Patent GB-815995-A (GB)
Title: Optical contour gauging apparatus
Inventor: CROOK WILLIAM CHARLES HERBERT
IPC: G02B21/00
Filed: 1956-05-16
Abstract: 815,995. Optical gauging apparatus. NAPIER & SON Ltd., D. May 8, 1957 [May 6, 1956; Sept. 6, 1956], Nos. 15279/56 and 27372/56. Class 106 (2). [Also in Group XX] Optical contour gauging apparatus of the kind in which the image 47 of a contour graticule 20, which may have an image of a master contour or of a contout being gauged, is compared on a screen with the image 48 of a feeler 37 tracing over an actual contour, comprises a light source 18, a condenser lens system 19, a projector lens system 22 connected to the feeler 37, a rotatable mounting 15 for an article 16, a rotatable mounting 28 for the contour graticule 20 and connecting means 32 between these mountings whereby they are constrained to rotate simultaneously and through equal angles. As shown for gauging turbine or compressor blades, a blade 16 is adjustably mounted on a shaft 24 and the condenser lens system 19 is mounted on a shaft 25, these shafts being connected to a hand wheel 14. Pivoted on a third shaft 35, midway between shafts 24, 25, is a feeler 37 spring-biased into engagement with the blade 16 and adjustable vertically, being held in a fixed vertical position by stops 39, 40. The projector lens system 22 is connected, by an arm 36, to the feeler 37, and carries a graticule 46 approximately in the focal plane of the system 22. Also approximately in this plane is the contour graticule 20 carried by the lamphouse 17. The graticule 46 bears a representation of part of the feeler 37, and may include oversize and undersize tolerance lines. The graticule 20 bears representations of the standard crosssections of the blade 16 at different vertical positions. When projected on a screen 45, the images appear as shown in Fig. 3. Rotational movements of the blade 16 and lamphouse 17 are shown as rotational movement of the image 47 of the selected contour on graticule 20. Motion of the feeler 37 is projected as rotational movement of the image 48 of the graticule 46. To set up the apparatus, the blade 16 is adjusted until, with the feeler moving over the platform 21 of the blade, the images on the screen of the feeler and of the platform contour on graticule 20 are in complete agreement during rotation, the contour graticule 20 having been adjusted so that a datum point on it remains fixed during rotation. In a modification, a stationary lens is placed above the projection lens system 22, thus eliminating the rotational effect of the system 22 and allowing the image 48 to remain stationary. In this case, the graticule 46 is dispensed with and the image of the feeler 37 can be drawn on the screen or on a transparent sheet placed against the screen. In this embodiment an optically flat lens is mounted in gimbals between the contour graticule 20 and the projection system 22. By this means, the " lean error," i.e. the angle by which the longitudinal axis of the blade is offset from the perpendicular, can be ascertained. The blade support 15 is angularly adjustable, and by this means, " twist error," i.e. an indication of the twist of the blade about its axis, can be ascertained. Reference has been directed by the Comptroller to Specifications 652,695 and 694,950.