Improvements in Fire-grates.
Year: 1892

page_text: Date of Application. 5th Jan., 1892-Accepted, 27th Feb., 1892
Improvements in Fire-grates.
A communication from ERNST JOSEPH KÖSTER, of Harkorten, near Haspe,
Westphalia, in the Empire of Germany.
I, ALFRED JULIUS BOULT of 323 High Holborn in the County of Middlesex,
M.I.M.E., 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 :-
The object of this invention is the better to utilize fuel in heating apparatus by
the employment of a grate offering the following advantages,
(1) A grate may at any time be readily cleaned as, owing to its peculiar arrange-
ment, no slag can adhere to it, but only solidifies as soon as it comes into contact
with the cooled surfaces of the grate.
(2) Hot air may be conducted under the grate and the direction of the flames
may be reversed so that the flame may enter and pass through the spaces between
the bars which it could not be made to do in grates as hitherto used.
(3) Thicker layers of fuel may be employed which enables not only a minimum
excess of blast or draught but also inferior qualities of fuel to be made serviceable.
(4) The step-like arrangement of the grate renders it exceedingly useful where
small coal, apt to produce much slag has to be employed, and
(5) The surface of this grate may be comparatively smaller than that of other
grates as owing to the bright flame it enables constantly to be kept up the heating
power is considerably increased.
Up to the present time fire-grates arranged for internal cooling where it was
important to retain the characteristic form of the bars in section have always been
cast, and in consequence rather wide bars have been produced and the open spaces
between them diminished in proportion.
The whole of the old arrangements moreover were somewhat heavy and the bars
were only interchangeable with difficulty. Where wrought iron was employed
ordinary cylindrical tubes were generally employed which shape is altogether
unsuited for the accomplishment of the essential object of the grate as it necessarily
narrows to a considerable extent the open spaces while at the same time offering
In the manufacture of
but an unsatisfactory supporting surface for the fuel.
the improved fire-grate herein described wrought iron or steel is preferably
employed.
As shown in Figs. 1, 2, 3 and 4 of the accompanying drawings the bars d' of the
grate are hollow and so wrought or forged as to have terminal trunnions fitting
suitable bearings in the cross pieces a a', nuts d being preferably used to secure
them in position therein. Or the trunnions of the bars may be unprovided with
any screw-threads the preferable arrangement being to have the two external or
outermost bars screw-threaded and fitted into nuts and the remaining bars made
plain two screw-nuts being sufficient to ensure the necessary tightness and firmness
of the whole grate.
In cases where the exchange or replacement of the bars is
known beforehand to be superfluous the terminal trunnions may be tapered and
driven or wedged into the transverse carriers whereby of course the grate will be
rendered still more rigid and secure.
The cooling liquid enters at b and fills the hollow space or chamber a up to the
wall or partition c, from thence through openings provided in the trunnions or ends
of the bars as shown in Figs. 2, 3 and 4 it passes into the bars themselves. After
thus filling the whole of the hollow cross piece a¹ it passes through the remaining
grate-bars into the other compartment of a whereupon it preferably issues from the
grate at b¹ though it may be discharged at any convenient point of the sides of the

page_text: transverse pipe or chamber a if more than one partition c is provided in it or if no
partitions at all are used.
In their central parts the bars assume the shape in section shown in Fig. 5 while
at the ends forming the trunnions they are considerably contracted and present a
different shape in section. The wider space situated on a lower level than the bars
of the trunnions in the centre facilitates the circulation of the cooling liquid
which is thereby enabled to flow more rapidly and to be heated to a higher
degree than it is in the trunnions and in the transverse pipes. Besides, the wider
central space by enabling a larger quantity of cooling liquid to collect in the
main body of each bar prevents the bars from becoming red-hot too quickly
should a momentary interruption occur in the feeding of the liquid. Again the
widened or expanded portion of the grate practically prevents obstruction the
impurities if any collecting at the bottom of it.
It is exceedingly easy to take the grate to pieces for cleaning or similar
purposes.
It will be seen that this grate essentially differs from all existing grates both
in object and construction and in this connection I would particularly point out
that the hollow bars are actually formed as grate-bars should be and are not
wholly or partly cylindrical for it is well-known that cylindrical bars offer the
most favourable surfaces of adhesion to slag which being thus allowed to accumulate
frequently forms big lumps or excrescences in all directions which seriously interfere
with the operation of the furnace and are apt, through the strain they necessitate
in stroking and cleaning to make the bars become loose, another feature common
to all tubular grate-bars hitherto employed is that they have the same inner
diameter or capacity from end to end the consequence being that very wide spaces
have to be left between them and when such a bar is disconnected it is scarcely
recognisable as a grate-bar at all. The bars of this improved grate on the contrary
are considerably reduced or contracted at the ends in comparison with their central
or main portion.
Hollow grates have before been devised for the circulation of hot water or steam
which it was their object to convey directly into the boiler so that they were really
used as a preliminary or feed-water heating-apparatus. The present fire grate is
intended to fulfil no such function but merely to enable the heating operation to be
better carried out and this result is fully ensured by the one circumstance alone
that the water circulating through the grate repels the slag so that it may neither
agglomerate nor adhere to the bars, but splits up into small fragments.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me by
my foreign correspondent, I declare that what I claim is ;-
19
A hollow fire-grate having no direct connection with the steam boiler (when
employed to heat such) but adapted to have water circulated through it to prevent
the "burning on of slag for which purpose its hollow bars forged or wrought of
homogeneous metal or material are wedge-shaped in section and connected with the
transverse carriers or bridges either frictionally or by means of screw-threads the
hollow terminal trunnions being of a different shape in section and narrower than
the bar proper substantially as described and illustrated in the accompanying
drawings.
2. The combination and arrangement of parts constituting the complete fire-
grate substantially as described and illustrated in the accompanying drawings.
Dated this 5th day of January 1809
W. P. THOMPSON & BOULT,
Agents for the Applicant.