The Mechanical Handling and Storing of Material

i6o THE MECHANICAL HANDLING OF MATERIAL the rail level, and one of the sides near the coal face is lower to facilitate filling. In this class are included the Mickley 1 and the Bothwell2 conveyors, which consist of low trucks which are pulled along in front of the coal face. With the latter type of trucks, trains are formed consisting of as many as twenty-four trucks. The Gibb3 conveyor (see Fig. 214) consists of eight or nine segments, each of which is supported by four cast-steel wheels. The first and last segments have closed ends, so that the whole is like one receptacle. Such a conveyor is in use at the Muiravonside Colliery in Linlithgowshire. It consists of nine segments with a total length of 56 ft., 16 in. wide and 8 in. deep at the side of the coal face, and 14 in. deep at the other side; this conveyor holds 2X tons of coal. Similar appliances of the same class are the Bunker conveyor,4 and the Cummings & Gardiner,5 Walton & Rayner,6 and Thomson conveyors.7 All these conveyors pass backward and forward along the coal face to the gateway where they deposit their load Fig. 214. Gibb Coal Face Conveyor. into ordinary mine tubs, and sometimes they pass beyond the gate to the coal face on the other side, alternately taking the coal from the face on either side of the gate. All these appliances run on rails of ordinary section except the Bothwell which runs on a U-shaped channel, and the Thomson, which is not supported by wheels, but slides in U-shaped channels. The drive is by steel rope which passes over rollers at the terminals, manipulated by hand or pneumatic gear. The unloading is effected in various ways. The Mickley and Bunker conveyors deliver through openings controlled by slides ; the Bothwell has an automatic tipping device by which each segment delivers its load by 1 Mickley. This is more fully described in the Transactions of the North of England Institute, vol. lv., page 176. 2 Bothwell. This is described in The Colliery Guardian, II., 1909, page 622. 3 Gibb. Tnis is fully described in The Colliery Guardian, II., 1909, page 59. 4 This is described in The Colliery Guardian, II., 1911, page 1286, and The Transactions of the Institute of Mining Engineers, 1912, page 391, also in “The Coal Age,” 1912, page 643. 5 Cummings & Gardiner, Colliery Guardian, II., 1911, page 167. 6 Walton & Rayner. Described in Colliery Guardian, I., 1911, page 1228. 7 Thomson. Described in Iron and Coal Trade Review, 1909, Nov. 26, and “Coal Age,” 1912, page 645.