. The pipe  53  functions as the water passage through which the water passage comprised of the pipe  50  communicates with an outside of the body.  
         [0059]    [0059]FIG. 5 is a rear view of the personal watercraft  1 . As shown in FIG. 5, an opening  53   a  at the tip end of the pipe  53  is located in the rear end face  15  of the watercraft  1 . The opening  53   a  is closed by a removable plug  54 . The water passage comprised of the pipe  53  is opened/closed by removing/attaching the plug  54 .  
         [0060]    The opening  53   a  and an opening  60  are provided lateral symmetrically in the rear end face  15 . The opening  60  is a discharge port through which the water inside of the body is discharged and is closed by a removable plug  62 .  
         [0061]    The personal watercraft  1  constituted as described above is driven with the opening  53   a  closed by the plug  54 .  
         [0062]    During driving of the personal watercraft  1 , the exhaust gas in the engine  4  flows through the exhaust manifold  31 , the exhaust pipe  32 , the expansion chamber  33 , the water muffler  34 , and the exhaust duct  35  and is discharged outside through the exhaust outlet  39 .  
         [0063]    The water is pumped into the pipe  50  by the water jet pump  7 . The water flows through the filter  51  provided on the pipe  50  and into the water passage  31   a  of the exhaust manifold  31  through the cooling water passage inlet  41 .  
         [0064]    The water flowing into the water passage  31   a  of the exhaust manifold  31  is divided so as to flow through the water passage of the cylinder block  21  and further into the water passage of the cylinder head  22 . The water that has finished heat exchange with the engine body portion  20  flows into the water passage  32   a  of the exhaust pipe  32 . The remaining water flowing through the water passage  31  a also flows directly into the water passage  32   a  of the exhaust pipe  32 .  
         [0065]    The water in the water passage  32   a  of the exhaust pipe  32  flows into the water passage  33   a  of the expansion chamber  33 . The water that has finished heat exchange with the exhaust system  30  flows into the pipe  56  through the cooling water passage outlet  42 . The water is discharged into the pump room of the water jet pump  7  through the pipe  56  and then outside the watercraft.  
         [0066]    Part of the water flowing through the water passage  33   a  of the expansion chamber  33  is supplied to the inside of the expansion chamber  33  through the water-supply hole  33   g . The water flows into the water muffler  34  along with the exhaust gas, and further through the exhaust duct  35 , to be discharged from the exhaust outlet  39  formed in a stem of the watercraft  1  to the outside of the watercraft  1 .  
         [0067]    After cruising of the personal watercraft  1 , the watercraft  1  is landed for maintenance of the engine  4  and the like. For example, the water is discharged from the cooling water passage of the engine  4 .  
         [0068]    While the personal watercraft  1  is landed, part of the water in the cooling water passage of the engine  4  and the pipe  56  is discharged into the pump room through the opening at the tip end of the pipe  56 . Simultaneously, part of the water in the pipe  50  is discharged into the water jet pump  7  through the opening at the base end of the pipe  50 .  
         [0069]    Even after part of the water is thus discharged from the cooling water passage of the engine  4  and the pipes  50 ,  56 , the substances contained in the water sometimes still remain. In the case of sea water, salt is adhered to the inner peripheral walls of the cooling water passage of the engine  4  or the pipes  50 ,  56 .  
         [0070]    All of the water in the cooling water passage of the engine  4  and the pipes  50 ,  56  is not discharged while the personal watercraft  1  is landed. Especially, since the portion of the pipe  50  where the filter  51  is provided is higher than the cooling water passage inlet  41 , the water remaining in the portion of the pipe  50  between the filter  51  and the cooling water passage inlet  41  is very difficult to discharge.  
         [0071]    For the purpose of full discharge of the water in the cooling water passage of the engine  4  and the pipes  50 ,  56 , the plug  54  attached to the opening  53   a  in the rear end face  15  of the personal watercraft  1  is removed. Thereby, part of the water remaining in the portion of the pipe  50  between the filter  51  and the cooling water passage inlet  41  flows through the pipe  53  and is discharged through the opening  53   a.    
         [0072]    After that, fresh water is forcibly sent as cleaning water from the opening  53   a . To this end, for example, the tip of a rubber hose connected to a water pipe is inserted into the opening  53   a , in which state the water is supplied from the water pipe into the pipe  53 . The cleaning water is divided at the branch point  59  so as to flow toward the tip end of the pipe  50  and toward the base end of the pipe  50 . The cleaning water flowing toward the base end of the pipe  50  serves to clean the filter  51  by a counter flow. The cleaning water flowing toward the tip end of the pipe  50  flows through the water passages through which the cooling water flows during driving of the personal watercraft  1 , and finally, is discharged into the pump room of the water jet pump  7 . As a result, the inside of the cooling water passage of the engine  4  and the pipes  50 ,  56  is cleaned by the cleaning water. At this time, the sea water remaining in the cooling water passage of the engine  4  and the pipes  50 , 56 , the substances such as small stones or waterborne plants, or salt adhered to the inner peripheral walls of the cooling water passage and the pipes  50 ,  56  are discharged. In this manner, the inside of the pipes  50 ,  56  is positively cleaned. Consequently, the degree of freedom of layout of the pipes  50 ,  56  is improved. For example, the curved pipe  50  of this embodiment may be used.  
         [0073]    The cleaning water sometimes remains in the cooling water passage of the engine  4  or the pipes  50 ,  56  after the water is stopped. It should be appreciated that, the cleaning water hardly damages the engine body portion  20  or the exhaust system  30  because the cleaning water is the fresh water free from substances.  
         [0074]    As described above, the opening  53   a  and the opening  60  are provided lateral symmetrically in the rear end face  15 . Since the opening  60  is the discharge port through which the water inside of the body of the watercraft is discharged, the plug  62  is removed from the opening  60  after the personal watercraft  1  is landed. Since the opening  53   a  and the opening  60  are provided lateral symmetrically in the rear end face  15 , the plug  54  is noticed by the user when the plug  62  is removed. This advantageously prevents the user from forgetting to discharge or clean the cooling water passage of the engine  4 .  
         [0075]    During driving of the personal watercraft  1 , if the temperature sensor  36  attached to the water muffler  34  detects that the temperature of the exhaust gas in the water muffler  34  is higher than a proper temperature, this shows that the water-supply hole  33   g  of the expansion chamber  33  might be clogged with substances. In that case, the personal watercraft  1  is first landed and then the plug  33   k  of the expansion chamber  33  is removed for the purpose of inspection of the water-supply hole  33   g . When it is detected that the water-supply hole  33   g  is clogged, the clogged water-supply hole  33   g  is cleaned. Thus, the inspection and maintenance of the water-supply hole  33   g  are easily carried out.  
         [0076]    Numerous modifications and alternative embodiments of the invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, the description is to be construed as illustrative only, and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure and/or function may be varied substantially without departing from the spirit of the invention and all modifications which come within the scope of the appended claims are reserved.