Fig. 61.
r is a false bottom perforated in its entire length with holes 12 millimeters (0.47 inch) in diameter, and is placed about 15 centimeters (5.9 inches) above the true bottom of the drum. It consists of two pieces, and is secured by two nuts, so that it can be easily removed and replaced. Its object is to prevent the bones from clogging up the pipe s, and the cocks t, u.
a, a, Fig. 61, are angular iron points inside of the drum e. Their object is to facilitate the shifting of the bones when the drum is revolving.
x, Fig. 59, is a cock near the manhole. It is opened about 2 millimeters (0.079 inch) during the operation in the drum. It serves also for the escape of the steam from the drum when the operation is finished.
The cocks t, u, placed in the lower part of the drum, serve for the escape of steam condensed during the operation.
The steam pipe p, Fig. 59, conducts the steam from the vessel a into the drum e.
y, Fig. 59, is a cock graduated into eight equal parts and placed on the steam pipe p, to conduct the steam from the box z, into the stuffing box a´, and from there into the pipe s, then under the false bottom r, into the drum e.
The lid of the cast-iron box z, is provided with a safety valve loaded with a weight corresponding to the pressure of one atmosphere.
The wooden vessel or box d, the ground-plan of which is shown in Fig. 62, serves for boiling the comminuted bones in order to extract the jelly. This box consists of the following parts:—
Fig. 62.