Mining or in situ disintegration of hard material – Automatic control; signaling or indicating – Of hard material disintegrating machine
Reexamination Certificate
1999-08-06
2002-04-16
Bagnell, David (Department: 3673)
Mining or in situ disintegration of hard material
Automatic control; signaling or indicating
Of hard material disintegrating machine
C404S084050
Reexamination Certificate
active
06371566
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a process for milling off traffic areas with a milling roller, a milling machine or a device for milling off traffic areas.
Such milling machines are required to first remove the old pavement of a traffic area prior to application of a new pavement.
Various systems are employed for automatic control of the milling depth of the milling roller used for road milling work. Common to all systems is that a constant desired value of the milling depth is determined once and this value remains unchanged until a new desired value is manually set. This desired value is thus independent of the position of the milling machine so that unevennesses in certain sections of the traffic area cannot be levelled out. Milling-off of an existing surface at a constantly set milling depth of the milling rollers results in copy-milling since the profile of the old surface reduced by the permanently adjusted milling depth is displayed on the new surface. To prevent such copying effect the actual milling depth (actual value) is measured via a sensor in various ways and compared with the desired milling depth (desired value) by a milling depth controller. This comparison is effected continuously and the determined desired value deviation is transferred into a control signal in the milling depth controller for height adjustment of the milling roller.
The following processes for measuring the actual value of the milling depth are applied in milling machines:
1. Height tracing with any sensor at the edge guard
Here a sensor measures the change in the distance between the edge guard of the milling machine tracing the road profile and a fixed point on the machine frame. The change in distance is the measure by which the edge guard is raised or lowered as it follows the road profile so that the milling depth can be automatically increased or decreased by this amount. The length of the edge guard is referred to here as tracing basis. Longitudinal waves with a wave length smaller than the edge guard length (approximately 1 to 2 m) are levelled out. Nevertheless copy-milling of the original actual profile is still effected since the edge guard runs on the existing profile and unevennesses of a larger wave length are copied into the new road profile.
2. Height tracing with a ski or measuring wheels mounted to a measuring rod
During this process a measuring ski or measuring wheel skis or rolls over the road surface. The ski or the wheel is vertically movable via a pivoted lever mounted to an angle of rotation transmitter which measures the change in the distance between measuring wheel or ski and the fixing point of the angle of rotation transmitter on the machine frame. The milling depth is then increased or reduced by the amount measured. The length of the ski or the measuring rod forms the tracing basis. Longitudinal unevennesses with a wave length exceeding the length of the ski or the measuring rod are copied, smaller longitudinal waves can be levelled out. Longitudinal waves with a wave length in the range from 5 to 10 m can be levelled out by extending the measuring rod or the ski.
3. Multiplex height tracing with a plurality of series-connected ultrasonic sensors
In this process known from EP-A-0 547 378 three ultrasonic sensors are permanently mounted in longitudinal direction of the machine on one machine side, i.e. one sensor at the front machine end, one sensor above the rotational axis of the milling roller and one sensor at the rear machine end. The sensors measure the change in distance between the machine frame and the road profile. From these measured values and in consideration of the longitudinal inclination of the machine contained in the values measured by the front and rear sensors, a mean value is calculated by which the milling depth is increased or reduced. Owing to this measure the tracing basis increases to the length of the milling machine, which allows longitudinal waves with a wave length smaller than the machine length to be levelled out. This procedure, too, improves the evenness of the road profile, however, copy-milling still takes place with long-wave unevennesses with a wave length of more than 5 to 10 m continuing to be transferred to the new profile.
4. Tracing of the height relative to an additionally created reference
4a. During this process a levelling wire is stretched along the surface to be milled, and positioned by a measuring and adjusting process. The basis for correct location by a measuring process is the previous survey of the existing surface profile. The wire is continuously traced by a distance measuring means (angle of rotation transmitter, Sonic-ski etc.) permanently arranged on the machine frame with the changes in the distance between the machine frame and the wire being a measure for the milling depth correction of the milling roller. When this procedure is applied, it is no longer the unevenness of the original road surface which is copied into the new surface but a surface parallel to the levelling wire. A guiding wire correctly located by said measuring and adjusting process theoretically allows obtaining of the desired new road profile.
When the height is traced on a levelling wire, there is the problem that the levelling wire must be stretched and located by said measuring and adjusting process in accordance with the previously determined desired profile. This is very time-consuming and disadvantageous due to the costs involved.
4b. Levelling using a laser
This procedure is based on the beam of a stationary rotational laser setting an artificial disk-shaped plane. A laser receiver which is permanently mounted to the machine frame continuously measures the change in distance between the machine frame and the artificially set plane. Here, too, survey of the road profile must previously take place. This process theoretically allows a plane surface and, if necessary, an inclined surface to be produced, however, it is not possible to create any profile desired since the rotational laser always produces a disk-shaped plane.
Accordingly, the possible applications of the laser are limited. Furthermore, the laser must be accurately positioned and adjusted, which is time-consuming and expensive. Another disadvantage is that the measuring accuracy is not as high as that achieved with a mechanical sensor.
To sum up it can be said that during tracing of the height relative to the ground it is only possible to copy the existing road profile with the existing longitudinal unevennesses being inevitably taken over. Although extension of the tracing basis allows levelling out of these longitudinal waves up to a certain extent but wave lengths of more than 5 to 10 m cannot be levelled out. Especially these long-wave unevennesses lead to rocking motions of vehicles at a certain driving speed. This reduces both driving comfort and safety. Further disadvantages of longitudinal unevennesses of the road are a higher noise level and increased fuel consumption.
SUMMARY OF THE INVENTION
It is the object of the invention to provide a process and a device for milling off traffic areas allowing levelling out of the longitudinal waviness of a traffic area in a simple way.
According to the process of the invention the following steps are provided:
surveying the actual profile of the traffic area and generating at least two-dimensional actual profile data (x, z) by assigning the measured profile values to the position data of a relative or absolute position determining means,
generating desired profile data from previously or on-line determined actual profile data with the desired profile data being corrected with regard to the longitudinal waviness of the traffic area, and
determining the current position of the milling machine and the adjusted milling depth as actual value,
controlling the milling depth of the milling roller, via a machine control unit, as a function of the difference between the actual value and the desired value from the desired profile data, the desired value being assigned to the current position of the milling
Bagnell David
Diller Ramik & Wight
Singh Sunil
Wirtgen GmbH
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