Improvements in Tunnelling Shields.
Year: 1891

page_text: Date of Application, 23rd Oct., 1891
Complete Specification Left, 23rd Aug. 1892-Accepted, 24th Sept., 1892
PROVISIONAL SPECIFICATION.
Improvements in Tunnelling Shields.
We, GEORGE PEARSON and WESTMAN DICKINSON PEARSON trading under
the style and title of S. Pearson & Son, of No. 10, Victoria Street, Westminster,
in the County of London, Contructors, do hereby declare the nature of this invention
to be as follows:-
This invention relates to improvements in tunnelling shields such as it is necessary
to use in tunnelling through water bearing strata, and its objects are to provide for
the men working in safety in respect of inrush of water, to prevent the lining
becoming displaced before, or during the process of filling up between it and the
tunnel, and to provide for the process of excavating to be carried on by stages in
each of which the work is done vertically. A practical consequence of this invention
is that the operation of tunnelling is reduced in point of fact to one of shaft sinking
under air pressure.
In carrying our invention into effect, the shield itself in respect of its outer
conformation and means for driving it forward is of the same construction as
heretofore. Internally however, it is divided by floors into several compartments
as may be necessary to meet the requirements of the particular job to which the
invention is to be applied.
Each compartment is subdivided by a vertical wall into two sub-compartments,
the front one of which is the working chamber and the back one a safety chamber.
This latter is after the nature of a diving bell as far as the occlusion of the air in
it is concerned, and into it the navvy can retreat before an unmanageable irruption
of water or other substance. Passage through the said wall is by means of any
suitable doorway or opening fixed at a sufficiently low level therein, so that when
the navvy has gained the safety chamber, his head will be in a sufficiently deep
stratum of air to render drowning impossible, for although the air is shut in by the
water, it will readily be understood that the air pressure is strong enough to keep
the water back.
In combination with or in addition to the safety chambers there are provided air
locks upon the opposite or outside of the shield, and suitable communication between
each chamber and its respective lock.
The front of each working chamber is provided with (preferably horizontal)
polling boards or shutters adapted in respect of the configuration of their contiguous
edges and of suitable packings or flexible webs to make a tight closure up against the
front of the shield. Each such board is carried upon the ends of a suitable number
of rams, screws, or other equivalent device, which are or may be supported by the
back of the shield and the wall above mentioned.
A flap of the nature of a moveable wier, is hinged to the top of the top or other
polling board or shutter in such a way that it can be pushed outwards and down-
wards by the navvy so as to give him free access through the excavating opening to
the stuff to be got out and also to act as a water seal. The flexible webs above
mentioned are made of some such material as sail canvas and rubber, or other
material combining toughness, flexibility and impermeability in respect of both air
and water. This web is made fast to the shield-front above the polling board and
suitable devices are provided by which its bottom edge can be rapidly and
properly secured to the top of the polling board below. The web is deep enough
to permit of the hereinafter mentioned travel of the polling boards and the shield
in respect of each other. In addition to the above dam or moveable wier, flaps of

page_text: suitable material are supplied by means of which any polling board can be fastened
to the one next above or below or to any part of the structure of the shield
and these flaps can be of such a length or width that they will allow of consider-
able relative movement between two polling boards or between the shield and any
polling board.
The bottom edge of the lowest polling board in any one compartment may be
made practically water and air tight by rubber flexible flaps or other suitable
device or clay packing.
If necessary these canvas flaps may be kept down by suitable devices of hinged
sliding doors or other device which is kept down by bolts passing through slotted
holes in the same which allow of relative motion. Clay may also take the place of
these canvas flaps which allow of play, or relative movement, kept down in some
similar way against pressure from without.
The bottom edges of the polling boards need only be water tight and not air tight,
as they will be water-sealed by the water in the working chamber.
The outer edges of the boards are packed to the sides of the shield in the following,
or other equivalent way. A chamber or a line of chambers are formed around the
working chamber of a suitable length to meet the requirement of the travel above
mentioned, by means of two angle bars one fixed to the shield and the other to the
polling board. The flange of the angle on the latter, which is next to the shield,
rests and slides upon the angle on the shield, thereby closing in the chamber. This
is filled with clay or puddle and as the said travel begins, it escapes through
suitable openings, but suffers sufficient compression to ensure a tight joint.
When soft quick stuff which is likely to flow through the top or other excavating
opening, has to be dealt with, a supplementary dry polling board is fitted above the
excavating hole, in suitable slides and which can be brought down vertically if
required to cut off or stop the said hole.
A clay smear may also be used at the level say of the second or any lower polling
board. This is to be packed down with flat boards, and will lock the working
chamber at that level with the effect of satisfactorily resisting the pressure of the
water on the unexcavated side of the shield.
The leading edges of the floors, as well as the top leading edge, are provided
with ploughs, which, as they advance readily loosen the stuff immediately beneath
them, seeing that it is more or less undercut. The side edges may also be fitted with
plough edges if the nature of the soil render such a construction desirable. Wood
pollings could easily be slipped in as the work proceeded.
When the navvies are ready for the shield to be moved forward the polling
boards are rammed to and the web packings fastened down. The shield is moved
forward of course leaving the polling boards behind and the work of excavating
proceeds as before.
One way in which the flexible web above mentioned can be advantageously
applied for the purposes of the present invention is as follows:—
A horizontal shelf is pivotted to the bottom edge of the polling board on the
chamber side thereof. The flexible web, of a sufficient width, is made fast by one
edge to the bottom edge of the polling board above. The other edge is made fast
to the top. edge. of the next polling board below, and a butterfly nutted bolt is
pivotted to the said next polling board and engages with the said shelf.
Another portion of this invention relates to packing behind the shield and around
the lining. Accordingly clay or equivalent material is forced out by suitable means
backwards at a greater rate than the shield advances, and as the shield is larger
than the lining, much in the same way that the cap of a telescope is larger than its
tube, the clay is driven evenly round the lining, packing it fairly all round, and
therefore preventing it from dropping or getting out of line from uneven packing,
and a sound packing is also established and maintained between the shield and the
lining.
An automatic air pressure regulator or regulators or reducing valve in connection,
is or may be used with each or any of the compartments in the shield by means of

page_text: which the hydrostatic head will itself control the amount of the air pressure in any
one compartment.
Dated this 23rd day of October 1891.
PHILLIPS & LEIGH,
Agents for the Applicants.
COMPLETE SPECIFICATION.
Improvements in Tunnelling Shields.
We,
GEORGE PEARSON, and WESTMAN DICKINSON PEARSON, trading under the
style and title of S. Pearson and Son, of No. 10, Victoria Street, Westminster, in
the County of London, Contractors, 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 :-
This invention relates to improvements in tunnelling shields such as it is
necessary to use in driving a tunnel through water bearing strata, and its objects
are:-
(a). To provide for the men working in safety in respect of any danger from an
inrush of water;
(b). To provide, by subdividing the shield, for its being adapted to different
pressures at different levels; and
(c). To provide for the process of excavation being carried on by stages in each
of which the work is or may be done vertically.
A practical consequence of the invention is that the work of driving a tunnel is
reduced, in point of fact, to one of shaft sinking under air pressure.
In order that our invention and the best means of carrying it into practice may
be thoroughly understood, we have illustrated the several constructional features in
the accompanying drawings which are to be taken as part of this Specification and
read therewith.
•
Fig. 1 is a sectional half elevation of the shield looking at it from the tunnel. It
is taken on the line 1-1 of Fig. 2.
Fig. 2 is a longitudinal section illustrating the internal construction and arrange-
ment of the shield.
Fig. 3 is an elevation of half the shield from the outside, i.e., from the unitunnelled
side.
Fig. 4 is a sectional plan taken on the line 4-4 of Fig. 1.
The shield itself is, in respect of its outer conformation and also in respect of the
means for driving it forward, of the same construction as heretofore. Internally,
however, it possesses sundry novel features.
a, a are transverse floors. These are fitted at equal distances apart, and so
divide the interior of the shield up into a corresponding number of compartments.
We do not confine ourselves in respect of the number of compartments which we
use but vary it so as to meet the requirements of the particular job for which the
shield is to be made. b, b are a series of hanging curtains in the respective
compartments. The space in the front of each curtain is the working chamber, and
that behind each alternate working chamber, is the safety chamber d for the
respective pair of working chambers c, c'. The navvy in the lower working
chamber of each pair has always, when there is an inrush of water, an air space in
front of the curtain b. A way d' is cut in the floor of the safety chamber above
him for him to climb up through. A suitable doorway e is provided through
which the navvies can escape into the air lock z. This doorway is at a sufficiently
low level to leave head room and a breathing space of sufficient capacity to prevent
his being drowned by the water which latter will be kept back by a volume of air
in the safety chamber the resisting power of which will, of course, exactly equal
the water pressure.
The front of each working chamber is made up with pollings or shutters h.

page_text: These are of any convenient cross section and are carried by a suitable number of
rams k, screws, or other equivalent device. They are supported from behind in
any convenient way. The adjacent edges are provided with suitable packings h¹.
h² are flexible webs made of some such material as sail canvas or rubber, or other
material combining toughness, flexibility and impermeability in respect of both air
and water. Each web is made fast to the adjacent edges of two pollings or in the
case of the bottom polling to the floor a. These webs can be of such a width that
they will allow of considerable relative movement between two pollings or between
the shield and any one polling.
The bottom edge of the lowest polling in any one compartment may be made
practically water and air tight by rubber flexible flaps, or other suitable device, or
by clay. packing.
If necessary, a flap may be kept down by a suitable hinged sliding door, or other
device, which is kept down by bolts passing through slotted holes in the same, so as
to allow of relative motion. Clay may also be used in the place of any of the
flexible packings or flaps.
The bottom edges of the pollings need only be water tight and not air tight, as
they will be water-sealed by the water in the working chamber.
A flap of the nature of a moveable wier, is hinged to the top of the top or other
polling or shutter in such a way that it can be pushed outwards and downwards by
the navvy so as to give him free access through the excavating opening to the stuff
to be got out and also to act as a water seal.
The outer edges of the pollings are packed to the sides of the shield in the
following, or other equivalent way. Chambers are formed around the working
chamber of a suitable length to meet the requirements of the travel above
mentioned, by means of two angle bars, one m fixed to the shield and the other n
to the polling. The flange of the angle on the latter, which is next to the shield,
rests and slides upon the angle on the shield, thereby closing in the chamber. This
is filled with clay or puddle and as the travel begins, it escapes through suitable
openings, but suffers sufficient compression to ensure a tight joint.
When soft quick stuff which is likely to flow through the top or other excavating
opening, has to be dealt with, a supplementary polling is fitted above the excavating
hole, which can be brought down vertically in suitable slides if required to stop the
Baid hole.
A clay smear may also be used at the level say of the second or any lower
polling. This is to be packed down with flat boards, and will lock the working
chamber at that level.
The leading edges of the floors, as well as the edge of the shield are provided
with ploughs p which, as they advance, readily loosen the stuff immediately adjacent
to them. The side edges 9 may also be fitted with plough edges if the nature of
the soil render such a construction desirable.
When the navvies are ready for the shield to be moved forward, the pollings
are rammed too, and the packings fastened down. The shield is moved forward,
of course leaving the pollings behind, and the work of excavating proceeds as
before.
One way in which the flexible web above mentioned can be advantageously
applied for the purposes of the present invention is as follows. A horizontal shelf
is pivotted to the bottom edge of the polling. The flexible web is made fast by one
edge to the bottom edge of the polling. The other edge is made fast to the top
edge of the next polling below, and a butterfly nutted bolt is pivotted to the said
next polling and engages with the said shelf.
Another portion of this invention relates to packing behind the shield and
around the lining. Accordingly, clay or equivalent material is forced out by
suitable means backwards at a greater rate than the shield advances, and as the
shield is larger than the lining much in the same way that the cap of a telescope is
larger than its tube, the clay is driven evenly round the lining, packing it fairly all
round, and therefore preventing it from dropping or getting out of line from

page_text: uneven packing, and a sound packing is also established and maintained between
the shield and the lining.
An automatic air pressure regulator or regulators or reducing valve in connection
is or may be used with each or any of the compartments in the shield by means of
which the hydrostatic head will itself control the amount of the air pressure in any
one compartment. The shield is subdivided vertically into two or more compart-
ments, y, and these two form two air tight chambers into which air can be
delivered at a pressure suitable to the hydrostatic head existing in each of the
compartments of the shield so subdivided.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
1. The combination in a tunnelling shield of tiers of working and safety chambers,
each pair of working and safety chambers being in the same level and provided
with suitable communication, as set forth.
2. The combination in a tunnelling shield of tiers of working and safety chambers.
each pair of working and safety chambers being on the same level and provided
with suitable communication and an air-lock establishing a communication between
the safety chamber and the tunnel, as set forth.
3. The combination in a tunnelling shield of working chambers arranged
above each other, the front of each chamber consisting of pollings, flexible or
extensible packings and closing devices and devices for advancing the pollings, as
set forth.
4. The angle iron packing devices between shield and working chambers, as set
forth.
5. The subdivision of the shield whereby it is adapted to different air pressures.
at different levels, as set forth.
Dated this 23rd day of August 1899
PHILLIPS & LEIGH,
No. 22, Southampton Buildings, Chancery Lane, London, W.C.,
Agents for the Applicants.