Method and device for cleaning a road surface of very open asphalt concrete

Abstract: For the purpose of removing dirt such as sand, mud, rubber particles and the like from the open spaces in a road surface of very open asphalt concrete, a flushing liquid is applied to the road surface and subsequently removed with the entrained dirt (32). The parts deeper down (31) can also be cleaned well if the road surface is covered locally in an essentially liquid-tight way (14), and in at least two road surface areas at a distance from each other and adjacent to the covered surface a pressure difference is generated in such a way that a liquid flow (31) forms in the covered road surface area. A device for carrying out this method comprises a covering element (1) for covering a road surface part, means for feeding the flushing liquid to the very open asphalt concrete in a first road surface area along a first peripheral edge of the covering element (1), and also means (26) for discharging the flushing liquid from the very open asphalt concrete in a second road surface area along a second peripheral edge of the covering element (1).

Description: The invention relates to a method for removing dirt such as sand, mud and possibly rubber particles and the like from the open spaces in a road surface of very open asphalt concrete, which road surface is covered locally by a covering which is movably supported with respect to the road surface, the covering having a contact surface which is in contact with the road surface, wherein a liquid is applied to the road surface and is then removed with entrained dirt by means of a vacuum which is applied at the locally covered road surface. Such method is known from DE-A-9017025. The covering applied has flexible strips which delimit a space accommodating jet nozzles. In operation, the covering with the flexible strips is dragged over the road surface to be cleaned, while jetting a liquid onto said surface. This method has the disadvantage that the road surface is cleaned only superficially, even though the liquid is compelled to flow beneath the flexible stips, through the porous upper layer of the road surface. The object of the invention is to improve said method, such that the complete layer is thoroughly cleaned. This object is achieved in that the contact surface of the covering is kept immobile with respect to the road surface during removal of water and entrained dirt from said road surface while the covering is moving. The contact surface of the covering provides a reliable seal without any gaps between the covering and the road surface, thus compelling the liquid to flow through the porous layer itself and thereby cleaning said layer over its full thickness. Preferably, the vacuum is applied through a passage which is central with respect to the covered road surface, and the liquid is applied outside the periphery of said covered road surface in such a way that a liquid flow running from the edge of the covered road surface to the central passage forms. By the application of a vacuum, the contact surface is compressed firmly onto the road surface, which gives an even better seal and thereby a better cleaning action. The pressure difference in combination with the covering, which is impermeable with respect to the liquid applied to the road surface, forces said liquid to take a flow path through the open spaces in the very open asphalt concrete. By selecting the dimensions of the covering in a suitable way, it can be ensured that the liquid flow thus produced also actually spreads over the whole thickness of the layer of asphalt concrete, and does not merely select the shortest route through the top layer. In order also to remove obstinate dirt, it can be beneficial to vary the vacuum. The vacuum can be interrupted, for example intermittently, with the result that a shock effect occurs in the liquid flow, which loosens the dirt. The invention is furthermore related to a device for carrying out the above method, comprising a covering element for covering a road surface, which covering element has a contact surface which can be brought into contact with the road surface, means for feeding a liquid, suction means for discharging the liquid with entrained dirt, and displacement means for displacing the covering element with respect to the road surface. According to the invention, means are provided for keeping the contact surface of the covering element immobile with respect to the road surface during removal of water and entrained dirt from said road surface while the covering element is being displaced with respect to the road surface. The supply or discharge of the flushing liquid can be carried out by, for example, pressure means or suction means which can be placed on the road surface. The covering passage of the device preferably comprises an essentially central passage which is connected in a liquid-tight manner to a feed or a discharge pipe. If a central discharge pipe is provided, the flushing liquid with dirt can be sucked away, and the flushing liquid can flow in uniformly from all sides. In order to ensure that no "leakage" can take place here, the covering element comprises a relatively soft material, the surface of which can adapt to the irregular surface shape of the asphalt concrete. Good results can be obtained if the covering element is of an approximately constant width measured from the passage. Said width must be such that the flushing liquid spreads over the whole thickness of the layer of very open asphalt concrete, and can thus entrain all dirt. According to a first embodiment, the covering element has a circular periphery. The passage is situated centrally here, in such a way that the distance from the periphery is the same everywhere. According to a second embodiment, the covering element has a rectangular periphery, and the passage is slit-shaped. In the case of these two embodiments it is conceivable to take a single piece of material for the covering element. In a device designed in this way the covering element must be moved stepwise over the road surface to be cleaned. For proper functioning of the device it is not just important to select the width of the covering element ensuring that it is not too small. If the width is selected too large, the flushing liquid must cover such a long distance through the open spaces in the very open asphalt concrete that the pressure difference required for producing the desired liquid flow is hardly attainable any longer. Of course, several of such covering elements with relatively small dimensions, and each with its own central passage, could also be used side by side. At each stage a number of road parts can then be cleaned simultaneously, thus increasing the working speed of the device. Another possibility, which is preferred, for increasing the working speed is the embodiment in which the slit-shaped passage is bounded by four endless belts, each of which is guided over corresponding pairs of rollers, of which the shafts are suspended in a frame and are parallel to two slit edges lying opposite each other. Such a device can travel over the road surface, cleaning as it goes, and thus produces a continuous action. Two of these belts lie next to each other in each case near the corners of the slit-shaped passage. Since all belts move at the same peripheral speed, it is no problem at all if the edges of the belts touch each other. A good sealing can be obtained in this way, and it can be further improved if the device is placed on the road surface, and the fairly soft material of the belts is compressed a little here under the influence of the vacuum and the weight of the device itself, and thus bulges outwards. In the case of this embodiment, provision is made for a slit-shaped nozzle extending in a close-fitting manner in the slit present between the belts in the direction of the bottom parts of the belts to be placed on the road surface. The walls of the nozzle adjoining the inner belts preferably extend to the level of the shafts, while the other two walls extend further to near the surface of the belts and in that direction flare out to shut off the opening between the inner belts and the outer belt concerned. In this case the nozzle opens out at the side facing away from the bottom parts into a pipe which is connected to a source of vacuum for sucking up the flushing liquid. An auxiliary frame is also provided according to the invention, the internal dimensions of which frame are greater than the corresponding external dimensions of the frame, which auxiliary frame has on its periphery rubber strips, in such a way that the auxiliary frame can form a basin which can be dragged along with the frame and is essentially watertight relative to the road surface. In an alternative embodiment, the auxiliary frame is provided on its periphery with four mutually sealing, endless belts which connect to each other and are guided over corresponding pairs of rollers of which the shafts are suspended in the auxiliary frame and are parallel to the shafts of the frame. According to a further alternative embodiment, the auxiliary frame is provided at its longitudinal sides in each case with an endless belt, and at its transverse sides in each case with a sealing roller having a surface of essentially the same material as the belts, which sealing rollers rest with their end faces against the parts of the belts guided around over the rollers. In order to improve the cleaning action even further a brush is provided at the front side of the auxiliary frame, viewed in the direction of movement for removing or loosening dirt present on the road surface. The service life of the belts is improved in case they are provided at their outer surface with a supple layer of wear-resistant material. The covering element may comprise closed cell foam rubber in order to provide a proper sealing with respect to the road surface. The invention will be explained further below with reference to an example of an embodiment shown in the figures. Figure 1 shows a view in perspective of the underside of the device according to the invention. Figure 2 shows a view along section II-II of Figure 1. The device shown in Figure 1 comprises a rectangular frame 1, composed of sections 2, 3. An auxiliary wheel 4 is provided at the four corner points of frame 1, by means of which wheel the frame can be supported on a road surface. These auxiliary wheels 4 also limit the compression of the belts 11, 12, 15, 16. Four shafts are suspended in frame 1, i.e. the outer shafts 5, 6 and the inner shafts 7, 8. Fitted on the outer shafts are rollers 9, 10, over which the outer endless belts 11, 12 are guided. Rollers 13, 14 are provided on the inner shafts 7, 8. The inner belts 15, 16 are now guided in each case over rollers 9, 13 and rollers 10, 14 respectively. The rollers 13, 14 also provide an additional support for the central region of the outer belts 11, 12. As shown, the inner belts 15, 16 lie with their edges against the outer edges of outer belts 11, 12, thus ensuring the seal at that point. The inner belts can be of a substantial width, for example several metres, so that a road surface part the width of a road lane or a part thereof can be cleaned in each case. The shafts must, however, be so rigid that even in the central part of these belts sufficiently great pressure on the road surface remains ensured. Shaft 9 is suspended in a fixed support 17 on frame 1. The shafts 10, 13 and 14 are each suspended in a suspension in the form of a slide block 18, 19, 20. These slide blocks 18 - 20 are supported between section 2 of frame 1 and parallel auxiliary sections 21, 22 welded thereto. The shafts 10, 13 and 14 can be displaced in a suitable manner by means of partially visible tensioning elements 23, 24 and 25, for tensioning the belts 11, 12, 15 and 16. A nozzle, indicated in its entirety by 26, is situated in the gap formed between the belts 11, 12, 15 and 16. This nozzle is rectangular and comprises two straight plates 27 and two flared plates 28. The plates 27 rest against the belts 15, 16 and extend no further than to the centre between the top and bottom parts of said belts 15, 16. The plates 28 are welded to the plates 27 to form a closed channel. However, plates 28 extend further than the plates 27, to a little before the surface of the belts. This can be seen in Figure 2. The plates 28 also extend over a short distance between the edges of the belts 11, 15, 16 and 12, 15, 16 facing each other. In operation, the belts are in friction contact with the plates 27, 28, but in this case the flushing liquid acts as a lubricant, so that hardly any wear occurs. The plates 27, 28 are covered at the top side by partition 29, in which a channel 30 which is connected to a source of vacuum (not shown) opens out. If the device is of greater width, several channels can, of course, also be used next to one another. In operation, a liquid flow, shown by arrows 31, 32 in Figure 2, is created by the vacuum. The flow 31 through the very open asphalt concrete ensures that the dirt present in that asphalt concrete is entrained. Owing to the very soft material layer 33 of the belts, such a sealing of the surface of the asphalt concrete is obtained that no leakage over that surface can occur. The compression of the soft material layer 33 on the road surface is ensured by, on the one hand, the rollers 9, 10, 13 and 14 and, on the other, the pre-tension in the belts. This pre-tension is absorbed by the material layer 34 of high tensile strength, which is guided over the rollers in question. However, the vacuum also makes a contribution to the compression of the belts on the road surface. Motor 35 drives the shaft 6 by means of chain transmission 36. The framework 37, comprising sections 38, 39, is also shown in Figure 1. The sections 38 are shown in cross-section; one of the sections 39 is omitted. This framework 37 is dragged along when the device is travelling over the road surface. The framework rests on the road surface by means of the rubber strips 40, 41. They form a seal relative to the road surface, in such a way that a layer of water of a level which is great enough to ensure proper functioning of the device can be applied within the framework. The framework shown is capable of being dragged along to the left in the figure. Strip 41 is therefore turned back and fixed by both edges to the corresponding section 38. Strip 41 cannot, therefore, flip over underneath the section 38 when the framework is being dragged along.

Claims: Method for removing dirt such as sand, mud and possibly rubber particles and the like from the open spaces in a road surface of very open asphalt concrete, which road surface is covered locally by a covering which is movably supported with respect to the road surface, the covering having a contact surface which is in contact with the road surface, wherein a liquid is applied to the road surface and is then removed with entrained dirt by means of a vacuum which is applied at the locally covered road surface, characterised in that the contact surface of the covering is kept immobile with respect to the road surface during removal of water and entrained dirt from said road surface while the covering is moving. Method according to claim 1, characterised in that the vacuum is applied through a passage (26) which is central with respect to the covered road surface, and in that the liquid is applied outside the periphery of said covered road surface in such a way that a liquid (31, 32) flow running from the edge of the covered road surface to the central passage (26) forms. Device for carrying out the method according to claim 1 or 2, comprising a covering element (11, 12, 15, 16) for covering a road surface, which covering element has a contact surface which can be brought into contact with the road surface, means for feeding a liquid (31, 32), suction means for discharging the liquid with entrained dirt, and displacement means for displacing the covering element with respect to the road surface, characterised in that means are provided for keeping the contact surface of the covering element immobile with respect to the road surface during removal of water and entrained dirt from said road surface while the covering element is being displaced with respect to the road surface. Device according to claim 3, characterised in that the covering element (11, 12, 15, 16) has a central passage (26) which is connected to the suction means, and that the means for feeding the liquid are provided on the outside of the covering element (11, 12, 15, 16). Device according to Claim 4, in which the covering element has an essentially central passage which is connected in a liquid-tight manner to a discharge pipe. Device according to Claim 5, in which the covering element comprises a relatively soft material, the surface of which can adapt to the irregular surface shape of the asphalt concrete. Device according to Claim 5 or 6, in which the covering element is of a constant width going from the passage in the peripheral direction. Device according to Claim 7, in which the covering element has a circular periphery. Device according to Claim 7, in which the covering element has a rectangular periphery, and the passage is slit-shaped. Device according to Claim 9, in which the slit-shaped passage is bounded by four endless belts (11, 12, 15, 16), each of which is guided over corresponding pairs of rollers (9,10,13,14), of which the shafts (5,6,7,8) are suspended in a frame (1) and run parallel to two slit edges lying opposite each other. Device according to Claim 10, in which in the direction parallel to the shafts the parts of the belts lying next to each other touch each other. Device according to Claim 10 or 11, in which in the direction at right angles to the shafts in total four shafts are provided, and the outer belts (11,12), viewed in the shaft direction, are guided over rollers (9,10) on the outer shafts, while the inner belts (15,16) are each guided over a roller on an outer shaft and a roller (13,14) on an inner shaft lying on the same side of the slit as the outer shaft concerned. Device according to one of Claims 10 - 12, in which a slit-shaped nozzle (26) is provided, extending in a tight fit in the slit present between the belts, in the direction of the bottom parts of the belts to be placed on the road surface. Device according to Claim 13, in which the walls (27) of the nozzle adjoining the inner belts extend to the level of the shafts, while the other two walls (28) extend further to near the surface of the belts and in that direction flare out to shut off the opening between the inner belts and the outer belt concerned. Device according to Claim 13 or 14, in which the nozzle opens out at the side facing away from the bottom parts into a pipe which is connected to a source of vacuum for sucking up the flushing liquid. Device according to Claim 12, 13, 14 or 15, in which one shaft (5) is fixed, and the other shafts (6,7,8) are adjustable, for tensioning the belts. Device according to Claim 12, 13, 14, 15 or 16, in which at the level of the outer belts the inner shafts (7,8) are also provided with rollers (13,14), in order to support said belts. Device according to one of Claims 10 - 17, in which the frame is provided with auxiliary wheels (4), for supporting it in such a way that the belts are compressed to a predetermined extent under the influence of the weight and the vacuum. Device according to one of Claims 10 - 18, in which a drive motor (35) which is connected to one or more shafts (6) is provided. Device according to one of Claims 10 - 19, in which each belt has a supporting layer (34) of high strength which is in contact with the rollers. Device according to one of Claims 10 - 20, in which an auxiliary frame of which the internal dimensions are greater than the corresponding outer dimensions of the frame is provided, which auxiliary frame can form a basin which can be dragged along with the frame and is essentially watertight relative to the road surface. Device according to Claim 21, in which the auxiliary frame is provided on its periphery with rubber strips (40,41) by means of which the auxiliary frame can be supported on the road surface. Device according to Claim 21, in which the auxiliary frame is provided on its periphery with four mutually sealing, endless belts which connect to each other and are guided over corresponding pairs of rollers of which the shafts are suspended in the auxiliary frame and are parallel to the shafts of the frame. Device according to Claim 21, in which the auxiliary frame is provided at its longitudinal sides in each case with an endless belt, and at its transverse sides in each case with a sealing roller having a surface of essentially the same material as the belts, which sealing rollers rest with their end faces against the parts of the belts guided around over the rollers. Device according to Claim 21, 22, 23 or 24, in which at the front side of the auxiliary frame, viewed in the direction of movement, a brush is provided, for removing or loosening dirt present on the road surface. Device according to one of Claims 10 - 25, in which the belts are provided at their outer surface with a supple layer (33) of wear-resistant material. Device according to one of Claims 3 - 26, in which the covering element comprises closed-cell foam rubber.

Inventors: HEERKENS JOSEPHUS CORNELIS PET, VAN BOCHOVE GERRIT GIJSBERTUS, HEERKENS, JOSEPHUS CORNELIS PETRUS, VAN BOCHOVE, GERRIT GIJSBERTUS
Applicants: HEIJMANS WEGENBOUWMIJ, WEGENBOUWMAATSCHAPPIJ J. HEIJMANS B.V.
Application year: 1993
Main classification: E01H1
IPC codes: E01H1