Year: 1888

page_text: I, BIRGER SJÖVALL of the Motala Works in the Kingdom of Sweden, Engineer, do
heroby declare the nature of this invention to be as follows:-
-
This valve gear is specially designed for steam engines having two cranks set at
right angles or nearly so, and with the valve chests placed at the front of tho
engine.
According to my invention each slido-valve-spindle is provided with a cross lever,
the two ends of which receive motion respectively from the two cranks, one end from
one of the cranks and the other end from the other crank. The centre of the lever
or the valve spindle thus obtains a resulting motion, as from an ordinary eccentric.
On sheet I of the illustrative drawings hereunto appended an ordinary two-cylinder
engine is diagrammatically shown, fitted with valve gear according to this invention;
the full lines and the capital letters represent the nearer cylinder with its moving
parts the further or rear cylinder with its parts is represented by the letters of the
swall alphabet and by dotted lines.
The piston rods are A and a, the connecting rods B and b, the cranks C and c; on
the slide. valve spindles D and d are pivoted cross levers E and e with gudgeons in
both ends. Two rocking shafts 1 and 2 parallel to the crank shaft are worked by
means of levers G and g, which are connected by links F and to the cross heads of
the piston rods; these links may, however, be connected to the connecting rods or to
the cranks. The ends of the rocking shafts which are opposite to the levers G and
are provided with curved links (coulisses) H and firmly fixed to the shafts but
allowing the blocks Mand m to be moved along the said links H and h. The blocks M
and m are by means of rods I and i connected to the one end of the cross-levers E
and e respectively; the position of the sliding blocks may be altered by means of the
reversing shaft 3 with its levers and suspending rods Land 4, for varying the cut-off
and reversing the motion. The opposite ends of the cross-levers E. and e are
connected by means of rods K and k to short levers on the rocking shafts opposite to
the levers G and g.
In the position of the reversing levers, which is shown on the drawing, the cranks
are moving in the direction of the arrow, and the rods K and k move in the opposite

page_text: direction to the cranks, while the rods I and i move as if they were worked by
eccentrics running 90° before the cranks. The slide valve spindles D and d receive
thus a resultant motion from the two different motions working on the ends of the
cross levers E and e.
If, by turning the reversing shaft 3, the blocks M and m
are removed to the opposite ends of their respective links, the rods I and receive a
motion as if they were worked by eccentrics running 90° after the cranks in this
case the motion of the engine is reversed.
The figures on Sheet 1 show the practical application of this valve gear to engines
with cylinders of different sizes, for instance as in an ordinary compound engine.
Figure 2 is a front elevation and Figure 4 a plan of such an engine; figure 1 shews
the low-pressure cylinder with its valve gear, figure 3 the high pressure cylinder and
valve gear; figure 5 is a horizontal section through the engine à little above the
rocking shafts.
The valve gear for the low pressure cylinder (figuro 4) is the same as that herein
above described with reference to the dotted lines of Sheet I, all parts are also
marked with corresponding letters. As regards the high pressure cylinder, on the
contrary, it will be seen that the rod K is moving not opposite to but directly with
the crank C, and the rod I moves as if it were worked by an eccentric running 90° after
the crank when the engine shaft is moving in the direction of the arrow; the resultant
motion on the slide valve spindle will be such as if it were worked by an eccentric
placed diametrically opposite to the usual position. The steam must therefore enter
on the inside of the valve and exhaust at the outside of it, for which reason it is
necessary to use a piston valve or its equivalent. This special arrangement for the
high pressure cylinder, designed to allow the slide valve to be placed nearer to the
cylinder, has besides the advantage that the stuffing box of the slide valve spindle
will only be exposed to the pressure of the exhaust steam from this cylinder.
By altering the positions of the sliding blocks on the links H and any desired
cut off may be obtained. If the ratio between the two arms of the cross levers E
and e is made changeable, the cut off in one cylinder can be varied independently
of the other.
"
This arrangement of valve gear may be used not only for two-cylinder but also
for three-and four-cylinder engines, if only the cranks are two in number.
It is to be understood that the details of the arrangement are susceptible of
variation to suit different applications and requirements; for instance, it is indifferent
which of the two rocking shafts is worked by the high- or low-pressure cylinder;
the levers G and g may be connected to either of the sides of the cross-heads or to
both sides; the rods K and k may be connected either directly to the lovers G and g
or to special levers on the rocking shafts.
The advantages of this valve gear are:
1° That the valve chests may be placed on the front of the engine, by which
arrangement the engine will be shorter and the valve chests more easily accessible.
2° That eccentrics are dispensed with; these occupy much space on the crank
shaft, cause great loss of power through friction and often get heated.
3° As each of the rods I and i as well as K and only do about the half of the
work of moving the slide valve spindle, the pressure on the pins and on the sliding
block will be only about the half of the pressure on corresponding parts in ordinary
valve gears; in case of wear in the block or in one of the pins, only the half of the
error is transferred to the slide valve spindle.
4° The lead, or opening of valve at commencement of the stroke, is constant at
different cut-offs.
5° The construction of the valve diagrams and the determining of the various
parts of the gear are extremely simple.
Dated this 26th day of March 1888.

page_text: I, BIRGER SJÖVALL, of the Motala Works in the Kingdom of Sweden, 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:-
Valve gear according to this invention is specially designed for steam engines
having two cranks set at right angles or nearly so and with the valve chests placed
at the front of the engine.
According to my invention each slide valve spindle is provided with a cross
lever the two ends of which receive motion respectively from the two cranks one
end from one of the cranks and the other end from the other crank. The centre
of the lever or the valve spindle thus obtains a resulting motion as from an ordinary
eccentric.
Referring to the drawings filed with my provisional specification
On sheet 2 an ordinary two cylinder engine is diagrammatically shewn fitted
with valve gear according to this invention; the full lines and the capital letters
represent the nearer cylinder with its moving parts: the further or rear cylinder
with its parts is represented by the small letters and by dotted lines.
The piston
rods are A and a, the connecting rods B and 6; the cranks C and c;
on the
slide valve spindles D and d are pivotted cross, levers E and e with gudgeons in
both ends. Two rocking shafts 1 and 2 parallel to the crank shaft are worked by
means of levers G and which are connected by links F and to the crossheads of
the piston rods; these links may however be connected to the connecting rods or to
the cranks. The ends of the rocking shafts which are opposite to the levers G and y
are provided with curved links (coulisses) H and h, firmly fixed to the shafts, but
allowing the blocks M and m to be moved along the said links H and h. The
blocks M and m are by means of rods I and i connected to the one end of the cross
levers E and e respectively the position of the sliding blocks may be altered by
means of the reversing shaft 3 with its levers and suspending rods Land for varying the
cut off and reversing the motion. The opposite ends of the cross levers E and e are
connected by means of rois K and k to short levers on the rocking shafts onnosite to
the levers G and g.

page_text: In the position of the reversing levers which is shewn on the drawings the cranks
are moving in the direction of the arrow and the rods K and move in the opposite
direction to the cranks, while the rods I and i move as if they were worked by
eccentrics running 90° before the cranks. The slide valve spindles D and receive
thus a resultant motion from the two different motions working on the ends of the
cross levers E and e.
If by turning the reversing shaft 3 the blocks M and m are removed to the opposite
ends of their respective links the rods I and i receive a motion as if they were
worked by eccentrics running 90° after the cranks; in this case the motion of the
engine is reversed.
The figures on sheet I shew the practical application of this
valve gear to engines with cylinders of different sizes; for instance as in an ordinary
compound engine.
Fig. 2 is a front elevation and fig. 4 a plan of such an engine; fig. 1 shews the
low pressure cylinder with its valve gear, fig. 3 the high pressure cylinder and valve
gear fig. 5 is a horizontal section through the engine a little above the rocking
shafts.
The valve gear for the low pressure cylinder (Fig. 4) is the same as that herein-
above described with reference to the dotted lines of sheet 1; all parts are also marked
with corresponding letters. As regards the high pressure cylinder, on the contrary,
it will be seen that the rod K is moving not opposite to but directly with the crank C,
and the rod I moves as if it were worked by an eccentric running 90° after the
crank when the engine shaft is moving in the direction of the arrow; the resultant
inotion ou the slide valve spindle will then be such as if it were worked by an
eccentric placed diametrically opposite to the usual position. The steam must therefore
enter on the inside of the valve and exhaust at the outside of it for which reason it is
necessary to use a piston valve or its equivalent.
This special arrangement for the high pressure cylinder designed to allow the slide
valve to be placed nearer to the cylinder has besides the advantage that the stuffing
box of the slide valve spindle will only be exposed to the pressure of the exhaust
steam from this cylinder."
By altering the positions of the sliding blocks on the links H and any desired
cut off may be obtained. If the ratio between the two arms of the cross levers E
and e is made changeable the cut off in one cylinder can be varied independently
of the other. This arrangement of valve gear may be used not only for two cylinder
but also for three and four cylinder engines if only the cranks are two in number.
It is to be understood that the details of the arrangement are susceptible of variation
to suit different applications and requirements; for instance it is indifferent which
of the two rocking shafts is worked by the high or low pressure cylinder the
levers G and g may be connected to either of the sides of tho crossheads or to both
sides; the rods K and & may be connected either directly to the levers G and y or
to special levers on the rocking shafts.
.
The advantages of this valve gear are:
1st. That the valve chests may be placed on the front of the engine, by which
arrangement the engine will be shorter and the valve chests more easily accessible.
2nd. That eccentrics, are dispensed with; these occupy much space on the crank-
shaft, cause great loss of power through friction and often get heated.
3rd. As each of the rods I and i as well as Kand, only do about the half of
the work of moving the slide valve spindle the pressure on the pins and on the sliding
block will be only about the half of the pressure on corresponding parts in ordinary
valve gears; in case of wear in the block or in one of the pins, only the half of the
error is transferred to the slide valve spindle.
4th. The lead or opening of valve at commencement of the stroke is constant at
different cut offs.
5th. The construction of the valve diagrams and the determining of the various parts
of the gear are extremely simple.

page_text: Having now particularly described and ascertained 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 valve gear for steam engines with two cranks set at right or nearly right angles,
consisting of cross levers. pivotted respectively to each slide valve spindle, the one end
of each such cross lever receiving a motion from the crank of the same cylinder, and
the other end a motion from the other crank, which last mentioned motion may be
increased, diminished or diametrically reversed for varying the cut off and reversing
the engine substantially as set forth.