Method for controlling mixtures especially for fabric processing

A method of processing a continuously moving web of wet fabric by the addition of a processing chemical thereto, which comprises,

• (a) providing a processing pan having a limited volumetric capacity for containing a small quantity of processing solution, including said processing chemical as a minor component and water as a major component in predetermined proportions,
• (b) the volumetric capacity of said processing pan being such that only a small portion of the moving fabric web is exposed to the processing solution at any time,
• (c) providing separate valve-controlled sources of a concentrated solution of said processing chemical in water and of said water,
• (d) continuously passing said wet fabric into and through said processing solution in a manner causing fabric to pick up and remove a first quantity of processing solution from said processing pan while the fabric causes the continuous introduction into said processing pan of a quantity of water which is dilutive of the processing solution,
• (e) continuously withdrawing processing solution from said processing pan and recirculating said withdrawn solution back to said processing pan,
• (f) said step of continuously withdrawing and recirculating said processing solution including a pumping stage, a mixing stage, and a measuring stage,
• (g) said pumping and mixing stages taking place in advance of said measuring stage,
• (h) the volumetric rate per minute of recirculation of said processing solution being greater than the volumetric capacity of said processing pan,
• (i) rapidly and repetitively measuring the content of said processing chemical in the continuously flowing, recirculating stream of said processing solution,
• (j) said step of rapidly and repetitively measuring the content of said processing chemical being performed by an in-line optical sensor positioned in optical exposure to the continuously flowing, recirculating processing solution, and
• (k) adding supplemental amounts of said concentrated solution of said processing chemical to said continuously flowing, recirculating solution as required in order to continuously maintain said predetermined proportions of said processing chemical and water in said processing solution,
• (l) the steps of adding supplemental amounts of said processing chemical including introducing said processing chemical into the continuously flowing, recirculating solution at a location in advance of said pumping and mixing stages.