IMPROVEMENTS IN SLIDE VALVES
Year: 1869

page_text: LETTERS PATENT to George Weir, of Glasgow, in the County of
Lanark, and James Weir, of Liverpool, in the County of Lancaster,
Engineers, for the Invention of "IMPROVEMENTS IN SLIDE VALVES."
Sealed the 14th June 1870, and dated the 17th December 1869.
PROVISIONAL SPECIFICATION left by the said George Weir and James.
Weir at the Office of the Commissioners of Patents, with their.
Petition, on the 17th December 1869..
We, GEORGE WEIR, of Glasgow, in the County of Lanark, and JAMES.
WEIR, of Liverpool, in the County of Lancaster, Engineers, do hereby
declare the nature of the said Invention for "IMPROVEMENTS IN SLIDE.
VALVES," to be as follows, that is to say :-
This Invention has for its object the reduction of the pressure
experienced on the back of ordinary slide valves in order that they may
be worked with less friction and wear. It consists in constructing the
valve with an outer shell enclosing a space into which the steam or
motive fluid is admitted from a port or ports in the same face in which
are the exhaust port and the cylinder ports; or the steam may be
admitted by a port or ports in a separate face covered by the valve.

page_text: Openings are formed in the face of the valve for the passage of the
steam into the additional space from the steam ports, and from that
space to the cylinder ports. With this arrangement the steam in the
steam ports presses the valve from the port face, whilst there is a pressure
towards the face corresponding to the area of the usual exhaust cavity
in the valve. The valve works within a valve casing as usual, but the
pressure of steam inside that casing and acting on the back of the valve
is regulated by any convenient appliance so as to be maintained always
at a pressure below that of the fresh steam. A suitable appliance for
regulating the pressure in the casing is a valve of the kind known as a
steam reducing valve, and may be applied directly to the slide valve or to
external pipes communicating with the casing.
The principal feature of the arrangement is the supplying of the fresh
steam to the interior of the valve without its acting in the valve casing
on the outside thereof, and the doing of this may be effected otherwise
than in the manner herein-before described. Thus, for example, the
steam may be admitted by a pipe in the line of the valve's motion and
entering one end of the valve by a stuffing box, or a pipe fixed to the
valve may work through a stuffing box into the steam pipe.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said George Weir and James Weir in the Great Seal
Patent Office on the 16th June 1870.
TO ALL TO WHOM THESE PRESENTS SHALL COME, we, GEORGE
WEIR, of Glasgow, in the County of Lanark, and JAMES WEIR, of
Liverpool, in the County of Lancaster, Engineers, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Seventeenth day of December, in the
year of our Lord One thousand eight hundred and sixty-nine, in the
thirty-third year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto us, the said George Weir and James Weir, Her
special licence that we, the said George Weir and James Weir, our
executors, administrators, and assigns, or such others as we, the said
George Weir and James Weir, our executors, administrators, and assigns,
should at any time agree with, and no others, from time to time and at
all times thereafter during the term therein expressed, should and lawfully

page_text: might make, use, exercise, and vend, within the United Kingdom of
Great Britain and Ireland, the Channel Islands, and Isle of Man, an
Invention for "IMPROVEMENTS IN SLIDE VALVES," upon the condition
(amongst others), that we, the said George Weir and James Weir, our
executors or administrators, by an instrument in writing under our, or
their, or one of their hands and seals, should particularly describe and
ascertain the nature of the said Invention, and in what manner the same
was to be performed, and cause the same to be filed in the Great Seal
Patent Office within six calendar months next and immediately after
the date of the said Letters Patent.
NOW KNOW YE, that we, the said George Weir and James Weir,
do hereby declare the nature of our said Invention, and in what manner
the same is to be performed, to be particularly described and ascertained
in and by the following statement in writing, reference being had to the
accompanying Drawings, that is to say :-
Our said Invention has for its object the reducing and regulating of
the pressure on the backs of the slide valves of steam and other engines
in order that the valves may be worked with less friction and wear than
is experienced with ordinary slide valves.
The Invention consists in arranging the parts so that the steam of full
pressure or that which is on its way to the cylinder tends to press the
valve from the port face, the exhaust being led away in the ordinary
way or otherwise, whilst steam of a suitably regulated pressure and
necessarily lower than the full pressure is contained in the casing and
bears on the outside of the valve so as to just keep it to the port face.
And in order that our said Invention and the manner of performing
the same may be properly understood we have hereunto appended a
Sheet of explanatory Drawings, to be herein-after referred to, and
representing the application of our improvements to a pair of "inside"
locomotive cylinders, and this being the most difficult case that can
present itself in practice on account of the very small space between the
cylinders no difficulty will be experienced by engineers in applying the
improvements in other cases. In the Drawings the same reference
numerals are used to mark the same or like parts wherever they are
repeated.
Figure 1 is a plan of the cylinders, Figure 2 an outer end view,
Figure 3 an inner end view, Figure 4 a horizontal section, Figure 5 a
transverse vertical section (as through the exhaust ports), Figure 6 a

page_text: showing the port face.
The port face of each cylinder is made with the usual ports, the
exhaust port 1 in the middle, and the ports 2, 2, of the cylinder passages
forward and abaft of it. Each valve is also made with the usual exhaust
cavity 3, and is in addition formed with internal spaces 4, and with four
additional ports, two of which ports 5, 5, serve for the steam to pass at
the proper times, when the valve is in the requisite positions, into the
cylinder ports 2, 2, whilst the other two ports 6, 6, serve for the
entrance of the steam into the spaces 4 from ports 7, 7, in the cylinder
port face. The steam finds its way to the ports 7, 7, by passages 8, 8,
formed in the casting and leading from the steam pipe inlet 9. The
pressure in the valve casing on the backs of the valves should be regu-
lated so that changes in the pressure of the steam in the boiler will not
cause either the lifting of the valves or the action of excessive pressure
on the backs of them. For this purpose we employ a reducing valve 10
arranged to act proportionally, and this valve opens into a space 11 com-
municating in any convenient way with the interior 12 of the valve
casing, whilst there is on the other side of it a space 13 into which
steam of full pressure is admitted. The high-pressure steam (as it may
be shortly termed) acts in an opposite direction on a piston 14 fixed by
a spindle 15 to the valve 10 and working in a cylindrical bore, of which
the further end 16 communicates with the exhaust 1. The effective area
of the piston 14 is made in the proportion to that of the valve 10 that
the difference between the high pressure and the reduced pressure has to
be to the high pressure in order to make the pressures on the under and
outer sides of the valve balance each other as nearly as possible. Thus,
if a reduced pressure of two-thirds the high pressure will balance the
valve the area of the piston 14 must be one-third that of the valve 10,
and with that proportion the valve 10 will open and admit steam into
the casing 12 whenever the pressure in the casing is under two-thirds of
the high pressure, and the slide valves will then be balanced whatever
the boiler pressure may be. The proper proportion for the reduced
pressure may be determined by calculation, the aggregate pressure
tending to lift the valve being taken to correspond with the position the
valve is in when that pressure is a maximum; or the proper proportion
may be easily ascertained by trial by gradually varying the pressure of
steam admitted to the back of the valve, it being known when the

page_text: reduced pressure is at all too low by the chattering of the valve. It is
generally considered desirable that the slide valve should not be perfectly
balanced, but that it should be kept against the port face by a slight
excess of pressure on the back. This may be obtained by suitably
proportioning the valve 10 and piston 14, but the excess of pressure
would then vary with the boiler pressure, which may not be considered
desirable. An excess of pressure which will not vary with the boiler
pressure and which can be adjusted is obtainable by extending the
spindle 15 of the valve 10 out through a stuffing box and by applying
pressure to it externally by means of an adjustable spring 17 or other-
wise. It may not be necessary in many cases to provide against the
pressure on the backs of the valves becoming greater than intended,
but if wished such excess of pressure may be prevented by allowing a
constant minute flow of steam from the casing 12 by a small aperture into
the exhaust, such flow being compensated for by the automatic action
of the valve 10, or a special valve 18 may be provided which will open
and allow steam to escape should the pressure ever become too great.
This valve 18 opens from the space 11 into a space 19 communicating
with the exhaust. Its spindle 20 has fixed to it a piston 21 working in
a cylindrical bore, and beyond this there is a space 22 into which the
high-pressure steam is admitted. The effective area of the piston 21 is
made in the proportion to that of the valve 18 that the reduced pressure
must have to the high pressure in order to balance the valve. The valve
spindle 20 is also continued out through a stuffing box, and pressure is
applied to it externally by a spring 23 or otherwise to correspond with
the pressure similarly applied to the spindle 15 of the inlet valve 10.
The valve pistons 14 and 21 are represented as rendered steam-tight by
diaphragms of vulcanised rubber, which rubber will be defended from
injurious action of the steam by water due to condensation. In many
cases however these diaphragms may be dispensed with, as if the pistons
are well fitted any leakage of steam past them will be immaterial.
Instead of the valve 10 being rigidly connected by a spindle 15 to a
piston 14 it may be connected to a lever, such lever being connected to
a piston or diaphragm either directly or through another lever. In this
case the valve and piston or diaphragm may be made of any convenient
relative areas, the desired proportional action being obtained by the
adjustment of the lever or levers. The arrangement of the valve 18 and
piston 21 may be similarly modified.

page_text: Our mode of reducing the friction and wear of slide valves by applying
a proportionally regulated pressure to counteract the full pressure, this
last being arranged to tend to lift the valve, is obviously applicable to
various modifications of slide valves, such as double-ported valves,
valves with two exhaust cavities, and others; and it may be applied
with separate cut-off slides arranged within the valve, or in the form of
movable seats or slides forming parts of the port faces or otherwise; also
the steam may be admitted to the valve by a port or ports in a face or
faces separate from the cylinder port face; or the steam may be admitted
to the interior of the valve by a pipe in the line of the valve's motion,
and entering one end of the valve by a stuffing box or by a pipe fixed to
the valve and working through a stuffing box into the steam pipe.
Having thus particularly described our said Invention, and the
manner in which the same is to be performed, we have to state that
we do not restrict ourselves to the precise details herein described or
delineated; but that what we believe to be novel and original, and claim
as the Invention secured to us by the herein-before in part recited
Letters Patent is, the applying of a proportionally regulated reduced
pressure to the backs of slide valves arranged so that the full pressure
tends to lift them, substantially as berein-before described.
In witness whereof, we, the said George Weir and James Weir,
have hereunto set our hands and seals, this Fifteenth day of
June, in the year of our Lord One thousand eight hundred and
seventy.
Witness,
EDMUND HUNT,
Patent Agent,
Glasgow.
GEORGE WEIR. (L.S.)
JAMES WEIR.
(L.S.)