IMPROVEMENT IN GAS ENGINES
Year: 1884

page_text: We EDWARD COBHAM & JOHN GILLESPIE, Engineers of Stevenage in the County
of Hertfordshire do hereby declare the nature of our Invention for IMPROVEMENT IN
GAS ENGINES to be as follows:-
We find that a gradual cut off of air & gas before the explosion takes plice
(where compression is not resorted to) detracts largely from the efficiency of a
Gas-engine because whilst the area in the cylinder behind the piston is largely
increased by the accelerated speed of the piston the opening of the valve inversely
decreases up to the moment of explosion, thus stopping the supply of the explosive
mixture at the moment when it is most required. To obviate this we employ a
valve admitting the proper mixture of gas & air which is closed by the explosion;
but as when this is done a certain amount of sound escapes both through the valve
which admits the air & also through the lighting valve chamber we carry the
openings to these through passages pipes or other suitable channels into one end
of a chamber or chambers by preference placed in the stand which supports the
cylinder The opposite end or ends of the said chamber or chambers is or are open
to the atmosphere and within the body or bodies of the chamber or chambers we
place ribs alternately protruding at short intervals from the top & bottom thereof.
Or when the depths of the chamber or chambers will admit the ribs are in some
cases alternately arranged on the interior of the opposite sides of the same.
consequence of the arrangement of the said ribs within the interior of the chamber
or chambers any current of air will pass through the chamber or chambers in a
zig zag course and the sound made by the explosion will be muffled.
In
Although chambers constructed as herein before described are specially advan-
tageous when connected with the air valve & lighting valves of gas engines
constructed as described they will also be found suitable to be applied in a similar
manner to the like parts of small gas-engines of other forms of construction.
Dated this third day of January 1884.

page_text: E. COBHAM-Stevenage Herts-Engineer J. GILLESPIE-Stevenage―Herts,-
Engineer, do hereby declare the nature of our invention for IMPROVEMENTS 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 :-
We find that a gradual cut off of air and gas before the explosion takes place
(where compression is not resorted to) detracts largely from the efficiency of a Gas
engine, because whilst the area in the cylinder behind the piston is largely increased
by the accelerated speed of the piston the opening of the valve or valves inversely
decreases up to the moment of explosion, thus stopping the supply of the explosive
mixture at the moment when it is most required, To obviate this we employ a valve
or valves admitting the proper mixture of gas and Air which is, or are, closed by the
explosion, but, as when this is done a certain amount of sound escapes through this,
or these, valves we carry the opening or openings to this or these valves through
pipes, passages, or other suitable channels into one end of a chamber or chambers
by preference placed in the stand which supports the cylinder-The opposite end
or ends of the said chamber or chambers is, or are open to the atmosphere and
within the body or bodies of the chamber or chambers we place ribs alternately
protruding at short intervals from the top and bottom thereof, or, where the
depths of the chainber or chambers will admit the ribs are in some cases alternately
arranged on the interior of the opposite sides of the same, In consequence of the
arrangement of the said ribs within the interior of the chamber or chambers any
current of air will pass through the chamber or chambers in a zigzag course and
the sound will be muffled-We sometimes also draw the necessary supply of air
for the ignition flame through this said chamber or chambers.
Although chamber or chambers constructed as herein-before described are
especially advantageous when connected with the air and lighing valves of gas
engines constructed as described they will also be found suitable to be applied
in a similar manner to the like parts of small gas engines of other forms of
construction.
In the following description reference will be made to the accompanying drawings
which represents a vertical section of a gas engine, embodying our invention but we
do not limit ourselves to the particular detail shewn therein.
The engine chiefly comprises a cylinder A containing a piston B, connected by a
rod C. with the crank D. The cylinder is surrounded by a water jacket G. as in
other gas engines, and rests on the bottom base-plate E. which is of special construc-
tion in order to serve as a silencing chamber, forming part of the air passage. To
the outer end of the cylinder is screwed a specially constructed cover Hadapted to
serve also as Air and gas inlet. O air inlet, N gas inlet, I valve spindle passing
through cover-The cover H, is cast in one piece with an axial tube, the inner end
of which forms a perforated disc fitting into the bore of the cylinder and serving
as a valve seat, while the lateral end has an opening N for the admission of
combustible gas.
The valve spindle I is placed in the axis of the cylinder and carries at the inner
end a valve K adapted to rest against the valve seat and allowed to slide on the
spindle between the enlarged head of the latter and the valves eat. The valve K
is made somewhat less in diameter than the bore of the cylinder in order to afford
a sufficient passage for the gas and air mixture-The inner end of the spindle is
axially guided by a sleeve N¹ sunk into the valve seat while, the outer end passes

page_text: through a stuffing box and is provided with a screw thread carrying a nut M
which serves to adjust the tension of the spring L placed between the stuffing box
and the nut. The object of this spring which may be replaced by any well known
equivalent is to hold the valve K against its seat with variable pressure. The
annular space O¹ around the axial tube of the cylinder cover H, serves as air inlet,
and communicates through a vertical port of the cylinder with the silencing
chamber E.
This chamber has a number of baffle plates P. P¹ and is limited by the flange Q
of the base plate, The silencing chamber has for its object the prevention of the
free transmission of the sound produced by the closing of valves, or the explosion
of the Air and gas mixture through the Air passage of the engine by interposing
into it obstructions adapted to deflect, disperse, or destroy any sound waves which
pass from the interior of the cylinder into the Air passage. Instead of the baffle
plates P, P¹ which force the sound waves to take a zigzag course corrugated plates,
perforated partitions or other equivalent obstacles, pulse valve or valves may
be employed-The air supply for the ignition apparatus R. S. T. may also be
derived from the silencing chamber in order to intercept any sound which may
come out of the ignition valve. The ignition apparatus and the outlet W for the
products of combustion may be arranged as in other gas engines-The engine
works as follows-When the piston B is in its innermost position and begins its
outstroke by virtue of the inertia of the rotating parts the valve K is lifted from
its sent by suction so as to allow Air to enter the cylinder through the port O and
gas through the port N. As soon as the piston has moved through the distance
necessary to cause the ignition of the mixture drawn into the cylinder the pressure
caused by the explosion suddenly closes the valvo K and drives the piston B to
the end of its stroke, At the beginning of the return stroke the outlet W which
had been previously closed is opened in the usual way and the valve K remains"
closed, so that during the return stroke of the piston produced by the energy stored
up in the fly-wheel the products of combustion are forced out through the opening W.
In gas engines in which the admission of explosive mixture is controlled by valves
set in motion by the crank shaft the inlet is gradually diminished or even entirely
cut off before the explosion takes place while the speed of the piston increases-in
consequence of this the cylinder is never quite full of explosive mixture at the
moment of explosion. In controlling the gas and air inlet by a valve operated by
the difference of pressure on the front or back of the valve we obtain a rapid
opening and closing of the Air and gas inlet at the required moment, a uniform
mixture of the explosive compounds and a simplified construction.
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, We declare that what
we claim is
1. Mode of admitting Air to the cylinder through a chamber or chambers.
constructed for the purpose of deadening sounds substantially as, and for the
purposes described.
2. Combination of a valve or valves closed by the explosion of the combustible
mixture with silencing chamber or chambers substantially as, and for the purposes
described.