CONTROLLER FOR SPECIFIC GRAVITY OF ETCHING SOLUTION

摘要

PURPOSE:To correctly control the specific gravity of an etching soln. within a control range and stabilize the etching operation by measuring the specific gravity during etching work and controlling the magnet valve of a water feed pipe in accordance with the measured value. CONSTITUTION:In the chemical etching of a shadow mask for a color cathode-ray tube or the like branching section 45 is attached to pipe 44 for feeding an etching soln. from tank 41 to etching chamber 43 under pressure, and part of the soln. is fed to specific gravity measuring section 47 to measure the specific gravity with hydrometer 48 and the temp. with temp. sensor 49. The specific gravity at the measured temp. is corrected to that at the temp. of the etching soln. in chamber 43. This value is inputted in control section 59, and in accordance with the signal from section 59 magnet regulation valve 57 attached to water feed pipe 52 is controlled to feed water to tank 41. Thus, the specific gravity of the soln. increased by etching work is regulated to 1.460+ or -0.001, and the etching work is performed stably.