Patent GB-862404-A (GB)
Title: Linear dimension measuring instrument
Filed: 1959-03-25
Abstract: 862,404. Linear-dimension gauges. SUNNEN, J. March 25, 1959 [May 21, 1958], No. 10330/59. Class 106 (2). A linear-dimension indicating instrument comprises a frame 12, a pair of spaced adjustable setting-devices 28, 36 mounted on the frame, each of said devices having a rotatable member 26, a member 114 threadedly co-operating with the rotatable member 26 and axially displaceable and in sliding connection with the frame 12 and a graduated scale, not shown, to indicate the positions of the two members. The device may be used either for setting gauges such as internal diameter gauges, to a fixed dimension, or for measuring external dimensions between contacts 120, 224. A mounting 44 and an adjustable screw 58 are used for fixing the device to a gauge to be set. In operation, coarse adjustment is effected by turning the sleeve 26 by means of a knob 106. The sleeve 26 is in threaded relationship with a screw 114 carrying a hardened contact 120 and guided for axial movement by an arm 124, the end of which moves between adjustable screws 140, Fig. 7, thus compensating for errors in the screw-thread 114, at each coarse setting-point. A pinion gear 88 rotatable in a bore 94 in the sleeve 26 meshes with teeth 98 formed internally on the housing 66 and also with teeth 84 formed internally on an annular indicator member 80 free to rotate on the sleeve 26. The annular member 80 has one more gear tooth than the housing 66, and so will move through a small distance (approximately <SP>1</SP>/ 60 th of its circumference) during one revolution of the knob 106 and sleeve 26. Indicia, representing desired coarse settings, e.g. every <SP>1</SP>/ 5  inch, are inscribed on the exterior of the member 80 and are viewed through a window in the housing 66. To lock the coarse adjustment accurately in its adjusted positions an arm 174 engages slots 178, 180, 181, formed respectively in a bearing-plate 70 fixed to the housing 66, a similar plate 78 fixed to the sleeve 26, and the indicator member 80. The arm 174 is split into portions of unequal thickness and the width of the slots 178, 180, 181 is slightly less than the diameter of the arm, thus ensuring a positive lock with no backlash. The arm 174 is operated by a handle 182 outside the casing. A device to limit movement of the member 80 to one revolution is also described. It consists of a projection 159 carried by the rotatable sleeve 26 and engaging with a pawl 164 when this has been moved to its operative position by a stop (not shown) on the member 80, at either end of the travel of the member 80. The fine adjustment is similar to the coarse, the screw 220 being moved axially by turning a knob 212. Errors in the thread of the screw 220 are corrected by a slot 232, Fig. 7, in which an arm 226 is guided, and a locking arm 276 is also provided. In this case, however, indication of the setting is by a tape 250 formed of flat spring-like material, one end of which is fastened to a spool 246 mounted on the sleeve 34 which corresponds to the sleeve 26, the other end being fastened to a smaller spool 254, rotatably mounted on the housing. A fine scale covering the range between adjacent coarse settings is marked on the tape and is visible from outside the housing through a window opening. A device to limit travel of the fine adjustment members and consisting of engaging gears with interlocking projections is also described. In a modification, Fig. 9 (not shown), the tape 250 is dispensed with and is replaced by two indicators, one mounted directly on the sleeve 34 and indicating relatively large adjustments, the other being operated by a pinion gear in a similar manner to that described for the coarse adjustment shown in Fig. 3. Specification 742,962 is referred to.