IMPROVEMENTS IN VALVE MOTIONS OF STEAM ENGINES
Year: 1885

page_text: This Specification was, upon the 19th day of October 1886, amended under
Sections 18 to 21 of the Patents, Designs, and Trade Marks Act, 1883.
I, WILLIAM SISSON of 10 Florence Place Falmouth in the County of Cornwall
Engineer do hereby declare the nature of said invention for IMPROVEMENTS IN
VALVE MOTIONS OF STEAM ENGINES to be as follows:-
In a Steam Engine in which the valve motion is actuated directly from the
connecting rod, a link forming a connection between a radius rod and a lever, is
pivotted in a suitable position on the connecting rod, and communicates motion to
the radius rod and lever. At mid stroke both the radius rod and the lever are
at right angles (or thereabouts) to a plane in which the centre line of the Engine
lies. In some kinds of Engines having a pump or pumps, worked by a lever, the
lever may be employed to serve as the radius rod in the. improved valve motion.
The radius rod is pivotted about a fixed centre, and the lever is pivotted about a
centre, moveable to and fro, along a path of suitable form the direction of which
(in the plane of the levers notion) can be varied according to requirement; the
valve rod of the Engine is attached to this lever in such a manner that it derives
the motion which it communicates to the valve spindle partly from the vibration
of the lever about its pivot, and partly from the to and fro movement of the lever
which is produced by the oscillation of the connecting rod (acting through the
pivotted link) and which is permitted by the centre about which the lever is
pivotted being moveable as mentioned above. The direction of the path of the
moveable centre regulates and determines the amount of steam admission, the
point of the stroke at which the steam is cut off and the direction in which
the Engine crank rotates. The moveable centre may be guided in the required
path either by means of a suitably formed guide mounted upon a rocking shaft,
or by means of a swinging link suspended from a lever which is secured upon a
rocking shaft. In either of these cases the direction of the path can be altered as
required, by moving the rocking shaft about its centre. Other methods also may
be employed for guiding the moveable centre.

page_text: I, WILLIAM SISSON of 10 Florence Place, Falmouth, in the County of Cornwall,
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:—
In This invention relates to the arrangement as hereinafter described with
reference to the drawings, of a steam engine in which the valve motion is actuated
directly from the connecting rod. A link, forming a connection between a radius
rod and a lever is pivotted in a suitable position on the connecting rod and
communicates motion to the radius rod and lever. At In such an engine, at
mid-stroke both the radius rod and lever are at right angles (or thereabouts) to
the plane in which the centre lines of the engine and of the crank shaft both lie.
In some kinds of engines having a pump or pumps worked by a lever, the lever
may be employed so as to serve also as the radius rod in the improved valve
motion. The radius rod is pivotted about a fixed centre, and the lever is pivotted
about a centre, movable to and fro along a path the direction of which (in the
plane of the lever's motion) can be varied according to requirement; the valve rod
of the engine is attached to this lever in such a manner that it derives the motion
2 which it communicates to the valve spindle partly from the vibration of the lever
about its pivot, and partly from the to and fro movement of the lever which is
produced by the oscillation of the connecting rod (acting through the pivotted
link), and which is permitted by the centre about which the lever is pivotted
being movable as mentioned.
The direction of the path of the movable centre regulates the point of "cut-off"
and also the direction in which the engine rotates. The movable centre may be
guided in its path either by means of a suitably formed guide mounted upon a
rocking shaft, or by means of a swinging link suspended from an arm secured upon
a rocking shaft..
In either of these cases the direction of the path is altered by moving the rocking
shaft about its centre. Other methods also may be employed for guiding the
movable centre.
Figs. 1, 2, 3, 4 in the accompanying sheet of drawings each show each a different
modifications of the improved valve gear as applied to inverted marine engines.
In each case B is the pivotted link, C the radius rod, D the lever, E the swinging
link, and H the valve rod... The link B is pivotted to the connecting rod at the
· point A and is connected with the radius rod O and lever D at the points P and Q
respectively.
In Figs. 1 and 3 the point A is situated between the points P and Q and in
Figs. 2 and 4 it is situated at the lower end of the link. Any other interchanges
in-the-relative-positions of the points A.-P. Q at which the connecting rod, radius
red,-G-and-lever Dare respectively-connected with the pivotted link By-may be

page_text: made as may be round-desirable in order to suit different designs of engines and
different-conditions-under-which-the-engines-may-be-required to work. When-the
point A-is-situated between the points P and Q the radius red C-and-lever D-are
placed at opposite sides of the link B, and when the point-A-is situated-at-either
end-of-the-link, then the radius red and lever are both placed on the-same side
of the link. In the arrangements shown in Figs. 1 and 3 it is convenient with
some designs of engines to interchange the points P and Q so that the radius rod C
is then connected to the lower end and the lever D to the upper end of the pivotted
link B. The ratio between the distances O. P and K. Q corresponds inversely
with the ratio between the distances A. P and A. Q more or less. O is the fixed
centre about which the radius rod C is pivotted, and K is the movable centre about
which the lever D is pivotted. L is the point at which the lever is connected
to the valve rod; this point may be situated either at one end of the lever
as shown in Figs. 1, 2, 93 4 which is the position suitable for working ordinary
slide valves, or it may be situated between the two points K and Q, as in Fig. 3.
which is the position suitable for working valves which admit steam at the inner
edges. In Figs. 1, 3, 4 G is an arm secured upon a rocking shaft, and from it is
suspended at the point M the swinging link E which connects with the lever D
at the point K. In Fig. 2, G is a fixed curved guide in which, by means of a
rocking shaft, arm and rod as shewn, a block (also shown) can be moved to any
desired position, and the swinging link E is pivotted to this block at the point M.
In Figs. 1, 2, 4 the radius rod C is one end of the lever which works the engine
pumps. In each of the Figs. 1, 3 the engine is shown in the mid-stroke position,
and it will be seen that the radius rod and lever are for this position of the engine,
approximately at right angles to the plane in which the centre lines of the engine
and of the crank shaft both lie. In each of the Figs. 2, 4, the engine is shown in
position for the commencement of the outwards stroke. When the engine is inf
imotion the lever D is oscillated about its pivot, and this pivot is constrained to
move to and fro in a path which is controlled by the action of the swing link E:
The direction of this path can be varied by moving the rocking shaft about
its centre and thus changing the position of the point M, about which the swinging
link oscillates. The oscillations of the lever D about its pivot and the to and fro
movements of this pivot are due respectively to the vertical and lateral movements
of the connecting rod, and together control and regulate the movements of the
valve, except when the valve mechanism is in mid-gear, in which position, the to
and fro movements of the pivot of the lever D practically cease to influence the
movements of the valve which is then actuated almost exclusively through the
oscillations of the lever about its pivot. According as the point M is set to one
side or other of the mid gear position the movements of the valve will correspond
to either the forward or the backward rotation of the engine and the extent of
these movements and the duration of steam admission to the cylinder will be
greater or less according as the distance of the point M from the mid-gear position
is greater or less. The object of the pivotted link B and of the radius rod C is to
neutralize the want of symmetry in the movements of the valve which would
result from the to and fro movements of the pivot of the lever D if the lever were
connected directly to the connecting rod, and which would cause an unequal
distribution of steam to the two ends of the cylinder.
The effect of the combination of the pivotted link B, radius rod C and lever D
and of the constraint imposed upon the movements of the movable centre K, is to
cause the point L at which the valve rod is connected to the lever D to move in
an approximately elliptical path when the engine is in motion.
When the valve mechanism is at mid-gear the major axis of the approximate
ellipse thus traced is horizontal, and when the mechanism is in either forward or
backward gear this axis is inclined to the horizontal either one way or the other
to an extent which varies according to the distance of the point M from the mid-
gear position. The pivot at the point A may be situated either so that it's axis

page_text: will intersect the centre line of the connecting rod as shown in Figs. 1 & 3 or so
that its axis will be at a distance from this centre line as shown in Figs. 2 and 4,
in which two latter cases a projection for carrying the pivot is formed upon the
connecting rod as shown; the arrangement shown in these two last named Figs.
allows the use of a longer lever and longer radius rod than is practicable in that
shown in Figs. 1 and 3, and is sometimes to be preferred on that account. The
path in which the pivot at the point K is constrained to move is made of a curved
form for the purpose of compensating for the want of symmetry in the movements
of the valve which would otherwise ensue in consequence of the oscillating_move-
ments of the valve rod H, and the amount of curvature of the said path affords a
means of varying the relative duration of steam admission at the two ends of the
cylinder; when the convexity of this path is downwards, or towards the crank
shaft as in Figs. 1, 3, 4 the valve rod extends upwards from the lever D to its
point of connection with the valve spindle, and when the convexity of the path is
upwards, or away from the crank shaft, as in Fig. 2, the valve rod extends
downwards from the lever D to the said point of connection with the valve spindle.
The valve mechanism which has been described in connection with Figs. 1, 2, 3, 4,
as applicable to inverted marine engines may be used also for other types of steam
engines.
In Figs. 5 and 6 on the accompanying sheet of drawings a modifications of the
improved valve gear are is shown in which a different method to those shown in
Figs. 1, 2, 3, 4 is employed for guiding the point K. In these this cases an
adjustable curved guide E is employed mounted upon a rocking shaft; a block
slides to and fro in this guide, and the lever D is connected to the block at the
point K; the direction in which the engine rotates and the point at which the
steam is cut off are controlled by the position of the guide E which is varied by
moving the rocking shaft about its centre.
In some cases the guides E in Figs. and-6 may be made straight instead of
curved, and other methods may be adopted for securing the compensatory effects
which result from the curved form. In order to obtain greater stability in the
valve mechanism and to prevent a twisting action on the connecting rod, the
pivotted link B, radius rod C and lever D may be applied in duplicate.
In the case of engines which are not required either to be reversed or to have a
variable "cut off," the mechanism for changing the direction of the path of the
movable centre K is omitted, and the direction of this path is made unalterable,
and in the case of engines which require to have a variable "cut-off" but do not
require to be reversed the direction of the path is made alterable only within the
limits corresponding to the earliest and latest points of "cut-off" required. The
improved arrangements of valve gear which have been described are applicable
not only to engines which are driven by steam but also to others which are driven
by other elastic fluids.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that I am
aware it has before been proposed to use in combination a link pivotted to the
connecting rod of an engine, a radius rod and a lever connected to the valve rod
of the engine, the lever being pivotted about a centre moveuble to and fro along a
path the direction of which (in the plane of the lever's motion) may be made
variable for the purpose of controlling the direction of rotation of the engine or
the point of "cut off" and it is to be noted that I make no general claim in
respect of any such combination otherwise than as hereinabove described with
reference to and illustrated in Figs. 1, 2, 3, 4, and 5, of the drawings annexed
but what I claim is :-
In The arrangement as shown in and described with reference to Fig. 1; Fig. 2,
Fig. 3, Fig. 4, or Fig. 5 of the annexed drawings of the valve gear of. a steam
engine, comprising the combination of a link B pivotted to the connecting rod of

page_text: the engine, of a radius rod O, and of a lever D connected to the valve rod of the
engine, the lever being pivotted about a centre movable to and fro along a path
the direction of which (in the plane of the lever's motion) may be made variable
for the purpose of controlling the direction of rotation of the engine or the point
of "cut-off" or both, or, in the case of engines which do not require either to be
reversed or to have a variable "cut-off" may be made unalterable, substantially as
shown and described.

page_text: I, WILLIAM SISSON of 10 Florence Place Falmouth in the County of Cornwall
Engineer do hereby declare the nature of said invention for IMPROVEMENTS IN
VALVE MOTIONS OF STEAM ENGINES to be as follows:-
In a Steam Engine in which the valve motion is actuated directly from the
3 connecting rod, a link forming a connection between a radius rod and a lever, is.
pivotted in a suitable position on the connecting rod, and communicates motion to
the radius rod and lever. At mid stroke both the radius rod and the lever are
at right angles (or thereabouts) to a plane in which the centre line of the Engine
lies. In some kinds of Engines having a pump or pumps, worked by a lever, the
lever may be employed to serve as the radius rod in the improved valve motion.
The radius rod is pivotted about a fixed centre, and the lever is pivotted about a
centre, moveable to and fro, along a path of suitable form the direction of which
(in the plane of the levers motion) can be varied according to requirement; the
valve rod of the Engine is attached to this lever in such a manner that it derives
the motion which it communicates to the valve spindle partly from the vibration
of the lever about its pivot, and partly from the to and fro movement of the lever
which is produced by the oscillation of the connecting rod (acting through the
pivotted link) and which is permitted by the centre about which the lever is
pivotted being moveable as mentioned above. The direction of the path of the
moveable centre regulates and determines the amount of steam .admission, the
point of the stroke at which the steam is cut off and the direction in which
the Engine crank rotates. The moveable centre may be guided in the required
path either by means of a suitably formed guide mounted upon a rocking shaft,
or by means of a swinging link suspended from a lever which is secured upon a
rocking shaft. In either of these cases the direction. of the path can be altered as
required, by moving the rocking shaft about its centre. Other methods also may
be employed for guiding the moveable centre.
WILLIAM SISSON.
W. Lloyd Wise,
Per Charles E. Brougham,
Applicant's Agent.

page_text: I, WILLIAM SISSON of 10 Florence Place, Falmouth, in the County of Cornwall,
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:-
In a steam engine in which the valve motion is actuated directly from the
connecting rod, a link, forming a connection between a radius rod and a lever is
pivotted in a suitable position on the connecting rod and communicates motion to
the radius rod and lever. At mid-stroke both the radius rod and lever are
at right angles (or thereabouts) to the plane in which the centre lines of the engine
and of the crank shaft both lie. In some kinds of engines having a pump or
pumps worked by a lever, the lever may be employed so as to serve also as the
radius rod in the improved valve motion. The radius rod is pivotted about a fixed
centre, and the lever is pivotted about a centre, movable to and fro along a path
the direction of which (in the plane of the lever's motion) can be varied according
to requirement; the valve rod of the engine is attached to this lever in such a
manner that it derives the motion which it communicates to the valve spindle
partly from the vibration of the lever about its pivot, and partly from the to and
fro movement of the lever which is produced by the oscillation of the connecting
rod (acting through the pivotted link), and which is permitted by the centre about
which the lever is pivotted being movable as mentioned.
The direction of the path of the movable centre regulates the point of "cut-off"
and also the direction in which the engine rotates. The movable centre may be
guided in its path either by means of a suitably formed guide mounted upon a
rocking shaft, or by means of a swinging link suspended from an arm secured upon
a rocking shaft.
In either of these cases the direction of the path is altered by moving the rocking
shaft about its centre. Other methods also may be employed for guiding the
movable centre.
Figs. 1, 2, 3, 4 in the accompanying sheet of drawings each show different
modifications of the improved valve gear as applied to inverted marine engines.
In each case B is the pivotted link, C the radius rod, D the lever, E the swinging
link, and H the valve rod. The link B is pivotted to the connecting rod at the
point A and is connected with the radius rod C and lever D at the points P and Q
respectively.
In Figs. 1 and 3 the point A is situated between the points P and Q and in
Figs. 2 and 4 it is situated at the lower end of the link. Any other interchanges
in the relative positions of the points A. P. Q at which the connecting rod, radius
rod, and lever D are respectively connected with the pivotted link B, may be
made as may be found desirable in order to suit different designs of engines and
different conditions under which the engines may be required to work. When the
point A is situated between the points P and Q the radius rod C and lever D are
placed at opposite sides of the link B, and when the point A is situated at either
end of the link, then the radius rod and lever are both placed on the same side
of the link. The ratio between the distances O. P and K. Q corresponds inversely

page_text: with the ratio between the distances A. P and A. Q more or less. O is the fixed
centre about which the radius rod Q is pivotted, and K is the movable centre about
which the lever D is pivotted. L is the point at which the lever is connected
to the valve rod; this point may be situated either at one end of the lever
as shown in Figs. 1, 2, 3, which is the position suitable for working ordinary
slide valves, or it may be situated between the two points K and Q, which is the
position suitable for working valves which admit steam at the inner edges.
In Figs. 1, 3, 4 G is an arm secured upon a rocking shaft, and from it is suspended
at the point M the swinging link E which connects with the lever D at the
point K. In Fig. 2, G is a fixed curved guide in which, by means of a rocking
shaft, arm and rod as shewn, a block (also shown) can be moved to any desired
position, and the swinging link E is pivotted to this block at the point M.
In Figs. 1, 2, 4 the radius rod C is one end of the lover which works the engine
pumps. In each of the Figs. 1, 3 the engine is shown in the mid-stroke position,
and it will be seen that the radius rod and lever are for this position of the engine,
approximately at right angles to the plane in which the centre lines of the engine
and of the crank shaft both lie. In each of the Figs. 2, 4, the engine is shown in
position for the commencement of the outwards stroke. When the engine is in
motion the lever D is oscillated about its pivot, and this pivot is constrained to
move to and fro in a path which is controlled by the action of the swing link E.
The direction of this path can be varied by moving the rocking shaft about
its centre and thus changing the position of the point M. about which the swinging
link oscillates. The oscillations of the lever D about its pivot and the to and fro
movements of this pivot are due respectively to the vertical and lateral movements
of the connecting rod, and together control and regulate the movements of the.
valve, except when the valve mechanism is in mid-gear, in which position, the to
and fro movements of the pivot of the lever D practically cease to influence the
movements of the valve which is then actuated almost exclusively through the
oscillations of the lever about its pivot. According as the point M is set to one
side or other of the mid gear position the movements of the valve will correspond
to either the forward or the backward rotation of the engine and the extent of
these movements and the duration of steam admission to the cylinder will be
greater or less according as the distance of the point M from the mid-gear position
is greater or less. The object of the pivotted link B and of the radius rod C is to
neutralize the want of symmetry in the movements of the valve which would
result from the to and fro movements of the pivot of the lever D if the lever were
connected directly to the connecting rod, and which would cause an unequal
distribution of steam to the two ends of the cylinder.
The effect of the combination of the pivotted link B, radius rod C and lever D:
and of the constraint imposed upon the movements of the movable centre K, is to
cause the point L at which the valve rod is connected to the lever D to move in
an approximately elliptical path when the engine is in motion.
When the valve mechanism is at mid-gear, the major axis of the approximate
ellipse thus traced is horizontal, and when the mechanism is in either forward or
backward gear this axis is inclined to the horizontal either one way or the other
to an extent which varies according to the distance of the point M from the mid-
gear position. The pivot at the point A may be situated either so that its axis
will intersect the centre line of the connecting rod as shown in Figs. 1 & 3 or so
that its axis will be at a distance froin this centre line as shown in Figs. 2 and 4,
in which two latter cases a projection for carrying the pivot is formed upon the
connecting rod as shown; the arrangement shown in these two last named Figs.
allows the use of a longer lever and longer radius rod than is practicable in that
shown in Figs. 1 and 3, and is sometimes to be preferred on that account.
path in which the pivot at the point K is constrained to move is made of a curved
form for the purpose of compensating for the want of symmetry in the movements
of the valve which would otherwise ensue in consequence of the oscillating move-
ments of the valve rod H, and the amount of curvature of the said path affords a
The

page_text: •
means of varying the relative duration of steam admission at the two ends of the
cylinder; when the convexity of this path is downwards, or towards the crank
shaft as in Figs. 1, 3, 4 the valve rod extends upwards from the lever D to its
point of connection with the valve spindle, and when the convexity of the path is
upwards, or away from the crank shaft, as in Fig. 2, the valve rod extends
downwards from the lever D to the said point of connection with the valve spindle.
The valve mechanism which has been described in connection with Figs. 1, 2, 3, 4,
as applicable to inverted marine engines may be used also for other types of steam
engines.
In Figs. 5 and 6 on the accompanying sheet of drawings modifications of the
improved valve gear are shown in which a different method to those shown in
Figs. 1, 2, 3, 4 is employed for guiding the point K. In those cases an adjustable
curved guide E is employed mounted upon a rocking shaft; a block slides to and
fro in this guide, and the lever D is connected to the block at the point K; the
direction in which the engine rotates and the point at which the steam is cut off
are controlled by the position of the guide E which is varied by moving the rocking
shaft about its centre.
In some cases the guides E in Figs. 5 and 6 may be made straight instead of
curved, and other methods may be adopted for securing the compensatory effects
which result from the curved form. In order to obtain greater stability in the
valve mechanism and to prevent a twisting action on the connecting rod, the
pivotted link B, radius rod C and lever D may be applied in duplicate.
In the case of engines which are not required either to be reversed or to have a
variable "cut off," the mechanism for changing the direction of the path of the
movable centre K is omitted, and the direction of this path is made unalterable,
and in the case of engines which require to have a variable "cut-off" but do not
require to be reversed the direction of the path is made alterable only within the
limits corresponding to the earliest and latest points of "cut-off" required. The
improved arrangements of valve gear which have been described are applicable
not only to engines which are driven by steam but also to others which are driven
by other elastic fluids.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is
In the valve gear of a steam engine, the combination of a link B pivotted to the
connecting rod of the engine, of a radius rod C, and of a lever D connected to the
valve rod of the engine, the lever being pivotted about a centre movable to and fro
along a path the direction of which (in the plane of the lever's motion) may be
made variable for the purpose of controlling the direction of rotation of the engine
or the point of "cut-off" or both, or, in the case of engines which do not require
either to be reversed or to have a variable "cut-off" may be made unalterable,
substantially as shown and described.