Patent ID: 8332970

Claim:
A flushing mechanism, comprising: a housing, including a housing wall and a housing bottom integrally formed with or connected to the housing wall, wherein the housing wall defines a cylindrical inner surface around an axial center line, and has an outlet formed at the housing bottom around said axis that connects to a drain line; a sleeve, axially fixed along and surrounding the axis within the housing; a first piston that hermetically slides on the cylindrical inner surface and the sleeve simultaneously along the axial direction, wherein the first piston divides an inner chamber surrounded by said cylindrical inner surface into a lower chamber contacting said housing bottom and an opposing upper chamber; a first piston loading spring, mounted in said upper chamber around said sleeve for applying spring force from the housing to the first piston so as to move the first piston downwards to reduce the volume of the lower chamber and to expand the volume of the upper chamber; a second piston that hermetically slides on the sleeve along the axial direction, wherein the second piston is disposed between the first piston and the housing bottom; a second piston loading spring, mounted around said sleeve for applying spring force from the housing to the second piston so as to move the second piston upward; a commuting valve; wherein said flushing mechanism has the following three operation states: (i) in a first state, the first piston pushes the second piston downwards against the housing bottom to form a ring-shaped exterior lower cavity around said axis and between said housing bottom and the second piston, and the exterior lower cavity is not connected with the chamber and is connected to said outlet; (ii) in a second state, said lower chamber is filled with supply water to separate the first piston from the second piston and expand the lower chamber, and the second piston overcomes the upward force of the second piston loading spring under the action of the water pressure to go against said housing bottom, and the exterior lower cavity is not connected with said outlet and said lower chamber; (iii) in a third state, the lower chamber is connected to the exterior lower cavity through a first side passage and the commuting valve, and the upward force of the second piston loading spring moves the second piston away from the housing bottom, such that the lower chamber, the exterior lower cavity and the outlet are connected with each other, and the water in the lower chamber drains through the outlet under the action of the pressure of the first piston; and the commuting valve closes the first side passage, then or simultaneously, wherein the first piston and the second piston reset to the first state.