IMPROVEMENTS IN THE CONSTRUCTION OF. SLIDING VALVES
Year: 1879

page_text: LETTERS PATENT to Percival Everitt, of Great Ryburgh, in the County of
Norfolk, Engineer, for the Invention of "IMPROVEMENTS IN THE CONSTRUCTION
OF. SLIDING VALVES."
Sealed the 7th November 1879, and dated the 23rd May 1879.
PROVISIONAL SPECIFICATION left by the said Percival Everitt at the
Office of the Commissioners of Patents on the 23rd May 1879.
PERCIVAL EVERITT, of Great Ryburgh, in the County of Norfolk, Engineer.
"IMPROVEMENTS IN THE CONSTRUCTION OF SLIDING VALVES."
The chief object of this Invention is to neutralize the pressure on the back of
sliding valves, and thereby to allow of their working with comparatively little
friction.
To this end I mount on the back of the valve a flat plate or its equivalent, which
is connected thereto by one or more stems or supports, and at such distance from
the valve that it will fit snugly upon the top of the valve box, and be free to slide
thereon like the valve upon its seat.
The portion of the valve box over which this plate traverses I close by a case,
which I connect with an exhaust pipe.
In the valve box below the sliding plate I form an opening, which is covered by
that plate, and which equals or nearly equals in size the area of the valve face.
This arrangement allows of the steam admitted to the valve box pressing upwards
against the sliding plate with equal or nearly equal force to that with which it
expends on the back of the valve, thus balancing the pressure and permitting the
valve to slide easily on its seat.
The slide valve rod will be connected with the valve by a loop as usual, and as it
slides in glands it will serve to resist the pressure of a spring placed between it and
the valve for holding the valve down to its seat.
1
This valve I propose to make rectangular, or it may be circular; in the latter
case I give the induction ports a segment shape corresponding to the periphery of
the valve.

page_text: The advantage of making the valve circular is that it will be free to turn on its
axis when the surface friction to which it is exposed becomes unequal, and thus the
wear on the valve face and on the face of the sliding plate carried by the valve
will be equalized.
'
The centre of the valve I recess to form a passage, which connects the exhaust
port with the eduction port as usual. Or I may, instead of forming an exhaust_
port in the cylinder, open a passage through the central stem or stems of the valve
for the escape of the exhaust steam.
When the exhaust is not effected through the valve I may find it desirable still
to have a communication through the valve between the casing above the sliding
plate and the exhaust pipe, for the purpose of carrying off any steam that might
leak into the casing and interfere with the proper action of the sliding plate.
An incidental advantage of this new construction of valve is that it possesses
double the wearing surface of the ordinary slide valve, and its durability will
therefore be proportionately increased.
This equilibrium or balanced valve, it will be understood, is applicable not only
for steam and other motive power engines, but for hydraulic apparatus and kindred
uses.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Percival Everitt in the Great Seal Patent Office on the 22nd
November 1879.
PERCIVAL EVERITT, of Great Ryburgh, in the County of Norfolk, Engineer.
"IMPROVEMENTS IN THE CONSTRUCTION OF SLIDING VALVES."
The chief object of this Invention is to neutralize the pressure on the back of
sliding valves, and thereby to allow of their working with comparatively little
friction.
To this end I mount on the back of the valve a flat plate or its equivalent, which
is connected thereto by one or more stems or supports, and at such distance from
the valve that it will fit snugly upon the top of the valve box, and be free to slide
thereon like the valve upon its seat.
The portion of the valve box over which this plate traverses I close by a case
which I connect with an exhaust pipe.
In the valve box below the sliding plate I form an opening, which is
covered by that plate, and which equals or nearly equals in size the area of the
valve face.
This arrangement allows of the steam admitted to the valve box pressing upwards
against the sliding plate with equal or nearly equal force to that with which it
expends on the back of the valve, thus balancing the pressure and permitting the
valve to slide easily on its seat.
The balanced valve I propose to make either rectangular or circular; in the latter
case I give the induction ports a segment shape corresponding to the periphery of
the valve.
The advantage of making the valve circular is that it will be free to turn on its
axis when the surface friction to which it is exposed becomes unequal, and thus the
wear on the valve face and on the face of the sliding plate carried by the valve will
be equalized.
The centre of the valve I recess to form a passage, which connects the exhaust
port with the eduction port as usual. Or I may, instead of forming an exhaust
port in the cylinder, open a passage through the central stem or stems of the valve
for the escape of the exhaust steam.
In the accompanying Drawings, Fig. 1 shews in sectional elevation my improved
arrangement of balanced sliding valve, and Fig. 2 shews the valve in plan view,
the plate which is connected to its stem being removed the better to represent the
form of the valve.
A, Fig. 1, is a portion of a steam engine cylinder, and a, a², are the steam ports,
which are covered by the sliding valve B.
This valve is represented as circular in Fig. 2, and the steam ports are therefore
made of a segment shape to correspond therewith, the inner edge of the ports being
an arc of a circle, which has the same radius as that which describes the central
recess in the valve.
This valve B is formed with a hollow stem B₁, which constitutes a passage for the
exhaust steam. C is the valve box cast with the cylinder A, and having flanges to
receiver a cover D. Between this cover and the valve box a plate E is fitted,
which has a central opening to receive the stem of the valve and allow it to slide
freely therein.
This plate E is faced up parallel to the valve face of the cylinder for the purpose
of receiving a circular sliding plate F, which is bolted to the stem of the valve B,
and closes the opening in the plate E with a lap that will permit of its sliding
without uncovering that opening. The working face of the plate F is formed with
a central circular recess having a superficial surface equal to or slightly less than
that of the back of the valve. The plate F is thus enabled to present to the supply

page_text: steam a surface which will take an upward pressure equal or nearly equal to the
downward pressure put upon the valve by the steam entering the valve box. The
cover D and plate E are made fast to the valve box by bolts passing through the
flanges of the valve box and cover, and through the plate E. D₁ is the exhaust
pipe for leading off the exhaust steam as it passes up through the hollow stem B¹
of the valve. Ğ is the valve rod connected with the valve by a loop, which permits
of the valve turning axially while receiving a reciprocating motion. This rod slides
in glands H, H, and between its loop and the valve are springs I, I, for holding the
valve to its seat.
When the exhaust is not effected through the valve stem, as in Fig. 1, I may find
it desirable still to have a communication through the valve between the cover D
above the sliding plate and the exhaust pipe, for the purpose of carrying off any
steam that might leak into the casing and interfere with the proper action of the
sliding plate.
This modification is illustrated in the sectional view, Fig. 3, where the same
letters of reference as those used in Fig. 1 indicate like parts.
In this Figure the exhaust, instead of being taken out of the case D, is taken out
of D in the cylinder, and the hollow stem B', instead of having a capacity sufficient
to carry off the exhaust steam, has a small bore sufficient for drawing off any steam
that may escape into the cover D.
An incidental advantage of my new construction of balanced valve is that it
possesses double the wearing surface of the ordinary slide valve, and its durability
will therefore be proportionately increased.
This equilibrium or balanced valve, it will be understood, is applicable not only
for steam and other motive power engines, but for hydraulic apparatus and kindred
uses.
Having now set forth the nature of my Invention of "Improvements in the
Construction of Sliding Valves," and explained the manner of carrying the same
into effect, I wish it to be understood that under the above in part recited Letters
Patent I claim, constructing and fitting equilibrium or balanced sliding valves in
the manner and for the purpose above described.
In witness whereof, I, the said Percival Everitt, have hereunto set my hand
and seal, the Twentieth day of November, in the year of our Lord One
thousand eight hundred and seventy nine.
PERCIVAL EVERITT.
(L.S.