US2731209A - Cyclone mills - Google Patents

Description

Jan. 17, 1956 E. MARE CYCLONE MILLS Filed Oct. 8, 1952 United States Patent CYCLONE MILLS Ernest Mare, Johannesburg, Transvaal, Union of South Africa Application October 8, 1952, Serial N 313,671

10 Claims. (Cl. 241-56) and relates particularly to the type of mill which comprises;

a chamber housing a rotor which latter acts to disintegrate 2,731,209 Patented Jan.v 17, 1956 which may be of any suitable shape, and the rotor 3 is fitted with projecting members of different types depend ing on the purpose for which the mill is to be used.

For example, in the milling of asbestos cobs, the rotor 3 is fitted with replaceable fins 23 and the material is fed into the conical chamber 1 through inlet 2 and directed onto the rotor 3 which projects it outwardly so that it impacts the liners 22 of the wall 6 causing a separation of the rock and fibre. The air-stream from the fan 16 passes through the passageways 9 and radially over the base 4 of the rotor 3 as indicated by the arrows, scavengingthe the material fed onto the rotor by projecting it outwardly against the walls of the chamber.

In this type of mill the light or fine material is entrained in an air stream to be discharged from the mill and the control of the degree of milling and/or separation is very largely dependent on the strength and direction of the air stream. It is the object of this invention to provide a mill in which the air stream through the mill may be more efiectively utilized for the separation of the material to be treated and also to provide means for the eflicient breaking up and/ or blending of the material.

According to this invention there is provided a mill comprising a chamber provided with a discharge opening and housing a rotor having an outwardly flanged base forming the floor of the chamber, inlet air passageways to the chamber through the lower part of the rotor, means for directing the inlet air radially over the flanged base, and a fan or the like for discharging a stream of air upwardly through said inlet air passageways.

This invention is illustrated in the accompanying drawings in which:

Fig. 1 is a sectional side elevation of the centrifugal mill;

Fig. 2 is a view similar to Fig. l but showing the top structure only of a modified type of mill, and

Fig. 3 is a view similar to Fig. 2 showing a further modified form of the invention.

As shown in Fig. 1 there is provided a truncated conical chamber 1 with a discharge opening 2 at its apex. Inside the chamber 1 is fitted centrally a conical rotor 3 with its axis vertical and having an outwardly flanged base 4 with a clearance space 5 between the walls 6 of-the chamber 1 and the periphery of the flanged base 4. The bottom of the rotor 3 is mounted on a boss 7 secured to the upper end of a vertical shaft 8. Air passageways 9 are provided curving outwardly below the coned portion of the rotor 3 to direct the air stream radially over the top of the flanged base 4 which forms the floor 10 of the chamber 1.

The walls 6 of the conical chamber 1 are mounted on suitable stanchions 11 to which are secured the bearings 12, 13 for the shaft 8 carrying the rotor 3, a pulley 14 being secured to the shaft 8 between the bearings 12, 13. Below the floor 10 of the conical chamber 1 is a second chamber 15 conveniently closed by the upper bearing 13 of the rotor shaft 8. A fan 16 is secured to the lower end of the rotor shaft 8 and is enclosed in a housing 17 attached to the stanchions 11 and connected by a suitable air duct 18 to said second chamber 15. The fan intake 24 is fitted with a sliding cover 19 or the like, to control the flow of air through the same.

The conical chamber 1 has a feed chute or pipe 20 directed towards the apex 21 of the rotor 3. The inner Walls 6 of the chamber are fitted with replaceable liners 22 separated fibre and lighter rock particles from the floor 10 of the chamber 1' and carrying them upwardly through the discharge duct 2 whence they are led to a decompression chamberand cyclone. separator in the normal way. The air may be discharged to atmosphere from the cyclone or alternatively led back to the fan intake 24 in a closed circuit thus obviating the necessity for an additional fan.

The particles which are too heavy to be entrained in the air stream are subjected to repeated attrition or impact in the mill until they have attained the requisite degree of fineness, the size of the particles-finally discharged being, of course, dependent on the strength of the air stream which can be controlled by the cover 19 of fan inlet 24. A certain amount of the air will flow through the clearance space 5 and assist in preventing material falling below the rotor 3. a

.The fan 16 may be connected to the rotor shaft 8 through suitable gearing so that its speed relative-to the rotor 3 may be varied. This is particularly desirable, for instance, in one modification of this invention, as shown in Fig. 3, in which balls are inserted in the chamber 1 to assist or effect the milling operation. In this case the rotor 3 will normally be rotated at a slower speed than the fan 16 and the flanged rotor base 4 and adjacent surfaces are curved to form an annular dished floor 25 for the chamber which assists in confining the movements of the balls 28. For normal operations however, and as shown in Fig. l the base 4 of the rotor 3 is flat and has mounted thereon a number of radially positioned beater bars 29, and fan 16 and rotor 3 are mounted on the same shaft 8.

The mill according to this invention is also applicable for use in the blending or mixing of materials particularly those which are in a finely divided and/or friable form, such as pigments for paints and milled asbestos fibres. In this case the inlet 20 is preferably closed and the material fed in through the fan inlet 24. The incoming material is initially broken up and mixed in its passage through the fan 16, duct 18 and chamber 15 and the process completed by the rotor 3 in the chamber 1. The mixing of the material-may be further assisted by fitting the rotor with outwardly and radially projecting arms 26, as in Fig. 2, which rotate between corresponding arms 27 projecting inwardly from the walls 2.

The mill may also be used for treatment of relatively soft materials such as the dehulling of tung nuts. in this case to prevent complete breakdown of the nuts it is generally necessary to remove the upper part of the rotor 3 and the beater bars 29 and for this reason, and also for replacement, they are made easily detachable.

In all cases the flow of air upwardly through the lower part of the rotor and outwardly over the flanged base of the same acts to ensure proper scavenging and control of the dimensions and/or weight of the product discharged through the outlet 2.

What I claim as new and desire to secure by Letters Patent is:

l. A cyclone mill comprising a housing having walls forming a chamber, a rotor having a conical upper surface and a flange-shaped base both rotatably supported in said chamber, said rotor having fins projecting radially from said conical surface, said base having beater bars 3 on its upper side forming grooves therebetween and extending radially from adjacent the bottom of said conical surface to the periphery of said base, said base also having passageways extending through it from bottom to top,

said passageways including means for forcing air upwardly through them; the peripheral edge of said base and the adjacent portion of said chamber walls being inclined upwardly and outwardly relative to the bottom of said base to form an annular space of matching inclination,

and means for forcing a stream of air upwardly through said annular space and for assisting flow through said passageways.

2'. A cyclone mill comprising a housing having first walls forming a chamber, a rotor having a conical upper surface and a flange-shaped base both rotatably supported in said chamber, said rotor" having fins projecting radiallyfrom said conicalsurface, the peripheral edge of saidbase being spaced from said chamber walls, and a 'fan for forcing air upwardly through the space between said base and said walls.

'3'. A cyclone mill as claimed in claim 2 in which said housing includes an inlet passage directed toward the center of-said rotor.

4'. A cyclone mill as claimed in claim 2- in which said chamber includes an inlet aperturepositioned above and 7. A cyclone mill as claimed in claim 2 in which said housing has second walls forming a fancasing, said fan being located in said casing, said casing being positioned below said rotor and having a discharge connection to a position adjacent the bottom of said base.

8. A cyclone mill comprising a housing having walls forming a chamber, a rotor having a conical upper surface and a flange-shaped base both rotatably supported in said chamber, said rotor having fins projecting radially from said conical surface, the peripheral edge of said base and the adjacent portion of said chamber walls being inclined upwardly and outwardly relative to the bottom of said base. to form anannular'space ofimatchingrincli-nation, means for forcing a stream of air upwardly through said annular space, and means for directing a flow of air radially outwardly across the top of said base.

9. A cyclone mill as claimed in claim 8 in which said rotor has at least one arm projecting radially outwardly from said conical surface and in which said chamber walls have adjacent said conical surfac'cat least one arm project-- ing radially inwardly, said" arms having an overlapping relation between them.

10; A cyclone mill as claimed in claim 8 in which said base has a dished upper surface, and balls distributed in said dished uppersmface;

References Cited'inthe file of this patent UNITED STATES PATENTS 2,092,307 Gaft'ney' Sept. 7',v 1937 FOREIGN PATENTS 352,443 GreatBritain "Minn-" Aug. 6,. 1.931

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