IMPROVE- MENTS IN OR CONNECTED WITH SPRING SAFETY VALVES.
Year: 1873

page_text: LETTERS PATENT to Thomas Davison, of Glasgow, in the County of
Lanark, North Britain, Engineer, for the Invention of "IMPROVE-
MENTS IN OR CONNECTED WITH SPRING SAFETY VALVES.
Sealed the 9th December 1873, and dated the 18th June 1873.
PROVISIONAL SPECIFICATION left by the said Thomas Davison at
the Office of the Commissioners of Patents, with his Petition, on
the 18th June 1873.
I, THOMAS DAVISON, of Glasgow, in the County of Lanark, North
Britain, Engineer, do hereby declare the nature of the said Inven-
tion for "IMPROVEMENTS IN OR CONNECTED WITH SPRING SAFETY VALVES," to be
as follows, that is to say:-
This Invention has for its object the applying of springs to safety
valves in an improved manner, and so that (when adjusted for the
purpose) they will offer no appreciable increase of resistance when the
valves are opened more or less or up to their fullest necessary extent.
The springs arranged in the improved manner may also be adjusted so.
that their resistance either diminishes or increases as the valves open.

page_text: In one simple modification of the improved arrangements two helical
springs of steel are applied directly to an ordinary safety valve so as to
be compressed by the opening of the valve, but instead of being arranged
in or parallel to the axis of the valve, they are placed on opposite sides
with their axes forming with that of the valve equal or nearly equal
angles of between 60 and 80 degrees cach as measured from the outer
part of a prolongation of the valve's axis. The joint effect of the two
springs on the valve depends on the angles of their inclinations, and
when the valve opens its movement causes an alteration in these angles,
which alteration modifies what would be the increase of resistance
simply due to the amount of compression of the springs.
If the outer ends of the springs are made adjustable in position, the
springs may be adjusted so that the resistance may either not vary
appreciably or diminish or increase somewhat as the valve opens.
Three or more springs arranged equidistantly round the valve may be
used instead of the two, or a single spring may be applied obliquely on
one side if a roller or equivalent detail is applied to the other side to
meet the lateral strain.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Thomas Davison in the Great Seal Patent Office 2
on the 17th December 1873.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
DAVISON, of Glasgow, in the County of Lanark, North Britain, Engineer,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her 2
Letters Patent, bearing date the Eighteenth day of June, in the year of
our Lord One thousand eight hundred and seventy-three, in the thirty-
sixth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Thomas Davison, Her special licence,
that I, the said Thomas Davison, my executors, administrators, and a
assigns, or such others as I, the said Thomas Davison, my 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 might make, use, excrcise,

page_text: and vend, within the United Kingdom of Great Britain and Ireland, the
Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
OR CONNECTED WITH SPRING SAFETY VALVES," upon the condition (amongst
others) that I, the said Thomas Davison, my executors or adminis..
trators, by an instrument in writing under my, 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 I, the said Thomas Davison, do hereby declare
the nature of my 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 :-
My said Invention has for its object the applying of springs to safety
valves in an improved manner, and so that (when adjusted for the
purpose) they will offer no appreciable increase of resistance on the
valves being opened more or less or up to their fullest necessary extent.
The springs arranged in the said improved manner may also be adjusted
so that their resistance cither diminishes or increases as the valves
open.
My Invention consists in a peculiar mode of applying the spring or
springs obliquely to the spindle of the valve, and in order that my im-
provements and their practical application may be properly understood,:
I hereunto append a Sheet of explanatory Drawings to be herein-after
referred to, and representing a safety valve with a pair of springs applied:
to it in accordance with my Invention. In these Drawings the same.
reference numerals are used to mark the samo or like parts wherever
they are repeated.
Figure 1 is a vertical section as at a plane parallel to that of the two
springs, and Figure 2 is a vertical section as at right angles to Figure 1,
but with the springs supposed to be removed.
The safety valve 1 which is of a well known form is represented as
applied to a seat 2 in a passage 3 communicating with the steam boiler,
and it is in a chamber 4 which has a lateral outlet 5 for the steam that
escapes past the valve. The valve 1 is pressed down by a vertical.

page_text: spindle 6 which enters the valve chamber 4 through a guide eye from a
chamber 7 above, and the upper end of which is also guided by an eye in
a bar or plate 8 fixed across the top of the chamber 7. The valve
spindle 6 is directly acted upon by two helical springs 9 of steel arranged
to be compressed by the opening of the valve 1, but instead of being in
or parallel to the axis of the valve, they are placed on diametrically
opposite sides, and in such positions that their axes form with that of
the valve spindle 6 equal or nearly equal angles of between 60 and 80
degrees cach, as measured from the upper part of the prolongation of the
valve's axis. The two springs 9 being adjusted to act equally or as
nearly so as possible, the oblique action of one neutralises that of the
other, and their joint or resultant effect is in the direction of the valve's
axis. Each spring 9 has end pieces 10, 11, fitted to it, and these are
formed with tubular portions working together telescopically to prevent
lateral displacement, whilst cach spring is by preference made in two
halves, as shown, one half being right-handed and the other left-handed,
so as to avoid the twisting action which takes place with a single helix.
A brass ring 12 is inserted between the two halves of the spring to
insure a proper bearing between them, and is formed with cylindrical
flanges which enter within the coils of the spring and keep the ring in
its place. The inner end pieces 10 of the springs are formed with blunt
knife edges 13 to bear against angular seats 14 formed on opposite sides
of the valve spindle 6, the knife edges and seats being formed with
flanges or projections to prevent displacement. The outer end pieces 11
of the springs bear against nuts 15, which are adjustable on short screw
spindles 16, formed with blunt knife edges 17, to bear against angular
seats 18, fixed to the inside of the case or chamber 7, enclosing the
springs (or to brackets when there is no casing). The knife edges 17.
and the angular seats 18 are formed with flanges or projections to
prevent any displacement of the parts, and the seats 18 are made.
with elongated bolt holes to admit of being nicely adjusted in position.
The spindles 16 at the outer ends of the springs might be simply
jointed to brackets or other fixtures, but I prefer the arrangement
with the knife edges. The main spindle 6 of the valve is formed with
a slotted enlargement 19, into which enters the end of a small curved
lever 20 formed on a horizontal shaft 21, which passing through the
sides of the casing 7, is externally connected in any convenient way
with a hand lever or wheel, so that it can be turned for easing the valve
when required. The easing shaft 21 is placed in its bearings before

page_text: placing the cross bar or plate 8 which secures it, the top of the casing 7
is closed by cover plates 22 which are formed with hooks catching under
snugs within the ends of the casing, and the whole is secured by a light
central cover 23 which is bolted on, the bolts being secured by padlocks
if required.
Three or more springs arranged equidistantly in plan round the valve
may be used instead of the two shown in the accompanying Drawings,
or a single spring may be applied obliquely on one side if a roller or
equivalent detail is applied to the other side to meet the lateral strain.
In adjusting the seats (18) for the outer ends of the springs the lowering
of the seats will cause the effective resistance of the springs to be
comparatively less for the more or less open positions of the valve, and
on the contrary the raising of the seats (18) will render the resistance
greater under like circumstances.
Having thus particularly described my said Invention, and the
manner of performing the same, I have to state that I do not restrict
myself to the precise details herein described or delineated, but that
what I believe to be novel and original and claim as the Invention
secured to me by the herein-before in part recited Letters Patent is, the
applying of inclined or angularly disposed springs directly to safety
valves or their spindles, substantially as and for the purposes herein-
before described.
In witness whereof, I, the said Thomas Davison, have hereunto set
my hand and scal, this Sixteenth day of December, in the year of
our Lord One thousand eight hundred and seventy-three.
Witness,
EDMUND HUNT,
Patent Agent,
Glasgow.
THOS. DAVISON. (L.S.)