AN IMPROVED VARIABLE EXPANSION VALVE FOR MOTIVE POWER ENGINES AND MECHANISM FOR WORKING THE SAME
Year: 1880

page_text: PROVISIONAL SPECIFICATION left by Francois Joseph Lemouche at the
Office of the Commissioners of Patents on the 24th July 1880.
FRANCOIS JOSEPH LEMOUCHE, of Brussels, in the Kingdom of Belgium, Engineer.
"AN IMPROVED VARIABLE EXPANSION VALVE FOR MOTIVE POWER ENGINES AND
MECHANISM FOR WORKING THE SAME,"
This Invention is composed of the expansion valve proper and an automatic
method of working.
The expansion gear is composed of three parts.
The first piece the distribution or D slide valve, which is actuated by a to and
fro motion. The two conduits which distribute the steam to the cylinder
communicate together, and have only one port made in the upper surface of the
slide valve. The part of this valve is to prevent the steam being let into the
cylinder simultaneously at each end of the cylinder, and and to form and to open a
passage for the discharge of the steam.
The change of position is made abruptly at the end of each stroke of the piston,
a little before the crank arrives at the dead point. When this has been passed the
valve has completely changed its position. This valve is surrounded by a stirrup
leaving the valve free to rise; the stirrup is fixed to a rod connected with the
eccentric stirrup. The eccentric is of special form; it is composed of a segment or
cam, which at each half turn of the crank shaft on which it is fixed acts against
rollers fixed on the eccentric stirrup and moves the slide valve, which keeps the
position whilst the roller is in contact with the cam or segment, that is, for half a
turn of the axle, then the segment acting on the opposing roller of the eccentric
stirrup, and the valve is again moved to the contrary position and during the next
half, and so on.
The second part is a movable partition or bell valve applied upon the slide
valve, and maintained in the position in the length of the steam valve chest by
grooves in which it works cut in the sides of the valve chest, so that it can descend
vertically as it wears but has no lateral motion; the lower edges work on the upper
face of the distributing valve; the cavity covers the upper part of the distributing
valve in any position that this latter takes. In the upper part of the bell valve
or cover is a hole or port, putting thus the interior of the steam chest in
communication with the cylinder.
The third part is a valve resting on the opening or last mentioned port of the
bell valve, working on the bell valve upper face and stopping the port as required.

page_text: It is attached to a rod passing through its upper part by two screws on the rod,
rigid as to the length, but leaving the valve free to play in the valve chest to
adjust itself for wear. The pressure of the steam keeps the valves pressed
together.
The arrangement of the three parts allows this expansion valve by only one
movement to open the port in the bell valve, and pass the steam on to the
distributing valve. The movement of this valve is given at each end of the piston's
stroke by the following automatic movement :-
The rod of this expansion valve is connected with a lever fixed on a small axle,
so that when the axle is rocked the valve is moved; the axle itself is actuated by a
grooved sleeve sliding on the rock shaft, which has a web in the sense of its length;
to this sleeve is attached an arm or lever which is acted on by two cams on the
crank axle, the cams increasing or decreasing on the length of the shaft, so that
the sleeve may be moved more or less as the sleeve is moved in the direction of the
length of the shaft, and thus greater or less action is given to the valve rod. The
sleeve is acted upon so as to slide along the rock shaft by a lever in connection
with a governor driven from the shaft in the usual way. Each stroke of the piston
puts one or other of the cams in motion, and the increasing or decreasing velocity
of the governor sliding the sleeve for the lever to be acted on by the greater or
less inclination of the cams, affects the action of the rod in connection with the
expansion valve; an oil pump is added to the governor levers to avoid too great
shocks.
The rod of the expansion valve is made of larger diameter where it passes out
of the valve chest, so that it may be acted on by the pressure of the steam. The
difference of the diameter is calculated in relation to the resistance to be overcome
to move the expansion valve, and this action is contrary to the line of force of the
variable cams.
.
To avoid shock an air pump is fixed at the end of the expansion valve rod at
the end of the valve chest.