METHOD AND DEVICE FOR CONCENTRATING LIQUID-DRENCHED MATERIAL

Abstract: The invention relates to a method and to an apparatus for concentrating liquid-drenched material while forming a string of material (25) embraced by straining cloth and terminating concentration of the material with said material covered with said cloth (1, 2) by rolling the material with said material located between outwardly spread, single sheets (1, 2; 1, 33) of straining cloth. For enclosing the string of material (25) two endless straining belts (1, 2) are used, neither of which has a width sufficient to fully embrace said string of material and of which one belt (2) is narrower than the other belt (1), wherein the longitudinally extending edge parts (21, 22) of the broader belt are caused to overlap the longitudinally extending edge parts of the narrower belt (2). Subsequent to initially concentating the material, the broader belt (1) is spread out into a single sheet and also used during the remainder of the concentrating process.

Description: METHOD AND DEVICE FOR CONCENTRATING LIQUID-DRENCHED MATERIAL The present invention relates to a method for concentrating liquid-drenched material, particularly for de-watering fibre suspensions, in which the material is formed into a string embraced by a straining cloth and rolled while covered with said cloth. The invention also relates to apparatus suitable for carrying out the method. A method and an apparatus for concentrating liquid-drenched material by rolling a string of said material while the string is embraced by an endless straining cloth belt are known, for instance, from US-A 4,017,398. Arrangements of this kind known hitherto are encumbered with certain drawbacks. For instance, a single straining cloth belt which embraces a material string has the tendency to rupture at the edge regions of the string when rolling at high pressure and has a width which is more than twice the breadth of the rolled material string, resulting in large space requirements . The object of the present invention is to provide a novel method and novel apparatus with which the aforesaid drawbacks are avoided at least to a substantial extent. To this end, there is proposed in accordance with the invention a method of the kind defined in the introduction in which at least a terminating part of the concentration process effected by rolling is carried out with the string of material located between outwardly spread, single sheets of straining cloth, wherein - for the purpose of enclosing the string of material there is used two belts of straining cloth each travelling in a respective endless path and each having a width which alone is insufficient to fully enclose the string of material; - the string is enclosed by a narrow belt and a broader belt of straining cloth and the longitudinally extending edge parts of the broader web are caused to overlap the longitudinally extending edge parts of the narrower belt; and wherein - at least the broader web is spread out to form a single straining cloth sheet subsequent to the initial stage of the concentration process and is also used during the remainder of said concentration process. The inventive method places no great strain on the straining cloth belts and enables the material to be concentrated at high roll pressures, since the terminating concentration process is carried out with the string of material located between outwardly spread, single sheets of cloth. Only a relatively small amount of space is required, since the broader belt can have a width which is substantially smaller than the circumference of the rolled string. According to the invention, apparatus suitable for carrying out the aforesaid method while achieving the advantages afforded thereby includes a first part through which the material is transported in an enclosure means during initial concentration of the material to form a string of material and which is comprised of two separately advanced endless belts of straining cloth, and a second part in which the material is finally concentrated by rolling the string of material as it is transported between two outwardly spread belts of straining material that move in two endless paths, wherein the enclosure means is formed by a narrower and a broader belt of straining cloth each having a width which alone is insufficient to form said enclosure means, and wherein at least the broader belt also extends through said second part and, in an outwardly spread state, also forms one of the transport belts used in this stage of the process. Further features of the invention and advantages afforded thereby will be apparent from the dependent Claims. The invention will now be described in more detail with reference to the accompanying drawings, in which Fig. 1 is a schematic illustration of a first embodiment of inventive apparatus; and Fig. 2 is a schematic illustration of a second embodiment of inventive apparatus. Those components that find agreement or general agreement in both Figures have been identified with the same reference signs . The apparatus for concentrating liquid-drenched material, such as fibre suspensions and then particularly paper pulp suspensions, shown in Fig. 1 includes two belts of straining cloth 1 and 2 which are each advanced in a respective endless path and which may comprise a plastic wire cloth. One belt 1 is guided around guide rollers 3-11 and is broader than the second belt 2, which is guided around guide rollers 12, 13 and 14 and also around the guide roller 8 used to guide the broader belt 1. The directions in which the belts 1, 2 move are indicated by respective arrows 15 and 16. Positioned beneath the guide roller 14 is a known folding device generally referenced 17 (see for instance WO 94/12260) that includes a first folding edge 18 which extends transversely to the movement direction of the belts 1 and 2 and over which the centre part of the belt 1 is folded. Connected to respective ends of the first folding edge 18 are second and third folding edges 19, 20 which, as seen in the direction of movement of the folded belt 1 extend obliquely forwards and outwards and obliquely forwards and inwards respectively. The longitudinally extending edge parts 21, 22 of the folded belt 1 are folded over the second folding edges 19 firstly in towards and over the centre part of the belt 1 and are then folded anew over the folding edges 20, so that said edges will partially cover and extend parallel with said centre part. As the edge parts 21, 22 of the belt 1 are folded, the belt 2, whose width corresponds generally to the length of the folding edge 18, is introduced into the folding device 17 in a manner such that the sides of the belt 2 will be overlapped by the edge parts 21, 22 of the belt 1 such as to form from the two belts 1, 2, an enclosure for a slurry of material to be concentrated delivered through a hopper 23 in the direction of arrow 24. In order to hold the belts 1 and 2 together in a position in which they embrace said material, the belts may be caused to run in a perforated tube (not shown) mounted between the folding device 17 and the guide roller 8, so as to form a string 25 of partially concentrated material, said material being further concentrated by rolling the material between pressure rolls 26, 27. Before finally concentrating the material between the rolls 26, 27, the edge parts 21, 22 of the belt 1 are spread out in a belt unfolding device generally referenced 28, said device including a first folding edge 29 which extends transversely to the movement direction of the belt 1. Connected to each end of the first folding edge 29 are respective second and third folding edges 30, 31 which, seen in the direction of belt movement, extend obliquely rearwards and outwards and obliquely rearwards and inwards respectively. The longitudinally extending edge parts of the belt 1 are therewith unfolded outwards around the third folding edge 31 and then rearwards around the second folding edges 30, while the centre part of the belt 1 is folded back over said first folding edge 29. The concentrating apparatus shown in Fig. 1 thus includes a first part located between the folding device 17 and the unfolding device 28, in which the material delivered at 23, 24 is concentrated into a coherent string 25 by straining the material through the enclosure formed by belts 1 and 2, and a second part located between the unfolding device 28 and the roller 12 in which the material is finally concentrated by rolling the string 25 situated between the belt 2 and the belt 1 outwardly spread in the unfolding device 28, said finally concentrated material departing in the direction of arrow 32. Rolls that operate at moderate pressure or pressures may also be provided in the region between the guide roller 8 and the unfolding device 28. However, in the case of high pressure rolling of the material, the string of material 25 shall be located between outwardly spread, single sheets of straining cloth. The devices required for collecting and conducting away liquid that drains from the material or is pressed therefrom have not been shown in the drawings, for the sake of clarity. Although not shown in detail, the belts 1 and 2 may be driven by driving one or more of the guide rollers 3-14 around which said belts pass. It will be seen from the illustrated arrangement of rolls 9-11 that the belt 1 unfolded in the device 28 forms a support for the string 25 immediately said string exits from the unfolding device. The use of devices 17 and 28 of the kind shown in Fig. 1 is favourable from both the aspect of space and from the aspect of stress, or strain, in comparison to successively shaping belts from a flat to a tubular section in accordance with US-A 4,017,398, for instance. It will be understood, however, that the invention is not restricted to the use of devices of the kind illustrated in Fig. 1. As before mentioned, in the case of the arrangement shown in Fig. 1 the width of the belt 2 corresponds to the lengths of the folding edges 18 and 29, so that overall it has the shape of an outwardly spread single sheet. In certain cases, it is desirable that the upper side of the string 25 has a straining belt 33 whose width exceeds the width of the string 25 as the string passes between the roll pairs 26, 27 as shown in the Fig. 2 embodiment, so as to avoid any direct contact between the string material and the upper rolls 26. Thus, according to Fig. 2, the belt 2 forming part of the enclosure formed in the folding device 17 also passes around and upwards from a guide roller 34 located immediately downstream of the unfolding device 28, in addition to passing round the guide rollers 14 and 18, and, via a guide roller 35 located above the guide roller 34, back towards and around the guide roller 14. The part of the apparatus in which the material is finally concentrated downstream of the unfolding device 28 uses a further straining belt 33 which, as before mentioned, is broader than the belt 2 and the string 25, but which is preferably narrower than the belt 1. The belt 33 extends in an endless path in the direction of arrow 36, around guide rollers 12 and 13 and around two guide rollers 37 and 38 located adjacent respective guide rollers 35 and 34. It will be understood that the invention is not restricted to the described and illustrated exemplifying embodiments thereof and that said invention can be implemented in any desired manner within the scope of the inventive concept defined in the following Claims.

Claims: CLAIMS 1. A method for concentrating liquid-drenched material, particularly for de-watering fibre suspensions, comprising the steps of forming a string (25) of material enclosed in a straining cloth and rolling the string of material with said string covered with the straining cloth (1, 2), characterised in that at least a terminating part of the concentrating process by rolling said string is effected with the string (25) located between outwardly spread single sheets (1, 2; 1, 33) of straining cloth, wherein - for the purpose of enclosing the string (25) there is used two straining belts (1, 2) which are each advanced in a respective endless path and each of which has a width which alone is insufficient to embrace said string; - the string (25) is enclosed by means of a narrow belt (2) and a broader belt (1) of straining cloth, wherein the longitudinally extending edge parts (21, 22) of the broader belt (1) are caused to overlap the longitudinally extending edge parts of the narrower belt (2) ; and - at least the broader belt (1) is spread out into a single straining sheet subsequent to the initial stage of the concentrating process and is also used during the remainder of the concentrating process. 2. A method according to Claim 1, characterised in that the concentrating process is terminated with the string (25) located between the outwardly spread, broader belt (1) and a further straining belt (33) which runs in an endless path and the width of which is greater than that of the belt (2) of narrower width. 3. A method according to Claim 1 or 2 , characterised in that the broader straining belt (1) guided for movement in an endless path is brought to a shape in which it partially embraces the material string (25) as it passes through a folding device (17) which has transversely to the movement direction of the belt (1) a first folding edge (18) over which the centre part of the belt is folded, wherein the folding device (17) includes at each end of the first folding edge respective second and third folding edges (19, 20) of which, when seen in the direction of. belt movement (16) , the second folding edge extends obliquely forwards and outwards and the third folding edge extends obliquely forwards and inwards, and wherein the longitudinally extending edge parts (21, 22) of the belt are folded over said second and third folding edges first inwardly over the centre part of the belt (1) and thereafter again folded so as to extend parallel with the centre part. 4. A method according to any one of Claims 1-3, characterised in that the broader straining belt (1) that moves in an endless path and partially surrounds the string (25) is spread out to form a single sheet as it passes through an unfolding device (28) which includes a first folding edge (29) that extends transversely to the direction of movement of the belt (1), wherein the unfolding device includes at respective ends of the first folding edge second and third folding edges (30, 31), wherein the second folding edge extends obliquely rearwards and outwards and the third folding edge extends obliquely rearwards and inwards as seen in the direction of belt movement, and wherein the longitudinally extending edge parts (21, 22) of the belt (1) are folded outwards and rearwards around said third folding edge (31) and thereafter around said second folding edges (30) , while the longitudinally extending centre part of the belt is folded back over said first folding edge (29) . 5. Apparatus for concentrating liquid-drenched material, particularly for de-watering fibre suspensions, characterised in that the apparatus includes a first part through which the material is transported in a material enclosing means during initial concentration of the material to form a material string (25) , said material enclosing means comprising two straining belts (1, 2) each moving in a respective endless path, and a second part in which the material is finally concentrated by rolling the string (25) while transporting said string between two outwardly spread straining belts (1, 2; 1, 33) moving in respective endless paths, wherein the material enclosing means is formed by a narrow straining belt (2) and a broader straining belt (1) , wherewith neither of said belts has a width sufficient to fully enclose said material, and wherewith at least the broader belt (1) also extends through said second part and forms in an outwardly spread state one of the conveyor belts (1, 2; 1, 33) used in said second part of the apparatus. 6. Apparatus according to Claim 5, characterised in that the narrower belt (2) extends only through said first part, and in that a further endless straining belt (33) extends in an outwardly spread state through said second part and forms one of the conveyor belts (1, 33) used in said part.

Inventors: HODEN EBBE, HODEN, EBBE
Applicants: HODEN EBBE, SUNDS DEFIBRATOR IND AB, HODEN, EBBE, SUNDS DEFIBRATOR INDUSTRIES AB
Application year: 1999
Main classification: D21F1
IPC codes: B30B9, D21F1