IMPROVEMENTS IN STEAM ENGINES
Year: 1838

page_text: TO ALL TO WHOM HESE PRESENTS SHALL COME, 1, JOSEPH
BUNNETT, of Deptford, in the County of Kent, Engineer, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Letters Patent under the Great Seal of Great Britain, bearing date at West-
minster, the Fourteenth day of June, in the first year of Her reign, did, for
Herself, Her heirs and successors, give and grant unto me, the said Joseph
Bunnett, Her especial license, full power, sole privilege and authority, that I,
the said Joseph Bunnett, my exors, admors, and assigns, or such others
as I, the said Joseph Bunnett, my exors, adñiors, 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 expressed, should and lawfully might make, use,
exercise, and vend, within England, Wales, and the Town of Berwick-upon-
Tweed, my Invention of "IMPROVEMENTS IN STEAM ENGINES;" in which said
Letters Patent is contained a proviso that I, the said Joseph Bunnett, shall
cause a particular description of the nature of my said Invention, and in what
manner the same is to be performed, to be inrolled in Her 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.
NOW KNOW YE, that in compliance with the said proviso, I, the said
Joseph Bunnett, do hereby declare the nature of my said Invention, and the
manner in which the same is to be performed, are fully described and ascer-
tained in and by the following statement thereof, reference being had to the

page_text: Drawing hereunto annexed, and to the figures and letters marked thereon,
that is to say
My Invention relates,-
First, to the application to a ring or circular piston rod to the piston of a
steam engine;
Secondly, to a mode of arranging the steam chamber, and piston working
therein, of a steam engine, as hereafter explained;
:
And, thirdly, to a mode of obtaining two revolutions of a crank by means
of a connecting rod, one end of which is caused to pass through an arc of a
circle; and in order to. give the best information in my power, I will proceed
to describe the Drawings hereunto annexed.
Figure 1 represents an elevation of a steam engine constructed according to
my Invention; Figure 2 shews a transverse section of the engine at the time
when the piston is at half stroke; Figure 3 is a plan of the engine at a time
when the piston is at one end of the stroke; and Figure 4 shews the metallic
packing of the piston rod, the section of which is square; though that figure
is not absolutely necessary, I prefer it, because it offers greater convenience of
making in the lathe than the circular or other sections do. The chamber a, in
which the piston 6 works, is produced by the space left between two cylinders
c, d, or portions of cylinders. There being suitable end plates or covers e at
each end of the cylinders c, d; only a portion of the space between the cylin-
ders c, d, is employed as the chamber in which steam acts, the upper part of
the cylinder c being used as a means of carrying the parts which work the
slides; and it has a slit or opening through which the connection of the con-
necting rod works, as is clearly shown in the Drawing. f is the piston rod,
which is a circular ring affixed to the piston, and working through two stuffing
boxes g, g, as is clearly shown in the Drawing, the piston rod being made in
two parts, and bolted together, in order to pass it through the stuffing boxes
9, g; h is a fixed axis on which the rocking arm i moves freely. The piston
rod f passes through the rocking arm i, and is keyed thereto; and the rock-
ing arm has a cross head or strong pin j, to which the forked connecting rod k
is connected by straps, as is shown, the other end of the rod k being connected
to the crank l, all which will readily be traced in the Drawing. m is an
eccentric on the crank shaft l, the eccentric working the slides n, by means
of the rods o, (which work through stuffing boxes,) these rods being worked
by the bell cranks p, such bell cranks being connected together by the rod q,
as is shewn in the Drawing; r is the steam ways into and from the cylinder,
and s is the eduction way leading to the condenser when used as a low-pressure
engine, or such eduction way leads, by a pipe or otherwise, to the atmosphere

page_text: when the engines is intended as a high-pressure engine, which is well under-
stood by engineers. It will only be desirable further to state in respect to
this engine, that I lay no claim to any of the parts separately other than the
application of the ring or circular piston rod working through the stuffing
boxes; and it will be evident that other arrangements of packing such piston
rod may be resorted to without departing from my Invention; and other
variations may be made so long as the piston rod be retained.
I will now proceed to describe the second and third parts of my Invention.
Figure 5 shows an elevation in section, and Figure 6 a plan in section of a
steam engine having the second and third parts of my Invention applied
thereto; and Figure 7 shews a diagram of the mode of obtaining the length
of crank, which will be caused to revolve twice by the connecting rod (the
opposite end of the connecting rod to that which is attached to the crank)
moving through a given arc of a circle. The chamber in which the steam
works the piston, is produced by means of two fixed cylinders A, B, the
inner cylinder B being shorter than [the outer cylinder A, and the two cylin-
ders A, B, are secured together by the partition C. These parts may be of
one casting, though I prefer they should be of separate parts. By that means
I am enabled to bore the cylinder A on the inside, and turn the outer surface
of the cylinder B more readily for the piston to work against than could be
performed by making these parts in one casting, as will readily be understood
by engineers. D is the piston which is affixed to the axis E by means of
bosses F; and it will be seen that those parts of the piston which are affixed
to the axis E, work between the ends of the cylinder B and the inner surface
of the covers of the cylinder A, consequently the surface of the piston which
comes in contact with such end surfaces, is to be packed steam-tight as well
as the surface which works against the cylinder B, and the surfaces of the
covers and cylinder A. The mode of packing the piston is clearly shewn in the
Drawing, though I do not confine myself to the mode there shewn, as varia-
tions may be made. The other parts of this engine, such as the steamways
and modes of working the slides, are similar to what has been described in
respect to the previous engine; but in this case the eccentric which works the
slides is not put on the crank shaft of the engine, but is placed on another
shaft which only revolves at half the speed of the crank shaft. On the axis E
is keyed the arm F, which carries the crank pin G, to which one end of the
connecting rod H is applied, to the other end of the connecting rod, being
attached to the crank on the shaft I. By this arrangement I am enabled to
obtain two revolutions of the crank shaft I, for each stroke of the engine, as

page_text: will be better understood when I further proceed to describe the third part of
my Invention. J is a rod attached at one end to a crank pin carried by a
projection, of the arm E, the centre of such crank pin being on a line at right
angles to that pin to which the connecting rod H is attached, the other end of
the rod J being attached to a crank pin of the axis which works the slides.
By this arrangement when the centres of the connecting rod H are in a right
line with the centre of the crank shaft, the parts will be insured to move
correctly and without shock. Figure 7 represents a diagram of the mode of
obtaining the length of throw of a crank for a given arc of a circle. Let a, b,
be the arc, and c, d, the length of a connecting rod, for which it is desired to
obtain the throw of a crank, to which it is desired to communicate two revo-
lutions for each time the end of the connecting rod is caused to move from
a to b and b to a. Open the compass from c to d,,which is to be the length of
the connecting rod determined on, and describe the arc d; then, from the
point a, describe the arc f,f, and from point 6 describe the arc e, e; then,
on a point on the line c, d, between the ares d, e, f, describe a circle which will
touch the arcs d, e, f, and half the diameter of such circle will be the throw
of crank desired, and which will be caused to revolve twice for
the end of the connecting rod at c is caused to move from a to
Hence, whatever be the description of steam engine to which it is desired to
apply this part of my Invention, it will be necessary so to arrange the parts
that one end of a connecting rod should constantly describe the arc of a
circle, and the other end of the connecting rod applied to a crank with a suit-
able throw for such arc, and such crank will be caused to revolve twice for
each movement of the other end of the connecting rod from a to b to b, a, of
the arc which it describes. I do not therefore confine myself to any particular
construction of steam engine, but claim to apply this part of my Invention to
any construction of steam engine from which such motion may be beneficially
produced.
every time
and b to a.
Having thus described the nature of my Invention, and the manner of
performing the same, I would have it understood] that what I claim under the
above-recited Letters Patent is,-
First, the application of a ring or circular piston rod to the piston of a
steam engine, as above described;
Secondly, I claim the mode of arranging and affixing the cylinder B within
the cylinder A, in combination with the peculiar construction of piston, as
above described;
And, thirdly, I claim the mode of obtaining the two revolutions of a crank