Improvements in Cowls or Tops for Chimneys and Ventilating Shafts.
Year: 1892

page_text: Date of Application, 16th Sept., 1892
Complete Specification Left, 29th Apr., 1893-Accepted, 2nd June, 1893
PROVISIONAL SPECIFICATION.
Improvements in Cowls or Tops for Chimneys and Ventilating
Shafts.
I WILLIAM DEARLE of 14 Medburn Street Saint Pancras in the County of
London Mechanical Draughtsman do hereby declare the nature of this invention to
be as follows:-
My invention has for its object to provide an improved cowl or top for chimneys
and ventilating shafts whereby down draughts are prevented and a more perfect
up draught is ensured.
A cowl or chimney top constructed according to my invention consists of two
tubes of any desired section arranged one within the other and of such relative
sizes or diameters as to provide between the said inner and outer tubes a space for
the passage of air. The inner tube is made to communicate at its lower end with
the chimney flue or ventilating shaft and its upper end is provided with a deflector
plate or cover preferably of a conical shape and arranged at a suitable distance
above the end of the tube to provide a passage of sufficient area between it and the
top of the tube to admit of the free escape of smoke gases or air from the chinney
or shaft, and at the same tine prevent rain and down currents of air from entering
the said tube. This inner tube may be of uniform diameter throughout or it may
taper or increase in diameter towards the upper end, or vice versa. I prefer,
however, to make the said tube in the form of two truncated cones connected
together at their smaller ends thereby providing a contraction or throat in the tube
of less area than the area of the top and bottom ends thereof. In the side or
sides of the inner tube a number of openings may be made through which air can
have access to the interior of the tube for the purpose of increasing the up draught
and may be provided with hoods or covers to conduct the air through the said
openings. These openings are preferably made just above the neck or contracted
passage when such is provided in the tube. The outer tube extends from below
these openings to a short distance above the space between the top of the inner
tube and the deflector plate so that down currents of air striking the deflector
plate will be deflected into the outer tube. The lower end of the outer tube may
be opened or closed as desired-in the latter case however openings must be made
at or near the bottom of the said tube for the passage of air and the escape of
water. In applying my invention to an ordinary chimney pot the inner tube may
be fitted onto the said chimney pot or the chimney pot may take the place of the
inner tube, in which case I arrange the deflector plate at a suitable distance above
the top of the pot, which deflector plate may be carried by the outer tube so that
when the said outer tube is placed in position over the chimney pot the deflector
plate will also be in position to deflect rain and down currents of air through or
into the space between the outer tube and the chimney pot. If the chimney pot is not
already provided with openings in the sides thereof 1 make openings therein before
fixing the outer tube in position.
Currents of air entering at the lower end of the outer tube pass out at the top
thereof, a portion of the said air passing into the inner tube or chimney pot through
the openings in the side or sides thereby increasing the up draught in the shaft or
chimney.
Dad his 10th Candomben 1000
WILLIAM DEARLE.

page_text: COMPLETE SPECIFICATION.
Improvements in Cowls or Tops for Chimneys and Ventilating
Shafts.
I WILLIAM DEARLE of 14 Medburn Street, St. Pancras in the County of
London, Mechanical Draughtsman do hereby declare the nature of my invention
and in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement :-
My invention relates to cowls or tops for chimneys and ventilating shafts and
has for its object to prevent down-draughts and improve the up draught therein. A
cowl or top constructed according to my invention consists of the combination of
two tubes arranged one within the other the inner tube being tapered or of conical
form with the larger end uppermost and with an air deflector arranged above the
upper end. Or the inner tube may be in the form of two truncated cones or
pyramids connected together at their small ends and with a deflector preferably of
a conical form arranged at a suitable distance above the upper end to admit of the
free escape of smoke gases or air from the chimney or shaft in communication with
the said inner tube. The outer tube extends from above the space between the
deflector and the top of the inner tube to a considerable distance below the said
space preferably to near the lower end of the said inner tube the outer tube being
of such a diameter as to leave an annular space between the two tubes for the free
passage of smoke and air. Openings may be provided in the side or sides of the
inner tube for the admission of air to the interior thereof to assist the up-draught,
or when the inner tube is in the form of two truncated cones or the like as herein-
before described the small end of the lower cone or the like may project into the
upper cone or the like leaving an annular space between the two cones for the
admission of air to the interior. The deflector arranged above the inner tube should
correspond in size and shape to the open top of the inner tube so that down
draughts of air entering the outer tube will be prevented from entering the inner
tube and caused to pass down through the space between them and out at the
bottom of the outer tube.
Upward currents of air which enter the outer tube at the lower end are directed
by the conical or tapered form of the inner tube against the inner surface of the
outer tube and past the space between the deflector and the upper end of the inner
tube. Owing to the annular space between the tubes being contracted at the top
of the inner tube the air rushing through this contracted space acts after the
manner of an ejector so as to draw the smoke gases or foul air from the chimney or
shaft. When openings are provided in the inner tube as hereinbefore described a
portion of the air which enters at the lower end of the outer tube will pass through
these openings into the inner tube and thereby assist the up-draught which
up-draught is further accelerated by the contraction in the inner tube formed by
the junction of the two truncated cones or the like.
In order that my invention may be well understood I have illustrated on the
accompanying drawing cowls or tops for chimneys or ventilating shafts constructed
according to my invention.
In Figure 1 the inner tube A is of a conical form the large end a being upper-
most the lower and small end 6 of the said tube being connected to a base B by which
the cowl or top may be secured in position on the chimney stack. At a suitable
distance above the upper end of this inner tube is arranged a conical deflector C
which may be connected to the inner tube by struts or their equivalents so as to
leave a space for the free escape of smoke. The outer tube D which may be
cylindrical or of any other suitable form may be connected by struts for the like to
the inner tube so as to leave an annular space 9 between the two tubes A and B
for the free passage of air. The outer tube extends from above the space e between
the top of the inner tube and the deflector C to near the bottom of the inner tube

page_text: 60 that currents of air entering the space 9 at the lower end of the outer tube will
pass upwards and out at the upper end thereof drawing with it the smoke from the
inner tube. Down currents of air which enter the upper end of the outer tube are
prevented by the conical deflector C from entering the inner tube B and caused to
pass down through the space and out at the lower end of the outer tube drawing
with them the smoke from the inner tube. Near the lower end of the inner tube B
openings may be provided through which a portion of the air which enters at the
lower end of the outer tube passes into the inner tube and assists in driving the
smoke upwards thereby increasing the up draught in the chimney.
In the arrangement shewn in Figure 2 the inner tube A is in the form of two
truncated cones connected together at their smaller ends as shewn at i thereby
forming a contraction in the inner tube which accelerates the up draught in the
chimney. By making the inner tube of a conical form with the larger end upper-
most the currents of air which enter the space g at the lower end of the outer tube
are directed against the inner surface of the outer tube past the space e and out at
the top of the outer tube. The space y by being contracted at the upper end of the
inner tube causes the air to act after the manner of an ejector to produce an
up-draught in the inner tube which up-draught may be further accelerated by
admitting air to the inner tube through openings h formed in the lower part of the
upper truncated cone as shewn or in the upper part of the lower truncated cone or
in both the upper and lower truncated cones if desired. Instead of connecting the
two truncated cones together direct as shewn in Figure 2 the smaller end of the
lower truncated cone of the inner tube may enter to a short distance the small end
of the upper cone as shewn in Figure 3 and be connected thereto by struts k or the
like so as to leave a space between the cones for the admission of air to accelerate
the up-draught.
Having now particularly described and ascertained the nature of my inven-
tion and in what manner the same is to be performed I declare that what 1
claim is:-
1st. In a cowl or top for chimneys or ventilating shafts the combination of two
tubes arranged one within the other the inner tube being of conical or tapered form
with the larger end uppermost and having a deflector arranged above the upper end
thereof substantially as herein before described.
2nd. In a cowl or top for chimneys or ventilating shafts the combination of two
tubes arranged one within the other the inner tube being in the form of two
truncated cones or their equivalents connected together at their smaller ends and a
deflector arranged above the upper end of the said inner tube substantially as
hereinbefore described.
3rd. A cowl or top for chimneys or ventilating shafts constructed substantially
as hereinbefore described and illustrated by Figure 1 of the accompanying
drawings.
4th. A cowl or top for chimneys or ventilating shafts constructed substantially
as hereinbefore described and illustrated by Figure 2 of the accompanying
drawings.
5th. A cowl or top for chimneys or ventilating shafts constructed substantially
as hereinbefore described and illustrated by Figure 3 of the accompanying
drawings.
...
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1000
WILLIAM DEARLE.