| 摘要 |
A valve unit for controlling the delivery of a fuel gas through a delivery duct ( 3 ) comprises a valve seat ( 6 ) in the duct, a closure member ( 5 ) associated with the seat, a motor-driven actuator ( 7 ) acting on the closure member in order to control it so as to open/close the valve seat, as well as an electromagnetic unit ( 22 ) with a first portion ( 23 ) carrying a magnetizing winding ( 24 ) and a second portion ( 25 ) which can be fixed firmly to the first position by magnetization. The electromagnetic unit ( 22 ) is associated with the actuator in order to act on the closure member ( 5 ) so as to close the valve seat ( 6 ), irrespective of the operative position of the actuator ( 7 ), upon the occurrence of a predetermined condition which requires the valve seat to be shut off, and the actuator means ( 7 ) is movable, together with the second portion ( 25 ) of the electromagnetic unit ( 5 ) so as to open/close the valve seat, the first portion ( 23 ) of the electromagnetic unit being connected to a stationary structure of the valve unit. |
