Improvements in Valve Gear for Steam Engines.
Year: 1887

page_text: Date of Application, 4th May, 1887
Complete Left, 4th Feb., 1888
Complete Accepted, 9th Mar., 1888
Improvements in Valve Gear for Steam Engines.
I, WALTER PAYTON of Brooklyn House Larkfield Richmond in the County of
Surrey Mechanical Engineer do hereby declare the nature of this invention to be as
follows:-
My said improvements relate to that part of steam engines known as the "Valve
Gearing" and used in such engines for the purpose of giving motion to their slide
valves, and they refer more particularly to that kind of gearing which in lieu of
excentrics is operated in part by means of the connecting rod and in part by the
crosshead of such engines, and the object of the said improvements is the construc-
tion of such gearing in such a manner as will enable it to operate the slide valves
with greater accuracy and uniformity of motion.
In carrying the said improvements into effect a lever is pivoted at one end to some
fixed part of the engine and its other end is connected by means of a pin jointed rod
to some part of the engine crosshead in such a manner as will permit of the too and
fro motion of the crosshead imparting vibratory motion to the said lever on either
side of a line at right angles to the line of motion of such crosshead.
The said lever is provided with a slotted link fitted to a saddle piece pivoted to the
lever at such a distance from its fulcrum as will enable each vibration of the lever to
move such slotted link through a distance equal to the travel of the slide valve of the
engine when moved between the two positions known as "lead" and corresponding to
the positions of the piston of the engine when at the ends of its strokes. The said
saddle piece is pivoted to the said lever in such a way as will permit of the said slotted
link vibrating upon its pivots, and the said pivots are placed at about the centre of the
slot of the said link.
The end of the said lever which is pinjointed to the rod connecting it with the
crosshead is provided with a bellcrank lever moving upon the pin of the said joint and
having one of its arms connected by a pinjointed rod to an arm attached to or
forming part of the connecting rod of the engine and the other arm of the bellcrank
lever is connected by a pinjointed rod to the saddle piece of the said slotted link in
such a way that the sideway motion of the engine connecting rod is made capable
of giving vibratory motion to the pivoted saddle piece and the slotted link fitted
to it.

page_text: The slot in the said link is curved and it is fitted with a curved block capable of
sliding within it and such block is connected to the slide valve of the engine by a
pinjointed rod the length of which is the same as the radius of the curve of the slot
and the position of the said block in the slot of the link may be varied by means of a
lever pivoted to the engine frame and connected to the valve rod by means of a pin-
jointed suspension rod or in any other usual manner, but in cases where such means
cannot be conveniently used I substitute for the said slotted link and saddle piece a
grooved plate or plates pivoted on the said lever and connected by a rod or rods with
the said bellcrank lever in a similar way to that above described and prolong the valve
connecting rod beyond the said plates and fit it within a sleeve pivoted upon the end
of a lever moving in bearings carried by the frame of the engine.
When the said block is so placed in the slot that the centre of its pinjoint is con-
centric with the pivots of the vibrating link the motion of the engine crosshead will
cause the slide valve to travel from "lead" to "lead" only but on shifting the block
to any other position in the slot the vibratory notion given to the link by means of
the connecting rod of the engine will cause the slide valve to travel an increased
distance the amount of which will vary with the position of the block in the slot, and
by shifting the block in the slotted link from one side of its centre of vibration to its
other side the motion of the engine will be reversed.
1000

page_text: Tig is a pian of the same.
Fig 3 is a diagram shewing the positions of the several parts at the moment the
piston is at the middle of a stroke.
Fig 4 illustrates a modification of the gear.
In Figs. 1. 2. 3. A is a lever which has its fulcrum A' working in bearings carried
by the frame of the engine, and the said lever is connected at A² to the rod B, the
other end of which is connected at B₁ to the arm C fixed upon the pin of the piston
rod's crosshead D and reciprocating with it.
Between the plates of the lever A is pivoted at A' the saddle E, having fixed upon
it the slotted link E', and the saddle is connected at E to the rod F, the other end
of which is connected at F¹ to the right angled bellcrank lever G, centred upon the
connecting pin A². The acting length of the rod F equals the distance between the
centres A and A³, and the distance between the centres A* and F¹ is the same as that
between A3 and E'.
The centres A' A² and A³ are upon the same right line, the centre of the slot in
the link E¹ coincides with the centre A, and the curved slot in the link treated as a
right line is at a right angle with a line drawn through the centres E' and A³.
The bell crank lever G is connected at G₁ to the rod H, the other end of which
is connected at H' to the arm J which is formed as part of the main connecting
rod K, and partakes of its motion. The rods B, and H, are of equal length, the
centres G and A2, are the same distance apart as the centres H¹ B', and the
centres H¹ B are on a right line at a right angle with the centre line of
the connecting rod K when the piston is at the end of a stroke.
The length of the arm J is determined by the amount of travel the slide valve
should have in order to fully open the steam ports.
The valve spindle L to which the slide valve is attached, is connected to the link E'
by the rod M, the lower end of which M' is provided with a pinjointed block fitted
within the slot of the link, and capable of being moved along the slot by means of
the rocking shaft and lever N and rod N³, and the curve of the slot is that of an arc
of which the rod M is a radius.
When the gear is in operation, the reciprocatory motion of the crosshead D gives
a vibratory motion to the lever A, and a reciprocatory motion to the link E, and

page_text: an additional rocking motion is imparted to the link by the vibrating arm J of the
connecting rod K, and such motions of the link combine and give a variable
reciprocatory motion to the slide valve attached to the valve spindle L.
When the centre M¹ is midway in the slot of the link E and concentric with
the centre A³, the rocking motion given to the link by the arm J. will have no effect
upon the slide valve, the reciprocations of which will be effected by the vibrations
given to the lever A by the crosshead D only; the extent of such reciprocations
being invariably the distance between the lead positions of the slide valve when the
piston is at the termination of its strokes, the parts of the lever A being so pro-
portioned to the length of such strokes as to produce that effect. But when the
rod M is shifted to either side of the centre of the link E, the rocking motion given
to the link by the connecting rod arm J will increase the travel of the slide valve
beyond the said lead positions so as to farther open the steam ports of the cylinder,
and such increase of travel will vary according to the position the rod may have in
relation to the centre of the link. By shifting the rod M from one side of the links
centre to its other side, the motion of the engine will be reversed.
The rod M may be shifted along the slot of the link E¹ as shewn in Figs. 1. 2. 3
but in some cases I prefer to use the modification illustrated in Fige 4 in which in
lieu of the rod N1, the rocking shaft lever N has pivoted upon its end the sleeve O,
within which the end of the rod M is made free to move, and to substitute for the
saddle E, and link E¹, two grooved plates R pivoted upon the two parts of the
lever A, and connected to the bellcrank lever G each by a separate rod.
The rod M. passes between the two plates, and it is moved along their grooves by
turning the rocking shaft upon its centre.
The diagram Fig 3 shews by thick lines the positions of the parts of the gear
when the piston is at the middle of a stroke, and by dotted lines the arcs through
which they move, and their positions when at the middle of the return stroke.
The positions of the centres of the parts as above set forth are those which cause
the reciprocations of the valve to be equal in extent, and uniform in time whatever
position the rod M may have in relation to the link E¹, but they may be varied
somewhat should constructive necessities require it without materially impairing the
valve's motion.
The lever A may be used as a pump lover as shown in Figs. 1. 2. 3, and it and the
rods and other parts may be single or double as may be desired.
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
1. The combination of the connecting rod arm J, the rod H, the bellcrank
lever G, and the rod B, so arranged as to give a rocking motion to a slotted link
or its equivalent pivoted upon a lever vibrated by the reciprocations of the piston of
the engine, such rocking motion being suitable for working the slide valve substan-
tially as above described in reference to the Figures 1. 2. 3 and 4.
2. The combination of the rocking shaft and lever N, the sleeve O, and the rod M,
substantially as and for the purpose hereinbefore described in reference to Fig. 4.
Dated this 3rd day of February 1888.