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湖 南 科 技 大 學(xué)
英文文獻(xiàn)翻譯
學(xué) 生 姓 名: 牛文建
學(xué) 院: 機(jī)電工程學(xué)院
專業(yè)及班級(jí): 機(jī)械設(shè)計(jì)制造及其自動(dòng)化(2)班
學(xué) 號(hào): 103010201
指導(dǎo)教師: 馬克新
2015 年 3 月 26 日
VIBRATORY HAMMER EXCITERS
Although there are many varitations in design and construction ,the vast majority of vibratory hammer are of the configuration like this .Briefly ,there are two main components of the system: the exciter , which produces the actual vibrating force ,and the power pack, which provides the usable energy for the motors on the hammer to spin the eccentrics.
We first need to look at the exciter; it is divided into three parts;
1)Vibrator case :This contains the eccentric weights and does the actual vibration. Thus, these eccentrics must be somehow both driven and synchronized.
The most common way to accomplish this is a gear system. The gears can actually function in various ways , depending upon how they are set up . Generally the eccentrics are mounted to the gear system , either partially or entirely; in either case the mounting is rigid. In some vibratory hammers, this rigidity is insured by insured by making the gear a one piece eccentric .Several types of gears have been used in vibratory hammer, including spur, helical ,and bevel. All types work best when the teeth are small but strong enough to transmit the power. Large teeth have two been used extensively in vibratory hammers over the years , but small ones are quieter , more efficient, and more reliable.
Other schemes of synchronization are: a) there are no gears , and most of the time the amplitude of the system synchronizes their rotation ,each eccentric driven by its own motor , or b) the gears are synchronized by a chain and each eccentrics is driven individually .
In any case , the dynamics forces generated by the eccentrics is transmitted to the case by the use of antifriction bearings , which also facilitate rotation. These can be cylindrical , spherical (“screen” bearings) ,or ball , but to work properly they must be sufficiently large for the load and adequately lubricated ,either by a pump system or well designed splash system .
Geared eccentrics can be connected to the motor either by pinion, or through belts or chain drives. For the latter two the motor is mounted on the static weight ; a pinion drive require that the motor be mounted directly to the vibrator case .Pinions are used as torque converters, which make optimum used of motors at their preferred operating speeds.
2)Clamp: This connects the vibrator case to the pile and thus transmits the vibrator’s power from the vibrator case to the pile. Generally speaking , most clamps pinch the pile using a hydraulic cylinder and jaws , thus making a frictional connection . A few vibrators actually bolt or pin the pile to the vibrator case , as was done with the old Vulcan or MKT impact extractors . Some clamps (Foster) use some kind of leverage to enable the use of a small cylinder to generate a large force . For hydraulic clamps ,both lever and direct cylinder clamps are shown.
3) Suspension: This is connected to the vibrator case by rubble or metal springs. In driving this provides additional weight to the system to force the pile into the ground without degrading the vibration of the system, although with most units additional bias weight can be attached to the suspension. In extraction the suspension system transmits static pull while dampening out vibration and thus protects the crane boom. For this to be effective the springs must be sufficiently soft and the bias weight sufficiently heavy to insure a suspension natural frequency that is much lower than the vibrator’s operating frequency. Occasionally additional static weight is helpful during and the weights which accomplish this (called “base weighst”) are attached to the suspension.
Impact-Vibration Exciters
Although impact –vibration hammers share common constructional features with their vibratory relatives , there are important differences .In common with more conventional vibratory hammers, it contains counter rotating eccentrics which impart vertical vibrations ;however, these are contained in a head which is not rigidly connected to the pile but is free to some degree . This freedom enables the units to impact the pile at a rate higher than conventional impact hammers . The alternating force of the eccentrics takes the place of the air , steam ,diesel combustion or hydraulic fluid in 4 moving the head up and down like a ram, with impact at either the top , bottom,or both ends of its “stroke”. Although this can produce variations in the eccentric rotational speed of up to 40%(as opposed to the 50% or so normal for vibratory hammers), this variation generally does not impede the continuous , stable operation of the equipment.
Some of the various parts of these hammer are dicussed below:
Exciter/Head : The exciter of these machines is similar in general principle to strictly vibrating machines ,with eccentrics driven by motors. With impact –vibration hammers ,the exciter has a constant source of amplitude within the springs ,and so the eccentrics are usually not synchronized with gears ,each one driven by a motor. Beaing life with these machine is critical ,and many of them must be used in the vibratory mode a good deal of their operation.
Frame/Springs : Frame design of these machines is critical since the frame provides both the regulation of the machine and its connection to the pile. The regulating springs are generally coil springs . The machine’s vibration within the springs is regulated by both the springs rate and the pretensioning of the springs . The latter can be either fixed or regulated by hydraulic or electric means . Part of the machine’s force on the pile is also transmitted by the springs if the frame is clamped to the pile.
Pile Connection: The most elementary of impact-vibration machines have no pile connection(or frame) at all and rest on the top like impact hammers .Although hydraulic clamps similar to ones in vibratory hammers can be used , other schemes to keep the frame on the pile include simply making the frame heavy than the upward springs force or bolting the machine to the pile.
Power Packs for Vibratory and Impact-Vibration Equipment
Turning to the power pack, a few vibrators , such as the bodine-guild resonant drivers ,some of the early Soviet vibrodrilling machines ,and some Japanese units ,drive rotating eccentrics straight from diesel or gasoline engines by mechanical couplings . However , most vibratory or impact-vibration hammers transmit energy from the prime mover to the eccentrics through either electric or hydraulic systems. Since construction site are usually remote , transportable power sources have been developed for vibratory hammers. These are referred to as power packs ( for hydraulic units) or generator sets ( for electric units) . These units are similar for both vibratory and impact-vibration equipments .
Electrics system : these usually employ three-phase induction motors driven at a single frequency, which has encourage the development of many system to vary the eccentric moment and thus the driving force .In some case electric vibratory hammers can be driven from a nearby three-phase mains , obviating the need for a generator set. The hammers thus only requires a switchbox to control it . A separate , small power pack , driven with an electric motor , is required to operate the hydraulic clamp , if there is one . This can either be on the ground or mounted on the static overweight . Electric systems are less and less popular because of maintenance and reliability consideration.
Hydraulic system: for a varity of reason hydraulic system have become dominant, and the major manufactures , such as Vulcan ,ICE ,and MKT, employ hydraulic drive almost exclusively. These system use a diesel engine to drive a hydraulic pump ,which In turn drives the motor on the exciter . A reservoir of varying size is used to store hydraulic fluid in case of leakage , fluid low , both in starting and stopping the 6 machine and during operation .Beyond these basic , these are specific differences between the various hydraulic power packs available; They are :
1) Pump Driven or Gearbox :the hydraulic pump is connected to the engine through a pump drive; sometimes this pump drive is a gearbox as well , acting as a speed changer to optimize the pump , while in others a direct drive is employed , eliminating gear losses.
2) Clamp Pumps :some units have separate pumps for the hydraulic clamp and some integrate these into the main power source .Impact-vibration hammers that do mot have a clamp on them do not have a clamp on them do not need a clamp circuit.
3) Variation of Frequency and Force :Both of these can be varied either by using varied displacement pumps in the power pack or by simply varying the engine speed. Variable disable displacement pumps can have very sophisticated flow control mechanisms.
4) Control Type : These units can employ air ,electric, or manual controls for the hydraulic circuitry .Manual controls are the simplest; however ,they confine the operate the machine . Remote controls allow more economical and there is better access to the parts for severice.
5) Enclosure : some power packs have a sheets metal enclosure and some do not . The principal advantage of an enclosed power pack is protection from weather and criminal activity . Enclosures are also helpful if they provide sound deadening , although many do not. Open power packs are more economical and there is better access to the parts of service.
6) Open and Close Loop Hydraulic System: Both appear on power pack in this application . Closed loop systems allow for better controlled starting , running ,and stopping of themechines , but have traditionally been more complicated, and the power packs less adaptable to other applications.
In some cases, the crane hydraulic system can be employed to power the vibratory hammer. Although this eliminates the external power pack and diesel engine , all of the control and operating features of these integral power units are the same.
振動(dòng)打樁機(jī)激振器
雖然在設(shè)計(jì)和施工中有很多變化,但絕大多數(shù)的振動(dòng)樁錘結(jié)構(gòu)都像這樣。簡(jiǎn)單的說(shuō),打樁機(jī)系統(tǒng)由兩個(gè)核心組件構(gòu)成:激振器——產(chǎn)生激振力;電源箱——提供能源使得位于振動(dòng)樁錘上的馬達(dá)帶動(dòng)偏心塊旋轉(zhuǎn)。
我們首先看一看激振器,它由三部分組成;
1)激振箱 :包含偏心塊,它能產(chǎn)生振動(dòng)。因此這些偏心塊一定是以某種方式被同步驅(qū)動(dòng)。
最常被用來(lái)實(shí)現(xiàn)這種同步驅(qū)動(dòng)的是齒輪系統(tǒng)。齒輪有多種運(yùn)用方式,這取決于它們是怎樣被安裝的。通常齒輪系統(tǒng)被整體或局部的安裝在激振器中,無(wú)論哪一種情況下,它都是被精確的安裝。在某些振動(dòng)樁錘中,齒輪配對(duì)加工以確保其精度。某些型號(hào)的齒輪被運(yùn)用到振動(dòng)樁錘中,包括直齒,園齒和圓錐持輪。這些齒輪齒形雖小但工作良好,強(qiáng)度足夠傳遞動(dòng)力。大型齒輪雖然多年來(lái)廣泛的運(yùn)用在振動(dòng)樁錘中,但是小齒輪更輕巧、更有效也更可靠。
其他的同步方案中不存在齒輪系統(tǒng),方案一:大多數(shù)的振動(dòng)系統(tǒng)中每一個(gè)偏心塊由獨(dú)立的馬達(dá)驅(qū)動(dòng),振幅隨著旋轉(zhuǎn)改變。方案二:由同步齒輪鏈條驅(qū)動(dòng),偏心塊仍由獨(dú)立的馬達(dá)驅(qū)動(dòng)。
無(wú)論在那種情況下,由偏心塊產(chǎn)生的激振力由潤(rùn)滑軸承旋轉(zhuǎn)傳遞到箱體內(nèi),這些軸承的滾珠可以是圓柱形、球形的,但是為良好工作,必須有足夠的強(qiáng)度和充分的潤(rùn)滑,潤(rùn)滑是由液壓系統(tǒng)或者是設(shè)計(jì)良好的油滴飛濺潤(rùn)滑來(lái)實(shí)現(xiàn)。
偏心塊既不是通過(guò)齒輪也不是帶和鏈傳動(dòng)連接到馬達(dá)上的,后兩者中馬達(dá)是被靜態(tài)安裝的;齒輪傳動(dòng)需要馬達(dá)直接被安裝在激振器箱體上,齒輪被用作旋轉(zhuǎn)轉(zhuǎn)化原件以便充分利用馬達(dá)工作轉(zhuǎn)速。
2)壓鉗:用來(lái)連接激振器和樁錘,因此傳遞遞激振器產(chǎn)生的激振力至樁錘??偟膩?lái)說(shuō),大多數(shù)的壓鉗采用液壓缸和下顎擠壓樁錘而產(chǎn)生摩擦連接。實(shí)際上一些振動(dòng)樁機(jī)采用螺栓或者螺釘將樁錘直接安裝在激振器箱體上,正如一些老式的Vulcan 和MTK的沖擊樁錘。一些壓鉗(福特斯)采用某種類型的杠桿以使缸體產(chǎn)生很大的擠壓力,對(duì)于液壓壓板來(lái)說(shuō),通常采用杠桿和直壓板。
3)懸架:懸架通過(guò)墊圈或金屬?gòu)椈砂惭b在激振器箱體上,大多數(shù)的部件都可以增加偏心塊重量,通過(guò)驅(qū)動(dòng)這些額外增加系統(tǒng)重量而不減少系統(tǒng)的振動(dòng)以使樁錘打入地面。在拔樁過(guò)程中,懸架傳遞靜拉力而不損壞起重吊臂。為了確保懸架的振動(dòng)頻率低于激振器工作頻率,彈簧和偏心塊必須有足夠彈性和重量。有時(shí)候,適當(dāng)?shù)脑黾討壹艿闹亓坑欣碛赏瓿纱驑哆^(guò)程。
沖擊振動(dòng)樁錘
盡管沖擊振動(dòng)打樁機(jī)和其它類型的打樁機(jī)一樣都具有類似的結(jié)構(gòu),但是還是存在顯著的區(qū)別。和傳統(tǒng)的打樁樁錘相同,它包括旋轉(zhuǎn)的偏心塊來(lái)產(chǎn)生豎直方向上的激振力,但是,沖擊樁錘的樁錘不是剛性的連接而是自由的還具有一定程度的自由度。這種自由連接的方式保證了沖擊樁錘比傳統(tǒng)樁錘上升的高度更高。偏心塊產(chǎn)生可變換的激振力取代了壓縮空氣、柴油燃燒或者液壓油驅(qū)動(dòng)樁體上升或下降,在樁體上身到頂部和底部時(shí)都能產(chǎn)生沖擊力。盡管偏心塊旋轉(zhuǎn)能產(chǎn)生高達(dá)40%的變速范圍(相對(duì)于正常樁錘的50%),但是變速范圍不影響設(shè)備的整體連續(xù)運(yùn)行。
激振器/ 連接頭:沖擊樁錘的激振器與嚴(yán)格的振動(dòng)打樁機(jī)激振器大體相似,其偏心塊都是有馬達(dá)驅(qū)動(dòng)。隨著沖擊樁錘運(yùn)動(dòng),激振器有連續(xù)的振幅,因此激振器不與齒輪同步驅(qū)動(dòng),每一個(gè)偏心塊都由獨(dú)立的馬達(dá)帶動(dòng)。設(shè)備中齒輪的壽命是至關(guān)重要的,因此大部分的齒輪振動(dòng)模式下才能正常運(yùn)行。
箱體/彈簧:箱體的設(shè)計(jì)是機(jī)器中至關(guān)重要的一項(xiàng),不僅提供機(jī)器的調(diào)節(jié)同時(shí)也連接樁錘。一般的調(diào)整彈簧是卷彈簧。機(jī)器的振動(dòng)是由彈簧的彈性比和彈簧的預(yù)緊力調(diào)節(jié)的。
樁錘連接:沖擊樁錘沒(méi)有任何的樁錘連接裝置因而就像停留在頂部的樁錘,盡管液壓夾具在振動(dòng)樁錘中能夠被運(yùn)用,其他方案中為了樁錘的箱體連接而箱體的重力大于向上的彈簧彈性力或者是直接采用螺栓連接。
振動(dòng)樁錘和沖擊樁錘的動(dòng)力裝置
提到動(dòng)力裝置,像一些蘇聯(lián)早期的振動(dòng)打鉆機(jī)和日本的柴油或汽油驅(qū)動(dòng)偏心塊豎直旋轉(zhuǎn)的機(jī)械連接裝置。但是,大多數(shù)的振動(dòng)樁錘通過(guò)電子或液壓系統(tǒng)將原始動(dòng)力傳遞給偏心塊。考慮到施工地點(diǎn)通常偏遠(yuǎn),振動(dòng)樁錘的便攜式動(dòng)力部分已經(jīng)改良。它們是經(jīng)常被提及的馬達(dá)(液壓裝置)和電動(dòng)機(jī)(電氣裝置)。這些裝置在振動(dòng)樁錘和沖擊樁錘中類似。
電氣系統(tǒng):通常采用單頻三相感應(yīng)電機(jī),它能夠調(diào)整偏心塊的運(yùn)動(dòng)進(jìn)而調(diào)節(jié)激振力。在某些情況下,電氣振動(dòng)打樁機(jī)能夠采用附近的三相輸電總線驅(qū)動(dòng)。因此樁錘僅僅需要一個(gè)轉(zhuǎn)換開(kāi)關(guān)就能控制。單獨(dú)分開(kāi)小型的電機(jī)驅(qū)動(dòng)動(dòng)力裝置需要啟動(dòng)液壓夾鉗如果配備的話,它可以靜態(tài)安裝在地面或其它部位,由于保養(yǎng)和可靠性差,電氣系統(tǒng)難受歡迎。
液壓系統(tǒng):有很多理由解釋液壓系統(tǒng)將成為主流,像Vulcan ,ICE ,and MKT都專門采用了液壓裝置。液壓系統(tǒng)采用柴油電機(jī)驅(qū)動(dòng)液壓泵,液壓泵驅(qū)動(dòng)激振器上的馬達(dá)?;赜拖溆脕?lái)儲(chǔ)存因在開(kāi)機(jī)或關(guān)機(jī)中導(dǎo)致的液壓油漏油和油路。除了這些基本的特點(diǎn)之外,一下還有顯著的液壓動(dòng)力箱的特點(diǎn):
1)液壓泵/變速箱:液壓泵通過(guò)液壓馬達(dá)與電機(jī)相連,有時(shí)候液壓驅(qū)動(dòng)也是變速箱,起著調(diào)節(jié)泵的轉(zhuǎn)速的作用,有時(shí)候被直接運(yùn)用到其它設(shè)備中以消除齒輪磨損。
2)液壓壓鉗:有些設(shè)備能將液壓泵與液夾鉗分隔開(kāi),有的則將兩者連接起來(lái)成為主要的動(dòng)力部分。沖擊樁錘沒(méi)有液壓夾鉗,因此也不需要液壓回路.
3)可便頻率和力矩:這兩者均可調(diào)節(jié)通過(guò)使用不同排量的液壓泵或者獨(dú)單的調(diào)節(jié)每個(gè)電機(jī)的轉(zhuǎn)速,可變排量的液壓泵由非常復(fù)雜的流量調(diào)節(jié)機(jī)制。
4)控制類型:液壓回路的控制單元可以使用空氣、電或者手動(dòng)控制。手動(dòng)控制是最簡(jiǎn)單的,但是這限制了設(shè)備的工作范圍。遠(yuǎn)程控制提供了更多的彈性操作但是增加了成本也導(dǎo)致了更多的問(wèn)題。
5)殼體:一些動(dòng)力箱有薄板包裹,一些則沒(méi)有。殼體的作用能保護(hù)動(dòng)力箱不受空氣影響和防止事故。不管配不配備隔音設(shè)備,殼體也是很有用的。開(kāi)放式的動(dòng)力箱更經(jīng)濟(jì)也便于拆裝零件。
6)開(kāi)放式和封閉式的液壓回路系統(tǒng):兩者共同出現(xiàn)在動(dòng)力箱上,閉合式的液壓回路系統(tǒng)能更好的控制啟動(dòng)、運(yùn)轉(zhuǎn)和停止,但是與傳統(tǒng)的控制相比越來(lái)越復(fù)雜,使得與其他元件的兼容性減低。
在某些情況下,液壓起重系統(tǒng)能夠被運(yùn)用到振動(dòng)樁錘的沉拔中。盡管減少了外部動(dòng)力箱和柴油發(fā)動(dòng)機(jī),但是動(dòng)力裝置的所有控制和操作特點(diǎn)都是一樣的。