Patent GB-1052807-A (GB)
IPC: B24B49/00
Filed: 1964-08-20
Abstract: 1,052,807. Grinding. NORTON CO. Aug. 20, 1964 [Aug. 20, 1963 (2)], No. 34183/64. Heading B3D. A process for improving the efficiency of a grinding operation by a given grade grinding wheel during relative rotation thereof comprising the step of regulating a characteristic of the grinding operation while determining the grinding ratio, i.e. the ratio of the volume of metal removed from the workpiece to the volume of wheel wear during the grinding operation, so as to change the effective hardness of said wheel during the grinding operation to increase the grinding ratio. The process may be applied to a machine for grinding flat surfaces or internal or external cylindrical surfaces. The grinding ratio is determined by measuring the volume of metal removed from the workpiece 13, Fig. 1, by multiplying the length b and the breadth a, by the depth y = (H - R) - (h - r) of the workpiece, H being the initial position and h the instantaneous position of the centre of the grinding wheel above a reference surface 15, and R and r being the initial and instantaneous radii of the grinding wheel, and dividing this by the reduction in volume of the grinding wheel, i.e. #t[(R + r)(R - r)], where t is the thickness of the wheel, r and h, Fig. 2, are continuously measured by servo-systems 22, 24, servosystem 22 having a sensing device 32, which may be of the magnetic or capacitance type and is carried by a rack 30 engaged by a pinion 26 driven by a motor M1 controlled by an amplifier responsive to the signal from the device 32. The pinion is connected to a wiper 34 of a potentiometer 36 across which is a voltage + V corresponding to the initial radius R of the grinding wheel, the position of the wiper producing a voltage corresponding to the instantaneous radius r of the wheel. The servo 24 has a transducer 44 consisting of a coil 48 which is carried by the frame 28 for the grinding wheel and is connected by an amplifier A2 to a motor M2 driving a pinion 38 engaging a rack 42 carrying an armature 46. The pinion is connected to the wiper 50 of a potentiometer 52 across which is a voltage + V corresponding to the initial height H of the grinding wheel, the wiper producing a voltage corresponding to the instantaneous height h of the grinding wheel. The voltages H and h are fed into a subtractor 58 which produces a voltage (H - h) to be fed into a further subtractor 62 which also receives a voltage (R - r) from a subtracter 60. The voltage (H - h) - (R - r) is fed into a multiplier 64 which also receives a voltage corresponding to the constant ab/#t and the product is fed to a divider 68 supplied also with a voltage (R + r) (R - r) from a multiplier 72. The quotient is the grinding ratio and is shown on an indicator 20. When the operator observes a fall in the grinding ratio he can adjust a motor 18 driving the grinding wheel to return the ratio to its maximum by increasing or decreasing the speed of the grinding wheel, and hence increasing or decreasing, respectively, the effective hardness of the wheel. The control of the speed of the grinding wheel may be effected automatically by feeding the value of the grinding ratio simultaneously to a delay means and a comparing means, the delay means feeding a signal equal to that it received after a short delay also to the comparing means which determines whether the last value of the grinding ratio is greater or less than that supplied from the delay means and adjust the speed of the motor accordingly to maintain the grinding ratio at a maximum. The Specification also describes similar circuits for maintaining the grinding ratio at a maximum during external or internal cylindrical grinding.