IMPROVEMENTS IN VALVE GEAR FOR DIRECT- ACTING STEAM ENGINES
Year: 1876

page_text: LETTERS PATENT to Robert Luke Howard, of Tottenham, in the County of
Middlesex, for the Invention of "IMPROVEMENTS IN VALVE GEAR FOR DIRECT-
ACTING STEAM ENGINES."
Sealed the 29th December 1876, and dated the 25th October 1876.
PROVISIONAL SPECIFICATION left by the said Robert Luke Howard at
the Office of the Commissioners of Patents on the 25th October 1876.
ROBERT LUKE HOWARD, of Tottenham, in the County of Middlesex. " IMPROVE-
MENTS IN VALVE GEAR FOR DIRECT-ACTING STEAM ENGINES."
Heretofore the movement of direct-acting steam engines has in various ways
been controlled or regulated according to the varying load thereon by means of
valve gear, wherein the main valve is worked by an auxiliary steam cylinder con-
trolled by a cataract or other governor, and receiving a secondary motion from
some moving part of the engine, or by an expansion valve working in an opposite
direction to the main slide valve, and controlled indirectly by a cataract.
Now the object or purpose of this Invention is to control or regulate direct-acting
steam engines. according to the varying load by means of valve gear wherein the
expansion valve is worked from the main steam piston, the main valve being
worked by a subsidiary piston controlled by a cataract or other governing appliance,
all operating as herein-after described.
For this purpose I employ by preference an ordinary D-shaped main slide valve
with ports passing through it, and I work an expansion valve on it. The main
slide valve is moved by means of an auxiliary steam piston controlled by a cataract
in a well-known manner. The expansion slide valve is worked from the main
steam piston in the same direction and in unison therewith, but with a shorter
stroke, the necessary connections being by a system of levers and connecting rods,
or any other well-known device, for imparting the motion to the expansion valve,
the latter being moved in unison with the main piston for the purpose in view,
and operating in such a manner that when the load on the engine is lessened, and
the tendency of the engine is to quicken its speed, the expansion valve (acting in
unison) also increases its speed in the same ratio as the main piston; but the
main steam valve continuing to move at the speed regulated by the cataract the
Price 621

page_text: expansion valve will overrun it, and cut off the steam. On the other hand, if the
load on the engine is increased, and the tendency of the main piston is to run
slower, the expansion steam valve will decrease its speed in the same ratio, but the
main valve (continuing to work at the speed regulated by the cataract) will overrun
the expansion valve, and will thus admit more steam as required.
This motion may be applied to direct-acting engines for various purposes for
which such engines are now applicable. It may also be applied not only to
ordinary slide valves, as here more particularly described, but also to rotary and
other valves.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Robert Luke Howard, in the Great Seal Patent Office on the 13th
March 1877.
ROBERT LUKE HOWARD, of Tottenham, in the County of Middlesex. " IMPROVE-
MENTS IN VALVE GEAR FOR DIRECT-ACTING STEAM ENGINES."
Heretofore the movement of direct-acting steam engines has in various ways
been controlled or regulated according to the varying load thereon by means of
valve gear, wherein the main valve is worked by an auxiliary steam cylinder con-
trolled by a cataract or other governor, and receiving a secondary motion from
some moving part of the engine, or by an expansion valve working in an opposite
direction to the main slide valve, and controlled indirectly by a cataract.
Now the object or purpose of this Invention is to control or regulate direct-acting
steam engines according to the varying load by means of valve gear wherein the
expansion valve is worked from the main steam piston, the main valve being
worked by a subsidiary piston controlled by a cataract or other governing appliance,
all operating as herein-after described.
For this purpose I employ by preference an ordinary D shaped main slide valve
with ports passing through it, and I work an expansion valve on it. The main
slide valve is moved by means of an auxiliary steam piston controlled by a cataract
in a well-known manner. The expansion slide valve is worked from the main
steam piston in the same direction and in unison therewith, but with a shorter
stroke, the necessary connection being by a system of levers and connecting rods,
or any other well-known device, for imparting the motion to the expansion valve,
the latter being moved in unison with the main piston for the purpose in view,
and operating in such a manner that when the load on the engine is lessened, and
the tendency of the engine is to quicken its speed, the expansion valve, acting in
unison, also quickens its speed in the same ratio as the main piston; but the main
steam valve continuing to move at the speed regulated by the cataract the expansion
valve will overrun it, and cut off the steam. On the other hand, if the load on the
engine is increased, and the tendency of the main piston is to run slower, the
expansion steam valve will decrease its speed in the same ratio, but the main
valve (continuing to work at the speed regulated by the cataract) will overrun the
expansion valve, and will thus admit more steam as required.
This motion may be applied to direct-acting engines for various purposes for
which such engines are now applicable. It may also be applied not only to
ordinary slide valves, as here more particularly described, but also to rotary and
other valves.
Fig. 1, Sheet 1, of the accompanying Drawings shows oue modification of my
improvements in valve gear wherein the expansion or regulating valve E receives
its motion from the main piston by means of levers, as represented, and the main
valve D receives its motion by the direct pressure of steam in the valve moving or
auxilary cylinder C¹. The motion of the main valve is regulated by the ordinary
cataract H through its piston G and rod D. A is the main steam cylinder; B, the

page_text: main piston; and C, the steam chest; D is the main valve moved, as before stated,
by the direct pressure of steam upon the valve moving piston; D¹ is the auxiliary
cylinder; E is the expansion or governing valve worked on the top of the main
valve D, and moved by motion taken from the main piston rod through the arm J,
link I, lever I, and rod I', as before mentioned; F is the auxiliary valve of the B
form, and provided with double cavaties h, h, for admitting and exhausting steam
from the auxiliary or valve moving cylinder C for moving the main valve D in the
right direction; it is operated by the contact of the lever I with the tappets k, k,
upon the rod K.
In operating the valves the lever first moves the auxiliary valve F, admitting
steam to the valve moving cylinder C¹. The valve D is then moved until it estab-
lishes communication between the steam and exhaust ports A¹, B', through the
cavity b, and brings one of the ports a into communication with the other main
steam port A¹, and with the cavity under the valve D. High steam then passes
through the ports a and A' in the valve D to one end of the cylinder, and is
exhausted from the other end through ports A¹, B¹, and cavity b. The main piston
then commences its motion, and if it move at the same relative velocity as the
valve moving piston the relative position of the valves will be unchanged, and the
admission of steam will be uniforin; but if the speed of the main piston becomes
greater or less than that of the valve moving piston the lever will at once begin to
act on the valve E, cutting off or admitting a larger supply of steam, as may be
required, the cut-off valve E producing the governing or regulating motion, as
herein-before described.
Fig. 2, Sheet 1, is another modification of the improvement. The main valve D
is moved similar to that in Fig. 1, and the valve moving and cateract cylinders are
stationery. The valves E and D move in the same direction at the same time to
cause the governing motion, but in opposite directions when changing the direction
of the stroke. The valve D is started to move in one direction by the valve moving
piston, and its motion carries the port a in the valve D past the valve E, and
brings the other port a into communication with the exhaust b through the cavity
in the valve E. Steam is them admitted to and exhausted from the main cylinder,
and the main piston commences its motion. The lever I at once begins to move
the valve E in the same direction the valve D is moving, and thereby governs and
regulates the proper pressure of steam to the main cylinder for obtaining the
required and a uniform piston motion under variable loads; that is, if the main
piston B is moving under its required velocity the main valve D by the pressure of
steam on the auxiliary piston D¹ is moved to open or increase the steam port
leading to the main cylinder, and consequently the motion of the main piston
is increased; but if the main piston is moving faster than its required velocity the
cut-off or regulating valve E is moved by the piston through the medium of the
arm J, link I, lever I, and rod I¹ to close or contract the steam port leading to the
cylinder sufficient to reduce the piston speed to the required velocity in the manner
herein-before stated.
Fig. 3, Sheet 2, is a further modification of the arrangement of valve gear, in
which the cut-off or regulating valve D is actuated by the main piston through the
modium of the arm J, link I¹¹, lever I, and rod I¹ similar to the plans before men-
tioned. The main valve E is actuated by the valve moving piston D' working in
the auxiliary cylinder C¹, which is cast to and made to form part of the steam
chest C. In this case the valve moving piston first moves the main valve E
in a direction to admit steam to the main cylinder. The valve D then follows the
main valve, and the same effect is produced under variations of loads, as in the
previous cases herein-before described, for obtaining a uniform velocity of piston.
The plan of working the auxiliary valve E through the rod K by the lever I coining
in contact with the tappets k, k, is substantially the same as the plans before
described. The motion of the main valve E is regulated by a cataract, the
cylinder H of what is attached to the steam chest C, as represented, the cataract

page_text: piston G, valve moving piston D¹, and valve E are arranged together, as shewn
in the Drawing.
Figs. 4 and 5, Sheet 2, illustrates an arrangement similar to those before shown
and described, but with oscelating or rotating cylindrical valves, which necessitates
some changes in the manner of operating them, the hollow cylinder E in the steam
chest C forms a movable valve seat, while D the main valve working in it is a
piston valve. The main valve D is moved by the direct pressure of steam upon the
valve moving piston D¹ through the instrumentality of the bent lever I', which is
attached to the valve, as shown in Fig. 5. The cylindrical valve seat E receives
motion from the main piston through the arm J and lever I, which is attached to
the valve seat, as shown in Fig. 5. The auxiliary valve F is moved from the main
lever I by means of a secondary lever M and rod K and finger N, or in any other
convenient way.
The valve moving piston rod is attached to the cataract piston for
controlling the motion of the main valve. In operation the main valve is started to
rotating in either direction by the valve moving piston. The main piston then
commences its stroke, and rotates the cylindrical seat in the same direction. If the
main piston and valve moving piston continue moving at the same velocity the
admission of steam will be constant, but if the velocity of the main piston vary the
admission of steam will be increased or diminished accordingly for keeping the
main piston B moving at the required velocity, substantially in the same manner
as the plans herein-before described and represented by Figs. 1, 2, and 3.
Having described the construction and manner of working my said improvement,
I wish it to be understood that I am aware, when taken separately, the parts
forming my improvement have been used for similar purposes, and therefore I do
not broadly claim the use of double valves, nor the means of working them by a
supplementary piston controlled by a cataract, or working them by the main piston
of the engine when separately used; but what I claim is,-
First, Fig. 1. The combination of the main valve D and cut-off valve E when the
former is operated by a valve moving piston D', and controlled in its motion by a
cataract, and the latter by the main piston B through the lever I or its equivalent
for regulating the admission of steam to the main cylinder, substantially as described
and for the purposes before mentioned.
Second, Fig. 2. The combination of the main valve D, cut-off valve E, valve
moving piston D', cataract H, lever I, and main piston B, constructed and operated
in the manner and for the purpose herein-before described.
Third, Fig. 3. The combination of the auxiliary cylinder C³, piston D¹, rod D¹¹,
cataract cylinder H, piston G, main valve E and cut-off valve D, rod 1¹, lever I,
cylinder A, and piston B, all constructed and operated for the purpose shown and
before described.
Fourth, Figs. 4 and 5. The combination of the piston valves D and the cylindrical
valve seat E, the former oscelated by a valve moving piston through the lever I',
and the latter by the main piston through the lever I, by means of which the
admission of steam to the main cylinder is controlled substantially for purposes
herein-before described.
In witness whereof, I, the said Robert Luke Howard, have hereunto set my
band and seal this Twelfth day of March. in the year of our Lord 1877.