IMPROVEMENTS IN THE TRAVELLING GRATES OF FURNACES
Year: 1884

page_text: I JOHN CRESSWELL BRENTNALL of Heaton Norris in the County of Lancaster,
Gentleman, do hereby declare the nature of the said Invention for "IMPROVEMENTS
IN THE TRAVELLING GRATES OF FURNACES " to be as follows:-
My Invention relates to the travelling grates adapted more particularly for
application inside the internal or furnace flues of Cornish and Lancashire boilers
and other internal flued steam generators but grates constructed in accordance with
my invention may be adapted to other descriptions of furnace.
I employ bars connected or linked together so as to form an endless chain and I
give notion to this chain of bars by means of revolving screws or helical drivers
which are mounted at each side of the furnace below the level of the fire grate
surface. In some cases I employ screws having a differential pitch so that the air
spaces between the bars are caused to vary as the bars travel from one end of the
furnace to the other as for example the spaces may be narrow at the front of the
furnace and wider in the centre and if considered to be desirable may be contracted
towards the back end. The links or connections are slotted or have an amount of
play so that whilst preventing the bars from being separated beyond a fixed limit
permit them to be brought closer together. Each screw may be a shaft with a
helical fin or rib cast upon it but I do not confine myself to the use of a cast metal
screw. The ends of the bars or ribs or projections thereon enter between the fins
and rest upon the shafts of the screws and the movement of the bars to carry the
fuel from end to end of the furnace is effected by rotating the screws in unison the
screws being rotated continuously by means of worms and wheels or by other
suitable gearing connected with the driving shafting or being rotated at intervals
as desired in each case. Stationary side gratings or shields protect the screws
from the fire the ends of the bars moving below these side gratings or if preferred
the said side gratings may be level with the moving grate surface. The spaces
between the bars when acting as a grate are contracted by the action of the screws
but when returning below the grate the bars are extended at their greatest distance
apart so that ashes falling through the air spaces in the grate can freely pass
between the lower bars. The bars may be arranged to travel from front to back
or from back to front as desired or considered to be most suitable.

page_text: "
I JOHN CRESWELL BRENTNALL of Heaton Norris in the County of Lancaster
Gentleman, do hereby declare the nature of the said invention for "IMPROVEMENTS
IN THE TRAVELLING GRATES OF FURNACES and in what manner the same is to
be performed, to be particularly described and ascertained in and by the following
statement and accompanying drawings :-
My Invention relates to the travelling grates adapted more particularly for
application inside the internal or furnace flues of Cornish and Lancashire boilers
and other internal flued steam generators but grates constructed in accordance with
my invention may be adapted to other descriptions of furnace.
I employ bars connected or linked together so as to form an endless chain and
I give motion to this chain of bars by means of revolving screws or helical drivers
which are. mounted at each side of the furnace below the level of the fire grate
surface. In some cases I employ screws having a differential pitch so that the air
spaces between the bars are caused to vary as the bars travel from one end of the
furnace to the other as for example the spaces may be narrow at the front of the
furnace and wider in the centre and if considered to be desirable may be contracted
towards the back end.
In the accompanying illustrative sheet of drawings Fig: 1. represents a cross
section of a travelling grate arranged to be actuated in accordance with my
Invention and Fig: 2. is a longitudinal section and Fig: 3. a side elevation of the
same shown as broken or curtailed in length. Fig: 4. is a plan of a portion of the
grate. In the said Figs: a. a. are the travelling bars. and b. b. are the actuating
screws. The curved line c. represents a portion of the inner surface of the boiler
furnace flue in which the grate is supposed to be mounted. The ends of each
screw are turned down and revolve in bearings d. d. the latter being outside the
furnace flue. The outer end f. of each screw is formed with inclined grooves or
recesses which are made suitable to engage with a worm which is indicated by
dotted lines and is fixed or formed on a shaft g. The two shafts which actuate the
two screws are extended in an upward direction and receive motion from a suitable
arrangement of shafting and gearing so as to revolve at the same speed. The two
screws are thus caused to revolve in unison. Each screw may be a shaft with a
helical fin or rib cast upon it but I do not confine myself to the use of cast metal
screws. The bars a. are formed with ribs or projections which enter the spiral
grooves of the screw and rest upon the bottoms thereof during the times when the
said bars are in their upper positions. The bars are linked together so as to form
an endless chain as indicated in Fig: 3. the links being slotted so as to permit the
bars to close up or to approach each other to some extent. The chain of bars passes
around pullies or wheels h. h. so that as the screws revolve the bars are caused to
travel continuously passing along and over the screws to the back or inner end of
the furnace and returning upon the bearers i below the screws to the furnace front
as indicated by the arrows in Fig: 2. or if preferred this direction of travel may
be reversed. In the example the screws have a variable pitch the front portion of
each screw that is to say the part to the left hand in the drawings having a less
pitch than the rear portion. The effect of this is that the bars whilst passing over
the front parts of the screws are comparatively close together but as they travel
toward the rear end of the furnace they are further separated as clearly indicated
in the drawings. This widening of the air spaces may take place gradually from
end to end of the furnace or the change may be more quickly effected when the
bars have travelled a suitable distance close together and it is desirable to allow

page_text: more air to pass through the fuel. When so arranged there is less loss of small
coal at the front end of the furnace and when the coal has become coked the air
spaces widen so as to allow more air to pass, the fire then being in a condition
favourable to the increased flow of air. The separation of the bars also tends to
clear the air spaces.
In some cases I may arrange for the air spaces to be again
contracted at the rear end of the furnace. As the bars return to the front of the
furnace they are separated to the utmost extent of which the slotted links will
permit and as the spaces may then be wider than at any part of the grate surface
as indicated in Fig: 2. there is less liability for the falling ashes to be intercepted
than in ordinary chain grates. I do not confine myself to the varying pitch of the
screws and may make the pitch uniform from end to end of the screws.
cases I may use shorter screws not extending to the rear end of the grate as in the
drawings. I do not confine myself to any special means for linking the bars
together so long as the attachment used permits the bars to approach and separate
so as to decrease and increase the air spaces when using screws of an irregular pitch
or when using regular pitch screws to make the spaces between the returning bars
wider than the air spaces. The means for actuating the screws may be varied. If
preferred the ends of the bars may travel upon bearers instead of the bars being
sustained by the screws.
In some
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:
1. The combination of parts substantially as and for the purpose set forth and
indicated herein before and in and by the accompanying drawings.
2. The employment of revolving screws to sustain and give motion to the bars
of "endless chain" travelling grates by acting directly upon such bars substantially
as set forth and indicated.
3. The employment for the said purpose of screws of varying pitch in order to
vary the spaces between the bars.
4. The employment of screws to give motion to the bars of endless grates
and the linking or connecting together of the bars so that the air spaces may
be contracted as compared with the spaces between the lower returning bars
substantially as set forth..
Dated this 21st day of October 1884.
EDWARD K. DUTTON,
41, John Dalton Street, Manchester,
Agent.