Rangers will step up patrols at Purdon Crossing on the South Yuba River State Park this summer to enforce a ban on overnight parking and camping on state park property.Park rangers will begin posting signs of the 10 p.m. to 6 a.m. park closure in coming weeks, said Jeremy McReynolds, supervising ranger for the state park. Though the overnight parking rule is nothing new, it has been ignored at Purdon more so than any other area of the state park system in the county. "It has been an anomaly," Reynolds said.The announcement comes after residents who live on Purdon Road …