IMPROVEMENTS IN GAS ENGINES
Year: 1881

page_text: LETTERS PATENT to Thomas Holden Lucas, of Birmingham, in the County of
Warwick, Foreman Pattern Maker, for an Invention of "IMPROVEMENTS IN
GAS ENGINES."
PROVISIONAL SPECIFICATION left by the said Thomas Holden Lucas at
the Office of the Commissioners of Patents on the 13th August 1881.
THOMAS HOLDEN LUCAS, of Birmingham, in the County of Warwick, Foreman
Pattern Maker. "IMPROVEMENTS IN GAS ENGINES."
My Invention consists of the construction and arrangement of the parts of gas
engines herein after described, whereby simplicity of construction and efficiency of
action are secured.
In the cylinder of the engine two pistons are situated, one of the ordinary kind,
and which I will call the piston, and the other which I will call the supplementary
piston, constituting as it were a moveable bottom to the cylinder.
I will first describe the motions of the said pistons and afterwards the mechanism
by which the motion of the supplementary piston is effected.
The piston being at its lowest position in the cylinder and the supplementary
piston being nearly at its lowest position, there is enclosed between them the
compressed gaseous mixture to be ignited. After ignition of the said gaseous
mixture the piston is caused by the expansion of the ignited gaseous mixture to
rise and communicate motion by the ordinary appliances to the principal shaft of
the engine. The supplementary piston next rises, diminishing the space between it
and the piston, and thus expelling the exhausted gas. The supplementary piston
next descends, the piston following at a slower rate. The space between the two is
thus increased and gas and air are drawn into the cylinder for a second ignition.
After the required gaseous mixture has been drawn into the cylinder the motion of
the supplementary piston slackens, while the piston continuing to advance the
gaseous mixture is compressed and afterwards ignited. The motions described are
repeated at each rotation of the principal shaft of the engine.
.
The motion of the supplementary piston is effected as follows:-The principal
shaft of the engine is made to rotate by the ascent of the piston in the ordinary
way, the motion being rendered nearly uniform by a fly wheel. Geared to the

page_text: principal shaft is a vertical shaft parallel to the axis of the cylinder. The gearing
of these shafts consists of two eccentric pinions fixed respectively on the said
shafts, the said eccentric pinions being so engaged with one another that that
portion of the one which is of shortest radius is engaged with that portion of the
other which is of longest radius. The uniform rotation of the principal shaft
consequently produces a rotation of variable rate in the vertical shaft. The lower
end of the vertical shaft is geared to a horizontal cranked shaft under the cylinder
and parallel to the principal shaft. The supplementary piston is connected by a
connecting rod to the crank of the said shaft. The gearing by which the motion
of the vertical shaft is transmitted to the horizontal cranked shaft described
consists of two eccentric pinions engaged together in the way herein before
described with respect to the gearing of the vertical shaft with the principal shaft,
the pinions being so set as to increase the irregularity of the motion produced
by the first described eccentric pinions.
The teeth of the several eccentric pinions are inclined to their respective shafts
at an angle of forty five degrees, but I do not limit myself to pinions of this kind
as eccentric bevil pinions having.teeth of the ordinary kind or other gearing may
be employed.
The parts of the gas engine I have not described are of the ordinary kind and
constitute no part of my Invention.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Thomas Holden Lucas in the Great Seal Patent Office on the
2nd February 1882.
THOMAS HOLDEN LUCAS, of Birmingham, in the County of Warwick, Foreman
Pattern Maker. IMPROVEMENTS IN GAS ENGINES."
:
My Invention consists of the construction and arrangement of the parts of gas
engines hereinafter described, whereby simplicity of construction and efficiency of
action are secured.
In the cylinder of the engine two pistons are situated, one of the ordinary kind,
and which I will call the piston, and the other which I will call the supplementary
piston, constituting as it were a moveable bottom to the cylinder.
I will first describe the motions of the said pistons and afterwards the mechanism
by which the motion of the supplementary piston is effected.
The piston being at its lowest position in the cylinder and the supplementary
piston being nearly at its lowest position, there is enclosed between them the
compressed gaseous mixture to be ignited. After ignition of the said gaseous
mixture the piston is caused by the expansion of the ignited gaseous mixture to
rise and communicate motion by the ordinary appliances to the principal shaft of
the engine.
The supplementary piston next rises, diminishing the space between it and the
piston, and thus expelling the exhausted gas. The supplementary piston next
descends, the piston following at a slower rate. The space between the two is
thus increased, and gas and air are drawn into the cylinder for a second ignition.
After the required gaseous mixture has been drawn into the cylinder the motion
of the supplementary piston slackens, while the piston continuing to advance the
gaseous mixture is compressed and afterwards ignited. The motions described are
repeated at each rotation of the principal shaft of the engine.
The motion of the supplementary piston is effected as follows:-The principal
shaft of the engine is made to rotate by the ascent of the piston in the ordinary
way, the motion being rendered nearly uniform by a flywheel. Geared to the
principal shaft is a vertical shaft parallel to the axis of the cylinder. The gearing
of these shafts consists of two eccentric pinions fixed respectively on the said
shafts, the said eccentric pinions being so engaged with one another that that
portion of the one which is of shortest radius is engaged with that portion of the
other which is of longest radius. The uniform rotation of the principal shaft
consequently produces a rotation of variable rate in the vertical shaft. The lower
end of the vertical shaft is geared to a horizontal crank shaft under the cylinder
and parallel to the principal shaft. The supplementary piston is connected by a
connecting rod to the crank of the said shaft. The gearing by which the motion
of the vertical shaft is transmitted to the horizontal cranked shaft described
consists of two eccentric pinions engaged together in the way hereinbefore
described with respect to the gearing of the vertical shaft with the principal shaft,
the pinions being so set as to increase the irregularity of the motion produced by
the first described eccentric pinions.
The teeth of the several eccentric pinions are inclined to their respective shafts
at an angle of forty five degrees, but I do not limit myself to pinions of this kind,
as eccentric bevel pinions having teeth of the ordinary kind or other gearing may
be employed.
The parts of the gas engine I have not described are of the ordinary kind and
constitute no part of my Invention.

page_text: I will now proceed to describe, with reference to the accompanying Drawings,
the manner in which my Invention is to be performed.
Figure 1 represents in vertical section, and Figure 2 in side elevation, a gas
engine containing my improvements. The same letters of reference indicato the
same parts in both Figures.
a is the cylinder of the gas engine supported upon the hollow base or foot b;
c is the crank or principal shaft to be driven by the piston e, and d is the flywheel
on the said shaft c for equalizing its motion. The ordinary or motor piston e
works in the upper half of the cylinder a; f is the piston rod of the piston e, the
said piston rod being connected to the crank of the crank shaft c; g is the
supplementary piston working in the lower half of the cylinder a and constituting
as it were a moveable bottom to the cylinder; h is the piston rod of the
supplementary piston, the said rod h being connected to the crank shaft i working
in the foot or hollow base b of the engine. The motion of the said supplementary
piston g in the cylinder a is irregular or variable and is effected by the following
mechanism-Geared to the principal shaft c, which has a nearly uniform rotatory
motion, is a vertical shaft k parallel to the axis of the cylinder. The gearing of
the two shafts c and k consists of two eccentric pinions marked respectively l
and m, the pinion 7 being fixed on the principal shaft c and the other pinion mon
the top of the vertical shaft k. These eccentric pinions l, m, have inclined teeth
resembling the teeth of a worm wheel, and the said pinions are so set or arranged
on their respective shafts that that portion of one of them which is of shortest
radius is engaged with that part of the other pinion which is of longest radius, as
will be understood by an examination of Figure 2, where it will be seen that the
part of shortest radius of the pinion is represented engaged with the part of
longest radius of the pinion m on the vertical shaft k. By thus gearing the vertical
shaft k to the driving shaft c the uniform motion of the latter shaft produces a
rotation of a variable rate in the former shaf The lower end of the vertical
shaft is geared to the horizontal crank shai, by which the supplementary
piston g is worked by two eccentric pinions n, p, sì. lar to those already described
and marked 1, m; but it will be seen by reference to Figure 2 that the said
pinions n, p, are differently arranged or set with respect to each other from the
pinions m, l, that is to say, while that part of the pinion m of largest radius of
the upper pair gears with the part of shortest radius of the other pinion 7 it will
be seen that the part of the pinion p of greatest radius of the lower pair gears
with the part of smallest radius of the other pinion n.
By thus arranging or setting the lower pair of pinions the irregularity of the
rotary motion produced in the shaft k by the first or upper pair of pinions l, m, is
increased.
The action of the parts constituting my Invention is as follows:-When the
piston e is at its lowest position in the cylinder a and the supplementary piston g
is at its lowest position, as represented in Figure 1, there is enclosed between the
said piston e,g, the compressed gaseous mixture to be ignited. On the ignition of
the said gaseous mixture the piston e is forced upwards and communicates through
its piston rod f motion to the crank shaft c. The supplementary piston g next
rises, thereby diminishing the space between it and the piston e and expelling the
exhausted gas from the cylinder a. The supplementary piston g next descends at
a rapid rate, the piston e following it at a slower rate. The space between the two
pistons is thus increased and the mixture of gas and air is drawn into the cylinder
for a second ignition; after the required gaseous mixture has been drawn into the
cylinder a the motion of the supplementary piston slackens, while the piston e
continuing to advance the gaseous mixture is compressed between the two
pistons e, g, which now occupy the positions represented in Figure 1, and the
compressed gaseous mixture is ready to be ignited. The irregular motions
described of the supplementary piston g are effected through the action of the
eccentric pinions l, m, shaft k, and eccentric pinions n, p, upon the shaft i, as
herein before explained. Thus it will be understood that the spent or exhaust

page_text: gases after the explosion are expelled from and the fresh charge of gaseous
mixture drawn into the cylinder a by the motions of the supplementary piston g
when the motor piston é is at or near the end of its outer stroke, and that the
compression of the gaseous charge is effected by the motor piston e during its
inward or return stroke in conjunction with the supplementary pistons g, the
motions described and the ignition of the charge being effected at each rotation of
the principal shaft c of the engine.
в
My improvements may be combined with any of the well known arrangements
for working the valves for admitting the gaseous mixture for allowing of the exit
of the exploded gases, and for igniting the charge.
In Figures 1 and 2 of the Drawings, the opening and closing of the slide valve q
by which the gaseous mixture is admitted into the cylinder at the proper time is
worked from the vertical shaft k by the lever q³ (see Figure 2) engaging in a box
cam q³ on the shaft k, and the valve s which opens and closes the exit passage r
for the exploded gases is worked by a similar lever 8 taking its motion from the
box cam & on the said vertical shaft k.
Instead of giving the irregular or variable motions described to the supplementary
piston ġ by means of eccentric gearing worked from the driving or principal shaft
of the engine, the said irregular or variable motion of the supplementary piston
may be effected by means of the gearing or arrangement of parts shown in the
gas engine, represented in vertical section in Figure 3, and side elevation in
Figure 4.
In this arrangement I make in the face of the flywheel on the driving shaft c
of the engine, a cam groove t, t, having the configuration best seen in side elevation
Figure 4. In the said cam groove a roller carried by the stud works; this
stud v is connected to the vertical slide w, and by the motion of the flywheel u a
variable motion is communicated to the said slide w. While the roller on the
stud v is working in the concentric part t of tho cam groove in the flywheel, the
slide w is stationary, but while the said roller is working in the other parts t³, t².
of the said cam groove, an irregular rising and falling motion is given to the said
slide. The motions of the slide ware transmitted to the supplementary piston g
by the mechanism represented in Figure 3; that is to say, the bottom of the
slide w is connected by the link w³ to the lever a, turning on the centre ², the free
end of the lever a being connected by the rod y to the supplementary piston g.
In this arrangement the slide valve for admitting the mixture of gas and air to
the cylinder a, and for opening and closing the exit passage for the exploded or
spent gases are worked by eccentrics and eccentric rods on the principal driving
shaft.
Although I have represented the best means with which I am acquainted for
giving the irregular or variable motions to the supplementary piston for effecting
the objects described, yet I do not limit myself to those arrangements, as other
equivalent arrangements for giving the motions to the supplementary piston may
be employed, and the supplementary piston having the movements described may
be used with all kinds of gas engines, whether arranged vertically, horizontally, or
otherwise to which it is applicable, and whether single or double acting. In
double acting gas engines the ignition of the gaseous mixture is effected at each
end of the stroke of the principal or motor piston instead of at each revolution of
the flywheel, as in the case of single acting gas engines herein described and
illustrated in the accompanying Drawings.
Having now described the nature of my Invention and the manner in which the
same is to be performed, I wish it to be understood that I claim as my Invention
of "Improvements in Gas Engines," the combination with the ordinary or motor
piston of the gas engine of a supplementary piston constituting as it were &
moveable bottom or end to the cylinder, the said supplementary piston having a
variable or irregular motion given to it for the purposes of expelling the exploded
gases from and for drawing into the cylinder the fresh charge of the gaseous
mixture, and in conjunction with the principal or motor piston for compressing the

page_text: said gaseous mixture, the drawing in, compressing and ignition of the gaseous
mixture, and the expulsion of the spent gases being effected in one cylinder, and
at each rotation of the principal shaft of the engine, or in double acting engines at
each end of the stroke of the principal or motor piston, substantially as described
and illustrated.
In witness whereof, I, the said Thomas Holden Lucas, have hereunto set
my hand and seal, this First day of February, in the year of our Lord
One thousand eight hundred and eighty two.
Witness,
RICHARD SKERRETT,
37, Temple Street,
Birmingham.
THOMAS HOLDEN LUCAS. (LS.)