IMPROVEMENTS IN AND RELATING TO GRATE-BARS FOR STEAM-BOILER AND OTHER LIKE FURNACES
Year: 1881

page_text: LETTERS PATENT to William Robert Lake, of the Firm of Haseltine, Lake,
& Co., Patent Agents, Southampton Buildings, London, for an Invention of
"IMPROVEMENTS IN AND RELATING TO GRATE-BARS FOR STEAM-BOILER AND
OTHER LIKE FURNACES." A communication from abroad by William U.
Fairbairn, of Boston, Massachusetts, United States of America.
COMPLETE SPECIFICATION filed by the said William Robert Lake at the
Office of the Commissioners of Patents on the 14th Juno 1881.
WILLIAM ROBERT LAKE, of the Firm of Haseltino, Lake, & Co., Patent Agents,
Southampton Buildings, London. "IMPROVEMENTS IN AND RELATING TO GRATE-
BARS FOR STEAM-BOILER AND OTHER LIKE FURNACES." A communication from
abroad by William U. Fairbairn, of Boston, Massachusetts, United States of
America.
In order to secure and maintain uniform combustion in a furnace it is essential
to supply the fuel with a uniform and sufficient quantity of oxygen or air well
distributed beneath the fire. In furnaces as ordinarily constructed having solid
grate-bars extending from the front rearwardly the air is very largely taken up by
the front section of the fire, and the back part of the fire or the part more remote
from the ash-pit, door, or damper for supplying air suffers in consequence, the results
being an unequal combustion of the fire and a consequent loss in the amount of the
heat developed from the fuel.
'
This Invention is designed to provide the rear or remote section of the fire with
sufficient air to maintain a combustion equal to that of the front section. I.
accomplish this result by providing the grate-bars with a chamber or passago
through which air is drawn by the action of the fire from a suitable source of
supply, and by which air is delivered at the said rear or back section of the fire. Jn
thus constructing my improved grate-bars to accomplish this purpose, I also succeed
in making a lighter and stronger bar from the same amount of metal, and the bar
is kept cool enough by the passage of the air to prevent its twisting under. the:
influence of heat.
The furnace is constructed in the ordinary manner with front and rear supports.
for the grate-bars, and the ash-pit is closed except at its front end, which is provided

page_text: with the ash-pit door and damper, through which the air to support combustion
enters the ash-pit chamber. The bars are of such a shapo as to rest upon the
supports, and are made separately so that they are removable.
In the accompanying Drawing,
Figure 1 is a perspective view of one form of grato bar constructed according to
this Invention.
Figure 2 is a perspective view of a modified form of the said bar, a portion of the
same being broken away.
Figures 3, 4, 5, and 6, are detail views hereinafter described.
Figure 7 is a vertical section of the bar supported in position.
Figure 8 represents in section a furnace supplied with my improved bars.
Figures 9 and 10 are detail views.
"
Some of the above named figures are drawn to a larger scale than others.
A is the ash-pit; A', the front support for the grate-bars; A², the rear support
therefor; As, the ash-pit door; and A, the grate-bars. Each grate-bar has, in the
web a, a passago a extending from the opening a at or near the front end of the
bar to the side opening or openings a³ at or near its rear end. The action of
the fire causes the bars to be heated and consequently the air therein, and tho
consumption of air at the rear of the fire causes the heated air in the passages to be
drawn through the rear openings, thereby establishing a draught through the
passages, the air being drawn from the front of the ash-pit chamber where the air
is most plentiful. The fire therefore is provided with air to support combustion
from the front of the ash-pit, and all the air for supporting combustion enters
through the ash-pit door or some opening in the front of the ash-pit.
The front section of the fire takes to itself as much air as may be desirable
from this source of supply, and the rear of the fire draws from the same source of
supply the quantity of air it demands through the passages in the grate-bars, and
as there are no openings from tho passages, except at or near the rear, the air is
consequently drawn to the place where it is most needed.
If there were openings from the passage along its entire length the bars would
bo no better for feeding and distributing air to the fire than the ordinary furnace
bars, as thero would not be sufficient draught established to cause the air to be
drawn to the rear of the fire, but it would leave the passago at the first openings.
The supply of air to the entire fire is regulated by the ash-pit door or the damper
therein. Each grate-bar has a fire-supporting surface a and also the end
supports a, which rest upon the grato-bar-supports. The mouth of the passage
may have any desired shape, but I prefer that represented. In some instances it
may be desirable to chock the flow of air through the passages, on account of the
draught that is created by combustion. In Figures 2, 3, 4, 5, and 6, I have repre-
sented a construction of bar for accomplishing this purpose. A number of devices
can be employed, and asbestos or other non-combustible material packed lightly in
the passage, so that air may be drawn therethrough may be used. Wire gauze in
one or more layers extending from side to side across the passage may also be used
to retard the flow of air; or the passage may be made thin by dividing it into two
compartments by means of a partition-plate, which may or may not be connected
at the bottom, the object of this portion of my Invention being to retard the flow
of the air and also to heat it in its progress through the passages. It is found
desirable to build a narrow hood or projection over the exits or air escape openings
to prevent ashes from falling into and clogging them, or the passage within the
bar;
and in Figures 2, 3, and 4, I represent a bar provided with these hoods. The 5
hood preferably is of the same length as the exit opening, and slants outwardly and
downwardly from the fire supporting surfaco so as not to increase its width
materially. It will be observed that in a furnace, employing my grate-bars, the
webs are practically suspended in the ash-pit chamber, so that the passages therein
are most advantageously located for receiving air.
Having thus fully described the said Invention, as communicatod to me by my

page_text: foreign correspondent, and the manner of performing the same, I wish it understood
that I claim,
First. A furnace grate consisting of hollow grate-bars, the cavities whereof com-
municate with the ash-pit by openings formed, as shewn, at their front ends, and
with the spaces between the grate-bars at their rear ends by perforations through
the sides or walls of the said cavities, substantially as described.
Second. A grate-bar having a fire supporting surface, a web, and an air-passage
in the web, extending from the front end of the bar and opening at or near the
back or rear end theroof, whereby air may be conducted from the front end of tho
said bar to one or more openings at or near its rear end, all substantially as and for
the purposes described.
Third. A hollow grate-bar, perforated at the rear end upon its sidos, for the
delivery of air among the products of combustion, and at the other end for the
reception of air, substantially as herein described.
Fourth. A hollow grate bar, the cavity whereof communicates with the ash-pit
only at its two ends, substantially as above described.
Fifth. A removablo grate-bar having end projections adapted to rest upon the
grate-bar supports and a web containing a passage open at or near the front
end of the bar, and at or near the rear end thereof, substantially as above
described.
•
Sixth. A hollow grate-bar having the oxit or exits from its cavity protected
by a hood or hoods, substantially as above set forth and for the purposes specified.
Seventh. A grate-bar having a passage in its web, through which air may be
drawn, and means substantially as described for checking or retarding the flow
of air in said passage, all as above set forth and for the purposes specified.
In witness whereof, I, the said William Robert Lake, have hereunto set my
hand and seal, this Fourteenth day of Juno, in the year of our Lord One
thousand oight hundred and eighty one.