专业英语11-15.doc

11. Belt drivesVocabulary:versatility 9v:sEtilEti 多功能性flexibility 7fleksE5biliti 适应性，弹性tolerance 5tClErEns 公差critical 5kritikEl 严格的shock FCk 冲击relatively 5relEtivli 相对的means mi:nz 手段，方法leather 5leTE 皮革fabric 5fAbrik 纺织物conventional kEn5venFEnl 常规的vertical 5vE:tikEl 垂直的constant 5kCnstEnt 不变的slippage 5slipidV 滑动inherent in5hiErEnt 固有的precise pri5sais 精确的pulley 5puli 滑轮plane plein 平面wrap rAp 缠绕Text: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 tolerances are not critical as is the case with gear drives. Another advantage of belt drives is that they reduce vibration and shock transmission. Furthermore, belt drives are relatively quiet.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.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.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.Note that the capacity of the belt drive is determined by the angle of wrap, , on the smaller pulley, and that this is particularly critical for drives involving pulleys of greatly differing size, spaced closely together.Appending:Conveyer Belt Conveyer, mechanical system for transporting materials from one site to another. Conveyers are widely used in industrial and business operations. They include simple chutes, the unpowered roller conveyers used to move cargo across sidewalks from trucks to stores, and a wide range of powered systems in which materials are carried along by belt, bucket, screw, trolley, or other arrangement. Pneumatic conveyers are tubes in which goods usually in a finely divided form are moved along by blowers. An important step in automation was Henry Fords introduction of powered conveyers into his automobile assembly line in 1913.12. Keys and SpringsVocabulary:prevent pri5vent 防止sprocket 5sprCkit 链齿轮lever 5li:vE 杆flywheel 5flaiwi:l 飞轮impeller im5pelE 叶轮numerous 5nju:mErEs 许多standardize 5stAndE7daiz 使标准square skwZE 四方的taper 5teipE 锥形, 锥度woodruff key 半圆键hub hQb 轮毂call for要求proportion prE5pC:FEn 比例approximately EprRksI5mEtlI 近似地diameter dai5AmitE 直径exert i5zE:t 施加tensile 5tensail 拉力的torsional 5tC:FEnEl 扭转的cantilever 5kAntili:vE 悬臂elliptical i5liptikEl 椭圆的washer 5wCFE 垫圈release ri5li:s 释放Text:Keys are used to prevent relative motion between a shaft and machine elements such as gears, pulleys, sprockets, cams, levers, flywheels, impellers, and so on. There are numerous kinds of key (some of which have been standardized) for various design requirement. The keys most frequently used are the square key, the tapered key, and the woodruff key.Perhaps the most common of these torque-transmitting shaft-to-hub connections are keys, of which the most common type is the square key. Standard proportions call for the key width to be approximately one-forth the shaft diameter. Keys are usually made of cold-finished low-carbon steel, but heat-treated alloy steels are used when greater strength is required.Mechanical springs are used in machines to exert force, to provide flexibility and to store or to absorb energy. In general, springs may be classified as either wire springs or flat springs, although there are variations within these divisions. Wire springs include helical springs of round, square, or special-section wire and are made to resist tensile, compressure or torsional loads. Under flat springs are included the cantilever and elliptical types, the clocktype power-springs and the flat spring washers, usually called Belleville springs.In one word, springs are elastic members that exert forces (or torques) and absorb energy (which is usually stored and later released). Springs are usually, but not necessarily, made of metal. Plastics can be used when loads are light.Appending:1. KeyKey, in mechanics, small part fitting a prepared recess cut in two joined parts or components, and thus employed to lock these parts together. Keys are most commonly used to lock wheels or gears firmly in their axles. Such a key is often composed of a thin strip of metal that fits tightly into a transverse groove cut in the axle shaft and into a parallel groove in the inner diameter of the wheel hub. Some keys are designed to prevent any play between wheel and axle, and others allow the wheel to slide along the axle but not to turn relative to it, although when sliding motion is needed, engineers usually prefer to use a splined shaft. 2. SpringSpring, in mechanics, device made of an elastic material that undergoes a significant change in shape, or deformation, under an applied load. Springs are used in spring balances for weighing and for the storage of mechanical energy, as in watch and clock springs or door-closing springs. Springs are also used to absorb impact, as in coil or leaf springs used for automobile suspensions, and to reduce vibration by the use of rubber blocks. The specific form of a spring depends on its use. A weighing spring, for example, is normally wound as a helix, and its elongation is proportional to the applied force, so that the spring can be calibrated to measure this force. Watch springs are wound as spiral coils, and sets of flat bars or leaves, superimposed on one another to form laminations, are used as leaf springs in automobile.13. ScrewVocabulary:screw skru: 螺钉fastener 5fB:snE 扣件wedge wedV 楔circular 5sE:kjulE 圆形的cylinder 5silindE 圆柱体truncate 5trQNkeit 截去顶端cone kEun 圆锥体moment 5mEumEnt 力矩groove ru:v 凹槽square skwZE 正方，直角hexagonal heksAEnEl 六边形的wrench rentF 扳手slot slCt 狭槽recess ri5ses 凹处screwdriver 5skru:draivE 螺丝起子oval 5EuvEl 椭圆的fillister 5filistE 槽口tap tAp 攻螺纹cap screw 帽螺钉clamp klAmp 夹紧bolt bEult 螺栓nut nQt 螺母stud stQd 柱头螺栓stretch stretF 伸长tight 5tait 拉紧的set screw 固定(定位)螺丝tensile 5tensail 拉力的substitute 5sQbstitju:t 替代品conjunction kEn5dVQNkFEn 联结dimple 5dimpl 微凹处Text:Screws have been used as fasteners for a long time. As indicated in the section on single machines, a screw acts with a wedging action and consists of a circular cylinder (or truncated cone) with a helical groove in it. When used for fastening, all screws are provided with means for applying a torque (twisting moment) to them; this may consist of a square of hexagonal head for a wrench, a head with a slot or a cross-shaped recess for a screwdriver, a cylindrical head with a recess fitting a special wrench, or a slot or recess on one end fitting a screwdriver or special wrench and no head.Screws with screwdriver slots have heads of several shapes, such as flat, oval, round, and fillister (cylindrical with a round top). Wood screws are tapered, and self-tapping screws have tapered ends and a variety of special points. The latter are usually hardened and cut or form a mating internal thread when screwed into the proper size hole.Screws with hexagonal heads are usually known as cap screws. Screws with other types of heads are also known as cap screws in the larger sizes and as machine screws in the small sizes. All of these screws are used to clamp machine parts together when one of the parts has an internal thread. If neither part is threaded a bolt must be used: this consist of a screw with a hexagonal head, a nut (hexagonal ring with an internal thread), and usually a washer (flat ring). A stud has threads on both ends and no means for turning. It is permanently screwed into one member and clamps by means of a nut on the other end. All of these fasteners stretch when tightened, and the tensile load created in this way clamps the members together.Set screws differ in form and function from the other type of screws. They are hardened and have cup, cone, oval, flat, and dog (cylindrical) ends or points. They are usually headless and are frequently used as substitutes for keys or in conjunction with keys in shaft-mounted members. The set screw fits in a threaded radial hole in the hub, and the point is tightened down into a hole, a flat, or a dimple in the shaft or key. Set screws are stressed in compression and in action they create a helical wedge between the connected parts.Appending:Common Wood ScrewsScrew, mechanical fastening device consists essentially of an inclined plane wound spirally around a cylinder or a cone. The ridges formed by the winding planes are called threads, and depending on the intended use, the threads may be square, triangular, or rounded in cross section. The distance between two corresponding points on adjacent threads is called the pitch. If the thread is on the outside of a cylinder, it is called a screw or male thread, and if it is on the inside of a cylinder, as in the case of a common nut, it is called a female screw. Screws and bolts used in machines employ a cylindrical shaft with a constant inner or minor diameter, but wood screws and pipe threads are cut on a tapering cone.14. ShaftsVocabulary:shaft FB:ft 转轴component kEm5pEunEnt 零件deliver di5livE 传送crank 5krANk 曲柄reciprocate ri5siprEkeit 往复的piston 5pistEn 活塞coupling 5kQpliN 联轴器chain tFein 链条pump pQmp 泵camshaft 5kAmFB:ft 凸轮轴actuate 5Aktjueit 开动, 促使stationary 5steiFnEri 固定的buggy 5bQi 双轮单座的轻马车carrying 5kAriiN 承载的, 装载的spindle 5spindl 心轴speak of 谈及, 说到magnitude 5mAnitju:d 数量大小twist twist 扭曲distortion dis5tC:FEn 扭曲变形Text:As a machine component, a shaft is commonly a cylindrical bar that supports and rotates with devices for receiving and delivering rotary motion and torque. The crankshaft of a reciprocating engine receives its rotary motion from each of the cranks, via the pistons and connecting rod (the slider-crank mechanisms), and delivers it by means of couplings, gears, chains, or belts to the transmission, camshaft, pumps, and other devices.The camshaft, driven by a gear or chain from the crankshaft, has only one receiver or input, but each cam on the shaft delivers rotary motion to the valve-actuating mechanisms.An axle is usually defined as a stationary cylindrical member on which wheels and pulleys can rotate, but the rotating shaft that drive the rear wheels of an automobile are also called axles, no doubt a carryover from horse-and-buggy days.It is common practice to speak of short shafts on machines as spindles, especially tool-carrying or work-carrying shafts on machine tools.In operation, shafts are subjected to a shearing stress, whose magnitude depends on the torque and the dimensions of the cross section. This stress is a measure of the resistance that the shaft material offers to the applied torque. All shafts that transmit a torque are subjected to torsional shearing stress.In addition to the shearing stresses, twisted shafts are also subjected to shearing distortions.The distorted state is usually defined by the angle of twist per unit length, i.e., the rotation of one cross section of a shaft relative to another cross section at a unit distance from it.Appending:Automobile SystemsAutomobiles are powered and controlled by a complicated interrelationship between several systems. This diagram shows the parts of a car with a gas engine and manual transmission. The major systems of the automobile are the power plant, the power train, the running gear, and the control system. Each of these major categories includes a number of subsystems, as shown here. The power plant includes the engine, fuel, electrical, exhaust, lubrication, and coolant systems. The power train includes the transmission and drive systems, including the clutch, differential, and drive shaft. Suspension, stabilizers, wheels, and tires are all part of the running gear, or support system. Steering and brake systems are the major components of the control system, by which the driver directs the car.15. BearingsVocabulary:bearing 5bZEriN 轴承connector kE5nEktE 连接器oppose E5pEuz 阻碍overcoming 7EuvE5kQm 克服co-act kEu5Akt 共同合作assemblage E5semblidV 集合pin-joint 铰接multitude 5mQltitju:d 多数essential i5senFEl 基本的severe si5viE 剧烈的interpose 7intE(:)5pEuz 放入，插入majority mE5dVCriti 大多数preassemble 5pri:E5sembl 预先安装radial 5reidjEl 半径的thrust WrQst 推力term tE:m 把称为angular 5ANjulE 有角的race reis 沟槽Text:A bearing is a connector that permits the connected members to either rotate or translate (move to and fro) relative to one another but prevents them from separating in the direction in which loads are applied. In many cases, one of the members is fixed, and the bearing acts as a support for the moving member.The relative motion in bearings is always opposed by friction, and the work done in overcoming friction is lost power in all machines. Consequently, much thought and effort have been devoted to the development of bearings with minimum friction. In all bearings, there are two surfaces (one belonging to each of the connected parts) that move relative to one another. To minimize friction, the co-acting surfaces may be partially or completely separated by a film of liquid or gas; these are known as sliding-contact bearings. The surfaces may be separated also by an assemblage of rolling elements such as balls and rollers; these are known as roll-contact bearing.Sliding bearings are the simplest to construct and, considering the multitude of pin-jointed devices and structures in use, are probably the most commonly used.The essential parts of a ball bearing - the inner and outer ring, the balls, and the separator - are shown in figure. The inner ring is mounted on a shaft and has a groove in which the balls ride. The outer ring is usually the stationary part of the bearing and also contains a groove to guide and support the balls. The separator prevents contact between the balls and thus reduces friction, wear, and noise from the regions where severe sliding conditions would occur. In a few applications where opera