Year: 1897

page_text: SAMUEL LEITH TOMKINS of 6 Old Park Avenue Balham London S.W., Gentleman,
do hereby declare the nature of this invention to be as follows:-
The invention consists of the following improvements in electricity meters, which
if desired can be used in whole or in part in substitution of corresponding parts of
the meters described in the previous Patent No. 20,360 of 1890.
The improved apparatus consists of a toothed arc of aluminium or other metal,
substituted for the index needle of the ammeter, with a rotary movement, commencing
at an angle of about 30 degrees from the vertical, and revolving downwards. The arc
is pivoted on the central spindle of the ammeter, and is balanced by a suitable
counterpoise..
The arc is locked by a second lever, independent of the clutch lever, and pivoted on
an independent bearing, which is set free at definite intervals by clockwork, to allow
the arc to take up a fresh position if the strength of the current has varied since the
previous locking.
At the lower extremity of the arc aforesaid a pin is fixed, on which the clutch lever
described in the previous Patent No. 20,360 of 1890, falls, after the arc has been
locked. The position of the pin which varies with the strength of the current
controls the amount of travel of the outer arm of the clutch lever operating the clutch
wheel. When at zero, and with no current passing, the pin is at the extremity of the
horizontal diameter of the ammeter, and there is no movement of the clutch wheel,
but the smallest movement downwards of the arc and resting pin, allows the inner
curved arm of the clutch lever to fall, thereby raising the outer arm, and allowing it
to grip the clutch wheel higher up, and each time the arm of the clock acts on the
lever, the clutch wheel and recording train register, the current passing. As the pin
falls lower and lower, the outer arm of the lever is raised more and more, with a
corresponding increase in the movement of the clutch wheel.
I further improve the clutch wheel by cutting teeth on the edge, and improve the.
clutch lever by pivoting it on an independent bearing, in a straight line with, but
separate from, the spindle of the clutch wheel. I also curve the inner arm of the lever
upwards instead of downwards, and I replace the spring which formerly gripped the
clutch wheel, by a weighted pawl, which does so more effectually.
Dated this 27th day of January 1897.

page_text: I, SAMUEL LEITH TOMKINS, of 6 Old Park Avenue Balham, London, S.W.
Gentleman, 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 invention consists of an improved apparatus whereby it is possible to measure
in ampere hours the amount of current passing along an electric circuit, more
accurately and more effectively than by the combination of an ammeter having an
index pointer, with pedometer mechanism and clockwork, as described in the previous
Patent No. 20360 of 1890.
The improvement consists of a toothed arc of aluminium or other metal substituted
for the index pointer of the ammeter, with a rotary movement downwards,
commencing at an angle of about 30 degrees from the vertical. The arc is locked by
a second lever, bent at a right angle, not by the clutch lever described in the previous
Patent No. 20360 of 1890. The second locking lever is pivoted on an independent
bearing, and set free at definite intervals by clockwork, in order to allow the arc to
take up a fresh position, if the strength of the current has varied since the previous
locking. At the lower extremity of the arc a pin is fixed, on which the curved arm of
the clutch lever falls after the arc has been locked. This lever is pivoted on an
independent bearing in a straight line with, but separate from, the spindle of the
clutch wheel, which should be toothed, and which forms the first of a recording train
of wheels.
When no current is passing the arc is at rest, and the pin at the lower extremity
keeps the clutch lever horizontal. In this position there is no movement of the
lever or the clutch wheel, and no record. When a current passes through the Meter
the arc revolves downwards more or less according to the strength of the current,
carrying with it the resting pin, and allowing a proportionate movement of the
clutch lever, the inner curved arm of which falls on the resting pin by its own
weight, while the outer straight arm of the lever is raised and grips the teeth of the
clutch wheel higher up by a weighted pawl, shortly after the arc has taken up a fresh
position, and has been locked by the locking lever first mentioned. The inner arm is
curved like a scythe, and the curve is adjusted so that as the outer edge falls on the
resting pin, the pawl on the outer arm grips the exact number of teeth on the
clutch wheel corresponding to the number of amperes and fractions of an ampere
indicated by the rotation of the toothed arc of the ammeter. The clutch wheel can
be made of any size, and any number of teeth, but should not be too small as more
teeth to an ampere give greater accuracy. Six teeth to an ampere are usually
sufficient. The wheel is made to revolve by the clock forcing the straight arm of
the lever downwards, the motion being communicated to the wheel by the pawl on
the lever.
The clock may be an ordinary lever one, wound by hand once a month, or a self
winding clock may be used if desired. It is fitted with an extra wheel revolving once
in 3 minutes to work the two levers. Near the circumference two pins are fixed,
opposite each other, a short one at the edge for raising the locking lever, and freeing
the toothed arc of the ammeter, short enough to pass behind the clutch lever without
disturbing it, and a longer one near the centre, so as not to touch the locking lever,
which in its revolution forces down the outer arm of the clutch lever with its
weighted pawl, thereby causing the clutch wheel to revolve in a forward direction,
and register ampere hours on the dials. Another pawl pivoted to the frame of the
clock prevents the clutch wheel being moved backwards.

page_text: Thus the fall of the ammeter arc, substituted for the ordinary index -pointer,
regulates the movement of the clutch lever proportionately to the strength of the
current, the locking lever prevents any disturbance of the ammeter arc by the fall of
the curved arm of the clutch lever, and the clock moves both levers, and by the
action of the clutch lever moves the recording train of wheels. The extra wheel of
the clock is made to revolve once in three minutes, but I claim to alter the time of
revolution if desirable.
With reference to the drawing, a is the curved arm of the clutch lever, b the
straight arm of the same, c the weighted pawl, d the toothed arc of the ammeter,
e the counterpoise, f the resting pin on which the curved arm falls, g the locking lever,
in which two or three notches are cut where the lifting pin raises it, in order
alternately to lock and free the ammeter arc, and thus control its swing, and sooner
bring it to a state of rest, h is the clutch wheel, the first of the recording train,
the pawl to prevent any backward movement, j the extra wheel of the clock, and
k the pins.
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. The substitution of a toothed are in place of an index pointer in any
ammeter.
arc.
2. The locking lever, with notches for controlling vibration, gripping the toothed
3. The independent bearing of the clutch lever, for reducing friction, and making
the work of the clock lighter.
4. The combination of the above with a clock movement for registering ampere
hours.
Dated this 27th day of October 1897