PLANT FOR REMOVING FINES FROM FIBRE FLUFF

Abstract: A plant serves for removing fines from fibre fluff. The plant comprises a forming wire (3), a forming head (2) which is placed above the forming wire (3) and arranged for air-laying fibre fluff into a layer upon the forming wire (3), at least one channel (8) for carrying, in a flow of air, fibres from a supply of fibres into the forming head (2), a suction box (4) placed at the lower side of the forming wire (3), at least one vacuum fan (6;7) connected to the suction box (4) for generating an air flow from the forming head (2), through the fluff, the forming wire (3), and the suction box (4) to the at least one vacuum fan (6;7). The mesh count of the forming wire (3) mainly allow only fines contained in the fluff to pass the forming wire (3). The troublesome and costly filtering of the water used in a hydroentangling process is advantageously eliminated when using fluff, which is freed from fines by means of the plant according to the invention. Air-laid webs produced of the fine-free fibres also have a high quality.

Description: Plant for removing fines from fibre fluff The invention relates to a plant for removing fines from fibre fluff comprising a forming wire, a forming head which is placed above the forming wire and arranged for air-laying fibre fluff into a layer upon the forming wire, at least one channel for carrying, in a flow of air, fibres from a supply of fibres into the forming head, a suction box placed at the lower side of the forming wire, at least one vacuum fan connected to the suction box for generating an air flow from the forming head, through the fluff, the forming wire, and the suction box to the at least one vacuum fan. Fluff of e.g. cellulose fibres and/or synthetic fibres is generally used for producing air-laid webs in plants where the fluff is air-laid in layers upon at least one wire, and the air-laid layers subsequently run through a number of further production steps for obtaining a wanted structure and quality of the web. Such webs are among other things used for the manufacturing of disposable non-woven products of which can be mentioned, absorbent core material for feminine hygiene articles, incontinence articles, diapers , table top napkins, hospital products such as bed protection sheets, wipes , and towels . The webs used for such products usually have a weight of about 20 - 80 g/m 2 . Heavy-duty webs having weights of about 80 - 2000 g/m 2 can advantageously be used for producing e.g. corrugated board and heat - and/or sound insulating materials. The fibre fluff normally contains fines which are small fibre particles in order of 10 - 50 μ. These fines tend to reduce the quality of the air-laid web and with that also the products which are manufactured of the web. The above named further production steps of the fluff frequently also include a hydroentangling process where jets of water are, under influence of a pressure of e.g. 100 bar, ejected through fine nozzles towards the fluff, thereby entangling the fluff into a coherent web. The water used for hydroentangling the fluff is normally recirculated back to the nozzles for being reused whereby fines in the fluff will be dispersed in the water penetrating the fluff. The dispersed fines in the reused water tend to get stuck in the fine nozzles which then stop to function thereby causing a costly stop-down for the total plant. In the recirculation cycle is therefore inserted a filter for removing fines from the water. Filtering particles as small as fines require, however, a complex filter having a number of filtering steps. The filter in itself and the servicing of the filter are therefore very costly. It is the object of the invention to provide a plant of the kind mentioned in the opening paragraph for in a simple way effectively separating the fines from the fluff. The novel and unique features according to the invention whereby this is achieved is the fact that the mesh count of the forming wire is chosen such that mainly only fines contained in the fluff are allowed to pass the forming wire. Thereby it is possible to obtain fine-free products of high quality. When the webs, during the production process, are hydroentangled, this process can also be carried out without the conventional troublesome and costly filtering of the water used to hydroentangle the web. The mesh count of the forming wire can according to the invention more specifically be between 14 and 30 meshes while the differential pressure between the forming head and the suction box can be between 80 - 150 mm water head. The invention will be explained in greater details below where further advantageous properties and an only exemplary embodiment are described with reference to the only figure of the drawing showing a diagrammatic view of a forming station 1 which mainly consists of a forming head 2 placed above a forming wire 3 and a suction box 4 placed below the forming wire. The forming wire runs, during operation, around four rolls 5 in the direction indicated by the arrow. A differential pressure is generated over the forming wire by means of a first - and second vacuum fan 6 and 7, which are connected to the suction box 4. Fibres from a supply of fibres (not shown) are via a channel 8 carried into the forming head in a flow of air. The fibres are by means of said differential pressure deposited in a layer of fluff onto the forming wire. The fluff normally contains fines, which are small fibre particles in order of 10 - 50 μ. For removing the fines from the fluff the mesh count of the forming wire and the differential pressure between the forming head and the suction box are chosen such that mainly only fines contained in the fluff are allowed to pass the forming wire. The mesh count of the forming wire is, more definite, about 14 - 30 meshes while the mesh count of a conventional forming wire normally is about 31 - 38 meshes. The coarser forming wire according to the invention results in a reduction of the differential pressure from the conventional about 180 - 270 mm water head to about 80 - 150 mm water head. The fluff on the forming wire is thereby deposited in a light and airy layer which is easily blown through by the flow of air with velocities so low that the fines but not the fibres are conveyed by the air which is flowing through the fluff and the forming wire. A filter 9 is arranged between the first - and second vacuum fan 6 and 7 for removing fines from the flow of air. The removed fines are collected in a sack 10 or a similar device. The fine-free fibres can be collected in containers or sacks (not shown) for afterwards being used in e.g. a plant for producing air-laid webs. The plant according to the invention also can constitute the forming station of such a plant whereby the fine-free fluff on the forming wire 3 directly is transferred to the subsequent production stations. When the production steps in a plant for producing air-laid webs include a hydroentangling process, the former troublesome and costly filtering of the water used in the process is advantageously eliminated. Air-laid webs produced of the fine-free fibres also have a high quality, which often is wanted for e.g. disposable non- woven products.

Claims: Claims 1. A plant for removing fines from fibre fluff comprising, a forming wire (3) , a forming head (2), which is placed above the forming wire (3) and arranged for air laying fibre fluff into a layer upon the forming wire (3), at least one channel (8) for carrying, in a flow of air, fibres from a supply of fibres into the forming head (2) , a suction box (4) placed at the lower side of the forming wire (3) , at least one vacuum fan (6; 7) connected to the suction box (4) for generating an air flow from the forming head (2) , through the fluff, the forming wire (3) , and the suction box (4) to the at least one vacuum fan (6; 7), characterized in that the mesh count of the forming wire (3) is chosen such that mainly only fines contained in the fluff are allowed to pass the forming wire (3) . 2. A plant according to claim 1, characterized in that the mesh count of the forming wire (3) is between 14 and 30 meshes. 3. A plant according to claim 1 or 2 , characterized in comprising means for adjusting the differential pressure between the forming head (2) and the suction box (4) to between 80 - 150 mm water head. 4. A plant according to claim 1, 2, or 3, characterized in comprising, a first vacuum fan (6) connected to the suction box (4) for generating an air flow from the forming head (2), through the fluff, the forming wire (3), and the suction box (4) to said first vacuum fan (6) , a filter (9) connected to the first vacuum fan (6) for removing fines from the air supplied to the filter (9) by the first vacuum fan (6), and a second vacuum fan (7) connected to the filter (9) for removing the filtered air from the filter (9) . 5. A plant according to claim 4, characterized in comprising a collector device (10) for collecting fines from the filter (9) . AMENDED CLAIMS [received by the International Bureau on 23 October 2001 (23.10.01); original claims 1-5 replaced by amended claims 1-3 (1 page)] l.A plant for removing fines from fibre fluff comprising, a forming wire (3) , - a forming head (2), which is placed above the forming wire (3) and arranged for air laying fibre fluff into a layer upon the forming wire (3), at least one channel (8) for carrying, in a flow of air, fibres from a supply of fibres into the forming head (2), a suction box (4) placed at the lower side of the forming wire (3) , at least one vacuum fan (6; 7) connected to the suction box (4) for generating an air flow from the forming head (2), through the fluff, the forming wire (3), and the suction box (4) to the at least one vacuum fan (6; 7), whereby the mesh count of the forming wire (3) is between 14 and 30 meshes, and the differential pressure between the forming head (2) and the suction box (4) is between 80 - 150 mm water head. 2.A plant according to claim 1, characterized in comprising, a first vacuum fan (6) connected to the suction box (4) for generating an air flow from the forming head (2), through the fluff, the forming wire (3), and the suction box (4) to said first vacuum fan (6) , a filter (9) connected to the first vacuum fan (6) for removing fines from the air supplied to the filter (9) by the first vacuum fan (6) , and - a second vacuum fan (7) connected to the filter (9) for removing the filtered air from the filter (9) . 3. A plant according to claim 1 or 2, characterized in comprising a collector device (10) for collecting fines from the filter (9) .

Inventors: BROECHNER JENS OLE, BROECHNER, JENS, OLE
Applicants: BROECHNER JENS OLE, M & J FIBRETECH AS, BROECHNER, JENS, OLE, M & J FIBRETECH A/S
Application year: 2000
Main classification: D04H1
IPC codes: D04H1