1. Field of the Invention
The present invention relates to the improvement in a flush valve for urinals, wherein a hollow pipe-like filtering net is provided at the side opposite to a water volume adjusting knob, an elastic element and a pad are provided in the central base portion of the filtering net to filter out impurity of water and to prevent the pipe structure from damage by reverse water hammering due to abrupt stopping of water.
2. Description of the Prior Art
A conventional flush valve for urinal (referring to FIG. 1) provides with an inlet pipe (11) extending rearwardly from a bowl-like main body (1), the inlet pipe (11) has on its top end a receiving hole (12) to receive an ajusting knob (2) having a soft plug. When water flows from the inlet pipe (11) to the main body (1), the volume of water can be adjusted with the adjusting knob (2), the main body (1) can receive a loading valve member (3), the receiving space can form a back pressure chamber (13) with an covering lid (31); The main body (1) further has a push button (4) on its front side for releasing water pressure formed in the back pressure chamber (13), an outlet (14) on the bottom end of the main body (1) is connected to a discharging pipe (5) with a screw; normally, the back pressure chamber (13) and the outlet (14) are separated by the loading valve member (3), while the back pressure chamber (13) is full of water to render the loading valve member (3) to seal the outlet (14), so that water from the inlet pipe (11) will not leak out from the outlet (14). When in use, the push button (4) can be pushed down (referring to FIG. 2) to open the loading valve member (3), so that the water in the back pressure chamber is driven out of the outlet (14) through a plurality of leaking holes (32) provided in the loading valve member (3), meantime, the pressure in the back pressure chamber (13) will be reduced due to leaking of water, and render the pressure of water source in the inlet pipe (11) to be larger than that of water in the back pressure chamber (13), and therefore raises the loading valve member (3) (as shown in FIG. 3), and water can flush out through the outlet (14). While during flushing, a small part of water can flow into the back pressure chamber (13) through the loading valve member (3), at the moment that the water in the loading valve member (3) accumulates for a period of time to render the water pressure in the loading valve member (3) to be larger than that of the pressure of flowing in water, the water pressure render the loading valve member (3) to lower to seal the outlet (14) again, so that water which originally flows out fluently through the outlet (14) will flow back due to accumulation thereof by the sealing of the loading valve member (3), a reverse water hammer is thereby formed and extended reversely to the pipe structure, this may easily damage a weak or old connection of pipe and make leaking, yet the leaking in the pipe is difficult to be cheked out for fixing, and hence is inconvenient for its user. Besides, the flush valve flushes by the pressure difference between the pressure in the back pressure chamber (13) on the top of the loading valve member (3) of the main body (1) and the pressure of flowing in water, if there is no device for filtering water with impurity, the impurity will destroy the above stated relation of pressure difference soon and render the urinal to have a non-stop leaking. Therefore, the conventional flush valve for urinals has to be improved. There is now in the market an automatic flushing device activated by a sensor via extra-red light, it is expensive in obtaining the automatic flushing and stopping water, yet no improvement is there in respect to the above mentioned defects. In view of this, the inventor of the present invention tested, studied, designed and improved for a long time against the defects resided in the conventional flush valve for a urinal and provides a novel flush valve for a urinal which can prevent from blocking and leaking of water, and prevent the pipe structure from being destroyed. In reality, a hollow pipe-like filtering net is provided at the side opposite to a water volume adjusting knob, and an elastic element and a pad are provided in the central base portion of the filtering net to get rid of the above mentioned defects.