PA28 suffers significant damage when the nose gear collapses and the aircraft exits the runway.

Narrative

Entered the downwind leg of the pattern on the 45 degree for a landing on runway. Normal flaps and speed on downwind; base and full flaps on final. The plane touched down and rolled down the runway on the main landing gear. The plane traveled slightly to the right of the centerline while still on the mains. Corrected with a small amount of left rudder. As the nosewheel contacted the runway; brakes were applied. The plane nosed down severely and darted quickly to the left and did not seem to respond to right rudder inputs. Full braking was applied as the plane went off the runway stopping approximately 20 FT off the runway in the grass. No one was hurt and no property damage occurred. Damage to the aircraft included: propeller strike; nose gear collapse; and right wingtip damage. Possible causes: Unsure why the plane darted so quickly to the left. Possible failure of the nose gear due to left rudder input with too much brake or failure of the nose gear due to wear. Prevention: Keep the nose gear up as long as possible when landing. More frequent inspections of the nose gear assembly.