IMPROVEMENTS IN TUNNELLING MACHINERY
Year: 1875

page_text: (This Invention received Provisional Protection only.)
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PROVISIONAL SPECIFICATION left by Edward Alfred Cowper at the
Office of the Commissioners of Patents, with his Petition, on
the 16th September 1875..
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I, EDWARD ALFRED COWPER, of No. 6, Great George Street, West-
minster, in the County of Middlesex, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN TUNNELLING MACHINERY," to be
as follows:-
31
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My Invention relates to machinery worked by compressed' air for
excavating' tunnels and cuttings in chalk, rock, or other materials. I
arrange the machinery to act in a manner similar to that described in
the Specification of a Patent granted to me on the 20th June 1871;
No. 1612, that is to say, to cut away portions of the face of the materials
or form chases therein,' the material left between those chases being
afterwards removed. I place the cutting tools closely together in groups
on an arm or arms of a head revolving continuously or reciprocally on a
central axis, the said arm or arms being so arranged: as always to leave'
the greater part of the face of the work accessible.

page_text: The cutting tool consists of a number of chisels or wedges actuated
each by its own piston for the purpose of cutting the chases and wedging
or breaking down the intermediate ridges of material, either by striking
such ridges on their faces or by wedging them off by causing the chisels
or wedges to enter the mouths of the chases. In order to make the
momentum-of-the-piston rod act more directly on the tool, I prefer to
employ for the outer row of tools a peculiar form-of-air-cylinder, in
which the piston rod is placed near to the outer side, the cylinder or
working chamber itself being formed of a flat or oval section or of a
rectangular shape, so that it may take up as little room as possible.
I make the axis of the machine hollow, with passages in it for the
supply of the compressed air to the several cylinders, and for the
discharge of the air after having don its work, as also for the supply of
water to the tools. In order to avoid the necessity for any mechanical
communication for actuating. slides or valves for the cylinders I prefer
to use cylinders of the kind which do not require separate slides or valves
for the admission and exit of the working fluid, but in which the pistons
themselves effect the required alternations in a well known manner.
The rock cutting machines or cylinders are capable of being easily
withdrawn separately or slid into holes provided for them in the head in
which they truly fit, and wherein they are at once fastened by nuts or
otherwise; the connection for the supply of the compressed air being
made complete at the same time by means of india-rubber rings.
"
Some of the cylinders may be set so that their chisels act obliquely
cither in cutting the chases or in knocking down the intermediate ridges.
_I.employ a centrifugal, helical, or rotary pump for lifting the water used
on the tools and throwing it up-for-use-over again.
In order that-the-head-and-the-carriage on which it is mounted may
be advanced uniformly and parallel, I employ three or more screws and
nuts made to act against fixed points in the tunnel or cutting, such
screws being driven by a separate air engine from that which drives the
head, so that the advance may be regulated as required. In cases where
the tunnel is not intended to be of a circular section, but is required to
be of some section varying from a circle, as for instance with a flat
"invert" at the bottom the parts beyond the circular outline are cut

page_text: I arrange immediately behind the cutting head one or more elevators
or dredgers by which the material is raised from the floor of the cutting
and delivered into trucks for its removal.
In cases where the tunnel is of such size as to admit of one or more
upper floors, the material falling on such floors may be carried backwards
to the trucks by means of travelling webs or scrapers.