Patent ID: 7140381

Claim:
In a valve element ( 20 ) comprising a frame ( 21 ), at least one first inlet ( 26 ), at least one second inlet ( 27 ), at least one outlet ( 28 ), at least one burst or rupture disk ( 23 ) which, when unbroken, closes a passage from the second inlet ( 27 ) at least to the outlet ( 28 ), and a piston element ( 25 ) comprising a piercing element ( 24 ) for piercing the burst or rupture disk, the improvements comprising: said piston element being movable between at least first and second positions when the burst or rupture disk has been pierced, in the first position the passage from the second inlet ( 27 ) to the outlet ( 28 ) being closed while in the second position the passage from the second inlet ( 27 ) to the outlet ( 28 ) is open; and the piston element being moved to the second position after a pressure difference between the second inlet and the first inlet is has reached a predetermined value.