Improvements in Steam Engine Valve Gear.
Year: 1890

page_text: Date of Application, 18th June, 1890
Complete Specification Left, 20th Apr., 1891-Accepted, 18th June, 1891
PROVISIONAL SPECIFICATION.
Improvements in Steam Engine Valve Gear.
We LEON DURANT and ALEXANDRE LENCAUCHEZ of 95 Boulevard Beau-
marchais Paris in the Republic of France Engineers do hereby declare the nature
of this invention to be as follows:-
:-
This invention relates to novel arrangements of valve gear or steam distribution
apparatus for steam engines as hereinafter explained whereby the steam is enabled
to act under more advantageous conditions the quantity of fuel consumed per
horse power being also reduced partly by the better utilisation of the steam in the
cylinders and partly by lessening the friction between the parts.
We will describe an arrangement of valves and gear according to our invention
with admission and exhaust valves of the oscillating type working on cylindrical
seats for example.
In order to reduce the injurious clearance space a pair of valves, an admission
valve and an exhaust valve are placed at each extremity of the cylinder. Each
admission valve is preferably constructed with a hollow or recess admitting of a
double introduction of steam which passes over the back of the valve and also past
the underside of the valve by a special passage in the valve face.
Each exhaust valve is preferably arranged for an exhaust through a number of
orifices. The arrangement of mechanism or valve gear employed for working the
admission and exhaust valves is applicable to any gear working with a link motion
and enables the period of the various phases of distribution to be very easily
regulated or adjusted. The said arrangement consists essentially in working the
two valve rods directly or indirectly connected to the admission and exhaust valves
respective by one slot or if preferred by two separate slots formed in one link
the said rot's being connected together by short connecting links of suitable length
and being hifted by one reversing shaft. By moving the two valve rods and
placing the nearer together or farther apart the relative conditions of admission,
exhaust and compression can be modified in such a manner as to enable the steam
to be employed in the most economical manner possible according to the conditions
under which the engine is called upon to work.
The mechanism is formed by a slotted link jointed to the eccentric rods and in
which link slide the die blocks of the two valve rods. These two valve rods are
connected together by short links one of which may be dispensed with by
employing one die block for the two rods. The link is shifted by means of levers
and rock shafts or any suitable metallic mechanical combination.
The movement may be transmitted to the slide valves either directly or by the
intervention of intermediate mechanism. For example the exhaust valve rod may
be worked by a two armed lever receiving motion from one of the short links con-
necting the rods receiving motion directly from the die blocks and oscillating on a
suitable support or link.
We will now proceed to explain the theoretical considerations which have led us
to combine these peculiar arrangements the action of which will be made clear at
the same time.
On examining the conditions under which the different stages of distribution of
steam take place with one slide valve operated in the customary manner it is found
that there is a prejudicial connection between the operations of admission and
exhaust and a large amount of admission corresponds with a late exhaust whilst the
latter becomes earlier with the diminution of the admission until it may be equal
to (i.e. may take place as early as) half the stroke of the piston. It results that

page_text: the steam commences to escape into the atmosphere long before it has exhausted its
power of expansion.
To make this point more clear the loss resulting in theory from this fact may be
calculated. At the dead point in the vicinity of which the valves are worked in
passenger trains on easy gradients the admission is about 10 per e n', the prejudicial
space representing a mean volume of 8 per cent. on each side of the piston the
admission at the dead point represents 18 per cent, of the volume produced by the
piston, the exhaust commencing at half stroke the possible expansion is 50 × 8
divided by 18 that is to say that if the steam at admission has a pressure of
10 kilos. this steam will cominence to exhaust at 32 kilos. and the loss resulting
from the premature exhaust of the steam at high pressure is greater in proportion
as the initial pressure is increased. The importance of causing the exhaust to
commence as near as possible to the end of the stroke of the piston and at the same
timme enabling the steam to escape without producing counter pressure is obvious.
This result is obtained according to our invention by rendering the introduction
and the exhaust independent of one another and by working the distribution valves
by means of mechanical arrangement such as those hereinbefore described.
This combination admits in fact of realising with greater advantage all the
benefits derived from the distribution as heretofore arranged by prolonging the
expansion and diminishing the compression within such limits as are suitable in
practice. The prejudicial or clearance spaces are greatly diminished and moreover
under these conditions the linear advance at the introduction or lead which is
ordinarily from 5 to 6 millimetres may be reduced to 3 or 4 millimetres and it then
becomes possible to admit at the dead point up to 5 or 6 per cent, so that the pre-
judicial space being 4 per cent. the true admission becomes 10 per cent. and the
expansion being prolonged to 80 per cen', the steam expands in a volume of 80 + 10
or 90.
The expansion may be 18 or 9 volumes. The steam being introduced at a
pressure of say 10 kilos. consequently escapes at 1 kilo. instead of at 3-2 kilos. as
herein before stated. The advantage in theory is thus indisputable and very
considerable.
Owing to the condensations and evaporations resulting from cooling and
fluctuations or drops in the pressure the results in practice will not agree strictly
with the theory but it is none the less evident that other things being equal there
must be an important advantage in obtaining the following results namely,
1. Prolongation of the expansion by an additional 30 cent.
per
2. Diminution of compression at the same time filling the prejudicial space at the
initial pressure.
3. Facilitating the introduction and exhaust of the steam by means of orifices
of large section.
4. Not allowing the exhaust steam to escape in contact (through a partition)
with the supply or live steam as in engines with one slide valve.
Independently of these advantages which may be termed thermic and which like
those sought to be obtained in compound arrangements tend to the adiabatic effect
of the steam, the new arrangement presents other advantages from several points
of view.
It facilitates the manipulation of the reversing lever the slide or distribution
valves being in great measure balanced. In running against the pressure of the
steam the resistance is increased owing to the reduction of the clearance space.
The arrangement of the exhaust valves at the lower side of the cylinder facilitates
the escape of the water of condensation.
Dated this 18th day of June 1890.
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, London, W.C., Agents.

page_text: COMPLETE SPECIFICATION.
Improvements in Steam Engine Valve Gear.
We LEON DURANT and ALEXANDRE LENCAUCHEZ, of 95 Boulevard Beau-
marchais, Paris, in the Republic of France, 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 relates to novel arrangements of valve gear or steam distribution
apparatus for steam engines as hereinafter explained whereby the steam is enabled
to act under more advantageous conditions in steam engines in which the reversing
is effected by means of a slide or link motion and in locomotive and marine engines
in particular. These arrangements have the effect of diminishing the quantity
of fuel consumed per horse power partly by the better utilization of the steam in
the cylinders & partly by reducing the friction between the parts.
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
the several figures on the annexed sheets of drawings the same letters of reference
indicating corresponding parts in all the figures.
The drawings illustrate an arrangement of valves and gear according to our
invention the admission and exhaust valves being of the oscillating type working
on cylindrical seats.
Figures 2 and 4 illustrate the arrangement of the working gear in elevation and
in plan respectively.
Figure 5 is a diagram showing the action of the valve gear and Figures 1 and 3.
illustrate details of the valves.
In order to reduce the injurious clearance space a pair of valves namely an
admission valve T and an exhaust valve T is placed at each extremity of the
cylinder. Each admission valve T is constructed with a hollow or recess C
admitting of a double introduction of steam which passes over the back of the
valve and also past the underside of the valve.
This double introduction of steam is obtained by arranging the valves as repre-
sented in Figure 6. When the right hand valve T for example is moved in the
direction of the arrow, the recess C first connects the admission port 1 with a
passage 2 enabling the steam to pass through the passage 2 and recess C into the
port L.
At the same time the hinder edge 3 of the valve uncovers the port and
allows the steam to pass over the back of the valve into the port as well as
through the recess C. The admission is thus doubled at the commencement of
the stroke.
This doubling of the initial introduction obviates the wire drawing of the steam
and waste of energy that would otherwise take place. After the valve has travelled
a certain distance the double introduction ceases as will be readily understood by
referring to the drawing. The exhaust valves are similarly arranged but as the
exhaust valves move in the opposite direction to the admission valves the double
introduction is enabled to continue during the whole of the time occupied by the
exhaust in order to obviate back or counter pressure.
Figs. 2 and 4 illustrate the arrangement of the valve gear. This arrangement
which is applicable to all distribution mechanism working with a link motion
enables the periods of the various phases of distribution to be very easily regulated
or adjusted. The said arrangement consists in working the two valve rods con-
nected respectively to the admission and exhaust valves by one slot or if preferred
by two separate slots formed in one link the said rods being connected together by
short connecting links of suitable length and being shifted by one reversing shaft.
By moving the two valve rods and placing them nearer together or farther apart
the relative conditions of admission, exhaust and compression can be modified in
such a manner as to enable the engine to employ the steam in the most economical

page_text: manner possible according to the conditions under which it is called upon
to work.
The valve gear is constructed with a link a suspended on a hanger 4 attached
to the frame at 5. The construction of the link a is illustrated, drawn to a larger
scale in side elevation and in horizontal section respectively in Figures 7.. and. 8.
The link is constructed with two trough shaped plates 6 tempered and hardened' on
the inner surfaces and connected together by suitable bolts and distance pieces.
Each plate is provided with a stud or trunnion 7 engaging with corresponding eyes
on the hanger 4. Other studs 8 and 9 connect the link with the excentric
rods e e.
The space between the plates 6 forms a passage in which works a die block or
slide 10 (represented separately and in elevation in Figure 9) composed of two
plates maintained at the required distance apart by shoulders formed on pins or
gudgeons 11 and 12 by which the slide is connected to the rods and which work
the valves.
The action of the valves is controlled by a suitable combination of links and
levers such as which may be connected directly to the slide 10 or to the rod ↳
for example so as to enable the position of the slide 10 to be readily adjusted in the
link a
may be transmitted to the valves either
The motion imparted to the rods
directly or by any suitable combination of mechanism. In the example illustrated
the rods are connected to a link g (Figure 2 and diagram Figure 5) which is
attached at y' to a two armed lever y whose fulcrum y is carried by a link P¹
capable of oscillating on a fixed point P. The lower end of the lever " is con-
nected to the exhaust valve rod 13 and the rod 14 of the admission valves is
connected to the lower end of the link '.
When the two slides are employed to work in the link & the rods being
connected together at one end by the link are connected at the other end by a
similar link but this link is not required with the arrangement illustrated in the
drawings.
We will now proceed to explain the theoretical considerations which have led us
to combine these peculiar arrangements the action of which will be made clear at
the same time.
On examining the conditions under which the different stages of distribution of
steam take place with one slide valve operated in the customary manner it is found
that there is a prejudicial connection between the operations of admission and
exhaust and a large amount of admission corresponds with a small advance at
the exhaust whilst the latter increases with the diminution of the admission until it
may be equal to half the stroke of the piston. It results that the steam commences
to escape into the atmosphere long before it has exhausted its power of expansion.
To make this point more clear the loss resulting in theory from this fact may be
calculated. At the dead point in the vicinity of which the valves are worked in
passenger trains on easy gradients the admission is about 10 per cent., the pre-
judicial space representing a mean volume of 8 per cent. on each side of the piston
the admission at the dead point represents 18 per cent. of the volume produced
by the piston, the exhaust commencing at half stroke the possible expansion
is 50 +8 divided by 18 that is to say that if the steam at admission has a
pressure of 10 kilos. this steam will commence to exhaust at 32 kilos. and it
must be observed that the loss resulting from this premature exhaust of the
steam at high pressure will be greater in proportion as the initial pressure is
increased and there is now a tendency to raise the initial pressure to upwards
of 12 kilos. The importance of causing the exhaust to commence as near as
possible to the end of the stroke of the piston and at the same time enabling the
Steam to escape without producing counter pressure is obvious.
This result is obtained by rendering the introduction and the exhaust independent
of one another and by working the slide valves by means of the arrangements
hereinbefore described.

page_text: This combination admits in fact of realising with greater advantage all the
benefits derived from the distribution as heretofore arranged by prolonging the
expansion and diminishing the compression within such limits as are suitable in
practice. The prejudicial spaces are greatly diminished and moreover under these
conditions the linear advance at the introduction or lead which is ordinarily from 5
to 6 millimetres may be reduced to 3 or 4 millimetres and it then becomes possible
to admit at the dead point up to 5 or 6 per cent, so that the prejudicial space being
4 per cent. the true admission becomes 10 per cent, and the expansion being pro-
The
longed to 80 per cen'. the steam expands in a volume of 80 + 10 or 90.
expansion may be 18 or 9 volumes. The steam being introduced at a pressure of
say 10 kilos. consequently escapes at 1 kilo. instead of at 32 kilos. as herein before
stated. The advantage in theory is thus indisputable and very considerable.
Owing to the condensations and evaporations resulting from cooling and
fluctuations or drops in the pressure the results in practice will not agree strictly
with the theory but it is none the less evident that other things being equal there
must be an important advantage in obtaining the following results namely
1. Prolongation of the expansion by an additional 30 per cent.
2. Diminution of compression at the same time filling the prejudicial space at the
initial pressure.
3. Facilitating the introduction and exhaust of the steam by means of orifices of
large section.
4. Not allowing the exhaust steam to escape in contact (through a partition) with
the supply or live steam as in engines with one slide valve.
Independently of these advantages which may be termed thermic and which like
those sought to be obtained in compound arrangements tend to the adiabatic
effect of the steam, the new arrangement presents other advantages from several
points of view.
It facilitates the manipulation of the reversing lever the slide or distribution
valves being in great measure balanced. In running against the pressure of the
steam the resistance is increased owing to the reduction of the clearance space.
The arrangement of the exhaust valves at the lower side of the cylinder facilitates
the escape of the water of condensation.
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. A system of distribution for variable expansion with independent admission
and exhaust slide valves for steam engines with reversing gear worked by a slide
under the conditions herein before set forth.
2. The arrangements and combinations of parts constituting the improvements
in steam engine valve gear substantially as herein before described with reference
to the accompanying drawings.
J. H. JOHNSON & Co.,
Agents.