Note: Descriptions are shown in the official language in which they were submitted.
CA 02426846 2007-04-25
MAGNETICALLY HARD OBJECT AND METHOD FOR ADJUSTING THE
DIRECTION AND POSITION OF A MAGNETIC VECTOR
DESCRIPTION
Technical Field
The invention relates to a hard magnetic object and a method for adjusting a
magnetic
vector of a hard magnetic object.
For the varying mechanical, technical and medical applications the use of hard
magnetic objects is known. Inter alia, hard magnetic objects are used for
measuring
devices and magnetic bearings. Magnetic bearings, especially for blood pumps,
implanted as heart support pumps into the body of a human being, are in
contrast to
common bearings free of wear and gentle to the blood.
For some applications a more specific geometric alignment of the magnetic
vector of
a hard magnetic object is necessary, exceeding the common north-south
alignment.
Especially in bearings of blood pumps, an exact alignment and correction of
the
direction and of the position of the magnetic vector of the hard magnetic
object is
very important for ensuring the bearing clearance of the magnetic bearing.
Background
For a bearing the bearing stiffness, the bearing clearance and the wear
behaviour are
generally characteristic. In a magnetic bearing the component guided in the
bearing
moves especially around or along an imagined magnetic axis without mechanical
contact with other components of the device and independent of its mechanical
geometry. During slow movements, depending on the application, a lower bearing
stiffness and accuracy can be tolerated. Especially for fast rotational
movements
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and/or large moving masses a high bearing stiffness within narrow tolerances
is
necessary because of the produced imbalance or the inertia of masses of the
guided
parts. In an axial blood pump used as an artificial heart support system for
small
dimensions high rotational speeds are necessary for the delivery capacity. To
keep the
stresses on the blood within justifiable limits in an optimised inner pump
geometry,
e.g. a maximal gap dimension between the rotor and the pump tube of 0.01 mm is
to
be maintained. Mechanical bearings (e.g. ball-bearings) would easily satisfy
the
mechanical requirements, but they destroy too much of the blood substance in
the
direct blood contact. If mechanical bearings for this application are
sealingly inserted,
the long term leak tightness, necessary for this application case, can not be
ensured
with the present State of the Art. Furthermore, at the transition between the
shaft and
the seal a blood damage is produced and an increased thrombosis danger exists
at the
boundaries of the seals. Pump rotors being free of wear and freely hovering by
means
of the magnetic forces, minimise these disadvantages. The bearing stiffness of
the
magnetic bearings of the rotor means, however, a limited bearing clearance,
which
cannot be undershot at a limited construction space and at hydrodynamic
loadings
necessary for the pump pressure. Additional bearing loadings caused by
imbalances
enlarge this bearing clearance. To minimise the imbalance, the magnetic
bearing axis
has to correspond as exactly as possible to the geometric bearing axis of the
driven
pump rotor. In the application case of the blood pump, for the limitation of
the
imbalance and for maintaining the clearance measurement, the angle deviations
of the
resultant magnetic vectors of the bearing magnets from the geometric
rotational axis
have to be below 0.3 . The common anisotropic highly coercive magnets,
necessary
for the capacity parameters of the magnetic bearing, have, however, measured
averaged deviations of up to around 3 to the normal of the pole faces, which
are
oriented statistically as a bell curve distribution around the respective
averaged value
correspondingly to the base orientation of the starting material. Magnets
traditionally
made from the standard material in one piece, achieve only an immensely low
yield of
magnets, which have a resultant magnetic vector deviation of less than 0.3 to
the pole
normal.
The reason for this is, that the optimal or desired direction and size of the
magnetic
vector of a moulding opposes the statistically distribution of all the
uncompensated
spinning moments, which are responsible for the magnetic behaviour. Only in
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faultless single-crystals, single-range districts are present without a
statistical
distribution. Their application can, however, not be considered because of
unsuitable
material characteristics (e.g. a too low energy product) for the manufacture
of
magnetic bearings or other technically relevant devices. Also in materials
with a
distinct anisotropy a distinct statistical distribution of the uncompensated
spinning
moments is present with a fluctuation width, however, strongly limited. It is
active
macroscopically in statistical direction fluctuations of the resultant
magnetic vector
within a specific tolerance range.
In the most technical applications for the permanent magnets this fact plays
an
inferior role, as fluctuations of the magnetic vector, caused by the
manufacture,
around a desired zero position are tolerable.
In some applications, like, e.g. implantable blood pumps, the statistical
direction
fluctuations are, however, disadvantageous, as the application of permanent
magnets
with a magnetic vector, deviating from the desired direction, lead to an
imbalance,
which is too large, and therefore, to a bearing clearance, which is too large.
Therefore, it is necessary for such applications, to change or correct,
respectively, the
direction and position of the magnetic vector of a generally hard magnetic
object in
the open magnetic circuit. Such a change or correction, respectively, can be
achieved
in different ways.
A simple possibility is the application of an isotropic, hard magnetic
material, which
can be magnetised in the desired direction and strength. For such a method at
the
moment only hard magnetic materials are known, which cover in the maximal
energy
density only the lower range of the technical crest value. Materials with such
a low
energy density can, however, not find any application for magnetic bearings of
the
above described type, as the required bearing stiffnesses are not achieved.
Insofar as higher energy densities are necessary, the possibility exists, to
realise the
amplitude of the desired magnetic vector by means of selection of the magnetic
material suitable for high energy densities, and the geometric form. The
approximation to the desired direction of the magnetic vector to the geometry
of the
component can then be achieved when exactly knowing the position of the
resulting
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magnetisation vector in the starting magnet by means of concerted "angle
cutting".
Disadvantageous are an increased work expenditure and material consumption as
well
as hitting accuracy of the direction of the magnetic vector to be achieved
only within
a distinct deviation.
Furthermore, it is known, to realise a change of the magnetic vector by means
of
concerted demagnetisation or magnetisation, respectively, of partial areas or
the
totality of a hard magnetic object. This demagnetisation or magnetisation can
be
achieved by means of partial fields, asymmetrical fields, a changed field
gradient or
other methods. Disadvantages of this method are, that in general the energy
content of
the magnet is not used in the full extend. This is also valid, when a change
of the
magnetic vector is achieved by means of using the temperature dependency of
the
magnetic characteristics, i.e. by means of local or asymmetrical warming or
cooling,
respectively. Furthermore, active influencing e.g., by means of coupling with
correspondingly formed and directed coils, which are variable in the
correction
possibilities by means of changed drive, are known. These necessitate,
however,
insertion space and additional energy.
The design of other hard magnetic objects and methods for the building up of
magnetic arrangements are known from GB 777 315, CH 304 762, US 47 77 464, US
23 20 632, DE 21 06 227 A and DE 26 07 197 Al.
In US 2320632 a method for connecting permanent magnetic and soft magnetic
component(s) by means of casting on of magnetic material and forming as an
integrally connected magnetic component, which takes up by a slot the thermal
deformation during the cooling process is described. The permanent magnetical
component is, in this case, arranged between the soft magnetic pole parts. Due
to this,
an influence on the direction of the magnetic field of the permanent magnetic
component is not possible for the above named technical applications.
In US 777315 and CH 304762 a magnetic yoke as a connection between permanent
magnetic and soft magnetic components is described. The yoke is part of a
closed
magnetic circuit, e.g. in an electrical measuring device. The permanent
magnetical
component is arranged between soft magnetic pole pieces. Because of this, an
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influencing of the direction of the magnetic field of the permanent magnetic
component is not possible.
In DE 2106227 A as well as DE 2607197 Al an air gap magnetic system is
described.
In this case, permanent magnetic parts are imbedded in soft magnetic parts in
a
magnetic circuit. An influencing of the direction of the magnetic field of the
permanent magnetic part is not intended and would also not be realisable, as
it would
be destroyed by means of the abutting soft magnetic parts.
In US 4777464 also a magnetic system with an air gap, having a closed magnetic
circuit is described. To a soft magnetic outer yoke two opposed permanent
magnetic
parts are single-sidedly coupled with the same magnetisation to the inner
sides, which
are combined, respectively, from two magnetic materials. On the side of these
permanent magnets facing each other, the working air gap is formed with a soft
magnetic pole shoe formed according to the invention. Target of the
arrangement is,
to achieve an as far as possible constant field distribution in the working
air gap. An
influencing of the direction of the magnetic field of the permanent magnetic
part is
not intended. The used magnets should have the same direction. Each direction
change would be destroyed at the soft magnetic yoke and at the pole shoe. The
amplitude of the magnetic vector is in the classical sense achieved by means
of a
change of the geometric relationships and dimensions of the used different
sorts of
magnets.
In summary it can be pointed out, that with none of the known methods the
direction
of the magnetic field of a hard magnetic part can be influenced. The core of
the above
described methods is that, by means of the closed magnetic circuit the
magnetic flux,
possible with the provided magnets (or coils) is coupled to a maximum into the
working field of this invention (air gap in US 2 320 632, DE 2 106 227 and DE
2 607
197 and soft magnetic test objects in US 777 315 as well as CH 304 762), or in
US 47
77 464 it is important, that in the air gap of the magnetic field at specific
values, an as
constant as possible distribution of the magnetic field is achieved.
Therefore, with the known methods an alignment of the magnetic field can not
be
achieved. Thus, the influence at a hard magnetic object for the direction of
the
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magnetic field is directly cancelled out by the arrangement with a closed
magnetic
circuit, provided in the above named methods, by means of the soft magnetic
parts
abutting the hard magnetic object. Therefore, each previous change or
adjustment of
the direction of the magnetic field is cancelled. The soft magnetic parts, not
working
in the saturation, concentrate in the contact face towards the hard magnetic
object the
magnetic flux in dependency of the difference in permeability, however,
independently of the direction. The magnetic flux extends within these parts
in
accordance with the difference gradient of the magnetic potential. The field
exits
perpendicular to the upper face of the position, at which the permeability
jump to the
surrounding or, to the neighbouring part takes place, the soft magnetic parts.
The
outer path of the field lines depends then on the provided outer magnetic
field
conditions. In the above described methods the field lines extend mainly
within the
predetermined magnetic circuits. With these arrangements an influencing of the
magnetic vector is not possible.
Therefore, invention is based on the object, to provide a hard magnetic object
and a
method for the manufacture thereof, which has, without influencing by means of
an
outer magnetic circuit, a desired resultant magnetic vector, which moves
within the
frame of a predetermined tolerance range and furthermore, that the hard
magnetic
object has a higher maximal energy density compared to the State of the Art.
Summary of the Invention
The object is solved as described below
The advantage of the invention is especially, that the adjustment or the
correction,
respectively, of the direction and the position of the magnetic vector of a
mainly hard
magnetic object can be achieved by utilisation of generally known materials in
a
simple way.
According to the invention a hard magnetic object, which magnetic vector is in
the
range of the open magnetic field largely in the frame of a predetermined
tolerance
range, consists of at least one hard magnetic moulding and at least of a
further
moulded element, which are combined with each other in such a way, that by
means
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of shape, bringing together and alignment of the mouldings and moulded
elements a
predetermined direction and position of the magnetic vectors of the hard
magnetic
object is achieved on the predetermined side(s). The magnetic vector of the
hard
magnetic object is the resultant magnetic vector of the magnetic vectors of
the hard
magnetic moulding and the moulded elements.
According to a preferred embodiment, the further moulded elements consist of
materials like ferrimagnetic, ferromagnetic, antiferromagnetic, paramagnetic,
superparamagnetic or diamagnetic materials.
According to another embodiment, the hard magnetic moulding and/or the moulded
elements are formed as rotational-symmetric bodies or as a non-rotational-
symmetrical formation of the hard magnetic moulding and of the moulded
elements.
The hard magnetic moulding and the moulded elements can be formed as compact
bodies or as hollow bodies.
Advantageously, the hard magnetic moulding and the moulded elements are
arranged
movable relative to each other and/or fixable.
In a further embodiment of the invention, the hard magnetic moulding and the
moulded elements are connected fixed to each other. A gluing of the parts is
especially suitable for this.
In a further embodiment of the invention, the moulded element is formed as a
hollow
chamber in the hard magnetic moulding.
The method for the adjustment of a magnetic vector of a hard magnetic object
according to the invention is characterised in that by means of connecting and
aligning of hard magnetic mouldings and moulded elements an adjustment of the
direction and the position of the resultant magnetic vector of the hard
magnetic
moulding and of the magnetic vectors of the moulded elements is carried out.
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According to an improvement, the method according to the invention is
characterised
in that a predetermination of the magnetic vectors as well as of the hard
magnetic
moulding as well as of the moulded elements in reference to their direction
and the
position is carried out and following by means of further change of shape, in
connection with the coupling and alignment of the moulded elements, a
predetermined direction and position of the resultant magnetic vectors is
achieved.
This purposeful superposition of the magnetic vectors of the mouldings
according to
the invention leads to a resultant magnetic vector in the frame of a
predetermined
tolerance range.
In a further embodiment of the method according to the invention, the
adjustment of
the direction and the position of the resultant magnetic vector of a hard
magnetic
object on the predetermined sides is achieved by means of the determination
and
control of the resultant magnetic vectors during or after the coupling of the
hard
magnetic object and of the repeated purposeful changing of this arrangement
correspondingly to the resulting change of the magnetic vector.
The purposeful superposition of the magnetic vector of a hard magnetic
moulding
with the magnetic vectors of several moulded elements according to the
invention is
possible with ferromagnetic, ferrimagnetic, antiferromagnetic, diamagnetic,
paramagnetic or superparamagnetic materials. In this case, the moulded parts
can be
arranged next to each other, on top of each other, completely or partially
within each
other, surfacewise fully against each other, partially against each other,
symmetrically
or non-symmetrically to the changed axis, contorted against each other,
rotationally
symmetrically and contorted against each other, rotationally symmetrically and
inclined, and can be used inclined or straight in connection with distance
effects, and
can be arranged with or without change of the strength and direction by means
of
washers, cut inclined, abutting each other wedged-shaped or in any other way,
arranged form-fittingly, glued or fixed in any other way.
The hard magnetic object according to the invention is used especially as part
of a
magnetic bearing.
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Brief Description of the Figures
The invention is described in detail by means of drawings and embodiments. It
shows:
Fig. 1 a rotational formation of a hard magnetic moulding.
Fig. 2 a rotational-symmetric embodiment of a further hard magnetic
moulding.
Fig. 3 a hard magnetic object according to the invention consisting of
a hard magnetic moulding and a moulded element,
Fig. 4a a hard magnetic object according to the invention consisting of
a hard magnetic moulding and two moulded elements,
Fig. 4b a top view onto a hard magnetic object according to the
invention, consisting of a hard magnetic moulding and two
moulded elements,
Fig. 5 a hard magnetic object according to the invention consisting of
a hard magnetic moulding and two moulded elements,
Figs. 6
and 7 a hard magnetic object according to the invention consisting of
a hard magnetic moulding, a moulded element and a soft
magnetic moulded element and
Figs. 8
to 17 further embodiments of hard magnetic objects.
Description of the Preferred Embodiments
Fig. 1 and Fig. 2 show a hard magnetic moulding 1 and a moulded element 11,
which
are formed as axially magnetised moulded elements and rotationally
symmetrically. A
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symmetry axis 2 of the moulding 1 and a symmetry axis 12 of the moulded
element
11 are arranged perpendicular on the end faces 3 and 13, formed, here
exemplary as a
magnetic north pole.
Fig. 3 shows a rotational symmetrical hard magnetic object according to the
invention, consisting of a hard magnetic moulding 1 and a moulded element 11.
The
moulding 1 has a magnetic vector 4 having an intensity 5 (length of the
vector). The
moulded element 11 has a magnetic vector 14 having an intensity 15. The angles
6
and 16 symbolise the incorrect position of the magnetic vectors 4 and 14 to
the
desired position (here to the symmetry axis). By means of superposition of the
magnetic vectors 4 and 14 a resultant magnetic vector 20 is produced, wherein
the
superposition of the magnetic vectors 4, 14 can be adjusted for example by
means of
rotating the moulding 1 or the moulded element 11, to adjust it to the
predetermined
tolerance range of the magnetic vector 20.
The compensation of the angles 6 and 16 in Fig. 3 is not simply achieved by
means of
known graphical addition. Therefore, the intensities 5 and 15 as well as the
angles 6
and 16 of Figures 1 to 3 are only to be seen for the demonstration of the
method
according to the invention. In Fig. 3 only the magnetic vectors of the upper
north side
are shown. The resultant of the south side lies outside of the symmetry axis.
In Fig. 3 the alignment of the resultant magnetic vector 20 should fall
together with
the symmetry axis 2 and 12. The purposeful alignment of the magnetic vector 20
necessitates an exact measuring of the position and amplitude of the magnetic
vectors
of the parts. For example initially the exact position of the magnetic vector
4 of the
moulding 1 is measured. The projection 4a of the magnetic vector 4 onto the
north
pole side is marked, for example on the end face 13 by means of a dash. The
component of the magnetic vector 4 of the moulding 1, acting perpendicular to
the
pole normal, is to be compensated by a component of the magnetic vector 14 of
the
moulded element 11, active in the upper face of the moulding 1, identical to
the
amplitude, however, off-set by 180 . It should be noted, that it is not the
measured
component of the magnetic vector 14 of the moulded element 11, active
perpendicular
to the pole normal, but that it is the amplitude of the component of the
magnetic
vector 14, which after the coupling of the magnetic object is active in the
upper face
CA 02426846 2007-04-25
of the moulding 1. I.e. a value of the component, measured under measuring
technical
comparable conditions like moulding 1 and arranged perpendicular to the pole
normal
of the magnetic vector 14 of the moulded element 11, has to be larger than the
component of the moulding 1 by a pairing factor dependent on the material and
on the
geometric dimension. The size of the amplitude of the magnetic vector directly
in the
normal direction of the pole is, however, not relevant for the compensation of
the
direction, but only for the size of the resulting amplitude of the hard
magnetic object.
The pairing factor has to be determined or has to be approximated by tests
with
following result check. The moulded element 11, having the angle value
allowable for
the compensation, is selected for example from a number of measured magnets
being
marked with the excursion direction in analogy to the moulding 1. The angle
value of
the moulded element 11 is only allowed to deviate in the range of an allowable
fluctuation width of an angle value determined by the multiplication of the
deviation
angle of the moulding 1 times the dimensionless pairing factor. To align the
resultant
magnetic vector in direction of the rotational symmetry axis in this example,
the
selected moulded element 11, having a marking, which represents the projection
14a,
rotated by 180 in the axis direction relative to the moulding element 1, is
positioned
with the magnetic north pole of the end face 13 in the centre of the magnetic
south
pole of the moulding 1.
Fig. 4a shows a hard magnetic object, consisting of a hard magnetic moulding 1
and
the moulded elements 11, 21. In this case, the two lower moulded elements 11
and 21
produce the compensation of the angle deviation of the magnetic vector 4 of
the
moulding 1 from the desired position. The moulded element 21 correlates with
the
magnetic vector 24. The lower resultant magnetic vector 27 is not parallel to
the
rotational axis. The projection of the magnetic vectors 4a, 14a, 24a into the
plane of
the end face 3 of the hard magnetic moulding 1 is represented in Fig. 4b as a
top view
onto the hard magnetic moulding 1 and the moulded elements 11, 21 and explains
the
principal of the magnetic vector alignment. The length of the arrows
corresponds to
the components of the magnetic vectors 4, 14, 24 of the individual moulded
parts (4a
as the component of the magnetic vector 4 of the moulding 1; 14a as the
component
of the magnetic vector 14 of the moulded element 11; 24a as the component of
the
magnetic vector 24 of the moulding element 21), active in the plane 3 of the
hard
magnetic moulding 1 perpendicular to the rotational axis. The components 14a
and
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24a have to be equal and have to have at least half the amplitude of the
component 4a;
then by means of rotating the parts 11 and 21 against each other around the
rotational
axis the compensation value in reference to the deflection of the magnetic
vector of
the moulding 1 can be adjusted between zero and the maximal possible force and
can
be adapted to the compensation value. The lower resultant magnetic vector 27
is
arranged in this embodiment outside of the rotational axis.
Fig. 5 shows a hard magnetic object, which consists of a hard magnetic
moulding 1
and the moulded elements 11, 21 arranged on a rotational axis. In this
arrangement of
the vectors 4, 14, 24 the upper resultant magnetic vector 20 as well as the
lower
resultant magnetic vector 27 are aligned in reference to the rotational axis.
The middle
moulded element 11 with its magnetic vector 14 produces by means of its length
and
direction the compensation for the vectors 4 and 24.
Fig. 6 shows a hard magnetic object, consisting of a moulding 1, the moulded
element
11 and a soft magnetic moulded element 21, arranged on the rotational axis. In
this
arrangement of the vectors 4, 14, the upper resultant magnetic vector 20 is
aligned in
reference to the rotational axis. The middle part 11 with its magnetic vector
14
produces by means of its length and direction the compensation for the vector
4. The
lower soft magnetic moulded element 21 is not arranged in saturation and
neutralises
the memorised angle position. The field lines exit the upper face of the soft
magnetic
moulded element 21 in the normal direction and follow then the outer magnetic
field.
Fig. 7 shows a hard magnetic object, consisting of a soft magnetic moulded
element
21 and a moulding 1 and the moulded element 11 arranged on the rotational
axis. In
this arrangement of the vectors 4, 14 the upper resultant magnetic vector 20
is to be
aligned in reference to the rotational axis. The middle part 1 with its
magnetic vector
4 produces by means of its position and direction the compensation for the
vector 14
of the moulded element 11. The soft magnetic moulded element 21 compensates
the
small area fluctuations of the magnetic vector amplitude of the hard magnetic
moulding 1 and of the moulded element 11. If the moulded element 21 is in the
saturation, the direction of the magnetic vector 20 produced beforehand from
the
superposition of the magnetic vectors 4 and 14 (resulting vector without
moulded
element 21) is not neutralised. The direction of the resultant magnetic vector
20a with
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the moulded element 21 retains more or less the direction of the magnetic
vector 20
and has, in this case, a changed amplitude.
The Figures 8a and 8b show hard magnetic objects, consisting of a moulding 1
and
the moulded element 11 arranged on the rotational axis. In this arrangement of
the
vectors 4, 14 the upper resultant magnetic vector 20 and the lower resultant
magnetic
vector 27 are aligned outside the symmetry axis.
The Figures 9a to 9f show examples of rotational symmetrical hard magnetic
objects,
composed of a hard magnetic moulding 1 and one or more moulded elements 11,
21,
31, wherein the moulded elements 11, 21, 31 are formed as hollow spaces in the
hard
magnetic moulding 1. The alignment of the vectors is in this case, for example
arrived
at in such a way, that the upper resultant magnetic vector 20 coincides with
the
symmetry axis.
Figures 9g and 9h show hard magnetic objects consisting of a moulding 1 and a
moulded element 11.
Figures 10a and 10b show examples of hard magnetic objects corresponding to
Figures 9g and 9h, which are for the uptake of the repelling forces enclosed
by a
nonmagnetic moulded element 21 (e.g. aluminium).
Figures 11 a to 11 f show examples of rotational symmetrical hard magnetic
objects,
composed of respectively, one hard magnetic moulding 1 and a moulded element
11.
These Figures show further examples of joining positions.
Figures 12a to 12s show examples of rectangular hard magnetic objects,
composed of
respectively a hard magnetic moulding 1 and a moulded element 11. These
drawings
show further examples for the composition of the components.
Figures l3a to 13b show two examples of rectangular hard magnetic objects,
composed from one hard magnetic moulding and several moulded elements 11, 21,
31, to achieve a resultant magnetic vector 20 arranged in the desired position
and
direction.
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Figures 14a and 14b show examples of randomly formed hard magnetic objects,
composed in the examples respectively from one hard magnetic moulding 1 and
one
moulded element 11. In the examples the resultant magnetic vector 20 is
aligned in
the normal direction in the magnetic centre of gravity. The hard magnetic
moulding 1
and the moulded element 11 can also have (different as shown in the example)
upper
sides and lower sides of any form. These moulded parts can be paired in any
position
form-fittingly or also not fittingly with the upper face or also with a
certain distance
from each other (e.g. in a glued connection or casted or other), so that by
means of
addition of the magnetic vectors of the moulded parts the position and the
direction of
the resultant magnetic vector 20 are achieved.
Figure 15b shows an example of a hard magnetic object, composed from a hard
magnetic moulding 1 and a moulded element 11 and a "nonmagnetic" (e.g. para-
or
diamagnetic) moulded element 21 and with its upper resultant magnetic vector
20
which has to coincide with the rotational axis. In Fig. 15a the fictitious
starting
condition is shown for explanation, in which the hard magnetic moulding 1 and
the
moulded element 11 are directly superposed without distance in the same
alignment
as in Figures 15b and 15c. The hard magnetic moulding 1 and the moulded
element
11 produce in this fictitious starting position a resulting magnetisation
vector 20
directed upwards and not coinciding with the axis of the rotational symmetry.
If in
this starting position the vector component of the moulded element 11, active
in the
upper face of the moulding 1, perpendicular to the pole normal, is larger than
the
vector component of the moulding 1, then the desired direction correction can
be
achieved by an increase of the distance. In Figures 15b and 15c the resultant
magnetic
vector 20a is corrected into the normal alignment of the magnetic vector,
desired in
the example, by means of the hard magnetic moulding 1 and the moulded element
11
in an alignment having the same pole, however off-set by 180 , of the vector
component of the moulding 1 active perpendicular to the pole normal, and of
the
moulded element 11, and especially by means of a distance increase by means of
a
"nonmagnetic" moulded element 21 or an empty space 38 (vacuum, gaseous or
liquid
filling), which are fixed by means of a spacer 37.
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Figure 16b shows an example of a hard magnetic object, composed of the hard
magnetic moulding 1 and the moulded element 11 and a nonmagnetic (para- or
diamagnetic material) moulded element 21. For explanation in Fig. 16a the
fictitious
starting condition for the hard magnetic object is shown corresponding to Fig.
16b.
The starting moulding 1 and the starting moulded element 11 would produce in
Fig.
16a in the magnetisation directed upwards, an alignment of the resulting
magnetisation vector 20, coinciding with the rotational axis. In Fig. 16b the
components of the moulding 1, filled by the "nonmagnetic" moulded element 21,
and
of the moulded element 11 are omitted. The contribution of these parts is also
missing
in the resultant magnetic vector 20a in correspondence with Fig. 16b. The
amplitude
of the resultant magnetic vector 20a is reduced in correspondence with the
missing
parts and the position moves into the new magnetic centre of gravity outside
of the
rotational axis. The direction in reference to the pole plane is kept more or
less. In
composed moulded parts the direction may also change.
Fig. l7b shows a further example of a hard magnetic object, composed of the
hard
magnetic moulding 1 and the moulded element 11 and a nonmagnetic (para- or
diamagnetic material) moulded element 21. For explanation reason in Fig. 17a
the
fictitious starting condition for the hard magnetic object is shown in
correspondence
to Fig. 17b. The starting moulding 1 and the starting moulded element 11 would
produce in Fig. 17a in the magnetisation directed upwards, an alignment of the
resultant magnetisation vector 20, which is arranged in the middle, however,
does not
coincide with the rotational axis. In Fig. 17b the part of the moulding 1,
filled by the
"nonmagnetic" moulded element 21, is omitted. The contribution of this moulded
part
is also missing in the resultant magnetic vector 20a of Fig. 17b. The
amplitude of the
resultant magnetic vector 20a decreases in correspondence with the missing
part, the
position moves into the new magnetic centre of gravity outside of the
rotational axis
and the direction changes in the example in direction of the pole normal.
The individual parts in the drawings Fig. 1 to Fig. 17 may also consist of
several
parts.
CA 02426846 2007-04-25
The invention is not limited to the here shown embodiment. Rather, it is
possible, by
means of combining and modifying of the named means and features to realise
further
variants, without leaving the scope of the invention.
16
