Image Number 2 for United States Patent #4589230.
A grinding machine including a grinding wheel spindle motor for rotating a grinding wheel, a workpiece spindle motor for rotating a workpiece such as a gear to be ground in mesh with the grinding wheel, and a traverse motor for moving a table supporting the workpiece spindle motor. A power detector and a comparator are connected to a driver circuit for the grinding wheel spindle motor. When a load on the grinding wheel in mesh with the workpiece is increased, such a load increase is detected by the power detector and applied to a comparator. If the load signal is in excess of a reference level, then the application of a drive signal to the traverse motor is interrupted or a speed at which the workpiece is traversed relatively to the grinding wheel is reduced.