Tài liệu tiếng anh - LAMNGHIEPVN.INFO (Hưng Bùi) unit 6

Tài liệu tiếng anh - LAMNGHIEPVN.INFO (Hưng Bùi) unit 6 tài liệu, giáo án, bài giảng , luận văn, luận án, đồ án, bài tập...

PART II: THE AGRICULTURAL MACHINERY

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General

1 The importance of agricultural tractors in the world today should never be

under-estimated They provide a great source of power which has almost entirely replaced the power of horse, and of man, for the many heavy and time-consuming tasks carried out on land

2 This power is being used to produce food for the nations of the world and there is

no more important task than this A tractor can do the work of numerous horses, and do this work in the same time, without having to be rested to recover from fatigue Provided reasonable attention is given to its lubrication and it is kept supplied with fuels, it will work on indefinitely The driver, of course, will require his rest, but it is not unusual for tractors to work around the clock when relief drivers are available

3 As more and more food production is required to feed the ever-increasing world

population, the numbers of tractors used will increase to meet the demand Great areas of land will yet be brought into food production and the tractor will supply the necessary power for the work

Tractor Types

4 The present-day tractor is a most useful machine, capable of supplying its power

to numerous farm tasks The most power absorbing of these tasks is usually the basic cultivation of land; therefore the tractor is designed to be able to do this task whilst at the same time being amply powered for the many other field tasks it is required to do, such as drilling seed, top dressing, spraying, haulage, etc

5 During the years since the First World War, and in particular during, say, the last

20 years, a great amount of progress has been made in developing a machine capable of operating efficiently a very wide range of implements and machines Many devices have been incorporated in the mechanism of the tractor for this purpose

6 The type of tractor used on the land depends on the type of work to be done Track-Laying Tractors (Fig 1)

7 These tractors are sometimes referred to as “crawlers” and are usually tractors

with a large horse-power and capable of doing very heavy work On farms, they may be used for pulling a five- or six- furrow plough or for heavy cultivation Yet, On the other hand, there is a very small track-laying tractor of no more than 6 h.p (horse-power) which is used for work on market gardens

Heavy Wheeled Tractors

8 Not only track-laying tractors are used for the heavy work on farms Very large

four-wheel-drive tractors are now common which are capable of pulling up to twelve furrow ploughs with engines of up to 500 h.p These large tractors may be equipped with twin wheels all round, and no longer run in the furrow when ploughing, but run on top in

the same way as a crawler tractor They also carry out very heavy cultivation.

Fig.1 A track-laying tractor.

General-purpose Tractors (Fig.2)

9 The general-purpose tractor is a wheeled tractor and the lighter type may be

powered by an engine of about 40 h.p whilst the other type may have an engine of 100 h.p Either one or both of these types may be used on most farms and they are the most common type used today

Fig 2 A General-purpose tractor

Two-wheeled Tractors

10 Another type of tractor to be found on many small holdings and market gardens

is the hand-operated This type is powerful enough to do light cultivation and is steered

by a walking operator

11 Most tractors nowadays are powered by internal combustion engines, which,

although they may vary slightly between one make and another as regards detail of construction, operate on the same basic principles

The Internal Combustion Engine

12 The tractor’s power is used for doing work in the field and also for driving

stationary machines

13 The power, which is produced by the engine, is transmitted through various

mechanisms until it reaches the rear wheels which rotate These mechanisms will be explained in later chapters The power unit must be considered first

14 In any internal combustion engine there are a number of essential parts which

are so arranged that a basic series of events occur This series of events is usually known

as the operating cycle and most tractor engines operate on what is known as the four-stroke cycle

15 The internal combustion engine is a form of heat engine and the name “heat

engine” is given to it because heat energy, produced by the burning of fuel within the engine, is changed into mechanical energy Different types of fuel are used in the different types of tractor engines but this does not alter the basic operation The fuels used are petrol or propane for spark ignition, and diesel fuel is used in compression ignition engines

This text was taken from SHIPPEN et al , Basic Farm Machinery, Pergamon

Press

I COMPREHENSION CHECK:

Now read the text carefully, looking up any new items in a dictionary or reference book Then answer the following questions:

1 What source of power have tractors largely replaced ?

2 What does the tractor need to work on indefinitely ?

3 Why will the number of tractors increase ?

4 Which farm task uses most tractor power ?

5 On what basis is the type of tractor chosen for use ?

6 Where is the smallest track-laying tractor used ?

7 What do heavy wheeled tractors and track-laying tractors have in common

8 Which is the commonest type of tractor ?

9 How are most tractors powered ?

10 What does the internal combustion engine change ?

II VOCABULARY:

In this section you should use your dictionary to help you answer the questions about the text

1 Look at paragraphs 1 -3 again What words have the same meaning as :

• taking a lot of time.

• tiredness

• get better

• thought too little of

• completely

• without any time limit

• a great many

2 Look at paragraphs 4 - 6 again What words have the opposite meaning to :

• unable to

• not enough

• taken out of

3 Look at paragraph 7 again Can you explain the words:

• heavy cultivation

• market garden

4 Look at paragraph 8 again Can you explain the words:

• plough

• furrow

5 Look at paragraph 9 again What word has the opposite meaning to :

• heavier

6 Look at paragraph 10 - 11 again Which words correspond to the definitions :

• general laws shown in the working of machines

• direct the course of a machine

• a small area of land usually farmed by the owner or tenant himself

• a little bit

7 Look at paragraphs 12 - 15 again What words have the same meaning as :

• sent through

• change

• turn in a circle

• not moving

III GRAMMAR :

1 Look at this table: General purpose tractor

hydraulic system raises and lowers implements; controls depths of

ploughs and harrows rear power take-off shaft drives implements e.g seeders and sprayers

drawbar pulls trailers and implements, e.g harvesters

Now look at the following sentences and answer the questions:

The rear power take-off shaft drives implements.

The rear power take-off shaft is used for driving implements.

The function of the rear power take-off shaft is to drive implements.

a) What is the hydraulic system used for ?

b) What is the function of the draw-bar ?

2 Look at the table below :

Plough lifts the topsoil and turns it over

Harrow breaks up the topsoil and prepares it for seeding

Sprayer applies herbicides, fungicides and insecticides to the crop

Seeder make a furrow and sows the seed

Harvester cuts forage and lifts root crops

Now ask and answer questions containing the words used for and function.

3 Look at these sentences:

The tractor can raise and lower implements.

For this purpose the hydraulic system is used.

Now write six similar sentences using the table in exercise 1

4 Look at these sentences :

The function of the draw-bar is to pull implements

whereas the hydraulic system is used for raising and lowering them

Now complete the following sentences:

a) The plough whereas the harrow

b) The plough lifts the topsoil and turns it over, whereas and sowing the seed

Make similar sentences contrasting the functions of the seeder and the harrow, and the harvester and the plough

5 The impersonal passive

Examine the following active and passive sentences, and note the verb form of each passive sentence Note that the words in brackets are optional, and are often omitted in scientific writing

We improve the fertility of the soil The fertility of the soil is improved

The fruit encloses the seeds The seeds are enclosed by the fruit.

We should plough under leguminous

plants

Leguminous plants should be ploughed under.

Now, write down the passive version of the following active sentences Then

combine the passive sentences you have written following the clues provided

E.g A: The tiny root hairs absorbed water and mineral An increase in the number

of root hairs increases the power of absorption

P: Water and mineral are absorbed by the tiny root hairs Therefore, the

power of absorption is increased by an increase in the number of root

hairs

1. A: The fruit encloses the seeds The fruit protects them while they are

developing

P: The seeds by the fruit Consequently, they while they are developing.

2 A: The plant takes in oxygen The plant uses oxygen to break down

carbohydrates

P: Oxygen in by the plant and to break down carbohydrates

3 A: Wind and insects transfer pollen from one flower to another They deposit the

pollen on the stigmas of the other flower

P: When pollen by the wind and insects from one flower to another, it on

the stigmas of the other flower

4 A: The human body requires small quantities of several minerals The human

body obtains these minerals from plants

P: Small quantities of several minerals which are by the human body from

plants

5 A: We can use some roots to reproduce the species We should remove the

whole root of harmful weeds such as docks instead ploughing them in lightly

P: Some roots to reproduce the species Thus, the whole root of harmful

weeds such as docks instead of lightly

6 A: Soil texture influences all aspects of root development A heavy compact soil

creates a physical barrier to root growth

P: All aspect of root development by soil texture For example, a physical

barrier to root growth by a heavy compact soil

7 A: Too much cultivation destroys the soil structure

A pasture phase under grass can improve the structure

P: Since soil structure by too much cultivation, the structure by a pasture

phase under grass

8 A: The plant manufactures food from chemical substances present in the soil &

air

The roots take in chemical substances from the soil

The leaves take in carbon dioxide from the air

P: Food is by the plant from chemical substances which from the soil by

the roots and from carbon dioxide which from the air by the leaves

9 A: We can use a unit called a soil profile to describe soils

When we wish to compare two soils, we examine their profiles

We can define a soil as having an individual profile

P: A unit called a soil profile to describe soils So when we wish to compare

two soils, their profiles , and each soil can thus as having an individual profile

10 A: Ploughing ‘turn in’ the whole surface of a field.

It buries and kills the weeds

It loosens and exposes the soil to the air

P: The whole surface of the field ‘ ’ by ploughing, with the result that weeds

and and the soil and to the air

New words and expressions:

- be under-estimated:

- source of power:

- time-consuming task:

- fatigue (n.):

- kept supplied with fuels:

- available (adj.):

- basic cultivation:

- a track-laying tractor:

- horse power:

- incorporated:

- furrow plough:

- carry out:

- general-purpose tractor:

- holdings (n.):

- detail of construction:

- basic principles:

- the internal combustion engine:

- the operating cycle:

- the four-stroke cycle:

- heat energy:

- mechanical energy:

- hydraulic system:

- rear power-take-off shaft:

- harrow (v.):

- harvester (n.):

đánh giá thấp nguồn năng lượng công việc mất nhiều thời gian

sự mệt nhọc được cung cấp nhiên liệu đầy đủ

có sẵn trồng trọt cơ bản máy kéo bánh xích

mã lực phối hợp luống cày tiến hành, thực hiện máy kéo đa năng khu đất nhỏ chi tiết cấu tạo những nguyên tắc cơ bản động cơ đốt trong

chu kỳ vận hành chu kỳ bốn thì nhiệt năng

cơ năng

hệ thủy lực trục thu công suất sau bừa

máy gặt

- soil texture:

- absorption (n.):

- leguminous plants:

- seeder (n.):

- sprayer (n.):

kết cấu đất

sự thẩm thấu cây họ đậu máy gieo hạt máy phun thuốc (trừ sâu)

Further reading:

Engine Classification

The engine can be classified in the following several ways:

(1) operating cycle(2) piston action, (3) piston connection, (4) cylinder arrangement, (5) method of fuel injection, and (6) speed

Operating cycle: Diesel and gas-burning engines can be divided into two groups

based on the number of piston strokes per cycle, either four or two An engine which needs four strokes to complete one cycle is a four-stroke cycle engine or, for short, a four-stroke engine If it need only two strokes to complete a cycle, it is called a two-stroke cycle engine or, for short, a two -cycle engine Thus, a two-cycle engine fires twice as often as a four -cycle engine

Piston action: An engine's piston action may be classified a (a) single action (b)

double-action, (c) opposed-piston

Single-acting engines use only one end of the cylinder and face of the piston to develop power This working space is at the end away from the crankshaft, that is, at the upper end of a vertical engine

Double-acting engines use both ends of the cylinder and both faces of the piston to develop power on the up-stroke as well as on the down-stroke The construction is complicated; therefore, double-acting engines are built only in large and comparatively low-speed units, generally to power motor-ships

An opposed-piston engine has cylinders in each of which two pistons travel in opposite directions The combustion space is in the middle of the cylinder between the pistons There are two crankshafts; the upper pistons drive one, the lower pistons drive the other Note that each piston is single-acting; that is, it develops power with only one face of the piston

Piston connection: The piston may be connected to the upper end of the

connecting rod either directly ("trunk piston" type) or indirectly ("crosshead" type)

In trunk-piston engines, a horizontal pin within the piston is encircled by the upper end of the connecting rod This by far the most common construction

In crosshead-type engines, the piston fastens to a vertical piston rod whose lower end is attached to a sliding member called a "crosshead", which slides up and down in guides The crosshead carries a crosshead pin which is encircled by the upper end of the connecting rod This more complicated construction is required in double-acting engines

It is also used in some large, slow-speed, single-acting engines

Cylinder arrangement: The four basic cylinder arrangements of a diesel or gas

-burning engine are: (a) cylinder-in-line, (b) V-arrangement, (c) flat and (d) radial

A cylinder-in-line arrangement This is the simplest and most common

arrangement, with all cylinders arranged vertically in line This construction is used for engines having up to 12 cylinders Engines are also built with horizontal cylinders, usually one or two, in a few cases with three cylinders

If an engine has more than eight cylinders, it becomes difficult to make a sufficiently rigid frame and crankshaft with an inline arrangement Also, the engine becomes quite long and take up considerable space The v-arrangement, with two

connecting rods attached to each crankpin, permits reducing the engine length by almost on-half, thus making it much more rigid, with a stiff crankshaft It also costs less to manufacture and install This is a common arrangement for engines with eight, twelve and sixteen cylinders Cylinder lying in one line are called a "bank", and the angle between the banks may vary, in manufacturing practice, from 300 to 1200, the most common angles being between 400 and 750 (a complete circle is 3600)

A flat engine is a v-engine with the angle between the banks increase to 180* This arrangement is used where there is little head room, as in trucks, buses and rail cars Flat engines are also called "opposed-cylinder" engines

In a radial engine, all the cylinders are set in a circle and all point toward the centre

of the circle The connecting rods of all the pistons work on a single crankpin, which rotates around the centre of the circle Such a radial engine occupies little floor space By attaching the connecting rods to a master disk surrounding the crankpin, as many as twelve cylinders have been made to work on a single crankpin

Method of fuel injection Diesel engines are divided into air-injection engines and

solid or mechanical injection engines Air-injection engines use a blast of highly compressed air to blow the fuel into the cylinder Air injection was commonly used on early diesel engines but with the development of solid-injection systems the air-injection engine is rapidly disappearing

Speed All diesel and gas-burning engines may be divided into three classes

according to speed: low-speed, medium-speed and high-speed engines Automotive diesel engines often run faster than 1,200 rpm, but the great majority of other engines run between 350 and 1,200 rpm and are termed medium-speed engines

New words and expressions:

- fuel injection:

- divide into :

- be based on :

- piston stroke:

- for short:

- (be) away from:

- trunk-piston engine:

- by far:

- gas-burning engine:

- cylinder-in-line:

- a sufficiently rigid frame:

- radial engine:

sự phun nhiên liệu chia thành được dựa trên hành trình piston gọi tắt, để ngắn lại cách xa so với động cơ piston nối trực tiếp nhiều đến mức

động cơ đốt bằng khí, động cơ chạy ga xylanh thẳng hàng

sườn đủ cứng động cơ hình sao o0o