Method for pre-balancing a rotating drum having a temporarily shifting unbalance

Abstract

The process for making an automatic balancing unit outbalance an unbalance condition in a rotating system, particularly a clothes washing machine with an outer casing an a suspended oscillating washing assembly comprising a wash tub, a cylindrically-shaped perforated drum housed in said tub and capable of rotating in the interior thereof about the axis of the cylinder during washing and spin-extraction, a motor capable of rotatably driving said drum at various speeds and provided with accessory means that are firmly associated with said tub, said drum being connected to said automatic balancing unit formed by at least one annular hollow body, forming a sealed closed-loop configuration and being mounted integrally with said cylindrical drum with their axis coinciding with the rotational axis of said perforated drum, and a plurality of moving masses capable of freely moving in a liquid filled in said hollow body, and which process incorporates that before at least a spin-extraction phase, the drum is driven to rotate in a continuous manner at a variable, relatively low speed in a single and same direction of rotation, wherein the frequency of said rotation is lower than the frequencies of translational eigen modes perpendicular to the rotational axis of the drum of said oscillating washing assembly, but anyway sufficient in view of causing the washload in the drum to keep adhering against the inner peripheral surface of the drum, wherein, for giving full repetitiveness to the outbalancing effect, minimizing any stiff body movements in the suspended assembly within the range of the actual speed variations around the distribution speed.