Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-09-15
2001-06-12
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S267000, C310S156030
Reexamination Certificate
active
06246147
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a device for forming a leno selvedge with an electric motor comprising a rotor and a stator accommodating the rotor, whereas the rotor is provided with at least two guiding apertures for the doup ends and whereas the rotor is provided with several magnetic poles oriented in axial direction.
2. Description of the Prior Art
The document EP 674 031 discloses a so-called rotary selvedge twisting apparatus for power-operated looms provided with a ring serving as a rotor and lodged in a casing designed as a stator. This ring, which may also be called a disc, has two guiding apertures for threading the doup ends. According to the state of the art, the ring is additionally provided radially, i.e. on its outer periphery, with magnets arranged thereon and cooperating with the corresponding laminations arranged in the stator casing. As the rotor revolves in the casing, the doup ends guided by the rotor in the two thread guiding apertures are twisted, whereas at each twist one weft thread is firmly locked in place by this twisting. The principle of operation of such a device for forming a leno selvedge is sufficiently well known.
This well-known device for forming a leno selvedge, which, as already described above, is designed as an electric motor, the magnets for the electric motor being tangentially arranged on the periphery of the rotor and the stator being accordingly provided with corresponding laminations, is characterized by a reduced speed and a high moment of inertia. This is a disadvantage since, when using this contrivance as a device for forming a full leno selvedge, the direction of rotation of the rotor must be reversed after a determined number of revolutions in order to undo a twisting of the doup ends on the feeding side of the doup ends. Since the time available for such an inversion of the direction of rotation is very short due to the high number of weft on modern power-operated looms, the motor must have an extremely high velocity while having a small moment of inertia.
A rotary selvedge twisting apparatus of the type mentioned above is described in DE 297 13723.9, said twisting apparatus being provided with a stator and a doup disc, the doup disc having on its one side magnets oriented toward the stator. These magnets are arranged on the actual disc body. The short circuit obviously occurs on one side of the disc, namely on the side facing the stator.
The disadvantage thereof is that the power density that may be achieved with this well-known structural shape of a rotary selvedge twisting apparatus is small.
U.S. Pat. No. 4,330,737 describes the rotor as being accommodated by the stator casing in axial direction on both sides, the stator casing being provided with iron cores with appropriate windings. The ends of the windings are pointing toward each other, though. As a result, the motor cannot have the required dynamics and power that would be necessary to utilize it in a device for forming a leno selvedge since the magnetic flux is not optimal.
U.S. Pat. No. 3,700,942 discloses a motor in which the rotor is locked on both sides by the stator casing. The rotor is also provided with magnetic poles but it has to be noted that the coil of the stator casing is arranged on the front relative to the rotor in the stator casing. This signifies that, in principle just as in the embodiment according to DE 297 13 723, the magnetic field lines form a leakage flux on account of the air gap to be overcome, which brings about a considerable decrease of performance.
SUMMARY OF THE INVENTION
The object of the present invention is therefor to provide a rotary selvedge twisting apparatus of the type mentioned above that has a high power density and that allows a fast inversion of the direction of rotation.
The solution of this object is to have the rotor provided with two spaced magnetic rings arranged in radial direction, the magnetic rings being provided with several magnet segments each, the magnet segments of the one magnetic ring being locally offset relative to those of the other magnetic ring, whereas the rotor is received on both sides in axial direction by the stator casing, whereas the stator casing is provided with iron cores with appropriate windings, the ends of which being oriented toward the magnetic poles of the rotor. The magnetic poles are thus oriented in the direction of the rotational axis of the rotor and the stator accordingly locks with its laminations the rotor on both sides in axial direction as well. This clearly shows that the flow of force runs axially; the entire surface on both sides of the rotor, which may be designed as a through disc or as an annular disc for example, is thus available as a magnetic surface. A large magnetic surface or a large number of magnetic poles occasions a high torque and hence a high acceleration of the rotor. The low moment of inertia is achieved by the fact that the disc accommodating the magnetic poles may be extremely thin, particularly if the disc itself is magnetized in segments, no additional weight being added by magnets arranged on the disc, as this is the case with prior art.
The following should furthermore be noted: The rotor has apertures for receiving doup ends. Due to this way of having the doup ends guided in the stator casing by the rotor, the magnetic short circuit is undone. The stator casing is thus composed of two parts or halves. This means that the magnetic reluctance of the short circuit is increased, the performance of the motor naturally decreasing as a result thereof. Particularly due to the fact that the rotor is provided with two radially spaced magnetic poles, each having several magnetic segments offset relative to each other, the radial arrangement of two magnetic rings causes this decrease of performance to be more than compensated by undoing the magnetic short circuit.
According to a particular characteristic of the invention, the stator is designed as a casing surrounding the rotor at least partially on the periphery, the rotor being rotatably carried in bearings in tangential arrangement, i.e. on its periphery in the casing. This may for example be achieved by providing the stator casing with ball or needle bearings which rotatably lock the rotor on its periphery. The rotor may however also be carried in a contactless manner by way of air or magnetic bearings. This clearly shows that the rotor and hence the motor may be mounted on the power-operated loom so as to be substantially perpendicular to said loom, the advantage thereof being that said rotor, thanks to its compact design, may also be arranged in axial direction between the heald frames of the power-operated loom.
More specifically, the stator casing has at least two preferably C-shaped iron cores which positively lock the rotor on both sides, i.e. on both sides in axial direction of the rotor. It is well known that there is an air gap between the rotor and the stator; this air gap is present in each electric motor and is due to construction; in the present case, it however also serves to guide the doup ends past the rotor during rotation of the same. As a result, the construction of an electric motor according to the teaching of the present invention makes it possible to have the rotor carried in bearings without a central axis being carried in the casing. The rotatable arrangement of the rotor by such a central axis is not conceivable since the doup ends would snarl around this central axis while the rotor were rotating. This means that the construction according to the invention realizes two advantages:
1. it allows to carry the rotor in the stator without hindering the path of the doup ends from one side of the rotor to the other side of the rotor;
2. thanks to its design, such a motor has a small moment of inertia while having a high torque, which allows a high acceleration rate with regard to an inversion of the direction of rotation.
Since the rotor is provided on its surface with a plurality of magnetic poles, extremely precise positioning is poss
Hockemeyer Kurt
Schwemmlein Christoph
Klocker-Entwicklungs-BmbH
Lam Thanh
Ramirez Nestor
Vigil Thomas R.
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