US Patent 7398663 Drum-type washing machine

A drum-type washing machine having a self-balancing outer tub assembly is provided by which balance of the outer tub assembly is maintained while the drum is rotated, without the use of a separately installed counterbalance for the front part of the tub assembly. The outer tub assembly includes a front outer tub having an open front and rear; and a rear outer tub having a closed end and an open end coupled to the front outer tub. The front outer tub is formed of a material having a specific gravity higher than that of the rear outer tub and/or has a thickness greater than that of the rear outer tub.