An Improved Construction of Steam Engine with Variable Expansion Gear, more particularly applicable for Motor Cars for Tramways and Common Roads.
Year: 1898

page_text: Date of Application, 21st Dec., 1898-Accepted, 11th Feb., 1899
COMPLETE SPECIFICATION.
An Improved Construction of Steam Engine with Variable Expansion
Gear, more particularly applicable for Motor Cars for Tramways
and Common Roads.
I, VALENTIN PURREY, of No. 97, Rue Saint-Lazare, Paris, France, 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 a construction of steam engine especially arranged with
a view to its application for the propulsion of motor cars on tramways and common
roads, but which is also applicable to a number of other purposes.
I will describe the said construction with reference to the accompanying draw-
ings, which shew the engine applied by way of example, as a horizontal two
cylinder engine.
Figure 1 shews a part sectional plan and part plan of the engine the section
being taken on line - Figure 2, which shews an end view.
Figure 3 shews a part end view and part cross section of the slide and expansion
valve the section being taken on line c d Figure 1.
Figure 4 shews a part sectional plan of the engine and reversing gear, taken on
line ab Figure 2.
Figure 5 shews a vertical longitudinal section of the said reversing gear, taken
on line e f Figure 1. Figure 6 shews a cross section on line
I h Figure 5.
Figures 7, 8 and 9 shew respectively a front view, side view and section on
line ij Figure 7 of the two parts of which the excentric is composed.
Figure 10 shews one of the excentric pins detached.
Figures 11 and 12 shew a side and end view of one of the reversing wedge
pieces; Figures 13 and 14 shew similar views of the other wedge piece.
Figures 15 and 16 shew respectively a front view and an end view of one of the
semi-plates that work the wedge pieces.
The engine possesses the following special features.
The framing, Figures 1 and 2 is cast in one piece, and is constituted by two
cylinders A A with guides CC connected together respectively by the slide valve
box B and by the transverse piece D which I will call the bridge piece and which
carries at its ends the plummer blocks EE for the engine shaft F, having two
cranks GG at right angles to each other. This construction has the advantage
of being very strong and allows the motor engine to be fixed in any required
position to the framing of the vehicle by means of a small number of screw bolts
without its being subject to any deformation such as the vehicle frame may be
liable to.
The steam is supplied to the cylinders by means of variable expansion gear, con-
sisting of two D slides HH receiving reciprocating motion by means of the
rods II of excentrics, having at their middle a flattened portion which afford
them the necessary degree of flexibility. On the backs of the slides HH' are
placed the flat expansion slides JJ¹ K K¹ controlling ports therein, and which
can slide in dove-tail grooves in the slides HH' as shewn at Figure 3. These

page_text: expansion slides move together with the main slides by reason of their adhesion
thereto caused by the steam pressure but such motion is arrested when the pro-
jections L thereon butt against the projections on the two stationary but adjustable
stops MN. As the slides H H' continue their motion the steam ports therein are
suddenly opened and closed by the expansion slides at the moments required for
the cut off.
The stops MN are mounted with right and left handed screw threads on a
correspondingly threaded rod 0, so that by rotating this rod in one direction or
the other by a crank handle, hand wheel or other device the two stops MN can
be moved towards or away from each other thereby varying in corresponding
manner the motion of the expansion slides relatively to the ports of the main
slide. By this means therefore the degree of expansive action of the steam can be
varied between wide limits without stopping the engine.
The reversal of the engine's motion is effected as follows by means of a single
excentric for each slide valve H H.
Each excentric P or P¹ is constructed of two parts of the form shewn at
Figures 7, 8 and 9, which are connected together by means of pins Q, Figure 10,
with countersunk heads; when thus connected as shewn at Figure 4, they form
an excentric disc having a rectangular opening, the larger sides of which can
slide with slight friction upon a square part R, Figure 4, formed on the crank
shaft F. In the said rectangular opening of each disc are engaged two wedges ST
of equal inclination but arranged in opposite directions, and having the form
shewn at Figures 11 to 14. These wedges can slide longitudinally in dovetail
grooves U U formed in diametrically opposite positions on the crank shaft F
parallel with the axis thereof, and consequently by their simultaneous motion in
one direction or the other, the wedges effect a corresponding displacement of the
excentric, to the extent of the total height of the inclined part of the wedges, so
that by this means if the wedges are shifted to the full extent the throw of the
excentrics is shifted relatively to the cranks through an angle of 180°, which is
necessary for reversing the motion of the engine.
The requisite motion is imparted to the wedges for the above purpose, whether
through the entire distance, or through part of the distance only according to the
effect required to be produced, by providing the wedges with projections V of
rectangular section, which projections are engaged with the hollow spaces between
two double plates W W', each of which is formed of two half plates of the con-
figuration shewn at Figures 15 and 16, and fitting with their bevilled edges in a
sliding frame formed by two brackets XX, Figures 2 and 5, which can slide on
the bridge piece D parallel with the shaft F. There exists between the circular
hole of said plates W W and the projections V of the wedges a sufficient amount
of play for allowing the latter to revolve with the crank shaft.
Thus in order to shift the excentrics through 180° on the crank shaft, the
sliding frame is moved in one direction or the other to an extent equal to the
length of the inclines of the wedges, which can be effected while the engine is
running by means of a looped transverse bar Y fixed to the brackets XX and
connected outside the engine frame by a suitable arrangement of levers Z and
connecting rods to a hand lever conveniently placed for the driver.
Having now particularly described and ascertained the nature of this
invention and in what manner the same is to be performed, I declare that what
I claim is;
-
1. In variable expansion gear for steam engines the combination of D slide
valves such as H H₁ actuated by excentrics, and having on their backs loose expan-
sion slides JJ and K K' controlling ports therein and having projections L which
during the travel abut against two stationary stops MN, the distance between
which can be varied by the rotation by hand of a rod having right and left handed
screw threads with which are engaged corresponding screw threads on the stops
substantially as described,

page_text: 2. Reversing gear for steam engines consisting of an excentric disc P mounted
with a rectangular opening upon the engine shaft so as to be capable of shifting
transversely thereon in the plane of the excentric, and wedges ST of equal but
opposite inclination engaged with the rectangular opening of the excentric and
sliding in dovetail grooves on diametrically opposite sides of the shaft, so that
according as the wedges are slid in one direction or the other, the throw of the
excentric is brought either to the one or other of two opposite positions relatively
to the engine crank so as to reverse the position of the slide or it is brought into
any intermediate position, substantially as described.
3. In reversing gear, such as is referred to in the second claim, the combination
with the wedges ST of a sliding frame X carrying plates W engaged with pro-
jections on the wedges in such manner that while these are free to revolve with
the engine shaft and excentric they can be slid by the frame in one direction or the
other for reversing the excentric, the frame being actuated for this purpose by a
looped bar Y and suitable lever gear, substantially as described.
4. A steam engine with variable expansion gear and reversing gear combined
and operating as herein described with reference to the drawings.
Dated this 21st day of December 1898.
ABEL & IMRAY,
Agents for the Applicant.