GB619599A - A new or improved current density indicating or control meter - Google Patents

Abstract

619,599. Automatic control systems. GUEST, KEEN & NETTLEFOLDS, Ltd., and WALLBANK, A. W. Dec. 16, 1946, No. 36960. [Class 38 (iv)] [Also in Group XXXVI] It is required to maintain constant or to periodically vary the current density in an electroplating vat. In the electroplating equipment shown devised for constant current density, the vat 12 is fed through a variable autotransformer 31 and rectifier 32. If for example, the current density as indicated by meter 26 increases a servo-mechanism 28 operates to apply a voltage to a control motor which then rotates a shaft 30 to reduce the output voltage of the auto-transformer 31 and restore the current density to its required value. The circuit may include a resistance 29, chosen so that the range of voltage variation across it suits the input characteristics of the servomechanism 28. The current density meter 26 operates in circuit with electrodes 13, 14 (with which it is calibrated) and a reversing switch 24. The latter is actuated at intervals by a synchronous motor 27 to interchange the polarities of the electrodes 13, 14 to avoid errors in the meter reading. It is stated that it may be arranged to reduce or increase the current density with the passage of time by the provision in the servo-mechanism of adjusting means actuated by the synchronous motor 27. The Provisional Specification mentions another scheme for maintaining constant current density in which limit contacts in the ammeter are connected to the motorized control of the auto-transformers.