IMPROVEMENTS IN THE SLIDE VALVES OF STEAM ENGINES AND ELASTIC POWER ENGINES GENERALLY
Year: 1869

page_text: LETTERS PATENT to Jules Piret, of 37, Boulevard Bonne Nouvelle,
Paris, in the Empire of France, Machinist, for the Invention of
"IMPROVEMENTS IN THE SLIDE VALVES OF STEAM ENGINES AND ELASTIC
POWER ENGINES GENERALLY."
Sealed the 26th October 1869, and dated the 13th July 1869.
COMPLETE SPECIFICATION filed by the said Jules Piret at the
Office of the Commissioners of Patents, with his Petition and.
Declaration, on the 13th July 1869, pursuant to the 9th Section
of the Patent Law Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JULES
PIRET, of 37, Boulevard Bonne Nouvelle, Paris, in the Empire of
France, Machinist, send greeting.
WHEREAS I am in possession of an Invention for "IMPROVEMENTS IN
THE SLIDE VALVES OF STEAM ENGINES AND ELASTIC POWER. ENGINES GENERALLY,"
and have petitioned Her Majesty to grant unto me, my executors,
administrators, and assigns, Her Royal Letters Patent for the same, and

page_text: have made solemn Declaration that I verily believe myself to be the
true and first Inventor thereof.
NOW KNOW YE, that I, the said Jules Piret, do hereby declare that
the following Complete Specification, under my hand and seal, fully
describes and ascertains the nature of my said Invention, and the
manner in which the same is to be performed, reference being had to
the accompanying Sheet of Drawing, and to the figures and letters
of reference marked thereon :-
My Invention consists in a novel system of slide valve with interior
distribution, kept in equilibrium by springs, with variable expansion
gear for steam engines and elastic force machines generally.
The various kinds of steam engines in actual use have a great defect,
namely, the pressure exercised by the steam upon the slide valve, which
in its come-and-go motion renders the frictions very heavy upon the
face or plate of the cylinder upon which the valve works. Further, there
are one or two stuffing box glands for setting the slide valve in motion
by a rod which is nearly always transversal and necessitates the use of
two stuffing box glands instead of one; there is therefore great resistance,
and great care is necessitated. The lubrication of the surfaces and
of the rod is very imperfectly exccuted, the lubricating matter being
absorbed by the steam. The rotary movement of the eccentric in its
ring is very stiff by reason of this heavy load which it has to set in
motion, and it therefore absorbs a good deal of the engine power, often
causes breakage of the rod or of the ring, and on railways this defect is
the cause of many delays and much trouble.
The construction of the cylinder is very difficult, because of the great
amount of workmanship in the slide box, which also hinders the dressing
or polishing of the face of the cylinder; the joint of this box very often
bursts in consequence of its large surface. The slide valve and the
part of the cylinder upon which it works wear out very fast by reason
of the heavy weight and the imperfect lubrication. This system is
therefore very onerous.
To obviate the difficulties above set forth I use a slide valve with two
ports C, C, (Fig. 2) covered with a concave plate fixed in the direction
of the movement of the slide valve, and receiving steam from the
generator by a pipe joining on to the opening A (Fig. 1) and communi-
cating it from thence to the cylinder by two orifices B, B, (Fig. 1) which

page_text: the slide valve exposes alternately by means of the two ports made for
this purpose. This forms the distribution, there being no other pressures
to be borne than those required to prevent steam leakage between the
surfaces. The concave plate will be held in its normal position by the
pieces I, I, (Fig. 3) and will only move in the direction indicated by
the arrow, Fig. 3. The adjusting screw is also intended to keep the
spring in its place, a ratchet preventing any slackening of the spring.
Grease boxes are adopted to suit the arrangement of the slide valves,
and so as to lubricate their surfaces.
Fig. 1 of the Drawing shows plate receiving steam from the generator
by the orifice A; Fig. 2, slide valve giving the steam from the orifice,
Fig. 1, to the cylinder by the ports C, C; Fig. 3, entire apparatus set
on the cylinder; Fig. 4, cylinder having no other steam duct than the
steam outlet; Fig. 5, slide valve communicating steam at each end of
the cylinder.
For machines in which the slide valves are placed opposite each other
a single screw will suffice, as shown at Fig. A. Under this system no
nore useless pressure on the slide valves, and consequently more gentle
frictions; there being no stuffing box glands the eccentric rings are
subject to less strain, which will prevent their breakage, and that of
the slide rods, such ruptures being very frequent in locomotives; the
slide box being suppressed the construction of the cylinder is very much
simplified, and it is more easily kept in order; the machinist can at
any moment ascertain the state of the slide valves and remedy any
defect in the distribution, the slide valves working exposed; there is no
useless weight on the slide valve, a very gentle friction by continuous
lubrication and economy in construction, maintenance, and power.
In adopting this system engines specially constructed will have an
advantage over such as are only transformed. In fact by relieving the
slide valve from all the weight of steam pressure I give it the entire
length of the cylinder, thus dispensing with all the conduits and making
the steam arrive at each end of the cylinder. By this means I at each
stroke of the piston economize the steam which fills these conduits
(Fig. 5).
In the second place I give a greater section to the steam outlet, an
advantage over ordinary machines, all of which have too small an escape
to permit the complete exit of the steam before the return of the piston;
hence a more perfect exercise of the steam power within the cylinder.

page_text: Engines of equal proportion giving much greater power, there is also a
great saving of fuel.
I claim the use of slide valves with interior distribution equilibrated
by means of springs with variable expansion gear, substantially as
herein set forth and illustrated on the accompanying Sheet of Drawing.
In witness whereof, I, the said Jules Piret, have hereunto set my
hand and seal, this Tenth day of July, in the year of our Lord
One thousand eight hundred and sixty-nine.
JULES PIRET. (L.S.)