Improvements in Apparatus for Measuring the Strength of Electric Currents.
Year: 1890

page_text: COMPLETE SPECIFICATION.
Improvements in Apparatus for Measuring the Strength of Electric
Currents.
I, STANLEY CHARLES CUTHBERT CURRIE, a subject of the Queen of Great Britain,
but now residing at Room 850 Dresell Building, 5th & Chestnut Streets, in the City
of Philadelphia, in the County of Philadelphia, and State of Pennsylvania, United
States of America, Electrical Engineer, do hereby declare the nature of my invention
for. IMPROVEMENTS IN APPARATUS FOR MEASURING THE STRENGTH OF ELECTRIC
CURRENTS, and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statements :-
In my invention relating in general to apparatus for measuring the strength of
electric currents use is made of finely divided iron filings and an insulating adhesive
material, whereby the apparatus or instrument is adapted to alternating as well as
direct currents.
The principal object of my invention is to provide a simple, durable and efficient
instrument for measuring the strength of electric currents.
My invention consists of an electric current indicator having the magnetizable parts
thereof composed of iron filings, chips or shavings mixed or combined with an
insulating adhesive substance or material.
The nature and characteristic features of the invention will be more fully under-
stood from the following description taken in connection with the accompanying
drawings forming part hereof; and in which
Figure 1 is a front elevation of an instrument embodying my invention and showing
a movable armature surrounded by one or more coils of wire.
Figure 2 is a transverse section on the line x, x, of Fig. 1 showing the detail
arrangement of the parts of the instrument
Figure 3 is a front elevation of an instrument embodying a modified form of my
invention and having the parts thereof arranged to form an electro-magnet; and
Figure 4 is a transverso central section of Fig. 3, showing the detail arrangement
of the parts of the instrument.
In the drawings a, is a base plate or panel for supporting the parts of the instrument.
a² is a cover or housing for protecting the internal parts of the device. a², is an
aperture formed in the front of the housing a¹, for observing a movable pointer. c is
a continuous coil secured to the panel a, and divided into two parts in order to permit
of the insertion and adjustment of an armature f. This armature f, consists of a bar
composed preferably of a compressed mixture of iron filings, chips or shavings and
an insulating adhesive substance or material as silicate of soda or analogous substance
or material and attached to a spindle f¹. g and g', are bearings or sockets supported
respectively by the panel and bracket g and adapted for the reception of the
spindle The pointer or index finger P, and one extremity of the spiral spring S,
are secured to the spindle f¹. The other extremity of the spiral spring S, is secured
to the bracket g³.
It may be remarked that the spring S, is adjusted so as to cause the armature f, to
occupy a position slightly at an angle to the plane of the winding of the coil C, when
no current is passing through the latter, so that when the current is permitted to pass
through the coil c, the armature f, and pointer or index finger P, will tend to turn in
the direction indicated by the arrow in Fig. 1. Moreover, the spring S, acts to
counterpoise the force of the magnetic attraction tending to deflect the arinature f.
Of course a weight S¹, may be used instead of a spring and such construction is shown
n Fig. 3. are binding posts secured to the panel a, and in communication with the
ends of the coil c, by means of the conductors . i, is a graduated dial secured to
he panel a, and located adjacent to the pointer or index finger P, and so as to be
observed through the aperture a².

page_text: The construction of the instrument illustrated in Figs. 3 and 4, is the same as above
described with reference to Figs. 1 and 2, with the following exceptions, that the coil c,
is wound around the cores m and m³, so as to form an electro-magnet, and the
armature f, is located between said cores m and m¹, and adapted to turn in the
direction indicated by the arrow in Fig. 3, when the electro-magnet is energized.
Excellent results have been obtained in practice by making the cores m and m², as
well as the armature f, out of a compressed mixture of finely divided iron and silicate
of soda and hence preference is given to these materials for their formation.
The mode of operation of my invention is as follows:-The instrument is included
either in a circuit or in a branch thereof by means of the binding posts, and the
The
current whose strength is to be ascertained is permitted to traverse the coil c.
coils (Figs. 1 and 2,) or the cores m and m (Figs. 3 and 4,) become energized,
thereby attracting the armature f, which tends to cause it and the pointer or index
finger P, to turn in the direction indicated by the arrows in the drawings. The
deflection of the pointer or index finger P, with reference to the dial i, may be readily
observed and the strength of the current ascertained for each position of the pointer
by experiment or the dial may be experimentally graduated by passing currents of
known strength through the coil c, or in any other preferred manner, so that the
strength of the current may be read from the dial in the usual manner.
It is obvious that portions of the invention may be used separately and that
modifications may be made as to details without departing from the spirit thereof.
Having now particularly described and ascertained the nature of my inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. The combination, in an apparatus for measuring the strength of electric currents,
of a circuit, one or more coils of wire interposed in said circuit, a pointer and index,
an armature composed of a mixture of iron filings, chips or shavings and an adhesive
insulating material and the said armature attached to said pointer, substantially as and
for the purposes set forth.
2. The combination, in an apparatus for measuring the strength of electric currents,
of a circuit, an electro-magnet interposed in said circuit, a pointer and index, an
armature attached to said pointer and the armature and cores of said magnet composed
of finely divided iron and an insulating substance, substantially as and for the purposes
set forth.
3. An electric current indicator having the magnetizable parts thereof composed
of iron filings, chips or shavings and an insulating adhesive substance or material,
substantially as and for the purposes set forth.
4. The combination, in an apparatus for measuring the strength of electric
currents, of a divided coil magnet or magnets and an armature formed of com-
pressed metallic chips or shavings and an insulating adhesive substance, substantially
as set forth.
5. The combination, in an apparatus for measuring the strength of electric currents,
of a circuit, a divided coil or electro-magnet included in said circuit, a pointer, an
index and an armature formed of compressed metallic chips or shavings and silicate
of soda or similar material, substantially as set forth.
6. The combination, in an apparatus for measuring the strength of electric currents,
of a panel, a housing provided with an aperture, a circuit, an electro-magnet interposed
in said circuit, a pointer and index, an armature attached to said pointer and the
armature and cores of the electro-magnet formed of compressed metal chips or
shavings and silicate of soda or similar materials, substantially as set forth.
Labod
W. P. THOMPSON & BOULT,
Agents for the Applicant