Engineering Wonders of the World
Volume I
Forfatter: Archibald Williams
År: 1945
Serie: Engineering Wonders of the World
Forlag: Thomas Nelson and Sons
Sted: London, Edinburgh, Dublin and New York
Sider: 456
UDK: 600 eng - gl.
Volume I with 520 Illustrations, Maps and Diagrams
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240
ENGINEERING WONDERS OF THE WORLD.
iron heads, which thrust against a circular
timber rib placed between them and the
flanges of the last-placed ring of iron lining.
The function of this rib is to distribute the
thrust of the rams over the ring, and act as a
stop to prevent the grout from pouring out
into the shield when the annular space between
the ground and the exterior of the last ring
of tunnel is being filled.
The “ front end ” of the shield, against
which the cylindrical castings containing the
rams abut, is formed of a stout casting made
in four segments, and has an external diameter
The
Cutting-
Edge.
shield when
from within
slightly larger than that of the rest of the
shield.
This casting is splayed to receive the cutting
edge, which consists of steel plates one inch
thick, forming a continuous
conical ring. The plates are
splayed at the front end. so as
to form a sharp edge, and can
be extended to cut wide of the
driving round curves.
The skin of the shield extends
a few inches of the cutting edge, to which it
is secured by set pins, to the tail of the shield.
(To be continued.)
ANOTHER VIEW OF A STATION SHIELD. (Photo, F. Milner.)
Note the ends of the 5|-inch hydraulic jacks, e e, pressing on tunnel ring.