1.  Field of the Invention
The present invention relates generally to regeneration tanks for water softeners and, more particularly, to a regeneration tank for water softeners which is controlled such that a flow rate of water, which is drawn into the regeneration tank, and pressure in the regeneration tank can be controlled, and which is provided with a coupling member to protect a connection part between the regeneration tank and a water softener. 
2.  Description of the Related Art
Generally, tap water, which is hard water, contains a large amount of chlorine used for purification.  In addition, due to factors, such as deteriorated pipes or water pollution, tap water may contain various kinds of heavy metals (ions), such as iron, zinc, lead, mercury, etc.,  having negative influences on human bodies.  Although such tap water is not fatal to human bodies, when tap water directly contacts the skin of users washing their skin, metal ions contained in water are bonded to fatty acid of soap, thus forming metallic impurities.  Such metallic impurities contact the skin of the users and induce skin diseases or promote skin aging. 
To prevent these problems, various water softeners, which change hard water into soft water using a method in which tap water passes through strongly acid cation exchange resins containing sodium ions (Na+) so that ingredients, such as calcium ions (Ca2+) and magnesium ions (Mg2+), of hard water are substituted with sodium ions of the cation exchange resins, have been developed and used. 
The water softeners are operated using the principle by which hard water is changed into soft water by substituting calcium ions and magnesium ions, contained in the hard water, for sodium ions.  For this, a soft water tank, which has ion exchange resins made of high molecular compounds containing sodium ions, is an indispensable element of such a water softener. 
Meanwhile, a large amount of ion exchange resins having fine grain shapes are stored in the soft water tank of the water softener.  In this state, soft water is formed by continuously passing tap water through the soft water and by bringing tap water into contact with the ion exchange resins.  As this process is repeated, sodium ingredients are largely removed from the ion exchange resins by continuous contact between tap water and the ion exchange resins.  Therefore, typically, the water softeners are provided with regeneration tanks, which contain regenerative substances to regenerate ion exchange resins.  Generally, salt, which forms sodium ions when melted in water, is used as a regenerative substance for regeneration of ion exchange resins. 
FIG.  1 is a view illustrating regeneration tanks 10 coupled to a water softener 20 according to a conventional technique. 
Referring to FIG.  1, the typical water softener 20 includes at least one regeneration tank 10, for example, two regeneration tanks 10, which store tap water therein.  A soft water discharge pipe 22 for discharging soft water is coupled to the lower end of the water softener 20.  Furthermore, a large amount of ion exchange resins having fine grain shapes is contained in the water softener 20.  While the ion exchange resins conduct a water softening function, the amount of sodium ingredients in the ion exchange resins is reduced.  The regeneration tanks 10 are coupled to the upper end of the water softener 20 to regenerate the ion exchange resins in the water softener 20. 
The regeneration tanks 10 are containers for containing regenerative substances therein.  Typically, salt is used as the regenerative substance. 
In the regeneration tanks 10, a regeneration solution is formed by dissolving the salt in a predetermined amount of water.  The regeneration tanks 10 serve to supply the formed regeneration solution into the water softener 10. 
Below, a process of regenerating the water softener 20 using the regeneration tanks 10 according to the conventional technique will be explained. 
In the case where the amount of sodium ions in the water softener 20 is reduced with the passage of time, the user can supply sodium ions into the water softener 20 using the regeneration tanks 10.  To achieve the above purpose, the user first supplies regenerative solution, which is made by dissolving salt in water, into the regeneration tanks 10.  Thereafter, the user couples the regeneration tanks 10 to the upper end of the water softener 20.  Then, the regenerative solution is drawn into the water softener 20 through an inlet 12 and is brought into contact with the ion exchange resins to provide sodium ions thereto, thus regenerating the water softener. 
However, in the conventional regeneration tank for water softeners, the pressure at which hard water is drawn into regeneration tank through the inlet 12 is not constant.  Therefore, depending on the pressure, the flow rate of water drawn into the regeneration tank and the amount of regenerative solution are not constant either.  As a result, there are problems in that the time required for regeneration and regeneration efficiency are not constant. 
Moreover, in the case of the conventional regeneration tank, because the flow rate of water drawn into the regeneration tank cannot be controlled, if the pressure at which water is drawn into the regeneration tank is relatively high, the regeneration tank may be damaged by the high internal water pressure.  In addition, when the regeneration tank is coupled to the water softener or is removed therefrom, a connection part between the regeneration tank and the water softener may be easily damaged, with the result that the regenerative solution may leak or contaminants may be drawn into the regeneration tank or the water softener through the damaged part.