Improvements in Fluid Pressure
Year: 1898

page_text: Improvements in Fluid Pressure Dugi
We, LA SOCIÉTÉ DES GÉNÉRATEURS À VAPORISATION INSTANTANÉE SYSTÈME L.
SERPOLLET, of 27, Rue des Clöys, Paris, France, do hereby declare the nature
of this invention and in what manner the same is to be performed, to be par-
ticularly described and ascertained in and by the following statement :----
This invention relates to improvements in steam engines and has for object
to construct engines which are adapted for the purpose of utilizing more par-
ticularly steam superheated to a very high temperature which may rise up to
400° and even 500° C.
Engines according to this invention are provided with valve gear of
great simplicity comprising a central cam of special form and operation; and
further objects are to dispense with packings of piston rods and of the slide
valves, and also with the surfaces on which the said slide valves work; to effect
an abundant lubrication without the aid of the usual lubricators and finally,
to provide successively a free exhaust without the aid of a slide valve, whilst
at the same time effecting compression of the remainder of the fluid imprisoned
in the cylinder on the return stroke of the piston.
The engine to which these means are applied and which shall now be
described, is of a known type, and comprises a group of two or more horizontal
or vertical cylinders arranged opposite to one another, or side by side, or
radiating, the said cylinders being single-acting and opening into a common
chamber, in which a simple drop feed lubricator maintains a constant level.
Through this chamber passes the engine-shaft and in it there moves the common
crank which just dips into the oil contained therein and to the crank pin of
which are attached the heads of each of the engine connecting rods situated
in the same plane. These connecting rods are each jointed directly to the
bottom of a hollow piston, which works in a corresponding cylinder. In adja-
cent parallel planes there may be arranged groups of two, three or
cylinders, arranged opposite to one another, and these groups may be connected
or coupled to crank pins arranged tandem-wise or at right angles, or if there
are three groups, at 120°, each group consisting of two or more cylinders
situated in different parallel planes.
more
In the accompanying drawings Fig. 1 is a half side elevation and half longi-
tudinal section of an engine having two cylinders arranged opposite to each

page_text: other in the same plane, and opening into a common chamber in which the
crank works.
Figs. 2 and 3 are plan and elevation respectively of the same. Fig. 4 is an
elevation, Fig. 5 a longitudinal axial section on the line b₁, b, and Fig. 6 an
end view of the distributing cam.
The two single-acting cylinders a, a¹ (Figs. 1 to 6) are mounted in line with
and facing each other on the frame b, having the general form of a cylindrical
box. The pistons are recessed, and have a considerable length relatively to
their diameter, which allows of jointing the connecting rods directly thereto,
and dispensing with the piston rod, its stuffing box, and the slides. The two
connecting rods have their heads cut away somewhat in the form of a crescent,
in such a manner as to be capable of being both supported in one and the same
plane of rotation by means of a common crank pin c as they only work in
compression the cap of the end bearing is superfluous. However, for the pur-
pose of avoiding any possible derangement, there are provided two collars d
which embrace the shoulders of the heads of the connecting rods and keep
them constantly up against the crank pin.
The steam enters the cylinders through the outer end of each of said cylinders
on the opening of the corresponding valve e which is operated by means of
mechanism hereinafter described. When each piston has arrived at the end of
its power-stroke it uncovers the orifices f, which are formed in the wall of the
cylinder and through which the fluid exhausts. However, the cylinder remains
full of the expanded steam at a pressure which may be slightly above that of
the atmosphere and which may besides depend on various causes, such as
counter pressure of exhaust, very short duration of the exhaust period etc.
This steam being imprisoned on the return stroke of the piston is compressed
up to the end of the stroke, without having to fear, as would be the case in all
slide valve engines, that the compression will exceed the pressure in the boiler.
In fact, as soon as the compression in the cylinders exceeds the pressure in
the generator, although the valve e is pulled by the tension of the spring ¹,
the said valve e will open and allow the compressed steam to return into the
supply pipe, whence it will return afterwards into the cylinder at the com-
mencement of the next power-stroke.
It will be readily understood that this faculty of limiting the pressure in the
cylinder to an extent practically equal to the pressure existing in the boiler,
will allow of practically doing away with the dead spaces and will thus effect a
considerable saving in steam.
The distributing gear employed in this engine is of special construction and
is of the valve type, and the valve mechanism is situated on or against the
framing. The mechanism comprises a small shaft g parallel to the engine shaft,
and rotated by the latter by means of a pair of toothed wheels h, h¹. This
small shaft carries a cylindrical cam which is adapted to slide along a feather,
and is thus capable of moving longitudinally when it is actuated by the nut i
which is provided with a forked tail embracing the circular groove formed in
the end of the cam. This nut is mounted on a screw parallel to the axis of
the said cam and moves when the said screw, which is held between two stops,
is turned either by hand or by a governor. In its rotary movement, the cam
moves successively, by means of one of its two noses or projections, the rollers 1,
mounted on the ends of the sliding rods k, and the end of which serves as a cap
or housing for the axle of these rollers. By these means the cam raises the
admission valves e which are normally pulled by opposing springs in such a
manner that these valves have a tendency to remain on their seats both by
reason of the tension of their springs, as also by the pressure of the steam.
If the engine which has just been described is intended to rotate in one
direction only, with a constant admission of steam, the cam would then only
have to be made of the total width of the two rollers, with an incline or pro-
jection whose length would correspond to the fixed period of admission which

page_text: was determined upon, but in order that the engine should be capable of being
reversed, and have a variable cut-off, either by hand or by the governor, the
cam is provided with two projections or incliness, arranged symmetrically
opposite to each other in the same plane, and each having the form somewhat
of a right-angled triangle. The apex of each of these triangles ends a few
millimetres distance from the central plane which is at right angles to the axis
of the cam, and it terminates in the cylindrical surface of the said cam. These
two triangles are thus opposed one to the other at their apices, which are
separated by a space equal to the thickness of one roller and corresponding to
the period or position of stoppage. They each have a side situated upon one
and the same generating line, and developed one to the right and the other to
the left. (See Fig. 4.) The consequence is that, according to the position of
the cam upon its longitudinal axis and opposite to the rollers 7, one on each
side of the cam, the sail rollers are raised or pushed back during the tangential
travel of the said cam which is greater or less, that is to say, during a shorter
or longer period, according as these rollers pass over the apex of the projecting
triangles on the opposite side which is most prominent towards the outside, or
over an intermediate circle situated between these two limits so that the admis-
sion can vary from zero (when the rollers are situated in the middle plane
between the apices of the triangles) up to the maximum degree when they
are situated quite close to the outer faces of the cam. Between these limits
there may be obtained an indefinite number of intermediate points and degrees
of cut-off or admission. In order to change the direction of motion, it is
sufficient to move the cam j forward on its axis, in such a manner as to change
the position (relatively to the rollers) of the triangular nose or projection of
that cam which actuates the said rollers, as above described.
It will be seen that the operation of the cam allows of producing forward
running of the engine with any desired admission of steam of stopping the
engine and of producing backward running with any desired degree of
admission.
The operation of the screw actuating the cam ; may be effected either by
hand or by means of a governor actuating it in any desired manner, for
example, as indicated in dotted lines in the drawings.
The lubrication of the cylinders, the heads of the connecting rods and the
bearings of the engine shaft, is effected in a very simple manner by means of
a drop feed lubricator, which drops oil into the lower part of the chamber into
which the crank dips and thereby at each revolution throws the lubricant in
all directions by its motion, and thus insures a very copious lubrication of the
pistons and working parts.
The engine hereinabove described is characterized by the absence of stuffing
boxes, slides, and slide valves, for the admission, which may vary between
very wide limits, as well as for the exhaust; the admission and exhaust being
effected, the former by means of a readily accessible valve actuated by a cam
having a variable throw, the latter, (the exhaust) by means of simple orifices f
which are formed at a suitable point in the wall of the cylinder, and to which
there is connected an exhaust pipe, the said orifices being opened or shut at a
desired moment by the piston itself.
"
It will be noted that the admission is effected in succession in each of the
cylinders situated in one and the same plane, by means of one and the same
cam whose incline or projection (either the one for forward travel, or the one
for backward travel which is situated symmetrically opposite thereto) moves
(at each half revolution if the engine has two opposite cylinders, or at each
third of a revolution, if the engine has three rotating cylinders situated in one
and the same plane) in front of the roller which operates the rod of the corre-
sponding admission valve.
When the cylinders are arranged two or three in one and the same plane,
and two or three in another adjacent and parallel plane, each separate group of

page_text: two or three cylinders situated in one and the same plane has its valves, its dis-
tributing cam, and all the parts or mechanism hereinabove described.
As already stated, the cylinders may be arranged vertically and side by side,
irrespective of the number of the cylinders; the frame serves to support the
cylinders and to protect the moving part arranged underneath.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed we declare that
what we claim is:-
i
1. A new superheated steam motor, with two or more cylinders provided
with a distributing cam having two projections which are situated symmetri-
cally opposite to each other, of which one effects the forward running and the
other the backward running, and which produce any desired degree of admis-
sion, by acting by means of the rollers mentioned and their rod (which is sur-
rounded by an opposing spring) upon the admission-valves, which the pressure
of the steam always holds upon their seat; the said cam also enabling one to
produce stoppage which occurs when the rollers are between the two projec-
tions of the cam, and being capable of being controlled by hand or by the
governor.
2. In a new superheated steam motor herein before specified, the exhaust of
steam, produced by means of simple apertures made through the wall of each
cylinder, and opened or closed by the simple motion of the corresponding
piston, in such a manner as thus to dispense with every moving distributing
part and to imprison in the cylinder, and to compress therein, a remaining por-
tion of the exhaust steam, which is regenerated by being mixed with the incom-
ing superheated steam, which immediately increases its temperature and
pressure.