An Electric Current Meter.
Year: 1889

page_text: Date of Application, 2nd Aug., 1889
Complete Specification Left, 30th Nov., 1889-Accepted, 11th Jan., 1890
PROVISIONAL SPECIFICATION.
An Electric Current Meter.
Sir CHARLES STEWART FORBES Baronet 23 Thurloe Square London S.W. do
hereby declare the nature of this invention to be as follows
A secondary cell is so arranged as to receive the whole or a part of the main
The inain, or a shunted
current passing, and stores a proportional part of the same.
part of the, main current passes round an electro magnet or equivalent and thereby
operates a switch contact so as to break the discharge circuit from the secondary
cell when the current is passing.
Upon its cessation the switch contact discharges the secondary cell through a
variable resistance and an electromagnet or polarized relay constructed so as to start
a clock, watch or any equivalent motor operating a suitably graded dial or other
similar device: The motor remaining in action until the secondary cell is discharged,
when the stored current can be read off upon the dial and is a measure of the
total current passed through the mains.
A
In the case of constant service mains two or more secondary cells are used.
float device or equivalent depending for its position of immersion upon the density
of the liquid contained in the cell or cells being employed to cut out the charged
cell; connect same to the relay, and couple up the discharged cell to the charging
circuit.
1 1000
FRANCIS M. ROGERS,
Agent for Applicant.
COMPLETE SPECIFICATION.
An Electric Current Meter.
Sir CHARLES STEWART FORBES Baronet 23 Thurloe Square, London S. W. 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 :-
A secondary cell is so arranged as to receive the whole or a part of the main
The main or a shunted
current passing and stores a proportional part of the same.
part of the main current passes round an electro magnet or equivalent, and thereby
operates a switch contact so as to break the discharge circuit from the secondary cell
when the current is passing.
Upon its cessation the switch contact discharges the secondary cell through a
variable resistance and an electro magnet or polarized relay constructed so as to
start a clock, watch or any equivalent motor operating a suitably graded dial or
other similar device. The motor remaining in action until the secondary coll is
discharged, when the stored current can be read off upon the dial and is a measure
of the total current passed through the mains.
more secondary cells are used, a
In the case of constant service mains two or
float device or equivalent depending for its position of immersion upon the density
of the liquid contained in the cell or cells being employed to cut out the charged
cell, connect same to the relay, and couple up the discharged cell to the charging
circuit.
To enable the construction and operation of my invention to be better understood
reference is made to the accompanying drawings in which :—
Fig. 1, is a front view of my improved Electric current meter, for intermittent

page_text: Fig. 2, is a side elevation of the same.
Fig. 3, is a front elevation shewing the arrangement of parts when a polarized
magnet replaces electro magnet 2.
Fig. 4, is a front elevation shewing the arrangement of parts when the electro
magnet 20, is replaced by a polarized magnet.
Fig. 5, is a front view of the current meter as constructed for constant service
mains, controlled by the hydroureters, the face of dial shewing upon the back of
case.
Fig. 6, is a side view, of the same.
Fig. 7, is a plan of switching magnet.
Fig. 8, is a front elevation to enlarged scale of pendulum tripping gear.
Fig. 9, is a side elevation of the same to enlarged scale.
1, Figs. 1, 2 is a terminal to which the + main circuit lead or wire is attached;
2, is an electromagnet surrounded by wire 3, of suitable size to carry the required
current, one end of wire 3, is connected to terminal 1, the other end after passing
round the bobbin of electromagnet 2, is connected to terminal 4. Directly under the
core 1, of electro magnet 2, is a soft iron armature 5, mounted upon a spring strip 6,
which is secured at one end to post 7, the other end of strip 6, being tipped with
platinum or equivalent unoxydizable substance for the purpose of engaging with the
adjustable contact screws 8, and 9, mounted upon posts 10, 11. A wire 3, connects
terminal 4, with the ingoing wire of resistance bobbin 12, the outgoing wire being
electrically connected to contact screw 8, by wire 3b. The post 7, is connected by
wire 3, with the positive plate 13, of secondary element 14, the negative plate 15,
being connected to terminal 16, by wire 3. The return circuit lead or wire is also
connected to terminal 16.
The contact screw 9, is connected by wire or strip 3 f, to sliding resistance contact 17,
engaging with the resistance coil 18, the open end of the wire 19, upon this coil being
connected by wire 3d to the end of ingoing wire upon electromagnet 20, the outgoing
end of this wire being carried down to terminal 16. Immediately above the core of electro
magnet 20, is a soft iron armature 22, mounted upon a thin metal strip 23, pivoted at 23ª.
A sliding balance weight 24, is fitted at one end of this strip, the other end being bent
up so as to engage with the pin 27, mounted upon the balance wheel 25, of clock, or
equivalent motor 26. To regulate the play of the pivoted strip an adjustable set
screw 28, is mounted as shewn.
The operation of this part of my invention which is more particularly applicable for
intermittent service is as follows:-
The main current entering by terminal 1, passes round the wire upon electro
magnet 2, which in this case is included in the main circuit. The iron core 1*, of
electro magnet 2, being energized thereby attracts armature 5, so causing it to make
contact with pin 8, and closing the shunt charging circuit, which includes the
resistance 12. The charging current flows from terminal 4, to resistance 12, and
contact screw 8, by strip 6, to post 7, and positive plate 13, of secondary battery 14,
returning from plate 15, to terminal 16, the secondary elements receiving a charge of
known proportion to the total current passing.
Upon the cessation of the main current the strip 6, drops upon screwed contact 9,
thereby cutting out battery 14, and resistance 12, from the charging circuit. The
stored current now passes from positive plate 13, to strip 6, by contact 9, sliding
contact 17, wire 19, upon variable resistance 18, round wire upon electro magnet 20,
returning by terminal 16, to plate 15. The core 21, of electromagnet 20, now attracts
the armature 22, thereby pulling away the end of strip 23, from the pin 27, on
balance wheel 25, of the clock 26, or equivalent motor and starting it.
Since the current passing into the cell is so regulated as to bear a fixed proportion
to that in the main circuit, and the current discharged from the secondary cell
can be regulated by the variable resistance 18, in such a manner as that a known
quantity shall flow through the electromagnet in a known time, it is evident that the
space of time elapsing during discharge as shewn by the hands of the clock can be so
interpreted as to shew the actual current passing in any desired units of current and

page_text: time.
If desired the clock dial may be replaced by a dial previously calibrated, so
that the pointer moving over its face shall shew ampère hours direct.
The electromagnets 2, 20 may be replaced by polarized magnets 2ª, 20. Fig. 3,
shews the arrangement of parts when the electro magnet 2, is replaced by polarized
magnet 2. This is a convenient arrangement when a shunted current is used to
operate the various parts controlled by the electromagnet 2, and for charging the
battery. Fig. 4, shews the position of the polarized magnet 20*. The current passing
round the bobbin causes the magnet core 21, to release the strip 23 so starting the
clock or equivalent motor. In fig. 3, the armature 5, is also released when the current
flows round the magnet 2ª.
The
For constant service mains 1 employ the device now described. See Figs. 5, 6.
1, is a terminal attached to the + main circuit lead, a shunt wire 3ª, passes from
terminal 1, to the ingoing wire upon resistance coil 12, the outgoing terminal thereof
being connected by wire 3b, with the base of the bracket S. Journaled in this bracket
is a cylindrical insulating block 29, having two cams 30, 31 formed upon it.
spindle 32, upon which the ebonite or other cylinder 29, turns is pivoted in a bracket Sa,
and in a metallic seating 8b, in the back of the instrument which is preferably formed
of slate or equivalent material, good electrical contact is formed between the spindle 32
and the tongue 33, which vibrates between the contact plates 34, 35. These contact
plates are metallically connected by separate wires 3, 301 with the positive
plates 13 13, of secondary batteries 14 14, which are set up preferably in glass jars.
The negative plate 15, 15, of each battery is connected by wire 3 with outgoing
terminal 16, which is attached to the return main lead. Each positive plate 13, 13",
is also connected by wires 35 with posts 71, 72, which carry spring contacts 61, 62,
electrically connected by plates 31, 32, wire 3, and variable resistance 18, with the
ingoing wire upon electromagnet 20, the outgoing wire of which 3, is joined to
terminal 16.
Mounted above electromagnet 20, is the armature 22, which in this case engages
with the point of pendulum 25, governing the clock or equivalent motor 26, by means
of a thin metal strip 23.
Secured to spindle 32, in front of cylinder 29, is an armature having two soft iron
plates 37, 38 superposed over the electro magnets, 39, 40, these magnets are connected
and operated as follows. In the liquid contained in secondary elements 14 145, are
two tubes of glass or equivalent 41 42, having perforations 43, so as to permit the
Within
free entrance and circulation of the electrolyte or liquid employed in the cells.
each of the tubes 41 42, is a hydrometer 44, the stem of which is formed into a
A local battery 47,
cup 45, for containing mercury or other conducting fluid 46.
is connected by a wire 48, having platinum ends 49, with each cup 15, the wire
being so arranged as to always dip beneath the surface of the conducting fluid or
medium 46. Two platinum wires 50 are arranged, so as to dip into the cups 45, but
are so secured as that only one at a time is in contact with the medium in each cup.
The platinum wires 50, aro repectively connected to the ingoing wires of the electro-
magnets 39, 40, the outgoing ends 51, being coupled together and united to the
other pole of local battery 47. It is well known that the specific gravity of the
electrolyte in a secondary cell varies considerably, but is greatest when the cell is
fully charged, I avail myself of this fact and by means of the hydrometers
immersed in the electrolyte control the apparatus just described in the following
manner:
The plates in cell 14, are fully charged, and the various parts of the instrument
are shewn in the drawing in their respective positions for charging the plates in
cell 14, and discharging those in 14". The shunt current entering by terminal 1;
passes through resistance coil 12, to bracket 8*, and through spindle 32; to tongue 33,
this being in contact with plate 35, the charging current passes to the positive plate 13,
of secondary battery 14, returning from the negative plate 15, to terminal 16. Tho
charging current is prevented from entering the discharging circuit by the action
of the insulated cam 30, which holds the spring 6', away from the contact plate 31*.

page_text: This together with contact plate 32, is connected to electromagnet 20. The
current from the charged elements in battery 145, passes to spring 6 plate 32b, and
through variable resistance 18 to electromagnet 20, which energized by the current
sets free the pendulum by drawing down the armature 22. The current after passing
round the coils of magnet 20 returns to terminal 16.
As the discharge from the cell 14ª, proceeds the sulphuric acid or its equivalent
decreases in density, and the hydrometer 44, sinks, thereby breaking battery circuit 47,
releasing armature 22, and stopping the clock.
By the action of the charging current the density of the electrolyte in cell 14,
attains its maximum, causing the hydrometer 44, to rise sufficiently to complete or
close the battery or shunt circuit 47, through electromagnet 39, energizing it
sufficiently to draw down the iron armature 37, and thereby breaking the charging
circuit to cell 14, and charging cell 14ª, through contact 34, and wire 3º1.
The charged cell 14, now discharges through spring 61, contact plate 31ª resistance 18,
and electro magnet 20, to terminal 16, thereby starting the clock in the manner before
described.
Although I have shewn a pendulum device, I do not confine myself to this specifically,
for this class of instrument, as the balance wheel arrangement described under figs. 1, 2,
will have the same effect.
The electromagnets may also be replaced by polarized magnets if desired, the
respective parts operated thereby being adjusted to suit such a modification.
A derived or shunt circuit taken from the main terminals may replace the
battery 47, if more convenient.
For the purposes of description I have shewn the secondary elements as forming
part of the two forms of instruments described; It is not essential to the proper
performance of the said instruments that they be placed as shewn in close contiguity;
These elements may be placed at a distance in any convenient position and be
connected by wires thereto. I find it desirable to discharge the secondary cells as
rapidly as possible.
I do not bind myself to the exact detail in arrangement of the respective parts, nor
the connections therefor, as shewn, as these may be varied to suit circumstances
without departing from the spirit of my invention.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed 1 declare that what I
claim is :-
1st. The particular combination of parts for measuring the electric current passing
in the main by the storage of a known part of said main current, and automatic
discharge of the same through the devices operating with and controlling the motor
employed for shewing current time as described.
2nd. In an electric current meter the combination of one or more secondary
batteries charged by a known proportion of the main current passing; with the
switch device regulating the charge and discharge, operated by the whole or a part of
the current passing as described.
3rd. In an electric current meter the combination of a storage cell or cells with a
switch device actuated by a polarized or electro magnet, round the coils of which the
whole or part of the current to be measured passes, for the purpose of charging or
discharging the stored current through a variable resistance, and electro magnet or
polarized magnet operating the releasing mechanism of a clock or equivalent time
motor calibrated or not so as to shew current time as set forth.
4th. The combination in or with an electric current meter of two or more hydro-
meters floating in the electrolytic fluid of the secondary cells, for the purpose of opening
and closing a battery or derived circuit operating devices for regulating the charge to
and discharge from said cells, and the releasing mechanism of current time motor as
herein described.
5th. The combination with an electric current meter of controlling devices depending

page_text: for their operation upon the varying specific gravity of the electrolyte contained in
the secondary batteries charged by a part of the measured current passing in the
mains in the way and manner herein set forth.
6th. The combination in or with an electric current ineter of secondary batteries
each having an inner perforated tube within which the hydrometer controlling the
charging and discharging circuits and releasing mechanism floats for the purposes set
forth.
7th. The combination in or with an electric current meter for intermittent or
continuous service of a suitable resistance for proportioning the current supplied to
the secondary cell or cells to that passing in the mains, and a variable resistance for
regulating the rate of discharge from said cell or cells as set forth.
Sth. The combination in or with an electric current meter of the balance wheel;
pendulum or equivalent device, operated by tripping gear in the way and mannor sot
forth.
FRANCIS M. ROGERS,
Agent.