外文翻译--采煤机.doc

附录1： 英文原文 SHEARERS INTRODUCTION Longwall mining in the United States is finally beginning to carve out a significant percentage of underground mining tonnage. Although longwall installations are continuing throughout the country –at last count in eleven states—the concentration is in the Eastern coal fields, with West Virginia leading all states. As a result of increased experience with longwall installations under different condition, certain improvements are being made. For instance, roof support shields are being utilized to a greater extent, and ruggedness is being stressed in all areas. Modifications are being considered in order to use the longwall in other types of seams and seam conditions. Evidently longwall users like the results that they have been getting because they have been installing more systems. Since longwall mining is obviously going to play a much larger role in the coal mining industry in the future, there is a great need for a comprehensive book that presents, systematically, every major subject in longwall mining. More than a decade of modern longwall mining in the United States has demonstrated that it is inherently safe and complies easily with current laws. It is also highly productive, provided it is properly designed and operated. However, the growth of longwall mining, though steady, has been slow. One of the reasons for this is the lack of a comprehensive technical background literature for training purposes. This book attempts to fill such a gap. For the first time, anyone who would like to learn more about longwall mining can find all of the major topics in one book. Thus, this book is a milestone in the development of longwall mining. SHEARERS Longwall equipment consists of three major components: the hydraulically powered roof support, the chain conveyor, and the coal-cutting machine. The two different types of coal-cutting equipment used in coal mines are shearers and plows. Plows are used in low seams, 42in. or less. The unit co