522 APPLIED MECHANICS 
necessitates the introduction of a hydraulic accumulator, which sha 
store up the pressure water when the pumps are delivering more th , 
required by the machines, and give it out again when the delivery of 
pumps is less than thé machines require. There are two principal ty, 
of the ordinary hydraulic accumulator. In the one type there is a fixe 
cylinder fitted with a loaded ram, and in the other there is a fixed rai 
on which is fitted a loaded cylinder. An example of the fixed ram tyy 
of accumulator is shown in Fig. 834, A is the ram, and B the cylinder 
When the delivery of the pumps is 
greater or less than is required by the 
machines, the water enters or leaves the 
cylinder at C through the ram, which 
is hollow. Resting on the flange at the 
lower end of. the cylinder is a strong 
cast-iron base D, which carries the 
remainder of the load. The remainder 
of the load may consist of a number of 
blocks of cast-iron, or, as in the form 
shown, D carries a cylindrical casing 
made of steel plates, which holds scrap 
iron,: stones, or other suitable heavy 
material. When at the bottom of its 
stroke, the load rests on the wood blocks 
shown. EE are two timber posts sunk 
in the-concrete foundation at their lower 
ends, and fixed at their upper ends to 
the walls of the building containing the 
accumulator, or in any other way con- 
venient, To the inside faces of these 
timber posts are attached steel or iron | 
channels, in which slide blocks attached 
to the load casing, as shown in the 
elevation, and more clearly in the cross 
section at (a). In this way the load is guided as it rises and 
A strong buffer or stop is provided to prevent the cylinder 
too high, and if there is only one accumulator, there are levers v 
are automatically brought into action at or near the top of the stroke, 
and which stop or restart the pumps. : 
In large installations where one accumulator would be inconvenie 
large two or more are used, in which case the second carries a hee 
load than the first, and the third a heavier load than the second. 
increase of load corresponds to an increase of pressure of about 20 Ib 
per square inch. The second accumulator does not come into action 1 
the first is fully charged, and the third does not come into action until the 
second is fully charged. Only when the last of the series is fully charg 
are the pumps stopped. a 
If d=diameter of ram in inches, p= pressure of water in lbs. per 
square inch, W=total moving load in lbs., and 4=stroke in feet, the: 
(tt sttbdltttdd ty 
SSS % 
Luda 
Uff VLLLIULLLMLDLLLLLLL LLM L MELEE LE Ea 
— 
Wd 
Y 
ay, 
Fie 834, 
neglecting friction, W=7e , and the capacity of the accumulator 4 
Wh ="@ph ft.bs. | : —_ 
