Year: 1895

page_text: Date of Application (in United Kingdom), 3rd May, 1895
Complete Specification Left 3rd May, 1895-Accepted, 27th July, 1895
We, GIUSEPPE POCCARDI & Co of Via Ponte Mosca No 22, Turin, in the
Kingdom of Italy, Founders, do hereby declare the nature of this invention and
in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement
This invention relates to an improvement in the class of safety valves for steam
boilers which are inaccessible to the attendant, the object being to provide an
effective form of safety valve the purpose of which is to avoid explosion or other
similar accident in case of over pressure in the boiler, and to render it impossible
for the attendant to overcharge the same
The apparatus is illustrated in the accompanying drawing in which A. B is a
casting, the part B containing a chamber for a differential piston valve F, and the
part A containing steam passages G G¹, a steam passage I and valves C C¹, the
latter being connected by a spindle D Above the part A is a chamber M on
which is superposed a chamber M¹ The chamber M is provided with a spring E
having a central rod E' carrying blocks E' E', the lower of which is fixed and has
a conical point which beais in a conical seat in the valve C₁, while the upper
block L is movable on the rod and is adjustable by means of the screwed tubular
rod S which passes through the part R and through which rod S passes the rod E¹
On the upper end of the rod is a head Q which is surrounded by the open portion P
of a lifting handle O, the part P enclosing the head Qin such a manner that the
only movement that can be given to the rod E' by the handle O is a lifting one
The apparatus being secured to a boiler the steam passes into it by the
passages G G and circulates in the passage H around the valve F, at the same
time passing by the valve C which is normally open (being kept down by the
spring E) and enters the passage L above the valve F by way of the passage I so
exerting pressure on valve F which keeps it shut An excess of pressure will now
cause the valve C to rise against the pressure of the spring, thus closing valve C
and allowing the steam in passages I and L to exhaust into the chamber M from
which it will escape by means of suitable apertures such as 1
When the pressure
has thus passed off, the valve F will rise by pressure from beneath it in the
passages H, and the steain will exhaust through orifice N until the pressure in the
boiler has fallen to the desired point when the valve C will open again (it having
meanwhile been kept closed by the pressure) adınıtting steam into passage L above
the valve H
It will be seen that when the spring E has been once adjusted the cover M' may
be screwed on and sealed so that the boiler attendant can only raise the rod E¹
by means of the handle O to see if the valve is working properly by letting off
steam

page_text: Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is
-
1 In a valve constructed substantially as described, the employment of a
differential piston valve working in a cylinder and pressed alternately by steam on
the two sides in the manner substantially as set forth
2 In a valve con.tructed substantially as described, the employment of a pan
of connected valves arranged at a point between steam passage and a casing,
substantially as and for the purpose set forth
3 In a valve constructed substantially as described the arrangement and con-
struction of the parts A and B, substantially as described
4 In a valve constructed substantially as described, the airangement and
construction of the casings and contained spring and parts, substantially as
described
The general arrangement and construction of the valve substantially as
described and illustrated
Dated the 3rd day of May 1895
PHILIP M JUSTICE,
Chartered Patent Agent, London,
For the Applicants