Improvements in Gas Engines.
Year: 1894

page_text: Date of Application, 18th June, 1894
Complete Specification Left, 16th Mar., 1895-Accepted, 20th Apr., 1895
PROVISIONAL SPECIFICATION.
Improvements in Gas Engines.
I, HENRY THOMAS DAWSON, of No. 7 Upper Woburn Place, London, W.C.,
Gentleman, do hereby declare the nature of this invention to be as follows :-
With the object of relieving gas engine exhaust valves from the pressure of the
gases at the end of the stroke, I provide a cylinder and piston of about the area of
the exhaust valve, this cylinder is in communication with the working cylinder
of the engine. A passage opens from the working cylinder which the working
piston uncovers near the end of its stroke and admits the gaseous pressure to the
smaller cylinder just before the exhaust valve is opened by the engine. A lever
or other suitable connection transmits the pressure from the small piston to the
exhaust valve and thus balances the pressure of the gases tending to keep the
exhaust valve closed. This relieves the engine's valve gear of any severe work.
With the same object 1 also construct the exhaust valve itself so as to relieve
closed. I form the valve as
it from the pressure of the gases tending to keep
a part piston and part mitre or seat valve-it consists of a piston working in a
cylinder but also closing on a seat or two seats, it may be upon one seat at each
The gaseous
end of its stroke, or on both together as a double beat valve.
pressure is admitted from the working cylinder to the side of the valve cylinder
and has no tendency to force the valve on its sent, it being held tight by a spring.
When the exhaust valve is opened the rush of hot gases passes by with very little
tendency to heat the valve. To keep the valve cool however under heavy work
fill the valve with water and maintain circulation by means of concentric pipes
or other devices.
I admit the gaseous pressure all round the valve so as to relieve it from side
pressure. 1 also use piston rings to assist in preventing leakage-and form at
the outer end of the valve an air space to cushion its opening. To improve the
governing of gas engines and to render the action of the gas valve cams more
certain, instead of shifting the cam or its roller so as to cause it to either lift the
gas valve or to miss, which arrangement tends to wear the edges of the cams and
otherwise cause imperfect working, so arrange that the gas cams and their
rollers and levers are always in position and do not slide off from each other-but
to cause the governor to act upon the valves I form the cam or cams as a clutch
on one of their sides, and against this a sliding clutch actuated by the governor
engages when gas is to be taken. The cams and clutches are mounted on a shaft
rotating at the required rate, and the cams are free to turn round on the shaft so
that unless the governor causes the clutch to engage, the gas valve does not open.
The can only engages in one position with respect to the shaft, the clutch only
having one jaw, so that it only admits gas at the proper times. The clutch edges
are formed of hardened steel removeable and renewable. They are made with as
long engaging edges as may be needful to secure durability and placed so that the
edges come truly parallel to each other. The edges are slightly hooked so as to
ensure at least one full action of the cam when they engage.
The engaging parts are very near each other when out of action so that a
slight movement of the sliding clutch causes engagement or release. The governor
may either be placed at the side of the gear shaft or upon the gear shaft itself.
Dated this 10th day of lune 1801

page_text: Improvements in Gas Engines.
I, HENRY THOMAS DAWSON, of No. 7 Upper Woburn Place, London, W.C.,
Gentleman, 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 :-
With the object of relieving gas engine exhaust valves from the pressure of the
gases at the end of the stroke I provide a cylinder and piston of about the area
of the exhaust valve, this cylinder is in communication with the working cylinder
of the engine. A passage opens from the working cylinder which the working
piston uncovers near the end of its stroke and admits the gaseous pressure to the
smaller cylinder just before the exhaust valve is opened by the engine. A lever
or other suitable connection transmits the pressure from the small piston to the
exhaust valve and thus balances the pressure of the gases tending to keep the
exhaust valve closed. This relieves the engine's valve gear of any severe work.
With the same object. I also construct the exhaust valve itself so as to relieve
it from the pressure of the gases tending to keep it closed. I form the valve as
apart piston and part mitre or seat valve-it consists of a piston working in a
cylinder but also closing on a seat or two sents, as a double beat valve. The
gaseous pressure is admitted from the working cylinder to the side of the valve
cylinder and has no tendency to force the valve on its seat, it being held tight by
a spring. When the exhaust valve is opened the rush of hot gases passes by with
very little tendency to hent the valve. To keep the valve coul however under
heavy work fill the valve with water and maintain circulation by means of
concentric pipes or other devices.
admit the gaseous pressure all round the valve so as to relieve it from side
pressure. I also use piston rings to assist in preventing leakage and I form at
the onter end of the valve an air space to cushion its opening.
To improve the governing of gas engines and to render the action of the gas
valve cams more certain, instead of shifting the cam or its roller so as to cause it
to either lift the gas valve or to miss, which arrangement tends to wear the edges
of the cams and otherwise cause imperfect working, so arrange that the gas
cams and their rollers and levers are always in position and do not slide off from
each other—but to cause the governor to net upon the valves I form the cam or
cams as a clutch on one of their sides, and against this a sliding clutch actuated by
the governor engages when gas is to be taken. The cams and clutches are mounted
on a shaft rotating at the required rate, and the cams are free to turn round on the
shaft so that unless the governor causes the clutch to engage, the gas valve does
The cam only engages in one position with respect to the shaft.
the clutch only having one jaw so that it only admits gas at the proper times.
The clutch edges are formed of hardened steel removeable and renewable.
They are made with as long engaging edges as may be needful to
durability and placed so that the edges come truly parallel to each other.
The edges are slightly hooked so as to ensure at least one full action of the
cam when they engage.
not open.
secure
The engaging parts are very near each other when out of action so that a
slight movement of the sliding clutch causes engagement or release. The governor
may either be placed at the side of the gear shaft or upon the gear shaft itself.
In order that my said invention may be fully understood am readily carried
into effect I will proceed to describe the drawings annexed.

page_text: Figure 1 illustrates my improvements in connection with the exhaust valve of
the engine in which the gaseous pressure on the valve is counteracted.
Figures 2, 3 and 4 illustrate my improvements in the construction of the exhaust
valve.
Figures 5, 6, 7 and 8 illustrate my improvements in connection with the admission
of gas to the engine.
In Figure 1A represents the cylinder of a gas engine.
B Bare balancing cylinders and pistons either of which may be employed.
The drawing represents two separate arrangements; it is not intended that both
should be fitted to one engine. C is a lever having a fulcrum D, C is in contact
at one end with the piston of the balancing cylinder B, and at the other end
engages with the spindle of exhaust valve E. F represents a passage opening
from the working cylinder into the balance cylinder, this passage is opened by the
working piston towards the end of its stroke. G represents the exhaust lever,
worked by the engine by means of a cam or other device as is usual. The action
is as follows, when the working piston approaches the point at which exhaust takes
place the small passage F is opened and the same pressure as exists in the working
cylinder then enters B, pressing on its piston and through lever C, upon the
exhaust valve E, tending to open it while the pressure in A tends to close the
exhaust valve.
The exhaust lever when it makes its movement to open the valve has
When the
consequently no pressure to overcome but that of the valve spring !.
working piston returns and the exhaust valve is required to close, ports H in the
working piston, open to the passage F, and the balancing cylinder then exhausts
allowing the spring I to close the exhaust valve E.
K is an exhaust valve of substantially the same class but its balancing cylinder B¹
is fitted in line with the valve K, and acts directly upon the valve spindle, thus
avoiding the use of a lever C. G¹ represents the exhaust lever worked by the
engine, engaging by means of a fork with the spindle of K.
These arrangements of balancing cylinders do not dispense with mechanical
devices for opening the exhaust at the proper time but only relieve the parts from
the strain of opening the exhaust valve against the terminal pressure of the
in the working cylinder. The parts may be arranged in any convenient positions
as well as those shown.
gases
Figures 2, 3 and 4 relate to that construction of exhaust valve in which the valve
itself is so formed as to relieve it from the pressure of the gases tending to close it.
Figure 2 is a section taken through the centre of the valve and in a direction
parallel to the axis of the working cylinder.
Figure 3 is a transverse section with parts removed.
Figure is a section taken on the axis of the cylinder.
A is a gas engine cylinder, B is a passage opening from it into a valve cylinder C,
truly bored and fitted with seats D and E. The passage B, is formed so as quite to
surround the valve F, see Figure 4, which is carefully fitted to the bore of the
cylinder C and beds tight upon D and E. The valve F is also fitted with piston
rings G, and the bore C is closed at one end by the cover H and at the other end
opens into the exhaust passage 1. The valve F is worked by the spindle K pressed
upon by the lever 1, moved by the engine at the proper times and the valve Fis
held firmly closed at other times by the spring M.
It will be seen that this valve is not affected so as to be held tightly upon its
seatings by the gaseous pressure in cylinder A but rather tends to be opened
thereby, which tendency is overcome by the spring M, and the result is a valve
that takes little power to open during work, thereby greatly easing the valve
gear.
The valve also keeps cool under work as the hot gases do not play freely round

page_text: may be
it as in the mushroom form of valve, but the valve is withdrawn from the passage
when opened and the gases pass neross its face only. Moreover the valve is in
contact over most of its surface with water cooled metal as will be seen from
Figures 3 and 4. Should it be desired to cool the valve itself still more it
fitted with a cover N, to which is allixed a hollow plunger O passing through
a close fitted hole in cover H, into a fitting P bolted on the cover H, and which
acts as a pump and has a gland Q. provided with packing. A suction passage R
enters the pump and is connected by a pipe with the cooler part of the jacket
water X and a delivery passage S, containing a non-return valve, is connected with
the upper or hotter part of the water jacket or otherwise led away. The hollow
plunger O, contains an internal pipe T between which and plunger O, is an annular
pace U, and both pipe T and space U communicate with the hollow valve F.
It will be seen therefore that the valve F, the pump P, pipe T and annular
space U, and the pipes lending thereto are constantly full of water when the engine
is in use and at each movement of valve F and plunger Q, when the valve Pis
opened the plunger is forced inwards and the water in space V is first shut off
by plunger 0, covering the suction passage R, and the remainder is forced down
pipe T, into the hollow valve F, and through annular space U, through holes aud
recess W, in the plunger O, and finally through valve and passage S, into the
upper part of the jacket or elsewhere, and as this circuit is performed each time
valve, opens, there is a constant forced circulation of water through the
valve F.
If the plunger O be made shorter so as not to close passage R, and if the valve S
be left out there will be a natural circulation through the valve F, of less quantity
than if forced.
The arrangement of parts may be altered, thus the valve may be worked from
the opposite end to that here shewn, leaving the exhaust passage I absolutely clear
and the valve F may be without seat E, or rings and the whole may be placed
in other relative positions to the cylinder A.
Figures 5, 6, 7 and 8 represent a method of governing gas engines by causing
the cams which move the gas valves, to stop when no charge is to be taken,
instead of slipping the cains or rollers out of contact with each other.
Figure is a longitudinal section of the governor. Figure 6 is an elevation and
Figure 7 is a plan of portions thereof. Figure & shows a modification and is an
elevation partly in section.
In Figure 5A is the countershaft of the engine, carrying the usual cams &c.-besides
that shown in the figures. B is a governor fixed upon the countershaft. C is a sleeve
moved longitudinally on the shaft by the governors action and sliding on a feather.
One part of sleeve C is formed as a flauge and carries a hardened steel jaw D, let
into its face and so fixed that it can be removed and replaced. E is a similar
sleeve and flange carrying a similar jaw D. The sleeve E is supported by a small
collar Frecessed partly within E and partly within C, leaving room for to work
freely endwise the shaft, and G is a collar fixed at the other end of sleeve E,
so that E cannot move endwise but is quite free to revolve about the shaft A.
H is a cam formed with or fixed to the sleeve E. I is a ruller bearing upon the
suitable manner
cam II, and working upon the lever K which is connected in any
to the gas valve of the engine. The lever Kit will be observed is not shown in its
operative position. L is a spring for resisting the expansion of the governor balls.
The spring L, fits loosely upon tube M, which in turn fits loosely upon shaft A,
and the milled mut N is made fast to tube M. The milled nut O, works on a thread
upon tube M, so as to compress the spring L P is a collar supporting the nuts N
and O, and tube M and spring L. in a proper position. The governor B may be
constructed otherwise than as shown.
It will be seen that the shaft A revolving while the engine works causes the
governor to expand when the desired speed is renched, it is shewn so expanded,
and the jaws Dare drawn out of contact with each other. In this position the
sleeve E carrying the cam H, is free and does not revolve with the shaft A, hence

page_text: the roller and lever K, are not moved, and the engine gets no gas.
The speel
then falls till the governor closes, and the sleeve C, is forced towards E, the
jaws D again engage and gas is again taken. The jaw and cam H upon sleeve E
are so placed that gas is admitted during the charging stroke of the engine while
the slightly hooked form of the jaws D, causes them to hold together while at
least one full charge of gas is taken.
The construction of spring L., tube M, and the nuts N and O, is such that while
the engine is at work there is no friction among these parts, but if it is desired to
alter the speed, on taking hold of the nut N, the spring and tube will cease to
revolve with the shaft A and the other parts, so that nut O may be screwed so as
to loosen or tighten the spring Lat pleasure. It is shown at its loosest, the nuts (
and N being in contact with each other.
Figure 8 shows substantially the same arrangement of sliding sleeve C, jaws D
and sleeve E carrying cam H, but the governor in this case is separate from
shaft A and is driven therefrom and is connected with sleeve C by a lever B
working upon a knife edge F. The requisite pressure is put on the governor by
the spring G and nut. The spring K, is merely to balance the weight of
sleeve C.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. A relieving cylinder connected substantially as described with the working
cylinder and operating by means of its piston upon the exhaust valve in such
manner as to counteract the gaseous pressure upon the valve tending to hold it to
its seat, thereby enabling the valve to be easily opened by other mechanism
provided to move it.
•
2. The construction of the exhaust valve substantially as described so that the
gaseous pressure in the engine does not tend to close it, or to force it to either side,
so that when open the valve is but little exposed to contact with the heated
gases, and so that the valve is for the most part in contact with water cooled
metal.
3. The arrangement substantially as described, for circulating water through the
valve and parts attached to it, their movement alternately drawing water into
and expelling it from a chamber forming part of the circulating system which
includes the hollow valve.
4. The arrangement substantially as described for controlling the admission of
gas to the engine, consisting of a pair of sleeves with engaging jaws, one of such
sleeves rotating with its shaft and being moved endwise thereon by a centrifugal
governor and the other sleeve being loose upon the shaft and carrying a can which
operates upon a lever connected with the gas valve; the whole arrangement being
such that the cam remains at rest except when the movement imparted by the
governor causes the jaws to engage.
5. Apparatus substantially as described and represented by the annexed
drawings.
Dated this 11th day of March 1895.
HENRY T. DAWSON.