IMPROVEMENTS IN STEAM ENGINES
Year: 1855

page_text: LETTERS PATENT to George Thomson, of Glasgow, in the County of
Lanark, North Britain, Engineer, for the Invention of "IMPROVEMENTS
IN STEAM ENGINES."
Sealed the 8th April 1856, and dated the 16th October 1855.
PROVISIONAL SPECIFICATION left by the said George Thomson at the
Office of the Commissioners of Patents, with his Petition, on the 16th
October 1855.
I, GEORGE THOMSON, of Glasgow, in the County of Lanark, North Britain,
Engineer, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN STEAM ENGINES" to be as follows, that is to say :-
This Invention relates to various mechanical contrivances applicable to the
valvular arrangements of all kinds of steam engines, and intended for the
purpose of cutting off the steam in such manner as to secure superior economy
in the expenditure of the steam, as well as the balancing or rendering uniform
the action of direct-acting engines:
In applying this Invention to a pair of direct-acting marine engines, the
whole of the valvular apparatus may be conveniently disposed between the two
steam cylinders, a single valve chest answering for both cylinders, the working
faces of the cylinders being opposite to and parallel with each other. The
cylinder thoroughfares are of the common three-ported kind, and each cylinder

page_text: face has fitted upon it a long working slide valve, having a central exhaust
cavity on its.inner face, and two duplex thoroughfares passing directly through
it, one at each end. Each of these. thoroughfares consists of one passage
directly through the valve from back to front, at the extreme end, with a
secondary branch passage opening from the back of the valve at a point con-
siderably nearer to the valve's longitudinal centre, and terminating at its other
end in the through passage. Hence, each of these duplex thoroughfares has
two ports on the back and one on the front face of the valve: The valve is
worked in the ordinary manner by an eccentric. The four-ported back of the
valve is planed true to receive three separate valve plates, the central one of
which is a plain flat traversing slide, disposed upon the blank portion of the
valve between the ports, and worked by a common eccentric, so as to govern
both the contiguous branch passages of the valve thoroughfares. The four
external ports of the main valve thoroughfares are governed by a set of four
adjustable plates, which are perfectly stationary during the regular working of
the valves, being only shifted when the cut-off is to be altered. These four
plates may be arranged in various ways. According to one plan 'the individual
plates of the upper and lower pairs are respectively placed upon the two oppo-
site ends of an upper and lower transverse spindle, passed across the space
between the two main slide valves in the valve chest. To the longitudinal
centre of each spindle is jointed one end of a short connecting link, the other
contiguous ends of which links are jointed to the two opposite ends of a short
double armed lever, carried upon a transverse spindle passing right through
the valve chest. One externally projecting end of this spindle has a lever fast
upon it, the outer end of this lever having a nut attached to it for the passage
through of a screwed spindle, fitted with a hand wheel.
.By this arrangement the attending engineer can always set the four cut-off
plates by turning this hand wheel, as its revolution causes the knee joint action-
of the intermediate connecting links to traverse outwards, or bring closer
together each pair of plates. This adjustment of the stationary cut-off plates
causes an earlier or later cut-off of the steam at the four external ports which
they govern, accordingly as the pairs of plates are approximated or sundered.
When the steam enters by the direct through passage to gain admission to the
cylinder port, the branch of this thoroughfare is closed by the central plate,
and it is only when steam is required to pass at the movement of the crank
being on the centre, that this branch is uncovered for the passage of the steam
by that route. The adjustment of the four cut-off plates may be effected by a
right and left screw spindle arrangement, either of direct action or working in
connection with angled links, or in other ways.
V

page_text: When the herein-before described arrangements of valves are applied to
vertical cylinder direct-acting-engines, provision is made for the admission of
more steam during the piston's up stroke for the purpose of balancing the
engine, by differentially proportioning the knee joint levers, angled links, or
other mechanical contrivances, which act upon the stationary cut-off plates,
so that any adjustment of them may act to a greater extent on the lower
plates; or when the plates are adjusted by screws by making the screws of
different pitches, so as to act in a similar manner.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said George Thomson in the Great Seal Patent Office on the
14th April 1856.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GEORGE
THOMSON, of Glasgow, in the County of Lanark, North Britain, Engineer,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Sixteenth day of October, in the year of our Lord
One thousand eight hundred and fifty-five, in the nineteenth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said George Thomson, Her special license that I, the said George Thomson,
my executors, administrators, and assigns, or such others as I, the said George
Thomson, my executors, administrators, or 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 George Thomson, by an
instrument in writing under my hand and seal, should particularly describe
and ascertain the nature of the said Invention, and in what manner the same
was to be performed, and cause the same to be filed in the Great Seal Patent
Office within six calendar months next and immediately after the date of the
said Letters Patent.
NOW KNOW YE, that I, the said George Thomson, do hereby declare
the nature of my said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement in writing, reference being had to the accompanying Drawings, and
to the letters and figures marked thereon, that is to say:-

page_text: '
My said Invention relates to various mechanical contrivances applicable to
the valvular arrangements of all kinds of steam engines, and intended for the
purpose of cutting' off the steam in such manner as to secure superior economy
in the expenditure of the steam, as well as the balancing or rendering uniform
the action of direct-acting engines. In applying this Invention to a pair of
direct-acting marine engines, the whole of the valvular apparatus may be
conveniently disposed between the two steam cylinders, a single valve chest
answering for both cylinders, the working. faces of the cylinders. being
opposite to .and parallel with each other. The: cylinder thoroughfares are
of the common three-ported kind, and each cylinder face has fitted upon it
a long working slide valve, having a central exhaust cavity on its inner
face, and two duplex thoroughfares passing directly through it, one at each
end. Each of these thoroughfares consists of one passage directly through
the valve from back to front at the extreme end, with a secondary branch
passage opening from the back of the valve, at a point considerably. neȧrer
to the, valve's longitudinal, centre, and terminating at its other end in the
through passage. Hence each of these duplex thoroughfares has two ports on
the back, and one on the front face of the valve. The valve is worked in, the
ordinary manner by an eccentric.. The four-ported back of the valve is planed
true to receive, three separate valve plates, the central one of which is a plain
flat traversing slide disposed upon the blank portion of the valve between the
ports, and worked by a common eccentric, so as to govern both the contiguous
branch passages of the valve thoroughfares. As adapted to a pair of steam
engine cylinders, the four external ports of the main valve thoroughfares are
governed, by a set of four adjustable plates, which are perfectly, stationary
during the regular working of the valves, being only shifted when the cut-off
is to be altered. These four plates may be arranged in various ways: according
to one plan the individual plates of the upper and lower pairs, are respectively
placed upon the two opposite ends of an upper and lower transverse spindle
passed across the space between the two main slide valves in the valve chest.
To the longitudinal centre of each spindle is jointed one end, of a short, connect-
ing link, the other.contiguous ends of which links are jointed to the two opposite
ends of a short double-armed lever, carried upon a transverse, spindle; passing
right through the valve chest.. One externally projecting end of this spindle
has a lever fast upon it, the outer end of this lever having a nut attached to it
for the passage through of a screwed, spindle fitted with a hand wheel. By
this arrangement the attending engineer can always set the four cut-off plates
by turning this hand wheel, as its revolution. causes the knee-joint action of
the intermediate connecting links to traverse outwards or bring closer together

page_text: each pair of plates. This adjustment of the stationary cut-off plates causes an
earlier or later cut-off of the steam at the four external ports which they
govern, accordingly as the pairs of plates are approximated or sundered.
When the steam enters by the direct through passage to gain admission to the
cylinder port, the branch of this thoroughfare is closed by the central plate,
and it is only when steam is required to pass at or about the moment of the
crank. being on the centre that this branch is uncovered for the passage of the
steam by that route. The adjustment of the four cut-off plates may be effected
by a right and left screw spindle arrangement, either of direct-action, or
working in connection with angled links, or in other ways.
When the herein-before described arrangements of valves. are applied to
vertical cylinder direct-acting engines provision is made for the admission of
more steam during the piston's up-stroke, for the purpose of balancing the
engine by differentially proportioning the knee-joint levers, angle links, or
other mechanical contrivances which act upon the stationary cut-off plates, so
that any adjustment of them may act to a greater extent on the lower plates;
or when these plates are adjusted by screws by making the screws: of different
pitches, so as to act in a similar manner.
And in order that my said Invention may be properly understood, I shall
now proceed to describe the several Figures on the illustrative Sheet of
explanatory Drawings, which I have appended hereunto.
'
Figure 1, on my Sheet of Drawings, is a longitudinal vertical section of one
modification of my improved valvular apparatus, as applied to a pair of inverted
marine steam-engine cylinders of the ordinary three-ported kind; Figure:2 on
the same Sheet of Drawings is a back face elevation of the arrangement as
regards one valve, the other being removed.;; Figure 3 is a horizontal transverse
section of the two valves, strictly corresponding with Figure 1; 'and Figure 4
is an external elevation of the duplex valve chest, shewing the adjusting screw
spindle, and the index pointing out the "set" of the apparatus. The main
steam-slide valve A in each case is truly faced on both the. back and front
sides, and it has a long central exhaust cavity B on:its cylinder. face; and two
separate duplex thoroughfares: C, D, and E, F, one near each end of the valve.
These duplex thoroughfares are so formed and arranged that they have three
separate ports, or entrance and exit ways, one on the cylinder face side, and
the other two on the back or cut-off valve side. One of the passages in each
case, as D and F, runs directly through the valve.from face to face, whilst the
secondary branches C.and E communicate between the back face of the valve
and the through passages. This main steam valve is worked in the ordinary
manner by an eccentric on the crank shaft connected with the valve spindle.G.

page_text: On the central portion of the back of the valve is a plain.flat valve plate or
traversing slide H, working upon the: blank face between the ports. It is
actuated by a separate eccentric, attached to the spindle I in such manner as
to govern or command both the contiguous ports of the branch passages C and
E. It is to be remarked that the steam slide valve for the opposite cylinder
is precisely the same as the one just described, and it has a plain slide plate on
its back-worked in a similar way. The four end thoroughfares marked D and
F in one valve: are all governed by the series of four adjustable plates J, K,
which are shifted only when the engine attendant wishes to alter the expan-
sion cut-off of the valves. These plates J,. K, are respectively attached to the
'opposite extremities of four transverse spindles :L, having helical springs
thereon for keeping the plates up to their working faces. The central slides
"H are similarly kept in due working contact with the backs of the main steam
valves by the central split spring M, attached to the inside of the top cover of
the valve chest. The set of the four plates J, K, is entirely performed by the
external hand wheels. N. upon the two opposite ends of a horizontal screw
spindle O, supported in bearing brackets bolted to the outside of the valve
chest. This screw spindle O is entered through a nut P fitted into the slotted
end of the forked pendant lever Q, fast. on the external projecting end of a
horizontal eccentric shaft R. This shaft R works in a stuffing box on the
front side of the valve chest, and it extends right through the space between
the two, main slide valves, having fast upon it four small eccentrics S, T,
placed in pairs. These eccentrics are fitted with externally squared slide ring
blocks, which again are fitted into the horizontal openings of four separate
eccentric frame pieces U.. The frames of the two outer eccentrics S are con-
nected to two short link pieces V, which have eyes upon their upper ends,
entered upon the two upper spindles L of the plates J. Similarly, the frames of
the two inner eccentrics T are connected to links W, which have eyes in their
lower ends entered upon the two spindles L of the lower plates K. Each of
the links V, W, is fitted with an eye X, through which short guide spindles
on the eccentric frames are passed to steady the eccentric action. In this way,
and by these means, the engine attendant can at any time cause the pairs of
plates J and K to approach to, or recede from each other, by turning the
hand wheels N, the amount of such adjustment being always pointed out by
the index hand Y of the lever Q, pointing to the graduations on the segmental
scale outside the valve chest. If the plates are made to recede from each
other, they produce a correspondingly late cut-off of the steam at the four
external ports in the main slide valves which they govern. If the plates on
the other hand are approximated closer to each other; the action of the

page_text: arrangement is such, that the steam is cut off from the cylinders at a corre-
spondingly earlier period, the plates J, K, being stationary during the regular
working of the engine, and the cut-off being performed entirely by the action.
of the main slide valves in their ordinary traverse. At the instant that
the steam enters by the direct thoroughfares D, F, to gain admission to the
working cylinder, the corresponding branches C, E, are about closed by the
central plate H of each valve. Steam is admitted to the cylinder through
these branches, only at the time when the crank of the engine is on the centre,
or thereabouts, and thus the traversing plates H, and the stationary adjustable
plates J, K, work together in concert for a most effective regulation of the
steam supply. In the example of valve which I have represented in my Sheet
of Drawings, provision is made for the steam balancing of the vertically acting
pistons of the engines, by making the eccentrics S for the upper plates J some-1
what larger than the others. This arrangement gives a greater proportional
traverse of the upper plates, so that more steam is thrown into the cylinders
below the pistons than above them, and the weight of the pistons and appur-
tenances is thus properly counterbalanced.
Having now described and particularly ascertained the nature of my said
Invention, and the manner in which the same is or may be used or carried
into effect, I may observe, in conclusion, that I do not confine or restrict myself
to the precise details or arrangements which I have had occasion to describe or
refer to, as many variations may be made therefrom without deviating from
the principles or main features of my Invention, but what I consider to be
novel and original, and therefore claim as the Invention secured to me by the
herein-before in part recited Letters Patent, is,―
First, the general arrangement and construction of the valves of steam
engines, as herein-before described.
Second, the application and use in steam engines of valves with duplex
thoroughfares or passages, for the purposes herein-before described.
Third, the system or mode of effecting the cut-off regulation of the steam in
the slide valves of steam engines, by the application of stationary cut-off plates
governing the end thoroughfares of valves, the secondary branch passages of
which thoroughfares are governed in concert therewith-by central traversing
slides.
Fourth, the system or mode of regulating the supply of steam to steam
engine cylinders in such manner that whilst stationary adjustable cut-off plates
admit the steam through direct thoroughfares in the slide valve, steam is also
admitted by secondary branches of such thoroughfares at the time when the
engine crank passes the centre or thereabouts.

page_text: Fifth, the system or mode of balancing or counterpoising the weight of
steam engine pistons and appurtenances, by giving the upper adjustable cut-off
plate of the valve an advance traverse as compared with the lower plate.
: In witness whereof, I, the said George Thomson, have hereunto set my
hand and seal, this Eleventh day of April, One thousand eight hundred
and fifty-six.
GEORGE THOMSON. (L.S.)