IMPROVEMENTS IN SAFETY VALVES
Year: 1883

page_text: LETTERS PATENT to John Henry Johnson, of 47 Lincolns Inn Fields, in the
County of Middlesex, Gentleman, for an Invention of "IMPROVEMENTS IN
SAFETY VALVES" communicated to him from Messieurs Lethuillier and Pinel
persons resident at Rouen in the Republic of France, Engineers.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson at the
Office of the Commissioners of Patents on the 13th July 1883.
"
JOHN HENRY JOHNSON of 47 Lincolns Inn Fields in the County of Middlesex
Gentleman "IMPROVEMENTS IN SAFETY VALVES a communication to me from
Messieurs Lethuillier and Pinel persons resident at Rouen in the Republic of
France Engineers
It is desirable that a safety valve should rise slowly and steadily from its seat
and that it should continue to rise in proportion as the pressure increases so that
the outlet orifice may be fully open when the maximum pressure is attained.
When the pressure is reduced below a given point the valve should return gently
to its seat
According to this Invention the valve is enclosed in a Cylindrical chamber
hereinafter described arranged above the Seat of the valve, and acting as a guide to
the latter
The disc or cone of the valve is surmounted by a Cylindrical conical or recessed
trunk or stem or its equivalent whereby it is connected to a disc flange or Collar
arranged above the valve proper. When the valve is open the steam rushing past
the valve being confined in the chamber is caused to impinge against the under
side of this disc flange or collar and thus tends to lift the valve still further from
its seat.
In carrying out this Invention the improved safety valve is provided with a
Cylindrical chamber at the lower part of which is formed a suitable seat for the
reception of the cone or disc of the valve-The upper part of the said chamber is
contracted by means of an internal flange or otherwise Ribs or guides are also
cast with the Cylinder and serve to steady the valve when lifted from its seat,

page_text: The valve proper is composed of a disc or cone fitted to the seat hereinbefore
referred to and connected to an upper disc by a trunk or webs which may also
assist in steadying the valve by bearing against the interior of the Cylindrical
Chamber
The sectional area of the annular passage formed between the external diameter
of the disc or valve and the internal diameter of the Cylinder or chamber is
somewhat greater than that of the outlet in order that the steam may escape
freely.
The valve being loaded in a similar manner to an ordinary safety valve thus
consists of a disc or cone keeping closed an orifice against a given pressure but
which when the pressure exceeds a certain maximum limit rises from the seat or
orifice and allows the steam to escape through a gradually increasing passage.
The valve rising slowly at first and continuing to rise, the annular space between
it and the side of the cylinder becomes filled with steam and the cylinder being
contracted by the flange herein before described a part of the steam is deflected and
caused to impinge against the under side of the upper disc connected to the valve
thereby compelling the latter to continue its upward movement to an extent
proportioned to the pressure of the escaping Steam
The pressure diminishes directly the section of the valve opening (calculated
according to the area of the grate and heating surface) is entirely free and the
contrary effect is then produced so that the valve descends gently and strictly in
proportion to the reduction of pressure.
Although it is preferred to employ a valve of the form described a similar result
may be obtained with other equivalent forms of valve presenting the same principle
of construction that is to say provided with a chamber or casing surrounding the
valve disc and confining or deflecting the steam so as to compel the latter to act
upon the valve in the manner herein before described.
For example a cylindrical valve or a valve slightly tapering downwards may be
employed and the sides of the chamber may be parallel or not contracted at the
upper part. In this case the outrush of Steam lifts the valve by the friction
resulting from the passage of the steam through the annular space between the
sides of the valve and of the chamber.
When the valve is provided with a disc or flange in combination with a chamber
having straight or parallel sides the steam impinges against the under side of the
disc and the valve is drawn up as in the arrangement:firstly herein before described
but closes more suddenly.
The chamber or cylinder may be enclosed in or form part of a close chamber
having a suitable outlet or outlets for the steam.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent and of
an Order of the Lord Chancellor filed by the said John Henry Johnson in
the Patent Office on the 6th February 1884.
JOHN HENRY JOHNSON of 47 Lincoln's Inn Fields in the County of Middlesex
Gentleman " IMPROVEMENTS IN SAFETY VALVES" a communication to me from
Messieurs Lethuillier and Pinel, persons resident at Rouen in the Republic of
France, Engineers
· All safety valves heretofore constructed may be divided into two classes. In one
class are included the ordinary so called safety valves which allow the steam to
escape directly the maximum pressure is attained but which rise or open to a small
extent only because as soon as the steam begins to escape the pressure per square
inch actually exerted on the under side of the valve when the steam is blowing off
becomes less than the static pressure exerted at other parts of the boiler and goes
on diminishing in proportion as the valve opens. Such valves therefore serve little
other purpose than that of giving warning of an excess of pressure. In the other
class are included valves that rise instantaneously owing to an increase of the
annular surface of the valve. It has been sufficiently demonstrated by actual
experience that when the pressure has attained its maximum limit it is dangerous
to open a valve instantaneously and thus suddenly throw open the whole area of
the outlet.
To obviate these defective workings it is necessary that the valve should rise
slowly so as to commence blowing off when the maximum pressure in the boiler
is about to be reached thus giving warning that either the fire is too fierce or the
water too low. Moreover it is necessary for the valve to continue to rise auto-
matically in proportion as the pressure increases so that the outlet orifice may be
fully open when the maximum pressure is attained in order to comply with the
conditions hereinbefore set forth. When the pressure is reduced below a given
point the valve should close without shock by returning gently to its seat and thus
obviate unnecessary wear.
This Invention has for its object to provide a safety valve capable of complying
with the foregoing conditions for proper working and applicable to stationary or
portable steam generators and to locomotive, marine engine and other boilers of all
descriptions.
The improved valve constructed according to this invention is provided with a
cylindrical chamber arranged above the seat of the disc forming the valve proper
and acting as a guide to the latter. The valve is provided with a cylinder or a
cone or recessed trunk or stem or its equivalent whereby it is connected to au
upper disc flange or collar arranged above the valve proper. When the valve is
open the steam rushing past the valve is confined in the cylindrical chamber and
caused to impinge against the under surface of the disc flange or collar and thus
tends to lift the valve still farther from its seat with a force that augments in the
same ratio as the pressure within the boiler.
This improved valve may be arranged to work in combination with any suitable
arrangements of levers, counter weights, springs and the like for directly or indirectly.
loading the valve as is well understood
And in order that the said Invention may be fully understood I shall now
proceed more particularly to describe the same and for that purpose shall refer to
the several figures on the annexed sheet of drawings the same letters of reference
indicating corresponding parts in all the figures.
Figure 1 of the accompanying drawing is a vertical section of the valve case
showing the valve in elevation and open and Figure 2 is a horizontal section of the
case and stem of the valve.
Figures 3.to 6 represent modifications hereinafter described.
;

page_text: In all the figures B is the valve disc or valve proper which is contained in a
cylindrical chamber A' communicating with the boiler through an orifice Y and with
the atmosphere through an orifice Z.
The chamber A is secured to the boiler shell by any suitable means and is
provided at its lower part with a seat a on which the valve disc B rests when
closed. The chamber A forms a passage which is contracted at its upper part Z by
an internal flange or shoulder a¹. Ribs or wings a² on the sides of the chamber A
act as guides for the valve disc B to steady it when lifted from its seat by an
excessive pressure of steam. The valve disc B or valve proper is connected to an
upper disc b by a stem or trunk and wings or webs b which bear, against the
flange a¹ and assist in steadying the valve. It is evident that the valve B' and
disc b may be supported or guided by a rod or other guide in place of the ribs or
wings a² and b².
In order that, the steam may escape freely the sectional area of the annular
passage formed at c between the edges of the valve B and the sides of the cylinder
or chamber A is greater than that of the outlet orifice.
The valve is loaded by any suitable means such as are commonly employed for
loading safety valves so that the disc or cone B is capable of keeping the orifice Y
closed against a given normal pressure but when the pressure exceeds a certain
limit the said disc B rises from its seat and allows the steam to blow off. Thus
far the action.is similar to that of an ordinary safety valve but by reason of the
arrangement hereinbefore described the degree of opening of the valve is duly
proportioned to the degree of excess pressure in the interior of the boiler. This
effect is produced by causing the steam escaping past the valve B to enter the
chamber A provided with the flange a¹ by which the current of steam is to a certain
extent deflected and caused to impinge against the under surface of the upper;
disc connected to the valve B. The force of the rush of steam thus directed
against the disc b drives up the latter and assists in causing the valve B to continue.
its upward movement and open to an extent proportioned to the pressure of the
steam. Hence it results that as the volume and force of the discharge increases the
valve B rises or opens in proportion
The pressure in the boiler begins to diminish directly the valve is open to the
full extent of the opening Y (calculated according to the area of the grate and.
heating surface) and the contrary effect is then produced the force of the steam
impinging on the under surface of the disc b being gradually diminished so that
the valve disc B descends gently and returns to its seat at a rate strictly in
proportion to the reduction of pressure in the boiler. My foreign correspondents
state that it has been proved by trials made with a manometer that the rise and
fall of the valve coincide or correspond exactly with the pressure indicated by the
manometer.
Although it is preferred to employ a valve of the form described and illustrated
a similar result may be obtained with other equivalent forms of valve presenting,
the same principle of construction that is to say provided with a chamber or casing
surrounding the valve disc and confining or deflecting the steam so as to compel
the latter to act in the manner hereinbefore described upon a surface connected
with the valve disc.
An important and essential feature of the invention consists in the arrangement
whereby the annular space c between the edges of the valve B and the sides of the
chamber A is caused to present a passage whose sectional area is larger than the
area of the said valve B (or orifice Y) so that the improved valve is enabled to act
in the first instance in precisely the same manner as an ordinary valve by rising
slightly from its seat when the pressure is on the point of exceeding the maximuu
allowed and then stopping as the pressure per square inch on the lower side of the
valve B under these conditions becomes less than the static pressure present in the
boiler. The steam now escapes freely through the annular passage C and if t
the quantity of steam produced in the boiler is less than the delivering capacity of,
the valve the latter closes again under the same conditions as an ordinary. valve.

page_text: When, on the other hand, the production of steam in the boiler goes on increasing
the improved valve continues to rise gradually owing to the fact that the increased
rush steam, through the chamber A is deflected by the contraction a¹ and caused
to impinge in a strong annular jet against the under surface of the upper disc b
attached to the valve B thereby causing the latter to rise progressively in
proportion to the increase of pressure in the boiler until the valve is fully open
and thereby renders it impossible for the maximum pressure to be exceeded
Hence it is evident that the action of the improved valve is totally different
from that of valves acting on the principle of increasing the area of the valve and
utilising the shock of the steam in the annular space resulting from such increase
for in such valves the steam cannot escape into the atmosphere without instantly
carrying the valve up with it so that in place of obtaining a progressive rise
there is a sharp sudden inovément directly the pressure attains the extreme limit.
Figure 3 of the accompanying drawings is a vertical section of a safety valve
constructed according to this Invention showing the valve disc in the closed or
normal position and loaded by means of a weighted lever L.
Figures 4 and 5 represent in vertical and horizontal section respectively a
modification in which the valve is enclosed in a chamber T whereby the escaping
steain is confined and discharged at X into a pipe leading to the exterior of the
building.
The valve B is loaded by means of a lever L resting on a rod P bearing on the
back of the valve. In the arrangement illustrated the lever is provided with a
fuleruni formed by an arm or pillar p but in some cases it may be more convenient
to provide a fulcrum by casting & lug or bracket on the side of the chamber T as
indicated by dotted lines in figure 4. The lever L is provided with knife edges.8
which engage with corresponding recesses in the arm or lug and in combination
with a notch on the lever engaging with the rod P prevent the lever from becoming
accidentally displaced.
Figure 6 represents a pair of valves partly in section which are loaded by means
of springs f. The two valves are enclosed in one chamber T serving to confine
the escaping steam. This arrangement is well suited for locomotive and marine
boilers.
Having now described and particularly ascertained the nature of the said
Invention and the manner in which the samé is or may be used or carried into
effect I would observe in conclusion that what I consider to be novel and
original and therefore claim as the Invention secured to me by the hereinbefore in
part recited Letters Patent is:―
First A safety valve so constructed or arranged that when the valve disc or
valve proper opens the escaping steam passes between the edges of the said valve
proper and the sides of a chamber surrounding the said valve proper and is
deflected so as to impinge against a disc or body attached to the valve proper and
thereby move the said valve proper away from its seat to an extent proportionate
to the positive increase of pressure within the boiler substantially as hereinbefore
described and illustrated by the accompanying drawings.
Second-The several arrangements and combinations of parts constituting the
safety valves herein before described and illustrated respectively in figures 1, and 2;
3; 4 and 5 and 6 of the accompanying drawings.
In witness whereof I the said John Henry Johnson have to this my Specification
set my hand and seal this Fourth day of February One thousand eight hundred
and eighty four,
1
J. HENRY JOHNSON (L.S.)