Hermetically sealed portable fire extinguisher with pressure indicator

1. A fire extinguisher, comprising:

a) a cylinder for storing a pressurized fire extinguishing agent and including a neck portion defining an outlet; and

b) a flexible hermetic seal supported across the outlet of the cylinder, wherein the flexible hermetic seal is adapted and configured to transition between:

an unexpanded condition corresponding to an unpressurized cylinder; an expanded condition corresponding to a pressurized cylinder; and a bursted condition corresponding to an opened cylinder, further comprising a valve assembly threadably associated with the neck portion of the cylinder and securing the hermetic seal in place across the outlet of the cylinder, wherein the valve assembly includes a valve housing having an interior cavity with an exit port and a piston having an elongated stem and a lower body portion, wherein the piston is mounted for movement within the interior cavity of the valve housing between:

a seated position, corresponding to an unpressurized cylinder, in which the lower body portion of the piston is in contact with the flexible seal while the seal is in an unexpanded condition;

a lifted position, corresponding to a pressurized cylinder, in which the lower body portion of the piston remains in contact with the flexible seal while the seal is in an expanded condition, wherein the lower body portion of the piston remains in contact with the flexible seal in both the seated position and in the lifted position to provide a visual indication from outside the cylinder of pressure level within the cylinder; and

an activated position, corresponding to an opened cylinder outlet, in which the lower body portion of the piston is displaced from and out of contact with the flexible seal, allowing the seal to burst and open the outlet of the cylinder.

2. A fire extinguisher as recited in claim 1 , wherein a pressure indicator beam extends perpendicularly outward from the stem of the piston, through a window in a side wall of the valve assembly to provide a visual indication of a pressure level within the cylinder.

3. A fire extinguisher as recited in claim 1 , wherein a release pin is operatively associated with the valve assembly and is mounted for movement between a locked condition in which the piston is maintained in the pressurized position and an unlocked condition in which the piston is free to move to the activated position.

4. A fire extinguisher as recited in claim 1 , wherein a coiled biasing spring is positioned around an upper portion of the stem of the piston between a pressure indicator beam and a top wall of the valve assembly.

5. A fire extinguisher as recited in claim 1 , wherein the valve assembly further includes a lever arm adapted and configured to move the piston within the valve assembly against the bias of a coiled compression spring to permit pressurized fire extinguishing agent to be selectively released through the exit port of the valve assembly.

6. A fire extinguisher as recited in claim 1 , wherein a siphon tube extends downwardly into the cylinder from the neck portion thereof for delivering pressurized fire extinguishing agent to the outlet of the cylinder.

7. A fire extinguisher as recited in claim 1 , wherein a sealing ring is positioned within an annular groove surrounding the lower body portion of the piston for sealing against an interior surface of the valve housing to control the egress of pressurized fire extinguishing agent from the exit port of the valve housing.

8. A fire extinguisher, comprising:

a) a cylinder for storing a pressurized fire extinguishing agent and including a neck portion defining an outlet; and

b) a flexible hermetic seal supported across the outlet of the cylinder, wherein the flexible hermetic seal is adapted and configured to transition between: an unexpanded condition corresponding to an unpressurized cylinder; an expanded condition corresponding to a pressurized cylinder; and a bursted condition corresponding to an opened cylinder, further comprising a valve assembly threadably associated with the neck portion of the cylinder and securing the hermetic seal in place across the outlet of the cylinder, wherein the valve assembly includes a valve housing having an interior cavity with an exit port and a piston having an elongated stem and a lower body portion, wherein a release pin is operatively associated with the valve assembly and is mounted for movement between a locked condition in which the piston is maintained in the pressurized position and an unlocked condition in which the piston is free to move to the activated position, wherein the release pin includes axially spaced apart upper and lower parallel retention arms intersecting the stem of the piston, wherein the upper arm is positioned to retain a pressure indicator beam when the piston is in the pressurized position, and the lower arm is positioned to retain a coiled compression spring in a compressed condition.

9. A fire extinguisher, comprising:

a) a cylinder for storing a pressurized fire extinguishing agent and including a neck portion defining an outlet; and

b) a flexible hermetic seal supported across the outlet of the cylinder, wherein the flexible hermetic seal is adapted and configured to transition between: an unexpanded condition corresponding to an unpressurized cylinder; an expanded condition corresponding to a pressurized cylinder; and a bursted condition corresponding to an opened cylinder, further comprising a valve assembly threadably associated with the neck portion of the cylinder and securing the hermetic seal in place across the outlet of the cylinder, wherein the valve assembly includes a valve housing having an interior cavity with an exit port and a piston having an elongated stem and a lower body portion, wherein an upper portion of the siphon tube defines a recess for accommodating an outer rim portion of the flexible hermetic seal, such that the rim is secured between an interior wall of the valve housing and the upper portion of a siphon tube.