专业英语第五课.docVIP

Lesson5 Keys, Couplings and Seals TEXT A Key is the machinery component placed at the interface between a shaft and the hub of a power-transmitting element for the purpose of transmitting torque see Figure 1.6 a .The key is demountable to facilitate assembly and disassembly of the shaft system. It is installed in an axial groove machined into the shaft, called a keyset. A similar groove in the hub of the power-transmitting element is usually called a keyway, but it is more properly also a keyset. The key is typically installed into the shaft keyset first; then the hub keyseat is aligned with the key, and the hub is said into position. Square and Rectangular parallel Keys The most common type of key for shafts up to 6.5 inches in diameter is the square key, as illustrated in Figure 1.6 b .The rectangular key illustrated in Figure 1.6 c is recommended for larger shafts and is used for smaller shafts where the shorter height can be tolerated. Both the square and the rectangular leys are referred to as parallel keys because the top, bottom and the sides of the key are parallel. The keyseats in the shaft and the hub are designed so that exactly one-half of the height of the key is bearing on the side of the shaft keyseat and the other half on the side of the hub keyseat. Couplings The term coupling refers to a device used to connect two shafts together at their ends for the purpose of transmitting power. 第五课 键，联轴器和密封件 课文 键是一种位于轴和动力传递的轮毂之间用于传递扭矩的机械零件（参见图1.6（一））。键是可拆卸的，以方便轴系统的装配和拆卸。它安装在一个轴向槽加工成的轴，称为键槽。一个类似的在动力传输元素间枢纽凹槽，通常被称为键沟，但更恰当的应该叫键槽。键通常被首先安装到轴的键槽，然后轮毂键槽与键对齐，轮毂就安装到位了。 1.方键和矩形键 最常见的键是轴直径为6.5英寸的方键，如在图1.6（b）项所示。长方形键（在图1.6（C）所示）一般用于较大的轴，或用于较短的可承受载荷的小轴。方形和长方形都因为顶部，底部和键的两侧是平行的被称为平行键。 在轴和轮毂的键槽被专门设计了，因此事实上键高度的1.5倍在承受轴的键槽的力，另一半力轮毂的轴承受。 2.联轴器 联轴器就是一种用来连接两根轴末端的，用于传递动能的装置。一般分为两种：刚性和柔性。 There 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 motion can occur b