Patent ID: 8607597

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 an 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 form an annular-shaped race having a closed internal space in which a plurality of balls and viscous fluid are accommodated, the first plastic member including a first side wall, a second side wall and a connecting wall to form a three-sided annular-shaped structure having an open side, and the second plastic member configured to cover the open side of the first plastic member, the three-sided annular-shaped structure having a U-shaped cross-section with a first rounded inside corner formed between the first side wall and the connecting wall and a second rounded inside corner formed between the second side wall and the connecting wall, 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 outer annular side wall establishing continuous circumferential physical contact with a predefined area of an inner surface of the cylindrical body, and the outer annular side wall being an outer wall of an annular recess dimensioned to accommodate the ball balancer therein, whereby during a rotation of the spin tub the ball balancer is supported in a direction of centrifugal force by both the outer annular side wall and the cylindrical body.