Improvements in Steam Engines:
Year: 1893

page_text: Date of Application, 27th Dec., 1893-Accepted, 10th Feb., 1894
COMPLETE SPECIFICATION.
Improvements in Steam Engines:
I, ADOLF LAVAUD, of 2 Prince Albrechtstrasse, Berlin, S.W. Germany,
Engineer, do hereby declare the nature of this invention and in what manner
the same is to be performed, to be particularly described and ascertained in and
by the following statement :-
This invention relates to steam engines and it has mainly for its object to obtain,
the instant the live steam is admitted to the cylinder, an immediate and uniform
pressure on the surface of the piston. The inlet to and outlet of steam from the
cylinder is also regulated and controlled in an improved manner.
In carrying out my invention I fit a ring shaped slide valve in the cylinder cover
and this valve is reciprocated by mechanism actuated from an eccentric on the
driving shaft of the machine.
And in order that my said invention may be properly understood, I have hereunto
appended an explanatory sheet of drawings, whereon,
Fig. 1 is a longitudinal section of the cover of a cylinder having my valve gear
fitted thereto.
Fig. 2 is a cross section on the line x-x, and Fig. 3 a cross section on the
line y-y Fig. 1.
Fig. 4 is a horizontal section through the centre of the cylinder showing the
slide valve and its connections.
Figs. 5 and 6 show in part the valve gear for both ends of the cylinder.
Referring to the drawings :-
The steam enters at a (Fig. 1) and passes into the annular space A', round the
interior shell of the cylinder A. From the space A' the steam passes to the annular
chamber 6 formed in the cover B. If the ring-shaped slide valve c, which is
D shaped in section, is moved to the left hand, (as hereinafter described) then the
ports d, which are shown in Fig. 1, as closed by the spring ring of the slide valve,
are opened and live steam passes from the annular chamber 6 through the ports bl
(Fig. 3) to the interior of the cylinder A and bears against the back of the
piston G. As will be seen from Fig. 1 the steam enters through the ring series of
ports d, at the centre of the cover and distributes itself radially all over the back
of the piston and therefore produces an immediate and uniform pressure over its
surface.
The spring ring f has, in it, at intervals, holes f¹ so that steam may pass from
the cylinder A, when the piston slide-valve c is at the mid position, behind the
spring ring and equalize the steam pressure on both of its sides.
If the slide valve is moved towards the right hand then the ports d are opened
for the steam exhaust. The escaping steam passes (see arrows) through the annular
space left between the slide valve c and the piston rod D, into the chamber e and
from thence to the atmosphere.
The motion of the slide valve e is produced as follows:-
An eccentric (not shown) on the main shaft is connected by an eccentric rod
with the bar h and reciprocates it. A bolt i¹ is secured to said bar and on this bolt
a bell-crank is securely fixed. The bell-crank, which has a tapered end k, is
normally pressed by a weak spring against the stud ". The horizontal arm of
the bell-crank has a hardened steel end which bears against the long arm of a
Both of the fork arms, m²,
lever pivotted at 2 to the end of the rocking lever m.
of the rocking lever m (Fig. 2) are pinned to jaws o on the outer end of the slide
valve c.
Clearance spaces m¹ are left around the pins.

page_text: Now, if the bar h (Fig. 5) is moved to the left the horizontal arm of the bell-
crank i will bear against the upper end of the lever and turn it slightly round at
the same time, as the lever is rigidly secured to the rocking lever m, turning it also,
and, as a consequence, moving the slide valve e to the left hand and opening the
ring ports d for the inlet of steam. The ports remain open so long as the end k of
the bell crank bears against the collar of the box r on rod q. As the bar h
travels forward the bell-crank (as its end, k, bears against said collar n) is gradually
turned over until the horizontal arm is eventually disengaged from the upper end
of lever (see Figs. 5 & 6).
Immediately the horizontal arm is disengaged, as aforesaid, the spring p, which is
in a box cast on the cylinder A, exerts its influence on the rod p (connected to the
lower end of lever ) and pulls back the lever to its former position, at the same
time turning the rocking lever m and reversing the movement of the slide valve c
and cutting off further steam supply to the cylinder A.
As will be seen if an early cut off is desired, it is necessary to cause the end k of
bell-crank to strike, at an early period in the stroke of the piston, against the
collar or rod y, and to produce a late cut off, the time of contact must be
delayed.
The period of cut off is regulated by means of a rod 7 which is directly connected
to the regulator of the engine by means of the arm s. The plug N, which has a
quick screw thread cut on it, is screwed into the box r, which is fixed to the rod q
and serves practically as a nut.
7 is a spring wedge for securing the plug N to the rod 7. This wedge q' can
travel as shown in a slot in the rod q. Now, if, by the action of the regulator, the
arms and rod is turned to the left or right the box is caused to turn in either
direction and consequently screw the plug N either inwards or outwards and
thereby lessen or increase the space between the collar n and the arm k of the bell-
crank i
The opening of the ports d is effected by means of bolt t, which is rigidly fitted
in the bar and has a steel roller t' at its end. When the bar his moved to the
right the roller bears against the lever and moves it and the rocking lever m and
slide valve e to the right, thereby opening the ports d and allowing the steam to
exhaust from the cylinder. The ports remain open until the bar his again moved.
to the left hand, when the influence of the spring p again brings the lever / and
slide valve back to the normal or mid position.
C
By the use of a second bell-crank i and its pin the steam exhaust could be
suddenly closed.
A single eccentric serves to move the bars h, h, and the mechanism connected
therewith at both ends of the cylinder.
In order to turn the rod 7 only a very small power is required and as a
consequence a small and a very sensitive regulator may be used to govern the
engine.
The cut-off can be varied from 0 to 0.9.
The valve motion is suitable for either horizontal or vertical engines, in the
latter case the slide valve may be made very light.
In the case of fast running engines the rocking lever m may be connected direct
to and be operated directly by the eccentric rod.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
consider novel and desire to claim is :-
1. In steam engines a slide valve fitted in the cylinder cover and having a circular
or ring shaped inlet and exhaust port (or a number of ports or passages arranged in
a ring) so arranged that the steam on entering the cylinder spreads from the centre
radially in all directions over the surface of the piston and produces an immediate
and uniform pressure on its surface, substantially as hereinbefore described with
reference to the drawings annexed.
-

page_text: 2. The combination of the rod q, actuated by a regulator, box or nut and
screwed plug N, substantially as and for the purpose hereinbefore set forth.
3. The general arrangement and combination of parts of the valve gear, substan-
tially as herein before described and shown on the drawings annexed.
Dated this 25th day of December 1893.
H. D. FITZPATRICK,
70, Wellington Street, Glasgow, Agent.