METHOD AND APPARATUS FOR VACUUM CLEANING MINERAL WOOL PRODUCTS WHILE COMPRESSING THE PRODUCT

Abstract: Method and apparatus for removing fibres and other particles from the surfaces of compressible mineral wool products, for instance mineral wool plates (2) by means of one or more suction slot nozzles which suck air from adjacent the surfaces of the mineral wool products so that loose fibres and other particles are brought with the air and into the suction slot or slots (5) in that the mineral wool products, while being actuated by the suction slot or slots (5) are subjected to a quick compression so that a part of the air enclosed in the mineral wool is pressed out towards the suction slot or slots (5) thereby bringing loose fibres and other particles at and adjacent the surfaces into the suction slot or slots (5).

Description: The present invention relates to a method and an apparatus for removing fibres and other particles from surfaces of compressible mineral wool products, for instance mineral wool plates by means of one or more suction apparatus which draws/draw air from adjacent said surfaces of the mineral wool products whereby loose fibres and other particles are moved by the air from said surfaces and out through the suction apparatus. When handling of mineral wool products large or small amounts of dust are formed, which dust includes fibres, among other things. It is a general aim to minimize the amount of dust, including fibrous dust, to which working people are exposed, and the present invention is intended to solve this problem. The invention is based on studies of the mechanisms which cause appearance of dust and also the mechanisms which can be used to prevent spreading of dust. These studies have shown that the air-borne dust which is produced when handling mineral wool mainly comprises thin, short mineral fibres. The studies also have shown that the air-borne fibres and other particles emanate from the surfaces of the mineral wool products. There are three mechanisms which, separately or in combination, can keep a fibre in a mineral wool product and can prevent the fibre from becoming air-borne. Said mechanisms are: binding fastening mechanical locking. The binding is effected by means of a binding substance. The binder generally is a thermosetting resin which in the form of small drops is distributed in the mineral wool products. If such a binder drop sticks to a fibre said fibre is prevented from becoming air-borne. The fastening is a less heavy binding. The fastening can be effected by means of a dust binding oil, which in the form of a thin layer covers large portions of the fibre surfaces. Two fibres which are in contact with each other, and one fibre of which has an oil film on its surface, get fastened to each other and said fastening generally is sufficient to prevent the fibre from becoming air borne. Investigations also have proved, however, that another type of fastening is of importance, namely an electrostatic fastening. The process of manufacturing mineral wool products includes a hardening stage in which the product and the binder for the product is heated to about 200°C, whereby the binder is finally hardened. During the hardening stage the product also becomes completely dried, and since the hardening stage is combined with a heavy gas flow through the products the fibres may become electrostatically charged. In the subsequent cutting and packing etc. of the mineral wool product said electrostatic charging is maintained and fibres which have become charged tend to be maintained in the product. Upon storing and transporting the product, however, becomes discharged and subsequently the fibres, which were once electrostatically fastened, then can become air borne. The third mechanism for keeping the fibres in the mineral wool mass is the mechanical one. A sufficiently long fibre will always be in contact with a large number of other fibres and said fibre will be kept in the product solely by means of friction and will be prevented from becoming air borne. The investigations also have shown that some fibres are so loosely fastened in the product, or not at all fastened, that they can easily be sucked off the product in that the product is moved passed a suction nozzle or a suction slot having a sufficient suction capacity. Other fibres and particles are so strongly fastened to the product that they can normally not at all be removed from the product. Between said two groups of fibres and particles there is a group of fibres and particles which can certainly not easily be sucked off the product but which can still become air borne, in particular after the electrostatic force has disappeared. An apparatus for removing loose fibres and other particles from a surface of a product is known from DE-A-2605895, which apparatus comprises a suction hood and a rotatory brush mounted therein which rotatory brush rubs up particles from the surface of the mineral wool product which particles are exhausted through the suction hood. The said apparatus is useful for removing particles which appear on the surface of the mineral wool plate but it can not remove fibres and other particles which are present slightly inside the outer surface of the mineral wool plate but which are still loose. Also, the brushes of said apparatus may release fibres and particles which would otherwise not have been loose, and the brushes may detoriate the otherwise good surface of the mineral wool plate. Mineral wool products having a reasonable density, for instance rock wool products having a density of less than 50 kg/m³ are compressible to a substantial degree. Depending on the low density the porosity of the product is very high, generally more than 95%. Therefore, if such a product is compressed to about half its original thickness, a volume of air corresponding to about half the original volume of the mineral wool body must be pressed out of the product. It has shown that the air pressed out of the mineral wool body can release and bring a substantial part of the loose fibres at the surface out of the product if the said compressing is made with a sufficient speed. This is the basis of the present invention. Thus, the invention relates to a method of removing fibres and other particles from the surfaces of compressible mineral wool products, for instance mineral wool plates, which method is executed by means of one or more slot-like suction nozzles which suck or exhaust air from adjacent the surfaces of the mineral wool products so that loose fibres and other particles are brought with the air into the suction nozzles. According to the invention the mineral wool products are subjected to a quick compression at the same time as the said surfaces of the products are actuated by the vacuum from said suction apparatus so that a part of the air originally enclosed in the mineral wool is pressed out through the suction apparatus together with fibres and other particles. An apparatus for executing said method is mainly characterized in that it comprises one or more pressure plates for compressing the mineral wool plates or the pile of mineral wool plates concurrently with applying said vacuum to the surfaces thereof, whereby air originally present in the mineral wool plates is pressed out through the surfaces covered by the suction apparatus and is exhausted through said suction apparatus together fibres and other particles released by the air pressed out from the mineral wool products. Depending on the compression according to the invention the particles which are imperfectly fastening or otherwise kept in the mineral wool mass are being subjected to a flow of air from inside the mineral wool mass, which air flow effectively releases fibres and particles. The suction force influencing the fibres and particles concurrently therewith moves said fibres and particles out of the mineral wool mass. It has shown that such low outflow speed as 0.5 m/sek has a noticable effect on the releasing of the fibres. Air speeds of 1 m/sek, or more preferably 2 m/sek, has a much better effect. Surprisingly it has shown that additional fibres are released if the compressing step is repeated. The explanation therefore may be that fibres are displaced during the first air outflow and the succeeding air backflow, so that such fibres can be removed during the next air outflow. Generally mineral wool products are made in layers so that most fibres are oriented in the plane of the product. This means that the products are most easily compressed by forces which are perpendicular to said planes. At the same time the edges of the products form a substantially less part of the total surface of the products. This can be utilized so that the products are compressed by means of air tight compressing means giving press forces which are perpendicular to the main planes of the products. The air volume which is thereby flowing out through the edge surfaces is relatively large and it is easy to cause such an air flow. This is especially the case if, in a first compressing step by means of air tight compression plates, air is prevented from flowing out through two opposite edge surfaces, and on the contrary, air is forced to flow out through the two remaining edge surfaces, and, in a second compressing step, air is allowed to flow out through the two first mentioned edge surfaces. This is a very effective method of releasing particles from the edge surfaces. It is especially advantageous and practical that the compressing step is executed after the mineral wool plates have been piled in layers over each other. In such case particles can be released from several edge surfaces at the same time. Preferably the amount of plates adapted to form a package are thereby compressed at the same time. A special problem in the mineral wool manufacture is that it is difficult to effectively suction treat the cut edges of the products while said products are maintained on the manufacturing line. In such case there is normally no space between the edges of two adjacent plates as seen in the partition cut extending along the manufacturing line. At the cross cut extending perpendicularly to the advancing direction of the mineral wool path it is indeed possible to provide a space between the mineral wool pieces, but it is still difficult to provide an effective suction treatment of a surface which is perpendicular to the advancing direction. If, however, cut pieces of for instance mineral wool are piled it is possible to remove particles and fibres from the edges of the pile of several mineral wool plates at the same time in that the entire pile is being compressed. Likewise, even rolled products can be treated. A rolled product can easily be suction treated on both flat surfaces, that is the upper surface and the bottom surface respectively, but as mentioned above there are problems in treating the edges. If, however, the product is rolled and the roll is violently compressed in that a pressure is applied to the envelope surface of the roll air is pressed out of the roll through the edge surfaces thereof. If the edges are thereby suction treated particles and fibres present on the edge surfaces thereby will be permanently removed. If the compression is made by means of a perforated press plate a part of the air enclosed in the product will flow out through the openings of said press plate. This is especially the case if any other air outflow is prevented. This method of executing the invention is partcularly advantageous for flat products the flat-surfaces of which are to be treated. The invention also can be executed so that the pressing is made by means of perforated plates in the form of grids or nets so that the air which is pressed out flows, also or solely through the flat-surfaces of the product. This variation of the invention alternatively can be executed in a two-stage process so that, in a first compressing step, a first flat-surface is compressed by means of a perforated press plate and the opposite flat surface is supported by an air tight surface, and then the second flat-surface is compressed by means of a perforated press plate whereas the other flat-surface is supported by an air-tight surface. In the following the invention is to be described with reference to figures 1 through 4 which all illustrate different methods of pressing fibres and particles out of compressable mineral wool products. The figures are seen in a vertical cross section. Figure 1 diagrammatically shows the principle of the invention. A mineral wool plate 2 is lieing on a support 1. Above the mineral wool plate 2 there is a pressure plate 3 which by a force 4 can be pressed onto the mineral wool plate 2. A mineral wool plate having a low density, for instance a desity of less than 30 kg/m³ can easily be compressed to e.g. 50% of its original thickness. This means that an air volume substantially corresponding to half the volume of the mineral wool plate must be pressed out of the product. Such compression causes and air flow symbolized by the arrows 5. Obviously the violency of said air flow is depending on the speed by which the compression is made. The mineral wool plate, however, is not influenced by said speed. The efficiency of the operation, as concerns releasing of particles, in this case releasing of particles from the edges of the mineral wool plate, therefore is restricted only by the available efficiency in the very compression work. The process indicated in connection to figure 1, of course, can as well be executed on a pile of mineral wool plates. Such an embodiment is illustrated in figure 2, in which there is illustrated a pile of mineral wool plates 6 positioned between two press plates 7 and 8. The press plates are, in turn, actuatable by the press cylinders 9 and 10 which are designed for exerting a high effect during a short period of time. Round the pile of plates suction apparatus 11 and 12 are mounted. The suction apparatus 11 and 12 are connected to suction conduits 13 and 14 through which air is exhausted. Substitution air for said exhaust air enters both over slots 15, 15′ and 16, 16′ and from the pile of mineral wool plates while being compressed. The air flowing out of the pile of mineral wool plates is indicated by the arrows 17 and 17′. Figure 3 shows an embodiment of the invention in which a plate 18 of mineral wool is being compressed by a press plate 19 comprising two cross support bars 20 and several profiles 21 engaging the mineral wool. Between the profiles 21 there are slots 22. When the press plate 19 is pressed onto the mineral wool plate and compresses same the air present in the mineral wool is at least partly pressed up through the slots 22 as indicated with the arrows 23. Round the press plate 19 there is an exhaust hood 24 which is connected to an exhaust conduit 25. The air flows leaving the mineral wool following the arrows 23 are brought together and leave the exhaust hood 25 as shown with the arrows 26 and 27. If the mineral wool plate 18′ to be treated is placed on a non-permeable support 28, as shown in figure 4, a large portion of the air which is pressed out of the mineral wool plate when being compressed will flow up through the upper mineral wool surface 29. Thereby the releasing at said surface of loosly of imperfectly bound particles or fibres becomes more effective. It is to be understood that the described embodiments of the invention are only illustrating examples and that the invention is restricted only by the appended claims.

Claims: 1. Method of removing fibres and other particles from the surfaces of compressible mineral wool products, for instance mineral wool plates (2; 18) by means of one or more suction apparatus (11, 12) which draw air from adjacent said surfaces of the mineral wool products whereby loose fibres and other particles are moved by the air from said surfaces and out through the suction apparatus (11, 12), characterized in that the mineral wool products are subjected to a quick compression at the same time as the said surfaces of the products are actuated by the vacuum from said suction apparatus (11, 12), so that a part of the air originally enclosed in the mineral wool is pressed out through the suction apparatus (11, 12) together with fibres and other particles. 2. Method according to claim 1, characterized in that the compressing is repeated once or several times. 3. Method according to claims 1 or 2, characterized in that the compressing is made perpendicularly to the main surfaces of the mineral wool products by means of non-pervious compression means (7, 8), and in that edge surfaces (17, 17′) of the mineral wool products are vacuum treated at the same time. 4. Method according to claim 3, characterized in that two opposite edge surfaces of the mineral wool products are covered in a first compression stage, so that the expelled air is forced to flow out through the remaining edge surfaces, and in that, in the second compression stage, those edge surfaces which were non-covered during the first compression stage are covered whereby the expelled air is forced to flow out through the two edges surfaces which were covered during the first compression stage. 5. Method according to claim 3, characterized in piling and compressing said piled mineral wool plates (2, 18; 6). 6. Method according to claims 1 or 2, characterized in compressing the mineral wool products by means of one or more perforated plates and by exhausting the part of the air originally enclosed in the mineral wool and pressed out through the openings of said one or more perforated plates. 7. Method according to claim 6, characterized in covering the surfaces other than the surface or surfaces which is/are being compressed by means of the perforated plate or plates, thereby preventing air from being exhausted from said covered surfaces. 8. Apparatus for removing fibres and other particles from surfaces of compressable mineral wool products, for instance mineral wool plates (2; 18), and comprising a suction apparatus (11, 12, 24, 25) for applying a vacuum to at least some of the surfaces of the mineral wool plates (2; 18), characterized in that the apparatus comprises one or more pressure plates (3; 7, 8; 19) for compressing the mineral wool plates (2; 18) or the pile of mineral wool plates (6) concurrently with applying said vacuum to the surfaces thereof, whereby air originally present in the mineral wool plates (2; 18) is pressed out through the surfaces covered by the suction apparatus (11, 12, 24, 25) and is exhausted through said suction apparatus (11, 12, 24, 25) together with fibres and other particles released by the air pressed out from the mineral wool products. 9. Apparatus according to claim 8, characterized in that the pressure plates (3; 7, 8; 19) are non-pervious to air and are adapted for compressing the mineral wool product from two surfaces thereof, wheras the exhausting of the air pressed out from the mineral wool plates (2; 18) is made by means of an exhaust hood included in the suction apparatus (11, 12) and provided on at least two other surfaces of the product. 10. Apparatus according to claim 8, characterized in that the compressing means comprises two or more perforated pressure plates (19) adapted to compress the mineral wool product from two of its surfaces and to provide an exhaust (by 24, 25) of pressed out air by means of an exhaust hood (24, 25) connected to the perforated pressure plate or plates (19).

Inventors: HARTUNG, GUNNAR, WOLFF, HAKAN
Applicants: ROCKWOOL AKTIEBOLAGET
Application year: 1989
Main classification: B08B5
IPC codes: C04B38, C04B41, B08B5