IMPROVEMENTS IN MOTIVE-POWER ENGINES
Year: 1869

page_text: LETTERS PATENT to Andrew Barclay, of Kilmarnock, in the County
of Ayr, North Britain, for the Invention of "IMPROVEMENTS IN
MOTIVE-POWER ENGINES."
Sealed the 22nd December 1869, and dated the 1st July 1869.
PROVISIONAL SPECIFICATION left by the said Andrew Barclay at the
Office of the Commissioners of Patents, with his Petition, on
the 1st July 1869.
I, ANDREW BARCLAY, of Kilmarnock, in the County of Ayr, North
Britain, do hereby declare the nature of the said Invention of "Im-
PROVEMENTS IN MOTIVE-POWER ENGINES," to be as follows, that is to say :-
This Invention, which relates to improvements in motive-power
engines, consists in a special arrangement and construction of the valves
by which the motive agent, such as steam, air, or gas (herein-after called
steam) is distributed and cut off from the cylinders in which it acts upon
the pistons. A double or compound valve is employed, that is to say,
a valve which travels in direct contact with the steam and exhaust ports,
and having another travelling on the back of it. The steam ports in the

page_text: lower side of the under valve are made large enough to leave the steam
ports on the cylinder full open during the entire time that the steam is
admitted in full by the ports in the top side of the valve; and the cover
or upper valve has one port made at its centre in such position that
immediately one of its edges begins to cut off the steam from entering
one of the larger and outer ports in the under valve the port in the top
valve passes over and opens one of the second ports in the upper side
of the under valve in the exact ratio that the larger port is being
closed, so that although the larger port is being gradually closed yet the
supply of steam remains constant until the larger port is half closed, at
which instant or position both the larger as well as the smaller ports are
quickly closed over by the upper valve through the action of the
eccentrics by which the valves are driven. From this arrangement it is
obvious that as the steam commences to be cut off only when the larger
port is half covered by the upper valve the cut off is effected with a
travel of valve equal to only half the width of the larger port in the
under valve, and thus a greater advantage is derived from the expansion
of the steam in the cylinder than in cases where the cut off is performed
in a longer interval of time. It is to be understood that both the larger
as well as the smaller ports in the upper side of the under valve com-
municate with each other, so that the steam escapes into the cylinder
by one steam port in the under side for either end.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Andrew Barclay in the Great Seal Patent Office
on the 1st January 1870.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ANDREW
BARCLAY, of Kilmarnock, in the County of Ayr, North Britain, send
greeting.
•
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the First day of July, in the year of:
our Lord One thousand eight hundred and sixty-nine, in the 33d
year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Andrew Barclay, Her special license that I,
the said Andrew Barclay, my executors, administrators, and assigns,

page_text: or such others as I, the said Andrew Barclay, my executors, adminis-
trators, 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
MOTIVE-POWER ENGINES," upon the condition (amongst others) that I, the
said Andrew Barclay, 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 Andrew Barclay, 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, reference being had to the accompanying
Drawings and to the letters and figures marked thereon, that is to
say:-
My said Invention, which relates to improvements in motive-power
engines, consists in a special arrangement and construction of the
valves by which the motive agent, such as steam, air, or gas (herein-after
called steam) is distributed and cut off from the cylinders in which it
acts upon the pistons. A double or compound slide valve is employed,
that is to say, a valve which travels in direct contact with the steam
and exhaust ports, and having another travelling on the back of it. The
steam ports in the lower side of the under valve are made large enough
to leave the steam ports in the cylinder full open during the entire time
that the steam is admitted in full by the admission ports in the top side
of the valve, and the cover or upper valve has one admission port made
at its centre in such a position that immediately one of its edges (that
is of the upper valve or cover) begins to cut off the steam from
entering one of the larger and outer admission ports in the under valve
the admission port in the top valve passes over and opens one of the
second or smaller admission ports in the upper side of the under valve
in the exact ratio that the larger admission port therein is being closed,
so that although the larger admission port is being gradually closed,
yet the supply of steam remains constant until this larger port is half

page_text: closed, after which instant or position both the larger as well as the smaller
admission ports are quickly closed over by the upper valve through
the action of the eccentrics by which the valves are driven. From this
arrangement it is obvious that as the steam commences to be cut off
only when the larger admission port is half covered by the upper valve
the cut off is effected with great rapidity, and with a travel of the
under valve of less linear extent than half the width of the larger
admission port therein, as both the valves (that is upper and under)
move in opposite directions, and thus a greater advantage is derived
from the expansion of the steam in the cylinder than in cases where
the cut off is performed in a longer interval of time. It is to be
understood that both the larger as well as the smaller admission ports
in the upper side of the under valve communicate with each other,
so that the steam escapes into the cylinder by one steam port in the
under side common to the two admission ports in the upper one for
either end.
And in order that my said Invention may be properly understood,
I now proceed more particularly to set forth the system, mode, or
manner in or under which the same is or may be used or practically
carried into effect.
On Sheet 1 of the appended Drawings Figures, 1, 2, and 3 represent
horizontal sections of a steam cylinder with the piston in three different
positions of its stroke.
At Figure 1 the eccentrics A and B by which the valves C and D are
driven together with the crank shaft B are shewn. The piston Fin
Figure 1 is at the beginning of the stroke. In the under valve D, G, G',
are the admission ports and H the exhaust port, G³ and G³ being the
passages by which the steam is admitted to the cylinder. As the piston
F in Figure 1 is about commencing its outward stroke the slide valve D is
being moved outwards in the direction of the arrow by the eccentric
B, so as to admit the steam by the port G into the passage G', at the
same time educing or exhausting the steam used for the previous inward
stroke of the piston through the passage G³, thence into the exhaust
port I through the exhaust cavity H. Whilst the under valve D is
moving in the direction indicated by the arrow the upper valve or cover
C is moved in the opposite direction by the eccentric A, until the front
edge a of the cover C meets the edge of the steam port of the under
valve, at which moment the front edge of the port W in the cover

page_text: C meets the edge d of the port e of the valve D, so that as the upper
valve or cover C closes over the port G of the valve D an equal ad-
mission of steam to that thereby cut off is admitted by the middle
admission port in the upper valve or cover C, until the port in the cover
C coincides with the port e in the valve D, at which period the larger
steam port G of the valve D is half closed by the cover C as shown
at Figure 2, where the valves are in position to commence the cut off
of the steam, it being explained that the port in the valve or cover C
is equal to the smaller port e in the valve D, this port e being half the
width of the larger port in the valve D, whilst the lower port L in the
valve D common to both the larger and smaller admission ports is of
such a breadth as to allow the steam passage G2 to remain full open to
the admission of steam, until it is entirely cut off from entering the
ports e and G by the valve or cover C as shown at Figure 3, in which
position the exhaust port H is also fully open. By means of the
arrangement herein-before set forth and shewn on the Sheet of Drawings
referred to it is obvious that the admission of steam is cut off in a
very short time with comparatively slow working engines, so that the
wiredrawing of the steam resulting from a gradual cut off or closing
of the admission port is either prevented or reduced to a minimum. The
description herein-before given with reference to that end of the valves
corresponding to the admission of steam for the outward stroke of the
piston would obviously apply to the valves when in position for the
admission of steam for effecting the inward stroke of the piston.
At Figures 1, 2, and 3, Sheet 2, a similar arrangement of upper valve.
or cover is shown applied to cylinders which have a separate admission
and exhaust port at each end of the cylinder, in place of an exhaust
port common to both ends of the cylinder as set forth in the arrange-
ment herein-before described with reference to the Figures on Sheet 1
of the Drawing. On account of the position and arrangement of the
steam and exhaust ports G and H at each end of the cylinder on Sheet
2 of the Drawings a separate valve D is required for each end of the
cylinder, having a steam port and exhaust port in it, in place of an
exhaust port common to both ends of the cylinder as in the arrangement
shown on Sheet 1. The valves D, on Sheet 2, are coupled together by a
link or buckle M, and the upper valves or covers C by a link or buckle
N. As the admission, cut off, and the exhaust of the steam is effected
in the arrangement of valves shown on Sheet 2 similarly to what is
herein-before described with reference to the admission, cut off, and

page_text: exhaust in the arrangement shewn in Sheet 1, it need not be further
referred to, as an inspection of the Drawings, which also shew the relative
positions of the eccentrics A and B, will render these actions obvious to
a practical engineer.
Having now described my said Invention, and having shown on the
appended Sheets of Drawings how it may be put into practice, I wish
to observe that I am aware that valves having a top slide or cover are
not new, and I therefore make no claim to such, but what I do consider
novel and original, and therefore claim as my Invention is, the arrange-
ment and construction of double or covered slide valves having the
ports therein arranged as herein-before described, and shown on the
appended Drawings, so as to produce the cut off of the steam with great
rapidity.
In witness whereof, I, the said Andrew Barclay, have hereunto set
my hand and seal, this Thirtieth day of December Eighteen
hundred and sixty-nine.
ANDREW BARCLAY. (L.S.)