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Riveting is the commonest method of assembling aircraft. A medium bomber requires 160. 000 rivets and a heavy bomber requires 400, 000 rivets. Some of the forms of rivets are solid rivets with chamfered shanks, tubular or hollow rivets, semitubular rivets, swaged rivets, split rivets, and blind rivets. Solid rivets are used where great strength is required. Tubular rivets are used in the fastening of leather braces. Split rivets are used frequently in the making of suitcases. The materials used in making rivets are aluminum alloys, Monet metal, brass, and steel. Aluminum rivets make possible the maximum saving in weight, and are also quite resistant to corrosion. Anodic coating of aluminum improves the resistance of the rivets to corrosion and also provides a better surface for painting. Steel rivets are stronger than aluminum rivets and offer certain advantages in ease of driving from the standpoint of equipment required; however, their use is limited to those applications in which the structure can be protected adequately against corrosion by painting. Some of the types of rivet heads are button, mushroom, brazier, universal, flat, cinners, and oval. Brazier and mushroom heads are used for interior work. The flat head is used for streamlined pieces.

Keys, Splines, and Pins

When power is being transmitted from a machine member such as a coupling, a clutch, a gear, a flywheel, or a pulley to the shaft on which it is mounted; means must be provided for preventing relative motion between the shaft and the member. On helical and bevel gears, relative movement along the shaft caused by the thrust (axial) loads is prevented by a step in the shaft or by having the gear contact the bearing directly or through a tubular spacer. When axial loads are incidental and of small magnitude, the members are kept from sliding along the shaft by means of a set screw. The primary purpose of keys, splines, and pins is to prevent relative rotary movement.

A commonly used type of key has a square cross section and is sunk half in the shaft and half in the hub of the other member. If the key is made of steel of the same strength as the shaft and has a width and depth equal to one fourth of the shaft diameter then it will have the same torque capacity as the solid shaft if its length is 1.57 times that of the shaft diameter. Another common type of key has a rectangular cross section with a depth to width ratio of 0. 75. Both of these keys may either be straight or tapered in depth. The straight keys fit snugly on the sides of the keyways only, the tapered keys on all sides. Gib-head keys are tapered keys with a projection on one end to facilitate removal.

Woodruff keys are widely used on machine tools and motor vehicles. The key is a segment of a disk and fits in a keyway in the shaft that is cut with a special milling cutter. Though the extra depth of these keys weakens the shaft considerably, it prevents any tendency of the key to rotate or move axially. Woodruff keys are particularly suitable for tapering shaft ends.

Because they weaken the shaft less, keys with straight or tapered circular cross sections are sometimes used in place of square and rectangular keys, but the keyways, half in the shaft and half in the hub, must be cut with a drill after assembly, and interchangeability of parts is practically impossible. When a large gear blank is made by shrinking a high-strength rim on a cheaper cast centre, circular keys, snugly fitted, are frequently used to ensure a permanent connection.

Splines are permanent keys integral with the shaft, fitting in keyways cut in the hub. The dimensions of splined fittings are standardized for both permanent (press) fits and sliding fits. The teeth have either straight or involutes profiles; the latter are stronger, more easily measured, and have a self-centering action when twisted.

Tapered circular pins can be used to restrain shaft-mounted members from both axial and rotary movement. The pin fits snugly in a reamed tapered hole that is perpendicular to the shaft axis and either radial or tangential to the shaft surface. A number of straight pins that grip by deforming elastically or plastically when driven into straight holes are commercially available.

All the keys and pins that have been described are standard driving devices. In some cases they are inadequate, and unorthodox means must be employed.

最新回答 (1条回答)

2009-12-15 回答
铆接装配是飞机最常见的方法。一辆中型轰炸机需要160。 000铆钉和重型轰炸机需要400,000铆钉。对一些表格铆钉与倒角柄,管状或空心铆钉,semitubular铆钉,锤造铆钉,铆钉分裂坚实铆钉和铆钉。实心铆钉的使用,伟大的力量是必需的。管状铆钉用于皮革括号紧固。斯普利特铆钉,频繁使用的行李箱决策。使铆钉,铝合金,莫奈金属,铜和钢铁所用的材料。铝铆钉成为可能的重量最大的节约使用,也非常耐腐蚀。铝阳极涂层提高了铆钉耐腐蚀,也提供了一个更好的表面涂装。不锈钢铆钉,强于铝铆钉,可以提供从设备所需的立场驾驶缓和某些优势,但是,它们的使用限制在其中的人的结构可以有防腐蚀保护充分绘画应用。铆钉头的一些类型的按钮,蘑菇,火盆,普遍的,扁平,cinners和椭圆形。火盆和蘑菇头用于室内工作。在平头用于简化件。 

键,花键和销 

当电源被传染的机器的成员,如耦合,离合器,齿轮,飞轮,或向其所安装轴滑轮;手段必须防止轴与之间的相对运动的成员提供。在螺旋纹与锥形齿轮,沿着推力引起的轴的相对运动(轴向)负荷是阻止在轴步骤或具备了齿轮,轴承接触直接或通过管状间隔。当轴向负荷是偶然和小规模,成员不断从沿轴滑动螺杆的一套方法。的钥匙,样条的主要目的,是为了防止引脚相对的旋转运动。 

阿主要有方形截面,是沉没在井下以及在其他成员枢纽一半常用的类型。如果密钥是由作为轴相同的强度钢,具有广度和深度等于一轴的直径第四那么它将作为实心轴相同的扭矩的能力,如果其长度为1.57倍,轴直径。另一个主要有,以宽度为0比矩形截面深入常见的类型。 75。这些项都既可以直接或深入的锥形。直键贴身地适合对键槽的双方只是,在各方的锥形键。培养液头键的一端圆锥投影键,方便清除。 

伍德拉夫键被广泛用于机床和机动车辆。关键是一个磁盘部分,并在与一个特殊的铣刀轴键槽切割适合。虽然这些额外的深度键轴大大削弱了,它可以防止任何键轴向旋转或移动的趋势。伍德拉夫键特别适合锥形轴端。 

因为他们削弱轴少,直或锥形截面圆形键有时被用在方形和矩形钥匙的地方,但键槽,在轴和枢纽一半,必须用组装后的演练,并削减零部件通用化实际上是不可能的。当一个大齿轮坯是便宜,大大缩小了投中心高强度沿岸地区,圆形按键紧贴安装,经常使用,以确保永久连接。 

样条与轴,在削减键槽的枢纽永久不可分割的关键配件。在花键件的尺寸为永久(新闻)符合规范和滑动适合。牙齿要么直接或渐开线的概况;后者更强大,更容易衡量,并有自定心行动时,扭曲。 

锥圆形引脚可以用来抑制轴装从轴流式和旋转运动的成员。该引脚正好符合了扩锥孔的垂直轴的轴线,要么径向或切向轴表面。阿直脚的数量,通过塑性变形弹性地或直孔成为驱动抓地力商用。 

所有的钥匙,并已被描述引脚标准传动装置。在某些情况下他们是不够的,非传统的方法必须采用。