Electrophoretic dipping system

Abstract

The invention relates to an electrophoretic dipping system comprising at least one dipping bowl (1) which can be filled with a liquid and an object which is to be coated and which can be dipped therein. At least one power supply unit (5A, 5B, 5C) produces DC voltage with definite residual ripple from AC voltage. The one pole thereof can be connected to at least one electrode of a first polarity (3A, 3B, 3C), said electrode being arranged in the dipping bowl (1) and the other pole thereof can be connected to the object which is to be coated. The power supply unit (5A, 5B, 5C) comprises one uncontrolled diode rectifier bridge (19) and an IGBT switch (22) which comprises a controllable oscillator (24) and a power transistor (23). The controllable oscillator (24) generates pulses having a repetition frequency ranging from between 5 and 30 kHz with variable pulse widths. The power transistor (23) is controlled by said pulses. The voltage pulses produced therefrom can be smoothed out with the aid of relatively small smoothing elements until a highly reduced residual ripple which benefits the quality, especially the smoothness and the roughness of the applied protective coating is obtained. Said power supply unit (5A, 5B, 5C) also has a highly improved cos Phi compared to currently known thyristor bridge switches used for the same purpose.

Description

technical field [0001] The present invention relates to a kind of electrophoretic dip coating equipment, comprising: [0002] a) at least one dipping tank, which can be filled with a paint solution and into which the object to be coated can be immersed; [0003] b) at least one electrode having a first polarity and disposed in said dipping tank; [0004] c) at least one power supply unit which generates from an alternating voltage a direct voltage with a defined residual ripple, one pole of which is connectable to said electrode with the first polarity and the other pole of which is connectable to the electrode to be painted object, and the power supply unit has smoothing elements for reducing residual ripple. Background technique [0005] Such electrophoretic, usually cationic electrophoretic dip coating systems are known on the market. Such dipping equipment must be able to supply a smoothed DC voltage with a variable voltage level to suit the given situation. Only in ...

AI Technical Summary

Problems solved by technology

The smoothing elements required to smooth this voltage require very large smoothing chokes, which are not only expensive but also heavy and take up a lot of space

Despite the use of such expensive smoothing elements, in known cationic electrophoretic dip coating installations there remains a non-negligible residual ripple in the voltage between the anode and the object to be coated, which is detrimental to the final coating obtained influences

Also impairs the durability of the dialysis unit that is typically placed around the anode in a dipping tank

Additionally, the cosφ of these known power supply units is small

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