| 摘要 |
In a casing (1) a wedge-type valve body (6) may be pressed by means of an actuation rod (3), against seats (7, 8) of two ends of a conduit (9, 10). The two inner rooms of the conduit (9, 10) are each in communication with the inside (12) of the casing through an auxiliary shut-off device (A, A1). The auxiliary shut-off devices (A, A1) operate as non return valves and, when the valve is closed they maintain in the inside (12) of the casing a pressure which is equal to that prevailing in the conduit (9, 10). The pressure in the inside (12) of the casing presses the wedge-type valve body (6) against the seats (7, 8) thereby insuring a safe closure. The subtended angle of the seats is relatively large and the wedge-type valve body (6) is displaceable in the casing (1). Thus, the friction between the sealing surfaces and therefore the wear are reduced. The auxiliary shut-off devices (A, A1) may be opened as desired before opening the valve in order to decrease the pressure in the inside (12) of the casing thereby facilitating the opening of the valve since the actuation rod (3) must not transmit large forces to displace the wedge-type valve body (6). |
