Improvements in Gas Furnaces and the Burners for Heating Them.
Year: 1897

page_text: Date of Application, 2nd Mar.,
1897
Complete Specification Left, 5th Nov., 1897-Accepted, 22nd Jan., 1898
PROVISIONAL SPECIFICATION.
Improvements in Gas Furnaces and the Burners for Heating Them.
JOHN HUTCHENS GARTRELL, 47, Chapel, Street, Penzance, Cornwall, Dentist, do
hereby declare the nature of this invention to be as follows:-
This invention relates more particularly to nickel muffle furnaces for "firing"
porcelain for dental purposes and to the gas burners for heating the furnaces.
In carrying out my invention I make the furnace in two parts of an iron casing
lined with fireclay. The upper part opens on a hinge so that the nickle inuffle held
between the two parts can be readily removed and replaced. It is made of sheet
nickel pressed to the shape of a flattened tube. The nickel has an alloy of about two
to three parts of Manganese which has an important effect in controlling the oxydation
of the nickel when strongly heated.
The furnace is fitted with a damper to admit air to the gas flame when working
the burner as a Bunsen. The burner is fitted to an opening in the bottom of the
furnace and the novel part of the burner is the construction of the gas valve for
instantly changing the flame from a Bunsen or atmospheric burner to a blast produced
by air under pressure. The tap or valve by which the gas and air are admitted to the
burner is the reverse of an ordinary blow-pipe where the air is forced through a
central tube and the gas through an outer tube. In my improvement for furnace
work gas presses through the central tube and air under pressure through the outer
tube.
A valve worked with a milled headed screw controls the gas so that when the valve
is closed a small hole only is open for the gas to pass to the tube of burner suitable
for a Bunsen flame and when the valve is opened by turning the milled headed screw
a larger quantity can pass suitable for burning with air under pressure.
The Bunsen flame is used first to dry and heat the work placed in the muffle of
furnace and then the change made to a blast to strongly heat the work. The change
is made instantly by a turn of the gas valve and blowing with a foot-hellows. It is
obvious that this description of burner may be used for heating crucible or other
furnaces.
D
14
Mach 1007
improvemen
I, JOHN HUTCHENS GARTRELL, Dentist, of 47, Chapel Street, Penzance, in the
County of Cornwall, do hereby declare the nature of this invention and in what
[Price 8d.]

page_text: manner the same is to be performed, to he particularly described and ascertained
in and by the following statement:-
66
This invention has for its object improvements in nickel muffle furnaces for
firing" porcelain and the like, for dental purposes, and in gas burners for heating
the same,
In carrying my invention into practical effect, I make an iron furnace lined with
fireclay. This furnace consists of an upper and a lower part, the two parts being
hinged together at one end or side and being so shaped as to readily admit the
insertion of a muffle between them.
The muffle, preferably in the shape of a flattened tube, I make of sheet nickel,
either with or without about two to three per cent. of manganese, the latter, when
used, having an important effect in controlling the oxidation of the nickel when
strongly heated.
The burner is fitted to an opening in the bottom of the furnace, the gas flame
passing round the muffle within the furnace and then passing out of a suitable opening
in the top of the furnace.
The burner and gas valve are so constructed that they may be adapted at will for
use as a Bunsen or atmospheric burner, or as a burner with a blast of air under
pressure.
I will now proceed to more particularly describe my invention with reference to
the accompanying drawings; the same letters of reference indicate similar parts in
the various figures.
Fig. 1 shows a perspective view of a muffle furnace and burner complete, made
according to my invention. The furnace consisting of two parts, a and b, hinged
together at one end or side as at 61 and lined internally with fireclay, the upper part a
having an opening 62 for the escape of the gas flame and fumes. The upper half of
the furnace is raised by means of a rod a¹ having any suitable number of notches such
as n therein, and having one end thereof pivoted to the upper half of the furnace a,
a knob or handle u² being affixed to the other end thereof. By means of this rod a¹
the top part of the furnace may be partially raised when required and retained in its
partially raised position, as shown in Fig. 1, by means of passing one of the notches n
over a pin n¹ fixed in the lower part 6 of the furnace. The muffle, such as c, is placed
within the furnace, its ends resting upon the ends of the lower part b specially shaped
to receive them. The ends of the upper part a of the furnace are also recessed or
shaped to closely fit the muffle, so that when the furnace is closed, the muffle is firmly
held in position between the two parts thereof. The lower part of the furnace is
provided with a shelf at the front thereof, which is found useful in manipulating the
work. A view of the back of the furnace is shown at Fig. 2, the furnace being shown
closed and with the muffle in position. A sufficient space is left between the fireclay
lining of the furnace and the muffle to allow the flame to pass freely round the
latter.
The bottom of the furnace has an opening therein, into which fits the top of the
burner p, the furnace resting upon the shoulder p¹ of the burner p, and being secured
by means of the set screw s. The lower end of the burner p has an opening for the
admission of air, such as p2, at either side thereof, and into it fits and is secured by
means of the set screw s¹, the top of the gas and air valve v, which has an opening
for the admission of gas at v¹ and another opening for the admission of air under
pressure at v².
Figs. 3 and 4 show this gas and air valve v, partly in section and separated from
the lower end of the burner. The valve consists of an inner and an outer casing 3
and 4 respectively, separated by an annular space s²; within 3 is situated the valve
spindle p³ the lower end of which terminates in a screw which, passing through the
bottom of the inner casing which is internally screw-threaded to receive it, is
operated by the milled head m. The top of this valve spindle p³ terminates in a
beadh so shaped as to be capable of closely fitting a seating in the top of the inner
case 3 when the said spindle p³ is screwed up. This valve spindle p³ is hollow and

page_text: has a small opening in the top thereof and also an opening o in the side thereof for a
purpose hereinafter explained. Gas is admitted into the inner casing when required
by means of the tube v¹ and air under pressure is admitted, when required, by means
of the tube 2, into the annular space s².
Fig. 5 is a longitudinal section of the burner with the valve attached and shows
the head of the burner h¹ in position.
Fig. 6 is a perspective view of the burner head h¹ which consists of a short cylinder
perforated longitudinally with a number of holes and having a shoulder formed at the
top thereof upon which it rests when in position.
Figs. 7, 8, and 9 show forms of muffles suitable for this class of furnace and made
of rolled nickel (with or without about 2 to 3 per cent. of manganese) bent to the
shape of flattened tubes and having the free ends of the sheet of metal of which they
are composed joined by means of riveting as in the case of Figs. 7 and 9: or by
means of a lapped joint as in the case of Fig. 8: or in any other convenient way, and
each muffle has one end closed and one end open.
The furnace burner and valve are supported on any suitable form of stand or
base.
When it is required to use the burner as an ordinary Bunsen or atmospheric burner.
the valve spindle p³ is screwed up by means of the milled head m until the head
thereof h closelv fits the seating in the top of the inner casing v³, as shown in Fig. 4.
Gas is now admitted through the tube v¹ into the inner casing and finds its way into
the opening o (shewn clearly in section in Fig. 5) and out at the opening in the top
of the head of the spindle p³, the burner is now lit at the top and acts as an
ordinary Bunsen, air being admitted at the openings p². If it is now required to use
an air blast, the spindle ps is lowered by means of unscrewing the milled head m, as
shown in Fig. 3, and a greater supply of gas thus admitted to the burner, a blast of
air, supplied by means of a foot bellows or other suitable means, being admitted
through tube v² to the annular space s² and thence to the burner.
When it is required to fire any porcelain or the like works, these are placed in the
nickel muffle and the latter properly placed in the furnace. The top of the furnace
is at first left partially open to admit air as shown at Fig. 1 and the muffle gently
heated by means of the Bunsen flame, in order to dry and heat the porcelain work;
when now the muffle is sufficiently heated the furnace is closed and the air blast
flame applied by means of unscrewing the milled head m and turning on the air blast,
as previously described, until the work is sufficiently fired.
To prevent the work from cooling too rapidly after the firing has ceased, the open
end of the muffle may be closed by means of the fireproof plug t, Fig. 1.
I have described this burner in connection with a muffle furnace only, but it is
obvious that it may be applied to crucible and other furnaces.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is
(1) For dental and other purposes a gas furnace composed of two parts, lined with
fireproof substance, hinged together and suitably shaped for receiving a muffle, the
said furnace being fitted with a burner and gas and air blast valve, and operated
substantially as herein described and illustrated.
•
(2) For use with gas furnaces a gas and air blast valve capable of being used either
with an atmospheric burner or with an air blast flame, and consisting of an inner and
outer casing, gas being admitted to the inner casing and an air blast being admitted
when required to an annular space between these two casings, operated and substantially
as herein described and illustrated.
(3) In muffle furnaces the use of muffles made of sheet nickel or of sheet nickel
alloyed with about two to three per cent. of manganese substantially as described.
(4) In gas furnaces for dental purposes the use of a burner having a head consisting

page_text: of a perforated cylinder and capable of use either as an atmospheric or as an air blast
burner substantially as described.
ليد
20
1
.
tahan 1007
66
CASTLE SMITH,
Invention" Office, Mitre Court, Fleet Street, London, E.C.
Agent for the Applicant.