Pumps – Motor driven – Axial thrust balancing means for rotary pump and motor
Reexamination Certificate
2000-04-20
2002-04-09
Freay, Charles G. (Department: 3746)
Pumps
Motor driven
Axial thrust balancing means for rotary pump and motor
C417S352000, C417S423120, C417S310000, C417S090000
Reexamination Certificate
active
06368075
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a pump for fluids, whereby under a fluid both a gas and a liquid is to be understood.
BACKGROUND OF THE INVENTION
For the displacement of sensitive liquids like especially blood, pumps have been developed in which a rotor is held in an equilibrium position within a support tube by mechanical field forces. Thus a blood pump is known from U.S. Pat. No. 5,695,471 which is configured as a radial pump with a radial rotor. The radial rotor is disposed within a support tube and has, in an inlet side projection, a plurality of rotor magnets which are juxtaposed with stator magnets on the support tube. Additionally, the radial rotor has distributed about its periphery a plurality of rod-shaped rotor magnets extending in axial direction and which are juxtaposed with ring-shaped stator magnets displaced on both sides of the radial rotor along the sides of the support tube. These rotor and stator magnets should support the radial journaling in the region of the projection of the rotor. The rotor is held purely mechanically in the axial direction at one end by a ball and at its opposite end on a point bearing.
The rotor is driven by means of a brushless rotary field or three phase motor. For this purpose, on sides of the support tube a coil is provided which cooperates with a spoked pole magnet set into the radial rotor. The drawback with this blood pump is that the journaling stability in the radial direction is not optimal and the pump, because of the multiplicity of rotor and stator magnets, requires considerable space and has a high weight. In addition, the purely mechanical bearing in the axial direction suffers from wear which is especially a disadvantage for implanted blood pumps.
Axial pumps are also known for use as blood pumps. In this case, the journaling is effected exclusively mechanically in guide wheels which are arranged at fixed locations in the support tube ahead of and behind the rotor. (Wernicke et al., A Fluid Dynamic Analysis Using Flow Visualization of the Baylor/NASA Implantable Axial Flow Blood Pump for Design Improvement, Artificial Organs 19(2), 1995, Pages 161-177). Such mechanical bearings are wear intensive and have in addition an unsatisfactory influence on sensitive liquids, especially body liquids like blood. Rotor devices with mechanically journaled rotors have been developed as well for measuring devices. Thus in German patent document 29 19 236 a turbine wheel counter is described for measurement of the flow of liquids, in which the rotor has two spaced-apart rotor magnets for radial stability which are configured as permanent magnets and are juxtaposed pairwise with stator magnets surrounding the support tube and also formed as permanent magnets. Thus the rotor and stator magnets are magnetized to repel each other in axial direction.
Between the stator magnets, an electric magnet coil is arranged which annularly surrounds the support tube. The magnet coil cooperates with a ferromagnetic flux conductive piece on the rotor which is arranged between the rotor magnets. In addition, a sensor is provided which detects the axial position of the rotor and cooperates with a control device which regulates the electric current in the magnetic coil. As soon as the field forces of the rotor and stator magnets determine that an axial shift of the rotor has occurred, the rotor is accelerated from the equilibrium position in the axial direction and the rotor, by measurement of the axial shift of the rotor, generates a signal which is effective to produce a counteracting, stabilizing field force in the magnetic coil. The rotor thus responds to an axial position shift in one or another of the devices to continuously return the rotor in one or the other direction upon an axial position shift. Thus the stabilizing axial force is so phaseshifted with respect to an axial position change that the rotor is both restored in position and is also shifted into its setpoint position by damping forces.
A drawback of the aforedescribed rotor device resides in that the rotor has only a relatively small bearing stiffness in the radial direction. The origin thereof is the distance between the stator and rotor magnets because of the annular channel provided between the carrier tube and the rotor and along which the fluid is displaced.
In German patent document DE-A-24 44 099, a magnetic bearing for rapidly moving bodies is known. This magnetic bearing has a rotor whose ends are provided with pole positions lying opposite one another and having permanent magnets and which apply attractive forces to the rotor to hold it in a stable position. By means of a contactless position sensing, deviations can be determined from the equilibrium position. Such devices are compensated by a powerless electromagnetic stray field control for which annular coils are provided which are arranged at the pole pieces proximal to the gaps with the rotor. Such a magnetic bearing is not suitable in a support tube through which a fluid is guided on spatial grounds.
OBJECT OF THE INVENTION
The invention has as its object to provide a pump of the aforedescribed type which has significantly higher bearing stiffness, especially in the radial direction and which permits highly versatile use thereof.
SUMMARY OF THE INVENTION
These objects are attained in accordance with the invention by the following features:
a) the pump has a support tube;
b) in the support tube a rotor is rotatably journaled;
c) the rotor has displacement elements for conveying the fluid through the support tube;
d) the rotor has at both ends axially magnetized permanently magnetic rotor magnets;
e) the ends of the rotor are juxtaposed with axially-opposite permanently magnetic stator magnets connected with the support tube;
f) each stator magnet has such axial magnetization that the neighboring stator and rotor magnets opposite one another attract each other;
g) the pump has a magnetic axial stabilizing unit for the rotor; and
h) the pump has an electric motor with a stator generating a rotary field on the support tube and a spoked pole magnet on the rotor.
The object is also attained by a pump with the following features:
a) the pump has a support tube;
b) a rotor is rotatably journaled in the support tube;
c) a rotor has displacement elements for conveying the fluid through the support tube;
d) on the ends of the rotor there are each an axially-magnetized permanently magnetic magnet and a flux guide piece opposite one another, whereby the magnets are either on the rotor as rotor magnets or are connected with the support tube (
2
) as stator magnets;
e) the pump has a magnetic axial stabilizer unit; and
f) the pump has an electric motor with a rotary field generating stator on the support tube and a spoked pole magnet on the rotor.
The basic concept of the invention is thus, by means of rotor and stator magnets in an end orientation, to generate a magnetic field bridging the gap between rotor and stator magnets in the axial direction so that the respective opposing pairs of rotor magnets and stator magnets oppositely attract one another. As a result, the bearing stiffness with the same geometry of the magnetic bearing of DE-A-29 19 236 is increased by at least the power of ten, without affecting significantly the annular channel between the support tube and the rotor hub.
The aforedescribed effect also arises when two magnets, i.e. rotor and stator magnets, are not juxtaposed with one another but rather at each end a magnet on one side and the flux guide piece on the other side are used. Thus the magnets can alternatively be used as rotor magnets which are affixed to the rotor and the flux-conducting pieces connected to the support tube or the flux-conductive pieces can be arranged on the rotor and the magnets can be seated on the support tube as stator magnets. For producing a high bearing stiffness, additional electric magnetic coils can be provided for reinforcing the magnetization of the flux-conducting pieces in the sense of increasing the attractive force between the magnet and the flux-conducti
Dubno Herbert
Forschungszentrum Julich GmbH
Solak Timothy P.
LandOfFree
Pump with a magnetically supported rotor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Pump with a magnetically supported rotor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pump with a magnetically supported rotor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2921064