IM- PROVEMENTS IN HOT-AIR ENGINES
Year: 1879

page_text: 26
LETTERS PATENT to Carl Pieper, Civil Engineer and Patent Agent, of
74, Belle Alliance Strasse, S.W., Berlin, Prussia, for the Invention of IM-
PROVEMENTS IN HOT-AIR ENGINES." A communication from Dirk Willem van
Rennes, of Utrecht, Holland,
Sealed the 28th October 1879, and dated the 3rd May 1879.
PROVISIONAL SPECIFICATION left by the said Carl Pieper at the Office of
the Commissioners of Patents on the 3rd May 1879.
"
CARL PIEPER, Civil Engineer and Patent Agent, of 74, Belle Alliance Strasse,
S.W., Berlin, Prussia. IMPROVEMENTS IN HOT-AIR ENGINES." A communica-
tion from Dirk Willem van Rennes, of Utrecht, Holland.
This Invention relates to that kind of hot-air engines in which an enclosed
volume of air is made to pass by means of a displacing piston from a heated to a
cooled part of a cylinder and vice versa, for the purpose of causing its pressure to
increase and diminish alternately, and thereby to actuate a working piston.
In the improved engine forming the subject-matter of this Specification, two
vertical cylinders are used having a concave bottom, which is heated by a fire
burning underneath, while the upper part of each cylinder (which may be made of
thin wrought iron plate) is surrounded by a water-jacket.
Each working-piston, which is of plunger shape, slides in a stuffing-box fitted to
the top of cylinder, and is suitably guided; it is connected by two links, arranged
on either side of its centre, to two parallel working beams keyed on the same axle.
One of these beams, which is longer than the other, transmits at one end motion
to the main crank by means of a connecting-rod, while at the other it works a
pump supplying water to the cylinder jackets. The piston-rod of either of the
displacing pistons passes through a stuffing-box in the centre of the working piston,
and is connected by a link to a third working beam oscillating freely on the axle
of the two first mentioned beams. One end of the said third beam is coupled by a
rod to a second crank placed at an angle of about 60 degrees to the main crank,
while the other end operates an air-pump by which air is compressed into a
receiver. This receiver communicates by pipes and suitable valves with both
cylinders, so that whenever the pressure in the latter decreases from loss of air
through the stuffing-box, &c., the deficiency is made up from the said receiver. In
case the lowest pressure in the cylinders is not to exceed the pressure of the atmo-
sphere, the said air-pump is not required, as in such case any lack will be compen-
sated from the outer air instead of from the receiver.

page_text: Between the two cylinders a pipe is inserted, which may be more or less opened
or entirely closed by a cock for the purpose of regulating the speed. If this cock
is actuated by a governor an automatic regulation will be obtained.
In the pipes by which the receiver for compressed air communicates with the
cylinders cocks are inserted, which should be closed whenever the engine is stopped.
When the engine is to be started again this may be done by first opening one cock
and subsequently, after the engine has made half a revolution, the other, the
necessity for turning the fly-wheel by hand is thus obviated.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Carl Pieper in the Great Seal Patent Office on the 30th October
1879.
CARL PIEPER, Civil Engineer and Patent Agent, of 74, Belle-Alliance-Strasse,
S.W., Berlin, Prussia. "IMPROVEMENTS IN HOT-AIR ENGINES." (A communica-
tion from Dirk Willem van Rennes, of Utrecht, Holland.)
This Invention relates to that kind of hot-air engines in which an enclosed volume
of air is made to pass by means of a displacing piston from a heated to a cooled
part of a cylinder and vice versa, for the purpose of causing its pressure to increase
and diminish alternately, and thereby to actuate a working piston.
On the annexed two Sheets of Drawings the improved engine which forms the
subject-matter of this Specification is represented in four views, Fig. 1 being a.
vertical longitudinal section, Fig. 2 a view from the crank-shaft end, Fig. 3 a plan,
and Fig. 4 a view from the end opposite to the crank-shaft.
A, A, are two vertical cylinders having a concave bottom made, by preference, of
cast-iron, which is heated by a fire burning underneath. The upper part of each
cylinder, which may be made of thin wrought-iron plate, is surrounded by a water-
jacket B, B¹.
The working pistons C, C₁, are open on their upper side to the pressure of the
atmosphere. They are made by preference of plunger shape, and slide in this case
in a stuffing-box fitted to the top of the cylinder, and packed with a ring i of
leather or in other suitable manner. These pistons are guided by rods m, m, and
m', m', and they are each connected by two links arranged on either side of their
centro to two parallel working beams R and S keyed on the same axle E. This
axle oscillates in the bearings Q, Q¹, which are mounted on the cylinders. The
beam R, which is longer than the beam S, transmits at one end motion to the crank-
shaft F by means of connecting-rod P. f is a fly-wheel keyed on shaft F.
D, D¹, are the two displacing pistons, which are by preference made bell-shaped at
their lower end to correspond with the bottom part of the cylinder, as is usual in
engines of this kind. The rods of the said pistons pass each through a stuffing-box
in the centre of the corresponding working piston, and are connected by links 8, 81,
to a third beam T oscillating freely on the axle E. This beam is coupled at one
end by a rod P¹ to a second crank G placed at an angle of about 60 degrees to the

page_text: main crank. The ends of the beams R and T opposite to those to which the
rods P and P¹ are attached work two pumps, i.e., an air-pump M, by which air is
compressed into a receiver L, and a pump O supplying water to the cylinder
jackets. According to the Drawing, the beam R operates the pump M, and the
beam T the pump O, but this arrangement may be inverted.
The air receiver L communicates with both cylinders by means of pipes c and c¹,
which are provided near their point of connection with the cylinders with valves
opening towards the interior of the said cylinders. Consequently, whenever the
pressure in the latter decreases from loss of air through the stuffing-boxes, &c.,
the deficiency is made up from the said receiver. In case the lowest pressure in
the cylinders is not to exceed the pressure of the atmosphere, the said air-pump is
not required, as in such case any lack will be compensated from the outer air,
instead of from the receiver.
From the foregoing description of the parts of the engine it will have become
evident that when the pistons C and C₁ are alternately moved up and down the
crank-shaft F is put into rotation. Furthermore, it will be seen that in consequence
of such rotation the crank G will, by means of rod P¹ and beam T, cause the
displacing pistons D and D2 to assume a reciprocating motion. The Drawing
represents the working pistons C and C at half stroke, while, on account of the
relative positions of the cranks F¹ and G, the piston D is nearly at the lowest and
the piston D' nearly at the highest point of its stroke.
In
In cylinder A the air is, at the time being, almost entirely contained in the space
between the pistons C and D, i.e., in the part of the cylinder which is cooled by
the water-jacket B; it is therefore at or near its minimum of pressure.
cylinder A, on the contrary, the space below the displacing piston, and between it
and the heated cylinder bottom, contains almost all the air. The air has therefore
here assumed a high temperature, and is at or near its maximum of pressure, which
being transmitted along the annular space between the walls of D¹ and A¹, acts on
the underside of piston C¹. In consequence of this state of the pressures in A and
A¹ the piston C¹ will rise, while piston C descends. After C has moved downwards
from the middle of its stroke a short distance, the displacing piston D begins to rise
and gradually forces the air from above its top into the space between its bottom
and the heated cylinder bottom, where it takes up heat and expands, and when a
sufficient amount of air has thus been displaced and heated the requisite pressure
will have been obtained for causing the piston C to begin its ascending motion,
which it continues until the piston D has again displaced a quantity of the enclosed
air from the heated to the cooled part of the cylinder. The same action takes
place in the cylinder A', but the pressure in one cylinder being at a maximum when
in the other it is at a minimum, one working piston will descend while the other
rises, and vice versa, wherefrom an oscillating motion of the working beams R
and S must result..
The direction of motion of the fly-wheel depends upon the position of the crank G
with regard to crank F¹, the former being always in advance of the latter. This
direction may therefore be changed by shifting the crank-disk H on the shaft, or
otherwise altering the position of crank pin G so as to have this pin on the other
side of crank F¹. In small engines the disk H may be fastened by a set-screw.
A constant renewal of the water in the jackets B and B is not necessarily
demanded in all cases, but it is certainly advantageous to keep it cool. For this
purpose the pump O has been provided, which communicates by its discharge pipe ƒ
and the branch-pipes f¹ and fll with the water-jackets. g, g', are waste or over-
flow pipes through which the warmed water flows off.
In the pipes c, cl, by which the receiver for compressed air L communicates with
the cylinders A, A', the cocks d, d¹, Fig. 3, or suitable valves are inserted, which,
after having been closed at any stoppage of the engine, may serve for starting the
same again. Supposing the engine to be in the position of the Drawing, the cock d
is opened first, whereby cylinder A' receives compressed air from the vessel L so
that piston C¹ is driven upward, The engine having made half a revolution, cock d

page_text: is opened for communication with cylinder A so as to cause the pressure to act on
piston C. The necessity for turning the fly-wheel by hand is thus obviated.
When it is intented to work without compressed air, the pipes c and o¹ and also
the connecting-rod N may be detached.
Between the two cylinders a pipe K, Fig. 1, is inserted, which may be opened
more or less or entirely closed by a cock or valve a, for the purpose of regulating
the speed. When the cock is closed the air in each cylinder will operate indepen-
dently of the air in the other cylinder, but when the cock is partly open the
difference of pressures in the two cylinders will be diminished more or less by air of
higher pressure passing from one cylinder into the cylinder containing at the
moment air of lower pressure. The engine will consequently act with less power
and run slower. When the cock is opened entirely the engine is stopped. This
cock may with facility be connected with a governor, whereby an automatic
regulation is obtained.
In case the engine is to work at half power for a length of time, it is but requisite
to keep the mean temperature of the heated air lower, i.e., to reduce the fires; the
inventor however, in such case, prefers to put out of use one of the cylinders by
disconnecting its working and its displacing cylinder from the corresponding
beams.
Having thus described the nature and the object of this Invention, and the
manner in which it is to be carried out in practice, as communicated to me by my
correspondent, I wish it to be understood that I do not limit myself to the precise
details of construction shown in the Drawing, and explained in the foregoing
Specification, but I claim as new and important features of the said Invention,-
1. In a hot-air engine having two cylinders, the transmission of power from the
working pistons by means of oscillating beams to a crank-shaft, substantially as and
for the purpose described.
2. In combination with a hot-air engine of the described system, an air-pump M
and air-reservoir L for supplying compressed air to the cylinders, as hereinbefore
specified.
3. In combination with a hot-air engine having two cylinders, the pipe K
inserted between the cylinders and provided with a cock or valve, as described and
for the purpose stated.
4. In combination with the pipes c and c¹ connecting the air-compressing
apparatus with the cylinders, the cocks or valves d and d by which the engine
may be started, as herein before set forth.
In witness whereof, I, the said Carl Pieper, have hereunto set my hand and
seal, this Third day of October, in the year of our Lord One thousand
eight hundred and seventy-nine.
ADT TIADAT