improvements in Electricity Meters.
Year: 1899

page_text: PROVISIONAL SPECIFICATION.
improvements in Electricity Meters.
I, GEORGE HOOKHAM, of 7 & 8, New Bartholomew Street, Birmingham,
Manufacturer, do hereby declare the nature of this invention to be as follows:-
My improvements apply principally to that class of meters in which the
deviations from normal time produced in a pendulum affected by the electric
current (or energy) to be metered are registered. The rate of such a pendulum
is generally compared with that of an unaffected pendulum & it is essential to
accurate registration that when no current is passing the two pendulums should
synchronize.
This condition has been found very difficult to realize the principal object
of the present invention is to secure such synchronism.
According to one method of carrying out my invention I arrange two
pendulums A & B. A being a free pendulum & B controlled by the current. A & B
are hung on knife edges & each is prolonged a short distance upwards beyond
the point of suspension. On the top of each I fix a small piece of soft iron &
horizontally above the pendulums I place a steel magnet so that one of its poles
is distant say an inch above one pendulum & the other the same distance above
the other pendulum the whole arrangement being in the first place roughly
symmetrical. The magnet is free to move about a central pivot so that either
pole may be approached to the pendulum immediately beneath it. The pendulums
are connected with a balance gear in a way well understood so that when the
pendulums synchronize the first spindle of the counting train is at rest. I
further arrange that when no current is passing the magnet is so connected
with this first spindle that any movement of the spindle causes the magnet
to turn on its pivot. We will suppose that (no current passing) A is beating
faster than B. The first spindle of the counting gear will slowly rotate but
in doing so it will withdraw the one pole from A while the other approaches B
until the pendulums are in perfect synchronism & the counting gear is at rest.
This will result whenever the current is switched off, which will usually happen
at sufficiently frequent intervals to keep the pendulums sensibly in synchronism.
In cases where the pendulum is controlled by the series current & a shunt
combined I may by means of a time-keeper break the shunt current for say
two minutes out of every three or more than three & by the same movement
throw the steel magnet in & out of gear.
A clock may be used for this timekeeper or I may use a Foucault brake
operated by an electric motor or a weight the system in each case being
preferably self-winding.
It will be observed that the regulation by means of the steel magnet com-

page_text: pensates for the earthsfield & within the limits of its range for all external
magnetic influences when the current to be measured or a portion of it passes
through the coil on the pendulum bob.
I may extend the range of the meter by means of a hot wire shunt or its
equivalent in a manner well understood.
I may replace the attraction of the poles of the steel magnet by light coiled
springs.
Dated this 23rd day of August 1899.
Improvements in Electricity Meters.
I, GEORGE HOOKшAM, of 7 and 8, New Bartholomew Street, in the City of
Birmingham, Electrical Engineer, 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 :-
-
My improvements apply principally to that class of meters in which the
deviations from normal time produced in a pendulum affected by the electric
current (or energy) to be metered are registered. The rate of such a pendulum
is generally compared with that of an unaffected pendulum and it is essential
to accurate registration that when no current is passing the two pendulums
should synchronize.
This condition has been found very difficult to realise and the principal
object of the present invention is to secure such synchronism.
My invention consists in automatically synchronizing two pendulums by
means of a beam or balance gear at periodic intervals in an electricity meter
in, which registration is effected by deviations from normal time produced in
one pendulum by the current or energy to be measured, neither pendulum being
affected by the current to be measured during the said periodic intervals; it
further consists in apparatus adapted to effect this synchronization.
According to one method of carrying out my invention I arrange two
pendulums A & B, A being a free pendulum and B controlled by the current.
A & B are hung on knife edges and each is prolonged a short distance upwards
beyond the point of suspension. On the top of each I fix a small piece of soft
iron and horizontally above the pendulums I place a steel magnet so that one
of its poles is distant say an inch above one pendulum and the other the same
distance above the other pendulum the whole arrangement being in the first
place roughly symmetrical. The magnet is free to move about a central pivot
so that either pole may be approached to the pendulum immediately beneath
it. The pendulums are connected with a differential gear in a way well under-
stood so that when the pendulums synchronize the first spindle of the counting
train is at rest. I further arrange that when no current is passing, the magnet
is so connected with this first spindle that any movement of the spindle causes
the magnet to turn on its pivot. We will suppose that (no current passing)
A is beating faster than B. The first spindle of the counting gear will slowly
rotate but in doing so it will withdraw the one pole from A while the other
approaches B until the pendulums are in perfect synchronism and the counting
gear is at rest.
This will result whenever the current is switched off, which
will usually happen at sufficiently frequent intervals to keep the pendulums
sensibly in synchronism.

page_text: In cases where the pendulums is controlled by the series current and a shunt
combined I may by means of a time-keeper break the shunt current for say
two minutes out of every three or more than three and by the same movement
throw the steel magnet in and out of gear.
A clock may be used for this timekeeper or I may use a Foucault current
brake controlling an electric motor or a motor in which the driving power is
furnished by a weight, the system in each case being preferably self-winding.
It will be observed that the regulation by means of my beam synchronizing
device compensates for the earths-field and within the limits of its range for
all external magnetic influences when the current to be measured or a portion
of it passes through the coil on the pendulum bob.
I may replace the attraction of the poles of the steel magnet by light coiled
springs.
.
Referring now to the accompanying six sheets of drawings which illustrate
meters in accordance with my invention.
Figure 1 is a front elevation of an alternating current meter having the motor
and front plate removed to show the clock-work. In this arrangement the beam
carries a steel magnet and the upward projections on the pendulums carry
pieces of soft iron.
Figure 2 is a similar front elevation of an alternating current meter in which
the poles of the magnet carried on the beam are replaced by springs against
which projections on the pendulums vibrate.
Figure 3 is a front, and Figure 4 a side elevation of the motor which I prefer
to use in alternating current meters.
Figure 5 is a plan view of the whole meter shewn in elevation in Figure 2
including both motor and clockwork.
Figure 6 is a side elevation and Figure 7 an end elevation on an enlarged
scale of a switching device adapted to effect the switching in and out, of the
shunt coil at periodic intervals, and also to bring the synchronizing device
into and out of operation.
Figure 8 is a diagram of the electric circuits of the meter shown in the
previous figures.
Figure 9 is a diagrammatic view showing a modified form of meter in which
the shunt coil is fixed to the meter case, and the series coil is carried by the
pendulum bob.
According to one method of carrying out my invention illustrated in Figure 1
of the drawings I arrange two pendulums a and b, a being a free pendulum
and b controlled by the current; a and b are hung on knife edges c and each
is prolonged a short distance upwards beyond the point of suspension. On the
top of each I fix a small piece of soft iron Dad horizontally above the
pendulums I place a steel magnet E so that one of its poles is distant about
five-eighths of an inch above one pendulum and the other the same distance
above the other pendulum the whole arrangement being in the first place
roughly symmetrical. The magnet E is free to move about a central pivot 2
so that either pole may be approached to the pendulum immediately beneath
it. The pendulums are connected with a differential gear in a way well under-
stood and more fully described below so that when the pendulums synchronize
the first spindle of the counting train is at rest. I further arrange that when
no current is passing the magnet E is so connected with this first spindle v
that any movement of the spindle causes the magnet to turn on its pivot. We
The first
will suppose that (no current passing) a is beating faster than b.
spindle of the counting gear will slowly rotate but in doing so it will with-
draw the one pole from while the other approaches b until the pendulums
are in perfect synchronism and the counting gear is at rest. This will result
whenever the current is switched off, which will usually happen at sufficiently
frequent intervals to keep the pendulums sensibly in synchronism.
The meter circuits and magnet operating gear are exactly the same as those

page_text: described below, with reference to Figures 2 to 7 in which a beam carrying
springs takes the place of the magnet and the arms d the place of the pieces
of iron D.
In Figures 2 to inclusive of the drawings, I have illustrated what I have
found to be the best way of carrying my invention into effect.
Here as before a is a free pendulum and a pendulum controlled by the current
to be measured. The pendulums are supported on pivots or knife edges c.
Pendulum a is not affected under any conditions by the current while pendulum b
carries a shunt coil which is acted on by a fixed series coil j whose terminals
are shown at k and 7. These coils may be arranged to affect one another in
any well known manner other than that shewn, for example the series coil j
may be placed with its axis vertical in which case the coil i carried on the
pendulum would be similarly disposed with its axis vertical and would swing
closely over the fixed coil j.
Each pendulum carries an escapement pawl m whereby it is driven by means
of an escapement wheel n springo and gear wheel 2, see plan Figure 5. These
gear wheels P each operate one of the spur wheels of a differential gear train.
The wheels each carry crown wheels s which both gear with a common
pinion t carried loose on a staff u fixed on the axle v. This axle carries an
aluminium disc won which rests a similar disc h fixed on a spindle 2, the
disch has its spindle 2 guided in a vertical plane. When in its lowest position
the disc rests on and is rotated by the disc w.
On spindle 2 is provided the synchronizing beam e which carries the very
light and nearly close spiral springs f. These are shown exaggerated in diameter
in the drawings for the sake of clearness. The upward projections d on the
pendulums are formed with edges struck from the centre of oscillation of the
beam e.. A further ‹lisc is provided on the axis 2. And a lever arm 3
pivoted at 4 has a knife edge block 5 which is pressed against the edge of the
disc g. The weight of the balance weight 103 is such that the lever 3 by means
of the knife edge 5 acting on the edge of the disc g holds up the spindle 2 with
its disc h clear of the disc w which is not then driven. The lifting device
holds the spindle 2 from rotation as well as takes it out of gear with the disc w
thus fixing the beam e in position. When the accelerated or retarded pendulum
is not being affected by the current to be measured the coil 6 is energised and
it pulls down the lever by the armature 7 thus setting the beam e free to
be rotated by the differential gear into a position, such as is shown in dotted
lines in Figures 1 and 2, to correct the want of synchronism of the pendulums.
The beam e carried on the spindle 2 has the two fine spiral springs supported
one at each end. These spirals are of small diameter closely coiled and of
such length that they offer a very small resisting force to deflection; they
therefore slightly accelerate the vibration of the pendulums a and b whose
extensions d strike against and bend the coils f at each vibration. When the
beam is horizontal the pendulums are in perfect synchronism, if the periods of
vibration of the two are the same and the springs falso are of equal strength.
If these be not quite the same the beam e will take up some other position
at which the pendulums are in perfect synchronism.
I provide the motor shown in plan in Figure 5 and in separate elevations
in Figures 3 and 4 to supply driving force to the clocks and also to act as a
time-keeper.
This motor has two copper discs carried on suitable bearings by spindles 10
and 11 respectively. These discs overlap between the pole pieces 12 and 13
of the two magnets 14 and 15. These pole pieces 12 and magnet. 15 are
supported by non-magnetic distance pieces 101 and screws 102.
The magnet 14 has a shunt winding or coil on the bobbin 16. The ends
of this shunt coil 16 are indicated at 17 and 18 Figures 1 and 2. Over the
shunt coil 16 is placed a secondary winding or coil 19 which is continuous and
forms a closed circuit with windings 20 on the magnet 15. These two magnetic

page_text: fields produce interacting eddy currents in each of the discs 8 and 9 which
cause them to rotate in opposite directions thus driving the pendulums through
the pinions 21 and 22 on the motor spindles 10 and 11. These pinions gear
directly with the large toothed wheels p. I use a switching device one form
of which is illustrated in Figures 6 and 7 to switch off the current to be
measured from the shunt coil and switch in the synchronizing gear at the
proper periodic times for synchronization of the pendulums.
In the form of switching device illustrated, a pinion 23 is fixed on the gear
wheel spindle of the unaffected pendulum a, this gears with a large toothed
wheel 24 on whose axle is fixed a disc 25 carrying pins 26. 27. The disc 25
rotates in the direction shown by the arrow 28 and between the pins 29 and 30
on a disc 31. The disc 31 is fixed to the axle of a cylindrical plug tumbler
switch 32 carried in bearings 33. On the other end of the axle of the tumbler
switch 32 a lever 34 is fixed carrying a tumbling weight 35.
The axis of the tumbler switch and its disc 31 is above the level of the axis
of the disc 25 so that the pins 26, 27 may clear the pins 29 and 30 in their
highest positions.
The cylindrical plug switch is of insulating material having contact pieces 36
and 37 let into the surface at the proper points on which bear spring contact
pieces 38, 39, and 40.
The disc 25 and its pins must be geared so as to make a complete revolution
in each four minutes if the tumbler switch is to be operated at periodic intervals
of two minutes.
When the pin 26. say. comes into engagement with the pin 30 it gradually
lifts the latter until the tumbler weight passes over the centre when it falls
over and changes the electrical connections of the meter.
In Figure 8 is shown diagrammatically the electric circuits within the meter.
the arrangement is the same as in Figures 1 and 2 except that in the latter
figures the secondary circuit of the motor is omitted for the sake of clearness.
The series current enters by terminal and passing through the series coil j
leaves by terminal 7.
In Figures 1, 2 and 8 the circuits are shewn in the position when the
pendulum is not affected by the current to be measured that is when there
is no current through coil i.
The shunt current then passes into the meter by the terminal 41 thence by
wire 43 through the motor shunt coil 16 entering at 17 and leaving at end 18.
It then passes by the wire 44 to the coil 6 from which by the wire 45 it passes
to the tumbler switch terminal 40. Here the contact piece 37 connects with
the common return terminal 39 which in turn connects with wire 46 conveying
the current to the second shunt terminal 42.
The secondary circuit of the shunt magnet coil 16 is indicated at 105. This
circuit is closed through the wire 106 passing round the upper magnet 15 and
back to the coil at 107. When the synchronizing period of say two minutes
has elapsed the tumbler switch reverses the shunt connections putting in the
pendulum shunt coil and taking out the coil 6 this then releases its armature 7
which is overbalanced by the counterweight 103. The lever arm 3 then by means
of its knife edge block lifts up the disc and thereby the beam e which is
thus held in the angular position determined by the last synchronizing operation.
The pivots 2 of the beam e are provided with vertical guides as shown at 108
Figures 1 and 2.
When reversal of the electrical connections has taken place by means of
the tumbler switch the shunt current flows as before through the shunt magnet
coil 16 and thence by the wire 44 to the point 47 where a branch wire 48
passes off to the pendulum shunt coil i whence it passes by way of the wire 49
to the terminal 38 and then through the contact pieces 36 and wire 46 to the
second shunt terminal 42. The pendulum b is now affected by the current to

page_text: be metered and a record takes place on the index 104 connected with the
spindle of the differential gear.
At the end of the next two minutes reversal of the circuit connections again
takes place the pendulum b being again unaffected and the electro-magnet 6
energised; the disc h is thus again lowered and any difference in the rates of
the two pendulums will cause the differential gear to rotate carrying with it
the disc w. This disc w thus drives the disc hand with it the beam e, which
carries the springs f into a position in which they correct the error of syn-
chronism by accelerating the slow pendulum and slowing up the pendulum
which is beating too fast, I find that by this means the want of synchronism
between the pendulums can be corrected for the purposes of an electricity
meter.
For the sake of preventing sparking I prefer to arrange the contact pieces 36
and 37 to overlap so that the two coils and 6 may be of nearly the same resis-
tance and that they will be for a very short interval in parallel with one another.
The shunt circuit is therefore never broken in the operation of the meter, and
the coil 16 is always in circuit.
I may in some cases arrange the motor shunt on a separate circuit which
is then not connected with the tumbler switch.
In Figure 9 I have shown an arrangement of meter in which the series coil
is carried on the pendulum b and the shunt coil is fixed. With this arrange-
ment the meter becomes independent of the earth's magnetic field and within
the limits of its range for all external magnetic influences.
In this case I use thin flat copper bands 108 zigzag form and of suitable
length, to lead in the current to the coil on the moving pendulum b. I also
cause these to be fixed to a point very near to the pendulum pivot so that an
exceedingly small motion of the connecting bands 108 will be required.
In all other respects the arrangements shewn in Figure 9 correspond with.
that in Figures 1 to 8.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:
-
1. In electricity meters in which two pendulums are compared, one being
affected at periodic intervals by the current to be measured and the other
beating normal time, a synchronizing device, consisting of a balance gear, adapted
to correct deviations from synchronism between the pendulums during the
alternate periods in which both pendulums are unaffected by the current or
energy to be measured.
2. In two pendulum electricity meters, a synchronizing device, consisting
of a pivoted beam carrying springs, against which projections on the pendulums
vibrate, and whose angular position is controlled at periodic intervals from the
differential gear connecting the pendulums, for the purpose of automatically
effecting thereby an acceleration of the slow pendulum, and a retardation of
the fast one, till synchronism is obtained, substantially as described.
3. In electricity meters, in combination, two pendulums, one affected by the
current or energy to be measured the other unaffected, and acting as a time-
keeper, a driving motor, switching means operated by the time-keeping pendulum
at periodic intervals, and synchronizing means brought into operation at periods
alternating with periods during which the current or energy affects one of the
pendulums substantially as described.
4. In electricity meters in combination, two pendulums, one unaffected and
acting as a time-keeper, the other carrying a coil through which the series
current passes a driving motor switching means operated by the time-keeping
pendulum at periodic intervals, and synchronizing means brought into operation
at periods alternating with periods during which the current or energy affects
one of the pendulums, substantially as described.

page_text: 5. In electricity meters automatically synchronizing two pendulums by
means of a pivoted magnet having its poles arranged to act on pieces of iron
carried on the pendulums substantially as described.
6. The improved electricity meters herein before described with referecne to
the accompanying drawings.