Liebherr PR 724 User Manual
Crawler Tractors
PR 724 – PR 764
Product information
Grade control systems
Grade control systems for crawler tractors
To be successful despite the constantly increasing cost and time pressures, construction machinery must meet the highest
demands regarding working speed and accuracy. Increasingly, automatic grade control systems are utilized to improve the
productivity of operator and machine.
They utilize existing planning data to automatically guide the machine attachments when removing or spreading material.
With the aid of the most up-to-date technology, complex surfaces and exact grades can be produced quickly and precisely.
Advantages of automatic
grade control systems:
The use of stakes and string lines, as well as personnel •
costs for these tasks are dramatically reduced
No loss of time due to constant measurement checks •
or extensive rework, resulting in better machine
utilization
Fewer passes mean less wear and lower fuel •
consumption
More accurate grading improves material economy •
due to controlled material usage
Signifi cant cost savings for the owner and •
ultimately higher profi ts
Liebherr crawler tractors are eminently suitable for application of automatic grade controls, thanks to their innovative
drive system. The hydrostatic drive provides uninterrupted power without the need to shift gears. Due to the long tracks
and the perfect match of front attachment, working hydraulics, and base machine, exceptional grading properties are
ensured.
Depending on the type of application, various technologies are utilized. To simplify the installation, Liebherr offers a
number of installation kits. They ensure that the retrofi t installation of the grade control system on the crawler can be
completed without requiring access into the interior of the machine.
Grade control systems
2
Laser control
Applications
Creation of horizontal or sloped grades with high accuracy •
Suitable for small to medium sized construction sites •
Application for construction of sports fi elds, storage or dump sites, road construction, •
housing and residential areas, etc.
Components
Symbol images only
In terrain On the dozer blade In the cab
Rotary laser 1 or 2 laser receivers Option:
Cross slope sensor
Control unit
How it works
The rotary laser rotates at high speed and in doing so generates a reference plane out of laser light. This plane can be
horizontal or sloped, but it is always planar (two dimensional).
The laser receivers are installed on masts on the blade of the crawler tractor. They catch the emitted laser beam and
determine the current elevation of the dozer blade in relation to the reference height. For applications with lower accuracy requirements, a single laser receiver is suffi cient to determine the elevation of the blade (single laser). Normally,
two masts or one mast and a slope sensor are installed, this “dual operation” allows both the blade elevation as well
as tilt to be determined).
The control unit processes the signals from the laser receivers and the slope sensor and constantly regulates the
elevation and tilt of the blade automatically via the working hydraulics.
When working in automatic mode, the operator only needs to steer the tractor, while the grade control automatically
regulates the movements of the blade, creating a grade parallel to the laser surface.
Useful information
Visual contact between the rotary laser and the crawler is required•
Simple and comparatively inexpensive system, however no 3D contours can be created•
Several machines can work in the same grading level with a single rotation laser•
Height accuracy < 1 cm•
Grade control systems
3
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