IMPROVEMENTS IN AND CONNECTED WITH GAS ENGINES
Year: 1882

page_text: LETTERS PATENT to James Arthur Drake and Richard Muirhead both of
Maidstone in the County of Kent Mechanical Engineers for an invention
of IMPROVEMENTS IN AND CONNECTED WITH GAS ENGINES
PROVISIONAL SPECIFICATION left by the said James Arthur Drake and
Richard Muirhead at the Office of the Commissioners of Patents on the
11th April 1882.
JAMES ARTHUR DRAKE and RICHARD MUIRHEAD both of Maidstone in the
County of Kent Mechanical Engineers 'IMPROVEMENTS IN AND CONNECTED WITH
GAS ENGINES
رو
66
Our Invention relates to motor engines of the kind in which a piston moving in
a cylinder and coupled by a connecting rod direct on to a crank as in a steam
engine, is worked by the expansive force resulting from the rapid consumption of
an intimate mixture of inflammable gas and atmospheric air introduced into the
cylinder and compressed therein.
In addition to the usual or motor piston which actuates the crank, we use, in
the same cylinder, a second, or auxiliary piston whose function is to expel the
residual gases and draw in a fresh charge of combustible mixture simultaneously,
and at every revolution of the crank shaft.
The mode of operation is as follows:―
Supposing the cylinder to contain a charge of inflammable mixture in a com-
pressed state, ignition takes place and the expansion of the gases drives the motor
piston to the end of its outstroke. When it is within a short distance of the end
of its outstroke, the piston passes some slots in the walls of the cylinder which
communicates with the exhaust pipe
Having arrived at this point and the pressure being reduced to that of the
atmosphere the second, or auxiliary piston, which until now has remained nearly
stationary, at or near the bottom of the cylinder, begins to move forward, slowly
at first but with a continually accelerated velocity, pushing before it the residual
gases, and expelling them, from the space between the two pistons through the
ID 77

page_text: above mentioned slots. At the same time it draws in a fresh charge of combustible
mixture behind it. The moment the auxiliary piston begins to return, the act of
reversing its motion causes a valve in it to open, towards the motor piston allowing
the mixture to flow through it freely thus transferring the charge from one side
of the auxiliary piston to the other.
The motor piston is at the same time making its instroke and compressing the
charge, after which it is fired completing the cycle of operation which are repeated
at every revolution of the crank shaft. It is to be clearly understood that the
pressure due to compression and expansion of the gases is not exerted between
the two pistons but between the motor piston and the solid bottom or end of the
cylinder. There is no pressure exerted on the auxiliary piston,-its valve being
open during the period of compression and the burning of the charge it is in a
state equilibrium The variable notion of the auxiliary piston may be produced
by cam on the crank shaft or by any known kind of mechanism but we prefer
using a pair of eccentric or elliptical spur wheels of the same size the point of
greatest eccentricity of one being made to engage with the point of least eccen-
tricity of the other and vice versu one being keyed on the crank shaft and the
other on a short countershaft placed parallel with it. The connection with the
auxiliary piston is made by any convenient arrangement of coupling rods and
levers, according to the construction of the engine horizontal or vertical-the
auxiliary piston being attached to a piston rod working through a gland and
stuffing box in the end of the cylinder
The slide valve for regulating the admission of the charge and igniting the same
is situated on the side of the cylinder and is worked by a small crank, eccentric,
or cam, placed either on the crank. shaft or countershaft as inay be most convenient
Hitherto, slide valves of this description have been faced on both sides to enable
them to work between two other faces, i.c. between the face of the cylinder and
the face of a cover held up constantly against the valve by bolts and nuts provided
with springs, clips, or other contrivances having sufficient strength to resist the
maximum internal pressure. Slides so constructed require a large amount of power
to work them which in engines of small size represents a very large percentage of
the gross indicated power, besides which the friction being constant the wear and
tear is considerable necessitating frequent refacing. To obviate these defects we
dispense with the outer face of the slide valve and the " cover" altogether and
in place of the "cover" substitute a bridge piece or crossbar between which
and the back of the valve we interpose a toothed rocking pin or "sector
"
The arc of the sector is placed against the back of the slide valve and the centre
(or apex) is supported by the middle of the cross bar.
By this means the reciprocating motion of the slide is imparted to the sector
and rolling substituted for sliding friction.
In order to relieve the valve of all unnecessary friction when there is little or
no pressure in the cylinder the arc of the sector is made slightly elliptical or in
other words the radius of one end of the are is greater than that of the other,
consequently as the sector rolls to and fro with the motion of the slide a slightly
reciprocating movement is imparted to the crossbar or bridge piece against which
the axis of the sector bears. Crossbar is held up by springs compressed and
released as the slide reciprocates that movement being so timed that the greatest
compression of the springs occurs at the time when the charge is ignited and as
when the pressure in the cylinder decreases the motion of the slide is reversed,
the pressure of the springs against the back of the valve and consequently of the
valve against the cylinder face is also diminished.
Thus during the time when there is little or no pressure in the cylinder the
slide valve is worked with very little friction and excessive wear and tear is
prevented.
Instead of making the are of the sector elliptical (or excentric) the same result
may be attained by making the arc circular and concentric and the back of the
slide on which it rolls in the form of an inclined plane the inclination of which

page_text: can be graduated to compress the springs in exact accordance with the varying
resistance they are required to exert to counteract the pressure in the cylinder.
By adding another crossbar with a third spring or rigid, stop to come into
operation at the moment when the greatest resistance is required the two other
springs may be made correspondingly lighter and the constant pressure by which
the slide is held up to the cylinder still further reduced.
The ignition of the charge is effected by an intermediate flame lighted by
a standing jet carried to the cylinder port in a cavity of the slide valve in the
usual way.
The admission and cut off of the gas are effected by an ordinary hinged or flap
valve which covers the orifices of both the air and gas inlets. Gas is by preference
admitted by a row of holes or a slot situated at the rear of the air port i-e
between the air inlet and the hinge of the valve and is conducted by a groove or
grooves on each side of the air inlet port towards the front part of the valve so
that when the valve is lifted by the suction of the auxiliary piston the gas and air
are drawn into the cylinder in proper proportions and thoroughly incorporated
so as to form an explosive mixture.
Or instead of the above arrangement of the orifices the gas inlet holes or slot
may be situated in the middle between two air ports. The speed of the engine
is regulated by the governors being arranged to hold open an air valve which is
lifted by a cam on the crank or countershaft whenever the normal speed of the
engine is exceeded. The area of this air valve being greater than the combined
areas of the air and gas inlets, the valve covering the latter will not be lifted so
long as the former is held open by the governors
In certain cases we arrange a separate cut off valve for the gas which is operated
upon by the governors instead of the above air valve.
Our improvements also relate to the means adopted for preventing excessive
heat in the slide valve and cylinder.
The bed or stand on which the engine is mounted is made in the form of a
hollow box or cistern to contain water which is caused to circulate round the
cylinder by a small pump actuated from a pin in the end of the countershaft.
The water first enters by a pipe situated immediately below and behind the
port leading into the cylinder and as close to the face on which the slide valve
works as possible. It then proceeds by suitably arranged passages around the
said port and is then discharged into the jacket surrounding the working cylinder.
After having circulated round the part of the cylinder in which the piston works
the water returns to the cistern beneath by a channel formed in the casting of the
cylinder casing.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said James Arthur Drake and Richard Muirhead in the Great Seal
Patent Office on the 11th October 1882.
JAMES ARTHUR DRAKE and RICHARD MUIRHEAD both of Maidstone in the
County of Kent, Mechanical Engineers IMPROVEMENTS IN AND CONNECTED WITH
GAS ENGINES
Our Invention relates to motor engines of the kind in which a piston moving in
a cylinder and coupled by a connecting rod direct on to a crank, as in a stean:
engine, is worked by the expansive force resulting from the rapid consumption of
an intimate mixture of inflammable gas and atmospheric air introduced into the
cylinder and compressed therein.
In addition to the usual or motor piston which actuates the crank we use in the
same cylinder a second or auxiliary piston whose function is to expel the residual
gases and draw in a fresh charge of combustible mixture simultaneously and at
every revolution of the crank shaft.
The construction or arrangement of parts constituting our improved gas engine
and the mode of operation are as follows referring to the annexed drawings,
Figure 1 on sheet 1 is a sectional plan; Figure 2 on the same sheet a side elevation;
Figure 3 a cross section through line A. B on Figure 2, Figures 4 to 13 are drawings
of details to be explained hereafter. The same reference numerals indicate the same
parts in all the figures.
Supposing both pistons, that is the motor piston 21 and the auxiliary piston 22
to be at the end of their instrokes and the back part of the cylinder 20 to contain
a homogeneous charge of inflammable mixture in a compressed state, ignition takes
place and the expansion of the gases drives the motor piston 21 to the end of its
out stroke. When it is within a short distance of the end of its out stroke the
motor piston 21 passes some slots 23 formed in the side of the cylinder liner, which
slots form the exhaust port and communicate with the exhaust pipe 24 which
conveys the burnt gases to the outside of the building.
The motor piston 21 having arrived at this point i.e. the inner edge of the
exliaust port 23, and the pressure in the cylinder being consequently reduced to
that of the atmosphere, the auxiliary piston 22 which until now has remained at
or near the back end or bottom of the cylinder, begins to move forward slowly at
first but with a continually accelerated velocity pushing before it the residual gases
and expelling them from the space between the two pistons through the above
mentioned slots 23 and exhaust pipe 24.
As the two pistons approximate very closely to one another at the ends of their
out or forward strokes, only sufficient clearance being allowed to prevent touching
when working, as shewn by Figure 4, it follows that practically the whole of the
residual gases are expelled from the cylinder by the forward stroke of the auxiliary
piston. While this is taking place on the front side of the auxiliary piston, the
slide valve 25 by means of a suitably arranged D passage 20 establishes a commu-
nication between the port 27 leading to the interior of the cylinder and the
induction port 28 and allows the auxiliary piston 22 to draw in a fresh charge of
combustible mixture behind it.
The moment the auxiliary piston 22 begins to return, the act of reversing the
direction of its motion causes a valve 32 in it-the construction of which will bo
explained hereafter-to open towards the motor piston 21, see Figures 5 and 8,
allowing the combustible mixture to flow through it freely, thus transferring the
charge from one side of the auxiliary piston to the other while it is performing its

page_text: in, or back stroke. The motor piston 21 is at the same time making its in, or back
stroke, and compressing the charge, after which it is fired completing the cycle of
operations, which can be repeated at every revolution of the crank shaft.
It is to be clearly understood that the pressure due to compression and subse-
quent combustion of the gases is not exerted between the two pistons 21 and 22
but between the motor piston 21 and the bottom cover or end 29 of the cylinder 20.
There is no more pressure exerted on one side of the auxiliary piston 22 than on
the other, its valve being open during the compression and burning of the charge,
see Figures 1 and 5, it is in a state of equilibrium.
Our Invention also relates to the construction of the auxiliary piston two modi-
fications of which are shown by Figures 4, 5, 6, 7, 8, 9. In the modification repre-
sented by Figures 4 and 5 the piston rod has attached to it two plates 30 and 31,
which form the body of the piston, the back one 30 being solid and the front one 31
perforated like a circular grating. Between these two plates an annular ring 32
fitting the cylinder is placed, the width of which ring is somewhat less than the
distance between the plates of the piston.
During the forward stroke the back plate 30 being in contact with the ring 32
as shewn in Figure 4 closes the aperture and forms a sufficiently tight piston to
push before it the whole of the residual gases and prevent them mixing with
and prematurely igniting the charge of combustible mixture being drawn in
simultaneously behind it, as already described.
When the motion of this piston is reversed at the end. of its forward stroke, the
width of the ring 32 being less than the distance between the plates forming the
body of the piston it remains at rest until the front plate, or grating 31 comes in
contact with it as shown in Figure 5.
The back plate 30 having now moved a short distance away from the ring and
the front plate 31 being perforated as shewn, a thoroughfare is formed through
which the charge just drawn in passes from one side of the auxiliary piston to the
other as indicated by the arrows.
The ring may be fitted with an additional packing ring or rings to ensure its
tightness in the cylinder in the usual way.
Figures 6, 7, 8 and 9 show another modification of the auxiliary piston by which
the same objects are accomplished.
In this case an ordinary valve 33 with wings or webs on the back of it 34 is
fitted on the end of the piston rod. The valve seat consists of a ring or flange 35
attached by bolts or screws to the front side of the annular ring 36.
During the forward or out stroke of the auxiliary piston represented by Figure 6,
the ring 36 is pushed by the valve 33 pressing against its seat 35 the passage being
thereby closed; but during the back or in stroke represented by Figure 8 the
annular ring is moved by the wings 34 on the back of the valve 33 coming in
contact with an internal flange 37 on the back of it. The valve being now away
from its seat, a thoroughfare is formed which permits the charge to pass from
one side of the auxiliary piston to the other, as indicated by the arrows.
The variable motion of the auxiliary piston may be produced by any known
kind of mechanism as for instance, a cam on the crank shaft, but we prefer using
the following arrangement:--Below the crank shaft 38 and parallel with it a counter
shaft 39 is placed, these two shafts are connected together by a pair of elliptical or
eccentric spur wheels 40, 41, of the same size, the point of greatest eccentricity of
one being made to engage with the point of least eccentricity of the other and
vice versa.
Near the centre of the counter shaft 39 there is a small crank (or
eccentric) 42 coupled by a connecting rod 43 to the middle of a rocking lever 44
situated about midway in the bed of the engine, the end of this rocking lever 44
is connected with a coupling rod 45 to the middle of another vibrating lever 46
the upper end of which actuates the auxiliary piston 22 through the medium
of a crosshead 47, sliding in the bored guide 48, and piston rod 49 working
through a stuffing box with metallic packing 50 in the bottom or end 29 of the
cylinder 20.

page_text: The slide valve 25 for regulating the adinission of the charge and igniting the
same is situated on the side of the cylinder as shown in Figures 1 and 2 and is
worked preferably by an eccentric 51 on the crank shaft as in a steam engine.
Hitherto slide valves in engines of this class have generally been faced on both
sides to enable them to work between two other faces i.e. between the face on the
cylinder and the face of a cover held up constantly against the valve by bolts and
nuts provided with strong springs, clips or other contrivances, having sufficient
strength to resist the maximum internal pressure. Slides so constructed and
arranged require a large amount of power to work them which in engines of small
size represents a very large percentage of the gross indicated power, besides which
the friction being constant the wear and tear is considerable necessitating frequent
refacing.
"
To obviate these defects we dispense with the face on the outer aide and in lieu
of the "cover' we substitute a bridge picco 52 or cross bar between which and
the back of the slide valve 25 we interpose a toothed rocking piece or "sector" 53
see Figures 1, 2, 10 and 11.
The toothed are of the sector 53 is placed in gear with a rack 54 on the back of
the slide valve 25 and the centre or axis against the middle of the bridge piece or
cross bar 53. It follows that the motion of the slide 25 is imparted to the sector 53
and rolling substituted for sliding friction. In order to relieve the slide valve of
all unnecessary friction when there is little or no pressure in the cylinder the are
of the sector is made slightly elliptical and eccentric or in other words the radius
of one end of the arc is greater than that of the other as shown on Figure 10 where
the truly circular are is dotted in.
As the sector vibrates to and fro with the motion of the slide, a reciprocating
movement corresponding to the amount of eccentricity of the arc is imparted to
the bridge piece 52 against which the axis of the sector 53 bears and consequently
the springs which hold the bridge piece up are alternately compressed and released,
that action being so timed that the greatest compression of the springs occurs at
the moment when the charge in the cylinder ignited. The slide valve is at
this time at the end of its forward stroke its motion is now reversed and as the
pressure in the cylinder falls the pressure of the springs against the back of the
slide and consequently of the slide against the cylinder face is also diminished.
Thus during the time when there is little or no pressure in the cylinder the
slide valve is worked with very little friction and excessive wear and tear
provented.
Instead of making the arc of the sector elliptical or eccentric, the same result
may be obtained by making the arc circular and concentric and the rack 54 on
which it rolls on the back of the slide in the form of an inclined plane as in
Figure 11, the inclination of which can be graduated to compress the springs in
exact accordance with the varying resistance they are required to exert to
counteract the pressure in the cylinder. By adding another cross bar behind the
bridge piece with an additional spring or rigid stop to come into operation only at
the moment when the maximum resistance is required the two other springs may
be made correspondingly lighter and the minimum pressure with which the slide
is held up to the cylinder face still further reduced.
Below the slide valve 25 there is a valve box 55 with which the induction
port 28 communicates and in which the cut off of the gas is effected by an ordinary
hinged or flap valve 56 (Figures 3, 12 and 13) which covers the orifices of both
the gas and air inlets when the engine is at rest and also when the normal speed
is oxceeded.
The gas is admitted to the valve box 55 by a row of holes or a slot 57 situated
by preference behind the air inlet 58, i.e. between the air inlet and the hinge of
the valve, and is conducted by a groove or grooves 59 see Figure 14 formed in the
valve seating on the bottom of the box on each side of the air inlot 58 towards the
front part of the valve so that when the valve is lifted by the suction of the
auxiliary piston the gas and air are drawn into the cylinder in proper proportions,

page_text: and thoroughly incorporated so as to form an explosive or combustible mixture.
Or, instead of the above arrangement of the orifices and to obviate the necessity
of having the aforesaid grooves 59 Figure 14 the gas inlet holes or slots 57¹ may
be situated in the middle between two air ports 58' placed lengthways with the
valve as in Figure 15
The valve 56 always remains closed except when lifted by the air drawn in
at 58 by the auxiliary piston and besides shutting off the gas when not required
by the engine it also acts as a check valve and in conjunction with the slide valve
prevents the escape of the charge during compression.
The power of the engine may be varied and the speed regulated by any suitable
kind of governor operating according to one or other of the following ways:-
According to one modification of our improved gas engine the governor is mounted
horizontally on the top of the cylinder as shown at 60 Figures 2 and 3 and is
connected by means of the lever 61 the bell crank 62 and shackle 63 to a roller 64
carried on the end of the link 65 situated below the coupling rod 45.
When by
reason of excessive speed the governor balls fly out the roller 64 rises comes in
contact with the under side of the coupling rod 45 and lifts the gab end 66 off
the pin 67 by which it is connected to the rocking lever 44. Being now thrown
out of gear the auxiliary piston remains at rest until the speed having become
sufficiently reduced the governor allows the coupling rod to fall into gear again
with the rocking lever 44. So long as the auxiliary piston remains at rest a charge
cannot be drawn into the cylinder. As it is important that the auxiliary piston
when out of gear should be at the back end or bottom of the cylinder out of the
way of the motor piston, a cross bar or "stop" 68 Figures 1 and 2 is provided to
prevent the coupling rod 45 from being lifted off the pin 67 except when the lever
etc are in the position shown by Figures 1 and 2. Should however it become
disengaged from any cause at any other point of its stroke the auxiliary piston
will always be pushed back to the end of the cylinder by the back horn of the
gab 66 which is made longer than the front horn for this purpose as shown.
The speed of the engine can be varied at pleasure by shifting the counter-
weight 69 Figure 3 nearer to or further from the end of the bell crank balance
lever 70 which has the effect of diminishing or increasing the load on the
governor.
In some cases instead of the above described method of governing the engine we
prefer the following plan, illustrated by Figures 12 and 13 and which is the other
method previously alluded to.
According to this mode of regulating, instead of disconnecting the auxiliary
piston, the governor is arranged to hold open an air valve 71 in the valve box 55
whenever the normal speed of the engine is exceeded. The valve is opened in the
following manner :-A bell crank lever 72 is jointed by a bracket 73 to the top
of the valve box, the short arm of the lever is connected by a forked end and pin
to the spindle of the valve 71, and to the upper end of the long arm of the lever
there is attached, by a loosely fitted joint pin, a bar 74. This bar 74 passes
through a slot in the link 75 which is connected directly to the governor at the
top and slides freely in a guide at the bottom. When the valve 71 is shut and
the governor balls in their lowest position the link 75 allows the bar 74 to occupy
the position shown in Figure 12 where it remains at rest. Directly the proper
speed is exceeded the governor lifts the link 75 and with it the bar 74 which is
thus brought into the direct path of a projecting lug 76 attached to the slide
valve 25. In its next backward stroke this lug 76 comes in contact with the end
of the bar 74 and pushing it before it thereby opens the valve 71 as shown in
Figure 13. The valve 71 would close again with the return stroke of the slide
were it not prevented from doing so by the following contrivance. On the lower
side of the bar 74 there is a catch latch or detent 77 which may form part of the
bar itself or be a separate piece attached to it by a hinged joint with a spring
behind it. In either case the inclined side of it will allow the bar 74 to pass freely
through the slot of the link 75 in one direction (like the latch of a door when

page_text: being shut), but the square end coming in contact with the bottom of the slot at
the beginning of the return stroke prevents the bar from passing back through it
so long as the excessive speed causes the link to be held up by the governor.
When the speed is sufficiently reduced the link 75 falls and the support it pre-
viously afforded being thus removed, the bar 74 drops again into the position
shown in Figure 12 and the valve 71 is closed by a spring on its spindle. The
area of this air valve being greater than the combined areas of the gas and air
inlets 57 and 58, the valve 56 should not be lifted so long as the valve 71 is beld
open by the governors, but to prevent the possibility of this happening we place
the air valve 71 immediately above the flap valve 56 so that when the former is
opened in the manner described, a small spring on the back of it presses on the
top of the flap valve 56, see Figure 13, and holds it firmly down to its seat as long
as the air valve remains open. In engines regulated according to the last described
method the coupling rod 45 Figure 2 is connected to the rocking lever 44 with an
ordinary joint and pin instead of the gab end shown. The ignition of the charge
may be effected by any known means but we prefer using an intermediate gas
flaine lighted by an external jet and carried to the cylinder port in a D shaped
cavity of the slide valve in the usual' way.
In engines of this kind in which the charge is compressed previous to ignition it
has been usual to establish a communication between the ignition chamber of the
slide and the interior of the cylinder by means of a small hole bored into the
cylinder or by a groove, or chase, formed in the face of the slide. The holes and
grooves alluded to are very apt to become choked up with soot and burnt oil and
their action thus destroyed; in order to obviate which defect we dispense with the
above named small holes or grooves altogether and instead thereof we so arrange
the hole in the face of the slide which conveys the gas to the intermediate flame
in the ignition chamber (which hole already exists as a necessity) relatively to the
cavity of the ignition chamber itself, that the said gas hole may communicate with
the cylinder port a little before the ignition chamber itself is presented to it and
by this means the pressure in the cylinder is transmitted to the ignition chamber
gradually and the liability of the igniting flame to be extinguished by the rush of
the gas is obviated without having any additional holes or grooves in the cylinder
face, or face of the slide.
The working barrel or liner of the cylinder is surrounded by a water jacket
connected by circulating pipes to a separate tank in the usual way. In some cases
however in order to reuder the engine self contained and portable the foundation
on which it is mounted, forms the tank for the water which is then circulated round
the cylinder by a small pump.
Having now described the nature of our said Invention and in what manner the
same is to be performed, we declare that we claim :-
First. The particular arrangement of gas-engine wherein a fresh charge of
combustible mixture is drawn into the cylinder and the products of combustion of
the previous charge is expelled therefrom simultaneously, by an auxiliary piston
when the main piston is at or near the end of its working stroke, as herein
described and substantially as shown in the annexed drawings Figures 1, 2, 3, 4
and 5.
Secondly. The employment of an auxiliary piston having one open worked or
perforated face and loose ring, as in Figures 1, 4 and 5 or provided with a movable
valve as in Figures 6, 7, 8 and 9 acting in the manner and for the purposes
described and substantially as shown in the annexed drawings.
Thirdly. The use in connection with the slide valvo of a gas engine of the
"sector" shaped rocking piece 53 acting in the manner and for the purposes
described and substantially as shown in the annexed drawings Figuros 1, 2, 10
and 11.
Fourthly. The method of regulating the engine by causing the governor to
operate upon the connecting mechanism of the auxiliary piston and put it in and
out of gear substantially in the manner and for the purpose described.

page_text: Fifthly. The combination of the air valve 71 with the flap valve 56 arranged
so that when the one is opened the other is held down to its seat; also the method
by which the opening and closing of them is controlled by the governor by means
of the slotted link 75, the bar 74, the lug 70, and the latch or detent 77 acting in
the manner and for the purposes described and substantially as shown in the
annexed drawings Figures 12 and 13.
In witness whereof we the said James Arthur Drake and Richard Muirhead
have hereunto set our hands and seals this Sixth day of October in the
year of our Lord One thousand eight hundred and eighty two.
JAMES ARTHUR DRAKE. (L.S.)
RICHARD MUIRHEAD.
(L.S.)