US1431475A - Means for crushing and grinding ore and rock - Google Patents

Description

W. T. MAcDONALD.

'MEANS FOR CRUSHING AND GRINDING ORE AND ROCK. APPLICATION FILED ocr.30,1920.

1L %311 fiT/fi Patented Oct. W; 11922.,

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1 lillilllllllllll] INVENTOIZ. W17! 1m TMmfionaZa! ATTORNEY WILLIAM T. MACDONALD, 0F HAYDEN, ARIZONA.

MEANS FOR GRUSHING AND GRINDING ORE AND BOOK.

Application filed October 30, 1920. Serial No. 420,612.

To all whom it may concern:

Be it known that 1, WILLIAM T. MAcDoN- ALD, a citizen of the United States, residing at Hayden,in the county of Gila and State of Arizona, have invented a new and useful Means for Crushing and Grinding Ore and Rock, of which the following is a specification.

This invention relates to the crushing or grinding of ore or rock material in tube mills, ball mills, cone mills, and the like, in which ore or rock is subjected to crushing and grinding action within rotating barrels, drums, or other suitable apparatus, containing crushing and grinding bodies in contact with the ore or rock and operating to crush aml grind the same in the tun1- bling, roiling, rubbing and agitating action due to the rotation of said apparatus. The crushing and grinding bodies used'for this purpose have generally consisted of socalled pebbles of naturally occuring hard rock, or of balls of metal, :such as iron. In the operation of mills of this character with balls or pebbles approximately sphe .roidal in form, the crushing and grindin action of the balls on the material is generally limited to points of contact, resulting in loss of efficiency and capacity in the crushing and grinding and in undue wear on the crushing bodies at such limited points of contact In some cases, rods of approximately circular cross-section have been used in the place of balls or pebbles and the con tact is then extended to a lineof contact but is still comparatively limited.

The main. object of the present invention is to provide a form of crushing body for use in mills of this character in which the grindin bodies are adapted for tumbling and falling action in. the usual manner of ball and pebble mills, and, in addition, as they approach each other in the tumbling, falling and rubbing action in the mill will present approximately plane surfaces to the material being crushed or ground between said bodies whereby a. larger sur face of contact for crushing or grinding is secured and at the same time increasing the crushing or grinding effect and decreasing the wear on the crushing or grinding bodies, compared to the effective grinding or crushing performed. This advantage is gained with little, if any, sacrifice of the ad visable or necessary interstitial space which should exist between adjacent grinding media in order to permit of the requisite flow of the ore pulp to, between and around such grinding media and through the con taining tube mill, ball mill, cone mill, or other suitable appliance.

Another object of the'invention is to provide a more effective crushing and grinding action by subjecting the material to be operated upon to a rubbing and sliding action between approximately plane or flat surfaces as well as to the crushing effect due to falling and tumbling action of the crushing bodies.

The accompanying drawings illustrate suitable embodiments of my invention, and referring thereto:

ldig. 1 is a perspective of one form of the crushing or grinding body;

Figs. 2 to 3 are perspectives of modified forms thereof; M

Fig. 4. is a partly broken side elevation of a tube mill provided with crushing and grinding bodies constructed according to my invention; v i Fig. 5 is a diagram showing the manner in which approaching grinding bodies constructed according to iny invention operate in producing a rubbing and shearing action on the material being crushed.

lhe crushing and grinding bodies used in accordance with my invention may con sist of any suitable material but are preferably of metal, for example, cast or wrought iron, or steel, formed in blocks or bodies having any desired number of plane surfaces, such bodies being preferably formed as polyhedrons, the preferable form being that of a cube or six sided polyhedron, as shown at l in Figs. 1 and 2, having the plane surfaces 2 mutually nearly perpendicular to one another. The corners or corners and edges of such cube or polyhedral body 'are purposely formed as curved, or comparatively narrow beveled surfaces, as indicated at 3 and 4, as the article is supplied for sale or use for crushing and grinding purposes. As shown at 7 in Fig. 3, a portion of the crushing or grinding body'may be in the form of an approximately spheroidal surface with the plane surfaces 2 formed thereon.

I find it advantageous that thesoballed cubes, or other polyhedral bodies, as hereinbefore described, but purposely formed with curved or comparatively narrow beveled sur faces at all places where otherwise corners and line edges would naturally have existed.

I wish to point out some of the essential benefits to be derived from purposely forming such' just mentioned corners or edges as curved or beveled surfaces. When the crushing or grinding mediaor bodies are thus shaped. it is impossible for them to be so placed but that interstitial spaces will exist between the adjacent crushing media or bodies, and as these interstitial spaces naturally become filled with the ore or rock particles to be crushed, such interstitial material is readily available and is introduced between anytwo adjacent surfaces of the grinding media and is subjected to the resulting rubbing, crushing and grinding action. Such interstices also permit of a desirable and necessary flow or travel of the ore or rock particles through the interior of the mill, while forcing them to enter between and to come in proper contact with the crushingmedia. Also, when the crushing and grinding media or bodies are thus purposely shaped a very material saving in grinding media. is effected as compared with the use of crushing or grinding media in which the natural corners or edges have not been so replaced. The corners or edges which would otherwise originally be present would constitute natural points of weakness. Such corners or edges when present wear away rapidly with a comparatively small amount of effective work having been performed. and thusreduce materially the total coinparative efficiency of such grinding media. The combination of flat surfaces and of rounded corners and edges that are thus provided in the grinding media herein described is highly desirable and both of these features while possessing their own specific advantages cooperate to effecta combined beneficial result as above pointed out.

I provide the crushing and grinding bodies above described as articles of manufacture for sale and use in tube mills, ball millscone mills, and like apparatus in which a rotary tubular or other suitably shaped barrel or member, such; for example, asindicated at 12 in Fig. 4; is mounted to rotate in suitable bearings 13 and 14. and is driven by operating means 15 and provided with means 17 and 18 for supply and discharge of the material to be crushed or ground; the crushing and grinding bodies 1 being placed in said barrel or rotary member in such manner to be in contact with the material to be operated upon, indicated atiQ- In the rotation of the mill 12 the mass of crushing and grinding bodies 1 and the ore or rock material 19 contained intthemill is turned over and over. being carried up on the ascending side of the tube, barrel. or drum 12, and falling, sliding and rolling over in well known manner to effect the crushing and grinding of the ore or rock. \Vhen the bodies or billets are of substantially cubical form, the rolling and falling or tumbling action takes place with approximately the came velocity and in the same manner as with spherical balls or pebbles. 'hile in some cases a polyhedral crushing and grinding body, as above de-. scribed, may in the I'Ollll'lg'. sliding or falling action come into contact with or aproach another such body at the pointed, curved or angular portion of one or the other of the bodies there will be a larger number of cases in which the bodies will approach one another under such conditions as to present toward one another the approximately plane surface constituted by the side of said bodies, as indicated, for example, in Fig. 5, and in addition to the movement of approach there will be more or less lateral or sliding movement of the approaching bodies relative to each other. The result of such an operation is to cause contact of the bodies with each other and with the ore or rock material, indicated at 19, throughout an extended surface, thereby increasing or distributing the crushing and grinding action over a larger portion of the ore and over a larger portion of the surfaces of the crushing and grinding bodies. This has the effect of increasing the crushing or grinding capacity, as a larger amount of ore or material is subjected to the operation than if the crushing and grinding bodies only approached at a single point. It is true that in this distributed crushing and grinding operation the violence or force of the impact or pressure per unit of area is correspondingly diminished but this is generally an advantage rather than otherwise as the effect of the extremely violent impact and pressure due to contact limited ap-- proximately to. points is beyond what is necessary for crushing and results in comminution of the. material, or a' portion thereof, to the condition of dust or to a fineness beyond that which is desired.

Furthermore, the distribution of the crushing and grinding action over a larger surface of the crushing and grinding bodies themselves tends to materially reduce the wear and attrition of these bodies, relative to the quantity and effectiveness of the grinding or crushing performed. A distinct advantage to be gained by the use of the flat grinding surfaces of the grinding bodies herein proposed, is the much greater relative evenness of the resulting ground material. For most metallurgical, and perhaps manufacturing purposes, after an ore or rock has been ground or reduced to a certain degree of fineness any additional reduction "in size, is not only wasteful of power, but is usually decidedly detrimental to the obtaining of the best final results, As lndi'cated elsewhere in this discussion, the

use of balls or pebbles of essentially spher- .iodal form, or at least of bodies bounded by curved surfaces and crushing by point con tacts instead of bysurface contact, is productive of a relatively unevenly sized product, and the consumptlonof an excessive amountof power is necessary to insure all material .be eflected. Relatively more material will be ground to at least the minimum size or mesh desired and relatively less will be ground finer than desired, while the total,

contained energy of the moving grinding me la will be much more efficiently utilized.

Another advantage in the use of crushing and grinding bodies having approximately plaiiie surfaces, as described, is that oppor operation of the crushing and grinding tunity is given for wedging and rubbing actlons due to the approach of the bodies obliquely toward one another, so that lateral components of motion are presentedtending to effect rubbing and shearing of the particles, it being recognized that crushing by rolling, rubbing, sliding and wedging action is especially efiicient and desirable, this being effected in large measure by the bodies having approximately plane surfaces,

as described, whereas, it cannot be efiected to any considerable degree by the ordinary rounded pebbles or balls.

It isbelieved that app'reciablyi better and cheaper grinding and crushing will result from the use of this proposed grinding me "possible. But when employing the shapeIofdium than is the case when employing either balls or rods of circular cross-section. When employing balls for this purpose, speaking broadly, only a one point crushing contact is probable or often possible between any two adjacent balls. ploying rods or circular cross-section, only a line crushing Contact is probable or often grinding medium herein proposed, anything from a point to a hue and then to a surface Contact is 'possible,--with the surface contact probable a very large percentage of the time.

When employing balls as a crushing nedium it is probable that most of the grindi'ngeffected results from the immense number of point contacts between fallingor i When similarly" em-.

moving adjacent balls, and that the particular particle, or small number of particles, of the material so crpshed is probably crushed finer than is necessary or often desirable, while a very considerable portion of the energy of the falling or moving balls is consumed in excessive shock and conse' quent injury and undue wear to thelgrinding medium itself. In a similar manner the line contact obtained by the use of rods of circular cross-section probably results in an undue proportion'of the energy expended being inefliciently, or probably even injuriously, applied. In the case of the grinding medium proposed the tendency toward surface contact between the individual adjacent crushin bodies or media would tend to more e ciently utilize the total contained energy in performing useful crushing or grinding of the material to be ground and would result in a minimum proportion of such energy being consumed in excessive wear of the grinding medium. By the use of grinding media of the form and shape proposed, effective crushing and grinding work results both from each original impact of any two adjacent grinding media and also from the subsequent rubbing action between any two adjacent grinding media surfaces, which through their tendency to come togcther-will grind or crush the intervening particles of the material. to be ground.

A grinding mediumef this form or shape can be cast or forged as cheap or cheaper than can spherical balls.

The power consumption will be less per unit of material crushed to any given size because of the more efficient grinding or crushing, and also because the containing mill can generally be run more slowly, due to the fact that when using thetype of grinding medium herein proposed, propora tionately less grinding and [crushing will result from the force of original impact between adjacent individual crushin media than is now the case with either 'alls or rods of circular cross'sections and 'propon tionately-more grinding a d crushing will be effected through rubbing as also through the efiective pressure existing at the contact areas of the crushing media whichat any given instance constitute the lower portion of the entire crushing media, such pressure resultlng from the cumulative weights of the superimposed crushing media. It will,-

therefore, not be necessary or advisable to lift the crushing media so high, thus result- .ing in a saving of power.

What I claim is: I 1.Means for crushlng or grinding ore or rock comprising a rotatably mounted barrel member provided'with means for rotating the same, and for admitting and discharging ore or rock material and crushing or grinding bodies contairped within said barrel.

with surfaces constructed to "provide Cleaance spaces between adJaeent grln'dlng bodles member, and formed substantially as cubes having flat faces, the corners of adjacent bodies constructed to provide clearance spaces therebetween. v,

2. A crushing and grinding mass of bodies each in the form of a cube having fiat faces 7 atthe junctions of the fiat-faces thereof.

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