=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.
[Illustration: 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.