Mill and beverage preparation apparatus including the same

1. A mill, comprising:

a first mill provided with a first grinding surface; and

a second mill provided with a second grinding surface,

the first grinding surface including a first groove in a curved shape which extends from a side of a center of rotation toward an outer circumference,

the second grinding surface including a second groove in a curved shape which extend from the side of the center of rotation toward the outer circumference, and

the first groove and the second groove not being completely superimposed on each other and an angle of intersection β between the first groove and the second groove being 10°≤β≤50° while the first grinding surface and the second grinding surface are superimposed on each other.

2. The mill according to claim 1 , wherein

the first groove has a shape extending along an equiangular spiral and an angle α 1 formed between a half line extending from the center of rotation and the first groove is 0°<α 1 <45°, and

the second groove has a shape extending along an equiangular spiral and angle α 1 formed between the half line extending from the center of rotation and the second groove is 0°<α 1 <45°.

3. The mill according to claim 1 , wherein

a plurality of second grooves are provided in rotation symmetry with respect to the center of rotation,

the plurality of second grooves further includes one branch portion or a plurality of branch portions and a third groove extending from the branch portion toward an outer circumferential portion, and

the third groove extending from the branch portion toward the outer circumferential portion is arranged in rotation symmetry between the plurality of second grooves and curved in a direction the same as the plurality of second grooves.

4. The mill according to claim 3 , wherein

the third groove is provided with the branch portion at a position satisfying 0.2×D 1 ≤dX≤0.6×D 1 , where D 1 represents an outer diameter of the second mill and dX represents a distance from the center of rotation to the branch portion.

5. The mill according to claim 1 , wherein

the first mill and/or the second mill further include(s) a plurality of fourth grooves provided in rotation symmetry with respect to the center of rotation, and

an angle α 2 formed between the half line extending from the center of rotation and the fourth groove is 45°<α 2 <90°.

6. The mill according to claim 5 , wherein

the first mill and/or the second mill further include(s) a side surface in a cylindrical shape which defines in a central portion, an inlet port through which an object to be grated is introduced, and an intake groove opening into the grinding surface from the side surface,

a plurality of intake grooves are provided in rotation symmetry with respect to the center of rotation,

each of the plurality of intake grooves has an inclined surface increasing in depth toward the center of rotation, and

each of the plurality of intake grooves corresponds to the fourth groove in number and has a terminal end coinciding with a starting point of the fourth groove.

7. The mill according to claim 6 , wherein

a condition of d 6 ≤0.5×D 1 and dE≤0.9×D 1 is satisfied, where D 1 represents an outer diameter of the first mill, d 6 represents a diameter of the terminal end of each of the plurality of intake grooves, and dE represents a diameter of the terminal end of the fourth groove,

each of the plurality of intake grooves is arranged in a region lying between the side surface and d 6 , and

the fourth groove is arranged in a region lying between the side surface and the diameter of the terminal end of the fourth groove.

8. The mill according to claim 5 , wherein

a flat portion where no first groove is present is provided around an entire circumference of an outermost circumferential portion of the first grinding surface,

a flat portion where no second groove is present is provided around an entire circumference of an outermost circumferential portion of the second grinding surface,

a width w of the fourth groove along a direction orthogonal to a direction of extension of the fourth groove is within a range of 0.3 mm≤w≤1.5 mm,

the fourth groove has an inclined surface increasing in depth toward the center of rotation,

a depth d from the first grinding surface at the terminal end of the fourth groove is within a range of 0.1 mm≤d≤2 mm, and

an angle of inclination Θ of the inclined surface with respect to the first grinding surface is within a range of 0°≤Θ≤4.5°.

9. The mill according to claim 3 , wherein

the first groove has a width w along a direction orthogonal to a direction of extension of the first groove within a range of 0.3 mm≤w≤1.5 mm, has an inclined surface increasing in depth toward the center of rotation, has a depth d from the first grinding surface on an outermost circumferential side of the inclined surface within a range of 0.1 mm≤d≤1 mm, and has an angle of inclination Θ of the inclined surface with respect to the first grinding surface of 0°≤Θ≤4.5°,

the second groove has width w along a direction orthogonal to a direction of extension of the second groove within a range of 0.3 mm≤w≤1.5 mm, has an inclined surface increasing in depth toward the center of rotation, has depth d from the second grinding surface on the outermost circumferential side of the inclined surface within a range of 0.1 mm≤d≤1 mm, and has angle of inclination Θ of the inclined surface with respect to the second grinding surface of 0°≤Θ≤4.5°, and

the third groove has width w along a direction orthogonal to a direction of extension of the third groove within a range of 0.3 mm≤w≤1.5 mm, has an inclined surface increasing in depth toward the center of rotation, and has depth d from the second grinding surface on the outermost circumferential side of the inclined surface within a range of 0.1 mm≤d≤1 mm.

10. A mill, comprising a first mill and a second mill each provided with a grinding surface,

the grinding surface of each of the first mill and the second mill including at least one groove extending from a center of rotation of the grinding surface toward an outer circumference of the grinding surface, and

the at least one groove having a shape extending along an equiangular spiral, wherein

the at least one groove is provided in rotation symmetry with respect to the center of rotation, and

an angle α 2 formed between a half line extending from the center of rotation and the at least one groove is 45°<α 2 <90°.

11. The mill according to claim 10 , wherein

the at least one groove includes a plurality of first grooves provided in rotation symmetry with respect to the center of rotation, and

an angle α 1 formed between the half line extending from the center of rotation and the plurality of first grooves is 0°<α 1 <45°.

12. The mill according to claim 11 , wherein

a flat portion, where none of the plurality of first grooves is present, is provided around an entire circumference of an outermost circumferential edge portion of the grinding surface,

a width w along a direction orthogonal to a direction of extension of the plurality of first grooves is within a range of 0.5 mm≤w≤1.5 mm,

the plurality of first grooves have an inclined surface increasing in depth toward the center of rotation,

a depth d from the grinding surface on an outermost circumferential side of the inclined surface is within a range of 0.1 mm≤d≤1 mm, and

an angle of inclination Θ of the inclined surface with respect to the grinding surface is 2.3°≤Θ≤4.5°.

13. A beverage preparation apparatus for preparing beverages with powders, comprising:

a milling machine for obtaining the powders by grating an object to be grated;

a tank for storing a liquid; and

an agitation tank supplied with the powders obtained by the milling machine and the liquid, for mixing the powders and the liquid,

the milling machine including the mill according to claim 1 .