Improvement in Electrically Heated Crucibles and Holders therefor.
Year: 1893

page_text: Date of Application, 4th Apr., 1893-Accepted, 13th May, 1893
COMPLETE SPECIFICATION.
Improvement in Electrically Heated Crucibles and Holders
therefor.
I WILLIS MITCHELL Electrician of Malden in the County of Middlesex
and State of Massachusetts, United States of North America do hereby declare
the nature of this invention for IMPROVEMENTS IN ELECTRICALLY HEATED
CRUCIBLES AND HOLDERS THEREFOR and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement :-
The object of this invention is to provide for heating a crucible by electricity
and to especially adapt the crucible to this procedure. The said invention consists
partly in a crucible consisting of two insulated parts; and also in the combination
therewith of a holder connected with circuit wires and having terminals in contact
with these parts respectively.
In the accompanying drawings,
Figure 1 represents a perspective view of a crucible and its holders embodying
my invention;
Figure 2 represents the parts of the crucible and their insulating bar detached ;
and
Figure 3 represents a perspective view of the holder.
A and B designate the two equal longitudinal parts or sections of my crucible
preferably formed by simply cutting through an ordinary plumbago crucible on
the line of its axis. C designates an U-shaped bar or partition of asbestos or fire
clay or a mixture of both or other insulating material, which is fitted between the
edges of these parts and cemented or otherwise secured thereto completing the
improved crucible. The latter may however be made in the first instance with
this bar or partition embedded in it but separating the material on each side to
secure the same results.
The holder consists of two bars or rods D of electrically conducting material
fastened by transverse insulated pins d and extending in parallel lines through a
handle E beyond which they are connected to wires FG forming part of an
electric circuit. The operating ends of these bars or rods are spread apart and
curved at D', to receive the crucible between them, being provided with terminal
plates H H that fits the sides of it neatly. Plate H is in contact with crucible
section A and plate H' with crucible section B; and as these sections are
insulated, the electrical current must cross the intervening space, the hollow
interior of the said crucible, through the ore or metal therein contained, exciting
a high degree of heat in overcoming the resistance encountered, both from the
plumbago of the crucible and from what it may contain.
Of course such crucibles may be of varying size according to the service
desired ; but this invention is particularly useful in the melting or softening of
small quantities of metal and the like, as for dentist and jewellers' use. The
form of the crucible may of course vary, the word being intended to include any
vessel thus constructed. Metal and other suitable material may be substituted for
plumbago; but the latter is best.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what
I claim is :-
First. A crucible consisting of the sections A. and B of electrically conducting
material and the U-shaped insulating bar or partition C substantially as set

page_text: Second. In combination with a crucible consisting of two insulated parts of
electrically conducting material, a holder which is provided with a handle adapted
to be held by the hand and with two terminal plates in contact with the said parts
respectively, these plates being insulated from each other and forming part of an
electric circuit substantially as set forth.
Third. In combination with a crucible consisting of two insulated parts of
conducting material a holder consisting of two bars in a handle, these bars being
adapted to fit against the said parts respectively and connected to wires completing
an electric circuit through them and through the said crucible substantially as
set forth.
Dated this Sixth day of March 1892
WILLIS MITCHELL.
F. W. Golby,
36; Chancery Lane, London, W.C., Patent Agent for the Applicant.