IMPROVEMENTS IN THE CONSTRUCTION OF CHIMNEY VENTILATING COWLS OR APPLIANCES
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by James White at the Office of the
Commissioners of Patents on the 9th December 1882.
JAMES WHITE, of the City and County of Edinburgh, North-Britain Plumber
and Gasfitter, " IMPROVEMENTS IN THE CONSTRUCTION OF CHIMNEY
VENTILATING COWLS OR APPLIANCES,"
AND
This said Invention has reference to the construction of cowls or ventilators,
which are fitted on the tops of chimneys, or other hollow shafts, pipes, or ducts, for
assisting the upward and outward escape or ventilation of smoke, or other gases or
air therefrom; And which have hitherto been constructed either of the revolving
or stationary class, the former having defects as regards the moving parts getting
out of order as well as obstructing the free escape of the gases when there is not
sufficient air or wind current outside to move them; While the stationary cowls
have usually inside or outside "baffle" plates opposite the outlet openings to deflect
the outward or inward currents, or both, and which also obstruct the free escape
of the exit current of gases when there is no wind or air current outside to assist
their action. While the improvements of this Invention have reference to special
new features in the construction and action of the stationary class of these cowls or
ventilators, which overcome the said defects of these as heretofore constructed, and
make them more efficient in their action in various circumstances, whether acting
as mere protecting and outlet cowls, or as suction inducing or exhaust cowls by the
action of currents of the air or wind outside. These new or improved cowls may .
be made of any ordinary cylindrical, polygonal, or ornamental shape, and with
their top end of a conical or other usual shape, and either closed in or of the same
outlet construction as the sides; and they would preferably be made of sheet-iron
galvanized, or of sheet zinc or other metal; but they may also be made of
earthenware as other stationary cowls are.
And the nature and novelty of the Invention consist in making such cowls with
free but narrow channel outlet openings, preferably narrowest at the outer lip, and
widening inwards, either annularly round the outer case and top, and preferably
diverging upwards; and these openings might be made longitudinally up the sides
and top without baffle plates outside or inside opposite the openings; whereby
these cowls will have a more free and direct eduction or escape of the smoke, gases,

page_text: or air, while acting or exhausting by natural draught alone, when there is no
current of the outer air or wind to assist their discharge.
A further improvement consists in forming the annular or longitudinal broad
bands, ribs or surfaces, of the outer case between the said narrow openings
of V or U, or other indented channel shape, preferably opening or expanding
outwards, with their close apex or surface inwards, so as to cause the outer current
of air or wind (from whatever direction it may come) to impinge direct on or in
these recesses, and be deflected back along their outer sides and surfaces forming
the outlet orifices; and by its force not only prevent the ingress of the outer air
through the narrow opening, but by its lateral action induce, suck, or exhaust the
smoke, gases, or air from the interior of the chimney, or shaft and cowl out through
the said narrow orifices, with an increasing effect proportionate to that of the
force of the air or wind outside and return or reflex current. When these V or
other shaped channels are made annularly round the outer surface, or longitudinally,
they would respectively have radial longitudinal, or horizontal transverse thin
plates, vanes, or ribs, fitted across the sets of channels at some distance apart,
to form pockets, as it were, to prevent the currents of air or wind outside from
running round the annular grooves, or up or down the longitudinal ones, and
effectually insure the return or reflex currents being forced out across the sides of
the channels and the narrow outlet slits or orifices to induce the outward suction
of the smoke or gases from the inside as herein before described. To prevent rain
or snow entering the narrow openings, the upper ends of these, when made annular,
might be made to project sufficiently over the under edge; and when they are
made longitudinally, the thin cross horizontal closing plates might be made to
project sufficiently for the like purpose, as the eaves or projections of the roofs and
slates of a house are for preventing the rain entering. And further, an annular
gutter may be formed all round the lower inside of these cowls below the close
apex or angles of the sides of the narrow outlet orifices and inner surface of the
channels to receive any water or moisture falling from these; And a hole or tube
would be formed or led through to the outside, to allow of the escape of the water
from the gutter.
Instead of the reflex surfaces of the cowl being formed of channel shapes as
described, they might be made cellular or of polygonal forms, as honey-combs for
example, with close conoidal bottoms, which would also form the narrow tapered
channels between them for the egress of the smoke and air or gases to be withdrawn
or exhausted from the chimney or shaft.