1、翻译部分 英文原文 SELF-ADVANCING HYDRAULIC POWERED SUPPORTS Modern longwall mining employs hydraulic powered supports at the face area . The support not only holds up the roof , pushes the face chain conveyor , and advances itself , but also provides a safe environment for all associated mining activities .
2、 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 powered support usually accounts for more than half of the initial capital for a longwall face . Therefore
3、both from technical and economic points of view , the powered support is a very important piece of equipment in a longwall face . The application of modern powered supports can be traced back to the early 1950s . Since then , following its adoption in every part of the world , there have been countl
4、ess models designed and manufactured in various countries . But unfortunately , there still is no uniform system of classification . A simplified classification is used in this section . since a powered support consists of four major components(i. e. , canopy , caving shield , hydraulic legs or prop
5、s , and base plate ) , the ways by which they are interrelated are used for classification . In this respect , two factors are most important : (1) presence or absence of a caving shield - if a caving shield is included , the support is a “ shield ” type , otherwise , a frame or a chock ; (2) number
6、 and type of arranging the hydraulic legs - since support capacity is generally proportional to the 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 highest efficiency of application whereas an inclined installation between the base and the caving shield has the least efficiency in supporting th
