IMPROVEMENTS IN THE CONSTRUCTION OF SMOKE PREVENTING FURNACES FOR BAKER'S OVENS
Year: 1884

page_text: I FREDERICK SMITH of Lambeth in the County of Surrey, Builder, do hereby
declare the nature of said invention for "IMPROVEMENTS IN THE CONSTRUCTION
OF SMOKE PREVENTING FURNACES FOR BAKER'S OVENS " to be as follows:-
The objects of this invention are to prevent smoke arising from furnaces con-
nected with baker's ovens which smoke is especially evolved when fresh fuel is
added, also to promote the more even combustion of the fuel than heretofore,
likewise to equalize the heat of the bottom and to keep the oven cleaner,
For this purpose I construct the furnace with a hanging bridge arrangement
provided with two separate inlets or sets of inlets one being for air and smoke or
gases combined and the other for atmospheric air only and so arranged that the
front admission of air takes place from an aperture or apertures through the
ordinary inner fire door-then passing over the fuel and over the top part of
the front hanging bridge whence it is conducted by the draught of the oven
through an aperture or slot or slots down on to the hottest part of the fire, thus on
its way commingling with the gases arising from the fuel such mixture passing
down on the fire at or near the ordinary bridge or butting lump, which latter
I prefer to make slightly higher than usual at the inner part and to slope towards
the front, for the purpose of retaining the fuel ashes and cinders within the furnace,
away from the interior and thus keeping the oven cleaner.
By the smoke or gas and the air being drawn over the top of first bridge I cause
the fire to burn more fiercely nearer the fire door than if the above arrangement did
not exist and thereby promote the more even combustion of fuel along the whole
length of firebars.
.
At a place a little in advance of the first opening and more towards the interior
of the oven I provide the aforesaid second hanging bridge with an aperture or
apertures for contributing an additional and separate supply of air to the furnace.
This air supply is by preference heated but is separately admitted at the front of
the furnace at the top of the outside frame or from the ashpit.
In order to heat this air as much as possible I provide one or more flues, built in
the brickwork or consisting of pipes which passing under the fire lump on one side
of the furnace are continued a little distance under the oven bottom at the hottest
part thereof and then return under the other side lump ascending from thence to
CD077

page_text: the space formed between the inner and the outer furnace frames or other con-
venient place and then over the covering of the furnace or by side of same and
descending through the second hanging bridge aperture on to the fire in the
furnace.
By this arrangement of air flue or flues under the hottest part of the oven
bottom I also attain the advantage of reducing the temperature of the oven bottom
in this part thus allowing the bread and other goods to be perfectly baked without
being charred.
In order to give greater facility for the admission of an extra quantity of air to
the furnace at such times when owing to the charging with fresh fuel or when a
greater quantity of tar vapour is liberated therefrom, I provide the outer door with
a projecting part or damper which normally when the door is closed partly covers
the opening of the aforesaid flue or flues leading from the front of the furnace at
the top of the outside frame or front of furnace to the air apertures nearest the
interior of the oven but which, when the outer door is opened fully exposes or
uncovers the aforesaid flue or flues.
The stoker if necessary may thus when he has put on a fresh charge of coals
re-open the outer fire-door and after a short interval close it.

page_text: I, FREDERICK SMITH of Lambeth in the County of Surrey Builder do hereby
declare the nature of said invention for "IMPROVEMENTS IN THE CONSTRUCTION
OF SMOKE PREVENTING FURNACES FOR BAKERS' OVENS" and in what manner the
same is to be performed to be particularly described and ascertained in and by
the following statement :-
The objects of this Invention are to prevent smoke arising from furnaces con-
nected with bakers' ovens which smoke is especially evolved when fresh fuel is
added, also to promote the more even combustion of the fuel than heretofore,
likewise to equalize the heat of the bottom and to keep the oven cleaner.
Figure 1 of the accompanying drawings is a vertical longitudinal section through
a bakers' oven constructed according to my invention and Figure 2 a plan section
of same on line X X Figures 3 and 4 are corresponding views of a modification,
and Figures 5 and 6 corresponding views of yet another modification.
For the purposes of my invention I construct the furnace A with a hanging
bridge arrangement provided with two separate inlets or sets of inlets one being
for air and smoke or gases combined and the other for atmospheric air only.
B, Figures 1 to 6 is the fire grate C the ordinary inner fire door and D the outer
fire door. The aforesaid two separate air admissions are so arranged that the front
admission of air takes place from an aperture or apertures E through the bottom
plate of the door frame, and then through one or more openings F in the ordinary
inner fire door then passing over the fuel and over the top part of the front
hanging bridge G as shown by the arrows whence it is conducted by the draught
of the oven through an aperture or slot or slots H down on to the hottest part of
the fire, thus on its way commingling with the gases arising from the fuel such
mixture passing down on the fire at or near the ordinary bridge or butting lump I
which latter I prefer to make slightly higher than usual at the inner part and to
slope towards the front as shown in Figures 1, 3 and 5 for the purpose of retaining
the fuel, ashes and cinders within the furnace, away from the interior of the oven K
and thus keeping the oven cleaner.
By the smoke or gas and the air being drawn over the top of first bridge G
I cause the fire to burn more fiercely nearer the fire door C than if the above
arrangement did not exist and thereby promote the more even combustion of fuel
along the whole length of fire bars B.
At a place a little in advance of the first bridge G and more towards the interior
of the oven K I provide the aforesaid second hanging bridge L with an aperture or
apertures L for contributing an additional and separate supply of air to the
furnace. This air supply is by preference heated but is separately admitted at the
front of the furnace at the top of the outside frame or from the ashpit.
In order to heat this air as much as possible I provide one or more flues, built in
the brickwork or consisting of pipes which passing under the firelump on one side
of the furnace are continued a little distance under the oven bottom at the bottest
part thereof and then return under the other side lump ascending from thence to
the space formed between the inner and the outer furnace frames or other con-
venient place and then over the covering of the furnace or by side of same and
descending through the second hanging bridge aperture onto the fire in the
furnace.
In Figures 1 and 2 this air supply enters by the opening M at one side of the
ashpit passes by the flue N under one side lump continues under the oven bottom
tiles K' and in a circuitous manner as shown at N' returns by the flue O under the

page_text: other side lump, rises by the flue P along the side of the furnace, enters the flue Q
over the top of the furnace, and finally descends in a heated condition through the
slot L' in the second hanging bridge L..
By this arrangement of air flue or flues N¹ under the hottest part of the oven
bottom K¹ I also attain the advantage of reducing the temperature of the oven
bottom in this part thus allowing the bread and other goods to be perfectly baked
without being charred.
In order to give greater facility for the admission of an extra quantity of air to
the furnace at such times when owing to the charging with fresh fuel or when a
greater quantity of tar vapour is liberated therefrom I provide a damper R at the
inlet M which may then be opened fully or more fully..
In Figures 3 and 4 I have shown a modified arrangement of air supply for the
bridge L. I provide the outer door D with a projecting part or damper R which
normally when the door is closed partly covers the opening to the aforesaid flue M
and flues. N N O P and Q leading from the front of the furnace at the top of the
outside frame or front of furnace under one side lump, under the oven bottom
under the other side lump rising to top of furnace and then descending to the air
apertures L¹ nearest the interior of, the oven K but which, when the outer door D
is opened fully exposes or uncovers the aforesaid flue or flues M.
The stoker if necessary may thus when he has put on a fresh charge of coals
re-open the outer firedoor and after a short interval close it.
In Figures 5 and 6 I have shown a modified arrangement of flues, and so as to
utilize the great heat imparted to the bridge G, which may be of cast iron in all
cases but which in this modification by being cast hollow is utilized as a f
L
flue.
The air admitted by the damper R as in Figures 1 and 2 (or by a damper or
flap R on the outer door D as in Figures 3 and 4) passes in this case by, the fiue, N
under one side lump, then by the flues N' under the oven bottom returns under
back part of the other side lump by the flue O, rises by the flue P, passes, through
the hollow bridge G, 'up and along the flue Q and then into the end of hanging
bridge L and down through the slot L' in the said hanging bridge L.
Having now particularly decribed 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
First In furnaces for bakers' ovens the double air admission to the furnace
gases by means of apertures in connection with hanging bridges at or near the back
end of furnace.
Second: The mode and means for heating air admitted at or near the back end
of a bakers' oven furnace that is to say by abstracting heat from the oven bottom
near the furnace.
Third: The construction and arrangement, of the hanging bridges and air inlet
passages, dampers, and flues as shown and described.
Dated this Kifteenth day of December 1884.