Apparatus for manufacturing a filtering medium in sheet form

Abstract: An apparatus for manufacturing a filtering medium (1) in sheet form, comprising at least one first continuous machine (7), adapted for manufacturing paper and the like and suitable to form at least one first web on a first conveyor, and at least one second continuous machine (10) also adapted for manufacturing paper and the like and suitable to form at least one second web on at least one second conveyor, the at least one second conveyor being arranged so as to make the at least one second web rest by gravity on the at least one first web, and at least one of the first and second continuous machines (7,10) being suitable to form a web which is not uniformly distributed.

Description: The present invention relates to an apparatus for manufacturing a filtering medium in sheet form. Filters for fluids which comprise a structure for supporting and containing a filtering mass, through which the fluid to be filtered is passed so as to flow from a region connected to an inlet connector to a region connected to an outlet connector, are conventionally widely used in various fields of technology. The filtering medium used most frequently is constituted by a sheet of paper, which is inserted in the filter after being folded and rolled up according to various methods; a filtering medium in sheet form has been recently proposed which comprises regions having a differentiated filtration degree and offers numerous advantages. In one embodiment of the filtering medium, for example, the medium comprises longitudinal bands which alternately have a different filtration degree. It is also known that paper-making technology entails the presence of at least two kinds of continuous machine. A first kind of machine, known as flat-screen machine, comprises a head box which conveys natural or synthetic fibers in an aqueous suspension over a conveyor constituted by a supporting screen, which moves above suction boxes suitable to collect the water that passes through the screen, so as to form on the screen a fiber mat, known as web, which is then gradually dried until it assumes the conventionally sheet-like configuration. A second type of machine, known as cylinder machine, comprises a container which contains a fibrous suspension in comprises a container which contains a fibrous suspension in water and a hollow cylinder which is partially immersed in the suspension and covered with a wire mesh or equivalent material and rotates about a horizontal axis. During rotation, the fibers cling to the surface of the wire mesh and are picked up by a conveyor constituted by a supporting felt, which is arranged tangent to the cylinder and is pushed against it by a presser roller. There are machines which have a cylinder with a uniformly transparent wire mesh and machines in which the cylinder has a wire mesh with closed regions where no fibers deposit on the supporting felt. US-A-3 640 839 discloses an apparatus for manufacturing a filtering medium as defined in the preamble of claim 1. WO 94 20679 discloses a method for making a paper sheet made by two paper layers one of which has a number of localized thinner regions. The aim of the present invention is to provide an innovative apparatus which is capable of forming the filtering medium and has regions having a differentiated filtration degree. This aim is achieved by an apparatus for manufacturing a filtering medium in sheet form according to the invention, as defined in the appended claims. Further characteristics and advantages of the present invention will become apparent from the following detailed description of a preferred but not exclusive embodiment of the invention, illustrated only by way of non-limitative example in the accompanying drawings, wherein: figure 1 is a perspective view of a portion of a sheet of filtering medium to be produced with the apparatus according to the invention; figure 2 is an elevation view of the portion of interest of the apparatus according to the invention; figures 3 and 4 are views of the cylinders of the two cylinder machines included in the apparatus according to the invention; figures 5, 6 and 7 are schematic sectional views taken along the planes V-V, VI-VI, VII-VII of figure 2, respectively; figure 8 is a perspective view of a detail of the apparatus according to the invention; figure 9 is a sectional view, taken along the plane IX-IX of figure 1. With reference to the above figure 1, the reference numeral 1 generally designates a portion of a sheet which forms a filtering medium, which comprises regions in the form of longitudinal bands having a different filtration degree; the regions 2, 3, and 4 in fact provide for a fine filtration degree, whilst the regions 5 and 6 provide for a coarse filtration degree; the lateral bands are not considered because they are meant to be inserted in the structure of a filter. An apparatus for producing the sheet of figure 1 comprises at least a first continuous machine of a kind suitable for manufacturing paper, more specifically of the flat-screen type, generally designated by the reference numeral 7, which comprises in a known manner a head box 8, which carries a fibrous suspension in water onto the conveyor constituted by the supporting screen 9 which acts between the cylinders 9a and 9b with underlying suction boxes such as 9c. A first web or mat of fibers is thus formed on the supporting screen 9 and is obtained by removing the water that contained the fibers in suspension, the entire system being uniformly distributed, as explained in greater detail when describing the operation of the invention. The reference numerals 10 and 11 furthermore respectively designate a second machine and a third machine of a kind suitable for manufacturing paper and more specifically of the cylinder type, which operate in combination with the conveyor constituted by the supporting felt 12 by depositing thereon two superimposed webs. The cylinder 13 provided in the machine 10 has a continuous wire mesh 13a and therefore the web formed by it on the supporting felt 12 is uniformly distributed, whilst the cylinder 14 provided in the machine 11 is provided with a wire mesh which is transparent only at the bands 14a, 14b and 14c, whilst the bands 14d, 14e are closed; accordingly, a web with longitudinal bands is obtained from said cylinder, as explained in greater detail when describing the operation. An important characteristic of the invention is constituted by the fact that the supporting felt 12 is arranged so as to make the superimposed webs formed thereon rest by gravity on the web formed on the supporting screen 9, as shown in the detail of figure 8. Operation of the invention is as follows. Whilst the uniformly distributed web, designated by the reference numeral 15, is formed on the supporting screen 9, the machine 10 forms on the supporting felt 12 the uniformly distributed web 16, on which the web formed by the machine 11 and constituted by the bands 17a, 17b and 17c is superimposed. When the supporting felt 12 deposits, as shown in figure 8, the webs formed thereon onto the web 15, resting them by gravity with a very gentle action, the layer 15 maintains its softness, thus forming a sheet 1, as shown schematically in the sectional view of figure 9, which has regions with a differentiated filtration degree determined by the different amount of fibers in the different regions of its thickness and has optimum characteristics as regards the filtration function. When it leaves the supporting mesh 9 of the flat-screen machine 7, the sheet 1 moves onto the wire mesh 18 and undergoes the action of devices such as 19, which emit infrared rays, and then moves on for the subsequent steps for drying and collection according to the prior art. The invention is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept: thus, for example, there may be two or more conveyors suitable to rest by gravity respective webs formed thereon in an intermediate position of a first conveyor on which at least one web has been formed: the number and type of the machines that operate in combination with the various conveyors may also be different from the one described. In the practical embodiment of the invention, all the details may furthermore be replaced with other technically equivalent elements; the materials employed, the shapes and the dimensions may also be any. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims: An apparatus for manufacturing a filtering medium (1) in sheet form, comprising at least one first continuous machine (7), adapted for manufacturing paper and the like and suitable to form at least one first web (15) on a first conveyor (9), and at least one second continuous machine (10) also adapted for manufacturing paper and the like and suitable to form at least one second web (16) on at least one second conveyor (12), at least one of said first and second continuous machines being suitable to form a web which is not uniformly distributed, characterized in that said at least one second conveyor (12) is arranged so as to make said at least one second web rest by gravity on said at least one first web. The apparatus according to claim 1, characterized in that said first continuous machine (7) is of the flat-screen type, which comprises a head box (8) and a substantially flat supporting screen (9), said at least one second conveyor (12) being arranged so as to make said at least one second web (16) rest on the web (15) formed by said first machine in an intermediate position of the corresponding supporting screen (9). The apparatus according to claim 1, characterized in that it comprises two machines of the cylinder type which are suitable to form superimposed webs on said second conveyor (12), at least one of said machines being suitable to form a web which is not uniformly distributed.

Inventors: DADEA GIANMARIA, DADEA, GIANMARIA
Applicants: FILTER MEDIA GROUP S R L, FILTER MEDIA GROUP S.R.L.
Application year: 1997
Main classification: D21F11
IPC codes: D21F11, B01D39