Текст 13

Задание 1. Слушайте и повторяйте:

Задание 2. Найдите соответствующий вариант перевода каждого английского словосочетания.

A). Flexible “piston rings”; fitting closely; to transmit the force of the explosion; mechanical and thermal conditions; installed with the utmost care; to avoid excessive inertia forces; to generate excessive friction.

B). Передавать силу взрыва; установленный с предельной точ­ностью; эластичные поршневые кольца; механические и температурные условия; создавать чрезмерное трение; избегать избыточных сил инерции; прилегающий плотно.

Задание 3. Прочтите текст " Piston" и найдите в нем эквива­ленты следующих слов и словосочетаний:

внутри цилиндра; чугун; рабочая температура; шатун; газонепро­ницаемость.

Составьте план текста на русском языке.

PISTON

The usual form of piston for an internal combustion engine is an inverted bucket-shape, machined to a close (but free sliding) fit in the cylinder barrel. Gas tightness is secured by means of flexible " piston-rings" fitting closely in grooves turned in the upper part of the piston.

The pressure of the gases is transmitted to the upper end of the connecting rod through the " gudgeon pin" on which the " small end" of the connecting-rod is free to swing.

Conventional pistons for internal combustion engines are shaped like a bucket, but many variations in the specific design are possible. They are usually made of cast iron or aluminium, carry three or four piston rings and may be flat, concave or convex on the outer surface of the closed end.

The piston pin may turn in the piston and be anchored in the upper end of the connecting rod.

Engine pistons serve several purposes; they transmit the force of the explosion on the crankshaft through the connecting rod they act as a guide for the upper end of the connecting rod, they also serve as a carrier for the piston rings used to seal the piston in cylinder.

Pistons operate under exceedingly difficult mechanical and thermal conditions and therefore must be made and installed with the utmost care. They must be strong enough to stand the force of the explosion and yet be as light as possible to avoid excessive inertia forces when their direction of travel is reversed twice each revolution.

As they must slide freely within the cylinder they cannot be fitted too tightly. If too closely fitted in the cylinder they will knock and rattle.

Pistons are made of cast iron and semi-steel. This material is strong enough for the stresses imposed, it has a melting point above the cylinder operating temperature, expands at the same rate as the cylinders and does not generate excessive friction when properly lubricated.

The principal objection is that of weight.

Aluminium is also used as a material for pistons. It is lighter than cast iron.

Between the piston and cylinder a certain amount of clea­rance is provided. The amount of clearance depends upon the design of the engine cylinders and cooling system, the piston design and material and to a certain extent the service conditions under which the engine operates. Surface treat­ment will also have a bearing on the piston clearance.

The clearance between cylinders and piston is measured in most саsеs by means of a feeler gauge inserted between the piston and cylinder.