Improvements in Slide Valve Mechanisms for Steam Engines or other Engines Operated by Expansible Fluid or Vapour.
Year: 1895

page_text: Date of Application, 19th July, 1895
Complete Specification Left, 4th Oct... 1895-Accepted, 16th Nov., 1895
PROVISIONAL SPECIFICATION.
Improvements in Slide Valve Mechanisms for Steam Engines or
other Engines Operated by Expansible Fluid or Vapour.
I, COURTENAY WILLIAM THOMPSON, of 5 Fair Street, Tooley Street, in the
County of Surrey, Mining Eugineer, do hereby declare the nature of this
invention to be as follows:-
This invention relates to improvements in expansion valve mechanisms such as
I have described in the Specification of my application for Letters. Patent
No. 3399 of 16th February 1895, wherein an expansion valve mechanisin capable
of being varied through such positions (the one conveniently placed on the forward
side and the other conveniently placed on the reverse side and to any suitable
extent on either side) that. a large variation in the cut-off could be effected.
According to my present invention I provide an expansion valve operating
mechanism which may be available for variation to various degrees of the extreme
points on either side of the central or intermediate position and one extreme point
of this gear may be represented by such central position, or by an approximation
of such central position, while the other extreme point may be the equivalent of the
reverse position with the varying points between such extreme points, the reverse
position will then be the early cut-off position and the central position will be the
late cut-off position. Suitable lead in the cut-off valve port may be allowed for
the early cut-off (or reverse) position, or the cut-off valve port may be closed
according to circumstances.
The valve slides may be like or equivalent to those represented in Figures 1
and 2 of the drawings of my said application for Patent No. 3399 of 1895.
I will now give, with reference to the drawings a few examples of how my
invention can be carried into effect. In Figure 1 the cut off valve block S2 may
be varied from the m* (reverse) end of the link to the centre of the link, without
allowance being made for variation to the other end m of the link, the central
position being then the latest cut-off and m² the earliest cut-off position.
In Figure 2, the eccentric n may be set approximately in a line with the crank,
which then, according to my invention will represent the central or late cut-off
eccentric or n may be set say 30° to either one side or to the other and the
eccentric O may be given any lead (shewn as one of 45°) in reverse position from
that shewn for n to a position Q at right angles to the crank and it will then be
the early cut-off eccentric; or the eccentric O may be set, in advance of the
eccentric n, to an extent still further (say 30° further) than the position Q.
In Figure 2 or in equivalent mechanisms, the earliest cut-off position may be
given such lead that the cut-off valve has closed the steam port before the
commencement of the stroke of the main piston, when this mechanism may be used
as a shut-off or starting valve.
In Figures 3 and 4, according to my invention the cut-off valve block is only
available from the extreme reverse position (or early cut-off position) in the link m
to approximately the centre of the same link m such central position being then the
late cut-off position.
In Figure 5 another example is shewn and the gear for operating both the main,
and cut-off, valves is shewn thus :-the eccentric k is set at right angles to the
crank and its rod is attached by the lever g to the rocking shaft y, the eccentric h
is set in a line with the crank and its rod is attached by the levert to the rocking

page_text: shaft y, the swinging lever D D7 transmits a resultant movement to'the attachment.S
for the main valve, the end at D receiving its movement from the levert and the
end at D receiving its movement from the lever q. If the eccentrick were
attached to the lever ✗on the rocking.shaft y, the engine would be reversed and
the reversal may be effected in any couvenient manner. For varying expansion,
the link m. m² operating the attachment S för. the cut-off valve, ist raised, or
lowered, by an attachment at R, and, at its lowest point, the cut-off valve has its
earliest cut-off due to Xand at its highest point, it has its latest cut-off due to t,
with the intermediate points between these two extreme points.
This mechanism may operate for a number of cylinders at right angles to each
other.
In Figure 5 an example, is shewn of an improved method, of transmitting, the
'movements of the eccentrics to, the link m. m² by means of the pins on the levers t
and X of the rocking shafts y2y; the feature of this method being that the two
movements, say of forward and reverse eccentrics, are brought close together and
then transmitted to the respective ends of a link, which link may then be varied
approximately on a centre; thus Figures 6 and 7 shew, for example, the movements.
of the rocking shafts and y2 brought to one. centre line S and then transmitted to
the respective ends of the link m, but the means for approximating the movements
'may be varied to produce equivalent results, and anyone rocking shaft may
transmit the same movement for annumber of valves..
Dated this 10th day of Jul 1905
JOHNSONS & WILLCOX.
47 Lincoln's Inn Fields, London, W.C., Agents for the Applicant..
1
Improvements in Slide: Valve Mechanisms for Steam Engines or
other Engines Operated by Expansible. Fluid or Vapour.
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 :-
J
This invention-relates to improvements in expansion valve mechanisms such as
I have described in the Specification of Letters-Patent No. 3399 of 16th February
1895 granted to me wherein an expansion valve mechanism is employed capable of
being varied through such positions (the one conveniently placed on the forward
side and the other conveniently placed on the reverse side and to any suitable
extent on either side) that a large variation in the cut off can be effected.
According to my present invention I provide an expansion valve operating
mechanism which is available for variation to various degrees of the extreme
points (in the equivalent of a reversing mechanism) by movement entirely on
either one side or the other of 'what is the central or intermediate-position in
the link or gear described under 33999. For example one extreme point' of the
gear according to the present invention may be represented by such' central-or
intermediate position or by an approximation of such central for intermediate
position whilst the other extreme point may be the equivalent of the reverse position
with the varying points between such extreme points. The reverse position will
then be the early cut off position and the central position will be the late cut
off position. Similarly whilst the said central or intermediate position (or an
approximation thereof) 'forms one extreme point the equivalent of the forward
position may form the other extreme point. The central position will then be the
early cut off position and the forward position, will the the late cut off position
with the varying points between those extreme points. Suitable lead in the cut

page_text: off valve port may be allowed for the early cut off position, or the cut, off valve
port may be closed according to circumstances.
The valve slides may be like or equivalent to those represented in Figures 2
and 3 of the drawings of my said Patent No. 3399 of 1895 but the valve slides
may be of other form for example they may be of piston form operating in a
fixed cylindrical casing and in convenient communication with the main flat. piston
or other valve.
I will now give, with reference to the drawings accompanying my Provisional
Specification and also with reference to Figures 5 and 54 accompanying this
Specification examples of how my invention can be carried into practica effect.
In the present Specification when refer to Figure 5 I refer to that filed
herewith in place of that lodged with my Provisional Specification as in the
Figure 5 'filed herewith I have corrected errors in the positions of certain of the
parts as shown in the Figure 5 accompanying my Provisional Specification. With
reference to the examples Figures 1, 3, 4 and 54 I describe arrangements wherein
the variation is between the central position as one extreme point and the reverse
position as the other extreme point but it will be understood that the forward
position may be the other extreine point if desired. In Figure 1 the cut off valve
block S2 may be varied from the reverse end m² of the link to the centre of the
link without allowance being made for variation to the other end m of the link,..
the central position being then the latest cut off and m² the earliest cut off position.
The other block shewn is the main valve block.
In Figure 2 the eccentric n may be set approximately in a line with the crank,
which then according to my invention, will represent the central, or late, cut off
eccentric, or the eccentric n may be set say 30° to either one side or to the other
and the eccentric o may be given any lead (shewn as one of 45°) in reverse position
from that shewn for the eccentric n to a position Q at right angles to the crank
and it will then be the early cut-off eccentric. Or the eccentric o may be set, in
advance of the eccentric n to an extent still further (say 30° further) than the
position Q. In Figure 2 or in equivalent mechanisms the earliest cut-off position
may be given such lead in advance of the right angular position at Q. that the
cut-off valve has closed the steam port before the commencement of the stroke
of the main piston when this mechanism may be used as a shut off or starting
valve and it is preferable in some cases that the late cut-off eccentric shall
have a shorter stroke than the early cut off eccentric so as to effect a later
cut off.
In this example Figure 2 if the early cut off excentric o be set in the position.Q
and it has a total travel of say 3 inches and if the late cut off eccentric n has a
total travel of say two inches and if the expansion valve in early cut off position
has a lead of an inch and in late cut off position a lead of 1 inches then the
earliest cut off will be at one thirtieth of the stroke of the main piston and the
latest cut off will be at three quarters of the stroke of the main piston. Thus if
the main valve opens to steam at say one sixteenth before the end of the stroke of
the main piston the back pressure will be greater than the forward or effective'
pressure, being one sixteenth to one thirtieth, thus constituting a cushioned brake
on the engine to prevent it running away in early cut off. position or again as
another example and also to prevent the engine running away, the eccentrics may
have the same relative length of travel as above mentioned and the lead of the
expansion valve may be the same and have the same cut off for the late cut
off position whereas the eccentric o may have say 30° more lead ahead of the
position Q when the expansion valve in the early cut off position may shut off
steam say 10 or 15° before the end of the stroke of the main piston with the
intermediate points in the link.
In Figures 3 and 4 according to my invention the cut off valve block is also
only available from the extreme reverse position (or early cut-off position) in
the link m to approximately the centre of the same link m such central position
being the late cut-off position.

page_text: When such combination mechanisms as are illustrated in Figures 3, 4 and 5 are
used in connection with these gears or those described in the Specification of my.
Patent 3399 the engine may be reversed by reversing in any convenient manner
the variable expansion rocking shafts and this without altering the rate of
expansion or the governor controlling such rate of expansion. The 'arrangement
Figure 4 is otherwise like that shewn in Figure 1 of the Specification of my
aforesaid Patent 339995.
In Figure 5 another example is shewn and the gear for operating both the main
and cut-off valves is shewn thus:-the eccentric kris set at right angles to the
crank and its rod is attached by the lever q to the rocking shaft y, the eccentric h
is set in a line with the crank and its rod is attached by the lever t to the rocking
shaft the swinging lever D D transmits a resultant movement to the attach-
ment S for the main valve, the end at D2 receiving its movement from the lever t
If the eccentric k were
and the end at D receiving its movement from the lever q.
attached to the lever X on the rocking shaft y the engine would be reversed and
the reversal may be effected in any convenient manner. For varying expansion
the link mm² operating the attachment S2 for the cut-off valve, is raised or
lowered, by an attachment at R and at its lowest point, the cut-off valve has its
earliest cut-off due to X and at its highest point, it has its latest cut-off due to t
with the intermediate cut-offs at points between these two extreme points.
This mechanism may operate for a number of cylinders at right angles to each
other.
'
In the said Figure 5 an example is shewn of an improved method of transmitting
the movements of the eccentrics to the link m m² by means of the pins, on the
levers and X of the rocking shafts y2 y, the feature of this method being that the
two movements say of forward and reverse eccentrics, are brought close together
and then transmitted to the respective ends of a link, which link may then be
varied approximately on a centre. Figure 5 illustrates another example of this
wherein the movements of two eccentrics are thus connected to two links the one
operating the main valve as at Sand the other operating the expansion valve as
at S. Figures 6 and 7 shew examples of the movements of the rocking shafts y
andy brought to one central axis S3 and then transmitted to the respective ends of
the link in, but the means for approximating the movements may be varied to
produce equivalent results, and any one rocking shaft may transmit the same
movement for a number of valves.
In the arrangements according to my present invention and according to my
former Patent No. 3399 when lead-opening to steam is given in the early cut-off
position, whereby the cut-off valve never shuts off steam at the commenceinent of
the stroke of the main piston, an auxiliary connection to a throttle valve suitably
governed may be provided so as to shut off steam if the engine tend to run away,
even after the earliest cut off position is practically reached..
1
Having now particularly described and ascertained the nature of my said inven-
declare that what I
tion and in what manner the same is to be performed
claim is:
―
1. An expansion gear with properties of movement equivalent to those of any
ordinary reversing mechanism, or connected to the same link, capable of varying
the cut-off from the central position, or any equivalent of the central position, as
one extreme point, to either the reverse, or forward positions, as the other extreme
point; all substantially as herein before described.
2. An expansion gear with the late cut-off eccentric in a line, or approximately
in a line, with the crank, and the early cut-off eccentric having such reverse lead
as is shewn in, or described in connection with, Figure 2; the expansion valve in its
carly cut-off position having lead opening in position from n, to Q, with, or without,
lead opening in advance of Q (Q indicating a position at right angles to n) all
substantially as hereinbefore described.
3. In combination mechanisms the means described in, connection with the
1

page_text: examples illustrated in Figures 3, 4 and 5 for use with valve gears whereby by
reversing the movement of the variable expansion rocking shafts the engine may
be reversed without altering the rate of cut-off or affecting the governor controlling
same all substantially as herein before described.
4. The means shewn and exemplified in Figures 5, 5ª, and 7 of the accom-
panying drawings whereby the movements of eccentrics or other equivalent
mechanisms are first brought into proximity with each other and then transmitted
for operating the main valve or the expansion valve, or both, to the respective
ends of the curved reversing or expansion link or links substantially as and for
the purposes herein before described.
5. The several arrangements of valve mechanisms as hereinbefore described and
illustrated in the several figures of the accompanying drawings.
Dated this 4th day of October 1895
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.