Patent GB-744864-A (GB)
Title: Process of grinding and machine therefor
IPC: B23H5/08
Filed: 1953-09-09
Abstract: 744,864. Electrolytic grinding. NORTON GRINDING WHEEL CO., Ltd., (Norton Co.). Sept. 9, 1953, No. 24930/53. Class 41. A process of dressing a grinding wheel 65 comprises electrolytically removing material from the wheel. The grinding machine has a tank 95 of electrolyte 96, e.g. salt water, which is delivered by a pump 99 to a hose 104 and thence to a deformable nozzle 110 from which it issues between the wheel 65 and the workpiece 71 in a holder 85. The liquid collects in a pan 111 and returns to the tank 95 by a pipe 114. To dress the wheel 65 electrolytically it is made the anode in an electric circuit in which the workpiece 71 is cathode. In Fig. 6, with the connections as shown, the workpiece 71 is connected to the positive of a battery 161 and a spindle 46 for the wheel 65 is connected to the negative terminal through bushes 120, so that the workpiece 71 is ground electrolytically. The spindle 46 is driven by an electric motor 51, and as the wheel 65 glazes this motor becomes overloaded, the subsequently increased current in a relay 141 moving arms 155, 156 to reverse the connections to the workpiece 71 and wheel 65 which is thereby dressed. Suspension of the removal of stock from the workpiece 71 would lead to the stalling of an electric motor 90 which advances a slide 14 which supports the workpiece 71, and therefore as shown in Fig. 6 the relay 141 additionally serves to move an arm 170 and break the circuit to the motor 90. On the return of the motor 51 to normal conditions, the reverse effect takes place and electrolytic grinding is resumed. If desired, the wheel 65 may contact the workpiece 71 to provide abrasive grinding in addition. Various alternative circuits are described in which the spindle 46 is permanently kept positive, i.e. no electrolytic grinding of the workpiece 71 is possible. In one, a switch 146 is operated manually according to the reading on an ammeter in the circuit of motor 51. In another, the current in the circuit of motor 51 actuates a solenoid which controls the pressure on a variable carbon resistance pile in the circuit of battery 161. In a third modification, the battery 161 is dispensed with and the motor circuit and " electrolytic " circuit, which includes a bridge rectifier, are coupled through a transformer, whereby increase in the motor current is accompanied by an increase in the electrolytic current and vice versa. In a further embodiment, Fig. 11, a cathode block 261, e.g. of tungsten carbide, is substituted for the workpiece 71 in any of the above described circuits, and electrolyte is delivered via a nozzle 284 between the block 261 and the wheel 65. The block 261 is supported between two horizontal plates and urged towards the wheel face by a spring. In a modification of the embodiment of Fig. 11, see Fig. 12, stock is removed from the wheel 65 and the workpiece 71 simultaneously, the workpiece 71 being positive and the wheel 65 being negative with respect to the workpiece 71 and positive with respect to the cathode 261. Variable resistances 291, 296 enable optimum stock removal to be obtained.-