A NEW AND Useful IMPROVEMENT IN STEAM ENGINES
Year: 1870

page_text: ETTERS PATENT to Henri Adrien Bonneville. of the British and
Foreign Patent Offices, 18, Chaussée d'Antin, Paris, in the Empire
of France, and 10, Sackville Street, Piccadilly, in the County of
Middlesex, Patent Agent, for the Invention of "A NEW AND Useful
IMPROVEMENT IN STEAM ENGINES."-A communication from Guillaume
T
Foreign Patent Offices, 18, Chaussée d'Antin, Paris, in the Empire
of France, and 10, Sackville Street, Piccadilly, in the County of
Middlesex, Patent Agent, for the Invention of "A NEW AND USEFUL
IMPROVEMENT IN STEAM ENGINES." -A communication from Guillaume
Marie Henri Audemar, residing at Montceau, in the Empire of
France, Mining Engineer.
-
Sealed the 3rd June 1870, and dated the 24th February 1870.
COMPLETE SPECIFICATION filed by the said Henri Adrien Bonneville-
at the Office of the Commissioners of Patents, with his Petition and
Declaration, on the 24th February 1870, pursuant to the 9th Section
of the Patent Law Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HENRI
ADRIEN BONNEVILLE, of the British and Foreign Patent Offices, 18,
Chaussée d'Antin, Paris, in the Empire of France, and 10, Sackville
Street, Piccadilly, in the County of Middlesex, Patent Agent, send
greeting.

page_text: These three conditions, which have hitherto been the obstacles herein-
before alluded to, are perfectly fulfilled by the system which is herein-
after fully described and indicated.
Given a steam engine without expansion and in which the distribution
is operated in any way whatever on the steam pipe, and before the point
of distribution is placed a valve which by its opening or shutting
operates the expansion of the steam in the cylinder. This valve is
operated by a cam with an uneven outline ("profil "), which cam per-
forms the same number of revolutions as the shaft of the machine. In
consequence of its unequal conformation the cam maintains the valve
open for a longer or shorter period, and thus lengthens the duration of
the expansion more or less according to what part of the exterior outline
acts upon the valve. So far in this description all that has been stated
has been well known for a long time as variable expansion by cam
and valve, and its application has been made to numerous machines
working in one direction only.
To make this new application to machines working in either direction
the arrangements herein-before .described have been retained, but the
ordinary cam has been modified in the following way:―
Reference being had to Fig. 1 of the accompanying Drawings, A
and B are two similar cams replacing the single one, they are placed
end to end; the ends in contact are those which correspond with the
least admission of steam, and the ends free are those corresponding
with the admission during the whole course of the piston. This cam
consequently forms a double cam composed of two parts, one of which
will produce the expansion in the forward working of the machine,
and the other in the backward working of the same. Thus if the
machine reverses its movement the movement of the cams also is
reversed, and the outline of said cams acting the valve thus finds itself
under suitable conditions. In order that this cam may present all its
points to the organs which raise the valve it is arranged so as to be
moveable on the shaft on which it is carried and which imparts to said
cam its rotating motion. This movement on the shaft is connected with
that of Stephenson's slide; a single lever in the hands of the mechanic
guides both these organs at once. This connexion is represented, Fig. 2,
by the two levers C, D, and it may be remarked that the weight of the
cam counterbalances that of the slide.

page_text: G, H, of whose lunctions in this particular case reference will be unde
hereafter.
If in order to appreciate the effects and advantages of this connexion
and double cam examination be made of the accompanying Drawings,
Figs. 2 and 3, it will be seen that when Stephenson's slide is at its
middle point, that is to say, its dead point, the cam also is at the point
at which the admission of the steam is nul at the same time as the
lever L held by the mechanic is in a vertical position. If it is desired to
make the machine work forwards it is only necessary to incline the
lever L forwards, Stephenson's slide departs from its middle point, but
simultaneously the cam does the same, and an expansion is thus obtained
proportionally less-prolonged.as-the-lever-is-further-inclined.-If,-by-con--
tinuing to incline the lever it reaches the limit of its inclination, the slide
and the cam will likewise simultaneously attain a similar limit of their
course and the free end of the cam which has been said to correspond
with the entire admission of steam commencing to act on the valve a
complete suppression of the expansion takes place. It is thus evident
that to vary or annul the expansion the mechanic has simply to incline
to a greater or less degree the lever. The same process takes place for
the backward movement, but in this latter case the other portion of the
slide would act as also the other portion of the cam would effect the
expansion. The connexion of the slide and the cam shewn, Fig. 3, is
applicable in the case that it is desired to maintain a considerable
opening for the admission and escape orifices, notwithstanding the
proximity of the slide to its dead point, which proximity as is known
tends to reduce these orifices. It results from the above movements,
figured graphically in Fig. 4, produced by the two-teethed sectors G, H,
of which G describes a short angle, and H half a circumference, that
for a very considerable change of place on the part of the cam between
its two extreme points the corresponding change of place on the part
of the slide is comparatively insignificant. This method of connexion is
only necessary in some particular cases, but generally speaking the
method much simpler, indicated Fig. 2, will be found to answer, or any
similar way. As a rule it is essential that the slide and the cam should
depend on one another, but there are some cases in which it is preferable
to render them independent. This system of slide and cam may be
operated otherwise than by the hand of the mechanic, either by a special

page_text: motive power or by the machine itself, which frequently may be arranged
so as to operate said slide and cam, both in its last and first revolutions,
just as the movements should be executed in the machines for extraction.
This species of machine commences and terminates working absolutely
without expansion.
The Inventor claims special attention for the double cam consisting
as herein-before indicated of two simple cams and having notably a
single middle point, denominated dead point, corresponding to the
admission of steam at nul, also having two extreme points corresponding
the one to the forward movement of the machine with full admission;
and the other to the reversed movement also with full admission. All
the intermediate degrees of expansion existing between these two points.
This double cam. has a natural concordance with Stephenson's slide,
which like it has a single middle point and two extreme points, the
one for the forward movement, the other for the reversed movement.
It is this resemblance that has permitted their movements to be rendered
concordant and acting together. It is evident. that this quality remains
the same whether the two cams constituting the double cam are in
contact or separate from one another when once the concordance with
the slide is rendered feasible. The cams may be made of any description
of metal; in the present application (Fig. 1) they are of white cast iron
with guides or crowns of bronze hooked towards their ends. It is not
necessary for them to be made to be displaced, a moveable lever may
be applied at their exterior outline, their rotating motion alone being
retained. The shaft carrying the same may be placed in any position,
horizontal, vertical, or inclined, according to the disposition of the
surrounding locality.
Having thus described the nature of the said Invention, and the
manner of carrying the same into effect, I would have it understood
I do not confine myself to the precise details above enumerated, as these
may obviously be modified without departing from the principle of the
Invention, according to the special construction and intended applica-
tions of the engines in which they are adopted; but what I claim and
desire to secure by the said Letters Patent is,―
1st. A so-called "double cam" applied to steam engines with reversed
movements, that is to say, a cam composed of two single corresponding
cams with an uneven outline increasing from the point where the

page_text: admission is nul to the point where the admission is full, substantially
as has been described and shewn in the Drawings.
2ond. The simultaneous action and the dependent movement of the
cam and Stephenson's reverse movement slide, said movement being
transmitted to said cam and slide by a single lever, as described and t
set forth.
3rd. The levers C, D, Fig. 2, combined with a double cam and
Stephenson's slide, and working together for the purposes indicated, and
substantially as has been described and set forth.
4th. The levers E, F, and sectors G, H, combined with the double 1
cam and Stephenson's slide, and working together for the purposes
indicated and substantially as has been described and set forth.
In witness whereof,-I,-the-said-Henri-Adrien-Bonneville, liave
hereto set my hand and seal, this Twenty-second day of
February, in the year of our Lord One thousand eight hundred 1
and seventy.