外文翻譯---電動平臺型起重機的典型數(shù)據(jù)

1、<p>　　HOISTS 10-15</p><p>　　Table 10.2.10 Typical Data for Electric Chain Hoists*</p><p>　　Table 10.2.11 Typical Data for Electric Wire Rope Hoists*</p><p>　　Some air hoists al

2、so include a Weston-type load brake. The hoist may be suspended by a hook, lug, or trolley; the latter may be plain, geared, or air-motor-driven. Horizontal movement is limited to about 25 ft (7.6 m) because of the air h

3、ose, although a run way system is available with a series of normally closed ports that are opened by a special trolley to supply air to the hoist.</p><p>　　Air hoists provide infinitely variable speed, acco

4、rding to the move ment of the control valve. Very high speeds are possible with light loads. When severely overloaded, the air motor stalls without damage. Air hoists are smaller and lighter than electric hoists of equal

5、 capacity and can be operated in explosive atm ospheres. They are more expensive than electric hoists, require mufflers for reasonably quiet operation, and normally are fitted with automatic lubricators in the air supply

6、.</p><p><b>　　Jacks</b></p><p>　　Jacks are portable, hand-operated devices for moving heavy loads through short distances. There are three types in common use: screw jacks, rack-and-

7、leverjacks, and hydraulic jacks. Bell-bottom screw jacks (Fig.10.2.23) are available in capacities to 24 tons and lifting ran ges to 14 in.The screw is rotated by a bar inserted in holes in the screw head or By aratchet

8、lever fitted to the head. Geared bridge jacks will lift up to 50 short tons (45 tonnes). A lever ratchet mechanism turns a bevel pi</p><p>　　MINE HOISTS AND SKIPS</p><p>　　by Burt Garofab</p&

9、gt;<p>　　There are two types of hoists, the drum hoist and the friction hoist. On a drum hoist, the rope is attached to the drum and is wound around and stored on the drum. A drum hoist may be single-drum or doubl

10、e-drum. There are also several different configurations of both the single-drum and the double-drum hoist. A drum hoist may be further divided as either unbalanced, partially balanced, or fully balanced.</p><p

11、>　　On a friction hoist, which is often referred to as a Koepe hoist, the rope is not wound around the drum, but rather passes over the drum. A friction hoist may utilize a single rope or multiple ropes.</p><

12、;p>　　The operation of hoists may be controlled manually, autom atically, or semiautomatically. There are also arrange ments that use combinations of the different control types.</p><p>　　There are current

13、ly three types of grooving being used on new drums for drum hoists. They are helical grooving, counterbalance (Lebus) grooving, and antis ynchronous grooving. Helical grooving is used primarily for applications where onl

14、y a single layer of rope is wound around the drum. Counterbalance and antisynchronous grooving are used for applications where multiple layers of rope are wound around the drum.</p><p>　　Mine hoists are gene

15、rally divided into (1) Metal-minehoists (e.g.,iron, copper, zinc, salt, gypsum, silver, gold, ores) and (2) coal-mine hoists. These classes subdivide into main hoists (for handling ores or coal) and hoists for men, timbe

16、rs, and supplies. They are designed for operating (1) mines hafts, vertical and inclined, balanced and unbalanced; and (2) slopes, balanced and unbalanced. When an empty cage or platform descends while the loaded cage or

17、 platform ascends, as when both cables a</p><p>　　Hoists for coal mines are principally of the keyed-drum type, for operating in balance from one level. For high rope speeds in shallow shafts, it is generall

18、y advantageous to use combined cylindrical and conical drums. The cylindroconical drum places the maximum rope pull (weight of ropeand loaded skip) on the small diameter so that during the acceleration period of the cycl

19、e, the weight of the opposing skip is offering the greatest counterbalance torque, reducing motor peak loads and slightly r</p><p>　　Skip hoists for industrial purposes such as power-plant fuel handling and

20、blast-furnace charging are similar to shallow-lift slow-speed coalmine hoists in that they operate from a single level. Speeds of 100 to 400 ft/min (0.5 to 2 m/s) are usual. For blast-furnace charging with combined bucke

21、t and load weights up to 31,000 lb (14,000 kg) and aspeed of 500 ft/min (2.5 m/s), modern plants consist of straight-drum geared engines, frequently with Ward Leonard control.</p><p>　　Industrial skip hoists

22、 may be specified where the lift is too high for a bucket elevator, where the lumps are too large for elevator buckets, or where the material is pulverized and extremely abrasive or actively corrosive. Forhigh lifts havi

23、ng a vertical or nearly vertical path, the skip with supporting structure usually costs less than a bucket elevator or an nclined-belt convey or with bridge. Typical paths are shown in (Fig.10.2.26), paths C and D being

24、suitable when the load is received thr</p><p>　　The skip may be manually loaded direct from a dump car or aut omatically loaded by a pivoted chute, which is actuated by the bucket and which, when upturned, s

25、erves as a cutoff gate (Fig. 10.2.27).</p><p>　　For small capacities, the skip can be manually loaded with semiautomatic control. When the bucket has been filled, the operator pushes the start button and the

26、 bucket ascends, dumps, and returns to loading position. With automatic loading and larger capacity, the skip may have full automatic control. For economy, the bucket is counterbalanced by a weight, usually equaling the

27、weight of the empty bucket plus half the load. For large capacity, a balanced skip in which one bucket rises as the other</p><p>　　There are various types of wire ropes used in hoisting. Hoist ropes can be c

28、ategorized into three main types, round strand, flattened strand, and locked coil. Round strand rope is used on drum hoists in applications when a single layer of rope is wound on the drum. Flattened strand rope is used

29、on drum hoists when multiple layers of rope are wound on the drum. Flattened strand rope can also be used on friction hoists. Locked coil rope is used on friction hoists.</p><p>　　Plow steel and improved plo

30、w steel are the most commonly used grades; the latter is used where the service is severe. Some state mining regulations require higher factors of safety than the usual hoisting require ments. The working capacity of new

31、 ropes is usually computed by using the minimum breaking strength given in the manufacturer’s tables and the following factors of safety: rope lengths of 500 ft (152 m) or less, minimum factor 8; 500 to 1,000 ft (152 to

32、305 m), 7; 1,000 to 2,000 ft (305</p><p>　　Brakes There are three main types of brakes used on hoists: the jaw brake, the parallel motion brake, and disk brakes. Brake control is accomplished through air o

33、r hydraulics. Brake shoes are steel with attached friction material surfaces.</p><p>　　Hoist Motors Determining the proper size of motor for driving a hoist calls for setting up a definite cycle of duty ba

34、sed upon the required daily or hourly tonnage.</p><p>　　The permissible hoisting speed for mine hoists largely depends upon the depth of the shaft; the greater the depth, the higher the allowable speed. Cons

35、erv ative max imum hoisting speeds, as recommended by Bu. Mines Bull. 75, are as follows:</p><p>　　High hoisting speeds call for rapid acceleration and retardation. For small hoists, the rate of acceleration

36、 may be made as low as 0.5 ft/s2 (0.15 m/s2 ). An average value of 3 ft/s2 is adopted for large hoists with fairly high speeds. Exceptional cases may require up to 6 ft/s2 (1.9 m/s2 ). The speed should also be considered

37、 with regard to the weight of the material to be hoisted per trip. The question of whether the load should be increased and the speed reduced or vice versa is controlled by</p><p>　　Electrical equipment for

38、driving mine hoists is of four classes:</p><p>　　1. Direct-current motors with resistance control for small hoists, usually series-wound but occasionally compound-wound in conjunction with dynamic braking co

39、ntrol.</p><p>　　2. Alternating-current s lip-ring-type motor with secondary resistance.</p><p>　　3. Ward Leonard system of control for higher efficiency, particularly on short lifts at high rope

40、 speeds, where the rheostatic losses during acceleration and retardation represent a large proportion of the net work done during the cycle; for accuracy of speeds, with high-speed hoists; and for equalization of power d

41、emands. Complete control of the speed from standstill to maximum is obtained for all values of load from maximum positive to maximum negative. The lowering of unbalanced loads without</p><p>　　4. The Ilgner

42、Ward Leonard system consists of a flywheel directly connected to a Ward Leonard motor-generator set and a device for automatically varying the speed through the secondary rheostatic control of the slip-ring induction mot

43、or driving the set. This form of equipment is used under conditions that prohibit the carrying of heavy loads or where power is purchased under heavy reservation charges for peak loads. It limits the power taken from the

44、 supply circuit to a certain predetermined val</p><p>　　The advent of the safety elevator changed the concept of the city by making high-rise buildings possible. Elevators are widely used to transport passen

45、gers and freight vertically or at an incline in buildings and structures. Elevators are broadly classified as low-rise, medium-rise, and high-rise units. Low-rise elevators typically serve buildings with between 2 and 7

46、floors, medium-rise elevators serve buildings with between 5 and 20 floors, while high-rise elevators serve buildings with mor et</p><p>　　Low rise elevators are usually oil-power hydraulic devices. The simp

47、lest version consists of a hydraulic jack buried in the ground beneath the elevator car. The jack is approximately centrally located beneath the car and the ram or plunger is connected to the platform or structure which

48、supports the car. The car is guided by guiderails which cover the full rise of the elevator hoistway. Guideshoes or guiderollers typically guide the elevator as it as cends and descends the hoistway. The hydrauli</p&g

49、t;<p>　　Hydraulic power is usually supplied by a screw-type positive disp lacement pump driven by an induction motor. It is common for the motor and pump to be coaxially mounted and submersed in the hydraulic rese

50、rvoir. Operating pressures are typically 300 to 600 lb/in2(2 to 4MPa). A hydraulic control valve controls the flow of oil to the hydraulic jack and hence the speed of the elevator. In the down direction, the pump is not

51、powered, and the elevator speed is controlled by bleeding fluid through the</p><p>　　Another manifestation of the hydraulic elevator is called the holeless hydraulic elevator. These typically have one or mor

52、e hydraulic jacks mounted vertically alongside the elevator car, the plunger being either directly attached to the car or connected to the car by steel wire cables (also known as wire ropes). Elevators of the latter type

53、 are known as roped hydraulic elevators. These elevators are often roped 1:2 so that the elevator moves at twice the speed of the hydraulic ram. The rise of t</p><p>　　Medium- and high-rise elevators are typ

54、ically traction-driven units; i.e., the rotary motion of the drive sheave is transmitted to the steel wire cables or ropes via friction. The elevators are typically counterweighted so that the motor and drive only need o

55、vercome the unbalanced load. The counterweight mass is typically the car mass plus approximately half the duty load (load of passengers or freight). With high-rise elevators, the weight of the rope is neutralized by comp

56、ensating chains hung </p><p>　　Medium-rise elevators are typically driven by geared machines which transm it the motor power to the drive sheave. Gear reduction ratios are typically in the range from 12:1 to

57、 30:1.</p><p>　　Right-angle worm reduction gear sets are most common; however, helical gears are becoming more acceptable because of their higher operating efficiency and low wear characteristics.</p>

58、<p>　　High-rise elevators are typically driven by gearless machines, which provide the smoothest and most precise performance of all elevators (see Fig. 10.2.28).</p><p>　　起重機 10-15</p><p&g

59、t;　　表10.2.10 電動平臺型起重機的典型數(shù)據(jù)</p><p>　　表10.2.11 電動鋼絲繩型起重機的典型數(shù)據(jù)</p><p>　　一些氣動起重機也包含了一個韋斯頓標準的載荷制動器。這類起重機可能通過使用吊鉤、拉繩和滾輪來使其懸浮于半空中的；后來的這類起重機可能使用簡單的齒輪嚙合傳動或者使用氣動馬達驅(qū)動。盡管使用一系列的普通端口可以得到一個運動軌道系統(tǒng)，而這些端口通過特殊的

60、開關(guān)控制打開來為系統(tǒng)提供氣體，但是氣體輸送管道的限制，水平運動的范圍被局限在大約25ft(7.6米)。</p><p>　　通過調(diào)整運動控制閥，氣動起重機能夠無限寬范圍的可變速度。當起重輕載荷的時候可以采用非常大的速度。當嚴重超載的時候，氣動馬達能夠自動停止而不會被損壞。在相同的起重能力條件下，氣動起重機和電動起重機相比，體積更小，重量更輕，并且能夠暴露在空氣中工作。氣動起重機比電動起重機貴，需要采用消聲器才能夠

61、實現(xiàn)無噪音工作，并且在有氣體的情況下就能夠?qū)崿F(xiàn)自動潤滑。</p><p><b>　　吊綜桿</b></p><p>　　吊綜桿是用來短距離移動重載荷的手動操作的輕便設(shè)備。通常使用的有三種類型：絲桿吊綜桿、桿架吊綜桿和液壓吊綜桿。貝爾末端的絲桿吊綜桿（Fig10.2.3）起重能力為24噸，抬升范圍為14英寸。絲桿是通過裝在絲桿頭部孔洞中的桿或者是通過裝在頭部的(防倒轉(zhuǎn)

62、的)棘齒來驅(qū)動旋轉(zhuǎn)的。齒輪連接的吊綜桿的提升能力達到50小噸（45公噸），一個棘齒輪驅(qū)動一個斜齒輪旋轉(zhuǎn)；而齒輪內(nèi)螺紋提升絲桿。桿架吊綜桿（Fig10.2.4）包含有一個鑄鐵或鍛鋼的機架，控制桿就安裝在機架上。架上的齒條穿過機架中間的孔洞；載荷可以在桿的頭部和底部之間的任何位置被抬升。棘爪控制桿被偏移來抬升或降低桿件，在回程撞擊中，機架棘爪能夠保持載荷。桿架吊綜桿能夠直接提升20小噸（18公噸）。齒輪嚙合傳動的桿架吊綜桿的提升能力能夠達到

63、35小噸（32公噸），提升高度為18英寸（0.46米）。軌道吊綜桿是能夠卸荷的桿架吊綜桿，它通常被使用在鐵路工作方面，但卻不能用作工業(yè)服務(wù)，因為對于工業(yè)來說，軌道平穩(wěn)操作是不合適的。液壓吊綜桿（Fig10.2.5）包括一個圓筒、活塞和一臺控制泵。提升能力能夠達到100小噸（91公噸），并且抬升高度能夠達到22英</p><p><b>　　礦井提升機</b></p><p

64、>　　有兩種類型的起重機：鼓形起重機和摩擦力起重機。在鼓形起重機中，鋼絲繩纏繞在鼓形圓筒上，并被儲存在圓筒中。一臺鼓形起重機可能是單圓筒，也可能是雙圓筒的。對于單圓筒和雙圓筒都有好幾種不同的結(jié)構(gòu)類型。鼓形起重機能夠進一步被細分成不均衡、部分均衡和完全均衡三類。</p><p>　　對于摩擦力起重機，經(jīng)常提及的是Koepe起重機，鋼絲繩不是纏繞在圓筒上，而是貫穿圓筒。摩擦力起重機可以采用單頭或多頭。</

65、p><p>　　起重機的控制操作可以是人工的、自動的和半自動的，也可以實現(xiàn)不同控制控制方法的交叉使用。</p><p>　　在鼓形起重機的新型圓筒上通常使用三種類型的孔型設(shè)計，分別是螺旋型孔型設(shè)計、補償型孔型設(shè)計和反向孔型設(shè)計。螺旋型孔型設(shè)計最初主要應(yīng)用在鼓形圓筒上只纏繞單層鋼絲繩的場合，而補償型孔型設(shè)計和反向孔型設(shè)計主要應(yīng)用在鼓形圓筒上纏繞多層鋼絲繩的場合。</p><p

66、>　　礦井起重機一般被分成（1）金屬礦起重機（例如鋼、銅、鋅、鹽、石膏、銀、金等含有金屬的礦石）（2）煤礦起重機。這類起重機再細分成主力起重機（用來提升金屬礦石和煤）和用來提升人、木料和其他供應(yīng)品的起重機。他們被設(shè)計用來操作（1）豎井，豎直的和傾斜的，均衡的和不均衡的。（2）斜井，均衡的或不均衡的。當一個空的貫籠下降的時候，另一個裝滿礦的貫籠就上升，因為這兩個貫籠都被連接在一個單鼓形圓筒上，這類起重機被稱為均衡型起重機。絕的部分的

67、中型和大型的起重機都是均衡操作的，因為載重量是根據(jù)給定載荷來確定的，鋼絲繩的運動速度是非均衡型起重機的兩倍，并且提升每噸載荷所消耗的能量將減少。也能夠通過使用一個平衡物體來實現(xiàn)均衡操作的。這個平衡物體（接近于所有的靜載荷加上動載荷的一半）通常安裝在機家內(nèi)部。金屬礦石礦井的平均深度在2000ft(610米)，而煤礦礦井的深度接近500ft(152米)。大部分金屬礦石起重機都采用雙圓筒型，一般都是均衡提升。每一個圓筒都裝有一個摩擦離合器，用

68、來改變在不同高度運作時SKIP的相對位置。</p><p>　　煤礦起重機主要都是鍵控圓筒型的，用來在某一高度的均衡運作。為了滿足較淺礦井起重機的高速運作，一般都采用圓柱和圓錐組合型的鼓形筒。在圓錐的小直徑端能夠產(chǎn)生較大的鋼絲繩拉力，以致于的運動周期的加速階段，反向跳動能夠提供最大的平衡扭矩，減小馬達的峰值載荷和略微的減少能量消耗。當豎井的深度越笑，起重機鋼絲繩的運行速度越快，峰值載荷將會減少的更多，因為隨著這些

69、條件的增加，大小直徑端面之間的過度將更加均衡。在加速階段，通過改變鼓形圓筒剖面上的直徑比例和鋼絲繩的配給方法，保持恒定的速度，就能夠改變動、靜載荷以產(chǎn)生最經(jīng)濟的能量消耗和使用最小尺寸的馬達。圓錐形圓筒不適合于多高度的操作場合，并且除非在特殊的場合，一般只采用單層鋼絲繩。</p><p>　　Skip起重機主要使用在工業(yè)上，例如動力燃料的輸送和爐料的輸送，和淺礦井低速提升相類似，它們只能在單一的高度進行操作。通常采

70、用的速度是100-400ft/min(0.5-2m/s)。對于筒裝爐料運輸，載荷達到31，000lb(14000kg)，速度達到500 ft/min(2.5m/s)的，現(xiàn)代的裝置包含了直圓筒齒輪連接驅(qū)動，并頻繁使用Ward Leonard控制。</p><p>　　對于有些場合，只能使用工業(yè)Skip起重機，例如對于桶吊來說高度太高的場合；對于吊桶來說煤塊太大的場合；或者是材料被磨成粉末、極度精磨和具有活潑腐蝕性的

71、場合。因為高度提升具有一個豎直或者接近豎直的運動軌道，具有支撐結(jié)構(gòu)的Skip起重機的制造成本會比筒式提升機和具有輸送架的傾斜輸送帶要低。在表10.2.26展示了典型的運動軌跡。當通過送料斗來接受載荷的時候，C和D軌跡相匹配。</p><p>　　Skip起重機可以直接從傾卸車上人工裝載，也可以通過回轉(zhuǎn)斜道自動裝載，斜道是通過勾斗來開動的，并且當它翻轉(zhuǎn)過來的時候，它就充當封閉門的作用。（Fig10.2.7）<

72、/p><p>　　對于小工作載荷，Skip起重機可以用手動實現(xiàn)半自動控制加載。當鏟斗被裝滿的時候，操作員按下啟動按鈕，鏟斗上升，卸料，然后回到原來裝載的位置。對于自動加載和大工作載荷，Skip起重機可是實現(xiàn)全自動控制。從經(jīng)濟上考慮，鏟斗通過一個重物來平衡，重物的重量等于空鏟斗的重量加上一半載荷的重量。對于大工作載荷，將使用平衡Skip起重機，在這類起重機中，當一個鏟斗上升的時候，另一個鏟斗將下降。而高速Skip起重機

73、通常在鏟斗接近轉(zhuǎn)載和卸載點的時候能夠自動減速（兩個速度用馬達）。</p><p>　　在起重機上使用的鋼絲繩有很多種類，起重機鋼絲繩能被分成三大類：圓形繩、扁平繩和自鎖卷。圓形鋼絲繩主要運用在圓筒上只纏繞單層鋼絲繩的鼓形起重機中，扁平鋼絲繩主要運用在圓筒上只纏繞多層鋼絲繩的鼓形起重機中。扁平鋼絲繩也經(jīng)常被使用在摩擦型起重機上。自鎖卷被使用在摩擦型起重機上。</p><p>　　精選鋼和改良

74、過的精選鋼是最普遍使用的；當嚴格維修時通常使用后者。一些國家的礦井規(guī)章中對安全性的要求比一般的起重機安全性要求要高。新鋼絲繩的工作能力通常是通過生產(chǎn)商給定的最小破壞強度和以下安全系數(shù)來估計的：長度小于或等于500ft（152米）的鋼絲繩，最小安全系數(shù)是8;500~1000ft（152到305米）的鋼絲繩的安全系數(shù)是7;1000~2000ft（305到610米的）的鋼絲繩的安全系數(shù)是6;2000~3000ft（610到914米）的鋼絲繩的

75、安全系數(shù)是5；大于等于3000ft（914米）的鋼絲繩的安全系數(shù)是4.5。根據(jù)假定載荷加上鋼絲繩的重量，可以確定在額定的最小破壞能力和最大靜力拉力之間的載荷總額。由于纏繞在圓筒上的鋼絲繩的加速和彎曲，以及對震動的適當補給，在大載荷和超高度提升中應(yīng)該考慮到網(wǎng)絡(luò)因素的影響。對于6-by-19鋼絲繩結(jié)構(gòu)，圓筒的直徑不能小于鋼絲繩直徑的60倍。圓筒是由鑄鐵或鑄鋼被機械加工上凹槽以適合于鋼絲繩的安裝。在大型起重機中，在圓筒鋼絲繩自由端上安裝有起重

76、設(shè)備以協(xié)助第一層鋼絲繩的雙向往返運動。</p><p>　　剎車 在起重機上使用的剎車主要有三種：鉗夾式剎車、平行機械機構(gòu)剎車和剎車片剎車。剎車控制是通過氣動或者液動來實現(xiàn)的。剎車片是鋼鐵表面附著著摩擦材料。</p><p>　　起重機馬達 要確定選擇驅(qū)動起重機的合適馬達，需要先確定每天或每小時提升載荷量的循環(huán)運動裝置。</p><p>　　礦井允許的最大起重速

77、度主要取決于礦井的深度；礦井越深，允許的提升速度就越大。根據(jù)Bu Mines Bull.75 保守估計的最大起重速度如下圖所示：</p><p>　　高速起重機需要有快速的加速和減速裝置。對于小工作載荷的起重機來說，加速度應(yīng)該為0.5ft/s2(0.15m/s2);具有高速度的大工作載荷的起重機的比較合適的平均加速度為30ft/s2。特殊情況下要求加速度為6 ft/s2（1.9m/s2）。速度值也應(yīng)該根據(jù)每次行

78、程所提升的材料的重量來確定。到底是增大載荷減小速度還是減小載荷增大速度，這要根據(jù)實際情況、礦井規(guī)章和實踐經(jīng)驗來確定。工作循環(huán)中的停止時間，例如底部的裝載所需時間和頂部卸載所需時間，取決于所使用的機器設(shè)備。從地下礦井送料斗裝載需要5到6秒的時間。除非是使用專門的或自動的裝載設(shè)備，最少需要8到10秒的裝載時間。當（1）提升速度，（2）貫籠重量，（3）載荷重量，（4）加速時間，（5）減速時間，（6）裝載時間已經(jīng)確定的時候，下一步是確定作用在馬

79、達上的連續(xù)載荷，考慮鋼絲繩和載荷重量的匹配，懸掛和旋轉(zhuǎn)裝置的加速度和減速度，以及機構(gòu)間的摩擦等等。在運作周期中，通常認為摩擦力保持不變。單級減速齒輪起重機的平均機械效率大約為80%，慢速馬達起重機的平均機械效率可以達到為85%。所選擇的馬達必須有足夠的啟動扭矩來滿足啟動過程的任何階段所出現(xiàn)的暫時</p><p>　　礦井起重機的電氣驅(qū)動設(shè)備主要有四類：</p><p>　　1.小型起重機使

80、用的帶可變電阻的直流馬達。通常是連續(xù)轉(zhuǎn)動的，但在動力制動控制時也采用間歇轉(zhuǎn)動。</p><p>　　2.帶有二級電阻的滑環(huán)型交流馬達。</p><p>　　3.針對于大功率的沃德控制系統(tǒng)，特別適用于短距離高速運作的場合，因為在加速和減速的階段，可變電阻器發(fā)揮不了作用；高速起重機并有速度精度要求的場合；以及動力需求相當?shù)膱龊希会槍恼蜃畲筝d荷到負向最大載荷的變化范圍，速度從零到最大值的變化

81、能夠得到完全的控制。不使用制動裝置的非平衡卸載起重機已經(jīng)成功面市了。</p><p>　　4.Ilgner Ward Leonard 包括一只直接連接到發(fā)電機裝置的調(diào)速輪，還包含了一個自動調(diào)速裝置，通過改變可變電阻器的電阻來驅(qū)動這個裝置。這種裝置主要使用在禁止重載荷的場合，以及動力設(shè)備是根據(jù)載荷峰值來確定的場合。它把循環(huán)中的載荷限定在一個預定的值，但當速度減少的時候，調(diào)速輪釋放出來的能量將使能量超過這個預定值。

82、</p><p>　　安全升降機的出現(xiàn)，使的高建筑物的建設(shè)成為可能，這改變了居民們原有的舊觀念。升降機廣泛的應(yīng)用于在建筑物的垂直方向或斜面運輸乘客和貨物。升降機具體被分成低等（普通）升降機、中等升降機和高等升降機。低等升降機主要在高度為2到7層的建筑物中使用，中等升降機主要在高度為5到20層的建筑物中使用，而高等升降機主要在高度大于150層的建筑物中使用。升降機的運作速度隨著建筑物高度的增加而增大，因此，從底部到

83、頂部的全部運行時間基本上是相等的。一臺典型的Fly time升降機的運作時間大約為一分鐘。低等升降機的常用速度達到200ft/min(1.0m/s); 中等升降機的常用速度達到400ft/min(2.0m/s)；等升降機的常用速度達到1800ft/min(9.0m/s)。</p><p>　　低等升降機一般采用油動力的液壓設(shè)備驅(qū)動。最簡單的液壓千斤頂埋藏在升降機機廂下面。千斤頂大致放在升降機機廂之下平面的中心位置

84、，而千斤頂活塞連接在支撐機廂的平臺上。分布在整個升降行程的導向軌道在升降機上升和下降時引導著機廂的運動。液壓圓筒端面裝有端蓋，用來密封軸承圈，活塞就安裝在這個軸承圈上。活塞一般都沿著圓筒內(nèi)部筒壁運動。密封型液壓缸能夠抗腐蝕。</p><p>　　液壓動力通常是通過由感應(yīng)電機驅(qū)動的螺旋型泵來提供的。一般來說，電機和泵要同軸安裝，并且放置在液壓缸中。工作壓力大約在300到600lb/in2(2到4兆帕)。一個液壓控制

85、閥控制著流向液壓千斤頂?shù)囊簤河偷牧髁浚虼丝刂屏松禉C的運動速度。在升降機下降的時候，泵不工作，而升降機的運動速度是通過流出液壓閥的流量來控制。</p><p>　　液壓升降機的另一類型被稱為無縫液壓升降機。這類液壓升降機的特點是有一個或多個液壓吊綜桿垂直的安裝在升降機機廂周圍，活塞直接安裝在機廂上，或者通過鋼絲繩連接（也被稱為金屬繩索）。后面一種被成為液壓繩索升降機。這類升降機一般纏繞1：2的鋼絲繩，使得升降機

86、的運動速度是液壓活塞運動速度的兩倍。機廂沖擊力也是活塞撞擊力的兩倍。無縫升降機，帶有直接連接到機廂的活塞，可能有單一吊綜桿或者多級伸縮吊綜桿，取決于要提升的高度。</p><p>　　中等和高等升降機是典型的牽引驅(qū)動單元；例如，通過摩擦將馬達的旋轉(zhuǎn)運動傳遞給鋼絲繩。升降機機廂是典型的平衡物體，所以馬達只要克服不平衡載荷就可以了。平衡物的重量等于機廂的重量加上一半負載重量（人或貨物的重量）。隨著升降機的上升，鋼絲繩

87、的重量被安裝在平衡物下面或成圈安裝在機廂底部的鏈條克服。如果這個補償重物的重量和懸掛鋼絲繩的重量匹配，并且不考慮機廂的位置，由于鋼絲繩的自重，整個系統(tǒng)就平衡了。安裝有滑輪來引導鋼絲繩的運動和提高牽引導向性。拉運比例可能是1：1或2：1。采用1：1比例的時候，機廂的運動速度等于鋼絲繩的運動速度；采用2：1比例的時候，機廂的運動速度等于鋼絲繩的運動速度的一半。</p><p>　　中等升降機是典型的齒輪連接機械驅(qū)動，