In principle, the method according to one embodiment of the present invention can be carried out manually by an operator in a step-wise manner by controlling the road milling machine accordingly. However, in order to relieve the operator as far as possible, it is preferred that at least step c), and in particular also steps d) and e), are carried out automatically, in particular triggered by a single control command from an operator. The milling of the ground in normal operation according to step a) and the approach of the road milling machine to the obstacle according to step b) are thus carried out or controlled by the operator as usual. To use the method according to one embodiment of the present invention, the operator then positions the road milling machine as close as possible to the obstacle. However, instead of then controlling the raising of the milling drum, the operator simply enters a control command on the road milling machine's control device; for example, via a control element such as a switch or a touchscreen. The lifting of the milling drum according to step c) is then carried out automatically by the control device of the road milling machine, wherein the rear blade and in particular the lower edge of the rear blade are guided in particular along the predetermined trajectory. Once the raising is completed, the operator can again control the moving over of the obstacle according to step d) and position the road milling machine behind the obstacle. By means of a further control command from the operator, the lowering according to step e) is then possibly carried out again automatically by the control device, wherein here in particular the working parameters which were already present before the lifting according to c) are set again. In this way, the work operation can be continued quickly and easily.

The operator can additionally enter an extension of the obstacle in the working direction in advance; for example, at the control device. If the extension of the obstacle in the working direction is entered by the operator in advance, all steps c), d) and e) triggered by a single control command from the operator can be carried out automatically, in particular by the control device. As described above, the operator thus positions the road milling machine as close as possible to the obstacle. Then the operator only gives the control command to the control device, whereupon it automatically carries out the raising of the milling drum according to step c), the moving over of the obstacle according to step d) and the lowering of the milling drum and the rear blade according to step e), without the operator having to take any further action. The operator therefore only carries out normal milling work up to just before the obstacle, then gives the control command, whereupon the road milling machine automatically mills around the obstacle, and can then continue the milling work in the working direction behind the obstacle as normal. In this way, not only is finishing work minimized, but the operator of the road milling machine is also relieved during working operation.

As described above, the method according to one embodiment of the present invention can be carried out by the operator of the road milling machine detecting the obstacle located in the ground to be milled and determining or specifying its extension in the working direction as a basis for automatic control. However, the detection of the obstacle itself and also of its dimensions, in particular its extension in the working direction, can alternatively also be carried out by a sensor device. For this purpose, it is possible that at least one sensor device is arranged in front of the milling drum in the working direction, which is designed to detect obstacles in the ground to be milled. For this purpose, the sensor device may comprise, for example, an inductive, capacitive or magnetic sensor, such as a metal detector. Additionally or alternatively, the sensor device may also comprise an optical sensor; for example, a camera or a thermal imaging camera, or a sound sensor; for example, an ultrasonic sensor. It is important that the sensor device is able to detect obstacles that are within the milling width of the road milling machine or milling drum. The detection range of the sensor device must therefore cover the entire milling width of the milling drum so that laterally offset obstacles can also be reliably detected. In order to achieve this, the sensor device can also have a plurality of sensors; for example, a plurality of sensors of different types, distributed transversely to the working direction, for example.

If the road milling machine has a sensor device which can detect an obstacle located in the ground to be milled, it is possible that step c), and in particular also steps d) and e), are carried out automatically, triggered by the detection of an obstacle by the sensor device. In particular, in order to carry out steps c), d) and e), the extension of the obstacle in the working direction is determined by the sensor device. The sensor device thus automatically detects a front edge of the obstacle in the working direction and a rear edge of the obstacle in the working direction and determines the extension of the obstacle in the working direction between these two edges. Thereupon, the raising of the milling drum according to step c), the moving over of the obstacle according to step d) and the lowering of the milling drum and the rear blade according to step e) are carried out without the operator having to take any further action. In particular, it is no longer even necessary for the operator to issue a control command that triggers these steps. This is also possibly carried out automatically by the control device on the basis of the detection of the obstacle.

In order to increase the flexibility and, if necessary, the safety of the method according to the present invention, it can also be provided that the sensor device detects the presence and, in particular, the dimensions of the obstacle, but that the operator nevertheless gives specific instructions for controlling, in particular, the raising according to step c) and moving over according to step d) and/or the lowering according to step e). In particular, the operator should be able to specify how much unmilled ground should be left around the obstacle. For this purpose, it is provided that the operator is shown a representation of the obstacle on a display device produced from data obtained from the sensor device, and in that the operator can specify on the display device the front and rear edges of the obstacle in the working direction, wherein steps c), d) and e) are then carried out in such a way that the milling drum remains out of contact with the edges of the obstacle specified by the operator. For example, the operator may be shown the image from a camera on the display device with the obstacle visible on the image. The operator can then use input elements, such as a touchscreen, to define the front and back edges of the obstacle in the working direction based on the image. These dimensions of the obstacle in the working direction, determined by the operator, are then used as the basis for further control. The control is such that the milling drum is raised out of the ground in front of the front edge of the obstacle in the working direction and is only lowered back into the ground behind the rear edge of the obstacle in the working direction. Potentially damaging contact between the milling drum and the obstacle is avoided.

According to one embodiment of the present invention, advancing the road milling machine in the working direction towards the obstacle located in the ground according to step b) is also carried out automatically by the control device. For this purpose, the control device can position the road milling machine as close as possible to the obstacle. On the one hand, the milling drum should be raised as close as possible to the obstacle in order to minimize protruding residues of the ground to be milled off, which have to be removed manually or mechanically afterwards. On the other hand, it should be ensured that neither the obstacle nor the milling drum are damaged by a collision. Due to the geometry of the milling drum, it should be noted that the road milling machine can approach obstacles from different distances depending on the milling depth. Due to the circular diameter of the milling drum, it must be raised earlier at high milling depths and can be raised later at lower milling depths to keep it out of contact with the obstacle. It is therefore provided that the position in the working direction at which the raising of the milling drum is carried out is determined taking into account the position of the obstacle, the milling depth and in particular also the geometry of the milling drum in order to keep it out of contact with the obstacle. In particular, this position is determined automatically by the control device, so that step b) of advancing the road milling machine in the working direction towards the obstacle located in the ground is also carried out automatically by the control device and without any intervention by the operator. In this case, the operator can fully concentrate on milling the ground according to step a). All further steps b) to e), which deal with the avoidance due to the obstacle, are possibly carried out automatically by the control device.

Since the road milling machine removes little to no milled material from the ground during steps c) and d), it is possibly provided that when these steps are carried out, a conveyor device of the road milling machine is put out of operation, in particular automatically. This can also be performed by the control device. In this way, additional attention does not have to be paid to the error-free and low-loss transfer of the milled material to a transport vehicle while these steps are being carried out. Corresponding sources of error are thus reduced and work safety increased. In addition, the conveyor device is possibly automatically reactivated in step e) in order to continue the milling process smoothly.

In order to ensure a simple, fast and seamless transition of the milling operations before the obstacle and after the obstacle, it is possibly provided that for continuing the milling of the ground according to step e) the same machine settings, in particular with regard to milling depth and/or advancement speed and/or operation of the conveyor device, are automatically set, in particular as they were in step a). The milling work should therefore be continued in the working direction behind the obstacle with the same machine settings that were set before the obstacle. Accordingly, the respective settings are stored by the control device and automatically restored in step e).

In order to leave as little milled material as possible on the obstacle as well, it is possibly provided that the rear blade, while moving over the obstacle according to step d), is kept in the raised positions either resting against the unmilled ground and the obstacle or floating above it with a safety distance, for example 2 cm. In this way, a large proportion of the milled material is transported out of the obstacle in the milling bed located in front of the obstacle in the working direction, then conveyed over the obstacle by the rear blade and retained in the milling drum case until the milling drum is lowered again. As soon as the milling work starts again in the working direction behind the obstacle, the milled material can then be transported to the conveyor device and disposed of as normal. The milling drum can again be positioned behind the obstacle in the working direction in exactly the same way as at the start of a new milling track. However, in order to leave as clean a milling bed as possible at the start of the new milling track in the working direction behind the obstacle, it may be preferable to control the lowering of the rear blade to the specified milled depth in the working direction behind the obstacle in such a way that the lower edge of the rear blade follows one of the trajectories described above in the reverse direction during lowering. In principle, this can be any of the trajectories described above. In particular, it is the same trajectory as during the excavation. The control of the lowering of the rear blade and the advancement speed of the road milling machine is therefore carried out in such a way that the corresponding trajectory is traversed in exactly the opposite direction. In this way, as little milled material as possible remains both in front of and behind the obstacle, which has to be removed during time-consuming finishing work.

The method can be further improved by storing obstacle widths during the method. In this case, the width of the obstacle refers to the extension of the obstacle in the travel or milling direction of the road milling machine. This can be useful, for example, for obstacles that have to be crossed several times and/or obstacles with standard widths, such as manhole covers, etc. In this case, the operator can, for example, signal the reaching of such an obstacle with a stored width with manual triggering. This determines the distance over which the milling drum and the rear blade are to be raised according to the above specifications. In particular, it also eliminates the need for the driver to trigger lowering as well. Additionally or alternatively, an offset can also be provided. This designates a distance, in particular which can also be defined manually, in front of and behind the obstacle in the milling direction. This can be defined individually for each obstacle by the operator or can be stored as a defined value in a memory device.

The above-mentioned aspect of the present invention is also achieved with a road milling machine for milling a ground in a working direction. The road milling machine according to the present invention comprises a milling drum case which is height-adjustable relative to the ground. This height adjustment can be achieved by means of an adjustment device designed in such a way that the milling drum case can be fully or partially adjusted in height relative to the machine frame. Additionally or alternatively, the machine frame can be connected to the travel devices running on the ground by means of vertically adjustable lifting devices. In this case, the milling drum case is thus adjusted in the vertical direction together with the machine frame. The milling drum case can have a front blade, a hold-down device, two side blades (one each on the front side of the milling drum) and a rear blade which can be adjusted in height relative to the machine frame. In addition, it comprises a milling drum rotatably mounted about an axis of rotation in the milling drum case, in particular horizontal and transverse to the working direction, and a control device. The road milling machine according to one embodiment of the present invention is characterized in that the control device is designed to carry out the method described above. All the features, effects and advantages mentioned above for the method therefore also apply in a figurative sense to the road milling machine according to the present invention and vice versa. Reference is made to the other respective statements merely to avoid repetition.

As described at the outset, the milling drum can either be designed to be height-adjustable within the milling drum case and relative thereto, or the milling case is designed to be height-adjustable together with the milling drum case. Depending on how the milling drum of the road milling machine is height-adjustable, it may be advantageous for the rear blade, and in particular the lower edge of the rear blade, to be designed to be lowered lower than the milling drum and in particular its lower apex. The lower apex of the milling drum is related to the largest cutting circles of the milling drum. In other words, it is possibly provided that the road milling machine has an adjusting device for adjusting the height of the rear blade, which is designed in such a way that the rear blade can be adjusted to below the lower apex of the milling drum, in particular by at least 10%, preferably by at least 20%, particularly preferably by at least 30%, of the diameter of the milling drum. This ensures in particular that the rear blade can still be in the working position while the milling drum is or has already been raised, even if the milling drum is always adjusted in height together with the entire milling drum case. In this case, the rear blade performs a counter-movement for compensation, during which the rear blade is moved vertically below the milling drum and, in particular, also below its lower apex.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the present invention will be described in more detail using the exemplary embodiments shown in the figures. The figures schematically show the following:

FIG. 1 shows a side view of a road milling machine;

FIG. 2 shows a top view of a milling drum case and a milling drum;

FIGS. 3-9 show a time sequence of milling operations with an obstacle located in the ground to be milled;

FIG. 10 shows a detailed view according to section X from FIG. 5;

FIG. 11 shows a detailed view according to FIG. 10 with a raised milling drum;

FIG. 12 shows a single-step trajectory;

FIG. 13 shows a further single-step trajectory with a displacement point shifted towards the front edge of the excavation area;

FIG. 14 shows a further single-step trajectory with a displacement point corresponding to the front edge of the excavation area;

FIG. 15 shows a multi-step trajectory;

FIG. 16 shows a multi-step trajectory with inclined sections;

FIG. 17 shows a single-step, inclined trajectory;

FIG. 18 shows a trajectory in which the lower edge of the rear blade is substantially in contact with the surface of the ramp in the excavation area;

FIG. 19 shows a sensor device with a sensor;

FIG. 20 shows a sensor device with a plurality of sensors;

FIG. 21 shows the influence of the milling depth on the position of the raising of the milling drum; and

FIG. 22 shows a flow diagram of the method.

Identical or identically acting components are designated with the same reference numerals. Repeated components are not designated separately in each figure.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a road milling machine 1—here a road milling machine or cold milling machine of the center rotor type—for milling a ground 8 in a working direction a. The road milling machine 1 has a machine frame 3 and a driver's cab 2. The machine frame 3 is supported by lifting columns 15, which connect the machine frame 3 to the travel devices 6, which in the exemplary embodiments shown are designed as crawler tracks, although they may also be wheels. The machine frame 3 can be adjusted in height or in the vertical direction relative to the ground 8 by means of the lifting columns 15. The road milling machine 1 further comprises a drive motor 4, which is typically a diesel internal combustion engine, although it may also be an electric motor, for example. A hybrid drive is also possible. As a primary working unit, the road milling machine 1 has a milling drum 9 which is mounted rotatably about an axis of rotation 10 in a milling drum case 7. During operation of the road milling machine 1, the milling drum 9 rotates about the axis of rotation 10, milling ground material from the ground 8. This milled off material is transferred from the milling drum case 7 to a conveyor device 5, which typically comprises a conveyor belt, and which is designed to transfer the milled material to a transport vehicle (not shown) for removal. The milling drum case 7 can be arranged stationary on the machine frame 3 in the vertical direction. Alternatively, an adjustment device can be provided which is designed in such a way that the milling drum case can be adjusted in the vertical direction relative to the machine frame. In this case, the lifting devices 15 could also be dispensed with. In the driver's cab 2, in the embodiment shown, there is a control device 18, which is part of the on-board computer of the road milling machine 1, for example. In particular, the control device 18 is provided with input means, by means of which an operator can input control commands to the control device 18 to control the road milling machine 1. Furthermore, the control device 18 is connected to a display device 26; for example, a display. The display device 26 can also simultaneously be designed as an input means; for example, as a touchscreen.

FIG. 2 shows a top view of a milling drum 9 arranged in the milling drum case 7. For the sake of clarity, a vertical closure at the top or a cover is not shown in FIG. 2. The milling drum 9 has a multiplicity of milling tools 11; for example, milling picks. The milling tools 11 are thus arranged distributed over the outer shell of the hollow cylindrical milling drum 9; for example, in spirals. Overall, the milling drum case 7 surrounds the milling drum 9 like a hood and is substantially only open in the direction to the ground 8, i.e., downwards (a material passage opening can also be provided in the front and/or rear blade). In the working direction a at the front, the milling drum case 7 is closed by a front blade 13. The front blade 13 may comprise a hold-down device. The hold-down device can also be arranged as a separate element in front of the front blade 13 in the working direction a. In particular, when the milling drum 9 rotates in the reverse direction of rotation with respect to the travel devices 6, the hold-down device pressing on the ground 8 in front of the milling drum 9 prevents larger clods from breaking out of the ground 8. Laterally, the milling drum case 7 is bounded by side blades 12, which are slid along on the ground 8 next to the milling drum 9 and prevent milled material from escaping laterally from the milling drum case 7. In the working direction a at the rear, the milling drum case 7 is closed by a rear blade 14. The rear blade 14 scrapes off the milled material lying on the ground 8 and ensures that this is transported along with the milling drum case 7 and channeled away from it. In this way, the milling bed is left as clean as possible. In principle, the front blade 13, the side blades 12 and the rear blade 14 can each be designed to be height-adjustable. For the sake of clarity, only one adjustment device 28 for adjusting the height of the rear blade 14 is shown. This comprises, for example, one or a plurality of, in particular double-acting, hydraulic cylinders. By means of the adjusting device 28, the rear blade 14 is designed to be height-adjustable, in particular relative to the machine frame 3 and/or to the milling drum 9 and/or to the ground 8.

FIGS. 3-9 show the time sequence of milling operations and an obstacle 16 located in the ground 8 to be milled. The obstacle 16 may be, for example, a manhole cover, a manhole or other fixed installation in the ground 8. In particular, the obstacle 16 should not be damaged or destroyed by the milling work. At the same time, the milling drum 9 or its milling tools 11 should also be protected from damage due to a collision with the obstacle 16. FIG. 3 thus shows the situation before the beginning of the milling work. The milling drum 9 is arranged in a raised position above the ground 8. It is then lowered into the ground 8 while rotating and while the road milling machine 1 moves over the ground 8 in the working direction a. The milling drum 9 thus removes the ground 8 and a milling track is created. This situation is shown in FIG. 4. The road milling machine 1 is moved to just in front of the obstacle 16 in the working direction a. FIG. 5 shows the situation in which the road milling machine 1 has been positioned and stopped in front of the obstacle 16. To prevent a collision between the milling drum 9 and the obstacle 16, the milling drum 9 is then raised vertically upwards by at least the specified milling depth of the milling track, as shown in FIG. 6. According to the present invention, the rear blade 14 remains in its working position for the time being and is therefore not moved vertically upwards from the ground 8 at the same time as the milling drum 9. If necessary, the rear blade 14 can be adjusted vertically downwards in relation to the milling drum 9. Next, the road milling machine 1 moves over the obstacle 16 with the milling drum 9 in such a way that the milling drum 9 does not touch the obstacle 16. How exactly the rear blade 14 can be raised out of the milling track in this case is explained in more detail below. The situation of moving over the obstacle 16 with the milling drum 9 raised and the rear blade 14 raised is shown in FIG. 7. FIG. 8, in turn, shows the next work step, in which the milling drum 9 is lowered back into the ground 8 behind the obstacle 16 in the working direction a and mills a new milling track behind the obstacle 16 in the working direction a. This milling work behind the obstacle 16 can then be continued as usual, as shown in FIG. 9. The present invention makes it possible to carry out only minimal finishing work both in front of and behind the obstacle 16 in the working direction a; for example, to remove ground material that has not been milled off or milled material that has been left lying around.

FIG. 10 shows the enlarged section X from FIG. 5. In the time sequence of the milling work, the road milling machine 1 or the milling drum 9 has been positioned just in front of the obstacle 16. Up to the obstacle 16, the milling drum 9 has cleared a milling track at a milling depth FT. As shown in FIG. 11, the milling drum 9 is now raised vertically out of the milling track by at least the milling depth FT. In addition to the milling depth FT, the milling drum 9 can also be raised by a safety distance, for example 2 cm. This ensures that the milling tools 11 of the milling drum 9 do not come into contact with the obstacle 16. As also shown in FIG. 11, the rear blade 14 is still in its working position. In particular, the lower edge 19 of the rear blade 14 is still in contact with the milling bed ground 27. Starting from the situation in FIG. 11, the raising of the rear blade 14 is controlled in such a way that the lower edge 19 of the rear blade 14 follows one of the trajectories T shown in FIGS. 12-18, described in more detail below.

FIG. 12 shows a case where the rear blade 14 is raised at the same time as the milling drum 19. The raising of the milling drum 9 creates an excavation area AB in front of the obstacle 16 in the working direction a, the shape of which corresponds substantially to the circumference of the milling drum 9 or its cutting circles, and which runs from the milling bed ground 27 to the unmilled ground 8. The line transverse to the working direction a at which the milling depth FT is still at a maximum, but then begins to decrease in the working direction a, is called the front edge VK of the excavation area AB. As can be seen from a comparison of FIGS. 11 and 12, the front edge VK of the excavation area AB lies directly vertically below the axis of rotation 10 of the milling drum 9 at the position where the milling drum 9 is raised out of the milling track. The distance between the axis of rotation 10 of the milling drum 9 and the rear blade 14 in the working direction a is denoted as x. FIG. 12 now shows the case in which the rear blade 14 is lifted out at the same time as the milling drum 9, i.e., the displacement point V1 at which the rear blade 14 is lifted out of the milling track is at a distance x from the front edge VK of the excavation area AB. In addition, the lower edge 19 of the rear blade 14 is guided along a single-step, right-angled trajectory T.

FIG. 13 shows a case in which the lower edges 19 of the rear blade 14 are raised out at a displacement point V₂, wherein the displacement point V₂is a distance y away from the front edge VK of the excavation area AB, wherein the distance y is smaller than the distance x. For this purpose, it is necessary that the rear blade 14 remains in the working position after the raising of the milling drum 9 and the road milling machine 1 moves further in the working direction a between the raising of the milling drum 9 and the raising of the rear blade 14, specifically by the difference of the distance x minus the distance y. Only after the road milling machine 1 has moved further in the working direction a, by this difference is the rear blade 14 raised out at the displacement point V₂. This has the advantage that the rear blade 14 still fulfills its function up to the displacement point V₂and transports the loose milled material accumulated in the milling drum case 17 together with the milling drum case 7. In this way, less milled material remains on the milled bed ground 27 after raising the rear blade 14. Also, in FIG. 13, the lower edge 19 of the rear blade 14 is guided along a single-step, right-angled trajectory T.

FIG. 14 shows a case in which the rear blade 14 is raised out of the milling track at a displacement point V₃, wherein the displacement point V₃corresponds to the front edge VK of the excavation area AB. In other words, the distance yin the case of FIG. 14 is zero. Thus, after the milling drum 9 has been raised out of the milling track, the rear blade 14 is kept in working position up to the front edge VK of the excavation area AB and is also only raised out of the milling track at the front edge VK. The rear blade 14 is therefore raised out of the milling track at the same position in the working direction a as the milling drum 9. Since the milling depth FT in the working direction a starts to decrease behind the front edge VK, it is necessary to raise the rear blade