Method of operating a grinder

A method of operating a grinder comprising at least a rotary grinding member, the method comprising acts of:

• starting a first grinding cycle having a duration;
• feeding the grinder with a given amount of material to be ground and grinding said material by rotating the rotary grinding member for a period of active grinding;
• idly rotating the rotary grinding member for a period of idle rotation following the period of active grinding, for removing residual ground material from the grinder, the period of active grinding and the period of idle rotation defining a grinding cycle;
• estimating when the given amount of material has been ground based on an operating parameter of the grinder;
• adapting the duration for a subsequent grinding cycle based on an estimated duration of the period of active grinding of the first grinding cycle;
• providing a sensor arrangement configured to detect rotation of the rotary grinding member and configured to generate rotation pulses corresponding to revolutions of the rotary grinding member;
• detecting time delays between pairs of subsequent rotation pulses, wherein a change of the rotation speed of the rotary grinding member is detected as a function of said time delays between the pairs of subsequent rotation pulses;
• storing the time delays between the pairs of subsequent rotation pulses during the grinding cycle;
• calculating a first average delay between the pairs of subsequent rotation pulses within the period of active grinding;
• calculating a second average delay between the pairs of subsequent rotation pulses within the period of idle rotation;
• calculating a threshold delay value between the first average delay and the second average delay;
• locating a rotation pulse number corresponding to the threshold delay;
• and
• setting a total number of rotation pulses between a start of the period of active grinding and the rotation pulse number corresponding to the threshold delay value as a duration of the period of active grinding.

A method of operating a grinder comprising at least a rotary grinding member for grinding a given amount of material to be ground, the method comprising acts of:

• starting a grinding cycle having a duration, the grinding cycle comprising a period of active grinding of the rotary grinding member and a period of idle rotation of the rotary grinding member;
• estimating when the given amount of material has been ground based on an operating parameter of the grinder;
• adapting the duration for a subsequent grinding cycle based on an estimated duration of the period of active grinding of the grinding cycle;
• providing a sensor arrangement configured to generate rotation pulses corresponding to revolutions of the rotary grinding member;
• detecting time delays between pairs of subsequent rotation pulses;
• storing the time delays between the pairs of subsequent rotation pulses during the grinding cycle;
• calculating a first average delay between the pairs of subsequent rotation pulses within the period of active grinding;
• calculating a second average delay between the pairs of subsequent rotation pulses within the period of idle rotation;
• calculating a threshold delay value between the first average delay and the second average delay.