IMPROVEMENTS IN VALVE GEAR FOR STEAM OR OTHER ENGINES
Year: 1885

page_text: I, THOMAS SWAN, of 152 Ellison Street Jarrow, in the County of Durham,
Engineer do hereby declare the nature of said invention for "IMPROVEMENTS IN
VALVE GEAR FOR STEAM OR OTHER ENGINES" to be as follows:-
My invention relates to improvements in the gearing by which the valves are
actuated, the movements of the valve being derived entirely from a single eccentric
or crank, main crank or main connecting rod.
It is applicable to marine locomotive or stationary engines of any type, and can
be applied to work in any position, vertically, diagonally or horizontally, by
modifications of the component parts, the essential principle being, that the move-
ment of the valve shall be the resultant of two motions, both derived from the
eccentric or cranks, main crank or main connecting rod one a rocking motion
imparted by the end of eccentric rod or its equivalent when worked off the main
crank or connecting rod to a curved link which has its point of support between
its ends and which link carries a sliding block to which the valve connecting rod
is attached; the other a positive movement of the curved link, in direction
corresponding with that of the valve, the result being that the "leads" remain
constant in both extreme and intermediate positions of link and at both ends of
stroke of piston and are equally effected whether engine is running in the one
direction or the other while the two motions of the curved link, counteracting each
other cause the valve to stand in the open position or to move very slowly for an
interval.
The following description is for an inverted cylinder marine engine, with eccentric
rod working in a vertical, or inclined direction (and is not applicable for working
from main crank or connecting rod) the gear being suitable for engines with valves
between cylinders (central with engine centre) and valves at side of cylinders with
valve face parallel to centre line of crank shaft in one and the same engines.
The curved link has its rocking centre on the end of one arm of a bell-crank or
lever (working on a weigh-shaft or other fixed centre for a fulcrum) and said link
is attached to end of eccentric rod, from which it derives its rocking motion, at
some distance away from its rocking centre.
The other arm of bell crank or lever is connected by a link or rod to an inter-
mediate point in the eccentric rod, the vibrating or side motion of which, combined
with its end or rocking motion, cause the bell-crank to impart a direct motion to

page_text: the rocking centre of curved link corresponding in direction to that of the valve,
the resultant of the rocking and direct motions being the desired movements
of the valve.
The point of attachment of the connecting link or rod from bell-crank or lever to
eccentric rod, may be varied, to suit circumstances, to any extent, the arm of bell-
crank or lever being made longer or shorter accordingly, so as to preserve the
parallelogram and it may in some cases be convenient to attach it to the strap of
the eccentric.
The valve rod works in suitable guides and the valve connecting rod is moved
in the curved link to reverse the engines and to give the intermediate grades of
expansive working by any of the ordinary hand, steam or other reversing
mechanism.
In a modification of this valve gear convenient for horizontal arrangement of
eccentric rod, on same description of engine the eccentric rod gives the rocking
motion, to curved link by taking hold of an arm at a right angle to its curve. The
curved link in this case has its rocking centre (not necessarily centre of link) on
one arm of a lever working on a fixed fulcrum the opposite arm being connected by
a link or rod to a point between the end of eccentric rod and the eccentric itself,
the vibrating or side motion of the eccentric rod, combined with its direct motion,
causing the lever to impart a motion to the rocking centre of curved link corre-
sponding in direction with that of the valve, with similar results, by the
combination of the two motions, on the functions of the valve as before.
In another form the curved link rocks on a fixed centre (not necessarily centre
of link) by the eccentric rod taking hold of an arm at a right angle to its curve the
alide block carrying a lever, one arm of which is connected by a link or rod to a
point between the end of eccentric rod and the eccentrio itself, and the other arm
of this lever takes hold of the end of valve connecting rod, the direct motion
derived from the vibration of the eccentric rod being thus communicated through
the lever to the valve connecting rod the curved link having only a rocking motion,
with similar results as to the functions of the valve.
Or the eccentric rod may be prolonged beyond its attachment to the arm on
back of curved link, a connecting link or rod joining its extreme end to an arm
or lever carried by the sliding block the valve connecting rod taking hold of arm
or lever at same or other point the result being similar.
The position of the eccentric relatively to the crank necessarily varies according
to the method of arranging the valve gear but its position is in all cases such as to
use the quick parts of eccentric path for both opening and shutting the valve and
also to use the counteracting of the end motion of eccentric rod, by its side move-
ment or vibration when valve is open to cause it to dwell or move very slowly for
an interval, and the component parts can be arranged so as to cause the functions
of the valve to be practically the same at top and bottom.
All these modifications described for working by an eccentric are applicable to
working off the main crank or main connecting rod instead of an eccentric and rod,
a lever attached to the main crank or to the connecting rod performing all the
functions of the eccentric rod with similar results, the proportions of the component
parts being alone modified.

page_text: I, THOMAS SWAN of 152 Ellison Street Jarrow, in the County of Durham
Engineer do hereby declare the nature of said invention and in what manner the
same is to be performed to be particularly described and ascertained in and by the
following statement:―
My invention relates to improvements in the gearing by which the valves are
actuated, the movements of the valve being derived entirely from a single eccentric
(or crank) from the main crank or main connecting rod.
It is applicable to marine locomotive or stationary engines of any type, and can
be applied to work in any position, vertically, diagonally or horizontally, by
modifications of the component parts, the essential principle being that the
movement of the valve shall be the resultant of two motions, both derived from
the eccentric (or crank) from the main crank or main connecting rod one a rocking
motion imparted by the end of eccentric rod or its equivalent (in the form of a
lever) when worked off the main crank or connecting rod, to a curved link which
has its point of support between its ends and which link carries a sliding block to
which the valve connecting rod is attached; the other a movement of the curved
link in direction or nearly always so corresponding with that of the valve, the
result being that the "leads" remain constant in both extreme and intermediate
positions of link and at both ends of stroke of piston and are equally affected
whether engine is running in the one direction or the other while the two motions
of the curved link, counteracting each other at and about the full open position
cause the valve to stand in the full open position or to move slowly for a
considerable interval of time.
The following description is for an inverted cylinder marine engine with eccentric
rod working in a vertical or inclined direction and is not applicable for working
from the main crank or connecting rod.
The gear is suitable for engines with valves between cylinders (central with
engine centre) and valves at side of cylinders with valve face parallel to centre line
of crank shaft in one and the same engines.
.
The curved link has its rocking centre on the end of an arm of a bell-crank or
lever working on a weigh-shaft or other fixed centre for a fulcrum and said link is
attached to end of eccentric rod from which it derives its rocking motion at some
distance away from its rocking centre.
The other arm of bell-crank or lever is connected by a link or rod to an
intermediate point in the eccentric rod, the vibrating or side motion of which,
combined with its end motion which gives the rocking motion to the link cause the
bell-crank to impart a direct motion to the rocking centre of curved link
corresponding in direction (or nearly always so) to that of the valve, the resultant
of the rocking and direct motions being the desired movements of the valvo.

page_text: The point of attachment of the connecting link or rod from bell-crank or lever to
eccentric rod, may be varied, to suit circumstances, to any extent, the arm of bell-
crank or lever being made longer or shorter accordingly so as to preserve the
parallelism of the link when crank is on top and bottom centre and it may in some
cases be convenient to attach it to the strap of the eccentric.
The valve rod works in suitable guides and the valve connecting rod is moved in
the curved link to reverse the engines and to give the intermediate grades of
expansive working by any of the ordinary hand steam or other reversing
mechanism.
In a modification of this valve gear convenient for horizontal arrangement of
eccentric rod, on same description of engine the eccentric rod gives the rocking
motion to curved link by taking hold of an arm at or about a right angle to its
curve. The curved link in this case has its rocking centre (not necessarily centre
of link but may be some distance toward one or other end) on one arm of a lever
working on a fixed fulcrum, which fulcrum will conveniently be used for carrying
the reversing levers, the opposite arm being connected by a link or rod to a point
between the end of eccentric rod and the eccentric itself or it may be to a point on
the strap of eccentric, the vibrating or side motion of the eccentric rod combined
with its end motion causing the lever to impart a motion to the rocking centre of
curved link corresponding in direction (or nearly always so) with that of the valve,
with similar results, by the combination of the two motions, on the functions of
the valve as before.
In another form the curved link, rocks on a fixed centre (not necessarily centre
of link) by the eccentric rod taking hold of an arm at or about a right angle to its
curve, the slide block carrying a lever, one arm of which is connected by a link or
rod to a point between the end of eccentric rod and the eccentric itself, and the
other arm of this lever takes hold of the end of valve connecting rod, the direct
motion derived from the vibration of the eccentric rod being thus communicated
through the lever to the valve connecting rod the curved link having only a
rocking motion, with similar results as to the functions of the valve.
Or the eccentric rod may be prolonged beyond its attachment to the arm on back
of curved link, a connecting link or rod joining its extreme end to an arm or lever
carried by the sliding block the valve connecting rod taking hold of arm or lever at
same or other point the result being similar.
The position of the eccentric relatively to the crank necessarily varies according
to the method of arranging the valve gear but its position in all cases is such as to
use the quickest parts of eccentric path for both opening and shutting the valve
and also to use the counteracting of the end motion of eccentric rod by its side
movement or vibration when valve is fully open to cause it to stand or dwell for
an interval of time and the component parts can be arranged so as to cause the
functions of the valve to be practically the same at top and bottom.
All these modifications described for working by an eccentric are applicable to
working off the main crank or main connecting rod, instead of an eccentric and
rod, a lever attached to the main crank or to the connecting rod performing all the
functions of the eccentric rod with similar results the proportions of the component
parts being alone modified.

page_text: (1) is the curved link freely centred on the end of one arm (2) which with a longer
arm (3) preferably forming a bell-crank lever works on a weigh-bar (4) which is
also the reversing weigh-bar. The eccentric rod (5) takes hold of an arm (6)
extending from one end of the curved link. A rod (7) connects the end of arm (3)
with the eccentric rod. The point of attachment of the rod (7) to the eccentric
rod (5) can be so adjusted as to counteract the disturbing effect of the angularity
of the connecting rod. The valve connecting rod (8) whose length forms the radius
of the curve of link has the slide block (9) at its lower end and is attached at its
upper end to valve rod (10) working in a guide (11) and is. moved to extreme or
intermediate positions in the link by a drag bar (12) attached to end of reversing
arm (13).
Figure 2, shews the gear applied to same type of engine but in which the valve
is on end of engine the arrangement of the gear being the same except that the
eccentric rod (5) is inclined and takes hold of the curved link (1) direct the
arm (6) being dispensed with and the throw of the eccentric is thus reduced.
Figure 3, shews the gear applied to a horizontal direct acting engine in which
type with the usual very short connecting rod-it has important advantages over
the ordinary gear, with two eccentrics and a link, both in operating the valve and
in facility of reversing. (1) is the curved reversing link freely centred on the end
of an arm (2) which with a longer arm (3) forming a lever works on a weigh-
bar (4) which is also the reversing weigh-bar. The eccentric rod (5) which is
vertical takes hold of an arm (6) projecting from back of curved link a link or
rod (7) connecting the end of arm (3) with the strap of eccentric. The valve
connecting rod (8) whose length forms the radius of the curve of reversing link (1)
has the slide block (9) at its outer end and at opposite end takes hold of valve
spindle (10) working in a guide (11).
Figure 4, shews a modification of the valve gear for marine engines working a
screw propeller the full lines as applied to work the valve the face of which is at
right angles to fore and aft centre line of engine on one cylinder and the dotted
lines as applied to work the valve the face of which is parallel with fore and aft
centre line on the other cylinder as is frequently required in one and the same
engine the object being to shew how conveniently this may be done with a single
reversing weigh-bar forming the point of support for both sets of gear the positions
of the eccentrics relatively to their cranks being properly adjusted. In both views
for simplicity the crank pins are shown in same position viz with piston at its
extreme distance from crank shaft but this would not be so in double or treble
throw cranks All the component parts of the gear are the same as previously
described but in one case the eccentric rod (5) takes hold direct of end of curved
link (1) which in the other it takes hold of the arm (6) projecting from back of
link. The reversing weigh-bar (4) runs fore and aft and carries arms (2) and (3)
of bell-crank or lever-The centre of one eccentric is here exactly 90°, in advance
of the crank as cranks are shewn and the centre of the other co-incident with it
but these relative positions are fixed by the proportions of parts of the gear to each
other and vary accordingly.
Figure 5, shews an arrangement in which the eccentric rod (5) works in an
ossillating guide (15) working in a fixed bracket and takes hold of arm (6) on back
of curved link and thus both the rocking and vertical movements of the link (1)
are derived direct from the eccentric rod which performs the functions of "lap"
and "lead" lever the rod (14) freely attached to reversing weigh-bar (4) and
to link (1) merely forming a rocking centre for the latter and for keeping it in
position.
Figures 6 and 7, shews two modifications of the principle of my invention
similar to Figure 5 but the eccentric rod (5) in these cases instead of working in a
guide is suspended from reversing weigh-bar (4) by a swinging link or rod (15) the
equivalent of the guide in Figure 5. The eccentric rod here also gives both rocking
and vertical movements to the link (1) and acts as a lap and lead lever but the

page_text: motion is not so good as in Figure 5 owing to the arc described by link (15) In
Figure 6 the reversing link (1) supported in a guide fixed (16) on some
convenient part of engine being freely attached to a centre on a slide block (17) on
which it rocks and with which it moves vertically in the fixed guide. This guide
applied to link combined with the guide or eccentric rod in Figure 5 would give
almost a perfect motion-On sheet 2 I have shewn some method of applying my
invention to operate the valve with motion arrived entirely from the connecting
rod or entirely from the crank. The same numerals indicate the same or equivalent
parts on all the figures.
Figure 8 shews an arrangement applied to an inverted direct acting engine with
valve on side the motion being derived from a point near lower end of connecting
rod (1) is the curved reversing link having a long arm (2) projecting downward
and carried on an arm (4) forming one end of a lever of the first order whose other
arm is (8) working on a fixed fulcrum at (5) and thus the link (1) is supported in
position The lower end of arm (2) is connected by a rod (6) to a pin (7) in
connecting rod and thus the rocking movement is given to the reversing link. The
vertical motion of link is given by the lever of first order the longer arm (8) of
which is freely connected by a rod (9) to a point (10) on rod (6) The combined
rocking and vertical movements of link acting through the valve connecting
rod (11) causes the valve to perform all its required functions. The leads of valve
are not constant in this modification and in order to equalise the cuts off the point
of attachment of the drag link (12) to arm (13) on reversing weigh-bar (14) is
raised as shewn and for the same purpose the radius of reversing link (1) is struck
from a point out of vertical centre line of valve gear so as to give greater leads in
this instance on top when engine is running astern.
Figure 9 shews a modification in which the motion is derived entirely from the
crank. The curved reversing link (1) is supported freely on a fixed centre the long
arm (2) being connected freely to the crank pin by a rod (6) the end of which
projects and is freely attached by a rod (9) to the end of a free link (10) centred
on slide block in reversing link the drag link (12) taking hold of slide block on
same centre. The valve connecting rod (11) does not take hold of the slide block
but is freely attached to end of the link (10) forming with the rod (9) a double
joint The same remarks made on describing Figure 8 apply here as to equalizing
the cuts off by the positions of drag link centre and of radial centre of valve
connecting rod. For small engines such as those of launches &c. the slide block
may be moved in the link to extreme positions in reversing or intermediate
positions for expansion working by a screw worked by a hand wheel in place of
the ordinary reversing levers and drag link. This form of valve gear is well
adapted for stationary engines running only in one direction when one half only of
the curved link (1) acting as an expansion link will be required the governor being
attached direct to the slide block.
Figure 10 shews an arrangement in which the motion is derived from a point
near the piston rod end of connecting rod as may be necessary in some cases such
for instance as for working the valve in locomotives though it involves more
jointed working parts. A rod (3) is freely attached at one end to a pin in
connecting rod its other end being supported by a radius rod (4) suspended from a
fixed centre (5) At an intermediate point in the rod (3) a rod (6) is freely attached
the other end of which takes hold of the end of long arm (2) on the curved link (1)
which is supported freely on shorter arm (7) of a lever of the first order working
on a fixed fulcrum (8) the longer arm (9) of which lever is freely attached by the
rod (10) to a point in the rod (6). The valve connecting rod (11) is attached to
slide block which it moves in reversing link by drag bar (12) and arm (13) on
reversing weigh-bar (14). This form of gear though involving more working
joints is almost indispensible, where the attachment is so situated in connecting
rod, to obtain good results and it has the advantage over other similar methods of

page_text: working off the connecting rod that the slide block has practically no motion when
the engine is running and that a long valve connecting rod is obtained.
Figure 11, shews another modification of the gear worked off the crank-
somewhat similar to that in Figure 9. A lever of the first order is centred on a
fulcrum (8) in the slide block the longer arm (9) being freely connected by a
rod (10) to the rod (6) which gives the motion to the gear from the crank. The
valve connecting rod is freely attached to the shorter arm (7) of the lever the drag
link (12) taking hold of slide block.
In Figures 9 and 11-the radius of curved link is such as to equalise leads and
cuts off as much as possible. The lead astern can also be similarly treated as
described with reference to Figures 8 and 9.
In all the forms described and illustrated as also in other possible modifications
of this valve gear, the principle upon which it depends is that except in the special
modifications just referred to the curve of the link shall be struck by, a radius
which is the length of the valve connecting rod; that the distance between the
centre line of the link when crank is on one "dead" centre and when it is on the
other "dead" centre (say the top and bottom in vertical engines) shall be equal to
the lap of valve plus the lead, if any, and that in each of these two extreme
positions the link shall be parallel to the position it previously occupied and the
"leads" remain exactly the same at both ends i.e, that when the link is in either
of these extreme positions the slide block may be moved from end to end of the
link without moving the valve unless purposely arranged otherwise as in Figures 8.
9 and 11 Sheet 2. That the bell-crank or other lever or its equivalent (as in
Figures 5, 6 and 7 where the eccentric rod itself forms that lever) with direct free
attachment to link, or to an arm forming part of link, shall so operate as to fulfil
the above conditions and in conjunction with the action of the other parts of the
valve gear, shall cause the valve to perform all its functions by a motion derived
in the manner described entirely from one eccentric (or equivalent crank) or
entirely from a single attachment to the main connecting rod or from a single
attachment to the main crank.
The chief advantages obtained by this valve gear may be briefly stated vizt.
The proper proportions of the gear are easily ascertained either by calculation or
by geometrical construction.
The travel of lap lever at link attachment is simply made equal to lap + lead
(if any) and eccentric travel may be less, equal to or greater than travel of valve
at full cut off position, it depending upon the length of link used which should not
be less than three times travel of valve (centre to centre of block in extreme cut off
positions)-Distance from centre of link to eccentric rod attachment to link can be
made any desired length with eccentric travel to suit so that the point of attach-
ment which actuates the lap lever shall give through other arm of lap lever the
desired lap (and lead if any).
In the best forms of the gear the quickest part of path of eccentric is used in
opening the valve while lap lever is stationary or nearly so-then motion of lap
lever counteracts end motion of eccentric rod after valve is open which causes it to
stand or dwell while in that position, and the best part of eccentric path derived
through the lap lever together with the end motion of eccentric rod-combine to
close the valve, thus being done at the quickest possible speed for such a motion as
that derived from an eccentric, or from a point on connecting rod or from a main
crank-I prefer not to angle the eccentric rod (Figure 1) much to the left as view
stands in order to get the best part of eccentric path.
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
First. For working the valves of steam or other engines the use of a reversing
link carried freely upon a lever, both link and lever having their motions derived

page_text: either from a single eccentric, or from a single attachment to the main connecting
rod, or from a single attachment to the main crank; substantially as described and
illustrated.
Second. The new combinations of parts-none of which parts are new separately,
constituting the valve gear in the various forms as described and illustrated by the
Figures 1. 2. 3. 4. 5. 6 and 7 (sheet 1 of drawings) worked from a single eccentric
and by Figures 8 9. 10 and 11 (sheet 2 of drawings) worked either from a single
attachment to the main connecting rod or from a single attachment to the main
crank substantially as described and shewn.
Dated the 20th day 01 February 1000.
Witness,
T. J. DANSON, F. Inst. P.A.,
Consulting Engineer & Patent Agent,
Newcastle-upon-Tyne.
THOMAS SWAN.