Improvements in Chimney Pots and the like.
Year: 1898

page_text: Improvements in Chimney Pots and the like.
I, JOSEPII WILLIAM THOMAS, F.I.C., F.C.S., of No. 2, Hampstead Hill Man-
sions, London. N.W., Consulting Sanitary Chemist, do hereby declare the nature
of this invention to be as follows:
The present invention relates to certain improvements in chimney pots and
the like, and the object of it is to provide means whereby to equalise
or balance
the atmospheric pressure at the orifice of the chimney when it is reduced by
the wind blowing over it. It does not aim at either assisting or increasing the
natural up-draught, but, on the contrary, its intention is to prevent or check the
excessive updraught produced by the aspiration of the wind, and the consequent
descent of smoke into the room beneath the chimney when the gust of wind
ceases and the tension on the air is released.
According to my invention, the aspiration of the wind upon the orifice of the
flue is checked in two ways, each specially suited according to the situation of
the stack upon which the chimney pot is to serve; but either method may be
adopted and used upon stacks in all situations with marked improvement over
those at present in use.
When the pot is for a stack in the teeth of the wind, so to speak, the top por-
tion is perforated and provided with two or more lateral wings, which may be
also perforated or not and so arranged that the wind instead of aspirating air
out of the perforations as it blows along the sides, forces it through them, and
thus increases the quantity of air getting into the pot to supply the extra volume
aspirated by the wind at the orifice of the pot, and so prevent excessive smoke
suction. When the wind blows against the said perforations in the top of the
pot, air passes through them into the pot and so furnishes the excess of volume
required by the aspiration of the wind over and above the usual quantity of
smoke which issues from the chimney, and consequently equalises or balances
the pressure at the orifice of the flue immediately below the perforations.
The modification in the above construction of chimney pot which I prefer
to employ for stacks in a more screened situation has for its object to make the
wind aspirate air and smoke and draw them together through the same
orifice. It is constructed as follows:
Over and around a central pipe which might correspond with an ordinary
round chimney pot both with regard to its position on the stack as well as its
form, is placed a kind of box or outer casing leaving a clear space all round
between the central pipe and the said box and also an opening at its base on
each side and at its top. These bottom openings are to admit the air into the
said box and to permit of its escape through the top of the pot, so that in prac-

page_text: tice a constant draught is created.
When the wind blows over the top of the
pot it sucks air out as well as smoke, and its aspirating effects upon the smoke
in the pipe are not great as it can get plenty of air to suck up through the
bottom openings in the side of the box or spaces left between the bottom of
the outer casing and the pot proper within.
The pots are made so as to form a complete chimney stack head or crown
and for this purpose are made in one or more pieces which are held together
with bolts and nuts or other like well-known clamping device, and preferably
with a layer of cement between.
The above is a description of my invention in its simplest forms and serves
to illustrate the principle upon which my chimney pot is constructed, but in
actual practice this construction may be somewhat more complicated. For
instance, the pot instead of being merely perforated at the top may be composed
of alternate plates ornamental or otherwise, standing on end and placed at right
angles to each other; the transverse fronts or wing plates having two or more
orifices on each side, for the express purpose of checking the main force of the
wind as it sweeps and aspirates along the sides of the stack whilst at the same
time allowing much air to get through into the space between the divisions. The
longitudinal plates are also perforated and the two sets of plates together con-
stitute one chimney pot.
In the second modification the front plates or wings are constructed as just
above described, but the side plates have an opening or space on each side at
the bottom to correspond with those above referred to when describing the box-
like outer casing.
The perforated wings of the division* or front plates may be made of alu-
minium or other metal and bolted to the clay or longitudinal divisions which are
to be made narrower for the purpose.
The pots can be made of clay which after burning is white, yellow, red or
any other colour; they can also be made of aluminium or any other metal or
substance and painted, galvanised, or enamelled.
Dated the 5th day of September 1898.
PHILLIPS & LEIGH,
Agents for the Applicant.
Improvements in Chimney Pots and the like.
I, JOSEPII WILLIAM THOMAS, F.I.C., F.C.S., of No. 2, Hampstead Hill Man-
sions, London N.W., Consulting Sanitary Chemist, do hereby declare the nature
of this invention and in what manner the same is to be performed, to be parti-
cularly described and ascertained in and by the following statement:-
The present invention relates to certain improvements in chimney-pots and
the like, and the object of it is, primarily, to prevent, or rather, entirely do
away with, what are popularly called "smoky" chimneys; and the object in
view in the peculiar design or construction and position of my chimney-pot or
the like is to prevent the wind from acting inductively, by aspiration or blowing
over and across the upper orifice or extremity of the chimney flue, upon the
column of hot gases and smoke in and issuing from the said flue.
I have discovered that the present theory that a smoky chimney, that is
to say, one out of the lower end of which the smoke is expelled at intervals into
the room beneath, is due to the pressure of the wind blowing down the chimney,
'65
"

page_text: is incorrect in the main particular, and that, on the contrary, a
smoky chim-
ney is caused primarily not by down-draught, but by back-pressure resulting
from the sudden relaxation or stoppage of an excessive up-draught.
Even with an ordinary plain chimney-pot an excessive up-draught is caused
by reason of the wind aspirating or blowing over and across the top or orifice
of the pot, and thus, by induction, drawing along with it the hot gases and
smoke issuing from the chimney-pot or top of the flue and consequently putting
a high tension on the column of hot gases and smoke in the chimney, causing
it (the said column) to ascend at a much greater velocity than it would do
without such assistance from the wind.
The high tension is not confined to the gases and smoke in the chimney; it
is communicated to the whole body of air in the room beneath when the doors
and windows are closed, and the result is that not only is there a greater velocity
in the gases and smoke ascending the chimney caused by the aspiration of the
wind over the orifice, but the whole volume of gases and smoke in the chimney
and of the air in the room is rarified and expanded by the induction of the
wind.
This being so, it follows that any variation in the rate of motion of the wind
across the top of the chimney-pot puts a greater or less tension on the column
of gases and smoke and accelerates or diminishes the velocity of the up-draught
through the chimney accordingly, and consequently when a gust of wind ceases,
the tension on the column in the chimney and upon the air in the room below,"
due to wind aspiration, is suddenly released, the result being a sudden back-
pressure to allow the expanded gases and air to contract again and the conse-*
quent expulsion of smoke out of the chimney into the room beneath.
*
"
Up to the present time, owing undoubtedly to the above-mentioned mistaken
idea regarding the cause of a smoky chimney, all attempts at remedying it have
been directed towards inducing and maintaining an increased up-draught.
Having discovered the real cause of a smoky chimney, my present inven-
tion does not aim at either assisting or increasing the natural up-draught or
the velocity of the column of gases and smoke ascending the chimney, because
these questions can only be satisfactorily determined by the form of grate used
and by the provision made for inlet air in the room beneath, and are not ques-
It is not the
tions which can be solved by chimney pots of reasonable height.
natural draught which is the general cause of smoky chimneys, but the effects
of wind upon that draught. My invention, therefore, differs from other chimney
pots in not seeking to cure a smoky chimney, but to prevent a smoky chimney
being formed. It aims at removing the cause so that the effect may cease, and
as the wind aspirating upon or above the orifice of the chimney pot is the cause,
as above stated, my invention is designed to protect the end of the flue, proper,
and shield it from the induction or suction power of the wind. The meaning
of the phrase "the flue proper" in this specification is, invariably, the extremity
of the short chimney pot inside or under the special box.
I stated in my Provisional Specification, that I sought to prevent the wind
aspirating across the orifice of the flue, in two ways, or rather, by two different
designs of chimney-pot, one however being merely a modification of the other
to suit the situation of the stack upon which the chimney-pot is to serve. I
have, however, since found that the form of pot I designed specially for screened
situations
teeth " of the wind, and even superior
equally serviceable in the
I have therefore con-
in this respect to the form I intended for that purpose.
fined this Complete Specification and claims to the one form of pot only.
"
The following is a description of my invention, reference being had to the
accompanying drawings illustrating the same, and in which:-
Figure 1 is a side elevation of the upper portion of a chimney stack with
four of my chimney-pots bolted together in position upon it.
Figure 2 is a plan of Figure 1.
Figure 3 is an end clevation of Figure 1.

page_text: Figure 4 is a vertical section of the chimney-pot taken on the line 4-4 01
Figure 3.
Figure 5 is a sectional plan taken on the line 55 of Figure 4.
Figure 6 is a vertical section through one of the chimney-pots taken on the
line 66 of Figure 1.
Figure 7 is an end elevation of one of the chimney-pots as in Figures 1 and 3
with a modified form of side wings.
Figure 8 is a sectional end elevation of the upper portion of a chimney stack
fitted with my chimney pot as modified to suit back-to-back flues.
Figure 9 is a side elevation of Figure 8.
Figure 10 is a plan of Figure 9, and
Figure 11 is a sectional end elevation of my chimney-pot fitted with a further
modification of wings.
Throughout the following description and drawings similar reference letters
denote the same parts: Over and around a central pipe a which might corre-
spond to an ordinary chimney-pot, both with regard to its position on the stack
as well as its form, but which is preferably made shorter than usual, is placed
a kind of box or outer casing B, leaving a clear space all around between the
said central pipe a and the said box B. Thus the upper end of the chimney
flue terminates in the short pot a and this pot is surrounded by a box-like
casing B either of which may be square, round or of any other configuration or
form. This casing B has an opening at its base on each side, is open at the
top c, and is made of such height as to extend above the top a¹ of the flue a
as shewn. This box or casing B serves to protect the chimney or flue top a
from the aspirating action of the wind, which is of course constantly playing
over and around the top orifice e of the said casing B in all directions, but which,
it will be seen, cannot touch or gain access to the orifice a' of the flue a, because
the latter is situated some distance below the top of the surrounding box or
outer casing B. When, therefore, the wind blows over and around the top
of the box B, it aspirates there as powerfully as it would upon an ordinary
chimney-pot, but the openings b in the base of the said box B admitting large
volumes of air from the external atmosphere into the space d enclosed by the
said box B around and above the short inner pot a which latter forms the
termination of the flue, thus supply the extra volume required to satisfy the
inductive action of the wind blowing over the top of the box so that it does
not require to draw upon the supply from the flue as usual. So long as the
wind aspirating over the top of the chimney-pot can get plenty of air from the
orifice over which it blows to satisfy its inductive action, it is quite immaterial
where that supply of air comes from, and as I provide, as above explained, an
amply sufficient supply for it to draw upon quite independently of the ordinary
supply from the chimney flue, consequently the aspiration of the air over
the chimney-pot only acts on this auxiliary supply and does not require to
draw upon the natural supply, that is, the column of gases and smoke in and
issuing from the top of the flue, and this latter supply not being acted on or
disturbed in any way, no increase in the natural up-draught is brought about
and consequently the pressure of the atmosphere at the orifice of the chimney
is equalised or balanced, as desired.
It will be understood that when the wind blows over the top of the box it
sucks or draws the air out of the box, which is constantly entering it through
the openings b as well as the smoke issuing in the ordinary course of its upward
movement out of the flue a, and its aspirating effects upon the smoke in the
short pot a are almost if not quite nil, as it can get plenty of air through the
openings 6 in the base or sides of my box-like chimney-pot to act on.
The openings to admit air into the pot B will differ in size and number
according to the situation of the pot and the size of the flue. For example, for
a stack with only one flue there may be perforations or openings for air on all
four sides. When the pot is for a large flue adjoining others in a single row,

page_text: there will be openings on either side of the pot, front and back, but as the short
inner pot a may be square or rectangular, there may be no space all around it,
but only on two sides where the openings are; hence the pot will be made wider
between the openings and the inner pot to give increased air space, as shown
in plan (Figure 5) where b, b, are the openings into the box B, the air space,
and a the rectangular short pot.
When two rows of pots are upon a stack, the pots are fixed back-to-back,
as shewn in Figures 8, 9, & 10, hence there can be only one opening or grating
in each pot and that in the front, and the area of this as well as of the air space
is increased. A series of pots for a double-row stack is shown in plan Figure 10
where 6 is the one opening into the pot B, d is the air space, and the pot a which
may advantageously be rectangular.
It should be noted that the said openings are purposely situated below the
orifice of the flue proper, and in no case lead into its interior. This I have
thought it advisable to point out as although special chimney-pots have been
constructed with one or more holes, passages or openings in them below the
orifice of the flue, these chimney-pots themselves have always constituted the
upper extremity of, and consequently become part-and-parcel of the flue, which
is just what mine is not. Moreover in my chimney-pot the lower portion of
the box B is not designed merely as a support to carry a cap for the purpose of
shielding the end of the flue from the action of the wind, but, is also so con-
structed as to prevent the wind aspirating underneath. The wind aspirates on
either side and underneath the openings of the cone-capped or louvre chimney-
pots, whilst the box-like construction of mine is intended to prevent such a
mistake.
It should be observed also that although plenty of fresh air is continually
being drawn into the space d and out again over the orifice a¹ of the flue a, it
nevertheless can never aspirate horizontally immediately over or across the said
flue orifice as the back wall of the pot stops its progress in a horizontal direc-
tion and deflects it upwards, and the space being of comparatively large size
holds sufficient air to provide a continual supply to satisfy the requirements of
the external air aspirating over the top of the pot B without appreciably lessen-
ing the amount always in the pot B over the flue orifice a¹, consequently the air
in the immediate vicinity of this orifice is not disturbed by the current of air
continually rushing in at the openings to maintain a constant supply in d.
There is no cap, valve or opening into the chimney or flue proper because this
ends in the short pot a surrounded by the box B, as above stated, and the open-
ings 6 in the bottom of the said box B are shielded from lateral wind aspiration
by wings e which are either bolted on to the front of the box, as shewn in
Figures 1, 2, 10, or else fixed between the pots when a number of them are
used upon one stack.
The box B would have no opening on the side next another chimney and the
pots are made wide enough to touch each other on a stack. and a number of
pots so fixed with a thin layer of cement between, each pot being bolted to the
next, will form a solid and rigid chimney-stack head or crown as shewn.
The above is a description of my invention in its simplest forms and serves
to illustrate the novel principle upon which my chimney-pot is constructed,
but in actual practice this construction may be somewhat modified or more
complicated to suit the size and shape of the stack upon which it is to serve..
For instance the pot instead of being single may be composed of any number
of plates ornamental or otherwise standing on end or vertically, and placed at
right angles to each other alternately, the transverse fronts or wing-plates hav-
ing their orifices on each side for the express purpose of checking the main force
of the wind as it sweeps and aspirates along the sides of the stack, whilst at
the same time allowing much air to get through into the space between the
divisions. The longitudinal plates are or may be also perforated as shewn ;
the two sets of plates together constituting one chimney-pot.

page_text: The closing of the box B all round excepting the openings b; is not only for
the purpose of giving strength and solidity to the structure, but it is also designed..
to obviate a very common mistake in other pots. In many houses, and especially
in flats, one or more of the chimneys acts as an inlet (bedroom chimneys gener-
ally), and when pots having openings in their sides such as the cone-capped or
louvre type, are fixed near each other upon a stack, the slightest movement of
the wind causes the smoke to pass to the next pot, and, if this acts as an inlet;
the smoke descends. My invention prevents this back-suction of smoke by sup-
plying air instead through the openings b.
An advantage of this pot is that it so steadies the column of smoke in the
chimney that the pot is almost as useful for chimneys which do not smoke. as
it is for those which do, because the atmosphere in the room below will not be
in constant motion under heavy and gusty winds; and, furthermore, what I
deem to be most important is, that ventilators can be fixed near the ceiling in
chimneys having this pot; and will be free from the up and down movements
which have caused such useful appliances to be so generally discarded.
A valuable feature is that the end of the chimney proper is protected from any.
downward movement of the wind as the force would be expended. chiefly in
driving air and smoke through the openings in the box B and the column of
smoke in the chimney would be practically unaffected.
The special characteristics of this chimney-pot are that the upper end of the
flue terminates inside the box or outer casing B, and that there are no openings
or valves whatever in the flue itself or into the pot which terminates the flue,
to cause irregular currents in the chimney.
The wings e which may be either perforated or solid, are provided to prevent
side aspiration by the wind. They may be made of clay, metal, or any other
suitable substance.
The pots can be made of clay which after burning, is white, yellow, red or
any other colour; they can also be made of aluminium, or any other suitable
metal or substance and painted, galvanized, or enamelled as desired.
The small inner pot a may be made either separate from or integral with the
outer box-like casing B.
Having now particularly described and ascertained the nature of my said in-
vention, and in what manner the same is to be performed, I declare that what
I claim is:
1. A chimney-pot or the like consisting of an outer pot or casing within
which at the bottom thereof is a much smaller pot, connected internally to the
outer one by means of webs or partitions, both said pots having parallel sides
and internal diameters unvarying throughout and the said outer pot having
one or more apertures in one or more of its sides at a level below that of the
top of the said inner pot but the latter having no lateral inlet holes or apertures,
substantially as and for the purposes described and shown.
2. The combination with a chimney-pot or the like consisting of an outer pot
or casing within which at the bottom thereof is a much smaller pot connected
internally to the outer pot by means of two webs or partitions, both said pots
having parallel sides and internal diameters unvarying throughout, and the
said outer pot having one or more apertures in one or more of its sides at a
level below that of the top of the said inner pot the latter having no lateral
inlet holes or, apertures, of lateral wings or plates perforated or unperforated pro-
jecting from the external surface of the outer pot, substantially as described
and shown.
3. The combination with the upper end of a chimney of a chimney-pot or
the like consisting of an outer pot or casing within which at the bottom thereof
is a much smaller pot, connected internally to the outer pot by means of two
webs or partitions, both said pots having parallel sides and internal diameter
unvarying throughout and the said outer pot having one or more apertures ir

page_text: one or more of its sides at a level below that of the top of the said inner pot,
the latter having no lateral inlet holes or apertures, of lateral wings or plates
perforated or unperforated projecting from the external surface of the outer pot,
substantially as described and shown.
D1
L
1 1
e
1
1000
PHILLIPS & LEIGH,
22, Southampton Buildings, Chancery Lane, W.C.,
Agents for the Applicant.