An Improvement in Tunnelling Apparatus.
Year: 1889

page_text: Date of Application, 4th Jan., 1889
Complete Specification Left, 4th Oct., 1889-Accepted. 9th Nov., 1889
PROVISIONAL SPECIFICATION.
An Improvement in Tunnelling Apparatus.
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 driving a cylindrical or nearly cylindrical tunnel provided with a shield which
is advanced from time to time as the boring proceeds, it is of advantage in sand,
gravel or similar soils, especially if they are water bearing, to displace the material
in front of the shield in a gradual and regular manner, so as to prevent the falling
in of loose material in such a way as to form cavities and disturb the superincumbent
material. Also, in such cases,
it is generally necessary to have within the shield an
air lock supplied with compressed air so as to prevent inflow of water from the.
material outside, and it is of advantage to present a little space as possible in front
of the shield for escape of air;
According to my present invention I mount in bearings in the shield a revolving.
shaft which carries in front of it blades inclined helically to the plane of rotation
each blade overlapping the next blade in order, so that there is only a narrow space
between each pair of blades for passage of excavated material inwards or for passage
of air outwards.
By causing these blades to revolve slowly as the shield advances, proportioning
their speed to the advance of the shield, the material in front, instead of being dis-
lodged in irregular masses leaving cavities, is gradually scooped out, the place of
the detached material being always filled by the advancing blades. In some cases
there may be a single helical blade presenting only one cutting edge overlapping its
leaving edge, or there may be two or more helical blades each presenting a cutting
edge overlapping the leaving edge of the next in order in front of it. The cutting
edges may either be straight or they may be serrated or provided with spikes or
rakes, according to the character of the material operated on.
In some cases, where the boring is of considerable diameter, there may be two or
more sets of blades on concentric shafts arranged to advance either simultaneously
or successively.
When the inner sets of blades are advanced beyond the outer sets, they should
be within cylindrical casings to prevent the falling in of material laterally. And
for the same reason the outer circumference of the blades should not extend beyond.
the front edge of the shield or of a lip projecting in front of the shield.
Dated this dib day of January 1889
ABEL & IMRAY;
Agents for the Applicant.
COMPLETE SPECIFICATION.
An Improvement in Tunnelling Apparatus.
1, 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 driving a cylindrical or nearly cylindrical tunnel provided with a shield which
is advanced from time to time as the boring proceeds, it is of advantage in sand,
gravel or similar soils, especially if they are water bearing, to displace the material
in front of the shield in a gradual and regular manner, so as to prevent the falling
Paine

page_text: .
in of loose material in such a way as to form cavities, and disturb the superincum-
bent material. Also, in such cases, it is generally necessary to have within the
shield an air lock supplied with compressed air so as to prevent inflow of water from
the material outside, and it is of advantage to present as little space as possible in
front of the shield for escape of air.
According to my present invention I mount in bearings in the shield a revolving
shaft which carries in front of it blades inclined helically to the plane of rotation
each blade overlapping the next blade in order, so that there is only a narrow space
between each pair of blades for passage of excavated material inwards, or for passage
of air outwards.
By causing these blades to revolve slowly as the shield advances, proportioning
their speed to the advance of the shield, the material in front, instead of being dis-
lodged in irregular masses leaving cavities, is gradually scooped out, the place of
the detached material being always filled by the advancing blades. In some cases
there may be a single helical blade presenting only one cutting edge, overlapping its
leaving edge, or there may be two or more helical blades each presenting a cutting
edge overlapping the leaving edge of the next in order in front of it. The cutting
edges may either be straight or they may be serrated or provided with spikes or
rakes, according to the character of the material operated on.
In some cases where the boring is of considerable diameter, there may be two
or more sets of blades on concentric shafts arranged to advance either simultaneously
or successively.
When the inner sets of blades are advanced beyond the outer sets, they should
be within cylindrical casings to prevent the falling in of material laterally. And
for the same reason the outer circumference of the blades should not extend
beyond the front edge of the shield or of a lip projecting in front of the shield.
Fig. 1 of the accompanying drawings is a longitudinal section shewing the front
part of a tunnel with a revolving head according to my invention. Fig. 2 is a
front view of such a head having two semicircular blades, and Fig. 3 is a section to
an enlarged scale on the line X X of Fig. 2.
A is part of the metallic lining of the tunnel, over the front part of which the
shield B loosely fits, so that, as material is excavated in front of the shield, it is from
time to time pressed forwards by hydraulic presses C. So far the construction and
operation of the apparatus are well understood and are practised. In the front part
of the shield I mount in bearings in a cross girder Da shaft E, which may be
tubular, and on this I fix two or more blades F F which are helically inclined so
that the edge of the one is a little in advance of the edge of the other, as shewn
in Fig. 3, and that these edges somewhat overlap each other, leaving only a narrow
space between them. One of these segments, nainely that in front is provided with
a cutting edge G, which as the head is made to revolve cuts the material in front
of it, the material thus excavated finding its way through the narrow space between
the edges of the blades into the interior of the shield whence it is removed through
the completed part of the tunnel. The shield with cutting head as above described
may be used in combination with the known means of removing the excavated
material by water as shewn by Fig. 4. In this case, the head revolves in a space
in front of the shield which is parted off from the hinder part of the shield by a
partition H.
Through this partition pass two pipes K and L, the one K admitting water under
pressure to the front compartment of the shield, and the other L conveying away the
water along with the excavated material.
Although I have shewn the cutting head as being made with two semicircular
blades FF, there might be only one such blade extending quite round the circle of
the head, or there. might be a greater number of blades each a sector of the circle,
the width of the blades being in all cases such that the front edge somewhat over-
laps the hinder edge. The cutting head may in some cases be of less diameter
than, the shield, the annular space left round it being covered by a coned mouth.

page_text: 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 I
claim is :-
In the shield of tunnelling apparatus a revolving head having blades helically
inclined with overlapping edges at a small distance apart, substantially as and for
the purpose set forth.
ABEL & IMRAY,
Agents for the Applicant.