16. Couplings
Vocabulary:
coupling [couple [adjacent [semipermanent [restore [emergency [exceptional [plant [propeller [rigid [flange [attach [alignment [misalignment [rabbet [projection [snugly [deflect [interfere [intensity [flexibility [shock [spatial [resilient [springy [compensate [
] 冲击
] 空间的
] 有回弹力的 ] 有弹性的
] 补偿
] 紧贴地 ] 偏斜
] 妨碍 ] 强度
] 挠性
] 槽口,榫头
] 凸出物
] 恢复
] 紧急情况 ] 异常的
] 工厂、车间、设备
] 螺旋推进器 ] 刚性的 ] 凸缘、法兰 ] 缚上, 系上
] 对准、同轴
] 不对准、不同轴
] 联接器 ] 连合, 连接
] 邻近的
] 非永久性的
Text:
A coupling is a device for connecting the ends of adjacent shafts. In machine construction, couplings are used to effect a semipermanent connection between adjacent rotating shafts. The connection is permanent in the sense that it is not meant to be broken during the useful life of the machine, but it can be broken and restored in an emergency or when worn parts are replaced.
There are several types of shaft couplings; their characteristics depend on the purpose for which they are used. If an exceptional long shaft is required for a line shaft in a manufacturing plant or a propeller shaft on a ship, it is made in sections that are coupled together with rigid couplings. A common type of rigid coupling consists of two mating radial flanges (disks) that are attached by key-driven hubs to the ends of adjacent shaft sections and bolted together through the flanges to form a rigid connection. Alignment of the connected shafts is usually effected by means of a rabbet joint on the face of the flanges, i.e., a short cylindrical projection on the face of one flange fits snugly in a circular recess on the face of the other flange.
In connecting shafts belonging to separate devices (such as an electric motor and a gear-box), precise aligning of the shafts is difficult and a flexible coupling is used. This coupling connects the shafts in such a way as to minimize the harmful effects of shaft misalignment. Flexible couplings also permit the shafts to deflect under their separate systems of loads and to move freely (float) in the axial direction without interfering with one another.Flexible couplings can also serve to reduce the intensity of shock loads and vibrations transmitted from one shaft to another.
The flexibility provided by a coupling may be only spatial, or it may be both spatial and resilient (springy); in other words the coupling may compensate for shaft misalignment but provide no resilience, or it may be resilient and provide also for a small amount of misalignment.
17. Clutches
Vocabulary:
clutch [rotatable [coaxial [convenient [
] 离合器
] 可旋转的 ] 同轴的
] 方便的
unload [rotational [inertia [switch [capacity [winding [excessive [current [intermediate [rotor [lineshaft [reverse [
] 倒转的 ] 转子, 回转轴
] 总轴
] 开关
] 能力 ] 线圈
] 过多的, 额外 ] 电流
] 中间的
] 惯性 ] 无负荷的
] 转动的
Text:
A clutch is a device for quickly and easily connecting or disconnecting a rotatable shaft and a rotating coaxial shaft. Clutches are usually placed between the input shaft to a machine and the output shaft from the driving motor, and provide a convenient means for starting and stopping the machine and permitting the driver motor or engine to be started in an unloaded state.
The rotor (rotating member) in an electric motor has rotational inertia, and a torque is required to bring it up to speed when the motor is started. If the motor shaft is rigidly connected to a load with a large rotational inertia, and the motor is started suddenly by closing a switch, the motor may not have sufficient torque capacity to bring the motor shaft up to speed before the windings in motor are burned out by the excessive current demands. A clutch between the motor and the load shafts will restrict the starting torque on the motor to that required to accelerate the rotor and parts of the clutch only.
On some machine tools, it is convenient to let the driving motor run continuously and to start and stop the machine by operating a clutch. Other machine tools receive the power from belts driven by pulleys on intermediate shafts that are themselves driven by belts from long lineshafts that serve a group of machine. Two pulleys that can be connected to the intermediate shaft by clutches, and driven in opposite directions by open and crossed belts from the lineshaft, can provide forward and reverse rotation for the machine.
Appending:
Manual transmission
A manual transmission has a gearbox from which the driver selects specific gears depending on road speed and engine load. Gears are selected with a shift lever located on the floor next to the driver or on the steering column. The driver presses on the clutch to disengage the transmission from the engine to permit a change of gears. The clutch disk attaches to the transmission’s input shaft. It presses against a circular plate attached to the engine’s flywheel. When the driver presses down on the clutch pedal to shift gears, a mechanical lever called a clutch fork and a device called a throw-out bearing separate the two disks. Releasing the clutch pedal presses the two disks together, transferring torque from the engine to the transmission.
18. Brakes
Vocabulary:
brake [flow [respect [resemble [arrest [engagement [stationary [serve [arrest [capacity [kinetic [hydraulically [electrically [
act on 对...起作用, 作用于 translate [dissipate [metallic [
] 平移 ] 耗尽 ] 金属(性)的
] 匹配, 适合
] 制动
] 能力
] (运)动的, 动力(学)的
] 液压的 ] 电力的
] 制动器 ] 趋向
] 方面 ] 类似 ] 停止；阻止
] 啮合，接合 ] 固定的
pneumatic [organic [ceramic [asbestos [majority [fading [effectiveness [coefficient [sinter [lining [prefer [drum [thermal [conductivity [particle [series [plat [alternate [pad [caliper [shoe [pinch [
] 闸瓦
] 收缩，夹紧
] 衬垫
] 卡钳
] 片
] 交替的, 轮流的 ] 微粒 ] 系列 ] 烧结, 熔结 ] 衬里, 内层 ] 首选
] 鼓形圆桶
] 热的
] 传导性, 传导率
] 衰退
] 效率; 效能 ] 系数 ] 气动的 ] 有机的 ] 陶质的 ] 石棉 ] 多数, 大半
Text:
Basically, brakes are devices for controlling the flow of motion in machine, and in this respect they resemble clutches; clutches start the flow while brakes arrest it. Before the engagement of a clutch or a brake, one of the two members in the device is moving while the other is stationary; after the engagement of a clutch both members are moving at the same speed, while after the application of a brake the moving member is either slowed down or stationary. In both cases the desired effects are produced by devices that are so alike, structurally, that they can
专业英语16-19
