Unit 10  Hydraulic System
10单元 液压系统
  The history of hydraulic power is a long one，dating from man’s prehistoric efforts to
harness the energy in the world around him．The only sources readily available were the
water and the wind—two free and moving streams.
液压动力的历史由来已久，始于人类为利用他周围的能源而作出的努力。来源只有现成的水和风—两种自由移动流。
    The watermill，the first hydraulic motor，was an early invention·  One is pictured on a
mosaic at the Great Palace in Byzantium，dating from the early fifth century·The mill had
been built by the Romans．  But the first record of a watermill goes back even further,  to
around 100 BC，and the origins may indeed have been much earlier·The domestication of
grain began some 5000 years before and some enterprising farmer is bound to have become
tired of pounding or grinding the grain by hand．Perhaps，  in fact，the inventor was some
farmer’s wife，since she often drew the heavy jobs·
水车，第一台液压马达，是一种早期的发明。是一张画在镶嵌在大皇宫在拜占庭的图片，可追溯到第五世纪初，被罗马人修建的工厂。但第一次记录水车去更久远，在公元前100年左右，起源可能更早。驯化谷物开始大约5000年前，有进取心的农夫一定厌倦了用手磨粒加工。也许，事实上，发明者是一些农民的妻子，因为她经常从事沉重的工作
Manv mills staved in use until the end of the 19th century，but they had been in the
process of being replaced by the Steam engine as a source of power for the previous 150
years．The transmission of the power generated by the waterwheels was by shafting and
crude gears or pulleys．The steam engine for the first time employed an enclosed moving
stream of fluid(steam) under pressure—the principle to be later employed in hydraulic
power transmission—for transmitting power continuously from the point of generation to
the place where it was used·
许多米尔斯避免使用直到第十九世纪末，但他们已经在这个过程中被蒸汽发动机取代作为动力源的前150年。电力传动产生的水车的轴系和齿轮或滑轮。蒸汽机的第一次使用利用一个封闭的移动流液（汽）压力，后来采用液压传动传递功率，在以后的时代不断被使用
The transmission of hydrostatic power to a distant point began long before that,however
．Hero of A1exandria，in the first century AD，built a device in which a fire on the temple
altar expanded air in a closed container．The air pressure forced water to travel along a tube
to the temple doors where，spilling into a container，it provided the force through ropes and
pulleys to magically open the doors
他在传输到一个遥远的水压力量点之前就开始了,但是亚历山大在公元一世纪,建造了一个设备,其中上底部的火增加了空气压力在一个封闭的容器，空气压力迫使水沿着一根管子到容器口,蔓延到一个容器,它提供的强行通过绳索和滑轮神奇地打开门
    Hero also produced a steam engine of sorts．  Its motion depended on the reaction forces
  from jets of steam，pulleysas in the present steam turbine，but it was little understood and it was no
  more than an interesting curiosity·
英雄也生产了各种各样的蒸汽引擎。它的运动取决于反应蒸汽喷发的速度,蒸汽涡轮机至今,但很少有人理解，它只不过是一个有趣的好奇心•
The invention of early forms of the hydraulic pump has a similarly early origin·The first pumps were not used to develop hydraulic power，however' but only to transfer water for  irrigation or to remove it from mines
这项发明的早期起源的形式是一个类似液压泵的东西，第一个泵已经不只用来开发液压动力,然而 但只有将用于矿山灌溉水
    Archimedes applied the principle of the screw to hydraulic machines in the third century BC．
  His screw pumps were used to raise water for irrigation or to the level of aqueducts·The piston
  pump，the first mechanical device capable of generating pressure in a column of liquid，is believed to have come from Egypt at a similarly early date．Like the screw pump，it was used only as a means for moving water and not as a means for generating hydraulic power·
在公元前3世纪阿基米德应用螺丝原理的液压机械在公元前3世纪。他的螺杆泵被用来提高灌溉用水或水平沟渠。柱塞泵是历史上第一台能够使液柱内产生压力的机械装置,它被认为来源于埃及且与螺旋泵有同样悠久的历史，它仅是用来作为一种移动水的手段,而不是作为一种生成液压动力的手段
In more recent years， the role of leadership in hydraulic power application has been taken over largely by some of the larger earthmoving and construction equipment manufacturers the total Power involved is often greater than that required in even the largest aircraft systems．the concentration of this power in a few very large loads，as compared to the multitude of smaller loads in an airplane，has spurred the system designer to find new，creative ways to distribute and control the power．This he has succeeded in doing to obtain maximum precision of control and productivity while minimizing power consumption．
近年来，一些规模较大的生产土建设备的厂商在液压动力应用方面一直站着主导地位。总功率涉及常常会超过需要,即使在最大的系统集中的飞机，这种力量也是非常大的负载,相比之
下,许多的小负荷,在飞机上促使系统设计者到新的有创意的方法来分配和控制蒸发式冷凝器，他成功地做到控制和生产力的精度,同时最小化能耗。
    in modern mobile and industrial applications，the system designer has made full use of
the wonderful flexibiIity and adaptability of hydraulics．  It can readily be directed around corners and past involving joints that virtually defy mechanical power transmission．  It can be divided easily to serve individual loads or recombined to power a high，single一load demand．
Electrical and pneumatic power distribution have similar flexibility，but lack the compactness
and certain of the other important characteristics of hydraulics．
在现代的移动和工业应用,系统设计者充分利用了美妙的柔性和适应性的水力学。在过去的涉及关节它随时会被定向转弯和,几乎可以忽略机械动力传输。它可以分为容易为各自的负载或重组来驱动一个高单一需求。电动、气动分布也有类似的灵活性,但缺乏的密实度和某些其他
的重要特征的水力学。