Several solutions have become known for the determination of the hardness of road surfaces. The measuring device appearing in the patent description registration number HU 199.018 is one of these. The essence of the construction is that a measuring disc with a point-like measuring head is fixed to a frame structure so that it may rotate and which frame structure may be towed by a vehicle. On meeting the road surface the measuring head moves the measuring disc in an upwards direction nearly perpendicular to the road, meanwhile the measuring head itself, as a consequence of the force on it due to the mass of the disc, penetrates the surface to a certain degree. There is a measuring part-unit fixed between the measuring disc and the frame structure that determines a value proportionate to the vertical displacement of the measuring disc. From this value the surface hardness can be determined.

The disadvantage of the solution is that during the rolling of the measuring disc delineated by a cylinder-jacket when in the moving process the measuring head meets the road and the measuring disc rises, following the roll over the measuring head the disc falls back to the road. Due to these regularly repeated impacts both the disc and the measuring head are subject to heavy-duty use, and so is quickly worn or deformed. As a result of the physical damage and wear the values provided by the measuring device are incorrect, and so in essence the measuring device becomes useless. As a consequence of the presented deficiency the measuring disc of the measuring device and the measuring head have to be frequently replaced, which increases the time required for the measuring, and over and above this it increases the measuring costs.

Our aim with the solution according to the invention was to overcome the deficiencies of the known measuring devices and to create a version that retains the condition of the measuring disc and measuring head and also reduces the amount of time necessary for the measurement, and the measuring costs as well as improve the measuring precision due to the moderation of deformation and wear.

The recognition that led us to the structure according to the invention was that if the rolling edge of the measuring disc is given a form different from the usual, and the measuring member is positioned in a new way on the measuring disc, then during measurement the measuring disc's repeated heavy impacts with the road surface can be terminated, and so the task can be solved.

In accordance with the set aim the measuring device according to the invention for the continuous determination of the hardness of road surfaces-which contains a frame structure, a measuring disc and rolling members attached to the frame structure and a signal transformer and measuring part-unit connected to the measuring disc through a mediating part-unit, the frame structure has a bearing body and an swinging-member that may be moved as compared to the bearing body, the measuring disc is connected to the swinging-member of the frame structure through a main axle so that it may rotate, while the rolling members are connected to the bearing body with the help of supplementary axles, and the measuring disc has a measuring head-is formed so that the rolling edge of the measuring disc is of a cycloid form, and the measuring head is positioned in the fixing zone falling in the vicinity of the closing section connecting the starting point and finishing point of the rolling edge.

A further criterion of the measuring device according to the invention is that the fixing zone has an accepting seating, and the main axis of the accepting seating is radial with respect to the measuring disc.

In a possible version of the measuring device the accepting seating of the fixing zone is at least partly surrounded by a supporting surface.

Again in a different construction form of the invention the measuring head is a hard metal body delineated by a conical surface ending in a spherical shell, and the measuring head has a clamping stem with a fixing form positioned on the clamping stem.

A favourable feature from the point of view of the measuring device may be that the longitudinal axis of the measuring head and the main axis of the accepting seat of the fixing zone are coaxial.

The most important advantage of the measuring device according to the invention is that due to the new form of the measuring disc, the unique positioning of the measuring head and its fixing method the repeated falling of the measuring disc onto the road surface can be prevented, and so the deformation of the measuring disc, and furthermore, the wearing of the measuring head can be reduced to a large extent. As a result of the less frequent replacements due to damage to the measuring discs the measuring time and with this the measuring cost can be reduced.

Another advantage is that due to the reduction in the wear on the measuring head the requirement to replace the measuring heads is reduced, as a consequence of which the number of correction tasks that have to be carried out when positioning a new measuring head is also reduced. The reduction of the number of corrections further aids the accomplishment of continuous measurement and leads to a further significant reduction in the time required to carry out the measurement.

Another favourable feature is that due to the reduction of the deformation of the measuring disc and the wear of the measuring head the measuring precision also increases, which widens the scope of use of the results.

The measuring device according to the invention will henceforward be described in detail in connection with construction examples, on the basis of a drawing. On the drawing Figure 1 is a side view of the measuring device, partly in section.

On figure 1 a possible version of the measuring device 1 according to the invention can be seen. The frame structure 10 is well visible, which includes the bearing body 11 and a fork- like swinging-member 13 connected to the bearing body 11 through the swivel-pin 15 so that it may swing. The metal, 40-60 kg measuring disc 20 is positioned between the forks of the swinging-member 13, through which the main axle 14 that is connected to the swinging-member 13 runs, and so the measuring disc 20 is connected to the swinging- member 13 on the main axle 14 so that it may rotate.

The measuring disc 20 rests on the surface 3 of the road 2 on the rolling edge 21. The rolling edge 21 of the measuring disc 20 is cycloid, between the starting point 22 of the rolling edge 21 and the finishing point 23 there is a closing section 24. The fixing zone 25 can be found in the vicinity of the closing section 24, near to the starting point 22. The fixing zone 25 has an accepting seating 25a and a supporting surface 25c surrounding the end of the accepting seating 25a lying on the rolling edge 21 side. The main axis 25b of the accepting seating 25a of the fixing zone 25 is radial with respect to the measuring disc 20.

Figure 1 also shows how the measuring head 26 is positioned in the accepting seating 25a of the fixing zone 25. The measuring head 26 is a hard metal body head delineated by a conical surface 28 ending in a spherical shell 27, the clamping stem 29 of which is fixed in the accepting seating 25a. The fixing of the measuring head 26 in a determined position is aided by the fixing form 29a, which in the case of the appropriate fitting of the measuring head 26 sits upon the supporting surface 25c of the fixing zone 25.

In the interest of attaining precise measurements the measuring head 26 is positioned in the accepting seating 25a so that the main axis of the accepting seating 25a and the longitudinal axis 26a of the measuring head 26 are coaxial. Here we also need to mention that in the interest of increasing measurement precision and making the replacement of the measuring head 26 simple, the supporting surface 25c is a plane surface sunk into the rolling edge 21, while the fixing form 29a of the clamping stem 29 of the measuring head 26 is a ring bordered by an also plane touch plate 29b running around the circumference of the clamping stem 29. For fixing the measuring head and the measuring disc together it is practical to use a suitably selected thread.

It can also be observed on figure 1 that the bearing body 11 of the frame structure 10 is fitted with rolling members 30, which are also connected to the bearing body l l so that they can rotate with the help of supplementary axles 12. The bearing body 11 of the frame structure 10 rests on the surface 3 of the road 2 on the rolling members 30. When moving the frame structure 10 the bearing body 11 rolls along the surface 3 of the road 2 with the help of the rolling members 30.

A signal transformer and measuring part-unit 50 is fitted between the measuring disc 20 and the frame structure 10 through a mediating part-unit 40.

On using the measuring device 1 first the measuring head 26 necessary for carrying out the measurement is fitted into the accepting seating 25a of the fixing zone 25. Following fitting the measuring head 26 the bearing body 11 of the frame structure 10-of the measuring device 1 is connected to a device suitable for towing-not visible on figure)- e. g. motor vehicle in such a way that the rolling members 30 of the bearing body 11 rest on the surface 3 of the road 2. With the frame structure in this position the rolling edge 21 of the measuring disc that is connected to the swinging-member also lies on the surface 3 of the road 2.

On starting the vehicle the frame structure 10 also starts moving, and the rolling members 30 connected to the supplementary axles 12 so that they may rotate roll on the surface 3 of the road 2. While the frame structure 10 is moving the measuring disc 20 also starts to move, the rolling edge 21 of which is in continuous contact with the surface 3.

The direction of rotation of the measuring disc 20-which is equal to the direction the arrow is pointing to on the drawing-is such that while the rolling edge 21 progresses the rolling edge 21 of the measuring disc 20 touches the surface 3 of the road 2 progressing from the direction of the finishing point 23 in the direction of the starting point 22. When during the rotation of the. measuring disc 20 the part of the rolling edge 21 touching the surface 3 of the road 2 reaches the starting point 22, and leaves it, then for a short period only the conical surface 28 ending in the spherical shell 27 of the measuring head 26 fixed in the measuring disc 20 rests on the surface 3 of the road 2.

The surface 3 and the measuring head coming into contact in this way touch on a very small area, and the mass force from the mass of the measuring disc 20 on the measuring head 26 pushes the spherical shell 27 of the measuring head 26 and a part of the conical surface 28 into the surface 3 of the road 2.

On the effect of the impression the vertical position of the measuring disc 20 changes, which is sensed by the signal transformer and measuring part-unit 50 with the help of the mediating part-unit 40. From the value of the sensed vertical position change-in a way known in itself and not detailed here-the hardness of the surface can be determined.

After the period of measuring, in other words during the impression of the measuring head into the surface 3 of the road 2, when the measuring disc 20 rolls on further the finishing point 23 of the rolling edge 21 reaches the surface 3 of the road 2. On the effect of this the measuring disc 20 is resting on the rolling edge 21 in the vicinity of the finishing point 23, and, on the one hand, relives the force from the measuring head 26, and, on the other hand, -due to the relative movement-the measuring head 26 is lifted out of the surface 3 of the road 2. Following this phase of the measuring process during the rotation of the rolling edge 21 the surface elements of the rolling edge 21 nearer to the starting point 22 touch the surface 3 of the road 2., and so again the measuring process in the above starts again. This cyclically repeated series of movements makes completely continuous measurement possible, during which the rolling edge 21 of the measuring disc 20 progresses smoothly along the surface 3 of the road 2.

The measuring device according to the invention can be well applied to continuously determine the surface hardness of any road quickly and precisely.

List of references 1 measuring device 2 road 3 surface 10 frame structure 11 bearing body 12 supplementary axles 13 swinging-member 14 main axle 15 swivel-pin 20 measuring disc 21 rolling edge 22 starting point 23 finishing point 24 closing section 25 fixing zone 25a accepting seating 25b main axis 25c supporting surface 26 measuring head 26a longitudinal axis 27 spherical shell 28 conical surface 29 clamping stem 29a fixing form 29b touch plate 30 rolling member 40 mediating part-unit 50 signal transformer and measuring part-unit