IMPROVEMENTS IN CHIMNEY COWLS AND VENTILATORS
Year: 1883

page_text: LETTERS PATENT to Frederick Leslie of 66 Hamilton Terrace in the County
of Middlesex Member of the Institute of Civil Engineers for an Invention
of "IMPROVEMENTS IN CHIMNEY COWLS AND VENTILATORS
"
PROVISIONAL SPECIFICATION left by the said Frederick Leslie at the
Office of the Commissioners of Patents on the 23rd November 1883.
FREDERICK LESLIE of 66 Hamilton Terrace in the County of Middlesex,
Member of the Institute of Civil Engineers "IMPROVEMENTS IN CHIMNEY COWLS
AND VENTILATORS
"
This invention has for its object improvements in chimney cowls and ventilators.
My improved chimney cowl consists of a flue pipe having at its upper end a
series of truncated conical shells mounted one above the other. The lowest cone
is fixed as a collar around the top of the flue pipe and the other cones which are
similar are supported from the first one over the other and parallel to it by four
equidistant radial partitions.
Level with the top of the uppermost cone an annular metal plate is fixed; the
opening in the centre of this plate is somewhat larger than that at the upper end
of the uppermost truncated cone so that a space about half an inch wide is left all
round between these parts. Finally a few inches over the top of the upper cone
and parallel to the annular plate there is another horizontal plate or disc which if
desired may have a domed top to throw off the rain.
The wind blowing against the parallel cone arrangement above described causes
currents of air to be directed upwards and outward between the horizontal plates
at the top and these currents carry with them the smoke ascending by the flue
pipe.
The radial partitions between the cones add much to the efficiency of the arrange-
iment by concentrating the blast arising from the pressure of the wind on the
windward side and directing it over the top of the flue pipe.
A like arrangement may be employed as a ventilator.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Frederick Leslie in the Patent Office on the 22nd May 1884.
FREDERICK LESLIE of 66 Hamilton Terrace in the County of Middlesex
Member of the Institute of Civil Engineers "IMPROVEMENTS IN CHIMNEY COWLS
AND VENTILATORS
"
This Invention has for its object improvements in chimney cowls and ventilators.
My improved chimney cowl consists of a flue pipe having at its upper end a
series of truncated conical shells mounted one above the other. The lowest cone
is fixed as a collar around the top of the flue pipe and the other cones which are
similar are supported from the first one over the other and parallel to it by four
equidistant radial partitions. Level with the top of the uppermost cone an annular
inetal plate is fixed; the opening in the centre of this plate is somewhat larger
than that at the upper end of the uppermost truncated cone so that a space about
half an inch wide is left all round between these parts. Finally a few inches over
the top of the upper cone and parallel to the annular plate there is another
horizontal plate or disc which if desired may have a domed top to throw off the
rain.
The wind blowing against the parallel cone arrangement above described causes
currents of air to be directed upwards and outward between the horizontal plates
at the top and these currents carry with them the smoke ascending by the flue
pipe.
The radial partitions between the cowls add much to the efficiency of the arrange-
ment by concentrating the blast arising from the pressure of the wind on the
windward side and directing it over the top of the flue pipe to the leeward side.
A like arrangement may be employed as a ventilator.
In order that my said invention may be most fully understood and readily carried
into effect I will proceed to describe the Drawings hereunto annexed.
Figure 1 is a side elevation and
Figure 2 is a vertical section of a chimney cowl constructed according to my
invention the same is applicable also for use as a ventilator.
A is a pipe by which the smoke or heated air to be delivered is caused to
ascend.
B'. B². B³. B. are a series of parallel conical shells supported above the upper end
of the pipe A by four radial partitions C. C. C. C. These partitions also serve as
brackets to carry the annular metal plate D; this plate is fixed upon the tops of
the brackets C.
E is another plate parallel to D and supported above it by the stems F. F. F. F.
G is a conical cover fixed upon the plate E and serving simply to prevent the
lodgment of water and dirt upon the top of it.
The course for the smoke or heated air is up the interior of the pipe A and out
between the plates D-and E. It is aided in its escape by wind currents entering
between the conical shells B¹ B2 B3 B' and also between the uppermost cone B' and
the plate D. The cones are so proportioned and arranged that the currents, of air
entering between B¹ B2 pass upwards clear of and over the edge of the cone B on
the opposite side and out between the plates D and E. The parts are also so
proportioned that the current ascending between the uppermost cones B³ and B
will strike the plate E at a point exterior to the circular area on the face of the
plate E which directly faces the tube A.

page_text: As one half of the cowl acts on the windward side and the other half of it on
the leeward side, I make the total open space at the top of the circumference of the
cowl which is between and divided by the truncated quadrated cones of twice
the area, of the area of the tube A.
For the same reason the distance between the plates D and E should be such as
to allow a similar exit area.
As the relative proportions of the parts is a matter of importance although
nevertheless they admit of some variation, I give below a table of the sizes which
I prefer to adopt in cowls and ventilators for pipes of various sizes from two inches
up to nine inches these being the sizes ordinarily used.
The information here given will suffice to enable the workman to construct cowla
or ventilators of any sizes.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is:-The construction of chimney cowls and ventilators substantially as
herein described.
In witness whereof I the said Frederick Leslie have hereunto set my hand and
seal this sixteenth day of May in the year of our Lord One thousand eight hundred
and eighty four.
FREDK LESLIE (L.S.)