Improved Cut-off Valves and Valve-gear for Engines.
Year: 1895

page_text: Date of Application, 1st Aug., 1895-Accepted, 29th Feb., 1896
Improved Cut-off Valves and Valve-gear for Engines.
I, JOHN BENJAMIN PITCHFORD, a citizen of the United States, residing at
728 Cole Street San Francisco, State of California, United States of America,
Manufacturer, hereby declare the nature of this invention and the manner in which
the same is to be performed to be particularly described and ascertained in and
by the following statement:-
The object of my invention is to provide a cut-off valve and valve gear which
will enable the engine to run at a high rate of speed with close regulation of the
steam so as to suit the work required and maintain a uniform number of revolutions ;
thus overcoming waste in steam and power of the engine.
In carrying out my invention, I provide a double-ported evenly-balanced cut-off
valve; which is so connected with the driving mechanism of the engine as to
automatically regulate or control the supply of steam to the main steam valves of
the engine, in accordance with the work required of the engine; said cut-off valve
being so connected as to perform its functions entirely independent of the main
steam valves.
I have shown my invention, in the present instance, as used in connection with
that class or style of steam engines known as the "Corliss engine"; but it is not
confined to its use in connection with this class of engines; for it may be used in
connection with any style of engines utilizing a main steam or inlet valve.
In order fully to comprehend my invention, reference must be had to the
accompanying sheets of drawings forming a part of this application; wherein -
Figure is a broken side view, in elevation, of a Corliss engine, showing my
valve mechanism connected thereto;
Figure 2 is a top plan view of the mechanism illustrated by Figure 1 ;
Figure 3 is an enlarged detail view in side elevation, partly broken away, of the
steam cylinder, showing the arrangement of the main steam valves, the exhaust
valves, the cut-off valves for controlling the supply of steam to the main valves
and a portion of the mechanism for operating the said valves; and
Figure 4 is a cross-sectional end view in elevation of the steam cylinder, taken
on line -x, Figure 3, and viewed in the direction of the arrow y.
In the drawings, the letter A indicates the steam cylinder casting of an ordinary
Corliss engine and A¹ the piston cylinder or chamber, within which works the
piston B. Above the piston cylinder or chamber is located the steam chest A';
at each end of which is formed the main valve chamber B', within which
chambers I locate the main steam valves B³. Connection is made between the
main valve chambers and the piston cylinder or chamber A¹ through the medium
of the ports a.
Below the said piston cylinder or chamber is located the exhaust
chamber A; at each end of which is formed the valve chamber B. Within
each of said chambers, I secure a rotatable exhaust valve B*; and communication
is established between said chambers and the piston cylinder or chamber A¹ through
the medium of the ports a¹. The main valves and the exhaust valves are of such
construction as to alternately open and close the ports a, a'. These features being
well known, call for no specific description in the present application for Letters
Patent.
In front of each main valve chamber is located the cut-off valve chamber C ;
which valve chamber communicates with the main valve chambers, by means of
the port b. The cut-off valve chamber C is provided with two ports, b1, b2, located

page_text: opposite to each other; through which ports steam enters, from the chest A³.
Within the cut-off valve chambers, I locate the cut-off valve C¹. This cut-off
valve, as rotated within the cut-off valve chamber,-as hereinafter described,―
opens and closes the ports b', 62; the cut-off valve being so constructed as to open
or close both ports at the same time. Inasmuch as the steam enters the cut-off
valve chambers through the ports 61, 62, located directly opposite to each other, it
is obvious that there is an even pressure upon the cut-off valve; consequently, the
said valve will be, at all times, evenly balanced. There is a passageway 63 formed
through the cut-off valve, so as to connect the upper port 6' of the cut-off chamber
with the lower port 62; and the said passageway is cut away or enlarged at the
lower part of the valve so as to equal the combined area of the two ports, as
shown at b.
The main steam valves B³ and the steam exhaust valves B are connected to
the rock plate C' by means of the rods C³, C; the outer ends of which rods
are connected to the crank arms d, d¹, secured to the outer ends of the valves B3, B4,
respectively, Figures 1 and 3. The rock plate C is secured to and oscillated
upon the stud D attached to the side of the cylinder A and said rock plate 18
connected to the fulcrumed rocker D1 by the conuecting rod D'. This fulcrumed
rocker is connected to the main eccentric D 3 secured to the drive shaft D* of
the engine by the eccentric rod D³. As the drive shaft is rotated,-by any
suitable mechanism,-the eccentric D³ is carried therewith; the movement of
which throws the eccentric rod Ds in and out and causes the fulcrumed rocker D
to move back and forth; the movement of which oscillates the rock plate C'
and causes the main steam valves B³ and the exhaust valves B' to rotate or
oscillate within the valve chambers B' and B, so as to alternately open and close
the ports a, a.
The rotatable cut-off valve is connected to the rock plate E, secured upon the
stud D, located behind the rock plate C2, by means of the rods E¹, which are
secured at one end to the said rock plate; the free end of said rods being con-
nected to the crank arms d' secured to and projecting from the outer end of the
rotatable cut-off valves. Connection is made between the rock plate E and the
fulcrumed rocker E2 by means of the rod E³. As the fulcrumed rocker is moved
back and forth, the rock plate E is oscillated upon the stud D and through its
connection with the cut-off valve causes the same to rotate or oscillate within
the valve chamber C, so as to open or close the ports b1, b2, simultaneously; the
port or passageway b, between the valve chamber Cand the main valve chamber B',
being always open. The fulcrumed rocker E2, which operates the rock plate E,
is moved back and forth, through the medium of the eccentric F, loosely fitted
upon the drive shaft D; which eccentric is connected to the said fulcrumed
standard by the eccentric rod F¹. To the eccentric F is connected the inner end
of the short rods ff; the outer ends of said rods being fastened to the inner end
of the arms 2,³, respectively, Figure 1. The outer end of the arms f³,
I secure to the spokes e, e' of the governor wheel G. The governor wheel is
rigidly secured to the shaft D and rotates therewith. The arms f³, f³, are
connected to the spokes, es, by means of the springs 1, 2; the resiliency of which,
as the speed of the engine is reduced, draws the said arms inward. These arms
have adjustably secured thereon the weights G. The weighted arms f, f, will
be moved in or out in accordance with the speed under which the governor
wheel revolves. If it is revolved at a high rate of speed, the weighted arms will
be thrown outward by centrifugal force; while if the governor wheel is revolved
at a low rate of speed, the resiliency of the springs 1, 2, will draw the weighted
arms inward. As these arms move in or out they impart a corresponding move-
ment to the eccentric F, which in turn moves the fulcrumed standard E, through
the medium of the eccentric rod F', forward or backward; the movement of which
standard oscillates the cut-off valves.
3
Inasmuch as the cut-off valve is evenly balanced, by the pressure of the steam
being the same above and below the valve, it is obvious that the said cut-off valve

page_text: will be extremely sensitive and rotate with the slightest variation in the speed of
the governor, so as wholly or partly to open or close the ports 61, b³.
It will be noticed that the cut-off valve mechanism is non-liberating, being at all
times in direct communication with the governor; consequently, the movement of
the cut-off valve is not only positive, but it is absolutely assured; whether the
engine runs under a high or under a low speed ;-which is not the case, where
the valve mechanism is automatically liberated at each cut-off movement of the
valve.
I am aware that it is not new to provide a single-ported cut-off valve; nor do
I wish to be understood as claiming the same as my invention; but I am not
aware that it is old to provide a cut-off valve capable of closing or controlling two
steam ports simultaneously ;-consequently, I wish to be understood as claiming this
feature.
Having thus described my invention, what I claim as new and desire to secure
protection in by Letters Patent is :
1. In an engine, the combination with the main valve, of an evenly-balanced
double-ported rotary cut-off valve.
2. In an engine, the combination with the main valve, of the double-ported
rotary cut-off valve which controls the supply of steam to the main valve and of
mechanism for operating said cut-off valve so as to control the admission of steam
to the main valve in accordance with the speed of the engine.
3. The combination with an engine, of an automatically operated cut-off valve
adapted to open or close two steam ports simultaneously.
4. In an engine, the combination with the main steam valve, the valve chamber
within which the valve is located, said chamber communicating with the piston
cylinder, the double-ported cut-off valve chamber, communicating with the main
valve chamber, the rotary cut-off valve chamber located within the double-ported
cut-off valve chamber, and of mechanism for rotating said cut-off valve in
accordance with the speed of the engine, so as to cause the valve to wholly or partly
open or close simultaneously the port openings of the double-ported cut-off valve
chamber.
5. In an engine, the combination with the double-ported evenly-balanced rotary
cut-off valve, of the governor and of mechanism forming a direct connection
between the governor and the cut-off valve, whereby the cut-off valve will be
operated by the slightest variation in the speed of the governor.
6. In an engine, the combination with the main valve, of a rotary evenly-
balanced double-ported non-liberating cut-off valve and of mechanism for imparting
movement to the said valve.
7. In an engine, the combination with the double-ported evenly-balanced rotary
cut-off valve, of the rock plate for rotating the valve, connection between the said
valve and the rock plate, the governor, the eccentric connected with the governor
and of devices for forming connection between the said eccentric and the rock
plate whereby the rock plate is oscillated in order to move the cut-off valve as
the eccentric is moved with the increased or decreased speed of the governor.
Dated this 5th day of June 1895.
JOHN BENJAMIN PITCHFORD.
Boult & Wade,
Agents for the Applicant.
JOHN BENJAMIN PITCHFORD.
Boult & Wade,
Agents for the Applicant.