US1536990A - Machine for grinding and pulverizing friable substances - Google Patents

Description

'May 5, 1925. 1,536,990

J. P. VAN GELDER MACHINE FOR GRINDING ANDv PULVERIZENG FRIABLE sUBsTANcEs Filed May 24. 1924 Johannes Pieer ran Gelder Y loer' MS To all 'whomit may concern:

PaniedpMay s, 1.925.

UNIT-ED STA JOHANNES PIETER VAN GELDER, F GRANVILLE, NEAR SYDNEY, NEW SOUTH WALES, AUSTRALIA.

IAGHINE FOR GRINDING AND PULVERIZING FRIAIBLE SUBSTANCES.

Application led May 24,

Be it known that I, JOHANNES PIETER VAN GELDER, subject of the King of Great Britain and Ireland, residing at 200 William Street, Granville, near Sydney, New South Wales, Australia, have `invented new and useful Improvements in Machines for Grinding and Pulverizing Friable Substances, of which the following is a specication.

Mills of the type in which reduction of friable dry substances is effected by the action of revolving beaters are not practically usable when it is required to obtain a product of uniform extreme fineness. Beaters (lo not act effectively on small particles, and it is consequently necessaryto subject products which contain granular particles to further treatment, for instance, in roller mills, or ball mills, or tube mills in `order to obtain the same in uniform very fine condition. In a known type of mill using the 'beater principle, crusher rolls are fitted with the nip" of the rolls disposed in the path of flight of `granular particles which are thrown off tangenti-ally by the beaters. 'lhese rolls operate to comminute the granular particles which reach them, and the thus comminuted material falls back into the beater casing from which it passes out through a screen. 'But the only granules' which suffer reduction in these mills are the particles which pass through therolls. The final product is therefore not uniformly tine in gauge. The coarsest portion of the milled product is gauged by the dimensions of the perforations in the screen, and the product is made up of a mixtureof granular particles which have missed the rolls and pass through the' perforations, and fines of various smaller gauges. The screen perforations must be of sufficient size to allow gran- -ularparticles to pass through them freely with the liner product; if they are made too small, they are liable to be choked so that the mill would sooner or later be flooded The mixed gauge product thus obtained must be separated after delivery from the mill 1f a product of uniformly tine gauge is required.

The larger particles separated from the selected fines must then be remilled if they are required to be brought to fine gauge.

The object of the resent invention is to' provide means whee y, in a crushing. mill y1,924. serial no. 715,610.

may be brought to a condition of uniform extreme lineness thereby to avoid the necessity for subquent remilling or separating, which means, when a uniform very fine product is not demanded, will be utilizable for producing a moderately finely ground product of irregular gauge.

With this obJect in View I have devised a mill in which the -irregularly sized products of beater action/other than those of already sufficiently fine gauge are subjected to regrinding by ball action, following beater action, that is to say, the granular product-s of beater action are subjected in the mill to the same treatment they would sustain if they were submitted to retreatment in a ball mill after their removal from the beater mill.

The body of my mill consists of a rotatable drum-like chamber mounted for slow rotation on a horizontal axis, with a-beater shaft armed with beaters mounted for fast rotation concentrically within it. Anvil bars against which the material under treatment is thrown by the beater action are mounted at 'their ends in the heads of this drum chamber, surrounding the beaters with clearance spaces between them. Steel or silica balls .of various sizes are placed in the annular part of the drum chamber outside the beltl of anvil bars; these balls locate by gravity in the lower part of the drum, covering a considerable arc of its inner surface. The beater shaft is driven at a relatively fast rate as is common practice with mills of the beater type. The drum easing is geared to the beater shaft so that it is rotated at a relatively slow rate. A

The feed of lumps or pieces of dry friable material to be treated is delivered from a hopper through a chute into the beater chamber of the drum through a central vent in one head of it. The other head. of the drum is vented centrally and this vent is connected into the 'suction opening of af centrifugal exhaust blower. The exhaust blower functions to aspirate fine products of the grinding assoon as they are released and' to deliver them into a flue through which they pass to a cyclone or other ex- 105 of the beater type, the whole of the product the beaters in the usual way, being smashed no by their direct action and by their impact in flight with the anvil bars by which the beaters are surrounded. The granular material passes out between the anvil bars and falls into the annular chamber and is there acted upon as in a ball mill by the balls which are operating in the bottom part ofsaid annular chamber as the mill body rotates. The fine product is aspiratedby the draught produced by the exhaust blower and is carried off suspended in air and delivered through the flue to the Separator. K

One'head of the mill body is formed with a cellular clearance space in it. The inner wall of this spaceis perforated with holes splayed outwardly, and it is also vented into the beater chamber. This cellular space is subdivided by radial ribs to form pockets. Coarse material which is not reduced rapidly by theball action ultimately finds 'its way out through the perforations into'the cellular pockets and is delivered back from them into the beater chambery as the drum rota-tes, and there again suders treatment by the beaters, and is in due course again returned to the annular ball chamber. The material 'which is delivered out of the mill is all sufciently fine to be carried in suspension in the air draught created by thc action of the exhaust blower. The granular portions until reduced to this fine gauge remain in the mill suffering repeated grinding.

In the accompanylng drawings f Fig. 1 is a longitudinal sectional elevation through the mill;

Fig. 2 1s an end sectional elevation looked at from the feed end of the mill with portion of the body shown broken away to expose the beaters and anvil bars and to show the rotatable 'mounting of the drum body and its driving gear;

F ig. 3 is a longitudinal -section through the body of the mill with the shaft and -s beaters removed and showing a hopper casing Fig.i4 isa which is attached to it when it is being operated without aspiration draught and a mixed granular/and fine gauge product iS. delivered; and

fragmentary sectional view indicating the construction of the hopper casing which is included in Fig. 3. This view is taken on the plane of the section line 4-4 Fig. 3. i l

10 isthe beater shaft. It is mounted for rotation in standard bearings -11, and is fitted at one end of it with adriving pulley 12. 13 are beaters mounted/on the central portion of the shaft 10 and located in the beater chamber of the'mill body. ,14 are anvil liars which are disposed as' a cage around the beaters on the shaft 10 so as to receive the impact of flying particles ,which have been thrown olf by the y beaters 13.

, 15 are collars on the shaft which cramp up one head of the drum shaped body of the mill, and 17 are the plates of the peripheral or belt portion of it, which latter are of torus section. 18 is a shellocasing in which the head plates 16' and the belt plates 17, which are in sections of appropriate dimensions are demountably housed. The casing 18 ,forms at the other end of the bill an outer cheek 20 which is formed with an entry mouth 25 through which the bottom end of the feed chute 24 is entered. 26 is a clearance space to allow of the rotation of the mill body relatively to the feed chute 24. 27 is a bearing collar or flange on the -cheel.20, which rides on trunnion rollers 28, the axles of which are supported in appropriateframes 29. 19 is a'ring gear fixed to the cheek 20. It meshes with a compound spur gear 37, which in turn meshes with a pinion 39 on the shaft 40 onv which a pulley 41 is keyed. This pulley may be driven from an independent motor or it may be belted to the beater shaft 10.

21.are perforated sectional head plates. Like the head plates 16 at the delivery end of the mill body they are demonntably fixed in the casing 18. The cellular clearance `space between the cheek portion 2O of thel casing 18 and the perforated head plates 21 is sub-divided radially to form pockets 22. 50 are vents at intervals surrounding the collar 23, and leading from the pockets 22 to the beater chamber of the mill. They are vprovided to allow granular material which finds its way outward through the perforations inthe plates 21 to return to the beater chamber. 36 are balls of steel or silica or like appropriate material sized for effecting ball milling. They are placed in the annular chamber of the mill body. As the mill body rotates theyfrun by gravity towards the bottom position therein as in a ball mill, submitting any material which may be intermixed with them to a crushing and rubbing action.

31 is an outlet sleeve in the delivery head of the mill body. It is loosely spigotted at 32 into the suction opening 33 of a centrifugal suction blower 34. The delivery mouth 35 of this blower is connected by a shown) to a cyclone (not shown or other known `type of separator in which the aspirated material is removed from the air current.

VVheIlr withdrawal of a uniformly fine product by aspiration is not practiced,

peripheral plates 44 are fitted in the mill gauze or finely perforated sheet metal perpherally enclosing the mill body. Granular particles which pass through the perforations 42 do' not pass to product when they are of too large a gaugeto go through pipe (not l the screen 46. They find their way back into the mill and there suffer regrinding by the balls. The fine gauge stu which passes the screen 46 is collected in the casing 47, which may be a sheet iron casing completerly surrounding the mill body with working clearanceV only, and terminating in a gravity delivery spout 52. The casing 47 is sufliciently deep on the flanges 48to cover only splayed outwardly and the said inner wall being vented into the said central beater chamber.

2. A grinding mill comp-rising a drum-like chamber mounted for rotation on a horizon? tal .a-Xis, means for applying rotational movement ata slow rate to said drum J chamber, a horizontal shaft armed Witlr beaters concentrically located in said drum chamber, an -zassembly of anvil bars supported at their ends in the hea-ds of said y drum chamber and surrounding the beaters,

an .annular chamber surrounding the assembly of anvil ba'rs and adapted to carry .a mass of grinder balls, the heads of said drum chamber being respectively provided with openings for receiving thesubstance to be milled and fory delivery ofthe milled product, and -ineans for creating air draught of sufiicient velocity through said drum chamber to aspirate and carry the milled product out of it.

3.LA. grinding mill comprising a drum like chamber mounted for'rotation ona horizontal axis, means for rotating it, a central shaft extending through said chamber and meansI for rapidly rotating such shaft, an assembly of beaters on said shaft Within said chamber, an assembly of anvil bars disposed in parallel order 4longitudinally of said chamber and surrounding the beaters and demountably fixed in vthe chamber body with clearance spaces between them adapted to permit granular particles to pass between them, a mass of grinder balls located in the annular space in the chamber surrounding the anvil bar assembly, and means, for re-` moving ground products out of the mill.

4. A grinding mill comprising a drunr `shaped body' fitted with '.demountable liner plates and with an assembly of demountable anvil bars which bars are arranged concentrically in it to divide it into outer and innerconent'ric chambers, a ring gear at one end of said body, roller -bearing supports for said body, open hub ends in either head of said body, the one associated with a feed chute and the other With aspiration eduction means, a horizontal shaft armed With beaters disposed axially in the' central chamber of the mill body, a mass of rinder balls -contained in the said outer c amber, and

means for applying. rapid" rotation to the shaft and slow rotation to the mill body.

In testimony whereof I have signed `my name to this specification.

JOHANNES PIETER vAN GELDEN.

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