Patent GB-712145-A (GB)
Title: Improvements in or relating to apparatus for gauging machine parts
IPC: G01B7/28
Filed: 1952-04-01
Abstract: 712,145. Surface and outline gauges. TANDLER, W. S. April 1, 1952 [April 9, 1951], No. 8212/52. Class 106 (2) A gauging apparatus for machine parts comprises means for accurately locating the part with reference to a surface gauging assembly and means for indicating the amount by which said adjustment differs from the setting of a standard machine part when this is accurately located in the apparatus. The apparatus comprises a holder 16, Fig. 1, for a standard pattern 10 or a test piece, the holder 16 being pivotally mounted on a stationary base member 12 and biased towards stop means 24, 25, 26 by a spring 40. The stop means 24, 25, 26 are carried by an upright member 23 mounted on a carriage 20, the carriage 20 being slidable towards or away from the base member 12 by means such as a lead screw actuated by an adjusting knob 21. Each of the stops 24, 25, 26 may be advanced individually to its operative position, with respect to the upright member 23 by means such as solenoids 30, 31 and 32. As shown in Fig. 3, a plan view of Fig. 1, the apparatus includes a contour gauging head 49 carrying a plurality of probes 50, the head 49 being adjustable to different elevations and movable towards and away from the blade 10. The probe elements 50 are so located that they will engage the surface of the blade 10 at specified stations taken with reference to the leading edge of the blade after the blade has been suitably adjusted about its pivot 13. The tips of the probes 50 normally lie along a line corresponding to the correct contour for the test piece 10 and as the head 49 moves towards the test piece 10 a recording head 51, Fig. 4, carrying a plurality of recording styli 53, equal in number to the probes 50, is drawn over a recording strip 52. When a probe 50 engages the test piece 10 an electric signal, amplified by suitable means 54, causes the corresponding stylus to make a mark on the record strip 52. The gauging head 49 carries two additional probes 55 and 56, Fig. 3, which are adapted to be moved into engagement. with surfaces 48 and 46 respectively of anvils 47 and 45, the anvil 47 being secured to the stationary base member 12 and having its said surface 48 parallel to the plane of motion of the test piece 10 about its pivot 13, and the anvil 45 being mounted on the pivoted holder 16 with its said face 46 in a plane at an angle to the plane of motion of the test piece 10 about its pivot 13. The probes 55 and 56, in conjunction with the anvils 47 and 45, enable any error in the location of the leading edge of a test blade 10 to be determined by measuring the amount of tilt of the holder 16 during a gauging operation, this tilt being proportional to the distance along a line perpendicular to the plane in which the tilt of the holder 16 occurs between the probes 55 and 56 when engaging their respective anvils 47 and 45. The recording head 51 has two additional styli 57 and 58 thereon, which styli correspond respectively to the said probes 55 and 56. Operation.-In a preferred operating procedure, the anvil 24 is advanced to the operating position by closing the switch 33. The position of the carriage 20 is then initially adjusted so that with a perfect blade in the holder 16 the blade is held with its longitudinal axis in the proper position as required by its design. The probes 50 are adjusted so that their tips lie along a line corresponding to the correct contour for the turbine blade which is to be gauged and the positions of the probes 55 and 56 are adjusted so that they will engage the surfaces 48 and 46 respectively, of the anvils 47 and 45, respectively, at substantially the same instant the probes 50 simultaneously engage the surface of the test blade 10. A perfect blade is shown in Fig. 5 and the position of the holder 16 with the blade mounted in it is shown in Fig. 5A. The record produced, by the gauging apparatus is shown in Fig. 5C from which it appears that the dots produced by the styli 53 on the recording head 51 all lie in a straight line. If now, a faulty blade of the type shown in Fig. 6, in which the leading edge tilts forwardly more than it should, is substituted for the correct blade, the holder 16 will be tilted to the left, as shown in Fig. 6A. Under these conditions, the stylus 56 will engage the surface 46 of the anvil 47 before the stylus 55 engages the surface 48 of the anvil 47 so that the dot 59 produced by the stylus 58 on the recording head 51 will occur above the line of dots produced by the other styli, as shown in Fig. 6C. The record obtained, therefore, indicates that the contour of the blade is correct but that the leading edge is in error. Further, the perpendicular distance from the dot 59 to a line through the reference dots is a measure of the error in the locations of the leading edge. If the blade 10 has a depression 60 formed in the leading edge thereof at the level where it would engage the knife edge 24, as shown in Fig. 7, the holder 16 will be tilted to the right as shown in Fig. 7A. Under these conditions, Fig. 7C, the dot 61 produced by the stylus 58 on the recording head 51 will lie below the reference dot 62. Further, since the location of the reference point A' is considerably in error, the dots produced by the remaining styli corresponding to the gauging probes on the gauging head 49 will appear to indicate that the contour is not correct. However, by adjusting the position of the knife edge 24 by means of the knob 21, Fig. 1, and making a record after each adjustment, the longitudinal axis of the blade 10 can be brought into the correct position, at which point the dots produced by the styli corresponding to the gauging probes on the gauging head 49 will lie substantially along a straight line if the contour of the blade is correct. The amount of adjustment of the knob 21 required to effect this result will then be a measure of the depth of the depression in the leading edge of the blade 10. By exploring in this fashion, it is possible to determine whether or not an error in the record obtained results from an error in the leading edge of the blade or from a depression or bump therein. After a blade has been gauged along the section line A, it can be gauged along the section lines C and E by opening the switch 33 and making separate gauging runs first with the switch 34 closed and then with only the switch 35 closed.