IMPROVEMENTS IN ROTARY STEAM ENGINES AND ROTARY PUMPS
Year: 1879

page_text: LETTERS PATENT to Edgar Ches. Cassot, of Marseilles, in the Republic of
France, for the Invention of "IMPROVEMENTS IN ROTARY STEAM ENGINES AND
ROTARY PUMPS."
Sealed the 19th September 1879, and dated the 31st March 1879.
PROVISIONAL SPECIFICATION left by the said Edgar Ches. Cassot at the
Office of the Commissioners of Patents on the 31st March 1879.
EDGAR CHES, CASSOT, of Marseilles, in the Republic of France.
IN ROTARY STEAM ENGINES AND ROTARY PUMPS."
"IMPROVEMENTS
The object of this Invention is to avoid complication so as to diminish as much
as possible the weight and dimensions of the engine, the loss of power caused by`
friction, the risk of getting out of order by wear and tear, and to prevent by a
perfect and continuous contact of the piston and the cylinder that loss of steam
which has hitherto been a cause of failure.
My improved rotary engine consists of a cylinder in which moves around its
inner circumference a cylindrical piston through which passes excentrically a shaft.
As surface of resistance for reaction on the piston I provide a rectangular plate
or valve which slides in a suitable chest.
The piston being in the position for starting steam enters between the dis-
tributing plate or valve, and its chest enters the cylinder and pushes the cylindrical
piston around its shaft.
Down to 180° (counting from the starting point) the valve, slides down, and
the pressure on the piston increases with the increasing surface of resistance.`
From that point the valve slides up, and when the piston has made an entir
revolution the valve is entirely in its chest, and there is no resistance as the flow
of steam has ceased (to recommence when the piston has passed that point by
first impulse).
I then use the pressure of steam to produce its distribution by means of the
herein before described plate or valve, and which slides without intermission on the

page_text: piston. By these means loss of steam is prevented when the parts are pro
perly jointed and fitted.
To obtain this result the valve is in communication at the top with the steam
from the boiler, and with the interior of the cylinder by one of the sides parallel
to the generatrix of the cylinder along a space or groove cut out of the said valve,
and between this valve and its chest. This space is for the steam inlet, and on
the other side is a similar space for steam outlet.
The adherence of the valve against the piston is maintained by the difference of
pressure on the top and the bottom of the valve. From the shape of this plate or
valve it only weighs on the piston by the medium of its thickness on a generatrix
of the piston. In this way one half of the thickness of the valve supports the
pressure of the steam, and the other half no pressure, as it communicates with
the steam outlet.
If S be taken as the equal surfaces of the top and bottom of the valve and the
pressure of steam be 4, the pressure on the top will be S x 4, and on the bottom
8 × 4 the difference is 4 S =2; 2 is therefore the pressure that causes the
valve to slide down; this pressure or less is quite sufficient to overcome the
resistance of friction.
2
-
4 S
2
The portion of the valve which slides out of its box or chest passes tight against
the two covers of the cylinder, and for this reason these covers must be properly
fitted so that their interior faces may be on the same plan as the corresponding
faces of the chest.
The section of the piston may be circular, elliptic, or of any other suitable form,
the angle formed by the valve and the tangent to the curve being as constant
as possible.
The valve chest carries on one side the steam inlet tube. This tube for engines
working in one direction only is placed about the middle of the valve chest. On
the other side and near the base of the chest is the steam outlet, communicating
with the groove cut out on that side of the distributing valve.
For engines having reversing motion, the only modification is in the position of
the steam inlet and outlet on the valve chest, and the shape of the upper part of
the valve. This valve carries on each side a flat groove cut out of the plato, but
this groove does not run quite up to the top.
At the top of this groove are two slits which pass through and out at the top of
the valve. These slits must be large enough for the steam to pass and maintain
the pressure on the top equal to that of the boiler, and for the return of the steam
as the valve ascends.
The top of the valve must be well planed, and carries a small plate or obturator
made of gun metal which closes up one or the other slit. This obturator is adapted
to a rod which may be turned round by means of a handle, and draws the
obturator over one of the slits. This rod ascends and descends with the valve,
and passes through the lid of the valve chest through a stuffing box.
If the engine is required to work from left to right, the obturator must be turned
over one of the slits so as to close it, then by means of the reversing valve herein-
after described the steam enters and passes against the valve, follows the flat
groove, descends into the cylinder, moves the piston, and ascends also through the
other slit, so as to establish the necessary pressure on the top of the valve.
If the reverse motion is required the small valve or obturator must be turned
over the slit and the first slit will be uncovered. The steam enters and follows the
reverse direction.
The reversing valve and its chest have the form of the valve and valve chest of
an ordinary steam engine. The valve is composed of a chest having on one side a
tube communicating with the boiler, and on the other side are three other tubes.
The middle one is for the steam outlet, and the other two communicate respectively
with the engine. In the interior these three tubes communicate with a plain

page_text: surface on which slides a valve made similarly to the distribution valve of an
ordinary engine. This valve carries a rod which passes through a stuffing box, and
carries at the other end a handle. This handle serves to draw the valve on one
side or the other. The valve must according to position leave open one of the holes
corresponding with the two ends of the tubes, the other corresponding with the
hollow under the valve, which hollow communicates with the escape tube.
My improved engine with the necessary modifications may be used as a pump.
These modifications are such as will be understood, and are required only on
account of the difference of fluidity between water and steam or air. For air
pumps no modifications are required.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Edgar Chos. Cassot in the Great Seal Patent Office on the 27th
September 1879.
EDGAR CHES, CASSOT, of Marseilles, in the Republic of France.
IN ROTARY STEAM ENGINES AND ROTARY PUMPS."
"IMPROVEMENTS
The object of this Invention is to avoid complication so as to diminish as much
as possible the weight and dimensions of the engine, the loss of power caused by
friction, the risk of getting out of order by wear and tear, and to prevent by a
perfect and continuous contact of the piston and the cylinder that loss of steam
which has hitherto been a cause of failure.
But to make my Invention better understood I will proceed to describe the same
by reference to the accompanying Drawing, in which Figure 1 is a vertical section
of my improved rotary engine; Figure 2, view of the top of the distributing valve
or plate; Figure 3, perspective view of the distributing valve; Figure 4, enlarged
section of the distributing valve showing the curve of contact surface; Figure 5,
section of the engine on the line A, B, of Figure 1; Figure 6, vertical section
shewing the arrangement of a reversible motion engine; Figure 7, section of
obturator with its rod and handle; Figure 8, enlarged view of the top of the
distributing valve with its obturator; Figure 9, perspective view of the same;
Figure 10, section of the valve and chest.
My improved rotary engine is constructed of a cylinder A, around the inner
circumference of which moves a cylindrical piston P, Figures 1 and 5, through
which piston P passes excentrically a shaft p.
As surface of resistance for reaction on the piston I provide a rectangular grooved
plate or valve T, Figures 1, 2, and 3, which slides in the valve chest D.
The piston P being in the position shewn in Figure 1, steam enters between the
distributing plate or valve T and its chest D through the inlet E, follows the
groove t of the plate or valve T, Figures 1, 2, 3, and 4, enters the cylinder A, and
moves the cylindrical piston P around its shaft p.
Down to one hundred and eighty degrees (counting from the starting point E¹¹),
the valve T slides downwards and the pressure on the piston increases with the
the increasing surface of resistance. From that point the valve T slides upwards,
and when the piston has completed an entire revolution the valve is wholly within
the valve chest D, and there is no resistance, the flow of steam having ceased to
recommence when the piston has passed that point by its first impulse.
I thus cause the pressure of the steam to effect its distribution by means of the
herein before described plate or valve T, the lower end of which is constantly in
contact with the surface of the piston on which it slides. By these means loss
of steam is prevented, provided all the joints are air tight and the parts well
fitted.
For this purpose the valve is in communication at the top with the steam from the
boiler and one side parallel to the generatrix of the cylinder, a space or groove tis
cut in the said valve, this space or groove t being horizontally of a width equal to
about one quarter of the length of the valve and of a depth about equal to one
half of the radius of the steam inlet (or one quarter of the diameter) of the steam
inlet. This groove t commences at the top and terminates at the bottom of the
valve, as shewn in Figure 3. On the other side of the valve is another groove t¹
of a width equal to about one half the length of the valve, and of a depth equal
to about one quarter of the diameter of the steam outlet, such groove t¹ commencing
at the top of the said steam outlet when the valve is at its lowest point, that
is to say, at a height from the top of the valve equal to about one quarter of
the distance from the top to the bottom of the valve. This groove extends to the
bottom of the valve as shewn.
The bottom of the valve, that is to say, the end which slides over the piston P,

page_text: is circular in section, the curve being an arc of a circle of a diameter equal to double
the thickness of the valve.
The thickness of the said valve may be about the eighth of the diameter of the
cylinder, (for cylinders of small diameters under five inches), and about one fifth of
the diameter of the cylinder for larger ones. This thickness must vary with the
steam pressure intended to be used, so as to overcome friction on the sides.
The adherence of the bottom of the valve against the piston P is maintained by
the difference of pressure on the top and the bottom of the valve. From the
shape of this plate or valve T it only weighs on the piston by the medium of its
thickness on a generatrix of the piston. In this way one half of the thickness of
the valve supports the pressure of the steam, and the other half has to support no
pressure as it communicates with the steam outlet.
4 S
valve, and the
on the bottom
If S be taken as the equal surfaces of the top and bottom of the
pressure of steam be 4, the pressure on the top will be S × 4 and
2 S;
the difference is 4 S - 2 S = 2 S; 2 S is therefore the pressure that
causes the valve to slide down; this pressare or less is sufficient to overcome the
resistance of friction.
2
The portion of the valve whicli slides out of its box or chest D into the cylinder A,
Figure 5, passes tight against the two covers or ends of the cylinder A, and for
this reason these covers must be properly fitted so that their interior faces may be
on tlie same plane as the corresponding faces of the valve chest.
To prevent or lessen the wear from friction I provide at one end of the valve
chest a steel plate or spring placed vertically, the upper end being screwed to the
top of the valve chest, as shewn at 8, Figure 5, and the other end is tightened
against the valve by means of a screw 8', Figure 5, which passes through the side
of the valve chest.
The cover of the valve chest carries a grease cup for lubricating the sides of the
valve.
The vertical section of the piston may be circular, elliptic, or of any other suitably
curved form. The circular form is the most suitable and is the one I have found to
answer best. The eccentricity of the shaft p of the piston P must not be more
than one eigth of the diameter of the cylinder, that is to say, that a cylinder
measuring twenty inches will have a piston of a diameter of 15 inches, the eccen-
tricity of the shaft being two and one half inches. When very rapid revolutions
are required from the engine, the eccentricity of the shaft of the piston should be
less. For example, for a cylinder measuring twenty inches and the engine being
required to make eight hundred revolutions per minute, the piston must measure
seventeen and one half or eighteen inches.
With these last proportions the engine will make from seven hundred and fifty
to eight hundred revolutions per minute almost silently and without over heating.
The construction of this piston is simple; all the work of turning and fitting may
be done by means of a lathe. The diameter of the piston should be such that the
greatest distance from the centre of the shaft hole to the circumference of the
piston shall be a fraction longer than the radius of the cylinder. The piston is
then placed on its shaft, and is again fitted on a lathe by the centre of the two
ends of the said shaft, and the surplus is taken off. In this way a portion of the
circular surface of the piston is made to have the same radius as the cylinder;
this portion f, g, Figure 1, must have a width slightly exceeding the distance m, n,
Figure 1. The above mentioned fraction must be determined by preliminary
drawing on paper. It must not be too great in order that the junction of the two
curves may not be too prominent. The two vertical sides of the piston must be
perfectly straight, so that they may fit well against the two covers of the cylinder A.
One of these covers is made in two parts, L and 1, Figure 5. The outer part L
carries a grease hole g and three or four screws 81, 8111, of which two are represented
in Figure 5. These screws are employed to push back the other part of the cover
when it is required to take up the wear of the inner surfaces of the cover and

page_text: of the piston. This arrangement is on the same side as the spring herein before
described.
. The other cover, not shewn in the Drawing, is in one piece, and when in place
its inner surface must correspond exactly with the corresponding surfaces of the
piston and of the valve chest.
The engine when well made requires no stuffing box to the cover, but if found
necessary it can be easily added.
The shaft may rotate directly on the centre of the two covers, or plummer blocks
may be added one on each side, and in this case they may be arranged with screws
to correct the displacement of the centre by wear and tear.
The height of the valve chest must be equal to the length of the radius of the
cylinder, or slightly more than equal.
The steam inlet E is placed in the middle, and the steam outlet E¹ in the middle
lengthwise and at a distance of 2/5 from the top, so that when the valve is at its
lowest point there will be no communication between the steam on the top and the
outlet.
The surface of the valve which slides on the piston should be lined with white
metal composed preferably of 6 parts of copper, 2 parts of antimony, and 92 parts
of tin.
. With this metal the wear of the piston is much diminished; but in any case the
part fg, of the piston which touches the circumference of the cylinder may be
made of a separate piece of cast iron, which may be removed when worn out; or
this piece may consist of a spring acting in place of the piston rings of ordinary
engines.
The side of the valve chest which carries the orifice of the steam outlet must
be well planed, as also must the corresponding surface of the valve, so that the
said valve may slide easily on the said surfaces and prevent the passage of steam
from the top, the pressure on the other side of the valve keeping it in constant
contact with the surface of the valve chest.
In consequence of this pressure produced by the steam it is not necessary that the
valve should be tight in the valve chest.
For engines having reversing motion the only modification required is in the
position of the steam inlet and outlet on the valve chest and the shape of the upper
part of the valve.
This valve carries on each side a flat groove similar to that shewn at T, :
Figure 1, but this groove does not run quite up to the top, and commences on
both sides at about a quarter of the distance from the top to the bottom.
At the top of each groove are two slits f, f¹, Figures 6, 8, and 9, which pass
through and out at the top of the valve. These slits must be large enough for the
steam to pass, and maintain the pressure on the top equal to that of the boiler, and
for the return of the steam as the valve ascends.
The top of the valve must be well planed, and carries a small plate or obturator O,
Figures 6, 7, and 8, made of gun metal, which closes up one or the other slit. This
obturator is adapted to a rod which may be turned round by means of a handle, so
as to draw the obturator with it. This rod ascends and descends with the valve T',
and passses through the lid of the valve chest and through a stuffing box.
If the engine is required to work from left to right the obturator O must be
turned over the slit f, so as to close it, then by means of the reversing valve herein-
after described the steam enters at E, Figure 6; E¹ is then the steam outlet. This
steam passes against the valve T¹, flows up the slit f¹ to create the necessary pres-
sure on the top, and follows also the groove, descends into the cylinder, and moves
the piston to the right.
If the reverse motion is required the small valve or obturator O must be turned
over the slit f¹ and the slit f will be uncovered. The steam enters at E¹ and escapes
at E.
The reversing valve and its chest have the form of the valve and valve chest of
an ordinary steam engine. The valve is composed of a chest having on one side an
4

page_text: orifice or a tube V, Figure 10, communicating with the boiler, and on the other side
are three other orifices R, E, and R¹. The middle one E is for the steam outlet, and
the other two, R and R¹, communicate with the steam outlet and inlet openings E
and E, Figure 6, respectively of the engine, Figure 6. In the interior these three
tubes communicate with a straight and plane surface on which slides a valve T,
Figure 10, made similarly to the distributing valve of an ordinary engine. This
valve carries a rod which passes through a stuffing box and carries at the other end
a handle. This handle serves to draw the valve on one side or the other. The
valve must according to position leave open one of the holes corresponding with the
two orifices R and R', the other corresponding with the hollow under the valve,
which hollow communicates with the escape orifice E.
My improved engine with the necessary modifications in the case of liquids may
be used as a pump, and will be found to be more efficacious than those hitherto
in use.
It may also be used as an air pump or air compressor, as a water pump for
feeding boilers, or for any other purpose for which a pump may be employed. When
used as a pump for liquids the passages and orifices must be of a diameter double
that required for steam or gas.
If the engine shewn in Figure 1 is to be used as a pump the piston must rotate
from right to left, and in that case E¹ would be the suction orifice, and E the com-
pression and overflow orifice.
Having thus described my Invention and the manner of performing the same I
wish it to be understood that I do not confine myself to the precise details herein
laid down and shewn in the Drawing, as the same may be varied without departing
from the peculiar character of the Invention; but what I do claim is,―
Firstly. The general arrangement and construction of the improved rotary
engine, operating substantially as hereinbefore described, and represented in the
accompanying Drawing.
Secondly. The method of effecting the distribution of the steam by its pressure
by means of the peculiar construction of distributing valve and chest, arranged and
operating as herein before described, and represented in the accompanying Drawing,
or any mere modification thereof.
Thirdly. In a rotary engine I claim a slide valve in continuous contact with a
circular or other suitably curved piston.
Fourthly. The application of the hereinbefore described improvements to the
construction of engines having a reversing motion, as herein before described.
Fifthly. The application of the herein before described improvements to the con-
struction of pumps, as herein before described.
In witness whereof, I, the said Edgar Ches. Cassot, have hereto set my
hand and seal, this Twenty fifth day of September, in the year of our Lord
One thousand eight hundred and seventy nine.
TDCAR CHES CASSOT 1T01