US3542300A - Ball hopper for ball mills - Google Patents

Description

O United States Patent [11135 [72] Inventors Kenneth F. Breclmell; [50] Field of Search 241/50, Ronald Arthur Ashdown, London, England 2 /1 21 App]. No. 697,046 1 1 ,162, 166, 169, 170

22 Filed Jan. 11, 1968 i4si Patented Nov. 24, 1970 [561 References CM [73] Assignee Foster Wheeler Corporation UNITED STATES PATENTS Livingston, New Jersey 1,095,193 5/1914 Curtis 221/188X a corporation of New York 3,401,893 9/1968 Reynolds 241/179X [32] Priority Jan. 4,1968 2,154,147 4/1939 Bensemann 221/86 [33] Great Britain 2,854,038 9/1958 Manley 222/166X [31 1 805/67 Primary Examiner-Robert C. Riordon Assistant Examiner-Martin G. Raskin Att0meyRichard H. Thomas and John Maier ll! [54] HOPPER 0R F MILLS ABSTRACT: This disclosure relates to those pulverizing mills 6 Clams 7 Draw'ng -known as ball mills, to the charging of new balls to such mills [52] us. Cl. 241/101, and to a h ging h pper- The n w balls are held in a 22 /86; 222/132, 222/144, 222/ l 62: 24l/l7l hopper and are fed to the mill a few at a time. They enter the [51] Int. Cl. ..B02c 17/18, il y r ll g re ly n h roll feeding device of the mill BOZc 23/02; B65g l/08 where they join the raw material and pass into the drum.

Paten ted Nov. 24, 1970 I of 6 Sheet Patiued New. 24, .1970 V Sheet 3 BALL HOPPER FOR BALL MILLS BACKGROUNDOF THE INVENTION This type of ball mill comprises a horizontal, cylindrical crushing drum which is rotated about its axis. Raw material to be pulverized, such as for example coal, limestone, or cement, is fed to this drum which also contains a large number of steel balls about 2 inches in diameter, and it is the cascading action of these balls resulting from rotating the drum at, say, about 20 r.p.m. which crushes the material. The finely crushed material is then picked up in an air current and taken through a classifier where oversize material is removed. In the case of coal, the entrained material is then taken from the classifier,

either directly to burners or is taken to a store for later use.

The steel balls rub against one another and the material and they inevitably wear away slowly. In order to keep the mill stocked up with the balls, therefore, new ones are fed to the mill from time to time.

It has been the practice to feed these new balls, together with the feed of raw material which normally takes place, through a delivery chute or pipe into a scroll feeding device which leads to the drum in a direction along the axis of the drum. This practice has the disadvantage, however, that the balls are much heavier and denser than the material to be crushed and, at the bottom of the chute or pipe, they have a considerable momentum when they impact upon the scroll feeding device. This often causes damage to this device, which is, of course, highly undesirable since the mill may have to be :stopped for repair.

The invention has been made these points in mind.

According to the invention, the balls are held in a hopper separate from the raw material to be crushed and they roll directly into the scroll feeding device where they join the raw material and are fed into the drum. It is not necessary to stop the mill while new balls are being fed and because they roll into the scroll feeding device and do not drop onto it, the chance of their damaging the scroll is very much reduced.

Also, according to the invention, there is provided a ball hopper having a ball outlet which can be connected directly to the mill so as to feed into the scroll feeding device, means for holding a charge of new balls and releasing them a few at a time to the outlet, and an inlet, which can be closed when the hopper is connected to the mill, through which the hopper can be given a fresh charge of new balls.

By working in accordance with the invention the possibility of the new balls damaging the scroll feeding device is eliminated or at least very considerably reduced, since the balls can be fed relatively slowly into the device in a direction slightly sloping to the horizontal.

DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. 1 the pulverizing mill comprises a rotatable horizontal drum 12 in which the raw material is crushed by the cascading action of steel balls contained in the drum when this rotates. Leading into the drum is a scroll feeding device 14 for the raw material which delivers raw material from an inlet pipe 16 of to the drum. Air is fed by an inlet 18 through a tube 19 coaxial with the scroll feeding device 14 to the interior of the drum and air and entrained pulverized material pass through the scroll feeding device in the opposite way to the raw material feed to a classifier 20 to remove oversize material. This oversized material is returned via the device 14 to the drum, while the air and entrained fine 'materia] are taken away through an outlet conduit 22. In the case of coal, air and fine coal could be delivered directlyto the burners of a boiler or the like.

In conventional practice, when new balls need feeding to the drum, they are added to the raw material and enter the mill through the pipe 16. The balls are very heavy and dense and when they fall onto the scrollfeeding device 14 they are liable to damage this and also the tube 19, with the result that these parts need frequent replacement and repair, and the availability for use of the mill is therefore reduced.

In accordance with the invention, however, this is not the practice. Instead, the new balls are contained in a ball hopper 30 and the are fed from this through an inlet pipe 32, having a valve 33 directly into the device 14. As can be seen they do not drop onto the device but instead roll relatively slowly down the inlet pipe 32 into the device. This avoids or considerably reduces the possibility of damage to the device.

The hopper 30 comprises an outer cylindrical casing 34 containing an inner compartment 35 for the balls, an outlet trough 36 arranged to be connected to the inlet 32 on the mill, and a quick-release sealed access door 38 through which a new charge of balls can be supplied to the hopper.

The inner compartmented container 35 is shown in detail in FIG. 4. It consists of a spindle 40 which is rotatably journalled in the casing 34, and a cylindrical casing 41 to which are attached a set of discs 42 fixed on the spindle and defining a number of subcompartments 44 for the balls. Each subcompartment 44 has a compartment outlet 46 and each of these outlets is staggered around the periphery of the container 35 in the manner shown in FIG. 4. Also as shown best in FIG. 5A, each compartment has an inlet 47, all ofwhich are in the same position around the periphery of the container 35, and through which the compartments are filled with balls when a new charge is supplied through the inlet 38. A sprocket 48 is fixed on one end of the spindle 40 and the whole container 35 can be rotated in the casing 34 by means of a hand wheel 50 and a worm 52 engaging the sprocket.

In operation the hopper 30 is first loaded with a charge of balls through the inlet 38 and the inner compartmented container 35 is in the position shown in FIG. 5A so that the halls pass into the compartments 44 through the inlets 47. The balls cannot escape from the outlets 46 since these are covered by a curved plate and, to empty balls into the trough 36, the container 35 is swivelled by means of the hand wheel 50 and this brings one or more of the outlets 46 of the compartments clear of the plate 54. Then balls from those compartments are able to run out into the passage 56 defined between the casing 41 of the container 35 and the hopper casing 34 into the trough 36. It will be seen from FIGS. 5A and 58 that each subcompartment 44 has a base plate 60 to ensure that the compart ments empty completely.

Once the hopper 30 has been filled with balls, and to do this it will normally be stood on the ground on its legs 62, it is picked up by, for example, a fork lift truck 64, the prongs 66 of which are shown in broken lines inFlG. 2, and lifted to such a position that the outlet from the trough coincides with the inlet pipe 32. The two are then connected together. The valve 33 is opened and, because the hopper is sealed, there will be a slight pressure adjustment but substantially no air will escape from or enter through the hopper, whether the mill is one working with air pressures above or below atmospheric pres sure. This is, of course, particularly important in the case of coal pulverizing for use in boilerswhere the air will probably have been preheated and so any loss is undesirable and could be highly dangerous. 4

With the hopper 30 in the position shown in FIG. 1, new balls can be added to the mill when necessary by the mill operator, who merely mounts the steps 68 and turns the handle 50. Because the outlets 46 are staggered the balls are released a few at a time under the complete control of the operator. Also the job is clean, quick and simple.

Once the supply of balls in the hopper 30 has been exhausted, the valve 33 is closed, the trough and inlet pipe 32 disconnected and the hopper lowered by the fork lift truck to ground level for restocking with balls.

It will be appreciated that the hopper can be of any convenient size, and in fact it can readily be designed to hold about a weeks supply of balls.

A latitude of modification, change and substitution is intended in the foregoing disclosure and in some instances some features of the invention will be employed without a corresponding use of other features. Accordingly it is appropriate that the appended claims be construed broadly and in a manner consistent with the spirit and scope of the invention herein.

We claim:

1. A ball hopper for use in the feeding of new balls to a ball mill along with the raw material through a screw feeding device of said mill, comprising a hopper casing in which a charge of new balls is held, a ball outlet adapted to be sealingly connected to said screw feeding device, an inner compartment for holding the charge of new balls, said inner compartment being substantially circular in cross section over a substantial portion thereof and being positioned within said hopper casing, a plurality of compartment outlets in said compartment spaced longitudinally and circumferentially over an upper portion of said compartment, means on said hopper extending downwardly and covering said outlets, said inner compartment being rotatably supported within said hopper casing so that it can be tilted relative to said casing to bring one or more of said compartment outlets below said means to thereby release new balls.

2. A hopper according to claim 1 in which said inner compartment is mounted in said hopper by bearings, said said hopper further comprisingmeans for manually tilting said inner compartment.

3. A ball hopper for use in the feeding of new balls to a ball mill, comprising a hopper casing in which a charge of new balls is held, a ball outlet adapted to be sealingly connected to said mill, a ball inlet which can be sealingly closed when said hopper is connected to said mill and through which said hopper can be replenished with new balls, an inner compartment for holding the chargeof new balls, said inner compartment being positioned within said hopper casing, bearing means for supporting said inner companment within said casing so that it can be tilted relative to said casing to release new balls, division plates in said inner compartment which subdivide said inner compartment into a number of subcomparn ments, each subcompartment having a compartment outlet through which balls can pass to said ball outlet as said inner compartment is tilted, said compartment outlets being arranged in such a way that tilting said inner compartment causes balls to pass mainly from one subcompartment and then mainly from another subcompartment.

4. A hopper according to claim 3 further comprising a cover plate which covers said outlets from said subcompartments until said inner compartment has been tiltedv 5. A hopper according to claim 2 in which said manual means include a hand-operated wheel, a worm wheel rotated by said wheel, and a worm gear meshing with said worm wheel and connected to said inner compartment.

6. A hopper according to claim 1 in which said ball outlet includes a guide which, when said hopper is connected to said mill, is slightly inclined to the horizontal and down which new balls roll on their way to the mill.

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