US3233877A

US3233877A - Method and plant for blending materials in bulk

Info

Publication number: US3233877A
Application number: US387130A
Authority: US
Inventors: Kelly Jacques Marie Michel
Original assignee: MINES DE FER de la MOURIERE SO
Current assignee: MINES DE FER de la MOURIERE SO; MINES DE FER de la MOURIERE Ste
Priority date: 1960-08-13
Filing date: 1964-08-03
Publication date: 1966-02-08
Anticipated expiration: 1983-02-08
Also published as: FR1272184A; OA00979A

Description

Feb. 8, 1966 J. M. M. KELLY I METHOD AND PLANT FOR BLENDING MATERIALS IN BULK Filed Aug. 3, 1964 '7 Sheets-Sheet 1 g N 4,; NW6.

4H'vrne g J. M. M. KELLY 3,233,877

METHOD AND PLANT FOR BLENDING MATERIALS IN BULK Feb. 8, 1966 7 Sheets-Sheet 2 Filed Aug. 3, 1964 [N268 Nef/t J- Fla- 2h Attof'ngj they Marie M J. M. M. KELLY 3,233,877

METHOD AND PLANT FOR BLENDING MATERIALS IN BULK Feb. 8, 1966 7 Sheets-Sheet 5 Filed Aug. 5, 1964 I' v r W M 0 4 I m m a m VA .U WM 1 (ls n e MU 30b Feb. 8, 1966 J. M. M. KELLY METHOD AND PLANT FOR BLENDING MATERIALS IN BULK 7 Sheets-Sheet 4 Filed Aug. 3, 1964 PrllIIl mhm Iv M WM H. T K m. w 5 A T; e M 3 J; M. M. KELLY 3,233,877

METHOD AND PLANT FOR BLENDING MATERIALS IN BULK Feb. 8, 1966 '7 Sheets-Sheet 5 Filed Aug. 3, 1964 3 3 q NKUZ Aflorne Feb. 8, 1966 J. M. M. KELLY 3,233,377

METHOD AND PLANT FOR BLENDING MATERIALS IN BULK Filed Aug. 3, 1964 '7 Sheets-Sheet 6 Atfo rme Feb. 8, 1966 J. M. M. KELLY 3,233,877

METHOD AND PLANT FOR BLENDING MATERIALS IN BULK Filed Aug. 3, 1964 '7 Sheets-Sheet 7 United States l atent O 3,233,877 METHOD AND PLANT FOR BLENDING MATERIALS IN BULK Jacques Marie Michel Kelly, Paris, France, assignor to Societe des Mines de Fer de la Mouriere, Paris, France, a corporation of France Filed Aug. 3, 1964, Ser. No. 387,130 Claims priority, application France, Aug. 13, 1960, 835,886; Jan. 13, 1961, 849,635; Aug. 9, 1963, 944,371, Patent 1,272,184

21 Claims. (Cl. 259-180) This is a continuation-in-part of applicants co-pending patent application Ser. No. 124,578, filed July 17, 1961, entitled Method and Plant for Rendering Homogeneous a Single Divided Product of Non-Uniform Quality or a Mixture of Two or More Divided Products Introduced in Fixed Proportions, now abandoned.

The present invention has for its main object a method of rendering homogeneous a single divided product of non-uniform quality or a mixture of two or more divided products introduced in fixed proportions. This method is of the type wherein the homogeneousness of the desired mixture is obtained or assisted by depositing the various constituents in heaps along substantially parallel layers and by reclaiming the product along likewise parallel slices made at an angle to the lie of the deposited layers.

When it is desired to render large tonnages homogeneous, it is commonplace to resort to a method known in the metallurgical industry by the name of bedding. This method consists in depositing the product to be made homogeneous in a heap, along horizontal layers, and in reclaiming this heap along inclined slices intersecting the planes of deposit.

When it is desired to obtain mixtures by the bedding method, it is necessary to have two storage areas: on one of these is the heap being reclaimed, on the other the heap in the course of constitution. The large amount of space needed and the fact that such discontinuous operation entails variations of quality each time a heap is changed are both drawbacks inherent to this method.

It has also been proposed to provide a pile of triangular cross section, the material to be blended being dispersed on the top of the pile in thin layers and reclaimed from the pile in thin layers at the base of the pile through a plurality of outlets.

If the different deposited layers were to remain parallel when the material goes down slowly and if the material was withdrawn at an equal rate by all the outlets, then the reclaimed layers would be of the same thickness along their entire length and would comprise an equal quantity of the materials of all deposited layers.

"Because of the great number of outlets, it will be diflicult to say which one exactly is involved, from the aspect of the variation of the surface of the pile. If the correction is not made on the correct outlet, there will be a further deformation of the layers which should remain parallel.

As the zone of deposit is just above the zone of withdrawl, these variations add indefinitely and even if it is possible to maintain the surface of the bin with the right shape the layers inside will be disturbed and the blending will not be satisfactory.

The present invention has for its object to overcome these drawbacks.

The method according to the invention is remarkable notably in that it comprises the steps of forming a heap by continuously distributing at a given rate said materials in substantially parallel layers, said layers being of different qualities, of simultaneously reclaiming at the same ice rate said materials along parallel cuts made at an angle to the lie of said layers, said heap thus retaining a constant mass and shape, one of said two simultaneous steps being carried out along a slope approximating the angle of repose of said materials, whereby said heap is caused to move with a velocity related to the rate of distributing said materials in parallel layers.

Consequently the pile moves slowly.

It is easy to see that during this movement, the different parallel deposited layers are not disturbed as the zone of reclaiming and'the zone of deposit are independent.

Moreover as the pile moves, the slightest variations that can occur in the withdrawal of the material are not added indefinitely, and the layers of reclaiming give very good samples of the pile.

According to one embodiment of the invention, the constituents of the mixture to be obtained are deposited along parallel planes slightly inclined relative to the horizontal, reclaiming being effected along slices close to the vertical, or along the slope of fall down the side of the heap, for example.

According to a further embodiment, the constituents of the mixture to be obtained are deposited along planes close to the vertical, corresponding to the slope of the fall down the side of the heap being constituted, reclaiming being effected along substantially horizontal slices.

According to a further embodiment, the component elements of the mixture to be formed are disposed on a substantially even circular area so that the heap thus built up has a gradually decreasing cross-sectional area, the heap-forming layers being slightly inclined to the horizontal and the material being picked up by mechanical means at the end of the heap which has the largest cross-sectional area along slices of which the longest slope forms with the horizontal an angle approximating the angle of repose of the heap.

According to another characteristic feature, the component elements of the mixture are deposited onto the upper surface of the heap supported by the aforesaid even circular area by means of a conveyor and/or a spout or the like describing with its outlet end a twofold alternating movement, one of circular configuration whereby this outlet end can sweep a sector limited by the two ends of the aforesaid circular heap, and the other in the radial direction for sweeping the entire length of the heap.

According to another characteristic feature of the invention, the materials are picked up in the form of slices having a degree of inclination approximating that of the aforesaid angle of repose, by using any suitable pickup means, such as a harrow associated with an Archimedean screw, adapted to drop the picked up and homogenized materials into an annular trough or the like disposed in the central region of said circular area.

According to a further characteristic feature of the invention, the aforesaid even circular area is defined by two cylindrcal coaxial walls constituting a kind of annular hopper of revolution of substantially rectangular cross-section and the aforesaid-heap when completed has a greater height at its outer periphery than centrally of said hopper, for a same radialcross-section.

It is a complementary feature of the invention that the aforesaid radial movement of the conveyor means forming the heap of component elements takes place at a variable speed depending on the distance existing be tween the place where the component elements are actually deposited and the center of the aforesaid even circular area.

It will be readily understood that this method is independent of the nature of these componet elements since it is not based on the principle of a more or less uniform natural heap formation.

The invention also covers a plant for rendering homogeneous a single divided product of non-uniform quality, or a mixture of two or more divided products introduced in fixed proportions.

A plant according to the invention is notably remarkable in that it comprises a single site adapted to receive a heap of said materials, distributing means for continuously distributing said materials onto said heap along substantially parallel layers, reclaiming means adapted to continuously remove said materials from said heap along parallel slices at an angle to the lie of said layers, regulating devices to equalize the rate of material removal of said reclaiming means and the rate of material delivery of said distributing means, arrangements to control the motions of said distributing means and reclaiming means whereby one of said means is caused to move along a slope approximating the angle of repose of said materials.

In accordance with one embodiment, the site intended for the heaping operation is a flat circular surface comprising, substantially in its middle, a cavity forming a central funnel or conical hopper, the means used for heaping the materials consisting in a belt conveyor,.a chute or similar device the end overhanging the heap of which describes an alternating circular motion enabling it to sweep a sector bounded by the two edges of the heap formed over said circular surface, while said reclaiming means consist of any convenient reclaiming device, such as an appliance with moving arms, a screw conveyor, a scraper and conveyor or the like adapted to discharge into said central funnel the materials reclaimed from the foot of the slope of fall down the heap.

According to a further embodiment, the site for heaping or stocking the materials consists of an annular hopper of revolution of substantially triangular cross-section, say, comprising at its bottom, a circular slit through which the reclaiming can be performed, and the means used for the heaping operation consist of a belt conveyor, a chute, or similar device, the end overhanging the heap of which is possessed of a continuous slow circular motion in step with the progression of the sloping face of the heap.

According to yet another embodiment, the plant comprises a prismatic hopper of elongated rectangular plan form and preferably triangular cross-section, in which the constituents of the mixture to be obtained are deposited in a heap, substantially over the slope of fall down the latter at the end of said heap having the greatest crosssection, the reclaiming operation being carried out through the bottom of said prismatic hopper.

According to another characteristic of this latter embodiment, when progression of the heap formed in the hopper has brought the foot of the slope of fall over which the deposits are made to the end of said hopper, further deposits on the heap cease and the formation of a fresh heap is begun at the opposite end of the hopper. The formation of this new heap is undertaken over an inclined surface which is preferably set transversely relative to the center-plane, of the hopper, said surface having approximately the same inclination as the slope of fall down the heap progressing along the prismatic hopper.

According to another embodiment of the invention, the location for forming the heap is an even circular area comprising in a substantially central position a cavity constituting an annular trough or the like, the heap-forming means consisting of a belt conveyor and a spout or the like of which the outlet end overlying the heap performs a twofold movement, that is, a circular alternating movement on the one hand for sweeping a sector defined by the two ends of the heap formed on said circular area, and a radial alternating movement on the other hand, for sweeping the heap transversely, the pick-up means consisting of a mechanical pick-u apparatus of any suitable iand known type adapted to drop into said central an nular trough the materials picked-up at the base of saidi heap at the heap end having the major cross-section.

According to another feature characterizing this em-' bodiment, the aforesaid even circular area is defined by two vertical coaxial cylindrical walls forming an annular' hopper of revolution of substantially rectangular crosssection, the aforesaid heap-forming means overlying saidl annular hopper.

It is a further feature of this invention and a specific: form of embodiment thereof that the aforesaid heap-- forming means consist .of a movable bridge structure: to which an alternating circular motion can be impressed; for sweeping therewith asector rotating very slowly; which is defined by the two circular ends of the heap formed thereunder, a frame bearing on said bridge structure and receiving a radial alternating motion, a beltor like conveyor being provided on said frame for delivering the component elements of the heap being formed to a spout or the like provided at the outlet end of said frame and overlying said heap.

Yet further characteristics of the invention will become apparent from the following description in which reference is had to the accompanying drawings given by way of example only and not limitation, and in which:

FIGURE 1 is a schematic illustration of the manner of heaping and reclaiming a product according to the method known as bedding.

FIGURE 2 is a highly diagrammatic illustration of the development of a heap as obtained according to the invention, the constituents of the mixture to be obtained being deposited along parallel planes slightly inclined to) the horizontal, and reclaiming being accomplished along: slices to the vertical, made along the slope of fall dowm the heap.

FIGURE 3 is a schematic illustration of the development of a different heap obtained in accordance with the invention, the constituents of the mixture to be ob-- tained being deposit-ed along planes close to the vertical, or along the slope of fall down the heap, for example,. and reclaiming being accomplished along substantially horizontal slices.

FIGURE 4 is a plan view of a mixing plant according; to the invention, comprising a flat circular area over: which the heap may be formed.

FIGURE 5 is a cross-section through the line VV' in FIGURE '4.

FIGURE 6 is a plan view of a mixing plant according to the invention, comprising an annular hopper for the heaping operation. 7

FIGURE 7 is a cross-section through the line VIIVII in FIGURE 6.

FIGURE 8 is a cross sectional view of a plant slightly different from the one shown in FIGURES 6 and '7.

FIGURE 9 is a highly diagrammatic longitudinal section through the vertical centre-plane of a mixing plant comprisinga prismatic hopper.

FIGURES l0 and 11 explain schematically the manner of progression of a heap in the installationshown in FIGURE'Q.

FIGURE 12 shows diagrammatically the manner inv which the materials are heaped and picked up according, to another method of this invention.

FIGURE 13 shows in plane view from above the complete arrangement of FIG. 12 according to the present invention.

FIGURE 14 is a diagram showing the contour lines of the heap of materials which is formed as illustrated in FIGURE 13.

FIGURE 15 is an elevational and sectional view with parts broken away. showing a complete installation con-.

structed according to the present invention, and

FIGURE 16 is a basic diagram showing in Cartesian co-ordinates the variable velocity of the spout delivering the materials to the heap as a function of the radial distance between the said spout and the center of the mixingplant.

The invention consists essentially in substituting for mixing methods utilizing purely static heaps and known as bedding methods, a method the principle of which is derived from said bedding methods but which causes the heap to progress along the stocking area.

Since the progression of the heap takes place on a single site, it is possible to perform the heaping and the reclaiming operations in continuous manner, a thing it is impossible to achieve otherwise.

Referring now to FIGURE 1, the reference numeral 1 designates a heap formed by the bedding method referred to previously. The figure shows the formation on this heap 1 of successive beds deposited substantially horizontally. The reference letters dd designate one of the layers in this heap. Once the heap has been formed with the number and thickness of layers needed to obtain the desired mixture when reclaiming, the latter is performed along slices denoted by ee' in FIGURE 1. These slices or reclaimings are effected, say, over the slope of fall down the heap until the latter is completely exhausted. In such cases the heap may be said to be consumed in sitju.

FIGURE 2 shows a heap 2 obtained by the method according to the invention. On this heap 2, the successively deposited parallel layers such as dd are slightly inclined to the horizontal, as a result of which said heap 2 has a maximum section in the vertical plane that passes through the point 4, which is the summit of the slope of fall.

Reclaiming is accomplished along slices ee over the slope of fall down the heap 2, and this reclaiming can be achieved by excavating at the foot 5 of said slope of fall.

In contradistinction to what occurred in the case of the heap 1 in FIGURE 1, the heap 2 need not disappear in situ. For this, it will suffice to continue to supply makeup materials along the deposit layers dd to compensate for the volume reclaimed at ee. An examination of FIG- URE 2 will show that the heap 2 will not remain static, but that it will be displaced in the direction of the arrow F2. Furthermore, there is no reason why the heap should not be formed along a near-closed curve with the point 5 at the base of the reclaiming slope close to the point 7 where the heap tapers away to its minimum section. This is in fact the arrangement adopted in the installation that will be described hereinbel-ow, such installation offering the advantage of being capable of continuous operation over a relatively small piece of ground.

The heap 3, which is likewise produced in accordance with the invention, is established by depositing the constituents of the desired mixture along successive beds which form layers dd substantially parallel to the slope of the heap, between the

points

8 and 9. Reclaiming is eifected along substantially horizontal slices ee at the base 8-40 of the heap.

Like the heap 2, the heap 3 can be maintained in continuous operation provided that the material reclaimed at 3-1$ is made up by further heaping at 89. The heap 3 will then progress in the direction of the arrow F3. As will be seen from the embodiments of installations described later, it is obviously possible to cause the heap to be formed over a near closed curve with the

points

8 and 10 in close proximity to each other, thereby ensuring a circular progression of the heap over a relatively small site.

FIGURES 4 and 5 show a plant designed for performing the method according to the invention.

The heap 2 is formed over a substantially circular area 12. The constituents of the mixture to be heaped are conveyed to the mixing plant by a conveyor 13 which spills them in proximity to the end 14 of a conveyor 15 adapted to slew about a vertical axis 16 to enable its end 17 to describe a circular path above the stocking site 12.

In the centre of said stocking site 12 is a conical 6 hopper or funnel 18, the substantially circular upper edge of which lies in the plane of the fiat stocking site 12.

A reclaiming appliance 19 is disposed radially above the site 12. This appliance is possessed of rotating motion about the axis 16 and its type will depend on the kind of material to be handled, examples of such an appliance being those equipped with mobile arms, conveyor screws, scrapers, conveyors and the like.

The manner of operation of the plant described hereinabove is extremely simple. The products to be mixed are brounght up by the conveyor 13 and distributed over the heap by the conveyor 15, which is possessed of a sufficiently rapid oscillating motion about the axis 16 to ensure that the layers of product deposited over the heap are not too thick. The amplitude of this oscillating motion will be close to a complete circle, and examination of the plan view in FIGURE 4 will show that travel of the conveyor 15 takes place from the point 4 to the point 7, and vice versa.

It will be appreciated that it will be necessary for the heap to advance in the direction of the arrow F2 as it is reduced from the base of its slope of fall (the summit of which is the point 4) by the reclaiming appliance 19, and to this end the rate of travel of said reclaiming appliance 19 is synchronized with the shift of the sector defined by the

angle

4, 16, 7.

The mixed and homogeneous product introduced by the reclaiming appliance 1% into the funnel-shaped hopper 18 is extracted and conveyed to its utilization point by a conveyor 20.

The plant shown in FIGURES 6 and 7 comprises, by way of storage means for the heap 3, an annular shaped hopper forming a body of revolution about a vertical axis 22. The products to be mixed are introduced into said hopper 21 by a conveyor 23 which is pivotable about the axis 22 and the end 24 which describes a circle the centre of which is located on the axis 22, above the annular hopper 21. At the base of hopper 21, the crosssection of which is substantially triangular, is a slit 26 through which can be extracted the products accumulated in the hopper 21. This extraction can be facilitated by scrapers (not shown); after passage through said slit 26, the product drops into a circular conveyor 27 comprising an endless chain of contiguous buckets designed to tip their contents into the hopper 28 which feeds a conveyor 29 the purpose of which is to evacuate the mixed and homogeneous product to the utilization point.

The manner of operation of the plant illustrated in FIGURES 6 and 7 is as follows: the constituents of the mixture are carried to the conveyor 23 by the conveyor 25. They then drop onto the heap 3 at the point 9 and distribute themselves through the hopper 21, over the slope of fall down the heap and between the

points

9 and 8, for example. Reclaiming takes place through the slit 26 provided at the bottom of the hopper 21.

If an examination he made of the plan view of the plant shown in FIGURE 6, it will be appreciated that the heap 3 will advance in the direction of the arrow F3, and that the displacement of the heap and that of the conveyor 23 which distributes the mixture constituents will be rigorously identical. It is manifest that proper adjustment of such a plant requires that the output of product from the conveyor 23 and that from the slit 26 be the same.

FIGURE 8 shows an alternative installation to that just described. This is much simpler in design, in the sense that it dispenses with the circular bucket conveyor and that the slit 26 discharges directly into a funnelshaped hopper 36 into which the product excavated by one or more scrapers 31 from the slit 26 drops before being evacuated by a conveyor 32. Another point which distinguishes the plant in FIGURE 8 from that in FIG- URES 6 and 7 is the fact that, in the case of the former, the heap 3 is fed through a chute 33 supplied with mixture constituents by a conveyor 34.

From the .description given above it will have been realized that the plant shown in FIGURES 4 and 5 corresponds to a heaping and reclaiming as schematically illustrated in FIGURE 2, whereas the installations of FIGURES 6, 7 and 8 correspond to a heaping and reclaiming of the form schematically illustrated in FIGURE 3.

To permit proper placement of the two circular forms of plant described hereinbefore, it is necessary to provide a site which is likewise circular or square, and of relatively large size. On the other hand, for reasons of availability between two existing installations, for instance, it may be found convenient to use a site of elongated shape and simultaneously provide suitable mechanical handling means such as conveyors or the like designed to operate in a straight line.

The installation illustrated schematically in FIGURE 9 is designed to be set up on a site of elongated shape. On this figure is shown a heap 111 obtained by depositing, as 112, the constituents of the mixture to be obtained, the latter sliding down the face 112-113 of the heap. This heap 111 is formed in a hopper 114 of substantially triangular section, the base of which comprises a horizontal slit through which travels an extraction device schematically illustrated at 115. 'This device may take the form, say, of a scraper possessed of to-and-fro motion between the

ends

116 and 117 of the base of the hopper 114. At its end 117, said hopper 114 is bounded by an inclined plane 117-118 having a substantially identical slope to that of the face 112-113 of the heap. The utility of this inclined surface 117-118 will become apparent from the description given later of the manner of operation of the installation.

Beneath the slit 116-117 through which travels the scraper 115 is arranged a straight conveyor belt 119 which conveys the mixed constituents extracted from the hopper 114 by the scraper 115 towards the utilization point.

A belt conveyor 120, preferably of the same type as the conveyor 119, is provided above the hopper 114, preferably in the vertical centre-plane thereof. A means of spilling the products transported by the conveyor 12) onto the heap 111 is illustrated schematically at 121, and this device 121 may be a spilling crab, for example, which travels in such a way as to ensure that the deposits made on the heap 111 effectively take place over the slope of fall 112-113 down said heap 111. In other words, the spilling-crab 121 travels in the direction of the arrow F, at the same speed as the heap 111 which it overhangs. The conveyor 120 is supplied by a device 122 (an intermediate hopper for example), into which are discharged, by a suitable conveyor such as a travelling chute, a noria hoist, a belt conveyor or the like, the products used to make up the mixture.

Two conditions must be fulfilled for the mixture to be effected correctly; the weight of deposited material must besubstantially equal at all times to that of the reclaimed material, secondly, the crab 121 must travel above the heap 111 at a speed which is directly proportional to the weight of material conveyed by the belt 120.

As an example, the rate of travel of the crab 121 may be controlled by indications given by a weigher A arranged on the conveyor 120, and the weight of material admitted through the hopper 122 controlled by means of a weigher B on the conveyor 119.

This installation may be controlled manually, semiautomatically or fully automatically. In the case of manual operation, an operator would have no difiiculty in regulating the quantity admitted through the hopper 122 in such a way as to ensure that the weights integrated by the weighers A and B are as nearly equal as possible at all times.

Assuming the various conditions of operation described above to have been fulfilled, the manner of functioning of the installation shown in FIGURES 9 to 11 is as follows:

Referring to FIGURE 9, it will be appreciated that the heap 111 and the crab 121 which feeds it will both advance in the direction of the arrow F, until the foot 113 of the slope 112-113 reaches the end 116 of the hopper 114. At this end 116, the hopper may indifferently be bounded by a vertical wall or be slightly inclined or even be open. Indeed, as soon as the foot 113 of the slope of fall down the heap reaches the point 116, deposits on the heap 111 are made to cease and the spilling crab 121 is quickly brought. above the point 118 on the inclined plane 117-118 which bounds the prismatic hopper 114.

FIGURE 10 is a diagrammatic illustration of the same installation shortly after the crab 121 has begun to discharge the product over the face 117-118. The heap which, when the spilling crab 121 ceases to discharge, has a profile as shown in broken lines in FIGURE 10, had begun to discharge through the slit at the bottom of the hopper 114. In the intervening time, under the action of the scraper 115, a tonnage identical to that discharged over the inclined surface 117-118 by the spilling-crab 121 has been discharged on to the belt 119.

If reference be now had to FIGURE 11, it will be seen that a heap 111a is being formed by the discharge of mixture constituents by the spilling crab 121 over the face 112a-113a. While this heap 111a is being formed and progresses in the direction F, the simultaneous gradual disappearance, in situ, of the heap 111 on the left of FIGURE 11 may be observed.

Since the tonnage deposited by the spilling-crab 121 is the same as that removed by the scraper 115, a constant tonnage is at all times available in the hopper 114, and this tonnage may take the form of a single heap (FIGURE 9) or that of two heaps, of which one, 111a is in the course of formation and the other, 111, in the course of disappearance (FIGURES 10 and 11). If it is assumed that the areas of the hatched sections in FIGURES 9 to 11 are substantially proportional to the tonnages of the heaps they respectively represent schematicaily, then it will be seen that the single heap 111 of FIGURE 9 can easily be reconstituted from the

heaps

111a and 111 of FIGURE 11. This can easily be demonstrated by imagining that the hatched triangle (the is joined to the shorter of the parallel sides of the trapezium 111a, as at ab'c.

In this latter embodiment, in other words, a to-and-fro motion within the hopper 114 has been substituted for the circular motion of the heap described in previous embodiments.

In the description given hereinabove it has been assumed that the inclined plane 117-118 has substantially the same slope as the face 112-113 of the heap 111. Clearly, the face 117-118 does not behave in rigorously the same way as the face 112-113 when the spilling crab 121 discharges its deposits. It is preferable for the face 117-118 to behave as much as possible like the natural slope of fall. down the heap. For this reason, it will be necessary to vary thoroughly study, empirically for example, the shape and nature of said face 117-113. The latter need not necessarily be plane and may embody various irregularities such as ripples, trenches or channels, which may be directed longitudinally or transversely.

More particularly, in FIGURES 2 and 4, there has been described a process wherein a substantially circular heap is formed by depositing the component elements of the mixture to be formed on a substantially even area. To this end a conveyor pours along a circular arc the component elements of the heap, the latter widening as it is brought down. At the end where the heap has its maximum cross-sectional area the component elements are picked up at the bottom or base of the heap by simply digging this heap which falls or slips down gradually. The materials are picked up by slices substantially par- 9 allel to the longest slope, or angle of repose of the heap.

Although this method and similar methods, such as the ones disclosed with reference to FIGURES 3 and 6 thereof, are definitely suited for handling dry ores having a uniform grain size, they are subject to various drawbacks when handling ores of very irregular grain size and/or having a variable moisture content.

In fact, under these conditions a certain segregation in the slices or layers deposited in succession along the angle of repose or heap slope is likely to take place. An irregular pick-up rate of the products deposited on the heap may also be expected. These two irregularities may result in a distortion of the parallelism of the slices deposited onto and picked up from the heap, and therefore the picked-up ore may not have exactly the average quality of the products previously delivered to form the heap.

To avoid these drawbacks the present embodiment provides, as shown in FIGURE 12, a method of depositing the component elements of the heap in the form of layers dd, the lines of longest slope of these slices forming with the horizontal a moderate angle inferior to the angle of repose of the heap. Under these conditions any segregation or irregularity in the successive layers thus deposited are definitely precluded.

On the other hand, the component elements of the heap are picked up in the form of slices era of which the line of longest slope forms with the horizontal an angle inferior to the angle of repose of the heap. Also in this case any possibility of segregation or irregularity in these slices is safely avoided.

The heap illustrated in FIGURE 12 advances substantially like the one described with reference to FIGURE 2. When the slices 2e are removed in succession by using adequate mechanical pick-up means as will be explained presently the heap 200 advances to the right, in the direction of the arrow F4. Since this heap is formed along a substantially circular curve it will move around as the component elements are deposited and picked up.

In FIGURE 13 of the attached drawings this circular heap is shown as viewed from above. In this example the heap is built up inside the annular space formed by two concentric

circular walls

201 and 202. The manner in which this two-walled hopper is constructed will be considered more in detail presently. FIGURE 13 shows diagrammatically the heap 203 of materials deposited according to the method illustrated in FIGURE 12.

The contour lines of FIGURE 14 show the shape assumed by the suruface of the heap tthus formed,

FIGURE 13 also shows the

mechanical means

204 and 205 provided for picking up the products or materials from the heap. The device 204- consists for example of a studded-harrow, and the device 205 associated therewith consists of an Archimedean screw or like device adapted to pick up the materials swept by the harrow 204 towards the bottom of the heap, that is, to their discharge place. In this figure there is also shown a movable bridge structure 206 adapted to revolve about a pivot (not shown) having its axis coincident with the center of the hopper and bearing on the other hand by means of casters, wheels or bearings 207 on the substantially flat rail-forming top edge of the outer circular wall 281. Inside this movable bridge structure 206 a movable frame 206a is mounted for longitudinal motion and carries a belt conveyor 209 adapted to feed a pouring spout 208.

A heap of the type shown diagrammatically in FIG- URE 12 is easily formed by means of this arrangement.

The component elements of the mixture are fed from the center 0 to the conveyor 209 and according to the variable position of the rotatably movable bridge structure 206 and of the radially movable pouring spout 208 the component elements of the mixture to be for-med are poured onto such other selected location of the heap 2113.

FIGURE 15 shows more in detail a typical arrange ment for carrying out the method set forth hereinabove.

In this FIGURE 15 there is illustrated inradial section with parts broken away an annular supporting area or bed 210 disposed between two vertical cylindrical coaxial walls, i.e. an outer wall 211 and an inner wall 212 constituting a hopper 213 formed in the resulting annular space. The area 210 and walls 211, 212-, may consist for example of reinforced concrete or like material. External pillars 214 and a central column 215 support the construction. Of course, the area 210 may also and preferably be formed directly on the ground. A stationary bridge 216 of trussed beams or concrete construction overlies the complete unit and is supported by pillars or like elements 217. These pillars or like elements 217 may have one or more portions merged into some of the aforesaid pillars 214 reinforced to this end.

Having thus described the main structure of the apparatus the means for forming the heap of ore or like material comprise a feed conveyor 218 mounted on the stationary bridge 216 and adapted to discharge the ore or like material into a spout 219. A vibrating distributor 220 is provided for assisting in delivering the material to a conveyor 22-1 mounted on a movable bridge structure 222. This movable bridge structure 222 is supported in the central portion of the assembly by a pintle 223 supported by and revolving in a cavity 224 provided to this end in the central column 215. The opposite ends of this movable bridge structure are adapted to roll, by means of suitable rolls, wheels or the like 225, on the upper flat face 226 constituting the upper edge of the outer wall 211. These rolls or wheels 225 may consist for example of a pair of tire-mounted wheels, one wheel being driven from a power unit through a reducing gearing (not shown) adapted to drive the outerends of bridge structure 222 at the desired and suitable speed. This bridge structure 222 is adapted, of course, to pivot about the axis of the hopper 213 formed by the concentric coaxial

vertical walls

211, 212. Control means shown only in diagrammatic form are provided and comprise a limit switch and a reversing switch 227 actuated by stop members carried by a movable annulus 228 so as to impart to the bridge structure 222 an alternating circular motion corresponding to the one described in the present invention. The movable annulus 228 revolves at a relatively slow rate corresponding to an angular speed proportional to the mass of material introduced into the apparatus. Thus, a heap having a contour substantially as shown by the reference letter T in FIGURE 15 is formed.

The conveyor 221 is mounted on the movable bridge structure 222 by means of a movable frame 229 to which a radial reciprocating motion is imparted so that the products being handled fall into a spout of which the two end positions are shown at 230 in thick lines and at 231 in broken lines, respectively. Of course, the radial reciprocating movements of the frame 229 are produced by means of a power unit and reduction gearing of the variable-speed type driving a chain or like transmission member. To simplify the drawing the power unit, reduction gearing and chain, on the one hand, and the means enabling the frame 229; to roll on the bridge structure 222 are not shown.

The ore or like material to be handled is picked up by mechanical means such as a harrow (not shown) adapted to bear on a pair of

circular rails

233, 234, embedded on the

walls

211, 212 and by an ore loading apparatus 235 consisting for instance of an Arcln'medean screw or the like. This loader 235 bears in turn on a rail 236 and on a bar or like member 237 permitting its rotation about the central column 215. Of course, this loader 235 is pushed towards the heap and driven in a manner corresponding substantially to the one described with reference to FIGURES 4 and 5 thereof. The ore picked up by these means is discharged into an annular space 238. In this annular space 238 doctors or like blades revolving in said space under the control of adequate rollers pick up the ore and deliver same toan orifice 240 formed through the bottom of the aforesaid annular space 238 onto a vibrating distributor 241 and a discharge conveyor 242.

The arrangement described hereinabove is characterized by other advantageous constructional features such as for instance the provision of ring collectors 243 for supplying current to the loader motor, a central ladder 244 in the hollow central column 215 to permit the regular inspection of various parts of the mechanism, notably the bearing of pintle 223 and the electrical contacts 245 provided at the bottom of pintle 223 for energizing the motors of the movable bridge structure 222 and of the conveyor 221.

Of course, as in the construction exemplified in the present invention, an automatic integrating sca-le (not shown) is provided on the conveyor 218 delivering the material to the heap, this scale being adapted to adjust the various creep rates of the heap, since the ends of this heap constantly move along a circular path as a consequence of the operation of the above-described

devices

227 and 228.

To obtain a heap built up according to the contour lines shown in FIGURE 14 it is necessary toimpart to the pouring spout 230 carried by the end of the movable conveyor 221 a variable-speed radial reciprocating motion.

In FIGURE 14, the reference numerals 0, 0.5, 1, 1.5, 2 l0, designate the height (for example in feet) of the contour line of the heap with respect to the bottom 210 (zero level) of the hopper.

More particularly, the rate of this reciprocating motion may be inversely proportional to the square of the distance measured from the spout 230 to the axis of the material-handling plant. This is clearly shown in FIGURE 16.

In the diagram of this figure the distances from the pouring spout 23% to the axis of the plant are plotted in abccissae against the rate of reciprocating motion of frame 229 in ordinates. On the other hand, the curve C showing the momentary speed of spout 23) is traced. More particularly it will be seen that when the spout reaches the central wall 212 the frame speed is maximum and corresponds to the ordinate V212. On the other hand, when the spout 230 reaches the outer wall 211, the frame speed is minimum and corresponds to the ordinate V2.11.

Of course, at these endmost points the movements are stopped and reversed. To obtain this law of variation of the frame speed a cam (not shown) may be used, this cam consisting for example of a plate element carried by the frame 229 and adapted, according to the sucoessive positions occupied by the frame on the bridge structure 222, to actuate for instance, through a rollers and levers system a variable-voltage device. If desired, this variable-voltage device'rnay be of the thyratron type adapted to control the energization of a direct-current motor impressing the aforesaid radial reciprocating motion to the frame 229. Thus, the heap will constantly assume the configuration illustrated in FIGURE 14 and any risk of crumbling or falling in of the heap, and therefore any risk of segregation, are definitely precluded.

Various other features of this invention may be used in practice. Thus, more particularly, the short reach of conveyor 221 which will operate under relatively severe conditions will be preferably of relatively great width. In fact, the greater belt width will make it possible to operate the conveyor at a relatively low linear speed and therefore to increase the useful life of the belt for a transported load.

On the other hand, as the 'ore is usually introduced and delivered batchwise to the heap, in order to avoid a non-uniform distribution and the detrimental introduction of similar qualities simultaneously, it will be well to use properly selected mean time periods for introducing the unitary batches, adequate oscillation frequencies of the movable bridge structure in rotation, and of the frame structure in radial translation, so that these time factors be in prime ratio to one another. Thus, if for instance during the beginning of the ore introduction the ore displays such or such special characteristic, the ore thus deposited will be distributed uniformly over the heap and will not interfere with the homogeneity of the component elements picked up therefrom.

The choice to be made between the different types of installation described hereinbefore, or between others of a similar type, will be made according to the characteristics of the constituents to be mixed and of the mixture to be obtained, due allowance being made for the tonnages to be processed, the peak output of the plant, the sieve size of the constituents, and so on.

Installations that operate an annular hopper instead of a flat stocking surface offer the advantage of having smaller overall dimensions. On the other hand, installations that make use of fiat surfaces for constitution of the heaps would appear to be better suited when the sieve size of the products covers a wide range and when a tendency towards physical segregation is to be feared.

By virtue of their faculty for continuous operation, all the types of mixer designed in accordance with the present invention lend themselves to automatic control.

With installations according to the invention, there is no further need to fear quality fluctuation-s such as those which arise when operation is intermittent due to changes from one heap to another, and it is possible to still further improve the functional characteristics of such installations by recycling part of the product emerging from the plant, a feature which can be incorporated without increasing the overall size of the plant.

The field of application of plant according to the invention is a very wide one. Such plant can be used with advantage in the metal, glass, cement and other industries. Embodiments built along the lines of those shown in FIG-

URES

3 and 7, which permit the obtainment of plants of relatively smaller size, canfiud application in the pharmaceutical, chemical, food and similar industries.

It is to be clearly understood that the present invention is by no means limited to the foregoing embodiments, which were described and illustrated by way of example only.

What I claim is:

1. A method of blending materials in bulk comprising the steps of forming a heap by continuously distributing at a given rate said materials in substantially parallel layers, said layers being of different qualities, and of simultaneously reclaiming at the same rate said materials along parallel cuts made at an angle to the lie of said layers, said heap thus retaining a constant mass andshape, one of said two simultaneous steps being carried out along a slope approximating the angle of repose of said materials, whereby said heap is caused to move with a velocity related to the rate of distributing said materials in parallel layers.

2. A method of blending materials in bulk comprising the steps of continuously distributing at a given rate said materials on a heap in substantially parallel layers slightly inclined to the horizontal, said layers being of different qualities, and of simultaneously reclaiming said materials at the same given rate along a slope approximating the angle of repose of said materials, said heap thus retaining a constant mass and shape and moving with a velocity depending on said distributing rate.

3. A method according to claim 2, wherein said materials are distributed according to a substantially circular heap of uniformly decreasing cross-section from the top of said slope.

4. A method of blending materials in bulk comprising the steps of continuously distributing at a given rate said materials on a heap in substantially parallel layers, said layers being of different qualities, along a slope approximating the angle of repose of said materials, and of simultaneously reclaiming at the same rate said materials in substantially parallel horizontal layers at the bottom of said heap, said heap thus retaining a constant mass and shape and moving with a velocity depending on said reclaiming rate.

5. A method of blending materials in bulk comprising the steps of continuously distributing at a given rate said materials on a heap in substantially parallel layers, said layers being of different qualities, the component elements of the mixture to be formed being deposited onto a substantially even circular area so that the heap thus built up has a gradually decreasing cross-sectional area, the heap-forming layers being moderately inclined to the horizontal, and of simultaneously reclaiming at the same rate said materials, the mixture being picked up by mechanical means at the end of said heap Where the heap has its maximum cross-sectional area by slices of which the longest slope forms with the horizontal an angle slightly inferior to the angle of repose of the heap, whereby saidheap is caused to move with a velocity related to the rate of distributing said materials in parallel layers.

6. A method according to claim wherein the component elements of the mixture are deposited onto the upper surface of the heap by conveyor means describing with its discharge end a path corresponding to a double reciprocating movement, that is, on the one hand, a circular reciprocating movement enabling said discharge end to sweep the sector limited by the two ends of said circular heap, and on the other hand a radial reciprocating movement enabling said discharge end to sweep the entire width of said heap.

7. A method according to claim 6 wherein said conveyor means includes spout means the pouring end of which describes said path and performs said circular and said radial movements.

8. A method according to claim 6 wherein the materials are picked up by slices having a degree of inclination approximating the aforesaid angle of repose, by using pick-up means adapted to drop the picked-up and hemogenized material into an annular or similar trough disposed in the central region of said circular area.

9. A method according to claim 8 wherein said pick-up means includes barrow means associated with an Archimedean screw.

10. A method according to claim 6 wherein the rate of said radial movement is variable as a function of the distance from the location where these elements are deposited to the centre of said even circular area.

11. A method according to claim 10 wherein the materials are deposited into an annular hopper constituted by two coaxial cylindrical walls built on said circular area and the radial velocity of said discharge end is proportional to the inverse of the square of the distance from the location where the component elements are deposited to the centre of said annular hopper.

12. A method according to claim 6 wherein the radial and circular oscillation periods of said discharge end are in a given relationship.

13. A method according to claim 12 wherein the component elements of the mixture are introduced batchwise, the mean duration of the introduction time of said batches, and the periods of said circular and said radial oscillations being in prime ratio to one another.

14. A plant for blending materials in bulk comprising a single site adapted to receive a heap of said materials, distributing means for continuously distributing said materials onto said heap along substantially parallel layers and reclaiming means adapted to continuously remove said materials from said heap along parallel slices at an angle to the lie of said layers, said distributing means, together with said reclaiming means, being effective to 14 cause a continuous resulting progression of said heap along the site.

15. A plant for blending materials in bulk comprising a fiat annular area, a cavity in the center of said area forming a delivery hopper, distributing means reciprocally and angularly swingable between two angular end positions above said area about a vertical axis passing through the center of said area for conveying said materials onto said area to form a heap thereon, deposits being made along substantially parallel layers between said two end positions, and reclaiming means radially disposed with respect to said vertical axis to be advanced into said heap along an exposed face slope determined by the angle of repose of said materials and to discharge said materials into said central cavity, said distributing means being adapted to continuous angular shifting of both of said end positions in the same direction and by the same angle as that of advancement of said reclaiming means, thus causing a progression of the heap onto said area.

16. A plant for blending materials in bulk comprising an annular hopper of revolution of substantially triangular cross-section, distributing means rotatable about the vertical axis of said hopper for depositing said materials into said hopper to form a heap therein, deposits being made along substantially parallel layers over an exposed face slope of said heap determined by the angle of repose of said materials, and reclaiming means comprising a circular slit at the bottom of said hopper and shifting scraper means in said slit to control the reclaiming of said materials out of said hopper so that the rate of reclaiming said materials is equal to the distributing rate of same, said distributing means being adapted to perform a slow continuous shifting, thus allowing a circular progression of the heap into said hopper.

17. A plant for blending materials in bulk comprising a prismatic hopper of elongated rectangular shape and substantially triangular cross-section, distributing means longitudinally movable above said hopper for depositing said materials into said hopper to form a heap therein, deposits being made along substantially parallel layers over an exposed face slope of said heap determined by the angle of repose of said materials, and reclaiming means comprising a longitudinal slit at the bottom of said hopper and shifting scraper means in said slit to control the reclaiming of said materials out of said hopper so that the rate of reclaiming said materials equalizes the distributing rate of same, said distributing means being adapted to perform a slow continuous motion, thus allowing a longitudinal progression of the heap into said hopper.

18. A plant as claimed in claim 17 wherein said prismatic hopper comprises an inclined end wall having a slope approximating the angle of repose of said heap face.

19. A plant for blending materials in bulk comprising an even circular area for building up the heap of said materials, said circular area comprising a cavity constituting an annular trough substantially located in the center of said circular area, the heap-building means comprising a first conveyor mounted on a stationary part of the plant overlying said area, axially located spout means fed by said first conveyor and feeding a second conveyor, a frame carrying said second conveyor, a bridge structure onto which said frame is mounted diametrically with respect to said area, second spout means carried by said frame and fed by said second conveyor, said bridge structure being adapted to receive a circular reciprocating motion, the reversing of said motion being ordered by two stop members carried by an annulus and contacted by said bridge structure, said annulus being adapted to revolve at a slow rate around its axis which passes through the center of said area, and said frame being adapted to receive a radial reciprocating motion so that said second spout means may describe a twofold movement, on the one hand a circular reciprocating movement for sweeping the sector limited by the two ends of the heap being formed on said even circular area, and on the other hand a radial reciprocating movement for sweeping the heap transversely, the means for picking up the mixture from the heap consisting on the other hand of a mechanical pick-up device of any suitable type to drop into said central annular trough the materials picked up at the base of said heap, at the heap end having the greatest crosssectional area, said heapbeing thus caused to move with a velocity related to the rate of picking up said mixture by the pick-up device.

29. A plant according to claim 19 wherein the aforesaid even circular area is limited by two vertical coaxial cylindrical walls -forming an annular hopper of revolution of substantially rectangular cross-section, said heapforming means overlying said annular hopper.

References Cited by the Examiner UNITED STATES PATENTS 2,385,494 9/1945 Boynton 2 5. 9180 WALTER A. SCHEEL, Primary Examiner.

JOHN M. BELL, Assistant Examiner.

Claims

1. A METHOD OF BLENDING MATERIALS IN BULKS COMPRISING THE STEPS OF FORMING A HEAP BY CONTINUOUSLY DISTRIBUTING AT A GIVEN RATE SAID MATERIALS IN SUBSTANTIALLY PARALLEL LAYERS, SAID LAYERS BEING OF DIFFERENT QUALITIES, AND OF SIMULTANEOUSLY RECLAIMING AT THE SAME RATE SAID MATERIALS ALONG PARALLEL CUTS MADE AT AN ANGLE TO THE LIE OF SAID LAYERS, SAID HEAP THUS RETAINING A CONSTANT MASS AND SHAPE,