The invention relates to the field of three-dimen- sional markers intended as temporary road closing markers, warning markers etc. on roads and the like, and as other forms of temporary indicators, and to a device for making such markers. A specific example of when markers of this type are required is in connection with painting of lane, centre, road edge and pedestrian lane lines and for temporary cordoning-off of areas for traffic accidents and the like. For warning drivers not to drive over freshly painted markings before they have dried, or in order to quickly cordon off traffic accidents, markers of the type intended here can be placed at suitable points and with suitable spacing.

For temporary marking in connection with road paint¬ ing, traffic accidents etc., warning markers are now put out, which often have the shape of triangles or cones and are made of sheet metal or plastic. For road painting for example, special personnel are required to put out and remove these markers. The handling is expensive and in- ^• volves hazards to the personnel.

The purpose of the present invention is to remove these disadvantages in the known art and produce temporary markers which are easily put in place and which save both materials and personnel.

This is achieved according to the invention with the method of obtaining a three-dimensional marker of the type mentioned by way of introduction, which is characterized by placing on the road surfaces or the like one or more foam bodies which are stable during a predetermined period of time and which adhere thereto. This foam body prefer¬ ably consists of an air-mechanically processed foam of air, - water and a foaming concentrate.

The foam can be based on a foaming component of in principle the same type as is used in foam for fire- extinguishing purposes, i.e. high foaming agents amongst

oil-based as well as cation-active, anion-active and non ion active synthetic tensides. Examples thereof are fatt alcohol sulphonates and dodecyl benzene sulphonates, e.g. ammonium lauryl ether sulphate. Even protein foam, such as casein foam, can be used. In addition to the foam- forming component, the foam-forming concentrate (which i the material available on the market and which is dilute with water into a so-called premix before being worked with air into a finished foam) also contains a solvent for the foam-forming component and a foam-stabilizing additive of known type. One example of a suitable solven for the above-mentioned ammonium lauryl ether sulphate i diethylene glycol monobutyl ether. In contrast to fire- extinguishing foam, there is no additive to enhance the flowability of the foam; rather the foam is allowed to b heavy with high viscosity and stickiness for cohesion. A foam with small bubbles of approximately uniform size is desirable according to the invention. The air enclosures between the bubbles will thus be reduced, making the foa stronger and able to resist bad weather and-wind and wil not collaps before the foam body has completed its intended task. If, after completing its task, the foam body has not collapsed by itself by being provided durin preparation with the right amount of foam stabilizer, it can easily be disintegrated by being sprayed with a foam destroying solvent or the like, or it can be quite simpl swept away with a brush. By selecting a premix with a concentration of at most 10 parts by volume and preferab about 1-2 parts by volume foam concentrate per 100 parts by volume water and using a foam generator which makes very small foam bubbles with ^' the correct air setting, this can be achieved. Such a foam generator is, for example, a stationary brush with radial, tight steel bristles placed in a tube. According to another embodiment, the foam can also be of chemical origin, i.e. obtained by adding a chemica blowing agent to an organic material, e.g. a more or les liσuid resin product. After activation at a certain

temperature, this blowing agent causes the resin product to expand into a foam body according to the invention.

The size and appearance of the foam bodies must of course be adapted from case to case to the intended purpose. For marking on a road surface, elongated ridges or pointed "piles" should be the most usual shapes. The foam bodies can also be provided with colors or color combinations suited to the marking purpose. It is also possible to provide them with light-reflecting, e.g. fluorescent, coating for use at night.

The invention will be illustrated in more detail below with reference to a preferred device for making foam bodies according to the invention.

Fig. 1 shows a block diagram with the main compo- nents included in such a device.

Fig. 2 shows in detail a preferred discharge device 3 as seen from the front, and

Fig. 3 shows the same discharge device in cross section at III-III in Fig. 2. A device for making a foam body according to the invention comprises a container 1 under pressure (Fig. 1) for the premixed, liquid foam-forming preparation, a form generator 2 connected to said container for mechanical working of the preparation with the aid of air into foam, and a discharge unit 3 connected to the foam generator via a tube and which determines the final size and shape of the foam bod . Between the foam generator 2 and -he discharge unit 3 there should be sufficient space for ex¬ pansion for the foam, e.g. a 3-6 meter long hose or pipe. The device can be portable or mobile and be stationary or in movement when the foam body is discharged creating the marking.

Fig. 1 shows a block diagram of an exar.ple of a device according to the invention, in which the three main components, i.e. the container 1, the foam generator 2 and the discharge unit 3, are operatively connected to each other via control units 4 for, firstly, regulating the amounts of air and premix fed to the foam generator 2',

secondly, opening and closing the foam feeder tube (30 in Figs. 2 and 3) to the discharge unit 3 ", and, thirdly, discharge of the foam body made in the discharge unit 3. The control units 4 can comprise timers and relays for example, which open and close valves and the like. The system can be controlled by time _r or distance travelled _y and c-an be operated pneumatically, hydraul ically or purely mechanically.

The individual components in the system can be built together as desired and thus, for example, the foam generator 2 can be built into the container 1 and form a single unit with the container. The system can suitably be built together into a compact unit, on wheels for example, and can be coupled directly to a road-painting truck for example. It is then possible to use the truck's compressor to supply air to the system.

The device functions in principle in the following manner: Premix is filled into the container, i.e. a mixture of foam-forming concentrate and water in a volume ratio of for example 1.5 : 100. Both the container 1 and the foam generator 2 are fed with compressed air from a compressor and the premix can be under a pressure of abou 6 bar. From the container 1 the premix is fed to the foam generator 2 into which predetermined proportions of air and premix are fed, forming foam which is allowed to expand in the tube 30 up to the discharge unit 3. The discharge unit 3, which is shown in more detail in Figs. and 3, can be controlled for example so that the foam chamber 31, in which the foam body is formed, is filled with foam for about three seconds, whereafter the dis¬ charge"plate 32 _r which is hydraulically controlled for example, is folded down and pushes out the foam body. It has proved suitable to use a push-out means in the form o a piston hydraulically operated by a cylinder 36. In orde to affect the shape of the foam body formed in the foam chamber 31 as little as possible, it is possible to give the push-out device the following velocity gradient: The discharge plate 32 during the first 3/4 of its pat from

the position shown in Fig. 3 to the stationary bottom plate 33 has an accelerated movement, but has a retarded movement during the last 1/4. The plate will thereby carefully cut off the foam body without remnants of the foam body trailing after and forming a tail. The foam chamber can have a height of about 300 mm for example, and a width of about 175 mm, and the plate can be of acid-proof steel.

After a foam body has been pushed out of the foam chamber 31, the control unit 4 determines via time or distance measurement (e.g. after 20 seconds or after 30 meters) when the next filling of the foam chamber with foam from the foam generator is to be initiated etc. Thus the device can operate completely automatically. As was mentioned above, even simple portable systems comprising said main components can be made for use where connection to painting machines or the like is impossible or unnecessary.