21. Buckets, such as are used for hoisting material during shaft sinking, are continued in use after mining begins when the amount of material to be hoisted is small.
CAR LOCKS
22. Several methods of keeping the car on the cage have already been illustrated: by chains, [Fig. 8]; by bails, Figs. [9], [10], and [12]; by omitting sections of the rail under the car wheels, [Fig. 11]; and by dropping a portion of the platform, [Fig. 13]. A very common way is merely to put a pin through the hole in the drawbar and into the floor of the cage. Another common device consists of a brake block that fits between the wheels and can be thrown in from the side by a lever when the car is in place. Another device consists of a yoke, which, by means of a lever, is raised when the car is in place so that it passes about the axle and thus holds the car. A device frequently used on self-dumping cages is shown in [Fig. 22].
Fig. 22
The curved bars a of iron, which just fit around the car wheels as shown, are attached to the loose bars b, on the ends of which are the weights c. When the cage is at the bottom, these weights strike on a cross-piece and are raised to the position shown by the dotted lines, throwing out the bars b, as shown by the dotted line, thus releasing the wheels. The devices shown in Figs. [11], [13], and [22] do not come into action until the cage leaves the landing and the cars must, therefore, be watched until that time.
CAGE GUIDES
23. Guides are used in all vertical shafts of any considerable depth and in many highly inclined shafts to keep the cage from swinging about and striking the sides of the shaft. They are made of wooden rails, iron rails, or wire ropes. In American mines, timber guides predominate, although some iron ones are used, and for small shafts at ore mines wire-rope guides are common. In English mines, wire ropes, called conductors, are very largely used. This difference in practice is probably due to the fact that in English mines the shafts are usually round and the cages are rectangular. In such a shaft, the wire-rope conductors hang from the head-frame without any cross-bracing, but they require a strong support, as both the weight of the ropes and the strain to give the necessary tension come on the head-frame. When both the shaft and the cage are rectangular, as in most American mines, timber guides are easily put in and they offer a good surface for the safety catches to grip.
Fig. 23