Patent GB-592311-A (GB)
IPC: G01B5/20
Abstract: 592,311. Gauging-apparatus. BRITISH POWER BOAT CO., Ltd., JAGGARD, R. W., and PULLEN, W. H. T. Nov. 23, 1944, No. 23372. [Class 106 (ii)] [Also in Group XX] In apparatus for recording variations in the surface contour of an article such as a propeller, the latter is held in a fixed position, an exploring pointer is arranged on a mounting constrained to move across the surface of the article and to allow the pointer to move transversely to the surface, a stylus contacting a record sheet is arranged to move with the pointer, the record sheet is carried by the mounting and means is provided for imparting movement to the record sheet relatively to the mounting in a direction transverse to the movement of the stylus and proportional to the movement of the mounting relatively to the fixed surface being explored. The machine comprises a triangular base 10, a column at each corner, a central boss 11 housing a Wormgear screw-jack 12 with a. conical centre 13 for supporting the propeller, and an upper conical centre 22 for the propeller carried by a rod 21 supported adjustably on a beam 18 carried by two corner columns 16, 17. The rod 21, which is supported in a top plate 25 secured on three columns, has a swing frame mounted thereon comprising two outer vertical bars 37, 38 connected by two horizontal bars 39, 40 on which slides horizontally a carriage carrying the stylus 51, propeller-contacting pointer 56, and record drum 58. The carriage includes upper and lower castings 43, 44 connected by two adjacent bars 45 and one bar 46, the two bars 45 serving as guides for rollers fixed to vertically slidable exploring bar 49 which passes through the lower casting 44 and carries the stylus 51 and pointer 56. The drum 58 is mounted on centres 57, 59, the latter being retractable against a spring by means of a cam trigger. The lower bar 40 is provided with rack teeth 63 engaged by a pinion operated by a hand wheel 66 on the carriage whereby the, carriage may be adjusted along the frame, the arrangement being such that the centre 59 is first retracted bv the hand wheel to lower the drum 58 before the carriage is moved. A scale 69 on the bar 40 is visible through a window 70 in the lower casing. The drum 58 is reversible, and is provided at each end with a springy, flat, circular plate 77, the upper one pressing against a friction-drive wheel 84 mounted on the upper casting 43 and bearing against a machine face 28 on the top plate 25. The axle of the wheel lies in the vertical plane containing the axes of the drum 58 and centres 13, 22 for the propeller, and the wheel lies in a plane tangent to the surface of the recording paper on the drum and containing the exploring point 56. The paper, which may be ordinary or have a waxed or slightly abrasive surface, is retained on the drum 58 by a spring wire clip engaged at each end in a recess in the top and bottom ends of the drum. The stylus 51 may be of brass or comprise an ink pen ; it is pressed forward by a spring and may be drawn back by a knurled nut 53. The exploring point 56 is shaped like a letter " U " lying on its side, or it may comprise a simple conical point, half of which has been cut away to leave a flat face. The propeller can be moved into the apparatus on a trolley 30 running on rails 31 secured to the base 10. The propeller is held against rotation by two double claw clamps 32 adjustable by nuts on threaded rods 33 at one end and secured to blocks 34 slidable on rods 35 on the base at the other end. In use, the carriage 43, 44 is set to the radius at'which it is desired to take a section of a propeller blade, the hand wheel 66 turned back to allow the drum to rise into contact with the frictiondrive wheel 84, the swing frame moved to bring the exploring point 56 to the highest edge of the blade, and the stylus 51 allowed to contact the paper on the drum by unscrewing the nut 53. Movement of the swing frame across the blade with the exploring point in contact with the latter results in a trace by the stylus which exactly reproduces the development of the contour of the upper face of the blade. To record the lower face and thereby complete the blade section, the drum and propeller are reversed, the height of the propeller being adjusted by the jack 12. The swing frame can be locked in the middle of its working arc by means of a pin 90 fitting holes in the frame and a plate 88 on the column 27, whereby the stylus may be 'moved up and down the paper to form a line which, where it intersects the blade outline, forms the strickle " line. From the diagrams it is possible to determine the pitch and rake of the blade. In a modification, the blade section can be traced without reversing the propeller and drum by providing a second exploring point on a U-shaped arm, either on the same exploring-bar with one or two styluses or on a separate bar with stylus. The frictiondrive wheel could be replaced by positivedrive change-speed gears.