Patent Application
20090108663
The invention refers to a self-propelled road milling machine, especially a cold milling machine, as well as a method for positioning the machine frame parallel to the ground.
In such road milling machines, the machine frame is supported by a track assembly comprising wheels or caterpillar tracks connected to the machine frame through lifting columns, the lifting columns allowing to adjust the machine frame to a specific horizontal plane or in parallel to the ground or under a predetermined longitudinal and/or transversal inclination.
A milling roller for working a ground or traffic surface is supported at the machine frame.
Near the front end sides of the milling roller, height-adjustable side plates are provided as edge protectors at an outer wall of the road milling machine, which side plates, in operation, rest on the ground or traffic surface at the lateral non-milled edges of the milling track. Behind the milling roller, seen in the traveling direction, a height-adjustable stripping means is provided which, in operation, may be lowered into the milling track formed by the milling roller to strip off milling material remaining in the milling track. Further, the road milling machine has a control means for controlling the milling depth of the milling roller and for controlling the setting of the lifting columns.
It is a problem with known road milling machines that, if the machine frame does not extend parallel to the ground, the stripping means will not rest on the ground with sufficient exactness behind the milling roller to allow for a residue-free stripping process to be performed on the surface under treatment. Further, the problem exists that, if the machine frame is not arranged parallel to the ground, the band shoe surrounding the transport band does not flatly rest thereon, so that material which has been milled off may intrude into the region between the band shoe and the still untreated ground surface, or that the function as a hold-down means is performed insufficiently so that chunks of ground material will warp in front of the milling roller and become adhered under the band shoe. Further, the problem exists that the milling depth can not be controlled accurately enough and that, for this reason, the milling depth has to be measured repeatedly by hand during the milling operation. Especially in cases where a hard traffic surface, e.g. concrete, is milled, the tools are worn heavily so that the milling depth set is corrupted by the decreasing diameter of the cutting circle. For example, the wear of the tools, when milling concrete, can cause a difference in the milling radius of 15 mm after only a few 100 meters, so that the measuring of a displacement of side plates, for example, with respect to the machine frame is not sufficiently accurate. If the milling depth is insufficient, a time-consuming reworking of the milling track has to be carried out. Should the milling track be too deep, more building material has to be applied afterwards in order to achieve the desired ground or traffic surface level.
Thus, it is an object of the invention to simplify the operating of the road milling machine and to improve the milling process.
The invention advantageously provides that the control device automatically controls the lifting condition of at least one rear and/or front lifting column, as seen in the traveling direction, for positioning the machine frame parallel to the ground or traffic surface or for positioning the machine frame at a predetermined milling level.
The invention is useful also for recycling machines.
The solution according to the invention has the advantage that the parallel orientation of the machine frame relative to the ground or traffic surface is automatically set and that the operating person does not have to readjust this parallel arrangement on his or her own, particularly not after a likewise automatic control of the milling depth. By keeping the machine frame held parallel to the treated or untreated ground or traffic surface, the correct functioning of other machine elements, e.g. of the stripping means and of the band shoe, is guaranteed. This will prevent operational disturbances caused by material accumulating under the band shoe or chunks of material becoming warped up due to an inaccurate setting of the parallel orientation, or by the impossibility to correctly strip off the already milled surface.
Further, the operating person can concentrate on the actual driving process and is not distracted by control processes which have to be performed manually.
For establishing the parallel orientation of the machine frame relative to the bottom or traffic surface, the control device can detect the longitudinal inclination of the machine frame relative to the treated or untreated ground.
Detection of the longitudinal inclination can be performed on the basis of two distance values indicating the distance between the machine frame and the treated or untreated ground, said distance values being displaced relative to each other in the traveling direction.
The longitudinal inclination can be detected from at least a first distance value between the machine frame and the treated ground, and at least one second distance value, displaced relative to the first distance value in the traveling direction, between the machine frame and the untreated ground, in connection with a measurement value for the milling depth.
The first or the second distance value between the machine frame and the treated or untreated ground can be detectable from the position of a chain track assembly running on the treated or untreated ground, relative to the machine frame.
The longitudinal inclination can be detectable from a first distance value between the machine frame and the treated ground and a second distance value between the machine frame and the treated ground, with the second distance value being detectable from the position of the stripping means or from the position of at least one of the track assemblies running on the treated ground, relative to the machine frame.
A transport band can be arranged on the machine frame, with a band shoe taking up the roll-side end of the transport band provided for discharge of the milled material.
The longitudinal inclination can be detectable from at least one first distance value between the machine frame and the untreated ground and a second distance value between the machine frame and the untreated ground, the second distance value being detectable from the position of the band shoe or from the position of at least one of the chain track assemblies running on the untreated ground or from the position of at least one of the side plates.
The distance values between the machine frame and the treated or untreated ground can be detectable with the aid of path measurement systems.
The path measurement systems can be integrated in the lifting columns or in the hydraulic cylinders of the lifting columns.
The longitudinal inclination of the machine frame relative to the untreated ground can be detectable from the relative angle, as seen in the traveling direction, between a side plate resting on the ground and the machine frame.
The longitudinal inclination of the machine frame relative to the treated or untreated ground can be detectable from the relative angle between at least one lifting column extending orthogonally to the machine frame and the track assembly extending parallel to the ground.
The automatic establishing of the parallel orientation of the machine frame relative to the treated or untreated ground can be performed by the control means only when the control means performs a readjustment of the milling depth or performs a setting of a predefinable milling depth.
The control means can decide whether the lifting condition of the front and/or the rear lifting columns will be controlled for adaptation to the milling depth.
The automatic establishing of the parallel orientation of the machine frame relative to the treated or untreated ground can be performed by the control means independently of the control of the milling depth.
The control means can control the milling depth of the milling roller independently on each of both sides of the machine frame as seen in the traveling direction.
At least one measuring means can detect the lifting of a first sensor means resting on the ground or traffic surface and/or the lowering of a second sensor means to the bottom of the milling track, the lifting or lowering being effected in correspondence with the present milling depth, wherein, from the measured values supplied by the at least one measuring means, the control means can determine the milling depth of the milling roller.
For establishing the parallel orientation of the machine frame relative to the ground or bottom surface or to the predetermined milling plane, the lifting condition of the rear and front lifting columns as seen in the traveling direction can be adapted to be changed to the effect that the machine frame is pivotable about the milling roller axis.
Since the controlling of the parallel orientation of the machine frame is performed in such a manner that the machine frame is pivoted about the milling roller axis, it is accomplished that the controlling of the parallel orientation will not influence the milling depth, i.e. the milling configuration.
A method for establishing the parallel orientation of the machine frame relative to the ground or traffic surface or to a predetermined milling plane, for use in road milling machines wherein a ground or traffic surface is milled by means of a milling roller, in that the road milling machine is lowered together with the milling roller so as to perform the milling in correspondence to a predetermined milling depth, can comprise the detecting of the longitudinal inclination of the machine frame relative to the treated or untreated ground by detection of measurement values, and the automatic controlling of the lifting condition of at least one rear and/or front lifting column as seen in the traveling direction, so as to establish the parallel orientation of the machine frame relative to the ground or traffic surface or to the predetermined milling plane in dependence on the longitudinal inclination of the machine frame.
There can be provided at least one measuring means which detects the lifting of a first sensor means resting on the ground or traffic surface and/or the lowering of a second sensor means to the bottom of the milling track, the lifting or lowering being effected in correspondence with the present milling depth. From the measured values supplied by the at least one measuring means, the control means can determine the milling depth at the level of the stripping means of the milling roller or the second sensor means.
Here, the measurement is effected preferably at the level of the stripping means arranged closely behind the milling roller, or immediately behind the stripping means, if a separate sensor means is provided.
The second sensor means can consist of the stripping means.
Using the stripping means as a sensor means is advantageous in that no measuring errors will be caused by some unevenness in the milling track. It is another advantage that the stripping means is protected against wear at its bottom edge.
As an alternative, the control means can use the measurement values of the at least one measuring means to determine the current milling depth of the milling roller at the level of the milling roller axis. Preferably, this is done by a calculation that may also take into account an inclined position of the machine frame.
The measuring means are preferably formed by path sensing means. In one embodiment, it is provided that the first sensor means is formed by at least one of the side plates arranged on either side at the front sides of the milling roller so as to be height-adjustable and pivotable with respect to the machine frame. The side plates rest on the ground or traffic surface or are pressed against these, so that a change of their position relative to the machine frame during operation allows for an exact detection of the milling depth, if a measurement of the change of the position of a second sensor means is performed additionally in the milling track relative to the machine frame.
The measuring means can comprise cable lines coupled to the first sensor means and/or the second sensor means, and cable-line sensors as path sensing means.
Also in side plates, advantage exists that their bottom edges are protected against wear.
Here, the measuring means may comprise cable lines coupled with the side plates and/or the stripping means, and associated cable-line sensors as the path sensors which measure the changes of the position of the side plates and the stripping means relative to the machine frame, or the relative displacement of at least one of the side plates in relation to the stripping means or the second sensor means.
Preferably, the cable lines coupled with the side plates and the stripping means are arranged transversely to the milling track in a substantially vertical plane extending approximately at the level of the stripping means.
Hereby, it can be avoided that a measurement error is caused by using different reference planes for the measurement at the side plates with respect to the measurement at the stripping plate.
To achieve this, it may be provided that a cable line is coupled on the one hand with the stripping means and, on the other hand, with at least one of the side plates via a guide roller, such that a cable-line sensor will immediately measure the milling depth, e.g. at the guide roller.
The measuring means can detect the displacement of the first sensor means relative to the second sensor means or the respective displacement of the first and second sensor means relative to the machine frame.
According to another alternative, it may be provided that the stripping means has a respective measuring means at the side edges facing the side plates, which measures the relative displacement of the stripping means with respect to the at least one adjacent side plate or the relative displacement of at least one side plate with respect to the stripping means.
According to another alternative embodiment, the stripping means may include at least one height-adjustable beam as the first sensing means, which is guided vertically and linearly in the stripping means and extends transversely to the traveling direction, said beam resting on the ground or traffic surface beside the milling track, the position of the beam relative to the stripping means, preferably with respect to height and/or inclination, being measurable by the measuring means.
Due to gravity, the side plates may rest on the edges of the ground or traffic surface beside the milling track milled by the milling machine, or they may alternatively be pressed on the edges by hydraulic means.
The stripping means may also be pressed on the surface of the milling track using hydraulic means.
The hydraulic means for pressing the side plates on the ground or traffic surface or for pressing the stripping means on the bottom of the milling track may comprise integrated path sensing systems.
For lifting or lowering the side plates and/or the stripping means, a plurality of—preferably two—respective piston/cylinder units with integrated position sensing systems may be provided, whose path sensing signals are used by the control means to calculate the current milling depth from the relative difference between the positions of the stripping means and the at least one first sensor means.
The control means that receives the path sensing signals from the measuring means is adapted to automatically control means the lifted condition of the rear lifting columns, seen in the traveling direction, to establish parallelism between the machine frame and the ground or traffic surface at a desired milling depth.
The side plates resting on the traffic surface so as to be pivotable with respect to the machine frame may comprise measuring means spaced apart in the traveling direction, the control means being capable to measure the longitudinal and/or the transversal inclination of the machine frame with respect to the ground or traffic surface on the basis of the difference between the measurement signals from the side plates and the stripping means.
The front and/or rear lifting columns may include a path sensing system to detect the lifted condition. The control means which receives the path sensing signals from the measuring means can control the condition of all lifting columns to the effect the machine frame has a predetermined inclination or a predetermined travel-distance-dependent transverse inclination across the traveling direction.
Preferably, the current set value for the milling depth of the milling roller is adjusted using the front lifting columns.
The current desired value of the milling depth of the milling roller can be adjustable by means of the front lifting columns.
The control means which receives the measurement signals of all measurement means, of the side plates and/or of the stripping means and/or of the band shoe and/or of all lifting columns, is configured to detect, in dependence on the path measurement signals of the measuring means and/or of the desired site-dependent change of a desired value of the milling depth in the course of the treated path, the resultant lifting position of the lifting columns.
The zero level of the measurement means (16) can be set to the unmilled ground or traffic surface.
Each lifting column can have its lower end provided with a support for a wheel or a chain track assembly, and a distance sensor can measure the distance from said support to the bottom and traffic surface and transmit a measuring signal to a control means for the lifting position of the lifting column and/or to a control means for the milling depth of the milling roller.
The milling roller can extend substantially along the whole working width of the machine frame.
The milling roller can be supported in the machine frame in a height-adjustable manner.
The control means can compute the current milling depth from the obtained path measurement signals and generate a control signal for the height adjustment of the milling roller.
In a method for measuring the milling depth of road milling machines wherein a ground or traffic surface is milled with the aid of a milling roller by lowering the road milling machine together with the milling roller in correspondence to the predetermined milling depth, wherein a side plate on at least one side beside the milling track is set onto the untreated ground and traffic surface and wherein a stripping plate is lowered into the milling track generated by the milling roller, the measuring of the milling depth of the milling track can be performed by detecting the measurement values of at least one first sensor means detecting the position of the untreated ground or traffic surface, in relation to the measurement values of a second sensor means detecting the position of the bottom of the milling track, or by measuring the measurement values of both sensor means in relation to the machine frame.
In the method, the side edges to the side of the milling track can be kept down with the aid of side plates, and at least one of the side plates can be used as a first sensor means, while the stripping plate for stripping the milled surface is used as the second sensor means.
In the method, also the correcting of the measured milling depth value can be performed in dependence on the distance between the second sensor means and the axis of rotation of the milling roller if the machine frame of the road milling machine should not extend parallel to the ground or traffic surface.
The following is a detailed description of a preferred embodiment of the invention with reference to the accompanying drawings.
a, b, c are schematic illustrations of the measurement error occurring at the stripping plate of the stripping means in the absence of parallelism between the machine frame and the ground or traffic surface.
The road milling machine illustrated in
Using the lifting columns 12,13, the machine frame 4 can be lifted or lowered or be moved to take a predetermined inclined position with respect to the ground or traffic surface 8. The milling roller 6 supported in the machine frame 4 is enclosed by a roll case 9 which is open at the front, seen in the traveling direction, towards a conveyor belt 11 that conveys the milled material in a front part of the machine frame 4 to a second conveyor means 13. The second conveyor means 13 by which the milled material may be delivered onto a truck, for example, is not fully illustrated in
Above the milling roller 6, a driver's stand 5 with a control panel for the vehicle operator is provided for all control functions of the driving and milling operations. It also includes a control means 23 for controlling the milling depth of the milling roller 6.
The side plates 10, arranged on either side near the front end of the milling roller 6, and the stripping means 14 are provided with measuring means 16 that allow the determination of the current milling depth at the level of the stripping means 14 or the calculation of the milling depth at the level of the rotational axis of the milling roller. Here, the milling depth is determined in a plane orthogonal to the ground or traffic surface, which plane is parallel to the rotational axis of the milling roller and includes the rotational axis.
The position of a first sensor means, e.g. the side plates 10, on the ground or traffic surface 8, and/or the lowering of a second sensor means, e.g. the stripping means, can thus be detected. Measuring means 16, preferably formed by position sensing means, will measure the displacements of the sensor means, e.g. the side plates 10 or a beam 20 or the stripping plate 15, with respect to the machine frame 4 or relative to each other.
The embodiment illustrated in
As is evident from
As an alternative and as illustrated in
The side plates 10 themselves can be used as first sensor means by monitoring their position with respect to the machine frame 4 or the second sensor means by means of a cable line and a cable-line sensor or by means of piston/cylinder units 30,32 with integrated position sensing means.
For example, the measuring means can also measure the displacement of the side plates 10 with respect to the machine frame 4. Should two measuring means be used, one in front of the side plates 10 and one behind the same, when seen in the traveling direction, it is also possible to determine the longitudinal inclination of the machine frame 4 with respect to the ground or traffic surface 8 or to also determine the transverse inclination of the machine frame 4 by a comparison of the measured values for both side plates 10 on both sides of the milling roller 6.
a to 7c illustrate the cable-line sensors 21 for the side plates 10 and the stripping plates 14, the drawings only indicating one cable-line sensor 21, since the cable-line sensors are arranged one behind the other in substantially the same plane.
a, b, c are to illustrate the case where the ground or traffic surface 8 is not parallel to the machine frame 4, the measured milling depth value indicated by the measuring means having to be corrected because of an angle error, because a longitudinal inclination of the machine frame 4 corrupts the measurement signal at the level of the stripping plate 15 or a second sensor means near the stripping means 14. Due to the fixed geometrical relations, i.e. the distance of the stripping plate 15 from the rotational axis of the milling roller 6, the measured milling depth value can be corrected, knowing the angular deviation from the horizontal in the traveling direction, and the current milling depth at the level of the milling roller axis can be calculated. The angular deviation in the traveling direction may be determined, for example, from the position of the lifting columns 12,13 of the caterpillar track assemblies 2,3 or the piston/cylinder units 30,32.
It is further evident from
c illustrates the position of the at least one side plate 10 for a ground-parallel position of the machine frame 4. The stripping plate 15 illustrated in
The control means 23 can calculate the current milling depth at the level of the milling roller axis from the position sensing signals received, and it can possibly also generate a control signal for a vertical adjustment of the milling roller 6.
Preferably, the control means 23 can automatically control the lifted condition of the front and/or rear lifting column 13, seen in the traveling direction, to establish parallelism between the machine frame 4 and the ground or traffic surface 8 or to the horizontal plane or to a predetermined desired milling plane.
For this purpose, all of the above described measuring means can be used also for detection of the angular orientation or longitudinal inclination in order to control the parallelism of machine frame 4 relative to the ground surface.
The first working cylinder 40 is the actuator for the lifting column on the left front, the second working cylinder 42 is the actuator for the lifting column on the right-hand front, the third working cylinder 44 is the actuator for the lifting column on the right-hand rear, and the fourth working cylinder 46 is the actuator for the lifting column on the left rear.
The first working chamber 48 of the first working cylinder 40 is connected to the first working chamber 60 of the fourth working cylinder 46 via a connection line 68. The second working chamber 50 of the first working cylinder 40 is connected to the second working chamber 54 of the second working cylinder 42 via a connection line 64. The first working chamber 52 of the second working cylinder 42 is connected to the first working chamber 56 of the third working cylinder 44 via a connection line 70. The second working chamber 58 of the third working cylinder 44 in turn is connected to the second working chamber of the fourth working cylinder 46 via a connection line 66. Thus, the working chambers 40,42,44,46 are arranged to form a closed system via the connection lines 64,66,68,70, thus improving the road comfort and the stability of road building machine 1.
The connection line 68 is connected, via a further connection line 72, to a connector B of a first 4/3-way valve 84. A 4/3-way valve comprises four connectors and three switch positions. A second connector T of the first 4/3-way valve 84 is connected, via a connection line 76, to a connector T of a second 4/3-way valve 86. Connection line 76 is connected, via a working line 87, to a pressure medium sink 80. A third connector P of the first 4/3-way valve is connected, via a connection line 78, to a second connector P of the second 4/3-way valve 86. Further, a working line 79 is connected to connection line 78, with an oil pump provided in working line 79. On its other end, working line 79 likewise opens into the pressure medium sink 80.
A third connector B of the second 4/3-way valve 86 is connected, via a connection line 77, to connection line 70. A fourth connector A of the first 4/3-way valve 84 is connected, via connection line 96, to a fourth connector A of the second 4/3-way valve 86.
Further, connection line 64 is connected, via connection line 75, to a connector of a 2/2-way valve 94 (two connectors, two switching positions). The second connector of the first 2/2-way valve 94 is connected, via connection line 98, to a connector as a back-check valve 92. The other connector of back-check valve 92 is connected, via connection line 81, to connection line 96. Back-check valve 92 is blocked against fluid flows from connection line 81 to connection line 98.
Connection line 96 is further connected, via connection line 83, to a connector of a further back-check valve 90. The other connector of back-check valve 90 is connected, via connection line 100, to a connector of a further 2/2-way valve 88. The other connector of 2/2-way valve 88 is connected, via connection line 74, to connection line 66. Back-check valve 90 is operative to block fluid flows from connection line 100 to connection line 83.
By setting the two 4/3 path valves, control means 23 will control the displacement of the working cylinders 40,42,44,46 and thus the extending and retracting of the lifting columns 12,13. By the extending and retracting of the lifting column cylinders 12,13, the milling depth is adjusted. According to one embodiment, the milling depth of the milling roller is controlled independently on both sides of machine frame 4 when viewed in the traveling direction, because it is possible to displace only the left working cylinders 40,46 or the right working cylinders 42,44.
In the preferred embodiment according to
Band shoe 122 receives the milling-roller-side end of the conveying means 102. The support of the rear end of conveying means 102 is a fixed point between band shoe 122 and conveying means 102. Provided on both sides of the front end of band shoe 122 are connection webs 128 preventing a pivoting movement of band shoe 122 relative to conveying means 102. Conveying means 102 preferably consists of a transport band 11.
Band shoe 12 consists of a grid 120 arranged parallel to the ground and serving a hold-down means and as a slide shoe. Grid 120 consists of a plurality of grid rods oriented parallel to the traveling direction. On the sides, grid 120 is delimited by vertical side walls 124. On the rear end of band shoe 122, a front region 126 is arranged substantially parallel to the transport band 11 of conveying means 102. Arranged on the rear end of the band shoe is a protective plate 121 for protection of the transport band 11, which plate is effective to prevent that the transport band 11 is damaged by sharp-edged material. A plate 118, slightly inclined in the traveling direction, has its upper region formed with a U-shaped recess for use as a passage opening for the milled-off material.
Path measurement systems, such as e.g. ultrasonic sensors or cable-line sensors, can be attached directly to the band shoe 122 or be integrated in the piston/cylinder unit 108. With the aid of the path measurement systems on the band shoe 122, the values of the distance between the machine frame 4 and the untreated ground can be detected.
In
According to a further embodiment, it can also be provided that two measuring means, arranged at a mutual distance in the longitudinal direction of the road milling machine, such as e.g. measuring means coupled to the piston/cylinder units 30,32, will detect the longitudinal inclination of machine frame 4.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20 2006 019 509.2 | Dec 2006 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2007/064520 | 12/21/2007 | WO | 00 | 10/16/2008 |
