Patent GB-662073-A (GB)
Title: Improvements relating to profile gauges
IPC: G01B5/20
Filed: 1949-03-23
Abstract: 662,073. Photo-electric control systems. TANDLER, W. S., and TANDLER, G. B. March 23, 1949 [March 23, 1948], No. 7948/49. [Class 40 (iii)] [Also in Group XIX] A micrometer calliper-type gauge is provided with a probe 343, Fig. 1, which makes electrical contact with the test-piece 336 resting against a support 337 so that the test-piece and probe are inserted in the circuit of an electrical signalling device 348 which indicates when the micrometer probe makes electrical contact with the test-piece. In a modification (Fig. 7), a recording profile gauge comprises a base 30 having a vice 31 securing the part to be tested such as a turbine-blade 32. The vice 31 is slidably mounted so as to permit adjustment of the level of the test part. The vice 32 is mounted on a carriage 37 supported on guiderails 38 and is moved by a lead screw 39 driven by a motor 40, through a gear reduction mechanism 41. The motor 40 is controlled by a drum 42 which carries a number of indicia 43 that are adapted to be scanned by a conventional photo-electric scanning means 44. The scanning means 44 feeds signals to a control circuit whereby the test part is placed progressively in a number of predetermined positions or test stations. Reciprocally-mounted in a suitable support 46 is a probe carried by a rack 48. The rack 48 engages with a pinion 49 driven by a motor 50 through a gear-box 50a. Also driven from the gear-box 50a is a lead-screw 51 moving a carriage 52 on which are mounted photo-electric scanning means 54 and 55. These are adapted to scan suitable forward and return indicia 56, 56a on a drum 57 mounted on a shaft 58 also driven by the gear-box 50a to control the forward and return motion of the probe 47. As shown in detail in Fig. 9 the probe 47 comprises a pin 69 urged forward by a spring 70 within a housing 71 secured in a tubular member 72 made of suitable insulating material on the rack 48. The base 30 also carries recording means 45 comprising a stylus 62 and record strip 59 of the type on which a visible mark is produced by passage of electric current. The recording strip is advanced simultaneously with the test-piece to the several gauging stations. The stylus 63a is driven by a pinion 64 through a clutch 65 which receives a drive from gear-box 50a via a shaft 66. The stylus 62 is thus moved across the record strip in proportion to the movement of the probe 47 but magnified by 100 times. The arm 63 carries an actuator member 67 which when tolerance limits are exceeded operates a switch 68 to shut down the system and thus reject the testpiece. In order to keep the width of the record strip 59 to a minimum, movement of the stylus 62 is not initiated until a short time before a reference mark indicating the desired contour is made. This is achieved by the clutch 65 in conjunction with suitable control circuits. The operation of the recording profile gauge is illustrated with reference to a turbine blade 32 shown in Fig. 13. It is assumed that the deviation from normal contour is to be measured at 12 stations at the perpendicular distance from the chord 110 to the surface of the part, as shown in Fig. 14. Fig. 14 represents the placing of the indicia 43 on drum 42 controlling the motor 40 to bring the test blade to each of the twelve stations. Similarly the locations of the controlling indicia on the drum 57 must also be accurately established, as shown in Fig. 15, so that the distance of the indicia from the baseline 113, represents the displacement that should be given to the probe arm 53 to bring the tip of the probe pin 69 to a position corresponding to the contour specified for the test blade 32. The record made is shown in Fig. 18, showing the deviation from zero at each station, maximum and minimum tolerances, and oversize and undersize reject zones.