IMPROVE- MENTS IN STEAM ENGINE VALVES
Year: 1874

page_text: LETTERS PATENT to William Henry Dugard, of Birmingham, in-the
County of Warwick, Engineer, for the Invention of "IMPROVE-
MENTS IN STEAM ENGINE VALVES.”
Sealed the 11th May 1875, and dated the 1st December 1874.
PROVISIONAL SPECIFICATION left by the said William Henry
Dugard at the Office of the Commissioners of Patents, with his
Petition, on the 1st December 1874.
I, WILLIAM HENRY DUGARD, of Birmingham, in the County of
Warwick, Engineer, do hereby declare the nature of the said Inven-
tion for "IMPROVEMENTS IN STEAM ENGINE VALVES," to be as follows, that
is to say
-
The object of my improvements is a simple arrangement of piston
valves so as to obtain a variable point of cut off of the steam without
altering the point of lead, exhaust, or compression, together with a small
capacity of the steam ports, thus effecting a saving of steam and fuel,
and at the same time having the valves in perfect equilibrium at every
part of their stroke, thereby reducing the power required to operate

page_text: them to a minimum. I employ two pairs of piston valves, one of each
pair working in a cylinder of the same diameter throughout at each end
of the engine cylinder, such cylinder being provided with separate steam
and exhaust ports. The two exhaust valves or pistons are coupled
together and have the same amount of travel which in working is
uniform; the two outer or steam pistons or valves are also connected
together, the travel of these being varied according to the point of cut
off. I connect the two exhaust valves by a tube through which the
rod connecting the two outer or steam valves works freely so that the
spaces between the two valves communicate with each other, thus
equalizing the pressure in each.
My Invention further consists in the arrangement of separate steam
and exhaust ports in the cylinder in which the piston valves work, and
at such distance from each other as to allow the exhaust valve to work
freely without interfering with the motion of the steam valve. The
exhaust piston being made of such a length that when the exhaust port
at one end of the cylinder is uncovered to its fullest extent the exhaust
port at the other end of the cylinder shall not be uncovered by the other
exhaust valve, the steam pistons or valves are also made of such a
length that when the steam valve is in mid-position of its travel the
steam ports are not uncovered by the inner edges of the pistons.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William Henry Dugard in the Great Seal Patent
Office on the 1st June 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
HENRY DUGARD, of Birmingham, in the County of Warwick, Engineer,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the First day of December, in the
year of our Lord One thousand eight hundred and seventy-four, in the
thirty-eighth year of Her reign, did, for Herself, Her heirs and suc-
cessors, give and grant unto me, the said William Henry Dugard,
Her special license that I, the said William Henry Dugard, my
executors, administrators, and assigns, or such others as I, the said

page_text: William Henry Dugard, my executors, administrators, and assigns,
should at any time agree with, and no others, from time to time
and at all tinies 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 ENGINE VALVES," upon the
condition (amongst others) that I, the said William Henry Dugard, 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 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 William Henry Dugard, 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, that is to say :-
The object of my improvements is a simple arrangement of piston
valves so as to obtain a variable point of cut off of the steam without
altering the point of lead, exhaust, or compression, together with a small
capacity of the steam ports, thus effecting a saving of steam and fuel,
and at the same time having the valves in perfect equilibrium at every
part of their stroke, thereby reducing the power required to operate
them to a minimum. I employ two pairs of piston valves, one of each
pair working in a cylinder of the same diameter throughout at each end
of the engine cylinder, such cylinder being provided with separate steam
and exhaust ports. The two exhaust valves or pistons are coupled
together and have the same amount of travel which in working is
uniform; the two outer or steam pistons or valves are also connected
together, the travel of these being varied according to the point of cut
off. I connect the two exhaust valves by a tube through which the
rod connecting the two outer or steam valves works freely, so that the
spaces between the two valves communicate with each other, thus
equalizing the pressure in each.
My Invention further consists in the arrangement of separate steam
and exhaust ports in the cylinder in which the piston valves work, and
at such distance from each other as to allow the exhaust valve to work'

page_text: freely without interfering with the motion of the steam valve. The
exhaust pistons being made of such a length that when the exhaust
port at one end of the cylinder is uncovered to its fullest extent the
exhaust port at the other end of the cylinder shall not be uncovered by
the other exhaust valve, the steam pistons or valves are also made of
such a length that when the steam valve is in mid-position of its travel
the steam ports are not uncovered by the inner edges of the pistons:
Ircely without interfering with the mo
exhaust pistons being made of such a length that when the exhaust
port at one end of the cylinder is uncovered to its fullest extent the
exhaust port at the other end of the cylinder shall not be uncovered by
the other exhaust valve, the steam pistons or valves are also made of
such a length that when the steam valve is in mid-position of its travel
the steam ports are not uncovered by the inner edges of the pistons:
DESCRIPTION OF THE DRAWINGS.
Fig. 1 is a longitudinal section of the improved valves and casing;
Fig. 2 is a half elevation and half sectional view of the same; and Fig. 3
is a.sectional plan on the line S, S.
A, A, are the steam passages to the engine cylinder; B, B, are the
steam ports; and C, C, are the exhaust ports, both formed in the working
cylinders D, D; E, E, are the two steam piston valves connected by the
valve rod F; G, G, are the exhaust piston valves connected by the
tube E which fits loosely around the valve spindle F; I is a lever
actuating the exhaust piston valves G, G, and keyed to a spindle
working through a stuffing box on the valve casing; J is a branch by
which the exhaust space K communicates with the condenser or atmo-
sphere; L, L, are branches cast on the working cylinders D, D, to which
the steam pipe is connected; M is a door by which access is obtained
to the lever I; N, N, are annular spaces by which the steam and
exhaust ports B, B, and C, C, communicate with the passages A, A.
The steam piston valves E, E, and the exhaust piston valves G, G, aro
made steam-tight by ordinary metallic packing, care being taken that the
annular space P in the exhaust piston valves G, G, communicates with
the annular space N to prevent the metallic packing being forced from
the face of the working cylinder D by the pressure of the steam on its
outer surface. The exhaust piston valves G, G, are so constructed
that at their extreme stroke the exhaust ports C, O, are not uncovered
by the outer edge Q of the valves, also the steam piston valves E, E, are
of such length that when they are midway between the extreme limits
of their stroke the steam ports are not uncovered by their inner edges
R, R.
The spaces O, O, are of sufficient length to allow the valves to
work properly without interfering with each others movements.
Having thus described the object and nature of my said Invention,
and the manner in which the same is to be carried into effect, I claim.

page_text: without limiting myself to these precise details, the arrangement of
separate steam and exhaust piston valves working in the same cylinder
at each end of the engine cylinder, the two steam piston valves being
coupled and having the same stroke, which is variable; the steam piston
valves likewise governing the points of admission and cut off of the steam
to the engine cylinder, and the exhaust piston valves also being coupled
and having the same fixed stroke and governing the points of exhaust and
compression or cushioning of the steam, substantially in manner as herein
more fully set forth and specified.
In witness whereof, I, the said William Henry Dugard, have
hereunto set my hand and seal, this 29th day of May, in the
year of our Lord (1875) One thousand eight hundred and
seventy-five.
'
WILLIAM HENRY DUGARD. (L.S.)