Patent ID: 8607596

Claim:
A drum type washing machine, comprising: a housing; a spin tub to hold laundry to be washed, the spin tub rotating with respect to a horizontal axis of the washing machine; and a ball balancer coupled to the spin tub to compensate for a dynamic imbalance during rotation thereof, the ball balancer comprising a first plastic member and a second plastic member joined to each other to define a closed internal space in which a plurality of balls and viscous fluid are accommodated, the first plastic member having an open side, and the second plastic member configured to cover the open side of the first plastic member, wherein the first plastic member and the second plastic member are configured such that the balls moving inside the ball balancer during operation of the washing machine cannot establish contact with a joined region where the first plastic member and the second plastic member are joined together, and wherein the spin tub includes a cylindrical body, a front cover and a rear cover, the front cover having a front wall with an opening formed therein for receiving laundry and an annular recess having a predefined depth formed in the front wall of the front cover such that an outer annular side wall defining the annular recess establishes continuous circumferential physical contact with a predefined circumferential area of an inner surface of the cylindrical body to provide a double wall structure to prevent breakage to the ball balancer or the annular recess of the spin tub, the balancer being installed in the annular recess of the spin tub such that a plurality of supports formed on an outer surfaces of an outer wall of the first plastic member establishes contact with the outer annular side wall of the annual recess.