Abstract:
A mixer/stirrer motor-reducer (e.g. as part of a mixer, stirrer or similar building machine), includes an electric motor ( 2 ) and a reducer ( 3 ) kinematically connected to the motor via a gear train ( 4, 6, 8 ) and with a relevant output shaft ( 9 ) intended for moving a mixing tank ( 10; 110 ). The motor-reducer ( 1 ) is provided with a box-shaped shell ( 15 ) made of insulating material. The shell ( 15 ) is open laterally, is able to include the casing ( 12 ) of the electric motor ( 2 ), is closable by a flange ( 19 ) and is made of electrically insulating material and is interposed between the motor ( 2 ) and the reducer ( 3 ).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of priority under 35 U.S.C. § 119 of Italian application FI2002U00071 filed Jul. 1, 2002. 
   FIELD OF THE INVENTION 
   The present invention refers to a motor-reducer to be used, in particular, for mixers, stirrers and similar machines of the building technical field and such stirrers having such a motor reducer. 
   BACKGROUND OF THE INVENTION 
   Numerous attempts have been made so far to solve the problem of the electrical insulation in building machines of the above mentioned type. 
   To improve the electrical insulation in motor-reducers used in building machines such as mixers and stirrers, a first approach is to insert the motor-reducer assembly within a cabin made of plastics material and containing all the above components. This solution, however, implies increased overall dimensions of the machine&#39;s part housing the motor and reducer. 
   A further attempt to solve the problem of the electrical insulation in a motor-reducer provides for separating the electric motor from the reducer, insulating only the motor and connecting the latter to the reducer via drive belts made of insulating material. This solution does not allow a direct connection between the motor and the reducer. 
   SUMMARY OF THE INVENTION 
   The main object of the present invention is to overcome the said drawbacks by constructing a motor-reducer provided with a dual insulation for the electrical parts. 
   This result has been achieved, according to the invention, by providing a motor-reducer having the characteristics indicated in the claim  1 . Further characteristics being set forth in the dependent claims. 
   The advantages deriving from the present invention lie essentially in the fact that the motor-reducer provides a dual insulation of the electrical parts; that an improved work safety conditions are obtained; that the motor-reducer in question has an output shaft on which a mixing tank for mixers and stirrers can be directly attached; that although the invention is relatively easy to carry out, it allows the construction of an extremely safe and resistant product able to maintain its characteristics unaltered over the whole service life of the machine. 
   These and other advantages and characteristics of the invention will be best understood by anyone skilled in the art from a reading of the following description in conjunction with the attached drawings given as a practical exemplification of the invention, but not to be considered in a limitative sense The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
       FIG. 1  is a schematic view in longitudinal section of a possible embodiment of a motor-reducer according to the present invention; 
       FIGS. 2A and 2B  show, respectively, a side view and a front view of a first possible example of application of the motor-reducer in question; 
       FIGS. 3A and 3B  show, respectively, a side view and a front view of a second possible example of application of the motor-reducer in question; 
       FIGS. 4A and 4B  show, respectively, a side view and a front view of a third possible example of application of the motor-reducer in question; 
       FIG. 5  shows a side view, with parts taken away, of a fourth possible example of application of the motorreducer in question; 
       FIG. 6  is a schematic view in longitudinal section of a further possible embodiment of a motor-reducer according to the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to the drawings in particular, the description which follows is made with reference to the schematic drawings of the attached figures wherein numeral ( 1 ) designates a motor-reducer as a whole, that is, comprising an electric motor ( 2 ) and a reducer ( 3 ). The electric motor ( 2 ) may be of known type having two to four poles and, accordingly, it is not described in detail. 
   The output of the motor ( 2 ) exhibits the toothed end ( 4 ) of a shaft ( 22 ) on which the relevant rotor ( 5 ) is keyed. The rotor&#39;s shaft ( 22 ,  4 ) is in meshing engagement with the first gear of a train of gears having parallel axes and making part of the reducer ( 3 ). The first gear ( 6 ) is engaged, via a pinion ( 7 ) being coaxial and solid with the same gear ( 6 ), with a second gear ( 8 ) provided with the output shaft ( 9 ) of the reducer ( 3 ). Possibly mounted directly on the output shaft ( 9 ), which can be conical as in the example of  FIG. 1 , is a mixer&#39;s tank ( 10 ). The output shaft ( 9 ) may be cylindrical as well, so as to allow the mounting thereof in a stirrer or other similar building machine. 
   Shown in  FIGS. 2A–B ,  3 A–B and  4 A–B are respectively, a mixer with rotary support, a drum mixer and a wheelbarrow mixer; in these figures, the building machine is designated with numeral ( 11 ) the tank with ( 10 ) and the motor-reducer with ( 1 ), while the other parts have not been numbered because of known type. In  FIG. 5 , the motor-reducer ( 1 ) is associated with the tank ( 110 ) and a stirrer ( 111 ). It will be appreciated that further application examples are possible, as those skilled in the art can easily understand. 
   According to the invention, the body of the electric motor ( 2 ) that is, the casing ( 12 ) holding the rotor ( 5 ), stator ( 13 ) and relevant windings, and the electric system&#39;s section ( 14 ), are housed within a coating shell ( 15 ) of insulating material. 
   The shell ( 15 ) comprises a main body having a substantially cylindrical shape, open in correspondence of a base, and an auxiliary body ( 16 ), located on top in the example of  FIG. 1 , able to enclose the group ( 14 ) of the electrical system&#39;s components (not shown) which are outside the motor ( 2 ). 
   The electrical system ( 14 ) can be constructed and mounted separately from the shell ( 15 ), and still leaving unaltered the operational capacity of the second electrical protection of the assembly. This solution being not illustrated for the sake of simplicity. 
   The shell ( 15 ) is provided with aeration apertures ( 18 ) in correspondence of the region of fan ( 17 ) of the electric motor ( 2 ) (left side in  FIG. 1 ). 
   On the opposite side, the shell ( 15 ) is closed by a flange ( 19 ) which is made of electrically insulating material and interposed between the right-side part of casing ( 12 ) and the reducer ( 3 ). In particular, the flange ( 19 ) is fastened by screw means ( 20 ) to the casing ( 12 ), and the connection portion ( 21 ) of reducer ( 3 ) is fastened on the flange ( 19 ); the screws ( 20 ) are isolated from the casing ( 12 ). To ensure the insulation degree around the rotor&#39;s shaft, in correspondence of the portion of shaft ( 22 ) on which the rotor ( 5 ) is fixed, there is provided a bush ( 23 ) in insulating material which, therefore, results interposed between the shaft ( 22 ) and rotor ( 5 ). 
   In this way, it is possible to fulfill the requirement of dual electrical insulation required for mixers, stirrers and similar building machines. 
   In the illustrated example of  FIG. 6 , the insulating bush ( 23 ) extends almost over the whole length of the shaft ( 22 ) of rotor ( 5 ). 
   Moreover, in place of screws ( 20 ) which, in the example of  FIG. 1 , fix the casing ( 12 ) to the portion ( 21 ) of reducer ( 3 ), provision is made for two sets of screws designated, respectively, with ( 120 ) and ( 121 ). The screws ( 120 ) and ( 121 ) may be disposed along respective concentric circumferences; in  FIG. 6 , the representation in longitudinal section allows only one of screws ( 120 ) and one of screws ( 121 ) to be seen. The screws ( 120 ) connect the motor&#39;s casing ( 12 ) to the flange ( 19 ). The screws ( 121 ) connect the flange ( 19 ) to the reducer ( 3 ), in correspondence of said connection portion ( 21 ). Practically, in this embodiment, the insulation of the rotor is developed over an extension greater than in the example of  FIG. 1  and, besides, the connection between the motor and reducer is made by connecting the flange to the two elements independently, that is, by means of the two separate sets of screws ( 120 ) and ( 121 ). 
   While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.