Improvements in Electricity Meters.
Year: 1898

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 to that class of meters in which the acceleration or re-
tardation of a pendulum (the bob of which is attracted or repelled by a coil
carrying the current to be metered) as compared with another pendulum beating
regularly, is registered by a counter and dials. The acceleration or retardation
being within limits proportional to the current (or energy as the case may be)
the apparatus registers the current (or energy) supplied through the meter in
a given time In such a meter absolute synchronism of the two pendulums
when no current is passing is generally a necessary condition, and it is a con-
dition which it is very difficult to fulfil. By my invention I use only one pen-
dulum. In one form this pendulum drives a ratchet wheel the pawl of which
is reversed at equal intervals of time say every five minutes, to that for one five
minutes the ratchet is driven forward, the rest 5 minutes it is driven back-
ward, and therefore, normally, at the end of each 10 minutes the effect on the
counter is mil. But if I cause the pendulum bob to be attracted by a coil carry-
ing current during the first 5 minutes, and not to be so attracted during the
second 5 minutes then the result of the acceleration during the first 5 minutes
is registered by the counter. This I may effect by attaching to the bob a coil
carrying a shunt current in a manner well understood and alternately making
and breaking this current at the end of each 5 minutes. Or I may reverse
the shunt current at each interval of time: in which case the difference between
the effects of acceleration and retardation will be registered. In the former
case it is evident the energy is "sampled" every 5 minutes, in the latter the
registration is continuous.
Dated this 18th day of October 1898.
Improvements in Electricity Meters.
I, GEORGE HOOKHAM, of 7 & 8, New Bartholomew Street, in the City of
Birmingham, Manufacturer, 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 to that class of meters in which the acceleration or re-
tardation of a pendulum (the bob of which is attracted or repelled by a ceil
carrying the current to be metered) as compared with another pendulum beating

page_text: regularly, is registered by a counter, and dials. The acceleration or retardation
being within limits proportional to the current (or energy as the case may be)
the apparatus registers the current (or energy) supplied through the meter in
a given time. In such a meter absolute synchronism of the two pendulums
when no current is passing is generally a necessary condition, and it is a con-
dition which it is very difficult to fulfil. By my invention I use only one pen-
dulum. In one form this pendulum drives a ratchet wheel, the pawl of which
is reversed at equal intervals of time say every five minutes, so that for one five
minutes the ratchet is driven forward, the next five minutes it is driven back-
ward, and therefore normally at the end of each ten minutes the effect on the
counter is nil. But if I cause the pendulum bob to be attracted by a coil carry-
ing current during the first five minutes, and not to be so attracted during the
second five minutes then the result of the acceleration during the first five minutes
is registered by the counter. This I may effect by attaching to the bob a coil
carrying a shunt current in a manner well understood, and alternately making
and breaking this current at the end of each five minutes. Or I may reverse
the shunt current at each interval of time, in which case the difference between
the recording effects of acceleration and retardation will be registered. In the
former case it is evident the energy is "sampled" every five minutes, in the
latter the registration is continuous.
Referring to the accompanying sheets of drawings :-
Figure is a front elevation;
Figure 2 is a side elevation; and
Figure 3 a plan of my new pendulum meter.
Figures 4, 5, 6, 7 and 8 show views of details of the same; and
Figure 9 shows a diagram of the electric connections of the reversing switch.
In carrying my invention into effect according to one modification, as illus-
trated in the drawings, A is a pendulum of any suitable type, carrying a shunt
coil A¹ The wires from the ends of the coil A¹ are led up the pendulum to a
point where there is but a small motion of the pendulum relatively to the case C
of the instrument, and there the wires are connected by fine spirals to suitable
contact pieces on the tumbler G. In a similar manner terminals on the
pawl are suitably joined up, one wire passing to an insulated shunt ter-
minal M, and the other to the main terminal B1. The electrical connections
must be such that no friction is caused which would interfere with the motion
of the pendulum. A series coil B is provided, connected with the series ter
minals B B2, which coil surrounds the moving shunt coil A', but in such
manner as to leave the latter free to vibrate within it. The pendulum A is
suspended by a thin flat spring A³ in a usual manner from the fixed point A'.
A lever D pivoted at D4 and D has a forked end D', which engages with the
pendulum, and to this lever D is fixed the escapement lever D². The escape-
ment wheel D³ is supported and driven from a spring or other clock device in
any usual manner. Fixed on another shaft I2 I provide two ratchet wheels I
and I, having their teeth formed for driving in opposite directions. The
pawl has two branches, one of which F1 drives the ratchet wheel I, the
other F2 drives the ratchet I', so that a change from driving by one pawl to
driving by the other involves reversal of the whole or part of the recording
train. The compound pawl F1 F2 is operated by a link E from the lever D,
and is supported on a pirot on the end of a double lever F pivoted on the axes
of the ratchet wheels. The pawl which is in action at any time is determined
by a tumbling lever G, more fully described below, and the lever G is operated
to simultaneously reverse both the operating pawl and the direction of current
flow through the moving coil A. The lever G is tumbled over, and reversal
effected by means of a lever K pivoted at K, and supported on a disc cam L
in such a manner that when its projections K' drops into the notch L' of the
disc L, the projection K2 on the lever K catches the pin G2 on the tumbler G,
and causes the latter to fall over to the right reversing the electrical connec-

page_text: tions at H (see Figure 9) and putting the pawl F¹ into operation on the wheel I.
Similarly, when the projection L2 of the cam L acts on the lever projection K¹
the projection K catches the pin G tumbling over the lever G, and reversing
the electrical connections again. On the shaft I of the ratchet wheels I I
there is provided a worm 13 (see Figure 2), gearing with a worm wheel It on
the shaft 1 of an ordinary recording train J. The disc cam L is driven from
an ordinary spring clock of cheap construction, or some other roughly correct
type of clock.
Accurate time-keeping by such a clock is not necessary, all that
is required is that its rate (whatever it be) shall be constant or approximately
constant, in successive intervals. The cam L then, as illustrated, makes half
a revolution before it reverses the tumbler G with its switch H and pawls F1 F2.
The cam L may be operated from any suitable periodic operating device,
instead of from a clock. For example, a suitable electrometer might be used
for this purpose.
In Figures 4, 5, 6, 7 and 8 the ratchet wheels I and I, with the pawl Fi
are shown enlarged. Figure 4 shows also a modified form of tumbler, in which
the inertia of the weight G cannot give trouble, as it is replaced by a spring G4
A block of insulated material H, shown in detail in Figure 9, is attached to
the tumbler G, and serves as part of the electric reversing switch. In Figure 9
also the internal shunt connections of the meter are shown diagrammatically.
The contact pieces F3, F4, F5 and F are attached to, but are insulated from
the pawl FF2 and Fare connected together and then to the negative
side of the supply main. Contact pieces F and F similarly are connected to
one another, and to the positive lead. On the four faces of the insulating
block H (see Figure 9) are placed contact pieces H H H and H. The con-
tact pieces H' and H² are connected by the wire H³, and the pieces H and H
are similarly connected by the wire H. From H¹ and H wires pass by means
of fine spirals, as is commonly done in electric meters, to the ends of the coil A¹,
which here represents the coil A in Figures 1 and 2. If now the tumbler be
lying to the right in Figure 1, then contact is made, from the positive shunt
wire of the meter to F, thence to contact piece H through the coil A',
and back through contact pieces H¹ and H², and F to the negative lead of the
meter. Similarly, if the tumbler be lying on the other side, i.e., to the left in
Figure 1, then current will be sent through the coil A' in the opposite
direction.
I will now briefly describe one method of operation of the above meter.
Assume that the pendulum A is to be accelerated during one period of say
five minutes, and retarded during the next. Then the series current which is
always passing in the coil B acts on the pendulum coil in one direction, causing
acceleration proportional to the current during the first period (which is re-
corded by means of the pawl F2 driving the index train), at the end of this
period the cam L drops into the notch L, as the disc L has made a half revolu-
tion.
On the next swing of the pendulum the hook K2 of the lever K catches
the pin G2 on the tumbler, and pulls the latter over, reversing the current in
the coil A', and driving the index train by means of the pawl F', in the reverse
direction but as the pendulum is now retarded in proportion to the series cur-
rent passing through the meter the index train will be brought back so that
at the end of this second period of five minutes it will show the exact amount
of current (or energy) passed through the meter during the ten minutes, and
so on.
I have described my invention only as applied in one modification, and I
would have it understood that I do not limit myself to the detail arrangements
shown on the drawings. My invention consists generally in a one pendulum
meter, capable of registering current or energy accurately, and in such a manner
as to he independent of the natural period of vibration of the pendulum, and
of the usual slow changes in that period.

page_text: The period of vibration of the pendulum need not be constant, provided the
changes in the period are not rapid in relation to the reversal period chosen.
If the current through the shunt coil be kept constant then the meter will
register current only as for example when the meter is placed on a constant
potential circuit such as is used for electric lighting.
In the form of my invention above described, where the current or energy
is sampled in each alternate period instead of being continuously recorded,
the only modification of the apparatus described with reference to the drawings
required is that instead of the electric reversing switch H, a make and break
switch would be used, so that the shunt circuit would only be energised during
each alternate period.
Instead of the ratchet wheels and their driving pawls F and F friction discs
may be used and friction driving pawls.
The lever E may be operated by a suitable device adapted to give a recipro-
cating motion from the escapement wheel 1ª, or from a wheel driven from D.
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 the use of a pendulum, suitably controlled for the
measurement of current or energy, the said pendulum driving a recording
wheel train and registering the difference of travel of the said train during
successive periods in which the pendulum is accelerated and retarded (or accele-
rated and unaffected: or retarded and unaffected) by the action of the electric
current this operation being performed without the intervention of any
second pendulum or timekeeper driving or tending to drive the said recording
wheel train.
2. In electricity meters the combination of a single pendulum suitably con-
trolled for the measurement of current or energy with a second pendulum or
other time-keeper whose sole function is to determine the required electrical and
mechanical reversals at fixed intervals.
3. The improved electricity meters hereinbefore described with reference to
the several figures of the drawings.
Dated this 14th day of August 1899.
MARKS & CLERK,
18, Southampton Buildings, London, W.C.
13, Temple Street, Birmingham, and
25, Cross Street, Manchester, Agents.