US Patent 7281753 Vehicle enclosure

Door assembly includes a doorframe that can be secured to the vehicle, and a preferably rigid door that is movable between an open and closed position. The door can be secured to the vehicle in the open position so that the passengers have the option of riding in the vehicle while the door remains open. A hinge system minimizes the clearance necessary to open and close the door, and provides an optional assist feature that helps urge or bias the door to the open or closed position and maintain it there.