机械专业英语(第三版)第9章

Unit 9
3．Place a“T”after sentences that are true and an“F”after those that are false.
(1) A coupling is used to join the shaft of a hydraulic turbine to an electric generator.( )
(3) ______ are used to prevent relative motion between a shaft and machine elements such as gears, pulleys, cams, flywheels and so on.
(4) Those applications which require the shafts to periodically disengage are called_____.
(7) Rigid couplings are permanent coupling.( )
Unit 9
4．Fill the blanks with the words and expressions given below:
pulleys, brakes, hinges, springs, axle, levers, keys, clutches, couplings, axis.
(2) Seals are used to connect two shafts.( ) (3) Coupling used for such typical applications are called temporary coupling, because their connections would only be broken for repairs or general maintenance.( ) (4) In industry, we seldom use the following keys: the square key, the tapered key and the woodruff key.( )
Unit 9
Unit 9
belt drive 皮带传动 fabric belt 纤维带 steel belt 钢带 formed steel 型钢
Unit 9
NOTES
1．They allow the designer considerable flexibility in location of driver and driven machinery, and tolerances are not critical as the case with gear drives.
Unit 9
(5) An axis is a shaft, either stationary or rotating, not subjected to a torsion load.( )
(6) Under wire springs are included the cantilever and elliptical.( )
Unit 9
Large flat leather belts were in general use many years ago, when the usual practice was to use one large engine to drive several different pieces of machinery. Some leather belts are in use at this time as well as flat steel, rubber, plastic, and fabric belts. Light, thin flat belts are practical on high speed machinery where vibration may be a problem.
采用皮带传动能使设计者在确定主动轮与从动装置的位 置时有相当大的机动性，而且公差的要求也不像齿轮传动装 置那样严格。
本句中as代表前半句中的tolerance are not critical。 2．when the usual practice was to use one large engine to drive several different pieces of machinery. 那时，通常是一台大功率的发动机来驱动数台不同的机器。 “when”引导的从句，在这里作进一步说明之用，可 译为“那时”。
Unit 9
3．Light, thin flat belts are practical on high speed machinery where vibration may be a problem. 轻薄的平皮带在引起振动的高速机械上很实用。
“where”引导的从句修饰前面的名词“high speed machinery”；“where”相当于“on high speed machinery”。从 上下文看，该句带有表示原因的意思，故翻译时可加上“因 为”。
V belts are probably the most common means of transmitting power between electric motor and driven machinery. Conventional V belts are made of rubber. Most often, both driver and driven pulleys lie in the same vertical plane, and the speed ratio is constant.
Unit 9
Smooth flat belts and V belts depend on friction on the pulleys, and some slippage is inherent in their operation. Therefore, speed ratios are not precise. Most heavy-duty pulleys are made of cast iron or formed steel.
(1) An_____ is a shaft, either stationary or rotating, not subjected to a torsion load.
(2) Mechanical______ are used in machines to exert force, to provide flexibility, and to store or absorb energy.
4． Smooth flat belts and V belts depend on friction on the pulleys, and some slippage is inherent in their operation.
平皮带和V型带依靠与带轮的摩擦产生运动，在工作中 必然存在一定的滑移量。
Unit 9
Mr. Wang: What are the problems? May I help you? Li Ying: Yes, what are the advantages of belt drive? Mr. Wang: Belt drive is a kind of flexibility transmission, so the location between driver and driven machinery can be easily adjusted. Another advantage of belt drive is that they can efficiently reduce vibration and shock transmission. Furthermore, belt drive is relatively quiet. Li Ying: It seems to be a very useful transmission method. Mr. Wang: Yes, you are right. Li Ying: You are very kind. Bye-bye. Mr. Wang: Bye.
Unit 9
EXERCISES
1．Discuss the following questions in English: (1) What are the advantages of belt drives? (2) Why are light, thin flat belts practical in high speed machinery? (3) What are conventional V belts made of ? (4) What do smooth flat belts and V belts depend on? 2．Use English for replacing Chinese or use Chinese for replacing English. (1) 橡胶带 (2) 塑料带 (3) 主动带轮 (4) Vibration of belt (5) Mean of transmitting power (6) Slippage of belts
Unit 9
Unit 9
TEXT LEARN TO SPEAK NEW WORDS AND EXPRESSIONS NOTES EXERCISES READING MATERIAL PROFESSIONAL WORDS AND PHRASES
Unit 9 TEXT
Belt Drives
Belt drives offer a maximum of versatility as power transmission elements. They allow the designer considerable flexibility in location of driver and driven machinery, and toleranceห้องสมุดไป่ตู้ are not critical as the case with gear drives. Another advantage of belt drives is that they reduce vibration and shock transmission. Furthermore, belt drives are relatively quiet.
Unit 9
belt pulley
Fig. 9-1 Belt and pulley
Unit 9
LEARN TO SPEAK
Li Ying: Good afternoon, Mr. Wang. Mr. Wang: Good afternoon, Li Ying. Where are you going? Li Ying: I am going to the library to borrow some books. Mr. Wang: What kinds of books do you want to borrow? Li Ying: I would like to borrow some books of machine elements. Mr. Wang: Why? Li Ying: I have been learning the course of mechanical design, but I have some trouble in learning the belt drive. So I need some reference books.