IMPROVEMENTS IN HOT-AIR ENGINES
Year: 1878

page_text: LETTERS PATENT to William Robert Lake, of the Firm of Haseltine, Lake,
& Co., Patent Agents, Southampton Buildings, London, for the Invention. of
"IMPROVEMENTS IN HOT-AIR ENGINES." A communication from abroad by
Jakob Schweizer, of Paris, France.
Sealed the 14th January 1879, and dated the 15th July 1878.
PROVISIONAL SPECIFICATION left by the said William Robert Lake at the
Office of the Commissioners of Patents on the 15th July 1878.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. "IMPROVEMENTS IN HOT-AIR ENGINES." [A
communication from abroad by Jakob Schweizer, of Paris, France.]
This Invention relates to an engine which is constructed upon the principle of
expelling cold air from and drawing hot air into a cylinder by the rapid movement
of a piston from one end to the other of the same; this hot air is then intercepted
and cooled as rapidly as possible in such a manner as to produce a vacuum.
The space within which the vacuum is thus produced is connected by a pipe with
the valve box (respectively through the exhaust ports of the steam pipes) of an
ordinary steam engine in such a manner that the exterior atmospheric pressure will
act by means of this engine in the space where the vacuum has been formed, and
will consequently produce the movement.
In order to obtain the vacuum more rapidly the volume of the hot-air cylinder
should be much greater than that of the steam engine cylinder, so that this engine
may make several strokes when it is necessary to fill the hot-air cylinder. All
descriptions of steam engines may be employed, but the volume of the cylinder
must be greater than is necessary to correspond to the lowest pressure, in order that
an equal power may be obtained.

page_text: The expansion valve is unnecessary, and the distributing mechanism should be
arranged in such a manner that the hot air may be admitted at full pressure into
the cylinder; and it will be understood that the pipes and the ports of the cylinder
should be larger than is necessary for the lowest pressure.
The hot-air cylinder may be vertical or horizontal. If vertical, the piston will
descend by its own weight, and allow the hot air to enter. If horizontal, the piston
will be put in motion by means of a spring or other suitable device.
With engines of large dimensions two hot-air cylinders should be employed,
acting alternately in such a manner that when one is about to cease working the
other is in full action, and consequently the propelling force will be constantly
maintained, which is a great advantage for double-acting engines.
The accompanying Drawings represent a hot-air engine constructed according to
my said Invention.
Figure 1 is a front elevation of the said engine; Figure 2 is a plan; and Figure 3
is a side view of the same.
Upon the driving shaft a of an ordinary high-pressure engine is fixed a pinion b,
with seventeen teeth, which gears with a wheel c having one hundred and seventy
teeth, so that for every ten complete strokes of the engine the wheel c will make
only one revolution. At the end of the driving shaft a, where the toothed wheel
is placed, there is keyed a crank, which by means of the connecting rod (7 operates
the beam e, and consequently the piston of the hot-air cylinder by the aid of the
two rods f, which are united by the cross piece g.
The arm h fastened to the piston rod effects by means of the rod i the opening
and closing of the slide valve at the proper times, thus permitting the entrance and
exit of the hot and cold air.
A cock is provided on the upper end of the hot-air cylinder, which is double, and
the lower end of which is pierced like a sieve in order to provide for a good distri-
bution of the water; this cock k is alternately opened and closed by means of a rod ?
attached to the arm h, and the rod m operated by the crank n. In this manner
the water injected by the pump o serves to cool at the desired moment the hot air
previously introduced.
The mechanism constructed as above described produces a vacuum in the air
cylinder p as follows, that is to say:-While the crank q moves from its lowest to
its highest position the rod d slides in a groove in the beam e, and reaches directly
the highest position of the crank q by means of the projecting piece r.
When tho
crank advances farther it draws with it the beam as well as the piston of the hot-
air cylinder until the crank has arrived at its lowest position, and the rod & strikes,
by means of its prolongation, the adjustable buffer s, which disengages the pro-
jecting piece r; consequently, the piston of the cylinder p falls, the hot air enters
at the upper end, and the cold air escapes at the lower end, but at the moment
when the piston of the cylinder p arrives at its highest position the arm h strikes
the tappet u and disengages it, so that by means of the two counterweights v
provided upon the distributing levers the slide valve rod rises, and the two slide
valves open.
When the piston falls the arm / strikes at the last moment the ring or collar x,
and causes the slide valve rod i to descend, thus closing again the slide valve; at
the same time the tappet u comes again to the upper end of the rod i.
The piston of the cylinder p is provided with a valve which opens when the
piston rises, and closes when it descends.
In order that the said piston may not cause a shock in its descent the distributing
mechanism is arranged in such a manner that the slide valve t for the hot air shall
close somewhat sooner or later, and the weight of the descending piston be utilized
to produce a compression of the hot air upon the piston, and also in order that the
latter may be checked in its descending movement.
For heating the air I employ an ordinary furnace, upon the grate of which is

page_text: secured a cast-iron boiler, open at its upper end and at one of its sides. Upon this
boiler is a pipe surrounded by a piece in spiral form, which is surrounded by a
cylinder, so as to better utilize the gases resulting from combustion. By these
means the gases resulting from the incomplete combustion of the coke or coal may
be directly employed, and the gases which escape will be forced to follow a spiral
path.
The volume of the boiler, as well as that of the pipe which is placed above, should
be at least as large as the volume of the hot-air cylinder, so that when the piston
descends no cold air can be removed.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said William Robert Lake in the Great Seal Patent Office on the 15th
January 1879.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. "IMPROVEMENTS IN HOT-AIR ENGINES." A
communication from abroad by Jakob Schweizer, of Paris, France.
This Invention relates to an engine, the peculiar feature of which is the rapid
movement of a piston within a cylinder from one end to the other of the same in
such a manner that the hot air and at the same time the gases resulting from com-
bustion are admitted at one side, and the cold air is expelled from the other side
of the said piston. The desired quantity of hot air having been admitted from the
heating apparatus to the cylinder the entry of more air is immediately intercepted
by the rapid movement of the piston; this air is then rapidly cooled, so that it may
produce a more or less perfect vacuum.
The space within which the vacuum is produced is connected by means of a pipe
with the valve casing (by the admission port) of a motor cylinder in the same
manner as a condenser communicates with the cylinder of a steam engine. The
motive power consists in the difference of pressure which is exerted on the two sides
of the cylinder, this difference being that which exists between the pressure of
the atmosphere and the vacuum.
In order to produce, the vacuum in an efficient manner I construct the chamber
in which it is formed (or the hot-air cylinder or the cold-air cylinder) of a much
greater size than required for the force which is to be developed, so that several
strokes of the piston in the cylinder correspond with the full introduction of the hot
air or with the vacuum in the cylinder.
Any suitable form of steam engine may be employed, and in consequence of the
low pressure which is exerted upon the piston of the cold-air cylinder the more
simple engines will be the most advantageous; cocks or cut-off or expansion valves
are unnecessary. The admission and exhaust ports of the hot air cylinder should
permit an easy and rapid passage, and be sufficiently large and powerful to operate
quickly.
The vacuum cylinder may be arranged vertically or horizontally. When arranged
vertically the piston falls by its own weight, and also forces out the cold gases.
When the cylinder is arranged horizontally the return movement of the piston is
imparted to it by means of a spring or by any other suitable means.
In engines of large dimensions it is advantageous to employ two hot-air cylinders
arranged in such a manner that when one has nearly ceased to act the other may be
in full force.
The accompanying Drawing represents one form of improved hot-air engine con-
structed according to this Invention.
Figure 1 is a front elevation of the said engine; Figure 2 is a plan; and Figure 3
is a side view of the same.
Figures 4 and 5 are front and side views of the mechanism for controlling the
descent of the piston.
a is the shaft, to which movement is imparted by the cold-air piston. On this
shaft is fixed a gear wheel b, which gears with the gear wheel c, the number of
teeth and speed of which are varied according to the size of the hot and cold air
cylinders.
The shaft d, which receives motion through the wheel c, is provided with a
crank e keyed to the said shaft, and corresponding with the cylinder in which the
vacuum is produced, whilst the pulley f, which is placed on one side is loose, and
carries a pin or stud g.

page_text: The crank pin forms the axis of an elbow lever h, which is maintained in its.
normal position by a spring. The said elbow lever h carries on its lower end a
tappet i, which during the revolution of the crank comes in contact with the pin or
stud g, and carries the same around with it. By these means the piston of the
cylinder in which the vacuum is produced is gradually raised by means of the strap
which is attached to the said pulley fand also to the piston rod k.
A lever attached to the extremity of the piston rod works in a slot in one of
uprights m of the engine; in this manner the said lever in its upward movement
strikes the ring or collar n on the valve rod o, and consequently operates the valves,
raising them to their highest position for regulating the proper admission to the
piston of the cylinder p, in which the vacuum is produced, and ensures the entrance
of gas and hot air into u, whilst it permits the cooled air below the piston to escape
into through the exhaust port during the falling of the piston, which takes place
immediately afterwards.
The rod o of the cock or valve is provided above the ring or collar n with a slot,
in which the pin or bolt q engages; the valve comes into position during the down-
ward movement of the piston p'.
Whilst the piston p¹ is in its highest position the arm r of the elbow lever h,
and which projects below the same, comes in contact with the projecting piece 8;
the small elbow lever h then turns to such an extent with the pin or stud of the
crank e as to leave a free passage for the pin or stud g on the pulley f, which is no
longer retained. The weight of the piston p then draws the same to the bottom or
to the lower portion of the cylinder.
The pin or stud g is then again in a position corresponding with the lowest
position of the piston p; it then awaits the arrival of the pin carried by the elbow
lever h, which then commences to operate.
Before the piston has arrived at the lowest part of its stroke the lever l, which
effects the movement of the piston, pulls down the adjustable ring or collar t of the
rod attached to the elbow lever q. By these means the valves are disengaged, and
the ports of the vacuum cylinder are able to open.
Immediately after the closing of the slide valve, and in consequence of the vis
viva still exerted upon the piston, as the valve v closes a little later, a still further
downward movement of the said piston is produced; a vacuum is consequently
formed, which brings into action a false bottom pierced with holes, and placed
below the upper cover of the cylinder, and assisting the production of a vacuum by
cooling the sides of the cylinder where the vacuum is produced. The water which
accumulates on the perforated false bottom is conducted by a pipe x into a suitable
reservoir y. On the other hand, during the upward movement of the piston p,
which takes place in the cylinder without appreciable friction, the space then left
above the said piston communicates with the space below by means of openings
formed in a suitable valve in the piston, which valve however closes immediately
on the return stroke.
The engine is controlled by means of a suitable regulator, which, through the
medium of a lever z in case of a very rapid speed permits the cold air to enter at ¹,
thereby producing a slight vacuum. If not sufficient however the side of the
lever actuates a valve 2 provided in the pipe, which establishes communication
between the vacuum cylinder and the cylinder which performs the work, thereby
limiting the action of the air.
In order to heat the air I may make use of a furnace or other suitable air-
heating apparatus placed in communication with the vacuum cylinder, or with the
hot-air cylinder.
Having thus fully described the said Invention as communicated to me by my
foreign correspondent, and the manner of performing the same, I wish it understood

page_text: that I claim, the improved hot-air engine, consisting of the parts constructed sub-
stantially as shewn in the accompanying Drawing, and operating as set forth.
In witness whereof, I, the said William Robert Lake, have hereunto set my
hand and seal, this Fifteenth day of January, in the year of our Lord One
thousand eight hundred and seventy-nine.