Improvements in or connected with Electric Meters.
Year: 1898

page_text: Reprinted as amended in accordance with the decision of the Comptroller-General,
dated the 6th day of March, 1900.
[The Amendments are shown in erased and italic type.]
Date of Application, 17th Aug., 1898
Complete Specification Left, 13th June, 1899-Accepted, 17th Aug., 1899
TROYINTURAL
Improvements in or connected with Electric Meters.
We, HENRY REASON, of 112, Glo'ster Road, Brighton, in the County of Sussex,
Electrical Engineer, and the Mutual Electric Trust, Limited, of 111,
Glo'ster Road, Brighton, in the County of Sussex, do hereby declare the nature of
this invention to be as follows:-
This invention relates to electric current meters of the so-called motor type
and by its means several advantages are obtained.
A known method of operating such meters is to employ a shunt winding for
magnetising purposes and a series winding for carrying the current to be measured
both windings acting on a single core circuit so to speak, that core circuit being
a closed or practically closed magnetic one, that is to say the core circuit is a
completely magnetic one except at the clearance space which exists between the
so-called pole pieces or in other words the space in which the armature or movable
part of the motor lies.
Now it has been discovered by one of us, namely by Henry Reason, that a great
advantage may be secured by the employment of an open core circuit, that is to
say a core circuit which is not only broken at the clearance space before men.
tioned but which is open or broken through some other part of the said circuit
than the mere narrow clearance space. This constitutes one of the features of our
present invention.
In our present invention we may so arrange or adapt the parts that the position
of the shunt winding upon the core circuit can be altered at will for the purpose of
altering the initial magnetism which it is necessary to employ in order to over-
come the so-called static friction of the meter. This may be effected by sliding
the shunt winding upon the core circuit towards or from the clearance space.
Or the same result may be attained by movably attaching a piece of iron or other
magnetic material so that it may offer a magnetic path to the lines of force which
would otherwise traverse the air. By making the position of this adjustable as for
example by an adjusting screw the magnetic resistance may be varied at will.
We may also, when the movable part of the motor consists say of a disc retarded
by vanes or the like in a mercury bath or its equivalent, construct such disc and such
bath of what at present would be considered abnormally large diameter. Thus we
contemplate making such a bath with a diameter equal to sixteen or even twenty
times its depth and using a disc of commensurate diameter, say of four or more
inches.
Another of our improvements consists in making the armature disc of the form of
an obtuse cone, the apex of which is placed so as to point upwards. We may
perforate the said armature disc at or near its apex for the purpose of allowing any
bubbles of air which may collect below the armature disc to escape.

page_text: For the purpose of facilitating rapid demagnetization we may make our field
magnets short and thick and when desired we may enlarge the ends. We may also
when desired divide the winding or windings so as to put one part thereof on each
side of the armature or clearance space.
Improvements in or connected with Electric Meters.
We, HENRY REASON, of 112, Glo'ster Road, Brighton, in the County of Sussex,
Electrical Engineer, and THE MUTUAL ELECTRIC TRUST, LIMITED, of 111, Glo'ster
Road, Brighton, in the County of Sussex, 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:-
This invention. relates to improvements in electric current ineters of the so-called
motor type, the said improvements being hereinafter specified in detail and illustrated
by the accompanying drawings, of which
Figure I is a diagram illustrating a well known form of core circuit.
Figure II is a diagram illustrating what we term a double break core circuit.
Figure III is a diagram illustrating a double break core circuit adjustable in
length.
Figure IV illustrates in vertical section an actual meter constructed under our
invention.
Figure V is a plan view of the disc or armature employed.
Figure VI is a section illustrating our short and thick field magnet with enlarged
end pieces but differing from Figure IV in that instead of embodying the form of
armature disc and bath of our present invention it embodies another form of
armature disc and bath.
A known method of operating such meters is to employ a shunt winding for
magnetizing purposes and a series winding for carrying the current to be measured,
both windings acting on a single core circuit so to speak, that core circuit being
'a closed (or practically closed) magnetic one, that is to say the core circuit is
a completely magnetic one (that is consisting of magnetic material) except at the
clearance space which exists between the so-called pole pieces or in other words the
space in which the armature or movable part of the motor lies.
Such a core circuit is diagrammatically represented in Figure I, in which 1 repre-
sents a core circuit of iron broken at the clearance space 2.
3 is the shunt winding
used for magnetizing purposes and 4 the series winding for carrying the current
to be measured.
Now it has been discovered by one of us, namely by Henry Reason, that a great
advantage may be secured by the employment of what we terin a double break core
circuit, (termed in our Provisional Specification an open core circuit) that is to say
a core circuit which is not only broken at the clearance space before mentioned
but which is open or broken at some other part of the said circuit than the mere
narrow clearance space. This constitutes one of the improvements embodied in the
present invention.
Such a core circuit is diagrammatically represented in Figure II where it will
be seen that the core circuit is not only open or broken at the clearance space. 2 but
also at another part 5.

page_text: By the adoption of a core circuit of this type the following beneficial results are
obtained. Residual magnetism is reduced, and over registration at low readings,
commonly noticed when meters with a closed magnetic core circuit are subjected
to the action of excessive currents, is avoided.
Another improvement embraced by the present invention consists in making the
core circuit adjustable in length so as to vary the amount of the open space 5. This
is diagrammatically illustrated in Figure III where it will be seen that the part 6
of the core, instead of being integral with the part 8 of the core, is adjustably
attached thereto as for example by passing through an orifice in the horizontal
part 7. Here it will be seen that as the vertical part 6 is raised or lowered the
space 5 is increased or diminished.
Figure IV illustrates in vertical central section an actual meter with a double
break core circuit as herein before described. In the said figure 1 is the iron core
circuit consisting of two circular iron cylinders 9, 10, between which is the clear-
ance or armature space 2. The cylinders 9, 10, are kept apart by two hard rubber
rings 11, 12 fitting closely to the edges of the cylinders 9, 10, and between the said
rings is a metallic T shaped ring 13, the purpose of which will be hereinafter
described. The remainder of the core circuit is made up of the two iron plates 14, 15,
(which in this case are square when seen in plan), and the adjustable iron bolt 16,
the said bolt corresponding with the part 6 shown in Figure III. 3 is the shunt
winding and 4 the series winding shown in this case as superposed but they may be
otherwise arranged as is well known in the art. Within the clearance space 2 is
placed the armature disc 17 dished to the form of a cone, hereinafter to be described,
carried by a spindle 18 which rests on a pivot 19 and which may be provided with
a worm 20 gearing with the counting mechanism. The clearance space 2 has an
abnormally large diameter equal say to sixteen times its depth and is filled with
mercury so as to constitute a bath in which the armature dise 17 is immersed.
The current to be measured passes from the ring 13 into the mercury and causes
the armature disc to rotate in the well known manner. The mercury bath and the
dise (shown also in plan in Figure V), are made in the form of an obtuse cone as
shown and with the apex projecting upwards and holes 21 are made in the said disc
so that any air bubbles which may collect in the bath and which would otherwise
give rise to erroneous readings may rise to the apex and escape through the said
holes.
For the purpose of facilitating rapid demagnetisation we make the field magnets
very short and thick and we may enlarge the ends thereof as is shown in Figure IV.
Here it will be seen that the cylinders 9, 10, together with the plates 14, 15,
constitute a very short and thick field magnet and that the plates 14, 15, constitute
enlarged ends. We look upon this short thick field magnet as of very great
importance and it constitutes one of the main improvements embraced by the
present invention.
In Figure VI we show an instrument similar to that shown in Figure IV but
differing therefrom in that we employ our short and thick field magnet with enlarged
ends not in conjunction with a conical bath and armature as shown in Figure IV
but in conjunction with a flat armature and bath as specified in the Complete
Specification filed in pursuance of our Application No. 17,026 of 1898.
When desired we may divide the winding or windings so as to put one part
thereof on each side of the arinature or clearance space. Thus for example we might
wind part of the main coil upon cylinder 9 and part of it upon cylinder 10, or, we
might treat the shunt coil in the same way, or, we might divide both coils putting
part of each on cylinder 9 and part of each on cylinder 10 in which last case the
two coils would be concentric.
We desire it to be understood that our double break core circuit, our method of
adjusting the length of the core circuit, our abnormally short and thick field magnet
and our enlarged field magnet end plates are not limited in their applicability to
motor meters of the mercury bath type. They are applicable to other motor meters
than those in which such baths are employed.
'

page_text: 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. In an electric meter of the so-called motor type, a double break core circuit
substantially as set forth.
2. In an electric meter of the so-called motor type, the method of and means for
adjusting the length of the core circuit substantially as set forth.
3. In an electric meter of the so called motor type, a conical bath-substantially
as set forth.
4. In an electric meter of the so-called-motor type, a conical armature substan-
tially as and for the purpose-set forth.
3. In an electric meter of the so-called motor type, a conical armature with
orifices for the escape of air bubbles substantially as set forth.
64. In an electric meter of the so-called motor type, an abnormally short and
thick field inagnet substantially as set forth.
7. 5. In an electric meter of the so-called motor type, a field, magnet with enlarged
ends substantially as set forth.
6. In an electric meter of the so-called motor type, the arrangement and
combination of parts substantially as set forth with reference to Figure IV.
BALCA
For the Applicants,
J. G. LORRAIN, M.1.E.E., &c.,
Norfolk House, Norfolk Street, London, W.C., Chartered Patent Agent.