Method and apparatus for testing bladed rotors

Claim 3

The method specified in claim 1 including: generating a calibration signal the amplitude of which is adjusted in relationship to the specific existing relationship between any axial displacement of the blade tips and the amount of change produced thereby in the amplitude of said second electrical signals, and comparing the amplitudes of said second electrical signals with the adjusted amplitude of the calibration signal to determine the amount of axial displacement of the blade tip.

Claim 4

The method specified in claim 1 including: storing each member of said succession of second electrical signals until a successive member signals is about to be produced by the passage of a succeeding blade, whereby the time duration of each member of said succession is lengthened appreciably.

Claim 5

The method specified in claim 1 including: attaching a magnetic indicator to the shaft of the rotor in relation to one of the blades, and positioning a magnetic pickup adjacent to the rotor in cooperating relation to the magnetic indicator whereby an identification signal is produced once per revolution of the rotor.

Claim 6

The method specified in claim 2 including: displaying the second electrical signals in comparative relation to said adjusted calibration signal.

Claim 7

The method specified in claim 1 including: displaying the secession of second electrical signals in time sequential relation to the identification signal, whereby each member of said succession can be identified with a particular blade.

Claim 8

The method specified in claim 1 including: focusing the optical image of the tip of each successive blade tip on an image plane containing an aperture; distributing the light from said image which passes through the aperture over a substantial portion of a photosensitive device the electrical output of said device having a linear relationship to the amount of incident light, thereby deriving a succession of said first electrical signals.

Claim 9

The Method specified in claim 1 including: applying said first electrical signals as the numerator signal to an electronic divider which also receives a denominator signal, said denominator signal being proportional to the brightness of the sky.

Claim 10

The method specified in claim 8 including: retaining the electrical signal from the electronic divider after reaching a minimum until restored to a maximum by a trigger signal.

Claim 13

The method of claim 10 wherein said succession of electrical signals comprise the quotient output signals from an electronic divider which receives as its denominator an electrical signal which is representative of the background illumination level, whereby said difference is caused to be substantially independent of the brightness of the sky.

Claim 14

The method specified in claim 11 including: applying the signals from the electronic divider to a peak holding amplifier which maintains its output substantially constant after reaching a minimum until restored to maximum by a trigger signal.

Claim 15

Apparatus for measuring during flight the distances by which the unmodified tips of a several bladed rotor are out-of-track comprising: an optical system for focusing an image of the area through which each successive blade tip travels, said optical system focusing an image of the tip of each blade on an image plane as it passes preselected azimuth, linear signal producing means receiving light from the image and producing therefrom, in synchronism with the rotor a succession of first electrical signals the maximum amplitude of said signals being proportional to the brightness of the sky, said succession containing signals the amplitudes of which are representative of the axial position of each successive blade tip, signal comparison means for comparing the amplitudes of portions of said first electrical signals which are proportional to the brightness of the sky with the amplitudes of those portions of said first electrical signals which are representative of the axial positions of the several blade tips, thereby deriving a succession of second electrical signals whose differences are proportional to the axial displacement of successive blade tips, said differences being independent of the brightness of the sky, signal generating means coupled to the rotor said means generating an identification signal in synchronism with rotation of the rotor, and signal display means accepting said second electrical signals together with the identification signal, said means producing indications of the out-of-track distance of each blade tip, said indications being identified with the individual blades.

Claim 16

Apparatus for measuring during flight the distances by which the unmodified tips of a several bladed rotor are out-of-track comprising: an optical system for focusing an image of the area through which each successive blade tip travels, said optical system focusing an image of the tip of each blade on an image plane as it passes preselected azimuth, linear signal producing means receiving light from the image and producing therefrom, in synchronism with the rotor a succession of first electrical signals the maximum amplitude of said signals being proportional to the brightness of the sky, said succession containing signals the amplitudes of which are representative of the axial position of each successive blade tip, signal comparison means for comparing the amplitudes of portions of said first electrical signals which are proportional to the brightness of the sky with the amplitudes of those portions of said first electrical signals which are representative of the axial positions of the several blade tips, thereby deriving a succession of second electrical signals whose differences are proportional to the axial displacement of successive blade tips, said differences being independent of the brightness of the sky, signal generating means coupled to the rotor said means generating an identification signal in synchronism with rotation of the rotor, and signal display means accepting said second electrical signals together with the identification signal, said means producing indications of the out-of-track distance of each blade tip, said indications being identified with the individual blades.

Claim 17

Apparatus specified in claim 13 wherein said signal comparison means includes a summing amplifier which receives the electrical signals from the signal producing means and also receives a continuous signal of opposite polarity.

Claim 18

Apparatus specified in claim 14 wherein said signal comparison meAns includes an electronic divider which receives the signal from the summing amplifier as its numerator signal, and as its denominator receives a signal proportional to the brightness of the sky, thereby producing from said divider dividend signals proportional to blade tip out-of-track distance which are substantially independent of said brightness.

Claim 19

The apparatus specified in claim 15 including a peak holding amplifier which receives the signal from the electronic divider and maintains its output substantially constant after reaching a minimum until restored to maximum by a trigger signal.

Claim 20

Apparatus for measuring during flight the distances by which the unmodified tips of a several bladed rotor are out-of-track comprising: an optical system for focusing an image of the tip of each blade on an image plane as it passes through a preselected field of view said image comprising a relatively dark area formed by that portion of the blade which is within the field of veiw superimposed on a relatively bright area formed by that portion of the sky which is within the field of view, image-dissecting means located approximate the image plane; the image-dissecting means accepting a selected portion of light consituting the image said portion including the interface between said areas; linear signal producing means coupled to the image-dissecting means receiving the light from the image-dissecting means such that equal amounts of light within any elementary part of said accepted portions will produce an equal amount of electrical signal; means isolating the apparatus so that any change of the elevation angle of the optical axis due to vibration is very slow in comparison with the rotation period of the rotor.

Claim 21

Apparatus for measuring during flight the distances by which the unmodified tips of a several bladed rotor are out-of-track comprising: an optical system for focusing an image of the tip of each blade on an image plane as it passes through a preselected field of view said image comprising a relatively dark area formed by that portion of the blade which is within the field of veiw superimposed on a relatively bright area formed by that portion of the sky which is within the field of view, image-dissecting means located approximate the image plane; the image-dissecting means accepting a selected portion of light consituting the image said portion including the interface between said areas; linear signal producing means coupled to the image-dissecting means receiving the light from the image-dissecting means such that equal amounts of light within any elementary part of said accepted portions will produce an equal amount of electrical signal; means isolating the apparatus so that any change of the elevation angle of the optical axis due to vibration is very slow in comparison with the rotation period of the rotor.