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中位放顶煤
液压
支架
设计
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中位放顶煤液压支架的设计,中位放顶煤,液压,支架,设计
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中国矿业大学2008届本科生毕业论文 第12页 英文原文Powered supportsPowered roof supports are used to support the roof at the face.They work in several steps mostly in the immediate forward support (IFS) type in order to support the newly exposed roof as soon as possible. In normal supporting condition the canopy of the support is set tightly against the roof strata,by the supporting resistances of the hydraulic legs. When the cutting machine cuts and passes several support units beyond the support in question, the support legs are lowered and pulled forward for a distance equal to the width of cut (web) by retracting the hydraulic advancing ram. The advancing ram acts against the face conveyor panline, whose position is held unchanged by the advancing rams, forces of the supports that are set on both sides of the support to be advanced. As soon as the support has been advanced to the designed position, the support is immediately reset against the roof. Finally, the advancing ram of the support in question is extended to push the conveyor forward and becomes ready for the next cut. The sequential steps described are for the advance of an individual support in the direction perpendicular to the faceline.But along the faceline direction, the conveyor cannot be advanced in a sharp step immediately after the shearer has passed it, due to the rigidity of the panline. Thus the fourth step is usually sometime after the shearer,s pass, resulting in a curved or snaked section.During panel development the panel entries are roof bolted as usual. But in the tailentry one or two rows of cribs are erected to supplement the roof bolting. During retreating mining, the roof at the headentry T-junction area (up to 500 ft (152m) outby the face) is generally reinforced with supports of some type to increase support density to cope with the moving front and side abutment pressures. Modern longwall mining employs hydraulic powered supports at the face area. The supports not only holds up the roof, pushes the face chain conveyor(AFC), and advances itself, but also provides a safe environment for all associated mining activities. Therefore its successful selection and application are the prerequisite for successful longwall mining. Furthermore, due to the large number of units required, the capital invested for the power support usually accounts for more than half of the initial capital for a longwall face. Therefore both from technical and economic points of view, the powered support is a very important piece of equipment in a longwall face. Classification of powered supportsThe application of modern powered supports can be traced back to early 1950s. Since then, following its adoption in every part of the world, there have been countless models design and manufactured in various countries. But unfortunately, there still is no uniform system of classification.In this section a simplified classification is used. Since a powered support consists of four major components (i. e , canopy, caving shield, hydraulic legs and props, and base plate), the ways by which they are interrelated are used for classification. In this respect, two factors are most important: (a) presence or absence of caving shield- if a caving shield is included, the support is a “shield” type, otherwise, a frame or a chock; (b) number and type of arranging the hydraulic legs- since support capacity is generally proportional to number of hydraulic legs, it is important to specify the number of hydraulic legs that a support has. Furthermore, the way the hydraulic legs are installed is important; for example, a vertical installation between the base and the canopy has the caving shield has the least efficiency in supporting the roof.Based on this concept, there are four types of powered support, that is, the frame, chock, shield and chock shield, in order of evolution of their development. However, it must be noted that the trend of development in each type is such that it becomes less distinguishable in terms of application.The four types of roof supports can be obtained for either longwall retreating or advancing systems, and they are available in standard, one-web-back, and immediate forward support (IFS) versions.With the standard system, the wining machine takes a cut or a slice, and the armored face conveyor is pushed over by the hydraulic rams that are fixed to the support units. The support units then are advanced sequentially to the conveyor. With the one-web-back system, a support is set back from the conveyor by a device that automatically keeps the leading edge of the support at a fix distance from the conveyor. This allows easy access though the face and employs the standard method of advancing; i. e , pushing the conveyor first, and then advancing the support.With the IFS system, the support units is advanced to the conveyor immediately after the cutting machine has passed, and the forward canopy of the support units is long enough to the support both the recently and newly exposed roof sections. After the supports have been advanced, the conveyor is pushed over. FrameThe frame support is an extension of the single hydraulic props conventionally used underground. Thus it is the first type developed in modern self-advancing hydraulic powered supports. It involves setting up two hydraulic props or legs vertically in tandem that are connected at the top by a single or two segmented canopies. The two segmented canopies can be hinge-jointed at any point between the legs or in front of the front leg. The base of the two hydraulic legs may be a circular steel shoe welded at bottom of each leg or solid base connecting both legs.Generally, a frame support consists of two or three sets of hydraulic legs. The set moving first is the secondary set, the set moving later is the primary set. There is a double-acting ram installed between each set. The piston of the ram is connected to the secondary set and the cylinder to the primary set. During support advance, the primary set is set against the roof while the secondary set is lowered and pushed forward by the piston. Having reached the new position, the secondary set is against the roof while the primary set is lowered and pulled forward by the cylinder. The distance of each advance ranges from 20 to 36 in.(0.50 0.91m)The frame support is very simple, but more flexible or less stable structurally. There are considerable uncovered spaces between the two pieces of canopy which allows broken roof rock to fall through. Consequently, the frame support is not suitable for a weak roof. Frames have become seldom used because they are less stable and require frequent maintenance. ChockIn a chock support, the canopy is a solid piece and the base may be either a solid or piece or two separate parts connected by steel bars at the rear and/or the front ends. In both cases a large open space is left at the center for locating the double-acting hydraulic ram which is used to push and pull the chain conveyor and the chock in a whole unit, respectively, a distinctive difference from the frame support. This setup is also used in the shields and chock shields.Again, all hydraulic legs are installed vertically between the base and the canopy. The number of legs ranges from three to six, but the four-leg chocks are by far the most popular ones. The six-leg chocks are designed for thin seams with two legs in the front and four legs in the rear, separated by a walkway. For the six-leg chocks, the canopy is generally hinge-jointed above the walkway. Most chock are also equipped with a gob window hanging at the rear end of the canopy. The gob window consists of several rectangular steel plates connected horizontally at both ends.In most chock supports, there are hinge joint connections between the legs and the canopy and between the legs and the base. But in order to increase the longitudinal stability, it is reinforced mostly with a box-shaped steel frame between the base and each leg. A leg restoring device is installed around each leg at the top of the box-shaped steel frame.The chocks are suitable for medium to hard roof. When the roof overhangs well into the gob and requires induced caving, the chocks can provide access to the gob. ShieldShields, a new entry in the early seventies, are characterized by the addition of a caving shield at the rear end between the base and the canopy. The caving shields, which in general are inclined, are hinge-jointed to the canopy and the base making the shield a kinematically stable support, a major advantage over the frames and the chocks. It also completely seals off the gob and prevents rock debris from getting into the face side of the support. Thus the shield-supported face is generally clean.The hydraulic legs in the shields are generally inclined to provide more open space for traffic. Because the canopy, caving shield, and base are interconnected, it can well resist the horizontal force without bending the legs. Thus, unlike the solid constraint in the frame/ chock supports, the pin connections between the legs and the canopy , and between the legs and the base in a shield support make it possible that the angle of inclination of the hydraulic legs varies with the mining heights. Since only the vertical component of hydraulic leg pressure is available for supporting the roof, the actual loading capacity of the shield also varies with the mining heights.There are many variations of the shield supports. In the following, six items are used to classify the shields , which enables a unified terminology to be developed for all kinds of shields. The types of motional traces of the canopy tip, leg positions and orientation, number of legs, canopy geometry, and other optional designs and devices can be clearly specified by the terminology .Types of motional traces for the leading edge of the canopy. This is the most commonly recognized way of classifying the shield. Based on this criterion, there are three types, lemniscate, caliper , and ellipse.Lemniscate. This is the most popular type. The caving shield and the base are jointed by two lemniscate bars which have a total of four hinges. As the hydraulic legs are raised and lowered, the dimentions of the lemniscate bars are selected such that the leading edge of the canopy moves up and down nearly vertically , thus maintaining a nearly constant unsupported distance between the face-line and the leading edge of the canopy .This is a feature that is widely considered most desirable for good roof control . There are clear limits of mining height within which the leading edge of the canopy moves nearly vertically. These limits are strictly controlled by the dimentional and positional arrangements of the canopy, caving shield, lemniscate bars, and the base. Beyond these limits, the edges will move rapidly away from the face-line creating a large unsupported area.Caliper. In a caliper shield, the caving shield and the base are connected by a single hinge .When the hydraulic legs are raised, the leading edge of the canopy moves in an arc away from the face, thus increasing the unsupported area. This is considered by most users the least desirable feature of the caliper shield .But in practice if the seam thickness varies little, the dimentional and positional arrangement of canopy, caving shield, and the base can be so designed that the distance change of unsupported area will not be significant. On the other hand, when the legs are lowered, it reduces the unsupported area. Ellipse. In this type the caving shield and the base are so connected that when the hydraulic legs are moved up and down, the leading edge of the canopy follows an elliptical trace. This type is seldom used. Chock shieldThe chock shield combines the features of the chocks and the shields. As such it possesses the advantages of both.If all of the four or six legs are installed between the canopy and the base, it is called a chock shield. There are regular four or six-leg chock shields in which all legs are vertical and parallel. Others form V or X shapes. Some canopies are a single piece and some are two pieces with a hydraulic ram at the hinge joint. The chock shield has the highest supporting efficiency. They are suitable for hard roof.Common elements of powered supportsThe modern powerd supports, regardless of the types ,consist of the following five common components:( 1 ) Load-bearing units. These include the canopy, base plate, caving shield, lemniscate bars, and joint pins.( 2 ) Hydraulic rams. These include the hydraulic rams for ( a ) pushing the chain conveyor and advancing the powered support, ( b ) operating the front canopy or face guards, ( c ) balancing or limiting the position of the canopy, and ( d ) operating other auxiliary equipment such as leg recovering devices and side shideds, and above all, operating the legs.( 3 ) Control and operating Units. These include internal control valves such as check and yield valves in the hydraulic legs, unit control valve, and high pressure hydraulic tubings.( 4 ) Auxiliary devices. These include support advancing,leg recovering, gob windows, face guards, base-lifting, lighting, and so on.( 5 ) Hydraulic fluid. This is the emulsion for operating the powered supports. 中文译文液压支架液压支架被用来支护工作面顶板。他们在立即前移支护系统里通常从事以下几步工作，为了尽可能快地支撑新暴露空间。在正常的支撑重要条件下，支架的顶梁是通过立柱的支撑阻力紧紧地靠着来阻止顶板岩层。当切割和通过几个支撑单位超过支架时，立柱降柱和向前移动一段距离，通过液压推进油缸的缩回来达到与切割的深度相等。推进油缸靠在工作面输送镏槽上，它的位置是通过支架的推进油缸的推进力来保持不变，作用在支架的两边。支架一推进到设计的位置，支架就立即重新靠在顶板上。最后，支架的推力油缸试图向前推进输送机和为下一次切割做准备。描述的顺序步骤就是为了单个支架的推移，在方向上要垂直于工作线。但是沿着工作线的方向，在采煤机通过输送机之后，输送机不会立即推移很大一段距离，由于镏槽的刚性。因此第四步通常是在采煤机通过之后的一段时间，导致了弯曲或矩形的方向。在采区推进期间，镏槽向导通常是锚杆支架。但是在尾部巷道一排或两排垛子被支撑去辅助顶板螺栓。在后退式采煤期间，在下顺槽T型接口的顶板（伸出工作面的距离达到了152m）一般是通过某些类型的支架来进行加固，以提高支护密度来处理向前移动和向旁边移动的支座压力。 现代长壁采煤工作面使用自移式液压支架（这种支架在这本书中通常被称为液压支架）。液压支架不仅支撑顶板，推移工作面刮板输送机，和它自己的移动前进，而且为了所有相互联系的采煤活动提供安全的环境。因而液压支架成功的选择和应用是长壁开采成功的选择和应用是长壁开采成功的前提条件。此外，由于需要大量的液压支架，为液压支架所投入的资金通常超过为长壁工作面所投入的初期资金的一半。因而从技术和经济两方面观点看，液压支架是长壁工作面非常重要的设备。液压支架的分类现代液压支架的使用可以追溯到20世纪50年早期。自从那时起，随着液压支架在世界上的应用，在不同的国家已经有了不计其数的设计模型和不计其数的液压支架被制造。但是不幸的是液压支架仍然没有一致的分类体系。在这一段一个简化的分类被使用。液压支架是由四大主要部分组成（顶梁、掩护梁、立柱和底座）。这些组成部分的使用是相互联系的，为了便于分类。在这一方面，两个因素是最重要的：（a）是否存在掩护梁-如果包括掩护梁，那么这种支架就是掩护型的，否则它就是节式或垛式支架；（b）立柱的数量和类型-立柱的负载量通常与立柱的数量成正比例，因而确定支架的立柱数量是重要的。此外，立柱被安装的方式是重要的；例如，在支护顶板方面，在顶梁和底座之间垂直的安装立柱有最高的应用效率然而在底座和掩护梁之间倾斜的安装立柱却有着最低的效梁。根据这个概念，有四种类型匠液压支架，那就是，节式，垛式，掩护式和支撑掩护式，随着他们的发展演变而来的。然而，必须强调的是每种类型的发展趋势都是为了在应用方面让液压支架变的容易区分。这四种类型的液压支架不仅可以用于后退式长壁回采工作面和前进式开采工作面，还可以用于标准方式、滞后支护方式和即时支护方式。对于标准支护方式，采煤机作切割或分段运动，工作面输送机由装在液压支架上的推移千斤顶推动前进。液压支架比输送机先移动。对于滞后式支护方式，支架不可能靠近输送机，因为有一个装置自动的使支架前端与输送机保持一定的距离。这就要求要有贯穿工作面的缓沟，并且采用前进式标准支护，比如：先推动刮板输送机，然后再让液压支架前进。对于即时支护方式，液压支架在截煤机过去之后立即跟随刮板输送机前进，液压支架前面的顶板有足够的长度来支护采过和将要采的顶板部分。在液压支架前进以后，刮板输送机也被推移前进。节式支架 节式支架是通常使用在地下的单体液压支柱的扩展。因此节式支架是在现代自移式液压支架中发展出的第一种类型的液压支架。它包含两排串列的液压支柱，在顶部由单个或两个扇形顶梁所连接。两个扇形顶梁可以在两个立柱之间或前柱的前面以任意的角度铰接。两个液压支柱的底座可能是一个环形的钢铁滑必履焊接在每个立柱的底部或整个底座连接两个立柱。如果钢铁滑履被使用，那么弹簧板连接着立柱就用来提高稳定性。通常节式支架包含两排或三排立柱。首先移动的那排立柱是辅助的立柱，后来移动的是主要的立柱。有一个双作用油缸安装在每排立柱之间。油缸的活塞连接到了辅助立柱上，气缸连接到了主要立柱上。在支架推移期间，主要立柱支撑顶板而辅助立柱是低的并且通过活塞向前推。达到了新的位置时，辅助立柱支撑顶板而主要立柱是低的并且通过气缸向前推。每次前移的距离是在20到36英寸之间。因此节式支架是非常简单的，不仅不是更加的灵活而且结构上不稳固。在两块顶梁之间有相当大的地方，不允许破落的顶板石块落在那里。因此，节式支架不适合用在支撑力弱的顶板上。节式支架已经变的极少使用因为它们不稳固而且需要经常维修。垛式支架在垛工支顶架里，顶梁是一整块和底座可能是一整块也可能是由后端梁和前端梁上的钢铁杆连接的两个分开的零件。在这两种情况里，一块大的空地方是在中心的左边，为了定位双作用液压缸，用来在整个机构里推拉刮板输送机和垛式支架。都分别不同于节式支架，这个装置也用在掩护工和支撑掩护式支架中。此外，所有的立柱都垂直地安装在底座和顶数值之间。立柱的三到六个，但是四柱的垛式支架是远远落后于最流行的垛式支架。六柱垛式支架的前面两个立柱和后面四个立柱都设计的有细小缝隙，被一个通道分开。因为六柱垛式支架也在顶兴的后部安装一个挡矸板。挡矸板由几个矩形的铁板组成，水平的连接在两端。在大多娄的垛式支架里，在立柱和顶梁，立柱和底座之间都有铰接的连接口。但是为了增加纵向的稳定性，在底座和每个立柱之间用一个箱形的铁架来进行加固。在箱形铁架的顶部，每个立柱的周围都安装一个立柱复位装置。垛式支架适用于中硬顶板。当顶板外伸进了采空区并且要求人工放顶，垛式支架就会给采空区提供通道。掩护式支架掩护式支架，十七世纪早期的一种新的发明，以在后部，底座和顶梁之间增加
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