US2019454A

US2019454A - Grinding mill

Info

Publication number: US2019454A
Application number: US629444A
Authority: US
Inventors: Larsen Axel
Original assignee: FLSmidth and Co AS
Current assignee: FLSmidth and Co AS
Priority date: 1931-11-23
Filing date: 1932-08-19
Publication date: 1935-10-29
Anticipated expiration: 1952-10-29

Description

0d. 29, 1935. LARSEN 2,019,454

GRINDING MILL Filed Aug. 19, 1932 2 Sheets-Sheet l INVENTOR Oct. 29, 1935. LARSEN 2,019,454

GRINDING MILL Filed Aug. 19, 1932 2 Sheets-Sheet 2 46 L L 1 3 11 1L l VIIIIII/IIIIIIII/ (ll KIZIZI SISI.

lNVENTOR Patented Oct. 29, -1935 UNITED STATES PATENT OFFICE Axel New Jersey Application m is,

In Great Britain This invention has been developed with particular reference to the grinding of cement raw material, either in the drylstate or in the. wet state, but, as will be obvious, it is capable, of adaptation to the grinding of other materials with full realization of its advantages. The improved mill overcomes disadvantages incident tothe use of ball mills and tube mills, such as have been used commonly heretofore in grinding of cement raw materials, in that, in the operation of the improved mill, it is possible to inspect the grinding operation at all times and to make from time to time such adjustments as may be necessary to establish the best workirm conditions. Furthermore, the power consumption is not great as compared with that of ball mills and tube mills, even with heavy charges, and the weight of the mill can be made considerably less thanthatofa ballmillortubemillofthesame capacity. As compared with impact pulverizers or hammer mills, in which the material is pulverized by the impact of hammers'carried by a rotating member the improved mill, by reason of the factthat it can be operated at a much slower speed, is much less subject to wear and tear and to damage occasioned by especially hard particles.

Furthermore, in the operation of the improved mill the grinding of the material is effected by the,

action of the grinding bodies, whether flint pebbles or metal balls or other bodies, which, with the material to be ground, make up the charge of the mill, the main function of the rotors or stirrers being to effect such relative movement of the grinding bodies as will accomplish the grinding of the material.

The improved mill, in its simplest form, comprises a stationary container or shell which may be open at the top and into which the material to be ground is fed at one end and from which the ground material is delivered at the other end, and a disc-like rotor or series of disc-like rotors which are rotated about the axis of the;

mill and cause relative rubbing movement without' impact of the grinding bodies with which the mill is charged so that they act by attrition rather than by impact. Provision is made for the passage of the material operated upon from the feeding end of the mill to the discharge end while the grinding bodies are retained. It will be understood that the details of construction ofthemillcanbevariedinmanywaystosuitthe conditions'of operation and while several .different embodiments of the invention are shown and described herein it will be understood that diiferent features of construction can be subsmiaui a 00., tierat, N. 1., a

signer-tollcorporation meanness! November-23,1381 '4 401m (cue-s) stituted for one another or can be used by themselves or in combination with other features, as

the conditions of operation may indicate, and

that, except as pointed out in, the accompanying v claims, the invention is not restricted'to any particular embodiment.

In the drawings, in which several different embodiments of the invention are illustrated- Figure 1 is a view, pai-uyin longitudinal section and partly in elevation, of a mill which embodies lo the invention.

Figure 2 is a view of the same as'seen from above.

Figure 3 is a vlewin transverse section, on the plane indicated by the broken line 3-3 of Figures 5 1 and 2, showing particularly the preferred construction of eachof the rotor discs.

Figure 4 is a transverse section on the plane indicated by the broken linel-l of Figures 1 and 2 illustrating particularly the preferred construcgo tionof eachofthepartitionsintermediate the rotor discs. 7 a

FigureSisa viewslmilartoFigure 1 butshowing the rotor discs of progressively increasing and the shell as conformed thereto.

Figured is a view in elevation of a rotor in the form of a cage, the intermediate partitions being 11 omitted.

Figures 7 and 8 are detail views, respectively in section and in elevation, illustrating a device for the control of the movement of the material being ground.

Figure 9 isa view similar to Figure 1, but

showing the rotors arranged in groups with a In the embodiment of the invention shown in Figures 1-4 the stationary non-rotating shell or casing or container I, whichmay be made of steel platesand conform generally, in its lower portion,totherotordiscstohereferredto,and

having ariopentomisshownasmounted ona suitahlebase ll anda'sreceivingaxiallyashaftso 2onwhicharemounted,soastorotatetherewith, discs 3, provided with suitable perforations I. The shaft, 2 may be rotated by any suitable means, as, for example, thro h a gear 5, a pinion ,and'abandpulley 8 keyed on the shaft I of the pinion. Suitable bearings may be provided at I for the shaft 2 and at IQ for the driving shaft I. All of these parts may be supported in any suitable manner as on the base or foundation I I. Suitable packing boxes, as at l2, may be provided in the ends of the shell I for the shaft 2.

In this embodiment of the invention there is provided for each disc 3 and in the same plane therewith a diaphragm or partition it which fits about theperiphery of the disc with a slight clearance, these diaphragms l3 being otherwise imperforate and closing the space between each disc and the casing so that the grinding bodies are held back and all of the material being ground is compelled to pass through the perforations of the disc on,its way to the discharge end of the casing. Intermediate the discs 3 with their diaphragms l3 are partitions ll, which may partially encircle the shaft 2 and the hubs of the discs 3 and are formed with perforations. as at M.

The stationary non-rotating shell may be provided, as at IS, with a feed hopper and near the other end with a screen It which permits the finely ground material to pw' through it while retaining the grinding bodies and insufliciently ground material, such finely ground material being delivered through a spout [1 into a suitable transport device not shown. For the purpose of controlling the discharge of the finely ground material the screen, as shown in Figures TI and 8, may be formed of two perforated plates l6 and I6, one of which may be shifted with respect to the other so as to vary the area of the opening 18 through which the material is permitted to pass.

In the operation of the mill shown in Figures 1-4 it being assumed that the mill has been charged with grinding bodies, as indicated at It in Figure l, and that the rotors have been set in motion, the material to be ground is fed continuously into the mill, entering the chamber formed between the end of the shell and the first rotor. The grinding bodies and the material in each compartment between successive rotor discs are held back by the imperforatepartitions l3, the grinding bodies being also retained by the intermediate partitions ll. By the action'of the rotor discs the grinding bodies adjacent the discs will have a relative rubbing motion imparted to them and act upon the material by attrition rather than by impact while the grinding bodies adjacent the stationary partitions II will have less relativetmovement. It will be understood, however, that the grinding bodies may be con stantly changing their positions between each rotor disc and the adjacent stationary partition. By reason of the relative rubbing movement of thegrindingbodies thusestablishedthematerial to be g ound. which fills the interstitial spacesbetweenthegrindingbodies,willbe ground between the faces of adjacent grinding bodiesandalsobetweenthefacesofthegrind ing bodiesand the faces of theadiacent partitions and rotor discs and such ground material willpassthroughtheperforationsloftherotor discsIandalsothroughtheperforationsllof the partitions I, being progressively reduced in finenesuntiltheilnely groundmaterial canpass throughthescreen'lt andsobe discharged from the. mill. The normal rate of rotation of the 'shaftlandtherotordisclwiilbecomparativelyslow'andastheprolrellofthegrindl ilcan beobservedfromthetopofthemilhitisasimple the material passed outside the disc 3 alon titions ll of Figure matter to vary the rate of rotation'to .produce the desired result.

It will be understood that the partitions l3, closely encircling the discs 3, serve to prevent jamming of the grinding bodies between the edges of the discs 3 and the wall of the mill and serve alsoto compel the material to pass through the apertures of the discs 3 and so obtain a greater grinding effect than would be possible if the 10 wall of the millv While the shell or wall of the container may be conveniently made of steel plates it will be understood that it might be made=of concrete, for example, for the wear on the wall of the mill is slight, as it is protected by grinding bodies. which have litle or no motion. The rotor discs 3 and the partitions ll should be made of a highly wear resistant material in order to withstand the action of the grinding bodies and for the samereason the rotor discs 3 should be pro- 1 vided with long hubs to cover completely the shaft 2.

It will be understoodthat if the operation of the mill be started when fully charged the re- 28 sistance offered by the perforated rotor discs to the moment of starting will be considerable because of the pressure of the grinding bodies and material against the discs. This difllculty may be overcome by provision of shown in Figure 10, one of which may be slipped in place in front of each rotor disc when the mill is empty or nearly empty to protect each disc from the pressure of the grinding bodies and material and so reduce the resistance of the mill asto the starting moment. When-the starting re- .sistance has been overcome the -plates can be withdrawn.

As another means of reducing resistance .to the starting moment each rotor disc 3*, as shownin b Figure 11, can be connected to the shaft 2 through the medium of a spiral spring 3 so that the rotation of the shaft maybe started readily and movement imparted gradually to each of the discs. 4.6 In the embodiment of the invention shown in Figure 1 the discs 3 are of the same diameter and the lower part of the shell of the mill is cylindrical to conform therewith. If it should be desired either to promote or retard the passage of the material through the mill the discs 3 might be made of successively different diameters, as shown in Figure 5, the shell I being 4 conformed thereto and the partitions l3 and I being shaped accordingly. In other respects the construction of the mill illustrated in Figure 5 may be the same. as that illustrated in Figure 1. I

It is obvious that with the partitions l4 omitted the several rotor discs 3 might be united go by bars 3' and stay bolts 3 to form a cage-like structure as illustrated in Figure 6, mounted on the shaft 2 to be rotated therewith. Except for I the function performed by the perforated par- 1 the operation 017 a mill '5 equipped with such a cage-like structure is the same as that already described with respect to 'Figure 1, the material as it is ground passing through the openings of the discs 3 while the grinding action is accomplished by the relative movement of the grinding bodies between the discs I.

ii are shown as arranged ingroups, with .8 P Ti slotted plates I9, 30-

forated partition I 4 between successive groups. The operation or such a mill will be readily understood without further explanation.

I claim as my invention: 7

1. In a grinding mill, the combination of a stationary, non-rotating shell adapted to receive a charge of grinding bodies and material to be ground and to discharge the ground material, a perforated rotor disc to efiect relative movement of the grinding bodies, means to rotate the rotor, and a partition encircling the rotor in the plane thereof and closing the space between-the rotor and the fixed shell.

2. In a grinding mill, the combination of a stationary, non-rotating shell adapted to receive, a charge of grinding bodies and material to be ground and to discharge the ground material, a plurality of rotors to effect relative movement of the grinding bodies, perforated partitions interposed between the rotors, fixed imperforate partitions encircling the rotors in the plane thereof and closing the space between the same and the shell, and means to rotate the rotors.

3. In a grinding mill, the combination of a stationary, non-rotating she-.1 mounted on a relative rubbing movement of the grinding bodies 5 without impact, means to rotate the rotor, and

a screen at the discharge end of the shell to permit the discharge of the flnelyground material and to retain the grinding bodies and coarsely ground material. l0 4. In a grinding mill, the combination of a stationary,non-rotating shell with a horizontal axis adapted to receive a charge of grinding bodies and material to be ground and to discharge the ground material, a perforated rotor disc 15 mounted on a horizontal axis to eflect relative rubbing movement of the grinding bodies without impact, means to rotate the rotor, a screen at the discharge end of the shell to permit the discharge oi the finely ground material and to 20 retain the grinding bodies and coarsely ground material, and means to regulate the discharge of the material through said screen.

am LARSEN. 25