Abstract:
An environmentally sound method for applying or fixing elements ( 2 ) to constructed objects used for road traffic. The element ( 2 ), which is at least partially made of a material that can be liquefied by mechanical energy, is positioned on the surface, is pressed against the surface, and is simultaneously subjected to a local mechanical stimulation to liquefy the liquefiable material, and the element ( 2 ) binds with the surface upon re-solidifying. A mobile device ( 1 ) for applying elements ( 2 ) of this type, includes device that can travel via rolls or rollers ( 4, 5 ) and that is provided with at least one oscillating unit ( 10 ) including a sonotrode ( 6 ), a converter ( 7 ) and of an amplifier ( 8 ), and with a generator ( 9 ). The element ( 2 ) may be a marking or signaling element to be applied to roads or tunnel walls.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The invention relates to a method according to the preamble of the first patent claim. The method serves for attaching or fastening elements on surfaces of construction objects in the road traffic field, for example for attaching marking elements or signalling elements on roads or squares, in garages or multi-storey car parks or on house or tunnel walls, that is to say on surfaces which in particular consist of asphalt or concrete. The invention also relates to a device for carrying out the method and to an element being able to be attached with the method, according in each case to the preambles of the respective patent claims.  
         [0002]     Known methods for attaching for example markings onto road surfaces are essentially based on two different processes, namely a process of thermally creating a material fit and a process of chemically creating a material fit.  
         [0003]     According to a method of the first group, thermoplastic strips and the asphalt surface lying below this are melted down with a gas flame, so that the molten materials bond to one another after cooling. The disadvantage of this method lies in the fact that on the one hand a very large volume of the road surface needs to be heated and on the other hand the method is very time consuming due to the long heating-up and cooling-down phases. Furthermore the energy requirement is very high and the melting process is difficult to control and therefore little suited for automation. Handling of naked flames and gas containers furthermore entails safety risks and is therefore connected with an increased handling effort.  
         [0004]     According to a method of the second group, solvent-containing coatings of paint are sprayed onto the designated surface. For this method the surface needs to be thoroughly cleaned prior to being coated, and then the marking geometries need to be covered or suitable stencils need to be positioned. Sprayed markings are deposited however only in a very superficial manner and, due to wear and abrasion, have mostly only a short serviceable life. Furthermore, during application or during abrasion of the coats of paint, solvent, colour particles and other partly noxious substances get into the environment. It is further known to attach premanufactured markings to surfaces using adhesives, such attaching having the same disadvantages as discussed above.  
         [0005]     It is the object of the invention to provide a method for permanent or temporary attachment of elements to surfaces of construction objects in the road traffic field, i.e. to surfaces which in particular consist of asphalt or concrete.  
       BRIEF SUMMARY OF THE INVENTION  
       [0006]     According to the invention the elements, for example marking or signalling elements consist at least partly of a material which is liquefiable by way of mechanical excitation, e.g. of a thermoplastic material. This means that the element consists of a material with at least one liquefiable (e.g. thermoplastic) component, or at least a region of the element to be directed towards the surface on which it is to be attached consists of such a material. The element is positioned on the surface on which it is to be attached and then it is at least locally pressed against the surface and mechanically excited in a manner such that the liquefiable material is liquefied at least locally and temporarily, and after re-solidification forms a bond between the surface and the element. The surface onto which the element is pressed may also be partly liquefied by the mechanical excitation. The mechanical excitation is usually based on excitation by a sonotrode (piezoelectric excitation for higher frequencies, magnetostrictive excitation for lower frequencies). The excitation is preferably based on mechanical oscillation at a frequency lying in the range of ultrasound, and as the case may be also at lower frequencies. The frequencies are selected depending on the field of application. By way of varying the frequency the extent to which the liquefiable material and, as the case may be, surrounding regions (background) are liquefied or heated may be determined. The amplitude, the frequency and the excitation duration influence the extent of liquefaction and heating. A further essential aspect is the way in which the mechanical oscillation is coupled into the element to be attached or into the element region which is to be liquefied respectively. For such coupling, the element may e.g. be made to be part of the oscillating body. By partially liquefying and subsequent re-solidification, advantageously combined with simultaneous pressing, a bond is produced between the element and the surface on which the element is to be attached.  
         [0007]     According to the invention the energy used for liquefying the liquefiable material is introduced in a locally and temporally controlled manner. By way of this locally and temporally controlled application of energy, adjacent regions are not unnecessarily heated, which fact creates various advantages. On the one hand the bond can be created using considerably less energy. All the same, the resulting bond, due to the way and manner in which it is created, is extremely lasting and has a high loading capacity. On the other hand the bond can be created in considerably less time since considerably less time is required for introducing the required energy. The method according to the invention is also environmentally friendly since no further auxiliary agents such as adhesives, solvents or other bonding agents comprising noxious substances are used.  
         [0008]     The strength of the bond is influenced by the intensity of the mechanical energy (impulse, frequency) and/or the excitation duration. According to the field of application it is thus possible to create bonds which are very lasting, or which may be easily detached again. By way of longer excitation duration or by way of a more intense excitation as a result of a higher frequency or amplitude, a stronger bond is achieved, because e.g. more material is liquefied.  
         [0009]     The method according to the invention is suitable for the most varied applications in the field of road traffic, as for example in road construction, realisation of signs or markings, sealing of gaps, etc. Amongst other things the method is suitable for attaching marking strips or marking images which for example are supplied in the form of suitably punched films and are for example attached to the surfaces of streets or tunnel walls, e.g. stripes marking middle or edge of roads, arrows or lettering.  
         [0010]     The method according to the invention is also suitable for applying signalling elements which are to project functionally beyond the surface on which they are attached. Such signalling elements are for example to be understood as elements which are to be attached in the region of the centre line or an edge line of a road and which elements when driven across notify the driver by vibrating his vehicle. When required, such elements may be designed reflecting so that they may be better seen particularly in poor light conditions. In particular on motorways these elements may be designed such that they have properties which are different with respect to direction. One example of such an element reflects white in the travel direction and red in the opposite direction. By way of this a person driving on the wrong side of the road is made aware of his mistake. Other designs are also possible.  
         [0011]     The method according to the invention is particularly suitable for fastening elements which are fabric-like or are based on a film material. These in particular are middle lines and side lines on roads, markings for pedestrian crossings, stop lines, direction indicators (arrows) etc. The elements may be quasi endless (continuous lines) or limited. The film material of such elements advantageously comprises a two-dimensional or net-like substrate film which for example is provided with a coating being liquefiable by way of mechanical excitation. This mechanically liquefiable coating is provided on the one side of the substrate to be directed towards the road surface and it is even or comprises projecting elements which serve as energy directors, i.e. for concentrating the exciting mechanical energy in a manner such that a locally intensified melting-down occurs.  
         [0012]     The side of the elements to be directed towards the surface on which the element is to be attached may be coated with a liquefiable material only in regions. Instead of the coating, three-dimensional regions of the liquefiable material may be provided, for example pins, rings or other shapes, which are for example uniformly distributed over the surface of the element to be attached to the road surface or other surface. The position of such three-dimensional shapes is suitably marked on the opposite side from which the mechanical oscillation is coupled in, so that the mechanical energy may be selectively introduced in the correct locations.  
         [0013]     A further field of application of the method according to the invention is the fastening of reinforcements to surfaces of construction objects in the field of road traffic. From the state of the art there are known methods with which bridges, in particular bridges of concrete are restored by attaching strips of high-tensile, stiff fibres (e.g. carbon fibres) on the lower bridge side, i.e. in the region in which the structure is loaded in tension. Such strips relieve the bridge structure or allow it to be more loaded. According to the state of the art such strips are attached by way of adhesive which is a cost-intensive and thus expensive method. It is furthermore not very suitable due to environmental aspects. On attaching the strips, the fibres must be prestressed so that the structure is relieved in an effective manner from the very beginning. However prestressing is not linear but must be greatest along the middle and lowest along at edges of the bridge. Using the method according to the invention, it becomes possible to process the above described reinforcement strips very simply and also inexpensively in a continuous process. The reinforcement strips are pressed onto the surface of the construction object to be reinforced, they are prestressed depending on location and are then connected to the surface by way of mechanical excitation and pressure. Since the connection is created in a very short time, non-linear prestressing ensuring optimal results is easily possible.  
         [0014]     The bonds created with the method according to the invention may be permanent or may be only temporary. Temporary bonds are to be understood as bonds which are only to be present for a forseeable time duration. Such bonds make sense, in particular in the field of building sites where it is necessary to divert the traffic for a certain time. Such bonds are created in a very simple manner and they can be easily detached later. In the field of building sites it makes particular sense to attach temporary markings which comprise a film, for example in the form of an endless tape as a base structure and which comprise a coating being able to be bonded to the road surface by way of mechanical excitation. Using a suitable device, endless or limited signalling elements may be attached very simply in a continuous process. In order to detach the elements the same device may be used in a reverse way and manner (new liquefaction, detachment and then removal). The bonds may be formed such that the strips can be detached without special tools. Pretreatment of the surface on which the elements are to be attached, e.g. for drying such surfaces, may be effected by preheating the surface by e.g. using a hot roller which is more suitable than a gas flame. In certain cases such pretreatment (drying, priming) may not be required. The method may be applied for various element thicknesses and element geometries. Other than in the known melt-on processes, the material thickness can be optimized. The time required for the mechanical excitation may be reduced and the bonding improved by way of preheating. Bonds created according to the invention are characterised by their good adhesion on the most varied of porous surfaces. They display a good resistance to specific influences such as weather, wear, etc.  
         [0015]     Since the method has no influence on the geometry of the element to be fastened, customer-specific geometries can be realized, as well as customer-specific surface structures and colourings. A surface structure may be embossed during attaching by the tool used for attaching or by a subsequent tool. This surface structure may assume additional functions, e.g. creating noise when in contact with a rotating tyre, so that the driver is made aware that he is crossing the marking.  
         [0016]     The advantages of the method according to the invention may be summarized as follows: 
        Carrying out the method is extremely simple and gives high performance at low operating and maintenance expense;     Good bonding between the attached element and the surface on which it is attached is achieved due to liquefaction of a part of the material during the fastening procedure;     Improved bonding with respect to known methods using an open gas flame is achieved, due to the fact that no incineration occurs and no soot particles contaminate the bonding surfaces;     Very short process times (time for mechanical excitation and for resolidification or cooling) are possible;     The device for attaching the elements does not need to carry liquid, volatile or inflammable substances, which fact considerably increases the working safety;     The method is environmentally friendly since above all no volatile substances or auxiliary agents are applied.        
 
         [0023]     In combination with the following Figures the method according to the invention and some exemplary embodiments of devices for carrying out the method according to the invention, and of elements being attachable on construction objects using the method are described in more detail. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0024]      FIG. 1  is a perspective view of a first embodiment of a device for attaching marking strips;  
         [0025]      FIG. 2  is a perspective view of a second embodiment of a device for attaching marking strips, the device comprising a link chain;  
         [0026]      FIG. 3  is a perspective view of a third embodiment of a device for attaching marking strips, the device comprising a sonotrode roller;  
         [0027]      FIG. 4  is a cross-sectional view a section through a sonotrode roller; and  
         [0028]     FIGS.  5  to  8  show further examples of elements which are attachable to surfaces of construction objects of road traffic using the method according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0029]      FIG. 1 , in a greatly simplified manner, shows the essential elements of a first embodiment of a fastening device for attaching an element  2 , for example a marking element (marking strip) on the surface of a road, for example of asphalt or concrete. The element  2  to be attached is strip-like and is separated from a tape, wherein the tape is rolled on a supply reel  3 . The element  2  for example comprises a substrate material which is coated on at least one side. It is for example a strip of plastic or metal film being coated with a material which can be melted down using mechanical excitation. This meltable or liquefiable material is for example a thermoplastic polymer material (e.g. polypropylene). The element  2  may also consist completely of the meltable material.  
         [0030]     While the fastening device  1  is moved in the working direction tape for the element  2  is rolled from the supply reel  3  and by way of a first roller  4  is pressed onto the surface (e.g. road surface) on which the element  2  is to adhere. The working direction is shown by an arrow X. Behind the first roller  4  three sonotrodes  6  are provided being actively connected to a converter (sound transducer)  7  and to a mechanical amplifier  8 . The converter  7  which serves for converting electrical into mechanical oscillation is driven via a generator  9 . The converter usually comprises piezoelements converting electrical oscillation with typical frequencies above 20 kHz into suitable mechanical oscillation. The working range of the converter is selected to suit the application. Normal frequencies lie in the range between 2 kHz and 400 kHz.  
         [0031]     The amplifier  8  functions as a mechanical amplifier due to its configuration. It transforms oscillation, concentrates this oscillation and transmits it to the sonotrode  6 . The sonotrode  6  together with the amplifier  8  and the converter  7  forms an oscillating unit  10 . The elements of the oscillating unit  10  are optimised to the field of application or to a frequency and preferably oscillate in resonance. The oscillating unit  10  excites into oscillation the element  2  and where appropriate the material of the surface to which the element  2  is to be attached. Through internal and external friction caused by the excitation, the element is melted, at least locally, and as the case may be, the surface material too. Due to high shear effects a high degree of plastification is achieved. The element  2  is advantageously pressed (roller  5 ) against the surface on which it is to be attached during liquefaction and afterwards, so that after resolidification the element and the surface are connected to one another. The shown fastening device  1  comprises three oscillating units  10 . These may be activated individually. It is of course to be understood that a device may have a different number of oscillating units.  
         [0032]     Behind the three oscillating units  10  there is a second roller  5  which presses the element  2  against the surface during the cooling. The first and the second rollers  4 ,  5  serve preferably for setting the distance between the sonotrodes  6  and the element  2 . The fastening device  1  serves for fastening the element  2  in a continuous or in a discontinuous process.  
         [0033]     A cutting device  11  is arranged behind the second roller  5 . This device serves for cutting off the element  2  if the marking strip to be deposited is not continuous as is shown. The discontinuous case is indicated schematically in  FIG. 1  by a first element  2  of a marking tape being shown behind the fastening device. In front of the first roller  4  there is a detaching device  12  which serves for detaching elements  2  from a surface on which they have previously been attached, following re-liquefaction of the element by the oscillating units.  
         [0034]     The type of the oscillation and the manner of its coupling into the element  2  to be fastened is determined by the shape of the sonotrode  6  and the other elements of the oscillating unit. Preferred are elongate or cylindrical shapes which extend over the whole width of the element  2  and taper downwards, i.e. towards the element  2  to be treated.  
         [0035]      FIG. 2  shows a further embodiment of a fastening device  1  for attaching an element  2  to a surface. The fastening device  1  comprises two lower rollers  13  and two upper rollers  14  which serve for guiding a circulating link chain  15 . The link chain  15  on its outer surface has an embossing structure  16  which serves for embossing a surface structure  17  into the element  2 . A sonotrode  6  is arranged between the two lower rollers  13  and serves for the indirect excitation of the element  2  via the link chain  15 . The element  2  being processed is arranged between the link chain  15  and the surface on which it is to be attached. The tape-like material for the element  2  is stored on a supply reel  3  and is pulled from this during the process. A cutting device  11  serves for cutting off an element  2  of material on the supply reel  3 . This cutting device may be arranged in front of or behind the link chain  15 . Different surface structures may be embossed into the element  2  by way of using link chains  15  with different embossing structures  16 .  
         [0036]     For driving the fastening device  1 , preferably electrical or hydraulic motors (not shown in detail) are used. The fastening device  1  is designed preferably self-travelling or may be used as a part of another machine. For processing differently shaped elements  2  it has a corresponding configuration.  
         [0037]      FIG. 3  shows a further embodiment of a fastening device  1  for attaching elements  2  on a surface. The fastening device  1  comprises an oscillating unit  10  with a rotating sonotrode  6 . The sonotrode  6  is designed as a sonotrode roller which is preferably excited by a converter  7  to oscillate in a radial direction. The oscillation is transmitted to the element  2  and has the effect that this element is plastified locally. Rollers  4 ,  5  are arranged in front of and behind the sonotrode roller  6  in the working direction (x-direction). These rollers serve for pressing the element  2  onto and into the surface of the background. If applicable, rollers  4 ,  5  are also guiding and support rollers. A cutting and detaching device  11 ,  12  are arranged in front of and behind the rollers. These devices comprise a blade each and when activated cut off the element  2  or detach it from the surface on which it is fastened.  
         [0038]      FIG. 4  shows a schematic section along the axis of the sonotrode roller  6  according to  FIG. 3 . As may be recognised, the sonotrode roller  6  consists of a plurality of stacked disks  18  being connected to one another centrically via thin locations  13 . The oscillation of the converter  7  is preferably introduced perpendicularly to the axis A of the sonotrode roller.  
         [0039]     The invention may be summarized as follows: an environmentally friendly and safe method for attaching or fastening elements on surfaces of construction objects in the field of road traffic which method comprises: positioning the element to be attached on the surface on which it is to be attached and liquefying the element by local mechanical excitation during an excitation time so that the element on its side facing the surface and where appropriate also the surface onto which the element is pressed is locally melted in a manner such that after cooling the element is fastened on the surface. A travelling device for attaching a marking strip for example onto the surface of a road comprises a means being capable of travelling on rolls or rollers  4 ,  5 , and further comprising at least one oscillating unit  10  consisting of sonotrode  6 , converter  7  and amplifier  8  and a generator  9 . The marking strips attached onto the surface of the road apart from their colouring may have a profiling which produces acoustic or various optical signals, such as e.g. white reflection in the one direction and red reflection in the other direction.  
         [0040]     FIGS.  5  to  8  show further elements  2  which may be attached to surfaces of construction objects according with the method according to the invention. These elements are discrete elements which may not be wound off from a supply reel. They may however be positioned in a per se known manner at predefined time intervals below the oscillation tool of a fastening device moving at a constant speed for example along a road, so that they are deposited onto the road surface at constant distances to one another. The elements may also be attached individually with a hand apparatus known from ultrasonic welding or with a similar apparatus.  
         [0041]      FIG. 5  shows a flat element  2  which is shown to be rectangular, but which however may have any shape. The element along the edge comprises nubs  20  arranged on the one element side which is to be directed towards the surface on which the element is to be attached. At least these nubs consist of the liquefiable material, where appropriate the whole edge region or the nub-side of the edge region consist of this material. For the attachment process, the element according to  FIG. 5  is positioned and is pressed against the surface and simultaneously excited (e.g. with an excited sonotrode) at least in its edge region (indicated by arrows).  
         [0042]     The element  2  according to  FIG. 6  is disk-like and for example comprises a reflector in the middle of its side facing outwards. On its opposite side which is to be directed towards the surface on which the element is to be attached, the element  2  comprises a fastening ring  2 . In the region of this ring  21  the element is excited from the outside, as this is illustrated by the arrows, and is pressed against the surface, for example with a corresponding tubular sonotrode. The fastening ring  21  may also be formed by a row of pins or nubs arranged along the edge of the element  2 . At least the fastening ring  21  or the pins or nubs serving the same purpose, or where appropriate the whole element  2  consist of a material which is liquefiable by way of mechanical oscillation.  
         [0043]      FIG. 7  shows a disk-like element similar to the element of  FIG. 6 . An electronic module  25  with an aerial  16 , as is used for traffic directing or controlling systems, is arranged on the side facing the surface on which the element is to be attached. By fastening the element with the fastening ring  21  a hermetically closed space is created for the electronic module. The element  2  according to  FIG. 7  may of course also have a shape other than a disk-like shape.  
         [0044]      FIG. 8  shows a further element with an integrated electronic module  25  comprising an aerial  26 . Module and aerial are positioned between two element parts  2 . 1  and  2 . 2 , wherein these two element parts may for example be connected to one another on fastening of the whole element. The element part  2 . 2  directed towards the fastening side of the element consists at least partly of the liquefiable material. The two element parts  2 . 1  and  2 . 2  may also be connected to one another e.g. by an adhesive prior to attachment of the element on the surface. It is also possible to integrate the electronic module into the element during manufacturing of the element  2  by e.g. moulding.