IMPROVEMENTS IN THE STEAM ENGINE
Year: 1833

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I JOHN
THOMPSON, late of the London Iron and Steel Works, and the Parade, Thames
Bank, near Chelsea, in the County of Middlesex, but now of Newhall Street,
Birmingham, in the County of Warwick, Esquire, send greeting.
WHEREAS His present most Excellent Majesty King William the Fourth,
by His Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Twenty-eighth day of February, One thousand eight hundred
and thirty-three, and in the third year of His reign, did, for Himself, His
heirs and successors, give and grant unto me, the said John Thompson, His
especial licence, full power, sole privilege and authority, that I, the said John
Thompson, my executors, administrators, and assigns, or such others as I, the
said John Thompson, my executors, administrators, or assigns, should at any
time agree with, and no others, from time to time and at all times during
the term of years therein mentioned, should and lawfully might make, use,
exercise, and vend, within England, Wales, and the Town of Berwick-upon-
Tweed, my Invention of "IMPROVEMENTS IN THE STEAM ENGINE;" in which said
Letters Patent is contained a proviso, obliging me, the said John Thompson,
by an instrument in writing under my hand and seal, particularly to describe
and ascertain the nature of my said Invention, and in what manner the same
is to be performed, and cause the same to be inrolled in His said Majesty's
High Court of Chancery within six calendar months next and immediately
after the date of the said in part recited Letters Patent, as in and by the same
-reference being thereunto had, will more fully and at large appear.

page_text: .
NOW KNOW YE, that in compliance with the said proviso, I, the said
John Thompson, do hereby declare that the nature of my said Invention,
and the manner in which the same is to be performed, are particularly
described and ascertained in and by the Drawings hereunto annexed, and the
following description thereof (that is to say) :-
My improvements in the steam engine apply, in the first place, to that con-
struction of steam engines which are commonly called semi-rotary or recipro-
cating rotary engines, that is, in which the pistons rotate or reciprocate within
annular or ring-formed. chambers. In my improved engines I employ two
pistons in each annular chamber or cylinder, the steam being admitted into the
chamber alternately on opposite sides of the pistons, and exerting its expansive
force between them and stationary steam stops, the pistons being attached to the
outer rim of the chamber or cylinder, and the steam, stops fixed in the statition-
ary drum or inner ring of the chamber; consequently the pistons and cylinder
reciprocate upon the drum, and communicate the moving power from the
engine; or the steam stops may be fixed on to the stationary outer casing or rim
of the circular chamber, and the pistons attached to the inner rim or drum,
and the moving power communicated from the engine by the shaft of the drum,
as will be fully explained hereafter.
And, in the second place, my improvements in the steam engine consist in a
new or improved construction of the air pump and condenser, applicable to
all steam engines which work upon the condensing or vacuum principle,
the piston of the air pump being constructed to rotate or reciprocate in an
annular or ring-formed chamber; all of which improvements are shewn in the
accompanied Drawings.
Figure 1 is a section taken through the cylinder of one of my improved
steam engines, with the working pistons attached to the outer rim of the
cylinder or ring-formed chamber, one of its sides being removed, the better to
shew the interior; but there are some of the outside working parts drawn in
the Figure to shew the connection of the slide valves. A, A, is the cylinder
"or ring-formed annular chamber, with its pistons B, B, connected to the outer
rim C, C, and consequently they rotate or reciprocate together upon the
stationary drum D, D, and communicate the driving power from the engine.
E, E, are the two steam stops, extending across the cylinder, and having
'metallic or other packing to prevent the escape of the steam. There is also
metallic or other packing placed at the junction of the sides of the cylinder
and the drum, which is let into the cylinder, in order to prevent the escape
of the steam. F, F, are steam boxes or chambers with pipes leading from
the boiler or generator to supply the engine; a, a, are the channels or

page_text: ways formed in the solid part of the drum, which act alternately, as
induction and eduction passages for the steam into and out of the cylinder;
b, b, are the slide valves, with their rods passed through stuffing boxes,
and worked by cranks or bent levers c, c, having. their fulcrums on the
outside of the drum, and connected together by a rod d. The slide valves
are worked by a connecting rod and excentric placed upon the crank shaft of
the engine, as will be described under Figures.2 and 3.. e is a pipe for the
escape of the steam from the engine. When the slide valves are in the posi-
tion shewn in the Figuré, steam will be allowed to enter the cylinder by the
passages a 1, a 1, and exerting its expansive force between the pistons and steam
stops, will cause the pistons and cylinder to rotate in the direction of the
arrows, and bring them into the position shewn by dots, that is, near to the
steam stops, when the valves will be changed, and the induction from the steam
from the boxes by the passages a 1, a 1, cut off, at the same time the passages
a 2, a 2, will be open for the free way of the steam into the cylinder, when the
pistons will be forced the reverse way, thereby producing a reciprocating semi-
rotary motion, which may be communicated from the engine by a crank and
connecting rod, or in any other convenient manner, the waste steam at the
same time being allowed to escape by the passage a 1, a 1, into the pipe e, and
from thence to the atmosphere or condenser, and on the pistons arriving at the
end of their stroke the steam will be cut off from their passages a 2; a 2, which
will then become eduction ways, and the steam again admitted through the
passages a 1; a 1. As the working of this kind of engine is so easily, under-
stood, it will not be necessary for me further to describe its minutiæ, it being
evident that a continuous rotary motion may be obtained from this semi-
rotary or reciprocating motion in many ways, either by employing a crank
shaft and connecting rod, or by using two or more cylinders and pistons; but
a single cylinder may be employ'd, and, perhaps, on some accounts (expense,
&c.). often preferr'd. Figure 2 is a side elevation of one of my improved
engines complète, consisting of two cylinders; Figure 3 is a front end eleva-
tion of the same, some of the parts being removed to prevent confusion. a is
the cylinder; b, the drum fixed on to the framework; c is the steam pipe..
leading from the boiler, and connected by branches to the steam.boxes d; e is
the pipe for the escape of the steam to the atmosphere or condenser; f is the
connecting rod from the engine to the crank g, the shaft of which turns upon
bearings in the framework, and carries a fly wheel on its end; h is an
excentric, placed upon the crank shaft, which works the slide valves, in the
manner before described, by means of the rod i connected to their bent levers:
k, k. Figure: 4 is a section taken through one of my improved steam engines,

page_text: with the pistons attached to the drum, which rotates upon its axles, the steam
stops being fixed upon the outer rim of the cylinder or annular ring-formed
chamber, which is stationary, being fixed by its framework and supports to the
floor of the engine room. A, A, is the cylinder; B, B, the pistons; C, C, the
drum; D, D, the outer rim of the cylinder, with the steam stops E, E, fixed
to it; steam is conducted by pipes to the chambers or boxes F, from whence
it passes alternately through the passages a, a, into the cylinder, and when it
has exhausted its expansive force in the engine it is allowed to escape through
those passages to the atmosphere or condenser by the pipe b, in the manner
before described. c, c, are the slide valves, worked by bent levers d, d, and rods,
or any other manner; fis the crank, to be connected by the rod g to the fly
wheel shaft.
Having now described the construction of my improved steam engines, it
only remains for me to remark, in order that the cylinders may be equipoised
and kept steady in motion upon the drum there should be arms connected to
the cylinder, as shewn at in Figure 3, which have bosses revolving upon a
stationary shaft, and that when two or more cylinders are used the steam may
be worked expansively, that is, the induction passages may be closed before
the pistons have arrived at the end of their stroke; or it may be used at a
certain pressure in one cylinder, and then passed into a second of larger
dimensions; and, lastly, that by using two cylinders with the pistons in opposite
positions, all inertia in passing the centres of the cranks will be overcome.
Figure 5 is a section taken through my improved air pump and condenser, which
consists of an annular or ring-formed chamber, divided into two portions by
stops or partitions extending across the chamber, one portion forming the
condenser, the other the air pump, in which there is a piston working with a
reciprocating or semi-rotary alternating motion, similar to the pistons of the
steam engine above described. A is the portion of the annular chamber which
forms the condenser; B, the air pump; the steam is conducted from its exit
passages in the engine into the condenser by the pipe a, when it meets with a
jet of cold water thrown into the condenser from the pipe b. The condensed
steam and water is drawn through the clack or foot valve in the partition c by
the piston or bucket d of the air pump as it ascends, and when the piston has
arrived to the end of its stroke the foot valve at c closes, and the one in the
piston d opens, and allows the condensed steam, air, and water to escape
through that valve as the piston descends; and on the next up-stroke of the
piston, the condensed steam, air, and water will be forced through the passage
and valve in the partition f, and escape by the waste water pipe g. The pistons
of the pump is connected to the drum h, which is actuated by a crank i and

page_text: connecting rod j leading from the engine; or it may be worked in any other
convenient manner. The partitions c and fare fixed upon the outer rim of
the annular chamber, and there is an elastic packing placed between their
ends and the periphery of the drum, so as to form an air-tight joint.
In witness whereof, I, the said John Thompson, have hereunto set my hand
and seal, this Twentieth day of August, One thousand eight hundred