Method of operating a grinder

1. 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; and

adapting the duration for a subsequent grinding cycle based on an estimated duration of the period of active grinding of the first grinding cycle.

2. The method of claim 1 , wherein the operating parameter of the grinder is a parameter linked to the rotation speed of the grinding member.

3. The method of claim 2 , wherein the operating parameter of the grinder is indicative of a variation of the rotation speed of the grinding member.

4. The method of claim 1 , comprising acts of:

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; and

detecting a change of the rotation speed of the rotary grinding member as a function of said time delays between the pairs of subsequent rotation pulses.

5. The method of claim 4 , comprising acts of:

storing at least some of the time delays between the pairs of subsequent rotation pulses; and

locating the change of rotation speed within the grinding cycle based on the stored time delays.

6. 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.

7. The method of claim 6 , comprising acts of:

setting a first detection window within the period of active grinding;

setting at second detection window within the period of idle rotation;

calculating the first average delay between the pairs of subsequent rotation pulses within the first detection window; and

calculating the second average delay between the pairs of subsequent rotation pulses within the second detection window.

8. The method of claim 6 , wherein the threshold delay value is calculated as a mean value between the first average delay and the second average delay.

9. The method of claim 6 , wherein if a difference between the first average delay and the second average delay is below a given threshold, the grinding cycle is aborted.

10. The method of claim 1 , wherein the operating parameter is one of a power required to drive the grinding member into rotation and a parameter linked to said power.

11. The method of claim 1 , wherein the rotary grinding member is rotated by an electric motor and wherein the operating parameter of the grinder is an electric parameter of the electric motor.

12. The method of claim 11 , wherein the electric parameter is an electric current absorbed by the electric motor.

13. The method of claim 1 , wherein the operating parameter is one of a torque applied to the grinding member and a function of said torque.

14. The method of claim 1 , wherein said material to be ground are coffee beans.

15. 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.

16. The method of claim 15 , comprising an act of:

locating a rotation pulse number corresponding to the threshold delay.

17. The method of claim 16 , comprising an act of:

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.

18. The method of claim 15 , wherein the sensor arrangement is configured to detect rotation of the rotary grinding member, 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.