Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-07-09
2001-05-01
Enad, Elvin (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S087000, C310S091000, C310S112000
Reexamination Certificate
active
06225719
ABSTRACT:
FIELD OF THE INVENTION
The present invention refers to a long electrical motor, where the rotor is divided into sections with at the least one low friction bearing arranged between the sections and in each end of the motor, whereby the stator is stacked continuously past the internal bearings, using thin sheet of either magnetic or non-magnetic metal discs in the areas surrounding the bearings, and thin sheets of magnetic metal discs between the bearings.
BACKGROUND OF THE INVENTION
Such a long electrical motor is known from U.S. Pat. No. 2,251,816, where the bearings are arranged in a groove in the rotor and consequently are made up of bearing rings that might be split in two half bearing rings held in place by butterfly keys. Such rings might contain a roller bearing in an internal groove for reducing the friction. The production and mounting of such bearings is elaborate and time consuming and therefor expensive. Further, the heat transfer properties are dependent on the stator, as the bearing rings are supported directly by the stator.
Another long electrical motor type is known from U.S. Pat. No. 3,136,905 and from DE-B 885 279, where the stator is divided in sections by bearing parts being much thicker than the single stator disc, but where the windings of the stator are cut off by the bearing parts and are not passing from one end to the other of the long electrical motor. Further, in U.S. Pat. No. 3,136,905 the bearings are not of a “low friction” type. Such motors is also very complicated to assemble and has a low degree of reliability due to the complicated production of the stator windings. This construction, also, ends up with a bad efficiency, as the magnetic flux is scattered by the relatively large gaps in the stator windings.
Further, a long electrical motor is known from U.S. Pat. No. 3,136,905, where the bearings are defined directly by the stacked discs between the sections. Those discs are thus made from a material that is not well suited for the purpose of defining a bearing with an uncontrolled friction. A bearing made of what could be regarded as a laminated material will under a relatively large friction provide a non-uniform wearing surface, thereby making a pattern of abrasion in the rotating axis. The friction causing an increase in the temperature is dependent on good heat transfer properties of the bearings. Such good heat transfer properties are not present, when the bearings are made from the stacked discs, as iron (Fe) has thermal conductivity of only 72.8 J/(m.s.K).
From U.S. Pat. No. 5,128,573 another long electrical motor with multiple sections is known, where a rotor bearing and sleeve assembly is arranged between each rotor section, each bearing including a fixed key for positioning in longitudinal spacings formed as part of the stator section, to prevent rotation of the bearing during use. Such bearing is evidently not a low friction type, as the fixed key evidently is necessary.
From U.S. Pat. No. 4,638,198 still another long electrical motor with multiple sections is known, where the upper rotor section of each pair of successive rotor sections may have its lower end supported on a rotor shaft protrusion, such as a ring mounted in an annular groove of the rotor shaft, and where further a chamfer at the end of the rotor bore locks the ring in place. Although this prior art has a protrusion for the support of the lower end, this protrusion can not be characterized as a bearing of low friction type. Also, the protrusion is locked on place by a chamfer at the end of the rotor bore, which is not reducing the friction.
Finally, a long electrical motor with multiple sections in known from U.S. Pat. No. 4,453,099, where the bearing is an assembly including a sleeve, that is keyed to the shaft, an inner portion, that rotably receives the sleeve, and a flange with a periphery, that frictionally engages the stator to prevent the bearing from rotating.
The state of the art has some drawbacks in that the threadening of the stator windings all the way through the stator package is not possible or very difficult. The threadening is very time consuming and expensive, and a means for reducing the costs, when threadening the stator windings in a long electrical motor, would be most convenient. Further, the state of the art is also dependent on the friction in that the friction in the bearings is not controlled, and the efficiency is relatively low due to the large magnetic gap between rotor and stator, necessary to avoid mechanical damages when the magnetic momentum is large. Finally, the costs for production and maintenance are high. The friction can lead to heating and premature wear of the bearings and will therefore cause loss of energy and materials.
SUMMARY OF THE INVENTION
It is therefore the object of the invention to provide a long electrical motor having a high efficiency, which motor being mechanically stable with an effective cooling of the bearings can be assembled under low time consumption at low costs, and which motor is easy to maintain and repair.
This object is achieved according to the invention in, that each single discs in the bearing pedestal is significantly thicker than the common stator discs and made of a paramagnetic metal with good heat transfer properties, that the inner diameter of each disc in the bearing pedestal is smaller than the common stator discs, that the bearing is inserted in and is held by a tight fit in the bearing pedestal, whereby the inner diameter of the bearing is fitting tightly to the axis of the rotor, and that the slots for the stator windings in all the metal discs are radially open towards the rotor.
A preferred embodiment according to the invention can be found in , that the bearings are ball bearings, either thrust ball bearings and/or radial ball bearings, thereby offering the lowest possible friction for either horizontal or vertical position of the motor during use. Also the possibility of combining the thrust ball bearings and the radial ball bearings in one motor, thereby making it universally applicable, is possible on the basis of the invention. It can also be advantageous to use a roller bearing.
In the long motor according to the invention, where the threadening is accomplished relatively fast and therefor at low costs, the slots are each forming a cavetto for each winding, and it is suggested, that each string in the winding has a non-circular cross section. Thereby it is achieved, that the winding can be guided through the openings for the rotor or the bearings and thereafter being put into the slots. The non-circular cross section will with this feature secure, that the windings fill most of the cavities in the cavetto, thereby providing a large magnetic flux in the rotor. The rotor can be of any type suited for this purpose.
REFERENCES:
patent: Re. 28094 (1974-07-01), Boyd
patent: 2205783 (1940-06-01), Arutunoff
patent: 2315917 (1943-04-01), Arutunoff
patent: 3136905 (1964-06-01), Zapt et al.
patent: 3506861 (1970-04-01), Boyd
patent: 3551714 (1970-12-01), Boyd
patent: 4453099 (1984-06-01), Flat
patent: 4638198 (1987-01-01), Cochran
patent: 5128573 (1992-07-01), Liu et al.
Enad Elvin
Nath Gary M.
Nath & Associates PLLC
Novick Harold L.
Welltec ApS
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