Improvements in Electricity-meters.
Year: 1891

page_text: .
Date of Application, 4th Mar., 1891--Accepted, 11th Apr., 1891
COMT IIELD OF MOITATIO
Improvements in Electricity-meters.
RANKIN KENNEDY, Electrician and Engineer, Carntyne Electric Works
Shettleston, Glasgow, N.B., do hereby declare the nature of this invention, and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement :-
These improvements consist principally in combining an Ammeter or Wattmeter
with two pendulums and a differential gearing the lengths of the pendulums being
controlled by the Ammeter or Wattmeter and the differential gearing recording
their difference of vibration.
This invention has for its object more especially the improvement of that class
of meters of electricity in which the recording dials are moved by a differential
gear between two trains of wheel work controlled each by a separate pendulum and
driven by a falling weight a spring or by an electromotor.
The pendulums are adjusted to vibrate synchronously when no electricity is
passing into the meter, they are hung on a Hexible strap passing over a pulley
which is mounted on a spindle and moves very freely, a pendulum hanging over
each side so that the pulley is in equilibrium.
The electricity to be measured and recorded in passing through the meter causes
the pulley over which the pendulums are suspended to rotate on its axis through an
angle proportionate to the electricity passing; this movement of the pulley
shortens one of the pendulums while it equally lengthens the other pendulum, and
this causes the differential gear to move in proportion to the amount of electricity
passing, and so the index moves proportionately. The movement of the pulley is
due to its being fixed on the moving spindle of an Ammeter or Wattmeter, thro'
the coils of said meter the electricity to be measured passes and causes a rotation
of the pulley through an angle proportionate to the amount of electricity passing.
An Ammeter is employed to rotate the pulley when the electricity is to be
measured in Coloumbs, or ampere hours.
A Wattmeter is employed to rotate the pulley when the clectricity is to be
measured in ergs.
The pendulums control two trains of wheels by an escapement movement,
between the two trains is placed the differential gear which drives the index.
In the accompanying sheet of drawings my invention is shown to enable those
skilled in the art to which it relates to understand the construction and mode of
action of a meter according to my invention.
Fig. 1 is an elevation showing the pendulums, escapements, pulley and meter
coils.
Fig. 2 is an elevation showing the trains of wheels, and differential gear and
meter coils.
2
Referring to Fig. 1 A and B are the two pendulums, both alike in size and
weight. C, D, are the two escapements driven by springs through the two separate
trains of wheels.
SS is the flexible strap passing over the pulley P mounted on spindle T.
On the same spindle T the meter movement is mounted, the meter is preferably
of the class in which coils of wire carrying the electricity repel each other and
consists of two fixed coils F, G, and two movable coils H and E mounted on the
pulley spindle T by a cross arm.
On passing electricity thro' the coils in the manner well known to electricians the
movable coils are repelled to a distance proportionate to the electricity passing,
and thus the one pendulum is pulled up and the other let down a distance pro-
portionally to the amount of electricity passing and their difference is recorded
by the index worked by the differential gear.

page_text: In Figure 2 the same reference letters apply to the same parts as in Figure 1.
W, is one train of wheels driven by spring in box k. X, is the other train driven
by spring . Y is the index train.
The differential gear consists of three bevel wheels, a driven by one train,
b driven by the other, the third wheel d is pivoted on c which is mounted on a
spindle R passing through the spindle of 6 which is hollow.
The speeds of bevels a. b. vary as the length of pendulums vary and carries
round the bevel d on spindle R moving the index; when the speed of a and b is
equal, simply rotates on the pivot, c, without moving spindle R. For use with
alternating currents the movable coils are replaced-by two discs of copper which
are repelled by the fixed coils when carrying electric current alternating or
pulsating.
The flexible strap S on which the pendulums are suspended is usually of thin
brass or copper and it is guided by two pulleys on each side and these pulleys
and the spindle T carrying the pulley P and the movement of the Watt or
Ammeter must be mounted to move with greatest amount of freedom from
friction.
The movement of the Wattmeter or Ammeter may be mounted apart from
spindle of pulley P, and the motion is then communicated to pulley P by a con-
necting rod or cord.
A long solenoid acting upon a core of iron wires which is pulled into the solenoid
against the resistance of a spring when the electricity passes is used as an Ammeter
with advantages; this motion of the core is readily communicated to the pulley, P,
by a cord passing round spindle, T, so that when electricity passes through the
solenoid the core is drawn in proportionally to the amount of electricity passing ;
and the pulley P pulled round by the cord proportionally to the amount of
electricity passing.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the saine is to be performed, I declare that what
I claim is --
First The method of measuring electricity by the difference in rates of vibration
between two pendulums said difference caused by lengthening and shortening said
pendulums, by means of the action of the electricity to be measured, while passing
through an Ammeter or Wattmeter.
Second The combination of an Ammeter or Wattmeter with two pendulums
one of which is shortened and the other lengthened by the movement of an Ammeter
or Wattmeter and with differential gear operating and controlling an index sub-
stantially as and for the purpose herein described.
Dated this Twenty-seventh day of February 1891.
RANKIN KENNEDY,
Carntyne, Glasgow, N.B.