机械工程专业英语 李光布.docx

Keys，Couplings and SealsA key is the machinery component placed at the interface between a shaft and the hub of apowertransmitting element for the purpose of transmitting torque(see Figure 16(a)Thekey is demountable to facilitate assembly and disassembly of the shaft systemIt is installed inan axial groove machined into the shaft，called a keyseatA similar groove in the hub of thepowertransmitting element is usually called a keyway，but it is more properly also a keyseatThekey is typically installed into the shaft keyseat first；then the hub keyseat is aligned with thekey，and the hub is S1d into positionFigure 16 Parallel keys1Square and Rectangular Pa rallel Keys The most common type of key for shafts uD to 65 inches in diameter is the square key，asillustrated in Figure 16(b)The rectangular key(illustrated in Figure 16(c)isrecommended for larger shafts and is used for smaller shafts where the shorter height can betoleratedBoth the square and the rectangular keys are referred to as parallel keys becausethe top，bottom and the sides of the key are parallel The keyseats in the shaft and the hub are designed so that exactly onehalf of the height ofthe key is bearing on the side of the shaft keyseat and the other half on the side of the hubkeyseat2Couplings The term coupling refers to a device used to connect two shafts together at their ends forthe purpose of transmitting powerThere are two general types of couplings：rigid and flexible 1)Rigid Couplings Rigid couplings are designed to draw two shafts together tightly so that no relative motioncan occur between themThis design is desirable for certain kinds of equipment in whichprecise alignment of two shafts is required and can be providedIn such cases，the couplingmust be desioned to be caoable of lransmittina thetnrn=Ip in thp thoft。A typical rigid coupling is shown in Figure 17，in whichflanges are mounted on the ends of each shaft and are drawntogether by a series of boltsThe load path is then from thedriving shaft to its flange，through the bolts，into the matingflange，and out to the driven shaftThe torque places thebolts in shearThe total shear force on the bolts depends onthe radius of the bolt circle and the torque Rigid couplings should be used only when the alignmentof the two shafts can be maintained very accurately，not onlyat the time of instaIIatjOn but aIsO during Operation Of the Figure 17 Rigid c。uplingmachinesIf significant angular，radial，or axial misal ignmentoccurs，stresses that are difficult to predict and that may lead to early failure due to fatigue willbe induced in the shaftsThese difficulties can be overcome by the use of flexible couplings 2)Flexible Couplings Flexible couplings are designed to transmit torque smoothly while permitting some axial，radial，and angular misalignmentThe flexibility is such that when misalignment does occur，parts of the coupling move with little or no resistanceThus，no significant axial or bendingstresses are developed in the shaft Many types of flexible couplings are available commerciallyEach of them is designed totransmit a given limiting torqueThe manufacturerS catalog lists the design data frOm whichyou can choose a suitable couplingRemember that torque equals power divided by rotationalspeedSo for a given size of coupling，as the speed of rotation increases，the amount of powerthat the coupling can transmit also increases，although not always in direct proportionOfcourse，centrifugal effects determine the uDDer Iimjt nf snppcourse，centrifugal effects determine the upper limit of speed 3SeaIS Seals are an important part of machineapply：design in situations where the following conditions Contaminants must be excluded from critical areas of a machine Lubricants must be contained within a space Pressurized fluids must be contained within a component such as a valve or a hydrauliccylinder Some of the parameters affecting the choice of the type of seal ink system，the materialsused，and the details of its design are as follows： The nature of the fluids to be contained or excluded Pressures on both sides of the seal The nature of any relative motion between the seal and the mating cOmpOnents Temperatures on all parts of the seal ing system The degree of sealing required Is some small amount of leakage permissible? The nature of the solid materials against which the seal must act：corrosion potential，smoothness，hardness，wear res istance Ease of service for replacement of worn seal ing elements l he number of designs for sealing systems is virtually limitless，and only a brief Overviewwill be presented hereOften-designers rely on technical information provided by manufacturersof complete sealing systems or specific sealing elementsAlsoin critical Or unusual situatiOns，testing of a proposed design is advisedA键和轮毂轴之间的界面下的机械组件电发送单元，用于传递转矩的目的（见图1.6 （一） ） 。关键是可拆除的，以方便组装和拆卸的轴system.It的安装在加工成轴的轴向槽，称为一个keyseat.A类似的凹槽中的枢纽动力传递元件，通常被称为一个键槽，但它是更适当地还设有一个keyseat.The第一密钥通常安装到轴的键槽，轮毂键槽对齐与键，和轮毂S1.d入到位。图1.6并行键1.Square和矩形霸rallel键最常见的类型的键轴UD到6.5英寸直径的平方的键，矩形键（图1.6 （c）条中所示）是图1.6 （b）条中示出。建议使用较大的轴，用于较短的高度可以减小轴tolerated.Both正方形和长方形的键被称为平行键，因为的顶部，底部和两侧的键是平行的。在轴与轮毂的keyseats完全相同的设计，使二分之一的高度键轴的键槽的一侧，而另一半上的轮毂侧轴承键槽。2.Couplings术语“耦合”指的是用于连接两轴在其端部的装置目的传递power.There的联轴器一般分为两种类型：刚性和柔性。1）刚性联轴器刚性接头设计绘制两个轴紧紧联系在一起，没有相对运动它们。设计之间可以发生某些类型的设备是理想的，其中两轴精确对准是必需的，可以provided.In这种情况下，耦合必须desioned是caoable lransmittina the.tnrn = IP THP thoft的公司。如图1.7所示，一个典型的刚性耦合凸缘被安装在各轴的端部，被吸引一起由一系列bolts.The的负载路径，然后再从驱动轴，其法兰通过螺栓，入配合法兰，进出的的驱动shaft.The扭矩地方螺栓shear.The总剪力螺栓取决于螺栓分布圆的半径和转矩。刚性接头时，应只用于对齐的两轴可以保持非常准确，不仅在图1.7刚性。 upling操作时间期间instaIIatjOn但AISOmachines.If显著的角，径向或轴向misal的ignment时，是很难预测的，这可能会导致早期失效因疲劳应力被诱导在shafts.These困难是可以克服的挠性接头的使用。2 ）弹性联轴器挠性接头设计顺利传递扭矩，同时允许一定的轴向，径