| 摘要 |
1,218,954. Detecting cracks in helicopter rotor blades. UNITED AIRCRAFT CORP. 9 May, 1968 [22 May, 1967], No. 21961/68. Heading B7W. [Also in Divisions G1 and H1] Apparatus 24, mounted in a preferred embodiment in communication with the hollow interior of a pressurized helicopter rotor blade structure comprises a rigid substantially circular casing 35, having a transparent cap member 30, with spaced circumferential opaque stripes 76 thereon sealed at 60, adjacent its open end, to a base-plate member 32, having a cylindrical end portion 46, a threaded stem portion 36, conduits 164, 162, 160 recessed aperture 108 and an annular, peripheral groove 54, said baseplate 32 and said transparent cap member 30 co-operating to define a sealed chamber 34, which communicates with a hollow helicopter rotor blade 22 containing the gas whose pressure is to be monitored, via conduits 164, 160 and 162 and houses a readily replaceable, pressurized, reference capsule 90, which comprises a hollow member 92, bellows 120, positive stop cylinder 130, a fixed rigid member 100 constructed from stem portion 102, shoulder section 106 and circular plate portion 104, said capsule carrying two series of stripes 93 and 94 corresponding to said spaced stripes on transparent portion 30, and being readily detachable from recessed aperture 108, and apparatus test button and plunger mechanism 200, Fig. 7, which opens chambers 34 and 150 to the atmosphere. When operating, gas from the rotor blade 22 enters sealed chamber 34 and chamber 150, the latter being formed from members 100, 92 and bellows 120, through filter 166 and conduits 162, 160 and 164, the pressure of said gas being greater than that contained within chamber 122 of reference capsule 90 to thus cause the latter to move downwards guided by circumferentially spaced, axially extending ribs 82, by bellows 120 extending so that surface 140 of hollow member 92 abuts surface 48 of cylindrical end portion 46, Fig. 4. In this position, stripes 94 lie behind stripes 76. Reduction in gas pressure due to cracks in the blade or rupture of apparatus 24 reduces the gas pressure differential between chambers 34, 150 and chamber 122 resulting in the capsule rising through contraction of bellows 120, the movement being limited by the abutment of shoulder section 106, with positive stop cylinder 130, so causing stripes 94 to align with windows 74 (Fig. 5) to provide a visual indication to loss of pressure. Since the gas pressure in chamber 122 of replacement capsules 90 and the position of member 100 of capsule 90 relative to window member 72 is kept constant capsules 90 may be interchanged without calibration. To provide a supplementary warning in a pilot's cockpit, electrical contacts (not shown) may be installed on the capsule and on transparent casing lid 35, and/or on base 32, to operate warning lights. As an alternative to sealing device 60, 0-rings may be placed either side of a thread connection (300, Fig. 8, not shown) co-operating cap member 30 and base-plate 32. |
