Patent GB-588296-A (GB)
Title: An improved comparator for measuring diameters
IPC: G01B5/08
Filed: 1944-05-04
Abstract: 588,296. Linear-dimension gauges. COVENTRY GAUGE & TOOL CO., Ltd., and HARLEY, S. J. May 4, 1944, No. 8419. [Class 106 (ii)] A machine for measuring diameters comprises a work-table adapted to be accurately rotated through 180 degrees, a carriage slidable in a plane parallel with the work-table and carrying a stylus, means for measuring the movement of the stylus and means for diametrically aligning the work-piece with respect to the line of movement of the stylus. The work-table 2 is adjustable vertically by a hand wheel 24, Fig. 3, secured to a threaded spindle 23 co-operating with a nut 22 secured to an axially slidable sleeve 12 carrying the table. Graduations are provided on a guide bar 26 and also on the hand wheel 24. The whole table and support plate assembly 14 are adjustable at right angles to the movement of a carriage 4, Figs. 1 and 3, by a hand wheel 36 operating through a screw 35 on a traversing bar 31, which supports the plate assembly and slides in a groove 33. The work-table is rotatable through 180 degrees, this movement being limited by a stop plate 16, adjustable by a screw 20. The table is formed with a diametral slot so that the stylus may lie in the plane of the table. The stylus 3, which is interchangeable, is supported in an arm 47, incorporating a spirit-level 66, which is resiliently connected to a cradle 49 by horizontal spring plates 48. Relative movement can be prevented by trapping a rearwardly extending arm 58 on the stylus arm 47 between anvils 55, 56, one of which 56 is adjustable by a hand wheel 57. In an alternative arrangement, the locking means co-operates with a lug extending laterally from the stylus arm. In both cases the locking means can be swung into an inoperative position, allowing upward movement of the arm 47, a ratchet 60 being used to hold the arm when lifted. The cradle 49 is resiliently supported in the sliding carriage 4 by vertical spring plates 50, thus allowing fore-and-aft movement which, however, is checked by a fiducial indicator 74, Fig. 9, engaging an anvil 52 on the cradle. A lug 78, mounted eccentrically on a rotatable spindle 77, can be engaged with a spring 76 attached to the cradle to bias the latter towards the fiducial indicator when measuring external diameters. The slidably-mounted carriage 4 comprises a micrometer screw 41, Fig. 1, either of the rotatable or non-rotatable type, held in engagement with a stationary adjustable anvil 42 by a weight 45. Gauge blocks may be inserted between: the anvil 42 and the micrometer screw 41. To dampen the movements of the stylus, an arm 70 attached to the member 47 carries a paddle 68 which is immersed in a container of liquid 71. In another embodiment, a microscope 86, Fig. 13, is used in conjunction with a glass scale 85 fixed to the sliding carriage 4 which is moved by a rack-and-pinion arrangement. A spindle 82 can be thrust against a spring 84 to engage an eccentrically-mounted pulley 80 with the cable 83 supporting the weight 45. Then, by rotating the spindle 82 certain amounts, the weight can be arranged to pull the carriage in either direction according to whether internal or external diameters are being measured.