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Hydraulic MachineFrom:The ColumbiaEncyclopedia,Sixth EditionDate:2008I21$Hydraulic machinethat derivesits powerfrom themotion orpressure ofwateror someother liquid.Hydraulic equipmentand technologyis somethingthat weare allatleast passinglyfamiliar with.If wethink aboutit,we knowthat theprinciples of hydraulicsare applied to makemany commonmachines work.For examplehydraulics areused inagriculturalequipment,giant earthmoving andmining machines,they areused tosteer andstabilizegiant oceanliners,help airplanesclimb andturn,and makethe brakesin ourcarswork.So hydraulicscan providegreat force,are obviouslyvery adaptableand usedin allkindsof applications,but howdo theyactually work飞yWhat isthis hydraulicsstuffHydraulics isbased ona verysimple factof nature-you cannotcompress a liquid.You cancompress agas thinkabout puttingmore andmore airinto atire,the moreyou putin,the higherthe pressure.If yourereally strongyou cancompress asolid massas well.But nomatter howmuch pressureyou applyonto aliquid,it isn*t possibleto compressit.Now ifyou putthat liquidinto asealed systemand pushon itat oneend,that pressureistransmitted through the liquid to the other end of the system.The pressureis notdiminished..Hydraulics isOld StuffThebasic conceptofhydraulics is notnew.The Greeksunderstood aboutusing watertoprovide liftand force,and thename hydraulicscome formthe Latinword forwater-HYDRA”.In themiddle Ages,Leonardo daVinci formulatedthe basicprinciple ofhydraulicscalled continuityand Galileoexperimented withhydraulics.Hydraulics wereevenused duringthe constructionof theEiffel Towerin Parisin thelate1880,s.Hydraulicjacks wereused tolevel thetower and align themetal girdersto anaccuracy of1millimeter Todaymost hydraulic systems utilizeoil ratherthan waterbut theprinciple isothesame.You cancompress aliquid,andaforce thatis appliedat onepoint istransmittedto anotherpoint bythat incompressiblefluid.Because ofits liquidnature,hydraulicsystems cantransmit forcethrough pipesof anyshape andlength,so theforce can beapplied atone centralpoint andtransmitted efficientlyto anotherpoint or to multiplepointsfar away.Think aboutthe mastercylinder inyou car*s brakesand how,by steppingon thebrakepedal,you applystopping pressure on thebrakes onall fourwheels.PhysicsBasic physicstells usthat wecan tradeoff forcefor distancein allmechanicalsystems.In ahydraulicsystem,we dothis bychanging therelative sizeof the pistons ateachendof thesystem.For example,a smallpiston movinga relativelylarge distancesaya footwill exertpressureona larger piston atthe otherend.The forcewill beenough tomove a heavyweight asmall distancemuch lessthan afoot.Engineers andphysicists cancalculateexactly howmuch distanceneeds tobe traveledand therelative sizesof thepistonsrequired to moveaparticular weight.Hydraulic EnginesWaterfalling fromone levelto alower oneis used to drivemachines likethe waterwheeland theturbine.The differencein heightbetween thehighest andthe lowestlevel iscalledthe headoThe amountof workproduced perpound offalling wateris proportionaltothe head.Water powercan beproduced inthis wayfrom manynatural sources,such aswaterfallsand dammedrivers.Where nonatural sourcesare available,an artificialoreservoircanbemade.When energyis plentiful,it is usedtopump waterinto thereservoir;the wateris thenavailable asa powersource todrive turbineswhen energybecomesscarce.In drivingcertain industrialhydraulic machinesan apparatuscalled anaccumulator isemployedto supplyhigh powerfor shortperiods oftime.One typeconsists essentially of acylinderenclosing apiston loadedwith weights.When wateris slowlypumped into thecylinder,thepistonand weightsare forcedup toa positionwhere theyare held.When theyarereleased,they forcethe waterout of the cylinderrapidly,providing themachine withhydraulicpower.Hydrostatic DevicesWateror oilunder pressureis commonlyused asa sourceof powerfor manytypes ofpresses,riveting machines,capstans,winches,and othermachines.The hydraulic press,orhydrostatic press,was inventedby JosephBramah andis thereforesometimes calledtheBramah press.It consistsessentially oftwo cylinderseach filled with liquidand eachfittedwith apiston;the cylindersare connected by a pipe alsofilledwiththe liquid.One cylinderisof smalldiameter,theotherof largediameter.According toPascaFs law,pressureexerted on the smaller piston istransmitted undiminishedthroughtheliquidtothe surfaceofthe larger piston,which isforced upward.Although thepressure forceper unitof areaisthe samefor bothpistons,the totalupward force onthe larger pistonis asmany timesgreaterthan theforce onthe smaller piston asthe areaofthe larger pistonis greaterthan theareaofthe smaller piston.If,for example,the smallerpiston hasan areaof2sq in.and aforceof100lb isexerted onit,then theforceonthe largerpiston havingan areaof50sq in.would be2,500lb100x50/2=2,
500.However,when thepistons move,the distance thesmaller pistontravels isproportionately greaterthan thedistancethelargerpistontravels,satisfying thelaw ofconservation ofenergy.If thesmallerpistonmoves25in.,the largeronewill onlymove1in.The hydraulicpress isused,for example,to formthree-dimensional objectsfrom sheetmetal andplastics andto compresslarge objects.Thehydraulic jack,also anapplication ofPascafs law,isusedto exertlarge forcesortoliftheavy loads.Like thehydraulicpressit consistsessentiallyoftwo different-sized pistonscontainedin cylindersthat areconnectedby apipe.When thesmallerpistonis movedbackand forthbyahandle connectedto it,it pumpsaliquidintothecylinder ofthelargerpiston,forcing thelargerpistontomove.In thisway aweak forceappliedtothesmallerpiston canraisea heavyload onthelargerone.The hydraulicelevator isalso anapplication ofPascafslaw.Totally understandinghydraulicsisvery complicated,but abasic understandingofthe principleof howit worksis actuallyvery straightforward.英文翻译液压机来源哥伦比亚百科全书,第六版日期
2008.液压机的能量来源于水或其它液体的压力或动力液压装置与技术是我们平时非常熟悉的事物,如果我们仔细的思考一下,就会发现很多机械的工作都是依靠液压原理来完成的例如液压被用于农业机械和矿山机械,它们被用于推动和保持巨轮的稳定,帮助飞机的飞行与转动,在汽车中,它可以很快的制刹,由于液压可以提供很大的推力,所以非常实用,被用于各种事物中,但它们是如何工作的呢?液压的本质是什么?液压以自然界中的简单现象为基础一一你不必压缩液体,你可以压缩气体(想一下,当你向轮胎中注入气体的时候,越多那么压力越大)如果你足够强壮的话,你可以尽最大力量作用于固体上,但是不论你加多大的力量,它都不会被压缩现在如果你将液体注入容器中,然后在一边施加压力,通过液体压力被传到了另一边,且压力无损失悠久的液压原理.液压的基本原理有悠久的历史,古稀腊人已懂得利用水来提供提升力与压力,液压的名字来源拉丁语中的水在中世纪的时候,大卫建立了水压基本原理,称为连续,嘎里以水压做试验后来年法国巴黎艾非尔铁塔的建设中,1880水压原理曾被使用液压千斤顶被用来校平铁塔与校准铁制横梁,此时它的精确度可以达到毫米今天液压系统使用油而不是水,但工作原理还是一样的你可以1压缩液体,施加于一点上的压力通过那些没有被压缩的液体而传到另一点,由于液体的自然属性,液压系统可以通过任何形状与长度的管道来传送压力,所以施加于中心点的压力可以很容易的传到另一点或更远的地方想一下你车刹中的主液压缸,是怎样通过刹车来完成四轮停转的物理学定律.物理学基本定律告诉我们在任意机械系统中可以控制压力与距离的关系在液压系统中,通过改变相连活塞的尺寸来控制例如,小活塞运动一个较大的距离(译为步)将会在另一端的大活塞上产生一个力,这个力将会足够推动大活塞移动一个较小的距离(原小于一步)工程师与物理学家可以精确的计算出要移动多大的距离和相对应的活塞尺寸根据需要移动的重量液压引擎水从高处流到低处所释放的能量被用来驱动水轮机和涡轮机这样的机器最高端与最低端之间的高度差被称为势能.每一磅水所做的功与势能成比例,通过这种办法,水能的形成可以来源于许多自然资源,诸如瀑布和大坝没有一个自然资源是可靠的,所以必须建造人工水库来解决这个弊端,当自然资源所产生的能量过于充足时,我们通过水泵将多余的水抽到水库中储存,当水资源产生的能量不够使用的时候,这时候库中的水就可以被利用作为能量来驱动涡轮机在使用特定的工业液压机的时候,设备要求能量源能够在短时间内提供高压任意类型的液压机都包含液压缸和被液压缸包围的液压活塞这些装置当水慢慢地被灌入液压机圆筒(液压缸)的时候,活塞和其负载被向上推,直到某个位置(液压缸的低部)停下来当它们被释放的时候,设备通过为机器提供液压力,强迫水从液压缸中快速流出流体静力学设备在压力下的水或油通常被许多类型的压力机,钾钉机,起锚机,绞车,以及其他的机器作为动力源液压或流体液压的发现者是英国的发明家约瑟夫布拉马,因此也叫布拉马压力这个装置包括两个液压缸,每个里面都有充满的液体和一个合适的活塞,两个缸之间通过充满液体的管道连接一个液压缸的直径比较小,另一个相对大一些根据帕斯卡原理,施加到较小活塞上的压力传播不受减损的,通过液体传到表面较大的活塞上,这是被动向上即使压力(每单位面积的压力)对于活塞来说作用是等同的,作用于大活塞上的压力要比小活塞上的压力大许多倍,倍数等于大活塞的面积与小活塞面积的商举例来说,如果规模较小的活塞的面积为平方英寸,并在其上施加一百磅的力,那么,施加到一个面积为平方英寸250面积的活塞上的力将是磅然而,当活塞移动时,距离较小的活塞行程与距2500离较大的活塞的行程成比例,满足能量守恒原则如果规模较小的活塞动作英25寸,规模较大的仅仅只会移动英寸举例来说,液压被用于形成三维立体从镀金,1塑胶到压缩大型物体液压千斤顶一般被用于施加大压力或顶起重物的场合,它也遵循帕斯卡定律和普通液压机一样,它由两个液压缸组成,两个液压缸的活塞有不同尺寸,中间通过管连接当规模较小的活塞移回或移出来推动液体进入大活塞液压缸,强迫大活塞运动通过这种方法一个较小的作用于小活塞上的力可以顶起一个较大物体的大载荷液压升降机也遵循帕斯卡法则总之,掌握液压是非常困难的,但是理解一些基本的工作原理还是非常简单的附录二产品实例数据库公称压力缓冲缸有无液压缸快降液压缸压制工作台长度工作台宽度KN速度速度样本120001907640400样本220000889800640样本3315018510800600样本431500958800600样本53150110081000800样本640001959800600样本740000877800600样本85000010081200900样本963000847800640样本106300196111200800样本11800011001216001400样本12800012514160012001。