Patent GB-328349-A (GB)
Title: Means for comparing the outlines of screws with standard outline charts by optical methods
IPC: G02B21/00
Filed: 1929-02-05
Abstract: 328,349. Jackson, L. Mellersh-, (Hartness, J.). Feb. 5, 1929. Surface, and outline gauges. - An optical comparator for gauging screws comprises a support on which the screws to be gauged may rest, an approximately vertical chart above the screw support, and in relatively close proximity thereto a source of light, together with means between the source of light and the chart for projecting an enlarged image of a screw upon the chart. Upon a flat table 11 at the front of a cabinet 10 slide two carriers 13, 14, each guided by a tongue fitting into a groove 16. The carrier may be locked in adjusted position by turning a screw 19. Located in a cavity on each carriage is a cradle of arcuate cross-section adapted to receive the screw to be examined and capable of adjustment about the axis of the screw and adapted to be locked in adjusted position. The cradle is provided with a flange 24 having a semi-cylindrical threaded recess adapted to engage the screw. The two carriers are adjustable longitudinally of the screw 25 to accommodate screws of different length and provided with interchangeable cradles to receive screws of different diameter. A movable finger 26 mounted on a rod 27 rotatable and slidable in brackets 28 may be operated by a handle 280 to engage the screw to hold the latter in position on the cradles. The rear portion 12 of the cabinet is provided with a hood part provided with a flat rim 29 against which rests a removable chart holder 30 having a screen 31 to protect it from extraneous light. The chart and holder are adjustable about pivots 33. The chart, Fig. 6, is provided with a marking of at least one perfect screw of given gauge and lead secured in position by clips 35. Projection apparatus. An electric bulb 370 located in a post 39 carried by a bracket from a tube 43 forming the front end of a yoke having a rear upright 44 and supporting the optical system. A condenser formed by lenses 48, 49 is supported by a sleeve 50 which may be adjusted vertically by a helical slot 52 and pin 51. At the upper end of the tube 43 is a prismatic reflector 53 mounted on a flanged sleeve 54 rotatably adjustable in the tube. The upright 44 carries a compound microscope comprising four lenses 56 - - 59 arranged in pairs mounted in ferrules at each end of the tube. A reflector 64 carried by a holder 55 on a pin 66 reflects the beam on to the chart. The yoke itself is adjustable horizontally vertically and laterally. It is supported on a link 70 and provided with screws 84, 81 which form abutments, the yoke being held by the pull of a single diagonal inclined spring 88 against a third abutment screw 86. A transformer is provided to transform down from the mains to a switch voltage of about six or eight. Operation. In use, a standard screw is first placed on the carriage and adjustments made until the shadow of the edge of the screw thrown on the chart, Fig. 6, is correctly outlined between the two heavy black lines representing permissible tolerance. The screw to be gauged is then substituted for the standard and deviations noted.