Improvements in Gas and other Internal Combustion Engines.
Year: 1894

page_text: Date of Application, 31st Jan., 1894
Complete Specification Left, 31st Oct., 1894-Accepted, 31st Jan., 1895
PROVISIONAL SPECIFICATION.
Improvements in Gas and other Internal Combustion Engines.
I, HERBERT FRASER FOSTER Engineer, of 64 Cornwall Road Westbourne
Park, London, in the County of Middlesex do hereby declare the nature of this
invention to be as follows:-
The object of this invention is to improve the construction and action of gas
motor engines in which a combustible mixture of gas and air or petroleum vapour
is employed and ignited within, the engine and used as a source of power;
furthermore another object is to get a higher grade of expansion of the working
gases, to give an impulse every revolution and to relieve the sudden shock or jar
due to the explosion on the working parts, by a special air compression buffer
device placed within the piston thereby ensuring the smoother running of the engine
at high speeds, and also when exhausting to entirely discharge the products of
combustion.
Hitherto, so far as I know, to obtain an impulse every revolution in one engine
it has been necessary to provide either a separate cylinder or similar arrangement
to act as a compressing pump to the working cylinder, the power being given off in
one cylinder only, or as sometimes is the case the crank chamber is enclosed and
used as a reservoir for gas and air the displacement of the piston in its motion acting
as the compressing device. In all methods operating as just stated the difficulty
experienced is in satisfactorly exploding the new charge and discharging the burnt
products of the previous charge in the same or return stroke; indeed, in some cases
the exhaust and admission valves are opened at the same time, an arrangement
having the disadvantage of permitting some of the unburnt gases to escape
unexploded, reducing the richness of the remaining explosible mixture, the
compression, and the economical working of the engine.
In an engine operating according to my invention the power is developed
alternately at each revolution in two cylinders placed one above the other, that is
to say an impulse is first given by the upper cylinder in one revolution and then by
the lower in the next revolution. In order to fulfil the objects of this invention as
aforesaid, I adopt a peculiar cycle of operations to effect the proper distribution of
the working gases by employing a trunk piston common to both cylinders, the lower
cylinder and piston forming an enlargement to the upper part, the annular space
thus formed being made equal in area (or any other suitable proportion) to the top
cylinder this piston being connected to the crank shaft by a connecting rod, and
has within it, the air buffer and compression chamber device before alluded to.
:
I now proceed to describe the cycle of operations and how I obtain an impulse
every revolution. In order to make it more clearly understood it will be
convenient to consider the action of each stroke successively.
First
First. On the (down) stroke. The upper cylinder's charge is
exploded whilst the bottom cylinder is taking in a new
charge.

page_text: Second
revolution.
Emiraty. On the (down) stroke. Ine Tower
пой
exploding, whilst the upper cylinder is taking in its new
charge.
Fourthly. On the (up) stroke. Whilst the lower cylinder is
exhausting the upper cylinder is now compressing its new
charge, and thus the cycle is repeated.
"
It is evident from the above that this particular "cycle consists in a peculiar
combination of two "four cycle operations" adapted to work in conjunction on one
crank, and that an impulse is given at every down stroke of the engine alternating
between the top and bottom cylinders.
The manner in which the valves are actuated is by a lay shaft made to revolve
at half the speed of the crank shaft by suitable gearing, with cams attached thereto
and designed so as to open and close the valve ports at the proper moment in
accordance with the above mentioned cycle. One important object I have had in
view in the construction of my improved form of gas engine is the subduing or
relieving the sudden shock of the explosion on the crank pin and working parts, and
to get a more sustained pressure throughout the working stroke thereby enabling
engines to be run at higher speeds and to be constructed for higher powers than
hitherto. Another object I have had in view in this invention is the complete
exhaustion of the products of combustion an advantage which cannot be over
estimated when using producer or "Dowson gas." One method of carrying out
these objects is to employ an air buffer placed within the piston which is composed
of two plungers elastically connected by a volute spring or the like, free to move
within defined limits, that is to say, they can only be compressed inwards. it must
be understood I do not depend only on the spring to return the motion due to any
compression but merely use it as a flexible coupling, or for the purpose of limiting
their travel, depending more particularly for this purpose on the resilience of the
air lying between the said plungers. According to another method of construction
these plungers can be contained in two separate air chambers within the piston and
can be made to act substantially for the same purpose as above. 1 may incidentally
remark that these improvements may advantageously be applied to existing gas
motor-engines working on the "four cycle principle" it being apparent that only
one air chamber and plunger will be required for the purpose. Now it is obvious
that any shock which would result from the suddeness of the explosion is avoided,
partly by the dispersion of the combustible charge on compressing the plunger, and
partly by the cushioning effect of the air buffer when the explosion occurs, and
owing to the gradual development of heat and expansion of the gases there is little
or no loss of useful effect, in fact, the work expended in compressing the air buffer
is given out again by its expansion as the pressure falls in the cylinder. I also
intend this air buffer device to act as the compression chamber to the respective
cylinders herein before mentioned and since the stroke of the piston is made to
enclose the whole area of the said cylinders, their contents will consequently force
the plungers forward on their compression strokes and thus automatically form the
necessary space for the gases.
Furthermore the additional advantage accruing from this device is the complete
elimination of the products of combustion as it is evident that the plungers will
return to their original positions at the ends of the piston as soon as the pressure is
relieved, which is the case when the exhaust valve is opened, with the result that
the waste gases will be entirely discharged on the upward stroke of the engine.
Another feature of my invention is that since the burnt products get completely
expelled the necessity of first opening the air valve for the purpose of neutralising
the carbonic acid gas is avoided, one valve being only required for the admission of
gas and air instead of two as hitherto. A simple modification of this invention
consists also in the governing valve apparatus, a chamber having ports for gas and
air with a constant relative proportion to each other, and made to cut off earlier or

page_text: later the supply according to the speed, preferably by a suitable form of inertia
governor to be more particularly described in my Complete Specification.
With reference to the air cushioning arrangement before alluded to, it may be
stated that the air chambers are open to the atmosphere by holes conveniently
situated in the cylinder, and which become uncovered by the plungers within the
piston when said piston is at the top of its stroke after exhausting; by this it will be
evident that the compression always commences at atmospheric pressure and is
constant and invariable in its results.
Improvements in Gas and other Internal Combustion Engines.
I, HERBERT FRASER FOSTER, Mechanical Engineer of 64, Cornwall Road,
London, in the County of Middlesex do hereby declare the nature of this inven
tion and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement :-
My invention relates more especially to an improved form of gas or explosive
vapour engine working on the tandem "Otto cycle" principle, and by a combina-
tion of two inner pistons working in accordance with the above mentioned cycle
within the main piston against air cushions. I am able to expel all the burnt
products of combustion and to obtain a higher grade of expansion than has hitherto
been attained, thus tending to materially increase the economy of the engine.
Moreover, by utilising this method of working I am enabled to relieve the sudden
impact of the explosion on the crank pin and considerably reduce the strain on the
working parts.
To ensure the efficient lubrication of the engine I provide a special chamber
placed between the two working cylinders. This chamber is filled with oil and
water under pressure or not as desired, preferably the former; from this the
lubricant is forced through suitably arranged channels to the working parts, as
shewn hereafter in the accompanying drawings.
The combustion chambers are formed within the main piston, not as hitherto in
existing types at the end of the cylinder; the advantage of this arrangement being
that the heat is more evenly distributed superficially, so avoiding extreme expansion
of the adjacent metal parts.
A modification of the gas motor engine embodying the above improvements may
be applied to already existing types working on the simple "Otto cycle" where
one cylinder only is employed.
The cycle of operations is as follows, and as before mentioned is on the four stroke
principle applied to two cylinders working in tandem, that is to say, exploding and
inhaling simultaneously and alternately in the respective cylinders, thereby obtaining
an impulse every revolution; an explosion is first given by the upper cylinder in
one revolution and then by the lower in the next revolution. In order to fulfil the
object of this invention as aforesaid, and to effect the proper distribution of the
working gases, I employ a trunk piston common to both cylinders; the lower
cylinder and piston forming an enlargement to the upper part, the annular space
thus formed being made equal in area, or any other suitable proportion (for the
purpose of adjusting the effect of inertia) to the top cylinder, this piston working
in the two cylinders being connected to the crank shaft by a connecting rod.
now proceed to describe the cycle in detail.
1. On the down stroke the top cylinder's charge is exploded whilst the bottom
cylinder is inhaling a new charge.

page_text: II. On the up stroke whilst the upper cylinder is exhausting the lower cylinder
is compressing its new charge.
III. On the down stroke the lower cylinder is now exploding while the upper
cylinder inhales its new charge.
IV. On the up stroke whilst the lower cylinder is exhausting, the upper cylinder
is now compressing its new charge.
It will be seen that during the four strokes two explosions have been obtained.
To ensure a higher grade of expansion and at the same time to relieve the shock
which would result from the suddenness of the explosion, I employ a free piston
with two heads connected with a piston rod, and working within the main piston,
against two air buffers as aforesaid, in which said cushioning or air chambers part
of the force of the explosion is received, and owing to the gradual development of
heat and expansion of the gases there is little or no loss of useful effect, in fact the
work expended in compressing the inner piston against the air cushion is given out
again by its expansion as the pressure falls in the working cylinders. I also intend
this inner piston device to form, due to its movement, the compression chambers of
the respective cylinders, hereinbefore mentioned, and since the stroke of the main
piston is made to include the whole area of the cylinders, the explosive mixture due
to the out stroke will consequently force the inner piston forward on its compression
or up stroke, and thus automatically form the necessary space for the gases.
Furthermore, the additional advantage accruing from this arrangement is the com-
plete elimination (or nearly so) of the products of combustion, the inner piston
being so arranged, that whilst forming the compression chamber of one cylinder it
expels by its movement the burnt products of the other. It may be noted that the
inner piston moves through the greater portion of its stroke during compression, as
the volumes in the air buffers vary inversely as the square of the pressures, and at
the moment of explosion, the movement of the said inuer piston, due to this fact,
will obviously be comparatively small.
.
The manner in which the valves are actuated in the engine is by a lay shaft
revolving at half speed with cams attached thereto and operating in the usual
manner.
In order that my said invention may be properly understood, I hereunto append
one sheet of explanatory drawing to be hereinafter referred to.
DESCRIPTION OF DRAWINGS.
Fig. 1, of the annexed drawings represents the gas motor engine with its essential
parts in section.
Similar lettering signifying like parts in the various figures.
I place two cylinders C and C, tandemwise having a trunk piston D common to
both cylinders, the bottom cylinder and piston forming an enlargement to the upper
part, the annular space E thus formed being made equal in area (or some other
suitable proportion) to the top cylinder C. This main piston operating in the two
cylinders being connected to the crank G by a connecting rod. Within the said
main piston D the inner pistons d and d₁ hereinbefore referred to, work so as to
form alternately the combustion chambers I. I, for the two cylinders, and also forming
at the same time two cushioning chambers band b₁ in which the impact of the
explosion is received and in part absorbed, to be given out again in the down stroke.
In the upper part of the shell of the lower cylinder is placed the lubricating
chamber L, which contains a mixture of oil and water, and which is in direct
contact with the main piston D, and with the inner piston rod K, through ports
suitably provided in the main working piston. The manner in which I achieve
this will be clearly shewn by referring to Fig. 2 which represents the section of the
engine through line A. B, Fig. 1. The lubricating chamber L contains the stuffing
box H, which seals the lower cylinder, and through which the oil and water
permeates, entirely surrounding the main working piston. The whole of the afore-
said lubricating chamber may be supplied with air under pressure, so as to ensure

page_text: the thorough distribution of the lubricant. It will be seen from the section of the
piston in Fig. 2, that it is divided into four chambers 11, ff, two of which form
through ports a means of lubrication of the inner piston rod K; the other two
chambers, ff, are provided for air inlets to the buffers and b.
With reference to Fig. 1, the action of the engine is as follows. We will assume
that the upper cylinder C, has taken in its explosive mixture at atmospheric
pressure, and that the bottom cylinder C, has exploded its charge. On the up
stroke the contents of the upper cylinder will compress into the space I forming
the combustion chamber, and will force the inner piston d into such a position that
the pressure in C is equal to the pressure in the air buffer b; at the same time the
lower piston, d, will force out the burnt products of the previous explosion in the
cylinder C₁ through the ports p, p, r, P. The top cylinder will now ignite its
charge, storing up the force of the explosion in b and expanding b, below atmosphere,
on the down stroke of the main piston, a new charge is inhaled in the cylinder C₁.
On the ensuing up stroke, the charge in the annulas E. E, is compressed into
the lower combustion chamber I, through the ports p, p, p, p. forcing the inner
piston up, thus expelling the products of combustion, from the top cylinder C,
in a similar manner to that before described in C, complete elimination taking
place at the moment of explosion of the lower charge, the air chamber b₁ being
compressed in its turn as in bin the previous stroke.
Having now particularly described the nature of my said invention and in what
manner the same is to be performed, I declare that what I claim is:
1. The combination and construction of gas engines substantially as hereinbefore
described.
2. The combination of a free inner piston or pistons, rigidly or flexibly connected,
working within the main piston in conjunction with the "Otto cycle" for the
purpose of automatically forming the combustion chambers and expelling the burnt
products of the working cylinder or cylinders.
3. The use of the air cushioning arrangement in conjunction with the inner
piston substantially as and for the purpose hereinbefore described.
4. The use of the combustion chamber within the main piston so as to distribute
the heat superficially over the working stroke.
5. The general arrangement and construction of the engine in combination with
the lubricating chamber substantially as and for the purpose hereinbefore described,
and forming the subject of this invention.
Dated 31st October 1894.
HERBERT F. FOSTER.