IMPROVEMENTS IN STEAM ENGINES
Year: 1863

page_text: LETTERS PATENT to Zerah Colburn, of No. 3, Upper Bedford Place,
Russell Square, in the County of Middlesex, for the Invention of
"IMPROVEMENTS IN STEAM ENGINES."
PROVISIONAL SPECIFICATION left by the said Zeral Colburn at the
Office of the Commissioners of Patents, with his Petition, on the
21st October 1863.
I, ZERAH COLBURN, of No. 3, Upper Bedford Place, Russell Square, in the
County of Middlesex, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN STEAM ENGINES," to be as follows:-
My said Invention of improvements in steam engines relates to that class of
steam engines in which the opposite working faces of the piston present
unequal arrears for the effective pressure of steam, and in which a pressure of
steam is continuously maintained upon that side of the piston having the
smaller effective area, while steam is admitted periodically upon the opposite or
larger side or working face of the piston, the steam thus periodically admitted
being afterwards exhausted at each double stroke of the piston either into
the atmosphere or into a condenser, feed water heater, or wherever else
required.
Engines upon this general arrangement have been before proposed, and it is
the object of my improvements to simplify such engines and to better adapt
them more especially to reciprocating, sawing, pumping, and other engines in
A

page_text: which a rotary motion is either not required at all or required only to
determine an exact length of stroke, and to assist in changing the directions
of the strokes. Where a rotary motion is employed I place the shaft, crank,
connecting rod, and the steam valve, and the apparatus for working it, all
directly within that part or end of the steam cylinder in which the pressure of
the steam is continuously maintained, and in which the steam is thus con-
tinuously pressing upon the smaller effective area of the piston. The shaft
comes through one or both sides of the cylinder, the bearings being formed in
stuffing boxes to prevent the escape of steam. The fly wheel is on the end
of the shaft and outside of the cylinder. This arrangement of rotative engine
is, I believe, the simplest that can be devised, and it is wholly self-contained
and very portable.
It
In some varieties of steam pumping engines, where no rotary motion is
effected, the steam valves are struck to and fro by tappets upon the piston
fod, such engines are however somewhat uncertain in their action, as the
steam valve occasionally stops where it covers all the ports. With the class
of engine, however, to which my present improvements relate, and which for
convenience may be called the differential steam engine, the valve may be
struck to and fro by the piston rod or piston either directly or through a lever
and without the chance of stopping the action of the engine. When it is to
be so moved I enclose the valve in that part of the steam cylinder in which the
steam is continuously maintained. The valve may be an ordinary slide, or it
may be in the form of a ring sliding within the cylinder, and the arrangement
of the steam and exhaust ports may be varied in many ways, the novel feature
being the placing of the valve directly within or in free communication with
that part of the steam cylinder in which steam is continuously maintained.
will be understood that the steam is admitted directly from the boiler into that
part of the cylinder within which the pressure is continuously maintained upon
the smaller effective working face of the piston, and that steam also passes
through this part of the cylinder and through the valve into the opposite end
of the cylinder, or that part into which steam is only periodically admitted,
once for each double stroke of the piston; where the exhaust or waste steam
passes into a chamber separated only by a piston from the live steam the
steam valve can be placed and worked in the exhaust steam chamber, but I do
not prefer this arrangement. Steam-moved valves may be preferred in some
cases, and in such the form of valve and general arrangement of the steam
and exhaust ports will be best made as represented in Figure 19 attached to
the Specification filed by me in pursuance of the conditions of. Letters Patent
granted to me on the Twenty-ninth day of July, Eighteen hundred and sixty-

page_text: two (No. 2145). In cases where rotary motion is not employed to determine
the length of the strokes of the piston it will be necessary (especially where
the working speed is considerable) to provide means for checking the piston
near the ends of its strokes. I effect this at one end of the stroke by allowing
the piston to pass completely over the induction port, and to compress the
waste steam against the cylinder cover. At the same time the tail of a
small spring valve or self-closing valve in the piston itself will strike the inner
face of the cylinder cover, and admit steam from the opposite side of the
piston. The steam may be cushioned also at the opposite end of the stroke
and the spring valve be there dispensed with. The opposite working faces of
the piston may obviously have any desired proportionate area, thus the face of
the piston upon which steam is periodically admitted may have twice, or three,
or four, or more times the area of the opposite working face.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Zerah Colburn in the Great Seal Patent Office on the
20th April 1864.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ZERAH
COLBURN, late of Number 3, Upper Bedford Place, in the County of Middlesex,
but now of No. 7, Gloucester Road, Regent's Park, in the aforesaid County
of Middlesex, Civil Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-first day of October, in the year of our Lord
One thousand eight hundred and sixty-three, in the twenty-seventh year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said Zerah Colburn, Her special licence that I, the said Zerah Colburn, my
executors, administrators, and assigns, or such others as I, the said Zerah
Colburn, 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 "IMPROVEMENTS IN
STEAM ENGINES," upon the condition (amongst others) that I, the said
Zerah Colburn, my executors or administrators, 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 said Invention, and in what manner
the same was to be performed, and cause the same to be filed in the Great

page_text: NOW KNOW YE, that I, the said Zerah Colburu, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:—
My said Invention of improvemets in steam engines relates to that class of
steam engines in which the opposite working faces of the piston present
unequal areas for the effective pressure of steam, and in which a pressure of
steam is continuously maintained upon that side of the piston having the
smaller effective area, while steam is admitted periodically upon the opposite
or larger side or working face of the piston, the steam thus periodically
admitted being afterwards exhausted at each double stroke of the piston either
into the atmosphere or into a condenser, feed water heater, or wherever
else required..
Engines upon this general arrangement have been before proposed, and it
is the object of my improvements to simplify such engines and to better adapt
them more especially to reciprocating, sawing, pumping, and other engines in
which a rotary motion is either not required at all, or required only to deter-
mine an exact length of stroke, and to assist in changing the direction of the
strokes. Where a rotary motion is employed, I place the shaft, crank, con-
necting rod, and the steam valve, and the apparatus for working it all directly
within that part or end of the steam cylinder in which the pressure of the
steam is continuously maintained, and within which the steam is thus con-
tinuously pressing upon the smaller effective area of the piston. The shaft
comes through one or both sides of the cylinder, the bearings being formed in
stuffing boxes to prevent the escape of steam; the fly wheel is on the end of
the shaft and outside of the cylinder. This arrangement of rotative engine is,
I believe, the simplest that can be devised, and it is wholly self-contained and
very portable.
In some varieties of steam-pumping engines, where no rotary motion is
effected, the steam valves are struck to and fro by tappets upon the piston
rod; such engines are, however, somewhat uncertain in their action, as the
steam valve occasionally stops when it covers all the ports. With the class of
engines, however, to which my present improvements relate, and which, for
convenience, may be called the differential steam engine, the valve may be
struck to and fro by the piston rod or piston either directly or through a lever,
and without the chance of stopping the action of the engine; when it is to be
so moved, I enclose the valve in that part of the steam cylinder in which the

page_text: steam is continuously maintained. The valve may be an ordinary slide, or it
may be in the form of a ring sliding within the cylinder, and the arrangement
of the steam and exhaust ports may be varied in many ways, the novel feature
being the placing of the valve directly within, or in free communication with
that part of the steam cylinder in which steam is continuously maintained.
It will be understood that the steam is admitted directly from the boiler into
that part of the cylinder within which the pressure is continuously maintained
upon the smaller effective working face of the piston, and that steam also
passes through this part of the cylinder and through the valve into the
opposite end of the cylinder or that part into which steam is only periodically
admitted once for each double stroke of the piston. Where the exhaust or
waste steam passes into a chamber separated only by piston from the live
steam, the steam valve can be placed and work in the exhaust steam chamber,
but I do not prefer this arrangement.
a
Steam-moved valves may be preferred in some cases, and in such the form
of valve and general arrangement of the steam and exhaust ports will be best
made as represented in Figure 19, attached to the Specification filed by
me in pursuance of the conditions of Letters Patent granted to me on
the Twenty-ninth day of July, One thousand eight hundred and sixty-two,
Number 2145.
In cases where rotary motion is not employed to determine the length of
the strokes of the piston, it will be necessary, especially where the working
speed is considerable, to provide means for checking the piston near the ends
of its strokes. I effect this at one end of the stroke by allowing the piston to
pass completely over the induction port, and to compress the waste steam
against the cylinder cover; at the same time the tail of a small spring valve
or self-closing valve in the piston itself will strike the inner face of the
cylinder cover, and admit steam from the opposite side of the piston. The
steam may be cushioned also at the opposite end of the stroke, and the spring
valve be there dispensed with. The opposite working faces of the piston may
obviously have any desired proportionate area; thus the area of the piston
upon which steam is periodically admitted may have twice or three, or four, or
more times the area of the opposite working face.
The foregoing statement of the nature of my Invention is the same as that
given in my Provisional Specification, filed October 21st, 1863, at which time
I was experimentally working a small steam-pumping engine upon my
improved construction and which engine was commenced September 17th,
1863, and first started on the 16th of the foliowing month of October.
I shall be better able to give a complete account of my Invention by

page_text: describing now the engine above referred to, and by relating my experience
with that and two other experimental steam engines (each combined with a
pump) which I have since constructed. I may also remark here, that since
July 1862 I have devoted almost constant attention to the improvement of
steam engines of the kind especially applicable to the driving of reciprocating
saws, piston or plunger pumps, and to other purposes where only a recipro-
cating motion is required. Besides a great amount of my time I have also
applied considerable means to this object, and I have now by me no less than
seven different experimental steam engines, some of which were made under
my former Patent of July 1862, while the others embody the Invention
protected by the present Patent.
The improvements which, in the case of each of these engines, I have
sought to effect, were not for any special economy in the use of steam, but for
economy of construction in the engines themselves. My engines have been
made for me in the best manner by engineers of standing, and notwith-
standing that each has been made from entirely different patterns, I find that
the cost of these engines is remarkably low, and my experience leads me to
believe that their cost, when made in considerable numbers, and with special
appliances, and under a proper division of labour, will be very much less than
that of any other description of steam engine of the like power and for like
purposes.
In the case of steam pumping engines, it appeared to me important, with a
view to economy in construction, to attach the steam cylinder directly to the
barrel of the pump, either by flanges and bolts or by casting both together.
This, in itself, was not new. James Samuel had, in April 1850, patented such
a combination, and it was again patented in November 1852 by John
Cameron, and in December 1852 by William Beckett Johnson. The first-
named Patent has expired, and the two last-named have lapsed by non-
payment of stamps. But according to my own experience it is most
inexpedient, if not impracticable, to bring live steam and cold water so nearly
into contact in a steam engine as was attempted by the patentees just named.
In my engines patented July 1862 I sought to keep the live steam and water
at some distance from each other, and in my Specification I especially
described an exhaust steam chamber or condenser occupying a portion of the
vessel intermediate between the working steam cylinder and the pump barrel.
As it was objectionable, moreover, to interpose a stuffing box between the
steam cylinder and pump barrel, where both were formed in the same casting,
I had to devise means for bringing back the steam and water pistons on their
return strokes. In my first pumping engines I effected this by atmospheric

page_text: pressure exerted through the water from which the pump drew its supply, a
vacuum being formed at each return stroke in the working steam cylinder. In
my present engines, as arranged for pumping, I effect the return stroke by a
constant pressure of steam upon a certain portion of the area of the back of
the working piston, steam being periodically admitted upon the whole area of
the front of that piston to effect the outward stroke. And to obviate the
necessity for a stuffing box between the steam cylinder and pump, I employ
an intermediate piston, as shown in Fig. 1, Sheet 1, of the accompanying
Drawings, Figs. 1, 2, and 3 being sections of the steam pumping engine first
worked experimentally by me October 16th, 1863.
A, A', A, and A", is a vessel of which the part A (in this case of 5 inches
bore) serves as the working steam cylinder, the part A' being a reservoir of
live steam having no direct communication with the exhaust passages; the
part A is an exhaust steam chamber, and the part A³, the barrel of the pump,
in this case of 4 inches bore. Fig. 2 shows a section of the water valves,
valve-box, and inlet and outlet passages for water as applied to the pump end
of the vessel just described. B, B', and B', are three pistons formed upon
one and the same rod. I call B the working piston; B¹ serves as a steam-
tight partition between the live steam space A' and the exhaust chamber A²;
B is the piston of the single-acting pump A³; the piston B' is smaller than
B, and consequently the steam which, when the engine is working, is always
present in A', tends to force the pistons into the position shown, and with a
force in proportion jointly to the pressure of the steam, and the excess of area
which B bas as compared with B'. When, however, steam is admitted upon
the opposite face of the piston B, or between it and the cylinder cover D, the
pistons B, B, and B, should move in a direction from D towards A³, and
with a force corresponding jointly to the pressure of the steam, and to so much
of the area of piston B as is equal to the area of B'; for the steam in A¹
presses in opposite directions against B and B³, and any effect produced in the
way of motion will be the same, merely as if B₁ were extended as a "trunk,"
and with its full diameter (in the present case 4 inches) up to B. There may
be those who will reason that when steam has been admitted to both sides of
the larger piston B it is simply in equilibrium, and that B' then becomes the
working piston for the outward stroke. I prefer, however, to consider B the
working piston, and shall so distinguish it here. Steam engines in which
the general action of the steam is as I have here described, and which
engines I.term differential-steam engines, have been long known, and among
others one is described in the Specification of a Patent granted to Mr. Bram-
well, in November 1854. Of themselves these engines cannot be said to

page_text: possess any advantages, and in the case of my modification shown in Figs. 1,
2, and 3, Sheet 1, it is demonstrable that the capacity of the steam cylinder,
when the whole motion of the piston B is allowed for, is necessarily more
than twice and a half greater than would be required with an ordinary steam
cylinder in which a single piston was made to work at the same number of
strokes per minute, and under the same pressure of steam per square inch.
But in applying such a differential steam engine to work a pump, the barrel
of which is cast with the steam cylinder, or bolted, or otherwise attached
directly to it, the objection of the large size of the steam cylinder for a given
power is more than compensated by the advantages obtained in cheapness and
simplicity of construction. It is in this way that I have effected an important
application of a class of engines otherwise possessing no advantages, and my
improvement in this respect; first described in connection with Figure 19,
Sheet 3, of Drawings attached to the Specification of my Patent of July
1862, consisted in the combination of a differential steam engine directly with
a pump barrel; an intervening chamber into which exhaust steam may be
admitted, or within which at least a body of air is present, being also inter-
posed between the live steam and the water. My Patent of July 1862 was
for steam pumps in which the return stroke of the piston was effected by
atmospheric pressure, and this mode of working, when properly carried out, is
preferable on account of cheapness of construction and economy of steam.
Before filing my Complete Specification, however, I found that in raising
water from considerable depths by suction, say 25 feet, I could not (especially
where the diameter of the pump was equal to or greater than that of the
steam cylinder) depend wholly upon the vacuum in my steam cylinder. It
would be necessary, I saw, in such cases, to have the means of applying a
direct pressure of steam to both sides of the steam piston, and I adopted the
differential arrangement of engine accordingly, as still retained in my present
Invention, working it, as I should still prefer to work it, in conjunction with
condensing apparatus, more especially of the simple description detailed in my
former Specification. Whether working with or without condensation, the
engine as a whole was an entirely original Invention of my own, although its
separate parts and the constant pressure of steam upon a portion only of one
side of a working piston were previously well known. By that engine I could
effect what had never before been done in engines in which the steam cylinder
and pump barrel were cast or otherwise directly connected together. For
while effecting the return stroke by atmospheric pressure or by steam pressure,
or by both combined, I kept the live steam and cold water well apart, pre-
venting undue conduction of beat from the former to the latter, and I further-

page_text: more avoided stuffing boxes between the steam and water pistons. In pumps
where the water piston is smaller than the steam piston, as is the case in all
so called "donkey pumps" for feeding steam boilers, this avoidance of stuffing
boxes is of special advantage, as by simply removing the cylinder cover, and
one or two easily detachable parts, the piston rod with its three pistons may
be at once taken out for inspection.
Thus keeping my former Invention of 1862 clearly in view, the importance
of the present Invention will be more distinctly appreciated. I had wished,
by effecting the return stroke of the pistons by atmospheric pressure, to reduce
my pumping engine to the last degree of simplicity, and also to effect a
certain economy of steam. After, however, I had found it necessary to provide
means for assisting the piston on its return stroke by the direct pressure of
steam, as in the differential engine, I discovered that the valve gear, of what-
ever description, might be enclosed within that portion of the cylinder which
is constantly occupied by live steam, and thus be worked without stuffing
boxes, and in most cases by the simplest possible mechanical means.
In my
former steam pumping engines I had proposed to employ steam moved valves
in most cases for effecting the distribution of steam to the engine, and I had
devised forms of such valves having considerable advantages over others pre-
viously used. But I find that without an improvement, which I have since
effected, these valves cannot be depended upon to carry the piston exactly
over its proper stroke, and to stop it always at the right point short of the
cylinder cover. At least elaborate arrangements for "cushioning" the piston
would be required to secure this end with ordinary steam moved valves.. The
simplest of these means is perhaps that of separate induction and eduction
ports, as employed in M. Sommelier's perforators in the Mont Cemis tunnel
(vide J. H. Johnson's Patent, No. 50, for 1859), and subsequently adopted
in the Worthington "duplex pump," patented in England by J. A. Knight
(No. 2422, for 1861).
In my Provisional Specification for the present Invention I proposed a self-
closing valve in the piston itself, this valve to be struck open whenever the
piston nearly reached the cylinder cover. Such valves inay, however, get out
of order, and only a considerable experience would determine whether they
could be employed with advantage. In the steam pumping engine, which I
worked for the first time in October 1863, I determined to employ a slide
valve to be struck directly to and fro by the pistons. This is shown in Figs. 1
and 3 of the accompanying Drawings. The peculiar form of this valve C
was adopted in order to avoid the necessity of making the steam and exhaust
ports to cross one another; as in the present case, the piston and valve move

page_text: at each stroke in the same direction when the latter is just admitting steam.
instead of in opposite directions, as in ordinary steam engines. Steam enters
at the sides of the valve into the opening C¹, as shown in Fig. 3, and the
exhaust steam is carried over through a passage C, and thence through b, b
into A, whence it escapes through a pipe, not shown. With steam of 30 lb.
pressure, and with but a very low lift on the pump, I worked this engine on
October 16th 1863, and for a long time afterwards, at from 12 to 180
double strokes per minute, each stroke ranging from 3 inches to 4 inches in
length. The pump valves made considerable noise, and I afterwards replaced
them by Perreaux's india-rubber valves. The blows of the pistons against
the valve did not cause much noise although, as the edges only of the pistons
struck the valve, I afterwards found that the piston rod was thereby bent, and
the pistons stuck fact in the cylinder. The valve too appeared to have yielded
a little at each end, so that its face acquired a slightly concave form in the
direction of its length, as was shown by the principal wear taking place at the
ends. This pump of 4 inches bore and 3 inches to 4 inches stroke pumped
steadily at the rate of from 1200 to 1500 imperial gallons per hour. I ascer-
tained that the movement of the valve was exceedingly short, hardly more
than ths inch except at the highest speeds. When pumping under con-
siderable pressure and at slow speed, I found I could not safely give any lap
to the valve, but that it was necessary to open the exhaust port at the instant
when the steam port was closed; there was therefore a leakage of steam
under the valve, which I had no difficulty in correcting in the next engine I
made. There was no mode of getting ready access to the valve, except by
removing its seat, and the valve occasionally stopped so as to cover all the
ports at once. This seldom occurred while the engine was going, but when I
purposely stopped it I found, on attempting to start again, that I could not
always do so from the cause mentioned; I readily saw too how this was to be
remedied, and to a considerable extent I did remedy it in my next engine, and
I have quite cured the evil in a third one since constructed. In pumping hot
water, or, indeed, whenever the part A of the cylinder became very hot the
engine would stick fast, notwithstanding that I had well fitted packing rings
on the pump piston, and, in the later trials, packing rings upon all the pistons.
My experience convinced me, however, that the principle of the engine was
sound, and that improvements in details were only required to insure success;
Nor have I had occasion to depart from the Invention which forms the sub-
stance of the present description, although I have certainly devised details
which had not occurred to me at the time when I filed my Provisional
Specification in October last. These details enable me the better to carry out

page_text: my original Invention, especially for engines employed to pump water under
considerable pressure and at a slow speed of piston, and where therefore the
utmost certainty of action of the steam valve is indispensable. Many of these
details are equally applicable also to other forms of steam engines, as, for
instance, those which have steam cylinders and double-acting pistons of the
ordinary kind, but which work without rotary motion. Such of these details
as are of my own Invention, and which have never been published until now,
will be distinguished as new in the present Specification.
Fig. 4, Sheet 1, is a section of a steam pumping engine, which, with a few
improvements in architectural design and mechanical detail (not shown on
the Drawing) was commenced for me towards the end of November 1863, and
which was first worked January 27th 1864. The parts marked A, A', and B,
B, B, correspond in purpose with those marked with the same designations
in Figs. 1 and 3. The exhaust steam is not discharged, however, into the
space A in Fig. 4, but is led off by a pipe. The space A³ is roomy, and is
open to the air. The distance between the live steam and the cold water is
increased, so far as the direct conduction of heat is concerned, by means of a
large swell upon the casting, which swell is, for appearance's sake, formed
as a large base moulding. The steam valve C was moved by the lever E
vibrating upon the pin or joint e, but instead of the lever E being struck, as
shown, by the faces of the pistons B and B the lever E was forked, and made
to reach to the centre of the piston rod, and stout coiled springs were applied
to the under side of piston B, and the upper side of B2 (Fig. 4) to strike the
inner end of the lever E. The valve C had also a spring at its back to insure
its contact at all times with the valve face. As the valve C has no lap I
considered it prudent to provide, as far as I could, against any leakage of
steam from the steam space into the exhaust port b. With this view I did not
allow the upper edge of the valve to admit steam to the cylinder, but I pro-
vided a passage C₁ within the valve, and through this passage all the steam
was made to first pass from the edge or corner Z of the valve face. The
distance between the ports on the valve and valve force were so adjusted that
exactly when the valve shut off the steam from the port a steam should also
be shut off at Z from the passage C'. The steam before entering the cylinder A
had thus to pass two governing edges of the valve, instead of one, as in the
usual construction, and in no case could steam work its way directly from the
slide valve box into the exhaust port, except by creeping between a con-
siderable extent of closely fitting surfaces. By means of a bar C³ in the exhaust
cavity of the valve, and by a due adjustment of distances between the ports,
the steam was also controlled at two edges, instead of one, in escaping from

page_text: the cylinder. The proper action is when the exhaust port b is opened o
closed exactly at the instant when the port a is opened or closed to the
passage C. With this valve the exhaust of the steam from the engine, show
in Fig. 4, was very sharp, showing that but little, if any, leakage took place
The piston B in the engine, shown in Fig. 4, was 5 inches in diameter, B
was 4 inches, and B was 21 inches in diameter. The length of stroke was
about 2 inches, requiring about 30 strokes to throw a gallon of water. The
engine would not work well under 120 double strokes per minute, but with
30 lb. of steam, and a load upon the delivery pipe, it went steadily and com-
paratively quietly at 288 double strokes per minute, throwing a measured
quantity of 350 imperial gallons of water per hour. The working speed could
be easily raised to more than 400 double strokes per minute. My first trials
with this engine were witnessed by my friends Messieurs William Bridges
Adams, George D. Kittoe (the maker), Alexander L. Holley, Vaughan Pendred,
William T. Carrington, Cowper Jackson, Frederick J. Slade, Thomas L.
Luders, and others.
Figs. 5 and 6 are from a design I made early in November 1863, for a steam
engine in which the valve was placed upon the piston rad, the movement of
the valve being effected at the end of each stroke by coming in contact with a
fixed object, which in this case is the end of the steam pipe. The action of
this engine is otherwise like that of the engines shown by Figs. 1 and 4, and
the several parts are the same so far as their general action and purpose is
concerned. They are lettered therefore with the same letters applied to the
respective parts in which Fig. 5 corresponds to Figs. 1 and 4.
Figs. 7 and 8 represent an engine substantially the same as Fig. 1, the
only difference of consequence being that Figs. 7 and 8 the valve C is
formed as a ring fitting the bore of the cylinder. This insures the constant
bearing of the valve upon the bridges between the ports a and b, while also
the valve is certain to be struck fairly at each stroke of the pistons and
without any tendency to bend the piston rod. As in nearly all the engines,
the principal parts are designated by the same letters as those employed in
Figs. 1, 2, and 3.
Fig. 9 on Sheet 2 is a section of a reciprocating steam engine, similar in
its general character to those already described, the valve gear being placed,
as in all the others, in the live steam space A'. The valve gear shown in
Fig. 9 is, however, in itself novel. To a piu m in the piston rod a link n is
attached, and this link is in turn attached to one end of a bent lever o, q,
which vibrates on the stud or joint p, shown also in Fig. 10.
lever or arm is connected to the slide valve C by means of
The end of the
a pair of short

page_text: inks r, s, forming a "toggle joint" with a pin at t.
tud p is a concentric wheel u,
between itself and the wheel u.
outer end of the pint of the toggle joint r, s.
oint or pair of links r, s, is so formed as to open or deflect in one direction
only when any pressure is applied to the pin t. The action of this valve gear
is as follows:-Keeping in mind that in Fig. 9 the steam port a is just
opening and the piston B is moving away from the cover D of the cylinder A,
as the piston moves forward the lever o, q, will move with it, the lever turning
with the wheel u around the stud 2. As the arm q descends it will tend to
bring the links r, s, into the same straight line with itself, thus moving the
valve C, and fully opening the steam port a. When, however, the piston B
has advanced so far that the arms and links q, r, s, are brought below a straight
line connecting p and w, the valve C will be drawn towards p, and the port a
will begin to close. Upon a further movement of the piston B and its attached
valve gear, the port a will be fully closed to the steam space A', and opened
to the exhaust port b. The motion of the piston B will then be reversed, and
it is now that the wheel u, friction strap v, and toggle joint r, s, come into
play to prevent the valve C from again opening the port a to the live, steam
space A. The valve C having already placed the steam port a in communi-
cation with the exhaust port b, should remain stationary during the return
stroke of the piston B towards the cylinder cover D. Inasmuch as the pin t
is further from the stud p than is the joint between the arm q and short link 2*
it follows that the friction strap u in moving will carry up the pin t, thus
opening or bending the toggle joint r, s, and that this opening will-proceed
faster than the outer end of the arm 7 can rise, the result will be that the
distance between P and w will either remain constant or diminish, in either of
which cases the valve will keep the port a well open to the exhaust b. The
piston B will meanwhile keep on towards D until the valve gear has carried
the upper projections, shown on the links 7, s, up against a stop d, on the
under side of the slide valve box cover. The toggle joint or links r, s, will
then take the position shown, thus moving the valve C so as to partly open
the port a to the live steam in readiness for another outward stroke. This
form of valve gear would not be certain to always fully open and close the
steam ports in the case of pumping engines working at a slow rate and under
considerable pressure, but where there was considerable weight put in motion
by the piston, and so that the momentum of this weight should tend to prolong
It is
each stroke of the piston the valve gear would be effective in all cases.
Fixed to the spindle or
having a strap v, which moves by friction
This strap v is forked so as to embrace the
It will be seen that the toggle

page_text: more especially intended for reciprocating sawing engines and those employed
for steam hammers or for pile driving.
Figs. 11 and 12, also on Sheet 2, are sections of a steam engine in which
a rotary motion is produced by the intervention of a connecting rod and crank,
both of which, with the valve gear, are inclosed in the live steam space. The
cylinder A, live steam space A', pistons B and B', cover D, and valve C, are
substantially the same in construction and purpose as in the engines shown in
the Figures on Sheet 1. In Figs. 11 and 12, however, the valve C slides on
a flat surface upon the piston rod, the latter having the ports a and b cast in it,
the exhaust port b being formed in a loop carried around the crank pin. The
eccentric c², instead of being fixed as usual on the revolving shaft on or near
the axis of its revolution, is fixed to that part of the crank which serves as the
crank pin, k, k, being the shaft, j the cranks, and i the crank pin; h, h, show
not so much the construction of the connecting rods, which may be of any
form preferred, but rather that connecting rods of some kind are to be em-
ployed between the pin 9 and crank pin i. The whole action of the valve gear
shown is the same as in an ordinary rotative engine, although the slide valve
moving on the piston rod by means of an eccentric on the crank pin is novel.
Fig. 13, Sheet 2, represents a mode of driving the valve directly from the
piston rod of a differential engine working at a very slow speed. It is intended
to be inclosed in the live steam space, but it is equally applicable to ordinary
double-acting engines, and may be fitted up in connection with the piston rod
at any point outside of the cylinder. The principle consists in putting in
motion, at the end of each stroke of the piston, of a considerable weight, which
weight is in itself quite disconnected from the piston rod except when the
weight is put in motion. So far the plan is similar to the old system of
tumbling weights, employed in some cases to work the valves of reciprocating
engines, but I have effected an important improvement upon this plan. I
make my weight in such form and so suspend it that it shall have no tendency
for any one position in particular, but shall move freely in either direction.
A circular vibrating fly wheel best answers this purpose, and such a one is
shown in Fig. 13, Sheet 2. B is the piston rod of an engine having on it a
pair of stops or collars answering to the intended length of stroke. These
collars may be guarded by spiral springs as shown, or with any other expedient
to neutralize shocks in striking the valve gear. b is a sleeve loose upon the
piston rod, the latter moving freely through it. The sleeve has teeth
formed upon its upper part, and into these the teeth of a segment upon the
spindle of a circular vibrating fly wheel are made to take, as shown; f is the
fly wheel vibrating upon the pin e; g is a pin fixed in the rim of this wheel,

page_text: and so adjusted as to strike at each vibration one or the other end of a shot in
the end of the slide valve spindle h. At the end of each stroke of the piston
rod B, and before the slide valve spindle h begins to be acted upon, a con-
siderable amount of momentum will be stored up in the wheel f, and as this is
not attached directly to the piston rod, the wheelf will continue to move,
expending its momentum upon the slide valve after the piston rod has been
brought to rest. In the old tumbling weight valve gear it is not so much
momentum as gravity that is called into play, and the weight has always a
tendency to assume one particular position, from which it is alternately forced to
one side or the other; such an apparatus can only work with considerable shock
at each action, but in my improved arrangement shown in Fig. 13, Sheet 2,
only momentum is called into play, and the weight will, when brought to rest,
remain so in any position in which it may have been placed. It may be of
considerable weight, so as effectually to insure the movement of the slide valve
at each stroke of the engine however slowly it may be going. The momentum
of the weight is best imparted to the valve spindle through a pin fixed in the
rim of the vibrating wheel itself, as shown; the shock is thus lessened upon
the neighbouring parts and the useful effect is increased. It is hardly neces-
sary to say that a vibrating fly wheel may be put into motion by many other
means than those shown, and that no part of the improvement I have made
in this variety of valve gear depends upon the particular means shown for
giving motion. If a vibrating fly wheel were connected directly to the piston
rod by a link or connecting rod so as to be all the time in motion with the
piston rod, the same effect as that above described would be produced, but
the necessary weight would be considerable and so would be the wear of
the parts.
Fig. 14, Sheet 2, shows another mode of working the valves of reciprocating
engines. B is the piston rod, with a ring a loose upon it, and fixed between
two springs, which are confined between two stops or pins on the rod. A
link connects a stud on the ring a with the end of a lever or vibrating arm f,
the upper end of which arm is connected with the end of the valve spindle to
be moved. In the lever f is a pin or stud e, moving in a curved or other
suitable slot in a fixed piece g. When the lever f has been moved so far as to
bring the stud e against either end of the slot or other opening in g, the stude
becomes a fulcrum, upon which the lever f vibrates, carrying over the valve
spindle connected to or being in itself the part shown at h. This arrangement
does not occupy much room, and will in many cases answer very well for short-
stroked engines. The springs shown upon the piston rod may of course be

page_text: replaced by others in the end of the slot in g, or by springs in the end of the
valve spindle. The novel feature in this arrangement is in having the lever
always in motion with the piston rod, and its action on the valve by the stude
or an equivalent part striking a fixed stop.
Fig. 15, Sheet 2, shows another plan of reciprocating steam engine, the
parts marked with capital letters having the same purpose as in the plans
represented on Sheet 1. The slide valve moves on the piston rod, in which
steam port a and exhaust port 6 are cast. The valve is moved by a lever i, i,
the upper end of which strikes a suitable stop at each end of the stroke, while
the lower end is fitted with a weight f to insure certainty of action. The
valve C does not move directly with the lever i, but only when the latter
strikes suitable stops on the former. The lever i is centred on the piston rod
ate, and consequently moves to and fro with it.
a
Figs. 16, 17, and 18, Sheet 2, are sections of a double-cylinder steam
engine, in which the valve to each cylinder is moved by the piston rod of its
fellow cylinder. This mode of working the valves of double-cylinder engines
is that employed in what is known in America as Worthington's "duplex
pump," which was illustrated and described in Holley's Railway Practice,"
book published by Messieurs Sampson, Low, Son, and Company, London, in
February 1861, and afterwards patented here by John Adams Knight,
September 28th, 1861, No. 2422. This mode of working the valves of double
engines was employed by the late Mr. Richard Roberts in 1834, and by
Mr. Melling of the Liverpool and Manchester Railway, in 1837, and it is also
represented in the Drawings attached to the Specification of Jonathan Dickson's
Patent, of 1837, No. 7439. My improvement in this respect consists, as in
nearly all the steam engines shown in the accompanying Drawings, in placing
the valve gear in the live steam space of a differential engine. In Fig. 16 a
link, jointed at i to each piston rod, is jointed also to one end of a lever f,
centred or having its fixed fulcrum at e. From the upper end of this lever
motion is imparted to the nearest slide
double cylinder are so arranged that in all cases each cylinder shall receive its
steam through or by the slide valve worked by the piston rod of the other
cylinder. Fig. 16 is a section through one cylinder only, and shows the
working gear of but one valve, but each cylinder is fitted alike with a valve,
valve lever, and all other parts requisite for working the valve. Fig. 17
shows a transverse section through the steam ports. Only one of the slide
valves is shown, but both are alike. It will be seen that the steam ports
communicate respectively with the cylinder opposite to that upon which the
valve, and the steam ports in the

page_text: valve covering the port is placed. This arrangement is novel, and greatly
simplifies the valve gear as compared with that of the Worthington pumping
engine already referred to. The exhaust ports b, b, are formed in one common
passage, as shown in Fig. 18.
In the arrangement shown in Figures 16, 17, and 18, Sheet 2, the piston
of neither cylinder is controlled by a valve worked by that piston. There may
be, therefore, a chance of either piston going too far on its stroke.
In going
from the cover D it may, however, be easily cushioned in the space A², as any
mechanic may readily see and provide for; or in the case of pumping engines
the pump piston or plunger may be made at a certain stage of its stroke to
gradually cover or close the outlet passage for the water, and thus bring the
piston to rest if the steam valve which controls the motion of that piston has
not already reached its proper place for that purpose. It remains, then, to
cushion the piston B (or both of them, as there is one in each cylinder,) when
it arrives too near the cover D. One mode of doing this is employed in the
Worthington duplex pump, and is described in J. A. Knight's Specification,
September 28th, 1861, No. 2422. The same mode of arresting a piston when
not under the proper control of its own valve is described, as herein-before
mentioned, in the Specification of an Invention communicated by M.
Sommelier to J. H. Johnson, and patented by the last-named gentleman,
No. 50, 1859. The mode referred to requires, however, a separate steam
port and induction port, there being in all ten separate passages for steam in
Worthington's duplex pumping engine. I have an exceedingly simple mode
of effecting the same purpose applicable alike to the differential and to the
ordinary steam engine cylinder, as employed in the Worthington engine. The
steam ports a, a, instead of entering their respective cylinders close to the
covers D, D, as shown in Fig. 16, Sheet 2, should enter the cylinder so far
from the cover that the packing ring of piston B may pass by and tightly close
the inner end of the port a. Any steam then left between the piston B and
the cover D will be compressed, and the piston brought to rest. To start the
piston again in the opposite direction, the spring valve, with a projecting tail
striking the cylinder cover may be used with the differential engine, as
described in my Provisional Specification. Or a very fine opening, say of th
inch diameter, may be made through the piston B, so as to be always free to
admit steam from the steam space A¹. This plan entails but a very slight loss
of steam during the time while steam is being exhausted from the working
face of the piston B. In the case of ordinary double-acting cylinders a like
small opening is to be made from the cylinder near or just under the cover,
and extending into the slide valve box, or wherever else a constant pressure of
B

page_text: steam is maintained. In steam pumping engines all the exhaust steam may,
in most cases, be discharged into the water from which the engine is pumping,
and in this case a little leakage of steam in the cylinder is no real loss. This
mode of cushioning the piston in engines of the kind shown in Fig. 16 is
of my own invention, and it enables me to considerably simplify such engines
as compared with Worthington's already referred to.
In Fig. 19, Sheet 2, I have shown a steam engine having a novel arrange-
ment of steam-moved valve for controlling the distribution of steam. The
parts A, A, A, B, B, C and D, have the like purpose as the respective parts
marked with the same characters in the Figures on Sheet 1. The piston rod,
which may be conveniently cast instead of being made from bar iron or steel, is
circular, except for a short portion of its length, where a flat seat is made
upon it for the slide valve C. The steam port a, and exhaust port 6, are
made in the piston rod, so that the cylinder A, A1, A2, is a plain casting like
a pipe, and without the usual intricate passages which require to be cored in
the metal of ordinary steam cylinders. A piston C¹ is made to fit the bore of
the cylinder A, and to this piston is firmly secured the slide valve C. The
piston C¹ is intended to slide upon the hollow piston rod, and the sliding
surfaces must be steam-tight, and I have shown a stuffing box in the piston C¹
for that purpose. The piston B¹ is not fixed to the piston rod, but is firmly
connected with the piston C¹ by any convenient means, a tie rod being shewn
in Figure 19. The piston rod must slide steam-tight through the piston B',
and to this end I have shown two small packing rings on the piston rod at the
part where it slides within B'. The sliding motion which can take place
between the piston rod and the piston B' is limited by any convenient means,
and I have shown collars upon the piston rod as one of the simplest means for
this purpose. As during the time the engine is at work steam is always
present in the space A', it will at all times press upon one face of the piston C
If steam be excluded from the space between the pistons B and C, these
pistons will be pressed near together, notwithstanding that C is connected to
the smaller piston B', and that B' has a constant pressure upon its inner face.
If, however, steam be admitted between B and C, the piston C¹ will be in
equilibrium, and it will be moved along the piston rod into the position shown
in Fig. 19, by virtue of the pressure always acting against the inner face of
the piston B, with which C¹ is connected. As the piston C moves, however,
or, which is the same thing, as the piston rod slides for any distance through it,
there is a corresponding change in the relative position of the valve C (con-
nected with C¹), and the ports a and b. In the position shown in the Drawing,
steam is passing from A¹ through the port a in the piston rod, and thus into

page_text: the cylinder A. The pistons B and C are both therefore in equilibrium, and
B¹ moves therefore with the pressure due to the difference between the area
of a circle, of its full diameter, and the cross sectional area of the piston rod
sliding within it. As B moves, it carries along all the other movable parts
in the cylinder with it. To effect a change in this movement, it is only neces-
sary to exhaust the steam from the space between the pistons B and C. When
this is done, these pistons must approach each other because of the steam
pressing them together. It is immaterial which of these two pistons moves,
or whether both move towards each other, for in either case the valve C will
attain that position over the parts a and b which is necessary to permit the
steam to escape from between the piston B and cylinder cover D. When
the exhaust has taken place, the constant pressure of the steam against the
face of C¹ will, by means of the tie rod which couples B' with it, cause the
piston B' to press against one of the collars on the piston rod (or C¹ may press
directly against B), and the result will be the whole of the moveable' 'parts in
the cylinder will move together towards the cylinder cover D, with a pressure
due to the difference of area between B and B. To effect the alternate
admission of steam to and its exhaustion from the space between the pistons
B and C, a small valve or cock o is employed, having a correspondingly small
A lever or tail is
steam port and exhaust port s in connection with it.
fixed to this small valve, as shewn by dotted lines, and when the assemblage of
parts moving within the cylinder has reached the proper point, this lever or
tail will strike against any proper stop fixed in the cylinder for that purpose,
and the motion of the valve o will be reversed. The whole arrangement shown
in Fig. 19 permits of using a steam cylinder without complicated ports cast
within it, and it permits of placing the piston which moves the slide valve
directly within the bore of the working cylinder without a separate cylinder
as would otherwise be necessary. These arrangements are quite novel
according to the best of my knowledge and belief, and I consider the engine
shown in Fig. 19 among the simplest which I have devised. At the same
time the whole of the valve gear is placed within the live steam space A¹,
strictly in accordance with the nature of the Invention described in my Pro-
visional Specification.
Figs. 20 and 21 on Sheet 3 show sections of a steam engine having the
general arrangement indicated in the description of the nature of my Invention
in my Provisional Specification, and having also a useful improvement in
connection with steam-moved valves. As I have already observed in the
present Specification, steam-moved valves do not always reverse the steam
with sufficient quickness upon the main piston to prevent the latter striking
B2

page_text: the cylinder cover. I have experienced this difficulty with my own steam-
moved valves, and at one time it occasioned me some anxiety.
I have now
insured proper action by providing a lever or other equivalent means which
shall, if the valve do not move sufficiently soon under the pressure of steam,
strike it well open when the piston has gone farther, than its intended stroke.
In Figs. 20 and 21 this lever J, J', J, vibrates upon a joint or fulcrum I
and is alternately struck by the pistons B and B at each double stroke. The
valve C has two pistons connected with it, C' and C, the area of C' being
about double that of C. The outer end of C2 is in free communication with
the air by means of holes, of which one is shewn at d. The piston C' tends,
therefore, when steam is admitted to the valve chamber, to move towards D'
with a pressure corresponding to the difference of area between C' and C.
The valve C has, however, sliding on its back a supplementary valve C which
may be caused to admit steam between C' and D'. In this case the valve C
will take the position shown in Fig. 20. The valve c is worked by the end J
of the lever already described, and the steam exhausted from the space between
Cand D¹ is sent through a small port in the back of the main valve C, and
thus off through the exhaust port b. The part J of the lever moves through
a slot in the stem, shank, or spindle of the valve C, and the length of this
slot with reference to J¹ is such that if the valve C do not move in time under
the pressure of steam on one or the other side of the piston C₁ the valve C
will be struck over by the lever J', thus reversing the motion of the piston B..
This lever is an important safeguard, and it enables me to work my valves
with much smaller pistons than would be otherwise necessary. The lever J,
which is forked to embrace the piston rod, may be struck directly, as shown,
or any kind of spring may be employed to relieve the shock. It is not
intended that the lever J shall regularly set over the valve C by actually
striking it, the steam pistons C' and C being depended upon for moving the
valve, and J only striking the valve over in occasional instances when the
piston B may be going too far. The piston C cushions itself in one direction
under the cover D2. I may add that the use of steam to move the valves of
steam engines has long been familiar to engineers, but that the differential
steam-moved valve, shown in Fig. 20, Sheet 3, is covered by my Patent of
July 1862, No. 2145.
Fig. 22, Sheet 3, is a partial section of a steam cylinder such as I am now
making. It is substantially the same as the engine shown in Fig. 20 on the
same Sheet, except that no supplementary slide valve is provided to control
the distribution of steam on the piston C. The distribution of steam is here
effected by the means shown in Fig. 19, Sheet 3, of the Drawings attached to

page_text: my Specification of July 29th, 1862, Letters Patent, No. 2145. The lever
J, J', is introduced in Fig. 22, Sheet 3, of the present Drawings, as a safe-
guard only, as already explained, the piston B and port y being so adjusted
with reference to each other that the steam is admitted to or exhausted from
the outer face of the piston C' before the lever J can be struck by the pistons
B or B. If the lever were struck before the port y had been uncovered by
one or the other edge of the piston B¹ a violent shock would ensue and the
engine might be broken. The lever J may be applied as a safeguard in con-
nection with other steam-moved valves, and I have shown its application in
Fig. 23 to the steam-moved valve described in the Specifation of my Patent
of July 1862, No. 2145, Figure 20, Sheet 3.
In Fig. 23 of the present Drawings the lever J is struck, whenever the
piston rod is going too far, by stops K, L, on the rod itself, but under ordinary
circumstances the lever J is not intended to be struck at all. I do not, of
course, confine myself to a lever, for the intended purposes will be accom-
plished by any means whereby the piston rod, when going beyond its intended
stroke, will directly or indirectly strike over the slide valve, which is other-
wise and under all ordinary circumstances to be moved by steam pressure
acting on the ends of the valve, or on a piston or pistons connected with it.
In no case must the valve or a lever connected with it be struck until after
the steam has been changed to give the proper movement of the valve.
Fig. 24, Sheet 3, shows the introduction of the lever as a safeguard for
insuring the opening of steam-moved valves in an ordinary double-acting
cylinder. In this arrangement, which is a very good one, the following points
are of my own Invention. The safeguard levers J, J, their position so as to
pass through the ports leading to the cylinder, their arrangement whereby
they work without affecting the steam-tightness of the several valve faces, the
controlling supplementary valves c, c, working on the backs of the slide
valves C, C, and the means by which the valves c, c, exhaust through a port
or ports e, e, in the main valves, a common exhaust port or ports b, b, in the
cylinder serving for both.
Figs. 25 and 26, Sheet 3, show sections of cylinders of steam engines to
which my present improvements are equally applicable, although the Figures
25 and 26 do not show any improvement of my own.
In each cylinder a
constant pressure of steam is maintained in the portions where "constant
pressure" is written in.
Fig. 27, Sheet 3, will show what unusual simplicity of construction I am
enabled to obtain in rotative engines by placing the connecting rod, erank,
valve, and valve gear within the live steam space of a differential steam

page_text: engine. Suppose I wish an engine of equal capacity to an ordinary double-
acting 10-inch cylinder, with 10-inch stroke of piston, I make the trunk B
10 inches in diameter, and the bore of the cylinder A 14 inches. The
Drawing shows the interior of the engine to a scale of 3 inches to one foot.
Steam is admitted, and while the engine is working is constantly present
in A' and within the trunk B. This tends to carry down the piston with a
force corresponding to the difference of area of B and B. The trunk B¹ is
slotted to allow it to rise and fall without interfering with the crank and
revolving shaft, which are turned by a connecting rod jointed in the upper
part of the trunk. There may be many ways of working the slide valve C.
which admits steam to and exhausts it from the under side of the piston B.
I have made a seat for the valve C on the upper side of the plate forming the
piston B. The steam port a is made directly through the plate just mentioned,
and the exhaust port is made in a hollow stem, which leaves the cylinder A
through a central stuffing box in the bottom cover. Thus the cylinder A is a
plain pipe casting without ports. To move the valve C I fix an eccentric upon
the revolving shaft, and hinge a bar near the top of the trunk B', employing
for convenience the pin of the connecting rod as a joint on which the bar
destined to work the valve may vibrate. This bar has a long slot of the right
width to embrace the eccentric, and the lower end of the bar may move the
valve C to and fro by a projection or other attachment or means of contact at
the back or sides of the valve. The slotted bar rises and falls with the
trunk B, and is swayed to and fro according to the position of the eccentric,
and thus moves the valve. The revolving shaft is to pass out through a
stuffing box in the side of the cylinder A, and it will be well to separate the
cylinder from the part in which the stuffing box for the trunk B' is made by
a joint intersecting the diameter of the revolving shaft. A little consideration
of the details will enable any skilled workman to bring all the parts properly
together, so that there shall be no interference. This engine requires but
little if any lubrication besides that supplied by the steam itself, and none of
the working parts require to be finished bright, excepting of course the wearing
surfaces. The engine is at the same time far more compact, and requires less
space than any other steam engine of equal power and working with steam of
the same pressure. This engine may be worked expansively, and to a greater
extent than would be supposed. For expansive working the annular working
area on the upper side of the piston B should be less than one-half, and in
some cases not more than one-fourth the area of the under side. Where
too the steam from the lower side of the piston B is condensed in a condenser
the opportunity for expansive working is still greater. Suppose, for example,

page_text: that the upper annular surface of B is equal to 100 square inches, and the
lower surface to 400 square inches; suppose the weight of B and the trunk B¹
and connecting rod to be 500 lbs.; if, now, steam of a pressure of 50 lbs. per
square inch above the atmosphere be employed, the constant downward
pressure on B will be 5,500 lbs. When too the lower side of B is in com-
munication with a condenser maintaining a vacuum of 12 lbs. per square
inch below the atmosphere, we shall have on the downward stroke an
additional pressure of 5,000 lbs. Of this, 3,750 lbs. are due to atmospheric
pressure on the 300 square inches of the upper surface of the trunk B', and
the remaining 1.250 lbs. are due to an additional pressure beyond 50 lbs. per
square inch of the steam pressing upon the upper annular surface of B; this
additional effective pressure being due to a vacuum of 12 lbs. per square inch
under the piston B. The whole constant pressure throughout the downward
stroke is therefore 10,500 lbs. On admitting steam of 50 lbs. per square
inch above the atmosphere under the piston, the total pressure there will be
20,000 lbs., from which is to be deducted the constant pressure and weight of
5,500 lbs. upon the upper surface of B, leaving 14,500 lbs. as the effective
upward pressure upon the piston, supposing no expansion to take place. As,
however, the mean upward effective pressure should be only equal to that
acting downward on the alternate stroke, a mean effective pressure under the
piston of 10,500 lbs. is all that is required, and this will be obtained by cutting
off the steam in the lower part of the cylinder A, after a little less than one
half of the upward stroke of the piston B has been completed. The total
mean pressure under B will thus be about 16,000 lbs., from which the constant
downward pressure and weight of 5,500 lbs. is to be deducted, leaving
10,500 lb. mean effective upward pressure as required.
The resulting
economy of steam is theoretically the same as that by cutting of steam at the
same part of the stroke in any other form of engine, but, practically, my engine
would have an advantage, as the cylinder is kept bot by the alternate descent
of full pressure steam to the bottom, the steam always acting with full force
on the top of the piston B. This in a great measure prevents cooling in the
cylinder during the time expansion is going on, and more especially while the
under side of the piston is in communication with the condenser. This
cooling in ordinary expansive engines, especially when working with a slow speed
of piston and in communication with a condenser is very considerable, and is
attended with a wasteful condensation of steam upon the inner surface of the
cylinder. The loss thus caused is generally far greater than would be caused
by external radiation from the large steam vessels of my improved engine now
described; my engine, it will be also seen, has an advantage in the extreme

page_text: shortness of its steam port, and this is opened but once at cach double
stroke.
There is another mode of working the steam valve of my differential engine
which possesses some advantage in the way of simplicity of arrangement and
certainty of action. In most of the engines shown in the accompanying
Drawings, more particularly those shown in Figs. 1 and 4, Sheet 1, a valve
may be placed so as to open a communication through the piston B. Thus a
circular opening may be made through this piston, and a valve formed like an
ordinary safety valve, or the pump valves shown in Fig. 2, Sheet 1, may be
made to work in this opening. The steam-tight scat of this valve is to be on
that face of the piston B next to the live steam space A', and the valve in
leaving its seat is to move more or less into the steam space A'. This valve
is to be pressed open by a spring of any convenient form, and placed in any
convenient manner, and the pressure of this spring is to be such as to force
the valve off its seat, leaving a communication through the piston B, so that
steam may pass freely. This spring may be a common coil of steel wire, and
fts force when compressed or extended is to be such only as will move the
valve already described clear of its seat when the piston valve and other parts
are in the open air. A total force equal to 10 lbs. or more in proportion to
the size and weight of the valve will commonly suffice for this spring, and it
should be allowed to move the valve only inch, or thereabouts, off its seat,
at which point the valve should meet a stop of any kind to prevent its opening
further. The steam cylinder is to have ports made as in Figs. 1, 4, and,
indeed, in most of the Drawings annexed; but the port marked a in these
Drawings is to serve only for exhausting the steam from the end A of the
cylinder A, A, A, and A. This port is to enter the cylinder at a short
distance from the cover D, say, from one inch to two inches in ordinary cases.
The object of this is to permit the piston B to pass under and completely close
the inner end of the port a, as explained in connection with Fig. 16, Sheet 2.
This insures the "cushioning" of the piston on the return stroke towards the
cover D. The valve covering the other end of the port a may be an ordinary
slide valve, but having so much lap as to prevent the admission of steam to
the cylinder, although this is not indispensable. This slide valve answering to
that marked C in nearly all the annexed Drawings, is to be moved by the
pistons B and B' either directly or through the intervention of a lever, or any
other convenient means of imparting motion, and in order to move the slide
valve C into that position where it will exhaust steam from the cylinder A, it
is intended that the valve C or its working lever shall be struck, not by the
piston B itself, but by the circular valve already described as opening a com-

page_text: munication through it. The whole arrangement as thus far described may be
sketched in upon nearly all the Drawings attached to the Specification, more
particularly Fig. 4, Sheet 1, and will be understood without any difficulty.
Now although while the circular valve seated on one of the faces of piston B
has a tendency to remain open as long as there is steam of equal pressure
upon both its sides, it will be closed by striking the valve C, or by striking the
lever or other part whereby the valve C is moved. The steain which has
pressed the piston B away from the cylinder cover D has thus far been
admitted through the circular valve in the piston B itself. This admission of
steam having been stopped, it is possible that the piston B will not move
enough further to place the valve C in its proper position for exhausting. To
insure this further movement, however, a slight leakage of steam is to be
provided for by a fine hole in the piston B, or in the circular valve working
within it, or in any other part of the cylinder A, where a very narrow but
direct passage will admit steam into the cylinder A. This admission of steam
being provided, the piston B is certain to be carried far enough along its
stroke to effect the exhaust from the cylinder B. In most cases the expansion
of the steam in A will, after the circular valve in the piston B. has been closed,
move the piston B far enough to secure a good exhaust, and this without the
slight leak or passage of steam just described, but even in these cases this
leakage of steam will be required at the beginning of the next outward stroke.
It is evident that when the passage has once been opened to exhaust the
steam from the cylinder A, the circular valve in the piston B will remain
closed, notwithstanding the tendency of its spring to open it, for it will have a
pressure of steam upon it on that face exposed to the live steam in A' much
greater than the force of the spring tending to open it. The return stroke
will then be made, and the valve C must be arranged to close the upper end of
the port a (or at least to place it out of communication with the port 6) at or
about the time at which the piston B is closing the inner end of the port a.
The piston will then cushion itself as it approaches the cover D, and this
cushioning, or in any case the slight leakage of steam already referred to, will,
by placing the circular valve in the piston B in equilibrium, cause it to open,
and thus to readmit steam for the next outward stroke.
In other cases a different mode of working the valves may be resorted to,
and this mode cannot well be employed otherwise than in connection with the
differential steam engine, to which nearly all the varieties of the Invention
herein described exclusively apply. It is the object in all the several steam
engines herein described to continue the motion of the valve after the piston
has stopped at the end of the stroke. This is necessary in order to prevent

page_text: the valve stopping midway over the steam and exhaust ports, the effect of
which would be to stop the engine. The plan now referred to is but another
variety of that resorted to in connection with one or two other varieties of
differential engines herein described. It is that of putting a heavy weight in
motion, which weight is free to continue its motion after the piston which has
put it in motion has stopped.
In the horizontal engine shown in Fig. 1, Sheet 1, the live steam space A
may be supposed to be supplied with steam through a vertical pipe rising
from A', although this pipe is not shown on the Drawing. This pipe need
not be circular in section, but its diameter may be greater in the direction of
the length of the cylinder A than in a direction at right angles thereto; this
will permit the swinging of a pendulum or weight suspended from two feet to
four feet above from a joint or stud in the steam pipe. The lower part of
this weight may be struck to and fro by the pistons B and B', and the weight
itself may strike the valve C in each direction. The momentum of this
weight, freely suspended from a pin at some distance above it (this pin being
in the steam pipe supplying the live steam space A¹) will be such that the
valve C will in every case be carried through the proper extent of its motion.
even if the piston B should stop before the whole movement of the valve C
should be completed.
In other cases the weight required to insure the proper movement of the
valve may be in the form of a vibrating fly wheel, fixed to and moving with
the pin forming the fulcrum of the valve lever shown in Fig. 4, Sheet 1, as
well as in various others of the annexed Drawings. The pin forming the
fulcrum of the valve lever, and to which the valve lever is in this case to be
tightly fixed, may project through a stuffing box in the side of the engine, and
the vibrating fly wheel just referred to may then be fixed outside of the
engine; this vibrating fly wheel will act like the balance wheel of a watch,
and its momentum at each vibration will carry the valve through the whole
distance it ought to move, even although the pistons B and B¹ may have
stopped shortly after the valve C begins to move.
In differential steam engines of the kind described the live steam space A¹
may be formed within, and may, indeed, form a part of the boiler supplying
the engine with steam. In this case the engine will be started, not by
admitting steam, for this, as long as the boiler contains steam, will be always
present), but the engine will be started by opening a cock in the exhaust
pipe, and this cock in the pipe or passage through which the steam is
exhausted from the working end of the engine will be the proper and only
starting cock or valve required.

page_text: In all the steam engines described, a "steam trap," as it is commonly
called, may be fitted to the live steam space A¹ to catch and let off any water
formed by the condensation of the steam within that space.
Where any of
these engines are employed to work pumps for feeding steam boilers, the
engine should be so placed that the lowest part of the live steam space A¹
may be above the highest level of the water in the boiler. When thus
arranged, any steam condensing in the live steam space A¹ will run back
directly into the boiler, provided only that the steam pipe is properly placed to
admit of this.
It should be distinctly understood that the various modes of working the
valves of differential steam engines by the pendulum weight, and also by the
vibrating fly wheel, already described, are original Inventions of my own; so
also is the arrangement wherein a circular valve admits steam through the
working piston to the working end of the cylinder, as already fully described.
The plan of making the live steam space (herein referred to as A¹) of differential
steam engines, so that it shall form a part of the boiler working the engine,
is also novel; and so also is the mode described for draining any condensed
steam from the live steam space directly into the boiler, where the engine is
separate from or external to the boiler. The mode of starting the differential
engine by opening the exhaust, or a valve or cock in the exhaust port or pipe,
as herein-before described, is also of my own Invention.
With certain alterations which may be readily understood and made,
without requiring further description here, the cylinders of most of the engines
herein described may be made to move while the pistons are stationary.
With the moving cylinder instead of the moving pistons the weight in motion
would be sufficient to insure the complete change of the valve at each stroke,
generally without the special arrangements described for completing the
motion of the steam or exhaust valve. The special arrangements herein
described for that purpose are intended more especially for engines the piston
rods of which are directly connected to the pistons or plungers of pumps
working at slow speed and under considerable pressure; and it is evident
that these engines. may be made to work any kind of reciprocating pump,
such as the ordinary plunge pump, or the double-acting pump, or Norton's
Patent "V-pump," or any other pump requiring a reciprocating motion. The
engines may be employed, also, for almost any purpose where a reciprocating
motion is required.
In nearly all the Drawings attached to this Specification no steam or
exhaust pipes are shown; but the steam spaces with which it is necessary

page_text: that the steam pipes should communicate are distinctly shown, and so also
are the ports from which the exhaust pipes should lead; the steam and
exhaust pipes will be connected, therefore, in any convenient manner, so long
as they serve their proper purpose.
Instead of the special means shown in Fig. 27, Sheet 3, and also in one
other Drawing, for producing rotary motion, the "slotted cross head," with a
block on the crank pin may be employed, as in Messieurs Carrett, Marshall,
and Company's, and Beyer, Peacock and Company's "donkey" pumping
engines. In this case the "slotted cross head" and block are to be placed in
the live steam space A¹ of the engine in accordance with the general nature
of the present Invention, as described in the Provisional Specification.
Where arrangements are made for cushioning the piston at each end of
the stroke, the slide valves, whether of differential or ordinary steam engines
may be worked quite independently of the piston or pistons in the cylinder.
The means for this purpose, as originally devised by myself, consist either
of a steam turbine, or water turbine, or reaction wheel. The steam turbine
may be placed in the pipe leading to the live steam space of the engine, or
it may be placed in the exhaust pipe, or it may be placed externally to the
engine, and its shaft or revolving axis may communicate directly with the steam
valve within, the revolving axis or shaft passing through a stuffing box. Or,
if a water turbine or reaction wheel be preferred, it may be placed either in the
inlet or the outlet pipe of any pump working in conjunction with the engine, or
it may be placed externally to the engine, and supplied with water from
any convenient source. The form and capacity of such turbine or reaction
wheel are to be adjusted to the work to be done and to the steam or
water available for working it. Where the turbine is placed in either of
the pipes of the engine or either of those of the pump, the engine would
have to be got into motion by other means, as by hand gear, or cocks
which might be turned for the purpose. A reaction wheel may be made
of exceeding simplicity, and I am disposed to look upon it as a useful
means of working the valves of certain kinds of steam engines. The
shaft of the wheel would have a cam upon it acting directly at each revo-
lution upon the valve.
Such a mode of working the valves would be applicable to the class of
engines especially which I have described in the Specification of my Patent
of July 1862, and they would be equally applicable to engines in which
the steam acts in but one direction, only the piston being returned either by a
weight hung upon an arm attached to the piston rod, or by a constant pressure

page_text: of water upon a small plunger in connection with a supply of water under
pressure.
It is obvious that a live steam space, such as that marked A¹ in
nearly all the accompanying Drawings, and which admits the simplest
possible varieties of valve gear, may also be provided in a double-acting
engine of the ordinary kind by lengthening the cylinder and providing two
pistons of equal diameter with a space constantly filled with live steam between
them.
No claim is herein made for the differential engine by itself, but
for improvements which are especially applicable to that construction of
engine. These improvements are however, equally applicable to any form
of engine having a live steam space in constant communication with the piston
or pistons.
I have shown steam-moved valves in several of the accompanying
Drawings, and in my Specification of July 1862, I described certain improve-
ments of my own in connection with valves moved by the direct pressure
of steam.
Several Patentees have recently attempted to appropriate to themselves the
working of engine valves by the direct pressure of steam. It will be as well,
therefore, to give herewith a list of various Patents for steam-moved valves,
most of which Patents have lapsed in the ordinary course of time or by non-
payment of stamps.
Steam-moved valves are described in the Specification of the following
Patents, to wit:-
James Nasmyth, July 24th, 1843, No. 9850; Philip Walther, October
12th, 1848, No. 9902; Nasmyth and Gaskell, February 23rd, 1848, No.
12,074; John Fowler, junior, October 17th, 1850, No. 18,285; William
Edward Newton, May 19th, 1858, No. 1239. Henry R. Worthington,
January 16th, 1856, No. 122, also describes water-moved valves, the action
of which is the same as steam-moved valves.
wit
Continuing the Specifications including steam-moved valves, there are, to
David Joy, April 3rd, 1857, No. 929; William Edward Newton, August
17th, 1857, No. 2185; David Joy, November 1st 1860, No. 2668; James
Peterkin Douglas Camp, February 22d, 1862, No. 478; Zerah Colburn,
July 29th, 1862, No. 2145; William Neill, junior, June 16th, 1863, No.
1510. David Joy has a Patent also dated February 3rd, 1862, No. 283,
which is related to steam-moved valves.

page_text: The American Patent Reports, which have long been publicly known in
this country, also contain many descriptions of steam-moved valves.
Taking the United States Patent Office Report for 1855, Norman W.
Wheeler's steam-moved valves are described on the 586th page of the
volume of text, and the 130th page of the volume of illustrations. Hubbard
and Conant's valves appear in the same volumes, to wit, page 577 of text and
page 126 of cuts.
In the United States Patent Reports for 1857, Wheeler's steam-moved
valves are described on page 35 of the volume of text, and page 298 of the
volume of cuts. In the same volumes, Rubert's steam-moved valves are
described, to wit, page 39 of text and page 301 of cuts.
In the United States Patent Reports for 1858 and 1859, we have,-
For the year 1858
Volume of texts.
page 16
Wheeler
Perkins
For the year 1859
Shepherd
"
Clayton
Knowles
Luis-
15
-
page 364
297
وو
149
"
708
ور
Volume of cuts.
page 276
"
277
page 252.
166
"
دو
5
668
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I have now fully described the nature and mode of carrying into practical
effect my improvements in steam engines, and the several features of my
Invention have been so distinctly pointed out that it will not be necessary to
add anything further in the way of specific claims.
In witness whereof, I, the said Zerah Colburn, have hereunto set my
hand and seal, this Twentieth day of April, in the year of our
Lord One thousand eight hundred and sixty-four (1864).
Witness,
BERNARD LUXTON,
163, Strand. W.C.
ZERAH COLBURN. (L.S.)