Improvements in Low-pressure Boilers for Use in Heating by Steam, and in Furnaces therefor.
Year: 1898

page_text: Date of Application, 22nd Mar., 1898-Accepted, 23rd July, 1898
CODEILDIN DI MUIFICATION.
Improvements in Low-pressure Boilers for Use in Heating by Steam,
and in Furnaces therefor.
We, JULES GROUVELLE and HENRI ARQUEMBOURG, trading as La Société Jules
Grouvelle et H. Arquembourg, of 71, Rue du Moulin-Vert, Paris, in the French
Republic, Manufacturers, 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 :—
This invention relates to steam-generators of the low-pressure type an] consists
in certain improvements whereby such boilers are rendered more particularly
adaptable for heating by steam.
In the accompanying drawings, Fig. 1 is an elevation of a low-pressure boiler
embodying our improvements. Fig. 2 is a vertical section of the same taken on the
line 2-2 in Fig. 4. Fig. 3 is a vertical section taken on the line 3-3 in Fig. 4.
Fig. 4 is a transverse section taken on the line 4-4 in Fig. 1, as regards the front
part, and on line 4-4 in Fig. 3, as regards the back portion. Fig. 5 is a trans-
verse section of the ash-pit door, taken on the line 5-5 in Fig. 1. Fig. 6 is a
transverse section of the pipe annexed, as steam-intercepting chamber, to the boiler
proper, taken on the line 6-6 in Fig. 2. Fig. 7 is an elevation of two devices
which are arranged at the base of the chimney, and which are shewn in section in
Fig. 3. Fig. 8 is a vertical section of a regulating device, taken on the line 8-8
in Fig. 4, and Fig. 9 is a diagrammatic view in section illustrating a safety-device
for use with low-pressure boilers of the type herein referred to.
"
As will be seen by referring to Figs. to 8, the boiler proper A is a multi-
tubular boiler, the tubes of the vertical series a being connected at the top and
bottom by cupped end plates a² a². The furnace is formed by a central shoot a³
(adapted to be filled for a considerable portion of its height with " close-burning'
fuel, and only requiring to be re-charged at rare intervals), and by a revoluble
grate a substantially approximating the form of a truncated cone, the frame
whereof is supported by three of more rollers a³. The advantage of the revoluble
grate a is that the several constituent sectors a** may, whenever the fire requires
stoking, be brought up in front of the fire-box door, or of the door of the ash-pit
presently to be described, either by hand and by the same tool which serves to stir
the fire, or, if desired, by suitable mechanical contrivances such as will readily
suggest themselves to those familiar with the art to which the invention pertains
(the dimensions of the said sectors ax being calculated to allow of their ready
insertion and removal through the fire-box door). The smoke-box a is closed by
an annular lid ax having at each edge a depending flange, which flanges dip into
annular channels supplied with sand constituting a double sand-joint, and the
central shoot 3 is likewise closed by a lid a³×, both lids ax and a³× being remove-
able, the former to enable the tubes to be cleaned, and the latter to admit fresh
charges of fuel.
From the smoke-box a there extends laterally a horizontal
flue a', of rectangular section, whence starts the chimney a8, which may be of
circular section. Three or more air-inlets aº, of small diameter, are provided a
short distance above the grate at for the purpose of expediting the combustion of
CD
27

page_text: the carbonic oxide generated by the slow combustion of the close-burning fuel
with which the furnace is charged. The furnace is supplied with air through an
inlet a fitted with a controlling device B, hereinafter more fully described and which
is so sensitive in action that it requires the ash-pit to be tightly closed. To this
end, the boiler A is erected upon a block of fire-resisting materials and, in the
process of fixing it in position, the angle-piece all at its base is placed upon a bed
of grout prepared with fire-clay, which, after drying, effectually keeps the air from
entering the ash-pit otherwise than through the above-mentioned inlet a¹º. Also,
in view of the uncommon sensitiveness of the controlling device B, the door a¹ of
the fire-box and the door a13 of the ash-pit have to be so arranged that the fire-box
door a may open and close at will, but that the ash-pit door a¹³ may not be
opened unless the said fire-box door a¹² be opened at the same time, it being
practicable however to close. the former whilst leaving the latter open, if need be.
To this end, the ash-pit door a¹³ is connected by the arms of a horizontal Y-shaped
picce a to a rod a¹5, the latter serving as a hinge-pin for the piece a¹. The upper
end of the shaft a carries an arm a¹ which, upon being moved in one direction,
operates a lateral extension 17 on the fire-box door a12. The free end of the
piece a¹ serves for closing the ash-pit door a¹³, an eccentric crank-handle a¹8 being
mounted in pivoting lugs a¹ for that purpose.
On one side of the boiler proper A there is disposed a vertical pipe A¹, com-
municating with the said boiler A both at the top and bottom, by means of
branch-tubes a20 a21 respectively, one of which is connected with the upper part
of the steam-chamber, while the other leads into the water in the said boiler A,
practically on a level with the end-plate a². The pipe A¹, at its lower part,
assumes a conoidal shape and furnished with an aperture for the removal of any
sediment, said aperture being closed by a screw-plug a22. At the upper part, the
said pipe A' is joined by a flange to the steam-outlet a23, the latter being provided
with a safety valve a controllable by means of a spiral spring.
Now from the
foregoing data it follows that the water rises to the same level in both the boiler A
and the pipe A', as indicated in the drawings. Within the upper part of the pipe A¹
there is located a separator for the water that is carried up, same comprising a series
of deflectors formed by concentric tubes a25, 26, 27, open, along a given generatrix,
at the opposite ends of their several diameters, the said tubes a25, a26, a 27 being
secured on to a common support held in an annular recess in the flange with
which the upper end of the said pipe A¹ is provided. The steam from the boiler A
can not therefore reach the steam-outlet until after having completed its circuit
23 is a return pipe for the
through the system of concentric tubes just described.
water of condensation from the heating apparatus; 2 is a waste-cock; 80 is a
water-gauge (which may be supplemented by a set of gauge cocks placed next to
it); ai is a pipe leading, from the steam-chamber in the tube A¹, first to a
pressure-gauge a and thence to the controlling device B, a being the steam-
outlet pipe.
The device B, for controlling the supply of air to the furnace, comprises two
chambers b, b, arranged within the casing which is secured to a support b², the
chambers communicating with each other through the tube and containing
mercury b. The chamber b is closed at the top and receives steam from the
boiler A through the pipe a1, and it also receives a small portion of the water of
condensation from such steam, the chamber b' being open to the atmosphere. Upon
the mercury in the chamber b' rests an iron float 65, mounted loosely upon a collar
of the rod 66, which takes the shape of a rack at its upper part, while, at its lower
end, it terminates in a smooth guide-rod 7. The rod 60 whereon the short tubular
body box is loosely passed is in a manner presently to be described-connected to
the ends of the fork-arms of the lever 68, while the other arm of such lever 68
supports the rod 69, the latter being furnished, towards its lower extremity, with
an ellipsoidal enlargement whereon rests a hollow cap 69. The cap 6x serves to
control the air-supply within the perforated dome 6, which forms the lower termi-
nation of the casing of the controlling device B, and is connected with the inlet a¹º

page_text: by the pipe alex, the upper extremity of which is furnished with a guide for the
lower portion of the rod 6º. In the vicinity of the lever b³ there is situated a bell-
crank lever 61, supported at or about its central part; one of the arms projecting
through the enclosing casing of the controlling device B and resting upon a
stop 611x situate within such casing. We will now revert to the manner in which
the rod b is connected to the ends of the fork-arms of the lever 6*, a method of
connection the object of which is to enable the distance between the float b' and the
said fork-ends to be either augmented or reduced, so as to vary accordingly the
relative initial positions about which the oscillations of the cap 6x take place for
the purpose of controlling the air-supply to the fire. To accomplish these objects,
the teeth of the rack-portion of the rod 66 are arranged to gear with a pinion b¹², the
spindle 63 of which terminates outside in a milled head 614, capable of being
turned in either direction by hand. The hollow portion 615, through which the
rod 6 is adapted to rise and descend with slight friction, is provided on one side
with a slotted sleeve 610 wherein the spindle 618 turns with considerable friction,
the said sleeve being provided externally with a conical screw-thread, and the
nut 610x serving to bring the lips of the slots more or less close together. The
hollow portion 615 is provided with pins, or coned centres, 615x, which work
in the ends of the fork-arms of the lever 68, while the said fork-arms are similarly
provided with pins, or coned centres, 6**, which work in the part 617 of the supporting
framework. It will thus be seen that the whole mechanism which serves to vary
the distance between the float 65 and the fork-ends of the lever 68 follows the rod bo
in all its movements. We may add that the weights of the several parts attached in
the manner above stated-viz. :-on the one hand to the arm of the lever 68, which
corresponds to the rod 6º, and, on the other hand, to the fork-arms of the said
lever bare such that, in view of the available lengths of the said lever-arm and
fork-arms, the cap 6x and rod 69 slightly preponderate. This being so, and
assuming that the steain in the boiler A either exceeds or falls below the normal
pressure, it will be seen that the float 6, in rising or descending (as the case may
be), will cause the cap 6x to sink or rise accordingly, thereby decreasing or
increasing the supply of air to the fire, and consequently exercising the requisite
control. Further, assuming that from any cause the steam-pressure in the
boiler A exceeds to a very appreciable extent the normal pressure, a
time will come when the controlling device B will be performing the
function of a safety-device; for, the cap 6x will presently rest upon the
upper end of the pipe a10x, and a momentary pause will immediately take place,
owing to the fact that the arm of the lever 68, which corresponds to the rod 6º,
will, by that time, be sustaining a lesser weight. Owing, however, to the
distribution of the respective weights which control the lever 68, the ellipsoidal
piece on the rod 60 will remain in contact with the cap box. In the event of the
almost complete interruption of the air supply to the fire, which thus results,
proving ineffectual in preventing a further increase of the steam-pressure in the
boiler A, the float b5 will continue to rise along the rod 66, carrying the sinall
tube box along with it, the latter eventually pressing against the lower
surface of the hollow portion 615. At this juncture, the rod 6º commences to
descend through the cap 6x, seated on the upper part of the pipe a10x, and the
bevelled end of the arm of the lever 68, corresponding to the rod 6, arrives in
contact and becomes engaged with the bevelled end of the arm of the lever b¹¹.
Hence it follows that the rod 6° can not rise again unless the attendant lifts by hand
the projecting end of the arm of the lever 61, and that the fire in the furnace must
not only have lost some of its intensity, but must tend to go out altogether if the
attendant's intervention should be too long delayed. At the upper end of the
rod 6 there is supported, by an arm 618, a suitably graduated bar 61, adapted to
move at the same time as the rod 66 behind a slotted index 620, which moves
together with the hollow portion 61 to which it is connected by an arm 62x. It will
therefore be readily understood that whatever the given re'ative position of the
cap 6× the readings of the graduated bar 60 and index 620 on the one hand, and

page_text: those of the pressure-gauge as on the other, must agree; thus showing in a
perfectly reliable manner that the boiler A is operating with the requisite
regularity. A glazed sight aperture 621 enables the above-mentioned readings
pertaining to the device B to be readily observed. (It will be understood that,
according to the space available, or for greater convenience in other respects,
and
the pipe A¹
those
air-inlet a may occupy other positions than
indicated in the drawings in relation to the doors a12, a¹3 of the boiler A.)
Having thus described the controlling apparatus and safety-device which we
place in position before the furnace, we will now proceed to describe the safety-
device and controlling apparatus which we fix in position after the furnace. The
safety device C is arranged upon the rectangular flue a', which leads from the
smoke-box a to the chimney as A revolving damper c is mounted upon a
transverse spindle c¹ in the said flue, the spindle carrying at one extremity a two-
armed lever c², c³, the arm c² being provided with an adjustable counter-weight c²*,
When the
while from the arm c³ is suspended a small thin-walled metal bath 3x.
bath x is empty, the counter-weight cx preponderates, and, as the several parts of
the device C occupy the positions represented in full lines, the damper c is fully
open. Now assuming that, to the return tube a23 for the water of condensation
from the heating apparatus, there is connected at a convenient height a small tube
a28x opening above the bath c³×, it will be seen that, as the water of condensation
is forced back by the steam-pressure in the boiler A until it rises to the point from
which the said tube a28x branches, such water of condensation will flow into the
said bath cax, which, the moment it becomes charged to a pre-determined level,
will, in its turn, preponderate, so that, as the several parts of the device C take up
the positions delineated by the dotted lines, the damper c becomes entirely closed.
Provided, therefore, the connection of the tube a28x has been made at the highest
point compatible with the degree of safety which it is desired to ensure, any
It should bo
danger will yet be avoided by the arrangement just described.
pointed out, however, that a small aperture c* is left in the damper c, so that, even
when the damper c is closed, the products of combustion are permitted to escape in
a small stream, whilst the fire in the fire-box and the steam-pressure is the boiler
A decline. In addition to this safety-device C, and at the end of the flue a' beyond
the chimney a³, we arrange a device D for controlling the depression. To the flue
a is attached a flanged box d having a perforated bottom, a partition d¹, for
open
a part of its height only, being interposed between the flanges, within the box d,
a thin plate 3 is adapted to slide upon a stationary vertical rod d², the said plate
being of light metal (preferably aluminium) and requiring no additional means
beyond the rod d³ for guiding it. By imparting the requisite weight to the plate
d³ to suit any case, the said plate may be rendered capable, as it rises or sinks by
reason of the variation in the depression in the box d, of admitting more or less
cold air at the base of the chimney as through the apertures in the bottom of the
said box d. Hence there will result a depression-regulating action after the
furnace which will, in a serviceable manner, supplement the air-supply regulation
before the furnace, and, when the damper c is closed, as a result of the causes stated
above, the controlling device D, which nevertheless continues to operate, will
effectually ventilate the apartment wherein the boiler A is erected.
We will now describe-with reference to Fig. 9-the arrangement which we
propose to employ where the low-pressure boiler is fitted with a safety-tube, that is
to say, a tube receiving water from the boiler, open to the atmosphere and extend-
ing upwards to a point corresponding with the normal steam-pressure in the said
boiler. The object of the device E is to prevent the boiler A and pipe A¹ being
emptied of the whole of their contents, and also to ensure the immediate replenish-
ing of the supply of water, should the said boiler and pipe become partially emptied,
whatever the cause of either contingency, viz. -whether arising from an abnormal
increase in the steam-pressure, a "rush" resulting from the emulsion of the water
produced by the steam, or any like phenomena. The normal level of the water is
supposed to be at x-x in the case of the boiler A and pipe A¹, and at ¹¹ in the

page_text: case of the safety-tube e, the latter being connected with the pipe A¹ on the
level y-y.
The distance H, between the levels x-x and xx³, serve to
determine-by the height of the water-the normal steam-pressure in the boiler.
Above the level ¹³, at a height determined under certain conditions presently
to be specified, we arrange a reservoir e' which communicates with the atmosphere
through the tabe ex. The tube e enters this reservoir and rises sufficiently high
therein to make the capacity existing between the bottom of such reservoir and a
level such as x-xll larger than the spaces occupied by the water, between the
levels and y-y, in the boiler A, in the pipe A', and in the tubes leading to
such pipe. The bottom of the reservoir e' communicates with the pipe A³ (and
also, consequently, with the boiler A) through a tube 2, opening below the
level y-y the available sectional area of which tube e2 should be properly
determined in each particular case. As regards the return tube 28, for the water
of condensation from the heating apparatus, it may terminate either at the
reservoir e¹, or, as indicated in dotted lines, at a convenient point of the tube e, but
always above the level a¹¹. When the steam-pressure exceeds its normal
standard, the water will be forced into the tubes e, e², and, through the latter, into
the reservoir el, so that the boiler A and pipe A¹ may be emptied between the
levels x- and y-y. But, by that time, the water will have reached the highest
level it is capable of attaining in the reservoir e¹, which level, however, (by reason
of the above-mentioned capacity of the said reservoir e¹) will still be below the
upper end of the tube e; so that after the water, contained in the said tube e, has
been forced back, an escape of steam from the boiler will take place through the
lower orifice of such tube e, which steam will be at liberty to pass off into the
atmosphere through the tube ex. The moment the steam has thus escaped,
the pressure in the boiler will become lower, and, by reason of the difference
between the levels x-x11 and y-y, the water from the reservoir e¹ will re-enter
the boiler through the pipe e², and soon close the lower orifice of the tube e, thereby
stopping any further escape of steam, so that the pressure may rise again to its
normal degree. From the foregoing statement it follows that the relative position
of the reservoir e¹ may be determined by considering a level such as xxl as the
level corresponding to the steam-pressure which from considerations of safety
should in no case be exceeded.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we claim
:-
1. A low-pressure boiler constructed or operating substantially as herein
described and comprising a shell, such as A, a steam-intercepting chamber, such
as A', and regulating devices, such as B, C and D, for controlling the supply
of air to the grate, and the draught through the furnace, in conjunction with a
safety-device, such as E, for ensuring the supply of water to the boiler under
all conditions of working.
2. In a low-pressure boiler of the character herein referred to, the employment
of a revoluble grate constructed or operating substantially as herein described
and whereby the operation of stoking is facilitated.
3. The herein described means for operating the fire-box and ash-pit doors;
whereby the latter door is secured against opening until the former is released,
when the opening of the ash-pit door simultaneously effects the opening of the
fire-box door.
4. In a low-pressure boiler having a closed ash-pit, controlling the supply of
air to the grate by means of steam taken direct from the boiler and which
operates, through the medium of suitable mechanism, a regulating valve or
damper, substantially as herein described.
5. In a low-pressure boiler of the character herein referred to, the employment
of a controlling device for regulating the supply of air to the grate, comprising
mercury chambers 6 and 6' in communication with each other by way of the pipe
3, the chamber b being placed at a lower level than the chamber b¹ and having the

page_text: steam pipe led thereto, while the chamber 61 is provided with a float connected by
a suitable arrangement of levers to a rod which supports the dome-shaped damper
Lox, substantially as set forth.
6. In a low-pressure boiler of the character herein referred to, the improved
means for regulating the draught through the furnace, same consisting of a damper,
such as c, operated by a counter-weighted lever, the latter being controlled by the
water of condensation, substantially as set forth.
7. For employment in connection with a low-pressure boiler of the general
character herein referred to, a safety-device constructed or operating substantially
as described with reference to Fig. 9 of the accompanying drawings, and whereby
the supply of water to the boiler is maintained.
8. The combination, with a low-pressure boiler, of a steam-intercepting chamber
A¹, an air-controlling device B and draught-regulating appliance C, arranged or
operating substantially as and for the purposes specified.
9. The combination, with a low-pressure boiler, of a steam-intercepting chamber
A¹, an air-controlling device B, a draught-regulating appliance C and a ventilating
device D, arranged or operating substantially as and for the purposes specified.
Dated this 17th day of March, 1898.
For the Applicants,
G. G. M. HARDINGHAM,
Chartered Patent Agent, 191, Fleet Street, London, E.C.