Patent GB-973078-A (GB)
Title: Gauge for measuring tire tread thickness variation
IPC: G01B7/28
Filed: 1960-11-09
Abstract: 973, 078. Electric indicating systems. GOODYEAR TIRE & RUBBER CO. Nov. 9, 1960 [Jan. 11, 1960], No. 38451/60. Heading G1N. A gauge for measuring tyre thickness variations includes means for supporting and driving the tyre arranged to contact the tyre at the interior crown area, and to position it horizontally and vertically, reciprocative means movable into contact with the outer tread area of the tyre, and means for determining the magnitude of the reciprocative movement during rotation of the tyre. The tyre is supported and driven by rotatable hemispherical members 14, an idler roller 16 riding along the crown centre line. Rollers 13 are mounted on arms which are pneumatically actuable to move the rollers downwards and outwards, pressing the tyre firmly against members 14. A bracket 18 is driven pneumatically in a vertical direction, and carries a further bracket 22 movable relative to bracket 18 by pneumatic cylinder 23. Bracket 22 carries gauging wheel 17 which is mounted on the movable member of a differential transformer 24. Limit switches 29, 30 limit the movement of bracket 18, and a disc brake 25 locks bracket 22 in its down position. If a tyre is acceptable it is marked by pen or swab 24, and after completion of a test the tyre is removed by "kicker" 31. Control circuitry (Figs. 6 and 7). On closing foot-switch 117, stepping switch 121 moves on one position, contacts 121 2,9  are closed, and coil 159 actuates cylinder 42 to move rollers 13 down. When the pressure in cylinder 42 reaches a predetermined value, pressure switch 124 closes and switch 121 advances. Contacts 121 3,8  close, energizing coil 149 to actuate cylinder 21, driving bracket 18 downwards. When limit switch 30 is closed switch 121 advances and contacts 121 4,8  close. Coil 151 then actuates cylinder 23 to lower bracket 22 until roller 17 contacts the tyre and centres differential transformer 24. Switch 126 steps switch 121 forward and contacts 121 5  close to energize relay 115/3 and time delay relay 116/1. Relay 115/3 closes contacts 115 1  to 115 3  to start the motor which rotates the tyre. The deviation of rotation is determined by relay 116/1. It closes contacts 116 1  to advance switch 121 1  whereupon contacts 121 6  close and time delay relay 118/1 is energized. After an interval for the tyre to stop rotating contacts 118 1  close and switch 121 advances, closing contacts 121 7  to energize coil 171 which actuates marker 34, and to energize time delay relay 120/1 which closes contacts 120 1  to advance switch 121. Contacts 121 8  are closed to energize coil 150 and contacts 121 3,8  open to deenergized coil 149, so that bracket 18 is raised. Simultaneously contacts 121 8 <SP>1</SP> are closed and 121 4,8  are opened to raise bracket 22. When limit switch 29 is operated switch 130 advances switch 121. Contacts 121 9 <SP>1</SP> close and 121 2   ,9  open to retract rollers 13. Simultaneously contacts 121 9  close energizing time delay relay 117/1, coil 162 and stepping counter 164. Coil 162 operates kicker 31, and contacts 117 1  subsequently advance switch 121 to close contacts 121 10 , which further advances switch 121 to position 1, completing the cycle. If a tyre is outside the tolerance limits over-tolerance relay 189/1 closes contacts 189 1  to energize relay 114/5, which in turn closes contacts 114 1 , 114 2 , and 114 3 . Simultaneously 114 4  and 114 5  are opened to disable the marking circuit. Closure of contacts 114 1  energizes relay 113/2 which lights lamp 133. Closure of contacts 114 2  completes a circuit through contacts 121 2 <SP>1</SP>, and switch 121 advances, eventually reaching position 8, whereupon the cycle continues as before. To start the machine or reset it to position 1, switch 109 is closed. Relay 111/3 is thereby energized, locks in through contacts 111 1 , and connects power lines 106, 107 to the main circuit. If the system is part of the way through a cycle and 109 is closed, relay 112/3 will also operate through contacts 121 2 , and will lock in through contacts 112 1 . Contacts 112 3  will disable the lower part of the circuit, while contacts 112 2  will energize stepping relay 123 so that switch 121 advances to position 1, whereupon contacts 121 2  are opened and normal operation is resumed. Servo unit (Fig. 4). Servomotor 46, connected to differential transformer 24, drives central shaft 50 coupled to potentiometer 52. Shaft 50 drives shafts 53, 54 having coupling members 59a, 59b arranged so that shaft 53 is driven anti-clockwise only, and shaft 54 is driven clockwise only. Brakes 61 lock the shafts in their positions of greatest displacement until the brakes are de-energized, whereupon springs 62 return the shafts to null. Shaft 54 carries a circular cam 63 adjacent a microswitch 65 normally held open until a groove 64 reaches roller 66. Switch 65 indicates when the system is at null and is equivalent to switch 126 in Fig. 6. The servo feedback is derived from eccentric cam 67 on shaft 50 acting on lever arm 68 to move the core 91 of a differential transformer 92. Potentiometers are provided on each shaft 53, 54. The output from potentiometer 52 may be fed to a chart recorder.