US1849871A - Pulverizing mill and the like - Google Patents

Description

March l5, 1932. E wL GREEN ET AL PULVERIZING'MILL AND THE LIKE Filed March 13, 193()A r2 Sheets-Sheet Ercan @gorge Tod/'Gm UNHIUVIK 72 L March 15, 1932.

E. w. GREEN ET AI.

PULVERIZING MILL AND THE LIKE Filed March l5, '1930 2 Sheets-Sheet 2 fia/ward Wfl/mm 67rd en.

Patented Mar. 15, 1932- UNlTl-:D STATES PATENT OFFICE EDWAED WILLIAM GREEN, or LONDON, AND eEoneE EoDm- UNrrnnNx, or' NEW SOUTHGATE, LONDON, ENGLAND, ASSIGNORS LIMITED, OF ENGLAND rULvEarzINe MILL AND THE LIKE Application led March 13, 1930, Serial No. 435,406, and in Great Britain March 14, 1929.

This invention relates to improvements in` pulverizing mills and the like in which pulverizatiqn is elected by a plurality of balls cooperating with tracks. v

5, The invention has for one of its objects the provision of means whereby more effective and regular grinding can be performed than is possible with known arrangements.

Another object of the invention is the provision of means whereby more effective discharge of pulverized material from the balls is obtained thereby enabling a pulverizing mill of higher duty to be produced than has been possible in the past.

Another object of the invention is the provision of means whereby' more eifective air currents are produced for conveying the pulverized material `delivered from vthe rotary track to the delivery orifice thereby enabling more efficient operation to be obtained.

A further objectv of the invention is an im'- proved construction particularly'adapted for the reduction of crushed coal into a powder of the neness which is necessary when coal is to be consumed in pulver'ized form.

A further object of the invention being the provision of means whereby the pulverized material delivered from the apparatus is more uniformly graded than has been usual with apparatus of this type.

The invention consists in the arrangement of a plurality of balls in a rotating track, said balls being maintained therein by an elastically loaded nonrotary track; means for feeding crushed material to said rotating A track to be pulverized; means for producing an annular stream of air for entraining the^ material delivered fr0m` said track, said streamfof air conveying particles of the pul- *0 verizedmaterial of less than a predetermined l mass to and through'a delivery passage whilst the heavier particles are returned by the force of gravity to the rotating track for further pulverization.

In the drawings Figure 1 illustrates in Sec# tional elevation one form of improved mill ,l constructed in accordance with this invention; p l

Figure 2 is a plan view inssection taken o n the line/2 2 of Figure 1;

material from the bevelled edge toI the delivl ery assage.

Als) illustrated part of this vertical sha a supported upon a suitable ballv thrust b and provided with worm and in 'the drawings forming vworm wheel gearing o to enable rotation of the shaft a to be effected although other ,T0 R. & H. GREEN' .AND SILLEY' WEZIIB4 sfpecification the mill comprises a l means of rotation may be employed if so desired. 'The vertical shaft a is provided with a journal d at its upper end adapted.

to rotate in a bearing e formed'inlthe Iupper partof the stationary structure f of themaf chine which also comprises va supply passage g for the admission of roughly crushedmaterial., a delivery passage h for the pulver` ized material and an air inlet orair inlets c'.

The roughly crushed material is supplied to the hopper k and is fedjby theJ screw conveyor l throughthe tunnel m to the orice g,

the conveyor Z being'rotated at the required f speed by means of the bevel wheels an. shaft o, crank p, lever q, pawl 1' and ratchet wheel ra, such means being provided'to prevent the admission of air' through the'hopper le as may be necessary. i

Beneath vthe supply passage g a stationary circular serrated element t' is located, the shaft a having feeder arms u and a conical toothed braker v at this point so that the material is forced by the feeder arms u between the4 serrations on the stationary element t and the teeth of the braker v means adapted to'be shearedy being provided, if necessary, should excessive torque be required from the shaft a.v

The material delivered from the serrated element t is discharged on to a track w mounted on and rotated by the vertical shafta. l A A A plurality of balls a: of suitable diameter are arrangedon the track w and maintained .in position by a nonrotating ring element 'y suitably loaded by springs a or the like, the

number of balls a: provided being insufficient to lill the track w completely so that a gap w1, see Fig. 2, exists between contiguous balls at one point. The dimension of the gap m1 depends upon a number of conditions but in a general way when the track w is suiiciently long to accommodate a given number of balls a single ball may be omitted. The configuration of a transverse section of the track w is such that the balls as engage therewith on a line extending substantially from a vertical plane to a horizontal plane said track lw being continued upwards at its larger diameter so as to form a bevelled edge` or fence w1. In transverse section the configuration of the bevelled edge or fence w1 is a portion of a paraboloid lying between two horizontal planes or approximates to such curve, the contour being so proportioned that the fuel whether ground or not is just able `to run up said bevelled edge w1 by centrifugal force.

In proximity with the bevelled edge rw1 and exteriorly thereof a stationary circular lipv wz is arranged, the lip fm2 cooperating with an adjustable sleeve w3 mounted on the cover f1 of the stationary structure f so as to form an annular jet supplied with air from the air inlet z', the sleeve 'w3 being raised or lowered by means of the finger operable nuts @v4 which cooperate with the screwed stems w5 attached to said sleeve.

Owing to the location of the air inlets z' i the direction of fiowof the air to the annular jet is fixed, the velocity and quantity of said air being independently controllable by varying either the area of the jet by raising or lowering the sleeve w3 or by varying the speed of the fan exhausting air from the separator the base of which is indicated by the letter S in Figures 1 and 2.

In operation crushed material, for eX- ample, coal, is fed by the conveyor Z through the supply passage g to the track w. As previously stated the track 'w is rotated at such a speed that the material under the action of centrifugal force can just pass up the bevelled edge w1. During the passage of the coal across the track 'w it is pulverized by the balls and the delivery from the edge w1 is entrained by the stream of air issuing from theannular nozzle formed by the lip wz and the sleeve w3 and carried in the direction of the arrow 3 between the back of the ring element y and the inside surface of the cover f to the delivery passage h particles having less than a predetermined mass being conveyed throughthe passage h to the separator whilst particles of greater -mass fall, as indicated by the arrow 4, under the action of gravity, and intermingle with the feed from the passage g, as diagrammatically illustrated in Figure 4E.

When coal is being pulverized in such an apparatusthe air supplied to the inlet mav be heated as desired in which case the air inlets i or some of them may be closed with suitable doors the heated airbeing supplied loaded non-rotary track, a series of balls dis-v posed between and travelling round said tracks, an annular suction passage round said tracks communicating with the external atmosphere, a beveled edge on the discharge periphery of the rotating track of the form of aparaboloid lying betweentwo horizontal planes, a stationary circular lip in proximity with the said beveled edge and an adjustable sleeve sliding on the upper part of the mill and having an outwardly and downwardly projecting lip arranged to direct the suction air to meet the stream of pulverized material l thrown'out centrifugally and direct the combinedstream in an upward and inwarddirection so that the heavier particles of solid material are returned by gravity to the inside Vof the said tracks for re-pulverizing.

2. In an improved mill as claimed in claim 1, a stationary serrated ring mounted in the supply passage of the mill, a rotating serrated element carried by ythe rotating track, and

yrotating feeder arms in the said supply passage adapted to crush the material supplied immediately before saidmaterial is applied to said rotating track for pulverization.

3. In an improved mill as claimed in claim 1, the arrangement of the balls between the two said tracks so that the aggregateof the,

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