IMPROVEMENTS IN STEAM BOILERS
Year: 1870

page_text: LETTERS PATENT to James Noah Paxman and Henry Matthews Davey,
of the Firm of Davey, Paxman, and Davey, of Colchester, in the
County of Essex, Engineers, for the Invention of "IMPROVEMENTS IN
STEAM BOILERS,"
Sealed the 17th January 1871, and dated the 19th July 1870.
PROVISIONAL SPECIFICATION left by the said James Noah Paxman
.
and Henry Matthews Davey at the Office of the Commissioners of
Patents with their Petition, on the 19th July 1870.
We, JAMES NOAH PAXMAN and HENRY MATTHEWS DAVEY, of the
Firm of Davey, Paxman, and Davey, of Colchester, in the County of
Essex, Engineers, do hereby declare the nature of our said Invention for
"IMPROVEMENTS IN STEAM BOILERS," to be as follows:-
Our improved steam boiler consists of an external shell, which may
be circular, oval, polygonal, or of other suitable construction. Within
this we put an internal fire-box, circular, oval, polygonal; or of other
suitable shape, and provided with water tubes. The said water tubes.
extend downwards from the crown plate of the internal fire-box to a

page_text: distance of about eighteen inches from the fire-grate, or at such other
distance as may be found most suitable for the combustion of any given
quantity or quality of fuel. The fire-grate is to be fixed in the bottom
of the internal fire-box. These tubes are bent at their lower extremities,
and their vent ends are inserted in the side of the internal fire-box, in
which, as well as in the crown plate, orifices are made for that purpose,
the tubes being tapered or made smaller at their bent ends for the
purpose of diminishing the rapidity of the circulation which takes place
through them when the boiler is at work, and also to avoid weakening
the fire-box by having large openings for the insertion of these tubes.
The sides of the fire-box at the level where the aforesaid tubes are fixed
we prefer to incline, so that the tubes may enter them at any angle
which may be necessary for our purpose. This arrangement will also
prevent leakage from the tubes. The outer shell of the boiler being
parallel with the upper or principal portion of the internal fire-box we
thereby obtain the advantage of a large space for the accumulation of
deposit or sediment in a locality where it can do no harm; and the
water passing through the tubes from a source where little ebullition
goes on is more dense than it would be in the absence of the increased
space provided by the peculiar shape of the fire-box, and therefore better
adapted to absorb heat from the products of combustion. At the upper
end of the tubes we fix plates for controlling the circulation of the
water. These plates may be flat, saucer, or bell shaped, & attached to
the crown of the fire-box or suspended from the top of the boiler, but
we prefer cones with mushroom heads and having projecting ribs, which
cones are placed or fixed in the top of the tubes, and which confine the
current of water to the size of the tubes, while they allow free egress
for the water, which striking against the mushroom head is directed
downwards or into its proper channel. By the aid of fire dispersers we
cause the flame and heated air to circulate among the tubes. The
internal fire-box may be made of corrrugated iron suitably stayed to
the outer shell, and we then arrange certain of the internal water tubes
with contracted lower orifices, as before described, so that the vertical
portions of the said tubes may correspond with and adapt themselves
to the hollows or corrugations in the internal fire-box, a convenient
space intervening between the fire-box and the tubes. We also in
certain cases use internal circular tubes with contracted ends, as before
described, which tubes may be corrugated externally in order to present
a larger surface to the action of the flame, and we in such case by pre-

page_text: ference dispose the tubes so that a free equal space may be left between
them for the play of the heated gases and flames, the projecting or belly
parts of one tube being set opposite the hollow parts of the next. In
large boilers we use two or more rows of tubes, the upper row or rows
having contracted or tapered ends, which are inserted into the upper
vertical or nearly vertical sides of the internal fire-box. We also in
certain cases combine the internal water tubes before described with
one or more vertical fire tubes leading from a smoke box submerged or
not as may be most convenient. The said tubes, however, we prefer to
pass to a non-submerged smoke box, so that the upper ends may act as
superheaters for drying the steam.
In order to further contract the lower water passage of the internal
tubes before described we sometimes use discs or cones supported on
three or more projections, and inserted into the tubes. These discs or
cones may be or may not be perforated. The mushroom caps at the
upper ends we in certain cases place in connection with tubes leading
from the mushroom caps to the space intervening between the internal
fire-box and the outer shell, that the water rising with the steam may
be conducted back to the lower part of the boiler. In some cases we
combine the use of the mushroom caps before described with trumpet
mouths adapted to the upper end of the aforesaid internal water tubes,
and in other cases we use internal tubes disposed in connection with
the trumpet mouths, that the water carried up and dispersing on the
mushroom caps is carried down again through the interior of the tubes;
and this arrangement will be found especially applicable to those cases
in which the outer water space, or that intervening between the two
shells, is reduced to save space. We also apply the said water tubes
with contracted or tapered ends to horizontal boilers having internal
flues.
› SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said James Noah Paxman and Henry Matthews Davey
in the Great Seal Patent Office on the 19th January 1871.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, JAMES
NOAH PAXMAN and HENRY MATTHEWS DAVEY, of the Firm of Davey,
› Paxman, and Davey, of Colchester, in the County of Essex, Engineers,
send greeting.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Nineteenth day of July, in the year
of our Lord One thousand eight hundred and seventy, in the thirty-
fourth year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto us, the said James Noah Paxman and Henry Matthews
Davey, Her special license that we, the said James Noah Paxman and
Henry Matthews Davey, our executors, administrators, and assigns, or
such others as we, the said James Noah Paxman and Henry Matthews
Davey, our executors, administrators, or assigns, should at any time
agree with, and no others, from time to time and at all times thereafter
during the term therein expressed, should and lawfully might make, use,
exercise, and vend, within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention for
"IM-
PROVEMENTS IN STEAM BOILERS," upon the condition (amongst others) that
we, the said James Noah Paxman and Henry Matthews Davey, our
executors or administrators, by an instrument in writing under our
hands and seals, or under the hand and seal of one of us, should par-
ticularly describe and ascertain the nature of the said Invention, and
in what manner the same was to be performed, and cause the same to
be filed in the Great Seal Patent Office within six calendar months next
and immediately after the date of the said Letters Patent.
.
NOW KNOW YE, that I, the said James Noah Paxman, on behalf
of myself and of the said Henry Matthews Davey, do hereby declare the
nature of our said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement, reference being had to the accompanying Drawings,
and to the letters and figures marked thereon, that is to say :-
'
Our said Invention relates to vertical as well as horizontal boilers,
and consists, as regards vertical boilers, of an external shell, which may
be circular, oval, polygonal, or other suitable shape. Within this we
introduce an internal fire-box of a circular, oval, polygonal, or other
suitable form, and provided with water tubes. The said water tubes
extend downwards from the crown plate of the internal fire-box, into
which they are expanded to a distance of about eighteen inches from the
fire-grate, or at such other distance as may be found most suitable for the
purposes of combustion. The fire-grate is to be fixed in the bottom of
the internal fire-box. These tubes are bent at their lower extremities,
and their bent ends are inserted into the side of the internal fire-box, in.

page_text: which, as well as in the crown plate, orifices are made for that purpose.
The said tubes are tapered or made smaller at their bent ends only for
the purpose of diminishing the rapidity of the circulation which takeś
place through them at their upper ends when the boiler is at work, of
avoiding the weakening of the fire-box by having large openings for
the insertion of the tubes, and also of causing a strong scouring action
in the bent ends or those parts of the tubes which are most exposed to
the fire, thereby preventing incrustation. In large boilers we prefer to
incline the sides of the fire-box at the level where the aforesaid tubes
are fixed, so that some or all of the tubes may enter them at any con-
venient angle. This arrangement will also tend to prevent leakage from
the tubes by affording a greater protection from the direct action of the
cold air. Moreover, from the fact of the outer shell of the boiler being
parallel with the upper or principal portion of the internal fire-box we
obtain the further advantage of a large space for the accumulation of
deposit or sediment in a locality where it can do no harm, and the
water passing through the tubes from a source where little ebullition
goes on is more dense than it would be in the absence of the increased
space provided by the inclined sides of the fire-box, and is therefore
better adapted for absorbing heat from the products of combustion. At
the upper end of each of the tubes we fix a plate for controlling and
directing or diverting the circulation of the water. These plates may
be flat, saucer, or bell-shaped, or of any other convenient form, and
may be attached to the crown of the fire-box or suspended from the
top of the boiler, but we prefer to use cones provided with mushroom
heads and having projecting ribs, which cones are placed or fixed in
the tops of the tubes, and tend to confine the current of water to the
sides of the tubes whilst allowing free egress for the water, which,
striking against the mushroom head, is directed downwards or into its
proper channel, again thereby reducing the tendency to priming. These
mushroom caps or deflecting plates may obviously be applied to ordinary
or other water tubes in steam generators, whether the same be of the
vertical or horizontal construction. By the aid of fire dispersers we
cause the flame and heated air to circulate among the tubes before
referred to. The internal fire-box may be made of corrugated iron
suitably stayed to the outer shell, and we then so arrange certain of the
internal water tubes with contracted lower orifices, as before described,
that the vertical portions of the said tubes may correspond with and
adapt themselves to the vertical hollows of the corrugations in the fire-

page_text: box, a convenient water space intervening between the fire-box and the
tubes. We also in certain cases use corrugated internal circular tubes
with contracted lower ends, as before described, the corrugations being
arranged annularly, whereby a larger surface is presented to the action
of the flame, the tubes being by preference so disposed that a free equal
space may be left between them for the circulation of the heated gases
and flames, the portions of larger diameter of one tube being set opposite
the smaller parts of the adjoining tube or tubes so as to break joint.
In large boilers we use two or more series of tubes, the said tubes being
contracted or tapered at their lower bent ends, and having their upper
extremities inserted into the upper part of the internal fire-box. If
desired the internal water tubes before described may be combined with
one or more vertical fire tubes leading from a smoke box submerged or
not as may be most convenient. The said tubes, however, we prefer to
pass to a non-submerged smoke box, so that the upper ends of such
tubes may act as superheaters for drying the steam.
In order to further contract the lower water passage of the internal
tubes before described we sometimes use discs or cones provided with
three or more projections, and inserted or fixed into the lower bent taper
ends of the said tubes. These discs or cones may be or may not be
perforated. In some cases we connect with the aforesaid mushroom
caps bent tubes, one end of such bent tubes being fixed in the cap
(which in this case is perforated), whilst the other end of the tube
terminates in the water space between the outer shell and the fire-box
of the boiler, so that the water rising with the steam up the water tubes
may be conducted back to the lower part of the boiler. As regards
horizontal boilers we apply the said water tubes with bent tapered
ends and mushroom-shaped caps or deflectors, either to internal flued
horizontal boilers or to boilers with external flues, the tubes with their
deflectors being fixed in such manner as to promote circulation of the
water, and prevent the accumulation of deposit in those parts of the
boiler most exposed to the action of the fire. For the purpose of
getting at the lower or tapered ends of the said tubes in order to repair
or remove them in certain cases of small vertical boilers where the
tapered end of the tube is attached to the fire-box in the usual manner,
namely, by expansion, we bolt the bottom of the fire-box to the bottom
of the shell of the boiler, and also bolt the up-take to the crown plate
of the shell of the boiler, by which means facility is afforded for

page_text: removing at pleasure the whole fire-box and tubes entire from the
interior of the boiler shell. In most cases, however, especially in larger
boilers, we prefer to cut a thread on the tapered end of the tube, and
also in the corresponding hole in the fire-box; these we connect by
means of a screw connection containing right and left-hand threads,
thereby joining the tube to the fire-box in the one act of screwing, and
enabling us in such case readily to disconnect the bottom end of the
tube from the inside of the fire-box without injury to the same or
necessity for removing the fire-box itself. No caulking on the outside
of the same is necessary, whilst at the same time the top end of the tube
is easily accessible from the man-hole.
For the purpose of obtaining a greater amount of heating surface in
boilers we in some cases prolong the central vertical flue or smoke
chamber downwards inside the fire-box, and encircle it with a casing-
joined to the bottom of the flue or smoke chamber at one end, and
attached to the crown plate of the fire-box at the other end, thereby
obtaining an extra water space and heating surface round the said
smoke chamber or flue, which is thus to a certain extent submerged.
Certain of the bent tubes with lower tapered ends may be attached
thereto as may be deemed advisable, and a baffle plate or disperser may
be fixed in such a manner as practice will determine for the better
dispersion of the heat and the more perfect retention of the same about
the heating surface.
. And in order that our said Invention may be fully understood I shall
now proceed more particularly to describe the same, and for that pur-
pose shall refer to the several Figures on the annexed Sheet of Drawings,
the same letters of reference indicating corresponding parts in all the
Figures.
Figure 1 of our Drawings represents a side or external elevation of
one of our improved vertical boilers; Figure 2 is a corresponding plan
of the same, both these views shewing the adjusting gear for regulating
the position of the baffle plate or disperser; Figure 3 is a vertical
sectional elevation of the said boiler; Figure 4 is a horizontal section of
the same taken along the line 1-2 in Figure 3, and shewing the crown
of the fire-box in plan.
In the Figures above enumerated, which are drawn to a scale of one
and a half inches to one foot, A represents the outer shell of the boiler

page_text: and B the fire-box, which is bolted, as shewn at a, a, (Figure 3) to the
outer shell at or near the bottom thereof, whilst to the centre of the
crown of the fire-box there is rivetted the up-take or flue C, which is
fitted with an annular flange at 6, whereby the said flue is bolted to
the crown of the outer shell of the boiler, as shewn clearly in Figure 3.
Round the interior of the fire-box there are disposed a number of bent
water tubes D (two of which only are shown in Figure 3). These tubes
are parallel throughout the greater portion of their length, and áre
tapered only at their lower bent ends. The upper ends of these tubes
are expanded or otherwise secured into the crown plate of the fire-box,
- whilst their lower bent and contracted or tapered ends are secured in
any convenient manner to the vertical sides of the fire-box. We prefer
to effect this connection by means of the combined screw and nut shewn
on an enlarged scale in detail section and elevation at Figure 5. The
projecting portion c of the screw nut has an external screw thread
formed thereon, which screws into a tapped hole made through the side
of the fire-box; a second screw thread (but in the reverse direction to
that at c) is made inside the nut, as shewn in the sectional view at d.
Into this last-named screw there is introduced the taper bent end of
the tube D, whilst the screwed part c of the connection or coupling is
screwed into the side of the fire-box, the act of screwing in such
coupling serving at the same time to draw home the screwed taper bent
end of the tube D inside the nut, thereby affecting a perfect joint, which
can be made and unmade as may be found requisite with the greatest
To the top of each tube D there is fitted the mushroom cap or
deflector E, one of which is shewn in detail elevation on an enlarged
scale inserted into a tube end at Figure 6, and in cross section taken
through the end of the tube at Figure 7. e represents the expanded.
portion of the head, and fa short tapered stem provided with projecting
ribs g, g, which stem is fitted into the upper mouth of each tube D, the
projecting ribs & leaving sufficient space for the upward circulation of the
water from the end of the tube, whilst the expanded or overhanging mush-
room head e deflects the current downwards and laterally. If desired a
plug having ribs thereon, and with or without a perforation therethrough,
may be driven into the lower end of the water tube, as shewn at e in
Figure 7, in order to ensure a scour or rapid circulation through the
lower bent end of such tube. F is the baffle plate or heat disperser,
which is adjustable towards or from the mouth or entrance to the central
flue C by means of the rod h, lever i, screwed spindle %, and hand wheel
case.

page_text: nut . G is the stoke hole; H, the man-hole; I, the mud holes; and
K, the fire-bars.
Figure 8 represents a vertical section of a larger size of vertical boiler
provided with three series of tubes, and drawn to a scale of one inch to
one foot; and Figure 9 is a horizontal section of the same taken along
the line 3-4 in Figure 8, shewing the top or crown of the fire-box in
plan view, with the numerous mushroom-shaped deflectors in their
places. Figure 8 shews the inclination inwards of the sides of the
fire-box at the lower portion thereof, whereby we obtain an annular
chamber m of increased area at the bottom of the boiler for the accu-
mulation of deposit, whilst, moreover, the water which passes through
the tubes D in connection with such enlarged annular chamber m will
be in a more quiescent state, and therefore denser and better adapted for
absorbing heat. D, D, D, represents the three series or concentric circles
of tubes, which descend to different depths along the fire-box sides.
L (Figure 9) is the fire-door frame. Figure 10 represents a vertical
section of a vertical boiler drawn to the same scale as the last two
Figures previously referred to; and Figure 11 is a horizontal section of
the same taken along the line 5-6 in Figure 10. In Figure 10. we
have represented the central flue or smoke chamber C as being pro-
longed or extended downwards into the chamber of the fire-box to
within a moderate distance, say eighteen inches, from the surface of the
fire-grate, and have shewn this extended portion of the flue or smoke
chamber as being enclosed in or surrounded by an annular water
space n, the sides of which are secured to the crown of the fire-box at o,
and to the bottom of the flue at p.. One or more series of bent tapered
tubes D¹, D', may be made to communicate with the lower portion of the
central annular water space n in addition to the other tubes D, which
communicate with the vertical sides of the fire-box, and all these tubes
are provided with deflectors E, as shown in our Drawings. Above the
top of the central annular water space n there is fitted, when found
requisite, round the flue C an annular deflector E¹ for the purpose of
arresting or controlling any undue or over energetic circulation of the
water in the said water space n, the said annular deflector being made
so as to be capable of adjustment higher or lower as required. The
baffle plate or heat disperser F, which serves to direct the flames and
heated gases amongst the tubes, in lieu of allowing them to pass
directly up the chimney, may be composed either of cast iron, as shewn
3

page_text: in Figures 3 and 8, or of fire-brick, as indicated in Figure 10, and will
be found serviceable also for regulating or controlling the draught.
We are aware that bent water tubes have been applied to the fire-
boxes of steam generators, and that in some cases such tubes have been
made with a gradual taper from one end to the other for the purpose of
facilitating the free egress of the steam as fast as it is generated, and
therefore we lay no general claim to the use of tapered water tubes.
Our improved tubes are made parallel throughout the greater portion
of their length, the taper or contracted portion existing only at their
lower bent end, or that end through which the colder water first enters
such tube, the essential object of such contraction being the imparting
of a more effectual and stronger scouring action to the current of water at
that part of the tube wherein deposit or incrustation is most likely to
take place, thereby preventing the collection of deposit or incrustation
in the lower part of the said tubes.
Having now described and particularly ascertained the nature of our
said Invention, and the manner in which the same is or may be used or
carried into effect, I would observe in conclusion that what WO̟ consider
to be novel and original, and therefore claim as the Invention secured to
us by the herein-before in part recited Letters Patent is,-
First. The application and use to and in steam ge ierators of water
tubes made parallel throughout the greater portion of their length, and
contracted or tapered at their lower bent ends only in combination or
not with deflecting plates or mushroom-shaped caps, substantially as and
for the purpose herein-before described.
Second. The application of a plug or its equivalent, perforated or not,
to the lower end of a water tube in a steam generator, so as to partially
close the same, for the purpose herein-before described.
Third. The application and use of deflectors to and in the upper ends
of ordinary water tubes of steam generators, substantially as and for the
purpose herein-before described.
Fourth. The combination of bent water tubes contracted at their lower
bent ends only with deflectors, substantially as and for the purpose
herein-before described.

page_text: Fifth. The combination with an annular water space in a steam
generator of an annular deflector for dispersing the water as it rises
from the annular water space, substantially as herein-before described.
In witness whereof, I, the said James Noah Paxman, on behalf of
myself and of the said Henry Matthews Davey, have hereunto
set my hand and seal, this Seventeenth day of January One
thousand eight hundred and seventy-one.