Improvements in the Method of and Means for Effecting the Artificial Ventilation of Tunnels.
Year: 1891

page_text: Date of Application, 2nd Sept., 1891-Accepted, 3rd Oct., 1891
COMPLETE SPECIFICATION.
Improvements in the Method of and Means for Effecting the
Artificial Ventilation of Tunnels.
A communication from abroad by MARCO SACCARDO, of 24, Via Rozzi, Mantua,
in the Kingdom of Italy, Civil Engineer.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E. of the Agency for
Foreign Patent Solicitors, 6 Lord Street, Liverpool and 6, Bank Street,
Manchester, both in the County of Lancaster and 323 High Holborn in the
County of Middlesex, Civil 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 :--
The artificial ventilation of tunnels which have no air shafts is a question
which has been solved, up to the present, only in certain cases and by very costly
methods.
It has been proposed to produce a current of air by means of a centrifugal
apparatus placed at the mouth of the tunnel, which sucks or blows air, but it has
been found that the use of a partition at the mouth of the tunnel, which that system
entails, is incompatible in most cases with the requirements of the service of the
tunnel.
In order to leave the mouth of the tunnels free, recourse has been had in certain
cases to the expedient of extracting the vitiated air from various intermediate
points in the tunnel by means of special pipes; but, in view of the length and the
large dimensions, which such pipes must have, very considerable expenditure is
incurred therefor.
With the system forming the object of the present invention, the required
ventilation is obtained, on the contrary, with much less expense for fixing and
working whilst the results are equal and even, in certain cases, superior, and the
mouths of the tunnels are always left free.
- This system of ventilation is illustrated on the accompanying sheet of drawings,
the two figures on which show a tunnel being ventilated, by this system, in either
direction.
The object of this invention is to obtain ventilation in any tunnel by means of a
continuous and convergent jet of air, passing from the circumference of the tunnel
and represented by the dotted lines at the letters m n of Figure 1 of the annexed
drawings.
This jet of air, by its active force, produces between its front and back parts a
difference of pressure capable of imparting to the air in the tunnel the necessary
movement for the desired ventilation.
In order to obtain this jet, an air chamber E of annular section (see Figure 1 of
the annexed drawings) is constructed, in which a given quantity of air can be forced
at a given pressure by means of a centrifugal blower or other suitable mechanical
means.
This chamber is formed with an additional converging tube of annular section,
the walls of which are formed by two funnels fg and I m in the shape of a pyramidal
cone or other suitable form. The air, by reason of the pressure which exists in the
chamber, emerging with great rapidity from this additional tube, will produce the
above mentioned jet.
In Figure 1, a b indicate the tunnel, and the arrow indicates the direction of the
current of air in the same.
The external wall f g of the additional tube may be suitably fitted to the cir-
cumference of the interior of the tunnel, which, at the points of the junction may

page_text: assume a different form to its normal one. This fitting is shown in Figure 1 by the
letters g h i.
The form and dimensions, both of the chambers and of the additional tube, must
be determined in each case by the nature of the circumstances, regard being had to
the size and length of the tunnel, as well as the quantity of air necessary for its
ventilatiop.
The apparatus above described may be fitted at the mouth of the tunnel as shown
in Figure 1, or even at any suitable intermediate point. It could also be fixed in a
reversed position, as shown in Figure 2. In this case, the current of air would be
in the opposite direction, as shown by the arrow, and the distributing tube or
conduit, shown in Figure 2, by the letters pq, could be added to the apparatus ;
and the air supplied by the engine T, which generates the jet, could be drawn either
from the exterior or the interior of the tunnel by the tube represented in dotted
lines r, s of Figure 2.
If the tunnel to be ventilated should be of large size, several apparatus could be
employed, arranged in series or in any other suitable manner.
If it be considered desirable, in certain cases, the jet may be dispensed with in
some part of the circumference of the tunnel.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, as communicated to me by
my foreign correspondent, I declare that what I claim is :-
1. The improved method of effecting the artificial ventilation of tunnels con-
sisting in the application, at one or other end or at any intermediate point or points
of the tunnel, and entirely or partially around it, of a continuous and convergent jet
of air for the purposes hereinbefore described.
2. The improved means for effecting the artificial ventilation of tunnels, consisting
in adapting to the tunnel to be ventilated, and at any suitable point or points,
chambers E for the purposes described, the exit walls of which along with the
opposed portion of the tunnel wall are so shaped as to cause a jet of air, for use in
the tunnel, to enter it, the tunnel, in a convergent manner, all arranged substan-
tially as hereinbefore described and shown.
3. In a tunnel constructed as described in Claim 2, slightly narrowing down the
wall of the tunnel, (g hi, Figure 1 or pq Figure 2) adjacent to the entrance (9 m)
for the continuous and convergent jet of air, substantially as hereinbefore described
and shown.
Dated this 1st day of September 1891.
WM. P. THOMPSON & Co.,
Agents for the Applicant.