机械专业英语课件4

1、1n单词复习：上一课回顾2Lesson 4 Threaded Fasteners 螺纹紧固件螺纹紧固件n重点词汇：n1.locate vt. 确定位置n2.clamp vt. 夹紧 n3. Mass production 大规模生产n4. Screw/Bolt/Stud/Nutn5.torque 扭矩n6.washer n. 垫片n7.helical spring lockwasher 弹簧垫圈3Paragraph 1nThreaded fasteners perform the function of locating, clamping, adjusting and transmittin

2、g force from one machine member to another. n螺纹紧固件起着定位、加紧、调整和从一个机器零螺纹紧固件起着定位、加紧、调整和从一个机器零件向另一个传递力的作用。件向另一个传递力的作用。nThey are thoroughly standardized and generally designed for use in mass production of machines(设计用于机床大批量生产). n它们已经完全标准化，且通常用于大批量生产的机它们已经完全标准化，且通常用于大批量生产的机器上。器上。 4nThe use of the threaded

3、 fasteners remains the basic assembly method in the design and construction of machines despite advances in other methods of joining. n尽管存在其它先进的联接方式，螺纹紧固件的应用仍尽管存在其它先进的联接方式，螺纹紧固件的应用仍保留了机器设计和制造过程中基本的装配方法。保留了机器设计和制造过程中基本的装配方法。 5nThus the designers must select standard fasteners of the type and size tha

4、t will most adequately suit the application at hand. n因此，设计者在满足使用要求时应用标准类型和尺寸因此，设计者在满足使用要求时应用标准类型和尺寸的螺纹紧固件。的螺纹紧固件。 6Paragraph 2: nA threaded fastener is a device that can effectively exert(施加) and maintain a large force in one direction (axially) through the application of a small force in another d

5、irection (tangentially). n螺纹紧固件是这样一个装置，在切线方向上施加一个螺纹紧固件是这样一个装置，在切线方向上施加一个较小的力，能在轴线方向上有效地产生并保持一个较较小的力，能在轴线方向上有效地产生并保持一个较大的力。大的力。 7nAll are based on the single threaded screw, a simple machine that yields a large mechanical advantage(机械增益) in minimal space and theoretically is self locking(自锁的). n所有这些都

6、是基于单头螺纹螺钉的，它是一个简单机所有这些都是基于单头螺纹螺钉的，它是一个简单机械，可以在最小的空间内产生很大的机械增益，而且械，可以在最小的空间内产生很大的机械增益，而且在理论上是自锁的。在理论上是自锁的。 8n Effective use however, requires the aid of two other simple machines: the lever(手柄) and the wheel-and-axle machine. The wrench(扳手) is basically a lever, the screwdriver is a wheel-and-axle ma

7、chine. n而这一有效应用，要借助两个其它简单机械：杠杆和而这一有效应用，要借助两个其它简单机械：杠杆和轮轴机械。扳手是一种基本杠杆；螺丝刀是一种轮轴轮轴机械。扳手是一种基本杠杆；螺丝刀是一种轮轴机械。机械。 9Paragraph 3:nThreaded fasteners are basically small, highly stressed tensile components. nThreads are helical(螺旋状的) ridges(凸起) formed by cutting or cold forming(冷加工) a groove(凹槽) onto the surf

8、ace of a cylindrical bar, thus producing what is known as a screw, bolt, or stud(双头螺栓). n螺纹紧固件是尺寸较小，承受高拉应力的零件。螺纹螺纹紧固件是尺寸较小，承受高拉应力的零件。螺纹是通过在圆柱形棒料上切削加工或冷压成型的沟槽形是通过在圆柱形棒料上切削加工或冷压成型的沟槽形成的螺旋凸起物，这样产生了大家所知的螺钉、螺栓、成的螺旋凸起物，这样产生了大家所知的螺钉、螺栓、双头螺柱。双头螺柱。 10nThreads are also formed internally in cylindrical holes a

9、nd constitute(构成) what is known as a nut(螺母). nMatching external and internal threads so that they may be assembled is the key to all threaded fasteners. n螺纹也可在孔的内圆柱表面上生成，这就形成了螺母。螺纹也可在孔的内圆柱表面上生成，这就形成了螺母。内外螺纹匹配是所有螺纹紧固件装配的关键。内外螺纹匹配是所有螺纹紧固件装配的关键。 11nThe rotary motion of a nut against a stationary screw

10、 first imparts an axial movement along the screw. n相对静止的螺栓，螺母的旋转运动会产生一个沿螺栓相对静止的螺栓，螺母的旋转运动会产生一个沿螺栓轴线方向的直线运动。轴线方向的直线运动。nWhen resistance is encountered, the threads generate an axial force as dictated by the principle of the wedge(斜楔原理). n受到阻力时，螺纹产生轴向力的现象可由斜面原理来受到阻力时，螺纹产生轴向力的现象可由斜面原理来解释。解释。 12n Further

11、 rotation demands increased efforts (torque), with a resulting increase in axial force.n再进一步旋转需要增加扭矩（再进一步旋转需要增加扭矩（torque）同时轴向力也）同时轴向力也增大。增大。n Thus the connection remains tight unless some external influence such as vibration or temperature change overrides the initial condition. n这样只要没有像振动、温度变化这些外部因

12、素改变初这样只要没有像振动、温度变化这些外部因素改变初始条件，这种联接就能维持紧固的状态。始条件，这种联接就能维持紧固的状态。 13Paragraph 4:nUnified standard thread is available in three basic series of diameter-pitch(直径螺距) combinations. n统一标准（统一标准（unified shandard）螺纹有三个基本系列）螺纹有三个基本系列的直径螺距组合。的直径螺距组合。 14nThe coarse-thread series (UNC) is most common and is reco

13、mmended for general assembly use where vibration is not a problem and where frequent disassembly is required. n统一标准粗牙螺纹系列是最普通的，推荐用于一般的统一标准粗牙螺纹系列是最普通的，推荐用于一般的装配场合装配场合振动较小，频繁拆卸振动较小，频繁拆卸。 15nThe fine-thread series (UNF) is somewhat stronger in tension and is more suitable where fine adjustment may be r

14、equired. nThis series is often used in aircraft assemblies. n统一标准细牙螺纹系列具有较大张紧力，较适用于精统一标准细牙螺纹系列具有较大张紧力，较适用于精密调整的场合。该系列常用于航空器的装配。密调整的场合。该系列常用于航空器的装配。 16nThe extra-fine-thread series (UNEF) is employed where the mating external thread is in a thin-walled member(薄壁件). n统一标准超细牙螺纹用于薄壁零件的外螺纹配合。统一标准超细牙螺纹用于薄

15、壁零件的外螺纹配合。nThis series is also more resistance to vibration and provides for very fine adjustment. n该系列用于要求抗振动性强的场合，及更精密调整的该系列用于要求抗振动性强的场合，及更精密调整的场合。场合。 17Paragraph 5nUnified standard threads are identified on drawings, parts lists(零件清单), and so forth, with a shorthand notation(简单标注法) that includes

16、size, thread series, class of fit, external or internal thread symbol (A is for external threads, B is for internal threads), and the hand of thread(螺纹旋向). n统一标准螺纹用一个简化符号标识在图形零件的细表统一标准螺纹用一个简化符号标识在图形零件的细表等场合。该符号包括：尺寸，螺纹系列，配合等级，等场合。该符号包括：尺寸，螺纹系列，配合等级，内外螺纹符号（内外螺纹符号（A外螺纹，外螺纹，B内螺纹）及旋向。内螺纹）及旋向。 18n For ex

17、ample, the designation 1/4-20UNC-2A-RH identifies an externally threaded part having a basic major diameter of 1/4 in., unified coarse thread with 20 threads per inch, tolerance class 2, and right-hand threads. n如标示：，表示：一外螺纹零件，公称直径英寸，如标示：，表示：一外螺纹零件，公称直径英寸，20牙牙/英寸的统一粗牙螺纹，公差等级英寸的统一粗牙螺纹，公差等级2，及右旋螺纹。，及右

18、旋螺纹。 19nUsually the hand designation is omitted for right-hand, since these are standard. Another example is 3/4-16UNF-2B-LH which designates an internal, left-hand thread having a basic major diameter of 3/4 in., and 16 unified fine threads per inch of length.n右旋螺纹由于是标准旋向，其右旋标示常省略。另一右旋螺纹由于是标准旋向，其右旋

19、标示常省略。另一例子：表示：内螺纹，左旋，公称尺寸（直径）英寸，例子：表示：内螺纹，左旋，公称尺寸（直径）英寸，统一细牙螺纹统一细牙螺纹16牙牙/英寸，公差等级英寸，公差等级2。 20Paragraph 6nISO standards include many diameter-pitch combinations, but proposed US standards specify a single diameter pitch series. nISO标准包含许多直径螺距组合系列，但推荐的美国标准包含许多直径螺距组合系列，但推荐的美国标准指定了单一的直径螺距组合系列。标准指定了单一的直径螺

20、距组合系列。 21nMetric threads(公制螺纹) are designated by the letter M followed by basic major diameter(公称直径) in millimeters, which is then followed by the pitch in millimeters separated by the symbol “x”. n公制螺纹标示为：字母公制螺纹标示为：字母M后接公称直径（后接公称直径（mm）X螺螺距（距（mm）。）。 22n For example, M4x0.7 specifies a metric thread

21、with basic major diameter of 4 mm and pitch of 0.7mm. n例如例如M40.7表示公制螺纹公称直径表示公制螺纹公称直径4mm，螺距，螺距0.7mm。 23nParagraph 7:nWashers(垫片、垫圈) are often used with threaded fasteners to provide a better bearing surface for nuts and bolt heads, to provide a bearing surface over large clearance holes(光孔) or slots,

22、 to distribute the load over a larger area, to prevent marring of parts during assembly, to improve torque-tension ratio (by reducing friction), and to provide locking, in some cases through spring action. n垫片经常与螺纹紧固件一同使用，为螺母和螺栓头提供垫片经常与螺纹紧固件一同使用，为螺母和螺栓头提供一个较好的支撑面；为在大的清洁的孔和狭槽上提供一一个较好的支撑面；为在大的清洁的孔和狭槽上

23、提供一个支撑面；为了在较大的面上分布载荷；为装配时免于个支撑面；为了在较大的面上分布载荷；为装配时免于零件损坏；为了改善扭矩零件损坏；为了改善扭矩张紧比（通过减少摩擦），张紧比（通过减少摩擦），为了在某些情况下通过弹簧（垫片）作用提供自锁。为了在某些情况下通过弹簧（垫片）作用提供自锁。 24n Flat washers(平垫) are thin, annular-shaped disks used primarily for bearing surface and load distribution and have no locking capacity. nHelical spring l

24、ock-washers are essentially single coil helical springs that flatten(变平) under load. n平垫圈是薄的环片，主要用于提供支撑面，分布载荷，平垫圈是薄的环片，主要用于提供支撑面，分布载荷，无自锁性能。无自锁性能。n弹簧垫片实际是在载荷作用下变平的单圈螺旋形弹簧。弹簧垫片实际是在载荷作用下变平的单圈螺旋形弹簧。 25nSpring action assists in maintaining the bolt load, while split edges(开口边缘) provide some locking acti

25、on by biting into the bearing surfaces. nLock washers (自锁垫圈)generally made of hardened steel(淬火钢). n弹簧作用有助于维持螺栓受力，同时开口咬入支承面弹簧作用有助于维持螺栓受力，同时开口咬入支承面提供自锁作用。提供自锁作用。n锁紧垫圈通常由淬硬钢锁紧垫圈通常由淬硬钢(hardened steel)制作。制作。 26Paragraph 8nCarbon steel(碳钢) and steel alloys(合金钢) are most commonly used fasteners materials. Many stainless steel alloys(不锈钢)