《机械制造专业英语》教案

1、1 / 51一、New Words:Coordinate system :The basic of all input AutoCAD is the Cartesiancoordinate system, and the various method of input(absolute orrelative) rely on this system.Coordinate value： 坐标值Cartesia n coord in ate axes笛卡尔坐标车由Perpendicularly垂直地Projectio n：投影Orthographic projection: 正投影1.1coord

2、inate systemCAD = computer-aided designFixed: firmly in position ; stationaryLocate: vt. To determine the position ofPositive and negative :Illustrate : to explainDrafting : n.制图1.2Types of ViewsAuxiliary:辅助视图Detail: n.详图；局部Derived :取得；由来Scaling :enlarge scaleUnit 1Engineering Drawing2 / 51Clarifica

3、tion :to make clearPla nar: tow-D draw ingCross-secti on:横截面Datum pla ne:基准面Fig. 1-3:Brush with spring:F带弹簧的电刷Han dle:手柄Needle bearing滚针轴承Retaining ring：挡圈Chuck spacer:夹头衬片Key:销Symmetrical对称的Con figurati on:：结构1.3 Multiview drawi ngengin eeri ng drawi ng is an abstract uni versal Ian guage used tore

4、present a designWr s idea to otherHome work:Page 9:Exercise:1. fill the blanks with a proper word according to the text.、Technical Reading3 / 51The following diagram shows what happens in a displacer typeStirling engine during one working cycle.A . The power piston is in its lowest and the displacer

5、 in its highestposition. All the working gas is in the cold space.B . The displacer is still in its highest position. But the power piston hasgone up and compressed the gas in the cold space.C . The power piston is now in its upper position and the displacer haspushed the gas through the cooler, the

6、 regenerator, and theheating pipes into the hot space.D . The hot gas is being expanded, and hest energy is beingtransformed into mechanical energy as the displacer and thepower piston are pushed down into their lowest positions. Thepiston will stay there while the displacer rises and pushes the gas

7、through the heating pipes, regenerator and cooler into the coldspace_and we are back where we started.Words:Diagram： 图表4 / 51Positi on：位置Stirling:斯特林（音译）Displacer:置换器Piston:活塞Rege nerato蓄热器Cooler：冷却器Expa nd:膨胀As：随之hest energy热能mechanical energy机械能译文：置换器型斯特林发动机工作循环如下所示：A置换器在最高位，动力活塞在最低位。所有的工作气体在 冷空间；

8、B置换器不动，动力活塞上升并挤压冷空间的气体；C.动力活塞到达最高位，置换器下移，推动气体经过冷却器、蓄热器、和加热管进入热空间；D.热气膨胀， 热能转变成机械能， 随之动力活塞和置换器 到达最低位。动力活塞不动，置换器上升推动气体经过加热管、蓄热器和冷却器进入冷空间回到起点5 / 51三、Grammar概论（一）什么是翻译？ 机械工程英语翻译的困难主要存在于正确理解原文的 含义和用确切的汉语文句准确表达原文的含义两个方面。 译者 除必须是有较好的英语基础， 较高的汉语修养， 较为丰富的机 械工程专业知识外，还必须懂得翻译的理论技巧和方法。本课将介绍翻译机械工程英语著作的基本理论知识， 技 巧

9、和方法，帮助同学们提高翻译水平和质量。（二）英汉两种语言的对比。1、一般特点（翻译的习惯，语序，省略）（1）When a=0,Eq（14-1） shows that the pressure is Zero.由式14-1可知，a=0时压力为零。（用when that连接 子句）Eqeq=equatier方程式、等式（2）It frequently happens, in the case of plane stress, that thetwo principal stresses?1and ?2have the same sign.平面应力的两个主压力?1和?2的符号往往相同。（用介词in,

10、 of和连词and连接词（组），用that引主语 从句）2、词汇现象。Phrase英汉两种语言在词的意义搭配和词序等词汇现象上也存 在着差别。6 / 51（1）词的意义1英语词汇和汉语词汇在词义的对应有三种不同的情 况。First,英汉词义对等：如：gear teeth齿轮轮齿stress- strain diagram压力一应变图bolted connection螺栓联接maximum bending moment最大弯矩2second英汉词义部分对应，即两者在词义所概括的 范围上不同，如gear既可专指“齿轮” ，又可泛指任何 类型的“传动装置” 。而pinion则专指“小齿轮” 。3在不

11、同场合下，同一汉语采用不同英语词汇。 “特性”一词举例。（1） In fact, many motors do have a nearly constanttorque-speed characteristic during starting.Characteristic:特性，特征Behavior :机器的运转状态，性能Constant :固定的，不变的，常量。事实上，许多电动机在启动时的扭矩转运特性几乎不 变。(2)Tolerances cover dimensional variation andsunface-roughness range and also the variation

12、 in mechanicalproperties resulting from heat treatment and other processing7 / 51operations.公差这个概念包括尺寸偏差范围和表面粗糙度范围，也 包括由热处理和其它处理操作所引起的机械特性的变 化。(3) These cams perform such important function in manycases that the behavior of the entire machine is dependentupon the design of the cam motion.这些凸轮起着相当重要的

13、作用， 在许多情况下， 整台机 器的特性都取决于凸轮运动的设计。4The thind一个英语词所表达的意义与几个具有不同的词义的汉语词分别对应：Shaft轴、箭、长柄、树干；Power电源、功率、动力、乘方、国家；Cutter刀具、锐刀、刀盘、切断机；Shaping刨削、成形；Joint接头、轴节、联接；5此外，英词还有些尚无确定的译法，主要指新词，如aerospace词。Aerospace“航空宇宙” -“航空公司” -“宇宙空8 / 51间” -“航天”Hydraulic motor： “液压电机” - “液压马达”2) 词的搭配 由于思维方式和语言形成过程的不同，英汉在同一搭配上存在着较

14、大的差别，这种差别主要表现在a和n / v和n的搭配上如build原义“建造”“建设”“构造”“造型”而当build与不同的n.搭配时，应有不同的译法。Build a house盖房Build a car制造汽车Build a ship造船Build a railway修筑9 / 51Unit 2 Mechanical Components一、New words :2.1Shaftssolid shaft:实心轴铁路Build a bridge架桥Build a fire生火Build a dam筑坝Heavy沉重的 ，重型的 ，重的，大量的。Heavy load重载大风暴Heavy mach

15、ine重型 机械丰收Heavy current强电流繁重的任务Heavy wire粗 浅traffic拥挤的交通Heavy fire强烈的炮火heavyheavyheavystormcropstaskheavy10 / 51flexible shaft:柔性轴cyli ndrical:圆柱形的bar:棒deliver:传递arran geme n安装、装酉己radii:pl . radius半径plain tran smissi on普通的传送装置stepped shaft阶梯车由mach ine tool spi ndle机床主车由cran kshaft机车由circlips:开口簧环woo

16、druff key:半圆键2.2 shaft accessoriessquare正方形sunken下陷的recta ngular矩形的ratio:比例2.3 Clutchescoaxial:同由的positive drive:强制传动2.4 Screwsfastener:紧固件11 / 51cap screw有头螺钉2.5 Springsload-se nsitive负载敏感（元件）Home work:Page 22:Exercise:1. fill the blanks with a proper word according to the text.二、Technical ReadingF

17、UTURE WATCHIN THE 1930s, the famous cartoon detective Dick Tracy used histhen-fantasticwrist whatchamacallitto make telephone calls.NowEuropean electronics giants Philips and British Telecom aredeveloping wrist devices Dick Tracy would envy : They would12 / 51combine such features as video phone, TV

18、 and radio reception, clock,electronic notebook, and a personal computer with wireless access tothe internets Woerlbd. Wide WThe basic technologies to makewrist communicatorsexisttoday, saysPhilips, though the Dutch company saysit likely wontcreate an operational model until at least the year 2003.

19、Thecomponents, including batteries , must be miniaturized .While an earlynonworking prototype demonstrates buttons for operation, Philipssays that voice-recognition technology and an interactive screen mightreplace tough control. Philips also envisions the wireless connection tothe World Wide Web fo

20、r graphics and video images.Researchers at BT(British Telecom)Laboratories in MartleshamHeath, England ,have taken their version of the idea a step further.The lab has been displaying a working prototype in Britain to potentialequipment manufactures. The somewhat bulky communicationsconsole includes

21、 cellular telephone , video phone ,fax, computer,clock, and batteries, and encircles most of a person s forearm.Words：Carto on：卡通13 / 51Whatchamacallit = what do you call it某它，叫不出名子的东西Detective：侦探Fantastic： 奇异的British Telecom:英国电信公司Comb ine：组合Feature：特性Access to： 进网World Wide Web:全球信息网Minaturize： 微型

22、化Dutch:荷兰Prototype:原型机Laboratory:实验室Graphic： 扫描Bulky:容量Cellular:蜂窝状Fax:传真En circle:缠绕译文:在本世紀30年代，著名的卡通人物侦探迪克.雷西用来打电话的是他当时带的一块非常奇异的叫不出名字的手表。如今，欧洲电子业巨头菲利普先生和英國電信公司正在研製連迪 克.特雷西也会嫉妒的手表：他们将把可视电话、电视、收音 机、时钟、电子记事簿以及能14 / 51与全球互联网络的个人电脑组合 在一起。菲利普公司称，制造腕式通信器的基本技术如今已具备， 但这家荷兰公司表示他们说不定得到2003年才能制造出可操 作的样机， 其包括电

23、池在内的零部件必须微型化， 虽然早一代 非实用原型机是用按钮操作来演示的，但菲利普公司认为声音 识别技术和可互视的屏幕有可能 取代触摸控制。该公司还设 想在扫描与可视图象方面同全球互联网络 。设在英格兰马特利香西思的英国通信公司的实验室的研 究人员， 已把这设想先行了一步， 该实验室已向英国未来的设 备制造商展示了一个可工作样机，这个容量颇大的通信控制器 包括了蜂窝电话、可视电话、传真、电脑、时钟和电池等，戴 时满绕使用者的大部分前臂。15 / 5116 / 51三、Grammar（3）词序词语的各个成分在句中的位置叫“词序”。1）共同点：就自然词序而言，主语、表语、宾语。许多英语可直译成汉语

24、女口：（1）The rim must have sufficient rigidity.轮缘必须有足够的刚度。（主）（2）The tension rod shown in Fig .2-12 is typical .图2-12所示的拉杆是 典型的。（表）（3）These twocon sta nts represe nt fun dame ntal properties ofmaterial.这两个常数表示材料的 基本性能。（宾）2）不同点：在定语和状语的词序上差别很大。在英语句子中，若定语是一个单词，则置前。若是一个短 语，则置后。在汉语中，定语一律置前。地点和时间状语正好相反。汉语：由大一

25、小，年月日（汉）02.3.1中国.上海.英语：由小一大，10/3/05（英）ShangHai of China.年-用基数词，日-用序数词1999/7/23 July 23,199917 / 51读：July(the) twenty-third, nineteen ninety-nine.1905nineteen hundred and five1800eighteen hundred2005twenty hundred and fiveUnit 3 Control Devices and PLC、New words3.1 Types of Control Devicespn eumatic

26、con trol气动控制18 / 51programmable logic con trol(PLC)可编程逻辑控制gover nor调速器cost effectively有效的，经济的Automated machine自动机床Be subject to易 于.It uses compressed air, valves, and switches to construct simple controllogic.利用压缩空气、阀和开关构成简单的控制逻辑。Build:造Relays, timers, cou nter继电器、定时器、计数器Movi ng:移动的Versatile通用的；多功能的

27、Strategy策 略Computation:计算量nIn terface:联系装置；接口In ternally:内部的Voltage电压；伏特数volts:伏特milliamper=milliampere:毫安(培)Filter out:滤除Custom-built：定做的3.2 Relay device componentspanel控制板19 / 51circuit:电路styles款式category种 类pole:极；杆；极点；电极proximity:接近，邻近level switches电位开关thumbwheel switches拨轮开关thumb wheel switch:拇指

28、旋转开关slide switches挡位开关Home work:Page 32:Exercises:1. Answer the following questions briefly.(1) (4)2. Translate the following sentences into Chines.(1) (3)、Technical ReadingTHE NEW FORD CARFORDS LATEST concept car gives shape to the ideas being exploredby the New Generation Vehicle Program-the effor

29、t by a U.S. consortium to20 / 51develop the so-called“super car”. The goal is to create an 80-mpg, full-sizeaffordable family sedan and make it available in the coming decade.The car is called Synergy 2010. Itsaluminum body saves some 400pounds over a comparable-size steel body, bringing curb weight

30、 down to about2,200 pounds. The carslow pro aerodynamic“fences”(vertical fenders)reflect the need to cut drag to about one-third that of today s. s sedanPower comes from a direct-injection diesel turbo alternator, which uses aflywheel to store energy for acceleration. Electric current produced by th

31、esystem powers a separate electric motor in each wheel hub, whileregenerativebraking rechargesthe flywheel during Deceleration. Theflywheel-based hybrid drive concept has been under investigation for decades,even at Ford, but problems remain with building a production flywheel system.Likewise the wh

32、eel-in-hub motors, which are easy to package but presentsafety problems in the event of a single-motor failure.The design comes with a layered glass roof. To avoid turningthe car into a hot-house, solar-powered cooling fans pull in cooler outside airand exhaust interior air. Another unusual feature

33、is a turn-over steering columnthat converts to right-hand drive without modification. Many interior controlsrespond to a new voice-activation system that operates without initial“training”. The development of a prototype thats ready for tlhl e road is stiseveral years away, Ford says.21 / 51New word

34、s:Latest:最新的the eve nt of： 万一Consortium:联营企业Sedan轿车Synergy协和的curb：控制；约束aerodynamic： 气动的drag： 阻力的diesel：柴油引擎发电机regenerativebraking：恢复式刹车shape体现come up with：提出Affordable：负担得起的mpg = miles per galloncomparable-size： 类似大小profile：外观；外形fender：护板direct-injection：直接喷射turbo alternator： 气轮交流22 / 51recharge再充电h

35、ybrid:复合式exhaust排出turn-over:翻转式steering column: 操纵杆voice-activation：:话音激活respond to对.有反应flywheel-based以飞轮为基础的away:尚由.时间译文： 福特汽车公司最新设计的汽车，给“新一代汽车研究计 划”正在探索的各种设想赋予了具体的形象。 该计划是一家美 国联营企业为研制所谓 “超级轿车” 而制定的， 其目标在于创 制一种每加仑油可行驶80英里、大小可供家庭使用的轿车， 拟在未来10年里投入使用。这种汽车名叫协和2010。其铝制车身较类似的钢制车身重量减轻了400磅左右，从而使控制重量减至大约22

36、00磅。这种车较低的外形和气动“栅栏” （纵向防护装置）可将阻力减少到现有轿车的大约1/3。动力来自一台直接喷射柴油涡轮交流发电机， 它用飞轮来 储备供加速用的能量。 用这个系统所产生的电流带动每个轮毂 上分别安装的电力发动机， 在减速时恢复式刹车给飞轮再次充 电。甚至在福特公司， 这种23 / 51以飞轮为基础的复合式驱动思想也 已经研究了几十年， 但是建造一个生产飞轮的系统仍然存在着 问题。而且， 轮毂内的发动机易于组装， 但万一单个发动机发 生鼓掌就会出现安全问题。这种设想提出一种分层的玻璃顶棚，为了避免把汽车变成 一间温室，太阳能风扇吸入车外的清凉空气， 排出车内的空气。 另一个与众不

37、同的特点是一个翻转式的操纵杆， 无须改动即可 转为右座驾驶。车内许多控制装置由一种新型的话音激活系统 控制， 无须初步训练即可操作。 福特公司说， 研制这种可供上 路的样车还需几年时间。三、Grammar机械工程英语的特点1陈述句型多 句子的谓语动词多数采用一般现在时态1)The maximum stresses occur atthe inner最大应力发生在内表面2)The same equation and assumptions simplecompression.该假定和方程也同样适用于简单压缩的情况24 / 513)Thetotal mass of the beam is pl,

38、wheresurfacehold forp is the mass per unitlength.梁的全部质量是pl,其中p是单位长度的質量。2被动语态多1) This problem can also be solved using the vector method.这个问题也可利用矢量法求解2) Herea tension load F is applied through pins at the ends of thebar.此时，拉伸载荷F是通过杆件两端的销子施加的3.省略表达多1) use of the equationT=f/a for a body,say a bolt ,in

39、 shear assumes auniform stress distribution too.公式t=f/a应用于承受剪切应力的物体(如螺栓)时， 同样假定应力是均布的T=f/ai卖：Tequal to F divided A2) In the above equation positive stresses indicate tension andnegative stresses compression上述各个公式中， 正应力表示拉应力， 负应力表示压应 力省略了indicate和状语in the above equation25 / 5126 / 514.复杂长句多Unit 4 NC

40、and CNC一、New words:4.1 The history of NC and CNC developmentNC = Numerical control数字控制CNC = Computer Numerical control计算机数字控制Execute:执行Automatically:自动的In sequenee按顺序As specified指定的Contain:包含Propose提出propose to向.求婚Miehiga n:密西根州Recomme nd提出；推荐Thru-axis curve过轴曲线thru = through美式口语Award：授予；给予Co ntract

41、:契约；合同Speed up加速27 / 51Productio n:产量，生产，产品，生产量Commissi on委托Massachusettsnstitute of technology (M.l.T.)麻省理工学院Massachusett：s美国马萨诸塞州Impleme ntatio n:实施Perforate打 孑LMature:成 熟的Powerful:强大的Microprocessors微处理机Supervisio n管理；监督Pu nch达孔Executio n:执行4.2 The application of NC/CNCIntroduction： 引进Pun ches: p冲

42、压机；冲床Electrical discharge mach ine = EDM电火花加工机床discharge放电Flame cutter火焰切割机床；线切割机床Grin der:磨床inspection :检验turret:转动架accept接 受28 / 51magaz ine期干刊；盒；仓库swiveled转 动cha nger转换器OD = outside diameter; outside dime nsionTailstock尾 座In tercha nge互换Traveli ng colu mn可动柱Pallet：托板In dex table索弓I表Home work:Page

43、 44:Exercises:1. Fill in the blank according to the text.(1) (3)2. Answer the following questions briefly.(1) (2)3. Say whether the following statements are true (T) or false (F)according to the text.(1) (3)4. Translate the following sentences into Chines.(1) (2)29 / 515. Translate the following phr

44、ases into English.30 / 51(1) (6)Technical ReadingMachines That Mimic ManMan has always used augmenters to increase the powers which natureendowed him. A simple stick, made into a lever to extend his reach and enablehim to move heavy objects, may have been his first machine. Slingshots helpedhim kill

45、 food animals that were at greater distances. The wheel easedhismovement and his burdens over the ground. But those were simple augmentersfor simple tasks. Man has made his world much more complex. With the rapiddevelopment of scienceand technology, mans augmentershave become muchmore sophisticated.

46、 They are designed not only to do the work of man, but also todo it in much the sameway a man would.Some simply amplify the muscular power of their human operators. The“walking truck”being constructed, for example, isa large device that might better be called a walking horse. A man sits inside,movin

47、g his arms and legs to make the“horse”moown four legs and carry far greater loads than the operator could.30 / 5132 / 51Another man, wearing a movable mechanical and electrical framework, lifts 1,500pounds six feet in six seconds.Other machines link a man to a computer and the computer to a workdevi

48、ce. Thanks to the computer, the man does not need to guide the devicethrough each step. The computerremembershow to direct the aromf sthe machine by itself through many work steps.Still other mimicking machines go where man cannot-into the ocean depths andinto nuclear reactors where radiation would

49、cause a human operator to becomesick or to die.Augmenters that extend mans mental and physical skills over longdistances-but still require mans remote control- are called“tele-operators”So.medaydoctors may use such systems to operate onpatients thousands of miles away.With machines and robots becomi

50、ng more and more sophisticated, will theysomeday take over the world from man? Most scientists dont think so.Instead, they say, robots will takeover more of mans heavy work, giving man more time for creative work.New words:Augmentor（作人类替身从事危险工作的）替身机器人或机 械手：辅助器械33 / 51Endow赋予子Lever杠杆即之范围Task工作拟Sophis

51、ticate复杂的大Slingshot弹弓远程的Take over接管 造；建造；构成Framework机 构 ； 构 造英里Tele-远距离 远程操作Stick棍Reach可Mimic模Amplify扩RemoteConstruct制MileTele-operator译文：模拟人的机器人类一直利用辅助器械来增强大自然所赋予的力量，用一根普通的棍子来扩大手臂可及之范围， 或者移动重物， 这可能34 / 5135 / 51是最早的机器了。 弹弓可以帮助人们猎食远处的动物。 轮子使 人便于在地上行走并减轻负担。 但这些都是用于做简单工作的 简易装置。 人们让世界变得越来越复杂了。 随着科技的迅猛发

52、 展，人类的辅助器械也越来越复杂， 设计这些装置不仅是为了 让他们做人的工作，而且要让他们和人一样的工作。有些器械只是加强操作者肌肉的力量。 例如：正在建造的 “步行车”就是一个大型的装置， 更恰当些说可称之为 “步行 马”，人坐其中，运动它的臂和腿，使“马”移动它的四条腿， 搬运的载荷远远超过人力所及。再有，一个人穿上一种可动的 机电装置，在6秒钟内可将1500磅的重物提高6英尺。还有一种机器可将人、计算机和工作设备联系起来。幸亏 有了计算机，人类不必亲临指导设备做每一个步骤， 计算机“记 得”如何指挥机械手做很多工作。还有一些模拟机可以到达人所不能到的地方，深入深海、 进入放射线强度可使人

53、患病甚至致死的核反应堆。被称为“远程操作”的装置可增强人的智能和体能，仍需 要人远程控制。 有朝一日， 医生可以利用这种系统为数千里外 的病人作手术。36 / 51随着机器和机器人变的越来越复杂化，他们是否有一天会 取代人类来掌管这个世界？大部分科学家认为不会。相反的， 他们认为， 机器人会接管更多的繁重任务， 给人类更多的时间 进行创造性工作。Grammar翻译的标准和过程1准确37 / 51科技用语必须符合我国科技界的习惯、规范和约定。译文 叙述的内容要准确、明白、无歧义。1) On the other hand , a material which obeys Hookes Law is

54、elastic.反之，凡是符合胡克定律的材料就是弹性材料。 (增词译法) 注释：不定冠词a在举例中含有“任何一种”的意义， 因此，在译句 中增译“凡是”一词。增译“材料”是为了符合汉语的习惯 增译“就”是为了加强肯定语气2) The portion of the tooth between the clearancecircle and thededendum circle is the fillet.齿廓在间隙圆和齿根圆之间的那一部分是圆角将tooth译为 齿廓是符合技术概念引申译法2通顺 指符合汉语的修辞规则和习惯 要注意的问题：1) 译句中各个语法成分的排列顺序和相互关系要符合汉语的习惯

55、2)句子之间要有呼应和关联3)恰当体现原句之时态，语态，情态，和语气The constants are found by solvingthesetwo equationssimulta neously将两个方程联合求解，则可求出上述两个常数find求出(引申译法)con sta nts-两个常数(增词译法)依据方程组求解知识，增译“则可”是为了前后呼应的需要，同时全句采用了“变序译法”(2) The assumpti on of a uni form distributi on of stress is frequently made in desig n在设计中，常常采用应力均布的假定(3

56、)ln a closed cyli nder a Ion gitud inal stress will exist because ofthe pressure upon the ends of the vessel.由于压力作用于容器的两端，故在封闭圆筒上，将产生纵向应力。3.简练1)What a straight bar is subjected to a tensile load, the bar36 / 5140 / 51becomes longer.直杆受拉，则伸长翻译过程分为三个阶段 ： 理解表达校核。41 / 51Unit 5 Safety and Maintenance For

57、 CNCMachineNew words:5.1 safety notes for CNC machine operationsconcern:关注metal-cutti ng:金属切肖Uautomated自动化的con seque ntl y因此；必然的hazard危险locate找出；探出pers onnel员工preve nt预防injury:伤害damage损害clampi ng:夹具carousel旋转木马；转盘conjun cti on:连接collision:冲突；抵触；碰撞hazardous: a,有危险的，冒险的unqualified:不合格的，不满足要求的prove n：被

58、证明的6.2 Daily maintenance42 / 51mach ine tool builder机床厂glove:手套glove compartme nt工具袋syn tax句法hook:爪子in sert插入6.3 Fault diag no sis and acti onchip:铁屑dull blade钝的movable table活 动工作台block:滑块；程序段clog:障 碍ambie nt:环境的；外界的home work:pages 65exercise:1、Give short answers according to the text.2、Translate th

59、e following sentence from English intoChinese.、Technical ReadingWAYS TO WATCH YOUR REAR END43 / 51A system has been developed to help drivers see what is happening atthe back of their vehicles.Articulated truck drivers have long had problems with blind spotswhen driving their vehicles. These have gr

60、adually been overcome withthe introduction of wide angle and roof mirrors which have made majorcontributions to the safe operation of these commercial vehicles.Pedestrians or objects, which were previously hidden from view,can now be seen at a glance, allowing the driver to take timely action.Unfort