Truck mixer with a device to make the drum of the concrete mixer rotate and corresponding method

Truck mixer comprising a vehicle provided with first motor means, connected by means of a drive shaft with a movement unit having wheels to effect the movement of said vehicle, a concrete mixer mounted on said vehicle and comprising a drum, and a device to selectively make said drum rotate by means of second motor means, said second motor means comprising an electric motor connected mechanically to said drum, and an electric energy generator unit suitable to selectively feed said electric motor, wherein said electric energy generator unit comprises:

• an alternator connected to said drive shaft of the first motor means by means of a driven shaft through the interposition of a speed reducer to transform the mechanical energy of the drive shaft into electric energy;
• first tension conversion means from alternate to continuous connected to said alternator in order to convert the electric energy produced by said alternator;
• at least a continuous electric energy accumulator connected to said first conversion means;
• second tension conversion means from continuous to alternate connected to said accumulator in order to supply alternate electric energy to said electric motor;
• third tension converter means from alternate to continuous connected to said accumulator to convert the electric energy supplied by an external source of electric energy to said accumulator.

Method to make rotate a drum of a truck mixer having a vehicle provided with first motor means which cooperate with a wheeled movement unit, to effect the movement of said vehicle, said method comprising a first step in which second motor means, comprising an electric motor connected to said drum, make said drum rotate, and a second step in which said electric motor is fed by an electric energy generator unit, wherein said second step provides to:

• connect said first motor means to an alternator to generate alternate electric energy,
• convert the alternate electric energy produced by said alternator into continuous electric energy,
• accumulate said continuous electric energy in an electric energy accumulator,
• convert said continuous electric energy of said accumulator once again into alternate energy,
• feed said electric motor with the alternate electric energy in order to directly make said drum rotate;
• connect said accumulator to an external source of electrical energy through a converter.