IMPROVEMENTS IN OPERATING THE CUT-OFF VALVES OF STEAM ENGINES
Year: 1863

page_text: LETTERS PATENT to Robert Stewart, of Elmira, in the State of New
York, in the United States of America, for the Invention of "IMPROVE-
A. "
Sealed the 25th September 1868, and dated the 31st July 1863.
COMPLETE SPECIFICATION filed by the said Robert Stewart at the
Office of the Commissioners of Patents, with his Petition and Declara-
tion, on the 81st July 1863, pursuant to the 9th Section of the Patent
Law Amendment Act; 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ROBERT
STEWART, of Elmira, in the State of New York, in the United States of
America, send greeting.
WHEREAS I am in possession of an Invention for "IMPROVEMENTS IN
OPERATING THE CUT-OFF VALVES OF STEAM ENGINES," and have petitioned Her
Majesty to grant unto me, my executors, administrators, and assigns, Her
Royal Letters Patent for the same, and have made solemn declaration that
I am the true and first Inventor thereof.
NOW KNOW YE, that I, the said Robert Stewart, do hereby declare
that the following Complete Specification under my hand and seal fully
describes and ascertains the nature of the said Invention, and in what manner
the same is to be performed, in and by the following statement :-
The nature of my Invention consists in the improved mode of operating the

page_text: cut-off valves of steam engines, as will herein-after fully appear, reference
being had to the accompanying Drawings forming a part of this Specification.
In the Drawings, Fig. 1 is a side elevation, Fig. 2 is a front elevation,
Fig 3 is a transverse vertical section thro' x-x, Fig. 1; Fig. 4 is a
longitudinal vertical section of steam pipe S, piston U, cross head Y, &c.
thro' oo, Fig. 2; Fig. 5 is a plan view of the operating levers Q and R,
wrist i, dog m, and guards n; Fig. 6 is a view of the operating lever R,
showing by red and blue lines its operation against pin P. Similar characters
refer to like parts.
I will first describe the valve which I have invented, and which I prefer
using, although I do not confine myself to the use of any particular valve.
A is the outer shell of the valve; B, the inner shell; C, the induction
pipe; D, the eduction pipe; E, the heads of the valve; a, screws for securing
heads to the valve. The interior construction of the valve is clearly shown in
Fig. 8, in which it is seen that the valve chest is cast in two shells, 1 & 2, with
an annular chamber between them, which is divided into two semi-annular
chambers 4, 4', by the divisions 5. Thro' the inner shell 2 are cut the
throats 6, just above the divisions 5. F, the valve; c', c, c, c', are the valve
ports, of a width equal to that of throats 6. The valve is cut away at 7, in
the same manner as at 8, so as to produce a perfect balance, and to diminish
the friction between the valve and the inner surface of the inner sell. G are
stuffing boxes for each end of the valve stem H, and are secured to the valvo
heads; I are studs on the lower corners of the valve shell 1, from which
depends the bracket K; L is the valve crank, secured to the valve stem H;
N, N, are lateral arms of the crank, giving it a T shape; O is a vertical sleeve
upon the lower extremity of the crank, & in which plays the weighted pin P,
the lower end of which should be of steel; Q, a lever, pivoted at e to the lower
end of bracket K, at the other end connected to a " governor or other
regulating device; i is a "wrist" upon the lever Q, & vertically under the
pin P; R, operating lever, connected to the eccentric or crank upon the
crank shaft of the engine; this lever has a horizontal reciprocating motion
upon the wrist (see Fig. 6); m is a steel "dog" upon the upper side of
lever R, and bites or takes against the pin P as it extends below sleeve O ;
11, 12, are guards near each end of the dog m; S is a steam pipe in connection
either with valve or boiler; its vertical limb should be provided with a stuffing
box and cylinder T; U is a piston working in cylinder T, its upper end
working in a cylindrical guide V, which is supported by platforms & braces X;
s is a set screw in top of cylinder V, & serves to force the packing v down
upon the upper head of the piston: Y is a cross head of an I form, secured to
"

page_text: the piston at shoulder a; Z are connecting rods, the upper ends of which are
embraced by the forks of the cross head Y. The upper ends of rods Z are
provided with books or teeth, so as to catch firmly upon cross head, as at w;
the pins keep these rods in proper position; the lower ends of the rods Z
are pivoted to outer ends of arms N of crank L.
In the operation of my Invention, the valve being properly attached, the
steam is applied at full pressure from the boiler, & passes thro' induction
pipe C, between shells 1 & 2 into semi-annular chamber 4. When the
engine is at rest crank L is vertical, & throats 6 are closed. Steam boing
admitted to the valve, crank L is oscillated a few times by hand, so as to bring
valve ports opposite the throats 6, & admit sufficient steam to start the
machinery. The course of steam is from induction pipe C into chamber 4,
thenco thro' throats 6 and valve ports into chamber 4', thence out of eduction
pipe D to cylinder of engine. The engine then being at work, gives motion
to its governor, which raises the end of lever Q; this lever correspondingly
raises or lowers the lever R. & its dog m; it will thus be seen that the degree
of bite or lap that the dog has against the pin P depends upon the rise or fall
of the governor. Now, as the lever R reciprocates, its dog malternately
pushes and pulls against the pin P, thereby oscillating the crank and opening
the valve ports, & at the same time depressing one of the arms N, and drawing
down the piston & its cross head. It is evident that the more bite the dog
has the further the pin will have to be oscillated before it will be raised above
the horizontal plane in which the dog traverses, and that the valve ports are
opened in propor as the pin is oscillated. When the pin is thus forced far
enough to the right or left to be raised above the plane in which the dog
traverses, it escapes from the bite or hold of the dog, & is instantly thrown
back to its vertical position by means of the steam in pipe S & cylinder T,
which forces the piston U & its cross head Y upwards, carrying with them the
hooked rods Z, thus instantly returning the crank to its vertical position, &
cutting off the steam. After the pin escapes, the dog continues on until the
full stroke is completed, the pin & dog thus move in opposite directions at the
same instant, which could not be if the pin did not rise in its sleeve so as to
yield to & slide over the dog, & drop down at its other end ready to receive
the action of the return stroke. The guards 22 will serve to catch against the
pin, & return it to its vertical position if by any reason the piston U should
fail in doing its duty.
The advantages of my Invention are, that the steam can follow the piston to
any distance in the (main) cylinder by using the full throw of the eccentric,
and at the same time be cut off at any point of the stroke, and thereby

page_text: regulate the motion. There is also a great saving of steam and a more
regular motion and application of the power of the engine. Generally the
whole pressure of the steam is upon the valve at all times, and at the "dead
points" of the crank the pressure is greatly increased, inasmuch as the steam
has a retarded motion at this time; but by means of my improved modo the
device which opens the valve is moved at the same instant that the lower
(or D) valve opens, & when cut off at any point it cuts off the communication
of the boiler with the cylinder, & consequently takes off the friction from the
valves in passing the "dead points," thus giving the engine a_ more uniform
motion.
Having thus fully described my Invention, what I claim as new is,-
First, the device herein-before described & ascertained for opening the valvo
ports.
Second, the device herein-before described & ascertained for closing the valvo
ports of cut-off valves.
In witness whereof, I, tho said Robert Stewart, have annexed my hand
& seal, this Seventh day of July, A.D. 1863.