Excavators

An excavator is an earth-digging machine designed for making trenches and pits, as well as for carrying out other kinds of earthwork involved in construction. A single bucket excavator is an intermittent action machine. Its working cycle consists of the following operations: cutting some amount of earth from a solid mass, carrying the dug soil to a dumping place, emptying the bucket and returning to the initial position.

The fundamental mechanism of an excavator consists of the undercarriage which includes the tracks or wheels, the frame and the final drive. The final drive has a hydraulic motor and gears that provide drive to the tracks. The operator’s cabin, engine, counterweights, hydraulic and fuel tanks are attached to the undercarriage to enable the excavator to swing 360 degrees without hindrance.

The workgroup of an excavator includes the boom, dipper or arm, and attachment (for example, bucket, auger or breaker). Mostly the boom can move only up and down, or in addition also shift towards the left and the right of the machine. An arm is attached to the boom end that imparts the force for digging into the ground. A bucket is fixed at the arm end for carrying the soil. In addition to the buckets, there are numerous other categories of different attachments and devices that are used for boring, crushing, lifting and ripping. This expands hydraulic excavator capabilities far beyond excavation tasks with buckets.

Vocabulary:

earth-digging ['WT'dIgIN] a. – землеройный

design [dI'zQIn] v.– проектировать, конструировать

intermittent ["Intq'mItqnt] a. – периодический

undercarriage ['Andq"kxrIG] n.– ходовая часть, шасси

tracks [trxks] n. – гусеницы

frame [freIm] n. – рама

final drive ['fQInl 'drQIv] – главная передача

gear [gIq] n.– шестерня, зубчатая передача; передаточный механизм, привод

engine ['enGIn] n. – двигатель

counterweight ['kQuntq"weIt]] n. – противовес

fuel tank ['fjuql 'txNk] – топливный бак

swing [swIN] n. v.– поворот; поворачивать

boom [bHm] n. – стрела

dipper ['dIpq] n. – ковш

auger ['Lgq] n. – бур, сверло

breaker ['breIkq] n. – дробилка

boring ['bLrIN] n. – бурение, сверление

crushing ['krASIN] n.– раздавливание, дробление

ripping ['rIpIN] n. – рыхление

Answer the following questions:

1. What are the main functions of an excavator?

2. What does the working cycle of an excavator consist of?

3. What does the undercarriage include?

4. What parts of an excavator do you know?

5. What mechanisms does the working group consist of?

6. How can the boom move?

7. How can an excavator be converted?

8. What expands hydraulic excavator capabilities?

НТТС (IV семестр)

Power installations of construction machinery

A power installation is a complex consisting of an engine and its servicing systems. It converts some kind of energy into mechanical work. Engines are machines which change heat into motion. Depending on the type of engine, power installations employed in present- day construction machinery, in tractors and trucks can be subdivided into the following groups: steam, internal- combustion, electric, pneumatic and hydraulic ones.

Steam engines and internal- combustion engines are prime movers. They transform energy taken from fuel into mechanical work. Electric, pneumatic and hydraulic engines are known as secondary movers. They convert into mechanical work the energy produced by generators.

Internal combustion engines are the principal power installations employed in mobile and self propelled construction machinery as well as in trucks and tractors. They are very efficient under all working conditions and do not depend on the external sources of energy.

Electric power installations incorporate generators transforming mechanical energy into electrical one. The latter is then used to drive electric motors.

The widespread use of electric drives in road making and construction machines is due to their considerable economical and operational advantages as compared to other types of drives.

Pneumatic and hydraulic power installations are employed for machine control systems, auxiliary devices and mechanical tools.