Patent ID: 7694355

Claim:
A pressure vessel comprising: a main vessel provided with a chamber for containing pressured water, a water entry, an opening and a pressure releasing hole at the top, and a drain exit at the bottom for releasing pressured water; an air entry valve able to let a mixture of the atmosphere and the pressured water flow from said water entry into said chamber of said main vessel; a water entry valve able to transmit pressured water to said air entry valve and prevent it from flowing reversely; a drain valve provided with a valve base, a piston unit and a spring, said valve base fixed at said opening of said pressure vessel; said piston unit inserted fixedly inside said valve base, the space between said piston unit and said valve base formed as a chamber; said spring fixed between said valve base and said piston unit and able to push down said piston unit by means of its elasticity so as to seal said drain exit of said main vessel, said chamber able to let pressured water flow in to force said piston unit to move up and to separate from said drain exit, enabling said drain exit to become disclosed; and a control valve able to store the pressured water coming from said pressure releasing hole of said main vessel and to control the pressured water to flow into said chamber of said drain valve; said drain exit of said main vessel is connected with a threaded base at the bottom, provided with an opening at a sidewall having an overflow valve able to close said opening in one way; and said overflow valve is provided with a cover, having plural overflow holes on the surface, able to close said opening of said threaded base, and a one-way stopper pivotally fixed at said opening able to prevent water from flowing out of said overflow holes and permit water flow inwards through them.