WO1984004084A1

WO1984004084A1 - Elevating apparatus

Info

Publication number: WO1984004084A1
Application number: PCT/GB1984/000131
Authority: WO
Inventors: Michael Bryon Osborne
Original assignee: Speed Up Holdings
Priority date: 1983-04-19
Filing date: 1984-04-18
Publication date: 1984-10-25
Also published as: ZA842881B; IT1176096B; CA1214134A; IN160724B; EP0140935A1; GB8310537D0; DD218599A5; IT8420627A0; IT8420627A1

Abstract

A method of, and apparatus for, elevating powders, granules, chips, pellets, and the like flowable solids materials and wherein a column (B) of said material is defined, material is added to the lower regions (A) of the column (B) and material is discharged from the upper regions of the column (B) to maintain the column at a substantially uniform height. In a preferred embodiment a conveyor band (12, 35) receives material to be elevated, conveys said material to an inlet to a duct (11, 12, 34, 35) supporting said column and the conveyor band (12, 35) forms a surface of said duct (11, 12, 34, 35) contacting the column (B) whereupon the column of material is maintained in a free-flowing condition.

Description

ELEVATING APPARATUS

This invention relates to elevating apparatus and has particular application to the elevation of solids materials in separated or divided form, such as powders, granules, chips pellets, and the like flowable solids materials, herein after referred to as "divided solids"

It is well known in the art to elevate divided solids on open conveyers and to provide the displacable part or parts of the conveyor with pockets or protrusions intended to present surfaces inclined to the direction of elevation to assist in supporting the divided solids throughout the elevating run of the conveyor.

The present invention is not concerned with such open conveyors.

It is also veil known in the art to elevate divided solids in "closed" elevators, that is to say in elevators wherein the divided solids is enclosed in a duct between an inlet to the duct and an outlet therefrom. The duct prevents loss of divided solids and protects the divided solids against contamination. As with the open conveyor it is the common practise to provide pockets or protrusions in a displacable member within, or forming part of, the duct to effect elevetion of the material within the duct.

Such closed elevators as depend on surfaces inclined to the direction of elevation to physically support the divided solids are essentially "batch" type elevators and the volume of material effectively elevated by such apparatus can vary from inclined surface to inclined surface so that the rate of elevated material delivered to the outlet is variable. Further such elevators are relatively inefficient from a power view point and the positive displacement between the fixed and moving parts is positive so that material being conveyed can be broken down between the said moving and fixed parts.

In another arrangement divided solids may be elevated in a closed elevator by air flows within the duct but such elevators are again inefficient, variable in performance and the air flows can introduce impurities into the material

Closed conveyors which do not rely on inclined surfaces to support the divided material are also well known in the art and conventionally comprise two flexible endless bands which cooperate to define an elevating run and the divided material is compacted between the cooperating bands and elevated therebetween. In such prior art constructions it is essential to load the endless bands towards one another over at least the elevating run.

The USSR patent No. 563329 discloses one such two belt system wherein the belts are loaded towards one another by mechanical means whilst the USA Patent No. 3948383 discloses a two belt system wherein the belts are loaded towards one another by fluid pressure means.

It should be noted that in such two belt systems the divided material is compacted between the belts so that the said material acts like a solid but flexible member elevated by friction between the solids mass and the belts. Such elevators are expensive to construct and operate and, as the rate of elevation of said divided solids material is dependant upon the cross-sectional area between the belts and said cross-sectional area can vary under the transverse loading on the belts, the said rate of elevation can vary considerably

In an alternative arrangement, shown for example in British Patent specification No. 1442875, the elevator is defined by a single flexible belt, the two side edges of which are brought together to form a duct over at least the elevating run of the belt, and the divided material is compacted in the duct to behave in identical manner to the above described operation for the above twobelt systems. Such single belts are difficult to seal along the adjacent edges and the belts are very expensive to construct as also is the support apparatus for the belts and this system is used only in very special circumstances.

It will thus be seen that in both two belt and single belt elevators described above the divided solids being elevated is reduced to the form of a solid but flexible mass,the compaction of the mass can cause breakdown of the divided solids, and the e vators can only work as batch conveyors by stopping and starting the belt or belts.

It should be observed that in all the above described prior art elevating apparatus the elevating forces are applied to the divided solids in the elevating run of the apparatus, that is to say where the elevation is effected by inclined surfaces the divided material on the elevating run is supported on and elevated by the upwardly moving inclined surfaces whilst with the compaction elevators the solid mass is frictionally elevated by the belt or belts.

It should also be observed that with all the above described prior art arrangements the elevating forces are substantially continuously and uniformly applied to the divided solids during elevation thereof.

The present invention seeks to provide a method for elevating divided solids which is simple and efficient in operation, can be operated in continuous or intermittent modes, and wherein the loading on the divided solids reduces as said divided solids are elevated. The present invention also invisages apparatus for performing the said method.

According to the present invention there is provided a method for elevating divided solids comprising the steps of establishing a column of free flowing divided solids, conveying divided solids into the lower regions of said column, and discharging divided souids from the upper regions of said column to maintain the column at a substantially constant height.

The present invention thus proposes that the divided solids in the column be free-flowing whereby the loading on any part of divided solids is substantially equal to the hydraulic head developed by the divided solids above that said part of divided solids and thus the loadings in the divided solids reduce towards the upper regions of the column.

The method proposed by the present invention can be continuous if the divided solids are continually supplied to the column, or intermittent if the divided solids are supplied intermitt tly to the column and this latter mode of operation offers grea advantage over prior art methods as will become apparent herinafter.

Preferably the column is contained in a duct and the method preferably includes the steps of displacing one or more surfaces of the duct in the height direction of the column to maintain the divided solids in free flowing condition within the column.

Preferably the method includes the steps of defining a duct-like entry to the lower regions of the said column of divided solids, conveying divided solids into the duct-like entry and frictionally loading the divided solids in said duct-like entry to force divided solids in said duct-like entry into the lower regions of the column of divided solids. It will now be seen that, unlike the prior art-methods, the maximum forces to which the divided solids can be subjected are the forces to urge the solids into the lower regions of the column, thereafter forces acting on the divided solids reduce as the divided solids are elevated up the column. The present invention also proposes apparatus for elevating divided solids comprising duct means for supporting a column of divided solids in free flowing condition between an inlet means to the lower regions of said column and an outlet from the upper regions of said column and wherein the inlet means comprise a duct-like entry to the lower regions of the column, and the said duct-like entry is at least partially defined by a surface movable in the direction of the column of divided solids whereby to frictionally convey divided solids in said duct-like entry into the lower regions of the column of divided solids. Preferably a surface extends from the duct-like inlet to receive divided solids,conveniently from any supply source such as a hopper or a conveyor, and is movable to convey said divided solids into the said duct-like inlet. Preferably also a surface of the duct supporting the column of divided solids comprises a surface movable in the direction of elevation for the column of divided solids.

In the combination of the preferred features for the appartus defined thus far divided solids are received on a surface, conveyed into the duct-like inlet, urged by friction with the movable surface within the duct-like inlet into the lower regions of the column of divided solids in the duct, and maintained in a free flowing condition within said duct until discharged from the outlet to the duct, which may discharge to a conveyor, hopper, or other discharge-receiving means. Preferably the said movable surface for conveying divided solids into the duct-like inlet, said movable surface in the duct-like inlet for loading divided solids into the lower regions of the column, and said movable surface defining a surface of the duct are surfaces defined by different runs of a single endless conveyor band.

In one embodiment for the apparatus in accordance with the invention the duct-like entry and the duct are defined by different limbs of a rigid structure cooperating with the endless band, the endless conveyor band is in continuous sliding engagement with the rigid structure over said duct-like entry and duct limbs of the rigid structure, and said rigid structure and endless conveyor band define, in combination, a substantially continuous duct of substantially uniform cross-section between the entry to the said duct-like inlet and the said duct outlet.

It will be noted that the above embodiment envisages constructions wherein the endless band is a flat band and the rigid structure has a chahnel-like cross section closed by the endless band in sliding engagement eith the free end surfaces of the side wells of the rigid channel-like section, constructions wherein the endless band has a channel-like cross section with the free ends of the side walls in sliding contact with a flat surface in the cross sectional direction of the rigid structure, and constructions wherein both the rigid structure and the endless band are of channel-like cross section and free ends of the side walls of the endless band are in sliding contact with the free ends of the side walls of the rigid structure. In another embodiment for the apparatus proposed by the invention the duct-like inlet and the duct are defined by different limbs of two endless bands which cooperate to define a continuous divided solids duct of substantially uniform cross section between the inlet to said duct-like inlet and the said outlet to said duct and one of said conveyor bands extends from the duct-like inlet to receive divided solids to be conveyed into the duct-like inlet, the endless bands being arranged for mutual displacement in the direction along said duct-like inlet to the lower regions of the duct and upwardly therefrom to the outlet for the duct.

It will be noted that the above embodiment envisages constructions wherein one or the other of the bands is flat and the other band has a channel-like cross section with the free ends of the side walls of the channel-like band in sealing engagement with the flat band over the cooperating runs of the bands and constructions wherein both bands are of channel-like construction and the free ends of the side walls of the bands are in sealing engagement over the cooperating runs of the bands. Whilst the terms "channel-like" and "side walls" used above may infer a rectangular form for the channel-like cross sections, and such a form is acceptable for the purposes of the invention, the channel-like cross sections of the elements are not restricted to rectangular forms and, by way of example, said cross sections may be of arcuate or other geometrical form and, particularly with large duct cross sections, the endless bands may include internal ribs or walls extending parallel to the direction of displacement and effectively increasing the surface area of the band in contact with the divided solids.

It will be appreciated that the apparatus will inelude meens for maintaining the band in the single band constructions in sliding engagement with the rigid structure and for maintaining the two bands in the two band structures in sealing engagement over the cooperating runs or parts of said structures and said means may conveniently comprise rollers, skid rails or skid surfaces but the object of said means is simply to ensure that the divided solids are contained and are not intended to exert transverse forces to said divided solids.

The invention will now be described further by way of example with reference to the accompanying drawings in which:Fig. 1 shows, diagramraatically, a side view of an elevator in accordance with the invention.

Fig. 2 shows a cross-section through the conveyor on the line II-II in Fig. 1

Fig. 3 shows diagrammatically, the principle upon which the elevator operates. Fig. 4 shows, diagrammatically, a perspective view of part of a single belt embodiment and;

Fig. 5 shows a cross-sectional view on the line Ill-Ill in Fig. 4.

In the example illustrated in Figs. 1 and 2 two endless conveyors 11 and 12 are each of channel-shaped crosssection, the endless conveyor 11 being defined by a base 11a with limbs 11b and 11c upstanding from the side regions thereof, and the endless conveyor 12 being defined by a base 12a with limbs 11b and 11c upstanding from the side regions thereof, the conveyor 11 being wider, between the limbs 11b and 11c, than the overall width of the conveyor 12 so that the limos 12b and 12c can enter between the limbs 11b and 11c of conveyor 11.

It will be observed from Fig. 2 that when the conveyors 11 and 12 are in engaging relationship, with the limbs 12b and

12c of conveyor 12 entered between the limbs 11b and 11c of conveyor 11, the said conveyors, in combination, define a substantially rectangular hollow cross-section, defined by the internal surface of base 12a and the internal surfaces of limbs 12b and 12c, and the internal surface of base 11a, and the said hollow cross-section, in the axial direction, defines a duct 13.

The conveyor 11 passes around rollers 14 and 15 to tra verse a substantially horizontal run with the channel shape of the conveyor opening downwardly and, after passing around roller 15, the conveyor 11 passes between arrays of rollers 16, 17, and/or skid plates 16a, 17a, in a substantially vertical direction. The conveyor 12 passes around a roller 18 to follow a substantially horizontal run with its channel-shared section upwardly opening, in traversing said run the conveyor 12 enters into the downwardly opening channel conveyor 11 as that conveyor passes around roller 14, and the two conveyors 11 and 12 pass, in cooperating relationship defining hollow cross section 13, around the roller 15 and up between the arrays of rollers 16 and 17 and/or skid plates 16a and 17a to pass, still in co-operating relationship, around a roller 19, engaged with the conveyor 12,and said conveyors 11 and 12 are turned, in rassing over roller 19, through substantially 180º so as to be traversing substantially downwardly from roller 19.

On passing around roller 19 the conveyors 11 and 12 are separated, the conveyor 12 being deflected by a deflector element 20,and the conveyor 11 passing around a roller 21, on leaving deflector element 20 the conveyor 12 passes around a roller 22 for return to roller 18 and the conveyor 11 passing over a roller 23 for return to roller 14.

As will be seen from Fig. 1 parts of the lengths of conveyors 11 and 12 are shown in cross-section, to indicate the location of the respective bases 11a and 12a along different runs of the convevors 11 and 12. It should be noted that the conveyors 11 and 12 are constructed from a flexible resilient material to allow said conveyors to pass over their respective rollers without permanent damage to the limbs 11b, 11c, 12b, and 12c. Drive means (not shown) are effective on the conveyors

11 and 12, conveniently by a direct drive to roller 19, to cause conveyor 11 to rotate in an anti-clockwise direction and conveyor

12 to rotate in a clockwise direction (as viewed in Fig. 1).

The vertical plane passing through the axis of roller 14 passes between the vertical planes passing through the axis of rollers 15 snd 18 so that as conveyor 12 passes around roller 18 with its base 12a in contact with said roller 18 the limbs 12b and 12c of the conveyor 12 define an upwardly opening channel section which is exposed before the conveyor 12 passes beneath roller 14 and into engagement with the conveyor 11. A hopper, generally indicated by reference numeral 24, discharges divided solids material into the channel-shaped conveyor 12 before conveyor 12 runs below roller 14 and this discharge of divided solids to the open run of conveyor 12 constitutes the input for the elevator. As the conveyor 12 passes beneath roller 14 the conveyor 11 is displaced into engagement with conveyor 12 to define the duct 13. As duct 13 is maintained whilst the conveyors 11 and 12 pass around roller 15, up the vertical run to pass over roller 19 and around roller 19 to the point of separation of the conveyors 11 and 12 on leaving roller 19 the divided solids is wholly contained within said duct 13 up to the point of separation of conveyors 11 and 12.

It will be observed from Fig. 1 that divided solids carried around the roller 19 within conveyors 11 and 12 can fall to any desired collection element for the elevated solids, diagrammatically illustrated in Fig. 1 by a collection hopper 25, the deflector element 20 conveniently enters into the channelshaped cross-sectionof the conveyor 12 and presents a scraper surface, indicated by reference numeral 20a, which removes any divided solids adhering to the conveyor 12, whilst a scraper 26 is entered into the open channel-shaped section of conveyor 11 as that conveyor passes around roller 21, again to remove any divided solids adhering to the conveyor 11.

In the embodiment shown in Figs. 4 and 5 a rigid channel-like member 31, defined by a base 31a and parallel side walls 31b 31c is bent with arcuate form, about an axis parallel to the base 31a and is supported by a rigid frame (not shown) to define a horizontal leg 32,an arcuate section 33 and a vertical leg 34. An endless conveyor band 35 cooperates with the member

31 to 34 and comprises a flat base 35a with walls or ribs 35b in spaced apart relationship upstanding from one face of base 35a and extending in the length direction of the band 35.

The conveyor band 35 is passed over rollers (not shown) so as to define a horizontal run which passes beneath a hopper 36 from which divided solids are released onto the band 35. From the hopper 36 the band 35 travels into engagement with the member 31 to 34, the side edges of the band 35 engaging in sliding relationship with the free edges of the side vails 31b and 31c, and the band 35 maintains contact with said free edgesof side walls 31b and 31c as the band 35 travels along the horizontal leg 32 around arcuate section 33 and up vertical leg 34 of the rigid member 31 to 34.

It should be observed that the walls or ribs 35b are upstanding from the base 35a as the endless band 35 passes beneath the hopper 36 so that said ribs 35b extend into the rectangular duct defined by the member 31 to 34 and band 35 and, in practise, said ribs 35b increase the surface area of the belt surface presented to divided solids in the said duct and thereby serve the dual purpose of increasing the surface area of the band 35 engaged with divided solids in the friction-generating horizontal leg 32 and arcuate section 33, thereby increasing the force urging divided solids into the vertical leg 34, and further assisting in maintaining the divided solids in the vertical leg 34 free flowing and free of blockages. With this embodiment divided solids are conveyed into the ductlike inlet, defined by the horizontal leg 32, by the conveyor band 35, the movement of band 35 around arcuate section 33 allows the arcuate section 33 of the duct to become choked with divided solids and, as conveyor 35 continuously conveys more divided solids into the said horizontal leg 33, divided solids are conveyed by the frictional contact with band 35 into the vertical leg 34 of the duct, the divided solids material conveyed into the vertical leg 34 upwardly displaces the divided solids material in the vertical leg 34, and the divided solids in said vertical leg 34 is upwardly displaced by the new divided solids material being conveyed into the horizontal leg 32.

The general principle upon which the elevatorsshown in Figs. 1 and 2 and 4 and 5 operate will now be described with reference to Fig. 3 which shows, diagrammatically, a duct 27 defined by front and rear walls 27a and 27b and two parallel side walls 27c and 27d. The duct 27 comprises a horizontal leg "A", a vertical leg E-and an arcuate section"C"connecting legs A and B.

Consider now that wall 27a is defined by a conveyor band and is displacable in the direction from leg A around section C and up leg B. When divided solids are dropped onto band 27a upstream from the horizontal leg A the band 27a carries the divided solids into the horizontal leg A, which defines a duct-like inlet to the duct 27,and initially the divided solids are conveyed by band 27a into and around the arcuate section C until said divided solids pass the point of maximum angle of repose for the divided solids when said divided solids fall back to choke the arcuate section C As band 27a continues to convey divided solids into the horizontal leg A the frictional forces developed between the divided solids and the face of band 27a in the horizontal leg A and the lower part of arcuate section C allow conveyor 27a to convey divided solids into the vertical leg B.

If the supply of divided solids to band 27a is terminated before the divided solids spills from the top of duct 27 the mass of divided solids will adopt a relatively stable position within the duct 27 with the hydraulic head generated by the free flowing divided solids in the vertical leg B and the upper regions of arcuate section C balanced by the frictional forces between the divided solids in the lower regions of the arcuate section C and the horizontal leg A. The divided solids within the mass will not be stable as conveyor band 27acontinues to carry divided solids into the vertical leg and divided solids remote from conveyor band 27a falls back to maintain the condition of equilibrium.

It will now be seen from the above that, for any given divided solids and conveyor band surface , there is a direct relationship between the height of divided solids in the vertical leg B and the length of solids in the horizontal leg "A" necessary to support that height and for most practical divided solids the height of divided solids as can be maintained on the vertical leg is many times greater than the length of divided solids in the horizontal leg required to support that "head".

The above statements are reinforced by the fact that if the conveyor 27a establishes an equilibrium position for a given volume of solids in the duct 27 and the conveyor is then stopped there is very little movement in the mess of divided solids material and the equilibrium condition is maintained.

It will be appreciated that as divided solids are added to the horizontal leg A the height of the column in leg B increases until the divided solids can flow from an outlet in the upper regions of the vertical leg B.

If new divided sol ids material is continuously supplied to the horizontal leg A divided solids material will be continuously discharged from the duct outlet and as when the system is fully charged with divided solids,the response time is very fast the rate of output from the discharge outlet will be substantialy identical to the rate at which divided solids is added to the horizontal leg A.

Further, if the supply of divided solids to the horizontal leg A is terminated the discharge from the outlet of the duct will be terminated but the system will remain fully charged with divided solids. If now a given volume of divided solids is added to the horizontal leg that exact volume will be discharged from the duct outlet.

Thus, the elevator proposed by the present invention can operate as a continuous elevator or a very accurate batch elevator and the batch mode of operation can be effected with the endless band 27a running at constant speed.

If now all four walls of the duct 27 are considered to be surfaces moving at substantially constant speed from the entry to the horizontal leg to the upper end of the vertical leg ( as is the case with Figs. 1 and 2 embodiment) it will be seen that the principle of operation is substantially identical as thct for a single movable wall. The divided solids in the vertical leg B are maintained in a free flowing condition and the hydraulic head in the vertical leg is supported by the frictional forces developed between the movable surfaces and the divided solids material in the horizontal leg and the lower regions of the arcuate section C.

Thus the above mode of operation can nov be considered with reference to the embodiment illustrated in Figs. 1 and 2 and wherein that section of the horizontal run of conveyors 11 and 12 extending between the vertical planes passing through the axes of rollers 14 and 15, and wherein the conveyor 12 is entered into the conveyor 11, constitutes the horizontal limb of the system, that part of the conveyors 11 and 12 passing around the roller 15 constitutes the section "C", and that part of the conveyors 11 and 12 between the horizontal plane passing through roller 15 and the upper regions of the roller 19 constitutes the "column" of divided solids and, as will be apparent from the foregoing, if the length of the horizontal limb is adequate a hydraulic head in excess of the height of the upper regions of the roller 19 can be established and maintained. Thus, in operation, divided solids delivered to the conveyor 12 by hopper 24 is conveyed by the lower limb of the system, the frictional forces developed between the divided solids and the conveyors 11 and 12 establish a hydraulic head, and divided solids in the upper regions of the hydraulic head will be "carried over" as the conveyors pass over roller 19 to discharge into hopper 25.

It will be appreciated that in the vertical leg of the elevators proposed above the principal force acting on the divided solids is gravity, and thus friction between the divided solids end the conveyor surfaces tends to "stir" the divided material, to effectively eliminate voids and maintain the vertical column fluid, rather than to frictionally assist elevation of the body of divided solids. The system is thus protected against "choking" of the duct. It will also be appreciated that as the divided solids material is contained within the duct, cleaning of the apparatus is substantially reduced to cleaning of the continuous conveyor or conveyors and, as the conveyors can be very readily washed over any run where the divided solids contacting surfaces are exposed, a ready and rapid cleaning is possible and product purity can be maintained.

Whilst the foregoing examples are limited to two-part elevators, one fixed track and one moving band or two moving bands, the invention is not restricted to two-part systems and many multiple part systems will become apparent to a reader skilled in the art. By way of example of such multiple part elevators an elevator may comprise one fixed track with two or more endless bands co-operating therewith and, depending upon the cross section of the fixed track, the combination may define one or more "ducts" for elevating divided solids. In another example the conveyor may be defined by two, spaced-apart, channelshaped tracks opening towards one another eith a single moving band therebetween and in sliding engagement with both tracks. The band may be of uniform cross section, in which case the construction will define two elevator ducts, or the band may include openings to allow divided solids to pass therethrough between the ducts.

When the construction defines more than one duct the ducts may be of equal or different cross-sectional shape or cross-sectional areas and, of course, when the ducts of a multiple duct construction are isolated from one another the ducts may elevate different divided solids materials.

Claims

1. A method for elevating divided solids comprising the steps of establishing a column of free-flowing divided solids, conveying divided solids into the lower regions of said column, and discharging divided solids from the upper regions of said column to maintain the column at a substantially constant height.

2. A method as claimed in claim 1 characterized by the steps of continuously conveying divided solids into the lower regions of the column and continuously discharging divided Solids from the upper regions of said column.

3. A method as claimed in claim 1 or claim 2 wherein the column is contained in a duct, characterized by the steps of displacing one or more surfaces of the duct in the height direction of the column to maintain the divided material in free-flowing condition within the column.

4. A. method as claimed in claim 1, 2 or 3, comprising the steps of defining a duct-like entry to the lower regions of the said column of divided material, conveying divided solids into the duct-like entry and frictionally loading the divided solids in said duct-like entry to force divided solids in said ductlike entry into the lower regions of the column of divided solids.

5. Apparatus for elevating divided solids comprising duct means for supporting a column of divided solids in free flowing condition between an inlet means to the lower regions of said column end an outlet from the upper regions of said column and wherein, the inlet means comprise a duct-like entry to the lower regions of the column and the said duct-like entry is at least partially defined by a surface movable in the direction of the column of divided solids whereby to frictionally convey divided solids in said duct-like entry into the lower regions of the column of divided solids. 6 Apparatus as claimed in claim 5 and wherein a surface extending from the duct-like inlet is arranged to receive divided solids and is movable to convey said divided solids into said duct-like inlet. 7. Apparatus as claimed in claim 5 or 6 and wherein a surface of the duct supporting the column of divided solids comprises a surface movable in the direction of elevation for the column of divided solids.

8 Apparatus as claimed in cl aim 5 , 6, or 7, and wherein said movable surface for conveying divided solids into the duct-like inlet, said movable surface in the duct-like inlet for loading divided solids into the lower regions of the column, and said movj ble surface defining a surface of the duct are surfaces defined by different runs of a single endless conveyor bend. 9. Apparatus as claimed in claim 8 and wherein the duct-like entry inlet and the duct ere defined by different limbs of a rigid structure cooperating vith the endless band, the endless conveyor band is in continuous sliding engagement with the rigid structure over said duct-like entry and duct limbs of the rigid structure, and said rigid structure and endless conveyor band define, in combination, a substantially continuous duct of substantially uniform cross-section between the entry to the said duct-like inlet and the said duct outlet. 10. Apparatus as claimed in claim 5,6,7or 8, and wherein the duct-like inlet and the duct are defined by different limbs of two endless bands which cooperate to define a continuous divided solids duct of substantially uniform cross section between the inlet to said duct-like inlet and the said outlet to seid duct and one of said conveyor bands extends from the duct-like inlet to receive divided solids to be conveyed into the duct-like inlet, the endless bends being arranged for mutual displacement in the direction along said duct-like inlet to the lower regions of the duct and upwardly therefrom to the outlet for the duct.