Improvements 19 Fectric Resistances
Year: 1899

page_text: I, FRIEDRICH WILHELM SCHINDLER, of Kennelbach, near Bregenz, Austria,
Manufacturer, do hereby declare the nature of this invention to be as follows:
In this invention the resistances are embedded in a difficultly melting isolating
body such as fire brick material and around this mass except at the places where
the resistances protrude is cast a metal housing which with said resistances and
the isolating body forms a solid part. In this way the resistances are very securely
protected from injury both internally and from the outside. The resistances are
so connected to contacts at an accessible place that they can be readily manipu-
lated and disconnected from the contacts and when necessary exchanged thus
avoiding the disadvantage of having to throw away with the resistances the
part carrying the contacts and contact lever, as also these parts, when they are
irremovably connected with the resistances. The metal housing enclosing the
isolating body may be either in fixed or removable connection with the disc or
bearer on which the contacts and contact lever are carried. In the former case
however the isolating body must be removable from the metal housing instead of
as in the latter case being enclosed in a single metal casting to form a fixed
whole. The contacts, screws for instance, and the contact lever are insulated and
the points of contact between the metal housing and disc or bearer reduced to a
minimum, and there being no other points of contact between these parts the
transmission of heat from the housing to the bearer or disc is prevented.
Dated this 17th day of January 1899.
THOMAS R. SHILLITO,
15, Took's Court, London, E.C., Agent for the Applicant.
Improvements 19 Fectric Resistances,
I, FRIEDRICH WILHELM SCHINDLER, of Kennelbach, near Bregenz, Austria,
Manufacturer, 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:-
Hitherto, in order to give regulable electric resistances a convenient form they,
together with all the organs appertaining to to them, have been fixed on a metal
plate. The insulation of the resistances from one another and from the metal plate
has been accomplished by embedding the resistances in a layer of enamel provided
on the metal plate. Such regulable resistances have the great disadvantage that

page_text: the enamel may easily be rent by the action of the heat developed when the
apparatus is set in operation whereby the resistance wires are exposed to the
oxidising action of the air and gradually rusted through. A single faulty place
however suffices to render the regulable resistance unserviceable and this in view
of its great cost renders its profitable employment doubtful.
The object of the invention is to remedy the above disadvantage and this is
attained by very securely protecting the resistances against internal and external
injury and which when desired can be removed and exchanged without having,
each time, to throw away therewith, the part carrying the contact pieces and
the contact lever, together with this latter. As is known an approved protection
of the resistances is afforded by embedding them in a difficulty melting isolating
body, as for instance, the material of which fire bricks are made, and enclosing
the whole in a metal housing. In order to be able to exchange the resistances
these must, immediately adjacent to the place where they protrude from the
metal housing, be so connected, at an accessible point with the contacts that the
connection may be easily and quickly severed whilst the connection of the metal
housing with the bearer on which the contacts and the contact lever are carried
may be releasable or not. In the former case the isolating body holding the
resistances and the metal housing may form a solid whole; in the latter case said
isolating body with the resistances must be removable from the metal housing.
In the accompanying drawing Fig. 1 is a sectional and Fig. 2 a plan view of a
form of apparatus, shewn by way of example, for carrying out the invention.
a is a metal disc on which are carried the contact screws b, contact lever c, and
hand wheel to which said contact lever is fixed. e are the resistances releasably
attached to the contact screws and embedded in a mass of fire brick or the like
material around which is cast a housing g of any suitable metal, preferably
cast iron, in such a way that apertures are left in the same where the resistances
protrude. The solid whole thus formed has attached to it by screws the
disc a so as to be removable. In order to minimize the transmission of heat
from the metal housing g to the disc a and to the organs attached thereto the
contact points are only at the connecting places and these latter are limited as
much as possible without affecting the solidity of the apparatus. To this end the
disc a
is provided with lugs and the metal housing with a similar number
of bosses which, with intermediate washers or dises 7 of a material that is a non
conductor of heat are fixed together by screws h.
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. A regulable electric resistance with a special bearer or carriage upon which
the contacts and the contact lever are carried, characterised in that the resistances
embedded in an isolating body are enclosed in a metal housing and removable
and exchangeable with or without said metal housing, substantially as described
and shewn.
2. The construction referred to in Claim 1 where the isolated resistances are
removable and exchangeable with the metal housing enclosing them, characterised
in that the metal housing enclosing the resistances forms a ring over the opening
of which is mounted the bearer or carriage which carries the contacts and the
contact lever, substantially as described and shewn.
Dated thin 10th do of Onta1 1900
THOMAS R. SHILLITO,
15, Took's Court, London, E.C., Agent for the Applicant.