Improvements in and relating to Grates for Furnaces.
Year: 1885

page_text: Improvements in and relating to Grates for Furnaces.
I, LOUIS SIMON DULAC, of 74 rue des Boulets Paris, in the Republic of France,
Mechanical Engineer do hereby declare the nature of my invention for "IMPROVE-
MENTS IN AND RELATING TO GRATES FOR FURNACES " and in what mauner the
same is to be performed, to be particularly described and ascertained in and by
the following statement :-
This invention relates to grates for furnaces and has for its objects to facilitate
the cleaning of grates, to enable them to be maintained or kept in repair without
great cost and to reduce their weight..
The grates for furnaces as heretofore constructed are composed of bars of variable
heights placed parallel to each other and supported at their extremities upon cross
bars termed bearing bars.
These furnace bars expanding and contracting parallel to each other do not
undergo any relative displacement, hence it follows that the fusible scoria or slag
participating in these movements readily unites with the grate, thereby necessitating
the expenditure of a considerable amount of labour in cleansing it.
Moreover in order to give the bars sufficient strength and to diminish as far as
possible the heating of the portion which is in contact with the fuel, they are
frequently made of parabolic form, and of a height about five times greater than
their thickness.
Although only the portion of the bar in contact with the fire is subjected to
burning, it nevertheless results that, when once this portion is damaged, the whole
bar is rendered unserviceable thereby causing a considerable waste.
Another disadvantage connected with the grates at present in use is that they
present, in most cases, a relatively limited passage for the air for supporting
combustion. In fact, the length of the bars renders the reduction of their
thickness almost impossible. Also, in order to avoid great spaces between the bars,
resulting in the loss of fuel, the free passage through the grate has been made
comparatively small.
To remedy the aforesaid disadvantages, I have constructed a grate for furnaces
which may be easily cleaned in consequence of the arrangement of the bars, the
latter being so constructed as to expand and contract in opposite directions thereby
preventing the adherence of the scoria to the grate.

page_text: The economical maintenance is the result of two distinct causes. First. To a
continuous cooling of the portions of the bars in direct contact with the fire, which
cooling is due, on the one hand, to an extreme division of the air and to the
relation between the heating surfaces, formed by the plane of the bars and by the
faces, and, on the other hand, to a current of cooling liquid circulating in the
bearing bars. Second. To the method of distributing the material, which permits
the burnt elements to be removed without touching the adjacent elements.
For this purpose I superpose two grates, the lower one having either solid or
hollow bars placed wide apart and constituting the support for the upper bars or
elements in direct contact with the ignited mass.
The lower grate has the double object of supporting the grate proper and of
cooling it. For this purpose through the said lower or bearing grate either air or
water, or any fluid at a sufficiently low temperature to attain the end in view, is
circulated. The heat derived from the grate raises the temperature of the cooling
liquid which may be utilized for any purposes.
In order to better illustrate the mode of construction and the principle of the
improved grate I will refer to the accompanying drawing, in which
Figures 1 and 1 bis show two vertical sections of the improved grate adapted for
the circulation of air, these sections being taken respectively through the middle
of the grate, and through a bearing bar.
Figure 1ter represents bearing bars adapted for the circulation of liquid and
surmounted by furnace bars, the said bearing bars being supported at the lower part
by U-irons, the function of which will be hereinafter described.
Figure 2 is a plan of the grate.
Figure 3 is a transverse section of a detail of the grate.
Figure 4 represents in vertical section a furnace grate adapted for the circulation
of water.
Figure 5 is a vertical section of the central double receiver at the bottom of the
furnace grate.
Figure 6 illustrates the methods of fastening the tubes in their receiver.
Figure 7 is a plan, partly in section, of a furnace grate.
Figure 8 shews the joining or connecting boxes or sockets in section.
Figure 9 is a longitudinal section of a tube of the grate fastened at one end to
its receiver and at the other in its connecting socket.
The supporting grate for the circulation of water or other fluid is formed of
bearing bars A of wrought or cast iron, having the form of a hollow cylinder as
shewn in Figures 4, 6 and 7, an elliptical form or the form of an inverted U as
shewn in Figure 1. These bars A which rest upon bearing bars and, are in the
form of tubes, through which water circulates, open at one end into a receiver B
transversely partitioned and arranged in front of the furnace, and at the other ends
are united in pairs to connecting boxes or sockets G so as to form a series of
U-shaped sections.
The receiver B is divided into compartments by means of vertical cross
partitions W. Each of the compartments has connected with it the adjacent tubes
of two adjacent U-shaped sections. By this arrangement, it will be seen, that the
water or any other fluid which traverses the grate passes from one extremity
through all the tubes before it escapes at the other extremity.
At the sides of the grate, the receiver B turns vertically so as to form, itself,
a U-shaped frame surrounding the grate on three sides. The two vertical
extensions C C¹ thus formed are likewise partitioned transversely and receive
tubes D D¹, which are situated respectively at the side of the grate corresponding
to the branch of the receiver to which they are connected and also over half the
bottom of this grate. These tubes, by reason of their direct connection with the
common receiver B C C¹, constitute a continuation of the coil of tubes A forming
the support of the upper grate.
A receiver E placed vertically close to the fire-bridge and in the centre of
the furnace has connected to it on opposite sides the tubes D D¹. A vertical

page_text: diaphragm divides this receiver E into two symmetrical portions and separates one
Transverse
coil formed by the tubes D from that formed by the tubes D¹.
partitions divide the receiver E into several chambers, to each of which are
connected two adjacent tubes. The partition walls of the receiver E and those of
the portions C C of the receiver B are arranged in such a manner relatively to
each other that two tubes, which are in communication in the same compartment
of the extensions C C¹, are on the contrary isolated in the receiver E. By this
arrangement, coils are formed situated on three sides of the furnace.
It is to be understood that I may employ any other analogous arrangement of
tubes which has for its object the use of coils having parallel protecting tubes for
the sides of the furnace. The receiver E for instance might be replaced by a series
of connecting boxes or sockets similar to those which will be hereinafter described,
or the connecting boxes or sockets and the transverse partitions of the vertical
extensions C C may be dispensed with, the extension C for instance then being
connected directly to the extension C¹ by a number of tubes surrounding the
furnace and opening into the extension C¹ isolated from the receiver B by a
partition placed at the lower portion.
In the arrangement employed for the circulation of water, the admission and
discharge orifices are arranged in a suitable position for ensuring a good circulation
of the liquid through the tubes and the receiver.
It is obvious that it is easy to reverse the direction of the course of the fluids
through the tubes and obtain, at will, an ascending or descending circulation
through the coils. The general system of the tubes can also be subdivided into
several distinct series, for instance, if my system is to be applied to large furnaces
it may be advantageous, for obtaining proper cooling, to provide for two absolutely
distinct circulations of the cooling liquid.
The various bars A of the grate and the tubes D, D₁ are fixed to their respective
receivers and connecting boxes or sockets by means of a special joint forming a
kind of stuffing box.
Each tube carries at its extremities a turned collar I, Figures 7 and 9, and is
prolonged by a circular projection J entering an orifice in the receiver or the
connecting socket. This orifice has a circular recess or cavity in which is located
a washer K of plastic material, which is compressed between the sides of the recess
and the collar I of the tube, as it would be in a stuffing box. This arrangement
ensures perfect tightness.
In order to maintain the tubes in their connecting sockets and to press them
firmly in place, I employ perforated flanges L through which bolts M pass.
These flanges, which are placed between two adjacent tubes, bear upon the collars I
of the said tubes, and, through the medium of a spherical projection P, upon the
rib O with which the receivers are provided. In order to facilitate the placing of
the bolts, the sides of the receivers are corrugated as shown in Figure 4 of the
drawing.
In order to ensure a perfect fastening and consequently, an intimate contact of
the flanges L upon the ribs O and the collars of the tubes, the flanges are provided
with spherical projections P bearing upon the rib O, and with concavities of
spherical form designed to contain discs P¹ of the same form, against which bear
the heads of the bolts M. This arrangement not only ensures an intimate contact
of the flange upon the rib and the collars of the tubes, but also an invariable,
pressure upon the contact surfaces.
It will be seen that, a tube being held by two flanges, if by accident one of them.
or one of the bolts breaks, the other flange will still hold the tube in its
stuffing box.
As shown in the drawing, the connecting boxes or sockets G represented in
Figure 8 have two orifices through which pass tubes which they serve to connect..
As in the case of the receivers, these orifices have circular cavities containing plastic
discs; the walls of the sockets are curved in the middle so as to permit the passage.

page_text: of the bolt-shanks which pass through the ribs O' of these sockets, and which
serve to hold the tubes through the medium of flanges of elliptical form and
provided with orifices enabling the fastening bolts and the tubes forming the coils
to pass through them.
When air or gas is used as the cooling agent, the bearing grate may be composed
of bars of various forms according to the nature of the fuel. The air after having
passed through these tubes can proceed to a receiver and thence be directed
immediately to the furnace to assist the combustion of the fuel, or to a calorifere
or any other apparatus.
In cases where the circulation of air or gas in the hollow bars cannot be suitably
employed, I substitute for the said bars hollow supports of inverted V or U forin,
Figures 1 and 1bis, perforated in their upper sides and presenting cooling surfaces
and a greater strength than solid supports of equal weight.
Above the orifices H of these bars is placed a cast iron cross bar H supported
by the bearing bar and conducting the air, which is evolved from below the bearing
bar, to the interior of the furnace.
The grate in contact with the fuel is constructed as before stated, with a view to
obtain expansions and contractions between the bars in opposite directions in order
to facilitate the cleansing.
These bars are composed of a series of elements constructed in two different
ways. The form of bar shown at R Figure 2 is that which is used for the central
portion of the grate and the other R¹ that which is used for the sides. The
elements assume in elevation the general form of the letter Ṭ, the vertical branch a
of which is located between the tubes of the lower-grate in such a manner that
their centre of gravity is brought below the points of support.
The horizontal branches of the T bars form the bars proper, a little play being
allowed each bar to permit a certain amount of expansion.
Projections a¹ determine the space between the elements, these projections being
preferably placed above the axis of the bearing bars.
The elements R¹ contain three branches and are placed on the sides of the
furnace, the tail of the T being integral with the large branch.
Each of the elements is formed of curved portions designed to facilitate the
passage of the stoking tools along the surface of the grate.
The two terminal wings of the upper bars can be prolonged on each side as
shown in Figure 1ter with the object of preventing the swinging motions of the
upper bars upon the bearing tubes. For the same purpose, below the tubes of
circular section I place a U-shaped iron upon which the extremities of the two
banging wings of the upper bars, Figure 1ter, bear.
It will be observed that the expansions and contractions of the juxtaposed
elements are free and cross wise relatively to each other. These opposing dilatations
prevent the adherence of the melted scoria to the bars.
To render this adherence impossible and to be able to break the cakes of dross
with facility during the operation of the furnace, the central portion or lower
branch of the T of each element R, R¹, descends sufficiently below the tubes A of
the lower grate to allow for their being moved through the medium of a stoking
iron. The movement of each element through the ash-pit thus has for its object
to cause the ashes to break and lift the layer of melted scoria and to provide
a passage for the air. For this purpose the flanges or parts of the abutment which
maintain the distance between the elements R R¹ have sloping edges, as illustrated
in Figure 3, so as to provide for a certain oscillation of the elements independently
of each other.
The grate as thus constructed is as a whole very stable and yet each element is
independent of the adjacent one and can be subjected to sufficiently strong
movements without fear of leaving its place.
The advantages of this grate are, that the scoria does not unite with the bars,
which have opposite dilatations, whereby its removal becomes easy and rapid.

page_text: The bars having a small length it is possible to reduce their thickness and
consequently the distance between the bars without diminishing the proportion of
intervening spaces to the area of the bars.
By reason of the number of the elements and their small length it will be seen
that a grate is obtained which, whilst having a very limited weight presents the
advantage of offering a very small horizontal surface relatively to the lateral
surfaces of the bars, that is to say, with respect to the radiating surfaces hence it
follows that this grate is under excellent conditions for preservation, as it always
remains at a relatively moderate temperature..
When, after long use, the replacement of an element becomes necessary,
the
weight of the cast iron thrown to waste is considerably smaller than with ordinary
bars; the total weight of the two grates is much less than the weight of an
ordinary grate of the same surface, and the distribution of the air through the
grate ensures the cooling of the bars, their efficiency and their duration.
It is possible to heat the air necessary for the combustion by causing it to
circulate in the first grate before entering the ashpit and passing to the fire,
without the employment of other apparatus; the two grates can, therefore, fulfil, in
the act of combustion, different functions conducing towards the same result.
It will accordingly be seen that I have succeeded in constructing a new furnace
grate which is formed of elements of variable form and the number of which
depends solely on the dimensions of the furnace, the small size of these elements
enabling very light grates to be obtained, although the height of the cooling faces
of the elements is considerable relatively to their thickness.
These improved grates present moreover the following distinctive features.
a. Constant cooling of the grate under the action of liquid or gaseous fluids
circulating in the supporting bars of the elements, and which can subsequently be
utilized, either in the operation of the furnace or for any other purposes.
b. Opposite dilatation of the elements of the grate in contact with the
incandescent fuel with the view of preventing the adherence of dross.
c. Reduction to the minimum of the loss of metal resulting from the wear of the
grate, it only being necessary to replace the injured parts.
d. The capability of constructing this grate of elements, the forms and dimensions
of which vary according to the nature of the furnace and fuel used, and of a variable
number of supporting bars which are hollow or bollowed out and cooled by the
rapid circulation of water, air, or the like according to circumstances.
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
First. The method herein before described of constructing grates for furnaces,
and based upon the employment of metallic elements juxtaposed and supported
upon a bearing grate, formed of longitudinal or transverse bars which are hollow
or hollowed out, and in which a fluid, designed to ensure the cooling of the elements
in contact with the fuel, circulates.
Second. The arrangement of the upper elements of the grate, presenting in
section the form of the letter, T, the central branch of each of which elements is
situated between the supporting bars so as to firmly maintain the element whilst
enabling the same to be rocked in order to cause the ashes to fall, the horizontal
upper surfaces of the said elements being by preference constructed in a corrugated
form for facilitating on the one hand the passage of the stoking tools along the
surface of the bars, and on the other hand the arrangement of the elements of two
adjacent rows for obtaining dilatations in opposite directions, thereby preventing
the adherence of the scoria to the bars.
Third. The above described arrangement of the bars of the supporting grate,
which bars are tubular and connected in pairs to a receiver provided internally
with transverse partitions which ensure a rapid circulation of the water in the

page_text: interiors of the tubes; or constructed in the form of an inverted U and so arranged
that the air which is heated therein contributes to the support of the combustion.
Fourth. The method herein described of uniting the tubes serving as supports
for the upper bars, with the object of ensuring the tightness of their joints with
the extensions arranged at the two extremities of the grate.
Fifth. The combined arrangement of the receivers, placed one in front and the
other in the rear of the furnace permitting the lower side walls of the said furnace
to be provided with tubes for the circulation of liquid, with the object of protecting
these parts of the apparatus against the action of great heat which rapidly injures
them.
HASELTINE, LAKE & Co.,
For the Applicant.