Casing construction for electric motors

Abstract: The casing comprises a first and second half-shells each of which is provided with an outer skirt with a bottom at one axial end portion thereof and being coupled, through fin members, to an inner circular envelope which defines a housing for holding the motor stator, the half-shell members being adapted to be assembled by tie rods in order to rotatably support the shaft of the motor rotor.

Description: BACKGROUND OF THE INVENTION The present invention relates to a casing construction for electric motors. As is known, conventional electric motors are usually provided with an enclosing cylindric casing bearing fins thereon, the casing cylindrical body having two open ends to which there are coupled two covers: thus, conventional electric motor casings comprise three main component parts which, because of inevitable tolerances of these parts, involves assembling errors which can excessively increase the electric gap between the stator and rotor members of the motor. Another drawback of conventional casings is that for accessing a portion of the electric motor, the casing must be fully dismantled. Yet another drawback is that a very great number of spare casing parts must be held in a store for replacing possible damaged casing parts. The document DE-C-3738592 discloses a casing construction for electric motors having substantially the features of the preamble of the main claim. SUMMARY OF THE INVENTION Accordingly, the aim of the present invention is to overcome the above mentioned drawbacks by providing an outer casing construction for electric motors which comprises a small number of component parts which can be easily and quickly assembled to one another. Within the scope of the above mentioned aim, a main object of the present invention is to provide such an electric motor casing which allows the electric motor parts to be efficiently cooled and which, moreover, is adapted to provide a very small gap between the rotor portion and stator portion of the motor so as to greatly improve the efficiency of the electric motor. Yet another object of the present invention is to provide such an electric motor casing to which optional fittings can be quickly and easily applied. According to one aspect of the present invention, the above mentioned aim and objects, as well as yet other objects, which will become more apparent hereinafter, are achieved by a casing construction for electric motors, according to the characterizing portion of the main claim. BRIEF DESCRIPTION OF THE DRAWINGS Further characteristics and advantages of the present invention will become more apparent hereinafter from the following detailed description of a preferred embodiment thereof, which is illustrated, by way of an indicative but not limitative example, in the figures of the accompanying drawings where: Figure 1 is a schematic perspective view showing an electric motor provided with an outer casing according to the present invention, and Figure 2 shows the electric motor in a fully assembled condition. DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to the figures of the accompanying drawings, the casing construction for electric motors according to the invention, which has been overally indicated at the reference number 1, comprises a first half-shell 2 and a second half-shell 3, which are identical to one another and advantageously made of an aluminium die-cast body. Each half-shell 2 and 3 is provided with an outer skirt 4 of substantially quadrangular shape which, through inner fin members 5, supports an inner circular envelope 6 so as to define a plurality of cooling air conveying channels. Inside the mentioned cylindrical envelope 6 there is formed, by suitable machining operations, the housing of the stator portion of the electric motor whereas on the bottom arranged at the axial end portion of each half-shell, there is machined a recess provided for housing a bearing for supporting the shaft 10 of the rotor portion, indicated at 11. Thus, by the disclosed machining method, it is possible to make a casing by simply coupling two like construction half-shells, which perfectly fit to one another and are coupled by tie-rods 20 engaging with ears 21 provided at the corner regions of the quadrangular shape skirt 4. With the disclosed half-shells, the electric motor can be restrained at a plurality of different positions, by foot members, brackets, foot members and brackets, thereby also allowing the assembling of special brackets since the latter can be simply restrained by four screws. The thus constructed box-like casing affords the possibility of easily making asynchronous three-phase and single-phase standardized electric motors, three-phase torque motors, and all a broad range of other electric motors. The disclosed casing has a great mechanical strength owing to the provision of the half shells which, due to the outer skirt and fin members, provide a ribbed construction and a very rigid casing body. Moreover, the possibility of performing very accurate machining operations reduces to a minimum the gap between the rotor portion and stator portion of the motors thereby providing an improved efficiency of the motor as well as allowing the motor to be easily and quickly assembled. The disclosed construction, in which ventilating air channels are easily formed, provides a quick and efficient cooling of the inner portion of the motor with a very reduced temperature of the outer casing. The cooling effect can be improved, as is known, by a fan keyed on the shaft of the motor, the air being conveyed by said fan through the channels for the overall length of the casing thereby further improving the motor efficiency. In this connection it should be also added that it will be also possible to provide the application of servofans, either of an axial or of a radial type, in order to provide constant air flow rates independently from the turning speed of the motor and, moreover, it will be also possible to apply to the motor a braking assembly without the need of performing additional machining operations. From the above disclosure it should be apparent that the subject casing fully achieves the intended aim and objects. While the invention has been disclosed and illustrated with reference to a preferred embodiment thereof, it should be apparent that the disclosed embodiment is susceptible to several modifications and variations all of which will come within the scope of the appended claims.

Claims: A casing construction (1) for electric motors, comprising a first and second half-shells (2,3) each of which is provided with an outer skirt (4) with a bottom at one axial portion thereof and being coupled to an inner circular envelope (6) which defines a housing for holding a stator portion of said electric motor, said half-shells (2, 3) being adapted to be coupled by tie-rods (20) so as to rotatably support a shaft member (10) of a rotor portion (11) of said electric motor, characterized in that said half-shells (2,3) have an identical construction, and that each said half-shell (2,3) is provided with a plurality of stiffening fin members (5) coupling said outer skirt (5) to said inner circular envelope (6) and extending through the overall length of each said half-shells, said fins being so designed and arranged that, as said half-shells are coupled to one another, said fins define a plurality of inner cooling air conveying parallel channels extending substantially through the overall length of said electric motor, and in that said outer skirts (4) directly define, as said half-shells (2,3) are coupled, the outer mantle of said casing construction. A casing according to Claim 1, characterized in that said skirt (4) has a substantially quadrangular shape. A casing according to the preceding claims, characterized in that said casing further comprises, at corner regions of said outer skirt (4), ear members (21) for engaging with said tie-rods (20). A casing according to one or more of the preceding claims, characterized in that said casing further comprises means for coupling to said casing outer optional fitting elements. A casing according to one or more of the preceding claims, characterized in that said half-shells (2,3) are made by die-casting an aluminium material, mechanically machining in said casing a housing for receiving the electric motor stator portion and mechanically machining recess portions for housing the bearings of the shaft (10) of the electric motor rotor portion (11).

Inventors: LANDONIO RINO NATALE C O OEMER, LANDONIO, RINO NATALE, C/O OEMER MOTORI ELETTRICI
Applicants: OEMER MOTORI ELETTRICI S P A, OEMER MOTORI ELETTRICI S.P.A.
Application year: 1990
Main classification: H02K9
IPC codes: H02K9, H02K5