Year: 1887

page_text: I, JAMES HENRY GREATHEAD of No. 8 Victoria Chambers, Westminster in the
County of Middlesex, Engineer, do hereby declare the nature of this invention to be
as follows:-
.
In my Specifications No. 5665 of 1884, and No. 5221 of 1886, I have described
means of excavating tunnels and shaffs, employing shields which are forced onwards
as the excavation proceeds.
My present invention relates to appliances to such shields whereby 1 avoid difficulties
attending their application under certain conditions, and facilitate the execution and
direction of the excavation,
When the shield for å tunnel is pushed forward in water bearing or soft material, it
may tend to sink therein and thus to give a direction which is false in level.
To obviate this, I provide within the shield in that part of its length which might
otherwise be filled with water or silt or displaced material several air chambers giving
sufficient buoyancy to prevent the shield from deflecting itself downwards.
Th excavating such material as clay, I place or attach in front of the shield a number
of tapering or wedge shaped spikes or piles, which, as the shield is pushed forwards
penetrate into the material beyond and so far disintegrate it as to facilitate its
removal. In such cases, I prefer to drive a central heading in front of the shield to
give space for the disintegrated material, and instead of driving such heading by hand
digging, I may work from within the shield a central boring. head which excavates a
circular heading in front of the shield. The spikes or piles may in some cases be
worked independently of the shield by hydraulic presses within the shield forcing
them forwards separately or in groups. Some of the hydraulic presses employed in
this manner may be those employed for pushing forward the shield, being arranged
with piston rods passing through the shield and carrying the spikes or piles in front of
it. By substituting for some of the spikes or piles thus worked blocks butting against
the undisturbed material in front, the shield may be forced backwards either entirely
or it may be more at one side than the other so as to vary or correct the direction of
the line of excavation.
Dated this 29th day of September 1887.
:

page_text: COMPLETE SPECIFICATION.
Improvements in Shields Used in Excavating-Tunnels or Shafts.
I, JAMES HENRY GREATHEAD of No. 8 Victoria Chambers, Westminster in the
County of Middlesex, Engineer do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
In my Specifications No. 5665 of 1884 and No. 5221 of 1886 I have described means
of excavating tunnels and shafts, employing shields which are forced onwards as the
excavation proceeds.
My present invention relates to appliances to such shields whereby I avoid difficulties
attending their application under certain conditions, and facilitate the execution and
direction of the excavation.
When a shield for a tunnel is pushed forward in water bearing or soft material, it
may tend to sink therein and thus to give a direction which is false in level.
To obviate this I provide within the shield, in that part of its length which might
otherwise be filled with water or silt or displaced material, several air chambers giving
sufficient buoyancy to prevent the shield from deflecting itself downwards.
Fig. 1 is a longitudinal section of .the front part of the tunnel with the shield S
provided with air chambers A to give it buoyancy. In order to avoid the necessity
of making these chambers strong and air tight they may be filled with light material
such as cork.
I
In excavating such material as clay I place or attach in front of the shield a number
of tapering or wedge shaped spikes or piles, which, as the shield is pushed forwards,
penetrate into the material beyond and so far disintegrate it as to facilitate its removal.
In such cases I prefer to drive a central heading in front of the shield to give space
for the disintegrated material, and, instead of driving such heading by hand digging,
may work from within the shield a central boring head which excavates a circular
heading in front of the shield. The spikes or piles may in some cases. be worked
independently of the shield by hydraulic presses within the shield forcing them
forwards separately or in groups. Some of the hydraulic presses employed in this
manner may be those employed for pushing forward the shield, being arranged with
piston rods passing through the shield and carrying the spikes or piles in front of it.
By substituting for some of the spikes or piles thus worked blocks butting against the
undisturbed material in front, the shield may be forced backwards either entirely or it
may be more at one side than the other so as to vary or correct the direction of the
line-of-excavation.-
-T
Fig. 2 is a front view and Fig. 3 a longitudinal section of the shield S with spikes
or piles P P and Q, and Figs. 4 and 5 are corresponding views of a shield S provided
with a central boring head H. The spikes or piles Q are fixed to the face of the
shield, and, when it is forced forwards, they advance with it penetrating and
breaking down the material in front. The piles P are attached to the plungers
of the hydraulic cylinders C which are employed for advancing the shield, abutting
against the last ring of the lining L. As the shield is advanced the sharp edge E of
the shield cuts its way into the material in front, the piles P being at that time

page_text: stationary: When the plungers are retracted from L so as to admit of a fresh ring
of lining being introduced, the piles P are advanced disintegrating the material in
front of the shield. There may be other piles P¹ worked hydraulically besides those P
which are attached to the advancing plungers.
Having now particularly described and ascertained the nature of this Inven-
tion and in what manner the same is to be performed I declare that what 1
claim is :-
:-
1. In a shield for excavating tunnels or shafts the arrangement of buoyant chambers
to prevent it from sinking in water bearing or soft material, substantially as described.
2. In combination with a shield for excavating tunnels or shafts, spikes or piles
arranged to disintegrate the material in front, substantially as described.
3. In combination with a shield for excavating tunnels or shafts a boring head
arranged to cut a central heading and spikes or piles arranged to disintegrate the
material in front, substantially as described.