Patent GB-652695-A (GB)
Title: Improvements in or relating to apparatus for optically gauging profiles
IPC: G02B21/00
Filed: 1948-02-18
Abstract: 652,695. Optical gauging apparatus. OPTICAL MEASURING TOOLS, Ltd., DIETRICH, C. F., and SMITH, H. J. Feb. 18, 1948, No. 4808. [Class 106 (ii)] In a gauging apparatus, a feeler 16 moves relative to the work-piece 11, Fig. 1, whose contour is to be gauged, and effects corresponding relative movements of a member 31, carrying a representation of the desired contour 32, and optical means for projecting an enlarged image of a part of the desired contour on to a screen 38 in proper relation to an index corresponding to the feeler. As shown diagrammatically in Fig. 1, two feelers 16, 17 carried by a table 12 are alternately spring-pressed into engagement with a turbine blade 11 to gauge opposite sides thereof. The table also carries a lantern 23 and a graticule 20 having two spots 21, 22, corresponding to the two feelers. Light from the lantern passes through a collecting lens 27, the graticule 20, a "roof" " prism 28 which reverses the beam left for right, an adjustable lens system 29, prism 30, lens 45, and the stationary graticule 31 carrying the master contour 32. A portion of this contour together with the image of the spot 21 or 22 focused on the graticule 31 is projected through a magnifying lens 35 carried by the table on to the screen 38 by means of mirrors 36, 37. Each spot is surrounded by a ring and if the image 41 of this ring on the screen crosses the image 40 of the master contour, the blade 11 does not depart from standard by more than the permitted tolerance. The lens 35 has two positions, one for each feeler and associated spot. The magnifications due to the lens system 29, and-lens 35 may be so related that the image of the spot is stationary on the screen. In the apparatus, the blade 11 is carried in a chuck 73, Fig. 2, rotatable about a bracket 71 slidable on a column 70. An index arm 74 secured to the chuck spindle overlies a disc 75 marked with a scale for angular setting of the blade, and the movement of the arm is limited by adjustable stop screws. The bracket 71 is held in its adjusted positions along the column 70 by a spring pawl engaging notches in a bar 91, and is further guided by a rod 87. The table 12 is moved across the blade by a hand wheel 100 through rack and pinion gearing, and the top portion carrying the feelers is urged towards or away from the blade by a spring 120, Fig. 8. This spring acts through levers 118, 116 and a pin 117 on one side or the other of the pivot 115 of a lever 114, having a roller 113 which engages a channel member 111, Fig. 5, secured to the table, so that one feeler or the other engages the blade 11. The spring action is automatically reversed, when the table has been moved a predetermined distance, by an adjustable dog 129 or 130, Figs. 2 and 8, which rocks a lever arm 128, link 125 and a lever 123 whose forked end engages and moves the pin 119 on the lever 118. At the same time a cam 138 on the link 125 operates or releases a micro-switch 139 in the circuit of a solenoid 135, Fig. 5, thus moving its plunger 136 which is connected to a pivoted link 34 carrying the lens 35. The lens in thus changed over to be associated with the image of the other spot 21 or 22. The graticule 31 is slid into place above the lens 45 in a mounting 141, and has three different sections of the blade 11 drawn thereon which are successively brought into operative position by turning a knob 144 to rotate the mounting until a spring-pressed pawl 145 engages one of three notches therein. Specification 639,131 is referred to.