IMPROVEMENTS IN SPRING BALANCES, CYTREETT ITT CITY TEIR CONNECTION AND ADJUSTMEN STEAM VALYES
Year: 1855

page_text: LETTERS PATENT to John Silvester, of Smethwick, in the County of
Stafford, Engineer, for the Invention of "IMPROVEMENTS IN SPRING
BALANCES,
CYTREETT ITT CITY
TEIR CONNECTION AND ADJUSTMEN
STEAM
VALYES.
PROVISIONAL SPECIFICATION left by the said John Silvester at the
Office of the Commissioners of Patents, with his Petition, on the 25th
April 1855.
I, JOHN SILVESTER, of Smethwick, in the County of Stafford, Engineer,
do hereby declare the nature of the said Invention for "IMPROVEMENTS IN
SPRING BALANCES, AND IN THEIR CONNECTION AND ADJUSTMENT TO STEAM VALVES,"
to be as follows, that is to say:-
The Invention consists in attaching to a vertical rod suspended from the
lever arm of steam valves a bent lever or plate, hooked at either end, one end
being pinned to a fulcrum on the boiler and the other to the vertical rod. To
the head of the spring balance is attached a friction roller, which plays up and
down (the hooked plate acting as a guide) according to the varying pressure of
the steam; or I also employ in lieu of this apparatus a triangular cam piece,
to the lower angle of which is attached the vertical bar from the valve arm,
and to the upper one the head of the spring balance, the third angle being
pinned to the fulcrum. By these means I obtain a more easy and regular
discharge of steam when the balance is screwed down to a given pressure.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said John Silvester in the Great Seal Patent Office on the
23rd October 1855.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
SILVESTER, of Smethwick, in the County of Stafford, Engineer, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Royal
Letters Patent, bearing date the Twenty-fifth day of April, in the year of our
Lord One thousand eight hundred and fifty-five, in the eighteenth year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said John Silvester, Her special licence that I, the said John Silvester,
my executors, administrators, and assigns, or such others as I, the said
John Silvester, my executors, administrators, and assigns, should at any
time agree with, and no others, from time to time and at all times there-
after during the term therein expressed, should and lawfully 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 "IMPROVE-
MENTS IN SPRING BALANCES, AND IN THEIR CONNECTION AND ADJUSTMENT TO STEAM
VALVES," upon the condition (amongst others) that I, the said John Silvester,
by an instrument in writing under my hand and seal, 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
dato of the said Letters Patent.
NOW KNOW YE, that I, the said John Silvester, do hereby declare the
nature of my said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement, reference being had to the Drawings hereunto annexed, and to the
letters and figures marked thereon, that is to say:
My Invention consists in the application to spring balances used to the
safety valves of steam boilers, of certain mechanical appliances that will ensure
a much more delicate action of the valves, and will admit of a regular and
easy discharge of steam immediately on the pressure exceeding the point
to which the balance is adjusted, and to any amount, without increase of
pressure, whilst by the same means any tampering with the valves is also
prevented..
DESCRIPTION OF THE DRAWINGS.
Figure 1 is an elevation of one of my improved balances regulated to a
pressure of one hundred pounds to the inch; Figure 2, the same as (Figure 1),

page_text: but indicating a pressure of a hundred and twenty pounds to the inch;
Figures 3 and 4, sections through the working parts. The same letters refer
to the same parts in all the Drawings.
I will now proceed to describe the action of this improved balance. (A) is a
barrel, similar to those of the balances in ordinary use; and (B) is an arm,
having a screw turned upon it for the greater portion of its length, and is
secured to the boiler at (D), and by the joint (D) to the piston (C); to the
arm (B) is attached the forked lever (E), working by means of the joint (F)
and screw box (G) in unison with the arm B. (H) is a three-armed axis, fur-
nished with three knife-edged centres (H, H", H",) Figure 4), and is securely
held in the jaws (I, I,) of the lever (E); (K, K,) are cheek pieces fixed on the
barrel (A), and in which the two knife centres (H¹, H",) work, the third
centre (H) working in the bow (M) at the foot of the screw (M'), see
Figure 3). (Figures 1 and 4) represent the balance, adjusted to a pressure of a
hundred pounds to the inch; and it will be seen on reference to (Figure 1) that
the centres (H', H", H) are in a vertical position, the lever (E) being in the
same plane at right angles with them; but as the pressure increases, the lever
arm of the safety valve engaging on the under side of the nut (O), the barrel
(A) is raised, drawing the lever (E) and the centres (H', H", H) out of the
plane in which they are seen in (Figure 1) into the position seen in (Figures 2
and 3), which action, by throwing the centres (H', H",) upon which the barrel
hangs nearer to the fulcrum (F), produces the effect of allowing the lever to-
rise without increase of pressure, whilst this motion of the centres from their
delicate adjustment allows the screw (M¹) upon the slightest increase of
pressure to raise and liberate the lever of the safety valve, and consequently
admits of the free escape of steam until the pressure is reduced to the gauge
indicated at (Figure 1), the parts of the balance then assume their original
position. This form of balance is not only self-acting, but should any attempt
be made to tamper with it, it is self-correcting; for, if by means of the nut (0)
the lever of the valve be screwed down to increase the pressure, the barrel (A),
by the nice adjustment of the centres or axes, already described, will imme-
diately be raised, and throwing the centres nearer to the fulcrum (F) will
prevent the pressure being increased; whilst the joint (F), being a locked
joint, or, if preferred, a nut and screw, as shewn, any attempt to alter the indi-
cated pressure, by running the screw box (G) up or down the screw (B), will
be impossible. It is therefore manifest that if this balance be gauged to a
pressure of a hundred pounds to the inch, or any other given pressure,
the safety valve will rise instantly on that pressure being exceeded, and
not, as is often the case with ordinary balances, requiring an extra pressure

page_text: to perhaps fifteen or twenty pounds on the inch before the necessary vent
is given. A modification of this apparatus may also be made by employing
in lieu of the centres or axes (H', H", H,) a triangular cam piece which
will answer for these centres. In this case the bar (M) is linked to the lower
angle of the cam, the upper one being linked to the head of the balance,
and the third angle pinned to a fulcrum on the boiler; but as the principle is
the same in both, further description is unnecessary.
Having thus described the nature of my said Invention, and in what
manner the same is to be performed, I wish it to be clearly understood that I
do not confine myself to these precise details; but that which I claim is,
the improvements described in spring balances, and in their connection and
adjustment to valves used for steam purposes, by which I am enabled to
obtain a more easy and regular discharge of steam instantly on a given pres-
sure being exceeded, and to any amount without further increase of pressure,
and by which also I can prevent any tampering with or undue alteration of
the pressure, as herein more fully set forth and specified.
In witness whereof, I; the said John Silvester, have hereunto set my
hand and seal, this Eighteenth day of October, in the year of our Lord
One thousand eight hundred and fifty-five.
JOHN (L.B.) SILVESTER.