Coffee grinder and coffee machine containing a coffee grinder
A method for grinding coffee beans in a coffee machine is described. The method the steps of: arranging a first grinding wheel ( 55 ) and a second grinding wheel ( 57 ) in a seat ( 53 ), the grinding wheels forming a grinding volume there between and rotating one with respect to the other; introducing coffee beans into said grinding volume and grinding the coffee beans by rotating the grinding wheels one with respect to the other. Rotation of the grinding wheels is continued after grinding of the coffee beans, thus removing ground coffee therefrom by centrifugal force.
1. A coffee grinder comprising:
a first grinding wheel and a second grinding wheel arranged in a seat delimited by a side wall having a circular cross section;
a grinding volume formed between the first grinding wheel and the second grinding wheel;
a motor for rotating the first grinding wheel;
a ground-coffee outlet opening in the side wall;
wherein the motor is controlled to rotate the first grinding wheel with respect to the second grinding wheel so that coffee beans introduced in the grinding volume are ground, and to continue rotating the first grinding wheel after grinding of the coffee beans, thus cleaning the grinding volume and the seat, wherein the ground-coffee outlet opening has a side surface that extends from the side wall for projection of the ground coffee into a ground-coffee chute;
wherein the coffee grinder further comprises means to detect actual exhaustion of the coffee beans in the grinding volume; and
a control unit for controlling the motor, wherein the control unit is configured to stop rotating the first grinding wheel after a predetermined extra rotation time or extra number of turns after exhaustion is detected to perform the cleaning of the grinding volume and the seat.
2. The coffee grinder according to claim 1 , wherein the side surface of the ground-coffee outlet opening forms with a geometrical tangent direction to the side wall at the point an angle between −10° and +40° and preferably between −5° and +20° and even more preferably between −5° and +10°.
3. The coffee grinder according to claim 1 , wherein the side surface extends from the side wall to the ground-coffee chute.
4. The coffee grinder according to claim 1 , wherein the ground-coffee chute has a nearly circular cross-section.
5. The coffee grinder according to claim 4 , comprising an impact shield arranged in the ground-coffee chute for reducing a velocity of the ground coffee upon projection from the ground-coffee outlet opening into the ground-coffee chute.
6. The coffee grinder according to claim 5 , wherein the impact shield has a substantially planar impact surface facing the ground-coffee outlet opening.
7. The coffee grinder according to claim 5 , wherein the impact shield has an impact surface substantially orthogonal to the side surface of the ground-coffee outlet opening.
8. The coffee grinder according to claim 1 , wherein the first grinding wheel is provided with radial projections configured and arranged for removing ground coffee collecting in the seat, between the side wall of the seat and the first grinding wheel and the second grinding wheel, and for conveying the ground coffee towards the ground-coffee outlet.
9. The coffee grinder according to claim 8 , wherein the radial projections extend from an annular shoulder of the first grinding wheel in an axial direction beyond a grinding surface of the rotating grinding wheel to span across a slit between the first grinding wheel and the second grinding wheel.
10. A coffee machine comprising a coffee grinder according to claim 1 and an infusion unit arranged underneath the coffee grinder.
11. The coffee machine according to claim 10 , comprising a coffee-beans metering device arranged above the coffee grinder.
12. The coffee grinder according to claim 1 , wherein the ground-coffee chute has a conical shape with a top width and bottom width, wherein the bottom width is wider than the top width.
13. A method for grinding coffee beans in a coffee machine, comprising the steps of:
arranging a first grinding wheel and a second grinding wheel in a seat delimited by a side wall having a circular cross section and a ground-coffee outlet opening with a side surface which extends from the side wall of the seat and oriented to facilitate projection of ground coffee from a grinding volume formed between the first grinding wheel and the second grinding wheel and from the seat by effect of centrifugal force into a ground-coffee chute; the first grinding wheel rotating with respect to the second grinding wheel;
introducing coffee beans into the grinding volume;
grinding the coffee beans by rotating the first grinding wheel with respect to the second grinding wheel;
detecting actual exhaustion of the coffee beans in the grinding volume;
continuing rotation of the first grinding wheel with respect to the second grinding wheel, thus cleaning the grinding volume and the seat removing ground coffee therefrom by centrifugal force; and
stopping rotation of the first grinding wheel after a predetermined extra rotation time or extra number of turns after exhaustion is detected to perform the cleaning of the grinding volume and the seat.
14. The method according to claim 13 , further comprising the steps of feeding a metered amount of coffee beans in the grinding volume and rotating the first grinding wheel and the second grinding wheel one with respect to the other to grind the metered amount of coffee beans.
15. The method according to claim 13 , further comprising the step of detecting exhaustion of the coffee beans in the grinding volume and continuing rotation of the grinding wheels one with respect to the other for a time interval after exhaustion of the coffee beans.