A drum having a side carrying wall of a latticed structure for machines for the manufacture of paper, paper-board, asbestos cement or the like

Description

[0001] The present invention relates to a forming and forming-suction drum adapted to be used in machines for the manufacture of paper, paper-board, asbestos cement or the like. This drum has a cylindrical shell wall of a latticed structure, which is obtained by means of two pluralities of small metal bars extending helically right-hand and left-hand respectively, crossing with each other and fixed relatively to each other at their cross points.

[0002] Drums are already known which have a perforated side wall and which are used as forming or suction drums in the machines for the manufacture of a web of paper, paper-board, asbestos cement or the like, and which will be formed around said drum which is covered by a wire cloth underneath of which a fabric undercloth is placed and through which passes the water separated from the employed mixture, this latter being compressed under the action of one or more mechanized pressure cylinders. The mixture can be applied on said cloths by means of a distribution box or it can be collected by means of the side wall of the drum which is partially plunged into a tank which contains the mixture.

[0003] Said known and broadly used drums are constituted of a pair of heads mounted on a longitudinal shaft and between which and on said shaft, also a plurality of arm dials are keyed which are equally spaced apart from each other respectively supporting a peripheral rim. Said heads and the rims, and/or the arms dials support longitudinal bars which are equally angularly spaced apart from each other so as to form a drum, having a perforated side wall, on which the wire cloth and the fabric cloth are applied, on which the web of paper or the like will be obtained under the action of the pressure applied to said web by means of the pressure cylinders with the interposition of a continuous felt band. The drum is caused to rotate by the mechanized rollers by means of its shaft said drum freely rotate into support sleeves.

[0004] In order to increase the efficiency of the machine, attempts have been made so as to increase the drum peripheral speed, but it has been found that when said speed is increased, the possibility to obtain a good formation of the web of paper or the like decreases, owing to the tendency that the fibrous particles of the mixture present, of moving awayfrom the outer wire cloth under the effect of the centrifugal force so that by means of the known drums, one can work only with peripheral speeds not higher than 2m/ second.

[0005] In order to overcome said inconvenience and to improve the efficiency, provision has been made that perforated pipes are mounted in the inside of the drums of the aforementioned type; said pipes are connected to a suction source so as to create, through the perforated wall of the drum and the cloths placed thereupon, a suction effect capable of counter-balancing the centrifugal force. But this solution has the inconvenience to be complicated and therefore expensive, since each suction pipe, which in the known drums had to be made integral with the drum - as a result of the presence of the shaft and of the interposed bar dials thereof - was able to operate only on a predetermined sector of the drum, which corresponds at most the 30-40% of the whole area of the side surface of the drum. Therefore the number of the suction pipes had to be considerable and therefore complicated connections of said pipes to the suction source were required.

[0006] Another important problem, concerning these drums consists in the fact that it is necessary to be able to carry out an efficient cleaning, in order to remove the residues of the mixture materials from the inside of the drums, residues which are drawn together with the drainage water and which can deposit on the external cloths or on the inner parts of the drum.

[0007] Such a cleaning system in the known drums could be only performed, acting from the outside, and in a little efficient manner, by employing pressurized washing jets, directed tangentially or nearly tangentially with respect to the side surface of the drum. This problem becomes more important in the case of the manufacture of webs or plates of asbestos cement, on account of the specific characteristics of the components of such a mixture, consisting of asbestos fibers and cement which is used as binding medium. The very small particles of the cement powder obstruct the cloths so that it results that a bad and irregular formation of the layers which compose the web takes place, so that at frequent time- intervals radical washings of the drums with a suitable cleaning solution become necessary. For such a purpose the drums have to be disassembled and transported to the repair shop for carrying out complete cleaning operations.

[0008] An Austrian Patent N. 297 474 is also known which provides a drum having a grating wall, formed by two pluralities of stripes helically wound around the axis of the drum and radially spaced away from said axis of a constant distance. Said stripes are formed by superposed layers of bands made of glass fibers covered by a plastic material.

[0009] But such drums can be used only as "dandy rolls" in a process for obtaining watermark paper, or as drying drums in the paper cycle, but said drums cannot be employed as forming or suction drums which have to withstand very high stresses.

[0010] The purpose of the present invention is thus that of overcoming the inconveniences of the known drums which are used in the machines for the manufacture of the paper, paper-board, asbestos cement and the like.

[0011] For such a purpose the invention provides a drum according to claim 1 which can be used, as forming drum or as suction drum, and which comprises two heads provided with central coaxial orifices and between which is fixed a peripheral cylindrical shell wall of a latticed structure. To the edges of said orifice tubular members are made integral which serve as means for supporting the drum and which also permit the free rotation of this latter about its axis, while through said orifices perforated washing pipes can be inserted in the inside of the drum, said pipes supplying a pressurized liquid fed from an external source. On account of the absence of the drum shaft as well as of the inner supports for the annular rims that there are in the known drums, said pipes can be now stationary or can swing about a fixed axis. In practice also one washing pipe can be sufficient in order to attain an optimal cleaning, since said pipe can be mounted near the lower portion of the revolving drum; said pipe is provided with radial nozzles for the delivery of the washing liquid facing the inner surface of the drum.

[0012] The peripheral shell wall of this drum is obtained by an interconnection of two pluralities of small metal bars extending helically right-hand and left-hand respectively and which are uniformly spaced apart from each other and are restrained to each other in their cross points, owing to the presence of transversal slots, having a length substantially equal to the half width of each bar at both its ends said wall is connected to the two heads and is capable of bearing all the involved stresses, without requiring that in the inside of the drum any supporting means for said wall have to be provided.

[0013] As a consequence it does not need any provision of an axial shaft for supporting the drum: furthermore the end flanges are shaped so as to form hollow supporting means: further there is no more any bar dial as in the conventional drums so that the inner cavity of the drums is entirely free so that one or more washing spray pipes can be inserted which passes through the orifices arranged in the heads, and said pipes can be stationary or can swing about a fixed axis. Of course, with an equal simplicity, stationary suction pipes could be mounted for the above mentioned purposes. On account of the fact that either each spray pipe or each suction pipe is stationary or swinging about a respective fixed axis, said pipe or pipes can be placed in the most con- venable position so as to be able to act on each cylindrical drum sector, when said sector passes in the front of said pipe. It results therefrom that in practice only one spray pipe could be mounted preferably facing the lower inner portion of the drums or also optionally a suction pipe, which in this case has to be mounted in close proximity of the sector about which the formation of the web of paper and the like takes place.

[0014] The so obtained latticed wall is such that the area of orifices or passages thereof will be equal to about 70-75% of the total side area of said side wall of the drums. Further the configuration of the wall structure is such as to present characteristics of strength which are substantially uniform in each direction so that the mixture will be distributed and compressed with a complete uniformity along said shell wall and that permits to attain better results as well as to enable the drum to work at speeds which do not only reach 2m/sec but are also higher than this latter, by means of the insertion in the inside of the drum of any sufficient number of suction devices.

[0015] These and other characteristics and advantages of the present invention become readily apparent in the following description of two embodiments thereof, reference being made to the accompanying drawings, in which:

Figure 1 is a perspective view of a portion of the cylindrical shell wall of a drum, when developed in a plan;

Figure 2 is a diagrammatic side view with a partial axial section of a drum, in the inside of which is mounted a washing pipe and in which, for clarity of representation, the bars are shown as in rectilinear form instead of in a helical form;

Figure 3 is an enlarged view of a portion of the cylindrical shell wall of the drum, assuming that it is developed in a plan, said portion being adjacent to one of the head rings;

Fig. 4 is a partial section taken on line A-A of Fig. 3;

Figure 5 is an axial section of the drum according to another embodiment; and

Figure 6 is the view of the drums of Figure 5, taken from one of its heads.

[0016] According to the embodiment shown in Figures 1 to 4, the drum comprises two end flanges generally marked 2, between which a peripherally cylindrical shell wall is mounted which is generally marked 1. Such a wall 1 consists of a strong latticed structure, which is constituted, in combination, of two pluralities 1a a and 1 b of small metal bars, fixed at their ends along the periphery of the flanges 2 and which extend helically, right-hand and left-hand respectively, with the same pitch and which are angularly spaced apart from each other, in such a manner as to form a latticed structure, through which are defined substantially radial passages each having a quadrangular cross section. The bars 1a, 1b cross each other and are mutually fixed to each other in their cross points by means of transversal slots 3a and 3b having a depth substantially equal to the half width of each bar 1a, 1b; slots 3a are cut through the outer edges of the bars 1a and the slots 3b are cut through the inner edges of the bars 1b (Figure 1). The connection between the bars 1a, 1b can be improved by weldings applied along the joint zones. Thus a cylindrical latticed side wall 1 is created which is supported at their ends only by the two flanges 2. These latter are constituted of peripheral rings generally marked 4 supported by a disc-like member 5 which axially extends outwardly with a hollow hub 5a; said hubs define inner coaxial openings. Each ring 4 has a longitudinal cylindrical flange extending towards the wall 1 respectively (Figures 2 to 4) which has an outer shoulder 4b of a depth lesser than the thickness of the cylindrical wall 1. On the cylindrical bottom surface of the shoulder 4a grooves 6 are arranged so shaped as to be able to receive the inner edges of the respective ends of the bars 1a, 1 b in their use position. The depth of the grooves 6 with the addition of that of the shoulder 4b is such to bring the outer edges of the bars 1 a, 1 b to come into alignment with the outer cylindrical side surface 4c of the rings 4. According to the shown embodiment each ring 4 has an annular shoulder 4b at its outer surface, which is designated to receive the radial peripheral flange 5b of the head disc 5 which is fixed to the respective ring 4, in any disassemblable manner, by means of screws, for instance inserted in the holes 17 (Figures 2 to 4).

[0017] Owing to the particular configuration of the drum constructed according to the invention neither a longitudinal shaft supporting the drum nor any inner carrying structure for the side wall 1 are now present, since the drum is supported, in a freely revolving manner, by means of the hollow hubs 5a housed in fixed tubular supporting members 7. The inner cavity of the drum is entirety free and accessible through the inner cavities of the hubs 5a through which can be inserted at least a pipe 8 which can be a stationary pipe, or a pipe swinging about a fixed axis, and which can have a two-elbowed configuration in order that said pipe can have an inner section 8a which can be positioned in close proximity of the inner surface of the wall 1, where said pipe section is provided with radial holes or nozzles 9, directed against the wall 1.

[0018] Each pipe 8, 8a will be connected at least at one of its ends, which the interposition of a control valve 10, to a feeding source of a pressurized washing liquid which may be water that could contain also any additive adapted to promote the removal of the deposits formed in the inside of the drum or on the cloths which are provided for filtering the draining water which passes through the wall 1. Thus by employing the improved drum in question, an efficient washing of the inner space of the drum can be attained by means of very strong pressurized liquid jets which, passing through the latticed wall 1 and the filtering cloths (not shown), maintain the drum and the cloths placed there-about in a condition of perfect efficiency. This advantage is of vital importance, in particular, in the machines for the manufacture of the asbestos cement products.

[0019] Of course, besides the insertion in the inside of the drum of at least one washing pipe, preferably mounted in close proximity of the lower portion of the inner surface of the drum in the inside of this latter one or more perforated suction pipes (not shown) can be mounted in an equally simple manner. Also these latter pipes will be stationary so that one or more can be mounted only in that zone before which successively passes that sector of the drum 1 through which has to be created a suction action adapted to compensate for the effect of the centrifugal force, in such a manner to permit to increase the operative peripheral speed of the drum in order to increase the efficiency of the machine. On account of the fact that the suction pipe is stationary, in general it will be sufficient to employ only one pipe in order to obtain a satisfactory suction effect. Provision is made that the drum is drawn to rotate by mechanized pressure rollers, but, of course, nothing prevents from providing of transmitting a revol- ing movement also directly to the drum itself by the provision of mounting on one of the hubs 5a, or one of the rings 4, a toothed crown that can mesh with a train of gears for the motion transmission to the drum.

[0020] Figures 5 and 6 show a second embodiment wherein the flanges 2a consist of peripheral rings 4 identical to those which have been shown and described in the first embodiment, while, instead of the discs, simple shaped rings, are provided generally indicated 12. Each ring 12 is provided with an inner radial rim 12a designated to be housed in the annular facing shoulder 4d of the respective ring so as to form a cylindrical guiding race surface 12b for at least two idle pulleys 13 mounted on small fixed longitudinal shafts 14. In the embodiment, shown in Figures 5 and 6, only two pulleys 13 are provided, which are mounted near the lower part of the drum, but nothing prevents that at least one or more guiding pulley be provided also in other positions.

[0021] In this embodiment orifices are thus created in the flanges 2a of this drum, which are so large that the advantage is obtained that the washing pipes 8A can extend rectilinearly as well as the optional suction pipes can be also rectilinear.

[0022] In addition through said wide orifices at the flanges 2a of the drum periodical mechanical operations of inner cleaning can be carried out, without having to disassemble the drum, and to employ implements such as brushes, swabs and the like.

Claims

1. A forming drum having a cylindrical shell wall (1) carried by two end flanges, for manufacturing paper, paper board, asbestos-cement webs and the like which shell wall (1) is formed by two groups of bars (1a, 1b) of a substantially rectangular cross section crossing each other and extending helically in a right-hand and a left-hand sense respectively along the shell wall (1), having the same helical pitch and being spaced apart from each other at equal distances so as to form a latticed structure defining radial passages of quadrangular cross section, said bars (1a, 1b) at their crossing points being fixed relatively to each other, characterized in that the bars (1a, 1b) are metal bars and that the two end flanges (2, 2a) consist of annular elements comprising means for supporting, rotating and guiding the drum, said flanges (2, 2a) having coaxial central orifices through which at least one suction perforated pipe connected to a vacuum source and at least one stationary washing pipe (8, 8a; 8A) provided with spray nozzles (9) passes into the interior of the drum, the spray nozzles (9) facing the inner cylindrical latticed surface of the shell wall, and said pipe (8, 8a; 8A) being connected to a source of a washing liquid.

2. A drum according to claim 1, wherein the annular elements of the end flanges (2, 2a) consist of peripheral rings (4), each provided with a short cylindrical rim (4a) carrying the ends of the shell wall (1), the outer surface (4b) of the rim (4a) having grooves (6) for receiving the inner edges of the end portions of the metal bars (1 a, 1 b), the position of the rim (4a) and the radial depth of the grooves (6) being such that the outer surfaces of the bars (1a, 1b) flush with the cylindrical outer surface of the respective peripheral ring (4).

3. A drum according to claims 1 and 2, wherein each annular element of the end flange (2) consists of a peripheral ring (4) connected, in disassemblable manner, to a circular disk-like element (5), having a central hole, carrying an outwardly extending hollow hub (5a) provided with a large axial orifice.

4. A drum according to claims 1 and 2, wherein each end flange (2a) consists of a peripheral ring (4) connected to a cylindrical rim (12a) which extends axially outwards with regard to the ring (4) so as to form an outer annular guiding race surface (12b) for the rolling of pulleys (13) which carry and guide the drum during the rotation thereof and which are mounted about fixed small shafts (14), the axes of which are parallel to that of the drum.

Ansprüche

1. Formtrommel mit einer zylindrischen Gehäusewandung (1), welche durch zwei Endflansche getragen ist, zur Herstellung von Papier, Karton, Asbestzementgeweben oder ähnlichem, wobei die Gehäusewandung (1) durch zwei Gruppen von Stegen (1a, 1b) von im wesentlichen rechteckigem Querschnitt gebildet ist, die einander kreuzen und sich schraubenförmig nach rechts bzw. nach links entlang der Gehäusewandung (1) erstrecken, die dieselbe Ganghöhe aufweisen und die sich voneinander im gleichen Abstand befinden, um so eine Gitterstruktur zu bilden, welche radiale Durchlässe von viereckigem Querschnitt begrenzt, wobei diese Stege (1a, 1 b) an ihren Kreuzungspunkten relativ aneinander fixiert sind, dadurch gekennzeichnet, dass die Stege (1a, 1b) Metallstege sind und dass die zwei Endflansche (2, 2a), aus ringförmigen Elementen bestehen, welche Mittel zur Halterung, Rotation und Führung der Trommel aufweisen, wobei die Flansche (2, 2a) koaxiale zentrale Öffnungen aufweisen, durch welche mindestens eine mit einer Vakuumquelle verbundene perforierte Saugleitung und mindestens eine mit Sprühdüsen (9) versehene stationäre Waschleitung (8, 8a; 8A) in das Innere der Trommel führen, wobei sich die Sprühdüsen (9) gegenüber der inneren zylindrischen gitterförmigen Fläche der Gehäusewandung befinden, und wobei die Leitung (8, 8a; 8A) mit einer Quelle für eine Reinigungsflüssigkeit verbunden ist.

2. Trommel nach Anspruch 1, bei der die ringförmigen Elemente der Endflansche (2, 2a) aus peripheren Ringen (4) bestehen, von denen ein jeder mit einem kurzen zylindrischen Wulst (4a) versehen ist, welcher des Ende der Gehäusewandung (1) trägt, wobei die äussere Fläche (4b) des Wulstes (4a) Rillen (6) zur Aufnahme der inneren Kanten der Endabschnitte der Metallstege (1a, 1b) aufweist, wobei die Position des Wulstes (4a) und die radiale Tiefe der Rillen (6) solche sind, dass die aussere Fläche der Stege (1 a, 1 b) mit der zylindrischen äusseren Fläche des entsprechenden peripheren Ringes (4) bündig ist.

3. Trommel nach den Ansprüchen 1 und 2, bei der jedes ringförmige Element des Endflansches (2) aus einem peripheren Ring (4) besteht, welcher, zerlegbar, mit einem kreisförmigen scheibenförmigen Bauteil (5) verbunden ist, welcher eine zentrale Öffnung aufweist, welcher eine sich nach aussen erstreckende hohle, mit einer grossen axialen Bohrung versehene Nabe (5a) trägt.

4. Trommel nach den Ansprüchen 1 und 2, bei der jeder Endflansch (2a) aus einem peripheren Ring (4) besteht, welcher mit einem zylindrischen Wulst (12a) verbunden ist, welcher sich axial in Bezug auf den Ring (4) nach aussen erstreckt, um so eine äussere ringförmige Führungslauffläche (12b) für das Rollen von Führungsrollen (13) zu bilden, welche die Trommel während deren Rotation tragen und führen und welche auf fixierten kleinen Stiften (14) lagern, deren Achsen parallel zu jener der Trommel stehen.

Revendications

1. Tambour de formation ayant une paroi périphérique cylindrique supportée par deux collerettes d'extrémités pour fabriquer des nappes de papier, de carton, de ciment d'amiante et de matières comparables, cette paroi périphérique (1) étant formée de deux groupes de barres (1a, 1 b) à section transversale pratiquement rectangulaire se croisant mutuellement et s'étendant en hélices respectivement à droite et à gauche le long de la paroi périphérique (1) en ayant le même pas et en étant écartées entre elles de distances égales de façon à former une structure grillagée délimitant des passages radiaux de forme quadrangulaire, lesdits barres (1a, 1b) étant fixées l'une à l'autre en leurs points de croisement, caractérisé en ce que les barres (1 a, 1b) sont des barres de métal et que les deux collerettes d'extrémités (2, 2a) consistent en éléments annulaires comprenant un moyen pour supporter, faire tourner et guider le tambour, les dites collerettes (2, 2a) ayant des orifices centraux coaxiaux à travers lesquels passent vers l'intérieur du tambour au moins un tuyau d'aspiration perforé raccordé à une source en dépression et au moins un tuyau de lavage fixe (8, 8a, 8A) comprenant des tuyères de projection (9) faisant face à la surface grillagée cylindrique intérieure, ledit tuyau (8, 8a, 8A) étant raccordé à une source de liquide de lavage.

2. Tambour selon la revendication 1, dans lequel les éléments annulaires des collerettes d'extrémités (2, 2a) consistent en collerettes périphériques (4), produites chacune avec un court rebord cylindrique (4a) portant les extrémités de la paroi périphérique (1), la surface extérieure (4b) du rebord (4a) ayant des rainures (6) pour recevoir les bords intérieurs des parties d'extrémités des barres de métal (1a, 1 b), la position du rebord (4a) et la profondeur radiale des gorges (6) étant telles que les surfaces extérieures des barres (1a, 1 b) soient au niveau de la surface extérieure cylindrique de la collerette périphérique respective (4).

3. Tambour selon les revendications 1 et 2, dans lequel chaque élément annulaire de la collerette d'extrémité (2) consiste en une couronne périphérique (4) raccordée, de manière séparable, à un élément en forme de disque circulaire (5) ayant un trou central, portant un moyeu creux (5a) qui s'étend vers l'extérieur en présentant un large orifice axial.

4. Tambour selon les revendications 1 et 2, dans lequel chaque collerette d'extrémité (2a) consiste en une couronne périphérique (4) raccordée à un rebord cylindrique (12a) qui s'étend axialement vers l'extérieur par rapport à la couronne (4) de façon à former une surface de guidage annulaire extérieur (12b) pour le roulement de poulies (13) qui supportent et guident le tambour pendant sa rotation et qui sont montées sur de petits arbres fixes (14) dont les axes sont parallèles à celui du tambour.

Drawing