| 摘要 |
The drain cock (1) comprises
a body (2) with a pipe (3) that leads to a valve seat (4),
a hand-actuated opening and closing member (6) screwed onto a formation (5b) on the body (2),
barrier members (15, 16, 19; 15, 16, 27; 19) connected to the opening and closing member (6) and able to act on the valve seat (4), in such a way that when said member (6) is, relative to the body (2), in a closed position and in an open position, respectively, these barrier members shut off and disengage from, respectively, the seat (4), preventing and permitting, respectively, communication between an upstream portion of the installation and a region downstream of the valve scat (4). The drain cock (1) also comprises a moveable barrier (19; 16; 31) separated from the opening and closing member (6) and stressed by a spring (12) towards a shutoff position in which it is able, when this member (6) is in the closed position, to prevent the passage of liquid between the pipe (3) of the body (2) and a discharge passage (8b; 32). The arrangement is such that said barrier (19; 16; 31) is able to move from the shutoff position, against the action of the spring (12), when the pressure of the fluid upstream of the seat (4) exceeds a predetermined value, to a position in which it allows fluid to be discharged from the portion of the installation upstream of the seat (4) to the discharge passage (8b; 32). |
