TM 5-3805-248-23-1
THEORY OF OPERATION - CONTINUED
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EARTHMOVING EQUIPMENT COMPONENTS
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The scraper system is controlled hydraulically from the operator station. It performs the scraping, loading, transporting
and ejecting of material. Bowl, apron and ejector can be individually controlled, or the bowl and apron can be controlled
together.
Bowl. The bowl uses two double-acting cylinders. Bowl control lever has raise, hold, power-down and quick-drop posi-
1.
tions. When the control lever is in the hold position, the quick-drop and check valves mounted on the bowl cylinders are
locked. This isolates the hydraulic circuit from the stress of the bowl.
2.
Apron. The apron opens and closes the scraper bowl. It uses one double-acting cylinder with a multiplier linkage that
controls the force, speed and length of travel. Apron lever has open, hold, positive-close and float positions. Closure
force is regulated by a relief valve to protect the apron and bowl. Circuit pressure is controlled by a sequence relief
valve.
Ejector. The ejector accepts loading, or forcibly unloads material. It is powered by a single double-acting cylinder. Ejec-
3.
tor lever has forward, hold and return positions with automatic kick-out included on return.
4.
Draft Frame Assembly. The draft frame assembly serves a twofold purpose. It is the main point of attachment for the
apron cylinder, bowl lower-raise cylinders, coupling of bowl assembly to the tractor, and routing for hydraulic-electric
lines. Secondly, it is the junction where all steering is accomplished through movement of articulation cylinders. At this
junction, bowl assembly and tractor are allowed to yaw while traversing rough terrains.
END OF WORK PACKAGE
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