Mixing of materials

In an apparatus for mixing materials which includes a mixing chamber, a mixing tool, and a motor driving the mixing tool, the improvement comprising:

• first means connected to the motor to derive therefrom a signal representative of the power consumption of the motor during operation under mixing load;
• second means providing a correcting signal representing power consumption of the motor when driving the mixing tool, but without mixing and being connected to the first means to provide a signal representing the difference between the signal as provided by the first means and the correcting signal;
• third means connected to be responsive to the different signal to provide a train of pulses at a frequency representing true mixing power;
• counter means connected to the third means for connecting the pulses as provided by the third means;
• externally programmable reference means responsive to external control manifestations and providing presettable digital reference signals representing predetermined mixing states in terms of work needed to obtain said state;
• means connected to the programmable reference means to provide thereto corrective values representing deviations of said predetermined work, so as to modify said reference signals;
• comparator means connected to said reference means, and said counter means for controlling the duration of mixing in response to agreement between the digital reference signals provided by the reference means and the state of the counter;
• means for sensing the temperature of the mixture in the chamber;
• and
• means connected to the means for sensing, for controlling the mixing operation in additional dependency upon temperature of the substance being mixed to reduce mixing power as expanded in the case of detecting a predetermined excess temperature.