IMPROVEMENTS IN COMPOUND STEAM ENGINES AND IN COMPRESSED AIR ENGINES
Year: 1884

page_text: | JOHN THOMAS DAWES of Blaen-y-roe St Asaph in the County of Flint
Mining Engineer do hereby declare the nature of the said Invention for
IMPROVEMENTS
IN COMPOUND STEAM ENGINES AND IN COMPRESSED AIR
ENGINES" to be as follows:-
My invention consists of the improvements hereinafter described which improve-
ments are principally applicable to compound steam engines but are also in part
applicable to compressed air engines as hereinafter explained.
In compound steam engines in which steam of high pressure is used it is
customary to admit the exhaust steam of the first or high pressure cylinder into.
a second cylinder of larger capacity than the first by the expansion of which
exhaust steam in the second cylinder additional motive power is obtained. The
high pressure steam introduced into the first or small cylinder works against the
back pressure of the exhaust steam its pressure being virtually diminished to an
extent equal to the pressure of the exhaust steam. According to my improvements
after the steam of high pressure has operated in the first cylinder and before its
introduction into the second cylinder it is allowed by the operation of a valve to
enter into a receiver. The communication between the said receiver and the
cylinder being cut off the portion of exhaust steam remaining in the cylinder is
allowed to escape into the air and the next charge of high pressure steam operates
without the back pressure of the exhaust steam. The exhaust steam in the receiver
described is admitted into the second and larger cylinder where by its expansion it
produces additional motive power. The exhaust side of both pistons may where
convenient be connected with condensers so that the pressure of the steam in both
cylinders may be virtually increased by the vacuum thereby obtained on the
exhaust side of the piston. The passage of the exhaust steam from the first
cylinder into the receiver and its passage from the receiver into the second cylinder
is effected by two slide valves or by one slide valve having double ports or by other
valves the said valve or valves being operated automatically by the engine.
In applying my improvements to engines worked by compressed air no condensers
are employed.
Dated this thirty first day of Ontahoz ké
W. T. WHITEMAN,
Agent for the Applicant.

page_text: COMPLETE SPECIFICATION.
Improvements in Compound Steam Engines and in Compressed
Air Engines.
I JOHN THOMAS DAWES of Blaen-y-roe, St Asaph in the County of Flint,
Mining Engineer, do hereby declare the nature of my Invention for "IMPROVE-
"and in
what manner the same is to be performed to be particularly described and
ascertained in and by the following statement:-
MENTS IN COMPOUND STEAM ENGINES AND IN COMPRESSED AIR ENGINES
My invention consists of the improvements hereinafter, described, which 'improve-
ments are principally applicable to compound steam engines but are, also in part
applicable to compressed air engines as herein after explained.
In compound steam engines in which steam of high pressure is used it is
customary to admit the exhaust steam of the first or high pressure cylinder into
a second cylinder of larger capacity than the first by the expansion of which exhaust
steam in the second cylinder additional motive power is obtained. The high
pressure steam introduced into the first or small cylinder works against the back
pressure of the exhaust steam, its effective pressure being thereby virtually
diminished to an extent equal to the working pressure of the steam in the large
or low pressure cylinder.
According to my improvements after the steam of high pressure has operated in
the first cylinder and before its introduction into the second cylinder it is allowed
by the operation of a valve to enter into a receiver. The communication between
the said receiver and the cylinder being cut off the portion of exhaust steam
remaining in the cylinder is allowed to escape into the air and the next-charge of
high pressure, steam operates without the back pressure of the exhaust steam. The
exhaust steam in the receiver described is admitted into the second and larger
cylinder where by its expansion it produces additional motive power. The exhaust
side of both pistons may where convenient be connected with condensers so that
the pressure of the steam in both cylinders may be virtually increased by the
vacuum thereby obtained on the exhaust side of the piston. The passage of the
exhaust steam from the first cylinder into the receiver and its passage from
the receiver into the second cylinder is effected by two slide valves, or by one slide
valve having double ports, or by other valves the said valve or valves being
operated automatically by the engine.
In applying my improvements to engines worked by compressed air no condensers
are employed.
In the accompanying Drawings Figure 1 represents in vertical section the slide
valve, steam chest, stop valve and receiver constructed according to my invention
as applied to a compound steam engine; Figure 2 represents a section of the same
taken in a plane at right angles to that in which the section of Figure 1 is taken;
Figures 3 and 4 are also sections in a plane at right angles to Figure 1 but with
the slide valve in different positions.

page_text: Steam having been admitted into the steam chest A, Figure 2, passes along the
port B to the high pressure cylinder and operates upon the piston therein. The
alide valve C by the action of the valve gear moves into the position represented
in Figure 3 and the exhaust or partially expanded high pressure steam
passes back
from the high pressure cylinder along the port B through the slide valve O into the
port D and through the stop valve E Figure 1 into the receiver F.
The slide valve C moving on to complete its stroke comes into the position shown
in Figure 4, which brings the opening G in the top of the said slide valve C
opposite the port H in the cover J of the steam chest A. which said port H and also
the corresponding port H¹ are covered by the small steam chest K, Figures 1 and 2,
which chest in the case of non-condensing engines is open to the atmosphere but in
the case of condensing engines is connected with the condenser. The pressure of
the exhaust steam being now removed from the stop valve E Figure 1 by the
opening of the said port H, Figure 4, the said stop valve E instantly closes by the
pressure of the steam in the receiver F, which steam in the said receiver F is
retained for use in the low pressure cylinder, the remainder of the exhaust steam
from the high pressure cylinder having been discharged through the port H or H¹.
The same action takes place on the return stroke of the piston of the bigh
pressure cylinder and brings the slide valve back into the position shown in
Figure 2.
In Figure 2, LL are strips or rings of metal which are pressed against the planed
surface of the cover J of the steam chest A by the action of springs, steam or other
means, so as to render the top of the slide valve C steam tight with the surface of
the cover J.
Figure 5 represents in plan the ports B, B' and D and the stop valve E; Figure 6
represents in plan the steam chest cover J and the ports H and H¹.
Figures 7 and 8 represent sections of an auxiliary valve by the use of which my
invention may be applied to existing high pressure engines. The said valve Figures 7
and 8 must be fixed on the exhaust outlet and actuated by separate and independent
valve gear.
a is the steam chest; b is the slide valve; c is the cavity in the slide valve;
e is the port from the exhaust; & is the opening in the top of the slide valve b;
g is a port communicating with the low pressure engine.
The exhaust steam from an ordinary high pressure engine having been discharged
when the slide valve b is in the position represented in Figure 7 passes into the
receiver through the port g in which receiver it is stored for use in the low pressure
cylinder.
The slide valve b moving into the position represented in Figure 8 closes the
port g and opens the port fand the remainder of the exhaust steam is discharged
through the said port f which communicates either with the condenser or with the
atmosphere.
The top of the slide valve 6 is made steam tight with the cover of the steam
clest a, Figures 7 and 8, by means of strips or rings as hereinbefore described.
I do not limit myself to any particular form of valve or number of valves.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
First. The combination or arrangement of parts herein before described and
illustrated in the accompanying Drawings of compound steam engines, whereby a
portion of the exhaust steam of the high pressure cylinder is stored in a receiver
for use in the low pressure cylinder, which receiver when charged is isolated from
the high pressure cylinder, the remaining or exhaust steam in which is then put
into communication either with the condenser or with the atmosphere and the

page_text: piston of the high pressure cylinder thereby relieved from the back pressure of
the exhaust steam the exhaust steam from the high pressure cylinder stored in
the receiver being utilized in the low pressure cylinder either with or without a
condenser substantially as described.
Secondly. The application of the arrangement described and represented without ä
the use of a condenser or condensers to compressed air engines.