- SOME HYDRAULIC PRESSURE MACHINES 521 
An objection to the U-leather packing is that the ram must be 
removed before the packing can be renewed, and this, in many cases, 
is very troublesome. In such cases the ordinary stuffing-box is generally 
used. The ordinary gland and stufling-box for hemp or other packing is 
shown in Fig. 799, p. 499. 
To give a smooth and non-corrosive surface to a ram, it is frequently 
sheathed with brass. Cylinders are also lined with brass for the same 
_ reasons and to make them non-porous at high pressures. 
450. Joints and Connections for Hydraulic Pipes. — Hydraulic 
mains are generally made of cast-iron. For a pressure of 800 lbs. per 
TUS 
ia S 
2 ee 
Wl 
Ww 
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Fig. 831. Fig. 832. 
square inch the diameter of these mains does not exceed 7} inches, 
The form of joint used for cast-iron hydraulic mains is shown in Fig. 831. 
The joint is made water-tight by a gutta-percha ring, which is forced into 
the V-shaped recess formed between the spigot and socket. 
For smaller pipes, solid-drawn steel tubes are used. A common form 
of joint for these tubes is shown in Fig. 832. Strong cast-iron flanges 
are screwed on to the ends of the tubes. One of the two flanges has 
a shallow socket to receive a spigot on the other. The joint is made 
water-tight by a leather or gutta-percha 
washer placed between the spigot and “Uy 
socket. The end of the spigot and the —Yy 
bottom of the socket in contact with the 
leather or gutta-percha have concentric Yi 
grooves turned on them, and the leather tay 
Z 
KOR , 
may | 
I _ 
is forced into these grooves. YZ 1a) 
A very convenient form of joint WY 
between a steel tube and a hydraulic Yj Yy 
cylinder is shown in Fig. 833. Ascrewed 
recess is formed in a boss on the 
cylinder, and into this is placed, first Fig. 833. 
a leather or gutta-percha washer, and 
then the end of the tube, on which is screwed a collar A. A gland B 
screwed into the recess completes the connection. 
451. Hydraulic Accumulator.—Hydraulic pressure machines are 
usually intermittent in their action, and their demand for power is 
therefore very variable. In an installation of these machines the 
pressure water is obtained from pumps, and it is desirable that the 
pumps should be kept, as far as possible, working continuously. This 
