Optics: measuring and testing – Inspection of flaws or impurities – Bore inspection
Patent
1997-11-03
2000-08-08
Font, Frank G.
Optics: measuring and testing
Inspection of flaws or impurities
Bore inspection
356376, 356372, 356237, G01N 2100
Patent
active
061009725
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention concerns an arrangement, which includes a scope, such as a rigid borescope, a flexible fibrescope, or a videoscope for example, for accurately measuring observed objects, object details, and object defects. The arrangement of the present invention is more accurate than known systems, yet is simple to use.
Scopes, such as flexible videoscopes and fibrescopes have been used to observe the interior of the body during diagnostic procedures or surgery. Scopes, such as rigid borescopes, have been used to observe and inspect manufactured parts otherwise inaccessible to the eye. Although such scopes have an almost limitless number of applications, the following example illustrates their value.
A gas turbine engine includes a series of compressor and turbine blades, any one of which may become damaged. Although the first and last stage compressor/turbine blades of a gas turbine engine can be inspected directly, other intermediate stage compressor/turbine blades cannot be directly inspected. In the past, to inspect these intermediate stage compressor/turbine blades, the engine had to be disassembled until the intermediate stage compressor/turbine blade could be directly inspected. However, more recent gas turbine engines are with apertures (or borescope ports) provided at critical areas. These borescope ports permit the intermediate stage blades to be inspected using a borescope.
The borescope includes a long, thin, insertion tube having a lens system at its distal end and a viewing means at its proximal end. When the insertion tube of the borescope is inserted into a borescope port of the gas turbine engine, the lens system at its distal end relays an image of an otherwise inaccessible intermediate compressor/turbine blade to the viewing means at the proximal end. The focus of the image (in some models) can be adjusted by control knobs at the proximal end of the borescope. Hence, as illustrated by this example, a borescope permits an intermediate compressor/turbine blade of a gas turbine engine to be inspected without needing to disassemble the engine.
Besides being used to indirectly inspect parts which cannot be inspected directly, borescopes can also be used to measure the size of defects on the part. For example, U.S. Pat. No. 4,980,763 (hereinafter "the '763 patent") discusses a system for measuring objects viewed through a borescope. The system discussed in the '763 patent projects an auxiliary image, such as a shadow, onto the object being viewed. Changes in the position or size of the auxiliary image correspond to the distance between the object being viewed and the borescope. The image is displayed on a monitor having a magnification and object distance scale overlay screen. The size of the object on the screen is measured with vernier calipers, or electronically with cursors. This size is then divided by the magnification which is determined by observing where the auxiliary image falls on the magnification overlay. Unfortunately, the system discussed in the '763 patent requires a user to manually determine the magnification factor based on the position of the auxiliary image on the display screen.
U.S. Pat. No. 4,207,594 (hereinafter "the '594 patent") discusses a system in which the dimensions of a defect are determined based upon a manually entered field-of-view value and a ratio of second crosshairs, arranged at edges of a defect image, to first crosshairs, arranged at edges of the field of view. Unfortunately, the system discussed in the '594 patent requires probe penetration values to be manually read from a scale on the probe barrel for determining the field-of-view. Since such scales do not have fine gradations and since they must be manually read, errors are introduced.
U.S. Pat. No. 4,820,043 (hereinafter "the '043 patent") discusses a technoscope for determining the length of a defect. The technoscope includes a graduated scale which is displacable in a direction transverse to the endoscope axis. The graduated scale is mechanically coupled with
REFERENCES:
patent: 4895431 (1990-01-01), Tsujiuchi
patent: 5412448 (1995-05-01), Kunishige
WO 96/20389 Jul. 4, 1996.
WO 89/12337 Dec. 14, 1989.
Coath Philip Michael
Harley Jennifer Marian
Luke Barry Edward
McLean Robert James
Font Frank G.
Keymed (Medical & Industrial Equipment) Ltd.
Ratliff Reginald A.
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