Задание 2. Переведите (устно) данный ниже текст, обращая внимание на новые слова.
Методические указания
A pneumatic cylinder requires one or more valves which will connect the cylinder port alternately to the main air supply or the exhaust line without allowing mains air to escape directly to the atmosphere. With few exceptions double-acting cylinders always have one end connected to the mains whilst they are in operation and standardized air valves are arranged accordingly. Single-acting cylinders are only permanently connected on the power stroke. The simplest valve for cylinder control is the 3-way (or 3-port) (Fig. 10) with one way to the cylinder, one to the air supply and the other to the exhaust.
In hydraulics, double-acting cylinders are always controlled by a single, usually 4-way valve, but this is by no means the case in pneumatics for the following reasons. As air is compressible, the volume of the pipe between the valve and cylinder may materially affect the amount of air to be admitted and the speed of response. A three-way valve be mounted close to or on the cylinder port it controls, where as a four-way valve must of necessity have a pipe to at least one end. A second 1 reason is that two three-way valves may be cheaper than one four- I way and this is especially true of some small solenoid valves.
Задание 3. Ответьте преподавателю (устно) на вопросы к данному тексту:
1. How many valves does pneumatic cylinder require? 2. What do they connect? 3. What are single-acting cylinders connected with? 4. What do 3 ways of the simplest cylinder connect? 5. How is common supply and exhaust valves connected? 6. How should 3-way valve be mounted?
Text 2
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Two of these can be used for a double-acting cylinder, but more commonly the two valves are combined in one and the result is a 4-way valve (Fig. 11) as the common supply and exhaust valves have been connected internally.
