Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02553795 2008-12-04
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ECCENTRIC SCREW PUMP WITH INTEGRATED DRIVE
Field of the Invention
The invention relates to a screw or eccentric screw pump
such as is used especially for conveying highly viscous
media or media mixed with solids.
Background
Eccentric screw pumps corresponding to the prior art
generally have a fixed external stator and a rotor running
therein. The rotor is generally driven by an external
electric motor which is connected to the rotor by means of a
Cardan shaft or flexible shaft. In the following
descriptions no further distinction is made between screw
and eccentric screw pumps since this has no effects on the
principle forming the basis of the invention.
However, known eccentric screw pumps have a long overall
shape and require maintenance because of the large number of
moving parts in the motor, Cardan shaft and pump. In
addition, in such an arrangement a seal with respect to the
Cardan shaft is required on at least one side of the pump.
The arrangement from DE 102 51 846 Al represents a
substantial improvement here. Herein the rotor of an
eccentric screw pump is at the same time part of the motor.
Thus, the Cardan shaft in particular can be omitted. Such an
arrangement has the disadvantage that only special rotors
equipped with expensive magnetic materials can be used.
Furthermore, as a result of the helical arrangement of the
stator, a relatively complex stator winding is obtained,
which also results in relatively high production costs.
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Another approach to the solution is presented in DE 43 13
442 Al. As disclosed in Figure 24 for example, an eccentric
screw pump is provided having an elastic stator and a rotor
driven by a magnetic coupling. As a result of this
arrangement, the magnetic coupling can be mounted using a
simple bearing since the movement of the screw is
compensated by the elastic stator. These pumps are not
suitable for high pressures as a result of the high
elasticity of the stators without jackets.
EP 0 357 317 B1 discloses a motor which simultaneously
implement a rotary movement and a lifting movement in
conjunction with an eccentric screw pump. Here also an
elastic stator a without jacket is used to compensate for
the eccentric movement of the screw. Thus, this pump is not
suitable for high pressures.
Summary of the Invention
It is the object of the invention to configure an eccentric
screw pump in such a manner that the torque required to
drive the pump can be supplied without additional means
which extend the overall shape of the pump and without shaft
seals and shaft bearings and at the same time, the pump is
also suitable for high pressures.
Certain exemplary embodiments can provide an eccentric screw
pump, comprising: a. a stator and a rotor running therein;
and b. a drive motor connected to the rotor for driving the
rotor; the drive motor includes a first stator winding and a
first armature; the first armature being constructed as an
approximately cylindrical armature rotatable on an eccentric
orbit inside an approximately cylindrical pot on which the
first stator winding is arranged; the first armature and the
rotor are rigidly connected.
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Other embodiments provide an eccentric screw pump,
comprising a stator and a rotor running therein. A drive
motor is provided for driving the rotor which is connected
to the rotor. This drive motor comprises an armature as well
as a stator winding. The armature is constructed as an
approximately cylindrical armature and rotates on an
eccentric orbit inside an approximately cylindrical pot as a
result of its rigid connection to the rotor. This pot is at
least partly enclosed by a stator winding. Alternatively,
the stator winding can also be integrated in this pot. As a
result of such an arrangement, the drive and pump are
integrated in an extremely space-saving manner in a single
unit. At the same time, the mechanical construction is
substantially simplified. Thus, no vulnerable Cardan shafts
are required since the rotor runs completely closed in the
system comprising stator and connected lines. No connection
or contact is required from the rotor to points outside the
system. Thus, the pump consisting of the rotor and the
stator can be flange-mounted into an existing pipe without
additional connections and shaft seals.
As a result of the arrangement according to various
embodiments, the conversion member such as a Cardan shaft or
a flexible shaft, for example, for transformation of the
centric rotation of the drive motor into the eccentric
movement of the rotor can also be omitted.
In a particularly advantageous embodiment, a second armature
is provided as an approximately cylindrical armature. This
armature is disposed on the end of the rotor opposite to the
first armature. This armature is rigidly connected to the
rotor and thus also rotates on an eccentric orbit inside a
second pot. This second pot is likewise enclosed by a second
stator winding or contains a second stator winding.
A further advantageous embodiment consists in that the motor
comprising the armature and the stator winding is embodied
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in the form of a reluctance motor. For this purpose, the
stator winding has coils for producing a rotating magnetic
field. Located in the armature is a preferably tooth-shaped
part made of magnetically conductive or soft magnetic
material, such as iron for example. In this case, the teeth
are aligned according to the magnetic field. A rotation of
the rotor can thus be achieved by a rotation of the magnetic
field.
A control unit is provided for controlling the corresponding
parts of the stator winding. This now controls the current
flow through the stator winding in such a manner that in
order to produce a torque, the flux is preferably guided
through those areas of the pot which are at a minimal
distance from the surface of the armature.
A position sensor which indicates the exact position of the
rotor or the armature in relation to the stator is
preferably provided for correct control of the coils. Such a
position sensor can, for example, be implemented using
magnets integrated in the rotor.
In a further advantageous embodiment, the motor is designed
in the form of an asynchronous motor. For this purpose, the
armature is embodied as a resistance armature or preferably
as a short-circuiting armature. Furthermore, windings for
producing a rotating field are provided in the stator
winding. The rotating field induces voltages in the rotor
windings or in the conducting rotor structure which results
in corresponding currents depending on the electrical
resistance of the windings or the conducting rotor
structure. These currents in turn produce a magnetic field
and therefore a torque. An optional control circuit,
advantageously a frequency inverter, is provided for
controlling the windings to produce the phase-shifted
signals of variable frequency to generate a rotating field
of the desired frequency of rotation.
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Grooves for receiving rotor windings can optionally be
provided in the rotor.
A different embodiment of the invention provides that axial
holes through which the medium can flow are preferably
provided in the armature. Thus, a diversion channel for the
medium is no longer necessary. A particularly compact,
space-saving structure of the arrangement is thus obtained.
In another advantageous embodiment of the invention, the
magnetic components or permanent magnets in the armature as
well as the coils in the stator are arranged so that a pre-
determined force is exerted in the axial direction on the
rotor. It is especially advantageous if the axial force
counteracts the pump pressure with the same strength.
Preferably used to monitor the rotor position is a position
controller which controls the position of the rotor using at
least one position sensor.
A further embodiment of the invention provides a rotor which
can be displaced in the axial direction by the axial force.
A reduction in the break-away torque when starting up the
pump can be achieved by means of this displaceability.
Likewise, the pump outlet can thereby be closed by the rotor
itself, for example. Alternatively, a valve body can
naturally also be actuated by the axial movement of the
rotor. Especially in the case of metering pumps, this allows
particularly fine metering, free from overrun.
In a further advantageous embodiment of the invention coils
in the armature have opposite polarity to the coils which
transmit the torque to the rotor. As a result of this
controllable reverse polarity, a force is produced in the
rotor which acts in the direction opposite to the direction
of flow of the pumped medium and thereby compensates or
reduced the hydraulic forces produced by the medium on the
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front sides of the rotor. The required numbers of coils of
inverse polarity can be variably adapted to the conveying
pressure produced.
Description of the Figures
The invention is described hereinafter using exemplary
embodiments with reference to the drawings without
restricting the general inventive idea.
Fig. 1 is a schematic view showing a device according to the
invention in general form.
Fig. 2 is a perspective view showing a device according to
the invention in general form.
Fig. 3 shows a device according to the invention with a
second armature.
Fig. 4 is a perspective view of a device according to the
invention with a second armature.
Detailed Description
Fig. 1 is a schematic diagram showing a device according to
the invention in a section perpendicular to the axis of
rotation. An eccentric screw pump has a rotor 1 which moves
in a stator 2. The rotor 1 is rigidly connected to an
armature 3. The armature rotates on an eccentric orbit
inside the pot 5. In this case, the medium to be conveyed
passes through the pot 5. At least one stator winding 4 is
provided to produce the torque. In the exemplary embodiment
the stator winding is integrated in the pot but can
preferably be arranged outside the pot and thus outside the
medium. However, it can optionally be integrated in the pot,
for example, potted. The stator winding comprises individual
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coils. These coils can optionally be supplied with current
by a control unit.
A position sensor which indicates the exact position of the
rotor or the armature in relation to the stator or the pot,
is preferably provided for correct control of the coils.
Such a position sensor can be implemented, for example by
means of or with the aid of the magnets integrated in the
rotor.
Figure 2 shows the arrangement shown previously in
perspective view.
Figure 3 shows another device according to the invention
with a second armature 3a. This second armature is arranged
on the end of the rotor opposite to the first armature.
Accordingly, a second pot 5a and a second stator winding 4a
are allocated to the second armature to produce the torque.
In such an arrangement it is advantageous if the two
armatures are constructed such that they produce an axial
thrust force directed towards one another which holds the
two armatures and the rotor in a predetermined position. For
this purpose the armatures can advantageously be constructed
as at least slightly tapered.
Fig. 4 shows the arrangement shown previously in perspective
view.
Reference list
1 Rotor
2 Stator
3 Armature
4 Winding
Pot
