Year: 1886

page_text: I HAMILTON WELDON PENDRED of Bay Tree House Artillery Street Colchester,
Mechanical Engineer do hereby declare the nature of this invention to be as
follows:-
On the back of the slide valve I fix a cylinder the axis of which is at right
angles to the valve face. In this cylinder I fit a plunger, not so long as the
cylinder. In the space intervening between its inner end and the back of the slide
valve I place an elastic compressible chamber, like for example that of an aneroid
barometer, and I secure one end of this chamber to the inner end of the plunger
and the other end of the chamber to the back of the slide valve, in such a way
that the chamber may be surrounded by the steam in the valve chest. The outer
end of the plunger, I hollow out and face the part left projecting so that it may
slide steam tight on the inside of the valve chest lid. When steam is admitted to
the valve chest, it will tend to force the slide valve down on its seat and to push
the plunger against the valve chest lid; but it also tends to compress the com-
pressible chamber and so to draw the plunger back into the cylinder and to raise
the valve off its seat. In this way the pressure on the back of the valve is reduced
which is the object of this invention.
The elastic chamber may be made in various ways, as for example of two elastic
steel plates cupped like watch glasses, one of which is fixed to the plunger and the
other to the valve, concavity to concavity The touching edges of the two plates
are then ground together steam tight. The space between them is put in com-
munication with the exhaust bridge of the slide valve. The steam outside them
will then tend to flatten them and so relieve the pressure on the valve face.
A single elastic plate carried by the rim on a cavity in the slide valve may be used
instead of two plates.

page_text: Improvements in Balanced Slide Valves for Fluid Pressure
Engines.
I HAMILTON WELDON PENDRED Mechanical Engineer, of Bay Tree House
Artillery Street, Colchester do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement :-
On the back of the slide valve I construct a cylinder or chamber whose axis is
at right angles with the plane of the valve face. In this chamber I fit a plunger.
I face up the inside of the valve chest lid or its equivalent. The outer end of the
plunger I hollow out, and I face up the projecting portion so that it moves steam
tight on the inside of the valve chest lid. Between the inner end of the plunger
and the valve I fit an elastic compressible chamber or its equivalent, one end of this
chamber I secure to the slide valve, the other end I secure to the inner end of the
plunger herein before mentioned. The inside of the elastic compressible chamber
may communicate with the exhaust port. The steam in the valve chest getting
access to the chamber on the back of the slide valve round the plunger, which does
not fit the walls of the chamber fluid tight, will tend to compress the elastic com-
pressible chamber, and to press the plunger against the lid of the valve chest and
the slide valve down on its seat. But inasmuch as the sides of the elastic com-
pressible chamber are secured to the slide valve and the plunger respectively, any
force tending to flatten it will also tend to pull both the plunger and the valve off
their seats, and so to reduce the pressure of the slide valve on its seat which is the
object of this invention. In some cases I make the slide valve itself form one end
of the elastic compressible chamber. The other end consisting of a disc attached
to the inner end of the plunger, said dise being made to fit the chamber fluid tight
on the back of the valve by means of a plate or diaphragm of pliable metal by
preference lead. I then employ a steel spring or springs to supply the requisite
elasticity The method of constructing the the elastic compressible chamber will
vary with the dimensions of the valve and the pressure of the working fluid.
In order to make the nature of my invention intelligible I have appended here-
unto a sheet of drawings shewing various modifications, each suitable for different
conditions. It will be understood that the said drawings are not made to scale,
and the form of the parts may be varied to suit different engines as required. The
same letters refer to the same parts or their equivalents throughout.
Fig. 1 is a longitudinal section and Fig. 2 is a half plan of a balanced slide valve
constructed according to my invention. The line T shows the inside of the valve
chest lid. The line V shows the valve seat in which are the ports (not shewn)
A is the slide valve, B the exhaust bridge. is the bridle and part of the valve
stem. E is the chamber, in this case, cylindrical, on the back of the slide valve G
is the plunger fitting E loosely. The heavy black lines D D show the two lead
diaphragms. P G H are three rings which make up the sides of the elastic com-
pressible chamber. The edges of the lead plates D D being clamped steam tight
between them, by screws (not shown) or other means. M M are two discs made

page_text: fast to to A and C by nuts L L as shewn. The discs M M support the lead plates.
D D, which which latter make the ends of the compressible chamber steam tight
while permitting a certain amount of movement to enable the valve and the
plunger respectively to fit the valve seat and the inside of the valve chest lid steam
tight. The inner edges of the lead plates are clamped steam tight between the
nuts and the collars on the bolts as shewn. I I are springs to impart elasticity and
keep the valve and plunger to their seats. The steam will tend to force the valve
on to its seat, and the plunger on to its seat on the inside of the valve chest lid.
But it also presses on the lead plates and dises M M, and tends to drive them
together, so tending to pull the valve and plunger off their seats as herein before
explained, and so to relieve the pressure on them and diminish friction. The area
of each disc M should be about equivalent to that of a plane cutting the bridge B
at the level of the valve seat, and the area of the hollow space in the outer end of
the plunger C may be about the same, but I do not confine myself to these pro-
portions, the strength of the springs II and the dimensions of the parts being
varied to get the best results according to circumstances.
Fig. 3 is a modification of Fig. 1, and Fig. 4 is a half section plan of the same.
Here one half or end of the elastic compressible chamber is suppressed, the valve
itself and the seat taking its place, C is the plunger A the slide valve, D the lead
diaphragm, E the chamber as before described, a flat spring S is used instead of
the coiled springs II in Fig. 1. In this case the disc M is supported by the
pressure of the steam on the under side of the plunger C, and an equivalent area
of the slide valve may be regarded as non existant, so that there is so much less
surface of the slide valve for the steam to act upon to force it down on its seat, and
so the friction is reduced. The space B then becomes virtually the inside of the
elastic compressible chamber A being the equivalent of G in Fig. 1. This modifi-
cation is very suitable for small valves. For very high pressures the modification
shown in Fig. 5 is suitable. Here the elastic compressible chamber is a brass or
copper steam tight box shewn in section at M. This is secured between the
plunger C and the valve A as shewn. The pressure of the steam will tend to
flatten it, and so to draw C & A off their seats and diminish friction. This device
is not suitable for small valves or low pressures, because the box M cannot be made
flexible enough if of small dimensions that is to say less than about six inches in
diameter. The natural elasticity of the box is sufficient to keep C and A on
their seats.
Fig. 6 shews a modification suitable for very high pressures, and large valves
such as are used in marine engines. The elastic compressible chamber is made of
two steel discs stamped concave. The edges are ground together. The pins L L
being first put in, lead is cast round the two, as shewn by the heavy black lines D
so as to make the joint at the edges steam tight The box thus made is used
precisely like the copper box M shewn in in Fig. 5. Fig. 7 is a section and Fig. 8
a plan of a modification. In this case a steel cup is put under a lead diaphragm D.
The action is nearly similar to that of the modification shewn in Fig. 3 The disc
is cut through radially in one or more places as shewn by the radial lines in Fig. 8
in order to give more elasticity. The lead diaphragm, of course prevents the passage
of steam through these cuts.
Figs. 9 & 10 are simply Figs. 3 and 4 inverted. In this case the slide valve A
plays the part taken by the plunger C in the other drawings. A is fitted into E as
shewn. The valve spindle H¹ passes through a hole in the slide valve, the ring E
being notched out as shewn by the dotted lines in Fig. 9, to make room for it, and
the valve is driven in the usual way by the two nuts and lock nuts J J on the
screwed valve spindle H. The balancing action is precisely the same as in Fig. 3
The inversion of the parts is intended to permit the substitution of a screwed valve
spindle for the bridle shewn in Fig. 1.
Although I have described the diaphragms D as being made of lead, any suitable
pliable material may be used, steel iron or other elastic non pliable metals will not
answer because they are too stiff and unacomodating. Lead on the contrary will

page_text: readily yield and permit the parts to assume various positions through a compara-
tively wide range. The valve will in a word adjust itself automatically in the
valve chest, and no devices are required for adjustment in the shape of screws bolts
ór wedges, such as have hitherto been necessary with balanced slide valves of most
descriptions. The lead will adapt itself to new conditions of position on the
principle of the flow of solids.
Having thus described the nature of my invention of improvements in balanced
slide valves for fluid pressure engines, I now proceed to state more particularly
what I claim, namely,
First. The construction of balanced slide valves for fluid pressure engines sub-
stantialy as herein before described.
Secondly. The use of lead or other imperfectly elastic yielding metal or alloy
nearly similar in character in the construction of balanced slide valves sub-
stantialy as herein before described, for the purpose of making steam tight
chambers capable of modifying their form under pressure.
Dated the eleventh day of June 1886.