US Patent 7506394 Wrap-around brush system for conveyor car wash

A wrap-around car wash structure comprising two staggered, vertical brushes. Each brush is mounted on a carriage which slides along a bifurcated boom pivotally mounted on a support base. The boom and carriages start in an extended position wherein the brushes are near the center of the wash lane; the booms swing in toward the sides of the lane as the brushes' carriages are pulled inwardly by reversible power cylinders. A control mechanism on at least one of the booms promptly reverses the power cylinder as the brush clears the side of the vehicle regardless of the width of the vehicle and the degree to which it has displaced the boom toward the side of the wash lane.