Improvements in Valve Gear for Operating the Valves of Engines Worked by Steam or other Expansible Fluid.
Year: 1895

page_text: Date of Application, 16th Feb., 1895
Complete Specification Lefl,"6th May, 1895-Accepted, 8th June, 1895
Improvements in Valve Gear for Operating the Valves of Engines
Worked by Steam or other Expansible Fluid.
I COURTENAY WILLIAM THOMPSON of 5 Fair Street, Tooley Street, in the
County of Surrey, Mining Engineer, do hereby declare the nature of my invention
to be as follows:-
My invention relates to mechanism for operating the valves of steam engines or
other engines worked by expansible fluid, which valves may be flat, piston,
oscillating, or other valves and my said invention has for its object to produce
simple and effective mechanisms for the purpose.
In ordinary valve gears, and in order to regulate the cut off for expansion
and other conditions of distribution of the motive fluid, the eccentric is set
somewhere in the second quadrant in lead of the main crank and the amount
of lead that is given to the eccentric in advance of the first quadrant
determines the conditions of distribution of the motive fluid. The circular
nature of the movements of an eccentric or crank is divided into two straight
line motions at right angles to each other and timed so that the first motion
in any one direction is in excess at the beginning of any quadrant and the
second motion, at right angles to the first, is in excess at the end of the same
quadrant. At the end of the first quadrant, in lead of the main crank, an eccentric
has what I call its first movement and is most effective in, say, opening 'valve
port, and at the end of the second quadrant an eccentric has its second movement
or preponderating movement at right angles to the first movement and therefore it
is principally holding the valve in, say, its open position preparatory to returning
the valve to close the port: therefore when the eccentric is placed in the second
quadrant in lead of the main crank, it is set, say, between the valve opening and
valve holding or neutralising movements and in proportion as the eccentric is set
near the first or the second of these movements or positions so the conditions of
distribution of the motive Huid are regulated. My invention depends upon
producing the two movements in parallel directions the first and the second as
herein before described and in applying them in such manner that I make the valve
partake of both movements and in such proportion of each that the required
conditions of distribution of motive fluid is obtained and regulated. 1 obtain the
first movement either from an eccentric or crank or equivalent mechanism at right
angles or approximately at right angles to the main crank, or from the crosshead
or equivalent mechanism out of a cylinder operating a crank approximately at
right angles and by means of a lever or other suitable device 1 transfer this first
movement thus obtained to a convenient position preferably approximately opposite
to the valve chest by means of levers, rocking shafts or otherwise.
obtain the second movement either from the cross-head, from an eccentric or
crank in a line with the main crank or from any equivalent mechanism such that
the line of direction of this movenient is parallel to, but in the opposite direction
to the movements of the main piston; in this Specification I refer throughout to
the ordinary D valve or equivalents, but my mechanism can be modified to suit the
requirements of a 'double D valve and other forms of valves: the second movement,
thus obtained, may be transferred to a convenient position in approximation to that
of the first movement by means of levers, rocking shafts or other suitable devices.

page_text: may manipulate the second movement and combine it with the first movement
with the object of obtaining the resultant movement as required for the valve
and as hereinbefore described by any of the following or equivalent means; for
example-
This
1st. I connect the first and the second movements to two points of a rocking and
swinging lever respectively and I connect the valve operating rod to a point in the
same rocking lever between the points of connection of the first and the second
movements just described; thus I obtain the required resultant movement for the
valve operating rod by the means described or by any equivalent means.
gear may be reversed by reversing the first movement alone by any suitable
reversing link mechanism, for example, the first movement rocking shaft may be
fitted with a link or the reversing link may slide on the first movement point in the
rocking lever and such link may be operated from the first movement rocking shaft
in any convenient manner, or the reversing mechanism may be of any convenient
description and I may vary the expansion to any of the intermediate points of such
reversing mechanisms or I may also vary the expansion by varying the position of
the point of connection of the valve rod in the rocking lever (which latter may be
in the form of a link) relatively to the two points of connection of the first and the
second movements respectively or any one point may be moved relatively to the
others all in the same rocking lever.
2nd. connect the fulcrum of motion of the second movement to the first
movement by several convenient and equivalent means but preferably by
attaching such fulcrum to, say, the first movement rocking shaft and I then
obtain the required resultant movement for the valve by attaching the valve
operating rod to the point of application of the second movement in the rocking
lever beyond the fulerum just described; this gear may be reversed by reversing
the first movement alone by any convenient means but preferably by reversing the
second movement fulcrum in the first movement rocking shaft (which latter may be
in the form of a link) and I may vary the expansion to any intermediate point in
this mechanism or link.
When two or more cylinders operate cranks at right angles respectively,
suitable movements may be transferred from any one cylinder to any other
cylinder and any one rocking shaft may operate suitably for two or more cylinders
and so on.
Or I set an eccentric or crank or equivalent mechanism in a line with the main
crank and by using, say, the eccentric connecting rod as an oscillating lever ]
produce the second movement in the opposite direction to the movement of the
piston but approximately parallel to it. The fulcrum of the eccentric connecting
rod, just referred to, has also the first movement, due to the motion of the eccentric,
but which is at right angles to the direction of the second movement: I convert
this first movement into a parallel direction (or approximately so) relatively to
that of the second movement by any convenient means, but preferably by causing
the fulcrum of the eccentric connecting rod (or lever) to reciprocate, by means of
its first movement, equally on each side of the pivot in a pivotted slide at right
angles to the direction of the second movement, but which slide is capable of being
turned on its pivot to either side of such position and by so turning the slide!
produce the first movement in the fulcrum parallel to the second movement:
attach the valve rod to the above mentioned oscillating lever in one of the
alternative positions as required, thus on the eccentric side of the fulcram, when
the eccentric is set opposite to the main crank and on the outside of the fulcrum
when the eccentric is set coincident with the main crank; the valve rod will thus
partake of the first movement and of the second movement and in such proportion
of each that the resultant movement may be obtained as required: this gear may
he reversed by reversing the first movement alone or by turning the slide from one
side to the other and expansion may be varied by varying the angle to which
the slide is turned to one side or the other. The valve rod, in my mechanisms,
may be connected to the valve direct or by the intervention of rocking shafts or
I

page_text: other similar mechanism as may be convenient. Any of my mechanisms may be
duplicated, producing the direction of the movement of one valve slide opposite to
that of its duplicate valve slide, or any one mechanism may be combined with any
other mechanism, as ordinary gears may be duplicated or combined and connected
to a duplicate or two-plated valve such as is shewn in Figure 5 of the drawings of
the Specification of my application for Letters Patent No. 17682 of 1894 whereby
the port opening may be increased or made double the size of those for the single
gear with the same length of stroke. Auxiliary cut off slides inay also be added
equivalent to those shewn in Figure 6 of the drawing of the Specification of my
said application for Letters Patent No. 17682 of 1894.
I may operate other cut off slides by any one of these gears and I may vary the
cut off by varying the extent of the first movement (the second movement
remaining unaltered) in what is equivalent, when used with the principal valve
slides, to either forward or reverse gear whereby (for the cut off slides) the latest
cut off is effected in what is equivalent to the position for full forward gear (for
the principal valve slides) and the earliest cut off is effected in what is equivalent
to the position of full reverse gear (for such principal valve slides): I may also
operate cut off slides by using what is known as Joy's gear and by modifying it so
that I may similarly vary the cut off for any point from full forward gear to full
reverse gear by angling the slide to any extent on either the forward or reverse
side, but in my cut off valve mechanisms I only vary the conditions of distribution
of motive fluid by reversing such mechanisms as above described and I do not
reverse the engine which latter requires to be reversed independently. Or 1 may
produce a reversing link, to slide on the valve rod pin, which link may operate
inain slides or cut off slides, as hereinbefore describe and I may apply any of the
gears hereinbefore described, or what is known as Joy's gear, to this link in two
motions and one on each side of the valve rod pin the one motion possessing
forward and the other motion possessing reverse action, so that by sliding the link
on the valve rod pin, reversions and expansions may be obtained and varied as in
ordinary double eccentric reversing link gears.
In operating such cut off slides I may use any equivalent mechanism in order to
vary the extent and direction of the first movement with relation to its effect on
such gear as a component part of the whole but preferably by introducing an
additional movement of the first movement order, with which I retard or assist the
first movement component part of such cut off mechanism. In operating such cut
off slides the second movement may be produced either in the same or the opposite
direction to that of the main piston, as circumstances may require, in which case
the direction of the first movement will vary accordingly I may operate such
cut off slides on the back of any valve slides or on the back of a fixed plate or
face, the ports of which plate communicate suitably with openings for the motive
fluid in the principal valve slides, with which latter the fixed plate may be
connected to balance the pressure of the motive fluid on them; great variety is
obtained in expansion by such cut off slides because in full forward gear the major
part of the movement is obtained during the latter half of the stroke and pro-
portionately for intermediate points; or may apply the ordmary double
eccentric reversing link gear or equivalent reversing mechanism to operate
cut off slides, additional to the main slides, similarly as hereinbefore described,
whereby I produce the advantages in variable expansion from, what is equivalent
to full forward, to full reverse gear, with intermediate points as hereinbefore
described.
1005

page_text: Improvements in Valve Gear for Operating the Valves of Engines
Worked by Steam or other Expansible Fluid.
I, COURTENAY WILLIAM THOMPSON, of 5 Fair Street, Tooley Street, in the
County of Surrey, Mining 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 :--
My invention relates to mechanism for operating the valves of steam engines,
or other engines worked by expansible fluid, which valves may be flat, piston,
oscillating or other slide valves, and my said invention has for its object to produce
simple and effective mechanism for the purpose.
In ordinary valve gears in order to regulate the cut off for expansion and other
conditions of distribution of the motive fluid, the eccentric is set somewhere in the
second quadrant in lead of the main crank, and the amount of lead that is given
to the said eccentric in advance of the first quadrant determines the condition of
the distribution of the motive fluid. The circular nature of the movements of an
eccentric or crank is divided into two straight line motions at right angles to each
other and timed so that the first movement in any one direction is in excess at the
beginning of any quadrant, and the second movement, at right angles to the first,
is in excess at the end of the same quadrant.
At the end of the first quadrant in lead of the main crank, an eccentric has what
I call its first movement and is most effective in, say, opening a valve port, and
at the end of the second quadrant an eccentric has its second movement or
preponderating movement at right angles to the first movement, and therefore it
is principally holding the valve, in say, its open position preparatory to returning
the valve to close the port, therefore when the eccentric is placed in the second
quadrant in lead of the main crank, it is set say between the valve opening and
valve holding or neutralising movements and in proportion as the eccentric is set
near the first or the second of these movements or positions so the conditions of
distribution of the motive fluid are regulated.
My invention depends upon producing the two movements (the first and the
second as hereinbefore described) in parallel directions and in applying them in
such manner that I make the valve partake of both movements and in such
proportion of each that the required condition of distribution of motive fluid is
obtained and regulated.
obtain the first movement either from an eccentric or crank or equivalent
mechanism at right angles or approximately at right angles to the main crank or
from the crosshead, or equivalent mechanism, out of a cylinder operating a crank
approximately at right angles and by means of a lever or other suitable device.
"I transfer this first movement, thus obtained, to a convenient position preferably
approximately, opposite to the valve chest by means of levers, rocking shafts or
otherwise. I obtain the second movement either from the crosshead, from an
eccentric or crank in a line with or approximately in a line with the main crank
or from any equivalent mechanism, such that the line of direction of this movement
is parallel to but in the opposite direction from the movements of the main piston;
in this Specification I refer throughout to the ordinary D valve or equivalents, but
my mechanism can be modified to suit the requirements of a double D valve and
other forms of valve. The second movement thus obtained may be transferred to
a convenient position in approximation to that of the first movement by means of
levers, rocking shafts or oilier suitable devices.
I may manipulate the second movement and combine it with the first movement
with the object of obtaining the resultant movement as required for the valve and

page_text: as hereinbefore.described by any of the following or equivalent means: for example
1st. I connect the first and the second movements to two points of a rocking and
swinging lever respectively and I connect the valve operating rod to a point in the
same rocking lever between the points of connection of the first and second
movements just described; thus I obtain the required resultant movement for the
vaive operating rod by the means described or by any equivalent means.
This
gear may be reversed by reversing the first movement alone by any suitable
reversing link mechanism for example the first movement rocking shaft may be
fitted with a link or the reversing link may slide on the first movement point in
the rocking lever and such link may be operated from the first movement rocking
shaft in any convenient manner; or the reversing mechanism may be of any
convenient description: and I may vary the expansion to any of the intermediate
points of such reversing mechanism; or I may also vary the expansion by varying
the position of the point of connection of the valve rod in the locking lever (which
latter may be in the form of a link) relatively to the two points of connection of
the first and the second movements respectively; or any one point may be moved
relatively to the others, all in the same rocking lever. 2nd. 1 connect the fulcrum
of motion of the second movement to the first movement by any suitable convenient
and equivalent means, but preferably by attaching such fulcrum to, say, the first
movement rocking shaft and I then obtain the required resultant movement for
the valve by attaching the valve operating rod to the point of application of the
second movement in the rocking lever beyond the fulcrum just described; this
gear may be reversed by reversing the first movement alone by any convenient
means but preferably by reversing the second movement fulcrum in the first
movement rocking shaft (which latter may be in the form of a link) and I may
vary the expansion to any intermediate point in this mechanism or link.
When two or more cylinders operate cranks at right angles respectively suitable
movements may be transferred from any one cylinder to any other cylinder and
any one rocking shaft may operate suitably for two or more cylinders and so on.
The valve rod in my mechanisms, may be connected to the valve direct or by
the intervention of rocking shafts or other similar mechanism as may be
convenient.
Auxiliary cut off slides may also be added equivalent to those shown in Figure 6
of the drawings of the Specification of my said application for Letters Patent
No. 17682 of 1894. I may operate other cut off slides by any of these gears and
I may vary the cut off by varying the extent of the first movement (the second
movement remaining unaltered) in what is equivalent, when used with the principal
valve slides, to either forward or reverse gear whereby (for the cut off slides) the
latest cut off is effected in what is equivalent to the position of full forward gear
(for the principal valve slides), and the earliest cut off is effected in what is
equivalent to the position of full reverse gear (for the principal valve slides).
may also operate cut off slides by using what is known as Joy's gear and by
modifying it so that I may similarly vary the cut off for any point from full
forward gear to full reverse gear by angling the slide to any extent on either the
forward or reverse side, but in my cut off valve mechanisms I only vary the
conditions of distribution of motive fluid by reversing such mechanisms as above
described and I do not reverse the engine, which latter requires to be reversed
independently.
may
Or may produce a reversing link to slide on the valve rod pin, which link
may operate main slides or cut off slides as herein before described and
apply any of the gears hereinbefore described, or what is known as Joy's gear to
this link in two motions and one on each side of the valve rod pin, the one motion
possessing forward and the other motion possessing reverse action, so that by
sliding the link on the valve rod pin reversion and expansion may be obtained and
varied as in ordinary double eccentric reversing link gears.
In operating such cut off slides I may use any equivalent mechanism in order to
vary the extent and direction of the first movement with relation to its effect on

page_text: such gear as a component part of the whole, but preferably by introducing an
additional movement of the first movement order, with which I retard or assist the
first movement component part of such cut off mechanism.
In operating such cut off slides the second movement may be produced either
in the same or the opposite direction to that of the main piston, as circumstances
may require, in which case the direction of the first movement will vary
accordingly.
I may operate such cut off slides on the back of any valve slides or on the back
of a fixed plate or face, the ports of which plate communicate suitably with
openings for the motive fluid in the principal valve slides, with which latter the
fixed plate may be connected to balance the pressure of the motive fluid on them.
With this object such fixed plate may be attached to a pressure relief piston or
other pressure relief mechanism and, while thus balancing the main valves, any
suitable cut off slides may be operated on its reverse-face in conjunction with the
ports already described or, in the case of piston valves, such fixed plate may consist
of a cylindrical plate placed within the main piston valve and between it and
suitable cut off valves within such plate itself.
Great variety is obtained in expansion by such cut-off valve mechanism and
slides because, in the full forward position of the cut off gear or mechanism the
major part of the movement of the cut off valves is obtained during the latter half
of the stroke of the main piston and in the full reverse position of the cut off gear
the major part of the movement of the cut off valves is obtained during the first
half of the stroke of the main piston and proportionately for intermediate points in
the cut off mechanism.
Or 1 may apply the ordinary double eccentric reversing link gear or equivalent
reversing mechanism to operate cut off slides, additional to the main slides, similarly
to the manner herein before described, whereby I produce the advantages in
variable expansion, from what is equivalent to full forward to full reverse gear
with intermediate points, as hereinbefore described.
I have described the cut off mechanism, which is hereinbefore set forth, with
reference to suitable reversing mechanisms because it will be thereby readily
understood (in all its modifications) by engineers, but I wish it to be understood
that, though the properties of the movements, are similar in both cases, the
functions of such cut off mechanism are not effective to reverse the engine but
are adapted to effect wide variations in the rate of expansion as herein before
described.
I will describe with reference to the accompanying drawings manners in which
my invention may be carried into effect but I do not limit myself to the precise
examples shewn.
The accompanying drawings illustrate arrangements according to my invention.
Figure 1 illustrates the application of my invention in the case of gears com-
bining two movements, from which the resultant movement for the valve rod is
obtained. The gear illustrated is of the kind known as Walscheard's gear.
A B is the face on which the valve slides. C is the working cylinder and
P is the piston. E is the crank shaft. H is the crosshead and the attachment
of the connecting link for the crosshead lever which lever is centered at F.
O is the crosshead lever having the second movement.
is the first movement
rocking shaft.
The resultant movement is obtained at S in the lever O, the
fulcrum F of which lever may be attached to a crank pin on the first movement
rocking shaft n.
In Figure 1 the rocking shaft n is shewn fitted with a reversing
link instead of a crank pin for reasons hereinafter explained. The rocking
shaft may be operated by a crosshead lever, by a crank, by an eccentric or by
any equivalent arrangement having movement or operating at right angles to the
main crank. This part of my invention consists in reversing the engine or in
varying the expansion by reversing or varying the mechanism which effects the
first movement itself as follows-for instance the first movement eccentric itself
or its equivalent may be reversed or varied in itself whereby the engine will be

page_text: reversed or the expansion varied. Or the first movement rocking shaft n (or
equivalent) itself may be reversed or its movement varied at its connection with
such first movement eccentric or its equivalent and thus the engine can be reversed
or the expansion varied. The ordinary method of reversing the gear illustrated
and similar gears is by reversing the fulcrum F in the link m or equivalently
operating in the case of other gears, which ordinary method may be combined with
the method herein before described. The link m may thus he used as an auxiliary
link and its principal use will be to provide means for varying the expansion by
moving the fulcrum F, by one lever or equivalent device in such link m, while
independently the reversal of the engine is effected by reversing the movement of
the rocking shaft n by another and independent lever or equivalent device.
C is the
Figure 2 illustrates a cut off valve operating on the back of a main valve.
A B is the face on which the valve slides. C is the main valve. D and D' are
the cut off valves, which are operated by any ordinary or suitable reversing valve
gear as hereinbefore described. Figure 3 illustrates my cut off valves operating
on the back of a fixed plate. A B is the face on which the valve slides.
main valve. E is the fixed plate shewn as being connected to the pressure relief
piston E for relieving pressure on the main valve C. D is the cut off valve which
is operated by any ordinary or suitable reversing valve gear as herein before
described. The ports F F in the fixed plate E co-operate between the steam
ports in the main valve C and the cut off valve D. ln Figure 3 the cut off
valve D is shown as one plate with a fixed lead, whereas in Figure 2 the cut off
valve is shewn in two pieces D and D' whereby they may act as starting valves
and their lead may be adjusted and the expansion further varied by adjusting the
valves D and D' to and from each other which may be effected by any ordinary or
suitable means; but it will be understood that the cut off valve may be arranged
as either one or two plates in either of these cases.
main valve in
A reversing link arrangement like that shown applied to a
Figure is suitable for application to cut off slides arranged as in Figures 2
and 3 wherein the movement for such cut off valve rod is obtained at S in the
lever O of Figure 1 and the expansion is varied by varying the fulcrum F in the
link M Figure 1 but I do not limit myself to the use of that precise arrangement.
My reversing expansion valve gear may be regulated by hand or by a governor
and also the adjustment of the two cut off plates may be regulated by hand or by
a governor in any ordinary or suitable manner for effecting like operations. The
cut off valves shewn in Figures 2 and 3 may operate in either the same or the
opposite direction to that of the main valves.
The fixed plate with pressure relief mechanism is illustrated in Figure 3 in
connection with the cut off valve D operated by reversing cut off gear as herein-
before described but for example the cut off valve D may be in two parts and may
be operated by any ordinary or suitable cut-off valve mechanism and the expansion
may be varied by adjusting the two separate parts of the cut off valve D to or from
each other.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. In valve mechanisms wherein there is a resultant movement for the valve rod
combining the first and the second movement the reversal of the engine or
regulation of expansion by the reversal or regulation of the mechanism by which
the first movement is itself effected substantially as hereinbefore described.
2. In valve mechanism wherein there is a resultant movement for the valve rod
combining the first and second movement the reversal of the engine or regulation
of expansion by the reversal or regulation of the mechanism by which the first
movement itself is effected combined with an auxiliary variation of expansion
substantially as herein before described.
3. For operating cut off valves the combination therewith of a reversing link or

page_text: gear adapted to give the necessary movement to such cut off valves independently
of the main valves, whereby the cut off for expansion is varied by varying such
link or gear to any suitable extent in the direction either of the forward or the
reverse position from any equivalent of the central or intermediate position (which
is the essential of a reversing mechanism) such cut off valve consisting either of
one slide with a fixed lead or of two slides with an adjustable lead, adjustable by
moving the two slides to or from each other all substantially as hereinbefore
described.
4. In. combination with valves a stationary or fixed plate placed between the
main slide or slides aud cut off slides, the said stationary or fixed plate having ports
co-operating with steam ports in a main-slide and with the cut-off slides respectively:
in flat slide valve such plate being in connection with a suitable balance mechanism
and in piston valves such plate being a cylindrical plate and having functions
similar to those of the cut off valves substantially as hereinbefore described..
Dated this 4th day of May 1895.
JOHNSONS & WILLCOX,
Agents.