Year: 1887

page_text: Date of Application, 27th Sept., 1887
Complete Left, 27th June, 1888
Complete Accepted, 27th July, 1888.
We LÉON DURANT and ALEXANDRE LENGAUCHEZ both of 53 Rue de Chateaudun
Paris in the Republic of France Engineers do hereby declare the nature of our said
Invention to be as follows:-
This Invention is applicable to steam Engines generally but is especially applicable
to locomotive Engines and has for its object to provide improved arrangements as
hereinafter described for the distribution of steam with variable expansion and fixed
exhaust the admission of steam to the Cylinder being by a valve or valves worked
independently of the exhaust valve or valves and rendered easy of being reversed
and the Cylinder being permitted to automatically clear itself of the exhaust steam
thereby decreasing the retarding action of the back steam whilst a reduction in
the consumption of fuel to work the Engine is effected by reason of the reduced
friction.
According to one mode of carrying out this Invention the valve for admitting
steam to the Cylinder is provided with grooves or passages each serving to admit
steam alternately to the opposite ends of the Cylinder whilst the valve chest is
constructed so as to admit of the motive fluid passing round the valve whereby a
double admission of steam is obtained.
The exhaust valve which is preferably arranged at the bottom or opposite
side of the Cylinder to that of the inlet valve is provided with only one groove
or passage which is caused to communicate alternately with the opposite ends of
the Cylinder..
The chest containing the exhaust valve is connected by a pipe with the inlet valve
chest so as to allow the steam to exert on the exhaust valve the necessary amount of
pressure the said pipe being provided with a cock or valve for the purpose of
governing the admission of steam to regulate the pressure as required.
Instead of a single admission valve with two passages or grooves and an exhaust
valve with one passage or groove as described an admission valve and an exhaust
valve may be employed at each end of the cylinder and these valves may be of the
oscillating cylindrical type.
The admission valve or valves may be worked in the ordinary manner of working
slide valves and the exhaust valve or valves may be worked by means of any suitablo

page_text: gear from the crank shaft or it may receive motion from the cross head and rod of
the piston which rod may be hollow and serve to carry off the exhaust without
complication of the mechanisin.
It is important that the exhaust should be commenced as soon as the piston has
completed a stroke or commences to make its return stroke so as to prevent counter-
pressure and this is obtained most effectually by rendering according to this Invention
the steam inlet and exhaust independent of each other, the ordinary slide valve
slightly modified being employed and operated for the admission either by means of
two eccentrics actuating the slide or by any other system and the special valve for the
exhaust receiving a reciprocating movement inverse to that of the piston and capable
of being regulated to exhaust in advance at any determined point of the stroke.
This arrangement according to this Invention allows of the realization of all the
phases of the actual distribution and also presents the advantage of adjusting the
exhaust to a fixed degree whilst the counter pressure which is the inverse complement
of the exhaust will be also fixed so that with each fresh charge of steam to the
Cylinder the counter pressure will have filled the clearance with steam at the same
pressure as the steam in the boiler the fresh steam becoming mixed with the compressed
steam therein without loss of charge in a space heated by the work of the compression.
Further under these conditions the lead may be reduced and it will be possible then
with the reversing lever in mid gear to admit steam to the Cylinder during 5 or 6 %
of the stroke.
In practice in consequence of the condensations and evaporations which result from
cooling and from reductions of pressure the working of steam in steam Engines is
not in conformity with theoretical calculations but it is not less evident all things
being otherwise equal that there must be a considerable economic advantage.
1st for extending the expansion.
2ndly for increasing the compression so as to fill up the clearance by the pressure
of the piston.
3rdly. And as a corollary of this compression in leaving the sides of the Cylinder
in contact with the atmosphere only during 20% of the double stroke of the piston
instead of during a greater period as is at present the case.
Independently of these advantages which may be called thermic, which as well as
those sought in the compound arrangements should tend to the adiabatic working of
the steam, the arrangement presented possesses the following additional advantages:-
The stroke and the surface of the introduction valve is reduced since the steam exhaust
port does not exist. The work of friction is therefore diminished by about half, the
working of the reversing motion facilitated and the effort expended on the fly wheel
in the reversing motion is diminished which constitutes a considerable advantage
especially in the case of sudden stoppage.,
By arranging the exhaust valve at the lower side of the Cylinder it allows of
natural purging by the exhaust and the blow off cocks may be dispensed with or their
size or number reduced.
Finally in the case of exhaust valves placed in a lower box which is in communi
cation with the steam admission box all the condensed water from the latter flows
into the exhaust box and there is no longer any fear that the admission steam will be
in contact with this condensed water: there will therefore probably be less water
carried away in the Cylinder.
The admission valve presents a special form which will allow the steam to be
introduced into the Cylinder on each side of. the steam inlet port. The rapidity with
which the steam is introduced to the Cylinder will therefore be increased.
Dated this 27th day of September 1887.

page_text: Improvements in Steam Engines.
We, LEON DURANT, and ALEXANDRE LENCAUCHEZ of 53 Ruo do Chateaudun
Paris in the Republic of Franco Engineers do hereby declare the nature of this
Invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
This Invention is applicable to steam engines generally but is especially applicable
to locomotive engines and has for its object to provide improved arrangements as
hereinafter described for the distribution of steam with variable expansion and fixed
exhaust, the admission of steam to the cylinder being by a valvo or valves worked
independently of the exhaust valve or valves as hereinafter described.
The advantages of this arrangement are as follows:-
-
1st. Diminishing the quantity of fuel consumed by the engine, partly by the better
utilisation of the steam in the cylinders and partly by the diminution of the friction
of the parts.
2ndly. Reducing the friction.
3rdly.
E the working of the engines by rendering the reversing gear
easier to work and by enabling the cylinders to automatically clear or purge them-
selves through the exhaust ports.
4thly. Increasing the retarding action of the counter steam on reversing.
The invention consists essentially in providing each steam cylinder with one or more
supply valves connected to the link motion and one or more exhaust valves independent
of the former this being a novel arrangement in engines in which a link motion is
employed for reversing. This arrangement is also combined according to this inven-
tion with means for purging and pressure reducing or obtaining expansion as herein-
after explained.
And in order that our said invention may be fully understood we shall now
proceed more particularly to describe the same and for that purpose shall refer to tho
several figures on the annexed sheets of drawings the same letters of reference indica-
ting corresponding parts in all the corresponding figures.
Figures 1 and 2 represent a cylinder with independent admission and exhaust
valves according to this invention in longitudinal and transverse section respectively
the said valves being constructed to work on plane surfaces or seats.
11"
•
Figures 3 and 4 are similar views illustrating steam inlet and exhaust valves of the
rotary or oscillating piston type the steam cylinder being provided with two admission
valves and two exhaust valves t₁ t," The dotted lines in Figure 3 show a
modification of this arrangement according to which one valve this employed for the
admission and one valve t₁ for the exhaust.
gear
for
Figures 5, 6 and 7 are diagrams illustrating different arrangements of the
operating the valves the exhaust valves being independent of the link motion.
Figure 5 represents an arrangement according to which motion is imparted to the
admission valves by means of an ordinary link 1 and to the exhaust valves by means

page_text: of a connection or bar 2 on the middle point of the link the latter being of the
stationary type AN AR are the eccentric rods and 6 is the radius link for the admission
valves. 7 is the exhaust valve link.
According to the arrangement illustrated in Figure 6 the exhaust valve is operated
by a lever 3 connected to the piston-rod crosshead and according to the arrangement
in Figure 7 the said valve receives its motion from an eccentric or crank 4 acting on
a lever 5 connected to the link working the exhaust valvo link 7.
Figures 8 and 9 represent partly in longitudinal and partly in transverse section
the fore part of a locomotive provided with automatic apparatus for preventing back
pressure at the end of the stroke, and also illustrate a steam blast apparatus placed on
the boiler as hereinafter described.
Figures 10 and 11 illustrate in longitudinal and transverse section respectively an
engine working expansively with a link motion and fixed exhaust the exhaust valve
being balanced by the steam at a reduced pressure.
Figures 12, & 13 represent an expansion or pressure reducing apparatus in section
the section in Figure 13 being taken at right angles, to the plane of the section in
Figure 12 and Figure 14 illustrates details of a piston used in this apparatus.
Figures 15 and 16, represent an automatic purging apparatus in longitudinal and
transverse section respectively.
Figures 17 and 18 represent in longitudinal and transverse section respectively a
steam cylinder arranged to admit. steam through the interior of the admission slide
the exhaust being independent of the link.
Our invention is independent of the construction of the valves employed which may
be of any known or suitable type.
In the case illustrated in Figures 1 and 2, 10 and 11 for example the cylinder is
provided with a valve T₁ constructed with two recesses or ports V V₁arranged for a
double introduction of the steam which is enabled to pass in the direction of the
arrows Figures 1 and 2 by means of a special construction of the steam chest enabling
the steam to pass around the sides of the slide. The exhaust valve T,.is provided with
one port or recess V. A pipe Z fig..11 connects the lower part of the steam chest
with the exhaust valve case and enables the steam to exert sufficient pressure on the
exhaust valve to maintain the latter in contact with its seat. This pressure can be
-regulated by means of a pressure reducing valve I Figure 2. The construction and
action of this valve shown more clearly in Figure 11 and in detail drawn to a larger
scale in Figures 12, 13 and 14 is hereinafter more fully explained.
In order to reduce the injurious space the admission and exhaust valves may be
duplicated and arranged at each end of the cylinder.
According to the construction illustrated in Figures 17 and 18 the admission valve
is differently arranged. In place of allowing the live steam to fill the valve chest the
steam is introduced through a central orifice g into a recess in the valve by which it
is delivered or distributed to ports h h in the valve scat. When this arrangement is
adopted the tube Z connecting the admission valve with the exhaust valve does not
require to be provided with a pressure reducing valve as the steam in the admission
valvo chest is not live steam but is steam which has previously been expanded in order
to balance the valve j and is consequently under the proper pressure for balancing the
exhaust valve.
According to the arrangement illustrated in Figures and 4 valves of tho
rotating or oscillating class are employed as hereinbefore stated in the description of
the figures.
By these examples it will be understood that the invention which consists mainly in
rendering the exhaust valves of steam engines with link motion independent of the
link is capable of being applied with any description of distribution valve.
The theoretical considerations which have led to the combination of these novel
arrangements are as follows.
If we examine the conditions under which are produced the different phases of a
distribution of steam with a link motion and with a single valve we find that the

page_text: degree of admission of the steam and the amount of lead of the exhaust are injuriously
connected with each other and that a strong admission corresponds to a small lead at
the exhaust whilst the latter increases with the diminution of the admission so far as
to become at the dead point equal to half the stroke of the piston so that the steam
begins to escape long before its expansive power is exhausted.
This may be demonstrated by calculating the loss which results theoretically from
this fact. At the dead point near which the gear is placed in running a locomotive
over level or easy sections for example the admission is about 10% the injurious
space representing a mean volume on each side of the piston of 8% the admission at
the dead point répresents 18% of the volume engendered by the piston. The exhaust.
beginning at half stroke the possible expansion is 50 + 8 divided by 18 or 3.2 volumes
that is to say, if the steam enters the cylinder at a pressure of 10 kilog. this steam
begins to escape at 3.1 kilog.; and it is to be observed that the loss resulting from this
premature exhaust of the steam at high pressure increases in proportion as the
indicated pressure is raised, and there exists a tendency to raise this pressure to
12 kilogrammes.
It is consequently very desirable that the exhaust should be cominenced as nearly
as possible at the end of the stroke of the piston, while allowing the steam to escape
without producing back pressure.
This is accomplished according to this invention by rendering the steam and
exhaust valves independent of each other; the ordinary valve as modified being
operated for the admission and for the expansion under conditions analogous to the
existing conditions either by means of 2 eccentrics actuating the link, or by any
other system and the separate valve for the exhaust receiving a reciprocating move-
ment inverse to that of the piston and allowing of the regulating of the lead of the
exhaust valve at a given point in the stroke.
This combination admits of the steam being distributed in the ordinary way but
under more advantageous conditions; it also presents the advantage of enabling the
commencement of the exhaust to be regulated at a fixed degree, which may be as
low as 10%
Moreover, the counter pressure, which is the inverse complement of the exhaust,
will be also fixed and so that with each fresh cylinder full of steam the counter
pressure fills the injurious spaces with steam at the boiler pressure and tho live steam
is received without loss of pressure in a space previously heated by the work of
compression. Further, under these conditions the linear advance at the introduction
which is generally about in. (from 5 to 6"/m) can be reduced to about 16 (3 or 4™/m)
thus enabling steam to be admitted at the dead point or mid gear during 5 or 6% of
the stroke, so that the injurious space having remained the same at 8% the true
admission is 14% and the steam is expanded in a volume of 90 + 8 or 98-The
expansion will therefore be 24 or 7 volumes. The steam being introduced at 10 kilog.
thus escapes at 1 kilog. 42 instead of 3 kilog. 2 as indicated above.
The theoretical gain or advantage will therefore be 3* 20-1 42 or 1x 78; this
figure compared to that which really corresponds to the pressure utilised which
is 10-3.2 or CK SO, represents a saving of, or 20%: Allowance must of course
be made in practice, for the condensation and evaporation which result from cooling
and from fall of pressure; but it is nevertheless evident other things being equal,
that a considerable advantage is gained as follows.
1st. By increasing the expansion by from 30 to 40%:
2ndly. By increasing the compression so as to fill up the injurious space at or about
the boiler pressure and
3rdly. As a corollary of this compression by keeping the sides of the cylinder out
of contact with the atmosphere except during about 20% of the double or in and
out stroke of the piston, instead of during a whole stroke, as usually the case.
these conditions cooperate to obtain a better utilisation of the steam.
All
Independently of these advantages which may be called thermic, which, as well as
those sought to be obtained by means of compound arrangements, tend to promote

page_text: the adiabatic yield of the steam, the improved arrangements possess several others
amongst which may be mentioned the following namely
It facilitates the reversing the stroke and the surface of the introduction slide or
valve being reduced, there being no steam exhaust port to provide for. The friction
is thus diminished by about one half and the effort required to operate the reversing
gear is diminished in the same proportion; which constitutes a considerablo
advantage when it is necessary to change quickly from forward to backward gear.
As the engine runs on with the gear reversed the period of suction is limited to 20%,
as that of exhaust in the forward gear and during all the rest of the stroke the
retarding power is produced.
The arrangement of the exhaust valve at the lower side of the cylinder allows of
the natural purging by gravitation through the exhaust and enables purging cocks to
be dispensed with altogether or one only may be employed to let out the water of
condensation in the case of the exhaust, valve. The engine can be started by a
limited admission of 80%.
Finally in the case of exhaust valves working on a flat seat and placed in a lower
box which is in communication with the steam admission valve box, all the condensed
water flows away into the exhaust valve box and is not allowed to come in contact
with and partially cool or condense the entering steam there will therefore probably.
be less water carried into the cylinder.
One of the economic advantages realised by our invention results as herein before
stated from the compression being arranged to cause all the injurious space to be filled
at the moment of admission with steam at the boiler pressure. This condition may
however at starting and in increasing the speed or where extra power is required
present certain disadvantages as the compression reduces the maximum power which
other things being equal it may be necessary to develop under these circumstances.
The arrangement next hereinafter described with reference to Figures 8, 9, 15
and 16 enables the compression to be stopped for a certain time either at starting or
when it is necessary to quickly obtain the maximum speed while running or to
increase the power. This arrangement also enables the steam to be utilized in
producing an augmented draught in the chimney.
In order to prevent back pressure in the cylinders when the piston approaches the
end of its stroke each cylinder is provided with cocks a Figures 8 and 9 which
cocks are placed in communication with one another by means of a special valve
apparatus Figures 15 and 16 enabling the two ends of the cylinder separated by the
valves to be alternately placed in communication with the atmosphere.
This purging apparatus (see longitudinal and transverse sections Figures 15 and 16)
is constructed with a valve box A communicating through the orifices B and B₁
respectively with purge or blow off cocks a and b (Figures 8 and 9) and through
an orifice with the atmosphere or preferably in the case of a locomotive with the
chimney. The box A is made with two similar parts separated by a central partition D
and is provided with two ends E E which are removeable being screwed into the
body of the box. These ends form small cylinders F F' closed by screwed plugs G G¹
projecting into the cylinders. By unscrewing the ends E E¹ two valves H H' are
enabled to be placed in the box. The valve H' is cast with a tube V which passes
through the partition D and is provided with a screw thread engaging with a sleeve H"
on the valve H. Helical springs J J or rubber springs (see detached detail
Figure 15) are placed in the annular spaces between the extension of the plugs G G₁
and the cylinders F F¹. These springs press against the ends of the tube V in such
a manner as to tend to maintain the two valves H H¹ normally at equal distances
from their respective seats.
The action of this apparatus is as follows. When the blow off cocks a and b are
closed the engine works with back pressure and compression at the end of every
stroke but when the valves a and are opened the steam enters the apparatus A by
the orifice B or B₁ which communicates with that side of the piston which is open to
the supply the other orifice being in communication with the exhaust end of the
cylinder for the time being. The steam entering through the opening B' for example

page_text: presses the valve H¹ to its scat at the same time increasing the opening of the
opposite valve H. Under these conditions the exhaust end of the cylinder communi-
cates with the orifice C of the apparatus, and no back pressure or compression can
take place.
When the action of the steam in the cylinder is reversed by the action of the
distribution valve the valve H is closed and the valve H' is opened thus placing the
other end of the cylinder when exhausting in communication with the orifice C.
When this relief apparatus is applied to a locomotive the orifices C of the two
apparatus are connected by pipes e c¹ (Figure 9) with a perforated ring d'arranged
at the base of the chimney and produce a supplementary blast. This arrangement is
illustrated in the detail in Figure 9 which shows the blast ring d of the purging
apparatus arranged concentrically with the ordinary steam blast ring or tube and the
nozzle connected with the variable, exhaust. By means of this arrangement the force
absorbed by the compression may be reduced to a trifle being diminished from say
about 15 or 20 pounds to two or three.
The pressure exerted on the exhaust valve in order to counterbalance the pressure
in the cylinder is regulated by means of an expansion or pressure reducing apparatus
arranged as hereinafter described. This apparatus also serves when applied to a
locomotive to prevent soot or cinders from being drawn into the cylinder when
running down inclines with the steam shut off or reversed. The arrangements for
balancing the exhaust valve by means of the expansion or pressure reducing apparatus
are illustrated in Figures 12, 13 and 14.
This pressure reducing apparatus is constructed with a cylinder I provided at its
base with an annular enlargement M' through which it is placed in communication
with the boiler by means of a pipe K. The said cylinder is closed at both ends by
covers L L' and communicates through a lateral tube M with the valve case. In the
interior of the cylinder I there is a piston of special construction being made with
two parts or chambers P and Q at the ends and provided with packing grooves so as
to work steam tight in the cylinder I. The chamber P communicates with the
cylinder I through the lower end of the piston which is open and through radial
orifices O. Grooves N of different lengths are formed in the side of the piston being
graduated as indicated at the lower part of Figure 14 which represents a development
of the surface of the piston below the orifices O. The chamber Q is closed at tho
lower end and contains a spring R guided by a prolongation of a screw S working
in the cover L. The spring R takes a bearing on the bottom of the chamber Q and
is compressed by means of a piston T adjusted by the screw S. The pressure of the
spring R can thus be regulated by turning the screw S..
The spring enters the annular space M and is compelled to pass through the
grooves N in order to reach the tube M. These grooves being of unequal length as
indicated in the lower part of Figure 14 it results that the sectional area of the steam
passage increases in proportion as the piston P is lowered.
The position of the piston P depends on the resultant of two contrary forces
namely the variable or adjustable tension of the spring R tending to lower the piston
on the ono hand and the constant pressure of the steam acting below the upper part Q
tending to raise the piston on the other hand. In proportion as the spring is screwed
down or compressed the piston has less tendency to rise and the pressure at M is
increased.
This apparatus is employed with exhaust valves for the purpose of placing them in
equilibrium.
Figure 11 shows how the steam is conveyed by a pipe Z from the steam chest of
the admission valve T¹ to the case of the exhaust valve T the pressure being reduced
by means of the apparatus I hereinbefore described in order to balance the pressure
on the valve T. This pressure reducing apparatus enables the steam to exert on the
exhaust valve the exact amount of pressure required to maintain the valve properly in
contact with its seat.
When working with a pressure of from about 10 to 12 kilogrammes in the boiler
a pressure of from about 3 to 3 kilogrammes will be sufficient for the exhaust valve

page_text: case.
This reduced pressure is obtained by adjusting the screw S which compresses
or relaxes the spring R until the desired degree of pressure is attained this pressure
being limited by means of a safety valve W.
In the case of a locomotive descending inclines with the steam shut off the admission
valve case at X Figure 11 is connected with the boiler at X Figure 8 through a
pressure reducing apparatus I which enables the valve case to be filled with dead and
watery steam for the purpose of lubricating the surfaces and preventing binding.
On the other hand a similar pressure reducing apparatus connects the boiler at Y
Figure 8 with the exhaust valve case at Y' Figure 11, in order to prevent the intro-
duction of dirt and smoke when the engine is running with the steam valve or
regulator closed.
These pressure reducing apparatus may be employed with ordinary distribution gear
the apparatus at X Figure 8 being connected with the introduction and the appa-
ratus Y with the exhaust. These apparatus or pressure reducing valves X Y can be
adjusted to give a pressure of from about to of a kilogramme in the admission
valve case as well as in the exhaust valve case. This low effective pressure which
may be still further reduced if desired never varies from the point for which the
apparatus is adjusted by means of the screw S Figure 13.
In the use of locomotives constructed with an admission valve in which the live
steam is admitted to a central orifice g as indicated in Figures 17 and 18 the steam
tends to lift the valve off its seat and force it against the cover or against the guides.
In order to obviate considerable friction the internal pressure of the valve is balanced
by supplying the valve case with steam at a pressure which is regulated by moans of
a pressure reducing apparatus placed on the boiler. This steam is admitted to the
valve case at X Figure 18. Under these conditions the exhaust valve is balanced by
steam which has previously served to balance the admission valve and for this purpose
the two slide valve boxes are directly connected by a pipe Z without the intervention
of a pressure reducing valve.
The purging and pressure reducing valves or apparatus can be employed to prevent
back pressure or to obviate binding and entry of smoke when in place of a sliding
exhaust valve under the cylinder two cylindrical or rotary or other valves or cocks are
employed.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
1. In engines with Stephenson or other analogous link motion for reversing, the
distribution of steam by means of one or more slide or other valves for the admission
operated by the intervention of the link and one or more slide or other valves for
the exhaust the said exhaust valves being independent of the link and conse-
quently independent of the changes in the expansion substantially as hereinbefore
described.
2. In engines with link motion for reversing with an exhaust independent of the
link and consequently independent of the changes in the expansion, the combination
with each steam cylinder of an automatic purging or relief apparatus Figures 15
and 16 connected with the two ends of the cylinder through stop cocks or valves a.b
Figures 8 and 9 the said purging or relief apparatus consisting essentially of a box A
provided with three openings or orifices two of which (B and B¹) communicate
respectively with the cocks a and whilst the third (C) is connected by a tube CC¹
with a steam blast pipe & situated in. the chimney the said box.being provided with a
pair of valves H H which are normally maintained by springs J J at equal distances
from their seats the said valves being operated automatically by the pressure of the
steam in the cylinder (when the cocks a and b are open) in such a manner that the
valve communicating with the exhausting end of the cylinder for the time being
is opened and places this end of the cylinder in communication with the blast
pipe din order to obviate back pressure at the ends of the strokes. when required

page_text: all substantially as herein before described with reference to the accompanying
drawings.
3. In engines with link motion valve gear and exhaust valves independent of the
link and consequently independent of the changes in the expansion the combination,
in order to supply steam at a reduced pressure to the admission valve case or to the
exhaust valve case or both for the purpose of balancing the valves and preventing the
introduction of smoke and cinders when running with the steam valve shut, of one or
more pressure reducing valves or apparatus consisting essentially of a cylinder I
closed at both ends by covers L L and provided with two orifices namely a circular
or annular or orifice M' for the admission of steam at boiler pressure and an orifice M
through which the steam is delivered at the desired degree of reduced pressure this
reduction of pressure being obtained by means of a long or double piston Q P the
chamber or hollow lower part P of the said piston working steam tight in the
cylinder I below the orifice M' and being provided with graduated grooves N situated
above the said orifice and the upper part of the said piston being closed at its base
and forming a chamber working steam tight in the cylinder above the orifice M, the
said piston being subjected to two opposing forces namely to the pressure of a
spring R adjustable by means of a screw S on the one hand and on the other hand to
the pressure of the steam which passing through the grooves N acts on the part Q
of the piston with a force increasing as the pressure of the steam increases sub-
stantially as hereinbefore described and illustrated in Figures 12, 13 and 14 of the
accompanying drawings.
4. The arrangements and combinations of parts constituting the improvements in
steam engines substantially as herein before described and illustrated in the accom-
panying drawings.