IMPROVEMENTS IN ROCK TUNNELLING AND SHAFT SINKING, AND IN MACHINERY TO BE USED FOR THESE PURPOSES
Year: 1875

page_text: PROVISIONAL SPECIFICATION left by Herbert Newton Penrice at the
Office of the Commissioners of Patents, with his Petition, on the
26th August 1875.
I, HERBERT NEWTON PENRICE, of Hatfield, in the County of Herts,.
do hereby declare the nature of the said Invention for "IMPROVEMENTS IN
ROCK TUNNELLING AND SHAFT SINKING, AND IN MACHINERY TO BE USED FOR THESE
PURPOSES," to be as follows:-
This Invention has for its object the formation of tunnels and shafts.
more quickly than heretofore practicable. This I effect partly by the
manner in which I form a tunnel, and by obviating the necessity of
blasting, and partly by so constructing the boring machinery that a
greater amount of power may be employed to effect the boring relatively
to the size of the bore. Heretofore it has been proposed to form tunnels
by cutting an annular groove, and then breaking down and removing
the central core.
The machinery which I employ operates in this manner: In order
to ensure the ample power requisite for rapid progress I construct the
cylinder or cylinders used for giving motion to the cutting head of a

page_text: diameter nearly equal to the bore cut by the apparatus, and in order
to-be enabled-to-carry-back-the-material-which is removed I continuously
enlarge the upper part of the bore just in rear of the cutting apparatus
as the work progresses. This enlargement of the bore is readily effected
when once a leading bore of small diameter has been formed in the
rock. By proceeding in this manner the materials cut away can be
conveyed back over the top of the machine, which is protected by a
shielu or cover. The lower part of the leading bore is always preserved
as the bottom, so that the machine can be moved to and fro along it in
a straight line.
The enlargement of the tunnel is effected by boring holes at intervals
at the sides and above the leading bore, and by dislodging the material
by means of wedges driven into these holes. When the annular groove
has been cut for a distance into the rock the machine is drawn back,
wedges are then introduced, and are driven in by means of a reciprocating
ram forming part of the boring machine or otherwise. When the
material has been removed the machine is again moved forward to
continue its work. It will be seen that by constructing a bore or tunnel
in the manner above described, a very small proportion only of the
material to be removed has to be pulverized and that the bulk of the
material can be removed in comparatively large pieces by which the
amount of work required to cut a bore or tunnel is greatly reduced.
-
The apparatus I employ for cutting the leading bore is constructed as
follows: The cutters for cutting the annular groove act percussively
and travel slowly around the groove. The cutters consist of a series of
chisels set close together in the form of a cylinder except that two spaces
are left one on either side for the escape of debris and for the passage
of tubes for conveying water to wash out the annular groove and cool
the tools. The chisels are held by wedges in a massive cutter head, and
the wedges are locked by right and left hand nuts, over which again a
keep is slidden. The edges of the chisels are placed circumferentially,
and so as to chase two separate grooves closer together, from between
which the rock flakes away as the work progresses; then the quantity of
rock which has actually to be pulverized in forming the bore is reduced
to a minimum.
The autton holden on hand

page_text: piston rod or ram which passes back through two or more cylinders,
and carries pistons to work in each cylinder.
The forward end of one of these cylinders is kept constantly in com-
munication with the supply of compressed air by which the engine is
worked. The forward ends of the other cylinders are open and the back
ends of all the cylinders are alternately opened to the compressed air
supply and to the exhaust by a valve or valves worked by a separate
engine at the rear end of the machine. By this means the cutter head
is moved to and fro with short quick strokes, and any desired amount of
power can be applied to it according to the number of cylinders
employed. In rear of the last cylinder the ram passes through an
internal toothed wheel, by means of which a slow revolving motion is
given to it.
In rear of this wheel is a small engine worked by compressed
air. The crank shaft of this engine is at right angles to the ram, and
has upon it a worm gearing into a worm wheel upon a strong shaft,
which at its hinder end can be clutched to the end of a long screw
which passes backwards from the rear end of the machine, and by which
the machine is when required moved rapidly forwards or backwards.
The shaft at its forward end carries a pinion to drive an intermediate
shaft, from which motion is transmitted to the internal toothed wheel
before mentioned, which is to give the slow revolving motion to the ram.
The small engine at the rear end of the machine also gives a to-and-fro
motion to a slide valve, by which compressed air is alternately admitted
to and allowed to escape from the back ends of all the cylinders used
for giving the to-and-fro motion to the ram. This slide valve is con-
structed in such a manner that the cutter head is caused to make two
strokes upon the work for each revolution of the engine. The same
engine also gives the slow forward feed to the apparatus whilst the rock
is being cut by means of pawls driving a ratchet wheel which is mounted
on the screw. The screw passes through a nut which is firmly fixed in
rear of the machine.