IMPROVEMENTS IN SLIDE VALVES
Year: 1869

page_text: LETTERS PATENT to Archibald Gilchrist, of Glasgow, in the County
of Lanark, North Britain, Engineer and Shipbuilder, for the Inven-
tion of "IMPROVEMENTS IN SLIDE VALVES."
tion of "IMPROVEMENTS IN SLIDE VALVES."
Sealed the 15th February 1870, and dated the 19th August 1869.
PROVISIONAL SPECIFICATION left by the said Archibald Gilchrist
at the Office of the Commissioners of Patents, with his Petition,
on the 19th August 1869.
I, ARCHIBALD GILCHRIST, of Glasgow, in the County of Lanark, North
Britain, Engineer and Shipbuilder, do hereby declare the nature of the
said Invention for "IMPROVEMENTS IN SLIDE VALVES," to be as follows, that
is to say :-
This Invention has for its object the constructing of slide valves in
an improved manner, and consists principally in adapting to what are
known as double-ported passages a valve which works between the
ordinary port face and a back plate fixed in the valve casing, so as
to prevent the pressure of the steam or other fluid from acting on the
back of the valve. The valve is in the form of a frame with parallel

page_text: faces and with three openings through it a narrow one at each end
and a larger one in the middle. The port face is made with the exhaust
port in the middle in the usual way, and with the two ports of one
cylinder passage at one end, and those of the other passage at the other
end. The fixed back plate is made with its working faces exactly
like those of the port face, and opposite to each pair of passage ports
in the port face there are two ports communicating with each other
by a passage formed in the back plate. The movement of the valve
brings the narrow opening or valve port at one end of it alternately
over the inner and outer ports of the cylinder passage at that end, and
when it is over the inner port the steam has access directly to the
outer port, and to the corresponding opposite port in the back plate,
by which last it enters the passage in the back plate, and finds its way
through the valve port to the inner passage port, but when the valve
port is over the outer passage port the inner passage communicates
directly with the exhaust, whilst the outer port also communicates
therewith through the valve port, and through the passage in the back
plate. The same actions take place between the valve port and passage
ports at the other end, but at different times. The back plate is
fixed in the valve casing in any convenient way, as, for example,
by taper keys or wedges, which hold it between ribs formed in the
sides of the casing. If it is wished to apply cut, off valves, passages
and ports are formed for the purpose in the back plate, and the cut off
valve or valves is or are applied on the back thereof.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Archibald Gilchrist in the Great Seal Patent Office
on the 18th February 1870.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ARCHIBALD
GILCHRIST, of Glasgow, in the County of Lanark, North. Britain,
Engineer and Shipbuilder, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria,, by. Her
Letters Patent, bearing date the Nineteenth day of August, in the year
of our Lord One thousand eight hundred and sixty-nine, in the thirty-
third year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Archibald Gilchrist, Her special licence

page_text: that I, the said Archibald Gilchrist, my executors, administrators, and
assigns, or such others as I, the said Archibald Gilchrist, my exccutors,
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 SLIDE
VALVES," upon the condition (amongst others) that I, the said Archibald
Gilchrist, my executors or administrators, by an instrument in writing
under my, or their, or one of their hands and scals, 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 Archibald Gilchrist, 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 in writing, reference being had to the accom-
panying Drawings, that is to say :-
My said Invention has for its object the constructing of slide valves
in an improved manner, and consists principally in adapting to what
are known as double-ported passages a valve which works between
the ordinary port face and a back plate fixed in the valve casing so
as to prevent the pressure of the steam or other fluid from acting on
the back of the valve.
And in order that my said Invention and the manner of performing
the same may be properly understood, I have hereunto appended a
Sheet of explanatory Drawings, to be herein-after referred to, and
representing two applications of my improved valve, one having
combined with it a separate cut off valve and the other being without
such separate valve. The valves are shown as applied to combined
high-pressure and low-pressure cylinders 1, 2, delineated in horizontal
section in Figure 1, and in vertical section in Figure 2; Figure 3 is an
elevation of the high-pressure port face 3; and Figure 4 is an elevation
of the low-pressure port face 4; whilst Figures 5 and 6 are face views
of the high-pressure valve '5 and low-pressure valve 6 respectively.
The valve 6 of the low-pressure cylinder 2 is the simpler of the two,
and is in the form of a frame, with parallel faces and with three openings

page_text: through it, a narrow one 7, 8, at each end and a larger one 9 in the
middle. The port face 4 is made with the exhaust port 10 in the middle
in the usual way, and with the two ports 11, 12, of one cylinder
passage 13 at the upper end, and those 14, 15, of the other
.
passage 16
at the bottom end. The fixed back plate 17 is made with its working
face exactly like the port face 4, and opposite to each pair of passage
ports 11, 12, and 14, 15, there are two ports communicating with each
other by a passage 18, 19, formed in the back plate. The movement
of the valve 6 brings the narrow opening or valve port 8 at one end
of it alternately over the inner and outer ports 14, 15, of the cylinder
passage 16 at that end, and when it is over the inner port 14, as shown,
the steam, as indicated by the black arrows, has access directly to the
outer port 15 and to the corresponding opposite port in the back plate 17,
by which last it enters the passage 19 in the back plate and finds its
way through the valve port 8 to the inner passage port 14, but when
the valve port is over the outer passage port, as is the case in the position
delineated, with the port 7 at the other end of the valve, the inner
passage port 11 communicates directly with the exhaust 10, whilst
the outer port 12 also communicates therewith through the valve port 7,
and through the passage 18 in the back plate 17. The same actions
of course take place at both ends but alternately. The back plate 17
may be fixed in the valve casing in any convenient way, as, for example,
by taper keys or wedges 20, which hold it between ribs 21 formed in
the sides of the casing as in the low-pressure casing, or it may be bolted
to lugs or flanges 22, as shown in the high-pressure casing. The valve 5
of the high-pressure cylinder 1 and its back plate 17 have the same ports
and passages as the valve 6 and its back plate, and they only differ in the
additions required when applying cut off valves 23. These cut off valves
act on the back of the plate 17, and control the entrance of the steam
through passages 24, 25, formed through the back plate. The valve 5
is extended and formed with additional ports or spaces 26, 27, at the
ends, into which the steam passes from the passages 24, 25, and from
which it proceeds in the manner herein-before explained with reference
to the low-pressure valve.
Having thus particularly described my said Invention, and the manner
in which the same is to be performed, I have to state that I do not
restrict myself to the precise details herein described or delineated; but
that what I believe to be novel and original, and claim as the Invention

page_text: secured to me by the hercin-before in part recited Letters Patent is,
the adapting of a slide valve working between the cylinder port face
ind a back plate to act for double-ported passages by making additional
ports in the valve and passages in the back plate, substantially as
herein-before described."
secured to me by the hercin-before in part recited Letters Patent is,
the adapting of a slide valve working between the cylinder port face
and a back plate to act for double-ported passages by making additional
ports in the valve and passages in the back plate, substantially as
herein-before described."
In witness whereof, I, the said Archibald Gilchrist, have hereunto
set my hand and seal, this Seventeenth day of February, in the
ind a back plate to act for double-ported passages by making additional
ports in the valve and passages in the back plate, substantially as
herein-before described.
In witness whereof, I, the said Archibald Gilchrist, have hereunto
set my hand and seal, this Seventeenth day of February, in the
year of our Lord One thousand eight hundred and seventy.
In witness whereof, I, the said Archibald Gilchrist, have hereunto
set my hand and seal, this Seventeenth day of February, in the
year of our Lord One thousand eight hundred and seventy.
ARCHP. GILCHRIST. (L.S.)