WO2009058019A1

WO2009058019A1 - Noise-protection screen, screen element and crash barrier

Info

Publication number: WO2009058019A1
Application number: PCT/NL2008/050691
Authority: WO
Inventors: Hendrikus Herman Wilhelmus Derks
Original assignee: Blue Temple B.V.
Priority date: 2007-11-01
Filing date: 2008-11-03
Publication date: 2009-05-07
Also published as: NL1034614C2

Abstract

A noise-protecting screen (30) comprises a first wall (33) which extends in a longitudinal direction and which leaves a space to a second wall (34) likewise extending in longitudinal direction in order to receive therebetween an airflow coming from a traffic route. The first wall leaves clear an inlet opening (41) to the space which debouches into at least one outflow opening (42). A system of transverse walls (32) at a mutual distance is placed transversely of the first wall (33) and the second wall (34) so as to thus form successive channels (40), which are each provided with at least one inlet opening (41) directed toward the traffic route and at least one corresponding outflow opening (42). A crash barrier (6) comprises barrier elements (61, 62, 63) which lie one above the other and which are mounted by means of resilient barrier supports (71, 72, 73). A barrier support of a barrier element herein crosses a barrier element lying thereunder on a rear side.

Description

Noise-protecting screen, screen element and crash barrier

The present invention relates to a noise-protecting screen for a traffic route, comprising a first wall which extends in a longitudinal direction and which leaves a space to a second wall likewise extending in longitudinal direction in order to receive therebetween an airflow coining from the traffic route, wherein the first wall leaves clear at a base at least one inlet opening to the space and wherein the space debouches into at least one outflow opening.

Noise-protecting screens of the type described in the preamble are applied on large scale along traffic routes, and in particular along motorways. The noise-protecting screen herein generally comprises a continuous, connected wall with a height of a minimum of about three to four metres, the object of this being to create a low-noise zone therebehind in order to thus limit noise nuisance of traffic over the traffic route to people living in the vicinity. In practice diverse materials and constructions are applied here for noise-protecting screens, varying from single walls of for instance wood, concrete or glass to solutions which are blended together with a neighbouring public utility building or residential building. In some cases the thus erected noise- protecting screen only forms a barrier against the penetration of sound to an area situated therebehind; in other cases the noise-protecting screen actively contributes toward a reduction in the noise impact on the surrounding area by absorbing and thus actually damping sound.

In addition to possible noise nuisance of traffic routes, there has also been an increasing focus in recent years on possible air contamination by traffic on traffic routes, particularly in respect of the nuisance to the immediate vicinity thereof. This relates particularly to the emission of fine dust and of nitrogen oxides by passing vehicles. A noise-protecting screen of the type described in the preamble is therefore known from European patent application EP 567.040 which, in addition to having a sound-proofing function, also has an air cleaning function. For this purpose the known noise-protecting screen forms part of a full covering of a traffic route. Created in a wall thereof is a cavity with an inlet opening toward the traffic route at a base thereof and an outflow opening at a top side. Between the inlet opening and the outlet opening an airflow entrains exhaust gases from the passing traffic. Arranged in the cavity in front of the outflow opening is an air filter with which fine particles are filtered from the air, so that the air coming from the outflow opening has at least part of the fine dust removed. The thus applied air filter moreover provides for an improved sound damping of the whole.

Although the known noise-protecting screen hereby aims at a dual operation, the efficiency of this screen depends on the full covering of the traffic route. This known screen is therefore a highly expensive solution, which will therefore be seldom put into practice. Without such a complete enclosing of the traffic route the actual effectiveness of this known screen is questionable, since only a very limited part of the exhaust gases emitted by the traffic will then be captured by the screen, and the greater part will go past the screen unfiltered.

The present invention has for its object, among others, to provide a noise-protecting screen of the type stated in the preamble, with an enhanced capacity for capturing ambient air.

In order to achieve the intended object a noise-protecting screen of the type described in the preamble has the feature according to the invention that a system of transverse walls, placed at a mutual distance from each other, extends at least substantially transversely of the longitudinal direction between the first wall and the second wall so as to form successive channels therebetween, and that the channels are each provided at a base of the screen with at least one inlet opening directed toward the traffic route and at least one corresponding outflow opening at a top of the screen, and are able and adapted to guide a part of the airflow therebetween. The noise-protecting screen thus comprises a number of successive channels which each individually draw in a part of the ambient air and thus together produce a considerably enhanced air exchange with the surrounding area. The air intake results on the one hand in an interaction with possible sound waves, which are damped thereby so that the noise load of the traffic route on the surrounding area is reduced. In addition, the airflow provides an excellent opportunity for an effective air treatment for the purpose of removing one or more harmful substances therefrom.

In a preferred embodiment the noise-protecting screen according to the invention is. characterized in that the channels of the at least one inlet opening narrow over at least a part of their length toward the at least one outflow opening. Because the channels function as it were as an elongate sequence of chimneys, the screen will continuously draw in contaminated air along the path of the traffic route. The narrowing in the channels here ensures that the speed of the air flowing therein is relatively low at the bottom and relatively high at the top. Fine dust and other contamination is hereby given the opportunity to deposit and to adhere, particularly to the walls inside the channels. An improved sound damping is thus also achieved.

Once accelerated via the narrowing, the through-flowing air comes from the outlet opening at a higher speed and thus disperses over a larger area. Part of the air contamination will always remain in the air flowing out at the top side. For this part of the contamination it is important to cause as much turbulence as possible. By creating turbulence at the outflow opening on the top side the dispersion of the air contamination can be maximized, and the concentration of fine dust and NOx can thereby be reduced in the environment behind the screen. The cross-section of the channel to the outflow opening is an important factor here as it influences the speed at which the air leaves the screen. A contamination load on the immediate vicinity of the traffic route can hereby be reduced.

In a particular embodiment the noise-protecting screen according to the invention has the feature here that the first wall and the second wall mutually enclose an acute apex angle. Due to the angle which the two walls thus form toward each other, the channel narrows gradually so as to gradually increase the air speed. By placing the first wall on the road side vertically, more overpressure is created on the underside than if the wall were to slope away at an angle. From an aesthetic viewpoint, and particularly the perception of the screen by a road user, a vertically placed front wall is however less desirable, to a further particular embodiment the noise-protecting screen is therefore characterized in that the apex angle amounts to about S-10 degrees and the first wall inclines out of the perpendicular toward the second wall. An optimal compromise is hereby achieved between an effectiveness of the screen on the one hand and the acceptance thereof by the road user on the other.

The noise-protecting screen according to the invention can per se be realized in relatively simple manner and thereby at a favourable cost price. A specific embodiment of the noise-protecting screen according to the invention has in this respect the feature that the second wall extends from a top side to a base and that the first wall maintains a distance from the base for the purpose of forming successive inlet openings thereunder on either side of a transverse wall. The noise-protecting screen is thus basically a system of flat wall parts mutually connected in the indicated manner. The desired inlet openings are left clear owing to the distance between the first wall and the base.

A further particular embodiment of the noise-protecting screen according to the invention has the feature that successive transverse walls are mutually connected in the longitudinal direction by wall parts of the first wall, which maintain a distance from an edge of the transverse walls. The distance of the first wall parts from the edge of the transverse walls allows part of the transverse edges to protrude as ribs, so as to thus form a profiled surface on the road side. This surface causes more turbulence, and thereby an improved sound-damping and dispersion of the exiting airflows which have not been captured.

A further preferred embodiment of the noise-protecting screen according to the invention has the feature that at least one of said walls has an active main surface which is able and adapted to at least bind at least one contaminant from the airflow. The main surface of at least a number of the walls of the noise-protecting screen thus make an active contribution toward purifying the flow-by air by binding contamination components thereto. A particular embodiment of the noise-protecting screen herein has the feature according to the invention that the at least one wall is composed of wood fibre concrete. Various field tests have shown that wood fibre concrete acts very effectively as a filter for the adhesion of fine dust. Wood fibre concrete has also proven itself in many applications in respect of sound-absorbing qualities. The fine open structure of wood fibre concrete moreover ensures that there is much adhesion potential for fine dust.

A further particular embodiment of the noise-protecting screen has the feature that the main surface is catalytic and is able and adapted to convert at least one contaminant, and more particularly that the main surface is provided with a covering, in particular a coating, which comprises a catalyst, in particular titanium dioxide, for breaking down a contaminant The screen thus makes an active contribution toward improvement of the air quality through a reduction of harmful substances. Titanium dioxide has proven itself in this respect as catalyst for the conversion of nitrogen oxides, referred to in short as NOx, into harmless nitrate.

In addition, an effective purification of the air flowing through a channel is possible in a further particular embodiment of the noise-protecting screen according to the invention, which embodiment is characterized in that a channel between the inlet opening and the at least one outlet opening thereof comprises an optionally active air filter. Through a suitable choice various contaminations can here be effectively eliminated from the airflow, or at least reduced. A filter usually produces air resistance therein, which will reduce the air speed, whereby a better interaction with the filter material is possible, but whereby a further damping of possible sound waves will also occur. An optimal balance can thus be sought in practice between the desired strength of the airflow, and thereby the suction action of a channel, and a desired degree of interaction with the through-flowing air.

Due to the adhesion of fine dust to the surface of one or more of the walls of the screen, these may become saturated in the course of time, and may lose effectiveness. In order to prevent this a further particular embodiment of the noise-protecting screen according to the invention has the feature that spraying means are arranged in the channel, which are able and adapted to subject at least a part of a main surface of at least some of the walls, optionally periodically, to a cleaning agent such as water, and in particular rainwater. The surface can thus be revitalized, periodically or otherwise.

Different airflows are important on and around a traffic route. Firstly, there is a primary airflow as a result of wind. This flow has a fairly constant force and direction and provides the supply of contaminated air to the screen on the leeward side of the road. Secondly, there are more local and temporary airflows as a result of passing traffic. These flows are turbulent, a pressure wave being alternated with a slipstream. So as to also utilize this airflow as efficiently as possible to generate an airflow through the channels, a further particular embodiment of the noise-protecting screen according to the invention has the feature that inlet openings are provided with a nonreturn valve which opens toward the channel in the case of an external overpressure and at least substantially closes in the case of an external underpressure, and more particularly that the non-return valve comprises a flat valve body which is arranged for pivoting about a pivot shaft on a base side and lies in a valve seat counter to a spring tension. The overpressure of a pressure wave of a passing vehicle will thus cause the non-return valve to open so that an airflow enters. Conversely, the valve will close as soon as the slipstream of the vehicle causes a subsequent underpressure, with the net result that an intermittent airflow to the inside will occur.

For the purpose of a further optimization of this secondary airflow action, a further particular embodiment of the noise-protecting screen according to the invention has the feature that the transverse walls on a base side comprise at least one connecting opening whereby successive channels are in open communication with each other on the base side. This connecting opening provides for a change in pressure - resulting from the progression of pressure wave and slipstream on the front side - via the rear side of the channels. The intensity of an excessively large-scale turbulence is hereby reduced.

In order to strengthen the effect of the primary airflow resulting from the wind flowing past, use can be made of the rapid suction at the top side of the screen to create more underpressure, whereby the proportion of inflow on the road side increases on the underside. Because carrying of this air through the screen would otherwise only be relevant for the screen on the leeward side of the road, a further particular embodiment of the noise-protecting screen according to the invention has the feature that the at least one outflow opening is provided in an outlet element, which is arranged rotatably about a vertical axis on a top side and which is able and adapted to orient itself to a wind direction with the outflow opening on a leeward side. The principle of a so-called "cowl" is thus applied on the top side of the screen. A cowl is a cap on a chimney which is made such that it co-rotates with the wind, this in a manner such that the wind cannot blow into the chimney channel but on the contrary creates an underpressure around the opening thereof and draws air out of the chimney, thereby enhancing the suction at the top edge. In a simplified, static form a similar operation can be achieved by a higher standing part on the windward side compared to the leeward side, although here the operation will depend on the actual wind direction.

In addition to the above stated primary and secondary airflows, use can further be made of a thermally induced airflow. This is achieved in a further preferred embodiment of the noise-protecting screen according to the invention, characterized in that at least one wall of a channel is able and adapted to enter into heat-exchanging contact with ambient light. Solar energy is thus utilized for the purpose of maintaining or intensifying the airflow through the screen, also when there is no wind. The heat- exchangύig contact with the sunlight provides for a heating of the air column in the channel, whereby it will rise, whereby air flows in at the bottom of the channel and air flows out at the top.

In order to enhance the incidence of sunlight here, a further particular embodiment of the noise-protecting screen according to the invention has the feature that at least one of the first and second walls, in particular the second wall, is at least partially translucent. The sun can thus enter the channel directly in order to heat the air therein. If for instance a rear side of the screen catches the sun for a significant part of the day, it is advantageously given a translucent form, for instance by applying glass or polymethyl raethacrylate (PMMA) as material for the wall on this side.

A further optimization of this thermal draught can be achieved with a further particular embodiment of the noise-protecting screen according to the invention, characterized in that the at least one wall has a surface with a dark tint and is particularly at least locally black. Owing to the darker tint the relevant wall will absorb more heat and men relinquish this heat to the immediate vicinity through radiation as well as conduction.

In a further particular embodiment the noise-protecting screen according to the invention has the feature that the first wall is provided on an outer side with a wall covering, and in particular with an exchangeable wall covering. Making use of a standard construction a plating or other type of covering, which harmonizes optimally with the surrounding area, can thus be applied on the road side. An exchangeable covering results here in more convenient maintenance, which thus need involve only a periodic change of the covering in order to keep the screen active and fresh, which work can be carried out almost regardless of the weather conditions.

In addition to use on a hard shoulder side of a traffic route, the noise-protecting screen according to the invention can also be applied in a central reservation or in other manner between lanes. With a view hereto, a particular embodiment of the noise- protecting screen according to the invention has the feature that, on a side of the second wall remote from the first wall, a second first wall extends in longitudinal direction and that the noise-protecting screen between the two first walls takes an at least substantially mirror-symmetrical form. Owing to the applied mirror symmetry this screen has an at least similar operation on both sides. A further particular embodiment of the noise-protecting screen according to the invention has the feature that the second wall comprises at least locally an outer wall of a ribbon development. The noise-protecting screen can thus be integrated smoothly into a possibly present ribbon development, which also saves cost as well as space.

A further particular embodiment of the noise-protecting screen according to the invention has the feature that the second wall comprises at least locally a wall of a tunnel or tunnel liner. The thus fully or partially sunken position of the noise- protecting screen on the one hand increases the efficiency of the screen in that airflows coming from the traffic route are as it were confined and can be better captured by the screen. A recessed position of the screen in a tunnel liner on the other hand allows a greater height of the screen, so that the operation of the screen is thereby also enhanced.

In order to simplify placing of the noise-protecting screen, a further particular embodiment thereof has the feature that the whole is based at least substantially on a sequence of successive screen elements, each comprising a system of successive transverse walls with a first wall segment on a first side and a second wall segment on an opposite side. The screen elements can thus be factory-assembled beforehand and then only need placing against each other on site. A further particular embodiment of the noise-protecting screen according to the invention herein has the feature that the screen elements comprise a foundation plate on which the system of transverse walls supports, wherein the second wall segment extends at least substantially to the foundation plate and the first wall segment is separated therefrom by a system of successive inlet openings, and more particularly that the foundation plate comprises a reinforced concrete plate. The base of the screen elements is thus formed by a foundation plate, for instance of concrete. By making use of prefab foundation plates as base for the screen, a simple rubble foundation along the road is often sufficient. The screen can hereby be placed, and also displaced, exceptionally quickly. A further functionality is achieved with a further embodiment of the noise-protecting screen which is characterized in that the foundation plate comprises a drainage gutter. In a further particular embodiment the noise-protecting screen according to the invention is characterized in that coupling means are provided between successive screen elements for an at least substantially connected coupling of successive screen elements. The coupling means can here comprise a physical connection or a loose S fitting. An alignment of successive screen elements can hereby be achieved in both cases, which facilitates a continuous placing of the whole and prevents possible subsidence or other settling of individual screen elements in the course of time.

A noise-protecting screen according to the invention comprises in principle a 0 repetition of successive screen elements at least substantially the same as each other. For the purpose of incorporating therein a bend of the traffic route, a particular embodiment of the noise-protecting screen according to the invention has the feature however that at least one of the screen elements is able and adapted to form at least a curve section of a bend. The invention likewise provides a further particular S embodiment which is characterized in that the screen elements end in a closing element which comprises a closing wall on a side remote from a preceding screen element in order to thereby form a start and end finish of the screen. A further particular embodiment of the noise-protecting screen according to the invention has in this respect the feature that the screen elements comprise crash barriers on a side0 directed toward the traffic route, and thereby provides a complete roadside finish for a traffic route.

The operation of the screen can be further optimized by placing the screen closer to the source. Traditional noise-protecting screens are generally positioned over two5 metres behind a crash barrier. This is related to the construction of a traditional crash barrier, which requires a free space to the rear thereof to be able to move sufficiently in the case of a collision. However, a further particular embodiment of the noise- protecting screen according to the invention has the feature that the crash barrier comprises a number of barrier elements which lie one above the other and which0 extend in the longitudinal direction and which are each resiliently mounted via an individual system of barrier supports distributed in longitudinal direction, wherein the barrier supports of a barrier element cross a barrier element lying thereunder on a rear side. By thus replacing the traditional, moving crash barrier with a resilient crash barrier the screen can be placed about a metre and a half closer to the source, whereby the effect thereof increases considerably. Owing to the specific embodiment of the crash barrier according to the invention a disruption of the wind and other airflows is moreover limited to a minimum.

The invention also relates to such a crash barrier and to a screen element for applying in the noise-protecting screen according to the invention, and will now be further elucidated on the basis of several exemplary embodiments and an accompanying drawing. In the drawing: figure 1 shows schematically a traffic route with an exemplary embodiment of a noise-protecting screen according to the invention; figure 2 shows a cross-section of a screen element of the noise-protecting screen of figure 1; figure 3 is a front view of the noise-protecting screen element of figure 2; figure 4 is a rear view of the noise-protecting screen element of figure 2; figure S shows schematically the operating principle of the noise-protecting screen according to the invention; figure 6 shows a first alternative embodiment of the noise-protecting screen according to the invention; and figure 7 shows a second alternative embodiment of the noise-protecting screen according to the invention.

The drawings are otherwise purely schematic and not drawn to scale. Some dimensions in particular may be exaggerated to greater or lesser extent for the sake of clarity. Corresponding parts are designated as far as possible in the figures with the same reference numeral.

Figure 1 shows schematically a traffic route 1 over which traffic 2 is travelling in different directions, with a noise-protecting screen 3,4,5 according to the invention along the sides as well as in the central reservation. Noise-protecting screen 4 in the central reservation is here a mirror-symmetrical embodiment of screens 3,5 on either side, which are identical to each other but in opposite orientation. The noise- protecting screens can in principle be deployed along any type of traffic route, but are applied mainly along motorways and railways.

Noise-protecting screens 3,4,5 have a modular construction in the form of a sequence of successive, more or less identical screen elements 30, one of which is shown in cross-section in figure 2, and in respectively front view and rear view in figures 3 and 4. The base of screen 30 is formed by a concrete foundation plate 31. By making use of a prefab foundation plate as base for the screen a simple rubble foundation along the road is often sufficient. The screen can hereby be placed, and also displaced, exceptionally quickly. Contributing toward this is a complementary profiling 36,37 on either side of foundation plate 31 (see figures 3 and 4), which provides a mutual fitting and mutual alignment of successive screen elements.

Ribs 32 of wood fibre concrete are placed on the foundation. These ribs have a height of about 4 metres and centre-to-centre are about 700 mm apart. By arranging reinforcement the ribs are suitable as carrier of the final construction, in which they form transverse walls between successive channels 40. On a road side the space between the ribs is closed with plates, likewise of wood fibre concrete. These plates form wall parts of a first wall 33 of the noise-protecting screen to be realized on this side. On their underside the plates 33 maintain a distance of about a metre from foundation plate 31 in order to form a series of inlet openings 41 for the relevant channels 40. Contaminated air can be drawn in via such an inlet opening 41.

On a rear side the screen is closed with transparent, at least translucent plates, which here form a second wall 34 of the screen. Polymethyl methacrylate (PMMA), also known under the brand name perspex, is in this example chosen for the second wall. Glass for instance is however also suitable instead, and the screen can optionally also be lightproof on this side and then be provided with for instance a black coating. The second wall ensures that, when the sun shines thereon, the temperature in the screen is increased, whereby a thermal draught is brought about in channels 40. If the rear side of the screen is a shadow side, it is embodied in wood fibre concrete.

The wood fibre concrete elements have been further developed into a highly sound- absorbing open structure with a very fine surface texture. Owing to the fine structure the surface is self-cleaning. The contamination captured on the outside of the screen is flushed away during a shower of rain. In order to also enable cleaning of the inside, a sprayer system (not further shown) is arranged at the top of the screen. The screens have a high aesthetic value. The absorbent covering can be separately replaced and, with a different design for each motorway, can determine the identity of the screen. The elements can be supplied in any desired colour and texture. The first wall 33 in particular, i.e. the visual side, can be provided with a separate plating or covering in order to adapt the screen to its surroundings. The elements can also be provided with decorative recesses. The elements are exchangeable and can be combined with other materials such as plastic, glass or wood. Diverse specific screen elements are available for the beginning and end of the screen, bends and escape routes.

The noise-protecting screen functions as one elongate series of successive chimneys, whereby contaminated air is continuously drawn in. First wall 33 and second wall 34 are both about 5-10 degrees out of the perpendicular and herein incline toward each other so that the channels 40 formed therebetween gradually narrow toward an outlet opening 42 on their top side. This ensures that the speed of the air at the bottom of the screen is low. Fine dust is hereby given the opportunity to deposit and to adhere to the walls of a channel. In air engineering terms a channel forms a "pressure relief cavity" for the through-flowing air. Due to the geometric ratios between the largest passage area at inlet opening 41 and the smallest passage area at outflow opening 42 the average air speed decreases as the cross-sections increase. With a suitable dimensioning of these provided cross-sections a speed is realized at inlet openings 41 which is at least a factor 3 lower than at outflow opening 42. This creates favourable conditions for capturing air contaminants. Like first wall 33, intermediate walls 32 of the channels are constructed from wood fibre concrete. Various field tests have shown that wood fibre concrete acts very effectively as filter for the adhesion of fine dust. The wood fibre concrete is moreover treated with a coating of titanium dioxide, which acts as catalyst for the conversion of S nitrogen oxides (NOx). Because practically all wood fibre concrete components of the screen come into contact with the contaminated air on two sides, the screen offers a considerably greater adhesion surface area for fine dust and NOx than a traditional sound-absorbing screen.

0 Different airflows are important on and around a motorway. This is shown schematically in figure 5. Firstly, there is usually an airflow 100 resulting from wind. This flow has a fairly constant force and direction and ensures the supply of contaminated air to the screen on the leeward side of the road. By placing the screen as vertically as possible an overpressure resulting from this wind can be maximized. S This is because more overpressure is created on the underside by placing the surface on the road side vertically than if the screen were to slope away at an angle. From an aesthetic viewpoint and in the perception of the road user a vertically placed screen is however less desirable, and a screen lying at an angle of about 80-85 degrees to the ground surface is therefore chosen in this example. Use is further made of rapid0 suction at the top side of the screen in order to create more underpressure there, whereby a suction on the underside also increases. This principle is also applied to chimneys in the form of a so-called "cowl", which co-rotates with the wind in order to keep outlet opening 42 always on the leeward side. In this example this is simplified to a higher standing part of the wall on the windward side relative to the wall on the5 leeward side. In figure 2 the first wall 33 is thus situated on the windward side of the screen.

Secondly, there are more local and temporary airflows 200 resulting from passing traffic. These flows are turbulent, a pressure wave being alternated with slipstream.0 Resilient non-return valves (not further shown), which open in the case of an overpressure from outside and close in the case of an underpressure, can be applied in the inlet openings. In this way a pressure wave from a passing vehicle can be admitted into a channel 40 of the screen, while the slipstream is prevented from then drawing the air outside again. The passing of vehicles is accompanied by a great deal of turbulence. By breaking and decelerating these flows to low speeds in the deposition zone, it is possible to prevent part of the released dust being entrained by the wind. Transverse walls 32 are provided on their rear side with connecting openings 35 which provide for an open communication between successive channels. Alternatively, it is also possible to opt for a (transparent) rear wall 34 which stands some distance separately of transverse walls 32 of the screen, whereby the channels are mutually connected on the rear side via a connecting gap. This connection ensures that an exchange of pressure - resulting from the progression of pressure wave and slipstream on the front side - is possible via the rear side of the compartments. The intensity of the large-scale turbulence is hereby reduced.

Thirdly, the noise-protecting screen makes use of thermal draught to generate an airflow through the screen. Solar energy is utilized for this purpose. Flow via the screen with fine dust-adsorbing surfaces can thus also be realized when there is no wind by applying this chimney principle. If a column of air in a channel 40 is warmer than the ambient air it will rise, whereby air flows in at the bottom of the channel and air flows out at the top. Sun 300 can enter channels 40 freely via transparent rear wall 34 and will increase the temperature in the screen through heat-exchanging contact with the inner walls of the channels. The wood fibre concrete on the inner side of the screen is preferably embodied for this purpose in a darker colour in order to absorb and generate as much heat as possible. Alternatively, a dark or even black steel plate could for instance also be applied as second wall, but this will also relinquish part of the absorbed heat to the outside air, which diminishes the effect.

For the shown screen, with inflow openings 41 of 1 x 0.7 metre and outflow openings 42 of 0.3 x 0.7 metre the resistance of the smallest opening 42 is critical. At an effective solar load of 500 W/m² and an effective height between inflow opening 41 and outflow opening 42 of 4 metres, a thermally driven pressure difference of about 1.2 Pa will thus occur. An air speed hereby results in outflow opening 42 of the screen which will generally be in the order of 0.6-0.7 m/s. This will thus produce about 700 m³/h of air displacement per running metre of screen. Although this is less than the above stated effects, it nevertheless further contributes to the effectiveness and 5 efficiency of the screen as a whole.

Part of the air contamination will inevitably remain behind in the air flowing out on the top side of the screen. For the part of the contamination which cannot be captured by creating efficient deposition conditions it is important to cause as much turbulence 0 as possible. This is because, by creating turbulence at the outflow opening on the top side, it is possible to maximize a dispersion of possibly remaining air contaminants and thereby reduce the concentration of fine dust and NOx in the environment behind the screen. The cross-section of the outflow opening is a significant factor here because it determines the speed at which the air leaves the screen. In addition, the S plate parts of first wall 33 lie slightly recessed between transverse walls 32 and thus maintain a certain distance from an edge of transverse walls 32. Transverse walls 32 hereby protrude as ribs on the road side of the screen and thus cause extra turbulence there, in addition to extra adhesion surface. 0 Traditional noise-protecting screens generally stand more than 2 metres behind a crash barrier so as to provide the crash barrier sufficient space to be able to move in a collision. In the present exemplary embodiment use is made of a new crash barrier 6 according to the invention. The crash barrier (see figure 2) comprises three crash barrier elements 61-63 which extend in longitudinal direction and which are each5 individually fixed to the ground 31 in resilient manner by means of plate-like barrier supports 71-73. Such barrier supports are optionally arranged in sets at regular distances in the longitudinal direction. A barrier support 71,72 of a guide element 61,62 here crosses in each case a guide element 62,63 situated thereunder on a rear side thereof. An upper guide element can thus bend rapidly rearward, yet the crash0 barrier as a whole has sufficient strength and capacity to bring a vehicle to a halt. By replacing a traditional crash barrier with such a resilient crash barrier according to the invention less free space is required therebehind, and the screen can be placed about 1.5 metres closer to the source, and thereby gain significantly in effectiveness. A disruption of the wind is moreover limited to a minimum by the design of the crash barrier. As shown in figure 2, crash barrier 6 is integrated on the foundation plate together with the screen and a drainage gutter 38. By joining screen elements together it is thus possible to assemble a complete crash barrier 6 and drainage gutter 38 together with the construction of the noise-protecting screen.

Because the screen functions as one elongate sequence of chimneys, contaminated air is drawn and blown in permanently and actively. The triangular cross-section of the screen ensures that the speed of the air at the bottom of the screen is low. Fine dust is hereby given the opportunity to deposit and adhere to the walls of the "chimney". Just as the whole screen, these walls are constructed from wood fibre concrete. The wood fibre concrete acts very effectively as a filter due to the adhesion of fine dust, hi addition, the wood fibre concrete is treated with a coating of titanium dioxide, which acts as a catalyst for the purpose of converting NOx. Positive results have already been achieved through use of this coating. The noise-protecting screen operates in that a continuous airflow through the screen is realized. The screen operates here wholly independently on the basis of physical principles, without extra energy having to be supplied for this purpose. Field tests have nevertheless shown that a fine dust reduction in the order of an average of about 30-40% can be achieved with the screen according to the invention, while an average reduction in NO2 of no less than about 40-50% has been realized.

The shown noise-protecting screen also provides significant advantages in respect of durability. The components of the screen are environmentally-friendly and can be produced with low energy consumption. The whole screen is further recyclable and the elements thereof can be individually replaced. In addition, the screen is reusable and displaceable.

An alternative embodiment of the noise-protecting screen is shown in figure 6. Noise- protecting screen 30 is applied here as outer wall covering of an already existing or to be erected ribbon development 70 along traffic route 1. In this way it is possible to build directly alongside the road. The ribbon development then provides for an improvement in the air quality for residential areas situated therebehind. A relatively high concentration of fine dust and NOx above road 1 therefore need not be an obstacle to new building developments.

A trend in the construction of new roads is recessed arrangement in a kind of open tunnel liner. It is ideal to apply the noise-protecting screen in a recessed road as shown in figure 7. There is relatively little dispersion of air contamination because the wind has less effect This creates ideal conditions for the suctioning at the side of the road. If a road is built 8 metres deep, it is very well possible to realize a 12 metre high noise-protecting screen, which then protrudes only 4 metres above the adjacent ground level. The higher the screen, the more draught it will produce. If the screen thus becomes higher, more air will be captured and purified by the screen. The adhesion surface for fine dust also increases exponentially.

Although the invention has been further elucidated with reference to only a few exemplary embodiments, it will be apparent that the invention is by no means limited thereto. On the contrary, many other variations and embodiments are possible within the scope of the invention. The indicated materials and dimensions are thus given by way of example, but it is possible to resort to other materials and other dimensions in accordance with the circumstances of a specific case. If desired, (more) partitions can be applied in the channels in order to create additional filtering surface area therein. In addition, the channels provide space for additional filter means and media, for instance for the purpose of removing specific contamination components from the through-flowing air.

Claims

1. Noise-protecting screen for a traffic route, comprising a first wall which extends in a longitudinal direction and which leaves a space to a second wall likewise extending in longitudinal direction in order to receive therebetween an airflow coming from the traffic route, wherein the first wall leaves clear at a base at least one inlet opening to the space and wherein the space debouches into at least one outflow opening, characterized in that a system of transverse walls, placed at a mutual distance from each other, extends at least substantially transversely of the longitudinal direction between the first wall and the second wall so as to form successive channels therebetween, and that the channels are each provided at a base of the screen with at least one inlet opening directed toward the traffic route and at least one corresponding outflow opening at a top of the screen, and are able and adapted to guide a part of the airflow therebetween.

2. Noise-protecting screen as claimed in claim 1 , characterized in that the channels of the at least one inlet opening narrow over at least a part of their length toward the at least one outflow opening.

3. Noise-protecting screen as claimed in claim 2, characterized in that the first wall and the second wall mutually enclose an acute apex angle.

4. Noise-protecting screen as claimed in claim 3, characterized in that the apex angle amounts to about S-10 degrees and the first wall inclines out of the perpendicular toward the second wall.

5. Noise-protecting screen as claimed in one or more of the foregoing claims, characterized in that the second wall extends from a top side to a base and that the first wall maintains a distance from the base for the purpose of forming successive inlet openings thereunder on either side of a transverse wall.

6. Noise-protecting screen as claimed in claim 5, characterized in that successive transverse walls are mutually connected in the longitudinal direction by wall parts of the first wall which maintain a distance from an edge of the transverse walls.

S 7. Noise-protecting screen as claimed in one or more of the foregoing claims, characterized in that at least one of said walls has an active main surface which is able and adapted to at least bind at least one contaminant from the airflow.

8. Noise-protecting screen as claimed in claim 7, characterized in that the at least 0 one wall is composed of wood fibre concrete.

9. Noise-protecting screen as claimed in claim 7 or 8, characterized in that the main surface is catalytic and is able and adapted to convert at least one contaminant. S

10. Noise-protecting screen as claimed in claim 8, characterized in that the main surface is provided with a covering, in particular a coating, which comprises a catalyst, in particular titanium dioxide, for breaking down a contaminant.

11. Noise-protecting screen as claimed in one or more of the foregoing claims,0 characterized in that a channel between the inlet opening and the at least one outlet opening thereof comprises an optionally active air filter.

12. Noise-protecting screen as claimed in one or more of the foregoing claims, characterized in that spraying means are arranged in the channel, which are able and5 adapted to subject at least a part of a main surface of at least some of the walls, optionally periodically, to a cleaning agent such as water, and in particular rainwater.

13. Noise-protecting screen as claimed in one or more of the foregoing claims, characterized in that inlet openings are provided with a non-return valve which opens0 toward the channel in the case of an external overpressure and at least substantially closes in the case of an external underpressure.

14. Noise-protecting screen as claimed in claim 13, characterized in that the nonreturn valve comprises a flat valve body which is arranged for pivoting about a pivot shaft on a base side and lies in a valve seat counter to a spring tension.

S 15. Noise-protecting screen as claimed in one or more of the foregoing claims, characterized in that the transverse walls on a base side comprise at least one connecting opening whereby successive channels are in open communication with each other on the base side. 0

16. Noise-protecting screen as claimed in one or more of the foregoing claims, characterized in that the at least one outflow opening is provided in an outlet element, which is arranged rotatably about a vertical axis on a top side and which is able and adapted to orient itself to a wind direction with the outflow opening on a leeward side. 5

17. Noise-protecting screen as claimed in one or more of the foregoing claims, characterized in that at least one wall of a channel is able and adapted to enter into heat-exchanging contact with ambient light

18. Noise-protecting screen as claimed in claim 17, characterized in that at least0 one of the first and second walls, in particular the second wall, is at least partially translucent

19. Noise-protecting screen as claimed in claim 18, characterized in that the at least one wall has a surface with a dark tint, and is particularly at least locally black.5

20. Noise-protecting screen as claimed in one or more of the foregoing claims, characterized in that the first wall is provided on an outer side with a wall covering, and in particular with an exchangeable wall covering. 0

21. Noise-protecting screen as claimed in one or more of the foregoing claims, characterized in that, on a side of the second wall remote from the first wall, a second first wall extends in longitudinal direction and that the noise-protecting screen between the two first walls takes an at least substantially mirror-symmetrical form.

22. Noise-protecting screen as claimed in one or more of the claims 1 -20, characterized in that the second wall comprises at least locally an outer wall of a ribbon development.

23. Noise-protecting screen as claimed in one or more of the claims 1 -20, characterized in that the second wall comprises at least locally a wall of a tunnel or tunnel liner.

24. Noise-protecting screen as claimed in one or more of the foregoing claims, characterized in that the whole is based at least substantially on a sequence of successive screen elements, each comprising a system of successive transverse walls with a first wall segment on a first side and a second wall segment on an opposite side.

25. Noise-protecting screen as claimed in claim 24, characterized in that the screen elements comprise a foundation plate on which the system of transverse walls supports, wherein the second wall segment extends at least substantially to the foundation plate and the first wall segment is separated therefrom by a system of successive inlet openings.

26. Noise-protecting screen as claimed in claim 25, characterized in that the foundation plate comprises a reinforced concrete plate.

27. Noise-protecting screen as claimed in claim 25 or 26, characterized in that the foundation plate comprises a drainage gutter.

28. Noise-protecting screen as claimed in one or more of the claims 24-27, characterized in that coupling means are provided between successive screen elements for an at least substantially connected coupling of successive screen elements.

29. Noise-protecting screen as claimed in one or more of the claims 24-28, characterized in that at least one of the screen elements is able and adapted to form at least a curve section of a bend.

30. Noise-protecting screen as claimed in one or more of the claims 24-29, characterized in that the screen elements end in a closing element which comprises a closing wall on a side remote from a preceding screen element.

31. Noise-protecting screen as claimed in one or more of the claims 24-30, characterized in that the screen elements comprise crash barriers on a side directed toward the traffic route.

32. Noise-protecting screen as claimed in claim 31 , characterized in that the crash barrier comprises a number of barrier elements which lie one above the other and which extend in the longitudinal direction and which are each resiliently mounted via an individual system of barrier supports distributed in longitudinal direction, wherein the barrier supports of a barrier element cross a barrier element lying thereunder on a rear side.

33. Crash barrier of the type as applied in the noise-protecting screen as claimed in claim 32.

34. Screen element of the type as applied in the noise-protecting screen as claimed in one or more of the claims 24-32.