Improvements in Motor Electric Meters parts of which are applicable to Motors and Dynamos generally.
Year: 1899

page_text: Date of Application, 30th June, 1899
Complete Specification Left, 30th Mar., 1900 - Accepted, 30th June, 1900
PROVISIONAL SPECIFICATION.
Improvements in Motor Electric Meters parts of which are
applicable to Motors and Dynamos generally.
We, EVERSHED AND VIGNOLES, LIMITED, of Woodfield Works, Harrow Road,
London, W., Electrical Engineers, and SYDNEY EVERSHED of the same address,
Electrical Engineer do hereby declare the nature of this invention to be as
follows:-
This invention relates to electric supply meters of the motor type and refers
more particularly to meters in which the motor has its rotating armature in shunt
to the work and its field coils in series with the work, and its speed controlled
by a Foucault current brake.
The object of our invention is to improve the accuracy and trustworthiness of
such meters, firstly by diminishing the mechanical friction of the commutator,
secondly by neutralising the effect of such friction as may be unavoidable, and
thirdly by providing means for ascertaining the strength of the brake magnets
at any time by inspection.
.
According to our invention the usual flat commutator brushes having sliding
friction upon the commutator are dispensed with and we use instead rotary
brushes conveniently in the form of rollers discs or cups of larger diameter than
the commutator and making essentially elastic rolling contact with the com-
mutator. Two discs or rollers may be mounted on axles one on each side of
the commutator and they serve to lead the current to and from the motor armature.
Connection between the discs and the source of current may be made through
the bearings of the disc axles or by means of light metallic brushes or springs
rubbing on the axles. In order to ensure perfect contact between commutator
and disc or roller brush we give to one or the other a certain amount of elasticity
in a radial direction. For example, our commutator may have its segments
formed by a number of fine wires fixed to an insulating collet on the motor axle
so that one end of each wire is rigidly fastened to the collet and the other
end is entirely free from restraint. The discs are caused to roll on the com-
mutator wires with their edges as close as may be to the free ends of the wires,
so that as the commutator revolves, the wires are able to elastically adapt them-
selves to any irregularities in the peripheries of the discs. The elastic segments
of our commutator are preferably parallel with the axle but we may modify the
arrangement by having the wires radial to the motor axle and arranging the
axles of the discs or roller brushes at right angles with the motor axle.
Instead of an elastic commutator we may use a rigid commutator built up in
the usual way by segments fixed in insulating collets or made as described in the
specification of Patent No. 9127 of 1897 and use elastic discs therewith.
Such discs may be made by stamping them out of thin sheet metal and mount-
ing them so that their axles are inclined at an angle to the motor axle. They
will then bear elastically on the commutator. The necessary elasticity may
also he obtained by using a bell shaped metal cup as the roller and mounting
it so that its lip rolls on the commutator. We may modify our invention in

page_text: several ways so long as the necessary elasticity is secured in either the commutator
or the rollers.
The small amount of friction which is unavoidable in a motor meter even
where our elastic rollers and commutator are used, may, according to our inven-
tion, be compensated for by a permanent magnet, so placed with regard to
the motor armature as to provide a constant turning moment equal in value
to the resisting moment of friction. Instead of a permanent magnet we may
for the same purpose use a rod of iron placed in the magnetic. field of the main
coils of the meter so that the induction from the iron rod will add to the driving
moment on the armature. The residual magnetism of the iron rod may be made
to compensate for friction in precisely the same manner as a permanent magnet.
In another modification we may use an iron rod having one end attached to
one pole of the brake magnets and the other adjacent to the motor armature so
that the magnetic induction which the iron rod draws from the brake magnets
serves to provide the required driving moment to compensate for friction.
The accuracy of a motor meter depends on the constancy of the controlling
brake and where this brake is of the Foucault current type in which permanent
or electro-magnets act on a metallic conductor we provide a magnetic gauge to
indicate the strength of the said maonets by means of an index on the meter
dial. Our gauge may be any simple form of magnetometer, preferably of the
type in which a piece of soft iron is attached to a spindle and placed so as to
be attracted by the brake magnets. The attraction being opposed by a spring
or by a weight on an arm attached to the said spindle, the motion of the iron is
controlled and the spindle rotates until equilibrium is established. An index
is fixed on the spindle adapted to range over a scale on the meter dial. The
position of the index being noted when the brake magnets have their normal
strength any change in their strength is at once detected and by providing a properly
calibrated scale the percentage change in the rate of the meter may be read off
without calculation.
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201
FELL & JAMES,
1, Queen Victoria Street, London, E.C.,
Agents for the Applicants.
Improvements in Motor Electric Meters parts of which are
applicable to Motors and Dynamos generally.
We, EVERSHED AND VIGNOLES, LIMITED, of Woodfield Works, Harrow Road,
London, W., Electrical Engineers, and SYDNEY EVERSHED of the same address,
Electrical Engineer, 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: ---
This invention relates to electric supply meters of the motor type and refers
more particularly to meters in which the motor has its rotating armature in shunt
to the work and its field coils in series with the work, and its speed controlled
by a Foucault current brake, but the elastic commutators and roller brushes are
cbviously applicable to motors and dynamos generally.
The object of our invention is to improve the accuracy and trustworthiness of
such meters, firstly by diminishing the mechanical friction of the commutator,
and secondly. by providing means for ascertaining the strength of the brake.
magnets at any time by inspection, and to improve the efficiency of motors or

page_text: dynamos generally by the adaptation of almost frictionless & elastic commutators
& roller brushes.
According to our invention the usual flat commutator brushes having sliding
friction upon the commutator are dispensed with and we use instead rotary
brushes conveniently in the form of rollers discs or cups of larger diameter than
the commutator and making essentially elastic rolling contact with the com-
mutator. Two dises or rollers may be mounted on axles one on each side of
the commutator and they serve to lead the current to and from the motor armature.
Connection between the discs and the source of current may be made through
the bearings of the disc axles or by means of light metallic brushes or springs
rubbing on the axles. In order to ensure perfect contact between commutator
and disc or roller brush we give to one or the other a certain amount of elasticity
in a radial direction. For example our commutator may have its segments
formed by a number of fine wires fixed to an insulating collet on the motor axle
so that one end of each wire is rigidly fastened to the collet and the other
end is entirely free from restraint. The discs are caused to roll on the com-
mutator wires with their edges as close as may be to the free ends of the wires,
so that as the commutator revolves, the wires are able to elastically adapt them-
selves to any irregularities in the peripheries of the discs. The elastic segments
of our commutator are preferably parallel with the axle but we may modify the
arrangement by having the wires radial to the motor axle and arranging the
axles of the discs or roller brushes at right angles with the motor axle.
-
Instead of an elastic commutator we may use a rigid commutator built up in
the usual way by segments fixed in insulating collets or made as described in the
specification of Patent No. 9127 of 1897 and use elastic discs therewith.
The necessary elasticity may be obtained by using a bell shaped metal cup
as the roller and mounting it so that its lip rolls on the commutator. We may
modify our invention in several ways so long as the necessary elasticity is secured
in either the contact strips of the commutator or in the roller as a consequence
of the inherent clasticity of the disc or roller.
The small amount of friction which is unavoidable in a motor meter even where
our elastic rollers and commutator are used, may, by means already known in
principle, be compensated for by a permanent magnet, so placed with regard to
the motor armature as to provide a constant turning moment equal in value
to the resisting moment of friction. Instead of a permanent magnet we may
for the same purpose use a rod of iron placed in the magnetic field of the main
coils of the meter so that the induction from the iron rod will add to the driving
moment on the armature. The residual magnetism of the iron rod may be made
to compensate for friction in precisely the same manner as a permanent magnet.
In another modification we may use an iron rod having one end attached to
one pole of the brake magnets and the other adjacent to the motor armature so
that the magnetic induction which the iron rod draws from the brake magnets
serves to provide the required driving moment to compensate for friction.
The accuracy of a motor meter depends on the constancy of the controlling
brake and where this brake is of the Foucault current type in which permanent
or electro-magnets act on a metallic conductor we provide a magnetic gauge to
indicate the strength of the said magnets by means of an index on the meter
dial. Our gauge may be any simple form of magnetometer, preferably of the
type in which a piece of soft iron is attached to a spindle and placed so as to
be attracted by the brake magnets. The attraction being opposed by a spring
or by a weight on an arm attached to the said spindle, the motion of the iron is
controlled and the spindle rotates until equilibrium is established. An index
is fixed on the spindle adapted to range over a scale on the meter dial. The
position of the index being noted when the brake magnets have their normal
strength any change in their strength is at once detected and by providing a properly
calibrated scale the percentage change in the rate of the meter may be read off
without calculation.

page_text: And in order that our invention may be the better understood we will describe
it with reference to the accompanying drawings of which Fig. 1 shows our
preferable form of commutator wires acting as segments and metallic rollers.
Figure 2 shows a rigid commutator with cup shaped elastic rollers to act as
brushes. Figure 3 shows an elastic commutator with the commutator wires spread
horizontally. Figures 4 and 5 show a simple form of magnetometer applied for
the purpose of giving a continuous indication of the strength of the brake magnets
employed in a Foucault brake, and known means for neutralizing residual friction.
In Figure 1 D is a collet of insulating material fixed upon the meter axle B
having an armature A. The commutator wires C are fixed in holes in the collet
and hang vertically downwards, the lower ends being free to move.
The rollers EE are fixed on vertical axles e e pivotted in frameworks a a
to which the wires b (which serve to carry the armature current) are attached.
The rollers are preferably made of thin sheet metal spun over on the edge as
shown. Their position is adjusted so that they press fightly against the com-
mutator at or near the free ends of the wires.
The commutator wires are made of platinum or other non-oxidisable metal,
preferably of iridio-platinum which has the advantage of being very strong and
elastic. The rollers may be made of a non-oxidisable metal but we prefer to make
them of brass or other cheap and light metal and coat or plate the rolling edge
with a thin film of platinum gold or other suitable non-oxidisable metal. In
order to ensure good contact between each roller and its framework we prefer
to make the lower pivot of the roller axle e of iridio-platinum, the step bearing
for the pivot being a little plate of iridio-platinum c.
Figure 2 shows rollers E of thin sheet metal in the form of a cup: this form
has the advantage of giving the necessary elastic contact between the rollers
and a rigid commutator C¹ by reason of the elastic form of the cup roller.
Figure 3 shows the commutator strips as elastic wires C² arranged radially
with contact rollers E having horizontal axes making contact with the under faces
of the radial wires C2. The axles of these rollers E may be arranged obliquely if
desired.
In Figure 2 we show a commutator built up in the ordinary manner but we
may employ commutators made as described in the specification of Patent No. 9127
of 1897 or we may employ commutators made as described with reference to
Figure 1, and the elasticity being provided in this case by the rollers, the com-
mutator wires shown in Figure 1 may in such cases as shown in Figure 2 be
made thicker and shorter. as it is not essential that they should be elastic.
It is to be understood that in applying our invention we prefer to use non-
oxidisable metals to form the elastic contacts.
In Figures 4 and 5 we show a simple form of soft iron magnetometer_applied
for the purpose of indicating the strength of Foucault brake magnets.
HH are
two magnets between whose poles N. S. the brake conductor G rotates upon the
meter axle B. The magnetometer is mounted immediately beneath the brake
conductor and consists of an axle N pivotted in a frame V upon which axle are
fixed two crank arms which serve to carry two rods of soft iron R. These rods
are attracted upwards by the brake magnets and the attraction is balanced by an
adjustable weight W. A pointer P is fixed to the axle and its end is bent round
so that it may traverse a short scale Q printed upon the dial of the meter train T.
When the meter has been standardised and is registering correctly the weight W
is adjusted until the magnetometer index stands at the central or fiducial mark
of the scale. If in course of time the magnet becomes weaker the meter will
run too fast; at the same time the attraction of the magnets upon the soft iron
rods will diminish and the weakening of the magnets will be indicated on the
magnetometer dial by the index moving upwards in the direction marked "fast."
The magnetometer scale may conveniently be one showing the percentage by
which the speed of the meter has been increased owing to the weakening of the
magnets the scale being calibrated by experiment for which purpose the

page_text: meter may be made to run too fast by diverting more or less of the magnetic
induction from the gap in which the brake conductor moves by means of a
piece of soft iron placed across the limbs of the magnet. By this means several
points on the magnetometer scale may be determined and the remainder inter-
polated. A magnet which has been improperly treated during the ageing process
will sometimes increase in strength: it is therefore desirable to provide a scale
below the fiducial mark showing the percentage by which the meter is running
slow. This part of the scale may be calibrated by putting a few turns of insu-
lated wire round each of the magnets and passing a current through the coils
so formed in such a direction as to increase the magnetism. A temporary increase
of 5 or 10 per cent. in the braking power of the magnets may be obtained in this
way without any permanent change in their strength. The same means may
be employed as an alternative for calibrating the scale above the fiducial point
the current being of course reversed in order to temporarily decrease the
magnetism.
We have described a form of magnetometer which we find well adapted for
the purpose of our invention but we may employ any known form of magnetometer
which is adapted for the purpose in view, although we prefer to employ the
simple forms in which pieces of soft iron are either attracted or rotated more or
less according to the strength of the magnets near which they are placed.
In Fig. 4, L shows a magnetic bar mounted on a standard M compensating
in a known manner for the residual friction of the meter.
Having now particularly described and ascertained the nature of this
invention and in what manner the same is to be performed, we declare that what
we claim is :-
1st. In an electric motor-meter, motor or dynamo, an elastic commutator formed
from resilient wires fixed at one end and free at the other, placed parallel with
or radially to the armature axis, in combination with freely pivotted wheels or
rollers, rolling in elastic contact with the free ends of said commutator segments
as brushes, substantially as and for the purposes described.
2nd. In an electric motor-meter, motor, or dynamo, an elastic freely pivotted
rotary brush in the form of a bowl, in combination with a commutator of rigid
sections, the bowl being adapted to make elastic rolling contact by its edge upon
the said commutator, substantially as and for the purposes described.
3rd. The combination with the brake magnets of an electric motor-meter of a
magnetometer, adapted to give a continuous and visible indication of the strength
of the said brake magnets, substantially as and for the purposes described.
Dated this 30th day of March 1900.
FELL & JAMES,
1, Queen Victoria Street, London, E.C.,
Agents for the Applicants.