Patent ID: 7281672

Claim:
An apparatus for dispensing fluid, comprising: a pressure vessel adapted to contain fluid at a first pressure P 1 ; a reservoir adapted to contain fluid at a second pressure P 2 , said reservoir being in communication with said pressure vessel via a first aperture and with an environment at a third pressure P 3 via a second aperture; a reservoir vent having open and closed positions, such that in said open position said reservoir vents therethrough to a fourth pressure P 4 , and in said closed position said reservoir does not vent therethrough; a piston moveably disposed within said reservoir proximate said first aperture, said piston defining at least one piston aperture therethrough; a first burst seal disposed in said first aperture so as to seal said pressure vessel from said reservoir, said first burst seal being engaged with said piston so as to be moveable therewith; a second burst seal disposed in said second aperture so as to seal said reservoir from said environment; a piston stop arranged so as to stop said piston from exiting said second aperture; wherein P 1 >P 3 , and P 1 >P 4 ; P 2 >P 3 , and P 2 >P 4 ; said second burst seal has a rupture strength S 2 , such that S 2 ≧|P 2 −P 3 |; when said reservoir vents to said fourth pressure P 4 , said first burst seal and said piston move toward said second aperture under a pressure difference |P 1 −P 4 | such that said piston ruptures said second burst seal; and said first burst seal has a rupture strength S 1 , such that S 1 >|P 1 −P 2 | and S 1 ≦|P 1 −P 3 |, whereby when said piston stop stops said piston, said pressure difference |P 1 −P 3 | ruptures said first burst seal, such that fluid passes through said piston apertures.