| 摘要 |
A valve apparatus including a housing having a plastic body defining an inlet opening, an outlet opening, and a fluid communication path and an abutment surface therebetween; a valve seat movably disposed in the communication path and adapted to engage the abutment surface, the seat defining a surface area exposed to fluid pressure at the inlet opening and a valve opening in the communication path; a valve adapted for movement between a closed position engaging the valve seat and closing the valve opening and an open position separated from the valve seat and opening the valve opening; and a bias means exerting between the housing and the valve a given force biasing the valve into the closed position. Pressure below a predetermined level at the inlet opening exerts on the surface area a force that moves the valve seat away from the abutment surface and exerts on the valve a force less than the given force and in opposition thereto. Conversely, pressure above the predetermined level at the inlet opening exerts on the valve a force greater than the given force so as to move the valve into its open position. Because of the floating valve seat, dimensional changes in the plastic body over time will not affect operation of the valve.
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