Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to an improvement in the present
machines for the mechanical tunnel boring, and particularly in
those machines which by a single tool, called a cutter head,
bore the entire cross-sectional area of the tunnel, and wherein the
head revolves about an axis coincident with that of the tunnel.
Up to now, the possibility of satisfactory use of said
machines is restricted to the grounds,the boring front of which,
is self-supporting.
According to this invention a device is disclosed which
is capable of being applied to rotary cutter heads either
already constructed, or to be constructed, thereby allowing such
machines to be used also where the boring front consists of an
entirely or partially not self-supporting ground.
As is known to persons skilled in the art, the cutter
heads of the existing machines are provided with tools of various
kinds. For soft rocks said tools consist generally of cutters
having various shapes; for hard rocks the tools are generally
discs idly mounted on the cutter head, and rotating about axes
located according to the radii of the head itself. Each disc
is provided with one or more rings made of very strong and hard
material, with sharp edged corners, or with embedded buttons of
hard material.
The tools of the cutters for soft rocks will scrape the
front and bore into it by an action like that of a "ripper",
or of a lathe or planing tool.
The tools for hard rocks operate by concentrating on
the rock, through the sharp cornered ring, or the buttons, a
heavy concentrated load breaEing the over-loaded zone by internal
stress.
In both cases, namely for the soft rocks and for the
hard rocks, in stable and uniform conditions of the ground, the
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excavated material consists of elements the rnaximum sizes of
which are about 2 x 8 x 15 cms for the hard rocks, while said
sizes increase for the soft rocks up to lS x 20 x 30 cms, and
sometimes also more.
The distance measured along the axis of rotation from
the boring surface to the surface of the tool-carrying structure
has always a remarkable value, also for constructive requirements,
and any way sensibly greater than that of the greatest element
produced by the boring operation.
The excavated material can fall between the tool support,
namely the rotary cutter head, and the tunnel face, and is
collected by a set of shovels, with which the head is provided,
and is carried by these shovels on a continuous conveyor belt,
carrying said material behind the cutter head.
By an arrangement of this kind, in various applications,
drawbacks set out hereafter frequently have been noted in all
types of cutter heads used up to-day.
When the boring front is unstable, and collapses, partial-
ly or entirely, both in the cutter head for soft rocks and in
those for hard rock, the material which moves away from the
front invades the space between said boring front and the cutter
head thereby increasing the resistance against rotation up to
a possible jamming thereof.
In other cases, the volume of the product of the boring
operation is greater than the volume corresponding to the
for~ard movement and to the bored section, so that recesses will
be generated, with the risk of collapsing and setting of the
ground. In these cases, it is compulsory to stop the operation
of the cutter head and either it will be necessary to carry
out reinforcing works, or it will be required to progress before
the cutter head with conventional systems, until the diffi~ulties
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will be overcome.
Another very frequent drawback, which occur8 for
instance in cracked rocks or in rocks including alternated
layers of soft rocks and hard rocks, is the breakaway from the
front, also under the action of the cutter heads themselves,
of blocks having such dimensions that the pick-up shovels
cannot take said materials and/or the predisposed means
cannot remove said mined materials.
Thereby damages will occur to the tools, their supports,
and/or to the conveying and removing means, with the
consequent discontinuances of work for the manual removal of
the blocks or the repair of the damages.
This invention is intended to minimize these drawbacks
reducing as much as possible their occurrence.
According to this invention a grid is mounted on the
cutter head parallel to the theoretical boring surface, and is
provided with a plurality of void spaces from which slightly
project the crushing tools or cutting elements, said void
spaces having a size corresponding to the "optimum" sizes of
the fragments of mined material.
Thus according to the present invention there is
provided a tunneling machine cutterhead of the rotary type
which in use is advanced in a direction coincident with its
axis of rotation and which comprises forwardly directed cutters
having cutting portions for cutting concentric kerfs in the
tunnel face, and passageways through which excavated material
passes, characterized in that said cutterhead includes a rigid
forward grid structure thereon having a forward face which is
substantially parallel to the theoretical tunnel face, and said
30 cutters are mounted on the cutterhead rear~ardly of said grid
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structure, with the cutting portions thereof projecting
slightly forwardly of the forward face of the grid structure
so as to penetrate into the cutter face, said grid structure
comprising a plurality of radially spaced apart concentric
breasting rings with gauge openings defined radially between
them corresponding to the optimum dimension of fragments of
excavated material, and positioned such that all excavated
material must pass through a said gauge opening before
entering a said passageway.
According to a preferred embodiment of the present
invention said grid consists of a plurality of annular bands,
concentric with the axis of rotation of the cutter head and
so radially spaced apart from one another as to allow the
passage therethrough of excavated material, the size of which
is less than a predetermined value. Also, the axial distance
of said bands from the body of the cutter head is related to
said predetermined value.
This invention will now be described with reference ~-
to the attached drawings, showing by way of non-limitative
example one preferred embodiment of the invention itself.
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In the drawings:
Figure 1 is a front elevation view of a boring cutter
head, having a spoke structure, and equipped with the device
according to this invention;
Figure 2 is a cross-sectional view taken along the
line II-II of Figure l;
Figure 3 located in the same sheet as Figure 1 is a
cross-sectional view taken along the line III-III of Figure
1:
Figures 4 and 5 located in the same sheet as Figure
2 show details of a variant of the cutter head of Figure 1,
in partial elevation, and in cross-sectional view taken along
the line V-V of Figure 4, respectively;
Figure 6 is a view similar to Figure 1, showing this
invention when applied to a closed type cutter head;
Figure 7 is a cross-sectional view taken along the
line VII-VII of Figure 6;
Figure 8 located on the same sheet as Figure 6, is
a cross-sectional view taken along the plane VIII-VIII of
Figure 6, in an enlarged scale; and :
Figure 9 located on the same sheet as Figure 7,
shows a cross-sectional view taken along the plane IX-IX
of Figure 8.
With reference to Figures 1 to 3, the numeral 1 denotes
the spokes of an "open" type cutter head. The spokes 1 have
a box-like structure, and each of them is provided with a
set of fork-like supports 2 carrying crushing or cutting
rollers or discs 3, idly mounted on said supports, and
rotatable about axes radially located with respect to the cutter
head.
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Said cutter head rotates as shown by the arrow F in
Figure l, and is connected to the internal stationary structure
4 by means of the rolling bearings 5.
The material coming from the boring face 10 is taken
by the radial shovels 6 inclined towards said face 10 and by
the curvilinear peripheral chutes 7 carried by said shovels
and is conveyed, as shown by the arrows of Figure 2, into the
hopper 8, which is a part of the stationary structure down-
stream of the cutter head. At the bottom of the hopper 8,
a belt conveyor 9 carries the mined material out of the tunnel.
This invention provides for a grid consisting of a
concentric set of metal annular rings ll, having an adequate
thickness, subdivided into sectors, welded or fixed to the
ends of the radial shovels 6 and to the supports 12 of Figure
2. As it is clearly shown in this Figure, the position of
the grid 11 with respect to the base of the cutter head is
such that only the cutting discs 3 will project from the grid
itself. In correspondence with the peripheral zone of the
cutter head, the annular band 11 is shaped as shown in 13 in
order to protect the peripheral zone when the outer discs 14
operate.
In Figures 4 and 5 where like numerals indicate the
same parts already described and indicated with these numerals,
the grid according to this invention is applied to one cutter
head for soft rocks provided with the pairs of cutters 15
instead of the crushing discs.
One or more sectors of the grid 11 can be removable in
order to allow the passage of the persons, and of the spare
parts which must pass through the cutter head, as well as for
allowing the periodical inspections to the tunneling front 10.
By way of example, Figures l and 3 show a system consisting
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of two sets of slots 16 into which is inserted a pair of locking
pins.
Figures 6 to 9 show the grid according to this invention
as applied to a "closed" type cutter head, consisting of a
part spherical member 17 provided with a crown of shovels 18
and 19 for conveying upwards the mined material, which is then
discharged on the previously described conveyor 9.
In this case, as no radial shovel exists, the annular
elements 11 of the grid are fixed to the shield 17 by pairs
of supports 20, as clearly shown in Figure 8.
For both described solutions, the mutual position
between the grid 11 and the tool 3 must be such that the
projection S (Figure 8) of the tools or discs 3 from the grid
will be the minimum, taking account of the limits as follows:
namely, the limit for which the efficiency of the machine is
still normal when operating~ion a stable and uniform front
where the previous cited drawbacks do not occur, and the limit
of the minor dimension of the biggest element as produced by
the boring operation in normal conditions, (stable, non-blocky
front).
The dimension of the clear part of the passage between
the bands 11 of the grid, as radially measured, must not be
greater than the maximum dimension of the element which can
pass in the conveying means, and must not be such as to hinder
the passage of the mined material in normal situation.
Downstream of the bands 11 of the grid, large passages
Sl must be arranged for the material which passes directly
through the grid, and/or for the material which will be loaded
by the shovels mounted on the cutter head.
By the above described grid device, when the entire
front of tunneling or part thereof tends to collapse, it will be
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supported by the annular bands 11 of the grid, while the tools
projecting therefrom will cause the crushing of the bigger
pieces and the passage of the little pieces. The amount of
the material passing through the grid will be limited, reducing
the risk of the passage of a volume greater than that corr~s-
ponding to the advancement of the machine.
Likewise, if breakaway blocks having large dimensions
are created during the boring operation, said blocks are held
in place by the bars of the grid until the tools will gradually
reduce said blocks to such dimensions as to allow their passage
through the grid.
As it is evidently shown in Figures 1, ~ and 7, the grid
according to thiS invention serves the shielding function also
in respect of the collecting members (buckets) for the mined
material, where said members operate directly in correspondence
with the tunneling front.
