IMPROVEMENTS IN ELECTRIC- CURRENT METERS
Year: 1881

page_text: LETTERS PATENT to Charles Ashley Carus-Wilson, of Grenville Place, in the
County of Middlesex, for an Invention of "IMPROVEMENTS IN ELECTRIC-
CURRENT METERS."
PROVISIONAL SPECIFICATION left by the said Charles Ashley Carus-
Wilson at the Office of the Commissioners of Patents on the 3rd November
1881.
CHARLES ASHLEY CARUS-WILSON, of Grenville Place, in the County of
Middlesex. "IMPROVEMENTS IN ELECTRIC-CURRENT METERS."
The object of this Invention is to register automatically the amount of electricity
which passes through a wire or conductor.
The Invention consists mainly of a peculiar method of obtaining a variable
rotation of one shaft from another shaft rotating with a constant angular velocity;
and, secondly, of a way in which the piece connecting the one shaft with the other
is moved in accordance with variations in the current to be measured.
For the purpose of obtaining a variable rotation of one shaft from another shaft
rotating with a constant angular velocity I employ two cones, whose generating
surfaces are segments of one and the same circle. I key these cones respectively
on two shafts, which are placed in the same horizontal plane in such a way that
the contours of the two cones in plan form parts of the circumference of the circle
of which the generating lines of the two cones are segments. The cones are also
placed so that their ends of smaller diameter point the same way, and should be of
such a size as regards length of generating surface that they form equal segments
of the same circumference, but this is not essential. I place a wheel of diameter
equal to or greater than the diameter of the above mentioned circle vertically
between the two cones above described, so that its circumference is in a plane at
right angles to the plane containing the axes of the two cones, and its axis is in a
plane parallel to the above plane, below it, above it, or actually coinciding with it. It
will follow from this that if I make the circumference touch the two cones the tangent
of each of the two touching points will be a tangent common to the wheel and to
.

page_text: the cone, and hence if I thus fix the 3 axes any rotation of the one cone will be com-
municated to the other, provided there is sufficient friction, and that if one cone has
a constant angular velocity the other cone will have an angular velocity depending
the angle which the axis of the wheel makes in plan with the axis of either
cone, and upon the actual size of the cones themselves. This action constitutes an
essential feature of my Invention.
upon
The variation of the above mentioned angle can be produced in several ways by
mechanical motion derived from variations in the current to be measured. One
way which I adopt for this purpose is as follows:-I use a small motor driven by
the current in question. On the shaft of this motor I mount two loose pulleys, and
between them I key to the shaft a third pulley. I take a rectangular shaped
piece, the ends of which are forked or of U form, so that it can fit loosely on the
shaft, and enclose all the three pulleys, and rest in a horizontal position. I pass a
band over the centre pulley, and attach it to the rectangular piece on the other
side. I carry two other bands respectively under the two loose pulleys, and attach
them to the rectangular piece at each side of the other band. To the other end of
these two bands I affix springs, or I pass them over pulleys to weights. I also
fasten a weight or spring to the hanging end of the centre band. Now if the
weights or springs are so adjusted that the rectangular piece is horizontal, and the
shaft rotates with a certain amount of torsion, the one weight or spring will drop
and the other rise, and the rectangular piece will for a certain torsion obtain a
certain position; the position of this piece in fact will depend upon the current
which drives the motor, and will vary as the current varies. I transmit the move-
ment of the said piece-to-the-shaft-of-the-wheel-which, as before explained, works
between the two cones, and this shaft is thus moved according to the strength of
the current. This shaft is made to work any suitable counting apparatus, so as to
register the number of revolutions.
The shaft, which rotates with a constant angular velocity, as first herein before
described, may be driven by the main electric current, or a local current made
constant for the purpose, or by clock work or otherwise.
<<
It will be understood that as the cones " hereinbefore described have generating
Burfaces which are segments of a circle, they are not true cones; I have only called
them cones for convenience of description.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Charles Ashley Carus-Wilson in the Great Seal Patent Office
on the 3rd May 1882.
CHARLES ASHLEY CARUS-WILSON, of Grenville Place, in the County of
Middlesex. IMPROVEMENTS IN ELECTRIC-CURRENT METERS."
The object of this Invention is to register automatically the amount of electricity
which passes through a wire or conductor.
The Invention consists mainly of a peculiar method of obtaining a variable
rotation of one shaft from another shaft rotating with a constaut angular velocity;
and, secondly, of means by which the piece connecting the one shaft with the other
is moved in accordance with variations in the current to be measured.
For the purpose of obtaining a variable rotation of one shaft from another shaft
rotating with a constant angular velocity, I employ two cones, as represented at A, A¹,
in plan in Figure 1, and in elevation in Figure 2, whose generating surfaces are
segments of one and the same circle. I key these cones respectively on two shafts
B, B', which are placed in the same horizontal plane in such a way that the contours
of the two cones in plan form parts of the circumference of the circle (represented
dotted in the Figure), of which the generating lines of the two cones are segments.
The cones are also placed so that their ends of smaller diameter point the same
way, and should be of such a size as regards length of generating surface that they
form equal segments of the same circumference, but this is not essential. I place a
wheel C of diameter equal to or greater than the diameter of the above mentioned
circle vertically between the two cones A and A¹, so that its circumference is in a plane
at right angles to the plane containing the axes of the two cones, and its axis D is
in & plane parallel to the above plane, below it, above it, or actually coinciding
with it. It will follow from this that if I make the circumference of the wheel C
touch the two cones A, A', the tangent at each of the two touching points will be a
tangent common to the wheel and to the cone, and hence if I thus fix the three axes
any rotation of the one cone will be communicated to the other, provided there is
sufficent friction, and that if one cone has a constant angular velocity the other
cone will have an angular velocity depending upon the angle which the axis of the
wheel makes in plan with the axis of either cone, and upon the actual relative
sizes of the cones themselves. This action constitutes an essential feature of my
Invention.
The variation of the above mentioned angle can be produced in several ways, by
mechanical motion derived from variations in the current to be measured.
Figure 3 illustrates a method of effecting this motion by employing an electric
motor in the main circuit, or in a shunt of the same, and fitting it with a dyna-
mometer, so that the amount of work done on the dynamometer by the motor
pulls the wheel round more or less.
In this Figure C is an end elevation of the wheel (the cones are not shewn);
D is the horizontal axis of rotation of the wheel; c is a fork holding D, and turning
on a pivoted shaft hat d; e is a smooth wheel keyed to the shaft h, round which
passes a band I, which is connected to the dynamometer; f is a watch spring
fastened to h and to a fixed piece k, and working against the direction indicated
by the arrow on g; the more current that passes the more work is done on the
motor, and g gets pulled round a little against the spring, thereby moving the
wheel C, and altering the relative diameters of the cones at the point of contact.
Now I make one of the shafts B, B', in Figure 1 rotate with a constant angular
velocity by an electric motor or other means, so that the position of the wheel C

page_text: makes the other shaft go round faster or slower according to the work being done
on the dynamometer, which is adjusted so that, say, when twice the work is being
done, it pulls the wheel round so that the second shaft rotates at twice the former
rate, and I fit it with a counting apparatus so that I can sum the amount of work
that has been done, that is, I can count in suitable units the amount of current
that has passed. Any suitable dynamometer and motor may be employed.
Another method I employ for moving the wheel C is illustrated in Figures
4, 5, 6, 7, and it is especially important, as it enables a meter to be made which
measures practically the amount of resistance in any circuit, so that the sum is not
affected by variations in the electromotive force in the mains.
In Figure 4, A, A, and B, B, represent the two mains from the generating
machine; r is a small resistance, a fraction of an ohm, in the main circuit; x is
the resistance in the circuit, consisting of a certain number of lamps; G is a
galvanometer joined up with r and x and two other resistances n, r, and n, x, so as
to form a Wheatstone's bridge; a is an electro magnet in the main circuit B, B.
Directly any current passes through x (and consequently B, B,) the lever bis moved
down and strikes against the stop e, thereby putting n,r, n, x, and G in circuit between
A, A, and B, B. When the galvanometer is in equilibrium we must have n, x, the
same function of x that n, r, is of r. I construct n, x, in the form of a box of
resistances. The galvanometer G is made as in Figure 5; as the needle oscillates
one way or the other it strikes against one or other of two metallic stops a, b,
thereby making a circuit through one or other of two wires; these wires are
arranged as in Figure 6. A, B, are the negative and positive wires from the
machine; G is the galvanometer; c, d, are two solenoids with a common core f;
g is a box containing-any-high-resistance.--The-connections-are-made-as.shewu.
The current goes from the positive wire A through one or other of the two solenoids c
or d to the stops a, b, on the galvanometer, then from the needle to the resistance g,
and so to the wire B, the result of the galvanometer moving one way or the other
being that the core f is dragged up or down. The points of contact are fitted
with platinum surfaces. Now I make the core factuate mechanism illustrated in
Figure 7.
In Figure 7, a is the core above mentioned; b is a lever with a fulcrum at c; at
the end is a fork which carries a shaft d, so that d can rotate on its axis; e is a
small wheel keyed to d, with a rim of teeth at top and bottom; f and gare two toothed
wheels, both driven (different ways) by the wheel h rotating on the shaft k
f, g, h, and k'are all fixed in suitable bearings, and rotate entirely independent of
the shaft d and wheel e, the centres of ƒ and g allowing d to pass through; f and
are each fitted with a rim of teeth to correspond to those on e. The lower end of d
carries a pinion gearing into a wheel m, and m rotates on a shaft n (which is
identical with the shaft h in Figure 3 carrying the wheel a). p and q are two springs
capable of being regulated so as to bear on the lever b, and keep e between f and g.
r is a second wheel gearing in l, and rotating upon the shaft 3. As the shaft s
rotates one way or another it puts in or takes out resistances in a conveniently
arranged rheostat, which rheostat is identical with the resistance n, x, in Figure 4.
The shaft is made to rotate by the same motor that moves the cone A, Figures 1
and 2.
Directly a lamp or lamps is put in the circuit x, Figure 4, the galvanometer
needle is deflected against, say, the stop a, a circuit is made through the solenoid c,
Figure 6, and the core a, Figure 7, gets pulled up, e engages with g, and d gets
turned round; this turns round both the shafts and s; the first makes the
wheel 'C, Figures 1 and 2, turn round and engage the two cones, whilst the latter puts
a resistance into the circuit n, x, Figure 4; both n and s are turned round until
enough resistance is in the circuit, when the galvanometer needle falls to the centre
between the two stops, and the lever b disengages e from g. The meter then
continues to register for as long as that particular resistance is in circuit, it being
arranged that when x ohms resistance is in circuit the wheel C (Figures 1 and 2)
has a definite position on the cones, and when 1/.x ohms, say, is in circuit, the second

page_text: cone is going twice as fast as before, due to the position of the wheel C;
this can
be contrived by properly placing the terminals of the resistances on the rheostat n, x,
Figure 4, with respect to the position of the wheel C. By altering the ratio n, r,
tor, Figure 4, I can make the meter capable of registering the smallest resistance
in x, that is, the greatest number of lamps, because then the wheels n and 8 will
only have to be moved through a fraction of their former angle for the same
number of lamps added in the circuit; thus in one case an addition of 10 lamps
may move the wheels round 30 degrees, whereas in another only 10°, so that I fit
the circuit n, r, Figure 4, with a series of resistances so as to enable the meter to
register a great or small number of lamps, of course allowing that the quantity
counted will represent different amounts, according to what unit the meter is set
for. The resistance n, x, must always be made very considerable, some thousands
of times x;
thus the meter can be made to give the product of the number of lamps
that have been burning in any circuit by the time they have been burning.
Differential coils may be employed in place of a Wheatstone's bridge.
Having now described the nature of my said Invention and in what manner the
same is to be performed, I declare that I claim as my "Improvements in Electric-
current Meters,"-
First. Obtaining a variable rotation of a shaft which works a counting apparatus
from another shaft rotating at a constant angular velocity by means of two cones
and an intermediate wheel, the angle which the axis of this wheel makes with the
axes of the two cones, and therefore the speed of the shaft which works the counting
apparatus, being varied by mechanical motion derived from variations in the current
to be measured, substantially as herein before described.
Second. The combination with a counting apparatus and with the arrangement
of cones and intermediate wheel, before described, of an electric motor and a
dynamometer by which the angle of the said wheel is varied according to
variations in the current, substantially as and for the purpose hereinbefore
described.
Third. The combination with a counting apparatus and with the arrangement of
cones and intermediate wheel, before described, of a Wheatstone's bridge or
differential coils and a rheostat, substantially as and for the purpose hereinbefore
described.
In witness whereof, I, the said Charles Ashley Carus-Wilson, have hereunto
set my hand and seal, this Twenty ninth day of April, One thousand eight
hundred and eighty two.
CHARLES ASHLEY CARUS-WILSON. (L.S.)