United States Patent: 3552661

[US Patent & Trademark Office, Patent Full Text and Image Database]

( 3906 of 3906 )

United States Patent	3,552,661
Bourne	January 5, 1971

MILL WITH ROTATING AIR STREAM

Abstract

A mill comprising a casing and a drumlike stator mounted axially within the casing and in spaced relationship to the wall thereof. The stator is open at the end adjacent the mill inlet and closed at the end adjacent the mill outlet. An inlet to the casing is provided through which air may be introduced into the interior of the stator. A plurality of vanes is associated with the peripheral wall of the stator and extends lengthwise thereof. Slots are provided between the vanes through which air emerges from the stator with a rotational movement imparted by the vanes. An inlet to the casing is provided through which material to be processed may be introduced into the annular space between the wall of the casing and the peripheral wall of the stator there to be contacted by the rotating air stream. An axial outlet from the casing is provided at the opposite end to the air inlet. A drive shaft extends axially into the casing with a vaned classifier rotor mounted on the inner end of the drive shaft between the stator and the outlet. The rotating airstream causes the material particles to rub against one another and also to be impacted against the interior of the casing.

Inventors:	Bourne; Ronald Frederick (Transvaal, ZA)
Assignee:
Appl. No.:	04/777,707
Filed:	November 21, 1968

Foreign Application Priority Data


Dec 06, 1967 [ZA]			67/7359

Current U.S. Class: 241/39

Current International Class: B02C 13/08 (20060101); B02C 13/00 (20060101); B02c 019/06 ()

Field of Search: 241/5,39,47,52,53,55,56,274,275

References Cited [Referenced By]

U.S. Patent Documents


2092307	September 1937	Gaffney
2981489	April 1961	Hannum
3423034	January 1969	Hippert

Foreign Patent Documents


510,849	Jan., 1933	DT

Primary Examiner: Kelly; Donald G.

Claims

I claim:

1. A mill comprising a casing; a hollow cylindrical stator mounted axially within the casing and in spaced relationship thereto, said stator having a peripheral wall and being open at one end and closed at the other; an inlet to the casing through which air may be introduced into the interior of the stator through the open end thereof; a plurality of vanes around the peripheral wall of the stator and extending lengthwise thereof; slots between the vanes through which air emerges from the stator with a rotational movement imparted by the vanes; an inlet to the casing through which material to be processed may be introduced into the space between the casing and the stator there to be contacted by the rotating airstream; an axial outlet from the casing at the opposite end to the air inlet; a drive shaft extending axially into the casing; a vaned classifier rotor mounted on the drive shaft between the closed end of the stator and the outlet; and means for inducing a flow of air into the casing.

2. The mill of claim 1, in which the air inlet is arranged to impart rotational movement to the airstream before it enters the stator.

Description

This invention relates to mills such as are used for reducing particles to finer fractions.

The main object of the invention is to provide a novel type of mill which will perform the function of grinding, separating and classifying materials.

A mill in accordance with the invention comprises a casing; a drumlike stator mounted axially within the casing and in spaced relationship to the wall thereof, said stator being open at the end adjacent the mill inlet and closed at the end adjacent the mill outlet; an inlet to the casing through which air may be introduced into the interior of the stator; a plurality of vanes associated with the peripheral wall of the stator and extending lengthwise thereof; slots between the vanes through which air emerges from the stator with a rotational movement imparted by the vanes; an inlet to the casing through which material to be processed may be introduced into the annular space between the wall of the casing and the peripheral wall of the stator there to be contacted by the rotating airstream; an axial outlet from the casing at the opposite end to the air inlet; a drive shaft extending axially into the casing; a vaned classifier rotor mounted on the inner end of the drive shaft between the stator and the outlet; and means for inducing a flow of air into the casing.

The air may be introduced under pressure. Alternatively, atmospheric air may be drawn into the casing under suction.

Also according to the invention, the air inlet is arranged to impart rotational movement to the air stream before it enters the casing.

The mill of the invention will be further described, purely by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a longitudinal section through a mill according to the invention;

FIG. 2 is a cross section on the line II-II of FIG. 1;

FIG. 3 is a cross section on the line III-III of FIG. 1, on an enlarged scale; and

FIG. 4 is a diagrammatic view of the mill and ancillary equipment.

Referring to the drawings, the casing 1 is in the form of a cylindrical drum having an inlet 2 for material to be treated at or near one end thereof. At the same end of the drum there is provided a conelike axially disposed inlet 3 for air. The air is introduced tangentially into the cone and it enters the mill in a rotating stream.

Within the casing 1 and adjacent the inlet end thereof, a stator 4 is mounted on an axial sleeve 5. The stator is in the form of a drum which is open at the end adjacent the air inlet 3 and closed at the other end. The periphery of the drum is provided with a plurality of lengthwise slots 6 extending between lengthwise vanes 7. The incoming airstream enters the interior of the stator and emerges through the slots at high velocity. The vanes 7 impart further rotational movement to the airstream.

An axial outlet duct 8 is provided at the opposite end of the casing to that in which the air inlet is disposed.

A drive shaft 9 extends through the stator-supporting sleeve 5 and it carries on its inner end a vaned rotor 10 which is disposed between the stator 4 and the outlet duct 8. The rotor comprises a plurality of blades 11 and concave annular shrouds 12 and 13 supported in spaced relationship to one another by the blades which extend between them.

Optionally, the lower part of the casing adjacent the rotor is provided with an outlet 14 for oversize material. The duct 8 is mounted in a cylindrical guide sleeve 15 which is carried by arms 16 and it is adjustable axially towards and away from the rotor 10. This adjustment enables the gap, and therefore any inward leak of atmospheric air, between the duct 8 and rotor 10 to be set at a minimum or as desired.

In one embodiment, air is introduced into the casing by means of a pressure fan 17 and is discharged therefrom via a suction fan 18. This arrangement will cause the highest velocity. The suction fan may be dispensed with if desired. In an alternative arrangement, the pressure fan is dispensed with and air flow induced by the suction fan alone.

In use, air emerges through the slots in the stator at a predetermined velocity. The rotating airstream causes the particles introduced into the casing to rub against one another and also to be impacted against the interior of the casing. This reduces the particles in size and they pass to the rotor zone where the rotor acts as a classifier. The fines together with air leaves the mill via the outlet duct and the oversize fraction is either retained for further reduction or, in the case where a separate outlet for oversize particles is provided, removed therethrough.

The mill of the invention not only has less wearing parts than the conventional type of impact mill but the effect on the material to be treated may be varied by altering the velocity of the airstream. Thus, in the treatment of asbestos a relatively low air velocity may be employed and fibre together with sized grit may be withdrawn from the mill with minimum damage to the fibre. This sized grit can all be removed subsequently by a suitable screening operation. On the other hand, extremely high velocities can be employed for materials for which they are especially suitable.

* * * * *

Current U.S. Class:	241/39
Current International Class:	B02C 13/08 (20060101); B02C 13/00 (20060101); B02c 019/06 ()
Field of Search:	241/5,39,47,52,53,55,56,274,275