Rotary drum mill and relevant inner lining

Abstract

 Mill comprising a drum (1) which can be rotated around its longitudinal axis and is provided with an inner lining (2, 3) made of an elastomeric material comprising at least one helicoidal rib of elastomeric material which develops along the inner surface of the drum (1) and substantially acts as a cochlea for the milling bodies and/or the material to be milled. The present invention also relates to an inner lining for this mill.

Description

[0001] The present invention relates to a rotary drum mill and in particular to a mill with a cylindrical or frusto-conical rotary drum having an inner lining which improves the efficiency of the milling bodies and allows to distribute them along the longitudinal axis according to their size.

[0002] US 2949247 discloses a mill having an inner lining which comprises a plurality of ribs which are parallel to each other and are slightly inclined with respect to the generatrixes of a cylindrical drum, for example with an angle of about 10°. With this arrangement, the milling bodies, during the rotation of the cylindrical drum, are hampered in their falling from said ribs, so that the bigger milling bodies immediately jump over the ribs, while the smaller ones initially tend to roll along them until the rotation of the drum does not allow their climbing. Therefore, the bigger milling bodies tend to arrange close to the entrance of the cylindrical drum, while the smaller ones arrange themselves at a distance from the entrance which is inversely proportional to their size.

[0003] However, this known lining has the drawback of reducing the efficiency of the whole mill, since said ribs, forming an obstacle to the motion of the milling bodies, lower their kinetic energy and thus their milling power.

[0004] Furthermore, said ribs tend to wear quickly, so that they must be often replaced, with a consequent increase of the costs and the interruptions for the maintenance.

[0005] It is therefore an object of the present invention to provide a mill having an inner lining which is free from said disadvantages. Said object is achieved with a mill and a lining, the main features of which are disclosed in claims 1 and 12, while other features are disclosed in the remaining claims.

[0006] As a matter of fact, the rotary drum of the mill according to the present invention is provided with a helicoidal rib which, acting as a cochlea, separates the smaller milling bodies and milled material from the bigger ones, since the latter undergo the effect of this cochlea in a lower manner, since they can climb their turns more easily. Therefore, the working principle of said helicoidal rib is completely different from the one of the ribs of the prior art.

[0007] Furthermore, said helicoidal rib does not hamper the motion of the milling bodies, which thus maintain their efficiency substantially unaltered, since its turns are almost perpendicular to the generatrixes of the rotary drum and not almost parallel thereto, as in the prior art.

[0008] According to a particular aspect of the invention, the inner lining of the mill is made up of elastomeric bars and/or panels which are easily replaceable thanks to a joint system for their mutual joining and/or fixing to the rotary drum, so as to reduce the maintenance costs and times.

[0009] Further advantages and features of the mill and the lining according to the present invention will become clear to those skilled in the art from the following detailed and non-limiting description of an embodiment thereof with reference to the attached drawings, wherein:

• figure 1 shows a side view in a longitudinal section of the mill according to said embodiment, which is partially provided with the inner lining;
• figure 2 shows an enlarged partial and sectioned view of the lining of the mill of figure 1;
• figure 3 shows a view sectioned along plane III-III of the lining of figure 2 (for clarity the curvature of the mill is not illustrated in figure 3).

[0010] Referring to said figures, it is seen that the mill according to the present embodiment of the invention comprises in a known way a drum 1, in particular substantially cylindrical or frusto-conical, which can be rotated by an external motor (not visible in the figure) around its longitudinal axis, which is arranged horizontally or slightly inclined. Drum 1 is provided with an inner lining made of an elastomeric material which protects its inner surface from the collisions of the milling bodies which are arranged therein together with the material to be milled.

[0011] According to the invention, one or more bars 2 of elastomeric material are arranged in drum 1 in a slightly curved manner one after the other so as to form at least one helicoidal rib which develops along the inner surface and substantially acts as a cochlea for the milling bodies and/or the material to be milled. Therefore, bars 2 form with the generatrixes of drum 1 a wide angle, at least greater than 60°, and not, as in the prior art, a small angle, in particular equal to about 10°, which does not allow that bars 2 form a helicoidal rib acting as a cochlea, since they start from one end to the other of drum 1 without even forming a turn inside it. In particular, in the present embodiment, the angle formed by bars 2 with the generatrixes of drum 1 is comprised between 75° and 85°.

[0012] One or more panels 3 of elastomeric material having a height smaller than the height of bars 2 and a substantially parallelepiped shape are further arranged between a turn of the helicoidal rib formed of bars 2 and an adjacent turn or an end of drum 1. Obviously, bars 2 and panels 3 are cut at the ends of drum 1, so that they do not protrude beyond them.

[0013] For increasing the efficiency of the milling bodies, panels 3 are provided with humps 4 preferably having a height lower than the difference between the heights of bars 2 and panels 3. In particular, the height of bars 2, of panels 3 and of the relevant humps 4 is comprised between 12 and 30 cm, 4 and 6 cm and 2 and 4 cm, respectively. Furthermore, humps 4 are preferably arranged in a manner substantially perpendicular to bars 2.

[0014] For facilitating the assemblage and the maintenance of the inner lining of the mill, a plurality of section bars 5 are fixed inside drum 1, preferably in a manner substantially perpendicular to bars 2. The cross-section of the section bars 5 is shaped for the joint into corresponding grooves made in the lower wall of bars 2 and/or panels 3. In panels 3 these grooves are preferably arranged under humps 4.

[0015] Furthermore, one or more side walls of bars 2 and/or panels 3 are provided with longitudinal ribs 6 and the opposite walls are provided with corresponding longitudinal grooves. With this arrangement, bars 2 and panels 3 can fit with the adjacent bars 2 and/or panels 3, thereby improving their mutual joining.

Claims

1. Mill comprising a drum (1) which can be rotated around its longitudinal axis and is provided with an inner lining (2, 3) made of an elastomeric material, characterized in that this inner lining (2, 3) comprises at least one helicoidal rib of elastomeric material which develops along the inner surface of the drum (1) and substantially acts as a cochlea for the milling bodies and/or the material to be milled.

2. Mill according to the previous claim, characterized in that said helicoidal rib is made up of one or more bars (2) of elastomeric material are arranged in a slightly curved manner one after the other.

3. Mill according to claim 2, characterized in that the drum (1) is substantially cylindrical or frusto-conical and the bars (2) form with the generatrixes of the drum (1) an angle greater than 60°.

4. Mill according to claim 3, characterized in that the bars (2) form with the generatrixes of the drum (1) an angle comprised between 75° and 85°.

5. Mill according to one of the previous claims, characterized in that one or more panels (3) of elastomeric material having a height smaller than the height of bars (2) and a substantially parallelepiped shape are arranged between a turn of the helicoidal rib formed of the bars (2) and an adjacent turn or an end of the drum (1).

6. Mill according to claim 5, characterized in that said panels (3) are provided with humps (4).

7. Mill according to claim 6, characterized in that the height of said humps (4) is lower than the difference between the heights of the bars (2) and of the panels (3).

8. Mill according to claim 6 or 7, characterized in that the humps (4) are arranged in a manner substantially perpendicular to the bars (2).

9. Mill according to one of the previous claims, characterized in that a plurality of section bars (5) are fixed inside the drum (1), the cross-section of these section bars (5) being shaped for the joint into corresponding grooves made in the lower wall of the bars (2) and/or of the panels (3).

10. Mill according to claim 9, characterized in that the section bars (5) are fixed inside the drum (1) in a manner substantially perpendicular to the helicoidal rib.

11. Mill according to claim 9 or 10, characterized in that the lower grooves of the panels (3) are arranged under the relevant humps (4).

12. Lining for mills with a rotary drum (1), characterized by comprising a bar (2) of elastomeric material having the lower wall provided with grooves for the joint into corresponding section bars (5) fixed inside the drum (1).

13. Lining according to claim 12, characterized in that one or more side walls of the bar (2) are provided with longitudinal ribs (6) and that the opposite walls are provided with corresponding longitudinal grooves.

14. Lining according to claim 12 or 13, characterized in that the height of the bar (2) is comprised between 12 and 30 cm.

Drawing