The working mechanisms of single-bucket excavators primarily take the form of power shovels, backhoes, draglines, and grabs; all of these are classified as cyclic-operation machinery.
The working cycle of a power shovel excavator consists of digging, slewing, dumping, and returning. During the digging phase, the bucket is lowered to the base of the working face; it is then hoisted while the dipper stick is simultaneously thrust forward to complete the excavation. Once the bucket clears the working face, the machine slews to the dumping position. The hinged bottom of the bucket is then opened to discharge the load. As the empty bucket returns to the digging face, its bottom automatically closes.
The working cycle of a backhoe excavator involves extending the bucket so that it rests upon the working face; the bucket is then retracted-pulled back toward the excavator-to perform the digging operation under the combined influence of gravity and traction force. Subsequently, the bucket and boom are hoisted, and the machine slews to the designated dumping site to discharge the material. Backhoe buckets are available in two configurations: those with hinged, openable bottoms and those with fixed, non-opening bottoms.
A dragline excavator operates by casting its bucket onto the working face, allowing the bucket teeth to cut into the soil layer under the force of gravity; the bucket is then dragged across the surface to perform the excavation. Once filled, the bucket is hoisted and the machine slews to discharge the excavated material. A grab excavator utilizes hydraulic cylinders or steel cables to actuate the opening and closing of its clamshell-like jaws, thereby grasping and lifting the material.
Hydraulically driven single-bucket excavators rely on hydraulic cylinders to execute operations such as digging, hoisting, and dumping; consequently, their operational capacity is superior to that of mechanically driven excavators of equivalent size. Both power shovels and backhoes offer a broad operational range, capable of performing excavation tasks both above and below the level of the machine's standing surface.
