14 BULLETIN 867, U. S. DEPARTMENT OF AGRICULTURE. 
This method has been abandoned for that of the cage press. Essen-— 
tially this latter is an ordinary hydraulic plate press with the plates 
removed to accommodate an iron box (or cage) with rectangular or 
cylindrical cross section, open at both ends, and with the walls per- 
forated over their entire surface. This cage is set vertically in the 
press in place of the removed plates, while the ram head just fits the 
cage and rises into it. A headblock above the cage and attached 
to the press frame likewise fits into the cage from above and supplies 
the resistance against which the ram operates. Other cages consist 
of vertical bars set closely and clamped by heavy rings to resist the 
bursting pressures. 
The method of filling the cages varies with different types of presses. 
Some cages are filled on a so-called charging press and are transferred 
with their contents to the finishing presses, while others press in only 
one operation. Im any case, when charging, the cages remain in 
position in the press frame with the ram raised to within a short 
distance of the top of the cage. The cage is filled with beans level 
with the top and.a plate is laid on, closely fitting the walls. Some- 
times a mat is laid on the plate. The ram with its charge then de- 
scends a given distance, leaving a space equal to the first one. This is 
filled level with beans and another plate added. The process is con- 
tinued until the ram has been lowered to the bottom of the cage, 
leaving the latter filled with layers of beans separated at given dis- 
tances by plates. The number of such plates may vary from 6 to 50. 
Other types have two horizontal rails in front of the cage whereby 
the latter can be pulled out from the press frame and either filled 
from above by dropping in measured quantities of beans separated 
by plates or discharged of its press cake by dumping below into a 
hopper or conveyor. The cage is then shoved back within the press 
frame for pressing. | 
Whatever preliminary method is used for charging the cage, the 
subsequent pressing operations are quite similar. The headblock is 
placed in position so as to engage in the top of the cage. As the ram 
rises, it compacts the charge of beans and presses it against the head- 
block, thus developing increasing pressures which cause the oil to 
start. Maximum yields and a better quality of oil are obtained by so 
adjusting the rate of rise of the ram that the pressures are developed 
slowly rather than suddenly or unevenly. Pressures on the ram of 
4,000 to 6,000 pounds per square inch are now in operation, and some 
foreign mills are being built to apply 8,000 pounds to the square inch. 
The duration of the operation varies from 15 minutes to 1 hour, 
depending on whether a large tonnage of beans is being handled with 
a higher content of oil in the cake or a less tonnage with a corre- 
spondingly greater yield of oil per bushel of beans. Typical cage 
presses are illustrated in figures 5 to 10. 
