Concrete mixer

DESCRIPTION

It is known that the concrete mixers used in the building industry for preparing relatively small quantities of various types of mixtures and concretes basically comprise a tank which is dragged into rotation by a suitable motion unit and in which the selected components are mixed, and a support structure with a tank-bearing arm. The motion unit comprises an electric motor and a speed reducer which connects the motor shaft to the tank axis. The tank bearing arm is connected to the support structure so that it can rotate around a horizontal axis and the tank can consequently rotate both around its axis, as it is connected to the motion unit, and around the hinge axis of said arm. The main aim of the present invention is to propose an improved concrete mixer.

According to the present invention, these results have been achieved by means of a concrete mixer having the features described in claim 1. Further features of the present invention are the subject of the dependent claims.

A concrete mixer according to the present invention is more noiseless, more compact, more reliable and economical, facilitates the maintenance and repair operations, features higher global mechanical performance and its support structure can be lightened.

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, wherein:

Fig. 1 represents a schematic side view with sectioned parts of a concrete mixer according to the present invention;

Fig. 2 represents an enlarged detail of the machine shown in Fig.l; Fig. 3 represents a further embodiment of the present invention.

A concrete mixer according to the present invention basically comprises a support structure (1), a tank (2), a tank-bearing arm (3) joined to two uppers (10) of the structure (1) so that it can rotate around a horizontal axis (x-x) and an electric motor (4) whose activation determines the rotation of the tank (2) around a corresponding rotation axis (y-y) . Said electric motor (4) is an electronically controlled brushless permanent- magnet motor which allows the variation of the rotation speed within relatively large limits. The structure and the functioning of a brushless permanent-magnet motor are well-known so they will not be described in detail. A speed reducer (6) is positioned between the output shaft of the motor (4) and the tank (2) .

The speed reducer (6) features an upper zone and a lower zone. The upper zone of the speed reducer (6) is inside the arm (3), the latter being a hollow arm. The lower zone of the speed reducer (6) and the motor (4) are external to the arm (3) .

The speed reducer (6) comprises a casing (60) containing corresponding gears which features, in correspondence of the upper zone of the speed

reducer, a lateral portion (61) - on the left in Fig. 1 and in Fig. 2 - and a deeper portion in correspondence of both the upper and the lower zone of the speed reducer. A motor (4) is coupled onto the lower side of the lateral portion (61) of the casing (60) . The shaft (40) of said motor goes into said lateral portion(61) of the casing (60) through an opening foreseen in the respective lower side. A first toothed wheel (62) is mounted on the free end of said shaft (40). Said first toothed wheel is housed in the lateral portion (61) of the casing (60) and is engaged to a second toothed wheel (63) . The said second toothed wheel is partly housed in said lateral portion (61) and is partly housed outside it, i.e. said second toothed wheel is partly in the lateral portion (61) of the casing (60) and partly in the deepest portion of the latter. Said second toothed wheel (63) is mounted on the upper end of a shaft (64) which is parallel to the shaft (40) of the motor (4) and is provided with a toothing (65) in its lower part where it engages with a third toothed wheel (66) . The latter is mounted on the lower end of the output shaft (67) of the speed reducer (6), said output shaft being parallel to the previously mentioned shafts (40, 64) . A tank (2) is mounted on the upper end of the said shaft (67) in a well -known manner. The upper side of said casing (60) is fixed to the tank-bearing arm by means of bolts (7) As previously said, the motor (4) is fixed to the lower side of the lateral portion (61) of said casing (60) More ^' in particular, with reference to the example shown in Fig. 1 and in Fig. 2, the

external upper base of the motor (4) is fixed to the lower side of said lateral portion so that a lateral external surface of the motor is in contact with a lower side (68) of the casing (60) . In practice, the casing (60) features a lateral extension (which corresponds to the lateral portion 61) under which the motor can be fixed

(4), so that said motor is lateral to the speed reducer (6) with its shaft (40) parallel to the output shaft (67) of the speed reducer. In other terms, the casing (60) features a lateral depression (which corresponds to the space under said lateral portion 61) where the motor (4) is positioned. With reference to the example shown in Fig. 3, the lateral portion (61) of said casing features a lower extension ( 610) which is basically cylindrical and extends downward, that is, towards the seat for the motor (4) . Said extension (610), foreseen on the lower side of the lateral portion (61) of the casing (60), features a seat for two bearings (611) through which the output shaft of the motor passes (4) . In this example, the skirt of the motor (4) can be built without the upper base, i.e. open on its upper side. In fact, said upper base is formed by the lower side of the portion (61) mentioned above. The drawings only show practical embodiments of the invention, which can vary in forms and arrangements without however departing from the scope of the concept on which the invention is based. Any reference numerals in the appended claims are provided purely to facilitate reading thereof in the light of the description and accompanying drawings, without limiting the scope of protection in any way.