IMPROVEMENTS IN GAS ENGINES
Year: 1886

page_text: I ROBERT SKENE of Wickham Street Lambeth in the County of Surrey Engineer
do hereby declare the nature of my said invention for IMPROVEMENTS IN GAS
ENGINES to be as follows: —
My improvements relate to that class of motors in which a mixture of inflam-
mable gas or vapour and atmospheric air are mixed together, compressed, and
exploded: the power being obtained from the rise in pressure of the exploded
charge.
My improvements are designed to effect greater economy in gas, by using an
aditional free piston in the space at the end of the cylinder into which the charge
of combustible gas and air is compressed, and serves for the following purposes
1st. To expell the products of combustion and prevent thier mixing with, and
heating the fresh charge; by which means a greater range of temperature is
obtained in the cylinder with a more deluted charge.
2nd. To obtain greater expansion of the ignited charge.
3rd. To provide an air cushion which will store up the energy suddenly given
out on ignition, when the piston is at the end of the stroke, and give it up again
as the piston advances.
My improved Engine may be made either vertical, or horozontal, with one or
more single acting cylinders, each giving an impulse every alternate revolution,
or with a double acting cylinder, or cylinders, one end being used to compress gas
and air, and the other end for exploding the mixture every revolution; or instead
of using one end of the cylinder for compressing the mixture, a seperate pump may
be used. In a single acting engine in which an explosion cannot take place
oftener than every alternate revolution, the expansion is determined by the position
of the exhaust port. If the port is placed at the end of the in stroke of the
piston, the piston will then take in a mixture of gas and air during the whole
suction stroke, in which case the engine will give out the most power but with the
least expansion.
:
If the port is placed in the cylinder at the middle of the piston stroke, then the
piston will draw in gas and air during half the suction stroke only the free
piston will advance near to the exhaust port during the exhaust stroke and clear
out all the products of combustion except what is in the port, and so much as will
prevent metallic contact between the two pistons, as the working piston will have
to forse the free piston back against its air cushion and spring to allow it to
compleet its stroke: with the port in this position, the expansion will be double
that in the former position, giving greater economy in gas but with a reduction of
the power of the engine.
One port may serve for exhaust and suction, or two may be used, and they may
be placed at any part of the stroke according to the desire, for power, or economy,
in the maker.

page_text: The free piston, has a small piston rod with a stop upon it to prevent it going
farther than close to the exhaust port.
Instead of a stuffing box, I use an air tight tube for the piston rod to work in.
A spring is also used as well as the air at the piston back to insure it reaching the
end of its travil.
In an Engine in which an explosion takes place in a cylinder every revolution,
the working, and free pistons, come nearly close together at the end of the in
stroke, the incoming charge forcing the free piston back to make room for it: in
this class of engine, the expansion is determined by the space at the back of the
free piston, as well as the amount of compression used, the smaller the space, and
the less the compression is, the greater the expansion will be, the larger the space,
and the greater the compression, the less the expansion will be. Another advantage
in this class of engine, of the free piston, is that the charge can be admited and
ignition take place at the commencement of the stroke, thus avoiding shock with
a rich mixture and too slow combustion with a very delute mixture, which take
place if the piston is allowed to travil so far as to make room for the charge,
before ignition.
In small engines with short piston stroke I find it very advantageus to be able
to dispense with the ignition valve (as the piston speed should not be less than
.300-feet per minute) In single acting, engines, in which an explosion can take
place only every alternate revolution, I have been able to dispense with an ignition
valve, in the following manner: a tube of iron, or other suitablé metal, from in.
to in. internal diameter, communicates with the combustion chamber in the
cylinder, and is closed at its outer end, this tube will contain the products of com-
bustion, but when a fresh charge is compressed, it will also compress the products
of combustion into the outer end of the tube, and allow the fresh charge to rise
in the tube, gaining its highest point when the piston has finished its compression
stroke, at this point the tube is keept red hot by an atmospheric gas burner, which
will ignite the charge within the time of ignition can be regulated by placing
the atmospheric burner nearer to, or farther from the combustion chamber.
For engines with long piston stroke, I prefer a valve operated by the engine,
This noval valve, consists chiefly of two tubes, the one working inside the other,
the outside one is screwed into or connected with the combustion chamber, and has
on its outer end a packing gland (to prevent leakage between the two tubes) and,
on its inner end a seat, to make a tight joint with a seat on the outside of the inner
end of the inner tube, which is larger at its inner end, the inner end is also closed,
except a very small pin hole, made to allow a little of the combustible charge to
pass through, and close to the pin hole, the tube is packed with wire gauze as far
as its seat on the outer tube, and close to its seat, and the wire gauze, is drilled a
small hole about in. diameter, for igniting the charge, When compression of a
combustible charge takes place, part of it will pass through the wire gauze, and be
ignited by an outside gas burner, the inner tube is then covered at its outer end,
and forsed from its seat, allowing the charge to enter into the flame in the inner
tube, through the in. hole igniteing the charge. Instead of the wire gauze being
placed in the inner end of the tube, I have found a roll of wire gauze, having a
small hole in its centre, and placed in the middle of the tube, to act equally well.
For governing gas engines, I use a pendulum, made to vibrate at the speed the
engine is desired to revolve at: The engine causes the pendulum to vibrate, and
any increase in speed, will increase the travil of the pendulum, which increase of
travil, is utilized to prevent the gas valve, being operated.
Deted this fifteenth day of February 1886.
:

page_text: Improvements in Gas Engines.
·I, ROBERT SKENE, of Wickham Street, Lambeth, in the County of Surrey,
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:-
My improvements relate to that class of motors in which inflammable gas or
vapour and atmospheric air are mixed together, compressed and exploded, the power
being obtained from the rise of pressure in the exploded charge.
My improvements consist in the use of an additional charge of atmospheric air
or vapour comfined in a closed chamber, preferably part of the cylinder, behind a
freely moving auxiliary piston, and separated air-tight from the explosive chargé
by the said auxiliary piston, the additional air or gas charge being thus compressed
like, and to the same pressure as, the explosive charge, during the compression
stroke, and also upon explosion of the latter; and, further, I give facilities for
increasing the volume of the said air-cushion or auxiliary charge and propor-
tionately decreasing the volume of the explosive charge, admitted during the.
suction stroke, by adjustment of the position of the exhaust and inlet ports, and
further I provide means of giving any desired expansion and at the same time
keeping the auxiliary charge proportionate to the combustible charge. I make.
improvements in the governor and the ignition device, to render the same simple
and effective.
My improvements confer the following advantages:
1st. The products of combustion are practically expelled on each exhaust stroke,
thus preventing the admixture with the fresh charge, whereby combustion is more
completely obtained and a greater range of temperature upon explosion with a
more dilute charge of inflammable gas, and thus giving greater economy.
2nd. I obtain further economy by giving greater expansion to the ignited
charge, and may adjust the desired range of expansion according to the economy or
power desired.
A
3rd. A perfectly elastic air-cushion is provided, which will store up the energy.
suddenly given it upon ignition of the inflammable charge, when the piston is at
the end of the stroke, and will give it up again as work, as the piston advances.
4th. By means of the auxiliary piston and air cushion in a cylinder giving an
explosion every revolution, ignition of the charge can take place nearly at the
position of dead centre, thus avoiding shock with a rich mixture, and too slow
combustion with a very dilute mixture, which takes place in such engines in which
the piston is allowed to travel over its dead centre so far as to make room for the
explosive charge before ignition.
5th. Rapidity and certainty of ignition, very suitable for high speed engines
with short strokes.
6th. A very sensitive governor.
My improved engine may be either vertical or horizontal, with one or more single
acting cylinders, each giving an impulse every alternate revolution; or with a
double acting cylinder, or cylinders, one end being used to compress gas and air,

page_text: and the other end for exploding the mixture every revolution; or, instead of using
one end of the cylinder for compressing the mixture, a separate pump may be used
therefor.
In order that my invention may be the better understood, I now proceed to
describe the same in relation to the drawings hereunto annexed, reference being had
to the letters and figures marked thereon. Like letters refer to like parts throughout
the figures.
Figure 1 is a vertical longitudinal section.
Figure 2 is an outside elevation of one form of my engine arranged vertically.
Figures 3 and 4 are longitudinal vertical sections through the cylinder inlet and
exhaust ports, showing modified positions of the said ports, and a modified form
and attachment of my auxiliary piston.
Figure 5 is a part longitudinal section and part elevation of a convenient hori-
zontal form of my engine.
Figure 6 is a modified ignition apparatus.
A is my working cylinder, and B the working piston therein, operating the
crank shaft by the usual connecting rod and crank; C is the auxiliary piston
provided with a guide tube D, and a light spiral spring E therein, in figures 1 and 2
which ensures the rise of the auxiliary piston as far as the stop e, (which is pro-
vided with a spring to deaden noise) will permit, during the exhaust stroke. This
is not required in the arrangements as shown at figures 3 and 4, where, in the latter
case, the weight of the auxiliary piston C answers the same purpose as the spiral
spring. An air check inlet valve is in this case provided in the main piston, by
which air may be drawn into the space behind the said piston, if at less than
atmospheric pressure, during the movement of the said auxiliary piston; G is the
charge inlet and exhaust passage, united in figures 1 and 4, but, in figure 3, G is
the inlet port only, and the exhaust passage, distinct from the former. The gas
is admitted by the gas valve H, operated by a cam h, on a rotating shaft a, or in
any other convenient and equivalent manner, and the air and gas is admitted
through the inlet valve K, which closes automatically against any back pressure,
during the working stroke. A secondary air inlet valve k is provided, to prevent
escape of gas, and to regulate the gas admission. L is the exhaust valve, operated by
the cam on the aforesaid rotating shaft a, against the reaction of a spiral spring,
which closes the valve when required. I do not confine myself to these arrange-
ments of inlet and exhaust valves, as either or both combined may be in the form
of a rotary valve, operated from any suitable part of the engine, such as from the
rotating shaft a; M is the governor, in the form of a pendulum swinging from the
pivot n, the movement of the said pendulum with a spring rod N being imparted
by a rod and bell crank m m, and a disc pin on the same rotating shaft a. Should
the movement of the engine accelerate, it causes the said pendulum to oscillate
over a greater arc, and thus the set screw P on the pendulum is caused to strike the
tappet p, through which the cam movement of the rotating shaft a is communicated
to the gas valve. When the roller Q is shifted out of the way of the cam upon
the shaft a, the cam no longer strikes the gas valve spindle, and thus no gas is then
admitted; R is the ignition tube, which is a closed tube, screwed into the side of
the cylinder near to the working piston when at the end of the in-stroke, the
combustible charge having access to the said tube on the compression stroke. The
said tube is made red hot at a suitable point by an external atmospheric burner S.
It is obvious that the products of combustion will remain in the ignition tube
after expansion. When a fresh combustible charge is admitted to the working
cylinder, and compressed, the products of combustion in the tube will be at the
same time compressed into the outer end of tube, the fresh charge rising in the
tube to a point proportionate to the length of the tube and the compression,
at which point the tube is kept red hot where ignition takes place, the operation
being repeated indefinitely according to the regulation by the governor M. I find
the best time for such ignition is when the piston is at dead centre. The time of
ignition is regulated by raising or lowering the atmospheric burner,

page_text: In a single acting engine in which an explosion cannot take place oftener than
every alternate revolution, the expansion is determined by the position of the
exhaust and suction ports. If the combined suction and inlet port G is placed at
the end of the in-stroke of the piston, as in figure 4, the piston will then take in a
mixture of gas and air during the whole suction stroke, in which case, the engine
will give out the most power, but with the least expansion. If the inlet port is
placed in the cylinder at a fractional portion of the piston stroke, such as a third
or a half, as in figure 3, the piston will then draw in gas and air during a part of
the stroke only; the auxiliary piston will advance near to the exhaust port, during
the exhaust stroke, and clear out the products of combustion, except what remains
in the port, and so much as will prevent metallic contact between the two pistons,
the working piston having to force back the auxiliary piston against its air cushion
and spring, to allow the former to complete its stroke. When the expansion is
considerable, I prefer to place the inlet port G separate from the exhaust port G³,
as in figure 3. In this case the air cushion underneath the auxiliary piston should
preferably be about half the volume of the combustible charge, and in this case the
auxiliary piston rod with its spring and stop may be dispensed with. To effect
this, I may make the piston of such a depth as to be rather more than sufficient to
cover the exhaust port, which will ensure retention of the fresh charge and the
auxiliary piston following the working piston in close contact, without the retention
of any of the waste products of combustion remaining between them as in the
former arrangement, which I consider an advantage. The back pressure during
the exhaust stroke, will uncover the exhaust port, and the working piston should
just reach the top of the exhaust port when at the end of the instroke. During
the suction stroke, the exhaust valve is kept open until the working piston nearly
reaches the inlet port G, thereby permitting the auxiliary piston to closely follow
the working piston by the admission of exhaust from the exhaust port under the
auxiliary piston, until the exhaust valve closes, which it does just before the main
piston passes the inlet port. The spring of the exhaust valve must be so strong
that it cannot open except by the mechanical action of the cam operated by the
engine. During the first part of the return compression stroke, the exhaust valve
is opened and allowed to remain open for the same period as it remained open
during the first part of the suction stroke, so as to permit discharge of that part
of the exhaust drawn in behind the auxiliary piston.
A similar arrangement of the inlet and exhaust ports G G¹ respectively in a
horizontal form of my engine is shown at figure 5, the working piston B and free
auxiliary piston C being shown in proper respective position at the farthest point
of travel of the auxiliary piston C, when the engine is working in the ordinary way
with supply of explosive mixture. The inlet valve is as shown just opening for
the admission of gas and air, whilst the exhaust valve L operated by the cam / on
the spur wheel a¹ has just been closed. In this arrangement I show how I can
dispense with any automatic operation of the gas valve, the gas inlet being then
merely fitted by an ordinary hand cock H. For example if the exhaust valve be
allowed to remain open in the position of the engine as shown in the drawing, the
two pistons will continue their travel in close proximity to one another, air being
drawn from the exhaust behind the auxiliary piston, and their being thus no
tendency to draw an explosive mixture through the inlet valve. The moment
however the exhaust valve is closed, (as it is much more heavily spring pressed
than the inlet valve), the travel of the auxiliary piston C ceases, and the working
piston then draws its combustible charge through the inlet valve. I may regulate
the engine by the exhaust valve by means of the governor, which is in the form of
a pendulum swinging from a pivot n. Movement is communicated to the said
pendulum M through a spring N by a rod m and a disc pin on the spur wheel a¹.
The acceleration of the said pendulum strikes a catch p, so as to hold the lever
operating the exhaust valve against the closing action of the recoil spring . Thus,
the exhaust valve may be prevented from closing, and, when thus held open, the
engine takes no combustible charge at all as before described.

page_text: The increased expansion gained by this position of the inlet port gives great
economy in gas, but with the consequent reduction of the maximum power of the
engine. The exhaust and inlet ports may be placed at any part of the piston
stroke in the cylinder, according to the desire for power or economy in the use of
the engine.
It is well to supply an air cock or valve to the cylinder under the auxiliary
piston opened by hand during the first suction stroke of the engine after standing,
to ensure an air-cushion under the said auxiliary piston, as, in the case of a vertical
engine, the air-cushion might have leaked away under the weight of the auxiliary
piston.
In an engine, in which an explosion takes place in a cylinder every revolution,
the working and auxiliary pistons come nearly close together at the end of the in-
stroke, the incoming charge forcing the auxiliary piston back, to make room for it.
In this class of engine the expansion is determined by the space at the back of the
auxiliary piston, as well as by the amount of compression used; thus, the smaller
the space and the less the compression, the greater the expansion will be; and the
larger the space and the greater the compression, the less the expansion will be
before exhaust.
For an engine with long piston stroke, I prefer an ignition valve operated by
the engine, shown at figure 6. This valve consists of two tubes X X¹, one working
inside the other. The outer one X is screwed into or connected to the combustion
chamber, and has at its outer end a packing gland, to prevent leakage between the
two tubes, and on its inner end a seat ¹ to make a tight joint with the seat on
the outside of the inner end of the inner tube, which is larger at that end. The
inner tube X¹ is closed at its inner end, except by a very small pin hole y¹ made to
allow a little of the combustible charge to pass through, and close to the pin hole
the tube is packed with wire gauze Y, as far as its seat on the outer tube; or it
may be packed at the end hard with wire gauze y as shown in figure 6. Close to
its seat, and near the wire gauze, is drilled a small hole 2¹, about of an inch in
diameter, for igniting the charge. When compression of a combustible charge
takes place, part of it will pass through the wire gauze, and be ignited by an
outside gas burner Z. The inner tube is then covered at its outer end and forced
from its seat, allowing the charge to enter into the flame in the inner tube, through
the of an inch small hole z¹, igniting the charge. A spring returns the inner
tube to its seat. A of an inch travel is sufficient to effect ignition in this
apparatus. The internal diameter of the inner tube X¹ may be about of an inch,
but can be varied without affecting the result. I have found a roll of wire gauze,
having a small hole in its centre, and placed in the middle of the tube, to act as
well as the gauze packing described.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, be it known that
I am aware that loose auxiliary pistons in explosive gas engines have been
employed, but so constructed as to be impracticable in their working, either by
reason of their sliding upon guide rods through their body, and thus not being
capable of separating the air cushion from the combustible charge, or not having
sufficient elasticity of spring or air cushion to prevent shock whilst working.
I therefore declare that what I claim is :-
1st. In a motor operated by the explosion of combustible gases, the employment
of an auxiliary charge or cushion of air confined in a closed portion of the cylinder,
and separated from the explosive charge by an auxiliary piston, made as gas tight
as possible without holes through its body, the additional air or gas charge being
thus compressed like and to the same pressure as the explosive charge, substantially
as and for the purposes described.
2nd. In such a motor the arrangement by which greater expansion is obtained
and the means of varving the expansion of the explosive charge by altering the

page_text: position of the inlet orifice nearer to or farther from the end of the piston stroke,
in combination with an auxiliary piston, substantially as described.
3rd. In such a motor, in which the products of combustion are ejected, the
construction of an ignition device in the form of a closed tube, in which no valve
or other moving part is used, connected to the combustion chamber, in which the
ignition is regulated by the moving of a heating atmospheric burner, nearer to or
farther from the combustion chamber.
4th. In a gas motor the construction of a modified ignition apparatus, substan-
tially as described in reference to Figure 6.
5th. In such a notor the construction of the governor, consisting of a pendulum,
oscillated by the rotation of the engine, so that any increase in the speed of the
engine increases the arc of oscillation of the pendulum, and thereby prevents the
gas valve from being operated to admit gas to the engine, or holds open the exhaust
valve, substantially as described.
6th. The construction of an explosive gas motor with a working and free
auxiliary piston in which the admission or non-admission of an explosive charge
is regulated by a governor controlling the closing of the exhaust valve, substantially
as described in reference to figure 5..
7th. The general construction of the working cylinders, pistons, and inlet
and exhaust ports and valves, substantially as described and illustrated by the
drawings annexed hereto.
..