IMPROVEMENTS IN VALVES AND VALVE GEAR OR APPARATUS FOR DISTRIBUTING AND REGULATING THE EXPANSION OF MOTIVE ELASTIC FLUIDS IN MOTIVE POWER ENGINES
Year: 1880

page_text: PROVISIONAL SPECIFICATION left by John Henry Johnson at the Office of
the Commissioners of Patents on the 27th April 1880. A communication
from abroad by Albert Michel Jouët-Pastré, of Paris, in the Republic of
France, Manager of the Société Nouvelle des Forges et Chantiers do la
Mediterraneé.
JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
Gentleman. "IMPROVEMENTS IN VALVES AND VALVE GEAR OR APPARATUS FOR
DISTRIBUTING AND REGULATING THE EXPANSION OF MOTIVE ELASTIC FLUIDS IN
MOTIVE POWER ENGINES." A communication from abroad by Albert Michel
Jouët-Pastré, of Paris, in the Republic of France, Manager of the Société Nouvelle
des Forges et Chantiers de la Mediterraneo.
This Invention relates to valves and valve gear or apparatus for distributing and
regulating the expansion of steam or other motive elastic fluids in motive power
engines, the said valves being controlled by the governor, in accordance with the
varying duty of the engine.
In carrying out this Invention as applied, for example, to a compound steam
engine, two gridiron expansion valves are provided respectively upon the two
elongated valve seats of the two cylinders; these valves are formed or carried by
the slide valves, and may be of flat or cylindrical form. In order to close tho
inlet for steam the valves are caused to move laterally by a small but very rapid
angular movement of the valve rod at a time fixed by the governor.
For this purpose the two expansion valves are connected to the slide valve rod
by means of two small levers, and the small angular motion referred to produces
the double effect of opening the ports on one side of the piston at the same time
that it closes those on the other, and this takes place at the time when the piston
is nearly at the end of its stroke.
The valves are each composed of two parts rigidly connected together, one part
being for the distribution of steam at the top of the cylinder, and the other for tho
distribution of steam at the bottom of the cylinder.
By means of this arrangement the volume of the passages is reduced to a
minimum.
The two expansion valves may have four ports, and be arranged to work on the
two seats of the one slide valve, and the other slide valve may be similarly
provided.
'

page_text: The two high pressure slide valves in this arrangement may be of a flat form,
and the low pressure expansion valves may be of a cylindrical form. The slide
valves are worked by excentrics and connecting rods; the small angular motion is
imparted to the valve rods, and consequently to the expansion valves, by one and
the same cam disc, and through tho intervention of a lever with regard to the slide
valve of the small cylinder acting upon the lugs of a socket or sleevo fitted on a
square prolongation of a rod acting as a guide to the sleeve, and through the
intervention of another lover and parallelogram with regard to the slide valve of
the large cylinder. In the latter case the lever last mentioned acts first on the
lugs of a sleevo, which is loose or free to revolve upon the sleeve previously
referred to, and the movement is transmitted by two connecting rods to lugs on
another sleeve, which is fitted on a square prolongation of a rod acting as a
guide.
The two slide valve rods thus have two movements imparted to them, viz., the
vertical rectilinear motion for the stroke of the slide valve, and the angular or
lateral motion of the expansion valves, the forks of the connecting rods being
attached to the valve rods by means of swivelling heads in order to admit of this
double motion.
The cams on the disc are made of a suitable spiral or other shape, and the
amplitude of the levers may be divided into five equal parts, the two extremo
parts serving alternately for covering the ports; they are joined by curves at the
cylindrical parts to ease the movement; the three middle parts effect the rapid
closing or cut off
A small hollow auxiliary spindle transmits motion from the engine to the
governor by toothed gearing; a spindle arranged inside the auxiliary spindle
transmits the same motion to the disc; these parts make the same number of
revolutions as the engine. The governor imparts vertical motion to the internal
spindle by its lower inovable sleeve, and thereby alters the angle of adjustment of
the disc, which is carried round by the threads of a very rapid screw provided on
the extremity of the internal spindle, and capable of sliding longitudinally through
the said disc. The rotary motion is effected by tho engine, the governor simply
acting for the purpose of shifting the angle of adjustment of the cam disc.
The proper resistance of the governor is adjusted by a helical spring, the tension
of which may be varied in order to regulate the number of revolutions of the
engine.
The expansion valves may be thrown out of gear and their action stopped when
desired by bringing the lever, which imparts the angular cut off motion to them,
into an intermediate position.