CERTAIN IMPROVE- MENTS IN CONNECTION WITH SAFETY VALVES
Year: 1881

page_text: LETTERS PATENT to Thomas Davies, of 36, Thomas Street, Broomball Street,
Sheffield, in the County of York, for an Invention of " CERTAIN IMPROVE-
MENTS IN CONNECTION WITH SAFETY VALVES."
PROVISIONAL SPECIFICATION left by the said Thomas Davies at the Office
of the Commissioners of Patents on the 8th September 1881.
THOMAS DAVIES, of 36, Thomas Street, Broomhall Street, Sheffield, in the County
of York. "CERTAIN IMPROVEMENTS IN CONNECTION WITH SAFETY VALVES."
The object of this Invention is providing safety or cheque valves used on
steam boilers or generators, with an auxillary means of force which will positively
prevent such valves sticking or locking when the pressure in the boiler or generator
is superior to the load on the valve.
The Invention consists in the novel application of copper or other metal,
combination of metals, or other material which expands with heat, and contracts
with cold, to a degree sufficient to cause a rod of such metal, metals, or material,
when suitably arranged and connected with a safety valve, to force the valve
proper from its seating for "blowing off" at a given degree of heat and so call the
attention of the engine driver or stoker.
It is well known that safety valves as at present constructed, are liable to stick
or lock and be silent at those times when they should "blow off" from excess of
pressure, as the only force exerted to raise them is that of steam.
Whereas according to my Invention, the novel use and adaptation to safety valves
of a copper or other metal rod or bar so placed that the steam or the heat thereof
will have full action upon it, must either break, bend, or force open the said valve.
In order therefore to prevent such rod breaking or bending under pressure when
expanding, it will be made sufficiently strong and so placed that one of its ends
will rest or bear against an adjustable support, and the other end against the
valve direct or levers in connection therewith, or otherwise in such a position in
relation thereto that sufficient space will be allowed for the due expansion of the
said rod to make its action effective.

page_text: the copper tube, its opposite end above the valve is connected by a link to the
finger gvide Fig. 2; the fulcrum of this finger is at h, and its pointer on the
segmental indicator i. The copper tube a at its top end has bearing upon it the
loaded lever r, which forces the valve b against the seating c with a pressure equal
to that which the steam should "blow off" at safety from the boiler. The action
of the several parts will now be understood by the following description, reference
being had to the Drawings.
The copper tube a extends from the valve b in a downward direction within the
perforated tube & to a point immediately above the screw plug e. This plug can
be adjusted as to its distance from the bottom of the copper tube a by means of a
screw first slackening the lock nut el. The distance between the two surfaces,
viz., the bottom of the tube a and the upper surface of the plug e, represents the
amount of expansion the copper rod is allowed free until an excessive pressure in
the boiler is attained. When this space has been adjusted, the lock nut e¹ is
screwed up so as to fix the plug e, and the valve is then ready, and during the
time the pressure and heat of the steam increases, the copper tube will freely expand
in a downward direction and carry with it the steel rod f, which by reason of its
connection with the finger g will cause such finger to indicate or register on the
segment i the advance or rise of pressure in the boiler until the maximum pressure
is attained at which the steam should blow off for safety. Immediately this
pressure is attained the continued expansion of the copper tube as it beds against
the surface of the fixed plug e, transfers the force of its expansion in the opposite
direction against the loaded lever i, the action of which relieves the valve b from
its seating, and allows the excess pressure of steam to "blow off" and so call the
attention of the engine driver or man in charge. Although the description herein
and Drawings annexed are setforth as an example of the application of the
Invention to a valve of small dimensions, I wish it to be understood that the
Invention is applicable to valves of all sizes, therefore what I claim as of my
Invention is,
The novel application to safety valves of steam boilers or other generators of the
copper or other expanding tube marked a in the Drawings, to be used in the
manner and for the purpose as herein substantially described, set forth, and fully
illustrated in the Drawings annexed.
In witness whereof, I, the said Thomas Davies, have hereunto set my hand
seal, the Third day March, in the year of our Lord One thousand eight
and hundred and eighty two.
Witness,
THOMAS WRIGLEY,
75, Chancery Lane,
London.
THOMAS DAVIES. (L.S.)