IMPROVEMENTS IN SLIDE-VALVES FOR STEAM-ENGINES
Year: 1881

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, for an Invention of "IMPROVEMENTS
IN SLIDE-VALVES FOR STEAM-ENGINES." A communication from abroad by
William Stewart Hughes and John Gregory, both of Long Island City, in the
County of Queen's, and Charles J. Howe, of New York City, in the County
of New York, both in the State of New York, United States of America,
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark
at the Office of the Commissioners of Patents on the 26th April 1881.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of
Middlesex, Patent Agent. "IMPROVEMENTS IN SLIDE-VALVES FOR STEAM
ENGINES." [A communication from abroad by William Stewart Hughes and
John Gregory, both of Long Island City, in the County of Queen's, and Charles J.
Howe, of New York City, in the County of New York, both in the State of New
York, United States of America.]
The main object of this Invention is to reduce or prevent the noise made by the
exhaust steam of engines, which has heretofore been attempted by the use of
muffles and similar devices. With the ordinary link motion and slide valves used
on locomotives, the exhaust edge of the valve must be moved the length of lap and
lead before the piston receives steam from the direction in which it has been
moving. In other words the exhaust opening begins before the piston finishes its
stroke and before the steam has finished its expansion. The exhaust being also
opened suddenly by the quick movement of the eccentric, a wasteful and disagreeable
explosion of steam from the cylinder takes place. To remove this evil I use devices
with or so arrange the valve cavity for obtaining a gradually increasing opening
so that exhaust previous to the completion of the piston stroke is limited, and the
exhaust steam, instead of being allowed to explode, is gradually released and without
back pressure. The Invention consists in a slide valve having devices whereby
the exhaust steam is detained and baffled, thereby lengthening out the force and
ensuring steady and almost noiseless passage of the steam to the exhaust nozzles.

page_text: In addition I secure steady draft on the fire and consequent saving in fuel. In one
form of slide valve the exhaust cavity of the valve is covered by a perforated
diaphragm that forms a portion of the valve face. The perforations are to be as
numerous as required and are placed in rows lengthwise of the valve and con-
sequently lengthwise of the ports, and the valve and perforations are proportioned
so that when both ports are covered, that is to say, when the inlet of steam is
closed to both ports, the first row of perforations shall be in position for receiving
the,exhaust steam.
In operation, the valve being moved from the middle position, the exhaust steam
passes through the rows of perforations as they come successively over the ports
into the exhaust cavity of the valve, and to the exhaust port through the middle
rows of perforations. The steam is thus cut up into small streams, first very finely,
and then larger as the perforations come fully over the steam port, instead of being
suddenly admitted through a single opening the full length of the valve as is
usually the case. The exhaust, instead of being an explosion, thus becomes an
almost noiseless passage of steam to the exhaust port and smoke stack, ensuring a
steady draft. There will be no back pressure for the reason that the first outlet of
exhaust takes place before the live steam is admitted. The continuous blast thus
obtained by the exhaust steam ensures a uniform consumption of fuel, and prevents
sparks and cinders from being thrown out.
Instead of the perforated diaphragm I may employ a double series of tapering
openings formed by V shaped tongues projecting inwards from the exhaust edges of
the valve over the exhaust cavity thereof, so that there will be first a number of
small openings exposed to the steam ports. This modification has this feature in
common with the perforated diaphragm that the exhaust cavity is partially cut
off by a solid portion of the valve face during the movement of the valve.
The same effect may be obtained by inclining the exhaust edges of the valve to
the ports, so that in the movements of the valve an opening at one corner is first
made, which opening gradually increases as the valve continues to move.
A further modification combines the perforated diaphragm with the inclined
cavity. Inclined or perforated lips project inwards at the exhaust edge of the
valve, and an inclined or diagonal vertical perforated partition divides the cavity.
In another modification the gradually increasing opening for escape of steam in
the exhaust cavity is obtained by increase of depth at the sides. The sides of the
cavity are formed in step like form, so that the depth of the cavity increases as the
valve moves forward, thereby giving an enlarged space or exhaust.
AV shaped perforated diaphragm may be placed in the cavity of the valve
formed with the step like sides.
Other modifications can be used to accomplish the same end. In all cases the
first escape of steam is small, and should increase sufficiently before the valve
admits like steam to the cylinder to allow free escape of the exhaust without back
pressure.

page_text: SPECIFICATION in pursuance, of the conditions of the Letters Patent filed
by the said Alexander Melville Clark in the Great Seal Patent Office on the
25th October 1881.
"
kr
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of
Middlesex, Patent Agent. IMPROVEMENTS IN SLIDE VALVES FOR STEAM-
ENGINES. A communication from abroad by William Stewart Hughes and
John Gregory, both of Long Island City, in the County of Queen's, and Charles J.
Howe, of New York City, in the County of New York, both in the State of New
York, United States of America.
The main object of this Invention is to reduce or prevent the noise made by the
exhaust steam of engines, which has heretofore been attempted by the use of
muffles and similar devices. With the ordinary link motion and slide valves used
on locomotives, the exhaust edge of the valve must be moved the. length of lap
and lead before the piston receives steam from the direction in which it has been
moving. In other words the exhaust opening begins before the piston finishes its
stroke and before the steam has finished its expansion. The exhaust being also
opened suddenly by the quick movement of the eccentric, a wasteful and
disagreeable explosion of steam from the cylinder takes place. To remove this
evil I use devices with, or so arrange the valve cavity for obtaining a gradually
increasing opening, that exhaust previous to the completion of the piston stroke is
limited, and the exhaust steam, instead of being allowed to explode, is gradually
released and without back pressure. The Invention consists in a slide valve
having devices whereby the exhaust steam is detained and baffled, thereby
lengthening out the force and ensuring a steady and almost noiseless passage of the
steam to the exhaust nozzles. In addition I. secure steady draft on the fire, and
consequent saving in fuel.
In the accompanying Drawing Figure 1 is a vertical transverse section of a
valve embodying the Invention; Figure 2 is a face view of the same. The other
Figures show variations, and are separately referred to hereinafter. Similar letters
of reference indicate corresponding parts.
A is the slide valve having exhaust cavity a; B, in Figure 1, is the valve seat
having steam ports b, b, and exhaust port c as usual; d is a perforated diaphragm
that forms a portion of the valve face. The perforations are to be as numerous as
required, and are placed in rows lengthwise of the valve, and consequently length-
wise of the ports b, and the valve and perforations are proportioned, so that when
both ports are covered, that is to say, when the inlet of steam is closed to both
ports, the first row of perforations shall be in position for receiving the exhaust
steam. In operation, the valve being moved from the middle position, the exhaust
steam passes through the rows of perforations as they come successively over the
ports 6 into the exhaust cavity a and to the exhaust port c, through the middle rows
of perforations. The steam is thus cut up into small streams, first, very finely, and
then larger, as the perforations come fully over the steam ports b instead of being
suddenly admitted through a single opening the full length of the valve, as is
usually the case. The exhaust, instead of being an explosion, thus becomes an
almost noiseless passage of steam to the exhaust port and smoke stack, ensuring a
steady draft. There will be no back pressure for the reason that the first outlet of
exhaust takes place before the live steam is admitted. The continuous blast thus
obtained by the exhaust steam ensures a uniform consumption of fuel and prevents
sparks and cinders from being thrown out.
The same principles of operation are involved in the modification shown. In
Figure 3 there is a double series of tapering openings formed by tongues e over the
exhaust cavity of the valve. The smaller ends of the openings are in the direction

page_text: the valve moves, so that there will be first a number of small openings exposed to
the steam ports. This modification has this feature in common with the perforated
diaphragm, that the exhaust cavity is partly cut off by a solid portion of the valve
face during the movement of the valve.
The same effect may be obtained by forming the edges of the exhaust cavity
inclined to the ports, as shown in Figure 4, so that in the movement of the valve
an opening at one corner is first made, which opening increases as the valvo
continues to move.
A further modification which combines the perforated diaphragm with the
inclined opening is shown in cross section in Figure 5, and plan in Figure 5;
ff, are lips projecting at the edges of the exhaust cavity; and g is a partition
placed diagonally in the said cavity. The outer edges of the lips f are inclined
lengthwise of the opening, and both the lips and the partition are perforated.
By the construction shown in Figure 6 the gradually increasing opening for
escape of steam in the exhaust cavity a is obtained by increase of depth at the
sides. The sides are formed in step like form, so that the depth increases as the
valve moves forward, thereby giving an enlarged space or exhaust.
In Figure 7 a V shaped perforated diaphragm g' is placed in the exhaust cavity
of the valve formed with step like sides. Other modifications can be used to
accomplish the same end.
In all cases the first escape of steam is small, and should increase sufficiently
before the valve admits live steam to the cylinder to allow free escape of the
exhaust without back pressure.
Having described the nature of the said Invention, and the manner of
performing the same, I declare that what I claim as the Invention to be protected
by the hereinbefore in part recited Letters Patent is,-
1st. A slide valve having its exhaust cavity so constructed with relation to the
steam and exhaust ports of the seat that by the movement of the valve the cavity is
opened by numerous small apertures, or by a gradually increasing aperture,
substantially as shown and described.
2nd. The combination of a slide valve' having exhaust cavity a, and valve scat
having ports b, b, c, and the valve face so extended that the exhaust cavity is
partially cut off during the movement of the valve, substantially as shown and
described.
3rd. The slide valve A having exhaust cavity a covered by a perforated
diaphragm d, substantially as and for the purpose set forth.
4th. In slide valves, the exhaust cavity formed with step like sides, substantially
as shown in Figure 6.
5th. The combination in a slide valve having its sides made in step like form of
the perforated diaphragm g', substantially as shown and described.
6th. In slide valves, the tapering tongues e forming a portion of the valve face
combined with the exhaust cavity a, substantially as shown and described.
In witness whereof, I; the said Alexander Melville Clark, have hereunto set
my hand and seal, this Twenty fifth day of October, A.D. 1881.
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