CERTAIN IMPROVEMENTS IN STEAM ENGINES
Year: 1864

page_text: LETTERS PATENT to William Martin, of the City of Manchester, Manager,
and Joseph Hodgson, of the same Place, Engineer, for the Invention of
"CERTAIN IMPROVEMENTS IN STEAM ENGINES."
Sealed the 23rd September 1864, and dated the 31st March 1864.
PROVISIONAL SPECIFICATION left by the said William Martin and
Joseph Hodgson at the Office of the Commissioners of Patents, with
their Petition, on the 31st March 1864.
We, WILLIAM MARTIN, of the City of Manchester, Manager, and JOSEPH
HODGSON, of the same Place, Engineer, do hereby declare the nature of the
said Invention for "CERTAIN IMPROVEMENTS IN STEAM ENGINES," to be as
follows:-
The object of our improvements in steam engines is to make all the steam
admitted into the cylinder available as motive power, and to entirely dispense
with resistance at the cylinder ends, thereby gaining considerable advantage
over the ordinary steam engines.
The manner of performing our Invention is as follows:-We employ two
pistons, each of a segmental form, working in a cylinder; these pistons are on
two shafts joining each other, or the one passes through the other, and instead
of the pistons moving in a straight line as usual, the steam is admitted
between the two segmental pistons, causing them to recede from and approach
each other in the arc of a circle in the cylinder, the aforesaid shafts being the
centre. The pistons are connected to a crank shaft by connecting rods jointed

page_text: to cranks on the shafts of the pistons, and to the cranks on the crank shaft.
The pistons are kept steam-tight by suitable packings, and the slide valves
are constructed and worked in the usual manner. This arrangement is
applicable to stationary, marine, locomotive, high-pressure, condensing, and
compound engines.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Martin and Joseph Hodgson in the Great Seal
Patent Office on the 28th September 1864.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, WILLIAM
MARTIN, of the City of Manchester, Manager, and JOSEPH HODGSON, of the
same Place, Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirty-first day of March, in the year of our
Lord One thousand eight hundred and sixty-four, in the twenty-seventh year
of Her reign, did, for Herself, Her heirs and successors, give and grant
unto us, the said William Martin and Joseph Hodgson, Her special license
that we, the said William Martin and Joseph Hodgson, our executors, admi-
nistrators, and assigns, or such others as we, the said William Martin and
Joseph Hodgson, our executors, administrators, and assigns, should at any
time agree with, and no others, from time to time and at all times there-
after 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 STEAM ENGINES," upon the condition (amongst others) that
we, the said William Martin and Joseph Hodgson, our executors or admi-
nistrators, by an instrument in writing under our, or their, or one of our or
their hands and seals, should particularly 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 we, the said William Martin and Joseph Hodgson,
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 (that is to say) :-
The object of our improvements in steam engines is to make all the steam

page_text: admitted into the cylinder available as motive power to dispense with resist-
ance at the cylinder ends, and also to secure increased facility for expansion,
thereby gaining considerable advantage over the ordinary steam engines.
The manner of performing our Invention is as follows:-We employ two
pistons, each of a segmental form working in a cylinder; these pistons are on
two shafts joining each other, or the one passing through the other; and
instead of the pistons moving in a straight line as usual the steam is admitted
between the two segmental pistons, causing them to recede from and approach
each other in the arc of a circle in the cylinder, the aforesaid shafts being the
centre. The pistons are connected to a crank shaft by connecting rods jointed
to cranks on the shafts of the pistons, and to the cranks on the crank shaft.
The pistons are kept steam-tight by suitable packings, and the slide valves are
constructed and worked in the usual manner. This arrangement is applicable
to stationary, marine, locomotive, high-pressure, condensing, and compound
engines.
And in order that our Invention may be fully understood and readily
carried into operation, we will proceed to describe the accompanying Sheet of
Drawings, reference being had to the figures and letters marked thereon.
Figure 1 is a front elevation of a steam engine constructed according to our
improvements, and Figure 2 is a longitudinal section of the same.
a, a, are two cylinders, to which are attached the steam chests or valve
boxes b, b, containing the valves c, c, which are moved to and fro by the
eccentrics d fixed to the crank shaft e, the links f, shewn by dotted lines in
Figure 1, the elbow levers g, and links h, or in any other convenient manner.
At each end of the cylinders a is a lid provided with a stuffing boxj; the
stuffing boxes are made with bushes j', and form the journals for the axles k
and I, which are either forged or cast with the segmental pistons m, m³, or fixed
thereto; the pistons are kept steam-tight circumferentially and endwise by spring
packings, as shewn, or in any other convenient manner; the lids i have also.
a bevel projesting rim fitting the piston for the same object, and a bevel ring a
keeps the steam from the axles and stuffing boxes; these rings are also acted
upon by springs to hold them up to the recesses in the piston. The axle k is
shewn with a projecting stud k¹ fitting in a recess in the piston m² to insure
a steady motion of the axles k and l; and on referring to Figure 2 it will be
seen that these axles pass through each lid of the cylinder, but by making
one of the axles solid and the other hollow, and passing the one through the
other, both the axles may be taken through one lid of the cylinder. To each
axle.is fixed a crank n, and these cranks are connected to the cranks o on the
crank shaft e by the connecting rods p, shewn by dotted lines in Figure 1. In

page_text: Fig. 1 the pistons m, m², in the right-hand cylinder a are shewn near to each
other, or in the positions they occupy when the steam from the steam chest b
is passing down the passager into the space between them; at this time
the exhaust port 8 is partly open to convey the exhaust steam through the
passage t and valve c to the condensor or to the blow-off pipe. The pistons
in the left-hand cylinder are at about half stroke; when the pistons arrive at
the end of their strokes, as shewn by dotted lines in both cylinders, the
positions of the valves are changed to admit steam between them through the
passages t, and to convey the exhaust steam away through the passages r.
From the above description and Drawing it will be clearly understood that
the expansive force of the steam acts equally on the two pistons, and forces
them apart with the power due to the area of the pistons and the pressure of
the steam, and that the force thus exerted on both the pistons is united and
conveyed to the crank shaft, whereas in steam engines of the usual con-
struction, with a piston working in a cylinder, half the force exerted is always
acting on one of the lids of the cylinder.
Having thus stated the nature of our Invention, and described the manner
of performing the same, we declare that we claim the combination of two
segmental pistons working in a cylinder, and the arrangement of parts shewn
and described, or other suitable arrangement of parts for connecting the
segmental pistons to the crank shaft.
In witness whereof, we, the said William Martin and Joseph Hodgson,
have hereunto set our hands and seals, this Twenty-seventh day of
September, in the year of our Lord One thousand eight hundred and
sixty-four.
WILLIAM MARTIN. (L.s.)
JOSEPH HODGSON. (L.B.)