Apparatus for controlling a soap concentration in cleaning solvent

An apparatus for controlling a soap concentration in cleaning solvent comprising:

• a pump for supplying a cleaning solvent to a washing tub;
• liquid quantity measuring means for measuring a quantity of the solvent supplied to the washing tub by the pump;
• soap supplying means supplying a soap to the washing tub;
• a sampling container for sampling the solvent;
• soap concentration measuring means for measuring a soap concentration in the sampled solvent;
• setting means for setting a desired soap concentration;
• arithmetic means for calculating the operating time of the soap supplying means required for making a soap concentration of the solvent in the washing tub approach to the set desired soap concentration on the basis of the measured quantity of solvent, the measured soap concentration and soap supplying capacity of the soap supplying means per unit time;
• and
• control means for operating the soap supplying means on the basis of the calculation result of the arithmetic means, wherein
• the soap supplying means comprise at least two soap supplying means having different supply capacities, large and small,
• the control means further provide means for comparing the difference between the set desired soap concentration and the measured soap concentration with a predetermined value, and
• the soap supplying means having large supply capacity are operable in case where the difference is bigger than the predetermined value, while the soap supplying means having small supply capacity are operable in case where the difference is smaller than the predetermined value.