FI122280B - A method of making a screen cylinder and a screen cylinder - Google Patents

Description

METHOD FOR MANUFACTURING SCREEN CYLINDER AND SCREEN CYLINDER

The present invention relates to a process for making a screening cylinder and a screening cylinder which is particularly suitable for screening, filtering, fractionating or sorting cellulose pulps or other similar suspensions in the pulp and paper industry. The present invention is particularly suitable for the manufacture of screening devices comprising a plurality of screening yarns disposed in parallel with each other, said plurality of screening yarns forming a screen surface per mass to be sorted and adjacent yarns forming an interstice passage through the screen opening. In particular, the present invention relates to the manufacture of sieve cylinder carrier rings, i.e. rings for attaching a sieve cylinder to the surrounding sieve cylinder shell or to another sieve cylinder in cases where the sorting element is formed from more than one sieve cylinder disposed axially on top of one another. Thus, the carrier ring may be located either in the central portion of the screen cylinder or at one end thereof. In the latter case, the carrier ring is most often referred to as the main tire.

Pressure separators used by the woodworking industry (as a general example, U.S. Patent No. 20,663,521) generally comprise a solid screen drum or screen cylinder within a substantially cylindrical outer jacket having screen mass inlet ports and accept and reject outlets. There may also be other inlet and outlet connections, for example, to the plastic resolved in the device, and to the diluent being fed into the device. In most cases, the device is mounted in a vertical position such that the axis of the substantially cylindrical jacket is substantially vertical. Then, the end of the device 5 can be easily opened or removed from a substantially cylindrical jacket and

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^ you are easy to maintain. The axis of the device passes through the opposite end of the device, i.e.

° usually at the lower end and usually rotates the rotor, although in some screeners the screen cylinder itself is rotatable. In addition to the rotor, there is also a screen or sieve inside the cylinder jacket.

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A £ 30 distillation cylinder, which is mostly cylindrical, although numerous cone-shaped screen drums have also been proposed. Usually, the screen cylinder is located radially rotatable

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^ rin outside. The sieve barrel is supported at both ends of the diaper, sometimes even from the o center by means of spacers. The sieve cylinder can also be constructed in at least two parts, which are joined at their ends by said support rings or end rings. The spacer rings are secured to the screen shroud and the screen cylinder 2 is connected to these spacer rings at least at each end by means of so-called end rings or carrier rings.

Of course, carrier rings have been used in connection with both milling screen cylinders 5 and so-called wedge screen screen cylinders. In milled screen cylinders, the screen surface is made of metal plates which are machined with either screen openings or sorting slots. The surface facing the fiber suspension to be treated is in many cases provided with grooves or ribs to provide a vortex in front of the screen openings to enhance sorting. The so-called wedge wire screen cylinders are such that the screened surface of the metal plate of the milled screen glass cylinder is replaced by a screen surface formed by adjacent bars of a certain cross-section with a screen gap between them. Rods of a certain cross-section, often referred to as yarns, are usually made by rolling and / or drawing steel. The cross-section of the yarns is such that the final screen surface resembles a milled cylinder. In other words, the yarns often have a longitudinal ridge on the surface facing the fiber suspension to be screened so that the screen gap between two adjacent rods is located substantially at the bottom of the groove between the two adjacent rods. Bars of a certain cross-sectional shape are normally arranged along the axis of the screen cylinder, although it has also been suggested that they be arranged in a spiral or circumferential manner.

Both metal plate cylinders and wedge cylinders made by milling are so weak in structure that they require additional support to maintain their round shape and mechanical integrity. The support is often in the form of round rings fixed at the height of the entire 25 cylinders at regular intervals on the surface of the screen cylinder to the accept side of the cylinder. The cross-section of the support element is normally rectangular, although other shapes such as circular and triangular shapes have been proposed. When the screen is made by milling on a thin metal plate, the supporting elements are secured to the metal plate by welding. When the sieve is made of sieve bars, the individual bars are initially attached

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£ 30 on supporting elements by welding. However, welding has proven to be a problematic method of attachment because the heat of welding weakens the sieve rod by changing the

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females, in which case the bar is relatively susceptible to fractures. At present, welding has been replaced by various types of tail or keyhole openings, notches, or recesses in which the sieve rod is mounted either by pushing in its longitudinal direction or perpendicular to the support element and the bar. Sometimes the screen bars are mounted in openings or recesses while the support elements are still straight. When the support elements are bent into circular rings, the apertures or recesses press the screening yarns into the recesses. Sometimes even this type of attachment head is secured by gluing, soldering or welding the screening threads into the slots or openings. Another way of attaching the screening yarns to the tu-5 tongue elements is described later in U.S. Patent 6,521,096. Often the cross-section of the support elements is so small that additional support rings have to be mounted on the annular support elements. Sometimes additional support is made by arranging a kind of mesh-like body around the cylinder over the support elements.

10 As for the support elements, there are a couple of ways to make them. One way is to make the element from a suitably sized metal bar, bend the bar to a circular shape and weld the ends together. Bending and welding can be done either before or after the attachment of the screening yarns to the support elements. Another way is to pre-fabricate the support elements into circular rings, for example by cutting the rings 15 from a suitable metal plate.

On the other hand, bearing rings, or more narrowly end rings, also called top-end and base rings, are normally somewhat more sturdy in construction than the support elements and support rings because they have to transfer various loads to the screen cylinder during sorting. Carrier rings or end rings are then used, as already mentioned above, to attach the screen cylinder to the screen of the screen.

There are at least four ways that are used to attach or arrange the screen glass cylinder to the sieve sheath. In the following, only the top and bottom rings are discussed, ς but the discussion also applies to the carrier rings arranged in the middle of the screen cylinder.

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^ I can. Carrier rings are most often treated in the same way as base tires.

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The first way is to arrange the screen cylinder as if it were floating on either

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£ 30 to reach. Rotation of the cylinder is prevented by means of pins between the carrier ring (s) of the sieve cylinder and the diaper, or spacer ring attached to the diaper. The bearing or end rings are preferably like radially extending flanges at the ends of the cylinder.

A third way to arrange the screen cylinder is to secure it from the second, normally upper 5, end as described above, i.e. by bolting the upper flange-like carrier ring to the spacer ring. However, in this version, for the opposite end, i.e. for the lower end of the screen cylinder, a second spacer ring is provided with an annular recess which fits the lower end ring suitably. In other words, the lower end of the screen cylinder floats within said recess so that the minimal radial gap is between the flange-like carrier ring and the spacer ring. However, the gap allows for radial vibration of the lower end of the screen cylinder. As the cylinder oscillates, the gap increases (i.e., the wear ring and / or its abutment surface is worn) slowly, whereby the stresses on the screen cylinder also increase. And, of course, tensions easily lead to the screen cylinder breaking. Normally the radial movement 15 of the screen cylinder head is blocked or attempted by blocking the O-ring between the surfaces of the carrier ring and the spacer ring. However, the O-ring is a relatively thin ring of the order of 6 mm, whereas the sieve drum is of the order of a meter. The use of an O-ring has many disadvantages. For example, it is difficult to install a screen cylinder so that the O-ring stays properly in place and difficult to detect if the ring is not properly seated. In the Edel-20, the O-ring hardens due to the thermal stresses and chemical stresses of the screenable pulp, which easily crumbles. Because the O-ring requires a certain mounting clearance, crumbling of the O-ring will, at worst, result in bad and uncontrolled vibration at the end of the screen cylinder.

A fourth way to attach the screen cylinder to the above-mentioned spacer ring is, on the other hand, to provide a conical seat surface on the inner edge of the lower spacer ring. Conical Chuck

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The tongue opens upwards and is oriented along the axis of the rotor facilitating the sorting of the pulp. The lower end ring or bottom ring of the screen cylinder is provided with a corresponding conical seat surface such that the screen cylinder sits centrally

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£ 30 per rotor. The center portion of the screen cylinder may be supported by a similar carrier / spacer combination on the screen sheath. The upper end ring is often

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<- provided with a flange extending above the upper spacer ring so that the flange can be bolted to the upper spacer ring.

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The carrier rings have so far been made of steel, since steel has been the easiest material to process and to connect different parts to each other. This has been especially true when the screen cylinders are made of metal plates, because welding the end rings to the screen cylinder provided an easy, cheap and reliable way of attaching the two parts to each other. With wedge-5 wire mesh cylinders now dominating the market, attaching an end ring or carrier ring to a wedge wire cylinder has proven problematic. As previously discussed, welding is not the best way to attach wedge wire mesh surfaces. The reason for this is that due to the high temperature, in addition to the variable properties of the metal material of the screening yarns, welding the yarns to the end rings results in relatively rigid attachment, which in turn greatly restricts movement in the screening cylinder. Wedge wire sieve cylinders are somewhat flexible, and the yarns tend to move either individually or in groups. Therefore, the boundary line between the carrier ring and the wire is a potential point for screen breakage. Minimal movements of the sieve cylinder can break the rigid joint, especially when the metal material of the sieve wires has hardened during the 15 welding stages.

Another problem associated with welding the carrier rings to the screening yarns is the reduction in the diameter of the carrier ring after welding. A characteristic feature of welding is that the diameter of the welded circular ring after welding is smaller than it was before welding. This results in the screen cylinders being somewhat barrel-shaped after welding the bearing or end rings on the wedge wires. Sometimes the change in diameter is so large that the screen cylinder has at least one end of its diameter smaller than the tolerances allow, and the manufacturer must either reject the entire cylinder or repair it to get the inside diameter to fit within the tolerances.

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The present invention provides a solution to the problem described above with other problems described below. The solution is to construct at least one carrier or main ring of composite material so that the attachment of the screening yarns is reliable-

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£ 30 and still allow some internal movement of the components of the screen cylinder, whereby loads on the screen yarns can be easily controlled.

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However, in the prior art, there are screening or screening drums or screens having at least partially end-rings of composite material. For example, 35 EP-A1-0512873 or US 5,255,791 speak of a screen made by rotating a U-6 metal sheet screen element strip in a spiral manner and welding the strips together to form a screen cylinder. The end ring, which must form a plane perpendicular to the cylinder axis, is made in a mold in which the cylinder end is positioned. The mold is a hollow, circular frame having the shape of an end-ring of a conventional sieve cylinder of cross-sectional shape. Further, the bottom of the mold has horizontally sealed holes arranged for internal portions required for making helical or non-helical cavities, such as those required for mounting in a sieve screen or for removing the screen from said screen or screen. There may also be an interior to prevent the screen from rotating. The screen ring cylinder-10 end ring assembly is made as follows. The mold is placed on a horizontal plane, the screen cylinder is brought there vertically, and it is held suspended in this position at a predetermined height in the mold. The mold is then filled with a curable plastic or thermoplastic or composite material. Preferably, the low mechanical properties of the material are at least comparable to those of stainless steel. After the minimum necessary cure time, the cylinder with its end ring is removed from the mold and the operation at the opposite end of the cylinder can be resumed.

EP-A1-1161308 discloses a screen cylinder which is essentially the same as EP-A1 -0512873 except that the screen cylinder is provided with special locking anchors to increase the contact area between the screen cylinder and the end ring material. The end rings are made of polymer, fiberglass, stuffed material or composite material.

In other words, the prior art refers to the manufacture of a screen cylinder 5 which has an end ring of plastic or composite material. However, in two

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The screen cylinders disclosed in the above-mentioned patent, namely EP-A1-0512873, and EP-A1-1161308, correspond to a metal plate screen cylinder. The reason for this is that the documented screen surface made of U-shaped metal sheet strips,

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£ 30 welded at its edges to form a sturdy screen cylinder is particularly stiff at £ 5 compared to conventional wire screen cylinders. Thus, the conditions and requirements that exist

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the ends of the wire mesh cylinder end region are set differently.

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As already discussed above, the problem with the existing wedge-wire wire mesh cylinders with steel end rings is the connection of a rather flexible wedge wire to the rigid end ring. Because wedge wire carpet is currently welded to the ends of the ends, welding changes the properties of the steel, making the part of the yarns subjected to the greatest stress the weakest to resist the stresses applied to them. When subjected to a dynamic load, steel screening wires typically break as the crack increases. Internal stresses and changes in physical properties in the so-called heat-affected zone (HAZ) caused by welding may expose the steel elements to increased cracking.

Another problem solved by the present invention is to securely attach the ends 10 of the screen yarns to the composite ring while still providing some flexibility.

Among other things, the above-mentioned problems can be solved by a screen cylinder according to the present invention and a process for its manufacture. The method of making the screen cylinder 15 comprises the steps of a) making annular support elements, b) attaching a plurality of screen yarns to the support elements so that a screen gap is left between adjacent screen yarns in steps a) and b) optionally to form a screen cylinder; supported within the screen of the sorter, d) fabricating at least one carrier ring from a composite material to multiple layers, and e) at least partially immersing said at least one annular support member in said composite carrier ring.

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A screening cylinder according to a preferred embodiment of the invention is formed by at least a plurality of screening yarns having a screen gap and substantially annular support members to which said screening yarns are attached and a carrier ring

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£ 30 is attached to said screening yarns, wherein said carrier ring is formed of two or more composite materials in multiple layers and at least ί part of the support element remains within said composite carrier ring.

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In solving at least some of the above problems, the present invention also provides a number of advantages, some of which are listed below: for sorters, etc. without clearance in the sorting unit - control of the vibration characteristics of the sorting unit.

It will be understood, however, that the listed advantages are merely optional, so that one or more of the said advantages will depend on the practical implementation of the invention.

The present invention will now be described in more detail with reference to the accompanying drawings in which

Figure 1 shows a prior art wire screen cylinder,

Figure 2 is a partial cross-sectional view of a first embodiment of the present invention, Figure 3 is a partial cross-sectional view of another preferred embodiment of the present invention,

Figure 4 is a partial, somewhat more detailed, cross-sectional view of a third preferred embodiment of the present invention.

Figure 1 shows a prior art sieve cylinder made of sieve 5 yarns, so-called wedge yarns. The method of such a wedge screen sieve cylinder

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The preparation of the preparation has been described in dozens of patents over the last twenty years, and there is no reason to describe the preparation in this context any further. Among others in the following patents, many

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Among other things, the manufacture and construction of a wire screen cylinder is described in more detail: US 6,426,003, US 6,521,096, US 6,785,964 and US 6,789,681. Featured-

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The present invention is applicable to all screen cylinders, and in particular to those generally shown in Fig. 1. The prior art screen cylinder 10 in Fig. 1 usually comprises axial screen strands 12 attached to circumferentially extending support members 14. Currently, strands 12 are often attached to support members 14 grooves transverse to the longitudinal direction. In some cases, the support elements are further supported on a support ring disposed radially outside the support element.

The screen cylinder 10 further comprises end or carrier rings 16 and 18 at each axial end of the cylinder. In prior art screen cylinders, end rings 16 and 18 sometimes have a circumferential groove into which the ends of screen screen wires 12 are mounted prior to welding. Occasionally, especially in the case of elongated screening cylinders, additional carrier rings are arranged between the ends of the screening cylinder to support the screening cylinder also in the middle of the screen housing.

Figure 2 illustrates a preferred embodiment of the present invention. The drawing illustrates a partial cross-section of the end of the screen cylinder 210 of the present invention. Figure 1 shows that the screening yarns 212 extend all the way to the end of the screen cylinder 15 on the right side of the figure. The figure also shows that very close to the cylinder end, the cylinder has an annular support element 214 attached to the screening threads 212. Any method known in the art may be used for attachment, for example, welding, form-locking, soldering, gluing, deformation. a combination of these. Similarly, the cross-sectional shape of the support element may be any one previously used, as may any new shape. Thus, neither the manner of attaching the support element to the screen yarns nor the shape of the support element has any effect on the present invention. Further, the screen cylinder of Figure 2 comprises a composite end or carrier ring 216 disposed so as to at least partially surround the support element 214. Thus, in addition to the position of the support element shown in Figure 2 ς, the term "support element at least partially surrounded by an end ring" at the ends where the axially outer surface of the tongue element, or part thereof, is flush with the axial end surface, or part thereof, of the end ring, or at a position where the supporting element is flush with the axially inner surface or part thereof.

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Figure 2 further shows a sloping surface 220 of the end or carrier ring 216.

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Even the inclined surface 220 is most often used at the lower end of the screen cylinder in connection with the corresponding inclined / conical surface of the spacer ring o by which the screen cylinder is mounted on the screen. However, the invention is not directed to the actual end-ring assembly-35 ways of the sorter itself, since the end or carrier rings can be formed to include all necessary shapes such as cones, flanges, etc. Thus, the carrier ring may be equally rectangular, i.e. without inclined surface. 220.

Figure 3 shows a screen cylinder 310 according to another preferred embodiment of the present invention. In this embodiment, the composite carrier ring 316 surrounds at least partially two support elements, inner element 314 'and outer element 314 ". Although the cross-sectional shape of the support element may vary 314 ', 314 ", which is described in more detail, for example, in U.S. Patent No. 6,426,003. The support element is a substantially U-10 shaped bar having a massive base portion 3142 having transverse spaces to which the screening yarns 312 are mounted and secured. The spaces can open into the space between the U-bar legs 3144, which in a way allows the portion of the screen yarns 312 extending into said space to hold the yarns in the spaces. If the spaces do not open into the space between the branches but leave a narrow heel, the wires can be welded to the support element through this heel.

Although Figure 3 shows the support elements 314 'and 314 "and the support ring 316 disposed relative to each other such that the substantially radial surface of the axially inner support element 314' is flush with the axially inner surface 20 of the support ring 316 and the axially outer support element 314" the surface being flush with the axially outer surface of the carrier ring 316, the support elements may be disposed so that they are completely within the carrier ring material. In any case, the structure of these U-shaped support elements is highly advantageous in connection with the composite material. When the composite material not only covers the surfaces of the rectangular or other shaped support element, but is able to fill the space between the branches of the U-shaped support element, the metal screen cylinder (

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^ support elements) and the bond between the composite carrier ring is as strong as possible.

° A plurality of radial elements are attached to the screening yarns, which penetrate into the carrier ring material, ensuring axial positioning of the carrier ring, even in mechanical-

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£ 30 ti, not to mention the carrier material attaches directly to the screen yarns.

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Figure 4 illustrates a preferred embodiment of the present invention.

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o a partial cross section of its screen cylinder end region. Figure 4 shows a more internal structure of the composite carrier ring 316. Thus, the support elements 414 shown in the drawing are more or less exemplary, and are intended essentially to show that the presence of at least one support element in direct contact with the composite carrier ring is a feature of the present invention. However, Figure 4 shows two support elements 414 and 414 ', the first (414) extending substantially a short distance from the screening yarns, while the second (414') extends up to or near the outer periphery of the carrier ring. Similarly, the design of the carrier ring is also exemplary and it should be borne in mind that the structure may comprise, for example, a conical portion shown in the drawing of the radial flange. In other words, Figure 4 shows that the carrier ring is not necessarily made of the same material as the screen yarns up to its outer surface.

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The innermost layer 4162 of the carrier ring 416 is intended either to insulate the screen yarns 412 from the composite material, or to connect the composite material to the screen yarns, for example by gluing, preferably with a flexible adhesive. The idea of the foregoing is to form a liquid-tight buffer layer so that the easy-flowing low viscosity 15 resin, possibly used in the outer layer, does not pass through the screen slits between screening yarns 412 and cure uncontrollably to the opposite side of the screening yarns Such a buffer layer may be formed, for example, from a thin sheet of metal disposed on the screening yarns 412 between the support elements 414. Of course, other materials may also be used as long as they serve their purpose and withstand all mechanical, chemical, and thermal stresses associated with the manufacture and use of the screen cylinder. Another alternative which also fulfills the requirements of the latter purpose is to use a suitable high viscosity resin or silicone or other suitable material which is unable to pass through the screen slits but remains on the side of the screen yarns where it is introduced.

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The second layer 4164, in accordance with a preferred embodiment of the present invention, is a layer that provides some flexibility in the connection between the screening yarns and the outer layer (s) of the end ring. The layer may be formed

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£ 30 of material that is somewhat compressible and allows small radial and / or angular movements of the screen yarns. Of course, one option is to choose a material that

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can meet the requirements of both the first and second layers and thus be able to combine the layers. An example of such a material is a suitable rubber or a specially designed elastomer.

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The third layer 4165 is a layer which provides the required stiffness or high elasticity to the carrier ring 416. In other words, the purpose of the layer 4165 is to ensure that the shape of the cylinder 410 is and remains round despite the loads generated in the screen. Numerous fiber-reinforced composites, such as glass fiber, carbon fiber, aramid fiber, or blends thereof, may be mentioned as stiffening layer material to name but a few. Since the stiffening layer also plays a significant role in the entire screen cylinder, numerous manufacturing methods can be contemplated for making the layer. One alternative is to wind the continuous fiber, or rovel, in a substantially circumferential direction between the support elements or between the removable mold halves 10 and add a suitable resin to obtain the desired layer properties. Another alternative is to wind the continuous fiber, or rovin, so that the fiber or rovin, for example, is at an angle of 45 degrees to the circumferential direction, in a sort of zigzag pattern. By doing this, the layer has fibers that are at 90 degrees to each other and at 45 degrees to both the axis and the circumferential direction. The same result can be achieved by using a cross-woven reinforcing strip wrapped in space between the mold halves or support elements. The reinforcing fibers may also be in the form of Textiles having a 2 or 3 dimensional structure. The properties of the reinforcing layer may still be radially variable due to variations in the fiber volume of the reinforcing material (by way of example only).

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The fourth layer 4166 can be called a spacing layer, for example, because its main purpose is to arrange the outer diameter of the carrier ring as desired. Thus, the layer does not necessarily have any other function in which it can be made of an inexpensive material which nevertheless withstands the various stresses involved both in the manufacture and use of the screen cylinder. The stresses can be divided into at least three groups: me-ς, and the chemical and thermal stresses. Mechanical stresses include the rest

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inter alia the strain caused by mounting the screen cylinder between the lower and upper spacer rings inside the screen of the screen. The strain is compressible because often the screen cylinder is positioned on a conical surface corresponding to its base cone with a lower spacer ring and then

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£ 30 bolted to the upper spacer ring through the upper flange to create significant clamping stress. This is done to ensure that the bottom end of the screen cylinder is

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firmly against the cone of the spacer ring. The second mechanical load is created by a rotor rotating within the screen cylinder when the rotor blades or other turbulence elements exert cyclically varying positive and negative pulses of the screen cylinder in the radius 35 direction. Chemical tensions are mainly due to the properties of the pulp being screened. Depending on the location of the screen cylinder in the pulp or paper mill, pulp may contain either cooking or bleaching chemicals or substantially no chemicals at all. If the end ring were to be designed as an all-round tire, it should be able to withstand both acidic and alkaline chemicals (chlorides, sulfuric acid, ozone, pe-5-oxide, lye, etc.) at moderate concentrations, including high temperatures, since the fiber suspension can . As already mentioned, the thermal stresses are mainly due to the fiber suspension being screened.

In the embodiment of Figure 4, the fourth layer has another additional role. It is a ply 10 which is machined to exact diameter before fitting the outermost layer so that the end ring has the desired diameter after fitting the outermost layer. Thus, the material used for the fourth layer should be easy to work with and also such that the outer layer can be easily and reliably attached to it.

The outermost layer 4168 is a special layer, particularly in the case of a bottom ring or a lower end ring or a carrier ring in the middle of a screen cylinder having a conical or similar surface which should be seated against it, for example with a surface of a spacer ring. Numerous requirements can be set for the outer layer. In addition to the conditions already listed, it should be able to dampen vibration from a rotating rotor. In a way, this layer functions in much the same way as the other layer, which is assumed to be shrinkable or flexible. However, the outermost layer is unlikely to be able to allow the angular movements produced by pulses directed against the rotor screen cylinder.

25 The material for the outer layer can be selected from a wide variety of polymeric materials, ς One alternative is a synthetic elastomer designed by blending different

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lymers to provide the desired material with the desired properties. In other words, the elastomer should have the right combination of surface hardness and damping properties above

In addition to the aforementioned requirements of £ 30 for mechanical, chemical and thermal loads.

I '- co T- It should be understood that the carrier ring structure described above in connection with Figure 4 is merely an exemplary structure, the sole purpose of which is to show that the carrier

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a tire can have several layers, each with its own function. However, the tasks may vary depending on the location of the screen where the screen cylinder is mounted.

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Thus, it is clear that the number of layers may change, as well as their mutual position in the carrier ring. In addition to or instead of the radial positioning of the layers, the carrier ring may have layers or regions in the axial direction having the same purpose as the layers of Figure 4. For example, the carrier ring may have surface layers at each of its 5 axial ends such that these layers are chemically resistant and that the inside of the carrier ring may be made of materials with insufficient resistance to chemicals. One such material that could be used inside the carrier ring is a foam filler which is primarily intended to act as a spacer (in the radial direction). Also, in the case of a carrier ring having a wide conical portion 10, it may be desirable to terminate the fiber reinforcement at a distance from the conical surface such that the conical surface is machined to its final dimensions in the resin layer.

Thus, it is clear that the characteristics of the carrier ring can change both radially and axially. It should also be understood that not only the reinforcing layer has no fiber reinforcement, but that one or more other layers may also have one.

It should further be borne in mind that additional layers may be added even though they are not discussed in connection with Figure 4. For example, if there are two adjacent layers of material that do not adhere well to one another, an additional adhesive layer may be provided between the two layers.

As for the support elements inside or in connection with the support ring, one alternative is to arrange an additional support ring radially outside the support element, whereby both the support element and the support ring are inside the support ring. The second option

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is to provide a radial disc-shaped member radially outside the support element having a dual purpose. First, it acts as a support ring by

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£ 30 per tire. In other words, the carrier ring may have a metallic (optional material) surface on one or both of its axial sides. Like this

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The surface (s) is / are particularly advantageous in the case of a carrier ring disposed at the upper end of the screen cylinder, whereby the metal surfaces and the carrier ring between them form a flange through which the screen cylinder is attached to the screen. Another alternative is to provide a disk-shaped member projecting radially outwardly from the central portion (axially) of the carrier ring. The member in the carrier ring could be located on the support element or on the screening yarns. The body divides the carrier ring into two parts, although the body could be provided with holes or openings that allow at least the resin to form a uniform structure. In any case, on the outer circumference of the carrier ring, the disc-like member could form an axially lower surface of the flange, whereby the carrier ring could terminate radially closer to the screen cylinder surface with its axially lower portion than its upper portion. The opposite structure of the naturally described structure is also an alternative.

Until now, the means for connecting the screen cylinder to the screen have not been discussed in more detail. Usually, the fixing or connection is effected by means of a flange at the top of the screen cylinder. A preferred way of making a flange is described above. In other words, the flange may be made of a composite material only, or the flange may be covered by a metal disc on one or both of its radial surfaces. For attaching the screen cylinder 15, the flange of the carrier ring must be provided with a suitable number of holes for the mounting bolts and possibly also holes for pins or the like, by means of which the screen cylinder is mounted exactly centrally to the rotor axis. If the flange is provided with at least a metal end surface, the mounting bolts do not require any additional washer between the bolt head and the flange, but if the flange is of a composite-only structure, it is preferable to provide wide washers or even a circular disk covering

In addition to the embodiments described above, there are a few optional structural details that may be briefly described.

First, in the above description, it is taught that the screening yarns extend from the end surface of the screen mat cylinders throughout the mat to its opposite end surface. However, it is possible that the screening yarns terminate at a certain distance from either or both-

Is also the end whereby the screen surface or surfaces and the bearing or end rings are also

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£ 30 completely coated with either composite resin or circular metal plate or circular plate of other suitable material. Similarly,

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The T-yarns may extend axially past the end or carrier rings if one is needed for some reason.

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Second, the above description of the invention has not yet spoken about the time at which carrier rings are made. It is normal practice to make carrier rings at the manufacturer of the screen cylinders. However, it is also possible to arrange the manufacture of the carrier rings or parts thereof to take place at the premises of the user of the screen drum, i.e. at the pulp mill. One of the 5 options is to pre-fabricate the carrier ring during the manufacture of the screen cylinder but leave the final step (s) to be performed only at the installation site. For example, a carrier ring can be made to have all layers, parts, and components except that it is secured or bonded to the ring. Thus, it is possible to fabricate or cast the last or two last 10 layers of the carrier ring at the mass mill so that they fit exactly into the mating surfaces of the spacer ring.

Third, in the above embodiments, there are talked about substantially separate layers having a different function and a different structure. However, it is possible to combine two or more layers, for example by gradually changing the composition of the reinforcing material and / or resin, or by changing the relative proportions of the materials of the layers. Also by changing the treatment time or treatment temperature gradually or by heating the composite material unevenly, for example, only one side, the properties of the layer (s) can be influenced as desired.

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It should be understood, however, that the above is merely an exemplary description of a new and inventive method of fabricating a screen cylinder. The foregoing is not to be construed as limiting the invention in any form, but the entire scope of the invention is defined only by the appended claims.

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Claims (36)

A method of making a screen cylinder, said method comprising the steps of: a) manufacturing annular support elements, b) attaching a plurality of screen yarns (312) to the support elements such that a screen gap is formed between adjacent screen yarns (312), optionally forming, a screening cylinder, c) for providing a screening cylinder with support rings (416) for supporting the cylinder (420) inside the screen of the screen, d) fabricating at least one support ring (416) from composite material into multiple layers, and e) at least one said annular support element (414 ', 414 "). ), at least in part, into said composite carrier ring (416). 15 A method according to claim 1, characterized in that the composite carrier ring (416) is formed of functionally different layers. Method according to any one of the preceding claims, characterized in that the support ring (416) is provided with at least two of the following layers: sealing layer (4162), elastic layer (4164), stiffening layer (4165), securing layer, distance layer (4166) and damping layer. (4168). Method according to claim 3, characterized in that said sealing layer (4162) is arranged radially on the outer surface of the screening yarns (312). δ CVJ Method according to Claim 3 or 4, characterized in that the sealing layer (4162) is formed from a fluid-retaining material or a high viscosity resin. I 30th A method according to claim 3, characterized in that said elastic layer (4164) is formed of a material that allows slight radial and / or angular movement of the screening yarns (312). Door Method according to claim 3 or 6, characterized in that an elastomeric material or rubber is used in said elastic layer (4164). A method according to claims 3 to 7, characterized in that said sealing (4162) and elastic layer (4164) are compounded. A method according to claim 3, characterized in that said stiffening layer (4165) is provided outside the sealing layer (4162) to provide sufficient strength to the carrier ring. 10 Method according to claim 3 or 9, characterized in that the stiffening layer (4165) is formed of a fiber reinforced polymeric material. A method according to claim 10, characterized in that the reinforcing fiber is selected from one or more of glass fiber, carbon fiber and aramid fiber. Method according to Claim 9 or 10, characterized in that the fiber reinforcement is made mainly in the circumferential direction. Method according to claim 9 or 10, characterized in that the fiber reinforcement is made mainly in a non-circumferential direction. A method according to claim 13, characterized in that the cross-woven strip is used as a fiber reinforcement. 25 A method according to claim 3, characterized in that said (M ^ distance layer) is used to give a radial dimension to the carrier ring (416). A method according to claim 3 or 15, characterized in that the distal layer (4166) of X £ 30 is made of foam or other suitable material. i ^. C/O A method according to claim 3, characterized in that the damping layer (4168) is arranged radially to the outermost layer of the carrier ring (416). 35 The method according to claim 3 or 17, characterized in that the damping layer (4168) is made of an elastomeric or rubber material. Method according to claim 3, characterized in that the layer inside the damping layer (4168) is machined to meet the requirements of the roundness and dimensions of the carrier ring (416), taking into account the requirements of the damping layer (4168). A method according to claim 3, characterized in that the adhesive layer 10 is used to secure the adhesion of one layer to another. A method according to any one of the preceding claims, characterized in that in step d) the composite carrier ring (416) is made between two halves of the mold. 15 A method according to any one of the preceding claims, characterized in that in step d) the second support element (414 ', 414') is at least partially embedded in the carrier ring (416). A method according to any one of the claims, characterized in that in step d) at least one support ring located radially over the support element (414 ', 414') is at least partially embedded within said composite carrier ring (416). A method according to claim 21 or 22 or 23, characterized in that at least one of said mold halves is formed at least partially from said ς support element (414 ', 414 ") or support ring. (M i 00 A method according to at least one of claims 21 to 24, characterized in that at least one of said mold halves remains permanently attached to said composite X £ 30 embroidery ring (416). h- · CD LO i- A method according to claims 21 to 25, characterized in that at least one of said mold halves forms the surface of a flange of the upper carrier ring (416), from which the carrier ring (416) is bolted to the screen. 35 Method according to any one of the preceding claims, characterized in that the screening yarns (312) extend all the way to the end of the screening cylinder, i.e. through the entire height of the composite ring (416). Method according to any one of the preceding claims, characterized in that two or more layers are combined by gradually changing at least one of the properties of the layer materials, the composition of the at least one layer material, the relative proportion of the layer materials, treatment temperature and treatment time. 10 A screening cylinder formed from at least a plurality of screening yarns (212, 312, 412) having a screen gap and a substantially annular support member (214, 314, 414) to which said screening yarns (212, 312, 412) are attached and a carrier ring attached to said screen yarns (212, 312, 412), characterized in that said carrier ring (216,316, 416) is formed of two or more composite materials and that at least a portion of the support element (214, 314 ', 314 ", 414) remains inside said composite carrier. (216, 316, 416). A screen cylinder according to claim 29, characterized in that the composite embroidery ring (216, 316, 416) is provided at least partially with a metal surface. A screen cylinder according to any one of claims 29 to 30, characterized in that said support ring (216, 316, 416) includes at least in part a second support element. 25 ς Screen sieve cylinder according to any one of claims 29 to 31, characterized in that said support ring (216, 316, 416) includes at least a portion of a support ring disposed radially on the support element (214, 314 ', 314 "), 414) on top. £ 30 A screen cylinder according to any one of claims 29 to 32, characterized in that said support element (214, 314 ', 314 ", 414) and / or said support ring forms at least part of the outer surface of the carrier ring (216, 316, 416). . A screen cylinder according to any one of claims 29 to 33, characterized in that said carrier ring (216, 316, 416) is provided with means for attaching it to the screen of the screen. A screen cylinder according to claim 34, characterized in that said connecting means are holes for fastening bolts. A screen cylinder according to claim 34, characterized in that said attachment device is a surface layer of said carrier ring (216, 316, 416). 10 δ CVJ 00 o l '' - X cc CL N- CD LO O O Cv!