IMPROVE- MENTS IN EXPANSION VALVES FOR STEAM AND OTHER LIKE MOTIVE POWER ENGINEO
Year: 1882

page_text: LETTERS PATENT to Joseph Hopwood of the Cottage Cleveleys Poulton-le-
Fylde in the County of Lancaster Engineer for an invention of "IMPROVE-
MENTS IN EXPANSION VALVES FOR STEAM AND OTHER LIKE MOTIVE POWER
ENGINEO"
PROVISIONAL SPECIFICATION left by the said Joseph Hopwood at the
Office of the Cominissioners of Patents on the 14th March 1882.
JOSEPH HOPWOOD of the Cottage Cleveleys Poulton-le-Fylde in the County of
Lancaster Engineer "IMPROVEMENTS IN EXPANSION VALVES FOR STEAM AND
OTHER LIKE MOTIVE POWER ENGINES."
"
This Invention has for its object to remedy certain imperfections in the ordinary
sliding cut off or expansion valve of the plate or gridiron class hereinafter
designated the "cut-off" whether composed of separate pieces for cutting off at
opposite ends of the main slide valve or in one piece centrally situated in reference
thereto and cutting off at each end alternately and whether working upon a fixed
surface or carried on the back of or within the main slide valve hereinafter referred
to as the "main slide" or "carrier" but its application is of especial advantage to
the latter class owing to the severe and fleeting character of the strains thrown
upon the driving gear of the main slide by the action of the cut off which vary
in intensity and in the periods of their occurrence relatively to the order in which
those changes take place which are inherent to the main slide with each alteration
in the grade or ratio of expansion and are chiefly dependent on the differences in
each instance between the initial terminal and exhaust pressures, the amount of
intertravel of the two valves whether arising from differences in the velocity or
direction of their motions or differences in both and the transfer of load from one
valve rod to the other on the closing or re-opening of the steam passages at the
back of the main slide by the cut-off the driving rod or gear of the former being
relieved of the amount of work at any instant performed by the driving rod or
gear of the cut-off less stuffing box friction-while they are moving in the same
direction and loaded with that additional amount of work while they are moving
divergently double the maximum load on the expansion rod or driving gear at the

page_text: various grades of working being practically the correct measure in each case of the
disturbing effect of the cut-off on the driving rod or gear of its carrier furthermore
while variations of pressure and range of inter-travel exclusively determine the
severity of the strains and duty cast upon the driver of the cut-off the driver of
the main slide is subject to the re-action of these on its back compounded with
those due to the more constant range of motion and action between its front and
the cylinder faces the strains on both sides moreover being intermittent and
relatively irregular in the times of their occurrence at varying grades. It is obvious
that all irregularities arising from the causes before mentioned and their
consequences upon the main slide may be avoided and that most of the power
absorbed in driving the cut-off will be saved if only one of the two essentials of
friction viz. Pressure-can be eliminated from the interacting surfaces of the two
valves. This invention therefore consists of a method of rendering the fluid
pressures nugatory by balancing their effect on the opposite surfaces of the cut-off
valve the main slide then being subject only to the same or practically the same
disturbances when carrying the cut-off as when that agent is carried upon a
separate fixed surface the power demanded for its propulsion being simultaneously
reduced to the amount necessary to overcome the friction of its stuffing box and
that due to the slight pressure of a balance ring hereinafter more specifically
referred to. Accordingly the proposed cut-off valve is composed of two plates
between which flows the entering steam or fluid the two forming parallel planes
sustained at the requisite distance apart by suitable connections at the sides or
ends or both, one of these plates has cut through it the steam ways or passages
and is truly surfaced on the outer side to work in contact with the back face of
the main slide or fixed surface as the case may be the other or back plate being
similarly surfaced on the outer side to maintain steam tight contact with a balance
ring of the ordinary construction between the front and back plates before mentioned
one or more pipes or steam ways are fitted or cast having an opening openings in
the face of the front plate which may be isolated portions of one or more of the
steamways elongated in the direction of travel when the cut-off has only one
steamway or when one pipe or passage only is provided between the plates of a
cut-off with several steamways but it is essential that such openings should singly
or conjointly have some portion open to one or other of the steam ways at the
back of the main slide in every position which they mutually occupy while at
work the opening or openings in the back face of the cut off may be of any
convenient form or size but must be so located as to remain within the inner periphery
of the balance ring under all conditions of working communication being thus
constantly maintained between the interior of the main slide and the space at the
back of the cut-off enclosed within the balance ring a separate balance ring is required
at each end of the main slide where the cut-off valve is composed of two parts and will
be most convenient of application if made oblong in the same direction as the steam
passages in the main slide but when the cut off is in one piece centrally situated and
cutting off at each end alternately a balance ring of the usual circular form is preferable
the back plate or cover which is ordinarily fitted and attached to the main slide and
surfaced on its exterior to work in conjunction with the ordinary balance ring located
inside the slide casing door is by the present invention further provided on its
underside with a suitable groove or grooves for the reception of the balance rings
of the cut-off and with recesses containing springs for maintaining contact between
the plane surface of the balance ring and the back of the cut-off in the ordinary
way; whether one or more balance rings be employed it is essential that the inner
periphery of the balance ring at the plane of contact should exactly equal the area
of steam opening in the back of the main slide or that portion of the collective
amount thereof which that individual ring is intended to balance and that the
centre of the superfices at the back of the cut-off enclosed by the balance ring should
be truly located opposite or over the centre or effective centre of the stean way or
collective steam way or opening at the back of the main slide. In those cases
where the cut off works upon a separate fixed surface independent of the main

page_text: slide the back plate or cover before referred to is fitted and attached thereto or to
any other adjacent and convenient fixed part of the slide casing so that the cut-off
works between the said plate or cover and the surface in which the steam ways are
cut as in the former case when carried on the back of the main slide the plate or
cover being similarly fitted with a groove and recesses for the reception of a
balance ring and springs the collective steam opening under the cut-off in the fixed
surface being equal and truly opposite or under the inner area of the balance ring
or accurately apportioned and opposite thereto when it is preferred to employ more
than one balance ring as may sometimes be judicious where the cut off valve is
very long in proportion to its breadth the advantages of the present invention in
these cases however is limited to the saving of power and reduction of strength of
driving gear and wear and tear from absence of friction.
By the arrangement and construction of cut-off valve and modification of the
usual fittings of the main slide or its casing herein before described the cut off will
in effect operate between two plane surfaces which whether fixed or moving
preserve the same positions relatively each to the other under all conditions and
in which are equal and opposite openings communicating with hollow spaces in
which the steam or other fluid under control is under all variations in pressure the
same in the one as in the other its effect therefore is nugatory on the cut-off
furthermore the inequality in the amount of interacting surface on opposite sides
of the cut-off due to difference of area between the working face of the balance
ring and the back face of the main slide or to the difference of area between the
collective steam way at the front and pipe or passage opening at the back of the
cut-off itself will cause no disturbance of balance the resilient force in the springs
holding the balance ring against the cut-off maintaining the latter in contact
with the back of the main slide also need not be of considerable amount and
exclusive of the friction occasioned by this slight pressure the cut-off moves in
equilibrium without encumbrance to the main slide or interference with its
ordinary action.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Joseph Hopwood in the Great Seal Patent Office on the
13th September 1882.
JOSEPH HOPWOOD of The Cottage Cleveleys Poulton-le-Fylde in the County
of Lancaster, Engineer "IMPROVEMENTS IN EXPANSION VALVES FOR STEAM AND
OTHER LIKE MOTIVE POWER ENGINES
"
My said invention has for its object to remedy certain imperfections in the
ordinary sliding cut-off or expansion valve of the plate or gridiron class hereinafter
designated the "cut-off" whether composed of separate pieces for cutting off at
opposite ends of the main slide valve or in one piece centrally situated in reference
thereto and cutting off at each end alternately; and whether working upon a fixed
surface or carried on the back of, or within, the main slide valve hereinafter referred
to as the "main slide" or "carrier." Its application is however of especial
advantage to the latter class owing to the severe and fleeting character of the
strains thrown upon the driving gear of the main slide by the action of the cut-off
which strains vary in intensity and in the periods of their occurrence, (relatively to
the order in which those changes take place which are inherent to the main slide)
with each alteration in the grade or ratio of expansion and are chiefly dependent
on the differences in each instance between the initial terminal and exhaust
pressures the amount of intertravel of the two valves (whether arising from
differences in the velocity or direction of their motions or differences in both)
and the transfer of load from one valve rod to the other on the closing or re-opening
of the steam passages at the back of the main slide by the cut-off, the driving rod
or gear of the former being relieved of the amount of work at any instant
performed by the driving rod or gear of the cut-off (less stuffing box friction),
while the main slide and cut-off are moving in the same direction and the cut-off
is travelling faster than its carrier, but loaded with that additional amount of work
while they are moving divergently or while the main slide travels faster than the
cut-off in the same direction; double the maximum load on the expansion rod or
driving gear at the various grades of working being practically or approximately
the correct measure in each case of the disturbing effect of the cut-off on the driving
rod or gear of its carrier. Furthermore while variations of pressure and range of
intertravel exclusively determine the severity of the strains and duty cast upon the
driver of the cut-off, the driver of the main slide is subject to the re-action of these
on its back compounded with those due to the more constant range of motion and
action between its front and the cylinder faces, the strains originated on both sides
moreover being intermittent and relatively irregular in the times of their occurrence
at varying grades. It is obvious that all irregularities arising from the causes
before mentioned and their consequences upon the main slide may be avoided and
that most of the power absorbed in driving the "cut-off" will be saved if only one
of the two essentials of friction, viz: Pressure can be eliminated from the inter-
acting surfaces of the two valves. My invention therefore consists of an improved
method of and arrangement for rendering the fluid pressures nugatory by balancing
their effect on the opposite surfaces of the "cut-off" valve the main slide then being
subject only to the same or practically the same disturbances when carrying the
"cut-off" as when that agent is carried upon a separate fixed surface the power
demanded for the propulsion of the cut-off being simultaneously reduced to the
amount necessary to overcome the friction of its stuffing box added to that due to
the slight pressure of a balance ring hereinafter more specifically referred to
For this purpose I make the proposed cut-off valve of two plates between which
flows the entering steam or fluid the two forming parallel planes sustained at the
requisite distance apart by suitable connections at the sides or ends or both. One
of these plates has cut through it the steain ways or passages and is truly surfaced

page_text: on the outer side to work in contact with the back face of the main slide or face of
the fixed surface as the case may be. The other or back plate is similarly surfaced
on the outer side to maintain steam tight contact with a balance ring of the
ordinary construction and mode of action or of modified structure when requisite.
Between the front and back plates before mentioned one or more pipes or steam-
ways are fitted or cast having an opening or openings in the face of the front
plate which may be isolated portions of one or more of the steamways elongated
in the direction of travel when the cut-off has only one steamway or when one
pipe or passage only is provided between the plates of a cut-off with several
steamways but it is essential that such openings should singly or conjointly have
some portion open to one or other of the steamways at the back of the main slide
in every position which they mutually occupy while at work. The opening or
openings in the back face of the cut-off may be of any convenient form or size but
must be so located as to remain within the inner periphery of the balance ring
under all conditions of working communication being thus (or by other alternative
device hereinafter described) constantly maintained between the interior of the
main slide and the space at the back of the cut-off enclosed within the balance
ring. A separate balance ring is required at each end of the main slide where the
cut-off valve is composed of two parts and will be most convenient of application
if made oblong in the same direction as the steam passages in the main slide but
when the cut-off is in one piece centrally situated and cutting off at each end
alternately a balance ring of the usual circular form is preferable. The back plate
or cover which is ordinarily fitted and attached to the main slide and surfaced on
its exterior to work in conjunction with the ordinary balance ring located inside
the slide casing door is by my present invention further provided on its underside
with a suitable groove or grooves for the reception of the balance rings of the
cut-off and with recesses containing springs for maintaining contact between the
plane surface of the balance ring and the back of the cut-off in the ordinary way
or such recesses may be formed within projections on the balance ring and the
springs carried therein as most convenient. Whether one or more balance rings
be employed it is essential in principle that the inner periphery of the balance
ring at the plane of contact should exactly equal the area of steam opening in the
back of the main slide or that portion of the collective amount thereof which that
individual ring is intended to balance and that the centre of the superficies at the
back of the cut-off enclosed by the balance ring should be truly located opposite or
over the centre or effective centre of the steam way or collective steam way or
opening at the back of the main slide. In those cases wherein the cut-off works
upon a separate fixed surface independent of the main slide the back plate or
cover before referred to is fitted and attached thereto or to any other adjacent and
convenient fixed part of the slide casing so that the cut-off works between the said
plate or cover and the surface in which the steam ways are cut as in the former
case when carried on the back of the main slide the plate or cover being similarly
fitted with a groove and recesses for the reception of a balance ring and springs
and the collective steam-opening under the cut-off in the fixed surface being equal
to and truly opposite or under the inner area of the balance ring or accurately
apportioned thereto. When it is preferred to employ more than one balance ring
as may sometimes be judicious in cases where the cut off valve is very long in
proportion to its breadth the advantages of the present invention in such cases
would be limited to the saving of power and reduction of strength of driving gear
and of wear and tear from absence of friction.
By the arrangement and construction of cut off valve and modification of the
usual fittings of the main slide or its casing hereinbefore described the cut-off will
in effect operate between two plane surfaces which whether fixed or moving
preserve the same positions relatively each to the other under all conditions, and in
which are equal and opposite openings communicating with hollow spaces in which
the steam or other fluid under control is under all variations in pressure the same
in the one as in the other Its effect therefore is nugatory on the cut-off and

page_text: furthermore the inequality in the amount of interacting surface on opposite sides
of the cut-off due to difference of area between the working face of the balance
ring and the back face of the main slide, or to the difference of area between the
collective steam way at the front and the pipe or passage opening at the back of
the cut-off itself, will cause no disturbance of balance the fundamental principle of
this invention being that the pressure of the steam (and generally of any other
elastic fluid) is not in any practical measure excluded from between the rubbing
surfaces of two sliding valves or plates of metal exposed to varying temperatures
which surfaces are nevertheless sufficiently close fitting to prevent apparent
leakage. The resilient force in the springs which hold the balance ring against
the cut-off and maintain the latter in contact with the back of the main slide also
need not be of considerable amount and exclusive of the friction occasioned by this
slight pressure the cut-off moves in equilibrium without encumbrance to the main
slide (considered as the carrier) or interference with its ordinary action.
And in order that my said invention may be fully understood I shall now
proceed more particularly to describe the same and for that purpose shall refer to
the several figures on the explanatory sheets of drawings hereunto annexed the
same letters of reference indicating corresponding parts throughout all the figures.
Figures 1 and 2 (Sheet 1 of my drawings) represent respectively back and end
views and Figure 3 a longitudinal mid-section of an ordinary double ported marine
engine slide valve in which the cut-off is effected at the middle for each end of
the cylinder alternately by a sliding cut-off valve in one piece carried on the back
of the main slide the back plate of which for convenience of illustration is removed
from figure 1 and shown separately with certain modifications and additional
fittings on Sheet 2 of my drawings. Figures 4 and 5 (Sheet 1) are separate
details of the balance ring g hereinafter more specifically referred to. My cut-off
valve in one of its forms as constructed according to the present invention and
applied to a main slide of the above mentioned class is shown in position with the
said balance ring g g laid loosely, but in its correct position on the back of the said
cut-off valve in figure 1 (sheet 1 of my drawings) also in the end view at figure 2
and in the longitudinal mid section at Figure 3. Separate views of the side, front,
back, and end of the said cut-off valve are severally shown at figures 1, 2, 3 and 5
respectively on sheet 2 of my drawings and alternative methods of giving elasticity
to the balance ring when necessary are shown at figures 6 and 7 and figures 8, 9,
and 10 of the same sheet.
In carrying out my invention I combine with an ordinary gridiron expansion
valve or cut-off plate a a a back plate bb these being connected together by
suitable framing or cast in one piece as shown in the drawings and I place over the
Baid back plate a balance ring g g (figures 4 and 5 sheet 1) which has an open area
equal to the aggregate area of the steam ports e e at the back of the main slide the
centre of such open area being directly opposite to or in the same line or perpen-
dicular to the plane of motion, as the common centre of those several openings. I
also establish an uninterrupted channel of communication between the space f
enclosed by the said balance ring g and the interior or steam port space of the
main slide in every position which the two valves can be placed in while working
by means of an enclosed passage c through the cut-off from face to back or in some
cases by a hollow passage cast or formed in the back plate in conjunction with
another like passage in the body of the main slide without passing through the
cut-off valve (but the latter expedient involves a greater increase to port space) to
this end the orifice of the passage c in the face of the cut-off (which as illustrated
is part of one of the steamways isolated and elongated in the line of motion) is
made sufficiently long to overlap as much as may be necessary in proportion to its
width the width of the bridges d d between the steam entrances ee of the main
slide. The orifice at the back may be of any form providing that half its length
in the line of travel together with the maximum intertravel of the valves do not
exceed the inner diameter of the balance ring. Also to avoid objectionable increase
of port space the balance ring enclosure is made as shallow in depth as is

page_text: compatible with a due provision for the expansive and vibratory movements of the
steam chest and of the two valves arising from changes of temperature and tremor
of working. The balance ring is carried in the groove or recess formed on the
underside of the back plate of the main slide (Figure 4 sheet 2) and is held in
contact with the back of the cut-off by the helical springs m m figure 5 (Sheet 1)
seated in the recesses nn formed within the projections oo on the balance ring
which in this case fits on its concave surface only to the corresponding surface of
the said groove. In figures 6 and 7 and in figures 8, 9 and 10 (sheet 2) I have
shown alternative modes of giving elasticity to the ring where may be necessary
(as in cut-off valves of very large dimensions which are subjected to extreme
variations of pressure) in which case the ring is cut and cross tongued as in
figures 6 and 7 or it is composed of two rings one within the other as shown in
figures 8, 9 and 10 the inner one being of small section and tongued at t to prevent
leakage while the outer one is provided with an internal flange all round and a
tongue at w to keep the two rings and the ends of the outer one truly in plane as
shown in figures 8 and 10. In both cases wherein the ring is cut there are semi-
circular projections p p on the exterior of each side of the cut (in the outer ring
only where two are employed) which are embraced and drawn together by the
tension of a coiled or helical spring threaded over them by rotation (as in the
common key keeper ring) until all the coils are passed inside the small protu-
berances rr which are rounded on the inside to prevent its accidental return. In
these balance rings the convex surfaces also are made to fit and to fill the groove at
the three segments 888 by which equality of diameter and accuracy of fit are
preserved between the steam excluding surfaces of the ring and grooves when
these expand or contract unequally and the differential motion thus set up is
restricted to take effect circumferentially tending to avert rather than to produce
any binding of the ring within the groove as is the case with the ordinary whole
ring fitting on both sides of the groove. In some cases it may be expedient to
make the convex surface of the balance ring and the concave surface of the groove,
the steam tight surfaces which may obviously be effected by a slight modification
of the details hereinbefore described or to make the ring fill the groove round a
greater portion of the circumference than is shown in the illustrations. From the
foregoing particulars it will be seen that the cut-off valve moves between the
balance ring opening f and the steam openings ee which being in fixed positions
within the same moveable part or main slide are permanently opposite to each
other in all positions of both valves. Premising that the common gridiron or plate
cut-off causes no appreciable disturbance to the carrier valve while the steamways
of each are open to the other the special function of the present invention is
obviously to avert disturbance during the time they are [closed.
Its action may
therefore be sufficiently described by commencing at the position in which the
steamways of the two valves are in the act of closing and setting forth the
conditions which prevail during the closed period observing that the pressure of
the steam (and generally of any other elastic fluid) under control is not in any
sensible degree excluded from between the rubbing surfaces of the two valves.
From the instant of the closing of the cut-off ports the pressure under that portion
of the surface of a a which covers tho steam ports e e rapidly decreases until the
steam ports in the face of the main slide are closed to the cylinder thereafter
remaining stationary until the re-opening of the cut-off ports. It is particularly
to be noted that the closing and re-opening of the cut-off ports simultaneously
closes and re-opens communication between the passage c and the outer or steam
chest pressure whereby all the variations of pressure within the steam space of the
main slide under a a are reciprocated by equal variations within the enclosure f
above b b owing to the maintainance of free communication between them through
the passage c (or other channel formed within the main slide and its back plate)
As the aggregate area of the openings e e under a a are equal and permanently
opposite to the open area of the balance ring enclosure fabove bb the surfaces
on both sides of the cut-off valve are subjected to equal pressures acting in

page_text: opposite directions in the same line or perpendicular to its plane of motion and
such pressures however variable are therefore nugatory upon it regarded as a
moving body. The circumstance of the reopening of the cut-off ports occurring
wholly on one side of the valve cannot affect its balance since the enclosure f is of
small capacity relatively to the passage c and as the entering steam has great
expansive velocity in proportion to the cavity to be filled it cannot but be equally
diffused throughout the entire space on both sides of the cut-off. It will be
evident that the principle of my said invention may be applied to other forms of
expansion or cut-off valves or plates of the sliding class whether the cut-off be
effected at the middle of the main slide (as shown in my drawings) or at each end
of the valve or cylinder separately by a cut-off valve composed of one or more
pieces and carried into effect by a mere modification and readjustment of the
details and proportions substantially as herein before described and that valves so
constructed may be usefully employed for other purposes than the one herein made
available for its illustration in controlling or regulating the flow or supply of other
fluids under pressure.
Having now described and particularly ascertained the nature of my said
invention and the manner in which the same is or may be used or carried into
effect I would observe in conclusion that what consider to be novel and original
and therefore claim as the invention secured to me by the herein before in part
recited letters patent is :-
First. The addition or connection of a back plate to the ordinary gridiron
expansion or cut-off valve or plate and the formation of an enclosure or enclosures
over the outside of the said back plate having an open area equal to the collective
or aggregate steam opening in the back of the main slide or other fixed surface
which the cut-off valve or plate is intended to cover by means of a balance ring
or rings of any convenient form also the so placing such ring or rings that the
centre or effective centre of their open area shall be and remain under all
conditions of working truly opposite to the effective centre of the steam opening
or openings in the back of the main slide or other fixed surface substantially as
specified.
Secondly. Maintaining an open channel of communication between the enclosure
or enclosures formed as above set forth and the steam port space within the main
slide or the interior of the steam chest as the case may be in all the working
positions of the two valves when acting in conjunction or in every position of the
cut-off valve when carried upon a separate fixed surface by one or more enclosed
passages through the cut-off valve from face to back or by other enclosed channels
cast or formed within the several parts of the main slide or of the steam chest as
the case may be substantially as specified.
Thirdly. The construction of balance rings of circular form in such manner that
one of their surfaces (either the concave or convex at will) shall truly and closely
fit the corresponding surface of the groove in which it is carried for the prevention
of leakage and of binding under minute variations of diameter arising from
inequality in the expansion and contraction of the ring and groove by constraining
such inequalities to take effect circumferentially substantially as herein before
described.
In witness whereof I the said Joseph Hopwood have hereunto set my
hand and seal this first day of September in the year of our Lord one
thousand eight hundred and sigher twen