Atmosphere detector for helicopter blades

Claim 2

Means for detecting an air leak in a sealed container the interior of which is substantially free of oxygen and has a gas fill at a pressure different from atmospheric, said detecting means comprising, in combination, a transparent envelope or bulb means mounted on said container to be clearly visible from the exterior thereof and in sealed communication with respect to the interior thereof, a quantity of barium coated on the interior surface of said envelope whereby any change in color of said barium coating is visible from outside of said envelope and container, said barium coaTing having been applied so as to have a substantially black appearance in the absence of oxygen, said fill gas being inert with respect to said barium coating, said bulb being mounted and sealed on said container by means including a diaphragm across the otherwise open end of said bulb facing said container, and means for piercing a hole in said diaphragm to provide said communication between the barium coated bulb and the interior of said container whereby said inert gas also fills said bulb to render said detecting means operational.

Claim 3

Detecting means according to claim 1 wherein said container is filled with nitrogen at a pressure different from atmospheric.

Claim 4

In combination with a hollow helicopter blade the interior of which is sealed off from the atmosphere and contains a substantially oxygen-free gas, an atmosphere detector for providing a visual indication of the presence or absence of a crack in said blade, said detector comprising, a transparent bulb mounted on said blade to be clearly visible from the exterior thereof in sealed communication with respect to the interior thereof, and a quantity of barium coated on the interior surface of said bulb whereby any change in color of said barium coating is visible from outside of said bulb and blade, the gas in said blade being inert with respect to said barium coating, and said barium coating having been applied so as to have a substantially black appearance in the absence of oxygen, said bulb being mounted to said blade and sealed by means including a diaphragm across the otherwise open end of said bulb facing said blade, and means for piercing said hole in said diaphragm to provide said communication between the barium coated bulb and the interior of said blade whereby said oxygen-free gas also fills said bulb to render said detector operational.

Claim 5

In combination with a hollow helicopter blade the interior of which is sealed off from the atmosphere and contains a substantially oxygen-free gas, an atmosphere detector for providing a visual indication of the presence or absence of a crack in said blade, said detector comprising, a transparent bulb mounted on said blade to be clearly visible from the exterior thereof in sealed communication with respect to the interior thereof, and a quantity of barium coated on the interior surface of said bulb whereby any change in color of said barium coating is visible from outside of said bulb and blade, the gas in said blade being inert with respect to said barium coating, and said barium coating having been applied so as to have a substantially black appearance in the absence of oxygen, said bulb being mounted to said blade and sealed by means including a diaphragm across the otherwise open end of said bulb facing said blade, and means for piercing said hole in said diaphragm to provide said communication between the barium coated bulb and the interior of said blade whereby said oxygen-free gas also fills said bulb to render said detector operational.

Claim 6

The combination of claim 3 wherein said piercing means is disposed over an opening in said blade and projects toward said diaphragm, and wherein said means for mounting the bulb to said blade further includes a bellows supporting said diaphragm away from said piercing means.

Claim 7

The combination of claim 4 wherein said bulb is glass, and said detector further includes a transparent plastic housing enclosing said glass bulb.

Claim 8

The combination of claim 4 wherein the fill gas in said blade is nitrogen at a pressure different from atmospheric.

Claim 9

The combination of claim 4 wherein said diaphragm comprises a metal plate having a tubular member projecting toward the interior of said bulb and adapted to receive said piercing means, the end of the tubular member of said diaphragm within said bulb being closed by a thin metal wall prior to the piercing of said diaphragm, said thin metal wall being the portion of said diaphragm which is pierced.