IMPROVEMENTS ELECTRICAL RESISTANCES
Year: 1881

page_text: LETTERS PATENT to Gustav Pfannkuche and Robert Edward Dunston, both
of 25, Charlotte Street, Fitzroy Square, in the County of Middlesex, for an
PROVISIONAL SPECIFICATION left by the said Gustav Pfannkuche and
Robert Edward Dunston at the Office of the Commissioners of Patents on the
31st December 1881.
GUSTAV PFANNKUCHE and ROBERT EDWARD DUNSTON, both of 25 Charlotte
Street, Fitzroy Square in the County of Middlesex. " IMPROVEMENTS
ELECTRICAL RESISTANCES."
IN
This Invention relates to certain improvements in the construction of electrical
resistances.
Such resistances serve as means for regulating electrical currents, or for being
substituted in the place of actual work done by the currents or for absorbing part
of this work, as for instance in turning out an electric lamp and letting the
current by means of automatic switches or otherwise pass through the resistances
instead of through the lamp, or letting the current go through the lamp and
through a part of the resistance, thus altering the intensity of the lamp.
On account of the heat developed in the resistance coils or boxes as at present
existing these arrangements are exceedingly bulky, unhandy and expensive, and it
is obvious that it is possible to use wires or other materials of very high resistance
and at the same time make provision for uniformly distributing and carrying away
the heat developed in these wires or other materials a very efficient and handy and
cheap resistance apparatus can be produced.
To effect this we propose to use wires or other suitable materials of high
resistance and of a size proportional to the required amount of resistance and to
embed or envelop the same in a mass of a bad conductor of electricity such as.
glass or plaster of Paris or asbestos or any other non conducting mass, shaping the
same in such a manner as to get as large as possible a cooling surface and to
rapidly take up the heat developed in the resistance wires or other material and
thus preventing the resistance material from being destroyed or fused when a
strong current is made to pass through it. It will be seen that in this manner
comparatively very small wires or other materials can be used as resistances for
large currents thereby materially reducing the size and expense of such resistance
apparatus.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Gustav Pfannkuche and Robert Edward Dunston in the Great Seal
Patent Office on the 30th June 1882.
GUSTAV PFANNKUCHE and ROBERT EDWARD DUNSTON both of 25 Charlotte
Street Fitzroy Square in the County of Middlesex. "IMPROVEMENTS IN
ELECTRICAL RESISTANCES."
This Invention relates to certain improvements in the construction of electrical
resistances.
On account of the heat developed in the resistance coils or boxes as at present
existing these arrangements are rendered exceedingly bulky unhandy and
expensive. It is obvious that if it be possible to make use of wires or other
conducting mediumns of high resistance, and at the same time to make provision for
the uniform distribution and dispersion of the heat developed therein, that an
efficient, bandy and inexpensive resistance apparatus will be the result. To effect
this object we propose to use wires or other suitable forms of conducting material
of a size proportional to the required amount of resistance and to embed or
envelope the same in the mass of a non conductor of electricity such as glass
plaster of Paris or other solid nonconducting substance or substances, arranging
and shaping the same in such a manner as to most rapidly take up the heat
developed in the conducting medium and to radiate the same from its increased
surface thus preventing the destruction or displacement of the conducting-medium-
by fusion or other cause to which it would otherwise have been liable. It will be
Been that by this arrangement comparatively small wires or other conducting
mediums can be used as resistance for large currents of electricity thereby
effecting a material reduction in the size, weight of metal and cost of such
resistance apparatus.
The objects and applications of these improved resistances are various and
may be classed under three heads, lighting, heating and regulation of electric
currents.
If it be desired to regulate the light given off by an incandescent lamp or group
of lamps of the usual construction, we insert our improved electrical resistance in
the circuit of that lamp or group of lamps.
The instrument may be of an ornamental form. Figure 1 is a sectional
elevation and Figure 2 a plan of a pendant resistance in which a is a hollow
cylinder of glass in which is embedded the spiral b of fine platinum wire one
end of which c is attached to the terminal d whilst the other end and. also a
number of graduated points in the spiral e. c. e. are in communication with the
cavity which is rendered annular by the insertion of a glass rod to reduce the
capacity..
Into the annular cavity a column of mercury can be caused to rise and can be
maintained at any height required by means of the bag g and plunger h, the
mercury being also in connection with the ingoing terminal i. The action is as
follows. When the mercury is lowered quite into the bag the circuit is broken,
when the piston is screwed up until the mercury makes contact with the lowest
point of the spiral connection is made but the whole resistance of the spiral is
thrown into the circuit of the lamp or lamps of which it forms a part; by screwing
the plunger until the mercury is at the top of the tube all resistance is thrown
out and the lamp or lamps burn at full power at intermediate points a portion of
the resistance is in circuit the light is thus regulated or extinguished at will as
easily as in the case of a gas jet. Figures 3 and 4 are an elevation and section of
a similar device arranged as a wall ornament. Here a zig zag platinum wire is
embedded in a flat slab of glass a which is substituted for the hollow cylinder and
the column of mercury is exchanged for a sliding contact b moving over stops c. c.
actuated by means of the screwed spindle e..

page_text: Figure 5 represents an urn fitted with a heater constructed on this principle in
which a. b. are the ingoing and the outgoing terminals situated on the wooden
base. c. d. and e. shown by dotted lines are the coils of wire embedded in plaster of
Paris or composition and covered by the metal casing g.
A very similar device is eminently adapted to the heating of railway carriages
steam ships houses &c.
In the case of railway carriages the resistance blocks may take the form of a
footstool running the breadth of the carriage, the blocks being coupled up in series
or in parallel circuit, as may be most desirable. The dynamo machine supplying
the current may be placed in any convenient carriage and worked off an axle thus
rendering the apparatus complete in itself without any connections to the
locomotive from which it derives its action. It is to be noted that this
arrangement acting as it does like a hot brick will not be unduly affected by
stoppages of ordinary duration and further that in consequence of this peculiarity
the dynamo-machine may be thrown out of gear on ascending heavy banks thus
economising the engine power when most needed.
When used for the purpose of regulating electric currents this form of resistance
may be used in conjunction with a system of solenoids which forms the subject of
our Patent No. 3655 of August 2nd 1881. In this case by the use of this form of
resistance we obtain compactness coupled with immunity from fire or other accident
in a greater degree than in the forms of resistance now in use. Figures 6 and 7
are an elevation and plan of a resistance box containing a resistance of seven
ohms and is capable of carrying with safety any current of electricity which in
ordinary practice could be sent through it.
Its construction is as follows:-a. a. a. are slabs of slate round which are wound
the resistance wires the ends of which are made fast to the broad strips of copper b
in connection with the terminals of the box. These slabs of slate a are placed in
a rectangular box c of thin sheet iron which is then cast full of a suitable
composition; this iron box is in its turn surrounded by a perforated iron casing e,
from the sides and bottom of which it is kept equidistant by means of distant
pieces d, thus allowing a free current of air to circulate round the heated inner box
carrying off the heat as soon as generated, at the same time preventing any
possibility of fire owing to the contact of inflammable substances with the inner
box. It will be seen from this example that with a given current of electricity
the heat generated will be that due to the resistance of the fine wire, whilst the
radiating surface has been increased from that of the wire to that of the box. The
radiating surface may be still further increased by a different arrangement of the
resistances in the insulating block. The connections to terminals are of such a
sectional area as to preclude the possibility of undue beating whilst the junctions
with the fine wire are embedded in the composition. It follows that even
should the fine wire become fused there can be no danger or interruption of the
circuit.
What we claim is our improved electrical resistances in which the conductor is
embedded in glass, plaster of Paris or other solid insulating material which aids
in defusing the heat resulting from the passage of the current substantially as
described.
In witness whereof I the said Robert Edward Dunston have hereunto set
my hand and seal this Eighth day of June in the year of our Lord One
thousand eight hundred and eighty trea
R. E. DUNSTON. (L.S.)