CA2048879A1 - Rotary grinder - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

The inner surface of the outer wall of the grinder portion of a grinder-classifier for grinding solid mineral into fine particles or powder is lined with rubber-like material. The mineral to be ground bounces off from the wall and collides with other similar particles of mineral thereby fragmenting them. This grinder can grind over 100 tons of mineral without showing any signs of wear appearing ususally in metal grinders.

Description

2~87~3 IMPROVEMENT IN ROTARY GRINDER

The present invention relates to an improvement in apparatuses for grinding solid mineral into fine particles. Particularly, the invention relates to lining the inner surface of the grinder chamber of a grinder-classifier apparatus with resilient material such that the grinding is done by colliding the mineral against itself.

Rotary grinder-classifiers for grinding solid mineral into a fine powder or particles generally function by forcing the mineral to be ground on the outer wall of ~ a grinding chamber by the fast rotation of hammers.
;~ 15 It has usually been understood with this type of grinders, whether the axis of rotation is vertical or horizontal, that the grinding action is done by the friction of the mineral between the metal wall and thé hammers.~However, since these grinders are all made of metal, the outer wall and hammers wear : ou~ rather rapidly.

It hae now surprisingly been found~that a better and faster~gr~inding can be achleved by lining the inner 25 surface o:E the o uter wall with a resilient material~
such~that~ the~ solid~ mineral does not fragmPnt upon e ~ r ~ t ~ ~_ne~ ~po~ hittl:~

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2 ~ 7 9 similar mineral after bounci~g from the wall.

Therefore, the present invention provides a rotary grinder-classifier for grinding solid mineral into fine par~icles, the grinder comprising a grinding chamber comprising inlet means, outlet means, and an outer ring having an inner surface, a rotor rotating around a central axle .for driving a plurality of hammers, these hammers forcing the mineral.against the ring, where the inner surface of the outer ring is lined with resilient material, in such a manner that the mineral bounces off against other mineral upon hitting the lined surface, thereby facilitating the grinding.

In drawings which illustrate 0xamples of embodiments . ~
~; of:the lnvention:

Figure 1 lS a~broken-away top plan view of a grinder according to the lnvention;

Figure 2 is~a broken-away cross-section view of the grinder: portion of a grinder-classifier of figure 1 when~out along~llnes 2-2.

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DETAILED DESCRIPTION OF EXAMPLES OF PREFERRED
EMBODIMENTS OF THE INVENTION.

Figure 1 shows the grindler portion of grinder-cl~ssifier. Two horizontal plates lOa and lOb are bolted 12 on top of each other and separated by a circular outer wall referred to as outer ring 14.
The space inside the plates and the ring defines a grinding chamber 16. Inside the chamber 16 there is a rotor plate 18 held and driven by a central vertical :~ axle 20. The rotor 18 is provided with a plurality of hammers 22 (anywhere from 4 to 16) which are : connected to its periphery at approximately an angle ; 15 of 10 degrees (arrow A) but will vary depending on the mineral to be ground. Of course, ~he hammers 22 are positioned at such a distance that they do not touch the outer ring 14 while rotating.
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The upper plate lOa has inlet means, preferably constituting of an inlet aperture 28 where the mineral is carried by a conveyor, an auger, or the like. The mlneral is inserted in the chamber 16 through this lnlet 28 and ~dispersed radially by the :: 25 action of the rotating rotor~lU and hammers 22. The mineral is thereby forced against the inner surface 24 of the~outer~rlng 14.

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This inner surface 24 of the outer ring 14 i8 lined with a layer of resilient material such as rubber~
like polymer natural or synthetic all around its circumference. Preferably, the hitting face of the hammer 22 (the side that faces the movement of rotation) is also lined with a layer of resili~nt material 26. This changes entirely the mechanism o~
grinding. The mineral is ground by bouncing on the rubber-lined surfaces and colliding with other particles of mineral.

Figure 2 shows the grinding chamber 16 where the solid mineral is inserted via the inlet 28 while the ~; 15 rotor plate rotates in the direction of the arrow B.
The mineral is forced to the inner surface 24 of the outer ring 14 by the rotation of the hammers 22 driven by the rotor plate. The rubber liner 26 of the hammer and o~ the outer ring 24 causes the mineral to bounce, there~ore colliding with each other and causing the~redùction in size.

In this type~ of grinder-classifier a variable air~ ;
velocity (arrows C) is created with a secondary ~system. The~air~current enters through the inlet Z8, picks ~up the~classified particles on its path and~
exits~;through~the~particle outlet 30 and~the exhaust~

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32 toward a collecting cyclone and dust arrester (not shown). The lower the air velocity, the finer the product will be because it will spend more time in the grinding chamber. The higher the air velocity, the coarser the particles will be.

EXAMPLE.

Basically, although the required changes are minimal, the improved performance of this rubber lined grinder is unexpected. For example, a grinder having an 18 inch diameter rotor plate rotating at 1700 rpm, and four hammers positioned at a 10 degree angle. The hammers and outer ring are lined with a 1 inch layer of polyurethane glued or bolted on the metal ;~ surfaces. Over 100 tons of mineral were ground without showing any signs of wear, whereas 2 to 3 ton~ of mineral can usually be ground with a conventional grinder before replacement of the~
hammers andjor the outer ring.

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Claims (5)

1 A rotary grinder-classifier for grinding solid mineral into fine particles, said grinder comprising:
- a grinding chamber comprising inlet means, outlet means, and an outer ring having an inner surface, - a rotor rotating around a central axle for driving a plurality of hammers, said hammers forcing the mineral against said inner surface of said ring, wherein said inner surface of said outer ring is lined with resilient material, whereby said mineral bounces off against other mineral upon hitting said lined surface, thereby facilitating said grinding.

2. A rotary grinder according to claim 1, wherein each hammer comprises two sides, at least one of said sides being lined with resilient material.

3. A rotary grinder according to claim 2, wherein said resilient material is bolted to said hammer.

4. A rotary grinder according to claim 1, 2 or 3, wherein said resilient material is glued to said wall.

5. A rotary grinder according to claim 1, 2 or 3, wherein said resilient material is rubber.