Patent ID: 8439553

Claim:
Mixer for concrete, comprising: a parallelepiped tank internally provided with one or more mixing shafts, at least one motor unit in an external position with respect to the tank to driven into rotation said one or more mixing shafts, said motor unit comprising a main motor, a gear motor, a cascade of intermediate and reducing gears interfaced with an end of said one or more mixing shafts, and a low-power auxiliary motor connected with the main motor of the motor unit through a free wheel; wherein the free wheel is configured to during a normal activation of the main motor and a contemporary deactivation of the auxiliary motor, prevent the auxiliary motor from being driven into rotation by the main motor, and during a deactivation of the main motor and a contemporary activation of the auxiliary motor, allow the auxiliary motor to drive the main motor into rotation, and said auxiliary motor has 1 horse power, and the motor unit connected to the auxiliary motor to reduce a rotation speed of a shaft of the auxiliary motor so that an operator is able to perform maintenance operation in the tank.