Scraper
The scraper (also motor scraper , motor scraper or scraper ) is a device for removing, transporting and filling up soil in layers. The scraper was invented by Robert Gilmour LeTourneau in the United States in the 1930s .
Structure and mode of operation
Motor scrapers consist of a front and a rear car. The driver's seat and at least one drive motor (for single-engine machines) that acts on the wheels of the front axle is located on the front of the vehicle. The rear section essentially consists of the hydraulically adjustable scraper and the rear axle. In the case of two-engine versions, there is another drive engine on the rear carriage that acts on the rear axle (twin-engine scraper, all-wheel drive). Both vehicle parts are connected with a hydraulically driven joint ( articulated steering ). To collect the earth, the scraper is lowered by means of hydraulics. As the machine moves forward, the cutting edge of the scraper loosens soil and pushes it into the bucket. After filling, the bucket is lifted and closed by means of a front wall (bucket door) that is also moved hydraulically. The machine then drives to the unloading point, the bucket door is opened and by pushing the rear bucket wall forward, the earth material is ejected again during the slow journey and is distributed over a large area.
Depending on the design, scrapers can take up material with a volume of 8 to 34 m³. The engine outputs are between approx. 140 and 470 kW. The maximum speed is up to 50 km / h.
Early scrapers (from the 30s to 50s) were equipped with complex cable pulls instead of hydraulics. In early forms, the front end consisted of a kind of oversized tractor as a towing vehicle before its smaller front axle was omitted and the now known form with articulated steering was created.
One variant is the so-called elevator scraper (conveyor scraper), in which the absorption of the soil into the bucket is supported by a special conveyor mechanism (band-like guided “bars” made of steel).
With single-engine scrapers, the pulling power is usually only sufficient for driving, but not for digging (since only two wheels are driven), at least in firmer soils. For this reason, these machines are usually supported by bulldozers during the digging process, which push the scraper at the rear using a spring-loaded pressure plate designed for this purpose (pushing aid, push-puller). Another variant is the coupling of several scrapers during the digging, which are filled one after the other so that the power of all vehicles is available (so-called push-pull scraper). For this purpose, the machines are equipped with appropriate spring-loaded coupling devices that can be hydraulically connected and disconnected from the driver's seat. After the labor-intensive digging, the vehicles separate and drive separately to the unloading point.
Another design are trailed scrapers without their own engine that are pulled by bulldozers or powerful wheeled tractors.
However, especially since the advent of hydraulic excavators , the use of scrapers for earthmoving has declined sharply, also in the USA, the home country of scrapers. There this type of machine always played a much greater role than in Europe. Scrapers can only be used to a very limited extent on rocky, very hard ground, but also in wet and muddy conditions. The Kassel Henschelwerke were the only German company to build scrapers based on the American model, but they were not widely used.
The typical US manufacturers of scrapers were or are companies such as Caterpillar , IHC , Euclid / Terex , John Deere , Le Tourneau and Allis-Chalmers , and Komatsu from Japan also builds scrapers.
literature
- Hermann Bauer: Construction company. Springer, Berlin, ISBN 3-540-32113-6 , pp. 128-132.
See also
Web links
Individual evidence
- ↑ LeTourneau earthmovers, Eric C. Orlemann, MBI, ISBN 0-7603-0840-3 .