CERTAIN IMPROVEMENTS IN THE STEAM ENGINE AND THE STEAM BOILER
Year: 1857

page_text: LETTERS PATENT to Thomas Craddock, of 137,Tachbrook Street, Pimlico,
in the County of Middlesex, Engineer, for the Invention of "CERTAIN
IMPROVEMENTS IN THE STEAM ENGINE AND THE STEAM BOILER,"
Sealed the 20th October 1857, and dated the 24th April 1857.
PROVISIONAL SPECIFICATION left by the said Thomas Craddock at the
Office of the Commissioners of Patents, with his Petition, on the 24th
April 1857.
I, THOMAS CRADDOCK, of 137, Tachbrook Street, Pimlico, in the County of
Middlesex, Engineer, do hereby declare the nature of the said Invention for
"CERTAIN IMPROVEMENTS IN THE STEAM ENGINE AND THE STEAM BOILER," to be
as follows:-
My Invention consists in or refers to a mode whereby the evil effects of
priming and those resulting from the steam becoming moist in its passage
through the engine(especially so when the steam is used in two or more cylin-
ders successively, as in my engines and those known as the Woolf engines,
is prevented, and any desired temperature, not being greater than that of
the steam by which the object is attained, can be imparted to the working
steam previous to its entering the cylinder, wheather there be one or more
more cylinders receiving the same steam in succession.
By my mode of applying steam for this purpose I am able to regulate at
pleasure the temperature it is most desirable to give the working steam on
[Price 1

page_text: its entering each working cylinder in succession; I am also able to so regulate
the heat imparted to the steam without rendering any obstruction or causing
any delay in its passage from the boiler to the first cylinder, or in its passage
from one cylinder to another, so that expansive engines will work with these
improvements in the same way as at present. I effect this improvement by
the agency of steam, which steam may either be that generated in the saine
boiler as generates the steam to drive the engine, or there may be a seperate
boiler for the purpose. The steam in either case is made to impart heat to
the working steam which is passing either from the boiler to the cylinder
or on its passage from one cylinder to another,) so, as above explained, I
have complete controul over the degree of heat which the working or
expanding steam cau receive. This is effected by causing the expanding
or moist steam to pass in a minutely subdivided state over metallick surface
heated by the non-expanded steam, the pressure and temperature of such
non-expanded steam being varied at pleasure.
SPECIFICATION in pursuance of the conditions of the Letters l'atent, filed
by the said Thomas Craddock in the Great Seal Patent Office on the
24th October 1857.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
CRADDOCK, of 137, Tachbrook Street, Pimlico, in the County of Middlesex,
Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-fourth day of April, in the year of our
Lord One thousand eight hundred and fifty-seven, in the twentieth year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said Thomas Craddock, Her special licence that I, the said Thomas
Craddock, my executors, administrators, and assigns, or such others as I, the
said Thomas Craddock, my executors, administrators, and 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 "CERTAIN
IMPROVEMENTS IN THE STEAM ENGINE AND THE STEAM BOILER," upon the condition
(amongst others) that I, the said Thomas Craddock, my executors or adminis-
trators, by an instrument in writing under my, or their, or one of their
hands and seals, should particularly describe and ascertain the nature of the

page_text: said Invention, and in what manner the same was to be performed, and cause
the same to be filed in the Great Seal l'atent Office within six calendar
months next and immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Thomas Craddock, do hereby declare
the nature of my said Invention, and in what manner the same is to be
perforined, to be particularly described and ascertained in and by the
following statement and accompanying Drawings, that is to say:―
This Invention, which is supplementary to other Invention of mine, for
which I obtained Letters Patent, bearing date March 16th, 1840, December
2nd, 1846, October 1st, 1842, September 2nd, 1854, and the 3rd April 1857,
has for its object the realization of great economy in the use of high-pressure
steam used expansively; this is effected by drying or superheating the steam
on its way from the boiler to the first cylinder, and also on its subsequent
passage to a second or other cylinders, and is done by causing the working
steam to pass through a number of small tubes which are heated by high-
pressure steam, generated either in a small boiler on purpose, as shown in the
accompanying Drawing, or by steam from the same boiler that works the
engine; these means act in conjunction with the other appliances described
hereafter in this Specification, and which control the temperature and pressure,
so as to obtain the desired result.
The same letters, as far as possible, refer to the same parts throughout the
Figures (except Figures 1 and 2); all the Figures are to a scale of one inch
to the foot.
In Fig 1 is shown a sectional elevation of the drying or superheating appa-
ratus,exhibiting its mode of construction and action. (This Fig. and Fig. 2 may
be taken either as full or half size). Figure 2 is a balf plan. c and d represent
the two plates into which the small tubes e, e, are inserted, as seen in Fig. 2
in plan. The parts c and d are supposed to be made of copper, and also the
Sinall tubes c, e; these tubes e, e, are inserted in the same way as in my con-
densers, but instead of the parts c and d being immersed in melted tin, as in
my condenser, hard solder is used. With the tubes so inserted, c and d fit into
a small cylinder, prepared in the manner shown in Fig. 1, so that the parts a,
6, and c form steam-tight junctions at c' and c', and also d, f, and bat d'
and d
The superheating steam enters the small cylindor through the ports or
pipes s, t, or a, and the water resulting from condensation returns to the
bottom of the superheating boiler (see Figs. 5, 6, 7, and 8,) through the ports
or pipes o, u, and y, and the pipes y, y, whilst the steam from the boiler which
drives the engine, see Fig. 4, enter the superheating apparatus at a, passes

page_text: through the small tubes e, e, and enters the cylinder through f, and a' and
all; on the steam passing from the high-pressure cylinder to the low it passes
through all to the branch fof the second superheating apparatus, from thence
it passes through a similar arrangement of copper tubes, as before explained,
and which, as in the former instance, are also surrounded by the superheating
steam from the superheating boiler, Fig. 5; on the steam arriving at a it
passes through the passage cast in the cylinder, as indicated by the dotted
lines, to d, e, in the low pressure cylinder face, from whence it is directed to
the top or bottom of the low-pressuro cylinder in the ordinary manner, or in
thic manner described in my former Specifications.
It is necessary to remark here, that when the second superheating appa-
ratus is used, as seen in Fig. 3, then the high-pressure valve 5 should bo
divided into two parts; the part connected with e and e' anda, and which
in my Specification of April 3rd, 1857, is called g, should be connected with
the low-pressure valve eccentric, so as to move along with the low-pressure
valve, and thereby regulate the flow of steam from the high-pressure
cylinder to the low, according to the requirements of the latter. The steam
valves are not shown on their faces as I have so fully described them in my
previous Specification, as to render further description of their action here
unnecessary. At 4' and 4, Fig. 3, is seen a valve, which for the convenience
of illustration is turned on its side opposite to the ports, the hollows of it
inclose, and it is there in section; if this valve be turned upon its face the
hollow 1 will incloset and s, the steam coming from the superheating boiler
through the pipe will arrive at t, and by the hollow of the valve 1' will be
directed to the top of the superheating cylinder b, whilst the water from con-
densation will by the hollow 2 and the ports u and pass through the pipe y
to the bottom of the superheating boiler, Fig. 5, as before. By this arrange-
ment it is not merely contemplated to superheat the steam, but also to give to
it any desired temperature at pleasure; for this purpose the valve 4' and the
arrangement shown Fig. 9, 10, and 11 are introduced.
Fig. 9 is a regulating damper, constructed as will be seen after the peculiar
arrangement of india-rubber and metal, which formed part of my Patent of
April 3rd, 1857, and is here combined with an air vessel . 6, 6, couples
the two pistons together; the one piston is at the bottom of the air vessel
and the other at the top of the part w; the air vessel 2 and the part w
are connected together by two small columns. 7 is a lever, having its
fulcrum at 8, the one end attached to the part 6, 6, and the other to the rod
10, which is connected to the lever 11 and damper 12; the action of this
apparatus is as follows:-The vessel z being full of air, either of an ordinary

page_text: density or any desired artificial density, a pipe having a tap in it being
inserted at 5, and the other end in communication with the boiler, Fig 5,
with the provision for keeping the water cold, so fully explained in my pre-
vious Specifications, ou opening the tap leading to Fig. 5 any pressure can be
given to the air in the vessel equal or inferior to that in the boiler, Fig. 5,
whilst by another pipe at which also communicates with the boiler, having
also the same provisien for keeping it cold as before explained,it will be seen
that the pistons and rod 6, 6, will rise or fall as the pressure in or wis the
greater,and thus open or close the damper 12 in such a way as to keep the
pressure of the steam in the boiler, Fig. 5, at any desired temperature, and
so govern the temperature of the superheated steam passing to the super-
heating apparatus. Fig. 10 is identical in figure and construction with Fig.9,
already described. The rod 10 in Fig. 10 is supposed to be connected with
the valve 4' in Fig. 3, but is shewn broken off. The use of this apparatus
is to give to the superheating steam any lower pressure and temperature that
may be desired than what it has in the boiler, Fig. 5. This is best illustrated
by supposing 150 lbs. pressure in the boiler, Fig. 5, whilst it is desired to have
40 lbs. or 50 lbs. only in the second or low-pressure superheating apparatus.
This end is attained by charging the air vessel with air or air and water to a
pressure of 40 or 50 lbs., as the case may be; it will then through the action
of the piston and rod 6,6, keep the valve in such a position that will main-
tain the pressure of 40 or 50 lbs. in the superheating apparatus referred to.
In this way any pressure lower than that in the boiler, Fig.5, may be given at
pleasure to the second superheating apparatus, but if this lower pressure be
thus maintained, then the water resulting from condensation and passing out
aty would require to be pumped by a small pump back into the boiler, Fig.5.
The apparatus described in my Specification, April 3rd, 1857, as that of a
water indicator or regulator, will, if applied to this second superheating
apparatus, with a cock or valve to the pipe y, allow the water to flow out as
it is accumulated without permitting the steam to escape, as by the weight of
a short column of water the requisite action is produced,and consequently the
tap or valve would remain closed when the water was not in excess, and when
the water was in excess the reverse action would ensue.
In Fig. 11 is shown another mode of effecting the same object as that
obtained by Figs. 9 and 10. In this case weights are substituted for the air
ve-sel z, and it is obvious that a spring can be substituted for either of the m
but after many years experience with the air vessel for such purposes I
believe it to be the best. These pistons also may be of slightly different arears,
and thereby diminish the amount of weight or force required to resist the

page_text: s team. This mode, although very good in connection with the action of
valves, is not so well suited for the purpose under consideration, as here we
require delicacy of action conjoined with some considerable amount of force;.
this it will be seeu will be obtained by such means as are shewn.
In the boiler, Fig. 5, which is a modification of those patented and
described in my Patent and Specification of April 3rd, 1857, there are some
peculiarities which require notice here, as it will be seen in plan, Fig. 7, and
end elevation, Fig.S, that the tubes are so bent or arranged as to contract the
end,shown in Fig. 8, so that the products of combustion pass through d,d,out
of the fire box and interior flue into the passage j.j, there imparting heat to
the exterior of the boiler.
The peculiarity of construction from which this result is obtained is so
clearly set forth in Fig. 7 and Fig. S as to need but little further explanation
and it will be seen that whilst such a boiler affords ample grate and heat-
absorbing surface,it is, from its thoroughly tubular mode ofconstruction,equal
to any pressure, even that of 1,000 lbs. on the square inch if it was desired.
,, is the fire grate, which may be extended farther if required; e, e, the
tubes; d, d, the internal flue; g,g, the external flue; k, k, hollow brick and
slicet iron casing; P, p, the smoke box; 2, q, the fire doors; r, r, the ash-
pits; i, one end of the top chamber, the bottom one being exactly aliko; ",
the steam chest; a, the steam pipe. It is an essential condition of my mode
of drying or superheating the steam that the steam to be heated or dried is
made to pass through very small tubes, of from to diameter, whilst the
hotter steam acts on the exterior of these tubes. By such means any desired
temperature is given to the steam working the engine by its passing through
these small tubes. From this complete subdivision and the large surface of
heated metal the working steam is thus brought into contact with, good and
controulable results are obtained in the most suitable way to fulfil all the
practical conditions, which must be attended to, to render the superheating
of steam at all valuable in practice.
The mode here described is equally
applicable to the heating of air as steam, and also to high or low-pressure
steam engines of every class.
In Fig. 3 the cylinders are shewn cast together, as that is the most diffi-
cult form in which to apply the superheating apparatus; but the super-
heating apparatus may be applied to the cylinders at any distance apart,
or any number of them.
In Fig. 1, 9, 9, and h, h, are lids which give ready access to the interior
of the copper tubes e, e; by this means, and the general arrangement of the
parts of the superheating apparatus, Fig. 1, it is adapted to admit of ready

page_text: connection to the steam pipes of any engine, the branches a and f fitting on
to the flanges of the steam pipes, whilst the superheating apparatus & need
not be but so much larger in area as to admit of the saine area through the
small pipes e, e, for the passage of the steam to the working cylinder as that
of the steam pipe. The length of the copper tubes and chamber b, b, can be
such as required, but are shewn broken off in Fig. 1.
Having explained the object and nature of my Invention, I observe that
I do not confine myself to the exact detail in the arrangements here given;
but I claim,
Firstly, so arranging and constructing a steam drying or superheating
apparatus as in the manner shewn in Fig. 1, and 2, and 3; the steam to be
heated is in a minutely subdivided stato made to pass through small pipes.
as described,whilst hotter steam is acting on the exterior surface of the so
subdividing pipes.
Secondly, I claim the peculiar method or methods shown in Figs. 5, 6, 7,
8, 9, 10, and 11, by which the superheating effect is produced and regulated
in conjunction with the other arrangements shown.
I further claim the arrangement scen in Figs. 5, 6, 7, 8, 9, 10, and 11,
whether such are used in conjunction with Figs. 1, 2, and 3, or otherwise.
In witness whereof, I, the said Thomas Craddock, have hereunto set
hand and scal, this Twenty-third day of October, in the year
of our Lord Oue thousand eight hundred and fifty-seven.
my