IMPROVE- MENTS IN GAS-ENGINES
Year: 1885

page_text: I, WILLIAM WALLER POPE, of Gotha Iron Works, Slough, in the county of
Bucks, Engineer, do hereby declare the nature of my invention for "IMPROVE-
MENTS IN GAS-ENGINES" 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 to gas-engines or motors of that class in which, when
working properly, an impulse is imparted to the piston at every out-stroke thereof,
and it comprises the improvements hereinafter described.
In the accompanying drawings,
Figure 1 is a side elevation, partly in section, of an engine or motor constructed
according to my invention.
Figure 2 is a central vertical longitudinal section of the same.
Figure 3 is a view, partly in section, of the cylinder-end of the said engine.
Figure 4 is a transverse section on the line x, x, Figure 2, and
Figure 5 is a horizontal section on the line x, x, Figure 2.
Similar letters indicate corresponding parts throughout the drawings.
A is the bed or frame on which the cylinder a, guide-bars b, crauk-shaft c, and
other parts of the engine are mounted.
d indicates a chamber attached to the rear end of the cylinder a, in which
chamber the explosive mixture of air and gas is compressed prior to ignition. For
effecting the ignition I may use any suitable apparatus. I have shewn at e a device
for this purpose which is described in the specification of Letters Patent dated
April 20th, A.D. 1881, Nº 1723.
The piston f, as will be seen by reference to Figure 2, is made hollow and of a
considerable length in proportion to its diameter. The said piston is provided with a
set of metal rings f1 at its rear end and another set of such rings f³ at its forward
end; and between these two sets of rings there is an annular space fª between the
piston and cylinder; 9, 9 are exhaust ports or apertures. h is a valve which
admits gas and air into the tube or passage i; this tube communicates with the
forward end of the cylinder a. k is a valve between the said tube i and the
ignition or explosion chamber d.
The crank is driven by the piston-rod f' through the medium of the connecting
rod f in the ordinary manner. An excentric is fixed on the crank-shaft in such
a position that its throw coincides with that of the crank c¹. From this excentric
a rod m extends and is pin-jointed to the sliding rod or bar n, which is supported,
with a capability of free endwise movement, in bearings at n¹, n¹. By reason of

page_text: the above specified relative positions of the crank and excentric, it is obvious that
the movements of this sliding bar will correspond in direction with those of the
piston.
Through the medium of this sliding bar n, the excentric operates the cut-off
valve o (which controls the admission of gas to the engine) by means of the
mechanism shewn in Figures 1 and 3. This mechanism is as follows:-p is a rod
connected to the stem of the said cut-off valve; q is a lever, which is pivotted at q*
to the bracket a¹ on the cylinder, and one arm q' of which is arranged to form an
inclined plane relatively to the movement of the sliding bar n; n² is a projection
on the said bar arranged to move in, and out of, contact with the said arm q¹ and
thus alternately depress and release the same as hereinafter set forth; t is a lever
which is pivotted at t* to the bracket a¹ and whose extremity is a catch or hook
arranged to engage with the lever q. t¹ is a lever-arm attached to the catch lever t
and arranged to form an inclined plane relatively to the movement of the bar n.
u is a block formed with a projection or tappet arranged to move into, and out of,
contact with the inclined plane or arm t¹, as the bar n moves to and fro, and thus
raise the said arm and permit it to fall again.
It is very desirable to be able to control the action of the above described
mechanism so as to vary or alter the time of action of the cut-off valve. For this
purpose, I arrange the tappet-block u between jaws n³ formed on the end of the
bar n, and I fit the said block upon a screw-rod v which is connected with the
hand-wheel in such a manner that the said screw-rod can slide freely through
the boss of the hand-wheel, but is compelled to turn therewith. And, by turning
the said hand-wheel and screw, the block u can be adjusted endwise relatively to the
inclined planet so that it will act thereon sooner or later relatively to the stroke
of the piston, as desired.
I provide for automatically controlling the working of the engine by means of a
governor of suitable construction. The governor shewn in the drawings is of the
ordinary kind, but I do not limit myself to the use of this particular kind or form
of such apparatus.
w is a bell-crank-lever, which is operated by the governor in the usual manner.
One arm of this lever has its extremity forked and inserted between collars w* on
the rod wwhich is fitted, with a capability of endwise movement, in the
bearings w² and m¹. The end of the rod w¹ is arranged to be moved by the
governor towards and away from the catch levert and to push the said lever
out of engagement with the lever q when the engine exceeds the desired velocity.
The cut-off valve o is arranged to communicate with an annular space or
channel y surrounding the inlet valve h; and small holes y¹ are formed through
the metal below the valve-seat for the passage of the gas from the said annular
space to the central space or passage of the valve. Below this valve is an air-
admission valve consisting preferably of a flap of india-rubber arranged over a
series of small apertures at x². This valve is simply used to silence or prevent the
noise which would otherwise be produced; it may, if desired, be dispensed with.
The operation of the above-described engine is as follows, that is to say:-
Assuming the parts to be in the positions shewn in the drawing and the engine to
have been started, the excentric 7, during the forward or out-stroke of the piston
moves the bar n forward. The projection n², towards the end of this forward
movement or stroke, comes in contact with the inclined plane q' and depresses the
same. The rod p, which is attached to the lever q, is thereby raised.
At the same
time, the block u is moved out of contact with the lever-arm t¹, thus permitting the
catch to drop beneath the lever q and retain the same in its raised position.
Therefore, when the crank reaches its forward "dead centre," the gas-valve will be
wide open.
The return or inward stroke of the piston f tends to create a vacuum in the
forward part of the cylinder a and in the pipe i, so that the air-valve x³ and
valve / rise and admit air, while gas enters through the small holes y', and, mixing
with the air passing through the valve h, forms a combustible mixture, which is

page_text: drawn into the tube or passage i. When the piston has performed three-fourths of
its in-stroke or any other portion thereof according to the position of the block or
tappet u on the tar n, the said block or tappet comes in contact with the lever-
arm t' attached to the catch lever t, thereby disengaging the latter from the end of
the lever q and releasing the gas cut-off valve o, which immediately closes ;
consequently, during the remainder of the in-stroke, air only is drawn into the
tube or passage i. The piston, in its subsequent forward or out-stroke, compresses
the charge contained in the forward part of the cylinder and in the tube i, and,
when the pressure in the chamber d and rear part of the cylinder is diminished by
reason of the opening of the exhaust as hereinafter described, forces first the air
in the rear part of this tube and then the combustible mixture in the forward part
thereof through the valve k into the said chamber and rear part of the cylinder.
The charge thus forced therein is compressed during the next inward stroke of the
piston and is ignited at, 'or about, the moment the crank is passing its rear or
"home" centre, another charge being drawn into the tube i in this inward stroke;
the expansion of the exploded gases drives the piston f forward until the exhaust
ports are uncovered; the products of the combustion of the gases can then escape
through the said ports into the atmosphere. During this forward or outward
movement of the piston, the charge drawn into the tube i as above described, is
compressed. When the exhaust ports g are opened as above described, the valve k,
which has till this moment been kept on its seat by the pressure of the ignited
charge above it, is lifted by the pressure beneath it, and the fresh charge enters the
chamber d, driving in front of it and out through the exhaust ports g most of the
products of combustion which have not before escaped. By the time the piston
has reached the end of its out-stroke, the whole of the said fresh charge will have
entered the chamber & and the rear part of the cylinder, while any of the products
of combustion of the previous charge still remaining in the cylinder will lie in
front of the fresh charge. The valve know closes, and the piston returns,
expelling more of the products of combustion through the exhaust ports g until it
passes over, and closes, the said ports; the further return of the piston then
compresses the combustible charge in the chamber d, which charge is ignited and
exploded as hereinbefore described.
It will, therefore, be seen that the piston, during each in-stroke, compresses the
charge in the chamber d and rear part of the cylinder, and draws a fresh charge
into the tube i; and, during each out-stroke, the said piston compresses the charge
in the tube i and, when the pressure above the valve is relieved or diminished as
above described, forces the said charge into the rear part of the cylinder through
the said valve. Therefore a combustible charge is drawn in, compressed, and
forced into the ignition chamber and the piston receives an impulse at every
outward or forward stroke, without the aid of any auxiliary cylinder or pump.
I prefer that the entrance of the gas shall be so regulated or controlled that a
charge of gas and air will be admitted into the tube i during a portion of the
inward stroke of the piston, and the gas will be then cut off, and air only taken
in for the remainder of such stroke. The object of thus controlling the supply or
admission of the gas is that a quantity of unmixed air shall occupy the part of
the tube in the immediate vicinity of the valve k and protect the combustible
charge in front of the unmixed air from ignition by any flame that might pass
down through the said valve, when the charge previously compressed behind the
piston, is ignited.
The passage i is, by preference, trapped or bent as shewn to avoid the possible
premature rising of the combustible mixture into the space beneath the valve k.
I prefer, moreover, that the cubic contents of the part between the bend and the
valve should be equal, or nearly equal, to one fourth of the capacity of the space
traversed by the piston in one stroke, so that the unmixed air drawn in at each
in-stroke of the piston will fill the part of the tube at the rear of the bend, and
also the greater portion of the bend.

page_text: By means of the hand-wheel v¹, the tappet u can be adjusted to accelerate or
retard the time of release of the cut-off valve relatively to the piston's stroke, as
.desired.
I usually so arrange the block or tappet u that it cannot be adjusted to cut off
the supply of gas later than at about three-fourths of the inward stroke. I thus
ensure the admission into the tube i of sufficient pure air to prevent the premature
rising of the combustible charge in the said tube into the space beneath the
valve k.
Excessive speed of the engine at at any time will be checked by the governor,
which will then act to depress the short arm of the bell-crank w. The rod w is
thus moved endwise and caused to act upon the catch t and push the same out of
engagement with the lever q, so that the gas cut-off valve will remain closed except
when the projection n³ acts upon the incline on the arm q¹. But the said catch can
obviously again engage with and support the lever g when the rod w¹ is drawn
back by the action of the governor.
I have found, when employing a piston of the ordinary length or depth (with say
three rings), that, if such rings are not very strong and accurately fitted to the
cylinder and generally in good condition, there is danger that, on the ignition of
the compressed charge in the chamber d and rear part of the cylinder, the flame
will pass them and reach and ignite the combustible mixture in front of the piston;
I, therefore, use a long piston with two sets of rings and with the annular space
between the two ends of the piston as above described. At the commencement,
and during a considerable portion, of the out-stroke, this annular space is in
communication with the exhaust ports g, so that, if the flame should pass the
rings f¹, it will enter the annular space f³ which is open to the exhaust. It,
therefore, cannot communicate with the combustible mixture contained in the space
in front of the piston.
The tube or passage i has the same, or nearly the same, cubical capacity as the
space traversed by the piston in one stroke; it is also desirable that this tube
should be made of as small a diameter as practicable consistent with such capacity,
so that there will be only a small area of surface in contact between the pure air
and the combustible mixture in the said tube. The liability of the unmixed air
and the combustible mixture to combine will thus be prevented or considerably
diminished, and the unmixed air will be forced through the valve k in front of the
combustible charge. The said unmixed air is, therefore, behind the combustible
charge in the tube i, but in front of the same in the cylinder.
The provision for adjusting the cut-off so that its action may be varied at will
(while the engine is running), to cut off the gas-supply at any desirable point of
the stroke, within suitable limits, and admit only pure or unmixed air for the
remainder of the stroke, permits very economical results to be obtained, as the
combustible charges always contain the same proportions of gas and air, whether
the cut-off takes place early or late, that is to say, the adjustment of the cut-off
mechanism is not intended to cause any variation in the explosive force of the
combustible mixture, but simply to vary the quantity of such mixture admitted
into the ignition chamber. I thus obtain a high initial pressure in all cases.
Although it is obvious that the combustible charge is liable to be slightly diluted
by admixture with air in the tube i or in the rear part of the cylinder, yet I have
found, in practice, that the explosive force of the said charge is not affected, or is
very slightly affected, thereby even when the cut-off of the gas-supply takes place
very early in the stroke of the piston.
The tappet u on the bar n can be adjusted to permit a full supply of the com-
bustible mixture when necessary (say for three-fourths of the stroke), and altered.
to reduce the supply thereof when the engine is not required to work up to its full
power, so that considerable economy can be effected in the working of the engine.
The mechanism for opening the gas cut-off valve is so arranged that the said
valve cannot close until say a quarter of the inward stroke has been completed,

page_text: therefore, although the catch t may be thrown out of engagement with the lever q
by the action of the governor, the valve cannot close too early in the stroke, and a
small combustible charge is always admitted into the tube i, which charge prevents
the admission of the following unmixed air into the forward end of the cylinder,
and the dilution of the combustible mixture therein below the firing point. This
provision is the more important as the action of the governor may sometimes keep
the said catch out of engagement with the lever during two or more consecutive
strokes of the piston.
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
First. A gas engine or motor provided with adjustable cut-off mechanism so
arranged and operating in combination with the other parts that every charge
of combustible mixture admitted into the ignition chamber will contain the same
proportions of gas and air, whether the cut-off takes place early or late, as above
specified.
Second. The employment of the tube or passage i in combination with the
cylinder, and with the valves h, k, whereby, without any auxiliary cylinder or
pump, a combustible charge will be drawn in, compressed and forced into the
ignition chamber so that the piston will receive an impulse at every forward or
outward stroke, as above specified.
Third. The piston provided with two sets of rings and so formed or constructed
that, when it is fitted in the cylinder, there will be an intermediate annular space
between the two sets of rings, for the purpose specified.
Fourth. The improvements relating to the exhaust port or ports arranged as
above set forth relatively to the stroke or movement of a piston which is con-
structed with two sets of rings and an intermediate annular space, for the purposes
specified.
Fifth. The improvements relating to the tube or passage communicating with
the cylinder in front of the piston and arranged in connection with the valves h
and whereby I provide for the admission and retension in the said tube of a
charge of pure or unmixed air at the back of, and separate from, the explosive
charge, for the purposes specified.
Sixth. The apparatus for raising and releasing the gas cut-off valve, consisting
of the parts shewn in Figures 1 and 3 arranged in combination with the excentric
and operated thereby at each stroke of the engine, as specified.
Seventh. The devices for effecting by hand the adjustment of the block or tappet
which acts on the inclined plane to disengage the catch t from the lever q which
holds up the cut-off valve, substantially as set forth.
Eighth. The combination, with the said catch, of the rod controlled by the
governor and operating as, and for the purpose, specified.
Ninth. The combination of the cut-off valve with the annular cavity y
surrounding the gas and air inlet valve, substantially as, and for the purpose,
specified.
Tenth. The engine consisting of the novel parts or devices herein described
constructed and combined with the other parts shewn in the drawings, or substan-
tially similar parts, and operating as, and for the purposes, specified.
11
HOLL
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