Year: 1888

page_text: I, NICOLAS ALEXIS BONNEFOND of 23 Boulevard de Strasbourg, Paris in the
Republic of France, Engineer, do hereby declare the nature of this invention to
bo as follows:-
for
My invention relates to the construction and arrangement of the valve gear
locomotive and other engines in such a manner as to facilitate the cut off of the
steam supply at any desired part of the stroke to deaden the shock attending
the sudden closing of the steam valves, and to provide for lead of exhaust without
loss of efficiency. For this purpose, the steam valve for each end of the cylinder,
which may be a slide or a piston valve, has a stem passing through a stuffing box
this stem being of such area that the steam pressure acting on it suffices to close
the valve, and on this stem there is a piston working in a cylindrical cavity of
the slide case.
The interior surface of this cavity has several longitudinal grooves cut
in it, these grooves being deepest at the mouth and dying out towards the end of
the cavity. Thus when the valve is open and the piston at the mouth of the cavity
steam can pass along the grooves so as to occupy the cavity beyond the piston, but
when the valve is free to be closed by the pressure acting on the area of its stem,
this piston in making its stroke closing the valve gradually reduces and ultimately
closes the area of escape by the grooves, and finally has imprisoned beyond it a
cushion of steam which deadens the shock of its sudden stoppage. The stems of
the valves for the two ends of the cylinder are presented towards each other and
terminate in edges between which along the middle of the cylinder a sliding piece
is caused to reciprocate by an eccentric or cam worked by the engine. On this
sliding piece are mounted two triggers each in the form of a bell crank. One limb
of the bell crank terminates in an edge facing the edge at the end of the valve stem,
the other limbs of the two bell cranks travel to and fro between helical wings
projecting from a spindle which is parallel to the main piston rod and is moved
longitudinally, either from the piston rod by a lever reducing stroke or otherwise,
so as to reciprocate always proportionally to the main piston. This spindle passes

page_text: •
through a boss fitted to it with a feather or otherwise so that the spindle can slide
through the boss but must turn with it. The boss being turned more or less round,
turning the spindle, any desired parts of the helical wings on the spindle can be
thus presented to the trigger levers on which they act as tappets, allowing the triggers
to be engaged with the valve stems during a greater or less portion of the stroke of
the sliding piece which carries the triggers. As this piece reciprocates, the edge of one
of its triggers meets the edge of one of the valve stems and presses the valve stem
inwards thus opening the steam supply valve, but when the other limb of the trigger
encounters the helical wing on the spindle, the trigger is disengaged from the
valve stem leaving the valve free to be closed suddenly but without shock, as above
described.
In order to give a desirablo lead to the exhaust slide valve without loss of
efficiency, I arrange the exhaust ports and the gap between the two pistons or ports
of the slide valve which cover those ports so that each port is well opened before the
other is closed, and this opening is made to take place before the main piston quite
completes its stroke so as to give a free exhaust by the one port; but as at this
moment the other exhaust port is still open, it would allow the escape of some of the
fresh steam admitted to the cylinder. To provide against this loss, I make the cylinder.
mouths of the exhaust ports at some distance from the ends of the cylinder so that
the piston in completing its stroke passes over and closes then, thus preventing
issue of the fresh steam and also imprisoning behind it a cushion of steam which acts
along with the fresh steam in propelling the piston.
Dated this 17th day of March 1888

page_text: I. EXPANSION GEAR.
The disengaging of the triggers that control the admission slides or pistons X X¹ is
effected by means of a rod a having a to and fro movement and provided with two
right and left handed screw wings c c', between which are the tappets 66 that serve
to release the triggers. The distance between these tappets and the helical surfaces
of the wings can be varied by the rotation of the rod in the one direction or
the other.
The rod a can be actuated either by an extension of the piston rod, as shown on
the drawing, or by the piston head under analogous conditions, or by an excentric
fixed on the driving crank; in all cases, the travel of this rod will be proportional to
the stroke of the piston and this correlation will admit of the disengaging of the
triggers at any point of this stroke.
It is evident, in effect, that the disengagement will take place earlier or later,
according as the distance travelled by the rod a before the tappets 66 come in
contact with the helical wings c c¹ is shorter or longer. Now this distance is made
variable at will by the rotation of the rod a, as the point of contact of the helical
wings with the tappets &¹is thereby moved forward or backward in proportion to
the extent of turning. The rotation of the rod a is effected by means of a transverse
shaft d which controls the expansion rods of both cylinders through the medium of a
bar e actuated by a screw or lover movement in connection with the governing
mechanism.
The advantage afforded by this system of disengaging or tripping gear combined
with the use of a cam for actuating the slides, over the tripping gear already employed,
is that the duration of admission can be varied between inuch wider limits, namely

page_text: locomotives; and also, that a much greater regularity of the intervals is obtained.
II. ARRANGEMENT OF PISTON FOR PREVENTING SHOCK.
The accompanying drawing shews clearly the arrangement provided for preventing
the shock which would otherwise be produced by the sudden return of the admission
pistons or slides.
The automatic return of these slides is effected by the difference of the surfaces
upon which the steam acts, the difference in diameter of the rods of the piston slides
being made to furnish the necessary differential surface for effecting the return
stroke by the steam pressure.
When the piston slide ƒ is in the position shewn in Fig. 5, that is to say, when
it uncovers the admission port, the annular space behind the buffer piston. is
full of steam at the same pressure as that in the valve box, such steam entering
through four grooves provided for this purpose. When the piston moves
suddenly backward, the steam confined behind it can only escape through the same
grooves, the sectional area of which is made to decrease until they entirely
disappear during the last part of the backstroke. The resistance afforded by the
cushion of steam thus obtained consequently increases gradually, thereby gradually
stopping the motion of the piston without shock before the contact with the bottom
of the stuffing box can take place.
This improved arrangement has the advantage that the resistance of the steam
cushion is regulated once for all, the pressure of the steam to be compressed by the
shock being always the same as the pressure of the steam which tends to cause the
shock and consequently the progressive resistance necessary for preventing the shock
is always proportional to the force tending to produce the same, which is not
the case with the arrangements usually employed in stationary machines.
III. POSITION OF THE ESCAPE PORTS IN THE STEAM OYLINDER.
In the arrangement heretofore employed by me, the advance of the admission and
exhaust slides being dependent on each other and simultaneous, the commencement
of the opening of the admission port corresponded, within a small amount, to the
moment of closing the exhaust port on the same side, and to the beginning of
the opening of the exhaust port on the opposite side.
It resulted from this arrangement that the compression was entirely done away
with, but there was also no lead of exhaust. But it is advantageous that the exhaust
should commence somewhat before the end of the stroke, and a small amount of
compression is not disadvantageous.
for
Fig. 6 of the drawings shews the arrangement which I employ for obtaining this
result without otherwise altering the action of the apparatus. The exhaust ports
open into the cylinder at a distanco from each end, such, that they are completely
covered by the piston when at end stroke at or k. It results that the port
example, ceases to allow steam to escape when the edge of the piston packing
arrives at the position shewn in dotted lines, and that consequently there is com-
pression during the remaining 5 or 6 per cent. of the stroke of the piston.
In regulating the distance between the exhaust piston slides m and n as shewn
at Fig. 6, the escape port is partly open before the cylinder-piston arrives at the
end of its stroke towards k, and thus the lead of exhaust is obtained without
inconvenience, as the port is closed by the engine piston; and before it is
uncovered at the return stroke thereof, it will have been closed by the piston slide m
which will have completed its stroke.
By the above described improvements in the variable expansion gear of the kind
referred to, and in employing independent admission slides instead of mounting
them on a common rod as previously employed by me, considerable advantages are
obtained.

page_text: Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The use for the release of the triggers controlling the admission slides, of a
rotatable reciprocating rod provided with two helical wings or flanges, the one.
being inclined to the right hand and the other to the left hand, between which are
situated the disengaging tappets of the triggers, in combination with a cam or
equivalent appliance actuating the slides, whereby the expansion can be varied
between 0 and 90 per cent. of the piston's stroke, by simply turning the said rod
with helical threads in one direction or the other, substantially as herein described
with reference to Figs. 1 to 4 of the drawings.
2. The arrangement of admission slides with differential pistons in which the
differential pressure producing the sudden return stroke results from the difference
of arca caused by the difference of diameters of the rods of the two pistons
substantially as herein described with reference to Figs. 3 and 5 of the drawings.
3. Preventing shocks resulting from the sudden return of the admission slides by
providing a cushion of steam behind a buffer piston connected to the slide, which
cushion offers increased resistance to motion as it is compressed, such resistance
being always in proportion to the forco that tends to produce the shock, substan-
tially as herein described with reference to Figs. 3 and 5 of the drawings."
4. The arrangement of the exhaust ports of the steam cylinder at a small distance
from the ends thereof so that the piston in approaching the end of its strokes, passes
beyond and entirely covers these ports, thereby affording a compression during the
remaining part of the stroke, in combination with an arrangement of the exhaust
slides, such, that the exhaust ports shall be opened thereby before the engine piston
has arrived at the position in which it closes the exhaust port, whereby the desired
lead of the exhaust is obtained substantially as herein described with reference to
Fig. 6 of the drawings.
5. The general improved arrangement of valve gear with variable expansion by
the use of independent admission slides as heroin described with reference to Figs. 1
to 5 of the drawings.