Controlling Devices Operated by Means of the Thermic Effects of Electric Currents.
Year: 1888

page_text: Controlling Devices Operated by Means of the Thermic Effects of
Electric Currents.
BERNARD MERVYN DRAKE JOHN MARSHALL GORHAM both of 2 Princes Mansions,
Victoria Street, Westminster, Electrical Engineers, EDWARD MANVILLE WILLIAM
LEONARD MADGEN both of 36 Albert Embankment London S.E. Electrical
Engineers do hereby declare the nature of this invention to be as follows:-
The object of our invention is to provide automatic controls & alarms to operate
in case of a current in an electric circuit exceeding or varying from a given
rate.
For this purpose we cause the whole, or part of the current, to pass through a
composite strip made of two or more different metals having unequal rates of
expansion under the influence of heat. As the current passing through the strips.
increases, the heat engendered, which causes the strips to bend also increases. The
movement thus obtained is utilized by suitable means to complete the circuit of an
electric bell or other electrical alarm or it may be communicated to a switch, cutout,
or other form of control suitably arranged to work.

page_text: Controlling Devices Operated by Means of the Thermic Effects of
Electric Currents.
BERNARD MERVYN DRAKE JOHN MARSHALL GORHAM both of 2 Princes Mansions,
Victoria Street, Westminster Electrical Engineers, EDWARD MANVILLE. WILLIAM
LEONARD MADGEN both of 36 Albert Embankment, London S.E., Electrical
Engineers 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 :-
The object of our invention is to provide automatic controls & alarms to operate
in case of a current in an electric circuit exceeding or varying from a given rate.
For this purpose we cause the whole, or part of the current to pass through a com-
posite strip made of two or more different metals having unequal rates of expansion
under the influence of heat. As the current passing through the strips increases,
the heat engendered, which causes the strips to bend also increases. The movement
thus obtained is utilized by suitable means to complete the circuit of an electric bell
or other electrical alarm or it may be communicated to a switch, cutout, or other
form of control suitably arranged to work.
The better to explain the meaning of our invention reference is made to the Drawings
annexed.
In these Fig. 1 represents a plan and Fig. 2 a side elevation of our apparatus con-
structed according to our invention in which a strip of composite metal A is partially
divided so that the electric current entering at B must pass completely along the strip
to emerge at C.
The heat produced by the passage of the current causes the strip to bend as
indicated by the dotted lines in Fig. 2 and as the current reaches, or exceeds, a pre-
arranged limit the end of the strip makes contact with the adjustable contact point D.
The contact point D and the strip A are normally the terminations of an electric
circuit which comprises a source of electricity and an electric bell, cut-out, or other
form of control so that when the contact is made as described the current passes
through the alarm or controlling apparatus which thereupon performs its proper
functions. Fig. 3 shows diagrammatically the manner in which we apply our inven-
tion for the purpose of checking an excessive charge being given to, or an excessive
discharge being taken from a battery of accumulators.
The current in either of these cases passes through the strip A so that as
the current reaches or exceeds the permissable limit arranged by the adjustment of
the contact point D, the circuit comprising the electric bell and one of the cells of the
battery is completed and the bell gives the alarm. Fig. 4 shows diagrammatically
our invention being used for the purpose of preventing an excess of current upon a
circuit. When contact takes place between the strip A and the contact point Da
current passes through a suitable form of cut-out and breaks the main circuit of the
dvnamo.

page_text: It is clear that there are other useful methods of connection with different forms
of electric alarms and controls.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is :-
1. The use for the purpose specified of a composite strip as above described
having a division at or near its centre so as to partially divide it longitudinally.
2. The use of a composite metal strip through which an electric current is passed
to actuate alarm or controlling devices in an electric circuit.
Dated this 9th day of November lððð.
BERNARD MERVYN DRAKE.
JOHN MARSHALL GORHAM.
EDWARD MANVILLE.
WILLIAM LEONARD MADGEN.