US2675967A - Discharging or unloading powdered material and the like from rotary mills and the like - Google Patents

Description

Apr1l 20, 1954 MQTE DISCHARGING OR UNLOADING POWDERED MATERIAL AND THE LIKE FROM ROTARY MILLS AND THE LIKE Filed June 20, 1950 3 Sheets-Sheet 1 v enter Jimpze April 20, 1954 MOTE DISCHARGING OR UNLOADING POWDERED MATERIAL AND v THE LIKE FROM ROTARY MILLS AND THE LIKE Filed June 20, 1950 3 Sheets-Sheet 2 E L FROM ROTARY M LIKE Aprll 20, 1954 MQTE 2,675,967

DISCHARG OR UNLOADING POWDERED MATERIAL AND TH ILLS AND THE Filed June 20, 195

3 Sheets-Sheet 3 Patented 'Apr. 20, 1954 .DISCHARGING OR UNLOADING POWDERED MATERIAL AND THE LIKE FROM ROTARY MILLS AND THE LIKE Horace Mote, London, England, assignor to Acheson Colloids Limited, London, England Application June 20, 1950,, Serial No. 169,182

Claims priority, applicationGreat Britain June 24, 1949 3 Claims. (01. 241-47 This invention relates .to discharging or unloading dry powders, finely comminuted material and the like (hereinafter .called powder) in :batcheszfrom rotary ball or rod mills, drums and the like, and is especially suitable for use .in connection with ball or rodmills or dry mixing machines where permanent grinding or mixing elements make the extraction :of the contents difficult or slow to accomplish. Vessels of the above kind to be unloaded will .be hereinafter referred to as mills, andan aim of the invention is to provide an improved method and means whereby in the unloading of mills in batches, :the dimculty of extracting the treated material from among the balls or treating elements issatisfactorily overcome-and the unloading operation considerably expedited.

Where the batch grinding .or treatment of powders toa finer particle orcolloidalsize is involved, the known means for discharging or unloading .such mills suffer from the objection that it is very .difiicult toavoidsome of the powder escaping, with the result that such becomes airborne .and pervades thesurrounding atmosphere. This trouble is particularly noticeable where pene- .trating and impalpable or colloidal powders are concerned as such may travel some distance from the mill :and become deposited as grime over surrounding surfaces. .Furthermore, this nuisance becomes a serious matter when material treated .isof a poisonous or obnoxious character.

The abatement of this troublehas been a longstanding problem, and a furtheraim of the invention-is to afford a satisfactory solution whereby powders may be unloaded in batches'and transferred to another vessel with insignificant or no escape'of material.

- The invention consists in discharging or unloading a batch from a mill in'motion pneumatically (preferably applied by the application of suctionlalong an enclosed path, part of which rotates with the mill and part of which'is stationary, with a sealed' connection between said parts permittinga relative rotation, leading-into a suitable receiver which is vented (-preferably to an evacuating source such as'a centrifugal fan -or pump.) through an air pervious filter, cyclone .or other separator. 1

As applied to a ball mill or other machines having free grinding or treating elements the entry to the enclosed path is screenedto'retain the balls or the like while permittingthe'outflow of a'ir'and powder,'theinflow of 'airjt'o the .2 According .to .one .form of the invention the enclosed path is provided by a conduit or piping which :may beseparatefrom the .mill or built into the walling and which isxdetachably connected or connected through a valve to a manhole .or

aperture in the .mill .such that as the mill is rotated the aperture is .periodically uncovered by the contents, while at other times such is covered by the gravitating material and balls with the consequence that both airborne particles within the mill and settled materials are extracted.

When the .mill is in use for grinding or mixing the manhole or other entry to the enclosed path is closed by a cover or the shutting of a valve and grinding proceeds in the normal manner.

. In the accompanying drawings:

Figure 1 is a diagrammatic sectional side elevation of a mill having discharging or unloading means according .to the present invention.

Figures .2, .3 and 4 are sectional side, plan and end elevations respectively of a discharging or unloading box for comprising part of the present invention.

Figures 5and ,6 area side elevation and plan view respectively of the unloading box shown in nector comprisingpart of the present invention,

and

Figure 9 is a sectional side elevation of an alternative form of connecting means, according to theinvention, for a solid trunnion.

In carrying the invention into efiect according to one mode as described in reference to a ball mill for reducing material or powders to finer or colloidal form, having hollow trunnions I and 2, and one or more manholes 3, each manhole is provided witha chamber or box l detachably securable to the manhole and sealed to the pe riphery thereof by a gasket or the like 4a. The box 4 is provided with a slotted or other grid 5 separating it from the interior of the drum. This grid has interstices of a size such as will prevent the escape of the balls but will freely allow powdered material to pass. To one side-of the box-4 or in any other suitable situation a conduit'or pipe 6 is secured. According to the preferred form (see Figures 3 and 5) the box at the side or portion? adjoining the connection tothe conduit or pipeline is flared out or made of funnel shape.

The conduit or pipe may be 7 built into thewall'of the drum of the mill or it may bespaced therefrom as illustrated. This;

conduit or pipe 6 is led to one of the hollow trunnions 2 of the mill and the end 8 remote from the box is connected to the said trunnion as at 9 and so with the interior of the trunnion which is detachably connected by a suitable pipeline or the like I to a receiving vessel H, which will be described below. In this way an enclosed path is formed for the discharge of the powder from the mill to the receiving vessel.

Assuming that the ball mill is provided (as illustrated) with a pair of diametrically opposite manholes 3, such as above referred to, which may be in the same or a different transverse plane, each manhole 3 is covered by a box 4 which is coupled by the conduit or pipeline 6 to the hollow trunnion 2 entering such at diametrically opposite points 9. V

The boxes 4 may conveniently be secured against the manhole opening by means of a. transverse bar 20 (Figures 5 and 6) spanning the box and anchored at either side thereof to the mill casing by pivotal links 2|, a central bolt 22 or the like being provided on the bar 20 to apply damping pressure to the upper surface of the box. In order to facilitate cleaning, the side or connecting portion 1 of the box has a removable plug 23 in alignment with the pipe 6, to allow access thereto.

The connection within the trunnion between the conduits or pipelines 6 and the pipe l0 leading to the receiver H is in a form which while permitting rotation of the mill provides an adequate seal so that no material can escape between the moving parts. According to one form where the bore of the hollow trunnion 2 extends into or is open to the interior of-the mill (see Figure l) a hollow cylindrical plug or sleeve 12 is introduced into said bore and is flanged at it outer end l3 (Figures "1 and 8). This flange I3 is secured by set screws or the like 14 to the bearing member l5 for the trunnion, so that the plug [2 is held stationary. If desired, the inward end of the plug may engage a sealing packing in the hollow trunnion to prevent the creeping of the ground powder between the plug and the interior surface of the trunnion.

The plug l2 in the plane of the entry of the conduits or pipes 6 from the manholes 3 is provided with a port 16 (or ports) extending around (preferably) nearly half the circumference of the plug (see Figure 8). As the mill rotates, this port ['6 will be brought alternately into communication with each pipe or conduit 6 from the pair of manhole boxes 4; thus each unloading box 4 in turn is exposed to the full suction of the evacuating means H. In the form illustrated in Figure 1 each box 4 will be drawing out powder from the interior of the mill over the greater part of the lower semicircle of its travel.

Instead of employing a hollow trunnion which communicates with the interior of the mill, a hollow trunnion having a blank or dead end or a bored solid trunnion (Figure 9) may be used, in which case the conduits or pipes 6 from the unloading boxes A are connected to such trunnion in a similar manner to that already described and so that they communicate with the interior bore 5| of the trunnion but instead of employing a plug such as the previously described plug i2, the outer end of the trunnion is provided with a running connection with a stationary member. 52 to which the pipeline in to the receiving vessel H is coupled, such that while rotary relative movement may take place there is no escape of powder at the connection. In a preferred form as illustrated in Figure 9, the running connection between the trunnion bore and the pipeline ID includes the stationary member 52 in the form of a closure having a circular flange 53 and a central cylindrical boss 54 adapted to be received within a counterbore 55 in the end of the "trunnion 50. Suitable packing 56 is interposed between the boss 54 and the end face of the counterbore 55, which may be recessed as at 51 to accommodate and retain the packing.

The receiver ll according to one appropriate form as illustrated in Figure l is a vessel comprising a lower portion 85 in which the delivered powder is collected and a detachable upper portion or dome BI is connected by a suitable pipeline 82 to an evacuating source such as the suction of a centrifugal fan or pump ll. This upper part or dome 8| also has fitted to it interiorly an inverted filter bag 84 of suitable fabric or a pervious material which may be detachably mounted in position. This filter 84 intervenes between the main portion of the receiver and the air exit pipe 82 and serves to hold back any powder, preventing its escape to the fan or pump 11 and thus to the outside air.

The pipe or conduit [0 from the mill may connect directly to the receiver portion 80 or may as illustrated be connected to an intermediate portion 85 of the receiver, which portion is supported by the lower portion 80 and provides support for the upper or filter portion 8|. By this arrangement the receiver H is easily dismantled and either the lower portion 30 or the upper portion 8| may be removed as required for emptying or cleaning.

Any suitable means may be provided for securing the lower or collecting portion 80 of the receiver to the upper portion or dome 8! or to the intermediate portion 85, alternatively to the form illustrated, the dome may be supported in any suitable manner as a fixture and have a pair of hooked levers pivoted thereto, the hooks of which are adapted to engage a pair of lugs or pins on the lower portion of the receiver. The pivots of the hooked levers may be on toggle links adapted to draw the lower portion of the receiver into sealing contact with the dome or upper portion.

The discharge pipe Ill from the hollow trunnion may alternatively enter the lower portion of the receiver in any suitable position and may be suitably detachably connected thereto, but it is preferred to connect the trunnion permanently to the upper part at a position below the filter.

According to another form of reception, the unloaded powder may be delivered directly to a storage bin, mixer or other vessel wherein a further treatment or operation is to be performed, for example the delivery may be to a vented mixer in which the powdered material is mixed with a liquid or semi-liquid or other agent. The vent of the mixer is connected to the source of suction through a filter or through a cyclone or other separator adapted to settle particles passing in the air stream to said source of suction. Alternatively,. the powder from the mill is delivered to a chamber or vessel the lower portion of which is in the form of a hopper provided at its lower end with a valve or controlled outlet from which the ground material passes by gravity or other feed into a weighing skip or to a plant unit for the next processing stage.

The interior of the mill is vented to atmosphere in order that the air drawn out by suction shall be correspondingly replaced. Where the other trunnion is hollow, communicating with.

the interior of the mill as shown in Figure 1, this may be conveniently used for the entry of air. Alternatively an air entry may be made by perforating the wall of the drum coaxially in the closed hollow trunnion type.

When the mill is to be arranged for operating under normal running conditions the boxes, or boxes 4 and pipe connections are removed, the covers for the manholes 3 replaced and the ported hollow plug I 5 referred to above replaced by a trunnion closing plug or cap (not shown). Similarly the air venting trunnion of the mill is closed. In the closed trunnion form the running connection to the receiver may be removed or it may remain in position, as desired.

Instead of providing detachable manhole covering boxes, permanent boxes may be provided which embody valve means, the valve of which is closed to shut the grids of the boxes when the machine is running for normal grinding purposes and opened for unloading. This valve device may be in the form of a sliding plate or a pivoted plate or rotary member, or alternatively it may be in the form of a shutter or hit-and-miss damper co-operating with a similar type of grid. If desired, for instance when dealing with hydroscopic material, the vent in the mill through which replacement air enters, may be coupled to a heat exchange device for warming the air on its way to the mill.

In operation, assuming the unloading mechanism to have been connected up as described, the centrifugal fan or pump I1 is started or connected to the pipe 82 coupling it with the dome 8| of the receiver so that suction is applied and a free flow of air takes place into the mill whilst it is revolving, the air being drawn through the grids 5 of the boxes 4 and along the pipelines 6 and through the hollow trunnion l2 to the pipe iii connection with the lower part 80 of the receiver I I. As the mill is revolving the contents are continuously disturbed and the powder gravitates towards the lower part of the mill and into the grid boxes 4 as they are moved through their lower arc of travel during rotation; the powder thus entering the boxes is withdrawn through the pipelines 6 by the air current. The powder-laden air as it enters the receiver H is filtered by the filter bag 84 and falls into the lower portion 80 of the receiver. Rotation of the mill and application of suction is continued until the powdered material is emptied from the mill. When the material in the receiver H has settled the lower portion 8| is detached and taken away for packing, further treatment or other purposes. After unloading the mill is restored to its normal running conditions ready for recharging by the detachment or adjustment of the parts employed in the unloading operation.

Pneumatic means may also be applied for loading or charging the mill, for example, an unloading box is replaced by a loading box or dome having a filtered air exit to the suction of a centrifugal fan or the like, one end of a charging pipe or conduit being connected to a hollow trunnion or other convenient entry while the other end is located in the supply of the powder with which the mill is to be charged.

Alternatively, a hollow trunnion may be fitted with a filtering tube or thimble projecting into the mill and suction applied to this trunnion, the unloading box (or one of them) being in this case connected (via the other hollow trunnion) to a charging pipe connected with the source of supply. According-to this'form the mill is first rotated so that the unloading box in question is above the level of the grinding elements and any unloading box under the grinding elements is cut off from communication with the charging trunnion.

What I claim is:

1. Apparatus for unloading through an enclosed path a batch of powdered material into a receiver from a moving rotary mill having a drum provided with a loading aperture and closure in the peripheral wall thereof and treatment elements, such as balls or rods, therein and a hollow trunnion on which the drum is journalled, comprising: a box locatable over the loading aperture in place of the closure for unloading purposes, means for releasably securing the box over said aperture, grid means associated with the box to prevent the entry therein of the treatment elements, conduit means rotatable with the drum and in pneumatic connection at one end with the box in situ, and at the other end with the interior of said hollow trunnion, stationary conduit means connected at one end to said receiver, means associated with said hollow trunnion for connecting the other end of said stationary conduit means to said rotatable conduit means whereby said enclosed path is completed, pneumatic means connected to one end of said path to provide a pneumatic system operable to cause displacement of the powdered material as an aerosol along said path from said drum and into said receiver, an air pervious filter associated with the receiver to filter the powdered material from the aerosol displaced from said drum, and means for venting the pneumatic system.

2. Apparatus as claimed in claim 1, wherein the stationary conduit means is pneumatically connected to the rotatable means by a stationary sleeve accommodated within the hollow trunnion and comprising valve means for connecting the stationary conduit means to the box and'rotary conduit means only when the box is passing over the lower half on its circular rotational path with the mill drum, rotary sealing means being provided between the sleeve and the trunnion.

3. Apparatus as claimed in claim 2, wherein the sleeve is in the form of a hollow plug, closed at its inner end and having an aperture in its cylindrical wall in the plane of entry of the rotary conduit means to the interior of the hollow trunnion, the sleeve aperture being disposed and extending around nearly half of the circumference of the sleeve on its underside.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 50,467 Hall Oct. 1'7, 1865 279,067 Wolf June 5, 1883 506,591 Guild Oct. 10, 1893 932,727 Suter Aug. 31, 1909 937,826 Lindhard Oct. 26, 1909 1,113,120 Howard Oct. 6, 1914 1,457,084 McLaughlin May 29, 1923 1,468,893 Wolever Sept. 25, 1923 2,241,848 Eckart May 13, 1941 FOREIGN PATENTS Number Country Date 15,454 Great Britain AD. 1908

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