Improvements in Electricity Meters.
Year: 1891

page_text: Improvements in Electricity Meters.
I GEORGE HOOKHAм of Nos. 7 and 8 New Bartholomew Street Birmingham in
the County of Warwick Manufacturer do hereby declare the nature of this invention
to be as follows :-
My improvements relate to that class of electricity meters which consist essentially
of a motor whose driving moment is proportional either to the current or the
electrical energy of the supply doing work against Foucault currents generated in a
metallic disc or other figure of revolution rotating in a constant magnetic field.
I
As is described in the Complete Specifications of two patents granted to me dated
respectively March 21. 1887 No. 4225 and December 20th 1887 No. 17502 the disc
cylinder or other figure of revolution may itself form the armature of the motor so
that the armature and the brake are combined in one moving piece. In the arrange-
ments shown in these specifications however the armature spindle is horizontal.
have found that when these simple forms of armature are used it is better totally to
submerge them in mercury. The surface of the mercury being broken by the
rotating part only at the spindle. When this is the arrangement I make the spindle
vertical and for facility in putting it in and lifting it out of the vessel containing the
mercury I prefer to make the armature a hollow cylinder.
The annular trough in
which the armature rotates is formed partly by the pole-pieces between which it
rotates but for the most part of non-conducting material such for example as wood or
ebonite. In order to economise magnetising force I reduce the cross section of the
pole pieces so that as a rule they do not subtend an angle of more than 90 degrees at
the axis of the spindle; and I similarly concentrate the current by so introducing
and carrying it off that the greater part of it flows between the pole pieces. The
upper and lower edges of the cylinder are amalgamated the rest being preferably
insulated by varnish or the like. The current enters the mercury at a point close to
one of these edges; divides itself in a constant ratio between the mercury and the
cylinder and passes out at a point close to the upper edge. This reduction of the
pole-piece area sufficient clearance being allowed in the case of permanent magnets
(which I construct according to the rule and proportions laid down in my before
mentioned specifications) involves great length in the magnets and I accordingly
construct the instrument as follows. I take two upright columns of permanent
magnets each column being say from 8 inches to 10 inches long and yoke them by
iron at the top (as in the well-known Edison dynamo); The lower ends carry the pole
pieces and are mounted upon a non-conducting bed plate. The poles closely approach
one another leaving a space such as above referred to in which the cylindrical

page_text: armature is to rotate. The pole pieces are turned down from the arms carrying them
and the inner one is cranked in such a way that both can be let bodily into a block
of non-conducting material in which the rest of the annular space for the armature is
formed. The lower end of the spindle of the armature rotates in a hollow conical
bearing formed in the inner pole piece; the upper end of the said spindle working
in a fixed bearing which may be carried by a bracket attached to the yoke. The
hollow cylinder and its spindle are made so buoyant that the lower end of the spindle
barely touches its bearing while only the upper part of the spindle protrudes above
or cuts the surface of the mercury. The spindle is connected with counting gear and
I prefer a form of gear in which a pin or projection on the spindle moves a wheel or
ratchet one tooth in a revolution of the spindle which is except when moving through
this angle of contact entirely free from such contact.
In the arrangement described electro-magnets may be substituted for permanent
magnets in which case it is necessary that they should be practically saturated;
which is best done by reducing the cross section of the core preferably at a point
between the coils and the pole piece for say a linear centimetre so that at this point
the iron is saturated while the rest of the core is far removed from saturation. If
however the intensity of the field varies with the electro motive force (or if the
currents are alternating) then it is necessary that the brake should be separate from
the armature; and for direct currents I make the pole pieces the one a cylinder
within the other a hollow cylinder so as to avoid the generation of Foucault currents.
In all cases the pole pieces are carefully insulated from the mercury.
If the brake is external to the mercury it is not necessary that the immersed part
should convey current; the said immersed part need only be carried round by the
rotation of the mercury which then conveys the whole current. The immersed part
in this case may be non-metallic and may have the form of any figure of revolution
smooth grooved or pierced with tubular channels or it may consist of vanes or blades
which may either be metallic or non-metallic and may or may not in the former case
convey current.
The solid rotating part is in all cases totally immersed in mercury.
The vanes should pass the pole pieces with small clearance in order to give
approximately positive driving and the poles should subtend an angle rather greater
than that contained by any two adjacent arms or vanes. For an external brake arms
may be carried froin the main magnet thus diverting part of the field. In the case
of electro magnets the field of the brake must be made by magnets which are
practically saturated. If the current in the magnets is alternating I use separate
steel magnets for the brake.
The electrical brake may be replaced by vanes moving in air or in a liquid. These
vanes are made flexible or cabable of turning on their supports under control of
springs or of gravity so that as the speed increases a smaller effective surface is
presented to the air or liquid.
The temperature error may be corrected by making the magnets or one of the
magnets of the brake capable of turning or moving under the influence of the
expansion of air oi metals so that with a rise of temperature the Foucault currents
are relatively increased.
If it is found that dirt tends to accumulate at the point where the mercury cuts the
spindle this may be obviated by amalgamating the spindle (or a ring fixed upon it)
at this part.
For larger installations part of the current may be shunted and in this case it is
well to use German silver or platinoid for the shunt as a partial temperature correction
is thus obtained. But in other cases I prefer to an external shunt so to introduce the
current that its line of greatest intensity does not coincide with the central line
of the poles and may even be outside the poles. When I do this I prefer to introduce
the current at two points symmetrically disposed with respect to the pole pieces and
carry the said current off at points also symmetrically disposed.
When I use a conducting armature I prefer to make it of copper with rings or strips
of German silver platinoid or cupro-nickel brazed to the copper along the lines where
the current enters and leaves the armature the whole being first nickel plated the

page_text: nickel scraped off at these lines and the German silver platinoid or cupro-nickel
amalgamated. This is easily performed with sodium amalgam.
nickel scraped off at these lines and the German silver platinoid or cupro-nickel
amalgamated. This is easily performed with sodium amalgam.
Dated the 6th day of March 1891.
W. T. WHITEMAN
Agent for the Applicant.
I GEORGE HOOKHAM of Nos. 7 and 8 New Bartholomew Street, Birmingham in
the County of Warwick Manufacturer, do hereby declare the nature of my 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 relate to that class of electricity meters which consist essentially
of a motor whose driving moment is proportional either to the current or the elec-
trical energy of the supply doing work against Foucault currents generated in a
metallic disc or other figure of revolution, rotating in a constant magnetic field as
described in the Complete Specifications of three patents granted to me dated respec-
tively March 21, 1887 No. 4225 and December 20th 1887 No. 17502 and January 1st
1891 No. 40.
The disc, cylinder or other figure of revolution may itself form the armature of
the motor so that the armature and the brake are combined in one moving piece. In
the arrangements shown in these specifications however, the armature spindle is
horizontal. I have found that when these simple forms of armature are used it is
better totally to submerge them in mercury, the surface of the mercury being only
broken by the spindle. When this is the arrangement I make the spindle vertical
and for facility in putting it in and lifting it out of the vessel containing the mercury
I prefer to make the armature of the figure of a hollow cylinder. The annular trough in
which the armature rotates is formed partly by the pole-pieces between which it rotates,
but for the most part of non-conducting material such for example as wood or ebonite.
In order to economize magnetising force I reduce the cross section of the pole pieces
so that as a rule they do not subtend an angle of more than 90 degrees at the axis of
the spindle that is at the centre of the annular trough in which the armature rotates
and I similarly concentrate the current by so introducing and carrying it off that the
greater part of it flows between the pole-pieces. The upper and lower edges of
the cylinder are amalgamated, the rest being preferably insulated by varnish or the
like. The current enters the mercury at a point close to one of these edges, divides
itself in a constant ratio between the mercury and the cylinder and passes out at a
point close to the upper edge. The reduction referred to of the pole piece area
(sufficient clearance being allowed) in the case of perinanent magnets, (which I con-
struct according to the rule and proportions laid down in my before mentioned
specifications) involves great length in the magnets and I accordingly construct the
instrument as follows; I take two upright columns of permanent magnets, each
column being, say, from 8 inches to 10 inches long and yoke them by iron at the top
(as in the well known Edison dynam³); the lower ends carry the pole pieces and are
mounted upon a non-conducting bed plate. The poles closely approach one another,
leaving a space such as above referred to in which the cylindrical armature is to
rotate. The pole pieces are turned down from the arms carrying them and the
inner one is cranked in such a way that both can be let bodily into a block of non-
conducting material in which the rest of the annular space for the armature is formed.
The lower end of the spindle of the armature rotates in a hollow conical bearing
formed in the inuer pole piece, the upper end of the said spindle working in a fixed
bearing which may be carried by a bracket attached to the yoke. The hollow cylinder
and its spindle are inade so buoyant that the lower end of the spindle barely touches

page_text: its bearing, while only the upper part of the spindle protudes above or cuts the surface
of the mercury. The spindle is connected with counting gear, and I prefer a form of
gear in which a pin or projection on the spindle noves a wheel or ratchet one tooth
in a rotation of the spindle, which is except when moving through this angle of contact
entirely free from such contact.
If the brake is
In the arrangement described electromagnets may be substituted for permanent
magnets, in which case it is necessary that they should be practically saturated,
which is best done by reducing the cross section of the core, preferably at a point
between the coils and the pole piece for, say, a linear centimetre so that at this point
the iron is saturated while the rest of the core is far removed from saturation. If
however the intensity of the field varies with the electro motive force (or if the
currents are alternating) then it is necessary that the brake should be separate from
the armature and for direct currents I make the pole pieces, the one a cylinder
within the other, a hollow cylinder, so as to avoid the generation of Foucault currents.
In all cases the pole-pieces are carefully insulated from the mercury.
external to the mercury it is not necessary that the immersed part should convey
current; the said immersed part need only be carried round by the rotation of the
The immersed part in this case
mercury which then conveys the whole current.
may be non-metallic and inay have the form of any figure of revolution, smooth,
grooved or pierced with tubular channels; or it may consist of arms or blades which
may either be metallic or non-metallic and may or may not in the former case convey
current. The solid rotating part is in all cases totally immersed in mercury.
arms or blade should pass the pole pieces with small clearance in order to give approxi-
mately positive driving and the poles should subtend an angle rather greater than
that contained by any two adjacent arms or blades.
The
The electrical brake may be replaced by vanes moving in air or in a liquid. These
vanes are made either flexible or capable of turning on their supports under control
of springs or of gravity so that as the speed increases a smaller effective surface is
presented to the air or liquid.
If it is found that dirt tends to accumulate at the point where the mercury cuts the
spindle this may be obviated by amalgamating the spindle (or a ring fixed upon it)
at this part.
For large installations part of the current may be shunted and in this case it is
well to use German silver or platinoid for the shunt as a partial temperature
correction is thus obtained. But instead of an external shunt I prefer so to introduce
the current that its line of greatest intensity does not coincide with the central line
When I do this I prefer to
of the poles and may even lie outside the poles.
introduce the current at two points symmetrically disposed with respect to the pole
pieces and carry the said current off at points also symmetrically disposed.
When I use a conducting armature I prefer to make it of copper with rings or
strips of German silver, platinoid or cupro-nickel brazed to the copper along the lines
where the current enters and leaves the armature, the whole being first nickel plated,
the nickel scraped off at these lines and the German silver, platinoid or cupro-nickel
amalgamated. Thus is easily performed with sodium amalgain
I will now proceed to describe with reference to the accompanying drawings the
manner in which my invention is to be performed.
Figure 1 represents in elevation Figure 2 in plan of underside with some of the
parts removed Figure 3 in elevation partly in section and Figure 4 an elevation
partly in section in a vertical plane at right angles to Figure 1 an electricity meter
constructed according to my invention. Figure 5 represents a portion of the same
drawn to a larger scale as hereinafter described.
The same letters of reference indicate the same parts in the several figures of the
drawings.
a a are permanent magnetic bars connected by the iron yoke b. The lower ends
The magnets & a are mounted on a
of these magnets carry the pole pieces c c².
bed plate d made of a non-magnetic metal. The pole pieces are formed as best seen
in Figures 2 and 3. The armature consists of a hollow vertical metallic cylinder

page_text: preferably of copper and rotating on the vertical spindle f. The armature e is situated
in a trough g in the base of the instrument which trough is filled with mercury
as best seen in Figure 4. The armature e is supported on the pole piece c² by a
pointed pin on the latter taking into a depression in the axis of the arma-
ture and the top of the spindle f of the said armature e has a depression in which a
pin h carried by the support i takes, the said armature working between the pole
piece cand the pink with little friction. By reference to Figures 2 and 3 it will
be seen that the ends of the pole pieces c care situated very near to each other
and that a part of the hollow cylindrical armature e is situated in the narrow
space between them. The space between the pole-pieces c, c² in which the armature
rotates is a strong and practically constant magnetic fluid.
land in are the conductors by which the current to be metered is passed through
the apparatus the said conductors terminating as represented near the top and bottom
respectively of the armature c. The current consequently passes mainly in a vertical
direction through that part of the armature e which is situated in the magnetic field
between the pole pieces c, c² and rotation is given to the armature carrying the current
by the action of the magnetism as is well understood. In order to prevent any
portion of the current passing through the magnets it is necessary to insulate the
pole pieces c, e from the mercury this I effect by varnishing or otherwise covering
with an insulating material all those parts of the pole pieces c, c² in contact with
the mercury.
The rotations of the spindle fare communicated to the counting or recording
mechanism by means of a pin or projection j on the said spindle f engaging with
the teeth of the first toothed wheel of the counting mechanism (see Figure 5)
the said wheel & being moved through a space of one tooth on each rotation of the
armature spindle f. By the arrangement of gearing described friction between the
wheel and spindle f takes place only through a small angle the spindle being quite
free from the wheel during the greater part of each rotation.
In the arrangement of my invention represented in Figures 1, 2, 3 and 4 electro-
magnets may be employed in place of the permanent inagnets described. When
however electro magnets are employed I make a depression or partial cutting through
of one or both pole pieces as represented in dotted lines at x in Figure 3 so as to
diminish the sectional area of the pole piece or pieces at the said parts. The
reduced area of the pole piece or pieces at the part x is so small that the said part or
parts is or are saturated by the lowest strength of the electro magnet.
When electro-magnets are used as represented in the arrangement Figures 6 and 7
instead of permanent magnets the intensity of the field may vary with the electro
motive force in which case, as well as when the currents are alternating, the brake
should be separate from the armature. This arrangement of my invention is repre-
sented in Figures 6, 7, 8 and 9; Figures 6 and 7 representing respectively an
elevation partly in section and a plan partly in horizontal section and Figures 8 and 9
representing parts of the same detached as hereinafter described.
I have represented the armature in the Figures 6 and 7 as a hollow cylinder
similar to the armature in Figures 1, 2, 3 and 4 and in Figure 8 I have represented
an armature composed of arms or blades n n connected at top and equidistantly
arranged with respect to the axis of rotation and with respect to each other; the said
armature may however have any figure of revolution given to it. Instead of making
the armature of metal it may be made of non-metallic material such for example as
vulcanite. In this case I prefer to make it of the figure represented in Figure 8 that
is having a series of radial arms or blades n n. This non-metallic armature is carried
round or made to rotate by the annular trough of mercury in which it is immersed.
The said mercury is in this case the only conductor in the magnetic field and is con-
sequently in a state of rapid rotation. The arms or blades n n rotate between the
insulated pole pieces c³, cof the magnet a, a one of the said pole pieces being
formed into a hollow cylinder in which the other pole piece c'having the figure of a
solid cylinder is concentrically situated.
I have represented the brake as being composed of vanes p q connected to the

page_text: air.
spindle fat p², p, q, q², the rotary motion of the said vanes p, q is retarded by the
The vanes are capable of turning on their supports p², q² under the control of
the springs r, (see Figure 9) so that the rate of rotation of the armature is
approximately proportional to the current to be metered. The strength of the springe
for bringing about this approximate result is determined by trial.
Having now particularly described and ascertained the nature of my invention
and in what manner the same is to be performed I declare that I claim as
my invention of "Improvements in electricity meters
FirstIn an electricity meter netuated by an-electro--motor-and-in--which-the
armature-is-a-dise; cylinder-or other figure of revolution-or-which-has-an-electrie
brake, the armature-being-immersed-in-mereury, the obtaining of the field for the
armature--or--the-brake-by--permanent--magnets proportioned-as-described so-as
to-ensure-constancy- substantially-as hereinbefore-described-and-illustrated-in-the
accompanying-drawings.
First
Secondly In an electricity meter actuated by an electro-motor, the
actuating of the counting gear by a pin or projection on the spindle of the motor in
such a manner that the motor is unconnected with the counter during the greater
part of each rotation of the counter substantially as hereinbefore described and
illustrated in the accompanying drawings.
Secondly: Thirdly In an electricity meter actuated by an electro motor,the field
being obtained by an electro-magnet, the obtaining of constancy in the said field by
reducing the cross section of a pole piece substantially as hereinbefore described and
illustrated in the accompanying drawings.
Fourthly In an electricity meter-netnated-by-an-electro-motor-and--in which
the armature--is--a--dise,-eylinder-or-other figure of revolution, the combination
with-the-motor-of vanes-or fans-moving-in-air-or-in-a-liquid-the-resistance-of-such
vanes-or-fans-being-relatively lessened as the speed increases, in such a manner-that
approximately the-resistance-inerenses-direetly-as-the-speed substantially-as-herein-
before-described-and illustrated in the accompanying drawings.
Thirdly-Fifthly. The composite disc, cylinder or other figure of revolution
consisting of copper with edges of German silver or other metal or alloy not readily
dissolved in mercury substantially as herein before described.
the 1th day of January 1892
W. T. WHITEMAN
Agent for the Applicant.