Improvements in connection with the Sheathing or Casing of Thermo-electric Elements.
Year: 1899

page_text: Date of Application, 17th Mar., 1899--Accepted, 29th Apr., 1899
COMPLETE SPECIFICATION.
Improvements in connection with the Sheathing or Casing of
Thermo-electric Elements.
I, JAMES YATE JOHNSON, of 47, Lincoln's Inn Fields, in the County of London,
Gentleman, do hereby declare the nature of this invention (which has been com-
municated to me from abroad by Messrs. Hartmann and Braun, of Bockenheim,
Frankfort-on-the-Main, in the German Empire) 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 remedy certain defects which have hitherto
existed in the sheathing or casing of thermo elements by reason of the extremely
fragile nature of the porcelain protecting sheathing or casing employed, and of
the facility with which the metal sleeves which in some cases surround the porce-
lain casings are destroyed.
According to this invention and as illustrated in the accompanying drawings
(which represent longitudinal sectional views at right angles to each other and
corresponding cross sections) the sheath is made of a piece or pieces, of fire-resist-
ing material, such as earthenware, porcelain, or the like, preferably cylindrical
and provided with three holes passing longitudinally, through it one being com-
paratively large and the other two being smaller and serving for the reception
of the two wires of the thermo-element. At the end of the sheath opposite to
that at which the wires enter and where they are joined, the two small holes run
into one and there may be a recess which can be filled with protective cement to
protect the wires against the influence of the furnace gases. Through the larger
hole a rod S is passed the material of which rod should be as dense and hard as
possible, and should well resist high temperatures. The lower part of this rod
has a projection so also has the upper part these being screw-threaded. The lower
projection may lie within a recess of the protecting sheath as shewn and be
covered over with fire-resisting cement. The top projection passes through a
plate and carries a nut m which presses upon the said plate p either direct or,
preferably (to make provision for expansion and contraction) through the medium
of a spring F between the nut and plate. Thus the protective sheath is securely
held together in the longitudinal direction by the rod S, so that, even if cracks
should form in the material of the sheath, it cannot fall to pieces.
The rod S may consist of fire resisting material or of suitable metal such as
iron, nickel, or platinum; and it may also if preferred, be in the form of a tube
and be composed of more than one metal. Owing to its situation within the pro-
tective sheath it is protected from the action of the furnace gases. The pro-
tective sheath may be glazed externally, and may also, if desired, for convenience
of manufacture, be sub-divided into a number of component parts or sections.
Where this is the case the ends of the several sections should be provided with
projections and recesses such for example as are shewn in the drawings, so that
when they are joined together they cannot turn out of the proper angular position
relatively to each other. In employing such sub-divided sheaths the holes bored
for the reception of the wires may be enlarged at both ends of each section, so as

page_text: to make room, at each of these points, for an additional short sleeve or tube of
porcelain clay or the like, closely surrounding the wires, to protect them at the
joints as shewn at r as illustrated in the drawings and the rod or tube S may be
similarly protected from the direct action of the furnace gases by providing re-
cesses at each joint of the protective sheath, a small additional sheath or tube
closely enveloping the said rod or tube.
To ensure greater sensitiveness it may under certain circumstances be desirable
to connect several thermo-elements in succession (or in series). For such batteries
of thermo-elements this improved fitting is particularly well suited, as it is only
necessary to provide the earthenware, clay, or other protecting pieces described,
with a correspondingly increased number of perforations to receive more than two
element wires in each fitting. Figures 3 and 4 of the accompanying drawings
illustrate a form of fitting for two pairs of thermo-element wires.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I claim
19:―
1. A protecting sheathing or casing, for thermo elements consisting of fire
resisting material with a longitudinal hole therethrough traversed by a rod or
tube capable of resisting high temperatures; such rod or tube being connected
with the outer protecting sheath by means of screws or springs so that it securely
holds the sheath together and in the case of any cracks forming therein, prevent-
ing it from falling to pieces substantially as herein before described.
2. Thermo elements provided with a fire-resisting protective and subdivided
sheath having the ends of the parts or sections thereof formed with projections
and recesses whereby they are prevented from turning out of position angularly
when the parts are bound together by a rod or tube (such as S) the wires of the
element and the said rod or tube passing through longitudinal holes in the sheath
and having small protective sheaths, or tubes, such as r, at the joints between
the sheath sections all substantially as herein before described.
3. A protecting sheathing or casing, for thermo-elements, such as hereinbefore
described and claimed but provided with openings to receive two pairs or more
than two pairs of thermo element wires substantially as hereinbefore described
with reference to Figures 3 and 4 of the accompanying drawings.
Dated this 17th day of March 1800
JOHNSONS & WILLCOX.
47, Lincoln's Inn Fields, London, W.C., Agents.