IMPROVEMENTS IN GAS ENGINES
Year: 1879

page_text: PROVISIONAL SPECIFICATION left by John Robert Johnson at the Office of
the Commissioners of Patents on the 4th July 1879.
JOHN ROBERT JOHNSON, of 23, Southampton Buildings, in the County of
Middlesex. "IMPROVEMENTS IN GAS ENGINES."
My Invention consists of certain improvements in that class of engines in which
the combustion of a mixture of atmospheric air and of a combustible gas or vapour
is utilised as a source of motive power.
It is well known that great difficulty has arisen in the application of this source
of force in consequence of the combustion of the gases employed occurring instan-
taneously so as to cause an explosion like that of gunpowder. When this is effected
in the cylinder of an engine similar to a high pressure steam engine fitted with a
piston the latter is driven forward as is a bullet from a gun, causing a sudden
shock and great strain upon the working parts, with many attendant dis-
advantages.
Many arrangements, too numerous to describe, have been devised to overcome
this difficulty.
Now by my first improvement I obviate the difficulty in question by interposing
a buffer, or, what is better, that which may be called a reservoir of power.
(a.) Between the explosive gases and the bottom of the piston, ram, or trunk
employed to receive the impetus of force.
(b.) Between the piston and the connecting rod; or
(c.) Between the connecting rod and the crank pin.
This reservoir of power may be of many forms and materials.
(a.) In the first place it may be a disc of metal, earthenware, or other suitable
material attached to the bottom of the piston by studs, or it may be held upon the
piston rod itself. In either case it must be capable of a sliding motion upon the
studs or rods respectively so as to approach the piston. If it were not separated
therefrom by some elastic body, such as asbestos, spun glass (Glaswölle), or by a
metal spring; or if the piston be extended by means of a thin cylinder of iron, the
disc may be ground air tight or otherwise closely fitted in such cylinder, in which
case the confined air forms an admirable spring and reservoir of power,
D

page_text: (b, c.) In the two latter cases the reservoir of power may be a spring of air (in a
close cylinder). of metal or of vulcanized caoutchouc, or of any other elastic material,
held between dises or plates of metal in such wise that when the explosion occurs
the piston driven forward cannot communicate its force-to-the-crank-pin.or_other_
object employed to utilise the force until the interposed spring has been compressed
and has thereby-absorbed the surplus power, which is again given out when the
explosion-has-occurred.
The instantaneous force is in this way distributed over a certain interval of time
of a duration depending upon the elasticity or length of travel under compression
of the spring, and therefore capable of adjustment. By this means the evil effects of
the shock are avoided.
My second improvement consists in a mode of more perfectly utilising the vacuum
which is formed below the piston when the products of the combustion of the gases
(water and carbonic acid) have cooled down to the temperature of the cylinder
refrigerated by the circulation of water around it.
1 In some engines this force is lost; in others it is only partially utilised in conse-
quence of the employment of imperfect means.
The
I effect the object in question by employing for the exit of the products of com-
bustion the ordinary equilibrium valve used in air pumps in combination with a
slide valve. The former is kept shut by the vaccum within the cylinder, but opens
readily when the piston has arrived at a certain part of its course, and the gases
within the cylinder have acquired the same tension as that of the ambient
atmosphere. I prevent the issue of the gases from the cylinder on the opening of
this valve during the explosion by a second valve placed behind the first.
second valve closes the entrance to the exhaust pipe. The two are arranged in a
box like an ordinary slide valve, so that the force of the explosion comes upon the
'back of the piece of metal which forms the slide, and closes the outlet and forces it
down upon its seat, so that it requires no spring or extra force to effect its duty.
By this arrangement the effect of explosion is fully maintained within the cylinder
without any deleterious strain or wear upon the working parts, and the vacuum is
fully utilised by the action of the equilibrium valve.
My third improvement consists in adapting the ordinary slide valve of the steam
engine, slightly modified, to effect the entry of the mixed air and gases into the
cylinder.
In one position of the valve these enter readily into the cylinder; in the other
they are cut off, and when the explosion takes place it is borne on the back of the
valve, so that its duty is aided by the force of the explosion, and is not impeded
thereby. For the same reason the explosion has no deleterious action on the face
of the valve, which in some gas engines requires constant refacing from the wear
caused by the explosion.
My fourth improvement is a new and improved mode of igniting the mixed gases,
-by-which-a-more certain-result is attained. The lighter is a gas jet at the extremity
of a radial arm within a hollow circular box, the passage for gas passing from the
centre of such box through the rod which gives it motion. At one end of the
quarter or part revolution which this box is made to travel the jet is opposite a
hole, at the back of which within a tube or elongated chamber another but stationary
gas jet is placed. At the other end of the quarter or part revolution the gas jet
arrives opposite the touch hole of the cylinder, and explodes the mixed gases. The
explosion usually extinguishes the moving light, but has no action upon the
stationary one, the hole in front of it being in this position closed by the flat bottom
of the circular box acting as a valve, and, as in the two preceding valves just
described, the effect of the explosion is made to aid the action of closing this aperture,
and not to prevent or impede it. On the return of the radial gas jet to its first
position, the hole being again uncovered, the gas is relighted from the stationary
burner. I have considered the outlet and inlet valves as a modification of the
ordinary slide valve of the steam engine, because they are based upon the same

page_text: principle, that is, the force which each has to bear is made to aid the perfect action
of the valve, and not to impede it. I prefer however to give a circular motion to
these valves instead of a linear one, both the valve itself and the usual box which
covers it being circular instead of rectangular, but other form may be employed.
My fifth improvement consists in employing a trunk or hollow ram instead of a
piston when the engine is single acting. The ram or trunk does not touch the
sides of the cylinder, but passes through a stuffing box at the open end of the
cylinder, both stuffing box and cylinder being formed with a hollow jacket for
the circulation of water to keep both cylinder and stuffing box cool.