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Concept
Wheel tractor-scraper
Summary
In civil engineering, a wheel tractor-scraper (also known as a land scraper , land leveler or 'tournapull') is a type of heavy equipment used for earthmoving. It has a pan/hopper for loading and carrying material. The pan has a tapered horizontal front cutting edge that cuts into the soil like a carpenter's plane or cheese slicer and fills the hopper which has a movable ejection system. The horsepower of the machine, depth of the cut, type of material, and slope of the cut area affect how quickly the pan is filled.
When full, the pan is raised, the apron is closed, and the scraper transports its load to the fill area. There the pan height is set and the lip is opened (the lip is what the bottom edge of the apron is called), so that the ejection system can be engaged for dumping the load. The forward momentum or speed of the machine affects how big an area is covered with the load. A high pan height and slow speed will dump the load over a short distance. With the pan set close to the ground, a higher speed will spread the material more thinly over a larger area.
In an "elevating scraper" a conveyor moves material from the cutting edge into the hopper.
R.G LeTourneau conceived the idea of the self-propelled motor scraper while recovering from a near-fatal auto accident. He was an earth moving contractor dealer in bulldozer accessories and envisaged a pulled trailer that could excavate and pick up earth as it moved. He approached bulldozer manufacturer Caterpillar in the mid 1930 with his idea but it was turned down so he founded his own company . The first Tournapull, called the Model A, was rolled out of his factory and into trials in 1937.
The scraper is a large piece of equipment which is used in mining, construction, agriculture and other earthmoving applications. The rear part has a vertically moveable hopper (also known as the bowl) with a sharp horizontal front edge. The hopper can be hydraulically lowered and raised. When the hopper is lowered, the front edge cuts into the soil or clay like a plane and fills the hopper.
Official source
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