Improved Magnetic Means for Resisting End Thrust in Shafts or Spindles in Electric Meters and other Apparatus.
Year: 1897

page_text: Date of Application, 24th Aug., 1897-Accepted, 20th Nov., 1897
COMPLETE SPECIFICATION.
Improved Magnetic Means for Resisting End Thrust in Shafts or
Spindles in Electric Meters and other Apparatus.
We, WILLIAM STANLEY and FREDERICK DARLINGTON, both of Pittsfield, Massa-
chusetts U.S.A., Electrical Engineers, do hereby declare the nature of this inven-
tion and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement:-
Our invention relates to revolving shafts and means for supporting the same in
journals, and has for its object to so support the shaft that the end thrust shall be
balanced or opposed under normal conditions, being resisted by a magnetic action
hereinafter described.
We
Briefly, our invention may be termed a magnetically suspended shaft.
have found it particularly useful in connection with meters where the shaft has
longitudinal vibration. In many mechanical appliances such as meters, the shaft
carrying the revolving armature is mounted upon jewels to reduce the friction.
If, however, there is a vibratory thrust against such jewels, they are in a com-
paratively short time worn, causing injurious friction. In making our invention,
we have solved the problem of how to avoid this destruction of the jewels.
We have illustrated our invention in a meter in which there is an end' thrust
on a continuously revolving shaft, and anticipate that it may be of great utility
in other applications as well.
Our invention involves a practical application of a well-known scientific fact
that a coil of wire, when energized, forms a magnetic system which will support
an iron core within its center. In practice, instead of a coil, we preferably use
a magnetic system consisting of a permanent magnet or magnets which will pro-
duce substantially the same magnetic effects as an energized coil.
The following is a description of our invention, reference being had to the
accompanying drawings, in which
Fig. 1, is a front elevation of a meter embodying our invention, partly in section.
Fig. 2, is a side elevation of the same partly in section.
Fig. 3 is a detail view of one of the parts.
Fig. 4, shows a modification.
In the apparatus shown M M are two permanent magnets, whose like poles are
opposed to one another and connected by pole pieces or yokes N N¹ having circular
openings 00, which serve to receive and radiate the resultant magnetic flux to
the armature A which constitutes the shaft to be supported.
The magnetic
system is supported by a suitable arm H. The armature or shaft A consists of a
round symmetrical stem of magnetic material with one or more projecting
rings R R and R R at each end as shown and supports the movable portion of
the instrument, which in the present case is a rotating disk B of an induction
meter.
At each end of the shaft A is a staff or bearing C with the axes of which the
magnetic armature A and the rotating disk B are concentric. These bearings C
are highly polished, and are guided in ring journals preferably jeweled D D¹
which are supported from the pole pieces N N by brackets E E. The

page_text: journals D D are concentric with the orifices 0 0' in the pole pieces N N and
serve to keep the shaft or armature A in the center of the said orifices 0 0'; but
in no way tend to sustain the weight of the armature and moving parts.
In the interior of each of the orifices 0 0 of the pole pieces N N are rings R² R³
corresponding to the rings on the shaft A. These are turned out so as to be con-
centric with the respective orifices and the axis of shaft A within the same.
The operation of the device is as follows: The magnetic armature or shaft A
being placed within the pole pieces of the magnetic system consisting of the
magnets M. M' and the pole pieces N N and properly centered by the journals D D',
receives a flux of constant density from all sides of the adjacent interior rings R³ R³
and is thereby attracted in a general resultant vertical direction. This attraction
with magnets of suitable strength, is sufficient to entirely counterbalance the force
of gravity and suspend the armature or shaft A, and the disk B attached thereto,
so as to make it free from any visible means of preventing longitudinal movement.
Such a device when constructed as shown and above described, has an extremely
small resistance to rotation. It is permanent in that there is practically no
liability to the destruction of its journals, and has a fixed co-efficient of friction.
It is therefore a very desirable means of support in all instruments of precision.
such as meters and measuring instruments.
In the disk meter, shown, the shaft A is connected by a train of wheels to the
recording mechanism. The disk B mounted thereon is acted upon by coils F F¹
which produce magnetic fluxes of different phase acting upon the disk B to produce
a movement of rotation in the well-known manner. The fluxes are approximately
at right angles to the plane of the disk 1, and cause an endwise vibration of the
shaft A to which it is attached. If this shaft bore endwise upon the jewels, this
vibration would be sufficient to pound the jewels to pieces in a comparatively
short time. With our invention there is no endwise bearing, and any end thrust
or jar is taken up by the magnetic suspension heretofore described.
We have found that the best results are obtained when the device is constructed
so that there is a definite position of the shaft or armature in which the magnetic
attraction is maximum. This is attained by the rings R R and R2 R on the
shaft A and pole pieces N N¹ respectively, which are concentric with the axis of
the shaft A and the orifices 00. In this construction the armature or shaft A is
attracted into the position in which the projecting rings R R on the shaft A are
in close proximity to the rings R2 R3 in the pole pieces N N', the tendency always
being to assume the position in the magnetic circuit, of minimum magnetic
reluctance. In the construction shown, the magnetic field, about the armature
is always as symmetrical as possible. As a result there are no currents induced in
the shaft A or its rings R R and there is no uncounterbalanced side pull causing
a side thrust against the journals D D¹.
As shown the magnets M M¹ are horseshoe in form. The movement of the disk
is controlled as may be necessary by a retarding device. In case the device is to
be used as a current meter a fan may be used. If it is to be connected up as a
Watt meter, a magnetic brake is a suitable drag. If it is desired to use a magnetic
brake, we may make the magnets M. M¹ each in two parts terminating on opposite
sides of the rotating disk, as shown in dotted lines, Fig. 1 and also in Fig. 4. In
such case the magnets M M serve to suspend the shaft A and also to produce a
flux acting as a magnetic brake. In such case, we support the lower portions of
the magnets M M independently by blocks as shown.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that what
we consider novel and desire to claim is:-
1. The combination of a rotatable shaft of magnetic material and a magnetic
system producing a magnetic flux symmetrical thereto and in supporting
relation thereto, substantially as described.
2. The combination of a rotatable shaft and bearings for the same, said shaft

page_text: having a capacity of limited longitudinal movement, and means for producing a
magnetic flux in suspending relation to said shaft and symmetrical thereto, sub-
stantially as described.
3. The combination of a rotatable shaft having projecting rings of magnetic
material concentric with its axis of revolution and a magnetic system supplying
magnetic flux symmetrical with said rings, substantially as described.
4. The combination of a rotatable shaft and bearings for the same permitting
of longitudinal movement and a permanent magnet supplying a magnetic flux
symmetrical with said shaft and acting upon said shaft in opposition to the force
of gravity, substantially as described.
5. The combination of a magnetic shaft, journalled in cylindrical bearings and
having projecting rings, of a permanent magnet having a consequent pole
surrounding said shaft and its projecting rings in suspending relation thereto,
substantially as described.
6. The combination of a magnetic shaft supported in suitable bearings, having
two sets of projecting rings, and a magnetic system having a consequent pole,
substantially in the plane of one set of rings, and a second consequent pole of
opposite polarity, substantially in the plane of the other set of rings, substantially
as described.
7. In an electrical measuring device, a shaft carrying a rotating disk of con-
ducting material in combination with a supporting magnetic system, said system
supplying a magnetic flux, passing through said disk near its periphery, substan-
tially as described.
1
200
W. D. FITZPATRICK,
70 Wellington Street, Glasgow, Agent.