IMPROVEMENTS IN AUTOMATIC CUT-OFF VALVES
Year: 1884

page_text: I, GEORGE FLETCHER, of Derby, in the county of Derby, Engineer do hereby
declare the nature of the said invention for "IMPROVEMENTS IN AUTOMATIC CUT-OFF
VALVES" partly a communication from abroad by James Henry Man of Denver,
Colorado, United States of America, Engineer to be as follows :—
This Invention relates to improvements in automatic cut-off valves for steam,
gas or other engines, the improvements having for object to effect automatic and
instantaneous cut-offs by means of a differential pressure acting on the valve.
In carrying out the invention when a valve of the differential double beat design
is employed a diaphragm separates the slide case proper from the passages that
lead to the cylinder. On each side of the diaphragin are two ports the lower one
being slightly the larger. Projecting into the passage and concentric with the
said ports is a spindle or bar firmly secured in said position; adapted to slide
longitudinally on this bar is the valve in shape similar to a bobbin and consisting
of a hollow stem of metal having two right angle flaring projections forming two
parallel discs.
These two discs are different in area, the smaller resting when the valve is closed
on the lower or inner edge of the upper port and the larger on the lower or outer
edge of the lower port. The valve rests normally on an adjustable stop which is
actuated by hand or by a governor according to the requirements of regulation.
In this valve the weight of the same keeps it normally in contact with the stop
and it is necessarily placed in an upright position.
The operation of the valve is as follows:-
The steam entering at the lower port being slightly impeded or throttled by the
disc of the valve would tend to force the said valve upwards till it engaged with
the edge of the valve scat thus cutting off the steam; but the steam also enters
the upper port and in consequence of the same throttling exerts a certain force
on the upper disc of the valve downwards, thus tending to keep it open; wero
the discs of the same size, the force exerted on each would be the same and the
valve would remain resting on the stop, its weight keeping it in the said position,
Price 611

page_text: but the upper disc being smaller than the lower disc the upward force must be the
greater and when the difference between these forces is sufficient to overcome the
weight of the valve it will close and the closing will be practically instantaneous
as the valve in closing reduces the area for the passage of the steam and causes it
to pass through the diminished opening with greater velocity, thereby exerting
a constantly increasing force on the valve, the operation being so quickly performed
as to be practically instantaneous as stated.
The operation is the same whether the resistance to the closing of the valve be
a spring or by weight as described.
The use of a spring allows the position of the valve to be other than perpen-
dicular as is evident.
Thus it will be seen, if the valve be so adjusted that the steam passing through
it at the moment when the piston acquires its maximum speed shall acquire a
certain velocity so as to become throttled and exert force enough to close the valve,
the steam will be cut off at about half stroke, and that if the adjustable stop
be raised so as to decrease the area presented for the passage of the steam, the
steam will become sufficiently throttled and the maximum velocity requisite to
close the valve will be attained earlier in the stroke, thus effecting cut-off at any
desired point earlier than half stroke.
To regulate such engines as are used for locomotive and marine purposes, suitable
mechanism can be applied to the stop so as to adjust its position at pleasure, but in
other engines requiring regulation of speed, any governor can be applied to actuate
the stop so as to automatically regulate the point of cut-off.
In the arrangement hereinbefore described each valve is placed in a box or
chamber cast on the back of a slide valve thorofare type; the said box or chamber
can also be made separate from the slide-valve and secured in a stationary position,
such that in the successive positions of the slide valve each thorofare port of the
slide valve is brought alternately opposite each corresponding valve chamber
respectively, but it will be obvious that the principle can be applied to a valve of
different construction from the ports of a thorofare slide valve.
For example the valve may consist of a flat piece of metal adapted to sit
over and close the usual induction port of the slide-valve. The valve can be
normally kept away from its seat by a suspensory spring preferably flat and of
elliptical shape.
The spring keeps the valve against the adjustable stop with a limited force.
The action of the valve depends on the velocity of the steam passing into and
through the port as does that of the differential double beat design already
described. It is obvious that the nearer the stop adjusts the valve to the port the
greater will be the speed of the steam passing through the diminished area; in
other words the steam will become sufficiently throttled and the maximum velocity
requisite to close the valve will be attained earlier in the stroke, thus effecting an
earlier cut-off and vice-versa; the greater the area, the later will be the cut-off.
In the application of the differential double beat design to separate induction
ports, one for each end of the cylinder, the function of the slide valve is to
admit steam to the cylinder for only a short portion of the stroke and to exhaust
in the usual way.
The differential double beat valve can be applied to an engine in which there is
no connection between the rotating shaft and the inlet valve, nor any slide valve
The point of cut-off is in this case determined by the amount of area presented
for the passage of the steam and the speed of the engine at the time: the exhaust
takes place at the end of the stroke by the piston uncovering an annular space,
the remaining steam being compressed by the piston on its return stroke till it
reaches the initial pressure, when the weight of the valve is free to exert its force
in opening the valve before the beginning of the next stroke.
It is obvious any form of valve actuated by a differential pressure can be applied
to this class of engines.

page_text: In the several applications of the valve described when the cut off has taken
place the pressure in the cylinder is being continually reduced by the expansion of
the steam and after the exhaust the pressure is still further reduced while the
pressure in the slide case reinains the same, which condition would cause the valve
to remain firmly closed, but at any time after the exhaust port is closed and before
the valve is again required for use at the beginning of the next stroke the pressure
within the valve chamber is raised so as to be equal to that in the slide caso; this
is effected in the case of its application to a slide valve by causing the slide-valve
in its travel to uncover a port for the admission of steam from the slide case to the
valve chamber; and in the application to separate induction ports by admitting
steam during the earlier portion of the stroke by means of the slide valve to the
valve chamber and the cylinder, and in the application to single acting trunk
piston engines by causing the piston on its return stroke to compress the steam
remaining in the cylinder at the end of the stroke till it reaches the initial
pressure.
G. F. REDFERN,
4, South Street, Finsbury, London,
Agent for the Applicant.

page_text: "
I GEORGE FLETCHER of Derby in the county of Derby Engineer do hereby
declare the nature of the said invention for "IMPROVEMENTS IN AUTOMATIC CUT
OFF VALVES partly a communication from abroad by James Henry Man of
Denver Colorado United States of America, and in what manner the same is to
be performed to be particularly described and ascertained in and by the following
statement:-
This invention relates to improvements in that class of Automatic cut off Valves
for Steam Gas or other Engines in which Automatic and instantaneous cut-offs are
effected by means of a differential pressure acting on the valve, as will be more
fully hereinafter setforth.
When steam (or gas) at any pressure passes through an orifice into any lower
pressure, its velocity is due to and varies approximately as the square root of the
difference of pressures, when this difference is small; if then the orifice be that of
a valve free to close but kept open by its own weight or a spring it is evident the
valve will not remain open when the difference of pressures on either side of itself
produces a force greater than that tending to keep it open, the valve is in equilibrium
when these forces are equal and opposite and the velocity of the steam at the
moment of equilibrium is therefore definable.
By introducing such a valve between the slide case and the cylinder so that the
velocity of the steam shall just produce equilibrium about the valve at the moment
of maximum piston speed, the valve will close and give an instantaneous cut-off at
about half stroke.
To effect the cut off earlier than half stroke the phenomenon of equilibrium has
merely to take place at some previous moment, which may be accomplished, first
by an increase in the speed of the engine, second a decrease in the area of the valve
and third a decrease in the load on the valve.
From a study of the first of these causes, it appears the valve when once adjusted
should be an automatic regulator of speed and this is actually the case to a limited
extent, but in practice it will be necessary to adopt one of the other causes.
Locomotive, marine, and other engines that require regulation of power at
varying speeds can be fitted with mechanism by which the area of the valve, or the
load on it, or both, can be altered at pleasure and so vary the point of cut off to
suit circumstances.
In other engines requiring regulation of speed any governor can be applied to
actuate the cut off valve or its load.
In order to enable the invention to be fully understood I will describe the same
by reference to the accompanying drawings in which figure I represents a vertical
sectional view of one form of the improved valve and its seat, with an adjustable
stop.
Figure 2 a section similar to figure I but reduced in size to shew the interior
arrangements of the slide case attached to a cylinder. Figure 3 an elevation view
of the slide case with cover removed, shewing the valves in position,

page_text: Figure 4, shewa a modification of the improved valve the view being a cross
section through the slide case.
Figure 5, a longitudinal section of the device shown in figure 4.
Figure 6, a cross section of a slide case shewing the valve of differential type
applied to induction ports, independent of the slide valve.
Figure 7, a longitudinal section of the application shown in figure 6 and
figures 8 and 9 are sectional views shewing the application of the improved valve
of differential type to the induction ports of a cylinder without the use of a slide
valve of any kind.
The valve consists primarily and essentially of a disc that when closed shall fit
or cover an orifice. It may be of any shape desired and is adapted to enter. its
seating or sit on the edge thereof. It may be of any suitable material and may be
either single or double beat, and there may be a single valve arranged to admit
steam alternately to each end of the cylinder or one or more valves for each end of
the cylinder.
In Figure I is shewn a valve of the differential double beat design A representing
the diaphragm separating the slide case proper from the passages that lead to the
cylinder.
On each side of this are ports B and O respectively the lower one C being
slightly the larger.
Projecting into the passage and concentric with the ports B and C is a spindle or
bar D firmly secured in said position; adapted to slide longitudinally on this bar
is the valve F in shape similar to a bobbin and consists of a hollow stem of metal
having two right angle flaring projections forming two parallel discs as shewn.
These two discs are different in area, the smaller resting when the valve is closed
on the lower or inner edge of the port B and the larger on the lower or outer edge
of the port C. The valve rests normally on the adjustable stop G which is
actuated by hand or by a governor according to the requirements of regulation.
In the valve described above and shewn in figures 1, 2, 3, 6, 7, 8 and 9 the weight
of the same keeps it normally in contact with the stop and it is necessarily placed
in an upright position.
The operation of the valve will be clearly evident from the statements heretofore
made.
The steam entering at the port C being slightly impeded or throttled by the
disc of the valve would tend to force the said valve upwards till it engaged with
the edge of the valve seat, thus cutting off the steam; but the steam also enters
the port B and in consequence of the same throttling exerts a certain force on the
upper disc of the valve downwards, thus tending to keep it open, were the discs of
the same size, the force exerted on each would be the same and the valve would
remain resting on the stop its weight keeping it in the said position, but the upper
disc being smaller than the lower disc the upward force must be the greater and
when the difference between these forces is sufficient to overcome the weight of the
valve it will close and the closing will be practically instantaneous as the valve in
closing reduces the area for the passage of the steam and causes it to pass through
the diminished opening with greater velocity, thereby exerting a constantly
increasing force on the valve, the operation being so quickly performed as to be
practically instantaneous as stated.
•
The operation is the same whether the resistance to the closing of the valve be
a spring or by weight as described.
The use of a spring allows the position of the valve to be other than perpen-
dicular as is evident.
Thus it will be seen, if the valve be so adjusted that the steam passing through
it at the moment when the piston acquires its maximum speed shall acquire a
certain velocity so as to become throttled and exert force enough to close the valve,
the steam will be cut off at about half stroke, and that if the adjustable stop be
raised so as to decrease the area presonted for the passage of the steam the steam
will become sufficiently throttled and the maximum velocity requisite to close the

page_text: valve will be attained earlier in the stroke, thus effecting cut-off at any desired
point earlier than half stroke.
To regulate such engines as are used for locomotive and marine purposes,
suitable mechanism can be applied to the stop so as to adjust its position at
pleasure, but in other engines requiring regulation of speed, any governor can
be applied to actuate the stop so as to automatically regulate the point of cut-off.
j
In figures 1, 2, and 3 already described each valve is placed in a box or chamber
cast on the back of a slide valve of the thorofare type; the said box or chamber
can also be made separate from the slide-valve and secured in a stationary
position, such that in the successive positions of the slide valve each thorofare port
of the slide valve is brought alternately opposite each corresponding valve chamber
respectively, but in figures 4 and 5 are shewn the application of the principle in a
valve of different construction to the ports of a thorofare slide valve. This latter
valve consists essentially of a flat piece of metal A adapted to sit over and close
the usual induction port of the slide valve. The valve is normally kept away
from its seat as shewn by a suspensory spring B preferably flat and of elliptical
shape as shewn.
The spring keeps the valve against the adjustable stop C with a limited force
The action of the valve depends on the velocity of the steam passing into and
through the port as does that of the differential double beat design already
described. It is obvious that the nearer the stop adjusts the valve to the port
the greater will be the speed of the steam passing. through the diminished area;
in other words the steam will become sufficiently throttled and the maximum
velocity requisite to close the valve will be attained earlier in the stroke, thus
effecting an earlier cut-off and vice-versa; the greater the area, the later will be
the cut off.
In figures 6 and 7 is shewn the application of the differential double beat design
to separate induction ports, one for each end of the cylinder, the function of the
slide valve being to admit steam to the cylinder for only a short portion of the
stroke and to exhaust in the usual way.
Figures 8 and 9 shew the application of the differential double beat valve to an
engine in which there is no connection between the rotating shaft and the inlet
valve, neither is there any slide valve. The point of cut off is determined by the
amount of area presented for the passage of the steam and the speed of the engine
at the time; the exhaust. takes place at the end of the stroke by the piston
uncovering an annular space, the remaining steam being compressed by the
piston on its return stroke till it reaches the initial pressure, when the weight of
the valve is free to exert its force in opening the valve before the beginning of the
next stroke.
It is obvious that any form of valve actuated by a differential pressure can be
applied to this class of engines.
In the several applications of the valve shewn and described when the cut off
has taken place the pressure in the cylinder is being continually reduced by the
expansion of the steam and after the exhaust the pressure is still further reduced
while the pressure in the slide case remains the same, which condition would cause
the valve to remain firmly closed, but at any time after the exhaust port is closed
and before the valve is again required for use at the beginning of the next stroke
the pressure within the valve chamber is raised so as to be equal to that in the
slide case;
this is effected in the case of its application to a slide valve by causing
the slide valve in its travel to uncover a port for the admission of steam from the
slide case to the valve chamber; and in the application to separate induction
ports by admitting steam during the earlier portion of the stroke by means of the
slide valve to the valve chamber and the cylinder; and in the application to single
acting trunk piston engines by causing the piston on its return stroke to compress
the steam remaining in the cylinder at the end of the stroke till it reaches the
initial pressure.

page_text: 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 in an engine of a cut off valve and means for producing the
differential pressures on opposite sides of the said valve substantially as set forth
and represented in the accompanying drawing.
2. In combination a valve actuated in one direction by differential pressure on
its opposite sides and means for adjusting the valve and thereby regulating the
area of the steam passages with relation to the speed of the engine and varying
the point of cut off substantially as specified and represented in the accompanying
drawing.
3. In combination a valve actuated in one direction by differential pressures on
its opposite sides and an adjustable stop operated by suitable means for effecting
an automatic regulation of speed as set forth and represented in the accompanying
drawing.
4. A valve consisting of a hollow stem having two flaring right angle projections
forming two parallel discs of different diameters, the stem being adapted to receive
a spindle or bar which supports and guides the said valve and which in turn is
firmly supported so as to bear a fixed position relative to the valve seats the whole
being arranged to operate to cut off the steam in its passage from the steam chest
to the cylinder substantially as and for the purpose set forth and illustrated in the
accompanying drawing.
5. The manufacture and use of the improved automatic cut off valve herein-
before described and illustrated in the accompanying drawing.
Dated the 1st day of August 1885.
G. F. REDFERN,
4, South Street, Finsbury, London,
Agent for the Applicant.
G. F. REDFERN,
4, South Street, Finsbury, London,
Agent for the Applicant.