1、英文原文 THE SHEARER Shearer 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
2、 less. The unit consists of steel construction equipped with carbon-tipped bits. This passive steel unit is engaged to a guiding system on the face conveyor. An endless round link chain powered by synchronized electric drives on each end of the face conveyor pulls the plow body at speeds between 120
3、 and 420 ft/min along the face. For the cutting process the plow has to be forced against the coal face. This is done by hydraulic cylinder attached to the gob side of the face conveyor and to the base of the supports, or by a separate hydraulic prop. Forces of between 1and 3 tons are applied per cy
4、linder. A plow drive is attached to each drive frame of the face conveyor. Only 30% to 60% of the drive power supplied to the plow is used for cutting and loading of coal； the remainder is lost in friction. This means that the power loss is considerably higher than that of a shearer, which uses 75%
5、to 85% of its power for the removal of the coal. As a result, rather large drives are required at the face ends. Although there are many models, the shearer has several common basic components. A double-ended ranging-drum shearer (Fig. 8. 1), for example, consists of four major components: electric
6、motors, gearheads, haulage unit (power pack), and cutting drums. The electric motor ranging from 300 to 1000 horsepower (223750kW) is the power source for the shearer. It provides power to run the hydraulic pumps in the haulage unit and the gearheads for the cutting drum. The large-capacity shearers
7、 are generally equipped with two electric motors: one for the haulage unit and one gearhead and the other for the other gearhead and other ancillary equipment. The motors can be remotely controlled. There are two gearheads, one on the left-hand the other on the right-hand side of the shearer. Each g
8、earherad consists of a gearhead gearbox and a ranging arm. The cutting drum is laced with spiral vanes on with spiral vanes on which the cutting bits are mounted. Its diameter ranges from 34 to 72 in. (0.861.83 m) with rotational speeds from 30 to 105 rpm. The trends are toward fewer but larger bits
9、 and slower drum speed for better cutting efficiency and less coal dust production. The drums are also equipped with power cowls to increase the coal loading efficiency. The power cowl is usually located behind the cutting drum. For that reason, it can be rotated a full 180. The electric motor, haul
10、age unit, and gearhead boxes combine to form the shearers body which is mounted on the underframe. The underframe has four sliding shoes. The face-side shoes are fitted and ride on the face-side top guide of the face conveyor pan, and the other two gob-side sliding shoes are fitted on a guide tube t
11、o prevent derailment. The tramming aped of the shearer ranges from 19 to 46 ft/min (5.814.0 m/min). In addition, the shearer is equipped with auxiliary hydraulic pumps and control valves for operating the ranging arms and power cowls, water spraying devices, cable, chain anchorage and tensioners, an
12、d so on In selecting the shearer, mining height should first be considered； that is, the diameter of the cutting drum, body height, length of the ranging arm, and swing angle must be properly selected. For the double-ended ranging-drum shearer, the maximum mining height cannot exceed twice the diame
13、ter of the cutting drum. The mining height can be determined by (Fig.8.3) H=Hb-B/2+Lsin+D/2 Where H=seam thickness or mining height Hb=shearers body height B=body depth L=length of the ranging arm =the angle between the ranging arm and the horizontal line when the ranging arm is raised to its maximu
14、m height D=diameter of the cutting drum For example, for the Eichhoff EDW-170 L double ranging-drum shearer, Hb=4.3 ft, L=3.90 ft, =52， and D=5.3 ft. Its maximum cutting height is H=9.2 ft. Types of modern shearers Since its first appearance in 1954,the shearer has undergone continuous changes both
15、in capability and structure. It is now the major cutting machine in longwall coal faces. There are two types of shearers, single-and double-drum. In the earlier models, the drum in the single-drum shearer is mounted on the shearers body and cannot be adjusted for height. Therefore it is not suitable
16、 for areas where there are constant changes in seam thickness and floor undulation. Thus the single-ended fixed-drum shearer is used mostly for thin seams. Figure 6.10 shows a single-drum shearer with a ranging arm. The cutting drum is mounted at the very end of the ranging arm. The ranging arm can
17、be raised up and down by hydraulic control to accommodate the changing seam thickness and floor undulation. But when the seam exceeds a certain thickness, the single-drum shearer cannot cut the entire seam height in one cut and a return cutting trip is necessary to complete a full web cut. Furthermo
18、re, since the drum is located on the headentry side, it generally requires a niche in the tailentry side. A niche is a precut face end, one web deep and a shearers length long. With a niche at the face end the shearer can turn around. Nowadays, the double ranging-drum shearers are used predominantly
19、. The shearer cuts the whole seam height in one trip. The two drums can be positioned to any required height (within the designed range) during cutting and lowered well below the floor level. The arrangement of the drums enables the whole seam to be cut in either direction of travel, thereby ensurin
20、g rapid face advance and shortening roof exposure time. There are various types of double ranging-drum shearers. Based on the location of the drums, there are two types: one with one drum mounted on each side of the shearers body and the other with both drums mounted on one side of the machine. The former type is the most widely used. Its advantage is that with one drum on each side of the shearer, it can sump in either direction. During the cutting trip, the leading drum cuts the upper 70% of the seam height while the rear drum cuts the
