IMPROVEMENTS IN AND APPLICABLE TO SLIDE VALVES FOR STEAM ENGINES
Year: 1857

page_text: LETTERS PATENT to Thomas Forsyth, of the City of Manchester, En-
gineer, for the Invention of "IMPROVEMENTS IN AND APPLICABLE TO SLIDE
VALVES FOR STEAM ENGINES."-A communication.
Sealed the 12th January 1858, and dated the 31st July 1857.
PROVISIONAL SPECIFICATION left by the said Thomas Forsyth at
the Office of the Commissioners of Patents, with his Petition, on the
31st July 1857.
I, THOMAS FORSYTH, of the City of Manchester, Engineer, do hereby
declare the nature of the said Invention for "IMPROVEMENTS IN AND APPLICABLE
TO SLIDE VALVES FOR STEAM ENGINES," being a communication from a foreigner
residing abroad, to be as follows:-
The object of this Invention is to reduce the pressure on slide valves,
thereby economising the power required for working them, and diminishing the
wearing of the valves and their seatings, and of the machinery for working
them.
In performing this Invention a plate is applied to the back of the valve,
and pressure is given to this plate by a wedge acted upon endwise by a spring.
A second spring is applied to the back plate and wedge, so as to allow the
valve to rise off its seating if necessary. Provision is made by set screws

page_text: passing through the lid of the valve chest or otherwise for keeping the valve
up to its seating as it wears away. The back of the valve is open, thereby
allowing the steam to assist in lubricating it, and also to facilitate in adjusting
the valve to the ports.
When this Invention is applied to inside cylinder locomotive engines or
other engines in which one steam chest answers for two valves, the back
plates are wedge-shaped, and one of them is acted upon by a spring endwise,
and the other by a regulating set screw. The back plates are united by ribs
on one, and grooves on the other, the grooves being sufficiently large to allow
the valve to lift off its facing to allow for the escape of water.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Thomas Forsyth in the Great Seal Patent Office on the
30th January 1858.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
FORSYTH, of the City of Manchester, Engineer, send greeting..
WHEREAS Her most, Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirty-first day of July, in the year of our Lord One.
thousand eight hundred and fifty-seven, in the twenty-first year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Thomas Forsyth, Her special licence that I, the said Thomas Forsyth, my
executors, administrators, and assigns, or such others as I, the said Thomas-
Forsyth, 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 Mau, an Invention: för "IMPROVEMENTS IN
AND APPLICABLE: TO SLIDE: VALVES: FOR. STEAM ENGINES," being a communication
from a foreigner residing abroad, upon the condition (amongst others)' that
I, the: said Thomas Forsyth, my executors; or administrators; by an instru-
ment 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. Seal Patent.Office within six calendar months next and immediately
after the date of tlie. said Letters Patent.
NOW KNOW YE, that I, the said Thomas Forsyth, do hereby declare
the nature of my said Invention; and in what manner the same is to be-per-

page_text: formed, to be particularly described and ascertained in and by the following
statement (that is to say):
The object of the said Invention of "Improvements in and applicable to
Slide Valves for Steam Engines" is to reduce the pressure on such valves,
thereby economising the power required for working them, and diminishing
the wearing of the valves and their seatings, and of the machinery by which
they are put in motion.
The nature of this Invention consists in applying a plate to the back of
the valve, to which pressure is given by a wedge acted upon endwise by an
adjustable external spring. A second spring is applied to the back plate and
wedge, acting on the valve so as to allow it to rise off its seating if necessary.
Provision is made by set screws passing through the lid of the valve chest or
otherwise for keeping the valve up to its seating as it wears away. The back
of the valve is open, thereby allowing the steam to assist in lubricating it, and
also to facilitate in adjusting the valve to the ports.
When this Invention is applied to inside cylinder locomotive engines or
other engines in which one steam chest answers for two valves, the back
plates are wedge-shaped, and one of them is acted upon endwise by an
external adjustable spring, and the other by a regulating set screw. The back
plates are united by ribs on one, and grooves on the other, the grooves being
sufficiently large to allow each valve to lift off its facing to allow for the
escape of water.
And in order that this Invention may be fully understood and readily
carried into operation, I will proceed to describe the accompanying Sheet of
Drawings, reference being had to the figures and letters marked thereon.
Figure 1 is a section of an outside cylinder locomotive steam engine
to which these improvements are applied; Figure 2 is a plan view, and
Figure 3 a transverse section of the same. a is the cylinder, b the steam chest,
and c is the lid of the steam chest, d is the slide valve, e the wedge, and f
the back plate, connected to the lid c by the four set screws g. To the wedge e
is fixed the spindle h, passing through the stuffing box i and connected to the
spring; the action of the spring presses the thin end of the wedge towards
the opposite side of the steam chest, and as the upper surface of the wedge is
pressed upon by the spring k, fixed to the back plate f, it is evident that the
combined action of the wedge and the spring k keep the slide valve d on its
face. The back of the valve is open, thereby admitting the steam to the
interior, and allowing it to assist in lubricating the face of the seating, and
affording facility in adjusting the valves to the ports, which are shewn in
Figure 3. The lock nuts on the spindle h of the wedge e are to regulate

page_text: the pressure of the spring on the wedge. When, owing to the wearing of
the valve on its seating, the wedge e has been moved until the thin end is
nearly in contact with the side of the steam chest, the wedge is drawn back
by hand or otherwise, and the set screws g are adjusted in order to move the
back plate f little nearer to the slide valve, by this means the parts are
again set for resuming work until the surfaces of the valve and seating are
again worn away, as before. The wedge e is guided in grooves in the back
plate f, as shewn in Figure 3, and the grooves are made rather larger than
the ribs sliding in them; the object of this is to allow the valve to lift off its
face for the escape of water or when otherwise necessary. When the valve
has been so lifted off its face, it is brought against it again by the spring.k.
Figure 4 is a section of the steam chest and part of the cylinders of an
inside cylinder locomotive steam engine, and Figure 5 a transverse section of
the same.
In these views m, m, are parts of the cylinders; n, n, the slide
valves; and o,p, the back plates, which are wedge-shaped, and pressed against
the valves by the spring u. These plates are connected together by ribs on
the plate o, taking into grooves in the plate p, sufficient space being left to
allow both the valves n to rise off their facings if requisite. The back plate o
has a spindle q passing through a stuffing box r, and furnished with a spring s
similar to the one marked j in Figures 1 and 2. The other back plate p is
acted upon by the set screw t to compensate for the wearing of the surfaces.
of the valves and facings. By this arrangement the pressure on slide valves
is considerably reduced, and much less force is necessary for moving them,
thereby greatly economising the motive power and diminishing the wearing.
of the valves and their seatings, and of the machinery by which they are put
in motion.
Although these improvements in and applicable to slide valves are only
shewn and described in reference to locomotive steam engines, it will be
apparent that they are also beneficial when applied to stationary or other
engines.
Having thus stated the nature of the Invention as communicated to me,
and described the means of carrying the same into practical operation, I wish
it to be understood that I am aware that wedges have before been applied in
various ways to the slidė valves of engines, and that I make no claim to
them; but what I do claim is,-
First, the back plate marked f, and adjusting screws g and the spring k
when used in combination with a wedge for keeping the valve up to its
seating, and allowing the valve to rise off its seating, as shewn and described
in reference to Figures 1, 2, and 3.

page_text: Secondly, the application of the adjustable external spring J or other
equivalent agent for pressing against the wedge to impart and regulate the
pressure on the valve.
And, lastly, the arrangement shewn and described, in reference to Figures
4 and 5, for giving pressure to two valves placed near to each other.
In witness whereof, I, the said Thomas Forsyth, have hereto set my
hand and seal, this Twenty-ninth day of January, in the year of our
Lord One thousand eight hundred and fifty-eight.
Witness,
H. B. BARLOW,
Manchester.
THOMAS FORSYTH. (L.S.)