Improvements in Locomotive Engines.
Year: 1889

page_text: Date of Application, 21st May, 1889
Complete Specification Left, 8th Feb., 1890-Accepted, 8th Mar., 1890
PROVISIONAL SPECIFICATION.
Improvements in Locomotive Engines.
I JULES THÉODORE ANATOLE MALLET of 128 Boulevard de Clichy, Paris,
France, Civil Engineer, do hereby declare the nature of this invention to be as
follows:-
My invention relates to compound locomotive engines and it consists in placing
the high and low pressure cylinders one in front of the other tandem fashion in the
longitudinal centre line of the engine instead of placing the two cylinders side by side
with n the frames, or one at each side of the engine outside the frames as in ordinary
locomotives.
The piston rods of the two cylinders arranged as above described are independent
each driving a centrally cranked axle, the wheels of the two cranked axles being
coupled in the ordinary way with their cranks at right angles to each other.
Or one of the pistons may drive a central crank and the other piston may by means
of a cross head and two outside connecting rods, drive outside cranks on the same axle
but at right angles to the centre crank, said axle being either independent of or coupled
with the other axles. By the above described arrangements the two following important
advantages are obtained.
1st. The effort of the pistons is exerted only in the longitudinal axis of the engine,
thus avoiding the oscillation due to the alternate action of the pistons situated at the
opposite sides as in ordinary engines and ensuring greater stability when running at
high speeds.
2nd. By placing the low pressure cylinder in the longitudinal axis of the engine,
the whole width between the sido frames is available and the cylinder can be three feet
or more in diameter.
Dated this 21st day of May 1889
COMPLETE SPECIFICATION.
Improvements in Locomotive Engines.
1, JULES THÉODORE ANATOLE MALLET, of 128 bts Boulevard de Clichy, Paris,
France, Civil 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 :-
My Invention relates to what are known as compound locomotive engines in which
the steam acts successively in two cylinders of different diameters; and it consists in
placing the high and low pressure cylinders one in front of the other, tandem fashion,
in the longitudinal centre line of the engine, the pistons of said cylinders acting on
cranks at right angles to each other.
The Invention is illustrated in the accompanying drawings, figure 1 of which
represents an elevation, and figure 2 a plan, of a six-wheel coupled locomotive in which
the high and low pressure cylinders are arranged tandem-wise in the longitudinal
centre line of the engine.
The low-pressure cylinder L P is coupled to the central crank on the axle b of the
second pair of wheels through the connecting rod a while the high pressure
cylinder H P is coupled, by means of a cross-head c and side connecting rods d d

page_text: to outside crank pins on the leading axle, which crank pins are necessarily in the same
line. In order, however, that the axles may be coupled with their coupling cranks at
opposite sides of the engine at 90° to each other the driving crank pins of the leading
axle carry return cranks e (the two return cranks of the leading axle being respectively
shewn in full and dotted lines in figure 3) from which it will be seen that the couplings
at opposite sides of the engine deviate in opposite directions to the extent of 45° from
the position of the driving cranks. By this arrangement, the strokes of the two
pistons are alternated as though they drove direct cranks at 90° to each other. By
placing the two cylinders tandem fashion in the longitudinal centre line of the engine,
instead of side by side or at opposite sides of the engine as usual, the two following
important advantages are obtained:-1st. The low-pressure cylinder may be of larger
diameter than in ordinary, limited only by the width between the side frames and may
be as much as 36 inches and even upwards. To obtain an equivalent result, two
cylinders of 25 inches would be required, the engine then having three or four cylinders
instead of two, to which it is desirable to limit it both for simplicity of construction
and to avoid an excessive amount of cooling surface. Moreover the relative volumes
of the two cylinders may be such as to enable a high grade of expansion to be obtained
and allow the valves of the two cylinders to be controlled by gear common to both.
2nd. The cylinders being in the longitudinal centre line of the engine, the oscillation
due to the alternate action of the pistons situated at opposite sides, as in ordinary
engines is avoided and greater stability ensured when running at high speeds for
which this arrangement is eminently adapted. If necessary, the front part of the
engine may be supported on a pair of leading wheels, as indicated in dotted lines in
figure 1.
Figure 4 shews the same principle as applied to an express engine having two pairs
of coupled wheels and a leading bogie. In this case both the high and low-pressure
pistons are coupled to the leading axle, the latter to a middle crank and the former by
a cross-head and side connecting-rods to outside crank pins placed at 90° to the
middle crank and carrying return cranks also at 90° to each other, as in figure 3,
coupled by side rods to those of the trailing axle. The side connecting rods coupling
the cross head to the outside crank pins of the leading axle are made in two parts
jointed together and to a radius lever foscillating on a centre g.
It will be readily understood that the details of the arrangement may be varied,
for example instead of the sliding cross-head a rock shaft may be used having
three parallel lever arms of which the centre one is connected to the high pressure
piston and the others to side connecting rods. The Invention although described as
applied to a coupled engine may be similarly applied to a single pair of drivers,
in which case the coupling rods would not be employed.
.
Figures 5, 6, and 7, shew a modified method of driving for high speed engines
in which the couplings for the two pistons are similar and symmetrically arranged.
The cylinders are placed tandem fashion between the two driving axles, to a central
crank 6 of each of which they are respectively coupled by a return connecting rod
and sliding cross-head connected to the corresponding piston rod by a triangular
or bifurcated extension of the piston rod commonly used in engines having return
connecting rods. The driving axles are coupled by outside cranks and rods which,
owing to the two axles being directly driven, have very little power to transmit.
The fire-box is arched to afford space for the rear driving mechanism and the
leading and trailing axles are radiating. In consequence of the arrangement of
the driving mechanism, the lateral stability of the engine is very great so that the
centre of the boiler will not be an excessive height above the rails. Instead of
either or both of the driving axles being cranked, I may adopt the outside cranks
and connecting rods previously described. The engine may be converted into a
non-coupled engine, by substituting for one pair of drivers a pair of wheels of the
same diameter as the leading and trailing wheels the cranked axle of those drivers
playing the part of a counter-shaft coupled to the driving axle.

page_text: Having now particularly described and ascertaine: the nature of the said inven
tion and in what manner the same is to be performed, I declare that what I
claim is ;
A compound locomotive engine having the high and low pressure cylinders placed
tandem-wise one in front of the other in the centre line of the engine their
pistons being coupled to cranks at 90° to each other by means substantially such
as herein described for the purpose specified.
Dated this σth day
J. T. A. MALLET.
By A. M. & Wm. Clark,
53, Chancery Lane, London, Patent Agents.