Abstract:
Provided are a drain water discharging method and a buoyancy type drain trap in which a float is accommodated in a case and drain water allowed to flow into the case can be discharged by buoyancy acting on the float. In a case where an inner diameter of the valve is increased in order to increase a discharge flow rate at a valve connected to an outlet port formed in the case, the movement of a valve seat for opening the valve is facilitated through addition of some force to increase the buoyancy or through a reduction in a weight of the float itself.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a technique of a buoyancy type drain trap, and more specifically, to a technique of discharging drain water accumulated in a drain trap by utilizing buoyancy with some force added thereto and by utilizing a suction force of a magnet.  
         [0003]     2. Description of the Related Art  
         [0004]     As a conventional technique related to a buoyancy type drain trap, there is known a structure having a float  200 A accommodated in a case  100 B.  
         [0005]     In the following, the conventional buoyancy type drain trap will be described with reference to  FIG. 8 .  
         [0006]     In  FIG. 8 , reference symbol  300 K indicates a drain trap composed of the case  100 B and the float  200 A. The case  100 B is integrally formed by a case main body  50 , a float bracket  7 , a valve  9 , an adjustment screw  21 , a packing  22 , and manual valve  4  equipped with an O-ring. Further, the case main body  50  is integrally formed by a first case  1 , a second case  2 , and a gasket  3 , and is completely sealed except for an inlet port  50   a  and an outlet port  50   b  so that no drain water leaks therefrom.  
         [0007]     The float  200 A is integrally formed by a float main body  5 , an arm  6 , and a rubber valve seat  8 . In this case, the arm  6  is formed in a substantially L-shaped configuration. At one end of the arm  6 , there is provided the float main body  5  which generates buoyancy when drain water flowing in through the inlet port  50   a  formed in the case  100 B has been accumulated to a certain degree. Besides, at the other end of the arm  6 , there is provided the rubber valve seat  8  that opens and closes the valve  9  connected to the outlet port  50   b  formed in the case  100 B. Further, at the bent portion of the arm  6 , rotation shafts  6   a  are formed, which are engaged with the float bracket  7  constituting a part of the case  100 B inside the case  100 B and which rotatably support the entire float  200 A.  
         [0008]     Thus, in a case where not much drain water has flowed into the case  100 B yet, no buoyancy acts on the float main body  5 , and the rubber valve seat  8  is held in intimate contact with the valve  9  due to a self-weight of the float  200 A. As a result, the drain trap is kept in a closed state. In contrast, in a case where a lot of drain water has flowed into the case  100 B to attain a level beyond a fixed position, buoyancy acts on the float main body  5 , and the rubber valve seat  8  is separated from the valve  9  due to the buoyancy. As a result, the drain trap is brought into an open state. It should be noted, however, that the opening and closing of the valve  9  is also influenced by a force of compressed air pressure allowed to flow into the case  100 B and act on the valve seat  9 , and by an elastic force of the rubber valve seat  8 .  
         [0009]     However, the conventional drain water discharging method and the conventional buoyancy type drain trap described above have the following problems.  
         [0010]     When an attempt is made to enlarge an inner diameter of the valve in order to increase a flow rate at both the inlet and outlet ports, the valve may become rather difficult to open or such the attempt may prove impossible.  
         [0011]     Further, since the opening and closing of the valve seat is effected mainly by the self-weight of the float and the buoyancy due to the float main body, the valve seat is often allowed to remain in a half-open state, the opening and closing of the valve seat being rather uncertain.  
       SUMMARY OF THE INVENTION  
       [0012]     To solve the above-mentioned problem, the present invention provides the following solving structure.  
         [0013]     According to the present invention, a buoyancy type drain trap includes: a float composed of an arm, a float main body provided at one end of the arm and capable of floating in water, a valve seat integrally provided at the other end of the arm, and a rotation shaft provided at a middle bent portion of the arm. Also, the buoyancy type drain trap includes a case integrally formed by a case main body having an inlet port through which drain water flows in and an outlet port through which drain water flows out, a valve connected to the outlet port, and a flow bracket at which the rotation shaft is situated to rotatably support the float, the rotation shaft being situated at the float bracket inside the case. In the buoyancy type drain trap, in a case where drain water has not flowed in to attain a fixed position in the case, the valve seat closes the valve by a self-weight G of the float, and in a case where drain water has flowed in to attain a position beyond the fixed position in the case, the valve seat opens the valve by buoyancy F of the float main body. The buoyancy type drain trap is characterized by further including an auxiliary buoyancy means for assisting an increase in the buoyancy F provided between the case and the float. Further, the buoyancy type drain trap is characterized in that the auxiliary buoyancy means is constructed of a coil spring provided between an adjustment screw and the arm to integrally hold the case main body and the float bracket by the adjustment screw and the valve. Still further, the buoyancy type drain trap is characterized in that a compression force of the coil spring can be adjusted by varying a thickness of an adjustment washer situated between the float bracket and the adjustment screw. Yet further, the buoyancy type drain trap is characterized in that the auxiliary buoyancy means is constructed of a compression spring arranged between the case main body and the float main body. Furthermore, the buoyancy type drain trap is characterized by further including: a magnet arranged at some position on the arm between the float main body and the rotation shaft; and an associated member for generating an suction force by the magnet arranged at some position inside the case, in which a relationship in terms of moment between the buoyancy F of the float, the suction force of the magnet, the self-weight G of the float, and positions X, Y, and Z where these forces are generated, and the relationship in terms of moment between the elastic force of the valve seat, the compression force of the coil spring, and a position K where these forces are generated, are summed up. Moreover, the buoyancy type drain trap is characterized in that the associated member is constructed of a plate spring and a plate spring bracket supporting the plate spring at some position inside the case. Thus, the present invention has solved the problems described above.  
         [0014]     The drain trap of the present invention, which is constructed as described above provides the following effects.  
         [0015]     First, in a drain water discharging method which makes it possible to discharge drain water having flowed into the case accommodating the float by buoyancy acting on the float, when the inner diameter of the valve connected to the outlet port formed in the case is enlarged in order to increase the discharge flow rate at the valve, movement of a rubber valve seat when opening the valve is facilitated by adding some force to enhance the buoyancy or by reducing a weight of the float itself, whereby it is possible to discharge drain water smoothly.  
         [0016]     Second, even in a case where an attempt is made to enlarge the inner diameter of the valve in order to increase the flow rate at the outlet port, the movement of the rubber valve seat when opening the valve is facilitated by positioning the coil spring or the compression spring between the case and the float as a device for adding some force, whereby it is possible to discharge drain water smoothly.  
         [0017]     Third, even in a case where an attempt is made to enlarge the inner diameter of the valve in order to increase the flow rate at the outlet port, the movement of the rubber valve seat when opening the valve is facilitated by arranging, as the auxiliary buoyancy device, the coil spring between the adjustment screw and the arm so as to be integrated with the adjustment screw and the valve while holding the case main body and the float bracket, with the compression force of the coil spring being adjustable by varying the thickness of an adjustment washer situated between the float bracket and the adjustment screw. Consequently, it is possible to discharge drain water smoothly.  
         [0018]     Fourth, by positioning the magnet between the case and the float, the suction force is generated, and, by taking into consideration the relationship between the buoyancy of the float, the suction force of the magnet, the self-weight of the float, and the positions where these forces are generated, and the relationship between the elastic force of the rubber valve seat, the compression force of the coil spring, and the position where these forces are generated, it is possible to prevent the valve seat from being constantly left in a half-open state due to the uncertainty of the opening and closing of the valve seat. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     In the accompanying drawings:  
         [0020]      FIG. 1  is a sectional view of a drain trap according to the present invention with its valve closed;  
         [0021]      FIG. 2  is a sectional view of a drain trap according to the present invention with its valve open;  
         [0022]      FIG. 3  is a perspective view of an arm and a rubber valve seat forming a drain trap according to the present invention;  
         [0023]      FIG. 4  is an enlarged sectional view of a valve forming a drain trap according to the present invention and the periphery thereof;  
         [0024]      FIG. 5  is a sectional view of another drain trap according to the present invention with its valve closed;  
         [0025]      FIG. 6  is a sectional view of still another drain trap according to the present invention with its valve closed;  
         [0026]      FIG. 7  is a schematic view of a relationship between forces exerted around a float forming a drain trap according to the present invention; and  
         [0027]      FIG. 8  is a sectional view of a conventional drain trap with its valve closed. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]     In the following, embodiments of the present invention will be described in detail with reference to the drawings.  
         [0029]     Here,  FIG. 1  is a diagram showing a drain trap according to the present invention with its valve closed;  FIG. 2  is a diagram showing a drain trap according to the present invention with its valve open;  FIG. 3  is a diagram showing an arm and a rubber valve seat forming a drain trap according to the present invention;  FIG. 4  is a detailed view of a valve forming a drain trap according to the present invention and the peripheral portions thereof;  FIG. 5  is a diagram showing another drain trap according to the present invention with its valve closed;  FIG. 6  is a diagram showing still another drain trap according to the present invention with its valve closed; and  FIG. 7  is a diagram showing the relationship between forces exerted around a float forming a drain trap according to the present invention.  
       First Embodiment  
       [0030]     As shown in  FIGS. 1, 2 ,  3 ,  4 , and  7 , reference symbol  300 A indicates a drain trap which is composed of a case  10 A, a float  200 A, and a coil spring  23  serving as an auxiliary buoyancy device situated between the case  100 A and the float  200 A.  
         [0031]     The case  100 A is integrally formed by a case main body  50 , a float bracket  7 , a valve  9 , an adjustment screw  21 , an adjustment washer  24 , a packing  22 , and manual valve  4  equipped with an O-ring.  
         [0032]     As shown in detail in  FIG. 4 , the valve  9  in this example is equipped with a flange, and the flange side of the valve  9  is situated on the outer side of the case main body  50  with the packing  22  therebetween. Further, the valve  9  is connected to the case main body  50  through thread engagement, and the other end thereof on the opposite side of the flange, that is, a screw portion protrudes into the case main body  50 . The protruding portion has the adjustment screw  21  equipped with a flange, the flange side of the adjustment screw  21  being positioned such that the adjustment washer  24  is held between the adjustment screw  21  and the inner side of the case main body  50 . Accordingly, the adjustment screw  21  is connected with the valve  9  through thread engagement. Thus, the valve  9  is constructed such that drain water flows from the side where there exists the adjustment screw  21  forming the screw portion on the inner side of the case main body  50  to the side where there exists the packing  22  forming the flange on the outer side of the case main body  50 .  
         [0033]     In a case where there are prepared various adjustment washers  24  differing in thickness so as to allow replacement, it is possible to adjust the compression amount of the coil spring  23  situated between the arm  6  constituting the float  200 A described in detail below, and the adjustment screw  21  which constitutes an integral unit in which there are arranged the case main body  50  constituting the case  10 A, the adjustment washer  24 , and the adjustment screw  21  in the stated order with the valve  9  extending therethrough. Thus, it is possible to adjust the compression force generated by the coil spring  23 .  
         [0034]     Further, the case main body  50  is integrally composed of a first case  1 , a second case  2 , and a gasket  3 , and is completely sealed except for an inlet port  50   a  and an outlet port  50   b  so that no drain water leaks therefrom.  
         [0035]     The float  200 A is integrally composed of a hollow float main body  5 , the arm  6 , and the rubber valve seat  8 . In this case, the arm  6  is formed in a substantially L-shaped configuration. At one end of the arm  6 , there is provided the float main body  5  which generates buoyancy F when drain water flowing in through the inlet port  50   a  formed in the case  100 A has been accumulated to a certain degree. Besides, at the other end of the arm  6 , as shown in  FIG. 3 , there is provided the rubber valve seat  8  that opens and closes the valve  9  connected to the outlet port  50   b  formed in the case  100 A. Further, at the bent portion of the arm  6 , rotation shafts  6   a  are formed, which are engaged with the float bracket  7  formed inside the case  100 A and which rotatably support the entire float  200 A.  
         [0036]     However, the configuration of the arm  6  is not restricted to the substantially L-shaped configuration. It is also possible for the arm  6  to adopt a substantially U-shaped configuration or some other configuration. Further, regarding the angle of the bent portion of the arm  6 , the angle may be 90 degrees or more or 90 degrees or less. In addition, regarding the arm  6 , it may be positioned so as to be parallel to the water surface L in a case where the rubber valve seat  8  keeps the valve  9  closed. However, it may also be positioned so as not to be parallel to the water surface. Further, it is also possible to form the arm  6  in a substantially I-shaped configuration of a flat plate, with the rubber valve seat  8  and the valve  9  being positioned not coaxially but at a right angle with respect to each other.  
         [0037]     In a case where drain water flows into the case  100 A as shown in  FIG. 1  or flows out therefrom as shown in  FIG. 2 , the entire float  200 A rotates around the rotation shafts  6   a , making it possible for the rubber valve seat  8  to open or close the valve  9 . While the rubber valve seat  8  keeps the valve  9  closed, an elastic force is generated.  
         [0038]     While the rubber valve seat  8  keeps the valve  9  closed, both the compression force due to the coil spring  23  and the elastic force due to the rubber valve seat  8  are generated; whereas, while the rubber valve seat  8  keeps the valve  9  open, the coil spring  23  and the rubber valve seat  8  have been expanded to the utmost, so no compression force or elastic force is generated. However, during the transition period, generation of the compression force due to the coil spring  23  may only be happened.  
         [0039]     In the following, the operation of the drain water discharging method and the buoyancy type drain trap of the present invention constructed as described above will be illustrated.  
         [0040]     First, drain water flows into the case  101 A of the drain trap  300 A through the inlet port  50   a . As shown in  FIGS. 1 and 4 , in a case where no or little drain water has flowed into the case  100 A yet, the arm  6 , which rotates around the rotation shafts  6   a  formed thereon, keeps the rubber valve seat  8  in intimate contact with the valve  9  due to the self-weight G of the float  200 A and the compressed air pressure exerted on the sectional area of the flow passage of the valve  9 .  
         [0041]     While the rubber valve seat  8  is held in intimate contact with the valve  9 , the compression force due to the coil spring  23  and the elastic force due to the rubber valve seat  8  are both generated. However, as soon as the rubber valve seat  8  opens the valve  9 , the elastic force due to the rubber valve seat  8  ceases to be exerted, and when the rubber valve  8  is further separated from the valve  9 , the compression force due to the coil spring  23  also ceases to be exerted.  
         [0042]     As the amount of drain water in the case  100 A increases, there is generated the buoyancy F to a degree corresponding to the amount of drain water displaced by the hollow float main body  5  as shown in  FIG. 2 . In other words, as will be illustrated with reference to  FIG. 7 , since the float main body  5  is a sphere, the buoyancy F is exerted upwards toward the center of the sphere. In contrast, the weight G of the float  200 A as a whole is constantly exerted downwards.  
         [0043]     Here, equation 1 is to be derived from  FIG. 7 . In the case of the first embodiment, equation  1  is applicable to a case in which an adjustment screw  10 , a nut  11 , a magnet seat  12 , and a magnet  13  are removed from the construction as shown in  FIG. 7 .  
         [0044]      M =(the buoyancy  F  of the float main body 5)×sin α× X −(the self-weight  G  of the float 200 A )×sin β× Z +{(the elastic force of the rubber valve seat 8)+(the compression force of the coil spring 23)}× K −(the sectional area of the flow passage of the valve 9)×(the compressed air pressure)× K,    [Equation 1] 
         [0000]     where, X represents the minimum distance from the rotation shafts  6   a  to the center of the buoyancy F of the float main body  5  as measured along the arm  6  or an extension thereof;  
         [0045]     Z represents the minimum distance from the rotation shafts  6   a  to the center of the self-weight G of the float  200 A as measured along the arm  6  or an extension thereof;  
         [0046]     K represents the distance from the rotation shafts  6   a  to the center of the rubber valve seat  8  on the arm  6 ;  
         [0047]     α represents the angle made by the vertical line along which the buoyancy F is generated and the arm  6 ; and  
         [0048]     β represents the angle made by the vertical line along which the self-weight G is generated and the arm  6 .  
         [0049]     In reality, the buoyancy F, the self-weight G, and the arm  6  are,-often in the same plane; in that case, α=β.  
         [0050]     Thus, when the value of M is negative, the rubber valve seat  8  keeps the valve  9  closed as shown in  FIGS. 1 and 4 , and when the value of M is positive, the rubber valve seat  8  keeps the valve  9  open as shown in  FIGS. 2 and 7 . That is, the above-mentioned condition to be satisfied varies depending on the magnitude of the buoyancy F of the float main body  5 , the self-weight G of the float  200 A, the elastic force of the rubber valve seat  8 , the compression force of the coil spring  23 , the sectional area of the flow passage of the valve  9 , the compressed air pressure, and the distances X, Z, and K between the rotation shafts  6   a  and the positions where the above-mentioned forces are exerted. Further, as the amount of drain water increases, the buoyancy F of the float main body  5  and the self-weight G of the float  200 A also vary depending on the angles α and β which are made by the vertical lines, along which the buoyancy F of the float main body  5  and the self-weight G of the float  200 A are generated, and the arm  6 .  
       Second Embodiment  
       [0051]     Referring to  FIGS. 5 and 7 , reference symbol  300 B indicates a drain trap which is composed of a case  100 B, a float  200 A, and a compression spring  25  situated between the case  100 B and the float  200 A and serving as an auxiliary buoyancy device  25 .  
         [0052]     In this case, the case  100 B is the same as that of the conventional technique as shown in  FIG. 8 , and the float  200 A is the same as that of the first embodiment as shown in  FIG. 1 , so description thereof will be omitted.  
         [0053]     Thus, the second embodiment differs from the first embodiment in that the compression spring  25  serving as the auxiliary buoyancy device is situated between the case main body  50  constituting the case  100 B and the float main body  5  constituting the float  200 A. Regarding the compression spring  25 , one end thereof may be fixed to the case main body  50  with the other end thereof not being fixed to the float main body  5 , so that when the float main body  5  rises due to the buoyancy F, the compression spring  25  is detached there from to allow no compression force to be exerted. In some cases, the other end may be fixed to the float main body  5  so that a tensile force is exerted during the rise of the float main body  5 .  
         [0054]     In the following, the operation of the drain water discharging method and the buoyancy type drain trap of the present invention constructed as described above will be illustrated.  
         [0055]     First, drain water flows into the case  100 B of the drain trap  300 B through the inlet port  50   a . When no or little drain water has flowed into the case  100 B, the arm  6 , which rotates around the rotation shafts  6   a  formed thereon, keeps the rubber valve seat  8  in intimate contact with the valve  9  due to the self-weight G of the float  200 A and the compressed air pressure exerted on the sectional area of the flow passage of the valve  9 .  
         [0056]     While the rubber valve seat  8  is held in intimate contact with the valve  9 , the compression force due to the compression spring  25  and the elastic force due to the rubber valve seat  8  are both generated. However, as soon as the rubber valve seat  8  opens the valve  9 , the elastic force due to the rubber valve seat  8  ceases to be exerted, and when the rubber valve  8  is further separated from the valve  9 , the compression force due to the compression spring  25  also ceases to be exerted. Unlike the coil spring  23  of the first embodiment situated near the valve  9 , the compression force of the compression spring  25  can be constructed so as to be capable of exerting the compression force even when the valve  9  is opened and is considerably separated from the rubber valve seat  8 . Further, it is also possible to construct the spring such that the tensile force begins to be exerted when the spring has been expanded to the utmost and the compression force has ceased to be exerted.  
         [0057]     As the amount of drain water in the case  100 B increases, there is generated the buoyancy F to a degree corresponding to the amount of drain water displaced by the hollow float main body  5 . In other words, as will be illustrated with reference to  FIG. 7 , since the float main body  5  is a sphere, the buoyancy F is exerted upwards toward the center of the sphere. In contrast, the weight G of the float  200 A as a whole is constantly exerted downwards.  
         [0058]     Here, equation 2 is to be derived from  FIG. 7 . In the case of the second embodiment, equation 2 is applicable to a case in which the adjustment screw  10 , the nut  11 , the magnet seat  12 , and the magnet  13  are removed from the construction as shown in  FIG. 7 . Further, although not shown specifically in  FIG. 7 , instead of the compression force of the coil spring  23 , the compression force of the compression spring  25  is exerted vertically upwards at the center of the lower portion of the float main body  5 . 
 
 M =(the buoyancy  F  of the float main body 5)×sin α× X −(the self-weight  G  of the float 200 A )×sin β× Z +(the elastic force of the rubber valve seat 8)× K −(the sectional area of the flow passage of the valve 9)×(the compressed air pressure)× K +(the compression force of the compression spring 25)×sin α×(the minimum distance from the rotation shafts 6 a  to the center of the compression force of the compression spring 25 as measured along the arm 6 or an extension thereof),   [Equation 2]
 
 where, X represents the minimum distance from the rotation shafts  6   a  to the center of the buoyancy F of the float main body  5  as measured along the arm  6  or an extension thereof; 
 
         [0059]     Z represents the minimum distance from the rotation shafts  6   a  to the center of the self-weight G of the float  200 A as measured along the arm  6  or an extension thereof;  
         [0060]     K represents the distance from the rotation shafts  6   a  to the center of the rubber valve seat  8  on the arm  6 ;  
         [0061]     α represents the angle made by the vertical line along which the buoyancy F is generated and the arm  6 ; and  
         [0062]     β represents the angle made by the vertical line along which the self-weight G is generated and the arm  6 .  
         [0063]     In reality, the buoyancy F, the self-weight G, and the arm  6  are often in the same plane; in that case, α=β.  
         [0064]     Thus, when the value of M is negative, the rubber valve seat  8  keeps the valve  9  closed as shown in  FIG. 5 , and when the value of M is positive, the rubber valve seat  8  keeps the valve  9  open as shown in  FIG. 7 . That is, the above-mentioned condition to be satisfied varies depending on the magnitude of the buoyancy F of the float main body  5 , the self-weight G of the float  200 A, the elastic force of the rubber valve seat  8 , the compression force of the compression spring  25 , the sectional area of the flow passage of the valve  9 , the compressed air pressure, and the distances X, Z, and K between the rotation shafts  6   a  and the positions where the above-mentioned forces are exerted. Further, as the amount of drain water increases, the buoyancy F of the float main body  5  and the self-weight G of the float  200 A also vary depending on the angles α and β which are made by the vertical lines, along which the buoyancy F of the float main body  5  and the self-weight G of the float  200 A are generated, and the arm  6 .  
       Third Embodiment  
       [0065]     Referring to  FIGS. 6 and 7 , reference symbol  300 C indicates a drain trap which is composed of a case  100 C, a float  200 B, and a compression spring  23  situated between the case  100 C and the float  200 B and serving as an auxiliary buoyancy device.  
         [0066]     In this case, regarding the case  100 C, as shown in  FIG. 6 , instead of the manual valve  4  of the case  100 A of the first embodiment of  FIG. 1 , there are provided a stay  16 , a washer  18 , a nut  19 , a plate spring bracket  15 , a fixation screw  17 , and a plate spring  14 ; regarding the float  200 B, instead of the arm  6  of the float  200 A of the first embodiment equipped with the rotation shafts  6   a , there is formed an arm  20  equipped with rotation shafts  20   a ; and further, there are added an adjustment screw  10 , a nut  11 , a magnet seat  12 , and a magnet  13 .  
         [0067]     Thus, the third embodiment differs from the first embodiment in that, in addition to the force of  FIG. 1 , there is to be expected an suction force due to the magnet  13  and the plate spring  14  situated on the arm  20  constituting the float  200 B at a position between the float main body  5  and the rotation shafts  20   a , whereby it is possible to prevent the rubber valve seat  8  and the valve  9  from being left in a half-open state due to the uncertainty of the opening and closing of the valve seat  8 .  
         [0068]     Regarding the magnet  13  constituting the float  200 B, the nut  11  and the magnet seat  12  are set with the arm  20  therebetween, and the three components are fixed together by the adjustment screw  10 , with the magnet  13  and the magnet seat  12  being fixed together by the magnetic suction force. Further, the adjustment screw  10  allows adjustment of the distance between the plate spring  14  constituting the case  100 C.  
         [0069]     The plate spring  14  is of a substantially L-shaped configuration, and is fixed to a substantially J-shaped plate spring bracket  15  by the fixation screw  17 , with the plate spring bracket  15  being fixed to the stay  16  by the washer  18  and the nut  19 . The stay  16  is fixed to the lower portion of the case main body  50  through thread engagement. While, in this example, the magnet  13  is provided on the float  200 B side, it may also be provided on the case  100 C side.  
         [0070]     The configuration of the plate spring  14  is not restricted to the substantially L-shaped configuration, and the plate spring  14  may also be formed in a substantially I-shaped configuration of a flat plate or some other configuration. Further, the configuration of the plate spring bracket  15  is not restricted to the J-shaped configuration either, and the plate spring bracket  15  may be of a substantially L-shaped configuration or some other configuration.  
         [0071]     Here, the plate spring bracket  15  also serves as a constraining device, which helps to prevent the right-angle portion of the substantially L-shaped plate spring  14  from having an angle of 90 degrees or more due to the suction force that is exerted when the plate spring  14  is attracted by the magnetic force of the magnet  13 . Thus, while this suction force is larger than the buoyancy F, that is, when the buoyancy F is still small and the rubber valve seat  8  has not opened the valve  9  yet, the valve  9  is kept closed by this suction force.  
         [0072]     In the following, the operation of the drain water discharging method and the buoyancy type drain trap of the present invention constructed as described above will be illustrated.  
         [0073]     First, drain water flows into the case  100 C of the drain trap  300 C through the inlet port  50   a . In a case where no or little drain water has flowed into the case  100 C, the arm  20 , which rotates around the rotation shafts  20   a  formed thereon, keeps the rubber valve seat  8  in intimate contact with the valve  9  due to the self-weight G of the float  200 B and the compressed air pressure exerted on the sectional area of the flow passage of the valve  9 . Further, while the rubber valve seat  8  is held in intimate contact with the valve  9 , the suction force of the magnet  13  is added.  
         [0074]     While the rubber valve seat  8  is held in intimate contact with the valve  9 , the compression force due to the coil spring  23  and the elastic force due to the rubber valve seat  8  are both generated. However, as soon as the rubber valve seat  8  opens the valve  9 , the elastic force due to the rubber valve seat  8  ceases to be exerted, and when the rubber valve  8  is further separated from the valve  9 , the compression force due to the coil spring  23  also ceases to be exerted.  
         [0075]     As the amount of drain water in the case  100 C increases, there is generated the buoyancy F to a degree corresponding to the amount of drain water displaced by the hollow float main body  5 . In other words, as will be illustrated with reference to  FIG. 7 , since the float main body  5  is a sphere, the buoyancy F is exerted upwards toward the center of the sphere. In contrast, the weight G of the float  200 B as a whole is constantly exerted downwards.  
         [0076]     Here, equation 3 is to be derived from  FIG. 7 . 
 
 M =(the buoyancy  F  of the float main body 5)×sin α× X −(the self-weight  G  of the float 200 B )×sin β× Z −(the suction force of the magnet 13)× Y +{(the elastic force of the rubber valve seat 8)+(the compression force of the coil spring 23)}× K −(the sectional area of the flow passage of the valve 9)×(the compressed air pressure)× K,    [Equation 3]
 
 where, X represents the minimum distance from the rotation shafts  20   a  to the center of the buoyancy F of the float main body  5  as measured along the arm  20  or an extension thereof; 
 
         [0077]     Y represents the distance from the rotation shafts  20   a  to the center of the magnet  13  on the arm  20 ;  
         [0078]     Z represents the minimum distance from the rotation shafts  20   a  to the center of the self-weight G of the float  200 B as measured along the arm  20  or an extension thereof;  
         [0079]     K represents the distance from the rotation shafts  20   a  to the center of the rubber valve seat  8  on the arm  20 ;  
         [0080]     α represents the angle made by the vertical line along which the buoyancy F is generated and the arm  20 ; and  
         [0081]     β represents the angle made by the vertical line along which the self-weight G is generated and the arm  20 .  
         [0082]     In reality, the buoyancy F, the self-weight G, and the arm  20  are often in the same plane; in that case, α=β.  
         [0083]     Thus, when the value of M is negative, the rubber valve seat  8  keeps the valve  9  closed as shown in  FIG. 6 , and when the value of M is positive, the rubber valve seat  8  keeps the valve  9  open as shown in  FIG. 7 . That is, the above-mentioned condition to be satisfied varies depending on the magnitude of the buoyancy F of the float main body  5 , the self-weight G of the float  200 B, the suction force of the magnet  13 , the elastic force of the rubber valve seat  8 , the compression force of the coil spring  23 , the sectional area of the flow passage of the valve  9 , the compressed air pressure, and the distances X, Z, and K between the rotation shafts  20   a  and the positions where the above-mentioned forces are exerted. Further, as the amount of drain water increases, the float main body  5  and the self-weight G of the float  200 B also vary depending on the angles α and β which are made by the vertical lines, along which the buoyancy F of the float main body  5  and the self-weight G of the float  200 B are generated, and the arm  6 .  
         [0084]     The third embodiment of the present invention shown in  FIG. 6 , to which the magnet  13  and the construction and function related thereto are added to the first embodiment shown in  FIG. 1 , is also applicable to, as a modification, an invention in which the magnet  13  and the construction and function related thereto are added to the second embodiment shown in  FIG. 5 .  
         [0085]     Further, instead of using the coil spring  23  and the compression spring  25  as auxiliary buoyancy devices  23  and  25  for increasing the buoyancy F, it is possible to use an elastic material for the substantially L-shaped arm  6  and  20 , and to set the arm at an angle several degrees larger than 90 degrees, whereby it is possible to cause the arm to function as an auxiliary buoyancy device.  
         [0086]     Further, instead of forming the rubber valve seat  8  with rubber, it is also possible to form with resin, metal, etc.