Patent GB-710865-A (GB)
IPC: G01B5/20
Abstract: 710,865. Gauging screw-threads; indicating-apparatus. TOLIMIT GAUGES, Ltd., WILLS, S. A., and GATHERCOLE, E. F. J. June 16, 1952 [March 16, 1951], No. 6401/51. Classes 106 (2) and 106 (4) Gauging apparatus of the kind employing two pairs of co-operating gauging elements designed to gauge respectively the full form and effective diameters of a screwthread, comprises a first support carrying one element of each of the two pairs, and a second support movable relative to the first support and carried by a parallel-motion linkage and on which is mounted the other element of each pair, and indicator means for indicating the displacement of the second support relative to the first support. As shown, Fig. 1, the apparatus comprises a casing 1 with horizontal base plate 2 and curved window 3 for viewing the position of an indicator needle 4 relative to a scale 5. Rolls 6, 7 are formed at opposite points on their circumferences with threaded portions suitable for gauging eg. "full form" and " effective "diameter" of a screw threaded object. The rolls 6, 7 are freely mounted on pins 8, 9 extending from cylinders 10, 11 bolted respectively in V-ways in a movable support 14 and relatively fixed support 15. The latter comprises an arm 16 pivoted between fixed pins 17, 18 and bearing at its opposite end on a plunger 19 sliding in a bore 20 and adjustable by means of a screw 21 threaded in a pin 22 and held against axial movement by a plate 23. The plunger 19 is locked by a set screw 27 and bolt 26 associated with split clamping pads (not shown). The movable support 14 is bolted to a bar 28 carried by a parallel-motion linkage comprising two leaf-springs 29, 30 each clamped to the bar 28 and to brackets 31, 32 and held rigid in its mid-portion by elements 33. A knifeedge 34 on the bar 28 bears on a rocking arm 35 pivoted to the casing by two leaf springs 36, 37 assembled at right angles and the other end of the arm 35 is connected through a pivoted link 39 to a toothed quadrant 40 pivoted on an axis 41 and co-operating with a pinion 42 provided with an arm 43 carrying the indicator needle 4. The dimensional characteristic to be gauged is selected by rotating the rolls 6, 7 to bring the appropriate threaded portion into gauging position by means of indexing mechanism comprising a bar 48 carried on two pivot pins 49, 50 mounted eccentrically on pinions 51, 52 freely mounted on pins 72, 73 carried by a plate 55 which is pivoted on a bushing surrounding a shaft 57 in fixed bearings. An operating arm 61 outside the casing is connected to the shaft 57 which has secured thereto a pinion 60 meshing with the pinions 51, 52 which turn through 180 degrees when the arm 61 is turned through 180 degrees so that the bar 48 moves parallel to itself in a circular sweeping motion, claws 53, 54 thereon thereby rotating the rolis 6, 7 through 180 degrees by co-operating in recesses 46, 47 in axial extensions 44, 45 of the rolls 6, 7. The claws 53, 54 are a loose fit in the recesses 46, 47 and so allow a slight rotation of the rolls 6, 7 when an object to be gauged is inserted between them. An adjusting bolt 59 with a friction head co-operates with a cut-away re-entrant 58 in the plate 55 and permits the complete pinion mechanism to be adjusted initially or after adjusting the locating plunger 19. Downward pressure on the movable support 14 is provided by means of a tensioning spring 62 connected to one end of a bell-crank lever 63, with fixed pivot 64, whose other end is connected to the bar 28 through a pin-andslot joint 65. The other end of the spring 62 is connected to a cord or belt 66 running over an adjustable pulley 67 mounted eccentrically on a shaft 68, and thence over a fixed pulley 69 to an anchorage 70 on the indexing bar 48. Movement of the bar 48 to its position remote from the pulley 69 therefore increases the tension in the spring and thus increases the pressure on the support 14 thus providing an automatic adjustment of pressure as e.g. a greater pressure is desirable for gauging "full form" than for "effective diameter." An external control knob 71 is provided on the shaft 68 for the manual adjustment of the pressure between the rolls to suit the known approximate dimensions of the object being gauged. Due to the angle between the belt 66 and bar 48 a slight pressure urges the bar 48 into engagement with the recesses 46, 47. To assist in locating an object in gauging position a back stop assembly is provided comprising a bar 75 carried by two leafsprings 76, 77 and urged towards the rolls by a spring 74, a replaceable back stop pin 78, supported in the bar 75, and arranged for movement between the rolls 6, 7 and a stop cam 79 mounted eccentrically on a shaft co-axial with the bolt 59 with an external graduated control knob for setting a limit to the rearward travel of the pin 78 in accordance with the approximate size of the object. Gripping means for small objects comprise a jaw 83 pivoted to a shoulder 82 of the stop bar 75 and urged by a light spring 85 towards the stop pin 78. If the jaw 83 is lifted and a screw 86 inserted the action of the spring will close the jaw 83 and urge the back stop assembly to the limit of its travel when the screw 86 will be in correct gauging position. Small manual adjustments of zero may be made through a cam 90 bearing on a quadrant arm 87 which carries the scale 5 and is urged towards the cam by a spring 89. Maximum and minimum acceptable limits may be indicated on the scale 5 by two pointers 91, 92 controlled by knobs 93, 94, Fig. 2. In another embodiment the pair of leaf springs 29, 30 is replaced by a pair of pivoted, parallel links 104, 105, Fig. 4, with forked extremities 106. The bar 28 has two transverse bores 100, 101 and brackets 31, 32 have two similar bores 102, 103. A pair of double-tapered conical bearings 107, Fig. 6, is mounted in each bore and each bearing projects to engage a recess 108 machined in the adjacent side of a fork 106 being maintained in position by a set screw 109 located in a threaded bore in the bar 28 on one of the brackets 31, 32. Two gauging elements are shown on each roll 6, 7 but any number may be provided and the indexing member may be modified accordingly.