Improvements in and relating to Gas Engines.
Year: 1897

page_text: Improvements in and relating to Gas Engines.
I, LEON ABEL LETOMBE, of No. 56, Rue d'Isly, Lille, in the Republic of France,
Engineer, do hereby declare the nature of this invention to be as follows:-
The invention hereinafter described is applicable to all kinds of motors capable
of acting under the control of a regulator, with variable charges of an explosive
mixture the volume of which is consequently independent of the space rendered
vacant by the piston in its stroke. In this class of motor in which the consump-
tion of gas may be very low even with a full charge, the control of the speed has
been effected hitherto principally either by the reduction of the explosive mixture
admitted or held in reserve by suitable means or by the simple reduction of the
gas. Now these two methods which are very suitable for avoiding abrupt changes
in the speed which are met with in the method of control of the ordinary gas
motors, unfortunately diminish the thermic efficiency in a great measure; the
first method in consequence of the diminution of compression insufficiently com-
pensated by the increase of the period of expansion; the second method in conse-
quence of deformations of the cycle resulting from the imperfect ignition which
occurs when the combustion of the explosive mixture is no longer in harmony
with the compression requisite in the machine. The mathematic analysis of the
cycles possible to be realised in a gas motor has indicated to us a new method of
control of gas motors by means of variable charges without diminishing the thermic
efficiency for the amount of work indicated. This new method consists in
diminishing the energy of the charges admitted, when the opposed work tends
to fall below its maximum, by means of a supercompression resulting from the
augmentation of the volume of admission the contents in gas of which must then
be varied, in such manner that the explosion may never be able to exceed a
maximum which has been fixed in advance. For this purpose it will be sufficient
that the volume of gas admitted during the aspirations, that is the normal aspira-
tion actually admitted (considered) and the one of which we make use in our
process, be proportioned with regard to one another in the same proportion as the
corresponding expansions. Finally there might be admitted the whole stroke
by reducing suitably the gas and even suppressing the same altogether if the
machine was too much discharged.
Supercompression such as we obtain it above the normal compression cannot
cause any disturbance because finally the pressure of the explosion can never
exceed a fixed amount if the gas be reduced successively in the proportion which
we have just indicated. By this process the contents of the mixture in gas
diminishes in proportion as the admissions increase, but as the compressions
increase at the same time the ignitions are properly effected.
In order to carry our process into practice we have devised the following
mechanical arrangements namely;-Let us take as example a 4 stroke cycle motor
of double effect. Each end of the cylinder possesses a box containing two valves
the one communicating with the cylinder by a port the other, communicating

page_text: with the first by means of an intermediate chamber but closing in the opposite
direction so as normally to cut off all communication with the exterior when a
depression tends to occur in the cylinder. The two valves can however be opened
in one and the same direction. The second valve which can open a little in advance
of the first meets on rising a third valve which it raises and which affords a passage
for the gas. The air is admitted at a suitable opening and the gas attanother.
For the purpose of regulation by supercompression the second valve when the
resistant work diminishes closes itself later and later, and the gas valve on the con-
trary sooner and sooner. Finally when the machine becomes too much unloaded
the second valve no longer raises itself sufficiently to actuate the third valve and
there is a void stroke. With regard to the foremost part of the cylinder the
action is so arranged that its void stroke precedes that of the hinder part. The
second valves are actuated by levers of any suitable shape bearing rollers which
receive their motion from stepped cams. The rollers are displaced transversely
by the regulator by means of spring grips and of the movement of a parallelogram.
The duration of the full aspiration corresponding to a determined angle, the
successively superposed steps have a form such as to provide four steps of which
two correspond to the advance and two are superposed so as to correspond to the
admission of the gas. The empty stroke corresponds to two steps or points of
the mentioned cams without superposition.
These arrangements the use of which is very suitable for a double effect motor
are obviously applicable also to single effect motors. In order to set in action
the motor of double effect the following method is made use of. During the stroke
for the explosion at the hinder part some gas is forced by means of a pump in
front so as to have first an explosive mixture and afterwards an explosive mixture
powerfully compressed behind. This compression is possible because the piston
is held back by its gaseous cushion in front. When the ignition of the hinder
part is caused the motor starts by giving two successive explosions which results
in the motor starting without preventing the compressions, the motor carrying
thus with itself a portion of the load. In order to stop the machine and to re-
commence shortly ignition is prevented whilst admitting of the entrance of gas,
and the escape valves are opened by suitable means. When the motor only
revolves slowly the front valve is closed, the piston works against compression
and the hinder valve is then immediately closed. After a few oscillations the
piston stops at the middle of its course. As soon as the ignition is caused again
the motor starts. If it be necessary to stop a minute without working the stop-
page is effected in the same manner but by suppressing the gas and in order to
restart the engine the pump is set working again.
Dated the 20th day of M 1907
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C., Patent Agents for the Applicant.
Improvements in and relating to Gas Engines.
I, LEON ABEL LETOMBE, of 56, Rue d'Isly, Lille, in the Republic of France,
Engineer, 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:-
The invention hereinafter described is applicable to all kinds of motors capable
of acting under the control of a regulator, with variable charges of an explosive
mixture the volume of which is consequently independent of the space rendered 5

page_text: vacant by the piston in its stroke. In this class of motor, the consumption of
gas in which may be very low even with a full charge, the control of the speed
has been effected hitherto principally either by the reduction of the explosive
mixture admitted or held back by means of an intermediate receptacle or by the
simple reduction of the gas. Now these two methods which are very suitable for
avoiding abrupt changes in the speed which are met in the method of control of
the ordinary gas motors, unfortunately diminish the thermic yield in a great
measure; the first method in consequence of the diminution of compression in-
sufficiently compensated by the increase of the period of expansion; the second
method in consequence of deformations of the cycle resulting from the imperfect
ignition which occurs when the composition of the explosive mixture is no longer
in harmony with the compression requisite in the machine.
The improvements in question have for their object to secure a new method of
regulation of gas engines, by means of variable charges without diminution of
the thermic yield for the indicated work. This method consists essentially in
reducing the force of the charges admitted when the resistance to be encountered
tends to become reduced below its maximum by a super-compression caused by
the augmentation of the volume of explosive mixture admitted, combined with the
simultaneous reduction of the percentage of gas in the said mixture in proportion
as the said admissions are increased.
In order to make more clear the nature of this invention, and the manner in
which it is carried into effect, I will proceed to describe it in detail as carried
into effect with reference to the accompanying drawings, in which,
Figure 1 is a diagram intended to facilitate the comprehension of my invention.
Figure 2 is a front elevation of the cylinder of a double acting gas engine con-
structed according to my invention.
Figure 3 shews a plan view of the same cylinder.
Figure 4 is a section on the line a y of Figure 2.
Figures 5, 6, 7, and 8, shew details of the controlling mechanism.
Referring first to the diagram shewn in Figure 1, this illustrates
the full charge of a machine having admission of gas independent
of the stroke; the action will be, no matter what the system employed, as
if there were admission from a to b, compression from 6 to c, explosion and
expansion from c to d and thence to e, and escape from e to a.
If it is desired to obtain a diagram of less area, and to effect regulation in con-
formity with my invention, the admission is increased, instead of being diminished,
up to a point b¹ taken between 6 and e which causes a super-compression at c¹,
but at the same time I diminish the quantity of gas in the mixture so that the
explosion can never exceed the point d, which is a maximum which has been
settled previously. For this purpose it is requisite that the volumes of gas
admitted during the aspirations ab and a b₁ should be proportioned as the
perpendiculars c d and cd. Obviously the surface b¹ c¹ àe is less than the
surface b c d e. At the limit when the motor becomes partly unloaded, the admis-
sion might be allowed to continue throughout the entire stroke, the proportion
of gas being suitably diminished or even suppressed altogether if the machine
were too much unloaded. Now, calculations will shew that the thermic yield
of the cycle under consideration increases in proportion as the surface diminishes
as I have indicated above. The super-compression such as c c in excess of the
normal compressions ac cannot cause any disturbance because the pressure of
the explosion can never exceed a fixed quantity if the gas be reduced successively
in such manner as is above specified..
It will be observed that the diagram does not indicate completely what occurs
in the cylinder unless the stroke of the engine is considered as varying with the
time for which the gas admission valve is kept open or unless said valve is open
during the whole of the suction stroke and the first portion of the compression
stroke, in other cases lines such as bf, b₁f should be added to the diagram shewing
the pressure in the cylinder during the latter portion of the suction stroke and

page_text: the first portion of the compression stroke. These additional lines, will moreover
be practically double inasmuch as the successive pressures during the latter part
of the suction stroke of the piston will be substantially the same as those occurring
during the first part of the compression stroke.
By making use of these means the content in gas of the mixture diminishes,
consequently in proportions as the admissions increase, but as the compression
increases at the same time, the ignition remains effective.
As already stated Figures 2 to 8 of the drawings shew arrangements devised
to admit of the application of this method of control to a double acting gas engine
having a cycle of four strokes.
Each end of the cylinder L (Figures 2, 3, 4) bears a chamber containing two
valves (Figure 5) one marked A which communicates with the cylinder L by the
port (Figure 4) the other marked B which communicates with the first by means
of the intermediate chamber C, as shewn in Figure 5, which gives a section on
the line of Figure 3. This valve B closes in the opposite direction so as
automatically to shut off all communication with the outside whenever a depres-
sion tends to be formed in the cylinder L. The two valves A and B can moreover,
as shewn in Figure 5, open in the same direction. The valve B, which can open
a little in advance of the valve A meets on opening with the valve G which it
also raises, and which gives access to the gas at m, as shewn at Figure 6, which
figure shews a section of these valves on the line u v of Figure 3. The air is
supplied through n Figure 5.
When the working is regulated by supercompression the valve B, when the
resisting load diminishes, closes later and later, and the gas valve G on the contrary
sooner and sooner. At the limit when the machine is finally unloaded, the valve B
no longer rises sufficiently to actuate the valve G and a void stroke is produced.
With regard to the forepart of the cylinder arrangements are made so that the
said void stroke precedes that of the back stroke.
The valves B are actuated by the levers K (Figures 2 and 4) having rollers J,
Figure 4, which receive their motion from stepped cams P mounted upon the
shaft 0 (Figures 2 and 4) actuated directly by the main shaft of the motor.
Figures 7 and 8 shew separately one of these stepped cams P. The rollers J
which rest against these cams can be displaced transversely by the regulating
mechanism so as to encounter, as will be shewn hereafter, respectively the one
or the other superposition of the cams P. This operation is effected by means
of the articulated parallelogram S T U V and of the clips, provided with springs
which prevent said clips gripping the rollers (Figures 2 and 4).
The duration of the full aspiration corresponds to the angle y 0 21 (Figure 7)
the superposed successive steps of the cams P are shewn as shaped at 4, 1, 2, 21
or 4, 1, 3, 31, etc. in which 4, 1, corresponds to the advance, and 1, 2, or 1, 3, and
so on to the superposition for the admission of the gas. The empty stroke corre-
sponds to 4, 41, without superposition.
These arrangements the use of which is very advantageous for a double acting
motor are obviously also applicable to single action motors.
are
In order to set in motion the double acting engine the following means
adopted when the engine is upon the course for the rear explosion there is in-
serted in front, by means of a gas pump, an explosive mixture, and an explosive
mixture strongly compressed behind. This compression is possible because the
piston is held back by its gaseous cushion in front.
Having caused the charge behind to ignite, the motor will start, giving two
successive explosions, which enables it to start without suppressing the compres-
sions, and carrying with it a part of the charge.
In order to stop the machine and to restart in a short time the ignition is pre-
vented, whilst the admissions of the gas are allowed to continue, and the escape
valves are raised by any convenient means. When the motor is only moving
slowly the front valve is closed, the piston stops against a compression, and the
hinder valve is immediately closed. After several oscillations the piston will

page_text: stop at the middle of its course, consequently there is no need of adjusting to this
point. If the ignition be again caused the motor starts again. If it be requisite
to stand for a moment without working the machine can be stopped in the same
manner, but the gas is suppressed, and in order to re-start use is made of the
pump.
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:
1. In a gas engine, in combination the augmentation of the admission of the
explosive mixture and the simultaneous diminution of the gas percentage of
the said mixture in proportion as the said admissions increase so as to obtain a
supercompression of the explosive charge, substantially as, and for the purpose
described.
2. In combination with a cylinder of a gas engine in which when the load tends
to be reduced below its maximum the regulation is effected by the increase of
the admission and the simultaneous diminution of the percentage of gas in the
explosive mixture, a chamber at each end of the cylinder, two valves placed in
these chambers, and a gas valve above one of the two valves aforesaid, together
with means for actuating the said valves, all substantially as, and for the purpose
described.
3. In a gas engine, in which when the load diminishes the regulation is effected
by the increase of the admission, and the simultaneous decrease of the gas
percentage of the explosive mixture, the combination of two valves at each end
of the cylinder, one of which raises the gas valve, together with a stepped cam
actuating the said valves by means of a lever K with roller, and means for dis-
placing transversely the said roller, substantially as, and for the purpose described.
4. In a gas engine, in which when the load diminishes the regulation is effected
by the increase of the admission, and the simultaneous decrease of the gas percen-
tage in the explosive mixture, in combination, two valves at each end of the
cylinder, a gas valve actuated by one of the said valves, a stepped cam controlling
the raising of the valves, by means of a lever with roller, and a jointed parallelo-
gram actuated by the regulator for the purpose of adjusting the roller of the said
lever upon the said stepped cam, substantially as and for the purposes described.
D
00 11
W. P. THOMPSON & Co.,
Patent Agents for the Applicant,
322, High Holborn, London, W.C.
W. P. THOMPSON & Co.,
Patent Agents for the Applicant,
322, High Holborn, London, W.c.