Automatic fill-stop valve

An automatic fill-stop valve for use in filling tanks for containing liquid which boils under ambient conditions, said fill-stop valve comprising:

• a valve body having a liquid passage therethrough, a bore in said body, a valve spool movably mounted in said bore for moving from a closed position wherein said liquid fill passage is closed to an open position wherein liquid filling can take place, said valve spool having a large piston thereon, said valve body having a drive chamber therein, said large piston being open to said drive chamber so that pressure in said drive chamber moves said spool toward the valve closed position a ram disc bore, in said drive chamber, said ram disc bore being of larger diameter than said large piston, a ram disc in said ram disc bore, said ram disc being movable in said ram disc bore in a direction to urge said valve spool in a valve closing direction, said valve spool lying against said ram disc when said valve spool is in its valve open position;
• a level-sensing system comprising a level-sensing tube and a first orifice in series with said tube, the side of said ram disc away from said valve spool being open to said level-sensing system so that increases in pressure in said level-sensing system urge said ram disc and said valve spool toward the valve closed position, said level-sensing system further including a second orifice and a manually operable valve, said drive chamber being connected to said level-sensing system between said first and second orifices.