SQUIRREL CAGE MOTOR WITH IMPROVED ROTOR BAR SECURING ARRANGEMENT

_AOE280A2AO> aql present invention relates to equipment type dynamoelectric cage écureui -1, and relates more particularly to fixing means of the rotor bars in the cage"

It is building of large motor rotors squirrel cage for axially drawing the bars in the slots of the core "The bars and the notches have are both substantially rectangular cross-section, with flat faces" After introduction of the bars in the notches, before or after the stirring rings ends to the bars, a étampeur can be introduced into the openings of the notches with application of a force for causing the faces of the bar and notches into engagement more intimate "Although this arrangement has been used very extensively and successfully, there is still cases where vibration of the rotor bars can produce, in a service stringent and in some circumstances, a failure of the bars by fatigue" An arrangement improved fastening system is particularly desirable with the thin bars.

According to the present invention, a dynamo-electric apparatus of the squirrel cage type, comprising a stator, a rotor mounted to be concentric with the inside of the stator, the rotor consisting of a magnetic core made of a number of stacked plates, is characterized in that the core is provided with a number of notches from the surface of the rotor and extending longitudinally from one end to the other of the core, and a rotor bar conductive material housed in each of these slots, having two inner faces extending radially in the core and having tâtions inden. daua which material from the bars have been thrust force so as to prevent vibrations"

The present disclosure does not introduce substantially no complication in the prior art squirrel cage rotors " The bars can be placed in the slots of the core or by introducing axial thrust by martellement by means of a mallet or by using a hydraulic ram.

After positioning of the bars in the slots, before or after the " solder rings ends, a drawing tool can be applied by introducing into the opening of the notch with application of sufficient force to produce the deformation of a certain amount of the bar material into the indentations of the walls of the groove. Ge working performs the positive locking bars within the notches.

The description of the invention is given below, by way of example, with reference to the accompanying drawings, on which s

-figure 1 is a perspective view, partially interrupted, main parts of a squirrel-cage motor;

-figure 2 is a partial view in cross-section, of a squirrel-cage rotor of one embodiment of the present invention to a preliminarily the manufacturing process}

-figure 3 is a partial view in cross-section of a squirrel-cage rotor according to the invention, after completion; and

-figure 4 is a partial cut of a rotor groove according to one embodiment of the invention, engagement of. the recess.

Figure 1 represents ua example of squirrel-cage motor comprising a core 10 carrying the stator windings 12, that concentrically surrounds a squirrel-cage rotor 14. The rotor 14 is rotatable around the shaft 15 and comprises a magnetic core 16 normally consisting of a number of stacked plates that the it is clearly shown in Figure 4. The core 16 is provided with a number of bars 18 of rotor slot-housed which extend axially from one end to the other of the core. The bars 18 are joined, e.g. by brazing, to the rings ends 20, at the axial ends of the core 16. The engine of Figure 1 is a three-phase motor which is an example of the most common type.

Figures 2 and 3 represent a single bar 18 in a notch 22 of the core 16. 16A The sheets of the core 16 are cut such that they form, after stack in a predetermined orientation, the notches 22 of the core.

The notches 22 have characterized as having a narrow opening 22k and a portion substantially rectangular 22B.

22B The latter portion houses the rectangular bar rotor 18 inserted axially. The notches and the bars may have other shapes, for example-shaped l.

Thus Fig. 2, the bar 18 does not grip the notch 22, during introduction thereof to the origin. Of course the axial introduction requires a certain play.

Unlike the prior art use, the walls of the notch 24, which extend radially outward, are not flat, but at least one, and preferably both, comprise indentations 26. These indentations 26, in a preferred embodiment, consist of one or more longitudinal grooves. In the present example, two of these grooves are used in each face 24 of the slots of the core. However, the indentations may take many other forms.

Of course the indentations 26 have a dimension greater than the variations in the walls 24 normally produced by irregularities 16A size sheets. Preferably, also, the indentations are to extend the length of the core 16, although spaced indentations can be suitable, but are less preferable, because of the need to use plates of different configurations.

It is important, provided to obtain the advantages of the invention, that the indentations 26 are located near the top (radial part Swimming them) faces 24.

Figure 3 represents the structure of Figure 2, after application at the top of the bar 18, in the opening 22A. of the notch, a punching tool 28 to deform the material in the 26 xairures for its positive locking in place. Notably, the lower half of the bar 18 can still does not engage intimately with the walls del ' notch, but it is without result. The solder the ends of the bars 18 gears 20 can be carried out either before, or after-the swaging operation.