Image Number 13 for United States Patent #5996606.
A four-port changeover valve in an emergency water storage tank facility for changing over the flow paths of the water main and to the tank by axially moving the valve rod. Three valve seats are formed axially in a valve box. The valve rod extends through the valve seats. As the four-port changeover valve, the three valve seats can be selectively opened and closed by one and the other of two valve bodies. The water storage tank is connected to a first and a fourth chamber, while the water main is connected to a second and a third chamber. The valve rod is raised and lowered by the cylinder. In a normal state when the water pressure in the water main is at a required level, the valve rod rises so that the tank and the water main communicate with each other. In an emergency when the water pressure is low, the valve rod is pushed down by a spring, so that the one valve body is pressed against the first valve seat, while the other valve body separates from the second valve body and is seated on the third valve body. The tank is thus shut off from the water main. Also, a three-way valve for operating the changeover valve is proposed which eliminates an unstable state in which the flow direction cannot be changed over.