| 主权项 |
1. A valve comprising a housing having a fluid inlet and a fluid outlet, the housing defining a fluid flow path between said fluid inlet and said fluid outlet, the valve further comprising means for restricting the flow between said fluid inlet and said fluid outlet, said means comprising fixed flow restriction means for applying a pre-determined counter-flow pressure, said fixed flow restriction means comprises flow path blocking means movable between more and less flow restricting positions and means for urging said blocking means toward a more flow restricting position., and means for applying an additional counter-flow pressure according to the pressure in an environment external to said valve, said additional counter-flow pressure applying means comprises means for applying said external pressure to said flow path blocking means, wherein said means for applying external pressure comprises means for connecting the housing to said source of additional pressure and means for transmitting the external pressure within the housing to said flow path blocking means and with said means for transmitting comprising a fluid pressure communication passage within said housing and extending from said means for connecting to said flow path blocking means. |
