Improvements in or connected with Furnaces employing Forced Draught.
Year: 1891

page_text: Date of Application, 27th Nov., 1891-Accepted, 2nd Jan., 1892
COMPLETE SPECIFICATION.
Improvements in or connected with Furnaces employing Forced
Draught.
We, JAMES JONES MELDRUM, and THOMAS FREDERICK MELDRUM, of
Atlantic Works, City Road, Manchester, Engineers, and WILLIAM THOMSON,
of Langlands Road, Govan, in the County of Lanark, Engineer, do hereby declare
the nature of this invention and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
Our invention has reference, mainly, to furnaces of steam generators and like or
analogous furnaces in connection with which forced draught is employed, and it has
mainly for its object to construct or provide means in connection with the furnaces,
whereby they can be worked, that is, fired, with greater effect and efficiency at all
times, and more particularly at such times as the fires are cleaned, and when the
door is of necessity opened.
To these ends, we provide a certain construction of the ashpit or means therein
whereby when say one half or portion of a grate is being cleaned and the bars more
or less bared, an efficient draught or passage of air takes place through the fuel on
the other half or portion of the grate, and also the air supply may be regulated
differentially to the different sides of the grate when the fuel thereon is in different
stages of combustion, such, for instance, as when on one side green fuel exists and
on the other coke only.
In the application of our invention to cases wherein a pressure in the ashpit is
greater than that of the atmosphere, that is to say in cases wherein a "plus-
pressure" is enployed in the ashpit, we effect the ends sought by our invention by
forming the ashpit or the space beneath the bars, into two separate chambers, that
is, in connection with each grate, we provide two ashpits and a separate supply of
air to each of said ashpits, said air supply being effected by steam jet blowers, fans,
or other suitable means.
In the drawings which serve to illustrate our invention, we shew its application
to some different examples of steam generators, namely, one to a Cornish type, two
of an externally fired egg-ended steam generator, and a fourth to a water tube
steam generator, the air being forced into the ashpit by steam jet blowers.
In these examples,
Figure 1 is a sectional elevation of the Cornish type, and Figure 2 is an end view
of same with part of the plate enclosing the ashpits broken away.
Figure 3 is a sectional elevation, and Figure 4 an end view, of one of the
externally fired steam generators provided with our improvements.
Figure 5 is an end view of the water tube steam generator with a portion of the
front broken away.
Figure 6 is a longitudinal section and Figure 7 is an end view of the other egg-
ended steam generator above referred to.
In all of these arrangements and applications, one steam jet blower (two in one
case) is provided in connection with each separate ashpit, and such blowers are, in
every case, disposed horizontally and mainly within said ashpit, but this arrange-
ment is not essential.
Referring now to the drawings, X is the shell of the steam generator; a' a² are
the two separate ashpits in each case, and a³ the partition separating said ashpits;
b', 6 are the blowers for the ashpits a¹ and a², respectively; c are the firebars
forming the grate; d is the furnace space or combustion space above the grate;
e is or are the fire door or doors, as the case may be; f¹f are the steam pipes
having each a regulating cock thereon; h is the plate or plates as the case may
be, enclosing the ashpits a a², and in and by which the blowers are fixed and

page_text: supported; iis or are the door or doors by which access to the ashpits a' and a² is
had, for any desired purpose; c¹ are the bearers which support the firebars c. In
operating according to this invention, in some cases, it is preferred to use such a
pressure in the ashpits as will cause the pressure above the grate to be about equal
to that of the atmosphere, so that when the door e is open, the flames will not
blow out. When the grate is cleaned, say at one side, the operations are as
follows: The steam supply to the blower supplying air to the ashpit under that
side of the grate to be cleaned is cut off by the cock f³ on its steam pipe, whilst
supply of steam and air to the other ashpit is continued and the pressure in this
ashpit remains unaffected by the condition of things in the other ashpit and the
fuel on the firebars over it will be burnt at practically the same rate as when no
cleaning is going on. Thus it is seen that the working of one part of the grate is
unaffected by the action of bareing the firebars being cleaned, and the cessation of
the supply of air into the other ashpit below them. Hence a continuous generation
of steam will take place, under all circumstances, in a steam generator thus con-
structed, and an improved efficiency thereby obtained. Moreover, by the use of
this invention when using bituminous fuel and employing forced draught, the
fireman can always bare one portion of the fire, on which carbon only exists,
while in the other there may exist fresh coal which is distilling, and by suitable
adjustment of the air supply, the discharge of black smoke may be prevented.
The division plate or partition a³ in some cases merely consists of a vertical
diaphragm or plate held at its upper part by the bars, and at the front end between
webs .
In the example shewn in Figure 1 and 2, this division plate or partition consists
of an ordinary plate held as just described; and in this case one ashpit door, only,
common to the two ashpits a' a², is provided. However, to separate ashpit doors,
that is, one for each ashpit, may be provided on the plate h, if desired.
In the arrangements shewn in Figures 3 and 4, and 6 and 7, the partition a³ is
shewn as a brick wall, the front end of which lies between the webs or flanges /',
and at the top where the joint or connection is made with the grate, special
inverted shaped bars c² are provided the horizontal part of such bars being deep
enough to prevent the ashes which lodge on them, reaching the firebars.
In the example illustrated in Figure 5, the furnace is shewn provided with two
furnace doors e, the partition a³ being a brick one as that specified with reference
to Figures 3 and 4, and the upper part of the partition consisting of the T shaped
bars c². In this steam generator two steam-jet blowers are provided for each
ashpit, as shewn, and two sets of steam pipes f, f, with steam regulating cocks f³,
feed said blowers with steam.
The above description sets forth our invention as applied to the furnaces of
steam generators, but it is not confined to such applications, since it may, obviously,
be applied to other heating furnaces. It is also susceptible of various modifications
as regards the particular form and construction of parts, and therefore is in no way
confined to the particular constructions set forth with reference to and shewn in
the drawings.
Having now particularly described and ascertained the nature of this inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is :-
1. The herein described improvement connected with furnaces, that is to say,
effecting the combustion of the fuel in furnaces by providing two or more separate
air supplies and introducing such air supplies, at a pressure greater than that of
the atmosphere, into separate duplex or multiplex ashpits below a grate, the space
above which is continuous or common to said ashpits; for the purposes specified.
2. In or in connection with a furnace, two or more closed ashpits; a grate above
said ashpits, common to said two or more ashpits; and suitable means for separately
supplying air to and maintaining it under pressure in each of said ashpits;
combined and adapted to operate substantially as and for the purposes set forth.

page_text: 3. In a steam generator or other furnace, the herein described construction or
arrangement thereof, namely, the construction or arrangement wherein the ashpit
is divided, forming two or more separate ashpits, and one or more steam jet blowers
are employed in connection with each of said ashpits and adapted to deliver air
into each of said ashpits; substantially as and for the purposes set forth.
4. In a furnace wherein a divided ashpit is employed, the construction and
employment of bars (such as c²) forming part of the partition dividing said ashpit;
substantially as and for the purposes set forth.
5. The arrangement and construction of furnace comprising the grate, partition,
and blowers, set forth with reference to and shewn in Figures I aud 2; Figures 3
and 4, and 6 and 7; and Figure 5, respectively.
Dated the 26th day of November 1891.
CHEESBROUGH & ROYSTON, Fels. Chart. Inst. P.A.,
15, Water Street, Liverpool, Applicants' Patent Agents.