Patent GB-416182-A (GB)
Title: Improvements in or relating to gauges for gauging the thickness of non-magnetic material
IPC: G01B7/06
Filed: 1933-08-29
Abstract: 416,182. Gauging-apparatus. FIRESTONE TYRE & RUBBER CO., Ltd., Great West Road, Brentford, Middlesex.-(Firestone Tire & Rubber Co. ; Akron, Ohio, U.S.A.) Aug. 29, 1933, No. 23932. [Class 106 (ii).] A thickness gauge for gauging non-magnetic material comprises a magnetic member adapted to support and permit movement thereover of said non-magnetic material and a balanced circuit including a pair of transformers adapted to be unbalanced by variation of the width of the gap between one transformer and an armature caused by varying thickness of the material, an armature of the other transformer being automatically adjustable to vary its gap to effect balance. A gauging unit shown in Fig. 2 contacts with the surface of non- magnetic material which lies against the magnetizable surface of a calender roll. The unit includes an open core transformer 12 having a core 13 about which is wound primary and secondary coils 14, 15. The transformer is mounted in a non-magnetic box 16 carrying the wheels 19 of a little carriage. The box 16 is pivotally supported on a bracket 20 on an arm 21 pivoted in turn about a shaft 22. The bracket and carriage can be traversed parallel to the roll by rack and pinion gear 24, 25 and clamped. A counterweight 30 normally holds the carriage lightly against the roll, though it may be held out of engagement therewith by a detent operated by handle 33 and engaging the rack 31. The parts are made of metal unaffected by changes of temperature. The similar balancing transformer 39 is mounted in the indicating and recording instrument shown in Figs. 7, 8. It is mounted on a member 45 pivoted at one end by flexible plates 47 to a rectangular frame 46 secured to the instrument case. An O-shaped bracket 50 fastened to the frame 46 supports a micrometer screw 51. A socket 52 screwed into the end of the member 45 rests by a ball and cup on the micrometer screw. A spring 57 abuting at the top in a cup 58 in the bracket 50 and at the other end in the socket 52 holds the member 45 against the micrometer screw. The core of the transformer 39 is partly completed by an armature 60 mounted in a Y-shaped member 61 pivoted by flexible plates 62 to the frame 46. A U-shaped bracket 63 fixed to the frame 46 supports a micrometer screw 65 which engages a ball 68 in a recess 60<a> of the armature 60. A spring 70 is located between members 45 and 61 keeps the armature 60 spaced from the core 40. The micrometer screw 51 is set by hand, the shaft 82 being turned by a key (not shown) and actuating through worm gear 81, 80 a fork 76 engaging a finger 75 on the screw. A bracket 85 supports at 86 a bell-crank lever 87 one arm 87<a> of which is forked to engage a stud 88 on a recording pen 89. The other arm 87b moves over a scale 90. The shaft 82 is threaded at 82<a> to co-operate with a stud 91 carried by the arm 87b so that turning of the shaft 82 to adjust the transformer also adjusts the initial positions of the pointer on the scale 90 and of the pen 89. The latter is carried on a guide 95 so as to engage a chart 96 operated by a motor 97. The micrometer screw 65 is operated by a balancing galvanometer of known type, Fig. 13. The galvanometer coil 100 is mounted between the poles of a magnet and carries a pointer 103 which moves between stops on a rocker arm 109 pivoted at 112, and below the horizontal arms 105, 106 of bell-crank levers pivoted at 107, 108. When the galvanometer indicates a balance, the arm 103 is in the position shown and when the rocker arm is swung upwards periodically by a cam 110 on the shaft 111, the arm 103 is merely lifted upwards in the gap between the ends of the arms 105, 106. When under one of these due to unbalance, it carries up the corresponding arm and swings the long arm over to cause a clutch member 115 to swing through an angle determined by the amount of unbalance, and when the cams 120 come round they engage the ends of the member 115 and restore them turning the other member, the disc 116, through an angle. The disc shaft 125 carries a pulley over the spiral groove of which is wound a cord 122 which passes over idler pulleys 123 to a second recording gear 124. The shaft also actuates through a fork and finger 128, 129 the screw 65. This moves the armature 60 to restore balance. A pair of adjustable arcuate plates may be carried by but spaced from the pulley on the shaft 125 to engage a pair of switches to indicate by bell or light the desired limits. The primaries of the transformers 12, 39 are connected in series with a condenser 140 to a source of alternating current. The secondaries are connected in series to the heater wires of vacuum thermocouples 141, 141, 142, 142. The junction circuits are connected in series in a balanced bridge circuit 143 with the galvanometer 100.