US2040196A - Apparatus for separating sized mixtures of material - Google Patents

Description

N. H. BERRISFORD APPARATUS FOR SEPARATING SIZED MIXTURES OF,MATERIAL May 12, 1936.

5 Sheets-Sheet -1 Filed June 19, 1934 Ma 3 N \\\\\\\\\\\\\x May 12, 1936. w. H. BERRISFORD APPARATUS FOR SEPARATING SIZED MIXTURES OF MATERIAL Filed June 19, 1934 5 Sheets-Sheet 2 May 1936f w. H. BERRISFORD 4 ,196

APPARATUS FOR SEPARATING SIZED MIXTURES OF MATERIAL Filed June 19, 1934 5 Sheets-Sheet 3 Patented May 12, 1936 PATENT OFFICE APPARATUS FoR SEPARATING SIZED MIXTURES OFMATERIAL William Henry Berrisford, Longton, Stoke-on-Trent, England Application June 19, 1934, Serial No. 731,357 In Great Britain June 22, 1933 6 Claims.

The invention relates to machines primarily for the dry cleaning of coal but is equally applicable to the separation of other sized minerals or mixtures of lump and/or granular materials without the use of liquid.

' According to the invention a mixture such as of coal and dirt is fed on to an inclined table to which a reciprocating motion is imparted tendingto conveythe material upward, and the slope of the table is such that one constituent of the mixture passes upwards to be taken off at the upper end and the other constituent passes downwards to be taken off at the lower end.

' Asimilarmovement of the constituents as regards direction has been carriedrout in the wet process of coal cleaning, but the principle of operation is fundamentally different since the scour of the water is relied on to remove the one constituent. A very efiicient separation is achieved by means of the presentinventionrwith apparatus which is very cheap in initial cost and .upkeep and without the drawbacks of the wet process which are particularly serious in the case of small coal.

Whenusedfor coal with an admixture of shale, pyrites, quartzand 1ike impurities a rapid stratification is produced by the reciprocation of the table in which the dirt is next the table with the coal above it. v The conveying motion takes the dirt to the upper end of'the table while the coal glides downwards over the dirt to the lower end.

The table may be supported on inclined legs as in the-case of "shaking'screens and shaker conveyors or may be supported by means of rollers and suitably inclined surfaces, but it is of very great advantage to have a reciprocating movement which comprises a jerk in the cycle, preferably the jerk is at right angles to the direction of reciprocation. A particularly suitable construction is one in which the path of the table is an elongated triangle. Such a movement is obtained-by the ratchet mechanism described in British patent specification No. 396,807.

It is also advisable in certain cases to impart the reciprocating movement to the table not by an ordinary crank or eccentric but by some mechanism giving a time-speed curve differing substantially from a sine curve. Such mechanisms are the Aitken drag-link gear, Whitworth quick return motion, a slotted link and crank or a, crank with relatively short connecting rod suitably positioned.

The separating effect is greatly assisted by making the table surface rough, say by the application of wire mesh or expanded 'metal, and

it may be further enhanced by an air blast pass ing upwards through the table, particularly if the blast is caused to pulsate in the rhythm of the table movements.

The accompanying drawings show how the invention'may beput into practice and therein Figure 1 is a sectional elevation of coal cleaning apparatus in accordance with the invention intended more particularly for small coal,

Figure 2 is a detail,

Figure 3 is a plan of the dirt discharge,

Figure 4 is a view similar to Figure 1 showing the incorporation of de-dusting apparatus, and

Figure 5 is a view similar to Figure 4 but with duplicated table and a screening arrangement.

Referring to Figure 1, a table I is mounted by means of hardened steel pads 2 on ratchet wheels 3 which are provided with retaining pawls 4. The ratchet wheels are mounted on the frame 5 pivoted at 6 and supported at I. The height of the support at I can be adjusted by any suitable means to secure the most suitable slope for the table I. The movement of the table is effected by means of a pulley 8 and eccentric 9 both mounted on a shaft journalled on the frame 5. A connecting rod l0 transmits the movement to the table which thus carries out a reciprocating movement with a jerk in the cycle as described in the above-mentioned patent specification.

Side walls or flanges H retain the material on the table I and these walls are connected together by coal feed baffles l2, l2a. The raw coal is fed into astationary hopper l3 and feeding is effected bymeans of the relative movement of the ,feed bafiles l2 and the bottom outlet of the hopper [3. It will be seen that the raw coal is discharged in a direction towards the upper end of the table. This feature is of assistance in securing satisfactory separation.

If the table is set at a suitable angle by adjusting the support I, the dirt sinks to the bottom and is conveyed upwards to the right hand end of the table to be discharged at M, while the clean coal travels down over the dirt to the lower end to be discharged at I5. This effect is assisted by varioussupplementary means which will now be described.

The table surface from It to I! is perforated, the size of the perforations being such as to retain practically all the material being treated. A stationary air chamber l8 below the table is supplied with air from a fan and the current of air is subdivided by baflles l9 to reduce the effect of differences in the air resistance imposed by different parts of the bed of material being treated.

The Walls of the air chamber I8 and the baffles I9 are connected by flexible impervious extensions 20 to the table I and a baflie plate is fitted at 2I over the outlet of the chamber I8 so as to constitute a plurality of small air compartments below the table. Each time the table drops over a tooth of the ratchets 3 a puff of air is thus directe'd'thro'ugh the table perforations and the bed of material.

The apparatus shown is particularly suitable for small coal and as this normally carries a substantial quantity of dust and in fact may comprise all sizes from a certain maximum down to zero, it is undesirable to allow the air which has passed through the bed to escape freely to atmosphere. The space above the perforated part of the table I6 Il is therefore enclosed as tightly as the relative movement of parts permits by baflles 22 and the air is discharged into a flue 23 so that it may be freed from dust by any suitable apparatus.

The table surface, at least over the part I6I I, is roughened or given a saw-tooth or ratchet section. Expanded metal may be used for this purpose. If a piece of expanded metal is viewed transversely to the direction in which expansion took place it resembles ratchet teeth and the perforations appear to have an oblique direction. The expanded metal used for the table is set so that the perforations are directed upwards in the direction of movement of the dirt and the quasi ratchet teeth also favour this movement up the slope of the material next the table.

In an alternative arrangement the table surface is of sheet metal with perforations so made that a bur is left on the upper surface at the side of each hole towards the end I5, the holes being clean out towards the end I4.

A more advantageous arrangement is to make the'table surface of wedge wire. The topsurface of the wedge wires of a wedge wire screen usually coincides with the surface of the table, but in the present case each individual wire has its upper surface 24 as shown in Figure 2 set at a steeper angle than the general level of the table surface indicated by the line 25. This also gives a saw-tooth arrangement to the surface and enables the known advantages of wedge wire to be attained.

It will be seen that with all these different forms of table surface the effect is further supported by the fact that the air is discharged obliquely upwards in relation to the table surface.

The roughened table surface is advantageously continued upwards over the impervious part to the dirt outlet, but it is usually better to keep the lower end smooth to facilitate the downward movement of the coal where it is no longer supported by a bed of dirt.

The upward end of the middle part of the table may be narrowed by making the flanges I I gradually approach each other. Another means for accomplishing the same purpose is shown in Figure 3 which is a plan of the dirt outlet I4. Two side walls 26 are hinged at 21 to the flanges II and serve to narrow the discharge. The width of opening can thus be adjusted to suit whatever material is being treated. By making the opening narrower than would correspond to the proportion of dirt to be removed the top surface of the dirt is given a steeper slope than the table. This does not in any way impede thedischarge of the dirt, but it allows any coal which may have strayed so far toreturn downwards and ultimately work its way to the coal outlet I5. Supplementary walls 29 in a V-shape may also be fitted if desired, and these walls are advantageously used for adjusting the width of aperture.

Figure 4 shows a very convenient arrangement in which a table as shown in Figure 1 is combined with a de-duster for removing dust from the coal on its way to the table. The various parts of the table have already been described above and will be recognized in the figure. The feed hopper 30 is however set higher above the 'table, and the coal is fed through a rotary valve 3| constituting an air lock on to a de-dusting surface built up of a number of plates 32 set on a curve and with gaps between them. A part of the air which has passed through the table I continues its path through these gaps and through the stream of coal falling from one plate to the next, carrying away the dust. The coal collects in a pocket formed by the inwardly curved last plate 32 of the de-duster and the baflles 33 and 34. The plate 32 and the baflie 34 are kept stationary, and the feed is effected by the relative movement thereto of the bafiie 33 fixed to the table I. The coal passes down the chute 35 on to the table I. The air passing between, the plates 32 together with the air from the part of the table I below the chute 35 pass up the flue 23, but to regulate the relative quantities and to compensate for the difference in air resistance in the two paths a division plate 36 is arranged within the flue 23, terminating in a damper 31 which can be set tochoke either air current to the desired extent. The distribution of air as between the upper and lower gaps between the plates 32 can also be adjusted by a damper 38. There is also a damper 54 at the end of a baffle 55 to regulate the distribution of air as between that passing through the upper part of the table and that drawn in over the lower part of the table.

It may occur that the rate of size of the material to be treated is too great for it to be conveniently treated on a single table as just described. For example with coal from one inch down to nothing it is advantageous not only to use a de-duster as shown in Figure 4, but to treat the coal above and. below, say, on separate tables. A form of apparatus will now be described with reference to Figure 5, which will de-dust the coal, screen it, and then clean the two grades separately.

The raw coal passes from the hopper 39 through the rotary valve 3I over the plates 32 for de-dusting and is delivered on to a screen plate 39 which forms a continuation of the coal chute 35. The larger coal falls off the end of the screen plate 39 on to the upper table 40 as in the case of Figure 4 and is cleaned, the clean coal passing out at 4| and down the chute 42 to join the smaller clean coal which will be subsequently referred to. The dirt is discharged at 43 and slides down the chute 44 to the dirt conveyor at 45.

The smaller coal which passes through the screen plate 39 falls on to a plate 46 and therefrom on to a feed plate 4! which discharges it in a direction towards the upper end of the lower table 48. The smaller dirt is discharged at 49 by a chute into the chute 44 carrying the larger dirt, while the 'smaller coal passes downwards over the end 50 by a chute to the clean coal conveyor 52. It will be seen that the larger clean coal chute 42 discharges on to the table 48 near its lower end. The two tables 49 and 48, the screen plate 39, and the feed baflies 34 and 35 are all connected together and are moved as a unit by the ratchet and eccentric gear as described in detail in connection with Figure 1. A damper 56 serves to regulate the air passing through the table 48 and cooperates with the dampers 31 and 38 to ensure that the relative quantities of air passing through the various parts are those best suited to the operation in hand.

A further feature shown in Figure 5 remains to be described. This feature can also be applied to the arrangements shown in Figures 1 and 4. At a certain distance below the feeding points on both tables 40 and 48 a step or low wall 53 extends across the whole width of the table. The function of this step is to impede any dirt which may have wandered down so far and to prevent it from passing off at the lower end with the coal. Each step 53 is thus in function a counterpart of the hinged walls 26 shown in Figure 3, but it also has the further effect of regulating the depth of bed of material under treatment.

It is of course possible to add to the arrangement of Figure 5 a further screen to pass, say, all material below 4;" and then to treat the fines on a third plate removing very fine dirt. This more accurate sizing makes it possible to use smaller wind pressures for the same quality of product. Further if one or other constituent is not sufficiently freed from the other where such sizing has taken place, some part of the product may be returned to the feed for retreatment. For example if the smaller material passing the screen plate 39 of Figure 5 contained very little dirt there might be a recoverable proportion of coal passing out at 49, though the amount of material here was relatively small. In this case arrangements would be made to subdivide this product. A middlings product or coally portion would be obtained, and be returned, preferably by a suitable conveyor, to the hopper 30. The rest of the material would pass out at 49 and would then be small in amount but would be practically all shale.

What I claim is:

1. Apparatus for separating sized mixtures of material in a dry state comprising in combination a longitudinally inclined table, a support for the said table, cooperating step members attached to the said support and table respectively, and driving means for reciprocating the table to drop over the step at a point in the up-stroke not later than the end thereof, the slope of the table being such that due to the combined reciprocating and drop movements the constituents of the mixture pass in opposite directions up and down the table.

2. Apparatus for separating sized mixtures of material in a dry state comprising in combination a longitudinally inclined table, pawls attached to the under side of the tabla-ratchet wheels supporting the pawls and having the teeth set in a direction to be driven by the pawls during the downward stroke of the table, and driving means for reciprocating the table, the slope of the table being such that due to the combination of the reciprocating movement and the drop when a pawl passes over a tooth the constituents of the mixture pass in opposite directions up and down the table.

3. Apparatus for separating sized mixtures of material in a dry state comprising in combination a longitudinally inclined table, pawls attached to the under side of the table, ratchet wheels supporting the pawls and having the teeth set in a, direction to be driven by the pawls during the downward stroke of the table, stationary pawls cooperating with the ratchet wheels to prevent rotation in one direction and permit it in the other, and driving means for reciprocating the table, the slope of the table being such that due to the combination of the reciprocating movement and the drop when a pawl passes over a tooth the constituents of the mixture pass in opposite directions up and down the table.

4. Apparatus for separating sized mixtures of material in a dry state comprising in combination a longitudinally inclined table having over at least a part of its length a, saw tooth section of the upper surface with the steeper faces directed towards the upper end, a support for the said table, cooperating step members attached to the said support and table respectively, and driving means for reciprocating the table to drop over the step at a point in the up-stroke not later than the end thereof, the slope of the table being such that due to the combined reciprocating and drop movements the constituents of the mixture pass in opposite directions up and down the table.

5. Apparatus for separating sized mixtures of materials in a dry state comprising in combination a longitudinally inclined pervious table, a support for the said table, cooperating step members attached to the said support and table respectively, driving means for reciprocating the table to drop over the step, and a stationary baflie with restricted aperture located below the table to form a partly closed air chamber of which the volume is suddenly reduced by the drop of the table over the step. 1

6. Apparatus for separating sized mixtures of material in a dry state comprising in combination a longitudinally inclined table, a support for the said table, cooperating step members attached to the said support and table respectively, driving means for reciprocating the table to drop over the step, and converging oblique side walls at the upper end of the table with adjustable aperture between them at the top end, the slope of the table being such that due to the combined reciprocating and drop movements the constituents of the mixture pass in opposite directions up and down the table.

WILLIAM HENRY BERRISFORD.

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