8-3 Haulage of Shearers

There are different types of shearer haulage: chain haulage [35] and chainless haulage [36], hydraulic haulage and electric haulage [37].

A. Chain Haulage

The haulage chain is a round-link chain [38], which extends along the whole face width and fixed on both ends at the head and tail drives [39] of the face chain conveyor, respectively. The chain also passes through the driving and deflecting��or guiding��sprockets [40] in the haulage unit of the shearer. As the driving sprocket rotates, its teeth [41] trap [42] to the matching chain links and move along the nonmoving haulage chain, thereby pulling the shearer along the face. When the driving sprocket rotates counterclockwise [43], the shearer moves to one direction. Conversely, when the sprocket rotates clockwise [44], the shearer moves to the opposite direction. That part of the chain in front of the moving shearer is generally tight or on tensioned side [45] whereas the other side, behind the moving shearer, is slack or on the slack side [46].

There are many problems with chain haulage:

��When the shearer travels, the haulage chain is subjected to a large tension, due to the haulage force, and deforms elastically [47]. Thus the tensioned chain contains considerable elastic energy. When the shearer stops or once the chain breaks, the elastic energy will be released suddenly, causing accidents [48].

��The haulage chain is suspended along the whole face width. If the faceline is not straight and the floor uneven, the chain may suddenly jump [49], injuring the crew.

�� Under the combined effects of the elastic rebound of the haulage chain and haulage resistance of the shearer, the haulage velocity of the shearer oscillates [50] and frequently produces sudden impacts [51]. This is damaging to many components of the shearer.

�� The existence of the haulage chain is inconvenient for crew travel and accident handling. This is especially true for thin seams [52].

�� As the power capacity of the shearer increases, the haulage force increases correspondingly. Therefore, the chain must be strong and the chain size must be increased. The heavy chain is inconvenient for transportation and maintenance.

B. Chainless Haulage

In response to all the disadvantages associated with chain haulage, the chainless haulage was developed. According to the haulage principles, the chainless haulage can be divided into three types: drive chain-rackatrack [53], drive wheel-rackatrack [54], and ram propulsion [55].

This is the double-ended ranging-drum shearer with a wheel-rackatrack haulage system. The system eliminates any types of drive chain. The shearer moves by driving sprocket matched with the rackatrack through an idler [56]. The haulage-driving unit is similar to the conventional ones. Th

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