RU2782810C2 - Lamella for clarifier and lamella module for clarifier - Google Patents

Abstract

FIELD: purification.

SUBSTANCE: invention relates to the field of purification of waste flows of liquids contaminated with impurities in the form of weighted solid particles; it is used, for example, for purification of wastewater or drinking water by separation of weighted solid particles. In the claim, a lamella intended for use in a lamella clarifier, as well as a lamella module intended for use in a lamella clarifier are described. Lamella (1) for the clarifier is formed by rectangular or square plate (5), upper edge (10a) and lower edge (10b) of which pass in parallel to transverse direction (T), and the rest two edges (15a, 15b) pass in parallel to longitudinal direction (L). The plate is equipped with longitudinal folds (20) bent in longitudinal direction (L) and passing from upper edge (10a) to lower edge (10b) of the plate. Plate (5) is bent in longitudinal direction (L) in such a way that a zone closer to lower edge (10b) of the plate is less tilted relatively to horizontal (H), compared to a zone closer to upper edge (10a). The lamella module contains two or more lamellas installed in parallel without a direct contact with each other and attached to support elements.

EFFECT: increase in the performance of purification of liquids, improvement of indicators relatively to contamination of lamellas, which stay pure during a longer time, providing increase in intervals between maintenance operations, provision of a possibility of increase in a speed of circulation of a liquid flow and, respectively, increase in the total flow rate of the liquid flow at an input of a clarifier.

19 cl, 11 dwg

Description

Technical field

The present invention relates to the field of devices and installations for cleaning waste streams of liquids contaminated with impurities in the form of suspended solids. Devices of this type, containing at least one lamella and/or lamella module, are commonly used (by way of example, without limitation) for the treatment of waste water or drinking water by separating suspended solids.

More specifically, the subject of the present invention is a lamella for use in a lamella clarifier, as well as a lamella module for use in a lamella clarifier.

State of the art

A clarifier is a device that is commonly used in processes for treating liquid effluent streams (i.e., liquids circulating in industrial plants) to remove suspended solids present in these liquids, and especially the treatment of wastewater and water intended for consumption.

Such a clarifier comprises a reservoir or vessel through which a stream of liquid containing contaminants in the form of suspended solids is passed and is capable of at least partially separating these suspended solids from the incoming liquid stream.

The effluent stream of liquid to be treated enters the clarifier at low velocity through inlets, which are usually located at the bottom of the sides of the tank. Since suspended solids have a specific gravity or density greater than the specific gravity or density of the liquid containing them, these particles usually sink to the bottom zone or to the bottom of the tank, where they gradually accumulate. This process of accumulation of solids in the bottom of the tank, referred to as "clarification", allows the subsequent discharge of accumulated solids. The solids-free fluid stream can now be removed from the clarifier tank through the collection channels or weirs at the top of the tank.

The rate of liquid flow in the downward or sideways direction should be such that the rate of separation of suspended solids allows them to reach the bottom of the tank before the liquid is withdrawn from the tank. Otherwise, the solid particles will come out with the liquid flow, i.e. the clarifier will not perform its function.

Some clarifiers are provided with lamellas and/or lamella modules to improve the performance of the clarifier. The introduction of lamellas and/or lamella modules into the clarifier makes it possible to increase the flow rate of the incoming liquid to be cleaned or to increase the efficiency of removing solid particles.

Lamellas are plates or shaped profiles, usually having an elongated shape. Namely, the lamellas typically have a large dimension in the major direction, referred to as the "longitudinal" direction, and a smaller, second dimension in the "transverse" direction along which the top edge of the plate and the bottom edge of the plate extend. Further, the lamellas arranged in parallel form a series of channels between the lamellas which are located inside the tank at an intermediate height and overlap the cross section of the tank, the lamellas being usually inclined at an angle ranging from 45° to 65° relative to the horizontal.

In this way, the lamellas cause the liquid to pass through the above channels in the direction determined by their inclination, so that an assembly of mini clarifiers is formed, which accelerates the clarification process. The outgoing liquid flow enters the lamellar clarifier through the inlet openings located in the lower zone of the sides of the tank, and it is distributed uniformly over the entire area of the tank under the lamellas. Since the purified liquid is taken from the upper part of the tank above the lamellae, the liquid flow must pass through the inclined channels formed by the lamellae. Due to the inclination of these channels, the solid particles are subjected to two different forces: the force created by the flow on its way up and in the direction of the channels formed by the lamellas, and the force of gravity directed downwards vertically. The addition of these two forces causes the solids to move so that they move closer to the bottom of the channel where they accumulate and form larger flocs. Due to this agglomeration of the solids into flakes, they overcome the frictional force generated by the rising flow much more easily, so that the rate of natural clarification is increased and a downward flow is created along the bottom surface of the channels formed by the lamellae. Thus, inside each channel formed by the lamellas, two continuous flows are formed in opposite directions: one is the flow of liquid directed upwards, and the other is formed by solid particles, which are combined into flakes on the lower surface, and directed downwards. When the solid particles exit the channel formed by the lamellas through its lower part, an increased cohesive force already occurs between them, and with a high degree of probability, the flakes are kept intact on their way down to the bottom of the tank, where they will be discharged. Finally, water or liquid waste, freed from solids, leaves the channels formed by the lamellas through their upper parts and continues its upward movement until it is discharged through collector channels or weirs located at the top of the tank and removing liquid from the tank. , to continue the cleaning process in the next steps.

The efficiency of the lamellar clarifier is usually evaluated by the following indicators: performance of the clarifier, that is, the amount of liquid that the lamellar clarifier is able to clean per unit time; removal efficiency of solid particles present in the treated liquid; and maintenance requirements for the lamella clarifier to ensure it operates at its proper performance and efficiency specifications. These maintenance requirements mainly depend on the processes of contamination, which occurs as a result of the gradual accumulation of solid particles adhering to the entire surface of the lamellas or lamella modules, as well as to the supporting structures supporting the lamellas or lamella modules.

As will be described in detail below, there is a need in the field of clarifying devices to provide: the highest possible productivity per unit area of the clarifier; the maximum possible reduction in the amount of suspended solids in the treated liquid; and at the same time minimum maintenance requirements, since maintenance involves taking the clarifier out of service and incurs costs associated with the associated cleaning tasks of the equipment.

These three main parameters depend, on the one hand, on the existing clarifier tank and, on the other hand, largely on the type of lamellas or lamella modules installed and their support structures.

The support structures of the lamella modules (or frames) are usually located outside the lamella modules themselves and inside the clarifier tank at a medium height, above the bottom of the tank, so that during the clarification process, the support structures and lamella modules will be completely immersed in the liquid. Some lamella modules, especially modules made from plastic materials having densities close to that of water, are also commonly provided with a structure that prevents them from floating, either as a result of the hydraulic pressure to which they are subjected, or because of their low density. This anti-float structure is usually located at the top of the lamella modules.

As regards the tank, the capacity and efficiency of the clarifier will depend on the dimensions of the tank, both surface area and total volume, as well as its geometry and design, which will provide a suitable distribution of liquid flow over its entire surface, suitable recovery of solids particles accumulated at the base of the tank, or a balanced discharge of the treated liquid through outlet weirs or channels. Tank features have little to no effect on maintenance if the solids or sludge discharge system is properly designed and sized.

With regard to installed lamellas or lamella modules, the performance, efficiency and maintenance of the installation will depend, among other things, on numerous and heterogeneous factors, such as: the geometric shape of the lamellas and lamella modules; their sizes; distance between lamellas; cross-sectional area of lamella channels; the angle of inclination of the lamellas; hydraulic characteristics; surface treatment of materials from which the lamellas are made; modules assembly systems; frames and support structures inside or outside the tank; loss of the working surface caused by frames and support structures that can block the channels of the lamellas; etc.

There are three main types of lamellas that are attached to each other to form lamella modules:

I. Flat slats. These well-known lamellas consist of flat sheets assembled on support structures that are pre-installed inside the tank. They are usually assembled to form independent modules using external frames made with side sheets or profiles, which are then mounted on support structures inside the tank. These flat slats form slat channels having a rectangular cross-section, the channel length being the slat width and the channel width being the distance between the installed slats or sheets. The lamella channels of this type are distinguished by good hydraulic characteristics, which are determined by the geometry of a continuous channel having a rectangular cross section, without intermediate partitions along the entire width, except for the side frames, resulting in relatively low hydraulic losses of the order of 2-3%. However, they are unsatisfactory in operation mainly due to their low ability to concentrate solids (also referred to as "sludge"). Since the lamellas have a flat surface, solid particles reaching the lower surface of the lamella channel are gradually deposited over its entire surface more or less evenly, and especially in the upper zone of the modules, so that a constantly growing layer is formed. When this happens due to the accumulation of these solid particles, they break off and may begin to sink, this process being of an intermittent nature, as a result of which the upward flow of liquid changes, so that part of the flakes of solid particles is destroyed and captured by the flow without any possibility of reaching again. the lower surface of the lamella channel, leaving the lamella modules together with the flow in the direction of the collector channels, as a result of which the efficiency of the clarifier is significantly reduced. Part of the solid particles that can exit the lamellas through their lower part exits along the entire lower edge of the lamella, forming a "veil" in which the cohesive forces between the particles are very weak, so that a weakly concentrated low density sludge is formed, resulting in flakes easily broken by the upward flow directed into the lamella modules. Some of these solids will again be taken up by the updraft directed to the lamella modules. All this significantly reduces the efficiency of the clarification process.

Lamellar modules made of flat lamellas are characterized by a large loss of working surface caused by the necessary support structures and collector channels, usually located between two lines of modules, as a result of which the surface available for the passage of liquid flow through the lamellas is limited. These losses can exceed 20% of the available surface of the tank, and to compensate for these losses, the length of the lamellae is increased, resulting in an increase in the height of the modules. In addition, due to the flat shape and considerable length of the lamellas, they must be made of high strength materials so that they are able to maintain their shape in the face of accumulation of large amounts of sludge due to pollution, that is, the flat shape of the lamellas entails a very large weight. designs. This, together with the need to prevent corrosion, practically forces the use of stainless steel, resulting in very expensive installations, the cost of which is 5-7 times higher than the cost of installations using plastic materials.

II. Tubular slats. These lamellas are formed by sequential assembly of profiles, most often extruded from a plastic material. As a result of the serial connection of these profiles with each other, closed channels (or passages) of the lamellas are formed, which run in parallel and are attached to each other until the calculated dimensions of the installed lamella module are obtained. Typically, these channels are hexagonal (honeycomb), rectangular, triangular, or square in cross-section, all having common internal baffles forming channels with small cross-sectional areas. This type of tubular lamella module has very high losses due to the hydraulic characteristics of the fluid flow inside the lamella channels and especially due to the high velocity gradient inside these channels, as is the case in any passage, and especially in the case of laminar flow. Along the entire perimeter of the channel, the lamellae of the zone with very low or zero velocity occupy a significant part of the cross section of the passage. In practice, these zones can be considered non-working, and the main part of the flow passes through the central zone of the lamella channel at a higher speed, so that most of the solid particles do not have enough time to reach the lower surface of the lamella channel, they are carried out together with the liquid being cleaned. Hydraulic losses in these cases range from 12% to 18%. Another disadvantage, also associated with intermediate baffles, is that a large part of the surface area of the material is in contact with the liquid and, accordingly, with the solids contained therein. This leads to a very rapid and also more pronounced deposition of dirt in the upper part of the lamella channels or lamella modules, with the contamination occurring faster the smaller the cross-sectional area of these closed lamella passages, resulting in more frequent maintenance. Maintenance operations require shutting down the plant, emptying the tank, and operators performing the associated cleaning operations, resulting in increased operating costs.

In addition, in modules made of tubular lamellas, the fastening systems between the profiles forming the modules usually contain longitudinal guides, welds, fixing clips, etc., forming zones in which sludge can easily adhere, as a result of which, again, the fouling process is accelerated. . The support structures required for this type of modules to be installed inside the tank must be sufficiently reinforced to withstand the expected high load of sludge accumulating on the modules, which entails high losses in the working surface associated with the dimensions of the required profiles. The modules are supported by these profiles in their peripheral areas, as a result of which many passages are partially or completely closed in their lower part. Losses of the working surface due to the closure of channels by supporting structures can range from 7% to 12%. In addition, the necessary increase in the size of these supporting structures entails a significant increase in their cost. Since modules of this type are made of plastic materials with densities similar to those of water, it is often necessary to use anti-float structures that close part of the passages of the modules, this time in their upper part, which also leads to the formation of zones in which solid particles are deposited, as a result, pollution processes are also accelerated. Finally, to form modules of this type, it is necessary to assemble from 80 to 140 profiles per cubic meter of the module, depending on the cross-sectional area of the formed channel, and these profiles must be fastened, welded or glued, which requires a lot of labor and manual labor, so that the manufacturing cost is very high.

III. Tubular lamellae formed by applying and gluing or clipping thermoformed plastic sheets. Since these sheets overlap each other, they form, as in the previous case, lamella channels having a certain geometric shape, most often a hexagonal shape is used. In this case, they differ from the above-described lamellas in the manner of manufacture and assembly, and their geometries are very similar, so that these lamellas have the same problems of loss of working surface and accelerated contamination. In addition, due to the small thickness of the thermoformed sheets used, most of the lamellar modules of this type require an external frame that provides the necessary mechanical strength, resulting in additional losses of the working surface that provides clarification, since part of the lamellar passages is covered by the frame, and gaps occur. introduced by the frames when they are installed in the tank. These frames form additional surfaces on which sludge can settle, resulting in premature fouling. These outer frames usually have to be made of stainless steel to prevent corrosion, which adds to the cost of the lamella module.

At present, all lamellas or lamella modules molded from plastic materials are only made using extrusion and thermoforming processes. These processes in no way make it possible to obtain lamellas or profiles forming modules with different thicknesses in each zone in accordance with the requirements for mechanical strength or for the stresses they must withstand, and this limits the configurations, geometries and assembly methods to those that used in known technical solutions. So far, no lamellas, sheets or profiles are known for forming lamella modules that can be produced using the injection molding technology of plastic products.

In addition, all of the prior art types of lamellas described above are straight in their longitudinal direction, that is, their inclination is constant along said direction. This means that the performance of the prior art lamellas is the same throughout the longitudinal direction, despite the fact that, as will be discussed in detail below in the present description, solids and solids streams, initially suspended in a liquid stream, behave differently. differently depending on their position in this longitudinal direction.

Premature contamination in the upper areas of straight lamellas is a typical pattern for all prior art technologies described. This is due to the fact that the solids that reach these upper zones have the smallest weight, i.e., the possibility of their separation from the flow is minimal, and therefore they are more likely to stick to the surface of the lamellas, so that there is a stable continuous accumulation. particles.

Disclosure of invention

The aim of the present invention is to eliminate or reduce the above problems and shortcomings of the known technical solutions.

To achieve this object, the first object of the present invention relates to a clarifier lamella formed by a rectangular or square plate, the top edge and bottom of which run parallel to the transverse direction, and the other two edges of the plate run parallel to the longitudinal direction, the lamella being characterized in that:

- the plate is bent in its longitudinal direction in such a way that, in its operating position, the area closer to the lower edge of the plate is less inclined relative to the horizontal than the area closer to the upper edge of the plate, and that

- the plate is provided with longitudinal folds that extend from the upper edge of the plate to the lower edge of the plate, and the longitudinal folds have a curvature in the longitudinal direction.

The lamellas of the present invention are designed to be installed, as described below, in their working position inside the clarifier tank as follows: the bottom edge of the lamella plates is oriented towards the bottom of the tank, while the top edge should be directed towards the top of the tank.

The fact that in the lamellas of the present invention the plates forming these lamellas are curved in their longitudinal direction, so that after they are placed in their working position, their lower part is less inclined relative to the horizontal compared to the upper part, improves processes that prevent the accumulation of solid particles in the upper zone of the lamellas by helping the solids to start sinking, whereby the fouling processes are slowed down and the lamellas remain clean under suitable working conditions for a longer time, so that the intervals between maintenance operations are increased and, accordingly, the costs of these operations are reduced.

When the lamellas are in their operating position, larger solids with their higher release capacity are deposited at the bottom of each lamella, as well as the solids flow resulting from the accumulation of all solids along the entire length of the lamella.

At the bottom of the lamellas there is a trapping effect created by these larger solids, which helps to release all the solids into this zone, thereby preventing continuous accumulation and gradual blockage of the lamella passage. For this reason, the angle of inclination of the lamellas according to the present invention relative to the horizontal in their lower part is smaller. This smaller angle of inclination reduces the vertical separation distance of suspended particles as they pass to the bottom surface of the lamella channel, resulting in a higher particle separation efficiency in this zone.

On the contrary, in the upper part of the lamella (i.e., in the area closer to its upper edge), fewer solid particles are received, which have the smallest weight, since these are the particles that take longer to reach the lower surface of the lamella channel. These solids are less well separated from the flow and are more likely to remain stuck to the channel surface, so that they can steadily and gradually accumulate on it, occupying an increasing part of the cross-sectional area of the lamella channel. This loss of cross-sectional area that is available for the fluid to flow causes its velocity to increase through these upper zones of the lamella module, until some of these solids are captured and discharged through the upper outlets of the lamella channels, so that they are discharged along with treated fluid flow through collection channels or weirs.

This entrainment and removal of solids with the processed stream is one of the factors that significantly reduces the efficiency of the operation of prior art installations. Indeed, according to some estimates, this effect entails a decrease in productivity by 3-15%.

To eliminate this disadvantage of the known technical solutions, the lamellas according to the present invention have, as already indicated, a greater inclination relative to the horizontal in their upper part. This special configuration causes these solid particles present in the upper region of the lamella, which are less readily separated from the flow, to begin to sink, so that their gradual accumulation slows down. Tests have been carried out by the Applicant which have shown that in some preferred embodiments of the lamellas of the present invention, the reduction in productivity due to loss of cross-sectional area and entrainment of solid particles was only 1-5%.

Similarly, once the lamellas of the present invention are in position within the clarifier tank, their longitudinal folds tend to concentrate solids in the lower zones or troughs of these folds. Under conditions of higher concentration, the cohesiveness of the solid particles is improved and their ability to form a descending flow is increased, so that the solid particles will exit the lamellas through their bottoms towards the bottom of the tank. This increased cohesiveness and increased concentration will ensure that, after being subjected to upward and sideways flow, they do not collapse, so that they reach the bottom of the tank more easily. This increased ability of solids to sink to the bottom of the tank reduces the performance loss associated with particle capture and evacuation compared to prior art lamellas.

The improved fouling performance of the lamellas of the present invention will allow the spacing between the surfaces of the lamellas to be reduced when placed in position in the lamella module within the clarifier tank, resulting in increased incoming fluid cleaning capacity per unit area.

The smaller the distance between the surfaces of the lamellas, the less time it takes for suspended solids to reach the bottom of the lamella channel, and this, in turn, allows an increase in the circulation rate of the liquid flow and, accordingly, an increase in the total liquid flow rate at the inlet of the clarifier.

The lamella must also have adequate mechanical strength characteristics to enable it to withstand the stresses that occur under certain conditions, especially when emptying the tank, when the whole structure must support its own weight plus the weight of accumulated sludge.

The fact that the lamella plate of the present invention is bent in its longitudinal direction provides a moment of inertia in the transverse direction, thereby increasing the resistance to bending of the lamella in the longitudinal direction.

In one of the preferred embodiments of the invention, the lamella contains at least one longitudinal fold, delimited by two sidewalls forming an obtuse angle between them, preferably in the range from 150° to 160°. This special configuration of the pleats in the lamellas of the present invention facilitates the concentration of suspended solids in the troughs of these pleats (forming part of the lamella channels) and accelerates the downward flow of solids within the clarifier tank.

In another preferred embodiment, the lamella also contains at least one longitudinal reinforcing rib, bent in the longitudinal direction and delimited by two sidewalls extending from the upper edge of the plate to the lower edge of the plate and forming a variable angle between them, the value of which is:

- is in the range from 80° to 90° in the region of the upper edge,

- is in the range from 80° to 90° in the region of the lower edge, and

- gradually increases to a value in the range from 115° to 120° in the central zone of the lamella.

The reinforcing ribs referred to in the previous paragraph give the lamellas in this particular embodiment of the invention additional mechanical strength to withstand the various stresses that the lamella may be subjected to when placed in position within the clarifier tank.

Thus, the angle in the range of 115-120°, formed by the sidewalls of the reinforcing rib in the central zone of the lamella, gives it sufficient mechanical strength, both in relation to transverse bending stresses, and in relation to compressive stresses acting in this zone. On the other hand, at the largest obtuse angle (between 80° and 90°) formed by the sidewalls of the reinforcing rib at the ends of the lamella (that is, in the region of its upper edge and lower edge), the mechanical strength is maximized with respect to the bending stresses acting in these zones which, in preferred embodiments, the lamellas of the present invention will act as attachment points.

In the lamellas of the present invention, at least one longitudinal reinforcing rib is preferably provided with attachment points for attaching to the supporting elements, the attachment points being located in the region of the upper edge of the plate and in the region of the lower edge of the plate.

Preferably, in this particular embodiment of the invention, the area closer to the top edge, the area closer to the bottom edge, and the central area of the reinforcing rib (or reinforcing ribs in other embodiments) are thicker than the rest of the reinforcing rib, and indicated by at least one reinforcing rib also has a thickness exceeding the thickness of the rest of the lamella.

Thus, those parts of the reinforcing rib that are subjected to increased stresses will be reinforced.

In this case, the region located in the region of the upper edge, the region located in the region of the lower edge, and the central region of the reinforcing rib (or reinforcing ribs in other embodiments) have an increased thickness in the range of 3 mm to 3.5 mm, and the thickness of the remaining parts is in the range from 2.5 mm to 3 mm.

The lamellas of the present invention are preferably manufactured by injection molding plastic products. Polypropylene, acrylonitrile butadiene styrene (ABS copolymer), polystyrene and recycled plastics are non-limiting examples of preferred plastics used to make the lamellas of the present invention.

In this sense, it is important to point out that none of the methods currently used in the art for the manufacture of plastic lamellas, namely extrusion and thermoforming of plastic products, does not allow the manufacture of lamellas with two or more zones having different thicknesses, as envisaged. in the various embodiments of the invention described above. This circumstance, as follows from the prior art, represents an obvious obstacle to the development of lamellas with the technical features provided in the above-described embodiments of the invention.

More specifically, extrusion is not a method that can be used to form a lamella with the technical features provided in the above-described embodiments of the invention, since the cross-section of the lamella of the present invention continuously changes along its entire length, and this method does not allow the manufacture of an article with a varying thick. Therefore, this method cannot ensure the production of longitudinal ribs, the thickness of which exceeds the thickness of the remaining parts of the lamella. Extrusion also does not provide the possibility of obtaining the curvature of the plate of the lamella in the longitudinal direction, one of the features of the lamella according to the present invention.

Thermoforming is not a method that will form a lamella with the technical features provided in the above described embodiments of the invention, since this method does not allow to obtain a product with a thickness that varies in accordance with the requirements of these features. Therefore, this method cannot ensure the production of longitudinal ribs, the thickness of which exceeds the thickness of the remaining parts of the lamella. Indeed, when attempting to manufacture lamellas with the technical features provided in the embodiments described above, the ribs will have a thinner thickness as they will be stretched more during the manufacturing process compared to the area between the ribs and the side zones to allow adjustment to a higher height. sides of the rib. In this case, reinforcing folds with greater strength compared to the rest of the lamella and weight reduction in the lateral areas of the lamella will not be provided. In fact, the result that can be obtained using the thermoforming process will be exactly the opposite of what is desired to obtain: reduced strength of the reinforcing ribs and increased weight of the zones located on both sides of the ribs.

The plastics used to make the lamellas in the above embodiments can optionally be provided with UV protection additives and/or reinforcing materials, such as for example glass fibers, to increase the rigidity of the lamellas.

In another additional preferred embodiment of the invention, the lamella comprises at least a first longitudinal reinforcing rib located at a distance of 1/3 of the total width of the lamella in the transverse direction, and at least one second longitudinal reinforcing rib located at a distance of 2/3 of the total width, and the first reinforcing rib and the second reinforcing rib are provided with attachment points for attaching to support elements located in the region of the upper edge of the plate and in the region of the lower edge of the plate.

In this particular embodiment of the invention referred to in the previous paragraph, the lamella is preferably divided transversely into three zones:

- a central zone located between the first reinforcing rib and the second reinforcing rib and supported by these reinforcing ribs;

- the first side zone located between the first reinforcing rib and the nearest side edge; and

- the second side zone located between the second reinforcing rib and the nearest side edge;

also characterized in that the first side zone and the second side zone hang freely (cantilevered) when the slat is installed in its working position inside the clarifier tank.

The first side region and the second side region are free-hanging, i.e., they extend beyond the attachment points supporting them (i.e., behind the attachment points of the first reinforcing rib in the case of the first side area and beyond the attachment points of the second reinforcing rib in the case of the second side area). These free hanging zones can potentially represent weaknesses in the lamella with respect to loads that cause buckling, such as the actual weight of the lamella and the weight of solids (or sludge) that may adhere to it, for example. However, and as shown above, the lamella of the present invention is provided with a longitudinal curvature, so that an additional moment of inertia in the transverse direction is provided, which would not be present without this curvature, and which significantly improves the resistance of the lamella to bending in the longitudinal direction.

Free hanging zones will create bending stresses in the longitudinal direction acting on the reinforcing rib and created by their own weight and the weight of the sludge that may accumulate on their surface. Therefore, these free-hanging zones preferably have a thickness that is less than the thickness of the rest of the lamella, in order to reduce as much as possible the load caused by their own weight.

The dimensions and construction envisaged in the embodiment described in the previous paragraphs above will ensure that the geometric shape of the lamellas is maintained in the event of stresses caused by their own weight and additional light loads. In this case, it will be possible, for example, for them to stay for an indefinite time in an empty tank without any deformation. On the contrary, if a significant amount of sludge has accumulated on their surface, then in the event that the tank emptying procedure is started, the lamellas will experience loads caused by the weight of the sludge and will deform in these side hanging zones, so that their deviation from the vertical will increase, as a result of which it is easier discharge of accumulated solids. After they are released from the load, they will immediately return, as a result of the elasticity of the plastic, to their original shape without any residual deformation.

In another embodiment of the invention, the plate is curved in its longitudinal direction with a first constant radius of curvature. In this embodiment, the value of the first constant radius of curvature is preferably 7-12 meters and more preferably 9-10 meters.

In the second, more preferable case (the radius of curvature is 9-10 meters), when the slats are installed in their working position, the tangent to the lower edge of the slats forms an angle of about 55 ° relative to the horizontal, and the tangent to the upper edge of the slats forms an angle of about 65 ° relative to the horizontal . If the bottom edge and the top edge of the lamella form these particular angles with respect to the horizontal, then the release of solid particles in the bottom of the lamella will be maximized, while the accumulation of solid particles in its upper part is minimized.

In another additional embodiment of the invention, the lamella comprises at least one reinforcing rib that is bent in its longitudinal direction with a second constant radius of curvature, the lamella plate is bent in its longitudinal direction with a first constant radius, and the second constant radius of curvature is less than the first constant radius of curvature.

Preferably, the value of the first constant radius of curvature (plate) is in the range of 9-10 meters, and the value of the second constant radius of curvature (reinforcing rib or reinforcing ribs in other embodiments) is in the range of 7-8.5 meters. This special configuration improves the resistance to bending of the rib or reinforcing ribs in the longitudinal direction, caused, as already described, by the free-hanging side zones.

In another additional embodiment of the invention, the lamella plate is polished, which helps to slow down the processes of pollution.

The second object of the present invention relates to a lamella module for a clarifier, comprising two or more lamellas, which are the first object of the invention, installed in parallel without direct contact with each other and attached to the supporting elements.

Therefore, in the lamella modules of the present invention, intermediate baffles are eliminated, which are necessary for known structures containing tubular lamellas to form tubular closed channels (passages) of the lamellas. Accordingly, the lamella modules of the present invention show improved hydraulic performance compared to the aforementioned structures containing tubular lamellas, since the intermediate baffles used create zones in which the fluid flow rate is zero or very low, so that the corresponding hydraulic losses increase.

In a preferred embodiment of the invention, the lamellar module is characterized in that:

- each lamella is provided with at least one longitudinal reinforcing rib, provided with attachment points in the form of through holes, which are located in the region of the upper edge of the lamella plate and in the region of the lower edge of the lamella plate, and that

- support elements include at least two groups of threaded rods, wherein the first group of threaded rods is installed in such a way that they pass through the through holes made in the area of the upper edge of the lamella plates, and the second group of threaded rods is installed in such a way that they pass through the through holes made in the area of the lower edge of the lamella plates.

In this preferred embodiment of the lamella module of the present invention described in the previous paragraph, the lamellas have no other points of contact with each other than threaded rods, so that the lamella channels are completely free of partitions, corners, fixing means, welds or fasteners, i.e., reduced the number of points where solid particles can easily be trapped. The improved fouling characteristics of the lamellas will allow for a reduction in the distance between the lamella surfaces in the lamella modules of the present invention, resulting in an improvement in plant productivity per unit area.

Therefore, the hydraulic characteristics of the fluid flow passing through the channels of the lamellas of this lamella module according to the present invention will be optimal, and therefore the flow velocity inside the lamella module will be as low as possible for a certain flow rate of the liquid to be treated, so that hydraulic losses are reduced to a minimum due to the velocity gradient, that is, the gradient , created by the upper and lower surfaces of two adjacent lamellas, which determine the corresponding clarification distance.

In the known technical solutions, the additional performance losses of the installation due to the hydraulic characteristics of the flat lamellas are in the range of 2-3% due to the partitions forming the outer frames of each module. The additional capacity losses of the plant due to the hydraulic performance of prior art tubular lamellas are in the range of 12-18% due to the baffles forming each passage.

In the preferred embodiment of the lamellar module of the present invention, the supporting elements, in addition to the two groups of threaded rods described above, also include:

- spacers installed in the region of the upper edge and in the region of the lower edge of the plates of each pair of adjacent lamellae, each of these spacers has a through hole to allow at least one of the threaded rods to pass through the spacer; and

- threaded tightening means mounted on at least one end of each threaded rod.

In this preferred embodiment of the lamella module of the present invention described in the previous paragraph, the lamellas have no other points of contact with each other than spacers and threaded rods passing through holes in these spacers.

In addition, in this preferred embodiment of the invention, the support elements are installed inside the lamella module, taking into account that the spacers are located between two adjacent lamellas, and the threaded rods pass through the various lamellas and spacers after they are inserted into the through holes and openings made in these two components. The spacers act as fastening and positioning elements for the lamellas of the lamella module, holding them in position and fixing them relative to each other, in cooperation with the threaded rods and their respective threaded tightening means. Therefore, the lamellar module of this embodiment of the invention will have its own independent and internal support elements which make it self-supporting and ready to be installed inside the tank.

This configuration represents an important difference from prior art lamella modules, in which the supporting elements are located outside the lamella module itself, covering part of the lamella channels. In fact, typical performance losses due to external support structures of prior art are in the range of 7-20%. In the considered preferred embodiment of the lamellar module of the present invention, the space occupied by the internal support elements results in a loss of only about 0.5%, which corresponds to the space occupied by the spacers and other components that are part of the support elements.

The spacers are preferably provided with internal frustoconical bushings, each such bushing being designed to receive at least one threaded rod and to be connected, after passing through the lamella, to at least one other bushing provided in an adjacent spacer or end portion.

The spacers are positioned in their support and attachment area at an angle relative to each lamella, which inclination will determine the final slope of each lamella when the lamella module is assembled. Due to this inclination and under the tightening force generated by the threaded means, these inclined supports will cause the spacers to slide vertically relative to each other and relative to the lamella, as a result of which these elements compress the threaded rod internally and become wedged. In this case, the precise transmission of the pressure generated at the ends of the threaded tightening means to the spacers and lamellas located in the central area of the lamella module will be prevented.

This configuration, by means of frustoconical bushings that pass through the lamella and are sequentially inserted into the bushing of an adjacent spacer, solves this problem by maintaining the position of the spacers relative to each other and, in turn, relative to the lamella, unloading the threaded rod along its entire length.

The end pieces will complete the assembly of the frame and will be in a vertical plane, perpendicular to the threaded rod, which facilitates adequate support for the tightening means securing the assembled assembly. These end parts will have different geometric shapes to match with the concave part of the lamella rib or with its convex part. Likewise, they will provide a frustoconical sleeve receiving or insertion area to mate with each end of the frame.

Spacers located in the region of the lower edge of the plates are preferably provided with connecting means for connection with the supporting base.

This support base is intended to be installed inside the clarifier tank, and in addition to the function of the base for supporting the lamella module of the present invention, it also serves as an anti-float device for the module, so that no additional structures are needed to perform this function.

In one of the preferred embodiments of the invention, the support base comprises at least one inverted T-shaped profile, and the connecting means, in turn, contain protrusions, by means of which the spacers located in the region of the lower edge of the plates are installed on this profile (or profiles). In addition, the protrusions of the connecting means are preferably provided with perforations coinciding with the corresponding holes in the inverted T-shaped profile(s). , through these perforations made in the protrusions. The penetrating elements can be, for example, screws or rivets.

The lamella modules of this preferred embodiment of the invention are located, in their operating position, within the clarifier tank, such that they are raised above the base of the inverted T-shaped profile(s) providing support without any areas of the module being obstructed. supporting base.

Inverted T profiles may be made of metal or other materials such as glass fiber reinforced polyester (non-limiting example).

In another preferred embodiment of the invention, the support base is provided by at least one cross member on which at least one inverted T profile is mounted. , the lamella module will also be raised above them so that there are no areas that can be covered.

These cross members are preferably reinforcing profiles or reinforcing beams to provide additional strength to the supporting base.

After passing through these support base structures, the flow of liquid continues to rise through the lamella module with a uniform distribution over the entire free surface inside the lamella channels, so that losses of the working surface due to these crossbars are minimized.

Thus, the loss of the working surface caused by the support base is practically zero.

Brief description of the drawings

To supplement the following description and to facilitate understanding of the technical features of the invention in accordance with the preferred illustrative practical options for its implementation, the application is accompanied by drawings forming an integral part of the description, which are only examples and not limitations, and which show:

in fig. 1A is a perspective view of one of the possible variants of the lamella according to the present invention;

in fig. 1B is a cross-sectional view of the lamella shown in FIG. 1A;

in fig. 2A is a side view of one possible embodiment of the lamellar module of the present invention;

in fig. 2B is a front view of the lamella module shown in FIG. 2A;

in fig. 2B is a perspective view showing other details of the lamellar module of FIG. 2A;

in fig. 2D is a bottom view of the device of FIG. 2A;

in fig. 2D is a side view of the partially disassembled lamella module of FIG. 2A;

in fig. 3A is a perspective view of a spacer located near the top edge of the lamella module shown in FIG. 2A-2D;

in fig. 3B is a perspective view of a spacer located near the bottom edge of the lamella module shown in FIG. 2A-2D;

in fig. 3B is a perspective view of a receiving end provided in the lamella module shown in FIG. 2A-2D;

in fig. 3D is a perspective view of an insert end provided in the lamellar module shown in FIG. 2A-2D.

Detailed description of the invention

The following is a detailed description of one of the preferred illustrative embodiments of the present invention with reference to the accompanying FIGS. 1A-3B.

Throughout the text of the description, as well as in the accompanying figures, elements with the same or similar functions are denoted by the same reference numbers.

In FIG. 1A shows, as a non-limiting example, one embodiment of a lamella 1 in accordance with the present invention.

This lamella 1 is formed by a plate 5, which in this particular embodiment of the invention has a rectangular shape and is made of glass fiber reinforced polypropylene using a plastic injection molding process. This plate 5 has an upper edge 10a and a lower edge 10b parallel to the transverse direction T, and two side edges 15a and 15b parallel to the longitudinal direction L. The total width of the lamella 1 is approximately one meter in the transverse direction and approximately 1.2 meters in the longitudinal direction . Plate 5 is also provided with:

- longitudinal pleats 20 extending from the top edge 10a to the bottom edge 10b and defining channels 25 of the lamella for concentrating solids in the lower regions of the troughs of the pleats 20 when the lamella is in its working position;

- the first longitudinal structural rib 30a, located at a distance of 1/3 of the total width of the lamella 1 in the transverse direction, and the second longitudinal structural rib 30b, located at a distance of 2/3 of the total width in the transverse direction; and

- fastening points 35 in the form of through holes formed on the structural ribs 30a and 30b and located near (in the region) of the upper edge 10a and near the lower edge 10b.

Lamel 1 is divided into three different zones in the transverse direction:

a central zone located between the first reinforcing rib 30a and the second reinforcing rib 30b and supported by these reinforcing ribs 30a, 30b;

- the first side zone located between the first reinforcing rib 30a and the nearest side edge 15a; and

- the second side zone located between the second reinforcing rib 30b and the nearest side edge 15b.

Therefore, as shown in detail in FIG. 2A-2E, the first side zone and the second side zone of the lamella 1 hang freely when the lamella 1 is installed in the working position inside the clarifier.

In this particular embodiment, the reinforcing ribs 30a and 30b have a thickness in the range of 3-3.5 mm near the top edge 10a, near the bottom edge 10b and in their central region 10c, with their thickness slightly reduced (to 2.5-3.5 mm). mm) in the remaining zones through which they pass. In addition, the average thickness of those parts of the lamella 1 which are not part of the reinforcing ribs is only 2 mm.

That is, the lamella has an increased thickness at locations that will be subject to increased loads (such as reinforcing ribs 30a and 30b, especially near attachment points 35) when the lamella is in its operating position, and a thinner thickness at other locations, so that the loads , created by the actual weight of the lamellas, are reduced and the manufacturing costs are reduced.

Fig. 1A also illustrates schematically how, in the present embodiment, the plate 5 is bent in the longitudinal direction L with a first constant radius R1 of curvature, and how the reinforcing ribs 30a, 30b are also bent in the longitudinal direction L with a second constant radius R2 of curvature. In this particular case, R1=10 meters, and R2=8 meters.

In turn, Fig. 1B illustrates how the longitudinal folds 20 of the lamella 1 are formed by two sidewalls 27 and 27' forming an obtuse angle α with each other, how the first reinforcing rib 30a is formed by two sidewalls 37a and 37a' forming a variable angle β with each other, and as a second reinforcing the rib 30b is formed by two sidewalls 37b and 37b' forming a variable angle β with each other. In this particular embodiment, the angle α has a constant value of 155° throughout the longitudinal direction of the lamella 1. In contrast, the angle β of the reinforcing ribs 30a and 30b has a value of 90° near the edges 10a and 10b, and this angle gradually increases, reaching the value 117° in the central zone 10s.

In FIG. 2A-2D show different views of the lamella module 100 in accordance with the present invention.

Such a lamella module 100 comprises several lamellas 1 identical to those shown in FIG. 1A and FIG. 1B, installed in parallel without direct contact with each other, and the lamellas are arranged obliquely with respect to the horizontal direction H. The lamellas 1 are attached to the supporting elements, which in the considered embodiment of the invention include the first group of threaded rods 60a, arranged in such a way that they pass through the through holes plates 5 of lamellas 1, made near the top edge 10a, and a second group of threaded rods 60b, arranged so that they pass through the through holes of the plates 5 of lamellas 1, made near the bottom edge 10b. Each rod of the first group of threaded rods 60a is attached at one of its ends to a threaded tightening means 80a, which in this embodiment is a nut. Similarly, each rod of the second group of threaded rods 60b is attached at one of its ends to a threaded tightening means 80b (also in the form of a nut). Between each nut 80a and 80b and the last lamella 1, i.e., the lamella that is closer to the end of the rod 60a or 60b (on which the corresponding nut 80a or 80b is screwed), an end part 70c is installed. These end portions 70c define a vertical plane perpendicular to the stem 60a or 60b so that the nuts 80a and 80b are properly supported.

In the considered embodiment of the invention, the support elements also include spacers 70a installed near the upper edge 10a between each pair of lamellas 1, and spacers 70b installed near the lower edge 10b of the plates 5 between each pair of lamellas 1.

As best seen in FIG. 3B, spacers 70b positioned near the lower edge 10b of the plates 5 are provided with connection means 73 for connection to the inverted T-shaped support base profiles 95.

The connecting means 73 in this embodiment of the invention are protrusions integral with the spacer 70b.

The inverted T-shaped support base profiles 95 are in turn attached to cross members 90 which also form part of the support base.

In FIG. 3A shows a spacer 70a which, in a lamella module such as the one shown in FIG. 2A-2D is mounted near the top edge 10a.

In the exemplary embodiment of the invention, spacer 70a is made from polypropylene using a plastic injection molding process. In addition, the spacer 70a is provided with a frustoconical bushing 77a for receiving a threaded rod 60a passing through the hole 75a of the bushing and being connected to at least another bushing of an adjacent spacer 70a or end portion 70c, which will be described in more detail below with links to Fig. 3B.

In FIG. 3B shows a spacer 70b designed to fit near the bottom edge 10b of the plates 5.

In this embodiment, spacers 70b are made from polypropylene using a plastic injection molding process. Similarly, the spacer 70b is provided with a frustoconical sleeve 77b to receive a threaded rod 60b passing through the sleeve bore 75b and coupled to at least another sleeve of an adjacent spacer 70b or insertion end 70d. As can be seen, the spacers 70b are also provided with protrusions 73 which allow the lamellar module 100 to be connected to the inverted T-shaped support base profiles 95.

In FIG. 3B shows a receiving end 70c made from polypropylene using a plastic injection molding process. This end portion 70c is provided with a cavity 75c for receiving a frustoconical sleeve 77a, 77b of a corresponding adjacent spacer 70a, 70b.

In FIG. 3D shows an insertion end 70d made from polypropylene using a plastic injection molding process. This insertion end portion 70d is provided with a frustoconical sleeve 77d with a through hole 75d.

REFERENCE NUMBERS IN THE FIGURES

1 - lamella,

5 - lamella plate,

10a - upper edge of the plate,

10b - lower edge of the plate,

10s - central zone,

15a, 15b - side edges of the plate,

20 - longitudinal folds,

25 - lamella channels,

27, 27' - sidewalls of longitudinal folds,

α - the angle formed by the sidewalls of the longitudinal folds,

30a, 30b - longitudinal reinforcing ribs,

35 - attachment points,

37a, 37a'; 37b, 37b' - sidewalls of reinforcing ribs,

β is the angle formed by the sidewalls of the reinforcing ribs,

60a - the first group of threaded rods,

60b - second group of threaded rods,

70a - spacers installed near the top edge,

70b - spacers installed near the bottom edge,

70s - receiving end part,

70d - insertable end,

73 - connecting means (protrusions) for attaching to the supporting base,

75a, 75b - through holes of spacers,

75c - cavity of the receiving end part,

75d - through hole of the inserted end part,

77a, 77b - inner bushings of spacers having the shape of a truncated cone,

77d - bushing of the inserted end part,

80a, 80b - threaded tightening means (nuts),

90 - cross members of the supporting base,

95 - profiles of the supporting base, having the shape of an inverted letter T,

100 - lamellar module,

L - longitudinal direction,

T - transverse direction,

H - horizontal direction,

R1 - first radius of curvature (plate),

R2 - second radius of curvature (reinforcing ribs).

Claims (31)

1. Lamella (1) for clarifier, formed by a rectangular or square plate (5), with the upper edge (10a) and the lower edge (10b) of the plate (5) running parallel to the transverse direction (T), and the other two edges (15a, 15b ) the plates (5) run parallel to the longitudinal direction (L), characterized in that: the plate (5) is bent in its longitudinal direction so that in its working position the area closer to the lower edge (10b) of the plate (5) is less inclined relative to the horizontal (H) compared to the area closer to the upper edge (10a ) plates (5); and the plate (5) is provided with longitudinal folds (20) extending from the upper edge (10a) of the plate (5) to the lower edge (10b) of the plate (5), and the longitudinal folds (20) are also curved in the longitudinal direction (L). 2. Lamella (1) according to claim 1, characterized in that it contains at least one longitudinal fold (20) delimited by two sidewalls (27, 27') forming an obtuse angle (α) between them, preferably in the range from 150° to 160°. 3. Lamella (1) according to any of the preceding claims, characterized in that it contains at least one longitudinal reinforcing rib (30a, 30b), bent in the longitudinal direction (L) and delimited by two sidewalls (37a, 37a'; 37b, 37b') extending from the upper edge (10a) of the plate to the lower edge (10b) of the plate and forming a variable angle (β) between them, the value of which is: is in the range from 80° to 90° in the region of the upper edge (10a); is in the range from 80° to 90° in the region of the lower edge (10b); and gradually increases to a value in the range from 115° to 120° in the central zone (10c) of the lamella (1). 4. Lamella (1) according to claim 3, characterized in that said at least one longitudinal reinforcing rib (30a, 30b) is provided with attachment points (35) for attaching to the support element, wherein the attachment points (35) are located in the region of the upper edge (10a) of the plate and in the region of the lower edge (10b) of the plate. 5. Lamel (1) according to claim 4, characterized in that the area in the area of the upper edge (10a), the area in the area of the lower edge (10b) and the central area (10 c) of the specified at least one reinforcing rib (30a, 30b ) are thicker than the rest of the reinforcing rib (30a, 30b), the reinforcing rib (30a, 30b) being thicker than the rest of the lamella (1). 6. Lamel (1) according to any one of paragraphs. 1-5, characterized in that it is made of plastic using a method of injection molding of plastic products. 7. Lamel (1) according to any one of paragraphs. 3-6, characterized in that it contains at least a first reinforcing rib (30a) located at a distance of 1/3 of the total width of the lamella in the transverse direction (T), and at least a second reinforcing rib (30b) located at a distance 2/3 of the total width in the transverse direction (T), wherein the first reinforcing rib (30a) and the second reinforcing rib (30b) are provided with attachment points (35) for attaching to the support elements, and the attachment points (35) are located in the region of the upper edge ( 10a) of the plate and in the region of the lower edge (10b) of the plate. 8. Lamel (1) according to claim 7, characterized in that it is divided in the transverse direction into three different zones: a central zone located between the first reinforcing rib (30a) and the second reinforcing rib (30b) and supported by these reinforcing ribs (30a, 30b); the first side zone located between the first reinforcing rib (30a) and the nearest side edge (15a); and a second side zone located between the second reinforcing rib (30b) and the nearest side edge (15b); and the first side zone and the second side zone hang freely when the slat (1) is installed in the working position. 9. Lamella (1) according to any one of the preceding claims, characterized in that the plate (5) is bent in its longitudinal direction (L) with a first constant radius (R1) of curvature. 10. Lamel (1) according to claim 9, characterized in that the value of the first constant radius (R1) of curvature of the plate is in the range from 7 to 12 meters, more preferably in the range from 9 to 10 meters. 11. Lamel (1) according to any one of paragraphs. 3-8, characterized in that it comprises at least one longitudinal reinforcing rib (30a, 30b) bent in the longitudinal direction (L) with a second constant radius (R2) of curvature, the plate (5) being also bent in its longitudinal direction (L) with a first constant radius (R1), and the value of the second curvature radius (R2) is less than the value of the first curvature radius (R1). 12. Lamel (1) according to claim 11, characterized in that the value of the first constant radius (R1) of curvature is in the range from 9 to 10 meters, and the value of the second constant radius (R2) of curvature is in the range from 7 to 8.5 meters. 13. Lamellar module (100) for clarifier, characterized in that it contains two or more lamellas (1) according to any one of paragraphs. 1-12, installed in parallel without direct contact with each other and attached to the supporting elements. 14. Lamellar module (100) according to claim 13, characterized in that: each lamella (1) is provided with at least one longitudinal reinforcing rib (30a, 30b) having attachment points (35) in the form of through holes (35), which are located in the region of the upper edge (10a) of the plates (5) of the lamellas (1) and in the region of the lower edge (10b) of the plates (5) of the lamellas (1); and the supporting elements include at least two groups of threaded rods (60a, 60b), the first group of threaded rods (60a) being installed so that they pass through the holes made in the area of the upper edge (10a) of the plates (5) of the lamellas (1), and the second group of threaded rods (60b) is installed so that they pass through the holes made in the region of the lower edge (10b) of the plates (5) of the lamellas (1). 15. Lamellar module (100) according to claim 14, characterized in that the supporting elements also include: spacers (70a) installed in the region of the upper edge (10a), and spacers (70b) installed in the region of the lower edge (10b) of the plates (5) of each pair of adjacent lamellas (1), each spacer (70a, 70b) having a through an opening (75a, 75b) so that at least one of the threaded rods (60a, 60b) can pass through the spacer (70a, 70b); and threaded tightening means (80a, 80b) mounted on at least one end of each threaded rod (60a, 60b). 16. Lamellar module (100) according to claim 15, characterized in that the spacers (70a, 70b) are provided with internal bushings (77a, 77b) having the shape of a truncated cone, and each of these bushings is designed to receive at least one threaded rod (60a, 60b) and for connection, by passing through the lamella (1), with at least one other sleeve (77a, 77b) in an adjacent spacer (70a, 70b) or in the end part (70c, 70d). 17. Lamellar module according to claim 15 or 16, characterized in that the spacers installed in the area of the lower edge of the plates are provided with connecting means (73) for attaching to the support base. 18. Lamellar module according to claim 17, characterized in that the support base contains at least one profile (95) having the shape of an inverted T. 19. The lamellar module according to claim 18, characterized in that the connecting means (73) are protrusions (73) provided with perforations coinciding with the corresponding holes made in the profile (95) having the shape of an inverted letter T, and the connecting means ( 73) include elements designed to be inserted into the holes in the profile (95) through the perforations in the projections (73).

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