IMPROVEMENTS IN SLIDE- VALVE GEAR FOR STEAM ENGINES
Year: 1879

page_text: LETTERS PATENT to Henry Simon, of No. 7, St. Peter's Square, Manchester,
in the County of Lancaster, for the Invention of IMPROVEMENTS IN SLIDE-
VALVE GEAR FOR STEAM ENGINES." A communication from abroad by Georg
Klug, of Hamburg, iu the German Empire.
PROVISIONAL SPECIFICATION left by the said Henry Simon at the Office
of the Commissioners of Patents on the 12th August 1879.
HENRY SIMON, of No. 7, St. Peter's Square, Manchester, in the County of
Lancaster. "IMPROVEMENTS IN SLIDE VALVE GEAR FOR STEAM ENGINES." [A
communication from abroad by Georg Klug, of Hamburg, in the German
Empire.]
In the ordinary mode of working slide valves of steam engines by eccentrics the
valve motion is such as to give the one end of the cylinder an appreciably greater
steam supply when cut-off and expansion is used than the other end, and as such
greater steam supply is that which drives the piston towards the crank, the weight
of the piston, piston rod, and connecting rods assists in rendering the motion of the
engine unequal when this has vertical inverted cylinders. Furthermore, with such
ordinary slide valve gear two eccentrics are required for varying the cut off and for
reversing.
According to the present Invention a construction of slide valve gear is employed
whereby such unequal steam supply is obviated, and whereby with a single
eccentric the cut-off can be varied and the reversing effected. The Invention
consists mainly in providing the eccentric with a short arm that is connected at its
free end to the slide rod situated at right angles to the middle position of the
eccentric, while at an intermediate position the arm works on a centre or fulcrum
that can move to and fro in a circular arc, so that the free end of the eccentric arm
performs an approximate elliptical motion which is compounded of that resulting
from the ordinary excentric motion and that resulting from the said curvilinear
motion of the fulcrum. When no reversal of the engine and no variation in the
cut-off is required the above mentioned motion of the fulcrum will always be the
ID 237

page_text: same, but when reversal and variation of cut-off are required the motion of the
fulcrum is render variable by suspending it by a link from a lever whose fulcrum
coincides with the position of the said fulcrum of the eccentric arm when in its
middle position, so that when such lever with the upper end of the suspension
link is moved over to its most angular position in the direction towards the free
end of the eccentric arm, the eccentric will work the slide with the least amount of
cut-off for running forward; when the lever is moved from such position towards
a middle position at right angles to the middle position of the eccentric arm the
degree of cut-off is increased; when in such middle position there is no motion of
the slide and the engine is stopped; when the lever is moved over to the other side
of such middle position the motion of the engine is reversed, the degree of cut-off
being decreased as the lever is moved farther away from the middle position.
By this arrangement when the engine is running forward, with about 0.60 cut
off, there is an equal steam supply on both sides of the piston; when the cut-off is
increased the steam supply becomes slightly unequal, that to the underside of the
piston becoming greater than the other, which is beneficial to the smooth working
of the engine; when the engine is reversed there is for all degrees of cut-off a slight
excess of steam supply on the underside. Lastly, in all cases the slide may be
made to open the ports for the underside of the piston quicker and wider than
those for the upper side. The before described lever from which the fulcruin of the
eccentric arm is suspended works in a quadrant slot having a bevil groove in which
slides a bevil tongue on the lever, the groove being capable of being tightened up
by a screw, so as to hold the lever securely in whatever position it is moved into.
In addition the lever carries a spring catch, taking into notches formed on the
quadrant in such positions as to correspond with the positions of the lever for
certain degrees of expansion.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Henry Simon in the Great Seal Patent Office on the 28th January
1880.
"
A
HENRY SIMON, of No. 7, St. Peter's Square, Manchester, in the County of
Lancaster. IMPROVEMENTS IN SLIDE-VALVE GEAR FOR STEAM ENGINES."
communication from abroad by Georg Klug, of Hamburg, in the German
Empire.
In the ordinary mode of working slide-valves of steam-engines by eccentrics the
valve motion is such as to give the one end of the cylinder an appreciably greater
steam supply when cut off and expansion is used than the other end, and as such
greater steam supply is that which drives the piston towards the crank, the weight
of the piston, piston-rod, and connecting-rods assists in rendering the motion of the
engine unequal when this has vertical inverted cylinders. Furthermore, with such
ordinary slide-valve gear two eccentrics are required for varying the cut off and for
reversing.
According to the present Invention a construction of slide-valve gear is employed
whereby such unequal steam-supply is obviated, and whereby with a single
eccentric the cut-off can be varied and the reversing effected. The Invention
consists mainly in providing the eccentric with a short arm that is connected at its
free end to the slide-rod situated at right angles to the middle position of the
eccentric rod, while at an intermediate position the arm works on a centre or
fulcrum that can move to and fro in a circular arc, so that the free end of the
eccentric arm performs an approximately elliptical motion which is compounded of
that resulting from the ordinary eccentric motion, and that resulting from the said
curvilinear motion of the fulcrum. When no reversal of the engine and no variation
in the cut-off is required the above-mentioned motion of the fulcrum will always
be the same, but when reversal and variation of cut-off are required the motion of
the fulcrum is rendered variable by suspending it by a link from a lever whose
fulcrum coincides with the position of the said fulcrum of the eccentric arm when
in its middle position, so that when such lever with the upper end of the suspension
link is moved over to its most angular position in the direction towards the free
end of the eccentric arm, the eccentric will work the slide with the least amount of
expansion for running forward; when the lever is moved from such position
towards a middle position at right angles to the middle position of the eccentric arm
the degree of expansion is increased; when in such "middle position there is a
motion of the slide equal to the opening when the engine is at dead centres and the
engine is stopped; when the lever is moved over to the other side of such middle
position the motion of the engine is reversed, the degree of expansion being
decreased as the lever is moved farther away from the middle position.
By this arrangement when the engine is running forward with about 0.60 cut-
off there is an equal steam-supply on both sides of the piston; when the cut off is
increased the steam supply becomes slightly unequal, that to the underside of the
piston becoming greater than the other, which is beneficial to the smooth working
of the engine; when the engine is reversed there is for all degrees of cut-off a
slight excess of steain on the underside. Lastly, in all cases the slide may be made
to open the ports for the underside of the piston quicker and wider than those for
the upper side. The before-described lever from which the fulcrum of the eccentric
arm is suspended works in a segment slot having a bevil groove in which slides
a bevil tongue on the lever, the groove being capable of being tightened up by_a
screw so as to hold the lever securely in whatever position it is moved into. In
addition, the lever carries a spring catch, taking into notches formed on the segment
in such positions as to correspond with the positions of the lever for certain degrees

page_text: gear, but can
ccording to circumstances
be variously modified. The slide gear contains in its principle of construction the
conditions for doing away with certain inequalities of the slide-motion; but as within
certain limits the extent of these inequalities, as also the determination as to which
end of the cylinder shall have the advantage, are dependent upon the judgment of
the constructor, the latter is by the above-described Invention afforded not only a
corrective for the irregularities before referred to, but also the means of arranging
the distribution of steam, so that it shall act in an equalizing manner relative to
the one-sided action of the momentum of the moving parts.
DESCRIPTION OF THE DRAWINGS.
Fig. 1 shews a side-view of the slide-gear with its connection to the slide in
section; Fig. 2 shews a sectional plan on line X, X; and Fig. 3 shews a vertical
section on line Y, Y. The slide gear has only one eccentric E lying in the line of
the engine crank, and whose comparatively short rod E, F, C, operates in a similar
manner to a straight double-ended lever that travels with its fulcrum and pivot F
to and fro in a circular arc. The slide motion is at right angles to the middle
position of the eccentric rod, and consequently the eccentric and slide rods C, D,
are connected together at right angles to each other (when in the middle position).
For producing the movement in a circular arc of the fulcrum F of the eccentric-rod
this is suspended at that point from a link F, G, that during the motion of the
eccentric oscillates like a pendulum upon the pivot G.
If the engine were intended to work always with one and the same degree of
cut-off, the fulcrum F would have to move always in one and the same path, and
consequently the point of suspension G could be absolutely fixed.
In the gear shewn on the Drawing, which is intended for variable cut off and
reversing, the point of suspension G of the link is connected to a moveable frame
and can be moved with the same in a circular arc, the centre M. of which lies in the
line of the middle position of the excentric rod. This point M can be considered as
the centre of the entire system.
If the frame M, G, should stand vertically upon the centre line of the excentric
rod at its middle position the engine will stand still; on moving the frame to the
one or the other side the engine will be caused to run in the one direction or the
other, and with a cut off increasing with the extent to which the frame is so
moved.
If with this construction,-
1. The length M, G, of the frame is accurately equal to the length G, F, of the
link.
2. The lines connecting the centre of the excentric E, the centre of the shaft W,
and the centre of the bearing M of the frame form a right angle when the crank is
on the dead centre, and
3. The length E, F, of the excentric rod is equal to the hypothenuse of this
triangle; than the points F and M will at the dead centre of the crank always
coincide, no matter how the gear may be situated relative to the degree of cut off
and the direction of motion of the engine, that is to say, in the dead centre position
of the crank the reversing of the gear will not be accompanied by any motion of
the excentric and slide rods, and the lead of the slide will be always the same for
all degrees of cut off and direction of motion of the engine.
The excentricity is comparatively small and does not alone determine the extent
of travel of the slide, which at large degrees of cut off may amount to double the
throw of the excentric. The travel of the slide varies with the degree of cut off
and is least when the slide gear is at "stop." "
As compared with the ordinary excentric slide gear the movement of the slide
here takes place rapidly at the times of opening and closing, and slowly while the

page_text: ports are open or closed; also in all positions of the slide gear there is a more rapid
and greater opening of one of the steam ports. This giving a greater or less
advantage to one end of the cylinder depends upon the less or greater length of the
link F, G, while the choice of the cylinder end to which the advantage is to be
given is determined by the position of the link on the one or the other side of the
eccentric.
A consideration of the curves shewn at C, Fig. 1, will make clear what has been
stated respecting the slide motion. In these curves the several points give the
positions of the eccentric rod and slide rod centres C for tenths of the piston stroke
during one stroke respectively of the forward and the backward motion of the
engine. The distance of these points from the lines X, X, X, X, and Y, Y, indi-
cating respectively the outer and inner lap or closing of the slide gives accurately
the opening and closing of the slide for the said positions of the piston and slide
gear. These curves are easily found by construction in proceeding from the corre-
sponding positions of the eccentric marked on the circular path of the latter.
Having thus described the nature of the said Invention, and in what manner
the same is to be performed, as communicated to me by my foreign correspondent,
I claim,―
The construction and application of reversing valve gear where the eccentric rod
works as a doubled ended lever and the fulcrum of the latter is guided in a circulur
arc of changeable direction, by which means valve motion is produced at the end
of the eccentric rod in a direction at right angles to the middle position of the rod,
substantially as herein described with reference to the accompanying Drawings.
In witness whereof, I, the said Henry Simon, have hereunto set my hand
and seal, this Twenty sixth day of January, in the year of our Lord One
thousand eight hundred and eighty.
HENRY SIMON, (L.S.)