IMPROVEMENTS IN SAFETY VALVES
Year: 1884

page_text: I THOMAS FOSTER, of The Owens College, Manchester, in the County of Lancaster,
Model Maker, do hereby declare the nature of my Invention for IMPROVEMENTS IN
SAFETY VALVES to be as follows:-
:-
The accompanying sketch, shows the valve as adapted to the dead weight
principle, but it may be loaded, by either springs or weights, in any of the
usual ways.
"
I prefer to make the valve A, Fig. 1, in the form of an inverted cup, but it may
be in any other convenient form. This valve must rest upon a loose seating B,
which loose seating, forms a lower valve, and as such rests upon an ordinary fixed
seating C. The loose seating B, must be in the form, of a short tube, with a
flange b, b, at its upper end. This flange may vary considerably in size, but
I prefer, to make it about twice the diameter of the valve, when the working, or
blowing off" pressure, is one hundred pounds to the square inch; and a
proportionately less diameter for lower pressures.
The outward portion b¹, of this flange, must be so formed, that its upper surface,
must lay along, and coincide, as near as may be, with the path of the steam as it
issues, from under the lip of the valve A, when " blowing off;" or it may not
coincide with, but in that case, must be so near, and approximately parallel, to the
said path of the issuing steam, that the pressure of the atmosphere, shall be thereby
swept from the said upper surface.
I prefer to make the face or lip of the valve A, horizontal, in which case the
outward portion 61 of the flange, must also be approximately horizontal, because
when "blowing off," the steam leaves the valve in a line approximately straight,
and parallel to the faces of the opening.
The lower face or lip of the loose seating, and the lip of the upper valve, need
not be broader than is necessary to resist the crushing stress, exerted by the load
placed upon the valve. I prefer to make the depth of the loose seating, about one
inch and three quarters; it may be made much greater, but it need not be greater
than is necessary to prevent the steam as it issues from under its lower face, from
striking the under side of the flange b¹; nor must the issuing steam, pass so near
this flange as materially to reduce the atmospheric pressure against it. An annular
ring F, may also be attached to the guides H, for the purpose of further assisting

page_text: to prevent the issuing steam, from sweeping the atmospheric pressure from the
under side of the flange b¹.
K, is a tube whose diameter may be from one third to one half, the diameter of
the valve. The object of this tube, is to convey the steam to the valve A, without
its pressure being reduced as it passes the opening B¹, when "blowing off." The
length of this tube may be greater than is shown in the sketch, and may extend
into the main steam space of the boiler, or other vessel, to which the valve is
applied. M, M, are guider ribs for the tube K. L, L, L, are guide ribs for the
valve A. N, is a stand pipe for carrying the seating C. O, is a pendulous bonnet,
for carrying the annular weights,, wherewith to load the valve.
In this "Provisional Specification" the word steam must be understood to mean,
steam or any other fluid.
Dated this 2nd day of January 1884

page_text: I THOMAS FOSTER of The Owens College, Manchester in the County of Lancaster
Model Maker do hereby declare the nature of my Invention for "IMPROVEMENTS
IN SAFETY VALVES" and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement:—
The object of my Invention is to insure a larger opening for the discharge of
steam or other fluid, without the usual large increase of pressure beyond the point
where the valve first begins to blow.
This object I attain by the means illustrated in the accompanying Drawings;
the same letters of reference being used to indicate corresponding parts in each
Drawing.
Fig. 2 is a vertical section of the valve as adapted to the dead weight principle;
but it may be loaded by either springs or weights in any of the usual ways.
I make the valve A preferably in the form of an inverted cup, although it may
be of other convenient shape. The lip of this valve rests upon a loose seating B
which loose seating forms a lower valve, and as such rests upon an ordinary fixed
seating C secured to and carried by a stand-pipe N. The loose seating B is made
in the form of a short tube with a flange b and b¹ at its upper end. This flange
may vary considerably in size; but I prefer to make it about twice the diameter
of the valve when the working or blowing off pressure is one hundred pounds to
the square inch, and proportionately less for lower pressures. The outward
portion b¹ of this flange is so formed that its upper surface lies along, and coincides
with the path of the steam or other fluid as it issues from under the lip of the
valve A, when blowing off; or it may not coincide with, but may be so
approximately near and parallel to the said path of the issuing steam or other
fluid, that the pressure of the atmosphere shall be thereby wholly or in part swept
from the said upper surface. The entire load upon the lower valve is thus reduced
during the whole time that the issuing steam sweeps its upper face.
•
I prefer to make the face or lip of the valve A horizontal; in which case the
outward portion 61 of the flange must also be approximately horizontal, because the
steam when blowing off, leaves the valve in a line nearly straight and parallel to
the faces of the opening.
The lip or face of both upper and lower valve need not be broader than is
necessary to resist the crushing strain caused by the load placed upon the valve.
A circular groove S may also be cut in the face of the flange b', for the purpose of
preventing a shoulder being formed by the wear and regrinding of the lip of the
valve A into the face b¹. I prefer to make the depth of the loose seating B about
one inch and three quarters; it may be much deeper but need not be deeper than
is necessary to prevent the steam or other fluid as it issues from under its lower
face from striking the under side of the flange b¹; nor must the issuing fluid pass
so near this flange as materially to reduce the atmospheric pressure beneath it.
An annular flange or ring F may also be attached to the guides H for the purpose
of further assisting to prevent the fluid as it issues from under the lower valve,
from striking the underside of the flange b¹. K is a tube secured to the flange b
for the purpose of supplying the upper valve A with steam without its pressure
being reduced as it passes the opening B' when blowing off. The diameter of this
tube may be from one third to one half the diameter of the valve. This tube may
also be so long as to dip into the main steam space of the boiler; or it may be cut
of at a point K¹ in which case I provide it with four guide ribs M which may be

page_text: cast in one piece with the seating C. The upper valve A is guided by four internal
ribs L cast upon B. The lower valve is guided by external ribs H cast upon the
seating C.
The valve is loaded by annular weights P placed upon a pendulous
bonnet O.
Fig. 3 is a vertical section, and Fig. 4 a horizontal section, showing another form
of the valve. The face of the upper valve A in this case is spherical, and the
flange b' instead of being horizontal is approximately tangential to that part of the
face of A which rests upon B. By this arrangement the necessity for guide-ribs for
the upper valve is avoided. The guide-ribs H for the lower valve may be internal
and cast in one piece with the valve B and the tube K.
"Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is to be performed, I declare that what
I claim is "
The application to a safety valve (having an upper valve seated on a lower one)
of a flange or broad face on the upper end of the lower valve; which upper face
shall be approximately coincident with the path of the steam or other fluid, as it
issues from under the lip of the upper valve, substantially as herein shown and
described.
T1 11°
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